linux-kernel - Re: [PATCH v3 02/16] kbuild: userprogs: also inherit byte order and ABI from kernel

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Message-ID: <20250617093523-e7f54d95-96d0-4411-92d6-dd80fe84ee98@linutronix.de>
Date: Tue, 17 Jun 2025 09:39:11 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Willy Tarreau <w@....eu>, 
	Thomas Weißschuh <linux@...ssschuh.net>, Brendan Higgins <brendan.higgins@...ux.dev>, 
	David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>, Shuah Khan <shuah@...nel.org>, 
	Jonathan Corbet <corbet@....net>, Nicolas Schier <nicolas.schier@...ux.dev>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>, 
	Christophe Leroy <christophe.leroy@...roup.eu>, linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com, linux-doc@...r.kernel.org, 
	linux-riscv@...ts.infradead.org, workflows@...r.kernel.org
Subject: Re: [PATCH v3 02/16] kbuild: userprogs: also inherit byte order and
 ABI from kernel

On Mon, Jun 16, 2025 at 11:49:41PM +0900, Masahiro Yamada wrote:
> On Wed, Jun 11, 2025 at 4:38 PM Thomas Weißschuh
> <thomas.weissschuh@...utronix.de> wrote:
> >
> > Make sure the byte order and ABI of the userprogs matches the one of the
> > kernel, similar to how the bit size is handled.
> > Otherwise the userprogs may not be executable.
> > This happens for example on powerpc little endian, or riscv32.
> >
> > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> > ---
> >  Makefile | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index c4293cf91e968ca8ee64452841fb266e24df63f6..b9aa1058321dabd3b3dd5610e45a2807dfa257f4 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -1129,8 +1129,8 @@ ifneq ($(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS),)
> >  LDFLAGS_vmlinux        += --emit-relocs --discard-none
> >  endif
> >
> > -# Align the bit size of userspace programs with the kernel
> > -USERFLAGS_FROM_KERNEL := -m32 -m64 --target=%
> > +# Align the bit size, byte order and architecture of userspace programs with the kernel
> > +USERFLAGS_FROM_KERNEL := -m32 -m64 -mlittle-endian -mbig-endian --target=% -march=% -mabi=%
> >  KBUILD_USERCFLAGS  += $(filter $(USERFLAGS_FROM_KERNEL), $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
> >  KBUILD_USERLDFLAGS += $(filter $(USERFLAGS_FROM_KERNEL), $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
> 
> 
> Why didn't you do like this?
> 
> USERFLAGS_FROM_KERNEL := $(filter -m32 -m64 -mlittle-endian
> -mbig-endian --target=% -march=% -mabi=%, $(KBUILD_CPPFLAGS)
> $(KBUILD_CFLAGS))
> KBUILD_USERCFLAGS  += $(USERFLAGS_FROM_KERNEL)
> KBUILD_USERLDFLAGS += $(USERFLAGS_FROM_KERNEL)

The idea was to keep the USERFLAGS_FROM_KERNEL line free of clutter, as it is
probably going to change more often. To improve reviewability and gain some
available horizontal space in case it should be needed at some point.

If you prefer the other layout I'll be happy to switch it around.


Thomas