xref: /linux/kernel/time/timekeeping.c (revision daa121128a2d2ac6006159e2c47676e4fcd21eab)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  Kernel timekeeping code and accessor functions. Based on code from
4  *  timer.c, moved in commit 8524070b7982.
5  */
6 #include <linux/timekeeper_internal.h>
7 #include <linux/module.h>
8 #include <linux/interrupt.h>
9 #include <linux/percpu.h>
10 #include <linux/init.h>
11 #include <linux/mm.h>
12 #include <linux/nmi.h>
13 #include <linux/sched.h>
14 #include <linux/sched/loadavg.h>
15 #include <linux/sched/clock.h>
16 #include <linux/syscore_ops.h>
17 #include <linux/clocksource.h>
18 #include <linux/jiffies.h>
19 #include <linux/time.h>
20 #include <linux/timex.h>
21 #include <linux/tick.h>
22 #include <linux/stop_machine.h>
23 #include <linux/pvclock_gtod.h>
24 #include <linux/compiler.h>
25 #include <linux/audit.h>
26 #include <linux/random.h>
27 
28 #include "tick-internal.h"
29 #include "ntp_internal.h"
30 #include "timekeeping_internal.h"
31 
32 #define TK_CLEAR_NTP		(1 << 0)
33 #define TK_MIRROR		(1 << 1)
34 #define TK_CLOCK_WAS_SET	(1 << 2)
35 
36 enum timekeeping_adv_mode {
37 	/* Update timekeeper when a tick has passed */
38 	TK_ADV_TICK,
39 
40 	/* Update timekeeper on a direct frequency change */
41 	TK_ADV_FREQ
42 };
43 
44 DEFINE_RAW_SPINLOCK(timekeeper_lock);
45 
46 /*
47  * The most important data for readout fits into a single 64 byte
48  * cache line.
49  */
50 static struct {
51 	seqcount_raw_spinlock_t	seq;
52 	struct timekeeper	timekeeper;
53 } tk_core ____cacheline_aligned = {
54 	.seq = SEQCNT_RAW_SPINLOCK_ZERO(tk_core.seq, &timekeeper_lock),
55 };
56 
57 static struct timekeeper shadow_timekeeper;
58 
59 /* flag for if timekeeping is suspended */
60 int __read_mostly timekeeping_suspended;
61 
62 /**
63  * struct tk_fast - NMI safe timekeeper
64  * @seq:	Sequence counter for protecting updates. The lowest bit
65  *		is the index for the tk_read_base array
66  * @base:	tk_read_base array. Access is indexed by the lowest bit of
67  *		@seq.
68  *
69  * See @update_fast_timekeeper() below.
70  */
71 struct tk_fast {
72 	seqcount_latch_t	seq;
73 	struct tk_read_base	base[2];
74 };
75 
76 /* Suspend-time cycles value for halted fast timekeeper. */
77 static u64 cycles_at_suspend;
78 
79 static u64 dummy_clock_read(struct clocksource *cs)
80 {
81 	if (timekeeping_suspended)
82 		return cycles_at_suspend;
83 	return local_clock();
84 }
85 
86 static struct clocksource dummy_clock = {
87 	.read = dummy_clock_read,
88 };
89 
90 /*
91  * Boot time initialization which allows local_clock() to be utilized
92  * during early boot when clocksources are not available. local_clock()
93  * returns nanoseconds already so no conversion is required, hence mult=1
94  * and shift=0. When the first proper clocksource is installed then
95  * the fast time keepers are updated with the correct values.
