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/errno.h>
33 #include <linux/smp_lock.h>
34 #include <linux/syscalls.h>
35 #include <linux/security.h>
37 #include <asm/uaccess.h>
38 #include <asm/unistd.h>
41 * The timezone where the local system is located. Used as a default by some
42 * programs who obtain this value by using gettimeofday.
44 struct timezone sys_tz;
46 EXPORT_SYMBOL(sys_tz);
48 #ifdef __ARCH_WANT_SYS_TIME
51 * sys_time() can be implemented in user-level using
52 * sys_gettimeofday(). Is this for backwards compatibility? If so,
53 * why not move it into the appropriate arch directory (for those
54 * architectures that need it).
56 * XXX This function is NOT 64-bit clean!
58 asmlinkage long sys_time(int __user * tloc)
74 * sys_stime() can be implemented in user-level using
75 * sys_settimeofday(). Is this for backwards compatibility? If so,
76 * why not move it into the appropriate arch directory (for those
77 * architectures that need it).
80 asmlinkage long sys_stime(time_t __user *tptr)
85 if (get_user(tv.tv_sec, tptr))
90 err = security_settime(&tv, NULL);
98 #endif /* __ARCH_WANT_SYS_TIME */
100 asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __user *tz)
102 if (likely(tv != NULL)) {
104 do_gettimeofday(&ktv);
105 if (copy_to_user(tv, &ktv, sizeof(ktv)))
108 if (unlikely(tz != NULL)) {
109 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
116 * Adjust the time obtained from the CMOS to be UTC time instead of
119 * This is ugly, but preferable to the alternatives. Otherwise we
120 * would either need to write a program to do it in /etc/rc (and risk
121 * confusion if the program gets run more than once; it would also be
122 * hard to make the program warp the clock precisely n hours) or
123 * compile in the timezone information into the kernel. Bad, bad....
127 * The best thing to do is to keep the CMOS clock in universal time (UTC)
128 * as real UNIX machines always do it. This avoids all headaches about
129 * daylight saving times and warping kernel clocks.
131 inline static void warp_clock(void)
133 write_seqlock_irq(&xtime_lock);
134 wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
135 xtime.tv_sec += sys_tz.tz_minuteswest * 60;
136 time_interpolator_reset();
137 write_sequnlock_irq(&xtime_lock);
142 * In case for some reason the CMOS clock has not already been running
143 * in UTC, but in some local time: The first time we set the timezone,
144 * we will warp the clock so that it is ticking UTC time instead of
145 * local time. Presumably, if someone is setting the timezone then we
146 * are running in an environment where the programs understand about
147 * timezones. This should be done at boot time in the /etc/rc script,
148 * as soon as possible, so that the clock can be set right. Otherwise,
149 * various programs will get confused when the clock gets warped.
152 int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
154 static int firsttime = 1;
157 error = security_settime(tv, tz);
162 /* SMP safe, global irq locking makes it work. */
172 /* SMP safe, again the code in arch/foo/time.c should
173 * globally block out interrupts when it runs.
175 return do_settimeofday(tv);
180 asmlinkage long sys_settimeofday(struct timeval __user *tv,
181 struct timezone __user *tz)
183 struct timeval user_tv;
184 struct timespec new_ts;
185 struct timezone new_tz;
188 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
190 new_ts.tv_sec = user_tv.tv_sec;
191 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
194 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
198 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
201 long pps_offset; /* pps time offset (us) */
202 long pps_jitter = MAXTIME; /* time dispersion (jitter) (us) */
204 long pps_freq; /* frequency offset (scaled ppm) */
205 long pps_stabil = MAXFREQ; /* frequency dispersion (scaled ppm) */
207 long pps_valid = PPS_VALID; /* pps signal watchdog counter */
209 int pps_shift = PPS_SHIFT; /* interval duration (s) (shift) */
211 long pps_jitcnt; /* jitter limit exceeded */
212 long pps_calcnt; /* calibration intervals */
213 long pps_errcnt; /* calibration errors */
214 long pps_stbcnt; /* stability limit exceeded */
216 /* hook for a loadable hardpps kernel module */
217 void (*hardpps_ptr)(struct timeval *);
219 /* adjtimex mainly allows reading (and writing, if superuser) of
220 * kernel time-keeping variables. used by xntpd.
