kernel/time/ntp.c

   1 /*
   2  * NTP state machine interfaces and logic.
   3  *
   4  * This code was mainly moved from kernel/timer.c and kernel/time.c
   5  * Please see those files for relevant copyright info and historical
   6  * changelogs.
   7  */
   8 #include <linux/capability.h>
   9 #include <linux/clocksource.h>
  10 #include <linux/workqueue.h>
  11 #include <linux/hrtimer.h>
  12 #include <linux/jiffies.h>
  13 #include <linux/math64.h>
  14 #include <linux/timex.h>
  15 #include <linux/time.h>
  16 #include <linux/mm.h>
  17 #include <linux/module.h>
  18 #include <linux/rtc.h>
  19
  20 #include "ntp_internal.h"
  21
  22 /*
  23  * NTP timekeeping variables:
  24  *
  25  * Note: All of the NTP state is protected by the timekeeping locks.
  26  */
  27
  28
  29 /* USER_HZ period (usecs): */
  30 unsigned long                   tick_usec = TICK_USEC;
  31
  32 /* SHIFTED_HZ period (nsecs): */
  33 unsigned long                   tick_nsec;
  34
  35 static u64                      tick_length;
  36 static u64                      tick_length_base;
  37
  38 #define SECS_PER_DAY            86400
  39 #define MAX_TICKADJ             500LL           /* usecs */
  40 #define MAX_TICKADJ_SCALED \
  41         (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
  42
  43 /*
  44  * phase-lock loop variables
  45  */
  46
  47 /*
  48  * clock synchronization status
  49  *
  50  * (TIME_ERROR prevents overwriting the CMOS clock)
  51  */
  52 static int                      time_state = TIME_OK;
  53
  54 /* clock status bits:                                                   */
  55 static int                      time_status = STA_UNSYNC;
  56
  57 /* time adjustment (nsecs):                                             */
  58 static s64                      time_offset;
  59
  60 /* pll time constant:                                                   */
  61 static long                     time_constant = 2;
  62
  63 /* maximum error (usecs):                                               */
  64 static long                     time_maxerror = NTP_PHASE_LIMIT;
  65
  66 /* estimated error (usecs):                                             */
  67 static long                     time_esterror = NTP_PHASE_LIMIT;
  68
  69 /* frequency offset (scaled nsecs/secs):                                */
  70 static s64                      time_freq;
  71
  72 /* time at last adjustment (secs):                                      */
  73 static long                     time_reftime;
  74
  75 static long                     time_adjust;
  76
  77 /* constant (boot-param configurable) NTP tick adjustment (upscaled)    */
  78 static s64                      ntp_tick_adj;
  79
  80 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */
  81 static time64_t                 ntp_next_leap_sec = TIME64_MAX;
  82
  83 #ifdef CONFIG_NTP_PPS
  84
  85 /*
  86  * The following variables are used when a pulse-per-second (PPS) signal
  87  * is available. They establish the engineering parameters of the clock
  88  * discipline loop when controlled by the PPS signal.
  89  */
  90 #define PPS_VALID       10      /* PPS signal watchdog max (s) */
  91 #define PPS_POPCORN     4       /* popcorn spike threshold (shift) */
  92 #define PPS_INTMIN      2       /* min freq interval (s) (shift) */
  93 #define PPS_INTMAX      8       /* max freq interval (s) (shift) */
  94 #define PPS_INTCOUNT    4       /* number of consecutive good intervals to
  95                                    increase pps_shift or consecutive bad
  96                                    intervals to decrease it */
  97 #define PPS_MAXWANDER   100000  /* max PPS freq wander (ns/s) */
  98
  99 static int pps_valid;           /* signal watchdog counter */
 100 static long pps_tf[3];          /* phase median filter */
 101 static long pps_jitter;         /* current jitter (ns) */
 102 static struct timespec64 pps_fbase; /* beginning of the last freq interval */
 103 static int pps_shift;           /* current interval duration (s) (shift) */
 104 static int pps_intcnt;          /* interval counter */
 105 static s64 pps_freq;            /* frequency offset (scaled ns/s) */
 106 static long pps_stabil;         /* current stability (scaled ns/s) */
 107
 108 /*
 109  * PPS signal quality monitors
 110  */
 111 static long pps_calcnt;         /* calibration intervals */
 112 static long pps_jitcnt;         /* jitter limit exceeded */
 113 static long pps_stbcnt;         /* stability limit exceeded */
 114 static long pps_errcnt;         /* calibration errors */
 115
 116
 117 /* PPS kernel consumer compensates the whole phase error immediately.
