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kbuild: allow architectures to override CC_CAN_LINK 

The generic test for CC_CAN_LINK assumes that all architectures use -m32
and -m64 to switch between 32-bit and 64-bit compilation. This is overly
simplistic. Architectures may use other flags (-mabi, -m31, etc.) or may
also require byte order handling (-mlittle-endian, -EL). Expressing all
of the different possibilities will be very complicated and brittle.
Instead allow architectures to supply their own logic which will be
easy to understand and evolve.

Both the boolean ARCH_HAS_CC_CAN_LINK and the string ARCH_USERFLAGS need
to be implemented as kconfig does not allow the reuse of string options.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20251114-kbuild-userprogs-bits-v3-3-4dee0d74d439@linutronix.de
Signed-off-by: Nicolas Schier <nsc@kernel.org>
This commit is contained in:
Thomas Weißschuh 2025-11-14 14:43:58 +01:00 committed by Nicolas Schier
parent 80623f2c83
commit deab487e0f
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GPG Key ID: 07520A7016261269
2 changed files with 15 additions and 2 deletions
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13
Makefile
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@ -1137,8 +1137,17 @@ ifneq ($(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS),)
LDFLAGS_vmlinux += --emit-relocs --discard-none
endif
# Align the bit size of userspace programs with the kernel
USERFLAGS_FROM_KERNEL := -m32 -m64 --target=%
# Align the architecture of userspace programs with the kernel
USERFLAGS_FROM_KERNEL := --target=%
ifdef CONFIG_ARCH_USERFLAGS
KBUILD_USERCFLAGS += $(CONFIG_ARCH_USERFLAGS)
KBUILD_USERLDFLAGS += $(CONFIG_ARCH_USERFLAGS)
else
# If not overridden also inherit the bit size
USERFLAGS_FROM_KERNEL += -m32 -m64
endif
KBUILD_USERCFLAGS += $(filter $(USERFLAGS_FROM_KERNEL), $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))
KBUILD_USERLDFLAGS += $(filter $(USERFLAGS_FROM_KERNEL), $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS))

4
init/Kconfig
View File

@ -82,8 +82,12 @@ config RUSTC_LLVM_VERSION
int
default $(rustc-llvm-version)
config ARCH_HAS_CC_CAN_LINK
bool
config CC_CAN_LINK
bool
default ARCH_CC_CAN_LINK if ARCH_HAS_CC_CAN_LINK
default $(cc_can_link_user,$(m64-flag)) if 64BIT
default $(cc_can_link_user,$(m32-flag))