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SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) 2 3================ 4bpftool-btf 5================ 6------------------------------------------------------------------------------- 7tool for inspection of BTF data 8------------------------------------------------------------------------------- 9 10:Manual section: 8 11 12.. include:: substitutions.rst 13 14SYNOPSIS 15======== 16 17**bpftool** [*OPTIONS*] **btf** *COMMAND* 18 19*OPTIONS* := { |COMMON_OPTIONS| | { **-B** | **--base-btf** } } 20 21*COMMANDS* := { **dump** | **help** } 22 23BTF COMMANDS 24============= 25 26| **bpftool** **btf** { **show** | **list** } [**id** *BTF_ID*] 27| **bpftool** **btf dump** *BTF_SRC* [**format** *FORMAT*] 28| **bpftool** **btf help** 29| 30| *BTF_SRC* := { **id** *BTF_ID* | **prog** *PROG* | **map** *MAP* [{**key** | **value** | **kv** | **all**}] | **file** *FILE* } 31| *FORMAT* := { **raw** | **c** [**unsorted**] } 32| *MAP* := { **id** *MAP_ID* | **pinned** *FILE* } 33| *PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* | **name** *PROG_NAME* } 34 35DESCRIPTION 36=========== 37bpftool btf { show | list } [id *BTF_ID*] 38 Show information about loaded BTF objects. If a BTF ID is specified, show 39 information only about given BTF object, otherwise list all BTF objects 40 currently loaded on the system. 41 42 Since Linux 5.8 bpftool is able to discover information about processes 43 that hold open file descriptors (FDs) against BTF objects. On such kernels 44 bpftool will automatically emit this information as well. 45 46bpftool btf dump *BTF_SRC* 47 Dump BTF entries from a given *BTF_SRC*. 48 49 When **id** is specified, BTF object with that ID will be loaded and all 50 its BTF types emitted. 51 52 When **map** is provided, it's expected that map has associated BTF object 53 with BTF types describing key and value. It's possible to select whether to 54 dump only BTF type(s) associated with key (**key**), value (**value**), 55 both key and value (**kv**), or all BTF types present in associated BTF 56 object (**all**). If not specified, **kv** is assumed. 57 58 When **prog** is provided, it's expected that program has associated BTF 59 object with BTF types. 60 61 When specifying *FILE*, an ELF file is expected, containing .BTF section 62 with well-defined BTF binary format data, typically produced by clang or 63 pahole. 64 65 **format** option can be used to override default (raw) output format. Raw 66 (**raw**) or C-syntax (**c**) output formats are supported. With C-style 67 formatting, the output is sorted by default. Use the **unsorted** option 68 to avoid sorting the output. 69 70bpftool btf help 71 Print short help message. 72 73OPTIONS 74======= 75.. include:: common_options.rst 76 77-B, --base-btf *FILE* 78 Pass a base BTF object. Base BTF objects are typically used with BTF 79 objects for kernel modules. To avoid duplicating all kernel symbols 80 required by modules, BTF objects for modules are "split", they are 81 built incrementally on top of the kernel (vmlinux) BTF object. So the 82 base BTF reference should usually point to the kernel BTF. 83 84 When the main BTF object to process (for example, the module BTF to 85 dump) is passed as a *FILE*, bpftool attempts to autodetect the path 86 for the base object, and passing this option is optional. When the main 87 BTF object is passed through other handles, this option becomes 88 necessary. 89 90EXAMPLES 91======== 92**# bpftool btf dump id 1226** 93 94:: 95 96 [1] PTR '(anon)' type_id=2 97 [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=2 98 'pad' type_id=3 bits_offset=0 99 'sock' type_id=4 bits_offset=64 100 [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none) 101 [4] PTR '(anon)' type_id=5 102 [5] FWD 'sock' fwd_kind=union 103 104This gives an example of default output for all supported BTF kinds. 