[unix-history] / usr / src / sys / kern / kern_time.c

/*
 * Copyright (c) 1982, 1986 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 *
 *	@(#)kern_time.c	7.7 (Berkeley) %G%
 */

#include "param.h"
#include "dir.h"		/* XXX */
#include "user.h"
#include "kernel.h"
#include "proc.h"

#include "machine/reg.h"
#include "machine/cpu.h"

/* 
 * 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.
 */

gettimeofday()
{
	register struct a {
		struct	timeval *tp;
		struct	timezone *tzp;
	} *uap = (struct a *)u.u_ap;
	struct timeval atv;

	if (uap->tp) {
		microtime(&atv);
		u.u_error = copyout((caddr_t)&atv, (caddr_t)uap->tp,
			sizeof (atv));
		if (u.u_error)
			return;
	}
	if (uap->tzp)
		u.u_error = copyout((caddr_t)&tz, (caddr_t)uap->tzp,
			sizeof (tz));
}

settimeofday()
{
	register struct a {
		struct	timeval *tv;
		struct	timezone *tzp;
	} *uap = (struct a *)u.u_ap;
	struct timeval atv;
	struct timezone atz;

	if (uap->tv) {
		u.u_error = copyin((caddr_t)uap->tv, (caddr_t)&atv,
			sizeof (struct timeval));
		if (u.u_error)
			return;
		setthetime(&atv);
	}
	if (uap->tzp && suser()) {
		u.u_error = copyin((caddr_t)uap->tzp, (caddr_t)&atz,
			sizeof (atz));
		if (u.u_error == 0)
			tz = atz;
	}
}

setthetime(tv)
	struct timeval *tv;
{
	int s;

	if (!suser())
		return;
/* WHAT DO WE DO ABOUT PENDING REAL-TIME TIMEOUTS??? */
	boottime.tv_sec += tv->tv_sec - time.tv_sec;
	s = splhigh(); time = *tv; splx(s);
	resettodr();
}

extern	int tickadj;			/* "standard" clock skew, us./tick */
int	tickdelta;			/* current clock skew, us. per tick */
long	timedelta;			/* unapplied time correction, us. */
long	bigadj = 1000000;		/* use 10x skew above bigadj us. */

adjtime()
{
	register struct a {
		struct timeval *delta;
		struct timeval *olddelta;
	} *uap = (struct a *)u.u_ap;
	struct timeval atv, oatv;
	register long ndelta;
	int s;

	if (!suser()) 
		return;
	u.u_error = copyin((caddr_t)uap->delta, (caddr_t)&atv,
		sizeof (struct timeval));
	if (u.u_error)
		return;
	ndelta = atv.tv_sec * 1000000 + atv.tv_usec;
	if (timedelta == 0)
		if (ndelta > bigadj)
			tickdelta = 10 * tickadj;
		else
			tickdelta = tickadj;
	if (ndelta % tickdelta)
		ndelta = ndelta / tickadj * tickadj;

	s = splclock();
	if (uap->olddelta) {
		oatv.tv_sec = timedelta / 1000000;
		oatv.tv_usec = timedelta % 1000000;
	}
	timedelta = ndelta;
	splx(s);

	if (uap->olddelta)
		(void) copyout((caddr_t)&oatv, (caddr_t)uap->olddelta,
			sizeof (struct timeval));
}

/*
 * Get value of an interval timer.  The process virtual and
 * profiling virtual time timers are kept in the u. 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.
 */
getitimer()
{
	register struct a {
		u_int	which;
		struct	itimerval *itv;
	} *uap = (struct a *)u.u_ap;
	struct itimerval aitv;
	int s;

	if (uap->which > ITIMER_PROF) {
		u.u_error = EINVAL;
		return;
	}
	s = splclock();
	if (uap->which == ITIMER_REAL) {
		/*
		 * Convert from absoulte 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.
		 */
		aitv = u.u_procp->p_realtimer;
		if (timerisset(&aitv.it_value))
			if (timercmp(&aitv.it_value, &time, <))
				timerclear(&aitv.it_value);
			else
				timevalsub(&aitv.it_value, &time);
	} else
		aitv = u.u_timer[uap->which];
	splx(s);
	u.u_error = copyout((caddr_t)&aitv, (caddr_t)uap->itv,
	    sizeof (struct itimerval));
}

setitimer()
{
	register struct a {
		u_int	which;
		struct	itimerval *itv, *oitv;
	} *uap = (struct a *)u.u_ap;
	struct itimerval aitv;
	register struct itimerval *itvp;
	int s;
	register struct proc *p = u.u_procp;

