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.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/module.h>
31 #include <linux/timex.h>
32 #include <linux/capability.h>
33 #include <linux/clocksource.h>
34 #include <linux/errno.h>
35 #include <linux/syscalls.h>
36 #include <linux/security.h>
38 #include <linux/slab.h>
39 #include <linux/math64.h>
40 #include <linux/ptrace.h>
42 #include <asm/uaccess.h>
43 #include <asm/unistd.h>
45 #include "timeconst.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 * Adjust the time obtained from the CMOS to be UTC time instead of
122 * This is ugly, but preferable to the alternatives. Otherwise we
123 * would either need to write a program to do it in /etc/rc (and risk
124 * confusion if the program gets run more than once; it would also be
125 * hard to make the program warp the clock precisely n hours) or
126 * compile in the timezone information into the kernel. Bad, bad....
130 * The best thing to do is to keep the CMOS clock in universal time (UTC)
131 * as real UNIX machines always do it. This avoids all headaches about
132 * daylight saving times and warping kernel clocks.
134 static inline void warp_clock(void)
136 write_seqlock_irq(&xtime_lock
);
137 wall_to_monotonic
.tv_sec
-= sys_tz
.tz_minuteswest
* 60;
138 xtime
.tv_sec
+= sys_tz
.tz_minuteswest
* 60;
139 write_sequnlock_irq(&xtime_lock
);
144 * In case for some reason the CMOS clock has not already been running
145 * in UTC, but in some local time: The first time we set the timezone,
146 * we will warp the clock so that it is ticking UTC time instead of
147 * local time. Presumably, if someone is setting the timezone then we
148 * are running in an environment where the programs understand about
149 * timezones. This should be done at boot time in the /etc/rc script,
150 * as soon as possible, so that the clock can be set right. Otherwise,
151 * various programs will get confused when the clock gets warped.
154 int do_sys_settimeofday(struct timespec
*tv
, struct timezone
*tz
)
156 static int firsttime
= 1;
159 if (tv
&& !timespec_valid(tv
))
162 error
= security_settime(tv
, tz
);
167 /* SMP safe, global irq locking makes it work. */
169 update_vsyscall_tz();
178 /* SMP safe, again the code in arch/foo/time.c should
179 * globally block out interrupts when it runs.
181 return do_settimeofday(tv
);
186 SYSCALL_DEFINE2(settimeofday
, struct timeval __user
*, tv
,
187 struct timezone __user
*, tz
)
189 struct timeval user_tv
;
190 struct timespec new_ts
;
191 struct timezone new_tz
;
194 if (copy_from_user(&user_tv
, tv
, sizeof(*tv
)))
196 new_ts
.tv_sec
= user_tv
.tv_sec
;
197 new_ts
.tv_nsec
= user_tv
.tv_usec
* NSEC_PER_USEC
;
200 if (copy_from_user(&new_tz
, tz
, sizeof(*tz
)))
204 return do_sys_settimeofday(tv
? &new_ts
: NULL
, tz
? &new_tz
: NULL
);
207 SYSCALL_DEFINE1(adjtimex
, struct timex __user
*, txc_p
)
209 struct timex txc
; /* Local copy of parameter */
212 /* Copy the user data space into the kernel copy
213 * structure. But bear in mind that the structures
216 if(copy_from_user(&txc
, txc_p
, sizeof(struct timex
)))
218 ret
= do_adjtimex(&txc
);
219 return copy_to_user(txc_p
, &txc
, sizeof(struct timex
)) ? -EFAULT
: ret
;
223 * current_fs_time - Return FS time
226 * Return the current time truncated to the time granularity supported by
229 struct timespec
current_fs_time(struct super_block
*sb
)
231 struct timespec now
= current_kernel_time();
232 return timespec_trunc(now
, sb
->s_time_gran
);
234 EXPORT_SYMBOL(current_fs_time
);
237 * Convert jiffies to milliseconds and back.