 118  * Otherwise, reduce the offset by a fixed factor times the time constant.
 119  */
 120 static inline s64 ntp_offset_chunk(s64 offset)
 121 {
 122         if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
 123                 return offset;
 124         else
 125                 return shift_right(offset, SHIFT_PLL + time_constant);
 126 }
 127
 128 static inline void pps_reset_freq_interval(void)
 129 {
 130         /* the PPS calibration interval may end
 131            surprisingly early */
 132         pps_shift = PPS_INTMIN;
 133         pps_intcnt = 0;
 134 }
 135
 136 /**
 137  * pps_clear - Clears the PPS state variables
 138  */
 139 static inline void pps_clear(void)
 140 {
 141         pps_reset_freq_interval();
 142         pps_tf[0] = 0;
 143         pps_tf[1] = 0;
 144         pps_tf[2] = 0;
 145         pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
 146         pps_freq = 0;
 147 }
 148
 149 /* Decrease pps_valid to indicate that another second has passed since
 150  * the last PPS signal. When it reaches 0, indicate that PPS signal is
 151  * missing.
 152  */
 153 static inline void pps_dec_valid(void)
 154 {
 155         if (pps_valid > 0)
 156                 pps_valid--;
 157         else {
 158                 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
 159                                  STA_PPSWANDER | STA_PPSERROR);
 160                 pps_clear();
 161         }
 162 }
 163
 164 static inline void pps_set_freq(s64 freq)
 165 {
 166         pps_freq = freq;
 167 }
 168
 169 static inline int is_error_status(int status)
 170 {
 171         return (status & (STA_UNSYNC|STA_CLOCKERR))
 172                 /* PPS signal lost when either PPS time or
 173                  * PPS frequency synchronization requested
 174                  */
 175                 || ((status & (STA_PPSFREQ|STA_PPSTIME))
 176                         && !(status & STA_PPSSIGNAL))
 177                 /* PPS jitter exceeded when
 178                  * PPS time synchronization requested */
 179                 || ((status & (STA_PPSTIME|STA_PPSJITTER))
 180                         == (STA_PPSTIME|STA_PPSJITTER))
 181                 /* PPS wander exceeded or calibration error when
 182                  * PPS frequency synchronization requested
 183                  */
 184                 || ((status & STA_PPSFREQ)
 185                         && (status & (STA_PPSWANDER|STA_PPSERROR)));
 186 }
 187
 188 static inline void pps_fill_timex(struct timex *txc)
 189 {
 190         txc->ppsfreq       = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
 191                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 192         txc->jitter        = pps_jitter;
 193         if (!(time_status & STA_NANO))
 194                 txc->jitter /= NSEC_PER_USEC;
 195         txc->shift         = pps_shift;
 196         txc->stabil        = pps_stabil;
 197         txc->jitcnt        = pps_jitcnt;
 198         txc->calcnt        = pps_calcnt;
 199         txc->errcnt        = pps_errcnt;
 200         txc->stbcnt        = pps_stbcnt;
 201 }
 202
 203 #else /* !CONFIG_NTP_PPS */
 204
 205 static inline s64 ntp_offset_chunk(s64 offset)
 206 {
 207         return shift_right(offset, SHIFT_PLL + time_constant);
 208 }
 209
 210 static inline void pps_reset_freq_interval(void) {}
 211 static inline void pps_clear(void) {}
 212 static inline void pps_dec_valid(void) {}
 213 static inline void pps_set_freq(s64 freq) {}
 214
 215 static inline int is_error_status(int status)
 216 {
 217         return status & (STA_UNSYNC|STA_CLOCKERR);
 218 }
 219
 220 static inline void pps_fill_timex(struct timex *txc)
 221 {
 222         /* PPS is not implemented, so these are zero */
 223         txc->ppsfreq       = 0;
 224         txc->jitter        = 0;
 225         txc->shift         = 0;
 226         txc->stabil        = 0;
 227         txc->jitcnt        = 0;
 228         txc->calcnt        = 0;
 229         txc->errcnt        = 0;
 230         txc->stbcnt        = 0;
 231 }
 232
 233 #endif /* CONFIG_NTP_PPS */
 234
 235
 236 /**
 237  * ntp_synced - Returns 1 if the NTP status is not UNSYNC
 238  *
 239  */
 240 static inline int ntp_synced(void)
 241 {
 242         return !(time_status & STA_UNSYNC);
 243 }
 244
 245
 246 /*
 247  * NTP methods:
 248  */
 249
 250 /*
 251  * Update (tick_length, tick_length_base, tick_nsec), based
