/*

   * linux/kernel/posix-timers.c

   *
   *
   * 2002-10-15  Posix Clocks & timers
   *                           by George Anzinger george@mvista.com
   *
   *			     Copyright (C) 2002 2003 by MontaVista Software.
   *
   * 2004-06-01  Fix CLOCK_REALTIME clock/timer TIMER_ABSTIME bug.
   *			     Copyright (C) 2004 Boris Hu
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or (at
   * your option) any later version.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
   * General Public License for more details.
  
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   *
   * MontaVista Software | 1237 East Arques Avenue | Sunnyvale | CA 94085 | USA
   */
  
  /* These are all the functions necessary to implement
   * POSIX clocks & timers
   */
  #include <linux/mm.h>

  #include <linux/interrupt.h>
  #include <linux/slab.h>
  #include <linux/time.h>

  #include <linux/mutex.h>

  #include <linux/sched/task.h>

  #include <linux/uaccess.h>

  #include <linux/list.h>
  #include <linux/init.h>
  #include <linux/compiler.h>

  #include <linux/hash.h>

  #include <linux/posix-clock.h>

  #include <linux/posix-timers.h>
  #include <linux/syscalls.h>
  #include <linux/wait.h>
  #include <linux/workqueue.h>

  #include <linux/export.h>

  #include <linux/hashtable.h>

  #include <linux/compat.h>

  #include <linux/nospec.h>

  #include "timekeeping.h"

  #include "posix-timers.h"

  /*

   * Management arrays for POSIX timers. Timers are now kept in static hash table
   * with 512 entries.
   * Timer ids are allocated by local routine, which selects proper hash head by
   * key, constructed from current->signal address and per signal struct counter.
   * This keeps timer ids unique per process, but now they can intersect between
   * processes.

   */
  
  /*
   * Lets keep our timers in a slab cache :-)
   */

  static struct kmem_cache *posix_timers_cache;

  
  static DEFINE_HASHTABLE(posix_timers_hashtable, 9);
  static DEFINE_SPINLOCK(hash_lock);

  static const struct k_clock * const posix_clocks[];
  static const struct k_clock *clockid_to_kclock(const clockid_t id);

  static const struct k_clock clock_realtime, clock_monotonic;

  /*

   * we assume that the new SIGEV_THREAD_ID shares no bits with the other
   * SIGEV values.  Here we put out an error if this assumption fails.
   */
  #if SIGEV_THREAD_ID != (SIGEV_THREAD_ID & \
                         ~(SIGEV_SIGNAL | SIGEV_NONE | SIGEV_THREAD))
  #error "SIGEV_THREAD_ID must not share bit with other SIGEV values!"
  #endif

  /*
   * parisc wants ENOTSUP instead of EOPNOTSUPP
   */
  #ifndef ENOTSUP
  # define ENANOSLEEP_NOTSUP EOPNOTSUPP
  #else
  # define ENANOSLEEP_NOTSUP ENOTSUP
  #endif

  
  /*
   * The timer ID is turned into a timer address by idr_find().
   * Verifying a valid ID consists of:
   *
   * a) checking that idr_find() returns other than -1.
   * b) checking that the timer id matches the one in the timer itself.
   * c) that the timer owner is in the callers thread group.
   */
  
  /*
   * CLOCKs: The POSIX standard calls for a couple of clocks and allows us
   *	    to implement others.  This structure defines the various

   *	    clocks.

   *
   * RESOLUTION: Clock resolution is used to round up timer and interval
   *	    times, NOT to report clock times, which are reported with as
   *	    much resolution as the system can muster.  In some cases this
   *	    resolution may depend on the underlying clock hardware and
   *	    may not be quantifiable until run time, and only then is the
   *	    necessary code is written.	The standard says we should say
   *	    something about this issue in the documentation...
   *

   * FUNCTIONS: The CLOCKs structure defines possible functions to
   *	    handle various clock functions.

   *

   *	    The standard POSIX timer management code assumes the
   *	    following: 1.) The k_itimer struct (sched.h) is used for
   *	    the timer.  2.) The list, it_lock, it_clock, it_id and
   *	    it_pid fields are not modified by timer code.

   *
   * Permissions: It is assumed that the clock_settime() function defined
   *	    for each clock will take care of permission checks.	 Some
   *	    clocks may be set able by any user (i.e. local process
   *	    clocks) others not.	 Currently the only set able clock we
   *	    have is CLOCK_REALTIME and its high res counter part, both of
   *	    which we beg off on and pass to do_sys_settimeofday().
   */

  static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags);
  
  #define lock_timer(tid, flags)						   \
  ({	struct k_itimer *__timr;					   \
  	__cond_lock(&__timr->it_lock, __timr = __lock_timer(tid, flags));  \
  	__timr;								   \
  })

  static int hash(struct signal_struct *sig, unsigned int nr)
  {
  	return hash_32(hash32_ptr(sig) ^ nr, HASH_BITS(posix_timers_hashtable));
  }
  
  static struct k_itimer *__posix_timers_find(struct hlist_head *head,
  					    struct signal_struct *sig,
  					    timer_t id)
  {

  	struct k_itimer *timer;
  
  	hlist_for_each_entry_rcu(timer, head, t_hash) {
  		if ((timer->it_signal == sig) && (timer->it_id == id))
  			return timer;
  	}
  	return NULL;
  }
  
  static struct k_itimer *posix_timer_by_id(timer_t id)
  {
  	struct signal_struct *sig = current->signal;
  	struct hlist_head *head = &posix_timers_hashtable[hash(sig, id)];
  
