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 * struct ntp_data - Structure holding all NTP related state
27 * @tick_usec: USER_HZ period in microseconds
28 * @tick_length: Adjusted tick length
29 * @tick_length_base: Base value for @tick_length
30 * @time_state: State of the clock synchronization
31 * @time_status: Clock status bits
32 * @time_offset: Time adjustment in nanoseconds
33 * @time_constant: PLL time constant
34 * @time_maxerror: Maximum error in microseconds holding the NTP sync distance
35 * (NTP dispersion + delay / 2)
36 * @time_esterror: Estimated error in microseconds holding NTP dispersion
37 * @time_freq: Frequency offset scaled nsecs/secs
38 * @time_reftime: Time at last adjustment in seconds
39 * @time_adjust: Adjustment value
40 * @ntp_tick_adj: Constant boot-param configurable NTP tick adjustment (upscaled)
41 * @ntp_next_leap_sec: Second value of the next pending leapsecond, or TIME64_MAX if no leap
42 *
43 * @pps_valid: PPS signal watchdog counter
44 * @pps_tf: PPS phase median filter
45 * @pps_jitter: PPS current jitter in nanoseconds
46 * @pps_fbase: PPS beginning of the last freq interval
47 * @pps_shift: PPS current interval duration in seconds (shift value)
48 * @pps_intcnt: PPS interval counter
49 * @pps_freq: PPS frequency offset in scaled ns/s
50 * @pps_stabil: PPS current stability in scaled ns/s
51 * @pps_calcnt: PPS monitor: calibration intervals
52 * @pps_jitcnt: PPS monitor: jitter limit exceeded
53 * @pps_stbcnt: PPS monitor: stability limit exceeded
54 * @pps_errcnt: PPS monitor: calibration errors
55 *
56 * Protected by the timekeeping locks.
57 */
58 struct ntp_data {
59 unsigned long tick_usec;
60 u64 tick_length;
61 u64 tick_length_base;
62 int time_state;
63 int time_status;
64 s64 time_offset;
65 long time_constant;
66 long time_maxerror;
67 long time_esterror;
68 s64 time_freq;
69 time64_t time_reftime;
70 long time_adjust;
71 s64 ntp_tick_adj;
72 time64_t ntp_next_leap_sec;
73 #ifdef CONFIG_NTP_PPS
74 int pps_valid;
75 long pps_tf[3];
76 long pps_jitter;
77 struct timespec64 pps_fbase;
78 int pps_shift;
79 int pps_intcnt;
80 s64 pps_freq;
81 long pps_stabil;
82 long pps_calcnt;
83 long pps_jitcnt;
84 long pps_stbcnt;
85 long pps_errcnt;
86 #endif
87 };
88
89 static struct ntp_data tk_ntp_data = {
90 .tick_usec = USER_TICK_USEC,
91 .time_state = TIME_OK,
92 .time_status = STA_UNSYNC,
93 .time_constant = 2,
94 .time_maxerror = NTP_PHASE_LIMIT,
95 .time_esterror = NTP_PHASE_LIMIT,
96 .ntp_next_leap_sec = TIME64_MAX,
97 };
98
99 #define SECS_PER_DAY 86400
100 #define MAX_TICKADJ 500LL /* usecs */
101 #define MAX_TICKADJ_SCALED \
102 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
103 #define MAX_TAI_OFFSET 100000
104
105 #ifdef CONFIG_NTP_PPS
106
107 /*
108 * The following variables are used when a pulse-per-second (PPS) signal
109 * is available. They establish the engineering parameters of the clock
110 * discipline loop when controlled by the PPS signal.
111 */
112 #define PPS_VALID 10 /* PPS signal watchdog max (s) */
113 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
114 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */
115 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */
116 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to
117 increase pps_shift or consecutive bad
118 intervals to decrease it */
119 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
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 */
ntp_offset_chunk(struct ntp_data * ntpdata,s64 offset)125 static inline s64 ntp_offset_chunk(struct ntp_data *ntpdata, s64 offset)
126 {
127 if (ntpdata->time_status & STA_PPSTIME && ntpdata->time_status & STA_PPSSIGNAL)
128 return offset;
129 else
130 return shift_right(offset, SHIFT_PLL + ntpdata->time_constant);
131 }
132
pps_reset_freq_interval(struct ntp_data * ntpdata)133 static inline void pps_reset_freq_interval(struct ntp_data *ntpdata)
134 {
135 /* The PPS calibration interval may end surprisingly early */
136 ntpdata->pps_shift = PPS_INTMIN;
137 ntpdata->pps_intcnt = 0;
138 }
139
140 /**
141 * pps_clear - Clears the PPS state variables
142 * @ntpdata: Pointer to ntp data
143 */
pps_clear(struct ntp_data * ntpdata)144 static inline void pps_clear(struct ntp_data *ntpdata)
145 {
146 pps_reset_freq_interval(ntpdata);
147 ntpdata->pps_tf[0] = 0;
148 ntpdata->pps_tf[1] = 0;
149 ntpdata->pps_tf[2] = 0;
150 ntpdata->pps_fbase.tv_sec = ntpdata->pps_fbase.tv_nsec = 0;
151 ntpdata->pps_freq = 0;
152 }
153
154 /*
155 * Decrease pps_valid to indicate that another second has passed since the
156 * last PPS signal. When it reaches 0, indicate that PPS signal is missing.
