Let's make kernel stacktraces easier to identify by including the build
ID[1] of a module if the stacktrace is printing a symbol from a module.
This makes it simpler for developers to locate a kernel module's full
debuginfo for a particular stacktrace. Combined with
scripts/decode_stracktrace.sh, a developer can download the matching
debuginfo from a debuginfod[2] server and find the exact file and line
number for the functions plus offsets in a stacktrace that match the
module. This is especially useful for pstore crash debugging where the
kernel crashes are recorded in something like console-ramoops and the
recovery kernel/modules are different or the debuginfo doesn't exist on
the device due to space concerns (the debuginfo can be too large for space
limited devices).
Originally, I put this on the %pS format, but that was quickly rejected
given that %pS is used in other places such as ftrace where build IDs
aren't meaningful. There was some discussions on the list to put every
module build ID into the "Modules linked in:" section of the stacktrace
message but that quickly becomes very hard to read once you have more than
three or four modules linked in. It also provides too much information
when we don't expect each module to be traversed in a stacktrace. Having
the build ID for modules that aren't important just makes things messy.
Splitting it to multiple lines for each module quickly explodes the number
of lines printed in an oops too, possibly wrapping the warning off the
console. And finally, trying to stash away each module used in a
callstack to provide the ID of each symbol printed is cumbersome and would
require changes to each architecture to stash away modules and return
their build IDs once unwinding has completed.
Instead, we opt for the simpler approach of introducing new printk formats
'%pS[R]b' for "pointer symbolic backtrace with module build ID" and '%pBb'
for "pointer backtrace with module build ID" and then updating the few
places in the architecture layer where the stacktrace is printed to use
this new format.
Before:
Call trace:
lkdtm_WARNING+0x28/0x30 [lkdtm]
direct_entry+0x16c/0x1b4 [lkdtm]
full_proxy_write+0x74/0xa4
vfs_write+0xec/0x2e8
After:
Call trace:
lkdtm_WARNING+0x28/0x30 [lkdtm 6c2215028606bda50de823490723dc4bc5bf46f9]
direct_entry+0x16c/0x1b4 [lkdtm 6c2215028606bda50de823490723dc4bc5bf46f9]
full_proxy_write+0x74/0xa4
vfs_write+0xec/0x2e8
[akpm@linux-foundation.org: fix build with CONFIG_MODULES=n, tweak code layout]
[rdunlap@infradead.org: fix build when CONFIG_MODULES is not set]
Link: https://lkml.kernel.org/r/20210513171510.20328-1-rdunlap@infradead.org
[akpm@linux-foundation.org: make kallsyms_lookup_buildid() static]
[cuibixuan@huawei.com: fix build error when CONFIG_SYSFS is disabled]
Link: https://lkml.kernel.org/r/20210525105049.34804-1-cuibixuan@huawei.com
Link: https://lkml.kernel.org/r/20210511003845.2429846-6-swboyd@chromium.org
Link: https://fedoraproject.org/wiki/Releases/FeatureBuildId [1]
Link: https://sourceware.org/elfutils/Debuginfod.html [2]
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Bixuan Cui <cuibixuan@huawei.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Evan Green <evgreen@chromium.org>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This change adds support for Clang’s forward-edge Control Flow
Integrity (CFI) checking. With CONFIG_CFI_CLANG, the compiler
injects a runtime check before each indirect function call to ensure
the target is a valid function with the correct static type. This
restricts possible call targets and makes it more difficult for
an attacker to exploit bugs that allow the modification of stored
function pointers. For more details, see:
https://clang.llvm.org/docs/ControlFlowIntegrity.html
Clang requires CONFIG_LTO_CLANG to be enabled with CFI to gain
visibility to possible call targets. Kernel modules are supported
with Clang’s cross-DSO CFI mode, which allows checking between
independently compiled components.
With CFI enabled, the compiler injects a __cfi_check() function into
the kernel and each module for validating local call targets. For
cross-module calls that cannot be validated locally, the compiler
calls the global __cfi_slowpath_diag() function, which determines
the target module and calls the correct __cfi_check() function. This
patch includes a slowpath implementation that uses __module_address()
to resolve call targets, and with CONFIG_CFI_CLANG_SHADOW enabled, a
shadow map that speeds up module look-ups by ~3x.
Clang implements indirect call checking using jump tables and
offers two methods of generating them. With canonical jump tables,
the compiler renames each address-taken function to <function>.cfi
and points the original symbol to a jump table entry, which passes
__cfi_check() validation. This isn’t compatible with stand-alone
assembly code, which the compiler doesn’t instrument, and would
result in indirect calls to assembly code to fail. Therefore, we
default to using non-canonical jump tables instead, where the compiler
generates a local jump table entry <function>.cfi_jt for each
address-taken function, and replaces all references to the function
with the address of the jump table entry.
Note that because non-canonical jump table addresses are local
to each component, they break cross-module function address
equality. Specifically, the address of a global function will be
different in each module, as it's replaced with the address of a local
jump table entry. If this address is passed to a different module,
it won’t match the address of the same function taken there. This
may break code that relies on comparing addresses passed from other
components.
