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

/*	$NetBSD: subr_time.c,v 1.34 2022/06/26 22:31:47 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 1.34 2022/06/26 22:31:47 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(kauth_cred_get(),
		    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;

	if ((flags & TIMER_ABSTIME) != 0 || start != NULL) {
		error = clock_gettime1(clock_id, &tsd);
		if (error != 0)
			return error;
		if (start != NULL)
			*start = tsd;
	}

	if ((flags & TIMER_ABSTIME) != 0) {
		if (!timespecsubok(ts, &tsd))
			return EINVAL;
		timespecsub(ts, &tsd, ts);
	}

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

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

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

	return 0;
}

bool
timespecaddok(const struct timespec *tsp, const struct timespec *usp)
{
	enum { TIME_MIN = __type_min(time_t), TIME_MAX = __type_max(time_t) };
	time_t a = tsp->tv_sec;
	time_t b = usp->tv_sec;
	bool carry;

	/*
	 * Caller is responsible for guaranteeing valid timespec
	 * inputs.  Any user-controlled inputs must be validated or
	 * adjusted.
	 */
	KASSERT(tsp->tv_nsec >= 0);
	KASSERT(usp->tv_nsec >= 0);
	KASSERT(tsp->tv_nsec < 1000000000L);
	KASSERT(usp->tv_nsec < 1000000000L);
	CTASSERT(1000000000L <= __type_max(long) - 1000000000L);

	/*
	 * Fail if a + b + carry overflows TIME_MAX, or if a + b
	 * overflows TIME_MIN because timespecadd adds the carry after
	 * computing a + b.
	 *
	 * Break it into two mutually exclusive and exhaustive cases:
	 * I. a >= 0
	 * II. a < 0
	 */
	carry = (tsp->tv_nsec + usp->tv_nsec >= 1000000000L);
	if (a >= 0) {
		/*
		 * Case I: a >= 0.  If b < 0, then b + 1 <= 0, so
		 *
		 *	a + b + 1 <= a + 0 <= TIME_MAX,
		 *
		 * and
		 *
		 *	a + b >= 0 + b = b >= TIME_MIN,
		 *
		 * so this can't overflow.
		 *
		 * If b >= 0, then a + b + carry >= a + b >= 0, so
		 * negative results and thus results below TIME_MIN are
		 * impossible; we need only avoid
		 *
		 *	a + b + carry > TIME_MAX,
		 *
		 * which we will do by rejecting if
		 *
		 *	b > TIME_MAX - a - carry,
		 *
		 * which in turn is incidentally always false if b < 0
		 * so we don't need extra logic to discriminate on the
		 * b >= 0 and b < 0 cases.
		 *
		 * Since 0 <= a <= TIME_MAX, we know
		 *
		 *	0 <= TIME_MAX - a <= TIME_MAX,
		 *
		 * and hence
		 *
		 *	-1 <= TIME_MAX - a - 1 < TIME_MAX.
		 *
		 * So we can compute TIME_MAX - a - carry (i.e., either
		 * TIME_MAX - a or TIME_MAX - a - 1) safely without
		 * overflow.
		 */
		if (b > TIME_MAX - a - carry)
			return false;
	} else {
		/*
		 * Case II: a < 0.  If b >= 0, then since a + 1 <= 0,
		 * we have
		 *
		 *	a + b + 1 <= b <= TIME_MAX,
		 *
		 * and
		 *
		 *	a + b >= a >= TIME_MIN,
		 *
		 * so this can't overflow.
		 *
		 * If b < 0, then the intermediate a + b is negative
		 * and the outcome a + b + 1 is nonpositive, so we need
		 * only avoid
		 *
		 *	a + b < TIME_MIN,
		 *
		 * which we will do by rejecting if
		 *
		 *	a < TIME_MIN - b.
		 *
		 * (Reminder: The carry is added afterward in
		 * timespecadd, so to avoid overflow it is not enough
		 * to merely reject a + b + carry < TIME_MIN.)
		 *
		 * It is safe to compute the difference TIME_MIN - b
		 * because b is negative, so the result lies in
		 * (TIME_MIN, 0].
		 */
		if (b < 0 && a < TIME_MIN - b)
			return false;
	}

	return true;
}

bool
timespecsubok(const struct timespec *tsp, const struct timespec *usp)
{
	enum { TIME_MIN = __type_min(time_t), TIME_MAX = __type_max(time_t) };
	time_t a = tsp->tv_sec, b = usp->tv_sec;
	bool borrow;

