Extend the existing bpf_map_lookup_and_delete_elem() functionality to
hashtab maps, in addition to stacks and queues.
Create a new hashtab bpf_map_ops function that does lookup and deletion
of the element under the same bucket lock and add the created map_ops to
bpf.h.
Add the appropriate test case to 'maps' selftests.
Signed-off-by: Denis Salopek <denis.salopek@xxxxxxxxxx>
Cc: Juraj Vijtiuk <juraj.vijtiuk@xxxxxxxxxx>
Cc: Luka Oreskovic <luka.oreskovic@xxxxxxxxxx>
Cc: Luka Perkov <luka.perkov@xxxxxxxxxx>
---
include/linux/bpf.h | 1 +
kernel/bpf/hashtab.c | 38 +++++++++++++++++++++++++
kernel/bpf/syscall.c | 9 ++++++
tools/testing/selftests/bpf/test_maps.c | 7 +++++
4 files changed, 55 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 1aac2af12fed..003c1505f0e3 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -77,6 +77,7 @@ struct bpf_map_ops {
/* funcs callable from userspace and from eBPF programs */
void *(*map_lookup_elem)(struct bpf_map *map, void *key);
+ int (*map_lookup_and_delete_elem)(struct bpf_map *map, void *key, void *value);
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_push_elem)(struct bpf_map *map, void *value, u64 flags);
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index c1ac7f964bc9..8d8463e0ea34 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -973,6 +973,43 @@ static int check_flags(struct bpf_htab *htab, struct htab_elem *l_old,
return 0;
}
+/* Called from syscall or from eBPF program */
+static int htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key, void *value)
+{
+ struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
+ struct hlist_nulls_head *head;
+ struct bucket *b;
+ struct htab_elem *l;
+ unsigned long flags;
+ u32 hash, key_size;
+ int ret;
+
+ WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held());
+
+ key_size = map->key_size;
+
+ hash = htab_map_hash(key, key_size, htab->hashrnd);
+ b = __select_bucket(htab, hash);
+ head = &b->head;
+
+ ret = htab_lock_bucket(htab, b, hash, &flags);
+ if (ret)
+ return ret;
+
+ l = lookup_elem_raw(head, hash, key, key_size);
+
+ if (l) {
+ copy_map_value(map, value, l->key + round_up(key_size, 8));
+ hlist_nulls_del_rcu(&l->hash_node);
+ free_htab_elem(htab, l);
+ } else {
+ ret = -ENOENT;
+ }
+
+ htab_unlock_bucket(htab, b, hash, flags);
+ return ret;
+}
+
/* Called from syscall or from eBPF program */
static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
u64 map_flags)
@@ -1877,6 +1914,7 @@ const struct bpf_map_ops htab_map_ops = {
.map_free = htab_map_free,
.map_get_next_key = htab_map_get_next_key,
.map_lookup_elem = htab_map_lookup_elem,
+ .map_lookup_and_delete_elem = htab_map_lookup_and_delete_elem,
.map_update_elem = htab_map_update_elem,
.map_delete_elem = htab_map_delete_elem,
.map_gen_lookup = htab_map_gen_lookup,
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index e5999d86c76e..4ff45c8d1077 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1505,6 +1505,15 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
if (map->map_type == BPF_MAP_TYPE_QUEUE ||
map->map_type == BPF_MAP_TYPE_STACK) {
err = map->ops->map_pop_elem(map, value);
+ } else if (map->map_type == BPF_MAP_TYPE_HASH) {
+ if (!bpf_map_is_dev_bound(map)) {
+ bpf_disable_instrumentation();
+ rcu_read_lock();
+ err = map->ops->map_lookup_and_delete_elem(map, key, value);
+ rcu_read_unlock();
+ bpf_enable_instrumentation();
+ maybe_wait_bpf_programs(map);
+ }
} else {
err = -ENOTSUPP;
}
diff --git a/tools/testing/selftests/bpf/test_maps.c b/tools/testing/selftests/bpf/test_maps.c
index 51adc42b2b40..3e1900e46e1d 100644
--- a/tools/testing/selftests/bpf/test_maps.c
+++ b/tools/testing/selftests/bpf/test_maps.c
@@ -65,6 +65,13 @@ static void test_hashmap(unsigned int task, void *data)
assert(bpf_map_lookup_elem(fd, &key, &value) == 0 && value == 1234);
key = 2;
+ value = 1234;
+ /* Insert key=2 element. */
+ assert(bpf_map_update_elem(fd, &key, &value, BPF_ANY) == 0);
+
+ /* Check that key=2 matches the value and delete it */
+ assert(bpf_map_lookup_and_delete_elem(fd, &key, &value) == 0 && value == 1234);
+
/* Check that key=2 is not found. */
assert(bpf_map_lookup_elem(fd, &key, &value) == -1 && errno == ENOENT);
--
2.26.2
