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/syscalls.h>
35 #include <linux/security.h>
37 #include <linux/module.h>
39 #include <asm/uaccess.h>
40 #include <asm/unistd.h>
43 * The timezone where the local system is located. Used as a default by some
44 * programs who obtain this value by using gettimeofday.
46 struct timezone sys_tz;
48 EXPORT_SYMBOL(sys_tz);
50 #ifdef __ARCH_WANT_SYS_TIME
53 * sys_time() can be implemented in user-level using
54 * sys_gettimeofday(). Is this for backwards compatibility? If so,
55 * why not move it into the appropriate arch directory (for those
56 * architectures that need it).
58 asmlinkage long sys_time(time_t __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 static inline 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 write_sequnlock_irq(&xtime_lock);
141 * In case for some reason the CMOS clock has not already been running
142 * in UTC, but in some local time: The first time we set the timezone,
143 * we will warp the clock so that it is ticking UTC time instead of
144 * local time. Presumably, if someone is setting the timezone then we
145 * are running in an environment where the programs understand about
146 * timezones. This should be done at boot time in the /etc/rc script,
147 * as soon as possible, so that the clock can be set right. Otherwise,
148 * various programs will get confused when the clock gets warped.
151 int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
153 static int firsttime = 1;
156 if (tv && !timespec_valid(tv))
159 error = security_settime(tv, tz);
164 /* SMP safe, global irq locking makes it work. */
174 /* SMP safe, again the code in arch/foo/time.c should
175 * globally block out interrupts when it runs.
177 return do_settimeofday(tv);
182 asmlinkage long sys_settimeofday(struct timeval __user *tv,
183 struct timezone __user *tz)
185 struct timeval user_tv;
186 struct timespec new_ts;
187 struct timezone new_tz;
190 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
192 new_ts.tv_sec = user_tv.tv_sec;
193 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
196 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
200 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
203 asmlinkage long sys_adjtimex(struct timex __user *txc_p)
205 struct timex txc; /* Local copy of parameter */
208 /* Copy the user data space into the kernel copy
209 * structure. But bear in mind that the structures
212 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
214 ret = do_adjtimex(&txc);
215 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
218 inline struct timespec current_kernel_time(void)
224 seq = read_seqbegin(&xtime_lock);
227 } while (read_seqretry(&xtime_lock, seq));
232 EXPORT_SYMBOL(current_kernel_time);
235 * current_fs_time - Return FS time
238 * Return the current time truncated to the time granularity supported by
241 struct timespec current_fs_time(struct super_block *sb)
243 struct timespec now = current_kernel_time();
244 return timespec_trunc(now, sb->s_time_gran);
246 EXPORT_SYMBOL(current_fs_time);
249 * Convert jiffies to milliseconds and back.
251 * Avoid unnecessary multiplications/divisions in the
252 * two most common HZ cases:
254 unsigned int inline jiffies_to_msecs(const unsigned long j)
256 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
257 return (MSEC_PER_SEC / HZ) * j;
258 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
259 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
261 return (j * MSEC_PER_SEC) / HZ;
264 EXPORT_SYMBOL(jiffies_to_msecs);
266 unsigned int inline jiffies_to_usecs(const unsigned long j)
268 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
269 return (USEC_PER_SEC / HZ) * j;
270 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
271 return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
273 return (j * USEC_PER_SEC) / HZ;
276 EXPORT_SYMBOL(jiffies_to_usecs);
279 * timespec_trunc - Truncate timespec to a granularity
281 * @gran: Granularity in ns.
283 * Truncate a timespec to a granularity. gran must be smaller than a second.
284 * Always rounds down.
286 * This function should be only used for timestamps returned by
287 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
288 * it doesn't handle the better resolution of the later.
290 struct timespec timespec_trunc(struct timespec t, unsigned gran)
293 * Division is pretty slow so avoid it for common cases.
294 * Currently current_kernel_time() never returns better than
295 * jiffies resolution. Exploit that.
