Loading...
Note: File does not exist in v3.15.
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/core.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/export.h>
31#include <linux/timex.h>
32#include <linux/capability.h>
33#include <linux/timekeeper_internal.h>
34#include <linux/errno.h>
35#include <linux/syscalls.h>
36#include <linux/security.h>
37#include <linux/fs.h>
38#include <linux/math64.h>
39#include <linux/ptrace.h>
40
41#include <asm/uaccess.h>
42#include <asm/unistd.h>
43
44#include <generated/timeconst.h>
45#include "timekeeping.h"
46
47/*
48 * The timezone where the local system is located. Used as a default by some
49 * programs who obtain this value by using gettimeofday.
50 */
51struct timezone sys_tz;
52
53EXPORT_SYMBOL(sys_tz);
54
55#ifdef __ARCH_WANT_SYS_TIME
56
57/*
58 * sys_time() can be implemented in user-level using
59 * sys_gettimeofday(). Is this for backwards compatibility? If so,
60 * why not move it into the appropriate arch directory (for those
61 * architectures that need it).
62 */
63SYSCALL_DEFINE1(time, time_t __user *, tloc)
64{
65 time_t i = get_seconds();
66
67 if (tloc) {
68 if (put_user(i,tloc))
69 return -EFAULT;
70 }
71 force_successful_syscall_return();
72 return i;
73}
74
75/*
76 * sys_stime() can be implemented in user-level using
77 * sys_settimeofday(). Is this for backwards compatibility? If so,
78 * why not move it into the appropriate arch directory (for those
79 * architectures that need it).
80 */
81
82SYSCALL_DEFINE1(stime, time_t __user *, tptr)
83{
84 struct timespec tv;
85 int err;
86
87 if (get_user(tv.tv_sec, tptr))
88 return -EFAULT;
89
90 tv.tv_nsec = 0;
91
92 err = security_settime(&tv, NULL);
93 if (err)
94 return err;
95
96 do_settimeofday(&tv);
97 return 0;
98}
99
100#endif /* __ARCH_WANT_SYS_TIME */
101
102SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv,
103 struct timezone __user *, tz)
104{
105 if (likely(tv != NULL)) {
106 struct timeval ktv;
107 do_gettimeofday(&ktv);
108 if (copy_to_user(tv, &ktv, sizeof(ktv)))
109 return -EFAULT;
110 }
111 if (unlikely(tz != NULL)) {
112 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
113 return -EFAULT;
114 }
115 return 0;
116}
117
118/*
119 * Indicates if there is an offset between the system clock and the hardware
120 * clock/persistent clock/rtc.
121 */
122int persistent_clock_is_local;
123
124/*
125 * Adjust the time obtained from the CMOS to be UTC time instead of
126 * local time.
127 *
128 * This is ugly, but preferable to the alternatives. Otherwise we
129 * would either need to write a program to do it in /etc/rc (and risk
130 * confusion if the program gets run more than once; it would also be
131 * hard to make the program warp the clock precisely n hours) or
132 * compile in the timezone information into the kernel. Bad, bad....
133 *
134 * - TYT, 1992-01-01
135 *
136 * The best thing to do is to keep the CMOS clock in universal time (UTC)
137 * as real UNIX machines always do it. This avoids all headaches about
138 * daylight saving times and warping kernel clocks.
139 */
140static inline void warp_clock(void)
141{
142 if (sys_tz.tz_minuteswest != 0) {
143 struct timespec adjust;
144
145 persistent_clock_is_local = 1;
146 adjust.tv_sec = sys_tz.tz_minuteswest * 60;
147 adjust.tv_nsec = 0;
148 timekeeping_inject_offset(&adjust);
149 }
150}
151
152/*
153 * In case for some reason the CMOS clock has not already been running
154 * in UTC, but in some local time: The first time we set the timezone,
155 * we will warp the clock so that it is ticking UTC time instead of
156 * local time. Presumably, if someone is setting the timezone then we
157 * are running in an environment where the programs understand about
158 * timezones. This should be done at boot time in the /etc/rc script,
159 * as soon as possible, so that the clock can be set right. Otherwise,
160 * various programs will get confused when the clock gets warped.