  	return __posix_timers_find(head, sig, id);
  }
  
  static int posix_timer_add(struct k_itimer *timer)
  {
  	struct signal_struct *sig = current->signal;
  	int first_free_id = sig->posix_timer_id;
  	struct hlist_head *head;
  	int ret = -ENOENT;
  
  	do {
  		spin_lock(&hash_lock);
  		head = &posix_timers_hashtable[hash(sig, sig->posix_timer_id)];
  		if (!__posix_timers_find(head, sig, sig->posix_timer_id)) {
  			hlist_add_head_rcu(&timer->t_hash, head);
  			ret = sig->posix_timer_id;
  		}
  		if (++sig->posix_timer_id < 0)
  			sig->posix_timer_id = 0;
  		if ((sig->posix_timer_id == first_free_id) && (ret == -ENOENT))
  			/* Loop over all possible ids completed */
  			ret = -EAGAIN;
  		spin_unlock(&hash_lock);
  	} while (ret == -ENOENT);
  	return ret;
  }

  static inline void unlock_timer(struct k_itimer *timr, unsigned long flags)
  {
  	spin_unlock_irqrestore(&timr->it_lock, flags);
  }

  /* Get clock_realtime */

  static int posix_clock_realtime_get(clockid_t which_clock, struct timespec64 *tp)

  {

  	ktime_get_real_ts64(tp);

  	return 0;
  }

  /* Set clock_realtime */
  static int posix_clock_realtime_set(const clockid_t which_clock,

  				    const struct timespec64 *tp)

  {

  	return do_sys_settimeofday64(tp, NULL);

  }

  static int posix_clock_realtime_adj(const clockid_t which_clock,
  				    struct timex *t)
  {
  	return do_adjtimex(t);
  }

  /*
   * Get monotonic time for posix timers
   */

  static int posix_ktime_get_ts(clockid_t which_clock, struct timespec64 *tp)

  {

  	ktime_get_ts64(tp);

  	return 0;
  }

  
  /*

   * Get monotonic-raw time for posix timers

   */

  static int posix_get_monotonic_raw(clockid_t which_clock, struct timespec64 *tp)

  {

  	getrawmonotonic64(tp);

  	return 0;
  }

  static int posix_get_realtime_coarse(clockid_t which_clock, struct timespec64 *tp)

  {

  	*tp = current_kernel_time64();

  	return 0;
  }
  
  static int posix_get_monotonic_coarse(clockid_t which_clock,

  						struct timespec64 *tp)

  {

  	*tp = get_monotonic_coarse64();

  	return 0;
  }

  static int posix_get_coarse_res(const clockid_t which_clock, struct timespec64 *tp)

  {

  	*tp = ktime_to_timespec64(KTIME_LOW_RES);

  	return 0;
  }

  static int posix_get_boottime(const clockid_t which_clock, struct timespec64 *tp)

  {

  	get_monotonic_boottime64(tp);

  	return 0;
  }

  static int posix_get_tai(clockid_t which_clock, struct timespec64 *tp)

  {

  	timekeeping_clocktai64(tp);

  	return 0;
  }

  static int posix_get_hrtimer_res(clockid_t which_clock, struct timespec64 *tp)

  {
  	tp->tv_sec = 0;
  	tp->tv_nsec = hrtimer_resolution;
  	return 0;
  }

  /*

   * Initialize everything, well, just everything in Posix clocks/timers ;)
   */
  static __init int init_posix_timers(void)
  {

  	posix_timers_cache = kmem_cache_create("posix_timers_cache",

  					sizeof (struct k_itimer), 0, SLAB_PANIC,
  					NULL);

  	return 0;
  }

  __initcall(init_posix_timers);

  /*
   * The siginfo si_overrun field and the return value of timer_getoverrun(2)
   * are of type int. Clamp the overrun value to INT_MAX
   */
  static inline int timer_overrun_to_int(struct k_itimer *timr, int baseval)
  {
  	s64 sum = timr->it_overrun_last + (s64)baseval;
  
  	return sum > (s64)INT_MAX ? INT_MAX : (int)sum;
  }

  static void common_hrtimer_rearm(struct k_itimer *timr)

  {

  	struct hrtimer *timer = &timr->it.real.timer;

  	timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(),
  					    timr->it_interval);

  	hrtimer_restart(timer);

  }
  
  /*
   * This function is exported for use by the signal deliver code.  It is
   * called just prior to the info block being released and passes that
   * block to us.  It's function is to update the overrun entry AND to
   * restart the timer.  It should only be called if the timer is to be
   * restarted (i.e. we have flagged this in the sys_private entry of the
   * info block).
   *

   * To protect against the timer going away while the interrupt is queued,

   * we require that the it_requeue_pending flag be set.
   */

  void posixtimer_rearm(struct siginfo *info)

  {
  	struct k_itimer *timr;
  	unsigned long flags;
  
  	timr = lock_timer(info->si_tid, &flags);

  	if (!timr)
  		return;

  	if (timr->it_interval && timr->it_requeue_pending == info->si_sys_private) {

  		timr->kclock->timer_rearm(timr);

  		timr->it_active = 1;

  		timr->it_overrun_last = timr->it_overrun;

  		timr->it_overrun = -1LL;

  		++timr->it_requeue_pending;

  		info->si_overrun = timer_overrun_to_int(timr, info->si_overrun);

  	}

  	unlock_timer(timr, flags);

  }

  int posix_timer_event(struct k_itimer *timr, int si_private)

  {

  	struct task_struct *task;
  	int shared, ret = -1;

  	/*
  	 * FIXME: if ->sigq is queued we can race with

  	 * dequeue_signal()->posixtimer_rearm().

  	 *
  	 * If dequeue_signal() sees the "right" value of

  	 * si_sys_private it calls posixtimer_rearm().

