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TOMOYO Linux Cross Reference
Linux/kernel/time/timekeeping.c

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  1 /*
  2  *  linux/kernel/time/timekeeping.c
  3  *
  4  *  Kernel timekeeping code and accessor functions
  5  *
  6  *  This code was moved from linux/kernel/timer.c.
  7  *  Please see that file for copyright and history logs.
  8  *
  9  */
 10 
 11 #include <linux/timekeeper_internal.h>
 12 #include <linux/module.h>
 13 #include <linux/interrupt.h>
 14 #include <linux/percpu.h>
 15 #include <linux/init.h>
 16 #include <linux/mm.h>
 17 #include <linux/nmi.h>
 18 #include <linux/sched.h>
 19 #include <linux/sched/loadavg.h>
 20 #include <linux/syscore_ops.h>
 21 #include <linux/clocksource.h>
 22 #include <linux/jiffies.h>
 23 #include <linux/time.h>
 24 #include <linux/tick.h>
 25 #include <linux/stop_machine.h>
 26 #include <linux/pvclock_gtod.h>
 27 #include <linux/compiler.h>
 28 #include <linux/ccsecurity.h>
 29 
 30 #include "tick-internal.h"
 31 #include "ntp_internal.h"
 32 #include "timekeeping_internal.h"
 33 
 34 #define TK_CLEAR_NTP            (1 << 0)
 35 #define TK_MIRROR               (1 << 1)
 36 #define TK_CLOCK_WAS_SET        (1 << 2)
 37 
 38 /*
 39  * The most important data for readout fits into a single 64 byte
 40  * cache line.
 41  */
 42 static struct {
 43         seqcount_t              seq;
 44         struct timekeeper       timekeeper;
 45 } tk_core ____cacheline_aligned;
 46 
 47 static DEFINE_RAW_SPINLOCK(timekeeper_lock);
 48 static struct timekeeper shadow_timekeeper;
 49 
 50 /**
 51  * struct tk_fast - NMI safe timekeeper
 52  * @seq:        Sequence counter for protecting updates. The lowest bit
 53  *              is the index for the tk_read_base array
 54  * @base:       tk_read_base array. Access is indexed by the lowest bit of
 55  *              @seq.
 56  *
 57  * See @update_fast_timekeeper() below.
 58  */
 59 struct tk_fast {
 60         seqcount_t              seq;
 61         struct tk_read_base     base[2];
 62 };
 63 
 64 /* Suspend-time cycles value for halted fast timekeeper. */
 65 static u64 cycles_at_suspend;
 66 
 67 static u64 dummy_clock_read(struct clocksource *cs)
 68 {
 69         return cycles_at_suspend;
 70 }
 71 
 72 static struct clocksource dummy_clock = {
 73         .read = dummy_clock_read,
 74 };
 75 
 76 static struct tk_fast tk_fast_mono ____cacheline_aligned = {
 77         .base[0] = { .clock = &dummy_clock, },
 78         .base[1] = { .clock = &dummy_clock, },
 79 };
 80 
 81 static struct tk_fast tk_fast_raw  ____cacheline_aligned = {
 82         .base[0] = { .clock = &dummy_clock, },
 83         .base[1] = { .clock = &dummy_clock, },
 84 };
 85 
 86 /* flag for if timekeeping is suspended */
 87 int __read_mostly timekeeping_suspended;
 88 
 89 static inline void tk_normalize_xtime(struct timekeeper *tk)
 90 {
 91         while (tk->tkr_mono.xtime_nsec >= ((u64)NSEC_PER_SEC << tk->tkr_mono.shift)) {
 92                 tk->tkr_mono.xtime_nsec -= (u64)NSEC_PER_SEC << tk->tkr_mono.shift;
 93                 tk->xtime_sec++;
 94         }
 95         while (tk->tkr_raw.xtime_nsec >= ((u64)NSEC_PER_SEC << tk->tkr_raw.shift)) {
 96                 tk->tkr_raw.xtime_nsec -= (u64)NSEC_PER_SEC << tk->tkr_raw.shift;
 97                 tk->raw_sec++;
 98         }
 99 }
100 
101 static inline struct timespec64 tk_xtime(struct timekeeper *tk)
102 {
103         struct timespec64 ts;
104 
105         ts.tv_sec = tk->xtime_sec;
106         ts.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
107         return ts;
108 }
109 
110 static void tk_set_xtime(struct timekeeper *tk, const struct timespec64 *ts)
111 {
112         tk->xtime_sec = ts->tv_sec;
113         tk->tkr_mono.xtime_nsec = (u64)ts->tv_nsec << tk->tkr_mono.shift;
114 }
115 
116 static void tk_xtime_add(struct timekeeper *tk, const struct timespec64 *ts)
117 {
118         tk->xtime_sec += ts->tv_sec;
119         tk->tkr_mono.xtime_nsec += (u64)ts->tv_nsec << tk->tkr_mono.shift;
120         tk_normalize_xtime(tk);
121 }
122 
123 static void tk_set_wall_to_mono(struct timekeeper *tk, struct timespec64 wtm)
124 {
125         struct timespec64 tmp;
126 
127         /*
128          * Verify consistency of: offset_real = -wall_to_monotonic
129          * before modifying anything
130          */
131         set_normalized_timespec64(&tmp, -tk->wall_to_monotonic.tv_sec,
132                                         -tk->wall_to_monotonic.tv_nsec);
133         WARN_ON_ONCE(tk->offs_real != timespec64_to_ktime(tmp));
134         tk->wall_to_monotonic = wtm;
135         set_normalized_timespec64(&tmp, -wtm.tv_sec, -wtm.tv_nsec);
136         tk->offs_real = timespec64_to_ktime(tmp);
137         tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tk->tai_offset, 0));
138 }
139 
140 static inline void tk_update_sleep_time(struct timekeeper *tk, ktime_t delta)
141 {
142         tk->offs_boot = ktime_add(tk->offs_boot, delta);
143 }
144 
145 /*
146  * tk_clock_read - atomic clocksource read() helper
147  *
148  * This helper is necessary to use in the read paths because, while the
149  * seqlock ensures we don't return a bad value while structures are updated,
150  * it doesn't protect from potential crashes. There is the possibility that
151  * the tkr's clocksource may change between the read reference, and the
152  * clock reference passed to the read function.  This can cause crashes if
153  * the wrong clocksource is passed to the wrong read function.
154  * This isn't necessary to use when holding the timekeeper_lock or doing
155  * a read of the fast-timekeeper tkrs (which is protected by its own locking
156  * and update logic).
157  */
158 static inline u64 tk_clock_read(struct tk_read_base *tkr)
159 {
160         struct clocksource *clock = READ_ONCE(tkr->clock);
161 
162         return clock->read(clock);
163 }
164 
165 #ifdef CONFIG_DEBUG_TIMEKEEPING
166 #define WARNING_FREQ (HZ*300) /* 5 minute rate-limiting */
167 
168 static void timekeeping_check_update(struct timekeeper *tk, u64 offset)
169 {
170 
171         u64 max_cycles = tk->tkr_mono.clock->max_cycles;
172         const char *name = tk->tkr_mono.clock->name;
173 
174         if (offset > max_cycles) {
175                 printk_deferred("WARNING: timekeeping: Cycle offset (%lld) is larger than allowed by the '%s' clock's max_cycles value (%lld): time overflow danger\n",
176                                 offset, name, max_cycles);
177                 printk_deferred("         timekeeping: Your kernel is sick, but tries to cope by capping time updates\n");
178         } else {
179                 if (offset > (max_cycles >> 1)) {
180                         printk_deferred("INFO: timekeeping: Cycle offset (%lld) is larger than the '%s' clock's 50%% safety margin (%lld)\n",
181                                         offset, name, max_cycles >> 1);
182                         printk_deferred("      timekeeping: Your kernel is still fine, but is feeling a bit nervous\n");
183                 }
184         }
185 
186         if (tk->underflow_seen) {
187                 if (jiffies - tk->last_warning > WARNING_FREQ) {
188                         printk_deferred("WARNING: Underflow in clocksource '%s' observed, time update ignored.\n", name);
189                         printk_deferred("         Please report this, consider using a different clocksource, if possible.\n");
190                         printk_deferred("         Your kernel is probably still fine.\n");
191                         tk->last_warning = jiffies;
192                 }
193                 tk->underflow_seen = 0;
194         }
195 
196         if (tk->overflow_seen) {
197                 if (jiffies - tk->last_warning > WARNING_FREQ) {
198                         printk_deferred("WARNING: Overflow in clocksource '%s' observed, time update capped.\n", name);
199                         printk_deferred("         Please report this, consider using a different clocksource, if possible.\n");
200                         printk_deferred("         Your kernel is probably still fine.\n");
201                         tk->last_warning = jiffies;
202                 }
203                 tk->overflow_seen = 0;
204         }
205 }
206 
207 static inline u64 timekeeping_get_delta(struct tk_read_base *tkr)
208 {
209         struct timekeeper *tk = &tk_core.timekeeper;
210         u64 now, last, mask, max, delta;
211         unsigned int seq;
212 
213         /*
214          * Since we're called holding a seqlock, the data may shift
215          * under us while we're doing the calculation. This can cause
216          * false positives, since we'd note a problem but throw the
217          * results away. So nest another seqlock here to atomically
218          * grab the points we are checking with.
219          */
220         do {
221                 seq = read_seqcount_begin(&tk_core.seq);
222                 now = tk_clock_read(tkr);
223                 last = tkr->cycle_last;
224                 mask = tkr->mask;
225                 max = tkr->clock->max_cycles;
226         } while (read_seqcount_retry(&tk_core.seq, seq));
227 
228         delta = clocksource_delta(now, last, mask);
229 
230         /*
231          * Try to catch underflows by checking if we are seeing small
232          * mask-relative negative values.
233          */
234         if (unlikely((~delta & mask) < (mask >> 3))) {
235                 tk->underflow_seen = 1;
236                 delta = 0;
237         }
238 
239         /* Cap delta value to the max_cycles values to avoid mult overflows */
240         if (unlikely(delta > max)) {
241                 tk->overflow_seen = 1;
242                 delta = tkr->clock->max_cycles;
243         }
244 
245         return delta;
246 }
247 #else
248 static inline void timekeeping_check_update(struct timekeeper *tk, u64 offset)
249 {
250 }
251 static inline u64 timekeeping_get_delta(struct tk_read_base *tkr)
252 {
253         u64 cycle_now, delta;
254 
255         /* read clocksource */
256         cycle_now = tk_clock_read(tkr);
257 
258         /* calculate the delta since the last update_wall_time */
259         delta = clocksource_delta(cycle_now, tkr->cycle_last, tkr->mask);
260 
261         return delta;
262 }
263 #endif
264 
265 /**
266  * tk_setup_internals - Set up internals to use clocksource clock.
267  *
268  * @tk:         The target timekeeper to setup.
269  * @clock:              Pointer to clocksource.
270  *
271  * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
272  * pair and interval request.
273  *
274  * Unless you're the timekeeping code, you should not be using this!
