[RFC PATCH 2/6] bpf: Add function map->ops->map_traverse_elem() to traverse map elems

[kaixu xia]

Sometimes we want to traverse the map elements and make use
of the map value one by one. So add new function
map->ops->map_traverse_elem() to traverse map elements.

Signed-off-by: kaixu xia <xiaka...@huawei.com>
---
 include/linux/bpf.h   |    3 +++
 kernel/bpf/arraymap.c |   17 +++++++++++++++++
 kernel/bpf/hashtab.c  |   27 +++++++++++++++++++++++++++
 3 files changed, 47 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2634a25..f593199 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -13,6 +13,8 @@
 
 struct bpf_map;
 
+typedef int (*bpf_map_traverse_callback)(void *value);
+
 /* map is generic key/value storage optionally accesible by eBPF programs */
 struct bpf_map_ops {
        /* funcs callable from userspace (via syscall) */
@@ -24,6 +26,7 @@ struct bpf_map_ops {
        void *(*map_lookup_elem)(struct bpf_map *map, void *key);
        int (*map_update_elem)(struct bpf_map *map, void *key, void *value, u64 
flags);
        int (*map_delete_elem)(struct bpf_map *map, void *key);
+       int (*map_traverse_elem)(bpf_map_traverse_callback func, struct bpf_map 
*map);
 };
 
 struct bpf_map {
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index cb31229..3306916 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -114,6 +114,22 @@ static int array_map_delete_elem(struct bpf_map *map, void 
*key)
        return -EINVAL;
 }
 
+static int array_map_traverse_elem(bpf_map_traverse_callback func, struct 
bpf_map *map)
+{
+       struct bpf_array *array = container_of(map, struct bpf_array, map);
+       void *value;
+       int i;
+
+       for(i = 0; i < array->map.max_entries; i++) {
+               value = array->value + array->elem_size * i;
+
+               if (func(value) < 0)
+               return -EINVAL;
+       }
+
+       return 0;
+}
+
 /* Called when map->refcnt goes to zero, either from workqueue or from syscall 
*/
 static void array_map_free(struct bpf_map *map)
 {
@@ -136,6 +152,7 @@ static const struct bpf_map_ops array_ops = {
        .map_lookup_elem = array_map_lookup_elem,
        .map_update_elem = array_map_update_elem,
        .map_delete_elem = array_map_delete_elem,
+       .map_traverse_elem = array_map_traverse_elem,
 };
 
 static struct bpf_map_type_list array_type __read_mostly = {
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 83c209d..fa7887e 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -325,6 +325,32 @@ static void delete_all_elements(struct bpf_htab *htab)
        }
 }
 
+static int htab_map_traverse_elem(bpf_map_traverse_callback func, struct 
bpf_map *map)
+{
+       struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
+       struct hlist_head *head;
+       struct htab_elem *l;
+       u32 key_size;
+       void *value;
+       int i;
+
+       key_size = map->key_size;
+
+       for (i = 0; i < htab->n_buckets; i++) {
+               head = select_bucket(htab, i);
+
+               hlist_for_each_entry_rcu(l, head, hash_node) {
+                       value = l->key + round_up(key_size, 8);
+
+                       if (func(value) < 0)
+                               return -EINVAL;
+               }
+
+       }
+
+       return 0;
+}
+
 /* Called when map->refcnt goes to zero, either from workqueue or from syscall 
*/
 static void htab_map_free(struct bpf_map *map)
 {
@@ -352,6 +378,7 @@ static const struct bpf_map_ops htab_ops = {
        .map_lookup_elem = htab_map_lookup_elem,
        .map_update_elem = htab_map_update_elem,
        .map_delete_elem = htab_map_delete_elem,
+       .map_traverse_elem = htab_map_traverse_elem,
 };
 
 static struct bpf_map_type_list htab_type __read_mostly = {
-- 
1.7.10.4

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