bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP

This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
the bpf_sk_storage_(get|delete) helper, so those tracing programs
can access the sk's bpf_local_storage and the later selftest
will show some examples.

The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
cg sockops...etc which is running either in softirq or
task context.

This patch adds bpf_sk_storage_get_tracing_proto and
bpf_sk_storage_delete_tracing_proto.  They will check
in runtime that the helpers can only be called when serving
softirq or running in a task context.  That should enable
most common tracing use cases on sk.

During the load time, the new tracing_allowed() function
will ensure the tracing prog using the bpf_sk_storage_(get|delete)
helper is not tracing any bpf_sk_storage*() function itself.
The sk is passed as "void *" when calling into bpf_local_storage.

This patch only allows tracing a kernel function.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201112211313.2587383-1-kafai@fb.com
This commit is contained in:
Martin KaFai Lau 2020-11-12 13:13:13 -08:00 committed by Alexei Starovoitov
parent e794bfddb8
commit 8e4597c627
3 changed files with 81 additions and 0 deletions

View file

@ -20,6 +20,8 @@ void bpf_sk_storage_free(struct sock *sk);
extern const struct bpf_func_proto bpf_sk_storage_get_proto;
extern const struct bpf_func_proto bpf_sk_storage_delete_proto;
extern const struct bpf_func_proto bpf_sk_storage_get_tracing_proto;
extern const struct bpf_func_proto bpf_sk_storage_delete_tracing_proto;
struct bpf_local_storage_elem;
struct bpf_sk_storage_diag;

View file

@ -16,6 +16,7 @@
#include <linux/syscalls.h>
#include <linux/error-injection.h>
#include <linux/btf_ids.h>
#include <net/bpf_sk_storage.h>
#include <uapi/linux/bpf.h>
#include <uapi/linux/btf.h>
@ -1735,6 +1736,10 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_skc_to_tcp_request_sock_proto;
case BPF_FUNC_skc_to_udp6_sock:
return &bpf_skc_to_udp6_sock_proto;
case BPF_FUNC_sk_storage_get:
return &bpf_sk_storage_get_tracing_proto;
case BPF_FUNC_sk_storage_delete:
return &bpf_sk_storage_delete_tracing_proto;
#endif
case BPF_FUNC_seq_printf:
return prog->expected_attach_type == BPF_TRACE_ITER ?

View file

@ -6,6 +6,7 @@
#include <linux/types.h>
#include <linux/spinlock.h>
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/btf_ids.h>
#include <linux/bpf_local_storage.h>
#include <net/bpf_sk_storage.h>
@ -378,6 +379,79 @@ const struct bpf_func_proto bpf_sk_storage_delete_proto = {
.arg2_type = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
};
static bool bpf_sk_storage_tracing_allowed(const struct bpf_prog *prog)
{
const struct btf *btf_vmlinux;
const struct btf_type *t;
const char *tname;
u32 btf_id;
if (prog->aux->dst_prog)
return false;
/* Ensure the tracing program is not tracing
* any bpf_sk_storage*() function and also
* use the bpf_sk_storage_(get|delete) helper.
*/
switch (prog->expected_attach_type) {
case BPF_TRACE_RAW_TP:
/* bpf_sk_storage has no trace point */
return true;
case BPF_TRACE_FENTRY:
case BPF_TRACE_FEXIT:
btf_vmlinux = bpf_get_btf_vmlinux();
btf_id = prog->aux->attach_btf_id;
t = btf_type_by_id(btf_vmlinux, btf_id);
tname = btf_name_by_offset(btf_vmlinux, t->name_off);
return !!strncmp(tname, "bpf_sk_storage",
strlen("bpf_sk_storage"));
default:
return false;
}
return false;
}
BPF_CALL_4(bpf_sk_storage_get_tracing, struct bpf_map *, map, struct sock *, sk,
void *, value, u64, flags)
{
if (!in_serving_softirq() && !in_task())
return (unsigned long)NULL;
return (unsigned long)____bpf_sk_storage_get(map, sk, value, flags);
}
BPF_CALL_2(bpf_sk_storage_delete_tracing, struct bpf_map *, map,
struct sock *, sk)
{
if (!in_serving_softirq() && !in_task())
return -EPERM;
return ____bpf_sk_storage_delete(map, sk);
}
const struct bpf_func_proto bpf_sk_storage_get_tracing_proto = {
.func = bpf_sk_storage_get_tracing,
.gpl_only = false,
.ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_PTR_TO_BTF_ID,
.arg2_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
.arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL,
.arg4_type = ARG_ANYTHING,
.allowed = bpf_sk_storage_tracing_allowed,
};
const struct bpf_func_proto bpf_sk_storage_delete_tracing_proto = {
.func = bpf_sk_storage_delete_tracing,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_PTR_TO_BTF_ID,
.arg2_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
.allowed = bpf_sk_storage_tracing_allowed,
};
struct bpf_sk_storage_diag {
u32 nr_maps;
struct bpf_map *maps[];