Messages in this thread Patch in this message | | | Date | Thu, 6 Aug 2020 12:17:14 -0700 | From | Sami Tolvanen <> | Subject | Re: [PATCH] arm64: tlb: fix ARM64_TLB_RANGE with LLVM's integrated assembler |
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On Thu, Aug 06, 2020 at 01:01:09PM +0100, Catalin Marinas wrote: > On Wed, Aug 05, 2020 at 11:19:20AM -0700, Sami Tolvanen wrote: > > diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h > > index d493174415db..66c2aab5e9cb 100644 > > --- a/arch/arm64/include/asm/tlbflush.h > > +++ b/arch/arm64/include/asm/tlbflush.h > > @@ -16,6 +16,16 @@ > > #include <asm/cputype.h> > > #include <asm/mmu.h> > > > > +/* > > + * Enable ARMv8.4-TLBI instructions with ARM64_TLB_RANGE. Note that binutils > > + * doesn't support .arch_extension tlb-rmi, so use .arch armv8.4-a instead. > > + */ > > +#ifdef CONFIG_ARM64_TLB_RANGE > > +#define __TLBI_PREAMBLE ".arch armv8.4-a\n" > > +#else > > +#define __TLBI_PREAMBLE > > +#endif > > + > > /* > > * Raw TLBI operations. > > * > > @@ -28,14 +38,16 @@ > > * not. The macros handles invoking the asm with or without the > > * register argument as appropriate. > > */ > > -#define __TLBI_0(op, arg) asm ("tlbi " #op "\n" \ > > +#define __TLBI_0(op, arg) asm (__TLBI_PREAMBLE \ > > + "tlbi " #op "\n" \ > > ALTERNATIVE("nop\n nop", \ > > "dsb ish\n tlbi " #op, \ > > ARM64_WORKAROUND_REPEAT_TLBI, \ > > CONFIG_ARM64_WORKAROUND_REPEAT_TLBI) \ > > : : ) > > > > -#define __TLBI_1(op, arg) asm ("tlbi " #op ", %0\n" \ > > +#define __TLBI_1(op, arg) asm (__TLBI_PREAMBLE \ > > + "tlbi " #op ", %0\n" \ > > ALTERNATIVE("nop\n nop", \ > > "dsb ish\n tlbi " #op ", %0", \ > > ARM64_WORKAROUND_REPEAT_TLBI, \ > > A potential problem here is that for gas (not sure about the integrated > assembler), .arch overrides any other .arch. So if we end up with two > preambles included in the same generated .S files in the future, it will > lead to some random behaviour. > > Does the LLVM integrated assembler have the same behaviour on .arch > overriding a prior .arch?
I would assume so, but each inline assembly block is independent in LLVM, so unless there are .arch changes within the block, that shouldn't be an issue for the integrated assembler.
> Maybe a better solution is for all inline asm on arm64 to have a > standard preamble which is the maximum supported architecture version. > We can add individual .arch_extension as those are not overriding.
Sure, that works. How would you feel about something like this, so we can keep the preamble in sync with future -Wa,-march changes? I'm not sure if asm/compiler.h is the correct place for the definition though.
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 55bc8546d9c7..0dd07059beaa 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -82,8 +82,8 @@ endif # compiler to generate them and consequently to break the single image contract # we pass it only to the assembler. This option is utilized only in case of non # integrated assemblers. -ifneq ($(CONFIG_AS_HAS_ARMV8_4), y) -branch-prot-flags-$(CONFIG_AS_HAS_PAC) += -Wa,-march=armv8.3-a +ifeq ($(CONFIG_AS_HAS_PAC), y) +asm-arch := armv8.3-a endif endif @@ -91,7 +91,12 @@ KBUILD_CFLAGS += $(branch-prot-flags-y) ifeq ($(CONFIG_AS_HAS_ARMV8_4), y) # make sure to pass the newest target architecture to -march. -KBUILD_CFLAGS += -Wa,-march=armv8.4-a +asm-arch := armv8.4-a +endif + +ifdef asm-arch +KBUILD_CFLAGS += -Wa,-march=$(asm-arch) \ + -DARM64_ASM_ARCH='"$(asm-arch)"' endif ifeq ($(CONFIG_SHADOW_CALL_STACK), y) diff --git a/arch/arm64/include/asm/compiler.h b/arch/arm64/include/asm/compiler.h index 51a7ce87cdfe..6fb2e6bcc392 100644 --- a/arch/arm64/include/asm/compiler.h +++ b/arch/arm64/include/asm/compiler.h @@ -2,6 +2,12 @@ #ifndef __ASM_COMPILER_H #define __ASM_COMPILER_H +#ifdef ARM64_ASM_ARCH +#define ARM64_ASM_PREAMBLE ".arch " ARM64_ASM_ARCH "\n" +#else +#define ARM64_ASM_PREAMBLE +#endif + /* * The EL0/EL1 pointer bits used by a pointer authentication code. * This is dependent on TBI0/TBI1 being enabled, or bits 63:56 would also apply. diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h index d493174415db..cc3f5a33ff9c 100644 --- a/arch/arm64/include/asm/tlbflush.h +++ b/arch/arm64/include/asm/tlbflush.h @@ -28,14 +28,16 @@ * not. The macros handles invoking the asm with or without the * register argument as appropriate. */ -#define __TLBI_0(op, arg) asm ("tlbi " #op "\n" \ +#define __TLBI_0(op, arg) asm (ARM64_ASM_PREAMBLE \ + "tlbi " #op "\n" \ ALTERNATIVE("nop\n nop", \ "dsb ish\n tlbi " #op, \ ARM64_WORKAROUND_REPEAT_TLBI, \ CONFIG_ARM64_WORKAROUND_REPEAT_TLBI) \ : : ) -#define __TLBI_1(op, arg) asm ("tlbi " #op ", %0\n" \ +#define __TLBI_1(op, arg) asm (ARM64_ASM_PREAMBLE \ + "tlbi " #op ", %0\n" \ ALTERNATIVE("nop\n nop", \ "dsb ish\n tlbi " #op ", %0", \ ARM64_WORKAROUND_REPEAT_TLBI, \ Sami
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