From: bot+bpf-ci@kernel.org
To: menglong8.dong@gmail.com,ast@kernel.org
Cc: daniel@iogearbox.net,john.fastabend@gmail.com,andrii@kernel.org,martin.lau@linux.dev,eddyz87@gmail.com,song@kernel.org,yonghong.song@linux.dev,kpsingh@kernel.org,sdf@fomichev.me,haoluo@google.com,jolsa@kernel.org,mattbobrowski@google.com,rostedt@goodmis.org,mhiramat@kernel.org,mathieu.desnoyers@efficios.com,bpf@vger.kernel.org,linux-kernel@vger.kernel.org,linux-trace-kernel@vger.kernel.org,ast@kernel.org,andrii@kernel.org,daniel@iogearbox.net,martin.lau@kernel.org,eddyz87@gmail.com,yonghong.song@linux.dev,clm@meta.com,ihor.solodrai@linux.dev
Subject: Re: [PATCH bpf-next 1/2] bpf: support bpf_get_func_arg() for BPF_TRACE_RAW_TP
Date: Fri, 16 Jan 2026 04:20:19 +0000 (UTC) [thread overview]
Message-ID: <bf8e99a4398ad6c1383a82fd33fa1e0cfdfc6b935c8d4d8f5216a64cafccb660@mail.kernel.org> (raw)
In-Reply-To: <20260116035024.98214-2-dongml2@chinatelecom.cn>
[-- Attachment #1: Type: text/plain, Size: 2728 bytes --]
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 7a375f608263..223e5b483bbd 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -23321,8 +23321,18 @@ 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) {
> + if (eatype == BPF_TRACE_RAW_TP) {
> + int nr_args;
> +
> + if (!prog->aux->attach_func_proto)
> + return -EINVAL;
> + nr_args = btf_type_vlen(prog->aux->attach_func_proto);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The attach_func_proto for raw tracepoints points to the BTF func_proto of
__bpf_trace_* or btf_trace_* which has an extra "void *__data" as the
first parameter. For example, a tracepoint declared with TP_PROTO(int a)
results in a btf_trace_* typedef of "void (*)(void *__data, int a)" which
has 2 parameters.
Does btf_type_vlen() return the count including the hidden __data param?
If so, a tracepoint with 1 actual argument would report nr_args=2, but
the BPF context only contains 1 argument. Calling bpf_get_func_arg(ctx, 1)
would pass the bounds check (1 < 2) but read out of bounds from ctx.
The bpf_trace_run* functions populate args[] with only the actual
tracepoint arguments (see __bpf_trace_run() in kernel/trace/bpf_trace.c),
not including __data. Should nr_args be adjusted by subtracting 1 to
account for the hidden first parameter?
> + /* 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);
> + }
[ ... ]
> @@ -23374,8 +23384,18 @@ 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) {
> + if (eatype == BPF_TRACE_RAW_TP) {
> + int nr_args;
> +
> + if (!prog->aux->attach_func_proto)
> + return -EINVAL;
> + nr_args = btf_type_vlen(prog->aux->attach_func_proto);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Same question here for bpf_get_func_arg_cnt() - should this subtract 1 to
exclude the __data parameter from the count returned to BPF programs?
> + /* Save nr_args to reg0 */
> + insn_buf[0] = BPF_MOV64_IMM(BPF_REG_0, nr_args);
[ ... ]
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/21055137351
next prev parent reply other threads:[~2026-01-16 4:20 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-16 3:50 [PATCH bpf-next 0/2] " Menglong Dong
2026-01-16 3:50 ` [PATCH bpf-next 1/2] " Menglong Dong
2026-01-16 4:20 ` bot+bpf-ci [this message]
2026-01-16 6:56 ` Menglong Dong
2026-01-16 3:50 ` [PATCH bpf-next 2/2] selftests/bpf: test bpf_get_func_arg() for tp_btf Menglong Dong
2026-01-16 4:09 ` bot+bpf-ci
2026-01-16 6:53 ` Menglong Dong
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