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kasan: use IS_ALIGNED in memory_is_poisoned_8() 

Use IS_ALIGNED() to determine whether the shadow span two bytes.  It
generates less code and more readable.  Also add some comments in shadow
check functions.

Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andrey Konovalov <adech.fo@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Xishi Qiu 2015-11-05 18:51:21 -08:00 committed by Linus Torvalds
parent e0d5771439
commit 10f702627e
1 changed files with 22 additions and 2 deletions
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24
mm/kasan/kasan.c
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@ -86,6 +86,11 @@ static __always_inline bool memory_is_poisoned_2(unsigned long addr)
if (memory_is_poisoned_1(addr + 1))
return true;
/*
* If single shadow byte covers 2-byte access, we don't
* need to do anything more. Otherwise, test the first
* shadow byte.
*/
if (likely(((addr + 1) & KASAN_SHADOW_MASK) != 0))
return false;
@ -103,6 +108,11 @@ static __always_inline bool memory_is_poisoned_4(unsigned long addr)
if (memory_is_poisoned_1(addr + 3))
return true;
/*
* If single shadow byte covers 4-byte access, we don't
* need to do anything more. Otherwise, test the first
* shadow byte.
*/
if (likely(((addr + 3) & KASAN_SHADOW_MASK) >= 3))
return false;
@ -120,7 +130,12 @@ static __always_inline bool memory_is_poisoned_8(unsigned long addr)
if (memory_is_poisoned_1(addr + 7))
return true;
if (likely(((addr + 7) & KASAN_SHADOW_MASK) >= 7))
/*
* If single shadow byte covers 8-byte access, we don't
* need to do anything more. Otherwise, test the first
* shadow byte.
*/
if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
return false;
return unlikely(*(u8 *)shadow_addr);
@ -139,7 +154,12 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr)
if (unlikely(shadow_first_bytes))
return true;
if (likely(IS_ALIGNED(addr, 8)))
/*
* If two shadow bytes covers 16-byte access, we don't
* need to do anything more. Otherwise, test the last
* shadow byte.
*/
if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
return false;
return memory_is_poisoned_1(addr + 15);