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>
41 #include <asm/uaccess.h>
42 #include <asm/unistd.h>
44 #include "timeconst.h"
47 * The timezone where the local system is located. Used as a default by some
48 * programs who obtain this value by using gettimeofday.
50 struct timezone sys_tz;
52 EXPORT_SYMBOL(sys_tz);
54 #ifdef __ARCH_WANT_SYS_TIME
57 * sys_time() can be implemented in user-level using
58 * sys_gettimeofday(). Is this for backwards compatibility? If so,
59 * why not move it into the appropriate arch directory (for those
60 * architectures that need it).
62 asmlinkage long sys_time(time_t __user * tloc)
64 time_t i = get_seconds();
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,
101 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 update_xtime_cache(0);
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. */
168 update_vsyscall_tz();
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;
222 * current_fs_time - Return FS time
225 * Return the current time truncated to the time granularity supported by
228 struct timespec current_fs_time(struct super_block *sb)
230 struct timespec now = current_kernel_time();
231 return timespec_trunc(now, sb->s_time_gran);
233 EXPORT_SYMBOL(current_fs_time);
236 * Convert jiffies to milliseconds and back.
238 * Avoid unnecessary multiplications/divisions in the
239 * two most common HZ cases:
241 unsigned int inline jiffies_to_msecs(const unsigned long j)
243 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
244 return (MSEC_PER_SEC / HZ) * j;
245 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
246 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
248 # if BITS_PER_LONG == 32
249 return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
251 return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
255 EXPORT_SYMBOL(jiffies_to_msecs);
257 unsigned int inline jiffies_to_usecs(const unsigned long j)
259 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
260 return (USEC_PER_SEC / HZ) * j;
261 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
262 return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
264 # if BITS_PER_LONG == 32
265 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
267 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
271 EXPORT_SYMBOL(jiffies_to_usecs);
274 * timespec_trunc - Truncate timespec to a granularity
276 * @gran: Granularity in ns.
278 * Truncate a timespec to a granularity. gran must be smaller than a second.
279 * Always rounds down.
281 * This function should be only used for timestamps returned by
282 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
283 * it doesn't handle the better resolution of the latter.
285 struct timespec timespec_trunc(struct timespec t, unsigned gran)
288 * Division is pretty slow so avoid it for common cases.
289 * Currently current_kernel_time() never returns better than
290 * jiffies resolution. Exploit that.
292 if (gran <= jiffies_to_usecs(1) * 1000) {
294 } else if (gran == 1000000000) {
297 t.tv_nsec -= t.tv_nsec % gran;
301 EXPORT_SYMBOL(timespec_trunc);
303 #ifndef CONFIG_GENERIC_TIME
305 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
306 * and therefore only yields usec accuracy
308 void getnstimeofday(struct timespec *tv)
313 tv->tv_sec = x.tv_sec;
314 tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
316 EXPORT_SYMBOL_GPL(getnstimeofday);
319 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
320 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
321 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
323 * [For the Julian calendar (which was used in Russia before 1917,
324 * Britain & colonies before 1752, anywhere else before 1582,
325 * and is still in use by some communities) leave out the
326 * -year/100+year/400 terms, and add 10.]
328 * This algorithm was first published by Gauss (I think).
330 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
331 * machines where long is 32-bit! (However, as time_t is signed, we
332 * will already get problems at other places on 2038-01-19 03:14:08)
335 mktime(const unsigned int year0, const unsigned int mon0,
336 const unsigned int day, const unsigned int hour,
337 const unsigned int min, const unsigned int sec)
339 unsigned int mon = mon0, year = year0;
341 /* 1..12 -> 11,12,1..10 */
342 if (0 >= (int) (mon -= 2)) {
343 mon += 12; /* Puts Feb last since it has leap day */
347 return ((((unsigned long)
348 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
350 )*24 + hour /* now have hours */
351 )*60 + min /* now have minutes */
352 )*60 + sec; /* finally seconds */
355 EXPORT_SYMBOL(mktime);
358 * set_normalized_timespec - set timespec sec and nsec parts and normalize
360 * @ts: pointer to timespec variable to be set
361 * @sec: seconds to set
362 * @nsec: nanoseconds to set
364 * Set seconds and nanoseconds field of a timespec variable and
365 * normalize to the timespec storage format
367 * Note: The tv_nsec part is always in the range of
368 * 0 <= tv_nsec < NSEC_PER_SEC
369 * For negative values only the tv_sec field is negative !
