1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * NTP state machine interfaces and logic. 4 * 5 * This code was mainly moved from kernel/timer.c and kernel/time.c 6 * Please see those files for relevant copyright info and historical 7 * changelogs. 8 */ 9 #include <linux/capability.h> 10 #include <linux/clocksource.h> 11 #include <linux/workqueue.h> 12 #include <linux/hrtimer.h> 13 #include <linux/jiffies.h> 14 #include <linux/math64.h> 15 #include <linux/timex.h> 16 #include <linux/time.h> 17 #include <linux/mm.h> 18 #include <linux/module.h> 19 #include <linux/rtc.h> 20 #include <linux/audit.h> 21 22 #include "ntp_internal.h" 23 #include "timekeeping_internal.h" 24 25 26 /* 27 * NTP timekeeping variables: 28 * 29 * Note: All of the NTP state is protected by the timekeeping locks. 30 */ 31 32 33 /* USER_HZ period (usecs): */ 34 unsigned long tick_usec = USER_TICK_USEC; 35 36 /* SHIFTED_HZ period (nsecs): */ 37 unsigned long tick_nsec; 38 39 static u64 tick_length; 40 static u64 tick_length_base; 41 42 #define SECS_PER_DAY 86400 43 #define MAX_TICKADJ 500LL /* usecs */ 44 #define MAX_TICKADJ_SCALED \ 45 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ) 46 #define MAX_TAI_OFFSET 100000 47 48 /* 49 * phase-lock loop variables 50 */ 51 52 /* 53 * clock synchronization status 54 * 55 * (TIME_ERROR prevents overwriting the CMOS clock) 56 */ 57 static int time_state = TIME_OK; 58 59 /* clock status bits: */ 60 static int time_status = STA_UNSYNC; 61 62 /* time adjustment (nsecs): */ 63 static s64 time_offset; 64 65 /* pll time constant: */ 66 static long time_constant = 2; 67 68 /* maximum error (usecs): */ 69 static long time_maxerror = NTP_PHASE_LIMIT; 70 71 /* estimated error (usecs): */ 72 static long time_esterror = NTP_PHASE_LIMIT; 73 74 /* frequency offset (scaled nsecs/secs): */ 75 static s64 time_freq; 76 77 /* time at last adjustment (secs): */ 78 static time64_t time_reftime; 79 80 static long time_adjust; 81 82 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */ 83 static s64 ntp_tick_adj; 84 85 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */ 86 static time64_t ntp_next_leap_sec = TIME64_MAX; 87 88 #ifdef CONFIG_NTP_PPS 89 90 /* 91 * The following variables are used when a pulse-per-second (PPS) signal 92 * is available. They establish the engineering parameters of the clock 93 * discipline loop when controlled by the PPS signal. 94 */ 95 #define PPS_VALID 10 /* PPS signal watchdog max (s) */ 96 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */ 97 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */ 98 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */ 99 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to 100 increase pps_shift or consecutive bad 101 intervals to decrease it */ 102 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */ 103 104 static int pps_valid; /* signal watchdog counter */ 105 static long pps_tf[3]; /* phase median filter */ 106 static long pps_jitter; /* current jitter (ns) */ 107 static struct timespec64 pps_fbase; /* beginning of the last freq interval */ 108 static int pps_shift; /* current interval duration (s) (shift) */ 109 static int pps_intcnt; /* interval counter */ 110 static s64 pps_freq; /* frequency offset (scaled ns/s) */ 111 static long pps_stabil; /* current stability (scaled ns/s) */ 112 113 /* 114 * PPS signal quality monitors 115 */ 116 static long pps_calcnt; /* calibration intervals */ 117 static long pps_jitcnt; /* jitter limit exceeded */ 118 static long pps_stbcnt; /* stability limit exceeded */ 119 static long pps_errcnt; /* calibration errors */ 120 121 122 /* PPS kernel consumer compensates the whole phase error immediately. 123 * Otherwise, reduce the offset by a fixed factor times the time constant. 