	if (uap->which > ITIMER_PROF) {
		u.u_error = EINVAL;
		return;
	}
	itvp = uap->itv;
	if (itvp && (u.u_error = copyin((caddr_t)itvp, (caddr_t)&aitv,
	    sizeof(struct itimerval))))
		return;
	if (uap->itv = uap->oitv) {
		getitimer();
		if (u.u_error)
			return;
	}
	if (itvp == 0)
		return;
	if (itimerfix(&aitv.it_value) || itimerfix(&aitv.it_interval)) {
		u.u_error = EINVAL;
		return;
	}
	s = splclock();
	if (uap->which == ITIMER_REAL) {
		untimeout(realitexpire, (caddr_t)p);
		if (timerisset(&aitv.it_value)) {
			timevaladd(&aitv.it_value, &time);
			timeout(realitexpire, (caddr_t)p, hzto(&aitv.it_value));
		}
		p->p_realtimer = aitv;
	} else
		u.u_timer[uap->which] = aitv;
	splx(s);
}

/*
 * 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.
 */
realitexpire(p)
	register struct proc *p;
{
	int s;

	psignal(p, SIGALRM);
	if (!timerisset(&p->p_realtimer.it_interval)) {
		timerclear(&p->p_realtimer.it_value);
		return;
	}
	for (;;) {
		s = splclock();
		timevaladd(&p->p_realtimer.it_value,
		    &p->p_realtimer.it_interval);
		if (timercmp(&p->p_realtimer.it_value, &time, >)) {
			timeout(realitexpire, (caddr_t)p,
			    hzto(&p->p_realtimer.it_value));
			splx(s);
			return;
		}
		splx(s);
	}
}

/*
 * 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.)
 */
itimerfix(tv)
	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
 * reducint 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.
 */
itimerdecr(itp, usec)
	register 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 (timerisset(&itp->it_value))
		return (1);
	/* expired, exactly at end of interval */
expire:
	if (timerisset(&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.
 */
timevaladd(t1, t2)
	struct timeval *t1, *t2;
{