96  */
97 #define FAST_TK_INIT						\
98 	{							\
99 		.clock		= &dummy_clock,			\
100 		.mask		= CLOCKSOURCE_MASK(64),		\
101 		.mult		= 1,				\
102 		.shift		= 0,				\
103 	}
104 
105 static struct tk_fast tk_fast_mono ____cacheline_aligned = {
106 	.seq     = SEQCNT_LATCH_ZERO(tk_fast_mono.seq),
107 	.base[0] = FAST_TK_INIT,
108 	.base[1] = FAST_TK_INIT,
109 };
110 
111 static struct tk_fast tk_fast_raw  ____cacheline_aligned = {
112 	.seq     = SEQCNT_LATCH_ZERO(tk_fast_raw.seq),
113 	.base[0] = FAST_TK_INIT,
114 	.base[1] = FAST_TK_INIT,
115 };
116 
117 static inline void tk_normalize_xtime(struct timekeeper *tk)
118 {
119 	while (tk->tkr_mono.xtime_nsec >= ((u64)NSEC_PER_SEC << tk->tkr_mono.shift)) {
120 		tk->tkr_mono.xtime_nsec -= (u64)NSEC_PER_SEC << tk->tkr_mono.shift;
121 		tk->xtime_sec++;
122 	}
123 	while (tk->tkr_raw.xtime_nsec >= ((u64)NSEC_PER_SEC << tk->tkr_raw.shift)) {
124 		tk->tkr_raw.xtime_nsec -= (u64)NSEC_PER_SEC << tk->tkr_raw.shift;
125 		tk->raw_sec++;
126 	}
127 }
128 
129 static inline struct timespec64 tk_xtime(const struct timekeeper *tk)
130 {
131 	struct timespec64 ts;
132 
133 	ts.tv_sec = tk->xtime_sec;
134 	ts.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
135 	return ts;
136 }
137 
138 static void tk_set_xtime(struct timekeeper *tk, const struct timespec64 *ts)
139 {
140 	tk->xtime_sec = ts->tv_sec;
141 	tk->tkr_mono.xtime_nsec = (u64)ts->tv_nsec << tk->tkr_mono.shift;
142 }
143 
144 static void tk_xtime_add(struct timekeeper *tk, const struct timespec64 *ts)
145 {
146 	tk->xtime_sec += ts->tv_sec;
147 	tk->tkr_mono.xtime_nsec += (u64)ts->tv_nsec << tk->tkr_mono.shift;
148 	tk_normalize_xtime(tk);
149 }
150 
151 static void tk_set_wall_to_mono(struct timekeeper *tk, struct timespec64 wtm)
152 {
153 	struct timespec64 tmp;
154 
155 	/*
156 	 * Verify consistency of: offset_real = -wall_to_monotonic
157 	 * before modifying anything
158 	 */
159 	set_normalized_timespec64(&tmp, -tk->wall_to_monotonic.tv_sec,
160 					-tk->wall_to_monotonic.tv_nsec);
161 	WARN_ON_ONCE(tk->offs_real != timespec64_to_ktime(tmp));
162 	tk->wall_to_monotonic = wtm;
163 	set_normalized_timespec64(&tmp, -wtm.tv_sec, -wtm.tv_nsec);
164 	tk->offs_real = timespec64_to_ktime(tmp);
165 	tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tk->tai_offset, 0));
166 }
167 
168 static inline void tk_update_sleep_time(struct timekeeper *tk, ktime_t delta)
169 {
170 	tk->offs_boot = ktime_add(tk->offs_boot, delta);
171 	/*
172 	 * Timespec representation for VDSO update to avoid 64bit division
173 	 * on every update.
174 	 */
175 	tk->monotonic_to_boot = ktime_to_timespec64(tk->offs_boot);
176 }
177 
178 /*
179  * tk_clock_read - atomic clocksource read() helper
180  *
181  * This helper is necessary to use in the read paths because, while the
182  * seqcount ensures we don't return a bad value while structures are updated,
183  * it doesn't protect from potential crashes. There is the possibility that
184  * the tkr's clocksource may change between the read reference, and the
185  * clock reference passed to the read function.  This can cause crashes if
186  * the wrong clocksource is passed to the wrong read function.
187  * This isn't necessary to use when holding the timekeeper_lock or doing
188  * a read of the fast-timekeeper tkrs (which is protected by its own locking
189  * and update logic).
190  */
191 static inline u64 tk_clock_read(const struct tk_read_base *tkr)
192 {
193 	struct clocksource *clock = READ_ONCE(tkr->clock);
194 
195 	return clock->read(clock);
196 }
197 
198 #ifdef CONFIG_DEBUG_TIMEKEEPING
199 #define WARNING_FREQ (HZ*300) /* 5 minute rate-limiting */
200 
201 static void timekeeping_check_update(struct timekeeper *tk, u64 offset)
202 {
203 
204 	u64 max_cycles = tk->tkr_mono.clock->max_cycles;
205 	const char *name = tk->tkr_mono.clock->name;
206 
207 	if (offset > max_cycles) {
208 		printk_deferred("WARNING: timekeeping: Cycle offset (%lld) is larger than allowed by the '%s' clock's max_cycles value (%lld): time overflow danger\n",
209 				offset, name, max_cycles);
210 		printk_deferred("         timekeeping: Your kernel is sick, but tries to cope by capping time updates\n");
211 	} else {
212 		if (offset > (max_cycles >> 1)) {
213 			printk_deferred("INFO: timekeeping: Cycle offset (%lld) is larger than the '%s' clock's 50%% safety margin (%lld)\n",
214 					offset, name, max_cycles >> 1);
215 			printk_deferred("      timekeeping: Your kernel is still fine, but is feeling a bit nervous\n");
216 		}
217 	}
218 
219 	if (tk->underflow_seen) {
220 		if (jiffies - tk->last_warning > WARNING_FREQ) {