275  */
276 static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
277 {
278         u64 interval;
279         u64 tmp, ntpinterval;
280         struct clocksource *old_clock;
281 
282         ++tk->cs_was_changed_seq;
283         old_clock = tk->tkr_mono.clock;
284         tk->tkr_mono.clock = clock;
285         tk->tkr_mono.mask = clock->mask;
286         tk->tkr_mono.cycle_last = tk_clock_read(&tk->tkr_mono);
287 
288         tk->tkr_raw.clock = clock;
289         tk->tkr_raw.mask = clock->mask;
290         tk->tkr_raw.cycle_last = tk->tkr_mono.cycle_last;
291 
292         /* Do the ns -> cycle conversion first, using original mult */
293         tmp = NTP_INTERVAL_LENGTH;
294         tmp <<= clock->shift;
295         ntpinterval = tmp;
296         tmp += clock->mult/2;
297         do_div(tmp, clock->mult);
298         if (tmp == 0)
299                 tmp = 1;
300 
301         interval = (u64) tmp;
302         tk->cycle_interval = interval;
303 
304         /* Go back from cycles -> shifted ns */
305         tk->xtime_interval = interval * clock->mult;
306         tk->xtime_remainder = ntpinterval - tk->xtime_interval;
307         tk->raw_interval = interval * clock->mult;
308 
309          /* if changing clocks, convert xtime_nsec shift units */
310         if (old_clock) {
311                 int shift_change = clock->shift - old_clock->shift;
312                 if (shift_change < 0) {
313                         tk->tkr_mono.xtime_nsec >>= -shift_change;
314                         tk->tkr_raw.xtime_nsec >>= -shift_change;
315                 } else {
316                         tk->tkr_mono.xtime_nsec <<= shift_change;
317                         tk->tkr_raw.xtime_nsec <<= shift_change;
318                 }
319         }
320 
321         tk->tkr_mono.shift = clock->shift;
322         tk->tkr_raw.shift = clock->shift;
323 
324         tk->ntp_error = 0;
325         tk->ntp_error_shift = NTP_SCALE_SHIFT - clock->shift;
326         tk->ntp_tick = ntpinterval << tk->ntp_error_shift;
327 
328         /*
329          * The timekeeper keeps its own mult values for the currently
330          * active clocksource. These value will be adjusted via NTP
331          * to counteract clock drifting.
332          */
333         tk->tkr_mono.mult = clock->mult;
334         tk->tkr_raw.mult = clock->mult;
335         tk->ntp_err_mult = 0;
336 }
337 
338 /* Timekeeper helper functions. */
339 
340 #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
341 static u32 default_arch_gettimeoffset(void) { return 0; }
342 u32 (*arch_gettimeoffset)(void) = default_arch_gettimeoffset;
343 #else
344 static inline u32 arch_gettimeoffset(void) { return 0; }
345 #endif
346 
347 static inline u64 timekeeping_delta_to_ns(struct tk_read_base *tkr, u64 delta)
348 {
349         u64 nsec;
350 
351         nsec = delta * tkr->mult + tkr->xtime_nsec;
352         nsec >>= tkr->shift;
353 
354         /* If arch requires, add in get_arch_timeoffset() */
355         return nsec + arch_gettimeoffset();
356 }
357 
358 static inline u64 timekeeping_get_ns(struct tk_read_base *tkr)
359 {
360         u64 delta;
361 
362         delta = timekeeping_get_delta(tkr);
363         return timekeeping_delta_to_ns(tkr, delta);
364 }
365 
366 static inline u64 timekeeping_cycles_to_ns(struct tk_read_base *tkr, u64 cycles)
367 {
368         u64 delta;
369 
370         /* calculate the delta since the last update_wall_time */
371         delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
372         return timekeeping_delta_to_ns(tkr, delta);
373 }
374 
375 /**
376  * update_fast_timekeeper - Update the fast and NMI safe monotonic timekeeper.
377  * @tkr: Timekeeping readout base from which we take the update
378  *
379  * We want to use this from any context including NMI and tracing /
380  * instrumenting the timekeeping code itself.
381  *
382  * Employ the latch technique; see @raw_write_seqcount_latch.
383  *
384  * So if a NMI hits the update of base[0] then it will use base[1]
385  * which is still consistent. In the worst case this can result is a
386  * slightly wrong timestamp (a few nanoseconds). See
387  * @ktime_get_mono_fast_ns.
388  */
389 static void update_fast_timekeeper(struct tk_read_base *tkr, struct tk_fast *tkf)
390 {
391         struct tk_read_base *base = tkf->base;
392 
393         /* Force readers off to base[1] */
394         raw_write_seqcount_latch(&tkf->seq);
395 
396         /* Update base[0] */
397         memcpy(base, tkr, sizeof(*base));
398 
399         /* Force readers back to base[0] */
400         raw_write_seqcount_latch(&tkf->seq);
401 
402         /* Update base[1] */
403         memcpy(base + 1, base, sizeof(*base));
404 }
405 
406 /**
407  * ktime_get_mono_fast_ns - Fast NMI safe access to clock monotonic
408  *
409  * This timestamp is not guaranteed to be monotonic across an update.
410  * The timestamp is calculated by:
411  *
412  *      now = base_mono + clock_delta * slope
413  *
414  * So if the update lowers the slope, readers who are forced to the
415  * not yet updated second array are still using the old steeper slope.
416  *
417  * tmono
418  * ^
419  * |    o  n
420  * |   o n
421  * |  u
422  * | o
423  * |o
424  * |12345678---> reader order
425  *
426  * o = old slope
427  * u = update
428  * n = new slope
429  *
430  * So reader 6 will observe time going backwards versus reader 5.
431  *
432  * While other CPUs are likely to be able observe that, the only way
433  * for a CPU local observation is when an NMI hits in the middle of
434  * the update. Timestamps taken from that NMI context might be ahead
435  * of the following timestamps. Callers need to be aware of that and
436  * deal with it.
437  */
438 static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
439 {
440         struct tk_read_base *tkr;
441         unsigned int seq;
442         u64 now;
443 
444         do {
445                 seq = raw_read_seqcount_latch(&tkf->seq);
446                 tkr = tkf->base + (seq & 0x01);
447                 now = ktime_to_ns(tkr->base);
448 
449                 now += timekeeping_delta_to_ns(tkr,
450                                 clocksource_delta(
451                                         tk_clock_read(tkr),
452                                         tkr->cycle_last,
453                                         tkr->mask));
454         } while (read_seqcount_retry(&tkf->seq, seq));
455 
456         return now;
457 }
458 
459 u64 ktime_get_mono_fast_ns(void)
460 {
461         return __ktime_get_fast_ns(&tk_fast_mono);
462 }
463 EXPORT_SYMBOL_GPL(ktime_get_mono_fast_ns);
464 
465 u64 ktime_get_raw_fast_ns(void)
466 {
467         return __ktime_get_fast_ns(&tk_fast_raw);
468 }
469 EXPORT_SYMBOL_GPL(ktime_get_raw_fast_ns);
470 
471 /**
472  * ktime_get_boot_fast_ns - NMI safe and fast access to boot clock.
473  *
474  * To keep it NMI safe since we're accessing from tracing, we're not using a
475  * separate timekeeper with updates to monotonic clock and boot offset
476  * protected with seqlocks. This has the following minor side effects:
477  *
478  * (1) Its possible that a timestamp be taken after the boot offset is updated
479  * but before the timekeeper is updated. If this happens, the new boot offset
480  * is added to the old timekeeping making the clock appear to update slightly
481  * earlier:
482  *    CPU 0                                        CPU 1
483  *    timekeeping_inject_sleeptime64()
484  *    __timekeeping_inject_sleeptime(tk, delta);
485  *                                                 timestamp();
486  *    timekeeping_update(tk, TK_CLEAR_NTP...);
487  *
488  * (2) On 32-bit systems, the 64-bit boot offset (tk->offs_boot) may be
489  * partially updated.  Since the tk->offs_boot update is a rare event, this
490  * should be a rare occurrence which postprocessing should be able to handle.
491  */
492 u64 notrace ktime_get_boot_fast_ns(void)
493 {
494         struct timekeeper *tk = &tk_core.timekeeper;
495 
496         return (ktime_get_mono_fast_ns() + ktime_to_ns(tk->offs_boot));
497 }
498 EXPORT_SYMBOL_GPL(ktime_get_boot_fast_ns);
499 
500 
501 /*
502  * See comment for __ktime_get_fast_ns() vs. timestamp ordering
503  */
504 static __always_inline u64 __ktime_get_real_fast_ns(struct tk_fast *tkf)
505 {
506         struct tk_read_base *tkr;
507         unsigned int seq;
508         u64 now;
509 
510         do {
511                 seq = raw_read_seqcount_latch(&tkf->seq);
512                 tkr = tkf->base + (seq & 0x01);
513                 now = ktime_to_ns(tkr->base_real);
514 
515                 now += timekeeping_delta_to_ns(tkr,
516                                 clocksource_delta(
517                                         tk_clock_read(tkr),
518                                         tkr->cycle_last,
519                                         tkr->mask));
520         } while (read_seqcount_retry(&tkf->seq, seq));
521 
522         return now;
523 }
524 
525 /**
526  * ktime_get_real_fast_ns: - NMI safe and fast access to clock realtime.
527  */
528 u64 ktime_get_real_fast_ns(void)
529 {
530         return __ktime_get_real_fast_ns(&tk_fast_mono);
531 }
532 EXPORT_SYMBOL_GPL(ktime_get_real_fast_ns);
533 
534 /**
535  * halt_fast_timekeeper - Prevent fast timekeeper from accessing clocksource.
536  * @tk: Timekeeper to snapshot.
537  *
538  * It generally is unsafe to access the clocksource after timekeeping has been
539  * suspended, so take a snapshot of the readout base of @tk and use it as the
540  * fast timekeeper's readout base while suspended.  It will return the same
541  * number of cycles every time until timekeeping is resumed at which time the
542  * proper readout base for the fast timekeeper will be restored automatically.
543  */
544 static void halt_fast_timekeeper(struct timekeeper *tk)
545 {
546         static struct tk_read_base tkr_dummy;
547         struct tk_read_base *tkr = &tk->tkr_mono;
548 
549         memcpy(&tkr_dummy, tkr, sizeof(tkr_dummy));
550         cycles_at_suspend = tk_clock_read(tkr);
551         tkr_dummy.clock = &dummy_clock;
552         tkr_dummy.base_real = tkr->base + tk->offs_real;
553         update_fast_timekeeper(&tkr_dummy, &tk_fast_mono);
554 
555         tkr = &tk->tkr_raw;
556         memcpy(&tkr_dummy, tkr, sizeof(tkr_dummy));
557         tkr_dummy.clock = &dummy_clock;
558         update_fast_timekeeper(&tkr_dummy, &tk_fast_raw);
559 }
560 
561 static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);
562 
563 static void update_pvclock_gtod(struct timekeeper *tk, bool was_set)
564 {
565         raw_notifier_call_chain(&pvclock_gtod_chain, was_set, tk);
566 }
567 
568 /**
569  * pvclock_gtod_register_notifier - register a pvclock timedata update listener
570  */
571 int pvclock_gtod_register_notifier(struct notifier_block *nb)
572 {
573         struct timekeeper *tk = &tk_core.timekeeper;
574         unsigned long flags;
575         int ret;
576 
577         raw_spin_lock_irqsave(&timekeeper_lock, flags);
578         ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);
579         update_pvclock_gtod(tk, true);
580         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
581 
582         return ret;
583 }
584 EXPORT_SYMBOL_GPL(pvclock_gtod_register_notifier);
585 
586 /**
587  * pvclock_gtod_unregister_notifier - unregister a pvclock
588  * timedata update listener
589  */
590 int pvclock_gtod_unregister_notifier(struct notifier_block *nb)
591 {
592         unsigned long flags;
593         int ret;
594 
595         raw_spin_lock_irqsave(&timekeeper_lock, flags);
596         ret = raw_notifier_chain_unregister(&pvclock_gtod_chain, nb);
597         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
598 
599         return ret;
600 }
601 EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);
602 
603 /*
604  * tk_update_leap_state - helper to update the next_leap_ktime
605  */
606 static inline void tk_update_leap_state(struct timekeeper *tk)
607 {
608         tk->next_leap_ktime = ntp_get_next_leap();
609         if (tk->next_leap_ktime != KTIME_MAX)
610                 /* Convert to monotonic time */
611                 tk->next_leap_ktime = ktime_sub(tk->next_leap_ktime, tk->offs_real);
612 }
613 
614 /*
615  * Update the ktime_t based scalar nsec members of the timekeeper
616  */
617 static inline void tk_update_ktime_data(struct timekeeper *tk)
618 {
619         u64 seconds;
620         u32 nsec;
621 
622         /*
623          * The xtime based monotonic readout is:
624          *      nsec = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec + now();
625          * The ktime based monotonic readout is:
626          *      nsec = base_mono + now();
627          * ==> base_mono = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec
628          */
629         seconds = (u64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec);
630         nsec = (u32) tk->wall_to_monotonic.tv_nsec;
631         tk->tkr_mono.base = ns_to_ktime(seconds * NSEC_PER_SEC + nsec);
632 
633         /*
634          * The sum of the nanoseconds portions of xtime and
635          * wall_to_monotonic can be greater/equal one second. Take
636          * this into account before updating tk->ktime_sec.
