1 .. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
6 -------------------------------------------------------------------------------
7 tool for inspection of BTF data
8 -------------------------------------------------------------------------------
12 .. include:: substitutions.rst
17 **bpftool** [*OPTIONS*] **btf** *COMMAND*
19 *OPTIONS* := { |COMMON_OPTIONS| | { **-B** | **--base-btf** } }
21 *COMMANDS* := { **dump** | **help** }
26 | **bpftool** **btf** { **show** | **list** } [**id** *BTF_ID*]
27 | **bpftool** **btf dump** *BTF_SRC* [**format** *FORMAT*]
28 | **bpftool** **btf help**
30 | *BTF_SRC* := { **id** *BTF_ID* | **prog** *PROG* | **map** *MAP* [{**key** | **value** | **kv** | **all**}] | **file** *FILE* }
31 | *FORMAT* := { **raw** | **c** }
32 | *MAP* := { **id** *MAP_ID* | **pinned** *FILE* }
33 | *PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* }
37 **bpftool btf { show | list }** [**id** *BTF_ID*]
38 Show information about loaded BTF objects. If a BTF ID is
39 specified, show information only about given BTF object,
40 otherwise list all BTF objects currently loaded on the
43 Since Linux 5.8 bpftool is able to discover information about
44 processes that hold open file descriptors (FDs) against BTF
45 objects. On such kernels bpftool will automatically emit this
48 **bpftool btf dump** *BTF_SRC*
49 Dump BTF entries from a given *BTF_SRC*.
51 When **id** is specified, BTF object with that ID will be
52 loaded and all its BTF types emitted.
54 When **map** is provided, it's expected that map has
55 associated BTF object with BTF types describing key and
56 value. It's possible to select whether to dump only BTF
57 type(s) associated with key (**key**), value (**value**),
58 both key and value (**kv**), or all BTF types present in
59 associated BTF object (**all**). If not specified, **kv**
62 When **prog** is provided, it's expected that program has
63 associated BTF object with BTF types.
65 When specifying *FILE*, an ELF file is expected, containing
66 .BTF section with well-defined BTF binary format data,
67 typically produced by clang or pahole.
69 **format** option can be used to override default (raw)
70 output format. Raw (**raw**) or C-syntax (**c**) output
71 formats are supported.
74 Print short help message.
78 .. include:: common_options.rst
81 Pass a base BTF object. Base BTF objects are typically used
82 with BTF objects for kernel modules. To avoid duplicating
83 all kernel symbols required by modules, BTF objects for
84 modules are "split", they are built incrementally on top of
85 the kernel (vmlinux) BTF object. So the base BTF reference
86 should usually point to the kernel BTF.
88 When the main BTF object to process (for example, the
89 module BTF to dump) is passed as a *FILE*, bpftool attempts
90 to autodetect the path for the base object, and passing
91 this option is optional. When the main BTF object is passed
92 through other handles, this option becomes necessary.
96 **# bpftool btf dump id 1226**
100 [1] PTR '(anon)' type_id=2
101 [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=2
102 'pad' type_id=3 bits_offset=0
103 'sock' type_id=4 bits_offset=64
104 [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none)