157 */
pps_dec_valid(struct ntp_data * ntpdata)158 static inline void pps_dec_valid(struct ntp_data *ntpdata)
159 {
160 if (ntpdata->pps_valid > 0) {
161 ntpdata->pps_valid--;
162 } else {
163 ntpdata->time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
164 STA_PPSWANDER | STA_PPSERROR);
165 pps_clear(ntpdata);
166 }
167 }
168
pps_set_freq(struct ntp_data * ntpdata)169 static inline void pps_set_freq(struct ntp_data *ntpdata)
170 {
171 ntpdata->pps_freq = ntpdata->time_freq;
172 }
173
is_error_status(int status)174 static inline bool is_error_status(int status)
175 {
176 return (status & (STA_UNSYNC|STA_CLOCKERR))
177 /*
178 * PPS signal lost when either PPS time or PPS frequency
179 * synchronization requested
180 */
181 || ((status & (STA_PPSFREQ|STA_PPSTIME))
182 && !(status & STA_PPSSIGNAL))
183 /*
184 * PPS jitter exceeded when PPS time synchronization
185 * requested
186 */
187 || ((status & (STA_PPSTIME|STA_PPSJITTER))
188 == (STA_PPSTIME|STA_PPSJITTER))
189 /*
190 * PPS wander exceeded or calibration error when PPS
191 * frequency synchronization requested
192 */
193 || ((status & STA_PPSFREQ)
194 && (status & (STA_PPSWANDER|STA_PPSERROR)));
195 }
196
pps_fill_timex(struct ntp_data * ntpdata,struct __kernel_timex * txc)197 static inline void pps_fill_timex(struct ntp_data *ntpdata, struct __kernel_timex *txc)
198 {
199 txc->ppsfreq = shift_right((ntpdata->pps_freq >> PPM_SCALE_INV_SHIFT) *
200 PPM_SCALE_INV, NTP_SCALE_SHIFT);
201 txc->jitter = ntpdata->pps_jitter;
202 if (!(ntpdata->time_status & STA_NANO))
203 txc->jitter = ntpdata->pps_jitter / NSEC_PER_USEC;
204 txc->shift = ntpdata->pps_shift;
205 txc->stabil = ntpdata->pps_stabil;
206 txc->jitcnt = ntpdata->pps_jitcnt;
207 txc->calcnt = ntpdata->pps_calcnt;
208 txc->errcnt = ntpdata->pps_errcnt;
209 txc->stbcnt = ntpdata->pps_stbcnt;
210 }
211
212 #else /* !CONFIG_NTP_PPS */
213
ntp_offset_chunk(struct ntp_data * ntpdata,s64 offset)214 static inline s64 ntp_offset_chunk(struct ntp_data *ntpdata, s64 offset)
215 {
216 return shift_right(offset, SHIFT_PLL + ntpdata->time_constant);
217 }
218
pps_reset_freq_interval(struct ntp_data * ntpdata)219 static inline void pps_reset_freq_interval(struct ntp_data *ntpdata) {}
pps_clear(struct ntp_data * ntpdata)220 static inline void pps_clear(struct ntp_data *ntpdata) {}
pps_dec_valid(struct ntp_data * ntpdata)221 static inline void pps_dec_valid(struct ntp_data *ntpdata) {}
pps_set_freq(struct ntp_data * ntpdata)222 static inline void pps_set_freq(struct ntp_data *ntpdata) {}
223
is_error_status(int status)224 static inline bool is_error_status(int status)
225 {
226 return status & (STA_UNSYNC|STA_CLOCKERR);
227 }
228
pps_fill_timex(struct ntp_data * ntpdata,struct __kernel_timex * txc)229 static inline void pps_fill_timex(struct ntp_data *ntpdata, struct __kernel_timex *txc)
230 {
231 /* PPS is not implemented, so these are zero */
232 txc->ppsfreq = 0;
233 txc->jitter = 0;
234 txc->shift = 0;
235 txc->stabil = 0;
236 txc->jitcnt = 0;
237 txc->calcnt = 0;
238 txc->errcnt = 0;
239 txc->stbcnt = 0;
240 }
241
242 #endif /* CONFIG_NTP_PPS */
243
244 /*
245 * Update tick_length and tick_length_base, based on tick_usec, ntp_tick_adj and
246 * time_freq:
247 */
ntp_update_frequency(struct ntp_data * ntpdata)248 static void ntp_update_frequency(struct ntp_data *ntpdata)
249 {
250 u64 second_length, new_base, tick_usec = (u64)ntpdata->tick_usec;
251
252 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << NTP_SCALE_SHIFT;
253
254 second_length += ntpdata->ntp_tick_adj;
255 second_length += ntpdata->time_freq;
256
257 new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
258
259 /*
260 * Don't wait for the next second_overflow, apply the change to the
261 * tick length immediately:
262 */
263 ntpdata->tick_length += new_base - ntpdata->tick_length_base;
264 ntpdata->tick_length_base = new_base;
265 }
266
ntp_update_offset_fll(struct ntp_data * ntpdata,s64 offset64,long secs)267 static inline s64 ntp_update_offset_fll(struct ntp_data *ntpdata, s64 offset64, long secs)
268 {
269 ntpdata->time_status &= ~STA_MODE;
270
271 if (secs < MINSEC)
272 return 0;
273
274 if (!(ntpdata->time_status & STA_FLL) && (secs <= MAXSEC))
275 return 0;
276
277 ntpdata->time_status |= STA_MODE;
278
279 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
280 }
281
ntp_update_offset(struct ntp_data * ntpdata,long offset)282 static void ntp_update_offset(struct ntp_data *ntpdata, long offset)
283 {
284 s64 freq_adj, offset64;
285 long secs, real_secs;
286
287 if (!(ntpdata->time_status & STA_PLL))
288 return;
289
290 if (!(ntpdata->time_status & STA_NANO)) {
291 /* Make sure the multiplication below won't overflow */
292 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
293 offset *= NSEC_PER_USEC;
294 }
295
296 /* Scale the phase adjustment and clamp to the operating range. */
297 offset = clamp(offset, -MAXPHASE, MAXPHASE);
298
299 /*
300 * Select how the frequency is to be controlled
301 * and in which mode (PLL or FLL).
