1 // SPDX-License-Identifier: GPL-2.0-only
2
3 #include <linux/user-return-notifier.h>
4 #include <linux/percpu.h>
5 #include <linux/sched.h>
6 #include <linux/export.h>
7
8 static DEFINE_PER_CPU(struct hlist_head, return_notifier_list);
9
10 /*
11 * Request a notification when the current cpu returns to userspace. Must be
12 * called in atomic context. The notifier will also be called in atomic
13 * context.
14 */
15 void user_return_notifier_register(struct user_return_notifier *urn)
16 {
17 set_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
18 hlist_add_head(&urn->link, this_cpu_ptr(&return_notifier_list));
19 }
20 EXPORT_SYMBOL_GPL(user_return_notifier_register);
21
22 /*
23 * Removes a registered user return notifier. Must be called from atomic
24 * context, and from the same cpu registration occurred in.
25 */
26 void user_return_notifier_unregister(struct user_return_notifier *urn)
27 {
28 hlist_del(&urn->link);
29 if (hlist_empty(this_cpu_ptr(&return_notifier_list)))
30 clear_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
31 }
32 EXPORT_SYMBOL_GPL(user_return_notifier_unregister);
33
34 /* Calls registered user return notifiers */
35 void fire_user_return_notifiers(void)
36 {
37 struct user_return_notifier *urn;
38 struct hlist_node *tmp2;
39 struct hlist_head *head;
40
41 head = &get_cpu_var(return_notifier_list);
42 hlist_for_each_entry_safe(urn, tmp2, head, link)
43 urn->on_user_return(urn);
44 put_cpu_var(return_notifier_list);
45 }
46
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