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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 -h, --help
75 Print short generic help message (similar to **bpftool help**).
76
77 -V, --version
78 Print version number (similar to **bpftool version**).
79
80 -j, --json
81 Generate JSON output. For commands that cannot produce JSON, this
82 option has no effect.
83
84 -p, --pretty
85 Generate human-readable JSON output. Implies **-j**.
86
87 -d, --debug
88 Print all logs available from libbpf, including debug-level
89 information.
90
91EXAMPLES
92========
93**# bpftool btf dump id 1226**
94::
95
96 [1] PTR '(anon)' type_id=2
97 [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=2
98 'pad' type_id=3 bits_offset=0
99 'sock' type_id=4 bits_offset=64
100 [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none)
101 [4] PTR '(anon)' type_id=5
102 [5] FWD 'sock' fwd_kind=union
103
104This gives an example of default output for all supported BTF kinds.
105
106**$ cat prog.c**
107::
108
109 struct fwd_struct;
110
111 enum my_enum {
112 VAL1 = 3,
113 VAL2 = 7,
114 };
115
116 typedef struct my_struct my_struct_t;
117
118 struct my_struct {
119 const unsigned int const_int_field;
120 int bitfield_field: 4;
121 char arr_field[16];
122 const struct fwd_struct *restrict fwd_field;
123 enum my_enum enum_field;
124 volatile my_struct_t *typedef_ptr_field;
125 };
126
127 union my_union {
128 int a;
129 struct my_struct b;
130 };
131
132 struct my_struct struct_global_var __attribute__((section("data_sec"))) = {
133 .bitfield_field = 3,
134 .enum_field = VAL1,
135 };
136 int global_var __attribute__((section("data_sec"))) = 7;
137
138 __attribute__((noinline))
139 int my_func(union my_union *arg1, int arg2)
140 {
141 static int static_var __attribute__((section("data_sec"))) = 123;
142 static_var++;
143 return static_var;
144 }
145
146**$ bpftool btf dump file prog.o**
147::
148
149 [1] PTR '(anon)' type_id=2
150 [2] UNION 'my_union' size=48 vlen=2
151 'a' type_id=3 bits_offset=0
152 'b' type_id=4 bits_offset=0
153 [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
154 [4] STRUCT 'my_struct' size=48 vlen=6
155 'const_int_field' type_id=5 bits_offset=0
156 'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4
157 'arr_field' type_id=8 bits_offset=40
158 'fwd_field' type_id=10 bits_offset=192
159 'enum_field' type_id=14 bits_offset=256
160 'typedef_ptr_field' type_id=15 bits_offset=320
161 [5] CONST '(anon)' type_id=6
162 [6] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none)
163 [7] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
164 [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16
165 [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
166 [10] RESTRICT '(anon)' type_id=11
167 [11] PTR '(anon)' type_id=12
168 [12] CONST '(anon)' type_id=13
169 [13] FWD 'fwd_struct' fwd_kind=union
170 [14] ENUM 'my_enum' size=4 vlen=2
171 'VAL1' val=3
172 'VAL2' val=7
173 [15] PTR '(anon)' type_id=16
174 [16] VOLATILE '(anon)' type_id=17
175 [17] TYPEDEF 'my_struct_t' type_id=4
176 [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2
177 'arg1' type_id=1
178 'arg2' type_id=3
179 [19] FUNC 'my_func' type_id=18
180 [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc
181 [21] VAR 'global_var' type_id=3, linkage=global-alloc
182 [22] VAR 'my_func.static_var' type_id=3, linkage=static
183 [23] DATASEC 'data_sec' size=0 vlen=3
184 type_id=20 offset=0 size=48
185 type_id=21 offset=0 size=4
186 type_id=22 offset=52 size=4
187
188The following commands print BTF types associated with specified map's key,
189value, both key and value, and all BTF types, respectively. By default, both
190key and value types will be printed.
191
192**# bpftool btf dump map id 123 key**
193
194::
195
196 [39] TYPEDEF 'u32' type_id=37
197
198**# bpftool btf dump map id 123 value**
199
200::
201
202 [86] PTR '(anon)' type_id=87
203
204**# bpftool btf dump map id 123 kv**
205
206::
207
208 [39] TYPEDEF 'u32' type_id=37
209 [86] PTR '(anon)' type_id=87
210
211**# bpftool btf dump map id 123 all**
212
213::
214
215 [1] PTR '(anon)' type_id=0
216 .
217 .
218 .
219 [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4
220
221All the standard ways to specify map or program are supported:
222
223**# bpftool btf dump map id 123**
224
225**# bpftool btf dump map pinned /sys/fs/bpf/map_name**
226
227**# bpftool btf dump prog id 456**
228
229**# bpftool btf dump prog tag b88e0a09b1d9759d**
230
231**# bpftool btf dump prog pinned /sys/fs/bpf/prog_name**
232
233SEE ALSO
234========
235 **bpf**\ (2),
236 **bpf-helpers**\ (7),
237 **bpftool**\ (8),
238 **bpftool-btf**\ (8),
239 **bpftool-cgroup**\ (8),
240 **bpftool-feature**\ (8),
241 **bpftool-gen**\ (8),
242 **bpftool-iter**\ (8),
243 **bpftool-link**\ (8),
244 **bpftool-map**\ (8),
245 **bpftool-net**\ (8),
246 **bpftool-perf**\ (8),
247 **bpftool-prog**\ (8),
248 **bpftool-struct_ops**\ (8)