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)
61 * We read xtime.tv_sec atomically - it's updated
62 * atomically by update_wall_time(), so no need to
63 * even read-lock the xtime seqlock:
65 time_t i = xtime.tv_sec;
67 smp_rmb(); /* sys_time() results are coherent */
70 if (put_user(i, tloc))
77 * sys_stime() can be implemented in user-level using
78 * sys_settimeofday(). Is this for backwards compatibility? If so,
79 * why not move it into the appropriate arch directory (for those
80 * architectures that need it).
83 asmlinkage long sys_stime(time_t __user *tptr)
88 if (get_user(tv.tv_sec, tptr))
93 err = security_settime(&tv, NULL);
101 #endif /* __ARCH_WANT_SYS_TIME */
103 asmlinkage long sys_gettimeofday(struct timeval __user *tv, 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 write_sequnlock_irq(&xtime_lock);
144 * In case for some reason the CMOS clock has not already been running
145 * in UTC, but in some local time: The first time we set the timezone,
146 * we will warp the clock so that it is ticking UTC time instead of
147 * local time. Presumably, if someone is setting the timezone then we
148 * are running in an environment where the programs understand about
149 * timezones. This should be done at boot time in the /etc/rc script,
150 * as soon as possible, so that the clock can be set right. Otherwise,
151 * various programs will get confused when the clock gets warped.
154 int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
156 static int firsttime = 1;
159 if (tv && !timespec_valid(tv))
162 error = security_settime(tv, tz);
167 /* SMP safe, global irq locking makes it work. */
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 asmlinkage long sys_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 asmlinkage long sys_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;
221 inline struct timespec current_kernel_time(void)
227 seq = read_seqbegin(&xtime_lock);
230 } while (read_seqretry(&xtime_lock, seq));
235 EXPORT_SYMBOL(current_kernel_time);
238 * current_fs_time - Return FS time
241 * Return the current time truncated to the time granularity supported by
244 struct timespec current_fs_time(struct super_block *sb)
246 struct timespec now = current_kernel_time();
247 return timespec_trunc(now, sb->s_time_gran);
249 EXPORT_SYMBOL(current_fs_time);
252 * Convert jiffies to milliseconds and back.
254 * Avoid unnecessary multiplications/divisions in the
255 * two most common HZ cases:
257 unsigned int inline jiffies_to_msecs(const unsigned long j)
259 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
260 return (MSEC_PER_SEC / HZ) * j;
261 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
262 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
264 return (j * MSEC_PER_SEC) / HZ;
267 EXPORT_SYMBOL(jiffies_to_msecs);
269 unsigned int inline jiffies_to_usecs(const unsigned long j)
271 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
272 return (USEC_PER_SEC / HZ) * j;
273 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
274 return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
276 return (j * USEC_PER_SEC) / HZ;
279 EXPORT_SYMBOL(jiffies_to_usecs);
282 * timespec_trunc - Truncate timespec to a granularity
284 * @gran: Granularity in ns.
286 * Truncate a timespec to a granularity. gran must be smaller than a second.
287 * Always rounds down.
289 * This function should be only used for timestamps returned by
290 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
291 * it doesn't handle the better resolution of the later.
293 struct timespec timespec_trunc(struct timespec t, unsigned gran)
296 * Division is pretty slow so avoid it for common cases.
297 * Currently current_kernel_time() never returns better than
298 * jiffies resolution. Exploit that.
300 if (gran <= jiffies_to_usecs(1) * 1000) {
302 } else if (gran == 1000000000) {
305 t.tv_nsec -= t.tv_nsec % gran;
309 EXPORT_SYMBOL(timespec_trunc);
311 #ifndef CONFIG_GENERIC_TIME
313 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
314 * and therefore only yields usec accuracy
316 void getnstimeofday(struct timespec *tv)
321 tv->tv_sec = x.tv_sec;
322 tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
324 EXPORT_SYMBOL_GPL(getnstimeofday);
327 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
328 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
329 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
331 * [For the Julian calendar (which was used in Russia before 1917,
332 * Britain & colonies before 1752, anywhere else before 1582,
333 * and is still in use by some communities) leave out the
334 * -year/100+year/400 terms, and add 10.]
