4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * This file contains the interface functions for the various
7 * time related system calls: time, stime, gettimeofday, settimeofday,
11 * Modification history kernel/time.c
13 * 1993-09-02 Philip Gladstone
14 * Created file with time related functions from sched/core.c and adjtimex()
15 * 1993-10-08 Torsten Duwe
16 * adjtime interface update and CMOS clock write code
17 * 1995-08-13 Torsten Duwe
18 * kernel PLL updated to 1994-12-13 specs (rfc-1589)
19 * 1999-01-16 Ulrich Windl
20 * Introduced error checking for many cases in adjtimex().
21 * Updated NTP code according to technical memorandum Jan '96
22 * "A Kernel Model for Precision Timekeeping" by Dave Mills
23 * Allow time_constant larger than MAXTC(6) for NTP v4 (MAXTC == 10)
24 * (Even though the technical memorandum forbids it)
25 * 2004-07-14 Christoph Lameter
26 * Added getnstimeofday to allow the posix timer functions to return
27 * with nanosecond accuracy
30 #include <linux/export.h>
31 #include <linux/timex.h>
32 #include <linux/capability.h>
33 #include <linux/timekeeper_internal.h>
34 #include <linux/errno.h>
35 #include <linux/syscalls.h>
36 #include <linux/security.h>
38 #include <linux/math64.h>
39 #include <linux/ptrace.h>
41 #include <linux/uaccess.h>
42 #include <asm/unistd.h>
44 #include <generated/timeconst.h>
45 #include "timekeeping.h"
48 * The timezone where the local system is located. Used as a default by some
49 * programs who obtain this value by using gettimeofday.
51 struct timezone sys_tz;
53 EXPORT_SYMBOL(sys_tz);
55 #ifdef __ARCH_WANT_SYS_TIME
58 * sys_time() can be implemented in user-level using
59 * sys_gettimeofday(). Is this for backwards compatibility? If so,
60 * why not move it into the appropriate arch directory (for those
61 * architectures that need it).
63 SYSCALL_DEFINE1(time, time_t __user *, tloc)
65 time_t i = get_seconds();
71 force_successful_syscall_return();
76 * sys_stime() can be implemented in user-level using
77 * sys_settimeofday(). Is this for backwards compatibility? If so,
78 * why not move it into the appropriate arch directory (for those
79 * architectures that need it).
82 SYSCALL_DEFINE1(stime, time_t __user *, tptr)
87 if (get_user(tv.tv_sec, tptr))
92 err = security_settime(&tv, NULL);
100 #endif /* __ARCH_WANT_SYS_TIME */
102 SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv,
103 struct timezone __user *, tz)
105 if (likely(tv != NULL)) {
107 do_gettimeofday(&ktv);
108 if (copy_to_user(tv, &ktv, sizeof(ktv)))
111 if (unlikely(tz != NULL)) {
112 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
119 * Indicates if there is an offset between the system clock and the hardware
120 * clock/persistent clock/rtc.
122 int persistent_clock_is_local;
125 * Adjust the time obtained from the CMOS to be UTC time instead of
128 * This is ugly, but preferable to the alternatives. Otherwise we
129 * would either need to write a program to do it in /etc/rc (and risk
130 * confusion if the program gets run more than once; it would also be
131 * hard to make the program warp the clock precisely n hours) or
132 * compile in the timezone information into the kernel. Bad, bad....
136 * The best thing to do is to keep the CMOS clock in universal time (UTC)
137 * as real UNIX machines always do it. This avoids all headaches about
138 * daylight saving times and warping kernel clocks.
