Commit 638e4b82 authored Feb 09, 2021 by Alexei Starovoitov Committed by Daniel Borkmann Feb 11, 2021

bpf: Allows per-cpu maps and map-in-map in sleepable programs



Since sleepable programs are now executing under migrate_disable
the per-cpu maps are safe to use.
The map-in-map were ok to use in sleepable from the time sleepable
progs were introduced.

Note that non-preallocated maps are still not safe, since there is
no rcu_read_lock yet in sleepable programs and dynamically allocated
map elements are relying on rcu protection. The sleepable programs
have rcu_read_lock_trace instead. That limitation will be addresses
in the future.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: KP Singh <kpsingh@kernel.org>
Link: https://lore.kernel.org/bpf/20210210033634.62081-9-alexei.starovoitov@gmail.com

parent dcf33b6f

kernel/bpf/hashtab.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1148,7 +1148,7 @@ static int __htab_percpu_map_update_elem(struct bpf_map map, void key,
		/* unknown flags */
		return -EINVAL;

		WARN_ON_ONCE(!rcu_read_lock_held());
		WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held());

		key_size = map->key_size;

		@@ -1202,7 +1202,7 @@ static int __htab_lru_percpu_map_update_elem(struct bpf_map map, void key,
		/* unknown flags */
		return -EINVAL;

		WARN_ON_ONCE(!rcu_read_lock_held());
		WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held());

		key_size = map->key_size;

kernel/bpf/verifier.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -10384,9 +10384,14 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
		case BPF_MAP_TYPE_HASH:
		case BPF_MAP_TYPE_LRU_HASH:
		case BPF_MAP_TYPE_ARRAY:
		case BPF_MAP_TYPE_PERCPU_HASH:
		case BPF_MAP_TYPE_PERCPU_ARRAY:
		case BPF_MAP_TYPE_LRU_PERCPU_HASH:
		case BPF_MAP_TYPE_ARRAY_OF_MAPS:
		case BPF_MAP_TYPE_HASH_OF_MAPS:
		if (!is_preallocated_map(map)) {
		verbose(env,
		"Sleepable programs can only use preallocated hash maps\n");
		"Sleepable programs can only use preallocated maps\n");
		return -EINVAL;
		}
		break;