Move files to match FreeBSD layout

1 files changed, 1522 insertions, 0 deletions

diff --git a/freebsd/sys/kern/kern_time.c b/freebsd/sys/kern/kern_time.c
new file mode 100644
index 00000000..8c760b48
--- /dev/null
+++ b/freebsd/sys/kern/kern_time.c
@@ -0,0 +1,1522 @@
+#include <freebsd/machine/rtems-bsd-config.h>
+
+/*-
+ * Copyright (c) 1982, 1986, 1989, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	@(#)kern_time.c	8.1 (Berkeley) 6/10/93
+ */
+
+#include <freebsd/sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <freebsd/sys/param.h>
+#include <freebsd/sys/systm.h>
+#include <freebsd/sys/limits.h>
+#ifndef __rtems__
+#include <freebsd/sys/clock.h>
+#endif /* __rtems__ */
+#include <freebsd/sys/lock.h>
+#include <freebsd/sys/mutex.h>
+#include <freebsd/sys/sysproto.h>
+#include <freebsd/sys/eventhandler.h>
+#include <freebsd/sys/resourcevar.h>
+#include <freebsd/sys/signalvar.h>
+#include <freebsd/sys/kernel.h>
+#include <freebsd/sys/syscallsubr.h>
+#include <freebsd/sys/sysctl.h>
+#include <freebsd/sys/sysent.h>
+#include <freebsd/sys/priv.h>
+#include <freebsd/sys/proc.h>
+#ifndef __rtems__
+#include <freebsd/sys/posix4.h>
+#include <freebsd/sys/time.h>
+#include <freebsd/sys/timers.h>
+#include <freebsd/sys/timetc.h>
+#include <freebsd/sys/vnode.h>
+
+#include <freebsd/vm/vm.h>
+#include <freebsd/vm/vm_extern.h>
+
+#define MAX_CLOCKS 	(CLOCK_MONOTONIC+1)
+
+static struct kclock	posix_clocks[MAX_CLOCKS];
+static uma_zone_t	itimer_zone = NULL;
+
+/*
+ * Time of day and interval timer support.
+ *
+ * These routines provide the kernel entry points to get and set
+ * the time-of-day and per-process interval timers.  Subroutines
+ * here provide support for adding and subtracting timeval structures
+ * and decrementing interval timers, optionally reloading the interval
+ * timers when they expire.
+ */
+
+static int	settime(struct thread *, struct timeval *);
+#endif /* __rtems__ */
+static void	timevalfix(struct timeval *);
+
+#ifndef __rtems__
+static void	itimer_start(void);
+static int	itimer_init(void *, int, int);
+static void	itimer_fini(void *, int);
+static void	itimer_enter(struct itimer *);
+static void	itimer_leave(struct itimer *);
+static struct itimer *itimer_find(struct proc *, int);
+static void	itimers_alloc(struct proc *);
+static void	itimers_event_hook_exec(void *arg, struct proc *p, struct image_params *imgp);
+static void	itimers_event_hook_exit(void *arg, struct proc *p);
+static int	realtimer_create(struct itimer *);
+static int	realtimer_gettime(struct itimer *, struct itimerspec *);
+static int	realtimer_settime(struct itimer *, int,
+			struct itimerspec *, struct itimerspec *);
+static int	realtimer_delete(struct itimer *);
+static void	realtimer_clocktime(clockid_t, struct timespec *);
+static void	realtimer_expire(void *);
+static int	kern_timer_create(struct thread *, clockid_t,
+			struct sigevent *, int *, int);
+static int	kern_timer_delete(struct thread *, int);
+
+int		register_posix_clock(int, struct kclock *);
+void		itimer_fire(struct itimer *it);
+int		itimespecfix(struct timespec *ts);
+
+#define CLOCK_CALL(clock, call, arglist)		\
+	((*posix_clocks[clock].call) arglist)
+
+SYSINIT(posix_timer, SI_SUB_P1003_1B, SI_ORDER_FIRST+4, itimer_start, NULL);
+
+
+static int
+settime(struct thread *td, struct timeval *tv)
+{
+	struct timeval delta, tv1, tv2;
+	static struct timeval maxtime, laststep;
+	struct timespec ts;
+	int s;
+
+	s = splclock();
+	microtime(&tv1);
+	delta = *tv;
+	timevalsub(&delta, &tv1);
+
+	/*
+	 * If the system is secure, we do not allow the time to be 
+	 * set to a value earlier than 1 second less than the highest
+	 * time we have yet seen. The worst a miscreant can do in
+	 * this circumstance is "freeze" time. He couldn't go
+	 * back to the past.
+	 *
+	 * We similarly do not allow the clock to be stepped more
+	 * than one second, nor more than once per second. This allows
+	 * a miscreant to make the clock march double-time, but no worse.
+	 */
+	if (securelevel_gt(td->td_ucred, 1) != 0) {
+		if (delta.tv_sec < 0 || delta.tv_usec < 0) {
+			/*
+			 * Update maxtime to latest time we've seen.