221 			printk_deferred("WARNING: Underflow in clocksource '%s' observed, time update ignored.\n", name);
222 			printk_deferred("         Please report this, consider using a different clocksource, if possible.\n");
223 			printk_deferred("         Your kernel is probably still fine.\n");
224 			tk->last_warning = jiffies;
225 		}
226 		tk->underflow_seen = 0;
227 	}
228 
229 	if (tk->overflow_seen) {
230 		if (jiffies - tk->last_warning > WARNING_FREQ) {
231 			printk_deferred("WARNING: Overflow in clocksource '%s' observed, time update capped.\n", name);
232 			printk_deferred("         Please report this, consider using a different clocksource, if possible.\n");
233 			printk_deferred("         Your kernel is probably still fine.\n");
234 			tk->last_warning = jiffies;
235 		}
236 		tk->overflow_seen = 0;
237 	}
238 }
239 
240 static inline u64 timekeeping_cycles_to_ns(const struct tk_read_base *tkr, u64 cycles);
241 
242 static inline u64 timekeeping_debug_get_ns(const struct tk_read_base *tkr)
243 {
244 	struct timekeeper *tk = &tk_core.timekeeper;
245 	u64 now, last, mask, max, delta;
246 	unsigned int seq;
247 
248 	/*
249 	 * Since we're called holding a seqcount, the data may shift
250 	 * under us while we're doing the calculation. This can cause
251 	 * false positives, since we'd note a problem but throw the
252 	 * results away. So nest another seqcount here to atomically
253 	 * grab the points we are checking with.
254 	 */
255 	do {
256 		seq = read_seqcount_begin(&tk_core.seq);
257 		now = tk_clock_read(tkr);
258 		last = tkr->cycle_last;
259 		mask = tkr->mask;
260 		max = tkr->clock->max_cycles;
261 	} while (read_seqcount_retry(&tk_core.seq, seq));
262 
263 	delta = clocksource_delta(now, last, mask);
264 
265 	/*
266 	 * Try to catch underflows by checking if we are seeing small
267 	 * mask-relative negative values.
268 	 */
269 	if (unlikely((~delta & mask) < (mask >> 3)))
270 		tk->underflow_seen = 1;
271 
272 	/* Check for multiplication overflows */
273 	if (unlikely(delta > max))
274 		tk->overflow_seen = 1;
275 
276 	/* timekeeping_cycles_to_ns() handles both under and overflow */
277 	return timekeeping_cycles_to_ns(tkr, now);
278 }
279 #else
280 static inline void timekeeping_check_update(struct timekeeper *tk, u64 offset)
281 {
282 }
283 static inline u64 timekeeping_debug_get_ns(const struct tk_read_base *tkr)
284 {
285 	BUG();
286 }
287 #endif
288 
289 /**
290  * tk_setup_internals - Set up internals to use clocksource clock.
291  *
292  * @tk:		The target timekeeper to setup.
293  * @clock:		Pointer to clocksource.
294  *
295  * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
296  * pair and interval request.
297  *
298  * Unless you're the timekeeping code, you should not be using this!
299  */
300 static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
301 {
302 	u64 interval;
303 	u64 tmp, ntpinterval;
304 	struct clocksource *old_clock;
305 
306 	++tk->cs_was_changed_seq;
307 	old_clock = tk->tkr_mono.clock;
308 	tk->tkr_mono.clock = clock;
309 	tk->tkr_mono.mask = clock->mask;
310 	tk->tkr_mono.cycle_last = tk_clock_read(&tk->tkr_mono);
311 
312 	tk->tkr_raw.clock = clock;
313 	tk->tkr_raw.mask = clock->mask;
314 	tk->tkr_raw.cycle_last = tk->tkr_mono.cycle_last;
315 
316 	/* Do the ns -> cycle conversion first, using original mult */
317 	tmp = NTP_INTERVAL_LENGTH;
318 	tmp <<= clock->shift;
319 	ntpinterval = tmp;
320 	tmp += clock->mult/2;
321 	do_div(tmp, clock->mult);
322 	if (tmp == 0)
323 		tmp = 1;
324 
325 	interval = (u64) tmp;
326 	tk->cycle_interval = interval;
327 
328 	/* Go back from cycles -> shifted ns */
329 	tk->xtime_interval = interval * clock->mult;
330 	tk->xtime_remainder = ntpinterval - tk->xtime_interval;
331 	tk->raw_interval = interval * clock->mult;
332 
333 	 /* if changing clocks, convert xtime_nsec shift units */
334 	if (old_clock) {
335 		int shift_change = clock->shift - old_clock->shift;
336 		if (shift_change < 0) {
337 			tk->tkr_mono.xtime_nsec >>= -shift_change;
338 			tk->tkr_raw.xtime_nsec >>= -shift_change;
339 		} else {
340 			tk->tkr_mono.xtime_nsec <<= shift_change;
341 			tk->tkr_raw.xtime_nsec <<= shift_change;
342 		}
343 	}
344 
345 	tk->tkr_mono.shift = clock->shift;
346 	tk->tkr_raw.shift = clock->shift;
347 
348 	tk->ntp_error = 0;
349 	tk->ntp_error_shift = NTP_SCALE_SHIFT - clock->shift;
350 	tk->ntp_tick = ntpinterval << tk->ntp_error_shift;
351 
352 	/*
353 	 * The timekeeper keeps its own mult values for the currently
354 	 * active clocksource. These value will be adjusted via NTP
355 	 * to counteract clock drifting.
