linux-kernel - Re: [PATCH v5 03/19] kasan: Fix inline mode for x86 tag-based mode

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Message-ID: <CA+fCnZeUvsvGy02k4zQwkGUkL7KbuLzah5XC7kp1m5uwp4bPVg@mail.gmail.com>
Date: Sat, 6 Sep 2025 19:17:36 +0200
From: Andrey Konovalov <andreyknvl@...il.com>
To: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
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Subject: Re: [PATCH v5 03/19] kasan: Fix inline mode for x86 tag-based mode

On Mon, Aug 25, 2025 at 10:26 PM Maciej Wieczor-Retman
<maciej.wieczor-retman@...el.com> wrote:
>
> The LLVM compiler uses hwasan-instrument-with-calls parameter to setup
> inline or outline mode in tag-based KASAN. If zeroed, it means the
> instrumentation implementation will be pasted into each relevant
> location along with KASAN related constants during compilation. If set
> to one all function instrumentation will be done with function calls
> instead.
>
> The default hwasan-instrument-with-calls value for the x86 architecture
> in the compiler is "1", which is not true for other architectures.
> Because of this, enabling inline mode in software tag-based KASAN
> doesn't work on x86 as the kernel script doesn't zero out the parameter
> and always sets up the outline mode.
>
> Explicitly zero out hwasan-instrument-with-calls when enabling inline
> mode in tag-based KASAN.
>
> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
> ---
> Changelog v3:
> - Add this patch to the series.
>
>  scripts/Makefile.kasan | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index 693dbbebebba..2c7be96727ac 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -76,8 +76,11 @@ CFLAGS_KASAN := -fsanitize=kernel-hwaddress
>  RUSTFLAGS_KASAN := -Zsanitizer=kernel-hwaddress \
>                    -Zsanitizer-recover=kernel-hwaddress
>
> +# LLVM sets hwasan-instrument-with-calls to 1 on x86 by default. Set it to 0
> +# when inline mode is enabled.
>  ifdef CONFIG_KASAN_INLINE
>         kasan_params += hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
> +       kasan_params += hwasan-instrument-with-calls=0
>  else
>         kasan_params += hwasan-instrument-with-calls=1
>  endif
> --
> 2.50.1
>

Reviewed-by: Andrey Konovalov <andreyknvl@...il.com>