161 */
162
163int do_sys_settimeofday(const struct timespec *tv, const struct timezone *tz)
164{
165 static int firsttime = 1;
166 int error = 0;
167
168 if (tv && !timespec_valid(tv))
169 return -EINVAL;
170
171 error = security_settime(tv, tz);
172 if (error)
173 return error;
174
175 if (tz) {
176 /* Verify we're witin the +-15 hrs range */
177 if (tz->tz_minuteswest > 15*60 || tz->tz_minuteswest < -15*60)
178 return -EINVAL;
179
180 sys_tz = *tz;
181 update_vsyscall_tz();
182 if (firsttime) {
183 firsttime = 0;
184 if (!tv)
185 warp_clock();
186 }
187 }
188 if (tv)
189 return do_settimeofday(tv);
190 return 0;
191}
192
193SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv,
194 struct timezone __user *, tz)
195{
196 struct timeval user_tv;
197 struct timespec new_ts;
198 struct timezone new_tz;
199
200 if (tv) {
201 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
202 return -EFAULT;
203
204 if (!timeval_valid(&user_tv))
205 return -EINVAL;
206
207 new_ts.tv_sec = user_tv.tv_sec;
208 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
209 }
210 if (tz) {
211 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
212 return -EFAULT;
213 }
214
215 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
216}
217
218SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p)
219{
220 struct timex txc; /* Local copy of parameter */
221 int ret;
222
223 /* Copy the user data space into the kernel copy
224 * structure. But bear in mind that the structures
225 * may change
226 */
227 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
228 return -EFAULT;
229 ret = do_adjtimex(&txc);
230 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
231}
232
233/**
234 * current_fs_time - Return FS time
235 * @sb: Superblock.
236 *
237 * Return the current time truncated to the time granularity supported by
238 * the fs.
239 */
240struct timespec current_fs_time(struct super_block *sb)
241{
242 struct timespec now = current_kernel_time();
243 return timespec_trunc(now, sb->s_time_gran);
244}
245EXPORT_SYMBOL(current_fs_time);
246
247/*
248 * Convert jiffies to milliseconds and back.
249 *
250 * Avoid unnecessary multiplications/divisions in the
251 * two most common HZ cases:
252 */
253unsigned int jiffies_to_msecs(const unsigned long j)
254{
255#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
256 return (MSEC_PER_SEC / HZ) * j;
257#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
258 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
259#else
260# if BITS_PER_LONG == 32
261 return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
262# else
263 return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
264# endif
265#endif
266}
267EXPORT_SYMBOL(jiffies_to_msecs);
268
269unsigned int jiffies_to_usecs(const unsigned long j)
270{
271 /*
272 * Hz usually doesn't go much further MSEC_PER_SEC.
273 * jiffies_to_usecs() and usecs_to_jiffies() depend on that.
274 */
275 BUILD_BUG_ON(HZ > USEC_PER_SEC);
276
277#if !(USEC_PER_SEC % HZ)
278 return (USEC_PER_SEC / HZ) * j;
279#else
280# if BITS_PER_LONG == 32
281 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
282# else
283 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
284# endif
285#endif
286}
287EXPORT_SYMBOL(jiffies_to_usecs);
288
289/**
290 * timespec_trunc - Truncate timespec to a granularity
291 * @t: Timespec
292 * @gran: Granularity in ns.
293 *
294 * Truncate a timespec to a granularity. Always rounds down. gran must
295 * not be 0 nor greater than a second (NSEC_PER_SEC, or 10^9 ns).
296 */
297struct timespec timespec_trunc(struct timespec t, unsigned gran)
298{
299 /* Avoid division in the common cases 1 ns and 1 s. */
300 if (gran == 1) {
301 /* nothing */
302 } else if (gran == NSEC_PER_SEC) {
303 t.tv_nsec = 0;
304 } else if (gran > 1 && gran < NSEC_PER_SEC) {
305 t.tv_nsec -= t.tv_nsec % gran;
306 } else {
307 WARN(1, "illegal file time granularity: %u", gran);
308 }
309 return t;
310}
311EXPORT_SYMBOL(timespec_trunc);
312
313/*
314 * mktime64 - Converts date to seconds.
315 * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
316 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
317 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
318 *
319 * [For the Julian calendar (which was used in Russia before 1917,
320 * Britain & colonies before 1752, anywhere else before 1582,
321 * and is still in use by some communities) leave out the
322 * -year/100+year/400 terms, and add 10.]
323 *
324 * This algorithm was first published by Gauss (I think).
325 *
326 * A leap second can be indicated by calling this function with sec as
327 * 60 (allowable under ISO 8601). The leap second is treated the same
328 * as the following second since they don't exist in UNIX time.
329 *
330 * An encoding of midnight at the end of the day as 24:00:00 - ie. midnight
331 * tomorrow - (allowable under ISO 8601) is supported.
