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