297 if (gran <= jiffies_to_usecs(1) * 1000) {
299 } else if (gran == 1000000000) {
302 t.tv_nsec -= t.tv_nsec % gran;
306 EXPORT_SYMBOL(timespec_trunc);
308 #ifndef CONFIG_GENERIC_TIME
310 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
311 * and therefore only yields usec accuracy
313 void getnstimeofday(struct timespec *tv)
318 tv->tv_sec = x.tv_sec;
319 tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
321 EXPORT_SYMBOL_GPL(getnstimeofday);
324 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
325 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
326 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
328 * [For the Julian calendar (which was used in Russia before 1917,
329 * Britain & colonies before 1752, anywhere else before 1582,
330 * and is still in use by some communities) leave out the
331 * -year/100+year/400 terms, and add 10.]
333 * This algorithm was first published by Gauss (I think).
335 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
336 * machines were long is 32-bit! (However, as time_t is signed, we
337 * will already get problems at other places on 2038-01-19 03:14:08)
340 mktime(const unsigned int year0, const unsigned int mon0,
341 const unsigned int day, const unsigned int hour,
342 const unsigned int min, const unsigned int sec)
344 unsigned int mon = mon0, year = year0;
346 /* 1..12 -> 11,12,1..10 */
347 if (0 >= (int) (mon -= 2)) {
348 mon += 12; /* Puts Feb last since it has leap day */
352 return ((((unsigned long)
353 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
355 )*24 + hour /* now have hours */
356 )*60 + min /* now have minutes */
357 )*60 + sec; /* finally seconds */
360 EXPORT_SYMBOL(mktime);
363 * set_normalized_timespec - set timespec sec and nsec parts and normalize
365 * @ts: pointer to timespec variable to be set
366 * @sec: seconds to set
367 * @nsec: nanoseconds to set
369 * Set seconds and nanoseconds field of a timespec variable and
370 * normalize to the timespec storage format
372 * Note: The tv_nsec part is always in the range of
373 * 0 <= tv_nsec < NSEC_PER_SEC
374 * For negative values only the tv_sec field is negative !
376 void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
378 while (nsec >= NSEC_PER_SEC) {
379 nsec -= NSEC_PER_SEC;
383 nsec += NSEC_PER_SEC;
391 * ns_to_timespec - Convert nanoseconds to timespec
392 * @nsec: the nanoseconds value to be converted
394 * Returns the timespec representation of the nsec parameter.
396 struct timespec ns_to_timespec(const s64 nsec)
401 return (struct timespec) {0, 0};
403 ts.tv_sec = div_long_long_rem_signed(nsec, NSEC_PER_SEC, &ts.tv_nsec);
404 if (unlikely(nsec < 0))
405 set_normalized_timespec(&ts, ts.tv_sec, ts.tv_nsec);
409 EXPORT_SYMBOL(ns_to_timespec);
412 * ns_to_timeval - Convert nanoseconds to timeval
413 * @nsec: the nanoseconds value to be converted
415 * Returns the timeval representation of the nsec parameter.
417 struct timeval ns_to_timeval(const s64 nsec)
419 struct timespec ts = ns_to_timespec(nsec);
422 tv.tv_sec = ts.tv_sec;
423 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
427 EXPORT_SYMBOL(ns_to_timeval);
430 * When we convert to jiffies then we interpret incoming values
433 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
435 * - 'too large' values [that would result in larger than
436 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
438 * - all other values are converted to jiffies by either multiplying
439 * the input value by a factor or dividing it with a factor
441 * We must also be careful about 32-bit overflows.
443 unsigned long msecs_to_jiffies(const unsigned int m)
446 * Negative value, means infinite timeout:
449 return MAX_JIFFY_OFFSET;
451 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
453 * HZ is equal to or smaller than 1000, and 1000 is a nice
454 * round multiple of HZ, divide with the factor between them,
457 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
458 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
460 * HZ is larger than 1000, and HZ is a nice round multiple of
461 * 1000 - simply multiply with the factor between them.
463 * But first make sure the multiplication result cannot
466 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
467 return MAX_JIFFY_OFFSET;
469 return m * (HZ / MSEC_PER_SEC);
472 * Generic case - multiply, round and divide. But first
473 * check that if we are doing a net multiplication, that
474 * we wouldnt overflow:
476 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
477 return MAX_JIFFY_OFFSET;
479 return (m * HZ + MSEC_PER_SEC - 1) / MSEC_PER_SEC;
482 EXPORT_SYMBOL(msecs_to_jiffies);
484 unsigned long usecs_to_jiffies(const unsigned int u)
486 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
487 return MAX_JIFFY_OFFSET;
488 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
489 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
490 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
491 return u * (HZ / USEC_PER_SEC);
493 return (u * HZ + USEC_PER_SEC - 1) / USEC_PER_SEC;
496 EXPORT_SYMBOL(usecs_to_jiffies);
499 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
500 * that a remainder subtract here would not do the right thing as the
501 * resolution values don't fall on second boundries. I.e. the line:
502 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
504 * Rather, we just shift the bits off the right.
