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Linux/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 #include <linux/math64.h>
 20 
 21 #include "ntp_internal.h"
 22 #include "timekeeping_internal.h"
 23 
 24 
 25 /*
 26  * NTP timekeeping variables:
 27  *
 28  * Note: All of the NTP state is protected by the timekeeping locks.
 29  */
 30 
 31 
 32 /* USER_HZ period (usecs): */
 33 unsigned long                   tick_usec = TICK_USEC;
 34 
 35 /* SHIFTED_HZ period (nsecs): */
 36 unsigned long                   tick_nsec;
 37 
 38 static u64                      tick_length;
 39 static u64                      tick_length_base;
 40 
 41 #define SECS_PER_DAY            86400
 42 #define MAX_TICKADJ             500LL           /* usecs */
 43 #define MAX_TICKADJ_SCALED \
 44         (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
 45 
 46 /*
 47  * phase-lock loop variables
 48  */
 49 
 50 /*
 51  * clock synchronization status
 52  *
 53  * (TIME_ERROR prevents overwriting the CMOS clock)
 54  */
 55 static int                      time_state = TIME_OK;
 56 
 57 /* clock status bits:                                                   */
 58 static int                      time_status = STA_UNSYNC;
 59 
 60 /* time adjustment (nsecs):                                             */
 61 static s64                      time_offset;
 62 
 63 /* pll time constant:                                                   */
 64 static long                     time_constant = 2;
 65 
 66 /* maximum error (usecs):                                               */
 67 static long                     time_maxerror = NTP_PHASE_LIMIT;
 68 
 69 /* estimated error (usecs):                                             */
 70 static long                     time_esterror = NTP_PHASE_LIMIT;
 71 
 72 /* frequency offset (scaled nsecs/secs):                                */
 73 static s64                      time_freq;
 74 
 75 /* time at last adjustment (secs):                                      */
 76 static time64_t         time_reftime;
 77 
 78 static long                     time_adjust;
 79 
 80 /* constant (boot-param configurable) NTP tick adjustment (upscaled)    */
 81 static s64                      ntp_tick_adj;
 82 
 83 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */
 84 static time64_t                 ntp_next_leap_sec = TIME64_MAX;
 85 
 86 #ifdef CONFIG_NTP_PPS
 87 
 88 /*
 89  * The following variables are used when a pulse-per-second (PPS) signal
 90  * is available. They establish the engineering parameters of the clock
 91  * discipline loop when controlled by the PPS signal.
 92  */
 93 #define PPS_VALID       10      /* PPS signal watchdog max (s) */
 94 #define PPS_POPCORN     4       /* popcorn spike threshold (shift) */
 95 #define PPS_INTMIN      2       /* min freq interval (s) (shift) */
 96 #define PPS_INTMAX      8       /* max freq interval (s) (shift) */
 97 #define PPS_INTCOUNT    4       /* number of consecutive good intervals to
 98                                    increase pps_shift or consecutive bad
 99                                    intervals to decrease it */
100 #define PPS_MAXWANDER   100000  /* max PPS freq wander (ns/s) */
101 
102 static int pps_valid;           /* signal watchdog counter */
103 static long pps_tf[3];          /* phase median filter */
104 static long pps_jitter;         /* current jitter (ns) */
105 static struct timespec64 pps_fbase; /* beginning of the last freq interval */
106 static int pps_shift;           /* current interval duration (s) (shift) */
107 static int pps_intcnt;          /* interval counter */
108 static s64 pps_freq;            /* frequency offset (scaled ns/s) */
109 static long pps_stabil;         /* current stability (scaled ns/s) */
110 
111 /*
112  * PPS signal quality monitors
113  */
114 static long pps_calcnt;         /* calibration intervals */
115 static long pps_jitcnt;         /* jitter limit exceeded */
116 static long pps_stbcnt;         /* stability limit exceeded */
117 static long pps_errcnt;         /* calibration errors */
118 
119 
120 /* PPS kernel consumer compensates the whole phase error immediately.
121  * Otherwise, reduce the offset by a fixed factor times the time constant.
