xref: /src/sys/kern/subr_time.c

/*	$NetBSD: subr_time.c,v 1.23 2020/05/04 18:23:37 riastradh Exp $	*/

/*
 * 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.
 * 3. 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_clock.c	8.5 (Berkeley) 1/21/94
 *	@(#)kern_time.c 8.4 (Berkeley) 5/26/95
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: subr_time.c,v 1.23 2020/05/04 18:23:37 riastradh Exp $");

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/kauth.h>
#include <sys/lwp.h>
#include <sys/timex.h>
#include <sys/time.h>
#include <sys/timetc.h>
#include <sys/intr.h>

#ifdef DEBUG_STICKS
#define DPRINTF(a) uprintf a
#else
#define DPRINTF(a)
#endif

/*
 * Compute number of hz until specified time.  Used to compute second
 * argument to callout_reset() from an absolute time.
 */
int
tvhzto(const struct timeval *tvp)
{
	struct timeval now, tv;

	tv = *tvp;	/* Don't modify original tvp. */
	getmicrotime(&now);
	timersub(&tv, &now, &tv);
	return tvtohz(&tv);
}

/*
 * Compute number of ticks in the specified amount of time.
 */
int
tvtohz(const struct timeval *tv)
{
	unsigned long ticks;
	long sec, usec;

	/*
	 * If the number of usecs in the whole seconds part of the time
	 * difference fits in a long, then the total number of usecs will
	 * fit in an unsigned long.  Compute the total and convert it to
	 * ticks, rounding up and adding 1 to allow for the current tick
	 * to expire.  Rounding also depends on unsigned long arithmetic
	 * to avoid overflow.
	 *
	 * Otherwise, if the number of ticks in the whole seconds part of
	 * the time difference fits in a long, then convert the parts to
	 * ticks separately and add, using similar rounding methods and
	 * overflow avoidance.  This method would work in the previous
	 * case, but it is slightly slower and assumes that hz is integral.
	 *
	 * Otherwise, round the time difference down to the maximum
	 * representable value.
	 *
	 * If ints are 32-bit, then the maximum value for any timeout in
	 * 10ms ticks is 248 days.
	 */
	sec = tv->tv_sec;
	usec = tv->tv_usec;

	KASSERT(usec >= 0 && usec < 1000000);

	/* catch overflows in conversion time_t->int */
	if (tv->tv_sec > INT_MAX)
		return INT_MAX;
	if (tv->tv_sec < 0)
		return 0;

	if (sec < 0 || (sec == 0 && usec == 0)) {
		/*
		 * Would expire now or in the past.  Return 0 ticks.
		 * This is different from the legacy tvhzto() interface,
		 * and callers need to check for it.
		 */
		ticks = 0;
	} else if (sec <= (LONG_MAX / 1000000))
		ticks = (((sec * 1000000) + (unsigned long)usec + (tick - 1))
		    / tick) + 1;
	else if (sec <= (LONG_MAX / hz))
		ticks = (sec * hz) +
		    (((unsigned long)usec + (tick - 1)) / tick) + 1;
	else
		ticks = LONG_MAX;

	if (ticks > INT_MAX)
		ticks = INT_MAX;

	return ((int)ticks);
}

int
tshzto(const struct timespec *tsp)
{
	struct timespec now, ts;

	ts = *tsp;	/* Don't modify original tsp. */
	getnanotime(&now);
	timespecsub(&ts, &now, &ts);
	return tstohz(&ts);
}

int
tshztoup(const struct timespec *tsp)
{
	struct timespec now, ts;

	ts = *tsp;	/* Don't modify original tsp. */
	getnanouptime(&now);
	timespecsub(&ts, &now, &ts);
	return tstohz(&ts);
}

/*
 * Compute number of ticks in the specified amount of time.
 */
int
tstohz(const struct timespec *ts)
{
	struct timeval tv;

	/*
	 * usec has great enough resolution for hz, so convert to a
	 * timeval and use tvtohz() above.
	 */
	TIMESPEC_TO_TIMEVAL(&tv, ts);
	return tvtohz(&tv);
}

/*
 * 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.). We don't
 * timeout the 0,0 value because this means to disable the
 * timer or the interval.
 */
int
itimerfix(struct timeval *tv)
{

	if (tv->tv_usec < 0 || tv->tv_usec >= 1000000)
		return EINVAL;
	if (tv->tv_sec < 0)
		return ETIMEDOUT;
	if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick)
		tv->tv_usec = tick;
	return 0;
}

int
itimespecfix(struct timespec *ts)
{

	if (ts->tv_nsec < 0 || ts->tv_nsec >= 1000000000)
		return EINVAL;
	if (ts->tv_sec < 0)
		return ETIMEDOUT;
	if (ts->tv_sec == 0 && ts->tv_nsec != 0 && ts->tv_nsec < tick * 1000)
		ts->tv_nsec = tick * 1000;
	return 0;
}

int
inittimeleft(struct timespec *ts, struct timespec *sleepts)
{

	if (itimespecfix(ts)) {
		return -1;
	}
	getnanouptime(sleepts);
	return 0;
}

int
gettimeleft(struct timespec *ts, struct timespec *sleepts)
{
	struct timespec sleptts;

