From: Menglong Dong <menglong.dong@linux.dev>
To: Menglong Dong <menglong8.dong@gmail.com>,
Andrii Nakryiko <andrii.nakryiko@gmail.com>,
ast@kernel.org
Cc: andrii@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev,
eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev,
john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me,
haoluo@google.com, jolsa@kernel.org, davem@davemloft.net,
dsahern@kernel.org, tglx@linutronix.de, mingo@redhat.com,
jiang.biao@linux.dev, bp@alien8.de, dave.hansen@linux.intel.com,
x86@kernel.org, hpa@zytor.com, bpf@vger.kernel.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf-next v6 00/10] bpf: fsession support
Date: Tue, 06 Jan 2026 11:04:47 +0800 [thread overview]
Message-ID: <3389151.aeNJFYEL58@7940hx> (raw)
In-Reply-To: <CAEf4BzbCyMWr5tq5i45SB3jPvUFd4zOAYwJG3KBBeaoWmEq8kw@mail.gmail.com>
On 2026/1/6 05:20 Andrii Nakryiko <andrii.nakryiko@gmail.com> write:
> On Sun, Jan 4, 2026 at 4:28 AM Menglong Dong <menglong8.dong@gmail.com> wrote:
> >
> > Hi, all.
> >
[......]
> > Maybe it's possible to reuse the existing bpf_session_cookie() and
> > bpf_session_is_return(). First, we move the nr_regs from stack to struct
> > bpf_tramp_run_ctx, as Andrii suggested before. Then, we define the session
> > cookies as flexible array in bpf_tramp_run_ctx like this:
> > struct bpf_tramp_run_ctx {
> > struct bpf_run_ctx run_ctx;
> > u64 bpf_cookie;
> > struct bpf_run_ctx *saved_run_ctx;
> > u64 func_meta; /* nr_args, cookie_index, etc */
> > u64 fsession_cookies[];
> > };
> >
> > The problem of this approach is that we can't inlined the bpf helper
> > anymore, such as get_func_arg, get_func_ret, get_func_arg_cnt, etc, as
> > we can't use the "current" in BPF assembly.
> >
>
> We can, as Alexei suggested on your other patch set. Is this still a
> valid concern?
Yeah, with the support of BPF_MOV64_PERCPU_REG, it's much easier
now.
So what approach should I use now? Change the prototype of
bpf_session_is_return/bpf_session_cookie, as Alexei suggested, or
use the approach here? I think both works, and I'm a little torn
now. Any suggestions?
Thanks!
Menglong Dong
>
> I think having separate duplicated ksession and fsession specific
> bpf_[f]session_{is_return,session_cookie}() APIs is really bad and
> confusing long-term.
>
> > So maybe it's better to use the new kfunc for now? And I'm analyzing that
>
> there is no "for now", this decision will be with us for a really long time...
>
> > if it is possible to inline "current" in verifier. Maybe we can convert to
> > the solu
[......]
> >
>
next prev parent reply other threads:[~2026-01-06 3:05 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-04 12:28 [PATCH bpf-next v6 00/10] bpf: fsession support Menglong Dong
2026-01-04 12:28 ` [PATCH bpf-next v6 01/10] bpf: add " Menglong Dong
2026-01-04 12:28 ` [PATCH bpf-next v6 02/10] bpf: use last 8-bits for the nr_args in trampoline Menglong Dong
2026-01-04 12:28 ` [PATCH bpf-next v6 03/10] bpf: add the kfunc bpf_fsession_is_return Menglong Dong
2026-01-04 12:28 ` [PATCH bpf-next v6 04/10] bpf: add the kfunc bpf_fsession_cookie Menglong Dong
2026-01-04 12:28 ` [PATCH bpf-next v6 05/10] bpf,x86: introduce emit_st_r0_imm64() for trampoline Menglong Dong
2026-01-04 12:28 ` [PATCH bpf-next v6 06/10] bpf,x86: add fsession support for x86_64 Menglong Dong
2026-01-04 12:28 ` [PATCH bpf-next v6 07/10] libbpf: add fsession support Menglong Dong
2026-01-04 12:28 ` [PATCH bpf-next v6 08/10] selftests/bpf: add testcases for fsession Menglong Dong
2026-01-04 12:28 ` [PATCH bpf-next v6 09/10] selftests/bpf: add testcases for fsession cookie Menglong Dong
2026-01-04 12:28 ` [PATCH bpf-next v6 10/10] selftests/bpf: test fsession mixed with fentry and fexit Menglong Dong
2026-01-05 21:20 ` [PATCH bpf-next v6 00/10] bpf: fsession support Andrii Nakryiko
2026-01-06 3:04 ` Menglong Dong [this message]
2026-01-06 4:20 ` Alexei Starovoitov
2026-01-06 7:10 ` Menglong Dong
2026-01-05 22:33 ` Alexei Starovoitov
2026-01-05 23:20 ` Andrii Nakryiko
2026-01-06 8:54 ` Jiri Olsa
2026-01-06 12:48 ` Menglong Dong
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