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>
40 #include <asm/uaccess.h>
41 #include <asm/unistd.h>
43 #include "timeconst.h"
46 * The timezone where the local system is located. Used as a default by some
47 * programs who obtain this value by using gettimeofday.
49 struct timezone sys_tz;
51 EXPORT_SYMBOL(sys_tz);
53 #ifdef __ARCH_WANT_SYS_TIME
56 * sys_time() can be implemented in user-level using
57 * sys_gettimeofday(). Is this for backwards compatibility? If so,
58 * why not move it into the appropriate arch directory (for those
59 * architectures that need it).
61 asmlinkage long sys_time(time_t __user * tloc)
63 time_t i = get_seconds();
73 * sys_stime() can be implemented in user-level using
74 * sys_settimeofday(). Is this for backwards compatibility? If so,
75 * why not move it into the appropriate arch directory (for those
76 * architectures that need it).
79 asmlinkage long sys_stime(time_t __user *tptr)
84 if (get_user(tv.tv_sec, tptr))
89 err = security_settime(&tv, NULL);
97 #endif /* __ARCH_WANT_SYS_TIME */
99 asmlinkage long sys_gettimeofday(struct timeval __user *tv,
100 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 update_xtime_cache(0);
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 if (tv && !timespec_valid(tv))
160 error = security_settime(tv, tz);
165 /* SMP safe, global irq locking makes it work. */
167 update_vsyscall_tz();
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 asmlinkage long sys_adjtimex(struct timex __user *txc_p)
207 struct timex txc; /* Local copy of parameter */
210 /* Copy the user data space into the kernel copy
211 * structure. But bear in mind that the structures
214 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
216 ret = do_adjtimex(&txc);
217 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
221 * current_fs_time - Return FS time
224 * Return the current time truncated to the time granularity supported by
227 struct timespec current_fs_time(struct super_block *sb)
229 struct timespec now = current_kernel_time();
230 return timespec_trunc(now, sb->s_time_gran);
232 EXPORT_SYMBOL(current_fs_time);
235 * Convert jiffies to milliseconds and back.
237 * Avoid unnecessary multiplications/divisions in the
238 * two most common HZ cases:
240 unsigned int inline jiffies_to_msecs(const unsigned long j)
242 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
243 return (MSEC_PER_SEC / HZ) * j;
244 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
245 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
247 # if BITS_PER_LONG == 32
248 return ((u64)HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
250 return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
254 EXPORT_SYMBOL(jiffies_to_msecs);
256 unsigned int inline jiffies_to_usecs(const unsigned long j)
258 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
259 return (USEC_PER_SEC / HZ) * j;
260 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
261 return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
263 # if BITS_PER_LONG == 32
264 return ((u64)HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
266 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
270 EXPORT_SYMBOL(jiffies_to_usecs);
273 * timespec_trunc - Truncate timespec to a granularity
275 * @gran: Granularity in ns.
277 * Truncate a timespec to a granularity. gran must be smaller than a second.
278 * Always rounds down.
280 * This function should be only used for timestamps returned by
281 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
282 * it doesn't handle the better resolution of the latter.
284 struct timespec timespec_trunc(struct timespec t, unsigned gran)
287 * Division is pretty slow so avoid it for common cases.
288 * Currently current_kernel_time() never returns better than
289 * jiffies resolution. Exploit that.
291 if (gran <= jiffies_to_usecs(1) * 1000) {
293 } else if (gran == 1000000000) {
296 t.tv_nsec -= t.tv_nsec % gran;
300 EXPORT_SYMBOL(timespec_trunc);
302 #ifndef CONFIG_GENERIC_TIME
304 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
305 * and therefore only yields usec accuracy
307 void getnstimeofday(struct timespec *tv)
312 tv->tv_sec = x.tv_sec;
313 tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
315 EXPORT_SYMBOL_GPL(getnstimeofday);
318 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
319 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
320 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
322 * [For the Julian calendar (which was used in Russia before 1917,
323 * Britain & colonies before 1752, anywhere else before 1582,
324 * and is still in use by some communities) leave out the
325 * -year/100+year/400 terms, and add 10.]
