linux-kernel - Re: [PATCH bpf-next v6 00/10] bpf: fsession support

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Message-ID: <CAEf4Bza4fD5WWWBxJk0dd_xvgPR0ORZpcp1wiahyMPjvdoWG0w@mail.gmail.com>
Date: Mon, 5 Jan 2026 15:20:13 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>, Jiri Olsa <jolsa@...nel.org>
Cc: Menglong Dong <menglong8.dong@...il.com>, Alexei Starovoitov <ast@...nel.org>, 
	Andrii Nakryiko <andrii@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eduard <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	"David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, jiang.biao@...ux.dev, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, X86 ML <x86@...nel.org>, 
	"H. Peter Anvin" <hpa@...or.com>, bpf <bpf@...r.kernel.org>, 
	Network Development <netdev@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v6 00/10] bpf: fsession support

On Mon, Jan 5, 2026 at 2:33 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Sun, Jan 4, 2026 at 4:28 AM Menglong Dong <menglong8.dong@...il.com> wrote:
> >
> > In current solution, we can't reuse the existing bpf_session_cookie() and
> > bpf_session_is_return(), as their prototype is different from
> > bpf_fsession_is_return() and bpf_fsession_cookie(). In
> > bpf_fsession_cookie(), we need the function argument "void *ctx" to get
> > the cookie. However, the prototype of bpf_session_cookie() is "void".
>
> I think it's ok to change proto to bpf_session_cookie(void *ctx)
> for kprobe-session. It's not widely used yet, so proto change is ok
> if it helps to simplify this tramp-session code.
> I see that you adjust get_kfunc_ptr_arg_type(), so the verifier
> will enforce PTR_TO_CTX for kprobe and trampoline.
> Potentially can relax and enforce r1==ctx only for trampoline,
> but I would do it for both for consistency.

Yeah, I'd support that. It's early enough that this shouldn't be
breaking a lot of users (if any).

Jiri, do you guys use bpf_session_is_return() or bpf_session_cookie()
anywhere already?