kern_time.c

来自「MIPS处理器的bootloader,龙芯就是用的修改过的PMON2」· C语言 代码 · 共 589 行 · 第 1/2 页

	} */ *uap = v;
	struct timeval atv;
	struct timezone atz;
	int error;

	if ((error = suser(p->p_ucred, &p->p_acflag)))
		return (error);
	/* Verify all parameters before changing time. */
	if (SCARG(uap, tv) && (error = copyin((void *)SCARG(uap, tv),
	    (void *)&atv, sizeof(atv))))
		return (error);
	if (SCARG(uap, tzp) && (error = copyin((void *)SCARG(uap, tzp),
	    (void *)&atz, sizeof(atz))))
		return (error);
	if (SCARG(uap, tv)) {
		/*
		 * If the system is secure, we do not allow the time to be
		 * set to an earlier value (it may be slowed using adjtime,
		 * but not set back). This feature prevent interlopers from
		 * setting arbitrary time stamps on files.
		 */
		if (securelevel > 1 && timercmp(&atv, &time, <))
			return (EPERM);
		settime(&atv);
	}
	if (SCARG(uap, tzp))
		tz = atz;
	return (0);
}

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

/* ARGSUSED */
int
sys_adjtime(p, v, retval)
	struct proc *p;
	void *v;
	register_t *retval;
{
	register struct sys_adjtime_args /* {
		syscallarg(struct timeval *) delta;
		syscallarg(struct timeval *) olddelta;
	} */ *uap = v;
	struct timeval atv;
	register long ndelta, ntickdelta, odelta;
	int s, error;

	if ((error = suser(p->p_ucred, &p->p_acflag)))
		return (error);
	if ((error = copyin((void *)SCARG(uap, delta), (void *)&atv,
	    sizeof(struct timeval))))
		return (error);

	/*
	 * Compute the total correction and the rate at which to apply it.
	 * Round the adjustment down to a whole multiple of the per-tick
	 * delta, so that after some number of incremental changes in
	 * hardclock(), tickdelta will become zero, lest the correction
	 * overshoot and start taking us away from the desired final time.
	 */
	ndelta = atv.tv_sec * 1000000 + atv.tv_usec;
	if (ndelta > bigadj)
		ntickdelta = 10 * tickadj;
	else
		ntickdelta = tickadj;
	if (ndelta % ntickdelta)
		ndelta = ndelta / ntickdelta * ntickdelta;

	/*
	 * To make hardclock()'s job easier, make the per-tick delta negative
	 * if we want time to run slower; then hardclock can simply compute
	 * tick + tickdelta, and subtract tickdelta from timedelta.
	 */
	if (ndelta < 0)
		ntickdelta = -ntickdelta;
	s = splclock();
	odelta = timedelta;
	timedelta = ndelta;
	tickdelta = ntickdelta;
	splx(s);

	if (SCARG(uap, olddelta)) {
		atv.tv_sec = odelta / 1000000;
		atv.tv_usec = odelta % 1000000;
		if ((error = copyout((void *)&atv, (void *)SCARG(uap, olddelta),
		    sizeof(struct timeval))))
			return (error);
	}
	return (0);
}
#endif /* NOTUSED_BY_PMON */

/*
 * 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.
 */
/* ARGSUSED */
int
sys_getitimer(p, v, retval)
	struct proc *p;
	void *v;
	register_t *retval;
{
	register struct sys_getitimer_args /* {
		syscallarg(u_int) which;
		syscallarg(struct itimerval *) itv;
	} */ *uap = v;
	struct itimerval aitv;
	int s;

	if (SCARG(uap, which) > ITIMER_PROF)
		return (EINVAL);
	s = splclock();
	if (SCARG(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.
		 */
		aitv = p->p_realtimer;
		if (timerisset(&aitv.it_value)) {
			if (timercmp(&aitv.it_value, &time, <))
				timerclear(&aitv.it_value);
			else
				timersub(&aitv.it_value, &time,
				    &aitv.it_value);
		}
	} else
		aitv = p->p_stats->p_timer[SCARG(uap, which)];
	splx(s);
	return (copyout((void *)&aitv, (void *)SCARG(uap, itv),
	    sizeof (struct itimerval)));
}

/* ARGSUSED */
int
sys_setitimer(p, v, retval)
	struct proc *p;
	register void *v;
	register_t *retval;
{
	register struct sys_setitimer_args /* {
		syscallarg(u_int) which;
		syscallarg(struct itimerval *) itv;
		syscallarg(struct itimerval *) oitv;
	} */ *uap = v;
	struct itimerval aitv;
	register const struct itimerval *itvp;
	int s, error;

	if (SCARG(uap, which) > ITIMER_PROF)
		return (EINVAL);
	itvp = SCARG(uap, itv);
	if (itvp && (error = copyin((void *)itvp, (void *)&aitv,
	    sizeof(struct itimerval))))
		return (error);
	if ((SCARG(uap, itv) = SCARG(uap, oitv)) &&
	    (error = sys_getitimer(p, uap, retval)))
		return (error);
	if (itvp == 0)
		return (0);
	if (itimerfix(&aitv.it_value) || itimerfix(&aitv.it_interval))
		return (EINVAL);
	s = splclock();
	if (SCARG(uap, which) == ITIMER_REAL) {
		untimeout(realitexpire, (void *)p);
		if (timerisset(&aitv.it_value)) {
			timeradd(&aitv.it_value, &time, &aitv.it_value);
			timeout(realitexpire, (void *)p, hzto(&aitv.it_value));
		}
		p->p_realtimer = aitv;
	} else
		p->p_stats->p_timer[SCARG(uap, which)] = aitv;
	splx(s);
	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.
 */
void
realitexpire(arg)
	void *arg;
{
	register struct proc *p;
	int s;

	p = (struct proc *)arg;
	psignal(p, SIGALRM);
	if (!timerisset(&p->p_realtimer.it_interval)) {
		timerclear(&p->p_realtimer.it_value);
		return;
	}
	for (;;) {
		s = splclock();
		timeradd(&p->p_realtimer.it_value,
		    &p->p_realtimer.it_interval, &p->p_realtimer.it_value);
		if (timercmp(&p->p_realtimer.it_value, &time, >)) {
			timeout(realitexpire, (void *)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.)
 */
int
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
 * 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(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);
}