================
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bpftool-map
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================
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-------------------------------------------------------------------------------
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tool for inspection and simple manipulation of eBPF maps
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-------------------------------------------------------------------------------
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:Manual section: 8
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SYNOPSIS
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========
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**bpftool** [*OPTIONS*] **map** *COMMAND*
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*OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] | { **-f** | **--bpffs** } }
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*COMMANDS* :=
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{ **show** | **list** | **create** | **dump** | **update** | **lookup** | **getnext**
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| **delete** | **pin** | **help** }
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MAP COMMANDS
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=============
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| **bpftool** **map** { **show** | **list** } [*MAP*]
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| **bpftool** **map create** *FILE* **type** *TYPE* **key** *KEY_SIZE* **value** *VALUE_SIZE* \
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| **entries** *MAX_ENTRIES* **name** *NAME* [**flags** *FLAGS*] [**inner_map** *MAP*] \
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| [**dev** *NAME*]
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| **bpftool** **map dump** *MAP*
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| **bpftool** **map update** *MAP* [**key** *DATA*] [**value** *VALUE*] [*UPDATE_FLAGS*]
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| **bpftool** **map lookup** *MAP* [**key** *DATA*]
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| **bpftool** **map getnext** *MAP* [**key** *DATA*]
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| **bpftool** **map delete** *MAP* **key** *DATA*
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| **bpftool** **map pin** *MAP* *FILE*
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| **bpftool** **map event_pipe** *MAP* [**cpu** *N* **index** *M*]
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| **bpftool** **map peek** *MAP*
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| **bpftool** **map push** *MAP* **value** *VALUE*
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| **bpftool** **map pop** *MAP*
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| **bpftool** **map enqueue** *MAP* **value** *VALUE*
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| **bpftool** **map dequeue** *MAP*
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| **bpftool** **map freeze** *MAP*
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| **bpftool** **map help**
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| *MAP* := { **id** *MAP_ID* | **pinned** *FILE* | **name** *MAP_NAME* }
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| *DATA* := { [**hex**] *BYTES* }
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| *PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* | **name** *PROG_NAME* }
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| *VALUE* := { *DATA* | *MAP* | *PROG* }
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| *UPDATE_FLAGS* := { **any** | **exist** | **noexist** }
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| *TYPE* := { **hash** | **array** | **prog_array** | **perf_event_array** | **percpu_hash**
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| | **percpu_array** | **stack_trace** | **cgroup_array** | **lru_hash**
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| | **lru_percpu_hash** | **lpm_trie** | **array_of_maps** | **hash_of_maps**
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| | **devmap** | **devmap_hash** | **sockmap** | **cpumap** | **xskmap** | **sockhash**
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| | **cgroup_storage** | **reuseport_sockarray** | **percpu_cgroup_storage**
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| | **queue** | **stack** | **sk_storage** | **struct_ops** | **ringbuf** | **inode_storage** }
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DESCRIPTION
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===========
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**bpftool map { show | list }** [*MAP*]
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Show information about loaded maps. If *MAP* is specified
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show information only about given maps, otherwise list all
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maps currently loaded on the system. In case of **name**,
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*MAP* may match several maps which will all be shown.
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Output will start with map ID followed by map type and
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zero or more named attributes (depending on kernel version).
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Since Linux 5.8 bpftool is able to discover information about
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processes that hold open file descriptors (FDs) against BPF
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maps. On such kernels bpftool will automatically emit this
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information as well.
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**bpftool map create** *FILE* **type** *TYPE* **key** *KEY_SIZE* **value** *VALUE_SIZE* **entries** *MAX_ENTRIES* **name** *NAME* [**flags** *FLAGS*] [**inner_map** *MAP*] [**dev** *NAME*]
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Create a new map with given parameters and pin it to *bpffs*
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as *FILE*.
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*FLAGS* should be an integer which is the combination of
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desired flags, e.g. 1024 for **BPF_F_MMAPABLE** (see bpf.h
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UAPI header for existing flags).
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To create maps of type array-of-maps or hash-of-maps, the
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**inner_map** keyword must be used to pass an inner map. The
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kernel needs it to collect metadata related to the inner maps
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that the new map will work with.
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Keyword **dev** expects a network interface name, and is used
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to request hardware offload for the map.
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**bpftool map dump** *MAP*
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Dump all entries in a given *MAP*. In case of **name**,
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*MAP* may match several maps which will all be dumped.
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**bpftool map update** *MAP* [**key** *DATA*] [**value** *VALUE*] [*UPDATE_FLAGS*]
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Update map entry for a given *KEY*.
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*UPDATE_FLAGS* can be one of: **any** update existing entry
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or add if doesn't exit; **exist** update only if entry already
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exists; **noexist** update only if entry doesn't exist.
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If the **hex** keyword is provided in front of the bytes
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sequence, the bytes are parsed as hexadecimal values, even if
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no "0x" prefix is added. If the keyword is not provided, then
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the bytes are parsed as decimal values, unless a "0x" prefix
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(for hexadecimal) or a "0" prefix (for octal) is provided.
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**bpftool map lookup** *MAP* [**key** *DATA*]
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Lookup **key** in the map.
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**bpftool map getnext** *MAP* [**key** *DATA*]
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Get next key. If *key* is not specified, get first key.
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**bpftool map delete** *MAP* **key** *DATA*
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Remove entry from the map.
