Messages in this thread | | | From | Nick Desaulniers <> | Date | Wed, 18 May 2022 13:45:15 -0700 | Subject | Re: [PATCH] riscv: Fix ALT_THEAD_PMA's asm parameters |
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On Wed, May 18, 2022 at 11:45 AM Nathan Chancellor <nathan@kernel.org> wrote: > > After commit a35707c3d850 ("riscv: add memory-type errata for T-Head"), > builds with LLVM's integrated assembler fail like: > > In file included from arch/riscv/kernel/asm-offsets.c:10: > In file included from ./include/linux/mm.h:29: > In file included from ./include/linux/pgtable.h:6: > In file included from ./arch/riscv/include/asm/pgtable.h:114: > ./arch/riscv/include/asm/pgtable-64.h:210:2: error: invalid input constraint '0' in asm > ALT_THEAD_PMA(prot_val); > ^ > ./arch/riscv/include/asm/errata_list.h:88:4: note: expanded from macro 'ALT_THEAD_PMA' > : "0"(_val), \ > ^ > > This was reported upstream to LLVM where Jessica pointed out a couple of > issues with the existing implementation of ALT_THEAD_PMA: > > * t3 is modified but not listed in the clobbers list. > > * "+r"(_val) marks _val as both an input and output of the asm but then > "0"(_val) marks _val as an input matching constraint, which does not > make much sense in this situation, as %1 is not actually used in the > asm and matching constraints are designed to be used for different > inputs that need to use the same register. > > Drop the matching contraint and shift all the operands by one, as %1 is
s/contraint/constraint/
Thanks for the fix! Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> unused, and mark t3 as clobbered. This resolves the build error and goes > not cause any problems with GNU as. > > Fixes: a35707c3d850 ("riscv: add memory-type errata for T-Head") > Link: https://github.com/ClangBuiltLinux/linux/issues/1641 > Link: https://github.com/llvm/llvm-project/issues/55514 > Link: https://gcc.gnu.org/onlinedocs/gcc/Simple-Constraints.html > Suggested-by: Jessica Clarke <jrtc27@jrtc27.com> > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > --- > arch/riscv/include/asm/errata_list.h | 14 +++++++------- > 1 file changed, 7 insertions(+), 7 deletions(-) > > diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h > index 9e2888dbb5b1..416ead0f9a65 100644 > --- a/arch/riscv/include/asm/errata_list.h > +++ b/arch/riscv/include/asm/errata_list.h > @@ -75,20 +75,20 @@ asm volatile(ALTERNATIVE( \ > "nop\n\t" \ > "nop\n\t" \ > "nop", \ > - "li t3, %2\n\t" \ > - "slli t3, t3, %4\n\t" \ > + "li t3, %1\n\t" \ > + "slli t3, t3, %3\n\t" \ > "and t3, %0, t3\n\t" \ > "bne t3, zero, 2f\n\t" \ > - "li t3, %3\n\t" \ > - "slli t3, t3, %4\n\t" \ > + "li t3, %2\n\t" \ > + "slli t3, t3, %3\n\t" \ > "or %0, %0, t3\n\t" \ > "2:", THEAD_VENDOR_ID, \ > ERRATA_THEAD_PBMT, CONFIG_ERRATA_THEAD_PBMT) \ > : "+r"(_val) \ > - : "0"(_val), \ > - "I"(_PAGE_MTMASK_THEAD >> ALT_THEAD_PBMT_SHIFT), \ > + : "I"(_PAGE_MTMASK_THEAD >> ALT_THEAD_PBMT_SHIFT), \ > "I"(_PAGE_PMA_THEAD >> ALT_THEAD_PBMT_SHIFT), \ > - "I"(ALT_THEAD_PBMT_SHIFT)) > + "I"(ALT_THEAD_PBMT_SHIFT) \ > + : "t3") > #else > #define ALT_THEAD_PMA(_val) > #endif > > base-commit: 93c0651617a62a69717299f1464dda798af8bebb > -- > 2.36.1 >
-- Thanks, ~Nick Desaulniers
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