On Wed, Oct 27, 2021 at 4:08 PM Yonghong Song <yhs@xxxxxx> wrote:
>
> Emit BTF BTF_KIND_DECL_TAGs for btf_decl_tag attributes attached to
> typedef declarations. The following is a simple example:
> $ cat t.c
> #define __tag1 __attribute__((btf_decl_tag("tag1")))
> #define __tag2 __attribute__((btf_decl_tag("tag2")))
> typedef struct { int a; int b; } __t __tag1 __tag2;
> __t g;
> $ clang -O2 -g -c t.c
> $ pahole -JV t.o
> btf_encoder__new: 't.o' doesn't have '.data..percpu' section
> Found 0 per-CPU variables!
> File t.o:
> [1] TYPEDEF __t type_id=2
> [2] STRUCT (anon) size=8
> a type_id=3 bits_offset=0
> b type_id=3 bits_offset=32
> [3] INT int size=4 nr_bits=32 encoding=SIGNED
> [4] DECL_TAG tag1 type_id=1 component_idx=-1
> [5] DECL_TAG tag2 type_id=1 component_idx=-1
>
> Signed-off-by: Yonghong Song <yhs@xxxxxx>
> ---
> btf_encoder.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/btf_encoder.c b/btf_encoder.c
> index 40f6aa3..2f1f4ae 100644
> --- a/btf_encoder.c
> +++ b/btf_encoder.c
> @@ -1437,19 +1437,25 @@ int btf_encoder__encode_cu(struct btf_encoder *encoder, struct cu *cu)
> }
>
> cu__for_each_type(cu, core_id, pos) {
> + const char *tag_name = "typedef";
> struct namespace *ns;
>
> - if (pos->tag != DW_TAG_structure_type && pos->tag != DW_TAG_union_type)
> + if (pos->tag != DW_TAG_structure_type && pos->tag != DW_TAG_union_type &&
> + pos->tag != DW_TAG_typedef)
> continue;
>
> + if (pos->tag == DW_TAG_structure_type)
> + tag_name = "struct";
> + else if (pos->tag == DW_TAG_union_type)
> + tag_name = "union";
nit: switch instead of these two related sets of if/else blocks would be cleaner
> +
> btf_type_id = type_id_off + core_id;
> ns = tag__namespace(pos);
> list_for_each_entry(annot, &ns->annots, node) {
> tag_type_id = btf_encoder__add_decl_tag(encoder, annot->value, btf_type_id, annot->component_idx);
> if (tag_type_id < 0) {
> fprintf(stderr, "error: failed to encode tag '%s' to %s '%s' with component_idx %d\n",
> - annot->value, pos->tag == DW_TAG_structure_type ? "struct" : "union",
> - namespace__name(ns), annot->component_idx);
> + annot->value, tag_name, namespace__name(ns), annot->component_idx);
> goto out;
> }
> }
> --
> 2.30.2
>
