projects/linux·blob v2.6.24 · refs

652 lines · 16.8 KiB

1/*
2 * linux/kernel/time.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 * This file contains the interface functions for the various
7 * time related system calls: time, stime, gettimeofday, settimeofday,
8 * adjtime
9 */
10/*
11 * Modification history kernel/time.c
12 *
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
28 */
29
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>
37#include <linux/fs.h>
38
39#include <asm/uaccess.h>
40#include <asm/unistd.h>
41
42/*
43 * The timezone where the local system is located. Used as a default by some
44 * programs who obtain this value by using gettimeofday.
45 */
46struct timezone sys_tz;
47
48EXPORT_SYMBOL(sys_tz);
49
50#ifdef __ARCH_WANT_SYS_TIME
51
52/*
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).
57 */
58asmlinkage long sys_time(time_t __user * tloc)
59{
60 time_t i = get_seconds();
61
62 if (tloc) {
63 if (put_user(i,tloc))
64 i = -EFAULT;
65 }
66 return i;
67}
68
69/*
70 * sys_stime() can be implemented in user-level using
71 * sys_settimeofday(). Is this for backwards compatibility? If so,
72 * why not move it into the appropriate arch directory (for those
73 * architectures that need it).
74 */
75
76asmlinkage long sys_stime(time_t __user *tptr)
77{
78 struct timespec tv;
79 int err;
80
81 if (get_user(tv.tv_sec, tptr))
82 return -EFAULT;
83
84 tv.tv_nsec = 0;
85
86 err = security_settime(&tv, NULL);
87 if (err)
88 return err;
89
90 do_settimeofday(&tv);
91 return 0;
92}
93
94#endif /* __ARCH_WANT_SYS_TIME */
95
96asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __user *tz)
97{
98 if (likely(tv != NULL)) {
99 struct timeval ktv;
100 do_gettimeofday(&ktv);
101 if (copy_to_user(tv, &ktv, sizeof(ktv)))
102 return -EFAULT;
103 }
104 if (unlikely(tz != NULL)) {
105 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
106 return -EFAULT;
107 }
108 return 0;
109}
110
111/*
112 * Adjust the time obtained from the CMOS to be UTC time instead of
113 * local time.
114 *
115 * This is ugly, but preferable to the alternatives. Otherwise we
116 * would either need to write a program to do it in /etc/rc (and risk
117 * confusion if the program gets run more than once; it would also be
118 * hard to make the program warp the clock precisely n hours) or
119 * compile in the timezone information into the kernel. Bad, bad....
120 *
121 * - TYT, 1992-01-01
122 *
123 * The best thing to do is to keep the CMOS clock in universal time (UTC)
124 * as real UNIX machines always do it. This avoids all headaches about
125 * daylight saving times and warping kernel clocks.
126 */
127static inline void warp_clock(void)
128{
129 write_seqlock_irq(&xtime_lock);
130 wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
131 xtime.tv_sec += sys_tz.tz_minuteswest * 60;
132 write_sequnlock_irq(&xtime_lock);
133 clock_was_set();
134}
135
136/*
137 * In case for some reason the CMOS clock has not already been running
138 * in UTC, but in some local time: The first time we set the timezone,
139 * we will warp the clock so that it is ticking UTC time instead of
140 * local time. Presumably, if someone is setting the timezone then we
141 * are running in an environment where the programs understand about
142 * timezones. This should be done at boot time in the /etc/rc script,
143 * as soon as possible, so that the clock can be set right. Otherwise,
144 * various programs will get confused when the clock gets warped.
145 */
146
147int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
148{
149 static int firsttime = 1;
150 int error = 0;
151
152 if (tv && !timespec_valid(tv))
153 return -EINVAL;
154
155 error = security_settime(tv, tz);
156 if (error)
157 return error;
158
159 if (tz) {
160 /* SMP safe, global irq locking makes it work. */
161 sys_tz = *tz;
162 update_vsyscall_tz();
163 if (firsttime) {
164 firsttime = 0;
165 if (!tv)
166 warp_clock();
167 }
168 }
169 if (tv)
170 {
171 /* SMP safe, again the code in arch/foo/time.c should
172 * globally block out interrupts when it runs.