302 */
303 real_secs = __ktime_get_real_seconds();
304 secs = (long)(real_secs - ntpdata->time_reftime);
305 if (unlikely(ntpdata->time_status & STA_FREQHOLD))
306 secs = 0;
307
308 ntpdata->time_reftime = real_secs;
309
310 offset64 = offset;
311 freq_adj = ntp_update_offset_fll(ntpdata, offset64, secs);
312
313 /*
314 * Clamp update interval to reduce PLL gain with low
315 * sampling rate (e.g. intermittent network connection)
316 * to avoid instability.
317 */
318 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + ntpdata->time_constant)))
319 secs = 1 << (SHIFT_PLL + 1 + ntpdata->time_constant);
320
321 freq_adj += (offset64 * secs) <<
322 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + ntpdata->time_constant));
323
324 freq_adj = min(freq_adj + ntpdata->time_freq, MAXFREQ_SCALED);
325
326 ntpdata->time_freq = max(freq_adj, -MAXFREQ_SCALED);
327
328 ntpdata->time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
329 }
330
__ntp_clear(struct ntp_data * ntpdata)331 static void __ntp_clear(struct ntp_data *ntpdata)
332 {
333 /* Stop active adjtime() */
334 ntpdata->time_adjust = 0;
335 ntpdata->time_status |= STA_UNSYNC;
336 ntpdata->time_maxerror = NTP_PHASE_LIMIT;
337 ntpdata->time_esterror = NTP_PHASE_LIMIT;
338
339 ntp_update_frequency(ntpdata);
340
341 ntpdata->tick_length = ntpdata->tick_length_base;
342 ntpdata->time_offset = 0;
343
344 ntpdata->ntp_next_leap_sec = TIME64_MAX;
345 /* Clear PPS state variables */
346 pps_clear(ntpdata);
347 }
348
349 /**
350 * ntp_clear - Clears the NTP state variables
351 */
ntp_clear(void)352 void ntp_clear(void)
353 {
354 __ntp_clear(&tk_ntp_data);
355 }
356
357
ntp_tick_length(void)358 u64 ntp_tick_length(void)
359 {
360 return tk_ntp_data.tick_length;
361 }
362
363 /**
364 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
365 *
366 * Provides the time of the next leapsecond against CLOCK_REALTIME in
367 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending.
368 */
ntp_get_next_leap(void)369 ktime_t ntp_get_next_leap(void)
370 {
371 struct ntp_data *ntpdata = &tk_ntp_data;
372 ktime_t ret;
373
374 if ((ntpdata->time_state == TIME_INS) && (ntpdata->time_status & STA_INS))
375 return ktime_set(ntpdata->ntp_next_leap_sec, 0);
376 ret = KTIME_MAX;
377 return ret;
378 }
379
380 /*
381 * This routine handles the overflow of the microsecond field
382 *
383 * The tricky bits of code to handle the accurate clock support
384 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
385 * They were originally developed for SUN and DEC kernels.
386 * All the kudos should go to Dave for this stuff.
387 *
388 * Also handles leap second processing, and returns leap offset
389 */
second_overflow(time64_t secs)390 int second_overflow(time64_t secs)
391 {
392 struct ntp_data *ntpdata = &tk_ntp_data;
393 s64 delta;
394 int leap = 0;
395 s32 rem;
396
397 /*
398 * Leap second processing. If in leap-insert state at the end of the
399 * day, the system clock is set back one second; if in leap-delete
400 * state, the system clock is set ahead one second.
