1 .. SPDX-License-Identifier: (GPL-2.0-only OR B <<
2 <<
3 ================ 1 ================
4 bpftool-btf 2 bpftool-btf
5 ================ 3 ================
6 ---------------------------------------------- 4 -------------------------------------------------------------------------------
7 tool for inspection of BTF data 5 tool for inspection of BTF data
8 ---------------------------------------------- 6 -------------------------------------------------------------------------------
9 7
10 :Manual section: 8 8 :Manual section: 8
11 9
12 .. include:: substitutions.rst <<
13 <<
14 SYNOPSIS 10 SYNOPSIS
15 ======== 11 ========
16 12
17 **bpftool** [*OPTIONS*] **btf** *COMMAND* !! 13 **bpftool** [*OPTIONS*] **btf** *COMMAND*
18 14
19 *OPTIONS* := { |COMMON_OPTIONS| | { **-B** | * !! 15 *OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] | {**-d** | **--debug** } |
>> 16 { **-B** | **--base-btf** } }
20 17
21 *COMMANDS* := { **dump** | **help** } !! 18 *COMMANDS* := { **dump** | **help** }
22 19
23 BTF COMMANDS 20 BTF COMMANDS
24 ============= 21 =============
25 22
26 | **bpftool** **btf** { **show** | **list** } !! 23 | **bpftool** **btf** { **show** | **list** } [**id** *BTF_ID*]
27 | **bpftool** **btf dump** *BTF_SRC* [**format !! 24 | **bpftool** **btf dump** *BTF_SRC* [**format** *FORMAT*]
28 | **bpftool** **btf help** !! 25 | **bpftool** **btf help**
29 | 26 |
30 | *BTF_SRC* := { **id** *BTF_ID* | **prog** *P !! 27 | *BTF_SRC* := { **id** *BTF_ID* | **prog** *PROG* | **map** *MAP* [{**key** | **value** | **kv** | **all**}] | **file** *FILE* }
31 | *FORMAT* := { **raw** | **c** [**unsorted**] !! 28 | *FORMAT* := { **raw** | **c** }
32 | *MAP* := { **id** *MAP_ID* | **pinned** *FIL !! 29 | *MAP* := { **id** *MAP_ID* | **pinned** *FILE* }
33 | *PROG* := { **id** *PROG_ID* | **pinned** *F !! 30 | *PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* }
34 31
35 DESCRIPTION 32 DESCRIPTION
36 =========== 33 ===========
37 bpftool btf { show | list } [id *BTF_ID*] !! 34 **bpftool btf { show | list }** [**id** *BTF_ID*]
38 Show information about loaded BTF objects. !! 35 Show information about loaded BTF objects. If a BTF ID is
39 information only about given BTF object, o !! 36 specified, show information only about given BTF object,
40 currently loaded on the system. !! 37 otherwise list all BTF objects currently loaded on the
41 !! 38 system.
42 Since Linux 5.8 bpftool is able to discove !! 39
43 that hold open file descriptors (FDs) agai !! 40 Since Linux 5.8 bpftool is able to discover information about
44 bpftool will automatically emit this infor !! 41 processes that hold open file descriptors (FDs) against BTF
45 !! 42 objects. On such kernels bpftool will automatically emit this
46 bpftool btf dump *BTF_SRC* !! 43 information as well.
47 Dump BTF entries from a given *BTF_SRC*. !! 44
48 !! 45 **bpftool btf dump** *BTF_SRC*
49 When **id** is specified, BTF object with !! 46 Dump BTF entries from a given *BTF_SRC*.
50 its BTF types emitted. !! 47
51 !! 48 When **id** is specified, BTF object with that ID will be
52 When **map** is provided, it's expected th !! 49 loaded and all its BTF types emitted.
53 with BTF types describing key and value. I !! 50
54 dump only BTF type(s) associated with key !! 51 When **map** is provided, it's expected that map has
55 both key and value (**kv**), or all BTF ty !! 52 associated BTF object with BTF types describing key and
56 object (**all**). If not specified, **kv** !! 53 value. It's possible to select whether to dump only BTF
57 !! 54 type(s) associated with key (**key**), value (**value**),
58 When **prog** is provided, it's expected t !! 55 both key and value (**kv**), or all BTF types present in
59 object with BTF types. !! 56 associated BTF object (**all**). If not specified, **kv**
60 !! 57 is assumed.
61 When specifying *FILE*, an ELF file is exp !! 58
62 with well-defined BTF binary format data, !! 59 When **prog** is provided, it's expected that program has
63 pahole. !! 60 associated BTF object with BTF types.