CFI checking can be disabled in a function with the __nocfi attribute.
Additionally, CFI can be disabled for an entire compilation unit by
filtering out CC_FLAGS_CFI.
By default, CFI failures result in a kernel panic to stop a potential
exploit. CONFIG_CFI_PERMISSIVE enables a permissive mode, where the
kernel prints out a rate-limited warning instead, and allows execution
to continue. This option is helpful for locating type mismatches, but
should only be enabled during development.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-2-samitolvanen@google.com
MODULE_SUPPORTED_DEVICE was added in pre-git era and never was
implemented. We can safely remove it, because the kernel has grown
to have many more reliable mechanisms to determine if device is
supported or not.
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
EXPORT_UNUSED_SYMBOL* is not actually used anywhere. Remove the
unused functionality as we generally just remove unused code anyway.
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
As far as I can tell this has never been used at all, and certainly
not any time recently.
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
struct symsearch is only used inside of module.h, so move the definition
out of module.h.
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Except for two lockdep asserts module_mutex is only used in module.c.
Remove the two asserts given that the functions they are in are not
exported and just called from the module code, and mark module_mutex
static.
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
kallsyms_on_each_symbol and module_kallsyms_on_each_symbol are only used
by the livepatching code, so don't build them if livepatching is not
enabled.
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Allow for a RCU-sched critical section around find_module, following
the lower level find_module_all helper, and switch the two callers
outside of module.c to use such a RCU-sched critical section instead
of module_mutex.
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Summary of modules changes for the 5.11 merge window:
- Fix a race condition between systemd/udev and the module loader.
The module loader was sending a uevent before the module was fully
initialized (i.e., before its init function has been called). This means
udev can start processing the module uevent before the module has
finished initializing, and some udev rules expect that the module has
initialized already upon receiving the uevent. This resulted in some
systemd mount units failing if udev processes the event faster than the
module can finish init. This is fixed by delaying the uevent until after
the module has called its init routine.
- Make the linker array sections for kernel params and module version
attributes more robust by switching to use the alignment of the type in
question. Namely, linker section arrays will be constructed using the
alignment required by the struct (using __alignof__()) as opposed to a
specific value such as sizeof(void *) or sizeof(long). This is less
likely to cause breakages should the size of the type ever change (from
Johan Hovold)
- Fix module state inconsistency by setting it back to GOING when a module
fails to load and is on its way out (from Miroslav Benes)
- Some comment and code cleanups (from Sergey Shtylyov)
Signed-off-by: Jessica Yu <jeyu@kernel.org>
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Merge tag 'modules-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux
Pull modules updates from Jessica Yu:
"Summary of modules changes for the 5.11 merge window:
- Fix a race condition between systemd/udev and the module loader.
The module loader was sending a uevent before the module was fully
initialized (i.e., before its init function has been called). This
means udev can start processing the module uevent before the module
has finished initializing, and some udev rules expect that the
module has initialized already upon receiving the uevent.
This resulted in some systemd mount units failing if udev processes
the event faster than the module can finish init. This is fixed by
delaying the uevent until after the module has called its init
routine.
- Make the linker array sections for kernel params and module version
attributes more robust by switching to use the alignment of the
type in question.
Namely, linker section arrays will be constructed using the
alignment required by the struct (using __alignof__()) as opposed
to a specific value such as sizeof(void *) or sizeof(long). This is
less likely to cause breakages should the size of the type ever
change (Johan Hovold)
- Fix module state inconsistency by setting it back to GOING when a
module fails to load and is on its way out (Miroslav Benes)
- Some comment and code cleanups (Sergey Shtylyov)"
* tag 'modules-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux:
module: delay kobject uevent until after module init call
module: drop semicolon from version macro
init: use type alignment for kernel parameters
params: clean up module-param macros
params: use type alignment for kernel parameters
params: drop redundant "unused" attributes
module: simplify version-attribute handling
module: drop version-attribute alignment
module: fix comment style
module: add more 'kernel-doc' comments
module: fix up 'kernel-doc' comments
module: only handle errors with the *switch* statement in module_sig_check()
module: avoid *goto*s in module_sig_check()
module: merge repetitive strings in module_sig_check()
module: set MODULE_STATE_GOING state when a module fails to load
Drop the trailing semicolon from the MODULE_VERSION() macro definition
which was left when removing the array-of-pointer indirection.
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Instead of using the array-of-pointers trick to avoid having gcc mess up
the built-in module-version array stride, specify type alignment when
declaring entries to prevent gcc from increasing alignment.
This is essentially an alternative (one-line) fix to the problem
addressed by commit b4bc842802 ("module: deal with alignment issues in
built-in module versions").
gcc can increase the alignment of larger objects with static extent as
an optimisation, but this can be suppressed by using the aligned
attribute when declaring variables.
