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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**
1.. 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** }
32| *MAP* := { **id** *MAP_ID* | **pinned** *FILE* }
33| *PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* }
34
35DESCRIPTION
36===========
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
41 system.
42
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
46 information as well.
47
48 **bpftool btf dump** *BTF_SRC*
49 Dump BTF entries from a given *BTF_SRC*.
50
51 When **id** is specified, BTF object with that ID will be
52 loaded and all its BTF types emitted.
53
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**
60 is assumed.
61
62 When **prog** is provided, it's expected that program has
63 associated BTF object with BTF types.
64
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.
68
69 **format** option can be used to override default (raw)
70 output format. Raw (**raw**) or C-syntax (**c**) output
71 formats are supported.
72
73 **bpftool btf help**
74 Print short help message.
75
76OPTIONS
77=======
78 .. include:: common_options.rst
79
80 -B, --base-btf *FILE*
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.
87
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.
93
94EXAMPLES
95========
96**# bpftool btf dump id 1226**
97
98::
99
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
107
108This gives an example of default output for all supported BTF kinds.
109
110**$ cat prog.c**
111
112::
113
114 struct fwd_struct;
115
116 enum my_enum {
117 VAL1 = 3,
118 VAL2 = 7,
119 };
120
121 typedef struct my_struct my_struct_t;
122
123 struct my_struct {
124 const unsigned int const_int_field;
125 int bitfield_field: 4;
126 char arr_field[16];
127 const struct fwd_struct *restrict fwd_field;
128 enum my_enum enum_field;
129 volatile my_struct_t *typedef_ptr_field;
130 };
131
132 union my_union {
133 int a;
134 struct my_struct b;
135 };
136
137 struct my_struct struct_global_var __attribute__((section("data_sec"))) = {
138 .bitfield_field = 3,
139 .enum_field = VAL1,
140 };
141 int global_var __attribute__((section("data_sec"))) = 7;
142
143 __attribute__((noinline))
144 int my_func(union my_union *arg1, int arg2)
145 {
146 static int static_var __attribute__((section("data_sec"))) = 123;
147 static_var++;
148 return static_var;
149 }
150
151**$ bpftool btf dump file prog.o**
152
153::
154
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
177 'VAL1' val=3
178 'VAL2' val=7
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
183 'arg1' type_id=1
184 'arg2' type_id=3
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
193
194The following commands print BTF types associated with specified map's key,
195value, both key and value, and all BTF types, respectively. By default, both
196key and value types will be printed.
197
198**# bpftool btf dump map id 123 key**
199
200::
201
202 [39] TYPEDEF 'u32' type_id=37
203
204**# bpftool btf dump map id 123 value**
205
206::
207
208 [86] PTR '(anon)' type_id=87
209
210**# bpftool btf dump map id 123 kv**
211
212::
213
214 [39] TYPEDEF 'u32' type_id=37
215 [86] PTR '(anon)' type_id=87
216
217**# bpftool btf dump map id 123 all**
218
219::
220
221 [1] PTR '(anon)' type_id=0
222 .
223 .
224 .
225 [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4
226
227All the standard ways to specify map or program are supported:
228
229**# bpftool btf dump map id 123**
230
231**# bpftool btf dump map pinned /sys/fs/bpf/map_name**
232
233**# bpftool btf dump prog id 456**
234
235**# bpftool btf dump prog tag b88e0a09b1d9759d**
236
237**# bpftool btf dump prog pinned /sys/fs/bpf/prog_name**
238
239|
240| **# bpftool btf dump file /sys/kernel/btf/i2c_smbus**
241| (or)
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**
244
245::
246
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
259 'ara' type_id=56050
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
263 'ara' type_id=56050
264 'id' type_id=56056
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