fs/timerfd.c - LeafOS-Devices/android_kernel_samsung_gta4xl - Gitiles

 // SPDX-License-Identifier: GPL-2.0
 /*
  *  fs/timerfd.c
  *
  *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
  *
  *
  *  Thanks to Thomas Gleixner for code reviews and useful comments.
  *
  */

 #include <linux/alarmtimer.h>
 #include <linux/file.h>
 #include <linux/poll.h>
 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/sched.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/time.h>
 #include <linux/hrtimer.h>
 #include <linux/anon_inodes.h>
 #include <linux/timerfd.h>
 #include <linux/syscalls.h>
 #include <linux/compat.h>
 #include <linux/rcupdate.h>

 struct timerfd_ctx {
 	union {
 		struct hrtimer tmr;
 		struct alarm alarm;
 	} t;
 	ktime_t tintv;
 	ktime_t moffs;
 	wait_queue_head_t wqh;
 	u64 ticks;
 	int clockid;
 	short unsigned expired;
 	short unsigned settime_flags;	/* to show in fdinfo */
 	struct rcu_head rcu;
 	struct list_head clist;
 	spinlock_t cancel_lock;
 	bool might_cancel;
 };

 static LIST_HEAD(cancel_list);
 static DEFINE_SPINLOCK(cancel_lock);

 static inline bool isalarm(struct timerfd_ctx *ctx)
 {
 	return ctx->clockid == CLOCK_REALTIME_ALARM ||
 		ctx->clockid == CLOCK_BOOTTIME_ALARM;
 }

 /*
  * This gets called when the timer event triggers. We set the "expired"
  * flag, but we do not re-arm the timer (in case it's necessary,
  * tintv != 0) until the timer is accessed.
  */
 static void timerfd_triggered(struct timerfd_ctx *ctx)
 {
 	unsigned long flags;

 	spin_lock_irqsave(&ctx->wqh.lock, flags);
 	ctx->expired = 1;
 	ctx->ticks++;
 	wake_up_locked(&ctx->wqh);
 	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
 }

 static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
 {
 	struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx,
 					       t.tmr);
 	timerfd_triggered(ctx);
 	return HRTIMER_NORESTART;
 }

 static enum alarmtimer_restart timerfd_alarmproc(struct alarm *alarm,
 	ktime_t now)
 {
 	struct timerfd_ctx *ctx = container_of(alarm, struct timerfd_ctx,
 					       t.alarm);
 	timerfd_triggered(ctx);
 	return ALARMTIMER_NORESTART;
 }

 /*
  * Called when the clock was set to cancel the timers in the cancel
  * list. This will wake up processes waiting on these timers. The
  * wake-up requires ctx->ticks to be non zero, therefore we increment
  * it before calling wake_up_locked().
  */
 void timerfd_clock_was_set(void)
 {
 	ktime_t moffs = ktime_mono_to_real(0);
 	struct timerfd_ctx *ctx;
 	unsigned long flags;

 	rcu_read_lock();
 	list_for_each_entry_rcu(ctx, &cancel_list, clist) {
 		if (!ctx->might_cancel)
 			continue;
 		spin_lock_irqsave(&ctx->wqh.lock, flags);
 		if (ctx->moffs != moffs) {
 			ctx->moffs = KTIME_MAX;
 			ctx->ticks++;
 			wake_up_locked(&ctx->wqh);
 		}
 		spin_unlock_irqrestore(&ctx->wqh.lock, flags);
 	}
 	rcu_read_unlock();
 }

 static void __timerfd_remove_cancel(struct timerfd_ctx *ctx)
 {
 	if (ctx->might_cancel) {
 		ctx->might_cancel = false;
 		spin_lock(&cancel_lock);
 		list_del_rcu(&ctx->clist);
 		spin_unlock(&cancel_lock);
 	}
 }

 static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
 {
 	spin_lock(&ctx->cancel_lock);
 	__timerfd_remove_cancel(ctx);
 	spin_unlock(&ctx->cancel_lock);
 }

 static bool timerfd_canceled(struct timerfd_ctx *ctx)
 {
 	if (!ctx->might_cancel || ctx->moffs != KTIME_MAX)
 		return false;
 	ctx->moffs = ktime_mono_to_real(0);
 	return true;
 }

