4 -------------------------------------------------------------------------------
5 tool for inspection of BTF data
6 -------------------------------------------------------------------------------
13 **bpftool** [*OPTIONS*] **btf** *COMMAND*
15 *OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] | {**-d** | **--debug** } |
16 { **-B** | **--base-btf** } }
18 *COMMANDS* := { **dump** | **help** }
23 | **bpftool** **btf** { **show** | **list** } [**id** *BTF_ID*]
24 | **bpftool** **btf dump** *BTF_SRC* [**format** *FORMAT*]
25 | **bpftool** **btf help**
27 | *BTF_SRC* := { **id** *BTF_ID* | **prog** *PROG* | **map** *MAP* [{**key** | **value** | **kv** | **all**}] | **file** *FILE* }
28 | *FORMAT* := { **raw** | **c** }
29 | *MAP* := { **id** *MAP_ID* | **pinned** *FILE* }
30 | *PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* }
34 **bpftool btf { show | list }** [**id** *BTF_ID*]
35 Show information about loaded BTF objects. If a BTF ID is
36 specified, show information only about given BTF object,
37 otherwise list all BTF objects currently loaded on the
40 Since Linux 5.8 bpftool is able to discover information about
41 processes that hold open file descriptors (FDs) against BTF
42 objects. On such kernels bpftool will automatically emit this
45 **bpftool btf dump** *BTF_SRC*
46 Dump BTF entries from a given *BTF_SRC*.
48 When **id** is specified, BTF object with that ID will be
49 loaded and all its BTF types emitted.
51 When **map** is provided, it's expected that map has
52 associated BTF object with BTF types describing key and
53 value. It's possible to select whether to dump only BTF
54 type(s) associated with key (**key**), value (**value**),
55 both key and value (**kv**), or all BTF types present in
56 associated BTF object (**all**). If not specified, **kv**
59 When **prog** is provided, it's expected that program has
60 associated BTF object with BTF types.
62 When specifying *FILE*, an ELF file is expected, containing
63 .BTF section with well-defined BTF binary format data,
64 typically produced by clang or pahole.
66 **format** option can be used to override default (raw)
67 output format. Raw (**raw**) or C-syntax (**c**) output
68 formats are supported.
71 Print short help message.
75 .. include:: common_options.rst
78 Pass a base BTF object. Base BTF objects are typically used
79 with BTF objects for kernel modules. To avoid duplicating
80 all kernel symbols required by modules, BTF objects for
81 modules are "split", they are built incrementally on top of
82 the kernel (vmlinux) BTF object. So the base BTF reference
83 should usually point to the kernel BTF.
85 When the main BTF object to process (for example, the
86 module BTF to dump) is passed as a *FILE*, bpftool attempts
87 to autodetect the path for the base object, and passing
88 this option is optional. When the main BTF object is passed
89 through other handles, this option becomes necessary.
93 **# bpftool btf dump id 1226**
97 [1] PTR '(anon)' type_id=2
98 [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=2
99 'pad' type_id=3 bits_offset=0
100 'sock' type_id=4 bits_offset=64
101 [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none)