637          */
638         nsec += (u32)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
639         if (nsec >= NSEC_PER_SEC)
640                 seconds++;
641         tk->ktime_sec = seconds;
642 
643         /* Update the monotonic raw base */
644         tk->tkr_raw.base = ns_to_ktime(tk->raw_sec * NSEC_PER_SEC);
645 }
646 
647 /* must hold timekeeper_lock */
648 static void timekeeping_update(struct timekeeper *tk, unsigned int action)
649 {
650         if (action & TK_CLEAR_NTP) {
651                 tk->ntp_error = 0;
652                 ntp_clear();
653         }
654 
655         tk_update_leap_state(tk);
656         tk_update_ktime_data(tk);
657 
658         update_vsyscall(tk);
659         update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
660 
661         tk->tkr_mono.base_real = tk->tkr_mono.base + tk->offs_real;
662         update_fast_timekeeper(&tk->tkr_mono, &tk_fast_mono);
663         update_fast_timekeeper(&tk->tkr_raw,  &tk_fast_raw);
664 
665         if (action & TK_CLOCK_WAS_SET)
666                 tk->clock_was_set_seq++;
667         /*
668          * The mirroring of the data to the shadow-timekeeper needs
669          * to happen last here to ensure we don't over-write the
670          * timekeeper structure on the next update with stale data
671          */
672         if (action & TK_MIRROR)
673                 memcpy(&shadow_timekeeper, &tk_core.timekeeper,
674                        sizeof(tk_core.timekeeper));
675 }
676 
677 /**
678  * timekeeping_forward_now - update clock to the current time
679  *
680  * Forward the current clock to update its state since the last call to
681  * update_wall_time(). This is useful before significant clock changes,
682  * as it avoids having to deal with this time offset explicitly.
683  */
684 static void timekeeping_forward_now(struct timekeeper *tk)
685 {
686         u64 cycle_now, delta;
687 
688         cycle_now = tk_clock_read(&tk->tkr_mono);
689         delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
690         tk->tkr_mono.cycle_last = cycle_now;
691         tk->tkr_raw.cycle_last  = cycle_now;
692 
693         tk->tkr_mono.xtime_nsec += delta * tk->tkr_mono.mult;
694 
695         /* If arch requires, add in get_arch_timeoffset() */
696         tk->tkr_mono.xtime_nsec += (u64)arch_gettimeoffset() << tk->tkr_mono.shift;
697 
698 
699         tk->tkr_raw.xtime_nsec += delta * tk->tkr_raw.mult;
700 
701         /* If arch requires, add in get_arch_timeoffset() */
702         tk->tkr_raw.xtime_nsec += (u64)arch_gettimeoffset() << tk->tkr_raw.shift;
703 
704         tk_normalize_xtime(tk);
705 }
706 
707 /**
708  * __getnstimeofday64 - Returns the time of day in a timespec64.
709  * @ts:         pointer to the timespec to be set
710  *
711  * Updates the time of day in the timespec.
712  * Returns 0 on success, or -ve when suspended (timespec will be undefined).
713  */
714 int __getnstimeofday64(struct timespec64 *ts)
715 {
716         struct timekeeper *tk = &tk_core.timekeeper;
717         unsigned long seq;
718         u64 nsecs;
719 
720         do {
721                 seq = read_seqcount_begin(&tk_core.seq);
722 
723                 ts->tv_sec = tk->xtime_sec;
724                 nsecs = timekeeping_get_ns(&tk->tkr_mono);
725 
726         } while (read_seqcount_retry(&tk_core.seq, seq));
727 
728         ts->tv_nsec = 0;
729         timespec64_add_ns(ts, nsecs);
730 
731         /*
732          * Do not bail out early, in case there were callers still using
733          * the value, even in the face of the WARN_ON.
734          */
735         if (unlikely(timekeeping_suspended))
736                 return -EAGAIN;
737         return 0;
738 }
739 EXPORT_SYMBOL(__getnstimeofday64);
740 
741 /**
742  * getnstimeofday64 - Returns the time of day in a timespec64.
743  * @ts:         pointer to the timespec64 to be set
744  *
745  * Returns the time of day in a timespec64 (WARN if suspended).
746  */
747 void getnstimeofday64(struct timespec64 *ts)
748 {
749         WARN_ON(__getnstimeofday64(ts));
750 }
751 EXPORT_SYMBOL(getnstimeofday64);
752 
753 ktime_t ktime_get(void)
754 {
755         struct timekeeper *tk = &tk_core.timekeeper;
756         unsigned int seq;
757         ktime_t base;
758         u64 nsecs;
759 
760         WARN_ON(timekeeping_suspended);
761 
762         do {
763                 seq = read_seqcount_begin(&tk_core.seq);
764                 base = tk->tkr_mono.base;
765                 nsecs = timekeeping_get_ns(&tk->tkr_mono);
766 
767         } while (read_seqcount_retry(&tk_core.seq, seq));
768 
769         return ktime_add_ns(base, nsecs);
770 }
771 EXPORT_SYMBOL_GPL(ktime_get);
772 
773 u32 ktime_get_resolution_ns(void)
774 {
775         struct timekeeper *tk = &tk_core.timekeeper;
776         unsigned int seq;
777         u32 nsecs;
778 
779         WARN_ON(timekeeping_suspended);
780 
781         do {
782                 seq = read_seqcount_begin(&tk_core.seq);
783                 nsecs = tk->tkr_mono.mult >> tk->tkr_mono.shift;
784         } while (read_seqcount_retry(&tk_core.seq, seq));
785 
786         return nsecs;
787 }
788 EXPORT_SYMBOL_GPL(ktime_get_resolution_ns);
789 
790 static ktime_t *offsets[TK_OFFS_MAX] = {
791         [TK_OFFS_REAL]  = &tk_core.timekeeper.offs_real,
792         [TK_OFFS_BOOT]  = &tk_core.timekeeper.offs_boot,
793         [TK_OFFS_TAI]   = &tk_core.timekeeper.offs_tai,
794 };
795 
796 ktime_t ktime_get_with_offset(enum tk_offsets offs)
797 {
798         struct timekeeper *tk = &tk_core.timekeeper;
799         unsigned int seq;
800         ktime_t base, *offset = offsets[offs];
801         u64 nsecs;
802 
803         WARN_ON(timekeeping_suspended);
804 
805         do {
806                 seq = read_seqcount_begin(&tk_core.seq);
807                 base = ktime_add(tk->tkr_mono.base, *offset);
808                 nsecs = timekeeping_get_ns(&tk->tkr_mono);
809 
810         } while (read_seqcount_retry(&tk_core.seq, seq));
811 
812         return ktime_add_ns(base, nsecs);
813 
814 }
815 EXPORT_SYMBOL_GPL(ktime_get_with_offset);
816 
817 /**
818  * ktime_mono_to_any() - convert mononotic time to any other time
819  * @tmono:      time to convert.
820  * @offs:       which offset to use
821  */
822 ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs)
823 {
824         ktime_t *offset = offsets[offs];
825         unsigned long seq;
826         ktime_t tconv;
827 
828         do {
829                 seq = read_seqcount_begin(&tk_core.seq);
830                 tconv = ktime_add(tmono, *offset);
831         } while (read_seqcount_retry(&tk_core.seq, seq));
832 
833         return tconv;
834 }
835 EXPORT_SYMBOL_GPL(ktime_mono_to_any);
836 
837 /**
838  * ktime_get_raw - Returns the raw monotonic time in ktime_t format
839  */
840 ktime_t ktime_get_raw(void)
841 {
842         struct timekeeper *tk = &tk_core.timekeeper;
843         unsigned int seq;
844         ktime_t base;
845         u64 nsecs;
846 
847         do {
848                 seq = read_seqcount_begin(&tk_core.seq);
849                 base = tk->tkr_raw.base;
850                 nsecs = timekeeping_get_ns(&tk->tkr_raw);
851 
852         } while (read_seqcount_retry(&tk_core.seq, seq));
853 
854         return ktime_add_ns(base, nsecs);
855 }
856 EXPORT_SYMBOL_GPL(ktime_get_raw);
857 
858 /**
859  * ktime_get_ts64 - get the monotonic clock in timespec64 format
860  * @ts:         pointer to timespec variable
861  *
862  * The function calculates the monotonic clock from the realtime
863  * clock and the wall_to_monotonic offset and stores the result
864  * in normalized timespec64 format in the variable pointed to by @ts.
865  */
866 void ktime_get_ts64(struct timespec64 *ts)
867 {
868         struct timekeeper *tk = &tk_core.timekeeper;
869         struct timespec64 tomono;
870         unsigned int seq;
871         u64 nsec;
872 
873         WARN_ON(timekeeping_suspended);
874 
875         do {
876                 seq = read_seqcount_begin(&tk_core.seq);
877                 ts->tv_sec = tk->xtime_sec;
878                 nsec = timekeeping_get_ns(&tk->tkr_mono);
879                 tomono = tk->wall_to_monotonic;
880 
881         } while (read_seqcount_retry(&tk_core.seq, seq));
882 
883         ts->tv_sec += tomono.tv_sec;
884         ts->tv_nsec = 0;
885         timespec64_add_ns(ts, nsec + tomono.tv_nsec);
886 }
887 EXPORT_SYMBOL_GPL(ktime_get_ts64);
888 
889 /**
890  * ktime_get_seconds - Get the seconds portion of CLOCK_MONOTONIC
891  *
892  * Returns the seconds portion of CLOCK_MONOTONIC with a single non
893  * serialized read. tk->ktime_sec is of type 'unsigned long' so this
894  * works on both 32 and 64 bit systems. On 32 bit systems the readout
895  * covers ~136 years of uptime which should be enough to prevent
896  * premature wrap arounds.
897  */
898 time64_t ktime_get_seconds(void)
899 {
900         struct timekeeper *tk = &tk_core.timekeeper;
901 
902         WARN_ON(timekeeping_suspended);
903         return tk->ktime_sec;
904 }
905 EXPORT_SYMBOL_GPL(ktime_get_seconds);
906 
907 /**
908  * ktime_get_real_seconds - Get the seconds portion of CLOCK_REALTIME
909  *
910  * Returns the wall clock seconds since 1970. This replaces the
911  * get_seconds() interface which is not y2038 safe on 32bit systems.
