From 10f702627e139e21465f4c9d44f63527bbca163c Mon Sep 17 00:00:00 2001 From: Xishi Qiu <qiuxishi@huawei.com> Date: Thu, 5 Nov 2015 18:51:21 -0800 Subject: [PATCH] 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> --- mm/kasan/kasan.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 2b21ccd55cd4a..d41b21bce6a03 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -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); -- GitLab