The following is an example with latest upstream clang:
$ cat t.c
#define __tag1 __attribute__((btf_tag("tag1")))
#define __tag2 __attribute__((btf_tag("tag2")))
struct t {
int a:1 __tag1;
int b __tag2;
} __tag1 __tag2;
int g __tag1 __attribute__((section(".data..percpu")));
int __tag1 foo(struct t *a1, int a2 __tag2) {
return a1->b + a2 + g;
}
$ clang -O2 -g -c t.c
$ pahole -JV t.o
Found per-CPU symbol 'g' at address 0x0
Found 1 per-CPU variables!
Found 1 functions!
File t.o:
[1] INT int size=4 nr_bits=32 encoding=SIGNED
[2] PTR (anon) type_id=3
[3] STRUCT t size=8
a type_id=1 bitfield_size=1 bits_offset=0
b type_id=1 bitfield_size=0 bits_offset=32
[4] TAG tag1 type_id=3 component_idx=0
[5] TAG tag2 type_id=3 component_idx=1
[6] TAG tag1 type_id=3 component_idx=-1
[7] TAG tag2 type_id=3 component_idx=-1
[8] FUNC_PROTO (anon) return=1 args=(2 a1, 1 a2)
[9] FUNC foo type_id=8
[10] TAG tag2 type_id=9 component_idx=1
[11] TAG tag1 type_id=9 component_idx=-1
search cu 't.c' for percpu global variables.
Variable 'g' from CU 't.c' at address 0x0 encoded
[12] VAR g type=1 linkage=1
[13] TAG tag1 type_id=12 component_idx=-1
[14] DATASEC .data..percpu size=4 vlen=1
type=12 offset=0 size=4
$ ...
With additional option --skip_encoding_btf_tag, pahole doesn't
generate BTF_KIND_TAGs any more.
$ pahole -JV --skip_encoding_btf_tag t.o
Found per-CPU symbol 'g' at address 0x0
Found 1 per-CPU variables!
Found 1 functions!
File t.o:
[1] INT int size=4 nr_bits=32 encoding=SIGNED
[2] PTR (anon) type_id=3
[3] STRUCT t size=8
a type_id=1 bitfield_size=1 bits_offset=0
b type_id=1 bitfield_size=0 bits_offset=32
[4] FUNC_PROTO (anon) return=1 args=(2 a1, 1 a2)
[5] FUNC foo type_id=4
search cu 't.c' for percpu global variables.
Variable 'g' from CU 't.c' at address 0x0 encoded
[6] VAR g type=1 linkage=1
[7] DATASEC .data..percpu size=4 vlen=1
type=6 offset=0 size=4
$ ...
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
btf_encoder.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/btf_encoder.c b/btf_encoder.c
index 1b4e83d..e983750 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -141,6 +141,7 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
[BTF_KIND_VAR] = "VAR",
[BTF_KIND_DATASEC] = "DATASEC",
[BTF_KIND_FLOAT] = "FLOAT",
+ [BTF_KIND_TAG] = "TAG",
};
static const char *btf__printable_name(const struct btf *btf, uint32_t offset)
@@ -644,6 +645,26 @@ static int32_t btf_encoder__add_datasec(struct btf_encoder *encoder, const char
return id;
}
+static int32_t btf_encoder__add_tag(struct btf_encoder *encoder, const char *value, uint32_t type,
+ int component_idx)
+{
+ struct btf *btf = encoder->btf;
+ const struct btf_type *t;
+ int32_t id;
+
+ id = btf__add_tag(btf, value, type, component_idx);
+ if (id > 0) {
+ t = btf__type_by_id(btf, id);
+ btf_encoder__log_type(encoder, t, false, true, "type_id=%u component_idx=%d",
+ t->type, component_idx);
+ } else {
+ btf__log_err(btf, BTF_KIND_TAG, value, true, "component_idx=%d Error emitting BTF type",
+ component_idx);
+ }
+
+ return id;
+}
+
/*
* This corresponds to the same macro defined in
* include/linux/kallsyms.h
@@ -1158,6 +1179,7 @@ static int btf_encoder__encode_cu_variables(struct btf_encoder *encoder, struct
struct variable *var = tag__variable(pos);
uint32_t size, type, linkage;
const char *name, *dwarf_name;
+ struct llvm_annotation *annot;
const struct tag *tag;
uint64_t addr;
int id;
@@ -1244,6 +1266,10 @@ static int btf_encoder__encode_cu_variables(struct btf_encoder *encoder, struct
goto out;
}
+ list_for_each_entry(annot, &var->annots, node) {
+ btf_encoder__add_tag(encoder, annot->value, id, annot->component_idx);
+ }
+
/*
* add a BTF_VAR_SECINFO in encoder->percpu_secinfo, which will be added into
* encoder->types later when we add BTF_VAR_DATASEC.
@@ -1359,6 +1385,7 @@ void btf_encoder__delete(struct btf_encoder *encoder)
int btf_encoder__encode_cu(struct btf_encoder *encoder, struct cu *cu)
{
uint32_t type_id_off = btf__get_nr_types(encoder->btf);
+ struct llvm_annotation *annot;
uint32_t core_id;
struct function *fn;
struct tag *pos;
@@ -1396,6 +1423,20 @@ int btf_encoder__encode_cu(struct btf_encoder *encoder, struct cu *cu)
encoder->has_index_type = true;
}
+ cu__for_each_type(cu, core_id, pos) {
+ struct namespace *ns;
+ int btf_type_id;
+
+ if (pos->tag != DW_TAG_structure_type && pos->tag != DW_TAG_union_type)
+ continue;
+
+ btf_type_id = type_id_off + core_id;
+ ns = tag__namespace(pos);
+ list_for_each_entry(annot, &ns->annots, node) {
+ btf_encoder__add_tag(encoder, annot->value, btf_type_id, annot->component_idx);
+ }
+ }
+
cu__for_each_function(cu, core_id, fn) {
int btf_fnproto_id, btf_fn_id;
const char *name;
@@ -1436,6 +1477,10 @@ int btf_encoder__encode_cu(struct btf_encoder *encoder, struct cu *cu)
printf("error: failed to encode function '%s'\n", function__name(fn));
goto out;
}
+
+ list_for_each_entry(annot, &fn->annots, node) {
+ btf_encoder__add_tag(encoder, annot->value, btf_fn_id, annot->component_idx);
+ }
}
if (!encoder->skip_encoding_vars)
--
2.30.2