371 void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
373 while (nsec >= NSEC_PER_SEC) {
374 nsec -= NSEC_PER_SEC;
378 nsec += NSEC_PER_SEC;
384 EXPORT_SYMBOL(set_normalized_timespec);
387 * ns_to_timespec - Convert nanoseconds to timespec
388 * @nsec: the nanoseconds value to be converted
390 * Returns the timespec representation of the nsec parameter.
392 struct timespec ns_to_timespec(const s64 nsec)
398 return (struct timespec) {0, 0};
400 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
401 if (unlikely(rem < 0)) {
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 wouldn't overflow:
476 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
477 return MAX_JIFFY_OFFSET;
479 return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
483 EXPORT_SYMBOL(msecs_to_jiffies);
485 unsigned long usecs_to_jiffies(const unsigned int u)
487 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
488 return MAX_JIFFY_OFFSET;
489 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
490 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
491 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
492 return u * (HZ / USEC_PER_SEC);
494 return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
498 EXPORT_SYMBOL(usecs_to_jiffies);
501 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
502 * that a remainder subtract here would not do the right thing as the
503 * resolution values don't fall on second boundries. I.e. the line:
504 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
506 * Rather, we just shift the bits off the right.
508 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
509 * value to a scaled second value.
512 timespec_to_jiffies(const struct timespec *value)
514 unsigned long sec = value->tv_sec;
515 long nsec = value->tv_nsec + TICK_NSEC - 1;
517 if (sec >= MAX_SEC_IN_JIFFIES){
518 sec = MAX_SEC_IN_JIFFIES;
521 return (((u64)sec * SEC_CONVERSION) +
522 (((u64)nsec * NSEC_CONVERSION) >>
523 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
526 EXPORT_SYMBOL(timespec_to_jiffies);
529 jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
532 * Convert jiffies to nanoseconds and separate with
536 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
538 value->tv_nsec = rem;
540 EXPORT_SYMBOL(jiffies_to_timespec);
542 /* Same for "timeval"
544 * Well, almost. The problem here is that the real system resolution is
545 * in nanoseconds and the value being converted is in micro seconds.
546 * Also for some machines (those that use HZ = 1024, in-particular),
547 * there is a LARGE error in the tick size in microseconds.
549 * The solution we use is to do the rounding AFTER we convert the
550 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
551 * Instruction wise, this should cost only an additional add with carry
552 * instruction above the way it was done above.
555 timeval_to_jiffies(const struct timeval *value)
557 unsigned long sec = value->tv_sec;
558 long usec = value->tv_usec;
560 if (sec >= MAX_SEC_IN_JIFFIES){
561 sec = MAX_SEC_IN_JIFFIES;
564 return (((u64)sec * SEC_CONVERSION) +
565 (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
566 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
568 EXPORT_SYMBOL(timeval_to_jiffies);
570 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
573 * Convert jiffies to nanoseconds and separate with
578 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
580 value->tv_usec = rem / NSEC_PER_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
591 return x * (USER_HZ / HZ);
593 return x / (HZ / USER_HZ);
596 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
599 EXPORT_SYMBOL(jiffies_to_clock_t);
601 unsigned long clock_t_to_jiffies(unsigned long x)
603 #if (HZ % USER_HZ)==0
604 if (x >= ~0UL / (HZ / USER_HZ))
606 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 */
613 return div_u64((u64)x * HZ, USER_HZ);
616 EXPORT_SYMBOL(clock_t_to_jiffies);
618 u64 jiffies_64_to_clock_t(u64 x)
620 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
622 x = div_u64(x * USER_HZ, HZ);
624 x = div_u64(x, HZ / USER_HZ);
630 * There are better ways that don't overflow early,
631 * but even this doesn't overflow in hundreds of years
634 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
638 EXPORT_SYMBOL(jiffies_64_to_clock_t);
640 u64 nsec_to_clock_t(u64 x)
642 #if (NSEC_PER_SEC % USER_HZ) == 0
643 return div_u64(x, NSEC_PER_SEC / USER_HZ);
644 #elif (USER_HZ % 512) == 0
645 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
648 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
649 * overflow after 64.99 years.
650 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
652 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
656 #if (BITS_PER_LONG < 64)
657 u64 get_jiffies_64(void)
663 seq = read_seqbegin(&xtime_lock);
665 } while (read_seqretry(&xtime_lock, seq));
668 EXPORT_SYMBOL(get_jiffies_64);
671 EXPORT_SYMBOL(jiffies);
674 * Add two timespec values and do a safety check for overflow.
675 * It's assumed that both values are valid (>= 0)
677 struct timespec timespec_add_safe(const struct timespec lhs,
678 const struct timespec rhs)
682 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
683 lhs.tv_nsec + rhs.tv_nsec);
685 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
686 res.tv_sec = TIME_T_MAX;