Add PROG_TEST_RUN support to BPF_PROG_TYPE_KPROBE

This patchset adds PROG_TEST_RUN support to BPF_PROG_TYPE_KPROBE progs. On top of being generally useful for unit testing kprobe progs, this feature more specifically helps solve a relability problem with bpftrace BEGIN and END probes.

BEGIN and END probes are run exactly once at the beginning and end of a bpftrace tracing session, respectively. bpftrace currently implements the probes by creating two dummy functions and attaching the BEGIN and END progs, if defined, to those functions and calling the dummy functions as appropriate. This works pretty well most of the time except for when distros strip symbols from bpftrace. Every now and then this happens and users get confused. Having PROG_TEST_RUN support will help solve this issue by allowing us to directly trigger uprobes from userspace.

Admittedly, this is a pretty specific problem and could probably be solved other ways. However, PROG_TEST_RUN also makes unit testing more convenient, especially as users start building more complex tracing applications. So I see this as killing two birds with one stone.

Daniel Xu (2):
bpf, test_run: Add PROG_TEST_RUN support to kprobe Add PROG_TEST_RUN selftest for BPF_PROG_TYPE_KPROBE

 include/linux/bpf.h                           | 10 ++++
 kernel/trace/bpf_trace.c                      |  1 +
 net/bpf/test_run.c                            | 36 ++++++++++++
 .../selftests/bpf/prog_tests/kprobe_ctx.c     | 57 +++++++++++++++++++
 .../testing/selftests/bpf/progs/kprobe_ctx.c  | 33 +++++++++++
 5 files changed, 137 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/kprobe_ctx.c
 create mode 100644 tools/testing/selftests/bpf/progs/kprobe_ctx.c

2.36.1