[PATCH bpf-next v2 00/10] bpf: tracing session supporting

Menglong Dong
2025-10-22T08:02:09Z

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 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 (10):
bpf: add tracing session support
bpf: add kfunc bpf_tracing_is_exit for TRACE_SESSION
bpf: add kfunc bpf_fsession_cookie for TRACING 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: test get_func_ip for fsession
selftests/bpf: add testcases for tracing session
selftests/bpf: add session cookie testcase for fsession
selftests/bpf: add testcase for mixing fsession, 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 | 214 ++++++++++++++++--
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 | 161 +++++++++++++
.../bpf/prog_tests/get_func_ip_test.c | 2 +
.../bpf/prog_tests/tracing_failure.c | 2 +-
.../selftests/bpf/progs/fsession_cookie.c | 49 ++++
.../selftests/bpf/progs/fsession_mixed.c | 45 ++++
.../selftests/bpf/progs/fsession_test.c | 175 ++++++++++++++
.../selftests/bpf/progs/get_func_ip_test.c | 14 ++
26 files changed, 776 insertions(+), 26 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/fsession_test.c
create mode 100644 tools/testing/selftests/bpf/progs/fsession_cookie.c
create mode 100644 tools/testing/selftests/bpf/progs/fsession_mixed.c
create mode 100644 tools/testing/selftests/bpf/progs/fsession_test.c

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2.51.1.dirty