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