64 !! 61
65 **format** option can be used to override !! 62 When specifying *FILE*, an ELF file is expected, containing
66 (**raw**) or C-syntax (**c**) output forma !! 63 .BTF section with well-defined BTF binary format data,
67 formatting, the output is sorted by defaul !! 64 typically produced by clang or pahole.
68 to avoid sorting the output. !! 65
>> 66 **format** option can be used to override default (raw)
>> 67 output format. Raw (**raw**) or C-syntax (**c**) output
>> 68 formats are supported.
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
79 objects for kernel modules. To avoid dupli !! 79 with BTF objects for kernel modules. To avoid duplicating
80 required by modules, BTF objects for modul !! 80 all kernel symbols required by modules, BTF objects for
81 built incrementally on top of the kernel ( !! 81 modules are "split", they are built incrementally on top of
82 base BTF reference should usually point to !! 82 the kernel (vmlinux) BTF object. So the base BTF reference
83 !! 83 should usually point to the kernel BTF.
84 When the main BTF object to process (for e !! 84
85 dump) is passed as a *FILE*, bpftool attem !! 85 When the main BTF object to process (for example, the
86 for the base object, and passing this opti !! 86 module BTF to dump) is passed as a *FILE*, bpftool attempts
87 BTF object is passed through other handles !! 87 to autodetect the path for the base object, and passing
88 necessary. !! 88 this option is optional. When the main BTF object is passed
>> 89 through other handles, this option becomes necessary.
89 90
90 EXAMPLES 91 EXAMPLES
91 ======== 92 ========
92 **# bpftool btf dump id 1226** 93 **# bpftool btf dump id 1226**
93 94
94 :: 95 ::
95 96
96 [1] PTR '(anon)' type_id=2 97 [1] PTR '(anon)' type_id=2
97 [2] STRUCT 'dummy_tracepoint_args' size=16 v 98 [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=2
98 'pad' type_id=3 bits_offset=0 99 'pad' type_id=3 bits_offset=0
99 'sock' type_id=4 bits_offset=64 100 'sock' type_id=4 bits_offset=64
100 [3] INT 'long long unsigned int' size=8 bits 101 [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none)
101 [4] PTR '(anon)' type_id=5 102 [4] PTR '(anon)' type_id=5
102 [5] FWD 'sock' fwd_kind=union 103 [5] FWD 'sock' fwd_kind=union
103 104
104 This gives an example of default output for al 105 This gives an example of default output for all supported BTF kinds.
105 106
106 **$ cat prog.c** 107 **$ cat prog.c**
107 108
108 :: 109 ::
109 110
110 struct fwd_struct; 111 struct fwd_struct;
111 112
112 enum my_enum { 113 enum my_enum {
113 VAL1 = 3, 114 VAL1 = 3,
114 VAL2 = 7, 115 VAL2 = 7,
115 }; 116 };
116 117
117 typedef struct my_struct my_struct_t; 118 typedef struct my_struct my_struct_t;
118 119
119 struct my_struct { 120 struct my_struct {
120 const unsigned int const_int_field; 121 const unsigned int const_int_field;
121 int bitfield_field: 4; 122 int bitfield_field: 4;
122 char arr_field[16]; 123 char arr_field[16];
123 const struct fwd_struct *restrict fw 124 const struct fwd_struct *restrict fwd_field;
124 enum my_enum enum_field; 125 enum my_enum enum_field;
125 volatile my_struct_t *typedef_ptr_fi 126 volatile my_struct_t *typedef_ptr_field;
126 }; 127 };
127 128
128 union my_union { 129 union my_union {
129 int a; 130 int a;
130 struct my_struct b; 131 struct my_struct b;
131 }; 132 };
132 133
133 struct my_struct struct_global_var __attribu 134 struct my_struct struct_global_var __attribute__((section("data_sec"))) = {
134 .bitfield_field = 3, 135 .bitfield_field = 3,
135 .enum_field = VAL1, 136 .enum_field = VAL1,
136 }; 137 };
137 int global_var __attribute__((section("data_ 138 int global_var __attribute__((section("data_sec"))) = 7;
138 139
139 __attribute__((noinline)) 140 __attribute__((noinline))
140 int my_func(union my_union *arg1, int arg2) 141 int my_func(union my_union *arg1, int arg2)
141 { 142 {
142 static int static_var __attribute__( 143 static int static_var __attribute__((section("data_sec"))) = 123;
143 static_var++; 144 static_var++;
144 return static_var; 145 return static_var;
145 } 146 }
146 147
147 **$ bpftool btf dump file prog.o** 148 **$ bpftool btf dump file prog.o**
148 149
149 :: 150 ::