122  */
123 static inline s64 ntp_offset_chunk(s64 offset)
124 {
125         if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
126                 return offset;
127         else
128                 return shift_right(offset, SHIFT_PLL + time_constant);
129 }
130 
131 static inline void pps_reset_freq_interval(void)
132 {
133         /* the PPS calibration interval may end
134            surprisingly early */
135         pps_shift = PPS_INTMIN;
136         pps_intcnt = 0;
137 }
138 
139 /**
140  * pps_clear - Clears the PPS state variables
141  */
142 static inline void pps_clear(void)
143 {
144         pps_reset_freq_interval();
145         pps_tf[0] = 0;
146         pps_tf[1] = 0;
147         pps_tf[2] = 0;
148         pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
149         pps_freq = 0;
150 }
151 
152 /* Decrease pps_valid to indicate that another second has passed since
153  * the last PPS signal. When it reaches 0, indicate that PPS signal is
154  * missing.
155  */
156 static inline void pps_dec_valid(void)
157 {
158         if (pps_valid > 0)
159                 pps_valid--;
160         else {
161                 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
162                                  STA_PPSWANDER | STA_PPSERROR);
163                 pps_clear();
164         }
165 }
166 
167 static inline void pps_set_freq(s64 freq)
168 {
169         pps_freq = freq;
170 }
171 
172 static inline int is_error_status(int status)
173 {
174         return (status & (STA_UNSYNC|STA_CLOCKERR))
175                 /* PPS signal lost when either PPS time or
176                  * PPS frequency synchronization requested
177                  */
178                 || ((status & (STA_PPSFREQ|STA_PPSTIME))
179                         && !(status & STA_PPSSIGNAL))
180                 /* PPS jitter exceeded when
181                  * PPS time synchronization requested */
182                 || ((status & (STA_PPSTIME|STA_PPSJITTER))
183                         == (STA_PPSTIME|STA_PPSJITTER))
184                 /* PPS wander exceeded or calibration error when
185                  * PPS frequency synchronization requested
186                  */
187                 || ((status & STA_PPSFREQ)
188                         && (status & (STA_PPSWANDER|STA_PPSERROR)));
189 }
190 
191 static inline void pps_fill_timex(struct timex *txc)
192 {
193         txc->ppsfreq       = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
194                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
195         txc->jitter        = pps_jitter;
196         if (!(time_status & STA_NANO))
197                 txc->jitter /= NSEC_PER_USEC;
198         txc->shift         = pps_shift;
199         txc->stabil        = pps_stabil;
200         txc->jitcnt        = pps_jitcnt;
201         txc->calcnt        = pps_calcnt;
202         txc->errcnt        = pps_errcnt;
203         txc->stbcnt        = pps_stbcnt;
204 }
205 
206 #else /* !CONFIG_NTP_PPS */
207 
208 static inline s64 ntp_offset_chunk(s64 offset)
209 {
210         return shift_right(offset, SHIFT_PLL + time_constant);
211 }
212 
213 static inline void pps_reset_freq_interval(void) {}
214 static inline void pps_clear(void) {}
215 static inline void pps_dec_valid(void) {}
216 static inline void pps_set_freq(s64 freq) {}
217 
218 static inline int is_error_status(int status)
219 {
220         return status & (STA_UNSYNC|STA_CLOCKERR);
221 }
222 
223 static inline void pps_fill_timex(struct timex *txc)
224 {
225         /* PPS is not implemented, so these are zero */
226         txc->ppsfreq       = 0;
227         txc->jitter        = 0;
228         txc->shift         = 0;
229         txc->stabil        = 0;
230         txc->jitcnt        = 0;
231         txc->calcnt        = 0;
232         txc->errcnt        = 0;
233         txc->stbcnt        = 0;
234 }
235 
236 #endif /* CONFIG_NTP_PPS */
237 
238 
239 /**
240  * ntp_synced - Returns 1 if the NTP status is not UNSYNC
241  *
242  */
243 static inline int ntp_synced(void)
244 {
245         return !(time_status & STA_UNSYNC);
246 }
247 
248 
249 /*
250  * NTP methods:
251  */
252 
253 /*
254  * Update (tick_length, tick_length_base, tick_nsec), based
255  * on (tick_usec, ntp_tick_adj, time_freq):
256  */
257 static void ntp_update_frequency(void)
258 {
259         u64 second_length;
260         u64 new_base;
261 
