projects/linux·blob v2.6.20 · refs

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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/errno.h>
34#include <linux/smp_lock.h>
35#include <linux/syscalls.h>
36#include <linux/security.h>
37#include <linux/fs.h>
38#include <linux/module.h>
39
40#include <asm/uaccess.h>
41#include <asm/unistd.h>
42
43/*
44 * The timezone where the local system is located. Used as a default by some
45 * programs who obtain this value by using gettimeofday.
46 */
47struct timezone sys_tz;
48
49EXPORT_SYMBOL(sys_tz);
50
51#ifdef __ARCH_WANT_SYS_TIME
52
53/*
54 * sys_time() can be implemented in user-level using
55 * sys_gettimeofday(). Is this for backwards compatibility? If so,
56 * why not move it into the appropriate arch directory (for those
57 * architectures that need it).
58 */
59asmlinkage long sys_time(time_t __user * tloc)
60{
61 time_t i;
62 struct timeval tv;
63
64 do_gettimeofday(&tv);
65 i = tv.tv_sec;
66
67 if (tloc) {
68 if (put_user(i,tloc))
69 i = -EFAULT;
70 }
71 return i;
72}
73
74/*
75 * sys_stime() can be implemented in user-level using
76 * sys_settimeofday(). Is this for backwards compatibility? If so,
77 * why not move it into the appropriate arch directory (for those
78 * architectures that need it).
79 */
80
81asmlinkage long sys_stime(time_t __user *tptr)
82{
83 struct timespec tv;
84 int err;
85
86 if (get_user(tv.tv_sec, tptr))
87 return -EFAULT;
88
89 tv.tv_nsec = 0;
90
91 err = security_settime(&tv, NULL);
92 if (err)
93 return err;
94
95 do_settimeofday(&tv);
96 return 0;
97}
98
99#endif /* __ARCH_WANT_SYS_TIME */
100
101asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __user *tz)
102{
103 if (likely(tv != NULL)) {
104 struct timeval ktv;
105 do_gettimeofday(&ktv);
106 if (copy_to_user(tv, &ktv, sizeof(ktv)))
107 return -EFAULT;
108 }
109 if (unlikely(tz != NULL)) {
110 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
111 return -EFAULT;
112 }
113 return 0;
114}
115
116/*
117 * Adjust the time obtained from the CMOS to be UTC time instead of
118 * local time.
119 *
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....
125 *
126 * - TYT, 1992-01-01
127 *
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.
131 */
132static inline void warp_clock(void)
133{
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 time_interpolator_reset();
138 write_sequnlock_irq(&xtime_lock);
139 clock_was_set();
140}
141
142/*
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.
151 */
152
153int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
154{
155 static int firsttime = 1;
156 int error = 0;
157
158 if (tv && !timespec_valid(tv))
159 return -EINVAL;
160
161 error = security_settime(tv, tz);
162 if (error)
163 return error;
164
165 if (tz) {
166 /* SMP safe, global irq locking makes it work. */
167 sys_tz = *tz;
168 if (firsttime) {
169 firsttime = 0;
170 if (!tv)
171 warp_clock();
172 }
173 }
174 if (tv)
175 {
176 /* SMP safe, again the code in arch/foo/time.c should
177 * globally block out interrupts when it runs.
178 */
179 return do_settimeofday(tv);
180 }
181 return 0;
182}
183
184asmlinkage long sys_settimeofday(struct timeval __user *tv,
185 struct timezone __user *tz)
186{
187 struct timeval user_tv;
188 struct timespec new_ts;
189 struct timezone new_tz;
190
191 if (tv) {
192 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
193 return -EFAULT;
194 new_ts.tv_sec = user_tv.tv_sec;
195 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
196 }
197 if (tz) {
198 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
199 return -EFAULT;
200 }
201
202 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
203}
204
205asmlinkage long sys_adjtimex(struct timex __user *txc_p)
206{
207 struct timex txc; /* Local copy of parameter */
208 int ret;
209
210 /* Copy the user data space into the kernel copy
211 * structure. But bear in mind that the structures
212 * may change
213 */
214 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
215 return -EFAULT;
216 ret = do_adjtimex(&txc);
217 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
218}
219
220inline struct timespec current_kernel_time(void)
221{
222 struct timespec now;
223 unsigned long seq;
224
225 do {
226 seq = read_seqbegin(&xtime_lock);
227
228 now = xtime;
229 } while (read_seqretry(&xtime_lock, seq));
230
231 return now;
232}
233
234EXPORT_SYMBOL(current_kernel_time);
235
236/**
237 * current_fs_time - Return FS time
238 * @sb: Superblock.
