[PATCHES 0/8] perf tools: Diagnostic offsets in skip messages + two hardening fixes

[Arnaldo Carvalho de Melo]

When perf report, perf sched, or perf timechart skip a malformed or
unprocessable event, the warning message doesn't say where in the
perf.data file the problem occurred.  This makes it hard to
cross-reference with 'perf report -D' output or to locate the
corrupted region with a hex editor.

This series adds a file_offset field to struct perf_sample, set in the
event delivery path (including the deferred callchain path), and
retrofits all skip/stop/error messages to include:

  - The file offset where the event was found
  - The event type name via perf_event__name() with the numeric
    type value in parentheses

For example, instead of:

  problem processing 10 event, skipping it.

a user now sees:

  WARNING: at offset 0x1a3f0: MMAP2 (10) event size 24 too small (min 64), skipping

The peek_event() path, which validates events during initial file
scanning, also gains file offsets in its three warning messages
(misaligned size, unsupported type, undersized event).

Two pre-existing bugs found by sashiko-bot are fixed:

  - builtin-timechart.c cat_backtrace(): use-after-free and
    double-free when an invalid callchain context triggers zfree()
    before fclose() on an open_memstream buffer.  The open_memstream
    contract requires fclose() before the buffer can be freed — see
    open_memstream(3).

  - builtin-sched.c: three BUG_ON(cpu >= MAX_CPUS || cpu < 0)
    that abort perf sched when PERF_SAMPLE_CPU is absent from the
    sample type and the CPU sentinel (u32)-1 is cast to signed -1.
    perf.data is untrusted input — a corrupted or truncated file
    should produce a warning, not an abort.

Arnaldo Carvalho de Melo (8):
  perf sample: Add file_offset field to struct perf_sample
  perf session: Include file offset in event skip/stop messages
  perf sched: Include file offset in event skip messages
  perf timechart: Include file offset in CPU bounds check messages
  perf tools: Include file offset and event type name in skip messages
  perf timechart: Fix cat_backtrace() use-after-free on corrupted callchain
  perf sched: Replace BUG_ON on invalid CPU with graceful skip
  perf test: Add file offset diagnostic test for corrupted perf.data

 15 files changed, 261 insertions(+), 101 deletions(-)

Developed with AI assistance (Claude/sashiko), tagged in commits.

Best regards,

- Arnaldo