 252  * on (tick_usec, ntp_tick_adj, time_freq):
 253  */
 254 static void ntp_update_frequency(void)
 255 {
 256         u64 second_length;
 257         u64 new_base;
 258
 259         second_length            = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
 260                                                 << NTP_SCALE_SHIFT;
 261
 262         second_length           += ntp_tick_adj;
 263         second_length           += time_freq;
 264
 265         tick_nsec                = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
 266         new_base                 = div_u64(second_length, NTP_INTERVAL_FREQ);
 267
 268         /*
 269          * Don't wait for the next second_overflow, apply
 270          * the change to the tick length immediately:
 271          */
 272         tick_length             += new_base - tick_length_base;
 273         tick_length_base         = new_base;
 274 }
 275
 276 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
 277 {
 278         time_status &= ~STA_MODE;
 279
 280         if (secs < MINSEC)
 281                 return 0;
 282
 283         if (!(time_status & STA_FLL) && (secs <= MAXSEC))
 284                 return 0;
 285
 286         time_status |= STA_MODE;
 287
 288         return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
 289 }
 290
 291 static void ntp_update_offset(long offset)
 292 {
 293         s64 freq_adj;
 294         s64 offset64;
 295         long secs;
 296
 297         if (!(time_status & STA_PLL))
 298                 return;
 299
 300         if (!(time_status & STA_NANO))
 301                 offset *= NSEC_PER_USEC;
 302
 303         /*
 304          * Scale the phase adjustment and
 305          * clamp to the operating range.
 306          */
 307         offset = min(offset, MAXPHASE);
 308         offset = max(offset, -MAXPHASE);
 309
 310         /*
 311          * Select how the frequency is to be controlled
 312          * and in which mode (PLL or FLL).
 313          */
 314         secs = get_seconds() - time_reftime;
 315         if (unlikely(time_status & STA_FREQHOLD))
 316                 secs = 0;
 317
 318         time_reftime = get_seconds();
 319
 320         offset64    = offset;
 321         freq_adj    = ntp_update_offset_fll(offset64, secs);
 322
 323         /*
 324          * Clamp update interval to reduce PLL gain with low
 325          * sampling rate (e.g. intermittent network connection)
 326          * to avoid instability.
 327          */
 328         if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
 329                 secs = 1 << (SHIFT_PLL + 1 + time_constant);
 330
 331         freq_adj    += (offset64 * secs) <<
 332                         (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
 333
 334         freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);
 335
 336         time_freq   = max(freq_adj, -MAXFREQ_SCALED);
 337
 338         time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
 339 }
 340
 341 /**
 342  * ntp_clear - Clears the NTP state variables
 343  */
 344 void ntp_clear(void)
 345 {
 346         time_adjust     = 0;            /* stop active adjtime() */
 347         time_status     |= STA_UNSYNC;
 348         time_maxerror   = NTP_PHASE_LIMIT;
 349         time_esterror   = NTP_PHASE_LIMIT;
 350
 351         ntp_update_frequency();
 352
 353         tick_length     = tick_length_base;
 354         time_offset     = 0;
 355
 356         ntp_next_leap_sec = TIME64_MAX;
 357         /* Clear PPS state variables */
 358         pps_clear();
 359 }
 360
 361
 362 u64 ntp_tick_length(void)
 363 {
 364         return tick_length;
 365 }
 366
 367 /**
 368  * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
 369  *
 370  * Provides the time of the next leapsecond against CLOCK_REALTIME in
 371  * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending.
 372  */
 373 ktime_t ntp_get_next_leap(void)
 374 {
 375         ktime_t ret;
 376
 377         if ((time_state == TIME_INS) && (time_status & STA_INS))
 378                 return ktime_set(ntp_next_leap_sec, 0);
 379         ret.tv64 = KTIME_MAX;
 380         return ret;
 381 }
 382
 383 /*
 384  * this routine handles the overflow of the microsecond field
 385  *
 386  * The tricky bits of code to handle the accurate clock support
 387  * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
 388  * They were originally developed for SUN and DEC kernels.