124 */ 125 static inline s64 ntp_offset_chunk(s64 offset) 126 { 127 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) 128 return offset; 129 else 130 return shift_right(offset, SHIFT_PLL + time_constant); 131 } 132 133 static inline void pps_reset_freq_interval(void) 134 { 135 /* the PPS calibration interval may end 136 surprisingly early */ 137 pps_shift = PPS_INTMIN; 138 pps_intcnt = 0; 139 } 140 141 /** 142 * pps_clear - Clears the PPS state variables 143 */ 144 static inline void pps_clear(void) 145 { 146 pps_reset_freq_interval(); 147 pps_tf[0] = 0; 148 pps_tf[1] = 0; 149 pps_tf[2] = 0; 150 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0; 151 pps_freq = 0; 152 } 153 154 /* Decrease pps_valid to indicate that another second has passed since 155 * the last PPS signal. When it reaches 0, indicate that PPS signal is 156 * missing. 157 */ 158 static inline void pps_dec_valid(void) 159 { 160 if (pps_valid > 0) 161 pps_valid--; 162 else { 163 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 164 STA_PPSWANDER | STA_PPSERROR); 165 pps_clear(); 166 } 167 } 168 169 static inline void pps_set_freq(s64 freq) 170 { 171 pps_freq = freq; 172 } 173 174 static inline int is_error_status(int status) 175 { 176 return (status & (STA_UNSYNC|STA_CLOCKERR)) 177 /* PPS signal lost when either PPS time or 178 * PPS frequency synchronization requested 179 */ 180 || ((status & (STA_PPSFREQ|STA_PPSTIME)) 181 && !(status & STA_PPSSIGNAL)) 182 /* PPS jitter exceeded when 183 * PPS time synchronization requested */ 184 || ((status & (STA_PPSTIME|STA_PPSJITTER)) 185 == (STA_PPSTIME|STA_PPSJITTER)) 186 /* PPS wander exceeded or calibration error when 187 * PPS frequency synchronization requested 188 */ 189 || ((status & STA_PPSFREQ) 190 && (status & (STA_PPSWANDER|STA_PPSERROR))); 191 } 192 193 static inline void pps_fill_timex(struct __kernel_timex *txc) 194 { 195 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) * 196 PPM_SCALE_INV, NTP_SCALE_SHIFT); 197 txc->jitter = pps_jitter; 198 if (!(time_status & STA_NANO)) 199 txc->jitter = pps_jitter / NSEC_PER_USEC; 200 txc->shift = pps_shift; 201 txc->stabil = pps_stabil; 202 txc->jitcnt = pps_jitcnt; 203 txc->calcnt = pps_calcnt; 204 txc->errcnt = pps_errcnt; 205 txc->stbcnt = pps_stbcnt; 206 } 207 208 #else /* !CONFIG_NTP_PPS */ 209 210 static inline s64 ntp_offset_chunk(s64 offset) 211 { 212 return shift_right(offset, SHIFT_PLL + time_constant); 213 } 214 215 static inline void pps_reset_freq_interval(void) {} 216 static inline void pps_clear(void) {} 217 static inline void pps_dec_valid(void) {} 218 static inline void pps_set_freq(s64 freq) {} 219 220 static inline int is_error_status(int status) 221 { 222 return status & (STA_UNSYNC|STA_CLOCKERR); 223 } 224 225 static inline void pps_fill_timex(struct __kernel_timex *txc) 226 { 227 /* PPS is not implemented, so these are zero */ 228 txc->ppsfreq = 0; 229 txc->jitter = 0; 230 txc->shift = 0; 231 txc->stabil = 0; 232 txc->jitcnt = 0; 233 txc->calcnt = 0; 234 txc->errcnt = 0; 235 txc->stbcnt = 0; 236 } 237 238 #endif /* CONFIG_NTP_PPS */ 239 240 241 /** 242 * ntp_synced - Returns 1 if the NTP status is not UNSYNC 243 * 244 */ 245 static inline int ntp_synced(void) 246 { 247 return !(time_status & STA_UNSYNC); 248 } 249 250 251 /* 252 * NTP methods: 253 */ 254 255 /* 256 * Update (tick_length, tick_length_base, tick_nsec), based 257 * on (tick_usec, ntp_tick_adj, time_freq): 258 */ 259 static void ntp_update_frequency(void) 260 { 261 u64 second_length; 262 u64 new_base; 263 264 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) 265 << NTP_SCALE_SHIFT; 266 267 second_length += ntp_tick_adj; 268 second_length += time_freq; 269 270 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT; 271 new_base = div_u64(second_length, NTP_INTERVAL_FREQ); 272 273 /* 274 * Don't wait for the next second_overflow, apply 275 * the change to the tick length immediately: 276 */ 277 tick_length += new_base - tick_length_base; 278 tick_length_base = new_base; 279 } 280 281 static inline s64 ntp_update_offset_fll(s64 offset64, long secs) 282 { 283 time_status &= ~STA_MODE; 284 285 if (secs < MINSEC) 286 return 0; 287 288 if (!