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 timeval user_tv;
197 struct timespec new_ts;
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_settimeofday(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 * current_fs_time - Return FS time
237 * Return the current time truncated to the time granularity supported by
240 struct timespec current_fs_time(struct super_block *sb)
242 struct timespec now = current_kernel_time();
243 return timespec_trunc(now, sb->s_time_gran);
245 EXPORT_SYMBOL(current_fs_time);
248 * Convert jiffies to milliseconds and back.
250 * Avoid unnecessary multiplications/divisions in the
251 * two most common HZ cases:
253 unsigned int jiffies_to_msecs(const unsigned long j)
255 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
256 return (MSEC_PER_SEC / HZ) * j;
257 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
258 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
260 # if BITS_PER_LONG == 32
261 return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
263 return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
267 EXPORT_SYMBOL(jiffies_to_msecs);
269 unsigned int jiffies_to_usecs(const unsigned long j)
272 * Hz usually doesn't go much further MSEC_PER_SEC.
273 * jiffies_to_usecs() and usecs_to_jiffies() depend on that.
275 BUILD_BUG_ON(HZ > USEC_PER_SEC);
277 #if !(USEC_PER_SEC % HZ)
278 return (USEC_PER_SEC / HZ) * j;
280 # if BITS_PER_LONG == 32
281 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
283 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
287 EXPORT_SYMBOL(jiffies_to_usecs);
290 * timespec_trunc - Truncate timespec to a granularity
292 * @gran: Granularity in ns.
294 * Truncate a timespec to a granularity. Always rounds down. gran must
295 * not be 0 nor greater than a second (NSEC_PER_SEC, or 10^9 ns).
297 struct timespec timespec_trunc(struct timespec t, unsigned gran)
299 /* Avoid division in the common cases 1 ns and 1 s. */
302 } else if (gran == NSEC_PER_SEC) {
304 } else if (gran > 1 && gran < NSEC_PER_SEC) {
305 t.tv_nsec -= t.tv_nsec % gran;
307 WARN(1, "illegal file time granularity: %u", gran);
311 EXPORT_SYMBOL(timespec_trunc);
314 * mktime64 - Converts date to seconds.
315 * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
316 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
317 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
319 * [For the Julian calendar (which was used in Russia before 1917,
320 * Britain & colonies before 1752, anywhere else before 1582,
321 * and is still in use by some communities) leave out the
322 * -year/100+year/400 terms, and add 10.]
324 * This algorithm was first published by Gauss (I think).
326 * A leap second can be indicated by calling this function with sec as
327 * 60 (allowable under ISO 8601). The leap second is treated the same
328 * as the following second since they don't exist in UNIX time.
330 * An encoding of midnight at the end of the day as 24:00:00 - ie. midnight
331 * tomorrow - (allowable under ISO 8601) is supported.
333 time64_t mktime64(const unsigned int year0, const unsigned int mon0,
334 const unsigned int day, const unsigned int hour,
335 const unsigned int min, const unsigned int sec)
337 unsigned int mon = mon0, year = year0;
339 /* 1..12 -> 11,12,1..10 */
340 if (0 >= (int) (mon -= 2)) {
341 mon += 12; /* Puts Feb last since it has leap day */
346 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
348 )*24 + hour /* now have hours - midnight tomorrow handled here */
349 )*60 + min /* now have minutes */
350 )*60 + sec; /* finally seconds */
352 EXPORT_SYMBOL(mktime64);
355 * set_normalized_timespec - set timespec sec and nsec parts and normalize
357 * @ts: pointer to timespec variable to be set
358 * @sec: seconds to set
359 * @nsec: nanoseconds to set
361 * Set seconds and nanoseconds field of a timespec variable and
362 * normalize to the timespec storage format
364 * Note: The tv_nsec part is always in the range of
365 * 0 <= tv_nsec < NSEC_PER_SEC
366 * For negative values only the tv_sec field is negative !
368 void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
370 while (nsec >= NSEC_PER_SEC) {
372 * The following asm() prevents the compiler from
373 * optimising this loop into a modulo operation. See
374 * also __iter_div_u64_rem() in include/linux/time.h
376 asm("" : "+rm"(nsec));
377 nsec -= NSEC_PER_SEC;
381 asm("" : "+rm"(nsec));
382 nsec += NSEC_PER_SEC;
388 EXPORT_SYMBOL(set_normalized_timespec);
391 * ns_to_timespec - Convert nanoseconds to timespec
392 * @nsec: the nanoseconds value to be converted
394 * Returns the timespec representation of the nsec parameter.
396 struct timespec ns_to_timespec(const s64 nsec)
402 return (struct timespec) {0, 0};
404 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
405 if (unlikely(rem < 0)) {
413 EXPORT_SYMBOL(ns_to_timespec);
416 * ns_to_timeval - Convert nanoseconds to timeval
417 * @nsec: the nanoseconds value to be converted
419 * Returns the timeval representation of the nsec parameter.
