linux-kernel - [PATCH v4 5/7] LoongArch: BPF: Adjust the jump offset of tail calls

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Message-Id: <20251217061435.802204-6-duanchenghao@kylinos.cn>
Date: Wed, 17 Dec 2025 14:14:33 +0800
From: Chenghao Duan <duanchenghao@...inos.cn>
To: yangtiezhu@...ngson.cn,
	rostedt@...dmis.org,
	mhiramat@...nel.org,
	mark.rutland@....com,
	hengqi.chen@...il.com,
	chenhuacai@...nel.org
Cc: kernel@...0n.name,
	zhangtianyang@...ngson.cn,
	masahiroy@...nel.org,
	linux-kernel@...r.kernel.org,
	loongarch@...ts.linux.dev,
	bpf@...r.kernel.org,
	duanchenghao@...inos.cn,
	youling.tang@...ux.dev,
	jianghaoran@...inos.cn,
	vincent.mc.li@...il.com,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH v4 5/7] LoongArch: BPF: Adjust the jump offset of tail calls

Call the next bpf prog and skip the first instruction of TCC
initialization.
A total of 7 instructions are skipped:
'move t0, ra'			1 inst
'move_imm + jirl'		5 inst
'addid REG_TCC, zero, 0'	1 inst

Relevant test cases: the tailcalls test item in selftests/bpf

Signed-off-by: Chenghao Duan <duanchenghao@...inos.cn>
---
 arch/loongarch/net/bpf_jit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index c560d1e14b9d..3dbabacc8856 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -239,7 +239,7 @@ static void __build_epilogue(struct jit_ctx *ctx, bool is_tail_call)
 		 * Call the next bpf prog and skip the first instruction
 		 * of TCC initialization.
 		 */
-		emit_insn(ctx, jirl, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_T3, 6);
+		emit_insn(ctx, jirl, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_T3, 7);
 	}
 }
 
-- 
2.25.1