140 static inline void warp_clock(void)
142 if (sys_tz.tz_minuteswest != 0) {
143 struct timespec adjust;
145 persistent_clock_is_local = 1;
146 adjust.tv_sec = sys_tz.tz_minuteswest * 60;
148 timekeeping_inject_offset(&adjust);
153 * In case for some reason the CMOS clock has not already been running
154 * in UTC, but in some local time: The first time we set the timezone,
155 * we will warp the clock so that it is ticking UTC time instead of
156 * local time. Presumably, if someone is setting the timezone then we
157 * are running in an environment where the programs understand about
158 * timezones. This should be done at boot time in the /etc/rc script,
159 * as soon as possible, so that the clock can be set right. Otherwise,
160 * various programs will get confused when the clock gets warped.
163 int do_sys_settimeofday64(const struct timespec64 *tv, const struct timezone *tz)
165 static int firsttime = 1;
168 if (tv && !timespec64_valid(tv))
171 error = security_settime64(tv, tz);
176 /* Verify we're witin the +-15 hrs range */
177 if (tz->tz_minuteswest > 15*60 || tz->tz_minuteswest < -15*60)
181 update_vsyscall_tz();
189 return do_settimeofday64(tv);
193 SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv,
194 struct timezone __user *, tz)
196 struct timespec64 new_ts;
197 struct timeval user_tv;
198 struct timezone new_tz;
201 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
204 if (!timeval_valid(&user_tv))
207 new_ts.tv_sec = user_tv.tv_sec;
208 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
211 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
215 return do_sys_settimeofday64(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
218 SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p)
220 struct timex txc; /* Local copy of parameter */
223 /* Copy the user data space into the kernel copy
224 * structure. But bear in mind that the structures
227 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
229 ret = do_adjtimex(&txc);
230 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
234 * Convert jiffies to milliseconds and back.
236 * Avoid unnecessary multiplications/divisions in the
237 * two most common HZ cases:
239 unsigned int jiffies_to_msecs(const unsigned long j)
241 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
242 return (MSEC_PER_SEC / HZ) * j;
243 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
244 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
246 # if BITS_PER_LONG == 32
247 return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
249 return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
253 EXPORT_SYMBOL(jiffies_to_msecs);
255 unsigned int jiffies_to_usecs(const unsigned long j)
258 * Hz usually doesn't go much further MSEC_PER_SEC.
259 * jiffies_to_usecs() and usecs_to_jiffies() depend on that.
261 BUILD_BUG_ON(HZ > USEC_PER_SEC);
263 #if !(USEC_PER_SEC % HZ)
264 return (USEC_PER_SEC / HZ) * j;
266 # if BITS_PER_LONG == 32
267 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
269 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
273 EXPORT_SYMBOL(jiffies_to_usecs);
276 * timespec_trunc - Truncate timespec to a granularity
278 * @gran: Granularity in ns.
280 * Truncate a timespec to a granularity. Always rounds down. gran must
281 * not be 0 nor greater than a second (NSEC_PER_SEC, or 10^9 ns).
283 struct timespec timespec_trunc(struct timespec t, unsigned gran)
285 /* Avoid division in the common cases 1 ns and 1 s. */
288 } else if (gran == NSEC_PER_SEC) {
290 } else if (gran > 1 && gran < NSEC_PER_SEC) {
291 t.tv_nsec -= t.tv_nsec % gran;
293 WARN(1, "illegal file time granularity: %u", gran);
297 EXPORT_SYMBOL(timespec_trunc);
300 * mktime64 - Converts date to seconds.
301 * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
302 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
303 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
305 * [For the Julian calendar (which was used in Russia before 1917,
306 * Britain & colonies before 1752, anywhere else before 1582,
307 * and is still in use by some communities) leave out the
308 * -year/100+year/400 terms, and add 10.]
310 * This algorithm was first published by Gauss (I think).
312 * A leap second can be indicated by calling this function with sec as
313 * 60 (allowable under ISO 8601). The leap second is treated the same
314 * as the following second since they don't exist in UNIX time.
316 * An encoding of midnight at the end of the day as 24:00:00 - ie. midnight
317 * tomorrow - (allowable under ISO 8601) is supported.
