cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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user-return-notifier.c (1379B)

      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
      8static 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 */
     15void 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}
     20EXPORT_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 */
     26void 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}
     32EXPORT_SYMBOL_GPL(user_return_notifier_unregister);
     33
     34/* Calls registered user return notifiers */
     35void 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}