 static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
 {
 	spin_lock(&ctx->cancel_lock);
 	if ((ctx->clockid == CLOCK_REALTIME ||
 	     ctx->clockid == CLOCK_REALTIME_ALARM) &&
 	    (flags & TFD_TIMER_ABSTIME) && (flags & TFD_TIMER_CANCEL_ON_SET)) {
 		if (!ctx->might_cancel) {
 			ctx->might_cancel = true;
 			spin_lock(&cancel_lock);
 			list_add_rcu(&ctx->clist, &cancel_list);
 			spin_unlock(&cancel_lock);
 		}
 	} else {
 		__timerfd_remove_cancel(ctx);
 	}
 	spin_unlock(&ctx->cancel_lock);
 }

 static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
 {
 	ktime_t remaining;

 	if (isalarm(ctx))
 		remaining = alarm_expires_remaining(&ctx->t.alarm);
 	else
 		remaining = hrtimer_expires_remaining_adjusted(&ctx->t.tmr);

 	return remaining < 0 ? 0: remaining;
 }

 static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
 			 const struct itimerspec64 *ktmr)
 {
 	enum hrtimer_mode htmode;
 	ktime_t texp;
 	int clockid = ctx->clockid;

 	htmode = (flags & TFD_TIMER_ABSTIME) ?
 		HRTIMER_MODE_ABS: HRTIMER_MODE_REL;

 	texp = timespec64_to_ktime(ktmr->it_value);
 	ctx->expired = 0;
 	ctx->ticks = 0;
 	ctx->tintv = timespec64_to_ktime(ktmr->it_interval);

 	if (isalarm(ctx)) {
 		alarm_init(&ctx->t.alarm,
 			   ctx->clockid == CLOCK_REALTIME_ALARM ?
 			   ALARM_REALTIME : ALARM_BOOTTIME,
 			   timerfd_alarmproc);
 	} else {
 		hrtimer_init(&ctx->t.tmr, clockid, htmode);
 		hrtimer_set_expires(&ctx->t.tmr, texp);
 		ctx->t.tmr.function = timerfd_tmrproc;
 	}

 	if (texp != 0) {
 		if (isalarm(ctx)) {
 			if (flags & TFD_TIMER_ABSTIME)
 				alarm_start(&ctx->t.alarm, texp);
 			else
 				alarm_start_relative(&ctx->t.alarm, texp);
 		} else {
 			hrtimer_start(&ctx->t.tmr, texp, htmode);
 		}

 		if (timerfd_canceled(ctx))
 			return -ECANCELED;
 	}

 	ctx->settime_flags = flags & TFD_SETTIME_FLAGS;
 	return 0;
 }

 static int timerfd_release(struct inode *inode, struct file *file)
 {
 	struct timerfd_ctx *ctx = file->private_data;

 	timerfd_remove_cancel(ctx);

 	if (isalarm(ctx))
 		alarm_cancel(&ctx->t.alarm);
 	else
 		hrtimer_cancel(&ctx->t.tmr);
 	kfree_rcu(ctx, rcu);
 	return 0;
 }

 static unsigned int timerfd_poll(struct file *file, poll_table *wait)
 {
 	struct timerfd_ctx *ctx = file->private_data;
 	unsigned int events = 0;
 	unsigned long flags;

 	poll_wait(file, &ctx->wqh, wait);

 	spin_lock_irqsave(&ctx->wqh.lock, flags);
 	if (ctx->ticks)
 		events |= POLLIN;
 	spin_unlock_irqrestore(&ctx->wqh.lock, flags);

 	return events;
 }

 static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
 			    loff_t *ppos)
 {
 	struct timerfd_ctx *ctx = file->private_data;
 	ssize_t res;
 	u64 ticks = 0;

 	if (count < sizeof(ticks))
 		return -EINVAL;
 	spin_lock_irq(&ctx->wqh.lock);
 	if (file->f_flags & O_NONBLOCK)
 		res = -EAGAIN;
 	else
 		res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);

 	/*
 	 * If clock has changed, we do not care about the
 	 * ticks and we do not rearm the timer. Userspace must
 	 * reevaluate anyway.
 	 */
 	if (timerfd_canceled(ctx)) {
 		ctx->ticks = 0;
 		ctx->expired = 0;
 		res = -ECANCELED;
 	}

 	if (ctx->ticks) {
 		ticks = ctx->ticks;

 		if (ctx->expired && ctx->tintv) {
 			/*
 			 * If tintv != 0, this is a periodic timer that
 			 * needs to be re-armed. We avoid doing it in the timer
 			 * callback to avoid DoS attacks specifying a very
 			 * short timer period.
 			 */
 			if (isalarm(ctx)) {
 				ticks += alarm_forward_now(
 					&ctx->t.alarm, ctx->tintv) - 1;
 				alarm_restart(&ctx->t.alarm);
 			} else {
 				ticks += hrtimer_forward_now(&ctx->t.tmr,
 							     ctx->tintv) - 1;
 				hrtimer_restart(&ctx->t.tmr);
 			}
 		}
 		ctx->expired = 0;
 		ctx->ticks = 0;
 	}
 	spin_unlock_irq(&ctx->wqh.lock);
 	if (ticks)
 		res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
 	return res;
 }

