From d99d551930cf4b4bc41eb5d68b7da69d718a6553 Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Mon, 22 Nov 2021 20:56:33 -0800 Subject: [PATCH] btf_encoder: Support btf_type_tag attribute MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit [$ ~] 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 be used to 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 [$ ~] Committer testing: $ rm -f t.o; clang -O2 -g -c t.c $ llvm-dwarfdump t.o t.o: file format elf64-x86-64 .debug_info contents: 0x00000000: Compile Unit: length = 0x0000005e, format = DWARF32, version = 0x0004, abbr_offset = 0x0000, addr_size = 0x08 (next unit at 0x00000062) 0x0000000b: DW_TAG_compile_unit DW_AT_producer ("clang version 14.0.0 (https://github.com/llvm/llvm-project 0d3add216f04b99ed1db1a05c39975d4a9c83e6b)") DW_AT_language (DW_LANG_C99) DW_AT_name ("t.c") DW_AT_stmt_list (0x00000000) DW_AT_comp_dir ("/var/home/acme/git/pahole") 0x0000001e: DW_TAG_variable DW_AT_name ("g") DW_AT_type (0x00000033 "int **") DW_AT_external (true) DW_AT_decl_file ("/var/home/acme/git/pahole/t.c") DW_AT_decl_line (3) DW_AT_location (DW_OP_addr 0x0) 0x00000033: DW_TAG_pointer_type DW_AT_type (0x0000004b "int *") 0x00000038: DW_TAG_LLVM_annotation DW_AT_name ("btf_type_tag") DW_AT_const_value ("tag1") 0x00000041: DW_TAG_LLVM_annotation DW_AT_name ("btf_type_tag") DW_AT_const_value ("tag2") 0x0000004a: NULL 0x0000004b: DW_TAG_pointer_type DW_AT_type (0x0000005a "int") 0x00000050: DW_TAG_LLVM_annotation DW_AT_name ("btf_type_tag") DW_AT_const_value ("tag1") 0x00000059: NULL 0x0000005a: DW_TAG_base_type DW_AT_name ("int") DW_AT_encoding (DW_ATE_signed) DW_AT_byte_size (0x04) 0x00000061: NULL $ 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 ⬢[acme@toolbox pahole]$ 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 Tested-by: Arnaldo Carvalho de Melo Acked-by: Andrii Nakryiko Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: bpf@vger.kernel.org Cc: dwarves@vger.kernel.org Cc: kernel-team@fb.com Signed-off-by: Arnaldo Carvalho de Melo --- 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