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 "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
);
177 update_vsyscall_tz();
185 return do_settimeofday(tv
);
189 SYSCALL_DEFINE2(settimeofday
, struct timeval __user
*, tv
,
190 struct timezone __user
*, tz
)
192 struct timeval user_tv
;
193 struct timespec new_ts
;
194 struct timezone new_tz
;
197 if (copy_from_user(&user_tv
, tv
, sizeof(*tv
)))
199 new_ts
.tv_sec
= user_tv
.tv_sec
;
200 new_ts
.tv_nsec
= user_tv
.tv_usec
* NSEC_PER_USEC
;
203 if (copy_from_user(&new_tz
, tz
, sizeof(*tz
)))
207 return do_sys_settimeofday(tv
? &new_ts
: NULL
, tz
? &new_tz
: NULL
);
210 SYSCALL_DEFINE1(adjtimex
, struct timex __user
*, txc_p
)
212 struct timex txc
; /* Local copy of parameter */
215 /* Copy the user data space into the kernel copy
216 * structure. But bear in mind that the structures
219 if(copy_from_user(&txc
, txc_p
, sizeof(struct timex
)))
221 ret
= do_adjtimex(&txc
);
222 return copy_to_user(txc_p
, &txc
, sizeof(struct timex
)) ? -EFAULT
: ret
;
226 * current_fs_time - Return FS time
229 * Return the current time truncated to the time granularity supported by
232 struct timespec
current_fs_time(struct super_block
*sb
)
234 struct timespec now
= current_kernel_time();
235 return timespec_trunc(now
, sb
->s_time_gran
);
237 EXPORT_SYMBOL(current_fs_time
);
240 * Convert jiffies to milliseconds and back.
242 * Avoid unnecessary multiplications/divisions in the
243 * two most common HZ cases:
245 unsigned int jiffies_to_msecs(const unsigned long j
)
247 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
248 return (MSEC_PER_SEC
/ HZ
) * j
;
249 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
250 return (j
+ (HZ
/ MSEC_PER_SEC
) - 1)/(HZ
/ MSEC_PER_SEC
);
252 # if BITS_PER_LONG == 32
253 return (HZ_TO_MSEC_MUL32
* j
) >> HZ_TO_MSEC_SHR32
;
255 return (j
* HZ_TO_MSEC_NUM
) / HZ_TO_MSEC_DEN
;
259 EXPORT_SYMBOL(jiffies_to_msecs
);
261 unsigned int jiffies_to_usecs(const unsigned long j
)
263 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
264 return (USEC_PER_SEC
/ HZ
) * j
;
265 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
266 return (j
+ (HZ
/ USEC_PER_SEC
) - 1)/(HZ
/ USEC_PER_SEC
);
268 # if BITS_PER_LONG == 32
269 return (HZ_TO_USEC_MUL32
* j
) >> HZ_TO_USEC_SHR32
;
271 return (j
* HZ_TO_USEC_NUM
) / HZ_TO_USEC_DEN
;
275 EXPORT_SYMBOL(jiffies_to_usecs
);
278 * timespec_trunc - Truncate timespec to a granularity
280 * @gran: Granularity in ns.
282 * Truncate a timespec to a granularity. gran must be smaller than a second.
283 * Always rounds down.
285 * This function should be only used for timestamps returned by
286 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
287 * it doesn't handle the better resolution of the latter.
289 struct timespec
timespec_trunc(struct timespec t
, unsigned gran
)
292 * Division is pretty slow so avoid it for common cases.
293 * Currently current_kernel_time() never returns better than
294 * jiffies resolution. Exploit that.
296 if (gran
<= jiffies_to_usecs(1) * 1000) {
298 } else if (gran
== 1000000000) {
301 t
.tv_nsec
-= t
.tv_nsec
% gran
;
305 EXPORT_SYMBOL(timespec_trunc
);
308 * mktime64 - Converts date to seconds.
