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 <asm/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_settimeofday(const struct timespec
*tv
, const struct timezone
*tz
)
165 static int firsttime
= 1;
168 if (tv
&& !timespec_valid(tv
))
171 error
= security_settime(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_settimeofday(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. gran must be smaller than a second.
295 * Always rounds down.
297 * This function should be only used for timestamps returned by
298 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
299 * it doesn't handle the better resolution of the latter.
301 struct timespec
timespec_trunc(struct timespec t
, unsigned gran
)
304 * Division is pretty slow so avoid it for common cases.
305 * Currently current_kernel_time() never returns better than
306 * jiffies resolution. Exploit that.
308 if (gran
<= jiffies_to_usecs(1) * 1000) {
310 } else if (gran
== 1000000000) {
313 t
.tv_nsec
-= t
.tv_nsec
% gran
;
317 EXPORT_SYMBOL(timespec_trunc
);
320 * mktime64 - Converts date to seconds.
321 * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
322 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
323 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
325 * [For the Julian calendar (which was used in Russia before 1917,
326 * Britain & colonies before 1752, anywhere else before 1582,
327 * and is still in use by some communities) leave out the
328 * -year/100+year/400 terms, and add 10.]
330 * This algorithm was first published by Gauss (I think).
332 time64_t
mktime64(const unsigned int year0
, const unsigned int mon0
,
333 const unsigned int day
, const unsigned int hour
,
334 const unsigned int min
, const unsigned int sec
)
336 unsigned int mon
= mon0
, year
= year0
;
338 /* 1..12 -> 11,12,1..10 */
339 if (0 >= (int) (mon
-= 2)) {
340 mon
+= 12; /* Puts Feb last since it has leap day */
345 (year
/4 - year
/100 + year
/400 + 367*mon
/12 + day
) +
347 )*24 + hour
/* now have hours */
348 )*60 + min
/* now have minutes */
349 )*60 + sec
; /* finally seconds */
351 EXPORT_SYMBOL(mktime64
);
354 * set_normalized_timespec - set timespec sec and nsec parts and normalize
356 * @ts: pointer to timespec variable to be set
357 * @sec: seconds to set
358 * @nsec: nanoseconds to set
360 * Set seconds and nanoseconds field of a timespec variable and
361 * normalize to the timespec storage format
363 * Note: The tv_nsec part is always in the range of
364 * 0 <= tv_nsec < NSEC_PER_SEC
365 * For negative values only the tv_sec field is negative !
367 void set_normalized_timespec(struct timespec
*ts
, time_t sec
, s64 nsec
)
369 while (nsec
>= NSEC_PER_SEC
) {
371 * The following asm() prevents the compiler from
372 * optimising this loop into a modulo operation. See
373 * also __iter_div_u64_rem() in include/linux/time.h
375 asm("" : "+rm"(nsec
));
376 nsec
-= NSEC_PER_SEC
;
380 asm("" : "+rm"(nsec
));
381 nsec
+= NSEC_PER_SEC
;
387 EXPORT_SYMBOL(set_normalized_timespec
);
390 * ns_to_timespec - Convert nanoseconds to timespec
391 * @nsec: the nanoseconds value to be converted
393 * Returns the timespec representation of the nsec parameter.
395 struct timespec
ns_to_timespec(const s64 nsec
)
401 return (struct timespec
) {0, 0};
403 ts
.tv_sec
= div_s64_rem(nsec
, NSEC_PER_SEC
, &rem
);
404 if (unlikely(rem
< 0)) {
412 EXPORT_SYMBOL(ns_to_timespec
);
415 * ns_to_timeval - Convert nanoseconds to timeval
416 * @nsec: the nanoseconds value to be converted
418 * Returns the timeval representation of the nsec parameter.
420 struct timeval
ns_to_timeval(const s64 nsec
)
422 struct timespec ts
= ns_to_timespec(nsec
);
425 tv
.tv_sec
= ts
.tv_sec
;
426 tv
.tv_usec
= (suseconds_t
) ts
.tv_nsec
/ 1000;
430 EXPORT_SYMBOL(ns_to_timeval
);
432 #if BITS_PER_LONG == 32
434 * set_normalized_timespec - set timespec sec and nsec parts and normalize
436 * @ts: pointer to timespec variable to be set
437 * @sec: seconds to set
438 * @nsec: nanoseconds to set
440 * Set seconds and nanoseconds field of a timespec variable and
441 * normalize to the timespec storage format
443 * Note: The tv_nsec part is always in the range of
444 * 0 <= tv_nsec < NSEC_PER_SEC
445 * For negative values only the tv_sec field is negative !