(time_status & STA_FLL) && (secs <= MAXSEC)) 289 return 0; 290 291 time_status |= STA_MODE; 292 293 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs); 294 } 295 296 static void ntp_update_offset(long offset) 297 { 298 s64 freq_adj; 299 s64 offset64; 300 long secs; 301 302 if (!(time_status & STA_PLL)) 303 return; 304 305 if (!(time_status & STA_NANO)) { 306 /* Make sure the multiplication below won't overflow */ 307 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC); 308 offset *= NSEC_PER_USEC; 309 } 310 311 /* 312 * Scale the phase adjustment and 313 * clamp to the operating range. 314 */ 315 offset = clamp(offset, -MAXPHASE, MAXPHASE); 316 317 /* 318 * Select how the frequency is to be controlled 319 * and in which mode (PLL or FLL). 320 */ 321 secs = (long)(__ktime_get_real_seconds() - time_reftime); 322 if (unlikely(time_status & STA_FREQHOLD)) 323 secs = 0; 324 325 time_reftime = __ktime_get_real_seconds(); 326 327 offset64 = offset; 328 freq_adj = ntp_update_offset_fll(offset64, secs); 329 330 /* 331 * Clamp update interval to reduce PLL gain with low 332 * sampling rate (e.g. intermittent network connection) 333 * to avoid instability. 334 */ 335 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant))) 336 secs = 1 << (SHIFT_PLL + 1 + time_constant); 337 338 freq_adj += (offset64 * secs) << 339 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant)); 340 341 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED); 342 343 time_freq = max(freq_adj, -MAXFREQ_SCALED); 344 345 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); 346 } 347 348 /** 349 * ntp_clear - Clears the NTP state variables 350 */ 351 void ntp_clear(void) 352 { 353 time_adjust = 0; /* stop active adjtime() */ 354 time_status |= STA_UNSYNC; 355 time_maxerror = NTP_PHASE_LIMIT; 356 time_esterror = NTP_PHASE_LIMIT; 357 358 ntp_update_frequency(); 359 360 tick_length = tick_length_base; 361 time_offset = 0; 362 363 ntp_next_leap_sec = TIME64_MAX; 364 /* Clear PPS state variables */ 365 pps_clear(); 366 } 367 368 369 u64 ntp_tick_length(void) 370 { 371 return tick_length; 372 } 373 374 /** 375 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t 376 * 377 * Provides the time of the next leapsecond against CLOCK_REALTIME in 378 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending. 379 */ 380 ktime_t ntp_get_next_leap(void) 381 { 382 ktime_t ret; 383 384 if ((time_state == TIME_INS) && (time_status & STA_INS)) 385 return ktime_set(ntp_next_leap_sec, 0); 386 ret = KTIME_MAX; 387 return ret; 388 } 389 390 /* 391 * this routine handles the overflow of the microsecond field 392 * 393 * The tricky bits of code to handle the accurate clock support 394 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. 395 * They were originally developed for SUN and DEC kernels. 396 * All the kudos should go to Dave for this stuff. 397 * 398 * Also handles leap second processing, and returns leap offset 399 */ 400 int second_overflow(time64_t secs) 401 { 402 s64 delta; 403 int leap = 0; 404 s32 rem; 405 406 /* 407 * Leap second processing. If in leap-insert state at the end of the 408 * day, the system clock is set back one second; if in leap-delete 409 * state, the system clock is set ahead one second. 410 */ 411 switch (time_state) { 412 case TIME_OK: 413 if (time_status & STA_INS) { 414 time_state = TIME_INS; 415 div_s64_rem(secs, SECS_PER_DAY, &rem); 416 ntp_next_leap_sec = secs + SECS_PER_DAY - rem; 417 } else if (time_status & STA_DEL) { 418 time_state = TIME_DEL; 419 div_s64_rem(secs + 1, SECS_PER_DAY, &rem); 420 ntp_next_leap_sec = secs + SECS_PER_DAY - rem; 421 } 422 break; 423 case TIME_INS: 424 if (!(time_status & STA_INS)) { 425 ntp_next_leap_sec = TIME64_MAX; 426 time_state = TIME_OK; 427 } else if (secs == ntp_next_leap_sec) { 428 leap = -1; 429 time_state = TIME_OOP; 430 printk(KERN_NOTICE 431 "Clock: inserting leap second 23:59:60 UTC\n"); 432 } 433 break; 434 case TIME_DEL: 435 if (!