Building the Linux kernel with Clang and LLVM
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From: Nathan Chancellor <nathan@kernel.org>
To: Kees Cook <kees@kernel.org>
Cc: "Thomas Weißschuh" <linux@weissschuh.net>,
	"Bill Wendling" <morbo@google.com>,
	"Justin Stitt" <justinstitt@google.com>,
	"Masahiro Yamada" <masahiroy@kernel.org>,
	"Nicolas Schier" <nicolas@fjasle.eu>,
	llvm@lists.linux.dev, linux-kbuild@vger.kernel.org,
	"David Gow" <davidgow@google.com>,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH v2] kbuild: clang: Support building UM with SUBARCH=i386
Date: Tue, 4 Mar 2025 17:28:45 +0100	[thread overview]
Message-ID: <20250304162845.GA1479759@ax162> (raw)
In-Reply-To: <20250304162124.it.785-kees@kernel.org>

On Tue, Mar 04, 2025 at 08:21:29AM -0800, Kees Cook wrote:
> The UM builds distinguish i386 from x86_64 via SUBARCH, but we don't
> support building i386 directly with Clang. To make SUBARCH work for
> i386 UM, we need to explicitly test for it.
> 
> This lets me run i386 KUnit tests with Clang:
> 
> $ ./tools/testing/kunit/kunit.py run \
> 	--make_options LLVM=1 \
> 	--make_options SUBARCH=i386
> ...
> 
> Fixes: c7500c1b53bf ("um: Allow builds with Clang")
> Signed-off-by: Kees Cook <kees@kernel.org>

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: Thomas Weißschuh <linux@weissschuh.net>
> Cc: Bill Wendling <morbo@google.com>
> Cc: Justin Stitt <justinstitt@google.com>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Nicolas Schier <nicolas@fjasle.eu>
> Cc: llvm@lists.linux.dev
> Cc: linux-kbuild@vger.kernel.org
> ---
>  scripts/Makefile.clang | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
> index 2435efae67f5..b67636b28c35 100644
> --- a/scripts/Makefile.clang
> +++ b/scripts/Makefile.clang
> @@ -12,6 +12,8 @@ CLANG_TARGET_FLAGS_riscv	:= riscv64-linux-gnu
>  CLANG_TARGET_FLAGS_s390		:= s390x-linux-gnu
>  CLANG_TARGET_FLAGS_sparc	:= sparc64-linux-gnu
>  CLANG_TARGET_FLAGS_x86		:= x86_64-linux-gnu
> +# This is only for i386 UM builds, which need the 32-bit target not -m32
> +CLANG_TARGET_FLAGS_i386		:= i386-linux-gnu
>  CLANG_TARGET_FLAGS_um		:= $(CLANG_TARGET_FLAGS_$(SUBARCH))
>  CLANG_TARGET_FLAGS		:= $(CLANG_TARGET_FLAGS_$(SRCARCH))
>  
> -- 
> 2.34.1
> 

  reply	other threads:[~2025-03-04 16:28 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-03-04 16:21 [PATCH v2] kbuild: clang: Support building UM with SUBARCH=i386 Kees Cook
2025-03-04 16:28 ` Nathan Chancellor [this message]
2025-03-04 17:50 ` Kees Cook
2025-03-06  8:59 ` David Gow
2025-03-07  3:41   ` Kees Cook

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