From e38e89e8539b144a23db396e0bab9c28d4ad6d0b Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Tue, 21 Sep 2021 19:13:32 -0700 Subject: [PATCH] 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 Tested-by: Arnaldo Carvalho de Melo Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Arnaldo Carvalho de Melo Cc: Daniel Borkmann 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 --- btf_encoder.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 62 insertions(+), 1 deletion(-) diff --git a/btf_encoder.c b/btf_encoder.c index 1b4e83d..c341f95 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)