262         second_length            = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
263                                                 << NTP_SCALE_SHIFT;
264 
265         second_length           += ntp_tick_adj;
266         second_length           += time_freq;
267 
268         tick_nsec                = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
269         new_base                 = div_u64(second_length, NTP_INTERVAL_FREQ);
270 
271         /*
272          * Don't wait for the next second_overflow, apply
273          * the change to the tick length immediately:
274          */
275         tick_length             += new_base - tick_length_base;
276         tick_length_base         = new_base;
277 }
278 
279 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
280 {
281         time_status &= ~STA_MODE;
282 
283         if (secs < MINSEC)
284                 return 0;
285 
286         if (!(time_status & STA_FLL) && (secs <= MAXSEC))
287                 return 0;
288 
289         time_status |= STA_MODE;
290 
291         return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
292 }
293 
294 static void ntp_update_offset(long offset)
295 {
296         s64 freq_adj;
297         s64 offset64;
298         long secs;
299 
300         if (!(time_status & STA_PLL))
301                 return;
302 
303         if (!(time_status & STA_NANO)) {
304                 /* Make sure the multiplication below won't overflow */
305                 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
306                 offset *= NSEC_PER_USEC;
307         }
308 
309         /*
310          * Scale the phase adjustment and
311          * clamp to the operating range.
312          */
313         offset = clamp(offset, -MAXPHASE, MAXPHASE);
314 
315         /*
316          * Select how the frequency is to be controlled
317          * and in which mode (PLL or FLL).
318          */
319         secs = (long)(__ktime_get_real_seconds() - time_reftime);
320         if (unlikely(time_status & STA_FREQHOLD))
321                 secs = 0;
322 
323         time_reftime = __ktime_get_real_seconds();
324 
325         offset64    = offset;
326         freq_adj    = ntp_update_offset_fll(offset64, secs);
327 
328         /*
329          * Clamp update interval to reduce PLL gain with low
330          * sampling rate (e.g. intermittent network connection)
331          * to avoid instability.
332          */
333         if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
334                 secs = 1 << (SHIFT_PLL + 1 + time_constant);
335 
336         freq_adj    += (offset64 * secs) <<
337                         (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
338 
339         freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);
340 
341         time_freq   = max(freq_adj, -MAXFREQ_SCALED);
342 
343         time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
344 }
345 
346 /**
347  * ntp_clear - Clears the NTP state variables
348  */
349 void ntp_clear(void)
350 {
351         time_adjust     = 0;            /* stop active adjtime() */
352         time_status     |= STA_UNSYNC;
353         time_maxerror   = NTP_PHASE_LIMIT;
354         time_esterror   = NTP_PHASE_LIMIT;
355 
356         ntp_update_frequency();
357 
358         tick_length     = tick_length_base;
359         time_offset     = 0;
360 
361         ntp_next_leap_sec = TIME64_MAX;
362         /* Clear PPS state variables */
363         pps_clear();
364 }
365 
366 
367 u64 ntp_tick_length(void)
368 {
369         return tick_length;
370 }
371 
372 /**
373  * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
374  *
375  * Provides the time of the next leapsecond against CLOCK_REALTIME in
376  * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending.
377  */
378 ktime_t ntp_get_next_leap(void)
379 {
380         ktime_t ret;
381 
382         if ((time_state == TIME_INS) && (time_status & STA_INS))
383                 return ktime_set(ntp_next_leap_sec, 0);
384         ret.tv64 = KTIME_MAX;
385         return ret;
386 }
387 
388 /*
389  * this routine handles the overflow of the microsecond field
390  *
391  * The tricky bits of code to handle the accurate clock support
392  * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
393  * They were originally developed for SUN and DEC kernels.
394  * All the kudos should go to Dave for this stuff.