Note that we have been relying on this behaviour for kernel parameters
for 16 years and it indeed hasn't changed since the introduction of the
aligned attribute in gcc-3.1.
Link: https://lore.kernel.org/lkml/20201103175711.10731-1-johan@kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Commit 98562ad8cb ("module: explicitly align module_version_attribute
structure") added an alignment attribute to the struct
module_version_attribute type in order to fix an alignment issue on m68k
where the structure is 2-byte aligned while MODULE_VERSION() forced the
__modver section entries to be 4-byte aligned (sizeof(void *)).
This was essentially an alternative fix to the problem addressed by
b4bc842802 ("module: deal with alignment issues in built-in module
versions") which used the array-of-pointer trick to prevent gcc from
increasing alignment of the version attribute entries. And with the
pointer indirection in place there's no need to increase the alignment
of the type.
Link: https://lore.kernel.org/lkml/20201103175711.10731-1-johan@kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Daniel Borkmann says:
====================
pull-request: bpf-next 2020-11-14
1) Add BTF generation for kernel modules and extend BTF infra in kernel
e.g. support for split BTF loading and validation, from Andrii Nakryiko.
2) Support for pointers beyond pkt_end to recognize LLVM generated patterns
on inlined branch conditions, from Alexei Starovoitov.
3) Implements bpf_local_storage for task_struct for BPF LSM, from KP Singh.
4) Enable FENTRY/FEXIT/RAW_TP tracing program to use the bpf_sk_storage
infra, from Martin KaFai Lau.
5) Add XDP bulk APIs that introduce a defer/flush mechanism to optimize the
XDP_REDIRECT path, from Lorenzo Bianconi.
6) Fix a potential (although rather theoretical) deadlock of hashtab in NMI
context, from Song Liu.
7) Fixes for cross and out-of-tree build of bpftool and runqslower allowing build
for different target archs on same source tree, from Jean-Philippe Brucker.
8) Fix error path in htab_map_alloc() triggered from syzbot, from Eric Dumazet.
9) Move functionality from test_tcpbpf_user into the test_progs framework so it
can run in BPF CI, from Alexander Duyck.
10) Lift hashtab key_size limit to be larger than MAX_BPF_STACK, from Florian Lehner.
Note that for the fix from Song we have seen a sparse report on context
imbalance which requires changes in sparse itself for proper annotation
detection where this is currently being discussed on linux-sparse among
developers [0]. Once we have more clarification/guidance after their fix,
Song will follow-up.
[0] https://lore.kernel.org/linux-sparse/CAHk-=wh4bx8A8dHnX612MsDO13st6uzAz1mJ1PaHHVevJx_ZCw@mail.gmail.com/T/https://lore.kernel.org/linux-sparse/20201109221345.uklbp3lzgq6g42zb@ltop.local/T/
* git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (66 commits)
net: mlx5: Add xdp tx return bulking support
net: mvpp2: Add xdp tx return bulking support
net: mvneta: Add xdp tx return bulking support
net: page_pool: Add bulk support for ptr_ring
net: xdp: Introduce bulking for xdp tx return path
bpf: Expose bpf_d_path helper to sleepable LSM hooks
bpf: Augment the set of sleepable LSM hooks
bpf: selftest: Use bpf_sk_storage in FENTRY/FEXIT/RAW_TP
bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP
bpf: Rename some functions in bpf_sk_storage
bpf: Folding omem_charge() into sk_storage_charge()
selftests/bpf: Add asm tests for pkt vs pkt_end comparison.
selftests/bpf: Add skb_pkt_end test
bpf: Support for pointers beyond pkt_end.
tools/bpf: Always run the *-clean recipes
tools/bpf: Add bootstrap/ to .gitignore
bpf: Fix NULL dereference in bpf_task_storage
tools/bpftool: Fix build slowdown
tools/runqslower: Build bpftool using HOSTCC
tools/runqslower: Enable out-of-tree build
...
====================
Link: https://lore.kernel.org/r/20201114020819.29584-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Add kernel module listener that will load/validate and unload module BTF.
Module BTFs gets ID generated for them, which makes it possible to iterate
them with existing BTF iteration API. They are given their respective module's
names, which will get reported through GET_OBJ_INFO API. They are also marked
as in-kernel BTFs for tooling to distinguish them from user-provided BTFs.
Also, similarly to vmlinux BTF, kernel module BTFs are exposed through
sysfs as /sys/kernel/btf/<module-name>. This is convenient for user-space
tools to inspect module BTF contents and dump their types with existing tools:
[vmuser@archvm bpf]$ ls -la /sys/kernel/btf
total 0
drwxr-xr-x 2 root root 0 Nov 4 19:46 .
drwxr-xr-x 13 root root 0 Nov 4 19:46 ..
...
