Yonghong Song 5698a42a73 selftests/bpf: Add a C test for btf_type_tag
The following is the main btf_type_tag usage in the
C test:
  #define __tag1 __attribute__((btf_type_tag("tag1")))
  #define __tag2 __attribute__((btf_type_tag("tag2")))
  struct btf_type_tag_test {
       int __tag1 * __tag1 __tag2 *p;
  } g;

The bpftool raw dump with related types:
  [4] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
  [11] STRUCT 'btf_type_tag_test' size=8 vlen=1
          'p' type_id=14 bits_offset=0
  [12] TYPE_TAG 'tag1' type_id=16
  [13] TYPE_TAG 'tag2' type_id=12
  [14] PTR '(anon)' type_id=13
  [15] TYPE_TAG 'tag1' type_id=4
  [16] PTR '(anon)' type_id=15
  [17] VAR 'g' type_id=11, linkage=global

With format C dump, we have
  struct btf_type_tag_test {
        int __attribute__((btf_type_tag("tag1"))) * __attribute__((btf_type_tag("tag1"))) __attribute__((btf_type_tag("tag2"))) *p;
  };
The result C code is identical to the original definition except macro's are gone.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211112012646.1508231-1-yhs@fb.com
2021-11-11 17:41:11 -08:00
2021-09-23 11:01:12 -04:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

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
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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