On Wed, Apr 24, 2019 at 09:55:37AM -0700, Kees Cook 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 uses > UNDEFINE_MRS_S and UNDEFINE_MSR_S to define corresponding macros > in-place and workaround gcc and clang limitations on redefining macros > across different assembler blocks. > > Specifically, the current state after preprocessing looks like this: > > asm volatile(".macro mXX_s ... .endm"); > void f() > { > asm volatile("mXX_s a, b"); > } > > With GCC, it gives macro redefinition error because sysreg.h is included > in multiple source files, and assembler code for all of them is later > combined for LTO (I've seen an intermediate file with hundreds of > identical definitions). > > With clang, it gives macro undefined error because clang doesn't allow > sharing macros between inline asm statements. > > I also seem to remember catching another sort of undefined error with > GCC due to reordering of macro definition asm statement and generated > asm code for function that uses the macro. > > The solution with defining and undefining for each use, while certainly > not elegant, satisfies both GCC and clang, LTO and non-LTO. > > Co-developed-by: Alex Matveev <[email protected]> > Co-developed-by: Yury Norov <[email protected]> > Co-developed-by: Sami Tolvanen <[email protected]> > Signed-off-by: Kees Cook <[email protected]>
I've given this a spin with the kernel.org crosstool GCC 8.1.0 toolchain, and I can confirm defconfig compiels cleanly and works as expected. AFAICT, all usage in inline assembly has been updated, and the removal of explicit stringification makes usage a bit easier to read, which is a nice bonus! I don't think we can make this any cleaner short of not having to manually assemble the instructions, so FWIW: Reviewed-by: Mark Rutland <[email protected]> I'll leave this to Catalin and Will. Thanks, Mark. > --- > v5: include register declaration in macro (rutland) > v4: move to using preprocessor entirely, split constraints for "rZ" case. > v3: added more uses in irqflags, updated commit log, based on > discussion in https://lore.kernel.org/patchwork/patch/851580/ > --- > arch/arm64/include/asm/irqflags.h | 8 +++--- > arch/arm64/include/asm/kvm_hyp.h | 4 +-- > arch/arm64/include/asm/sysreg.h | 45 ++++++++++++++++++++++--------- > 3 files changed, 38 insertions(+), 19 deletions(-) > > diff --git a/arch/arm64/include/asm/irqflags.h > b/arch/arm64/include/asm/irqflags.h > index 43d8366c1e87..629963189085 100644 > --- a/arch/arm64/include/asm/irqflags.h > +++ b/arch/arm64/include/asm/irqflags.h > @@ -43,7 +43,7 @@ static inline void arch_local_irq_enable(void) > asm volatile(ALTERNATIVE( > "msr daifclr, #2 // arch_local_irq_enable\n" > "nop", > - "msr_s " __stringify(SYS_ICC_PMR_EL1) ",%0\n" > + __msr_s(SYS_ICC_PMR_EL1, "%0") > "dsb sy", > ARM64_HAS_IRQ_PRIO_MASKING) > : > @@ -55,7 +55,7 @@ static inline void arch_local_irq_disable(void) > { > asm volatile(ALTERNATIVE( > "msr daifset, #2 // arch_local_irq_disable", > - "msr_s " __stringify(SYS_ICC_PMR_EL1) ", %0", > + __msr_s(SYS_ICC_PMR_EL1, "%0"), > ARM64_HAS_IRQ_PRIO_MASKING) > : > : "r" ((unsigned long) GIC_PRIO_IRQOFF) > @@ -86,7 +86,7 @@ static inline unsigned long arch_local_save_flags(void) > "mov %0, %1\n" > "nop\n" > "nop", > - "mrs_s %0, " __stringify(SYS_ICC_PMR_EL1) "\n" > + __mrs_s("%0", SYS_ICC_PMR_EL1) > "ands %1, %1, " __stringify(PSR_I_BIT) "\n" > "csel %0, %0, %2, eq", > ARM64_HAS_IRQ_PRIO_MASKING) > @@ -116,7 +116,7 @@ static inline void arch_local_irq_restore(unsigned long > flags) > asm volatile(ALTERNATIVE( > "msr daif, %0\n" > "nop", > - "msr_s " __stringify(SYS_ICC_PMR_EL1) ", %0\n" > + __msr_s(SYS_ICC_PMR_EL1, "%0") > "dsb sy", > ARM64_HAS_IRQ_PRIO_MASKING) > : "+r" (flags) > diff --git a/arch/arm64/include/asm/kvm_hyp.h > b/arch/arm64/include/asm/kvm_hyp.h > index 4da765f2cca5..c3060833b7a5 100644 > --- a/arch/arm64/include/asm/kvm_hyp.h > +++ b/arch/arm64/include/asm/kvm_hyp.h > @@ -30,7 +30,7 @@ > ({ \ > u64 reg; \ > asm volatile(ALTERNATIVE("mrs %0, " __stringify(r##nvh),\ > - "mrs_s %0, " __stringify(r##vh),\ > + __mrs_s("%0", r##vh), \ > ARM64_HAS_VIRT_HOST_EXTN) \ > : "=r" (reg)); \ > reg; \ > @@ -40,7 +40,7 @@ > do { \ > u64 __val = (u64)(v); \ > asm volatile(ALTERNATIVE("msr " __stringify(r##nvh) ", %x0",\ > - "msr_s " __stringify(r##vh) ", %x0",\ > + __msr_s(r##vh, "%x0"), \ > ARM64_HAS_VIRT_HOST_EXTN) \ > : : "rZ" (__val)); \ > } while (0) > diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h > index 5b267dec6194..3b2c09eddd8f 100644 > --- a/arch/arm64/include/asm/sysreg.h > +++ b/arch/arm64/include/asm/sysreg.h > @@ -746,20 +746,39 @@ > #include <linux/build_bug.h> > #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 __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 DEFINE_MRS_S \ > + __DEFINE_MRS_MSR_S_REGNUM \ > +" .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 DEFINE_MSR_S \ > + __DEFINE_MRS_MSR_S_REGNUM \ > +" .macro msr_s, sreg, rt\n" \ > + __emit_inst(0xd5000000|(\\sreg)|(.L__reg_num_\\rt)) \ > " .endm\n" > -); > + > +#define UNDEFINE_MRS_S \ > +" .purgem mrs_s\n" > + > +#define UNDEFINE_MSR_S \ > +" .purgem msr_s\n" > + > +#define __mrs_s(v, r) \ > + DEFINE_MRS_S \ > +" mrs_s " v ", " __stringify(r) "\n" \ > + UNDEFINE_MRS_S > + > +#define __msr_s(r, v) \ > + DEFINE_MSR_S \ > +" msr_s " __stringify(r) ", " v "\n" \ > + UNDEFINE_MSR_S > > /* > * Unlike read_cpuid, calls to read_sysreg are never expected to be > @@ -787,13 +806,13 @@ asm( > */ > #define read_sysreg_s(r) ({ \ > u64 __val; \ > - asm volatile("mrs_s %0, " __stringify(r) : "=r" (__val)); \ > + asm volatile(__mrs_s("%0", r) : "=r" (__val)); \ > __val; \ > }) > > #define write_sysreg_s(v, r) do { \ > u64 __val = (u64)(v); \ > - asm volatile("msr_s " __stringify(r) ", %x0" : : "rZ" (__val)); \ > + asm volatile(__msr_s(r, "%x0") : : "rZ" (__val)); \ > } while (0) > > /* > -- > 2.17.1 > > > -- > Kees Cook
