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/export.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/math64.h>
39 #include <linux/ptrace.h>
41 #include <asm/uaccess.h>
42 #include <asm/unistd.h>
44 #include "timeconst.h"
47 * The timezone where the local system is located. Used as a default by some
48 * programs who obtain this value by using gettimeofday.
50 struct timezone sys_tz
;
52 EXPORT_SYMBOL(sys_tz
);
54 #ifdef __ARCH_WANT_SYS_TIME
57 * sys_time() can be implemented in user-level using
58 * sys_gettimeofday(). Is this for backwards compatibility? If so,
59 * why not move it into the appropriate arch directory (for those
60 * architectures that need it).
62 SYSCALL_DEFINE1(time
, time_t __user
*, tloc
)
64 time_t i
= get_seconds();
70 force_successful_syscall_return();
75 * sys_stime() can be implemented in user-level using
76 * sys_settimeofday(). Is this for backwards compatibility? If so,
77 * why not move it into the appropriate arch directory (for those
78 * architectures that need it).
81 SYSCALL_DEFINE1(stime
, time_t __user
*, tptr
)
86 if (get_user(tv
.tv_sec
, tptr
))
91 err
= security_settime(&tv
, NULL
);
99 #endif /* __ARCH_WANT_SYS_TIME */
101 SYSCALL_DEFINE2(gettimeofday
, struct timeval __user
*, tv
,
102 struct timezone __user
*, tz
)
104 if (likely(tv
!= NULL
)) {
106 do_gettimeofday(&ktv
);
107 if (copy_to_user(tv
, &ktv
, sizeof(ktv
)))
110 if (unlikely(tz
!= NULL
)) {
111 if (copy_to_user(tz
, &sys_tz
, sizeof(sys_tz
)))
118 * Adjust the time obtained from the CMOS to be UTC time instead of
121 * This is ugly, but preferable to the alternatives. Otherwise we
122 * would either need to write a program to do it in /etc/rc (and risk
123 * confusion if the program gets run more than once; it would also be
124 * hard to make the program warp the clock precisely n hours) or
125 * compile in the timezone information into the kernel. Bad, bad....
129 * The best thing to do is to keep the CMOS clock in universal time (UTC)
130 * as real UNIX machines always do it. This avoids all headaches about
131 * daylight saving times and warping kernel clocks.
133 static inline void warp_clock(void)
135 struct timespec adjust
;
137 adjust
= current_kernel_time();
138 adjust
.tv_sec
+= sys_tz
.tz_minuteswest
* 60;
139 do_settimeofday(&adjust
);
143 * In case for some reason the CMOS clock has not already been running
144 * in UTC, but in some local time: The first time we set the timezone,
145 * we will warp the clock so that it is ticking UTC time instead of
146 * local time. Presumably, if someone is setting the timezone then we
147 * are running in an environment where the programs understand about
148 * timezones. This should be done at boot time in the /etc/rc script,
149 * as soon as possible, so that the clock can be set right. Otherwise,
150 * various programs will get confused when the clock gets warped.
153 int do_sys_settimeofday(const struct timespec
*tv
, const struct timezone
*tz
)
155 static int firsttime
= 1;
158 if (tv
&& !timespec_valid(tv
))
161 error
= security_settime(tv
, tz
);
166 /* SMP safe, global irq locking makes it work. */
168 update_vsyscall_tz();
177 /* SMP safe, again the code in arch/foo/time.c should
178 * globally block out interrupts when it runs.
180 return do_settimeofday(tv
);
185 SYSCALL_DEFINE2(settimeofday
, struct timeval __user
*, tv
,
186 struct timezone __user
*, tz
)
188 struct timeval user_tv
;
189 struct timespec new_ts
;
190 struct timezone new_tz
;
193 if (copy_from_user(&user_tv
, tv
, sizeof(*tv
)))
195 new_ts
.tv_sec
= user_tv
.tv_sec
;
196 new_ts
.tv_nsec
= user_tv
.tv_usec
* NSEC_PER_USEC
;
199 if (copy_from_user(&new_tz
, tz
, sizeof(*tz
)))
203 return do_sys_settimeofday(tv
? &new_ts
: NULL
, tz
? &new_tz
: NULL
);
206 SYSCALL_DEFINE1(adjtimex
, struct timex __user
*, txc_p
)
208 struct timex txc
; /* Local copy of parameter */
211 /* Copy the user data space into the kernel copy
212 * structure. But bear in mind that the structures
215 if(copy_from_user(&txc
, txc_p
, sizeof(struct timex
)))
217 ret
= do_adjtimex(&txc
);
218 return copy_to_user(txc_p
, &txc
, sizeof(struct timex
)) ? -EFAULT
: ret
;
222 * current_fs_time - Return FS time
225 * Return the current time truncated to the time granularity supported by
228 struct timespec
current_fs_time(struct super_block
*sb
)
230 struct timespec now
= current_kernel_time();
231 return timespec_trunc(now
, sb
->s_time_gran
);
233 EXPORT_SYMBOL(current_fs_time
);
236 * Convert jiffies to milliseconds and back.