-r--r--r-- 1 root root 888 Nov 4 19:46 irqbypass
-r--r--r-- 1 root root 100225 Nov 4 19:46 kvm
-r--r--r-- 1 root root 35401 Nov 4 19:46 kvm_intel
-r--r--r-- 1 root root 120 Nov 4 19:46 pcspkr
-r--r--r-- 1 root root 399 Nov 4 19:46 serio_raw
-r--r--r-- 1 root root 4094095 Nov 4 19:46 vmlinux
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/bpf/20201110011932.3201430-5-andrii@kernel.org
Geert reports that commit be2881824a ("arm64/build: Assert for
unwanted sections") results in build errors on arm64 for configurations
that have CONFIG_MODULES disabled.
The commit in question added ASSERT()s to the arm64 linker script to
ensure that linker generated sections such as .got.plt etc are empty,
but as it turns out, there are corner cases where the linker does emit
content into those sections. More specifically, weak references to
function symbols (which can remain unsatisfied, and can therefore not
be emitted as relative references) will be emitted as GOT and PLT
entries when linking the kernel in PIE mode (which is the case when
CONFIG_RELOCATABLE is enabled, which is on by default).
What happens is that code such as
struct device *(*fn)(struct device *dev);
struct device *iommu_device;
fn = symbol_get(mdev_get_iommu_device);
if (fn) {
iommu_device = fn(dev);
essentially gets converted into the following when CONFIG_MODULES is off:
struct device *iommu_device;
if (&mdev_get_iommu_device) {
iommu_device = mdev_get_iommu_device(dev);
where mdev_get_iommu_device is emitted as a weak symbol reference into
the object file. The first reference is decorated with an ordinary
ABS64 data relocation (which yields 0x0 if the reference remains
unsatisfied). However, the indirect call is turned into a direct call
covered by a R_AARCH64_CALL26 relocation, which is converted into a
call via a PLT entry taking the target address from the associated
GOT entry.
Given that such GOT and PLT entries are unnecessary for fully linked
binaries such as the kernel, let's give these weak symbol references
hidden visibility, so that the linker knows that the weak reference
via R_AARCH64_CALL26 can simply remain unsatisfied.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Fangrui Song <maskray@google.com>
Acked-by: Jessica Yu <jeyu@kernel.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20201027151132.14066-1-ardb@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Use a more generic form for __section that requires quotes to avoid
complications with clang and gcc differences.
Remove the quote operator # from compiler_attributes.h __section macro.
Convert all unquoted __section(foo) uses to quoted __section("foo").
Also convert __attribute__((section("foo"))) uses to __section("foo")
even if the __attribute__ has multiple list entry forms.
Conversion done using the script at:
https://lore.kernel.org/lkml/75393e5ddc272dc7403de74d645e6c6e0f4e70eb.camel@perches.com/2-convert_section.pl
Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@gooogle.com>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add infrastructure for an arch-specific CONFIG_HAVE_STATIC_CALL_INLINE
option, which is a faster version of CONFIG_HAVE_STATIC_CALL. At
runtime, the static call sites are patched directly, rather than using
the out-of-line trampolines.
Compared to out-of-line static calls, the performance benefits are more
modest, but still measurable. Steven Rostedt did some tracepoint
measurements:
https://lkml.kernel.org/r/20181126155405.72b4f718@gandalf.local.home
This code is heavily inspired by the jump label code (aka "static
jumps"), as some of the concepts are very similar.
For more details, see the comments in include/linux/static_call.h.
[peterz: simplified interface; merged trampolines]
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20200818135804.684334440@infradead.org
If a TAINT_PROPRIETARY_MODULE exports symbol, inherit the taint flag
for all modules importing these symbols, and don't allow loading
symbols from TAINT_PROPRIETARY_MODULE modules if the module previously
imported gplonly symbols. Add a anti-circumvention devices so people
don't accidentally get themselves into trouble this way.
Comment from Greg:
"Ah, the proven-to-be-illegal "GPL Condom" defense :)"
[jeyu: pr_info -> pr_err and pr_warn as per discussion]
Link: http://lore.kernel.org/r/20200730162957.GA22469@lst.de
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Pull livepatching updates from Jiri Kosina:
- simplifications and improvements for issues Peter Ziljstra found
during his previous work on W^X cleanups.
This allows us to remove livepatch arch-specific .klp.arch sections
and add proper support for jump labels in patched code.
Also, this patchset removes the last module_disable_ro() usage in the
tree.
Patches from Josh Poimboeuf and Peter Zijlstra
- a few other minor cleanups
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching:
MAINTAINERS: add lib/livepatch to LIVE PATCHING
livepatch: add arch-specific headers to MAINTAINERS
livepatch: Make klp_apply_object_relocs static
MAINTAINERS: adjust to livepatch .klp.arch removal
module: Make module_enable_ro() static again
x86/module: Use text_mutex in apply_relocate_add()
module: Remove module_disable_ro()
livepatch: Remove module_disable_ro() usage
x86/module: Use text_poke() for late relocations
s390/module: Use s390_kernel_write() for late relocations
s390: Change s390_kernel_write() return type to match memcpy()
livepatch: Prevent module-specific KLP rela sections from referencing vmlinux symbols
livepatch: Remove .klp.arch
livepatch: Apply vmlinux-specific KLP relocations early
livepatch: Disallow vmlinux.ko
Instrumentation is forbidden in the .noinstr.text section. Make kprobes
respect this.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lkml.kernel.org/r/20200505134100.179862032@linutronix.de
Support NOKPROBE_SYMBOL() in modules. NOKPROBE_SYMBOL() records only symbol
address in "_kprobe_blacklist" section in the module.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200505134059.771170126@linutronix.de
Support __kprobes attribute for blacklist functions in modules. The
__kprobes attribute functions are stored in .kprobes.text section.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200505134059.678201813@linutronix.de
Now that module_enable_ro() has no more external users, make it static
again.
