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>
This commit is contained in:
parent
a35353bb9e
commit
ac605bee0b
|
@ -24,6 +24,10 @@
|
|||
*/
|
||||
static __always_inline int arch_atomic_read(const atomic_t *v)
|
||||
{
|
||||
/*
|
||||
* Note for KASAN: we deliberately don't use READ_ONCE_NOCHECK() here,
|
||||
* it's non-inlined function that increases binary size and stack usage.
|
||||
*/
|
||||
return READ_ONCE((v)->counter);
|
||||
}
|
||||
|
||||
|
|
|
@ -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)); \
|
||||
|
|
Loading…
Reference in a new issue