222 int do_adjtimex(struct timex *txc)
224 long ltemp, mtemp, save_adjust;
227 /* In order to modify anything, you gotta be super-user! */
228 if (txc->modes && !capable(CAP_SYS_TIME))
231 /* Now we validate the data before disabling interrupts */
233 if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
234 /* singleshot must not be used with any other mode bits */
235 if (txc->modes != ADJ_OFFSET_SINGLESHOT)
238 if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET))
239 /* adjustment Offset limited to +- .512 seconds */
240 if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE )
243 /* if the quartz is off by more than 10% something is VERY wrong ! */
244 if (txc->modes & ADJ_TICK)
245 if (txc->tick < 900000/USER_HZ ||
246 txc->tick > 1100000/USER_HZ)
249 write_seqlock_irq(&xtime_lock);
250 result = time_state; /* mostly `TIME_OK' */
252 /* Save for later - semantics of adjtime is to return old value */
253 save_adjust = time_next_adjust ? time_next_adjust : time_adjust;
255 #if 0 /* STA_CLOCKERR is never set yet */
256 time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */
258 /* If there are input parameters, then process them */
261 if (txc->modes & ADJ_STATUS) /* only set allowed bits */
262 time_status = (txc->status & ~STA_RONLY) |
263 (time_status & STA_RONLY);
265 if (txc->modes & ADJ_FREQUENCY) { /* p. 22 */
266 if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) {
270 time_freq = txc->freq - pps_freq;
273 if (txc->modes & ADJ_MAXERROR) {
274 if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) {
278 time_maxerror = txc->maxerror;
281 if (txc->modes & ADJ_ESTERROR) {
282 if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) {
286 time_esterror = txc->esterror;
289 if (txc->modes & ADJ_TIMECONST) { /* p. 24 */
290 if (txc->constant < 0) { /* NTP v4 uses values > 6 */
294 time_constant = txc->constant;
297 if (txc->modes & ADJ_OFFSET) { /* values checked earlier */
298 if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
299 /* adjtime() is independent from ntp_adjtime() */
300 if ((time_next_adjust = txc->offset) == 0)
303 else if ( time_status & (STA_PLL | STA_PPSTIME) ) {
304 ltemp = (time_status & (STA_PPSTIME | STA_PPSSIGNAL)) ==
305 (STA_PPSTIME | STA_PPSSIGNAL) ?
306 pps_offset : txc->offset;
309 * Scale the phase adjustment and
310 * clamp to the operating range.
312 if (ltemp > MAXPHASE)
313 time_offset = MAXPHASE << SHIFT_UPDATE;
314 else if (ltemp < -MAXPHASE)
315 time_offset = -(MAXPHASE << SHIFT_UPDATE);
317 time_offset = ltemp << SHIFT_UPDATE;
320 * Select whether the frequency is to be controlled
321 * and in which mode (PLL or FLL). Clamp to the operating
322 * range. Ugly multiply/divide should be replaced someday.
325 if (time_status & STA_FREQHOLD || time_reftime == 0)
326 time_reftime = xtime.tv_sec;
327 mtemp = xtime.tv_sec - time_reftime;
328 time_reftime = xtime.tv_sec;
329 if (time_status & STA_FLL) {
330 if (mtemp >= MINSEC) {
331 ltemp = (time_offset / mtemp) << (SHIFT_USEC -
334 time_freq -= -ltemp >> SHIFT_KH;
336 time_freq += ltemp >> SHIFT_KH;
337 } else /* calibration interval too short (p. 12) */
339 } else { /* PLL mode */
340 if (mtemp < MAXSEC) {
343 time_freq -= -ltemp >> (time_constant +
345 SHIFT_KF - SHIFT_USEC);
347 time_freq += ltemp >> (time_constant +
349 SHIFT_KF - SHIFT_USEC);
350 } else /* calibration interval too long (p. 12) */
353 if (time_freq > time_tolerance)
354 time_freq = time_tolerance;
355 else if (time_freq < -time_tolerance)
356 time_freq = -time_tolerance;
357 } /* STA_PLL || STA_PPSTIME */
358 } /* txc->modes & ADJ_OFFSET */
359 if (txc->modes & ADJ_TICK) {
360 tick_usec = txc->tick;
361 tick_nsec = TICK_USEC_TO_NSEC(tick_usec);
364 leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0
