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/kernel.h>
32 #include <linux/timex.h>
33 #include <linux/capability.h>
34 #include <linux/timekeeper_internal.h>
35 #include <linux/errno.h>
36 #include <linux/syscalls.h>
37 #include <linux/security.h>
39 #include <linux/math64.h>
40 #include <linux/ptrace.h>
42 #include <asm/uaccess.h>
43 #include <asm/unistd.h>
45 #include <generated/timeconst.h>
46 #include "timekeeping.h"
49 * The timezone where the local system is located. Used as a default by some
50 * programs who obtain this value by using gettimeofday.
52 struct timezone sys_tz;
54 EXPORT_SYMBOL(sys_tz);
56 #ifdef __ARCH_WANT_SYS_TIME
59 * sys_time() can be implemented in user-level using
60 * sys_gettimeofday(). Is this for backwards compatibility? If so,
61 * why not move it into the appropriate arch directory (for those
62 * architectures that need it).
64 SYSCALL_DEFINE1(time, time_t __user *, tloc)
66 time_t i = get_seconds();
72 force_successful_syscall_return();
77 * sys_stime() can be implemented in user-level using
78 * sys_settimeofday(). Is this for backwards compatibility? If so,
79 * why not move it into the appropriate arch directory (for those
80 * architectures that need it).
83 SYSCALL_DEFINE1(stime, time_t __user *, tptr)
88 if (get_user(tv.tv_sec, tptr))
93 err = security_settime(&tv, NULL);
101 #endif /* __ARCH_WANT_SYS_TIME */
103 SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv,
104 struct timezone __user *, tz)
106 if (likely(tv != NULL)) {
108 do_gettimeofday(&ktv);
109 if (copy_to_user(tv, &ktv, sizeof(ktv)))
112 if (unlikely(tz != NULL)) {
113 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
120 * Indicates if there is an offset between the system clock and the hardware
121 * clock/persistent clock/rtc.
123 int persistent_clock_is_local;
126 * Adjust the time obtained from the CMOS to be UTC time instead of
129 * This is ugly, but preferable to the alternatives. Otherwise we
130 * would either need to write a program to do it in /etc/rc (and risk
131 * confusion if the program gets run more than once; it would also be
132 * hard to make the program warp the clock precisely n hours) or
133 * compile in the timezone information into the kernel. Bad, bad....
137 * The best thing to do is to keep the CMOS clock in universal time (UTC)
138 * as real UNIX machines always do it. This avoids all headaches about
139 * daylight saving times and warping kernel clocks.
141 static inline void warp_clock(void)
143 if (sys_tz.tz_minuteswest != 0) {
144 struct timespec adjust;
146 persistent_clock_is_local = 1;
147 adjust.tv_sec = sys_tz.tz_minuteswest * 60;
149 timekeeping_inject_offset(&adjust);
154 * In case for some reason the CMOS clock has not already been running
155 * in UTC, but in some local time: The first time we set the timezone,
156 * we will warp the clock so that it is ticking UTC time instead of
157 * local time. Presumably, if someone is setting the timezone then we
158 * are running in an environment where the programs understand about
159 * timezones. This should be done at boot time in the /etc/rc script,
160 * as soon as possible, so that the clock can be set right. Otherwise,
161 * various programs will get confused when the clock gets warped.
164 int do_sys_settimeofday(const struct timespec *tv, const struct timezone *tz)
166 static int firsttime = 1;
169 if (tv && !timespec_valid(tv))
172 error = security_settime(tv, tz);
177 /* Verify we're witin the +-15 hrs range */
178 if (tz->tz_minuteswest > 15*60 || tz->tz_minuteswest < -15*60)
182 update_vsyscall_tz();
190 return do_settimeofday(tv);
194 SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv,
195 struct timezone __user *, tz)
197 struct timeval user_tv;
198 struct timespec new_ts;
199 struct timezone new_tz;
202 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
205 if (!timeval_valid(&user_tv))
208 new_ts.tv_sec = user_tv.tv_sec;
209 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
212 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
216 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
219 SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p)
221 struct timex txc; /* Local copy of parameter */
224 /* Copy the user data space into the kernel copy
225 * structure. But bear in mind that the structures
228 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
230 ret = do_adjtimex(&txc);
231 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
235 * current_fs_time - Return FS time
238 * Return the current time truncated to the time granularity supported by
241 struct timespec current_fs_time(struct super_block *sb)
243 struct timespec now = current_kernel_time();
244 return timespec_trunc(now, sb->s_time_gran);
246 EXPORT_SYMBOL(current_fs_time);
249 * Convert jiffies to milliseconds and back.