105 106**$ cat prog.c** 107 108:: 109 110 struct fwd_struct; 111 112 enum my_enum { 113 VAL1 = 3, 114 VAL2 = 7, 115 }; 116 117 typedef struct my_struct my_struct_t; 118 119 struct my_struct { 120 const unsigned int const_int_field; 121 int bitfield_field: 4; 122 char arr_field[16]; 123 const struct fwd_struct *restrict fwd_field; 124 enum my_enum enum_field; 125 volatile my_struct_t *typedef_ptr_field; 126 }; 127 128 union my_union { 129 int a; 130 struct my_struct b; 131 }; 132 133 struct my_struct struct_global_var __attribute__((section("data_sec"))) = { 134 .bitfield_field = 3, 135 .enum_field = VAL1, 136 }; 137 int global_var __attribute__((section("data_sec"))) = 7; 138 139 __attribute__((noinline)) 140 int my_func(union my_union *arg1, int arg2) 141 { 142 static int static_var __attribute__((section("data_sec"))) = 123; 143 static_var++; 144 return static_var; 145 } 146 147**$ bpftool btf dump file prog.o** 148 149:: 150 151 [1] PTR '(anon)' type_id=2 152 [2] UNION 'my_union' size=48 vlen=2 153 'a' type_id=3 bits_offset=0 154 'b' type_id=4 bits_offset=0 155 [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED 156 [4] STRUCT 'my_struct' size=48 vlen=6 157 'const_int_field' type_id=5 bits_offset=0 158 'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4 159 'arr_field' type_id=8 bits_offset=40 160 'fwd_field' type_id=10 bits_offset=192 161 'enum_field' type_id=14 bits_offset=256 162 'typedef_ptr_field' type_id=15 bits_offset=320 163 [5] CONST '(anon)' type_id=6 164 [6] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none) 165 [7] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED 166 [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16 167 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none) 168 [10] RESTRICT '(anon)' type_id=11 169 [11] PTR '(anon)' type_id=12 170 [12] CONST '(anon)' type_id=13 171 [13] FWD 'fwd_struct' fwd_kind=union 172 [14] ENUM 'my_enum' size=4 vlen=2 173 'VAL1' val=3 174 'VAL2' val=7 175 [15] PTR '(anon)' type_id=16 176 [16] VOLATILE '(anon)' type_id=17 177 [17] TYPEDEF 'my_struct_t' type_id=4 178 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2 179 'arg1' type_id=1 180 'arg2' type_id=3 181 [19] FUNC 'my_func' type_id=18 182 [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc 183 [21] VAR 'global_var' type_id=3, linkage=global-alloc 184 [22] VAR 'my_func.static_var' type_id=3, linkage=static 185 [23] DATASEC 'data_sec' size=0 vlen=3 186 type_id=20 offset=0 size=48 187 type_id=21 offset=0 size=4 188 type_id=22 offset=52 size=4 189 190The following commands print BTF types associated with specified map's key, 191value, both key and value, and all BTF types, respectively. By default, both 192key and value types will be printed. 193 194**# bpftool btf dump map id 123 key** 195 196:: 197 198 [39] TYPEDEF 'u32' type_id=37 199 200**# bpftool btf dump map id 123 value** 201 202:: 203 204 [86] PTR '(anon)' type_id=87 205 206**# bpftool btf dump map id 123 kv** 207 208:: 209 210 [39] TYPEDEF 'u32' type_id=37 211 [86] PTR '(anon)' type_id=87 212 213**# bpftool btf dump map id 123 all** 214 215:: 216 217 [1] PTR '(anon)' type_id=0 218 . 219 . 220 . 221 [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4 222 223All the standard ways to specify map or program are supported: 224 225**# bpftool btf dump map id 123** 226 227**# bpftool btf dump map pinned /sys/fs/bpf/map_name** 228 229**# bpftool btf dump prog id 456** 230 231**# bpftool btf dump prog tag b88e0a09b1d9759d** 232 233**# bpftool btf dump prog pinned /sys/fs/bpf/prog_name** 234 235| 236| **# bpftool btf dump file /sys/kernel/btf/i2c_smbus** 237| (or) 238| **# I2C_SMBUS_ID=$(bpftool btf show -p | jq '.[] | select(.name=="i2c_smbus").id')** 239| **# bpftool btf dump id ${I2C_SMBUS_ID} -B /sys/kernel/btf/vmlinux** 240 241:: 242 243 [104848] STRUCT 'i2c_smbus_alert' size=40 vlen=2 244 'alert' type_id=393 bits_offset=0 245 'ara' type_id=56050 bits_offset=256 246 [104849] STRUCT 'alert_data' size=12 vlen=3 247 'addr' type_id=16 bits_offset=0 248 'type' type_id=56053 bits_offset=32 249 'data' type_id=7 bits_offset=64 250 [104850] PTR '(anon)' type_id=104848 251 [104851] PTR '(anon)' type_id=104849 252 [104852] FUNC 'i2c_register_spd' type_id=84745 linkage=static 253 [104853] FUNC 'smbalert_driver_init' type_id=1213 linkage=static 254 [104854] FUNC_PROTO '(anon)' ret_type_id=18 vlen=1 255 'ara' type_id=56050 256 [104855] FUNC 'i2c_handle_smbus_alert' type_id=104854 linkage=static 257 [104856] FUNC 'smbalert_remove' type_id=104854 linkage=static 258 [104857] FUNC_PROTO '(anon)' ret_type_id=18 vlen=2 259 'ara' type_id=56050 260 'id' type_id=56056 261 [104858] FUNC 'smbalert_probe' type_id=104857 linkage=static 262 [104859] FUNC 'smbalert_work' type_id=9695 linkage=static 263 [104860] FUNC 'smbus_alert' type_id=71367 linkage=static 264 [104861] FUNC 'smbus_do_alert' type_id=84827 linkage=static 265