336 * This algorithm was first published by Gauss (I think).
338 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
339 * machines were long is 32-bit! (However, as time_t is signed, we
340 * will already get problems at other places on 2038-01-19 03:14:08)
343 mktime(const unsigned int year0, const unsigned int mon0,
344 const unsigned int day, const unsigned int hour,
345 const unsigned int min, const unsigned int sec)
347 unsigned int mon = mon0, year = year0;
349 /* 1..12 -> 11,12,1..10 */
350 if (0 >= (int) (mon -= 2)) {
351 mon += 12; /* Puts Feb last since it has leap day */
355 return ((((unsigned long)
356 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
358 )*24 + hour /* now have hours */
359 )*60 + min /* now have minutes */
360 )*60 + sec; /* finally seconds */
363 EXPORT_SYMBOL(mktime);
366 * set_normalized_timespec - set timespec sec and nsec parts and normalize
368 * @ts: pointer to timespec variable to be set
369 * @sec: seconds to set
370 * @nsec: nanoseconds to set
372 * Set seconds and nanoseconds field of a timespec variable and
373 * normalize to the timespec storage format
375 * Note: The tv_nsec part is always in the range of
376 * 0 <= tv_nsec < NSEC_PER_SEC
377 * For negative values only the tv_sec field is negative !
379 void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
381 while (nsec >= NSEC_PER_SEC) {
382 nsec -= NSEC_PER_SEC;
386 nsec += NSEC_PER_SEC;
394 * ns_to_timespec - Convert nanoseconds to timespec
395 * @nsec: the nanoseconds value to be converted
397 * Returns the timespec representation of the nsec parameter.
399 struct timespec ns_to_timespec(const s64 nsec)
404 return (struct timespec) {0, 0};
406 ts.tv_sec = div_long_long_rem_signed(nsec, NSEC_PER_SEC, &ts.tv_nsec);
407 if (unlikely(nsec < 0))
408 set_normalized_timespec(&ts, ts.tv_sec, ts.tv_nsec);
412 EXPORT_SYMBOL(ns_to_timespec);
415 * ns_to_timeval - Convert nanoseconds to timeval
416 * @nsec: the nanoseconds value to be converted
418 * Returns the timeval representation of the nsec parameter.
420 struct timeval ns_to_timeval(const s64 nsec)
422 struct timespec ts = ns_to_timespec(nsec);
425 tv.tv_sec = ts.tv_sec;
426 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
430 EXPORT_SYMBOL(ns_to_timeval);
433 * When we convert to jiffies then we interpret incoming values
436 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
438 * - 'too large' values [that would result in larger than
439 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
441 * - all other values are converted to jiffies by either multiplying
442 * the input value by a factor or dividing it with a factor
444 * We must also be careful about 32-bit overflows.
446 unsigned long msecs_to_jiffies(const unsigned int m)
449 * Negative value, means infinite timeout:
452 return MAX_JIFFY_OFFSET;
454 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
456 * HZ is equal to or smaller than 1000, and 1000 is a nice
457 * round multiple of HZ, divide with the factor between them,
460 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
461 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
463 * HZ is larger than 1000, and HZ is a nice round multiple of
464 * 1000 - simply multiply with the factor between them.
466 * But first make sure the multiplication result cannot
469 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
470 return MAX_JIFFY_OFFSET;
472 return m * (HZ / MSEC_PER_SEC);
475 * Generic case - multiply, round and divide. But first
476 * check that if we are doing a net multiplication, that
477 * we wouldnt overflow:
479 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
480 return MAX_JIFFY_OFFSET;
482 return (m * HZ + MSEC_PER_SEC - 1) / MSEC_PER_SEC;
485 EXPORT_SYMBOL(msecs_to_jiffies);
487 unsigned long usecs_to_jiffies(const unsigned int u)
489 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
490 return MAX_JIFFY_OFFSET;
491 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
492 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
493 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
494 return u * (HZ / USEC_PER_SEC);
496 return (u * HZ + USEC_PER_SEC - 1) / USEC_PER_SEC;
499 EXPORT_SYMBOL(usecs_to_jiffies);
502 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
503 * that a remainder subtract here would not do the right thing as the
504 * resolution values don't fall on second boundries. I.e. the line:
505 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
507 * Rather, we just shift the bits off the right.
