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Commit 7f1e541f authored by Andrey Ryabinin's avatar Andrey Ryabinin Committed by Linus Torvalds
Browse files

compiler.h: Add read_word_at_a_time() function. 



Sometimes we know that it's safe to do potentially out-of-bounds access
because we know it won't cross a page boundary.  Still, KASAN will
report this as a bug.

Add read_word_at_a_time() function which is supposed to be used in such
cases.  In read_word_at_a_time() KASAN performs relaxed check - only the
first byte of access is validated.

Signed-off-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bdb5ac80

include/linux/compiler.h

+8 −0
Original line number Diff line number Diff line
@@ -238,6 +238,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s 
 * required ordering.

 */

#include <asm/barrier.h>

#include <linux/kasan-checks.h>



#define __READ_ONCE(x, check)						\

({									\
@@ -257,6 +258,13 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s 
 */

#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)



static __no_kasan_or_inline

unsigned long read_word_at_a_time(const void *addr)

{

	kasan_check_read(addr, 1);

	return *(unsigned long *)addr;

}



#define WRITE_ONCE(x, val) \

({							\

	union { typeof(x) __val; char __c[1]; } __u =	\