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** }
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.
67 formatting, the output is sorted by defaul <<
68 to avoid sorting the output. <<
69 67
70 bpftool btf help 68 bpftool btf help
71 Print short help message. 69 Print short help message.
72 70
73 OPTIONS 71 OPTIONS
74 ======= 72 =======
75 .. include:: common_options.rst 73 .. include:: common_options.rst
76 74
77 -B, --base-btf *FILE* 75 -B, --base-btf *FILE*
78 Pass a base BTF object. Base BTF objects a 76 Pass a base BTF object. Base BTF objects are typically used with BTF
79 objects for kernel modules. To avoid dupli 77 objects for kernel modules. To avoid duplicating all kernel symbols
80 required by modules, BTF objects for modul 78 required by modules, BTF objects for modules are "split", they are
81 built incrementally on top of the kernel ( 79 built incrementally on top of the kernel (vmlinux) BTF object. So the
82 base BTF reference should usually point to 80 base BTF reference should usually point to the kernel BTF.
83 81
84 When the main BTF object to process (for e 82 When the main BTF object to process (for example, the module BTF to
85 dump) is passed as a *FILE*, bpftool attem 83 dump) is passed as a *FILE*, bpftool attempts to autodetect the path
86 for the base object, and passing this opti 84 for the base object, and passing this option is optional. When the main
87 BTF object is passed through other handles 85 BTF object is passed through other handles, this option becomes
88 necessary. 86 necessary.
89 87
90 EXAMPLES 88 EXAMPLES
91 ======== 89 ========
92 **# bpftool btf dump id 1226** 90 **# bpftool btf dump id 1226**
93 91
94 :: 92 ::
95 93
96 [1] PTR '(anon)' type_id=2 94 [1] PTR '(anon)' type_id=2
97 [2] STRUCT 'dummy_tracepoint_args' size=16 v 95 [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=2
98 'pad' type_id=3 bits_offset=0 96 'pad' type_id=3 bits_offset=0
99 'sock' type_id=4 bits_offset=64 97 'sock' type_id=4 bits_offset=64
100 [3] INT 'long long unsigned int' size=8 bits 98 [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none)
101 [4] PTR '(anon)' type_id=5 99 [4] PTR '(anon)' type_id=5
102 [5] FWD 'sock' fwd_kind=union 100 [5] FWD 'sock' fwd_kind=union
103 101
104 This gives an example of default output for al 102 This gives an example of default output for all supported BTF kinds.
105 103
106 **$ cat prog.c** 104 **$ cat prog.c**
107 105
108 :: 106 ::
109 107
110 struct fwd_struct; 108 struct fwd_struct;
111 109
112 enum my_enum { 110 enum my_enum {
113 VAL1 = 3, 111 VAL1 = 3,
114 VAL2 = 7, 112 VAL2 = 7,
115 }; 113 };
116 114
117 typedef struct my_struct my_struct_t; 115 typedef struct my_struct my_struct_t;
118 116
119 struct my_struct { 117 struct my_struct {
120 const unsigned int const_int_field; 118 const unsigned int const_int_field;
121 int bitfield_field: 4; 119 int bitfield_field: 4;
122 char arr_field[16]; 120 char arr_field[16];
123 const struct fwd_struct *restrict fw 121 const struct fwd_struct *restrict fwd_field;
124 enum my_enum enum_field; 122 enum my_enum enum_field;
125 volatile my_struct_t *typedef_ptr_fi 123 volatile my_struct_t *typedef_ptr_field;
126 }; 124 };
127 125
128 union my_union { 126 union my_union {
129 int a; 127 int a;
130 struct my_struct b; 128 struct my_struct b;
131 }; 129 };
132 130
133 struct my_struct struct_global_var __attribu 131 struct my_struct struct_global_var __attribute__((section("data_sec"))) = {
134 .bitfield_field = 3, 132 .bitfield_field = 3,
135 .enum_field = VAL1, 133 .enum_field = VAL1,
136 }; 134 };
137 int global_var __attribute__((section("data_ 135 int global_var __attribute__((section("data_sec"))) = 7;
138 136
139 __attribute__((noinline)) 137 __attribute__((noinline))
140 int my_func(union my_union *arg1, int arg2) 138 int my_func(union my_union *arg1, int arg2)
141 { 139 {
142 static int static_var __attribute__( 140 static int static_var __attribute__((section("data_sec"))) = 123;
143 static_var++; 141 static_var++;
144 return static_var; 142 return static_var;
145 } 143 }
146 144
147 **$ bpftool btf dump file prog.o** 145 **$ bpftool btf dump file prog.o**
148 146
149 :: 147 ::