	/*
	 * Reduce ts by elapsed time based on monotonic time scale.
	 */
	getnanouptime(&sleptts);
	timespecadd(ts, sleepts, ts);
	timespecsub(ts, &sleptts, ts);
	*sleepts = sleptts;

	return tstohz(ts);
}

void
clock_timeleft(clockid_t clockid, struct timespec *ts, struct timespec *sleepts)
{
	struct timespec sleptts;

	clock_gettime1(clockid, &sleptts);
	timespecadd(ts, sleepts, ts);
	timespecsub(ts, &sleptts, ts);
	*sleepts = sleptts;
}

static void
ticks2ts(uint64_t ticks, struct timespec *ts)
{
	ts->tv_sec = ticks / hz;
	uint64_t sticks = ticks - ts->tv_sec * hz;
	if (sticks > BINTIME_SCALE_MS)	/* floor(2^64 / 1000) */
		ts->tv_nsec = sticks / hz * 1000000000LL;
   	else if (sticks > BINTIME_SCALE_US)	/* floor(2^64 / 1000000) */
   		ts->tv_nsec = sticks * 1000LL / hz * 1000000LL;
	else
   		ts->tv_nsec = sticks * 1000000000LL / hz;
	DPRINTF(("%s: %ju/%ju -> %ju.%ju\n", __func__,
	    (uintmax_t)ticks, (uintmax_t)sticks,
	    (uintmax_t)ts->tv_sec, (uintmax_t)ts->tv_nsec));
}

int
clock_gettime1(clockid_t clock_id, struct timespec *ts)
{
	int error;
	uint64_t ticks;
	struct proc *p;

#define CPUCLOCK_ID_MASK (~(CLOCK_THREAD_CPUTIME_ID|CLOCK_PROCESS_CPUTIME_ID))
	if (clock_id & CLOCK_PROCESS_CPUTIME_ID) {
		pid_t pid = clock_id & CPUCLOCK_ID_MASK;

		mutex_enter(proc_lock);
		p = pid == 0 ? curproc : proc_find(pid);
		if (p == NULL) {
			mutex_exit(proc_lock);
			return ESRCH;
		}
		ticks = p->p_uticks + p->p_sticks + p->p_iticks;
		DPRINTF(("%s: u=%ju, s=%ju, i=%ju\n", __func__,
		    (uintmax_t)p->p_uticks, (uintmax_t)p->p_sticks,
		    (uintmax_t)p->p_iticks));
		mutex_exit(proc_lock);

		// XXX: Perhaps create a special kauth type
		error = kauth_authorize_process(curlwp->l_cred,
		    KAUTH_PROCESS_PTRACE, p,
		    KAUTH_ARG(KAUTH_REQ_PROCESS_CANSEE_ENTRY), NULL, NULL);
		if (error)
			return error;
	} else if (clock_id & CLOCK_THREAD_CPUTIME_ID) {
		struct lwp *l;
		lwpid_t lid = clock_id & CPUCLOCK_ID_MASK;
		p = curproc;
		mutex_enter(p->p_lock);
		l = lid == 0 ? curlwp : lwp_find(p, lid);
		if (l == NULL) {
			mutex_exit(p->p_lock);
			return ESRCH;
		}
		ticks = l->l_rticksum + l->l_slpticksum;
		DPRINTF(("%s: r=%ju, s=%ju\n", __func__,
		    (uintmax_t)l->l_rticksum, (uintmax_t)l->l_slpticksum));
		mutex_exit(p->p_lock);
        } else
		ticks = (uint64_t)-1;

	if (ticks != (uint64_t)-1) {
		ticks2ts(ticks, ts);
		return 0;
	}

	switch (clock_id) {
	case CLOCK_REALTIME:
		nanotime(ts);
		break;
	case CLOCK_MONOTONIC:
		nanouptime(ts);
		break;
	default:
		return EINVAL;
	}

	return 0;
}

/*
 * Calculate delta and convert from struct timespec to the ticks.
 */
int
ts2timo(clockid_t clock_id, int flags, struct timespec *ts,
    int *timo, struct timespec *start)
{
	int error;
	struct timespec tsd;

	if (ts->tv_nsec < 0 || ts->tv_nsec >= 1000000000L)
		return EINVAL;

	flags &= TIMER_ABSTIME;
	if (start == NULL)
		start = &tsd;

	if (flags || start != &tsd)
		if ((error = clock_gettime1(clock_id, start)) != 0)
			return error;

	if (flags)
		timespecsub(ts, start, ts);

	if ((error = itimespecfix(ts)) != 0)
		return error;

	if (ts->tv_sec == 0 && ts->tv_nsec == 0)
		return ETIMEDOUT;

