netdev - [PATCH bpf-next 3/4] riscv, bpf: Add RV_TAILCALL_OFFSET macro to format tailcall offset

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Date: Tue, 19 Sep 2023 11:57:10 +0800
From: Pu Lehui <pulehui@...weicloud.com>
To: bpf@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	netdev@...r.kernel.org
Cc: Björn Töpel <bjorn@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Palmer Dabbelt <palmer@...belt.com>,
	Conor Dooley <conor@...nel.org>,
	Luke Nelson <luke.r.nels@...il.com>,
	Pu Lehui <pulehui@...wei.com>,
	Pu Lehui <pulehui@...weicloud.com>
Subject: [PATCH bpf-next 3/4] riscv, bpf: Add RV_TAILCALL_OFFSET macro to format tailcall offset

From: Pu Lehui <pulehui@...wei.com>

Add RV_TAILCALL_OFFSET macro to format tailcall offset, and correct the
relevant comments.

Signed-off-by: Pu Lehui <pulehui@...wei.com>
---
 arch/riscv/net/bpf_jit_comp64.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 57535cfe1..f2ded1151 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -13,7 +13,9 @@
 #include <asm/patch.h>
 #include "bpf_jit.h"
 
-#define RV_FENTRY_NINSNS 2
+#define RV_FENTRY_NINSNS	2
+/* fentry and TCC init insns will be skipped on tailcall */
+#define RV_TAILCALL_OFFSET	((RV_FENTRY_NINSNS + 1) * 4)
 
 #define RV_REG_TCC RV_REG_A6
 #define RV_REG_TCC_SAVED RV_REG_S6 /* Store A6 in S6 if program do calls */
@@ -243,8 +245,7 @@ static void __build_epilogue(bool is_tail_call, struct rv_jit_context *ctx)
 	if (!is_tail_call)
 		emit_mv(RV_REG_A0, RV_REG_A5, ctx);
 	emit_jalr(RV_REG_ZERO, is_tail_call ? RV_REG_T3 : RV_REG_RA,
-		  is_tail_call ? (RV_FENTRY_NINSNS + 1) * 4 : 0, /* skip reserved nops and TCC init */
-		  ctx);
+		  is_tail_call ? RV_TAILCALL_OFFSET : 0, ctx);
 }
 
 static void emit_bcc(u8 cond, u8 rd, u8 rs, int rvoff,
@@ -371,7 +372,7 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx)
 	off = ninsns_rvoff(tc_ninsn - (ctx->ninsns - start_insn));
 	emit_branch(BPF_JEQ, RV_REG_T2, RV_REG_ZERO, off, ctx);
 
-	/* goto *(prog->bpf_func + 4); */
+	/* goto *(prog->bpf_func + RV_TAILCALL_OFFSET); */
 	off = offsetof(struct bpf_prog, bpf_func);
 	if (is_12b_check(off, insn))
 		return -1;
-- 
2.25.1