  	 * We re-queue ->sigq and drop ->it_lock().

  	 * posixtimer_rearm() locks the timer

  	 * and re-schedules it while ->sigq is pending.
  	 * Not really bad, but not that we want.
  	 */

  	timr->sigq->info.si_sys_private = si_private;

  	rcu_read_lock();
  	task = pid_task(timr->it_pid, PIDTYPE_PID);
  	if (task) {
  		shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
  		ret = send_sigqueue(timr->sigq, task, shared);
  	}
  	rcu_read_unlock();

  	/* If we failed to send the signal the timer stops. */
  	return ret > 0;

  }

  
  /*
   * This function gets called when a POSIX.1b interval timer expires.  It
   * is used as a callback from the kernel internal timer.  The
   * run_timer_list code ALWAYS calls with interrupts on.
  
   * This code is for CLOCK_REALTIME* and CLOCK_MONOTONIC* timers.
   */

  static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)

  {

  	struct k_itimer *timr;

  	unsigned long flags;

  	int si_private = 0;

  	enum hrtimer_restart ret = HRTIMER_NORESTART;

  	timr = container_of(timer, struct k_itimer, it.real.timer);

  	spin_lock_irqsave(&timr->it_lock, flags);

  	timr->it_active = 0;

  	if (timr->it_interval != 0)

  		si_private = ++timr->it_requeue_pending;

  	if (posix_timer_event(timr, si_private)) {
  		/*
  		 * signal was not sent because of sig_ignor
  		 * we will not get a call back to restart it AND
  		 * it should be restarted.
  		 */

  		if (timr->it_interval != 0) {

  			ktime_t now = hrtimer_cb_get_time(timer);
  
  			/*
  			 * FIXME: What we really want, is to stop this
  			 * timer completely and restart it in case the
  			 * SIG_IGN is removed. This is a non trivial
  			 * change which involves sighand locking
  			 * (sigh !), which we don't want to do late in
  			 * the release cycle.
  			 *
  			 * For now we just let timers with an interval
  			 * less than a jiffie expire every jiffie to
  			 * avoid softirq starvation in case of SIG_IGN
  			 * and a very small interval, which would put
  			 * the timer right back on the softirq pending
  			 * list. By moving now ahead of time we trick
  			 * hrtimer_forward() to expire the timer
  			 * later, while we still maintain the overrun
  			 * accuracy, but have some inconsistency in
  			 * the timer_gettime() case. This is at least
  			 * better than a starved softirq. A more
  			 * complex fix which solves also another related
  			 * inconsistency is already in the pipeline.
  			 */
  #ifdef CONFIG_HIGH_RES_TIMERS
  			{

  				ktime_t kj = NSEC_PER_SEC / HZ;

  				if (timr->it_interval < kj)

  					now = ktime_add(now, kj);
  			}
  #endif

  			timr->it_overrun += hrtimer_forward(timer, now,
  							    timr->it_interval);

  			ret = HRTIMER_RESTART;

  			++timr->it_requeue_pending;

  			timr->it_active = 1;

  		}

  	}

  	unlock_timer(timr, flags);
  	return ret;
  }

  static struct pid *good_sigevent(sigevent_t * event)

  {
  	struct task_struct *rtn = current->group_leader;

  	switch (event->sigev_notify) {
  	case SIGEV_SIGNAL | SIGEV_THREAD_ID:
  		rtn = find_task_by_vpid(event->sigev_notify_thread_id);
  		if (!rtn || !same_thread_group(rtn, current))
  			return NULL;
  		/* FALLTHRU */
  	case SIGEV_SIGNAL:
  	case SIGEV_THREAD:
  		if (event->sigev_signo <= 0 || event->sigev_signo > SIGRTMAX)
  			return NULL;
  		/* FALLTHRU */
  	case SIGEV_NONE:
  		return task_pid(rtn);
  	default:

  		return NULL;

  	}

  }

  static struct k_itimer * alloc_posix_timer(void)
  {
  	struct k_itimer *tmr;

  	tmr = kmem_cache_zalloc(posix_timers_cache, GFP_KERNEL);

  	if (!tmr)
  		return tmr;

  	if (unlikely(!(tmr->sigq = sigqueue_alloc()))) {
  		kmem_cache_free(posix_timers_cache, tmr);

  		return NULL;

  	}

  	memset(&tmr->sigq->info, 0, sizeof(siginfo_t));

  	return tmr;
  }

  static void k_itimer_rcu_free(struct rcu_head *head)
  {
  	struct k_itimer *tmr = container_of(head, struct k_itimer, it.rcu);
  
  	kmem_cache_free(posix_timers_cache, tmr);
  }

  #define IT_ID_SET	1
  #define IT_ID_NOT_SET	0
  static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
  {
  	if (it_id_set) {
  		unsigned long flags;

  		spin_lock_irqsave(&hash_lock, flags);
  		hlist_del_rcu(&tmr->t_hash);
  		spin_unlock_irqrestore(&hash_lock, flags);

  	}

  	put_pid(tmr->it_pid);

  	sigqueue_free(tmr->sigq);

  	call_rcu(&tmr->it.rcu, k_itimer_rcu_free);

  }

  static int common_timer_create(struct k_itimer *new_timer)
  {
  	hrtimer_init(&new_timer->it.real.timer, new_timer->it_clock, 0);
  	return 0;
  }

  /* Create a POSIX.1b interval timer. */

  static int do_timer_create(clockid_t which_clock, struct sigevent *event,
  			   timer_t __user *created_timer_id)