319 time64_t mktime64(const unsigned int year0, const unsigned int mon0,
320 const unsigned int day, const unsigned int hour,
321 const unsigned int min, const unsigned int sec)
323 unsigned int mon = mon0, year = year0;
325 /* 1..12 -> 11,12,1..10 */
326 if (0 >= (int) (mon -= 2)) {
327 mon += 12; /* Puts Feb last since it has leap day */
332 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
334 )*24 + hour /* now have hours - midnight tomorrow handled here */
335 )*60 + min /* now have minutes */
336 )*60 + sec; /* finally seconds */
338 EXPORT_SYMBOL(mktime64);
341 * set_normalized_timespec - set timespec sec and nsec parts and normalize
343 * @ts: pointer to timespec variable to be set
344 * @sec: seconds to set
345 * @nsec: nanoseconds to set
347 * Set seconds and nanoseconds field of a timespec variable and
348 * normalize to the timespec storage format
350 * Note: The tv_nsec part is always in the range of
351 * 0 <= tv_nsec < NSEC_PER_SEC
352 * For negative values only the tv_sec field is negative !
354 void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
356 while (nsec >= NSEC_PER_SEC) {
358 * The following asm() prevents the compiler from
359 * optimising this loop into a modulo operation. See
360 * also __iter_div_u64_rem() in include/linux/time.h
362 asm("" : "+rm"(nsec));
363 nsec -= NSEC_PER_SEC;
367 asm("" : "+rm"(nsec));
368 nsec += NSEC_PER_SEC;
374 EXPORT_SYMBOL(set_normalized_timespec);
377 * ns_to_timespec - Convert nanoseconds to timespec
378 * @nsec: the nanoseconds value to be converted
380 * Returns the timespec representation of the nsec parameter.
382 struct timespec ns_to_timespec(const s64 nsec)
388 return (struct timespec) {0, 0};
390 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
391 if (unlikely(rem < 0)) {
399 EXPORT_SYMBOL(ns_to_timespec);
402 * ns_to_timeval - Convert nanoseconds to timeval
403 * @nsec: the nanoseconds value to be converted
405 * Returns the timeval representation of the nsec parameter.
407 struct timeval ns_to_timeval(const s64 nsec)
409 struct timespec ts = ns_to_timespec(nsec);
412 tv.tv_sec = ts.tv_sec;
413 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
417 EXPORT_SYMBOL(ns_to_timeval);
419 #if BITS_PER_LONG == 32
421 * set_normalized_timespec - set timespec sec and nsec parts and normalize
423 * @ts: pointer to timespec variable to be set
424 * @sec: seconds to set
425 * @nsec: nanoseconds to set
427 * Set seconds and nanoseconds field of a timespec variable and
428 * normalize to the timespec storage format
430 * Note: The tv_nsec part is always in the range of
431 * 0 <= tv_nsec < NSEC_PER_SEC
432 * For negative values only the tv_sec field is negative !
434 void set_normalized_timespec64(struct timespec64 *ts, time64_t sec, s64 nsec)
436 while (nsec >= NSEC_PER_SEC) {
438 * The following asm() prevents the compiler from
439 * optimising this loop into a modulo operation. See
440 * also __iter_div_u64_rem() in include/linux/time.h
442 asm("" : "+rm"(nsec));
443 nsec -= NSEC_PER_SEC;
447 asm("" : "+rm"(nsec));
448 nsec += NSEC_PER_SEC;
454 EXPORT_SYMBOL(set_normalized_timespec64);
457 * ns_to_timespec64 - Convert nanoseconds to timespec64
458 * @nsec: the nanoseconds value to be converted
460 * Returns the timespec64 representation of the nsec parameter.
