Re: [patch 05/16] kasan: fix hwasan build for gcc

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On Fri, Apr 9, 2021 at 10:27 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> From: Arnd Bergmann <arnd@xxxxxxxx>
> Subject: kasan: fix hwasan build for gcc
>
> 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.
>
> Link: https://lkml.kernel.org/r/20210323124112.1229772-1-arnd@xxxxxxxxxx
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
> Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> Cc: Michal Marek <michal.lkml@xxxxxxxxxxx>
> Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
> Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
> Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> Cc: Alexander Potapenko <glider@xxxxxxxxxx>
> Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
>
>  scripts/Makefile.kasan |    8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> --- a/scripts/Makefile.kasan~kasan-fix-hwasan-build-for-gcc
> +++ a/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
> _

Hi,

As I commented on the patch, this 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!




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