+			 */
+			if (tv1.tv_sec > maxtime.tv_sec)
+				maxtime = tv1;
+			tv2 = *tv;
+			timevalsub(&tv2, &maxtime);
+			if (tv2.tv_sec < -1) {
+				tv->tv_sec = maxtime.tv_sec - 1;
+				printf("Time adjustment clamped to -1 second\n");
+			}
+		} else {
+			if (tv1.tv_sec == laststep.tv_sec) {
+				splx(s);
+				return (EPERM);
+			}
+			if (delta.tv_sec > 1) {
+				tv->tv_sec = tv1.tv_sec + 1;
+				printf("Time adjustment clamped to +1 second\n");
+			}
+			laststep = *tv;
+		}
+	}
+
+	ts.tv_sec = tv->tv_sec;
+	ts.tv_nsec = tv->tv_usec * 1000;
+	mtx_lock(&Giant);
+	tc_setclock(&ts);
+	resettodr();
+	mtx_unlock(&Giant);
+	return (0);
+}
+
+#ifndef _SYS_SYSPROTO_HH_
+struct clock_gettime_args {
+	clockid_t clock_id;
+	struct	timespec *tp;
+};
+#endif
+#ifndef __rtems__
+/* ARGSUSED */
+int
+clock_gettime(struct thread *td, struct clock_gettime_args *uap)
+{
+	struct timespec ats;
+	int error;
+
+	error = kern_clock_gettime(td, uap->clock_id, &ats);
+	if (error == 0)
+		error = copyout(&ats, uap->tp, sizeof(ats));
+
+	return (error);
+}
+#endif
+
+#ifndef __rtems__
+int
+kern_clock_gettime(struct thread *td, clockid_t clock_id, struct timespec *ats)
+{
+	struct timeval sys, user;
+	struct proc *p;
+	uint64_t runtime, curtime, switchtime;
+
+	p = td->td_proc;
+	switch (clock_id) {
+	case CLOCK_REALTIME:		/* Default to precise. */
+	case CLOCK_REALTIME_PRECISE:
+		nanotime(ats);
+		break;
+	case CLOCK_REALTIME_FAST:
+		getnanotime(ats);
+		break;
+	case CLOCK_VIRTUAL:
+		PROC_LOCK(p);
+		PROC_SLOCK(p);
+		calcru(p, &user, &sys);
+		PROC_SUNLOCK(p);
+		PROC_UNLOCK(p);
+		TIMEVAL_TO_TIMESPEC(&user, ats);
+		break;
+	case CLOCK_PROF:
+		PROC_LOCK(p);
+		PROC_SLOCK(p);
+		calcru(p, &user, &sys);
+		PROC_SUNLOCK(p);
+		PROC_UNLOCK(p);
+		timevaladd(&user, &sys);
+		TIMEVAL_TO_TIMESPEC(&user, ats);
+		break;
+	case CLOCK_MONOTONIC:		/* Default to precise. */
+	case CLOCK_MONOTONIC_PRECISE:
+	case CLOCK_UPTIME:
+	case CLOCK_UPTIME_PRECISE:
+		nanouptime(ats);
+		break;
+	case CLOCK_UPTIME_FAST:
+	case CLOCK_MONOTONIC_FAST:
+		getnanouptime(ats);
+		break;
+	case CLOCK_SECOND:
+		ats->tv_sec = time_second;
+		ats->tv_nsec = 0;
+		break;
+	case CLOCK_THREAD_CPUTIME_ID:
+		critical_enter();
+		switchtime = PCPU_GET(switchtime);
+		curtime = cpu_ticks();
+		runtime = td->td_runtime;
+		critical_exit();
+		runtime = cputick2usec(runtime + curtime - switchtime);
+		ats->tv_sec = runtime / 1000000;
+		ats->tv_nsec = runtime % 1000000 * 1000;
+		break;
+	default:
+		return (EINVAL);
+	}
+	return (0);
+}
+#endif
+
+#ifndef _SYS_SYSPROTO_HH_
+struct clock_settime_args {
+	clockid_t clock_id;
+	const struct	timespec *tp;
+};
+#endif
+#ifndef __rtems__
+/* ARGSUSED */
+int
+clock_settime(struct thread *td, struct clock_settime_args *uap)
+{
+	struct timespec ats;
+	int error;
+
+	if ((error = copyin(uap->tp, &ats, sizeof(ats))) != 0)
+		return (error);
+	return (kern_clock_settime(td, uap->clock_id, &ats));
+}
+
+int
+kern_clock_settime(struct thread *td, clockid_t clock_id, struct timespec *ats)
+{
+	struct timeval atv;
+	int error;
+
+	if ((error = priv_check(td, PRIV_CLOCK_SETTIME)) != 0)
+		return (error);
+	if (clock_id != CLOCK_REALTIME)
+		return (EINVAL);
+	if (ats->tv_nsec < 0 || ats->tv_nsec >= 1000000000)
+		return (EINVAL);
+	/* XXX Don't convert nsec->usec and back */
+	TIMESPEC_TO_TIMEVAL(&atv, ats);
+	error = settime(td, &atv);
+	return (error);
+}
+#endif
+
+#ifndef _SYS_SYSPROTO_HH_
+struct clock_getres_args {
+	clockid_t clock_id;
+	struct	timespec *tp;
+};
+#endif
+#ifndef __rtems__
+int
+clock_getres(struct thread *td, struct clock_getres_args *uap)
+{
+	struct timespec ts;
+	int error;
+
+	if (uap->tp == NULL)
+		return (0);
+
+	error = kern_clock_getres(td, uap->clock_id, &ts);
+	if (error == 0)
+		error = copyout(&ts, uap->tp, sizeof(ts));
+	return (error);
+}
+
+int
+kern_clock_getres(struct thread *td, clockid_t clock_id, struct timespec *ts)
+{
+
+	ts->tv_sec = 0;
+	switch (clock_id) {
+	case CLOCK_REALTIME:
+	case CLOCK_REALTIME_FAST:
+	case CLOCK_REALTIME_PRECISE:
+	case CLOCK_MONOTONIC:
+	case CLOCK_MONOTONIC_FAST:
+	case CLOCK_MONOTONIC_PRECISE:
+	case CLOCK_UPTIME:
+	case CLOCK_UPTIME_FAST:
+	case CLOCK_UPTIME_PRECISE:
+		/*
+		 * Round up the result of the division cheaply by adding 1.
+		 * Rounding up is especially important if rounding down
+		 * would give 0.  Perfect rounding is unimportant.