(time_status & STA_DEL)) { 436 ntp_next_leap_sec = TIME64_MAX; 437 time_state = TIME_OK; 438 } else if (secs == ntp_next_leap_sec) { 439 leap = 1; 440 ntp_next_leap_sec = TIME64_MAX; 441 time_state = TIME_WAIT; 442 printk(KERN_NOTICE 443 "Clock: deleting leap second 23:59:59 UTC\n"); 444 } 445 break; 446 case TIME_OOP: 447 ntp_next_leap_sec = TIME64_MAX; 448 time_state = TIME_WAIT; 449 break; 450 case TIME_WAIT: 451 if (!(time_status & (STA_INS | STA_DEL))) 452 time_state = TIME_OK; 453 break; 454 } 455 456 457 /* Bump the maxerror field */ 458 time_maxerror += MAXFREQ / NSEC_PER_USEC; 459 if (time_maxerror > NTP_PHASE_LIMIT) { 460 time_maxerror = NTP_PHASE_LIMIT; 461 time_status |= STA_UNSYNC; 462 } 463 464 /* Compute the phase adjustment for the next second */ 465 tick_length = tick_length_base; 466 467 delta = ntp_offset_chunk(time_offset); 468 time_offset -= delta; 469 tick_length += delta; 470 471 /* Check PPS signal */ 472 pps_dec_valid(); 473 474 if (!time_adjust) 475 goto out; 476 477 if (time_adjust > MAX_TICKADJ) { 478 time_adjust -= MAX_TICKADJ; 479 tick_length += MAX_TICKADJ_SCALED; 480 goto out; 481 } 482 483 if (time_adjust < -MAX_TICKADJ) { 484 time_adjust += MAX_TICKADJ; 485 tick_length -= MAX_TICKADJ_SCALED; 486 goto out; 487 } 488 489 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ) 490 << NTP_SCALE_SHIFT; 491 time_adjust = 0; 492 493 out: 494 return leap; 495 } 496 497 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) 498 static void sync_hw_clock(struct work_struct *work); 499 static DECLARE_WORK(sync_work, sync_hw_clock); 500 static struct hrtimer sync_hrtimer; 501 #define SYNC_PERIOD_NS (11ULL * 60 * NSEC_PER_SEC) 502 503 static enum hrtimer_restart sync_timer_callback(struct hrtimer *timer) 504 { 505 queue_work(system_freezable_power_efficient_wq, &sync_work); 506 507 return HRTIMER_NORESTART; 508 } 509 510 static void sched_sync_hw_clock(unsigned long offset_nsec, bool retry) 511 { 512 ktime_t exp = ktime_set(ktime_get_real_seconds(), 0); 513 514 if (retry) 515 exp = ktime_add_ns(exp, 2ULL * NSEC_PER_SEC - offset_nsec); 516 else 517 exp = ktime_add_ns(exp, SYNC_PERIOD_NS - offset_nsec); 518 519 hrtimer_start(&sync_hrtimer, exp, HRTIMER_MODE_ABS); 520 } 521 522 /* 523 * Check whether @now is correct versus the required time to update the RTC 524 * and calculate the value which needs to be written to the RTC so that the 525 * next seconds increment of the RTC after the write is aligned with the next 526 * seconds increment of clock REALTIME. 527 * 528 * tsched t1 write(t2.tv_sec - 1sec)) t2 RTC increments seconds 529 * 530 * t2.tv_nsec == 0 531 * tsched = t2 - set_offset_nsec 532 * newval = t2 - NSEC_PER_SEC 533 * 534 * ==> neval = tsched + set_offset_nsec - NSEC_PER_SEC 535 * 536 * As the execution of this code is not guaranteed to happen exactly at 537 * tsched this allows it to happen within a fuzzy region: 538 * 539 * abs(now - tsched) < FUZZ 540 * 541 * If @now is not inside the allowed window the function returns false. 542 */ 543 static inline bool rtc_tv_nsec_ok(unsigned long set_offset_nsec, 544 struct timespec64 *to_set, 545 const struct timespec64 *now) 546 { 547 /* Allowed error in tv_nsec, arbitrarily set to 5 jiffies in ns. */ 548 const unsigned long TIME_SET_NSEC_FUZZ = TICK_NSEC * 5; 549 struct timespec64 delay = {.tv_sec = -1, 550 .tv_nsec = set_offset_nsec}; 551 552 *to_set = timespec64_add(*now, delay); 553 554 if (to_set->tv_nsec < TIME_SET_NSEC_FUZZ) { 555 to_set->tv_nsec = 0; 556 return true; 557 } 558 559 if (to_set->tv_nsec > NSEC_PER_SEC - TIME_SET_NSEC_FUZZ) { 560 to_set->tv_sec++; 561 to_set->tv_nsec = 0; 562 return true; 563 } 564 return false; 565 } 566 567 #ifdef CONFIG_GENERIC_CMOS_UPDATE 568 int __weak update_persistent_clock64(struct timespec64 now64) 569 { 570 return -ENODEV; 571 } 572 #else 573 static inline int update_persistent_clock64(struct timespec64 now64) 574 { 575 return -ENODEV; 