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 Since Linux 5.8 bpftool is able to discover information about 40 processes that hold open file descriptors (FDs) against BTF 41 objects. On such kernels bpftool will automatically emit this 42 information as well. 43 44 **bpftool btf dump** *BTF_SRC* 45 Dump BTF entries from a given *BTF_SRC*. 46 47 When **id** is specified, BTF object with that ID will be 48 loaded and all its BTF types emitted. 49 50 When **map** is provided, it's expected that map has 51 associated BTF object with BTF types describing key and 52 value. It's possible to select whether to dump only BTF 53 type(s) associated with key (**key**), value (**value**), 54 both key and value (**kv**), or all BTF types present in 55 associated BTF object (**all**). If not specified, **kv** 56 is assumed. 57 58 When **prog** is provided, it's expected that program has 59 associated BTF object with BTF types. 60 61 When specifying *FILE*, an ELF file is expected, containing 62 .BTF section with well-defined BTF binary format data, 63 typically produced by clang or pahole. 64 65 **format** option can be used to override default (raw) 66 output format. Raw (**raw**) or C-syntax (**c**) output 67 formats are supported. 68 69 **bpftool btf help** 70 Print short help message. 71 72OPTIONS 73======= 74 .. include:: common_options.rst 75 76EXAMPLES 77======== 78**# bpftool btf dump id 1226** 79 80:: 81 82 [1] PTR '(anon)' type_id=2 83 [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=2 84 'pad' type_id=3 bits_offset=0 85 'sock' type_id=4 bits_offset=64 86 [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none) 87 [4] PTR '(anon)' type_id=5 88 [5] FWD 'sock' fwd_kind=union 89 90This gives an example of default output for all supported BTF kinds. 91 92**$ cat prog.c** 93 94:: 95 96 struct fwd_struct; 97 98 enum my_enum { 99 VAL1 = 3, 100 VAL2 = 7, 101 }; 102 103 typedef struct my_struct my_struct_t; 104 105 struct my_struct { 106 const unsigned int const_int_field; 107 int bitfield_field: 4; 108 char arr_field[16]; 109 const struct fwd_struct *restrict fwd_field; 110 enum my_enum enum_field; 111 volatile my_struct_t *typedef_ptr_field; 112 }; 113 114 union my_union { 115 int a; 116 struct my_struct b; 117 }; 118 119 struct my_struct struct_global_var __attribute__((section("data_sec"))) = { 120 .bitfield_field = 3, 121 .enum_field = VAL1, 122 }; 123 int global_var __attribute__((section("data_sec"))) = 7; 124 125 __attribute__((noinline)) 126 int my_func(union my_union *arg1, int arg2) 127 { 128 static int static_var __attribute__((section("data_sec"))) = 123; 129 static_var++; 130 return static_var; 131 } 132 133**$ bpftool btf dump file prog.o** 134 135:: 136 137 [1] PTR '(anon)' type_id=2 138 [2] UNION 'my_union' size=48 vlen=2 139 'a' type_id=3 bits_offset=0 140 'b' type_id=4 bits_offset=0 141 [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED 142 [4] STRUCT 'my_struct' size=48 vlen=6 143 'const_int_field' type_id=5 bits_offset=0 144 'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4 145 'arr_field' type_id=8 bits_offset=40 146 'fwd_field' type_id=10 bits_offset=192 147 'enum_field' type_id=14 bits_offset=256 148 'typedef_ptr_field' type_id=15 bits_offset=320 149 [5] CONST '(anon)' type_id=6 150 [6] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none) 151 [7] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED 152 [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16 153 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none) 154 [10] RESTRICT '(anon)' type_id=11 155 [11] PTR '(anon)' type_id=12 156 [12] CONST '(anon)' type_id=13 157 [13] FWD 'fwd_struct' fwd_kind=union 158 [14] ENUM 'my_enum' size=4 vlen=2 159 'VAL1' val=3 160 'VAL2' val=7 161 [15] PTR '(anon)' type_id=16 162 [16] VOLATILE '(anon)' type_id=17 163 [17] TYPEDEF 'my_struct_t' type_id=4 164 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2 165 'arg1' type_id=1 166 'arg2' type_id=3 167 [19] FUNC 'my_func' type_id=18 168 [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc 169 [21] VAR 'global_var' type_id=3, linkage=global-alloc 170 [22] VAR 'my_func.static_var' type_id=3, linkage=static 171 [23] DATASEC 'data_sec' size=0 vlen=3 172 type_id=20 offset=0 size=48 173 type_id=21 offset=0 size=4 174 type_id=22 offset=52 size=4 175 176The following commands print BTF types associated with specified map's key, 177value, both key and value, and all BTF types, respectively. By default, both 178key and value types will be printed. 179 180**# bpftool btf dump map id 123 key** 181 182:: 183 184 [39] TYPEDEF 'u32' type_id=37 185 186**# bpftool btf dump map id 123 value** 187 188:: 189 190 [86] PTR '(anon)' type_id=87 191 192**# bpftool btf dump map id 123 kv** 193 194:: 195 196 [39] TYPEDEF 'u32' type_id=37 197 [86] PTR '(anon)' type_id=87 198 199**# bpftool btf dump map id 123 all** 200 201:: 202 203 [1] PTR '(anon)' type_id=0 204 . 205 . 206 . 207 [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4 208 209All the standard ways to specify map or program are supported: 210 211**# bpftool btf dump map id 123** 212 213**# bpftool btf dump map pinned /sys/fs/bpf/map_name** 214 215**# bpftool btf dump prog id 456** 216 217**# bpftool btf dump prog tag b88e0a09b1d9759d** 218 219**# bpftool btf dump prog pinned /sys/fs/bpf/prog_name** 220