	*timo = tstohz(ts);
	KASSERT(*timo > 0);

	return 0;
}

/*
 * timedwaitclock_setup(T, timeout, clockid, flags, epsilon)
 *
 *	Initialize state for a timedwaitclock, to be used subsequently
 *	with timedwaitclock_begin/end, possibly many times in a row.
 *
 *	No cleanup action required at the end; the caller-allocated
 *	(typically stack-allocated) timedwaitclock just holds
 *	parameters and a little state for timedwaitclock_begin/end.
 */
void
timedwaitclock_setup(struct timedwaitclock *T, struct timespec *timeout,
    clockid_t clockid, int flags, const struct bintime *epsilon)
{

	memset(T, 0, sizeof(*T));
	T->timeout = timeout;
	T->clockid = clockid;
	T->flags = flags;
	T->epsilon = epsilon;
	T->starttime = (struct timespec){0,0};
}

/*
 * timedwaitclock_begin(T, timo)
 *
 *	Decide how many ticks to wait for the timedwaitclock T and
 *	store it in *timo.  Keep state for timedwaitclock_end.  May
 *	fail with EINVAL if the specified timeout is invalid, or if the
 *	specified clock fails.  Fails with ETIMEDOUT if there is no
 *	time left to wait.
 */
int
timedwaitclock_begin(struct timedwaitclock *T, int *timo)
{
	struct timespec delta;
	const struct timespec *deltap;
	int error;

	/* Sanity-check timeout -- may have come from userland.  */
	if (T->timeout->tv_nsec < 0 || T->timeout->tv_nsec >= 1000000000L)
		return EINVAL;

	/*
	 * Compute the time delta.
	 */
	if ((T->flags & TIMER_ABSTIME) == TIMER_ABSTIME) {
		/* Check our watch.  */
		error = clock_gettime1(T->clockid, &T->starttime);
		if (error)
			return error;

		/* If the deadline has passed, we're done.  */
		if (timespeccmp(T->timeout, &T->starttime, <=))
			return ETIMEDOUT;

		/* Count how much time is left.  */
		timespecsub(T->timeout, &T->starttime, &delta);
		deltap = &delta;
	} else {
		/* The user specified how much time is left.  */
		deltap = T->timeout;

		/* If there's none left, we've timed out.  */
		if (deltap->tv_sec == 0 && deltap->tv_nsec == 0)
			return ETIMEDOUT;
	}

	/*
	 * Convert to ticks, but clamp to be >=1.
	 *
	 * XXX In the tickless future, use a high-resolution timer if
	 * timo would round to zero.
	 */
	*timo = tstohz(deltap);
	KASSERTMSG(*timo >= 0, "negative ticks: %d", *timo);
	if (*timo == 0)
		*timo = 1;

	/* Success!  */
	return 0;
}

/*
 * timedwaitclock_end(T)
 *
 *	If the timedwaitclock T was relative, update the caller's
 *	original timeout to reflect how much time is left, or zero if
 *	there is no time left or if the clock has gone bad, so that the
 *	next timedwaitclock_begin will immediately time out.
 */
void
timedwaitclock_end(struct timedwaitclock *T)
{
	struct timespec endtime, delta;

	/* If the timeout is absolute, nothing to do.  */
	if ((T->flags & TIMER_ABSTIME) == TIMER_ABSTIME)
		return;

	/*
	 * Check our watch.  If anything goes wrong with it, make sure
	 * that the next time we immediately time out rather than fail
	 * to deduct the time elapsed.
	 */
	if (clock_gettime1(T->clockid, &endtime)) {
		T->timeout->tv_sec = 0;
		T->timeout->tv_nsec = 0;
		return;
	}

	/* Find how much time elapsed while we waited.  */
	timespecsub(&endtime, &T->starttime, &delta);

	/*
	 * Paranoia: If the clock went backwards, treat it as if no
	 * time elapsed at all rather than adding anything.
	 */
	if (delta.tv_sec < 0 ||
	    (delta.tv_sec == 0 && delta.tv_nsec < 0)) {
		delta.tv_sec = 0;
		delta.tv_nsec = 0;
	}

	/*
	 * Set it to the time left, or zero, whichever is larger.  We
	 * do not fail with EWOULDBLOCK here because this may have been
	 * an explicit wakeup, so the caller needs to check before they
	 * give up or else cv_signal would be lost.
	 */
	if (timespeccmp(T->timeout, &delta, <=)) {
		T->timeout->tv_sec = 0;
		T->timeout->tv_nsec = 0;
	} else {
		timespecsub(T->timeout, &delta, T->timeout);
	}
}