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| author | Dmitry Vyukov <dvyukov@google.com> | 2018-01-29 18:26:07 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-03-12 12:15:35 +0100 |
| commit | ac605bee0bfab40fd5d11964705e907d2d5a32de (patch) | |
| tree | 0f16f12d231f572f275e44ed30362bceacca2f7e /include/asm-generic/atomic-instrumented.h | |
| parent | a35353bb9eb1990a44a0d7585f99e9589bcdb682 (diff) | |
| download | lwn-ac605bee0bfab40fd5d11964705e907d2d5a32de.tar.gz lwn-ac605bee0bfab40fd5d11964705e907d2d5a32de.zip | |
locking/atomic, asm-generic, x86: Add comments for atomic instrumentation
The comments are factored out from the code changes to make them
easier to read. Add them separately to explain some non-obvious
aspects.
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: kasan-dev@googlegroups.com
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/cc595efc644bb905407012d82d3eb8bac3368e7a.1517246437.git.dvyukov@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/asm-generic/atomic-instrumented.h')
| -rw-r--r-- | include/asm-generic/atomic-instrumented.h | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/include/asm-generic/atomic-instrumented.h b/include/asm-generic/atomic-instrumented.h index 82e080505982..ec07f23678ea 100644 --- a/include/asm-generic/atomic-instrumented.h +++ b/include/asm-generic/atomic-instrumented.h @@ -1,3 +1,15 @@ +/* + * This file provides wrappers with KASAN instrumentation for atomic operations. + * To use this functionality an arch's atomic.h file needs to define all + * atomic operations with arch_ prefix (e.g. arch_atomic_read()) and include + * this file at the end. This file provides atomic_read() that forwards to + * arch_atomic_read() for actual atomic operation. + * Note: if an arch atomic operation is implemented by means of other atomic + * operations (e.g. atomic_read()/atomic_cmpxchg() loop), then it needs to use + * arch_ variants (i.e. arch_atomic_read()/arch_atomic_cmpxchg()) to avoid + * double instrumentation. + */ + #ifndef _LINUX_ATOMIC_INSTRUMENTED_H #define _LINUX_ATOMIC_INSTRUMENTED_H @@ -442,6 +454,15 @@ cmpxchg64_local_size(volatile u64 *ptr, u64 old, u64 new) (u64)(new))); \ }) +/* + * Originally we had the following code here: + * __typeof__(p1) ____p1 = (p1); + * kasan_check_write(____p1, 2 * sizeof(*____p1)); + * arch_cmpxchg_double(____p1, (p2), (o1), (o2), (n1), (n2)); + * But it leads to compilation failures (see gcc issue 72873). + * So for now it's left non-instrumented. + * There are few callers of cmpxchg_double(), so it's not critical. + */ #define cmpxchg_double(p1, p2, o1, o2, n1, n2) \ ({ \ arch_cmpxchg_double((p1), (p2), (o1), (o2), (n1), (n2)); \ |