Re: [PATCH -tip v4 1/3] kasan: Emit different calls for instrumentable memintrinsics

[Andrey Konovalov]

On Fri, Feb 17, 2023 at 12:45 AM Marco Elver <elver@xxxxxxxxxx> wrote:
>
> Clang 15 provides an option to prefix memcpy/memset/memmove calls with
> __asan_/__hwasan_ in instrumented functions: https://reviews.llvm.org/D122724
>
> GCC will add support in future:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108777
>
> Use it to regain KASAN instrumentation of memcpy/memset/memmove on
> architectures that require noinstr to be really free from instrumented
> mem*() functions (all GENERIC_ENTRY architectures).
>
> Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
> Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> ---
> v4:
> * Also enable it for KASAN_SW_TAGS (__hwasan_mem*).
>
> v3:
> * No change.
>
> v2:
> * Use asan-kernel-mem-intrinsic-prefix=1, so that once GCC supports the
>   param, it also works there (it needs the =1).
>
> The Fixes tag is just there to show the dependency, and that people
> shouldn't apply this patch without 69d4c0d32186.
> ---
>  mm/kasan/kasan.h       |  4 ++++
>  mm/kasan/shadow.c      | 11 +++++++++++
>  scripts/Makefile.kasan |  8 ++++++++
>  3 files changed, 23 insertions(+)
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 71c15438afcf..172713b87556 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -637,4 +637,8 @@ void __hwasan_storeN_noabort(unsigned long addr, size_t size);
>
>  void __hwasan_tag_memory(unsigned long addr, u8 tag, unsigned long size);
>
> +void *__hwasan_memset(void *addr, int c, size_t len);
> +void *__hwasan_memmove(void *dest, const void *src, size_t len);
> +void *__hwasan_memcpy(void *dest, const void *src, size_t len);
> +
>  #endif /* __MM_KASAN_KASAN_H */
> diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
> index 98269936a5e4..f8a47cb299cb 100644
> --- a/mm/kasan/shadow.c
> +++ b/mm/kasan/shadow.c
> @@ -107,6 +107,17 @@ void *__asan_memcpy(void *dest, const void *src, size_t len)
>  }
>  EXPORT_SYMBOL(__asan_memcpy);
>
> +#ifdef CONFIG_KASAN_SW_TAGS
> +void *__hwasan_memset(void *addr, int c, size_t len) __alias(__asan_memset);
> +EXPORT_SYMBOL(__hwasan_memset);
> +#ifdef __HAVE_ARCH_MEMMOVE
> +void *__hwasan_memmove(void *dest, const void *src, size_t len) __alias(__asan_memmove);
> +EXPORT_SYMBOL(__hwasan_memmove);
> +#endif
> +void *__hwasan_memcpy(void *dest, const void *src, size_t len) __alias(__asan_memcpy);
> +EXPORT_SYMBOL(__hwasan_memcpy);
> +#endif
> +
>  void kasan_poison(const void *addr, size_t size, u8 value, bool init)
>  {
>         void *shadow_start, *shadow_end;
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index b9e94c5e7097..fa9f836f8039 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -38,6 +38,11 @@ endif
>
>  CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable))
>
> +# Instrument memcpy/memset/memmove calls by using instrumented __asan_mem*()
> +# instead. With compilers that don't support this option, compiler-inserted
> +# memintrinsics won't be checked by KASAN on GENERIC_ENTRY architectures.
> +CFLAGS_KASAN += $(call cc-param,asan-kernel-mem-intrinsic-prefix=1)
> +
>  endif # CONFIG_KASAN_GENERIC
>
>  ifdef CONFIG_KASAN_SW_TAGS
> @@ -54,6 +59,9 @@ CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
>                 $(call cc-param,hwasan-inline-all-checks=0) \
>                 $(instrumentation_flags)
>
> +# Instrument memcpy/memset/memmove calls by using instrumented __hwasan_mem*().
> +CFLAGS_KASAN += $(call cc-param,hwasan-kernel-mem-intrinsic-prefix=1)
> +
>  endif # CONFIG_KASAN_SW_TAGS
>
>  export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE
> --
> 2.39.2.637.g21b0678d19-goog
>

Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>