509 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
510 * value to a scaled second value.
513 timespec_to_jiffies(const struct timespec *value)
515 unsigned long sec = value->tv_sec;
516 long nsec = value->tv_nsec + TICK_NSEC - 1;
518 if (sec >= MAX_SEC_IN_JIFFIES){
519 sec = MAX_SEC_IN_JIFFIES;
522 return (((u64)sec * SEC_CONVERSION) +
523 (((u64)nsec * NSEC_CONVERSION) >>
524 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
527 EXPORT_SYMBOL(timespec_to_jiffies);
530 jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
533 * Convert jiffies to nanoseconds and separate with
536 u64 nsec = (u64)jiffies * TICK_NSEC;
537 value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_nsec);
539 EXPORT_SYMBOL(jiffies_to_timespec);
541 /* Same for "timeval"
543 * Well, almost. The problem here is that the real system resolution is
544 * in nanoseconds and the value being converted is in micro seconds.
545 * Also for some machines (those that use HZ = 1024, in-particular),
546 * there is a LARGE error in the tick size in microseconds.
548 * The solution we use is to do the rounding AFTER we convert the
549 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
550 * Instruction wise, this should cost only an additional add with carry
551 * instruction above the way it was done above.
554 timeval_to_jiffies(const struct timeval *value)
556 unsigned long sec = value->tv_sec;
557 long usec = value->tv_usec;
559 if (sec >= MAX_SEC_IN_JIFFIES){
560 sec = MAX_SEC_IN_JIFFIES;
563 return (((u64)sec * SEC_CONVERSION) +
564 (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
565 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
567 EXPORT_SYMBOL(timeval_to_jiffies);
569 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
572 * Convert jiffies to nanoseconds and separate with
575 u64 nsec = (u64)jiffies * TICK_NSEC;
578 value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &tv_usec);
579 tv_usec /= NSEC_PER_USEC;
580 value->tv_usec = tv_usec;
582 EXPORT_SYMBOL(jiffies_to_timeval);
585 * Convert jiffies/jiffies_64 to clock_t and back.
587 clock_t jiffies_to_clock_t(long x)
589 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
590 return x / (HZ / USER_HZ);
592 u64 tmp = (u64)x * TICK_NSEC;
593 do_div(tmp, (NSEC_PER_SEC / USER_HZ));
597 EXPORT_SYMBOL(jiffies_to_clock_t);
599 unsigned long clock_t_to_jiffies(unsigned long x)
601 #if (HZ % USER_HZ)==0
602 if (x >= ~0UL / (HZ / USER_HZ))
604 return x * (HZ / USER_HZ);
608 /* Don't worry about loss of precision here .. */
609 if (x >= ~0UL / HZ * USER_HZ)
612 /* .. but do try to contain it here */
614 do_div(jif, USER_HZ);
618 EXPORT_SYMBOL(clock_t_to_jiffies);
620 u64 jiffies_64_to_clock_t(u64 x)
622 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
623 do_div(x, HZ / USER_HZ);
626 * There are better ways that don't overflow early,
627 * but even this doesn't overflow in hundreds of years
631 do_div(x, (NSEC_PER_SEC / USER_HZ));
636 EXPORT_SYMBOL(jiffies_64_to_clock_t);
638 u64 nsec_to_clock_t(u64 x)
640 #if (NSEC_PER_SEC % USER_HZ) == 0
641 do_div(x, (NSEC_PER_SEC / USER_HZ));
642 #elif (USER_HZ % 512) == 0
644 do_div(x, (NSEC_PER_SEC / 512));
647 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
648 * overflow after 64.99 years.
649 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
652 do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2)) /
658 #if (BITS_PER_LONG < 64)
659 u64 get_jiffies_64(void)
665 seq = read_seqbegin(&xtime_lock);
667 } while (read_seqretry(&xtime_lock, seq));
671 EXPORT_SYMBOL(get_jiffies_64);
674 EXPORT_SYMBOL(jiffies);