From: Yonghong Song <yhs@fb.com>
Subject: [PATCH bpf-next v3 0/8] bpf: btf: fix struct/union/fwd types with kind_flag
Date: Sat, 15 Dec 2018 22:13:50 -0800
Message-ID: <20181216061350.301750-1-yhs@fb.com>
Mime-Version: 1.0
Content-Type: text/plain
Cc: Alexei Starovoitov <ast@fb.com>,
        Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>,
        Martin KaFai Lau <kafai@fb.com>
To: <netdev@vger.kernel.org>
Sender: netdev-owner@vger.kernel.org

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.

Patch #1 refactors function btf_int_bits_seq_show() so Patch #2
can reuse part of the function.
Patch #2 implemented kind_flag support for struct/union/fwd types.
Patch #3 added kind_flag support for cgroup local storage map pretty print.
Patch #4 syncs kernel uapi btf.h to tools directory.
Patch #5 added unit tests for kind_flag.
Patch #6 added tests for kernel bpffs based pretty print with kind_flag.
Patch #7 refactors function btf_dumper_int_bits() so Patch #8
can reuse part of the function.
Patch #8 added bpftool support of pretty print with kind_flag set.

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

Change logs:
  v2 -> v3:
    . Relocated comments about bitfield_size/bit_offset interpretation
      of the "offset" field right before the "offset" struct member.
    . Added missing byte alignment checking for non-bitfield enum
      member of a struct with kind_flag set.
    . Added two test cases in unit tests for struct type, kind_flag set,
      non-bitfield int/enum member, not-byte aligned bit offsets.
    . Added comments to help understand there is no overflow for
      total_bits_offset in bpftool function btf_dumper_int_bits().
    . Added explanation of typedef type dumping fix in Patch #8 commit
      message.

  v1 -> v2:
    . If kind_flag is set for a structure, ensure an int member,
      whether it is a bitfield or not, is a regular int type.
    . Added support so cgroup local storage map pretty print
      works with kind_flag.

Yonghong Song (8):
  bpf: btf: refactor btf_int_bits_seq_show()
  bpf: btf: fix struct/union/fwd types with kind_flag
  bpf: enable cgroup local storage map pretty print 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/linux/btf.h                    |   5 +-
 include/uapi/linux/btf.h               |  20 +-
 kernel/bpf/btf.c                       | 352 +++++++++++--
 kernel/bpf/local_storage.c             |  17 +-
 tools/bpf/bpftool/btf_dumper.c         |  61 ++-
 tools/include/uapi/linux/btf.h         |  20 +-
 tools/testing/selftests/bpf/test_btf.c | 664 ++++++++++++++++++++++++-
 7 files changed, 1047 insertions(+), 92 deletions(-)

-- 
2.17.1