+		 */
+		ts->tv_nsec = 1000000000 / tc_getfrequency() + 1;
+		break;
+	case CLOCK_VIRTUAL:
+	case CLOCK_PROF:
+		/* Accurately round up here because we can do so cheaply. */
+		ts->tv_nsec = (1000000000 + hz - 1) / hz;
+		break;
+	case CLOCK_SECOND:
+		ts->tv_sec = 1;
+		ts->tv_nsec = 0;
+		break;
+	case CLOCK_THREAD_CPUTIME_ID:
+		/* sync with cputick2usec */
+		ts->tv_nsec = 1000000 / cpu_tickrate();
+		if (ts->tv_nsec == 0)
+			ts->tv_nsec = 1000;
+		break;
+	default:
+		return (EINVAL);
+	}
+	return (0);
+}
+#endif
+
+static int nanowait;
+
+int
+kern_nanosleep(struct thread *td, struct timespec *rqt, struct timespec *rmt)
+{
+	struct timespec ts, ts2, ts3;
+	struct timeval tv;
+	int error;
+
+	if (rqt->tv_nsec < 0 || rqt->tv_nsec >= 1000000000)
+		return (EINVAL);
+	if (rqt->tv_sec < 0 || (rqt->tv_sec == 0 && rqt->tv_nsec == 0))
+		return (0);
+	getnanouptime(&ts);
+	timespecadd(&ts, rqt);
+	TIMESPEC_TO_TIMEVAL(&tv, rqt);
+	for (;;) {
+		error = tsleep(&nanowait, PWAIT | PCATCH, "nanslp",
+		    tvtohz(&tv));
+		getnanouptime(&ts2);
+		if (error != EWOULDBLOCK) {
+			if (error == ERESTART)
+				error = EINTR;
+			if (rmt != NULL) {
+				timespecsub(&ts, &ts2);
+				if (ts.tv_sec < 0)
+					timespecclear(&ts);
+				*rmt = ts;
+			}
+			return (error);
+		}
+		if (timespeccmp(&ts2, &ts, >=))
+			return (0);
+		ts3 = ts;
+		timespecsub(&ts3, &ts2);
+		TIMESPEC_TO_TIMEVAL(&tv, &ts3);
+	}
+}
+
+#ifndef _SYS_SYSPROTO_HH_
+struct nanosleep_args {
+	struct	timespec *rqtp;
+	struct	timespec *rmtp;
+};
+#endif
+/* ARGSUSED */
+int
+nanosleep(struct thread *td, struct nanosleep_args *uap)
+{
+	struct timespec rmt, rqt;
+	int error;
+
+	error = copyin(uap->rqtp, &rqt, sizeof(rqt));
+	if (error)
+		return (error);
+
+	if (uap->rmtp &&
+	    !useracc((caddr_t)uap->rmtp, sizeof(rmt), VM_PROT_WRITE))
+			return (EFAULT);
+	error = kern_nanosleep(td, &rqt, &rmt);
+	if (error && uap->rmtp) {
+		int error2;
+
+		error2 = copyout(&rmt, uap->rmtp, sizeof(rmt));
+		if (error2)
+			error = error2;
+	}
+	return (error);
+}
+
+#ifndef _SYS_SYSPROTO_HH_
+struct gettimeofday_args {
+	struct	timeval *tp;
+	struct	timezone *tzp;
+};
+#endif
+/* ARGSUSED */
+int
+gettimeofday(struct thread *td, struct gettimeofday_args *uap)
+{
+	struct timeval atv;
+	struct timezone rtz;
+	int error = 0;
+
+	if (uap->tp) {
+		microtime(&atv);
+		error = copyout(&atv, uap->tp, sizeof (atv));
+	}
+	if (error == 0 && uap->tzp != NULL) {
+		rtz.tz_minuteswest = tz_minuteswest;
+		rtz.tz_dsttime = tz_dsttime;
+		error = copyout(&rtz, uap->tzp, sizeof (rtz));
+	}
+	return (error);
+}
+
+#ifndef _SYS_SYSPROTO_HH_
+struct settimeofday_args {
+	struct	timeval *tv;
+	struct	timezone *tzp;
+};
+#endif
+/* ARGSUSED */
+int
+settimeofday(struct thread *td, struct settimeofday_args *uap)
+{
+	struct timeval atv, *tvp;
+	struct timezone atz, *tzp;
+	int error;
+
+	if (uap->tv) {
+		error = copyin(uap->tv, &atv, sizeof(atv));
+		if (error)
+			return (error);
+		tvp = &atv;
+	} else
+		tvp = NULL;
+	if (uap->tzp) {
+		error = copyin(uap->tzp, &atz, sizeof(atz));
+		if (error)
+			return (error);
+		tzp = &atz;
+	} else
+		tzp = NULL;
+	return (kern_settimeofday(td, tvp, tzp));
+}
+
+int
+kern_settimeofday(struct thread *td, struct timeval *tv, struct timezone *tzp)
+{
+	int error;
+
+	error = priv_check(td, PRIV_SETTIMEOFDAY);
+	if (error)
+		return (error);
+	/* Verify all parameters before changing time. */
+	if (tv) {
+		if (tv->tv_usec < 0 || tv->tv_usec >= 1000000)
+			return (EINVAL);
+		error = settime(td, tv);
+	}
+	if (tzp && error == 0) {
+		tz_minuteswest = tzp->tz_minuteswest;
+		tz_dsttime = tzp->tz_dsttime;
+	}
+	return (error);
+}
+
+/*
+ * Get value of an interval timer.  The process virtual and profiling virtual
+ * time timers are kept in the p_stats area, since they can be swapped out.
+ * These are kept internally in the way they are specified externally: in
+ * time until they expire.
+ *
+ * The real time interval timer is kept in the process table slot for the
+ * process, and its value (it_value) is kept as an absolute time rather than
+ * as a delta, so that it is easy to keep periodic real-time signals from
+ * drifting.
+ *
+ * Virtual time timers are processed in the hardclock() routine of
+ * kern_clock.c.  The real time timer is processed by a timeout routine,
+ * called from the softclock() routine.  Since a callout may be delayed in
+ * real time due to interrupt processing in the system, it is possible for
+ * the real time timeout routine (realitexpire, given below), to be delayed
+ * in real time past when it is supposed to occur.  It does not suffice,
+ * therefore, to reload the real timer .it_value from the real time timers
+ * .it_interval.  Rather, we compute the next time in absolute time the timer
+ * should go off.
+ */
+#ifndef _SYS_SYSPROTO_HH_
+struct getitimer_args {
+	u_int	which;
+	struct	itimerval *itv;
+};
+#endif
+int
+getitimer(struct thread *td, struct getitimer_args *uap)
+{
+	struct itimerval aitv;
+	int error;
+
+	error = kern_getitimer(td, uap->which, &aitv);
+	if (error != 0)
+		return (error);
+	return (copyout(&aitv, uap->itv, sizeof (struct itimerval)));
+}
+
+int
+kern_getitimer(struct thread *td, u_int which, struct itimerval *aitv)
+{
+	struct proc *p = td->td_proc;
+	struct timeval ctv;
+
+	if (which > ITIMER_PROF)
+		return (EINVAL);
+
+	if (which == ITIMER_REAL) {
+		/*
+		 * Convert from absolute to relative time in .it_value
+		 * part of real time timer.  If time for real time timer
+		 * has passed return 0, else return difference between
+		 * current time and time for the timer to go off.