 389  * All the kudos should go to Dave for this stuff.
 390  *
 391  * Also handles leap second processing, and returns leap offset
 392  */
 393 int second_overflow(unsigned long secs)
 394 {
 395         s64 delta;
 396         int leap = 0;
 397
 398         /*
 399          * Leap second processing. If in leap-insert state at the end of the
 400          * day, the system clock is set back one second; if in leap-delete
 401          * state, the system clock is set ahead one second.
 402          */
 403         switch (time_state) {
 404         case TIME_OK:
 405                 if (time_status & STA_INS) {
 406                         time_state = TIME_INS;
 407                         ntp_next_leap_sec = secs + SECS_PER_DAY -
 408                                                 (secs % SECS_PER_DAY);
 409                 } else if (time_status & STA_DEL) {
 410                         time_state = TIME_DEL;
 411                         ntp_next_leap_sec = secs + SECS_PER_DAY -
 412                                                  ((secs+1) % SECS_PER_DAY);
 413                 }
 414                 break;
 415         case TIME_INS:
 416                 if (!(time_status & STA_INS)) {
 417                         ntp_next_leap_sec = TIME64_MAX;
 418                         time_state = TIME_OK;
 419                 } else if (secs % SECS_PER_DAY == 0) {
 420                         leap = -1;
 421                         time_state = TIME_OOP;
 422                         printk(KERN_NOTICE
 423                                 "Clock: inserting leap second 23:59:60 UTC\n");
 424                 }
 425                 break;
 426         case TIME_DEL:
 427                 if (!(time_status & STA_DEL)) {
 428                         ntp_next_leap_sec = TIME64_MAX;
 429                         time_state = TIME_OK;
 430                 } else if ((secs + 1) % SECS_PER_DAY == 0) {
 431                         leap = 1;
 432                         ntp_next_leap_sec = TIME64_MAX;
 433                         time_state = TIME_WAIT;
 434                         printk(KERN_NOTICE
 435                                 "Clock: deleting leap second 23:59:59 UTC\n");
 436                 }
 437                 break;
 438         case TIME_OOP:
 439                 ntp_next_leap_sec = TIME64_MAX;
 440                 time_state = TIME_WAIT;
 441                 break;
 442         case TIME_WAIT:
 443                 if (!(time_status & (STA_INS | STA_DEL)))
 444                         time_state = TIME_OK;
 445                 break;
 446         }
 447
 448
 449         /* Bump the maxerror field */
 450         time_maxerror += MAXFREQ / NSEC_PER_USEC;
 451         if (time_maxerror > NTP_PHASE_LIMIT) {
 452                 time_maxerror = NTP_PHASE_LIMIT;
 453                 time_status |= STA_UNSYNC;
 454         }
 455
 456         /* Compute the phase adjustment for the next second */
 457         tick_length      = tick_length_base;
 458
 459         delta            = ntp_offset_chunk(time_offset);
 460         time_offset     -= delta;
 461         tick_length     += delta;
 462
 463         /* Check PPS signal */
 464         pps_dec_valid();
 465
 466         if (!time_adjust)
 467                 goto out;
 468
 469         if (time_adjust > MAX_TICKADJ) {
 470                 time_adjust -= MAX_TICKADJ;
 471                 tick_length += MAX_TICKADJ_SCALED;
 472                 goto out;
 473         }
 474
 475         if (time_adjust < -MAX_TICKADJ) {
 476                 time_adjust += MAX_TICKADJ;
 477                 tick_length -= MAX_TICKADJ_SCALED;
 478                 goto out;
 479         }
 480
 481         tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
 482                                                          << NTP_SCALE_SHIFT;
 483         time_adjust = 0;
 484
 485 out:
 486         return leap;
 487 }
 488
 489 #ifdef CONFIG_GENERIC_CMOS_UPDATE
 490 int __weak update_persistent_clock(struct timespec now)
 491 {
 492         return -ENODEV;
 493 }
 494
 495 int __weak update_persistent_clock64(struct timespec64 now64)
 496 {
 497         struct timespec now;
 498
 499         now = timespec64_to_timespec(now64);
 500         return update_persistent_clock(now);
 501 }
 502 #endif
 503
 504 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
 505 static void sync_cmos_clock(struct work_struct *work);
 506
 507 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
 508
 509 static void sync_cmos_clock(struct work_struct *work)
 510 {
 511         struct timespec64 now;
 512         struct timespec64 next;
 513         int fail = 1;
 514
 515         /*
 516          * If we have an externally synchronized Linux clock, then update
 517          * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
 518          * called as close as possible to 500 ms before the new second starts.
