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