	t1->tv_sec += t2->tv_sec;
	t1->tv_usec += t2->tv_usec;
	timevalfix(t1);
}

timevalsub(t1, t2)
	struct timeval *t1, *t2;
{

	t1->tv_sec -= t2->tv_sec;
	t1->tv_usec -= t2->tv_usec;
	timevalfix(t1);
}

timevalfix(t1)
	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;
	}
}
Commit	Line	Data
da7c5cc6	1	/*
0880b18e	2	* Copyright (c) 1982, 1986 Regents of the University of California.
da7c5cc6 KM	3	* All rights reserved. The Berkeley software License Agreement
	4	* specifies the terms and conditions for redistribution.
	5	*
d301d150	6	* @(#)kern_time.c 7.7 (Berkeley) %G%
da7c5cc6	7	*/
961945a8	8
94368568 JB	9	#include "param.h"
	10	#include "dir.h" /* XXX */
	11	#include "user.h"
	12	#include "kernel.h"
94368568	13	#include "proc.h"
b6f30e0a	14
d301d150 KM	15	#include "machine/reg.h"
d301d150 KM	16	#include "machine/cpu.h"
fb1db32c	17
1edb1cf8 BJ	18	/*
1edb1cf8 BJ	19	* Time of day and interval timer support.
aa261505 BJ	20	*
	21	* These routines provide the kernel entry points to get and set
	22	* the time-of-day and per-process interval timers. Subroutines
	23	* here provide support for adding and subtracting timeval structures
	24	* and decrementing interval timers, optionally reloading the interval
	25	* timers when they expire.
1edb1cf8 BJ	26	*/
1edb1cf8 BJ	27
b6f30e0a	28	gettimeofday()
4147b3f6	29	{
b6f30e0a BJ	30	register struct a {
	31	struct timeval *tp;
	32	struct timezone *tzp;
	33	} uap = (struct a )u.u_ap;
	34	struct timeval atv;
4147b3f6	35
2b6a7e0f KB	36	if (uap->tp) {
	37	microtime(&atv);
	38	u.u_error = copyout((caddr_t)&atv, (caddr_t)uap->tp,
	39	sizeof (atv));
	40	if (u.u_error)
	41	return;
	42	}
	43	if (uap->tzp)
	44	u.u_error = copyout((caddr_t)&tz, (caddr_t)uap->tzp,
	45	sizeof (tz));
4147b3f6 BJ	46	}
4147b3f6 BJ	47
b6f30e0a	48	settimeofday()
aac7ea5b	49	{
b6f30e0a	50	register struct a {
1edb1cf8 BJ	51	struct timeval *tv;
1edb1cf8 BJ	52	struct timezone *tzp;
b6f30e0a BJ	53	} uap = (struct a )u.u_ap;
	54	struct timeval atv;
	55	struct timezone atz;
4147b3f6	56
2b6a7e0f KB	57	if (uap->tv) {
	58	u.u_error = copyin((caddr_t)uap->tv, (caddr_t)&atv,
	59	sizeof (struct timeval));
	60	if (u.u_error)
	61	return;
	62	setthetime(&atv);
	63	}
1edb1cf8	64	if (uap->tzp && suser()) {
127f7d76 SL	65	u.u_error = copyin((caddr_t)uap->tzp, (caddr_t)&atz,
127f7d76 SL	66	sizeof (atz));
747d2bea SL	67	if (u.u_error == 0)
747d2bea SL	68	tz = atz;
b6f30e0a	69	}
4147b3f6 BJ	70	}
4147b3f6 BJ	71
1edb1cf8 BJ	72	setthetime(tv)
	73	struct timeval *tv;
	74	{
1edb1cf8 BJ	75	int s;
	76
	77	if (!suser())
	78	return;
aa261505	79	/* WHAT DO WE DO ABOUT PENDING REAL-TIME TIMEOUTS??? */
1edb1cf8	80	boottime.tv_sec += tv->tv_sec - time.tv_sec;
fa5e5ab4	81	s = splhigh(); time = *tv; splx(s);
993113c5	82	resettodr();
1edb1cf8 BJ	83	}
1edb1cf8 BJ	84
4ca0d0d6 MK	85	extern int tickadj; /* "standard" clock skew, us./tick */
	86	int tickdelta; /* current clock skew, us. per tick */
	87	long timedelta; /* unapplied time correction, us. */
	88	long bigadj = 1000000; /* use 10x skew above bigadj us. */
99e47f6b MK	89
	90	adjtime()
	91	{
	92	register struct a {
	93	struct timeval *delta;
	94	struct timeval *olddelta;
	95	} uap = (struct a )u.u_ap;
99e47f6b	96	struct timeval atv, oatv;
4ca0d0d6	97	register long ndelta;
8efc019f	98	int s;
99e47f6b MK	99
	100	if (!suser())
	101	return;
	102	u.u_error = copyin((caddr_t)uap->delta, (caddr_t)&atv,
	103	sizeof (struct timeval));
	104	if (u.u_error)
	105	return;
4ca0d0d6 MK	106	ndelta = atv.tv_sec * 1000000 + atv.tv_usec;
	107	if (timedelta == 0)
	108	if (ndelta > bigadj)
	109	tickdelta = 10 * tickadj;
	110	else
	111	tickdelta = tickadj;
	112	if (ndelta % tickdelta)
	113	ndelta = ndelta / tickadj * tickadj;
	114
8efc019f	115	s = splclock();
99e47f6b	116	if (uap->olddelta) {
4ca0d0d6 MK	117	oatv.tv_sec = timedelta / 1000000;
4ca0d0d6 MK	118	oatv.tv_usec = timedelta % 1000000;
99e47f6b	119	}
4ca0d0d6	120	timedelta = ndelta;