  {

  	const struct k_clock *kc = clockid_to_kclock(which_clock);

  	struct k_itimer *new_timer;

  	int error, new_timer_id;

  	int it_id_set = IT_ID_NOT_SET;

  	if (!kc)

  		return -EINVAL;

  	if (!kc->timer_create)
  		return -EOPNOTSUPP;

  
  	new_timer = alloc_posix_timer();
  	if (unlikely(!new_timer))
  		return -EAGAIN;
  
  	spin_lock_init(&new_timer->it_lock);

  	new_timer_id = posix_timer_add(new_timer);
  	if (new_timer_id < 0) {
  		error = new_timer_id;

  		goto out;
  	}
  
  	it_id_set = IT_ID_SET;
  	new_timer->it_id = (timer_t) new_timer_id;
  	new_timer->it_clock = which_clock;

  	new_timer->kclock = kc;

  	new_timer->it_overrun = -1LL;

  	if (event) {

  		rcu_read_lock();

  		new_timer->it_pid = get_pid(good_sigevent(event));

  		rcu_read_unlock();

  		if (!new_timer->it_pid) {

  			error = -EINVAL;
  			goto out;
  		}

  		new_timer->it_sigev_notify     = event->sigev_notify;
  		new_timer->sigq->info.si_signo = event->sigev_signo;
  		new_timer->sigq->info.si_value = event->sigev_value;

  	} else {

  		new_timer->it_sigev_notify     = SIGEV_SIGNAL;
  		new_timer->sigq->info.si_signo = SIGALRM;
  		memset(&new_timer->sigq->info.si_value, 0, sizeof(sigval_t));
  		new_timer->sigq->info.si_value.sival_int = new_timer->it_id;

  		new_timer->it_pid = get_pid(task_tgid(current));

  	}

  	new_timer->sigq->info.si_tid   = new_timer->it_id;

  	new_timer->sigq->info.si_code  = SI_TIMER;

  	if (copy_to_user(created_timer_id,
  			 &new_timer_id, sizeof (new_timer_id))) {
  		error = -EFAULT;
  		goto out;
  	}

  	error = kc->timer_create(new_timer);

  	if (error)
  		goto out;

  	spin_lock_irq(&current->sighand->siglock);

  	new_timer->it_signal = current->signal;

  	list_add(&new_timer->list, &current->signal->posix_timers);
  	spin_unlock_irq(&current->sighand->siglock);

  
  	return 0;

  	/*

  	 * In the case of the timer belonging to another task, after
  	 * the task is unlocked, the timer is owned by the other task
  	 * and may cease to exist at any time.  Don't use or modify
  	 * new_timer after the unlock call.
  	 */

  out:

  	release_posix_timer(new_timer, it_id_set);

  	return error;
  }

  SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
  		struct sigevent __user *, timer_event_spec,
  		timer_t __user *, created_timer_id)
  {
  	if (timer_event_spec) {
  		sigevent_t event;
  
  		if (copy_from_user(&event, timer_event_spec, sizeof (event)))
  			return -EFAULT;
  		return do_timer_create(which_clock, &event, created_timer_id);
  	}
  	return do_timer_create(which_clock, NULL, created_timer_id);
  }
  
  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE3(timer_create, clockid_t, which_clock,
  		       struct compat_sigevent __user *, timer_event_spec,
  		       timer_t __user *, created_timer_id)
  {
  	if (timer_event_spec) {
  		sigevent_t event;
  
  		if (get_compat_sigevent(&event, timer_event_spec))
  			return -EFAULT;
  		return do_timer_create(which_clock, &event, created_timer_id);
  	}
  	return do_timer_create(which_clock, NULL, created_timer_id);
  }
  #endif

  /*

   * Locking issues: We need to protect the result of the id look up until
   * we get the timer locked down so it is not deleted under us.  The
   * removal is done under the idr spinlock so we use that here to bridge
   * the find to the timer lock.  To avoid a dead lock, the timer id MUST
   * be release with out holding the timer lock.
   */

  static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)

  {
  	struct k_itimer *timr;

  	/*
  	 * timer_t could be any type >= int and we want to make sure any
  	 * @timer_id outside positive int range fails lookup.
  	 */
  	if ((unsigned long long)timer_id > INT_MAX)
  		return NULL;

  	rcu_read_lock();

  	timr = posix_timer_by_id(timer_id);

  	if (timr) {

  		spin_lock_irqsave(&timr->it_lock, *flags);

  		if (timr->it_signal == current->signal) {

  			rcu_read_unlock();

  			return timr;
  		}

  		spin_unlock_irqrestore(&timr->it_lock, *flags);

  	}

  	rcu_read_unlock();

  	return NULL;

  }

  static ktime_t common_hrtimer_remaining(struct k_itimer *timr, ktime_t now)
  {
  	struct hrtimer *timer = &timr->it.real.timer;
  
  	return __hrtimer_expires_remaining_adjusted(timer, now);
  }

  static s64 common_hrtimer_forward(struct k_itimer *timr, ktime_t now)

  {
  	struct hrtimer *timer = &timr->it.real.timer;

  	return hrtimer_forward(timer, now, timr->it_interval);

  }

  /*
   * Get the time remaining on a POSIX.1b interval timer.  This function
   * is ALWAYS called with spin_lock_irq on the timer, thus it must not
   * mess with irq.
   *
   * We have a couple of messes to clean up here.  First there is the case
   * of a timer that has a requeue pending.  These timers should appear to
   * be in the timer list with an expiry as if we were to requeue them
   * now.
   *
   * The second issue is the SIGEV_NONE timer which may be active but is
   * not really ever put in the timer list (to save system resources).
   * This timer may be expired, and if so, we will do it here.  Otherwise
   * it is the same as a requeue pending timer WRT to what we should
   * report.
   */

  void common_timer_get(struct k_itimer *timr, struct itimerspec64 *cur_setting)