576 } 577 #endif 578 579 #ifdef CONFIG_RTC_SYSTOHC 580 /* Save NTP synchronized time to the RTC */ 581 static int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec) 582 { 583 struct rtc_device *rtc; 584 struct rtc_time tm; 585 int err = -ENODEV; 586 587 rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE); 588 if (!rtc) 589 return -ENODEV; 590 591 if (!rtc->ops || !rtc->ops->set_time) 592 goto out_close; 593 594 /* First call might not have the correct offset */ 595 if (*offset_nsec == rtc->set_offset_nsec) { 596 rtc_time64_to_tm(to_set->tv_sec, &tm); 597 err = rtc_set_time(rtc, &tm); 598 } else { 599 /* Store the update offset and let the caller try again */ 600 *offset_nsec = rtc->set_offset_nsec; 601 err = -EAGAIN; 602 } 603 out_close: 604 rtc_class_close(rtc); 605 return err; 606 } 607 #else 608 static inline int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec) 609 { 610 return -ENODEV; 611 } 612 #endif 613 614 /* 615 * If we have an externally synchronized Linux clock, then update RTC clock 616 * accordingly every ~11 minutes. Generally RTCs can only store second 617 * precision, but many RTCs will adjust the phase of their second tick to 618 * match the moment of update. This infrastructure arranges to call to the RTC 619 * set at the correct moment to phase synchronize the RTC second tick over 620 * with the kernel clock. 621 */ 622 static void sync_hw_clock(struct work_struct *work) 623 { 624 /* 625 * The default synchronization offset is 500ms for the deprecated 626 * update_persistent_clock64() under the assumption that it uses 627 * the infamous CMOS clock (MC146818). 628 */ 629 static unsigned long offset_nsec = NSEC_PER_SEC / 2; 630 struct timespec64 now, to_set; 631 int res = -EAGAIN; 632 633 /* 634 * Don't update if STA_UNSYNC is set and if ntp_notify_cmos_timer() 635 * managed to schedule the work between the timer firing and the 636 * work being able to rearm the timer. Wait for the timer to expire. 637 */ 638 if (!ntp_synced() || hrtimer_is_queued(&sync_hrtimer)) 639 return; 640 641 ktime_get_real_ts64(&now); 642 /* If @now is not in the allowed window, try again */ 643 if (!rtc_tv_nsec_ok(offset_nsec, &to_set, &now)) 644 goto rearm; 645 646 /* Take timezone adjusted RTCs into account */ 647 if (persistent_clock_is_local) 648 to_set.tv_sec -= (sys_tz.tz_minuteswest * 60); 649 650 /* Try the legacy RTC first. */ 651 res = update_persistent_clock64(to_set); 652 if (res != -ENODEV) 653 goto rearm; 654 655 /* Try the RTC class */ 656 res = update_rtc(&to_set, &offset_nsec); 657 if (res == -ENODEV) 658 return; 659 rearm: 660 sched_sync_hw_clock(offset_nsec, res != 0); 661 } 662 663 void ntp_notify_cmos_timer(void) 664 { 665 /* 666 * When the work is currently executed but has not yet the timer 667 * rearmed this queues the work immediately again. No big issue, 668 * just a pointless work scheduled. 669 */ 670 if (ntp_synced() && !hrtimer_is_queued(&sync_hrtimer)) 671 queue_work(system_freezable_power_efficient_wq, &sync_work); 672 } 673 674 static void __init ntp_init_cmos_sync(void) 675 { 676 hrtimer_init(&sync_hrtimer, CLOCK_REALTIME, HRTIMER_MODE_ABS); 677 sync_hrtimer.function = sync_timer_callback; 678 } 679 #else /* CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */ 680 static inline void __init ntp_init_cmos_sync(void) { } 681 #endif /* !CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */ 682 683 /* 684 * Propagate a new txc->status value into the NTP state: 685 */ 686 static inline void process_adj_status(const struct __kernel_timex *txc) 687 { 688 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { 689 time_state = TIME_OK; 690 time_status = STA_UNSYNC; 691 ntp_next_leap_sec = TIME64_MAX; 692 /* restart PPS frequency calibration */ 693 pps_reset_freq_interval(); 694 } 695 696 /* 697 * If we turn on PLL adjustments then reset the 698 * reference time to current time. 699 */ 700 if (!