linux-kernel - [PATCH] kbuild: userprogs: use correct linker when mixing clang and GNU ld

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Message-Id: <20250724-userprogs-clang-gnu-ld-v1-1-3d3d071e53a7@linutronix.de>
Date: Thu, 24 Jul 2025 10:32:45 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Masahiro Yamada <masahiroy@...nel.org>, 
 Nathan Chancellor <nathan@...nel.org>, 
 Nicolas Schier <nicolas.schier@...ux.dev>, 
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
 llvm@...ts.linux.dev, stable@...r.kernel.org, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH] kbuild: userprogs: use correct linker when mixing clang
 and GNU ld

The userprogs infrastructure does not expect clang being used with GNU ld
and in that case uses /usr/bin/ld for linking, not the configured $(LD).
This fallback is problematic as it will break when cross-compiling.
Mixing clang and GNU ld is used for example when building for SPARC64,
as ld.lld is not sufficient; see Documentation/kbuild/llvm.rst.

Relax the check around --ld-path so it gets used for all linkers.

Fixes: dfc1b168a8c4 ("kbuild: userprogs: use correct lld when linking through clang")
Cc: stable@...r.kernel.org
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
---
Nathan, you originally proposed the check for $(CONFIG_LD_IS_LLD) [0],
could you take a look at this?

[0] https://lore.kernel.org/all/20250213175437.GA2756218@ax162/
---
 Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index c09766beb7eff4780574682b8ea44475fc0a5188..e300c6546c845c300edb5f0033719963c7da8f9b 100644
--- a/Makefile
+++ b/Makefile
@@ -1134,7 +1134,7 @@ KBUILD_USERCFLAGS  += $(filter -m32 -m64 --target=%, $(KBUILD_CPPFLAGS) $(KBUILD
 KBUILD_USERLDFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
 
 # userspace programs are linked via the compiler, use the correct linker
-ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_LD_IS_LLD),yy)
+ifneq ($(CONFIG_CC_IS_CLANG),)
 KBUILD_USERLDFLAGS += --ld-path=$(LD)
 endif
 

---
base-commit: 6832a9317eee280117cd695fa885b2b7a7a38daf
change-id: 20250723-userprogs-clang-gnu-ld-7a1c16fc852d

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@...utronix.de>