2019-05-28 17:10:09 +00:00
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/* SPDX-License-Identifier: GPL-2.0-only */
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2014-09-26 07:16:57 +00:00
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/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
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*/
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#ifndef _LINUX_BPF_H
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#define _LINUX_BPF_H 1
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#include <uapi/linux/bpf.h>
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2022-06-14 23:10:42 +00:00
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#include <uapi/linux/filter.h>
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bpf: make jited programs visible in traces
Long standing issue with JITed programs is that stack traces from
function tracing check whether a given address is kernel code
through {__,}kernel_text_address(), which checks for code in core
kernel, modules and dynamically allocated ftrace trampolines. But
what is still missing is BPF JITed programs (interpreted programs
are not an issue as __bpf_prog_run() will be attributed to them),
thus when a stack trace is triggered, the code walking the stack
won't see any of the JITed ones. The same for address correlation
done from user space via reading /proc/kallsyms. This is read by
tools like perf, but the latter is also useful for permanent live
tracing with eBPF itself in combination with stack maps when other
eBPF types are part of the callchain. See offwaketime example on
dumping stack from a map.
This work tries to tackle that issue by making the addresses and
symbols known to the kernel. The lookup from *kernel_text_address()
is implemented through a latched RB tree that can be read under
RCU in fast-path that is also shared for symbol/size/offset lookup
for a specific given address in kallsyms. The slow-path iteration
through all symbols in the seq file done via RCU list, which holds
a tiny fraction of all exported ksyms, usually below 0.1 percent.
Function symbols are exported as bpf_prog_<tag>, in order to aide
debugging and attribution. This facility is currently enabled for
root-only when bpf_jit_kallsyms is set to 1, and disabled if hardening
is active in any mode. The rationale behind this is that still a lot
of systems ship with world read permissions on kallsyms thus addresses
should not get suddenly exposed for them. If that situation gets
much better in future, we always have the option to change the
default on this. Likewise, unprivileged programs are not allowed
to add entries there either, but that is less of a concern as most
such programs types relevant in this context are for root-only anyway.
If enabled, call graphs and stack traces will then show a correct
attribution; one example is illustrated below, where the trace is
now visible in tooling such as perf script --kallsyms=/proc/kallsyms
and friends.
Before:
7fff8166889d bpf_clone_redirect+0x80007f0020ed (/lib/modules/4.9.0-rc8+/build/vmlinux)
f5d80 __sendmsg_nocancel+0xffff006451f1a007 (/usr/lib64/libc-2.18.so)
After:
7fff816688b7 bpf_clone_redirect+0x80007f002107 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fffa0575728 bpf_prog_33c45a467c9e061a+0x8000600020fb (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fffa07ef1fc cls_bpf_classify+0x8000600020dc (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff81678b68 tc_classify+0x80007f002078 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8164d40b __netif_receive_skb_core+0x80007f0025fb (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8164d718 __netif_receive_skb+0x80007f002018 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8164e565 process_backlog+0x80007f002095 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8164dc71 net_rx_action+0x80007f002231 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff81767461 __softirqentry_text_start+0x80007f0020d1 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff817658ac do_softirq_own_stack+0x80007f00201c (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff810a2c20 do_softirq+0x80007f002050 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff810a2cb5 __local_bh_enable_ip+0x80007f002085 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8168d452 ip_finish_output2+0x80007f002152 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8168ea3d ip_finish_output+0x80007f00217d (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8168f2af ip_output+0x80007f00203f (/lib/modules/4.9.0-rc8+/build/vmlinux)
[...]
7fff81005854 do_syscall_64+0x80007f002054 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff817649eb return_from_SYSCALL_64+0x80007f002000 (/lib/modules/4.9.0-rc8+/build/vmlinux)
f5d80 __sendmsg_nocancel+0xffff01c484812007 (/usr/lib64/libc-2.18.so)
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-02-16 21:24:50 +00:00
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2014-09-26 07:16:57 +00:00
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#include <linux/workqueue.h>
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bpf: add lookup/update/delete/iterate methods to BPF maps
'maps' is a generic storage of different types for sharing data between kernel
and userspace.
The maps are accessed from user space via BPF syscall, which has commands:
- create a map with given type and attributes
fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)
returns fd or negative error
- lookup key in a given map referenced by fd
err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->value
returns zero and stores found elem into value or negative error
- create or update key/value pair in a given map
err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->value
returns zero or negative error
- find and delete element by key in a given map
err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key
- iterate map elements (based on input key return next_key)
err = bpf(BPF_MAP_GET_NEXT_KEY, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->next_key
- close(fd) deletes the map
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:16:59 +00:00
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#include <linux/file.h>
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2016-03-08 05:57:13 +00:00
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#include <linux/percpu.h>
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bpf: fix missing header inclusion
Commit 0fc174dea545 ("ebpf: make internal bpf API independent of
CONFIG_BPF_SYSCALL ifdefs") introduced usage of ERR_PTR() in
bpf_prog_get(), however did not include linux/err.h.
Without this patch, when compiling arm64 BPF without CONFIG_BPF_SYSCALL:
...
In file included from arch/arm64/net/bpf_jit_comp.c:21:0:
include/linux/bpf.h: In function 'bpf_prog_get':
include/linux/bpf.h:235:9: error: implicit declaration of function 'ERR_PTR' [-Werror=implicit-function-declaration]
return ERR_PTR(-EOPNOTSUPP);
^
include/linux/bpf.h:235:9: warning: return makes pointer from integer without a cast [-Wint-conversion]
In file included from include/linux/rwsem.h:17:0,
from include/linux/mm_types.h:10,
from include/linux/sched.h:27,
from arch/arm64/include/asm/compat.h:25,
from arch/arm64/include/asm/stat.h:23,
from include/linux/stat.h:5,
from include/linux/compat.h:12,
from include/linux/filter.h:10,
from arch/arm64/net/bpf_jit_comp.c:22:
include/linux/err.h: At top level:
include/linux/err.h:23:35: error: conflicting types for 'ERR_PTR'
static inline void * __must_check ERR_PTR(long error)
^
In file included from arch/arm64/net/bpf_jit_comp.c:21:0:
include/linux/bpf.h:235:9: note: previous implicit declaration of 'ERR_PTR' was here
return ERR_PTR(-EOPNOTSUPP);
^
...
Fixes: 0fc174dea545 ("ebpf: make internal bpf API independent of CONFIG_BPF_SYSCALL ifdefs")
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Zi Shen Lim <zlim.lnx@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-06-09 04:18:47 +00:00
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#include <linux/err.h>
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bpf: make jited programs visible in traces
Long standing issue with JITed programs is that stack traces from
function tracing check whether a given address is kernel code
through {__,}kernel_text_address(), which checks for code in core
kernel, modules and dynamically allocated ftrace trampolines. But
what is still missing is BPF JITed programs (interpreted programs
are not an issue as __bpf_prog_run() will be attributed to them),
thus when a stack trace is triggered, the code walking the stack
won't see any of the JITed ones. The same for address correlation
done from user space via reading /proc/kallsyms. This is read by
tools like perf, but the latter is also useful for permanent live
tracing with eBPF itself in combination with stack maps when other
eBPF types are part of the callchain. See offwaketime example on
dumping stack from a map.
This work tries to tackle that issue by making the addresses and
symbols known to the kernel. The lookup from *kernel_text_address()
is implemented through a latched RB tree that can be read under
RCU in fast-path that is also shared for symbol/size/offset lookup
for a specific given address in kallsyms. The slow-path iteration
through all symbols in the seq file done via RCU list, which holds
a tiny fraction of all exported ksyms, usually below 0.1 percent.
Function symbols are exported as bpf_prog_<tag>, in order to aide
debugging and attribution. This facility is currently enabled for
root-only when bpf_jit_kallsyms is set to 1, and disabled if hardening
is active in any mode. The rationale behind this is that still a lot
of systems ship with world read permissions on kallsyms thus addresses
should not get suddenly exposed for them. If that situation gets
much better in future, we always have the option to change the
default on this. Likewise, unprivileged programs are not allowed
to add entries there either, but that is less of a concern as most
such programs types relevant in this context are for root-only anyway.
If enabled, call graphs and stack traces will then show a correct
attribution; one example is illustrated below, where the trace is
now visible in tooling such as perf script --kallsyms=/proc/kallsyms
and friends.
Before:
7fff8166889d bpf_clone_redirect+0x80007f0020ed (/lib/modules/4.9.0-rc8+/build/vmlinux)
f5d80 __sendmsg_nocancel+0xffff006451f1a007 (/usr/lib64/libc-2.18.so)
After:
7fff816688b7 bpf_clone_redirect+0x80007f002107 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fffa0575728 bpf_prog_33c45a467c9e061a+0x8000600020fb (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fffa07ef1fc cls_bpf_classify+0x8000600020dc (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff81678b68 tc_classify+0x80007f002078 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8164d40b __netif_receive_skb_core+0x80007f0025fb (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8164d718 __netif_receive_skb+0x80007f002018 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8164e565 process_backlog+0x80007f002095 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8164dc71 net_rx_action+0x80007f002231 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff81767461 __softirqentry_text_start+0x80007f0020d1 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff817658ac do_softirq_own_stack+0x80007f00201c (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff810a2c20 do_softirq+0x80007f002050 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff810a2cb5 __local_bh_enable_ip+0x80007f002085 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8168d452 ip_finish_output2+0x80007f002152 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8168ea3d ip_finish_output+0x80007f00217d (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff8168f2af ip_output+0x80007f00203f (/lib/modules/4.9.0-rc8+/build/vmlinux)
[...]
7fff81005854 do_syscall_64+0x80007f002054 (/lib/modules/4.9.0-rc8+/build/vmlinux)
7fff817649eb return_from_SYSCALL_64+0x80007f002000 (/lib/modules/4.9.0-rc8+/build/vmlinux)
f5d80 __sendmsg_nocancel+0xffff01c484812007 (/usr/lib64/libc-2.18.so)
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-02-16 21:24:50 +00:00
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#include <linux/rbtree_latch.h>
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2017-08-20 06:34:03 +00:00
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#include <linux/numa.h>
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bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY
Add ability to memory-map contents of BPF array map. This is extremely useful
for working with BPF global data from userspace programs. It allows to avoid
typical bpf_map_{lookup,update}_elem operations, improving both performance
and usability.
There had to be special considerations for map freezing, to avoid having
writable memory view into a frozen map. To solve this issue, map freezing and
mmap-ing is happening under mutex now:
- if map is already frozen, no writable mapping is allowed;
- if map has writable memory mappings active (accounted in map->writecnt),
map freezing will keep failing with -EBUSY;
- once number of writable memory mappings drops to zero, map freezing can be
performed again.
Only non-per-CPU plain arrays are supported right now. Maps with spinlocks
can't be memory mapped either.
For BPF_F_MMAPABLE array, memory allocation has to be done through vmalloc()
to be mmap()'able. We also need to make sure that array data memory is
page-sized and page-aligned, so we over-allocate memory in such a way that
struct bpf_array is at the end of a single page of memory with array->value
being aligned with the start of the second page. On deallocation we need to
accomodate this memory arrangement to free vmalloc()'ed memory correctly.
One important consideration regarding how memory-mapping subsystem functions.
Memory-mapping subsystem provides few optional callbacks, among them open()
and close(). close() is called for each memory region that is unmapped, so
that users can decrease their reference counters and free up resources, if
necessary. open() is *almost* symmetrical: it's called for each memory region
that is being mapped, **except** the very first one. So bpf_map_mmap does
initial refcnt bump, while open() will do any extra ones after that. Thus
number of close() calls is equal to number of open() calls plus one more.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/bpf/20191117172806.2195367-4-andriin@fb.com
2019-11-17 17:28:04 +00:00
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#include <linux/mm_types.h>
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2017-11-03 20:56:17 +00:00
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#include <linux/wait.h>
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2019-11-14 18:57:04 +00:00
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#include <linux/refcount.h>
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#include <linux/mutex.h>
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bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 00:35:05 +00:00
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#include <linux/module.h>
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2020-03-12 19:55:59 +00:00
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#include <linux/kallsyms.h>
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2020-05-13 23:03:54 +00:00
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#include <linux/capability.h>
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2020-12-01 21:58:32 +00:00
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#include <linux/sched/mm.h>
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#include <linux/slab.h>
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2021-03-16 21:00:07 +00:00
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#include <linux/percpu-refcount.h>
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2022-06-14 23:10:42 +00:00
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#include <linux/stddef.h>
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2021-05-14 00:36:05 +00:00
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#include <linux/bpfptr.h>
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bpf: Wire up freeing of referenced kptr
A destructor kfunc can be defined as void func(type *), where type may
be void or any other pointer type as per convenience.
In this patch, we ensure that the type is sane and capture the function
pointer into off_desc of ptr_off_tab for the specific pointer offset,
with the invariant that the dtor pointer is always set when 'kptr_ref'
tag is applied to the pointer's pointee type, which is indicated by the
flag BPF_MAP_VALUE_OFF_F_REF.
Note that only BTF IDs whose destructor kfunc is registered, thus become
the allowed BTF IDs for embedding as referenced kptr. Hence it serves
the purpose of finding dtor kfunc BTF ID, as well acting as a check
against the whitelist of allowed BTF IDs for this purpose.
Finally, wire up the actual freeing of the referenced pointer if any at
all available offsets, so that no references are leaked after the BPF
map goes away and the BPF program previously moved the ownership a
referenced pointer into it.
The behavior is similar to BPF timers, where bpf_map_{update,delete}_elem
will free any existing referenced kptr. The same case is with LRU map's
bpf_lru_push_free/htab_lru_push_free functions, which are extended to
reset unreferenced and free referenced kptr.
Note that unlike BPF timers, kptr is not reset or freed when map uref
drops to zero.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-8-memxor@gmail.com
2022-04-24 21:48:55 +00:00
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#include <linux/btf.h>
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bpf: implement sleepable uprobes by chaining gps
uprobes work by raising a trap, setting a task flag from within the
interrupt handler, and processing the actual work for the uprobe on the
way back to userspace. As a result, uprobe handlers already execute in a
might_fault/_sleep context. The primary obstacle to sleepable bpf uprobe
programs is therefore on the bpf side.
Namely, the bpf_prog_array attached to the uprobe is protected by normal
rcu. In order for uprobe bpf programs to become sleepable, it has to be
protected by the tasks_trace rcu flavor instead (and kfree() called after
a corresponding grace period).
Therefore, the free path for bpf_prog_array now chains a tasks_trace and
normal grace periods one after the other.
Users who iterate under tasks_trace read section would
be safe, as would users who iterate under normal read sections (from
non-sleepable locations).
The downside is that the tasks_trace latency affects all perf_event-attached
bpf programs (and not just uprobe ones). This is deemed safe given the
possible attach rates for kprobe/uprobe/tp programs.
Separately, non-sleepable programs need access to dynamically sized
rcu-protected maps, so bpf_run_prog_array_sleepables now conditionally takes
an rcu read section, in addition to the overarching tasks_trace section.
Signed-off-by: Delyan Kratunov <delyank@fb.com>
Link: https://lore.kernel.org/r/ce844d62a2fd0443b08c5ab02e95bc7149f9aeb1.1655248076.git.delyank@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-06-14 23:10:46 +00:00
|
|
|
#include <linux/rcupdate_trace.h>
|
2014-09-26 07:16:57 +00:00
|
|
|
|
2017-12-28 02:39:05 +00:00
|
|
|
struct bpf_verifier_env;
|
2019-10-16 03:25:00 +00:00
|
|
|
struct bpf_verifier_log;
|
bpf, maps: flush own entries on perf map release
The behavior of perf event arrays are quite different from all
others as they are tightly coupled to perf event fds, f.e. shown
recently by commit e03e7ee34fdd ("perf/bpf: Convert perf_event_array
to use struct file") to make refcounting on perf event more robust.
A remaining issue that the current code still has is that since
additions to the perf event array take a reference on the struct
file via perf_event_get() and are only released via fput() (that
cleans up the perf event eventually via perf_event_release_kernel())
when the element is either manually removed from the map from user
space or automatically when the last reference on the perf event
map is dropped. However, this leads us to dangling struct file's
when the map gets pinned after the application owning the perf
event descriptor exits, and since the struct file reference will
in such case only be manually dropped or via pinned file removal,
it leads to the perf event living longer than necessary, consuming
needlessly resources for that time.
Relations between perf event fds and bpf perf event map fds can be
rather complex. F.e. maps can act as demuxers among different perf
event fds that can possibly be owned by different threads and based
on the index selection from the program, events get dispatched to
one of the per-cpu fd endpoints. One perf event fd (or, rather a
per-cpu set of them) can also live in multiple perf event maps at
the same time, listening for events. Also, another requirement is
that perf event fds can get closed from application side after they
have been attached to the perf event map, so that on exit perf event
map will take care of dropping their references eventually. Likewise,
when such maps are pinned, the intended behavior is that a user
application does bpf_obj_get(), puts its fds in there and on exit
when fd is released, they are dropped from the map again, so the map
acts rather as connector endpoint. This also makes perf event maps
inherently different from program arrays as described in more detail
in commit c9da161c6517 ("bpf: fix clearing on persistent program
array maps").
To tackle this, map entries are marked by the map struct file that
added the element to the map. And when the last reference to that map
struct file is released from user space, then the tracked entries
are purged from the map. This is okay, because new map struct files
instances resp. frontends to the anon inode are provided via
bpf_map_new_fd() that is called when we invoke bpf_obj_get_user()
for retrieving a pinned map, but also when an initial instance is
created via map_create(). The rest is resolved by the vfs layer
automatically for us by keeping reference count on the map's struct
file. Any concurrent updates on the map slot are fine as well, it
just means that perf_event_fd_array_release() needs to delete less
of its own entires.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-06-15 20:47:14 +00:00
|
|
|
struct perf_event;
|
2017-08-16 05:32:47 +00:00
|
|
|
struct bpf_prog;
|
2019-11-22 20:07:58 +00:00
|
|
|
struct bpf_prog_aux;
|
2014-09-26 07:16:57 +00:00
|
|
|
struct bpf_map;
|
bpf: create tcp_bpf_ulp allowing BPF to monitor socket TX/RX data
This implements a BPF ULP layer to allow policy enforcement and
monitoring at the socket layer. In order to support this a new
program type BPF_PROG_TYPE_SK_MSG is used to run the policy at
the sendmsg/sendpage hook. To attach the policy to sockets a
sockmap is used with a new program attach type BPF_SK_MSG_VERDICT.
Similar to previous sockmap usages when a sock is added to a
sockmap, via a map update, if the map contains a BPF_SK_MSG_VERDICT
program type attached then the BPF ULP layer is created on the
socket and the attached BPF_PROG_TYPE_SK_MSG program is run for
every msg in sendmsg case and page/offset in sendpage case.
BPF_PROG_TYPE_SK_MSG Semantics/API:
BPF_PROG_TYPE_SK_MSG supports only two return codes SK_PASS and
SK_DROP. Returning SK_DROP free's the copied data in the sendmsg
case and in the sendpage case leaves the data untouched. Both cases
return -EACESS to the user. Returning SK_PASS will allow the msg to
be sent.
In the sendmsg case data is copied into kernel space buffers before
running the BPF program. The kernel space buffers are stored in a
scatterlist object where each element is a kernel memory buffer.
Some effort is made to coalesce data from the sendmsg call here.
For example a sendmsg call with many one byte iov entries will
likely be pushed into a single entry. The BPF program is run with
data pointers (start/end) pointing to the first sg element.
In the sendpage case data is not copied. We opt not to copy the
data by default here, because the BPF infrastructure does not
know what bytes will be needed nor when they will be needed. So
copying all bytes may be wasteful. Because of this the initial
start/end data pointers are (0,0). Meaning no data can be read or
written. This avoids reading data that may be modified by the
user. A new helper is added later in this series if reading and
writing the data is needed. The helper call will do a copy by
default so that the page is exclusively owned by the BPF call.
The verdict from the BPF_PROG_TYPE_SK_MSG applies to the entire msg
in the sendmsg() case and the entire page/offset in the sendpage case.
This avoids ambiguity on how to handle mixed return codes in the
sendmsg case. Again a helper is added later in the series if
a verdict needs to apply to multiple system calls and/or only
a subpart of the currently being processed message.
The helper msg_redirect_map() can be used to select the socket to
send the data on. This is used similar to existing redirect use
cases. This allows policy to redirect msgs.
Pseudo code simple example:
The basic logic to attach a program to a socket is as follows,
// load the programs
bpf_prog_load(SOCKMAP_TCP_MSG_PROG, BPF_PROG_TYPE_SK_MSG,
&obj, &msg_prog);
// lookup the sockmap
bpf_map_msg = bpf_object__find_map_by_name(obj, "my_sock_map");
// get fd for sockmap
map_fd_msg = bpf_map__fd(bpf_map_msg);
// attach program to sockmap
bpf_prog_attach(msg_prog, map_fd_msg, BPF_SK_MSG_VERDICT, 0);
Adding sockets to the map is done in the normal way,
// Add a socket 'fd' to sockmap at location 'i'
bpf_map_update_elem(map_fd_msg, &i, fd, BPF_ANY);
After the above any socket attached to "my_sock_map", in this case
'fd', will run the BPF msg verdict program (msg_prog) on every
sendmsg and sendpage system call.
For a complete example see BPF selftests or sockmap samples.
Implementation notes:
It seemed the simplest, to me at least, to use a refcnt to ensure
psock is not lost across the sendmsg copy into the sg, the bpf program
running on the data in sg_data, and the final pass to the TCP stack.
Some performance testing may show a better method to do this and avoid
the refcnt cost, but for now use the simpler method.
Another item that will come after basic support is in place is
supporting MSG_MORE flag. At the moment we call sendpages even if
the MSG_MORE flag is set. An enhancement would be to collect the
pages into a larger scatterlist and pass down the stack. Notice that
bpf_tcp_sendmsg() could support this with some additional state saved
across sendmsg calls. I built the code to support this without having
to do refactoring work. Other features TBD include ZEROCOPY and the
TCP_RECV_QUEUE/TCP_NO_QUEUE support. This will follow initial series
shortly.
Future work could improve size limits on the scatterlist rings used
here. Currently, we use MAX_SKB_FRAGS simply because this was being
used already in the TLS case. Future work could extend the kernel sk
APIs to tune this depending on workload. This is a trade-off
between memory usage and throughput performance.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-03-18 19:57:10 +00:00
|
|
|
struct sock;
|
2018-04-18 22:56:03 +00:00
|
|
|
struct seq_file;
|
2018-12-10 23:43:00 +00:00
|
|
|
struct btf;
|
2018-08-11 23:59:17 +00:00
|
|
|
struct btf_type;
|
2019-10-16 03:25:03 +00:00
|
|
|
struct exception_table_entry;
|
2020-05-09 17:58:59 +00:00
|
|
|
struct seq_operations;
|
2020-07-23 18:41:10 +00:00
|
|
|
struct bpf_iter_aux_info;
|
2020-08-25 18:29:15 +00:00
|
|
|
struct bpf_local_storage;
|
|
|
|
struct bpf_local_storage_map;
|
2020-11-10 01:19:31 +00:00
|
|
|
struct kobject;
|
2020-12-01 21:58:32 +00:00
|
|
|
struct mem_cgroup;
|
2021-03-26 10:59:00 +00:00
|
|
|
struct module;
|
bpf: Add bpf_for_each_map_elem() helper
The bpf_for_each_map_elem() helper is introduced which
iterates all map elements with a callback function. The
helper signature looks like
long bpf_for_each_map_elem(map, callback_fn, callback_ctx, flags)
and for each map element, the callback_fn will be called. For example,
like hashmap, the callback signature may look like
long callback_fn(map, key, val, callback_ctx)
There are two known use cases for this. One is from upstream ([1]) where
a for_each_map_elem helper may help implement a timeout mechanism
in a more generic way. Another is from our internal discussion
for a firewall use case where a map contains all the rules. The packet
data can be compared to all these rules to decide allow or deny
the packet.
For array maps, users can already use a bounded loop to traverse
elements. Using this helper can avoid using bounded loop. For other
type of maps (e.g., hash maps) where bounded loop is hard or
impossible to use, this helper provides a convenient way to
operate on all elements.
For callback_fn, besides map and map element, a callback_ctx,
allocated on caller stack, is also passed to the callback
function. This callback_ctx argument can provide additional
input and allow to write to caller stack for output.
If the callback_fn returns 0, the helper will iterate through next
element if available. If the callback_fn returns 1, the helper
will stop iterating and returns to the bpf program. Other return
values are not used for now.
Currently, this helper is only available with jit. It is possible
to make it work with interpreter with so effort but I leave it
as the future work.
[1]: https://lore.kernel.org/bpf/20210122205415.113822-1-xiyou.wangcong@gmail.com/
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210226204925.3884923-1-yhs@fb.com
2021-02-26 20:49:25 +00:00
|
|
|
struct bpf_func_state;
|
2022-07-20 00:21:26 +00:00
|
|
|
struct ftrace_ops;
|
2014-09-26 07:16:57 +00:00
|
|
|
|
2019-08-20 09:31:50 +00:00
|
|
|
extern struct idr btf_idr;
|
|
|
|
extern spinlock_t btf_idr_lock;
|
2020-11-10 01:19:31 +00:00
|
|
|
extern struct kobject *btf_kobj;
|
2019-08-20 09:31:50 +00:00
|
|
|
|
2021-09-28 23:09:46 +00:00
|
|
|
typedef u64 (*bpf_callback_t)(u64, u64, u64, u64, u64);
|
2020-07-23 18:41:10 +00:00
|
|
|
typedef int (*bpf_iter_init_seq_priv_t)(void *private_data,
|
|
|
|
struct bpf_iter_aux_info *aux);
|
2020-07-23 18:41:09 +00:00
|
|
|
typedef void (*bpf_iter_fini_seq_priv_t)(void *private_data);
|
2022-06-28 17:43:04 +00:00
|
|
|
typedef unsigned int (*bpf_func_t)(const void *,
|
|
|
|
const struct bpf_insn *);
|
2020-07-23 18:41:09 +00:00
|
|
|
struct bpf_iter_seq_info {
|
|
|
|
const struct seq_operations *seq_ops;
|
|
|
|
bpf_iter_init_seq_priv_t init_seq_private;
|
|
|
|
bpf_iter_fini_seq_priv_t fini_seq_private;
|
|
|
|
u32 seq_priv_size;
|
|
|
|
};
|
|
|
|
|
2021-03-18 20:22:22 +00:00
|
|
|
/* map is generic key/value storage optionally accessible by eBPF programs */
|
2014-09-26 07:16:57 +00:00
|
|
|
struct bpf_map_ops {
|
|
|
|
/* funcs callable from userspace (via syscall) */
|
2018-01-12 04:29:03 +00:00
|
|
|
int (*map_alloc_check)(union bpf_attr *attr);
|
2014-09-26 07:16:57 +00:00
|
|
|
struct bpf_map *(*map_alloc)(union bpf_attr *attr);
|
2016-06-15 20:47:12 +00:00
|
|
|
void (*map_release)(struct bpf_map *map, struct file *map_file);
|
|
|
|
void (*map_free)(struct bpf_map *map);
|
bpf: add lookup/update/delete/iterate methods to BPF maps
'maps' is a generic storage of different types for sharing data between kernel
and userspace.
The maps are accessed from user space via BPF syscall, which has commands:
- create a map with given type and attributes
fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)
returns fd or negative error
- lookup key in a given map referenced by fd
err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->value
returns zero and stores found elem into value or negative error
- create or update key/value pair in a given map
err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->value
returns zero or negative error
- find and delete element by key in a given map
err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key
- iterate map elements (based on input key return next_key)
err = bpf(BPF_MAP_GET_NEXT_KEY, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->next_key
- close(fd) deletes the map
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:16:59 +00:00
|
|
|
int (*map_get_next_key)(struct bpf_map *map, void *key, void *next_key);
|
2018-04-23 22:39:23 +00:00
|
|
|
void (*map_release_uref)(struct bpf_map *map);
|
2019-05-13 23:18:55 +00:00
|
|
|
void *(*map_lookup_elem_sys_only)(struct bpf_map *map, void *key);
|
2020-01-15 18:43:01 +00:00
|
|
|
int (*map_lookup_batch)(struct bpf_map *map, const union bpf_attr *attr,
|
|
|
|
union bpf_attr __user *uattr);
|
2021-05-11 21:00:04 +00:00
|
|
|
int (*map_lookup_and_delete_elem)(struct bpf_map *map, void *key,
|
|
|
|
void *value, u64 flags);
|
2020-01-15 18:43:04 +00:00
|
|
|
int (*map_lookup_and_delete_batch)(struct bpf_map *map,
|
|
|
|
const union bpf_attr *attr,
|
|
|
|
union bpf_attr __user *uattr);
|
2020-01-15 18:43:02 +00:00
|
|
|
int (*map_update_batch)(struct bpf_map *map, const union bpf_attr *attr,
|
|
|
|
union bpf_attr __user *uattr);
|
|
|
|
int (*map_delete_batch)(struct bpf_map *map, const union bpf_attr *attr,
|
|
|
|
union bpf_attr __user *uattr);
|
bpf: add lookup/update/delete/iterate methods to BPF maps
'maps' is a generic storage of different types for sharing data between kernel
and userspace.
The maps are accessed from user space via BPF syscall, which has commands:
- create a map with given type and attributes
fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)
returns fd or negative error
- lookup key in a given map referenced by fd
err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->value
returns zero and stores found elem into value or negative error
- create or update key/value pair in a given map
err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->value
returns zero or negative error
- find and delete element by key in a given map
err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key
- iterate map elements (based on input key return next_key)
err = bpf(BPF_MAP_GET_NEXT_KEY, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->next_key
- close(fd) deletes the map
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:16:59 +00:00
|
|
|
|
|
|
|
/* funcs callable from userspace and from eBPF programs */
|
|
|
|
void *(*map_lookup_elem)(struct bpf_map *map, void *key);
|
bpf: add 'flags' attribute to BPF_MAP_UPDATE_ELEM command
the current meaning of BPF_MAP_UPDATE_ELEM syscall command is:
either update existing map element or create a new one.
Initially the plan was to add a new command to handle the case of
'create new element if it didn't exist', but 'flags' style looks
cleaner and overall diff is much smaller (more code reused), so add 'flags'
attribute to BPF_MAP_UPDATE_ELEM command with the following meaning:
#define BPF_ANY 0 /* create new element or update existing */
#define BPF_NOEXIST 1 /* create new element if it didn't exist */
#define BPF_EXIST 2 /* update existing element */
bpf_update_elem(fd, key, value, BPF_NOEXIST) call can fail with EEXIST
if element already exists.
bpf_update_elem(fd, key, value, BPF_EXIST) can fail with ENOENT
if element doesn't exist.
Userspace will call it as:
int bpf_update_elem(int fd, void *key, void *value, __u64 flags)
{
union bpf_attr attr = {
.map_fd = fd,
.key = ptr_to_u64(key),
.value = ptr_to_u64(value),
.flags = flags;
};
return bpf(BPF_MAP_UPDATE_ELEM, &attr, sizeof(attr));
}
First two bits of 'flags' are used to encode style of bpf_update_elem() command.
Bits 2-63 are reserved for future use.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-11-14 01:36:44 +00:00
|
|
|
int (*map_update_elem)(struct bpf_map *map, void *key, void *value, u64 flags);
|
bpf: add lookup/update/delete/iterate methods to BPF maps
'maps' is a generic storage of different types for sharing data between kernel
and userspace.
The maps are accessed from user space via BPF syscall, which has commands:
- create a map with given type and attributes
fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)
returns fd or negative error
- lookup key in a given map referenced by fd
err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->value
returns zero and stores found elem into value or negative error
- create or update key/value pair in a given map
err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->value
returns zero or negative error
- find and delete element by key in a given map
err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key
- iterate map elements (based on input key return next_key)
err = bpf(BPF_MAP_GET_NEXT_KEY, union bpf_attr *attr, u32 size)
using attr->map_fd, attr->key, attr->next_key
- close(fd) deletes the map
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:16:59 +00:00
|
|
|
int (*map_delete_elem)(struct bpf_map *map, void *key);
|
2018-10-18 13:16:25 +00:00
|
|
|
int (*map_push_elem)(struct bpf_map *map, void *value, u64 flags);
|
|
|
|
int (*map_pop_elem)(struct bpf_map *map, void *value);
|
|
|
|
int (*map_peek_elem)(struct bpf_map *map, void *value);
|
2022-05-11 09:38:53 +00:00
|
|
|
void *(*map_lookup_percpu_elem)(struct bpf_map *map, void *key, u32 cpu);
|
2015-08-06 07:02:33 +00:00
|
|
|
|
|
|
|
/* funcs called by prog_array and perf_event_array map */
|
2016-06-15 20:47:13 +00:00
|
|
|
void *(*map_fd_get_ptr)(struct bpf_map *map, struct file *map_file,
|
|
|
|
int fd);
|
|
|
|
void (*map_fd_put_ptr)(void *ptr);
|
2020-10-10 23:40:03 +00:00
|
|
|
int (*map_gen_lookup)(struct bpf_map *map, struct bpf_insn *insn_buf);
|
2017-06-28 06:08:34 +00:00
|
|
|
u32 (*map_fd_sys_lookup_elem)(void *ptr);
|
2018-04-18 22:56:03 +00:00
|
|
|
void (*map_seq_show_elem)(struct bpf_map *map, void *key,
|
|
|
|
struct seq_file *m);
|
2018-08-11 23:59:17 +00:00
|
|
|
int (*map_check_btf)(const struct bpf_map *map,
|
2018-12-10 23:43:00 +00:00
|
|
|
const struct btf *btf,
|
2018-08-11 23:59:17 +00:00
|
|
|
const struct btf_type *key_type,
|
|
|
|
const struct btf_type *value_type);
|
bpf: implement lookup-free direct value access for maps
This generic extension to BPF maps allows for directly loading
an address residing inside a BPF map value as a single BPF
ldimm64 instruction!
The idea is similar to what BPF_PSEUDO_MAP_FD does today, which
is a special src_reg flag for ldimm64 instruction that indicates
that inside the first part of the double insns's imm field is a
file descriptor which the verifier then replaces as a full 64bit
address of the map into both imm parts. For the newly added
BPF_PSEUDO_MAP_VALUE src_reg flag, the idea is the following:
the first part of the double insns's imm field is again a file
descriptor corresponding to the map, and the second part of the
imm field is an offset into the value. The verifier will then
replace both imm parts with an address that points into the BPF
map value at the given value offset for maps that support this
operation. Currently supported is array map with single entry.
It is possible to support more than just single map element by
reusing both 16bit off fields of the insns as a map index, so
full array map lookup could be expressed that way. It hasn't
been implemented here due to lack of concrete use case, but
could easily be done so in future in a compatible way, since
both off fields right now have to be 0 and would correctly
denote a map index 0.
The BPF_PSEUDO_MAP_VALUE is a distinct flag as otherwise with
BPF_PSEUDO_MAP_FD we could not differ offset 0 between load of
map pointer versus load of map's value at offset 0, and changing
BPF_PSEUDO_MAP_FD's encoding into off by one to differ between
regular map pointer and map value pointer would add unnecessary
complexity and increases barrier for debugability thus less
suitable. Using the second part of the imm field as an offset
into the value does /not/ come with limitations since maximum
possible value size is in u32 universe anyway.
This optimization allows for efficiently retrieving an address
to a map value memory area without having to issue a helper call
which needs to prepare registers according to calling convention,
etc, without needing the extra NULL test, and without having to
add the offset in an additional instruction to the value base
pointer. The verifier then treats the destination register as
PTR_TO_MAP_VALUE with constant reg->off from the user passed
offset from the second imm field, and guarantees that this is
within bounds of the map value. Any subsequent operations are
normally treated as typical map value handling without anything
extra needed from verification side.
The two map operations for direct value access have been added to
array map for now. In future other types could be supported as
well depending on the use case. The main use case for this commit
is to allow for BPF loader support for global variables that
reside in .data/.rodata/.bss sections such that we can directly
load the address of them with minimal additional infrastructure
required. Loader support has been added in subsequent commits for
libbpf library.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-04-09 21:20:03 +00:00
|
|
|
|
2019-11-22 20:07:58 +00:00
|
|
|
/* Prog poke tracking helpers. */
|
|
|
|
int (*map_poke_track)(struct bpf_map *map, struct bpf_prog_aux *aux);
|
|
|
|
void (*map_poke_untrack)(struct bpf_map *map, struct bpf_prog_aux *aux);
|
|
|
|
void (*map_poke_run)(struct bpf_map *map, u32 key, struct bpf_prog *old,
|
|
|
|
struct bpf_prog *new);
|
|
|
|
|
bpf: implement lookup-free direct value access for maps
This generic extension to BPF maps allows for directly loading
an address residing inside a BPF map value as a single BPF
ldimm64 instruction!
The idea is similar to what BPF_PSEUDO_MAP_FD does today, which
is a special src_reg flag for ldimm64 instruction that indicates
that inside the first part of the double insns's imm field is a
file descriptor which the verifier then replaces as a full 64bit
address of the map into both imm parts. For the newly added
BPF_PSEUDO_MAP_VALUE src_reg flag, the idea is the following:
the first part of the double insns's imm field is again a file
descriptor corresponding to the map, and the second part of the
imm field is an offset into the value. The verifier will then
replace both imm parts with an address that points into the BPF
map value at the given value offset for maps that support this
operation. Currently supported is array map with single entry.
It is possible to support more than just single map element by
reusing both 16bit off fields of the insns as a map index, so
full array map lookup could be expressed that way. It hasn't
been implemented here due to lack of concrete use case, but
could easily be done so in future in a compatible way, since
both off fields right now have to be 0 and would correctly
denote a map index 0.
The BPF_PSEUDO_MAP_VALUE is a distinct flag as otherwise with
BPF_PSEUDO_MAP_FD we could not differ offset 0 between load of
map pointer versus load of map's value at offset 0, and changing
BPF_PSEUDO_MAP_FD's encoding into off by one to differ between
regular map pointer and map value pointer would add unnecessary
complexity and increases barrier for debugability thus less
suitable. Using the second part of the imm field as an offset
into the value does /not/ come with limitations since maximum
possible value size is in u32 universe anyway.
This optimization allows for efficiently retrieving an address
to a map value memory area without having to issue a helper call
which needs to prepare registers according to calling convention,
etc, without needing the extra NULL test, and without having to
add the offset in an additional instruction to the value base
pointer. The verifier then treats the destination register as
PTR_TO_MAP_VALUE with constant reg->off from the user passed
offset from the second imm field, and guarantees that this is
within bounds of the map value. Any subsequent operations are
normally treated as typical map value handling without anything
extra needed from verification side.
The two map operations for direct value access have been added to
array map for now. In future other types could be supported as
well depending on the use case. The main use case for this commit
is to allow for BPF loader support for global variables that
reside in .data/.rodata/.bss sections such that we can directly
load the address of them with minimal additional infrastructure
required. Loader support has been added in subsequent commits for
libbpf library.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-04-09 21:20:03 +00:00
|
|
|
/* Direct value access helpers. */
|
|
|
|
int (*map_direct_value_addr)(const struct bpf_map *map,
|
|
|
|
u64 *imm, u32 off);
|
|
|
|
int (*map_direct_value_meta)(const struct bpf_map *map,
|
|
|
|
u64 imm, u32 *off);
|
bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY
Add ability to memory-map contents of BPF array map. This is extremely useful
for working with BPF global data from userspace programs. It allows to avoid
typical bpf_map_{lookup,update}_elem operations, improving both performance
and usability.
There had to be special considerations for map freezing, to avoid having
writable memory view into a frozen map. To solve this issue, map freezing and
mmap-ing is happening under mutex now:
- if map is already frozen, no writable mapping is allowed;
- if map has writable memory mappings active (accounted in map->writecnt),
map freezing will keep failing with -EBUSY;
- once number of writable memory mappings drops to zero, map freezing can be
performed again.
Only non-per-CPU plain arrays are supported right now. Maps with spinlocks
can't be memory mapped either.
For BPF_F_MMAPABLE array, memory allocation has to be done through vmalloc()
to be mmap()'able. We also need to make sure that array data memory is
page-sized and page-aligned, so we over-allocate memory in such a way that
struct bpf_array is at the end of a single page of memory with array->value
being aligned with the start of the second page. On deallocation we need to
accomodate this memory arrangement to free vmalloc()'ed memory correctly.
One important consideration regarding how memory-mapping subsystem functions.
Memory-mapping subsystem provides few optional callbacks, among them open()
and close(). close() is called for each memory region that is unmapped, so
that users can decrease their reference counters and free up resources, if
necessary. open() is *almost* symmetrical: it's called for each memory region
that is being mapped, **except** the very first one. So bpf_map_mmap does
initial refcnt bump, while open() will do any extra ones after that. Thus
number of close() calls is equal to number of open() calls plus one more.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/bpf/20191117172806.2195367-4-andriin@fb.com
2019-11-17 17:28:04 +00:00
|
|
|
int (*map_mmap)(struct bpf_map *map, struct vm_area_struct *vma);
|
bpf: Implement BPF ring buffer and verifier support for it
This commit adds a new MPSC ring buffer implementation into BPF ecosystem,
which allows multiple CPUs to submit data to a single shared ring buffer. On
the consumption side, only single consumer is assumed.
Motivation
----------
There are two distinctive motivators for this work, which are not satisfied by
existing perf buffer, which prompted creation of a new ring buffer
implementation.
- more efficient memory utilization by sharing ring buffer across CPUs;
- preserving ordering of events that happen sequentially in time, even
across multiple CPUs (e.g., fork/exec/exit events for a task).
These two problems are independent, but perf buffer fails to satisfy both.
Both are a result of a choice to have per-CPU perf ring buffer. Both can be
also solved by having an MPSC implementation of ring buffer. The ordering
problem could technically be solved for perf buffer with some in-kernel
counting, but given the first one requires an MPSC buffer, the same solution
would solve the second problem automatically.
Semantics and APIs
------------------
Single ring buffer is presented to BPF programs as an instance of BPF map of
type BPF_MAP_TYPE_RINGBUF. Two other alternatives considered, but ultimately
rejected.
One way would be to, similar to BPF_MAP_TYPE_PERF_EVENT_ARRAY, make
BPF_MAP_TYPE_RINGBUF could represent an array of ring buffers, but not enforce
"same CPU only" rule. This would be more familiar interface compatible with
existing perf buffer use in BPF, but would fail if application needed more
advanced logic to lookup ring buffer by arbitrary key. HASH_OF_MAPS addresses
this with current approach. Additionally, given the performance of BPF
ringbuf, many use cases would just opt into a simple single ring buffer shared
among all CPUs, for which current approach would be an overkill.
Another approach could introduce a new concept, alongside BPF map, to
represent generic "container" object, which doesn't necessarily have key/value
interface with lookup/update/delete operations. This approach would add a lot
of extra infrastructure that has to be built for observability and verifier
support. It would also add another concept that BPF developers would have to
familiarize themselves with, new syntax in libbpf, etc. But then would really
provide no additional benefits over the approach of using a map.
BPF_MAP_TYPE_RINGBUF doesn't support lookup/update/delete operations, but so
doesn't few other map types (e.g., queue and stack; array doesn't support
delete, etc).
The approach chosen has an advantage of re-using existing BPF map
infrastructure (introspection APIs in kernel, libbpf support, etc), being
familiar concept (no need to teach users a new type of object in BPF program),
and utilizing existing tooling (bpftool). For common scenario of using
a single ring buffer for all CPUs, it's as simple and straightforward, as
would be with a dedicated "container" object. On the other hand, by being
a map, it can be combined with ARRAY_OF_MAPS and HASH_OF_MAPS map-in-maps to
implement a wide variety of topologies, from one ring buffer for each CPU
(e.g., as a replacement for perf buffer use cases), to a complicated
application hashing/sharding of ring buffers (e.g., having a small pool of
ring buffers with hashed task's tgid being a look up key to preserve order,
but reduce contention).
Key and value sizes are enforced to be zero. max_entries is used to specify
the size of ring buffer and has to be a power of 2 value.
There are a bunch of similarities between perf buffer
(BPF_MAP_TYPE_PERF_EVENT_ARRAY) and new BPF ring buffer semantics:
- variable-length records;
- if there is no more space left in ring buffer, reservation fails, no
blocking;
- memory-mappable data area for user-space applications for ease of
consumption and high performance;
- epoll notifications for new incoming data;
- but still the ability to do busy polling for new data to achieve the
lowest latency, if necessary.
BPF ringbuf provides two sets of APIs to BPF programs:
- bpf_ringbuf_output() allows to *copy* data from one place to a ring
buffer, similarly to bpf_perf_event_output();
- bpf_ringbuf_reserve()/bpf_ringbuf_commit()/bpf_ringbuf_discard() APIs
split the whole process into two steps. First, a fixed amount of space is
reserved. If successful, a pointer to a data inside ring buffer data area
is returned, which BPF programs can use similarly to a data inside
array/hash maps. Once ready, this piece of memory is either committed or
discarded. Discard is similar to commit, but makes consumer ignore the
record.
bpf_ringbuf_output() has disadvantage of incurring extra memory copy, because
record has to be prepared in some other place first. But it allows to submit
records of the length that's not known to verifier beforehand. It also closely
matches bpf_perf_event_output(), so will simplify migration significantly.
bpf_ringbuf_reserve() avoids the extra copy of memory by providing a memory
pointer directly to ring buffer memory. In a lot of cases records are larger
than BPF stack space allows, so many programs have use extra per-CPU array as
a temporary heap for preparing sample. bpf_ringbuf_reserve() avoid this needs
completely. But in exchange, it only allows a known constant size of memory to
be reserved, such that verifier can verify that BPF program can't access
memory outside its reserved record space. bpf_ringbuf_output(), while slightly
slower due to extra memory copy, covers some use cases that are not suitable
for bpf_ringbuf_reserve().
The difference between commit and discard is very small. Discard just marks
a record as discarded, and such records are supposed to be ignored by consumer
code. Discard is useful for some advanced use-cases, such as ensuring
all-or-nothing multi-record submission, or emulating temporary malloc()/free()
within single BPF program invocation.
Each reserved record is tracked by verifier through existing
reference-tracking logic, similar to socket ref-tracking. It is thus
impossible to reserve a record, but forget to submit (or discard) it.
bpf_ringbuf_query() helper allows to query various properties of ring buffer.
Currently 4 are supported:
- BPF_RB_AVAIL_DATA returns amount of unconsumed data in ring buffer;
- BPF_RB_RING_SIZE returns the size of ring buffer;
- BPF_RB_CONS_POS/BPF_RB_PROD_POS returns current logical possition of
consumer/producer, respectively.
Returned values are momentarily snapshots of ring buffer state and could be
off by the time helper returns, so this should be used only for
debugging/reporting reasons or for implementing various heuristics, that take
into account highly-changeable nature of some of those characteristics.
One such heuristic might involve more fine-grained control over poll/epoll
notifications about new data availability in ring buffer. Together with
BPF_RB_NO_WAKEUP/BPF_RB_FORCE_WAKEUP flags for output/commit/discard helpers,
it allows BPF program a high degree of control and, e.g., more efficient
batched notifications. Default self-balancing strategy, though, should be
adequate for most applications and will work reliable and efficiently already.
Design and implementation
-------------------------
This reserve/commit schema allows a natural way for multiple producers, either
on different CPUs or even on the same CPU/in the same BPF program, to reserve
independent records and work with them without blocking other producers. This
means that if BPF program was interruped by another BPF program sharing the
same ring buffer, they will both get a record reserved (provided there is
enough space left) and can work with it and submit it independently. This
applies to NMI context as well, except that due to using a spinlock during
reservation, in NMI context, bpf_ringbuf_reserve() might fail to get a lock,
in which case reservation will fail even if ring buffer is not full.
The ring buffer itself internally is implemented as a power-of-2 sized
circular buffer, with two logical and ever-increasing counters (which might
wrap around on 32-bit architectures, that's not a problem):
- consumer counter shows up to which logical position consumer consumed the
data;
- producer counter denotes amount of data reserved by all producers.
Each time a record is reserved, producer that "owns" the record will
successfully advance producer counter. At that point, data is still not yet
ready to be consumed, though. Each record has 8 byte header, which contains
the length of reserved record, as well as two extra bits: busy bit to denote
that record is still being worked on, and discard bit, which might be set at
commit time if record is discarded. In the latter case, consumer is supposed
to skip the record and move on to the next one. Record header also encodes
record's relative offset from the beginning of ring buffer data area (in
pages). This allows bpf_ringbuf_commit()/bpf_ringbuf_discard() to accept only
the pointer to the record itself, without requiring also the pointer to ring
buffer itself. Ring buffer memory location will be restored from record
metadata header. This significantly simplifies verifier, as well as improving
API usability.
Producer counter increments are serialized under spinlock, so there is
a strict ordering between reservations. Commits, on the other hand, are
completely lockless and independent. All records become available to consumer
in the order of reservations, but only after all previous records where
already committed. It is thus possible for slow producers to temporarily hold
off submitted records, that were reserved later.
Reservation/commit/consumer protocol is verified by litmus tests in
Documentation/litmus-test/bpf-rb.
One interesting implementation bit, that significantly simplifies (and thus
speeds up as well) implementation of both producers and consumers is how data
area is mapped twice contiguously back-to-back in the virtual memory. This
allows to not take any special measures for samples that have to wrap around
at the end of the circular buffer data area, because the next page after the
last data page would be first data page again, and thus the sample will still
appear completely contiguous in virtual memory. See comment and a simple ASCII
diagram showing this visually in bpf_ringbuf_area_alloc().
Another feature that distinguishes BPF ringbuf from perf ring buffer is
a self-pacing notifications of new data being availability.
bpf_ringbuf_commit() implementation will send a notification of new record
being available after commit only if consumer has already caught up right up
to the record being committed. If not, consumer still has to catch up and thus
will see new data anyways without needing an extra poll notification.
Benchmarks (see tools/testing/selftests/bpf/benchs/bench_ringbuf.c) show that
this allows to achieve a very high throughput without having to resort to
tricks like "notify only every Nth sample", which are necessary with perf
buffer. For extreme cases, when BPF program wants more manual control of
notifications, commit/discard/output helpers accept BPF_RB_NO_WAKEUP and
BPF_RB_FORCE_WAKEUP flags, which give full control over notifications of data
availability, but require extra caution and diligence in using this API.
Comparison to alternatives
--------------------------
Before considering implementing BPF ring buffer from scratch existing
alternatives in kernel were evaluated, but didn't seem to meet the needs. They
largely fell into few categores:
- per-CPU buffers (perf, ftrace, etc), which don't satisfy two motivations
outlined above (ordering and memory consumption);
- linked list-based implementations; while some were multi-producer designs,
consuming these from user-space would be very complicated and most
probably not performant; memory-mapping contiguous piece of memory is
simpler and more performant for user-space consumers;
- io_uring is SPSC, but also requires fixed-sized elements. Naively turning
SPSC queue into MPSC w/ lock would have subpar performance compared to
locked reserve + lockless commit, as with BPF ring buffer. Fixed sized
elements would be too limiting for BPF programs, given existing BPF
programs heavily rely on variable-sized perf buffer already;
- specialized implementations (like a new printk ring buffer, [0]) with lots
of printk-specific limitations and implications, that didn't seem to fit
well for intended use with BPF programs.
[0] https://lwn.net/Articles/779550/
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200529075424.3139988-2-andriin@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2020-05-29 07:54:20 +00:00
|
|
|
__poll_t (*map_poll)(struct bpf_map *map, struct file *filp,
|
|
|
|
struct poll_table_struct *pts);
|
bpf: Support access to bpf map fields
There are multiple use-cases when it's convenient to have access to bpf
map fields, both `struct bpf_map` and map type specific struct-s such as
`struct bpf_array`, `struct bpf_htab`, etc.
For example while working with sock arrays it can be necessary to
calculate the key based on map->max_entries (some_hash % max_entries).
Currently this is solved by communicating max_entries via "out-of-band"
channel, e.g. via additional map with known key to get info about target
map. That works, but is not very convenient and error-prone while
working with many maps.
In other cases necessary data is dynamic (i.e. unknown at loading time)
and it's impossible to get it at all. For example while working with a
hash table it can be convenient to know how much capacity is already
used (bpf_htab.count.counter for BPF_F_NO_PREALLOC case).
At the same time kernel knows this info and can provide it to bpf
program.
Fill this gap by adding support to access bpf map fields from bpf
program for both `struct bpf_map` and map type specific fields.
Support is implemented via btf_struct_access() so that a user can define
their own `struct bpf_map` or map type specific struct in their program
with only necessary fields and preserve_access_index attribute, cast a
map to this struct and use a field.
For example:
struct bpf_map {
__u32 max_entries;
} __attribute__((preserve_access_index));
struct bpf_array {
struct bpf_map map;
__u32 elem_size;
} __attribute__((preserve_access_index));
struct {
__uint(type, BPF_MAP_TYPE_ARRAY);
__uint(max_entries, 4);
__type(key, __u32);
__type(value, __u32);
} m_array SEC(".maps");
SEC("cgroup_skb/egress")
int cg_skb(void *ctx)
{
struct bpf_array *array = (struct bpf_array *)&m_array;
struct bpf_map *map = (struct bpf_map *)&m_array;
/* .. use map->max_entries or array->map.max_entries .. */
}
Similarly to other btf_struct_access() use-cases (e.g. struct tcp_sock
in net/ipv4/bpf_tcp_ca.c) the patch allows access to any fields of
corresponding struct. Only reading from map fields is supported.
For btf_struct_access() to work there should be a way to know btf id of
a struct that corresponds to a map type. To get btf id there should be a
way to get a stringified name of map-specific struct, such as
"bpf_array", "bpf_htab", etc for a map type. Two new fields are added to
`struct bpf_map_ops` to handle it:
* .map_btf_name keeps a btf name of a struct returned by map_alloc();
* .map_btf_id is used to cache btf id of that struct.
To make btf ids calculation cheaper they're calculated once while
preparing btf_vmlinux and cached same way as it's done for btf_id field
of `struct bpf_func_proto`
While calculating btf ids, struct names are NOT checked for collision.
Collisions will be checked as a part of the work to prepare btf ids used
in verifier in compile time that should land soon. The only known
collision for `struct bpf_htab` (kernel/bpf/hashtab.c vs
net/core/sock_map.c) was fixed earlier.
Both new fields .map_btf_name and .map_btf_id must be set for a map type
for the feature to work. If neither is set for a map type, verifier will
return ENOTSUPP on a try to access map_ptr of corresponding type. If
just one of them set, it's verifier misconfiguration.
Only `struct bpf_array` for BPF_MAP_TYPE_ARRAY and `struct bpf_htab` for
BPF_MAP_TYPE_HASH are supported by this patch. Other map types will be
supported separately.
The feature is available only for CONFIG_DEBUG_INFO_BTF=y and gated by
perfmon_capable() so that unpriv programs won't have access to bpf map
fields.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/6479686a0cd1e9067993df57b4c3eef0e276fec9.1592600985.git.rdna@fb.com
2020-06-19 21:11:43 +00:00
|
|
|
|
2020-08-25 18:29:15 +00:00
|
|
|
/* Functions called by bpf_local_storage maps */
|
|
|
|
int (*map_local_storage_charge)(struct bpf_local_storage_map *smap,
|
|
|
|
void *owner, u32 size);
|
|
|
|
void (*map_local_storage_uncharge)(struct bpf_local_storage_map *smap,
|
|
|
|
void *owner, u32 size);
|
|
|
|
struct bpf_local_storage __rcu ** (*map_owner_storage_ptr)(void *owner);
|
2020-08-28 01:18:06 +00:00
|
|
|
|
2021-03-08 11:29:06 +00:00
|
|
|
/* Misc helpers.*/
|
|
|
|
int (*map_redirect)(struct bpf_map *map, u32 ifindex, u64 flags);
|
|
|
|
|
2020-08-28 01:18:06 +00:00
|
|
|
/* map_meta_equal must be implemented for maps that can be
|
|
|
|
* used as an inner map. It is a runtime check to ensure
|
|
|
|
* an inner map can be inserted to an outer map.
|
|
|
|
*
|
|
|
|
* Some properties of the inner map has been used during the
|
|
|
|
* verification time. When inserting an inner map at the runtime,
|
|
|
|
* map_meta_equal has to ensure the inserting map has the same
|
|
|
|
* properties that the verifier has used earlier.
|
|
|
|
*/
|
|
|
|
bool (*map_meta_equal)(const struct bpf_map *meta0,
|
|
|
|
const struct bpf_map *meta1);
|
|
|
|
|
bpf: Add bpf_for_each_map_elem() helper
The bpf_for_each_map_elem() helper is introduced which
iterates all map elements with a callback function. The
helper signature looks like
long bpf_for_each_map_elem(map, callback_fn, callback_ctx, flags)
and for each map element, the callback_fn will be called. For example,
like hashmap, the callback signature may look like
long callback_fn(map, key, val, callback_ctx)
There are two known use cases for this. One is from upstream ([1]) where
a for_each_map_elem helper may help implement a timeout mechanism
in a more generic way. Another is from our internal discussion
for a firewall use case where a map contains all the rules. The packet
data can be compared to all these rules to decide allow or deny
the packet.
For array maps, users can already use a bounded loop to traverse
elements. Using this helper can avoid using bounded loop. For other
type of maps (e.g., hash maps) where bounded loop is hard or
impossible to use, this helper provides a convenient way to
operate on all elements.
For callback_fn, besides map and map element, a callback_ctx,
allocated on caller stack, is also passed to the callback
function. This callback_ctx argument can provide additional
input and allow to write to caller stack for output.
If the callback_fn returns 0, the helper will iterate through next
element if available. If the callback_fn returns 1, the helper
will stop iterating and returns to the bpf program. Other return
values are not used for now.
Currently, this helper is only available with jit. It is possible
to make it work with interpreter with so effort but I leave it
as the future work.
[1]: https://lore.kernel.org/bpf/20210122205415.113822-1-xiyou.wangcong@gmail.com/
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210226204925.3884923-1-yhs@fb.com
2021-02-26 20:49:25 +00:00
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int (*map_set_for_each_callback_args)(struct bpf_verifier_env *env,
|
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struct bpf_func_state *caller,
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struct bpf_func_state *callee);
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2021-09-28 23:09:46 +00:00
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int (*map_for_each_callback)(struct bpf_map *map,
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bpf_callback_t callback_fn,
|
bpf: Add bpf_for_each_map_elem() helper
The bpf_for_each_map_elem() helper is introduced which
iterates all map elements with a callback function. The
helper signature looks like
long bpf_for_each_map_elem(map, callback_fn, callback_ctx, flags)
and for each map element, the callback_fn will be called. For example,
like hashmap, the callback signature may look like
long callback_fn(map, key, val, callback_ctx)
There are two known use cases for this. One is from upstream ([1]) where
a for_each_map_elem helper may help implement a timeout mechanism
in a more generic way. Another is from our internal discussion
for a firewall use case where a map contains all the rules. The packet
data can be compared to all these rules to decide allow or deny
the packet.
For array maps, users can already use a bounded loop to traverse
elements. Using this helper can avoid using bounded loop. For other
type of maps (e.g., hash maps) where bounded loop is hard or
impossible to use, this helper provides a convenient way to
operate on all elements.
For callback_fn, besides map and map element, a callback_ctx,
allocated on caller stack, is also passed to the callback
function. This callback_ctx argument can provide additional
input and allow to write to caller stack for output.
If the callback_fn returns 0, the helper will iterate through next
element if available. If the callback_fn returns 1, the helper
will stop iterating and returns to the bpf program. Other return
values are not used for now.
Currently, this helper is only available with jit. It is possible
to make it work with interpreter with so effort but I leave it
as the future work.
[1]: https://lore.kernel.org/bpf/20210122205415.113822-1-xiyou.wangcong@gmail.com/
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210226204925.3884923-1-yhs@fb.com
2021-02-26 20:49:25 +00:00
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void *callback_ctx, u64 flags);
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2022-04-25 13:32:47 +00:00
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/* BTF id of struct allocated by map_alloc */
|
bpf: Support access to bpf map fields
There are multiple use-cases when it's convenient to have access to bpf
map fields, both `struct bpf_map` and map type specific struct-s such as
`struct bpf_array`, `struct bpf_htab`, etc.
For example while working with sock arrays it can be necessary to
calculate the key based on map->max_entries (some_hash % max_entries).
Currently this is solved by communicating max_entries via "out-of-band"
channel, e.g. via additional map with known key to get info about target
map. That works, but is not very convenient and error-prone while
working with many maps.
In other cases necessary data is dynamic (i.e. unknown at loading time)
and it's impossible to get it at all. For example while working with a
hash table it can be convenient to know how much capacity is already
used (bpf_htab.count.counter for BPF_F_NO_PREALLOC case).
At the same time kernel knows this info and can provide it to bpf
program.
Fill this gap by adding support to access bpf map fields from bpf
program for both `struct bpf_map` and map type specific fields.
Support is implemented via btf_struct_access() so that a user can define
their own `struct bpf_map` or map type specific struct in their program
with only necessary fields and preserve_access_index attribute, cast a
map to this struct and use a field.
For example:
struct bpf_map {
__u32 max_entries;
} __attribute__((preserve_access_index));
struct bpf_array {
struct bpf_map map;
__u32 elem_size;
} __attribute__((preserve_access_index));
struct {
__uint(type, BPF_MAP_TYPE_ARRAY);
__uint(max_entries, 4);
__type(key, __u32);
__type(value, __u32);
} m_array SEC(".maps");
SEC("cgroup_skb/egress")
int cg_skb(void *ctx)
{
struct bpf_array *array = (struct bpf_array *)&m_array;
struct bpf_map *map = (struct bpf_map *)&m_array;
/* .. use map->max_entries or array->map.max_entries .. */
}
Similarly to other btf_struct_access() use-cases (e.g. struct tcp_sock
in net/ipv4/bpf_tcp_ca.c) the patch allows access to any fields of
corresponding struct. Only reading from map fields is supported.
For btf_struct_access() to work there should be a way to know btf id of
a struct that corresponds to a map type. To get btf id there should be a
way to get a stringified name of map-specific struct, such as
"bpf_array", "bpf_htab", etc for a map type. Two new fields are added to
`struct bpf_map_ops` to handle it:
* .map_btf_name keeps a btf name of a struct returned by map_alloc();
* .map_btf_id is used to cache btf id of that struct.
To make btf ids calculation cheaper they're calculated once while
preparing btf_vmlinux and cached same way as it's done for btf_id field
of `struct bpf_func_proto`
While calculating btf ids, struct names are NOT checked for collision.
Collisions will be checked as a part of the work to prepare btf ids used
in verifier in compile time that should land soon. The only known
collision for `struct bpf_htab` (kernel/bpf/hashtab.c vs
net/core/sock_map.c) was fixed earlier.
Both new fields .map_btf_name and .map_btf_id must be set for a map type
for the feature to work. If neither is set for a map type, verifier will
return ENOTSUPP on a try to access map_ptr of corresponding type. If
just one of them set, it's verifier misconfiguration.
Only `struct bpf_array` for BPF_MAP_TYPE_ARRAY and `struct bpf_htab` for
BPF_MAP_TYPE_HASH are supported by this patch. Other map types will be
supported separately.
The feature is available only for CONFIG_DEBUG_INFO_BTF=y and gated by
perfmon_capable() so that unpriv programs won't have access to bpf map
fields.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/6479686a0cd1e9067993df57b4c3eef0e276fec9.1592600985.git.rdna@fb.com
2020-06-19 21:11:43 +00:00
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int *map_btf_id;
|
bpf: Implement bpf iterator for map elements
The bpf iterator for map elements are implemented.
The bpf program will receive four parameters:
bpf_iter_meta *meta: the meta data
bpf_map *map: the bpf_map whose elements are traversed
void *key: the key of one element
void *value: the value of the same element
Here, meta and map pointers are always valid, and
key has register type PTR_TO_RDONLY_BUF_OR_NULL and
value has register type PTR_TO_RDWR_BUF_OR_NULL.
The kernel will track the access range of key and value
during verification time. Later, these values will be compared
against the values in the actual map to ensure all accesses
are within range.
A new field iter_seq_info is added to bpf_map_ops which
is used to add map type specific information, i.e., seq_ops,
init/fini seq_file func and seq_file private data size.
Subsequent patches will have actual implementation
for bpf_map_ops->iter_seq_info.
In user space, BPF_ITER_LINK_MAP_FD needs to be
specified in prog attr->link_create.flags, which indicates
that attr->link_create.target_fd is a map_fd.
The reason for such an explicit flag is for possible
future cases where one bpf iterator may allow more than
one possible customization, e.g., pid and cgroup id for
task_file.
Current kernel internal implementation only allows
the target to register at most one required bpf_iter_link_info.
To support the above case, optional bpf_iter_link_info's
are needed, the target can be extended to register such link
infos, and user provided link_info needs to match one of
target supported ones.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184112.590360-1-yhs@fb.com
2020-07-23 18:41:12 +00:00
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/* bpf_iter info used to open a seq_file */
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const struct bpf_iter_seq_info *iter_seq_info;
|
2014-09-26 07:16:57 +00:00
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|
|
};
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|
bpf: Allow storing unreferenced kptr in map
This commit introduces a new pointer type 'kptr' which can be embedded
in a map value to hold a PTR_TO_BTF_ID stored by a BPF program during
its invocation. When storing such a kptr, BPF program's PTR_TO_BTF_ID
register must have the same type as in the map value's BTF, and loading
a kptr marks the destination register as PTR_TO_BTF_ID with the correct
kernel BTF and BTF ID.
Such kptr are unreferenced, i.e. by the time another invocation of the
BPF program loads this pointer, the object which the pointer points to
may not longer exist. Since PTR_TO_BTF_ID loads (using BPF_LDX) are
patched to PROBE_MEM loads by the verifier, it would safe to allow user
to still access such invalid pointer, but passing such pointers into
BPF helpers and kfuncs should not be permitted. A future patch in this
series will close this gap.
The flexibility offered by allowing programs to dereference such invalid
pointers while being safe at runtime frees the verifier from doing
complex lifetime tracking. As long as the user may ensure that the
object remains valid, it can ensure data read by it from the kernel
object is valid.
The user indicates that a certain pointer must be treated as kptr
capable of accepting stores of PTR_TO_BTF_ID of a certain type, by using
a BTF type tag 'kptr' on the pointed to type of the pointer. Then, this
information is recorded in the object BTF which will be passed into the
kernel by way of map's BTF information. The name and kind from the map
value BTF is used to look up the in-kernel type, and the actual BTF and
BTF ID is recorded in the map struct in a new kptr_off_tab member. For
now, only storing pointers to structs is permitted.
An example of this specification is shown below:
#define __kptr __attribute__((btf_type_tag("kptr")))
struct map_value {
...
struct task_struct __kptr *task;
...
};
Then, in a BPF program, user may store PTR_TO_BTF_ID with the type
task_struct into the map, and then load it later.
Note that the destination register is marked PTR_TO_BTF_ID_OR_NULL, as
the verifier cannot know whether the value is NULL or not statically, it
must treat all potential loads at that map value offset as loading a
possibly NULL pointer.
Only BPF_LDX, BPF_STX, and BPF_ST (with insn->imm = 0 to denote NULL)
are allowed instructions that can access such a pointer. On BPF_LDX, the
destination register is updated to be a PTR_TO_BTF_ID, and on BPF_STX,
it is checked whether the source register type is a PTR_TO_BTF_ID with
same BTF type as specified in the map BTF. The access size must always
be BPF_DW.
For the map in map support, the kptr_off_tab for outer map is copied
from the inner map's kptr_off_tab. It was chosen to do a deep copy
instead of introducing a refcount to kptr_off_tab, because the copy only
needs to be done when paramterizing using inner_map_fd in the map in map
case, hence would be unnecessary for all other users.
It is not permitted to use MAP_FREEZE command and mmap for BPF map
having kptrs, similar to the bpf_timer case. A kptr also requires that
BPF program has both read and write access to the map (hence both
BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG are disallowed).
Note that check_map_access must be called from both
check_helper_mem_access and for the BPF instructions, hence the kptr
check must distinguish between ACCESS_DIRECT and ACCESS_HELPER, and
reject ACCESS_HELPER cases. We rename stack_access_src to bpf_access_src
and reuse it for this purpose.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-2-memxor@gmail.com
2022-04-24 21:48:49 +00:00
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enum {
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/* Support at most 8 pointers in a BPF map value */
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BPF_MAP_VALUE_OFF_MAX = 8,
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2022-04-24 21:48:53 +00:00
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BPF_MAP_OFF_ARR_MAX = BPF_MAP_VALUE_OFF_MAX +
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1 + /* for bpf_spin_lock */
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1, /* for bpf_timer */
|
bpf: Allow storing unreferenced kptr in map
This commit introduces a new pointer type 'kptr' which can be embedded
in a map value to hold a PTR_TO_BTF_ID stored by a BPF program during
its invocation. When storing such a kptr, BPF program's PTR_TO_BTF_ID
register must have the same type as in the map value's BTF, and loading
a kptr marks the destination register as PTR_TO_BTF_ID with the correct
kernel BTF and BTF ID.
Such kptr are unreferenced, i.e. by the time another invocation of the
BPF program loads this pointer, the object which the pointer points to
may not longer exist. Since PTR_TO_BTF_ID loads (using BPF_LDX) are
patched to PROBE_MEM loads by the verifier, it would safe to allow user
to still access such invalid pointer, but passing such pointers into
BPF helpers and kfuncs should not be permitted. A future patch in this
series will close this gap.
The flexibility offered by allowing programs to dereference such invalid
pointers while being safe at runtime frees the verifier from doing
complex lifetime tracking. As long as the user may ensure that the
object remains valid, it can ensure data read by it from the kernel
object is valid.
The user indicates that a certain pointer must be treated as kptr
capable of accepting stores of PTR_TO_BTF_ID of a certain type, by using
a BTF type tag 'kptr' on the pointed to type of the pointer. Then, this
information is recorded in the object BTF which will be passed into the
kernel by way of map's BTF information. The name and kind from the map
value BTF is used to look up the in-kernel type, and the actual BTF and
BTF ID is recorded in the map struct in a new kptr_off_tab member. For
now, only storing pointers to structs is permitted.
An example of this specification is shown below:
#define __kptr __attribute__((btf_type_tag("kptr")))
struct map_value {
...
struct task_struct __kptr *task;
...
};
Then, in a BPF program, user may store PTR_TO_BTF_ID with the type
task_struct into the map, and then load it later.
Note that the destination register is marked PTR_TO_BTF_ID_OR_NULL, as
the verifier cannot know whether the value is NULL or not statically, it
must treat all potential loads at that map value offset as loading a
possibly NULL pointer.
Only BPF_LDX, BPF_STX, and BPF_ST (with insn->imm = 0 to denote NULL)
are allowed instructions that can access such a pointer. On BPF_LDX, the
destination register is updated to be a PTR_TO_BTF_ID, and on BPF_STX,
it is checked whether the source register type is a PTR_TO_BTF_ID with
same BTF type as specified in the map BTF. The access size must always
be BPF_DW.
For the map in map support, the kptr_off_tab for outer map is copied
from the inner map's kptr_off_tab. It was chosen to do a deep copy
instead of introducing a refcount to kptr_off_tab, because the copy only
needs to be done when paramterizing using inner_map_fd in the map in map
case, hence would be unnecessary for all other users.
It is not permitted to use MAP_FREEZE command and mmap for BPF map
having kptrs, similar to the bpf_timer case. A kptr also requires that
BPF program has both read and write access to the map (hence both
BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG are disallowed).
Note that check_map_access must be called from both
check_helper_mem_access and for the BPF instructions, hence the kptr
check must distinguish between ACCESS_DIRECT and ACCESS_HELPER, and
reject ACCESS_HELPER cases. We rename stack_access_src to bpf_access_src
and reuse it for this purpose.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-2-memxor@gmail.com
2022-04-24 21:48:49 +00:00
|
|
|
};
|
|
|
|
|
bpf: Allow storing referenced kptr in map
Extending the code in previous commits, introduce referenced kptr
support, which needs to be tagged using 'kptr_ref' tag instead. Unlike
unreferenced kptr, referenced kptr have a lot more restrictions. In
addition to the type matching, only a newly introduced bpf_kptr_xchg
helper is allowed to modify the map value at that offset. This transfers
the referenced pointer being stored into the map, releasing the
references state for the program, and returning the old value and
creating new reference state for the returned pointer.
Similar to unreferenced pointer case, return value for this case will
also be PTR_TO_BTF_ID_OR_NULL. The reference for the returned pointer
must either be eventually released by calling the corresponding release
function, otherwise it must be transferred into another map.
It is also allowed to call bpf_kptr_xchg with a NULL pointer, to clear
the value, and obtain the old value if any.
BPF_LDX, BPF_STX, and BPF_ST cannot access referenced kptr. A future
commit will permit using BPF_LDX for such pointers, but attempt at
making it safe, since the lifetime of object won't be guaranteed.
There are valid reasons to enforce the restriction of permitting only
bpf_kptr_xchg to operate on referenced kptr. The pointer value must be
consistent in face of concurrent modification, and any prior values
contained in the map must also be released before a new one is moved
into the map. To ensure proper transfer of this ownership, bpf_kptr_xchg
returns the old value, which the verifier would require the user to
either free or move into another map, and releases the reference held
for the pointer being moved in.
In the future, direct BPF_XCHG instruction may also be permitted to work
like bpf_kptr_xchg helper.
Note that process_kptr_func doesn't have to call
check_helper_mem_access, since we already disallow rdonly/wronly flags
for map, which is what check_map_access_type checks, and we already
ensure the PTR_TO_MAP_VALUE refers to kptr by obtaining its off_desc,
so check_map_access is also not required.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-4-memxor@gmail.com
2022-04-24 21:48:51 +00:00
|
|
|
enum bpf_kptr_type {
|
|
|
|
BPF_KPTR_UNREF,
|
|
|
|
BPF_KPTR_REF,
|
|
|
|
};
|
|
|
|
|
bpf: Allow storing unreferenced kptr in map
This commit introduces a new pointer type 'kptr' which can be embedded
in a map value to hold a PTR_TO_BTF_ID stored by a BPF program during
its invocation. When storing such a kptr, BPF program's PTR_TO_BTF_ID
register must have the same type as in the map value's BTF, and loading
a kptr marks the destination register as PTR_TO_BTF_ID with the correct
kernel BTF and BTF ID.
