This patchset eliminates all known discrepancies between DWARF/BTF, as
tested on typical and allyesconfig Linux kernels.
Patch #1 disables enum recoding, which can lose important enum size info.
Patch #2 enforces fix up of negative bitfield_offsets early on in btf_loader.
Patch #3 brings dwarf bitfield fixup logic closer to latest btf_encoder logic.
Patch #4 completely rewrites bit/byte hole detection logic, fixing a lot of
corners cases.
Patch #5 simplifies __class__fprintf logic by relying on data calculated during
hole detection phase.
Patch #6 records ELF/CU endianness in DWARF/BTF/CTF loaders.
Patch #7 changes semantics of bit offset for little-endian to be a natural
extension of byte offset, as opposed to de-facto DWARF representation (which
goes against DWARF standard recommendation).
Patch #4, when considered without patches #6-#7 emit lots of false warnings
for bit holes for big-endian binaries, due to the fact that it's impossible to
calculate correct bit_start and bit_end on both platforms uniformly without
knowing which one it is, as underlying DWARF output is non-uniform.
I tested little- and big-endian outputs on many small examples, as well as on
default and allyesconfig kernels. I don't know how to test CTF output, though.
I also never used dwarves_reorganize, so that part isn't tested well as well.
So I'd really appreciate some more independent testing to make sure nothing is
broken. Thanks!
v1->v2:
- Take note of ELF endianness;
- Recode little-endian bit offsets to follow DWARF recommendation, making big-
and little-endian manipulations identical beyond tiny initial adjustment;
- Bit offset unification fixed big-endian hole logic automatically.
Andrii Nakryiko (7):
dwarf_loader: don't recode enums and use real enum size in
calculations
btf_loader: adjust negative bitfield offsets early on
dwarf_loader: fix bitfield fixup logic for DWARF
dwarves: revamp bit/byte holes detection logic
dwarves: use bit sizes and bit/byte hole info in __class__fprintf
loaders: record CU's endianness in dwarf/btf/ctf loaders
dwarf_loader: use DWARF recommended uniform bit offset scheme
btf_encoder.c | 29 ++--------
btf_loader.c | 9 +++-
ctf_loader.c | 1 +
dwarf_loader.c | 133 +++++++++++++++++++++++++++++++--------------
dwarves.c | 135 +++++++++++++++++++++++-----------------------
dwarves.h | 1 +
dwarves_fprintf.c | 94 ++++++++++++--------------------
7 files changed, 210 insertions(+), 192 deletions(-)
--
2.17.1