238 * Avoid unnecessary multiplications/divisions in the
239 * two most common HZ cases:
241 inline unsigned int jiffies_to_msecs(const unsigned long j
)
243 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
244 return (MSEC_PER_SEC
/ HZ
) * j
;
245 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
246 return (j
+ (HZ
/ MSEC_PER_SEC
) - 1)/(HZ
/ MSEC_PER_SEC
);
248 # if BITS_PER_LONG == 32
249 return (HZ_TO_MSEC_MUL32
* j
) >> HZ_TO_MSEC_SHR32
;
251 return (j
* HZ_TO_MSEC_NUM
) / HZ_TO_MSEC_DEN
;
255 EXPORT_SYMBOL(jiffies_to_msecs
);
257 inline unsigned int jiffies_to_usecs(const unsigned long j
)
259 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
260 return (USEC_PER_SEC
/ HZ
) * j
;
261 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
262 return (j
+ (HZ
/ USEC_PER_SEC
) - 1)/(HZ
/ USEC_PER_SEC
);
264 # if BITS_PER_LONG == 32
265 return (HZ_TO_USEC_MUL32
* j
) >> HZ_TO_USEC_SHR32
;
267 return (j
* HZ_TO_USEC_NUM
) / HZ_TO_USEC_DEN
;
271 EXPORT_SYMBOL(jiffies_to_usecs
);
274 * timespec_trunc - Truncate timespec to a granularity
276 * @gran: Granularity in ns.
278 * Truncate a timespec to a granularity. gran must be smaller than a second.
279 * Always rounds down.
281 * This function should be only used for timestamps returned by
282 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
283 * it doesn't handle the better resolution of the latter.
285 struct timespec
timespec_trunc(struct timespec t
, unsigned gran
)
288 * Division is pretty slow so avoid it for common cases.
289 * Currently current_kernel_time() never returns better than
290 * jiffies resolution. Exploit that.
292 if (gran
<= jiffies_to_usecs(1) * 1000) {
294 } else if (gran
== 1000000000) {
297 t
.tv_nsec
-= t
.tv_nsec
% gran
;
301 EXPORT_SYMBOL(timespec_trunc
);
303 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
304 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
305 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
307 * [For the Julian calendar (which was used in Russia before 1917,
308 * Britain & colonies before 1752, anywhere else before 1582,
309 * and is still in use by some communities) leave out the
310 * -year/100+year/400 terms, and add 10.]
312 * This algorithm was first published by Gauss (I think).
314 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
315 * machines where long is 32-bit! (However, as time_t is signed, we
316 * will already get problems at other places on 2038-01-19 03:14:08)
319 mktime(const unsigned int year0
, const unsigned int mon0
,
320 const unsigned int day
, const unsigned int hour
,
321 const unsigned int min
, const unsigned int sec
)
323 unsigned int mon
= mon0
, year
= year0
;
325 /* 1..12 -> 11,12,1..10 */
326 if (0 >= (int) (mon
-= 2)) {
327 mon
+= 12; /* Puts Feb last since it has leap day */
331 return ((((unsigned long)
332 (year
/4 - year
/100 + year
/400 + 367*mon
/12 + day
) +
334 )*24 + hour
/* now have hours */
335 )*60 + min
/* now have minutes */
336 )*60 + sec
; /* finally seconds */
339 EXPORT_SYMBOL(mktime
);
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
);
421 * When we convert to jiffies then we interpret incoming values
424 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
426 * - 'too large' values [that would result in larger than
427 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
429 * - all other values are converted to jiffies by either multiplying
430 * the input value by a factor or dividing it with a factor
432 * We must also be careful about 32-bit overflows.