239 *
240 * Return the current time truncated to the time granularity supported by
241 * the fs.
242 */
243struct timespec current_fs_time(struct super_block *sb)
244{
245 struct timespec now = current_kernel_time();
246 return timespec_trunc(now, sb->s_time_gran);
247}
248EXPORT_SYMBOL(current_fs_time);
249
250/**
251 * timespec_trunc - Truncate timespec to a granularity
252 * @t: Timespec
253 * @gran: Granularity in ns.
254 *
255 * Truncate a timespec to a granularity. gran must be smaller than a second.
256 * Always rounds down.
257 *
258 * This function should be only used for timestamps returned by
259 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
260 * it doesn't handle the better resolution of the later.
261 */
262struct timespec timespec_trunc(struct timespec t, unsigned gran)
263{
264 /*
265 * Division is pretty slow so avoid it for common cases.
266 * Currently current_kernel_time() never returns better than
267 * jiffies resolution. Exploit that.
268 */
269 if (gran <= jiffies_to_usecs(1) * 1000) {
270 /* nothing */
271 } else if (gran == 1000000000) {
272 t.tv_nsec = 0;
273 } else {
274 t.tv_nsec -= t.tv_nsec % gran;
275 }
276 return t;
277}
278EXPORT_SYMBOL(timespec_trunc);
279
280#ifdef CONFIG_TIME_INTERPOLATION
281void getnstimeofday (struct timespec *tv)
282{
283 unsigned long seq,sec,nsec;
284
285 do {
286 seq = read_seqbegin(&xtime_lock);
287 sec = xtime.tv_sec;
288 nsec = xtime.tv_nsec+time_interpolator_get_offset();
289 } while (unlikely(read_seqretry(&xtime_lock, seq)));
290
291 while (unlikely(nsec >= NSEC_PER_SEC)) {
292 nsec -= NSEC_PER_SEC;
293 ++sec;
294 }
295 tv->tv_sec = sec;
296 tv->tv_nsec = nsec;
297}
298EXPORT_SYMBOL_GPL(getnstimeofday);
299
300int do_settimeofday (struct timespec *tv)
301{
302 time_t wtm_sec, sec = tv->tv_sec;
303 long wtm_nsec, nsec = tv->tv_nsec;
304
305 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
306 return -EINVAL;
307
308 write_seqlock_irq(&xtime_lock);
309 {
310 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
311 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
312
313 set_normalized_timespec(&xtime, sec, nsec);
314 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
315
316 time_adjust = 0; /* stop active adjtime() */
317 time_status |= STA_UNSYNC;
318 time_maxerror = NTP_PHASE_LIMIT;
319 time_esterror = NTP_PHASE_LIMIT;
320 time_interpolator_reset();
321 }
322 write_sequnlock_irq(&xtime_lock);
323 clock_was_set();
324 return 0;
325}
326EXPORT_SYMBOL(do_settimeofday);
327
328void do_gettimeofday (struct timeval *tv)
329{
330 unsigned long seq, nsec, usec, sec, offset;
331 do {
332 seq = read_seqbegin(&xtime_lock);
333 offset = time_interpolator_get_offset();
334 sec = xtime.tv_sec;
335 nsec = xtime.tv_nsec;
336 } while (unlikely(read_seqretry(&xtime_lock, seq)));
337
338 usec = (nsec + offset) / 1000;
339
340 while (unlikely(usec >= USEC_PER_SEC)) {
341 usec -= USEC_PER_SEC;
342 ++sec;
343 }
344
345 tv->tv_sec = sec;
346 tv->tv_usec = usec;
347}
348
349EXPORT_SYMBOL(do_gettimeofday);
350
351
352#else
353#ifndef CONFIG_GENERIC_TIME
354/*
355 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
356 * and therefore only yields usec accuracy
357 */
358void getnstimeofday(struct timespec *tv)
359{
360 struct timeval x;
361
362 do_gettimeofday(&x);
363 tv->tv_sec = x.tv_sec;
364 tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
365}
366EXPORT_SYMBOL_GPL(getnstimeofday);
367#endif
368#endif
369
370/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
371 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
372 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
373 *
374 * [For the Julian calendar (which was used in Russia before 1917,
375 * Britain & colonies before 1752, anywhere else before 1582,
376 * and is still in use by some communities) leave out the
377 * -year/100+year/400 terms, and add 10.]
