[PATCH v2 4/6] selftests/bpf: Add test case for bpf_list_add_impl

[Chengkaitao <pilgrimtao@gmail.com>]

From: Kaitao Cheng <chengkaitao@kylinos.cn>

Extend refcounted_kptr test (test_list_add_del) to exercise bpf_list_add:
add a second node after the first, then bpf_list_del both nodes.

Signed-off-by: Kaitao Cheng <chengkaitao@kylinos.cn>
---
 .../testing/selftests/bpf/bpf_experimental.h  | 13 +++++
 .../selftests/bpf/progs/refcounted_kptr.c     | 51 +++++++++++++++----
 2 files changed, 53 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index c7c950e10501..dc3919deab89 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -109,6 +109,19 @@ extern struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head) __ksy
  */
 extern struct bpf_list_node *bpf_list_del(struct bpf_list_node *node) __ksym;
 
+/* Description
+ *	Insert 'node' after 'prev' in the BPF linked list. Both must be in the
+ *	same list; 'prev' must be in the list. The 'meta' and 'off' parameters
+ *	are rewritten by the verifier, no need for BPF programs to set them.
+ * Returns
+ *	0 on success, -EINVAL if prev is not in a list or node is already in a list.
+ */
+extern int bpf_list_add_impl(struct bpf_list_node *prev, struct bpf_list_node *node,
+			     void *meta, __u64 off) __ksym;
+
+/* Convenience macro to wrap over bpf_list_add_impl */
+#define bpf_list_add(prev, node) bpf_list_add_impl(prev, node, NULL, 0)
+
 /* Description
  *	Remove 'node' from rbtree with root 'root'
  * Returns
diff --git a/tools/testing/selftests/bpf/progs/refcounted_kptr.c b/tools/testing/selftests/bpf/progs/refcounted_kptr.c
index 86f7f5f8e4c8..a3d5995d4302 100644
--- a/tools/testing/selftests/bpf/progs/refcounted_kptr.c
+++ b/tools/testing/selftests/bpf/progs/refcounted_kptr.c
@@ -367,18 +367,19 @@ long insert_rbtree_and_stash__del_tree_##rem_tree(void *ctx)		\
 INSERT_STASH_READ(true, "insert_stash_read: remove from tree");
 INSERT_STASH_READ(false, "insert_stash_read: don't remove from tree");
 
-/* Insert node_data into both rbtree and list, remove from tree, then remove
- * from list via bpf_list_del using the node obtained from the tree.
+/* Insert one node in tree and list, remove it from tree, add a second
+ * node after it in list with bpf_list_add, then remove both nodes from
+ * list via bpf_list_del.
  */
 SEC("tc")
-__description("test_bpf_list_del: remove an arbitrary node from the list")
+__description("test_list_add_del: test bpf_list_add/del")
 __success __retval(0)
-long test_bpf_list_del(void *ctx)
+long test_list_add_del(void *ctx)
 {
-	long err;
+	long err = 0;
 	struct bpf_rb_node *rb;
-	struct bpf_list_node *l;
-	struct node_data *n;
+	struct bpf_list_node *l, *l_1;
+	struct node_data *n, *n_1, *m_1;
 
 	err = __insert_in_tree_and_list(&head, &root, &lock);
 	if (err)
@@ -397,15 +398,43 @@ long test_bpf_list_del(void *ctx)
 		return -5;
 	n = container_of(rb, struct node_data, r);
 
+	n_1 = bpf_obj_new(typeof(*n_1));
+	if (!n_1) {
+		bpf_obj_drop(n);
+		return -1;
+	}
+	m_1 = bpf_refcount_acquire(n_1);
+	if (!m_1) {
+		bpf_obj_drop(n);
+		bpf_obj_drop(n_1);
+		return -1;
+	}
+
 	bpf_spin_lock(&lock);
+	if (bpf_list_add(&n->l, &n_1->l)) {
+		bpf_spin_unlock(&lock);
+		bpf_obj_drop(n);
+		bpf_obj_drop(m_1);
+		return -8;
+	}
+
 	l = bpf_list_del(&n->l);
+	l_1 = bpf_list_del(&m_1->l);
 	bpf_spin_unlock(&lock);
 	bpf_obj_drop(n);
-	if (!l)
-		return -6;
+	bpf_obj_drop(m_1);
 
-	bpf_obj_drop(container_of(l, struct node_data, l));
-	return 0;
+	if (l)
+		bpf_obj_drop(container_of(l, struct node_data, l));
+	else
+		err = -6;
+
+	if (l_1)
+		bpf_obj_drop(container_of(l_1, struct node_data, l));
+	else
+		err = -6;
+
+	return err;
 }
 
 SEC("tc")
-- 
2.50.1 (Apple Git-155)