434 unsigned long msecs_to_jiffies(const unsigned int m
)
437 * Negative value, means infinite timeout:
440 return MAX_JIFFY_OFFSET
;
442 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
444 * HZ is equal to or smaller than 1000, and 1000 is a nice
445 * round multiple of HZ, divide with the factor between them,
448 return (m
+ (MSEC_PER_SEC
/ HZ
) - 1) / (MSEC_PER_SEC
/ HZ
);
449 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
451 * HZ is larger than 1000, and HZ is a nice round multiple of
452 * 1000 - simply multiply with the factor between them.
454 * But first make sure the multiplication result cannot
457 if (m
> jiffies_to_msecs(MAX_JIFFY_OFFSET
))
458 return MAX_JIFFY_OFFSET
;
460 return m
* (HZ
/ MSEC_PER_SEC
);
463 * Generic case - multiply, round and divide. But first
464 * check that if we are doing a net multiplication, that
465 * we wouldn't overflow:
467 if (HZ
> MSEC_PER_SEC
&& m
> jiffies_to_msecs(MAX_JIFFY_OFFSET
))
468 return MAX_JIFFY_OFFSET
;
470 return (MSEC_TO_HZ_MUL32
* m
+ MSEC_TO_HZ_ADJ32
)
474 EXPORT_SYMBOL(msecs_to_jiffies
);
476 unsigned long usecs_to_jiffies(const unsigned int u
)
478 if (u
> jiffies_to_usecs(MAX_JIFFY_OFFSET
))
479 return MAX_JIFFY_OFFSET
;
480 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
481 return (u
+ (USEC_PER_SEC
/ HZ
) - 1) / (USEC_PER_SEC
/ HZ
);
482 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
483 return u
* (HZ
/ USEC_PER_SEC
);
485 return (USEC_TO_HZ_MUL32
* u
+ USEC_TO_HZ_ADJ32
)
489 EXPORT_SYMBOL(usecs_to_jiffies
);
492 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
493 * that a remainder subtract here would not do the right thing as the
494 * resolution values don't fall on second boundries. I.e. the line:
495 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
497 * Rather, we just shift the bits off the right.
499 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
500 * value to a scaled second value.
503 timespec_to_jiffies(const struct timespec
*value
)
505 unsigned long sec
= value
->tv_sec
;
506 long nsec
= value
->tv_nsec
+ TICK_NSEC
- 1;
508 if (sec
>= MAX_SEC_IN_JIFFIES
){
509 sec
= MAX_SEC_IN_JIFFIES
;
512 return (((u64
)sec
* SEC_CONVERSION
) +
513 (((u64
)nsec
* NSEC_CONVERSION
) >>
514 (NSEC_JIFFIE_SC
- SEC_JIFFIE_SC
))) >> SEC_JIFFIE_SC
;
517 EXPORT_SYMBOL(timespec_to_jiffies
);
520 jiffies_to_timespec(const unsigned long jiffies
, struct timespec
*value
)
523 * Convert jiffies to nanoseconds and separate with
527 value
->tv_sec
= div_u64_rem((u64
)jiffies
* TICK_NSEC
,
529 value
->tv_nsec
= rem
;
531 EXPORT_SYMBOL(jiffies_to_timespec
);
533 /* Same for "timeval"
535 * Well, almost. The problem here is that the real system resolution is
536 * in nanoseconds and the value being converted is in micro seconds.
537 * Also for some machines (those that use HZ = 1024, in-particular),
538 * there is a LARGE error in the tick size in microseconds.
540 * The solution we use is to do the rounding AFTER we convert the
541 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
542 * Instruction wise, this should cost only an additional add with carry
543 * instruction above the way it was done above.
