1 .. SPDX-License-Identifier: (GPL-2.0-only OR B 1 .. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2 2
3 ================ 3 ================
4 bpftool-btf 4 bpftool-btf
5 ================ 5 ================
6 ---------------------------------------------- 6 -------------------------------------------------------------------------------
7 tool for inspection of BTF data 7 tool for inspection of BTF data
8 ---------------------------------------------- 8 -------------------------------------------------------------------------------
9 9
10 :Manual section: 8 10 :Manual section: 8
11 11
12 .. include:: substitutions.rst 12 .. include:: substitutions.rst
13 13
14 SYNOPSIS 14 SYNOPSIS
15 ======== 15 ========
16 16
17 **bpftool** [*OPTIONS*] **btf** *COMMAND* 17 **bpftool** [*OPTIONS*] **btf** *COMMAND*
18 18
19 *OPTIONS* := { |COMMON_OPTIONS| | { **-B** | * 19 *OPTIONS* := { |COMMON_OPTIONS| | { **-B** | **--base-btf** } }
20 20
21 *COMMANDS* := { **dump** | **help** } 21 *COMMANDS* := { **dump** | **help** }
22 22
23 BTF COMMANDS 23 BTF COMMANDS
24 ============= 24 =============
25 25
26 | **bpftool** **btf** { **show** | **list** } 26 | **bpftool** **btf** { **show** | **list** } [**id** *BTF_ID*]
27 | **bpftool** **btf dump** *BTF_SRC* [**format 27 | **bpftool** **btf dump** *BTF_SRC* [**format** *FORMAT*]
28 | **bpftool** **btf help** 28 | **bpftool** **btf help**
29 | 29 |
30 | *BTF_SRC* := { **id** *BTF_ID* | **prog** *P 30 | *BTF_SRC* := { **id** *BTF_ID* | **prog** *PROG* | **map** *MAP* [{**key** | **value** | **kv** | **all**}] | **file** *FILE* }
31 | *FORMAT* := { **raw** | **c** [**unsorted**] 31 | *FORMAT* := { **raw** | **c** [**unsorted**] }
32 | *MAP* := { **id** *MAP_ID* | **pinned** *FIL 32 | *MAP* := { **id** *MAP_ID* | **pinned** *FILE* }
33 | *PROG* := { **id** *PROG_ID* | **pinned** *F 33 | *PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* | **name** *PROG_NAME* }
34 34
35 DESCRIPTION 35 DESCRIPTION
36 =========== 36 ===========
37 bpftool btf { show | list } [id *BTF_ID*] 37 bpftool btf { show | list } [id *BTF_ID*]
38 Show information about loaded BTF objects. 38 Show information about loaded BTF objects. If a BTF ID is specified, show
39 information only about given BTF object, o 39 information only about given BTF object, otherwise list all BTF objects
40 currently loaded on the system. 40 currently loaded on the system.
41 41
42 Since Linux 5.8 bpftool is able to discove 42 Since Linux 5.8 bpftool is able to discover information about processes
43 that hold open file descriptors (FDs) agai 43 that hold open file descriptors (FDs) against BTF objects. On such kernels
44 bpftool will automatically emit this infor 44 bpftool will automatically emit this information as well.
45 45
46 bpftool btf dump *BTF_SRC* 46 bpftool btf dump *BTF_SRC*
47 Dump BTF entries from a given *BTF_SRC*. 47 Dump BTF entries from a given *BTF_SRC*.
48 48
49 When **id** is specified, BTF object with 49 When **id** is specified, BTF object with that ID will be loaded and all
50 its BTF types emitted. 50 its BTF types emitted.
51 51
52 When **map** is provided, it's expected th 52 When **map** is provided, it's expected that map has associated BTF object
53 with BTF types describing key and value. I 53 with BTF types describing key and value. It's possible to select whether to
54 dump only BTF type(s) associated with key 54 dump only BTF type(s) associated with key (**key**), value (**value**),
55 both key and value (**kv**), or all BTF ty 55 both key and value (**kv**), or all BTF types present in associated BTF
56 object (**all**). If not specified, **kv** 56 object (**all**). If not specified, **kv** is assumed.
57 57
58 When **prog** is provided, it's expected t 58 When **prog** is provided, it's expected that program has associated BTF
59 object with BTF types. 59 object with BTF types.
60 60
61 When specifying *FILE*, an ELF file is exp 61 When specifying *FILE*, an ELF file is expected, containing .BTF section
62 with well-defined BTF binary format data, 62 with well-defined BTF binary format data, typically produced by clang or
63 pahole. 63 pahole.