332 */
333time64_t mktime64(const unsigned int year0, const unsigned int mon0,
334 const unsigned int day, const unsigned int hour,
335 const unsigned int min, const unsigned int sec)
336{
337 unsigned int mon = mon0, year = year0;
338
339 /* 1..12 -> 11,12,1..10 */
340 if (0 >= (int) (mon -= 2)) {
341 mon += 12; /* Puts Feb last since it has leap day */
342 year -= 1;
343 }
344
345 return ((((time64_t)
346 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
347 year*365 - 719499
348 )*24 + hour /* now have hours - midnight tomorrow handled here */
349 )*60 + min /* now have minutes */
350 )*60 + sec; /* finally seconds */
351}
352EXPORT_SYMBOL(mktime64);
353
354/**
355 * set_normalized_timespec - set timespec sec and nsec parts and normalize
356 *
357 * @ts: pointer to timespec variable to be set
358 * @sec: seconds to set
359 * @nsec: nanoseconds to set
360 *
361 * Set seconds and nanoseconds field of a timespec variable and
362 * normalize to the timespec storage format
363 *
364 * Note: The tv_nsec part is always in the range of
365 * 0 <= tv_nsec < NSEC_PER_SEC
366 * For negative values only the tv_sec field is negative !
367 */
368void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
369{
370 while (nsec >= NSEC_PER_SEC) {
371 /*
372 * The following asm() prevents the compiler from
373 * optimising this loop into a modulo operation. See
374 * also __iter_div_u64_rem() in include/linux/time.h
375 */
376 asm("" : "+rm"(nsec));
377 nsec -= NSEC_PER_SEC;
378 ++sec;
379 }
380 while (nsec < 0) {
381 asm("" : "+rm"(nsec));
382 nsec += NSEC_PER_SEC;
383 --sec;
384 }
385 ts->tv_sec = sec;
386 ts->tv_nsec = nsec;
387}
388EXPORT_SYMBOL(set_normalized_timespec);
389
390/**
391 * ns_to_timespec - Convert nanoseconds to timespec
392 * @nsec: the nanoseconds value to be converted
393 *
394 * Returns the timespec representation of the nsec parameter.
395 */
396struct timespec ns_to_timespec(const s64 nsec)
397{
398 struct timespec ts;
399 s32 rem;
400
401 if (!nsec)
402 return (struct timespec) {0, 0};
403
404 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
405 if (unlikely(rem < 0)) {
406 ts.tv_sec--;
407 rem += NSEC_PER_SEC;
408 }
409 ts.tv_nsec = rem;
410
411 return ts;
412}
413EXPORT_SYMBOL(ns_to_timespec);
414
415/**
416 * ns_to_timeval - Convert nanoseconds to timeval
417 * @nsec: the nanoseconds value to be converted
418 *
419 * Returns the timeval representation of the nsec parameter.
420 */
421struct timeval ns_to_timeval(const s64 nsec)
422{
423 struct timespec ts = ns_to_timespec(nsec);
424 struct timeval tv;
425
426 tv.tv_sec = ts.tv_sec;
427 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
428
429 return tv;
430}
431EXPORT_SYMBOL(ns_to_timeval);
432
433#if BITS_PER_LONG == 32
434/**
435 * set_normalized_timespec - set timespec sec and nsec parts and normalize
436 *
437 * @ts: pointer to timespec variable to be set
438 * @sec: seconds to set
439 * @nsec: nanoseconds to set
440 *
441 * Set seconds and nanoseconds field of a timespec variable and
442 * normalize to the timespec storage format
443 *
444 * Note: The tv_nsec part is always in the range of
445 * 0 <= tv_nsec < NSEC_PER_SEC
446 * For negative values only the tv_sec field is negative !
447 */
448void set_normalized_timespec64(struct timespec64 *ts, time64_t sec, s64 nsec)
449{
450 while (nsec >= NSEC_PER_SEC) {
451 /*
452 * The following asm() prevents the compiler from
453 * optimising this loop into a modulo operation. See
454 * also __iter_div_u64_rem() in include/linux/time.h
455 */
456 asm("" : "+rm"(nsec));
457 nsec -= NSEC_PER_SEC;
458 ++sec;
459 }
460 while (nsec < 0) {
461 asm("" : "+rm"(nsec));
462 nsec += NSEC_PER_SEC;
463 --sec;
464 }
465 ts->tv_sec = sec;
466 ts->tv_nsec = nsec;
467}
468EXPORT_SYMBOL(set_normalized_timespec64);
469
470/**
471 * ns_to_timespec64 - Convert nanoseconds to timespec64
472 * @nsec: the nanoseconds value to be converted
473 *
474 * Returns the timespec64 representation of the nsec parameter.
