linux-kernel - [PATCH 0/3] perf: generate events for BPF metadata

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Message-ID: <20250521222725.3895192-1-blakejones@google.com>
Date: Wed, 21 May 2025 15:27:22 -0700
From: Blake Jones <blakejones@...gle.com>
To: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Ian Rogers <irogers@...gle.com>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>
Cc: Chun-Tse Shao <ctshao@...gle.com>, Zhongqiu Han <quic_zhonhan@...cinc.com>, 
	James Clark <james.clark@...aro.org>, Charlie Jenkins <charlie@...osinc.com>, 
	Andi Kleen <ak@...ux.intel.com>, Dmitry Vyukov <dvyukov@...gle.com>, Leo Yan <leo.yan@....com>, 
	Yujie Liu <yujie.liu@...el.com>, Graham Woodward <graham.woodward@....com>, 
	Yicong Yang <yangyicong@...ilicon.com>, Ben Gainey <ben.gainey@....com>, 
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, Blake Jones <blakejones@...gle.com>
Subject: [PATCH 0/3] perf: generate events for BPF metadata

Commit ffa915f46193 ("Merge branch 'bpf_metadata'"), from September 2020,
added support to the kernel, libbpf, and bpftool to treat read-only BPF
variables that have names starting with 'bpf_metadata_' specially. This
patch series updates perf to handle these variables similarly, allowing a
perf.data file to capture relevant information about BPF programs on the
system being profiled.

When it encounters a BPF program, it reads the program's maps to find an
'.rodata' map with 'bpf_metadata_' variables. If it finds one, it extracts
their values as strings, and creates a new PERF_RECORD_BPF_METADATA
synthetic event using that data. It does this both for BPF programs that
were loaded when a 'perf record' starts, as well as for programs that are
loaded while the profile is running. For the latter case, it stores the
metadata for the duration of the profile, and then dumps it at the end of
the profile, where it's in a better context to do so.

The PERF_RECORD_BPF_METADATA event holds an array of key-value pairs, where
the key is the variable name (minus the "bpf_metadata_" prefix) and the
value is the variable's value, formatted as a string. The event also
includes the BPF program's name, so it can be correlated with
PERF_RECORD_KSYMBOL events.

Blake Jones (3):
  perf: add support for printing BTF character arrays as strings
  perf: collect BPF metadata from existing BPF programs
  perf: collect BPF metadata from new programs, and display the new
    event

 tools/lib/bpf/btf.h                          |   3 +-
 tools/lib/bpf/btf_dump.c                     |  51 ++-
 tools/lib/perf/include/perf/event.h          |  18 +
 tools/perf/builtin-inject.c                  |   1 +
 tools/perf/builtin-record.c                  |   8 +
 tools/perf/builtin-script.c                  |  15 +-
 tools/perf/tests/shell/test_bpf_metadata.sh  |  67 ++++
 tools/perf/util/bpf-event.c                  | 356 +++++++++++++++++++
 tools/perf/util/bpf-event.h                  |  14 +
 tools/perf/util/bpf_skel/sample_filter.bpf.c |   4 +
 tools/perf/util/env.c                        |  19 +-
 tools/perf/util/env.h                        |   4 +
 tools/perf/util/event.c                      |  21 ++
 tools/perf/util/event.h                      |   1 +
 tools/perf/util/header.c                     |   1 +
 tools/perf/util/session.c                    |   4 +
 tools/perf/util/synthetic-events.h           |   2 +
 tools/perf/util/tool.c                       |  14 +
 tools/perf/util/tool.h                       |   3 +-
 19 files changed, 600 insertions(+), 6 deletions(-)
 create mode 100644 tools/perf/tests/shell/test_bpf_metadata.sh

-- 
2.49.0.1143.g0be31eac6b-goog