 #ifdef CONFIG_PROC_FS
 static void timerfd_show(struct seq_file *m, struct file *file)
 {
 	struct timerfd_ctx *ctx = file->private_data;
 	struct itimerspec t;

 	spin_lock_irq(&ctx->wqh.lock);
 	t.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
 	t.it_interval = ktime_to_timespec(ctx->tintv);
 	spin_unlock_irq(&ctx->wqh.lock);

 	seq_printf(m,
 		   "clockid: %d\n"
 		   "ticks: %llu\n"
 		   "settime flags: 0%o\n"
 		   "it_value: (%llu, %llu)\n"
 		   "it_interval: (%llu, %llu)\n",
 		   ctx->clockid,
 		   (unsigned long long)ctx->ticks,
 		   ctx->settime_flags,
 		   (unsigned long long)t.it_value.tv_sec,
 		   (unsigned long long)t.it_value.tv_nsec,
 		   (unsigned long long)t.it_interval.tv_sec,
 		   (unsigned long long)t.it_interval.tv_nsec);
 }
 #else
 #define timerfd_show NULL
 #endif

 #ifdef CONFIG_CHECKPOINT_RESTORE
 static long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	struct timerfd_ctx *ctx = file->private_data;
 	int ret = 0;

 	switch (cmd) {
 	case TFD_IOC_SET_TICKS: {
 		u64 ticks;

 		if (copy_from_user(&ticks, (u64 __user *)arg, sizeof(ticks)))
 			return -EFAULT;
 		if (!ticks)
 			return -EINVAL;

 		spin_lock_irq(&ctx->wqh.lock);
 		if (!timerfd_canceled(ctx)) {
 			ctx->ticks = ticks;
 			wake_up_locked(&ctx->wqh);
 		} else
 			ret = -ECANCELED;
 		spin_unlock_irq(&ctx->wqh.lock);
 		break;
 	}
 	default:
 		ret = -ENOTTY;
 		break;
 	}

 	return ret;
 }
 #else
 #define timerfd_ioctl NULL
 #endif

 static const struct file_operations timerfd_fops = {
 	.release	= timerfd_release,
 	.poll		= timerfd_poll,
 	.read		= timerfd_read,
 	.llseek		= noop_llseek,
 	.show_fdinfo	= timerfd_show,
 	.unlocked_ioctl	= timerfd_ioctl,
 };

 static int timerfd_fget(int fd, struct fd *p)
 {
 	struct fd f = fdget(fd);
 	if (!f.file)
 		return -EBADF;
 	if (f.file->f_op != &timerfd_fops) {
 		fdput(f);
 		return -EINVAL;
 	}
 	*p = f;
 	return 0;
 }

 SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
 {
 	int ufd;
 	struct timerfd_ctx *ctx;

 	/* Check the TFD_* constants for consistency.  */
 	BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
 	BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);

 	if ((flags & ~TFD_CREATE_FLAGS) ||
 	    (clockid != CLOCK_MONOTONIC &&
 	     clockid != CLOCK_REALTIME &&
 	     clockid != CLOCK_REALTIME_ALARM &&
 	     clockid != CLOCK_BOOTTIME &&
 	     clockid != CLOCK_BOOTTIME_ALARM))
 		return -EINVAL;

 	if ((clockid == CLOCK_REALTIME_ALARM ||
 	     clockid == CLOCK_BOOTTIME_ALARM) &&
 	    !capable(CAP_WAKE_ALARM))
 		return -EPERM;

 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
 	if (!ctx)
 		return -ENOMEM;

 	init_waitqueue_head(&ctx->wqh);
 	spin_lock_init(&ctx->cancel_lock);
 	ctx->clockid = clockid;

 	if (isalarm(ctx))
 		alarm_init(&ctx->t.alarm,
 			   ctx->clockid == CLOCK_REALTIME_ALARM ?
 			   ALARM_REALTIME : ALARM_BOOTTIME,
 			   timerfd_alarmproc);
 	else
 		hrtimer_init(&ctx->t.tmr, clockid, HRTIMER_MODE_ABS);

 	ctx->moffs = ktime_mono_to_real(0);