546 timeval_to_jiffies(const struct timeval
*value
)
548 unsigned long sec
= value
->tv_sec
;
549 long usec
= value
->tv_usec
;
551 if (sec
>= MAX_SEC_IN_JIFFIES
){
552 sec
= MAX_SEC_IN_JIFFIES
;
555 return (((u64
)sec
* SEC_CONVERSION
) +
556 (((u64
)usec
* USEC_CONVERSION
+ USEC_ROUND
) >>
557 (USEC_JIFFIE_SC
- SEC_JIFFIE_SC
))) >> SEC_JIFFIE_SC
;
559 EXPORT_SYMBOL(timeval_to_jiffies
);
561 void jiffies_to_timeval(const unsigned long jiffies
, struct timeval
*value
)
564 * Convert jiffies to nanoseconds and separate with
569 value
->tv_sec
= div_u64_rem((u64
)jiffies
* TICK_NSEC
,
571 value
->tv_usec
= rem
/ NSEC_PER_USEC
;
573 EXPORT_SYMBOL(jiffies_to_timeval
);
576 * Convert jiffies/jiffies_64 to clock_t and back.
578 clock_t jiffies_to_clock_t(long x
)
580 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
582 return x
* (USER_HZ
/ HZ
);
584 return x
/ (HZ
/ USER_HZ
);
587 return div_u64((u64
)x
* TICK_NSEC
, NSEC_PER_SEC
/ USER_HZ
);
590 EXPORT_SYMBOL(jiffies_to_clock_t
);
592 unsigned long clock_t_to_jiffies(unsigned long x
)
594 #if (HZ % USER_HZ)==0
595 if (x
>= ~0UL / (HZ
/ USER_HZ
))
597 return x
* (HZ
/ USER_HZ
);
599 /* Don't worry about loss of precision here .. */
600 if (x
>= ~0UL / HZ
* USER_HZ
)
603 /* .. but do try to contain it here */
604 return div_u64((u64
)x
* HZ
, USER_HZ
);
607 EXPORT_SYMBOL(clock_t_to_jiffies
);
609 u64
jiffies_64_to_clock_t(u64 x
)
611 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
613 x
= div_u64(x
* USER_HZ
, HZ
);
615 x
= div_u64(x
, HZ
/ USER_HZ
);
621 * There are better ways that don't overflow early,
622 * but even this doesn't overflow in hundreds of years
625 x
= div_u64(x
* TICK_NSEC
, (NSEC_PER_SEC
/ USER_HZ
));
629 EXPORT_SYMBOL(jiffies_64_to_clock_t
);
631 u64
nsec_to_clock_t(u64 x
)
633 #if (NSEC_PER_SEC % USER_HZ) == 0
634 return div_u64(x
, NSEC_PER_SEC
/ USER_HZ
);
635 #elif (USER_HZ % 512) == 0
636 return div_u64(x
* USER_HZ
/ 512, NSEC_PER_SEC
/ 512);
639 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
640 * overflow after 64.99 years.
641 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
643 return div_u64(x
* 9, (9ull * NSEC_PER_SEC
+ (USER_HZ
/ 2)) / USER_HZ
);
648 * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
652 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
653 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
654 * for scheduler, not for use in device drivers to calculate timeout value.
657 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
658 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
660 u64
nsecs_to_jiffies64(u64 n
)
662 #if (NSEC_PER_SEC % HZ) == 0
663 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
664 return div_u64(n
, NSEC_PER_SEC
/ HZ
);
665 #elif (HZ % 512) == 0
666 /* overflow after 292 years if HZ = 1024 */
667 return div_u64(n
* HZ
/ 512, NSEC_PER_SEC
/ 512);
670 * Generic case - optimized for cases where HZ is a multiple of 3.
671 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
673 return div_u64(n
* 9, (9ull * NSEC_PER_SEC
+ HZ
/ 2) / HZ
);
678 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
682 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
683 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
684 * for scheduler, not for use in device drivers to calculate timeout value.
687 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
688 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
690 unsigned long nsecs_to_jiffies(u64 n
)
692 return (unsigned long)nsecs_to_jiffies64(n
);
696 * Add two timespec values and do a safety check for overflow.
697 * It's assumed that both values are valid (>= 0)
699 struct timespec
timespec_add_safe(const struct timespec lhs
,
700 const struct timespec rhs
)
704 set_normalized_timespec(&res
, lhs
.tv_sec
+ rhs
.tv_sec
,
705 lhs
.tv_nsec
+ rhs
.tv_nsec
);
707 if (res
.tv_sec
< lhs
.tv_sec
|| res
.tv_sec
< rhs
.tv_sec
)
708 res
.tv_sec
= TIME_T_MAX
;