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 <linux/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 */ 51 struct timezone sys_tz; 52 53 EXPORT_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 */ 63 SYSCALL_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 82 SYSCALL_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 */ 101 102 SYSCALL_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 */ 122 int 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 */ 140 static 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 */ 162 163 int do_sys_settimeofday64(const struct timespec64 *tv, const struct timezone *tz) 164 { 165 static int firsttime = 1; 166 int error = 0; 167 168 if (tv && !timespec64_valid(tv)) 169 return -EINVAL; 170 171 error = security_settime64(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_settimeofday64(tv); 190 return 0; 191 } 192 193 SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv, 194 struct timezone __user *, tz) 195 { 196 struct timespec64 new_ts; 197 struct timeval user_tv; 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_settimeofday64(tv ? &new_ts : NULL, tz ? &new_tz : NULL); 216 } 217 218 SYSCALL_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 * Convert jiffies to milliseconds and back. 235 * 236 * Avoid unnecessary multiplications/divisions in the 237 * two most common HZ cases: 238 */ 239 unsigned int jiffies_to_msecs(const unsigned long j) 240 { 241 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) 242 return (MSEC_PER_SEC / HZ) * j; 243 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) 244 return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC); 245 #else 246 # if BITS_PER_LONG == 32 247 return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32; 248 # else 249 return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN; 250 # endif 251 #endif 252 } 253 EXPORT_SYMBOL(jiffies_to_msecs); 254 255 unsigned int jiffies_to_usecs(const unsigned long j) 256 { 257 /* 258 * Hz usually doesn't go much further MSEC_PER_SEC. 259 * jiffies_to_usecs() and usecs_to_jiffies() depend on that. 260 */ 261 BUILD_BUG_ON(HZ > USEC_PER_SEC); 262 263 #if !(USEC_PER_SEC % HZ) 264 return (USEC_PER_SEC / HZ) * j; 265 #else 266 # if BITS_PER_LONG == 32 267 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32; 268 # else 269 return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN; 270 # endif 271 #endif 272 } 273 EXPORT_SYMBOL(jiffies_to_usecs); 274 275 /** 276 * timespec_trunc - Truncate timespec to a granularity 277 * @t: Timespec 278 * @gran: Granularity in ns. 279 * 280 * Truncate a timespec to a granularity. Always rounds down. gran must 281 * not be 0 nor greater than a second (NSEC_PER_SEC, or 10^9 ns). 282 */ 283 struct timespec timespec_trunc(struct timespec t, unsigned gran) 284 { 285 /* Avoid division in the common cases 1 ns and 1 s. */ 286 if (gran == 1) { 287 /* nothing */ 288 } else if (gran == NSEC_PER_SEC) { 289 t.tv_nsec = 0; 290 } else if (gran > 1 && gran < NSEC_PER_SEC) { 291 t.tv_nsec -= t.tv_nsec % gran; 292 } else { 293 WARN(1, "illegal file time granularity: %u", gran); 294 } 295 return t; 296 } 297 EXPORT_SYMBOL(timespec_trunc); 298 299 /* 300 * mktime64 - Converts date to seconds. 301 * Converts Gregorian date to seconds since 1970-01-01 00:00:00. 302 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59 303 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59. 304 * 305 * [For the Julian calendar (which was used in Russia before 1917, 306 * Britain & colonies before 1752, anywhere else before 1582, 307 * and is still in use by some communities) leave out the 308 * -year/100+year/400 terms, and add 10.] 