+		 */
+		PROC_LOCK(p);
+		*aitv = p->p_realtimer;
+		PROC_UNLOCK(p);
+		if (timevalisset(&aitv->it_value)) {
+			getmicrouptime(&ctv);
+			if (timevalcmp(&aitv->it_value, &ctv, <))
+				timevalclear(&aitv->it_value);
+			else
+				timevalsub(&aitv->it_value, &ctv);
+		}
+	} else {
+		PROC_SLOCK(p);
+		*aitv = p->p_stats->p_timer[which];
+		PROC_SUNLOCK(p);
+	}
+	return (0);
+}
+
+#ifndef _SYS_SYSPROTO_HH_
+struct setitimer_args {
+	u_int	which;
+	struct	itimerval *itv, *oitv;
+};
+#endif
+int
+setitimer(struct thread *td, struct setitimer_args *uap)
+{
+	struct itimerval aitv, oitv;
+	int error;
+
+	if (uap->itv == NULL) {
+		uap->itv = uap->oitv;
+		return (getitimer(td, (struct getitimer_args *)uap));
+	}
+
+	if ((error = copyin(uap->itv, &aitv, sizeof(struct itimerval))))
+		return (error);
+	error = kern_setitimer(td, uap->which, &aitv, &oitv);
+	if (error != 0 || uap->oitv == NULL)
+		return (error);
+	return (copyout(&oitv, uap->oitv, sizeof(struct itimerval)));
+}
+
+int
+kern_setitimer(struct thread *td, u_int which, struct itimerval *aitv,
+    struct itimerval *oitv)
+{
+	struct proc *p = td->td_proc;
+	struct timeval ctv;
+
+	if (aitv == NULL)
+		return (kern_getitimer(td, which, oitv));
+
+	if (which > ITIMER_PROF)
+		return (EINVAL);
+	if (itimerfix(&aitv->it_value))
+		return (EINVAL);
+	if (!timevalisset(&aitv->it_value))
+		timevalclear(&aitv->it_interval);
+	else if (itimerfix(&aitv->it_interval))
+		return (EINVAL);
+
+	if (which == ITIMER_REAL) {
+		PROC_LOCK(p);
+		if (timevalisset(&p->p_realtimer.it_value))
+			callout_stop(&p->p_itcallout);
+		getmicrouptime(&ctv);
+		if (timevalisset(&aitv->it_value)) {
+			callout_reset(&p->p_itcallout, tvtohz(&aitv->it_value),
+			    realitexpire, p);
+			timevaladd(&aitv->it_value, &ctv);
+		}
+		*oitv = p->p_realtimer;
+		p->p_realtimer = *aitv;
+		PROC_UNLOCK(p);
+		if (timevalisset(&oitv->it_value)) {
+			if (timevalcmp(&oitv->it_value, &ctv, <))
+				timevalclear(&oitv->it_value);
+			else
+				timevalsub(&oitv->it_value, &ctv);
+		}
+	} else {
+		PROC_SLOCK(p);
+		*oitv = p->p_stats->p_timer[which];
+		p->p_stats->p_timer[which] = *aitv;
+		PROC_SUNLOCK(p);
+	}
+	return (0);
+}
+
+/*
+ * Real interval timer expired:
+ * send process whose timer expired an alarm signal.
+ * If time is not set up to reload, then just return.
+ * Else compute next time timer should go off which is > current time.
+ * This is where delay in processing this timeout causes multiple
+ * SIGALRM calls to be compressed into one.
+ * tvtohz() always adds 1 to allow for the time until the next clock
+ * interrupt being strictly less than 1 clock tick, but we don't want
+ * that here since we want to appear to be in sync with the clock
+ * interrupt even when we're delayed.
+ */
+void
+realitexpire(void *arg)
+{
+	struct proc *p;
+	struct timeval ctv, ntv;
+
+	p = (struct proc *)arg;
+	PROC_LOCK(p);
+	psignal(p, SIGALRM);
+	if (!timevalisset(&p->p_realtimer.it_interval)) {
+		timevalclear(&p->p_realtimer.it_value);
+		if (p->p_flag & P_WEXIT)
+			wakeup(&p->p_itcallout);
+		PROC_UNLOCK(p);
+		return;
+	}
+	for (;;) {
+		timevaladd(&p->p_realtimer.it_value,
+		    &p->p_realtimer.it_interval);
+		getmicrouptime(&ctv);
+		if (timevalcmp(&p->p_realtimer.it_value, &ctv, >)) {
+			ntv = p->p_realtimer.it_value;
+			timevalsub(&ntv, &ctv);
+			callout_reset(&p->p_itcallout, tvtohz(&ntv) - 1,
+			    realitexpire, p);
+			PROC_UNLOCK(p);
+			return;
+		}
+	}
+	/*NOTREACHED*/
+}
+#endif /* __rtems__ */
+
+/*
+ * Check that a proposed value to load into the .it_value or
+ * .it_interval part of an interval timer is acceptable, and
+ * fix it to have at least minimal value (i.e. if it is less
+ * than the resolution of the clock, round it up.)
+ */
+int
+itimerfix(struct timeval *tv)
+{
+
+	if (tv->tv_sec < 0 || tv->tv_usec < 0 || tv->tv_usec >= 1000000)
+		return (EINVAL);
+	if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick)
+		tv->tv_usec = tick;
+	return (0);
+}
+
+#ifndef __rtems__
+/*
+ * Decrement an interval timer by a specified number
+ * of microseconds, which must be less than a second,
+ * i.e. < 1000000.  If the timer expires, then reload
+ * it.  In this case, carry over (usec - old value) to
+ * reduce the value reloaded into the timer so that
+ * the timer does not drift.  This routine assumes
+ * that it is called in a context where the timers
+ * on which it is operating cannot change in value.
+ */
+int
+itimerdecr(struct itimerval *itp, int usec)
+{
+
+	if (itp->it_value.tv_usec < usec) {
+		if (itp->it_value.tv_sec == 0) {
+			/* expired, and already in next interval */
+			usec -= itp->it_value.tv_usec;
+			goto expire;
+		}
+		itp->it_value.tv_usec += 1000000;
+		itp->it_value.tv_sec--;
+	}
+	itp->it_value.tv_usec -= usec;
+	usec = 0;
+	if (timevalisset(&itp->it_value))
+		return (1);
+	/* expired, exactly at end of interval */
+expire:
+	if (timevalisset(&itp->it_interval)) {
+		itp->it_value = itp->it_interval;
+		itp->it_value.tv_usec -= usec;
+		if (itp->it_value.tv_usec < 0) {
+			itp->it_value.tv_usec += 1000000;
+			itp->it_value.tv_sec--;
+		}
+	} else
+		itp->it_value.tv_usec = 0;		/* sec is already 0 */
+	return (0);
+}
+#endif /* __rtems__ */
+
+/*
+ * Add and subtract routines for timevals.
