source: rtems-libbsd/freebsd/sys/kern/kern_time.c @ 2017a6d

#include <machine/rtems-bsd-kernel-space.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 <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <rtems/bsd/sys/param.h>
#include <sys/systm.h>
#include <sys/limits.h>
#include <sys/clock.h>
#include <rtems/bsd/sys/lock.h>
#include <sys/mutex.h>
#include <sys/sysproto.h>
#include <sys/eventhandler.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/kernel.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/posix4.h>
#include <sys/time.h>
#include <sys/timers.h>
#include <sys/timetc.h>
#include <sys/vnode.h>

#include <vm/vm.h>
#include <vm/vm_extern.h>

#define MAX_CLOCKS      (CLOCK_MONOTONIC+1)
#define CPUCLOCK_BIT            0x80000000
#define CPUCLOCK_PROCESS_BIT    0x40000000
#define CPUCLOCK_ID_MASK        (~(CPUCLOCK_BIT|CPUCLOCK_PROCESS_BIT))
#define MAKE_THREAD_CPUCLOCK(tid)       (CPUCLOCK_BIT|(tid))
#define MAKE_PROCESS_CPUCLOCK(pid)      \
        (CPUCLOCK_BIT|CPUCLOCK_PROCESS_BIT|(pid))

#ifndef __rtems__
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 *);

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_H_
struct clock_getcpuclockid2_args {
        id_t id;
        int which,
        clockid_t *clock_id;
};
#endif
/* ARGSUSED */
int
sys_clock_getcpuclockid2(struct thread *td, struct clock_getcpuclockid2_args *uap)
{
        clockid_t clk_id;
        int error;

        error = kern_clock_getcpuclockid2(td, uap->id, uap->which, &clk_id);
        if (error == 0)
                error = copyout(&clk_id, uap->clock_id, sizeof(clockid_t));
        return (error);
}

int
kern_clock_getcpuclockid2(struct thread *td, id_t id, int which,
    clockid_t *clk_id)
{
        struct proc *p;
        pid_t pid;
        lwpid_t tid;
        int error;

        switch (which) {
        case CPUCLOCK_WHICH_PID:
                if (id != 0) {
                        error = pget(id, PGET_CANSEE | PGET_NOTID, &p);
                        if (error != 0)
                                return (error);
                        PROC_UNLOCK(p);
                        pid = id;
                } else {
                        pid = td->td_proc->p_pid;
                }
                *clk_id = MAKE_PROCESS_CPUCLOCK(pid);
                return (0);
        case CPUCLOCK_WHICH_TID:
                tid = id == 0 ? td->td_tid : id;
                *clk_id = MAKE_THREAD_CPUCLOCK(tid);
                return (0);
        default:
                return (EINVAL);
        }
}

#ifndef _SYS_SYSPROTO_H_
struct clock_gettime_args {
        clockid_t clock_id;
        struct  timespec *tp;
};
#endif
#ifndef __rtems__
/* ARGSUSED */
int
sys_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__
static inline void 
cputick2timespec(uint64_t runtime, struct timespec *ats)
{
        runtime = cputick2usec(runtime);
        ats->tv_sec = runtime / 1000000;
        ats->tv_nsec = runtime % 1000000 * 1000;
}

static void
get_thread_cputime(struct thread *targettd, struct timespec *ats)
{
        uint64_t runtime, curtime, switchtime;

        if (targettd == NULL) { /* current thread */
                critical_enter();
                switchtime = PCPU_GET(switchtime);
                curtime = cpu_ticks();
                runtime = curthread->td_runtime;
                critical_exit();
                runtime += curtime - switchtime;
        } else {
                thread_lock(targettd);
                runtime = targettd->td_runtime;
                thread_unlock(targettd);
        }
        cputick2timespec(runtime, ats);
}

static void
get_process_cputime(struct proc *targetp, struct timespec *ats)
{
        uint64_t runtime;
        struct rusage ru;