309 * 310 * This algorithm was first published by Gauss (I think). 311 * 312 * A leap second can be indicated by calling this function with sec as 313 * 60 (allowable under ISO 8601). The leap second is treated the same 314 * as the following second since they don't exist in UNIX time. 315 * 316 * An encoding of midnight at the end of the day as 24:00:00 - ie. midnight 317 * tomorrow - (allowable under ISO 8601) is supported. 318 */ 319 time64_t mktime64(const unsigned int year0, const unsigned int mon0, 320 const unsigned int day, const unsigned int hour, 321 const unsigned int min, const unsigned int sec) 322 { 323 unsigned int mon = mon0, year = year0; 324 325 /* 1..12 -> 11,12,1..10 */ 326 if (0 >= (int) (mon -= 2)) { 327 mon += 12; /* Puts Feb last since it has leap day */ 328 year -= 1; 329 } 330 331 return ((((time64_t) 332 (year/4 - year/100 + year/400 + 367*mon/12 + day) + 333 year*365 - 719499 334 )*24 + hour /* now have hours - midnight tomorrow handled here */ 335 )*60 + min /* now have minutes */ 336 )*60 + sec; /* finally seconds */ 337 } 338 EXPORT_SYMBOL(mktime64); 339 340 /** 341 * set_normalized_timespec - set timespec sec and nsec parts and normalize 342 * 343 * @ts: pointer to timespec variable to be set 344 * @sec: seconds to set 345 * @nsec: nanoseconds to set 346 * 347 * Set seconds and nanoseconds field of a timespec variable and 348 * normalize to the timespec storage format 349 * 350 * Note: The tv_nsec part is always in the range of 351 * 0 <= tv_nsec < NSEC_PER_SEC 352 * For negative values only the tv_sec field is negative ! 353 */ 354 void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec) 355 { 356 while (nsec >= NSEC_PER_SEC) { 357 /* 358 * The following asm() prevents the compiler from 359 * optimising this loop into a modulo operation. See 360 * also __iter_div_u64_rem() in include/linux/time.h 361 */ 362 asm("" : "+rm"(nsec)); 363 nsec -= NSEC_PER_SEC; 364 ++sec; 365 } 366 while (nsec < 0) { 367 asm("" : "+rm"(nsec)); 368 nsec += NSEC_PER_SEC; 369 --sec; 370 } 371 ts->tv_sec = sec; 372 ts->tv_nsec = nsec; 373 } 374 EXPORT_SYMBOL(set_normalized_timespec); 375 376 /** 377 * ns_to_timespec - Convert nanoseconds to timespec 378 * @nsec: the nanoseconds value to be converted 379 * 380 * Returns the timespec representation of the nsec parameter. 381 */ 382 struct timespec ns_to_timespec(const s64 nsec) 383 { 384 struct timespec ts; 385 s32 rem; 386 387 if (!nsec) 388 return (struct timespec) {0, 0}; 389 390 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem); 391 if (unlikely(rem < 0)) { 392 ts.tv_sec--; 393 rem += NSEC_PER_SEC; 394 } 395 ts.tv_nsec = rem; 396 397 return ts; 398 } 399 EXPORT_SYMBOL(ns_to_timespec); 400 401 /** 402 * ns_to_timeval - Convert nanoseconds to timeval 403 * @nsec: the nanoseconds value to be converted 404 * 405 * Returns the timeval representation of the nsec parameter. 406 */ 407 struct timeval ns_to_timeval(const s64 nsec) 408 { 409 struct timespec ts = ns_to_timespec(nsec); 410 struct timeval tv; 411 412 tv.tv_sec = ts.tv_sec; 413 tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000; 414 415 return tv; 416 } 417 EXPORT_SYMBOL(ns_to_timeval); 418 419 #if BITS_PER_LONG == 32 420 /** 421 * set_normalized_timespec - set timespec sec and nsec parts and normalize 422 * 423 * @ts: pointer to timespec variable to be set 424 * @sec: seconds to set 425 * @nsec: nanoseconds to set 426 * 427 * Set seconds and nanoseconds field of a timespec variable and 428 * normalize to the timespec storage format 429 * 430 * Note: The tv_nsec part is always in the range of 431 * 0 <= tv_nsec < NSEC_PER_SEC 432 * For negative values only the tv_sec field is negative ! 