462 struct timespec64 ns_to_timespec64(const s64 nsec)
464 struct timespec64 ts;
468 return (struct timespec64) {0, 0};
470 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
471 if (unlikely(rem < 0)) {
479 EXPORT_SYMBOL(ns_to_timespec64);
482 * msecs_to_jiffies: - convert milliseconds to jiffies
483 * @m: time in milliseconds
485 * conversion is done as follows:
487 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
489 * - 'too large' values [that would result in larger than
490 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
492 * - all other values are converted to jiffies by either multiplying
493 * the input value by a factor or dividing it with a factor and
494 * handling any 32-bit overflows.
495 * for the details see __msecs_to_jiffies()
497 * msecs_to_jiffies() checks for the passed in value being a constant
498 * via __builtin_constant_p() allowing gcc to eliminate most of the
499 * code, __msecs_to_jiffies() is called if the value passed does not
500 * allow constant folding and the actual conversion must be done at
502 * the _msecs_to_jiffies helpers are the HZ dependent conversion
503 * routines found in include/linux/jiffies.h
505 unsigned long __msecs_to_jiffies(const unsigned int m)
508 * Negative value, means infinite timeout:
511 return MAX_JIFFY_OFFSET;
512 return _msecs_to_jiffies(m);
514 EXPORT_SYMBOL(__msecs_to_jiffies);
516 unsigned long __usecs_to_jiffies(const unsigned int u)
518 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
519 return MAX_JIFFY_OFFSET;
520 return _usecs_to_jiffies(u);
522 EXPORT_SYMBOL(__usecs_to_jiffies);
525 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
526 * that a remainder subtract here would not do the right thing as the
527 * resolution values don't fall on second boundries. I.e. the line:
528 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
529 * Note that due to the small error in the multiplier here, this
530 * rounding is incorrect for sufficiently large values of tv_nsec, but
531 * well formed timespecs should have tv_nsec < NSEC_PER_SEC, so we're
534 * Rather, we just shift the bits off the right.
536 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
537 * value to a scaled second value.
540 __timespec64_to_jiffies(u64 sec, long nsec)
542 nsec = nsec + TICK_NSEC - 1;
544 if (sec >= MAX_SEC_IN_JIFFIES){
545 sec = MAX_SEC_IN_JIFFIES;
548 return ((sec * SEC_CONVERSION) +
549 (((u64)nsec * NSEC_CONVERSION) >>
550 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
555 __timespec_to_jiffies(unsigned long sec, long nsec)
557 return __timespec64_to_jiffies((u64)sec, nsec);
561 timespec64_to_jiffies(const struct timespec64 *value)
563 return __timespec64_to_jiffies(value->tv_sec, value->tv_nsec);
565 EXPORT_SYMBOL(timespec64_to_jiffies);
568 jiffies_to_timespec64(const unsigned long jiffies, struct timespec64 *value)
571 * Convert jiffies to nanoseconds and separate with
575 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
577 value->tv_nsec = rem;
579 EXPORT_SYMBOL(jiffies_to_timespec64);
582 * We could use a similar algorithm to timespec_to_jiffies (with a
583 * different multiplier for usec instead of nsec). But this has a
584 * problem with rounding: we can't exactly add TICK_NSEC - 1 to the
585 * usec value, since it's not necessarily integral.
587 * We could instead round in the intermediate scaled representation
588 * (i.e. in units of 1/2^(large scale) jiffies) but that's also
589 * perilous: the scaling introduces a small positive error, which
590 * combined with a division-rounding-upward (i.e. adding 2^(scale) - 1
591 * units to the intermediate before shifting) leads to accidental
592 * overflow and overestimates.
594 * At the cost of one additional multiplication by a constant, just
595 * use the timespec implementation.
598 timeval_to_jiffies(const struct timeval *value)
600 return __timespec_to_jiffies(value->tv_sec,
601 value->tv_usec * NSEC_PER_USEC);
603 EXPORT_SYMBOL(timeval_to_jiffies);
605 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
608 * Convert jiffies to nanoseconds and separate with
613 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
615 value->tv_usec = rem / NSEC_PER_USEC;
617 EXPORT_SYMBOL(jiffies_to_timeval);
620 * Convert jiffies/jiffies_64 to clock_t and back.