912  *
913  * For 64bit systems the fast access to tk->xtime_sec is preserved. On
914  * 32bit systems the access must be protected with the sequence
915  * counter to provide "atomic" access to the 64bit tk->xtime_sec
916  * value.
917  */
918 time64_t ktime_get_real_seconds(void)
919 {
920         struct timekeeper *tk = &tk_core.timekeeper;
921         time64_t seconds;
922         unsigned int seq;
923 
924         if (IS_ENABLED(CONFIG_64BIT))
925                 return tk->xtime_sec;
926 
927         do {
928                 seq = read_seqcount_begin(&tk_core.seq);
929                 seconds = tk->xtime_sec;
930 
931         } while (read_seqcount_retry(&tk_core.seq, seq));
932 
933         return seconds;
934 }
935 EXPORT_SYMBOL_GPL(ktime_get_real_seconds);
936 
937 /**
938  * __ktime_get_real_seconds - The same as ktime_get_real_seconds
939  * but without the sequence counter protect. This internal function
940  * is called just when timekeeping lock is already held.
941  */
942 time64_t __ktime_get_real_seconds(void)
943 {
944         struct timekeeper *tk = &tk_core.timekeeper;
945 
946         return tk->xtime_sec;
947 }
948 
949 /**
950  * ktime_get_snapshot - snapshots the realtime/monotonic raw clocks with counter
951  * @systime_snapshot:   pointer to struct receiving the system time snapshot
952  */
953 void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
954 {
955         struct timekeeper *tk = &tk_core.timekeeper;
956         unsigned long seq;
957         ktime_t base_raw;
958         ktime_t base_real;
959         u64 nsec_raw;
960         u64 nsec_real;
961         u64 now;
962 
963         WARN_ON_ONCE(timekeeping_suspended);
964 
965         do {
966                 seq = read_seqcount_begin(&tk_core.seq);
967                 now = tk_clock_read(&tk->tkr_mono);
968                 systime_snapshot->cs_was_changed_seq = tk->cs_was_changed_seq;
969                 systime_snapshot->clock_was_set_seq = tk->clock_was_set_seq;
970                 base_real = ktime_add(tk->tkr_mono.base,
971                                       tk_core.timekeeper.offs_real);
972                 base_raw = tk->tkr_raw.base;
973                 nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, now);
974                 nsec_raw  = timekeeping_cycles_to_ns(&tk->tkr_raw, now);
975         } while (read_seqcount_retry(&tk_core.seq, seq));
976 
977         systime_snapshot->cycles = now;
978         systime_snapshot->real = ktime_add_ns(base_real, nsec_real);
979         systime_snapshot->raw = ktime_add_ns(base_raw, nsec_raw);
980 }
981 EXPORT_SYMBOL_GPL(ktime_get_snapshot);
982 
983 /* Scale base by mult/div checking for overflow */
984 static int scale64_check_overflow(u64 mult, u64 div, u64 *base)
985 {
986         u64 tmp, rem;
987 
988         tmp = div64_u64_rem(*base, div, &rem);
989 
990         if (((int)sizeof(u64)*8 - fls64(mult) < fls64(tmp)) ||
991             ((int)sizeof(u64)*8 - fls64(mult) < fls64(rem)))
992                 return -EOVERFLOW;
993         tmp *= mult;
994         rem *= mult;
995 
996         do_div(rem, div);
997         *base = tmp + rem;
998         return 0;
999 }
1000 
1001 /**
1002  * adjust_historical_crosststamp - adjust crosstimestamp previous to current interval
1003  * @history:                    Snapshot representing start of history
1004  * @partial_history_cycles:     Cycle offset into history (fractional part)
1005  * @total_history_cycles:       Total history length in cycles
1006  * @discontinuity:              True indicates clock was set on history period
1007  * @ts:                         Cross timestamp that should be adjusted using
1008  *      partial/total ratio
1009  *
1010  * Helper function used by get_device_system_crosststamp() to correct the
1011  * crosstimestamp corresponding to the start of the current interval to the
1012  * system counter value (timestamp point) provided by the driver. The
1013  * total_history_* quantities are the total history starting at the provided
1014  * reference point and ending at the start of the current interval. The cycle
1015  * count between the driver timestamp point and the start of the current
1016  * interval is partial_history_cycles.
1017  */
1018 static int adjust_historical_crosststamp(struct system_time_snapshot *history,
1019                                          u64 partial_history_cycles,
1020                                          u64 total_history_cycles,
1021                                          bool discontinuity,
1022                                          struct system_device_crosststamp *ts)
1023 {
1024         struct timekeeper *tk = &tk_core.timekeeper;
1025         u64 corr_raw, corr_real;
1026         bool interp_forward;
1027         int ret;
1028 
1029         if (total_history_cycles == 0 || partial_history_cycles == 0)
1030                 return 0;
1031 
1032         /* Interpolate shortest distance from beginning or end of history */
1033         interp_forward = partial_history_cycles > total_history_cycles / 2;
1034         partial_history_cycles = interp_forward ?
1035                 total_history_cycles - partial_history_cycles :
1036                 partial_history_cycles;
1037 
1038         /*
1039          * Scale the monotonic raw time delta by:
1040          *      partial_history_cycles / total_history_cycles
1041          */
1042         corr_raw = (u64)ktime_to_ns(
1043                 ktime_sub(ts->sys_monoraw, history->raw));
1044         ret = scale64_check_overflow(partial_history_cycles,
1045                                      total_history_cycles, &corr_raw);
1046         if (ret)
1047                 return ret;
1048 
1049         /*
1050          * If there is a discontinuity in the history, scale monotonic raw
1051          *      correction by:
1052          *      mult(real)/mult(raw) yielding the realtime correction
1053          * Otherwise, calculate the realtime correction similar to monotonic
1054          *      raw calculation
1055          */
1056         if (discontinuity) {
1057                 corr_real = mul_u64_u32_div
1058                         (corr_raw, tk->tkr_mono.mult, tk->tkr_raw.mult);
1059         } else {
1060                 corr_real = (u64)ktime_to_ns(
1061                         ktime_sub(ts->sys_realtime, history->real));
1062                 ret = scale64_check_overflow(partial_history_cycles,
1063                                              total_history_cycles, &corr_real);
1064                 if (ret)
1065                         return ret;
1066         }
1067 
1068         /* Fixup monotonic raw and real time time values */
1069         if (interp_forward) {
1070                 ts->sys_monoraw = ktime_add_ns(history->raw, corr_raw);
1071                 ts->sys_realtime = ktime_add_ns(history->real, corr_real);
1072         } else {
1073                 ts->sys_monoraw = ktime_sub_ns(ts->sys_monoraw, corr_raw);
1074                 ts->sys_realtime = ktime_sub_ns(ts->sys_realtime, corr_real);
1075         }
1076 
1077         return 0;
1078 }
1079 
1080 /*
1081  * cycle_between - true if test occurs chronologically between before and after
1082  */
1083 static bool cycle_between(u64 before, u64 test, u64 after)
1084 {
1085         if (test > before && test < after)
1086                 return true;
1087         if (test < before && before > after)
1088                 return true;
1089         return false;
1090 }
1091 
1092 /**
1093  * get_device_system_crosststamp - Synchronously capture system/device timestamp
1094  * @get_time_fn:        Callback to get simultaneous device time and
1095  *      system counter from the device driver
1096  * @ctx:                Context passed to get_time_fn()
1097  * @history_begin:      Historical reference point used to interpolate system
1098  *      time when counter provided by the driver is before the current interval
1099  * @xtstamp:            Receives simultaneously captured system and device time
1100  *
1101  * Reads a timestamp from a device and correlates it to system time
1102  */
1103 int get_device_system_crosststamp(int (*get_time_fn)
1104                                   (ktime_t *device_time,
1105                                    struct system_counterval_t *sys_counterval,
1106                                    void *ctx),
1107                                   void *ctx,
1108                                   struct system_time_snapshot *history_begin,
1109                                   struct system_device_crosststamp *xtstamp)
1110 {
1111         struct system_counterval_t system_counterval;
1112         struct timekeeper *tk = &tk_core.timekeeper;
1113         u64 cycles, now, interval_start;
1114         unsigned int clock_was_set_seq = 0;
1115         ktime_t base_real, base_raw;
1116         u64 nsec_real, nsec_raw;
1117         u8 cs_was_changed_seq;
1118         unsigned long seq;
1119         bool do_interp;
1120         int ret;
1121 
1122         do {
1123                 seq = read_seqcount_begin(&tk_core.seq);
1124                 /*
1125                  * Try to synchronously capture device time and a system
1126                  * counter value calling back into the device driver
1127                  */
1128                 ret = get_time_fn(&xtstamp->device, &system_counterval, ctx);
1129                 if (ret)
1130                         return ret;
1131 
1132                 /*
1133                  * Verify that the clocksource associated with the captured
1134                  * system counter value is the same as the currently installed
1135                  * timekeeper clocksource
1136                  */
1137                 if (tk->tkr_mono.clock != system_counterval.cs)
1138                         return -ENODEV;
1139                 cycles = system_counterval.cycles;
1140 
1141                 /*
1142                  * Check whether the system counter value provided by the
1143                  * device driver is on the current timekeeping interval.
1144                  */
1145                 now = tk_clock_read(&tk->tkr_mono);
1146                 interval_start = tk->tkr_mono.cycle_last;
1147                 if (!cycle_between(interval_start, cycles, now)) {
1148                         clock_was_set_seq = tk->clock_was_set_seq;
1149                         cs_was_changed_seq = tk->cs_was_changed_seq;
1150                         cycles = interval_start;
1151                         do_interp = true;
1152                 } else {
1153                         do_interp = false;
1154                 }
1155 
1156                 base_real = ktime_add(tk->tkr_mono.base,
1157                                       tk_core.timekeeper.offs_real);
1158                 base_raw = tk->tkr_raw.base;
1159 
1160                 nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono,
1161                                                      system_counterval.cycles);
1162                 nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw,
1163                                                     system_counterval.cycles);
1164         } while (read_seqcount_retry(&tk_core.seq, seq));
1165 
1166         xtstamp->sys_realtime = ktime_add_ns(base_real, nsec_real);
1167         xtstamp->sys_monoraw = ktime_add_ns(base_raw, nsec_raw);
1168 
1169         /*
1170          * Interpolate if necessary, adjusting back from the start of the
1171          * current interval
1172          */
1173         if (do_interp) {
1174                 u64 partial_history_cycles, total_history_cycles;
1175                 bool discontinuity;
1176 
1177                 /*
1178                  * Check that the counter value occurs after the provided
1179                  * history reference and that the history doesn't cross a
1180                  * clocksource change
1181                  */
1182                 if (!history_begin ||
1183                     !cycle_between(history_begin->cycles,
1184                                    system_counterval.cycles, cycles) ||
1185                     history_begin->cs_was_changed_seq != cs_was_changed_seq)
1186                         return -EINVAL;
1187                 partial_history_cycles = cycles - system_counterval.cycles;
1188                 total_history_cycles = cycles - history_begin->cycles;
1189                 discontinuity =
1190                         history_begin->clock_was_set_seq != clock_was_set_seq;
1191 
1192                 ret = adjust_historical_crosststamp(history_begin,
1193                                                     partial_history_cycles,
1194                                                     total_history_cycles,
1195                                                     discontinuity, xtstamp);
1196                 if (ret)
1197                         return ret;
1198         }
1199 
1200         return 0;
1201 }
1202 EXPORT_SYMBOL_GPL(get_device_system_crosststamp);
1203 
1204 /**
1205  * do_gettimeofday - Returns the time of day in a timeval
1206  * @tv:         pointer to the timeval to be set
1207  *
1208  * NOTE: Users should be converted to using getnstimeofday()
1209  */
1210 void do_gettimeofday(struct timeval *tv)
1211 {
1212         struct timespec64 now;
1213 
1214         getnstimeofday64(&now);
1215         tv->tv_sec = now.tv_sec;
1216         tv->tv_usec = now.tv_nsec/1000;
1217 }
1218 EXPORT_SYMBOL(do_gettimeofday);
1219 
1220 /**
1221  * do_settimeofday64 - Sets the time of day.
