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

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Message-ID: <CAK7LNARr-ypWkNR52-my2WJFQ3b26EGV===J8b1MROLuf31oRw@mail.gmail.com>
Date: Wed, 18 Jun 2025 10:14:07 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
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 Tue, Jun 17, 2025 at 4:39 PM Thomas Weißschuh
<thomas.weissschuh@...utronix.de> wrote:
>
> 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.


$(filter ... $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))

is duplicated in the two lines.

That is the reason for my suggestion.



-- 
Best Regards
Masahiro Yamada