Messages in this thread | | | Date | Thu, 02 Jun 2022 18:34:41 -0700 (PDT) | Subject | Re: [PATCH] riscv: Move alternative length validation into subsection | From | Palmer Dabbelt <> |
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On Mon, 16 May 2022 14:45:21 PDT (-0700), nathan@kernel.org wrote: > After commit 49b290e430d3 ("riscv: prevent compressed instructions in > alternatives"), builds with LLVM's integrated assembler fail: > > In file included from arch/riscv/mm/init.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:108: > ./arch/riscv/include/asm/tlbflush.h:23:2: error: expected assembly-time absolute expression > ALT_FLUSH_TLB_PAGE(__asm__ __volatile__ ("sfence.vma %0" : : "r" (addr) : "memory")); > ^ > ./arch/riscv/include/asm/errata_list.h:33:5: note: expanded from macro 'ALT_FLUSH_TLB_PAGE' > asm(ALTERNATIVE("sfence.vma %0", "sfence.vma", SIFIVE_VENDOR_ID, \ > ^ > ./arch/riscv/include/asm/alternative-macros.h:187:2: note: expanded from macro 'ALTERNATIVE' > _ALTERNATIVE_CFG(old_content, new_content, vendor_id, errata_id, CONFIG_k) > ^ > ./arch/riscv/include/asm/alternative-macros.h:113:2: note: expanded from macro '_ALTERNATIVE_CFG' > __ALTERNATIVE_CFG(old_c, new_c, vendor_id, errata_id, IS_ENABLED(CONFIG_k)) > ^ > ./arch/riscv/include/asm/alternative-macros.h:110:2: note: expanded from macro '__ALTERNATIVE_CFG' > ALT_NEW_CONTENT(vendor_id, errata_id, enable, new_c) > ^ > ./arch/riscv/include/asm/alternative-macros.h:99:3: note: expanded from macro 'ALT_NEW_CONTENT' > ".org . - (889b - 888b) + (887b - 886b)\n" \ > ^ > <inline asm>:26:6: note: instantiated into assembly here > .org . - (889b - 888b) + (887b - 886b) > ^ > > This error happens because LLVM's integrated assembler has a one-pass > design, which means it cannot figure out the instruction lengths when > the .org directive is outside of the subsection that contains the > instructions, which was changed by the .option directives added by the > above change. > > Move the .org directives before the .previous directive so that these > directives are always within the same subsection, which resolves the > failures and does not introduce any new issues with GNU as. This was > done for arm64 in commit 966a0acce2fc ("arm64/alternatives: move length > validation inside the subsection") and commit 22315a2296f4 ("arm64: > alternatives: Move length validation in alternative_{insn, endif}"). > > While there is no error from the assembly versions of the macro, they > appear to have the same problem so just make the same change there as > well so that there are no problems in the future. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1640 > Reported-by: kernel test robot <lkp@intel.com> > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > --- > arch/riscv/include/asm/alternative-macros.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/riscv/include/asm/alternative-macros.h b/arch/riscv/include/asm/alternative-macros.h > index e13b1f6bb400..ec2f3f1b836f 100644 > --- a/arch/riscv/include/asm/alternative-macros.h > +++ b/arch/riscv/include/asm/alternative-macros.h > @@ -27,9 +27,9 @@ > \new_c > .option pop > 889 : > - .previous > .org . - (889b - 888b) + (887b - 886b) > .org . - (887b - 886b) + (889b - 888b) > + .previous > .endif > .endm > > @@ -94,9 +94,9 @@ > new_c "\n" \ > ".option pop\n" \ > "889 :\n" \ > - ".previous\n" \ > ".org . - (887b - 886b) + (889b - 888b)\n" \ > ".org . - (889b - 888b) + (887b - 886b)\n" \ > + ".previous\n" \ > ".endif\n" > > #define __ALTERNATIVE_CFG(old_c, new_c, vendor_id, errata_id, enable) \ > > base-commit: 93c0651617a62a69717299f1464dda798af8bebb
Thanks, this in on for-next (still for 5.19). I'm going to CC stable so it'll get backported, as it seems pretty harmless.
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