Such kptr are unreferenced, i.e. by the time another invocation of the
BPF program loads this pointer, the object which the pointer points to
may not longer exist. Since PTR_TO_BTF_ID loads (using BPF_LDX) are
patched to PROBE_MEM loads by the verifier, it would safe to allow user
to still access such invalid pointer, but passing such pointers into
BPF helpers and kfuncs should not be permitted. A future patch in this
series will close this gap.
The flexibility offered by allowing programs to dereference such invalid
pointers while being safe at runtime frees the verifier from doing
complex lifetime tracking. As long as the user may ensure that the
object remains valid, it can ensure data read by it from the kernel
object is valid.
The user indicates that a certain pointer must be treated as kptr
capable of accepting stores of PTR_TO_BTF_ID of a certain type, by using
a BTF type tag 'kptr' on the pointed to type of the pointer. Then, this
information is recorded in the object BTF which will be passed into the
kernel by way of map's BTF information. The name and kind from the map
value BTF is used to look up the in-kernel type, and the actual BTF and
BTF ID is recorded in the map struct in a new kptr_off_tab member. For
now, only storing pointers to structs is permitted.
An example of this specification is shown below:
#define __kptr __attribute__((btf_type_tag("kptr")))
struct map_value {
...
struct task_struct __kptr *task;
...
};
Then, in a BPF program, user may store PTR_TO_BTF_ID with the type
task_struct into the map, and then load it later.
Note that the destination register is marked PTR_TO_BTF_ID_OR_NULL, as
the verifier cannot know whether the value is NULL or not statically, it
must treat all potential loads at that map value offset as loading a
possibly NULL pointer.
Only BPF_LDX, BPF_STX, and BPF_ST (with insn->imm = 0 to denote NULL)
are allowed instructions that can access such a pointer. On BPF_LDX, the
destination register is updated to be a PTR_TO_BTF_ID, and on BPF_STX,
it is checked whether the source register type is a PTR_TO_BTF_ID with
same BTF type as specified in the map BTF. The access size must always
be BPF_DW.
For the map in map support, the kptr_off_tab for outer map is copied
from the inner map's kptr_off_tab. It was chosen to do a deep copy
instead of introducing a refcount to kptr_off_tab, because the copy only
needs to be done when paramterizing using inner_map_fd in the map in map
case, hence would be unnecessary for all other users.
It is not permitted to use MAP_FREEZE command and mmap for BPF map
having kptrs, similar to the bpf_timer case. A kptr also requires that
BPF program has both read and write access to the map (hence both
BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG are disallowed).
Note that check_map_access must be called from both
check_helper_mem_access and for the BPF instructions, hence the kptr
check must distinguish between ACCESS_DIRECT and ACCESS_HELPER, and
reject ACCESS_HELPER cases. We rename stack_access_src to bpf_access_src
and reuse it for this purpose.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-2-memxor@gmail.com
2022-04-24 21:48:49 +00:00
|
|
|
struct bpf_map_value_off_desc {
|
|
|
|
u32 offset;
|
bpf: Allow storing referenced kptr in map
Extending the code in previous commits, introduce referenced kptr
support, which needs to be tagged using 'kptr_ref' tag instead. Unlike
unreferenced kptr, referenced kptr have a lot more restrictions. In
addition to the type matching, only a newly introduced bpf_kptr_xchg
helper is allowed to modify the map value at that offset. This transfers
the referenced pointer being stored into the map, releasing the
references state for the program, and returning the old value and
creating new reference state for the returned pointer.
Similar to unreferenced pointer case, return value for this case will
also be PTR_TO_BTF_ID_OR_NULL. The reference for the returned pointer
must either be eventually released by calling the corresponding release
function, otherwise it must be transferred into another map.
It is also allowed to call bpf_kptr_xchg with a NULL pointer, to clear
the value, and obtain the old value if any.
BPF_LDX, BPF_STX, and BPF_ST cannot access referenced kptr. A future
commit will permit using BPF_LDX for such pointers, but attempt at
making it safe, since the lifetime of object won't be guaranteed.
There are valid reasons to enforce the restriction of permitting only
bpf_kptr_xchg to operate on referenced kptr. The pointer value must be
consistent in face of concurrent modification, and any prior values
contained in the map must also be released before a new one is moved
into the map. To ensure proper transfer of this ownership, bpf_kptr_xchg
returns the old value, which the verifier would require the user to
either free or move into another map, and releases the reference held
for the pointer being moved in.
In the future, direct BPF_XCHG instruction may also be permitted to work
like bpf_kptr_xchg helper.
Note that process_kptr_func doesn't have to call
check_helper_mem_access, since we already disallow rdonly/wronly flags
for map, which is what check_map_access_type checks, and we already
ensure the PTR_TO_MAP_VALUE refers to kptr by obtaining its off_desc,
so check_map_access is also not required.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-4-memxor@gmail.com
2022-04-24 21:48:51 +00:00
|
|
|
enum bpf_kptr_type type;
|
bpf: Allow storing unreferenced kptr in map
This commit introduces a new pointer type 'kptr' which can be embedded
in a map value to hold a PTR_TO_BTF_ID stored by a BPF program during
its invocation. When storing such a kptr, BPF program's PTR_TO_BTF_ID
register must have the same type as in the map value's BTF, and loading
a kptr marks the destination register as PTR_TO_BTF_ID with the correct
kernel BTF and BTF ID.
Such kptr are unreferenced, i.e. by the time another invocation of the
BPF program loads this pointer, the object which the pointer points to
may not longer exist. Since PTR_TO_BTF_ID loads (using BPF_LDX) are
patched to PROBE_MEM loads by the verifier, it would safe to allow user
to still access such invalid pointer, but passing such pointers into
BPF helpers and kfuncs should not be permitted. A future patch in this
series will close this gap.
The flexibility offered by allowing programs to dereference such invalid
pointers while being safe at runtime frees the verifier from doing
complex lifetime tracking. As long as the user may ensure that the
object remains valid, it can ensure data read by it from the kernel
object is valid.
The user indicates that a certain pointer must be treated as kptr
capable of accepting stores of PTR_TO_BTF_ID of a certain type, by using
a BTF type tag 'kptr' on the pointed to type of the pointer. Then, this
information is recorded in the object BTF which will be passed into the
kernel by way of map's BTF information. The name and kind from the map
value BTF is used to look up the in-kernel type, and the actual BTF and
BTF ID is recorded in the map struct in a new kptr_off_tab member. For
now, only storing pointers to structs is permitted.
An example of this specification is shown below:
#define __kptr __attribute__((btf_type_tag("kptr")))
struct map_value {
...
struct task_struct __kptr *task;
...
};
Then, in a BPF program, user may store PTR_TO_BTF_ID with the type
task_struct into the map, and then load it later.
Note that the destination register is marked PTR_TO_BTF_ID_OR_NULL, as
the verifier cannot know whether the value is NULL or not statically, it
must treat all potential loads at that map value offset as loading a
possibly NULL pointer.
Only BPF_LDX, BPF_STX, and BPF_ST (with insn->imm = 0 to denote NULL)
are allowed instructions that can access such a pointer. On BPF_LDX, the
destination register is updated to be a PTR_TO_BTF_ID, and on BPF_STX,
it is checked whether the source register type is a PTR_TO_BTF_ID with
same BTF type as specified in the map BTF. The access size must always
be BPF_DW.
For the map in map support, the kptr_off_tab for outer map is copied
from the inner map's kptr_off_tab. It was chosen to do a deep copy
instead of introducing a refcount to kptr_off_tab, because the copy only
needs to be done when paramterizing using inner_map_fd in the map in map
case, hence would be unnecessary for all other users.
It is not permitted to use MAP_FREEZE command and mmap for BPF map
having kptrs, similar to the bpf_timer case. A kptr also requires that
BPF program has both read and write access to the map (hence both
BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG are disallowed).
Note that check_map_access must be called from both
check_helper_mem_access and for the BPF instructions, hence the kptr
check must distinguish between ACCESS_DIRECT and ACCESS_HELPER, and
reject ACCESS_HELPER cases. We rename stack_access_src to bpf_access_src
and reuse it for this purpose.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-2-memxor@gmail.com
2022-04-24 21:48:49 +00:00
|
|
|
struct {
|
|
|
|
struct btf *btf;
|
bpf: Wire up freeing of referenced kptr
A destructor kfunc can be defined as void func(type *), where type may
be void or any other pointer type as per convenience.
In this patch, we ensure that the type is sane and capture the function
pointer into off_desc of ptr_off_tab for the specific pointer offset,
with the invariant that the dtor pointer is always set when 'kptr_ref'
tag is applied to the pointer's pointee type, which is indicated by the
flag BPF_MAP_VALUE_OFF_F_REF.
Note that only BTF IDs whose destructor kfunc is registered, thus become
the allowed BTF IDs for embedding as referenced kptr. Hence it serves
the purpose of finding dtor kfunc BTF ID, as well acting as a check
against the whitelist of allowed BTF IDs for this purpose.
Finally, wire up the actual freeing of the referenced pointer if any at
all available offsets, so that no references are leaked after the BPF
map goes away and the BPF program previously moved the ownership a
referenced pointer into it.
The behavior is similar to BPF timers, where bpf_map_{update,delete}_elem
will free any existing referenced kptr. The same case is with LRU map's
bpf_lru_push_free/htab_lru_push_free functions, which are extended to
reset unreferenced and free referenced kptr.
Note that unlike BPF timers, kptr is not reset or freed when map uref
drops to zero.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-8-memxor@gmail.com
2022-04-24 21:48:55 +00:00
|
|
|
struct module *module;
|
|
|
|
btf_dtor_kfunc_t dtor;
|
bpf: Allow storing unreferenced kptr in map
This commit introduces a new pointer type 'kptr' which can be embedded
in a map value to hold a PTR_TO_BTF_ID stored by a BPF program during
its invocation. When storing such a kptr, BPF program's PTR_TO_BTF_ID
register must have the same type as in the map value's BTF, and loading
a kptr marks the destination register as PTR_TO_BTF_ID with the correct
kernel BTF and BTF ID.
Such kptr are unreferenced, i.e. by the time another invocation of the
BPF program loads this pointer, the object which the pointer points to
may not longer exist. Since PTR_TO_BTF_ID loads (using BPF_LDX) are
patched to PROBE_MEM loads by the verifier, it would safe to allow user
to still access such invalid pointer, but passing such pointers into
BPF helpers and kfuncs should not be permitted. A future patch in this
series will close this gap.
The flexibility offered by allowing programs to dereference such invalid
pointers while being safe at runtime frees the verifier from doing
complex lifetime tracking. As long as the user may ensure that the
object remains valid, it can ensure data read by it from the kernel
object is valid.
The user indicates that a certain pointer must be treated as kptr
capable of accepting stores of PTR_TO_BTF_ID of a certain type, by using
a BTF type tag 'kptr' on the pointed to type of the pointer. Then, this
information is recorded in the object BTF which will be passed into the
kernel by way of map's BTF information. The name and kind from the map
value BTF is used to look up the in-kernel type, and the actual BTF and
BTF ID is recorded in the map struct in a new kptr_off_tab member. For
now, only storing pointers to structs is permitted.
An example of this specification is shown below:
#define __kptr __attribute__((btf_type_tag("kptr")))
struct map_value {
...
struct task_struct __kptr *task;
...
};
Then, in a BPF program, user may store PTR_TO_BTF_ID with the type
task_struct into the map, and then load it later.
Note that the destination register is marked PTR_TO_BTF_ID_OR_NULL, as
the verifier cannot know whether the value is NULL or not statically, it
must treat all potential loads at that map value offset as loading a
possibly NULL pointer.
Only BPF_LDX, BPF_STX, and BPF_ST (with insn->imm = 0 to denote NULL)
are allowed instructions that can access such a pointer. On BPF_LDX, the
destination register is updated to be a PTR_TO_BTF_ID, and on BPF_STX,
it is checked whether the source register type is a PTR_TO_BTF_ID with
same BTF type as specified in the map BTF. The access size must always
be BPF_DW.
For the map in map support, the kptr_off_tab for outer map is copied
from the inner map's kptr_off_tab. It was chosen to do a deep copy
instead of introducing a refcount to kptr_off_tab, because the copy only
needs to be done when paramterizing using inner_map_fd in the map in map
case, hence would be unnecessary for all other users.
It is not permitted to use MAP_FREEZE command and mmap for BPF map
having kptrs, similar to the bpf_timer case. A kptr also requires that
BPF program has both read and write access to the map (hence both
BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG are disallowed).
Note that check_map_access must be called from both
check_helper_mem_access and for the BPF instructions, hence the kptr
check must distinguish between ACCESS_DIRECT and ACCESS_HELPER, and
reject ACCESS_HELPER cases. We rename stack_access_src to bpf_access_src
and reuse it for this purpose.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-2-memxor@gmail.com
2022-04-24 21:48:49 +00:00
|
|
|
u32 btf_id;
|
|
|
|
} kptr;
|
|
|
|
};
|
|
|
|
|
|
|
|
struct bpf_map_value_off {
|
|
|
|
u32 nr_off;
|
|
|
|
struct bpf_map_value_off_desc off[];
|
|
|
|
};
|
|
|
|
|
2022-04-24 21:48:53 +00:00
|
|
|
struct bpf_map_off_arr {
|
|
|
|
u32 cnt;
|
|
|
|
u32 field_off[BPF_MAP_OFF_ARR_MAX];
|
|
|
|
u8 field_sz[BPF_MAP_OFF_ARR_MAX];
|
|
|
|
};
|
|
|
|
|
2014-09-26 07:16:57 +00:00
|
|
|
struct bpf_map {
|
2018-04-18 22:56:03 +00:00
|
|
|
/* The first two cachelines with read-mostly members of which some
|
bpf: avoid false sharing of map refcount with max_entries
In addition to commit b2157399cc98 ("bpf: prevent out-of-bounds
speculation") also change the layout of struct bpf_map such that
false sharing of fast-path members like max_entries is avoided
when the maps reference counter is altered. Therefore enforce
them to be placed into separate cachelines.
pahole dump after change:
struct bpf_map {
const struct bpf_map_ops * ops; /* 0 8 */
struct bpf_map * inner_map_meta; /* 8 8 */
void * security; /* 16 8 */
enum bpf_map_type map_type; /* 24 4 */
u32 key_size; /* 28 4 */
u32 value_size; /* 32 4 */
u32 max_entries; /* 36 4 */
u32 map_flags; /* 40 4 */
u32 pages; /* 44 4 */
u32 id; /* 48 4 */
int numa_node; /* 52 4 */
bool unpriv_array; /* 56 1 */
/* XXX 7 bytes hole, try to pack */
/* --- cacheline 1 boundary (64 bytes) --- */
struct user_struct * user; /* 64 8 */
atomic_t refcnt; /* 72 4 */
atomic_t usercnt; /* 76 4 */
struct work_struct work; /* 80 32 */
char name[16]; /* 112 16 */
/* --- cacheline 2 boundary (128 bytes) --- */
/* size: 128, cachelines: 2, members: 17 */
/* sum members: 121, holes: 1, sum holes: 7 */
};
Now all entries in the first cacheline are read only throughout
the life time of the map, set up once during map creation. Overall
struct size and number of cachelines doesn't change from the
reordering. struct bpf_map is usually first member and embedded
in map structs in specific map implementations, so also avoid those
members to sit at the end where it could potentially share the
cacheline with first map values e.g. in the array since remote
CPUs could trigger map updates just as well for those (easily
dirtying members like max_entries intentionally as well) while
having subsequent values in cache.
Quoting from Google's Project Zero blog [1]:
Additionally, at least on the Intel machine on which this was
tested, bouncing modified cache lines between cores is slow,
apparently because the MESI protocol is used for cache coherence
[8]. Changing the reference counter of an eBPF array on one
physical CPU core causes the cache line containing the reference
counter to be bounced over to that CPU core, making reads of the
reference counter on all other CPU cores slow until the changed
reference counter has been written back to memory. Because the
length and the reference counter of an eBPF array are stored in
the same cache line, this also means that changing the reference
counter on one physical CPU core causes reads of the eBPF array's
length to be slow on other physical CPU cores (intentional false
sharing).
While this doesn't 'control' the out-of-bounds speculation through
masking the index as in commit b2157399cc98, triggering a manipulation
of the map's reference counter is really trivial, so lets not allow
to easily affect max_entries from it.
Splitting to separate cachelines also generally makes sense from
a performance perspective anyway in that fast-path won't have a
cache miss if the map gets pinned, reused in other progs, etc out
of control path, thus also avoids unintentional false sharing.
[1] https://googleprojectzero.blogspot.ch/2018/01/reading-privileged-memory-with-side.html
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-01-09 12:17:44 +00:00
|
|
|
* are also accessed in fast-path (e.g. ops, max_entries).
|
|
|
|
*/
|
|
|
|
const struct bpf_map_ops *ops ____cacheline_aligned;
|
|
|
|
struct bpf_map *inner_map_meta;
|
|
|
|
#ifdef CONFIG_SECURITY
|
|
|
|
void *security;
|
|
|
|
#endif
|
2014-09-26 07:16:57 +00:00
|
|
|
enum bpf_map_type map_type;
|
|
|
|
u32 key_size;
|
|
|
|
u32 value_size;
|
|
|
|
u32 max_entries;
|
bpf: Add bloom filter map implementation
This patch adds the kernel-side changes for the implementation of
a bpf bloom filter map.
The bloom filter map supports peek (determining whether an element
is present in the map) and push (adding an element to the map)
operations.These operations are exposed to userspace applications
through the already existing syscalls in the following way:
BPF_MAP_LOOKUP_ELEM -> peek
BPF_MAP_UPDATE_ELEM -> push
The bloom filter map does not have keys, only values. In light of
this, the bloom filter map's API matches that of queue stack maps:
user applications use BPF_MAP_LOOKUP_ELEM/BPF_MAP_UPDATE_ELEM
which correspond internally to bpf_map_peek_elem/bpf_map_push_elem,
and bpf programs must use the bpf_map_peek_elem and bpf_map_push_elem
APIs to query or add an element to the bloom filter map. When the
bloom filter map is created, it must be created with a key_size of 0.
For updates, the user will pass in the element to add to the map
as the value, with a NULL key. For lookups, the user will pass in the
element to query in the map as the value, with a NULL key. In the
verifier layer, this requires us to modify the argument type of
a bloom filter's BPF_FUNC_map_peek_elem call to ARG_PTR_TO_MAP_VALUE;
as well, in the syscall layer, we need to copy over the user value
so that in bpf_map_peek_elem, we know which specific value to query.
A few things to please take note of:
* If there are any concurrent lookups + updates, the user is
responsible for synchronizing this to ensure no false negative lookups
occur.
* The number of hashes to use for the bloom filter is configurable from
userspace. If no number is specified, the default used will be 5 hash
functions. The benchmarks later in this patchset can help compare the
performance of using different number of hashes on different entry
sizes. In general, using more hashes decreases both the false positive
rate and the speed of a lookup.
* Deleting an element in the bloom filter map is not supported.
* The bloom filter map may be used as an inner map.
* The "max_entries" size that is specified at map creation time is used
to approximate a reasonable bitmap size for the bloom filter, and is not
otherwise strictly enforced. If the user wishes to insert more entries
into the bloom filter than "max_entries", they may do so but they should
be aware that this may lead to a higher false positive rate.
Signed-off-by: Joanne Koong <joannekoong@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211027234504.30744-2-joannekoong@fb.com
2021-10-27 23:45:00 +00:00
|
|
|
u64 map_extra; /* any per-map-type extra fields */
|
bpf: pre-allocate hash map elements
If kprobe is placed on spin_unlock then calling kmalloc/kfree from
bpf programs is not safe, since the following dead lock is possible:
kfree->spin_lock(kmem_cache_node->lock)...spin_unlock->kprobe->
bpf_prog->map_update->kmalloc->spin_lock(of the same kmem_cache_node->lock)
and deadlocks.
The following solutions were considered and some implemented, but
eventually discarded
- kmem_cache_create for every map
- add recursion check to slow-path of slub
- use reserved memory in bpf_map_update for in_irq or in preempt_disabled
- kmalloc via irq_work
At the end pre-allocation of all map elements turned out to be the simplest
solution and since the user is charged upfront for all the memory, such
pre-allocation doesn't affect the user space visible behavior.
Since it's impossible to tell whether kprobe is triggered in a safe
location from kmalloc point of view, use pre-allocation by default
and introduce new BPF_F_NO_PREALLOC flag.
While testing of per-cpu hash maps it was discovered
that alloc_percpu(GFP_ATOMIC) has odd corner cases and often
fails to allocate memory even when 90% of it is free.
The pre-allocation of per-cpu hash elements solves this problem as well.
Turned out that bpf_map_update() quickly followed by
bpf_map_lookup()+bpf_map_delete() is very common pattern used
in many of iovisor/bcc/tools, so there is additional benefit of
pre-allocation, since such use cases are must faster.
Since all hash map elements are now pre-allocated we can remove
atomic increment of htab->count and save few more cycles.
Also add bpf_map_precharge_memlock() to check rlimit_memlock early to avoid
large malloc/free done by users who don't have sufficient limits.
Pre-allocation is done with vmalloc and alloc/free is done
via percpu_freelist. Here are performance numbers for different
pre-allocation algorithms that were implemented, but discarded
in favor of percpu_freelist:
1 cpu:
pcpu_ida 2.1M
pcpu_ida nolock 2.3M
bt 2.4M
kmalloc 1.8M
hlist+spinlock 2.3M
pcpu_freelist 2.6M
4 cpu:
pcpu_ida 1.5M
pcpu_ida nolock 1.8M
bt w/smp_align 1.7M
bt no/smp_align 1.1M
kmalloc 0.7M
hlist+spinlock 0.2M
pcpu_freelist 2.0M
8 cpu:
pcpu_ida 0.7M
bt w/smp_align 0.8M
kmalloc 0.4M
pcpu_freelist 1.5M
32 cpu:
kmalloc 0.13M
pcpu_freelist 0.49M
pcpu_ida nolock is a modified percpu_ida algorithm without
percpu_ida_cpu locks and without cross-cpu tag stealing.
It's faster than existing percpu_ida, but not as fast as pcpu_freelist.
bt is a variant of block/blk-mq-tag.c simlified and customized
for bpf use case. bt w/smp_align is using cache line for every 'long'
(similar to blk-mq-tag). bt no/smp_align allocates 'long'
bitmasks continuously to save memory. It's comparable to percpu_ida
and in some cases faster, but slower than percpu_freelist
hlist+spinlock is the simplest free list with single spinlock.
As expeceted it has very bad scaling in SMP.
kmalloc is existing implementation which is still available via
BPF_F_NO_PREALLOC flag. It's significantly slower in single cpu and
in 8 cpu setup it's 3 times slower than pre-allocation with pcpu_freelist,
but saves memory, so in cases where map->max_entries can be large
and number of map update/delete per second is low, it may make
sense to use it.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-03-08 05:57:15 +00:00
|
|
|
u32 map_flags;
|
2019-01-31 23:40:04 +00:00
|
|
|
int spin_lock_off; /* >=0 valid offset, <0 error */
|
bpf: Allow storing unreferenced kptr in map
This commit introduces a new pointer type 'kptr' which can be embedded
in a map value to hold a PTR_TO_BTF_ID stored by a BPF program during
its invocation. When storing such a kptr, BPF program's PTR_TO_BTF_ID
register must have the same type as in the map value's BTF, and loading
a kptr marks the destination register as PTR_TO_BTF_ID with the correct
kernel BTF and BTF ID.
Such kptr are unreferenced, i.e. by the time another invocation of the
BPF program loads this pointer, the object which the pointer points to
may not longer exist. Since PTR_TO_BTF_ID loads (using BPF_LDX) are
patched to PROBE_MEM loads by the verifier, it would safe to allow user
to still access such invalid pointer, but passing such pointers into
BPF helpers and kfuncs should not be permitted. A future patch in this
series will close this gap.
The flexibility offered by allowing programs to dereference such invalid
pointers while being safe at runtime frees the verifier from doing
complex lifetime tracking. As long as the user may ensure that the
object remains valid, it can ensure data read by it from the kernel
object is valid.
The user indicates that a certain pointer must be treated as kptr
capable of accepting stores of PTR_TO_BTF_ID of a certain type, by using
a BTF type tag 'kptr' on the pointed to type of the pointer. Then, this
information is recorded in the object BTF which will be passed into the
kernel by way of map's BTF information. The name and kind from the map
value BTF is used to look up the in-kernel type, and the actual BTF and
BTF ID is recorded in the map struct in a new kptr_off_tab member. For
now, only storing pointers to structs is permitted.
An example of this specification is shown below:
#define __kptr __attribute__((btf_type_tag("kptr")))
struct map_value {
...
struct task_struct __kptr *task;
...
};
Then, in a BPF program, user may store PTR_TO_BTF_ID with the type
task_struct into the map, and then load it later.
Note that the destination register is marked PTR_TO_BTF_ID_OR_NULL, as
the verifier cannot know whether the value is NULL or not statically, it
must treat all potential loads at that map value offset as loading a
possibly NULL pointer.
Only BPF_LDX, BPF_STX, and BPF_ST (with insn->imm = 0 to denote NULL)
are allowed instructions that can access such a pointer. On BPF_LDX, the
destination register is updated to be a PTR_TO_BTF_ID, and on BPF_STX,
it is checked whether the source register type is a PTR_TO_BTF_ID with
same BTF type as specified in the map BTF. The access size must always
be BPF_DW.
For the map in map support, the kptr_off_tab for outer map is copied
from the inner map's kptr_off_tab. It was chosen to do a deep copy
instead of introducing a refcount to kptr_off_tab, because the copy only
needs to be done when paramterizing using inner_map_fd in the map in map
case, hence would be unnecessary for all other users.
It is not permitted to use MAP_FREEZE command and mmap for BPF map
having kptrs, similar to the bpf_timer case. A kptr also requires that
BPF program has both read and write access to the map (hence both
BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG are disallowed).
Note that check_map_access must be called from both
check_helper_mem_access and for the BPF instructions, hence the kptr
check must distinguish between ACCESS_DIRECT and ACCESS_HELPER, and
reject ACCESS_HELPER cases. We rename stack_access_src to bpf_access_src
and reuse it for this purpose.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-2-memxor@gmail.com
2022-04-24 21:48:49 +00:00
|
|
|
struct bpf_map_value_off *kptr_off_tab;
|
bpf: Introduce bpf timers.
Introduce 'struct bpf_timer { __u64 :64; __u64 :64; };' that can be embedded
in hash/array/lru maps as a regular field and helpers to operate on it:
// Initialize the timer.
// First 4 bits of 'flags' specify clockid.
// Only CLOCK_MONOTONIC, CLOCK_REALTIME, CLOCK_BOOTTIME are allowed.
long bpf_timer_init(struct bpf_timer *timer, struct bpf_map *map, int flags);
// Configure the timer to call 'callback_fn' static function.
long bpf_timer_set_callback(struct bpf_timer *timer, void *callback_fn);
// Arm the timer to expire 'nsec' nanoseconds from the current time.
long bpf_timer_start(struct bpf_timer *timer, u64 nsec, u64 flags);
// Cancel the timer and wait for callback_fn to finish if it was running.
long bpf_timer_cancel(struct bpf_timer *timer);
Here is how BPF program might look like:
struct map_elem {
int counter;
struct bpf_timer timer;
};
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 1000);
__type(key, int);
__type(value, struct map_elem);
} hmap SEC(".maps");
static int timer_cb(void *map, int *key, struct map_elem *val);
/* val points to particular map element that contains bpf_timer. */
SEC("fentry/bpf_fentry_test1")
int BPF_PROG(test1, int a)
{
struct map_elem *val;
int key = 0;
val = bpf_map_lookup_elem(&hmap, &key);
if (val) {
bpf_timer_init(&val->timer, &hmap, CLOCK_REALTIME);
bpf_timer_set_callback(&val->timer, timer_cb);
bpf_timer_start(&val->timer, 1000 /* call timer_cb2 in 1 usec */, 0);
}
}
This patch adds helper implementations that rely on hrtimers
to call bpf functions as timers expire.
The following patches add necessary safety checks.
Only programs with CAP_BPF are allowed to use bpf_timer.
The amount of timers used by the program is constrained by
the memcg recorded at map creation time.
The bpf_timer_init() helper needs explicit 'map' argument because inner maps
are dynamic and not known at load time. While the bpf_timer_set_callback() is
receiving hidden 'aux->prog' argument supplied by the verifier.
The prog pointer is needed to do refcnting of bpf program to make sure that
program doesn't get freed while the timer is armed. This approach relies on
"user refcnt" scheme used in prog_array that stores bpf programs for
bpf_tail_call. The bpf_timer_set_callback() will increment the prog refcnt which is
paired with bpf_timer_cancel() that will drop the prog refcnt. The
ops->map_release_uref is responsible for cancelling the timers and dropping
prog refcnt when user space reference to a map reaches zero.
This uref approach is done to make sure that Ctrl-C of user space process will
not leave timers running forever unless the user space explicitly pinned a map
that contained timers in bpffs.
bpf_timer_init() and bpf_timer_set_callback() will return -EPERM if map doesn't
have user references (is not held by open file descriptor from user space and
not pinned in bpffs).
The bpf_map_delete_elem() and bpf_map_update_elem() operations cancel
and free the timer if given map element had it allocated.
"bpftool map update" command can be used to cancel timers.
The 'struct bpf_timer' is explicitly __attribute__((aligned(8))) because
'__u64 :64' has 1 byte alignment of 8 byte padding.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210715005417.78572-4-alexei.starovoitov@gmail.com
2021-07-15 00:54:09 +00:00
|
|
|
int timer_off; /* >=0 valid offset, <0 error */
|
2017-06-05 19:15:47 +00:00
|
|
|
u32 id;
|
2017-08-18 18:28:00 +00:00
|
|
|
int numa_node;
|
2018-05-22 21:57:21 +00:00
|
|
|
u32 btf_key_type_id;
|
|
|
|
u32 btf_value_type_id;
|
bpf: Add alignment padding for "map_extra" + consolidate holes
This patch makes 2 changes regarding alignment padding
for the "map_extra" field.
1) In the kernel header, "map_extra" and "btf_value_type_id"
are rearranged to consolidate the hole.
Before:
struct bpf_map {
...
u32 max_entries; /* 36 4 */
u32 map_flags; /* 40 4 */
/* XXX 4 bytes hole, try to pack */
u64 map_extra; /* 48 8 */
int spin_lock_off; /* 56 4 */
int timer_off; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
u32 id; /* 64 4 */
int numa_node; /* 68 4 */
...
bool frozen; /* 117 1 */
/* XXX 10 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
...
struct work_struct work; /* 144 72 */
/* --- cacheline 3 boundary (192 bytes) was 24 bytes ago --- */
struct mutex freeze_mutex; /* 216 144 */
/* --- cacheline 5 boundary (320 bytes) was 40 bytes ago --- */
u64 writecnt; /* 360 8 */
/* size: 384, cachelines: 6, members: 26 */
/* sum members: 354, holes: 2, sum holes: 14 */
/* padding: 16 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 10 */
} __attribute__((__aligned__(64)));
After:
struct bpf_map {
...
u32 max_entries; /* 36 4 */
u64 map_extra; /* 40 8 */
u32 map_flags; /* 48 4 */
int spin_lock_off; /* 52 4 */
int timer_off; /* 56 4 */
u32 id; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
int numa_node; /* 64 4 */
...
bool frozen /* 113 1 */
/* XXX 14 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
...
struct work_struct work; /* 144 72 */
/* --- cacheline 3 boundary (192 bytes) was 24 bytes ago --- */
struct mutex freeze_mutex; /* 216 144 */
/* --- cacheline 5 boundary (320 bytes) was 40 bytes ago --- */
u64 writecnt; /* 360 8 */
/* size: 384, cachelines: 6, members: 26 */
/* sum members: 354, holes: 1, sum holes: 14 */
/* padding: 16 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 14 */
} __attribute__((__aligned__(64)));
2) Add alignment padding to the bpf_map_info struct
More details can be found in commit 36f9814a494a ("bpf: fix uapi hole
for 32 bit compat applications")
Signed-off-by: Joanne Koong <joannekoong@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211029224909.1721024-3-joannekoong@fb.com
2021-10-29 22:49:08 +00:00
|
|
|
u32 btf_vmlinux_value_type_id;
|
2018-04-18 22:56:03 +00:00
|
|
|
struct btf *btf;
|
2020-12-01 21:58:32 +00:00
|
|
|
#ifdef CONFIG_MEMCG_KMEM
|
2022-07-11 16:28:27 +00:00
|
|
|
struct obj_cgroup *objcg;
|
2020-12-01 21:58:32 +00:00
|
|
|
#endif
|
bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY
Add ability to memory-map contents of BPF array map. This is extremely useful
for working with BPF global data from userspace programs. It allows to avoid
typical bpf_map_{lookup,update}_elem operations, improving both performance
and usability.
There had to be special considerations for map freezing, to avoid having
writable memory view into a frozen map. To solve this issue, map freezing and
mmap-ing is happening under mutex now:
- if map is already frozen, no writable mapping is allowed;
- if map has writable memory mappings active (accounted in map->writecnt),
map freezing will keep failing with -EBUSY;
- once number of writable memory mappings drops to zero, map freezing can be
performed again.
Only non-per-CPU plain arrays are supported right now. Maps with spinlocks
can't be memory mapped either.
For BPF_F_MMAPABLE array, memory allocation has to be done through vmalloc()
to be mmap()'able. We also need to make sure that array data memory is
page-sized and page-aligned, so we over-allocate memory in such a way that
struct bpf_array is at the end of a single page of memory with array->value
being aligned with the start of the second page. On deallocation we need to
accomodate this memory arrangement to free vmalloc()'ed memory correctly.
One important consideration regarding how memory-mapping subsystem functions.
Memory-mapping subsystem provides few optional callbacks, among them open()
and close(). close() is called for each memory region that is unmapped, so
that users can decrease their reference counters and free up resources, if
necessary. open() is *almost* symmetrical: it's called for each memory region
that is being mapped, **except** the very first one. So bpf_map_mmap does
initial refcnt bump, while open() will do any extra ones after that. Thus
number of close() calls is equal to number of open() calls plus one more.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/bpf/20191117172806.2195367-4-andriin@fb.com
2019-11-17 17:28:04 +00:00
|
|
|
char name[BPF_OBJ_NAME_LEN];
|
2022-04-24 21:48:53 +00:00
|
|
|
struct bpf_map_off_arr *off_arr;
|
2018-04-18 22:56:03 +00:00
|
|
|
/* The 3rd and 4th cacheline with misc members to avoid false sharing
|
bpf: avoid false sharing of map refcount with max_entries
In addition to commit b2157399cc98 ("bpf: prevent out-of-bounds
speculation") also change the layout of struct bpf_map such that
false sharing of fast-path members like max_entries is avoided
when the maps reference counter is altered. Therefore enforce
them to be placed into separate cachelines.
pahole dump after change:
struct bpf_map {
const struct bpf_map_ops * ops; /* 0 8 */
struct bpf_map * inner_map_meta; /* 8 8 */
void * security; /* 16 8 */
enum bpf_map_type map_type; /* 24 4 */
u32 key_size; /* 28 4 */
u32 value_size; /* 32 4 */
u32 max_entries; /* 36 4 */
u32 map_flags; /* 40 4 */
u32 pages; /* 44 4 */
u32 id; /* 48 4 */
int numa_node; /* 52 4 */
bool unpriv_array; /* 56 1 */
/* XXX 7 bytes hole, try to pack */
/* --- cacheline 1 boundary (64 bytes) --- */
struct user_struct * user; /* 64 8 */
atomic_t refcnt; /* 72 4 */
atomic_t usercnt; /* 76 4 */
struct work_struct work; /* 80 32 */
char name[16]; /* 112 16 */
/* --- cacheline 2 boundary (128 bytes) --- */
/* size: 128, cachelines: 2, members: 17 */
/* sum members: 121, holes: 1, sum holes: 7 */
};
Now all entries in the first cacheline are read only throughout
the life time of the map, set up once during map creation. Overall
struct size and number of cachelines doesn't change from the
reordering. struct bpf_map is usually first member and embedded
in map structs in specific map implementations, so also avoid those
members to sit at the end where it could potentially share the
cacheline with first map values e.g. in the array since remote
CPUs could trigger map updates just as well for those (easily
dirtying members like max_entries intentionally as well) while
having subsequent values in cache.
Quoting from Google's Project Zero blog [1]:
Additionally, at least on the Intel machine on which this was
tested, bouncing modified cache lines between cores is slow,
apparently because the MESI protocol is used for cache coherence
[8]. Changing the reference counter of an eBPF array on one
physical CPU core causes the cache line containing the reference
counter to be bounced over to that CPU core, making reads of the
reference counter on all other CPU cores slow until the changed
reference counter has been written back to memory. Because the
length and the reference counter of an eBPF array are stored in
the same cache line, this also means that changing the reference
counter on one physical CPU core causes reads of the eBPF array's
length to be slow on other physical CPU cores (intentional false
sharing).
While this doesn't 'control' the out-of-bounds speculation through
masking the index as in commit b2157399cc98, triggering a manipulation
of the map's reference counter is really trivial, so lets not allow
to easily affect max_entries from it.
Splitting to separate cachelines also generally makes sense from
a performance perspective anyway in that fast-path won't have a
cache miss if the map gets pinned, reused in other progs, etc out
of control path, thus also avoids unintentional false sharing.
[1] https://googleprojectzero.blogspot.ch/2018/01/reading-privileged-memory-with-side.html
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-01-09 12:17:44 +00:00
|
|
|
* particularly with refcounting.
|
|
|
|
*/
|
bpf: Switch bpf_map ref counter to atomic64_t so bpf_map_inc() never fails
92117d8443bc ("bpf: fix refcnt overflow") turned refcounting of bpf_map into
potentially failing operation, when refcount reaches BPF_MAX_REFCNT limit
(32k). Due to using 32-bit counter, it's possible in practice to overflow
refcounter and make it wrap around to 0, causing erroneous map free, while
there are still references to it, causing use-after-free problems.
But having a failing refcounting operations are problematic in some cases. One
example is mmap() interface. After establishing initial memory-mapping, user
is allowed to arbitrarily map/remap/unmap parts of mapped memory, arbitrarily
splitting it into multiple non-contiguous regions. All this happening without
any control from the users of mmap subsystem. Rather mmap subsystem sends
notifications to original creator of memory mapping through open/close
callbacks, which are optionally specified during initial memory mapping
creation. These callbacks are used to maintain accurate refcount for bpf_map
(see next patch in this series). The problem is that open() callback is not
supposed to fail, because memory-mapped resource is set up and properly
referenced. This is posing a problem for using memory-mapping with BPF maps.
One solution to this is to maintain separate refcount for just memory-mappings
and do single bpf_map_inc/bpf_map_put when it goes from/to zero, respectively.
There are similar use cases in current work on tcp-bpf, necessitating extra
counter as well. This seems like a rather unfortunate and ugly solution that
doesn't scale well to various new use cases.
Another approach to solve this is to use non-failing refcount_t type, which
uses 32-bit counter internally, but, once reaching overflow state at UINT_MAX,
stays there. This utlimately causes memory leak, but prevents use after free.
But given refcounting is not the most performance-critical operation with BPF
maps (it's not used from running BPF program code), we can also just switch to
64-bit counter that can't overflow in practice, potentially disadvantaging
32-bit platforms a tiny bit. This simplifies semantics and allows above
described scenarios to not worry about failing refcount increment operation.
In terms of struct bpf_map size, we are still good and use the same amount of
space:
BEFORE (3 cache lines, 8 bytes of padding at the end):
struct bpf_map {
const struct bpf_map_ops * ops __attribute__((__aligned__(64))); /* 0 8 */
struct bpf_map * inner_map_meta; /* 8 8 */
void * security; /* 16 8 */
enum bpf_map_type map_type; /* 24 4 */
u32 key_size; /* 28 4 */
u32 value_size; /* 32 4 */
u32 max_entries; /* 36 4 */
u32 map_flags; /* 40 4 */
int spin_lock_off; /* 44 4 */
u32 id; /* 48 4 */
int numa_node; /* 52 4 */
u32 btf_key_type_id; /* 56 4 */
u32 btf_value_type_id; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct btf * btf; /* 64 8 */
struct bpf_map_memory memory; /* 72 16 */
bool unpriv_array; /* 88 1 */
bool frozen; /* 89 1 */
/* XXX 38 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
atomic_t refcnt __attribute__((__aligned__(64))); /* 128 4 */
atomic_t usercnt; /* 132 4 */
struct work_struct work; /* 136 32 */
char name[16]; /* 168 16 */
/* size: 192, cachelines: 3, members: 21 */
/* sum members: 146, holes: 1, sum holes: 38 */
/* padding: 8 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 38 */
} __attribute__((__aligned__(64)));
AFTER (same 3 cache lines, no extra padding now):
struct bpf_map {
const struct bpf_map_ops * ops __attribute__((__aligned__(64))); /* 0 8 */
struct bpf_map * inner_map_meta; /* 8 8 */
void * security; /* 16 8 */
enum bpf_map_type map_type; /* 24 4 */
u32 key_size; /* 28 4 */
u32 value_size; /* 32 4 */
u32 max_entries; /* 36 4 */
u32 map_flags; /* 40 4 */
int spin_lock_off; /* 44 4 */
u32 id; /* 48 4 */
int numa_node; /* 52 4 */
u32 btf_key_type_id; /* 56 4 */
u32 btf_value_type_id; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct btf * btf; /* 64 8 */
struct bpf_map_memory memory; /* 72 16 */
bool unpriv_array; /* 88 1 */
bool frozen; /* 89 1 */
/* XXX 38 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
atomic64_t refcnt __attribute__((__aligned__(64))); /* 128 8 */
atomic64_t usercnt; /* 136 8 */
struct work_struct work; /* 144 32 */
char name[16]; /* 176 16 */
/* size: 192, cachelines: 3, members: 21 */
/* sum members: 154, holes: 1, sum holes: 38 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 38 */
} __attribute__((__aligned__(64)));
This patch, while modifying all users of bpf_map_inc, also cleans up its
interface to match bpf_map_put with separate operations for bpf_map_inc and
bpf_map_inc_with_uref (to match bpf_map_put and bpf_map_put_with_uref,
respectively). Also, given there are no users of bpf_map_inc_not_zero
specifying uref=true, remove uref flag and default to uref=false internally.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191117172806.2195367-2-andriin@fb.com
2019-11-17 17:28:02 +00:00
|
|
|
atomic64_t refcnt ____cacheline_aligned;
|
|
|
|
atomic64_t usercnt;
|
bpf: avoid false sharing of map refcount with max_entries
In addition to commit b2157399cc98 ("bpf: prevent out-of-bounds
speculation") also change the layout of struct bpf_map such that
false sharing of fast-path members like max_entries is avoided
when the maps reference counter is altered. Therefore enforce
them to be placed into separate cachelines.
pahole dump after change:
struct bpf_map {
const struct bpf_map_ops * ops; /* 0 8 */
struct bpf_map * inner_map_meta; /* 8 8 */
void * security; /* 16 8 */
enum bpf_map_type map_type; /* 24 4 */
u32 key_size; /* 28 4 */
u32 value_size; /* 32 4 */
u32 max_entries; /* 36 4 */
u32 map_flags; /* 40 4 */
u32 pages; /* 44 4 */
u32 id; /* 48 4 */
int numa_node; /* 52 4 */
bool unpriv_array; /* 56 1 */
/* XXX 7 bytes hole, try to pack */
/* --- cacheline 1 boundary (64 bytes) --- */
struct user_struct * user; /* 64 8 */
atomic_t refcnt; /* 72 4 */
atomic_t usercnt; /* 76 4 */
struct work_struct work; /* 80 32 */
char name[16]; /* 112 16 */
/* --- cacheline 2 boundary (128 bytes) --- */
/* size: 128, cachelines: 2, members: 17 */
/* sum members: 121, holes: 1, sum holes: 7 */
};
Now all entries in the first cacheline are read only throughout
the life time of the map, set up once during map creation. Overall
struct size and number of cachelines doesn't change from the
reordering. struct bpf_map is usually first member and embedded
in map structs in specific map implementations, so also avoid those
members to sit at the end where it could potentially share the
cacheline with first map values e.g. in the array since remote
CPUs could trigger map updates just as well for those (easily
dirtying members like max_entries intentionally as well) while
having subsequent values in cache.
Quoting from Google's Project Zero blog [1]:
Additionally, at least on the Intel machine on which this was
tested, bouncing modified cache lines between cores is slow,
apparently because the MESI protocol is used for cache coherence
[8]. Changing the reference counter of an eBPF array on one
physical CPU core causes the cache line containing the reference
counter to be bounced over to that CPU core, making reads of the
reference counter on all other CPU cores slow until the changed
reference counter has been written back to memory. Because the
length and the reference counter of an eBPF array are stored in
the same cache line, this also means that changing the reference
counter on one physical CPU core causes reads of the eBPF array's
length to be slow on other physical CPU cores (intentional false
sharing).
While this doesn't 'control' the out-of-bounds speculation through
masking the index as in commit b2157399cc98, triggering a manipulation
of the map's reference counter is really trivial, so lets not allow
to easily affect max_entries from it.
Splitting to separate cachelines also generally makes sense from
a performance perspective anyway in that fast-path won't have a
cache miss if the map gets pinned, reused in other progs, etc out
of control path, thus also avoids unintentional false sharing.
[1] https://googleprojectzero.blogspot.ch/2018/01/reading-privileged-memory-with-side.html
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-01-09 12:17:44 +00:00
|
|
|
struct work_struct work;
|
bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY
Add ability to memory-map contents of BPF array map. This is extremely useful
for working with BPF global data from userspace programs. It allows to avoid
typical bpf_map_{lookup,update}_elem operations, improving both performance
and usability.
There had to be special considerations for map freezing, to avoid having
writable memory view into a frozen map. To solve this issue, map freezing and
mmap-ing is happening under mutex now:
- if map is already frozen, no writable mapping is allowed;
- if map has writable memory mappings active (accounted in map->writecnt),
map freezing will keep failing with -EBUSY;
- once number of writable memory mappings drops to zero, map freezing can be
performed again.
Only non-per-CPU plain arrays are supported right now. Maps with spinlocks
can't be memory mapped either.
For BPF_F_MMAPABLE array, memory allocation has to be done through vmalloc()
to be mmap()'able. We also need to make sure that array data memory is
page-sized and page-aligned, so we over-allocate memory in such a way that
struct bpf_array is at the end of a single page of memory with array->value
being aligned with the start of the second page. On deallocation we need to
accomodate this memory arrangement to free vmalloc()'ed memory correctly.
One important consideration regarding how memory-mapping subsystem functions.
Memory-mapping subsystem provides few optional callbacks, among them open()
and close(). close() is called for each memory region that is unmapped, so
that users can decrease their reference counters and free up resources, if
necessary. open() is *almost* symmetrical: it's called for each memory region
that is being mapped, **except** the very first one. So bpf_map_mmap does
initial refcnt bump, while open() will do any extra ones after that. Thus
number of close() calls is equal to number of open() calls plus one more.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/bpf/20191117172806.2195367-4-andriin@fb.com
2019-11-17 17:28:04 +00:00
|
|
|
struct mutex freeze_mutex;
|
bpf: Fix toctou on read-only map's constant scalar tracking
Commit a23740ec43ba ("bpf: Track contents of read-only maps as scalars") is
checking whether maps are read-only both from BPF program side and user space
side, and then, given their content is constant, reading out their data via
map->ops->map_direct_value_addr() which is then subsequently used as known
scalar value for the register, that is, it is marked as __mark_reg_known()
with the read value at verification time. Before a23740ec43ba, the register
content was marked as an unknown scalar so the verifier could not make any
assumptions about the map content.
The current implementation however is prone to a TOCTOU race, meaning, the
value read as known scalar for the register is not guaranteed to be exactly
the same at a later point when the program is executed, and as such, the
prior made assumptions of the verifier with regards to the program will be
invalid which can cause issues such as OOB access, etc.
While the BPF_F_RDONLY_PROG map flag is always fixed and required to be
specified at map creation time, the map->frozen property is initially set to
false for the map given the map value needs to be populated, e.g. for global
data sections. Once complete, the loader "freezes" the map from user space
such that no subsequent updates/deletes are possible anymore. For the rest
of the lifetime of the map, this freeze one-time trigger cannot be undone
anymore after a successful BPF_MAP_FREEZE cmd return. Meaning, any new BPF_*
cmd calls which would update/delete map entries will be rejected with -EPERM
since map_get_sys_perms() removes the FMODE_CAN_WRITE permission. This also
means that pending update/delete map entries must still complete before this
guarantee is given. This corner case is not an issue for loaders since they
create and prepare such program private map in successive steps.
However, a malicious user is able to trigger this TOCTOU race in two different
ways: i) via userfaultfd, and ii) via batched updates. For i) userfaultfd is
used to expand the competition interval, so that map_update_elem() can modify
the contents of the map after map_freeze() and bpf_prog_load() were executed.
This works, because userfaultfd halts the parallel thread which triggered a
map_update_elem() at the time where we copy key/value from the user buffer and
this already passed the FMODE_CAN_WRITE capability test given at that time the
map was not "frozen". Then, the main thread performs the map_freeze() and
bpf_prog_load(), and once that had completed successfully, the other thread
is woken up to complete the pending map_update_elem() which then changes the
map content. For ii) the idea of the batched update is similar, meaning, when
there are a large number of updates to be processed, it can increase the
competition interval between the two. It is therefore possible in practice to
modify the contents of the map after executing map_freeze() and bpf_prog_load().
One way to fix both i) and ii) at the same time is to expand the use of the
map's map->writecnt. The latter was introduced in fc9702273e2e ("bpf: Add mmap()
support for BPF_MAP_TYPE_ARRAY") and further refined in 1f6cb19be2e2 ("bpf:
Prevent re-mmap()'ing BPF map as writable for initially r/o mapping") with
the rationale to make a writable mmap()'ing of a map mutually exclusive with
read-only freezing. The counter indicates writable mmap() mappings and then
prevents/fails the freeze operation. Its semantics can be expanded beyond
just mmap() by generally indicating ongoing write phases. This would essentially
span any parallel regular and batched flavor of update/delete operation and
then also have map_freeze() fail with -EBUSY. For the check_mem_access() in
the verifier we expand upon the bpf_map_is_rdonly() check ensuring that all
last pending writes have completed via bpf_map_write_active() test. Once the
map->frozen is set and bpf_map_write_active() indicates a map->writecnt of 0
only then we are really guaranteed to use the map's data as known constants.
For map->frozen being set and pending writes in process of still being completed
we fall back to marking that register as unknown scalar so we don't end up
making assumptions about it. With this, both TOCTOU reproducers from i) and
ii) are fixed.
Note that the map->writecnt has been converted into a atomic64 in the fix in
order to avoid a double freeze_mutex mutex_{un,}lock() pair when updating
map->writecnt in the various map update/delete BPF_* cmd flavors. Spanning
the freeze_mutex over entire map update/delete operations in syscall side
would not be possible due to then causing everything to be serialized.
Similarly, something like synchronize_rcu() after setting map->frozen to wait
for update/deletes to complete is not possible either since it would also
have to span the user copy which can sleep. On the libbpf side, this won't
break d66562fba1ce ("libbpf: Add BPF object skeleton support") as the
anonymous mmap()-ed "map initialization image" is remapped as a BPF map-backed
mmap()-ed memory where for .rodata it's non-writable.
Fixes: a23740ec43ba ("bpf: Track contents of read-only maps as scalars")
Reported-by: w1tcher.bupt@gmail.com
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2021-11-09 18:48:08 +00:00
|
|
|
atomic64_t writecnt;
|
2022-01-21 10:10:02 +00:00
|
|
|
/* 'Ownership' of program-containing map is claimed by the first program
|
|
|
|
* that is going to use this map or by the first program which FD is
|
|
|
|
* stored in the map to make sure that all callers and callees have the
|
|
|
|
* same prog type, JITed flag and xdp_has_frags flag.
|
|
|
|
*/
|
|
|
|
struct {
|
|
|
|
spinlock_t lock;
|
|
|
|
enum bpf_prog_type type;
|
|
|
|
bool jited;
|
|
|
|
bool xdp_has_frags;
|
|
|
|
} owner;
|
2022-04-24 21:48:53 +00:00
|
|
|
bool bypass_spec_v1;
|
|
|
|
bool frozen; /* write-once; write-protected by freeze_mutex */
|
2014-09-26 07:16:57 +00:00
|
|
|
};
|
|
|
|
|
2019-01-31 23:40:04 +00:00
|
|
|
static inline bool map_value_has_spin_lock(const struct bpf_map *map)
|
|
|
|
{
|
|
|
|
return map->spin_lock_off >= 0;
|
|
|
|
}
|
|
|
|
|
2021-07-15 00:54:10 +00:00
|
|
|
static inline bool map_value_has_timer(const struct bpf_map *map)
|
2019-01-31 23:40:04 +00:00
|
|
|
{
|
2021-07-15 00:54:10 +00:00
|
|
|
return map->timer_off >= 0;
|
2019-01-31 23:40:04 +00:00
|
|
|
}
|
|
|
|
|
bpf: Allow storing unreferenced kptr in map
This commit introduces a new pointer type 'kptr' which can be embedded
in a map value to hold a PTR_TO_BTF_ID stored by a BPF program during
its invocation. When storing such a kptr, BPF program's PTR_TO_BTF_ID
register must have the same type as in the map value's BTF, and loading
a kptr marks the destination register as PTR_TO_BTF_ID with the correct
kernel BTF and BTF ID.
Such kptr are unreferenced, i.e. by the time another invocation of the
BPF program loads this pointer, the object which the pointer points to
may not longer exist. Since PTR_TO_BTF_ID loads (using BPF_LDX) are
patched to PROBE_MEM loads by the verifier, it would safe to allow user
to still access such invalid pointer, but passing such pointers into
BPF helpers and kfuncs should not be permitted. A future patch in this
series will close this gap.
The flexibility offered by allowing programs to dereference such invalid
pointers while being safe at runtime frees the verifier from doing
complex lifetime tracking. As long as the user may ensure that the
object remains valid, it can ensure data read by it from the kernel
object is valid.
The user indicates that a certain pointer must be treated as kptr
capable of accepting stores of PTR_TO_BTF_ID of a certain type, by using
a BTF type tag 'kptr' on the pointed to type of the pointer. Then, this
information is recorded in the object BTF which will be passed into the
kernel by way of map's BTF information. The name and kind from the map
value BTF is used to look up the in-kernel type, and the actual BTF and
BTF ID is recorded in the map struct in a new kptr_off_tab member. For
now, only storing pointers to structs is permitted.
An example of this specification is shown below:
#define __kptr __attribute__((btf_type_tag("kptr")))
struct map_value {
...
struct task_struct __kptr *task;
...
};
Then, in a BPF program, user may store PTR_TO_BTF_ID with the type
task_struct into the map, and then load it later.
Note that the destination register is marked PTR_TO_BTF_ID_OR_NULL, as
the verifier cannot know whether the value is NULL or not statically, it
must treat all potential loads at that map value offset as loading a
possibly NULL pointer.
Only BPF_LDX, BPF_STX, and BPF_ST (with insn->imm = 0 to denote NULL)
are allowed instructions that can access such a pointer. On BPF_LDX, the
destination register is updated to be a PTR_TO_BTF_ID, and on BPF_STX,
it is checked whether the source register type is a PTR_TO_BTF_ID with
same BTF type as specified in the map BTF. The access size must always
be BPF_DW.
For the map in map support, the kptr_off_tab for outer map is copied
from the inner map's kptr_off_tab. It was chosen to do a deep copy
instead of introducing a refcount to kptr_off_tab, because the copy only
needs to be done when paramterizing using inner_map_fd in the map in map
case, hence would be unnecessary for all other users.
It is not permitted to use MAP_FREEZE command and mmap for BPF map
having kptrs, similar to the bpf_timer case. A kptr also requires that
BPF program has both read and write access to the map (hence both
BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG are disallowed).
Note that check_map_access must be called from both
check_helper_mem_access and for the BPF instructions, hence the kptr
check must distinguish between ACCESS_DIRECT and ACCESS_HELPER, and
reject ACCESS_HELPER cases. We rename stack_access_src to bpf_access_src
and reuse it for this purpose.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-2-memxor@gmail.com
2022-04-24 21:48:49 +00:00
|
|
|
static inline bool map_value_has_kptrs(const struct bpf_map *map)
|
|
|
|
{
|
|
|
|
return !IS_ERR_OR_NULL(map->kptr_off_tab);
|
|
|
|
}
|
|
|
|
|
2021-07-15 00:54:10 +00:00
|
|
|
static inline void check_and_init_map_value(struct bpf_map *map, void *dst)
|
|
|
|
{
|
|
|
|
if (unlikely(map_value_has_spin_lock(map)))
|
bpf: Fix a bpf_timer initialization issue
The patch in [1] intends to fix a bpf_timer related issue,
but the fix caused existing 'timer' selftest to fail with
hang or some random errors. After some debug, I found
an issue with check_and_init_map_value() in the hashtab.c.
More specifically, in hashtab.c, we have code
l_new = bpf_map_kmalloc_node(&htab->map, ...)
check_and_init_map_value(&htab->map, l_new...)
Note that bpf_map_kmalloc_node() does not do initialization
so l_new contains random value.
The function check_and_init_map_value() intends to zero the
bpf_spin_lock and bpf_timer if they exist in the map.
But I found bpf_spin_lock is zero'ed but bpf_timer is not zero'ed.
With [1], later copy_map_value() skips copying of
bpf_spin_lock and bpf_timer. The non-zero bpf_timer caused
random failures for 'timer' selftest.
Without [1], for both bpf_spin_lock and bpf_timer case,
bpf_timer will be zero'ed, so 'timer' self test is okay.
For check_and_init_map_value(), why bpf_spin_lock is zero'ed
properly while bpf_timer not. In bpf uapi header, we have
struct bpf_spin_lock {
__u32 val;
};
struct bpf_timer {
__u64 :64;
__u64 :64;
} __attribute__((aligned(8)));
The initialization code:
*(struct bpf_spin_lock *)(dst + map->spin_lock_off) =
(struct bpf_spin_lock){};
*(struct bpf_timer *)(dst + map->timer_off) =
(struct bpf_timer){};
It appears the compiler has no obligation to initialize anonymous fields.
For example, let us use clang with bpf target as below:
$ cat t.c
struct bpf_timer {
unsigned long long :64;
};
struct bpf_timer2 {
unsigned long long a;
};
void test(struct bpf_timer *t) {
*t = (struct bpf_timer){};
}
void test2(struct bpf_timer2 *t) {
*t = (struct bpf_timer2){};
}
$ clang -target bpf -O2 -c -g t.c
$ llvm-objdump -d t.o
...
0000000000000000 <test>:
0: 95 00 00 00 00 00 00 00 exit
0000000000000008 <test2>:
1: b7 02 00 00 00 00 00 00 r2 = 0
2: 7b 21 00 00 00 00 00 00 *(u64 *)(r1 + 0) = r2
3: 95 00 00 00 00 00 00 00 exit
gcc11.2 does not have the above issue. But from
INTERNATIONAL STANDARD ©ISO/IEC ISO/IEC 9899:201x
Programming languages — C
http://www.open-std.org/Jtc1/sc22/wg14/www/docs/n1547.pdf
page 157:
Except where explicitly stated otherwise, for the purposes of
this subclause unnamed members of objects of structure and union
type do not participate in initialization. Unnamed members of
structure objects have indeterminate value even after initialization.
To fix the problem, let use memset for bpf_timer case in
check_and_init_map_value(). For consistency, memset is also
used for bpf_spin_lock case.
[1] https://lore.kernel.org/bpf/20220209070324.1093182-2-memxor@gmail.com/
Fixes: 68134668c17f3 ("bpf: Add map side support for bpf timers.")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220211194953.3142152-1-yhs@fb.com
2022-02-11 19:49:53 +00:00
|
|
|
memset(dst + map->spin_lock_off, 0, sizeof(struct bpf_spin_lock));
|
2021-07-15 00:54:10 +00:00
|
|
|
if (unlikely(map_value_has_timer(map)))
|
bpf: Fix a bpf_timer initialization issue
The patch in [1] intends to fix a bpf_timer related issue,
but the fix caused existing 'timer' selftest to fail with
hang or some random errors. After some debug, I found
an issue with check_and_init_map_value() in the hashtab.c.
More specifically, in hashtab.c, we have code
l_new = bpf_map_kmalloc_node(&htab->map, ...)
check_and_init_map_value(&htab->map, l_new...)
Note that bpf_map_kmalloc_node() does not do initialization
so l_new contains random value.
The function check_and_init_map_value() intends to zero the
bpf_spin_lock and bpf_timer if they exist in the map.
But I found bpf_spin_lock is zero'ed but bpf_timer is not zero'ed.
With [1], later copy_map_value() skips copying of
bpf_spin_lock and bpf_timer. The non-zero bpf_timer caused
random failures for 'timer' selftest.
Without [1], for both bpf_spin_lock and bpf_timer case,
bpf_timer will be zero'ed, so 'timer' self test is okay.
For check_and_init_map_value(), why bpf_spin_lock is zero'ed
properly while bpf_timer not. In bpf uapi header, we have
struct bpf_spin_lock {
__u32 val;
};
struct bpf_timer {
__u64 :64;
__u64 :64;
} __attribute__((aligned(8)));
The initialization code:
*(struct bpf_spin_lock *)(dst + map->spin_lock_off) =
(struct bpf_spin_lock){};
*(struct bpf_timer *)(dst + map->timer_off) =
(struct bpf_timer){};
It appears the compiler has no obligation to initialize anonymous fields.
For example, let us use clang with bpf target as below:
$ cat t.c
struct bpf_timer {
unsigned long long :64;
};
struct bpf_timer2 {
unsigned long long a;
};
void test(struct bpf_timer *t) {
*t = (struct bpf_timer){};
}
void test2(struct bpf_timer2 *t) {
*t = (struct bpf_timer2){};
}
$ clang -target bpf -O2 -c -g t.c
$ llvm-objdump -d t.o
...
0000000000000000 <test>:
0: 95 00 00 00 00 00 00 00 exit
0000000000000008 <test2>:
1: b7 02 00 00 00 00 00 00 r2 = 0
2: 7b 21 00 00 00 00 00 00 *(u64 *)(r1 + 0) = r2
3: 95 00 00 00 00 00 00 00 exit
gcc11.2 does not have the above issue. But from
INTERNATIONAL STANDARD ©ISO/IEC ISO/IEC 9899:201x
Programming languages — C
http://www.open-std.org/Jtc1/sc22/wg14/www/docs/n1547.pdf
page 157:
Except where explicitly stated otherwise, for the purposes of
this subclause unnamed members of objects of structure and union
type do not participate in initialization. Unnamed members of
structure objects have indeterminate value even after initialization.
To fix the problem, let use memset for bpf_timer case in
check_and_init_map_value(). For consistency, memset is also
used for bpf_spin_lock case.
[1] https://lore.kernel.org/bpf/20220209070324.1093182-2-memxor@gmail.com/
Fixes: 68134668c17f3 ("bpf: Add map side support for bpf timers.")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220211194953.3142152-1-yhs@fb.com
2022-02-11 19:49:53 +00:00
|
|
|
memset(dst + map->timer_off, 0, sizeof(struct bpf_timer));
|
2022-04-24 21:48:53 +00:00
|
|
|
if (unlikely(map_value_has_kptrs(map))) {
|
|
|
|
struct bpf_map_value_off *tab = map->kptr_off_tab;
|
|
|
|
int i;
|
|
|
|
|
|
|
|
for (i = 0; i < tab->nr_off; i++)
|
|
|
|
*(u64 *)(dst + tab->off[i].offset) = 0;
|
|
|
|
}
|
2021-07-15 00:54:10 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
/* copy everything but bpf_spin_lock and bpf_timer. There could be one of each. */
|
2019-01-31 23:40:04 +00:00
|
|
|
static inline void copy_map_value(struct bpf_map *map, void *dst, void *src)
|
|
|
|
{
|
2022-04-24 21:48:53 +00:00
|
|
|
u32 curr_off = 0;
|
|
|
|
int i;
|
2021-07-15 00:54:10 +00:00
|
|
|
|
2022-04-24 21:48:53 +00:00
|
|
|
if (likely(!map->off_arr)) {
|
|
|
|
memcpy(dst, src, map->value_size);
|
|
|
|
return;
|
2021-07-15 00:54:10 +00:00
|
|
|
}
|
2019-01-31 23:40:04 +00:00
|
|
|
|
2022-04-24 21:48:53 +00:00
|
|
|
for (i = 0; i < map->off_arr->cnt; i++) {
|
|
|
|
u32 next_off = map->off_arr->field_off[i];
|
|
|
|
|
|
|
|
memcpy(dst + curr_off, src + curr_off, next_off - curr_off);
|
|
|
|
curr_off += map->off_arr->field_sz[i];
|
2019-01-31 23:40:04 +00:00
|
|
|
}
|
2022-04-24 21:48:53 +00:00
|
|
|
memcpy(dst + curr_off, src + curr_off, map->value_size - curr_off);
|
2019-01-31 23:40:04 +00:00
|
|
|
}
|
2019-01-31 23:40:09 +00:00
|
|
|
void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,
|
|
|
|
bool lock_src);
|
bpf: Introduce bpf timers.
Introduce 'struct bpf_timer { __u64 :64; __u64 :64; };' that can be embedded
in hash/array/lru maps as a regular field and helpers to operate on it:
// Initialize the timer.
// First 4 bits of 'flags' specify clockid.
// Only CLOCK_MONOTONIC, CLOCK_REALTIME, CLOCK_BOOTTIME are allowed.
long bpf_timer_init(struct bpf_timer *timer, struct bpf_map *map, int flags);
// Configure the timer to call 'callback_fn' static function.
long bpf_timer_set_callback(struct bpf_timer *timer, void *callback_fn);
// Arm the timer to expire 'nsec' nanoseconds from the current time.
long bpf_timer_start(struct bpf_timer *timer, u64 nsec, u64 flags);
// Cancel the timer and wait for callback_fn to finish if it was running.
long bpf_timer_cancel(struct bpf_timer *timer);
Here is how BPF program might look like:
struct map_elem {
int counter;
struct bpf_timer timer;
};
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 1000);
__type(key, int);
__type(value, struct map_elem);
} hmap SEC(".maps");
static int timer_cb(void *map, int *key, struct map_elem *val);
/* val points to particular map element that contains bpf_timer. */
SEC("fentry/bpf_fentry_test1")
int BPF_PROG(test1, int a)
{
struct map_elem *val;
int key = 0;
val = bpf_map_lookup_elem(&hmap, &key);
if (val) {
bpf_timer_init(&val->timer, &hmap, CLOCK_REALTIME);
bpf_timer_set_callback(&val->timer, timer_cb);
bpf_timer_start(&val->timer, 1000 /* call timer_cb2 in 1 usec */, 0);
}
}
This patch adds helper implementations that rely on hrtimers
to call bpf functions as timers expire.
The following patches add necessary safety checks.
Only programs with CAP_BPF are allowed to use bpf_timer.
The amount of timers used by the program is constrained by
the memcg recorded at map creation time.
The bpf_timer_init() helper needs explicit 'map' argument because inner maps
are dynamic and not known at load time. While the bpf_timer_set_callback() is
receiving hidden 'aux->prog' argument supplied by the verifier.
The prog pointer is needed to do refcnting of bpf program to make sure that
program doesn't get freed while the timer is armed. This approach relies on
"user refcnt" scheme used in prog_array that stores bpf programs for
bpf_tail_call. The bpf_timer_set_callback() will increment the prog refcnt which is
paired with bpf_timer_cancel() that will drop the prog refcnt. The
ops->map_release_uref is responsible for cancelling the timers and dropping
prog refcnt when user space reference to a map reaches zero.
This uref approach is done to make sure that Ctrl-C of user space process will
not leave timers running forever unless the user space explicitly pinned a map
that contained timers in bpffs.
bpf_timer_init() and bpf_timer_set_callback() will return -EPERM if map doesn't
have user references (is not held by open file descriptor from user space and
not pinned in bpffs).
The bpf_map_delete_elem() and bpf_map_update_elem() operations cancel
and free the timer if given map element had it allocated.
"bpftool map update" command can be used to cancel timers.
The 'struct bpf_timer' is explicitly __attribute__((aligned(8))) because
'__u64 :64' has 1 byte alignment of 8 byte padding.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210715005417.78572-4-alexei.starovoitov@gmail.com
2021-07-15 00:54:09 +00:00
|
|
|
void bpf_timer_cancel_and_free(void *timer);
|
2020-03-14 01:02:09 +00:00
|
|
|
int bpf_obj_name_cpy(char *dst, const char *src, unsigned int size);
|
2019-01-31 23:40:04 +00:00
|
|
|
|
2018-07-17 17:53:25 +00:00
|
|
|
struct bpf_offload_dev;
|
2018-01-12 04:29:09 +00:00
|
|
|
struct bpf_offloaded_map;
|
|
|
|
|
|
|
|
struct bpf_map_dev_ops {
|
|
|
|
int (*map_get_next_key)(struct bpf_offloaded_map *map,
|
|
|
|
void *key, void *next_key);
|
|
|
|
int (*map_lookup_elem)(struct bpf_offloaded_map *map,
|
|
|
|
void *key, void *value);
|
|
|
|
int (*map_update_elem)(struct bpf_offloaded_map *map,
|
|
|
|
void *key, void *value, u64 flags);
|
|
|
|
int (*map_delete_elem)(struct bpf_offloaded_map *map, void *key);
|
|
|
|
};
|
|
|
|
|
|
|
|
struct bpf_offloaded_map {
|
|
|
|
struct bpf_map map;
|
|
|
|
struct net_device *netdev;
|
|
|
|
const struct bpf_map_dev_ops *dev_ops;
|
|
|
|
void *dev_priv;
|
|
|
|
struct list_head offloads;
|
|
|
|
};
|
|
|
|
|
|
|
|
static inline struct bpf_offloaded_map *map_to_offmap(struct bpf_map *map)
|
|
|
|
{
|
|
|
|
return container_of(map, struct bpf_offloaded_map, map);
|
|
|
|
}
|
|
|
|
|
2018-05-04 01:37:08 +00:00
|
|
|
static inline bool bpf_map_offload_neutral(const struct bpf_map *map)
|
|
|
|
{
|
|
|
|
return map->map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY;
|
|
|
|
}
|
|
|
|
|
2018-04-18 22:56:03 +00:00
|
|
|
static inline bool bpf_map_support_seq_show(const struct bpf_map *map)
|
|
|
|
{
|
bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 00:35:05 +00:00
|
|
|
return (map->btf_value_type_id || map->btf_vmlinux_value_type_id) &&
|
|
|
|
map->ops->map_seq_show_elem;
|
2018-04-18 22:56:03 +00:00
|
|
|
}
|
|
|
|
|
2018-08-11 23:59:17 +00:00
|
|
|
int map_check_no_btf(const struct bpf_map *map,
|
2018-12-10 23:43:00 +00:00
|
|
|
const struct btf *btf,
|
2018-08-11 23:59:17 +00:00
|
|
|
const struct btf_type *key_type,
|
|
|
|
const struct btf_type *value_type);
|
|
|
|
|
2020-08-28 01:18:06 +00:00
|
|
|
bool bpf_map_meta_equal(const struct bpf_map *meta0,
|
|
|
|
const struct bpf_map *meta1);
|
|
|
|
|
2018-01-12 04:29:09 +00:00
|
|
|
extern const struct bpf_map_ops bpf_map_offload_ops;
|
|
|
|
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
/* bpf_type_flag contains a set of flags that are applicable to the values of
|
|
|
|
* arg_type, ret_type and reg_type. For example, a pointer value may be null,
|
|
|
|
* or a memory is read-only. We classify types into two categories: base types
|
|
|
|
* and extended types. Extended types are base types combined with a type flag.
|
|
|
|
*
|
|
|
|
* Currently there are no more than 32 base types in arg_type, ret_type and
|
|
|
|
* reg_types.
|
|
|
|
*/
|
|
|
|
#define BPF_BASE_TYPE_BITS 8
|
|
|
|
|
|
|
|
enum bpf_type_flag {
|
|
|
|
/* PTR may be NULL. */
|
|
|
|
PTR_MAYBE_NULL = BIT(0 + BPF_BASE_TYPE_BITS),
|
|
|
|
|
2021-12-17 00:31:51 +00:00
|
|
|
/* MEM is read-only. When applied on bpf_arg, it indicates the arg is
|
|
|
|
* compatible with both mutable and immutable memory.
|
|
|
|
*/
|
2021-12-17 00:31:48 +00:00
|
|
|
MEM_RDONLY = BIT(1 + BPF_BASE_TYPE_BITS),
|
|
|
|
|
2022-01-13 11:11:30 +00:00
|
|
|
/* MEM was "allocated" from a different helper, and cannot be mixed
|
|
|
|
* with regular non-MEM_ALLOC'ed MEM types.
|
|
|
|
*/
|
|
|
|
MEM_ALLOC = BIT(2 + BPF_BASE_TYPE_BITS),
|
|
|
|
|
bpf: reject program if a __user tagged memory accessed in kernel way
BPF verifier supports direct memory access for BPF_PROG_TYPE_TRACING type
of bpf programs, e.g., a->b. If "a" is a pointer
pointing to kernel memory, bpf verifier will allow user to write
code in C like a->b and the verifier will translate it to a kernel
load properly. If "a" is a pointer to user memory, it is expected
that bpf developer should be bpf_probe_read_user() helper to
get the value a->b. Without utilizing BTF __user tagging information,
current verifier will assume that a->b is a kernel memory access
and this may generate incorrect result.
Now BTF contains __user information, it can check whether the
pointer points to a user memory or not. If it is, the verifier
can reject the program and force users to use bpf_probe_read_user()
helper explicitly.
