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/errno.h>
34 #include <linux/smp_lock.h>
35 #include <linux/syscalls.h>
36 #include <linux/security.h>
38 #include <linux/module.h>
40 #include <asm/uaccess.h>
41 #include <asm/unistd.h>
44 * The timezone where the local system is located. Used as a default by some
45 * programs who obtain this value by using gettimeofday.
47 struct timezone sys_tz;
49 EXPORT_SYMBOL(sys_tz);
51 #ifdef __ARCH_WANT_SYS_TIME
54 * sys_time() can be implemented in user-level using
55 * sys_gettimeofday(). Is this for backwards compatibility? If so,
56 * why not move it into the appropriate arch directory (for those
57 * architectures that need it).
59 asmlinkage long sys_time(time_t __user * tloc)
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 asmlinkage long sys_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 asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __user *tz)
103 if (likely(tv != NULL)) {
105 do_gettimeofday(&ktv);
106 if (copy_to_user(tv, &ktv, sizeof(ktv)))
109 if (unlikely(tz != NULL)) {
110 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
117 * Adjust the time obtained from the CMOS to be UTC time instead of
120 * This is ugly, but preferable to the alternatives. Otherwise we
121 * would either need to write a program to do it in /etc/rc (and risk
122 * confusion if the program gets run more than once; it would also be
123 * hard to make the program warp the clock precisely n hours) or
124 * compile in the timezone information into the kernel. Bad, bad....
128 * The best thing to do is to keep the CMOS clock in universal time (UTC)
129 * as real UNIX machines always do it. This avoids all headaches about
130 * daylight saving times and warping kernel clocks.
132 static inline void warp_clock(void)
134 write_seqlock_irq(&xtime_lock);
135 wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
136 xtime.tv_sec += sys_tz.tz_minuteswest * 60;
137 time_interpolator_reset();
138 write_sequnlock_irq(&xtime_lock);
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(struct timespec *tv, 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. */
176 /* SMP safe, again the code in arch/foo/time.c should
177 * globally block out interrupts when it runs.
179 return do_settimeofday(tv);
184 asmlinkage long sys_settimeofday(struct timeval __user *tv,
185 struct timezone __user *tz)
187 struct timeval user_tv;
188 struct timespec new_ts;
189 struct timezone new_tz;
192 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
194 new_ts.tv_sec = user_tv.tv_sec;
195 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
198 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
202 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
205 /* we call this to notify the arch when the clock is being
206 * controlled. If no such arch routine, do nothing.
208 void __attribute__ ((weak)) notify_arch_cmos_timer(void)
210 /* Workaround http://gcc.gnu.org/PR27781 */
215 /* adjtimex mainly allows reading (and writing, if superuser) of
216 * kernel time-keeping variables. used by xntpd.
218 int do_adjtimex(struct timex *txc)
220 long ltemp, mtemp, save_adjust;
223 /* In order to modify anything, you gotta be super-user! */
224 if (txc->modes && !capable(CAP_SYS_TIME))
227 /* Now we validate the data before disabling interrupts */
229 if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
230 /* singleshot must not be used with any other mode bits */
231 if (txc->modes != ADJ_OFFSET_SINGLESHOT)
234 if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET))
235 /* adjustment Offset limited to +- .512 seconds */
236 if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE )
239 /* if the quartz is off by more than 10% something is VERY wrong ! */
240 if (txc->modes & ADJ_TICK)
241 if (txc->tick < 900000/USER_HZ ||
242 txc->tick > 1100000/USER_HZ)
245 write_seqlock_irq(&xtime_lock);
246 result = time_state; /* mostly `TIME_OK' */
248 /* Save for later - semantics of adjtime is to return old value */
249 save_adjust = time_next_adjust ? time_next_adjust : time_adjust;
251 #if 0 /* STA_CLOCKERR is never set yet */
252 time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */
254 /* If there are input parameters, then process them */
257 if (txc->modes & ADJ_STATUS) /* only set allowed bits */
258 time_status = (txc->status & ~STA_RONLY) |
259 (time_status & STA_RONLY);
261 if (txc->modes & ADJ_FREQUENCY) { /* p. 22 */
262 if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) {
266 time_freq = txc->freq;
269 if (txc->modes & ADJ_MAXERROR) {
270 if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) {
274 time_maxerror = txc->maxerror;
277 if (txc->modes & ADJ_ESTERROR) {
278 if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) {
282 time_esterror = txc->esterror;
285 if (txc->modes & ADJ_TIMECONST) { /* p. 24 */
286 if (txc->constant < 0) { /* NTP v4 uses values > 6 */
290 time_constant = txc->constant;
293 if (txc->modes & ADJ_OFFSET) { /* values checked earlier */
294 if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
295 /* adjtime() is independent from ntp_adjtime() */
296 if ((time_next_adjust = txc->offset) == 0)
299 else if (time_status & STA_PLL) {
303 * Scale the phase adjustment and
304 * clamp to the operating range.
