[dwarves,00/11] Switch BTF loading and encoding to libbpf APIs

Message

Andrii Nakryiko Sept. 30, 2020, 4:27 a.m. UTC

This patch set switches pahole to use libbpf-provided BTF loading and encoding
APIs. This reduces pahole's own BTF encoding code, speeds up the process,
reduces amount of RAM needed for DWARF-to-BTF conversion. Also, pahole finally
gets support to generating BTF for cross-compiled ELF binaries with different
endianness (patch #11).

Additionally, patch #6 fixes previously missed problem with invalid array
index type generation.

Patches #7-10 are speeding up DWARF-to-BTF convertion/dedup pretty
significantly, saving overall about 9 seconds out of current 27 or so.

Patch #8 revamps how per-CPU BTF variables are emitted, eliminating repeated
and expensive looping over ELF symbols table.

Patch #10 admittedly has some hacky parts to satisfy CTF use case, but its
speed ups are greatest. So I'll understand if it gets dropped, but it would be
a pity.

More details could be found in respective patches.

Andrii Nakryiko (11):
  libbpf: update to latest libbpf version
  btf_encoder: detect BTF encoding errors and exit
  dwarves: expose and maintain active debug info loader operations
  btf_loader: use libbpf to load BTF
  btf_encoder: use libbpf APIs to encode BTF type info
  btf_encoder: fix emitting __ARRAY_SIZE_TYPE__ as index range type
  btf_encoder: discard CUs after BTF encoding
  btf_encoder: revamp how per-CPU variables are encoded
  dwarf_loader: increase the size of lookup hash map
  strings: use BTF's string APIs for strings management
  btf_encoder: support cross-compiled ELF binaries with different
    endianness

 btf_encoder.c  | 361 +++++++++++++++------------
 btf_loader.c   | 244 +++++++-----------
 ctf_encoder.c  |   2 +-
 dwarf_loader.c |   2 +-
 dwarves.c      |   8 +
 lib/bpf        |   2 +-
 libbtf.c       | 661 +++++++++++++++++++++----------------------------
 libbtf.h       |  41 ++-
 libctf.c       |  14 +-
 libctf.h       |   4 +-
 pahole.c       |   9 +-
 strings.c      |  91 +++----
 strings.h      |  32 +--
 13 files changed, 653 insertions(+), 818 deletions(-)