173 */
174 return do_settimeofday(tv);
175 }
176 return 0;
177}
178
179asmlinkage long sys_settimeofday(struct timeval __user *tv,
180 struct timezone __user *tz)
181{
182 struct timeval user_tv;
183 struct timespec new_ts;
184 struct timezone new_tz;
185
186 if (tv) {
187 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
188 return -EFAULT;
189 new_ts.tv_sec = user_tv.tv_sec;
190 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
191 }
192 if (tz) {
193 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
194 return -EFAULT;
195 }
196
197 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
198}
199
200asmlinkage long sys_adjtimex(struct timex __user *txc_p)
201{
202 struct timex txc; /* Local copy of parameter */
203 int ret;
204
205 /* Copy the user data space into the kernel copy
206 * structure. But bear in mind that the structures
207 * may change
208 */
209 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
210 return -EFAULT;
211 ret = do_adjtimex(&txc);
212 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
213}
214
215/**
216 * current_fs_time - Return FS time
217 * @sb: Superblock.
218 *
219 * Return the current time truncated to the time granularity supported by
220 * the fs.
221 */
222struct timespec current_fs_time(struct super_block *sb)
223{
224 struct timespec now = current_kernel_time();
225 return timespec_trunc(now, sb->s_time_gran);
226}
227EXPORT_SYMBOL(current_fs_time);
228
229/*
230 * Convert jiffies to milliseconds and back.
231 *
232 * Avoid unnecessary multiplications/divisions in the
233 * two most common HZ cases:
234 */
235unsigned int inline jiffies_to_msecs(const unsigned long j)
236{
237#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
238 return (MSEC_PER_SEC / HZ) * j;
239#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
240 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
241#else
242 return (j * MSEC_PER_SEC) / HZ;
243#endif
244}
245EXPORT_SYMBOL(jiffies_to_msecs);
246
247unsigned int inline jiffies_to_usecs(const unsigned long j)
248{
249#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
250 return (USEC_PER_SEC / HZ) * j;
251#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
252 return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
253#else
254 return (j * USEC_PER_SEC) / HZ;
255#endif
256}
257EXPORT_SYMBOL(jiffies_to_usecs);
258
259/**
260 * timespec_trunc - Truncate timespec to a granularity
261 * @t: Timespec
262 * @gran: Granularity in ns.
263 *
264 * Truncate a timespec to a granularity. gran must be smaller than a second.
265 * Always rounds down.
266 *
267 * This function should be only used for timestamps returned by
268 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
269 * it doesn't handle the better resolution of the later.
270 */
271struct timespec timespec_trunc(struct timespec t, unsigned gran)
272{
273 /*
274 * Division is pretty slow so avoid it for common cases.
275 * Currently current_kernel_time() never returns better than
276 * jiffies resolution. Exploit that.
277 */
278 if (gran <= jiffies_to_usecs(1) * 1000) {
279 /* nothing */
280 } else if (gran == 1000000000) {
281 t.tv_nsec = 0;
282 } else {
283 t.tv_nsec -= t.tv_nsec % gran;
284 }
285 return t;
286}
287EXPORT_SYMBOL(timespec_trunc);
288
289#ifndef CONFIG_GENERIC_TIME
290/*
291 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
292 * and therefore only yields usec accuracy
293 */
294void getnstimeofday(struct timespec *tv)
295{
296 struct timeval x;
297
298 do_gettimeofday(&x);
299 tv->tv_sec = x.tv_sec;
300 tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
301}
302EXPORT_SYMBOL_GPL(getnstimeofday);
303#endif
304
305/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
306 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
307 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
308 *
309 * [For the Julian calendar (which was used in Russia before 1917,
310 * Britain & colonies before 1752, anywhere else before 1582,
311 * and is still in use by some communities) leave out the
312 * -year/100+year/400 terms, and add 10.]
313 *
314 * This algorithm was first published by Gauss (I think).
315 *
316 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
317 * machines were long is 32-bit! (However, as time_t is signed, we
318 * will already get problems at other places on 2038-01-19 03:14:08)
319 */
320unsigned long
321mktime(const unsigned int year0, const unsigned int mon0,
322 const unsigned int day, const unsigned int hour,
323 const unsigned int min, const unsigned int sec)
324{
325 unsigned int mon = mon0, year = year0;
326
327 /* 1..12 -> 11,12,1..10 */
328 if (0 >= (int) (mon -= 2)) {
329 mon += 12; /* Puts Feb last since it has leap day */
330 year -= 1;
331 }
332
333 return ((((unsigned long)
334 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
335 year*365 - 719499
336 )*24 + hour /* now have hours */
337 )*60 + min /* now have minutes */
338 )*60 + sec; /* finally seconds */
339}
340
341EXPORT_SYMBOL(mktime);
342
343/**
344 * set_normalized_timespec - set timespec sec and nsec parts and normalize
345 *
346 * @ts: pointer to timespec variable to be set
347 * @sec: seconds to set
348 * @nsec: nanoseconds to set
349 *
350 * Set seconds and nanoseconds field of a timespec variable and
351 * normalize to the timespec storage format
352 *
353 * Note: The tv_nsec part is always in the range of
354 * 0 <= tv_nsec < NSEC_PER_SEC
355 * For negative values only the tv_sec field is negative !
