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