linux-kernel - Re: [PATCH RFC bpf-next 3/7] bpf: fix the usage of BPF_TRAMP_F_SKIP

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Message-ID: <CAADnVQL9cOcQpPkE05p9m8oeZcKSVqMwvF8DnrzNrqT5HozV=g@mail.gmail.com>
Date: Fri, 14 Nov 2025 10:23:21 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Menglong Dong <menglong8.dong@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, 
	Daniel Borkmann <daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Eduard <eddyz87@...il.com>, 
	Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, bpf <bpf@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	linux-trace-kernel <linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC bpf-next 3/7] bpf: fix the usage of BPF_TRAMP_F_SKIP_FRAME

On Fri, Nov 14, 2025 at 1:25 AM Menglong Dong <menglong8.dong@...il.com> wrote:
>
> Some places calculate the origin_call by checking if
> BPF_TRAMP_F_SKIP_FRAME is set. However, it should use
> BPF_TRAMP_F_ORIG_STACK for this propose. Just fix them.
>
> Signed-off-by: Menglong Dong <dongml2@...natelecom.cn>
> ---
>  arch/riscv/net/bpf_jit_comp64.c | 2 +-
>  arch/x86/net/bpf_jit_comp.c     | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
> index 45cbc7c6fe49..21c70ae3296b 100644
> --- a/arch/riscv/net/bpf_jit_comp64.c
> +++ b/arch/riscv/net/bpf_jit_comp64.c
> @@ -1131,7 +1131,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
>         store_args(nr_arg_slots, args_off, ctx);
>
>         /* skip to actual body of traced function */
> -       if (flags & BPF_TRAMP_F_SKIP_FRAME)
> +       if (flags & BPF_TRAMP_F_ORIG_STACK)
>                 orig_call += RV_FENTRY_NINSNS * 4;
>
>         if (flags & BPF_TRAMP_F_CALL_ORIG) {
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index de5083cb1d37..2d300ab37cdd 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -3272,7 +3272,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im
>
>         arg_stack_off = stack_size;
>
> -       if (flags & BPF_TRAMP_F_SKIP_FRAME) {
> +       if (flags & BPF_TRAMP_F_CALL_ORIG) {

Good catch. Ack. Pls carry it in respin, so I don't
forget that I looked at it.