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bpf/verifier: Optimize ID mapping reset in states_equal

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Currently, reset_idmap_scratch() performs a 4.7KB memset() in every
states_equal() call. Optimize this by using a counter to track used
ID mappings, replacing the O(N) memset() with an O(1) reset and
bounding the search loop in check_ids().

Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20260120023234.77673-1-realwujing@gmail.com
This commit is contained in:
Qiliang Yuan 2026-01-20 10:32:34 +08:00 committed by Andrii Nakryiko
parent 713edc7144
commit f81c07a6e9
2 changed files with 15 additions and 9 deletions
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1
include/linux/bpf_verifier.h
View File

@ -692,6 +692,7 @@ struct bpf_id_pair {
struct bpf_idmap {
u32 tmp_id_gen;
u32 cnt;
struct bpf_id_pair map[BPF_ID_MAP_SIZE];
};

23
kernel/bpf/verifier.c
View File

@ -19000,18 +19000,21 @@ static bool check_ids(u32 old_id, u32 cur_id, struct bpf_idmap *idmap)
if (old_id == 0) /* cur_id == 0 as well */
return true;
for (i = 0; i < BPF_ID_MAP_SIZE; i++) {
if (!map[i].old) {
/* Reached an empty slot; haven't seen this id before */
map[i].old = old_id;
map[i].cur = cur_id;
return true;
}
for (i = 0; i < idmap->cnt; i++) {
if (map[i].old == old_id)
return map[i].cur == cur_id;
if (map[i].cur == cur_id)
return false;
}
/* Reached the end of known mappings; haven't seen this id before */
if (idmap->cnt < BPF_ID_MAP_SIZE) {
map[idmap->cnt].old = old_id;
map[idmap->cnt].cur = cur_id;
idmap->cnt++;
return true;
}
/* We ran out of idmap slots, which should be impossible */
WARN_ON_ONCE(1);
return false;
@ -19520,8 +19523,10 @@ static bool func_states_equal(struct bpf_verifier_env *env, struct bpf_func_stat
static void reset_idmap_scratch(struct bpf_verifier_env *env)
{
env->idmap_scratch.tmp_id_gen = env->id_gen;
memset(&env->idmap_scratch.map, 0, sizeof(env->idmap_scratch.map));
struct bpf_idmap *idmap = &env->idmap_scratch;
idmap->tmp_id_gen = env->id_gen;
idmap->cnt = 0;
}
static bool states_equal(struct bpf_verifier_env *env,