Commit | Line | Data |
---|---|---|
bc84e959 CH |
1 | |
2 | ========= | |
3 | eBPF maps | |
5931d9a3 | 4 | ========= |
bc84e959 CH |
5 | |
6 | 'maps' is a generic storage of different types for sharing data between kernel | |
7 | and userspace. | |
8 | ||
9 | The maps are accessed from user space via BPF syscall, which has commands: | |
10 | ||
11 | - create a map with given type and attributes | |
12 | ``map_fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)`` | |
13 | using attr->map_type, attr->key_size, attr->value_size, attr->max_entries | |
14 | returns process-local file descriptor or negative error | |
15 | ||
16 | - lookup key in a given map | |
17 | ``err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)`` | |
18 | using attr->map_fd, attr->key, attr->value | |
19 | returns zero and stores found elem into value or negative error | |
20 | ||
21 | - create or update key/value pair in a given map | |
22 | ``err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)`` | |
23 | using attr->map_fd, attr->key, attr->value | |
24 | returns zero or negative error | |
25 | ||
26 | - find and delete element by key in a given map | |
27 | ``err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)`` | |
28 | using attr->map_fd, attr->key | |
29 | ||
30 | - to delete map: close(fd) | |
31 | Exiting process will delete maps automatically | |
32 | ||
33 | userspace programs use this syscall to create/access maps that eBPF programs | |
34 | are concurrently updating. | |
35 | ||
36 | maps can have different types: hash, array, bloom filter, radix-tree, etc. | |
37 | ||
38 | The map is defined by: | |
39 | ||
40 | - type | |
41 | - max number of elements | |
42 | - key size in bytes | |
43 | - value size in bytes | |
44 | ||
5931d9a3 DT |
45 | Map Types |
46 | ========= | |
47 | ||
48 | .. toctree:: | |
49 | :maxdepth: 1 | |
50 | :glob: | |
51 | ||
52 | map_* |