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Support BTF_KIND_TYPE_TAG for btf_type_tag attributes #2100

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Support BTF_KIND_TYPE_TAG for btf_type_tag attributes #2100

wants to merge 11 commits into from

Commits on Nov 12, 2021

  1. adding ci files

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  2. bpf: Support BTF_KIND_TYPE_TAG for btf_type_tag attributes 

    LLVM patches ([1] for clang, [2] and [3] for BPF backend)
added support for btf_type_tag attributes. This patch
added support for the kernel.

The main motivation for btf_type_tag is to bring kernel
annotations __user, __rcu etc. to btf. With such information
available in btf, bpf verifier can detect mis-usages
and reject the program. For example, for __user tagged pointer,
developers can then use proper helper like bpf_probe_read_user()
etc. to read the data.

BTF_KIND_TYPE_TAG may also useful for other tracing
facility where instead of to require user to specify
kernel/user address type, the kernel can detect it
by itself with btf.

  [1] https://reviews.llvm.org/D111199
  [2] https://reviews.llvm.org/D113222
  [3] https://reviews.llvm.org/D113496

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
    @yonghong-song
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  3. libbpf: Support BTF_KIND_TYPE_TAG 

    Add libbpf support for BTF_KIND_TYPE_TAG.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
    @yonghong-song
    yonghong-song authored and Nobody committed Nov 12, 2021
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  4. bpftool: Support BTF_KIND_TYPE_TAG 

    Add bpftool support for BTF_KIND_TYPE_TAG.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
    @yonghong-song
    yonghong-song authored and Nobody committed Nov 12, 2021
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  5. selftests/bpf: Test libbpf API function btf__add_type_tag() 

    Add unit tests for btf__add_type_tag().

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
    @yonghong-song
    yonghong-song authored and Nobody committed Nov 12, 2021
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  6. selftests/bpf: Add BTF_KIND_TYPE_TAG unit tests 

    Add BTF_KIND_TYPE_TAG unit tests.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
    @yonghong-song
    yonghong-song authored and Nobody committed Nov 12, 2021
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  7. selftests/bpf: Test BTF_KIND_DECL_TAG for deduplication 

    Add BTF_KIND_TYPE_TAG duplication unit tests.

Signed-off-by: Yonghong Song <yhs@fb.com>
    @yonghong-song
    yonghong-song authored and Nobody committed Nov 12, 2021
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  8. selftests/bpf: Rename progs/tag.c to progs/btf_decl_tag.c 

    Rename progs/tag.c to progs/btf_decl_tag.c so we can introduce
progs/btf_type_tag.c in the next patch.

Also create a subtest for btf_decl_tag in prog_tests/btf_tag.c
so we can introduce btf_type_tag subtest in the next patch.

I also took opportunity to remove the check whether __has_attribute
is defined or not in progs/btf_decl_tag.c since all recent
clangs should already support this macro.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
    @yonghong-song
    yonghong-song authored and Nobody committed Nov 12, 2021
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  9. 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>
    @yonghong-song
    yonghong-song authored and Nobody committed Nov 12, 2021
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  10. selftests/bpf: Clarify llvm dependency with btf_tag selftest 

    btf_tag selftest needs certain llvm versions (>= llvm14).
Make it clear in the selftests README.rst file.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
    @yonghong-song
    yonghong-song authored and Nobody committed Nov 12, 2021
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  11. docs/bpf: Update documentation for BTF_KIND_TYPE_TAG support 

    Add BTF_KIND_TYPE_TAG documentation in btf.rst.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
    @yonghong-song
    yonghong-song authored and Nobody committed Nov 12, 2021
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