In the future, we can easily extend btf_add_space for other
address space tagging, for example, rcu/percpu etc.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20220127154606.654961-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-01-27 15:46:06 +00:00
|
|
|
/* MEM is in user address space. */
|
|
|
|
MEM_USER = BIT(3 + BPF_BASE_TYPE_BITS),
|
|
|
|
|
2022-03-04 19:16:56 +00:00
|
|
|
/* MEM is a percpu memory. MEM_PERCPU tags PTR_TO_BTF_ID. When tagged
|
|
|
|
* with MEM_PERCPU, PTR_TO_BTF_ID _cannot_ be directly accessed. In
|
|
|
|
* order to drop this tag, it must be passed into bpf_per_cpu_ptr()
|
|
|
|
* or bpf_this_cpu_ptr(), which will return the pointer corresponding
|
|
|
|
* to the specified cpu.
|
|
|
|
*/
|
|
|
|
MEM_PERCPU = BIT(4 + BPF_BASE_TYPE_BITS),
|
|
|
|
|
bpf: Tag argument to be released in bpf_func_proto
Add a new type flag for bpf_arg_type that when set tells verifier that
for a release function, that argument's register will be the one for
which meta.ref_obj_id will be set, and which will then be released
using release_reference. To capture the regno, introduce a new field
release_regno in bpf_call_arg_meta.
This would be required in the next patch, where we may either pass NULL
or a refcounted pointer as an argument to the release function
bpf_kptr_xchg. Just releasing only when meta.ref_obj_id is set is not
enough, as there is a case where the type of argument needed matches,
but the ref_obj_id is set to 0. Hence, we must enforce that whenever
meta.ref_obj_id is zero, the register that is to be released can only
be NULL for a release function.
Since we now indicate whether an argument is to be released in
bpf_func_proto itself, is_release_function helper has lost its utitlity,
hence refactor code to work without it, and just rely on
meta.release_regno to know when to release state for a ref_obj_id.
Still, the restriction of one release argument and only one ref_obj_id
passed to BPF helper or kfunc remains. This may be lifted in the future.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-3-memxor@gmail.com
2022-04-24 21:48:50 +00:00
|
|
|
/* Indicates that the argument will be released. */
|
|
|
|
OBJ_RELEASE = BIT(5 + BPF_BASE_TYPE_BITS),
|
|
|
|
|
bpf: Prevent escaping of kptr loaded from maps
While we can guarantee that even for unreferenced kptr, the object
pointer points to being freed etc. can be handled by the verifier's
exception handling (normal load patching to PROBE_MEM loads), we still
cannot allow the user to pass these pointers to BPF helpers and kfunc,
because the same exception handling won't be done for accesses inside
the kernel. The same is true if a referenced pointer is loaded using
normal load instruction. Since the reference is not guaranteed to be
held while the pointer is used, it must be marked as untrusted.
Hence introduce a new type flag, PTR_UNTRUSTED, which is used to mark
all registers loading unreferenced and referenced kptr from BPF maps,
and ensure they can never escape the BPF program and into the kernel by
way of calling stable/unstable helpers.
In check_ptr_to_btf_access, the !type_may_be_null check to reject type
flags is still correct, as apart from PTR_MAYBE_NULL, only MEM_USER,
MEM_PERCPU, and PTR_UNTRUSTED may be set for PTR_TO_BTF_ID. The first
two are checked inside the function and rejected using a proper error
message, but we still want to allow dereference of untrusted case.
Also, we make sure to inherit PTR_UNTRUSTED when chain of pointers are
walked, so that this flag is never dropped once it has been set on a
PTR_TO_BTF_ID (i.e. trusted to untrusted transition can only be in one
direction).
In convert_ctx_accesses, extend the switch case to consider untrusted
PTR_TO_BTF_ID in addition to normal PTR_TO_BTF_ID for PROBE_MEM
conversion for BPF_LDX.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-5-memxor@gmail.com
2022-04-24 21:48:52 +00:00
|
|
|
/* PTR is not trusted. This is only used with PTR_TO_BTF_ID, to mark
|
|
|
|
* unreferenced and referenced kptr loaded from map value using a load
|
|
|
|
* instruction, so that they can only be dereferenced but not escape the
|
|
|
|
* BPF program into the kernel (i.e. cannot be passed as arguments to
|
|
|
|
* kfunc or bpf helpers).
|
|
|
|
*/
|
|
|
|
PTR_UNTRUSTED = BIT(6 + BPF_BASE_TYPE_BITS),
|
|
|
|
|
2022-05-09 22:42:52 +00:00
|
|
|
MEM_UNINIT = BIT(7 + BPF_BASE_TYPE_BITS),
|
|
|
|
|
bpf: Add verifier support for dynptrs
This patch adds the bulk of the verifier work for supporting dynamic
pointers (dynptrs) in bpf.
A bpf_dynptr is opaque to the bpf program. It is a 16-byte structure
defined internally as:
struct bpf_dynptr_kern {
void *data;
u32 size;
u32 offset;
} __aligned(8);
The upper 8 bits of *size* is reserved (it contains extra metadata about
read-only status and dynptr type). Consequently, a dynptr only supports
memory less than 16 MB.
There are different types of dynptrs (eg malloc, ringbuf, ...). In this
patchset, the most basic one, dynptrs to a bpf program's local memory,
is added. For now only local memory that is of reg type PTR_TO_MAP_VALUE
is supported.
In the verifier, dynptr state information will be tracked in stack
slots. When the program passes in an uninitialized dynptr
(ARG_PTR_TO_DYNPTR | MEM_UNINIT), the stack slots corresponding
to the frame pointer where the dynptr resides at are marked
STACK_DYNPTR. For helper functions that take in initialized dynptrs (eg
bpf_dynptr_read + bpf_dynptr_write which are added later in this
patchset), the verifier enforces that the dynptr has been initialized
properly by checking that their corresponding stack slots have been
marked as STACK_DYNPTR.
The 6th patch in this patchset adds test cases that the verifier should
successfully reject, such as for example attempting to use a dynptr
after doing a direct write into it inside the bpf program.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20220523210712.3641569-2-joannelkoong@gmail.com
2022-05-23 21:07:07 +00:00
|
|
|
/* DYNPTR points to memory local to the bpf program. */
|
|
|
|
DYNPTR_TYPE_LOCAL = BIT(8 + BPF_BASE_TYPE_BITS),
|
|
|
|
|
2022-05-23 21:07:09 +00:00
|
|
|
/* DYNPTR points to a ringbuf record. */
|
|
|
|
DYNPTR_TYPE_RINGBUF = BIT(9 + BPF_BASE_TYPE_BITS),
|
|
|
|
|
2022-06-15 13:48:43 +00:00
|
|
|
/* Size is known at compile time. */
|
|
|
|
MEM_FIXED_SIZE = BIT(10 + BPF_BASE_TYPE_BITS),
|
|
|
|
|
2022-05-09 22:42:52 +00:00
|
|
|
__BPF_TYPE_FLAG_MAX,
|
|
|
|
__BPF_TYPE_LAST_FLAG = __BPF_TYPE_FLAG_MAX - 1,
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
};
|
|
|
|
|
2022-05-23 21:07:09 +00:00
|
|
|
#define DYNPTR_TYPE_FLAG_MASK (DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF)
|
bpf: Add verifier support for dynptrs
This patch adds the bulk of the verifier work for supporting dynamic
pointers (dynptrs) in bpf.
A bpf_dynptr is opaque to the bpf program. It is a 16-byte structure
defined internally as:
struct bpf_dynptr_kern {
void *data;
u32 size;
u32 offset;
} __aligned(8);
The upper 8 bits of *size* is reserved (it contains extra metadata about
read-only status and dynptr type). Consequently, a dynptr only supports
memory less than 16 MB.
There are different types of dynptrs (eg malloc, ringbuf, ...). In this
patchset, the most basic one, dynptrs to a bpf program's local memory,
is added. For now only local memory that is of reg type PTR_TO_MAP_VALUE
is supported.
In the verifier, dynptr state information will be tracked in stack
slots. When the program passes in an uninitialized dynptr
(ARG_PTR_TO_DYNPTR | MEM_UNINIT), the stack slots corresponding
to the frame pointer where the dynptr resides at are marked
STACK_DYNPTR. For helper functions that take in initialized dynptrs (eg
bpf_dynptr_read + bpf_dynptr_write which are added later in this
patchset), the verifier enforces that the dynptr has been initialized
properly by checking that their corresponding stack slots have been
marked as STACK_DYNPTR.
The 6th patch in this patchset adds test cases that the verifier should
successfully reject, such as for example attempting to use a dynptr
after doing a direct write into it inside the bpf program.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20220523210712.3641569-2-joannelkoong@gmail.com
2022-05-23 21:07:07 +00:00
|
|
|
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
/* Max number of base types. */
|
|
|
|
#define BPF_BASE_TYPE_LIMIT (1UL << BPF_BASE_TYPE_BITS)
|
|
|
|
|
|
|
|
/* Max number of all types. */
|
|
|
|
#define BPF_TYPE_LIMIT (__BPF_TYPE_LAST_FLAG | (__BPF_TYPE_LAST_FLAG - 1))
|
|
|
|
|
bpf: verifier (add verifier core)
This patch adds verifier core which simulates execution of every insn and
records the state of registers and program stack. Every branch instruction seen
during simulation is pushed into state stack. When verifier reaches BPF_EXIT,
it pops the state from the stack and continues until it reaches BPF_EXIT again.
For program:
1: bpf_mov r1, xxx
2: if (r1 == 0) goto 5
3: bpf_mov r0, 1
4: goto 6
5: bpf_mov r0, 2
6: bpf_exit
The verifier will walk insns: 1, 2, 3, 4, 6
then it will pop the state recorded at insn#2 and will continue: 5, 6
This way it walks all possible paths through the program and checks all
possible values of registers. While doing so, it checks for:
- invalid instructions
- uninitialized register access
- uninitialized stack access
- misaligned stack access
- out of range stack access
- invalid calling convention
- instruction encoding is not using reserved fields
Kernel subsystem configures the verifier with two callbacks:
- bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
that provides information to the verifer which fields of 'ctx'
are accessible (remember 'ctx' is the first argument to eBPF program)
- const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id);
returns argument constraints of kernel helper functions that eBPF program
may call, so that verifier can checks that R1-R5 types match the prototype
More details in Documentation/networking/filter.txt and in kernel/bpf/verifier.c
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:17:06 +00:00
|
|
|
/* function argument constraints */
|
|
|
|
enum bpf_arg_type {
|
2015-03-12 16:21:42 +00:00
|
|
|
ARG_DONTCARE = 0, /* unused argument in helper function */
|
bpf: verifier (add verifier core)
This patch adds verifier core which simulates execution of every insn and
records the state of registers and program stack. Every branch instruction seen
during simulation is pushed into state stack. When verifier reaches BPF_EXIT,
it pops the state from the stack and continues until it reaches BPF_EXIT again.
For program:
1: bpf_mov r1, xxx
2: if (r1 == 0) goto 5
3: bpf_mov r0, 1
4: goto 6
5: bpf_mov r0, 2
6: bpf_exit
The verifier will walk insns: 1, 2, 3, 4, 6
then it will pop the state recorded at insn#2 and will continue: 5, 6
This way it walks all possible paths through the program and checks all
possible values of registers. While doing so, it checks for:
- invalid instructions
- uninitialized register access
- uninitialized stack access
- misaligned stack access
- out of range stack access
- invalid calling convention
- instruction encoding is not using reserved fields
Kernel subsystem configures the verifier with two callbacks:
- bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
that provides information to the verifer which fields of 'ctx'
are accessible (remember 'ctx' is the first argument to eBPF program)
- const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id);
returns argument constraints of kernel helper functions that eBPF program
may call, so that verifier can checks that R1-R5 types match the prototype
More details in Documentation/networking/filter.txt and in kernel/bpf/verifier.c
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:17:06 +00:00
|
|
|
|
|
|
|
/* the following constraints used to prototype
|
|
|
|
* bpf_map_lookup/update/delete_elem() functions
|
|
|
|
*/
|
|
|
|
ARG_CONST_MAP_PTR, /* const argument used as pointer to bpf_map */
|
|
|
|
ARG_PTR_TO_MAP_KEY, /* pointer to stack used as map key */
|
|
|
|
ARG_PTR_TO_MAP_VALUE, /* pointer to stack used as map value */
|
|
|
|
|
2022-05-09 22:42:52 +00:00
|
|
|
/* Used to prototype bpf_memcmp() and other functions that access data
|
|
|
|
* on eBPF program stack
|
bpf: verifier (add verifier core)
This patch adds verifier core which simulates execution of every insn and
records the state of registers and program stack. Every branch instruction seen
during simulation is pushed into state stack. When verifier reaches BPF_EXIT,
it pops the state from the stack and continues until it reaches BPF_EXIT again.
For program:
1: bpf_mov r1, xxx
2: if (r1 == 0) goto 5
3: bpf_mov r0, 1
4: goto 6
5: bpf_mov r0, 2
6: bpf_exit
The verifier will walk insns: 1, 2, 3, 4, 6
then it will pop the state recorded at insn#2 and will continue: 5, 6
This way it walks all possible paths through the program and checks all
possible values of registers. While doing so, it checks for:
- invalid instructions
- uninitialized register access
- uninitialized stack access
- misaligned stack access
- out of range stack access
- invalid calling convention
- instruction encoding is not using reserved fields
Kernel subsystem configures the verifier with two callbacks:
- bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
that provides information to the verifer which fields of 'ctx'
are accessible (remember 'ctx' is the first argument to eBPF program)
- const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id);
returns argument constraints of kernel helper functions that eBPF program
may call, so that verifier can checks that R1-R5 types match the prototype
More details in Documentation/networking/filter.txt and in kernel/bpf/verifier.c
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:17:06 +00:00
|
|
|
*/
|
2017-01-09 18:19:50 +00:00
|
|
|
ARG_PTR_TO_MEM, /* pointer to valid memory (stack, packet, map value) */
|
bpf, verifier: add ARG_PTR_TO_RAW_STACK type
When passing buffers from eBPF stack space into a helper function, we have
ARG_PTR_TO_STACK argument type for helpers available. The verifier makes sure
that such buffers are initialized, within boundaries, etc.
However, the downside with this is that we have a couple of helper functions
such as bpf_skb_load_bytes() that fill out the passed buffer in the expected
success case anyway, so zero initializing them prior to the helper call is
unneeded/wasted instructions in the eBPF program that can be avoided.
Therefore, add a new helper function argument type called ARG_PTR_TO_RAW_STACK.
The idea is to skip the STACK_MISC check in check_stack_boundary() and color
the related stack slots as STACK_MISC after we checked all call arguments.
Helper functions using ARG_PTR_TO_RAW_STACK must make sure that every path of
the helper function will fill the provided buffer area, so that we cannot leak
any uninitialized stack memory. This f.e. means that error paths need to
memset() the buffers, but the expected fast-path doesn't have to do this
anymore.
Since there's no such helper needing more than at most one ARG_PTR_TO_RAW_STACK
argument, we can keep it simple and don't need to check for multiple areas.
Should in future such a use-case really appear, we have check_raw_mode() that
will make sure we implement support for it first.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-04-12 22:10:51 +00:00
|
|
|
|
2017-01-09 18:19:50 +00:00
|
|
|
ARG_CONST_SIZE, /* number of bytes accessed from memory */
|
|
|
|
ARG_CONST_SIZE_OR_ZERO, /* number of bytes accessed from memory or 0 */
|
2015-03-12 16:21:42 +00:00
|
|
|
|
2015-03-27 02:53:57 +00:00
|
|
|
ARG_PTR_TO_CTX, /* pointer to context */
|
2015-03-12 16:21:42 +00:00
|
|
|
ARG_ANYTHING, /* any (initialized) argument is ok */
|
2019-01-31 23:40:04 +00:00
|
|
|
ARG_PTR_TO_SPIN_LOCK, /* pointer to bpf_spin_lock */
|
bpf: Add a bpf_sock pointer to __sk_buff and a bpf_sk_fullsock helper
In kernel, it is common to check "skb->sk && sk_fullsock(skb->sk)"
before accessing the fields in sock. For example, in __netdev_pick_tx:
static u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb,
struct net_device *sb_dev)
{
/* ... */
struct sock *sk = skb->sk;
if (queue_index != new_index && sk &&
sk_fullsock(sk) &&
rcu_access_pointer(sk->sk_dst_cache))
sk_tx_queue_set(sk, new_index);
/* ... */
return queue_index;
}
This patch adds a "struct bpf_sock *sk" pointer to the "struct __sk_buff"
where a few of the convert_ctx_access() in filter.c has already been
accessing the skb->sk sock_common's fields,
e.g. sock_ops_convert_ctx_access().
"__sk_buff->sk" is a PTR_TO_SOCK_COMMON_OR_NULL in the verifier.
Some of the fileds in "bpf_sock" will not be directly
accessible through the "__sk_buff->sk" pointer. It is limited
by the new "bpf_sock_common_is_valid_access()".
e.g. The existing "type", "protocol", "mark" and "priority" in bpf_sock
are not allowed.
The newly added "struct bpf_sock *bpf_sk_fullsock(struct bpf_sock *sk)"
can be used to get a sk with all accessible fields in "bpf_sock".
This helper is added to both cg_skb and sched_(cls|act).
int cg_skb_foo(struct __sk_buff *skb) {
struct bpf_sock *sk;
sk = skb->sk;
if (!sk)
return 1;
sk = bpf_sk_fullsock(sk);
if (!sk)
return 1;
if (sk->family != AF_INET6 || sk->protocol != IPPROTO_TCP)
return 1;
/* some_traffic_shaping(); */
return 1;
}
(1) The sk is read only
(2) There is no new "struct bpf_sock_common" introduced.
(3) Future kernel sock's members could be added to bpf_sock only
instead of repeatedly adding at multiple places like currently
in bpf_sock_ops_md, bpf_sock_addr_md, sk_reuseport_md...etc.
(4) After "sk = skb->sk", the reg holding sk is in type
PTR_TO_SOCK_COMMON_OR_NULL.
(5) After bpf_sk_fullsock(), the return type will be in type
PTR_TO_SOCKET_OR_NULL which is the same as the return type of
bpf_sk_lookup_xxx().
However, bpf_sk_fullsock() does not take refcnt. The
acquire_reference_state() is only depending on the return type now.
To avoid it, a new is_acquire_function() is checked before calling
acquire_reference_state().
(6) The WARN_ON in "release_reference_state()" is no longer an
internal verifier bug.
When reg->id is not found in state->refs[], it means the
bpf_prog does something wrong like
"bpf_sk_release(bpf_sk_fullsock(skb->sk))" where reference has
never been acquired by calling "bpf_sk_fullsock(skb->sk)".
A -EINVAL and a verbose are done instead of WARN_ON. A test is
added to the test_verifier in a later patch.
Since the WARN_ON in "release_reference_state()" is no longer
needed, "__release_reference_state()" is folded into
"release_reference_state()" also.
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-02-10 07:22:20 +00:00
|
|
|
ARG_PTR_TO_SOCK_COMMON, /* pointer to sock_common */
|
2019-03-18 23:57:10 +00:00
|
|
|
ARG_PTR_TO_INT, /* pointer to int */
|
|
|
|
ARG_PTR_TO_LONG, /* pointer to long */
|
bpf: Introduce bpf sk local storage
After allowing a bpf prog to
- directly read the skb->sk ptr
- get the fullsock bpf_sock by "bpf_sk_fullsock()"
- get the bpf_tcp_sock by "bpf_tcp_sock()"
- get the listener sock by "bpf_get_listener_sock()"
- avoid duplicating the fields of "(bpf_)sock" and "(bpf_)tcp_sock"
into different bpf running context.
this patch is another effort to make bpf's network programming
more intuitive to do (together with memory and performance benefit).
When bpf prog needs to store data for a sk, the current practice is to
define a map with the usual 4-tuples (src/dst ip/port) as the key.
If multiple bpf progs require to store different sk data, multiple maps
have to be defined. Hence, wasting memory to store the duplicated
keys (i.e. 4 tuples here) in each of the bpf map.
[ The smallest key could be the sk pointer itself which requires
some enhancement in the verifier and it is a separate topic. ]
Also, the bpf prog needs to clean up the elem when sk is freed.
Otherwise, the bpf map will become full and un-usable quickly.
The sk-free tracking currently could be done during sk state
transition (e.g. BPF_SOCK_OPS_STATE_CB).
The size of the map needs to be predefined which then usually ended-up
with an over-provisioned map in production. Even the map was re-sizable,
while the sk naturally come and go away already, this potential re-size
operation is arguably redundant if the data can be directly connected
to the sk itself instead of proxy-ing through a bpf map.
This patch introduces sk->sk_bpf_storage to provide local storage space
at sk for bpf prog to use. The space will be allocated when the first bpf
prog has created data for this particular sk.
The design optimizes the bpf prog's lookup (and then optionally followed by
an inline update). bpf_spin_lock should be used if the inline update needs
to be protected.
BPF_MAP_TYPE_SK_STORAGE:
-----------------------
To define a bpf "sk-local-storage", a BPF_MAP_TYPE_SK_STORAGE map (new in
this patch) needs to be created. Multiple BPF_MAP_TYPE_SK_STORAGE maps can
be created to fit different bpf progs' needs. The map enforces
BTF to allow printing the sk-local-storage during a system-wise
sk dump (e.g. "ss -ta") in the future.
The purpose of a BPF_MAP_TYPE_SK_STORAGE map is not for lookup/update/delete
a "sk-local-storage" data from a particular sk.
Think of the map as a meta-data (or "type") of a "sk-local-storage". This
particular "type" of "sk-local-storage" data can then be stored in any sk.
The main purposes of this map are mostly:
1. Define the size of a "sk-local-storage" type.
2. Provide a similar syscall userspace API as the map (e.g. lookup/update,
map-id, map-btf...etc.)
3. Keep track of all sk's storages of this "type" and clean them up
when the map is freed.
sk->sk_bpf_storage:
------------------
The main lookup/update/delete is done on sk->sk_bpf_storage (which
is a "struct bpf_sk_storage"). When doing a lookup,
the "map" pointer is now used as the "key" to search on the
sk_storage->list. The "map" pointer is actually serving
as the "type" of the "sk-local-storage" that is being
requested.
To allow very fast lookup, it should be as fast as looking up an
array at a stable-offset. At the same time, it is not ideal to
set a hard limit on the number of sk-local-storage "type" that the
system can have. Hence, this patch takes a cache approach.
The last search result from sk_storage->list is cached in
sk_storage->cache[] which is a stable sized array. Each
"sk-local-storage" type has a stable offset to the cache[] array.
In the future, a map's flag could be introduced to do cache
opt-out/enforcement if it became necessary.
The cache size is 16 (i.e. 16 types of "sk-local-storage").
Programs can share map. On the program side, having a few bpf_progs
running in the networking hotpath is already a lot. The bpf_prog
should have already consolidated the existing sock-key-ed map usage
to minimize the map lookup penalty. 16 has enough runway to grow.
All sk-local-storage data will be removed from sk->sk_bpf_storage
during sk destruction.
bpf_sk_storage_get() and bpf_sk_storage_delete():
------------------------------------------------
Instead of using bpf_map_(lookup|update|delete)_elem(),
the bpf prog needs to use the new helper bpf_sk_storage_get() and
bpf_sk_storage_delete(). The verifier can then enforce the
ARG_PTR_TO_SOCKET argument. The bpf_sk_storage_get() also allows to
"create" new elem if one does not exist in the sk. It is done by
the new BPF_SK_STORAGE_GET_F_CREATE flag. An optional value can also be
provided as the initial value during BPF_SK_STORAGE_GET_F_CREATE.
The BPF_MAP_TYPE_SK_STORAGE also supports bpf_spin_lock. Together,
it has eliminated the potential use cases for an equivalent
bpf_map_update_elem() API (for bpf_prog) in this patch.
Misc notes:
----------
1. map_get_next_key is not supported. From the userspace syscall
perspective, the map has the socket fd as the key while the map
can be shared by pinned-file or map-id.
Since btf is enforced, the existing "ss" could be enhanced to pretty
print the local-storage.
Supporting a kernel defined btf with 4 tuples as the return key could
be explored later also.
2. The sk->sk_lock cannot be acquired. Atomic operations is used instead.
e.g. cmpxchg is done on the sk->sk_bpf_storage ptr.
Please refer to the source code comments for the details in
synchronization cases and considerations.
3. The mem is charged to the sk->sk_omem_alloc as the sk filter does.
Benchmark:
---------
Here is the benchmark data collected by turning on
the "kernel.bpf_stats_enabled" sysctl.
Two bpf progs are tested:
One bpf prog with the usual bpf hashmap (max_entries = 8192) with the
sk ptr as the key. (verifier is modified to support sk ptr as the key
That should have shortened the key lookup time.)
Another bpf prog is with the new BPF_MAP_TYPE_SK_STORAGE.
Both are storing a "u32 cnt", do a lookup on "egress_skb/cgroup" for
each egress skb and then bump the cnt. netperf is used to drive
data with 4096 connected UDP sockets.
BPF_MAP_TYPE_HASH with a modifier verifier (152ns per bpf run)
27: cgroup_skb name egress_sk_map tag 74f56e832918070b run_time_ns 58280107540 run_cnt 381347633
loaded_at 2019-04-15T13:46:39-0700 uid 0
xlated 344B jited 258B memlock 4096B map_ids 16
btf_id 5
BPF_MAP_TYPE_SK_STORAGE in this patch (66ns per bpf run)
30: cgroup_skb name egress_sk_stora tag d4aa70984cc7bbf6 run_time_ns 25617093319 run_cnt 390989739
loaded_at 2019-04-15T13:47:54-0700 uid 0
xlated 168B jited 156B memlock 4096B map_ids 17
btf_id 6
Here is a high-level picture on how are the objects organized:
sk
┌──────┐
│ │
│ │
│ │
│*sk_bpf_storage─────▶ bpf_sk_storage
└──────┘ ┌───────┐
┌───────────┤ list │
│ │ │
│ │ │
│ │ │
│ └───────┘
│
│ elem
│ ┌────────┐
├─▶│ snode │
│ ├────────┤
│ │ data │ bpf_map
│ ├────────┤ ┌─────────┐
│ │map_node│◀─┬─────┤ list │
│ └────────┘ │ │ │
│ │ │ │
│ elem │ │ │
│ ┌────────┐ │ └─────────┘
└─▶│ snode │ │
├────────┤ │
bpf_map │ data │ │
┌─────────┐ ├────────┤ │
│ list ├───────▶│map_node│ │
│ │ └────────┘ │
│ │ │
│ │ elem │
└─────────┘ ┌────────┐ │
┌─▶│ snode │ │
│ ├────────┤ │
│ │ data │ │
│ ├────────┤ │
│ │map_node│◀─┘
│ └────────┘
│
│
│ ┌───────┐
sk └──────────│ list │
┌──────┐ │ │
│ │ │ │
│ │ │ │
│ │ └───────┘
│*sk_bpf_storage───────▶bpf_sk_storage
└──────┘
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-04-26 23:39:39 +00:00
|
|
|
ARG_PTR_TO_SOCKET, /* pointer to bpf_sock (fullsock) */
|
2019-10-16 03:25:04 +00:00
|
|
|
ARG_PTR_TO_BTF_ID, /* pointer to in-kernel struct */
|
bpf: Implement BPF ring buffer and verifier support for it
This commit adds a new MPSC ring buffer implementation into BPF ecosystem,
which allows multiple CPUs to submit data to a single shared ring buffer. On
the consumption side, only single consumer is assumed.
Motivation
----------
There are two distinctive motivators for this work, which are not satisfied by
existing perf buffer, which prompted creation of a new ring buffer
implementation.
- more efficient memory utilization by sharing ring buffer across CPUs;
- preserving ordering of events that happen sequentially in time, even
across multiple CPUs (e.g., fork/exec/exit events for a task).
These two problems are independent, but perf buffer fails to satisfy both.
Both are a result of a choice to have per-CPU perf ring buffer. Both can be
also solved by having an MPSC implementation of ring buffer. The ordering
problem could technically be solved for perf buffer with some in-kernel
counting, but given the first one requires an MPSC buffer, the same solution
would solve the second problem automatically.
Semantics and APIs
------------------
Single ring buffer is presented to BPF programs as an instance of BPF map of
type BPF_MAP_TYPE_RINGBUF. Two other alternatives considered, but ultimately
rejected.
One way would be to, similar to BPF_MAP_TYPE_PERF_EVENT_ARRAY, make
BPF_MAP_TYPE_RINGBUF could represent an array of ring buffers, but not enforce
"same CPU only" rule. This would be more familiar interface compatible with
existing perf buffer use in BPF, but would fail if application needed more
advanced logic to lookup ring buffer by arbitrary key. HASH_OF_MAPS addresses
this with current approach. Additionally, given the performance of BPF
ringbuf, many use cases would just opt into a simple single ring buffer shared
among all CPUs, for which current approach would be an overkill.
Another approach could introduce a new concept, alongside BPF map, to
represent generic "container" object, which doesn't necessarily have key/value
interface with lookup/update/delete operations. This approach would add a lot
of extra infrastructure that has to be built for observability and verifier
support. It would also add another concept that BPF developers would have to
familiarize themselves with, new syntax in libbpf, etc. But then would really
provide no additional benefits over the approach of using a map.
BPF_MAP_TYPE_RINGBUF doesn't support lookup/update/delete operations, but so
doesn't few other map types (e.g., queue and stack; array doesn't support
delete, etc).
The approach chosen has an advantage of re-using existing BPF map
infrastructure (introspection APIs in kernel, libbpf support, etc), being
familiar concept (no need to teach users a new type of object in BPF program),
and utilizing existing tooling (bpftool). For common scenario of using
a single ring buffer for all CPUs, it's as simple and straightforward, as
would be with a dedicated "container" object. On the other hand, by being
a map, it can be combined with ARRAY_OF_MAPS and HASH_OF_MAPS map-in-maps to
implement a wide variety of topologies, from one ring buffer for each CPU
(e.g., as a replacement for perf buffer use cases), to a complicated
application hashing/sharding of ring buffers (e.g., having a small pool of
ring buffers with hashed task's tgid being a look up key to preserve order,
but reduce contention).
Key and value sizes are enforced to be zero. max_entries is used to specify
the size of ring buffer and has to be a power of 2 value.
There are a bunch of similarities between perf buffer
(BPF_MAP_TYPE_PERF_EVENT_ARRAY) and new BPF ring buffer semantics:
- variable-length records;
- if there is no more space left in ring buffer, reservation fails, no
blocking;
- memory-mappable data area for user-space applications for ease of
consumption and high performance;
- epoll notifications for new incoming data;
- but still the ability to do busy polling for new data to achieve the
lowest latency, if necessary.
BPF ringbuf provides two sets of APIs to BPF programs:
- bpf_ringbuf_output() allows to *copy* data from one place to a ring
buffer, similarly to bpf_perf_event_output();
- bpf_ringbuf_reserve()/bpf_ringbuf_commit()/bpf_ringbuf_discard() APIs
split the whole process into two steps. First, a fixed amount of space is
reserved. If successful, a pointer to a data inside ring buffer data area
is returned, which BPF programs can use similarly to a data inside
array/hash maps. Once ready, this piece of memory is either committed or
discarded. Discard is similar to commit, but makes consumer ignore the
record.
bpf_ringbuf_output() has disadvantage of incurring extra memory copy, because
record has to be prepared in some other place first. But it allows to submit
records of the length that's not known to verifier beforehand. It also closely
matches bpf_perf_event_output(), so will simplify migration significantly.
bpf_ringbuf_reserve() avoids the extra copy of memory by providing a memory
pointer directly to ring buffer memory. In a lot of cases records are larger
than BPF stack space allows, so many programs have use extra per-CPU array as
a temporary heap for preparing sample. bpf_ringbuf_reserve() avoid this needs
completely. But in exchange, it only allows a known constant size of memory to
be reserved, such that verifier can verify that BPF program can't access
memory outside its reserved record space. bpf_ringbuf_output(), while slightly
slower due to extra memory copy, covers some use cases that are not suitable
for bpf_ringbuf_reserve().
The difference between commit and discard is very small. Discard just marks
a record as discarded, and such records are supposed to be ignored by consumer
code. Discard is useful for some advanced use-cases, such as ensuring
all-or-nothing multi-record submission, or emulating temporary malloc()/free()
within single BPF program invocation.
Each reserved record is tracked by verifier through existing
reference-tracking logic, similar to socket ref-tracking. It is thus
impossible to reserve a record, but forget to submit (or discard) it.
bpf_ringbuf_query() helper allows to query various properties of ring buffer.
Currently 4 are supported:
- BPF_RB_AVAIL_DATA returns amount of unconsumed data in ring buffer;
- BPF_RB_RING_SIZE returns the size of ring buffer;
- BPF_RB_CONS_POS/BPF_RB_PROD_POS returns current logical possition of
consumer/producer, respectively.
Returned values are momentarily snapshots of ring buffer state and could be
off by the time helper returns, so this should be used only for
debugging/reporting reasons or for implementing various heuristics, that take
into account highly-changeable nature of some of those characteristics.
One such heuristic might involve more fine-grained control over poll/epoll
notifications about new data availability in ring buffer. Together with
BPF_RB_NO_WAKEUP/BPF_RB_FORCE_WAKEUP flags for output/commit/discard helpers,
it allows BPF program a high degree of control and, e.g., more efficient
batched notifications. Default self-balancing strategy, though, should be
adequate for most applications and will work reliable and efficiently already.
Design and implementation
-------------------------
This reserve/commit schema allows a natural way for multiple producers, either
on different CPUs or even on the same CPU/in the same BPF program, to reserve
independent records and work with them without blocking other producers. This
means that if BPF program was interruped by another BPF program sharing the
same ring buffer, they will both get a record reserved (provided there is
enough space left) and can work with it and submit it independently. This
applies to NMI context as well, except that due to using a spinlock during
reservation, in NMI context, bpf_ringbuf_reserve() might fail to get a lock,
in which case reservation will fail even if ring buffer is not full.
The ring buffer itself internally is implemented as a power-of-2 sized
circular buffer, with two logical and ever-increasing counters (which might
wrap around on 32-bit architectures, that's not a problem):
- consumer counter shows up to which logical position consumer consumed the
data;
- producer counter denotes amount of data reserved by all producers.
Each time a record is reserved, producer that "owns" the record will
successfully advance producer counter. At that point, data is still not yet
ready to be consumed, though. Each record has 8 byte header, which contains
the length of reserved record, as well as two extra bits: busy bit to denote
that record is still being worked on, and discard bit, which might be set at
commit time if record is discarded. In the latter case, consumer is supposed
to skip the record and move on to the next one. Record header also encodes
record's relative offset from the beginning of ring buffer data area (in
pages). This allows bpf_ringbuf_commit()/bpf_ringbuf_discard() to accept only
the pointer to the record itself, without requiring also the pointer to ring
buffer itself. Ring buffer memory location will be restored from record
metadata header. This significantly simplifies verifier, as well as improving
API usability.
Producer counter increments are serialized under spinlock, so there is
a strict ordering between reservations. Commits, on the other hand, are
completely lockless and independent. All records become available to consumer
in the order of reservations, but only after all previous records where
already committed. It is thus possible for slow producers to temporarily hold
off submitted records, that were reserved later.
Reservation/commit/consumer protocol is verified by litmus tests in
Documentation/litmus-test/bpf-rb.
One interesting implementation bit, that significantly simplifies (and thus
speeds up as well) implementation of both producers and consumers is how data
area is mapped twice contiguously back-to-back in the virtual memory. This
allows to not take any special measures for samples that have to wrap around
at the end of the circular buffer data area, because the next page after the
last data page would be first data page again, and thus the sample will still
appear completely contiguous in virtual memory. See comment and a simple ASCII
diagram showing this visually in bpf_ringbuf_area_alloc().
Another feature that distinguishes BPF ringbuf from perf ring buffer is
a self-pacing notifications of new data being availability.
bpf_ringbuf_commit() implementation will send a notification of new record
being available after commit only if consumer has already caught up right up
to the record being committed. If not, consumer still has to catch up and thus
will see new data anyways without needing an extra poll notification.
Benchmarks (see tools/testing/selftests/bpf/benchs/bench_ringbuf.c) show that
this allows to achieve a very high throughput without having to resort to
tricks like "notify only every Nth sample", which are necessary with perf
buffer. For extreme cases, when BPF program wants more manual control of
notifications, commit/discard/output helpers accept BPF_RB_NO_WAKEUP and
BPF_RB_FORCE_WAKEUP flags, which give full control over notifications of data
availability, but require extra caution and diligence in using this API.
Comparison to alternatives
--------------------------
Before considering implementing BPF ring buffer from scratch existing
alternatives in kernel were evaluated, but didn't seem to meet the needs. They
largely fell into few categores:
- per-CPU buffers (perf, ftrace, etc), which don't satisfy two motivations
outlined above (ordering and memory consumption);
- linked list-based implementations; while some were multi-producer designs,
consuming these from user-space would be very complicated and most
probably not performant; memory-mapping contiguous piece of memory is
simpler and more performant for user-space consumers;
- io_uring is SPSC, but also requires fixed-sized elements. Naively turning
SPSC queue into MPSC w/ lock would have subpar performance compared to
locked reserve + lockless commit, as with BPF ring buffer. Fixed sized
elements would be too limiting for BPF programs, given existing BPF
programs heavily rely on variable-sized perf buffer already;
- specialized implementations (like a new printk ring buffer, [0]) with lots
of printk-specific limitations and implications, that didn't seem to fit
well for intended use with BPF programs.
[0] https://lwn.net/Articles/779550/
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200529075424.3139988-2-andriin@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2020-05-29 07:54:20 +00:00
|
|
|
ARG_PTR_TO_ALLOC_MEM, /* pointer to dynamically allocated memory */
|
|
|
|
ARG_CONST_ALLOC_SIZE_OR_ZERO, /* number of allocated bytes requested */
|
2020-09-25 00:03:50 +00:00
|
|
|
ARG_PTR_TO_BTF_ID_SOCK_COMMON, /* pointer to in-kernel sock_common or bpf-mirrored bpf_sock */
|
2020-09-29 23:50:47 +00:00
|
|
|
ARG_PTR_TO_PERCPU_BTF_ID, /* pointer to in-kernel percpu type */
|
bpf: Add bpf_for_each_map_elem() helper
The bpf_for_each_map_elem() helper is introduced which
iterates all map elements with a callback function. The
helper signature looks like
long bpf_for_each_map_elem(map, callback_fn, callback_ctx, flags)
and for each map element, the callback_fn will be called. For example,
like hashmap, the callback signature may look like
long callback_fn(map, key, val, callback_ctx)
There are two known use cases for this. One is from upstream ([1]) where
a for_each_map_elem helper may help implement a timeout mechanism
in a more generic way. Another is from our internal discussion
for a firewall use case where a map contains all the rules. The packet
data can be compared to all these rules to decide allow or deny
the packet.
For array maps, users can already use a bounded loop to traverse
elements. Using this helper can avoid using bounded loop. For other
type of maps (e.g., hash maps) where bounded loop is hard or
impossible to use, this helper provides a convenient way to
operate on all elements.
For callback_fn, besides map and map element, a callback_ctx,
allocated on caller stack, is also passed to the callback
function. This callback_ctx argument can provide additional
input and allow to write to caller stack for output.
If the callback_fn returns 0, the helper will iterate through next
element if available. If the callback_fn returns 1, the helper
will stop iterating and returns to the bpf program. Other return
values are not used for now.
Currently, this helper is only available with jit. It is possible
to make it work with interpreter with so effort but I leave it
as the future work.
[1]: https://lore.kernel.org/bpf/20210122205415.113822-1-xiyou.wangcong@gmail.com/
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210226204925.3884923-1-yhs@fb.com
2021-02-26 20:49:25 +00:00
|
|
|
ARG_PTR_TO_FUNC, /* pointer to a bpf program function */
|
2021-12-17 00:31:45 +00:00
|
|
|
ARG_PTR_TO_STACK, /* pointer to stack */
|
2021-04-19 15:52:39 +00:00
|
|
|
ARG_PTR_TO_CONST_STR, /* pointer to a null terminated read-only string */
|
bpf: Introduce bpf timers.
Introduce 'struct bpf_timer { __u64 :64; __u64 :64; };' that can be embedded
in hash/array/lru maps as a regular field and helpers to operate on it:
// Initialize the timer.
// First 4 bits of 'flags' specify clockid.
// Only CLOCK_MONOTONIC, CLOCK_REALTIME, CLOCK_BOOTTIME are allowed.
long bpf_timer_init(struct bpf_timer *timer, struct bpf_map *map, int flags);
// Configure the timer to call 'callback_fn' static function.
long bpf_timer_set_callback(struct bpf_timer *timer, void *callback_fn);
// Arm the timer to expire 'nsec' nanoseconds from the current time.
long bpf_timer_start(struct bpf_timer *timer, u64 nsec, u64 flags);
// Cancel the timer and wait for callback_fn to finish if it was running.
long bpf_timer_cancel(struct bpf_timer *timer);
Here is how BPF program might look like:
struct map_elem {
int counter;
struct bpf_timer timer;
};
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 1000);
__type(key, int);
__type(value, struct map_elem);
} hmap SEC(".maps");
static int timer_cb(void *map, int *key, struct map_elem *val);
/* val points to particular map element that contains bpf_timer. */
SEC("fentry/bpf_fentry_test1")
int BPF_PROG(test1, int a)
{
struct map_elem *val;
int key = 0;
val = bpf_map_lookup_elem(&hmap, &key);
if (val) {
bpf_timer_init(&val->timer, &hmap, CLOCK_REALTIME);
bpf_timer_set_callback(&val->timer, timer_cb);
bpf_timer_start(&val->timer, 1000 /* call timer_cb2 in 1 usec */, 0);
}
}
This patch adds helper implementations that rely on hrtimers
to call bpf functions as timers expire.
The following patches add necessary safety checks.
Only programs with CAP_BPF are allowed to use bpf_timer.
The amount of timers used by the program is constrained by
the memcg recorded at map creation time.
The bpf_timer_init() helper needs explicit 'map' argument because inner maps
are dynamic and not known at load time. While the bpf_timer_set_callback() is
receiving hidden 'aux->prog' argument supplied by the verifier.
The prog pointer is needed to do refcnting of bpf program to make sure that
program doesn't get freed while the timer is armed. This approach relies on
"user refcnt" scheme used in prog_array that stores bpf programs for
bpf_tail_call. The bpf_timer_set_callback() will increment the prog refcnt which is
paired with bpf_timer_cancel() that will drop the prog refcnt. The
ops->map_release_uref is responsible for cancelling the timers and dropping
prog refcnt when user space reference to a map reaches zero.
This uref approach is done to make sure that Ctrl-C of user space process will
not leave timers running forever unless the user space explicitly pinned a map
that contained timers in bpffs.
bpf_timer_init() and bpf_timer_set_callback() will return -EPERM if map doesn't
have user references (is not held by open file descriptor from user space and
not pinned in bpffs).
The bpf_map_delete_elem() and bpf_map_update_elem() operations cancel
and free the timer if given map element had it allocated.
"bpftool map update" command can be used to cancel timers.
The 'struct bpf_timer' is explicitly __attribute__((aligned(8))) because
'__u64 :64' has 1 byte alignment of 8 byte padding.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210715005417.78572-4-alexei.starovoitov@gmail.com
2021-07-15 00:54:09 +00:00
|
|
|
ARG_PTR_TO_TIMER, /* pointer to bpf_timer */
|
bpf: Allow storing referenced kptr in map
Extending the code in previous commits, introduce referenced kptr
support, which needs to be tagged using 'kptr_ref' tag instead. Unlike
unreferenced kptr, referenced kptr have a lot more restrictions. In
addition to the type matching, only a newly introduced bpf_kptr_xchg
helper is allowed to modify the map value at that offset. This transfers
the referenced pointer being stored into the map, releasing the
references state for the program, and returning the old value and
creating new reference state for the returned pointer.
Similar to unreferenced pointer case, return value for this case will
also be PTR_TO_BTF_ID_OR_NULL. The reference for the returned pointer
must either be eventually released by calling the corresponding release
function, otherwise it must be transferred into another map.
It is also allowed to call bpf_kptr_xchg with a NULL pointer, to clear
the value, and obtain the old value if any.
BPF_LDX, BPF_STX, and BPF_ST cannot access referenced kptr. A future
commit will permit using BPF_LDX for such pointers, but attempt at
making it safe, since the lifetime of object won't be guaranteed.
There are valid reasons to enforce the restriction of permitting only
bpf_kptr_xchg to operate on referenced kptr. The pointer value must be
consistent in face of concurrent modification, and any prior values
contained in the map must also be released before a new one is moved
into the map. To ensure proper transfer of this ownership, bpf_kptr_xchg
returns the old value, which the verifier would require the user to
either free or move into another map, and releases the reference held
for the pointer being moved in.
In the future, direct BPF_XCHG instruction may also be permitted to work
like bpf_kptr_xchg helper.
Note that process_kptr_func doesn't have to call
check_helper_mem_access, since we already disallow rdonly/wronly flags
for map, which is what check_map_access_type checks, and we already
ensure the PTR_TO_MAP_VALUE refers to kptr by obtaining its off_desc,
so check_map_access is also not required.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-4-memxor@gmail.com
2022-04-24 21:48:51 +00:00
|
|
|
ARG_PTR_TO_KPTR, /* pointer to referenced kptr */
|
bpf: Add verifier support for dynptrs
This patch adds the bulk of the verifier work for supporting dynamic
pointers (dynptrs) in bpf.
A bpf_dynptr is opaque to the bpf program. It is a 16-byte structure
defined internally as:
struct bpf_dynptr_kern {
void *data;
u32 size;
u32 offset;
} __aligned(8);
The upper 8 bits of *size* is reserved (it contains extra metadata about
read-only status and dynptr type). Consequently, a dynptr only supports
memory less than 16 MB.
There are different types of dynptrs (eg malloc, ringbuf, ...). In this
patchset, the most basic one, dynptrs to a bpf program's local memory,
is added. For now only local memory that is of reg type PTR_TO_MAP_VALUE
is supported.
In the verifier, dynptr state information will be tracked in stack
slots. When the program passes in an uninitialized dynptr
(ARG_PTR_TO_DYNPTR | MEM_UNINIT), the stack slots corresponding
to the frame pointer where the dynptr resides at are marked
STACK_DYNPTR. For helper functions that take in initialized dynptrs (eg
bpf_dynptr_read + bpf_dynptr_write which are added later in this
patchset), the verifier enforces that the dynptr has been initialized
properly by checking that their corresponding stack slots have been
marked as STACK_DYNPTR.
The 6th patch in this patchset adds test cases that the verifier should
successfully reject, such as for example attempting to use a dynptr
after doing a direct write into it inside the bpf program.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20220523210712.3641569-2-joannelkoong@gmail.com
2022-05-23 21:07:07 +00:00
|
|
|
ARG_PTR_TO_DYNPTR, /* pointer to bpf_dynptr. See bpf_type_flag for dynptr type */
|
2020-09-21 12:12:27 +00:00
|
|
|
__BPF_ARG_TYPE_MAX,
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
|
2021-12-17 00:31:45 +00:00
|
|
|
/* Extended arg_types. */
|
|
|
|
ARG_PTR_TO_MAP_VALUE_OR_NULL = PTR_MAYBE_NULL | ARG_PTR_TO_MAP_VALUE,
|
|
|
|
ARG_PTR_TO_MEM_OR_NULL = PTR_MAYBE_NULL | ARG_PTR_TO_MEM,
|
|
|
|
ARG_PTR_TO_CTX_OR_NULL = PTR_MAYBE_NULL | ARG_PTR_TO_CTX,
|
|
|
|
ARG_PTR_TO_SOCKET_OR_NULL = PTR_MAYBE_NULL | ARG_PTR_TO_SOCKET,
|
|
|
|
ARG_PTR_TO_ALLOC_MEM_OR_NULL = PTR_MAYBE_NULL | ARG_PTR_TO_ALLOC_MEM,
|
|
|
|
ARG_PTR_TO_STACK_OR_NULL = PTR_MAYBE_NULL | ARG_PTR_TO_STACK,
|
bpf: Allow storing referenced kptr in map
Extending the code in previous commits, introduce referenced kptr
support, which needs to be tagged using 'kptr_ref' tag instead. Unlike
unreferenced kptr, referenced kptr have a lot more restrictions. In
addition to the type matching, only a newly introduced bpf_kptr_xchg
helper is allowed to modify the map value at that offset. This transfers
the referenced pointer being stored into the map, releasing the
references state for the program, and returning the old value and
creating new reference state for the returned pointer.
Similar to unreferenced pointer case, return value for this case will
also be PTR_TO_BTF_ID_OR_NULL. The reference for the returned pointer
must either be eventually released by calling the corresponding release
function, otherwise it must be transferred into another map.
It is also allowed to call bpf_kptr_xchg with a NULL pointer, to clear
the value, and obtain the old value if any.
BPF_LDX, BPF_STX, and BPF_ST cannot access referenced kptr. A future
commit will permit using BPF_LDX for such pointers, but attempt at
making it safe, since the lifetime of object won't be guaranteed.
There are valid reasons to enforce the restriction of permitting only
bpf_kptr_xchg to operate on referenced kptr. The pointer value must be
consistent in face of concurrent modification, and any prior values
contained in the map must also be released before a new one is moved
into the map. To ensure proper transfer of this ownership, bpf_kptr_xchg
returns the old value, which the verifier would require the user to
either free or move into another map, and releases the reference held
for the pointer being moved in.
In the future, direct BPF_XCHG instruction may also be permitted to work
like bpf_kptr_xchg helper.
Note that process_kptr_func doesn't have to call
check_helper_mem_access, since we already disallow rdonly/wronly flags
for map, which is what check_map_access_type checks, and we already
ensure the PTR_TO_MAP_VALUE refers to kptr by obtaining its off_desc,
so check_map_access is also not required.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-4-memxor@gmail.com
2022-04-24 21:48:51 +00:00
|
|
|
ARG_PTR_TO_BTF_ID_OR_NULL = PTR_MAYBE_NULL | ARG_PTR_TO_BTF_ID,
|
2022-05-09 22:42:52 +00:00
|
|
|
/* pointer to memory does not need to be initialized, helper function must fill
|
|
|
|
* all bytes or clear them in error case.
|
|
|
|
*/
|
|
|
|
ARG_PTR_TO_UNINIT_MEM = MEM_UNINIT | ARG_PTR_TO_MEM,
|
2022-06-15 13:48:43 +00:00
|
|
|
/* Pointer to valid memory of size known at compile time. */
|
|
|
|
ARG_PTR_TO_FIXED_SIZE_MEM = MEM_FIXED_SIZE | ARG_PTR_TO_MEM,
|
2021-12-17 00:31:45 +00:00
|
|
|
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
/* This must be the last entry. Its purpose is to ensure the enum is
|
|
|
|
* wide enough to hold the higher bits reserved for bpf_type_flag.
|
|
|
|
*/
|
|
|
|
__BPF_ARG_TYPE_LIMIT = BPF_TYPE_LIMIT,
|
bpf: verifier (add verifier core)
This patch adds verifier core which simulates execution of every insn and
records the state of registers and program stack. Every branch instruction seen
during simulation is pushed into state stack. When verifier reaches BPF_EXIT,
it pops the state from the stack and continues until it reaches BPF_EXIT again.
For program:
1: bpf_mov r1, xxx
2: if (r1 == 0) goto 5
3: bpf_mov r0, 1
4: goto 6
5: bpf_mov r0, 2
6: bpf_exit
The verifier will walk insns: 1, 2, 3, 4, 6
then it will pop the state recorded at insn#2 and will continue: 5, 6
This way it walks all possible paths through the program and checks all
possible values of registers. While doing so, it checks for:
- invalid instructions
- uninitialized register access
- uninitialized stack access
- misaligned stack access
- out of range stack access
- invalid calling convention
- instruction encoding is not using reserved fields
Kernel subsystem configures the verifier with two callbacks:
- bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
that provides information to the verifer which fields of 'ctx'
are accessible (remember 'ctx' is the first argument to eBPF program)
- const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id);
returns argument constraints of kernel helper functions that eBPF program
may call, so that verifier can checks that R1-R5 types match the prototype
More details in Documentation/networking/filter.txt and in kernel/bpf/verifier.c
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:17:06 +00:00
|
|
|
};
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
static_assert(__BPF_ARG_TYPE_MAX <= BPF_BASE_TYPE_LIMIT);
|
bpf: verifier (add verifier core)
This patch adds verifier core which simulates execution of every insn and
records the state of registers and program stack. Every branch instruction seen
during simulation is pushed into state stack. When verifier reaches BPF_EXIT,
it pops the state from the stack and continues until it reaches BPF_EXIT again.
For program:
1: bpf_mov r1, xxx
2: if (r1 == 0) goto 5
3: bpf_mov r0, 1
4: goto 6
5: bpf_mov r0, 2
6: bpf_exit
The verifier will walk insns: 1, 2, 3, 4, 6
then it will pop the state recorded at insn#2 and will continue: 5, 6
This way it walks all possible paths through the program and checks all
possible values of registers. While doing so, it checks for:
- invalid instructions
- uninitialized register access
- uninitialized stack access
- misaligned stack access
- out of range stack access
- invalid calling convention
- instruction encoding is not using reserved fields
Kernel subsystem configures the verifier with two callbacks:
- bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
that provides information to the verifer which fields of 'ctx'
are accessible (remember 'ctx' is the first argument to eBPF program)
- const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id);
returns argument constraints of kernel helper functions that eBPF program
may call, so that verifier can checks that R1-R5 types match the prototype
More details in Documentation/networking/filter.txt and in kernel/bpf/verifier.c
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:17:06 +00:00
|
|
|
|
|
|
|
/* type of values returned from helper functions */
|
|
|
|
enum bpf_return_type {
|
|
|
|
RET_INTEGER, /* function returns integer */
|
|
|
|
RET_VOID, /* function doesn't return anything */
|
2018-08-02 21:27:22 +00:00
|
|
|
RET_PTR_TO_MAP_VALUE, /* returns a pointer to map elem value */
|
2021-12-17 00:31:46 +00:00
|
|
|
RET_PTR_TO_SOCKET, /* returns a pointer to a socket */
|
|
|
|
RET_PTR_TO_TCP_SOCK, /* returns a pointer to a tcp_sock */
|
|
|
|
RET_PTR_TO_SOCK_COMMON, /* returns a pointer to a sock_common */
|
|
|
|
RET_PTR_TO_ALLOC_MEM, /* returns a pointer to dynamically allocated memory */
|
2020-09-29 23:50:48 +00:00
|
|
|
RET_PTR_TO_MEM_OR_BTF_ID, /* returns a pointer to a valid memory or a btf_id */
|
2020-11-06 10:37:43 +00:00
|
|
|
RET_PTR_TO_BTF_ID, /* returns a pointer to a btf_id */
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
__BPF_RET_TYPE_MAX,
|
|
|
|
|
2021-12-17 00:31:46 +00:00
|
|
|
/* Extended ret_types. */
|
|
|
|
RET_PTR_TO_MAP_VALUE_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_MAP_VALUE,
|
|
|
|
RET_PTR_TO_SOCKET_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_SOCKET,
|
|
|
|
RET_PTR_TO_TCP_SOCK_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_TCP_SOCK,
|
|
|
|
RET_PTR_TO_SOCK_COMMON_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_SOCK_COMMON,
|
2022-01-13 11:11:30 +00:00
|
|
|
RET_PTR_TO_ALLOC_MEM_OR_NULL = PTR_MAYBE_NULL | MEM_ALLOC | RET_PTR_TO_ALLOC_MEM,
|
2022-05-23 21:07:11 +00:00
|
|
|
RET_PTR_TO_DYNPTR_MEM_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_ALLOC_MEM,
|
2021-12-17 00:31:46 +00:00
|
|
|
RET_PTR_TO_BTF_ID_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_BTF_ID,
|
|
|
|
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
/* This must be the last entry. Its purpose is to ensure the enum is
|
|
|
|
* wide enough to hold the higher bits reserved for bpf_type_flag.
|
|
|
|
*/
|
|
|
|
__BPF_RET_TYPE_LIMIT = BPF_TYPE_LIMIT,
|
bpf: verifier (add verifier core)
This patch adds verifier core which simulates execution of every insn and
records the state of registers and program stack. Every branch instruction seen
during simulation is pushed into state stack. When verifier reaches BPF_EXIT,
it pops the state from the stack and continues until it reaches BPF_EXIT again.
For program:
1: bpf_mov r1, xxx
2: if (r1 == 0) goto 5
3: bpf_mov r0, 1
4: goto 6
5: bpf_mov r0, 2
6: bpf_exit
The verifier will walk insns: 1, 2, 3, 4, 6
then it will pop the state recorded at insn#2 and will continue: 5, 6
This way it walks all possible paths through the program and checks all
possible values of registers. While doing so, it checks for:
- invalid instructions
- uninitialized register access
- uninitialized stack access
- misaligned stack access
- out of range stack access
- invalid calling convention
- instruction encoding is not using reserved fields
Kernel subsystem configures the verifier with two callbacks:
- bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
that provides information to the verifer which fields of 'ctx'
are accessible (remember 'ctx' is the first argument to eBPF program)
- const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id);
returns argument constraints of kernel helper functions that eBPF program
may call, so that verifier can checks that R1-R5 types match the prototype
More details in Documentation/networking/filter.txt and in kernel/bpf/verifier.c
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:17:06 +00:00
|
|
|
};
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
static_assert(__BPF_RET_TYPE_MAX <= BPF_BASE_TYPE_LIMIT);
|
bpf: verifier (add verifier core)
This patch adds verifier core which simulates execution of every insn and
records the state of registers and program stack. Every branch instruction seen
during simulation is pushed into state stack. When verifier reaches BPF_EXIT,
it pops the state from the stack and continues until it reaches BPF_EXIT again.
For program:
1: bpf_mov r1, xxx
2: if (r1 == 0) goto 5
3: bpf_mov r0, 1
4: goto 6
5: bpf_mov r0, 2
6: bpf_exit
The verifier will walk insns: 1, 2, 3, 4, 6
then it will pop the state recorded at insn#2 and will continue: 5, 6
This way it walks all possible paths through the program and checks all
possible values of registers. While doing so, it checks for:
- invalid instructions
- uninitialized register access
- uninitialized stack access
- misaligned stack access
- out of range stack access
- invalid calling convention
- instruction encoding is not using reserved fields
Kernel subsystem configures the verifier with two callbacks:
- bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
that provides information to the verifer which fields of 'ctx'
are accessible (remember 'ctx' is the first argument to eBPF program)
- const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id);
returns argument constraints of kernel helper functions that eBPF program
may call, so that verifier can checks that R1-R5 types match the prototype
More details in Documentation/networking/filter.txt and in kernel/bpf/verifier.c
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:17:06 +00:00
|
|
|
|
2014-09-26 07:17:00 +00:00
|
|
|
/* eBPF function prototype used by verifier to allow BPF_CALLs from eBPF programs
|
|
|
|
* to in-kernel helper functions and for adjusting imm32 field in BPF_CALL
|
|
|
|
* instructions after verifying
|
|
|
|
*/
|
|
|
|
struct bpf_func_proto {
|
|
|
|
u64 (*func)(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
|
|
|
|
bool gpl_only;
|
bpf: direct packet write and access for helpers for clsact progs
This work implements direct packet access for helpers and direct packet
write in a similar fashion as already available for XDP types via commits
4acf6c0b84c9 ("bpf: enable direct packet data write for xdp progs") and
6841de8b0d03 ("bpf: allow helpers access the packet directly"), and as a
complementary feature to the already available direct packet read for tc
(cls/act) programs.
For enabling this, we need to introduce two helpers, bpf_skb_pull_data()
and bpf_csum_update(). The first is generally needed for both, read and
write, because they would otherwise only be limited to the current linear
skb head. Usually, when the data_end test fails, programs just bail out,
or, in the direct read case, use bpf_skb_load_bytes() as an alternative
to overcome this limitation. If such data sits in non-linear parts, we
can just pull them in once with the new helper, retest and eventually
access them.
At the same time, this also makes sure the skb is uncloned, which is, of
course, a necessary condition for direct write. As this needs to be an
invariant for the write part only, the verifier detects writes and adds
a prologue that is calling bpf_skb_pull_data() to effectively unclone the
skb from the very beginning in case it is indeed cloned. The heuristic
makes use of a similar trick that was done in 233577a22089 ("net: filter:
constify detection of pkt_type_offset"). This comes at zero cost for other
programs that do not use the direct write feature. Should a program use
this feature only sparsely and has read access for the most parts with,
for example, drop return codes, then such write action can be delegated
to a tail called program for mitigating this cost of potential uncloning
to a late point in time where it would have been paid similarly with the
bpf_skb_store_bytes() as well. Advantage of direct write is that the
writes are inlined whereas the helper cannot make any length assumptions
and thus needs to generate a call to memcpy() also for small sizes, as well
as cost of helper call itself with sanity checks are avoided. Plus, when
direct read is already used, we don't need to cache or perform rechecks
on the data boundaries (due to verifier invalidating previous checks for
helpers that change skb->data), so more complex programs using rewrites
can benefit from switching to direct read plus write.
For direct packet access to helpers, we save the otherwise needed copy into
a temp struct sitting on stack memory when use-case allows. Both facilities
are enabled via may_access_direct_pkt_data() in verifier. For now, we limit
this to map helpers and csum_diff, and can successively enable other helpers
where we find it makes sense. Helpers that definitely cannot be allowed for
this are those part of bpf_helper_changes_skb_data() since they can change
underlying data, and those that write into memory as this could happen for
packet typed args when still cloned. bpf_csum_update() helper accommodates
for the fact that we need to fixup checksum_complete when using direct write
instead of bpf_skb_store_bytes(), meaning the programs can use available
helpers like bpf_csum_diff(), and implement csum_add(), csum_sub(),
csum_block_add(), csum_block_sub() equivalents in eBPF together with the
new helper. A usage example will be provided for iproute2's examples/bpf/
directory.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-09-19 22:26:13 +00:00
|
|
|
bool pkt_access;
|
bpf: verifier (add verifier core)
This patch adds verifier core which simulates execution of every insn and
records the state of registers and program stack. Every branch instruction seen
during simulation is pushed into state stack. When verifier reaches BPF_EXIT,
it pops the state from the stack and continues until it reaches BPF_EXIT again.
For program:
1: bpf_mov r1, xxx
2: if (r1 == 0) goto 5
3: bpf_mov r0, 1
4: goto 6
5: bpf_mov r0, 2
6: bpf_exit
The verifier will walk insns: 1, 2, 3, 4, 6
then it will pop the state recorded at insn#2 and will continue: 5, 6
This way it walks all possible paths through the program and checks all
possible values of registers. While doing so, it checks for:
- invalid instructions
- uninitialized register access
- uninitialized stack access
- misaligned stack access
- out of range stack access
- invalid calling convention
- instruction encoding is not using reserved fields
Kernel subsystem configures the verifier with two callbacks:
- bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
that provides information to the verifer which fields of 'ctx'
are accessible (remember 'ctx' is the first argument to eBPF program)
- const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id);
returns argument constraints of kernel helper functions that eBPF program
may call, so that verifier can checks that R1-R5 types match the prototype
More details in Documentation/networking/filter.txt and in kernel/bpf/verifier.c
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:17:06 +00:00
|
|
|
enum bpf_return_type ret_type;
|
2019-10-16 03:25:04 +00:00
|
|
|
union {
|
|
|
|
struct {
|
|
|
|
enum bpf_arg_type arg1_type;
|
|
|
|
enum bpf_arg_type arg2_type;
|
|
|
|
enum bpf_arg_type arg3_type;
|
|
|
|
enum bpf_arg_type arg4_type;
|
|
|
|
enum bpf_arg_type arg5_type;
|
|
|
|
};
|
|
|
|
enum bpf_arg_type arg_type[5];
|
|
|
|
};
|
2020-09-21 12:12:20 +00:00
|
|
|
union {
|
|
|
|
struct {
|
|
|
|
u32 *arg1_btf_id;
|
|
|
|
u32 *arg2_btf_id;
|
|
|
|
u32 *arg3_btf_id;
|
|
|
|
u32 *arg4_btf_id;
|
|
|
|
u32 *arg5_btf_id;
|
|
|
|
};
|
|
|
|
u32 *arg_btf_id[5];
|
2022-06-15 13:48:43 +00:00
|
|
|
struct {
|
|
|
|
size_t arg1_size;
|
|
|
|
size_t arg2_size;
|
|
|
|
size_t arg3_size;
|
|
|
|
size_t arg4_size;
|
|
|
|
size_t arg5_size;
|
|
|
|
};
|
|
|
|
size_t arg_size[5];
|
2020-09-21 12:12:20 +00:00
|
|
|
};
|
2020-06-23 23:08:09 +00:00
|
|
|
int *ret_btf_id; /* return value btf_id */
|
2020-08-25 19:21:19 +00:00
|
|
|
bool (*allowed)(const struct bpf_prog *prog);
|
bpf: verifier (add verifier core)
This patch adds verifier core which simulates execution of every insn and
records the state of registers and program stack. Every branch instruction seen
during simulation is pushed into state stack. When verifier reaches BPF_EXIT,
it pops the state from the stack and continues until it reaches BPF_EXIT again.
For program:
1: bpf_mov r1, xxx
2: if (r1 == 0) goto 5
3: bpf_mov r0, 1
4: goto 6
5: bpf_mov r0, 2
6: bpf_exit
The verifier will walk insns: 1, 2, 3, 4, 6
then it will pop the state recorded at insn#2 and will continue: 5, 6
This way it walks all possible paths through the program and checks all
possible values of registers. While doing so, it checks for:
- invalid instructions
- uninitialized register access
- uninitialized stack access
- misaligned stack access
- out of range stack access
- invalid calling convention
- instruction encoding is not using reserved fields
Kernel subsystem configures the verifier with two callbacks:
- bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
that provides information to the verifer which fields of 'ctx'
are accessible (remember 'ctx' is the first argument to eBPF program)
- const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id);
returns argument constraints of kernel helper functions that eBPF program
may call, so that verifier can checks that R1-R5 types match the prototype
More details in Documentation/networking/filter.txt and in kernel/bpf/verifier.c
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:17:06 +00:00
|
|
|
};
|
|
|
|
|
|
|
|
/* bpf_context is intentionally undefined structure. Pointer to bpf_context is
|
|
|
|
* the first argument to eBPF programs.
|
|
|
|
* For socket filters: 'struct bpf_context *' == 'struct sk_buff *'
|
|
|
|
*/
|
|
|
|
struct bpf_context;
|
|
|
|
|
|
|
|
enum bpf_access_type {
|
|
|
|
BPF_READ = 1,
|
|
|
|
BPF_WRITE = 2
|
2014-09-26 07:17:00 +00:00
|
|
|
};
|
|
|
|
|
2016-06-16 01:25:38 +00:00
|
|
|
/* types of values stored in eBPF registers */
|
2017-08-07 14:26:19 +00:00
|
|
|
/* Pointer types represent:
|
|
|
|
* pointer
|
|
|
|
* pointer + imm
|
|
|
|
* pointer + (u16) var
|
|
|
|
* pointer + (u16) var + imm
|
|
|
|
* if (range > 0) then [ptr, ptr + range - off) is safe to access
|
|
|
|
* if (id > 0) means that some 'var' was added
|
|
|
|
* if (off > 0) means that 'imm' was added
|
|
|
|
*/
|
2016-06-16 01:25:38 +00:00
|
|
|
enum bpf_reg_type {
|
|
|
|
NOT_INIT = 0, /* nothing was written into register */
|
2017-08-07 14:26:19 +00:00
|
|
|
SCALAR_VALUE, /* reg doesn't contain a valid pointer */
|
2016-06-16 01:25:38 +00:00
|
|
|
PTR_TO_CTX, /* reg points to bpf_context */
|
|
|
|
CONST_PTR_TO_MAP, /* reg points to struct bpf_map */
|
|
|
|
PTR_TO_MAP_VALUE, /* reg points to map element value */
|
2021-12-17 00:31:47 +00:00
|
|
|
PTR_TO_MAP_KEY, /* reg points to a map element key */
|
2017-08-07 14:26:19 +00:00
|
|
|
PTR_TO_STACK, /* reg == frame_pointer + offset */
|
bpf: add meta pointer for direct access
This work enables generic transfer of metadata from XDP into skb. The
basic idea is that we can make use of the fact that the resulting skb
must be linear and already comes with a larger headroom for supporting
bpf_xdp_adjust_head(), which mangles xdp->data. Here, we base our work
on a similar principle and introduce a small helper bpf_xdp_adjust_meta()
for adjusting a new pointer called xdp->data_meta. Thus, the packet has
a flexible and programmable room for meta data, followed by the actual
packet data. struct xdp_buff is therefore laid out that we first point
to data_hard_start, then data_meta directly prepended to data followed
by data_end marking the end of packet. bpf_xdp_adjust_head() takes into
account whether we have meta data already prepended and if so, memmove()s
this along with the given offset provided there's enough room.
xdp->data_meta is optional and programs are not required to use it. The
rationale is that when we process the packet in XDP (e.g. as DoS filter),
we can push further meta data along with it for the XDP_PASS case, and
give the guarantee that a clsact ingress BPF program on the same device
can pick this up for further post-processing. Since we work with skb
there, we can also set skb->mark, skb->priority or other skb meta data
out of BPF, thus having this scratch space generic and programmable
allows for more flexibility than defining a direct 1:1 transfer of
potentially new XDP members into skb (it's also more efficient as we
don't need to initialize/handle each of such new members). The facility
also works together with GRO aggregation. The scratch space at the head
of the packet can be multiple of 4 byte up to 32 byte large. Drivers not
yet supporting xdp->data_meta can simply be set up with xdp->data_meta
as xdp->data + 1 as bpf_xdp_adjust_meta() will detect this and bail out,
such that the subsequent match against xdp->data for later access is
guaranteed to fail.
The verifier treats xdp->data_meta/xdp->data the same way as we treat
xdp->data/xdp->data_end pointer comparisons. The requirement for doing
the compare against xdp->data is that it hasn't been modified from it's
original address we got from ctx access. It may have a range marking
already from prior successful xdp->data/xdp->data_end pointer comparisons
though.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-25 00:25:51 +00:00
|
|
|
PTR_TO_PACKET_META, /* skb->data - meta_len */
|
2017-08-07 14:26:19 +00:00
|
|
|
PTR_TO_PACKET, /* reg points to skb->data */
|
2016-06-16 01:25:38 +00:00
|
|
|
PTR_TO_PACKET_END, /* skb->data + headlen */
|
2018-09-14 14:46:18 +00:00
|
|
|
PTR_TO_FLOW_KEYS, /* reg points to bpf_flow_keys */
|
2018-10-02 20:35:33 +00:00
|
|
|
PTR_TO_SOCKET, /* reg points to struct bpf_sock */
|
bpf: Add a bpf_sock pointer to __sk_buff and a bpf_sk_fullsock helper
In kernel, it is common to check "skb->sk && sk_fullsock(skb->sk)"
before accessing the fields in sock. For example, in __netdev_pick_tx:
static u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb,
struct net_device *sb_dev)
{
/* ... */
struct sock *sk = skb->sk;
if (queue_index != new_index && sk &&
sk_fullsock(sk) &&
rcu_access_pointer(sk->sk_dst_cache))
sk_tx_queue_set(sk, new_index);
/* ... */
return queue_index;
}
This patch adds a "struct bpf_sock *sk" pointer to the "struct __sk_buff"
where a few of the convert_ctx_access() in filter.c has already been
accessing the skb->sk sock_common's fields,
e.g. sock_ops_convert_ctx_access().
"__sk_buff->sk" is a PTR_TO_SOCK_COMMON_OR_NULL in the verifier.
Some of the fileds in "bpf_sock" will not be directly
accessible through the "__sk_buff->sk" pointer. It is limited
by the new "bpf_sock_common_is_valid_access()".
e.g. The existing "type", "protocol", "mark" and "priority" in bpf_sock
are not allowed.
The newly added "struct bpf_sock *bpf_sk_fullsock(struct bpf_sock *sk)"
can be used to get a sk with all accessible fields in "bpf_sock".
This helper is added to both cg_skb and sched_(cls|act).
int cg_skb_foo(struct __sk_buff *skb) {
struct bpf_sock *sk;
sk = skb->sk;
if (!sk)
return 1;
sk = bpf_sk_fullsock(sk);
if (!sk)
return 1;
if (sk->family != AF_INET6 || sk->protocol != IPPROTO_TCP)
return 1;
/* some_traffic_shaping(); */
return 1;
}
(1) The sk is read only
(2) There is no new "struct bpf_sock_common" introduced.
(3) Future kernel sock's members could be added to bpf_sock only
instead of repeatedly adding at multiple places like currently
in bpf_sock_ops_md, bpf_sock_addr_md, sk_reuseport_md...etc.
(4) After "sk = skb->sk", the reg holding sk is in type
PTR_TO_SOCK_COMMON_OR_NULL.
(5) After bpf_sk_fullsock(), the return type will be in type
PTR_TO_SOCKET_OR_NULL which is the same as the return type of
bpf_sk_lookup_xxx().
However, bpf_sk_fullsock() does not take refcnt. The
acquire_reference_state() is only depending on the return type now.
To avoid it, a new is_acquire_function() is checked before calling
acquire_reference_state().
(6) The WARN_ON in "release_reference_state()" is no longer an
internal verifier bug.
When reg->id is not found in state->refs[], it means the
bpf_prog does something wrong like
"bpf_sk_release(bpf_sk_fullsock(skb->sk))" where reference has
never been acquired by calling "bpf_sk_fullsock(skb->sk)".
A -EINVAL and a verbose are done instead of WARN_ON. A test is
added to the test_verifier in a later patch.
Since the WARN_ON in "release_reference_state()" is no longer
needed, "__release_reference_state()" is folded into
"release_reference_state()" also.
