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dwarf_loader: support typedef DW_TAG_LLVM_annotation 

llvm commit ([1]) added support for btf_decl_tag attribute
with typedef declaration. Eventually, DW_TAG_LLVM_annotation
tag may appear inside dwarf typedef declaration tag.

kernel support for typedef BTF_KIND_DECL_TAG support
is introduced in [2]. There is no additional libbpf
change needed as the previous libbpf BTF_KIND_DECL_TAG
support is generic enough to cover new typedef use
cases.

This patch added parsing of DW_TAG_LLVM_annotation
for dwarf typedef decl.

  $ cat t.c
  $ clang -O2 -g -c t.c
  $ llvm-dwarfdump --debug-info t.o
    ......
    0x00000033:   DW_TAG_typedef
                    DW_AT_type      (0x00000051 "structure ")
                    DW_AT_name      ("__t")
                    DW_AT_decl_file ("/home/yhs/t.c")
                    DW_AT_decl_line (3)

    0x0000003e:     DW_TAG_LLVM_annotation
                      DW_AT_name    ("btf_decl_tag")
                      DW_AT_const_value     ("tag1")

    0x00000047:     DW_TAG_LLVM_annotation
                      DW_AT_name    ("btf_decl_tag")
                      DW_AT_const_value     ("tag2")

    0x00000050:     NULL

Previously, pahole will issue a warning if typedef tag
contains any child tag. I removed this warning since
it is not true any more. Note that dwarf standard doesn't
prevent typedef decl tag from having nested tags.
In the future if we need to process any tag inside
typedef tag, we can just add code to process it.

  [1] https://reviews.llvm.org/D110127
  [2] https://lore.kernel.org/bpf/20211021195628.4018847-1-yhs@fb.com

Signed-off-by: Yonghong Song <yhs@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: bpf@vger.kernel.org
Cc: dwarves@vger.kernel.org
Cc: kernel-team@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Yonghong Song 2021-11-02 16:35:05 -07:00 committed by Arnaldo Carvalho de Melo
parent 696c621804
commit 468b4196f6
1 changed files with 2 additions and 5 deletions
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7
dwarf_loader.c
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@ -1296,11 +1296,8 @@ static struct tag *die__create_new_typedef(Dwarf_Die *die, struct cu *cu, struct
if (tdef == NULL)
return NULL;
if (dwarf_haschildren(die)) {
struct dwarf_tag *dtag = tdef->namespace.tag.priv;
fprintf(stderr, "%s: DW_TAG_typedef %llx WITH children!\n",
__func__, (unsigned long long)dtag->id);
}
if (add_child_llvm_annotations(die, -1, conf, &tdef->namespace.annots))
return NULL;
return &tdef->namespace.tag;
}