475 */
476struct timespec64 ns_to_timespec64(const s64 nsec)
477{
478 struct timespec64 ts;
479 s32 rem;
480
481 if (!nsec)
482 return (struct timespec64) {0, 0};
483
484 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
485 if (unlikely(rem < 0)) {
486 ts.tv_sec--;
487 rem += NSEC_PER_SEC;
488 }
489 ts.tv_nsec = rem;
490
491 return ts;
492}
493EXPORT_SYMBOL(ns_to_timespec64);
494#endif
495/**
496 * msecs_to_jiffies: - convert milliseconds to jiffies
497 * @m: time in milliseconds
498 *
499 * conversion is done as follows:
500 *
501 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
502 *
503 * - 'too large' values [that would result in larger than
504 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
505 *
506 * - all other values are converted to jiffies by either multiplying
507 * the input value by a factor or dividing it with a factor and
508 * handling any 32-bit overflows.
509 * for the details see __msecs_to_jiffies()
510 *
511 * msecs_to_jiffies() checks for the passed in value being a constant
512 * via __builtin_constant_p() allowing gcc to eliminate most of the
513 * code, __msecs_to_jiffies() is called if the value passed does not
514 * allow constant folding and the actual conversion must be done at
515 * runtime.
516 * the _msecs_to_jiffies helpers are the HZ dependent conversion
517 * routines found in include/linux/jiffies.h
518 */
519unsigned long __msecs_to_jiffies(const unsigned int m)
520{
521 /*
522 * Negative value, means infinite timeout:
523 */
524 if ((int)m < 0)
525 return MAX_JIFFY_OFFSET;
526 return _msecs_to_jiffies(m);
527}
528EXPORT_SYMBOL(__msecs_to_jiffies);
529
530unsigned long __usecs_to_jiffies(const unsigned int u)
531{
532 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
533 return MAX_JIFFY_OFFSET;
534 return _usecs_to_jiffies(u);
535}
536EXPORT_SYMBOL(__usecs_to_jiffies);
537
538/*
539 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
540 * that a remainder subtract here would not do the right thing as the
541 * resolution values don't fall on second boundries. I.e. the line:
542 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
543 * Note that due to the small error in the multiplier here, this
544 * rounding is incorrect for sufficiently large values of tv_nsec, but
545 * well formed timespecs should have tv_nsec < NSEC_PER_SEC, so we're
546 * OK.
547 *
548 * Rather, we just shift the bits off the right.
549 *
550 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
551 * value to a scaled second value.
552 */
553static unsigned long
554__timespec64_to_jiffies(u64 sec, long nsec)
555{
556 nsec = nsec + TICK_NSEC - 1;
557
558 if (sec >= MAX_SEC_IN_JIFFIES){
559 sec = MAX_SEC_IN_JIFFIES;
560 nsec = 0;
561 }
562 return ((sec * SEC_CONVERSION) +
563 (((u64)nsec * NSEC_CONVERSION) >>
564 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
565
566}
567
568static unsigned long
569__timespec_to_jiffies(unsigned long sec, long nsec)
570{
571 return __timespec64_to_jiffies((u64)sec, nsec);
572}
573
574unsigned long
575timespec64_to_jiffies(const struct timespec64 *value)
576{
577 return __timespec64_to_jiffies(value->tv_sec, value->tv_nsec);
578}
579EXPORT_SYMBOL(timespec64_to_jiffies);
580
581void
582jiffies_to_timespec64(const unsigned long jiffies, struct timespec64 *value)
583{
584 /*
585 * Convert jiffies to nanoseconds and separate with
586 * one divide.
587 */
588 u32 rem;
589 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
590 NSEC_PER_SEC, &rem);
591 value->tv_nsec = rem;
592}
593EXPORT_SYMBOL(jiffies_to_timespec64);
594
595/*
596 * We could use a similar algorithm to timespec_to_jiffies (with a
597 * different multiplier for usec instead of nsec). But this has a
598 * problem with rounding: we can't exactly add TICK_NSEC - 1 to the
599 * usec value, since it's not necessarily integral.
600 *
601 * We could instead round in the intermediate scaled representation
602 * (i.e. in units of 1/2^(large scale) jiffies) but that's also
603 * perilous: the scaling introduces a small positive error, which
604 * combined with a division-rounding-upward (i.e. adding 2^(scale) - 1
605 * units to the intermediate before shifting) leads to accidental
606 * overflow and overestimates.
