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References: <20230301143933.2374658-1-glider@google.com> <20230301143933.2374658-3-glider@google.com>
In-Reply-To: <20230301143933.2374658-3-glider@google.com>
From:   Marco Elver <elver@google.com>
Date:   Thu, 2 Mar 2023 12:18:59 +0100
Message-ID: <CANpmjNMd6YA1FGaE2ePsHU4OvTz=-2yXxCOwPDyDpCFTD5ns2Q@mail.gmail.com>
Subject: Re: [PATCH 3/4] x86: kmsan: use C versions of memset16/memset32/memset64
To:     Alexander Potapenko <glider@google.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org,
        dave.hansen@linux.intel.com, hpa@zytor.com,
        akpm@linux-foundation.org, dvyukov@google.com, nathan@kernel.org,
        ndesaulniers@google.com, kasan-dev@googlegroups.com,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Daniel Vetter <daniel@ffwll.ch>, Helge Deller <deller@gmx.de>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
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Precedence: bulk

On Wed, 1 Mar 2023 at 15:39, 'Alexander Potapenko' via kasan-dev
<kasan-dev@googlegroups.com> wrote:
>
> KMSAN must see as many memory accesses as possible to prevent false
> positive reports. Fall back to versions of
> memset16()/memset32()/memset64() implemented in lib/string.c instead of
> those written in assembly.
>
> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Helge Deller <deller@gmx.de>
> Suggested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
> Signed-off-by: Alexander Potapenko <glider@google.com>

Reviewed-by: Marco Elver <elver@google.com>

> ---
>  arch/x86/include/asm/string_64.h | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h
> index 9be401d971a99..e9c736f4686f5 100644
> --- a/arch/x86/include/asm/string_64.h
> +++ b/arch/x86/include/asm/string_64.h
> @@ -22,6 +22,11 @@ extern void *__memcpy(void *to, const void *from, size_t len);
>  void *memset(void *s, int c, size_t n);
>  void *__memset(void *s, int c, size_t n);
>
> +/*
> + * KMSAN needs to instrument as much code as possible. Use C versions of
> + * memsetXX() from lib/string.c under KMSAN.
> + */
> +#if !defined(CONFIG_KMSAN)
>  #define __HAVE_ARCH_MEMSET16
>  static inline void *memset16(uint16_t *s, uint16_t v, size_t n)
>  {
> @@ -57,6 +62,7 @@ static inline void *memset64(uint64_t *s, uint64_t v, size_t n)
>                      : "memory");
>         return s;
>  }
> +#endif
>
>  #define __HAVE_ARCH_MEMMOVE
>  void *memmove(void *dest, const void *src, size_t count);
> --
> 2.39.2.722.g9855ee24e9-goog
>
> --
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