421 struct timeval ns_to_timeval(const s64 nsec)
423 struct timespec ts = ns_to_timespec(nsec);
426 tv.tv_sec = ts.tv_sec;
427 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
431 EXPORT_SYMBOL(ns_to_timeval);
433 #if BITS_PER_LONG == 32
435 * set_normalized_timespec - set timespec sec and nsec parts and normalize
437 * @ts: pointer to timespec variable to be set
438 * @sec: seconds to set
439 * @nsec: nanoseconds to set
441 * Set seconds and nanoseconds field of a timespec variable and
442 * normalize to the timespec storage format
444 * Note: The tv_nsec part is always in the range of
445 * 0 <= tv_nsec < NSEC_PER_SEC
446 * For negative values only the tv_sec field is negative !
448 void set_normalized_timespec64(struct timespec64 *ts, time64_t sec, s64 nsec)
450 while (nsec >= NSEC_PER_SEC) {
452 * The following asm() prevents the compiler from
453 * optimising this loop into a modulo operation. See
454 * also __iter_div_u64_rem() in include/linux/time.h
456 asm("" : "+rm"(nsec));
457 nsec -= NSEC_PER_SEC;
461 asm("" : "+rm"(nsec));
462 nsec += NSEC_PER_SEC;
468 EXPORT_SYMBOL(set_normalized_timespec64);
471 * ns_to_timespec64 - Convert nanoseconds to timespec64
472 * @nsec: the nanoseconds value to be converted
474 * Returns the timespec64 representation of the nsec parameter.
476 struct timespec64 ns_to_timespec64(const s64 nsec)
478 struct timespec64 ts;
482 return (struct timespec64) {0, 0};
484 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
485 if (unlikely(rem < 0)) {
493 EXPORT_SYMBOL(ns_to_timespec64);
496 * msecs_to_jiffies: - convert milliseconds to jiffies
497 * @m: time in milliseconds
499 * conversion is done as follows:
501 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
503 * - 'too large' values [that would result in larger than
504 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
506 * - all other values are converted to jiffies by either multiplying
507 * the input value by a factor or dividing it with a factor and
508 * handling any 32-bit overflows.
509 * for the details see __msecs_to_jiffies()
511 * msecs_to_jiffies() checks for the passed in value being a constant
512 * via __builtin_constant_p() allowing gcc to eliminate most of the
513 * code, __msecs_to_jiffies() is called if the value passed does not
514 * allow constant folding and the actual conversion must be done at
516 * the _msecs_to_jiffies helpers are the HZ dependent conversion
517 * routines found in include/linux/jiffies.h
519 unsigned long __msecs_to_jiffies(const unsigned int m)
522 * Negative value, means infinite timeout:
525 return MAX_JIFFY_OFFSET;
526 return _msecs_to_jiffies(m);
528 EXPORT_SYMBOL(__msecs_to_jiffies);
530 unsigned long __usecs_to_jiffies(const unsigned int u)
532 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
533 return MAX_JIFFY_OFFSET;
534 return _usecs_to_jiffies(u);
536 EXPORT_SYMBOL(__usecs_to_jiffies);
539 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
540 * that a remainder subtract here would not do the right thing as the
541 * resolution values don't fall on second boundries. I.e. the line:
542 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
543 * Note that due to the small error in the multiplier here, this
544 * rounding is incorrect for sufficiently large values of tv_nsec, but
545 * well formed timespecs should have tv_nsec < NSEC_PER_SEC, so we're
548 * Rather, we just shift the bits off the right.
550 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
551 * value to a scaled second value.
554 __timespec64_to_jiffies(u64 sec, long nsec)
556 nsec = nsec + TICK_NSEC - 1;
558 if (sec >= MAX_SEC_IN_JIFFIES){
559 sec = MAX_SEC_IN_JIFFIES;
562 return ((sec * SEC_CONVERSION) +
563 (((u64)nsec * NSEC_CONVERSION) >>
564 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
569 __timespec_to_jiffies(unsigned long sec, long nsec)
571 return __timespec64_to_jiffies((u64)sec, nsec);
575 timespec64_to_jiffies(const struct timespec64 *value)
577 return __timespec64_to_jiffies(value->tv_sec, value->tv_nsec);
579 EXPORT_SYMBOL(timespec64_to_jiffies);
582 jiffies_to_timespec64(const unsigned long jiffies, struct timespec64 *value)
585 * Convert jiffies to nanoseconds and separate with
589 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
591 value->tv_nsec = rem;
593 EXPORT_SYMBOL(jiffies_to_timespec64);
596 * We could use a similar algorithm to timespec_to_jiffies (with a
597 * different multiplier for usec instead of nsec). But this has a
598 * problem with rounding: we can't exactly add TICK_NSEC - 1 to the
599 * usec value, since it's not necessarily integral.
