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Diffstat (limited to 'Documentation/bpf/map_cpumap.rst')
| -rw-r--r-- | Documentation/bpf/map_cpumap.rst | 59 |
1 files changed, 35 insertions, 24 deletions
diff --git a/Documentation/bpf/map_cpumap.rst b/Documentation/bpf/map_cpumap.rst index eaf57b38cafd..923cfc8ab51f 100644 --- a/Documentation/bpf/map_cpumap.rst +++ b/Documentation/bpf/map_cpumap.rst @@ -30,30 +30,35 @@ Usage Kernel BPF ---------- -.. c:function:: +bpf_redirect_map() +^^^^^^^^^^^^^^^^^^ +.. code-block:: c + long bpf_redirect_map(struct bpf_map *map, u32 key, u64 flags) - Redirect the packet to the endpoint referenced by ``map`` at index ``key``. - For ``BPF_MAP_TYPE_CPUMAP`` this map contains references to CPUs. +Redirect the packet to the endpoint referenced by ``map`` at index ``key``. +For ``BPF_MAP_TYPE_CPUMAP`` this map contains references to CPUs. - The lower two bits of ``flags`` are used as the return code if the map lookup - fails. This is so that the return value can be one of the XDP program return - codes up to ``XDP_TX``, as chosen by the caller. +The lower two bits of ``flags`` are used as the return code if the map lookup +fails. This is so that the return value can be one of the XDP program return +codes up to ``XDP_TX``, as chosen by the caller. -Userspace ---------- +User space +---------- .. note:: CPUMAP entries can only be updated/looked up/deleted from user space and not from an eBPF program. Trying to call these functions from a kernel eBPF program will result in the program failing to load and a verifier warning. -.. c:function:: - int bpf_map_update_elem(int fd, const void *key, const void *value, - __u64 flags); +bpf_map_update_elem() +^^^^^^^^^^^^^^^^^^^^^ +.. code-block:: c + + int bpf_map_update_elem(int fd, const void *key, const void *value, __u64 flags); - CPU entries can be added or updated using the ``bpf_map_update_elem()`` - helper. This helper replaces existing elements atomically. The ``value`` parameter - can be ``struct bpf_cpumap_val``. +CPU entries can be added or updated using the ``bpf_map_update_elem()`` +helper. This helper replaces existing elements atomically. The ``value`` parameter +can be ``struct bpf_cpumap_val``. .. code-block:: c @@ -65,23 +70,29 @@ Userspace } bpf_prog; }; - The flags argument can be one of the following: +The flags argument can be one of the following: - BPF_ANY: Create a new element or update an existing element. - BPF_NOEXIST: Create a new element only if it did not exist. - BPF_EXIST: Update an existing element. -.. c:function:: +bpf_map_lookup_elem() +^^^^^^^^^^^^^^^^^^^^^ +.. code-block:: c + int bpf_map_lookup_elem(int fd, const void *key, void *value); - CPU entries can be retrieved using the ``bpf_map_lookup_elem()`` - helper. +CPU entries can be retrieved using the ``bpf_map_lookup_elem()`` +helper. + +bpf_map_delete_elem() +^^^^^^^^^^^^^^^^^^^^^ +.. code-block:: c -.. c:function:: int bpf_map_delete_elem(int fd, const void *key); - CPU entries can be deleted using the ``bpf_map_delete_elem()`` - helper. This helper will return 0 on success, or negative error in case of - failure. +CPU entries can be deleted using the ``bpf_map_delete_elem()`` +helper. This helper will return 0 on success, or negative error in case of +failure. Examples ======== @@ -142,8 +153,8 @@ The following code snippet shows how to declare a ``BPF_MAP_TYPE_CPUMAP`` called return bpf_redirect_map(&cpu_map, cpu_dest, 0); } -Userspace ---------- +User space +---------- The following code snippet shows how to dynamically set the max_entries for a CPUMAP to the max number of cpus available on the system. |