150 148
151 [1] PTR '(anon)' type_id=2 149 [1] PTR '(anon)' type_id=2
152 [2] UNION 'my_union' size=48 vlen=2 150 [2] UNION 'my_union' size=48 vlen=2
153 'a' type_id=3 bits_offset=0 151 'a' type_id=3 bits_offset=0
154 'b' type_id=4 bits_offset=0 152 'b' type_id=4 bits_offset=0
155 [3] INT 'int' size=4 bits_offset=0 nr_bits=3 153 [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
156 [4] STRUCT 'my_struct' size=48 vlen=6 154 [4] STRUCT 'my_struct' size=48 vlen=6
157 'const_int_field' type_id=5 bits_off 155 'const_int_field' type_id=5 bits_offset=0
158 'bitfield_field' type_id=3 bits_offs 156 'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4
159 'arr_field' type_id=8 bits_offset=40 157 'arr_field' type_id=8 bits_offset=40
160 'fwd_field' type_id=10 bits_offset=1 158 'fwd_field' type_id=10 bits_offset=192
161 'enum_field' type_id=14 bits_offset= 159 'enum_field' type_id=14 bits_offset=256
162 'typedef_ptr_field' type_id=15 bits_ 160 'typedef_ptr_field' type_id=15 bits_offset=320
163 [5] CONST '(anon)' type_id=6 161 [5] CONST '(anon)' type_id=6
164 [6] INT 'unsigned int' size=4 bits_offset=0 162 [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= 163 [7] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
166 [8] ARRAY '(anon)' type_id=7 index_type_id=9 164 [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16
167 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_of 165 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
168 [10] RESTRICT '(anon)' type_id=11 166 [10] RESTRICT '(anon)' type_id=11
169 [11] PTR '(anon)' type_id=12 167 [11] PTR '(anon)' type_id=12
170 [12] CONST '(anon)' type_id=13 168 [12] CONST '(anon)' type_id=13
171 [13] FWD 'fwd_struct' fwd_kind=union 169 [13] FWD 'fwd_struct' fwd_kind=union
172 [14] ENUM 'my_enum' size=4 vlen=2 170 [14] ENUM 'my_enum' size=4 vlen=2
173 'VAL1' val=3 171 'VAL1' val=3
174 'VAL2' val=7 172 'VAL2' val=7
175 [15] PTR '(anon)' type_id=16 173 [15] PTR '(anon)' type_id=16
176 [16] VOLATILE '(anon)' type_id=17 174 [16] VOLATILE '(anon)' type_id=17
177 [17] TYPEDEF 'my_struct_t' type_id=4 175 [17] TYPEDEF 'my_struct_t' type_id=4
178 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen= 176 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2
179 'arg1' type_id=1 177 'arg1' type_id=1
180 'arg2' type_id=3 178 'arg2' type_id=3
181 [19] FUNC 'my_func' type_id=18 179 [19] FUNC 'my_func' type_id=18
182 [20] VAR 'struct_global_var' type_id=4, link 180 [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc
183 [21] VAR 'global_var' type_id=3, linkage=glo 181 [21] VAR 'global_var' type_id=3, linkage=global-alloc
184 [22] VAR 'my_func.static_var' type_id=3, lin 182 [22] VAR 'my_func.static_var' type_id=3, linkage=static
185 [23] DATASEC 'data_sec' size=0 vlen=3 183 [23] DATASEC 'data_sec' size=0 vlen=3
186 type_id=20 offset=0 size=48 184 type_id=20 offset=0 size=48
187 type_id=21 offset=0 size=4 185 type_id=21 offset=0 size=4
188 type_id=22 offset=52 size=4 186 type_id=22 offset=52 size=4
189 187
190 The following commands print BTF types associa 188 The following commands print BTF types associated with specified map's key,
191 value, both key and value, and all BTF types, 189 value, both key and value, and all BTF types, respectively. By default, both
192 key and value types will be printed. 190 key and value types will be printed.
193 191
194 **# bpftool btf dump map id 123 key** 192 **# bpftool btf dump map id 123 key**
195 193
196 :: 194 ::
197 195
198 [39] TYPEDEF 'u32' type_id=37 196 [39] TYPEDEF 'u32' type_id=37
199 197
200 **# bpftool btf dump map id 123 value** 198 **# bpftool btf dump map id 123 value**
201 199
202 :: 200 ::
203 201
204 [86] PTR '(anon)' type_id=87 202 [86] PTR '(anon)' type_id=87
205 203
206 **# bpftool btf dump map id 123 kv** 204 **# bpftool btf dump map id 123 kv**
207 205
208 :: 206 ::
209 207
210 [39] TYPEDEF 'u32' type_id=37 208 [39] TYPEDEF 'u32' type_id=37
211 [86] PTR '(anon)' type_id=87 209 [86] PTR '(anon)' type_id=87
212 210
213 **# bpftool btf dump map id 123 all** 211 **# bpftool btf dump map id 123 all**
214 212
215 :: 213 ::
216 214
217 [1] PTR '(anon)' type_id=0 215 [1] PTR '(anon)' type_id=0
218 . 216 .