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-02-10 07:22:20 +00:00
|
|
|
PTR_TO_SOCK_COMMON, /* reg points to sock_common */
|
2019-02-10 07:22:24 +00:00
|
|
|
PTR_TO_TCP_SOCK, /* reg points to struct tcp_sock */
|
2019-04-26 18:49:47 +00:00
|
|
|
PTR_TO_TP_BUFFER, /* reg points to a writable raw tp's buffer */
|
2019-06-06 20:59:40 +00:00
|
|
|
PTR_TO_XDP_SOCK, /* reg points to struct xdp_sock */
|
2020-09-24 19:58:40 +00:00
|
|
|
/* PTR_TO_BTF_ID points to a kernel struct that does not need
|
|
|
|
* to be null checked by the BPF program. This does not imply the
|
|
|
|
* pointer is _not_ null and in practice this can easily be a null
|
|
|
|
* pointer when reading pointer chains. The assumption is program
|
|
|
|
* context will handle null pointer dereference typically via fault
|
|
|
|
* handling. The verifier must keep this in mind and can make no
|
|
|
|
* assumptions about null or non-null when doing branch analysis.
|
|
|
|
* Further, when passed into helpers the helpers can not, without
|
|
|
|
* additional context, assume the value is non-null.
|
|
|
|
*/
|
|
|
|
PTR_TO_BTF_ID,
|
|
|
|
/* PTR_TO_BTF_ID_OR_NULL points to a kernel struct that has not
|
|
|
|
* been checked for null. Used primarily to inform the verifier
|
|
|
|
* an explicit null check is required for this struct.
|
|
|
|
*/
|
bpf: Implement BPF ring buffer and verifier support for it
This commit adds a new MPSC ring buffer implementation into BPF ecosystem,
which allows multiple CPUs to submit data to a single shared ring buffer. On
the consumption side, only single consumer is assumed.
Motivation
----------
There are two distinctive motivators for this work, which are not satisfied by
existing perf buffer, which prompted creation of a new ring buffer
implementation.
- more efficient memory utilization by sharing ring buffer across CPUs;
- preserving ordering of events that happen sequentially in time, even
across multiple CPUs (e.g., fork/exec/exit events for a task).
These two problems are independent, but perf buffer fails to satisfy both.
Both are a result of a choice to have per-CPU perf ring buffer. Both can be
also solved by having an MPSC implementation of ring buffer. The ordering
problem could technically be solved for perf buffer with some in-kernel
counting, but given the first one requires an MPSC buffer, the same solution
would solve the second problem automatically.
Semantics and APIs
------------------
Single ring buffer is presented to BPF programs as an instance of BPF map of
type BPF_MAP_TYPE_RINGBUF. Two other alternatives considered, but ultimately
rejected.
One way would be to, similar to BPF_MAP_TYPE_PERF_EVENT_ARRAY, make
BPF_MAP_TYPE_RINGBUF could represent an array of ring buffers, but not enforce
"same CPU only" rule. This would be more familiar interface compatible with
existing perf buffer use in BPF, but would fail if application needed more
advanced logic to lookup ring buffer by arbitrary key. HASH_OF_MAPS addresses
this with current approach. Additionally, given the performance of BPF
ringbuf, many use cases would just opt into a simple single ring buffer shared
among all CPUs, for which current approach would be an overkill.
Another approach could introduce a new concept, alongside BPF map, to
represent generic "container" object, which doesn't necessarily have key/value
interface with lookup/update/delete operations. This approach would add a lot
of extra infrastructure that has to be built for observability and verifier
support. It would also add another concept that BPF developers would have to
familiarize themselves with, new syntax in libbpf, etc. But then would really
provide no additional benefits over the approach of using a map.
BPF_MAP_TYPE_RINGBUF doesn't support lookup/update/delete operations, but so
doesn't few other map types (e.g., queue and stack; array doesn't support
delete, etc).
The approach chosen has an advantage of re-using existing BPF map
infrastructure (introspection APIs in kernel, libbpf support, etc), being
familiar concept (no need to teach users a new type of object in BPF program),
and utilizing existing tooling (bpftool). For common scenario of using
a single ring buffer for all CPUs, it's as simple and straightforward, as
would be with a dedicated "container" object. On the other hand, by being
a map, it can be combined with ARRAY_OF_MAPS and HASH_OF_MAPS map-in-maps to
implement a wide variety of topologies, from one ring buffer for each CPU
(e.g., as a replacement for perf buffer use cases), to a complicated
application hashing/sharding of ring buffers (e.g., having a small pool of
ring buffers with hashed task's tgid being a look up key to preserve order,
but reduce contention).
Key and value sizes are enforced to be zero. max_entries is used to specify
the size of ring buffer and has to be a power of 2 value.
There are a bunch of similarities between perf buffer
(BPF_MAP_TYPE_PERF_EVENT_ARRAY) and new BPF ring buffer semantics:
- variable-length records;
- if there is no more space left in ring buffer, reservation fails, no
blocking;
- memory-mappable data area for user-space applications for ease of
consumption and high performance;
- epoll notifications for new incoming data;
- but still the ability to do busy polling for new data to achieve the
lowest latency, if necessary.
BPF ringbuf provides two sets of APIs to BPF programs:
- bpf_ringbuf_output() allows to *copy* data from one place to a ring
buffer, similarly to bpf_perf_event_output();
- bpf_ringbuf_reserve()/bpf_ringbuf_commit()/bpf_ringbuf_discard() APIs
split the whole process into two steps. First, a fixed amount of space is
reserved. If successful, a pointer to a data inside ring buffer data area
is returned, which BPF programs can use similarly to a data inside
array/hash maps. Once ready, this piece of memory is either committed or
discarded. Discard is similar to commit, but makes consumer ignore the
record.
bpf_ringbuf_output() has disadvantage of incurring extra memory copy, because
record has to be prepared in some other place first. But it allows to submit
records of the length that's not known to verifier beforehand. It also closely
matches bpf_perf_event_output(), so will simplify migration significantly.
bpf_ringbuf_reserve() avoids the extra copy of memory by providing a memory
pointer directly to ring buffer memory. In a lot of cases records are larger
than BPF stack space allows, so many programs have use extra per-CPU array as
a temporary heap for preparing sample. bpf_ringbuf_reserve() avoid this needs
completely. But in exchange, it only allows a known constant size of memory to
be reserved, such that verifier can verify that BPF program can't access
memory outside its reserved record space. bpf_ringbuf_output(), while slightly
slower due to extra memory copy, covers some use cases that are not suitable
for bpf_ringbuf_reserve().
The difference between commit and discard is very small. Discard just marks
a record as discarded, and such records are supposed to be ignored by consumer
code. Discard is useful for some advanced use-cases, such as ensuring
all-or-nothing multi-record submission, or emulating temporary malloc()/free()
within single BPF program invocation.
Each reserved record is tracked by verifier through existing
reference-tracking logic, similar to socket ref-tracking. It is thus
impossible to reserve a record, but forget to submit (or discard) it.
bpf_ringbuf_query() helper allows to query various properties of ring buffer.
Currently 4 are supported:
- BPF_RB_AVAIL_DATA returns amount of unconsumed data in ring buffer;
- BPF_RB_RING_SIZE returns the size of ring buffer;
- BPF_RB_CONS_POS/BPF_RB_PROD_POS returns current logical possition of
consumer/producer, respectively.
Returned values are momentarily snapshots of ring buffer state and could be
off by the time helper returns, so this should be used only for
debugging/reporting reasons or for implementing various heuristics, that take
into account highly-changeable nature of some of those characteristics.
One such heuristic might involve more fine-grained control over poll/epoll
notifications about new data availability in ring buffer. Together with
BPF_RB_NO_WAKEUP/BPF_RB_FORCE_WAKEUP flags for output/commit/discard helpers,
it allows BPF program a high degree of control and, e.g., more efficient
batched notifications. Default self-balancing strategy, though, should be
adequate for most applications and will work reliable and efficiently already.
Design and implementation
-------------------------
This reserve/commit schema allows a natural way for multiple producers, either
on different CPUs or even on the same CPU/in the same BPF program, to reserve
independent records and work with them without blocking other producers. This
means that if BPF program was interruped by another BPF program sharing the
same ring buffer, they will both get a record reserved (provided there is
enough space left) and can work with it and submit it independently. This
applies to NMI context as well, except that due to using a spinlock during
reservation, in NMI context, bpf_ringbuf_reserve() might fail to get a lock,
in which case reservation will fail even if ring buffer is not full.
The ring buffer itself internally is implemented as a power-of-2 sized
circular buffer, with two logical and ever-increasing counters (which might
wrap around on 32-bit architectures, that's not a problem):
- consumer counter shows up to which logical position consumer consumed the
data;
- producer counter denotes amount of data reserved by all producers.
Each time a record is reserved, producer that "owns" the record will
successfully advance producer counter. At that point, data is still not yet
ready to be consumed, though. Each record has 8 byte header, which contains
the length of reserved record, as well as two extra bits: busy bit to denote
that record is still being worked on, and discard bit, which might be set at
commit time if record is discarded. In the latter case, consumer is supposed
to skip the record and move on to the next one. Record header also encodes
record's relative offset from the beginning of ring buffer data area (in
pages). This allows bpf_ringbuf_commit()/bpf_ringbuf_discard() to accept only
the pointer to the record itself, without requiring also the pointer to ring
buffer itself. Ring buffer memory location will be restored from record
metadata header. This significantly simplifies verifier, as well as improving
API usability.
Producer counter increments are serialized under spinlock, so there is
a strict ordering between reservations. Commits, on the other hand, are
completely lockless and independent. All records become available to consumer
in the order of reservations, but only after all previous records where
already committed. It is thus possible for slow producers to temporarily hold
off submitted records, that were reserved later.
Reservation/commit/consumer protocol is verified by litmus tests in
Documentation/litmus-test/bpf-rb.
One interesting implementation bit, that significantly simplifies (and thus
speeds up as well) implementation of both producers and consumers is how data
area is mapped twice contiguously back-to-back in the virtual memory. This
allows to not take any special measures for samples that have to wrap around
at the end of the circular buffer data area, because the next page after the
last data page would be first data page again, and thus the sample will still
appear completely contiguous in virtual memory. See comment and a simple ASCII
diagram showing this visually in bpf_ringbuf_area_alloc().
Another feature that distinguishes BPF ringbuf from perf ring buffer is
a self-pacing notifications of new data being availability.
bpf_ringbuf_commit() implementation will send a notification of new record
being available after commit only if consumer has already caught up right up
to the record being committed. If not, consumer still has to catch up and thus
will see new data anyways without needing an extra poll notification.
Benchmarks (see tools/testing/selftests/bpf/benchs/bench_ringbuf.c) show that
this allows to achieve a very high throughput without having to resort to
tricks like "notify only every Nth sample", which are necessary with perf
buffer. For extreme cases, when BPF program wants more manual control of
notifications, commit/discard/output helpers accept BPF_RB_NO_WAKEUP and
BPF_RB_FORCE_WAKEUP flags, which give full control over notifications of data
availability, but require extra caution and diligence in using this API.
Comparison to alternatives
--------------------------
Before considering implementing BPF ring buffer from scratch existing
alternatives in kernel were evaluated, but didn't seem to meet the needs. They
largely fell into few categores:
- per-CPU buffers (perf, ftrace, etc), which don't satisfy two motivations
outlined above (ordering and memory consumption);
- linked list-based implementations; while some were multi-producer designs,
consuming these from user-space would be very complicated and most
probably not performant; memory-mapping contiguous piece of memory is
simpler and more performant for user-space consumers;
- io_uring is SPSC, but also requires fixed-sized elements. Naively turning
SPSC queue into MPSC w/ lock would have subpar performance compared to
locked reserve + lockless commit, as with BPF ring buffer. Fixed sized
elements would be too limiting for BPF programs, given existing BPF
programs heavily rely on variable-sized perf buffer already;
- specialized implementations (like a new printk ring buffer, [0]) with lots
of printk-specific limitations and implications, that didn't seem to fit
well for intended use with BPF programs.
[0] https://lwn.net/Articles/779550/
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200529075424.3139988-2-andriin@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2020-05-29 07:54:20 +00:00
|
|
|
PTR_TO_MEM, /* reg points to valid memory region */
|
2021-12-17 00:31:48 +00:00
|
|
|
PTR_TO_BUF, /* reg points to a read/write buffer */
|
bpf: Add bpf_for_each_map_elem() helper
The bpf_for_each_map_elem() helper is introduced which
iterates all map elements with a callback function. The
helper signature looks like
long bpf_for_each_map_elem(map, callback_fn, callback_ctx, flags)
and for each map element, the callback_fn will be called. For example,
like hashmap, the callback signature may look like
long callback_fn(map, key, val, callback_ctx)
There are two known use cases for this. One is from upstream ([1]) where
a for_each_map_elem helper may help implement a timeout mechanism
in a more generic way. Another is from our internal discussion
for a firewall use case where a map contains all the rules. The packet
data can be compared to all these rules to decide allow or deny
the packet.
For array maps, users can already use a bounded loop to traverse
elements. Using this helper can avoid using bounded loop. For other
type of maps (e.g., hash maps) where bounded loop is hard or
impossible to use, this helper provides a convenient way to
operate on all elements.
For callback_fn, besides map and map element, a callback_ctx,
allocated on caller stack, is also passed to the callback
function. This callback_ctx argument can provide additional
input and allow to write to caller stack for output.
If the callback_fn returns 0, the helper will iterate through next
element if available. If the callback_fn returns 1, the helper
will stop iterating and returns to the bpf program. Other return
values are not used for now.
Currently, this helper is only available with jit. It is possible
to make it work with interpreter with so effort but I leave it
as the future work.
[1]: https://lore.kernel.org/bpf/20210122205415.113822-1-xiyou.wangcong@gmail.com/
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210226204925.3884923-1-yhs@fb.com
2021-02-26 20:49:25 +00:00
|
|
|
PTR_TO_FUNC, /* reg points to a bpf program function */
|
bpf: Support bpf program calling kernel function
This patch adds support to BPF verifier to allow bpf program calling
kernel function directly.
The use case included in this set is to allow bpf-tcp-cc to directly
call some tcp-cc helper functions (e.g. "tcp_cong_avoid_ai()"). Those
functions have already been used by some kernel tcp-cc implementations.
This set will also allow the bpf-tcp-cc program to directly call the
kernel tcp-cc implementation, For example, a bpf_dctcp may only want to
implement its own dctcp_cwnd_event() and reuse other dctcp_*() directly
from the kernel tcp_dctcp.c instead of reimplementing (or
copy-and-pasting) them.
The tcp-cc kernel functions mentioned above will be white listed
for the struct_ops bpf-tcp-cc programs to use in a later patch.
The white listed functions are not bounded to a fixed ABI contract.
Those functions have already been used by the existing kernel tcp-cc.
If any of them has changed, both in-tree and out-of-tree kernel tcp-cc
implementations have to be changed. The same goes for the struct_ops
bpf-tcp-cc programs which have to be adjusted accordingly.
This patch is to make the required changes in the bpf verifier.
First change is in btf.c, it adds a case in "btf_check_func_arg_match()".
When the passed in "btf->kernel_btf == true", it means matching the
verifier regs' states with a kernel function. This will handle the
PTR_TO_BTF_ID reg. It also maps PTR_TO_SOCK_COMMON, PTR_TO_SOCKET,
and PTR_TO_TCP_SOCK to its kernel's btf_id.
In the later libbpf patch, the insn calling a kernel function will
look like:
insn->code == (BPF_JMP | BPF_CALL)
insn->src_reg == BPF_PSEUDO_KFUNC_CALL /* <- new in this patch */
insn->imm == func_btf_id /* btf_id of the running kernel */
[ For the future calling function-in-kernel-module support, an array
of module btf_fds can be passed at the load time and insn->off
can be used to index into this array. ]
At the early stage of verifier, the verifier will collect all kernel
function calls into "struct bpf_kfunc_desc". Those
descriptors are stored in "prog->aux->kfunc_tab" and will
be available to the JIT. Since this "add" operation is similar
to the current "add_subprog()" and looking for the same insn->code,
they are done together in the new "add_subprog_and_kfunc()".
In the "do_check()" stage, the new "check_kfunc_call()" is added
to verify the kernel function call instruction:
1. Ensure the kernel function can be used by a particular BPF_PROG_TYPE.
A new bpf_verifier_ops "check_kfunc_call" is added to do that.
The bpf-tcp-cc struct_ops program will implement this function in
a later patch.
2. Call "btf_check_kfunc_args_match()" to ensure the regs can be
used as the args of a kernel function.
3. Mark the regs' type, subreg_def, and zext_dst.
At the later do_misc_fixups() stage, the new fixup_kfunc_call()
will replace the insn->imm with the function address (relative
to __bpf_call_base). If needed, the jit can find the btf_func_model
by calling the new bpf_jit_find_kfunc_model(prog, insn).
With the imm set to the function address, "bpftool prog dump xlated"
will be able to display the kernel function calls the same way as
it displays other bpf helper calls.
gpl_compatible program is required to call kernel function.
This feature currently requires JIT.
The verifier selftests are adjusted because of the changes in
the verbose log in add_subprog_and_kfunc().
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015142.1544736-1-kafai@fb.com
2021-03-25 01:51:42 +00:00
|
|
|
__BPF_REG_TYPE_MAX,
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
|
2021-12-17 00:31:47 +00:00
|
|
|
/* Extended reg_types. */
|
|
|
|
PTR_TO_MAP_VALUE_OR_NULL = PTR_MAYBE_NULL | PTR_TO_MAP_VALUE,
|
|
|
|
PTR_TO_SOCKET_OR_NULL = PTR_MAYBE_NULL | PTR_TO_SOCKET,
|
|
|
|
PTR_TO_SOCK_COMMON_OR_NULL = PTR_MAYBE_NULL | PTR_TO_SOCK_COMMON,
|
|
|
|
PTR_TO_TCP_SOCK_OR_NULL = PTR_MAYBE_NULL | PTR_TO_TCP_SOCK,
|
|
|
|
PTR_TO_BTF_ID_OR_NULL = PTR_MAYBE_NULL | PTR_TO_BTF_ID,
|
|
|
|
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
/* This must be the last entry. Its purpose is to ensure the enum is
|
|
|
|
* wide enough to hold the higher bits reserved for bpf_type_flag.
|
|
|
|
*/
|
|
|
|
__BPF_REG_TYPE_LIMIT = BPF_TYPE_LIMIT,
|
2016-06-16 01:25:38 +00:00
|
|
|
};
|
bpf: Introduce composable reg, ret and arg types.
There are some common properties shared between bpf reg, ret and arg
values. For instance, a value may be a NULL pointer, or a pointer to
a read-only memory. Previously, to express these properties, enumeration
was used. For example, in order to test whether a reg value can be NULL,
reg_type_may_be_null() simply enumerates all types that are possibly
NULL. The problem of this approach is that it's not scalable and causes
a lot of duplication. These properties can be combined, for example, a
type could be either MAYBE_NULL or RDONLY, or both.
This patch series rewrites the layout of reg_type, arg_type and
ret_type, so that common properties can be extracted and represented as
composable flag. For example, one can write
ARG_PTR_TO_MEM | PTR_MAYBE_NULL
which is equivalent to the previous
ARG_PTR_TO_MEM_OR_NULL
The type ARG_PTR_TO_MEM are called "base type" in this patch. Base
types can be extended with flags. A flag occupies the higher bits while
base types sits in the lower bits.
This patch in particular sets up a set of macro for this purpose. The
following patches will rewrite arg_types, ret_types and reg_types
respectively.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-2-haoluo@google.com
2021-12-17 00:31:44 +00:00
|
|
|
static_assert(__BPF_REG_TYPE_MAX <= BPF_BASE_TYPE_LIMIT);
|
2016-06-16 01:25:38 +00:00
|
|
|
|
2017-06-22 22:07:39 +00:00
|
|
|
/* The information passed from prog-specific *_is_valid_access
|
|
|
|
* back to the verifier.
|
|
|
|
*/
|
|
|
|
struct bpf_insn_access_aux {
|
|
|
|
enum bpf_reg_type reg_type;
|
2019-10-16 03:25:00 +00:00
|
|
|
union {
|
|
|
|
int ctx_field_size;
|
bpf: Remove hard-coded btf_vmlinux assumption from BPF verifier
Remove a permeating assumption thoughout BPF verifier of vmlinux BTF. Instead,
wherever BTF type IDs are involved, also track the instance of struct btf that
goes along with the type ID. This allows to gradually add support for kernel
module BTFs and using/tracking module types across BPF helper calls and
registers.
This patch also renames btf_id() function to btf_obj_id() to minimize naming
clash with using btf_id to denote BTF *type* ID, rather than BTF *object*'s ID.
Also, altough btf_vmlinux can't get destructed and thus doesn't need
refcounting, module BTFs need that, so apply BTF refcounting universally when
BPF program is using BTF-powered attachment (tp_btf, fentry/fexit, etc). This
makes for simpler clean up code.
Now that BTF type ID is not enough to uniquely identify a BTF type, extend BPF
trampoline key to include BTF object ID. To differentiate that from target
program BPF ID, set 31st bit of type ID. BTF type IDs (at least currently) are
not allowed to take full 32 bits, so there is no danger of confusing that bit
with a valid BTF type ID.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201203204634.1325171-10-andrii@kernel.org
2020-12-03 20:46:29 +00:00
|
|
|
struct {
|
|
|
|
struct btf *btf;
|
|
|
|
u32 btf_id;
|
|
|
|
};
|
2019-10-16 03:25:00 +00:00
|
|
|
};
|
|
|
|
struct bpf_verifier_log *log; /* for verbose logs */
|
2017-06-22 22:07:39 +00:00
|
|
|
};
|
|
|
|
|
bpf: simplify narrower ctx access
This work tries to make the semantics and code around the
narrower ctx access a bit easier to follow. Right now
everything is done inside the .is_valid_access(). Offset
matching is done differently for read/write types, meaning
writes don't support narrower access and thus matching only
on offsetof(struct foo, bar) is enough whereas for read
case that supports narrower access we must check for
offsetof(struct foo, bar) + offsetof(struct foo, bar) +
sizeof(<bar>) - 1 for each of the cases. For read cases of
individual members that don't support narrower access (like
packet pointers or skb->cb[] case which has its own narrow
access logic), we check as usual only offsetof(struct foo,
bar) like in write case. Then, for the case where narrower
access is allowed, we also need to set the aux info for the
access. Meaning, ctx_field_size and converted_op_size have
to be set. First is the original field size e.g. sizeof(<bar>)
as in above example from the user facing ctx, and latter
one is the target size after actual rewrite happened, thus
for the kernel facing ctx. Also here we need the range match
and we need to keep track changing convert_ctx_access() and
converted_op_size from is_valid_access() as both are not at
the same location.
We can simplify the code a bit: check_ctx_access() becomes
simpler in that we only store ctx_field_size as a meta data
and later in convert_ctx_accesses() we fetch the target_size
right from the location where we do convert. Should the verifier
be misconfigured we do reject for BPF_WRITE cases or target_size
that are not provided. For the subsystems, we always work on
ranges in is_valid_access() and add small helpers for ranges
and narrow access, convert_ctx_accesses() sets target_size
for the relevant instruction.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Cc: Yonghong Song <yhs@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-07-02 00:13:27 +00:00
|
|
|
static inline void
|
|
|
|
bpf_ctx_record_field_size(struct bpf_insn_access_aux *aux, u32 size)
|
|
|
|
{
|
|
|
|
aux->ctx_field_size = size;
|
|
|
|
}
|
|
|
|
|
2021-11-06 01:40:14 +00:00
|
|
|
static inline bool bpf_pseudo_func(const struct bpf_insn *insn)
|
|
|
|
{
|
|
|
|
return insn->code == (BPF_LD | BPF_IMM | BPF_DW) &&
|
|
|
|
insn->src_reg == BPF_PSEUDO_FUNC;
|
|
|
|
}
|
|
|
|
|
2017-10-16 23:40:53 +00:00
|
|
|
struct bpf_prog_ops {
|
|
|
|
int (*test_run)(struct bpf_prog *prog, const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr);
|
|
|
|
};
|
|
|
|
|
2014-09-26 07:17:00 +00:00
|
|
|
struct bpf_verifier_ops {
|
|
|
|
/* return eBPF function prototype for verification */
|
2018-03-30 22:08:00 +00:00
|
|
|
const struct bpf_func_proto *
|
|
|
|
(*get_func_proto)(enum bpf_func_id func_id,
|
|
|
|
const struct bpf_prog *prog);
|
bpf: verifier (add verifier core)
This patch adds verifier core which simulates execution of every insn and
records the state of registers and program stack. Every branch instruction seen
during simulation is pushed into state stack. When verifier reaches BPF_EXIT,
it pops the state from the stack and continues until it reaches BPF_EXIT again.
For program:
1: bpf_mov r1, xxx
2: if (r1 == 0) goto 5
3: bpf_mov r0, 1
4: goto 6
5: bpf_mov r0, 2
6: bpf_exit
The verifier will walk insns: 1, 2, 3, 4, 6
then it will pop the state recorded at insn#2 and will continue: 5, 6
This way it walks all possible paths through the program and checks all
possible values of registers. While doing so, it checks for:
- invalid instructions
- uninitialized register access
- uninitialized stack access
- misaligned stack access
- out of range stack access
- invalid calling convention
- instruction encoding is not using reserved fields
Kernel subsystem configures the verifier with two callbacks:
- bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
that provides information to the verifer which fields of 'ctx'
are accessible (remember 'ctx' is the first argument to eBPF program)
- const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id);
returns argument constraints of kernel helper functions that eBPF program
may call, so that verifier can checks that R1-R5 types match the prototype
More details in Documentation/networking/filter.txt and in kernel/bpf/verifier.c
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-26 07:17:06 +00:00
|
|
|
|
|
|
|
/* return true if 'size' wide access at offset 'off' within bpf_context
|
|
|
|
* with 'type' (read or write) is allowed
|
|
|
|
*/
|
2016-06-16 01:25:38 +00:00
|
|
|
bool (*is_valid_access)(int off, int size, enum bpf_access_type type,
|
2018-03-30 22:08:00 +00:00
|
|
|
const struct bpf_prog *prog,
|
2017-06-22 22:07:39 +00:00
|
|
|
struct bpf_insn_access_aux *info);
|
bpf: direct packet write and access for helpers for clsact progs
This work implements direct packet access for helpers and direct packet
write in a similar fashion as already available for XDP types via commits
4acf6c0b84c9 ("bpf: enable direct packet data write for xdp progs") and
6841de8b0d03 ("bpf: allow helpers access the packet directly"), and as a
complementary feature to the already available direct packet read for tc
(cls/act) programs.
For enabling this, we need to introduce two helpers, bpf_skb_pull_data()
and bpf_csum_update(). The first is generally needed for both, read and
write, because they would otherwise only be limited to the current linear
skb head. Usually, when the data_end test fails, programs just bail out,
or, in the direct read case, use bpf_skb_load_bytes() as an alternative
to overcome this limitation. If such data sits in non-linear parts, we
can just pull them in once with the new helper, retest and eventually
access them.
At the same time, this also makes sure the skb is uncloned, which is, of
course, a necessary condition for direct write. As this needs to be an
invariant for the write part only, the verifier detects writes and adds
a prologue that is calling bpf_skb_pull_data() to effectively unclone the
skb from the very beginning in case it is indeed cloned. The heuristic
makes use of a similar trick that was done in 233577a22089 ("net: filter:
constify detection of pkt_type_offset"). This comes at zero cost for other
programs that do not use the direct write feature. Should a program use
this feature only sparsely and has read access for the most parts with,
for example, drop return codes, then such write action can be delegated
to a tail called program for mitigating this cost of potential uncloning
to a late point in time where it would have been paid similarly with the
bpf_skb_store_bytes() as well. Advantage of direct write is that the
writes are inlined whereas the helper cannot make any length assumptions
and thus needs to generate a call to memcpy() also for small sizes, as well
as cost of helper call itself with sanity checks are avoided. Plus, when
direct read is already used, we don't need to cache or perform rechecks
on the data boundaries (due to verifier invalidating previous checks for
helpers that change skb->data), so more complex programs using rewrites
can benefit from switching to direct read plus write.
For direct packet access to helpers, we save the otherwise needed copy into
a temp struct sitting on stack memory when use-case allows. Both facilities
are enabled via may_access_direct_pkt_data() in verifier. For now, we limit
this to map helpers and csum_diff, and can successively enable other helpers
where we find it makes sense. Helpers that definitely cannot be allowed for
this are those part of bpf_helper_changes_skb_data() since they can change
underlying data, and those that write into memory as this could happen for
packet typed args when still cloned. bpf_csum_update() helper accommodates
for the fact that we need to fixup checksum_complete when using direct write
instead of bpf_skb_store_bytes(), meaning the programs can use available
helpers like bpf_csum_diff(), and implement csum_add(), csum_sub(),
csum_block_add(), csum_block_sub() equivalents in eBPF together with the
new helper. A usage example will be provided for iproute2's examples/bpf/
directory.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-09-19 22:26:13 +00:00
|
|
|
int (*gen_prologue)(struct bpf_insn *insn, bool direct_write,
|
|
|
|
const struct bpf_prog *prog);
|
bpf: implement ld_abs/ld_ind in native bpf
The main part of this work is to finally allow removal of LD_ABS
and LD_IND from the BPF core by reimplementing them through native
eBPF instead. Both LD_ABS/LD_IND were carried over from cBPF and
keeping them around in native eBPF caused way more trouble than
actually worth it. To just list some of the security issues in
the past:
* fdfaf64e7539 ("x86: bpf_jit: support negative offsets")
* 35607b02dbef ("sparc: bpf_jit: fix loads from negative offsets")
* e0ee9c12157d ("x86: bpf_jit: fix two bugs in eBPF JIT compiler")
* 07aee9439454 ("bpf, sparc: fix usage of wrong reg for load_skb_regs after call")
* 6d59b7dbf72e ("bpf, s390x: do not reload skb pointers in non-skb context")
* 87338c8e2cbb ("bpf, ppc64: do not reload skb pointers in non-skb context")
For programs in native eBPF, LD_ABS/LD_IND are pretty much legacy
these days due to their limitations and more efficient/flexible
alternatives that have been developed over time such as direct
packet access. LD_ABS/LD_IND only cover 1/2/4 byte loads into a
register, the load happens in host endianness and its exception
handling can yield unexpected behavior. The latter is explained
in depth in f6b1b3bf0d5f ("bpf: fix subprog verifier bypass by
div/mod by 0 exception") with similar cases of exceptions we had.
In native eBPF more recent program types will disable LD_ABS/LD_IND
altogether through may_access_skb() in verifier, and given the
limitations in terms of exception handling, it's also disabled
in programs that use BPF to BPF calls.
In terms of cBPF, the LD_ABS/LD_IND is used in networking programs
to access packet data. It is not used in seccomp-BPF but programs
that use it for socket filtering or reuseport for demuxing with
cBPF. This is mostly relevant for applications that have not yet
migrated to native eBPF.
The main complexity and source of bugs in LD_ABS/LD_IND is coming
from their implementation in the various JITs. Most of them keep
the model around from cBPF times by implementing a fastpath written
in asm. They use typically two from the BPF program hidden CPU
registers for caching the skb's headlen (skb->len - skb->data_len)
and skb->data. Throughout the JIT phase this requires to keep track
whether LD_ABS/LD_IND are used and if so, the two registers need
to be recached each time a BPF helper would change the underlying
packet data in native eBPF case. At least in eBPF case, available
CPU registers are rare and the additional exit path out of the
asm written JIT helper makes it also inflexible since not all
parts of the JITer are in control from plain C. A LD_ABS/LD_IND
implementation in eBPF therefore allows to significantly reduce
the complexity in JITs with comparable performance results for
them, e.g.:
test_bpf tcpdump port 22 tcpdump complex
x64 - before 15 21 10 14 19 18
- after 7 10 10 7 10 15
arm64 - before 40 91 92 40 91 151
- after 51 64 73 51 62 113
For cBPF we now track any usage of LD_ABS/LD_IND in bpf_convert_filter()
and cache the skb's headlen and data in the cBPF prologue. The
BPF_REG_TMP gets remapped from R8 to R2 since it's mainly just
used as a local temporary variable. This allows to shrink the
image on x86_64 also for seccomp programs slightly since mapping
to %rsi is not an ereg. In callee-saved R8 and R9 we now track
skb data and headlen, respectively. For normal prologue emission
in the JITs this does not add any extra instructions since R8, R9
are pushed to stack in any case from eBPF side. cBPF uses the
convert_bpf_ld_abs() emitter which probes the fast path inline
already and falls back to bpf_skb_load_helper_{8,16,32}() helper
relying on the cached skb data and headlen as well. R8 and R9
never need to be reloaded due to bpf_helper_changes_pkt_data()
since all skb access in cBPF is read-only. Then, for the case
of native eBPF, we use the bpf_gen_ld_abs() emitter, which calls
the bpf_skb_load_helper_{8,16,32}_no_cache() helper unconditionally,
does neither cache skb data and headlen nor has an inlined fast
path. The reason for the latter is that native eBPF does not have
any extra registers available anyway, but even if there were, it
avoids any reload of skb data and headlen in the first place.
Additionally, for the negative offsets, we provide an alternative
bpf_skb_load_bytes_relative() helper in eBPF which operates
similarly as bpf_skb_load_bytes() and allows for more flexibility.
Tested myself on x64, arm64, s390x, from Sandipan on ppc64.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-05-03 23:08:14 +00:00
|
|
|
int (*gen_ld_abs)(const struct bpf_insn *orig,
|
|
|
|
struct bpf_insn *insn_buf);
|
2017-01-12 10:51:32 +00:00
|
|
|
u32 (*convert_ctx_access)(enum bpf_access_type type,
|
|
|
|
const struct bpf_insn *src,
|
|
|
|
struct bpf_insn *dst,
|
bpf: simplify narrower ctx access
This work tries to make the semantics and code around the
narrower ctx access a bit easier to follow. Right now
everything is done inside the .is_valid_access(). Offset
matching is done differently for read/write types, meaning
writes don't support narrower access and thus matching only
on offsetof(struct foo, bar) is enough whereas for read
case that supports narrower access we must check for
offsetof(struct foo, bar) + offsetof(struct foo, bar) +
sizeof(<bar>) - 1 for each of the cases. For read cases of
individual members that don't support narrower access (like
packet pointers or skb->cb[] case which has its own narrow
access logic), we check as usual only offsetof(struct foo,
bar) like in write case. Then, for the case where narrower
access is allowed, we also need to set the aux info for the
access. Meaning, ctx_field_size and converted_op_size have
to be set. First is the original field size e.g. sizeof(<bar>)
as in above example from the user facing ctx, and latter
one is the target size after actual rewrite happened, thus
for the kernel facing ctx. Also here we need the range match
and we need to keep track changing convert_ctx_access() and
converted_op_size from is_valid_access() as both are not at
the same location.
We can simplify the code a bit: check_ctx_access() becomes
simpler in that we only store ctx_field_size as a meta data
and later in convert_ctx_accesses() we fetch the target_size
right from the location where we do convert. Should the verifier
be misconfigured we do reject for BPF_WRITE cases or target_size
that are not provided. For the subsystems, we always work on
ranges in is_valid_access() and add small helpers for ranges
and narrow access, convert_ctx_accesses() sets target_size
for the relevant instruction.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Cc: Yonghong Song <yhs@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-07-02 00:13:27 +00:00
|
|
|
struct bpf_prog *prog, u32 *target_size);
|
2020-01-09 00:35:03 +00:00
|
|
|
int (*btf_struct_access)(struct bpf_verifier_log *log,
|
bpf: Remove hard-coded btf_vmlinux assumption from BPF verifier
Remove a permeating assumption thoughout BPF verifier of vmlinux BTF. Instead,
wherever BTF type IDs are involved, also track the instance of struct btf that
goes along with the type ID. This allows to gradually add support for kernel
module BTFs and using/tracking module types across BPF helper calls and
registers.
This patch also renames btf_id() function to btf_obj_id() to minimize naming
clash with using btf_id to denote BTF *type* ID, rather than BTF *object*'s ID.
Also, altough btf_vmlinux can't get destructed and thus doesn't need
refcounting, module BTFs need that, so apply BTF refcounting universally when
BPF program is using BTF-powered attachment (tp_btf, fentry/fexit, etc). This
makes for simpler clean up code.
Now that BTF type ID is not enough to uniquely identify a BTF type, extend BPF
trampoline key to include BTF object ID. To differentiate that from target
program BPF ID, set 31st bit of type ID. BTF type IDs (at least currently) are
not allowed to take full 32 bits, so there is no danger of confusing that bit
with a valid BTF type ID.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201203204634.1325171-10-andrii@kernel.org
2020-12-03 20:46:29 +00:00
|
|
|
const struct btf *btf,
|
2020-01-09 00:35:03 +00:00
|
|
|
const struct btf_type *t, int off, int size,
|
|
|
|
enum bpf_access_type atype,
|
bpf: reject program if a __user tagged memory accessed in kernel way
BPF verifier supports direct memory access for BPF_PROG_TYPE_TRACING type
of bpf programs, e.g., a->b. If "a" is a pointer
pointing to kernel memory, bpf verifier will allow user to write
code in C like a->b and the verifier will translate it to a kernel
load properly. If "a" is a pointer to user memory, it is expected
that bpf developer should be bpf_probe_read_user() helper to
get the value a->b. Without utilizing BTF __user tagging information,
current verifier will assume that a->b is a kernel memory access
and this may generate incorrect result.
Now BTF contains __user information, it can check whether the
pointer points to a user memory or not. If it is, the verifier
can reject the program and force users to use bpf_probe_read_user()
helper explicitly.
In the future, we can easily extend btf_add_space for other
address space tagging, for example, rcu/percpu etc.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20220127154606.654961-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-01-27 15:46:06 +00:00
|
|
|
u32 *next_btf_id, enum bpf_type_flag *flag);
|
2014-09-26 07:17:00 +00:00
|
|
|
};
|
|
|
|
|
2017-12-28 02:39:05 +00:00
|
|
|
struct bpf_prog_offload_ops {
|
2019-01-23 06:45:24 +00:00
|
|
|
/* verifier basic callbacks */
|
2017-12-28 02:39:05 +00:00
|
|
|
int (*insn_hook)(struct bpf_verifier_env *env,
|
|
|
|
int insn_idx, int prev_insn_idx);
|
2018-10-07 11:56:47 +00:00
|
|
|
int (*finalize)(struct bpf_verifier_env *env);
|
2019-01-23 06:45:24 +00:00
|
|
|
/* verifier optimization callbacks (called after .finalize) */
|
|
|
|
int (*replace_insn)(struct bpf_verifier_env *env, u32 off,
|
|
|
|
struct bpf_insn *insn);
|
|
|
|
int (*remove_insns)(struct bpf_verifier_env *env, u32 off, u32 cnt);
|
|
|
|
/* program management callbacks */
|
2018-11-09 13:03:32 +00:00
|
|
|
int (*prepare)(struct bpf_prog *prog);
|
|
|
|
int (*translate)(struct bpf_prog *prog);
|
2018-11-09 13:03:30 +00:00
|
|
|
void (*destroy)(struct bpf_prog *prog);
|
2017-12-28 02:39:05 +00:00
|
|
|
};
|
|
|
|
|
2018-01-12 04:29:07 +00:00
|
|
|
struct bpf_prog_offload {
|
2017-11-03 20:56:17 +00:00
|
|
|
struct bpf_prog *prog;
|
|
|
|
struct net_device *netdev;
|
2018-11-09 13:03:26 +00:00
|
|
|
struct bpf_offload_dev *offdev;
|
2017-11-03 20:56:17 +00:00
|
|
|
void *dev_priv;
|
|
|
|
struct list_head offloads;
|
|
|
|
bool dev_state;
|
2019-01-23 06:45:24 +00:00
|
|
|
bool opt_failed;
|
2018-01-17 00:05:19 +00:00
|
|
|
void *jited_image;
|
|
|
|
u32 jited_len;
|
2017-11-03 20:56:17 +00:00
|
|
|
};
|
|
|
|
|
2018-09-28 14:45:36 +00:00
|
|
|
enum bpf_cgroup_storage_type {
|
|
|
|
BPF_CGROUP_STORAGE_SHARED,
|
2018-09-28 14:45:43 +00:00
|
|
|
BPF_CGROUP_STORAGE_PERCPU,
|
2018-09-28 14:45:36 +00:00
|
|
|
__BPF_CGROUP_STORAGE_MAX
|
|
|
|
};
|
|
|
|
|
|
|
|
#define MAX_BPF_CGROUP_STORAGE_TYPE __BPF_CGROUP_STORAGE_MAX
|
|
|
|
|
2019-10-30 22:32:11 +00:00
|
|
|
/* The longest tracepoint has 12 args.
|
|
|
|
* See include/trace/bpf_probe.h
|
|
|
|
*/
|
|
|
|
#define MAX_BPF_FUNC_ARGS 12
|
|
|
|
|
2021-02-25 20:26:29 +00:00
|
|
|
/* The maximum number of arguments passed through registers
|
|
|
|
* a single function may have.
|
|
|
|
*/
|
|
|
|
#define MAX_BPF_FUNC_REG_ARGS 5
|
|
|
|
|
2019-11-14 18:57:04 +00:00
|
|
|
struct btf_func_model {
|
|
|
|
u8 ret_size;
|
|
|
|
u8 nr_args;
|
|
|
|
u8 arg_size[MAX_BPF_FUNC_ARGS];
|
|
|
|
};
|
|
|
|
|
|
|
|
/* Restore arguments before returning from trampoline to let original function
|
|
|
|
* continue executing. This flag is used for fentry progs when there are no
|
|
|
|
* fexit progs.
|
|
|
|
*/
|
|
|
|
#define BPF_TRAMP_F_RESTORE_REGS BIT(0)
|
|
|
|
/* Call original function after fentry progs, but before fexit progs.
|
|
|
|
* Makes sense for fentry/fexit, normal calls and indirect calls.
|
|
|
|
*/
|
|
|
|
#define BPF_TRAMP_F_CALL_ORIG BIT(1)
|
|
|
|
/* Skip current frame and return to parent. Makes sense for fentry/fexit
|
|
|
|
* programs only. Should not be used with normal calls and indirect calls.
|
|
|
|
*/
|
|
|
|
#define BPF_TRAMP_F_SKIP_FRAME BIT(2)
|
2021-07-14 09:43:53 +00:00
|
|
|
/* Store IP address of the caller on the trampoline stack,
|
|
|
|
* so it's available for trampoline's programs.
|
|
|
|
*/
|
|
|
|
#define BPF_TRAMP_F_IP_ARG BIT(3)
|
2021-09-14 02:33:51 +00:00
|
|
|
/* Return the return value of fentry prog. Only used by bpf_struct_ops. */
|
|
|
|
#define BPF_TRAMP_F_RET_FENTRY_RET BIT(4)
|
2021-07-14 09:43:53 +00:00
|
|
|
|
2022-07-20 00:21:25 +00:00
|
|
|
/* Get original function from stack instead of from provided direct address.
|
|
|
|
* Makes sense for trampolines with fexit or fmod_ret programs.
|
|
|
|
*/
|
|
|
|
#define BPF_TRAMP_F_ORIG_STACK BIT(5)
|
|
|
|
|
2022-07-20 00:21:26 +00:00
|
|
|
/* This trampoline is on a function with another ftrace_ops with IPMODIFY,
|
|
|
|
* e.g., a live patch. This flag is set and cleared by ftrace call backs,
|
|
|
|
*/
|
|
|
|
#define BPF_TRAMP_F_SHARE_IPMODIFY BIT(6)
|
|
|
|
|
2020-03-04 19:18:47 +00:00
|
|
|
/* Each call __bpf_prog_enter + call bpf_func + call __bpf_prog_exit is ~50
|
2022-05-19 15:06:10 +00:00
|
|
|
* bytes on x86.
|
2020-03-04 19:18:47 +00:00
|
|
|
*/
|
2022-05-10 20:59:19 +00:00
|
|
|
#define BPF_MAX_TRAMP_LINKS 38
|
2020-03-04 19:18:47 +00:00
|
|
|
|
2022-05-10 20:59:19 +00:00
|
|
|
struct bpf_tramp_links {
|
|
|
|
struct bpf_tramp_link *links[BPF_MAX_TRAMP_LINKS];
|
|
|
|
int nr_links;
|
2020-03-04 19:18:47 +00:00
|
|
|
};
|
|
|
|
|
2022-05-10 20:59:20 +00:00
|
|
|
struct bpf_tramp_run_ctx;
|
|
|
|
|
2019-11-14 18:57:04 +00:00
|
|
|
/* Different use cases for BPF trampoline:
|
|
|
|
* 1. replace nop at the function entry (kprobe equivalent)
|
|
|
|
* flags = BPF_TRAMP_F_RESTORE_REGS
|
|
|
|
* fentry = a set of programs to run before returning from trampoline
|
|
|
|
*
|
|
|
|
* 2. replace nop at the function entry (kprobe + kretprobe equivalent)
|
|
|
|
* flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME
|
|
|
|
* orig_call = fentry_ip + MCOUNT_INSN_SIZE
|
|
|
|
* fentry = a set of program to run before calling original function
|
|
|
|
* fexit = a set of program to run after original function
|
|
|
|
*
|
|
|
|
* 3. replace direct call instruction anywhere in the function body
|
|
|
|
* or assign a function pointer for indirect call (like tcp_congestion_ops->cong_avoid)
|
|
|
|
* With flags = 0
|
|
|
|
* fentry = a set of programs to run before returning from trampoline
|
|
|
|
* With flags = BPF_TRAMP_F_CALL_ORIG
|
|
|
|
* orig_call = original callback addr or direct function addr
|
|
|
|
* fentry = a set of program to run before calling original function
|
|
|
|
* fexit = a set of program to run after original function
|
|
|
|
*/
|
2021-03-16 21:00:07 +00:00
|
|
|
struct bpf_tramp_image;
|
|
|
|
int arch_prepare_bpf_trampoline(struct bpf_tramp_image *tr, void *image, void *image_end,
|
bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 00:35:05 +00:00
|
|
|
const struct btf_func_model *m, u32 flags,
|
2022-05-10 20:59:19 +00:00
|
|
|
struct bpf_tramp_links *tlinks,
|
2019-11-14 18:57:04 +00:00
|
|
|
void *orig_call);
|
|
|
|
/* these two functions are called from generated trampoline */
|
2022-05-10 20:59:20 +00:00
|
|
|
u64 notrace __bpf_prog_enter(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx);
|
|
|
|
void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start, struct bpf_tramp_run_ctx *run_ctx);
|
|
|
|
u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx);
|
|
|
|
void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
|
|
|
|
struct bpf_tramp_run_ctx *run_ctx);
|
2022-06-28 17:43:06 +00:00
|
|
|
u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog,
|
|
|
|
struct bpf_tramp_run_ctx *run_ctx);
|
|
|
|
void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start,
|
|
|
|
struct bpf_tramp_run_ctx *run_ctx);
|
2021-03-16 21:00:07 +00:00
|
|
|
void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr);
|
|
|
|
void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr);
|
2019-11-14 18:57:04 +00:00
|
|
|
|
2020-03-12 19:55:58 +00:00
|
|
|
struct bpf_ksym {
|
|
|
|
unsigned long start;
|
|
|
|
unsigned long end;
|
2020-03-12 19:55:59 +00:00
|
|
|
char name[KSYM_NAME_LEN];
|
2020-03-12 19:56:00 +00:00
|
|
|
struct list_head lnode;
|
2020-03-12 19:56:01 +00:00
|
|
|
struct latch_tree_node tnode;
|
2020-03-12 19:56:03 +00:00
|
|
|
bool prog;
|
2020-03-12 19:55:58 +00:00
|
|
|
};
|
|
|
|
|
2019-11-14 18:57:04 +00:00
|
|
|
enum bpf_tramp_prog_type {
|
|
|
|
BPF_TRAMP_FENTRY,
|
|
|
|
BPF_TRAMP_FEXIT,
|
2020-03-04 19:18:49 +00:00
|
|
|
BPF_TRAMP_MODIFY_RETURN,
|
2020-01-21 00:53:46 +00:00
|
|
|
BPF_TRAMP_MAX,
|
|
|
|
BPF_TRAMP_REPLACE, /* more than MAX */
|
2019-11-14 18:57:04 +00:00
|
|
|
};
|
|
|
|
|
2021-03-16 21:00:07 +00:00
|
|
|
struct bpf_tramp_image {
|
|
|
|
void *image;
|
|
|
|
struct bpf_ksym ksym;
|
|
|
|
struct percpu_ref pcref;
|
|
|
|
void *ip_after_call;
|
|
|
|
void *ip_epilogue;
|
|
|
|
union {
|
|
|
|
struct rcu_head rcu;
|
|
|
|
struct work_struct work;
|
|
|
|
};
|
|
|
|
};
|
|
|
|
|
2019-11-14 18:57:04 +00:00
|
|
|
struct bpf_trampoline {
|
|
|
|
/* hlist for trampoline_table */
|
|
|
|
struct hlist_node hlist;
|
2022-07-20 00:21:26 +00:00
|
|
|
struct ftrace_ops *fops;
|
2019-11-14 18:57:04 +00:00
|
|
|
/* serializes access to fields of this trampoline */
|
|
|
|
struct mutex mutex;
|
|
|
|
refcount_t refcnt;
|
2022-07-20 00:21:26 +00:00
|
|
|
u32 flags;
|
2019-11-14 18:57:04 +00:00
|
|
|
u64 key;
|
|
|
|
struct {
|
|
|
|
struct btf_func_model model;
|
|
|
|
void *addr;
|
2019-12-09 00:01:13 +00:00
|
|
|
bool ftrace_managed;
|
2019-11-14 18:57:04 +00:00
|
|
|
} func;
|
2020-01-21 00:53:46 +00:00
|
|
|
/* if !NULL this is BPF_PROG_TYPE_EXT program that extends another BPF
|
|
|
|
* program by replacing one of its functions. func.addr is the address
|
|
|
|
* of the function it replaced.
|
|
|
|
*/
|
|
|
|
struct bpf_prog *extension_prog;
|
2019-11-14 18:57:04 +00:00
|
|
|
/* list of BPF programs using this trampoline */
|
|
|
|
struct hlist_head progs_hlist[BPF_TRAMP_MAX];
|
|
|
|
/* Number of attached programs. A counter per kind. */
|
|
|
|
int progs_cnt[BPF_TRAMP_MAX];
|
|
|
|
/* Executable image of trampoline */
|
2021-03-16 21:00:07 +00:00
|
|
|
struct bpf_tramp_image *cur_image;
|
2019-11-14 18:57:04 +00:00
|
|
|
u64 selector;
|
2021-03-26 10:59:00 +00:00
|
|
|
struct module *mod;
|
2019-11-14 18:57:04 +00:00
|
|
|
};
|
2019-12-13 17:51:08 +00:00
|
|
|
|
2020-09-25 21:25:02 +00:00
|
|
|
struct bpf_attach_target_info {
|
|
|
|
struct btf_func_model fmodel;
|
|
|
|
long tgt_addr;
|
|
|
|
const char *tgt_name;
|
|
|
|
const struct btf_type *tgt_type;
|
|
|
|
};
|
|
|
|
|
2019-12-13 17:51:12 +00:00
|
|
|
#define BPF_DISPATCHER_MAX 48 /* Fits in 2048B */
|
2019-12-13 17:51:08 +00:00
|
|
|
|
|
|
|
struct bpf_dispatcher_prog {
|
|
|
|
struct bpf_prog *prog;
|
|
|
|
refcount_t users;
|
|
|
|
};
|
|
|
|
|
|
|
|
struct bpf_dispatcher {
|
|
|
|
/* dispatcher mutex */
|
|
|
|
struct mutex mutex;
|
|
|
|
void *func;
|
|
|
|
struct bpf_dispatcher_prog progs[BPF_DISPATCHER_MAX];
|
|
|
|
int num_progs;
|
|
|
|
void *image;
|
2022-09-26 18:47:38 +00:00
|
|
|
void *rw_image;
|
2019-12-13 17:51:08 +00:00
|
|
|
u32 image_off;
|
2020-03-12 19:56:06 +00:00
|
|
|
struct bpf_ksym ksym;
|
2019-12-13 17:51:08 +00:00
|
|
|
};
|
|
|
|
|
2021-04-08 18:28:33 +00:00
|
|
|
static __always_inline __nocfi unsigned int bpf_dispatcher_nop_func(
|
2019-12-13 17:51:09 +00:00
|
|
|
const void *ctx,
|
|
|
|
const struct bpf_insn *insnsi,
|
2022-06-28 17:43:04 +00:00
|
|
|
bpf_func_t bpf_func)
|
2019-12-13 17:51:09 +00:00
|
|
|
{
|
|
|
|
return bpf_func(ctx, insnsi);
|
|
|
|
}
|
2022-05-10 20:59:19 +00:00
|
|
|
|
2019-11-14 18:57:04 +00:00
|
|
|
#ifdef CONFIG_BPF_JIT
|
2022-05-10 20:59:19 +00:00
|
|
|
int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr);
|
|
|
|
int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr);
|
2020-09-25 21:25:02 +00:00
|
|
|
struct bpf_trampoline *bpf_trampoline_get(u64 key,
|
|
|
|
struct bpf_attach_target_info *tgt_info);
|
2019-11-14 18:57:04 +00:00
|
|
|
void bpf_trampoline_put(struct bpf_trampoline *tr);
|
2022-09-26 18:47:38 +00:00
|
|
|
int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_funcs);
|
2020-03-12 19:56:06 +00:00
|
|
|
#define BPF_DISPATCHER_INIT(_name) { \
|
|
|
|
.mutex = __MUTEX_INITIALIZER(_name.mutex), \
|
|
|
|
.func = &_name##_func, \
|
|
|
|
.progs = {}, \
|
|
|
|
.num_progs = 0, \
|
|
|
|
.image = NULL, \
|
|
|
|
.image_off = 0, \
|
|
|
|
.ksym = { \
|
|
|
|
.name = #_name, \
|
|
|
|
.lnode = LIST_HEAD_INIT(_name.ksym.lnode), \
|
|
|
|
}, \
|
2019-12-13 17:51:08 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
#define DEFINE_BPF_DISPATCHER(name) \
|
2021-04-08 18:28:33 +00:00
|
|
|
noinline __nocfi unsigned int bpf_dispatcher_##name##_func( \
|
2019-12-13 17:51:08 +00:00
|
|
|
const void *ctx, \
|
|
|
|
const struct bpf_insn *insnsi, \
|
2022-06-28 17:43:04 +00:00
|
|
|
bpf_func_t bpf_func) \
|
2019-12-13 17:51:08 +00:00
|
|
|
{ \
|
|
|
|
return bpf_func(ctx, insnsi); \
|
|
|
|
} \
|
2020-03-12 19:55:57 +00:00
|
|
|
EXPORT_SYMBOL(bpf_dispatcher_##name##_func); \
|
|
|
|
struct bpf_dispatcher bpf_dispatcher_##name = \
|
|
|
|
BPF_DISPATCHER_INIT(bpf_dispatcher_##name);
|
2019-12-13 17:51:08 +00:00
|
|
|
#define DECLARE_BPF_DISPATCHER(name) \
|
2020-03-12 19:55:57 +00:00
|
|
|
unsigned int bpf_dispatcher_##name##_func( \
|
2019-12-13 17:51:08 +00:00
|
|
|
const void *ctx, \
|
|
|
|
const struct bpf_insn *insnsi, \
|
2022-06-28 17:43:04 +00:00
|
|
|
bpf_func_t bpf_func); \
|
2020-03-12 19:55:57 +00:00
|
|
|
extern struct bpf_dispatcher bpf_dispatcher_##name;
|
|
|
|
#define BPF_DISPATCHER_FUNC(name) bpf_dispatcher_##name##_func
|
|
|
|
#define BPF_DISPATCHER_PTR(name) (&bpf_dispatcher_##name)
|
2019-12-13 17:51:08 +00:00
|
|
|
void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from,
|
|
|
|
struct bpf_prog *to);
|
2020-03-12 19:56:04 +00:00
|
|
|
/* Called only from JIT-enabled code, so there's no need for stubs. */
|
2020-03-12 19:56:07 +00:00
|
|
|
void *bpf_jit_alloc_exec_page(void);
|
2020-03-12 19:56:05 +00:00
|
|
|
void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym);
|
|
|
|
void bpf_image_ksym_del(struct bpf_ksym *ksym);
|
2020-03-12 19:56:04 +00:00
|
|
|
void bpf_ksym_add(struct bpf_ksym *ksym);
|
|
|
|
void bpf_ksym_del(struct bpf_ksym *ksym);
|
2022-02-04 18:57:35 +00:00
|
|
|
int bpf_jit_charge_modmem(u32 size);
|
|
|
|
void bpf_jit_uncharge_modmem(u32 size);
|
2021-12-08 19:32:44 +00:00
|
|
|
bool bpf_prog_has_trampoline(const struct bpf_prog *prog);
|
2019-11-14 18:57:04 +00:00
|
|
|
#else
|
2022-05-10 20:59:19 +00:00
|
|
|
static inline int bpf_trampoline_link_prog(struct bpf_tramp_link *link,
|
2020-09-29 12:45:50 +00:00
|
|
|
struct bpf_trampoline *tr)
|
2019-11-14 18:57:04 +00:00
|
|
|
{
|
|
|
|
return -ENOTSUPP;
|
|
|
|
}
|
2022-05-10 20:59:19 +00:00
|
|
|
static inline int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link,
|
2020-09-29 12:45:50 +00:00
|
|
|
struct bpf_trampoline *tr)
|
2019-11-14 18:57:04 +00:00
|
|
|
{
|
|
|
|
return -ENOTSUPP;
|
|
|
|
}
|
2020-09-25 21:25:02 +00:00
|
|
|
static inline struct bpf_trampoline *bpf_trampoline_get(u64 key,
|
|
|
|
struct bpf_attach_target_info *tgt_info)
|
|
|
|
{
|
|
|
|
return ERR_PTR(-EOPNOTSUPP);
|
|
|
|
}
|
2019-11-14 18:57:04 +00:00
|
|
|
static inline void bpf_trampoline_put(struct bpf_trampoline *tr) {}
|
2019-12-13 17:51:08 +00:00
|
|
|
#define DEFINE_BPF_DISPATCHER(name)
|
|
|
|
#define DECLARE_BPF_DISPATCHER(name)
|
2020-03-12 19:55:57 +00:00
|
|
|
#define BPF_DISPATCHER_FUNC(name) bpf_dispatcher_nop_func
|
2019-12-13 17:51:08 +00:00
|
|
|
#define BPF_DISPATCHER_PTR(name) NULL
|
|
|
|
static inline void bpf_dispatcher_change_prog(struct bpf_dispatcher *d,
|
|
|
|
struct bpf_prog *from,
|
|
|
|
struct bpf_prog *to) {}
|
2020-01-23 16:15:07 +00:00
|
|
|
static inline bool is_bpf_image_address(unsigned long address)
|
|
|
|
{
|
|
|
|
return false;
|
|
|
|
}
|
2021-12-08 19:32:44 +00:00
|
|
|
static inline bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
|
|
|
|
{
|
|
|
|
return false;
|
|
|
|
}
|
2019-11-14 18:57:04 +00:00
|
|
|
#endif
|
|
|
|
|
2019-11-14 18:57:16 +00:00
|
|
|
struct bpf_func_info_aux {
|
2020-01-10 06:41:20 +00:00
|
|
|
u16 linkage;
|
2019-11-14 18:57:16 +00:00
|
|
|
bool unreliable;
|
|
|
|
};
|
|
|
|
|
2019-11-22 20:07:57 +00:00
|
|
|
enum bpf_jit_poke_reason {
|
|
|
|
BPF_POKE_REASON_TAIL_CALL,
|
|
|
|
};
|
|
|
|
|
|
|
|
/* Descriptor of pokes pointing /into/ the JITed image. */
|
|
|
|
struct bpf_jit_poke_descriptor {
|
2020-09-16 21:10:06 +00:00
|
|
|
void *tailcall_target;
|
bpf, x64: rework pro/epilogue and tailcall handling in JIT
This commit serves two things:
1) it optimizes BPF prologue/epilogue generation
2) it makes possible to have tailcalls within BPF subprogram
Both points are related to each other since without 1), 2) could not be
achieved.
In [1], Alexei says:
"The prologue will look like:
nop5
xor eax,eax // two new bytes if bpf_tail_call() is used in this
// function
push rbp
mov rbp, rsp
sub rsp, rounded_stack_depth
push rax // zero init tail_call counter
variable number of push rbx,r13,r14,r15
Then bpf_tail_call will pop variable number rbx,..
and final 'pop rax'
Then 'add rsp, size_of_current_stack_frame'
jmp to next function and skip over 'nop5; xor eax,eax; push rpb; mov
rbp, rsp'
This way new function will set its own stack size and will init tail
call
counter with whatever value the parent had.
If next function doesn't use bpf_tail_call it won't have 'xor eax,eax'.
Instead it would need to have 'nop2' in there."
Implement that suggestion.
Since the layout of stack is changed, tail call counter handling can not
rely anymore on popping it to rbx just like it have been handled for
constant prologue case and later overwrite of rbx with actual value of
rbx pushed to stack. Therefore, let's use one of the register (%rcx) that
is considered to be volatile/caller-saved and pop the value of tail call
counter in there in the epilogue.
Drop the BUILD_BUG_ON in emit_prologue and in
emit_bpf_tail_call_indirect where instruction layout is not constant
anymore.
Introduce new poke target, 'tailcall_bypass' to poke descriptor that is
dedicated for skipping the register pops and stack unwind that are
generated right before the actual jump to target program.
For case when the target program is not present, BPF program will skip
the pop instructions and nop5 dedicated for jmpq $target. An example of
such state when only R6 of callee saved registers is used by program:
ffffffffc0513aa1: e9 0e 00 00 00 jmpq 0xffffffffc0513ab4
ffffffffc0513aa6: 5b pop %rbx
ffffffffc0513aa7: 58 pop %rax
ffffffffc0513aa8: 48 81 c4 00 00 00 00 add $0x0,%rsp
ffffffffc0513aaf: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
ffffffffc0513ab4: 48 89 df mov %rbx,%rdi
When target program is inserted, the jump that was there to skip
pops/nop5 will become the nop5, so CPU will go over pops and do the
actual tailcall.
One might ask why there simply can not be pushes after the nop5?
In the following example snippet:
ffffffffc037030c: 48 89 fb mov %rdi,%rbx
(...)
ffffffffc0370332: 5b pop %rbx
ffffffffc0370333: 58 pop %rax
ffffffffc0370334: 48 81 c4 00 00 00 00 add $0x0,%rsp
ffffffffc037033b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
ffffffffc0370340: 48 81 ec 00 00 00 00 sub $0x0,%rsp
ffffffffc0370347: 50 push %rax
ffffffffc0370348: 53 push %rbx
ffffffffc0370349: 48 89 df mov %rbx,%rdi
ffffffffc037034c: e8 f7 21 00 00 callq 0xffffffffc0372548
There is the bpf2bpf call (at ffffffffc037034c) right after the tailcall
and jump target is not present. ctx is in %rbx register and BPF
subprogram that we will call into on ffffffffc037034c is relying on it,
e.g. it will pick ctx from there. Such code layout is therefore broken
as we would overwrite the content of %rbx with the value that was pushed
on the prologue. That is the reason for the 'bypass' approach.
Special care needs to be taken during the install/update/remove of
tailcall target. In case when target program is not present, the CPU
must not execute the pop instructions that precede the tailcall.
To address that, the following states can be defined:
A nop, unwind, nop
B nop, unwind, tail
C skip, unwind, nop
D skip, unwind, tail
A is forbidden (lead to incorrectness). The state transitions between
tailcall install/update/remove will work as follows:
First install tail call f: C->D->B(f)
* poke the tailcall, after that get rid of the skip
Update tail call f to f': B(f)->B(f')
* poke the tailcall (poke->tailcall_target) and do NOT touch the
poke->tailcall_bypass
Remove tail call: B(f')->C(f')
* poke->tailcall_bypass is poked back to jump, then we wait the RCU
grace period so that other programs will finish its execution and
after that we are safe to remove the poke->tailcall_target
Install new tail call (f''): C(f')->D(f'')->B(f'').
* same as first step
This way CPU can never be exposed to "unwind, tail" state.
Last but not least, when tailcalls get mixed with bpf2bpf calls, it
would be possible to encounter the endless loop due to clearing the
tailcall counter if for example we would use the tailcall3-like from BPF
selftests program that would be subprogram-based, meaning the tailcall
would be present within the BPF subprogram.
This test, broken down to particular steps, would do:
entry -> set tailcall counter to 0, bump it by 1, tailcall to func0
func0 -> call subprog_tail
(we are NOT skipping the first 11 bytes of prologue and this subprogram
has a tailcall, therefore we clear the counter...)
subprog -> do the same thing as entry
and then loop forever.
To address this, the idea is to go through the call chain of bpf2bpf progs
and look for a tailcall presence throughout whole chain. If we saw a single
tail call then each node in this call chain needs to be marked as a subprog
that can reach the tailcall. We would later feed the JIT with this info
and:
- set eax to 0 only when tailcall is reachable and this is the entry prog
- if tailcall is reachable but there's no tailcall in insns of currently
JITed prog then push rax anyway, so that it will be possible to
propagate further down the call chain
- finally if tailcall is reachable, then we need to precede the 'call'
insn with mov rax, [rbp - (stack_depth + 8)]
Tail call related cases from test_verifier kselftest are also working
fine. Sample BPF programs that utilize tail calls (sockex3, tracex5)
work properly as well.
[1]: https://lore.kernel.org/bpf/20200517043227.2gpq22ifoq37ogst@ast-mbp.dhcp.thefacebook.com/
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2020-09-16 21:10:08 +00:00
|
|
|
void *tailcall_bypass;
|
|
|
|
void *bypass_addr;
|
bpf: Track subprog poke descriptors correctly and fix use-after-free
Subprograms are calling map_poke_track(), but on program release there is no
hook to call map_poke_untrack(). However, on program release, the aux memory
(and poke descriptor table) is freed even though we still have a reference to
it in the element list of the map aux data. When we run map_poke_run(), we then
end up accessing free'd memory, triggering KASAN in prog_array_map_poke_run():
[...]
[ 402.824689] BUG: KASAN: use-after-free in prog_array_map_poke_run+0xc2/0x34e
[ 402.824698] Read of size 4 at addr ffff8881905a7940 by task hubble-fgs/4337
[ 402.824705] CPU: 1 PID: 4337 Comm: hubble-fgs Tainted: G I 5.12.0+ #399
[ 402.824715] Call Trace:
[ 402.824719] dump_stack+0x93/0xc2
[ 402.824727] print_address_description.constprop.0+0x1a/0x140
[ 402.824736] ? prog_array_map_poke_run+0xc2/0x34e
[ 402.824740] ? prog_array_map_poke_run+0xc2/0x34e
[ 402.824744] kasan_report.cold+0x7c/0xd8
[ 402.824752] ? prog_array_map_poke_run+0xc2/0x34e
[ 402.824757] prog_array_map_poke_run+0xc2/0x34e
[ 402.824765] bpf_fd_array_map_update_elem+0x124/0x1a0
[...]
The elements concerned are walked as follows:
for (i = 0; i < elem->aux->size_poke_tab; i++) {
poke = &elem->aux->poke_tab[i];
[...]
The access to size_poke_tab is a 4 byte read, verified by checking offsets
in the KASAN dump:
[ 402.825004] The buggy address belongs to the object at ffff8881905a7800
which belongs to the cache kmalloc-1k of size 1024
[ 402.825008] The buggy address is located 320 bytes inside of
1024-byte region [ffff8881905a7800, ffff8881905a7c00)
The pahole output of bpf_prog_aux:
struct bpf_prog_aux {
[...]
/* --- cacheline 5 boundary (320 bytes) --- */
u32 size_poke_tab; /* 320 4 */
[...]
In general, subprograms do not necessarily manage their own data structures.
For example, BTF func_info and linfo are just pointers to the main program
structure. This allows reference counting and cleanup to be done on the latter
which simplifies their management a bit. The aux->poke_tab struct, however,
did not follow this logic. The initial proposed fix for this use-after-free
bug further embedded poke data tracking into the subprogram with proper
reference counting. However, Daniel and Alexei questioned why we were treating
these objects special; I agree, its unnecessary. The fix here removes the per
subprogram poke table allocation and map tracking and instead simply points
the aux->poke_tab pointer at the main programs poke table. This way, map
tracking is simplified to the main program and we do not need to manage them
per subprogram.
This also means, bpf_prog_free_deferred(), which unwinds the program reference
counting and kfrees objects, needs to ensure that we don't try to double free
the poke_tab when free'ing the subprog structures. This is easily solved by
NULL'ing the poke_tab pointer. The second detail is to ensure that per
subprogram JIT logic only does fixups on poke_tab[] entries it owns. To do
this, we add a pointer in the poke structure to point at the subprogram value
so JITs can easily check while walking the poke_tab structure if the current
entry belongs to the current program. The aux pointer is stable and therefore
suitable for such comparison. On the jit_subprogs() error path, we omit
cleaning up the poke->aux field because these are only ever referenced from
the JIT side, but on error we will never make it to the JIT, so its fine to
leave them dangling. Removing these pointers would complicate the error path
for no reason. However, we do need to untrack all poke descriptors from the
main program as otherwise they could race with the freeing of JIT memory from
the subprograms. Lastly, a748c6975dea3 ("bpf: propagate poke descriptors to
subprograms") had an off-by-one on the subprogram instruction index range
check as it was testing 'insn_idx >= subprog_start && insn_idx <= subprog_end'.
However, subprog_end is the next subprogram's start instruction.
Fixes: a748c6975dea3 ("bpf: propagate poke descriptors to subprograms")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210707223848.14580-2-john.fastabend@gmail.com
2021-07-07 22:38:47 +00:00
|
|
|
void *aux;
|
2019-11-22 20:07:57 +00:00
|
|
|
union {
|
|
|
|
struct {
|
|
|
|
struct bpf_map *map;
|
|
|
|
u32 key;
|
|
|
|
} tail_call;
|
|
|
|
};
|
2020-09-16 21:10:06 +00:00
|
|
|
bool tailcall_target_stable;
|
2019-11-22 20:07:57 +00:00
|
|
|
u8 adj_off;
|
|
|
|
u16 reason;
|
2020-09-16 21:10:05 +00:00
|
|
|
u32 insn_idx;
|
2019-11-22 20:07:57 +00:00
|
|
|
};
|
|
|
|
|
2020-05-13 18:02:21 +00:00
|
|
|
/* reg_type info for ctx arguments */
|
|
|
|
struct bpf_ctx_arg_aux {
|
|
|
|
u32 offset;
|
|
|
|
enum bpf_reg_type reg_type;
|
2020-07-20 16:34:03 +00:00
|
|
|
u32 btf_id;
|
2020-05-13 18:02:21 +00:00
|
|
|
};
|
|
|
|
|
2021-01-12 07:55:18 +00:00
|
|
|
struct btf_mod_pair {
|
|
|
|
struct btf *btf;
|
|
|
|
struct module *module;
|
|
|
|
};
|
|
|
|
|
bpf: Support bpf program calling kernel function
This patch adds support to BPF verifier to allow bpf program calling
kernel function directly.
The use case included in this set is to allow bpf-tcp-cc to directly
call some tcp-cc helper functions (e.g. "tcp_cong_avoid_ai()"). Those
functions have already been used by some kernel tcp-cc implementations.
This set will also allow the bpf-tcp-cc program to directly call the
kernel tcp-cc implementation, For example, a bpf_dctcp may only want to
implement its own dctcp_cwnd_event() and reuse other dctcp_*() directly
from the kernel tcp_dctcp.c instead of reimplementing (or
copy-and-pasting) them.
The tcp-cc kernel functions mentioned above will be white listed
for the struct_ops bpf-tcp-cc programs to use in a later patch.
The white listed functions are not bounded to a fixed ABI contract.
Those functions have already been used by the existing kernel tcp-cc.
If any of them has changed, both in-tree and out-of-tree kernel tcp-cc
implementations have to be changed. The same goes for the struct_ops
bpf-tcp-cc programs which have to be adjusted accordingly.
This patch is to make the required changes in the bpf verifier.
First change is in btf.c, it adds a case in "btf_check_func_arg_match()".
When the passed in "btf->kernel_btf == true", it means matching the
verifier regs' states with a kernel function. This will handle the
PTR_TO_BTF_ID reg. It also maps PTR_TO_SOCK_COMMON, PTR_TO_SOCKET,
and PTR_TO_TCP_SOCK to its kernel's btf_id.
In the later libbpf patch, the insn calling a kernel function will
look like:
insn->code == (BPF_JMP | BPF_CALL)
insn->src_reg == BPF_PSEUDO_KFUNC_CALL /* <- new in this patch */
insn->imm == func_btf_id /* btf_id of the running kernel */
[ For the future calling function-in-kernel-module support, an array
of module btf_fds can be passed at the load time and insn->off
can be used to index into this array. ]
At the early stage of verifier, the verifier will collect all kernel
function calls into "struct bpf_kfunc_desc". Those
descriptors are stored in "prog->aux->kfunc_tab" and will
be available to the JIT. Since this "add" operation is similar
to the current "add_subprog()" and looking for the same insn->code,
they are done together in the new "add_subprog_and_kfunc()".
In the "do_check()" stage, the new "check_kfunc_call()" is added
to verify the kernel function call instruction:
1. Ensure the kernel function can be used by a particular BPF_PROG_TYPE.
A new bpf_verifier_ops "check_kfunc_call" is added to do that.
The bpf-tcp-cc struct_ops program will implement this function in
a later patch.
2. Call "btf_check_kfunc_args_match()" to ensure the regs can be
used as the args of a kernel function.
3. Mark the regs' type, subreg_def, and zext_dst.
At the later do_misc_fixups() stage, the new fixup_kfunc_call()
will replace the insn->imm with the function address (relative
to __bpf_call_base). If needed, the jit can find the btf_func_model
by calling the new bpf_jit_find_kfunc_model(prog, insn).
With the imm set to the function address, "bpftool prog dump xlated"
will be able to display the kernel function calls the same way as
it displays other bpf helper calls.
gpl_compatible program is required to call kernel function.
This feature currently requires JIT.
The verifier selftests are adjusted because of the changes in
the verbose log in add_subprog_and_kfunc().
