[PATCH v5 0/6] perf annotate-data: Fix hangs on broken debug info, AMD mem record

[Arnaldo Carvalho de Melo]

Hi,

This originated in another patch series, 'perf tools: Annotate fixes,
stdio progress indication, debuginfo-client in more places', and is
being split off so that these fixes can be reviewed right away; the
debuginfod download feature work from it will come later, separately,
based on this series.

  - 'perf report -s type' spins forever on the dwz compressed debug info of
    zlib-ng (libz.so.1): die_collect_vars() saves a type DIE offset that is
    relative to the file the DIE lives in, the dwz alt file for types shared
    by several CUs, and resolving it in the main file parses whatever is at
    that offset, here a typedef whose DW_AT_type refers to itself, making the
    typedef/qualifier chase spin (patch 3), with the chases bounded so that
    other kinds of broken debug info don't hang perf either (patches 1, 2
    and 4);

  - 'perf mem record' requests PERF_SAMPLE_CPU (patch 5) and uses the IBS
    swfilt filter when the kernel exposes it (patch 6), with the tables
    carrying the term kept in the arch/x86 code, where the knowledge that
    IBS needs it stays, as Ravi Bangoria suggested reviewing Namhyung
    Kim's v6 review remark on this patch
    (<4349c387-5b8a-4e8d-932a-5175a7598e1e@xxxxxxx>, replying to
    <aqsRVABj23jaaiSq@xxxxxxxxxx>).

About PATCH 5, answering Namhyung Kim's v6 review question
(<aqsPKGVUkWk6wvYA@xxxxxxxxxx>) about the --sample-cpu default: the
data source field is about the memory hierarchy level of the access,
it has no record of which CPU issued it, and while the TID is in
every sample and in the CTF stream, a thread time-sliced on one CPU
or moved between SMT siblings is not told apart by it from cross-core
contention, so it is the CPU id that keys it, and it is what the
false-sharing detector in pahole needs.  The TID is recorded as well.

Requires elfutils 0.160 for dwarf_cu_getdwarf(), so the libdw feature test
probes for it and Makefile.config says 0.160: older versions now disable
dwarf support with that message instead of failing to link.

Best regards,

- Arnaldo

What changed from v4:

- Added Ravi Bangoria's Reviewed-by (<76ef085b-e8e3-41a5-b029-2cd0489aa430@xxxxxxx>),
  given together with his rationale for keeping the IBS swfilt selection
  explicit: 'perf record' fails rather than transparently retrying with
  /swfilt=1/, so that the user is aware software filtering is being used
  and that it is not overhead free.
- Trimmed the comment on the AMD mem event tables in
  tools/perf/arch/x86/util/mem-events.c per that review, dropping its
  last sentence about how 'perf record' handles exclude bits on open
  failure; the code is unchanged.
- Patch 4: reworded the comment on the truncated flag; the JSON exporter
  that reads it is added in a later series.
- Patch 6: dropped a leftover no-op hunk from tools/perf/util/mem-events.c;
  the swfilt selection is all in the arch/x86 code.
  Command to see this delta: git diff eb568956a7129c91..HEAD

What changed from v3:

- Dropped patch 5/7, "perf annotate-data: Show the sample count in the
  data-type browser": it is already in perf-tools-next as commit
  9db4e9d6cc7c, so the series is now 6 patches and the subject no longer
  mentions it.
- Rebased onto current perf-tools-next (base-commit below; v3 was based on
  29f320d221c1), patch 4 adapted to the upstream __add_member_cb() cleanup
  that dropped the member_type local, no behavior change.

What changed from v2:

Only aggregate (struct/union) members are marked as truncated when the
MAX_MEMBER_DEPTH limit is reached in the member nesting recursion (patch
4), addressing a sashiko [Medium] review finding
(<20260921165704.38DBD1F000FF@xxxxxxxxxxxxxxx>): the v2 check was made
before looking at the member's type, so a primitive field that merely
landed on the limit, e.g. an int in a struct nested 31 deep, was marked
as truncated and logged even though it has no children to expand.  The
limit still bounds the recursion, as only aggregates are expanded.

What changed from v1:

Bump MAX_MEMBER_DEPTH from 8 to 32, addressing a review comment from Namhyung.

 tools/build/feature/test-libdw.c           |  10 ++-
 tools/perf/Documentation/perf-mem.txt      |   4 +
 tools/perf/Makefile.config                 |   2 +-
 tools/perf/arch/x86/util/mem-events.c      |  17 ++++
 tools/perf/arch/x86/util/mem-events.h      |   2 +
 tools/perf/arch/x86/util/pmu.c             |  10 ++-
 tools/perf/builtin-mem.c                   |   7 +-
 tools/perf/tests/shell/test_data_symbol.sh |   6 +-
 tools/perf/util/annotate-data.c            |  41 +++++++--
 tools/perf/util/annotate-data.h            |   3 +
 tools/perf/util/dwarf-aux.c                | 140 ++++++++++++++++++++++++-----
 tools/perf/util/dwarf-aux.h                |  13 +++
 12 files changed, 217 insertions(+), 38 deletions(-)

v4-head: eb568956a7129c91a8c0ccebb5979440a046c7ef
v3-head: e2504280f5c4086e9851a758ed1bae8df7ef269e
base-commit: edd8a9fe2eca009599e013a29c421c7a6b5ad1b9
--