37c7b1caea
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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
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