105 [4] PTR '(anon)' type_id=5
106 [5] FWD 'sock' fwd_kind=union
108 This gives an example of default output for all supported BTF kinds.
121 typedef struct my_struct my_struct_t;
124 const unsigned int const_int_field;
125 int bitfield_field: 4;
127 const struct fwd_struct *restrict fwd_field;
128 enum my_enum enum_field;
129 volatile my_struct_t *typedef_ptr_field;
137 struct my_struct struct_global_var __attribute__((section("data_sec"))) = {
141 int global_var __attribute__((section("data_sec"))) = 7;
143 __attribute__((noinline))
144 int my_func(union my_union *arg1, int arg2)
146 static int static_var __attribute__((section("data_sec"))) = 123;
151 **$ bpftool btf dump file prog.o**
155 [1] PTR '(anon)' type_id=2
156 [2] UNION 'my_union' size=48 vlen=2
157 'a' type_id=3 bits_offset=0
158 'b' type_id=4 bits_offset=0
159 [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
160 [4] STRUCT 'my_struct' size=48 vlen=6
161 'const_int_field' type_id=5 bits_offset=0
162 'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4
163 'arr_field' type_id=8 bits_offset=40
164 'fwd_field' type_id=10 bits_offset=192
165 'enum_field' type_id=14 bits_offset=256
166 'typedef_ptr_field' type_id=15 bits_offset=320
167 [5] CONST '(anon)' type_id=6
168 [6] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none)
169 [7] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
170 [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16
171 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
172 [10] RESTRICT '(anon)' type_id=11
173 [11] PTR '(anon)' type_id=12
174 [12] CONST '(anon)' type_id=13
175 [13] FWD 'fwd_struct' fwd_kind=union
176 [14] ENUM 'my_enum' size=4 vlen=2
179 [15] PTR '(anon)' type_id=16
180 [16] VOLATILE '(anon)' type_id=17
181 [17] TYPEDEF 'my_struct_t' type_id=4
182 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2
185 [19] FUNC 'my_func' type_id=18
186 [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc
187 [21] VAR 'global_var' type_id=3, linkage=global-alloc
188 [22] VAR 'my_func.static_var' type_id=3, linkage=static
189 [23] DATASEC 'data_sec' size=0 vlen=3
190 type_id=20 offset=0 size=48
191 type_id=21 offset=0 size=4
192 type_id=22 offset=52 size=4
194 The following commands print BTF types associated with specified map's key,
195 value, both key and value, and all BTF types, respectively. By default, both
196 key and value types will be printed.
198 **# bpftool btf dump map id 123 key**
202 [39] TYPEDEF 'u32' type_id=37
204 **# bpftool btf dump map id 123 value**
208 [86] PTR '(anon)' type_id=87
210 **# bpftool btf dump map id 123 kv**
214 [39] TYPEDEF 'u32' type_id=37
215 [86] PTR '(anon)' type_id=87
217 **# bpftool btf dump map id 123 all**
221 [1] PTR '(anon)' type_id=0
225 [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4
227 All the standard ways to specify map or program are supported:
229 **# bpftool btf dump map id 123**
231 **# bpftool btf dump map pinned /sys/fs/bpf/map_name**
233 **# bpftool btf dump prog id 456**
235 **# bpftool btf dump prog tag b88e0a09b1d9759d**
237 **# bpftool btf dump prog pinned /sys/fs/bpf/prog_name**
240 | **# bpftool btf dump file /sys/kernel/btf/i2c_smbus**
242 | **# I2C_SMBUS_ID=$(bpftool btf show -p | jq '.[] | select(.name=="i2c_smbus").id')**
243 | **# bpftool btf dump id ${I2C_SMBUS_ID} -B /sys/kernel/btf/vmlinux**
247 [104848] STRUCT 'i2c_smbus_alert' size=40 vlen=2
248 'alert' type_id=393 bits_offset=0
249 'ara' type_id=56050 bits_offset=256
250 [104849] STRUCT 'alert_data' size=12 vlen=3
251 'addr' type_id=16 bits_offset=0
252 'type' type_id=56053 bits_offset=32
253 'data' type_id=7 bits_offset=64
254 [104850] PTR '(anon)' type_id=104848
255 [104851] PTR '(anon)' type_id=104849
256 [104852] FUNC 'i2c_register_spd' type_id=84745 linkage=static
257 [104853] FUNC 'smbalert_driver_init' type_id=1213 linkage=static
258 [104854] FUNC_PROTO '(anon)' ret_type_id=18 vlen=1
260 [104855] FUNC 'i2c_handle_smbus_alert' type_id=104854 linkage=static
261 [104856] FUNC 'smbalert_remove' type_id=104854 linkage=static
262 [104857] FUNC_PROTO '(anon)' ret_type_id=18 vlen=2
265 [104858] FUNC 'smbalert_probe' type_id=104857 linkage=static
266 [104859] FUNC 'smbalert_work' type_id=9695 linkage=static
267 [104860] FUNC 'smbus_alert' type_id=71367 linkage=static
268 [104861] FUNC 'smbus_do_alert' type_id=84827 linkage=static