306 if (ltemp > MAXPHASE)
307 time_offset = MAXPHASE << SHIFT_UPDATE;
308 else if (ltemp < -MAXPHASE)
309 time_offset = -(MAXPHASE << SHIFT_UPDATE);
311 time_offset = ltemp << SHIFT_UPDATE;
314 * Select whether the frequency is to be controlled
315 * and in which mode (PLL or FLL). Clamp to the operating
316 * range. Ugly multiply/divide should be replaced someday.
319 if (time_status & STA_FREQHOLD || time_reftime == 0)
320 time_reftime = xtime.tv_sec;
321 mtemp = xtime.tv_sec - time_reftime;
322 time_reftime = xtime.tv_sec;
323 if (time_status & STA_FLL) {
324 if (mtemp >= MINSEC) {
325 ltemp = (time_offset / mtemp) << (SHIFT_USEC -
327 time_freq += shift_right(ltemp, SHIFT_KH);
328 } else /* calibration interval too short (p. 12) */
330 } else { /* PLL mode */
331 if (mtemp < MAXSEC) {
333 time_freq += shift_right(ltemp,(time_constant +
335 SHIFT_KF - SHIFT_USEC));
336 } else /* calibration interval too long (p. 12) */
339 time_freq = min(time_freq, time_tolerance);
340 time_freq = max(time_freq, -time_tolerance);
342 } /* txc->modes & ADJ_OFFSET */
343 if (txc->modes & ADJ_TICK) {
344 tick_usec = txc->tick;
345 tick_nsec = TICK_USEC_TO_NSEC(tick_usec);
348 leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
351 if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
352 txc->offset = save_adjust;
354 txc->offset = shift_right(time_offset, SHIFT_UPDATE);
356 txc->freq = time_freq;
357 txc->maxerror = time_maxerror;
358 txc->esterror = time_esterror;
359 txc->status = time_status;
360 txc->constant = time_constant;
361 txc->precision = time_precision;
362 txc->tolerance = time_tolerance;
363 txc->tick = tick_usec;
365 /* PPS is not implemented, so these are zero */
374 write_sequnlock_irq(&xtime_lock);
375 do_gettimeofday(&txc->time);
376 notify_arch_cmos_timer();
380 asmlinkage long sys_adjtimex(struct timex __user *txc_p)
382 struct timex txc; /* Local copy of parameter */
385 /* Copy the user data space into the kernel copy
386 * structure. But bear in mind that the structures
389 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
391 ret = do_adjtimex(&txc);
392 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
395 inline struct timespec current_kernel_time(void)
401 seq = read_seqbegin(&xtime_lock);
404 } while (read_seqretry(&xtime_lock, seq));
409 EXPORT_SYMBOL(current_kernel_time);
412 * current_fs_time - Return FS time
415 * Return the current time truncated to the time granularity supported by
418 struct timespec current_fs_time(struct super_block *sb)
420 struct timespec now = current_kernel_time();
421 return timespec_trunc(now, sb->s_time_gran);
423 EXPORT_SYMBOL(current_fs_time);
426 * timespec_trunc - Truncate timespec to a granularity
428 * @gran: Granularity in ns.
430 * Truncate a timespec to a granularity. gran must be smaller than a second.
431 * Always rounds down.
433 * This function should be only used for timestamps returned by
434 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
435 * it doesn't handle the better resolution of the later.
437 struct timespec timespec_trunc(struct timespec t, unsigned gran)
440 * Division is pretty slow so avoid it for common cases.
441 * Currently current_kernel_time() never returns better than
442 * jiffies resolution. Exploit that.