239 * Avoid unnecessary multiplications/divisions in the
240 * two most common HZ cases:
242 unsigned int inline jiffies_to_msecs(const unsigned long j
)
244 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
245 return (MSEC_PER_SEC
/ HZ
) * j
;
246 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
247 return (j
+ (HZ
/ MSEC_PER_SEC
) - 1)/(HZ
/ MSEC_PER_SEC
);
249 # if BITS_PER_LONG == 32
250 return (HZ_TO_MSEC_MUL32
* j
) >> HZ_TO_MSEC_SHR32
;
252 return (j
* HZ_TO_MSEC_NUM
) / HZ_TO_MSEC_DEN
;
256 EXPORT_SYMBOL(jiffies_to_msecs
);
258 unsigned int inline jiffies_to_usecs(const unsigned long j
)
260 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
261 return (USEC_PER_SEC
/ HZ
) * j
;
262 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
263 return (j
+ (HZ
/ USEC_PER_SEC
) - 1)/(HZ
/ USEC_PER_SEC
);
265 # if BITS_PER_LONG == 32
266 return (HZ_TO_USEC_MUL32
* j
) >> HZ_TO_USEC_SHR32
;
268 return (j
* HZ_TO_USEC_NUM
) / HZ_TO_USEC_DEN
;
272 EXPORT_SYMBOL(jiffies_to_usecs
);
275 * timespec_trunc - Truncate timespec to a granularity
277 * @gran: Granularity in ns.
279 * Truncate a timespec to a granularity. gran must be smaller than a second.
280 * Always rounds down.
282 * This function should be only used for timestamps returned by
283 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
284 * it doesn't handle the better resolution of the latter.
286 struct timespec
timespec_trunc(struct timespec t
, unsigned gran
)
289 * Division is pretty slow so avoid it for common cases.
290 * Currently current_kernel_time() never returns better than
291 * jiffies resolution. Exploit that.
293 if (gran
<= jiffies_to_usecs(1) * 1000) {
295 } else if (gran
== 1000000000) {
298 t
.tv_nsec
-= t
.tv_nsec
% gran
;
302 EXPORT_SYMBOL(timespec_trunc
);
304 #ifndef CONFIG_GENERIC_TIME
306 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
307 * and therefore only yields usec accuracy
309 void getnstimeofday(struct timespec
*tv
)
314 tv
->tv_sec
= x
.tv_sec
;
315 tv
->tv_nsec
= x
.tv_usec
* NSEC_PER_USEC
;
317 EXPORT_SYMBOL_GPL(getnstimeofday
);
320 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
321 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
322 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
324 * [For the Julian calendar (which was used in Russia before 1917,
325 * Britain & colonies before 1752, anywhere else before 1582,
326 * and is still in use by some communities) leave out the
327 * -year/100+year/400 terms, and add 10.]
329 * This algorithm was first published by Gauss (I think).
331 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
332 * machines where long is 32-bit! (However, as time_t is signed, we
333 * will already get problems at other places on 2038-01-19 03:14:08)
336 mktime(const unsigned int year0
, const unsigned int mon0
,
337 const unsigned int day
, const unsigned int hour
,
338 const unsigned int min
, const unsigned int sec
)
340 unsigned int mon
= mon0
, year
= year0
;
342 /* 1..12 -> 11,12,1..10 */
343 if (0 >= (int) (mon
-= 2)) {
344 mon
+= 12; /* Puts Feb last since it has leap day */
348 return ((((unsigned long)
349 (year
/4 - year
/100 + year
/400 + 367*mon
/12 + day
) +
351 )*24 + hour
/* now have hours */
352 )*60 + min
/* now have minutes */
353 )*60 + sec
; /* finally seconds */
356 EXPORT_SYMBOL(mktime
);
359 * set_normalized_timespec - set timespec sec and nsec parts and normalize
361 * @ts: pointer to timespec variable to be set
362 * @sec: seconds to set
363 * @nsec: nanoseconds to set
365 * Set seconds and nanoseconds field of a timespec variable and
366 * normalize to the timespec storage format
368 * Note: The tv_nsec part is always in the range of
369 * 0 <= tv_nsec < NSEC_PER_SEC
370 * For negative values only the tv_sec field is negative !
372 void set_normalized_timespec(struct timespec
*ts
, time_t sec
, s64 nsec
)
374 while (nsec
>= NSEC_PER_SEC
) {
376 * The following asm() prevents the compiler from
377 * optimising this loop into a modulo operation. See
378 * also __iter_div_u64_rem() in include/linux/time.h
380 asm("" : "+rm"(nsec
));
381 nsec
-= NSEC_PER_SEC
;
385 asm("" : "+rm"(nsec
));
386 nsec
+= NSEC_PER_SEC
;
392 EXPORT_SYMBOL(set_normalized_timespec
);
395 * ns_to_timespec - Convert nanoseconds to timespec
396 * @nsec: the nanoseconds value to be converted
398 * Returns the timespec representation of the nsec parameter.
400 struct timespec
ns_to_timespec(const s64 nsec
)
406 return (struct timespec
) {0, 0};
408 ts
.tv_sec
= div_s64_rem(nsec
, NSEC_PER_SEC
, &rem
);
409 if (unlikely(rem
< 0)) {
417 EXPORT_SYMBOL(ns_to_timespec
);
420 * ns_to_timeval - Convert nanoseconds to timeval
421 * @nsec: the nanoseconds value to be converted
423 * Returns the timeval representation of the nsec parameter.
