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[FOR-NEXT] riscv: Add norvc after .option arch in runtime const

Message ID 20250331-fix_runtime_const_norvc-v1-1-89bc62687ab8@rivosinc.com (mailing list archive)
State Accepted
Commit 95c18b7ccdd1b2e6704651b66565339ada318ba2
Headers show
Series [FOR-NEXT] riscv: Add norvc after .option arch in runtime const | expand

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Commit Message

Charlie Jenkins March 31, 2025, 6:45 p.m. UTC
.option arch clobbers .option norvc. Prevent gas from emitting
compressed instructions in the runtime const alternative blocks by
setting .option norvc after .option arch. This issue starts appearing on
gcc 15, which adds zca to the march.

Reported by: Klara Modin <klarasmodin@gmail.com>

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Fixes: a44fb5722199 ("riscv: Add runtime constant support")
Closes: https://lore.kernel.org/all/cc8f3525-20b7-445b-877b-2add28a160a2@gmail.com/
---
 arch/riscv/include/asm/runtime-const.h | 2 ++
 1 file changed, 2 insertions(+)


---
base-commit: b2117b630c48be69d2782ed79fefe35dcd192ce6
change-id: 20250331-fix_runtime_const_norvc-407af1f24541

Comments

Palmer Dabbelt March 31, 2025, 6:54 p.m. UTC | #1
On Mon, 31 Mar 2025 11:45:24 PDT (-0700), Charlie Jenkins wrote:
> .option arch clobbers .option norvc. Prevent gas from emitting
> compressed instructions in the runtime const alternative blocks by
> setting .option norvc after .option arch. This issue starts appearing on
> gcc 15, which adds zca to the march.

There's some clunkiness around ".option arch" and ".option rvc".  So 
this might be an assembler bug, but IMO it's sane to just work around it 
in Linux -- at a bare minimum it'll manifest for users, as binutils 
already released (and GCC 15 is just enabling the Kconfig that triggers 
the bug).

> Reported by: Klara Modin <klarasmodin@gmail.com>

There shouldn't be a newline here, I'll just drop it.

> Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> Fixes: a44fb5722199 ("riscv: Add runtime constant support")
> Closes: https://lore.kernel.org/all/cc8f3525-20b7-445b-877b-2add28a160a2@gmail.com/
> ---
>  arch/riscv/include/asm/runtime-const.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/riscv/include/asm/runtime-const.h b/arch/riscv/include/asm/runtime-const.h
> index c07d049fdd5d2999c57d8a90e7363829c5462368..451fd76b881152919f22de8f5c56b51171acbf3c 100644
> --- a/arch/riscv/include/asm/runtime-const.h
> +++ b/arch/riscv/include/asm/runtime-const.h
> @@ -56,6 +56,7 @@
>  #define RISCV_RUNTIME_CONST_64_ZBA				\
>  	".option push\n\t"					\
>  	".option arch,+zba\n\t"					\
> +	".option norvc\n\t"					\
>  	"slli	%[__tmp],%[__tmp],32\n\t"			\
>  	"add.uw %[__ret],%[__ret],%[__tmp]\n\t"			\
>  	"nop\n\t"						\
> @@ -65,6 +66,7 @@
>  #define RISCV_RUNTIME_CONST_64_ZBKB				\
>  	".option push\n\t"					\
>  	".option arch,+zbkb\n\t"				\
> +	".option norvc\n\t"					\
>  	"pack	%[__ret],%[__ret],%[__tmp]\n\t"			\
>  	"nop\n\t"						\
>  	"nop\n\t"						\
>
> ---
> base-commit: b2117b630c48be69d2782ed79fefe35dcd192ce6
> change-id: 20250331-fix_runtime_const_norvc-407af1f24541

Thanks!
Klara Modin March 31, 2025, 7:39 p.m. UTC | #2
On 2025-03-31 20:45, Charlie Jenkins wrote:
> .option arch clobbers .option norvc. Prevent gas from emitting
> compressed instructions in the runtime const alternative blocks by
> setting .option norvc after .option arch. This issue starts appearing on
> gcc 15, which adds zca to the march.
> 
> Reported by: Klara Modin <klarasmodin@gmail.com>
> 
> Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> Fixes: a44fb5722199 ("riscv: Add runtime constant support")
> Closes: https://lore.kernel.org/all/cc8f3525-20b7-445b-877b-2add28a160a2@gmail.com/
> ---
>   arch/riscv/include/asm/runtime-const.h | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/runtime-const.h b/arch/riscv/include/asm/runtime-const.h
> index c07d049fdd5d2999c57d8a90e7363829c5462368..451fd76b881152919f22de8f5c56b51171acbf3c 100644
> --- a/arch/riscv/include/asm/runtime-const.h
> +++ b/arch/riscv/include/asm/runtime-const.h
> @@ -56,6 +56,7 @@
>   #define RISCV_RUNTIME_CONST_64_ZBA				\
>   	".option push\n\t"					\
>   	".option arch,+zba\n\t"					\
> +	".option norvc\n\t"					\
>   	"slli	%[__tmp],%[__tmp],32\n\t"			\
>   	"add.uw %[__ret],%[__ret],%[__tmp]\n\t"			\
>   	"nop\n\t"						\
> @@ -65,6 +66,7 @@
>   #define RISCV_RUNTIME_CONST_64_ZBKB				\
>   	".option push\n\t"					\
>   	".option arch,+zbkb\n\t"				\
> +	".option norvc\n\t"					\
>   	"pack	%[__ret],%[__ret],%[__tmp]\n\t"			\
>   	"nop\n\t"						\
>   	"nop\n\t"						\
> 
> ---
> base-commit: b2117b630c48be69d2782ed79fefe35dcd192ce6
> change-id: 20250331-fix_runtime_const_norvc-407af1f24541