+ * N.B.: subtract routine doesn't deal with
+ * results which are before the beginning,
+ * it just gets very confused in this case.
+ * Caveat emptor.
+ */
+void
+timevaladd(struct timeval *t1, const struct timeval *t2)
+{
+
+	t1->tv_sec += t2->tv_sec;
+	t1->tv_usec += t2->tv_usec;
+	timevalfix(t1);
+}
+
+void
+timevalsub(struct timeval *t1, const struct timeval *t2)
+{
+
+	t1->tv_sec -= t2->tv_sec;
+	t1->tv_usec -= t2->tv_usec;
+	timevalfix(t1);
+}
+
+static void
+timevalfix(struct timeval *t1)
+{
+
+	if (t1->tv_usec < 0) {
+		t1->tv_sec--;
+		t1->tv_usec += 1000000;
+	}
+	if (t1->tv_usec >= 1000000) {
+		t1->tv_sec++;
+		t1->tv_usec -= 1000000;
+	}
+}
+
+/*
+ * ratecheck(): simple time-based rate-limit checking.
+ */
+int
+ratecheck(struct timeval *lasttime, const struct timeval *mininterval)
+{
+	struct timeval tv, delta;
+	int rv = 0;
+
+	getmicrouptime(&tv);		/* NB: 10ms precision */
+	delta = tv;
+	timevalsub(&delta, lasttime);
+
+	/*
+	 * check for 0,0 is so that the message will be seen at least once,
+	 * even if interval is huge.
+	 */
+	if (timevalcmp(&delta, mininterval, >=) ||
+	    (lasttime->tv_sec == 0 && lasttime->tv_usec == 0)) {
+		*lasttime = tv;
+		rv = 1;
+	}
+
+	return (rv);
+}
+
+/*
+ * ppsratecheck(): packets (or events) per second limitation.
+ *
+ * Return 0 if the limit is to be enforced (e.g. the caller
+ * should drop a packet because of the rate limitation).
+ *
+ * maxpps of 0 always causes zero to be returned.  maxpps of -1
+ * always causes 1 to be returned; this effectively defeats rate
+ * limiting.
+ *
+ * Note that we maintain the struct timeval for compatibility
+ * with other bsd systems.  We reuse the storage and just monitor
+ * clock ticks for minimal overhead.  
+ */
+int
+ppsratecheck(struct timeval *lasttime, int *curpps, int maxpps)
+{
+	int now;
+
+	/*
+	 * Reset the last time and counter if this is the first call
+	 * or more than a second has passed since the last update of
+	 * lasttime.
+	 */
+	now = ticks;
+	if (lasttime->tv_sec == 0 || (u_int)(now - lasttime->tv_sec) >= hz) {
+		lasttime->tv_sec = now;
+		*curpps = 1;
+		return (maxpps != 0);
+	} else {
+		(*curpps)++;		/* NB: ignore potential overflow */
+		return (maxpps < 0 || *curpps < maxpps);
+	}
+}
+
+#ifndef __rtems__
+static void
+itimer_start(void)
+{
+	struct kclock rt_clock = {
+		.timer_create  = realtimer_create,
+		.timer_delete  = realtimer_delete,
+		.timer_settime = realtimer_settime,
+		.timer_gettime = realtimer_gettime,
+		.event_hook    = NULL
+	};
+
+	itimer_zone = uma_zcreate("itimer", sizeof(struct itimer),
+		NULL, NULL, itimer_init, itimer_fini, UMA_ALIGN_PTR, 0);
+	register_posix_clock(CLOCK_REALTIME,  &rt_clock);
+	register_posix_clock(CLOCK_MONOTONIC, &rt_clock);
+	p31b_setcfg(CTL_P1003_1B_TIMERS, 200112L);
+	p31b_setcfg(CTL_P1003_1B_DELAYTIMER_MAX, INT_MAX);
+	p31b_setcfg(CTL_P1003_1B_TIMER_MAX, TIMER_MAX);
+	EVENTHANDLER_REGISTER(process_exit, itimers_event_hook_exit,
+		(void *)ITIMER_EV_EXIT, EVENTHANDLER_PRI_ANY);
+	EVENTHANDLER_REGISTER(process_exec, itimers_event_hook_exec,
+		(void *)ITIMER_EV_EXEC, EVENTHANDLER_PRI_ANY);
+}
+
+int
+register_posix_clock(int clockid, struct kclock *clk)
+{
+	if ((unsigned)clockid >= MAX_CLOCKS) {
+		printf("%s: invalid clockid\n", __func__);
+		return (0);
+	}
+	posix_clocks[clockid] = *clk;
+	return (1);
+}
+
+static int
+itimer_init(void *mem, int size, int flags)
+{
+	struct itimer *it;
+
+	it = (struct itimer *)mem;
+	mtx_init(&it->it_mtx, "itimer lock", NULL, MTX_DEF);
+	return (0);
+}
+
+static void
+itimer_fini(void *mem, int size)
+{
+	struct itimer *it;
+
+	it = (struct itimer *)mem;
+	mtx_destroy(&it->it_mtx);
+}
+
+static void
+itimer_enter(struct itimer *it)
+{
+
+	mtx_assert(&it->it_mtx, MA_OWNED);
+	it->it_usecount++;
+}
+
+static void
+itimer_leave(struct itimer *it)
+{
+
+	mtx_assert(&it->it_mtx, MA_OWNED);
+	KASSERT(it->it_usecount > 0, ("invalid it_usecount"));
+
+	if (--it->it_usecount == 0 && (it->it_flags & ITF_WANTED) != 0)
+		wakeup(it);
+}
+
+#ifndef _SYS_SYSPROTO_HH_
+struct ktimer_create_args {
+	clockid_t clock_id;
+	struct sigevent * evp;
+	int * timerid;
+};
+#endif
+int
+ktimer_create(struct thread *td, struct ktimer_create_args *uap)