Suggested-by: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
module_disable_ro() has no more users. Remove it.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
- detect missing include guard in UAPI headers
- do not create orphan built-in.a or obj-y objects
- generate modules.builtin more simply, and drop tristate.conf
- simplify built-in initramfs creation
- make linux-headers deb package thinner
- optimize the deb package build script
- misc cleanups
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Merge tag 'kbuild-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- detect missing include guard in UAPI headers
- do not create orphan built-in.a or obj-y objects
- generate modules.builtin more simply, and drop tristate.conf
- simplify built-in initramfs creation
- make linux-headers deb package thinner
- optimize the deb package build script
- misc cleanups
* tag 'kbuild-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (34 commits)
builddeb: split libc headers deployment out into a function
builddeb: split kernel headers deployment out into a function
builddeb: remove redundant make for ARCH=um
builddeb: avoid invoking sub-shells where possible
builddeb: remove redundant $objtree/
builddeb: match temporary directory name to the package name
builddeb: remove unneeded files in hdrobjfiles for headers package
kbuild: use -S instead of -E for precise cc-option test in Kconfig
builddeb: allow selection of .deb compressor
kbuild: remove 'Building modules, stage 2.' log
kbuild: remove *.tmp file when filechk fails
kbuild: remove PYTHON2 variable
modpost: assume STT_SPARC_REGISTER is defined
gen_initramfs.sh: remove intermediate cpio_list on errors
initramfs: refactor the initramfs build rules
gen_initramfs.sh: always output cpio even without -o option
initramfs: add default_cpio_list, and delete -d option support
initramfs: generate dependency list and cpio at the same time
initramfs: specify $(src)/gen_initramfs.sh as a prerequisite in Makefile
initramfs: make initramfs compression choice non-optional
...
Summary of modules changes for the 5.6 merge window:
- Add "MS" (SHF_MERGE|SHF_STRINGS) section flags to __ksymtab_strings to
indicate to the linker that it can perform string deduplication (i.e.,
duplicate strings are reduced to a single copy in the string table).
This means any repeated namespace string would be merged to just one
entry in __ksymtab_strings.
- Various code cleanups and small fixes (fix small memleak in error path,
improve moduleparam docs, silence rcu warnings, improve error logging)
Signed-off-by: Jessica Yu <jeyu@kernel.org>
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Merge tag 'modules-for-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux
Pull module updates from Jessica Yu:
"Summary of modules changes for the 5.6 merge window:
- Add "MS" (SHF_MERGE|SHF_STRINGS) section flags to __ksymtab_strings
to indicate to the linker that it can perform string deduplication
(i.e., duplicate strings are reduced to a single copy in the string
table). This means any repeated namespace string would be merged to
just one entry in __ksymtab_strings.
- Various code cleanups and small fixes (fix small memleak in error
path, improve moduleparam docs, silence rcu warnings, improve error
logging)"
* tag 'modules-for-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux:
module.h: Annotate mod_kallsyms with __rcu
module: avoid setting info->name early in case we can fall back to info->mod->name
modsign: print module name along with error message
kernel/module: Fix memleak in module_add_modinfo_attrs()
export.h: reduce __ksymtab_strings string duplication by using "MS" section flags
moduleparam: fix kerneldoc
modules: lockdep: Suppress suspicious RCU usage warning
Commit bc081dd6e9 ("kbuild: generate modules.builtin") added
infrastructure to generate modules.builtin, the list of all
builtin modules.
Basically, it works like this:
- Kconfig generates include/config/tristate.conf, the list of
tristate CONFIG options with a value in a capital letter.
- scripts/Makefile.modbuiltin makes Kbuild descend into
directories to collect the information of builtin modules.
I am not a big fan of it because Kbuild ends up with traversing
the source tree twice.
I am not sure how perfectly it should work, but this approach cannot
avoid false positives; even if the relevant CONFIG option is tristate,
some Makefiles forces obj-m to obj-y.
Some examples are:
arch/powerpc/platforms/powermac/Makefile:
obj-$(CONFIG_NVRAM:m=y) += nvram.o
net/ipv6/Makefile:
obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_hashtables.o
net/netlabel/Makefile:
obj-$(subst m,y,$(CONFIG_IPV6)) += netlabel_calipso.o
Nobody has complained about (or noticed) it, so it is probably fine to
have false positives in modules.builtin.