 	ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
 			       O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
 	if (ufd < 0)
 		kfree(ctx);

 	return ufd;
 }

 static int do_timerfd_settime(int ufd, int flags,
 		const struct itimerspec64 *new,
 		struct itimerspec64 *old)
 {
 	struct fd f;
 	struct timerfd_ctx *ctx;
 	int ret;

 	if ((flags & ~TFD_SETTIME_FLAGS) ||
 		 !itimerspec64_valid(new))
 		return -EINVAL;

 	ret = timerfd_fget(ufd, &f);
 	if (ret)
 		return ret;
 	ctx = f.file->private_data;

 	if (isalarm(ctx) && !capable(CAP_WAKE_ALARM)) {
 		fdput(f);
 		return -EPERM;
 	}

 	timerfd_setup_cancel(ctx, flags);

 	/*
 	 * We need to stop the existing timer before reprogramming
 	 * it to the new values.
 	 */
 	for (;;) {
 		spin_lock_irq(&ctx->wqh.lock);

 		if (isalarm(ctx)) {
 			if (alarm_try_to_cancel(&ctx->t.alarm) >= 0)
 				break;
 		} else {
 			if (hrtimer_try_to_cancel(&ctx->t.tmr) >= 0)
 				break;
 		}
 		spin_unlock_irq(&ctx->wqh.lock);
 		cpu_relax();
 	}

 	/*
 	 * If the timer is expired and it's periodic, we need to advance it
 	 * because the caller may want to know the previous expiration time.
 	 * We do not update "ticks" and "expired" since the timer will be
 	 * re-programmed again in the following timerfd_setup() call.
 	 */
 	if (ctx->expired && ctx->tintv) {
 		if (isalarm(ctx))
 			alarm_forward_now(&ctx->t.alarm, ctx->tintv);
 		else
 			hrtimer_forward_now(&ctx->t.tmr, ctx->tintv);
 	}

 	old->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
 	old->it_interval = ktime_to_timespec64(ctx->tintv);

 	/*
 	 * Re-program the timer to the new value ...
 	 */
 	ret = timerfd_setup(ctx, flags, new);

 	spin_unlock_irq(&ctx->wqh.lock);
 	fdput(f);
 	return ret;
 }

 static int do_timerfd_gettime(int ufd, struct itimerspec64 *t)
 {
 	struct fd f;
 	struct timerfd_ctx *ctx;
 	int ret = timerfd_fget(ufd, &f);
 	if (ret)
 		return ret;
 	ctx = f.file->private_data;

 	spin_lock_irq(&ctx->wqh.lock);
 	if (ctx->expired && ctx->tintv) {
 		ctx->expired = 0;

 		if (isalarm(ctx)) {
 			ctx->ticks +=
 				alarm_forward_now(
 					&ctx->t.alarm, ctx->tintv) - 1;
 			alarm_restart(&ctx->t.alarm);
 		} else {
 			ctx->ticks +=
 				hrtimer_forward_now(&ctx->t.tmr, ctx->tintv)
 				- 1;
 			hrtimer_restart(&ctx->t.tmr);
 		}
 	}
 	t->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
 	t->it_interval = ktime_to_timespec64(ctx->tintv);
 	spin_unlock_irq(&ctx->wqh.lock);
 	fdput(f);
 	return 0;
 }

 SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
 		const struct itimerspec __user *, utmr,
 		struct itimerspec __user *, otmr)
 {
 	struct itimerspec64 new, old;
 	int ret;

 	if (get_itimerspec64(&new, utmr))
 		return -EFAULT;
 	ret = do_timerfd_settime(ufd, flags, &new, &old);
 	if (ret)
 		return ret;
 	if (otmr && put_itimerspec64(&old, otmr))
 		return -EFAULT;

 	return ret;
 }

 SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
 {
 	struct itimerspec64 kotmr;
 	int ret = do_timerfd_gettime(ufd, &kotmr);
 	if (ret)
 		return ret;
 	return put_itimerspec64(&kotmr, otmr) ? -EFAULT : 0;
 }

 #ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
 		const struct compat_itimerspec __user *, utmr,
 		struct compat_itimerspec __user *, otmr)
 {
 	struct itimerspec64 new, old;
 	int ret;

 	if (get_compat_itimerspec64(&new, utmr))
 		return -EFAULT;
 	ret = do_timerfd_settime(ufd, flags, &new, &old);
 	if (ret)
 		return ret;
 	if (otmr && put_compat_itimerspec64(&old, otmr))
 		return -EFAULT;
 	return ret;
 }