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**bpftool map pin** *MAP* *FILE*
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Pin map *MAP* as *FILE*.
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Note: *FILE* must be located in *bpffs* mount. It must not
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contain a dot character ('.'), which is reserved for future
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extensions of *bpffs*.
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**bpftool** **map event_pipe** *MAP* [**cpu** *N* **index** *M*]
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Read events from a **BPF_MAP_TYPE_PERF_EVENT_ARRAY** map.
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Install perf rings into a perf event array map and dump
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output of any **bpf_perf_event_output**\ () call in the kernel.
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By default read the number of CPUs on the system and
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install perf ring for each CPU in the corresponding index
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in the array.
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If **cpu** and **index** are specified, install perf ring
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for given **cpu** at **index** in the array (single ring).
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Note that installing a perf ring into an array will silently
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replace any existing ring. Any other application will stop
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receiving events if it installed its rings earlier.
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**bpftool map peek** *MAP*
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Peek next value in the queue or stack.
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**bpftool map push** *MAP* **value** *VALUE*
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Push *VALUE* onto the stack.
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**bpftool map pop** *MAP*
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Pop and print value from the stack.
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**bpftool map enqueue** *MAP* **value** *VALUE*
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Enqueue *VALUE* into the queue.
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**bpftool map dequeue** *MAP*
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Dequeue and print value from the queue.
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**bpftool map freeze** *MAP*
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Freeze the map as read-only from user space. Entries from a
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frozen map can not longer be updated or deleted with the
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**bpf**\ () system call. This operation is not reversible,
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and the map remains immutable from user space until its
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destruction. However, read and write permissions for BPF
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programs to the map remain unchanged.
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**bpftool map help**
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Print short help message.
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OPTIONS
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=======
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.. include:: common_options.rst
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-f, --bpffs
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Show file names of pinned maps.
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-n, --nomount
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Do not automatically attempt to mount any virtual file system
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(such as tracefs or BPF virtual file system) when necessary.
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EXAMPLES
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========
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**# bpftool map show**
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::
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10: hash name some_map flags 0x0
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key 4B value 8B max_entries 2048 memlock 167936B
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pids systemd(1)
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The following three commands are equivalent:
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| **# bpftool map update id 10 key hex 20 c4 b7 00 value hex 0f ff ff ab 01 02 03 4c**
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| **# bpftool map update id 10 key 0x20 0xc4 0xb7 0x00 value 0x0f 0xff 0xff 0xab 0x01 0x02 0x03 0x4c**
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| **# bpftool map update id 10 key 32 196 183 0 value 15 255 255 171 1 2 3 76**
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**# bpftool map lookup id 10 key 0 1 2 3**
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::
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key: 00 01 02 03 value: 00 01 02 03 04 05 06 07
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**# bpftool map dump id 10**
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::
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key: 00 01 02 03 value: 00 01 02 03 04 05 06 07
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key: 0d 00 07 00 value: 02 00 00 00 01 02 03 04
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Found 2 elements
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**# bpftool map getnext id 10 key 0 1 2 3**
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::
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key:
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00 01 02 03
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next key:
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0d 00 07 00
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| **# mount -t bpf none /sys/fs/bpf/**
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| **# bpftool map pin id 10 /sys/fs/bpf/map**
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| **# bpftool map del pinned /sys/fs/bpf/map key 13 00 07 00**
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Note that map update can also be used in order to change the program references
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hold by a program array map. This can be used, for example, to change the
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programs used for tail-call jumps at runtime, without having to reload the
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entry-point program. Below is an example for this use case: we load a program
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defining a prog array map, and with a main function that contains a tail call
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to other programs that can be used either to "process" packets or to "debug"
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processing. Note that the prog array map MUST be pinned into the BPF virtual
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file system for the map update to work successfully, as kernel flushes prog
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array maps when they have no more references from user space (and the update
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would be lost as soon as bpftool exits).
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| **# bpftool prog loadall tail_calls.o /sys/fs/bpf/foo type xdp**
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| **# bpftool prog --bpffs**
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::
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545: xdp name main_func tag 674b4b5597193dc3 gpl
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loaded_at 2018-12-12T15:02:58+0000 uid 0
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xlated 240B jited 257B memlock 4096B map_ids 294
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pinned /sys/fs/bpf/foo/xdp
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546: xdp name bpf_func_process tag e369a529024751fc gpl
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loaded_at 2018-12-12T15:02:58+0000 uid 0
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xlated 200B jited 164B memlock 4096B
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pinned /sys/fs/bpf/foo/process
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547: xdp name bpf_func_debug tag 0b597868bc7f0976 gpl
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loaded_at 2018-12-12T15:02:58+0000 uid 0
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xlated 200B jited 164B memlock 4096B
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pinned /sys/fs/bpf/foo/debug
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**# bpftool map**
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::
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294: prog_array name jmp_table flags 0x0
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key 4B value 4B max_entries 1 memlock 4096B
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owner_prog_type xdp owner jited
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| **# bpftool map pin id 294 /sys/fs/bpf/bar**
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| **# bpftool map dump pinned /sys/fs/bpf/bar**
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::
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Found 0 elements
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| **# bpftool map update pinned /sys/fs/bpf/bar key 0 0 0 0 value pinned /sys/fs/bpf/foo/debug**
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| **# bpftool map dump pinned /sys/fs/bpf/bar**
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::
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key: 00 00 00 00 value: 22 02 00 00
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Found 1 element
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