607 *
608 * At the cost of one additional multiplication by a constant, just
609 * use the timespec implementation.
610 */
611unsigned long
612timeval_to_jiffies(const struct timeval *value)
613{
614 return __timespec_to_jiffies(value->tv_sec,
615 value->tv_usec * NSEC_PER_USEC);
616}
617EXPORT_SYMBOL(timeval_to_jiffies);
618
619void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
620{
621 /*
622 * Convert jiffies to nanoseconds and separate with
623 * one divide.
624 */
625 u32 rem;
626
627 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
628 NSEC_PER_SEC, &rem);
629 value->tv_usec = rem / NSEC_PER_USEC;
630}
631EXPORT_SYMBOL(jiffies_to_timeval);
632
633/*
634 * Convert jiffies/jiffies_64 to clock_t and back.
635 */
636clock_t jiffies_to_clock_t(unsigned long x)
637{
638#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
639# if HZ < USER_HZ
640 return x * (USER_HZ / HZ);
641# else
642 return x / (HZ / USER_HZ);
643# endif
644#else
645 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
646#endif
647}
648EXPORT_SYMBOL(jiffies_to_clock_t);
649
650unsigned long clock_t_to_jiffies(unsigned long x)
651{
652#if (HZ % USER_HZ)==0
653 if (x >= ~0UL / (HZ / USER_HZ))
654 return ~0UL;
655 return x * (HZ / USER_HZ);
656#else
657 /* Don't worry about loss of precision here .. */
658 if (x >= ~0UL / HZ * USER_HZ)
659 return ~0UL;
660
661 /* .. but do try to contain it here */
662 return div_u64((u64)x * HZ, USER_HZ);
663#endif
664}
665EXPORT_SYMBOL(clock_t_to_jiffies);
666
667u64 jiffies_64_to_clock_t(u64 x)
668{
669#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
670# if HZ < USER_HZ
671 x = div_u64(x * USER_HZ, HZ);
672# elif HZ > USER_HZ
673 x = div_u64(x, HZ / USER_HZ);
674# else
675 /* Nothing to do */
676# endif
677#else
678 /*
679 * There are better ways that don't overflow early,
680 * but even this doesn't overflow in hundreds of years
681 * in 64 bits, so..
682 */
683 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
684#endif
685 return x;
686}
687EXPORT_SYMBOL(jiffies_64_to_clock_t);
688
689u64 nsec_to_clock_t(u64 x)
690{
691#if (NSEC_PER_SEC % USER_HZ) == 0
692 return div_u64(x, NSEC_PER_SEC / USER_HZ);
693#elif (USER_HZ % 512) == 0
694 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
695#else
696 /*
697 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
698 * overflow after 64.99 years.
699 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
700 */
701 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
702#endif
703}
704
705/**
706 * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
707 *
708 * @n: nsecs in u64
709 *
710 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
711 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
712 * for scheduler, not for use in device drivers to calculate timeout value.
713 *
714 * note:
715 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
716 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
717 */
718u64 nsecs_to_jiffies64(u64 n)
719{
720#if (NSEC_PER_SEC % HZ) == 0
721 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
722 return div_u64(n, NSEC_PER_SEC / HZ);
723#elif (HZ % 512) == 0
724 /* overflow after 292 years if HZ = 1024 */
725 return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
726#else
727 /*
728 * Generic case - optimized for cases where HZ is a multiple of 3.
729 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
730 */
731 return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
732#endif
733}
734EXPORT_SYMBOL(nsecs_to_jiffies64);
735
736/**
737 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
738 *
739 * @n: nsecs in u64
740 *
741 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
742 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
743 * for scheduler, not for use in device drivers to calculate timeout value.
744 *
745 * note:
746 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
747 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
748 */
749unsigned long nsecs_to_jiffies(u64 n)
750{
751 return (unsigned long)nsecs_to_jiffies64(n);
752}
753EXPORT_SYMBOL_GPL(nsecs_to_jiffies);
754
755/*
756 * Add two timespec values and do a safety check for overflow.
757 * It's assumed that both values are valid (>= 0)
758 */
759struct timespec timespec_add_safe(const struct timespec lhs,
760 const struct timespec rhs)
761{
762 struct timespec res;
763
764 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
765 lhs.tv_nsec + rhs.tv_nsec);
766
767 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
768 res.tv_sec = TIME_T_MAX;
769
770 return res;
771}