Message-ID: <20251026030143.23807-1-dongml2@chinatelecom.cn>
Date: Sun, 26 Oct 2025 11:01:36 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: ast@...nel.org,
	jolsa@...nel.org
Cc: daniel@...earbox.net,
	john.fastabend@...il.com,
	andrii@...nel.org,
	martin.lau@...ux.dev,
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	leon.hwang@...ux.dev,
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	linux-trace-kernel@...r.kernel.org
Subject: [PATCH bpf-next v3 0/7] bpf: tracing session supporting

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 also supported with the kfunc bpf_fsession_cookie().

The kfunc bpf_tracing_is_exit() and bpf_fsession_cookie() are both inlined
in the verifier.

We allow the usage of bpf_get_func_ret() to get the return value in the
fentry of the tracing session, as it will always get "0", which is safe
enough and is OK.

The while fsession stuff is arch related, so the -EOPNOTSUPP will be
returned if it is not supported yet by the arch. In this series, we only
support x86_64. And later, other arch will be implemented.

Changes since v2:
* squeeze some patches:
  - the 2 patches for the kfunc bpf_tracing_is_exit() and
    bpf_fsession_cookie() are merged into the second patch.
  - the testcases for fsession are also squeezed.

* fix the CI error by move the testcase for bpf_get_func_ip to
  fsession_test.c

Changes since v1:
* session cookie support.
  In this version, session cookie is implemented, and the kfunc
  bpf_fsession_cookie() is added.

* restructure the layout of the stack.
  In this version, the session stuff that stored in the stack is changed,
  and we locate them after the return value to not break
  bpf_get_func_ip().

* testcase enhancement.
  Some nits in the testcase that suggested by Jiri is fixed. Meanwhile,
  the testcase for get_func_ip and session cookie is added too.

Menglong Dong (7):
  bpf: add tracing session support
  bpf: add two kfunc for TRACE_SESSION
  bpf,x86: add ret_off to invoke_bpf()
  bpf,x86: add tracing session supporting for x86_64
  libbpf: add support for tracing session
  selftests/bpf: add testcases for tracing session
  selftests/bpf: test fsession mixed with fentry and fexit

 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                   | 221 +++++++++++++--
 include/linux/bpf.h                           |   2 +
 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                         |  45 ++-
 kernel/trace/bpf_trace.c                      |  59 +++-
 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  |  95 +++++++
 .../bpf/prog_tests/tracing_failure.c          |   2 +-
 .../selftests/bpf/progs/fsession_test.c       | 264 ++++++++++++++++++
 22 files changed, 694 insertions(+), 28 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/fsession_test.c
 create mode 100644 tools/testing/selftests/bpf/progs/fsession_test.c

-- 
2.51.1

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