linux-kernel - [PATCH 6.18] LoongArch: BPF: Enhance the bpf_arch_text

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Message-ID: <20260106025502.951868-1-chenhuacai@loongson.cn>
Date: Tue,  6 Jan 2026 10:55:02 +0800
From: Huacai Chen <chenhuacai@...ngson.cn>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sasha Levin <sashal@...nel.org>,
	Huacai Chen <chenhuacai@...nel.org>
Cc: Xuerui Wang <kernel@...0n.name>,
	stable@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	loongarch@...ts.linux.dev,
	Chenghao Duan <duanchenghao@...inos.cn>,
	Huacai Chen <chenhuacai@...ngson.cn>
Subject: [PATCH 6.18] LoongArch: BPF: Enhance the bpf_arch_text_poke() function

From: Chenghao Duan <duanchenghao@...inos.cn>

commit 73721d8676771c6c7b06d4e636cc053fc76afefd upstream.

Enhance the bpf_arch_text_poke() function to enable accurate location
of BPF program entry points.

When modifying the entry point of a BPF program, skip the "move t0, ra"
instruction to ensure the correct logic and copy of the jump address.

Cc: stable@...r.kernel.org
Fixes: 677e6123e3d2 ("LoongArch: BPF: Disable trampoline for kernel module function trace")
Signed-off-by: Chenghao Duan <duanchenghao@...inos.cn>
Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
---
 arch/loongarch/net/bpf_jit.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index 95c214e2cf09..87ff02513787 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -1307,6 +1307,10 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
 		       void *old_addr, void *new_addr)
 {
 	int ret;
+	unsigned long size = 0;
+	unsigned long offset = 0;
+	void *image = NULL;
+	char namebuf[KSYM_NAME_LEN];
 	bool is_call = (poke_type == BPF_MOD_CALL);
 	u32 old_insns[LOONGARCH_LONG_JUMP_NINSNS] = {[0 ... 4] = INSN_NOP};
 	u32 new_insns[LOONGARCH_LONG_JUMP_NINSNS] = {[0 ... 4] = INSN_NOP};
@@ -1314,9 +1318,20 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
 	/* Only poking bpf text is supported. Since kernel function entry
 	 * is set up by ftrace, we rely on ftrace to poke kernel functions.
 	 */
-	if (!is_bpf_text_address((unsigned long)ip))
+	if (!__bpf_address_lookup((unsigned long)ip, &size, &offset, namebuf))
 		return -ENOTSUPP;
 
+	image = ip - offset;
+
+	/* zero offset means we're poking bpf prog entry */
+	if (offset == 0) {
+		/* skip to the nop instruction in bpf prog entry:
+		 * move t0, ra
+		 * nop
+		 */
+		ip = image + LOONGARCH_INSN_SIZE;
+	}
+
 	ret = emit_jump_or_nops(old_addr, ip, old_insns, is_call);
 	if (ret)
 		return ret;
-- 
2.47.3