diff options
Diffstat (limited to 'Documentation/bpf/map_array.rst')
| -rw-r--r-- | Documentation/bpf/map_array.rst | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/Documentation/bpf/map_array.rst b/Documentation/bpf/map_array.rst index b2cceb6c696b..f2f51a53e8ae 100644 --- a/Documentation/bpf/map_array.rst +++ b/Documentation/bpf/map_array.rst @@ -32,7 +32,11 @@ Usage Kernel BPF ---------- -.. c:function:: +bpf_map_lookup_elem() +~~~~~~~~~~~~~~~~~~~~~ + +.. code-block:: c + void *bpf_map_lookup_elem(struct bpf_map *map, const void *key) Array elements can be retrieved using the ``bpf_map_lookup_elem()`` helper. @@ -40,7 +44,11 @@ This helper returns a pointer into the array element, so to avoid data races with userspace reading the value, the user must use primitives like ``__sync_fetch_and_add()`` when updating the value in-place. -.. c:function:: +bpf_map_update_elem() +~~~~~~~~~~~~~~~~~~~~~ + +.. code-block:: c + long bpf_map_update_elem(struct bpf_map *map, const void *key, const void *value, u64 flags) Array elements can be updated using the ``bpf_map_update_elem()`` helper. @@ -53,7 +61,7 @@ To clear an array element, you may use ``bpf_map_update_elem()`` to insert a zero value to that index. Per CPU Array -~~~~~~~~~~~~~ +------------- Values stored in ``BPF_MAP_TYPE_ARRAY`` can be accessed by multiple programs across different CPUs. To restrict storage to a single CPU, you may use a @@ -63,7 +71,11 @@ When using a ``BPF_MAP_TYPE_PERCPU_ARRAY`` the ``bpf_map_update_elem()`` and ``bpf_map_lookup_elem()`` helpers automatically access the slot for the current CPU. -.. c:function:: +bpf_map_lookup_percpu_elem() +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. code-block:: c + void *bpf_map_lookup_percpu_elem(struct bpf_map *map, const void *key, u32 cpu) The ``bpf_map_lookup_percpu_elem()`` helper can be used to lookup the array @@ -119,7 +131,7 @@ This example BPF program shows how to access an array element. index = ip.protocol; value = bpf_map_lookup_elem(&my_map, &index); if (value) - __sync_fetch_and_add(&value, skb->len); + __sync_fetch_and_add(value, skb->len); return 0; } |