1.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2
3================
4bpftool-map
5================
6-------------------------------------------------------------------------------
7tool for inspection and simple manipulation of eBPF maps
8-------------------------------------------------------------------------------
9
10:Manual section: 8
11
12.. include:: substitutions.rst
13
14SYNOPSIS
15========
16
17	**bpftool** [*OPTIONS*] **map** *COMMAND*
18
19	*OPTIONS* := { |COMMON_OPTIONS| | { **-f** | **--bpffs** } | { **-n** | **--nomount** } }
20
21	*COMMANDS* :=
22	{ **show** | **list** | **create** | **dump** | **update** | **lookup** | **getnext** |
23	**delete** | **pin** | **help** }
24
25MAP COMMANDS
26=============
27
28|	**bpftool** **map** { **show** | **list** }   [*MAP*]
29|	**bpftool** **map create**     *FILE* **type** *TYPE* **key** *KEY_SIZE* **value** *VALUE_SIZE* \
30|		**entries** *MAX_ENTRIES* **name** *NAME* [**flags** *FLAGS*] [**inner_map** *MAP*] \
31|		[**dev** *NAME*]
32|	**bpftool** **map dump**       *MAP*
33|	**bpftool** **map update**     *MAP* [**key** *DATA*] [**value** *VALUE*] [*UPDATE_FLAGS*]
34|	**bpftool** **map lookup**     *MAP* [**key** *DATA*]
35|	**bpftool** **map getnext**    *MAP* [**key** *DATA*]
36|	**bpftool** **map delete**     *MAP*  **key** *DATA*
37|	**bpftool** **map pin**        *MAP*  *FILE*
38|	**bpftool** **map event_pipe** *MAP* [**cpu** *N* **index** *M*]
39|	**bpftool** **map peek**       *MAP*
40|	**bpftool** **map push**       *MAP* **value** *VALUE*
41|	**bpftool** **map pop**        *MAP*
42|	**bpftool** **map enqueue**    *MAP* **value** *VALUE*
43|	**bpftool** **map dequeue**    *MAP*
44|	**bpftool** **map freeze**     *MAP*
45|	**bpftool** **map help**
46|
47|	*MAP* := { **id** *MAP_ID* | **pinned** *FILE* | **name** *MAP_NAME* }
48|	*DATA* := { [**hex**] *BYTES* }
49|	*PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* | **name** *PROG_NAME* }
50|	*VALUE* := { *DATA* | *MAP* | *PROG* }
51|	*UPDATE_FLAGS* := { **any** | **exist** | **noexist** }
52|	*TYPE* := { **hash** | **array** | **prog_array** | **perf_event_array** | **percpu_hash**
53|		| **percpu_array** | **stack_trace** | **cgroup_array** | **lru_hash**
54|		| **lru_percpu_hash** | **lpm_trie** | **array_of_maps** | **hash_of_maps**
55|		| **devmap** | **devmap_hash** | **sockmap** | **cpumap** | **xskmap** | **sockhash**
56|		| **cgroup_storage** | **reuseport_sockarray** | **percpu_cgroup_storage**
57|		| **queue** | **stack** | **sk_storage** | **struct_ops** | **ringbuf** | **inode_storage**
58|		| **task_storage** | **bloom_filter** | **user_ringbuf** | **cgrp_storage** }
59
60DESCRIPTION
61===========
62	**bpftool map { show | list }**   [*MAP*]
63		  Show information about loaded maps.  If *MAP* is specified
64		  show information only about given maps, otherwise list all
65		  maps currently loaded on the system.  In case of **name**,
66		  *MAP* may match several maps which will all be shown.
67
68		  Output will start with map ID followed by map type and
69		  zero or more named attributes (depending on kernel version).
70
71		  Since Linux 5.8 bpftool is able to discover information about
72		  processes that hold open file descriptors (FDs) against BPF
73		  maps. On such kernels bpftool will automatically emit this
74		  information as well.