 COMPAT_SYSCALL_DEFINE2(timerfd_gettime, int, ufd,
 		struct compat_itimerspec __user *, otmr)
 {
 	struct itimerspec64 kotmr;
 	int ret = do_timerfd_gettime(ufd, &kotmr);
 	if (ret)
 		return ret;
 	return put_compat_itimerspec64(&kotmr, otmr) ? -EFAULT : 0;
 }
 #endif
	// SPDX-License-Identifier: GPL-2.0
	/*
	* fs/timerfd.c
	*
	* Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
	*
	*
	* Thanks to Thomas Gleixner for code reviews and useful comments.
	*
	*/

	#include <linux/alarmtimer.h>
	#include <linux/file.h>
	#include <linux/poll.h>
	#include <linux/init.h>
	#include <linux/fs.h>
	#include <linux/sched.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/list.h>
	#include <linux/spinlock.h>
	#include <linux/time.h>
	#include <linux/hrtimer.h>
	#include <linux/anon_inodes.h>
	#include <linux/timerfd.h>
	#include <linux/syscalls.h>
	#include <linux/compat.h>
	#include <linux/rcupdate.h>

	struct timerfd_ctx {
	union {
	struct hrtimer tmr;
	struct alarm alarm;
	} t;
	ktime_t tintv;
	ktime_t moffs;
	wait_queue_head_t wqh;
	u64 ticks;
	int clockid;
	short unsigned expired;
	short unsigned settime_flags; /* to show in fdinfo */
	struct rcu_head rcu;
	struct list_head clist;
	spinlock_t cancel_lock;
	bool might_cancel;
	};

	static LIST_HEAD(cancel_list);
	static DEFINE_SPINLOCK(cancel_lock);

	static inline bool isalarm(struct timerfd_ctx *ctx)
	{
	return ctx->clockid == CLOCK_REALTIME_ALARM \|\|
	ctx->clockid == CLOCK_BOOTTIME_ALARM;
	}

	/*
	* This gets called when the timer event triggers. We set the "expired"
	* flag, but we do not re-arm the timer (in case it's necessary,
	* tintv != 0) until the timer is accessed.
	*/
	static void timerfd_triggered(struct timerfd_ctx *ctx)
	{
	unsigned long flags;

	spin_lock_irqsave(&ctx->wqh.lock, flags);
	ctx->expired = 1;
	ctx->ticks++;
	wake_up_locked(&ctx->wqh);
	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
	}

	static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
	{
	struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx,
	t.tmr);
	timerfd_triggered(ctx);
	return HRTIMER_NORESTART;
	}

	static enum alarmtimer_restart timerfd_alarmproc(struct alarm *alarm,
	ktime_t now)
	{
	struct timerfd_ctx *ctx = container_of(alarm, struct timerfd_ctx,
	t.alarm);
	timerfd_triggered(ctx);
	return ALARMTIMER_NORESTART;
	}

	/*
	* Called when the clock was set to cancel the timers in the cancel
	* list. This will wake up processes waiting on these timers. The
	* wake-up requires ctx->ticks to be non zero, therefore we increment
	* it before calling wake_up_locked().
	*/
	void timerfd_clock_was_set(void)
	{
	ktime_t moffs = ktime_mono_to_real(0);
	struct timerfd_ctx *ctx;
	unsigned long flags;

	rcu_read_lock();
	list_for_each_entry_rcu(ctx, &cancel_list, clist) {
	if (!ctx->might_cancel)
	continue;
	spin_lock_irqsave(&ctx->wqh.lock, flags);
	if (ctx->moffs != moffs) {
	ctx->moffs = KTIME_MAX;
	ctx->ticks++;
	wake_up_locked(&ctx->wqh);
	}
	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
	}
	rcu_read_unlock();
	}

	static void __timerfd_remove_cancel(struct timerfd_ctx *ctx)
	{
	if (ctx->might_cancel) {
	ctx->might_cancel = false;
	spin_lock(&cancel_lock);
	list_del_rcu(&ctx->clist);
	spin_unlock(&cancel_lock);
	}
	}

	static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
	{
	spin_lock(&ctx->cancel_lock);
	__timerfd_remove_cancel(ctx);
	spin_unlock(&ctx->cancel_lock);
	}

	static bool timerfd_canceled(struct timerfd_ctx *ctx)
	{
	if (!ctx->might_cancel \|\| ctx->moffs != KTIME_MAX)
	return false;
	ctx->moffs = ktime_mono_to_real(0);
	return true;
	}