395  *
396  * Also handles leap second processing, and returns leap offset
397  */
398 int second_overflow(time64_t secs)
399 {
400         s64 delta;
401         int leap = 0;
402         s32 rem;
403 
404         /*
405          * Leap second processing. If in leap-insert state at the end of the
406          * day, the system clock is set back one second; if in leap-delete
407          * state, the system clock is set ahead one second.
408          */
409         switch (time_state) {
410         case TIME_OK:
411                 if (time_status & STA_INS) {
412                         time_state = TIME_INS;
413                         div_s64_rem(secs, SECS_PER_DAY, &rem);
414                         ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
415                 } else if (time_status & STA_DEL) {
416                         time_state = TIME_DEL;
417                         div_s64_rem(secs + 1, SECS_PER_DAY, &rem);
418                         ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
419                 }
420                 break;
421         case TIME_INS:
422                 if (!(time_status & STA_INS)) {
423                         ntp_next_leap_sec = TIME64_MAX;
424                         time_state = TIME_OK;
425                 } else if (secs == ntp_next_leap_sec) {
426                         leap = -1;
427                         time_state = TIME_OOP;
428                         printk(KERN_NOTICE
429                                 "Clock: inserting leap second 23:59:60 UTC\n");
430                 }
431                 break;
432         case TIME_DEL:
433                 if (!(time_status & STA_DEL)) {
434                         ntp_next_leap_sec = TIME64_MAX;
435                         time_state = TIME_OK;
436                 } else if (secs == ntp_next_leap_sec) {
437                         leap = 1;
438                         ntp_next_leap_sec = TIME64_MAX;
439                         time_state = TIME_WAIT;
440                         printk(KERN_NOTICE
441                                 "Clock: deleting leap second 23:59:59 UTC\n");
442                 }
443                 break;
444         case TIME_OOP:
445                 ntp_next_leap_sec = TIME64_MAX;
446                 time_state = TIME_WAIT;
447                 break;
448         case TIME_WAIT:
449                 if (!(time_status & (STA_INS | STA_DEL)))
450                         time_state = TIME_OK;
451                 break;
452         }
453 
454 
455         /* Bump the maxerror field */
456         time_maxerror += MAXFREQ / NSEC_PER_USEC;
457         if (time_maxerror > NTP_PHASE_LIMIT) {
458                 time_maxerror = NTP_PHASE_LIMIT;
459                 time_status |= STA_UNSYNC;
460         }
461 
462         /* Compute the phase adjustment for the next second */
463         tick_length      = tick_length_base;
464 
465         delta            = ntp_offset_chunk(time_offset);
466         time_offset     -= delta;
467         tick_length     += delta;
468 
469         /* Check PPS signal */
470         pps_dec_valid();
471 
472         if (!time_adjust)
473                 goto out;
474 
475         if (time_adjust > MAX_TICKADJ) {
476                 time_adjust -= MAX_TICKADJ;
477                 tick_length += MAX_TICKADJ_SCALED;
478                 goto out;
479         }
480 
481         if (time_adjust < -MAX_TICKADJ) {
482                 time_adjust += MAX_TICKADJ;
483                 tick_length -= MAX_TICKADJ_SCALED;
484                 goto out;
485         }
486 
487         tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
488                                                          << NTP_SCALE_SHIFT;
489         time_adjust = 0;
490 
491 out:
492         return leap;
493 }
494 
495 #ifdef CONFIG_GENERIC_CMOS_UPDATE
496 int __weak update_persistent_clock(struct timespec now)
497 {
498         return -ENODEV;
499 }
500 
501 int __weak update_persistent_clock64(struct timespec64 now64)
502 {
503         struct timespec now;
504 
505         now = timespec64_to_timespec(now64);
506         return update_persistent_clock(now);
507 }
508 #endif
509 
510 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
511 static void sync_cmos_clock(struct work_struct *work);
512 
513 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
514 
515 static void sync_cmos_clock(struct work_struct *work)
516 {
517         struct timespec64 now;
518         struct timespec64 next;
519         int fail = 1;
520 
521         /*
522          * If we have an externally synchronized Linux clock, then update
523          * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
524          * called as close as possible to 500 ms before the new second starts.
525          * This code is run on a timer.  If the clock is set, that timer
526          * may not expire at the correct time.  Thus, we adjust...
