bpf: add lookup/update/delete/iterate methods to BPF 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
  fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)
  returns fd or negative error

- lookup key in a given map referenced by fd
  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

- iterate map elements (based on input key return next_key)
  err = bpf(BPF_MAP_GET_NEXT_KEY, union bpf_attr *attr, u32 size)
  using attr->map_fd, attr->key, attr->next_key

- close(fd) deletes the map

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 46 insertions, 0 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 48014a71f0fe..2887f3f9da59 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -9,6 +9,7 @@
 
 #include <uapi/linux/bpf.h>
 #include <linux/workqueue.h>
+#include <linux/file.h>
 
 struct bpf_map;
 
@@ -17,6 +18,12 @@ struct bpf_map_ops {
         /* funcs callable from userspace (via syscall) */
         struct bpf_map *(*map_alloc)(union bpf_attr *attr);
         void (*map_free)(struct bpf_map *);
+        int (*map_get_next_key)(struct bpf_map *map, void *key, void *next_key);
+
+        /* funcs callable from userspace and from eBPF programs */
+        void *(*map_lookup_elem)(struct bpf_map *map, void *key);
+        int (*map_update_elem)(struct bpf_map *map, void *key, void *value);
+        int (*map_delete_elem)(struct bpf_map *map, void *key);
 };
 
 struct bpf_map {
@@ -37,5 +44,6 @@ struct bpf_map_type_list {
 
 void bpf_register_map_type(struct bpf_map_type_list *tl);
 void bpf_map_put(struct bpf_map *map);
+struct bpf_map *bpf_map_get(struct fd f);
 
 #endif /* _LINUX_BPF_H */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index f58a10f9670c..395cabd2ca0a 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -70,6 +70,35 @@ enum bpf_cmd {
          * map is deleted when fd is closed
          */
         BPF_MAP_CREATE,
+
+        /* 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
+         */
+        BPF_MAP_LOOKUP_ELEM,
+
+        /* 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
+         */
+        BPF_MAP_UPDATE_ELEM,
+
+        /* find and delete elem by key in a given map
+         * err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)
+         * Using attr->map_fd, attr->key
+         * returns zero or negative error
+         */
+        BPF_MAP_DELETE_ELEM,
+
+        /* lookup key in a given map and return next key
+         * err = bpf(BPF_MAP_GET_NEXT_KEY, union bpf_attr *attr, u32 size)
+         * Using attr->map_fd, attr->key, attr->next_key
+         * returns zero and stores next key or negative error
+         */
+        BPF_MAP_GET_NEXT_KEY,
 };
 
 enum bpf_map_type {
@@ -83,6 +112,15 @@ union bpf_attr {
                 __u32   value_size;     /* size of value in bytes */
                 __u32   max_entries;    /* max number of entries in a map */
         };
+
+        struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */
+                __u32           map_fd;
+                __aligned_u64   key;
+                union {
+                        __aligned_u64 value;
+                        __aligned_u64 next_key;
+                };
+        };
 } __attribute__((aligned(8)));
 
 #endif /* _UAPI__LINUX_BPF_H__ */