1222  * @ts:     pointer to the timespec64 variable containing the new time
1223  *
1224  * Sets the time of day to the new time and update NTP and notify hrtimers
1225  */
1226 int do_settimeofday64(const struct timespec64 *ts)
1227 {
1228         struct timekeeper *tk = &tk_core.timekeeper;
1229         struct timespec64 ts_delta, xt;
1230         unsigned long flags;
1231         int ret = 0;
1232 
1233         if (!timespec64_valid_strict(ts))
1234                 return -EINVAL;
1235 
1236         raw_spin_lock_irqsave(&timekeeper_lock, flags);
1237         write_seqcount_begin(&tk_core.seq);
1238 
1239         timekeeping_forward_now(tk);
1240 
1241         xt = tk_xtime(tk);
1242         ts_delta.tv_sec = ts->tv_sec - xt.tv_sec;
1243         ts_delta.tv_nsec = ts->tv_nsec - xt.tv_nsec;
1244 
1245         if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) {
1246                 ret = -EINVAL;
1247                 goto out;
1248         }
1249 
1250         tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta));
1251 
1252         tk_set_xtime(tk, ts);
1253 out:
1254         timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1255 
1256         write_seqcount_end(&tk_core.seq);
1257         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1258 
1259         /* signal hrtimers about time change */
1260         clock_was_set();
1261 
1262         return ret;
1263 }
1264 EXPORT_SYMBOL(do_settimeofday64);
1265 
1266 /**
1267  * timekeeping_inject_offset - Adds or subtracts from the current time.
1268  * @tv:         pointer to the timespec variable containing the offset
1269  *
1270  * Adds or subtracts an offset value from the current time.
1271  */
1272 static int timekeeping_inject_offset(struct timespec64 *ts)
1273 {
1274         struct timekeeper *tk = &tk_core.timekeeper;
1275         unsigned long flags;
1276         struct timespec64 tmp;
1277         int ret = 0;
1278 
1279         if (ts->tv_nsec < 0 || ts->tv_nsec >= NSEC_PER_SEC)
1280                 return -EINVAL;
1281 
1282         raw_spin_lock_irqsave(&timekeeper_lock, flags);
1283         write_seqcount_begin(&tk_core.seq);
1284 
1285         timekeeping_forward_now(tk);
1286 
1287         /* Make sure the proposed value is valid */
1288         tmp = timespec64_add(tk_xtime(tk), *ts);
1289         if (timespec64_compare(&tk->wall_to_monotonic, ts) > 0 ||
1290             !timespec64_valid_strict(&tmp)) {
1291                 ret = -EINVAL;
1292                 goto error;
1293         }
1294 
1295         tk_xtime_add(tk, ts);
1296         tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *ts));
1297 
1298 error: /* even if we error out, we forwarded the time, so call update */
1299         timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1300 
1301         write_seqcount_end(&tk_core.seq);
1302         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1303 
1304         /* signal hrtimers about time change */
1305         clock_was_set();
1306 
1307         return ret;
1308 }
1309 
1310 /*
1311  * Indicates if there is an offset between the system clock and the hardware
1312  * clock/persistent clock/rtc.
1313  */
1314 int persistent_clock_is_local;
1315 
1316 /*
1317  * Adjust the time obtained from the CMOS to be UTC time instead of
1318  * local time.
1319  *
1320  * This is ugly, but preferable to the alternatives.  Otherwise we
1321  * would either need to write a program to do it in /etc/rc (and risk
1322  * confusion if the program gets run more than once; it would also be
1323  * hard to make the program warp the clock precisely n hours)  or
1324  * compile in the timezone information into the kernel.  Bad, bad....
1325  *
1326  *                                              - TYT, 1992-01-01
1327  *
1328  * The best thing to do is to keep the CMOS clock in universal time (UTC)
1329  * as real UNIX machines always do it. This avoids all headaches about
1330  * daylight saving times and warping kernel clocks.
1331  */
1332 void timekeeping_warp_clock(void)
1333 {
1334         if (sys_tz.tz_minuteswest != 0) {
1335                 struct timespec64 adjust;
1336 
1337                 persistent_clock_is_local = 1;
1338                 adjust.tv_sec = sys_tz.tz_minuteswest * 60;
1339                 adjust.tv_nsec = 0;
1340                 timekeeping_inject_offset(&adjust);
1341         }
1342 }
1343 
1344 /**
1345  * __timekeeping_set_tai_offset - Sets the TAI offset from UTC and monotonic
1346  *
1347  */
1348 static void __timekeeping_set_tai_offset(struct timekeeper *tk, s32 tai_offset)
1349 {
1350         tk->tai_offset = tai_offset;
1351         tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tai_offset, 0));
1352 }
1353 
1354 /**
1355  * change_clocksource - Swaps clocksources if a new one is available
1356  *
1357  * Accumulates current time interval and initializes new clocksource
1358  */
1359 static int change_clocksource(void *data)
1360 {
1361         struct timekeeper *tk = &tk_core.timekeeper;
1362         struct clocksource *new, *old;
1363         unsigned long flags;
1364 
1365         new = (struct clocksource *) data;
1366 
1367         raw_spin_lock_irqsave(&timekeeper_lock, flags);
1368         write_seqcount_begin(&tk_core.seq);
1369 
1370         timekeeping_forward_now(tk);
1371         /*
1372          * If the cs is in module, get a module reference. Succeeds
1373          * for built-in code (owner == NULL) as well.
1374          */
1375         if (try_module_get(new->owner)) {
1376                 if (!new->enable || new->enable(new) == 0) {
1377                         old = tk->tkr_mono.clock;
1378                         tk_setup_internals(tk, new);
1379                         if (old->disable)
1380                                 old->disable(old);
1381                         module_put(old->owner);
1382                 } else {
1383                         module_put(new->owner);
1384                 }
1385         }
1386         timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1387 
1388         write_seqcount_end(&tk_core.seq);
1389         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1390 
1391         return 0;
1392 }
1393 
1394 /**
1395  * timekeeping_notify - Install a new clock source
1396  * @clock:              pointer to the clock source
1397  *
1398  * This function is called from clocksource.c after a new, better clock
1399  * source has been registered. The caller holds the clocksource_mutex.
1400  */
1401 int timekeeping_notify(struct clocksource *clock)
1402 {
1403         struct timekeeper *tk = &tk_core.timekeeper;
1404 
1405         if (tk->tkr_mono.clock == clock)
1406                 return 0;
1407         stop_machine(change_clocksource, clock, NULL);
1408         tick_clock_notify();
1409         return tk->tkr_mono.clock == clock ? 0 : -1;
1410 }
1411 
1412 /**
1413  * getrawmonotonic64 - Returns the raw monotonic time in a timespec
1414  * @ts:         pointer to the timespec64 to be set
1415  *
1416  * Returns the raw monotonic time (completely un-modified by ntp)
1417  */
1418 void getrawmonotonic64(struct timespec64 *ts)
1419 {
1420         struct timekeeper *tk = &tk_core.timekeeper;
1421         unsigned long seq;
1422         u64 nsecs;
1423 
1424         do {
1425                 seq = read_seqcount_begin(&tk_core.seq);
1426                 ts->tv_sec = tk->raw_sec;
1427                 nsecs = timekeeping_get_ns(&tk->tkr_raw);
1428 
1429         } while (read_seqcount_retry(&tk_core.seq, seq));
1430 
1431         ts->tv_nsec = 0;
1432         timespec64_add_ns(ts, nsecs);
1433 }
1434 EXPORT_SYMBOL(getrawmonotonic64);
1435 
1436 
1437 /**
1438  * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
1439  */
1440 int timekeeping_valid_for_hres(void)
1441 {
1442         struct timekeeper *tk = &tk_core.timekeeper;
1443         unsigned long seq;
1444         int ret;
1445 
1446         do {
1447                 seq = read_seqcount_begin(&tk_core.seq);
1448 
1449                 ret = tk->tkr_mono.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
1450 
1451         } while (read_seqcount_retry(&tk_core.seq, seq));
1452 
1453         return ret;
1454 }
1455 
1456 /**
1457  * timekeeping_max_deferment - Returns max time the clocksource can be deferred
1458  */
1459 u64 timekeeping_max_deferment(void)
1460 {
1461         struct timekeeper *tk = &tk_core.timekeeper;
1462         unsigned long seq;
1463         u64 ret;
1464 
1465         do {
1466                 seq = read_seqcount_begin(&tk_core.seq);
1467 
1468                 ret = tk->tkr_mono.clock->max_idle_ns;
1469 
1470         } while (read_seqcount_retry(&tk_core.seq, seq));
1471 
1472         return ret;
1473 }
1474 
1475 /**
1476  * read_persistent_clock -  Return time from the persistent clock.
1477  *
1478  * Weak dummy function for arches that do not yet support it.
1479  * Reads the time from the battery backed persistent clock.
1480  * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
1481  *
1482  *  XXX - Do be sure to remove it once all arches implement it.
1483  */
1484 void __weak read_persistent_clock(struct timespec *ts)
1485 {
1486         ts->tv_sec = 0;
1487         ts->tv_nsec = 0;
1488 }
1489 
1490 void __weak read_persistent_clock64(struct timespec64 *ts64)
1491 {
1492         struct timespec ts;
1493 
1494         read_persistent_clock(&ts);
1495         *ts64 = timespec_to_timespec64(ts);
1496 }
1497 
1498 /**
1499  * read_boot_clock64 -  Return time of the system start.
1500  *
1501  * Weak dummy function for arches that do not yet support it.
1502  * Function to read the exact time the system has been started.
1503  * Returns a timespec64 with tv_sec=0 and tv_nsec=0 if unsupported.
1504  *
1505  *  XXX - Do be sure to remove it once all arches implement it.