309 * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
310 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
311 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
313 * [For the Julian calendar (which was used in Russia before 1917,
314 * Britain & colonies before 1752, anywhere else before 1582,
315 * and is still in use by some communities) leave out the
316 * -year/100+year/400 terms, and add 10.]
318 * This algorithm was first published by Gauss (I think).
320 time64_t
mktime64(const unsigned int year0
, const unsigned int mon0
,
321 const unsigned int day
, const unsigned int hour
,
322 const unsigned int min
, const unsigned int sec
)
324 unsigned int mon
= mon0
, year
= year0
;
326 /* 1..12 -> 11,12,1..10 */
327 if (0 >= (int) (mon
-= 2)) {
328 mon
+= 12; /* Puts Feb last since it has leap day */
333 (year
/4 - year
/100 + year
/400 + 367*mon
/12 + day
) +
335 )*24 + hour
/* now have hours */
336 )*60 + min
/* now have minutes */
337 )*60 + sec
; /* finally seconds */
339 EXPORT_SYMBOL(mktime64
);
342 * set_normalized_timespec - set timespec sec and nsec parts and normalize
344 * @ts: pointer to timespec variable to be set
345 * @sec: seconds to set
346 * @nsec: nanoseconds to set
348 * Set seconds and nanoseconds field of a timespec variable and
349 * normalize to the timespec storage format
351 * Note: The tv_nsec part is always in the range of
352 * 0 <= tv_nsec < NSEC_PER_SEC
353 * For negative values only the tv_sec field is negative !
355 void set_normalized_timespec(struct timespec
*ts
, time_t sec
, s64 nsec
)
357 while (nsec
>= NSEC_PER_SEC
) {
359 * The following asm() prevents the compiler from
360 * optimising this loop into a modulo operation. See
361 * also __iter_div_u64_rem() in include/linux/time.h
363 asm("" : "+rm"(nsec
));
364 nsec
-= NSEC_PER_SEC
;
368 asm("" : "+rm"(nsec
));
369 nsec
+= NSEC_PER_SEC
;
375 EXPORT_SYMBOL(set_normalized_timespec
);
378 * ns_to_timespec - Convert nanoseconds to timespec
379 * @nsec: the nanoseconds value to be converted
381 * Returns the timespec representation of the nsec parameter.
383 struct timespec
ns_to_timespec(const s64 nsec
)
389 return (struct timespec
) {0, 0};
391 ts
.tv_sec
= div_s64_rem(nsec
, NSEC_PER_SEC
, &rem
);
392 if (unlikely(rem
< 0)) {
400 EXPORT_SYMBOL(ns_to_timespec
);
403 * ns_to_timeval - Convert nanoseconds to timeval
404 * @nsec: the nanoseconds value to be converted
406 * Returns the timeval representation of the nsec parameter.
408 struct timeval
ns_to_timeval(const s64 nsec
)
410 struct timespec ts
= ns_to_timespec(nsec
);
413 tv
.tv_sec
= ts
.tv_sec
;
414 tv
.tv_usec
= (suseconds_t
) ts
.tv_nsec
/ 1000;
418 EXPORT_SYMBOL(ns_to_timeval
);
420 #if BITS_PER_LONG == 32
422 * set_normalized_timespec - set timespec sec and nsec parts and normalize
424 * @ts: pointer to timespec variable to be set
425 * @sec: seconds to set
426 * @nsec: nanoseconds to set
428 * Set seconds and nanoseconds field of a timespec variable and
429 * normalize to the timespec storage format
431 * Note: The tv_nsec part is always in the range of
432 * 0 <= tv_nsec < NSEC_PER_SEC
433 * For negative values only the tv_sec field is negative !
435 void set_normalized_timespec64(struct timespec64
*ts
, time64_t sec
, s64 nsec
)
437 while (nsec
>= NSEC_PER_SEC
) {
439 * The following asm() prevents the compiler from
440 * optimising this loop into a modulo operation. See
441 * also __iter_div_u64_rem() in include/linux/time.h
443 asm("" : "+rm"(nsec
));
444 nsec
-= NSEC_PER_SEC
;
448 asm("" : "+rm"(nsec
));
449 nsec
+= NSEC_PER_SEC
;
455 EXPORT_SYMBOL(set_normalized_timespec64
);
458 * ns_to_timespec64 - Convert nanoseconds to timespec64
459 * @nsec: the nanoseconds value to be converted
461 * Returns the timespec64 representation of the nsec parameter.
