[PATCH bpf-next 0/7] bpf: btf: fix struct/union/fwd types with kind_flag

[Yonghong Song <yhs@fb.com>]

Commit 69b693f0aefa ("bpf: btf: Introduce BPF Type Format (BTF)")
introduced BTF, a debug info format for BTF.

The original design has a couple of issues though.
First, the bitfield size is only encoded in int type.
If the struct member bitfield type is enum, pahole ([1])
or llvm is forced to replace enum with int type. As a result, the original
type information gets lost.

Second, the original BTF design does not envision the possibility of
BTF=>header_file conversion ([2]), hence does not encode "struct" or
"union" info for a forward type. Such information is necessary to
convert BTF to a header file.

This patch set fixed the issue by introducing kind_flag, using one bit
in type->info. When kind_flag, the struct/union btf_member->offset
will encode both bitfield_size and bit_offset, covering both
int and enum base types. The kind_flag is also used to indicate whether
the forward type is a union (when set) or a struct.

Please see each individual patches for details.

[1] https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=b18354f64cc215368c3bc0df4a7e5341c55c378c
[2] https://lwn.net/SubscriberLink/773198/fe3074838f5c3f26/

Yonghong Song (7):
  bpf: btf: refactor btf_int_bits_seq_show()
  bpf: btf: fix struct/union/fwd types with kind_flag
  tools/bpf: sync btf.h header from kernel to tools
  tools/bpf: add test_btf unit tests for kind_flag
  tools/bpf: test kernel bpffs map pretty print with struct kind_flag
  tools: bpftool: refactor btf_dumper_int_bits()
  tools: bpftool: support pretty print with kind_flag set

 include/uapi/linux/btf.h               |  15 +-
 kernel/bpf/btf.c                       | 266 +++++++++--
 tools/bpf/bpftool/btf_dumper.c         |  58 ++-
 tools/include/uapi/linux/btf.h         |  15 +-
 tools/testing/selftests/bpf/test_btf.c | 593 ++++++++++++++++++++++++-
 5 files changed, 881 insertions(+), 66 deletions(-)

-- 
2.17.1