linux-kernel - [PATCH bpf-next 0/2] Add PROG_TEST_RUN support to BPF_PROG_TYPE

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Message-Id: <cover.1653861287.git.dxu@dxuuu.xyz>
Date:   Sun, 29 May 2022 17:06:04 -0500
From:   Daniel Xu <dxu@...uu.xyz>
To:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org
Cc:     Daniel Xu <dxu@...uu.xyz>, linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next 0/2] 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