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

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Message-ID: <aRToC77bNUy2sKAK@derry.ads.avm.de>
Date: Wed, 12 Nov 2025 21:03:23 +0100
From: Nicolas Schier <nsc@...nel.org>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
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 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.

Other opinions?

Kind regards,
Nicolas