 519          * This code is run on a timer.  If the clock is set, that timer
 520          * may not expire at the correct time.  Thus, we adjust...
 521          * We want the clock to be within a couple of ticks from the target.
 522          */
 523         if (!ntp_synced()) {
 524                 /*
 525                  * Not synced, exit, do not restart a timer (if one is
 526                  * running, let it run out).
 527                  */
 528                 return;
 529         }
 530
 531         getnstimeofday64(&now);
 532         if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) {
 533                 struct timespec64 adjust = now;
 534
 535                 fail = -ENODEV;
 536                 if (persistent_clock_is_local)
 537                         adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
 538 #ifdef CONFIG_GENERIC_CMOS_UPDATE
 539                 fail = update_persistent_clock64(adjust);
 540 #endif
 541
 542 #ifdef CONFIG_RTC_SYSTOHC
 543                 if (fail == -ENODEV)
 544                         fail = rtc_set_ntp_time(adjust);
 545 #endif
 546         }
 547
 548         next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
 549         if (next.tv_nsec <= 0)
 550                 next.tv_nsec += NSEC_PER_SEC;
 551
 552         if (!fail || fail == -ENODEV)
 553                 next.tv_sec = 659;
 554         else
 555                 next.tv_sec = 0;
 556
 557         if (next.tv_nsec >= NSEC_PER_SEC) {
 558                 next.tv_sec++;
 559                 next.tv_nsec -= NSEC_PER_SEC;
 560         }
 561         queue_delayed_work(system_power_efficient_wq,
 562                            &sync_cmos_work, timespec64_to_jiffies(&next));
 563 }
 564
 565 void ntp_notify_cmos_timer(void)
 566 {
 567         queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, 0);
 568 }
 569
 570 #else
 571 void ntp_notify_cmos_timer(void) { }
 572 #endif
 573
 574
 575 /*
 576  * Propagate a new txc->status value into the NTP state:
 577  */
 578 static inline void process_adj_status(struct timex *txc, struct timespec64 *ts)
 579 {
 580         if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
 581                 time_state = TIME_OK;
 582                 time_status = STA_UNSYNC;
 583                 ntp_next_leap_sec = TIME64_MAX;
 584                 /* restart PPS frequency calibration */
 585                 pps_reset_freq_interval();
 586         }
 587
 588         /*
 589          * If we turn on PLL adjustments then reset the
 590          * reference time to current time.
 591          */
 592         if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
 593                 time_reftime = get_seconds();
 594
 595         /* only set allowed bits */
 596         time_status &= STA_RONLY;
 597         time_status |= txc->status & ~STA_RONLY;
 598 }
 599
 600
 601 static inline void process_adjtimex_modes(struct timex *txc,
 602                                                 struct timespec64 *ts,
 603                                                 s32 *time_tai)
 604 {
 605         if (txc->modes & ADJ_STATUS)
 606                 process_adj_status(txc, ts);
 607
 608         if (txc->modes & ADJ_NANO)
 609                 time_status |= STA_NANO;
 610
 611         if (txc->modes & ADJ_MICRO)
 612                 time_status &= ~STA_NANO;
 613
 614         if (txc->modes & ADJ_FREQUENCY) {
 615                 time_freq = txc->freq * PPM_SCALE;
 616                 time_freq = min(time_freq, MAXFREQ_SCALED);
 617                 time_freq = max(time_freq, -MAXFREQ_SCALED);
 618                 /* update pps_freq */
 619                 pps_set_freq(time_freq);
 620         }
 621
 622         if (txc->modes & ADJ_MAXERROR)
 623                 time_maxerror = txc->maxerror;
 624
 625         if (txc->modes & ADJ_ESTERROR)
 626                 time_esterror = txc->esterror;
 627
 628         if (txc->modes & ADJ_TIMECONST) {
 629                 time_constant = txc->constant;
 630                 if (!(time_status & STA_NANO))
 631                         time_constant += 4;
 632                 time_constant = min(time_constant, (long)MAXTC);
 633                 time_constant = max(time_constant, 0l);
 634         }
 635
 636         if (txc->modes & ADJ_TAI && txc->constant > 0)
 637                 *time_tai = txc->constant;
 638
 639         if (txc->modes & ADJ_OFFSET)
 640                 ntp_update_offset(txc->offset);
 641
 642         if (txc->modes & ADJ_TICK)
 643                 tick_usec = txc->tick;
 644
 645         if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
 646                 ntp_update_frequency();
 647 }
 648
 649
 650
 651 /**
 652  * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex
 653  */
 654 int ntp_validate_timex(struct timex *txc)
 655 {
 656         if (txc->modes & ADJ_ADJTIME) {
 657                 /* singleshot must not be used with any other mode bits */
 658                 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
 659                         return -EINVAL;
 660                 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
 661                     !capable(CAP_SYS_TIME))
 662                         return -EPERM;
 663         } else {
 664                 /* In order to modify anything, you gotta be super-user! */
 665                  if (txc->modes && !capable(CAP_SYS_TIME))
 666                         return -EPERM;
 667                 /*
 668                  * if the quartz is off by more than 10% then
 669                  * something is VERY wrong!
