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

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

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2.51.0