1506  */
1507 void __weak read_boot_clock64(struct timespec64 *ts)
1508 {
1509         ts->tv_sec = 0;
1510         ts->tv_nsec = 0;
1511 }
1512 
1513 /* Flag for if timekeeping_resume() has injected sleeptime */
1514 static bool sleeptime_injected;
1515 
1516 /* Flag for if there is a persistent clock on this platform */
1517 static bool persistent_clock_exists;
1518 
1519 /*
1520  * timekeeping_init - Initializes the clocksource and common timekeeping values
1521  */
1522 void __init timekeeping_init(void)
1523 {
1524         struct timekeeper *tk = &tk_core.timekeeper;
1525         struct clocksource *clock;
1526         unsigned long flags;
1527         struct timespec64 now, boot, tmp;
1528 
1529         read_persistent_clock64(&now);
1530         if (!timespec64_valid_strict(&now)) {
1531                 pr_warn("WARNING: Persistent clock returned invalid value!\n"
1532                         "         Check your CMOS/BIOS settings.\n");
1533                 now.tv_sec = 0;
1534                 now.tv_nsec = 0;
1535         } else if (now.tv_sec || now.tv_nsec)
1536                 persistent_clock_exists = true;
1537 
1538         read_boot_clock64(&boot);
1539         if (!timespec64_valid_strict(&boot)) {
1540                 pr_warn("WARNING: Boot clock returned invalid value!\n"
1541                         "         Check your CMOS/BIOS settings.\n");
1542                 boot.tv_sec = 0;
1543                 boot.tv_nsec = 0;
1544         }
1545 
1546         raw_spin_lock_irqsave(&timekeeper_lock, flags);
1547         write_seqcount_begin(&tk_core.seq);
1548         ntp_init();
1549 
1550         clock = clocksource_default_clock();
1551         if (clock->enable)
1552                 clock->enable(clock);
1553         tk_setup_internals(tk, clock);
1554 
1555         tk_set_xtime(tk, &now);
1556         tk->raw_sec = 0;
1557         if (boot.tv_sec == 0 && boot.tv_nsec == 0)
1558                 boot = tk_xtime(tk);
1559 
1560         set_normalized_timespec64(&tmp, -boot.tv_sec, -boot.tv_nsec);
1561         tk_set_wall_to_mono(tk, tmp);
1562 
1563         timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
1564 
1565         write_seqcount_end(&tk_core.seq);
1566         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1567 }
1568 
1569 /* time in seconds when suspend began for persistent clock */
1570 static struct timespec64 timekeeping_suspend_time;
1571 
1572 /**
1573  * __timekeeping_inject_sleeptime - Internal function to add sleep interval
1574  * @delta: pointer to a timespec delta value
1575  *
1576  * Takes a timespec offset measuring a suspend interval and properly
1577  * adds the sleep offset to the timekeeping variables.
1578  */
1579 static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
1580                                            struct timespec64 *delta)
1581 {
1582         if (!timespec64_valid_strict(delta)) {
1583                 printk_deferred(KERN_WARNING
1584                                 "__timekeeping_inject_sleeptime: Invalid "
1585                                 "sleep delta value!\n");
1586                 return;
1587         }
1588         tk_xtime_add(tk, delta);
1589         tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *delta));
1590         tk_update_sleep_time(tk, timespec64_to_ktime(*delta));
1591         tk_debug_account_sleep_time(delta);
1592 }
1593 
1594 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
1595 /**
1596  * We have three kinds of time sources to use for sleep time
1597  * injection, the preference order is:
1598  * 1) non-stop clocksource
1599  * 2) persistent clock (ie: RTC accessible when irqs are off)
1600  * 3) RTC
1601  *
1602  * 1) and 2) are used by timekeeping, 3) by RTC subsystem.
1603  * If system has neither 1) nor 2), 3) will be used finally.
1604  *
1605  *
1606  * If timekeeping has injected sleeptime via either 1) or 2),
1607  * 3) becomes needless, so in this case we don't need to call
1608  * rtc_resume(), and this is what timekeeping_rtc_skipresume()
1609  * means.
1610  */
1611 bool timekeeping_rtc_skipresume(void)
1612 {
1613         return sleeptime_injected;
1614 }
1615 
1616 /**
1617  * 1) can be determined whether to use or not only when doing
1618  * timekeeping_resume() which is invoked after rtc_suspend(),
1619  * so we can't skip rtc_suspend() surely if system has 1).
1620  *
1621  * But if system has 2), 2) will definitely be used, so in this
1622  * case we don't need to call rtc_suspend(), and this is what
1623  * timekeeping_rtc_skipsuspend() means.
1624  */
1625 bool timekeeping_rtc_skipsuspend(void)
1626 {
1627         return persistent_clock_exists;
1628 }
1629 
1630 /**
1631  * timekeeping_inject_sleeptime64 - Adds suspend interval to timeekeeping values
1632  * @delta: pointer to a timespec64 delta value
1633  *
1634  * This hook is for architectures that cannot support read_persistent_clock64
1635  * because their RTC/persistent clock is only accessible when irqs are enabled.
1636  * and also don't have an effective nonstop clocksource.
1637  *
1638  * This function should only be called by rtc_resume(), and allows
1639  * a suspend offset to be injected into the timekeeping values.
1640  */
1641 void timekeeping_inject_sleeptime64(struct timespec64 *delta)
1642 {
1643         struct timekeeper *tk = &tk_core.timekeeper;
1644         unsigned long flags;
1645 
1646         raw_spin_lock_irqsave(&timekeeper_lock, flags);
1647         write_seqcount_begin(&tk_core.seq);
1648 
1649         timekeeping_forward_now(tk);
1650 
1651         __timekeeping_inject_sleeptime(tk, delta);
1652 
1653         timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1654 
1655         write_seqcount_end(&tk_core.seq);
1656         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1657 
1658         /* signal hrtimers about time change */
1659         clock_was_set();
1660 }
1661 #endif
1662 
1663 /**
1664  * timekeeping_resume - Resumes the generic timekeeping subsystem.
1665  */
1666 void timekeeping_resume(void)
1667 {
1668         struct timekeeper *tk = &tk_core.timekeeper;
1669         struct clocksource *clock = tk->tkr_mono.clock;
1670         unsigned long flags;
1671         struct timespec64 ts_new, ts_delta;
1672         u64 cycle_now;
1673 
1674         sleeptime_injected = false;
1675         read_persistent_clock64(&ts_new);
1676 
1677         clockevents_resume();
1678         clocksource_resume();
1679 
1680         raw_spin_lock_irqsave(&timekeeper_lock, flags);
1681         write_seqcount_begin(&tk_core.seq);
1682 
1683         /*
1684          * After system resumes, we need to calculate the suspended time and
1685          * compensate it for the OS time. There are 3 sources that could be
1686          * used: Nonstop clocksource during suspend, persistent clock and rtc
1687          * device.
1688          *
1689          * One specific platform may have 1 or 2 or all of them, and the
1690          * preference will be:
1691          *      suspend-nonstop clocksource -> persistent clock -> rtc
1692          * The less preferred source will only be tried if there is no better
1693          * usable source. The rtc part is handled separately in rtc core code.
1694          */
1695         cycle_now = tk_clock_read(&tk->tkr_mono);
1696         if ((clock->flags & CLOCK_SOURCE_SUSPEND_NONSTOP) &&
1697                 cycle_now > tk->tkr_mono.cycle_last) {
1698                 u64 nsec, cyc_delta;
1699 
1700                 cyc_delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last,
1701                                               tk->tkr_mono.mask);
1702                 nsec = mul_u64_u32_shr(cyc_delta, clock->mult, clock->shift);
1703                 ts_delta = ns_to_timespec64(nsec);
1704                 sleeptime_injected = true;
1705         } else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {
1706                 ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);
1707                 sleeptime_injected = true;
1708         }
1709 
1710         if (sleeptime_injected)
1711                 __timekeeping_inject_sleeptime(tk, &ts_delta);
1712 
1713         /* Re-base the last cycle value */
1714         tk->tkr_mono.cycle_last = cycle_now;
1715         tk->tkr_raw.cycle_last  = cycle_now;
1716 
1717         tk->ntp_error = 0;
1718         timekeeping_suspended = 0;
1719         timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
1720         write_seqcount_end(&tk_core.seq);
1721         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1722 
1723         touch_softlockup_watchdog();
1724 
1725         tick_resume();
1726         hrtimers_resume();
1727 }
1728 
1729 int timekeeping_suspend(void)
1730 {
1731         struct timekeeper *tk = &tk_core.timekeeper;
1732         unsigned long flags;
1733         struct timespec64               delta, delta_delta;
1734         static struct timespec64        old_delta;
1735 
1736         read_persistent_clock64(&timekeeping_suspend_time);
1737 
1738         /*
1739          * On some systems the persistent_clock can not be detected at
1740          * timekeeping_init by its return value, so if we see a valid
1741          * value returned, update the persistent_clock_exists flag.
1742          */
1743         if (timekeeping_suspend_time.tv_sec || timekeeping_suspend_time.tv_nsec)
1744                 persistent_clock_exists = true;
1745 
1746         raw_spin_lock_irqsave(&timekeeper_lock, flags);
1747         write_seqcount_begin(&tk_core.seq);
1748         timekeeping_forward_now(tk);
1749         timekeeping_suspended = 1;
1750 
1751         if (persistent_clock_exists) {
1752                 /*
1753                  * To avoid drift caused by repeated suspend/resumes,
1754                  * which each can add ~1 second drift error,
1755                  * try to compensate so the difference in system time
1756                  * and persistent_clock time stays close to constant.
1757                  */
1758                 delta = timespec64_sub(tk_xtime(tk), timekeeping_suspend_time);
1759                 delta_delta = timespec64_sub(delta, old_delta);
1760                 if (abs(delta_delta.tv_sec) >= 2) {
1761                         /*
1762                          * if delta_delta is too large, assume time correction
1763                          * has occurred and set old_delta to the current delta.
1764                          */
1765                         old_delta = delta;
1766                 } else {
1767                         /* Otherwise try to adjust old_system to compensate */
1768                         timekeeping_suspend_time =
1769                                 timespec64_add(timekeeping_suspend_time, delta_delta);
1770                 }
1771         }
1772 
1773         timekeeping_update(tk, TK_MIRROR);
1774         halt_fast_timekeeper(tk);
1775         write_seqcount_end(&tk_core.seq);
1776         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1777 
1778         tick_suspend();
1779         clocksource_suspend();
1780         clockevents_suspend();
1781 
1782         return 0;
1783 }
1784 
1785 /* sysfs resume/suspend bits for timekeeping */
1786 static struct syscore_ops timekeeping_syscore_ops = {
1787         .resume         = timekeeping_resume,
1788         .suspend        = timekeeping_suspend,
1789 };
1790 
1791 static int __init timekeeping_init_ops(void)
1792 {
1793         register_syscore_ops(&timekeeping_syscore_ops);
1794         return 0;
1795 }
1796 device_initcall(timekeeping_init_ops);
1797 
1798 /*
1799  * Apply a multiplier adjustment to the timekeeper
1800  */
1801 static __always_inline void timekeeping_apply_adjustment(struct timekeeper *tk,
1802                                                          s64 offset,
1803                                                          bool negative,
1804                                                          int adj_scale)
1805 {
1806         s64 interval = tk->cycle_interval;
1807         s32 mult_adj = 1;
1808 
1809         if (negative) {
1810                 mult_adj = -mult_adj;
1811                 interval = -interval;
1812                 offset  = -offset;
1813         }
1814         mult_adj <<= adj_scale;
1815         interval <<= adj_scale;
1816         offset <<= adj_scale;
1817 
1818         /*
1819          * So the following can be confusing.
1820          *
1821          * To keep things simple, lets assume mult_adj == 1 for now.
1822          *
1823          * When mult_adj != 1, remember that the interval and offset values
1824          * have been appropriately scaled so the math is the same.
1825          *
1826          * The basic idea here is that we're increasing the multiplier
1827          * by one, this causes the xtime_interval to be incremented by
1828          * one cycle_interval. This is because:
1829          *      xtime_interval = cycle_interval * mult
1830          * So if mult is being incremented by one:
1831          *      xtime_interval = cycle_interval * (mult + 1)
1832          * Its the same as:
1833          *      xtime_interval = (cycle_interval * mult) + cycle_interval
1834          * Which can be shortened to:
1835          *      xtime_interval += cycle_interval
1836          *
1837          * So offset stores the non-accumulated cycles. Thus the current
1838          * time (in shifted nanoseconds) is:
1839          *      now = (offset * adj) + xtime_nsec
1840          * Now, even though we're adjusting the clock frequency, we have
1841          * to keep time consistent. In other words, we can't jump back
1842          * in time, and we also want to avoid jumping forward in time.
