On Tue, Oct 09, 2012 at 05:23:00PM +0200, Arnd Bergmann wrote: > The Linaro cross toolchain and probably others nowadays default to > building in THUMB2 mode. When building a kernel for a CPU that does > not support THUMB2, the compiler complains about incorrect flags. > We can work around this by setting -marm for all non-T2 builds. > > Without this patch, building assabet_defconfig results in: > > usr/initramfs_data.S:1:0: warning: target CPU does not support THUMB > instructions [enabled by default] > arch/arm/nwfpe/entry.S:1:0: warning: target CPU does not support THUMB > instructions [enabled by default] > firmware/cis/PCMLM28.cis.gen.S:1:0: warning: target CPU does not support > THUMB instructions [enabled by default] > (and many more) > > Signed-off-by: Arnd Bergmann <a...@arndb.de> > Acked-by: Nicolas Pitre <n...@linaro.org> > Cc: Russell King <rmk+ker...@arm.linux.org.uk> > Cc: Dave Martin <dave.mar...@linaro.org>
This looks like a sensible fix, but it could be worth amending the commit message to explain what was fixed, since it took me a moment or two to puzzle out why the code this patch removes was broken. Maybe something like: -marm was passed unconditionally for C files previously, but nothing was passed to the gcc frontend when processing .S files, resulting in a warning. The assembler never defaults to ARM unless -Wa,-mthumb is supplied explicitly, so the files were still assembled correctly. This patch makes sure that -marm is passed for .S files too, and also avoids the redundant gcc -marm -mthumb in Thumb kernels. Preferably with that (or equivalent): Acked-by: Dave Martin <dave.mar...@linaro.org> > --- > arch/arm/Makefile | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/arch/arm/Makefile b/arch/arm/Makefile > index f023e3a..5f914fc 100644 > --- a/arch/arm/Makefile > +++ b/arch/arm/Makefile > @@ -21,8 +21,6 @@ endif > OBJCOPYFLAGS :=-O binary -R .comment -S > GZFLAGS :=-9 > #KBUILD_CFLAGS +=-pipe > -# Explicitly specifiy 32-bit ARM ISA since toolchain default can be -mthumb: > -KBUILD_CFLAGS +=$(call cc-option,-marm,) > > # Never generate .eh_frame > KBUILD_CFLAGS += $(call cc-option,-fno-dwarf2-cfi-asm) > @@ -105,17 +103,20 @@ endif > ifeq ($(CONFIG_THUMB2_KERNEL),y) > AFLAGS_AUTOIT :=$(call > as-option,-Wa$(comma)-mimplicit-it=always,-Wa$(comma)-mauto-it) > AFLAGS_NOWARN :=$(call > as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W) > -CFLAGS_THUMB2 :=-mthumb $(AFLAGS_AUTOIT) $(AFLAGS_NOWARN) > -AFLAGS_THUMB2 :=$(CFLAGS_THUMB2) -Wa$(comma)-mthumb > +CFLAGS_ISA :=-mthumb $(AFLAGS_AUTOIT) $(AFLAGS_NOWARN) > +AFLAGS_ISA :=$(CFLAGS_ISA) -Wa$(comma)-mthumb > # Work around buggy relocation from gas if requested: > ifeq ($(CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11),y) > CFLAGS_MODULE +=-fno-optimize-sibling-calls > endif > +else > +CFLAGS_ISA :=$(call cc-option,-marm,) > +AFLAGS_ISA :=$(CFLAGS_ISA) > endif > > # Need -Uarm for gcc < 3.x > -KBUILD_CFLAGS +=$(CFLAGS_ABI) $(CFLAGS_THUMB2) $(arch-y) $(tune-y) > $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,)) > -msoft-float -Uarm > -KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_THUMB2) $(arch-y) $(tune-y) > -include asm/unified.h -msoft-float > +KBUILD_CFLAGS +=$(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 > > CHECKFLAGS += -D__arm__ > > -- > 1.7.10 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