  {

  	const struct k_clock *kc = timr->kclock;

  	ktime_t now, remaining, iv;

  	struct timespec64 ts64;
  	bool sig_none;

  	sig_none = timr->it_sigev_notify == SIGEV_NONE;

  	iv = timr->it_interval;

  	/* interval timer ? */

  	if (iv) {

  		cur_setting->it_interval = ktime_to_timespec64(iv);

  	} else if (!timr->it_active) {
  		/*
  		 * SIGEV_NONE oneshot timers are never queued. Check them
  		 * below.
  		 */
  		if (!sig_none)
  			return;
  	}

  	/*
  	 * The timespec64 based conversion is suboptimal, but it's not
  	 * worth to implement yet another callback.
  	 */
  	kc->clock_get(timr->it_clock, &ts64);
  	now = timespec64_to_ktime(ts64);

  	/*

  	 * When a requeue is pending or this is a SIGEV_NONE timer move the
  	 * expiry time forward by intervals, so expiry is > now.

  	 */

  	if (iv && (timr->it_requeue_pending & REQUEUE_PENDING || sig_none))

  		timr->it_overrun += kc->timer_forward(timr, now);

  	remaining = kc->timer_remaining(timr, now);

  	/* Return 0 only, when the timer is expired and not pending */

  	if (remaining <= 0) {

  		/*
  		 * A single shot SIGEV_NONE timer must return 0, when
  		 * it is expired !
  		 */

  		if (!sig_none)

  			cur_setting->it_value.tv_nsec = 1;

  	} else {

  		cur_setting->it_value = ktime_to_timespec64(remaining);

  	}

  }
  
  /* Get the time remaining on a POSIX.1b interval timer. */

  static int do_timer_gettime(timer_t timer_id,  struct itimerspec64 *setting)

  {

  	struct k_itimer *timr;

  	const struct k_clock *kc;

  	unsigned long flags;

  	int ret = 0;

  
  	timr = lock_timer(timer_id, &flags);
  	if (!timr)
  		return -EINVAL;

  	memset(setting, 0, sizeof(*setting));

  	kc = timr->kclock;

  	if (WARN_ON_ONCE(!kc || !kc->timer_get))
  		ret = -EINVAL;
  	else

  		kc->timer_get(timr, setting);

  
  	unlock_timer(timr, flags);

  	return ret;
  }

  /* Get the time remaining on a POSIX.1b interval timer. */
  SYSCALL_DEFINE2(timer_gettime, timer_t, timer_id,
  		struct itimerspec __user *, setting)
  {

  	struct itimerspec64 cur_setting;

  	int ret = do_timer_gettime(timer_id, &cur_setting);

  	if (!ret) {

  		if (put_itimerspec64(&cur_setting, setting))

  			ret = -EFAULT;
  	}

  	return ret;

  }

  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE2(timer_gettime, timer_t, timer_id,
  		       struct compat_itimerspec __user *, setting)
  {

  	struct itimerspec64 cur_setting;

  	int ret = do_timer_gettime(timer_id, &cur_setting);

  	if (!ret) {

  		if (put_compat_itimerspec64(&cur_setting, setting))

  			ret = -EFAULT;
  	}
  	return ret;
  }
  #endif

  /*
   * Get the number of overruns of a POSIX.1b interval timer.  This is to
   * be the overrun of the timer last delivered.  At the same time we are
   * accumulating overruns on the next timer.  The overrun is frozen when
   * the signal is delivered, either at the notify time (if the info block
   * is not queued) or at the actual delivery time (as we are informed by

   * the call back to posixtimer_rearm().  So all we need to do is

   * to pick up the frozen overrun.
   */

  SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id)

  {
  	struct k_itimer *timr;
  	int overrun;

  	unsigned long flags;

  
  	timr = lock_timer(timer_id, &flags);
  	if (!timr)
  		return -EINVAL;

  	overrun = timer_overrun_to_int(timr, 0);

  	unlock_timer(timr, flags);
  
  	return overrun;
  }

  static void common_hrtimer_arm(struct k_itimer *timr, ktime_t expires,
  			       bool absolute, bool sigev_none)
  {
  	struct hrtimer *timer = &timr->it.real.timer;
  	enum hrtimer_mode mode;
  
  	mode = absolute ? HRTIMER_MODE_ABS : HRTIMER_MODE_REL;

  	/*
  	 * Posix magic: Relative CLOCK_REALTIME timers are not affected by
  	 * clock modifications, so they become CLOCK_MONOTONIC based under the
  	 * hood. See hrtimer_init(). Update timr->kclock, so the generic
  	 * functions which use timr->kclock->clock_get() work.
  	 *
  	 * Note: it_clock stays unmodified, because the next timer_set() might
  	 * use ABSTIME, so it needs to switch back.
  	 */
  	if (timr->it_clock == CLOCK_REALTIME)
  		timr->kclock = absolute ? &clock_realtime : &clock_monotonic;

  	hrtimer_init(&timr->it.real.timer, timr->it_clock, mode);
  	timr->it.real.timer.function = posix_timer_fn;
  
  	if (!absolute)
  		expires = ktime_add_safe(expires, timer->base->get_time());
  	hrtimer_set_expires(timer, expires);
  
  	if (!sigev_none)
  		hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
  }
  
  static int common_hrtimer_try_to_cancel(struct k_itimer *timr)
  {
  	return hrtimer_try_to_cancel(&timr->it.real.timer);
  }

  /* Set a POSIX.1b interval timer. */

  int common_timer_set(struct k_itimer *timr, int flags,
  		     struct itimerspec64 *new_setting,
  		     struct itimerspec64 *old_setting)

  {

  	const struct k_clock *kc = timr->kclock;
  	bool sigev_none;
  	ktime_t expires;

  
  	if (old_setting)
  		common_timer_get(timr, old_setting);

  	/* Prevent rearming by clearing the interval */

  	timr->it_interval = 0;

  	/*

  	 * Careful here. On SMP systems the timer expiry function could be
  	 * active and spinning on timr->it_lock.