 670                  */
 671                 if (txc->modes & ADJ_TICK &&
 672                     (txc->tick <  900000/USER_HZ ||
 673                      txc->tick > 1100000/USER_HZ))
 674                         return -EINVAL;
 675         }
 676
 677         if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME)))
 678                 return -EPERM;
 679
 680         /*
 681          * Check for potential multiplication overflows that can
 682          * only happen on 64-bit systems:
 683          */
 684         if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) {
 685                 if (LLONG_MIN / PPM_SCALE > txc->freq)
 686                         return -EINVAL;
 687                 if (LLONG_MAX / PPM_SCALE < txc->freq)
 688                         return -EINVAL;
 689         }
 690
 691         return 0;
 692 }
 693
 694
 695 /*
 696  * adjtimex mainly allows reading (and writing, if superuser) of
 697  * kernel time-keeping variables. used by xntpd.
 698  */
 699 int __do_adjtimex(struct timex *txc, struct timespec64 *ts, s32 *time_tai)
 700 {
 701         int result;
 702
 703         if (txc->modes & ADJ_ADJTIME) {
 704                 long save_adjust = time_adjust;
 705
 706                 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
 707                         /* adjtime() is independent from ntp_adjtime() */
 708                         time_adjust = txc->offset;
 709                         ntp_update_frequency();
 710                 }
 711                 txc->offset = save_adjust;
 712         } else {
 713
 714                 /* If there are input parameters, then process them: */
 715                 if (txc->modes)
 716                         process_adjtimex_modes(txc, ts, time_tai);
 717
 718                 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
 719                                   NTP_SCALE_SHIFT);
 720                 if (!(time_status & STA_NANO))
 721                         txc->offset /= NSEC_PER_USEC;
 722         }
 723
 724         result = time_state;    /* mostly `TIME_OK' */
 725         /* check for errors */
 726         if (is_error_status(time_status))
 727                 result = TIME_ERROR;
 728
 729         txc->freq          = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
 730                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 731         txc->maxerror      = time_maxerror;
 732         txc->esterror      = time_esterror;
 733         txc->status        = time_status;
 734         txc->constant      = time_constant;
 735         txc->precision     = 1;
 736         txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
 737         txc->tick          = tick_usec;
 738         txc->tai           = *time_tai;
 739
 740         /* fill PPS status fields */
 741         pps_fill_timex(txc);
 742
 743         txc->time.tv_sec = (time_t)ts->tv_sec;
 744         txc->time.tv_usec = ts->tv_nsec;
 745         if (!(time_status & STA_NANO))
 746                 txc->time.tv_usec /= NSEC_PER_USEC;
 747
 748         /* Handle leapsec adjustments */
 749         if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) {
 750                 if ((time_state == TIME_INS) && (time_status & STA_INS)) {
 751                         result = TIME_OOP;
 752                         txc->tai++;
 753                         txc->time.tv_sec--;
 754                 }
 755                 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) {
 756                         result = TIME_WAIT;
 757                         txc->tai--;
 758                         txc->time.tv_sec++;
 759                 }
 760                 if ((time_state == TIME_OOP) &&
 761                                         (ts->tv_sec == ntp_next_leap_sec)) {
 762                         result = TIME_WAIT;
