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/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 "timeconst.h"
45
46 /*
47 * The timezone where the local system is located. Used as a default by some
48 * programs who obtain this value by using gettimeofday.
49 */
50 struct timezone sys_tz;
51
52 EXPORT_SYMBOL(sys_tz);
53
54 #ifdef __ARCH_WANT_SYS_TIME
55
56 /*
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).
61 */
SYSCALL_DEFINE1(time,time_t __user *,tloc)62 SYSCALL_DEFINE1(time, time_t __user *, tloc)
63 {
64 time_t i = get_seconds();
65
66 if (tloc) {
67 if (put_user(i,tloc))
68 return -EFAULT;
69 }
70 force_successful_syscall_return();
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
SYSCALL_DEFINE1(stime,time_t __user *,tptr)81 SYSCALL_DEFINE1(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
SYSCALL_DEFINE2(gettimeofday,struct timeval __user *,tv,struct timezone __user *,tz)101 SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv,
102 struct timezone __user *, tz)
103 {
104 if (likely(tv != NULL)) {
105 struct timeval ktv;
106 do_gettimeofday(&ktv);
107 if (copy_to_user(tv, &ktv, sizeof(ktv)))
108 return -EFAULT;
109 }
110 if (unlikely(tz != NULL)) {
111 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
112 return -EFAULT;
113 }
114 return 0;
115 }
116
117 /*
118 * Indicates if there is an offset between the system clock and the hardware
119 * clock/persistent clock/rtc.
120 */
121 int persistent_clock_is_local;
122
123 /*
124 * Adjust the time obtained from the CMOS to be UTC time instead of
125 * local time.
126 *
127 * This is ugly, but preferable to the alternatives. Otherwise we
128 * would either need to write a program to do it in /etc/rc (and risk
129 * confusion if the program gets run more than once; it would also be
130 * hard to make the program warp the clock precisely n hours) or
131 * compile in the timezone information into the kernel. Bad, bad....
132 *
133 * - TYT, 1992-01-01
134 *
135 * The best thing to do is to keep the CMOS clock in universal time (UTC)
136 * as real UNIX machines always do it. This avoids all headaches about
137 * daylight saving times and warping kernel clocks.
138 */
warp_clock(void)139 static inline void warp_clock(void)
140 {
141 if (sys_tz.tz_minuteswest != 0) {
142 struct timespec adjust;
143
144 persistent_clock_is_local = 1;
145 adjust.tv_sec = sys_tz.tz_minuteswest * 60;
146 adjust.tv_nsec = 0;
147 timekeeping_inject_offset(&adjust);
148 }
149 }
150
151 /*
152 * In case for some reason the CMOS clock has not already been running
153 * in UTC, but in some local time: The first time we set the timezone,
154 * we will warp the clock so that it is ticking UTC time instead of
155 * local time. Presumably, if someone is setting the timezone then we
156 * are running in an environment where the programs understand about
157 * timezones. This should be done at boot time in the /etc/rc script,
158 * as soon as possible, so that the clock can be set right. Otherwise,
159 * various programs will get confused when the clock gets warped.
160 */
161
do_sys_settimeofday(const struct timespec * tv,const struct timezone * tz)162 int do_sys_settimeofday(const struct timespec *tv, const struct timezone *tz)
163 {
164 static int firsttime = 1;
165 int error = 0;
166
167 if (tv && !timespec_valid(tv))
168 return -EINVAL;
169
170 error = security_settime(tv, tz);
171 if (error)
172 return error;
173
174 if (tz) {
175 sys_tz = *tz;
176 update_vsyscall_tz();
177 if (firsttime) {
178 firsttime = 0;
179 if (!tv)
180 warp_clock();
181 }
182 }
183 if (tv)
184 return do_settimeofday(tv);
185 return 0;
186 }
187
SYSCALL_DEFINE2(settimeofday,struct timeval __user *,tv,struct timezone __user *,tz)188 SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv,
189 struct timezone __user *, tz)
190 {
191 struct timeval user_tv;
192 struct timespec new_ts;
193 struct timezone new_tz;
194
195 if (tv) {
196 if (copy_from_user(&user_tv, tv, sizeof(*tv)))
197 return -EFAULT;
198 new_ts.tv_sec = user_tv.tv_sec;
199 new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
200 }
201 if (tz) {
202 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
203 return -EFAULT;
204 }
205
206 return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
207 }
208
SYSCALL_DEFINE1(adjtimex,struct timex __user *,txc_p)209 SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p)
210 {
211 struct timex txc; /* Local copy of parameter */
212 int ret;
213
214 /* Copy the user data space into the kernel copy
215 * structure. But bear in mind that the structures
216 * may change
217 */
218 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
219 return -EFAULT;
220 ret = do_adjtimex(&txc);
221 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
222 }
223
224 /**
225 * current_fs_time - Return FS time
226 * @sb: Superblock.