(time_status & STA_PLL) && (txc->status & STA_PLL)) 701 time_reftime = __ktime_get_real_seconds(); 702 703 /* only set allowed bits */ 704 time_status &= STA_RONLY; 705 time_status |= txc->status & ~STA_RONLY; 706 } 707 708 709 static inline void process_adjtimex_modes(const struct __kernel_timex *txc, 710 s32 *time_tai) 711 { 712 if (txc->modes & ADJ_STATUS) 713 process_adj_status(txc); 714 715 if (txc->modes & ADJ_NANO) 716 time_status |= STA_NANO; 717 718 if (txc->modes & ADJ_MICRO) 719 time_status &= ~STA_NANO; 720 721 if (txc->modes & ADJ_FREQUENCY) { 722 time_freq = txc->freq * PPM_SCALE; 723 time_freq = min(time_freq, MAXFREQ_SCALED); 724 time_freq = max(time_freq, -MAXFREQ_SCALED); 725 /* update pps_freq */ 726 pps_set_freq(time_freq); 727 } 728 729 if (txc->modes & ADJ_MAXERROR) 730 time_maxerror = clamp(txc->maxerror, 0, NTP_PHASE_LIMIT); 731 732 if (txc->modes & ADJ_ESTERROR) 733 time_esterror = clamp(txc->esterror, 0, NTP_PHASE_LIMIT); 734 735 if (txc->modes & ADJ_TIMECONST) { 736 time_constant = clamp(txc->constant, 0, MAXTC); 737 if (!(time_status & STA_NANO)) 738 time_constant += 4; 739 time_constant = clamp(time_constant, 0, MAXTC); 740 } 741 742 if (txc->modes & ADJ_TAI && 743 txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET) 744 *time_tai = txc->constant; 745 746 if (txc->modes & ADJ_OFFSET) 747 ntp_update_offset(txc->offset); 748 749 if (txc->modes & ADJ_TICK) 750 tick_usec = txc->tick; 751 752 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 753 ntp_update_frequency(); 754 } 755 756 757 /* 758 * adjtimex mainly allows reading (and writing, if superuser) of 759 * kernel time-keeping variables. used by xntpd. 760 */ 761 int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts, 762 s32 *time_tai, struct audit_ntp_data *ad) 763 { 764 int result; 765 766 if (txc->modes & ADJ_ADJTIME) { 767 long save_adjust = time_adjust; 768 769 if (!(txc->modes & ADJ_OFFSET_READONLY)) { 770 /* adjtime() is independent from ntp_adjtime() */ 771 time_adjust = txc->offset; 772 ntp_update_frequency(); 773 774 audit_ntp_set_old(ad, AUDIT_NTP_ADJUST, save_adjust); 775 audit_ntp_set_new(ad, AUDIT_NTP_ADJUST, time_adjust); 776 } 777 txc->offset = save_adjust; 778 } else { 779 /* If there are input parameters, then process them: */ 780 if (txc->modes) { 781 audit_ntp_set_old(ad, AUDIT_NTP_OFFSET, time_offset); 782 audit_ntp_set_old(ad, AUDIT_NTP_FREQ, time_freq); 783 audit_ntp_set_old(ad, AUDIT_NTP_STATUS, time_status); 784 audit_ntp_set_old(ad, AUDIT_NTP_TAI, *time_tai); 785 audit_ntp_set_old(ad, AUDIT_NTP_TICK, tick_usec); 786 787 process_adjtimex_modes(txc, time_tai); 788 789 audit_ntp_set_new(ad, AUDIT_NTP_OFFSET, time_offset); 790 audit_ntp_set_new(ad, AUDIT_NTP_FREQ, time_freq); 791 audit_ntp_set_new(ad, AUDIT_NTP_STATUS, time_status); 792 audit_ntp_set_new(ad, AUDIT_NTP_TAI, *time_tai); 793 audit_ntp_set_new(ad, AUDIT_NTP_TICK, tick_usec); 794 } 795 796 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, 797 NTP_SCALE_SHIFT); 798 if (!(time_status & STA_NANO)) 799 txc->offset = (u32)txc->offset / NSEC_PER_USEC; 800 } 801 802 result = time_state; /* mostly `TIME_OK' */ 803 /* check for errors */ 804 if (is_error_status(time_status)) 805 result = TIME_ERROR; 806 807 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * 808 PPM_SCALE_INV, NTP_SCALE_SHIFT); 809 txc->maxerror = time_maxerror; 810 txc->esterror = time_esterror; 811 txc->status = time_status; 812 txc->constant = time_constant; 813 txc->precision = 1; 814 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; 815 txc->tick = tick_usec; 816 txc->tai = *time_tai; 817 818 /* fill PPS status fields */ 819 pps_fill_timex(txc); 820 821 txc->time.tv_sec = ts->tv_sec; 822 txc->time.tv_usec = ts->tv_nsec; 823 if (!