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author | Alexei Starovoitov <ast@plumgrid.com> | 2014-09-26 00:16:57 -0700 |
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committer | David S. Miller <davem@davemloft.net> | 2014-09-26 15:05:14 -0400 |
commit | 99c55f7d47c0dc6fc64729f37bf435abf43f4c60 (patch) | |
tree | 12f09f26bee9813ae33cfc195582c41e94b2e4e9 /Documentation/networking | |
parent | 4a8e320c929991c9480a7b936512c57ea02d87b2 (diff) | |
download | linux-99c55f7d47c0dc6fc64729f37bf435abf43f4c60.tar.gz linux-99c55f7d47c0dc6fc64729f37bf435abf43f4c60.tar.bz2 linux-99c55f7d47c0dc6fc64729f37bf435abf43f4c60.zip |
bpf: introduce BPF syscall and maps
BPF syscall is a multiplexor for a range of different operations on eBPF.
This patch introduces syscall with single command to create a map.
Next patch adds commands to access maps.
'maps' is a generic storage of different types for sharing data between kernel
and userspace.
Userspace example:
/* this syscall wrapper creates a map with given type and attributes
* and returns map_fd on success.
* use close(map_fd) to delete the map
*/
int bpf_create_map(enum bpf_map_type map_type, int key_size,
int value_size, int max_entries)
{
union bpf_attr attr = {
.map_type = map_type,
.key_size = key_size,
.value_size = value_size,
.max_entries = max_entries
};
return bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
}
'union bpf_attr' is backwards compatible with future extensions.
More details in Documentation/networking/filter.txt and in manpage
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/networking')
-rw-r--r-- | Documentation/networking/filter.txt | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.txt index 014e0319a5c4..4a01d71785e9 100644 --- a/Documentation/networking/filter.txt +++ b/Documentation/networking/filter.txt @@ -1001,6 +1001,45 @@ instruction that loads 64-bit immediate value into a dst_reg. Classic BPF has similar instruction: BPF_LD | BPF_W | BPF_IMM which loads 32-bit immediate value into a register. +eBPF maps +--------- +'maps' is a generic storage of different types for sharing data between kernel +and userspace. + +The maps are accessed from user space via BPF syscall, which has commands: +- create a map with given type and attributes + map_fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size) + using attr->map_type, attr->key_size, attr->value_size, attr->max_entries + returns process-local file descriptor or negative error + +- lookup key in a given map + err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size) + using attr->map_fd, attr->key, attr->value + returns zero and stores found elem into value or negative error + +- create or update key/value pair in a given map + err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size) + using attr->map_fd, attr->key, attr->value + returns zero or negative error + +- find and delete element by key in a given map + err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size) + using attr->map_fd, attr->key + +- to delete map: close(fd) + Exiting process will delete maps automatically + +userspace programs use this syscall to create/access maps that eBPF programs +are concurrently updating. + +maps can have different types: hash, array, bloom filter, radix-tree, etc. + +The map is defined by: + . type + . max number of elements + . key size in bytes + . value size in bytes + Testing ------- |