64 64
65 **format** option can be used to override 65 **format** option can be used to override default (raw) output format. Raw
66 (**raw**) or C-syntax (**c**) output forma 66 (**raw**) or C-syntax (**c**) output formats are supported. With C-style
67 formatting, the output is sorted by defaul 67 formatting, the output is sorted by default. Use the **unsorted** option
68 to avoid sorting the output. 68 to avoid sorting the output.
69 69
70 bpftool btf help 70 bpftool btf help
71 Print short help message. 71 Print short help message.
72 72
73 OPTIONS 73 OPTIONS
74 ======= 74 =======
75 .. include:: common_options.rst 75 .. include:: common_options.rst
76 76
77 -B, --base-btf *FILE* 77 -B, --base-btf *FILE*
78 Pass a base BTF object. Base BTF objects a 78 Pass a base BTF object. Base BTF objects are typically used with BTF
79 objects for kernel modules. To avoid dupli 79 objects for kernel modules. To avoid duplicating all kernel symbols
80 required by modules, BTF objects for modul 80 required by modules, BTF objects for modules are "split", they are
81 built incrementally on top of the kernel ( 81 built incrementally on top of the kernel (vmlinux) BTF object. So the
82 base BTF reference should usually point to 82 base BTF reference should usually point to the kernel BTF.
83 83
84 When the main BTF object to process (for e 84 When the main BTF object to process (for example, the module BTF to
85 dump) is passed as a *FILE*, bpftool attem 85 dump) is passed as a *FILE*, bpftool attempts to autodetect the path
86 for the base object, and passing this opti 86 for the base object, and passing this option is optional. When the main
87 BTF object is passed through other handles 87 BTF object is passed through other handles, this option becomes
88 necessary. 88 necessary.
89 89
90 EXAMPLES 90 EXAMPLES
91 ======== 91 ========
92 **# bpftool btf dump id 1226** 92 **# bpftool btf dump id 1226**
93 93
94 :: 94 ::
95 95
96 [1] PTR '(anon)' type_id=2 96 [1] PTR '(anon)' type_id=2
97 [2] STRUCT 'dummy_tracepoint_args' size=16 v 97 [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=2
98 'pad' type_id=3 bits_offset=0 98 'pad' type_id=3 bits_offset=0
99 'sock' type_id=4 bits_offset=64 99 'sock' type_id=4 bits_offset=64
100 [3] INT 'long long unsigned int' size=8 bits 100 [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none)
101 [4] PTR '(anon)' type_id=5 101 [4] PTR '(anon)' type_id=5
102 [5] FWD 'sock' fwd_kind=union 102 [5] FWD 'sock' fwd_kind=union
103 103
104 This gives an example of default output for al 104 This gives an example of default output for all supported BTF kinds.
105 105
106 **$ cat prog.c** 106 **$ cat prog.c**
107 107
108 :: 108 ::
109 109
110 struct fwd_struct; 110 struct fwd_struct;
111 111
112 enum my_enum { 112 enum my_enum {
113 VAL1 = 3, 113 VAL1 = 3,
114 VAL2 = 7, 114 VAL2 = 7,
115 }; 115 };
116 116
117 typedef struct my_struct my_struct_t; 117 typedef struct my_struct my_struct_t;
118 118
119 struct my_struct { 119 struct my_struct {
120 const unsigned int const_int_field; 120 const unsigned int const_int_field;
121 int bitfield_field: 4; 121 int bitfield_field: 4;
122 char arr_field[16]; 122 char arr_field[16];
123 const struct fwd_struct *restrict fw 123 const struct fwd_struct *restrict fwd_field;
124 enum my_enum enum_field; 124 enum my_enum enum_field;
125 volatile my_struct_t *typedef_ptr_fi 125 volatile my_struct_t *typedef_ptr_field;
126 }; 126 };
127 127
128 union my_union { 128 union my_union {
129 int a; 129 int a;
130 struct my_struct b; 130 struct my_struct b;
131 }; 131 };
132 132
133 struct my_struct struct_global_var __attribu 133 struct my_struct struct_global_var __attribute__((section("data_sec"))) = {
134 .bitfield_field = 3, 134 .bitfield_field = 3,
135 .enum_field = VAL1, 135 .enum_field = VAL1,
136 }; 136 };
137 int global_var __attribute__((section("data_ 137 int global_var __attribute__((section("data_sec"))) = 7;
138 138
139 __attribute__((noinline)) 139 __attribute__((noinline))
140 int my_func(union my_union *arg1, int arg2) 140 int my_func(union my_union *arg1, int arg2)
141 { 141 {
142 static int static_var __attribute__( 142 static int static_var __attribute__((section("data_sec"))) = 123;
143 static_var++; 143 static_var++;
144 return static_var; 144 return static_var;