        PROC_SLOCK(targetp);
        rufetch(targetp, &ru);
        runtime = targetp->p_rux.rux_runtime;
        PROC_SUNLOCK(targetp);
        cputick2timespec(runtime, ats);
}

static int
get_cputime(struct thread *td, clockid_t clock_id, struct timespec *ats)
{
        struct proc *p, *p2;
        struct thread *td2;
        lwpid_t tid;
        pid_t pid;
        int error;

        p = td->td_proc;
        if ((clock_id & CPUCLOCK_PROCESS_BIT) == 0) {
                tid = clock_id & CPUCLOCK_ID_MASK;
                td2 = tdfind(tid, p->p_pid);
                if (td2 == NULL)
                        return (EINVAL);
                get_thread_cputime(td2, ats);
                PROC_UNLOCK(td2->td_proc);
        } else {
                pid = clock_id & CPUCLOCK_ID_MASK;
                error = pget(pid, PGET_CANSEE, &p2);
                if (error != 0)
                        return (EINVAL);
                get_process_cputime(p2, ats);
                PROC_UNLOCK(p2);
        }
        return (0);
}

int
kern_clock_gettime(struct thread *td, clockid_t clock_id, struct timespec *ats)
{
        struct timeval sys, user;
        struct proc *p;

        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:
                get_thread_cputime(NULL, ats);
                break;
        case CLOCK_PROCESS_CPUTIME_ID:
                PROC_LOCK(p);
                get_process_cputime(p, ats);
                PROC_UNLOCK(p);
                break;
        default:
                if ((int)clock_id >= 0)
                        return (EINVAL);
                return (get_cputime(td, clock_id, ats));
        }
        return (0);
}
#endif

#ifndef _SYS_SYSPROTO_H_
struct clock_settime_args {
        clockid_t clock_id;
        const struct    timespec *tp;
};
#endif
#ifndef __rtems__
/* ARGSUSED */
int
sys_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_H_
struct clock_getres_args {
        clockid_t clock_id;
        struct  timespec *tp;
};
#endif
#ifndef __rtems__
int
sys_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:
        case CLOCK_PROCESS_CPUTIME_ID:
        cputime:
                /* sync with cputick2usec */
                ts->tv_nsec = 1000000 / cpu_tickrate();
                if (ts->tv_nsec == 0)
                        ts->tv_nsec = 1000;
                break;
        default:
                if ((int)clock_id < 0)
                        goto cputime;
                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_H_
struct nanosleep_args {
        struct  timespec *rqtp;
        struct  timespec *rmtp;
};
#endif
/* ARGSUSED */
int
sys_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_H_
struct gettimeofday_args {
        struct  timeval *tp;
        struct  timezone *tzp;
};
#endif
/* ARGSUSED */
int
sys_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_H_
struct settimeofday_args {
        struct  timeval *tv;
        struct  timezone *tzp;
};
#endif
/* ARGSUSED */
int
sys_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_H_
struct getitimer_args {
        u_int   which;
        struct  itimerval *itv;
};
#endif
int
sys_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_H_
struct setitimer_args {
        u_int   which;
        struct  itimerval *itv, *oitv;
};
#endif
int
sys_setitimer(struct thread *td, struct setitimer_args *uap)
{
        struct itimerval aitv, oitv;
        int error;

        if (uap->itv == NULL) {
                uap->itv = uap->oitv;
                return (sys_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;
        kern_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);
                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);
                        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_H_
struct ktimer_create_args {
        clockid_t clock_id;
        struct sigevent * evp;
        int * timerid;
};
#endif
int
sys_ktimer_create(struct thread *td, struct ktimer_create_args *uap)
{
        struct sigevent *evp, ev;
        int id;
        int error;

        if (uap->evp == NULL) {
                evp = NULL;
        } else {
                error = copyin(uap->evp, &ev, sizeof(ev));
                if (error != 0)
                        return (error);
                evp = &ev;
        }
        error = kern_ktimer_create(td, uap->clock_id, evp, &id, -1);
        if (error == 0) {
                error = copyout(&id, uap->timerid, sizeof(int));
                if (error != 0)
                        kern_ktimer_delete(td, id);
        }
        return (error);
}

