[bpf-next,0/3] Add target-less tracing SEC() definitions

Message

Andrii Nakryiko April 8, 2022, 8:34 p.m. UTC

Allow specifying "target-less" SEC() definitions for tracing BPF programs,
both non-BTF-backed (kprobes, tracepoints, raw tracepoints) and BTF-backed
(fentry/fexit, iter, lsm, etc).

There are various situations where attach target cannot be known at
compilation time, so libbpf's insistence on specifying something leads to
users having to add random test like SEC("kprobe/whatever") and then
specifying correct target at runtime using APIs like
bpf_program__attach_kprobe().

So this patch set improves ergonomics by allowing simple SEC() definitions
that define BPF program type and nothing else. Such programs won't be
auto-attachable, of course, but they also won't fail skeleton auto-attachment,
just like we do this for uprobes.

Andrii Nakryiko (3):
  libbpf: allow "incomplete" basic tracing SEC() definitions
  libbpf: support target-less SEC() definitions for BTF-backed programs
  selftests/bpf: use target-less SEC() definitions in various tests

 tools/lib/bpf/libbpf.c                        | 118 ++++++++++++------
 .../selftests/bpf/prog_tests/attach_probe.c   |  10 ++
 .../bpf/prog_tests/kprobe_multi_test.c        |  14 +--
 .../selftests/bpf/progs/kprobe_multi.c        |  14 +++
 .../selftests/bpf/progs/test_attach_probe.c   |  23 +++-
 .../selftests/bpf/progs/test_module_attach.c  |   2 +-
 6 files changed, 135 insertions(+), 46 deletions(-)