linux-kernel - Re: [PATCH 2/2] kbuild: userprogs: also inherit byte order and ABI from kernel

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Message-ID: <aL0W9xvpktaLE9m2@levanger>
Date: Sun, 7 Sep 2025 07:24:07 +0200
From: Nicolas Schier <nsc@...nel.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
	Masahiro Yamada <masahiroy@...nel.org>
Subject: Re: [PATCH 2/2] kbuild: userprogs: also inherit byte order and ABI
 from kernel

On Wed, Sep 03, 2025 at 03:31:31PM -0700, Nathan Chancellor wrote:
> On Mon, Sep 01, 2025 at 11:51:03AM +0200, Thomas Weißschuh wrote:
> > Exactly. The normal cases can be handled generically. For example the kconfig
> > below works for architectures which only differ in byte order and 32bit/64bit,
> > which are most of them. MIPS should require more logic.
> > Also I'm ignoring x32, as it is never the kernel's native ABI.
> > 
> >  config CC_CAN_LINK
> >         bool
> > +       default $(cc_can_link_user,$(m64-flag) -mlittle-endian) if 64BIT && CPU_LITTLE_ENDIAN
> > +       default $(cc_can_link_user,$(m64-flag) -mbig-endian) if 64BIT && CPU_BIG_ENDIAN
> >         default $(cc_can_link_user,$(m64-flag)) if 64BIT
> > +       default $(cc_can_link_user,$(m32-flag) -mlittle-endian) if CPU_LITTLE_ENDIAN
> > +       default $(cc_can_link_user,$(m32-flag) -mbig-endian) if CPU_BIG_ENDIAN
> >         default $(cc_can_link_user,$(m32-flag))
> > 
> > 
> > > Feels like that could get complicated quickly but this would probably be
> > > the objectively most robust and "hands off" option.
> > 
> > Agreed.
> 
> Nicolas might feel differently but this does not seem terrible to me,
> especially with a macro to wrap the common logic, which is where I felt
> like things could get unwieldy. Feel free to send an RFC if it is not
> too much work.

yes, at a first glance this looks ok to me, too.

Thanks,
Nicolas