227 *
228 * Return the current time truncated to the time granularity supported by
229 * the fs.
230 */
current_fs_time(struct super_block * sb)231 struct timespec current_fs_time(struct super_block *sb)
232 {
233 struct timespec now = current_kernel_time();
234 return timespec_trunc(now, sb->s_time_gran);
235 }
236 EXPORT_SYMBOL(current_fs_time);
237
238 /*
239 * Convert jiffies to milliseconds and back.
240 *
241 * Avoid unnecessary multiplications/divisions in the
242 * two most common HZ cases:
243 */
jiffies_to_msecs(const unsigned long j)244 unsigned int jiffies_to_msecs(const unsigned long j)
245 {
246 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
247 return (MSEC_PER_SEC / HZ) * j;
248 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
249 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
250 #else
251 # if BITS_PER_LONG == 32
252 return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
253 # else
254 return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
255 # endif
256 #endif
257 }
258 EXPORT_SYMBOL(jiffies_to_msecs);
259
jiffies_to_usecs(const unsigned long j)260 unsigned int jiffies_to_usecs(const unsigned long j)
261 {
262 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
263 return (USEC_PER_SEC / HZ) * j;
264 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
265 return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
266 #else
267 # if BITS_PER_LONG == 32
268 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
269 # else
270 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
271 # endif
272 #endif
273 }
274 EXPORT_SYMBOL(jiffies_to_usecs);
275
276 /**
277 * timespec_trunc - Truncate timespec to a granularity
278 * @t: Timespec
279 * @gran: Granularity in ns.
280 *
281 * Truncate a timespec to a granularity. gran must be smaller than a second.
282 * Always rounds down.
283 *
284 * This function should be only used for timestamps returned by
285 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
286 * it doesn't handle the better resolution of the latter.
287 */
timespec_trunc(struct timespec t,unsigned gran)288 struct timespec timespec_trunc(struct timespec t, unsigned gran)
289 {
290 /*
291 * Division is pretty slow so avoid it for common cases.
292 * Currently current_kernel_time() never returns better than
293 * jiffies resolution. Exploit that.
294 */
295 if (gran <= jiffies_to_usecs(1) * 1000) {
296 /* nothing */
297 } else if (gran == 1000000000) {
298 t.tv_nsec = 0;
299 } else {
300 t.tv_nsec -= t.tv_nsec % gran;
301 }
302 return t;
303 }
304 EXPORT_SYMBOL(timespec_trunc);
305
306 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
307 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
308 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
309 *
310 * [For the Julian calendar (which was used in Russia before 1917,
311 * Britain & colonies before 1752, anywhere else before 1582,
312 * and is still in use by some communities) leave out the
313 * -year/100+year/400 terms, and add 10.]
314 *
315 * This algorithm was first published by Gauss (I think).