	static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
	{
	spin_lock(&ctx->cancel_lock);
	if ((ctx->clockid == CLOCK_REALTIME \|\|
	ctx->clockid == CLOCK_REALTIME_ALARM) &&
	(flags & TFD_TIMER_ABSTIME) && (flags & TFD_TIMER_CANCEL_ON_SET)) {
	if (!ctx->might_cancel) {
	ctx->might_cancel = true;
	spin_lock(&cancel_lock);
	list_add_rcu(&ctx->clist, &cancel_list);
	spin_unlock(&cancel_lock);
	}
	} else {
	__timerfd_remove_cancel(ctx);
	}
	spin_unlock(&ctx->cancel_lock);
	}

	static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
	{
	ktime_t remaining;

	if (isalarm(ctx))
	remaining = alarm_expires_remaining(&ctx->t.alarm);
	else
	remaining = hrtimer_expires_remaining_adjusted(&ctx->t.tmr);

	return remaining < 0 ? 0: remaining;
	}

	static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
	const struct itimerspec64 *ktmr)
	{
	enum hrtimer_mode htmode;
	ktime_t texp;
	int clockid = ctx->clockid;

	htmode = (flags & TFD_TIMER_ABSTIME) ?
	HRTIMER_MODE_ABS: HRTIMER_MODE_REL;

	texp = timespec64_to_ktime(ktmr->it_value);
	ctx->expired = 0;
	ctx->ticks = 0;
	ctx->tintv = timespec64_to_ktime(ktmr->it_interval);

	if (isalarm(ctx)) {
	alarm_init(&ctx->t.alarm,
	ctx->clockid == CLOCK_REALTIME_ALARM ?
	ALARM_REALTIME : ALARM_BOOTTIME,
	timerfd_alarmproc);
	} else {
	hrtimer_init(&ctx->t.tmr, clockid, htmode);
	hrtimer_set_expires(&ctx->t.tmr, texp);
	ctx->t.tmr.function = timerfd_tmrproc;
	}

	if (texp != 0) {
	if (isalarm(ctx)) {
	if (flags & TFD_TIMER_ABSTIME)
	alarm_start(&ctx->t.alarm, texp);
	else
	alarm_start_relative(&ctx->t.alarm, texp);
	} else {
	hrtimer_start(&ctx->t.tmr, texp, htmode);
	}

	if (timerfd_canceled(ctx))
	return -ECANCELED;
	}

	ctx->settime_flags = flags & TFD_SETTIME_FLAGS;
	return 0;
	}

	static int timerfd_release(struct inode inode, struct file file)
	{
	struct timerfd_ctx *ctx = file->private_data;

	timerfd_remove_cancel(ctx);

	if (isalarm(ctx))
	alarm_cancel(&ctx->t.alarm);
	else
	hrtimer_cancel(&ctx->t.tmr);
	kfree_rcu(ctx, rcu);
	return 0;
	}

	static unsigned int timerfd_poll(struct file file, poll_table wait)
	{
	struct timerfd_ctx *ctx = file->private_data;
	unsigned int events = 0;
	unsigned long flags;

	poll_wait(file, &ctx->wqh, wait);

	spin_lock_irqsave(&ctx->wqh.lock, flags);
	if (ctx->ticks)
	events \|= POLLIN;
	spin_unlock_irqrestore(&ctx->wqh.lock, flags);

	return events;
	}

	static ssize_t timerfd_read(struct file file, char __user buf, size_t count,
	loff_t *ppos)
	{
	struct timerfd_ctx *ctx = file->private_data;
	ssize_t res;
	u64 ticks = 0;

	if (count < sizeof(ticks))
	return -EINVAL;
	spin_lock_irq(&ctx->wqh.lock);
	if (file->f_flags & O_NONBLOCK)
	res = -EAGAIN;
	else
	res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);

	/*
	* If clock has changed, we do not care about the
	* ticks and we do not rearm the timer. Userspace must
	* reevaluate anyway.
	*/
	if (timerfd_canceled(ctx)) {
	ctx->ticks = 0;
	ctx->expired = 0;
	res = -ECANCELED;
	}

	if (ctx->ticks) {
	ticks = ctx->ticks;

	if (ctx->expired && ctx->tintv) {
	/*
	* If tintv != 0, this is a periodic timer that
	* needs to be re-armed. We avoid doing it in the timer
	* callback to avoid DoS attacks specifying a very
	* short timer period.
	*/
	if (isalarm(ctx)) {
	ticks += alarm_forward_now(
	&ctx->t.alarm, ctx->tintv) - 1;
	alarm_restart(&ctx->t.alarm);
	} else {
	ticks += hrtimer_forward_now(&ctx->t.tmr,
	ctx->tintv) - 1;
	hrtimer_restart(&ctx->t.tmr);
	}
	}
	ctx->expired = 0;
	ctx->ticks = 0;
	}
	spin_unlock_irq(&ctx->wqh.lock);
	if (ticks)
	res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
	return res;
	}