75
76	**bpftool map create** *FILE* **type** *TYPE* **key** *KEY_SIZE* **value** *VALUE_SIZE*  **entries** *MAX_ENTRIES* **name** *NAME* [**flags** *FLAGS*] [**inner_map** *MAP*] [**dev** *NAME*]
77		  Create a new map with given parameters and pin it to *bpffs*
78		  as *FILE*.
79
80		  *FLAGS* should be an integer which is the combination of
81		  desired flags, e.g. 1024 for **BPF_F_MMAPABLE** (see bpf.h
82		  UAPI header for existing flags).
83
84		  To create maps of type array-of-maps or hash-of-maps, the
85		  **inner_map** keyword must be used to pass an inner map. The
86		  kernel needs it to collect metadata related to the inner maps
87		  that the new map will work with.
88
89		  Keyword **dev** expects a network interface name, and is used
90		  to request hardware offload for the map.
91
92	**bpftool map dump**    *MAP*
93		  Dump all entries in a given *MAP*.  In case of **name**,
94		  *MAP* may match several maps which will all be dumped.
95
96	**bpftool map update**  *MAP* [**key** *DATA*] [**value** *VALUE*] [*UPDATE_FLAGS*]
97		  Update map entry for a given *KEY*.
98
99		  *UPDATE_FLAGS* can be one of: **any** update existing entry
100		  or add if doesn't exit; **exist** update only if entry already
101		  exists; **noexist** update only if entry doesn't exist.
102
103		  If the **hex** keyword is provided in front of the bytes
104		  sequence, the bytes are parsed as hexadecimal values, even if
105		  no "0x" prefix is added. If the keyword is not provided, then
106		  the bytes are parsed as decimal values, unless a "0x" prefix
107		  (for hexadecimal) or a "0" prefix (for octal) is provided.
108
109	**bpftool map lookup**  *MAP* [**key** *DATA*]
110		  Lookup **key** in the map.
111
112	**bpftool map getnext** *MAP* [**key** *DATA*]
113		  Get next key.  If *key* is not specified, get first key.
114
115	**bpftool map delete**  *MAP*  **key** *DATA*
116		  Remove entry from the map.
117
118	**bpftool map pin**     *MAP*  *FILE*
119		  Pin map *MAP* as *FILE*.
120
121		  Note: *FILE* must be located in *bpffs* mount. It must not
122		  contain a dot character ('.'), which is reserved for future
123		  extensions of *bpffs*.
124
125	**bpftool** **map event_pipe** *MAP* [**cpu** *N* **index** *M*]
126		  Read events from a **BPF_MAP_TYPE_PERF_EVENT_ARRAY** map.
127
128		  Install perf rings into a perf event array map and dump
129		  output of any **bpf_perf_event_output**\ () call in the kernel.
130		  By default read the number of CPUs on the system and
131		  install perf ring for each CPU in the corresponding index
132		  in the array.
133
134		  If **cpu** and **index** are specified, install perf ring
135		  for given **cpu** at **index** in the array (single ring).
136
137		  Note that installing a perf ring into an array will silently
138		  replace any existing ring.  Any other application will stop
139		  receiving events if it installed its rings earlier.
140
141	**bpftool map peek**  *MAP*
142		  Peek next value in the queue or stack.
143
144	**bpftool map push**  *MAP* **value** *VALUE*
145		  Push *VALUE* onto the stack.
146
147	**bpftool map pop**  *MAP*
148		  Pop and print value from the stack.
149
150	**bpftool map enqueue**  *MAP* **value** *VALUE*
151		  Enqueue *VALUE* into the queue.
152
153	**bpftool map dequeue**  *MAP*
154		  Dequeue and print value from the queue.
155
156	**bpftool map freeze**  *MAP*
157		  Freeze the map as read-only from user space. Entries from a
158		  frozen map can not longer be updated or deleted with the
159		  **bpf**\ () system call. This operation is not reversible,
160		  and the map remains immutable from user space until its
161		  destruction. However, read and write permissions for BPF
162		  programs to the map remain unchanged.
