Merge branch 'bpf-btf-type-fixes'

Yonghong Song says:

====================
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.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 58000d7e06e3..12502e25e767 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -7,6 +7,7 @@
 #include <linux/types.h>
 
 struct btf;
+struct btf_member;
 struct btf_type;
 union bpf_attr;
 
@@ -46,7 +47,9 @@ void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
 		       struct seq_file *m);
 int btf_get_fd_by_id(u32 id);
 u32 btf_id(const struct btf *btf);
-bool btf_type_is_reg_int(const struct btf_type *t, u32 expected_size);
+bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
+			   const struct btf_member *m,
+			   u32 expected_offset, u32 expected_size);
 
 #ifdef CONFIG_BPF_SYSCALL
 const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id);