1================ 2bpftool-btf 3================ 4------------------------------------------------------------------------------- 5tool for inspection of BTF data 6------------------------------------------------------------------------------- 7 8:Manual section: 8 9 10SYNOPSIS 11======== 12 13 **bpftool** [*OPTIONS*] **btf** *COMMAND* 14 15 *OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] } 16 17 *COMMANDS* := { **dump** | **help** } 18 19BTF COMMANDS 20============= 21 22| **bpftool** **btf** { **show** | **list** } [**id** *BTF_ID*] 23| **bpftool** **btf dump** *BTF_SRC* [**format** *FORMAT*] 24| **bpftool** **btf help** 25| 26| *BTF_SRC* := { **id** *BTF_ID* | **prog** *PROG* | **map** *MAP* [{**key** | **value** | **kv** | **all**}] | **file** *FILE* } 27| *FORMAT* := { **raw** | **c** } 28| *MAP* := { **id** *MAP_ID* | **pinned** *FILE* } 29| *PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* } 30 31DESCRIPTION 32=========== 33 **bpftool btf { show | list }** [**id** *BTF_ID*] 34 Show information about loaded BTF objects. If a BTF ID is 35 specified, show information only about given BTF object, 36 otherwise list all BTF objects currently loaded on the 37 system. 38 39 **bpftool btf dump** *BTF_SRC* 40 Dump BTF entries from a given *BTF_SRC*. 41 42 When **id** is specified, BTF object with that ID will be 43 loaded and all its BTF types emitted. 44 45 When **map** is provided, it's expected that map has 46 associated BTF object with BTF types describing key and 47 value. It's possible to select whether to dump only BTF 48 type(s) associated with key (**key**), value (**value**), 49 both key and value (**kv**), or all BTF types present in 50 associated BTF object (**all**). If not specified, **kv** 51 is assumed. 52 53 When **prog** is provided, it's expected that program has 54 associated BTF object with BTF types. 55 56 When specifying *FILE*, an ELF file is expected, containing 57 .BTF section with well-defined BTF binary format data, 58 typically produced by clang or pahole. 59 60 **format** option can be used to override default (raw) 61 output format. Raw (**raw**) or C-syntax (**c**) output 62 formats are supported. 63 64 **bpftool btf help** 65 Print short help message. 66 67OPTIONS 68======= 69 -h, --help 70 Print short generic help message (similar to **bpftool help**). 71 72 -V, --version 73 Print version number (similar to **bpftool version**). 74 75 -j, --json 76 Generate JSON output. For commands that cannot produce JSON, this 77 option has no effect. 78 79 -p, --pretty 80 Generate human-readable JSON output. Implies **-j**. 81 82 -d, --debug 83 Print all logs available from libbpf, including debug-level 84 information. 85 86EXAMPLES 87======== 88**# bpftool btf dump id 1226** 89:: 90 91 [1] PTR '(anon)' type_id=2 92 [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=2 93 'pad' type_id=3 bits_offset=0 94 'sock' type_id=4 bits_offset=64 95 [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none) 96 [4] PTR '(anon)' type_id=5 97 [5] FWD 'sock' fwd_kind=union 98 99This gives an example of default output for all supported BTF kinds. 100 101**$ cat prog.c** 102:: 103 104 struct fwd_struct; 105 106 enum my_enum { 107 VAL1 = 3, 108 VAL2 = 7, 109 }; 110 111 typedef struct my_struct my_struct_t; 112 113 struct my_struct { 114 const unsigned int const_int_field; 115 int bitfield_field: 4; 116 char arr_field[16]; 117 const struct fwd_struct *restrict fwd_field; 118 enum my_enum enum_field; 119 volatile my_struct_t *typedef_ptr_field; 120 }; 121 122 union my_union { 123 int a; 124 struct my_struct b; 125 }; 126 127 struct my_struct struct_global_var __attribute__((section("data_sec"))) = { 128 .bitfield_field = 3, 129 .enum_field = VAL1, 130 }; 131 int global_var __attribute__((section("data_sec"))) = 7; 132 133 __attribute__((noinline)) 134 int my_func(union my_union *arg1, int arg2) 135 { 136 static int static_var __attribute__((section("data_sec"))) = 123; 137 static_var++; 138 return static_var; 139 } 140 141**$ bpftool btf dump file prog.o** 142:: 143 144 [1] PTR '(anon)' type_id=2 145 [2] UNION 'my_union' size=48 vlen=2 146 'a' type_id=3 bits_offset=0 147 'b' type_id=4 bits_offset=0 148 [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED 149 [4] STRUCT 'my_struct' size=48 vlen=6 150 'const_int_field' type_id=5 bits_offset=0 151 'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4 152 'arr_field' type_id=8 bits_offset=40 153 'fwd_field' type_id=10 bits_offset=192 154 'enum_field' type_id=14 bits_offset=256 155 'typedef_ptr_field' type_id=15 bits_offset=320 156 [5] CONST '(anon)' type_id=6 157 [6] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none) 158 [7] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED 159 [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16 160 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none) 161 [10] RESTRICT '(anon)' type_id=11 162 [11] PTR '(anon)' type_id=12 163 [12] CONST '(anon)' type_id=13 164 [13] FWD 'fwd_struct' fwd_kind=union 165 [14] ENUM 'my_enum' size=4 vlen=2 166 'VAL1' val=3 167 'VAL2' val=7 168 [15] PTR '(anon)' type_id=16 169 [16] VOLATILE '(anon)' type_id=17 170 [17] TYPEDEF 'my_struct_t' type_id=4 171 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2 172 'arg1' type_id=1 173 'arg2' type_id=3 174 [19] FUNC 'my_func' type_id=18 175 [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc 176 [21] VAR 'global_var' type_id=3, linkage=global-alloc 177 [22] VAR 'my_func.static_var' type_id=3, linkage=static 178 [23] DATASEC 'data_sec' size=0 vlen=3 179 type_id=20 offset=0 size=48 180 type_id=21 offset=0 size=4 181 type_id=22 offset=52 size=4 182 183The following commands print BTF types associated with specified map's key, 184value, both key and value, and all BTF types, respectively. By default, both 185key and value types will be printed. 186 187**# bpftool btf dump map id 123 key** 188 189:: 190 191 [39] TYPEDEF 'u32' type_id=37 192 193**# bpftool btf dump map id 123 value** 194 195:: 196 197 [86] PTR '(anon)' type_id=87 198 199**# bpftool btf dump map id 123 kv** 200 201:: 202 203 [39] TYPEDEF 'u32' type_id=37 204 [86] PTR '(anon)' type_id=87 205 206**# bpftool btf dump map id 123 all** 207 208:: 209 210 [1] PTR '(anon)' type_id=0 211 . 212 . 213 . 214 [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4 215 216All the standard ways to specify map or program are supported: 217 218**# bpftool btf dump map id 123** 219 220**# bpftool btf dump map pinned /sys/fs/bpf/map_name** 221 222**# bpftool btf dump prog id 456** 223 224**# bpftool btf dump prog tag b88e0a09b1d9759d** 225 226**# bpftool btf dump prog pinned /sys/fs/bpf/prog_name** 227 228SEE ALSO 229======== 230 **bpf**\ (2), 231 **bpf-helpers**\ (7), 232 **bpftool**\ (8), 233 **bpftool-map**\ (8), 234 **bpftool-prog**\ (8), 235 **bpftool-cgroup**\ (8), 236 **bpftool-feature**\ (8), 237 **bpftool-net**\ (8), 238 **bpftool-perf**\ (8) 239