Thanks!

Tested-by: Klara Modin <klarasmodin@gmail.com>
Clément Léger April 1, 2025, 9:27 a.m. UTC | #3
On 31/03/2025 20:45, Charlie Jenkins wrote:
> .option arch clobbers .option norvc. Prevent gas from emitting
> compressed instructions in the runtime const alternative blocks by
> setting .option norvc after .option arch. This issue starts appearing on
> gcc 15, which adds zca to the march.
> 
> Reported by: Klara Modin <klarasmodin@gmail.com>
> 
> Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> Fixes: a44fb5722199 ("riscv: Add runtime constant support")
> Closes: https://lore.kernel.org/all/cc8f3525-20b7-445b-877b-2add28a160a2@gmail.com/
> ---
>  arch/riscv/include/asm/runtime-const.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/runtime-const.h b/arch/riscv/include/asm/runtime-const.h
> index c07d049fdd5d2999c57d8a90e7363829c5462368..451fd76b881152919f22de8f5c56b51171acbf3c 100644
> --- a/arch/riscv/include/asm/runtime-const.h
> +++ b/arch/riscv/include/asm/runtime-const.h
> @@ -56,6 +56,7 @@
>  #define RISCV_RUNTIME_CONST_64_ZBA				\
>  	".option push\n\t"					\
>  	".option arch,+zba\n\t"					\
> +	".option norvc\n\t"					\

Hey Charlie,

Could ".option arch,+zba,-c" be used as well ? That way, c is treated
like any other arch option. Or does norvc has other side effects ?

Thanks,

Clément

>  	"slli	%[__tmp],%[__tmp],32\n\t"			\
>  	"add.uw %[__ret],%[__ret],%[__tmp]\n\t"			\
>  	"nop\n\t"						\
> @@ -65,6 +66,7 @@
>  #define RISCV_RUNTIME_CONST_64_ZBKB				\
>  	".option push\n\t"					\
>  	".option arch,+zbkb\n\t"				\
> +	".option norvc\n\t"					\
>  	"pack	%[__ret],%[__ret],%[__tmp]\n\t"			\
>  	"nop\n\t"						\
>  	"nop\n\t"						\
> 
> ---
> base-commit: b2117b630c48be69d2782ed79fefe35dcd192ce6
> change-id: 20250331-fix_runtime_const_norvc-407af1f24541
patchwork-bot+linux-riscv@kernel.org April 1, 2025, 2:10 p.m. UTC | #4
Hello:

This patch was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Mon, 31 Mar 2025 11:45:24 -0700 you wrote:
> .option arch clobbers .option norvc. Prevent gas from emitting
> compressed instructions in the runtime const alternative blocks by
> setting .option norvc after .option arch. This issue starts appearing on
> gcc 15, which adds zca to the march.
> 
> Reported by: Klara Modin <klarasmodin@gmail.com>
> 
> [...]

Here is the summary with links:
  - [FOR-NEXT] riscv: Add norvc after .option arch in runtime const
    https://git.kernel.org/riscv/c/95c18b7ccdd1

You are awesome, thank you!
diff mbox series

Patch

diff --git a/arch/riscv/include/asm/runtime-const.h b/arch/riscv/include/asm/runtime-const.h
index c07d049fdd5d2999c57d8a90e7363829c5462368..451fd76b881152919f22de8f5c56b51171acbf3c 100644
--- a/arch/riscv/include/asm/runtime-const.h
+++ b/arch/riscv/include/asm/runtime-const.h
@@ -56,6 +56,7 @@ 
 #define RISCV_RUNTIME_CONST_64_ZBA				\
 	".option push\n\t"					\
 	".option arch,+zba\n\t"					\
+	".option norvc\n\t"					\
 	"slli	%[__tmp],%[__tmp],32\n\t"			\
 	"add.uw %[__ret],%[__ret],%[__tmp]\n\t"			\
 	"nop\n\t"						\
@@ -65,6 +66,7 @@ 
 #define RISCV_RUNTIME_CONST_64_ZBKB				\
 	".option push\n\t"					\
 	".option arch,+zbkb\n\t"				\
+	".option norvc\n\t"					\
 	"pack	%[__ret],%[__ret],%[__tmp]\n\t"			\
 	"nop\n\t"						\
 	"nop\n\t"						\