This commit simplifies the implementation. Let's exploit the fact
that every module has MODULE_LICENSE(). (modpost shows a warning if
MODULE_LICENSE is missing. If so, 0-day bot would already have blocked
such a module.)
I added MODULE_FILE to <linux/module.h>. When the code is being compiled
as builtin, it will be filled with the file path of the module, and
collected into modules.builtin.info. Then, scripts/link-vmlinux.sh
extracts the list of builtin modules out of it.
This new approach fixes the false-positives above, but adds another
type of false-positives; non-modular code may have MODULE_LICENSE()
by mistake. This is not a big deal, it is just the code is always
orphan. We can clean it up if we like. You can see cleanup examples by:
$ git log --grep='make.* explicitly non-modular'
To sum up, this commits deletes lots of code, but still produces almost
equivalent results. Please note it does not increase the vmlinux size at
all. As you can see in include/asm-generic/vmlinux.lds.h, the .modinfo
section is discarded in the link stage.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Now that there are no users of set_all_modules_text_*() left, remove
it.
While it appears nds32 uses it, it does not have STRICT_MODULE_RWX and
therefore ends up with the NOP stubs.
Tested-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Chen <deanbo422@gmail.com>
Link: https://lkml.kernel.org/r/20191111132458.284298307@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Commit b24413180f ("License cleanup: add SPDX GPL-2.0 license
identifier to files with no license") took care of a lot of files
without any license information.
These headers were not processed by the tool perhaps because they
contain "GPL" in the code.
I do not see any license boilerplate in them, so they fall back to
GPL version 2 only, which is the project default.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Link: https://lore.kernel.org/r/20191018045053.8424-1-yamada.masahiro@socionext.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Pull integrity updates from Mimi Zohar:
"The major feature in this time is IMA support for measuring and
appraising appended file signatures. In addition are a couple of bug
fixes and code cleanup to use struct_size().
In addition to the PE/COFF and IMA xattr signatures, the kexec kernel
image may be signed with an appended signature, using the same
scripts/sign-file tool that is used to sign kernel modules.
Similarly, the initramfs may contain an appended signature.
This contained a lot of refactoring of the existing appended signature
verification code, so that IMA could retain the existing framework of
calculating the file hash once, storing it in the IMA measurement list
and extending the TPM, verifying the file's integrity based on a file
hash or signature (eg. xattrs), and adding an audit record containing
the file hash, all based on policy. (The IMA support for appended
signatures patch set was posted and reviewed 11 times.)
The support for appended signature paves the way for adding other
signature verification methods, such as fs-verity, based on a single
system-wide policy. The file hash used for verifying the signature and
the signature, itself, can be included in the IMA measurement list"
* 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity:
ima: ima_api: Use struct_size() in kzalloc()
ima: use struct_size() in kzalloc()
sefltest/ima: support appended signatures (modsig)
ima: Fix use after free in ima_read_modsig()
MODSIGN: make new include file self contained
ima: fix freeing ongoing ahash_request
ima: always return negative code for error
ima: Store the measurement again when appraising a modsig
ima: Define ima-modsig template
ima: Collect modsig
ima: Implement support for module-style appended signatures
ima: Factor xattr_verify() out of ima_appraise_measurement()
ima: Add modsig appraise_type option for module-style appended signatures
integrity: Select CONFIG_KEYS instead of depending on it
PKCS#7: Introduce pkcs7_get_digest()
PKCS#7: Refactor verify_pkcs7_signature()
MODSIGN: Export module signature definitions
ima: initialize the "template" field with the default template
It's an unusual configuration, and was apparently never tested, and not
caught in linux-next because of a combination of travels and it making
it into the tree too late.
The fix is to simply move the #define to outside the CONFIG_MODULE
section, since MODULE_INFO() will do the right thing.
Cc: Martijn Coenen <maco@android.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Matthias Maennich <maennich@google.com>
Cc: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The EXPORT_SYMBOL_NS() and EXPORT_SYMBOL_NS_GPL() macros can be used to
export a symbol to a specific namespace. There are no _GPL_FUTURE and
_UNUSED variants because these are currently unused, and I'm not sure
they are necessary.
I didn't add EXPORT_SYMBOL_NS() for ASM exports; this patch sets the
namespace of ASM exports to NULL by default. In case of relative
references, it will be relocatable to NULL. If there's a need, this
should be pretty easy to add.
A module that wants to use a symbol exported to a namespace must add a
MODULE_IMPORT_NS() statement to their module code; otherwise, modpost
will complain when building the module, and the kernel module loader
will emit an error and fail when loading the module.
MODULE_IMPORT_NS() adds a modinfo tag 'import_ns' to the module. That
tag can be observed by the modinfo command, modpost and kernel/module.c
at the time of loading the module.
The ELF symbols are renamed to include the namespace with an asm label;
for example, symbol 'usb_stor_suspend' in namespace USB_STORAGE becomes
'usb_stor_suspend.USB_STORAGE'. This allows modpost to do namespace
checking, without having to go through all the effort of parsing ELF and
relocation records just to get to the struct kernel_symbols.
