linux-kernel - [PATCH bpf-next v2 1/2] bpf: support bpf_get_func_arg() for BPF_TRACE_RAW

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Message-ID: <20260116071739.121182-2-dongml2@chinatelecom.cn>
Date: Fri, 16 Jan 2026 15:17:38 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: ast@...nel.org
Cc: daniel@...earbox.net,
	john.fastabend@...il.com,
	andrii@...nel.org,
	martin.lau@...ux.dev,
	eddyz87@...il.com,
	song@...nel.org,
	yonghong.song@...ux.dev,
	kpsingh@...nel.org,
	sdf@...ichev.me,
	haoluo@...gle.com,
	jolsa@...nel.org,
	mattbobrowski@...gle.com,
	rostedt@...dmis.org,
	mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com,
	bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH bpf-next v2 1/2] bpf: support bpf_get_func_arg() for BPF_TRACE_RAW_TP

For now, bpf_get_func_arg() and bpf_get_func_arg_cnt() is not supported by
the BPF_TRACE_RAW_TP, which is not convenient to get the argument of the
tracepoint, especially for the case that the position of the arguments in
a tracepoint can change.

The target tracepoint BTF type id is specified during loading time,
therefore we can get the function argument count from the function
prototype instead of the stack.

Signed-off-by: Menglong Dong <dongml2@...natelecom.cn>
---
v2:
- for nr_args, skip first 'void *__data' argument in btf_trace_##name
  typedef
---
 kernel/bpf/verifier.c    | 36 ++++++++++++++++++++++++++++++++----
 kernel/trace/bpf_trace.c |  4 ++--
 2 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index faa1ecc1fe9d..422d35c100ff 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -23316,8 +23316,22 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 		/* Implement bpf_get_func_arg inline. */
 		if (prog_type == BPF_PROG_TYPE_TRACING &&
 		    insn->imm == BPF_FUNC_get_func_arg) {
-			/* Load nr_args from ctx - 8 */
-			insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8);
+			if (eatype == BPF_TRACE_RAW_TP) {
+				int nr_args;
+
+				if (!prog->aux->attach_func_proto)
+					return -EINVAL;
+				/*
+				 * skip first 'void *__data' argument in btf_trace_##name
+				 * typedef
+				 */
+				nr_args = btf_type_vlen(prog->aux->attach_func_proto) - 1;
+				/* Save nr_args to reg0 */
+				insn_buf[0] = BPF_MOV64_IMM(BPF_REG_0, nr_args);
+			} else {
+				/* Load nr_args from ctx - 8 */
+				insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8);
+			}
 			insn_buf[1] = BPF_JMP32_REG(BPF_JGE, BPF_REG_2, BPF_REG_0, 6);
 			insn_buf[2] = BPF_ALU64_IMM(BPF_LSH, BPF_REG_2, 3);
 			insn_buf[3] = BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_1);
@@ -23369,8 +23383,22 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 		/* Implement get_func_arg_cnt inline. */
 		if (prog_type == BPF_PROG_TYPE_TRACING &&
 		    insn->imm == BPF_FUNC_get_func_arg_cnt) {
-			/* Load nr_args from ctx - 8 */
-			insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8);
+			if (eatype == BPF_TRACE_RAW_TP) {
+				int nr_args;
+
+				if (!prog->aux->attach_func_proto)
+					return -EINVAL;
+				/*
+				 * skip first 'void *__data' argument in btf_trace_##name
+				 * typedef
+				 */
+				nr_args = btf_type_vlen(prog->aux->attach_func_proto) - 1;
+				/* Save nr_args to reg0 */
+				insn_buf[0] = BPF_MOV64_IMM(BPF_REG_0, nr_args);
+			} else {
+				/* Load nr_args from ctx - 8 */
+				insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8);
+			}
 
 			new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, 1);
 			if (!new_prog)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 6e076485bf70..9b1b56851d26 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1734,11 +1734,11 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_d_path:
 		return &bpf_d_path_proto;
 	case BPF_FUNC_get_func_arg:
-		return bpf_prog_has_trampoline(prog) ? &bpf_get_func_arg_proto : NULL;
+		return &bpf_get_func_arg_proto;
 	case BPF_FUNC_get_func_ret:
 		return bpf_prog_has_trampoline(prog) ? &bpf_get_func_ret_proto : NULL;
 	case BPF_FUNC_get_func_arg_cnt:
-		return bpf_prog_has_trampoline(prog) ? &bpf_get_func_arg_cnt_proto : NULL;
+		return &bpf_get_func_arg_cnt_proto;
 	case BPF_FUNC_get_attach_cookie:
 		if (prog->type == BPF_PROG_TYPE_TRACING &&
 		    prog->expected_attach_type == BPF_TRACE_RAW_TP)
-- 
2.52.0