463 struct timespec64
ns_to_timespec64(const s64 nsec
)
465 struct timespec64 ts
;
469 return (struct timespec64
) {0, 0};
471 ts
.tv_sec
= div_s64_rem(nsec
, NSEC_PER_SEC
, &rem
);
472 if (unlikely(rem
< 0)) {
480 EXPORT_SYMBOL(ns_to_timespec64
);
483 * When we convert to jiffies then we interpret incoming values
486 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
488 * - 'too large' values [that would result in larger than
489 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
491 * - all other values are converted to jiffies by either multiplying
492 * the input value by a factor or dividing it with a factor
494 * We must also be careful about 32-bit overflows.
496 unsigned long msecs_to_jiffies(const unsigned int m
)
499 * Negative value, means infinite timeout:
502 return MAX_JIFFY_OFFSET
;
504 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
506 * HZ is equal to or smaller than 1000, and 1000 is a nice
507 * round multiple of HZ, divide with the factor between them,
510 return (m
+ (MSEC_PER_SEC
/ HZ
) - 1) / (MSEC_PER_SEC
/ HZ
);
511 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
513 * HZ is larger than 1000, and HZ is a nice round multiple of
514 * 1000 - simply multiply with the factor between them.
516 * But first make sure the multiplication result cannot
519 if (m
> jiffies_to_msecs(MAX_JIFFY_OFFSET
))
520 return MAX_JIFFY_OFFSET
;
522 return m
* (HZ
/ MSEC_PER_SEC
);
525 * Generic case - multiply, round and divide. But first
526 * check that if we are doing a net multiplication, that
527 * we wouldn't overflow:
529 if (HZ
> MSEC_PER_SEC
&& m
> jiffies_to_msecs(MAX_JIFFY_OFFSET
))
530 return MAX_JIFFY_OFFSET
;
532 return (MSEC_TO_HZ_MUL32
* m
+ MSEC_TO_HZ_ADJ32
)
536 EXPORT_SYMBOL(msecs_to_jiffies
);
538 unsigned long usecs_to_jiffies(const unsigned int u
)
540 if (u
> jiffies_to_usecs(MAX_JIFFY_OFFSET
))
541 return MAX_JIFFY_OFFSET
;
542 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
543 return (u
+ (USEC_PER_SEC
/ HZ
) - 1) / (USEC_PER_SEC
/ HZ
);
544 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
545 return u
* (HZ
/ USEC_PER_SEC
);
547 return (USEC_TO_HZ_MUL32
* u
+ USEC_TO_HZ_ADJ32
)
551 EXPORT_SYMBOL(usecs_to_jiffies
);
554 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
555 * that a remainder subtract here would not do the right thing as the
556 * resolution values don't fall on second boundries. I.e. the line:
557 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
558 * Note that due to the small error in the multiplier here, this
559 * rounding is incorrect for sufficiently large values of tv_nsec, but
560 * well formed timespecs should have tv_nsec < NSEC_PER_SEC, so we're
563 * Rather, we just shift the bits off the right.
565 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
566 * value to a scaled second value.