  	 */

  	if (kc->timer_try_to_cancel(timr) < 0)

  		return TIMER_RETRY;

  	timr->it_active = 0;
  	timr->it_requeue_pending = (timr->it_requeue_pending + 2) &

  		~REQUEUE_PENDING;
  	timr->it_overrun_last = 0;

  	/* Switch off the timer when it_value is zero */

  	if (!new_setting->it_value.tv_sec && !new_setting->it_value.tv_nsec)
  		return 0;

  	timr->it_interval = timespec64_to_ktime(new_setting->it_interval);

  	expires = timespec64_to_ktime(new_setting->it_value);

  	sigev_none = timr->it_sigev_notify == SIGEV_NONE;

  	kc->timer_arm(timr, expires, flags & TIMER_ABSTIME, sigev_none);
  	timr->it_active = !sigev_none;

  	return 0;
  }

  static int do_timer_settime(timer_t timer_id, int flags,
  			    struct itimerspec64 *new_spec64,
  			    struct itimerspec64 *old_spec64)

  {

  	const struct k_clock *kc;

  	struct k_itimer *timr;

  	unsigned long flag;

  	int error = 0;

  	if (!timespec64_valid(&new_spec64->it_interval) ||
  	    !timespec64_valid(&new_spec64->it_value))

  		return -EINVAL;

  	if (old_spec64)
  		memset(old_spec64, 0, sizeof(*old_spec64));

  retry:
  	timr = lock_timer(timer_id, &flag);
  	if (!timr)
  		return -EINVAL;

  	kc = timr->kclock;

  	if (WARN_ON_ONCE(!kc || !kc->timer_set))
  		error = -EINVAL;
  	else

  		error = kc->timer_set(timr, flags, new_spec64, old_spec64);

  
  	unlock_timer(timr, flag);
  	if (error == TIMER_RETRY) {

  		old_spec64 = NULL;	// We already got the old time...

  		goto retry;
  	}

  	return error;
  }

  /* Set a POSIX.1b interval timer */
  SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
  		const struct itimerspec __user *, new_setting,
  		struct itimerspec __user *, old_setting)
  {

  	struct itimerspec64 new_spec, old_spec;
  	struct itimerspec64 *rtn = old_setting ? &old_spec : NULL;

  	int error = 0;
  
  	if (!new_setting)
  		return -EINVAL;

  	if (get_itimerspec64(&new_spec, new_setting))

  		return -EFAULT;

  	error = do_timer_settime(timer_id, flags, &new_spec, rtn);

  	if (!error && old_setting) {

  		if (put_itimerspec64(&old_spec, old_setting))

  			error = -EFAULT;
  	}
  	return error;
  }
  
  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
  		       struct compat_itimerspec __user *, new,
  		       struct compat_itimerspec __user *, old)
  {

  	struct itimerspec64 new_spec, old_spec;
  	struct itimerspec64 *rtn = old ? &old_spec : NULL;

  	int error = 0;
  
  	if (!new)
  		return -EINVAL;

  	if (get_compat_itimerspec64(&new_spec, new))

  		return -EFAULT;

  	error = do_timer_settime(timer_id, flags, &new_spec, rtn);

  	if (!error && old) {

  		if (put_compat_itimerspec64(&old_spec, old))

  			error = -EFAULT;
  	}

  	return error;
  }

  #endif

  int common_timer_del(struct k_itimer *timer)

  {

  	const struct k_clock *kc = timer->kclock;

  	timer->it_interval = 0;
  	if (kc->timer_try_to_cancel(timer) < 0)

  		return TIMER_RETRY;

  	timer->it_active = 0;

  	return 0;
  }
  
  static inline int timer_delete_hook(struct k_itimer *timer)
  {

  	const struct k_clock *kc = timer->kclock;

  
  	if (WARN_ON_ONCE(!kc || !kc->timer_del))
  		return -EINVAL;
  	return kc->timer_del(timer);

  }
  
  /* Delete a POSIX.1b interval timer. */

  SYSCALL_DEFINE1(timer_delete, timer_t, timer_id)

  {
  	struct k_itimer *timer;

  	unsigned long flags;

  retry_delete:

  	timer = lock_timer(timer_id, &flags);
  	if (!timer)
  		return -EINVAL;

  	if (timer_delete_hook(timer) == TIMER_RETRY) {

  		unlock_timer(timer, flags);
  		goto retry_delete;
  	}

  	spin_lock(&current->sighand->siglock);
  	list_del(&timer->list);
  	spin_unlock(&current->sighand->siglock);
  	/*
  	 * This keeps any tasks waiting on the spin lock from thinking
  	 * they got something (see the lock code above).
  	 */

  	timer->it_signal = NULL;

  	unlock_timer(timer, flags);
  	release_posix_timer(timer, IT_ID_SET);
  	return 0;
  }

  /*
   * return timer owned by the process, used by exit_itimers
   */

  static void itimer_delete(struct k_itimer *timer)

