Use IS_ALIGNED() to determine whether the shadow span two bytes. It generates less code and more readable. Add some comments in shadow check functions. Please apply "kasan: fix last shadow judgement in memory_is_poisoned_16()" first. Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx> --- mm/kasan/kasan.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 8da2114..00d5605 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -86,6 +86,10 @@ static __always_inline bool memory_is_poisoned_2(unsigned long addr) if (memory_is_poisoned_1(addr + 1)) return true; + /* + * If the shadow spans two bytes, the first byte should + * be zero. + */ if (likely(((addr + 1) & KASAN_SHADOW_MASK) != 0)) return false; @@ -103,6 +107,10 @@ static __always_inline bool memory_is_poisoned_4(unsigned long addr) if (memory_is_poisoned_1(addr + 3)) return true; + /* + * If the shadow spans two bytes, the first byte should + * be zero. + */ if (likely(((addr + 3) & KASAN_SHADOW_MASK) >= 3)) return false; @@ -120,7 +128,11 @@ 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 the shadow spans two bytes, the first byte should + * be zero. + */ + if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE))) return false; return unlikely(*(u8 *)shadow_addr); @@ -139,7 +151,12 @@ 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 the shadow spans three bytes, we should continue to + * check the last byte. The first two bytes which we + * checked above should always be zero. + */ + if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE))) return false; return memory_is_poisoned_1(addr + 15); -- 2.0.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>