365 || ((time_status & (STA_PPSFREQ|STA_PPSTIME)) != 0
366 && (time_status & STA_PPSSIGNAL) == 0)
368 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
369 == (STA_PPSTIME|STA_PPSJITTER))
371 || ((time_status & STA_PPSFREQ) != 0
372 && (time_status & (STA_PPSWANDER|STA_PPSERROR)) != 0))
376 if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
377 txc->offset = save_adjust;
380 txc->offset = -(-time_offset >> SHIFT_UPDATE);
382 txc->offset = time_offset >> SHIFT_UPDATE;
384 txc->freq = time_freq + pps_freq;
385 txc->maxerror = time_maxerror;
386 txc->esterror = time_esterror;
387 txc->status = time_status;
388 txc->constant = time_constant;
389 txc->precision = time_precision;
390 txc->tolerance = time_tolerance;
391 txc->tick = tick_usec;
392 txc->ppsfreq = pps_freq;
393 txc->jitter = pps_jitter >> PPS_AVG;
394 txc->shift = pps_shift;
395 txc->stabil = pps_stabil;
396 txc->jitcnt = pps_jitcnt;
397 txc->calcnt = pps_calcnt;
398 txc->errcnt = pps_errcnt;
399 txc->stbcnt = pps_stbcnt;
400 write_sequnlock_irq(&xtime_lock);
401 do_gettimeofday(&txc->time);
405 asmlinkage long sys_adjtimex(struct timex __user *txc_p)
407 struct timex txc; /* Local copy of parameter */
410 /* Copy the user data space into the kernel copy
411 * structure. But bear in mind that the structures
414 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
416 ret = do_adjtimex(&txc);
417 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
420 struct timespec current_kernel_time(void)
426 seq = read_seqbegin(&xtime_lock);
429 } while (read_seqretry(&xtime_lock, seq));
434 EXPORT_SYMBOL(current_kernel_time);
436 #ifdef CONFIG_TIME_INTERPOLATION
437 void getnstimeofday (struct timespec *tv)
439 unsigned long seq,sec,nsec;
442 seq = read_seqbegin(&xtime_lock);
444 nsec = xtime.tv_nsec+time_interpolator_get_offset();
445 } while (unlikely(read_seqretry(&xtime_lock, seq)));
447 while (unlikely(nsec >= NSEC_PER_SEC)) {
448 nsec -= NSEC_PER_SEC;
455 int do_settimeofday (struct timespec *tv)
457 time_t wtm_sec, sec = tv->tv_sec;
458 long wtm_nsec, nsec = tv->tv_nsec;
460 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
463 write_seqlock_irq(&xtime_lock);
466 * This is revolting. We need to set "xtime" correctly. However, the value
467 * in this location is the value at the most recent update of wall time.
468 * Discover what correction gettimeofday would have done, and then undo
471 nsec -= time_interpolator_get_offset();
473 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
474 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
476 set_normalized_timespec(&xtime, sec, nsec);
477 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
479 time_adjust = 0; /* stop active adjtime() */
480 time_status |= STA_UNSYNC;
481 time_maxerror = NTP_PHASE_LIMIT;
482 time_esterror = NTP_PHASE_LIMIT;
483 time_interpolator_reset();
485 write_sequnlock_irq(&xtime_lock);
490 void do_gettimeofday (struct timeval *tv)
492 unsigned long seq, nsec, usec, sec, offset;
494 seq = read_seqbegin(&xtime_lock);
495 offset = time_interpolator_get_offset();
497 nsec = xtime.tv_nsec;
498 } while (unlikely(read_seqretry(&xtime_lock, seq)));
500 usec = (nsec + offset) / 1000;
502 while (unlikely(usec >= USEC_PER_SEC)) {
503 usec -= USEC_PER_SEC;
511 EXPORT_SYMBOL(do_gettimeofday);
516 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
517 * and therefore only yields usec accuracy
519 void getnstimeofday(struct timespec *tv)
524 tv->tv_sec = x.tv_sec;
525 tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
529 #if (BITS_PER_LONG < 64)
530 u64 get_jiffies_64(void)
536 seq = read_seqbegin(&xtime_lock);
538 } while (read_seqretry(&xtime_lock, seq));
542 EXPORT_SYMBOL(get_jiffies_64);
545 EXPORT_SYMBOL(jiffies);