On 3/20/23 12:56 PM, Kui-Feng Lee wrote:
+static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map *new_map,
+ struct bpf_map *expected_old_map)
+{
+ struct bpf_struct_ops_map *st_map, *old_st_map;
+ struct bpf_map *old_map;
+ struct bpf_struct_ops_link *st_link;
+ int err = 0;
+
+ st_link = container_of(link, struct bpf_struct_ops_link, link);
+ st_map = container_of(new_map, struct bpf_struct_ops_map, map);
+
+ if (!bpf_struct_ops_valid_to_reg(new_map))
+ return -EINVAL;
+
+ mutex_lock(&update_mutex);
+
+ old_map = rcu_dereference_protected(st_link->map, lockdep_is_held(&update_mutex));
+ if (expected_old_map && old_map != expected_old_map) {
+ err = -EINVAL;
+ goto err_out;
+ }
+
+ old_st_map = container_of(old_map, struct bpf_struct_ops_map, map);
+ /* The new and old struct_ops must be the same type. */
+ if (st_map->st_ops != old_st_map->st_ops) {
+ err = -EINVAL;
Other ".update_prog" implementation returns -EPERM. eg. take a look at
cgroup_bpf_replace().
+ goto err_out;
+ }
+
+ err = st_map->st_ops->update(st_map->kvalue.data, old_st_map->kvalue.data);
+ if (err)
+ goto err_out;
+
+ bpf_map_inc(new_map);
+ rcu_assign_pointer(st_link->map, new_map);
+ bpf_map_put(old_map);
+
+err_out:
+ mutex_unlock(&update_mutex);
+
+ return err;
+}
+