(time_status & STA_NANO)) 824 txc->time.tv_usec = ts->tv_nsec / NSEC_PER_USEC; 825 826 /* Handle leapsec adjustments */ 827 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) { 828 if ((time_state == TIME_INS) && (time_status & STA_INS)) { 829 result = TIME_OOP; 830 txc->tai++; 831 txc->time.tv_sec--; 832 } 833 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) { 834 result = TIME_WAIT; 835 txc->tai--; 836 txc->time.tv_sec++; 837 } 838 if ((time_state == TIME_OOP) && 839 (ts->tv_sec == ntp_next_leap_sec)) { 840 result = TIME_WAIT; 841 } 842 } 843 844 return result; 845 } 846 847 #ifdef CONFIG_NTP_PPS 848 849 /* actually struct pps_normtime is good old struct timespec, but it is 850 * semantically different (and it is the reason why it was invented): 851 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] 852 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */ 853 struct pps_normtime { 854 s64 sec; /* seconds */ 855 long nsec; /* nanoseconds */ 856 }; 857 858 /* normalize the timestamp so that nsec is in the 859 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */ 860 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts) 861 { 862 struct pps_normtime norm = { 863 .sec = ts.tv_sec, 864 .nsec = ts.tv_nsec 865 }; 866 867 if (norm.nsec > (NSEC_PER_SEC >> 1)) { 868 norm.nsec -= NSEC_PER_SEC; 869 norm.sec++; 870 } 871 872 return norm; 873 } 874 875 /* get current phase correction and jitter */ 876 static inline long pps_phase_filter_get(long *jitter) 877 { 878 *jitter = pps_tf[0] - pps_tf[1]; 879 if (*jitter < 0) 880 *jitter = -*jitter; 881 882 /* TODO: test various filters */ 883 return pps_tf[0]; 884 } 885 886 /* add the sample to the phase filter */ 887 static inline void pps_phase_filter_add(long err) 888 { 889 pps_tf[2] = pps_tf[1]; 890 pps_tf[1] = pps_tf[0]; 891 pps_tf[0] = err; 892 } 893 894 /* decrease frequency calibration interval length. 895 * It is halved after four consecutive unstable intervals. 896 */ 897 static inline void pps_dec_freq_interval(void) 898 { 899 if (--pps_intcnt <= -PPS_INTCOUNT) { 900 pps_intcnt = -PPS_INTCOUNT; 901 if (pps_shift > PPS_INTMIN) { 902 pps_shift--; 903 pps_intcnt = 0; 904 } 905 } 906 } 907 908 /* increase frequency calibration interval length. 909 * It is doubled after four consecutive stable intervals. 910 */ 911 static inline void pps_inc_freq_interval(void) 912 { 913 if (++pps_intcnt >= PPS_INTCOUNT) { 914 pps_intcnt = PPS_INTCOUNT; 915 if (pps_shift < PPS_INTMAX) { 916 pps_shift++; 917 pps_intcnt = 0; 918 } 919 } 920 } 921 922 /* update clock frequency based on MONOTONIC_RAW clock PPS signal 923 * timestamps 924 * 925 * At the end of the calibration interval the difference between the 926 * first and last MONOTONIC_RAW clock timestamps divided by the length 927 * of the interval becomes the frequency update. If the interval was 928 * too long, the data are discarded. 929 * Returns the difference between old and new frequency values. 930 */ 931 static long hardpps_update_freq(struct pps_normtime freq_norm) 932 { 933 long delta, delta_mod; 934 s64 ftemp; 935 936 /* check if the frequency interval was too long */ 937 if (freq_norm.sec > (2 << pps_shift)) { 938 time_status |= STA_PPSERROR; 939 pps_errcnt++; 940 pps_dec_freq_interval(); 941 printk_deferred(KERN_ERR 942 "hardpps: PPSERROR: interval too long - %lld s\n", 943 freq_norm.sec); 944 return 0; 945 } 946 947 /* here the raw frequency offset and wander (stability) is 948 * calculated. If the wander is less than the wander threshold 949 * the interval is increased; otherwise it is decreased. 950 */ 951 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT, 952 freq_norm.sec); 953 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT); 954 pps_freq = ftemp; 955 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) { 956 printk_deferred(KERN_WARNING 957 "hardpps: PPSWANDER: change=%ld\n", delta); 958 time_status |= STA_PPSWANDER; 959 pps_stbcnt++; 960 pps_dec_freq_interval(); 961 } else { /* good sample */ 962 pps_inc_freq_interval(); 963 } 964 965 /* the stability metric is calculated as the average of recent 966 * frequency changes, but is used only for performance 967 * monitoring 968 */ 969 delta_mod = delta; 970 if (delta_mod < 0) 971 delta_mod = -delta_mod; 972 pps_stabil += (div_s64(((s64)delta_mod) << 973 (NTP_SCALE_SHIFT - SHIFT_USEC), 974 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN; 975 976 /* if enabled, the system clock frequency is updated */ 977 if ((time_status & STA_PPSFREQ) != 0 && 978 (time_status & STA_FREQHOLD) == 0) { 979 time_freq = pps_freq; 980 ntp_update_frequency(); 981 } 982 983 return delta; 984 } 985 986 /* correct REALTIME clock phase error against PPS signal */ 987 static void hardpps_update_phase(long error) 988 { 989 long correction = -error; 990 long jitter; 991 992 /* add the sample to the median filter */ 993 pps_phase_filter_add(correction); 994 correction = pps_phase_filter_get(&jitter); 995 996 /* Nominal jitter is due to PPS signal noise. If it exceeds the 997 * threshold, the sample is discarded; otherwise, if so enabled, 998 * the time offset is updated. 999 */ 1000 if (jitter > (pps_jitter << PPS_POPCORN)) { 1001 printk_deferred(KERN_WARNING 1002 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n", 1003 jitter, (pps_jitter << PPS_POPCORN)); 1004 time_status |= STA_PPSJITTER; 1005 pps_jitcnt++; 1006 } else if (time_status & STA_PPSTIME) { 1007 /* correct the time using the phase offset */ 1008 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT, 1009 NTP_INTERVAL_FREQ); 1010 /* cancel running adjtime() */ 1011 time_adjust = 0; 1012 } 1013 /* update jitter */ 1014 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN; 1015 } 1016 1017 /* 1018 * __hardpps() - discipline CPU clock oscillator to external PPS signal 1019 * 1020 * This routine is called at each PPS signal arrival in order to 1021 * discipline the CPU clock oscillator to the PPS signal. It takes two 1022 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former 1023 * is used to correct clock phase error and the latter is used to 1024 * correct the frequency. 1025 * 1026 * This code is based on David Mills's reference nanokernel 1027 * implementation. It was mostly rewritten but keeps the same idea. 1028 */ 1029 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts) 1030 { 1031 struct pps_normtime pts_norm, freq_norm; 1032 1033 pts_norm = pps_normalize_ts(*phase_ts); 1034 1035 /* clear the error bits, they will be set again if needed */ 1036 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 1037 1038 /* indicate signal presence */ 1039 time_status |= STA_PPSSIGNAL; 1040 pps_valid = PPS_VALID; 1041 1042 /* when called for the first time, 1043 * just start the frequency interval */ 1044 if (unlikely(pps_fbase.tv_sec == 0)) { 1045 pps_fbase = *raw_ts; 1046 return; 1047 } 1048 1049 /* ok, now we have a base for frequency calculation */ 1050 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase)); 1051 1052 /* check that the signal is in the range 1053 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */ 1054 if ((freq_norm.sec == 0) || 1055 (freq_norm.nsec > MAXFREQ * freq_norm.sec) || 1056 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) { 1057 time_status |= STA_PPSJITTER; 1058 /* restart the frequency calibration interval */ 1059 pps_fbase = *raw_ts; 1060 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n"); 1061 return; 1062 } 1063 1064 /* signal is ok */ 1065 1066 /* check if the current frequency interval is finished */ 1067 if (freq_norm.sec >= (1 << pps_shift)) { 1068 pps_calcnt++; 1069 /* restart the frequency calibration interval */ 1070 pps_fbase = *raw_ts; 1071 hardpps_update_freq(freq_norm); 1072 } 1073 1074 hardpps_update_phase(pts_norm.nsec); 1075 1076 } 1077 #endif /* CONFIG_NTP_PPS */ 1078 1079 static int __init ntp_tick_adj_setup(char *str) 1080 { 1081 int rc = kstrtos64(str, 0, &ntp_tick_adj); 1082 if (rc) 1083 return rc; 1084 1085 ntp_tick_adj <<= NTP_SCALE_SHIFT; 1086 return 1; 1087 } 1088 1089 __setup("ntp_tick_adj=", ntp_tick_adj_setup); 1090 1091 void __init ntp_init(void) 1092 { 1093 ntp_clear(); 1094 ntp_init_cmos_sync(); 1095 } 1096