Re: [PATCH fixes] riscv: Fix CONFIG_AS_HAS_INSN for new .insn usage

[Paul Walmsley <pjw@kernel.org>]

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Hi Nathan,

On Fri, 7 Nov 2025, Nathan Chancellor wrote:

> After commit 44aa25c000b4 ("riscv: asm: use .insn for making custom
> instructions"), builds using LLVM older that 19 or binutils older than
> 2.38 fail with:
> 
>   arch/riscv/include/asm/vdso/processor.h: Assembler messages:
>   arch/riscv/include/asm/vdso/processor.h:27: Error: unrecognized opcode `0x100000f'
>   arch/riscv/include/asm/vdso/processor.h:27: Error: unrecognized opcode `0x100000f'
>   arch/riscv/include/asm/vdso/processor.h:27: Error: unrecognized opcode `0x100000f'
>   arch/riscv/include/asm/vdso/processor.h:27: Error: unrecognized opcode `0x100000f'
>   make[4]: *** [scripts/Makefile.build:287: arch/riscv/kernel/vdso/vgettimeofday.o] Error 1
> 
>   In file included from <built-in>:4:
>   In file included from lib/vdso/gettimeofday.c:6:
>   In file included from include/vdso/datapage.h:21:
>   In file included from include/vdso/processor.h:10:
>   arch/riscv/include/asm/vdso/processor.h:23:2: error: expected instruction format
>      23 |         ALT_RISCV_PAUSE();
>         |         ^
>   arch/riscv/include/asm/errata_list.h:47:3: note: expanded from macro 'ALT_RISCV_PAUSE'
>      47 |                 RISCV_PAUSE, /* Original RISC‑V pause insn */ \
>         |                 ^
>   arch/riscv/include/asm/insn-def.h:259:21: note: expanded from macro 'RISCV_PAUSE'
>     259 | #define RISCV_PAUSE     ASM_INSN_I("0x100000f")
>         |                         ^
>   arch/riscv/include/asm/asm.h:16:26: note: expanded from macro 'ASM_INSN_I'
>      16 | #define ASM_INSN_I(__x) ".insn " __x
>         |                          ^
>   <inline asm>:5:7: note: instantiated into assembly here
>       5 | .insn 0x100000f
>         |       ^
> 
> binutils gained support for '.insn <value>' in 2.38 [1] and LLVM gained
> support in 19 [2]. Adjust the test for CONFIG_AS_HAS_INSN to ensure that
> all versions of .insn are supported before being used.
> 
> Fixes: 44aa25c000b4 ("riscv: asm: use .insn for making custom instructions")
> Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=a262b82fdbf4cda3b0648b1adc32245ca3f78b7a [1]
> Link: https://github.com/llvm/llvm-project/commit/2a086dce691e3cc34a2fc27f4fb255bb2cbbfac9 [2]
> Suggested-by: Andrew Jones <ajones@ventanamicro.com>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
>  arch/riscv/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

Thanks for the fast fix, and sorry for the trouble. 

Clearly we're not doing sufficiently broad build testing here, either 
before branch submission, or on -next.  We'll fix this ASAP on the branch 
submission case, and work on improving -next autobuilds.

Queued for v6.18-rc.


- Paul