601 * We could instead round in the intermediate scaled representation
602 * (i.e. in units of 1/2^(large scale) jiffies) but that's also
603 * perilous: the scaling introduces a small positive error, which
604 * combined with a division-rounding-upward (i.e. adding 2^(scale) - 1
605 * units to the intermediate before shifting) leads to accidental
606 * overflow and overestimates.
608 * At the cost of one additional multiplication by a constant, just
609 * use the timespec implementation.
612 timeval_to_jiffies(const struct timeval *value)
614 return __timespec_to_jiffies(value->tv_sec,
615 value->tv_usec * NSEC_PER_USEC);
617 EXPORT_SYMBOL(timeval_to_jiffies);
619 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
622 * Convert jiffies to nanoseconds and separate with
627 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
629 value->tv_usec = rem / NSEC_PER_USEC;
631 EXPORT_SYMBOL(jiffies_to_timeval);
634 * Convert jiffies/jiffies_64 to clock_t and back.
636 clock_t jiffies_to_clock_t(unsigned long x)
638 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
640 return x * (USER_HZ / HZ);
642 return x / (HZ / USER_HZ);
645 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
648 EXPORT_SYMBOL(jiffies_to_clock_t);
650 unsigned long clock_t_to_jiffies(unsigned long x)
652 #if (HZ % USER_HZ)==0
653 if (x >= ~0UL / (HZ / USER_HZ))
655 return x * (HZ / USER_HZ);
657 /* Don't worry about loss of precision here .. */
658 if (x >= ~0UL / HZ * USER_HZ)
661 /* .. but do try to contain it here */
662 return div_u64((u64)x * HZ, USER_HZ);
665 EXPORT_SYMBOL(clock_t_to_jiffies);
667 u64 jiffies_64_to_clock_t(u64 x)
669 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
671 x = div_u64(x * USER_HZ, HZ);
673 x = div_u64(x, HZ / USER_HZ);
679 * There are better ways that don't overflow early,
680 * but even this doesn't overflow in hundreds of years
683 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
687 EXPORT_SYMBOL(jiffies_64_to_clock_t);
689 u64 nsec_to_clock_t(u64 x)
691 #if (NSEC_PER_SEC % USER_HZ) == 0
692 return div_u64(x, NSEC_PER_SEC / USER_HZ);
693 #elif (USER_HZ % 512) == 0
694 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
697 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
698 * overflow after 64.99 years.
699 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
701 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
705 u64 jiffies64_to_nsecs(u64 j)
707 #if !(NSEC_PER_SEC % HZ)
708 return (NSEC_PER_SEC / HZ) * j;
710 return div_u64(j * HZ_TO_NSEC_NUM, HZ_TO_NSEC_DEN);
713 EXPORT_SYMBOL(jiffies64_to_nsecs);
716 * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
720 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
721 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
722 * for scheduler, not for use in device drivers to calculate timeout value.
725 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
726 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
728 u64 nsecs_to_jiffies64(u64 n)
730 #if (NSEC_PER_SEC % HZ) == 0
731 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
732 return div_u64(n, NSEC_PER_SEC / HZ);
733 #elif (HZ % 512) == 0
734 /* overflow after 292 years if HZ = 1024 */
735 return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
738 * Generic case - optimized for cases where HZ is a multiple of 3.
739 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
741 return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
744 EXPORT_SYMBOL(nsecs_to_jiffies64);
747 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
751 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
752 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
753 * for scheduler, not for use in device drivers to calculate timeout value.
756 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
757 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
759 unsigned long nsecs_to_jiffies(u64 n)
761 return (unsigned long)nsecs_to_jiffies64(n);
763 EXPORT_SYMBOL_GPL(nsecs_to_jiffies);
766 * Add two timespec values and do a safety check for overflow.
767 * It's assumed that both values are valid (>= 0)
769 struct timespec timespec_add_safe(const struct timespec lhs,
770 const struct timespec rhs)
774 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
775 lhs.tv_nsec + rhs.tv_nsec);
777 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
778 res.tv_sec = TIME_T_MAX;
784 * Add two timespec64 values and do a safety check for overflow.
785 * It's assumed that both values are valid (>= 0).
786 * And, each timespec64 is in normalized form.
788 struct timespec64 timespec64_add_safe(const struct timespec64 lhs,
789 const struct timespec64 rhs)
791 struct timespec64 res;
793 set_normalized_timespec64(&res, (timeu64_t) lhs.tv_sec + rhs.tv_sec,
794 lhs.tv_nsec + rhs.tv_nsec);
796 if (unlikely(res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)) {
797 res.tv_sec = TIME64_MAX;