316 *
317 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
318 * machines where long is 32-bit! (However, as time_t is signed, we
319 * will already get problems at other places on 2038-01-19 03:14:08)
320 */
321 unsigned long
mktime(const unsigned int year0,const unsigned int mon0,const unsigned int day,const unsigned int hour,const unsigned int min,const unsigned int sec)322 mktime(const unsigned int year0, const unsigned int mon0,
323 const unsigned int day, const unsigned int hour,
324 const unsigned int min, const unsigned int sec)
325 {
326 unsigned int mon = mon0, year = year0;
327
328 /* 1..12 -> 11,12,1..10 */
329 if (0 >= (int) (mon -= 2)) {
330 mon += 12; /* Puts Feb last since it has leap day */
331 year -= 1;
332 }
333
334 return ((((unsigned long)
335 (year/4 - year/100 + year/400 + 367*mon/12 + day) +
336 year*365 - 719499
337 )*24 + hour /* now have hours */
338 )*60 + min /* now have minutes */
339 )*60 + sec; /* finally seconds */
340 }
341
342 EXPORT_SYMBOL(mktime);
343
344 /**
345 * set_normalized_timespec - set timespec sec and nsec parts and normalize
346 *
347 * @ts: pointer to timespec variable to be set
348 * @sec: seconds to set
349 * @nsec: nanoseconds to set
350 *
351 * Set seconds and nanoseconds field of a timespec variable and
352 * normalize to the timespec storage format
353 *
354 * Note: The tv_nsec part is always in the range of
355 * 0 <= tv_nsec < NSEC_PER_SEC
356 * For negative values only the tv_sec field is negative !
357 */
set_normalized_timespec(struct timespec * ts,time_t sec,s64 nsec)358 void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
359 {
360 while (nsec >= NSEC_PER_SEC) {
361 /*
362 * The following asm() prevents the compiler from
363 * optimising this loop into a modulo operation. See
364 * also __iter_div_u64_rem() in include/linux/time.h
365 */
366 asm("" : "+rm"(nsec));
367 nsec -= NSEC_PER_SEC;
368 ++sec;
369 }
370 while (nsec < 0) {
371 asm("" : "+rm"(nsec));
372 nsec += NSEC_PER_SEC;
373 --sec;
374 }
375 ts->tv_sec = sec;
376 ts->tv_nsec = nsec;
377 }
378 EXPORT_SYMBOL(set_normalized_timespec);
379
380 /**
381 * ns_to_timespec - Convert nanoseconds to timespec
382 * @nsec: the nanoseconds value to be converted
383 *
384 * Returns the timespec representation of the nsec parameter.
385 */
ns_to_timespec(const s64 nsec)386 struct timespec ns_to_timespec(const s64 nsec)
387 {
388 struct timespec ts;
389 s32 rem;
390
391 if (!nsec)
392 return (struct timespec) {0, 0};
393
394 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
395 if (unlikely(rem < 0)) {
396 ts.tv_sec--;
397 rem += NSEC_PER_SEC;
398 }
399 ts.tv_nsec = rem;
400
401 return ts;
402 }
403 EXPORT_SYMBOL(ns_to_timespec);
404
405 /**
406 * ns_to_timeval - Convert nanoseconds to timeval
407 * @nsec: the nanoseconds value to be converted
408 *
409 * Returns the timeval representation of the nsec parameter.
410 */
ns_to_timeval(const s64 nsec)411 struct timeval ns_to_timeval(const s64 nsec)
412 {
413 struct timespec ts = ns_to_timespec(nsec);
414 struct timeval tv;
415
416 tv.tv_sec = ts.tv_sec;
417 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
418
419 return tv;
420 }
421 EXPORT_SYMBOL(ns_to_timeval);
422
423 /*
424 * When we convert to jiffies then we interpret incoming values
425 * the following way:
426 *
427 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
428 *
429 * - 'too large' values [that would result in larger than
430 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
431 *
432 * - all other values are converted to jiffies by either multiplying
433 * the input value by a factor or dividing it with a factor
434 *
435 * We must also be careful about 32-bit overflows.
436 */
msecs_to_jiffies(const unsigned int m)437 unsigned long msecs_to_jiffies(const unsigned int m)
438 {
439 /*
440 * Negative value, means infinite timeout:
441 */
442 if ((int)m < 0)
443 return MAX_JIFFY_OFFSET;
444
445 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
446 /*
447 * HZ is equal to or smaller than 1000, and 1000 is a nice
448 * round multiple of HZ, divide with the factor between them,
449 * but round upwards:
450 */
451 return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
452 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
453 /*
454 * HZ is larger than 1000, and HZ is a nice round multiple of
455 * 1000 - simply multiply with the factor between them.
