linux-kernel - Re: [PATCH v2 00/10] kbuild: userprogs: introduce architecture-specific CC_CAN

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Message-ID: <20251113102307-ca2180c8-4876-46ea-8678-aaedd9ba36f0@linutronix.de>
Date: Thu, 13 Nov 2025 10:31:10 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Nicolas Schier <nsc@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>, Paul Walmsley <pjw@...nel.org>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Alexandre Ghiti <alex@...ti.fr>, Heiko Carstens <hca@...ux.ibm.com>, 
	Vasily Gorbik <gor@...ux.ibm.com>, Alexander Gordeev <agordeev@...ux.ibm.com>, 
	Christian Borntraeger <borntraeger@...ux.ibm.com>, Sven Schnelle <svens@...ux.ibm.com>, 
	Madhavan Srinivasan <maddy@...ux.ibm.com>, Michael Ellerman <mpe@...erman.id.au>, 
	Nicholas Piggin <npiggin@...il.com>, Christophe Leroy <christophe.leroy@...roup.eu>, 
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, 
	"David S. Miller" <davem@...emloft.net>, Andreas Larsson <andreas@...sler.com>, 
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Masahiro Yamada <masahiroy@...nel.org>, linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, linux-mips@...r.kernel.org, sparclinux@...r.kernel.org
Subject: Re: [PATCH v2 00/10] kbuild: userprogs: introduce
 architecture-specific CC_CAN_LINK and userprog flags

On Wed, Nov 12, 2025 at 09:03:23PM +0100, Nicolas Schier wrote:
> On Tue, Oct 14, 2025 at 03:05:15PM +0200, Thomas Weißschuh wrote:
> > The current logic to inherit -m32/-m64 from the kernel build only works
> > for a few architectures. It does not handle byte order differences,
> > architectures using different compiler flags or different kinds of ABIs.
> > 
> > Introduce a per-architecture override mechanism to set CC_CAN_LINK and
> > the flags used for userprogs.
> > 
> > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> > ---
> > Changes in v2:
> > - Rebase and drop already applied patch
> > - Disable CC_CAN_LINK if the test program generates warnings
> > - Move to architecture-specific logic
> > - Link to v1: https://lore.kernel.org/r/20250813-kbuild-userprogs-bits-v1-0-2d9f7f411083@linutronix.de
> > 
> > ---
> > Thomas Weißschuh (10):
> >       kbuild: don't enable CC_CAN_LINK if the dummy program generates warnings
> >       init: deduplicate cc-can-link.sh invocations
> >       kbuild: allow architectures to override CC_CAN_LINK
> >       riscv: Implement custom CC_CAN_LINK
> >       s390: Implement custom CC_CAN_LINK
> >       powerpc: Implement custom CC_CAN_LINK
> >       MIPS: Implement custom CC_CAN_LINK
> >       x86/Kconfig: Implement custom CC_CAN_LINK
> >       sparc: Implement custom CC_CAN_LINK
> >       kbuild: simplify CC_CAN_LINK
> > 
> >  Makefile                |  8 ++++++--
> >  arch/mips/Kconfig       | 15 +++++++++++++++
> >  arch/powerpc/Kconfig    | 15 +++++++++++++++
> >  arch/riscv/Kconfig      | 11 +++++++++++
> >  arch/s390/Kconfig       | 11 +++++++++++
> >  arch/sparc/Kconfig      | 11 +++++++++++
> >  arch/x86/Kconfig        | 11 +++++++++++
> >  init/Kconfig            |  7 +++++--
> >  scripts/Kconfig.include |  3 +++
> >  scripts/cc-can-link.sh  |  2 +-
> >  10 files changed, 89 insertions(+), 5 deletions(-)
> > ---
> > base-commit: 10f8210c7a7098897fcee5ca70236167b39eb797
> > change-id: 20250813-kbuild-userprogs-bits-03c117da4d50
> > 
> > Best regards,
> > -- 
> > Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> > 
> 
> Thanks for the patch set and all the work behind!  I found only one
> issue in patch 3, the rest looks good to me as they are.
> 
> I haven't reviewed the compiler flags for the archs, but from the formal
> point of view they look good to me, too.
> 
> How shall we proceed with here?  I think, easiest would be if we get
> appropriate acks from the architecture maintainers, so we could take
> this via kbuild.

That would surely be the best option. Unfortunately quite frequently it is hard
to get architecture maintainer's feedback on a cross-architecture series.

> Other opinions?

It would also work to only take the first three patches through the kbuild tree
and push the other ones through the architecture trees.

I don't really have a clear preference.


Thomas