  {
  	unsigned long flags;

  retry_delete:

  	spin_lock_irqsave(&timer->it_lock, flags);

  	if (timer_delete_hook(timer) == TIMER_RETRY) {

  		unlock_timer(timer, flags);
  		goto retry_delete;
  	}

  	list_del(&timer->list);
  	/*
  	 * This keeps any tasks waiting on the spin lock from thinking
  	 * they got something (see the lock code above).
  	 */

  	timer->it_signal = NULL;

  	unlock_timer(timer, flags);
  	release_posix_timer(timer, IT_ID_SET);
  }
  
  /*

   * This is called by do_exit or de_thread, only when there are no more

   * references to the shared signal_struct.
   */
  void exit_itimers(struct signal_struct *sig)
  {
  	struct k_itimer *tmr;
  
  	while (!list_empty(&sig->posix_timers)) {
  		tmr = list_entry(sig->posix_timers.next, struct k_itimer, list);
  		itimer_delete(tmr);
  	}
  }

  SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,
  		const struct timespec __user *, tp)

  {

  	const struct k_clock *kc = clockid_to_kclock(which_clock);

  	struct timespec64 new_tp;

  	if (!kc || !kc->clock_set)

  		return -EINVAL;

  	if (get_timespec64(&new_tp, tp))

  		return -EFAULT;

  	return kc->clock_set(which_clock, &new_tp);

  }

  SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,
  		struct timespec __user *,tp)

  {

  	const struct k_clock *kc = clockid_to_kclock(which_clock);

  	struct timespec64 kernel_tp;

  	int error;

  	if (!kc)

  		return -EINVAL;

  	error = kc->clock_get(which_clock, &kernel_tp);

  	if (!error && put_timespec64(&kernel_tp, tp))

  		error = -EFAULT;
  
  	return error;

  }

  SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
  		struct timex __user *, utx)
  {

  	const struct k_clock *kc = clockid_to_kclock(which_clock);

  	struct timex ktx;
  	int err;
  
  	if (!kc)
  		return -EINVAL;
  	if (!kc->clock_adj)
  		return -EOPNOTSUPP;
  
  	if (copy_from_user(&ktx, utx, sizeof(ktx)))
  		return -EFAULT;
  
  	err = kc->clock_adj(which_clock, &ktx);

  	if (err >= 0 && copy_to_user(utx, &ktx, sizeof(ktx)))

  		return -EFAULT;
  
  	return err;
  }

  SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock,
  		struct timespec __user *, tp)
  {
  	const struct k_clock *kc = clockid_to_kclock(which_clock);

  	struct timespec64 rtn_tp;

  	int error;
  
  	if (!kc)
  		return -EINVAL;

  	error = kc->clock_getres(which_clock, &rtn_tp);

  	if (!error && tp && put_timespec64(&rtn_tp, tp))

  		error = -EFAULT;
  
  	return error;
  }

  #ifdef CONFIG_COMPAT

  COMPAT_SYSCALL_DEFINE2(clock_settime, clockid_t, which_clock,
  		       struct compat_timespec __user *, tp)
  {
  	const struct k_clock *kc = clockid_to_kclock(which_clock);

  	struct timespec64 ts;

  
  	if (!kc || !kc->clock_set)
  		return -EINVAL;

  	if (compat_get_timespec64(&ts, tp))

  		return -EFAULT;

  	return kc->clock_set(which_clock, &ts);

  }
  
  COMPAT_SYSCALL_DEFINE2(clock_gettime, clockid_t, which_clock,
  		       struct compat_timespec __user *, tp)
  {
  	const struct k_clock *kc = clockid_to_kclock(which_clock);

  	struct timespec64 ts;
  	int err;

  
  	if (!kc)
  		return -EINVAL;

  	err = kc->clock_get(which_clock, &ts);

  	if (!err && compat_put_timespec64(&ts, tp))
  		err = -EFAULT;

  	return err;

  }

  COMPAT_SYSCALL_DEFINE2(clock_adjtime, clockid_t, which_clock,
  		       struct compat_timex __user *, utp)
  {
  	const struct k_clock *kc = clockid_to_kclock(which_clock);
  	struct timex ktx;
  	int err;
  
  	if (!kc)
  		return -EINVAL;
  	if (!kc->clock_adj)
  		return -EOPNOTSUPP;
  
  	err = compat_get_timex(&ktx, utp);
  	if (err)
  		return err;
  
  	err = kc->clock_adj(which_clock, &ktx);
  
  	if (err >= 0)
  		err = compat_put_timex(utp, &ktx);
  
  	return err;
  }

  COMPAT_SYSCALL_DEFINE2(clock_getres, clockid_t, which_clock,
  		       struct compat_timespec __user *, tp)

  {

  	const struct k_clock *kc = clockid_to_kclock(which_clock);

  	struct timespec64 ts;
  	int err;

  	if (!kc)

  		return -EINVAL;

  	err = kc->clock_getres(which_clock, &ts);
  	if (!err && tp && compat_put_timespec64(&ts, tp))
  		return -EFAULT;

  	return err;

  }

  #endif

  /*

   * nanosleep for monotonic and realtime clocks
   */
  static int common_nsleep(const clockid_t which_clock, int flags,

  			 const struct timespec64 *rqtp)

  {

  	return hrtimer_nanosleep(rqtp, flags & TIMER_ABSTIME ?

