[PATCH v2 0/9] pahole: Support cross-CU type references and dwz alternate debug files

[Arnaldo Carvalho de Melo <acme@kernel.org>]

From: Arnaldo Carvalho de Melo <acme@redhat.com>

Add support for cross-CU type references and dwz alternate debug
files so pahole can process binaries (e.g. a perf binary with rust
objects, or Firefox) that use DW_FORM_ref_addr inter-CU references or
dwz-compressed .dwz alternate debug files.

Cross-CU type references:

  Force-merge CUs that contain inter-CU references (DW_FORM_ref_addr)
  so type lookups resolve correctly.  Handle same-file partial units
  where types are shared across CUs via DW_TAG_imported_unit.  Fix
  cus__merging_cu failing to detect DW_FORM_ref_addr when
  DW_FORM_implicit_const causes dwarf_getabbrevattr() to fail.

dwz alternate debug file support:

  Handle DW_FORM_GNU_ref_alt references to dwz-compressed alternate
  debug files (.dwz).  Pre-processes all alternate partial units with
  separate hash tables and dedup tracking.

  Before (Firefox): 1774 "has no entry in cu" errors
  After:             processes cleanly with 0 errors

Also add an inter-CU type reference comparison test and
scripts/vmlinux_comparison.py for DWARF/BTF analysis across kernel
configs.

What changed from v1:

  v1 (12 patches) also carried the Rust enum discriminant support
  (DW_TAG_variant_part population, BTF union-member encoding and
  DW_FORM_block discriminant handling, plus tests/block_endian.sh).
  That work is being submitted as a separate series based on this one,
  so v2 drops those 3 patches and the block_endian.sh test.  The
  remaining 9 patches are the cross-CU reference and dwz alternate
  debug file support, now self-contained (tests/dwz_alt_file.sh and
  tests/inter_cu_refs.sh are included).

Best regards,

- Arnaldo

Assisted-by: opencode:hy3-free

Arnaldo Carvalho de Melo (9):
  dwarf_loader: Initial support for DW_TAG_variant_part
  dwarf_loader: Initial support for DW_TAG_subprogram in
    DW_TAG_enumeration
  dwarf_loader: Allow forcing the merge of CUs for solving inter CU tag
    references
  dwarf_loader: Support DW_TAG_imported_unit for same-file partial units
  dwarf_loader: Fix cus__merging_cu failing to detect DW_FORM_ref_addr
  tests: Add inter-CU type reference comparison test
  dwarf_loader: Add cu parameter to tag__set_spec() and
    dwarf_tag__set_attr_type()
  dwarf_loader: Support DW_FORM_GNU_ref_alt references to dwz alternate
    debug files
  scripts: Add vmlinux_comparison.py for DWARF/BTF analysis

 btf_encoder.c                 |  22 +-
 ctf_encoder.c                 |  26 +-
 dwarf_loader.c                | 829 ++++++++++++++++++++++++++++++----
 dwarves.c                     |  44 +-
 dwarves.h                     |  20 +-
 dwarves_emit.c                |  10 +-
 dwarves_fprintf.c             |  54 ++-
 man-pages/pahole.1            |  19 +-
 pahole.c                      |  28 +-
 scripts/vmlinux_comparison.py | 612 +++++++++++++++++++++++++
 tests/dwz_alt_file.sh         | 204 +++++++++
 tests/inter_cu_refs.sh        |  50 ++
 tests/prettify_perf.data.sh   |   4 +-
 13 files changed, 1801 insertions(+), 121 deletions(-)
 create mode 100755 scripts/vmlinux_comparison.py
 create mode 100755 tests/dwz_alt_file.sh
 create mode 100755 tests/inter_cu_refs.sh

-- 
2.55.0