527          * We want the clock to be within a couple of ticks from the target.
528          */
529         if (!ntp_synced()) {
530                 /*
531                  * Not synced, exit, do not restart a timer (if one is
532                  * running, let it run out).
533                  */
534                 return;
535         }
536 
537         getnstimeofday64(&now);
538         if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) {
539                 struct timespec64 adjust = now;
540 
541                 fail = -ENODEV;
542                 if (persistent_clock_is_local)
543                         adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
544 #ifdef CONFIG_GENERIC_CMOS_UPDATE
545                 fail = update_persistent_clock64(adjust);
546 #endif
547 
548 #ifdef CONFIG_RTC_SYSTOHC
549                 if (fail == -ENODEV)
550                         fail = rtc_set_ntp_time(adjust);
551 #endif
552         }
553 
554         next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
555         if (next.tv_nsec <= 0)
556                 next.tv_nsec += NSEC_PER_SEC;
557 
558         if (!fail || fail == -ENODEV)
559                 next.tv_sec = 659;
560         else
561                 next.tv_sec = 0;
562 
563         if (next.tv_nsec >= NSEC_PER_SEC) {
564                 next.tv_sec++;
565                 next.tv_nsec -= NSEC_PER_SEC;
566         }
567         queue_delayed_work(system_power_efficient_wq,
568                            &sync_cmos_work, timespec64_to_jiffies(&next));
569 }
570 
571 void ntp_notify_cmos_timer(void)
572 {
573         queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, 0);
574 }
575 
576 #else
577 void ntp_notify_cmos_timer(void) { }
578 #endif
579 
580 
581 /*
582  * Propagate a new txc->status value into the NTP state:
583  */
584 static inline void process_adj_status(struct timex *txc, struct timespec64 *ts)
585 {
586         if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
587                 time_state = TIME_OK;
588                 time_status = STA_UNSYNC;
589                 ntp_next_leap_sec = TIME64_MAX;
590                 /* restart PPS frequency calibration */
591                 pps_reset_freq_interval();
592         }
593 
594         /*
595          * If we turn on PLL adjustments then reset the
596          * reference time to current time.
597          */
598         if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
599                 time_reftime = __ktime_get_real_seconds();
600 
601         /* only set allowed bits */
602         time_status &= STA_RONLY;
603         time_status |= txc->status & ~STA_RONLY;
604 }
605 
606 
607 static inline void process_adjtimex_modes(struct timex *txc,
608                                                 struct timespec64 *ts,
609                                                 s32 *time_tai)
610 {
611         if (txc->modes & ADJ_STATUS)
612                 process_adj_status(txc, ts);
613 
614         if (txc->modes & ADJ_NANO)
615                 time_status |= STA_NANO;
616 
617         if (txc->modes & ADJ_MICRO)
618                 time_status &= ~STA_NANO;
619 
620         if (txc->modes & ADJ_FREQUENCY) {
621                 time_freq = txc->freq * PPM_SCALE;
622                 time_freq = min(time_freq, MAXFREQ_SCALED);
623                 time_freq = max(time_freq, -MAXFREQ_SCALED);
624                 /* update pps_freq */
625                 pps_set_freq(time_freq);
626         }
627 
628         if (txc->modes & ADJ_MAXERROR)
629                 time_maxerror = txc->maxerror;
630 
631         if (txc->modes & ADJ_ESTERROR)
632                 time_esterror = txc->esterror;
633 
634         if (txc->modes & ADJ_TIMECONST) {
635                 time_constant = txc->constant;
636                 if (!(time_status & STA_NANO))
637                         time_constant += 4;
638                 time_constant = min(time_constant, (long)MAXTC);
639                 time_constant = max(time_constant, 0l);
640         }
641 
642         if (txc->modes & ADJ_TAI && txc->constant > 0)
643                 *time_tai = txc->constant;
644 
645         if (txc->modes & ADJ_OFFSET)
646                 ntp_update_offset(txc->offset);
647 
648         if (txc->modes & ADJ_TICK)
649                 tick_usec = txc->tick;
650 
651         if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
652                 ntp_update_frequency();
653 }
654 
655 
656 
657 /**
658  * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex
659  */
660 int ntp_validate_timex(struct timex *txc)
661 {
662         if (txc->modes & ADJ_ADJTIME) {
663                 /* singleshot must not be used with any other mode bits */
664                 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
665                         return -EINVAL;
666                 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
667                     !capable(CAP_SYS_TIME))
668                         return -EPERM;
669         } else {
670                 /* In order to modify anything, you gotta be super-user! */
671                  if (txc->modes && !capable(CAP_SYS_TIME))
672                         return -EPERM;
673                 /*
674                  * if the quartz is off by more than 10% then
675                  * something is VERY wrong!