447 void set_normalized_timespec64(struct timespec64
*ts
, time64_t sec
, s64 nsec
)
449 while (nsec
>= NSEC_PER_SEC
) {
451 * The following asm() prevents the compiler from
452 * optimising this loop into a modulo operation. See
453 * also __iter_div_u64_rem() in include/linux/time.h
455 asm("" : "+rm"(nsec
));
456 nsec
-= NSEC_PER_SEC
;
460 asm("" : "+rm"(nsec
));
461 nsec
+= NSEC_PER_SEC
;
467 EXPORT_SYMBOL(set_normalized_timespec64
);
470 * ns_to_timespec64 - Convert nanoseconds to timespec64
471 * @nsec: the nanoseconds value to be converted
473 * Returns the timespec64 representation of the nsec parameter.
475 struct timespec64
ns_to_timespec64(const s64 nsec
)
477 struct timespec64 ts
;
481 return (struct timespec64
) {0, 0};
483 ts
.tv_sec
= div_s64_rem(nsec
, NSEC_PER_SEC
, &rem
);
484 if (unlikely(rem
< 0)) {
492 EXPORT_SYMBOL(ns_to_timespec64
);
495 * msecs_to_jiffies: - convert milliseconds to jiffies
496 * @m: time in milliseconds
498 * conversion is done as follows:
500 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
502 * - 'too large' values [that would result in larger than
503 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
505 * - all other values are converted to jiffies by either multiplying
506 * the input value by a factor or dividing it with a factor and
507 * handling any 32-bit overflows.
508 * for the details see __msecs_to_jiffies()
510 * msecs_to_jiffies() checks for the passed in value being a constant
511 * via __builtin_constant_p() allowing gcc to eliminate most of the
512 * code, __msecs_to_jiffies() is called if the value passed does not
513 * allow constant folding and the actual conversion must be done at
515 * the _msecs_to_jiffies helpers are the HZ dependent conversion
516 * routines found in include/linux/jiffies.h
518 unsigned long __msecs_to_jiffies(const unsigned int m
)
521 * Negative value, means infinite timeout:
524 return MAX_JIFFY_OFFSET
;
525 return _msecs_to_jiffies(m
);
527 EXPORT_SYMBOL(__msecs_to_jiffies
);
529 unsigned long __usecs_to_jiffies(const unsigned int u
)
531 if (u
> jiffies_to_usecs(MAX_JIFFY_OFFSET
))
532 return MAX_JIFFY_OFFSET
;
533 return _usecs_to_jiffies(u
);
535 EXPORT_SYMBOL(__usecs_to_jiffies
);
538 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
539 * that a remainder subtract here would not do the right thing as the
540 * resolution values don't fall on second boundries. I.e. the line:
541 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
542 * Note that due to the small error in the multiplier here, this
543 * rounding is incorrect for sufficiently large values of tv_nsec, but
544 * well formed timespecs should have tv_nsec < NSEC_PER_SEC, so we're
547 * Rather, we just shift the bits off the right.
549 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
550 * value to a scaled second value.
553 __timespec_to_jiffies(unsigned long sec
, long nsec
)
555 nsec
= nsec
+ TICK_NSEC
- 1;
557 if (sec
>= MAX_SEC_IN_JIFFIES
){
558 sec
= MAX_SEC_IN_JIFFIES
;
561 return (((u64
)sec
* SEC_CONVERSION
) +
562 (((u64
)nsec
* NSEC_CONVERSION
) >>
563 (NSEC_JIFFIE_SC
- SEC_JIFFIE_SC
))) >> SEC_JIFFIE_SC
;
568 timespec_to_jiffies(const struct timespec
*value
)
570 return __timespec_to_jiffies(value
->tv_sec
, value
->tv_nsec
);
573 EXPORT_SYMBOL(timespec_to_jiffies
);
576 jiffies_to_timespec(const unsigned long jiffies
, struct timespec
*value
)
579 * Convert jiffies to nanoseconds and separate with
583 value
->tv_sec
= div_u64_rem((u64
)jiffies
* TICK_NSEC
,
585 value
->tv_nsec
= rem
;
587 EXPORT_SYMBOL(jiffies_to_timespec
);
590 * We could use a similar algorithm to timespec_to_jiffies (with a
591 * different multiplier for usec instead of nsec). But this has a
592 * problem with rounding: we can't exactly add TICK_NSEC - 1 to the
593 * usec value, since it's not necessarily integral.
595 * We could instead round in the intermediate scaled representation
596 * (i.e. in units of 1/2^(large scale) jiffies) but that's also
597 * perilous: the scaling introduces a small positive error, which
598 * combined with a division-rounding-upward (i.e. adding 2^(scale) - 1
599 * units to the intermediate before shifting) leads to accidental
600 * overflow and overestimates.