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015142.1544736-1-kafai@fb.com
2021-03-25 01:51:42 +00:00
|
|
|
struct bpf_kfunc_desc_tab;
|
|
|
|
|
2014-09-26 07:17:00 +00:00
|
|
|
struct bpf_prog_aux {
|
2019-11-17 17:28:03 +00:00
|
|
|
atomic64_t refcnt;
|
2015-03-01 11:31:47 +00:00
|
|
|
u32 used_map_cnt;
|
2021-01-12 07:55:18 +00:00
|
|
|
u32 used_btf_cnt;
|
2016-04-07 01:43:28 +00:00
|
|
|
u32 max_ctx_offset;
|
2018-11-08 09:08:42 +00:00
|
|
|
u32 max_pkt_offset;
|
2019-04-26 18:49:47 +00:00
|
|
|
u32 max_tp_access;
|
2017-05-30 20:31:29 +00:00
|
|
|
u32 stack_depth;
|
2017-06-05 19:15:46 +00:00
|
|
|
u32 id;
|
2018-11-25 07:20:44 +00:00
|
|
|
u32 func_cnt; /* used by non-func prog as the number of func progs */
|
|
|
|
u32 func_idx; /* 0 for non-func prog, the index in func array for func prog */
|
2019-10-16 03:24:58 +00:00
|
|
|
u32 attach_btf_id; /* in-kernel BTF type id to attach to */
|
2020-05-13 18:02:21 +00:00
|
|
|
u32 ctx_arg_info_size;
|
2020-07-23 18:41:11 +00:00
|
|
|
u32 max_rdonly_access;
|
|
|
|
u32 max_rdwr_access;
|
bpf: Remove hard-coded btf_vmlinux assumption from BPF verifier
Remove a permeating assumption thoughout BPF verifier of vmlinux BTF. Instead,
wherever BTF type IDs are involved, also track the instance of struct btf that
goes along with the type ID. This allows to gradually add support for kernel
module BTFs and using/tracking module types across BPF helper calls and
registers.
This patch also renames btf_id() function to btf_obj_id() to minimize naming
clash with using btf_id to denote BTF *type* ID, rather than BTF *object*'s ID.
Also, altough btf_vmlinux can't get destructed and thus doesn't need
refcounting, module BTFs need that, so apply BTF refcounting universally when
BPF program is using BTF-powered attachment (tp_btf, fentry/fexit, etc). This
makes for simpler clean up code.
Now that BTF type ID is not enough to uniquely identify a BTF type, extend BPF
trampoline key to include BTF object ID. To differentiate that from target
program BPF ID, set 31st bit of type ID. BTF type IDs (at least currently) are
not allowed to take full 32 bits, so there is no danger of confusing that bit
with a valid BTF type ID.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201203204634.1325171-10-andrii@kernel.org
2020-12-03 20:46:29 +00:00
|
|
|
struct btf *attach_btf;
|
2020-05-13 18:02:21 +00:00
|
|
|
const struct bpf_ctx_arg_aux *ctx_arg_info;
|
2020-09-29 12:45:50 +00:00
|
|
|
struct mutex dst_mutex; /* protects dst_* pointers below, *after* prog becomes visible */
|
|
|
|
struct bpf_prog *dst_prog;
|
|
|
|
struct bpf_trampoline *dst_trampoline;
|
2020-09-29 12:45:51 +00:00
|
|
|
enum bpf_prog_type saved_dst_prog_type;
|
|
|
|
enum bpf_attach_type saved_dst_attach_type;
|
bpf: verifier: insert zero extension according to analysis result
After previous patches, verifier will mark a insn if it really needs zero
extension on dst_reg.
It is then for back-ends to decide how to use such information to eliminate
unnecessary zero extension code-gen during JIT compilation.
One approach is verifier insert explicit zero extension for those insns
that need zero extension in a generic way, JIT back-ends then do not
generate zero extension for sub-register write at default.
However, only those back-ends which do not have hardware zero extension
want this optimization. Back-ends like x86_64 and AArch64 have hardware
zero extension support that the insertion should be disabled.
This patch introduces new target hook "bpf_jit_needs_zext" which returns
false at default, meaning verifier zero extension insertion is disabled at
default. A back-end could override this hook to return true if it doesn't
have hardware support and want verifier insert zero extension explicitly.
Offload targets do not use this native target hook, instead, they could
get the optimization results using bpf_prog_offload_ops.finalize.
NOTE: arches could have diversified features, it is possible for one arch
to have hardware zero extension support for some sub-register write insns
but not for all. For example, PowerPC, SPARC have zero extended loads, but
not for alu32. So when verifier zero extension insertion enabled, these JIT
back-ends need to peephole insns to remove those zero extension inserted
for insn that actually has hardware zero extension support. The peephole
could be as simple as looking the next insn, if it is a special zero
extension insn then it is safe to eliminate it if the current insn has
hardware zero extension support.
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-05-24 22:25:15 +00:00
|
|
|
bool verifier_zext; /* Zero extensions has been inserted by verifier. */
|
2017-12-28 02:39:04 +00:00
|
|
|
bool offload_requested;
|
2019-10-25 00:18:11 +00:00
|
|
|
bool attach_btf_trace; /* true if attaching to BTF-enabled raw tp */
|
2019-11-14 18:57:16 +00:00
|
|
|
bool func_proto_unreliable;
|
2020-08-27 22:01:11 +00:00
|
|
|
bool sleepable;
|
bpf, x64: rework pro/epilogue and tailcall handling in JIT
This commit serves two things:
1) it optimizes BPF prologue/epilogue generation
2) it makes possible to have tailcalls within BPF subprogram
Both points are related to each other since without 1), 2) could not be
achieved.
In [1], Alexei says:
"The prologue will look like:
nop5
xor eax,eax // two new bytes if bpf_tail_call() is used in this
// function
push rbp
mov rbp, rsp
sub rsp, rounded_stack_depth
push rax // zero init tail_call counter
variable number of push rbx,r13,r14,r15
Then bpf_tail_call will pop variable number rbx,..
and final 'pop rax'
Then 'add rsp, size_of_current_stack_frame'
jmp to next function and skip over 'nop5; xor eax,eax; push rpb; mov
rbp, rsp'
This way new function will set its own stack size and will init tail
call
counter with whatever value the parent had.
If next function doesn't use bpf_tail_call it won't have 'xor eax,eax'.
Instead it would need to have 'nop2' in there."
Implement that suggestion.
Since the layout of stack is changed, tail call counter handling can not
rely anymore on popping it to rbx just like it have been handled for
constant prologue case and later overwrite of rbx with actual value of
rbx pushed to stack. Therefore, let's use one of the register (%rcx) that
is considered to be volatile/caller-saved and pop the value of tail call
counter in there in the epilogue.
Drop the BUILD_BUG_ON in emit_prologue and in
emit_bpf_tail_call_indirect where instruction layout is not constant
anymore.
Introduce new poke target, 'tailcall_bypass' to poke descriptor that is
dedicated for skipping the register pops and stack unwind that are
generated right before the actual jump to target program.
For case when the target program is not present, BPF program will skip
the pop instructions and nop5 dedicated for jmpq $target. An example of
such state when only R6 of callee saved registers is used by program:
ffffffffc0513aa1: e9 0e 00 00 00 jmpq 0xffffffffc0513ab4
ffffffffc0513aa6: 5b pop %rbx
ffffffffc0513aa7: 58 pop %rax
ffffffffc0513aa8: 48 81 c4 00 00 00 00 add $0x0,%rsp
ffffffffc0513aaf: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
ffffffffc0513ab4: 48 89 df mov %rbx,%rdi
When target program is inserted, the jump that was there to skip
pops/nop5 will become the nop5, so CPU will go over pops and do the
actual tailcall.
One might ask why there simply can not be pushes after the nop5?
In the following example snippet:
ffffffffc037030c: 48 89 fb mov %rdi,%rbx
(...)
ffffffffc0370332: 5b pop %rbx
ffffffffc0370333: 58 pop %rax
ffffffffc0370334: 48 81 c4 00 00 00 00 add $0x0,%rsp
ffffffffc037033b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
ffffffffc0370340: 48 81 ec 00 00 00 00 sub $0x0,%rsp
ffffffffc0370347: 50 push %rax
ffffffffc0370348: 53 push %rbx
ffffffffc0370349: 48 89 df mov %rbx,%rdi
ffffffffc037034c: e8 f7 21 00 00 callq 0xffffffffc0372548
There is the bpf2bpf call (at ffffffffc037034c) right after the tailcall
and jump target is not present. ctx is in %rbx register and BPF
subprogram that we will call into on ffffffffc037034c is relying on it,
e.g. it will pick ctx from there. Such code layout is therefore broken
as we would overwrite the content of %rbx with the value that was pushed
on the prologue. That is the reason for the 'bypass' approach.
Special care needs to be taken during the install/update/remove of
tailcall target. In case when target program is not present, the CPU
must not execute the pop instructions that precede the tailcall.
To address that, the following states can be defined:
A nop, unwind, nop
B nop, unwind, tail
C skip, unwind, nop
D skip, unwind, tail
A is forbidden (lead to incorrectness). The state transitions between
tailcall install/update/remove will work as follows:
First install tail call f: C->D->B(f)
* poke the tailcall, after that get rid of the skip
Update tail call f to f': B(f)->B(f')
* poke the tailcall (poke->tailcall_target) and do NOT touch the
poke->tailcall_bypass
Remove tail call: B(f')->C(f')
* poke->tailcall_bypass is poked back to jump, then we wait the RCU
grace period so that other programs will finish its execution and
after that we are safe to remove the poke->tailcall_target
Install new tail call (f''): C(f')->D(f'')->B(f'').
* same as first step
This way CPU can never be exposed to "unwind, tail" state.
Last but not least, when tailcalls get mixed with bpf2bpf calls, it
would be possible to encounter the endless loop due to clearing the
tailcall counter if for example we would use the tailcall3-like from BPF
selftests program that would be subprogram-based, meaning the tailcall
would be present within the BPF subprogram.
This test, broken down to particular steps, would do:
entry -> set tailcall counter to 0, bump it by 1, tailcall to func0
func0 -> call subprog_tail
(we are NOT skipping the first 11 bytes of prologue and this subprogram
has a tailcall, therefore we clear the counter...)
subprog -> do the same thing as entry
and then loop forever.
To address this, the idea is to go through the call chain of bpf2bpf progs
and look for a tailcall presence throughout whole chain. If we saw a single
tail call then each node in this call chain needs to be marked as a subprog
that can reach the tailcall. We would later feed the JIT with this info
and:
- set eax to 0 only when tailcall is reachable and this is the entry prog
- if tailcall is reachable but there's no tailcall in insns of currently
JITed prog then push rax anyway, so that it will be possible to
propagate further down the call chain
- finally if tailcall is reachable, then we need to precede the 'call'
insn with mov rax, [rbp - (stack_depth + 8)]
Tail call related cases from test_verifier kselftest are also working
fine. Sample BPF programs that utilize tail calls (sockex3, tracex5)
work properly as well.
[1]: https://lore.kernel.org/bpf/20200517043227.2gpq22ifoq37ogst@ast-mbp.dhcp.thefacebook.com/
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2020-09-16 21:10:08 +00:00
|
|
|
bool tail_call_reachable;
|
2022-01-21 10:09:52 +00:00
|
|
|
bool xdp_has_frags;
|
2019-10-25 00:18:11 +00:00
|
|
|
/* BTF_KIND_FUNC_PROTO for valid attach_btf_id */
|
|
|
|
const struct btf_type *attach_func_proto;
|
|
|
|
/* function name for valid attach_btf_id */
|
|
|
|
const char *attach_func_name;
|
2017-12-15 01:55:15 +00:00
|
|
|
struct bpf_prog **func;
|
|
|
|
void *jit_data; /* JIT specific data. arch dependent */
|
2019-11-22 20:07:57 +00:00
|
|
|
struct bpf_jit_poke_descriptor *poke_tab;
|
bpf: Support bpf program calling kernel function
This patch adds support to BPF verifier to allow bpf program calling
kernel function directly.
The use case included in this set is to allow bpf-tcp-cc to directly
call some tcp-cc helper functions (e.g. "tcp_cong_avoid_ai()"). Those
functions have already been used by some kernel tcp-cc implementations.
This set will also allow the bpf-tcp-cc program to directly call the
kernel tcp-cc implementation, For example, a bpf_dctcp may only want to
implement its own dctcp_cwnd_event() and reuse other dctcp_*() directly
from the kernel tcp_dctcp.c instead of reimplementing (or
copy-and-pasting) them.
The tcp-cc kernel functions mentioned above will be white listed
for the struct_ops bpf-tcp-cc programs to use in a later patch.
The white listed functions are not bounded to a fixed ABI contract.
Those functions have already been used by the existing kernel tcp-cc.
If any of them has changed, both in-tree and out-of-tree kernel tcp-cc
implementations have to be changed. The same goes for the struct_ops
bpf-tcp-cc programs which have to be adjusted accordingly.
This patch is to make the required changes in the bpf verifier.
First change is in btf.c, it adds a case in "btf_check_func_arg_match()".
When the passed in "btf->kernel_btf == true", it means matching the
verifier regs' states with a kernel function. This will handle the
PTR_TO_BTF_ID reg. It also maps PTR_TO_SOCK_COMMON, PTR_TO_SOCKET,
and PTR_TO_TCP_SOCK to its kernel's btf_id.
In the later libbpf patch, the insn calling a kernel function will
look like:
insn->code == (BPF_JMP | BPF_CALL)
insn->src_reg == BPF_PSEUDO_KFUNC_CALL /* <- new in this patch */
insn->imm == func_btf_id /* btf_id of the running kernel */
[ For the future calling function-in-kernel-module support, an array
of module btf_fds can be passed at the load time and insn->off
can be used to index into this array. ]
At the early stage of verifier, the verifier will collect all kernel
function calls into "struct bpf_kfunc_desc". Those
descriptors are stored in "prog->aux->kfunc_tab" and will
be available to the JIT. Since this "add" operation is similar
to the current "add_subprog()" and looking for the same insn->code,
they are done together in the new "add_subprog_and_kfunc()".
In the "do_check()" stage, the new "check_kfunc_call()" is added
to verify the kernel function call instruction:
1. Ensure the kernel function can be used by a particular BPF_PROG_TYPE.
A new bpf_verifier_ops "check_kfunc_call" is added to do that.
The bpf-tcp-cc struct_ops program will implement this function in
a later patch.
2. Call "btf_check_kfunc_args_match()" to ensure the regs can be
used as the args of a kernel function.
3. Mark the regs' type, subreg_def, and zext_dst.
At the later do_misc_fixups() stage, the new fixup_kfunc_call()
will replace the insn->imm with the function address (relative
to __bpf_call_base). If needed, the jit can find the btf_func_model
by calling the new bpf_jit_find_kfunc_model(prog, insn).
With the imm set to the function address, "bpftool prog dump xlated"
will be able to display the kernel function calls the same way as
it displays other bpf helper calls.
gpl_compatible program is required to call kernel function.
This feature currently requires JIT.
The verifier selftests are adjusted because of the changes in
the verbose log in add_subprog_and_kfunc().
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015142.1544736-1-kafai@fb.com
2021-03-25 01:51:42 +00:00
|
|
|
struct bpf_kfunc_desc_tab *kfunc_tab;
|
bpf: Introduce BPF support for kernel module function calls
This change adds support on the kernel side to allow for BPF programs to
call kernel module functions. Userspace will prepare an array of module
BTF fds that is passed in during BPF_PROG_LOAD using fd_array parameter.
In the kernel, the module BTFs are placed in the auxilliary struct for
bpf_prog, and loaded as needed.
The verifier then uses insn->off to index into the fd_array. insn->off
0 is reserved for vmlinux BTF (for backwards compat), so userspace must
use an fd_array index > 0 for module kfunc support. kfunc_btf_tab is
sorted based on offset in an array, and each offset corresponds to one
descriptor, with a max limit up to 256 such module BTFs.
We also change existing kfunc_tab to distinguish each element based on
imm, off pair as each such call will now be distinct.
Another change is to check_kfunc_call callback, which now include a
struct module * pointer, this is to be used in later patch such that the
kfunc_id and module pointer are matched for dynamically registered BTF
sets from loadable modules, so that same kfunc_id in two modules doesn't
lead to check_kfunc_call succeeding. For the duration of the
check_kfunc_call, the reference to struct module exists, as it returns
the pointer stored in kfunc_btf_tab.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211002011757.311265-2-memxor@gmail.com
2021-10-02 01:17:49 +00:00
|
|
|
struct bpf_kfunc_btf_tab *kfunc_btf_tab;
|
2019-11-22 20:07:57 +00:00
|
|
|
u32 size_poke_tab;
|
2020-03-12 19:55:58 +00:00
|
|
|
struct bpf_ksym ksym;
|
2017-10-16 23:40:53 +00:00
|
|
|
const struct bpf_prog_ops *ops;
|
2014-09-26 07:17:00 +00:00
|
|
|
struct bpf_map **used_maps;
|
2020-09-15 23:45:39 +00:00
|
|
|
struct mutex used_maps_mutex; /* mutex for used_maps and used_map_cnt */
|
2021-01-12 07:55:18 +00:00
|
|
|
struct btf_mod_pair *used_btfs;
|
2014-09-26 07:17:00 +00:00
|
|
|
struct bpf_prog *prog;
|
2015-10-08 05:23:22 +00:00
|
|
|
struct user_struct *user;
|
2017-09-27 21:37:52 +00:00
|
|
|
u64 load_time; /* ns since boottime */
|
2021-10-20 07:48:17 +00:00
|
|
|
u32 verified_insns;
|
2022-06-28 17:43:06 +00:00
|
|
|
int cgroup_atype; /* enum cgroup_bpf_attach_type */
|
2018-09-28 14:45:36 +00:00
|
|
|
struct bpf_map *cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE];
|
2017-10-06 04:52:12 +00:00
|
|
|
char name[BPF_OBJ_NAME_LEN];
|
2017-10-18 20:00:24 +00:00
|
|
|
#ifdef CONFIG_SECURITY
|
|
|
|
void *security;
|
|
|
|
#endif
|
2018-01-12 04:29:07 +00:00
|
|
|
struct bpf_prog_offload *offload;
|
bpf: Introduce bpf_func_info
This patch added interface to load a program with the following
additional information:
. prog_btf_fd
. func_info, func_info_rec_size and func_info_cnt
where func_info will provide function range and type_id
corresponding to each function.
The func_info_rec_size is introduced in the UAPI to specify
struct bpf_func_info size passed from user space. This
intends to make bpf_func_info structure growable in the future.
If the kernel gets a different bpf_func_info size from userspace,
it will try to handle user request with part of bpf_func_info
it can understand. In this patch, kernel can understand
struct bpf_func_info {
__u32 insn_offset;
__u32 type_id;
};
If user passed a bpf func_info record size of 16 bytes, the
kernel can still handle part of records with the above definition.
If verifier agrees with function range provided by the user,
the bpf_prog ksym for each function will use the func name
provided in the type_id, which is supposed to provide better
encoding as it is not limited by 16 bytes program name
limitation and this is better for bpf program which contains
multiple subprograms.
The bpf_prog_info interface is also extended to
return btf_id, func_info, func_info_rec_size and func_info_cnt
to userspace, so userspace can print out the function prototype
for each xlated function. The insn_offset in the returned
func_info corresponds to the insn offset for xlated functions.
With other jit related fields in bpf_prog_info, userspace can also
print out function prototypes for each jited function.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-11-19 23:29:11 +00:00
|
|
|
struct btf *btf;
|
2018-11-25 07:20:44 +00:00
|
|
|
struct bpf_func_info *func_info;
|
2019-11-14 18:57:16 +00:00
|
|
|
struct bpf_func_info_aux *func_info_aux;
|
2018-12-08 00:42:25 +00:00
|
|
|
/* bpf_line_info loaded from userspace. linfo->insn_off
|
|
|
|
* has the xlated insn offset.
|
|
|
|
* Both the main and sub prog share the same linfo.
|
|
|
|
* The subprog can access its first linfo by
|
|
|
|
* using the linfo_idx.
|
|
|
|
*/
|
|
|
|
struct bpf_line_info *linfo;
|
|
|
|
/* jited_linfo is the jited addr of the linfo. It has a
|
|
|
|
* one to one mapping to linfo:
|
|
|
|
* jited_linfo[i] is the jited addr for the linfo[i]->insn_off.
|
|
|
|
* Both the main and sub prog share the same jited_linfo.
|
|
|
|
* The subprog can access its first jited_linfo by
|
|
|
|
* using the linfo_idx.
|
|
|
|
*/
|
|
|
|
void **jited_linfo;
|
2018-11-25 07:20:44 +00:00
|
|
|
u32 func_info_cnt;
|
2018-12-08 00:42:25 +00:00
|
|
|
u32 nr_linfo;
|
|
|
|
/* subprog can use linfo_idx to access its first linfo and
|
|
|
|
* jited_linfo.
|
|
|
|
* main prog always has linfo_idx == 0
|
|
|
|
*/
|
|
|
|
u32 linfo_idx;
|
2019-10-16 03:25:03 +00:00
|
|
|
u32 num_exentries;
|
|
|
|
struct exception_table_entry *extable;
|
2015-05-29 02:26:02 +00:00
|
|
|
union {
|
|
|
|
struct work_struct work;
|
|
|
|
struct rcu_head rcu;
|
|
|
|
};
|
2014-09-26 07:17:00 +00:00
|
|
|
};
|
|
|
|
|
2022-06-14 23:10:42 +00:00
|
|
|
struct bpf_prog {
|
|
|
|
u16 pages; /* Number of allocated pages */
|
|
|
|
u16 jited:1, /* Is our filter JIT'ed? */
|
|
|
|
jit_requested:1,/* archs need to JIT the prog */
|
|
|
|
gpl_compatible:1, /* Is filter GPL compatible? */
|
|
|
|
cb_access:1, /* Is control block accessed? */
|
|
|
|
dst_needed:1, /* Do we need dst entry? */
|
|
|
|
blinding_requested:1, /* needs constant blinding */
|
|
|
|
blinded:1, /* Was blinded */
|
|
|
|
is_func:1, /* program is a bpf function */
|
|
|
|
kprobe_override:1, /* Do we override a kprobe? */
|
|
|
|
has_callchain_buf:1, /* callchain buffer allocated? */
|
|
|
|
enforce_expected_attach_type:1, /* Enforce expected_attach_type checking at attach time */
|
|
|
|
call_get_stack:1, /* Do we call bpf_get_stack() or bpf_get_stackid() */
|
|
|
|
call_get_func_ip:1, /* Do we call get_func_ip() */
|
|
|
|
tstamp_type_access:1; /* Accessed __sk_buff->tstamp_type */
|
|
|
|
enum bpf_prog_type type; /* Type of BPF program */
|
|
|
|
enum bpf_attach_type expected_attach_type; /* For some prog types */
|
|
|
|
u32 len; /* Number of filter blocks */
|
|
|
|
u32 jited_len; /* Size of jited insns in bytes */
|
|
|
|
u8 tag[BPF_TAG_SIZE];
|
|
|
|
struct bpf_prog_stats __percpu *stats;
|
|
|
|
int __percpu *active;
|
|
|
|
unsigned int (*bpf_func)(const void *ctx,
|
|
|
|
const struct bpf_insn *insn);
|
|
|
|
struct bpf_prog_aux *aux; /* Auxiliary fields */
|
|
|
|
struct sock_fprog_kern *orig_prog; /* Original BPF program */
|
|
|
|
/* Instructions for interpreter */
|
|
|
|
union {
|
|
|
|
DECLARE_FLEX_ARRAY(struct sock_filter, insns);
|
|
|
|
DECLARE_FLEX_ARRAY(struct bpf_insn, insnsi);
|
|
|
|
};
|
|
|
|
};
|
|
|
|
|
2019-11-22 20:07:56 +00:00
|
|
|
struct bpf_array_aux {
|
2019-11-22 20:07:58 +00:00
|
|
|
/* Programs with direct jumps into programs part of this array. */
|
|
|
|
struct list_head poke_progs;
|
|
|
|
struct bpf_map *map;
|
|
|
|
struct mutex poke_mutex;
|
|
|
|
struct work_struct work;
|
2019-11-22 20:07:56 +00:00
|
|
|
};
|
|
|
|
|
2020-07-22 06:45:54 +00:00
|
|
|
struct bpf_link {
|
|
|
|
atomic64_t refcnt;
|
|
|
|
u32 id;
|
|
|
|
enum bpf_link_type type;
|
|
|
|
const struct bpf_link_ops *ops;
|
|
|
|
struct bpf_prog *prog;
|
|
|
|
struct work_struct work;
|
|
|
|
};
|
|
|
|
|
|
|
|
struct bpf_link_ops {
|
|
|
|
void (*release)(struct bpf_link *link);
|
|
|
|
void (*dealloc)(struct bpf_link *link);
|
2020-07-31 18:28:26 +00:00
|
|
|
int (*detach)(struct bpf_link *link);
|
2020-07-22 06:45:54 +00:00
|
|
|
int (*update_prog)(struct bpf_link *link, struct bpf_prog *new_prog,
|
|
|
|
struct bpf_prog *old_prog);
|
|
|
|
void (*show_fdinfo)(const struct bpf_link *link, struct seq_file *seq);
|
|
|
|
int (*fill_link_info)(const struct bpf_link *link,
|
|
|
|
struct bpf_link_info *info);
|
|
|
|
};
|
|
|
|
|
2022-05-10 20:59:19 +00:00
|
|
|
struct bpf_tramp_link {
|
|
|
|
struct bpf_link link;
|
|
|
|
struct hlist_node tramp_hlist;
|
2022-05-10 20:59:21 +00:00
|
|
|
u64 cookie;
|
2022-05-10 20:59:19 +00:00
|
|
|
};
|
|
|
|
|
2022-06-28 17:43:06 +00:00
|
|
|
struct bpf_shim_tramp_link {
|
|
|
|
struct bpf_tramp_link link;
|
|
|
|
struct bpf_trampoline *trampoline;
|
|
|
|
};
|
|
|
|
|
2022-05-10 20:59:19 +00:00
|
|
|
struct bpf_tracing_link {
|
|
|
|
struct bpf_tramp_link link;
|
|
|
|
enum bpf_attach_type attach_type;
|
|
|
|
struct bpf_trampoline *trampoline;
|
|
|
|
struct bpf_prog *tgt_prog;
|
|
|
|
};
|
|
|
|
|
2020-07-22 06:45:54 +00:00
|
|
|
struct bpf_link_primer {
|
|
|
|
struct bpf_link *link;
|
|
|
|
struct file *file;
|
|
|
|
int fd;
|
|
|
|
u32 id;
|
|
|
|
};
|
|
|
|
|
bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 00:35:05 +00:00
|
|
|
struct bpf_struct_ops_value;
|
2020-01-09 00:35:03 +00:00
|
|
|
struct btf_member;
|
|
|
|
|
|
|
|
#define BPF_STRUCT_OPS_MAX_NR_MEMBERS 64
|
|
|
|
struct bpf_struct_ops {
|
|
|
|
const struct bpf_verifier_ops *verifier_ops;
|
|
|
|
int (*init)(struct btf *btf);
|
|
|
|
int (*check_member)(const struct btf_type *t,
|
|
|
|
const struct btf_member *member);
|
bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 00:35:05 +00:00
|
|
|
int (*init_member)(const struct btf_type *t,
|
|
|
|
const struct btf_member *member,
|
|
|
|
void *kdata, const void *udata);
|
|
|
|
int (*reg)(void *kdata);
|
|
|
|
void (*unreg)(void *kdata);
|
2020-01-09 00:35:03 +00:00
|
|
|
const struct btf_type *type;
|
bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 00:35:05 +00:00
|
|
|
const struct btf_type *value_type;
|
2020-01-09 00:35:03 +00:00
|
|
|
const char *name;
|
|
|
|
struct btf_func_model func_models[BPF_STRUCT_OPS_MAX_NR_MEMBERS];
|
|
|
|
u32 type_id;
|
bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 00:35:05 +00:00
|
|
|
u32 value_id;
|
2020-01-09 00:35:03 +00:00
|
|
|
};
|
|
|
|
|
|
|
|
#if defined(CONFIG_BPF_JIT) && defined(CONFIG_BPF_SYSCALL)
|
bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 00:35:05 +00:00
|
|
|
#define BPF_MODULE_OWNER ((void *)((0xeB9FUL << 2) + POISON_POINTER_DELTA))
|
2020-01-09 00:35:03 +00:00
|
|
|
const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id);
|
2020-01-27 17:51:45 +00:00
|
|
|
void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log);
|
bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 00:35:05 +00:00
|
|
|
bool bpf_struct_ops_get(const void *kdata);
|
|
|
|
void bpf_struct_ops_put(const void *kdata);
|
|
|
|
int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
|
|
|
|
void *value);
|
2022-05-10 20:59:19 +00:00
|
|
|
int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
|
|
|
|
struct bpf_tramp_link *link,
|
2021-10-25 06:40:22 +00:00
|
|
|
const struct btf_func_model *model,
|
|
|
|
void *image, void *image_end);
|
bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 00:35:05 +00:00
|
|
|
static inline bool bpf_try_module_get(const void *data, struct module *owner)
|
|
|
|
{
|
|
|
|
if (owner == BPF_MODULE_OWNER)
|
|
|
|
return bpf_struct_ops_get(data);
|
|
|
|
else
|
|
|
|
return try_module_get(owner);
|
|
|
|
}
|
|
|
|
static inline void bpf_module_put(const void *data, struct module *owner)
|
|
|
|
{
|
|
|
|
if (owner == BPF_MODULE_OWNER)
|
|
|
|
bpf_struct_ops_put(data);
|
|
|
|
else
|
|
|
|
module_put(owner);
|
|
|
|
}
|
2021-10-25 06:40:24 +00:00
|
|
|
|
|
|
|
#ifdef CONFIG_NET
|
|
|
|
/* Define it here to avoid the use of forward declaration */
|
|
|
|
struct bpf_dummy_ops_state {
|
|
|
|
int val;
|
|
|
|
};
|
|
|
|
|
|
|
|
struct bpf_dummy_ops {
|
|
|
|
int (*test_1)(struct bpf_dummy_ops_state *cb);
|
|
|
|
int (*test_2)(struct bpf_dummy_ops_state *cb, int a1, unsigned short a2,
|
|
|
|
char a3, unsigned long a4);
|
|
|
|
};
|
|
|
|
|
|
|
|
int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr);
|
|
|
|
#endif
|
2020-01-09 00:35:03 +00:00
|
|
|
#else
|
|
|
|
static inline const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id)
|
|
|
|
{
|
|
|
|
return NULL;
|
|
|
|
}
|
2020-01-27 17:51:45 +00:00
|
|
|
static inline void bpf_struct_ops_init(struct btf *btf,
|
|
|
|
struct bpf_verifier_log *log)
|
|
|
|
{
|
|
|
|
}
|
bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 00:35:05 +00:00
|
|
|
static inline bool bpf_try_module_get(const void *data, struct module *owner)
|
|
|
|
{
|
|
|
|
return try_module_get(owner);
|
|
|
|
}
|
|
|
|
static inline void bpf_module_put(const void *data, struct module *owner)
|
|
|
|
{
|
|
|
|
module_put(owner);
|
|
|
|
}
|
|
|
|
static inline int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map,
|
|
|
|
void *key,
|
|
|
|
void *value)
|
|
|
|
{
|
|
|
|
return -EINVAL;
|
|
|
|
}
|
2022-07-20 15:52:20 +00:00
|
|
|
#endif
|
|
|
|
|
|
|
|
#if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM)
|
|
|
|
int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
|
|
|
|
int cgroup_atype);
|
|
|
|
void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog);
|
|
|
|
#else
|
2022-06-28 17:43:06 +00:00
|
|
|
static inline int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
|
|
|
|
int cgroup_atype)
|
|
|
|
{
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
}
|
|
|
|
static inline void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)
|
|
|
|
{
|
|
|
|
}
|
2020-01-09 00:35:03 +00:00
|
|
|
#endif
|
|
|
|
|
bpf: allow bpf programs to tail-call other bpf programs
introduce bpf_tail_call(ctx, &jmp_table, index) helper function
which can be used from BPF programs like:
int bpf_prog(struct pt_regs *ctx)
{
...
bpf_tail_call(ctx, &jmp_table, index);
...
}
that is roughly equivalent to:
int bpf_prog(struct pt_regs *ctx)
{
...
if (jmp_table[index])
return (*jmp_table[index])(ctx);
...
}
The important detail that it's not a normal call, but a tail call.
The kernel stack is precious, so this helper reuses the current
stack frame and jumps into another BPF program without adding
extra call frame.
It's trivially done in interpreter and a bit trickier in JITs.
In case of x64 JIT the bigger part of generated assembler prologue
is common for all programs, so it is simply skipped while jumping.
Other JITs can do similar prologue-skipping optimization or
do stack unwind before jumping into the next program.
bpf_tail_call() arguments:
ctx - context pointer
jmp_table - one of BPF_MAP_TYPE_PROG_ARRAY maps used as the jump table
index - index in the jump table
Since all BPF programs are idenitified by file descriptor, user space
need to populate the jmp_table with FDs of other BPF programs.
If jmp_table[index] is empty the bpf_tail_call() doesn't jump anywhere
and program execution continues as normal.
New BPF_MAP_TYPE_PROG_ARRAY map type is introduced so that user space can
populate this jmp_table array with FDs of other bpf programs.
Programs can share the same jmp_table array or use multiple jmp_tables.
The chain of tail calls can form unpredictable dynamic loops therefore
tail_call_cnt is used to limit the number of calls and currently is set to 32.
Use cases:
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
==========
- simplify complex programs by splitting them into a sequence of small programs
- dispatch routine
For tracing and future seccomp the program may be triggered on all system
calls, but processing of syscall arguments will be different. It's more
efficient to implement them as:
int syscall_entry(struct seccomp_data *ctx)
{
bpf_tail_call(ctx, &syscall_jmp_table, ctx->nr /* syscall number */);
... default: process unknown syscall ...
}
int sys_write_event(struct seccomp_data *ctx) {...}
int sys_read_event(struct seccomp_data *ctx) {...}
syscall_jmp_table[__NR_write] = sys_write_event;
syscall_jmp_table[__NR_read] = sys_read_event;
For networking the program may call into different parsers depending on
packet format, like:
int packet_parser(struct __sk_buff *skb)
{
... parse L2, L3 here ...
__u8 ipproto = load_byte(skb, ... offsetof(struct iphdr, protocol));
bpf_tail_call(skb, &ipproto_jmp_table, ipproto);
... default: process unknown protocol ...
}
int parse_tcp(struct __sk_buff *skb) {...}
int parse_udp(struct __sk_buff *skb) {...}
ipproto_jmp_table[IPPROTO_TCP] = parse_tcp;
ipproto_jmp_table[IPPROTO_UDP] = parse_udp;
- for TC use case, bpf_tail_call() allows to implement reclassify-like logic
- bpf_map_update_elem/delete calls into BPF_MAP_TYPE_PROG_ARRAY jump table
are atomic, so user space can build chains of BPF programs on the fly
Implementation details:
=======================
- high performance of bpf_tail_call() is the goal.
It could have been implemented without JIT changes as a wrapper on top of
BPF_PROG_RUN() macro, but with two downsides:
. all programs would have to pay performance penalty for this feature and
tail call itself would be slower, since mandatory stack unwind, return,
stack allocate would be done for every tailcall.
. tailcall would be limited to programs running preempt_disabled, since
generic 'void *ctx' doesn't have room for 'tail_call_cnt' and it would
need to be either global per_cpu variable accessed by helper and by wrapper
or global variable protected by locks.
In this implementation x64 JIT bypasses stack unwind and jumps into the
callee program after prologue.
- bpf_prog_array_compatible() ensures that prog_type of callee and caller
are the same and JITed/non-JITed flag is the same, since calling JITed
program from non-JITed is invalid, since stack frames are different.
Similarly calling kprobe type program from socket type program is invalid.
- jump table is implemented as BPF_MAP_TYPE_PROG_ARRAY to reuse 'map'
abstraction, its user space API and all of verifier logic.
It's in the existing arraymap.c file, since several functions are
shared with regular array map.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-05-19 23:59:03 +00:00
|
|
|
struct bpf_array {
|
|
|
|
struct bpf_map map;
|
|
|
|
u32 elem_size;
|
bpf: prevent out-of-bounds speculation
Under speculation, CPUs may mis-predict branches in bounds checks. Thus,
memory accesses under a bounds check may be speculated even if the
bounds check fails, providing a primitive for building a side channel.
To avoid leaking kernel data round up array-based maps and mask the index
after bounds check, so speculated load with out of bounds index will load
either valid value from the array or zero from the padded area.
Unconditionally mask index for all array types even when max_entries
are not rounded to power of 2 for root user.
When map is created by unpriv user generate a sequence of bpf insns
that includes AND operation to make sure that JITed code includes
the same 'index & index_mask' operation.
If prog_array map is created by unpriv user replace
bpf_tail_call(ctx, map, index);
with
if (index >= max_entries) {
index &= map->index_mask;
bpf_tail_call(ctx, map, index);
}
(along with roundup to power 2) to prevent out-of-bounds speculation.
There is secondary redundant 'if (index >= max_entries)' in the interpreter
and in all JITs, but they can be optimized later if necessary.
Other array-like maps (cpumap, devmap, sockmap, perf_event_array, cgroup_array)
cannot be used by unpriv, so no changes there.
That fixes bpf side of "Variant 1: bounds check bypass (CVE-2017-5753)" on
all architectures with and without JIT.
v2->v3:
Daniel noticed that attack potentially can be crafted via syscall commands
without loading the program, so add masking to those paths as well.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-01-08 01:33:02 +00:00
|
|
|
u32 index_mask;
|
2019-11-22 20:07:56 +00:00
|
|
|
struct bpf_array_aux *aux;
|
bpf: allow bpf programs to tail-call other bpf programs
introduce bpf_tail_call(ctx, &jmp_table, index) helper function
which can be used from BPF programs like:
int bpf_prog(struct pt_regs *ctx)
{
...
bpf_tail_call(ctx, &jmp_table, index);
...
}
that is roughly equivalent to:
int bpf_prog(struct pt_regs *ctx)
{
...
if (jmp_table[index])
return (*jmp_table[index])(ctx);
...
}
The important detail that it's not a normal call, but a tail call.
The kernel stack is precious, so this helper reuses the current
stack frame and jumps into another BPF program without adding
extra call frame.
It's trivially done in interpreter and a bit trickier in JITs.
In case of x64 JIT the bigger part of generated assembler prologue
is common for all programs, so it is simply skipped while jumping.
Other JITs can do similar prologue-skipping optimization or
do stack unwind before jumping into the next program.
bpf_tail_call() arguments:
ctx - context pointer
jmp_table - one of BPF_MAP_TYPE_PROG_ARRAY maps used as the jump table
index - index in the jump table
Since all BPF programs are idenitified by file descriptor, user space
need to populate the jmp_table with FDs of other BPF programs.
If jmp_table[index] is empty the bpf_tail_call() doesn't jump anywhere
and program execution continues as normal.
New BPF_MAP_TYPE_PROG_ARRAY map type is introduced so that user space can
populate this jmp_table array with FDs of other bpf programs.
Programs can share the same jmp_table array or use multiple jmp_tables.
The chain of tail calls can form unpredictable dynamic loops therefore
tail_call_cnt is used to limit the number of calls and currently is set to 32.
Use cases:
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
==========
- simplify complex programs by splitting them into a sequence of small programs
- dispatch routine
For tracing and future seccomp the program may be triggered on all system
calls, but processing of syscall arguments will be different. It's more
efficient to implement them as:
int syscall_entry(struct seccomp_data *ctx)
{
bpf_tail_call(ctx, &syscall_jmp_table, ctx->nr /* syscall number */);
... default: process unknown syscall ...
}
int sys_write_event(struct seccomp_data *ctx) {...}
int sys_read_event(struct seccomp_data *ctx) {...}
syscall_jmp_table[__NR_write] = sys_write_event;
syscall_jmp_table[__NR_read] = sys_read_event;
For networking the program may call into different parsers depending on
packet format, like:
int packet_parser(struct __sk_buff *skb)
{
... parse L2, L3 here ...
__u8 ipproto = load_byte(skb, ... offsetof(struct iphdr, protocol));
bpf_tail_call(skb, &ipproto_jmp_table, ipproto);
... default: process unknown protocol ...
}
int parse_tcp(struct __sk_buff *skb) {...}
int parse_udp(struct __sk_buff *skb) {...}
ipproto_jmp_table[IPPROTO_TCP] = parse_tcp;
ipproto_jmp_table[IPPROTO_UDP] = parse_udp;
- for TC use case, bpf_tail_call() allows to implement reclassify-like logic
- bpf_map_update_elem/delete calls into BPF_MAP_TYPE_PROG_ARRAY jump table
are atomic, so user space can build chains of BPF programs on the fly
Implementation details:
=======================
- high performance of bpf_tail_call() is the goal.
It could have been implemented without JIT changes as a wrapper on top of
BPF_PROG_RUN() macro, but with two downsides:
. all programs would have to pay performance penalty for this feature and
tail call itself would be slower, since mandatory stack unwind, return,
stack allocate would be done for every tailcall.
. tailcall would be limited to programs running preempt_disabled, since
generic 'void *ctx' doesn't have room for 'tail_call_cnt' and it would
need to be either global per_cpu variable accessed by helper and by wrapper
or global variable protected by locks.
In this implementation x64 JIT bypasses stack unwind and jumps into the
callee program after prologue.
- bpf_prog_array_compatible() ensures that prog_type of callee and caller
are the same and JITed/non-JITed flag is the same, since calling JITed
program from non-JITed is invalid, since stack frames are different.
Similarly calling kprobe type program from socket type program is invalid.
- jump table is implemented as BPF_MAP_TYPE_PROG_ARRAY to reuse 'map'
abstraction, its user space API and all of verifier logic.
It's in the existing arraymap.c file, since several functions are
shared with regular array map.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-05-19 23:59:03 +00:00
|
|
|
union {
|
|
|
|
char value[0] __aligned(8);
|
2015-08-06 07:02:33 +00:00
|
|
|
void *ptrs[0] __aligned(8);
|
2016-02-02 06:39:54 +00:00
|
|
|
void __percpu *pptrs[0] __aligned(8);
|
bpf: allow bpf programs to tail-call other bpf programs
introduce bpf_tail_call(ctx, &jmp_table, index) helper function
which can be used from BPF programs like:
int bpf_prog(struct pt_regs *ctx)
{
...
bpf_tail_call(ctx, &jmp_table, index);
...
}
that is roughly equivalent to:
int bpf_prog(struct pt_regs *ctx)
{
...
if (jmp_table[index])
return (*jmp_table[index])(ctx);
...
}
The important detail that it's not a normal call, but a tail call.
The kernel stack is precious, so this helper reuses the current
stack frame and jumps into another BPF program without adding
extra call frame.
It's trivially done in interpreter and a bit trickier in JITs.
In case of x64 JIT the bigger part of generated assembler prologue
is common for all programs, so it is simply skipped while jumping.
Other JITs can do similar prologue-skipping optimization or
do stack unwind before jumping into the next program.
bpf_tail_call() arguments:
ctx - context pointer
jmp_table - one of BPF_MAP_TYPE_PROG_ARRAY maps used as the jump table
index - index in the jump table
Since all BPF programs are idenitified by file descriptor, user space
need to populate the jmp_table with FDs of other BPF programs.
If jmp_table[index] is empty the bpf_tail_call() doesn't jump anywhere
and program execution continues as normal.
New BPF_MAP_TYPE_PROG_ARRAY map type is introduced so that user space can
populate this jmp_table array with FDs of other bpf programs.
Programs can share the same jmp_table array or use multiple jmp_tables.
The chain of tail calls can form unpredictable dynamic loops therefore
tail_call_cnt is used to limit the number of calls and currently is set to 32.
Use cases:
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
==========
- simplify complex programs by splitting them into a sequence of small programs
- dispatch routine
For tracing and future seccomp the program may be triggered on all system
calls, but processing of syscall arguments will be different. It's more
efficient to implement them as:
int syscall_entry(struct seccomp_data *ctx)
{
bpf_tail_call(ctx, &syscall_jmp_table, ctx->nr /* syscall number */);
... default: process unknown syscall ...
}
int sys_write_event(struct seccomp_data *ctx) {...}
int sys_read_event(struct seccomp_data *ctx) {...}
syscall_jmp_table[__NR_write] = sys_write_event;
syscall_jmp_table[__NR_read] = sys_read_event;
For networking the program may call into different parsers depending on
packet format, like:
int packet_parser(struct __sk_buff *skb)
{
... parse L2, L3 here ...
__u8 ipproto = load_byte(skb, ... offsetof(struct iphdr, protocol));
bpf_tail_call(skb, &ipproto_jmp_table, ipproto);
... default: process unknown protocol ...
}
int parse_tcp(struct __sk_buff *skb) {...}
int parse_udp(struct __sk_buff *skb) {...}
ipproto_jmp_table[IPPROTO_TCP] = parse_tcp;
ipproto_jmp_table[IPPROTO_UDP] = parse_udp;
- for TC use case, bpf_tail_call() allows to implement reclassify-like logic
- bpf_map_update_elem/delete calls into BPF_MAP_TYPE_PROG_ARRAY jump table
are atomic, so user space can build chains of BPF programs on the fly
Implementation details:
=======================
- high performance of bpf_tail_call() is the goal.
It could have been implemented without JIT changes as a wrapper on top of
BPF_PROG_RUN() macro, but with two downsides:
. all programs would have to pay performance penalty for this feature and
tail call itself would be slower, since mandatory stack unwind, return,
stack allocate would be done for every tailcall.
. tailcall would be limited to programs running preempt_disabled, since
generic 'void *ctx' doesn't have room for 'tail_call_cnt' and it would
need to be either global per_cpu variable accessed by helper and by wrapper
or global variable protected by locks.
In this implementation x64 JIT bypasses stack unwind and jumps into the
callee program after prologue.
- bpf_prog_array_compatible() ensures that prog_type of callee and caller
are the same and JITed/non-JITed flag is the same, since calling JITed
program from non-JITed is invalid, since stack frames are different.
Similarly calling kprobe type program from socket type program is invalid.
- jump table is implemented as BPF_MAP_TYPE_PROG_ARRAY to reuse 'map'
abstraction, its user space API and all of verifier logic.
It's in the existing arraymap.c file, since several functions are
shared with regular array map.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-05-19 23:59:03 +00:00
|
|
|
};
|
|
|
|
};
|
bpf, maps: flush own entries on perf map release
The behavior of perf event arrays are quite different from all
others as they are tightly coupled to perf event fds, f.e. shown
recently by commit e03e7ee34fdd ("perf/bpf: Convert perf_event_array
to use struct file") to make refcounting on perf event more robust.
A remaining issue that the current code still has is that since
additions to the perf event array take a reference on the struct
file via perf_event_get() and are only released via fput() (that
cleans up the perf event eventually via perf_event_release_kernel())
when the element is either manually removed from the map from user
space or automatically when the last reference on the perf event
map is dropped. However, this leads us to dangling struct file's
when the map gets pinned after the application owning the perf
event descriptor exits, and since the struct file reference will
in such case only be manually dropped or via pinned file removal,
it leads to the perf event living longer than necessary, consuming
needlessly resources for that time.
Relations between perf event fds and bpf perf event map fds can be
rather complex. F.e. maps can act as demuxers among different perf
event fds that can possibly be owned by different threads and based
on the index selection from the program, events get dispatched to
one of the per-cpu fd endpoints. One perf event fd (or, rather a
per-cpu set of them) can also live in multiple perf event maps at
the same time, listening for events. Also, another requirement is
that perf event fds can get closed from application side after they
have been attached to the perf event map, so that on exit perf event
map will take care of dropping their references eventually. Likewise,
when such maps are pinned, the intended behavior is that a user
application does bpf_obj_get(), puts its fds in there and on exit
when fd is released, they are dropped from the map again, so the map
acts rather as connector endpoint. This also makes perf event maps
inherently different from program arrays as described in more detail
in commit c9da161c6517 ("bpf: fix clearing on persistent program
array maps").
To tackle this, map entries are marked by the map struct file that
added the element to the map. And when the last reference to that map
struct file is released from user space, then the tracked entries
are purged from the map. This is okay, because new map struct files
instances resp. frontends to the anon inode are provided via
bpf_map_new_fd() that is called when we invoke bpf_obj_get_user()
for retrieving a pinned map, but also when an initial instance is
created via map_create(). The rest is resolved by the vfs layer
automatically for us by keeping reference count on the map's struct
file. Any concurrent updates on the map slot are fine as well, it
just means that perf_event_fd_array_release() needs to delete less
of its own entires.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-06-15 20:47:14 +00:00
|
|
|
|
2019-04-02 04:27:45 +00:00
|
|
|
#define BPF_COMPLEXITY_LIMIT_INSNS 1000000 /* yes. 1M insns */
|
bpf: Change value of MAX_TAIL_CALL_CNT from 32 to 33
In the current code, the actual max tail call count is 33 which is greater
than MAX_TAIL_CALL_CNT (defined as 32). The actual limit is not consistent
with the meaning of MAX_TAIL_CALL_CNT and thus confusing at first glance.
We can see the historical evolution from commit 04fd61ab36ec ("bpf: allow
bpf programs to tail-call other bpf programs") and commit f9dabe016b63
("bpf: Undo off-by-one in interpreter tail call count limit"). In order
to avoid changing existing behavior, the actual limit is 33 now, this is
reasonable.
After commit 874be05f525e ("bpf, tests: Add tail call test suite"), we can
see there exists failed testcase.
On all archs when CONFIG_BPF_JIT_ALWAYS_ON is not set:
# echo 0 > /proc/sys/net/core/bpf_jit_enable
# modprobe test_bpf
# dmesg | grep -w FAIL
Tail call error path, max count reached jited:0 ret 34 != 33 FAIL
On some archs:
# echo 1 > /proc/sys/net/core/bpf_jit_enable
# modprobe test_bpf
# dmesg | grep -w FAIL
Tail call error path, max count reached jited:1 ret 34 != 33 FAIL
Although the above failed testcase has been fixed in commit 18935a72eb25
("bpf/tests: Fix error in tail call limit tests"), it would still be good
to change the value of MAX_TAIL_CALL_CNT from 32 to 33 to make the code
more readable.
The 32-bit x86 JIT was using a limit of 32, just fix the wrong comments and
limit to 33 tail calls as the constant MAX_TAIL_CALL_CNT updated. For the
mips64 JIT, use "ori" instead of "addiu" as suggested by Johan Almbladh.
For the riscv JIT, use RV_REG_TCC directly to save one register move as
suggested by Björn Töpel. For the other implementations, no function changes,
it does not change the current limit 33, the new value of MAX_TAIL_CALL_CNT
can reflect the actual max tail call count, the related tail call testcases
in test_bpf module and selftests can work well for the interpreter and the
JIT.
Here are the test results on x86_64:
# uname -m
x86_64
# echo 0 > /proc/sys/net/core/bpf_jit_enable
# modprobe test_bpf test_suite=test_tail_calls
# dmesg | tail -1
test_bpf: test_tail_calls: Summary: 8 PASSED, 0 FAILED, [0/8 JIT'ed]
# rmmod test_bpf
# echo 1 > /proc/sys/net/core/bpf_jit_enable
# modprobe test_bpf test_suite=test_tail_calls
# dmesg | tail -1
test_bpf: test_tail_calls: Summary: 8 PASSED, 0 FAILED, [8/8 JIT'ed]
# rmmod test_bpf
# ./test_progs -t tailcalls
#142 tailcalls:OK
Summary: 1/11 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Tested-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Björn Töpel <bjorn@kernel.org>
Acked-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/bpf/1636075800-3264-1-git-send-email-yangtiezhu@loongson.cn
2021-11-05 01:30:00 +00:00
|
|
|
#define MAX_TAIL_CALL_CNT 33
|
bpf: allow bpf programs to tail-call other bpf programs
introduce bpf_tail_call(ctx, &jmp_table, index) helper function
which can be used from BPF programs like:
int bpf_prog(struct pt_regs *ctx)
{
...
bpf_tail_call(ctx, &jmp_table, index);
...
}
that is roughly equivalent to:
int bpf_prog(struct pt_regs *ctx)
{
...
if (jmp_table[index])
return (*jmp_table[index])(ctx);
...
}
The important detail that it's not a normal call, but a tail call.
The kernel stack is precious, so this helper reuses the current
stack frame and jumps into another BPF program without adding
extra call frame.
It's trivially done in interpreter and a bit trickier in JITs.
In case of x64 JIT the bigger part of generated assembler prologue
is common for all programs, so it is simply skipped while jumping.
Other JITs can do similar prologue-skipping optimization or
do stack unwind before jumping into the next program.
bpf_tail_call() arguments:
ctx - context pointer
jmp_table - one of BPF_MAP_TYPE_PROG_ARRAY maps used as the jump table
index - index in the jump table
Since all BPF programs are idenitified by file descriptor, user space
need to populate the jmp_table with FDs of other BPF programs.
If jmp_table[index] is empty the bpf_tail_call() doesn't jump anywhere
and program execution continues as normal.
New BPF_MAP_TYPE_PROG_ARRAY map type is introduced so that user space can
populate this jmp_table array with FDs of other bpf programs.
Programs can share the same jmp_table array or use multiple jmp_tables.
The chain of tail calls can form unpredictable dynamic loops therefore
tail_call_cnt is used to limit the number of calls and currently is set to 32.
Use cases:
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
==========
- simplify complex programs by splitting them into a sequence of small programs
- dispatch routine
For tracing and future seccomp the program may be triggered on all system
calls, but processing of syscall arguments will be different. It's more
efficient to implement them as:
int syscall_entry(struct seccomp_data *ctx)
{
bpf_tail_call(ctx, &syscall_jmp_table, ctx->nr /* syscall number */);
... default: process unknown syscall ...
}
int sys_write_event(struct seccomp_data *ctx) {...}
int sys_read_event(struct seccomp_data *ctx) {...}
syscall_jmp_table[__NR_write] = sys_write_event;
syscall_jmp_table[__NR_read] = sys_read_event;
For networking the program may call into different parsers depending on
packet format, like:
int packet_parser(struct __sk_buff *skb)
{
... parse L2, L3 here ...
__u8 ipproto = load_byte(skb, ... offsetof(struct iphdr, protocol));
bpf_tail_call(skb, &ipproto_jmp_table, ipproto);
... default: process unknown protocol ...
}
int parse_tcp(struct __sk_buff *skb) {...}
int parse_udp(struct __sk_buff *skb) {...}
ipproto_jmp_table[IPPROTO_TCP] = parse_tcp;
ipproto_jmp_table[IPPROTO_UDP] = parse_udp;
- for TC use case, bpf_tail_call() allows to implement reclassify-like logic
- bpf_map_update_elem/delete calls into BPF_MAP_TYPE_PROG_ARRAY jump table
are atomic, so user space can build chains of BPF programs on the fly
Implementation details:
=======================
- high performance of bpf_tail_call() is the goal.
It could have been implemented without JIT changes as a wrapper on top of
BPF_PROG_RUN() macro, but with two downsides:
. all programs would have to pay performance penalty for this feature and
tail call itself would be slower, since mandatory stack unwind, return,
stack allocate would be done for every tailcall.
. tailcall would be limited to programs running preempt_disabled, since
generic 'void *ctx' doesn't have room for 'tail_call_cnt' and it would
need to be either global per_cpu variable accessed by helper and by wrapper
or global variable protected by locks.
In this implementation x64 JIT bypasses stack unwind and jumps into the
callee program after prologue.
- bpf_prog_array_compatible() ensures that prog_type of callee and caller
are the same and JITed/non-JITed flag is the same, since calling JITed
program from non-JITed is invalid, since stack frames are different.
Similarly calling kprobe type program from socket type program is invalid.
- jump table is implemented as BPF_MAP_TYPE_PROG_ARRAY to reuse 'map'
abstraction, its user space API and all of verifier logic.
It's in the existing arraymap.c file, since several functions are
shared with regular array map.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-05-19 23:59:03 +00:00
|
|
|
|
2022-06-20 23:53:42 +00:00
|
|
|
/* Maximum number of loops for bpf_loop */
|
|
|
|
#define BPF_MAX_LOOPS BIT(23)
|
|
|
|
|
bpf: add program side {rd, wr}only support for maps
This work adds two new map creation flags BPF_F_RDONLY_PROG
and BPF_F_WRONLY_PROG in order to allow for read-only or
write-only BPF maps from a BPF program side.
Today we have BPF_F_RDONLY and BPF_F_WRONLY, but this only
applies to system call side, meaning the BPF program has full
read/write access to the map as usual while bpf(2) calls with
map fd can either only read or write into the map depending
on the flags. BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG allows
for the exact opposite such that verifier is going to reject
program loads if write into a read-only map or a read into a
write-only map is detected. For read-only map case also some
helpers are forbidden for programs that would alter the map
state such as map deletion, update, etc. As opposed to the two
BPF_F_RDONLY / BPF_F_WRONLY flags, BPF_F_RDONLY_PROG as well
as BPF_F_WRONLY_PROG really do correspond to the map lifetime.
We've enabled this generic map extension to various non-special
maps holding normal user data: array, hash, lru, lpm, local
storage, queue and stack. Further generic map types could be
followed up in future depending on use-case. Main use case
here is to forbid writes into .rodata map values from verifier
side.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-04-09 21:20:05 +00:00
|
|
|
#define BPF_F_ACCESS_MASK (BPF_F_RDONLY | \
|
|
|
|
BPF_F_RDONLY_PROG | \
|
|
|
|
BPF_F_WRONLY | \
|
|
|
|
BPF_F_WRONLY_PROG)
|
|
|
|
|
|
|
|
#define BPF_MAP_CAN_READ BIT(0)
|
|
|
|
#define BPF_MAP_CAN_WRITE BIT(1)
|
|
|
|
|
|
|
|
static inline u32 bpf_map_flags_to_cap(struct bpf_map *map)
|
|
|
|
{
|
|
|
|
u32 access_flags = map->map_flags & (BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG);
|
|
|
|
|
|
|
|
/* Combination of BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG is
|
|
|
|
* not possible.
|
|
|
|
*/
|
|
|
|
if (access_flags & BPF_F_RDONLY_PROG)
|
|
|
|
return BPF_MAP_CAN_READ;
|
|
|
|
else if (access_flags & BPF_F_WRONLY_PROG)
|
|
|
|
return BPF_MAP_CAN_WRITE;
|
|
|
|
else
|
|
|
|
return BPF_MAP_CAN_READ | BPF_MAP_CAN_WRITE;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline bool bpf_map_flags_access_ok(u32 access_flags)
|
|
|
|
{
|
|
|
|
return (access_flags & (BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG)) !=
|
|
|
|
(BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG);
|
|
|
|
}
|
|
|
|
|
bpf, maps: flush own entries on perf map release
The behavior of perf event arrays are quite different from all
others as they are tightly coupled to perf event fds, f.e. shown
recently by commit e03e7ee34fdd ("perf/bpf: Convert perf_event_array
to use struct file") to make refcounting on perf event more robust.
A remaining issue that the current code still has is that since
additions to the perf event array take a reference on the struct
file via perf_event_get() and are only released via fput() (that
cleans up the perf event eventually via perf_event_release_kernel())
when the element is either manually removed from the map from user
space or automatically when the last reference on the perf event
map is dropped. However, this leads us to dangling struct file's
when the map gets pinned after the application owning the perf
event descriptor exits, and since the struct file reference will
in such case only be manually dropped or via pinned file removal,
it leads to the perf event living longer than necessary, consuming
needlessly resources for that time.
Relations between perf event fds and bpf perf event map fds can be
rather complex. F.e. maps can act as demuxers among different perf
event fds that can possibly be owned by different threads and based
on the index selection from the program, events get dispatched to
one of the per-cpu fd endpoints. One perf event fd (or, rather a
per-cpu set of them) can also live in multiple perf event maps at
the same time, listening for events. Also, another requirement is
that perf event fds can get closed from application side after they
have been attached to the perf event map, so that on exit perf event
map will take care of dropping their references eventually. Likewise,
when such maps are pinned, the intended behavior is that a user
application does bpf_obj_get(), puts its fds in there and on exit
when fd is released, they are dropped from the map again, so the map
acts rather as connector endpoint. This also makes perf event maps
inherently different from program arrays as described in more detail
in commit c9da161c6517 ("bpf: fix clearing on persistent program
array maps").
To tackle this, map entries are marked by the map struct file that
added the element to the map. And when the last reference to that map
struct file is released from user space, then the tracked entries
are purged from the map. This is okay, because new map struct files
instances resp. frontends to the anon inode are provided via
bpf_map_new_fd() that is called when we invoke bpf_obj_get_user()
for retrieving a pinned map, but also when an initial instance is
created via map_create(). The rest is resolved by the vfs layer
automatically for us by keeping reference count on the map's struct
file. Any concurrent updates on the map slot are fine as well, it
just means that perf_event_fd_array_release() needs to delete less
of its own entires.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-06-15 20:47:14 +00:00
|
|
|
struct bpf_event_entry {
|
|
|
|
struct perf_event *event;
|
|
|
|
struct file *perf_file;
|
|
|
|
struct file *map_file;
|
|
|
|
struct rcu_head rcu;
|
|
|
|
};
|
|
|
|
|
2022-01-21 10:10:02 +00:00
|
|
|
static inline bool map_type_contains_progs(struct bpf_map *map)
|
|
|
|
{
|
|
|
|
return map->map_type == BPF_MAP_TYPE_PROG_ARRAY ||
|
|
|
|
map->map_type == BPF_MAP_TYPE_DEVMAP ||
|
|
|
|
map->map_type == BPF_MAP_TYPE_CPUMAP;
|
|
|
|
}
|
|
|
|
|
|
|
|
bool bpf_prog_map_compatible(struct bpf_map *map, const struct bpf_prog *fp);
|
2017-01-13 22:38:15 +00:00
|
|
|
int bpf_prog_calc_tag(struct bpf_prog *fp);
|
bpf: add event output helper for notifications/sampling/logging
This patch adds a new helper for cls/act programs that can push events
to user space applications. For networking, this can be f.e. for sampling,
debugging, logging purposes or pushing of arbitrary wake-up events. The
idea is similar to a43eec304259 ("bpf: introduce bpf_perf_event_output()
helper") and 39111695b1b8 ("samples: bpf: add bpf_perf_event_output example").
The eBPF program utilizes a perf event array map that user space populates
with fds from perf_event_open(), the eBPF program calls into the helper
f.e. as skb_event_output(skb, &my_map, BPF_F_CURRENT_CPU, raw, sizeof(raw))
so that the raw data is pushed into the fd f.e. at the map index of the
current CPU.
User space can poll/mmap/etc on this and has a data channel for receiving
events that can be post-processed. The nice thing is that since the eBPF
program and user space application making use of it are tightly coupled,
they can define their own arbitrary raw data format and what/when they
want to push.
While f.e. packet headers could be one part of the meta data that is being
pushed, this is not a substitute for things like packet sockets as whole
packet is not being pushed and push is only done in a single direction.
Intention is more of a generically usable, efficient event pipe to applications.
Workflow is that tc can pin the map and applications can attach themselves
e.g. after cls/act setup to one or multiple map slots, demuxing is done by
the eBPF program.
Adding this facility is with minimal effort, it reuses the helper
introduced in a43eec304259 ("bpf: introduce bpf_perf_event_output() helper")
and we get its functionality for free by overloading its BPF_FUNC_ identifier
for cls/act programs, ctx is currently unused, but will be made use of in
future. Example will be added to iproute2's BPF example files.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-04-18 19:01:24 +00:00
|
|
|
|
2015-06-13 02:39:13 +00:00
|
|
|
const struct bpf_func_proto *bpf_get_trace_printk_proto(void);
|
2021-09-17 18:29:05 +00:00
|
|
|
const struct bpf_func_proto *bpf_get_trace_vprintk_proto(void);
|
2016-07-14 16:08:05 +00:00
|
|
|
|
|
|
|
typedef unsigned long (*bpf_ctx_copy_t)(void *dst, const void *src,
|
bpf, events: fix offset in skb copy handler
This patch fixes the __output_custom() routine we currently use with
bpf_skb_copy(). I missed that when len is larger than the size of the
current handle, we can issue multiple invocations of copy_func, and
__output_custom() advances destination but also source buffer by the
written amount of bytes. When we have __output_custom(), this is actually
wrong since in that case the source buffer points to a non-linear object,
in our case an skb, which the copy_func helper is supposed to walk.
Therefore, since this is non-linear we thus need to pass the offset into
the helper, so that copy_func can use it for extracting the data from
the source object.
Therefore, adjust the callback signatures properly and pass offset
into the skb_header_pointer() invoked from bpf_skb_copy() callback. The
__DEFINE_OUTPUT_COPY_BODY() is adjusted to accommodate for two things:
i) to pass in whether we should advance source buffer or not; this is
a compile-time constant condition, ii) to pass in the offset for
__output_custom(), which we do with help of __VA_ARGS__, so everything
can stay inlined as is currently. Both changes allow for adapting the
__output_* fast-path helpers w/o extra overhead.
Fixes: 555c8a8623a3 ("bpf: avoid stack copy and use skb ctx for event output")
Fixes: 7e3f977edd0b ("perf, events: add non-linear data support for raw records")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-07-21 23:19:42 +00:00
|
|
|
unsigned long off, unsigned long len);
|
2018-10-02 20:35:33 +00:00
|
|
|
typedef u32 (*bpf_convert_ctx_access_t)(enum bpf_access_type type,
|
|
|
|
const struct bpf_insn *src,
|
|
|
|
struct bpf_insn *dst,
|
|
|
|
struct bpf_prog *prog,
|
|
|
|
u32 *target_size);
|
2016-07-14 16:08:05 +00:00
|
|
|
|
|
|
|
u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
|
|
|
|
void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy);
|
bpf: allow bpf programs to tail-call other bpf programs
introduce bpf_tail_call(ctx, &jmp_table, index) helper function
which can be used from BPF programs like:
int bpf_prog(struct pt_regs *ctx)
{
...
bpf_tail_call(ctx, &jmp_table, index);
...
}
that is roughly equivalent to:
int bpf_prog(struct pt_regs *ctx)
{
...
if (jmp_table[index])
return (*jmp_table[index])(ctx);
...
}
The important detail that it's not a normal call, but a tail call.
The kernel stack is precious, so this helper reuses the current
stack frame and jumps into another BPF program without adding
extra call frame.
It's trivially done in interpreter and a bit trickier in JITs.
In case of x64 JIT the bigger part of generated assembler prologue
is common for all programs, so it is simply skipped while jumping.
Other JITs can do similar prologue-skipping optimization or
do stack unwind before jumping into the next program.
bpf_tail_call() arguments:
ctx - context pointer
jmp_table - one of BPF_MAP_TYPE_PROG_ARRAY maps used as the jump table
index - index in the jump table
Since all BPF programs are idenitified by file descriptor, user space
need to populate the jmp_table with FDs of other BPF programs.
If jmp_table[index] is empty the bpf_tail_call() doesn't jump anywhere
and program execution continues as normal.
New BPF_MAP_TYPE_PROG_ARRAY map type is introduced so that user space can
populate this jmp_table array with FDs of other bpf programs.
Programs can share the same jmp_table array or use multiple jmp_tables.
The chain of tail calls can form unpredictable dynamic loops therefore
tail_call_cnt is used to limit the number of calls and currently is set to 32.
Use cases:
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
==========
- simplify complex programs by splitting them into a sequence of small programs
- dispatch routine
For tracing and future seccomp the program may be triggered on all system
calls, but processing of syscall arguments will be different. It's more
efficient to implement them as:
int syscall_entry(struct seccomp_data *ctx)
{
bpf_tail_call(ctx, &syscall_jmp_table, ctx->nr /* syscall number */);
... default: process unknown syscall ...
}
int sys_write_event(struct seccomp_data *ctx) {...}
int sys_read_event(struct seccomp_data *ctx) {...}
syscall_jmp_table[__NR_write] = sys_write_event;
syscall_jmp_table[__NR_read] = sys_read_event;
For networking the program may call into different parsers depending on
packet format, like:
int packet_parser(struct __sk_buff *skb)
{
... parse L2, L3 here ...
__u8 ipproto = load_byte(skb, ... offsetof(struct iphdr, protocol));
bpf_tail_call(skb, &ipproto_jmp_table, ipproto);
... default: process unknown protocol ...
}
int parse_tcp(struct __sk_buff *skb) {...}
int parse_udp(struct __sk_buff *skb) {...}
ipproto_jmp_table[IPPROTO_TCP] = parse_tcp;
ipproto_jmp_table[IPPROTO_UDP] = parse_udp;
- for TC use case, bpf_tail_call() allows to implement reclassify-like logic
- bpf_map_update_elem/delete calls into BPF_MAP_TYPE_PROG_ARRAY jump table
are atomic, so user space can build chains of BPF programs on the fly
Implementation details:
=======================
- high performance of bpf_tail_call() is the goal.
It could have been implemented without JIT changes as a wrapper on top of
BPF_PROG_RUN() macro, but with two downsides:
. all programs would have to pay performance penalty for this feature and
tail call itself would be slower, since mandatory stack unwind, return,
stack allocate would be done for every tailcall.
. tailcall would be limited to programs running preempt_disabled, since
generic 'void *ctx' doesn't have room for 'tail_call_cnt' and it would
need to be either global per_cpu variable accessed by helper and by wrapper
or global variable protected by locks.
In this implementation x64 JIT bypasses stack unwind and jumps into the
callee program after prologue.
- bpf_prog_array_compatible() ensures that prog_type of callee and caller
are the same and JITed/non-JITed flag is the same, since calling JITed
program from non-JITed is invalid, since stack frames are different.
Similarly calling kprobe type program from socket type program is invalid.
- jump table is implemented as BPF_MAP_TYPE_PROG_ARRAY to reuse 'map'
abstraction, its user space API and all of verifier logic.
It's in the existing arraymap.c file, since several functions are
shared with regular array map.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-05-19 23:59:03 +00:00
|
|
|
|
2017-10-03 05:50:21 +00:00
|
|
|
/* an array of programs to be executed under rcu_lock.
|
|
|
|
*
|
|
|
|
* Typical usage:
|
2022-04-14 16:12:33 +00:00
|
|
|
* ret = bpf_prog_run_array(rcu_dereference(&bpf_prog_array), ctx, bpf_prog_run);
|
2017-10-03 05:50:21 +00:00
|
|
|
*
|
|
|
|
* the structure returned by bpf_prog_array_alloc() should be populated
|
|
|
|
* with program pointers and the last pointer must be NULL.
|
|
|
|
* The user has to keep refcnt on the program and make sure the program
|
|
|
|
* is removed from the array before bpf_prog_put().
|
|
|
|
* The 'struct bpf_prog_array *' should only be replaced with xchg()
|
|
|
|
* since other cpus are walking the array of pointers in parallel.
|
|
|
|
*/
|
2018-08-02 21:27:21 +00:00
|
|
|
struct bpf_prog_array_item {
|
|
|
|
struct bpf_prog *prog;
|
bpf: Allow to specify user-provided bpf_cookie for BPF perf links
Add ability for users to specify custom u64 value (bpf_cookie) when creating
BPF link for perf_event-backed BPF programs (kprobe/uprobe, perf_event,
tracepoints).
This is useful for cases when the same BPF program is used for attaching and
processing invocation of different tracepoints/kprobes/uprobes in a generic
fashion, but such that each invocation is distinguished from each other (e.g.,
BPF program can look up additional information associated with a specific
kernel function without having to rely on function IP lookups). This enables
new use cases to be implemented simply and efficiently that previously were
possible only through code generation (and thus multiple instances of almost
identical BPF program) or compilation at runtime (BCC-style) on target hosts
(even more expensive resource-wise). For uprobes it is not even possible in
some cases to know function IP before hand (e.g., when attaching to shared
library without PID filtering, in which case base load address is not known
for a library).
This is done by storing u64 bpf_cookie in struct bpf_prog_array_item,
corresponding to each attached and run BPF program. Given cgroup BPF programs
already use two 8-byte pointers for their needs and cgroup BPF programs don't
have (yet?) support for bpf_cookie, reuse that space through union of
cgroup_storage and new bpf_cookie field.
Make it available to kprobe/tracepoint BPF programs through bpf_trace_run_ctx.
This is set by BPF_PROG_RUN_ARRAY, used by kprobe/uprobe/tracepoint BPF
program execution code, which luckily is now also split from
BPF_PROG_RUN_ARRAY_CG. This run context will be utilized by a new BPF helper
giving access to this user-provided cookie value from inside a BPF program.
Generic perf_event BPF programs will access this value from perf_event itself
through passed in BPF program context.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20210815070609.987780-6-andrii@kernel.org
2021-08-15 07:05:58 +00:00
|
|
|
union {
|
|
|
|
struct bpf_cgroup_storage *cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE];
|
|
|
|
u64 bpf_cookie;
|
|
|
|
};
|
2018-08-02 21:27:21 +00:00
|
|
|
};
|
|
|
|
|
2017-10-03 05:50:21 +00:00
|
|
|
struct bpf_prog_array {
|
|
|
|
struct rcu_head rcu;
|
2020-02-27 00:17:44 +00:00
|
|
|
struct bpf_prog_array_item items[];
|
2017-10-03 05:50:21 +00:00
|
|
|
};
|
|
|
|
|
2022-01-27 14:09:13 +00:00
|
|
|
struct bpf_empty_prog_array {
|
|
|
|
struct bpf_prog_array hdr;
|
|
|
|
struct bpf_prog *null_prog;
|
|
|
|
};
|
|
|
|
|
|
|
|
/* to avoid allocating empty bpf_prog_array for cgroups that
|
|
|
|
* don't have bpf program attached use one global 'bpf_empty_prog_array'
|
|
|
|
* It will not be modified the caller of bpf_prog_array_alloc()
|
|
|
|
* (since caller requested prog_cnt == 0)
|
|
|
|
* that pointer should be 'freed' by bpf_prog_array_free()
|
|
|
|
*/
|
|
|
|
extern struct bpf_empty_prog_array bpf_empty_prog_array;
|
|
|
|
|
2018-07-13 19:41:10 +00:00
|
|
|
struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags);
|
2019-05-28 21:14:41 +00:00
|
|
|
void bpf_prog_array_free(struct bpf_prog_array *progs);
|
bpf: implement sleepable uprobes by chaining gps
uprobes work by raising a trap, setting a task flag from within the
interrupt handler, and processing the actual work for the uprobe on the
way back to userspace. As a result, uprobe handlers already execute in a
might_fault/_sleep context. The primary obstacle to sleepable bpf uprobe
programs is therefore on the bpf side.