	/*
	 * Caller is responsible for guaranteeing valid timespec
	 * inputs.  Any user-controlled inputs must be validated or
	 * adjusted.
	 */
	KASSERT(tsp->tv_nsec >= 0);
	KASSERT(usp->tv_nsec >= 0);
	KASSERT(tsp->tv_nsec < 1000000000L);
	KASSERT(usp->tv_nsec < 1000000000L);
	CTASSERT(1000000000L <= __type_max(long) - 1000000000L);

	/*
	 * Fail if a - b - borrow overflows TIME_MIN, or if a - b
	 * overflows TIME_MAX because timespecsub subtracts the borrow
	 * after computing a - b.
	 *
	 * Break it into two mutually exclusive and exhaustive cases:
	 * I. a < 0
	 * II. a >= 0
	 */
	borrow = (tsp->tv_nsec - usp->tv_nsec < 0);
	if (a < 0) {
		/*
		 * Case I: a < 0.  If b < 0, then -b - 1 >= 0, so
		 *
		 *	a - b - 1 >= a + 0 >= TIME_MIN,
		 *
		 * and, since a <= -1, provided that TIME_MIN <=
		 * -TIME_MAX - 1 so that TIME_MAX <= -TIME_MIN - 1 (in
		 * fact, equality holds, under the assumption of
		 * two's-complement arithmetic),
		 *
		 *	a - b <= -1 - b = -b - 1 <= TIME_MAX,
		 *
		 * so this can't overflow.
		 */
		CTASSERT(TIME_MIN <= -TIME_MAX - 1);

		/*
		 * If b >= 0, then a - b - borrow <= a - b < 0, so
		 * positive results and thus results above TIME_MAX are
		 * impossible; we need only avoid
		 *
		 *	a - b - borrow < TIME_MIN,
		 *
		 * which we will do by rejecting if
		 *
		 *	a < TIME_MIN + b + borrow.
		 *
		 * The right-hand side is safe to evaluate for any
		 * values of b and borrow as long as TIME_MIN +
		 * TIME_MAX + 1 <= TIME_MAX, i.e., TIME_MIN <= -1.
		 * (Note: If time_t were unsigned, this would fail!)
		 *
		 * Note: Unlike Case I in timespecaddok, this criterion
		 * does not work for b < 0, nor can the roles of a and
		 * b in the inequality be reversed (e.g., -b < TIME_MIN
		 * - a + borrow) without extra cases like checking for
		 * b = TEST_MIN.
		 */
		CTASSERT(TIME_MIN < -1);
		if (b >= 0 && a < TIME_MIN + b + borrow)
			return false;
	} else {
		/*
		 * Case II: a >= 0.  If b >= 0, then
		 *
		 *	a - b <= a <= TIME_MAX,
		 *
		 * and, provided TIME_MIN <= -TIME_MAX - 1 (in fact,
		 * equality holds, under the assumption of
		 * two's-complement arithmetic)
		 *
		 *	a - b - 1 >= -b - 1 >= -TIME_MAX - 1 >= TIME_MIN,
		 *
		 * so this can't overflow.
		 */
		CTASSERT(TIME_MIN <= -TIME_MAX - 1);

		/*
		 * If b < 0, then a - b >= a >= 0, so negative results
		 * and thus results below TIME_MIN are impossible; we
		 * need only avoid
		 *
		 *	a - b > TIME_MAX,
		 *
		 * which we will do by rejecting if
		 *
		 *	a > TIME_MAX + b.
		 *
		 * (Reminder: The borrow is subtracted afterward in
		 * timespecsub, so to avoid overflow it is not enough
		 * to merely reject a - b - borrow > TIME_MAX.)
		 *
		 * It is safe to compute the sum TIME_MAX + b because b
		 * is negative, so the result lies in [0, TIME_MAX).
		 */
		if (b < 0 && a > TIME_MAX + b)
			return false;
	}

	return true;
}