2022-07-06 14:35:45

by Yixun Lan

Subject: [PATCH] riscv, libbpf: use a0 for RC register

According to the RISC-V calling convention register usage here[1],
a0 is used as return value register, so rename it to make it consistent
with the spec.

[1] section 18.2, table 18.2
https://riscv.org/wp-content/uploads/2015/01/riscv-calling.pdf

Fixes: 589fed479ba1 ("riscv, libbpf: Add RISC-V (RV64) support to bpf_tracing.h")
Signed-off-by: Yixun Lan <[email protected]>

---

I'm adding a Fixes tag here, although the original version may just work fine,
and shouldn't be considered as a real error. But, the benefit is that we could
make it consistent with RISC-V spec, and all other tools will follow the same usage.

thanks, and let's me if there is any issue that I may not noticed..
---
tools/lib/bpf/bpf_tracing.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index 01ce121c302df..11f9096407fc4 100644
--- a/tools/lib/bpf/bpf_tracing.h
+++ b/tools/lib/bpf/bpf_tracing.h
@@ -233,7 +233,7 @@ struct pt_regs___arm64 {
#define __PT_PARM5_REG a4
#define __PT_RET_REG ra
#define __PT_FP_REG s0
-#define __PT_RC_REG a5
+#define __PT_RC_REG a0
#define __PT_SP_REG sp
#define __PT_IP_REG pc
/* riscv does not select ARCH_HAS_SYSCALL_WRAPPER. */
--
2.35.1

2022-07-07 09:38:49

by Björn Töpel

Subject: Re: [PATCH] riscv, libbpf: use a0 for RC register

On Wed, 6 Jul 2022 at 16:03, Yixun Lan <[email protected]> wrote:
>
> According to the RISC-V calling convention register usage here[1],
> a0 is used as return value register, so rename it to make it consistent
> with the spec.
>
> [1] section 18.2, table 18.2
> https://riscv.org/wp-content/uploads/2015/01/riscv-calling.pdf
>
> Fixes: 589fed479ba1 ("riscv, libbpf: Add RISC-V (RV64) support to bpf_tracing.h")
> Signed-off-by: Yixun Lan <[email protected]>

Nice catch!

Acked-by: Björn Töpel <[email protected]>

2022-07-07 14:29:18

by Amjad Ouled-Ameur

Subject: Re: [PATCH] riscv, libbpf: use a0 for RC register

Acked-by: Amjad OULED-AMEUR <[email protected]>

2022-07-07 15:34:19

by patchwork-bot+netdevbpf

Subject: Re: [PATCH] riscv, libbpf: use a0 for RC register

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <[email protected]>:

On Wed, 6 Jul 2022 22:02:04 +0800 you wrote:
> According to the RISC-V calling convention register usage here[1],
> a0 is used as return value register, so rename it to make it consistent
> with the spec.
>
> [1] section 18.2, table 18.2
> https://riscv.org/wp-content/uploads/2015/01/riscv-calling.pdf
>
> [...]

Here is the summary with links:
- riscv, libbpf: use a0 for RC register
https://git.kernel.org/bpf/bpf-next/c/935dc35c7531

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html