[PATCH bpf-next v9 4/9] bpf: Introduce the bpf_list_del kfunc.

[Chengkaitao <pilgrimtao@gmail.com>]

From: Kaitao Cheng <chengkaitao@kylinos.cn>

Allow users to remove any node from a linked list.

We have added an additional parameter bpf_list_head *head to
bpf_list_del, as the verifier requires the head parameter to
check whether the lock is being held.

Signed-off-by: Kaitao Cheng <chengkaitao@kylinos.cn>
---
 kernel/bpf/helpers.c  | 10 ++++++++++
 kernel/bpf/verifier.c |  4 ++++
 2 files changed, 14 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 8abb99712043..6dddb2377047 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2471,6 +2471,15 @@ __bpf_kfunc struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head)
 	return __bpf_list_del(head, h->prev);
 }
 
+__bpf_kfunc struct bpf_list_node *bpf_list_del(struct bpf_list_head *head,
+					       struct bpf_list_node *node)
+{
+	struct bpf_list_node_kern *kn = (void *)node;
+
+	/* verifier to guarantee n is a list node rather than the head */
+	return __bpf_list_del(head, &kn->list_head);
+}
+
 __bpf_kfunc struct bpf_list_node *bpf_list_front(struct bpf_list_head *head)
 {
 	struct list_head *h = (struct list_head *)head;
@@ -4557,6 +4566,7 @@ BTF_ID_FLAGS(func, bpf_list_push_front_impl)
 BTF_ID_FLAGS(func, bpf_list_push_back_impl)
 BTF_ID_FLAGS(func, bpf_list_pop_front, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_list_pop_back, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_list_del, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_list_front, KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_list_back, KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index f2d9863bb290..ae8d1f2e32de 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -12480,6 +12480,7 @@ enum special_kfunc_type {
 	KF_bpf_list_push_back_impl,
 	KF_bpf_list_pop_front,
 	KF_bpf_list_pop_back,
+	KF_bpf_list_del,
 	KF_bpf_list_front,
 	KF_bpf_list_back,
 	KF_bpf_cast_to_kern_ctx,
@@ -12540,6 +12541,7 @@ BTF_ID(func, bpf_list_push_front_impl)
 BTF_ID(func, bpf_list_push_back_impl)
 BTF_ID(func, bpf_list_pop_front)
 BTF_ID(func, bpf_list_pop_back)
+BTF_ID(func, bpf_list_del)
 BTF_ID(func, bpf_list_front)
 BTF_ID(func, bpf_list_back)
 BTF_ID(func, bpf_cast_to_kern_ctx)
@@ -12617,6 +12619,7 @@ static const enum special_kfunc_type bpf_list_api_kfuncs[] = {
 	KF_bpf_list_push_back_impl,
 	KF_bpf_list_pop_front,
 	KF_bpf_list_pop_back,
+	KF_bpf_list_del,
 	KF_bpf_list_front,
 	KF_bpf_list_back,
 };
@@ -12625,6 +12628,7 @@ static const enum special_kfunc_type bpf_list_api_kfuncs[] = {
 static const enum special_kfunc_type bpf_list_node_api_kfuncs[] = {
 	KF_bpf_list_push_front_impl,
 	KF_bpf_list_push_back_impl,
+	KF_bpf_list_del,
 };
 
 /* Kfuncs that take an rbtree node argument (bpf_rb_node *). */
-- 
2.50.1 (Apple Git-155)