676                  */
677                 if (txc->modes & ADJ_TICK &&
678                     (txc->tick <  900000/USER_HZ ||
679                      txc->tick > 1100000/USER_HZ))
680                         return -EINVAL;
681         }
682 
683         if (txc->modes & ADJ_SETOFFSET) {
684                 /* In order to inject time, you gotta be super-user! */
685                 if (!capable(CAP_SYS_TIME))
686                         return -EPERM;
687 
688                 if (txc->modes & ADJ_NANO) {
689                         struct timespec ts;
690 
691                         ts.tv_sec = txc->time.tv_sec;
692                         ts.tv_nsec = txc->time.tv_usec;
693                         if (!timespec_inject_offset_valid(&ts))
694                                 return -EINVAL;
695 
696                 } else {
697                         if (!timeval_inject_offset_valid(&txc->time))
698                                 return -EINVAL;
699                 }
700         }
701 
702         /*
703          * Check for potential multiplication overflows that can
704          * only happen on 64-bit systems:
705          */
706         if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) {
707                 if (LLONG_MIN / PPM_SCALE > txc->freq)
708                         return -EINVAL;
709                 if (LLONG_MAX / PPM_SCALE < txc->freq)
710                         return -EINVAL;
711         }
712 
713         return 0;
714 }
715 
716 
717 /*
718  * adjtimex mainly allows reading (and writing, if superuser) of
719  * kernel time-keeping variables. used by xntpd.
720  */
721 int __do_adjtimex(struct timex *txc, struct timespec64 *ts, s32 *time_tai)
722 {
723         int result;
724 
725         if (txc->modes & ADJ_ADJTIME) {
726                 long save_adjust = time_adjust;
727 
728                 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
729                         /* adjtime() is independent from ntp_adjtime() */
730                         time_adjust = txc->offset;
731                         ntp_update_frequency();
732                 }
733                 txc->offset = save_adjust;
734         } else {
735 
736                 /* If there are input parameters, then process them: */
737                 if (txc->modes)
738                         process_adjtimex_modes(txc, ts, time_tai);
739 
740                 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
741                                   NTP_SCALE_SHIFT);
742                 if (!(time_status & STA_NANO))
743                         txc->offset /= NSEC_PER_USEC;
744         }
745 
746         result = time_state;    /* mostly `TIME_OK' */
747         /* check for errors */
748         if (is_error_status(time_status))
749                 result = TIME_ERROR;
750 
751         txc->freq          = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
752                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
753         txc->maxerror      = time_maxerror;
754         txc->esterror      = time_esterror;
755         txc->status        = time_status;
756         txc->constant      = time_constant;
757         txc->precision     = 1;
758         txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
759         txc->tick          = tick_usec;
760         txc->tai           = *time_tai;
761 
762         /* fill PPS status fields */
763         pps_fill_timex(txc);
764 
765         txc->time.tv_sec = (time_t)ts->tv_sec;
766         txc->time.tv_usec = ts->tv_nsec;
767         if (!(time_status & STA_NANO))
768                 txc->time.tv_usec /= NSEC_PER_USEC;
769 
770         /* Handle leapsec adjustments */
771         if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) {
772                 if ((time_state == TIME_INS) && (time_status & STA_INS)) {
773                         result = TIME_OOP;
774                         txc->tai++;
775                         txc->time.tv_sec--;
776                 }
777                 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) {