+{
+	struct sigevent *evp1, ev;
+	int id;
+	int error;
+
+	if (uap->evp != NULL) {
+		error = copyin(uap->evp, &ev, sizeof(ev));
+		if (error != 0)
+			return (error);
+		evp1 = &ev;
+	} else
+		evp1 = NULL;
+
+	error = kern_timer_create(td, uap->clock_id, evp1, &id, -1);
+
+	if (error == 0) {
+		error = copyout(&id, uap->timerid, sizeof(int));
+		if (error != 0)
+			kern_timer_delete(td, id);
+	}
+	return (error);
+}
+
+static int
+kern_timer_create(struct thread *td, clockid_t clock_id,
+	struct sigevent *evp, int *timerid, int preset_id)
+{
+	struct proc *p = td->td_proc;
+	struct itimer *it;
+	int id;
+	int error;
+
+	if (clock_id < 0 || clock_id >= MAX_CLOCKS)
+		return (EINVAL);
+
+	if (posix_clocks[clock_id].timer_create == NULL)
+		return (EINVAL);
+
+	if (evp != NULL) {
+		if (evp->sigev_notify != SIGEV_NONE &&
+		    evp->sigev_notify != SIGEV_SIGNAL &&
+		    evp->sigev_notify != SIGEV_THREAD_ID)
+			return (EINVAL);
+		if ((evp->sigev_notify == SIGEV_SIGNAL ||
+		     evp->sigev_notify == SIGEV_THREAD_ID) &&
+			!_SIG_VALID(evp->sigev_signo))
+			return (EINVAL);
+	}
+	
+	if (p->p_itimers == NULL)
+		itimers_alloc(p);
+	
+	it = uma_zalloc(itimer_zone, M_WAITOK);
+	it->it_flags = 0;
+	it->it_usecount = 0;
+	it->it_active = 0;
+	timespecclear(&it->it_time.it_value);
+	timespecclear(&it->it_time.it_interval);
+	it->it_overrun = 0;
+	it->it_overrun_last = 0;
+	it->it_clockid = clock_id;
+	it->it_timerid = -1;
+	it->it_proc = p;
+	ksiginfo_init(&it->it_ksi);
+	it->it_ksi.ksi_flags |= KSI_INS | KSI_EXT;
+	error = CLOCK_CALL(clock_id, timer_create, (it));
+	if (error != 0)
+		goto out;
+
+	PROC_LOCK(p);
+	if (preset_id != -1) {
+		KASSERT(preset_id >= 0 && preset_id < 3, ("invalid preset_id"));
+		id = preset_id;
+		if (p->p_itimers->its_timers[id] != NULL) {
+			PROC_UNLOCK(p);
+			error = 0;
+			goto out;
+		}
+	} else {
+		/*
+		 * Find a free timer slot, skipping those reserved
+		 * for setitimer().
+		 */
+		for (id = 3; id < TIMER_MAX; id++)
+			if (p->p_itimers->its_timers[id] == NULL)
+				break;
+		if (id == TIMER_MAX) {
+			PROC_UNLOCK(p);
+			error = EAGAIN;
+			goto out;
+		}
+	}
+	it->it_timerid = id;
+	p->p_itimers->its_timers[id] = it;
+	if (evp != NULL)
+		it->it_sigev = *evp;
+	else {
+		it->it_sigev.sigev_notify = SIGEV_SIGNAL;
+		switch (clock_id) {
+		default:
+		case CLOCK_REALTIME:
+			it->it_sigev.sigev_signo = SIGALRM;
+			break;
+		case CLOCK_VIRTUAL:
+ 			it->it_sigev.sigev_signo = SIGVTALRM;
+			break;
+		case CLOCK_PROF:
+			it->it_sigev.sigev_signo = SIGPROF;
+			break;
+		}
+		it->it_sigev.sigev_value.sival_int = id;
+	}
+
+	if (it->it_sigev.sigev_notify == SIGEV_SIGNAL ||
+	    it->it_sigev.sigev_notify == SIGEV_THREAD_ID) {
+		it->it_ksi.ksi_signo = it->it_sigev.sigev_signo;
+		it->it_ksi.ksi_code = SI_TIMER;
+		it->it_ksi.ksi_value = it->it_sigev.sigev_value;
+		it->it_ksi.ksi_timerid = id;
+	}
+	PROC_UNLOCK(p);
+	*timerid = id;
+	return (0);
+
+out:
+	ITIMER_LOCK(it);
+	CLOCK_CALL(it->it_clockid, timer_delete, (it));
+	ITIMER_UNLOCK(it);
+	uma_zfree(itimer_zone, it);
+	return (error);
+}
+
+#ifndef _SYS_SYSPROTO_HH_
+struct ktimer_delete_args {
+	int timerid;
+};
+#endif
+int
+ktimer_delete(struct thread *td, struct ktimer_delete_args *uap)
+{
+	return (kern_timer_delete(td, uap->timerid));
+}
+
+static struct itimer *
+itimer_find(struct proc *p, int timerid)
+{
+	struct itimer *it;
+
+	PROC_LOCK_ASSERT(p, MA_OWNED);
+	if ((p->p_itimers == NULL) ||
+	    (timerid < 0) || (timerid >= TIMER_MAX) ||
+	    (it = p->p_itimers->its_timers[timerid]) == NULL) {
+		return (NULL);
+	}
+	ITIMER_LOCK(it);
+	if ((it->it_flags & ITF_DELETING) != 0) {
+		ITIMER_UNLOCK(it);
+		it = NULL;
+	}
+	return (it);
+}
+
+static int
+kern_timer_delete(struct thread *td, int timerid)
+{
+	struct proc *p = td->td_proc;
+	struct itimer *it;
+
+	PROC_LOCK(p);
+	it = itimer_find(p, timerid);
+	if (it == NULL) {
+		PROC_UNLOCK(p);
+		return (EINVAL);
+	}
+	PROC_UNLOCK(p);
+
+	it->it_flags |= ITF_DELETING;
+	while (it->it_usecount > 0) {
+		it->it_flags |= ITF_WANTED;
+		msleep(it, &it->it_mtx, PPAUSE, "itimer", 0);
+	}
+	it->it_flags &= ~ITF_WANTED;
+	CLOCK_CALL(it->it_clockid, timer_delete, (it));
+	ITIMER_UNLOCK(it);
+
+	PROC_LOCK(p);