On x86_64 I saw no difference in binary size (compression), but at
runtime this will require a word of memory per export to hold the
namespace. An alternative could be to store namespaced symbols in their
own section and use a separate 'struct namespaced_kernel_symbol' for
that section, at the cost of making the module loader more complex.
Co-developed-by: Martijn Coenen <maco@android.com>
Signed-off-by: Martijn Coenen <maco@android.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
IMA will use the module_signature format for append signatures, so export
the relevant definitions and factor out the code which verifies that the
appended signature trailer is valid.
Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
and be able to use mod_check_sig() without having to depend on either
CONFIG_MODULE_SIG or CONFIG_MODULES.
s390 duplicated the definition of struct module_signature so now they can
use the new <linux/module_signature.h> header instead.
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Acked-by: Jessica Yu <jeyu@kernel.org>
Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Adding DEFINE_SRCU() or DEFINE_STATIC_SRCU() to a loadable module requires
that the size of the reserved region be increased, which is not something
we want to be doing all that often. One approach would be to require
that loadable modules define an srcu_struct and invoke init_srcu_struct()
from their module_init function and cleanup_srcu_struct() from their
module_exit function. However, this is more than a bit user unfriendly.
This commit therefore creates an ___srcu_struct_ptrs linker section,
and pointers to srcu_struct structures created by DEFINE_SRCU() and
DEFINE_STATIC_SRCU() within a module are placed into that module's
___srcu_struct_ptrs section. The required init_srcu_struct() and
cleanup_srcu_struct() functions are then automatically invoked as needed
when that module is loaded and unloaded, thus allowing modules to continue
to use DEFINE_SRCU() and DEFINE_STATIC_SRCU() while avoiding the need
to increase the size of the reserved region.
Many of the algorithms and some of the code was cheerfully cherry-picked
from other code making use of linker sections, perhaps most notably from
tracepoints. All bugs are nevertheless the sole property of the author.
Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
[ paulmck: Use __section() and use "default" in srcu_module_notify()'s
"switch" statement as suggested by Joel Fernandes. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Tested-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Summary of modules changes for the 5.2 merge window:
- Use a separate table to store symbol types instead of
hijacking fields in struct Elf_Sym
- Trivial code cleanups
Signed-off-by: Jessica Yu <jeyu@kernel.org>
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Merge tag 'modules-for-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux
Pull modules updates from Jessica Yu:
- Use a separate table to store symbol types instead of hijacking
fields in struct Elf_Sym
- Trivial code cleanups
* tag 'modules-for-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux:
module: add stubs for within_module functions
kallsyms: store type information in its own array
vmlinux.lds.h: drop unused __vermagic
Pull intgrity updates from James Morris:
"This contains just three patches, the remainder were either included
in other pull requests (eg. audit, lockdown) or will be upstreamed via
other subsystems (eg. kselftests, Power).
Included here is one bug fix, one documentation update, and extending
the x86 IMA arch policy rules to coordinate the different kernel
module signature verification methods"
* 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
doc/kernel-parameters.txt: Deprecate ima_appraise_tcb
x86/ima: add missing include
x86/ima: require signed kernel modules
- allow users to invoke 'make' out of the source tree
- refactor scripts/mkmakefile
- deprecate KBUILD_SRC, which was used to track the source tree
location for O= build.
- fix recordmcount.pl in case objdump output is localized
- turn unresolved symbols in external modules to errors from warnings
by default; pass KBUILD_MODPOST_WARN=1 to get them back to warnings
- generate modules.builtin.modinfo to collect .modinfo data from
built-in modules
- misc Makefile cleanups
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Merge tag 'kbuild-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- allow users to invoke 'make' out of the source tree
- refactor scripts/mkmakefile
- deprecate KBUILD_SRC, which was used to track the source tree
location for O= build.
- fix recordmcount.pl in case objdump output is localized
- turn unresolved symbols in external modules to errors from warnings
by default; pass KBUILD_MODPOST_WARN=1 to get them back to warnings
- generate modules.builtin.modinfo to collect .modinfo data from
built-in modules
- misc Makefile cleanups
* tag 'kbuild-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (21 commits)
.gitignore: add more all*.config patterns
moduleparam: Save information about built-in modules in separate file
Remove MODULE_ALIAS() calls that take undefined macro
.gitignore: add leading and trailing slashes to generated directories
scripts/tags.sh: fix direct execution of scripts/tags.sh
scripts: override locale from environment when running recordmcount.pl
samples: kobject: allow CONFIG_SAMPLE_KOBJECT to become y
samples: seccomp: turn CONFIG_SAMPLE_SECCOMP into a bool option
kbuild: move Documentation to vmlinux-alldirs
kbuild: move samples/ to KBUILD_VMLINUX_OBJS
modpost: make KBUILD_MODPOST_WARN also configurable for external modules
kbuild: check arch/$(SRCARCH)/include/generated before out-of-tree build
kbuild: remove unneeded dependency for include/config/kernel.release
memory: squash drivers/memory/Makefile.asm-offsets
kbuild: use $(srctree) instead of KBUILD_SRC to check out-of-tree build
kbuild: mkmakefile: generate a simple wrapper of top Makefile
kbuild: mkmakefile: do not check the generated Makefile marker
kbuild: allow Kbuild to start from any directory
kbuild: pass $(MAKECMDGOALS) to sub-make as is
kbuild: fix warning "overriding recipe for target 'Makefile'"
...