327 * This algorithm was first published by Gauss (I think).
329 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
330 * machines where long is 32-bit! (However, as time_t is signed, we
331 * will already get problems at other places on 2038-01-19 03:14:08)
334 mktime(const unsigned int year0, const unsigned int mon0,
335 const unsigned int day, const unsigned int hour,
336 const unsigned int min, const unsigned int sec)
338 unsigned int mon = mon0, year = year0;
340 /* 1..12 -> 11,12,1..10 */
341 if (0 >= (int) (mon -= 2)) {
342 mon += 12; /* Puts Feb last since it has leap day */
346 return ((((unsigned long)
347 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
349 )*24 + hour /* now have hours */
350 )*60 + min /* now have minutes */
351 )*60 + sec; /* finally seconds */
354 EXPORT_SYMBOL(mktime);
357 * set_normalized_timespec - set timespec sec and nsec parts and normalize
359 * @ts: pointer to timespec variable to be set
360 * @sec: seconds to set
361 * @nsec: nanoseconds to set
363 * Set seconds and nanoseconds field of a timespec variable and
364 * normalize to the timespec storage format
366 * Note: The tv_nsec part is always in the range of
367 * 0 <= tv_nsec < NSEC_PER_SEC
368 * For negative values only the tv_sec field is negative !
370 void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
372 while (nsec >= NSEC_PER_SEC) {
373 nsec -= NSEC_PER_SEC;
377 nsec += NSEC_PER_SEC;
383 EXPORT_SYMBOL(set_normalized_timespec);
386 * ns_to_timespec - Convert nanoseconds to timespec
387 * @nsec: the nanoseconds value to be converted
389 * Returns the timespec representation of the nsec parameter.
391 struct timespec ns_to_timespec(const s64 nsec)
396 return (struct timespec) {0, 0};
398 ts.tv_sec = div_long_long_rem_signed(nsec, NSEC_PER_SEC, &ts.tv_nsec);
399 if (unlikely(nsec < 0))
400 set_normalized_timespec(&ts, ts.tv_sec, ts.tv_nsec);
404 EXPORT_SYMBOL(ns_to_timespec);
407 * ns_to_timeval - Convert nanoseconds to timeval
408 * @nsec: the nanoseconds value to be converted
410 * Returns the timeval representation of the nsec parameter.
412 struct timeval ns_to_timeval(const s64 nsec)
414 struct timespec ts = ns_to_timespec(nsec);
417 tv.tv_sec = ts.tv_sec;
418 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
422 EXPORT_SYMBOL(ns_to_timeval);
425 * When we convert to jiffies then we interpret incoming values
428 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
430 * - 'too large' values [that would result in larger than
431 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
433 * - all other values are converted to jiffies by either multiplying
434 * the input value by a factor or dividing it with a factor
436 * We must also be careful about 32-bit overflows.
438 unsigned long msecs_to_jiffies(const unsigned int m)
441 * Negative value, means infinite timeout:
444 return MAX_JIFFY_OFFSET;
446 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
448 * HZ is equal to or smaller than 1000, and 1000 is a nice
449 * round multiple of HZ, divide with the factor between them,
452 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
453 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
455 * HZ is larger than 1000, and HZ is a nice round multiple of
456 * 1000 - simply multiply with the factor between them.
458 * But first make sure the multiplication result cannot
461 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
462 return MAX_JIFFY_OFFSET;
464 return m * (HZ / MSEC_PER_SEC);
467 * Generic case - multiply, round and divide. But first
468 * check that if we are doing a net multiplication, that
469 * we wouldn't overflow:
471 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
472 return MAX_JIFFY_OFFSET;
474 return ((u64)MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
478 EXPORT_SYMBOL(msecs_to_jiffies);
480 unsigned long usecs_to_jiffies(const unsigned int u)
482 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
483 return MAX_JIFFY_OFFSET;
484 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
485 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
486 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
487 return u * (HZ / USEC_PER_SEC);
489 return ((u64)USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
493 EXPORT_SYMBOL(usecs_to_jiffies);
496 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
497 * that a remainder subtract here would not do the right thing as the
498 * resolution values don't fall on second boundries. I.e. the line:
499 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
501 * Rather, we just shift the bits off the right.