Namely, the bpf_prog_array attached to the uprobe is protected by normal
rcu. In order for uprobe bpf programs to become sleepable, it has to be
protected by the tasks_trace rcu flavor instead (and kfree() called after
a corresponding grace period).
Therefore, the free path for bpf_prog_array now chains a tasks_trace and
normal grace periods one after the other.
Users who iterate under tasks_trace read section would
be safe, as would users who iterate under normal read sections (from
non-sleepable locations).
The downside is that the tasks_trace latency affects all perf_event-attached
bpf programs (and not just uprobe ones). This is deemed safe given the
possible attach rates for kprobe/uprobe/tp programs.
Separately, non-sleepable programs need access to dynamically sized
rcu-protected maps, so bpf_run_prog_array_sleepables now conditionally takes
an rcu read section, in addition to the overarching tasks_trace section.
Signed-off-by: Delyan Kratunov <delyank@fb.com>
Link: https://lore.kernel.org/r/ce844d62a2fd0443b08c5ab02e95bc7149f9aeb1.1655248076.git.delyank@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-06-14 23:10:46 +00:00
|
|
|
/* Use when traversal over the bpf_prog_array uses tasks_trace rcu */
|
|
|
|
void bpf_prog_array_free_sleepable(struct bpf_prog_array *progs);
|
2019-05-28 21:14:41 +00:00
|
|
|
int bpf_prog_array_length(struct bpf_prog_array *progs);
|
bpf: implement getsockopt and setsockopt hooks
Implement new BPF_PROG_TYPE_CGROUP_SOCKOPT program type and
BPF_CGROUP_{G,S}ETSOCKOPT cgroup hooks.
BPF_CGROUP_SETSOCKOPT can modify user setsockopt arguments before
passing them down to the kernel or bypass kernel completely.
BPF_CGROUP_GETSOCKOPT can can inspect/modify getsockopt arguments that
kernel returns.
Both hooks reuse existing PTR_TO_PACKET{,_END} infrastructure.
The buffer memory is pre-allocated (because I don't think there is
a precedent for working with __user memory from bpf). This might be
slow to do for each {s,g}etsockopt call, that's why I've added
__cgroup_bpf_prog_array_is_empty that exits early if there is nothing
attached to a cgroup. Note, however, that there is a race between
__cgroup_bpf_prog_array_is_empty and BPF_PROG_RUN_ARRAY where cgroup
program layout might have changed; this should not be a problem
because in general there is a race between multiple calls to
{s,g}etsocktop and user adding/removing bpf progs from a cgroup.
The return code of the BPF program is handled as follows:
* 0: EPERM
* 1: success, continue with next BPF program in the cgroup chain
v9:
* allow overwriting setsockopt arguments (Alexei Starovoitov):
* use set_fs (same as kernel_setsockopt)
* buffer is always kzalloc'd (no small on-stack buffer)
v8:
* use s32 for optlen (Andrii Nakryiko)
v7:
* return only 0 or 1 (Alexei Starovoitov)
* always run all progs (Alexei Starovoitov)
* use optval=0 as kernel bypass in setsockopt (Alexei Starovoitov)
(decided to use optval=-1 instead, optval=0 might be a valid input)
* call getsockopt hook after kernel handlers (Alexei Starovoitov)
v6:
* rework cgroup chaining; stop as soon as bpf program returns
0 or 2; see patch with the documentation for the details
* drop Andrii's and Martin's Acked-by (not sure they are comfortable
with the new state of things)
v5:
* skip copy_to_user() and put_user() when ret == 0 (Martin Lau)
v4:
* don't export bpf_sk_fullsock helper (Martin Lau)
* size != sizeof(__u64) for uapi pointers (Martin Lau)
* offsetof instead of bpf_ctx_range when checking ctx access (Martin Lau)
v3:
* typos in BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY comments (Andrii Nakryiko)
* reverse christmas tree in BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY (Andrii
Nakryiko)
* use __bpf_md_ptr instead of __u32 for optval{,_end} (Martin Lau)
* use BPF_FIELD_SIZEOF() for consistency (Martin Lau)
* new CG_SOCKOPT_ACCESS macro to wrap repeated parts
v2:
* moved bpf_sockopt_kern fields around to remove a hole (Martin Lau)
* aligned bpf_sockopt_kern->buf to 8 bytes (Martin Lau)
* bpf_prog_array_is_empty instead of bpf_prog_array_length (Martin Lau)
* added [0,2] return code check to verifier (Martin Lau)
* dropped unused buf[64] from the stack (Martin Lau)
* use PTR_TO_SOCKET for bpf_sockopt->sk (Martin Lau)
* dropped bpf_target_off from ctx rewrites (Martin Lau)
* use return code for kernel bypass (Martin Lau & Andrii Nakryiko)
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: Martin Lau <kafai@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-06-27 20:38:47 +00:00
|
|
|
bool bpf_prog_array_is_empty(struct bpf_prog_array *array);
|
2019-05-28 21:14:41 +00:00
|
|
|
int bpf_prog_array_copy_to_user(struct bpf_prog_array *progs,
|
2017-10-03 05:50:22 +00:00
|
|
|
__u32 __user *prog_ids, u32 cnt);
|
2017-10-03 05:50:21 +00:00
|
|
|
|
2019-05-28 21:14:41 +00:00
|
|
|
void bpf_prog_array_delete_safe(struct bpf_prog_array *progs,
|
2017-10-24 06:53:08 +00:00
|
|
|
struct bpf_prog *old_prog);
|
2020-07-17 10:35:22 +00:00
|
|
|
int bpf_prog_array_delete_safe_at(struct bpf_prog_array *array, int index);
|
|
|
|
int bpf_prog_array_update_at(struct bpf_prog_array *array, int index,
|
|
|
|
struct bpf_prog *prog);
|
2019-05-28 21:14:41 +00:00
|
|
|
int bpf_prog_array_copy_info(struct bpf_prog_array *array,
|
2018-04-10 16:37:32 +00:00
|
|
|
u32 *prog_ids, u32 request_cnt,
|
|
|
|
u32 *prog_cnt);
|
2019-05-28 21:14:41 +00:00
|
|
|
int bpf_prog_array_copy(struct bpf_prog_array *old_array,
|
2017-10-24 06:53:08 +00:00
|
|
|
struct bpf_prog *exclude_prog,
|
|
|
|
struct bpf_prog *include_prog,
|
bpf: Allow to specify user-provided bpf_cookie for BPF perf links
Add ability for users to specify custom u64 value (bpf_cookie) when creating
BPF link for perf_event-backed BPF programs (kprobe/uprobe, perf_event,
tracepoints).
This is useful for cases when the same BPF program is used for attaching and
processing invocation of different tracepoints/kprobes/uprobes in a generic
fashion, but such that each invocation is distinguished from each other (e.g.,
BPF program can look up additional information associated with a specific
kernel function without having to rely on function IP lookups). This enables
new use cases to be implemented simply and efficiently that previously were
possible only through code generation (and thus multiple instances of almost
identical BPF program) or compilation at runtime (BCC-style) on target hosts
(even more expensive resource-wise). For uprobes it is not even possible in
some cases to know function IP before hand (e.g., when attaching to shared
library without PID filtering, in which case base load address is not known
for a library).
This is done by storing u64 bpf_cookie in struct bpf_prog_array_item,
corresponding to each attached and run BPF program. Given cgroup BPF programs
already use two 8-byte pointers for their needs and cgroup BPF programs don't
have (yet?) support for bpf_cookie, reuse that space through union of
cgroup_storage and new bpf_cookie field.
Make it available to kprobe/tracepoint BPF programs through bpf_trace_run_ctx.
This is set by BPF_PROG_RUN_ARRAY, used by kprobe/uprobe/tracepoint BPF
program execution code, which luckily is now also split from
BPF_PROG_RUN_ARRAY_CG. This run context will be utilized by a new BPF helper
giving access to this user-provided cookie value from inside a BPF program.
Generic perf_event BPF programs will access this value from perf_event itself
through passed in BPF program context.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20210815070609.987780-6-andrii@kernel.org
2021-08-15 07:05:58 +00:00
|
|
|
u64 bpf_cookie,
|
2017-10-24 06:53:08 +00:00
|
|
|
struct bpf_prog_array **new_array);
|
|
|
|
|
bpf: Add ambient BPF runtime context stored in current
b910eaaaa4b8 ("bpf: Fix NULL pointer dereference in bpf_get_local_storage()
helper") fixed the problem with cgroup-local storage use in BPF by
pre-allocating per-CPU array of 8 cgroup storage pointers to accommodate
possible BPF program preemptions and nested executions.
While this seems to work good in practice, it introduces new and unnecessary
failure mode in which not all BPF programs might be executed if we fail to
find an unused slot for cgroup storage, however unlikely it is. It might also
not be so unlikely when/if we allow sleepable cgroup BPF programs in the
future.
Further, the way that cgroup storage is implemented as ambiently-available
property during entire BPF program execution is a convenient way to pass extra
information to BPF program and helpers without requiring user code to pass
around extra arguments explicitly. So it would be good to have a generic
solution that can allow implementing this without arbitrary restrictions.
Ideally, such solution would work for both preemptable and sleepable BPF
programs in exactly the same way.
This patch introduces such solution, bpf_run_ctx. It adds one pointer field
(bpf_ctx) to task_struct. This field is maintained by BPF_PROG_RUN family of
macros in such a way that it always stays valid throughout BPF program
execution. BPF program preemption is handled by remembering previous
current->bpf_ctx value locally while executing nested BPF program and
restoring old value after nested BPF program finishes. This is handled by two
helper functions, bpf_set_run_ctx() and bpf_reset_run_ctx(), which are
supposed to be used before and after BPF program runs, respectively.
Restoring old value of the pointer handles preemption, while bpf_run_ctx
pointer being a property of current task_struct naturally solves this problem
for sleepable BPF programs by "following" BPF program execution as it is
scheduled in and out of CPU. It would even allow CPU migration of BPF
programs, even though it's not currently allowed by BPF infra.
This patch cleans up cgroup local storage handling as a first application. The
design itself is generic, though, with bpf_run_ctx being an empty struct that
is supposed to be embedded into a specific struct for a given BPF program type
(bpf_cg_run_ctx in this case). Follow up patches are planned that will expand
this mechanism for other uses within tracing BPF programs.
To verify that this change doesn't revert the fix to the original cgroup
storage issue, I ran the same repro as in the original report ([0]) and didn't
get any problems. Replacing bpf_reset_run_ctx(old_run_ctx) with
bpf_reset_run_ctx(NULL) triggers the issue pretty quickly (so repro does work).
[0] https://lore.kernel.org/bpf/YEEvBUiJl2pJkxTd@krava/
Fixes: b910eaaaa4b8 ("bpf: Fix NULL pointer dereference in bpf_get_local_storage() helper")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210712230615.3525979-1-andrii@kernel.org
2021-07-12 23:06:15 +00:00
|
|
|
struct bpf_run_ctx {};
|
|
|
|
|
|
|
|
struct bpf_cg_run_ctx {
|
|
|
|
struct bpf_run_ctx run_ctx;
|
2021-08-15 07:05:55 +00:00
|
|
|
const struct bpf_prog_array_item *prog_item;
|
2021-12-16 02:04:26 +00:00
|
|
|
int retval;
|
bpf: Add ambient BPF runtime context stored in current
b910eaaaa4b8 ("bpf: Fix NULL pointer dereference in bpf_get_local_storage()
helper") fixed the problem with cgroup-local storage use in BPF by
pre-allocating per-CPU array of 8 cgroup storage pointers to accommodate
possible BPF program preemptions and nested executions.
While this seems to work good in practice, it introduces new and unnecessary
failure mode in which not all BPF programs might be executed if we fail to
find an unused slot for cgroup storage, however unlikely it is. It might also
not be so unlikely when/if we allow sleepable cgroup BPF programs in the
future.
Further, the way that cgroup storage is implemented as ambiently-available
property during entire BPF program execution is a convenient way to pass extra
information to BPF program and helpers without requiring user code to pass
around extra arguments explicitly. So it would be good to have a generic
solution that can allow implementing this without arbitrary restrictions.
Ideally, such solution would work for both preemptable and sleepable BPF
programs in exactly the same way.
This patch introduces such solution, bpf_run_ctx. It adds one pointer field
(bpf_ctx) to task_struct. This field is maintained by BPF_PROG_RUN family of
macros in such a way that it always stays valid throughout BPF program
execution. BPF program preemption is handled by remembering previous
current->bpf_ctx value locally while executing nested BPF program and
restoring old value after nested BPF program finishes. This is handled by two
helper functions, bpf_set_run_ctx() and bpf_reset_run_ctx(), which are
supposed to be used before and after BPF program runs, respectively.
Restoring old value of the pointer handles preemption, while bpf_run_ctx
pointer being a property of current task_struct naturally solves this problem
for sleepable BPF programs by "following" BPF program execution as it is
scheduled in and out of CPU. It would even allow CPU migration of BPF
programs, even though it's not currently allowed by BPF infra.
This patch cleans up cgroup local storage handling as a first application. The
design itself is generic, though, with bpf_run_ctx being an empty struct that
is supposed to be embedded into a specific struct for a given BPF program type
(bpf_cg_run_ctx in this case). Follow up patches are planned that will expand
this mechanism for other uses within tracing BPF programs.
To verify that this change doesn't revert the fix to the original cgroup
storage issue, I ran the same repro as in the original report ([0]) and didn't
get any problems. Replacing bpf_reset_run_ctx(old_run_ctx) with
bpf_reset_run_ctx(NULL) triggers the issue pretty quickly (so repro does work).
[0] https://lore.kernel.org/bpf/YEEvBUiJl2pJkxTd@krava/
Fixes: b910eaaaa4b8 ("bpf: Fix NULL pointer dereference in bpf_get_local_storage() helper")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210712230615.3525979-1-andrii@kernel.org
2021-07-12 23:06:15 +00:00
|
|
|
};
|
|
|
|
|
bpf: Allow to specify user-provided bpf_cookie for BPF perf links
Add ability for users to specify custom u64 value (bpf_cookie) when creating
BPF link for perf_event-backed BPF programs (kprobe/uprobe, perf_event,
tracepoints).
This is useful for cases when the same BPF program is used for attaching and
processing invocation of different tracepoints/kprobes/uprobes in a generic
fashion, but such that each invocation is distinguished from each other (e.g.,
BPF program can look up additional information associated with a specific
kernel function without having to rely on function IP lookups). This enables
new use cases to be implemented simply and efficiently that previously were
possible only through code generation (and thus multiple instances of almost
identical BPF program) or compilation at runtime (BCC-style) on target hosts
(even more expensive resource-wise). For uprobes it is not even possible in
some cases to know function IP before hand (e.g., when attaching to shared
library without PID filtering, in which case base load address is not known
for a library).
This is done by storing u64 bpf_cookie in struct bpf_prog_array_item,
corresponding to each attached and run BPF program. Given cgroup BPF programs
already use two 8-byte pointers for their needs and cgroup BPF programs don't
have (yet?) support for bpf_cookie, reuse that space through union of
cgroup_storage and new bpf_cookie field.
Make it available to kprobe/tracepoint BPF programs through bpf_trace_run_ctx.
This is set by BPF_PROG_RUN_ARRAY, used by kprobe/uprobe/tracepoint BPF
program execution code, which luckily is now also split from
BPF_PROG_RUN_ARRAY_CG. This run context will be utilized by a new BPF helper
giving access to this user-provided cookie value from inside a BPF program.
Generic perf_event BPF programs will access this value from perf_event itself
through passed in BPF program context.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20210815070609.987780-6-andrii@kernel.org
2021-08-15 07:05:58 +00:00
|
|
|
struct bpf_trace_run_ctx {
|
|
|
|
struct bpf_run_ctx run_ctx;
|
|
|
|
u64 bpf_cookie;
|
|
|
|
};
|
|
|
|
|
2022-05-10 20:59:20 +00:00
|
|
|
struct bpf_tramp_run_ctx {
|
|
|
|
struct bpf_run_ctx run_ctx;
|
|
|
|
u64 bpf_cookie;
|
|
|
|
struct bpf_run_ctx *saved_run_ctx;
|
|
|
|
};
|
|
|
|
|
2021-08-15 07:05:55 +00:00
|
|
|
static inline struct bpf_run_ctx *bpf_set_run_ctx(struct bpf_run_ctx *new_ctx)
|
|
|
|
{
|
|
|
|
struct bpf_run_ctx *old_ctx = NULL;
|
|
|
|
|
|
|
|
#ifdef CONFIG_BPF_SYSCALL
|
|
|
|
old_ctx = current->bpf_ctx;
|
|
|
|
current->bpf_ctx = new_ctx;
|
|
|
|
#endif
|
|
|
|
return old_ctx;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline void bpf_reset_run_ctx(struct bpf_run_ctx *old_ctx)
|
|
|
|
{
|
|
|
|
#ifdef CONFIG_BPF_SYSCALL
|
|
|
|
current->bpf_ctx = old_ctx;
|
|
|
|
#endif
|
|
|
|
}
|
|
|
|
|
2021-01-27 19:31:39 +00:00
|
|
|
/* BPF program asks to bypass CAP_NET_BIND_SERVICE in bind. */
|
|
|
|
#define BPF_RET_BIND_NO_CAP_NET_BIND_SERVICE (1 << 0)
|
|
|
|
/* BPF program asks to set CN on the packet. */
|
|
|
|
#define BPF_RET_SET_CN (1 << 0)
|
|
|
|
|
2021-08-15 07:05:55 +00:00
|
|
|
typedef u32 (*bpf_prog_run_fn)(const struct bpf_prog *prog, const void *ctx);
|
|
|
|
|
|
|
|
static __always_inline u32
|
2022-04-14 16:12:33 +00:00
|
|
|
bpf_prog_run_array(const struct bpf_prog_array *array,
|
2021-08-15 07:05:55 +00:00
|
|
|
const void *ctx, bpf_prog_run_fn run_prog)
|
|
|
|
{
|
|
|
|
const struct bpf_prog_array_item *item;
|
|
|
|
const struct bpf_prog *prog;
|
bpf: Allow to specify user-provided bpf_cookie for BPF perf links
Add ability for users to specify custom u64 value (bpf_cookie) when creating
BPF link for perf_event-backed BPF programs (kprobe/uprobe, perf_event,
tracepoints).
This is useful for cases when the same BPF program is used for attaching and
processing invocation of different tracepoints/kprobes/uprobes in a generic
fashion, but such that each invocation is distinguished from each other (e.g.,
BPF program can look up additional information associated with a specific
kernel function without having to rely on function IP lookups). This enables
new use cases to be implemented simply and efficiently that previously were
possible only through code generation (and thus multiple instances of almost
identical BPF program) or compilation at runtime (BCC-style) on target hosts
(even more expensive resource-wise). For uprobes it is not even possible in
some cases to know function IP before hand (e.g., when attaching to shared
library without PID filtering, in which case base load address is not known
for a library).
This is done by storing u64 bpf_cookie in struct bpf_prog_array_item,
corresponding to each attached and run BPF program. Given cgroup BPF programs
already use two 8-byte pointers for their needs and cgroup BPF programs don't
have (yet?) support for bpf_cookie, reuse that space through union of
cgroup_storage and new bpf_cookie field.
Make it available to kprobe/tracepoint BPF programs through bpf_trace_run_ctx.
This is set by BPF_PROG_RUN_ARRAY, used by kprobe/uprobe/tracepoint BPF
program execution code, which luckily is now also split from
BPF_PROG_RUN_ARRAY_CG. This run context will be utilized by a new BPF helper
giving access to this user-provided cookie value from inside a BPF program.
Generic perf_event BPF programs will access this value from perf_event itself
through passed in BPF program context.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20210815070609.987780-6-andrii@kernel.org
2021-08-15 07:05:58 +00:00
|
|
|
struct bpf_run_ctx *old_run_ctx;
|
|
|
|
struct bpf_trace_run_ctx run_ctx;
|
2021-08-15 07:05:55 +00:00
|
|
|
u32 ret = 1;
|
|
|
|
|
2022-04-14 16:12:33 +00:00
|
|
|
RCU_LOCKDEP_WARN(!rcu_read_lock_held(), "no rcu lock held");
|
|
|
|
|
2021-08-15 07:05:55 +00:00
|
|
|
if (unlikely(!array))
|
2022-04-14 16:12:33 +00:00
|
|
|
return ret;
|
|
|
|
|
|
|
|
migrate_disable();
|
bpf: Allow to specify user-provided bpf_cookie for BPF perf links
Add ability for users to specify custom u64 value (bpf_cookie) when creating
BPF link for perf_event-backed BPF programs (kprobe/uprobe, perf_event,
tracepoints).
This is useful for cases when the same BPF program is used for attaching and
processing invocation of different tracepoints/kprobes/uprobes in a generic
fashion, but such that each invocation is distinguished from each other (e.g.,
BPF program can look up additional information associated with a specific
kernel function without having to rely on function IP lookups). This enables
new use cases to be implemented simply and efficiently that previously were
possible only through code generation (and thus multiple instances of almost
identical BPF program) or compilation at runtime (BCC-style) on target hosts
(even more expensive resource-wise). For uprobes it is not even possible in
some cases to know function IP before hand (e.g., when attaching to shared
library without PID filtering, in which case base load address is not known
for a library).
This is done by storing u64 bpf_cookie in struct bpf_prog_array_item,
corresponding to each attached and run BPF program. Given cgroup BPF programs
already use two 8-byte pointers for their needs and cgroup BPF programs don't
have (yet?) support for bpf_cookie, reuse that space through union of
cgroup_storage and new bpf_cookie field.
Make it available to kprobe/tracepoint BPF programs through bpf_trace_run_ctx.
This is set by BPF_PROG_RUN_ARRAY, used by kprobe/uprobe/tracepoint BPF
program execution code, which luckily is now also split from
BPF_PROG_RUN_ARRAY_CG. This run context will be utilized by a new BPF helper
giving access to this user-provided cookie value from inside a BPF program.
Generic perf_event BPF programs will access this value from perf_event itself
through passed in BPF program context.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20210815070609.987780-6-andrii@kernel.org
2021-08-15 07:05:58 +00:00
|
|
|
old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
|
2021-08-15 07:05:55 +00:00
|
|
|
item = &array->items[0];
|
|
|
|
while ((prog = READ_ONCE(item->prog))) {
|
bpf: Allow to specify user-provided bpf_cookie for BPF perf links
Add ability for users to specify custom u64 value (bpf_cookie) when creating
BPF link for perf_event-backed BPF programs (kprobe/uprobe, perf_event,
tracepoints).
This is useful for cases when the same BPF program is used for attaching and
processing invocation of different tracepoints/kprobes/uprobes in a generic
fashion, but such that each invocation is distinguished from each other (e.g.,
BPF program can look up additional information associated with a specific
kernel function without having to rely on function IP lookups). This enables
new use cases to be implemented simply and efficiently that previously were
possible only through code generation (and thus multiple instances of almost
identical BPF program) or compilation at runtime (BCC-style) on target hosts
(even more expensive resource-wise). For uprobes it is not even possible in
some cases to know function IP before hand (e.g., when attaching to shared
library without PID filtering, in which case base load address is not known
for a library).
This is done by storing u64 bpf_cookie in struct bpf_prog_array_item,
corresponding to each attached and run BPF program. Given cgroup BPF programs
already use two 8-byte pointers for their needs and cgroup BPF programs don't
have (yet?) support for bpf_cookie, reuse that space through union of
cgroup_storage and new bpf_cookie field.
Make it available to kprobe/tracepoint BPF programs through bpf_trace_run_ctx.
This is set by BPF_PROG_RUN_ARRAY, used by kprobe/uprobe/tracepoint BPF
program execution code, which luckily is now also split from
BPF_PROG_RUN_ARRAY_CG. This run context will be utilized by a new BPF helper
giving access to this user-provided cookie value from inside a BPF program.
Generic perf_event BPF programs will access this value from perf_event itself
through passed in BPF program context.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20210815070609.987780-6-andrii@kernel.org
2021-08-15 07:05:58 +00:00
|
|
|
run_ctx.bpf_cookie = item->bpf_cookie;
|
2021-08-15 07:05:55 +00:00
|
|
|
ret &= run_prog(prog, ctx);
|
|
|
|
item++;
|
|
|
|
}
|
bpf: Allow to specify user-provided bpf_cookie for BPF perf links
Add ability for users to specify custom u64 value (bpf_cookie) when creating
BPF link for perf_event-backed BPF programs (kprobe/uprobe, perf_event,
tracepoints).
This is useful for cases when the same BPF program is used for attaching and
processing invocation of different tracepoints/kprobes/uprobes in a generic
fashion, but such that each invocation is distinguished from each other (e.g.,
BPF program can look up additional information associated with a specific
kernel function without having to rely on function IP lookups). This enables
new use cases to be implemented simply and efficiently that previously were
possible only through code generation (and thus multiple instances of almost
identical BPF program) or compilation at runtime (BCC-style) on target hosts
(even more expensive resource-wise). For uprobes it is not even possible in
some cases to know function IP before hand (e.g., when attaching to shared
library without PID filtering, in which case base load address is not known
for a library).
This is done by storing u64 bpf_cookie in struct bpf_prog_array_item,
corresponding to each attached and run BPF program. Given cgroup BPF programs
already use two 8-byte pointers for their needs and cgroup BPF programs don't
have (yet?) support for bpf_cookie, reuse that space through union of
cgroup_storage and new bpf_cookie field.
Make it available to kprobe/tracepoint BPF programs through bpf_trace_run_ctx.
This is set by BPF_PROG_RUN_ARRAY, used by kprobe/uprobe/tracepoint BPF
program execution code, which luckily is now also split from
BPF_PROG_RUN_ARRAY_CG. This run context will be utilized by a new BPF helper
giving access to this user-provided cookie value from inside a BPF program.
Generic perf_event BPF programs will access this value from perf_event itself
through passed in BPF program context.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20210815070609.987780-6-andrii@kernel.org
2021-08-15 07:05:58 +00:00
|
|
|
bpf_reset_run_ctx(old_run_ctx);
|
2021-08-15 07:05:55 +00:00
|
|
|
migrate_enable();
|
|
|
|
return ret;
|
|
|
|
}
|
2017-10-03 05:50:21 +00:00
|
|
|
|
bpf: implement sleepable uprobes by chaining gps
uprobes work by raising a trap, setting a task flag from within the
interrupt handler, and processing the actual work for the uprobe on the
way back to userspace. As a result, uprobe handlers already execute in a
might_fault/_sleep context. The primary obstacle to sleepable bpf uprobe
programs is therefore on the bpf side.
Namely, the bpf_prog_array attached to the uprobe is protected by normal
rcu. In order for uprobe bpf programs to become sleepable, it has to be
protected by the tasks_trace rcu flavor instead (and kfree() called after
a corresponding grace period).
Therefore, the free path for bpf_prog_array now chains a tasks_trace and
normal grace periods one after the other.
Users who iterate under tasks_trace read section would
be safe, as would users who iterate under normal read sections (from
non-sleepable locations).
The downside is that the tasks_trace latency affects all perf_event-attached
bpf programs (and not just uprobe ones). This is deemed safe given the
possible attach rates for kprobe/uprobe/tp programs.
Separately, non-sleepable programs need access to dynamically sized
rcu-protected maps, so bpf_run_prog_array_sleepables now conditionally takes
an rcu read section, in addition to the overarching tasks_trace section.
Signed-off-by: Delyan Kratunov <delyank@fb.com>
Link: https://lore.kernel.org/r/ce844d62a2fd0443b08c5ab02e95bc7149f9aeb1.1655248076.git.delyank@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-06-14 23:10:46 +00:00
|
|
|
/* Notes on RCU design for bpf_prog_arrays containing sleepable programs:
|
|
|
|
*
|
|
|
|
* We use the tasks_trace rcu flavor read section to protect the bpf_prog_array
|
|
|
|
* overall. As a result, we must use the bpf_prog_array_free_sleepable
|
|
|
|
* in order to use the tasks_trace rcu grace period.
|
|
|
|
*
|
|
|
|
* When a non-sleepable program is inside the array, we take the rcu read
|
|
|
|
* section and disable preemption for that program alone, so it can access
|
|
|
|
* rcu-protected dynamically sized maps.
|
|
|
|
*/
|
|
|
|
static __always_inline u32
|
|
|
|
bpf_prog_run_array_sleepable(const struct bpf_prog_array __rcu *array_rcu,
|
|
|
|
const void *ctx, bpf_prog_run_fn run_prog)
|
|
|
|
{
|
|
|
|
const struct bpf_prog_array_item *item;
|
|
|
|
const struct bpf_prog *prog;
|
|
|
|
const struct bpf_prog_array *array;
|
|
|
|
struct bpf_run_ctx *old_run_ctx;
|
|
|
|
struct bpf_trace_run_ctx run_ctx;
|
|
|
|
u32 ret = 1;
|
|
|
|
|
|
|
|
might_fault();
|
|
|
|
|
|
|
|
rcu_read_lock_trace();
|
|
|
|
migrate_disable();
|
|
|
|
|
|
|
|
array = rcu_dereference_check(array_rcu, rcu_read_lock_trace_held());
|
|
|
|
if (unlikely(!array))
|
|
|
|
goto out;
|
|
|
|
old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
|
|
|
|
item = &array->items[0];
|
|
|
|
while ((prog = READ_ONCE(item->prog))) {
|
|
|
|
if (!prog->aux->sleepable)
|
|
|
|
rcu_read_lock();
|
|
|
|
|
|
|
|
run_ctx.bpf_cookie = item->bpf_cookie;
|
|
|
|
ret &= run_prog(prog, ctx);
|
|
|
|
item++;
|
|
|
|
|
|
|
|
if (!prog->aux->sleepable)
|
|
|
|
rcu_read_unlock();
|
|
|
|
}
|
|
|
|
bpf_reset_run_ctx(old_run_ctx);
|
|
|
|
out:
|
|
|
|
migrate_enable();
|
|
|
|
rcu_read_unlock_trace();
|
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
|
2014-12-01 23:06:35 +00:00
|
|
|
#ifdef CONFIG_BPF_SYSCALL
|
2016-03-08 05:57:13 +00:00
|
|
|
DECLARE_PER_CPU(int, bpf_prog_active);
|
bpf: Sharing bpf runtime stats with BPF_ENABLE_STATS
Currently, sysctl kernel.bpf_stats_enabled controls BPF runtime stats.
Typical userspace tools use kernel.bpf_stats_enabled as follows:
1. Enable kernel.bpf_stats_enabled;
2. Check program run_time_ns;
3. Sleep for the monitoring period;
4. Check program run_time_ns again, calculate the difference;
5. Disable kernel.bpf_stats_enabled.
The problem with this approach is that only one userspace tool can toggle
this sysctl. If multiple tools toggle the sysctl at the same time, the
measurement may be inaccurate.
To fix this problem while keep backward compatibility, introduce a new
bpf command BPF_ENABLE_STATS. On success, this command enables stats and
returns a valid fd. BPF_ENABLE_STATS takes argument "type". Currently,
only one type, BPF_STATS_RUN_TIME, is supported. We can extend the
command to support other types of stats in the future.
With BPF_ENABLE_STATS, user space tool would have the following flow:
1. Get a fd with BPF_ENABLE_STATS, and make sure it is valid;
2. Check program run_time_ns;
3. Sleep for the monitoring period;
4. Check program run_time_ns again, calculate the difference;
5. Close the fd.
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200430071506.1408910-2-songliubraving@fb.com
2020-04-30 07:15:04 +00:00
|
|
|
extern struct mutex bpf_stats_enabled_mutex;
|
2016-03-08 05:57:13 +00:00
|
|
|
|
2020-02-24 14:01:47 +00:00
|
|
|
/*
|
|
|
|
* Block execution of BPF programs attached to instrumentation (perf,
|
|
|
|
* kprobes, tracepoints) to prevent deadlocks on map operations as any of
|
|
|
|
* these events can happen inside a region which holds a map bucket lock
|
|
|
|
* and can deadlock on it.
|
|
|
|
*/
|
|
|
|
static inline void bpf_disable_instrumentation(void)
|
|
|
|
{
|
|
|
|
migrate_disable();
|
2021-11-27 16:32:00 +00:00
|
|
|
this_cpu_inc(bpf_prog_active);
|
2020-02-24 14:01:47 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
static inline void bpf_enable_instrumentation(void)
|
|
|
|
{
|
2021-11-27 16:32:00 +00:00
|
|
|
this_cpu_dec(bpf_prog_active);
|
2020-02-24 14:01:47 +00:00
|
|
|
migrate_enable();
|
|
|
|
}
|
|
|
|
|
2017-10-18 20:00:26 +00:00
|
|
|
extern const struct file_operations bpf_map_fops;
|
|
|
|
extern const struct file_operations bpf_prog_fops;
|
2020-05-09 17:59:06 +00:00
|
|
|
extern const struct file_operations bpf_iter_fops;
|
2017-10-18 20:00:26 +00:00
|
|
|
|
2019-11-14 18:57:15 +00:00
|
|
|
#define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \
|
2017-10-16 23:40:53 +00:00
|
|
|
extern const struct bpf_prog_ops _name ## _prog_ops; \
|
|
|
|
extern const struct bpf_verifier_ops _name ## _verifier_ops;
|
2017-04-11 13:34:58 +00:00
|
|
|
#define BPF_MAP_TYPE(_id, _ops) \
|
|
|
|
extern const struct bpf_map_ops _ops;
|
2020-04-29 00:16:08 +00:00
|
|
|
#define BPF_LINK_TYPE(_id, _name)
|
2017-04-11 13:34:57 +00:00
|
|
|
#include <linux/bpf_types.h>
|
|
|
|
#undef BPF_PROG_TYPE
|
2017-04-11 13:34:58 +00:00
|
|
|
#undef BPF_MAP_TYPE
|
2020-04-29 00:16:08 +00:00
|
|
|
#undef BPF_LINK_TYPE
|
2015-03-01 11:31:44 +00:00
|
|
|
|
2017-11-03 20:56:17 +00:00
|
|
|
extern const struct bpf_prog_ops bpf_offload_prog_ops;
|
2017-10-16 23:40:55 +00:00
|
|
|
extern const struct bpf_verifier_ops tc_cls_act_analyzer_ops;
|
|
|
|
extern const struct bpf_verifier_ops xdp_analyzer_ops;
|
|
|
|
|
2015-03-01 11:31:44 +00:00
|
|
|
struct bpf_prog *bpf_prog_get(u32 ufd);
|
2017-11-03 20:56:20 +00:00
|
|
|
struct bpf_prog *bpf_prog_get_type_dev(u32 ufd, enum bpf_prog_type type,
|
2017-11-20 23:21:54 +00:00
|
|
|
bool attach_drv);
|
2019-11-17 17:28:03 +00:00
|
|
|
void bpf_prog_add(struct bpf_prog *prog, int i);
|
2016-11-09 21:02:34 +00:00
|
|
|
void bpf_prog_sub(struct bpf_prog *prog, int i);
|
2019-11-17 17:28:03 +00:00
|
|
|
void bpf_prog_inc(struct bpf_prog *prog);
|
2017-08-16 05:32:22 +00:00
|
|
|
struct bpf_prog * __must_check bpf_prog_inc_not_zero(struct bpf_prog *prog);
|
2015-03-02 14:21:55 +00:00
|
|
|
void bpf_prog_put(struct bpf_prog *prog);
|
|
|
|
|
2017-12-28 02:39:07 +00:00
|
|
|
void bpf_prog_free_id(struct bpf_prog *prog, bool do_idr_lock);
|
2018-01-12 04:29:09 +00:00
|
|
|
void bpf_map_free_id(struct bpf_map *map, bool do_idr_lock);
|
2017-12-28 02:39:07 +00:00
|
|
|
|
bpf: Allow storing unreferenced kptr in map
This commit introduces a new pointer type 'kptr' which can be embedded
in a map value to hold a PTR_TO_BTF_ID stored by a BPF program during
its invocation. When storing such a kptr, BPF program's PTR_TO_BTF_ID
register must have the same type as in the map value's BTF, and loading
a kptr marks the destination register as PTR_TO_BTF_ID with the correct
kernel BTF and BTF ID.
Such kptr are unreferenced, i.e. by the time another invocation of the
BPF program loads this pointer, the object which the pointer points to
may not longer exist. Since PTR_TO_BTF_ID loads (using BPF_LDX) are
patched to PROBE_MEM loads by the verifier, it would safe to allow user
to still access such invalid pointer, but passing such pointers into
BPF helpers and kfuncs should not be permitted. A future patch in this
series will close this gap.
The flexibility offered by allowing programs to dereference such invalid
pointers while being safe at runtime frees the verifier from doing
complex lifetime tracking. As long as the user may ensure that the
object remains valid, it can ensure data read by it from the kernel
object is valid.
The user indicates that a certain pointer must be treated as kptr
capable of accepting stores of PTR_TO_BTF_ID of a certain type, by using
a BTF type tag 'kptr' on the pointed to type of the pointer. Then, this
information is recorded in the object BTF which will be passed into the
kernel by way of map's BTF information. The name and kind from the map
value BTF is used to look up the in-kernel type, and the actual BTF and
BTF ID is recorded in the map struct in a new kptr_off_tab member. For
now, only storing pointers to structs is permitted.
An example of this specification is shown below:
#define __kptr __attribute__((btf_type_tag("kptr")))
struct map_value {
...
struct task_struct __kptr *task;
...
};
Then, in a BPF program, user may store PTR_TO_BTF_ID with the type
task_struct into the map, and then load it later.
Note that the destination register is marked PTR_TO_BTF_ID_OR_NULL, as
the verifier cannot know whether the value is NULL or not statically, it
must treat all potential loads at that map value offset as loading a
possibly NULL pointer.
Only BPF_LDX, BPF_STX, and BPF_ST (with insn->imm = 0 to denote NULL)
are allowed instructions that can access such a pointer. On BPF_LDX, the
destination register is updated to be a PTR_TO_BTF_ID, and on BPF_STX,
it is checked whether the source register type is a PTR_TO_BTF_ID with
same BTF type as specified in the map BTF. The access size must always
be BPF_DW.
For the map in map support, the kptr_off_tab for outer map is copied
from the inner map's kptr_off_tab. It was chosen to do a deep copy
instead of introducing a refcount to kptr_off_tab, because the copy only
needs to be done when paramterizing using inner_map_fd in the map in map
case, hence would be unnecessary for all other users.
It is not permitted to use MAP_FREEZE command and mmap for BPF map
having kptrs, similar to the bpf_timer case. A kptr also requires that
BPF program has both read and write access to the map (hence both
BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG are disallowed).
Note that check_map_access must be called from both
check_helper_mem_access and for the BPF instructions, hence the kptr
check must distinguish between ACCESS_DIRECT and ACCESS_HELPER, and
reject ACCESS_HELPER cases. We rename stack_access_src to bpf_access_src
and reuse it for this purpose.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-2-memxor@gmail.com
2022-04-24 21:48:49 +00:00
|
|
|
struct bpf_map_value_off_desc *bpf_map_kptr_off_contains(struct bpf_map *map, u32 offset);
|
|
|
|
void bpf_map_free_kptr_off_tab(struct bpf_map *map);
|
|
|
|
struct bpf_map_value_off *bpf_map_copy_kptr_off_tab(const struct bpf_map *map);
|
|
|
|
bool bpf_map_equal_kptr_off_tab(const struct bpf_map *map_a, const struct bpf_map *map_b);
|
bpf: Wire up freeing of referenced kptr
A destructor kfunc can be defined as void func(type *), where type may
be void or any other pointer type as per convenience.
In this patch, we ensure that the type is sane and capture the function
pointer into off_desc of ptr_off_tab for the specific pointer offset,
with the invariant that the dtor pointer is always set when 'kptr_ref'
tag is applied to the pointer's pointee type, which is indicated by the
flag BPF_MAP_VALUE_OFF_F_REF.
Note that only BTF IDs whose destructor kfunc is registered, thus become
the allowed BTF IDs for embedding as referenced kptr. Hence it serves
the purpose of finding dtor kfunc BTF ID, as well acting as a check
against the whitelist of allowed BTF IDs for this purpose.
Finally, wire up the actual freeing of the referenced pointer if any at
all available offsets, so that no references are leaked after the BPF
map goes away and the BPF program previously moved the ownership a
referenced pointer into it.
The behavior is similar to BPF timers, where bpf_map_{update,delete}_elem
will free any existing referenced kptr. The same case is with LRU map's
bpf_lru_push_free/htab_lru_push_free functions, which are extended to
reset unreferenced and free referenced kptr.
Note that unlike BPF timers, kptr is not reset or freed when map uref
drops to zero.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-8-memxor@gmail.com
2022-04-24 21:48:55 +00:00
|
|
|
void bpf_map_free_kptrs(struct bpf_map *map, void *map_value);
|
bpf: Allow storing unreferenced kptr in map
This commit introduces a new pointer type 'kptr' which can be embedded
in a map value to hold a PTR_TO_BTF_ID stored by a BPF program during
its invocation. When storing such a kptr, BPF program's PTR_TO_BTF_ID
register must have the same type as in the map value's BTF, and loading
a kptr marks the destination register as PTR_TO_BTF_ID with the correct
kernel BTF and BTF ID.
Such kptr are unreferenced, i.e. by the time another invocation of the
BPF program loads this pointer, the object which the pointer points to
may not longer exist. Since PTR_TO_BTF_ID loads (using BPF_LDX) are
patched to PROBE_MEM loads by the verifier, it would safe to allow user
to still access such invalid pointer, but passing such pointers into
BPF helpers and kfuncs should not be permitted. A future patch in this
series will close this gap.
The flexibility offered by allowing programs to dereference such invalid
pointers while being safe at runtime frees the verifier from doing
complex lifetime tracking. As long as the user may ensure that the
object remains valid, it can ensure data read by it from the kernel
object is valid.
The user indicates that a certain pointer must be treated as kptr
capable of accepting stores of PTR_TO_BTF_ID of a certain type, by using
a BTF type tag 'kptr' on the pointed to type of the pointer. Then, this
information is recorded in the object BTF which will be passed into the
kernel by way of map's BTF information. The name and kind from the map
value BTF is used to look up the in-kernel type, and the actual BTF and
BTF ID is recorded in the map struct in a new kptr_off_tab member. For
now, only storing pointers to structs is permitted.
An example of this specification is shown below:
#define __kptr __attribute__((btf_type_tag("kptr")))
struct map_value {
...
struct task_struct __kptr *task;
...
};
Then, in a BPF program, user may store PTR_TO_BTF_ID with the type
task_struct into the map, and then load it later.
Note that the destination register is marked PTR_TO_BTF_ID_OR_NULL, as
the verifier cannot know whether the value is NULL or not statically, it
must treat all potential loads at that map value offset as loading a
possibly NULL pointer.
Only BPF_LDX, BPF_STX, and BPF_ST (with insn->imm = 0 to denote NULL)
are allowed instructions that can access such a pointer. On BPF_LDX, the
destination register is updated to be a PTR_TO_BTF_ID, and on BPF_STX,
it is checked whether the source register type is a PTR_TO_BTF_ID with
same BTF type as specified in the map BTF. The access size must always
be BPF_DW.
For the map in map support, the kptr_off_tab for outer map is copied
from the inner map's kptr_off_tab. It was chosen to do a deep copy
instead of introducing a refcount to kptr_off_tab, because the copy only
needs to be done when paramterizing using inner_map_fd in the map in map
case, hence would be unnecessary for all other users.
It is not permitted to use MAP_FREEZE command and mmap for BPF map
having kptrs, similar to the bpf_timer case. A kptr also requires that
BPF program has both read and write access to the map (hence both
BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG are disallowed).
Note that check_map_access must be called from both
check_helper_mem_access and for the BPF instructions, hence the kptr
check must distinguish between ACCESS_DIRECT and ACCESS_HELPER, and
reject ACCESS_HELPER cases. We rename stack_access_src to bpf_access_src
and reuse it for this purpose.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-2-memxor@gmail.com
2022-04-24 21:48:49 +00:00
|
|
|
|
2020-02-25 23:04:21 +00:00
|
|
|
struct bpf_map *bpf_map_get(u32 ufd);
|
bpf: fix clearing on persistent program array maps
Currently, when having map file descriptors pointing to program arrays,
there's still the issue that we unconditionally flush program array
contents via bpf_fd_array_map_clear() in bpf_map_release(). This happens
when such a file descriptor is released and is independent of the map's
refcount.
Having this flush independent of the refcount is for a reason: there
can be arbitrary complex dependency chains among tail calls, also circular
ones (direct or indirect, nesting limit determined during runtime), and
we need to make sure that the map drops all references to eBPF programs
it holds, so that the map's refcount can eventually drop to zero and
initiate its freeing. Btw, a walk of the whole dependency graph would
not be possible for various reasons, one being complexity and another
one inconsistency, i.e. new programs can be added to parts of the graph
at any time, so there's no guaranteed consistent state for the time of
such a walk.
Now, the program array pinning itself works, but the issue is that each
derived file descriptor on close would nevertheless call unconditionally
into bpf_fd_array_map_clear(). Instead, keep track of users and postpone
this flush until the last reference to a user is dropped. As this only
concerns a subset of references (f.e. a prog array could hold a program
that itself has reference on the prog array holding it, etc), we need to
track them separately.
Short analysis on the refcounting: on map creation time usercnt will be
one, so there's no change in behaviour for bpf_map_release(), if unpinned.
If we already fail in map_create(), we are immediately freed, and no
file descriptor has been made public yet. In bpf_obj_pin_user(), we need
to probe for a possible map in bpf_fd_probe_obj() already with a usercnt
reference, so before we drop the reference on the fd with fdput().
Therefore, if actual pinning fails, we need to drop that reference again
in bpf_any_put(), otherwise we keep holding it. When last reference
drops on the inode, the bpf_any_put() in bpf_evict_inode() will take
care of dropping the usercnt again. In the bpf_obj_get_user() case, the
bpf_any_get() will grab a reference on the usercnt, still at a time when
we have the reference on the path. Should we later on fail to grab a new
file descriptor, bpf_any_put() will drop it, otherwise we hold it until
bpf_map_release() time.
Joint work with Alexei.
Fixes: b2197755b263 ("bpf: add support for persistent maps/progs")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-11-24 20:28:15 +00:00
|
|
|
struct bpf_map *bpf_map_get_with_uref(u32 ufd);
|
2015-10-29 13:58:07 +00:00
|
|
|
struct bpf_map *__bpf_map_get(struct fd f);
|
bpf: Switch bpf_map ref counter to atomic64_t so bpf_map_inc() never fails
92117d8443bc ("bpf: fix refcnt overflow") turned refcounting of bpf_map into
potentially failing operation, when refcount reaches BPF_MAX_REFCNT limit
(32k). Due to using 32-bit counter, it's possible in practice to overflow
refcounter and make it wrap around to 0, causing erroneous map free, while
there are still references to it, causing use-after-free problems.
But having a failing refcounting operations are problematic in some cases. One
example is mmap() interface. After establishing initial memory-mapping, user
is allowed to arbitrarily map/remap/unmap parts of mapped memory, arbitrarily
splitting it into multiple non-contiguous regions. All this happening without
any control from the users of mmap subsystem. Rather mmap subsystem sends
notifications to original creator of memory mapping through open/close
callbacks, which are optionally specified during initial memory mapping
creation. These callbacks are used to maintain accurate refcount for bpf_map
(see next patch in this series). The problem is that open() callback is not
supposed to fail, because memory-mapped resource is set up and properly
referenced. This is posing a problem for using memory-mapping with BPF maps.
One solution to this is to maintain separate refcount for just memory-mappings
and do single bpf_map_inc/bpf_map_put when it goes from/to zero, respectively.
There are similar use cases in current work on tcp-bpf, necessitating extra
counter as well. This seems like a rather unfortunate and ugly solution that
doesn't scale well to various new use cases.
Another approach to solve this is to use non-failing refcount_t type, which
uses 32-bit counter internally, but, once reaching overflow state at UINT_MAX,
stays there. This utlimately causes memory leak, but prevents use after free.
But given refcounting is not the most performance-critical operation with BPF
maps (it's not used from running BPF program code), we can also just switch to
64-bit counter that can't overflow in practice, potentially disadvantaging
32-bit platforms a tiny bit. This simplifies semantics and allows above
described scenarios to not worry about failing refcount increment operation.
In terms of struct bpf_map size, we are still good and use the same amount of
space:
BEFORE (3 cache lines, 8 bytes of padding at the end):
struct bpf_map {
const struct bpf_map_ops * ops __attribute__((__aligned__(64))); /* 0 8 */
struct bpf_map * inner_map_meta; /* 8 8 */
void * security; /* 16 8 */
enum bpf_map_type map_type; /* 24 4 */
u32 key_size; /* 28 4 */
u32 value_size; /* 32 4 */
u32 max_entries; /* 36 4 */
u32 map_flags; /* 40 4 */
int spin_lock_off; /* 44 4 */
u32 id; /* 48 4 */
int numa_node; /* 52 4 */
u32 btf_key_type_id; /* 56 4 */
u32 btf_value_type_id; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct btf * btf; /* 64 8 */
struct bpf_map_memory memory; /* 72 16 */
bool unpriv_array; /* 88 1 */
bool frozen; /* 89 1 */
/* XXX 38 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
atomic_t refcnt __attribute__((__aligned__(64))); /* 128 4 */
atomic_t usercnt; /* 132 4 */
struct work_struct work; /* 136 32 */
char name[16]; /* 168 16 */
/* size: 192, cachelines: 3, members: 21 */
/* sum members: 146, holes: 1, sum holes: 38 */
/* padding: 8 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 38 */
} __attribute__((__aligned__(64)));
AFTER (same 3 cache lines, no extra padding now):
struct bpf_map {
const struct bpf_map_ops * ops __attribute__((__aligned__(64))); /* 0 8 */
struct bpf_map * inner_map_meta; /* 8 8 */
void * security; /* 16 8 */
enum bpf_map_type map_type; /* 24 4 */
u32 key_size; /* 28 4 */
u32 value_size; /* 32 4 */
u32 max_entries; /* 36 4 */
u32 map_flags; /* 40 4 */
int spin_lock_off; /* 44 4 */
u32 id; /* 48 4 */
int numa_node; /* 52 4 */
u32 btf_key_type_id; /* 56 4 */
u32 btf_value_type_id; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct btf * btf; /* 64 8 */
struct bpf_map_memory memory; /* 72 16 */
bool unpriv_array; /* 88 1 */
bool frozen; /* 89 1 */
/* XXX 38 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
atomic64_t refcnt __attribute__((__aligned__(64))); /* 128 8 */
atomic64_t usercnt; /* 136 8 */
struct work_struct work; /* 144 32 */
char name[16]; /* 176 16 */
/* size: 192, cachelines: 3, members: 21 */
/* sum members: 154, holes: 1, sum holes: 38 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 38 */
} __attribute__((__aligned__(64)));
This patch, while modifying all users of bpf_map_inc, also cleans up its
interface to match bpf_map_put with separate operations for bpf_map_inc and
bpf_map_inc_with_uref (to match bpf_map_put and bpf_map_put_with_uref,
respectively). Also, given there are no users of bpf_map_inc_not_zero
specifying uref=true, remove uref flag and default to uref=false internally.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191117172806.2195367-2-andriin@fb.com
2019-11-17 17:28:02 +00:00
|
|
|
void bpf_map_inc(struct bpf_map *map);
|
|
|
|
void bpf_map_inc_with_uref(struct bpf_map *map);
|
|
|
|
struct bpf_map * __must_check bpf_map_inc_not_zero(struct bpf_map *map);
|
bpf: fix clearing on persistent program array maps
Currently, when having map file descriptors pointing to program arrays,
there's still the issue that we unconditionally flush program array
contents via bpf_fd_array_map_clear() in bpf_map_release(). This happens
when such a file descriptor is released and is independent of the map's
refcount.
Having this flush independent of the refcount is for a reason: there
can be arbitrary complex dependency chains among tail calls, also circular
ones (direct or indirect, nesting limit determined during runtime), and
we need to make sure that the map drops all references to eBPF programs
it holds, so that the map's refcount can eventually drop to zero and
initiate its freeing. Btw, a walk of the whole dependency graph would
not be possible for various reasons, one being complexity and another
one inconsistency, i.e. new programs can be added to parts of the graph
at any time, so there's no guaranteed consistent state for the time of
such a walk.
Now, the program array pinning itself works, but the issue is that each
derived file descriptor on close would nevertheless call unconditionally
into bpf_fd_array_map_clear(). Instead, keep track of users and postpone
this flush until the last reference to a user is dropped. As this only
concerns a subset of references (f.e. a prog array could hold a program
that itself has reference on the prog array holding it, etc), we need to
track them separately.
Short analysis on the refcounting: on map creation time usercnt will be
one, so there's no change in behaviour for bpf_map_release(), if unpinned.
If we already fail in map_create(), we are immediately freed, and no
file descriptor has been made public yet. In bpf_obj_pin_user(), we need
to probe for a possible map in bpf_fd_probe_obj() already with a usercnt
reference, so before we drop the reference on the fd with fdput().
Therefore, if actual pinning fails, we need to drop that reference again
in bpf_any_put(), otherwise we keep holding it. When last reference
drops on the inode, the bpf_any_put() in bpf_evict_inode() will take
care of dropping the usercnt again. In the bpf_obj_get_user() case, the
bpf_any_get() will grab a reference on the usercnt, still at a time when
we have the reference on the path. Should we later on fail to grab a new
file descriptor, bpf_any_put() will drop it, otherwise we hold it until
bpf_map_release() time.
Joint work with Alexei.
Fixes: b2197755b263 ("bpf: add support for persistent maps/progs")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-11-24 20:28:15 +00:00
|
|
|
void bpf_map_put_with_uref(struct bpf_map *map);
|
2015-03-02 14:21:55 +00:00
|
|
|
void bpf_map_put(struct bpf_map *map);
|
2019-11-20 22:04:44 +00:00
|
|
|
void *bpf_map_area_alloc(u64 size, int numa_node);
|
|
|
|
void *bpf_map_area_mmapable_alloc(u64 size, int numa_node);
|
bpf: don't trigger OOM killer under pressure with map alloc
This patch adds two helpers, bpf_map_area_alloc() and bpf_map_area_free(),
that are to be used for map allocations. Using kmalloc() for very large
allocations can cause excessive work within the page allocator, so i) fall
back earlier to vmalloc() when the attempt is considered costly anyway,
and even more importantly ii) don't trigger OOM killer with any of the
allocators.
Since this is based on a user space request, for example, when creating
maps with element pre-allocation, we really want such requests to fail
instead of killing other user space processes.
Also, don't spam the kernel log with warnings should any of the allocations
fail under pressure. Given that, we can make backend selection in
bpf_map_area_alloc() generic, and convert all maps over to use this API
for spots with potentially large allocation requests.
Note, replacing the one kmalloc_array() is fine as overflow checks happen
earlier in htab_map_alloc(), since it must also protect the multiplication
for vmalloc() should kmalloc_array() fail.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-01-18 14:14:17 +00:00
|
|
|
void bpf_map_area_free(void *base);
|
bpf: Fix toctou on read-only map's constant scalar tracking
Commit a23740ec43ba ("bpf: Track contents of read-only maps as scalars") is
checking whether maps are read-only both from BPF program side and user space
side, and then, given their content is constant, reading out their data via
map->ops->map_direct_value_addr() which is then subsequently used as known
scalar value for the register, that is, it is marked as __mark_reg_known()
with the read value at verification time. Before a23740ec43ba, the register
content was marked as an unknown scalar so the verifier could not make any
assumptions about the map content.
The current implementation however is prone to a TOCTOU race, meaning, the
value read as known scalar for the register is not guaranteed to be exactly
the same at a later point when the program is executed, and as such, the
prior made assumptions of the verifier with regards to the program will be
invalid which can cause issues such as OOB access, etc.
While the BPF_F_RDONLY_PROG map flag is always fixed and required to be
specified at map creation time, the map->frozen property is initially set to
false for the map given the map value needs to be populated, e.g. for global
data sections. Once complete, the loader "freezes" the map from user space
such that no subsequent updates/deletes are possible anymore. For the rest
of the lifetime of the map, this freeze one-time trigger cannot be undone
anymore after a successful BPF_MAP_FREEZE cmd return. Meaning, any new BPF_*
cmd calls which would update/delete map entries will be rejected with -EPERM
since map_get_sys_perms() removes the FMODE_CAN_WRITE permission. This also
means that pending update/delete map entries must still complete before this
guarantee is given. This corner case is not an issue for loaders since they
create and prepare such program private map in successive steps.
However, a malicious user is able to trigger this TOCTOU race in two different
ways: i) via userfaultfd, and ii) via batched updates. For i) userfaultfd is
used to expand the competition interval, so that map_update_elem() can modify
the contents of the map after map_freeze() and bpf_prog_load() were executed.
This works, because userfaultfd halts the parallel thread which triggered a
map_update_elem() at the time where we copy key/value from the user buffer and
this already passed the FMODE_CAN_WRITE capability test given at that time the
map was not "frozen". Then, the main thread performs the map_freeze() and
bpf_prog_load(), and once that had completed successfully, the other thread
is woken up to complete the pending map_update_elem() which then changes the
map content. For ii) the idea of the batched update is similar, meaning, when
there are a large number of updates to be processed, it can increase the
competition interval between the two. It is therefore possible in practice to
modify the contents of the map after executing map_freeze() and bpf_prog_load().
One way to fix both i) and ii) at the same time is to expand the use of the
map's map->writecnt. The latter was introduced in fc9702273e2e ("bpf: Add mmap()
support for BPF_MAP_TYPE_ARRAY") and further refined in 1f6cb19be2e2 ("bpf:
Prevent re-mmap()'ing BPF map as writable for initially r/o mapping") with
the rationale to make a writable mmap()'ing of a map mutually exclusive with
read-only freezing. The counter indicates writable mmap() mappings and then
prevents/fails the freeze operation. Its semantics can be expanded beyond
just mmap() by generally indicating ongoing write phases. This would essentially
span any parallel regular and batched flavor of update/delete operation and
then also have map_freeze() fail with -EBUSY. For the check_mem_access() in
the verifier we expand upon the bpf_map_is_rdonly() check ensuring that all
last pending writes have completed via bpf_map_write_active() test. Once the
map->frozen is set and bpf_map_write_active() indicates a map->writecnt of 0
only then we are really guaranteed to use the map's data as known constants.
For map->frozen being set and pending writes in process of still being completed
we fall back to marking that register as unknown scalar so we don't end up
making assumptions about it. With this, both TOCTOU reproducers from i) and
ii) are fixed.
Note that the map->writecnt has been converted into a atomic64 in the fix in
order to avoid a double freeze_mutex mutex_{un,}lock() pair when updating
map->writecnt in the various map update/delete BPF_* cmd flavors. Spanning
the freeze_mutex over entire map update/delete operations in syscall side
would not be possible due to then causing everything to be serialized.
Similarly, something like synchronize_rcu() after setting map->frozen to wait
for update/deletes to complete is not possible either since it would also
have to span the user copy which can sleep. On the libbpf side, this won't
break d66562fba1ce ("libbpf: Add BPF object skeleton support") as the
anonymous mmap()-ed "map initialization image" is remapped as a BPF map-backed
mmap()-ed memory where for .rodata it's non-writable.
Fixes: a23740ec43ba ("bpf: Track contents of read-only maps as scalars")
Reported-by: w1tcher.bupt@gmail.com
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2021-11-09 18:48:08 +00:00
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bool bpf_map_write_active(const struct bpf_map *map);
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2018-01-12 04:29:06 +00:00
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void bpf_map_init_from_attr(struct bpf_map *map, union bpf_attr *attr);
|
2020-01-15 18:43:01 +00:00
|
|
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int generic_map_lookup_batch(struct bpf_map *map,
|
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const union bpf_attr *attr,
|
2020-01-15 18:43:02 +00:00
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union bpf_attr __user *uattr);
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int generic_map_update_batch(struct bpf_map *map,
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const union bpf_attr *attr,
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union bpf_attr __user *uattr);
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int generic_map_delete_batch(struct bpf_map *map,
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const union bpf_attr *attr,
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2020-01-15 18:43:01 +00:00
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union bpf_attr __user *uattr);
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2020-05-09 17:59:09 +00:00
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struct bpf_map *bpf_map_get_curr_or_next(u32 *id);
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2020-07-02 01:10:18 +00:00
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struct bpf_prog *bpf_prog_get_curr_or_next(u32 *id);
|
2015-03-02 14:21:55 +00:00
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2020-12-01 21:58:32 +00:00
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#ifdef CONFIG_MEMCG_KMEM
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void *bpf_map_kmalloc_node(const struct bpf_map *map, size_t size, gfp_t flags,
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int node);
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void *bpf_map_kzalloc(const struct bpf_map *map, size_t size, gfp_t flags);
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void __percpu *bpf_map_alloc_percpu(const struct bpf_map *map, size_t size,
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size_t align, gfp_t flags);
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#else
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static inline void *
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bpf_map_kmalloc_node(const struct bpf_map *map, size_t size, gfp_t flags,
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int node)
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{
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return kmalloc_node(size, flags, node);
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}
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static inline void *
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bpf_map_kzalloc(const struct bpf_map *map, size_t size, gfp_t flags)
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{
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return kzalloc(size, flags);
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}
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static inline void __percpu *
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bpf_map_alloc_percpu(const struct bpf_map *map, size_t size, size_t align,
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gfp_t flags)
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{
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return __alloc_percpu_gfp(size, align, flags);
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}
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#endif
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bpf: enable non-root eBPF programs
In order to let unprivileged users load and execute eBPF programs
teach verifier to prevent pointer leaks.
Verifier will prevent
- any arithmetic on pointers
(except R10+Imm which is used to compute stack addresses)
- comparison of pointers
(except if (map_value_ptr == 0) ... )
- passing pointers to helper functions
- indirectly passing pointers in stack to helper functions
- returning pointer from bpf program
- storing pointers into ctx or maps
Spill/fill of pointers into stack is allowed, but mangling
of pointers stored in the stack or reading them byte by byte is not.
Within bpf programs the pointers do exist, since programs need to
be able to access maps, pass skb pointer to LD_ABS insns, etc
but programs cannot pass such pointer values to the outside
or obfuscate them.
Only allow BPF_PROG_TYPE_SOCKET_FILTER unprivileged programs,
so that socket filters (tcpdump), af_packet (quic acceleration)
and future kcm can use it.
tracing and tc cls/act program types still require root permissions,
since tracing actually needs to be able to see all kernel pointers
and tc is for root only.
For example, the following unprivileged socket filter program is allowed:
int bpf_prog1(struct __sk_buff *skb)
{
u32 index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
u64 *value = bpf_map_lookup_elem(&my_map, &index);
if (value)
*value += skb->len;
return 0;
}
but the following program is not:
int bpf_prog1(struct __sk_buff *skb)
{
u32 index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
u64 *value = bpf_map_lookup_elem(&my_map, &index);
if (value)
*value += (u64) skb;
return 0;
}
since it would leak the kernel address into the map.
Unprivileged socket filter bpf programs have access to the
following helper functions:
- map lookup/update/delete (but they cannot store kernel pointers into them)
- get_random (it's already exposed to unprivileged user space)
- get_smp_processor_id
- tail_call into another socket filter program
- ktime_get_ns
The feature is controlled by sysctl kernel.unprivileged_bpf_disabled.
This toggle defaults to off (0), but can be set true (1). Once true,
bpf programs and maps cannot be accessed from unprivileged process,
and the toggle cannot be set back to false.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-08 05:23:21 +00:00
|
|
|
extern int sysctl_unprivileged_bpf_disabled;
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|
|
2020-05-13 23:03:54 +00:00
|
|
|
static inline bool bpf_allow_ptr_leaks(void)
|
|
|
|
{
|
|
|
|
return perfmon_capable();
|
|
|
|
}
|
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|
|
bpf: Allow variable-offset stack access
Before this patch, variable offset access to the stack was dissalowed
for regular instructions, but was allowed for "indirect" accesses (i.e.
helpers). This patch removes the restriction, allowing reading and
writing to the stack through stack pointers with variable offsets. This
makes stack-allocated buffers more usable in programs, and brings stack
pointers closer to other types of pointers.
The motivation is being able to use stack-allocated buffers for data
manipulation. When the stack size limit is sufficient, allocating
buffers on the stack is simpler than per-cpu arrays, or other
alternatives.
In unpriviledged programs, variable-offset reads and writes are
disallowed (they were already disallowed for the indirect access case)
because the speculative execution checking code doesn't support them.
Additionally, when writing through a variable-offset stack pointer, if
any pointers are in the accessible range, there's possilibities of later
leaking pointers because the write cannot be tracked precisely.
Writes with variable offset mark the whole range as initialized, even
though we don't know which stack slots are actually written. This is in
order to not reject future reads to these slots. Note that this doesn't
affect writes done through helpers; like before, helpers need the whole
stack range to be initialized to begin with.
All the stack slots are in range are considered scalars after the write;
variable-offset register spills are not tracked.
For reads, all the stack slots in the variable range needs to be
initialized (but see above about what writes do), otherwise the read is
rejected. All register spilled in stack slots that might be read are
marked as having been read, however reads through such pointers don't do
register filling; the target register will always be either a scalar or
a constant zero.
Signed-off-by: Andrei Matei <andreimatei1@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210207011027.676572-2-andreimatei1@gmail.com
2021-02-07 01:10:24 +00:00
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|
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static inline bool bpf_allow_uninit_stack(void)
|
|
|
|
{
|
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|
|
return perfmon_capable();
|
|
|
|
}
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|
|
bpf: Support access to bpf map fields
There are multiple use-cases when it's convenient to have access to bpf
map fields, both `struct bpf_map` and map type specific struct-s such as
`struct bpf_array`, `struct bpf_htab`, etc.
For example while working with sock arrays it can be necessary to
calculate the key based on map->max_entries (some_hash % max_entries).
Currently this is solved by communicating max_entries via "out-of-band"
channel, e.g. via additional map with known key to get info about target
map. That works, but is not very convenient and error-prone while
working with many maps.
In other cases necessary data is dynamic (i.e. unknown at loading time)
and it's impossible to get it at all. For example while working with a
hash table it can be convenient to know how much capacity is already
used (bpf_htab.count.counter for BPF_F_NO_PREALLOC case).
At the same time kernel knows this info and can provide it to bpf
program.
Fill this gap by adding support to access bpf map fields from bpf
program for both `struct bpf_map` and map type specific fields.
Support is implemented via btf_struct_access() so that a user can define
their own `struct bpf_map` or map type specific struct in their program
with only necessary fields and preserve_access_index attribute, cast a
map to this struct and use a field.
For example:
struct bpf_map {
__u32 max_entries;
} __attribute__((preserve_access_index));
struct bpf_array {
struct bpf_map map;
__u32 elem_size;
} __attribute__((preserve_access_index));
struct {
__uint(type, BPF_MAP_TYPE_ARRAY);
__uint(max_entries, 4);
__type(key, __u32);
__type(value, __u32);
} m_array SEC(".maps");
SEC("cgroup_skb/egress")
int cg_skb(void *ctx)
{
struct bpf_array *array = (struct bpf_array *)&m_array;
struct bpf_map *map = (struct bpf_map *)&m_array;
/* .. use map->max_entries or array->map.max_entries .. */
}
Similarly to other btf_struct_access() use-cases (e.g. struct tcp_sock
in net/ipv4/bpf_tcp_ca.c) the patch allows access to any fields of
corresponding struct. Only reading from map fields is supported.
For btf_struct_access() to work there should be a way to know btf id of
a struct that corresponds to a map type. To get btf id there should be a
way to get a stringified name of map-specific struct, such as
"bpf_array", "bpf_htab", etc for a map type. Two new fields are added to
`struct bpf_map_ops` to handle it:
* .map_btf_name keeps a btf name of a struct returned by map_alloc();
* .map_btf_id is used to cache btf id of that struct.
To make btf ids calculation cheaper they're calculated once while
preparing btf_vmlinux and cached same way as it's done for btf_id field
of `struct bpf_func_proto`
While calculating btf ids, struct names are NOT checked for collision.
Collisions will be checked as a part of the work to prepare btf ids used
in verifier in compile time that should land soon. The only known
collision for `struct bpf_htab` (kernel/bpf/hashtab.c vs
net/core/sock_map.c) was fixed earlier.
Both new fields .map_btf_name and .map_btf_id must be set for a map type
for the feature to work. If neither is set for a map type, verifier will
return ENOTSUPP on a try to access map_ptr of corresponding type. If
just one of them set, it's verifier misconfiguration.
Only `struct bpf_array` for BPF_MAP_TYPE_ARRAY and `struct bpf_htab` for
BPF_MAP_TYPE_HASH are supported by this patch. Other map types will be
supported separately.
The feature is available only for CONFIG_DEBUG_INFO_BTF=y and gated by
perfmon_capable() so that unpriv programs won't have access to bpf map
fields.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/6479686a0cd1e9067993df57b4c3eef0e276fec9.1592600985.git.rdna@fb.com
2020-06-19 21:11:43 +00:00
|
|
|
static inline bool bpf_allow_ptr_to_map_access(void)
|
|
|
|
{
|
|
|
|
return perfmon_capable();
|
|
|
|
}
|
|
|
|
|
2020-05-13 23:03:54 +00:00
|
|
|
static inline bool bpf_bypass_spec_v1(void)
|
|
|
|
{
|
|
|
|
return perfmon_capable();
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline bool bpf_bypass_spec_v4(void)
|
|
|
|
{
|
|
|
|
return perfmon_capable();
|
|
|
|
}
|
|
|
|
|
2017-10-18 20:00:22 +00:00
|
|
|
int bpf_map_new_fd(struct bpf_map *map, int flags);
|
2015-10-29 13:58:09 +00:00
|
|
|
int bpf_prog_new_fd(struct bpf_prog *prog);
|
|
|
|
|
2020-04-29 00:16:08 +00:00
|
|
|
void bpf_link_init(struct bpf_link *link, enum bpf_link_type type,
|
2020-04-29 00:16:06 +00:00
|
|
|
const struct bpf_link_ops *ops, struct bpf_prog *prog);
|
|
|
|
int bpf_link_prime(struct bpf_link *link, struct bpf_link_primer *primer);
|
|
|
|
int bpf_link_settle(struct bpf_link_primer *primer);
|
|
|
|
void bpf_link_cleanup(struct bpf_link_primer *primer);
|
bpf: Introduce pinnable bpf_link abstraction
Introduce bpf_link abstraction, representing an attachment of BPF program to
a BPF hook point (e.g., tracepoint, perf event, etc). bpf_link encapsulates
ownership of attached BPF program, reference counting of a link itself, when
reference from multiple anonymous inodes, as well as ensures that release
callback will be called from a process context, so that users can safely take
mutex locks and sleep.
Additionally, with a new abstraction it's now possible to generalize pinning
of a link object in BPF FS, allowing to explicitly prevent BPF program
detachment on process exit by pinning it in a BPF FS and let it open from
independent other process to keep working with it.
Convert two existing bpf_link-like objects (raw tracepoint and tracing BPF
program attachments) into utilizing bpf_link framework, making them pinnable
in BPF FS. More FD-based bpf_links will be added in follow up patches.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200303043159.323675-2-andriin@fb.com
2020-03-03 04:31:57 +00:00
|
|
|
void bpf_link_inc(struct bpf_link *link);
|
|
|
|
void bpf_link_put(struct bpf_link *link);
|
|
|
|
int bpf_link_new_fd(struct bpf_link *link);
|
bpf: Add bpf_link_new_file that doesn't install FD
Add bpf_link_new_file() API for cases when we need to ensure anon_inode is
successfully created before we proceed with expensive BPF program attachment
procedure, which will require equally (if not more so) expensive and
potentially failing compensation detachment procedure just because anon_inode
creation failed. This API allows to simplify code by ensuring first that
anon_inode is created and after BPF program is attached proceed with
fd_install() that can't fail.
After anon_inode file is created, link can't be just kfree()'d anymore,
because its destruction will be performed by deferred file_operations->release
call. For this, bpf_link API required specifying two separate operations:
release() and dealloc(), former performing detachment only, while the latter
frees memory used by bpf_link itself. dealloc() needs to be specified, because
struct bpf_link is frequently embedded into link type-specific container
struct (e.g., struct bpf_raw_tp_link), so bpf_link itself doesn't know how to
properly free the memory. In case when anon_inode file was successfully
created, but subsequent BPF attachment failed, bpf_link needs to be marked as
"defunct", so that file's release() callback will perform only memory
deallocation, but no detachment.
Convert raw tracepoint and tracing attachment to new API and eliminate
detachment from error handling path.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200309231051.1270337-1-andriin@fb.com
2020-03-09 23:10:51 +00:00
|
|
|
struct file *bpf_link_new_file(struct bpf_link *link, int *reserved_fd);
|
bpf: Introduce pinnable bpf_link abstraction
Introduce bpf_link abstraction, representing an attachment of BPF program to
a BPF hook point (e.g., tracepoint, perf event, etc). bpf_link encapsulates
ownership of attached BPF program, reference counting of a link itself, when
reference from multiple anonymous inodes, as well as ensures that release
callback will be called from a process context, so that users can safely take
mutex locks and sleep.
Additionally, with a new abstraction it's now possible to generalize pinning
of a link object in BPF FS, allowing to explicitly prevent BPF program
detachment on process exit by pinning it in a BPF FS and let it open from
independent other process to keep working with it.
Convert two existing bpf_link-like objects (raw tracepoint and tracing BPF
program attachments) into utilizing bpf_link framework, making them pinnable
in BPF FS. More FD-based bpf_links will be added in follow up patches.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200303043159.323675-2-andriin@fb.com
2020-03-03 04:31:57 +00:00
|
|
|
struct bpf_link *bpf_link_get_from_fd(u32 ufd);
|
2022-05-10 15:52:30 +00:00
|
|
|
struct bpf_link *bpf_link_get_curr_or_next(u32 *id);
|
bpf: Introduce pinnable bpf_link abstraction
Introduce bpf_link abstraction, representing an attachment of BPF program to
a BPF hook point (e.g., tracepoint, perf event, etc). bpf_link encapsulates
ownership of attached BPF program, reference counting of a link itself, when
reference from multiple anonymous inodes, as well as ensures that release
callback will be called from a process context, so that users can safely take
mutex locks and sleep.