602 * At the cost of one additional multiplication by a constant, just
603 * use the timespec implementation.
606 timeval_to_jiffies(const struct timeval
*value
)
608 return __timespec_to_jiffies(value
->tv_sec
,
609 value
->tv_usec
* NSEC_PER_USEC
);
611 EXPORT_SYMBOL(timeval_to_jiffies
);
613 void jiffies_to_timeval(const unsigned long jiffies
, struct timeval
*value
)
616 * Convert jiffies to nanoseconds and separate with
621 value
->tv_sec
= div_u64_rem((u64
)jiffies
* TICK_NSEC
,
623 value
->tv_usec
= rem
/ NSEC_PER_USEC
;
625 EXPORT_SYMBOL(jiffies_to_timeval
);
628 * Convert jiffies/jiffies_64 to clock_t and back.
630 clock_t jiffies_to_clock_t(unsigned long x
)
632 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
634 return x
* (USER_HZ
/ HZ
);
636 return x
/ (HZ
/ USER_HZ
);
639 return div_u64((u64
)x
* TICK_NSEC
, NSEC_PER_SEC
/ USER_HZ
);
642 EXPORT_SYMBOL(jiffies_to_clock_t
);
644 unsigned long clock_t_to_jiffies(unsigned long x
)
646 #if (HZ % USER_HZ)==0
647 if (x
>= ~0UL / (HZ
/ USER_HZ
))
649 return x
* (HZ
/ USER_HZ
);
651 /* Don't worry about loss of precision here .. */
652 if (x
>= ~0UL / HZ
* USER_HZ
)
655 /* .. but do try to contain it here */
656 return div_u64((u64
)x
* HZ
, USER_HZ
);
659 EXPORT_SYMBOL(clock_t_to_jiffies
);
661 u64
jiffies_64_to_clock_t(u64 x
)
663 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
665 x
= div_u64(x
* USER_HZ
, HZ
);
667 x
= div_u64(x
, HZ
/ USER_HZ
);
673 * There are better ways that don't overflow early,
674 * but even this doesn't overflow in hundreds of years
677 x
= div_u64(x
* TICK_NSEC
, (NSEC_PER_SEC
/ USER_HZ
));
681 EXPORT_SYMBOL(jiffies_64_to_clock_t
);
683 u64
nsec_to_clock_t(u64 x
)
685 #if (NSEC_PER_SEC % USER_HZ) == 0
686 return div_u64(x
, NSEC_PER_SEC
/ USER_HZ
);
687 #elif (USER_HZ % 512) == 0
688 return div_u64(x
* USER_HZ
/ 512, NSEC_PER_SEC
/ 512);
691 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
692 * overflow after 64.99 years.
693 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
695 return div_u64(x
* 9, (9ull * NSEC_PER_SEC
+ (USER_HZ
/ 2)) / USER_HZ
);
700 * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
704 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
705 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
706 * for scheduler, not for use in device drivers to calculate timeout value.
709 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
710 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
712 u64
nsecs_to_jiffies64(u64 n
)
714 #if (NSEC_PER_SEC % HZ) == 0
715 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
716 return div_u64(n
, NSEC_PER_SEC
/ HZ
);
717 #elif (HZ % 512) == 0
718 /* overflow after 292 years if HZ = 1024 */
719 return div_u64(n
* HZ
/ 512, NSEC_PER_SEC
/ 512);
722 * Generic case - optimized for cases where HZ is a multiple of 3.
723 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
725 return div_u64(n
* 9, (9ull * NSEC_PER_SEC
+ HZ
/ 2) / HZ
);
728 EXPORT_SYMBOL(nsecs_to_jiffies64
);
731 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
735 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
736 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
737 * for scheduler, not for use in device drivers to calculate timeout value.
740 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
741 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
743 unsigned long nsecs_to_jiffies(u64 n
)
745 return (unsigned long)nsecs_to_jiffies64(n
);
747 EXPORT_SYMBOL_GPL(nsecs_to_jiffies
);
750 * Add two timespec values and do a safety check for overflow.
751 * It's assumed that both values are valid (>= 0)
753 struct timespec
timespec_add_safe(const struct timespec lhs
,
754 const struct timespec rhs
)
758 set_normalized_timespec(&res
, lhs
.tv_sec
+ rhs
.tv_sec
,
759 lhs
.tv_nsec
+ rhs
.tv_nsec
);
761 if (res
.tv_sec
< lhs
.tv_sec
|| res
.tv_sec
< rhs
.tv_sec
)
762 res
.tv_sec
= TIME_T_MAX
;