[RFC 0/2] Introduce perf-stat -b for BPF programs

[Song Liu]

This set introduces perf-stat -b option to count events for BPF programs.
This is similar to bpftool-prog-profile. But perf-stat makes it much more
flexible.

Sending as RFC because I would like comments on some key design choices:
  1. We are using BPF skeletons here, which is by far the easiest way to
     write and ship BPF programs. However, this requires bpftool, which
     makes building perf slower.
  2. A Makefile is added to tools/perf/util/bpf_skel/ to build bpftool,
     and BPF skeletons. This keeps main perf Makefiles simple. But we may
     not like it for some reason?

Some known limitations (or work to be done):
  1. Only counting events for one BPF program at a time.
  2. Need extra logic in target__validate().

Song Liu (2):
  perf: support build BPF skeletons with perf
  perf-stat: enable counting events for BPF programs

 tools/build/Makefile.feature                  |   3 +-
 tools/perf/Makefile.config                    |   8 +
 tools/perf/Makefile.perf                      |  15 +-
 tools/perf/builtin-stat.c                     |  59 ++++-
 tools/perf/util/Build                         |   1 +
 tools/perf/util/bpf_counter.c                 | 215 ++++++++++++++++++
 tools/perf/util/bpf_counter.h                 |  71 ++++++
 tools/perf/util/bpf_skel/.gitignore           |   3 +
 tools/perf/util/bpf_skel/Makefile             |  71 ++++++
 .../util/bpf_skel/bpf_prog_profiler.bpf.c     |  96 ++++++++
 tools/perf/util/bpf_skel/dummy.bpf.c          |  19 ++
 tools/perf/util/evsel.c                       |  10 +
 tools/perf/util/evsel.h                       |   5 +
 tools/perf/util/target.h                      |   6 +
 14 files changed, 571 insertions(+), 11 deletions(-)
 create mode 100644 tools/perf/util/bpf_counter.c
 create mode 100644 tools/perf/util/bpf_counter.h
 create mode 100644 tools/perf/util/bpf_skel/.gitignore
 create mode 100644 tools/perf/util/bpf_skel/Makefile
 create mode 100644 tools/perf/util/bpf_skel/bpf_prog_profiler.bpf.c
 create mode 100644 tools/perf/util/bpf_skel/dummy.bpf.c

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2.24.1