Additionally, with a new abstraction it's now possible to generalize pinning
of a link object in BPF FS, allowing to explicitly prevent BPF program
detachment on process exit by pinning it in a BPF FS and let it open from
independent other process to keep working with it.
Convert two existing bpf_link-like objects (raw tracepoint and tracing BPF
program attachments) into utilizing bpf_link framework, making them pinnable
in BPF FS. More FD-based bpf_links will be added in follow up patches.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200303043159.323675-2-andriin@fb.com
2020-03-03 04:31:57 +00:00
|
|
|
|
2015-10-29 13:58:09 +00:00
|
|
|
int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
|
2017-10-18 20:00:22 +00:00
|
|
|
int bpf_obj_get_user(const char __user *pathname, int flags);
|
2015-10-29 13:58:09 +00:00
|
|
|
|
2020-05-13 18:02:16 +00:00
|
|
|
#define BPF_ITER_FUNC_PREFIX "bpf_iter_"
|
2020-05-09 17:59:07 +00:00
|
|
|
#define DEFINE_BPF_ITER_FUNC(target, args...) \
|
2020-05-13 18:02:16 +00:00
|
|
|
extern int bpf_iter_ ## target(args); \
|
|
|
|
int __init bpf_iter_ ## target(args) { return 0; }
|
2020-05-09 17:59:00 +00:00
|
|
|
|
2020-07-23 18:41:10 +00:00
|
|
|
struct bpf_iter_aux_info {
|
bpf: Implement bpf iterator for map elements
The bpf iterator for map elements are implemented.
The bpf program will receive four parameters:
bpf_iter_meta *meta: the meta data
bpf_map *map: the bpf_map whose elements are traversed
void *key: the key of one element
void *value: the value of the same element
Here, meta and map pointers are always valid, and
key has register type PTR_TO_RDONLY_BUF_OR_NULL and
value has register type PTR_TO_RDWR_BUF_OR_NULL.
The kernel will track the access range of key and value
during verification time. Later, these values will be compared
against the values in the actual map to ensure all accesses
are within range.
A new field iter_seq_info is added to bpf_map_ops which
is used to add map type specific information, i.e., seq_ops,
init/fini seq_file func and seq_file private data size.
Subsequent patches will have actual implementation
for bpf_map_ops->iter_seq_info.
In user space, BPF_ITER_LINK_MAP_FD needs to be
specified in prog attr->link_create.flags, which indicates
that attr->link_create.target_fd is a map_fd.
The reason for such an explicit flag is for possible
future cases where one bpf iterator may allow more than
one possible customization, e.g., pid and cgroup id for
task_file.
Current kernel internal implementation only allows
the target to register at most one required bpf_iter_link_info.
To support the above case, optional bpf_iter_link_info's
are needed, the target can be extended to register such link
infos, and user provided link_info needs to match one of
target supported ones.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184112.590360-1-yhs@fb.com
2020-07-23 18:41:12 +00:00
|
|
|
struct bpf_map *map;
|
2020-07-23 18:41:10 +00:00
|
|
|
};
|
|
|
|
|
bpf: Change uapi for bpf iterator map elements
Commit a5cbe05a6673 ("bpf: Implement bpf iterator for
map elements") added bpf iterator support for
map elements. The map element bpf iterator requires
info to identify a particular map. In the above
commit, the attr->link_create.target_fd is used
to carry map_fd and an enum bpf_iter_link_info
is added to uapi to specify the target_fd actually
representing a map_fd:
enum bpf_iter_link_info {
BPF_ITER_LINK_UNSPEC = 0,
BPF_ITER_LINK_MAP_FD = 1,
MAX_BPF_ITER_LINK_INFO,
};
This is an extensible approach as we can grow
enumerator for pid, cgroup_id, etc. and we can
unionize target_fd for pid, cgroup_id, etc.
But in the future, there are chances that
more complex customization may happen, e.g.,
for tasks, it could be filtered based on
both cgroup_id and user_id.
This patch changed the uapi to have fields
__aligned_u64 iter_info;
__u32 iter_info_len;
for additional iter_info for link_create.
The iter_info is defined as
union bpf_iter_link_info {
struct {
__u32 map_fd;
} map;
};
So future extension for additional customization
will be easier. The bpf_iter_link_info will be
passed to target callback to validate and generic
bpf_iter framework does not need to deal it any
more.
Note that map_fd = 0 will be considered invalid
and -EBADF will be returned to user space.
Fixes: a5cbe05a6673 ("bpf: Implement bpf iterator for map elements")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200805055056.1457463-1-yhs@fb.com
2020-08-05 05:50:56 +00:00
|
|
|
typedef int (*bpf_iter_attach_target_t)(struct bpf_prog *prog,
|
|
|
|
union bpf_iter_link_info *linfo,
|
|
|
|
struct bpf_iter_aux_info *aux);
|
|
|
|
typedef void (*bpf_iter_detach_target_t)(struct bpf_iter_aux_info *aux);
|
2020-08-21 18:44:18 +00:00
|
|
|
typedef void (*bpf_iter_show_fdinfo_t) (const struct bpf_iter_aux_info *aux,
|
|
|
|
struct seq_file *seq);
|
|
|
|
typedef int (*bpf_iter_fill_link_info_t)(const struct bpf_iter_aux_info *aux,
|
|
|
|
struct bpf_link_info *info);
|
2021-07-01 20:06:19 +00:00
|
|
|
typedef const struct bpf_func_proto *
|
|
|
|
(*bpf_iter_get_func_proto_t)(enum bpf_func_id func_id,
|
|
|
|
const struct bpf_prog *prog);
|
bpf: Implement bpf iterator for map elements
The bpf iterator for map elements are implemented.
The bpf program will receive four parameters:
bpf_iter_meta *meta: the meta data
bpf_map *map: the bpf_map whose elements are traversed
void *key: the key of one element
void *value: the value of the same element
Here, meta and map pointers are always valid, and
key has register type PTR_TO_RDONLY_BUF_OR_NULL and
value has register type PTR_TO_RDWR_BUF_OR_NULL.
The kernel will track the access range of key and value
during verification time. Later, these values will be compared
against the values in the actual map to ensure all accesses
are within range.
A new field iter_seq_info is added to bpf_map_ops which
is used to add map type specific information, i.e., seq_ops,
init/fini seq_file func and seq_file private data size.
Subsequent patches will have actual implementation
for bpf_map_ops->iter_seq_info.
In user space, BPF_ITER_LINK_MAP_FD needs to be
specified in prog attr->link_create.flags, which indicates
that attr->link_create.target_fd is a map_fd.
The reason for such an explicit flag is for possible
future cases where one bpf iterator may allow more than
one possible customization, e.g., pid and cgroup id for
task_file.
Current kernel internal implementation only allows
the target to register at most one required bpf_iter_link_info.
To support the above case, optional bpf_iter_link_info's
are needed, the target can be extended to register such link
infos, and user provided link_info needs to match one of
target supported ones.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184112.590360-1-yhs@fb.com
2020-07-23 18:41:12 +00:00
|
|
|
|
bpf: Permit cond_resched for some iterators
Commit e679654a704e ("bpf: Fix a rcu_sched stall issue with
bpf task/task_file iterator") tries to fix rcu stalls warning
which is caused by bpf task_file iterator when running
"bpftool prog".
rcu: INFO: rcu_sched self-detected stall on CPU
rcu: \x097-....: (20999 ticks this GP) idle=302/1/0x4000000000000000 softirq=1508852/1508852 fqs=4913
\x09(t=21031 jiffies g=2534773 q=179750)
NMI backtrace for cpu 7
CPU: 7 PID: 184195 Comm: bpftool Kdump: loaded Tainted: G W 5.8.0-00004-g68bfc7f8c1b4 #6
Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A17 05/03/2019
Call Trace:
<IRQ>
dump_stack+0x57/0x70
nmi_cpu_backtrace.cold+0x14/0x53
? lapic_can_unplug_cpu.cold+0x39/0x39
nmi_trigger_cpumask_backtrace+0xb7/0xc7
rcu_dump_cpu_stacks+0xa2/0xd0
rcu_sched_clock_irq.cold+0x1ff/0x3d9
? tick_nohz_handler+0x100/0x100
update_process_times+0x5b/0x90
tick_sched_timer+0x5e/0xf0
__hrtimer_run_queues+0x12a/0x2a0
hrtimer_interrupt+0x10e/0x280
__sysvec_apic_timer_interrupt+0x51/0xe0
asm_call_on_stack+0xf/0x20
</IRQ>
sysvec_apic_timer_interrupt+0x6f/0x80
...
task_file_seq_next+0x52/0xa0
bpf_seq_read+0xb9/0x320
vfs_read+0x9d/0x180
ksys_read+0x5f/0xe0
do_syscall_64+0x38/0x60
entry_SYSCALL_64_after_hwframe+0x44/0xa9
The fix is to limit the number of bpf program runs to be
one million. This fixed the program in most cases. But
we also found under heavy load, which can increase the wallclock
time for bpf_seq_read(), the warning may still be possible.
For example, calling bpf_delay() in the "while" loop of
bpf_seq_read(), which will introduce artificial delay,
the warning will show up in my qemu run.
static unsigned q;
volatile unsigned *p = &q;
volatile unsigned long long ll;
static void bpf_delay(void)
{
int i, j;
for (i = 0; i < 10000; i++)
for (j = 0; j < 10000; j++)
ll += *p;
}
There are two ways to fix this issue. One is to reduce the above
one million threshold to say 100,000 and hopefully rcu warning will
not show up any more. Another is to introduce a target feature
which enables bpf_seq_read() calling cond_resched().
This patch took second approach as the first approach may cause
more -EAGAIN failures for read() syscalls. Note that not all bpf_iter
targets can permit cond_resched() in bpf_seq_read() as some, e.g.,
netlink seq iterator, rcu read lock critical section spans through
seq_ops->next() -> seq_ops->show() -> seq_ops->next().
For the kernel code with the above hack, "bpftool p" roughly takes
38 seconds to finish on my VM with 184 bpf program runs.
Using the following command, I am able to collect the number of
context switches:
perf stat -e context-switches -- ./bpftool p >& log
Without this patch,
69 context-switches
With this patch,
75 context-switches
This patch added additional 6 context switches, roughly every 6 seconds
to reschedule, to avoid lengthy no-rescheduling which may cause the
above RCU warnings.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201028061054.1411116-1-yhs@fb.com
2020-10-28 06:10:54 +00:00
|
|
|
enum bpf_iter_feature {
|
|
|
|
BPF_ITER_RESCHED = BIT(0),
|
|
|
|
};
|
|
|
|
|
2020-05-13 18:02:21 +00:00
|
|
|
#define BPF_ITER_CTX_ARG_MAX 2
|
2020-05-09 17:58:59 +00:00
|
|
|
struct bpf_iter_reg {
|
|
|
|
const char *target;
|
bpf: Change uapi for bpf iterator map elements
Commit a5cbe05a6673 ("bpf: Implement bpf iterator for
map elements") added bpf iterator support for
map elements. The map element bpf iterator requires
info to identify a particular map. In the above
commit, the attr->link_create.target_fd is used
to carry map_fd and an enum bpf_iter_link_info
is added to uapi to specify the target_fd actually
representing a map_fd:
enum bpf_iter_link_info {
BPF_ITER_LINK_UNSPEC = 0,
BPF_ITER_LINK_MAP_FD = 1,
MAX_BPF_ITER_LINK_INFO,
};
This is an extensible approach as we can grow
enumerator for pid, cgroup_id, etc. and we can
unionize target_fd for pid, cgroup_id, etc.
But in the future, there are chances that
more complex customization may happen, e.g.,
for tasks, it could be filtered based on
both cgroup_id and user_id.
This patch changed the uapi to have fields
__aligned_u64 iter_info;
__u32 iter_info_len;
for additional iter_info for link_create.
The iter_info is defined as
union bpf_iter_link_info {
struct {
__u32 map_fd;
} map;
};
So future extension for additional customization
will be easier. The bpf_iter_link_info will be
passed to target callback to validate and generic
bpf_iter framework does not need to deal it any
more.
Note that map_fd = 0 will be considered invalid
and -EBADF will be returned to user space.
Fixes: a5cbe05a6673 ("bpf: Implement bpf iterator for map elements")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200805055056.1457463-1-yhs@fb.com
2020-08-05 05:50:56 +00:00
|
|
|
bpf_iter_attach_target_t attach_target;
|
|
|
|
bpf_iter_detach_target_t detach_target;
|
2020-08-21 18:44:18 +00:00
|
|
|
bpf_iter_show_fdinfo_t show_fdinfo;
|
|
|
|
bpf_iter_fill_link_info_t fill_link_info;
|
2021-07-01 20:06:19 +00:00
|
|
|
bpf_iter_get_func_proto_t get_func_proto;
|
2020-05-13 18:02:21 +00:00
|
|
|
u32 ctx_arg_info_size;
|
bpf: Permit cond_resched for some iterators
Commit e679654a704e ("bpf: Fix a rcu_sched stall issue with
bpf task/task_file iterator") tries to fix rcu stalls warning
which is caused by bpf task_file iterator when running
"bpftool prog".
rcu: INFO: rcu_sched self-detected stall on CPU
rcu: \x097-....: (20999 ticks this GP) idle=302/1/0x4000000000000000 softirq=1508852/1508852 fqs=4913
\x09(t=21031 jiffies g=2534773 q=179750)
NMI backtrace for cpu 7
CPU: 7 PID: 184195 Comm: bpftool Kdump: loaded Tainted: G W 5.8.0-00004-g68bfc7f8c1b4 #6
Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A17 05/03/2019
Call Trace:
<IRQ>
dump_stack+0x57/0x70
nmi_cpu_backtrace.cold+0x14/0x53
? lapic_can_unplug_cpu.cold+0x39/0x39
nmi_trigger_cpumask_backtrace+0xb7/0xc7
rcu_dump_cpu_stacks+0xa2/0xd0
rcu_sched_clock_irq.cold+0x1ff/0x3d9
? tick_nohz_handler+0x100/0x100
update_process_times+0x5b/0x90
tick_sched_timer+0x5e/0xf0
__hrtimer_run_queues+0x12a/0x2a0
hrtimer_interrupt+0x10e/0x280
__sysvec_apic_timer_interrupt+0x51/0xe0
asm_call_on_stack+0xf/0x20
</IRQ>
sysvec_apic_timer_interrupt+0x6f/0x80
...
task_file_seq_next+0x52/0xa0
bpf_seq_read+0xb9/0x320
vfs_read+0x9d/0x180
ksys_read+0x5f/0xe0
do_syscall_64+0x38/0x60
entry_SYSCALL_64_after_hwframe+0x44/0xa9
The fix is to limit the number of bpf program runs to be
one million. This fixed the program in most cases. But
we also found under heavy load, which can increase the wallclock
time for bpf_seq_read(), the warning may still be possible.
For example, calling bpf_delay() in the "while" loop of
bpf_seq_read(), which will introduce artificial delay,
the warning will show up in my qemu run.
static unsigned q;
volatile unsigned *p = &q;
volatile unsigned long long ll;
static void bpf_delay(void)
{
int i, j;
for (i = 0; i < 10000; i++)
for (j = 0; j < 10000; j++)
ll += *p;
}
There are two ways to fix this issue. One is to reduce the above
one million threshold to say 100,000 and hopefully rcu warning will
not show up any more. Another is to introduce a target feature
which enables bpf_seq_read() calling cond_resched().
This patch took second approach as the first approach may cause
more -EAGAIN failures for read() syscalls. Note that not all bpf_iter
targets can permit cond_resched() in bpf_seq_read() as some, e.g.,
netlink seq iterator, rcu read lock critical section spans through
seq_ops->next() -> seq_ops->show() -> seq_ops->next().
For the kernel code with the above hack, "bpftool p" roughly takes
38 seconds to finish on my VM with 184 bpf program runs.
Using the following command, I am able to collect the number of
context switches:
perf stat -e context-switches -- ./bpftool p >& log
Without this patch,
69 context-switches
With this patch,
75 context-switches
This patch added additional 6 context switches, roughly every 6 seconds
to reschedule, to avoid lengthy no-rescheduling which may cause the
above RCU warnings.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201028061054.1411116-1-yhs@fb.com
2020-10-28 06:10:54 +00:00
|
|
|
u32 feature;
|
2020-05-13 18:02:21 +00:00
|
|
|
struct bpf_ctx_arg_aux ctx_arg_info[BPF_ITER_CTX_ARG_MAX];
|
2020-07-23 18:41:09 +00:00
|
|
|
const struct bpf_iter_seq_info *seq_info;
|
2020-05-09 17:58:59 +00:00
|
|
|
};
|
|
|
|
|
2020-05-09 17:59:07 +00:00
|
|
|
struct bpf_iter_meta {
|
|
|
|
__bpf_md_ptr(struct seq_file *, seq);
|
|
|
|
u64 session_id;
|
|
|
|
u64 seq_num;
|
|
|
|
};
|
|
|
|
|
bpf: Implement bpf iterator for map elements
The bpf iterator for map elements are implemented.
The bpf program will receive four parameters:
bpf_iter_meta *meta: the meta data
bpf_map *map: the bpf_map whose elements are traversed
void *key: the key of one element
void *value: the value of the same element
Here, meta and map pointers are always valid, and
key has register type PTR_TO_RDONLY_BUF_OR_NULL and
value has register type PTR_TO_RDWR_BUF_OR_NULL.
The kernel will track the access range of key and value
during verification time. Later, these values will be compared
against the values in the actual map to ensure all accesses
are within range.
A new field iter_seq_info is added to bpf_map_ops which
is used to add map type specific information, i.e., seq_ops,
init/fini seq_file func and seq_file private data size.
Subsequent patches will have actual implementation
for bpf_map_ops->iter_seq_info.
In user space, BPF_ITER_LINK_MAP_FD needs to be
specified in prog attr->link_create.flags, which indicates
that attr->link_create.target_fd is a map_fd.
The reason for such an explicit flag is for possible
future cases where one bpf iterator may allow more than
one possible customization, e.g., pid and cgroup id for
task_file.
Current kernel internal implementation only allows
the target to register at most one required bpf_iter_link_info.
To support the above case, optional bpf_iter_link_info's
are needed, the target can be extended to register such link
infos, and user provided link_info needs to match one of
target supported ones.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184112.590360-1-yhs@fb.com
2020-07-23 18:41:12 +00:00
|
|
|
struct bpf_iter__bpf_map_elem {
|
|
|
|
__bpf_md_ptr(struct bpf_iter_meta *, meta);
|
|
|
|
__bpf_md_ptr(struct bpf_map *, map);
|
|
|
|
__bpf_md_ptr(void *, key);
|
|
|
|
__bpf_md_ptr(void *, value);
|
|
|
|
};
|
|
|
|
|
2020-05-13 18:02:19 +00:00
|
|
|
int bpf_iter_reg_target(const struct bpf_iter_reg *reg_info);
|
2020-05-13 18:02:20 +00:00
|
|
|
void bpf_iter_unreg_target(const struct bpf_iter_reg *reg_info);
|
2020-05-09 17:59:00 +00:00
|
|
|
bool bpf_iter_prog_supported(struct bpf_prog *prog);
|
2021-07-01 20:06:19 +00:00
|
|
|
const struct bpf_func_proto *
|
|
|
|
bpf_iter_get_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog);
|
2021-05-14 00:36:05 +00:00
|
|
|
int bpf_iter_link_attach(const union bpf_attr *attr, bpfptr_t uattr, struct bpf_prog *prog);
|
2020-05-09 17:59:05 +00:00
|
|
|
int bpf_iter_new_fd(struct bpf_link *link);
|
2020-05-09 17:59:06 +00:00
|
|
|
bool bpf_link_is_iter(struct bpf_link *link);
|
2020-05-09 17:59:07 +00:00
|
|
|
struct bpf_prog *bpf_iter_get_info(struct bpf_iter_meta *meta, bool in_stop);
|
|
|
|
int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx);
|
2020-08-21 18:44:19 +00:00
|
|
|
void bpf_iter_map_show_fdinfo(const struct bpf_iter_aux_info *aux,
|
|
|
|
struct seq_file *seq);
|
|
|
|
int bpf_iter_map_fill_link_info(const struct bpf_iter_aux_info *aux,
|
|
|
|
struct bpf_link_info *info);
|
2020-05-09 17:58:59 +00:00
|
|
|
|
2021-02-26 20:49:27 +00:00
|
|
|
int map_set_for_each_callback_args(struct bpf_verifier_env *env,
|
|
|
|
struct bpf_func_state *caller,
|
|
|
|
struct bpf_func_state *callee);
|
|
|
|
|
bpf: add lookup/update support for per-cpu hash and array maps
The functions bpf_map_lookup_elem(map, key, value) and
bpf_map_update_elem(map, key, value, flags) need to get/set
values from all-cpus for per-cpu hash and array maps,
so that user space can aggregate/update them as necessary.
Example of single counter aggregation in user space:
unsigned int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
long values[nr_cpus];
long value = 0;
bpf_lookup_elem(fd, key, values);
for (i = 0; i < nr_cpus; i++)
value += values[i];
The user space must provide round_up(value_size, 8) * nr_cpus
array to get/set values, since kernel will use 'long' copy
of per-cpu values to try to copy good counters atomically.
It's a best-effort, since bpf programs and user space are racing
to access the same memory.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-02-02 06:39:55 +00:00
|
|
|
int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
|
|
|
|
int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);
|
|
|
|
int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
|
|
|
|
u64 flags);
|
|
|
|
int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
|
|
|
|
u64 flags);
|
2016-06-15 20:47:13 +00:00
|
|
|
|
2016-03-08 05:57:17 +00:00
|
|
|
int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value);
|
bpf: add lookup/update support for per-cpu hash and array maps
The functions bpf_map_lookup_elem(map, key, value) and
bpf_map_update_elem(map, key, value, flags) need to get/set
values from all-cpus for per-cpu hash and array maps,
so that user space can aggregate/update them as necessary.
Example of single counter aggregation in user space:
unsigned int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
long values[nr_cpus];
long value = 0;
bpf_lookup_elem(fd, key, values);
for (i = 0; i < nr_cpus; i++)
value += values[i];
The user space must provide round_up(value_size, 8) * nr_cpus
array to get/set values, since kernel will use 'long' copy
of per-cpu values to try to copy good counters atomically.
It's a best-effort, since bpf programs and user space are racing
to access the same memory.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-02-02 06:39:55 +00:00
|
|
|
|
2016-06-15 20:47:13 +00:00
|
|
|
int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file,
|
|
|
|
void *key, void *value, u64 map_flags);
|
2017-06-28 06:08:34 +00:00
|
|
|
int bpf_fd_array_map_lookup_elem(struct bpf_map *map, void *key, u32 *value);
|
2017-03-22 17:00:34 +00:00
|
|
|
int bpf_fd_htab_map_update_elem(struct bpf_map *map, struct file *map_file,
|
|
|
|
void *key, void *value, u64 map_flags);
|
2017-06-28 06:08:34 +00:00
|
|
|
int bpf_fd_htab_map_lookup_elem(struct bpf_map *map, void *key, u32 *value);
|
2016-06-15 20:47:13 +00:00
|
|
|
|
2017-10-18 20:00:22 +00:00
|
|
|
int bpf_get_file_flag(int flags);
|
2021-05-14 00:36:05 +00:00
|
|
|
int bpf_check_uarg_tail_zero(bpfptr_t uaddr, size_t expected_size,
|
2018-05-22 22:03:31 +00:00
|
|
|
size_t actual_size);
|
2017-10-18 20:00:22 +00:00
|
|
|
|
bpf: add lookup/update support for per-cpu hash and array maps
The functions bpf_map_lookup_elem(map, key, value) and
bpf_map_update_elem(map, key, value, flags) need to get/set
values from all-cpus for per-cpu hash and array maps,
so that user space can aggregate/update them as necessary.
Example of single counter aggregation in user space:
unsigned int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
long values[nr_cpus];
long value = 0;
bpf_lookup_elem(fd, key, values);
for (i = 0; i < nr_cpus; i++)
value += values[i];
The user space must provide round_up(value_size, 8) * nr_cpus
array to get/set values, since kernel will use 'long' copy
of per-cpu values to try to copy good counters atomically.
It's a best-effort, since bpf programs and user space are racing
to access the same memory.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-02-02 06:39:55 +00:00
|
|
|
/* memcpy that is used with 8-byte aligned pointers, power-of-8 size and
|
|
|
|
* forced to use 'long' read/writes to try to atomically copy long counters.
|
|
|
|
* Best-effort only. No barriers here, since it _will_ race with concurrent
|
|
|
|
* updates from BPF programs. Called from bpf syscall and mostly used with
|
|
|
|
* size 8 or 16 bytes, so ask compiler to inline it.
|
|
|
|
*/
|
|
|
|
static inline void bpf_long_memcpy(void *dst, const void *src, u32 size)
|
|
|
|
{
|
|
|
|
const long *lsrc = src;
|
|
|
|
long *ldst = dst;
|
|
|
|
|
|
|
|
size /= sizeof(long);
|
|
|
|
while (size--)
|
|
|
|
*ldst++ = *lsrc++;
|
|
|
|
}
|
|
|
|
|
2015-03-02 14:21:55 +00:00
|
|
|
/* verify correctness of eBPF program */
|
2021-05-14 00:36:05 +00:00
|
|
|
int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr);
|
2021-01-12 07:55:14 +00:00
|
|
|
|
|
|
|
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
|
2017-12-15 01:55:13 +00:00
|
|
|
void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);
|
2021-01-12 07:55:14 +00:00
|
|
|
#endif
|
2017-07-18 04:56:48 +00:00
|
|
|
|
2020-09-28 11:31:03 +00:00
|
|
|
struct btf *bpf_get_btf_vmlinux(void);
|
|
|
|
|
2017-07-18 04:56:48 +00:00
|
|
|
/* Map specifics */
|
2022-01-03 15:08:09 +00:00
|
|
|
struct xdp_frame;
|
2018-06-14 02:07:42 +00:00
|
|
|
struct sk_buff;
|
2021-03-08 11:29:06 +00:00
|
|
|
struct bpf_dtab_netdev;
|
|
|
|
struct bpf_cpu_map_entry;
|
2018-05-24 14:45:46 +00:00
|
|
|
|
xdp: Use bulking for non-map XDP_REDIRECT and consolidate code paths
Since the bulk queue used by XDP_REDIRECT now lives in struct net_device,
we can re-use the bulking for the non-map version of the bpf_redirect()
helper. This is a simple matter of having xdp_do_redirect_slow() queue the
frame on the bulk queue instead of sending it out with __bpf_tx_xdp().
Unfortunately we can't make the bpf_redirect() helper return an error if
the ifindex doesn't exit (as bpf_redirect_map() does), because we don't
have a reference to the network namespace of the ingress device at the time
the helper is called. So we have to leave it as-is and keep the device
lookup in xdp_do_redirect_slow().
Since this leaves less reason to have the non-map redirect code in a
separate function, so we get rid of the xdp_do_redirect_slow() function
entirely. This does lose us the tracepoint disambiguation, but fortunately
the xdp_redirect and xdp_redirect_map tracepoints use the same tracepoint
entry structures. This means both can contain a map index, so we can just
amend the tracepoint definitions so we always emit the xdp_redirect(_err)
tracepoints, but with the map ID only populated if a map is present. This
means we retire the xdp_redirect_map(_err) tracepoints entirely, but keep
the definitions around in case someone is still listening for them.
With this change, the performance of the xdp_redirect sample program goes
from 5Mpps to 8.4Mpps (a 68% increase).
Since the flush functions are no longer map-specific, rename the flush()
functions to drop _map from their names. One of the renamed functions is
the xdp_do_flush_map() callback used in all the xdp-enabled drivers. To
keep from having to update all drivers, use a #define to keep the old name
working, and only update the virtual drivers in this patch.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/157918768505.1458396.17518057312953572912.stgit@toke.dk
2020-01-16 15:14:45 +00:00
|
|
|
void __dev_flush(void);
|
2022-01-03 15:08:09 +00:00
|
|
|
int dev_xdp_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
|
xdp: Use bulking for non-map XDP_REDIRECT and consolidate code paths
Since the bulk queue used by XDP_REDIRECT now lives in struct net_device,
we can re-use the bulking for the non-map version of the bpf_redirect()
helper. This is a simple matter of having xdp_do_redirect_slow() queue the
frame on the bulk queue instead of sending it out with __bpf_tx_xdp().
Unfortunately we can't make the bpf_redirect() helper return an error if
the ifindex doesn't exit (as bpf_redirect_map() does), because we don't
have a reference to the network namespace of the ingress device at the time
the helper is called. So we have to leave it as-is and keep the device
lookup in xdp_do_redirect_slow().
Since this leaves less reason to have the non-map redirect code in a
separate function, so we get rid of the xdp_do_redirect_slow() function
entirely. This does lose us the tracepoint disambiguation, but fortunately
the xdp_redirect and xdp_redirect_map tracepoints use the same tracepoint
entry structures. This means both can contain a map index, so we can just
amend the tracepoint definitions so we always emit the xdp_redirect(_err)
tracepoints, but with the map ID only populated if a map is present. This
means we retire the xdp_redirect_map(_err) tracepoints entirely, but keep
the definitions around in case someone is still listening for them.
With this change, the performance of the xdp_redirect sample program goes
from 5Mpps to 8.4Mpps (a 68% increase).
Since the flush functions are no longer map-specific, rename the flush()
functions to drop _map from their names. One of the renamed functions is
the xdp_do_flush_map() callback used in all the xdp-enabled drivers. To
keep from having to update all drivers, use a #define to keep the old name
working, and only update the virtual drivers in this patch.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/157918768505.1458396.17518057312953572912.stgit@toke.dk
2020-01-16 15:14:45 +00:00
|
|
|
struct net_device *dev_rx);
|
2022-01-03 15:08:09 +00:00
|
|
|
int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_frame *xdpf,
|
2018-05-24 14:45:57 +00:00
|
|
|
struct net_device *dev_rx);
|
2022-01-03 15:08:09 +00:00
|
|
|
int dev_map_enqueue_multi(struct xdp_frame *xdpf, struct net_device *dev_rx,
|
2021-05-19 09:07:45 +00:00
|
|
|
struct bpf_map *map, bool exclude_ingress);
|
2018-06-14 02:07:42 +00:00
|
|
|
int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
|
|
|
|
struct bpf_prog *xdp_prog);
|
2021-05-19 09:07:45 +00:00
|
|
|
int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb,
|
|
|
|
struct bpf_prog *xdp_prog, struct bpf_map *map,
|
|
|
|
bool exclude_ingress);
|
2017-07-18 04:56:48 +00:00
|
|
|
|
2019-12-19 06:10:04 +00:00
|
|
|
void __cpu_map_flush(void);
|
2022-01-03 15:08:09 +00:00
|
|
|
int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf,
|
2017-10-16 10:19:34 +00:00
|
|
|
struct net_device *dev_rx);
|
2021-07-02 11:18:23 +00:00
|
|
|
int cpu_map_generic_redirect(struct bpf_cpu_map_entry *rcpu,
|
|
|
|
struct sk_buff *skb);
|
2017-10-16 10:19:34 +00:00
|
|
|
|
2017-08-18 18:28:00 +00:00
|
|
|
/* Return map's numa specified by userspace */
|
|
|
|
static inline int bpf_map_attr_numa_node(const union bpf_attr *attr)
|
|
|
|
{
|
|
|
|
return (attr->map_flags & BPF_F_NUMA_NODE) ?
|
|
|
|
attr->numa_node : NUMA_NO_NODE;
|
|
|
|
}
|
|
|
|
|
2017-12-03 01:20:38 +00:00
|
|
|
struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type);
|
bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY
This patch introduces a new map type BPF_MAP_TYPE_REUSEPORT_SOCKARRAY.
To unleash the full potential of a bpf prog, it is essential for the
userspace to be capable of directly setting up a bpf map which can then
be consumed by the bpf prog to make decision. In this case, decide which
SO_REUSEPORT sk to serve the incoming request.
By adding BPF_MAP_TYPE_REUSEPORT_SOCKARRAY, the userspace has total control
and visibility on where a SO_REUSEPORT sk should be located in a bpf map.
The later patch will introduce BPF_PROG_TYPE_SK_REUSEPORT such that
the bpf prog can directly select a sk from the bpf map. That will
raise the programmability of the bpf prog attached to a reuseport
group (a group of sk serving the same IP:PORT).
For example, in UDP, the bpf prog can peek into the payload (e.g.
through the "data" pointer introduced in the later patch) to learn
the application level's connection information and then decide which sk
to pick from a bpf map. The userspace can tightly couple the sk's location
in a bpf map with the application logic in generating the UDP payload's
connection information. This connection info contact/API stays within the
userspace.
Also, when used with map-in-map, the userspace can switch the
old-server-process's inner map to a new-server-process's inner map
in one call "bpf_map_update_elem(outer_map, &index, &new_reuseport_array)".
The bpf prog will then direct incoming requests to the new process instead
of the old process. The old process can finish draining the pending
requests (e.g. by "accept()") before closing the old-fds. [Note that
deleting a fd from a bpf map does not necessary mean the fd is closed]
During map_update_elem(),
Only SO_REUSEPORT sk (i.e. which has already been added
to a reuse->socks[]) can be used. That means a SO_REUSEPORT sk that is
"bind()" for UDP or "bind()+listen()" for TCP. These conditions are
ensured in "reuseport_array_update_check()".
A SO_REUSEPORT sk can only be added once to a map (i.e. the
same sk cannot be added twice even to the same map). SO_REUSEPORT
already allows another sk to be created for the same IP:PORT.
There is no need to re-create a similar usage in the BPF side.
When a SO_REUSEPORT is deleted from the "reuse->socks[]" (e.g. "close()"),
it will notify the bpf map to remove it from the map also. It is
done through "bpf_sk_reuseport_detach()" and it will only be called
if >=1 of the "reuse->sock[]" has ever been added to a bpf map.
The map_update()/map_delete() has to be in-sync with the
"reuse->socks[]". Hence, the same "reuseport_lock" used
by "reuse->socks[]" has to be used here also. Care has
been taken to ensure the lock is only acquired when the
adding sk passes some strict tests. and
freeing the map does not require the reuseport_lock.
The reuseport_array will also support lookup from the syscall
side. It will return a sock_gen_cookie(). The sock_gen_cookie()
is on-demand (i.e. a sk's cookie is not generated until the very
first map_lookup_elem()).
The lookup cookie is 64bits but it goes against the logical userspace
expectation on 32bits sizeof(fd) (and as other fd based bpf maps do also).
It may catch user in surprise if we enforce value_size=8 while
userspace still pass a 32bits fd during update. Supporting different
value_size between lookup and update seems unintuitive also.
We also need to consider what if other existing fd based maps want
to return 64bits value from syscall's lookup in the future.
Hence, reuseport_array supports both value_size 4 and 8, and
assuming user will usually use value_size=4. The syscall's lookup
will return ENOSPC on value_size=4. It will will only
return 64bits value from sock_gen_cookie() when user consciously
choose value_size=8 (as a signal that lookup is desired) which then
requires a 64bits value in both lookup and update.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-08-08 08:01:24 +00:00
|
|
|
int array_map_alloc_check(union bpf_attr *attr);
|
2017-12-03 01:20:38 +00:00
|
|
|
|
2019-04-11 16:12:02 +00:00
|
|
|
int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr);
|
|
|
|
int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr);
|
2020-03-04 19:18:52 +00:00
|
|
|
int bpf_prog_test_run_tracing(struct bpf_prog *prog,
|
|
|
|
const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr);
|
2019-04-11 16:12:02 +00:00
|
|
|
int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
|
|
|
|
const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr);
|
2020-09-25 20:54:29 +00:00
|
|
|
int bpf_prog_test_run_raw_tp(struct bpf_prog *prog,
|
|
|
|
const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr);
|
2021-03-03 10:18:13 +00:00
|
|
|
int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog,
|
|
|
|
const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr);
|
2019-10-16 03:25:00 +00:00
|
|
|
bool btf_ctx_access(int off, int size, enum bpf_access_type type,
|
|
|
|
const struct bpf_prog *prog,
|
|
|
|
struct bpf_insn_access_aux *info);
|
2021-10-25 06:40:23 +00:00
|
|
|
|
|
|
|
static inline bool bpf_tracing_ctx_access(int off, int size,
|
|
|
|
enum bpf_access_type type)
|
|
|
|
{
|
|
|
|
if (off < 0 || off >= sizeof(__u64) * MAX_BPF_FUNC_ARGS)
|
|
|
|
return false;
|
|
|
|
if (type != BPF_READ)
|
|
|
|
return false;
|
|
|
|
if (off % size != 0)
|
|
|
|
return false;
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline bool bpf_tracing_btf_ctx_access(int off, int size,
|
|
|
|
enum bpf_access_type type,
|
|
|
|
const struct bpf_prog *prog,
|
|
|
|
struct bpf_insn_access_aux *info)
|
|
|
|
{
|
|
|
|
if (!bpf_tracing_ctx_access(off, size, type))
|
|
|
|
return false;
|
|
|
|
return btf_ctx_access(off, size, type, prog, info);
|
|
|
|
}
|
|
|
|
|
bpf: Remove hard-coded btf_vmlinux assumption from BPF verifier
Remove a permeating assumption thoughout BPF verifier of vmlinux BTF. Instead,
wherever BTF type IDs are involved, also track the instance of struct btf that
goes along with the type ID. This allows to gradually add support for kernel
module BTFs and using/tracking module types across BPF helper calls and
registers.
This patch also renames btf_id() function to btf_obj_id() to minimize naming
clash with using btf_id to denote BTF *type* ID, rather than BTF *object*'s ID.
Also, altough btf_vmlinux can't get destructed and thus doesn't need
refcounting, module BTFs need that, so apply BTF refcounting universally when
BPF program is using BTF-powered attachment (tp_btf, fentry/fexit, etc). This
makes for simpler clean up code.
Now that BTF type ID is not enough to uniquely identify a BTF type, extend BPF
trampoline key to include BTF object ID. To differentiate that from target
program BPF ID, set 31st bit of type ID. BTF type IDs (at least currently) are
not allowed to take full 32 bits, so there is no danger of confusing that bit
with a valid BTF type ID.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201203204634.1325171-10-andrii@kernel.org
2020-12-03 20:46:29 +00:00
|
|
|
int btf_struct_access(struct bpf_verifier_log *log, const struct btf *btf,
|
2019-10-16 03:25:00 +00:00
|
|
|
const struct btf_type *t, int off, int size,
|
|
|
|
enum bpf_access_type atype,
|
bpf: reject program if a __user tagged memory accessed in kernel way
BPF verifier supports direct memory access for BPF_PROG_TYPE_TRACING type
of bpf programs, e.g., a->b. If "a" is a pointer
pointing to kernel memory, bpf verifier will allow user to write
code in C like a->b and the verifier will translate it to a kernel
load properly. If "a" is a pointer to user memory, it is expected
that bpf developer should be bpf_probe_read_user() helper to
get the value a->b. Without utilizing BTF __user tagging information,
current verifier will assume that a->b is a kernel memory access
and this may generate incorrect result.
Now BTF contains __user information, it can check whether the
pointer points to a user memory or not. If it is, the verifier
can reject the program and force users to use bpf_probe_read_user()
helper explicitly.
In the future, we can easily extend btf_add_space for other
address space tagging, for example, rcu/percpu etc.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20220127154606.654961-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-01-27 15:46:06 +00:00
|
|
|
u32 *next_btf_id, enum bpf_type_flag *flag);
|
2020-08-25 19:21:18 +00:00
|
|
|
bool btf_struct_ids_match(struct bpf_verifier_log *log,
|
bpf: Remove hard-coded btf_vmlinux assumption from BPF verifier
Remove a permeating assumption thoughout BPF verifier of vmlinux BTF. Instead,
wherever BTF type IDs are involved, also track the instance of struct btf that
goes along with the type ID. This allows to gradually add support for kernel
module BTFs and using/tracking module types across BPF helper calls and
registers.
This patch also renames btf_id() function to btf_obj_id() to minimize naming
clash with using btf_id to denote BTF *type* ID, rather than BTF *object*'s ID.
Also, altough btf_vmlinux can't get destructed and thus doesn't need
refcounting, module BTFs need that, so apply BTF refcounting universally when
BPF program is using BTF-powered attachment (tp_btf, fentry/fexit, etc). This
makes for simpler clean up code.
Now that BTF type ID is not enough to uniquely identify a BTF type, extend BPF
trampoline key to include BTF object ID. To differentiate that from target
program BPF ID, set 31st bit of type ID. BTF type IDs (at least currently) are
not allowed to take full 32 bits, so there is no danger of confusing that bit
with a valid BTF type ID.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201203204634.1325171-10-andrii@kernel.org
2020-12-03 20:46:29 +00:00
|
|
|
const struct btf *btf, u32 id, int off,
|
2022-04-24 21:48:57 +00:00
|
|
|
const struct btf *need_btf, u32 need_type_id,
|
|
|
|
bool strict);
|
2019-10-16 03:25:00 +00:00
|
|
|
|
2019-11-14 18:57:04 +00:00
|
|
|
int btf_distill_func_proto(struct bpf_verifier_log *log,
|
|
|
|
struct btf *btf,
|
|
|
|
const struct btf_type *func_proto,
|
|
|
|
const char *func_name,
|
|
|
|
struct btf_func_model *m);
|
|
|
|
|
2020-01-10 06:41:20 +00:00
|
|
|
struct bpf_reg_state;
|
2021-03-25 01:51:36 +00:00
|
|
|
int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
|
|
|
|
struct bpf_reg_state *regs);
|
bpf: Support bpf program calling kernel function
This patch adds support to BPF verifier to allow bpf program calling
kernel function directly.
The use case included in this set is to allow bpf-tcp-cc to directly
call some tcp-cc helper functions (e.g. "tcp_cong_avoid_ai()"). Those
functions have already been used by some kernel tcp-cc implementations.
This set will also allow the bpf-tcp-cc program to directly call the
kernel tcp-cc implementation, For example, a bpf_dctcp may only want to
implement its own dctcp_cwnd_event() and reuse other dctcp_*() directly
from the kernel tcp_dctcp.c instead of reimplementing (or
copy-and-pasting) them.
The tcp-cc kernel functions mentioned above will be white listed
for the struct_ops bpf-tcp-cc programs to use in a later patch.
The white listed functions are not bounded to a fixed ABI contract.
Those functions have already been used by the existing kernel tcp-cc.
If any of them has changed, both in-tree and out-of-tree kernel tcp-cc
implementations have to be changed. The same goes for the struct_ops
bpf-tcp-cc programs which have to be adjusted accordingly.
This patch is to make the required changes in the bpf verifier.
First change is in btf.c, it adds a case in "btf_check_func_arg_match()".
When the passed in "btf->kernel_btf == true", it means matching the
verifier regs' states with a kernel function. This will handle the
PTR_TO_BTF_ID reg. It also maps PTR_TO_SOCK_COMMON, PTR_TO_SOCKET,
and PTR_TO_TCP_SOCK to its kernel's btf_id.
In the later libbpf patch, the insn calling a kernel function will
look like:
insn->code == (BPF_JMP | BPF_CALL)
insn->src_reg == BPF_PSEUDO_KFUNC_CALL /* <- new in this patch */
insn->imm == func_btf_id /* btf_id of the running kernel */
[ For the future calling function-in-kernel-module support, an array
of module btf_fds can be passed at the load time and insn->off
can be used to index into this array. ]
At the early stage of verifier, the verifier will collect all kernel
function calls into "struct bpf_kfunc_desc". Those
descriptors are stored in "prog->aux->kfunc_tab" and will
be available to the JIT. Since this "add" operation is similar
to the current "add_subprog()" and looking for the same insn->code,
they are done together in the new "add_subprog_and_kfunc()".
In the "do_check()" stage, the new "check_kfunc_call()" is added
to verify the kernel function call instruction:
1. Ensure the kernel function can be used by a particular BPF_PROG_TYPE.
A new bpf_verifier_ops "check_kfunc_call" is added to do that.
The bpf-tcp-cc struct_ops program will implement this function in
a later patch.
2. Call "btf_check_kfunc_args_match()" to ensure the regs can be
used as the args of a kernel function.
3. Mark the regs' type, subreg_def, and zext_dst.
At the later do_misc_fixups() stage, the new fixup_kfunc_call()
will replace the insn->imm with the function address (relative
to __bpf_call_base). If needed, the jit can find the btf_func_model
by calling the new bpf_jit_find_kfunc_model(prog, insn).
With the imm set to the function address, "bpftool prog dump xlated"
will be able to display the kernel function calls the same way as
it displays other bpf helper calls.
gpl_compatible program is required to call kernel function.
This feature currently requires JIT.
The verifier selftests are adjusted because of the changes in
the verbose log in add_subprog_and_kfunc().
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015142.1544736-1-kafai@fb.com
2021-03-25 01:51:42 +00:00
|
|
|
int btf_check_kfunc_arg_match(struct bpf_verifier_env *env,
|
|
|
|
const struct btf *btf, u32 func_id,
|
2022-07-21 13:42:35 +00:00
|
|
|
struct bpf_reg_state *regs,
|
|
|
|
u32 kfunc_flags);
|
2020-01-10 06:41:20 +00:00
|
|
|
int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
|
|
|
|
struct bpf_reg_state *reg);
|
2020-09-25 21:25:01 +00:00
|
|
|
int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *prog,
|
2020-01-21 00:53:46 +00:00
|
|
|
struct btf *btf, const struct btf_type *t);
|
2019-11-14 18:57:16 +00:00
|
|
|
|
2019-12-13 17:51:09 +00:00
|
|
|
struct bpf_prog *bpf_prog_by_id(u32 id);
|
2020-08-19 04:27:56 +00:00
|
|
|
struct bpf_link *bpf_link_by_id(u32 id);
|
2019-12-13 17:51:09 +00:00
|
|
|
|
2020-04-24 23:59:41 +00:00
|
|
|
const struct bpf_func_proto *bpf_base_func_proto(enum bpf_func_id func_id);
|
2021-02-25 23:43:14 +00:00
|
|
|
void bpf_task_storage_free(struct task_struct *task);
|
bpf: Support bpf program calling kernel function
This patch adds support to BPF verifier to allow bpf program calling
kernel function directly.
The use case included in this set is to allow bpf-tcp-cc to directly
call some tcp-cc helper functions (e.g. "tcp_cong_avoid_ai()"). Those
functions have already been used by some kernel tcp-cc implementations.
This set will also allow the bpf-tcp-cc program to directly call the
kernel tcp-cc implementation, For example, a bpf_dctcp may only want to
implement its own dctcp_cwnd_event() and reuse other dctcp_*() directly
from the kernel tcp_dctcp.c instead of reimplementing (or
copy-and-pasting) them.
The tcp-cc kernel functions mentioned above will be white listed
for the struct_ops bpf-tcp-cc programs to use in a later patch.
The white listed functions are not bounded to a fixed ABI contract.
Those functions have already been used by the existing kernel tcp-cc.
If any of them has changed, both in-tree and out-of-tree kernel tcp-cc
implementations have to be changed. The same goes for the struct_ops
bpf-tcp-cc programs which have to be adjusted accordingly.
This patch is to make the required changes in the bpf verifier.
First change is in btf.c, it adds a case in "btf_check_func_arg_match()".
When the passed in "btf->kernel_btf == true", it means matching the
verifier regs' states with a kernel function. This will handle the
PTR_TO_BTF_ID reg. It also maps PTR_TO_SOCK_COMMON, PTR_TO_SOCKET,
and PTR_TO_TCP_SOCK to its kernel's btf_id.
In the later libbpf patch, the insn calling a kernel function will
look like:
insn->code == (BPF_JMP | BPF_CALL)
insn->src_reg == BPF_PSEUDO_KFUNC_CALL /* <- new in this patch */
insn->imm == func_btf_id /* btf_id of the running kernel */
[ For the future calling function-in-kernel-module support, an array
of module btf_fds can be passed at the load time and insn->off
can be used to index into this array. ]
At the early stage of verifier, the verifier will collect all kernel
function calls into "struct bpf_kfunc_desc". Those
descriptors are stored in "prog->aux->kfunc_tab" and will
be available to the JIT. Since this "add" operation is similar
to the current "add_subprog()" and looking for the same insn->code,
they are done together in the new "add_subprog_and_kfunc()".
In the "do_check()" stage, the new "check_kfunc_call()" is added
to verify the kernel function call instruction:
1. Ensure the kernel function can be used by a particular BPF_PROG_TYPE.
A new bpf_verifier_ops "check_kfunc_call" is added to do that.
The bpf-tcp-cc struct_ops program will implement this function in
a later patch.
2. Call "btf_check_kfunc_args_match()" to ensure the regs can be
used as the args of a kernel function.
3. Mark the regs' type, subreg_def, and zext_dst.
At the later do_misc_fixups() stage, the new fixup_kfunc_call()
will replace the insn->imm with the function address (relative
to __bpf_call_base). If needed, the jit can find the btf_func_model
by calling the new bpf_jit_find_kfunc_model(prog, insn).
With the imm set to the function address, "bpftool prog dump xlated"
will be able to display the kernel function calls the same way as
it displays other bpf helper calls.
gpl_compatible program is required to call kernel function.
This feature currently requires JIT.
The verifier selftests are adjusted because of the changes in
the verbose log in add_subprog_and_kfunc().
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015142.1544736-1-kafai@fb.com
2021-03-25 01:51:42 +00:00
|
|
|
bool bpf_prog_has_kfunc_call(const struct bpf_prog *prog);
|
|
|
|
const struct btf_func_model *
|
|
|
|
bpf_jit_find_kfunc_model(const struct bpf_prog *prog,
|
|
|
|
const struct bpf_insn *insn);
|
2021-12-01 18:10:28 +00:00
|
|
|
struct bpf_core_ctx {
|
|
|
|
struct bpf_verifier_log *log;
|
|
|
|
const struct btf *btf;
|
|
|
|
};
|
|
|
|
|
|
|
|
int bpf_core_apply(struct bpf_core_ctx *ctx, const struct bpf_core_relo *relo,
|
|
|
|
int relo_idx, void *insn);
|
|
|
|
|
2022-02-18 19:49:08 +00:00
|
|
|
static inline bool unprivileged_ebpf_enabled(void)
|
|
|
|
{
|
|
|
|
return !sysctl_unprivileged_bpf_disabled;
|
|
|
|
}
|
|
|
|
|
2022-09-16 07:19:14 +00:00
|
|
|
void notrace bpf_prog_inc_misses_counter(struct bpf_prog *prog);
|
2017-10-16 10:19:34 +00:00
|
|
|
#else /* !CONFIG_BPF_SYSCALL */
|
2015-03-01 11:31:44 +00:00
|
|
|
static inline struct bpf_prog *bpf_prog_get(u32 ufd)
|
|
|
|
{
|
|
|
|
return ERR_PTR(-EOPNOTSUPP);
|
|
|
|
}
|
|
|
|
|
2017-11-03 20:56:20 +00:00
|
|
|
static inline struct bpf_prog *bpf_prog_get_type_dev(u32 ufd,
|
|
|
|
enum bpf_prog_type type,
|
2017-11-20 23:21:54 +00:00
|
|
|
bool attach_drv)
|
2017-11-03 20:56:20 +00:00
|
|
|
{
|
|
|
|
return ERR_PTR(-EOPNOTSUPP);
|
|
|
|
}
|
|
|
|
|
2019-11-17 17:28:03 +00:00
|
|
|
static inline void bpf_prog_add(struct bpf_prog *prog, int i)
|
2016-07-20 14:55:52 +00:00
|
|
|
{
|
|
|
|
}
|
2016-06-30 15:24:44 +00:00
|
|
|
|
2016-11-09 21:02:34 +00:00
|
|
|
static inline void bpf_prog_sub(struct bpf_prog *prog, int i)
|
|
|
|
{
|
|
|
|
}
|
|
|
|
|
2015-03-01 11:31:44 +00:00
|
|
|
static inline void bpf_prog_put(struct bpf_prog *prog)
|
|
|
|
{
|
|
|
|
}
|
2016-11-19 00:45:03 +00:00
|
|
|
|
2019-11-17 17:28:03 +00:00
|
|
|
static inline void bpf_prog_inc(struct bpf_prog *prog)
|
2016-09-02 01:37:24 +00:00
|
|
|
{
|
|
|
|
}
|
bpf: fix overflow in prog accounting
Commit aaac3ba95e4c ("bpf: charge user for creation of BPF maps and
programs") made a wrong assumption of charging against prog->pages.
Unlike map->pages, prog->pages are still subject to change when we
need to expand the program through bpf_prog_realloc().
This can for example happen during verification stage when we need to
expand and rewrite parts of the program. Should the required space
cross a page boundary, then prog->pages is not the same anymore as
its original value that we used to bpf_prog_charge_memlock() on. Thus,
we'll hit a wrap-around during bpf_prog_uncharge_memlock() when prog
is freed eventually. I noticed this that despite having unlimited
memlock, programs suddenly refused to load with EPERM error due to
insufficient memlock.
There are two ways to fix this issue. One would be to add a cached
variable to struct bpf_prog that takes a snapshot of prog->pages at the
time of charging. The other approach is to also account for resizes. I
chose to go with the latter for a couple of reasons: i) We want accounting
rather to be more accurate instead of further fooling limits, ii) adding
yet another page counter on struct bpf_prog would also be a waste just
for this purpose. We also do want to charge as early as possible to
avoid going into the verifier just to find out later on that we crossed
limits. The only place that needs to be fixed is bpf_prog_realloc(),
since only here we expand the program, so we try to account for the
needed delta and should we fail, call-sites check for outcome anyway.
On cBPF to eBPF migrations, we don't grab a reference to the user as
they are charged differently. With that in place, my test case worked
fine.
Fixes: aaac3ba95e4c ("bpf: charge user for creation of BPF maps and programs")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-12-18 00:52:58 +00:00
|
|
|
|
2017-08-16 05:32:22 +00:00
|
|
|
static inline struct bpf_prog *__must_check
|
|
|
|
bpf_prog_inc_not_zero(struct bpf_prog *prog)
|
|
|
|
{
|
|
|
|
return ERR_PTR(-EOPNOTSUPP);
|
|
|
|
}
|
|
|
|
|
2020-07-22 06:45:54 +00:00
|
|
|
static inline void bpf_link_init(struct bpf_link *link, enum bpf_link_type type,
|
|
|
|
const struct bpf_link_ops *ops,
|
|
|
|
struct bpf_prog *prog)
|
|
|
|
{
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline int bpf_link_prime(struct bpf_link *link,
|
|
|
|
struct bpf_link_primer *primer)
|
|
|
|
{
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline int bpf_link_settle(struct bpf_link_primer *primer)
|
|
|
|
{
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline void bpf_link_cleanup(struct bpf_link_primer *primer)
|
|
|
|
{
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline void bpf_link_inc(struct bpf_link *link)
|
|
|
|
{
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline void bpf_link_put(struct bpf_link *link)
|
|
|
|
{
|
|
|
|
}
|
|
|
|
|
2017-10-18 20:00:22 +00:00
|
|
|
static inline int bpf_obj_get_user(const char __user *pathname, int flags)
|
netfilter: xt_bpf: Fix XT_BPF_MODE_FD_PINNED mode of 'xt_bpf_info_v1'
Commit 2c16d6033264 ("netfilter: xt_bpf: support ebpf") introduced
support for attaching an eBPF object by an fd, with the
'bpf_mt_check_v1' ABI expecting the '.fd' to be specified upon each
IPT_SO_SET_REPLACE call.
However this breaks subsequent iptables calls:
# iptables -A INPUT -m bpf --object-pinned /sys/fs/bpf/xxx -j ACCEPT
# iptables -A INPUT -s 5.6.7.8 -j ACCEPT
iptables: Invalid argument. Run `dmesg' for more information.
That's because iptables works by loading existing rules using
IPT_SO_GET_ENTRIES to userspace, then issuing IPT_SO_SET_REPLACE with
the replacement set.
However, the loaded 'xt_bpf_info_v1' has an arbitrary '.fd' number
(from the initial "iptables -m bpf" invocation) - so when 2nd invocation
occurs, userspace passes a bogus fd number, which leads to
'bpf_mt_check_v1' to fail.
One suggested solution [1] was to hack iptables userspace, to perform a
"entries fixup" immediatley after IPT_SO_GET_ENTRIES, by opening a new,
process-local fd per every 'xt_bpf_info_v1' entry seen.
However, in [2] both Pablo Neira Ayuso and Willem de Bruijn suggested to
depricate the xt_bpf_info_v1 ABI dealing with pinned ebpf objects.
This fix changes the XT_BPF_MODE_FD_PINNED behavior to ignore the given
'.fd' and instead perform an in-kernel lookup for the bpf object given
the provided '.path'.
It also defines an alias for the XT_BPF_MODE_FD_PINNED mode, named
XT_BPF_MODE_PATH_PINNED, to better reflect the fact that the user is
expected to provide the path of the pinned object.
Existing XT_BPF_MODE_FD_ELF behavior (non-pinned fd mode) is preserved.
References: [1] https://marc.info/?l=netfilter-devel&m=150564724607440&w=2
[2] https://marc.info/?l=netfilter-devel&m=150575727129880&w=2
Reported-by: Rafael Buchbinder <rafi@rbk.ms>
Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2017-10-09 12:27:15 +00:00
|
|
|
{
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
}
|
|
|
|
|
xdp: Use bulking for non-map XDP_REDIRECT and consolidate code paths
Since the bulk queue used by XDP_REDIRECT now lives in struct net_device,
we can re-use the bulking for the non-map version of the bpf_redirect()
helper. This is a simple matter of having xdp_do_redirect_slow() queue the
frame on the bulk queue instead of sending it out with __bpf_tx_xdp().
Unfortunately we can't make the bpf_redirect() helper return an error if
the ifindex doesn't exit (as bpf_redirect_map() does), because we don't
have a reference to the network namespace of the ingress device at the time
the helper is called. So we have to leave it as-is and keep the device
lookup in xdp_do_redirect_slow().
Since this leaves less reason to have the non-map redirect code in a
separate function, so we get rid of the xdp_do_redirect_slow() function
entirely. This does lose us the tracepoint disambiguation, but fortunately
the xdp_redirect and xdp_redirect_map tracepoints use the same tracepoint
entry structures. This means both can contain a map index, so we can just
amend the tracepoint definitions so we always emit the xdp_redirect(_err)
tracepoints, but with the map ID only populated if a map is present. This
means we retire the xdp_redirect_map(_err) tracepoints entirely, but keep
the definitions around in case someone is still listening for them.
With this change, the performance of the xdp_redirect sample program goes
from 5Mpps to 8.4Mpps (a 68% increase).
Since the flush functions are no longer map-specific, rename the flush()
functions to drop _map from their names. One of the renamed functions is
the xdp_do_flush_map() callback used in all the xdp-enabled drivers. To
keep from having to update all drivers, use a #define to keep the old name
working, and only update the virtual drivers in this patch.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/157918768505.1458396.17518057312953572912.stgit@toke.dk
2020-01-16 15:14:45 +00:00
|
|
|
static inline void __dev_flush(void)
|
2017-07-18 04:56:48 +00:00
|
|
|
{
|
|
|
|
}
|
2017-10-16 10:19:34 +00:00
|
|
|
|
2022-01-03 15:08:09 +00:00
|
|
|
struct xdp_frame;
|
2018-05-24 14:45:46 +00:00
|
|
|
struct bpf_dtab_netdev;
|
2021-03-08 11:29:06 +00:00
|
|
|
struct bpf_cpu_map_entry;
|
2018-05-24 14:45:46 +00:00
|
|
|
|
xdp: Use bulking for non-map XDP_REDIRECT and consolidate code paths
Since the bulk queue used by XDP_REDIRECT now lives in struct net_device,
we can re-use the bulking for the non-map version of the bpf_redirect()
helper. This is a simple matter of having xdp_do_redirect_slow() queue the
frame on the bulk queue instead of sending it out with __bpf_tx_xdp().
Unfortunately we can't make the bpf_redirect() helper return an error if
the ifindex doesn't exit (as bpf_redirect_map() does), because we don't
have a reference to the network namespace of the ingress device at the time
the helper is called. So we have to leave it as-is and keep the device
lookup in xdp_do_redirect_slow().
Since this leaves less reason to have the non-map redirect code in a
separate function, so we get rid of the xdp_do_redirect_slow() function
entirely. This does lose us the tracepoint disambiguation, but fortunately
the xdp_redirect and xdp_redirect_map tracepoints use the same tracepoint
entry structures. This means both can contain a map index, so we can just
amend the tracepoint definitions so we always emit the xdp_redirect(_err)
tracepoints, but with the map ID only populated if a map is present. This
means we retire the xdp_redirect_map(_err) tracepoints entirely, but keep
the definitions around in case someone is still listening for them.
With this change, the performance of the xdp_redirect sample program goes
from 5Mpps to 8.4Mpps (a 68% increase).
Since the flush functions are no longer map-specific, rename the flush()
functions to drop _map from their names. One of the renamed functions is
the xdp_do_flush_map() callback used in all the xdp-enabled drivers. To
keep from having to update all drivers, use a #define to keep the old name
working, and only update the virtual drivers in this patch.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/157918768505.1458396.17518057312953572912.stgit@toke.dk
2020-01-16 15:14:45 +00:00
|
|
|
static inline
|
2022-01-03 15:08:09 +00:00
|
|
|
int dev_xdp_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
|
xdp: Use bulking for non-map XDP_REDIRECT and consolidate code paths
Since the bulk queue used by XDP_REDIRECT now lives in struct net_device,
we can re-use the bulking for the non-map version of the bpf_redirect()
helper. This is a simple matter of having xdp_do_redirect_slow() queue the
frame on the bulk queue instead of sending it out with __bpf_tx_xdp().
Unfortunately we can't make the bpf_redirect() helper return an error if
the ifindex doesn't exit (as bpf_redirect_map() does), because we don't
have a reference to the network namespace of the ingress device at the time
the helper is called. So we have to leave it as-is and keep the device
lookup in xdp_do_redirect_slow().
Since this leaves less reason to have the non-map redirect code in a
separate function, so we get rid of the xdp_do_redirect_slow() function
entirely. This does lose us the tracepoint disambiguation, but fortunately
the xdp_redirect and xdp_redirect_map tracepoints use the same tracepoint
entry structures. This means both can contain a map index, so we can just
amend the tracepoint definitions so we always emit the xdp_redirect(_err)
tracepoints, but with the map ID only populated if a map is present. This
means we retire the xdp_redirect_map(_err) tracepoints entirely, but keep
the definitions around in case someone is still listening for them.
With this change, the performance of the xdp_redirect sample program goes
from 5Mpps to 8.4Mpps (a 68% increase).
Since the flush functions are no longer map-specific, rename the flush()
functions to drop _map from their names. One of the renamed functions is
the xdp_do_flush_map() callback used in all the xdp-enabled drivers. To
keep from having to update all drivers, use a #define to keep the old name
working, and only update the virtual drivers in this patch.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/157918768505.1458396.17518057312953572912.stgit@toke.dk
2020-01-16 15:14:45 +00:00
|
|
|
struct net_device *dev_rx)
|
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2018-05-24 14:45:46 +00:00
|
|
|
static inline
|
2022-01-03 15:08:09 +00:00
|
|
|
int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_frame *xdpf,
|
2018-05-24 14:45:57 +00:00
|
|
|
struct net_device *dev_rx)
|
2018-05-24 14:45:46 +00:00
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2021-05-19 09:07:45 +00:00
|
|
|
static inline
|
2022-01-03 15:08:09 +00:00
|
|
|
int dev_map_enqueue_multi(struct xdp_frame *xdpf, struct net_device *dev_rx,
|
2021-05-19 09:07:45 +00:00
|
|
|
struct bpf_map *map, bool exclude_ingress)
|
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2018-06-14 02:07:42 +00:00
|
|
|
struct sk_buff;
|
|
|
|
|
|
|
|
static inline int dev_map_generic_redirect(struct bpf_dtab_netdev *dst,
|
|
|
|
struct sk_buff *skb,
|
|
|
|
struct bpf_prog *xdp_prog)
|
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2021-05-19 09:07:45 +00:00
|
|
|
static inline
|
|
|
|
int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb,
|
|
|
|
struct bpf_prog *xdp_prog, struct bpf_map *map,
|
|
|
|
bool exclude_ingress)
|
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2019-12-19 06:10:04 +00:00
|
|
|
static inline void __cpu_map_flush(void)
|
2017-10-16 10:19:34 +00:00
|
|
|
{
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu,
|
2022-01-03 15:08:09 +00:00
|
|
|
struct xdp_frame *xdpf,
|
2017-10-16 10:19:34 +00:00
|
|
|
struct net_device *dev_rx)
|
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
2017-12-03 01:20:38 +00:00
|
|
|
|
2021-07-02 11:18:23 +00:00
|
|
|
static inline int cpu_map_generic_redirect(struct bpf_cpu_map_entry *rcpu,
|
|
|
|
struct sk_buff *skb)
|
|
|
|
{
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
}
|
|
|
|
|
2017-12-03 01:20:38 +00:00
|
|
|
static inline struct bpf_prog *bpf_prog_get_type_path(const char *name,
|
|
|
|
enum bpf_prog_type type)
|
|
|
|
{
|
|
|
|
return ERR_PTR(-EOPNOTSUPP);
|
|
|
|
}
|
2019-04-11 16:12:02 +00:00
|
|
|
|
|
|
|
static inline int bpf_prog_test_run_xdp(struct bpf_prog *prog,
|
|
|
|
const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr)
|
|
|
|
{
|
|
|
|
return -ENOTSUPP;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline int bpf_prog_test_run_skb(struct bpf_prog *prog,
|
|
|
|
const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr)
|
|
|
|
{
|
|
|
|
return -ENOTSUPP;
|
|
|
|
}
|
|
|
|
|
2020-03-04 19:18:52 +00:00
|
|
|
static inline int bpf_prog_test_run_tracing(struct bpf_prog *prog,
|
|
|
|
const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr)
|
|
|
|
{
|
|
|
|
return -ENOTSUPP;
|
|
|
|
}
|
|
|
|
|
2019-04-11 16:12:02 +00:00
|
|
|
static inline int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
|
|
|
|
const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr)
|
|
|
|
{
|
|
|
|
return -ENOTSUPP;
|
|
|
|
}
|
2019-11-22 20:07:55 +00:00
|
|
|
|
2021-03-03 10:18:13 +00:00
|
|
|
static inline int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog,
|
|
|
|
const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr)
|
|
|
|
{
|
|
|
|
return -ENOTSUPP;
|
|
|
|
}
|
|
|
|
|
2019-11-22 20:07:55 +00:00
|
|
|
static inline void bpf_map_put(struct bpf_map *map)
|
|
|
|
{
|
|
|
|
}
|
2019-12-13 17:51:09 +00:00
|
|
|
|
|
|
|
static inline struct bpf_prog *bpf_prog_by_id(u32 id)
|
|
|
|
{
|
|
|
|
return ERR_PTR(-ENOTSUPP);
|
|
|
|
}
|
2020-04-24 23:59:41 +00:00
|
|
|
|
|
|
|
static inline const struct bpf_func_proto *
|
|
|
|
bpf_base_func_proto(enum bpf_func_id func_id)
|
|
|
|
{
|
|
|
|
return NULL;
|
|
|
|
}
|
2021-02-25 23:43:14 +00:00
|
|
|
|
|
|
|
static inline void bpf_task_storage_free(struct task_struct *task)
|
|
|
|
{
|
|
|
|
}
|
bpf: Support bpf program calling kernel function
This patch adds support to BPF verifier to allow bpf program calling
kernel function directly.
The use case included in this set is to allow bpf-tcp-cc to directly
call some tcp-cc helper functions (e.g. "tcp_cong_avoid_ai()"). Those
functions have already been used by some kernel tcp-cc implementations.
This set will also allow the bpf-tcp-cc program to directly call the
kernel tcp-cc implementation, For example, a bpf_dctcp may only want to
implement its own dctcp_cwnd_event() and reuse other dctcp_*() directly
from the kernel tcp_dctcp.c instead of reimplementing (or
copy-and-pasting) them.
The tcp-cc kernel functions mentioned above will be white listed
for the struct_ops bpf-tcp-cc programs to use in a later patch.
The white listed functions are not bounded to a fixed ABI contract.
Those functions have already been used by the existing kernel tcp-cc.
If any of them has changed, both in-tree and out-of-tree kernel tcp-cc
implementations have to be changed. The same goes for the struct_ops
bpf-tcp-cc programs which have to be adjusted accordingly.
This patch is to make the required changes in the bpf verifier.
First change is in btf.c, it adds a case in "btf_check_func_arg_match()".
When the passed in "btf->kernel_btf == true", it means matching the
verifier regs' states with a kernel function. This will handle the
PTR_TO_BTF_ID reg. It also maps PTR_TO_SOCK_COMMON, PTR_TO_SOCKET,
and PTR_TO_TCP_SOCK to its kernel's btf_id.
In the later libbpf patch, the insn calling a kernel function will
look like:
insn->code == (BPF_JMP | BPF_CALL)
insn->src_reg == BPF_PSEUDO_KFUNC_CALL /* <- new in this patch */
insn->imm == func_btf_id /* btf_id of the running kernel */
[ For the future calling function-in-kernel-module support, an array
of module btf_fds can be passed at the load time and insn->off
can be used to index into this array. ]
At the early stage of verifier, the verifier will collect all kernel
function calls into "struct bpf_kfunc_desc". Those
descriptors are stored in "prog->aux->kfunc_tab" and will
be available to the JIT. Since this "add" operation is similar
to the current "add_subprog()" and looking for the same insn->code,
they are done together in the new "add_subprog_and_kfunc()".
In the "do_check()" stage, the new "check_kfunc_call()" is added
to verify the kernel function call instruction:
1. Ensure the kernel function can be used by a particular BPF_PROG_TYPE.
A new bpf_verifier_ops "check_kfunc_call" is added to do that.
The bpf-tcp-cc struct_ops program will implement this function in
a later patch.
2. Call "btf_check_kfunc_args_match()" to ensure the regs can be
used as the args of a kernel function.
3. Mark the regs' type, subreg_def, and zext_dst.
At the later do_misc_fixups() stage, the new fixup_kfunc_call()
will replace the insn->imm with the function address (relative
to __bpf_call_base). If needed, the jit can find the btf_func_model
by calling the new bpf_jit_find_kfunc_model(prog, insn).
With the imm set to the function address, "bpftool prog dump xlated"
will be able to display the kernel function calls the same way as
it displays other bpf helper calls.
gpl_compatible program is required to call kernel function.
This feature currently requires JIT.
The verifier selftests are adjusted because of the changes in
the verbose log in add_subprog_and_kfunc().