102 [4] PTR '(anon)' type_id=5
103 [5] FWD 'sock' fwd_kind=union
105 This gives an example of default output for all supported BTF kinds.
118 typedef struct my_struct my_struct_t;
121 const unsigned int const_int_field;
122 int bitfield_field: 4;
124 const struct fwd_struct *restrict fwd_field;
125 enum my_enum enum_field;
126 volatile my_struct_t *typedef_ptr_field;
134 struct my_struct struct_global_var __attribute__((section("data_sec"))) = {
138 int global_var __attribute__((section("data_sec"))) = 7;
140 __attribute__((noinline))
141 int my_func(union my_union *arg1, int arg2)
143 static int static_var __attribute__((section("data_sec"))) = 123;
148 **$ bpftool btf dump file prog.o**
152 [1] PTR '(anon)' type_id=2
153 [2] UNION 'my_union' size=48 vlen=2
154 'a' type_id=3 bits_offset=0
155 'b' type_id=4 bits_offset=0
156 [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
157 [4] STRUCT 'my_struct' size=48 vlen=6
158 'const_int_field' type_id=5 bits_offset=0
159 'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4
160 'arr_field' type_id=8 bits_offset=40
161 'fwd_field' type_id=10 bits_offset=192
162 'enum_field' type_id=14 bits_offset=256
163 'typedef_ptr_field' type_id=15 bits_offset=320
164 [5] CONST '(anon)' type_id=6
165 [6] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none)
166 [7] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
167 [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16
168 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
169 [10] RESTRICT '(anon)' type_id=11
170 [11] PTR '(anon)' type_id=12
171 [12] CONST '(anon)' type_id=13
172 [13] FWD 'fwd_struct' fwd_kind=union
173 [14] ENUM 'my_enum' size=4 vlen=2
176 [15] PTR '(anon)' type_id=16
177 [16] VOLATILE '(anon)' type_id=17
178 [17] TYPEDEF 'my_struct_t' type_id=4
179 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2
182 [19] FUNC 'my_func' type_id=18
183 [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc
184 [21] VAR 'global_var' type_id=3, linkage=global-alloc
185 [22] VAR 'my_func.static_var' type_id=3, linkage=static
186 [23] DATASEC 'data_sec' size=0 vlen=3
187 type_id=20 offset=0 size=48
188 type_id=21 offset=0 size=4
189 type_id=22 offset=52 size=4
191 The following commands print BTF types associated with specified map's key,
192 value, both key and value, and all BTF types, respectively. By default, both
193 key and value types will be printed.
195 **# bpftool btf dump map id 123 key**
199 [39] TYPEDEF 'u32' type_id=37
201 **# bpftool btf dump map id 123 value**
205 [86] PTR '(anon)' type_id=87
207 **# bpftool btf dump map id 123 kv**
211 [39] TYPEDEF 'u32' type_id=37
212 [86] PTR '(anon)' type_id=87
214 **# bpftool btf dump map id 123 all**
218 [1] PTR '(anon)' type_id=0
222 [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4
224 All the standard ways to specify map or program are supported:
226 **# bpftool btf dump map id 123**
228 **# bpftool btf dump map pinned /sys/fs/bpf/map_name**
230 **# bpftool btf dump prog id 456**
232 **# bpftool btf dump prog tag b88e0a09b1d9759d**
234 **# bpftool btf dump prog pinned /sys/fs/bpf/prog_name**
237 | **# bpftool btf dump file /sys/kernel/btf/i2c_smbus**
239 | **# I2C_SMBUS_ID=$(bpftool btf show -p | jq '.[] | select(.name=="i2c_smbus").id')**
240 | **# bpftool btf dump id ${I2C_SMBUS_ID} -B /sys/kernel/btf/vmlinux**
244 [104848] STRUCT 'i2c_smbus_alert' size=40 vlen=2
245 'alert' type_id=393 bits_offset=0
246 'ara' type_id=56050 bits_offset=256
247 [104849] STRUCT 'alert_data' size=12 vlen=3
248 'addr' type_id=16 bits_offset=0
249 'type' type_id=56053 bits_offset=32
250 'data' type_id=7 bits_offset=64
251 [104850] PTR '(anon)' type_id=104848
252 [104851] PTR '(anon)' type_id=104849
253 [104852] FUNC 'i2c_register_spd' type_id=84745 linkage=static
254 [104853] FUNC 'smbalert_driver_init' type_id=1213 linkage=static
255 [104854] FUNC_PROTO '(anon)' ret_type_id=18 vlen=1
257 [104855] FUNC 'i2c_handle_smbus_alert' type_id=104854 linkage=static
258 [104856] FUNC 'smbalert_remove' type_id=104854 linkage=static
259 [104857] FUNC_PROTO '(anon)' ret_type_id=18 vlen=2
262 [104858] FUNC 'smbalert_probe' type_id=104857 linkage=static
263 [104859] FUNC 'smbalert_work' type_id=9695 linkage=static
264 [104860] FUNC 'smbus_alert' type_id=71367 linkage=static
265 [104861] FUNC 'smbus_do_alert' type_id=84827 linkage=static