401 */
402 switch (ntpdata->time_state) {
403 case TIME_OK:
404 if (ntpdata->time_status & STA_INS) {
405 ntpdata->time_state = TIME_INS;
406 div_s64_rem(secs, SECS_PER_DAY, &rem);
407 ntpdata->ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
408 } else if (ntpdata->time_status & STA_DEL) {
409 ntpdata->time_state = TIME_DEL;
410 div_s64_rem(secs + 1, SECS_PER_DAY, &rem);
411 ntpdata->ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
412 }
413 break;
414 case TIME_INS:
415 if (!(ntpdata->time_status & STA_INS)) {
416 ntpdata->ntp_next_leap_sec = TIME64_MAX;
417 ntpdata->time_state = TIME_OK;
418 } else if (secs == ntpdata->ntp_next_leap_sec) {
419 leap = -1;
420 ntpdata->time_state = TIME_OOP;
421 pr_notice("Clock: inserting leap second 23:59:60 UTC\n");
422 }
423 break;
424 case TIME_DEL:
425 if (!(ntpdata->time_status & STA_DEL)) {
426 ntpdata->ntp_next_leap_sec = TIME64_MAX;
427 ntpdata->time_state = TIME_OK;
428 } else if (secs == ntpdata->ntp_next_leap_sec) {
429 leap = 1;
430 ntpdata->ntp_next_leap_sec = TIME64_MAX;
431 ntpdata->time_state = TIME_WAIT;
432 pr_notice("Clock: deleting leap second 23:59:59 UTC\n");
433 }
434 break;
435 case TIME_OOP:
436 ntpdata->ntp_next_leap_sec = TIME64_MAX;
437 ntpdata->time_state = TIME_WAIT;
438 break;
439 case TIME_WAIT:
440 if (!(ntpdata->time_status & (STA_INS | STA_DEL)))
441 ntpdata->time_state = TIME_OK;
442 break;
443 }
444
445 /* Bump the maxerror field */
446 ntpdata->time_maxerror += MAXFREQ / NSEC_PER_USEC;
447 if (ntpdata->time_maxerror > NTP_PHASE_LIMIT) {
448 ntpdata->time_maxerror = NTP_PHASE_LIMIT;
449 ntpdata->time_status |= STA_UNSYNC;
450 }
451
452 /* Compute the phase adjustment for the next second */
453 ntpdata->tick_length = ntpdata->tick_length_base;
454
455 delta = ntp_offset_chunk(ntpdata, ntpdata->time_offset);
456 ntpdata->time_offset -= delta;
457 ntpdata->tick_length += delta;
458
459 /* Check PPS signal */
460 pps_dec_valid(ntpdata);
461
462 if (!ntpdata->time_adjust)
463 goto out;
464
465 if (ntpdata->time_adjust > MAX_TICKADJ) {
466 ntpdata->time_adjust -= MAX_TICKADJ;
467 ntpdata->tick_length += MAX_TICKADJ_SCALED;
468 goto out;
469 }
470
471 if (ntpdata->time_adjust < -MAX_TICKADJ) {
472 ntpdata->time_adjust += MAX_TICKADJ;
473 ntpdata->tick_length -= MAX_TICKADJ_SCALED;
474 goto out;
475 }
476
477 ntpdata->tick_length += (s64)(ntpdata->time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
478 << NTP_SCALE_SHIFT;
479 ntpdata->time_adjust = 0;
480
481 out:
482 return leap;
483 }
484
485 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
486 static void sync_hw_clock(struct work_struct *work);
487 static DECLARE_WORK(sync_work, sync_hw_clock);
488 static struct hrtimer sync_hrtimer;
489 #define SYNC_PERIOD_NS (11ULL * 60 * NSEC_PER_SEC)
490
sync_timer_callback(struct hrtimer * timer)491 static enum hrtimer_restart sync_timer_callback(struct hrtimer *timer)
492 {
493 queue_work(system_freezable_power_efficient_wq, &sync_work);
494
495 return HRTIMER_NORESTART;
496 }
497
sched_sync_hw_clock(unsigned long offset_nsec,bool retry)498 static void sched_sync_hw_clock(unsigned long offset_nsec, bool retry)
499 {
500 ktime_t exp = ktime_set(ktime_get_real_seconds(), 0);
501
502 if (retry)
503 exp = ktime_add_ns(exp, 2ULL * NSEC_PER_SEC - offset_nsec);
504 else
505 exp = ktime_add_ns(exp, SYNC_PERIOD_NS - offset_nsec);
506
507 hrtimer_start(&sync_hrtimer, exp, HRTIMER_MODE_ABS);
508 }
509
510 /*
511 * Check whether @now is correct versus the required time to update the RTC
512 * and calculate the value which needs to be written to the RTC so that the
513 * next seconds increment of the RTC after the write is aligned with the next
514 * seconds increment of clock REALTIME.
515 *
516 * tsched t1 write(t2.tv_sec - 1sec)) t2 RTC increments seconds
517 *
518 * t2.tv_nsec == 0
519 * tsched = t2 - set_offset_nsec
520 * newval = t2 - NSEC_PER_SEC
521 *
522 * ==> neval = tsched + set_offset_nsec - NSEC_PER_SEC
523 *
524 * As the execution of this code is not guaranteed to happen exactly at
525 * tsched this allows it to happen within a fuzzy region:
526 *
527 * abs(now - tsched) < FUZZ
528 *
529 * If @now is not inside the allowed window the function returns false.