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015142.1544736-1-kafai@fb.com
2021-03-25 01:51:42 +00:00
|
|
|
|
|
|
|
static inline bool bpf_prog_has_kfunc_call(const struct bpf_prog *prog)
|
|
|
|
{
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline const struct btf_func_model *
|
|
|
|
bpf_jit_find_kfunc_model(const struct bpf_prog *prog,
|
|
|
|
const struct bpf_insn *insn)
|
|
|
|
{
|
|
|
|
return NULL;
|
|
|
|
}
|
2022-02-18 19:49:08 +00:00
|
|
|
|
|
|
|
static inline bool unprivileged_ebpf_enabled(void)
|
|
|
|
{
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
2022-09-16 07:19:14 +00:00
|
|
|
static inline void bpf_prog_inc_misses_counter(struct bpf_prog *prog)
|
|
|
|
{
|
|
|
|
}
|
2015-03-02 14:21:55 +00:00
|
|
|
#endif /* CONFIG_BPF_SYSCALL */
|
2014-09-26 07:17:00 +00:00
|
|
|
|
2021-01-12 07:55:18 +00:00
|
|
|
void __bpf_free_used_btfs(struct bpf_prog_aux *aux,
|
|
|
|
struct btf_mod_pair *used_btfs, u32 len);
|
|
|
|
|
2017-11-20 23:21:56 +00:00
|
|
|
static inline struct bpf_prog *bpf_prog_get_type(u32 ufd,
|
|
|
|
enum bpf_prog_type type)
|
|
|
|
{
|
|
|
|
return bpf_prog_get_type_dev(ufd, type, false);
|
|
|
|
}
|
|
|
|
|
2021-01-12 07:55:16 +00:00
|
|
|
void __bpf_free_used_maps(struct bpf_prog_aux *aux,
|
|
|
|
struct bpf_map **used_maps, u32 len);
|
|
|
|
|
2017-12-03 01:20:38 +00:00
|
|
|
bool bpf_prog_get_ok(struct bpf_prog *, enum bpf_prog_type *, bool);
|
|
|
|
|
2017-11-03 20:56:17 +00:00
|
|
|
int bpf_prog_offload_compile(struct bpf_prog *prog);
|
|
|
|
void bpf_prog_offload_destroy(struct bpf_prog *prog);
|
2017-12-28 02:39:09 +00:00
|
|
|
int bpf_prog_offload_info_fill(struct bpf_prog_info *info,
|
|
|
|
struct bpf_prog *prog);
|
2017-11-03 20:56:17 +00:00
|
|
|
|
2018-01-18 03:13:28 +00:00
|
|
|
int bpf_map_offload_info_fill(struct bpf_map_info *info, struct bpf_map *map);
|
|
|
|
|
2018-01-12 04:29:09 +00:00
|
|
|
int bpf_map_offload_lookup_elem(struct bpf_map *map, void *key, void *value);
|
|
|
|
int bpf_map_offload_update_elem(struct bpf_map *map,
|
|
|
|
void *key, void *value, u64 flags);
|
|
|
|
int bpf_map_offload_delete_elem(struct bpf_map *map, void *key);
|
|
|
|
int bpf_map_offload_get_next_key(struct bpf_map *map,
|
|
|
|
void *key, void *next_key);
|
|
|
|
|
2018-07-17 17:53:23 +00:00
|
|
|
bool bpf_offload_prog_map_match(struct bpf_prog *prog, struct bpf_map *map);
|
2018-01-12 04:29:09 +00:00
|
|
|
|
2018-11-09 13:03:25 +00:00
|
|
|
struct bpf_offload_dev *
|
2019-02-12 08:20:39 +00:00
|
|
|
bpf_offload_dev_create(const struct bpf_prog_offload_ops *ops, void *priv);
|
2018-07-17 17:53:25 +00:00
|
|
|
void bpf_offload_dev_destroy(struct bpf_offload_dev *offdev);
|
2019-02-12 08:20:39 +00:00
|
|
|
void *bpf_offload_dev_priv(struct bpf_offload_dev *offdev);
|
2018-07-17 17:53:25 +00:00
|
|
|
int bpf_offload_dev_netdev_register(struct bpf_offload_dev *offdev,
|
|
|
|
struct net_device *netdev);
|
|
|
|
void bpf_offload_dev_netdev_unregister(struct bpf_offload_dev *offdev,
|
|
|
|
struct net_device *netdev);
|
2018-07-17 17:53:26 +00:00
|
|
|
bool bpf_offload_dev_match(struct bpf_prog *prog, struct net_device *netdev);
|
2018-07-17 17:53:24 +00:00
|
|
|
|
2022-04-25 23:40:02 +00:00
|
|
|
void unpriv_ebpf_notify(int new_state);
|
|
|
|
|
2017-11-03 20:56:17 +00:00
|
|
|
#if defined(CONFIG_NET) && defined(CONFIG_BPF_SYSCALL)
|
|
|
|
int bpf_prog_offload_init(struct bpf_prog *prog, union bpf_attr *attr);
|
|
|
|
|
2018-05-09 02:37:06 +00:00
|
|
|
static inline bool bpf_prog_is_dev_bound(const struct bpf_prog_aux *aux)
|
2017-11-03 20:56:17 +00:00
|
|
|
{
|
2017-12-28 02:39:04 +00:00
|
|
|
return aux->offload_requested;
|
2017-11-03 20:56:17 +00:00
|
|
|
}
|
2018-01-12 04:29:09 +00:00
|
|
|
|
|
|
|
static inline bool bpf_map_is_dev_bound(struct bpf_map *map)
|
|
|
|
{
|
|
|
|
return unlikely(map->ops == &bpf_map_offload_ops);
|
|
|
|
}
|
|
|
|
|
|
|
|
struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr);
|
|
|
|
void bpf_map_offload_map_free(struct bpf_map *map);
|
2021-05-14 00:36:03 +00:00
|
|
|
int bpf_prog_test_run_syscall(struct bpf_prog *prog,
|
|
|
|
const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr);
|
2021-07-04 19:02:42 +00:00
|
|
|
|
|
|
|
int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog);
|
|
|
|
int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype);
|
|
|
|
int sock_map_update_elem_sys(struct bpf_map *map, void *key, void *value, u64 flags);
|
2022-01-19 01:40:04 +00:00
|
|
|
int sock_map_bpf_prog_query(const union bpf_attr *attr,
|
|
|
|
union bpf_attr __user *uattr);
|
|
|
|
|
2021-07-04 19:02:42 +00:00
|
|
|
void sock_map_unhash(struct sock *sk);
|
2022-05-24 07:53:11 +00:00
|
|
|
void sock_map_destroy(struct sock *sk);
|
2021-07-04 19:02:42 +00:00
|
|
|
void sock_map_close(struct sock *sk, long timeout);
|
2017-11-03 20:56:17 +00:00
|
|
|
#else
|
|
|
|
static inline int bpf_prog_offload_init(struct bpf_prog *prog,
|
|
|
|
union bpf_attr *attr)
|
|
|
|
{
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline bool bpf_prog_is_dev_bound(struct bpf_prog_aux *aux)
|
|
|
|
{
|
|
|
|
return false;
|
|
|
|
}
|
2018-01-12 04:29:09 +00:00
|
|
|
|
|
|
|
static inline bool bpf_map_is_dev_bound(struct bpf_map *map)
|
|
|
|
{
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr)
|
|
|
|
{
|
|
|
|
return ERR_PTR(-EOPNOTSUPP);
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline void bpf_map_offload_map_free(struct bpf_map *map)
|
|
|
|
{
|
|
|
|
}
|
2021-05-14 00:36:03 +00:00
|
|
|
|
|
|
|
static inline int bpf_prog_test_run_syscall(struct bpf_prog *prog,
|
|
|
|
const union bpf_attr *kattr,
|
|
|
|
union bpf_attr __user *uattr)
|
|
|
|
{
|
|
|
|
return -ENOTSUPP;
|
|
|
|
}
|
2018-06-18 23:04:24 +00:00
|
|
|
|
2021-02-23 18:49:26 +00:00
|
|
|
#ifdef CONFIG_BPF_SYSCALL
|
bpf, sockmap: convert to generic sk_msg interface
Add a generic sk_msg layer, and convert current sockmap and later
kTLS over to make use of it. While sk_buff handles network packet
representation from netdevice up to socket, sk_msg handles data
representation from application to socket layer.
This means that sk_msg framework spans across ULP users in the
kernel, and enables features such as introspection or filtering
of data with the help of BPF programs that operate on this data
structure.
Latter becomes in particular useful for kTLS where data encryption
is deferred into the kernel, and as such enabling the kernel to
perform L7 introspection and policy based on BPF for TLS connections
where the record is being encrypted after BPF has run and came to
a verdict. In order to get there, first step is to transform open
coding of scatter-gather list handling into a common core framework
that subsystems can use.
The code itself has been split and refactored into three bigger
pieces: i) the generic sk_msg API which deals with managing the
scatter gather ring, providing helpers for walking and mangling,
transferring application data from user space into it, and preparing
it for BPF pre/post-processing, ii) the plain sock map itself
where sockets can be attached to or detached from; these bits
are independent of i) which can now be used also without sock
map, and iii) the integration with plain TCP as one protocol
to be used for processing L7 application data (later this could
e.g. also be extended to other protocols like UDP). The semantics
are the same with the old sock map code and therefore no change
of user facing behavior or APIs. While pursuing this work it
also helped finding a number of bugs in the old sockmap code
that we've fixed already in earlier commits. The test_sockmap
kselftest suite passes through fine as well.
Joint work with John.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-10-13 00:45:58 +00:00
|
|
|
static inline int sock_map_get_from_fd(const union bpf_attr *attr,
|
|
|
|
struct bpf_prog *prog)
|
2018-06-18 23:04:24 +00:00
|
|
|
{
|
|
|
|
return -EINVAL;
|
|
|
|
}
|
2020-06-29 09:56:28 +00:00
|
|
|
|
|
|
|
static inline int sock_map_prog_detach(const union bpf_attr *attr,
|
|
|
|
enum bpf_prog_type ptype)
|
|
|
|
{
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
}
|
2020-08-21 10:29:45 +00:00
|
|
|
|
|
|
|
static inline int sock_map_update_elem_sys(struct bpf_map *map, void *key, void *value,
|
|
|
|
u64 flags)
|
|
|
|
{
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
}
|
2022-01-19 01:40:04 +00:00
|
|
|
|
|
|
|
static inline int sock_map_bpf_prog_query(const union bpf_attr *attr,
|
|
|
|
union bpf_attr __user *uattr)
|
|
|
|
{
|
|
|
|
return -EINVAL;
|
|
|
|
}
|
2021-07-04 19:02:42 +00:00
|
|
|
#endif /* CONFIG_BPF_SYSCALL */
|
|
|
|
#endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
|
bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY
This patch introduces a new map type BPF_MAP_TYPE_REUSEPORT_SOCKARRAY.
To unleash the full potential of a bpf prog, it is essential for the
userspace to be capable of directly setting up a bpf map which can then
be consumed by the bpf prog to make decision. In this case, decide which
SO_REUSEPORT sk to serve the incoming request.
By adding BPF_MAP_TYPE_REUSEPORT_SOCKARRAY, the userspace has total control
and visibility on where a SO_REUSEPORT sk should be located in a bpf map.
The later patch will introduce BPF_PROG_TYPE_SK_REUSEPORT such that
the bpf prog can directly select a sk from the bpf map. That will
raise the programmability of the bpf prog attached to a reuseport
group (a group of sk serving the same IP:PORT).
For example, in UDP, the bpf prog can peek into the payload (e.g.
through the "data" pointer introduced in the later patch) to learn
the application level's connection information and then decide which sk
to pick from a bpf map. The userspace can tightly couple the sk's location
in a bpf map with the application logic in generating the UDP payload's
connection information. This connection info contact/API stays within the
userspace.
Also, when used with map-in-map, the userspace can switch the
old-server-process's inner map to a new-server-process's inner map
in one call "bpf_map_update_elem(outer_map, &index, &new_reuseport_array)".
The bpf prog will then direct incoming requests to the new process instead
of the old process. The old process can finish draining the pending
requests (e.g. by "accept()") before closing the old-fds. [Note that
deleting a fd from a bpf map does not necessary mean the fd is closed]
During map_update_elem(),
Only SO_REUSEPORT sk (i.e. which has already been added
to a reuse->socks[]) can be used. That means a SO_REUSEPORT sk that is
"bind()" for UDP or "bind()+listen()" for TCP. These conditions are
ensured in "reuseport_array_update_check()".
A SO_REUSEPORT sk can only be added once to a map (i.e. the
same sk cannot be added twice even to the same map). SO_REUSEPORT
already allows another sk to be created for the same IP:PORT.
There is no need to re-create a similar usage in the BPF side.
When a SO_REUSEPORT is deleted from the "reuse->socks[]" (e.g. "close()"),
it will notify the bpf map to remove it from the map also. It is
done through "bpf_sk_reuseport_detach()" and it will only be called
if >=1 of the "reuse->sock[]" has ever been added to a bpf map.
The map_update()/map_delete() has to be in-sync with the
"reuse->socks[]". Hence, the same "reuseport_lock" used
by "reuse->socks[]" has to be used here also. Care has
been taken to ensure the lock is only acquired when the
adding sk passes some strict tests. and
freeing the map does not require the reuseport_lock.
The reuseport_array will also support lookup from the syscall
side. It will return a sock_gen_cookie(). The sock_gen_cookie()
is on-demand (i.e. a sk's cookie is not generated until the very
first map_lookup_elem()).
The lookup cookie is 64bits but it goes against the logical userspace
expectation on 32bits sizeof(fd) (and as other fd based bpf maps do also).
It may catch user in surprise if we enforce value_size=8 while
userspace still pass a 32bits fd during update. Supporting different
value_size between lookup and update seems unintuitive also.
We also need to consider what if other existing fd based maps want
to return 64bits value from syscall's lookup in the future.
Hence, reuseport_array supports both value_size 4 and 8, and
assuming user will usually use value_size=4. The syscall's lookup
will return ENOSPC on value_size=4. It will will only
return 64bits value from sock_gen_cookie() when user consciously
choose value_size=8 (as a signal that lookup is desired) which then
requires a 64bits value in both lookup and update.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-08-08 08:01:24 +00:00
|
|
|
|
2021-07-04 19:02:42 +00:00
|
|
|
#if defined(CONFIG_INET) && defined(CONFIG_BPF_SYSCALL)
|
|
|
|
void bpf_sk_reuseport_detach(struct sock *sk);
|
|
|
|
int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
|
|
|
|
void *value);
|
|
|
|
int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
|
|
|
|
void *value, u64 map_flags);
|
|
|
|
#else
|
|
|
|
static inline void bpf_sk_reuseport_detach(struct sock *sk)
|
|
|
|
{
|
|
|
|
}
|
bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY
This patch introduces a new map type BPF_MAP_TYPE_REUSEPORT_SOCKARRAY.
To unleash the full potential of a bpf prog, it is essential for the
userspace to be capable of directly setting up a bpf map which can then
be consumed by the bpf prog to make decision. In this case, decide which
SO_REUSEPORT sk to serve the incoming request.
By adding BPF_MAP_TYPE_REUSEPORT_SOCKARRAY, the userspace has total control
and visibility on where a SO_REUSEPORT sk should be located in a bpf map.
The later patch will introduce BPF_PROG_TYPE_SK_REUSEPORT such that
the bpf prog can directly select a sk from the bpf map. That will
raise the programmability of the bpf prog attached to a reuseport
group (a group of sk serving the same IP:PORT).
For example, in UDP, the bpf prog can peek into the payload (e.g.
through the "data" pointer introduced in the later patch) to learn
the application level's connection information and then decide which sk
to pick from a bpf map. The userspace can tightly couple the sk's location
in a bpf map with the application logic in generating the UDP payload's
connection information. This connection info contact/API stays within the
userspace.
Also, when used with map-in-map, the userspace can switch the
old-server-process's inner map to a new-server-process's inner map
in one call "bpf_map_update_elem(outer_map, &index, &new_reuseport_array)".
The bpf prog will then direct incoming requests to the new process instead
of the old process. The old process can finish draining the pending
requests (e.g. by "accept()") before closing the old-fds. [Note that
deleting a fd from a bpf map does not necessary mean the fd is closed]
During map_update_elem(),
Only SO_REUSEPORT sk (i.e. which has already been added
to a reuse->socks[]) can be used. That means a SO_REUSEPORT sk that is
"bind()" for UDP or "bind()+listen()" for TCP. These conditions are
ensured in "reuseport_array_update_check()".
A SO_REUSEPORT sk can only be added once to a map (i.e. the
same sk cannot be added twice even to the same map). SO_REUSEPORT
already allows another sk to be created for the same IP:PORT.
There is no need to re-create a similar usage in the BPF side.
When a SO_REUSEPORT is deleted from the "reuse->socks[]" (e.g. "close()"),
it will notify the bpf map to remove it from the map also. It is
done through "bpf_sk_reuseport_detach()" and it will only be called
if >=1 of the "reuse->sock[]" has ever been added to a bpf map.
The map_update()/map_delete() has to be in-sync with the
"reuse->socks[]". Hence, the same "reuseport_lock" used
by "reuse->socks[]" has to be used here also. Care has
been taken to ensure the lock is only acquired when the
adding sk passes some strict tests. and
freeing the map does not require the reuseport_lock.
The reuseport_array will also support lookup from the syscall
side. It will return a sock_gen_cookie(). The sock_gen_cookie()
is on-demand (i.e. a sk's cookie is not generated until the very
first map_lookup_elem()).
The lookup cookie is 64bits but it goes against the logical userspace
expectation on 32bits sizeof(fd) (and as other fd based bpf maps do also).
It may catch user in surprise if we enforce value_size=8 while
userspace still pass a 32bits fd during update. Supporting different
value_size between lookup and update seems unintuitive also.
We also need to consider what if other existing fd based maps want
to return 64bits value from syscall's lookup in the future.
Hence, reuseport_array supports both value_size 4 and 8, and
assuming user will usually use value_size=4. The syscall's lookup
will return ENOSPC on value_size=4. It will will only
return 64bits value from sock_gen_cookie() when user consciously
choose value_size=8 (as a signal that lookup is desired) which then
requires a 64bits value in both lookup and update.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-08-08 08:01:24 +00:00
|
|
|
|
2021-07-04 19:02:42 +00:00
|
|
|
#ifdef CONFIG_BPF_SYSCALL
|
bpf: Introduce BPF_MAP_TYPE_REUSEPORT_SOCKARRAY
This patch introduces a new map type BPF_MAP_TYPE_REUSEPORT_SOCKARRAY.
To unleash the full potential of a bpf prog, it is essential for the
userspace to be capable of directly setting up a bpf map which can then
be consumed by the bpf prog to make decision. In this case, decide which
SO_REUSEPORT sk to serve the incoming request.
By adding BPF_MAP_TYPE_REUSEPORT_SOCKARRAY, the userspace has total control
and visibility on where a SO_REUSEPORT sk should be located in a bpf map.
The later patch will introduce BPF_PROG_TYPE_SK_REUSEPORT such that
the bpf prog can directly select a sk from the bpf map. That will
raise the programmability of the bpf prog attached to a reuseport
group (a group of sk serving the same IP:PORT).
For example, in UDP, the bpf prog can peek into the payload (e.g.
through the "data" pointer introduced in the later patch) to learn
the application level's connection information and then decide which sk
to pick from a bpf map. The userspace can tightly couple the sk's location
in a bpf map with the application logic in generating the UDP payload's
connection information. This connection info contact/API stays within the
userspace.
Also, when used with map-in-map, the userspace can switch the
old-server-process's inner map to a new-server-process's inner map
in one call "bpf_map_update_elem(outer_map, &index, &new_reuseport_array)".
The bpf prog will then direct incoming requests to the new process instead
of the old process. The old process can finish draining the pending
requests (e.g. by "accept()") before closing the old-fds. [Note that
deleting a fd from a bpf map does not necessary mean the fd is closed]
During map_update_elem(),
Only SO_REUSEPORT sk (i.e. which has already been added
to a reuse->socks[]) can be used. That means a SO_REUSEPORT sk that is
"bind()" for UDP or "bind()+listen()" for TCP. These conditions are
ensured in "reuseport_array_update_check()".
A SO_REUSEPORT sk can only be added once to a map (i.e. the
same sk cannot be added twice even to the same map). SO_REUSEPORT
already allows another sk to be created for the same IP:PORT.
There is no need to re-create a similar usage in the BPF side.
When a SO_REUSEPORT is deleted from the "reuse->socks[]" (e.g. "close()"),
it will notify the bpf map to remove it from the map also. It is
done through "bpf_sk_reuseport_detach()" and it will only be called
if >=1 of the "reuse->sock[]" has ever been added to a bpf map.
The map_update()/map_delete() has to be in-sync with the
"reuse->socks[]". Hence, the same "reuseport_lock" used
by "reuse->socks[]" has to be used here also. Care has
been taken to ensure the lock is only acquired when the
adding sk passes some strict tests. and
freeing the map does not require the reuseport_lock.
The reuseport_array will also support lookup from the syscall
side. It will return a sock_gen_cookie(). The sock_gen_cookie()
is on-demand (i.e. a sk's cookie is not generated until the very
first map_lookup_elem()).
The lookup cookie is 64bits but it goes against the logical userspace
expectation on 32bits sizeof(fd) (and as other fd based bpf maps do also).
It may catch user in surprise if we enforce value_size=8 while
userspace still pass a 32bits fd during update. Supporting different
value_size between lookup and update seems unintuitive also.
We also need to consider what if other existing fd based maps want
to return 64bits value from syscall's lookup in the future.
Hence, reuseport_array supports both value_size 4 and 8, and
assuming user will usually use value_size=4. The syscall's lookup
will return ENOSPC on value_size=4. It will will only
return 64bits value from sock_gen_cookie() when user consciously
choose value_size=8 (as a signal that lookup is desired) which then
requires a 64bits value in both lookup and update.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-08-08 08:01:24 +00:00
|
|
|
static inline int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map,
|
|
|
|
void *key, void *value)
|
|
|
|
{
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline int bpf_fd_reuseport_array_update_elem(struct bpf_map *map,
|
|
|
|
void *key, void *value,
|
|
|
|
u64 map_flags)
|
|
|
|
{
|
|
|
|
return -EOPNOTSUPP;
|
|
|
|
}
|
|
|
|
#endif /* CONFIG_BPF_SYSCALL */
|
|
|
|
#endif /* defined(CONFIG_INET) && defined(CONFIG_BPF_SYSCALL) */
|
|
|
|
|
2014-11-14 01:36:49 +00:00
|
|
|
/* verifier prototypes for helper functions called from eBPF programs */
|
2015-03-01 11:31:42 +00:00
|
|
|
extern const struct bpf_func_proto bpf_map_lookup_elem_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_map_update_elem_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_map_delete_elem_proto;
|
2018-10-18 13:16:25 +00:00
|
|
|
extern const struct bpf_func_proto bpf_map_push_elem_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_map_pop_elem_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_map_peek_elem_proto;
|
2022-05-11 09:38:53 +00:00
|
|
|
extern const struct bpf_func_proto bpf_map_lookup_percpu_elem_proto;
|
2014-11-14 01:36:49 +00:00
|
|
|
|
2015-03-14 01:27:16 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_prandom_u32_proto;
|
2015-03-14 01:27:17 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_smp_processor_id_proto;
|
2016-10-21 10:46:33 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_numa_node_id_proto;
|
bpf: allow bpf programs to tail-call other bpf programs
introduce bpf_tail_call(ctx, &jmp_table, index) helper function
which can be used from BPF programs like:
int bpf_prog(struct pt_regs *ctx)
{
...
bpf_tail_call(ctx, &jmp_table, index);
...
}
that is roughly equivalent to:
int bpf_prog(struct pt_regs *ctx)
{
...
if (jmp_table[index])
return (*jmp_table[index])(ctx);
...
}
The important detail that it's not a normal call, but a tail call.
The kernel stack is precious, so this helper reuses the current
stack frame and jumps into another BPF program without adding
extra call frame.
It's trivially done in interpreter and a bit trickier in JITs.
In case of x64 JIT the bigger part of generated assembler prologue
is common for all programs, so it is simply skipped while jumping.
Other JITs can do similar prologue-skipping optimization or
do stack unwind before jumping into the next program.
bpf_tail_call() arguments:
ctx - context pointer
jmp_table - one of BPF_MAP_TYPE_PROG_ARRAY maps used as the jump table
index - index in the jump table
Since all BPF programs are idenitified by file descriptor, user space
need to populate the jmp_table with FDs of other BPF programs.
If jmp_table[index] is empty the bpf_tail_call() doesn't jump anywhere
and program execution continues as normal.
New BPF_MAP_TYPE_PROG_ARRAY map type is introduced so that user space can
populate this jmp_table array with FDs of other bpf programs.
Programs can share the same jmp_table array or use multiple jmp_tables.
The chain of tail calls can form unpredictable dynamic loops therefore
tail_call_cnt is used to limit the number of calls and currently is set to 32.
Use cases:
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
==========
- simplify complex programs by splitting them into a sequence of small programs
- dispatch routine
For tracing and future seccomp the program may be triggered on all system
calls, but processing of syscall arguments will be different. It's more
efficient to implement them as:
int syscall_entry(struct seccomp_data *ctx)
{
bpf_tail_call(ctx, &syscall_jmp_table, ctx->nr /* syscall number */);
... default: process unknown syscall ...
}
int sys_write_event(struct seccomp_data *ctx) {...}
int sys_read_event(struct seccomp_data *ctx) {...}
syscall_jmp_table[__NR_write] = sys_write_event;
syscall_jmp_table[__NR_read] = sys_read_event;
For networking the program may call into different parsers depending on
packet format, like:
int packet_parser(struct __sk_buff *skb)
{
... parse L2, L3 here ...
__u8 ipproto = load_byte(skb, ... offsetof(struct iphdr, protocol));
bpf_tail_call(skb, &ipproto_jmp_table, ipproto);
... default: process unknown protocol ...
}
int parse_tcp(struct __sk_buff *skb) {...}
int parse_udp(struct __sk_buff *skb) {...}
ipproto_jmp_table[IPPROTO_TCP] = parse_tcp;
ipproto_jmp_table[IPPROTO_UDP] = parse_udp;
- for TC use case, bpf_tail_call() allows to implement reclassify-like logic
- bpf_map_update_elem/delete calls into BPF_MAP_TYPE_PROG_ARRAY jump table
are atomic, so user space can build chains of BPF programs on the fly
Implementation details:
=======================
- high performance of bpf_tail_call() is the goal.
It could have been implemented without JIT changes as a wrapper on top of
BPF_PROG_RUN() macro, but with two downsides:
. all programs would have to pay performance penalty for this feature and
tail call itself would be slower, since mandatory stack unwind, return,
stack allocate would be done for every tailcall.
. tailcall would be limited to programs running preempt_disabled, since
generic 'void *ctx' doesn't have room for 'tail_call_cnt' and it would
need to be either global per_cpu variable accessed by helper and by wrapper
or global variable protected by locks.
In this implementation x64 JIT bypasses stack unwind and jumps into the
callee program after prologue.
- bpf_prog_array_compatible() ensures that prog_type of callee and caller
are the same and JITed/non-JITed flag is the same, since calling JITed
program from non-JITed is invalid, since stack frames are different.
Similarly calling kprobe type program from socket type program is invalid.
- jump table is implemented as BPF_MAP_TYPE_PROG_ARRAY to reuse 'map'
abstraction, its user space API and all of verifier logic.
It's in the existing arraymap.c file, since several functions are
shared with regular array map.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-05-19 23:59:03 +00:00
|
|
|
extern const struct bpf_func_proto bpf_tail_call_proto;
|
2015-05-29 21:23:06 +00:00
|
|
|
extern const struct bpf_func_proto bpf_ktime_get_ns_proto;
|
2020-04-26 16:15:25 +00:00
|
|
|
extern const struct bpf_func_proto bpf_ktime_get_boot_ns_proto;
|
2015-06-13 02:39:12 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_current_pid_tgid_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_get_current_uid_gid_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_get_current_comm_proto;
|
2016-02-18 03:58:58 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_stackid_proto;
|
2018-04-29 05:28:08 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_stack_proto;
|
2020-06-30 06:28:44 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_task_stack_proto;
|
2020-07-23 18:06:44 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_stackid_proto_pe;
|
|
|
|
extern const struct bpf_func_proto bpf_get_stack_proto_pe;
|
2017-08-16 05:32:47 +00:00
|
|
|
extern const struct bpf_func_proto bpf_sock_map_update_proto;
|
2018-05-14 17:00:17 +00:00
|
|
|
extern const struct bpf_func_proto bpf_sock_hash_update_proto;
|
2018-06-03 22:59:41 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_current_cgroup_id_proto;
|
2020-03-27 15:58:54 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto;
|
bpf, sockmap: convert to generic sk_msg interface
Add a generic sk_msg layer, and convert current sockmap and later
kTLS over to make use of it. While sk_buff handles network packet
representation from netdevice up to socket, sk_msg handles data
representation from application to socket layer.
This means that sk_msg framework spans across ULP users in the
kernel, and enables features such as introspection or filtering
of data with the help of BPF programs that operate on this data
structure.
Latter becomes in particular useful for kTLS where data encryption
is deferred into the kernel, and as such enabling the kernel to
perform L7 introspection and policy based on BPF for TLS connections
where the record is being encrypted after BPF has run and came to
a verdict. In order to get there, first step is to transform open
coding of scatter-gather list handling into a common core framework
that subsystems can use.
The code itself has been split and refactored into three bigger
pieces: i) the generic sk_msg API which deals with managing the
scatter gather ring, providing helpers for walking and mangling,
transferring application data from user space into it, and preparing
it for BPF pre/post-processing, ii) the plain sock map itself
where sockets can be attached to or detached from; these bits
are independent of i) which can now be used also without sock
map, and iii) the integration with plain TCP as one protocol
to be used for processing L7 application data (later this could
e.g. also be extended to other protocols like UDP). The semantics
are the same with the old sock map code and therefore no change
of user facing behavior or APIs. While pursuing this work it
also helped finding a number of bugs in the old sockmap code
that we've fixed already in earlier commits. The test_sockmap
kselftest suite passes through fine as well.
Joint work with John.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-10-13 00:45:58 +00:00
|
|
|
extern const struct bpf_func_proto bpf_msg_redirect_hash_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_msg_redirect_map_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_sk_redirect_hash_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_sk_redirect_map_proto;
|
2019-01-31 23:40:04 +00:00
|
|
|
extern const struct bpf_func_proto bpf_spin_lock_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_spin_unlock_proto;
|
2018-08-02 21:27:24 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_local_storage_proto;
|
2019-03-19 00:55:26 +00:00
|
|
|
extern const struct bpf_func_proto bpf_strtol_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_strtoul_proto;
|
bpf: implement getsockopt and setsockopt hooks
Implement new BPF_PROG_TYPE_CGROUP_SOCKOPT program type and
BPF_CGROUP_{G,S}ETSOCKOPT cgroup hooks.
BPF_CGROUP_SETSOCKOPT can modify user setsockopt arguments before
passing them down to the kernel or bypass kernel completely.
BPF_CGROUP_GETSOCKOPT can can inspect/modify getsockopt arguments that
kernel returns.
Both hooks reuse existing PTR_TO_PACKET{,_END} infrastructure.
The buffer memory is pre-allocated (because I don't think there is
a precedent for working with __user memory from bpf). This might be
slow to do for each {s,g}etsockopt call, that's why I've added
__cgroup_bpf_prog_array_is_empty that exits early if there is nothing
attached to a cgroup. Note, however, that there is a race between
__cgroup_bpf_prog_array_is_empty and BPF_PROG_RUN_ARRAY where cgroup
program layout might have changed; this should not be a problem
because in general there is a race between multiple calls to
{s,g}etsocktop and user adding/removing bpf progs from a cgroup.
The return code of the BPF program is handled as follows:
* 0: EPERM
* 1: success, continue with next BPF program in the cgroup chain
v9:
* allow overwriting setsockopt arguments (Alexei Starovoitov):
* use set_fs (same as kernel_setsockopt)
* buffer is always kzalloc'd (no small on-stack buffer)
v8:
* use s32 for optlen (Andrii Nakryiko)
v7:
* return only 0 or 1 (Alexei Starovoitov)
* always run all progs (Alexei Starovoitov)
* use optval=0 as kernel bypass in setsockopt (Alexei Starovoitov)
(decided to use optval=-1 instead, optval=0 might be a valid input)
* call getsockopt hook after kernel handlers (Alexei Starovoitov)
v6:
* rework cgroup chaining; stop as soon as bpf program returns
0 or 2; see patch with the documentation for the details
* drop Andrii's and Martin's Acked-by (not sure they are comfortable
with the new state of things)
v5:
* skip copy_to_user() and put_user() when ret == 0 (Martin Lau)
v4:
* don't export bpf_sk_fullsock helper (Martin Lau)
* size != sizeof(__u64) for uapi pointers (Martin Lau)
* offsetof instead of bpf_ctx_range when checking ctx access (Martin Lau)
v3:
* typos in BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY comments (Andrii Nakryiko)
* reverse christmas tree in BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY (Andrii
Nakryiko)
* use __bpf_md_ptr instead of __u32 for optval{,_end} (Martin Lau)
* use BPF_FIELD_SIZEOF() for consistency (Martin Lau)
* new CG_SOCKOPT_ACCESS macro to wrap repeated parts
v2:
* moved bpf_sockopt_kern fields around to remove a hole (Martin Lau)
* aligned bpf_sockopt_kern->buf to 8 bytes (Martin Lau)
* bpf_prog_array_is_empty instead of bpf_prog_array_length (Martin Lau)
* added [0,2] return code check to verifier (Martin Lau)
* dropped unused buf[64] from the stack (Martin Lau)
* use PTR_TO_SOCKET for bpf_sockopt->sk (Martin Lau)
* dropped bpf_target_off from ctx rewrites (Martin Lau)
* use return code for kernel bypass (Martin Lau & Andrii Nakryiko)
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: Martin Lau <kafai@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-06-27 20:38:47 +00:00
|
|
|
extern const struct bpf_func_proto bpf_tcp_sock_proto;
|
2020-01-22 23:36:46 +00:00
|
|
|
extern const struct bpf_func_proto bpf_jiffies64_proto;
|
2020-03-04 20:41:56 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_ns_current_pid_tgid_proto;
|
2020-04-20 17:46:10 +00:00
|
|
|
extern const struct bpf_func_proto bpf_event_output_data_proto;
|
bpf: Implement BPF ring buffer and verifier support for it
This commit adds a new MPSC ring buffer implementation into BPF ecosystem,
which allows multiple CPUs to submit data to a single shared ring buffer. On
the consumption side, only single consumer is assumed.
Motivation
----------
There are two distinctive motivators for this work, which are not satisfied by
existing perf buffer, which prompted creation of a new ring buffer
implementation.
- more efficient memory utilization by sharing ring buffer across CPUs;
- preserving ordering of events that happen sequentially in time, even
across multiple CPUs (e.g., fork/exec/exit events for a task).
These two problems are independent, but perf buffer fails to satisfy both.
Both are a result of a choice to have per-CPU perf ring buffer. Both can be
also solved by having an MPSC implementation of ring buffer. The ordering
problem could technically be solved for perf buffer with some in-kernel
counting, but given the first one requires an MPSC buffer, the same solution
would solve the second problem automatically.
Semantics and APIs
------------------
Single ring buffer is presented to BPF programs as an instance of BPF map of
type BPF_MAP_TYPE_RINGBUF. Two other alternatives considered, but ultimately
rejected.
One way would be to, similar to BPF_MAP_TYPE_PERF_EVENT_ARRAY, make
BPF_MAP_TYPE_RINGBUF could represent an array of ring buffers, but not enforce
"same CPU only" rule. This would be more familiar interface compatible with
existing perf buffer use in BPF, but would fail if application needed more
advanced logic to lookup ring buffer by arbitrary key. HASH_OF_MAPS addresses
this with current approach. Additionally, given the performance of BPF
ringbuf, many use cases would just opt into a simple single ring buffer shared
among all CPUs, for which current approach would be an overkill.
Another approach could introduce a new concept, alongside BPF map, to
represent generic "container" object, which doesn't necessarily have key/value
interface with lookup/update/delete operations. This approach would add a lot
of extra infrastructure that has to be built for observability and verifier
support. It would also add another concept that BPF developers would have to
familiarize themselves with, new syntax in libbpf, etc. But then would really
provide no additional benefits over the approach of using a map.
BPF_MAP_TYPE_RINGBUF doesn't support lookup/update/delete operations, but so
doesn't few other map types (e.g., queue and stack; array doesn't support
delete, etc).
The approach chosen has an advantage of re-using existing BPF map
infrastructure (introspection APIs in kernel, libbpf support, etc), being
familiar concept (no need to teach users a new type of object in BPF program),
and utilizing existing tooling (bpftool). For common scenario of using
a single ring buffer for all CPUs, it's as simple and straightforward, as
would be with a dedicated "container" object. On the other hand, by being
a map, it can be combined with ARRAY_OF_MAPS and HASH_OF_MAPS map-in-maps to
implement a wide variety of topologies, from one ring buffer for each CPU
(e.g., as a replacement for perf buffer use cases), to a complicated
application hashing/sharding of ring buffers (e.g., having a small pool of
ring buffers with hashed task's tgid being a look up key to preserve order,
but reduce contention).
Key and value sizes are enforced to be zero. max_entries is used to specify
the size of ring buffer and has to be a power of 2 value.
There are a bunch of similarities between perf buffer
(BPF_MAP_TYPE_PERF_EVENT_ARRAY) and new BPF ring buffer semantics:
- variable-length records;
- if there is no more space left in ring buffer, reservation fails, no
blocking;
- memory-mappable data area for user-space applications for ease of
consumption and high performance;
- epoll notifications for new incoming data;
- but still the ability to do busy polling for new data to achieve the
lowest latency, if necessary.
BPF ringbuf provides two sets of APIs to BPF programs:
- bpf_ringbuf_output() allows to *copy* data from one place to a ring
buffer, similarly to bpf_perf_event_output();
- bpf_ringbuf_reserve()/bpf_ringbuf_commit()/bpf_ringbuf_discard() APIs
split the whole process into two steps. First, a fixed amount of space is
reserved. If successful, a pointer to a data inside ring buffer data area
is returned, which BPF programs can use similarly to a data inside
array/hash maps. Once ready, this piece of memory is either committed or
discarded. Discard is similar to commit, but makes consumer ignore the
record.
bpf_ringbuf_output() has disadvantage of incurring extra memory copy, because
record has to be prepared in some other place first. But it allows to submit
records of the length that's not known to verifier beforehand. It also closely
matches bpf_perf_event_output(), so will simplify migration significantly.
bpf_ringbuf_reserve() avoids the extra copy of memory by providing a memory
pointer directly to ring buffer memory. In a lot of cases records are larger
than BPF stack space allows, so many programs have use extra per-CPU array as
a temporary heap for preparing sample. bpf_ringbuf_reserve() avoid this needs
completely. But in exchange, it only allows a known constant size of memory to
be reserved, such that verifier can verify that BPF program can't access
memory outside its reserved record space. bpf_ringbuf_output(), while slightly
slower due to extra memory copy, covers some use cases that are not suitable
for bpf_ringbuf_reserve().
The difference between commit and discard is very small. Discard just marks
a record as discarded, and such records are supposed to be ignored by consumer
code. Discard is useful for some advanced use-cases, such as ensuring
all-or-nothing multi-record submission, or emulating temporary malloc()/free()
within single BPF program invocation.
Each reserved record is tracked by verifier through existing
reference-tracking logic, similar to socket ref-tracking. It is thus
impossible to reserve a record, but forget to submit (or discard) it.
bpf_ringbuf_query() helper allows to query various properties of ring buffer.
Currently 4 are supported:
- BPF_RB_AVAIL_DATA returns amount of unconsumed data in ring buffer;
- BPF_RB_RING_SIZE returns the size of ring buffer;
- BPF_RB_CONS_POS/BPF_RB_PROD_POS returns current logical possition of
consumer/producer, respectively.
Returned values are momentarily snapshots of ring buffer state and could be
off by the time helper returns, so this should be used only for
debugging/reporting reasons or for implementing various heuristics, that take
into account highly-changeable nature of some of those characteristics.
One such heuristic might involve more fine-grained control over poll/epoll
notifications about new data availability in ring buffer. Together with
BPF_RB_NO_WAKEUP/BPF_RB_FORCE_WAKEUP flags for output/commit/discard helpers,
it allows BPF program a high degree of control and, e.g., more efficient
batched notifications. Default self-balancing strategy, though, should be
adequate for most applications and will work reliable and efficiently already.
Design and implementation
-------------------------
This reserve/commit schema allows a natural way for multiple producers, either
on different CPUs or even on the same CPU/in the same BPF program, to reserve
independent records and work with them without blocking other producers. This
means that if BPF program was interruped by another BPF program sharing the
same ring buffer, they will both get a record reserved (provided there is
enough space left) and can work with it and submit it independently. This
applies to NMI context as well, except that due to using a spinlock during
reservation, in NMI context, bpf_ringbuf_reserve() might fail to get a lock,
in which case reservation will fail even if ring buffer is not full.
The ring buffer itself internally is implemented as a power-of-2 sized
circular buffer, with two logical and ever-increasing counters (which might
wrap around on 32-bit architectures, that's not a problem):
- consumer counter shows up to which logical position consumer consumed the
data;
- producer counter denotes amount of data reserved by all producers.
Each time a record is reserved, producer that "owns" the record will
successfully advance producer counter. At that point, data is still not yet
ready to be consumed, though. Each record has 8 byte header, which contains
the length of reserved record, as well as two extra bits: busy bit to denote
that record is still being worked on, and discard bit, which might be set at
commit time if record is discarded. In the latter case, consumer is supposed
to skip the record and move on to the next one. Record header also encodes
record's relative offset from the beginning of ring buffer data area (in
pages). This allows bpf_ringbuf_commit()/bpf_ringbuf_discard() to accept only
the pointer to the record itself, without requiring also the pointer to ring
buffer itself. Ring buffer memory location will be restored from record
metadata header. This significantly simplifies verifier, as well as improving
API usability.
Producer counter increments are serialized under spinlock, so there is
a strict ordering between reservations. Commits, on the other hand, are
completely lockless and independent. All records become available to consumer
in the order of reservations, but only after all previous records where
already committed. It is thus possible for slow producers to temporarily hold
off submitted records, that were reserved later.
Reservation/commit/consumer protocol is verified by litmus tests in
Documentation/litmus-test/bpf-rb.
One interesting implementation bit, that significantly simplifies (and thus
speeds up as well) implementation of both producers and consumers is how data
area is mapped twice contiguously back-to-back in the virtual memory. This
allows to not take any special measures for samples that have to wrap around
at the end of the circular buffer data area, because the next page after the
last data page would be first data page again, and thus the sample will still
appear completely contiguous in virtual memory. See comment and a simple ASCII
diagram showing this visually in bpf_ringbuf_area_alloc().
Another feature that distinguishes BPF ringbuf from perf ring buffer is
a self-pacing notifications of new data being availability.
bpf_ringbuf_commit() implementation will send a notification of new record
being available after commit only if consumer has already caught up right up
to the record being committed. If not, consumer still has to catch up and thus
will see new data anyways without needing an extra poll notification.
Benchmarks (see tools/testing/selftests/bpf/benchs/bench_ringbuf.c) show that
this allows to achieve a very high throughput without having to resort to
tricks like "notify only every Nth sample", which are necessary with perf
buffer. For extreme cases, when BPF program wants more manual control of
notifications, commit/discard/output helpers accept BPF_RB_NO_WAKEUP and
BPF_RB_FORCE_WAKEUP flags, which give full control over notifications of data
availability, but require extra caution and diligence in using this API.
Comparison to alternatives
--------------------------
Before considering implementing BPF ring buffer from scratch existing
alternatives in kernel were evaluated, but didn't seem to meet the needs. They
largely fell into few categores:
- per-CPU buffers (perf, ftrace, etc), which don't satisfy two motivations
outlined above (ordering and memory consumption);
- linked list-based implementations; while some were multi-producer designs,
consuming these from user-space would be very complicated and most
probably not performant; memory-mapping contiguous piece of memory is
simpler and more performant for user-space consumers;
- io_uring is SPSC, but also requires fixed-sized elements. Naively turning
SPSC queue into MPSC w/ lock would have subpar performance compared to
locked reserve + lockless commit, as with BPF ring buffer. Fixed sized
elements would be too limiting for BPF programs, given existing BPF
programs heavily rely on variable-sized perf buffer already;
- specialized implementations (like a new printk ring buffer, [0]) with lots
of printk-specific limitations and implications, that didn't seem to fit
well for intended use with BPF programs.
[0] https://lwn.net/Articles/779550/
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200529075424.3139988-2-andriin@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2020-05-29 07:54:20 +00:00
|
|
|
extern const struct bpf_func_proto bpf_ringbuf_output_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_ringbuf_reserve_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_ringbuf_submit_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_ringbuf_discard_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_ringbuf_query_proto;
|
2022-05-23 21:07:09 +00:00
|
|
|
extern const struct bpf_func_proto bpf_ringbuf_reserve_dynptr_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_ringbuf_submit_dynptr_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_ringbuf_discard_dynptr_proto;
|
2020-06-23 23:08:09 +00:00
|
|
|
extern const struct bpf_func_proto bpf_skc_to_tcp6_sock_proto;
|
2020-06-23 23:08:11 +00:00
|
|
|
extern const struct bpf_func_proto bpf_skc_to_tcp_sock_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_skc_to_tcp_timewait_sock_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_skc_to_tcp_request_sock_proto;
|
2020-06-23 23:08:15 +00:00
|
|
|
extern const struct bpf_func_proto bpf_skc_to_udp6_sock_proto;
|
2021-10-21 13:47:51 +00:00
|
|
|
extern const struct bpf_func_proto bpf_skc_to_unix_sock_proto;
|
2022-05-19 23:30:10 +00:00
|
|
|
extern const struct bpf_func_proto bpf_skc_to_mptcp_sock_proto;
|
2020-08-27 22:01:12 +00:00
|
|
|
extern const struct bpf_func_proto bpf_copy_from_user_proto;
|
bpf: Add bpf_snprintf_btf helper
A helper is added to support tracing kernel type information in BPF
using the BPF Type Format (BTF). Its signature is
long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr,
u32 btf_ptr_size, u64 flags);
struct btf_ptr * specifies
- a pointer to the data to be traced
- the BTF id of the type of data pointed to
- a flags field is provided for future use; these flags
are not to be confused with the BTF_F_* flags
below that control how the btf_ptr is displayed; the
flags member of the struct btf_ptr may be used to
disambiguate types in kernel versus module BTF, etc;
the main distinction is the flags relate to the type
and information needed in identifying it; not how it
is displayed.
For example a BPF program with a struct sk_buff *skb
could do the following:
static struct btf_ptr b = { };
b.ptr = skb;
b.type_id = __builtin_btf_type_id(struct sk_buff, 1);
bpf_snprintf_btf(str, sizeof(str), &b, sizeof(b), 0, 0);
Default output looks like this:
(struct sk_buff){
.transport_header = (__u16)65535,
.mac_header = (__u16)65535,
.end = (sk_buff_data_t)192,
.head = (unsigned char *)0x000000007524fd8b,
.data = (unsigned char *)0x000000007524fd8b,
.truesize = (unsigned int)768,
.users = (refcount_t){
.refs = (atomic_t){
.counter = (int)1,
},
},
}
Flags modifying display are as follows:
- BTF_F_COMPACT: no formatting around type information
- BTF_F_NONAME: no struct/union member names/types
- BTF_F_PTR_RAW: show raw (unobfuscated) pointer values;
equivalent to %px.
- BTF_F_ZERO: show zero-valued struct/union members;
they are not displayed by default
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/1601292670-1616-4-git-send-email-alan.maguire@oracle.com
2020-09-28 11:31:05 +00:00
|
|
|
extern const struct bpf_func_proto bpf_snprintf_btf_proto;
|
2021-04-19 15:52:40 +00:00
|
|
|
extern const struct bpf_func_proto bpf_snprintf_proto;
|
2020-09-29 23:50:47 +00:00
|
|
|
extern const struct bpf_func_proto bpf_per_cpu_ptr_proto;
|
2020-09-29 23:50:48 +00:00
|
|
|
extern const struct bpf_func_proto bpf_this_cpu_ptr_proto;
|
2020-11-17 18:45:49 +00:00
|
|
|
extern const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto;
|
2020-12-08 17:36:23 +00:00
|
|
|
extern const struct bpf_func_proto bpf_sock_from_file_proto;
|
2021-02-10 11:14:03 +00:00
|
|
|
extern const struct bpf_func_proto bpf_get_socket_ptr_cookie_proto;
|
2021-02-25 23:43:14 +00:00
|
|
|
extern const struct bpf_func_proto bpf_task_storage_get_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_task_storage_delete_proto;
|
bpf: Add bpf_for_each_map_elem() helper
The bpf_for_each_map_elem() helper is introduced which
iterates all map elements with a callback function. The
helper signature looks like
long bpf_for_each_map_elem(map, callback_fn, callback_ctx, flags)
and for each map element, the callback_fn will be called. For example,
like hashmap, the callback signature may look like
long callback_fn(map, key, val, callback_ctx)
There are two known use cases for this. One is from upstream ([1]) where
a for_each_map_elem helper may help implement a timeout mechanism
in a more generic way. Another is from our internal discussion
for a firewall use case where a map contains all the rules. The packet
data can be compared to all these rules to decide allow or deny
the packet.
For array maps, users can already use a bounded loop to traverse
elements. Using this helper can avoid using bounded loop. For other
type of maps (e.g., hash maps) where bounded loop is hard or
impossible to use, this helper provides a convenient way to
operate on all elements.
For callback_fn, besides map and map element, a callback_ctx,
allocated on caller stack, is also passed to the callback
function. This callback_ctx argument can provide additional
input and allow to write to caller stack for output.
If the callback_fn returns 0, the helper will iterate through next
element if available. If the callback_fn returns 1, the helper
will stop iterating and returns to the bpf program. Other return
values are not used for now.
Currently, this helper is only available with jit. It is possible
to make it work with interpreter with so effort but I leave it
as the future work.
[1]: https://lore.kernel.org/bpf/20210122205415.113822-1-xiyou.wangcong@gmail.com/
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210226204925.3884923-1-yhs@fb.com
2021-02-26 20:49:25 +00:00
|
|
|
extern const struct bpf_func_proto bpf_for_each_map_elem_proto;
|
2021-05-14 00:36:11 +00:00
|
|
|
extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
|
2021-07-01 20:06:19 +00:00
|
|
|
extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_sk_getsockopt_proto;
|
2022-06-28 17:43:09 +00:00
|
|
|
extern const struct bpf_func_proto bpf_unlocked_sk_setsockopt_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_unlocked_sk_getsockopt_proto;
|
2021-11-05 23:23:29 +00:00
|
|
|
extern const struct bpf_func_proto bpf_find_vma_proto;
|
2021-11-30 03:06:19 +00:00
|
|
|
extern const struct bpf_func_proto bpf_loop_proto;
|
2022-01-24 18:54:01 +00:00
|
|
|
extern const struct bpf_func_proto bpf_copy_from_user_task_proto;
|
2022-06-28 17:43:06 +00:00
|
|
|
extern const struct bpf_func_proto bpf_set_retval_proto;
|
|
|
|
extern const struct bpf_func_proto bpf_get_retval_proto;
|
2018-08-02 21:27:24 +00:00
|
|
|
|
2020-05-31 15:42:55 +00:00
|
|
|
const struct bpf_func_proto *tracing_prog_func_proto(
|
|
|
|
enum bpf_func_id func_id, const struct bpf_prog *prog);
|
|
|
|
|
bpf: split state from prandom_u32() and consolidate {c, e}BPF prngs
While recently arguing on a seccomp discussion that raw prandom_u32()
access shouldn't be exposed to unpriviledged user space, I forgot the
fact that SKF_AD_RANDOM extension actually already does it for some time
in cBPF via commit 4cd3675ebf74 ("filter: added BPF random opcode").
Since prandom_u32() is being used in a lot of critical networking code,
lets be more conservative and split their states. Furthermore, consolidate
eBPF and cBPF prandom handlers to use the new internal PRNG. For eBPF,
bpf_get_prandom_u32() was only accessible for priviledged users, but
should that change one day, we also don't want to leak raw sequences
through things like eBPF maps.
One thought was also to have own per bpf_prog states, but due to ABI
reasons this is not easily possible, i.e. the program code currently
cannot access bpf_prog itself, and copying the rnd_state to/from the
stack scratch space whenever a program uses the prng seems not really
worth the trouble and seems too hacky. If needed, taus113 could in such
cases be implemented within eBPF using a map entry to keep the state
space, or get_random_bytes() could become a second helper in cases where
performance would not be critical.
Both sides can trigger a one-time late init via prandom_init_once() on
the shared state. Performance-wise, there should even be a tiny gain
as bpf_user_rnd_u32() saves one function call. The PRNG needs to live
inside the BPF core since kernels could have a NET-less config as well.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Cc: Chema Gonzalez <chema@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-07 23:20:39 +00:00
|
|
|
/* Shared helpers among cBPF and eBPF. */
|
|
|
|
void bpf_user_rnd_init_once(void);
|
|
|
|
u64 bpf_user_rnd_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
|
2020-04-24 23:59:41 +00:00
|
|
|
u64 bpf_get_raw_cpu_id(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
|
bpf: split state from prandom_u32() and consolidate {c, e}BPF prngs
While recently arguing on a seccomp discussion that raw prandom_u32()
access shouldn't be exposed to unpriviledged user space, I forgot the
fact that SKF_AD_RANDOM extension actually already does it for some time
in cBPF via commit 4cd3675ebf74 ("filter: added BPF random opcode").
Since prandom_u32() is being used in a lot of critical networking code,
lets be more conservative and split their states. Furthermore, consolidate
eBPF and cBPF prandom handlers to use the new internal PRNG. For eBPF,
bpf_get_prandom_u32() was only accessible for priviledged users, but
should that change one day, we also don't want to leak raw sequences
through things like eBPF maps.
One thought was also to have own per bpf_prog states, but due to ABI
reasons this is not easily possible, i.e. the program code currently
cannot access bpf_prog itself, and copying the rnd_state to/from the
stack scratch space whenever a program uses the prng seems not really
worth the trouble and seems too hacky. If needed, taus113 could in such
cases be implemented within eBPF using a map entry to keep the state
space, or get_random_bytes() could become a second helper in cases where
performance would not be critical.
Both sides can trigger a one-time late init via prandom_init_once() on
the shared state. Performance-wise, there should even be a tiny gain
as bpf_user_rnd_u32() saves one function call. The PRNG needs to live
inside the BPF core since kernels could have a NET-less config as well.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Cc: Chema Gonzalez <chema@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-07 23:20:39 +00:00
|
|
|
|
2018-10-02 20:35:33 +00:00
|
|
|
#if defined(CONFIG_NET)
|
bpf: Add a bpf_sock pointer to __sk_buff and a bpf_sk_fullsock helper
In kernel, it is common to check "skb->sk && sk_fullsock(skb->sk)"
before accessing the fields in sock. For example, in __netdev_pick_tx:
static u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb,
struct net_device *sb_dev)
{
/* ... */
struct sock *sk = skb->sk;
if (queue_index != new_index && sk &&
sk_fullsock(sk) &&
rcu_access_pointer(sk->sk_dst_cache))
sk_tx_queue_set(sk, new_index);
/* ... */
return queue_index;
}
This patch adds a "struct bpf_sock *sk" pointer to the "struct __sk_buff"
where a few of the convert_ctx_access() in filter.c has already been
accessing the skb->sk sock_common's fields,
e.g. sock_ops_convert_ctx_access().
"__sk_buff->sk" is a PTR_TO_SOCK_COMMON_OR_NULL in the verifier.
Some of the fileds in "bpf_sock" will not be directly
accessible through the "__sk_buff->sk" pointer. It is limited
by the new "bpf_sock_common_is_valid_access()".
e.g. The existing "type", "protocol", "mark" and "priority" in bpf_sock
are not allowed.
The newly added "struct bpf_sock *bpf_sk_fullsock(struct bpf_sock *sk)"
can be used to get a sk with all accessible fields in "bpf_sock".
This helper is added to both cg_skb and sched_(cls|act).
int cg_skb_foo(struct __sk_buff *skb) {
struct bpf_sock *sk;
sk = skb->sk;
if (!sk)
return 1;
sk = bpf_sk_fullsock(sk);
if (!sk)
return 1;
if (sk->family != AF_INET6 || sk->protocol != IPPROTO_TCP)
return 1;
/* some_traffic_shaping(); */
return 1;
}
(1) The sk is read only
(2) There is no new "struct bpf_sock_common" introduced.
(3) Future kernel sock's members could be added to bpf_sock only
instead of repeatedly adding at multiple places like currently
in bpf_sock_ops_md, bpf_sock_addr_md, sk_reuseport_md...etc.
(4) After "sk = skb->sk", the reg holding sk is in type
PTR_TO_SOCK_COMMON_OR_NULL.
(5) After bpf_sk_fullsock(), the return type will be in type
PTR_TO_SOCKET_OR_NULL which is the same as the return type of
bpf_sk_lookup_xxx().
However, bpf_sk_fullsock() does not take refcnt. The
acquire_reference_state() is only depending on the return type now.
To avoid it, a new is_acquire_function() is checked before calling
acquire_reference_state().
(6) The WARN_ON in "release_reference_state()" is no longer an
internal verifier bug.
When reg->id is not found in state->refs[], it means the
bpf_prog does something wrong like
"bpf_sk_release(bpf_sk_fullsock(skb->sk))" where reference has
never been acquired by calling "bpf_sk_fullsock(skb->sk)".
A -EINVAL and a verbose are done instead of WARN_ON. A test is
added to the test_verifier in a later patch.
Since the WARN_ON in "release_reference_state()" is no longer
needed, "__release_reference_state()" is folded into
"release_reference_state()" also.
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-02-10 07:22:20 +00:00
|
|
|
bool bpf_sock_common_is_valid_access(int off, int size,
|
|
|
|
enum bpf_access_type type,
|
|
|
|
struct bpf_insn_access_aux *info);
|
2018-10-02 20:35:33 +00:00
|
|
|
bool bpf_sock_is_valid_access(int off, int size, enum bpf_access_type type,
|
|
|
|
struct bpf_insn_access_aux *info);
|
|
|
|
u32 bpf_sock_convert_ctx_access(enum bpf_access_type type,
|
|
|
|
const struct bpf_insn *si,
|
|
|
|
struct bpf_insn *insn_buf,
|
|
|
|
struct bpf_prog *prog,
|
|
|
|
u32 *target_size);
|
|
|
|
#else
|
bpf: Add a bpf_sock pointer to __sk_buff and a bpf_sk_fullsock helper
In kernel, it is common to check "skb->sk && sk_fullsock(skb->sk)"
before accessing the fields in sock. For example, in __netdev_pick_tx:
static u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb,
struct net_device *sb_dev)
{
/* ... */
struct sock *sk = skb->sk;
if (queue_index != new_index && sk &&
sk_fullsock(sk) &&
rcu_access_pointer(sk->sk_dst_cache))
sk_tx_queue_set(sk, new_index);
/* ... */
return queue_index;
}
This patch adds a "struct bpf_sock *sk" pointer to the "struct __sk_buff"
where a few of the convert_ctx_access() in filter.c has already been
accessing the skb->sk sock_common's fields,
e.g. sock_ops_convert_ctx_access().
"__sk_buff->sk" is a PTR_TO_SOCK_COMMON_OR_NULL in the verifier.
Some of the fileds in "bpf_sock" will not be directly
accessible through the "__sk_buff->sk" pointer. It is limited
by the new "bpf_sock_common_is_valid_access()".
e.g. The existing "type", "protocol", "mark" and "priority" in bpf_sock
are not allowed.
The newly added "struct bpf_sock *bpf_sk_fullsock(struct bpf_sock *sk)"
can be used to get a sk with all accessible fields in "bpf_sock".
This helper is added to both cg_skb and sched_(cls|act).
int cg_skb_foo(struct __sk_buff *skb) {
struct bpf_sock *sk;
sk = skb->sk;
if (!sk)
return 1;
sk = bpf_sk_fullsock(sk);
if (!sk)
return 1;
if (sk->family != AF_INET6 || sk->protocol != IPPROTO_TCP)
return 1;
/* some_traffic_shaping(); */
return 1;
}
(1) The sk is read only
(2) There is no new "struct bpf_sock_common" introduced.
(3) Future kernel sock's members could be added to bpf_sock only
instead of repeatedly adding at multiple places like currently
in bpf_sock_ops_md, bpf_sock_addr_md, sk_reuseport_md...etc.
(4) After "sk = skb->sk", the reg holding sk is in type
PTR_TO_SOCK_COMMON_OR_NULL.
(5) After bpf_sk_fullsock(), the return type will be in type
PTR_TO_SOCKET_OR_NULL which is the same as the return type of
bpf_sk_lookup_xxx().
However, bpf_sk_fullsock() does not take refcnt. The
acquire_reference_state() is only depending on the return type now.
To avoid it, a new is_acquire_function() is checked before calling
acquire_reference_state().
(6) The WARN_ON in "release_reference_state()" is no longer an
internal verifier bug.
When reg->id is not found in state->refs[], it means the
bpf_prog does something wrong like
"bpf_sk_release(bpf_sk_fullsock(skb->sk))" where reference has
never been acquired by calling "bpf_sk_fullsock(skb->sk)".
A -EINVAL and a verbose are done instead of WARN_ON. A test is
added to the test_verifier in a later patch.
Since the WARN_ON in "release_reference_state()" is no longer
needed, "__release_reference_state()" is folded into
"release_reference_state()" also.
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-02-10 07:22:20 +00:00
|
|
|
static inline bool bpf_sock_common_is_valid_access(int off, int size,
|
|
|
|
enum bpf_access_type type,
|
|
|
|
struct bpf_insn_access_aux *info)
|
|
|
|
{
|
|
|
|
return false;
|
|
|
|
}
|
2018-10-02 20:35:33 +00:00
|
|
|
static inline bool bpf_sock_is_valid_access(int off, int size,
|
|
|
|
enum bpf_access_type type,
|
|
|
|
struct bpf_insn_access_aux *info)
|
|
|
|
{
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
static inline u32 bpf_sock_convert_ctx_access(enum bpf_access_type type,
|
|
|
|
const struct bpf_insn *si,
|
|
|
|
struct bpf_insn *insn_buf,
|
|
|
|
struct bpf_prog *prog,
|
|
|
|
u32 *target_size)
|
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
#endif
|
|
|
|
|
2019-02-10 07:22:24 +00:00
|
|
|
#ifdef CONFIG_INET
|
2019-11-14 18:57:15 +00:00
|
|
|
struct sk_reuseport_kern {
|
|
|
|
struct sk_buff *skb;
|
|
|
|
struct sock *sk;
|
|
|
|
struct sock *selected_sk;
|
bpf: Support socket migration by eBPF.
This patch introduces a new bpf_attach_type for BPF_PROG_TYPE_SK_REUSEPORT
to check if the attached eBPF program is capable of migrating sockets. When
the eBPF program is attached, we run it for socket migration if the
expected_attach_type is BPF_SK_REUSEPORT_SELECT_OR_MIGRATE or
net.ipv4.tcp_migrate_req is enabled.
Currently, the expected_attach_type is not enforced for the
BPF_PROG_TYPE_SK_REUSEPORT type of program. Thus, this commit follows the
earlier idea in the commit aac3fc320d94 ("bpf: Post-hooks for sys_bind") to
fix up the zero expected_attach_type in bpf_prog_load_fixup_attach_type().
Moreover, this patch adds a new field (migrating_sk) to sk_reuseport_md to
select a new listener based on the child socket. migrating_sk varies
depending on if it is migrating a request in the accept queue or during
3WHS.
- accept_queue : sock (ESTABLISHED/SYN_RECV)
- 3WHS : request_sock (NEW_SYN_RECV)
In the eBPF program, we can select a new listener by
BPF_FUNC_sk_select_reuseport(). Also, we can cancel migration by returning
SK_DROP. This feature is useful when listeners have different settings at
the socket API level or when we want to free resources as soon as possible.
- SK_PASS with selected_sk, select it as a new listener
- SK_PASS with selected_sk NULL, fallbacks to the random selection
- SK_DROP, cancel the migration.
There is a noteworthy point. We select a listening socket in three places,
but we do not have struct skb at closing a listener or retransmitting a
SYN+ACK. On the other hand, some helper functions do not expect skb is NULL
(e.g. skb_header_pointer() in BPF_FUNC_skb_load_bytes(), skb_tail_pointer()
in BPF_FUNC_skb_load_bytes_relative()). So we allocate an empty skb
temporarily before running the eBPF program.
Suggested-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/netdev/20201123003828.xjpjdtk4ygl6tg6h@kafai-mbp.dhcp.thefacebook.com/
Link: https://lore.kernel.org/netdev/20201203042402.6cskdlit5f3mw4ru@kafai-mbp.dhcp.thefacebook.com/
Link: https://lore.kernel.org/netdev/20201209030903.hhow5r53l6fmozjn@kafai-mbp.dhcp.thefacebook.com/
Link: https://lore.kernel.org/bpf/20210612123224.12525-10-kuniyu@amazon.co.jp
2021-06-12 12:32:22 +00:00
|
|
|
struct sock *migrating_sk;
|
2019-11-14 18:57:15 +00:00
|
|
|
void *data_end;
|
|
|
|
u32 hash;
|
|
|
|
u32 reuseport_id;
|
|
|
|
bool bind_inany;
|
|
|
|
};
|
2019-02-10 07:22:24 +00:00
|
|
|
bool bpf_tcp_sock_is_valid_access(int off, int size, enum bpf_access_type type,
|
|
|
|
struct bpf_insn_access_aux *info);
|
|
|
|
|
|
|
|
u32 bpf_tcp_sock_convert_ctx_access(enum bpf_access_type type,
|
|
|
|
const struct bpf_insn *si,
|
|
|
|
struct bpf_insn *insn_buf,
|
|
|
|
struct bpf_prog *prog,
|
|
|
|
u32 *target_size);
|
2019-06-12 09:18:47 +00:00
|
|
|
|
|
|
|
bool bpf_xdp_sock_is_valid_access(int off, int size, enum bpf_access_type type,
|
|
|
|
struct bpf_insn_access_aux *info);
|
|
|
|
|
|
|
|
u32 bpf_xdp_sock_convert_ctx_access(enum bpf_access_type type,
|
|
|
|
const struct bpf_insn *si,
|
|
|
|
struct bpf_insn *insn_buf,
|
|
|
|
struct bpf_prog *prog,
|
|
|
|
u32 *target_size);
|
2019-02-10 07:22:24 +00:00
|
|
|
#else
|
|
|
|
static inline bool bpf_tcp_sock_is_valid_access(int off, int size,
|
|
|
|
enum bpf_access_type type,
|
|
|
|
struct bpf_insn_access_aux *info)
|
|
|
|
{
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline u32 bpf_tcp_sock_convert_ctx_access(enum bpf_access_type type,
|
|
|
|
const struct bpf_insn *si,
|
|
|
|
struct bpf_insn *insn_buf,
|
|
|
|
struct bpf_prog *prog,
|
|
|
|
u32 *target_size)
|
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
2019-06-12 09:18:47 +00:00
|
|
|
static inline bool bpf_xdp_sock_is_valid_access(int off, int size,
|
|
|
|
enum bpf_access_type type,
|
|
|
|
struct bpf_insn_access_aux *info)
|
|
|
|
{
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline u32 bpf_xdp_sock_convert_ctx_access(enum bpf_access_type type,
|
|
|
|
const struct bpf_insn *si,
|
|
|
|
struct bpf_insn *insn_buf,
|
|
|
|
struct bpf_prog *prog,
|
|
|
|
u32 *target_size)
|
|
|
|
{
|
|
|
|
return 0;
|
|
|
|
}
|
2019-02-10 07:22:24 +00:00
|
|
|
#endif /* CONFIG_INET */
|
|
|
|
|
2019-11-14 18:57:03 +00:00
|
|
|
enum bpf_text_poke_type {
|
2019-11-24 00:39:42 +00:00
|
|
|
BPF_MOD_CALL,
|
|
|
|
BPF_MOD_JUMP,
|
2019-11-14 18:57:03 +00:00
|
|
|
};
|
2019-11-22 20:07:54 +00:00
|
|
|
|
2019-11-14 18:57:03 +00:00
|
|
|
int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
|
|
|
|
void *addr1, void *addr2);
|
|
|
|
|
2022-02-04 18:57:39 +00:00
|
|
|
void *bpf_arch_text_copy(void *dst, void *src, size_t len);
|
2022-05-20 23:57:53 +00:00
|
|
|
int bpf_arch_text_invalidate(void *dst, size_t len);
|
2022-02-04 18:57:39 +00:00
|
|
|
|
2020-08-25 19:21:19 +00:00
|
|
|
struct btf_id_set;
|
2020-09-21 12:12:17 +00:00
|
|
|
bool btf_id_set_contains(const struct btf_id_set *set, u32 id);
|
2020-08-25 19:21:19 +00:00
|
|
|
|
2021-09-17 18:29:03 +00:00
|
|
|
#define MAX_BPRINTF_VARARGS 12
|
|
|
|
|
bpf: Implement formatted output helpers with bstr_printf
BPF has three formatted output helpers: bpf_trace_printk, bpf_seq_printf
and bpf_snprintf. Their signatures specify that all arguments are
provided from the BPF world as u64s (in an array or as registers). All
of these helpers are currently implemented by calling functions such as
snprintf() whose signatures take a variable number of arguments, then
placed in a va_list by the compiler to call vsnprintf().
"d9c9e4db bpf: Factorize bpf_trace_printk and bpf_seq_printf" introduced
a bpf_printf_prepare function that fills an array of u64 sanitized
arguments with an array of "modifiers" which indicate what the "real"
size of each argument should be (given by the format specifier). The
BPF_CAST_FMT_ARG macro consumes these arrays and casts each argument to
its real size. However, the C promotion rules implicitely cast them all
back to u64s. Therefore, the arguments given to snprintf are u64s and
the va_list constructed by the compiler will use 64 bits for each
argument. On 64 bit machines, this happens to work well because 32 bit
arguments in va_lists need to occupy 64 bits anyway, but on 32 bit
architectures this breaks the layout of the va_list expected by the
called function and mangles values.
In "88a5c690b6 bpf: fix bpf_trace_printk on 32 bit archs", this problem
had been solved for bpf_trace_printk only with a "horrid workaround"
that emitted multiple calls to trace_printk where each call had
different argument types and generated different va_list layouts. One of
the call would be dynamically chosen at runtime. This was ok with the 3
arguments that bpf_trace_printk takes but bpf_seq_printf and
bpf_snprintf accept up to 12 arguments. Because this approach scales
code exponentially, it is not a viable option anymore.
Because the promotion rules are part of the language and because the
construction of a va_list is an arch-specific ABI, it's best to just
avoid variadic arguments and va_lists altogether. Thankfully the
kernel's snprintf() has an alternative in the form of bstr_printf() that
accepts arguments in a "binary buffer representation". These binary
buffers are currently created by vbin_printf and used in the tracing
subsystem to split the cost of printing into two parts: a fast one that
only dereferences and remembers values, and a slower one, called later,
that does the pretty-printing.
This patch refactors bpf_printf_prepare to construct binary buffers of
arguments consumable by bstr_printf() instead of arrays of arguments and
modifiers. This gets rid of BPF_CAST_FMT_ARG and greatly simplifies the
bpf_printf_prepare usage but there are a few gotchas that change how
bpf_printf_prepare needs to do things.
Currently, bpf_printf_prepare uses a per cpu temporary buffer as a
generic storage for strings and IP addresses. With this refactoring, the
temporary buffers now holds all the arguments in a structured binary
format.
To comply with the format expected by bstr_printf, certain format
specifiers also need to be pre-formatted: %pB and %pi6/%pi4/%pI4/%pI6.
Because vsnprintf subroutines for these specifiers are hard to expose,
we pre-format these arguments with calls to snprintf().
Reported-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210427174313.860948-3-revest@chromium.org
2021-04-27 17:43:13 +00:00
|
|
|
int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
|
|
|
|
u32 **bin_buf, u32 num_args);
|
|
|
|
void bpf_bprintf_cleanup(void);
|
2021-04-19 15:52:38 +00:00
|
|
|
|
bpf: Add verifier support for dynptrs
This patch adds the bulk of the verifier work for supporting dynamic
pointers (dynptrs) in bpf.
A bpf_dynptr is opaque to the bpf program. It is a 16-byte structure
defined internally as:
struct bpf_dynptr_kern {
void *data;
u32 size;
u32 offset;
} __aligned(8);
The upper 8 bits of *size* is reserved (it contains extra metadata about
read-only status and dynptr type). Consequently, a dynptr only supports
memory less than 16 MB.
There are different types of dynptrs (eg malloc, ringbuf, ...). In this
patchset, the most basic one, dynptrs to a bpf program's local memory,
is added. For now only local memory that is of reg type PTR_TO_MAP_VALUE
is supported.
In the verifier, dynptr state information will be tracked in stack
slots. When the program passes in an uninitialized dynptr
(ARG_PTR_TO_DYNPTR | MEM_UNINIT), the stack slots corresponding
to the frame pointer where the dynptr resides at are marked
STACK_DYNPTR. For helper functions that take in initialized dynptrs (eg
bpf_dynptr_read + bpf_dynptr_write which are added later in this
patchset), the verifier enforces that the dynptr has been initialized
properly by checking that their corresponding stack slots have been
marked as STACK_DYNPTR.
The 6th patch in this patchset adds test cases that the verifier should
successfully reject, such as for example attempting to use a dynptr
after doing a direct write into it inside the bpf program.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20220523210712.3641569-2-joannelkoong@gmail.com
2022-05-23 21:07:07 +00:00
|
|
|
/* the implementation of the opaque uapi struct bpf_dynptr */
|
|
|
|
struct bpf_dynptr_kern {
|
|
|
|
void *data;
|
|
|
|
/* Size represents the number of usable bytes of dynptr data.
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* If for example the offset is at 4 for a local dynptr whose data is
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* of type u64, the number of usable bytes is 4.
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*
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* The upper 8 bits are reserved. It is as follows:
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* Bits 0 - 23 = size
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* Bits 24 - 30 = dynptr type
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* Bit 31 = whether dynptr is read-only
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*/
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u32 size;
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u32 offset;
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} __aligned(8);
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enum bpf_dynptr_type {
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BPF_DYNPTR_TYPE_INVALID,
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|
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/* Points to memory that is local to the bpf program */
|
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BPF_DYNPTR_TYPE_LOCAL,
|
2022-05-23 21:07:09 +00:00
|
|
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/* Underlying data is a ringbuf record */
|
|
|
|
BPF_DYNPTR_TYPE_RINGBUF,
|
bpf: Add verifier support for dynptrs
This patch adds the bulk of the verifier work for supporting dynamic
pointers (dynptrs) in bpf.
A bpf_dynptr is opaque to the bpf program. It is a 16-byte structure
defined internally as:
struct bpf_dynptr_kern {
void *data;
u32 size;
u32 offset;
} __aligned(8);
The upper 8 bits of *size* is reserved (it contains extra metadata about
read-only status and dynptr type). Consequently, a dynptr only supports
memory less than 16 MB.
There are different types of dynptrs (eg malloc, ringbuf, ...). In this
patchset, the most basic one, dynptrs to a bpf program's local memory,
is added. For now only local memory that is of reg type PTR_TO_MAP_VALUE
is supported.
In the verifier, dynptr state information will be tracked in stack
slots. When the program passes in an uninitialized dynptr
(ARG_PTR_TO_DYNPTR | MEM_UNINIT), the stack slots corresponding
to the frame pointer where the dynptr resides at are marked
STACK_DYNPTR. For helper functions that take in initialized dynptrs (eg
bpf_dynptr_read + bpf_dynptr_write which are added later in this
patchset), the verifier enforces that the dynptr has been initialized
properly by checking that their corresponding stack slots have been
marked as STACK_DYNPTR.
The 6th patch in this patchset adds test cases that the verifier should
successfully reject, such as for example attempting to use a dynptr
after doing a direct write into it inside the bpf program.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20220523210712.3641569-2-joannelkoong@gmail.com
2022-05-23 21:07:07 +00:00
|
|
|
};
|
|
|
|
|
2022-05-23 21:07:09 +00:00
|
|
|
void bpf_dynptr_init(struct bpf_dynptr_kern *ptr, void *data,
|
|
|
|
enum bpf_dynptr_type type, u32 offset, u32 size);
|
|
|
|
void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr);
|
|
|
|
int bpf_dynptr_check_size(u32 size);
|
|
|
|
|
2022-06-28 17:43:07 +00:00
|
|
|
#ifdef CONFIG_BPF_LSM
|
|
|
|
void bpf_cgroup_atype_get(u32 attach_btf_id, int cgroup_atype);
|
|
|
|
void bpf_cgroup_atype_put(int cgroup_atype);
|
|
|
|
#else
|
|
|
|
static inline void bpf_cgroup_atype_get(u32 attach_btf_id, int cgroup_atype) {}
|
|
|
|
static inline void bpf_cgroup_atype_put(int cgroup_atype) {}
|
|
|
|
#endif /* CONFIG_BPF_LSM */
|
|
|
|
|
2014-09-26 07:16:57 +00:00
|
|
|
#endif /* _LINUX_BPF_H */
|