diff options
author | Andrey Ryabinin <aryabinin@virtuozzo.com> | 2015-10-19 11:37:17 +0300 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2015-10-20 11:04:19 +0200 |
commit | d976441f44bc5d48635d081d277aa76556ffbf8b (patch) | |
tree | d53718bcf6247f0e201e84f73b925e9293bf1462 /include | |
parent | a75ca545e8d57473da47ece828ad98a10727ec6f (diff) | |
download | linux-d976441f44bc5d48635d081d277aa76556ffbf8b.tar.bz2 |
compiler, atomics, kasan: Provide READ_ONCE_NOCHECK()
Some code may perform racy by design memory reads. This could be
harmless, yet such code may produce KASAN warnings.
To hide such accesses from KASAN this patch introduces
READ_ONCE_NOCHECK() macro. KASAN will not check the memory
accessed by READ_ONCE_NOCHECK(). The KernelThreadSanitizer
(KTSAN) is going to ignore it as well.
This patch creates __read_once_size_nocheck() a clone of
__read_once_size(). The only difference between them is
'no_sanitized_address' attribute appended to '*_nocheck'
function. This attribute tells the compiler that instrumentation
of memory accesses should not be applied to that function. We
declare it as static '__maybe_unsed' because GCC is not capable
to inline such function:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
With KASAN=n READ_ONCE_NOCHECK() is just a clone of READ_ONCE().
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wolfram Gloger <wmglo@dent.med.uni-muenchen.de>
Cc: kasan-dev <kasan-dev@googlegroups.com>
Link: http://lkml.kernel.org/r/1445243838-17763-2-git-send-email-aryabinin@virtuozzo.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/compiler-gcc.h | 13 | ||||
-rw-r--r-- | include/linux/compiler.h | 66 |
2 files changed, 66 insertions, 13 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index dfaa7b3e9ae9..8efb40e61d6e 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -237,12 +237,25 @@ #define KASAN_ABI_VERSION 3 #endif +#if GCC_VERSION >= 40902 +/* + * Tell the compiler that address safety instrumentation (KASAN) + * should not be applied to that function. + * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368 + */ +#define __no_sanitize_address __attribute__((no_sanitize_address)) +#endif + #endif /* gcc version >= 40000 specific checks */ #if !defined(__noclone) #define __noclone /* not needed */ #endif +#if !defined(__no_sanitize_address) +#define __no_sanitize_address +#endif + /* * A trick to suppress uninitialized variable warning without generating any * code diff --git a/include/linux/compiler.h b/include/linux/compiler.h index c836eb2dc44d..3d7810341b57 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -198,19 +198,45 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); #include <uapi/linux/types.h> -static __always_inline void __read_once_size(const volatile void *p, void *res, int size) +#define __READ_ONCE_SIZE \ +({ \ + switch (size) { \ + case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \ + case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \ + case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \ + case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \ + default: \ + barrier(); \ + __builtin_memcpy((void *)res, (const void *)p, size); \ + barrier(); \ + } \ +}) + +static __always_inline +void __read_once_size(const volatile void *p, void *res, int size) { - switch (size) { - case 1: *(__u8 *)res = *(volatile __u8 *)p; break; - case 2: *(__u16 *)res = *(volatile __u16 *)p; break; - case 4: *(__u32 *)res = *(volatile __u32 *)p; break; - case 8: *(__u64 *)res = *(volatile __u64 *)p; break; - default: - barrier(); - __builtin_memcpy((void *)res, (const void *)p, size); - barrier(); - } + __READ_ONCE_SIZE; +} + +#ifdef CONFIG_KASAN +/* + * This function is not 'inline' because __no_sanitize_address confilcts + * with inlining. Attempt to inline it may cause a build failure. + * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368 + * '__maybe_unused' allows us to avoid defined-but-not-used warnings. + */ +static __no_sanitize_address __maybe_unused +void __read_once_size_nocheck(const volatile void *p, void *res, int size) +{ + __READ_ONCE_SIZE; +} +#else +static __always_inline +void __read_once_size_nocheck(const volatile void *p, void *res, int size) +{ + __READ_ONCE_SIZE; } +#endif static __always_inline void __write_once_size(volatile void *p, void *res, int size) { @@ -248,8 +274,22 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s * required ordering. */ -#define READ_ONCE(x) \ - ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; }) +#define __READ_ONCE(x, check) \ +({ \ + union { typeof(x) __val; char __c[1]; } __u; \ + if (check) \ + __read_once_size(&(x), __u.__c, sizeof(x)); \ + else \ + __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \ + __u.__val; \ +}) +#define READ_ONCE(x) __READ_ONCE(x, 1) + +/* + * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need + * to hide memory access from KASAN. + */ +#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0) #define WRITE_ONCE(x, val) \ ({ \ |