The following is an example.
[$ ~] cat t.c
#define __tag1 __attribute__((btf_type_tag("tag1")))
#define __tag2 __attribute__((btf_type_tag("tag2")))
int __tag1 * __tag1 __tag2 *g __attribute__((section(".data..percpu")));
[$ ~] clang -O2 -g -c t.c
[$ ~] pahole -JV t.o
Found per-CPU symbol 'g' at address 0x0
Found 1 per-CPU variables!
File t.o:
[1] TYPE_TAG tag1 type_id=5
[2] TYPE_TAG tag2 type_id=1
[3] PTR (anon) type_id=2
[4] TYPE_TAG tag1 type_id=6
[5] PTR (anon) type_id=4
[6] INT int size=4 nr_bits=32 encoding=SIGNED
search cu 't.c' for percpu global variables.
Variable 'g' from CU 't.c' at address 0x0 encoded
[7] VAR g type=3 linkage=1
[8] DATASEC .data..percpu size=8 vlen=1
type=7 offset=0 size=8
[$ ~]
You can see for the source
int __tag1 * __tag1 __tag2 *g __attribute__((section(".data..percpu")));
the following type chain is generated:
var -> ptr -> tag2 -> tag1 -> ptr -> tag1 -> int
The following shows pahole option "--skip_encoding_btf_type_tag"
can prevent BTF_KIND_TYPE_TAG generation.
[$ ~] pahole -JV t.o --skip_encoding_btf_type_tag
Found per-CPU symbol 'g' at address 0x0
Found 1 per-CPU variables!
File t.o:
[1] PTR (anon) type_id=2
[2] PTR (anon) type_id=3
[3] INT int size=4 nr_bits=32 encoding=SIGNED
search cu 't.c' for percpu global variables.
Variable 'g' from CU 't.c' at address 0x0 encoded
[4] VAR g type=1 linkage=1
[5] DATASEC .data..percpu size=8 vlen=1
type=4 offset=0 size=8
[$ ~]
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
btf_encoder.c | 7 +++++++
dwarves.h | 5 +++++
2 files changed, 12 insertions(+)
diff --git a/btf_encoder.c b/btf_encoder.c
index 117656e..9d015f3 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -143,6 +143,7 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
[BTF_KIND_DATASEC] = "DATASEC",
[BTF_KIND_FLOAT] = "FLOAT",
[BTF_KIND_DECL_TAG] = "DECL_TAG",
+ [BTF_KIND_TYPE_TAG] = "TYPE_TAG",
};
static const char *btf__printable_name(const struct btf *btf, uint32_t offset)
@@ -393,6 +394,9 @@ static int32_t btf_encoder__add_ref_type(struct btf_encoder *encoder, uint16_t k
case BTF_KIND_TYPEDEF:
id = btf__add_typedef(btf, name, type);
break;
+ case BTF_KIND_TYPE_TAG:
+ id = btf__add_type_tag(btf, name, type);
+ break;
case BTF_KIND_FWD:
id = btf__add_fwd(btf, name, kind_flag);
break;
@@ -862,6 +866,9 @@ static int btf_encoder__encode_tag(struct btf_encoder *encoder, struct tag *tag,
case DW_TAG_typedef:
name = namespace__name(tag__namespace(tag));
return btf_encoder__add_ref_type(encoder, BTF_KIND_TYPEDEF, ref_type_id, name, false);
+ case DW_TAG_LLVM_annotation:
+ name = tag__btf_type_tag(tag)->value;
+ return btf_encoder__add_ref_type(encoder, BTF_KIND_TYPE_TAG, ref_type_id, name, false);
case DW_TAG_structure_type:
case DW_TAG_union_type:
case DW_TAG_class_type:
diff --git a/dwarves.h b/dwarves.h
index 4425d3c..52d162d 100644
--- a/dwarves.h
+++ b/dwarves.h
@@ -637,6 +637,11 @@ static inline struct btf_type_tag_ptr_type *tag__btf_type_tag_ptr(struct tag *ta
return (struct btf_type_tag_ptr_type *)tag;
}
+static inline struct btf_type_tag_type *tag__btf_type_tag(struct tag *tag)
+{
+ return (struct btf_type_tag_type *)tag;
+}
+
/** struct namespace - base class for enums, structs, unions, typedefs, etc
*
* @tags - class_member, enumerators, etc
--
2.30.2