503 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
504 * value to a scaled second value.
507 timespec_to_jiffies(const struct timespec *value)
509 unsigned long sec = value->tv_sec;
510 long nsec = value->tv_nsec + TICK_NSEC - 1;
512 if (sec >= MAX_SEC_IN_JIFFIES){
513 sec = MAX_SEC_IN_JIFFIES;
516 return (((u64)sec * SEC_CONVERSION) +
517 (((u64)nsec * NSEC_CONVERSION) >>
518 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
521 EXPORT_SYMBOL(timespec_to_jiffies);
524 jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
527 * Convert jiffies to nanoseconds and separate with
530 u64 nsec = (u64)jiffies * TICK_NSEC;
531 value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_nsec);
533 EXPORT_SYMBOL(jiffies_to_timespec);
535 /* Same for "timeval"
537 * Well, almost. The problem here is that the real system resolution is
538 * in nanoseconds and the value being converted is in micro seconds.
539 * Also for some machines (those that use HZ = 1024, in-particular),
540 * there is a LARGE error in the tick size in microseconds.
542 * The solution we use is to do the rounding AFTER we convert the
543 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
544 * Instruction wise, this should cost only an additional add with carry
545 * instruction above the way it was done above.
548 timeval_to_jiffies(const struct timeval *value)
550 unsigned long sec = value->tv_sec;
551 long usec = value->tv_usec;
553 if (sec >= MAX_SEC_IN_JIFFIES){
554 sec = MAX_SEC_IN_JIFFIES;
557 return (((u64)sec * SEC_CONVERSION) +
558 (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
559 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
561 EXPORT_SYMBOL(timeval_to_jiffies);
563 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
566 * Convert jiffies to nanoseconds and separate with
569 u64 nsec = (u64)jiffies * TICK_NSEC;
572 value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &tv_usec);
573 tv_usec /= NSEC_PER_USEC;
574 value->tv_usec = tv_usec;
576 EXPORT_SYMBOL(jiffies_to_timeval);
579 * Convert jiffies/jiffies_64 to clock_t and back.
581 clock_t jiffies_to_clock_t(long x)
583 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
585 return x * (USER_HZ / HZ);
587 return x / (HZ / USER_HZ);
590 u64 tmp = (u64)x * TICK_NSEC;
591 do_div(tmp, (NSEC_PER_SEC / USER_HZ));
595 EXPORT_SYMBOL(jiffies_to_clock_t);
597 unsigned long clock_t_to_jiffies(unsigned long x)
599 #if (HZ % USER_HZ)==0
600 if (x >= ~0UL / (HZ / USER_HZ))
602 return x * (HZ / USER_HZ);
606 /* Don't worry about loss of precision here .. */
607 if (x >= ~0UL / HZ * USER_HZ)
610 /* .. but do try to contain it here */
612 do_div(jif, 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
625 do_div(x, HZ / USER_HZ);
631 * There are better ways that don't overflow early,
632 * but even this doesn't overflow in hundreds of years
636 do_div(x, (NSEC_PER_SEC / USER_HZ));
640 EXPORT_SYMBOL(jiffies_64_to_clock_t);
642 u64 nsec_to_clock_t(u64 x)
644 #if (NSEC_PER_SEC % USER_HZ) == 0
645 do_div(x, (NSEC_PER_SEC / USER_HZ));
646 #elif (USER_HZ % 512) == 0
648 do_div(x, (NSEC_PER_SEC / 512));
651 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
652 * overflow after 64.99 years.
653 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
656 do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2)) /
662 #if (BITS_PER_LONG < 64)
663 u64 get_jiffies_64(void)
669 seq = read_seqbegin(&xtime_lock);
671 } while (read_seqretry(&xtime_lock, seq));
674 EXPORT_SYMBOL(get_jiffies_64);
677 EXPORT_SYMBOL(jiffies);