219 . 217 .
220 . 218 .
221 [2866] ARRAY '(anon)' type_id=52 index_type_ 219 [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4
222 220
223 All the standard ways to specify map or progra 221 All the standard ways to specify map or program are supported:
224 222
225 **# bpftool btf dump map id 123** 223 **# bpftool btf dump map id 123**
226 224
227 **# bpftool btf dump map pinned /sys/fs/bpf/ma 225 **# bpftool btf dump map pinned /sys/fs/bpf/map_name**
228 226
229 **# bpftool btf dump prog id 456** 227 **# bpftool btf dump prog id 456**
230 228
231 **# bpftool btf dump prog tag b88e0a09b1d9759d 229 **# bpftool btf dump prog tag b88e0a09b1d9759d**
232 230
233 **# bpftool btf dump prog pinned /sys/fs/bpf/p 231 **# bpftool btf dump prog pinned /sys/fs/bpf/prog_name**
234 232
235 | 233 |
236 | **# bpftool btf dump file /sys/kernel/btf/i2 234 | **# bpftool btf dump file /sys/kernel/btf/i2c_smbus**
237 | (or) 235 | (or)
238 | **# I2C_SMBUS_ID=$(bpftool btf show -p | jq 236 | **# I2C_SMBUS_ID=$(bpftool btf show -p | jq '.[] | select(.name=="i2c_smbus").id')**
239 | **# bpftool btf dump id ${I2C_SMBUS_ID} -B / 237 | **# bpftool btf dump id ${I2C_SMBUS_ID} -B /sys/kernel/btf/vmlinux**
240 238
241 :: 239 ::
242 240
243 [104848] STRUCT 'i2c_smbus_alert' size=40 vl 241 [104848] STRUCT 'i2c_smbus_alert' size=40 vlen=2
244 'alert' type_id=393 bits_offset=0 242 'alert' type_id=393 bits_offset=0
245 'ara' type_id=56050 bits_offset=256 243 'ara' type_id=56050 bits_offset=256
246 [104849] STRUCT 'alert_data' size=12 vlen=3 244 [104849] STRUCT 'alert_data' size=12 vlen=3
247 'addr' type_id=16 bits_offset=0 245 'addr' type_id=16 bits_offset=0
248 'type' type_id=56053 bits_offset=32 246 'type' type_id=56053 bits_offset=32
249 'data' type_id=7 bits_offset=64 247 'data' type_id=7 bits_offset=64
250 [104850] PTR '(anon)' type_id=104848 248 [104850] PTR '(anon)' type_id=104848
251 [104851] PTR '(anon)' type_id=104849 249 [104851] PTR '(anon)' type_id=104849
252 [104852] FUNC 'i2c_register_spd' type_id=847 250 [104852] FUNC 'i2c_register_spd' type_id=84745 linkage=static
253 [104853] FUNC 'smbalert_driver_init' type_id 251 [104853] FUNC 'smbalert_driver_init' type_id=1213 linkage=static
254 [104854] FUNC_PROTO '(anon)' ret_type_id=18 252 [104854] FUNC_PROTO '(anon)' ret_type_id=18 vlen=1
255 'ara' type_id=56050 253 'ara' type_id=56050
256 [104855] FUNC 'i2c_handle_smbus_alert' type_ 254 [104855] FUNC 'i2c_handle_smbus_alert' type_id=104854 linkage=static
257 [104856] FUNC 'smbalert_remove' type_id=1048 255 [104856] FUNC 'smbalert_remove' type_id=104854 linkage=static
258 [104857] FUNC_PROTO '(anon)' ret_type_id=18 256 [104857] FUNC_PROTO '(anon)' ret_type_id=18 vlen=2
259 'ara' type_id=56050 257 'ara' type_id=56050
260 'id' type_id=56056 258 'id' type_id=56056
261 [104858] FUNC 'smbalert_probe' type_id=10485 259 [104858] FUNC 'smbalert_probe' type_id=104857 linkage=static
262 [104859] FUNC 'smbalert_work' type_id=9695 l 260 [104859] FUNC 'smbalert_work' type_id=9695 linkage=static
263 [104860] FUNC 'smbus_alert' type_id=71367 li 261 [104860] FUNC 'smbus_alert' type_id=71367 linkage=static
264 [104861] FUNC 'smbus_do_alert' type_id=84827 262 [104861] FUNC 'smbus_do_alert' type_id=84827 linkage=static
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