150 151
151 [1] PTR '(anon)' type_id=2 152 [1] PTR '(anon)' type_id=2
152 [2] UNION 'my_union' size=48 vlen=2 153 [2] UNION 'my_union' size=48 vlen=2
153 'a' type_id=3 bits_offset=0 154 'a' type_id=3 bits_offset=0
154 'b' type_id=4 bits_offset=0 155 'b' type_id=4 bits_offset=0
155 [3] INT 'int' size=4 bits_offset=0 nr_bits=3 156 [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
156 [4] STRUCT 'my_struct' size=48 vlen=6 157 [4] STRUCT 'my_struct' size=48 vlen=6
157 'const_int_field' type_id=5 bits_off 158 'const_int_field' type_id=5 bits_offset=0
158 'bitfield_field' type_id=3 bits_offs 159 'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4
159 'arr_field' type_id=8 bits_offset=40 160 'arr_field' type_id=8 bits_offset=40
160 'fwd_field' type_id=10 bits_offset=1 161 'fwd_field' type_id=10 bits_offset=192
161 'enum_field' type_id=14 bits_offset= 162 'enum_field' type_id=14 bits_offset=256
162 'typedef_ptr_field' type_id=15 bits_ 163 'typedef_ptr_field' type_id=15 bits_offset=320
163 [5] CONST '(anon)' type_id=6 164 [5] CONST '(anon)' type_id=6
164 [6] INT 'unsigned int' size=4 bits_offset=0 165 [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= 166 [7] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
166 [8] ARRAY '(anon)' type_id=7 index_type_id=9 167 [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16
167 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_of 168 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
168 [10] RESTRICT '(anon)' type_id=11 169 [10] RESTRICT '(anon)' type_id=11
169 [11] PTR '(anon)' type_id=12 170 [11] PTR '(anon)' type_id=12
170 [12] CONST '(anon)' type_id=13 171 [12] CONST '(anon)' type_id=13
171 [13] FWD 'fwd_struct' fwd_kind=union 172 [13] FWD 'fwd_struct' fwd_kind=union
172 [14] ENUM 'my_enum' size=4 vlen=2 173 [14] ENUM 'my_enum' size=4 vlen=2
173 'VAL1' val=3 174 'VAL1' val=3
174 'VAL2' val=7 175 'VAL2' val=7
175 [15] PTR '(anon)' type_id=16 176 [15] PTR '(anon)' type_id=16
176 [16] VOLATILE '(anon)' type_id=17 177 [16] VOLATILE '(anon)' type_id=17
177 [17] TYPEDEF 'my_struct_t' type_id=4 178 [17] TYPEDEF 'my_struct_t' type_id=4
178 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen= 179 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2
179 'arg1' type_id=1 180 'arg1' type_id=1
180 'arg2' type_id=3 181 'arg2' type_id=3
181 [19] FUNC 'my_func' type_id=18 182 [19] FUNC 'my_func' type_id=18
182 [20] VAR 'struct_global_var' type_id=4, link 183 [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc
183 [21] VAR 'global_var' type_id=3, linkage=glo 184 [21] VAR 'global_var' type_id=3, linkage=global-alloc
184 [22] VAR 'my_func.static_var' type_id=3, lin 185 [22] VAR 'my_func.static_var' type_id=3, linkage=static
185 [23] DATASEC 'data_sec' size=0 vlen=3 186 [23] DATASEC 'data_sec' size=0 vlen=3
186 type_id=20 offset=0 size=48 187 type_id=20 offset=0 size=48
187 type_id=21 offset=0 size=4 188 type_id=21 offset=0 size=4
188 type_id=22 offset=52 size=4 189 type_id=22 offset=52 size=4
189 190
190 The following commands print BTF types associa 191 The following commands print BTF types associated with specified map's key,
191 value, both key and value, and all BTF types, 192 value, both key and value, and all BTF types, respectively. By default, both
192 key and value types will be printed. 193 key and value types will be printed.
193 194
194 **# bpftool btf dump map id 123 key** 195 **# bpftool btf dump map id 123 key**
195 196
196 :: 197 ::
197 198
198 [39] TYPEDEF 'u32' type_id=37 199 [39] TYPEDEF 'u32' type_id=37
199 200
200 **# bpftool btf dump map id 123 value** 201 **# bpftool btf dump map id 123 value**
201 202
202 :: 203 ::
203 204
204 [86] PTR '(anon)' type_id=87 205 [86] PTR '(anon)' type_id=87
205 206
206 **# bpftool btf dump map id 123 kv** 207 **# bpftool btf dump map id 123 kv**
207 208
208 :: 209 ::
209 210
210 [39] TYPEDEF 'u32' type_id=37 211 [39] TYPEDEF 'u32' type_id=37
211 [86] PTR '(anon)' type_id=87 212 [86] PTR '(anon)' type_id=87
212 213
213 **# bpftool btf dump map id 123 all** 214 **# bpftool btf dump map id 123 all**
214 215
215 :: 216 ::
216 217
217 [1] PTR '(anon)' type_id=0 218 [1] PTR '(anon)' type_id=0
218 . 219 .
