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SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)2 3================4bpftool-btf5================6-------------------------------------------------------------------------------7tool for inspection of BTF data8-------------------------------------------------------------------------------9 10:Manual section: 811 12.. include:: substitutions.rst13 14SYNOPSIS15========16 17**bpftool** [*OPTIONS*] **btf** *COMMAND*18 19*OPTIONS* := { |COMMON_OPTIONS| | { **-B** | **--base-btf** } }20 21*COMMANDS* := { **dump** | **help** }22 23BTF COMMANDS24=============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 35DESCRIPTION36===========37bpftool btf { show | list } [id *BTF_ID*]38 Show information about loaded BTF objects. If a BTF ID is specified, show39 information only about given BTF object, otherwise list all BTF objects40 currently loaded on the system.41 42 Since Linux 5.8 bpftool is able to discover information about processes43 that hold open file descriptors (FDs) against BTF objects. On such kernels44 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 all50 its BTF types emitted.51 52 When **map** is provided, it's expected that map has associated BTF object53 with BTF types describing key and value. It's possible to select whether to54 dump only BTF type(s) associated with key (**key**), value (**value**),55 both key and value (**kv**), or all BTF types present in associated BTF56 object (**all**). If not specified, **kv** is assumed.57 58 When **prog** is provided, it's expected that program has associated BTF59 object with BTF types.60 61 When specifying *FILE*, an ELF file is expected, containing .BTF section62 with well-defined BTF binary format data, typically produced by clang or63 pahole.64 65 **format** option can be used to override default (raw) output format. Raw66 (**raw**) or C-syntax (**c**) output formats are supported. With C-style67 formatting, the output is sorted by default. Use the **unsorted** option68 to avoid sorting the output.69 70bpftool btf help71 Print short help message.72 73OPTIONS74=======75.. include:: common_options.rst76 77-B, --base-btf *FILE*78 Pass a base BTF object. Base BTF objects are typically used with BTF79 objects for kernel modules. To avoid duplicating all kernel symbols80 required by modules, BTF objects for modules are "split", they are81 built incrementally on top of the kernel (vmlinux) BTF object. So the82 base BTF reference should usually point to the kernel BTF.83 84 When the main BTF object to process (for example, the module BTF to85 dump) is passed as a *FILE*, bpftool attempts to autodetect the path86 for the base object, and passing this option is optional. When the main87 BTF object is passed through other handles, this option becomes88 necessary.89 90EXAMPLES91========92**# bpftool btf dump id 1226**93 94::95 96 [1] PTR '(anon)' type_id=297 [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=298 'pad' type_id=3 bits_offset=099 'sock' type_id=4 bits_offset=64100 [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none)101 [4] PTR '(anon)' type_id=5102 [5] FWD 'sock' fwd_kind=union103 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=2152 [2] UNION 'my_union' size=48 vlen=2153 'a' type_id=3 bits_offset=0154 'b' type_id=4 bits_offset=0155 [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED156 [4] STRUCT 'my_struct' size=48 vlen=6157 'const_int_field' type_id=5 bits_offset=0158 'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4159 'arr_field' type_id=8 bits_offset=40160 'fwd_field' type_id=10 bits_offset=192161 'enum_field' type_id=14 bits_offset=256162 'typedef_ptr_field' type_id=15 bits_offset=320163 [5] CONST '(anon)' type_id=6164 [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=SIGNED166 [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16167 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)168 [10] RESTRICT '(anon)' type_id=11169 [11] PTR '(anon)' type_id=12170 [12] CONST '(anon)' type_id=13171 [13] FWD 'fwd_struct' fwd_kind=union172 [14] ENUM 'my_enum' size=4 vlen=2173 'VAL1' val=3174 'VAL2' val=7175 [15] PTR '(anon)' type_id=16176 [16] VOLATILE '(anon)' type_id=17177 [17] TYPEDEF 'my_struct_t' type_id=4178 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2179 'arg1' type_id=1180 'arg2' type_id=3181 [19] FUNC 'my_func' type_id=18182 [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc183 [21] VAR 'global_var' type_id=3, linkage=global-alloc184 [22] VAR 'my_func.static_var' type_id=3, linkage=static185 [23] DATASEC 'data_sec' size=0 vlen=3186 type_id=20 offset=0 size=48187 type_id=21 offset=0 size=4188 type_id=22 offset=52 size=4189 190The following commands print BTF types associated with specified map's key,191value, both key and value, and all BTF types, respectively. By default, both192key and value types will be printed.193 194**# bpftool btf dump map id 123 key**195 196::197 198 [39] TYPEDEF 'u32' type_id=37199 200**# bpftool btf dump map id 123 value**201 202::203 204 [86] PTR '(anon)' type_id=87205 206**# bpftool btf dump map id 123 kv**207 208::209 210 [39] TYPEDEF 'u32' type_id=37211 [86] PTR '(anon)' type_id=87212 213**# bpftool btf dump map id 123 all**214 215::216 217 [1] PTR '(anon)' type_id=0218 .219 .220 .221 [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4222 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=2244 'alert' type_id=393 bits_offset=0245 'ara' type_id=56050 bits_offset=256246 [104849] STRUCT 'alert_data' size=12 vlen=3247 'addr' type_id=16 bits_offset=0248 'type' type_id=56053 bits_offset=32249 'data' type_id=7 bits_offset=64250 [104850] PTR '(anon)' type_id=104848251 [104851] PTR '(anon)' type_id=104849252 [104852] FUNC 'i2c_register_spd' type_id=84745 linkage=static253 [104853] FUNC 'smbalert_driver_init' type_id=1213 linkage=static254 [104854] FUNC_PROTO '(anon)' ret_type_id=18 vlen=1255 'ara' type_id=56050256 [104855] FUNC 'i2c_handle_smbus_alert' type_id=104854 linkage=static257 [104856] FUNC 'smbalert_remove' type_id=104854 linkage=static258 [104857] FUNC_PROTO '(anon)' ret_type_id=18 vlen=2259 'ara' type_id=56050260 'id' type_id=56056261 [104858] FUNC 'smbalert_probe' type_id=104857 linkage=static262 [104859] FUNC 'smbalert_work' type_id=9695 linkage=static263 [104860] FUNC 'smbus_alert' type_id=71367 linkage=static264 [104861] FUNC 'smbus_do_alert' type_id=84827 linkage=static265