linux-kernel - Re: [PATCH RFC bpf-next 7/7] bpf: implement "jmp" mode for trampoline

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Message-ID: <CAADnVQJiHExkioeh3t=4y1CWPiUkeV08ZHjeJfpZChkY6dNvhg@mail.gmail.com>
Date: Fri, 14 Nov 2025 18:42:48 -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 7/7] bpf: implement "jmp" mode for trampoline

On Fri, Nov 14, 2025 at 6:39 PM Menglong Dong <menglong8.dong@...il.com> wrote:
> >
> > How about bpf_trampoline_must_jmp() ?
> > and drop if (!ret) fallback and BPF_TRAMP_F_JMPED bit.
> > It doesn't look to be necessary.
>
> I think you are right. We can check if current trampoline is in "jmp"
> mode with the "orig_flags" instead, and remove the
> BPF_TRAMP_F_JMPED. That means that I need to pass the
> "orig_flags" to
> modify_fentry -> bpf_trampoline_update_fentry(bpf_text_poke).

Yep. Makes sense to me.