diff options
author | Yonghong Song <yhs@fb.com> | 2021-09-21 19:13:32 -0700 |
---|---|---|
committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2021-09-27 17:59:40 -0300 |
commit | e38e89e8539b144a23db396e0bab9c28d4ad6d0b (patch) | |
tree | 70e4b4922b7ac1247bf12b7fdd4b23a60cd8c3d1 | |
parent | aa8c494e65a77fa5d0bebeb8ea2b68bca3d468f5 (diff) | |
download | pahole-e38e89e8539b144a23db396e0bab9c28d4ad6d0b.tar.gz |
btf_encoder: Generate BTF_KIND_TAG from llvm annotations
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@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: bpf@vger.kernel.org
Cc: dwarves@vger.kernel.org
Cc: kernel-team@fb.com
Link: https://lore.kernel.org/r/20210922021332.2287418-1-yhs@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
-rw-r--r-- | btf_encoder.c | 63 |
1 files changed, 62 insertions, 1 deletions
diff --git a/btf_encoder.c b/btf_encoder.c index 1b4e83d6..c341f950 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 +1266,15 @@ static int btf_encoder__encode_cu_variables(struct btf_encoder *encoder, struct goto out; } + list_for_each_entry(annot, &var->annots, node) { + int tag_type_id = btf_encoder__add_tag(encoder, annot->value, id, annot->component_idx); + if (tag_type_id < 0) { + fprintf(stderr, "error: failed to encode tag '%s' to variable '%s' with component_idx %d\n", + annot->value, name, annot->component_idx); + goto out; + } + } + /* * 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 +1390,8 @@ 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; + int btf_type_id, tag_type_id; uint32_t core_id; struct function *fn; struct tag *pos; @@ -1378,7 +1411,7 @@ int btf_encoder__encode_cu(struct btf_encoder *encoder, struct cu *cu) } cu__for_each_type(cu, core_id, pos) { - int32_t btf_type_id = btf_encoder__encode_tag(encoder, pos, type_id_off); + btf_type_id = btf_encoder__encode_tag(encoder, pos, type_id_off); if (btf_type_id < 0 || tag__check_id_drift(pos, core_id, btf_type_id, type_id_off)) { @@ -1396,6 +1429,25 @@ 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; + + 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) { + tag_type_id = btf_encoder__add_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); + goto out; + } + } + } + cu__for_each_function(cu, core_id, fn) { int btf_fnproto_id, btf_fn_id; const char *name; @@ -1436,6 +1488,15 @@ 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) { + tag_type_id = btf_encoder__add_tag(encoder, annot->value, btf_fn_id, annot->component_idx); + if (tag_type_id < 0) { + fprintf(stderr, "error: failed to encode tag '%s' to func %s with component_idx %d\n", + annot->value, name, annot->component_idx); + goto out; + } + } } if (!encoder->skip_encoding_vars) |