Re: [PATCH] kasan: fix hwasan build for gcc

[Andrey Konovalov]

On Tue, Mar 23, 2021 at 1:41 PM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
>
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> gcc-11 adds support for -fsanitize=kernel-hwaddress, so it becomes
> possible to enable CONFIG_KASAN_SW_TAGS.
>
> Unfortunately this fails to build at the moment, because the
> corresponding command line arguments use llvm specific syntax.
>
> Change it to use the cc-param macro instead, which works on both
> clang and gcc.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  scripts/Makefile.kasan | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index 1e000cc2e7b4..0a2789783d1b 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -36,14 +36,14 @@ endif # CONFIG_KASAN_GENERIC
>  ifdef CONFIG_KASAN_SW_TAGS
>
>  ifdef CONFIG_KASAN_INLINE
> -    instrumentation_flags := -mllvm -hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
> +    instrumentation_flags := $(call cc-param,hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET))
>  else
> -    instrumentation_flags := -mllvm -hwasan-instrument-with-calls=1
> +    instrumentation_flags := $(call cc-param,hwasan-instrument-with-calls=1)
>  endif
>
>  CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
> -               -mllvm -hwasan-instrument-stack=$(CONFIG_KASAN_STACK) \
> -               -mllvm -hwasan-use-short-granules=0 \
> +               $(call cc-param,hwasan-instrument-stack=$(CONFIG_KASAN_STACK)) \
> +               $(call cc-param,hwasan-use-short-granules=0) \
>                 $(instrumentation_flags)
>
>  endif # CONFIG_KASAN_SW_TAGS
> --
> 2.29.2
>

Hi Arnd,

This patch breaks SW_TAGS build with Clang for me with:

arch/arm64/include/asm/current.h:19: undefined reference to `__hwasan_tls'

The reason for this is that cc-param is only defined for
KASAN_GENERIC, the definition needs to be moved.

Thanks!