778                         result = TIME_WAIT;
779                         txc->tai--;
780                         txc->time.tv_sec++;
781                 }
782                 if ((time_state == TIME_OOP) &&
783                                         (ts->tv_sec == ntp_next_leap_sec)) {
784                         result = TIME_WAIT;
785                 }
786         }
787 
788         return result;
789 }
790 
791 #ifdef  CONFIG_NTP_PPS
792 
793 /* actually struct pps_normtime is good old struct timespec, but it is
794  * semantically different (and it is the reason why it was invented):
795  * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
796  * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
797 struct pps_normtime {
798         s64             sec;    /* seconds */
799         long            nsec;   /* nanoseconds */
800 };
801 
802 /* normalize the timestamp so that nsec is in the
803    ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
804 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
805 {
806         struct pps_normtime norm = {
807                 .sec = ts.tv_sec,
808                 .nsec = ts.tv_nsec
809         };
810 
811         if (norm.nsec > (NSEC_PER_SEC >> 1)) {
812                 norm.nsec -= NSEC_PER_SEC;
813                 norm.sec++;
814         }
815 
816         return norm;
817 }
818 
819 /* get current phase correction and jitter */
820 static inline long pps_phase_filter_get(long *jitter)
821 {
822         *jitter = pps_tf[0] - pps_tf[1];
823         if (*jitter < 0)
824                 *jitter = -*jitter;
825 
826         /* TODO: test various filters */
827         return pps_tf[0];
828 }
829 
830 /* add the sample to the phase filter */
831 static inline void pps_phase_filter_add(long err)
832 {
833         pps_tf[2] = pps_tf[1];
834         pps_tf[1] = pps_tf[0];
835         pps_tf[0] = err;
836 }
837 
838 /* decrease frequency calibration interval length.
839  * It is halved after four consecutive unstable intervals.
840  */
841 static inline void pps_dec_freq_interval(void)
842 {
843         if (--pps_intcnt <= -PPS_INTCOUNT) {
844                 pps_intcnt = -PPS_INTCOUNT;
845                 if (pps_shift > PPS_INTMIN) {
846                         pps_shift--;
847                         pps_intcnt = 0;
848                 }
849         }
850 }
851 
852 /* increase frequency calibration interval length.
853  * It is doubled after four consecutive stable intervals.
854  */
855 static inline void pps_inc_freq_interval(void)
856 {
857         if (++pps_intcnt >= PPS_INTCOUNT) {
858                 pps_intcnt = PPS_INTCOUNT;
859                 if (pps_shift < PPS_INTMAX) {
860                         pps_shift++;
861                         pps_intcnt = 0;
862                 }
863         }
864 }
865 
866 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
867  * timestamps
868  *
869  * At the end of the calibration interval the difference between the
870  * first and last MONOTONIC_RAW clock timestamps divided by the length
871  * of the interval becomes the frequency update. If the interval was
872  * too long, the data are discarded.
873  * Returns the difference between old and new frequency values.
874  */
875 static long hardpps_update_freq(struct pps_normtime freq_norm)
876 {
877         long delta, delta_mod;
878         s64 ftemp;
879 
880         /* check if the frequency interval was too long */
881         if (freq_norm.sec > (2 << pps_shift)) {
882                 time_status |= STA_PPSERROR;
883                 pps_errcnt++;
884                 pps_dec_freq_interval();
885                 printk_deferred(KERN_ERR
886                         "hardpps: PPSERROR: interval too long - %lld s\n",
887                         freq_norm.sec);
888                 return 0;
889         }
890 
891         /* here the raw frequency offset and wander (stability) is
892          * calculated. If the wander is less than the wander threshold
893          * the interval is increased; otherwise it is decreased.