251 * Avoid unnecessary multiplications/divisions in the
252 * two most common HZ cases:
254 unsigned int jiffies_to_msecs(const unsigned long j)
256 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
257 return (MSEC_PER_SEC / HZ) * j;
258 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
259 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
261 # if BITS_PER_LONG == 32
262 return (HZ_TO_MSEC_MUL32 * j + (1ULL << HZ_TO_MSEC_SHR32) - 1) >>
265 return DIV_ROUND_UP(j * HZ_TO_MSEC_NUM, HZ_TO_MSEC_DEN);
269 EXPORT_SYMBOL(jiffies_to_msecs);
271 unsigned int jiffies_to_usecs(const unsigned long j)
274 * Hz usually doesn't go much further MSEC_PER_SEC.
275 * jiffies_to_usecs() and usecs_to_jiffies() depend on that.
277 BUILD_BUG_ON(HZ > USEC_PER_SEC);
279 #if !(USEC_PER_SEC % HZ)
280 return (USEC_PER_SEC / HZ) * j;
282 # if BITS_PER_LONG == 32
283 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
285 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
289 EXPORT_SYMBOL(jiffies_to_usecs);
292 * timespec_trunc - Truncate timespec to a granularity
294 * @gran: Granularity in ns.
296 * Truncate a timespec to a granularity. Always rounds down. gran must
297 * not be 0 nor greater than a second (NSEC_PER_SEC, or 10^9 ns).
299 struct timespec timespec_trunc(struct timespec t, unsigned gran)
301 /* Avoid division in the common cases 1 ns and 1 s. */
304 } else if (gran == NSEC_PER_SEC) {
306 } else if (gran > 1 && gran < NSEC_PER_SEC) {
307 t.tv_nsec -= t.tv_nsec % gran;
309 WARN(1, "illegal file time granularity: %u", gran);
313 EXPORT_SYMBOL(timespec_trunc);
316 * mktime64 - Converts date to seconds.
317 * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
318 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
319 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
321 * [For the Julian calendar (which was used in Russia before 1917,
322 * Britain & colonies before 1752, anywhere else before 1582,
323 * and is still in use by some communities) leave out the
324 * -year/100+year/400 terms, and add 10.]
326 * This algorithm was first published by Gauss (I think).
328 time64_t mktime64(const unsigned int year0, const unsigned int mon0,
329 const unsigned int day, const unsigned int hour,
330 const unsigned int min, const unsigned int sec)
332 unsigned int mon = mon0, year = year0;
334 /* 1..12 -> 11,12,1..10 */
335 if (0 >= (int) (mon -= 2)) {
336 mon += 12; /* Puts Feb last since it has leap day */
341 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
343 )*24 + hour /* now have hours */
344 )*60 + min /* now have minutes */
345 )*60 + sec; /* finally seconds */
347 EXPORT_SYMBOL(mktime64);
350 * set_normalized_timespec - set timespec sec and nsec parts and normalize
352 * @ts: pointer to timespec variable to be set
353 * @sec: seconds to set
354 * @nsec: nanoseconds to set
356 * Set seconds and nanoseconds field of a timespec variable and
357 * normalize to the timespec storage format
359 * Note: The tv_nsec part is always in the range of
360 * 0 <= tv_nsec < NSEC_PER_SEC
361 * For negative values only the tv_sec field is negative !
363 void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
365 while (nsec >= NSEC_PER_SEC) {
367 * The following asm() prevents the compiler from
368 * optimising this loop into a modulo operation. See
369 * also __iter_div_u64_rem() in include/linux/time.h
371 asm("" : "+rm"(nsec));
372 nsec -= NSEC_PER_SEC;
376 asm("" : "+rm"(nsec));
377 nsec += NSEC_PER_SEC;
383 EXPORT_SYMBOL(set_normalized_timespec);
386 * ns_to_timespec - Convert nanoseconds to timespec
387 * @nsec: the nanoseconds value to be converted
389 * Returns the timespec representation of the nsec parameter.