433 */ 434 void set_normalized_timespec64(struct timespec64 *ts, time64_t sec, s64 nsec) 435 { 436 while (nsec >= NSEC_PER_SEC) { 437 /* 438 * The following asm() prevents the compiler from 439 * optimising this loop into a modulo operation. See 440 * also __iter_div_u64_rem() in include/linux/time.h 441 */ 442 asm("" : "+rm"(nsec)); 443 nsec -= NSEC_PER_SEC; 444 ++sec; 445 } 446 while (nsec < 0) { 447 asm("" : "+rm"(nsec)); 448 nsec += NSEC_PER_SEC; 449 --sec; 450 } 451 ts->tv_sec = sec; 452 ts->tv_nsec = nsec; 453 } 454 EXPORT_SYMBOL(set_normalized_timespec64); 455 456 /** 457 * ns_to_timespec64 - Convert nanoseconds to timespec64 458 * @nsec: the nanoseconds value to be converted 459 * 460 * Returns the timespec64 representation of the nsec parameter. 461 */ 462 struct timespec64 ns_to_timespec64(const s64 nsec) 463 { 464 struct timespec64 ts; 465 s32 rem; 466 467 if (!nsec) 468 return (struct timespec64) {0, 0}; 469 470 ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem); 471 if (unlikely(rem < 0)) { 472 ts.tv_sec--; 473 rem += NSEC_PER_SEC; 474 } 475 ts.tv_nsec = rem; 476 477 return ts; 478 } 479 EXPORT_SYMBOL(ns_to_timespec64); 480 #endif 481 /** 482 * msecs_to_jiffies: - convert milliseconds to jiffies 483 * @m: time in milliseconds 484 * 485 * conversion is done as follows: 486 * 487 * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET) 488 * 489 * - 'too large' values [that would result in larger than 490 * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too. 491 * 492 * - all other values are converted to jiffies by either multiplying 493 * the input value by a factor or dividing it with a factor and 494 * handling any 32-bit overflows. 495 * for the details see __msecs_to_jiffies() 496 * 497 * msecs_to_jiffies() checks for the passed in value being a constant 498 * via __builtin_constant_p() allowing gcc to eliminate most of the 499 * code, __msecs_to_jiffies() is called if the value passed does not 500 * allow constant folding and the actual conversion must be done at 501 * runtime. 502 * the _msecs_to_jiffies helpers are the HZ dependent conversion 503 * routines found in include/linux/jiffies.h 504 */ 505 unsigned long __msecs_to_jiffies(const unsigned int m) 506 { 507 /* 508 * Negative value, means infinite timeout: 509 */ 510 if ((int)m < 0) 511 return MAX_JIFFY_OFFSET; 512 return _msecs_to_jiffies(m); 513 } 514 EXPORT_SYMBOL(__msecs_to_jiffies); 515 516 unsigned long __usecs_to_jiffies(const unsigned int u) 517 { 518 if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET)) 519 return MAX_JIFFY_OFFSET; 520 return _usecs_to_jiffies(u); 521 } 522 EXPORT_SYMBOL(__usecs_to_jiffies); 523 524 /* 525 * The TICK_NSEC - 1 rounds up the value to the next resolution. Note 526 * that a remainder subtract here would not do the right thing as the 527 * resolution values don't fall on second boundries. I.e. the line: 528 * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding. 529 * Note that due to the small error in the multiplier here, this 530 * rounding is incorrect for sufficiently large values of tv_nsec, but 531 * well formed timespecs should have tv_nsec < NSEC_PER_SEC, so we're 532 * OK. 533 * 534 * Rather, we just shift the bits off the right. 535 * 536 * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec 537 * value to a scaled second value. 