linux-kernel - Re: [PATCH v2 2/2] kbuild: make Clang build userprogs for target architecture

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Date:   Tue, 30 Jun 2020 14:14:28 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Sam Ravnborg <sam@...nborg.org>,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH v2 2/2] kbuild: make Clang build userprogs for target
 architecture

On Wed, Jul 01, 2020 at 12:06:25AM +0900, Masahiro Yamada wrote:
> Programs added 'userprogs' should be compiled for the target
> architecture i.e. the same architecture as the kernel.
> 
> GCC does this correctly since the target architecture is implied
> by the toolchain prefix.
> 
> Clang builds userspace programs always for the host architecture
> because the target triple is currently missing.
> 
> Fix this.
> 
> Fixes: 7f3a59db274c ("kbuild: add infrastructure to build userspace programs")
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

Reviewed-by: Nathan Chancellor <natechancellor@...il.com>

> ---
> 
> (no changes since v1)
> 
>  Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index ac2c61c37a73..bc48810d1655 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -970,8 +970,8 @@ LDFLAGS_vmlinux	+= --pack-dyn-relocs=relr
>  endif
>  
>  # Align the bit size of userspace programs with the kernel
> -KBUILD_USERCFLAGS  += $(filter -m32 -m64, $(KBUILD_CFLAGS))
> -KBUILD_USERLDFLAGS += $(filter -m32 -m64, $(KBUILD_CFLAGS))
> +KBUILD_USERCFLAGS  += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))
> +KBUILD_USERLDFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))
>  
>  # make the checker run with the right architecture
>  CHECKFLAGS += --arch=$(ARCH)
> -- 
> 2.25.1