FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_time.c

     /*-
      * 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: releng/5.4/sys/kern/kern_time.c 145335 2005-04-20 19:11:07Z cvs2svn $");
    
    #include "opt_mac.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/sysproto.h>
    #include <sys/resourcevar.h>
    #include <sys/signalvar.h>
    #include <sys/kernel.h>
    #include <sys/mac.h>
    #include <sys/syscallsubr.h>
    #include <sys/sysent.h>
    #include <sys/proc.h>
    #include <sys/time.h>
    #include <sys/timetc.h>
    #include <sys/vnode.h>
    
    #include <vm/vm.h>
    #include <vm/vm_extern.h>
    
    int tz_minuteswest;
    int tz_dsttime;
    
    /*
     * 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 *);
    static void     timevalfix(struct timeval *);
    static void     no_lease_updatetime(int);
    
    static void 
    no_lease_updatetime(deltat)
            int deltat;
    {
    }
    
    void (*lease_updatetime)(int)  = no_lease_updatetime;
    
    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);
           (void) splsoftclock();
           lease_updatetime(delta.tv_sec);
           splx(s);
           resettodr();
           mtx_unlock(&Giant);
           return (0);
   }
   
   #ifndef _SYS_SYSPROTO_H_
   struct clock_gettime_args {
           clockid_t clock_id;
           struct  timespec *tp;
   };
   #endif
   
   /*
    * MPSAFE
    */
   /* ARGSUSED */
   int
   clock_gettime(struct thread *td, struct clock_gettime_args *uap)
   {
           struct timespec ats;
           struct timeval sys, user;
   
           switch (uap->clock_id) {
           case CLOCK_REALTIME:
                   nanotime(&ats);
                   break;
           case CLOCK_VIRTUAL:
                   mtx_lock_spin(&sched_lock);
                   calcru(td->td_proc, &user, &sys, NULL);
                   mtx_unlock_spin(&sched_lock);
                   TIMEVAL_TO_TIMESPEC(&user, &ats);
                   break;
           case CLOCK_PROF:
                   mtx_lock_spin(&sched_lock);
                   calcru(td->td_proc, &user, &sys, NULL);
                   mtx_unlock_spin(&sched_lock);
                   timevaladd(&user, &sys);
                   TIMEVAL_TO_TIMESPEC(&user, &ats);
                   break;
           case CLOCK_MONOTONIC:
                   nanouptime(&ats);
                   break;
           default:
                   return (EINVAL);
           }
           return (copyout(&ats, uap->tp, sizeof(ats)));
   }
   
   #ifndef _SYS_SYSPROTO_H_
   struct clock_settime_args {
           clockid_t clock_id;
           const struct    timespec *tp;
   };
   #endif
   
   /*
    * MPSAFE
    */
   /* ARGSUSED */
   int
   clock_settime(struct thread *td, struct clock_settime_args *uap)
   {
           struct timeval atv;
           struct timespec ats;
           int error;
   
   #ifdef MAC
           error = mac_check_system_settime(td->td_ucred);
           if (error)
                   return (error);
   #endif
           if ((error = suser(td)) != 0)
                   return (error);
           if (uap->clock_id != CLOCK_REALTIME)
                   return (EINVAL);
           if ((error = copyin(uap->tp, &ats, sizeof(ats))) != 0)
                   return (error);
           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);
   }
   
   #ifndef _SYS_SYSPROTO_H_
   struct clock_getres_args {
           clockid_t clock_id;
           struct  timespec *tp;
   };
   #endif
   
   int
   clock_getres(struct thread *td, struct clock_getres_args *uap)
   {
           struct timespec ts;
   
           ts.tv_sec = 0;
           switch (uap->clock_id) {
           case CLOCK_REALTIME:
           case CLOCK_MONOTONIC:
                   /*
                    * 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;
           default:
                   return (EINVAL);
           }
           if (uap->tp == NULL)
                   return (0);
           return (copyout(&ts, uap->tp, sizeof(ts)));
   }
   
   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
   
   /* 
    * MPSAFE
    */
   /* 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_H_
   struct gettimeofday_args {
           struct  timeval *tp;
           struct  timezone *tzp;
   };
   #endif
   /*
    * MPSAFE
    */
   /* 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_H_
   struct settimeofday_args {
           struct  timeval *tv;
           struct  timezone *tzp;
   };
   #endif
   /*
    * MPSAFE
    */
   /* ARGSUSED */
   int
   settimeofday(struct thread *td, struct settimeofday_args *uap)
   {
           struct timeval atv;
           struct timezone atz;
           int error = 0;
   
   #ifdef MAC
           error = mac_check_system_settime(td->td_ucred);
           if (error)
                   return (error);
   #endif
           if ((error = suser(td)))
                   return (error);
           /* Verify all parameters before changing time. */
           if (uap->tv) {
                   if ((error = copyin(uap->tv, &atv, sizeof(atv))))
                           return (error);
                   if (atv.tv_usec < 0 || atv.tv_usec >= 1000000)
                           return (EINVAL);
           }
           if (uap->tzp &&
               (error = copyin(uap->tzp, &atz, sizeof(atz))))
                   return (error);
           
           if (uap->tv && (error = settime(td, &atv)))
                   return (error);
           if (uap->tzp) {
                   tz_minuteswest = atz.tz_minuteswest;
                   tz_dsttime = atz.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
   /*
    * MPSAFE
    */
   int
   getitimer(struct thread *td, struct getitimer_args *uap)
   {
           struct proc *p = td->td_proc;
           struct timeval ctv;
           struct itimerval aitv;
   
           if (uap->which > ITIMER_PROF)
                   return (EINVAL);
   
           if (uap->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 {
                   mtx_lock_spin(&sched_lock);
                   aitv = p->p_stats->p_timer[uap->which];
                   mtx_unlock_spin(&sched_lock);
           }
           return (copyout(&aitv, uap->itv, sizeof (struct itimerval)));
   }
   
   #ifndef _SYS_SYSPROTO_H_
   struct setitimer_args {
           u_int   which;
           struct  itimerval *itv, *oitv;
   };
   #endif
   /*
    * MPSAFE
    */
   int
   setitimer(struct thread *td, struct setitimer_args *uap)
   {
           struct proc *p = td->td_proc;
           struct itimerval aitv, oitv;
           struct timeval ctv;
           int error;
   
           if (uap->itv == NULL) {
                   uap->itv = uap->oitv;
                   return (getitimer(td, (struct getitimer_args *)uap));
           }
   
           if (uap->which > ITIMER_PROF)
                   return (EINVAL);
           if ((error = copyin(uap->itv, &aitv, sizeof(struct itimerval))))
                   return (error);
           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 (uap->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 {
                   mtx_lock_spin(&sched_lock);
                   oitv = p->p_stats->p_timer[uap->which];
                   p->p_stats->p_timer[uap->which] = aitv;
                   mtx_unlock_spin(&sched_lock);
           }
           if (uap->oitv == NULL)
                   return (0);
           return (copyout(&oitv, uap->oitv, sizeof(struct itimerval)));
   }
   
   /*
    * 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*/
   }
   
   /*
    * 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_sec > 100000000 ||
               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);
   }
   
   /*
    * 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);
   }
   
   /*
    * 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);
           }
   }

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