530 */
rtc_tv_nsec_ok(unsigned long set_offset_nsec,struct timespec64 * to_set,const struct timespec64 * now)531 static inline bool rtc_tv_nsec_ok(unsigned long set_offset_nsec,
532 struct timespec64 *to_set,
533 const struct timespec64 *now)
534 {
535 /* Allowed error in tv_nsec, arbitrarily set to 5 jiffies in ns. */
536 const unsigned long TIME_SET_NSEC_FUZZ = TICK_NSEC * 5;
537 struct timespec64 delay = {.tv_sec = -1,
538 .tv_nsec = set_offset_nsec};
539
540 *to_set = timespec64_add(*now, delay);
541
542 if (to_set->tv_nsec < TIME_SET_NSEC_FUZZ) {
543 to_set->tv_nsec = 0;
544 return true;
545 }
546
547 if (to_set->tv_nsec > NSEC_PER_SEC - TIME_SET_NSEC_FUZZ) {
548 to_set->tv_sec++;
549 to_set->tv_nsec = 0;
550 return true;
551 }
552 return false;
553 }
554
555 #ifdef CONFIG_GENERIC_CMOS_UPDATE
update_persistent_clock64(struct timespec64 now64)556 int __weak update_persistent_clock64(struct timespec64 now64)
557 {
558 return -ENODEV;
559 }
560 #else
update_persistent_clock64(struct timespec64 now64)561 static inline int update_persistent_clock64(struct timespec64 now64)
562 {
563 return -ENODEV;
564 }
565 #endif
566
567 #ifdef CONFIG_RTC_SYSTOHC
568 /* Save NTP synchronized time to the RTC */
update_rtc(struct timespec64 * to_set,unsigned long * offset_nsec)569 static int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
570 {
571 struct rtc_device *rtc;
572 struct rtc_time tm;
573 int err = -ENODEV;
574
575 rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
576 if (!rtc)
577 return -ENODEV;
578
579 if (!rtc->ops || !rtc->ops->set_time)
580 goto out_close;
581
582 /* First call might not have the correct offset */
583 if (*offset_nsec == rtc->set_offset_nsec) {
584 rtc_time64_to_tm(to_set->tv_sec, &tm);
585 err = rtc_set_time(rtc, &tm);
586 } else {
587 /* Store the update offset and let the caller try again */
588 *offset_nsec = rtc->set_offset_nsec;
589 err = -EAGAIN;
590 }
591 out_close:
592 rtc_class_close(rtc);
593 return err;
594 }
595 #else
update_rtc(struct timespec64 * to_set,unsigned long * offset_nsec)596 static inline int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
597 {
598 return -ENODEV;
599 }
600 #endif
601
602 /**
603 * ntp_synced - Tells whether the NTP status is not UNSYNC
604 * Returns: true if not UNSYNC, false otherwise
605 */
ntp_synced(void)606 static inline bool ntp_synced(void)
607 {
608 return !(tk_ntp_data.time_status & STA_UNSYNC);
609 }
610
611 /*
612 * If we have an externally synchronized Linux clock, then update RTC clock
613 * accordingly every ~11 minutes. Generally RTCs can only store second
614 * precision, but many RTCs will adjust the phase of their second tick to
615 * match the moment of update. This infrastructure arranges to call to the RTC
616 * set at the correct moment to phase synchronize the RTC second tick over
617 * with the kernel clock.
618 */
sync_hw_clock(struct work_struct * work)619 static void sync_hw_clock(struct work_struct *work)
620 {
621 /*
622 * The default synchronization offset is 500ms for the deprecated
623 * update_persistent_clock64() under the assumption that it uses
624 * the infamous CMOS clock (MC146818).
625 */
626 static unsigned long offset_nsec = NSEC_PER_SEC / 2;
627 struct timespec64 now, to_set;
628 int res = -EAGAIN;
629
630 /*
631 * Don't update if STA_UNSYNC is set and if ntp_notify_cmos_timer()
632 * managed to schedule the work between the timer firing and the
633 * work being able to rearm the timer. Wait for the timer to expire.
634 */
635 if (!ntp_synced() || hrtimer_is_queued(&sync_hrtimer))
636 return;
637
638 ktime_get_real_ts64(&now);
639 /* If @now is not in the allowed window, try again */
640 if (!rtc_tv_nsec_ok(offset_nsec, &to_set, &now))
641 goto rearm;
642
643 /* Take timezone adjusted RTCs into account */
644 if (persistent_clock_is_local)
645 to_set.tv_sec -= (sys_tz.tz_minuteswest * 60);
646
647 /* Try the legacy RTC first. */
648 res = update_persistent_clock64(to_set);
649 if (res != -ENODEV)
650 goto rearm;
651
652 /* Try the RTC class */
653 res = update_rtc(&to_set, &offset_nsec);
654 if (res == -ENODEV)
655 return;
656 rearm:
657 sched_sync_hw_clock(offset_nsec, res != 0);
658 }
659
ntp_notify_cmos_timer(bool offset_set)660 void ntp_notify_cmos_timer(bool offset_set)
661 {
662 /*
663 * If the time jumped (using ADJ_SETOFFSET) cancels sync timer,
664 * which may have been running if the time was synchronized
665 * prior to the ADJ_SETOFFSET call.
666 */
667 if (offset_set)
668 hrtimer_cancel(&sync_hrtimer);
669
670 /*
671 * When the work is currently executed but has not yet the timer
672 * rearmed this queues the work immediately again. No big issue,
673 * just a pointless work scheduled.
674 */
675 if (ntp_synced() && !hrtimer_is_queued(&sync_hrtimer))
676 queue_work(system_freezable_power_efficient_wq, &sync_work);
677 }
678
ntp_init_cmos_sync(void)679 static void __init ntp_init_cmos_sync(void)
680 {
681 hrtimer_init(&sync_hrtimer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
682 sync_hrtimer.function = sync_timer_callback;
683 }
684 #else /* CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
ntp_init_cmos_sync(void)685 static inline void __init ntp_init_cmos_sync(void) { }
686 #endif /* !CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
687
688 /*
689 * Propagate a new txc->status value into the NTP state:
690 */
process_adj_status(struct ntp_data * ntpdata,const struct __kernel_timex * txc)691 static inline void process_adj_status(struct ntp_data *ntpdata, const struct __kernel_timex *txc)
692 {
693 if ((ntpdata->time_status & STA_PLL) && !(txc->status & STA_PLL)) {
694 ntpdata->time_state = TIME_OK;
695 ntpdata->time_status = STA_UNSYNC;
696 ntpdata->ntp_next_leap_sec = TIME64_MAX;
697 /* Restart PPS frequency calibration */
698 pps_reset_freq_interval(ntpdata);
699 }
700
701 /*
702 * If we turn on PLL adjustments then reset the
703 * reference time to current time.