425 struct timeval
ns_to_timeval(const s64 nsec
)
427 struct timespec ts
= ns_to_timespec(nsec
);
430 tv
.tv_sec
= ts
.tv_sec
;
431 tv
.tv_usec
= (suseconds_t
) ts
.tv_nsec
/ 1000;
435 EXPORT_SYMBOL(ns_to_timeval
);
438 * When we convert to jiffies then we interpret incoming values
441 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
443 * - 'too large' values [that would result in larger than
444 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
446 * - all other values are converted to jiffies by either multiplying
447 * the input value by a factor or dividing it with a factor
449 * We must also be careful about 32-bit overflows.
451 unsigned long msecs_to_jiffies(const unsigned int m
)
454 * Negative value, means infinite timeout:
457 return MAX_JIFFY_OFFSET
;
459 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
461 * HZ is equal to or smaller than 1000, and 1000 is a nice
462 * round multiple of HZ, divide with the factor between them,
465 return (m
+ (MSEC_PER_SEC
/ HZ
) - 1) / (MSEC_PER_SEC
/ HZ
);
466 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
468 * HZ is larger than 1000, and HZ is a nice round multiple of
469 * 1000 - simply multiply with the factor between them.
471 * But first make sure the multiplication result cannot
474 if (m
> jiffies_to_msecs(MAX_JIFFY_OFFSET
))
475 return MAX_JIFFY_OFFSET
;
477 return m
* (HZ
/ MSEC_PER_SEC
);
480 * Generic case - multiply, round and divide. But first
481 * check that if we are doing a net multiplication, that
482 * we wouldn't overflow:
484 if (HZ
> MSEC_PER_SEC
&& m
> jiffies_to_msecs(MAX_JIFFY_OFFSET
))
485 return MAX_JIFFY_OFFSET
;
487 return (MSEC_TO_HZ_MUL32
* m
+ MSEC_TO_HZ_ADJ32
)
491 EXPORT_SYMBOL(msecs_to_jiffies
);
493 unsigned long usecs_to_jiffies(const unsigned int u
)
495 if (u
> jiffies_to_usecs(MAX_JIFFY_OFFSET
))
496 return MAX_JIFFY_OFFSET
;
497 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
498 return (u
+ (USEC_PER_SEC
/ HZ
) - 1) / (USEC_PER_SEC
/ HZ
);
499 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
500 return u
* (HZ
/ USEC_PER_SEC
);
502 return (USEC_TO_HZ_MUL32
* u
+ USEC_TO_HZ_ADJ32
)
506 EXPORT_SYMBOL(usecs_to_jiffies
);
509 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
510 * that a remainder subtract here would not do the right thing as the
511 * resolution values don't fall on second boundries. I.e. the line:
512 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
514 * Rather, we just shift the bits off the right.
516 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
517 * value to a scaled second value.
520 timespec_to_jiffies(const struct timespec
*value
)
522 unsigned long sec
= value
->tv_sec
;
523 long nsec
= value
->tv_nsec
+ TICK_NSEC
- 1;
525 if (sec
>= MAX_SEC_IN_JIFFIES
){
526 sec
= MAX_SEC_IN_JIFFIES
;
529 return (((u64
)sec
* SEC_CONVERSION
) +
530 (((u64
)nsec
* NSEC_CONVERSION
) >>
531 (NSEC_JIFFIE_SC
- SEC_JIFFIE_SC
))) >> SEC_JIFFIE_SC
;
534 EXPORT_SYMBOL(timespec_to_jiffies
);
537 jiffies_to_timespec(const unsigned long jiffies
, struct timespec
*value
)
540 * Convert jiffies to nanoseconds and separate with
544 value
->tv_sec
= div_u64_rem((u64
)jiffies
* TICK_NSEC
,
546 value
->tv_nsec
= rem
;
548 EXPORT_SYMBOL(jiffies_to_timespec
);
550 /* Same for "timeval"
552 * Well, almost. The problem here is that the real system resolution is
553 * in nanoseconds and the value being converted is in micro seconds.
554 * Also for some machines (those that use HZ = 1024, in-particular),
555 * there is a LARGE error in the tick size in microseconds.
557 * The solution we use is to do the rounding AFTER we convert the
558 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
559 * Instruction wise, this should cost only an additional add with carry
560 * instruction above the way it was done above.