506 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
507 * value to a scaled second value.
510 timespec_to_jiffies(const struct timespec *value)
512 unsigned long sec = value->tv_sec;
513 long nsec = value->tv_nsec + TICK_NSEC - 1;
515 if (sec >= MAX_SEC_IN_JIFFIES){
516 sec = MAX_SEC_IN_JIFFIES;
519 return (((u64)sec * SEC_CONVERSION) +
520 (((u64)nsec * NSEC_CONVERSION) >>
521 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
524 EXPORT_SYMBOL(timespec_to_jiffies);
527 jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
530 * Convert jiffies to nanoseconds and separate with
533 u64 nsec = (u64)jiffies * TICK_NSEC;
534 value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_nsec);
536 EXPORT_SYMBOL(jiffies_to_timespec);
538 /* Same for "timeval"
540 * Well, almost. The problem here is that the real system resolution is
541 * in nanoseconds and the value being converted is in micro seconds.
542 * Also for some machines (those that use HZ = 1024, in-particular),
543 * there is a LARGE error in the tick size in microseconds.
545 * The solution we use is to do the rounding AFTER we convert the
546 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
547 * Instruction wise, this should cost only an additional add with carry
548 * instruction above the way it was done above.
551 timeval_to_jiffies(const struct timeval *value)
553 unsigned long sec = value->tv_sec;
554 long usec = value->tv_usec;
556 if (sec >= MAX_SEC_IN_JIFFIES){
557 sec = MAX_SEC_IN_JIFFIES;
560 return (((u64)sec * SEC_CONVERSION) +
561 (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
562 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
564 EXPORT_SYMBOL(timeval_to_jiffies);
566 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
569 * Convert jiffies to nanoseconds and separate with
572 u64 nsec = (u64)jiffies * TICK_NSEC;
575 value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &tv_usec);
576 tv_usec /= NSEC_PER_USEC;
577 value->tv_usec = tv_usec;
579 EXPORT_SYMBOL(jiffies_to_timeval);
582 * Convert jiffies/jiffies_64 to clock_t and back.
584 clock_t jiffies_to_clock_t(long x)
586 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
587 return x / (HZ / USER_HZ);
589 u64 tmp = (u64)x * TICK_NSEC;
590 do_div(tmp, (NSEC_PER_SEC / USER_HZ));
594 EXPORT_SYMBOL(jiffies_to_clock_t);
596 unsigned long clock_t_to_jiffies(unsigned long x)
598 #if (HZ % USER_HZ)==0
599 if (x >= ~0UL / (HZ / USER_HZ))
601 return x * (HZ / USER_HZ);
605 /* Don't worry about loss of precision here .. */
606 if (x >= ~0UL / HZ * USER_HZ)
609 /* .. but do try to contain it here */
611 do_div(jif, USER_HZ);
615 EXPORT_SYMBOL(clock_t_to_jiffies);
617 u64 jiffies_64_to_clock_t(u64 x)
619 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
620 do_div(x, HZ / USER_HZ);
623 * There are better ways that don't overflow early,
624 * but even this doesn't overflow in hundreds of years
628 do_div(x, (NSEC_PER_SEC / USER_HZ));
633 EXPORT_SYMBOL(jiffies_64_to_clock_t);
635 u64 nsec_to_clock_t(u64 x)
637 #if (NSEC_PER_SEC % USER_HZ) == 0
638 do_div(x, (NSEC_PER_SEC / USER_HZ));
639 #elif (USER_HZ % 512) == 0
641 do_div(x, (NSEC_PER_SEC / 512));
644 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
645 * overflow after 64.99 years.
646 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
649 do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2)) /
655 #if (BITS_PER_LONG < 64)
656 u64 get_jiffies_64(void)
662 seq = read_seqbegin(&xtime_lock);
664 } while (read_seqretry(&xtime_lock, seq));
668 EXPORT_SYMBOL(get_jiffies_64);
671 EXPORT_SYMBOL(jiffies);