704 */
705 if (!(ntpdata->time_status & STA_PLL) && (txc->status & STA_PLL))
706 ntpdata->time_reftime = __ktime_get_real_seconds();
707
708 /* only set allowed bits */
709 ntpdata->time_status &= STA_RONLY;
710 ntpdata->time_status |= txc->status & ~STA_RONLY;
711 }
712
process_adjtimex_modes(struct ntp_data * ntpdata,const struct __kernel_timex * txc,s32 * time_tai)713 static inline void process_adjtimex_modes(struct ntp_data *ntpdata, const struct __kernel_timex *txc,
714 s32 *time_tai)
715 {
716 if (txc->modes & ADJ_STATUS)
717 process_adj_status(ntpdata, txc);
718
719 if (txc->modes & ADJ_NANO)
720 ntpdata->time_status |= STA_NANO;
721
722 if (txc->modes & ADJ_MICRO)
723 ntpdata->time_status &= ~STA_NANO;
724
725 if (txc->modes & ADJ_FREQUENCY) {
726 ntpdata->time_freq = txc->freq * PPM_SCALE;
727 ntpdata->time_freq = min(ntpdata->time_freq, MAXFREQ_SCALED);
728 ntpdata->time_freq = max(ntpdata->time_freq, -MAXFREQ_SCALED);
729 /* Update pps_freq */
730 pps_set_freq(ntpdata);
731 }
732
733 if (txc->modes & ADJ_MAXERROR)
734 ntpdata->time_maxerror = clamp(txc->maxerror, 0, NTP_PHASE_LIMIT);
735
736 if (txc->modes & ADJ_ESTERROR)
737 ntpdata->time_esterror = clamp(txc->esterror, 0, NTP_PHASE_LIMIT);
738
739 if (txc->modes & ADJ_TIMECONST) {
740 ntpdata->time_constant = clamp(txc->constant, 0, MAXTC);
741 if (!(ntpdata->time_status & STA_NANO))
742 ntpdata->time_constant += 4;
743 ntpdata->time_constant = clamp(ntpdata->time_constant, 0, MAXTC);
744 }
745
746 if (txc->modes & ADJ_TAI && txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET)
747 *time_tai = txc->constant;
748
749 if (txc->modes & ADJ_OFFSET)
750 ntp_update_offset(ntpdata, txc->offset);
751
752 if (txc->modes & ADJ_TICK)
753 ntpdata->tick_usec = txc->tick;
754
755 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
756 ntp_update_frequency(ntpdata);
757 }
758
759 /*
760 * adjtimex() mainly allows reading (and writing, if superuser) of
761 * kernel time-keeping variables. used by xntpd.
762 */
__do_adjtimex(struct __kernel_timex * txc,const struct timespec64 * ts,s32 * time_tai,struct audit_ntp_data * ad)763 int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts,
764 s32 *time_tai, struct audit_ntp_data *ad)
765 {
766 struct ntp_data *ntpdata = &tk_ntp_data;
767 int result;
768
769 if (txc->modes & ADJ_ADJTIME) {
770 long save_adjust = ntpdata->time_adjust;
771
772 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
773 /* adjtime() is independent from ntp_adjtime() */
774 ntpdata->time_adjust = txc->offset;
775 ntp_update_frequency(ntpdata);
776
777 audit_ntp_set_old(ad, AUDIT_NTP_ADJUST, save_adjust);
778 audit_ntp_set_new(ad, AUDIT_NTP_ADJUST, ntpdata->time_adjust);
779 }
780 txc->offset = save_adjust;
781 } else {
782 /* If there are input parameters, then process them: */
783 if (txc->modes) {
784 audit_ntp_set_old(ad, AUDIT_NTP_OFFSET, ntpdata->time_offset);
785 audit_ntp_set_old(ad, AUDIT_NTP_FREQ, ntpdata->time_freq);
786 audit_ntp_set_old(ad, AUDIT_NTP_STATUS, ntpdata->time_status);
787 audit_ntp_set_old(ad, AUDIT_NTP_TAI, *time_tai);
788 audit_ntp_set_old(ad, AUDIT_NTP_TICK, ntpdata->tick_usec);
789
790 process_adjtimex_modes(ntpdata, txc, time_tai);
791
792 audit_ntp_set_new(ad, AUDIT_NTP_OFFSET, ntpdata->time_offset);
793 audit_ntp_set_new(ad, AUDIT_NTP_FREQ, ntpdata->time_freq);
794 audit_ntp_set_new(ad, AUDIT_NTP_STATUS, ntpdata->time_status);
795 audit_ntp_set_new(ad, AUDIT_NTP_TAI, *time_tai);
796 audit_ntp_set_new(ad, AUDIT_NTP_TICK, ntpdata->tick_usec);
797 }
798
799 txc->offset = shift_right(ntpdata->time_offset * NTP_INTERVAL_FREQ, NTP_SCALE_SHIFT);
800 if (!(ntpdata->time_status & STA_NANO))
801 txc->offset = div_s64(txc->offset, NSEC_PER_USEC);
802 }
803
804 result = ntpdata->time_state;
805 if (is_error_status(ntpdata->time_status))
806 result = TIME_ERROR;
807
808 txc->freq = shift_right((ntpdata->time_freq >> PPM_SCALE_INV_SHIFT) *
809 PPM_SCALE_INV, NTP_SCALE_SHIFT);
810 txc->maxerror = ntpdata->time_maxerror;
811 txc->esterror = ntpdata->time_esterror;
812 txc->status = ntpdata->time_status;
813 txc->constant = ntpdata->time_constant;
814 txc->precision = 1;
815 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
816 txc->tick = ntpdata->tick_usec;
817 txc->tai = *time_tai;
818
819 /* Fill PPS status fields */