456 *
457 * But first make sure the multiplication result cannot
458 * overflow:
459 */
460 if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
461 return MAX_JIFFY_OFFSET;
462
463 return m * (HZ / MSEC_PER_SEC);
464 #else
465 /*
466 * Generic case - multiply, round and divide. But first
467 * check that if we are doing a net multiplication, that
468 * we wouldn't overflow:
469 */
470 if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
471 return MAX_JIFFY_OFFSET;
472
473 return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
474 >> MSEC_TO_HZ_SHR32;
475 #endif
476 }
477 EXPORT_SYMBOL(msecs_to_jiffies);
478
usecs_to_jiffies(const unsigned int u)479 unsigned long usecs_to_jiffies(const unsigned int u)
480 {
481 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
482 return MAX_JIFFY_OFFSET;
483 #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
484 return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
485 #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
486 return u * (HZ / USEC_PER_SEC);
487 #else
488 return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
489 >> USEC_TO_HZ_SHR32;
490 #endif
491 }
492 EXPORT_SYMBOL(usecs_to_jiffies);
493
494 /*
495 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note
496 * that a remainder subtract here would not do the right thing as the
497 * resolution values don't fall on second boundries. I.e. the line:
498 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
499 *
500 * Rather, we just shift the bits off the right.
501 *
502 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
503 * value to a scaled second value.
504 */
505 unsigned long
timespec_to_jiffies(const struct timespec * value)506 timespec_to_jiffies(const struct timespec *value)
507 {
508 unsigned long sec = value->tv_sec;
509 long nsec = value->tv_nsec + TICK_NSEC - 1;
510
511 if (sec >= MAX_SEC_IN_JIFFIES){
512 sec = MAX_SEC_IN_JIFFIES;
513 nsec = 0;
514 }
515 return (((u64)sec * SEC_CONVERSION) +
516 (((u64)nsec * NSEC_CONVERSION) >>
517 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
518
519 }
520 EXPORT_SYMBOL(timespec_to_jiffies);
521
522 void
jiffies_to_timespec(const unsigned long jiffies,struct timespec * value)523 jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
524 {
525 /*
526 * Convert jiffies to nanoseconds and separate with
527 * one divide.
528 */
529 u32 rem;
530 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
531 NSEC_PER_SEC, &rem);
532 value->tv_nsec = rem;
533 }
534 EXPORT_SYMBOL(jiffies_to_timespec);
535
536 /* Same for "timeval"
537 *
538 * Well, almost. The problem here is that the real system resolution is
539 * in nanoseconds and the value being converted is in micro seconds.
540 * Also for some machines (those that use HZ = 1024, in-particular),
541 * there is a LARGE error in the tick size in microseconds.
542
543 * The solution we use is to do the rounding AFTER we convert the
544 * microsecond part. Thus the USEC_ROUND, the bits to be shifted off.
545 * Instruction wise, this should cost only an additional add with carry
546 * instruction above the way it was done above.
547 */
548 unsigned long
timeval_to_jiffies(const struct timeval * value)549 timeval_to_jiffies(const struct timeval *value)
550 {
551 unsigned long sec = value->tv_sec;
552 long usec = value->tv_usec;
553
554 if (sec >= MAX_SEC_IN_JIFFIES){
555 sec = MAX_SEC_IN_JIFFIES;
556 usec = 0;
557 }
558 return (((u64)sec * SEC_CONVERSION) +
559 (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
560 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
561 }
562 EXPORT_SYMBOL(timeval_to_jiffies);
563
jiffies_to_timeval(const unsigned long jiffies,struct timeval * value)564 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
565 {
566 /*
567 * Convert jiffies to nanoseconds and separate with
568 * one divide.
569 */
570 u32 rem;
571
572 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
573 NSEC_PER_SEC, &rem);
574 value->tv_usec = rem / NSEC_PER_USEC;
575 }
576 EXPORT_SYMBOL(jiffies_to_timeval);
577
578 /*
579 * Convert jiffies/jiffies_64 to clock_t and back.