563 timeval_to_jiffies(const struct timeval
*value
)
565 unsigned long sec
= value
->tv_sec
;
566 long usec
= value
->tv_usec
;
568 if (sec
>= MAX_SEC_IN_JIFFIES
){
569 sec
= MAX_SEC_IN_JIFFIES
;
572 return (((u64
)sec
* SEC_CONVERSION
) +
573 (((u64
)usec
* USEC_CONVERSION
+ USEC_ROUND
) >>
574 (USEC_JIFFIE_SC
- SEC_JIFFIE_SC
))) >> SEC_JIFFIE_SC
;
576 EXPORT_SYMBOL(timeval_to_jiffies
);
578 void jiffies_to_timeval(const unsigned long jiffies
, struct timeval
*value
)
581 * Convert jiffies to nanoseconds and separate with
586 value
->tv_sec
= div_u64_rem((u64
)jiffies
* TICK_NSEC
,
588 value
->tv_usec
= rem
/ NSEC_PER_USEC
;
590 EXPORT_SYMBOL(jiffies_to_timeval
);
593 * Convert jiffies/jiffies_64 to clock_t and back.
595 clock_t jiffies_to_clock_t(long x
)
597 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
599 return x
* (USER_HZ
/ HZ
);
601 return x
/ (HZ
/ USER_HZ
);
604 return div_u64((u64
)x
* TICK_NSEC
, NSEC_PER_SEC
/ USER_HZ
);
607 EXPORT_SYMBOL(jiffies_to_clock_t
);
609 unsigned long clock_t_to_jiffies(unsigned long x
)
611 #if (HZ % USER_HZ)==0
612 if (x
>= ~0UL / (HZ
/ USER_HZ
))
614 return x
* (HZ
/ USER_HZ
);
616 /* Don't worry about loss of precision here .. */
617 if (x
>= ~0UL / HZ
* USER_HZ
)
620 /* .. but do try to contain it here */
621 return div_u64((u64
)x
* HZ
, USER_HZ
);
624 EXPORT_SYMBOL(clock_t_to_jiffies
);
626 u64
jiffies_64_to_clock_t(u64 x
)
628 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
630 x
= div_u64(x
* USER_HZ
, HZ
);
632 x
= div_u64(x
, HZ
/ USER_HZ
);
638 * There are better ways that don't overflow early,
639 * but even this doesn't overflow in hundreds of years
642 x
= div_u64(x
* TICK_NSEC
, (NSEC_PER_SEC
/ USER_HZ
));
646 EXPORT_SYMBOL(jiffies_64_to_clock_t
);
648 u64
nsec_to_clock_t(u64 x
)
650 #if (NSEC_PER_SEC % USER_HZ) == 0
651 return div_u64(x
, NSEC_PER_SEC
/ USER_HZ
);
652 #elif (USER_HZ % 512) == 0
653 return div_u64(x
* USER_HZ
/ 512, NSEC_PER_SEC
/ 512);
656 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
657 * overflow after 64.99 years.
658 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
660 return div_u64(x
* 9, (9ull * NSEC_PER_SEC
+ (USER_HZ
/ 2)) / USER_HZ
);
665 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
669 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
670 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
671 * for scheduler, not for use in device drivers to calculate timeout value.
674 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
675 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
677 unsigned long nsecs_to_jiffies(u64 n
)
679 #if (NSEC_PER_SEC % HZ) == 0
680 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
681 return div_u64(n
, NSEC_PER_SEC
/ HZ
);
682 #elif (HZ % 512) == 0
683 /* overflow after 292 years if HZ = 1024 */
684 return div_u64(n
* HZ
/ 512, NSEC_PER_SEC
/ 512);
687 * Generic case - optimized for cases where HZ is a multiple of 3.
688 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
690 return div_u64(n
* 9, (9ull * NSEC_PER_SEC
+ HZ
/ 2) / HZ
);
694 #if (BITS_PER_LONG < 64)
695 u64
get_jiffies_64(void)
701 seq
= read_seqbegin(&xtime_lock
);
703 } while (read_seqretry(&xtime_lock
, seq
));
706 EXPORT_SYMBOL(get_jiffies_64
);
709 EXPORT_SYMBOL(jiffies
);
712 * Add two timespec values and do a safety check for overflow.
713 * It's assumed that both values are valid (>= 0)
715 struct timespec
timespec_add_safe(const struct timespec lhs
,
716 const struct timespec rhs
)
720 set_normalized_timespec(&res
, lhs
.tv_sec
+ rhs
.tv_sec
,
721 lhs
.tv_nsec
+ rhs
.tv_nsec
);
723 if (res
.tv_sec
< lhs
.tv_sec
|| res
.tv_sec
< rhs
.tv_sec
)
724 res
.tv_sec
= TIME_T_MAX
;
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