  				 HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
  				 which_clock);

  }

  SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags,
  		const struct timespec __user *, rqtp,
  		struct timespec __user *, rmtp)

  {

  	const struct k_clock *kc = clockid_to_kclock(which_clock);

  	struct timespec64 t;

  	if (!kc)

  		return -EINVAL;

  	if (!kc->nsleep)
  		return -ENANOSLEEP_NOTSUP;

  	if (get_timespec64(&t, rqtp))

  		return -EFAULT;

  	if (!timespec64_valid(&t))

  		return -EINVAL;

  	if (flags & TIMER_ABSTIME)
  		rmtp = NULL;

  	current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE;

  	current->restart_block.nanosleep.rmtp = rmtp;

  	return kc->nsleep(which_clock, flags, &t);

  }

  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE4(clock_nanosleep, clockid_t, which_clock, int, flags,
  		       struct compat_timespec __user *, rqtp,
  		       struct compat_timespec __user *, rmtp)

  {

  	const struct k_clock *kc = clockid_to_kclock(which_clock);

  	struct timespec64 t;

  	if (!kc)

  		return -EINVAL;

  	if (!kc->nsleep)
  		return -ENANOSLEEP_NOTSUP;

  	if (compat_get_timespec64(&t, rqtp))

  		return -EFAULT;

  	if (!timespec64_valid(&t))

  		return -EINVAL;
  	if (flags & TIMER_ABSTIME)
  		rmtp = NULL;
  	current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE;
  	current->restart_block.nanosleep.compat_rmtp = rmtp;

  	return kc->nsleep(which_clock, flags, &t);

  }

  #endif

  
  static const struct k_clock clock_realtime = {

  	.clock_getres		= posix_get_hrtimer_res,
  	.clock_get		= posix_clock_realtime_get,
  	.clock_set		= posix_clock_realtime_set,
  	.clock_adj		= posix_clock_realtime_adj,
  	.nsleep			= common_nsleep,

  	.timer_create		= common_timer_create,
  	.timer_set		= common_timer_set,
  	.timer_get		= common_timer_get,
  	.timer_del		= common_timer_del,
  	.timer_rearm		= common_hrtimer_rearm,
  	.timer_forward		= common_hrtimer_forward,
  	.timer_remaining	= common_hrtimer_remaining,
  	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
  	.timer_arm		= common_hrtimer_arm,

  };
  
  static const struct k_clock clock_monotonic = {

  	.clock_getres		= posix_get_hrtimer_res,
  	.clock_get		= posix_ktime_get_ts,
  	.nsleep			= common_nsleep,

  	.timer_create		= common_timer_create,
  	.timer_set		= common_timer_set,
  	.timer_get		= common_timer_get,
  	.timer_del		= common_timer_del,
  	.timer_rearm		= common_hrtimer_rearm,
  	.timer_forward		= common_hrtimer_forward,
  	.timer_remaining	= common_hrtimer_remaining,
  	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
  	.timer_arm		= common_hrtimer_arm,

  };
  
  static const struct k_clock clock_monotonic_raw = {

  	.clock_getres		= posix_get_hrtimer_res,
  	.clock_get		= posix_get_monotonic_raw,

  };
  
  static const struct k_clock clock_realtime_coarse = {

  	.clock_getres		= posix_get_coarse_res,
  	.clock_get		= posix_get_realtime_coarse,

  };
  
  static const struct k_clock clock_monotonic_coarse = {

  	.clock_getres		= posix_get_coarse_res,
  	.clock_get		= posix_get_monotonic_coarse,

  };
  
  static const struct k_clock clock_tai = {

  	.clock_getres		= posix_get_hrtimer_res,
  	.clock_get		= posix_get_tai,
  	.nsleep			= common_nsleep,

  	.timer_create		= common_timer_create,
  	.timer_set		= common_timer_set,
  	.timer_get		= common_timer_get,
  	.timer_del		= common_timer_del,
  	.timer_rearm		= common_hrtimer_rearm,
  	.timer_forward		= common_hrtimer_forward,
  	.timer_remaining	= common_hrtimer_remaining,
  	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
  	.timer_arm		= common_hrtimer_arm,

  };
  
  static const struct k_clock clock_boottime = {

  	.clock_getres		= posix_get_hrtimer_res,
  	.clock_get		= posix_get_boottime,
  	.nsleep			= common_nsleep,

  	.timer_create		= common_timer_create,
  	.timer_set		= common_timer_set,
  	.timer_get		= common_timer_get,
  	.timer_del		= common_timer_del,
  	.timer_rearm		= common_hrtimer_rearm,
  	.timer_forward		= common_hrtimer_forward,
  	.timer_remaining	= common_hrtimer_remaining,
  	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
  	.timer_arm		= common_hrtimer_arm,

  };
  
  static const struct k_clock * const posix_clocks[] = {
  	[CLOCK_REALTIME]		= &clock_realtime,
  	[CLOCK_MONOTONIC]		= &clock_monotonic,
  	[CLOCK_PROCESS_CPUTIME_ID]	= &clock_process,
  	[CLOCK_THREAD_CPUTIME_ID]	= &clock_thread,
  	[CLOCK_MONOTONIC_RAW]		= &clock_monotonic_raw,
  	[CLOCK_REALTIME_COARSE]		= &clock_realtime_coarse,
  	[CLOCK_MONOTONIC_COARSE]	= &clock_monotonic_coarse,
  	[CLOCK_BOOTTIME]		= &clock_boottime,
  	[CLOCK_REALTIME_ALARM]		= &alarm_clock,
  	[CLOCK_BOOTTIME_ALARM]		= &alarm_clock,
  	[CLOCK_TAI]			= &clock_tai,
  };
  
  static const struct k_clock *clockid_to_kclock(const clockid_t id)
  {

  	clockid_t idx = id;
  
  	if (id < 0) {

  		return (id & CLOCKFD_MASK) == CLOCKFD ?
  			&clock_posix_dynamic : &clock_posix_cpu;

  	}

  	if (id >= ARRAY_SIZE(posix_clocks))

  		return NULL;

  
  	return posix_clocks[array_index_nospec(idx, ARRAY_SIZE(posix_clocks))];

  }