8efc019f	121	splx(s);
4ca0d0d6 MK	122
	123	if (uap->olddelta)
	124	(void) copyout((caddr_t)&oatv, (caddr_t)uap->olddelta,
	125	sizeof (struct timeval));
99e47f6b MK	126	}
99e47f6b MK	127
aa261505 BJ	128	/*
	129	* Get value of an interval timer. The process virtual and
	130	* profiling virtual time timers are kept in the u. area, since
	131	* they can be swapped out. These are kept internally in the
	132	* way they are specified externally: in time until they expire.
	133	*
	134	* The real time interval timer is kept in the process table slot
	135	* for the process, and its value (it_value) is kept as an
	136	* absolute time rather than as a delta, so that it is easy to keep
	137	* periodic real-time signals from drifting.
	138	*
	139	* Virtual time timers are processed in the hardclock() routine of
	140	* kern_clock.c. The real time timer is processed by a timeout
	141	* routine, called from the softclock() routine. Since a callout
	142	* may be delayed in real time due to interrupt processing in the system,
	143	* it is possible for the real time timeout routine (realitexpire, given below),
	144	* to be delayed in real time past when it is supposed to occur. It
	145	* does not suffice, therefore, to reload the real timer .it_value from the
	146	* real time timers .it_interval. Rather, we compute the next time in
	147	* absolute time the timer should go off.
	148	*/
b6f30e0a	149	getitimer()
aac7ea5b BJ	150	{
aac7ea5b BJ	151	register struct a {
b6f30e0a BJ	152	u_int which;
	153	struct itimerval *itv;
	154	} uap = (struct a )u.u_ap;
d01b68d6	155	struct itimerval aitv;
b6f30e0a	156	int s;
aac7ea5b	157
c4bbb24f	158	if (uap->which > ITIMER_PROF) {
b6f30e0a BJ	159	u.u_error = EINVAL;
b6f30e0a BJ	160	return;
aac7ea5b	161	}
fa5e5ab4	162	s = splclock();
d01b68d6	163	if (uap->which == ITIMER_REAL) {
aa261505 BJ	164	/*
	165	* Convert from absoulte to relative time in .it_value
	166	* part of real time timer. If time for real time timer
	167	* has passed return 0, else return difference between
	168	* current time and time for the timer to go off.
	169	*/
d01b68d6 BJ	170	aitv = u.u_procp->p_realtimer;
	171	if (timerisset(&aitv.it_value))
	172	if (timercmp(&aitv.it_value, &time, <))
	173	timerclear(&aitv.it_value);
	174	else
	175	timevalsub(&aitv.it_value, &time);
	176	} else
	177	aitv = u.u_timer[uap->which];
	178	splx(s);
127f7d76 SL	179	u.u_error = copyout((caddr_t)&aitv, (caddr_t)uap->itv,
127f7d76 SL	180	sizeof (struct itimerval));
aac7ea5b BJ	181	}
aac7ea5b BJ	182
b6f30e0a	183	setitimer()
aac7ea5b BJ	184	{
aac7ea5b BJ	185	register struct a {
b6f30e0a	186	u_int which;
1edb1cf8	187	struct itimerval itv, oitv;
b6f30e0a	188	} uap = (struct a )u.u_ap;
c4bbb24f KB	189	struct itimerval aitv;
c4bbb24f KB	190	register struct itimerval *itvp;
b6f30e0a	191	int s;
d01b68d6	192	register struct proc *p = u.u_procp;
aac7ea5b	193
c4bbb24f	194	if (uap->which > ITIMER_PROF) {
b6f30e0a	195	u.u_error = EINVAL;
1edb1cf8	196	return;
b6f30e0a	197	}
c4bbb24f KB	198	itvp = uap->itv;
	199	if (itvp && (u.u_error = copyin((caddr_t)itvp, (caddr_t)&aitv,
	200	sizeof(struct itimerval))))
	201	return;
	202	if (uap->itv = uap->oitv) {
1edb1cf8	203	getitimer();
c4bbb24f KB	204	if (u.u_error)
c4bbb24f KB	205	return;
b6f30e0a	206	}
c4bbb24f	207	if (itvp == 0)
7dbf2493	208	return;
1edb1cf8 BJ	209	if (itimerfix(&aitv.it_value) \|\| itimerfix(&aitv.it_interval)) {
	210	u.u_error = EINVAL;
	211	return;
	212	}
fa5e5ab4	213	s = splclock();
d01b68d6	214	if (uap->which == ITIMER_REAL) {
b32450f4	215	untimeout(realitexpire, (caddr_t)p);
d01b68d6 BJ	216	if (timerisset(&aitv.it_value)) {
d01b68d6 BJ	217	timevaladd(&aitv.it_value, &time);
b32450f4	218	timeout(realitexpire, (caddr_t)p, hzto(&aitv.it_value));
d01b68d6 BJ	219	}
	220	p->p_realtimer = aitv;
	221	} else
1edb1cf8	222	u.u_timer[uap->which] = aitv;
b6f30e0a	223	splx(s);
b6f30e0a BJ	224	}
b6f30e0a BJ	225
aa261505 BJ	226	/*
	227	* Real interval timer expired:
	228	* send process whose timer expired an alarm signal.
	229	* If time is not set up to reload, then just return.
	230	* Else compute next time timer should go off which is > current time.
	231	* This is where delay in processing this timeout causes multiple
	232	* SIGALRM calls to be compressed into one.
	233	*/
	234	realitexpire(p)
d01b68d6 BJ	235	register struct proc *p;
	236	{
	237	int s;
	238
	239	psignal(p, SIGALRM);
	240	if (!timerisset(&p->p_realtimer.it_interval)) {
	241	timerclear(&p->p_realtimer.it_value);
	242	return;
	243	}
	244	for (;;) {
fa5e5ab4	245	s = splclock();
d01b68d6 BJ	246	timevaladd(&p->p_realtimer.it_value,
	247	&p->p_realtimer.it_interval);
	248	if (timercmp(&p->p_realtimer.it_value, &time, >)) {
b32450f4 BJ	249	timeout(realitexpire, (caddr_t)p,
b32450f4 BJ	250	hzto(&p->p_realtimer.it_value));
d01b68d6 BJ	251	splx(s);
	252	return;
	253	}
	254	splx(s);
	255	}
	256	}
	257
aa261505 BJ	258	/*
	259	* Check that a proposed value to load into the .it_value or
	260	* .it_interval part of an interval timer is acceptable, and
	261	* fix it to have at least minimal value (i.e. if it is less
	262	* than the resolution of the clock, round it up.)
	263	*/
1edb1cf8 BJ	264	itimerfix(tv)
1edb1cf8 BJ	265	struct timeval *tv;
b6f30e0a	266	{
b6f30e0a	267
d01b68d6 BJ	268	if (tv->tv_sec < 0 \|\| tv->tv_sec > 100000000 \|\|
d01b68d6 BJ	269	tv->tv_usec < 0 \|\| tv->tv_usec >= 1000000)
1edb1cf8	270	return (EINVAL);
c45fcba6	271	if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick)
1edb1cf8 BJ	272	tv->tv_usec = tick;
1edb1cf8 BJ	273	return (0);
b6f30e0a BJ	274	}
b6f30e0a BJ	275
aa261505 BJ	276	/*
	277	* Decrement an interval timer by a specified number
	278	* of microseconds, which must be less than a second,
	279	* i.e. < 1000000. If the timer expires, then reload
	280	* it. In this case, carry over (usec - old value) to
	281	* reducint the value reloaded into the timer so that
	282	* the timer does not drift. This routine assumes
	283	* that it is called in a context where the timers
	284	* on which it is operating cannot change in value.
	285	*/
b6f30e0a BJ	286	itimerdecr(itp, usec)
	287	register struct itimerval *itp;
	288	int usec;
	289	{
	290
1edb1cf8 BJ	291	if (itp->it_value.tv_usec < usec) {
1edb1cf8 BJ	292	if (itp->it_value.tv_sec == 0) {
aa261505	293	/* expired, and already in next interval */
1edb1cf8	294	usec -= itp->it_value.tv_usec;
b6f30e0a	295	goto expire;
1edb1cf8 BJ	296	}
	297	itp->it_value.tv_usec += 1000000;
	298	itp->it_value.tv_sec--;
aac7ea5b	299	}
1edb1cf8 BJ	300	itp->it_value.tv_usec -= usec;
	301	usec = 0;
	302	if (timerisset(&itp->it_value))
b6f30e0a	303	return (1);
aa261505	304	/* expired, exactly at end of interval */
b6f30e0a	305	expire:
1edb1cf8 BJ	306	if (timerisset(&itp->it_interval)) {
	307	itp->it_value = itp->it_interval;
	308	itp->it_value.tv_usec -= usec;
	309	if (itp->it_value.tv_usec < 0) {
	310	itp->it_value.tv_usec += 1000000;
	311	itp->it_value.tv_sec--;
	312	}
	313	} else
aa261505	314	itp->it_value.tv_usec = 0; /* sec is already 0 */
b6f30e0a	315	return (0);
aac7ea5b BJ	316	}
aac7ea5b BJ	317
aa261505 BJ	318	/*
	319	* Add and subtract routines for timevals.
	320	* N.B.: subtract routine doesn't deal with
	321	* results which are before the beginning,
	322	* it just gets very confused in this case.
	323	* Caveat emptor.
	324	*/
	325	timevaladd(t1, t2)
	326	struct timeval t1, t2;
	327	{
	328
	329	t1->tv_sec += t2->tv_sec;
	330	t1->tv_usec += t2->tv_usec;
	331	timevalfix(t1);
	332	}
	333
	334	timevalsub(t1, t2)
	335	struct timeval t1, t2;
	336	{
	337
	338	t1->tv_sec -= t2->tv_sec;
	339	t1->tv_usec -= t2->tv_usec;
	340	timevalfix(t1);
	341	}
	342
	343	timevalfix(t1)
	344	struct timeval *t1;
	345	{
	346
	347	if (t1->tv_usec < 0) {
	348	t1->tv_sec--;
	349	t1->tv_usec += 1000000;
	350	}
	351	if (t1->tv_usec >= 1000000) {
	352	t1->tv_sec++;
	353	t1->tv_usec -= 1000000;
	354	}
	355	}