1843          *
1844          * So given the same offset value, we need the time to be the same
1845          * both before and after the freq adjustment.
1846          *      now = (offset * adj_1) + xtime_nsec_1
1847          *      now = (offset * adj_2) + xtime_nsec_2
1848          * So:
1849          *      (offset * adj_1) + xtime_nsec_1 =
1850          *              (offset * adj_2) + xtime_nsec_2
1851          * And we know:
1852          *      adj_2 = adj_1 + 1
1853          * So:
1854          *      (offset * adj_1) + xtime_nsec_1 =
1855          *              (offset * (adj_1+1)) + xtime_nsec_2
1856          *      (offset * adj_1) + xtime_nsec_1 =
1857          *              (offset * adj_1) + offset + xtime_nsec_2
1858          * Canceling the sides:
1859          *      xtime_nsec_1 = offset + xtime_nsec_2
1860          * Which gives us:
1861          *      xtime_nsec_2 = xtime_nsec_1 - offset
1862          * Which simplfies to:
1863          *      xtime_nsec -= offset
1864          *
1865          * XXX - TODO: Doc ntp_error calculation.
1866          */
1867         if ((mult_adj > 0) && (tk->tkr_mono.mult + mult_adj < mult_adj)) {
1868                 /* NTP adjustment caused clocksource mult overflow */
1869                 WARN_ON_ONCE(1);
1870                 return;
1871         }
1872 
1873         tk->tkr_mono.mult += mult_adj;
1874         tk->xtime_interval += interval;
1875         tk->tkr_mono.xtime_nsec -= offset;
1876         tk->ntp_error -= (interval - offset) << tk->ntp_error_shift;
1877 }
1878 
1879 /*
1880  * Calculate the multiplier adjustment needed to match the frequency
1881  * specified by NTP
1882  */
1883 static __always_inline void timekeeping_freqadjust(struct timekeeper *tk,
1884                                                         s64 offset)
1885 {
1886         s64 interval = tk->cycle_interval;
1887         s64 xinterval = tk->xtime_interval;
1888         u32 base = tk->tkr_mono.clock->mult;
1889         u32 max = tk->tkr_mono.clock->maxadj;
1890         u32 cur_adj = tk->tkr_mono.mult;
1891         s64 tick_error;
1892         bool negative;
1893         u32 adj_scale;
1894 
1895         /* Remove any current error adj from freq calculation */
1896         if (tk->ntp_err_mult)
1897                 xinterval -= tk->cycle_interval;
1898 
1899         tk->ntp_tick = ntp_tick_length();
1900 
1901         /* Calculate current error per tick */
1902         tick_error = ntp_tick_length() >> tk->ntp_error_shift;
1903         tick_error -= (xinterval + tk->xtime_remainder);
1904 
1905         /* Don't worry about correcting it if its small */
1906         if (likely((tick_error >= 0) && (tick_error <= interval)))
1907                 return;
1908 
1909         /* preserve the direction of correction */
1910         negative = (tick_error < 0);
1911 
1912         /* If any adjustment would pass the max, just return */
1913         if (negative && (cur_adj - 1) <= (base - max))
1914                 return;
1915         if (!negative && (cur_adj + 1) >= (base + max))
1916                 return;
1917         /*
1918          * Sort out the magnitude of the correction, but
1919          * avoid making so large a correction that we go
1920          * over the max adjustment.
1921          */
1922         adj_scale = 0;
1923         tick_error = abs(tick_error);
1924         while (tick_error > interval) {
1925                 u32 adj = 1 << (adj_scale + 1);
1926 
1927                 /* Check if adjustment gets us within 1 unit from the max */
1928                 if (negative && (cur_adj - adj) <= (base - max))
1929                         break;
1930                 if (!negative && (cur_adj + adj) >= (base + max))
1931                         break;
1932 
1933                 adj_scale++;
1934                 tick_error >>= 1;
1935         }
1936 
1937         /* scale the corrections */
1938         timekeeping_apply_adjustment(tk, offset, negative, adj_scale);
1939 }
1940 
1941 /*
1942  * Adjust the timekeeper's multiplier to the correct frequency
1943  * and also to reduce the accumulated error value.
1944  */
1945 static void timekeeping_adjust(struct timekeeper *tk, s64 offset)
1946 {
1947         /* Correct for the current frequency error */
1948         timekeeping_freqadjust(tk, offset);
1949 
1950         /* Next make a small adjustment to fix any cumulative error */
1951         if (!tk->ntp_err_mult && (tk->ntp_error > 0)) {
1952                 tk->ntp_err_mult = 1;
1953                 timekeeping_apply_adjustment(tk, offset, 0, 0);
1954         } else if (tk->ntp_err_mult && (tk->ntp_error <= 0)) {
1955                 /* Undo any existing error adjustment */
1956                 timekeeping_apply_adjustment(tk, offset, 1, 0);
1957                 tk->ntp_err_mult = 0;
1958         }
1959 
1960         if (unlikely(tk->tkr_mono.clock->maxadj &&
1961                 (abs(tk->tkr_mono.mult - tk->tkr_mono.clock->mult)
1962                         > tk->tkr_mono.clock->maxadj))) {
1963                 printk_once(KERN_WARNING
1964                         "Adjusting %s more than 11%% (%ld vs %ld)\n",
1965                         tk->tkr_mono.clock->name, (long)tk->tkr_mono.mult,
1966                         (long)tk->tkr_mono.clock->mult + tk->tkr_mono.clock->maxadj);
1967         }
1968 
1969         /*
1970          * It may be possible that when we entered this function, xtime_nsec
1971          * was very small.  Further, if we're slightly speeding the clocksource
1972          * in the code above, its possible the required corrective factor to
1973          * xtime_nsec could cause it to underflow.
1974          *
1975          * Now, since we already accumulated the second, cannot simply roll
1976          * the accumulated second back, since the NTP subsystem has been
1977          * notified via second_overflow. So instead we push xtime_nsec forward
1978          * by the amount we underflowed, and add that amount into the error.
1979          *
1980          * We'll correct this error next time through this function, when
1981          * xtime_nsec is not as small.
1982          */
1983         if (unlikely((s64)tk->tkr_mono.xtime_nsec < 0)) {
1984                 s64 neg = -(s64)tk->tkr_mono.xtime_nsec;
1985                 tk->tkr_mono.xtime_nsec = 0;
1986                 tk->ntp_error += neg << tk->ntp_error_shift;
1987         }
1988 }
1989 
1990 /**
1991  * accumulate_nsecs_to_secs - Accumulates nsecs into secs
1992  *
1993  * Helper function that accumulates the nsecs greater than a second
1994  * from the xtime_nsec field to the xtime_secs field.
1995  * It also calls into the NTP code to handle leapsecond processing.
1996  *
1997  */
1998 static inline unsigned int accumulate_nsecs_to_secs(struct timekeeper *tk)
1999 {
2000         u64 nsecps = (u64)NSEC_PER_SEC << tk->tkr_mono.shift;
2001         unsigned int clock_set = 0;
2002 
2003         while (tk->tkr_mono.xtime_nsec >= nsecps) {
2004                 int leap;
2005 
2006                 tk->tkr_mono.xtime_nsec -= nsecps;
2007                 tk->xtime_sec++;
2008 
2009                 /* Figure out if its a leap sec and apply if needed */
2010                 leap = second_overflow(tk->xtime_sec);
2011                 if (unlikely(leap)) {
2012                         struct timespec64 ts;
2013 
2014                         tk->xtime_sec += leap;
2015 
2016                         ts.tv_sec = leap;
2017                         ts.tv_nsec = 0;
2018                         tk_set_wall_to_mono(tk,
2019                                 timespec64_sub(tk->wall_to_monotonic, ts));
2020 
2021                         __timekeeping_set_tai_offset(tk, tk->tai_offset - leap);
2022 
2023                         clock_set = TK_CLOCK_WAS_SET;
2024                 }
2025         }
2026         return clock_set;
2027 }
2028 
2029 /**
2030  * logarithmic_accumulation - shifted accumulation of cycles
2031  *
2032  * This functions accumulates a shifted interval of cycles into
2033  * into a shifted interval nanoseconds. Allows for O(log) accumulation
2034  * loop.
2035  *
2036  * Returns the unconsumed cycles.
2037  */
2038 static u64 logarithmic_accumulation(struct timekeeper *tk, u64 offset,
2039                                     u32 shift, unsigned int *clock_set)
2040 {
2041         u64 interval = tk->cycle_interval << shift;
2042         u64 snsec_per_sec;
2043 
2044         /* If the offset is smaller than a shifted interval, do nothing */
2045         if (offset < interval)
2046                 return offset;
2047 
2048         /* Accumulate one shifted interval */
2049         offset -= interval;
2050         tk->tkr_mono.cycle_last += interval;
2051         tk->tkr_raw.cycle_last  += interval;
2052 
2053         tk->tkr_mono.xtime_nsec += tk->xtime_interval << shift;
2054         *clock_set |= accumulate_nsecs_to_secs(tk);
2055 
2056         /* Accumulate raw time */
2057         tk->tkr_raw.xtime_nsec += tk->raw_interval << shift;
2058         snsec_per_sec = (u64)NSEC_PER_SEC << tk->tkr_raw.shift;
2059         while (tk->tkr_raw.xtime_nsec >= snsec_per_sec) {
2060                 tk->tkr_raw.xtime_nsec -= snsec_per_sec;
2061                 tk->raw_sec++;
2062         }
2063 
2064         /* Accumulate error between NTP and clock interval */
2065         tk->ntp_error += tk->ntp_tick << shift;
2066         tk->ntp_error -= (tk->xtime_interval + tk->xtime_remainder) <<
2067                                                 (tk->ntp_error_shift + shift);
2068 
2069         return offset;
2070 }
2071 
2072 /**
2073  * update_wall_time - Uses the current clocksource to increment the wall time
2074  *
2075  */
2076 void update_wall_time(void)
2077 {
2078         struct timekeeper *real_tk = &tk_core.timekeeper;
2079         struct timekeeper *tk = &shadow_timekeeper;
2080         u64 offset;
2081         int shift = 0, maxshift;
2082         unsigned int clock_set = 0;
2083         unsigned long flags;
2084 
2085         raw_spin_lock_irqsave(&timekeeper_lock, flags);
2086 
2087         /* Make sure we're fully resumed: */
2088         if (unlikely(timekeeping_suspended))
2089                 goto out;
2090 
2091 #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
2092         offset = real_tk->cycle_interval;
2093 #else
2094         offset = clocksource_delta(tk_clock_read(&tk->tkr_mono),
2095                                    tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
2096 #endif
2097 
2098         /* Check if there's really nothing to do */
2099         if (offset < real_tk->cycle_interval)
2100                 goto out;
2101 
2102         /* Do some additional sanity checking */
2103         timekeeping_check_update(tk, offset);
2104 
2105         /*
2106          * With NO_HZ we may have to accumulate many cycle_intervals
2107          * (think "ticks") worth of time at once. To do this efficiently,
2108          * we calculate the largest doubling multiple of cycle_intervals
2109          * that is smaller than the offset.  We then accumulate that
2110          * chunk in one go, and then try to consume the next smaller
2111          * doubled multiple.