int
kern_ktimer_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_H_
struct ktimer_delete_args {
        int timerid;
};
#endif
int
sys_ktimer_delete(struct thread *td, struct ktimer_delete_args *uap)
{

        return (kern_ktimer_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);
}

int
kern_ktimer_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_H_
struct ktimer_settime_args {
        int timerid;
        int flags;
        const struct itimerspec * value;
        struct itimerspec * ovalue;
};
#endif
int
sys_ktimer_settime(struct thread *td, struct ktimer_settime_args *uap)
{
        struct itimerspec val, oval, *ovalp;
        int error;

        error = copyin(uap->value, &val, sizeof(val));
        if (error != 0)
                return (error);
        ovalp = uap->ovalue != NULL ? &oval : NULL;
        error = kern_ktimer_settime(td, uap->timerid, uap->flags, &val, ovalp);
        if (error == 0 && uap->ovalue != NULL)
                error = copyout(ovalp, uap->ovalue, sizeof(*ovalp));
        return (error);
}

int
kern_ktimer_settime(struct thread *td, int timer_id, int flags,
    struct itimerspec *val, struct itimerspec *oval)
{
        struct proc *p;
        struct itimer *it;
        int error;

        p = td->td_proc;
        PROC_LOCK(p);
        if (timer_id < 3 || (it = itimer_find(p, timer_id)) == NULL) {
                PROC_UNLOCK(p);
                error = EINVAL;
        } else {
                PROC_UNLOCK(p);
                itimer_enter(it);
                error = CLOCK_CALL(it->it_clockid, timer_settime, (it,
                    flags, val, oval));
                itimer_leave(it);
                ITIMER_UNLOCK(it);
        }
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct ktimer_gettime_args {
        int timerid;
        struct itimerspec * value;
};
#endif
int
sys_ktimer_gettime(struct thread *td, struct ktimer_gettime_args *uap)
{
        struct itimerspec val;
        int error;

        error = kern_ktimer_gettime(td, uap->timerid, &val);
        if (error == 0)
                error = copyout(&val, uap->value, sizeof(val));
        return (error);
}

int
kern_ktimer_gettime(struct thread *td, int timer_id, struct itimerspec *val)
{
        struct proc *p;
        struct itimer *it;
        int error;

        p = td->td_proc;
        PROC_LOCK(p);
        if (timer_id < 3 || (it = itimer_find(p, timer_id)) == 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);
        }
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct timer_getoverrun_args {
        int timerid;
};
#endif
int
sys_ktimer_getoverrun(struct thread *td, struct ktimer_getoverrun_args *uap)
{

        return (kern_ktimer_getoverrun(td, uap->timerid));
}

int
kern_ktimer_getoverrun(struct thread *td, int timer_id)
{
        struct proc *p = td->td_proc;
        struct itimer *it;
        int error ;

        PROC_LOCK(p);
        if (timer_id < 3 ||
            (it = itimer_find(p, timer_id)) == 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;
        struct thread *td;

        if (it->it_sigev.sigev_notify == SIGEV_SIGNAL ||
            it->it_sigev.sigev_notify == SIGEV_THREAD_ID) {
                if (sigev_findtd(p, &it->it_sigev, &td) != 0) {
                        ITIMER_LOCK(it);
                        timespecclear(&it->it_time.it_value);
                        timespecclear(&it->it_time.it_interval);
                        callout_stop(&it->it_callout);
                        ITIMER_UNLOCK(it);
                        return;
                }
                if (!KSI_ONQ(&it->it_ksi)) {
                        it->it_ksi.ksi_errno = 0;
                        ksiginfo_set_sigev(&it->it_ksi, &it->it_sigev);
                        tdsendsignal(p, td, it->it_ksi.ksi_signo, &it->it_ksi);
                } 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_ktimer_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__ */