 763                 }
 764         }
 765
 766         return result;
 767 }
 768
 769 #ifdef  CONFIG_NTP_PPS
 770
 771 /* actually struct pps_normtime is good old struct timespec, but it is
 772  * semantically different (and it is the reason why it was invented):
 773  * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
 774  * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
 775 struct pps_normtime {
 776         s64             sec;    /* seconds */
 777         long            nsec;   /* nanoseconds */
 778 };
 779
 780 /* normalize the timestamp so that nsec is in the
 781    ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
 782 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
 783 {
 784         struct pps_normtime norm = {
 785                 .sec = ts.tv_sec,
 786                 .nsec = ts.tv_nsec
 787         };
 788
 789         if (norm.nsec > (NSEC_PER_SEC >> 1)) {
 790                 norm.nsec -= NSEC_PER_SEC;
 791                 norm.sec++;
 792         }
 793
 794         return norm;
 795 }
 796
 797 /* get current phase correction and jitter */
 798 static inline long pps_phase_filter_get(long *jitter)
 799 {
 800         *jitter = pps_tf[0] - pps_tf[1];
 801         if (*jitter < 0)
 802                 *jitter = -*jitter;
 803
 804         /* TODO: test various filters */
 805         return pps_tf[0];
 806 }
 807
 808 /* add the sample to the phase filter */
 809 static inline void pps_phase_filter_add(long err)
 810 {
 811         pps_tf[2] = pps_tf[1];
 812         pps_tf[1] = pps_tf[0];
 813         pps_tf[0] = err;
 814 }
 815
 816 /* decrease frequency calibration interval length.
 817  * It is halved after four consecutive unstable intervals.
 818  */
 819 static inline void pps_dec_freq_interval(void)
 820 {
 821         if (--pps_intcnt <= -PPS_INTCOUNT) {
 822                 pps_intcnt = -PPS_INTCOUNT;
 823                 if (pps_shift > PPS_INTMIN) {
 824                         pps_shift--;
 825                         pps_intcnt = 0;
 826                 }
 827         }
 828 }
 829
 830 /* increase frequency calibration interval length.
 831  * It is doubled after four consecutive stable intervals.
 832  */
 833 static inline void pps_inc_freq_interval(void)
 834 {
 835         if (++pps_intcnt >= PPS_INTCOUNT) {
 836                 pps_intcnt = PPS_INTCOUNT;
 837                 if (pps_shift < PPS_INTMAX) {
 838                         pps_shift++;
 839                         pps_intcnt = 0;
 840                 }
 841         }
 842 }
 843
 844 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
 845  * timestamps
 846  *
 847  * At the end of the calibration interval the difference between the
 848  * first and last MONOTONIC_RAW clock timestamps divided by the length
 849  * of the interval becomes the frequency update. If the interval was
 850  * too long, the data are discarded.
 851  * Returns the difference between old and new frequency values.
 852  */
 853 static long hardpps_update_freq(struct pps_normtime freq_norm)
 854 {
 855         long delta, delta_mod;
 856         s64 ftemp;
 857
 858         /* check if the frequency interval was too long */
 859         if (freq_norm.sec > (2 << pps_shift)) {
 860                 time_status |= STA_PPSERROR;
 861                 pps_errcnt++;
 862                 pps_dec_freq_interval();
 863                 printk_deferred(KERN_ERR
 864                         "hardpps: PPSERROR: interval too long - %lld s\n",
 865                         freq_norm.sec);
 866                 return 0;
 867         }
 868
 869         /* here the raw frequency offset and wander (stability) is
 870          * calculated. If the wander is less than the wander threshold
 871          * the interval is increased; otherwise it is decreased.
