linux-kernel - [PATCH v2 01/10] kbuild: don't enable CC_CAN_LINK if the dummy program generates warnings

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Message-Id: <20251014-kbuild-userprogs-bits-v2-1-faeec46e887a@linutronix.de>
Date: Tue, 14 Oct 2025 15:05:16 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Nathan Chancellor <nathan@...nel.org>, 
 Nicolas Schier <nicolas.schier@...ux.dev>, Nicolas Schier <nsc@...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>
Cc: 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, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH v2 01/10] kbuild: don't enable CC_CAN_LINK if the dummy
 program generates warnings

It is possible that the kernel toolchain generates warnings when used
together with the system toolchain. This happens for example when the
older kernel toolchain does not handle new versions of sframe debug
information. While these warnings where ignored during the evaluation
of CC_CAN_LINK, together with CONFIG_WERROR the actual userprog build
will later fail.

Example warning:

.../x86_64-linux/13.2.0/../../../../x86_64-linux/bin/ld:
error in /lib/../lib64/crt1.o(.sframe); no .sframe will be created
collect2: error: ld returned 1 exit status

Make sure that the very simple example program does not generate
warnings already to avoid breaking the userprog compilations.

Fixes: ec4a3992bc0b ("kbuild: respect CONFIG_WERROR for linker and assembler")
Fixes: 3f0ff4cc6ffb ("kbuild: respect CONFIG_WERROR for userprogs")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
---
 scripts/cc-can-link.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/cc-can-link.sh b/scripts/cc-can-link.sh
index 6efcead3198989d2ab2ab6772c72d8bb61c89c4e..e67fd8d7b6841e53341045b28dc5196cc1327cbe 100755
--- a/scripts/cc-can-link.sh
+++ b/scripts/cc-can-link.sh
@@ -1,7 +1,7 @@
 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0

-cat << "END" | $@ -x c - -o /dev/null >/dev/null 2>&1
+cat << "END" | $@ -Werror -Wl,--fatal-warnings -x c - -o /dev/null >/dev/null 2>&1
 #include <stdio.h>
 int main(void)
 {

-- 
2.51.0