+	if (KSI_ONQ(&it->it_ksi))
+		sigqueue_take(&it->it_ksi);
+	p->p_itimers->its_timers[timerid] = NULL;
+	PROC_UNLOCK(p);
+	uma_zfree(itimer_zone, it);
+	return (0);
+}
+
+#ifndef _SYS_SYSPROTO_HH_
+struct ktimer_settime_args {
+	int timerid;
+	int flags;
+	const struct itimerspec * value;
+	struct itimerspec * ovalue;
+};
+#endif
+int
+ktimer_settime(struct thread *td, struct ktimer_settime_args *uap)
+{
+	struct proc *p = td->td_proc;
+	struct itimer *it;
+	struct itimerspec val, oval, *ovalp;
+	int error;
+
+	error = copyin(uap->value, &val, sizeof(val));
+	if (error != 0)
+		return (error);
+	
+	if (uap->ovalue != NULL)
+		ovalp = &oval;
+	else
+		ovalp = NULL;
+
+	PROC_LOCK(p);
+	if (uap->timerid < 3 ||
+	    (it = itimer_find(p, uap->timerid)) == NULL) {
+		PROC_UNLOCK(p);
+		error = EINVAL;
+	} else {
+		PROC_UNLOCK(p);
+		itimer_enter(it);
+		error = CLOCK_CALL(it->it_clockid, timer_settime,
+				(it, uap->flags, &val, ovalp));
+		itimer_leave(it);
+		ITIMER_UNLOCK(it);
+	}
+	if (error == 0 && uap->ovalue != NULL)
+		error = copyout(ovalp, uap->ovalue, sizeof(*ovalp));
+	return (error);
+}
+
+#ifndef _SYS_SYSPROTO_HH_
+struct ktimer_gettime_args {
+	int timerid;
+	struct itimerspec * value;
+};
+#endif
+int
+ktimer_gettime(struct thread *td, struct ktimer_gettime_args *uap)
+{
+	struct proc *p = td->td_proc;
+	struct itimer *it;
+	struct itimerspec val;
+	int error;
+
+	PROC_LOCK(p);
+	if (uap->timerid < 3 ||
+	   (it = itimer_find(p, uap->timerid)) == NULL) {
+		PROC_UNLOCK(p);
+		error = EINVAL;
+	} else {
+		PROC_UNLOCK(p);
+		itimer_enter(it);
+		error = CLOCK_CALL(it->it_clockid, timer_gettime,
+				(it, &val));
+		itimer_leave(it);
+		ITIMER_UNLOCK(it);
+	}
+	if (error == 0)
+		error = copyout(&val, uap->value, sizeof(val));
+	return (error);
+}
+
+#ifndef _SYS_SYSPROTO_HH_
+struct timer_getoverrun_args {
+	int timerid;
+};
+#endif
+int
+ktimer_getoverrun(struct thread *td, struct ktimer_getoverrun_args *uap)
+{
+	struct proc *p = td->td_proc;
+	struct itimer *it;
+	int error ;
+
+	PROC_LOCK(p);
+	if (uap->timerid < 3 ||
+	    (it = itimer_find(p, uap->timerid)) == NULL) {
+		PROC_UNLOCK(p);
+		error = EINVAL;
+	} else {
+		td->td_retval[0] = it->it_overrun_last;
+		ITIMER_UNLOCK(it);
+		PROC_UNLOCK(p);
+		error = 0;
+	}
+	return (error);
+}
+
+static int
+realtimer_create(struct itimer *it)
+{
+	callout_init_mtx(&it->it_callout, &it->it_mtx, 0);
+	return (0);
+}
+
+static int
+realtimer_delete(struct itimer *it)
+{
+	mtx_assert(&it->it_mtx, MA_OWNED);
+	
+	/*
+	 * clear timer's value and interval to tell realtimer_expire
+	 * to not rearm the timer.
+	 */
+	timespecclear(&it->it_time.it_value);
+	timespecclear(&it->it_time.it_interval);
+	ITIMER_UNLOCK(it);
+	callout_drain(&it->it_callout);
+	ITIMER_LOCK(it);
+	return (0);
+}
+
+static int
+realtimer_gettime(struct itimer *it, struct itimerspec *ovalue)
+{
+	struct timespec cts;
+
+	mtx_assert(&it->it_mtx, MA_OWNED);
+
+	realtimer_clocktime(it->it_clockid, &cts);
+	*ovalue = it->it_time;
+	if (ovalue->it_value.tv_sec != 0 || ovalue->it_value.tv_nsec != 0) {
+		timespecsub(&ovalue->it_value, &cts);
+		if (ovalue->it_value.tv_sec < 0 ||
+		    (ovalue->it_value.tv_sec == 0 &&
+		     ovalue->it_value.tv_nsec == 0)) {
+			ovalue->it_value.tv_sec  = 0;
+			ovalue->it_value.tv_nsec = 1;
+		}
+	}
+	return (0);
+}
+
+static int
+realtimer_settime(struct itimer *it, int flags,
+	struct itimerspec *value, struct itimerspec *ovalue)
+{
+	struct timespec cts, ts;
+	struct timeval tv;
+	struct itimerspec val;
+
+	mtx_assert(&it->it_mtx, MA_OWNED);
+
+	val = *value;
+	if (itimespecfix(&val.it_value))
+		return (EINVAL);
+
+	if (timespecisset(&val.it_value)) {
+		if (itimespecfix(&val.it_interval))
+			return (EINVAL);
+	} else {
+		timespecclear(&val.it_interval);
+	}
+	
+	if (ovalue != NULL)
+		realtimer_gettime(it, ovalue);
+
+	it->it_time = val;
+	if (timespecisset(&val.it_value)) {
+		realtimer_clocktime(it->it_clockid, &cts);
+		ts = val.it_value;
+		if ((flags & TIMER_ABSTIME) == 0) {
+			/* Convert to absolute time. */
+			timespecadd(&it->it_time.it_value, &cts);
+		} else {
+			timespecsub(&ts, &cts);
+			/*
+			 * We don't care if ts is negative, tztohz will
+			 * fix it.