 872          */
 873         ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
 874                         freq_norm.sec);
 875         delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
 876         pps_freq = ftemp;
 877         if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
 878                 printk_deferred(KERN_WARNING
 879                                 "hardpps: PPSWANDER: change=%ld\n", delta);
 880                 time_status |= STA_PPSWANDER;
 881                 pps_stbcnt++;
 882                 pps_dec_freq_interval();
 883         } else {        /* good sample */
 884                 pps_inc_freq_interval();
 885         }
 886
 887         /* the stability metric is calculated as the average of recent
 888          * frequency changes, but is used only for performance
 889          * monitoring
 890          */
 891         delta_mod = delta;
 892         if (delta_mod < 0)
 893                 delta_mod = -delta_mod;
 894         pps_stabil += (div_s64(((s64)delta_mod) <<
 895                                 (NTP_SCALE_SHIFT - SHIFT_USEC),
 896                                 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
 897
 898         /* if enabled, the system clock frequency is updated */
 899         if ((time_status & STA_PPSFREQ) != 0 &&
 900             (time_status & STA_FREQHOLD) == 0) {
 901                 time_freq = pps_freq;
 902                 ntp_update_frequency();
 903         }
 904
 905         return delta;
 906 }
 907
 908 /* correct REALTIME clock phase error against PPS signal */
 909 static void hardpps_update_phase(long error)
 910 {
 911         long correction = -error;
 912         long jitter;
 913
 914         /* add the sample to the median filter */
 915         pps_phase_filter_add(correction);
 916         correction = pps_phase_filter_get(&jitter);
 917
 918         /* Nominal jitter is due to PPS signal noise. If it exceeds the
 919          * threshold, the sample is discarded; otherwise, if so enabled,
 920          * the time offset is updated.
 921          */
 922         if (jitter > (pps_jitter << PPS_POPCORN)) {
 923                 printk_deferred(KERN_WARNING
 924                                 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
 925                                 jitter, (pps_jitter << PPS_POPCORN));
 926                 time_status |= STA_PPSJITTER;
 927                 pps_jitcnt++;
 928         } else if (time_status & STA_PPSTIME) {
 929                 /* correct the time using the phase offset */
 930                 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
 931                                 NTP_INTERVAL_FREQ);
 932                 /* cancel running adjtime() */
 933                 time_adjust = 0;
 934         }
 935         /* update jitter */
 936         pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
 937 }
 938
 939 /*
 940  * __hardpps() - discipline CPU clock oscillator to external PPS signal
 941  *
 942  * This routine is called at each PPS signal arrival in order to
 943  * discipline the CPU clock oscillator to the PPS signal. It takes two
 944  * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
 945  * is used to correct clock phase error and the latter is used to
 946  * correct the frequency.
 947  *
 948  * This code is based on David Mills's reference nanokernel
 949  * implementation. It was mostly rewritten but keeps the same idea.
 950  */
 951 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
 952 {
 953         struct pps_normtime pts_norm, freq_norm;
 954
 955         pts_norm = pps_normalize_ts(*phase_ts);
 956
 957         /* clear the error bits, they will be set again if needed */
 958         time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
 959
 960         /* indicate signal presence */
 961         time_status |= STA_PPSSIGNAL;
 962         pps_valid = PPS_VALID;
 963
 964         /* when called for the first time,
 965          * just start the frequency interval */
 966         if (unlikely(pps_fbase.tv_sec == 0)) {
 967                 pps_fbase = *raw_ts;
 968                 return;
 969         }
 970
 971         /* ok, now we have a base for frequency calculation */
 972         freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase));
 973
 974         /* check that the signal is in the range
 975          * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
 976         if ((freq_norm.sec == 0) ||
 977                         (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
 978                         (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
 979                 time_status |= STA_PPSJITTER;
 980                 /* restart the frequency calibration interval */
 981                 pps_fbase = *raw_ts;
 982                 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
 983                 return;
 984         }
 985
 986         /* signal is ok */
 987
 988         /* check if the current frequency interval is finished */
 989         if (freq_norm.sec >= (1 << pps_shift)) {
 990                 pps_calcnt++;
 991                 /* restart the frequency calibration interval */
 992                 pps_fbase = *raw_ts;
 993                 hardpps_update_freq(freq_norm);
 994         }
 995
 996         hardpps_update_phase(pts_norm.nsec);
 997
 998 }
 999 #endif  /* CONFIG_NTP_PPS */
1000
1001 static int __init ntp_tick_adj_setup(char *str)
1002 {
1003         int rc = kstrtol(str, 0, (long *)&ntp_tick_adj);
1004
1005         if (rc)
1006                 return rc;
1007         ntp_tick_adj <<= NTP_SCALE_SHIFT;
1008
1009         return 1;
1010 }
1011
1012 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
1013
1014 void __init ntp_init(void)
1015 {
1016         ntp_clear();
1017 }