391 struct timespec ns_to_timespec(const s64 nsec)
397 return (struct timespec) {0, 0};
399 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
400 if (unlikely(rem < 0)) {
408 EXPORT_SYMBOL(ns_to_timespec);
411 * ns_to_timeval - Convert nanoseconds to timeval
412 * @nsec: the nanoseconds value to be converted
414 * Returns the timeval representation of the nsec parameter.
416 struct timeval ns_to_timeval(const s64 nsec)
418 struct timespec ts = ns_to_timespec(nsec);
421 tv.tv_sec = ts.tv_sec;
422 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
426 EXPORT_SYMBOL(ns_to_timeval);
428 #if BITS_PER_LONG == 32
430 * set_normalized_timespec - set timespec sec and nsec parts and normalize
432 * @ts: pointer to timespec variable to be set
433 * @sec: seconds to set
434 * @nsec: nanoseconds to set
436 * Set seconds and nanoseconds field of a timespec variable and
437 * normalize to the timespec storage format
439 * Note: The tv_nsec part is always in the range of
440 * 0 <= tv_nsec < NSEC_PER_SEC
441 * For negative values only the tv_sec field is negative !
443 void set_normalized_timespec64(struct timespec64 *ts, time64_t sec, s64 nsec)
445 while (nsec >= NSEC_PER_SEC) {
447 * The following asm() prevents the compiler from
448 * optimising this loop into a modulo operation. See
449 * also __iter_div_u64_rem() in include/linux/time.h
451 asm("" : "+rm"(nsec));
452 nsec -= NSEC_PER_SEC;
456 asm("" : "+rm"(nsec));
457 nsec += NSEC_PER_SEC;
463 EXPORT_SYMBOL(set_normalized_timespec64);
466 * ns_to_timespec64 - Convert nanoseconds to timespec64
467 * @nsec: the nanoseconds value to be converted
469 * Returns the timespec64 representation of the nsec parameter.
471 struct timespec64 ns_to_timespec64(const s64 nsec)
473 struct timespec64 ts;
477 return (struct timespec64) {0, 0};
479 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
480 if (unlikely(rem < 0)) {
488 EXPORT_SYMBOL(ns_to_timespec64);
491 * msecs_to_jiffies: - convert milliseconds to jiffies
492 * @m: time in milliseconds
494 * conversion is done as follows:
496 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
498 * - 'too large' values [that would result in larger than
499 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
501 * - all other values are converted to jiffies by either multiplying
502 * the input value by a factor or dividing it with a factor and
503 * handling any 32-bit overflows.
504 * for the details see __msecs_to_jiffies()
506 * msecs_to_jiffies() checks for the passed in value being a constant
507 * via __builtin_constant_p() allowing gcc to eliminate most of the
508 * code, __msecs_to_jiffies() is called if the value passed does not
509 * allow constant folding and the actual conversion must be done at
511 * the _msecs_to_jiffies helpers are the HZ dependent conversion
512 * routines found in include/linux/jiffies.h
514 unsigned long __msecs_to_jiffies(const unsigned int m)
517 * Negative value, means infinite timeout:
520 return MAX_JIFFY_OFFSET;
521 return _msecs_to_jiffies(m);
523 EXPORT_SYMBOL(__msecs_to_jiffies);
525 unsigned long __usecs_to_jiffies(const unsigned int u)
527 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
528 return MAX_JIFFY_OFFSET;
529 return _usecs_to_jiffies(u);
531 EXPORT_SYMBOL(__usecs_to_jiffies);
534 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
535 * that a remainder subtract here would not do the right thing as the
536 * resolution values don't fall on second boundries. I.e. the line:
537 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
538 * Note that due to the small error in the multiplier here, this
539 * rounding is incorrect for sufficiently large values of tv_nsec, but
540 * well formed timespecs should have tv_nsec < NSEC_PER_SEC, so we're
543 * Rather, we just shift the bits off the right.
545 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
546 * value to a scaled second value.