538 */ 539 static unsigned long 540 __timespec64_to_jiffies(u64 sec, long nsec) 541 { 542 nsec = nsec + TICK_NSEC - 1; 543 544 if (sec >= MAX_SEC_IN_JIFFIES){ 545 sec = MAX_SEC_IN_JIFFIES; 546 nsec = 0; 547 } 548 return ((sec * SEC_CONVERSION) + 549 (((u64)nsec * NSEC_CONVERSION) >> 550 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC; 551 552 } 553 554 static unsigned long 555 __timespec_to_jiffies(unsigned long sec, long nsec) 556 { 557 return __timespec64_to_jiffies((u64)sec, nsec); 558 } 559 560 unsigned long 561 timespec64_to_jiffies(const struct timespec64 *value) 562 { 563 return __timespec64_to_jiffies(value->tv_sec, value->tv_nsec); 564 } 565 EXPORT_SYMBOL(timespec64_to_jiffies); 566 567 void 568 jiffies_to_timespec64(const unsigned long jiffies, struct timespec64 *value) 569 { 570 /* 571 * Convert jiffies to nanoseconds and separate with 572 * one divide. 573 */ 574 u32 rem; 575 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC, 576 NSEC_PER_SEC, &rem); 577 value->tv_nsec = rem; 578 } 579 EXPORT_SYMBOL(jiffies_to_timespec64); 580 581 /* 582 * We could use a similar algorithm to timespec_to_jiffies (with a 583 * different multiplier for usec instead of nsec). But this has a 584 * problem with rounding: we can't exactly add TICK_NSEC - 1 to the 585 * usec value, since it's not necessarily integral. 586 * 587 * We could instead round in the intermediate scaled representation 588 * (i.e. in units of 1/2^(large scale) jiffies) but that's also 589 * perilous: the scaling introduces a small positive error, which 590 * combined with a division-rounding-upward (i.e. adding 2^(scale) - 1 591 * units to the intermediate before shifting) leads to accidental 592 * overflow and overestimates. 593 * 594 * At the cost of one additional multiplication by a constant, just 595 * use the timespec implementation. 596 */ 597 unsigned long 598 timeval_to_jiffies(const struct timeval *value) 599 { 600 return __timespec_to_jiffies(value->tv_sec, 601 value->tv_usec * NSEC_PER_USEC); 602 } 603 EXPORT_SYMBOL(timeval_to_jiffies); 604 605 void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value) 606 { 607 /* 608 * Convert jiffies to nanoseconds and separate with 609 * one divide. 610 */ 611 u32 rem; 612 613 value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC, 614 NSEC_PER_SEC, &rem); 615 value->tv_usec = rem / NSEC_PER_USEC; 616 } 617 EXPORT_SYMBOL(jiffies_to_timeval); 618 619 /* 620 * Convert jiffies/jiffies_64 to clock_t and back. 621 */ 622 clock_t jiffies_to_clock_t(unsigned long x) 623 { 624 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 625 # if HZ < USER_HZ 626 return x * (USER_HZ / HZ); 627 # else 628 return x / (HZ / USER_HZ); 629 # endif 630 #else 631 return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ); 632 #endif 633 } 634 EXPORT_SYMBOL(jiffies_to_clock_t); 635 636 unsigned long clock_t_to_jiffies(unsigned long x) 637 { 638 #if (HZ % USER_HZ)==0 639 if (x >= ~0UL / (HZ / USER_HZ)) 640 return ~0UL; 641 return x * (HZ / USER_HZ); 642 #else 643 /* Don't worry about loss of precision here .. */ 644 if (x >= ~0UL / HZ * USER_HZ) 645 return ~0UL; 646 647 /* .. but do try to contain it here */ 648 return div_u64((u64)x * HZ, USER_HZ); 649 #endif 650 } 651 EXPORT_SYMBOL(clock_t_to_jiffies); 652 653 u64 jiffies_64_to_clock_t(u64 x) 654 { 655 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 656 # if HZ < USER_HZ 657 x = div_u64(x * USER_HZ, HZ); 658 # elif HZ > USER_HZ 659 x = div_u64(x, HZ / USER_HZ); 660 # else 661 /* Nothing to do */ 662 # endif 663 #else 664 /* 665 * There are better ways that don't overflow early, 666 * but even this doesn't overflow in hundreds of years 667 * in 64 bits, so.. 668 */ 669 x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ)); 670 #endif 671 return x; 672 } 673 EXPORT_SYMBOL(jiffies_64_to_clock_t); 674 675 u64 nsec_to_clock_t(u64 x) 676 { 677 #if (NSEC_PER_SEC % USER_HZ) == 0 678 return div_u64(x, NSEC_PER_SEC / USER_HZ); 679 #elif (USER_HZ % 512) == 0 680 return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512); 681 #else 682 /* 683 * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024, 684 * overflow after 64.99 years. 