145 } 145 }
146 146
147 **$ bpftool btf dump file prog.o** 147 **$ bpftool btf dump file prog.o**
148 148
149 :: 149 ::
150 150
151 [1] PTR '(anon)' type_id=2 151 [1] PTR '(anon)' type_id=2
152 [2] UNION 'my_union' size=48 vlen=2 152 [2] UNION 'my_union' size=48 vlen=2
153 'a' type_id=3 bits_offset=0 153 'a' type_id=3 bits_offset=0
154 'b' type_id=4 bits_offset=0 154 'b' type_id=4 bits_offset=0
155 [3] INT 'int' size=4 bits_offset=0 nr_bits=3 155 [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
156 [4] STRUCT 'my_struct' size=48 vlen=6 156 [4] STRUCT 'my_struct' size=48 vlen=6
157 'const_int_field' type_id=5 bits_off 157 'const_int_field' type_id=5 bits_offset=0
158 'bitfield_field' type_id=3 bits_offs 158 'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4
159 'arr_field' type_id=8 bits_offset=40 159 'arr_field' type_id=8 bits_offset=40
160 'fwd_field' type_id=10 bits_offset=1 160 'fwd_field' type_id=10 bits_offset=192
161 'enum_field' type_id=14 bits_offset= 161 'enum_field' type_id=14 bits_offset=256
162 'typedef_ptr_field' type_id=15 bits_ 162 'typedef_ptr_field' type_id=15 bits_offset=320
163 [5] CONST '(anon)' type_id=6 163 [5] CONST '(anon)' type_id=6
164 [6] INT 'unsigned int' size=4 bits_offset=0 164 [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= 165 [7] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
166 [8] ARRAY '(anon)' type_id=7 index_type_id=9 166 [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16
167 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_of 167 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
168 [10] RESTRICT '(anon)' type_id=11 168 [10] RESTRICT '(anon)' type_id=11
169 [11] PTR '(anon)' type_id=12 169 [11] PTR '(anon)' type_id=12
170 [12] CONST '(anon)' type_id=13 170 [12] CONST '(anon)' type_id=13
171 [13] FWD 'fwd_struct' fwd_kind=union 171 [13] FWD 'fwd_struct' fwd_kind=union
172 [14] ENUM 'my_enum' size=4 vlen=2 172 [14] ENUM 'my_enum' size=4 vlen=2
173 'VAL1' val=3 173 'VAL1' val=3
174 'VAL2' val=7 174 'VAL2' val=7
175 [15] PTR '(anon)' type_id=16 175 [15] PTR '(anon)' type_id=16
176 [16] VOLATILE '(anon)' type_id=17 176 [16] VOLATILE '(anon)' type_id=17
177 [17] TYPEDEF 'my_struct_t' type_id=4 177 [17] TYPEDEF 'my_struct_t' type_id=4
178 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen= 178 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2
179 'arg1' type_id=1 179 'arg1' type_id=1
180 'arg2' type_id=3 180 'arg2' type_id=3
181 [19] FUNC 'my_func' type_id=18 181 [19] FUNC 'my_func' type_id=18
182 [20] VAR 'struct_global_var' type_id=4, link 182 [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc
183 [21] VAR 'global_var' type_id=3, linkage=glo 183 [21] VAR 'global_var' type_id=3, linkage=global-alloc
184 [22] VAR 'my_func.static_var' type_id=3, lin 184 [22] VAR 'my_func.static_var' type_id=3, linkage=static
185 [23] DATASEC 'data_sec' size=0 vlen=3 185 [23] DATASEC 'data_sec' size=0 vlen=3
186 type_id=20 offset=0 size=48 186 type_id=20 offset=0 size=48
187 type_id=21 offset=0 size=4 187 type_id=21 offset=0 size=4
188 type_id=22 offset=52 size=4 188 type_id=22 offset=52 size=4
189 189
190 The following commands print BTF types associa 190 The following commands print BTF types associated with specified map's key,
191 value, both key and value, and all BTF types, 191 value, both key and value, and all BTF types, respectively. By default, both
192 key and value types will be printed. 192 key and value types will be printed.
193 193
194 **# bpftool btf dump map id 123 key** 194 **# bpftool btf dump map id 123 key**
195 195
196 :: 196 ::
197 197
198 [39] TYPEDEF 'u32' type_id=37 198 [39] TYPEDEF 'u32' type_id=37
199 199
200 **# bpftool btf dump map id 123 value** 200 **# bpftool btf dump map id 123 value**
201 201
202 :: 202 ::
203 203
204 [86] PTR '(anon)' type_id=87 204 [86] PTR '(anon)' type_id=87
205 205
206 **# bpftool btf dump map id 123 kv** 206 **# bpftool btf dump map id 123 kv**
207 207
208 :: 208 ::
209 209
210 [39] TYPEDEF 'u32' type_id=37 210 [39] TYPEDEF 'u32' type_id=37
211 [86] PTR '(anon)' type_id=87 211 [86] PTR '(anon)' type_id=87
212 212
213 **# bpftool btf dump map id 123 all** 213 **# bpftool btf dump map id 123 all**
214 214
215 :: 215 ::
216 216
217 [1] PTR '(anon)' type_id=0 217 [1] PTR '(anon)' type_id=0
218 . 218 .