356 */
357void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
358{
359 while (nsec >= NSEC_PER_SEC) {
360 nsec -= NSEC_PER_SEC;
361 ++sec;
362 }
363 while (nsec < 0) {
364 nsec += NSEC_PER_SEC;
365 --sec;
366 }
367 ts->tv_sec = sec;
368 ts->tv_nsec = nsec;
369}
370
371/**
372 * ns_to_timespec - Convert nanoseconds to timespec
373 * @nsec: the nanoseconds value to be converted
374 *
375 * Returns the timespec representation of the nsec parameter.
376 */
377struct timespec ns_to_timespec(const s64 nsec)
378{
379 struct timespec ts;
380
381 if (!nsec)
382 return (struct timespec) {0, 0};
383
384 ts.tv_sec = div_long_long_rem_signed(nsec, NSEC_PER_SEC, &ts.tv_nsec);
385 if (unlikely(nsec < 0))
386 set_normalized_timespec(&ts, ts.tv_sec, ts.tv_nsec);
387
388 return ts;
389}
390EXPORT_SYMBOL(ns_to_timespec);
391
392/**
393 * ns_to_timeval - Convert nanoseconds to timeval
394 * @nsec: the nanoseconds value to be converted
395 *
396 * Returns the timeval representation of the nsec parameter.
397 */
398struct timeval ns_to_timeval(const s64 nsec)
399{
400 struct timespec ts = ns_to_timespec(nsec);
401 struct timeval tv;
402
403 tv.tv_sec = ts.tv_sec;
404 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
405
406 return tv;
407}
408EXPORT_SYMBOL(ns_to_timeval);
409
410/*
411 * When we convert to jiffies then we interpret incoming values
412 * the following way:
413 *
414 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
415 *
416 * - 'too large' values [that would result in larger than
417 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
418 *
419 * - all other values are converted to jiffies by either multiplying
420 * the input value by a factor or dividing it with a factor
421 *
422 * We must also be careful about 32-bit overflows.
423 */
424unsigned long msecs_to_jiffies(const unsigned int m)
425{
426 /*
427 * Negative value, means infinite timeout:
428 */
429 if ((int)m < 0)
430 return MAX_JIFFY_OFFSET;
431
432#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
433 /*
434 * HZ is equal to or smaller than 1000, and 1000 is a nice
435 * round multiple of HZ, divide with the factor between them,
436 * but round upwards:
437 */
438 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
439#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
440 /*
441 * HZ is larger than 1000, and HZ is a nice round multiple of
442 * 1000 - simply multiply with the factor between them.
443 *
444 * But first make sure the multiplication result cannot
445 * overflow:
446 */
447 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
448 return MAX_JIFFY_OFFSET;
449
450 return m * (HZ / MSEC_PER_SEC);
451#else
452 /*
453 * Generic case - multiply, round and divide. But first
454 * check that if we are doing a net multiplication, that
455 * we wouldnt overflow:
456 */
457 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
458 return MAX_JIFFY_OFFSET;
459
460 return (m * HZ + MSEC_PER_SEC - 1) / MSEC_PER_SEC;
461#endif
462}
463EXPORT_SYMBOL(msecs_to_jiffies);
464
465unsigned long usecs_to_jiffies(const unsigned int u)
466{
467 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
468 return MAX_JIFFY_OFFSET;
469#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
470 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
471#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
472 return u * (HZ / USEC_PER_SEC);
473#else
474 return (u * HZ + USEC_PER_SEC - 1) / USEC_PER_SEC;
475#endif
476}
477EXPORT_SYMBOL(usecs_to_jiffies);
478
479/*
480 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
481 * that a remainder subtract here would not do the right thing as the
482 * resolution values don't fall on second boundries. I.e. the line:
483 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
484 *
485 * Rather, we just shift the bits off the right.
486 *
487 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
488 * value to a scaled second value.
489 */
490unsigned long
491timespec_to_jiffies(const struct timespec *value)
492{
493 unsigned long sec = value->tv_sec;
494 long nsec = value->tv_nsec + TICK_NSEC - 1;
495
496 if (sec >= MAX_SEC_IN_JIFFIES){
497 sec = MAX_SEC_IN_JIFFIES;
498 nsec = 0;
499 }
500 return (((u64)sec * SEC_CONVERSION) +
501 (((u64)nsec * NSEC_CONVERSION) >>
502 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
503
504}
505EXPORT_SYMBOL(timespec_to_jiffies);
506
507void
508jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
509{
510 /*
511 * Convert jiffies to nanoseconds and separate with
512 * one divide.
