From 1d2e9b67b001f8c0d10138797b9df4779609c03c Mon Sep 17 00:00:00 2001 From: Nick Desaulniers Date: Mon, 24 Oct 2022 20:46:05 +0100 Subject: [PATCH] ARM: 9265/1: pass -march= only to compiler When both -march= and -Wa,-march= are specified for assembler or assembler-with-cpp sources, GCC and Clang will prefer the -Wa,-march= value but Clang will warn that -march= is unused. warning: argument unused during compilation: '-march=armv6k' [-Wunused-command-line-argument] This is the top group of warnings we observe when using clang to assemble the kernel via `ARCH=arm make LLVM=1`. Split the arch-y make variable into two, so that -march= flags only get passed to the compiler, not the assembler. -D flags are added to KBUILD_CPPFLAGS which is used for both C and assembler-with-cpp sources. Clang is trying to warn that it doesn't support different values for -march= and -Wa,-march= (like GCC does, but the kernel doesn't need this) though the value of the preprocessor define __thumb2__ is based on -march=. Make sure to re-set __thumb2__ via -D flag for assembler sources now that we're no longer passing -march= to the assembler. Set it to a different value than the preprocessor would for -march= in case -march= gets accidentally re-added to KBUILD_AFLAGS in the future. Thanks to Ard and Nathan for this suggestion. Link: https://github.com/ClangBuiltLinux/linux/issues/1315 Link: https://github.com/ClangBuiltLinux/linux/issues/1587 Link: https://github.com/llvm/llvm-project/issues/55656 Suggested-by: Ard Biesheuvel Suggested-by: Nathan Chancellor Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor Signed-off-by: Nick Desaulniers Signed-off-by: Russell King (Oracle) --- arch/arm/Makefile | 36 +++++++++++++++++++++++++----------- 1 file changed, 25 insertions(+), 11 deletions(-) diff --git a/arch/arm/Makefile b/arch/arm/Makefile index 5fdd6b9..357f0d9 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -60,21 +60,34 @@ endif KBUILD_CFLAGS += $(call cc-option,-fno-ipa-sra) # This selects which instruction set is used. +arch-$(CONFIG_CPU_32v7M) :=-march=armv7-m +arch-$(CONFIG_CPU_32v7) :=-march=armv7-a +arch-$(CONFIG_CPU_32v6) :=-march=armv6 +# Only override the compiler option if ARMv6. The ARMv6K extensions are +# always available in ARMv7 +ifeq ($(CONFIG_CPU_32v6),y) +arch-$(CONFIG_CPU_32v6K) :=-march=armv6k +endif +arch-$(CONFIG_CPU_32v5) :=-march=armv5te +arch-$(CONFIG_CPU_32v4T) :=-march=armv4t +arch-$(CONFIG_CPU_32v4) :=-march=armv4 +arch-$(CONFIG_CPU_32v3) :=-march=armv3m + # Note that GCC does not numerically define an architecture version # macro, but instead defines a whole series of macros which makes # testing for a specific architecture or later rather impossible. -arch-$(CONFIG_CPU_32v7M) :=-D__LINUX_ARM_ARCH__=7 -march=armv7-m -arch-$(CONFIG_CPU_32v7) :=-D__LINUX_ARM_ARCH__=7 -march=armv7-a -arch-$(CONFIG_CPU_32v6) :=-D__LINUX_ARM_ARCH__=6 -march=armv6 -# Only override the compiler opt:ion if ARMv6. The ARMv6K extensions are +cpp-$(CONFIG_CPU_32v7M) :=-D__LINUX_ARM_ARCH__=7 +cpp-$(CONFIG_CPU_32v7) :=-D__LINUX_ARM_ARCH__=7 +cpp-$(CONFIG_CPU_32v6) :=-D__LINUX_ARM_ARCH__=6 +# Only override the compiler option if ARMv6. The ARMv6K extensions are # always available in ARMv7 ifeq ($(CONFIG_CPU_32v6),y) -arch-$(CONFIG_CPU_32v6K) :=-D__LINUX_ARM_ARCH__=6 -march=armv6k +cpp-$(CONFIG_CPU_32v6K) :=-D__LINUX_ARM_ARCH__=6 endif -arch-$(CONFIG_CPU_32v5) :=-D__LINUX_ARM_ARCH__=5 -march=armv5te -arch-$(CONFIG_CPU_32v4T) :=-D__LINUX_ARM_ARCH__=4 -march=armv4t -arch-$(CONFIG_CPU_32v4) :=-D__LINUX_ARM_ARCH__=4 -march=armv4 -arch-$(CONFIG_CPU_32v3) :=-D__LINUX_ARM_ARCH__=3 -march=armv3m +cpp-$(CONFIG_CPU_32v5) :=-D__LINUX_ARM_ARCH__=5 +cpp-$(CONFIG_CPU_32v4T) :=-D__LINUX_ARM_ARCH__=4 +cpp-$(CONFIG_CPU_32v4) :=-D__LINUX_ARM_ARCH__=4 +cpp-$(CONFIG_CPU_32v3) :=-D__LINUX_ARM_ARCH__=3 # This selects how we optimise for the processor. tune-$(CONFIG_CPU_ARM7TDMI) :=-mtune=arm7tdmi @@ -119,15 +132,16 @@ AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W) ifeq ($(CONFIG_THUMB2_KERNEL),y) CFLAGS_ISA :=-mthumb -Wa,-mimplicit-it=always $(AFLAGS_NOWARN) -AFLAGS_ISA :=$(CFLAGS_ISA) -Wa$(comma)-mthumb +AFLAGS_ISA :=$(CFLAGS_ISA) -Wa$(comma)-mthumb -D__thumb2__=2 else CFLAGS_ISA :=$(call cc-option,-marm,) $(AFLAGS_NOWARN) AFLAGS_ISA :=$(CFLAGS_ISA) endif # Need -Uarm for gcc < 3.x +KBUILD_CPPFLAGS +=$(cpp-y) KBUILD_CFLAGS +=$(CFLAGS_ABI) $(CFLAGS_ISA) $(arch-y) $(tune-y) $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,)) -msoft-float -Uarm -KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) $(arch-y) $(tune-y) -include asm/unified.h -msoft-float +KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) -Wa,$(arch-y) $(tune-y) -include asm/unified.h -msoft-float CHECKFLAGS += -D__arm__ -- 2.7.4