894          */
895         ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
896                         freq_norm.sec);
897         delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
898         pps_freq = ftemp;
899         if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
900                 printk_deferred(KERN_WARNING
901                                 "hardpps: PPSWANDER: change=%ld\n", delta);
902                 time_status |= STA_PPSWANDER;
903                 pps_stbcnt++;
904                 pps_dec_freq_interval();
905         } else {        /* good sample */
906                 pps_inc_freq_interval();
907         }
908 
909         /* the stability metric is calculated as the average of recent
910          * frequency changes, but is used only for performance
911          * monitoring
912          */
913         delta_mod = delta;
914         if (delta_mod < 0)
915                 delta_mod = -delta_mod;
916         pps_stabil += (div_s64(((s64)delta_mod) <<
917                                 (NTP_SCALE_SHIFT - SHIFT_USEC),
918                                 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
919 
920         /* if enabled, the system clock frequency is updated */
921         if ((time_status & STA_PPSFREQ) != 0 &&
922             (time_status & STA_FREQHOLD) == 0) {
923                 time_freq = pps_freq;
924                 ntp_update_frequency();
925         }
926 
927         return delta;
928 }
929 
930 /* correct REALTIME clock phase error against PPS signal */
931 static void hardpps_update_phase(long error)
932 {
933         long correction = -error;
934         long jitter;
935 
936         /* add the sample to the median filter */
937         pps_phase_filter_add(correction);
938         correction = pps_phase_filter_get(&jitter);
939 
940         /* Nominal jitter is due to PPS signal noise. If it exceeds the
941          * threshold, the sample is discarded; otherwise, if so enabled,
942          * the time offset is updated.
943          */
944         if (jitter > (pps_jitter << PPS_POPCORN)) {
945                 printk_deferred(KERN_WARNING
946                                 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
947                                 jitter, (pps_jitter << PPS_POPCORN));
948                 time_status |= STA_PPSJITTER;
949                 pps_jitcnt++;
950         } else if (time_status & STA_PPSTIME) {
951                 /* correct the time using the phase offset */
952                 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
953                                 NTP_INTERVAL_FREQ);
954                 /* cancel running adjtime() */
955                 time_adjust = 0;
956         }
957         /* update jitter */
958         pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
959 }
960 
961 /*
962  * __hardpps() - discipline CPU clock oscillator to external PPS signal
963  *
964  * This routine is called at each PPS signal arrival in order to
965  * discipline the CPU clock oscillator to the PPS signal. It takes two
966  * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
967  * is used to correct clock phase error and the latter is used to
968  * correct the frequency.
969  *
970  * This code is based on David Mills's reference nanokernel
971  * implementation. It was mostly rewritten but keeps the same idea.
972  */
973 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
974 {
975         struct pps_normtime pts_norm, freq_norm;
976 
977         pts_norm = pps_normalize_ts(*phase_ts);
978 
979         /* clear the error bits, they will be set again if needed */
980         time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
981 
982         /* indicate signal presence */
983         time_status |= STA_PPSSIGNAL;
984         pps_valid = PPS_VALID;
985 
986         /* when called for the first time,
987          * just start the frequency interval */
988         if (unlikely(pps_fbase.tv_sec == 0)) {
989                 pps_fbase = *raw_ts;
990                 return;
991         }
992 
993         /* ok, now we have a base for frequency calculation */
994         freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase));
995 
996         /* check that the signal is in the range
997          * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
998         if ((freq_norm.sec == 0) ||
999                         (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
1000                         (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
1001                 time_status |= STA_PPSJITTER;
1002                 /* restart the frequency calibration interval */
1003                 pps_fbase = *raw_ts;
1004                 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
1005                 return;
1006         }
1007 
1008         /* signal is ok */
1009 
1010         /* check if the current frequency interval is finished */
1011         if (freq_norm.sec >= (1 << pps_shift)) {
1012                 pps_calcnt++;
1013                 /* restart the frequency calibration interval */
1014                 pps_fbase = *raw_ts;
1015                 hardpps_update_freq(freq_norm);
1016         }
1017 
1018         hardpps_update_phase(pts_norm.nsec);
1019 
1020 }
1021 #endif  /* CONFIG_NTP_PPS */
1022 
1023 static int __init ntp_tick_adj_setup(char *str)
1024 {
1025         int rc = kstrtol(str, 0, (long *)&ntp_tick_adj);
1026 
1027         if (rc)
1028                 return rc;
1029         ntp_tick_adj <<= NTP_SCALE_SHIFT;
1030 
1031         return 1;
1032 }
1033 
1034 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
1035 
1036 void __init ntp_init(void)
1037 {
1038         ntp_clear();
1039 }
1040 

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