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 update_xtime_cache(0);
140 write_sequnlock_irq(&xtime_lock);
145 * In case for some reason the CMOS clock has not already been running
146 * in UTC, but in some local time: The first time we set the timezone,
147 * we will warp the clock so that it is ticking UTC time instead of
148 * local time. Presumably, if someone is setting the timezone then we
149 * are running in an environment where the programs understand about
150 * timezones. This should be done at boot time in the /etc/rc script,
151 * as soon as possible, so that the clock can be set right. Otherwise,
152 * various programs will get confused when the clock gets warped.
155 int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
157 static int firsttime = 1;
160 if (tv && !timespec_valid(tv))
163 error = security_settime(tv, tz);
168 /* SMP safe, global irq locking makes it work. */
170 update_vsyscall_tz();
179 /* SMP safe, again the code in arch/foo/time.c should
180 * globally block out interrupts when it runs.
182 return do_settimeofday(tv);
187 SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv,
188 struct timezone __user *, tz)
190 struct timeval user_tv;
191 struct timespec new_ts;
192 struct timezone new_tz;
195 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
197 new_ts.tv_sec = user_tv.tv_sec;
198 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
201 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
205 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
208 SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p)
210 struct timex txc; /* Local copy of parameter */
213 /* Copy the user data space into the kernel copy
214 * structure. But bear in mind that the structures
217 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
219 ret = do_adjtimex(&txc);
220 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
224 * current_fs_time - Return FS time
227 * Return the current time truncated to the time granularity supported by
230 struct timespec current_fs_time(struct super_block *sb)
232 struct timespec now = current_kernel_time();
233 return timespec_trunc(now, sb->s_time_gran);
235 EXPORT_SYMBOL(current_fs_time);
238 * Convert jiffies to milliseconds and back.
240 * Avoid unnecessary multiplications/divisions in the
241 * two most common HZ cases:
243 unsigned int inline jiffies_to_msecs(const unsigned long j)
245 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
246 return (MSEC_PER_SEC / HZ) * j;
247 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
248 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
250 # if BITS_PER_LONG == 32
251 return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
253 return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
257 EXPORT_SYMBOL(jiffies_to_msecs);
259 unsigned int inline jiffies_to_usecs(const unsigned long j)
261 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
262 return (USEC_PER_SEC / HZ) * j;
263 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
264 return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
266 # if BITS_PER_LONG == 32
267 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
269 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
273 EXPORT_SYMBOL(jiffies_to_usecs);
276 * timespec_trunc - Truncate timespec to a granularity
278 * @gran: Granularity in ns.
280 * Truncate a timespec to a granularity. gran must be smaller than a second.
281 * Always rounds down.
283 * This function should be only used for timestamps returned by
284 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
285 * it doesn't handle the better resolution of the latter.
287 struct timespec timespec_trunc(struct timespec t, unsigned gran)
290 * Division is pretty slow so avoid it for common cases.
291 * Currently current_kernel_time() never returns better than
292 * jiffies resolution. Exploit that.
294 if (gran <= jiffies_to_usecs(1) * 1000) {
296 } else if (gran == 1000000000) {
299 t.tv_nsec -= t.tv_nsec % gran;
303 EXPORT_SYMBOL(timespec_trunc);
305 #ifndef CONFIG_GENERIC_TIME
307 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
308 * and therefore only yields usec accuracy
310 void getnstimeofday(struct timespec *tv)
315 tv->tv_sec = x.tv_sec;
316 tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
318 EXPORT_SYMBOL_GPL(getnstimeofday);
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 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
333 * machines where long is 32-bit! (However, as time_t is signed, we
334 * will already get problems at other places on 2038-01-19 03:14:08)
337 mktime(const unsigned int year0, const unsigned int mon0,
338 const unsigned int day, const unsigned int hour,
339 const unsigned int min, const unsigned int sec)
341 unsigned int mon = mon0, year = year0;
343 /* 1..12 -> 11,12,1..10 */
344 if (0 >= (int) (mon -= 2)) {
345 mon += 12; /* Puts Feb last since it has leap day */
349 return ((((unsigned long)
350 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
352 )*24 + hour /* now have hours */
353 )*60 + min /* now have minutes */
354 )*60 + sec; /* finally seconds */
357 EXPORT_SYMBOL(mktime);
360 * set_normalized_timespec - set timespec sec and nsec parts and normalize
362 * @ts: pointer to timespec variable to be set
363 * @sec: seconds to set
364 * @nsec: nanoseconds to set
366 * Set seconds and nanoseconds field of a timespec variable and
367 * normalize to the timespec storage format
369 * Note: The tv_nsec part is always in the range of
370 * 0 <= tv_nsec < NSEC_PER_SEC
371 * For negative values only the tv_sec field is negative !
