Re: [PATCH v3 1/3] kasan: Archs don't check memmove if not support it.

[Palmer Dabbelt]

On Mon, 07 Oct 2019 23:11:51 PDT (-0700), nickhu@xxxxxxxxxxxxx wrote:
> Skip the memmove checking for those archs who don't support it.
>
> Signed-off-by: Nick Hu <nickhu@xxxxxxxxxxxxx>
> ---
>  mm/kasan/common.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 6814d6d6a023..897f9520bab3 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -107,6 +107,7 @@ void *memset(void *addr, int c, size_t len)
>  	return __memset(addr, c, len);
>  }
>
> +#ifdef __HAVE_ARCH_MEMMOVE
>  #undef memmove
>  void *memmove(void *dest, const void *src, size_t len)
>  {
> @@ -115,6 +116,7 @@ void *memmove(void *dest, const void *src, size_t len)
>
>  	return __memmove(dest, src, len);
>  }
> +#endif
>
>  #undef memcpy
>  void *memcpy(void *dest, const void *src, size_t len)

I think this is backwards: we shouldn't be defining an arch-specific memmove 
symbol when KASAN is enabled.  If we do it this way then we're defeating the 
memmove checks, which doesn't seem like the right way to go.