685 * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ... 686 */ 687 return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ); 688 #endif 689 } 690 691 u64 jiffies64_to_nsecs(u64 j) 692 { 693 #if !(NSEC_PER_SEC % HZ) 694 return (NSEC_PER_SEC / HZ) * j; 695 # else 696 return div_u64(j * HZ_TO_NSEC_NUM, HZ_TO_NSEC_DEN); 697 #endif 698 } 699 EXPORT_SYMBOL(jiffies64_to_nsecs); 700 701 /** 702 * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64 703 * 704 * @n: nsecs in u64 705 * 706 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64. 707 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed 708 * for scheduler, not for use in device drivers to calculate timeout value. 709 * 710 * note: 711 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512) 712 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years 713 */ 714 u64 nsecs_to_jiffies64(u64 n) 715 { 716 #if (NSEC_PER_SEC % HZ) == 0 717 /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */ 718 return div_u64(n, NSEC_PER_SEC / HZ); 719 #elif (HZ % 512) == 0 720 /* overflow after 292 years if HZ = 1024 */ 721 return div_u64(n * HZ / 512, NSEC_PER_SEC / 512); 722 #else 723 /* 724 * Generic case - optimized for cases where HZ is a multiple of 3. 725 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc. 726 */ 727 return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ); 728 #endif 729 } 730 EXPORT_SYMBOL(nsecs_to_jiffies64); 731 732 /** 733 * nsecs_to_jiffies - Convert nsecs in u64 to jiffies 734 * 735 * @n: nsecs in u64 736 * 737 * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64. 738 * And this doesn't return MAX_JIFFY_OFFSET since this function is designed 739 * for scheduler, not for use in device drivers to calculate timeout value. 740 * 741 * note: 742 * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512) 743 * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years 744 */ 745 unsigned long nsecs_to_jiffies(u64 n) 746 { 747 return (unsigned long)nsecs_to_jiffies64(n); 748 } 749 EXPORT_SYMBOL_GPL(nsecs_to_jiffies); 750 751 /* 752 * Add two timespec values and do a safety check for overflow. 753 * It's assumed that both values are valid (>= 0) 754 */ 755 struct timespec timespec_add_safe(const struct timespec lhs, 756 const struct timespec rhs) 757 { 758 struct timespec res; 759 760 set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec, 761 lhs.tv_nsec + rhs.tv_nsec); 762 763 if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec) 764 res.tv_sec = TIME_T_MAX; 765 766 return res; 767 } 768 769 /* 770 * Add two timespec64 values and do a safety check for overflow. 771 * It's assumed that both values are valid (>= 0). 772 * And, each timespec64 is in normalized form. 773 */ 774 struct timespec64 timespec64_add_safe(const struct timespec64 lhs, 775 const struct timespec64 rhs) 776 { 777 struct timespec64 res; 778 779 set_normalized_timespec64(&res, (timeu64_t) lhs.tv_sec + rhs.tv_sec, 780 lhs.tv_nsec + rhs.tv_nsec); 781 782 if (unlikely(res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)) { 783 res.tv_sec = TIME64_MAX; 784 res.tv_nsec = 0; 785 } 786 787 return res; 788 } 789