linux-kernel - Re: [PATCH RFC bpf-next 0/5] bpf: tracing session supporting

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Message-ID: <3379104.aeNJFYEL58@7950hx>
Date: Mon, 20 Oct 2025 16:55:22 +0800
From: Menglong Dong <menglong.dong@...ux.dev>
To: Menglong Dong <menglong8.dong@...il.com>, Jiri Olsa <olsajiri@...il.com>
Cc: ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com,
 andrii@...nel.org, martin.lau@...ux.dev, eddyz87@...il.com, song@...nel.org,
 yonghong.song@...ux.dev, kpsingh@...nel.org, sdf@...ichev.me,
 haoluo@...gle.com, mattbobrowski@...gle.com, rostedt@...dmis.org,
 mhiramat@...nel.org, mathieu.desnoyers@...icios.com, leon.hwang@...ux.dev,
 bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH RFC bpf-next 0/5] bpf: tracing session supporting

On 2025/10/20 16:18, Jiri Olsa wrote:
> On Sat, Oct 18, 2025 at 10:21:19PM +0800, Menglong Dong wrote:
> > Sometimes, we need to hook both the entry and exit of a function with
> > TRACING. Therefore, we need define a FENTRY and a FEXIT for the target
> > function, which is not convenient.
> > 
> > Therefore, we add a tracing session support for TRACING. Generally
> > speaking, it's similar to kprobe session, which can hook both the entry
> > and exit of a function with a single BPF program. Meanwhile, it can also
> > control the execution of the fexit with the return value of the fentry.
> > session cookie is not supported yet, and I'm not sure if it's necessary.
> 
> hi,
> I think it'd be useful to have support for cookie, people that use kprobe
> session because of multi attach, could easily migrate to trampolines once
> we have fast multi attach for trampolines

OK, I'll implement it in the next version.

> 
> jirka
> 
> 
> > 
> > For now, only x86_64 is supported. Other architectures will be supported
> > later.
> > 
> > Menglong Dong (5):
> >   bpf: add tracing session support
> >   bpf: add kfunc bpf_tracing_is_exit for TRACE_SESSION
> >   bpf,x86: add tracing session supporting for x86_64
> >   libbpf: add support for tracing session
> >   selftests/bpf: add testcases for tracing session
> > 
> >  arch/arm64/net/bpf_jit_comp.c                 |   3 +
> >  arch/loongarch/net/bpf_jit.c                  |   3 +
> >  arch/powerpc/net/bpf_jit_comp.c               |   3 +
> >  arch/riscv/net/bpf_jit_comp64.c               |   3 +
> >  arch/s390/net/bpf_jit_comp.c                  |   3 +
> >  arch/x86/net/bpf_jit_comp.c                   | 115 ++++++++++-
> >  include/linux/bpf.h                           |   1 +
> >  include/uapi/linux/bpf.h                      |   1 +
> >  kernel/bpf/btf.c                              |   2 +
> >  kernel/bpf/syscall.c                          |   2 +
> >  kernel/bpf/trampoline.c                       |   5 +-
> >  kernel/bpf/verifier.c                         |  17 +-
> >  kernel/trace/bpf_trace.c                      |  43 ++++-
> >  net/bpf/test_run.c                            |   1 +
> >  net/core/bpf_sk_storage.c                     |   1 +
> >  tools/bpf/bpftool/common.c                    |   1 +
> >  tools/include/uapi/linux/bpf.h                |   1 +
> >  tools/lib/bpf/bpf.c                           |   2 +
> >  tools/lib/bpf/libbpf.c                        |   3 +
> >  .../selftests/bpf/prog_tests/fsession_test.c  | 132 +++++++++++++
> >  .../selftests/bpf/progs/fsession_test.c       | 178 ++++++++++++++++++
> >  21 files changed, 511 insertions(+), 9 deletions(-)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/fsession_test.c
> >  create mode 100644 tools/testing/selftests/bpf/progs/fsession_test.c
> > 
> 
>