580 */
jiffies_to_clock_t(unsigned long x)581 clock_t jiffies_to_clock_t(unsigned long x)
582 {
583 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
584 # if HZ < USER_HZ
585 return x * (USER_HZ / HZ);
586 # else
587 return x / (HZ / USER_HZ);
588 # endif
589 #else
590 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
591 #endif
592 }
593 EXPORT_SYMBOL(jiffies_to_clock_t);
594
clock_t_to_jiffies(unsigned long x)595 unsigned long clock_t_to_jiffies(unsigned long x)
596 {
597 #if (HZ % USER_HZ)==0
598 if (x >= ~0UL / (HZ / USER_HZ))
599 return ~0UL;
600 return x * (HZ / USER_HZ);
601 #else
602 /* Don't worry about loss of precision here .. */
603 if (x >= ~0UL / HZ * USER_HZ)
604 return ~0UL;
605
606 /* .. but do try to contain it here */
607 return div_u64((u64)x * HZ, USER_HZ);
608 #endif
609 }
610 EXPORT_SYMBOL(clock_t_to_jiffies);
611
jiffies_64_to_clock_t(u64 x)612 u64 jiffies_64_to_clock_t(u64 x)
613 {
614 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
615 # if HZ < USER_HZ
616 x = div_u64(x * USER_HZ, HZ);
617 # elif HZ > USER_HZ
618 x = div_u64(x, HZ / USER_HZ);
619 # else
620 /* Nothing to do */
621 # endif
622 #else
623 /*
624 * There are better ways that don't overflow early,
625 * but even this doesn't overflow in hundreds of years
626 * in 64 bits, so..
627 */
628 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
629 #endif
630 return x;
631 }
632 EXPORT_SYMBOL(jiffies_64_to_clock_t);
633
nsec_to_clock_t(u64 x)634 u64 nsec_to_clock_t(u64 x)
635 {
636 #if (NSEC_PER_SEC % USER_HZ) == 0
637 return div_u64(x, NSEC_PER_SEC / USER_HZ);
638 #elif (USER_HZ % 512) == 0
639 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
640 #else
641 /*
642 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
643 * overflow after 64.99 years.
644 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
645 */
646 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
647 #endif
648 }
649
650 /**
651 * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
652 *
653 * @n: nsecs in u64
654 *
655 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
656 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
657 * for scheduler, not for use in device drivers to calculate timeout value.
658 *
659 * note:
660 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
661 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
662 */
nsecs_to_jiffies64(u64 n)663 u64 nsecs_to_jiffies64(u64 n)
664 {
665 #if (NSEC_PER_SEC % HZ) == 0
666 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
667 return div_u64(n, NSEC_PER_SEC / HZ);
668 #elif (HZ % 512) == 0
669 /* overflow after 292 years if HZ = 1024 */
670 return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
671 #else
672 /*
673 * Generic case - optimized for cases where HZ is a multiple of 3.
674 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
675 */
676 return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
677 #endif
678 }
679
680 /**
681 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
682 *
683 * @n: nsecs in u64
684 *
685 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
686 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
687 * for scheduler, not for use in device drivers to calculate timeout value.
688 *
689 * note:
690 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
691 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
692 */
nsecs_to_jiffies(u64 n)693 unsigned long nsecs_to_jiffies(u64 n)
694 {
695 return (unsigned long)nsecs_to_jiffies64(n);
696 }
697
698 /*
699 * Add two timespec values and do a safety check for overflow.
700 * It's assumed that both values are valid (>= 0)
701 */
timespec_add_safe(const struct timespec lhs,const struct timespec rhs)702 struct timespec timespec_add_safe(const struct timespec lhs,
703 const struct timespec rhs)
704 {
705 struct timespec res;
706
707 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
708 lhs.tv_nsec + rhs.tv_nsec);
709
710 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
711 res.tv_sec = TIME_T_MAX;
712
713 return res;
714 }
715