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References: <20240129175033.work.813-kees@kernel.org> <20240129180046.3774731-1-keescook@chromium.org>
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From: Fangrui Song <maskray@google.com>
Date: Mon, 29 Jan 2024 10:59:55 -0800
Message-ID: <CAFP8O3LhmXqqKKf1fOw1_0zGYOyN7ivm2yYSQJqSQr_megOq8Q@mail.gmail.com>
Subject: Re: [PATCH 1/6] ubsan: Use Clang's -fsanitize-trap=undefined option
To: Kees Cook <keescook@chromium.org>
Cc: Marco Elver <elver@google.com>, Nathan Chancellor <nathan@kernel.org>, 
	Masahiro Yamada <masahiroy@kernel.org>, Nicolas Schier <nicolas@fjasle.eu>, 
	Nick Desaulniers <ndesaulniers@google.com>, Bill Wendling <morbo@google.com>, 
	Justin Stitt <justinstitt@google.com>, linux-kbuild@vger.kernel.org, llvm@lists.linux.dev, 
	Andrey Konovalov <andreyknvl@gmail.com>, linux-kernel@vger.kernel.org, 
	linux-hardening@vger.kernel.org
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On Mon, Jan 29, 2024 at 10:00=E2=80=AFAM Kees Cook <keescook@chromium.org> =
wrote:
>
> Clang changed the way it enables UBSan trapping mode. Update the Makefile
> logic to discover it.
>
> Suggested-by: Fangrui Song <maskray@google.com>
> Link: https://lore.kernel.org/lkml/CAFP8O3JivZh+AAV7N90Nk7U2BHRNST6MRP0zH=
tfQ-Vj0m4+pDA@mail.gmail.com/
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Nicolas Schier <nicolas@fjasle.eu>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Bill Wendling <morbo@google.com>
> Cc: Justin Stitt <justinstitt@google.com>
> Cc: linux-kbuild@vger.kernel.org
> Cc: llvm@lists.linux.dev
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  scripts/Makefile.ubsan | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
> index 4749865c1b2c..7cf42231042b 100644
> --- a/scripts/Makefile.ubsan
> +++ b/scripts/Makefile.ubsan
> @@ -10,6 +10,6 @@ ubsan-cflags-$(CONFIG_UBSAN_DIV_ZERO)         +=3D -fsa=
nitize=3Dinteger-divide-by-zero
>  ubsan-cflags-$(CONFIG_UBSAN_UNREACHABLE)       +=3D -fsanitize=3Dunreach=
able
>  ubsan-cflags-$(CONFIG_UBSAN_BOOL)              +=3D -fsanitize=3Dbool
>  ubsan-cflags-$(CONFIG_UBSAN_ENUM)              +=3D -fsanitize=3Denum
> -ubsan-cflags-$(CONFIG_UBSAN_TRAP)              +=3D -fsanitize-undefined=
-trap-on-error
> +ubsan-cflags-$(CONFIG_UBSAN_TRAP)              +=3D $(call cc-option,-fs=
anitize-trap=3Dundefined,-fsanitize-undefined-trap-on-error)
>
>  export CFLAGS_UBSAN :=3D $(ubsan-cflags-y)
> --
> 2.34.1

Thanks for the patch. Clang has had -fsanitize-trap=3D since 2015.
GCC added -fsanitize-trap=3Dundefined in 2022
(https://gcc.gnu.org/git/gitweb.cgi?p=3Dgcc.git;h=3D2c7cfc7b418564 ;
milestone: 13.1), so we cannot use -fsanitize-trap=3Dundefined
unconditionally.

Reviewed-by: Fangrui Song <maskray@google.com>


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