On Tue, Oct 29, 2024 at 09:49:07PM +0700, Koakuma via B4 Relay wrote: > From: Koakuma <koachan@xxxxxxxxxxxxxx> > > Place -fcall-used* flags behind cc-option so that clang (which doesn't > support them) can still compile the kernel. > > This is a safe change, the reasoning is as follows: > > In the (normal) 32-bit ABI, %g5 and %g7 is normally reserved, and in > the 64-bit ABI, %g7 is the reserved one. > Linux turns them into volatile registers by the way of -fcall-used-*, > but on the other hand, omitting the flags shouldn't be harmful; > compilers will now simply refuse to touch them, and any assembly > code that happens to touch them would still work like usual (because > Linux' conventions already treats them as volatile anyway). > > Signed-off-by: Koakuma <koachan@xxxxxxxxxxxxxx> Clang builds now succeed with this series and builds with GCC 14.2.0 continue to pass and boot successfully. Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx> Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx> One comment below, please carry these tags forward if there are future revisions without substantial technical changes. > --- > arch/sparc/Makefile | 4 ++-- > arch/sparc/vdso/Makefile | 2 +- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/arch/sparc/Makefile b/arch/sparc/Makefile > index 757451c3ea1df63b948e68a45988c78f5974f9ea..0400078076e588be93a702d1c64eb9fd34466075 100644 > --- a/arch/sparc/Makefile > +++ b/arch/sparc/Makefile > @@ -29,7 +29,7 @@ UTS_MACHINE := sparc > # versions of gcc. Some gcc versions won't pass -Av8 to binutils when you > # give -mcpu=v8. This silently worked with older bintutils versions but > # does not any more. > -KBUILD_CFLAGS += -m32 -mcpu=v8 -pipe -mno-fpu -fcall-used-g5 -fcall-used-g7 > +KBUILD_CFLAGS += -m32 -mcpu=v8 -pipe -mno-fpu $(call cc-option,-fcall-used-g5) $(call cc-option,-fcall-used-g7) Small nit, this (and the one in the vdso) could probably be one cc-option call? Is it likely that one flag would be implemented in the compiler without the other? $(call cc-option,-fcall-used-g5 -fcall-used-g7) > KBUILD_CFLAGS += -Wa,-Av8 > > KBUILD_AFLAGS += -m32 -Wa,-Av8 > @@ -45,7 +45,7 @@ export BITS := 64 > UTS_MACHINE := sparc64 > > KBUILD_CFLAGS += -m64 -pipe -mno-fpu -mcpu=ultrasparc -mcmodel=medlow > -KBUILD_CFLAGS += -ffixed-g4 -ffixed-g5 -fcall-used-g7 -Wno-sign-compare > +KBUILD_CFLAGS += -ffixed-g4 -ffixed-g5 $(call cc-option,-fcall-used-g7) -Wno-sign-compare > KBUILD_CFLAGS += -Wa,--undeclared-regs > KBUILD_CFLAGS += $(call cc-option,-mtune=ultrasparc3) > KBUILD_AFLAGS += -m64 -mcpu=ultrasparc -Wa,--undeclared-regs > diff --git a/arch/sparc/vdso/Makefile b/arch/sparc/vdso/Makefile > index 243dbfc4609d804fc221c3591eebe891107ffdab..50ec2978cda5397841daad6ffdc9682811b9b38e 100644 > --- a/arch/sparc/vdso/Makefile > +++ b/arch/sparc/vdso/Makefile > @@ -46,7 +46,7 @@ CFL := $(PROFILING) -mcmodel=medlow -fPIC -O2 -fasynchronous-unwind-tables -m64 > -fno-omit-frame-pointer -foptimize-sibling-calls \ > -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO > > -SPARC_REG_CFLAGS = -ffixed-g4 -ffixed-g5 -fcall-used-g5 -fcall-used-g7 > +SPARC_REG_CFLAGS = -ffixed-g4 -ffixed-g5 $(call cc-option,-fcall-used-g5) $(call cc-option,-fcall-used-g7) > > $(vobjs): KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(SPARC_REG_CFLAGS),$(KBUILD_CFLAGS)) $(CFL) > > > -- > 2.47.0 > > >