378 *
379 * This algorithm was first published by Gauss (I think).
380 *
381 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
382 * machines were long is 32-bit! (However, as time_t is signed, we
383 * will already get problems at other places on 2038-01-19 03:14:08)
384 */
385unsigned long
386mktime(const unsigned int year0, const unsigned int mon0,
387 const unsigned int day, const unsigned int hour,
388 const unsigned int min, const unsigned int sec)
389{
390 unsigned int mon = mon0, year = year0;
391
392 /* 1..12 -> 11,12,1..10 */
393 if (0 >= (int) (mon -= 2)) {
394 mon += 12; /* Puts Feb last since it has leap day */
395 year -= 1;
396 }
397
398 return ((((unsigned long)
399 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
400 year*365 - 719499
401 )*24 + hour /* now have hours */
402 )*60 + min /* now have minutes */
403 )*60 + sec; /* finally seconds */
404}
405
406EXPORT_SYMBOL(mktime);
407
408/**
409 * set_normalized_timespec - set timespec sec and nsec parts and normalize
410 *
411 * @ts: pointer to timespec variable to be set
412 * @sec: seconds to set
413 * @nsec: nanoseconds to set
414 *
415 * Set seconds and nanoseconds field of a timespec variable and
416 * normalize to the timespec storage format
417 *
418 * Note: The tv_nsec part is always in the range of
419 * 0 <= tv_nsec < NSEC_PER_SEC
420 * For negative values only the tv_sec field is negative !
421 */
422void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
423{
424 while (nsec >= NSEC_PER_SEC) {
425 nsec -= NSEC_PER_SEC;
426 ++sec;
427 }
428 while (nsec < 0) {
429 nsec += NSEC_PER_SEC;
430 --sec;
431 }
432 ts->tv_sec = sec;
433 ts->tv_nsec = nsec;
434}
435
436/**
437 * ns_to_timespec - Convert nanoseconds to timespec
438 * @nsec: the nanoseconds value to be converted
439 *
440 * Returns the timespec representation of the nsec parameter.
441 */
442struct timespec ns_to_timespec(const s64 nsec)
443{
444 struct timespec ts;
445
446 if (!nsec)
447 return (struct timespec) {0, 0};
448
449 ts.tv_sec = div_long_long_rem_signed(nsec, NSEC_PER_SEC, &ts.tv_nsec);
450 if (unlikely(nsec < 0))
451 set_normalized_timespec(&ts, ts.tv_sec, ts.tv_nsec);
452
453 return ts;
454}
455
456/**
457 * ns_to_timeval - Convert nanoseconds to timeval
458 * @nsec: the nanoseconds value to be converted
459 *
460 * Returns the timeval representation of the nsec parameter.
461 */
462struct timeval ns_to_timeval(const s64 nsec)
463{
464 struct timespec ts = ns_to_timespec(nsec);
465 struct timeval tv;
466
467 tv.tv_sec = ts.tv_sec;
468 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
469
470 return tv;
471}
472
473#if (BITS_PER_LONG < 64)
474u64 get_jiffies_64(void)
475{
476 unsigned long seq;
477 u64 ret;
478
479 do {
480 seq = read_seqbegin(&xtime_lock);
481 ret = jiffies_64;
482 } while (read_seqretry(&xtime_lock, seq));
483 return ret;
484}
485
486EXPORT_SYMBOL(get_jiffies_64);
487#endif
488
489EXPORT_SYMBOL(jiffies);