Problem:
When a kernel module is compiled as a separate module, some important
information about the kernel module is available via .modinfo section of
the module. In contrast, when the kernel module is compiled into the
kernel, that information is not available.
Information about built-in modules is necessary in the following cases:
1. When it is necessary to find out what additional parameters can be
passed to the kernel at boot time.
2. When you need to know which module names and their aliases are in
the kernel. This is very useful for creating an initrd image.
Proposal:
The proposed patch does not remove .modinfo section with module
information from the vmlinux at the build time and saves it into a
separate file after kernel linking. So, the kernel does not increase in
size and no additional information remains in it. Information is stored
in the same format as in the separate modules (null-terminated string
array). Because the .modinfo section is already exported with a separate
modules, we are not creating a new API.
It can be easily read in the userspace:
$ tr '\0' '\n' < modules.builtin.modinfo
ext4.softdep=pre: crc32c
ext4.license=GPL
ext4.description=Fourth Extended Filesystem
ext4.author=Remy Card, Stephen Tweedie, Andrew Morton, Andreas Dilger, Theodore Ts'o and others
ext4.alias=fs-ext4
ext4.alias=ext3
ext4.alias=fs-ext3
ext4.alias=ext2
ext4.alias=fs-ext2
md_mod.alias=block-major-9-*
md_mod.alias=md
md_mod.description=MD RAID framework
md_mod.license=GPL
md_mod.parmtype=create_on_open:bool
md_mod.parmtype=start_dirty_degraded:int
...
Co-Developed-by: Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>
Signed-off-by: Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>
Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
Acked-by: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Provide stubs for within_module_core(), within_module_init(), and
within_module() to prevent build errors when !CONFIG_MODULES.
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kbuild test robot <lkp@intel.com>
Link: https://marc.info/?l=linux-mm&m=155384681109231&w=2
Signed-off-by: Tri Vo <trong@android.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
When a module is loaded, its symbols' Elf_Sym information is stored
in a symtab. Further, type information is also captured. Since
Elf_Sym has no type field, historically the st_info field has been
hijacked for storing type: st_info was overwritten.
commit 5439c985c5 ("module: Overwrite
st_size instead of st_info") changes that practice, as its one-liner
indicates. Unfortunately, this change overwrites symbol size,
information that a tool like DTrace expects to find.
Allocate a typetab array to store type information so that no Elf_Sym
field needs to be overwritten.
Fixes: 5439c985c5 ("module: Overwrite st_size instead of st_info")
Signed-off-by: Eugene Loh <eugene.loh@oracle.com>
Reviewed-by: Nick Alcock <nick.alcock@oracle.com>
[jeyu: renamed typeoff -> typeoffs ]
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Have the IMA architecture specific policy require signed kernel modules
on systems with secure boot mode enabled; and coordinate the different
signature verification methods, so only one signature is required.
Requiring appended kernel module signatures may be configured, enabled
on the boot command line, or with this patch enabled in secure boot
mode. This patch defines set_module_sig_enforced().
To coordinate between appended kernel module signatures and IMA
signatures, only define an IMA MODULE_CHECK policy rule if
CONFIG_MODULE_SIG is not enabled. A custom IMA policy may still define
and require an IMA signature.
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Acked-by: Jessica Yu <jeyu@kernel.org>
Implement the ability for filesystems to log error, warning and
informational messages through the fs_context. These can be extracted by
userspace by reading from an fd created by fsopen().
Error messages are prefixed with "e ", warnings with "w " and informational
messages with "i ".
Inside the kernel, formatted messages are malloc'd but unformatted messages
are not copied if they're either in the core .rodata section or in the
.rodata section of the filesystem module pinned by fs_context::fs_type.
The messages are only good till the fs_type is released.
Note that the logging object is shared between duplicated fs_context
structures. This is so that such as NFS which do a mount within a mount
can get at least some of the errors from the inner mount.
Five logging functions are provided for this:
(1) void logfc(struct fs_context *fc, const char *fmt, ...);
This logs a message into the context. If the buffer is full, the
earliest message is discarded.
(2) void errorf(fc, fmt, ...);
This wraps logfc() to log an error.
(3) void invalf(fc, fmt, ...);
This wraps errorf() and returns -EINVAL for convenience.
(4) void warnf(fc, fmt, ...);
This wraps logfc() to log a warning.
(5) void infof(fc, fmt, ...);
This wraps logfc() to log an informational message.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Stephen Boyd