Building the Linux kernel with Clang and LLVM
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From: Nathan Chancellor <nathan@kernel.org>
To: "Thomas Weißschuh" <thomas.weissschuh@linutronix.de>
Cc: 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>,
	Sam Ravnborg <sam@ravnborg.org>,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	llvm@lists.linux.dev, stable@vger.kernel.org
Subject: Re: [PATCH 1/2] kbuild: userprogs: fix bitsize and target detection on clang
Date: Thu, 13 Feb 2025 10:55:39 -0700	[thread overview]
Message-ID: <20250213175539.GB2756218@ax162> (raw)
In-Reply-To: <20250213-kbuild-userprog-fixes-v1-1-f255fb477d98@linutronix.de>

On Thu, Feb 13, 2025 at 03:55:17PM +0100, Thomas Weißschuh wrote:
> scripts/Makefile.clang was changed in the linked commit to move --target from
> KBUILD_CFLAGS to KBUILD_CPPFLAGS, as that generally has a broader scope.
> However that variable is not inspected by the userprogs logic,
> breaking cross compilation on clang.
> 
> Use both variables to detect bitsize and target arguments for userprogs.
> 
> Fixes: feb843a469fb ("kbuild: add $(CLANG_FLAGS) to KBUILD_CPPFLAGS")
> Cc: stable@vger.kernel.org
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

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

> ---
>  Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 9e0d63d9d94b90672f91929e5e148e5a0c346cb6..bb5737ce7f9e79f4023c9c1f578a49a951d1e239 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1120,8 +1120,8 @@ LDFLAGS_vmlinux += --orphan-handling=$(CONFIG_LD_ORPHAN_WARN_LEVEL)
>  endif
>  
>  # Align the bit size of userspace programs with the kernel
> -KBUILD_USERCFLAGS  += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))
> -KBUILD_USERLDFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))
> +KBUILD_USERCFLAGS  += $(filter -m32 -m64 --target=%, $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
> +KBUILD_USERLDFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
>  
>  # make the checker run with the right architecture
>  CHECKFLAGS += --arch=$(ARCH)
> 
> -- 
> 2.48.1
> 

  reply	other threads:[~2025-02-13 17:55 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-02-13 14:55 [PATCH 0/2] kbuild: userprogs: two fixes for LLVM=1 Thomas Weißschuh
2025-02-13 14:55 ` [PATCH 1/2] kbuild: userprogs: fix bitsize and target detection on clang Thomas Weißschuh
2025-02-13 17:55   ` Nathan Chancellor [this message]
2025-02-15 18:10   ` Masahiro Yamada
2025-02-13 14:55 ` [PATCH 2/2] kbuild: userprogs: use lld to link through clang Thomas Weißschuh
2025-02-13 17:54   ` Nathan Chancellor
2025-02-14  7:40     ` Thomas Weißschuh
2025-02-15  4:15       ` Nathan Chancellor

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