[PATCH bpf-next v8 1/8] bpf: refactor kfunc checks using table-driven approach in verifier

Chengkaitao
2026-03-16T11:29:03Z

From: Kaitao Cheng <chengkaitao@kylinos.cn>

Replace per-kfunc btf_id chains in list/rbtree/res_lock and graph node
checks with btf_id_in_kfunc_table() and static kfunc tables for easier
maintenance.

Prepare for future extensions to the bpf_list API family.

Signed-off-by: Kaitao Cheng <chengkaitao@kylinos.cn>
---
kernel/bpf/verifier.c | 79 +++++++++++++++++++++++++++++++------------
1 file changed, 57 insertions(+), 22 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4fbacd2149cd..64c1f8343dfa 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -12639,6 +12639,53 @@ BTF_ID(func, bpf_session_is_return)
BTF_ID(func, bpf_stream_vprintk)
BTF_ID(func, bpf_stream_print_stack)

+static const enum special_kfunc_type bpf_list_api_kfuncs[] = {
+ KF_bpf_list_push_front_impl,
+ KF_bpf_list_push_back_impl,
+ KF_bpf_list_pop_front,
+ KF_bpf_list_pop_back,
+ KF_bpf_list_front,
+ KF_bpf_list_back,
+};
+
+/* Kfuncs that take a list node argument (bpf_list_node *). */
+static const enum special_kfunc_type bpf_list_node_api_kfuncs[] = {
+ KF_bpf_list_push_front_impl,
+ KF_bpf_list_push_back_impl,
+};
+
+/* Kfuncs that take an rbtree node argument (bpf_rb_node *). */
+static const enum special_kfunc_type bpf_rbtree_node_api_kfuncs[] = {
+ KF_bpf_rbtree_remove,
+ KF_bpf_rbtree_add_impl,
+ KF_bpf_rbtree_left,
+ KF_bpf_rbtree_right,
+};
+
+static const enum special_kfunc_type bpf_rbtree_api_kfuncs[] = {
+ KF_bpf_rbtree_add_impl,
+ KF_bpf_rbtree_remove,
+ KF_bpf_rbtree_first,
+ KF_bpf_rbtree_root,
+ KF_bpf_rbtree_left,
+ KF_bpf_rbtree_right,
+};
+
+static const enum special_kfunc_type bpf_res_spin_lock_kfuncs[] = {
+ KF_bpf_res_spin_lock,
+ KF_bpf_res_spin_unlock,
+ KF_bpf_res_spin_lock_irqsave,
+ KF_bpf_res_spin_unlock_irqrestore,
+};
+
+static bool btf_id_in_kfunc_table(u32 btf_id, const enum special_kfunc_type *kfuncs, int n)
+{
+ for (int i = 0; i < n; i++)
+ if (btf_id == special_kfunc_list[kfuncs[i]])
+ return true;
+ return false;
+}
+
static bool is_task_work_add_kfunc(u32 func_id)
{
return func_id == special_kfunc_list[KF_bpf_task_work_schedule_signal] ||
@@ -13038,22 +13085,14 @@ static int check_reg_allocation_locked(struct bpf_verifier_env *env, struct bpf_

static bool is_bpf_list_api_kfunc(u32 btf_id)
{
- return btf_id == special_kfunc_list[KF_bpf_list_push_front_impl] ||
- btf_id == special_kfunc_list[KF_bpf_list_push_back_impl] ||
- btf_id == special_kfunc_list[KF_bpf_list_pop_front] ||
- btf_id == special_kfunc_list[KF_bpf_list_pop_back] ||
- btf_id == special_kfunc_list[KF_bpf_list_front] ||
- btf_id == special_kfunc_list[KF_bpf_list_back];
+ return btf_id_in_kfunc_table(btf_id, bpf_list_api_kfuncs,
+ ARRAY_SIZE(bpf_list_api_kfuncs));
}

static bool is_bpf_rbtree_api_kfunc(u32 btf_id)
{
- return btf_id == special_kfunc_list[KF_bpf_rbtree_add_impl] ||
- btf_id == special_kfunc_list[KF_bpf_rbtree_remove] ||
- btf_id == special_kfunc_list[KF_bpf_rbtree_first] ||
- btf_id == special_kfunc_list[KF_bpf_rbtree_root] ||
- btf_id == special_kfunc_list[KF_bpf_rbtree_left] ||
- btf_id == special_kfunc_list[KF_bpf_rbtree_right];
+ return btf_id_in_kfunc_table(btf_id, bpf_rbtree_api_kfuncs,
+ ARRAY_SIZE(bpf_rbtree_api_kfuncs));
}

static bool is_bpf_iter_num_api_kfunc(u32 btf_id)
@@ -13071,10 +13110,8 @@ static bool is_bpf_graph_api_kfunc(u32 btf_id)

static bool is_bpf_res_spin_lock_kfunc(u32 btf_id)
{
- return btf_id == special_kfunc_list[KF_bpf_res_spin_lock] ||
- btf_id == special_kfunc_list[KF_bpf_res_spin_unlock] ||
- btf_id == special_kfunc_list[KF_bpf_res_spin_lock_irqsave] ||
- btf_id == special_kfunc_list[KF_bpf_res_spin_unlock_irqrestore];
+ return btf_id_in_kfunc_table(btf_id, bpf_res_spin_lock_kfuncs,
+ ARRAY_SIZE(bpf_res_spin_lock_kfuncs));
}

static bool is_bpf_arena_kfunc(u32 btf_id)
@@ -13163,14 +13200,12 @@ static bool check_kfunc_is_graph_node_api(struct bpf_verifier_env *env,

switch (node_field_type) {
case BPF_LIST_NODE:
- ret = (kfunc_btf_id == special_kfunc_list[KF_bpf_list_push_front_impl] ||
- kfunc_btf_id == special_kfunc_list[KF_bpf_list_push_back_impl]);
+ ret = btf_id_in_kfunc_table(kfunc_btf_id, bpf_list_node_api_kfuncs,
+ ARRAY_SIZE(bpf_list_node_api_kfuncs));
break;
case BPF_RB_NODE:
- ret = (kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_remove] ||
- kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_add_impl] ||
- kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_left] ||
- kfunc_btf_id == special_kfunc_list[KF_bpf_rbtree_right]);
+ ret = btf_id_in_kfunc_table(kfunc_btf_id, bpf_rbtree_node_api_kfuncs,
+ ARRAY_SIZE(bpf_rbtree_node_api_kfuncs));
break;
default:
verbose(env, "verifier internal error: unexpected graph node argument type %s\n",
--
2.50.1 (Apple Git-155)