2112          */
2113         shift = ilog2(offset) - ilog2(tk->cycle_interval);
2114         shift = max(0, shift);
2115         /* Bound shift to one less than what overflows tick_length */
2116         maxshift = (64 - (ilog2(ntp_tick_length())+1)) - 1;
2117         shift = min(shift, maxshift);
2118         while (offset >= tk->cycle_interval) {
2119                 offset = logarithmic_accumulation(tk, offset, shift,
2120                                                         &clock_set);
2121                 if (offset < tk->cycle_interval<<shift)
2122                         shift--;
2123         }
2124 
2125         /* correct the clock when NTP error is too big */
2126         timekeeping_adjust(tk, offset);
2127 
2128         /*
2129          * Finally, make sure that after the rounding
2130          * xtime_nsec isn't larger than NSEC_PER_SEC
2131          */
2132         clock_set |= accumulate_nsecs_to_secs(tk);
2133 
2134         write_seqcount_begin(&tk_core.seq);
2135         /*
2136          * Update the real timekeeper.
2137          *
2138          * We could avoid this memcpy by switching pointers, but that
2139          * requires changes to all other timekeeper usage sites as
2140          * well, i.e. move the timekeeper pointer getter into the
2141          * spinlocked/seqcount protected sections. And we trade this
2142          * memcpy under the tk_core.seq against one before we start
2143          * updating.
2144          */
2145         timekeeping_update(tk, clock_set);
2146         memcpy(real_tk, tk, sizeof(*tk));
2147         /* The memcpy must come last. Do not put anything here! */
2148         write_seqcount_end(&tk_core.seq);
2149 out:
2150         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2151         if (clock_set)
2152                 /* Have to call _delayed version, since in irq context*/
2153                 clock_was_set_delayed();
2154 }
2155 
2156 /**
2157  * getboottime64 - Return the real time of system boot.
2158  * @ts:         pointer to the timespec64 to be set
2159  *
2160  * Returns the wall-time of boot in a timespec64.
2161  *
2162  * This is based on the wall_to_monotonic offset and the total suspend
2163  * time. Calls to settimeofday will affect the value returned (which
2164  * basically means that however wrong your real time clock is at boot time,
2165  * you get the right time here).
2166  */
2167 void getboottime64(struct timespec64 *ts)
2168 {
2169         struct timekeeper *tk = &tk_core.timekeeper;
2170         ktime_t t = ktime_sub(tk->offs_real, tk->offs_boot);
2171 
2172         *ts = ktime_to_timespec64(t);
2173 }
2174 EXPORT_SYMBOL_GPL(getboottime64);
2175 
2176 unsigned long get_seconds(void)
2177 {
2178         struct timekeeper *tk = &tk_core.timekeeper;
2179 
2180         return tk->xtime_sec;
2181 }
2182 EXPORT_SYMBOL(get_seconds);
2183 
2184 struct timespec __current_kernel_time(void)
2185 {
2186         struct timekeeper *tk = &tk_core.timekeeper;
2187 
2188         return timespec64_to_timespec(tk_xtime(tk));
2189 }
2190 
2191 struct timespec64 current_kernel_time64(void)
2192 {
2193         struct timekeeper *tk = &tk_core.timekeeper;
2194         struct timespec64 now;
2195         unsigned long seq;
2196 
2197         do {
2198                 seq = read_seqcount_begin(&tk_core.seq);
2199 
2200                 now = tk_xtime(tk);
2201         } while (read_seqcount_retry(&tk_core.seq, seq));
2202 
2203         return now;
2204 }
2205 EXPORT_SYMBOL(current_kernel_time64);
2206 
2207 struct timespec64 get_monotonic_coarse64(void)
2208 {
2209         struct timekeeper *tk = &tk_core.timekeeper;
2210         struct timespec64 now, mono;
2211         unsigned long seq;
2212 
2213         do {
2214                 seq = read_seqcount_begin(&tk_core.seq);
2215 
2216                 now = tk_xtime(tk);
2217                 mono = tk->wall_to_monotonic;
2218         } while (read_seqcount_retry(&tk_core.seq, seq));
2219 
2220         set_normalized_timespec64(&now, now.tv_sec + mono.tv_sec,
2221                                 now.tv_nsec + mono.tv_nsec);
2222 
2223         return now;
2224 }
2225 EXPORT_SYMBOL(get_monotonic_coarse64);
2226 
2227 /*
2228  * Must hold jiffies_lock
2229  */
2230 void do_timer(unsigned long ticks)
2231 {
2232         jiffies_64 += ticks;
2233         calc_global_load(ticks);
2234 }
2235 
2236 /**
2237  * ktime_get_update_offsets_now - hrtimer helper
2238  * @cwsseq:     pointer to check and store the clock was set sequence number
2239  * @offs_real:  pointer to storage for monotonic -> realtime offset
2240  * @offs_boot:  pointer to storage for monotonic -> boottime offset
2241  * @offs_tai:   pointer to storage for monotonic -> clock tai offset
2242  *
2243  * Returns current monotonic time and updates the offsets if the
2244  * sequence number in @cwsseq and timekeeper.clock_was_set_seq are
2245  * different.
2246  *
2247  * Called from hrtimer_interrupt() or retrigger_next_event()
2248  */
2249 ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq, ktime_t *offs_real,
2250                                      ktime_t *offs_boot, ktime_t *offs_tai)
2251 {
2252         struct timekeeper *tk = &tk_core.timekeeper;
2253         unsigned int seq;
2254         ktime_t base;
2255         u64 nsecs;
2256 
2257         do {
2258                 seq = read_seqcount_begin(&tk_core.seq);
2259 
2260                 base = tk->tkr_mono.base;
2261                 nsecs = timekeeping_get_ns(&tk->tkr_mono);
2262                 base = ktime_add_ns(base, nsecs);
2263 
2264                 if (*cwsseq != tk->clock_was_set_seq) {
2265                         *cwsseq = tk->clock_was_set_seq;
2266                         *offs_real = tk->offs_real;
2267                         *offs_boot = tk->offs_boot;
2268                         *offs_tai = tk->offs_tai;
2269                 }
2270 
2271                 /* Handle leapsecond insertion adjustments */
2272                 if (unlikely(base >= tk->next_leap_ktime))
2273                         *offs_real = ktime_sub(tk->offs_real, ktime_set(1, 0));
2274 
2275         } while (read_seqcount_retry(&tk_core.seq, seq));
2276 
2277         return base;
2278 }
2279 
2280 /**
2281  * timekeeping_validate_timex - Ensures the timex is ok for use in do_adjtimex
2282  */
2283 static int timekeeping_validate_timex(struct timex *txc)
2284 {
2285         if (txc->modes & ADJ_ADJTIME) {
2286                 /* singleshot must not be used with any other mode bits */
2287                 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
2288                         return -EINVAL;
2289                 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
2290                     !capable(CAP_SYS_TIME))
2291                         return -EPERM;
2292                 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
2293                     !ccs_capable(CCS_SYS_SETTIME))
2294                         return -EPERM;
2295         } else {
2296                 /* In order to modify anything, you gotta be super-user! */
2297                 if (txc->modes && !capable(CAP_SYS_TIME))
2298                         return -EPERM;
2299                 if (txc->modes && !ccs_capable(CCS_SYS_SETTIME))
2300                         return -EPERM;
2301                 /*
2302                  * if the quartz is off by more than 10% then
2303                  * something is VERY wrong!
2304                  */
2305                 if (txc->modes & ADJ_TICK &&
2306                     (txc->tick <  900000/USER_HZ ||
2307                      txc->tick > 1100000/USER_HZ))
2308                         return -EINVAL;
2309         }
2310 
2311         if (txc->modes & ADJ_SETOFFSET) {
2312                 /* In order to inject time, you gotta be super-user! */
2313                 if (!capable(CAP_SYS_TIME))
2314                         return -EPERM;
2315                 if (!ccs_capable(CCS_SYS_SETTIME))
2316                         return -EPERM;
2317 
2318                 /*
2319                  * Validate if a timespec/timeval used to inject a time
2320                  * offset is valid.  Offsets can be postive or negative, so
2321                  * we don't check tv_sec. The value of the timeval/timespec
2322                  * is the sum of its fields,but *NOTE*:
2323                  * The field tv_usec/tv_nsec must always be non-negative and
2324                  * we can't have more nanoseconds/microseconds than a second.
2325                  */
2326                 if (txc->time.tv_usec < 0)
2327                         return -EINVAL;
2328 
2329                 if (txc->modes & ADJ_NANO) {
2330                         if (txc->time.tv_usec >= NSEC_PER_SEC)
2331                                 return -EINVAL;
2332                 } else {
2333                         if (txc->time.tv_usec >= USEC_PER_SEC)
2334                                 return -EINVAL;
2335                 }
2336         }
2337 
2338         /*
2339          * Check for potential multiplication overflows that can
2340          * only happen on 64-bit systems:
2341          */
2342         if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) {
2343                 if (LLONG_MIN / PPM_SCALE > txc->freq)
2344                         return -EINVAL;
2345                 if (LLONG_MAX / PPM_SCALE < txc->freq)
2346                         return -EINVAL;
2347         }
2348 
2349         return 0;
2350 }
2351 
2352 
2353 /**
2354  * do_adjtimex() - Accessor function to NTP __do_adjtimex function
2355  */
2356 int do_adjtimex(struct timex *txc)
2357 {
2358         struct timekeeper *tk = &tk_core.timekeeper;
2359         unsigned long flags;
2360         struct timespec64 ts;
2361         s32 orig_tai, tai;
2362         int ret;
2363 
2364         /* Validate the data before disabling interrupts */
2365         ret = timekeeping_validate_timex(txc);
2366         if (ret)
2367                 return ret;
2368 
2369         if (txc->modes & ADJ_SETOFFSET) {
2370                 struct timespec64 delta;
2371                 delta.tv_sec  = txc->time.tv_sec;
2372                 delta.tv_nsec = txc->time.tv_usec;
2373                 if (!(txc->modes & ADJ_NANO))
2374                         delta.tv_nsec *= 1000;
2375                 ret = timekeeping_inject_offset(&delta);
2376                 if (ret)
2377                         return ret;
2378         }
2379 
2380         getnstimeofday64(&ts);
2381 
2382         raw_spin_lock_irqsave(&timekeeper_lock, flags);
2383         write_seqcount_begin(&tk_core.seq);
2384 
2385         orig_tai = tai = tk->tai_offset;
2386         ret = __do_adjtimex(txc, &ts, &tai);
2387 
2388         if (tai != orig_tai) {
2389                 __timekeeping_set_tai_offset(tk, tai);
2390                 timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
2391         }
2392         tk_update_leap_state(tk);
2393 
2394         write_seqcount_end(&tk_core.seq);
2395         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2396 
2397         if (tai != orig_tai)
2398                 clock_was_set();
2399 
2400         ntp_notify_cmos_timer();
2401 
2402         return ret;
2403 }
2404 
2405 #ifdef CONFIG_NTP_PPS
2406 /**
2407  * hardpps() - Accessor function to NTP __hardpps function
2408  */
2409 void hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
2410 {
2411         unsigned long flags;
2412 
2413         raw_spin_lock_irqsave(&timekeeper_lock, flags);
2414         write_seqcount_begin(&tk_core.seq);
2415 
2416         __hardpps(phase_ts, raw_ts);
2417 
2418         write_seqcount_end(&tk_core.seq);
2419         raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2420 }
2421 EXPORT_SYMBOL(hardpps);
2422 #endif /* CONFIG_NTP_PPS */
2423 
2424 /**
2425  * xtime_update() - advances the timekeeping infrastructure
2426  * @ticks:      number of ticks, that have elapsed since the last call.
2427  *
2428  * Must be called with interrupts disabled.
2429  */
2430 void xtime_update(unsigned long ticks)
2431 {
2432         write_seqlock(&jiffies_lock);
2433         do_timer(ticks);
2434         write_sequnlock(&jiffies_lock);
2435         update_wall_time();
2436 }
2437 

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