373 void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
375 while (nsec >= NSEC_PER_SEC) {
377 * The following asm() prevents the compiler from
378 * optimising this loop into a modulo operation. See
379 * also __iter_div_u64_rem() in include/linux/time.h
381 asm("" : "+rm"(nsec));
382 nsec -= NSEC_PER_SEC;
386 asm("" : "+rm"(nsec));
387 nsec += NSEC_PER_SEC;
393 EXPORT_SYMBOL(set_normalized_timespec);
396 * ns_to_timespec - Convert nanoseconds to timespec
397 * @nsec: the nanoseconds value to be converted
399 * Returns the timespec representation of the nsec parameter.
401 struct timespec ns_to_timespec(const s64 nsec)
407 return (struct timespec) {0, 0};
409 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
410 if (unlikely(rem < 0)) {
418 EXPORT_SYMBOL(ns_to_timespec);
421 * ns_to_timeval - Convert nanoseconds to timeval
422 * @nsec: the nanoseconds value to be converted
424 * Returns the timeval representation of the nsec parameter.
426 struct timeval ns_to_timeval(const s64 nsec)
428 struct timespec ts = ns_to_timespec(nsec);
431 tv.tv_sec = ts.tv_sec;
432 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
436 EXPORT_SYMBOL(ns_to_timeval);
439 * When we convert to jiffies then we interpret incoming values
442 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
444 * - 'too large' values [that would result in larger than
445 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
447 * - all other values are converted to jiffies by either multiplying
448 * the input value by a factor or dividing it with a factor
450 * We must also be careful about 32-bit overflows.
452 unsigned long msecs_to_jiffies(const unsigned int m)
455 * Negative value, means infinite timeout:
458 return MAX_JIFFY_OFFSET;
460 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
462 * HZ is equal to or smaller than 1000, and 1000 is a nice
463 * round multiple of HZ, divide with the factor between them,
466 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
467 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
469 * HZ is larger than 1000, and HZ is a nice round multiple of
470 * 1000 - simply multiply with the factor between them.
472 * But first make sure the multiplication result cannot
475 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
476 return MAX_JIFFY_OFFSET;
478 return m * (HZ / MSEC_PER_SEC);
481 * Generic case - multiply, round and divide. But first
482 * check that if we are doing a net multiplication, that
483 * we wouldn't overflow:
485 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
486 return MAX_JIFFY_OFFSET;
488 return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
492 EXPORT_SYMBOL(msecs_to_jiffies);
494 unsigned long usecs_to_jiffies(const unsigned int u)
496 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
497 return MAX_JIFFY_OFFSET;
498 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
499 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
500 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
501 return u * (HZ / USEC_PER_SEC);
503 return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
507 EXPORT_SYMBOL(usecs_to_jiffies);
510 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
511 * that a remainder subtract here would not do the right thing as the
512 * resolution values don't fall on second boundries. I.e. the line:
513 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
515 * Rather, we just shift the bits off the right.
517 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
518 * value to a scaled second value.