219 . 219 .
220 . 220 .
221 [2866] ARRAY '(anon)' type_id=52 index_type_ 221 [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4
222 222
223 All the standard ways to specify map or progra 223 All the standard ways to specify map or program are supported:
224 224
225 **# bpftool btf dump map id 123** 225 **# bpftool btf dump map id 123**
226 226
227 **# bpftool btf dump map pinned /sys/fs/bpf/ma 227 **# bpftool btf dump map pinned /sys/fs/bpf/map_name**
228 228
229 **# bpftool btf dump prog id 456** 229 **# bpftool btf dump prog id 456**
230 230
231 **# bpftool btf dump prog tag b88e0a09b1d9759d 231 **# bpftool btf dump prog tag b88e0a09b1d9759d**
232 232
233 **# bpftool btf dump prog pinned /sys/fs/bpf/p 233 **# bpftool btf dump prog pinned /sys/fs/bpf/prog_name**
234 234
235 | 235 |
236 | **# bpftool btf dump file /sys/kernel/btf/i2 236 | **# bpftool btf dump file /sys/kernel/btf/i2c_smbus**
237 | (or) 237 | (or)
238 | **# I2C_SMBUS_ID=$(bpftool btf show -p | jq 238 | **# I2C_SMBUS_ID=$(bpftool btf show -p | jq '.[] | select(.name=="i2c_smbus").id')**
239 | **# bpftool btf dump id ${I2C_SMBUS_ID} -B / 239 | **# bpftool btf dump id ${I2C_SMBUS_ID} -B /sys/kernel/btf/vmlinux**
240 240
241 :: 241 ::
242 242
243 [104848] STRUCT 'i2c_smbus_alert' size=40 vl 243 [104848] STRUCT 'i2c_smbus_alert' size=40 vlen=2
244 'alert' type_id=393 bits_offset=0 244 'alert' type_id=393 bits_offset=0
245 'ara' type_id=56050 bits_offset=256 245 'ara' type_id=56050 bits_offset=256
246 [104849] STRUCT 'alert_data' size=12 vlen=3 246 [104849] STRUCT 'alert_data' size=12 vlen=3
247 'addr' type_id=16 bits_offset=0 247 'addr' type_id=16 bits_offset=0
248 'type' type_id=56053 bits_offset=32 248 'type' type_id=56053 bits_offset=32
249 'data' type_id=7 bits_offset=64 249 'data' type_id=7 bits_offset=64
250 [104850] PTR '(anon)' type_id=104848 250 [104850] PTR '(anon)' type_id=104848
251 [104851] PTR '(anon)' type_id=104849 251 [104851] PTR '(anon)' type_id=104849
252 [104852] FUNC 'i2c_register_spd' type_id=847 252 [104852] FUNC 'i2c_register_spd' type_id=84745 linkage=static
253 [104853] FUNC 'smbalert_driver_init' type_id 253 [104853] FUNC 'smbalert_driver_init' type_id=1213 linkage=static
254 [104854] FUNC_PROTO '(anon)' ret_type_id=18 254 [104854] FUNC_PROTO '(anon)' ret_type_id=18 vlen=1
255 'ara' type_id=56050 255 'ara' type_id=56050
256 [104855] FUNC 'i2c_handle_smbus_alert' type_ 256 [104855] FUNC 'i2c_handle_smbus_alert' type_id=104854 linkage=static
257 [104856] FUNC 'smbalert_remove' type_id=1048 257 [104856] FUNC 'smbalert_remove' type_id=104854 linkage=static
258 [104857] FUNC_PROTO '(anon)' ret_type_id=18 258 [104857] FUNC_PROTO '(anon)' ret_type_id=18 vlen=2
259 'ara' type_id=56050 259 'ara' type_id=56050
260 'id' type_id=56056 260 'id' type_id=56056
261 [104858] FUNC 'smbalert_probe' type_id=10485 261 [104858] FUNC 'smbalert_probe' type_id=104857 linkage=static
262 [104859] FUNC 'smbalert_work' type_id=9695 l 262 [104859] FUNC 'smbalert_work' type_id=9695 linkage=static
263 [104860] FUNC 'smbus_alert' type_id=71367 li 263 [104860] FUNC 'smbus_alert' type_id=71367 linkage=static
264 [104861] FUNC 'smbus_do_alert' type_id=84827 264 [104861] FUNC 'smbus_do_alert' type_id=84827 linkage=static
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.