820 pps_fill_timex(ntpdata, txc);
821
822 txc->time.tv_sec = ts->tv_sec;
823 txc->time.tv_usec = ts->tv_nsec;
824 if (!(ntpdata->time_status & STA_NANO))
825 txc->time.tv_usec = ts->tv_nsec / NSEC_PER_USEC;
826
827 /* Handle leapsec adjustments */
828 if (unlikely(ts->tv_sec >= ntpdata->ntp_next_leap_sec)) {
829 if ((ntpdata->time_state == TIME_INS) && (ntpdata->time_status & STA_INS)) {
830 result = TIME_OOP;
831 txc->tai++;
832 txc->time.tv_sec--;
833 }
834 if ((ntpdata->time_state == TIME_DEL) && (ntpdata->time_status & STA_DEL)) {
835 result = TIME_WAIT;
836 txc->tai--;
837 txc->time.tv_sec++;
838 }
839 if ((ntpdata->time_state == TIME_OOP) && (ts->tv_sec == ntpdata->ntp_next_leap_sec))
840 result = TIME_WAIT;
841 }
842
843 return result;
844 }
845
846 #ifdef CONFIG_NTP_PPS
847
848 /*
849 * struct pps_normtime is basically a 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 */
854 struct pps_normtime {
855 s64 sec; /* seconds */
856 long nsec; /* nanoseconds */
857 };
858
859 /*
860 * Normalize the timestamp so that nsec is in the
861 * [ -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval
862 */
pps_normalize_ts(struct timespec64 ts)863 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
864 {
865 struct pps_normtime norm = {
866 .sec = ts.tv_sec,
867 .nsec = ts.tv_nsec
868 };
869
870 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
871 norm.nsec -= NSEC_PER_SEC;
872 norm.sec++;
873 }
874
875 return norm;
876 }
877
878 /* Get current phase correction and jitter */
pps_phase_filter_get(struct ntp_data * ntpdata,long * jitter)879 static inline long pps_phase_filter_get(struct ntp_data *ntpdata, long *jitter)
880 {
881 *jitter = ntpdata->pps_tf[0] - ntpdata->pps_tf[1];
882 if (*jitter < 0)
883 *jitter = -*jitter;
884
885 /* TODO: test various filters */
886 return ntpdata->pps_tf[0];
887 }
888
889 /* Add the sample to the phase filter */
pps_phase_filter_add(struct ntp_data * ntpdata,long err)890 static inline void pps_phase_filter_add(struct ntp_data *ntpdata, long err)
891 {
892 ntpdata->pps_tf[2] = ntpdata->pps_tf[1];
893 ntpdata->pps_tf[1] = ntpdata->pps_tf[0];
894 ntpdata->pps_tf[0] = err;
895 }
896
897 /*
898 * Decrease frequency calibration interval length. It is halved after four
899 * consecutive unstable intervals.
900 */
pps_dec_freq_interval(struct ntp_data * ntpdata)901 static inline void pps_dec_freq_interval(struct ntp_data *ntpdata)
902 {
903 if (--ntpdata->pps_intcnt <= -PPS_INTCOUNT) {
904 ntpdata->pps_intcnt = -PPS_INTCOUNT;
905 if (ntpdata->pps_shift > PPS_INTMIN) {
906 ntpdata->pps_shift--;
907 ntpdata->pps_intcnt = 0;
908 }
909 }
910 }
911
912 /*
913 * Increase frequency calibration interval length. It is doubled after
914 * four consecutive stable intervals.
915 */
pps_inc_freq_interval(struct ntp_data * ntpdata)916 static inline void pps_inc_freq_interval(struct ntp_data *ntpdata)
917 {
918 if (++ntpdata->pps_intcnt >= PPS_INTCOUNT) {
919 ntpdata->pps_intcnt = PPS_INTCOUNT;
920 if (ntpdata->pps_shift < PPS_INTMAX) {
921 ntpdata->pps_shift++;
922 ntpdata->pps_intcnt = 0;
923 }
924 }
925 }
926
927 /*
928 * Update clock frequency based on MONOTONIC_RAW clock PPS signal
929 * timestamps
930 *
931 * At the end of the calibration interval the difference between the
932 * first and last MONOTONIC_RAW clock timestamps divided by the length
933 * of the interval becomes the frequency update. If the interval was
934 * too long, the data are discarded.
935 * Returns the difference between old and new frequency values.
936 */
hardpps_update_freq(struct ntp_data * ntpdata,struct pps_normtime freq_norm)937 static long hardpps_update_freq(struct ntp_data *ntpdata, struct pps_normtime freq_norm)
938 {
939 long delta, delta_mod;
940 s64 ftemp;
941
942 /* Check if the frequency interval was too long */
943 if (freq_norm.sec > (2 << ntpdata->pps_shift)) {
944 ntpdata->time_status |= STA_PPSERROR;
945 ntpdata->pps_errcnt++;
946 pps_dec_freq_interval(ntpdata);
947 printk_deferred(KERN_ERR "hardpps: PPSERROR: interval too long - %lld s\n",
948 freq_norm.sec);
949 return 0;
950 }
951
952 /*
953 * Here the raw frequency offset and wander (stability) is
954 * calculated. If the wander is less than the wander threshold the
955 * interval is increased; otherwise it is decreased.
