These mrs_s and msr_s macros in particular were preventing us from linking arm64 with Clang's integrated assembler, regardless of LTO. Those macros ran into: https://bugs.llvm.org/show_bug.cgi?id=19749. So while I appreciate how clever they are, they prevent us from assembling with Clang so I would like to see them go.
On Fri, Nov 3, 2017 at 10:12 AM, Sami Tolvanen <samitolva...@google.com> wrote: > Clang's integrated assembler does not allow assembly macros defined > in one inline asm block using the .macro directive to be used across > separate asm blocks. LLVM developers consider this a feature and not a > bug, recommending code refactoring: > > https://bugs.llvm.org/show_bug.cgi?id=19749 > > As binutils doesn't allow macros to be redefined, this change adds C > preprocessor macros that define the assembly macros globally for binutils > and locally for clang's integrated assembler. > > Suggested-by: Greg Hackmann <ghackm...@google.com> > Suggested-by: Nick Desaulniers <ndesaulni...@google.com> > Signed-off-by: Sami Tolvanen <samitolva...@google.com> > --- > arch/arm64/include/asm/kvm_hyp.h | 2 ++ > arch/arm64/include/asm/sysreg.h | 71 > ++++++++++++++++++++++++++++++---------- > 2 files changed, 56 insertions(+), 17 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_hyp.h > b/arch/arm64/include/asm/kvm_hyp.h > index 4572a9b560fa..6840704ea894 100644 > --- a/arch/arm64/include/asm/kvm_hyp.h > +++ b/arch/arm64/include/asm/kvm_hyp.h > @@ -29,6 +29,7 @@ > ({ \ > u64 reg; \ > asm volatile(ALTERNATIVE("mrs %0, " __stringify(r##nvh),\ > + DEFINE_MRS_S \ > "mrs_s %0, " __stringify(r##vh),\ > ARM64_HAS_VIRT_HOST_EXTN) \ > : "=r" (reg)); \ > @@ -39,6 +40,7 @@ > do { \ > u64 __val = (u64)(v); \ > asm volatile(ALTERNATIVE("msr " __stringify(r##nvh) ", %x0",\ > + DEFINE_MSR_S \ > "msr_s " __stringify(r##vh) ", %x0",\ > ARM64_HAS_VIRT_HOST_EXTN) \ > : : "rZ" (__val)); \ > diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h > index f707fed5886f..1588ac3f3690 100644 > --- a/arch/arm64/include/asm/sysreg.h > +++ b/arch/arm64/include/asm/sysreg.h > @@ -463,21 +463,58 @@ > > #include <linux/types.h> > > -asm( > -" .irp > num,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30\n" > -" .equ .L__reg_num_x\\num, \\num\n" > -" .endr\n" > +#define ___MRS_MSR_S_REGNUM \ > +" .irp > num,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30\n" > \ > +" .equ .L__reg_num_x\\num, \\num\n" \ > +" .endr\n" \ > " .equ .L__reg_num_xzr, 31\n" > -"\n" > -" .macro mrs_s, rt, sreg\n" > - __emit_inst(0xd5200000|(\\sreg)|(.L__reg_num_\\rt)) > + > +#define ___MRS_S \ > +" .macro mrs_s, rt, sreg\n" \ > + __emit_inst(0xd5200000|(\\sreg)|(.L__reg_num_\\rt)) \ > " .endm\n" > -"\n" > -" .macro msr_s, sreg, rt\n" > - __emit_inst(0xd5000000|(\\sreg)|(.L__reg_num_\\rt)) > + > +#define ___MSR_S \ > +" .macro msr_s, sreg, rt\n" \ > + __emit_inst(0xd5000000|(\\sreg)|(.L__reg_num_\\rt)) \ > " .endm\n" > + > +/* > + * llvm-as doesn't allow macros defined in an asm block to be used in other > + * asm blocks, which means we cannot define them globally. > + */ > +#if !defined(CONFIG_CLANG_LTO) > +asm( > + ___MRS_MSR_S_REGNUM > + ___MRS_S > + ___MSR_S > ); > > +#undef ___MRS_MSR_S_REGNUM > +#define ___MRS_MSR_S_REGNUM > +#undef ___MRS_S > +#define ___MRS_S > +#undef ___MSR_S > +#define ___MSR_S > +#endif > + > +#define DEFINE_MRS_S \ > + ___MRS_MSR_S_REGNUM \ > + ___MRS_S > + > +#define DEFINE_MSR_S \ > + ___MRS_MSR_S_REGNUM \ > + ___MSR_S > + > + > +#define __mrs_s(r, v) \ > + DEFINE_MRS_S \ > +" mrs_s %0, " __stringify(r) : "=r" (v) > + > +#define __msr_s(r, v) \ > + DEFINE_MSR_S \ > +" msr_s " __stringify(r) ", %0" : : "r" (v) > + > /* > * Unlike read_cpuid, calls to read_sysreg are never expected to be > * optimized away or replaced with synthetic values. > @@ -502,15 +539,15 @@ asm( > * For registers without architectural names, or simply unsupported by > * GAS. > */ > -#define read_sysreg_s(r) ({ \ > - u64 __val; \ > - asm volatile("mrs_s %0, " __stringify(r) : "=r" (__val)); \ > - __val; \ > +#define read_sysreg_s(r) ({ \ > + u64 __val; \ > + asm volatile(__mrs_s(r, __val)); \ > + __val; \ > }) > > -#define write_sysreg_s(v, r) do { \ > - u64 __val = (u64)(v); \ > - asm volatile("msr_s " __stringify(r) ", %x0" : : "rZ" (__val)); \ > +#define write_sysreg_s(v, r) do { \ > + u64 __val = (u64)(v); \ > + asm volatile(__msr_s(r, __val)); \ > } while (0) > > static inline void config_sctlr_el1(u32 clear, u32 set) > -- > 2.15.0.403.gc27cc4dac6-goog > -- Thanks, ~Nick Desaulniers