	#ifdef CONFIG_PROC_FS
	static void timerfd_show(struct seq_file m, struct file file)
	{
	struct timerfd_ctx *ctx = file->private_data;
	struct itimerspec t;

	spin_lock_irq(&ctx->wqh.lock);
	t.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
	t.it_interval = ktime_to_timespec(ctx->tintv);
	spin_unlock_irq(&ctx->wqh.lock);

	seq_printf(m,
	"clockid: %d\n"
	"ticks: %llu\n"
	"settime flags: 0%o\n"
	"it_value: (%llu, %llu)\n"
	"it_interval: (%llu, %llu)\n",
	ctx->clockid,
	(unsigned long long)ctx->ticks,
	ctx->settime_flags,
	(unsigned long long)t.it_value.tv_sec,
	(unsigned long long)t.it_value.tv_nsec,
	(unsigned long long)t.it_interval.tv_sec,
	(unsigned long long)t.it_interval.tv_nsec);
	}
	#else
	#define timerfd_show NULL
	#endif

	#ifdef CONFIG_CHECKPOINT_RESTORE
	static long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
	{
	struct timerfd_ctx *ctx = file->private_data;
	int ret = 0;

	switch (cmd) {
	case TFD_IOC_SET_TICKS: {
	u64 ticks;

	if (copy_from_user(&ticks, (u64 __user *)arg, sizeof(ticks)))
	return -EFAULT;
	if (!ticks)
	return -EINVAL;

	spin_lock_irq(&ctx->wqh.lock);
	if (!timerfd_canceled(ctx)) {
	ctx->ticks = ticks;
	wake_up_locked(&ctx->wqh);
	} else
	ret = -ECANCELED;
	spin_unlock_irq(&ctx->wqh.lock);
	break;
	}
	default:
	ret = -ENOTTY;
	break;
	}

	return ret;
	}
	#else
	#define timerfd_ioctl NULL
	#endif

	static const struct file_operations timerfd_fops = {
	.release = timerfd_release,
	.poll = timerfd_poll,
	.read = timerfd_read,
	.llseek = noop_llseek,
	.show_fdinfo = timerfd_show,
	.unlocked_ioctl = timerfd_ioctl,
	};

	static int timerfd_fget(int fd, struct fd *p)
	{
	struct fd f = fdget(fd);
	if (!f.file)
	return -EBADF;
	if (f.file->f_op != &timerfd_fops) {
	fdput(f);
	return -EINVAL;
	}
	*p = f;
	return 0;
	}

	SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
	{
	int ufd;
	struct timerfd_ctx *ctx;

	/* Check the TFD_* constants for consistency. */
	BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
	BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);

	if ((flags & ~TFD_CREATE_FLAGS) \|\|
	(clockid != CLOCK_MONOTONIC &&
	clockid != CLOCK_REALTIME &&
	clockid != CLOCK_REALTIME_ALARM &&
	clockid != CLOCK_BOOTTIME &&
	clockid != CLOCK_BOOTTIME_ALARM))
	return -EINVAL;

	if ((clockid == CLOCK_REALTIME_ALARM \|\|
	clockid == CLOCK_BOOTTIME_ALARM) &&
	!capable(CAP_WAKE_ALARM))
	return -EPERM;

	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
	if (!ctx)
	return -ENOMEM;

	init_waitqueue_head(&ctx->wqh);
	spin_lock_init(&ctx->cancel_lock);
	ctx->clockid = clockid;

	if (isalarm(ctx))
	alarm_init(&ctx->t.alarm,
	ctx->clockid == CLOCK_REALTIME_ALARM ?
	ALARM_REALTIME : ALARM_BOOTTIME,
	timerfd_alarmproc);
	else
	hrtimer_init(&ctx->t.tmr, clockid, HRTIMER_MODE_ABS);

	ctx->moffs = ktime_mono_to_real(0);

	ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
	O_RDWR \| (flags & TFD_SHARED_FCNTL_FLAGS));
	if (ufd < 0)
	kfree(ctx);

	return ufd;
	}

	static int do_timerfd_settime(int ufd, int flags,
	const struct itimerspec64 *new,
	struct itimerspec64 *old)
	{
	struct fd f;
	struct timerfd_ctx *ctx;
	int ret;

	if ((flags & ~TFD_SETTIME_FLAGS) \|\|
	!itimerspec64_valid(new))
	return -EINVAL;

	ret = timerfd_fget(ufd, &f);
	if (ret)
	return ret;
	ctx = f.file->private_data;

	if (isalarm(ctx) && !capable(CAP_WAKE_ALARM)) {
	fdput(f);
	return -EPERM;
	}

	timerfd_setup_cancel(ctx, flags);

	/*
	* We need to stop the existing timer before reprogramming
	* it to the new values.
	*/
	for (;;) {
	spin_lock_irq(&ctx->wqh.lock);

	if (isalarm(ctx)) {
	if (alarm_try_to_cancel(&ctx->t.alarm) >= 0)
	break;
	} else {
	if (hrtimer_try_to_cancel(&ctx->t.tmr) >= 0)
	break;
	}
	spin_unlock_irq(&ctx->wqh.lock);
	cpu_relax();
	}

	/*
	* If the timer is expired and it's periodic, we need to advance it
	* because the caller may want to know the previous expiration time.
	* We do not update "ticks" and "expired" since the timer will be
	* re-programmed again in the following timerfd_setup() call.
	*/
	if (ctx->expired && ctx->tintv) {
	if (isalarm(ctx))
	alarm_forward_now(&ctx->t.alarm, ctx->tintv);
	else
	hrtimer_forward_now(&ctx->t.tmr, ctx->tintv);
	}

	old->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
	old->it_interval = ktime_to_timespec64(ctx->tintv);

	/*
	* Re-program the timer to the new value ...
	*/
	ret = timerfd_setup(ctx, flags, new);

	spin_unlock_irq(&ctx->wqh.lock);
	fdput(f);
	return ret;
	}

	static int do_timerfd_gettime(int ufd, struct itimerspec64 *t)
	{
	struct fd f;
	struct timerfd_ctx *ctx;
	int ret = timerfd_fget(ufd, &f);
	if (ret)
	return ret;
	ctx = f.file->private_data;

	spin_lock_irq(&ctx->wqh.lock);
	if (ctx->expired && ctx->tintv) {
	ctx->expired = 0;

	if (isalarm(ctx)) {
	ctx->ticks +=
	alarm_forward_now(
	&ctx->t.alarm, ctx->tintv) - 1;
	alarm_restart(&ctx->t.alarm);
	} else {
	ctx->ticks +=
	hrtimer_forward_now(&ctx->t.tmr, ctx->tintv)
	- 1;
	hrtimer_restart(&ctx->t.tmr);
	}
	}
	t->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
	t->it_interval = ktime_to_timespec64(ctx->tintv);
	spin_unlock_irq(&ctx->wqh.lock);
	fdput(f);
	return 0;
	}

	SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
	const struct itimerspec __user *, utmr,
	struct itimerspec __user *, otmr)
	{
	struct itimerspec64 new, old;
	int ret;

	if (get_itimerspec64(&new, utmr))
	return -EFAULT;
	ret = do_timerfd_settime(ufd, flags, &new, &old);
	if (ret)
	return ret;
	if (otmr && put_itimerspec64(&old, otmr))
	return -EFAULT;

	return ret;
	}

	SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
	{
	struct itimerspec64 kotmr;
	int ret = do_timerfd_gettime(ufd, &kotmr);
	if (ret)
	return ret;
	return put_itimerspec64(&kotmr, otmr) ? -EFAULT : 0;
	}

	#ifdef CONFIG_COMPAT
	COMPAT_SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
	const struct compat_itimerspec __user *, utmr,
	struct compat_itimerspec __user *, otmr)
	{
	struct itimerspec64 new, old;
	int ret;

	if (get_compat_itimerspec64(&new, utmr))
	return -EFAULT;
	ret = do_timerfd_settime(ufd, flags, &new, &old);
	if (ret)
	return ret;
	if (otmr && put_compat_itimerspec64(&old, otmr))
	return -EFAULT;
	return ret;
	}

	COMPAT_SYSCALL_DEFINE2(timerfd_gettime, int, ufd,
	struct compat_itimerspec __user *, otmr)
	{
	struct itimerspec64 kotmr;
	int ret = do_timerfd_gettime(ufd, &kotmr);
	if (ret)
	return ret;
	return put_compat_itimerspec64(&kotmr, otmr) ? -EFAULT : 0;
	}
	#endif