On Wed, 11 Oct 2017 16:22:22 +0800 Abbott Liu <liuwenliang@xxxxxxxxxx> wrote:
> Because arm instruction set don't support access the address which is
> not aligned, so must change memory_is_poisoned_16 for arm.
>
> ...
>
> --- a/mm/kasan/kasan.c
> +++ b/mm/kasan/kasan.c
> @@ -149,6 +149,25 @@ static __always_inline bool memory_is_poisoned_2_4_8(unsigned long addr,
> return memory_is_poisoned_1(addr + size - 1);
> }
>
> +#ifdef CONFIG_ARM
> +static __always_inline bool memory_is_poisoned_16(unsigned long addr)
> +{
> + u8 *shadow_addr = (u8 *)kasan_mem_to_shadow((void *)addr);
> +
> + if (unlikely(shadow_addr[0] || shadow_addr[1])) return true;
Coding-style is messed up. Please use scripts/checkpatch.pl.
> + else {
> + /*
> + * 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);
> + }
> +}
> +
> +#else
> static __always_inline bool memory_is_poisoned_16(unsigned long addr)
> {
> u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
> @@ -159,6 +178,7 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr)
>
> return *shadow_addr;
> }
> +#endif
- I don't understand why this is necessary. memory_is_poisoned_16()
already handles unaligned addresses?
- If it's needed on ARM then presumably it will be needed on other
architectures, so CONFIG_ARM is insufficiently general.
- If the present memory_is_poisoned_16() indeed doesn't work on ARM,
it would be better to generalize/fix it in some fashion rather than
creating a new variant of the function.
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