[RFC PATCH 7/7] kasan: sw_tags: Support runtime stack tagging control for RISC-V

[Andrey Konovalov]

On Wed, Aug 14, 2024 at 10:56 AM Samuel Holland
<samuel.holland at sifive.com> wrote:
>
> This allows the kernel to boot on systems without pointer masking
> support when stack tagging is enabled.
>
> Signed-off-by: Samuel Holland <samuel.holland at sifive.com>

Reviewed-by: Andrey Konovalov <andreyknvl at gmail.com>

But see a nit below.

> ---
>
>  mm/kasan/kasan.h       | 2 ++
>  mm/kasan/sw_tags.c     | 9 +++++++++
>  scripts/Makefile.kasan | 5 +++++
>  3 files changed, 16 insertions(+)
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index fb2b9ac0659a..01e945cb111d 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -630,6 +630,8 @@ void *__asan_memset(void *addr, int c, ssize_t len);
>  void *__asan_memmove(void *dest, const void *src, ssize_t len);
>  void *__asan_memcpy(void *dest, const void *src, ssize_t len);
>
> +u8 __hwasan_generate_tag(void);
> +
>  void __hwasan_load1_noabort(void *);
>  void __hwasan_store1_noabort(void *);
>  void __hwasan_load2_noabort(void *);
> diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c
> index 220b5d4c6876..32435d33583a 100644
> --- a/mm/kasan/sw_tags.c
> +++ b/mm/kasan/sw_tags.c
> @@ -70,6 +70,15 @@ u8 kasan_random_tag(void)
>         return (u8)(state % (KASAN_TAG_MAX + 1));
>  }
>
> +u8 __hwasan_generate_tag(void)
> +{
> +       if (!kasan_enabled())
> +               return KASAN_TAG_KERNEL;
> +
> +       return kasan_random_tag();
> +}
> +EXPORT_SYMBOL(__hwasan_generate_tag);
> +
>  bool kasan_check_range(const void *addr, size_t size, bool write,
>                         unsigned long ret_ip)
>  {
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index 390658a2d5b7..f64c1aca3e97 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -73,6 +73,11 @@ ifeq ($(call clang-min-version, 150000)$(call gcc-min-version, 130000),y)
>  CFLAGS_KASAN += $(call cc-param,hwasan-kernel-mem-intrinsic-prefix=1)
>  endif
>
> +# RISC-V requires dynamically determining if stack tagging can be enabled.
> +ifdef CONFIG_RISCV
> +CFLAGS_KASAN += $(call cc-param,hwasan-generate-tags-with-calls=1)

Let's indent this line by 1 tab (I already sent a patch that fixes
indentation in the other parts of this Makefile [1]).

[1] https://lore.kernel.org/linux-mm/20240813224027.84503-1-andrey.konovalov@linux.dev/T/#u


> +endif
> +
>  endif # CONFIG_KASAN_SW_TAGS
>
>  export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE
> --
> 2.45.1
>