163
164	**bpftool map help**
165		  Print short help message.
166
167OPTIONS
168=======
169	.. include:: common_options.rst
170
171	-f, --bpffs
172		  Show file names of pinned maps.
173
174	-n, --nomount
175		  Do not automatically attempt to mount any virtual file system
176		  (such as tracefs or BPF virtual file system) when necessary.
177
178EXAMPLES
179========
180**# bpftool map show**
181
182::
183
184  10: hash  name some_map  flags 0x0
185        key 4B  value 8B  max_entries 2048  memlock 167936B
186        pids systemd(1)
187
188The following three commands are equivalent:
189
190|
191| **# bpftool map update id 10 key hex   20   c4   b7   00 value hex   0f   ff   ff   ab   01   02   03   4c**
192| **# bpftool map update id 10 key     0x20 0xc4 0xb7 0x00 value     0x0f 0xff 0xff 0xab 0x01 0x02 0x03 0x4c**
193| **# bpftool map update id 10 key       32  196  183    0 value       15  255  255  171    1    2    3   76**
194
195**# bpftool map lookup id 10 key 0 1 2 3**
196
197::
198
199  key: 00 01 02 03 value: 00 01 02 03 04 05 06 07
200
201
202**# bpftool map dump id 10**
203
204::
205
206  key: 00 01 02 03  value: 00 01 02 03 04 05 06 07
207  key: 0d 00 07 00  value: 02 00 00 00 01 02 03 04
208  Found 2 elements
209
210**# bpftool map getnext id 10 key 0 1 2 3**
211
212::
213
214  key:
215  00 01 02 03
216  next key:
217  0d 00 07 00
218
219|
220| **# mount -t bpf none /sys/fs/bpf/**
221| **# bpftool map pin id 10 /sys/fs/bpf/map**
222| **# bpftool map del pinned /sys/fs/bpf/map key 13 00 07 00**
223
224Note that map update can also be used in order to change the program references
225hold by a program array map. This can be used, for example, to change the
226programs used for tail-call jumps at runtime, without having to reload the
227entry-point program. Below is an example for this use case: we load a program
228defining a prog array map, and with a main function that contains a tail call
229to other programs that can be used either to "process" packets or to "debug"
230processing. Note that the prog array map MUST be pinned into the BPF virtual
231file system for the map update to work successfully, as kernel flushes prog
232array maps when they have no more references from user space (and the update
233would be lost as soon as bpftool exits).
234
235|
236| **# bpftool prog loadall tail_calls.o /sys/fs/bpf/foo type xdp**
237| **# bpftool prog --bpffs**
238
239::
240
241  545: xdp  name main_func  tag 674b4b5597193dc3  gpl
242          loaded_at 2018-12-12T15:02:58+0000  uid 0
243          xlated 240B  jited 257B  memlock 4096B  map_ids 294
244          pinned /sys/fs/bpf/foo/xdp
245  546: xdp  name bpf_func_process  tag e369a529024751fc  gpl
246          loaded_at 2018-12-12T15:02:58+0000  uid 0
247          xlated 200B  jited 164B  memlock 4096B
248          pinned /sys/fs/bpf/foo/process
249  547: xdp  name bpf_func_debug  tag 0b597868bc7f0976  gpl
250          loaded_at 2018-12-12T15:02:58+0000  uid 0
251          xlated 200B  jited 164B  memlock 4096B
252          pinned /sys/fs/bpf/foo/debug
253
254**# bpftool map**
255
256::
257
258  294: prog_array  name jmp_table  flags 0x0
259          key 4B  value 4B  max_entries 1  memlock 4096B
260          owner_prog_type xdp  owner jited
261
262|
263| **# bpftool map pin id 294 /sys/fs/bpf/bar**
264| **# bpftool map dump pinned /sys/fs/bpf/bar**
265
266::
267
268  Found 0 elements
269
270|
271| **# bpftool map update pinned /sys/fs/bpf/bar key 0 0 0 0 value pinned /sys/fs/bpf/foo/debug**
272| **# bpftool map dump pinned /sys/fs/bpf/bar**
273
274::
275
276  key: 00 00 00 00  value: 22 02 00 00
277  Found 1 element
278