From: Masahiro Yamada <masahiroy@kernel.org>
To: Alexander Potapenko <glider@google.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Andrew Morton <akpm@linux-foundation.org>,
Kees Cook <keescook@chromium.org>,
Nick Desaulniers <ndesaulniers@google.com>,
linux-kbuild@vger.kernel.org
Subject: Re: [PATCH 3/5] Kconfig.debug: disable CONFIG_FRAME_WARN for KMSAN by default
Date: Thu, 27 Oct 2022 23:31:49 +0900 [thread overview]
Message-ID: <CAK7LNARfKkiNSUfZAqDQd15O8NAhpX13dHDuGn3OPL_b_F_92g@mail.gmail.com> (raw)
In-Reply-To: <20221024212144.2852069-3-glider@google.com>
On Tue, Oct 25, 2022 at 6:22 AM Alexander Potapenko <glider@google.com> wrote:
>
> KMSAN adds a lot of instrumentation to the code, which results in
> increased stack usage (up to 2048 bytes and more in some cases).
> It's hard to predict how big the stack frames can be, so we disable
> the warnings for KMSAN instead.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: linux-kbuild@vger.kernel.org
> Link: https://github.com/google/kmsan/issues/89
> Signed-off-by: Alexander Potapenko <glider@google.com>
> ---
> lib/Kconfig.debug | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 3fc7abffc7aa2..29280072dc0e4 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -400,8 +400,9 @@ config FRAME_WARN
> default 1536 if (!64BIT && XTENSA)
> default 1024 if !64BIT
> default 2048 if 64BIT
> + default 0 if KMSAN
This is wrong.
Kconfig picks up the first default entry which has
true 'if' condition.
Since (!64BIT || 64BIT) covers all the possible cases,
this patch is just adding dead code.
> help
> - Tell gcc to warn at build time for stack frames larger than this.
> + Tell the compiler to warn at build time for stack frames larger than this.
> Setting this too low will cause a lot of warnings.
> Setting it to 0 disables the warning.
>
> --
> 2.38.0.135.g90850a2211-goog
>
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2022-10-27 14:32 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-24 21:21 [PATCH 1/5] mm: kmsan: export kmsan_copy_page_meta() Alexander Potapenko
2022-10-24 21:21 ` [PATCH 2/5] x86/purgatory: disable KMSAN instrumentation Alexander Potapenko
2022-10-24 21:21 ` [PATCH 3/5] Kconfig.debug: disable CONFIG_FRAME_WARN for KMSAN by default Alexander Potapenko
2022-10-27 14:31 ` Masahiro Yamada [this message]
2022-10-27 16:41 ` Alexander Potapenko
2022-10-24 21:21 ` [PATCH 4/5] x86: asm: make sure __put_user_size() evaluates pointer once Alexander Potapenko
2022-10-24 21:21 ` [PATCH 5/5] x86: fortify: kmsan: fix KMSAN fortify builds Alexander Potapenko
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