569 __timespec_to_jiffies(unsigned long sec
, long nsec
)
571 nsec
= nsec
+ TICK_NSEC
- 1;
573 if (sec
>= MAX_SEC_IN_JIFFIES
){
574 sec
= MAX_SEC_IN_JIFFIES
;
577 return (((u64
)sec
* SEC_CONVERSION
) +
578 (((u64
)nsec
* NSEC_CONVERSION
) >>
579 (NSEC_JIFFIE_SC
- SEC_JIFFIE_SC
))) >> SEC_JIFFIE_SC
;
584 timespec_to_jiffies(const struct timespec
*value
)
586 return __timespec_to_jiffies(value
->tv_sec
, value
->tv_nsec
);
589 EXPORT_SYMBOL(timespec_to_jiffies
);
592 jiffies_to_timespec(const unsigned long jiffies
, struct timespec
*value
)
595 * Convert jiffies to nanoseconds and separate with
599 value
->tv_sec
= div_u64_rem((u64
)jiffies
* TICK_NSEC
,
601 value
->tv_nsec
= rem
;
603 EXPORT_SYMBOL(jiffies_to_timespec
);
606 * We could use a similar algorithm to timespec_to_jiffies (with a
607 * different multiplier for usec instead of nsec). But this has a
608 * problem with rounding: we can't exactly add TICK_NSEC - 1 to the
609 * usec value, since it's not necessarily integral.
611 * We could instead round in the intermediate scaled representation
612 * (i.e. in units of 1/2^(large scale) jiffies) but that's also
613 * perilous: the scaling introduces a small positive error, which
614 * combined with a division-rounding-upward (i.e. adding 2^(scale) - 1
615 * units to the intermediate before shifting) leads to accidental
616 * overflow and overestimates.
618 * At the cost of one additional multiplication by a constant, just
619 * use the timespec implementation.
622 timeval_to_jiffies(const struct timeval
*value
)
624 return __timespec_to_jiffies(value
->tv_sec
,
625 value
->tv_usec
* NSEC_PER_USEC
);
627 EXPORT_SYMBOL(timeval_to_jiffies
);
629 void jiffies_to_timeval(const unsigned long jiffies
, struct timeval
*value
)
632 * Convert jiffies to nanoseconds and separate with
637 value
->tv_sec
= div_u64_rem((u64
)jiffies
* TICK_NSEC
,
639 value
->tv_usec
= rem
/ NSEC_PER_USEC
;
641 EXPORT_SYMBOL(jiffies_to_timeval
);
644 * Convert jiffies/jiffies_64 to clock_t and back.
646 clock_t jiffies_to_clock_t(unsigned long x
)
648 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
650 return x
* (USER_HZ
/ HZ
);
652 return x
/ (HZ
/ USER_HZ
);
655 return div_u64((u64
)x
* TICK_NSEC
, NSEC_PER_SEC
/ USER_HZ
);
658 EXPORT_SYMBOL(jiffies_to_clock_t
);
660 unsigned long clock_t_to_jiffies(unsigned long x
)
662 #if (HZ % USER_HZ)==0
663 if (x
>= ~0UL / (HZ
/ USER_HZ
))
665 return x
* (HZ
/ USER_HZ
);
667 /* Don't worry about loss of precision here .. */
668 if (x
>= ~0UL / HZ
* USER_HZ
)
671 /* .. but do try to contain it here */
672 return div_u64((u64
)x
* HZ
, USER_HZ
);
675 EXPORT_SYMBOL(clock_t_to_jiffies
);
677 u64
jiffies_64_to_clock_t(u64 x
)
679 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
681 x
= div_u64(x
* USER_HZ
, HZ
);
683 x
= div_u64(x
, HZ
/ USER_HZ
);
689 * There are better ways that don't overflow early,
690 * but even this doesn't overflow in hundreds of years
693 x
= div_u64(x
* TICK_NSEC
, (NSEC_PER_SEC
/ USER_HZ
));
697 EXPORT_SYMBOL(jiffies_64_to_clock_t
);
699 u64
nsec_to_clock_t(u64 x
)
701 #if (NSEC_PER_SEC % USER_HZ) == 0
702 return div_u64(x
, NSEC_PER_SEC
/ USER_HZ
);
703 #elif (USER_HZ % 512) == 0
704 return div_u64(x
* USER_HZ
/ 512, NSEC_PER_SEC
/ 512);
707 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
708 * overflow after 64.99 years.
709 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
711 return div_u64(x
* 9, (9ull * NSEC_PER_SEC
+ (USER_HZ
/ 2)) / USER_HZ
);
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
;