444 if (gran <= jiffies_to_usecs(1) * 1000) {
446 } else if (gran == 1000000000) {
449 t.tv_nsec -= t.tv_nsec % gran;
453 EXPORT_SYMBOL(timespec_trunc);
455 #ifdef CONFIG_TIME_INTERPOLATION
456 void getnstimeofday (struct timespec *tv)
458 unsigned long seq,sec,nsec;
461 seq = read_seqbegin(&xtime_lock);
463 nsec = xtime.tv_nsec+time_interpolator_get_offset();
464 } while (unlikely(read_seqretry(&xtime_lock, seq)));
466 while (unlikely(nsec >= NSEC_PER_SEC)) {
467 nsec -= NSEC_PER_SEC;
473 EXPORT_SYMBOL_GPL(getnstimeofday);
475 int do_settimeofday (struct timespec *tv)
477 time_t wtm_sec, sec = tv->tv_sec;
478 long wtm_nsec, nsec = tv->tv_nsec;
480 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
483 write_seqlock_irq(&xtime_lock);
485 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
486 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
488 set_normalized_timespec(&xtime, sec, nsec);
489 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
491 time_adjust = 0; /* stop active adjtime() */
492 time_status |= STA_UNSYNC;
493 time_maxerror = NTP_PHASE_LIMIT;
494 time_esterror = NTP_PHASE_LIMIT;
495 time_interpolator_reset();
497 write_sequnlock_irq(&xtime_lock);
501 EXPORT_SYMBOL(do_settimeofday);
503 void do_gettimeofday (struct timeval *tv)
505 unsigned long seq, nsec, usec, sec, offset;
507 seq = read_seqbegin(&xtime_lock);
508 offset = time_interpolator_get_offset();
510 nsec = xtime.tv_nsec;
511 } while (unlikely(read_seqretry(&xtime_lock, seq)));
513 usec = (nsec + offset) / 1000;
515 while (unlikely(usec >= USEC_PER_SEC)) {
516 usec -= USEC_PER_SEC;
524 EXPORT_SYMBOL(do_gettimeofday);
528 #ifndef CONFIG_GENERIC_TIME
530 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
531 * and therefore only yields usec accuracy
533 void getnstimeofday(struct timespec *tv)
538 tv->tv_sec = x.tv_sec;
539 tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
541 EXPORT_SYMBOL_GPL(getnstimeofday);
545 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
546 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
547 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
549 * [For the Julian calendar (which was used in Russia before 1917,
550 * Britain & colonies before 1752, anywhere else before 1582,
551 * and is still in use by some communities) leave out the
552 * -year/100+year/400 terms, and add 10.]
554 * This algorithm was first published by Gauss (I think).
556 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
557 * machines were long is 32-bit! (However, as time_t is signed, we
558 * will already get problems at other places on 2038-01-19 03:14:08)
561 mktime(const unsigned int year0, const unsigned int mon0,
562 const unsigned int day, const unsigned int hour,
563 const unsigned int min, const unsigned int sec)
565 unsigned int mon = mon0, year = year0;
567 /* 1..12 -> 11,12,1..10 */
568 if (0 >= (int) (mon -= 2)) {
569 mon += 12; /* Puts Feb last since it has leap day */
573 return ((((unsigned long)
574 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
576 )*24 + hour /* now have hours */
577 )*60 + min /* now have minutes */
578 )*60 + sec; /* finally seconds */
581 EXPORT_SYMBOL(mktime);
584 * set_normalized_timespec - set timespec sec and nsec parts and normalize
586 * @ts: pointer to timespec variable to be set
587 * @sec: seconds to set
588 * @nsec: nanoseconds to set
590 * Set seconds and nanoseconds field of a timespec variable and
591 * normalize to the timespec storage format
593 * Note: The tv_nsec part is always in the range of
594 * 0 <= tv_nsec < NSEC_PER_SEC
595 * For negative values only the tv_sec field is negative !
597 void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
599 while (nsec >= NSEC_PER_SEC) {
600 nsec -= NSEC_PER_SEC;
604 nsec += NSEC_PER_SEC;
612 * ns_to_timespec - Convert nanoseconds to timespec
613 * @nsec: the nanoseconds value to be converted
615 * Returns the timespec representation of the nsec parameter.
617 struct timespec ns_to_timespec(const s64 nsec)
622 return (struct timespec) {0, 0};
624 ts.tv_sec = div_long_long_rem_signed(nsec, NSEC_PER_SEC, &ts.tv_nsec);
625 if (unlikely(nsec < 0))
626 set_normalized_timespec(&ts, ts.tv_sec, ts.tv_nsec);
632 * ns_to_timeval - Convert nanoseconds to timeval
633 * @nsec: the nanoseconds value to be converted
635 * Returns the timeval representation of the nsec parameter.
637 struct timeval ns_to_timeval(const s64 nsec)
639 struct timespec ts = ns_to_timespec(nsec);
642 tv.tv_sec = ts.tv_sec;
643 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
648 #if (BITS_PER_LONG < 64)
649 u64 get_jiffies_64(void)
655 seq = read_seqbegin(&xtime_lock);
657 } while (read_seqretry(&xtime_lock, seq));
661 EXPORT_SYMBOL(get_jiffies_64);
664 EXPORT_SYMBOL(jiffies);