+			 */
+		}
+		TIMESPEC_TO_TIMEVAL(&tv, &ts);
+		callout_reset(&it->it_callout, tvtohz(&tv),
+			realtimer_expire, it);
+	} else {
+		callout_stop(&it->it_callout);
+	}
+
+	return (0);
+}
+
+static void
+realtimer_clocktime(clockid_t id, struct timespec *ts)
+{
+	if (id == CLOCK_REALTIME)
+		getnanotime(ts);
+	else	/* CLOCK_MONOTONIC */
+		getnanouptime(ts);
+}
+
+int
+itimer_accept(struct proc *p, int timerid, ksiginfo_t *ksi)
+{
+	struct itimer *it;
+
+	PROC_LOCK_ASSERT(p, MA_OWNED);
+	it = itimer_find(p, timerid);
+	if (it != NULL) {
+		ksi->ksi_overrun = it->it_overrun;
+		it->it_overrun_last = it->it_overrun;
+		it->it_overrun = 0;
+		ITIMER_UNLOCK(it);
+		return (0);
+	}
+	return (EINVAL);
+}
+
+int
+itimespecfix(struct timespec *ts)
+{
+
+	if (ts->tv_sec < 0 || ts->tv_nsec < 0 || ts->tv_nsec >= 1000000000)
+		return (EINVAL);
+	if (ts->tv_sec == 0 && ts->tv_nsec != 0 && ts->tv_nsec < tick * 1000)
+		ts->tv_nsec = tick * 1000;
+	return (0);
+}
+
+/* Timeout callback for realtime timer */
+static void
+realtimer_expire(void *arg)
+{
+	struct timespec cts, ts;
+	struct timeval tv;
+	struct itimer *it;
+
+	it = (struct itimer *)arg;
+
+	realtimer_clocktime(it->it_clockid, &cts);
+	/* Only fire if time is reached. */
+	if (timespeccmp(&cts, &it->it_time.it_value, >=)) {
+		if (timespecisset(&it->it_time.it_interval)) {
+			timespecadd(&it->it_time.it_value,
+				    &it->it_time.it_interval);
+			while (timespeccmp(&cts, &it->it_time.it_value, >=)) {
+				if (it->it_overrun < INT_MAX)
+					it->it_overrun++;
+				else
+					it->it_ksi.ksi_errno = ERANGE;
+				timespecadd(&it->it_time.it_value,
+					    &it->it_time.it_interval);
+			}
+		} else {
+			/* single shot timer ? */
+			timespecclear(&it->it_time.it_value);
+		}
+		if (timespecisset(&it->it_time.it_value)) {
+			ts = it->it_time.it_value;
+			timespecsub(&ts, &cts);
+			TIMESPEC_TO_TIMEVAL(&tv, &ts);
+			callout_reset(&it->it_callout, tvtohz(&tv),
+				 realtimer_expire, it);
+		}
+		itimer_enter(it);
+		ITIMER_UNLOCK(it);
+		itimer_fire(it);
+		ITIMER_LOCK(it);
+		itimer_leave(it);
+	} else if (timespecisset(&it->it_time.it_value)) {
+		ts = it->it_time.it_value;
+		timespecsub(&ts, &cts);
+		TIMESPEC_TO_TIMEVAL(&tv, &ts);
+		callout_reset(&it->it_callout, tvtohz(&tv), realtimer_expire,
+ 			it);
+	}
+}
+
+void
+itimer_fire(struct itimer *it)
+{
+	struct proc *p = it->it_proc;
+	int ret;
+
+	if (it->it_sigev.sigev_notify == SIGEV_SIGNAL ||
+	    it->it_sigev.sigev_notify == SIGEV_THREAD_ID) {
+		PROC_LOCK(p);
+		if (!KSI_ONQ(&it->it_ksi)) {
+			it->it_ksi.ksi_errno = 0;
+			ret = psignal_event(p, &it->it_sigev, &it->it_ksi);
+			if (__predict_false(ret != 0)) {
+				it->it_overrun++;
+				/*
+				 * Broken userland code, thread went
+				 * away, disarm the timer.
+				 */
+				if (ret == ESRCH) {
+					ITIMER_LOCK(it);
+					timespecclear(&it->it_time.it_value);
+					timespecclear(&it->it_time.it_interval);
+					callout_stop(&it->it_callout);
+					ITIMER_UNLOCK(it);
+				}
+			}
+		} else {
+			if (it->it_overrun < INT_MAX)
+				it->it_overrun++;
+			else
+				it->it_ksi.ksi_errno = ERANGE;
+		}
+		PROC_UNLOCK(p);
+	}
+}
+
+static void
+itimers_alloc(struct proc *p)
+{
+	struct itimers *its;
+	int i;
+
+	its = malloc(sizeof (struct itimers), M_SUBPROC, M_WAITOK | M_ZERO);
+	LIST_INIT(&its->its_virtual);
+	LIST_INIT(&its->its_prof);
+	TAILQ_INIT(&its->its_worklist);
+	for (i = 0; i < TIMER_MAX; i++)
+		its->its_timers[i] = NULL;
+	PROC_LOCK(p);
+	if (p->p_itimers == NULL) {
+		p->p_itimers = its;
+		PROC_UNLOCK(p);
+	}
+	else {
+		PROC_UNLOCK(p);
+		free(its, M_SUBPROC);
+	}
+}
+
+static void
+itimers_event_hook_exec(void *arg, struct proc *p, struct image_params *imgp __unused)
+{
+	itimers_event_hook_exit(arg, p);
+}
+
+/* Clean up timers when some process events are being triggered. */
+static void
+itimers_event_hook_exit(void *arg, struct proc *p)
+{
+	struct itimers *its;
+	struct itimer *it;
+	int event = (int)(intptr_t)arg;
+	int i;
+
+	if (p->p_itimers != NULL) {
+		its = p->p_itimers;
+		for (i = 0; i < MAX_CLOCKS; ++i) {
+			if (posix_clocks[i].event_hook != NULL)
+				CLOCK_CALL(i, event_hook, (p, i, event));
+		}
+		/*
+		 * According to susv3, XSI interval timers should be inherited
+		 * by new image.
+		 */
+		if (event == ITIMER_EV_EXEC)
+			i = 3;
+		else if (event == ITIMER_EV_EXIT)
+			i = 0;
+		else
+			panic("unhandled event");
+		for (; i < TIMER_MAX; ++i) {
+			if ((it = its->its_timers[i]) != NULL)
+				kern_timer_delete(curthread, i);
+		}
+		if (its->its_timers[0] == NULL &&
+		    its->its_timers[1] == NULL &&
+		    its->its_timers[2] == NULL) {
+			free(its, M_SUBPROC);
+			p->p_itimers = NULL;
+		}
+	}
+}
+#endif /* __rtems__ */