956 */
957 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
958 freq_norm.sec);
959 delta = shift_right(ftemp - ntpdata->pps_freq, NTP_SCALE_SHIFT);
960 ntpdata->pps_freq = ftemp;
961 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
962 printk_deferred(KERN_WARNING "hardpps: PPSWANDER: change=%ld\n", delta);
963 ntpdata->time_status |= STA_PPSWANDER;
964 ntpdata->pps_stbcnt++;
965 pps_dec_freq_interval(ntpdata);
966 } else {
967 /* Good sample */
968 pps_inc_freq_interval(ntpdata);
969 }
970
971 /*
972 * The stability metric is calculated as the average of recent
973 * frequency changes, but is used only for performance monitoring
974 */
975 delta_mod = delta;
976 if (delta_mod < 0)
977 delta_mod = -delta_mod;
978 ntpdata->pps_stabil += (div_s64(((s64)delta_mod) << (NTP_SCALE_SHIFT - SHIFT_USEC),
979 NSEC_PER_USEC) - ntpdata->pps_stabil) >> PPS_INTMIN;
980
981 /* If enabled, the system clock frequency is updated */
982 if ((ntpdata->time_status & STA_PPSFREQ) && !(ntpdata->time_status & STA_FREQHOLD)) {
983 ntpdata->time_freq = ntpdata->pps_freq;
984 ntp_update_frequency(ntpdata);
985 }
986
987 return delta;
988 }
989
990 /* Correct REALTIME clock phase error against PPS signal */
hardpps_update_phase(struct ntp_data * ntpdata,long error)991 static void hardpps_update_phase(struct ntp_data *ntpdata, long error)
992 {
993 long correction = -error;
994 long jitter;
995
996 /* Add the sample to the median filter */
997 pps_phase_filter_add(ntpdata, correction);
998 correction = pps_phase_filter_get(ntpdata, &jitter);
999
1000 /*
1001 * Nominal jitter is due to PPS signal noise. If it exceeds the
1002 * threshold, the sample is discarded; otherwise, if so enabled,
1003 * the time offset is updated.
1004 */
1005 if (jitter > (ntpdata->pps_jitter << PPS_POPCORN)) {
1006 printk_deferred(KERN_WARNING "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
1007 jitter, (ntpdata->pps_jitter << PPS_POPCORN));
1008 ntpdata->time_status |= STA_PPSJITTER;
1009 ntpdata->pps_jitcnt++;
1010 } else if (ntpdata->time_status & STA_PPSTIME) {
1011 /* Correct the time using the phase offset */
1012 ntpdata->time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
1013 NTP_INTERVAL_FREQ);
1014 /* Cancel running adjtime() */
1015 ntpdata->time_adjust = 0;
1016 }
1017 /* Update jitter */
1018 ntpdata->pps_jitter += (jitter - ntpdata->pps_jitter) >> PPS_INTMIN;
1019 }
1020
1021 /*
1022 * __hardpps() - discipline CPU clock oscillator to external PPS signal
1023 *
1024 * This routine is called at each PPS signal arrival in order to
1025 * discipline the CPU clock oscillator to the PPS signal. It takes two
1026 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
1027 * is used to correct clock phase error and the latter is used to
1028 * correct the frequency.
1029 *
1030 * This code is based on David Mills's reference nanokernel
1031 * implementation. It was mostly rewritten but keeps the same idea.
1032 */
__hardpps(const struct timespec64 * phase_ts,const struct timespec64 * raw_ts)1033 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
1034 {
1035 struct pps_normtime pts_norm, freq_norm;
1036 struct ntp_data *ntpdata = &tk_ntp_data;
1037
1038 pts_norm = pps_normalize_ts(*phase_ts);
1039
1040 /* Clear the error bits, they will be set again if needed */
1041 ntpdata->time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
1042
1043 /* indicate signal presence */
1044 ntpdata->time_status |= STA_PPSSIGNAL;
1045 ntpdata->pps_valid = PPS_VALID;
1046
1047 /*
1048 * When called for the first time, just start the frequency
1049 * interval
1050 */
1051 if (unlikely(ntpdata->pps_fbase.tv_sec == 0)) {
1052 ntpdata->pps_fbase = *raw_ts;
1053 return;
1054 }
1055
1056 /* Ok, now we have a base for frequency calculation */
1057 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, ntpdata->pps_fbase));
1058
1059 /*
1060 * Check that the signal is in the range
1061 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it
1062 */
1063 if ((freq_norm.sec == 0) || (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
1064 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
1065 ntpdata->time_status |= STA_PPSJITTER;
1066 /* Restart the frequency calibration interval */
1067 ntpdata->pps_fbase = *raw_ts;
1068 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
1069 return;
1070 }
1071
1072 /* Signal is ok. Check if the current frequency interval is finished */
1073 if (freq_norm.sec >= (1 << ntpdata->pps_shift)) {
1074 ntpdata->pps_calcnt++;
1075 /* Restart the frequency calibration interval */
1076 ntpdata->pps_fbase = *raw_ts;
1077 hardpps_update_freq(ntpdata, freq_norm);
1078 }
1079
1080 hardpps_update_phase(ntpdata, pts_norm.nsec);
1081
1082 }
1083 #endif /* CONFIG_NTP_PPS */
1084
ntp_tick_adj_setup(char * str)1085 static int __init ntp_tick_adj_setup(char *str)
1086 {
1087 int rc = kstrtos64(str, 0, &tk_ntp_data.ntp_tick_adj);
1088 if (rc)
1089 return rc;
1090
1091 tk_ntp_data.ntp_tick_adj <<= NTP_SCALE_SHIFT;
1092 return 1;
1093 }
1094
1095 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
1096
ntp_init(void)1097 void __init ntp_init(void)
1098 {
1099 ntp_clear();
1100 ntp_init_cmos_sync();
1101 }
1102