622 clock_t jiffies_to_clock_t(unsigned long x)
624 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
626 return x * (USER_HZ / HZ);
628 return x / (HZ / USER_HZ);
631 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
634 EXPORT_SYMBOL(jiffies_to_clock_t);
636 unsigned long clock_t_to_jiffies(unsigned long x)
638 #if (HZ % USER_HZ)==0
639 if (x >= ~0UL / (HZ / USER_HZ))
641 return x * (HZ / USER_HZ);
643 /* Don't worry about loss of precision here .. */
644 if (x >= ~0UL / HZ * USER_HZ)
647 /* .. but do try to contain it here */
648 return div_u64((u64)x * HZ, USER_HZ);
651 EXPORT_SYMBOL(clock_t_to_jiffies);
653 u64 jiffies_64_to_clock_t(u64 x)
655 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
657 x = div_u64(x * USER_HZ, HZ);
659 x = div_u64(x, HZ / USER_HZ);
665 * There are better ways that don't overflow early,
666 * but even this doesn't overflow in hundreds of years
669 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
673 EXPORT_SYMBOL(jiffies_64_to_clock_t);
675 u64 nsec_to_clock_t(u64 x)
677 #if (NSEC_PER_SEC % USER_HZ) == 0
678 return div_u64(x, NSEC_PER_SEC / USER_HZ);
679 #elif (USER_HZ % 512) == 0
680 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
683 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
684 * overflow after 64.99 years.
685 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
687 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
691 u64 jiffies64_to_nsecs(u64 j)
693 #if !(NSEC_PER_SEC % HZ)
694 return (NSEC_PER_SEC / HZ) * j;
696 return div_u64(j * HZ_TO_NSEC_NUM, HZ_TO_NSEC_DEN);
699 EXPORT_SYMBOL(jiffies64_to_nsecs);
702 * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
706 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
707 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
708 * for scheduler, not for use in device drivers to calculate timeout value.
711 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
712 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
714 u64 nsecs_to_jiffies64(u64 n)
716 #if (NSEC_PER_SEC % HZ) == 0
717 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
718 return div_u64(n, NSEC_PER_SEC / HZ);
719 #elif (HZ % 512) == 0
720 /* overflow after 292 years if HZ = 1024 */
721 return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
724 * Generic case - optimized for cases where HZ is a multiple of 3.
725 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
727 return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
730 EXPORT_SYMBOL(nsecs_to_jiffies64);
733 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
737 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
738 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
739 * for scheduler, not for use in device drivers to calculate timeout value.
742 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
743 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
745 unsigned long nsecs_to_jiffies(u64 n)
747 return (unsigned long)nsecs_to_jiffies64(n);
749 EXPORT_SYMBOL_GPL(nsecs_to_jiffies);
752 * Add two timespec values and do a safety check for overflow.
753 * It's assumed that both values are valid (>= 0)
755 struct timespec timespec_add_safe(const struct timespec lhs,
756 const struct timespec rhs)
760 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
761 lhs.tv_nsec + rhs.tv_nsec);
763 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
764 res.tv_sec = TIME_T_MAX;
770 * Add two timespec64 values and do a safety check for overflow.
771 * It's assumed that both values are valid (>= 0).
772 * And, each timespec64 is in normalized form.
774 struct timespec64 timespec64_add_safe(const struct timespec64 lhs,
775 const struct timespec64 rhs)
777 struct timespec64 res;
779 set_normalized_timespec64(&res, (timeu64_t) lhs.tv_sec + rhs.tv_sec,
780 lhs.tv_nsec + rhs.tv_nsec);
782 if (unlikely(res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)) {
783 res.tv_sec = TIME64_MAX;