513 */
514 u64 nsec = (u64)jiffies * TICK_NSEC;
515 value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_nsec);
516}
517EXPORT_SYMBOL(jiffies_to_timespec);
518
519/* Same for "timeval"
520 *
521 * Well, almost. The problem here is that the real system resolution is
522 * in nanoseconds and the value being converted is in micro seconds.
523 * Also for some machines (those that use HZ = 1024, in-particular),
524 * there is a LARGE error in the tick size in microseconds.
525
526 * The solution we use is to do the rounding AFTER we convert the
527 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
528 * Instruction wise, this should cost only an additional add with carry
529 * instruction above the way it was done above.
530 */
531unsigned long
532timeval_to_jiffies(const struct timeval *value)
533{
534 unsigned long sec = value->tv_sec;
535 long usec = value->tv_usec;
536
537 if (sec >= MAX_SEC_IN_JIFFIES){
538 sec = MAX_SEC_IN_JIFFIES;
539 usec = 0;
540 }
541 return (((u64)sec * SEC_CONVERSION) +
542 (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
543 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
544}
545EXPORT_SYMBOL(timeval_to_jiffies);
546
547void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
548{
549 /*
550 * Convert jiffies to nanoseconds and separate with
551 * one divide.
552 */
553 u64 nsec = (u64)jiffies * TICK_NSEC;
554 long tv_usec;
555
556 value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &tv_usec);
557 tv_usec /= NSEC_PER_USEC;
558 value->tv_usec = tv_usec;
559}
560EXPORT_SYMBOL(jiffies_to_timeval);
561
562/*
563 * Convert jiffies/jiffies_64 to clock_t and back.
564 */
565clock_t jiffies_to_clock_t(long x)
566{
567#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
568 return x / (HZ / USER_HZ);
569#else
570 u64 tmp = (u64)x * TICK_NSEC;
571 do_div(tmp, (NSEC_PER_SEC / USER_HZ));
572 return (long)tmp;
573#endif
574}
575EXPORT_SYMBOL(jiffies_to_clock_t);
576
577unsigned long clock_t_to_jiffies(unsigned long x)
578{
579#if (HZ % USER_HZ)==0
580 if (x >= ~0UL / (HZ / USER_HZ))
581 return ~0UL;
582 return x * (HZ / USER_HZ);
583#else
584 u64 jif;
585
586 /* Don't worry about loss of precision here .. */
587 if (x >= ~0UL / HZ * USER_HZ)
588 return ~0UL;
589
590 /* .. but do try to contain it here */
591 jif = x * (u64) HZ;
592 do_div(jif, USER_HZ);
593 return jif;
594#endif
595}
596EXPORT_SYMBOL(clock_t_to_jiffies);
597
598u64 jiffies_64_to_clock_t(u64 x)
599{
600#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
601 do_div(x, HZ / USER_HZ);
602#else
603 /*
604 * There are better ways that don't overflow early,
605 * but even this doesn't overflow in hundreds of years
606 * in 64 bits, so..
607 */
608 x *= TICK_NSEC;
609 do_div(x, (NSEC_PER_SEC / USER_HZ));
610#endif
611 return x;
612}
613
614EXPORT_SYMBOL(jiffies_64_to_clock_t);
615
616u64 nsec_to_clock_t(u64 x)
617{
618#if (NSEC_PER_SEC % USER_HZ) == 0
619 do_div(x, (NSEC_PER_SEC / USER_HZ));
620#elif (USER_HZ % 512) == 0
621 x *= USER_HZ/512;
622 do_div(x, (NSEC_PER_SEC / 512));
623#else
624 /*
625 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
626 * overflow after 64.99 years.
627 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
628 */
629 x *= 9;
630 do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2)) /
631 USER_HZ));
632#endif
633 return x;
634}
635
636#if (BITS_PER_LONG < 64)
637u64 get_jiffies_64(void)
638{
639 unsigned long seq;
640 u64 ret;
641
642 do {
643 seq = read_seqbegin(&xtime_lock);
644 ret = jiffies_64;
645 } while (read_seqretry(&xtime_lock, seq));
646 return ret;
647}
648
649EXPORT_SYMBOL(get_jiffies_64);
650#endif
651
652EXPORT_SYMBOL(jiffies);