521 timespec_to_jiffies(const struct timespec *value)
523 unsigned long sec = value->tv_sec;
524 long nsec = value->tv_nsec + TICK_NSEC - 1;
526 if (sec >= MAX_SEC_IN_JIFFIES){
527 sec = MAX_SEC_IN_JIFFIES;
530 return (((u64)sec * SEC_CONVERSION) +
531 (((u64)nsec * NSEC_CONVERSION) >>
532 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
535 EXPORT_SYMBOL(timespec_to_jiffies);
538 jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
541 * Convert jiffies to nanoseconds and separate with
545 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
547 value->tv_nsec = rem;
549 EXPORT_SYMBOL(jiffies_to_timespec);
551 /* Same for "timeval"
553 * Well, almost. The problem here is that the real system resolution is
554 * in nanoseconds and the value being converted is in micro seconds.
555 * Also for some machines (those that use HZ = 1024, in-particular),
556 * there is a LARGE error in the tick size in microseconds.
558 * The solution we use is to do the rounding AFTER we convert the
559 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
560 * Instruction wise, this should cost only an additional add with carry
561 * instruction above the way it was done above.
564 timeval_to_jiffies(const struct timeval *value)
566 unsigned long sec = value->tv_sec;
567 long usec = value->tv_usec;
569 if (sec >= MAX_SEC_IN_JIFFIES){
570 sec = MAX_SEC_IN_JIFFIES;
573 return (((u64)sec * SEC_CONVERSION) +
574 (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
575 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
577 EXPORT_SYMBOL(timeval_to_jiffies);
579 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
582 * Convert jiffies to nanoseconds and separate with
587 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
589 value->tv_usec = rem / NSEC_PER_USEC;
591 EXPORT_SYMBOL(jiffies_to_timeval);
594 * Convert jiffies/jiffies_64 to clock_t and back.
596 clock_t jiffies_to_clock_t(unsigned long x)
598 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
600 return x * (USER_HZ / HZ);
602 return x / (HZ / USER_HZ);
605 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
608 EXPORT_SYMBOL(jiffies_to_clock_t);
610 unsigned long clock_t_to_jiffies(unsigned long x)
612 #if (HZ % USER_HZ)==0
613 if (x >= ~0UL / (HZ / USER_HZ))
615 return x * (HZ / USER_HZ);
617 /* Don't worry about loss of precision here .. */
618 if (x >= ~0UL / HZ * USER_HZ)
621 /* .. but do try to contain it here */
622 return div_u64((u64)x * HZ, USER_HZ);
625 EXPORT_SYMBOL(clock_t_to_jiffies);
627 u64 jiffies_64_to_clock_t(u64 x)
629 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
631 x = div_u64(x * USER_HZ, HZ);
633 x = div_u64(x, HZ / USER_HZ);
639 * There are better ways that don't overflow early,
640 * but even this doesn't overflow in hundreds of years
643 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
647 EXPORT_SYMBOL(jiffies_64_to_clock_t);
649 u64 nsec_to_clock_t(u64 x)
651 #if (NSEC_PER_SEC % USER_HZ) == 0
652 return div_u64(x, NSEC_PER_SEC / USER_HZ);
653 #elif (USER_HZ % 512) == 0
654 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
657 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
658 * overflow after 64.99 years.
659 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
661 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
665 #if (BITS_PER_LONG < 64)
666 u64 get_jiffies_64(void)
672 seq = read_seqbegin(&xtime_lock);
674 } while (read_seqretry(&xtime_lock, seq));
677 EXPORT_SYMBOL(get_jiffies_64);
680 EXPORT_SYMBOL(jiffies);
683 * Add two timespec values and do a safety check for overflow.
684 * It's assumed that both values are valid (>= 0)
686 struct timespec timespec_add_safe(const struct timespec lhs,
687 const struct timespec rhs)
691 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
692 lhs.tv_nsec + rhs.tv_nsec);
694 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
695 res.tv_sec = TIME_T_MAX;