549 __timespec64_to_jiffies(u64 sec, long nsec)
551 nsec = nsec + TICK_NSEC - 1;
553 if (sec >= MAX_SEC_IN_JIFFIES){
554 sec = MAX_SEC_IN_JIFFIES;
557 return ((sec * SEC_CONVERSION) +
558 (((u64)nsec * NSEC_CONVERSION) >>
559 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
564 __timespec_to_jiffies(unsigned long sec, long nsec)
566 return __timespec64_to_jiffies((u64)sec, nsec);
570 timespec64_to_jiffies(const struct timespec64 *value)
572 return __timespec64_to_jiffies(value->tv_sec, value->tv_nsec);
574 EXPORT_SYMBOL(timespec64_to_jiffies);
577 jiffies_to_timespec64(const unsigned long jiffies, struct timespec64 *value)
580 * Convert jiffies to nanoseconds and separate with
584 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
586 value->tv_nsec = rem;
588 EXPORT_SYMBOL(jiffies_to_timespec64);
591 * We could use a similar algorithm to timespec_to_jiffies (with a
592 * different multiplier for usec instead of nsec). But this has a
593 * problem with rounding: we can't exactly add TICK_NSEC - 1 to the
594 * usec value, since it's not necessarily integral.
596 * We could instead round in the intermediate scaled representation
597 * (i.e. in units of 1/2^(large scale) jiffies) but that's also
598 * perilous: the scaling introduces a small positive error, which
599 * combined with a division-rounding-upward (i.e. adding 2^(scale) - 1
600 * units to the intermediate before shifting) leads to accidental
601 * overflow and overestimates.
603 * At the cost of one additional multiplication by a constant, just
604 * use the timespec implementation.
607 timeval_to_jiffies(const struct timeval *value)
609 return __timespec_to_jiffies(value->tv_sec,
610 value->tv_usec * NSEC_PER_USEC);
612 EXPORT_SYMBOL(timeval_to_jiffies);
614 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
617 * Convert jiffies to nanoseconds and separate with
622 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
624 value->tv_usec = rem / NSEC_PER_USEC;
626 EXPORT_SYMBOL(jiffies_to_timeval);
629 * Convert jiffies/jiffies_64 to clock_t and back.
631 clock_t jiffies_to_clock_t(unsigned long x)
633 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
635 return x * (USER_HZ / HZ);
637 return x / (HZ / USER_HZ);
640 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
643 EXPORT_SYMBOL(jiffies_to_clock_t);
645 unsigned long clock_t_to_jiffies(unsigned long x)
647 #if (HZ % USER_HZ)==0
648 if (x >= ~0UL / (HZ / USER_HZ))
650 return x * (HZ / USER_HZ);
652 /* Don't worry about loss of precision here .. */
653 if (x >= ~0UL / HZ * USER_HZ)
656 /* .. but do try to contain it here */
657 return div_u64((u64)x * HZ, USER_HZ);
660 EXPORT_SYMBOL(clock_t_to_jiffies);
662 u64 jiffies_64_to_clock_t(u64 x)
664 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
666 x = div_u64(x * USER_HZ, HZ);
668 x = div_u64(x, HZ / USER_HZ);
674 * There are better ways that don't overflow early,
675 * but even this doesn't overflow in hundreds of years
678 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
682 EXPORT_SYMBOL(jiffies_64_to_clock_t);
684 u64 nsec_to_clock_t(u64 x)
686 #if (NSEC_PER_SEC % USER_HZ) == 0
687 return div_u64(x, NSEC_PER_SEC / USER_HZ);
688 #elif (USER_HZ % 512) == 0
689 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
692 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
693 * overflow after 64.99 years.
694 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
696 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
701 * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
705 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
706 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
707 * for scheduler, not for use in device drivers to calculate timeout value.
710 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
711 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
713 u64 nsecs_to_jiffies64(u64 n)
715 #if (NSEC_PER_SEC % HZ) == 0
716 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
717 return div_u64(n, NSEC_PER_SEC / HZ);
718 #elif (HZ % 512) == 0
719 /* overflow after 292 years if HZ = 1024 */
720 return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
723 * Generic case - optimized for cases where HZ is a multiple of 3.
724 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
726 return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
729 EXPORT_SYMBOL(nsecs_to_jiffies64);
732 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
736 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
737 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
738 * for scheduler, not for use in device drivers to calculate timeout value.
741 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
742 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
744 unsigned long nsecs_to_jiffies(u64 n)
746 return (unsigned long)nsecs_to_jiffies64(n);
748 EXPORT_SYMBOL_GPL(nsecs_to_jiffies);
751 * Add two timespec values and do a safety check for overflow.
752 * It's assumed that both values are valid (>= 0)
754 struct timespec timespec_add_safe(const struct timespec lhs,
755 const struct timespec rhs)
759 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
760 lhs.tv_nsec + rhs.tv_nsec);
762 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
763 res.tv_sec = TIME_T_MAX;