219 . 220 .
220 . 221 .
221 [2866] ARRAY '(anon)' type_id=52 index_type_ 222 [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4
222 223
223 All the standard ways to specify map or progra 224 All the standard ways to specify map or program are supported:
224 225
225 **# bpftool btf dump map id 123** 226 **# bpftool btf dump map id 123**
226 227
227 **# bpftool btf dump map pinned /sys/fs/bpf/ma 228 **# bpftool btf dump map pinned /sys/fs/bpf/map_name**
228 229
229 **# bpftool btf dump prog id 456** 230 **# bpftool btf dump prog id 456**
230 231
231 **# bpftool btf dump prog tag b88e0a09b1d9759d 232 **# bpftool btf dump prog tag b88e0a09b1d9759d**
232 233
233 **# bpftool btf dump prog pinned /sys/fs/bpf/p 234 **# bpftool btf dump prog pinned /sys/fs/bpf/prog_name**
234 235
235 | 236 |
236 | **# bpftool btf dump file /sys/kernel/btf/i2 237 | **# bpftool btf dump file /sys/kernel/btf/i2c_smbus**
237 | (or) 238 | (or)
238 | **# I2C_SMBUS_ID=$(bpftool btf show -p | jq 239 | **# I2C_SMBUS_ID=$(bpftool btf show -p | jq '.[] | select(.name=="i2c_smbus").id')**
239 | **# bpftool btf dump id ${I2C_SMBUS_ID} -B / 240 | **# bpftool btf dump id ${I2C_SMBUS_ID} -B /sys/kernel/btf/vmlinux**
240 241
241 :: 242 ::
242 243
243 [104848] STRUCT 'i2c_smbus_alert' size=40 vl 244 [104848] STRUCT 'i2c_smbus_alert' size=40 vlen=2
244 'alert' type_id=393 bits_offset=0 245 'alert' type_id=393 bits_offset=0
245 'ara' type_id=56050 bits_offset=256 246 'ara' type_id=56050 bits_offset=256
246 [104849] STRUCT 'alert_data' size=12 vlen=3 247 [104849] STRUCT 'alert_data' size=12 vlen=3
247 'addr' type_id=16 bits_offset=0 248 'addr' type_id=16 bits_offset=0
248 'type' type_id=56053 bits_offset=32 249 'type' type_id=56053 bits_offset=32
249 'data' type_id=7 bits_offset=64 250 'data' type_id=7 bits_offset=64
250 [104850] PTR '(anon)' type_id=104848 251 [104850] PTR '(anon)' type_id=104848
251 [104851] PTR '(anon)' type_id=104849 252 [104851] PTR '(anon)' type_id=104849
252 [104852] FUNC 'i2c_register_spd' type_id=847 253 [104852] FUNC 'i2c_register_spd' type_id=84745 linkage=static
253 [104853] FUNC 'smbalert_driver_init' type_id 254 [104853] FUNC 'smbalert_driver_init' type_id=1213 linkage=static
254 [104854] FUNC_PROTO '(anon)' ret_type_id=18 255 [104854] FUNC_PROTO '(anon)' ret_type_id=18 vlen=1
255 'ara' type_id=56050 256 'ara' type_id=56050
256 [104855] FUNC 'i2c_handle_smbus_alert' type_ 257 [104855] FUNC 'i2c_handle_smbus_alert' type_id=104854 linkage=static
257 [104856] FUNC 'smbalert_remove' type_id=1048 258 [104856] FUNC 'smbalert_remove' type_id=104854 linkage=static
258 [104857] FUNC_PROTO '(anon)' ret_type_id=18 259 [104857] FUNC_PROTO '(anon)' ret_type_id=18 vlen=2
259 'ara' type_id=56050 260 'ara' type_id=56050
260 'id' type_id=56056 261 'id' type_id=56056
261 [104858] FUNC 'smbalert_probe' type_id=10485 262 [104858] FUNC 'smbalert_probe' type_id=104857 linkage=static
262 [104859] FUNC 'smbalert_work' type_id=9695 l 263 [104859] FUNC 'smbalert_work' type_id=9695 linkage=static
263 [104860] FUNC 'smbus_alert' type_id=71367 li 264 [104860] FUNC 'smbus_alert' type_id=71367 linkage=static
264 [104861] FUNC 'smbus_do_alert' type_id=84827 265 [104861] FUNC 'smbus_do_alert' type_id=84827 linkage=static
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