linux-kernel - [PATCH] riscv, libbpf: use a0 for RC register

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Message-Id: <20220706140204.47926-1-dlan@gentoo.org>
Date:   Wed,  6 Jul 2022 22:02:04 +0800
From:   Yixun Lan <dlan@...too.org>
To:     linux-riscv@...ts.infradead.org,
        Björn Töpel <bjorn@...nel.org>,
        bpf@...r.kernel.org
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Hengqi Chen <chenhengqi@...look.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Yixun Lan <dlan@...too.org>
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 <dlan@...too.org>

---

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