356 	 */
357 	tk->tkr_mono.mult = clock->mult;
358 	tk->tkr_raw.mult = clock->mult;
359 	tk->ntp_err_mult = 0;
360 	tk->skip_second_overflow = 0;
361 }
362 
363 /* Timekeeper helper functions. */
364 static noinline u64 delta_to_ns_safe(const struct tk_read_base *tkr, u64 delta)
365 {
366 	return mul_u64_u32_add_u64_shr(delta, tkr->mult, tkr->xtime_nsec, tkr->shift);
367 }
368 
369 static inline u64 timekeeping_cycles_to_ns(const struct tk_read_base *tkr, u64 cycles)
370 {
371 	/* Calculate the delta since the last update_wall_time() */
372 	u64 mask = tkr->mask, delta = (cycles - tkr->cycle_last) & mask;
373 
374 	/*
375 	 * This detects both negative motion and the case where the delta
376 	 * overflows the multiplication with tkr->mult.
377 	 */
378 	if (unlikely(delta > tkr->clock->max_cycles)) {
379 		/*
380 		 * Handle clocksource inconsistency between CPUs to prevent
381 		 * time from going backwards by checking for the MSB of the
382 		 * mask being set in the delta.
383 		 */
384 		if (delta & ~(mask >> 1))
385 			return tkr->xtime_nsec >> tkr->shift;
386 
387 		return delta_to_ns_safe(tkr, delta);
388 	}
389 
390 	return ((delta * tkr->mult) + tkr->xtime_nsec) >> tkr->shift;
391 }
392 
393 static __always_inline u64 __timekeeping_get_ns(const struct tk_read_base *tkr)
394 {
395 	return timekeeping_cycles_to_ns(tkr, tk_clock_read(tkr));
396 }
397 
398 static inline u64 timekeeping_get_ns(const struct tk_read_base *tkr)
399 {
400 	if (IS_ENABLED(CONFIG_DEBUG_TIMEKEEPING))
401 		return timekeeping_debug_get_ns(tkr);
402 
403 	return __timekeeping_get_ns(tkr);
404 }
405 
406 /**
407  * update_fast_timekeeper - Update the fast and NMI safe monotonic timekeeper.
408  * @tkr: Timekeeping readout base from which we take the update
409  * @tkf: Pointer to NMI safe timekeeper
410  *
411  * We want to use this from any context including NMI and tracing /
412  * instrumenting the timekeeping code itself.
413  *
414  * Employ the latch technique; see @raw_write_seqcount_latch.
415  *
416  * So if a NMI hits the update of base[0] then it will use base[1]
417  * which is still consistent. In the worst case this can result is a
418  * slightly wrong timestamp (a few nanoseconds). See
419  * @ktime_get_mono_fast_ns.
420  */
421 static void update_fast_timekeeper(const struct tk_read_base *tkr,
422 				   struct tk_fast *tkf)
423 {
424 	struct tk_read_base *base = tkf->base;
425 
426 	/* Force readers off to base[1] */
427 	raw_write_seqcount_latch(&tkf->seq);
428 
429 	/* Update base[0] */
430 	memcpy(base, tkr, sizeof(*base));
431 
432 	/* Force readers back to base[0] */
433 	raw_write_seqcount_latch(&tkf->seq);
434 
435 	/* Update base[1] */
436 	memcpy(base + 1, base, sizeof(*base));
437 }
438 
439 static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
440 {
441 	struct tk_read_base *tkr;
442 	unsigned int seq;
443 	u64 now;
444 
445 	do {
446 		seq = raw_read_seqcount_latch(&tkf->seq);
447 		tkr = tkf->base + (seq & 0x01);
448 		now = ktime_to_ns(tkr->base);
449 		now += __timekeeping_get_ns(tkr);
450 	} while (raw_read_seqcount_latch_retry(&tkf->seq, seq));
451 
452 	return now;
453 }
454 
455 /**
456  * ktime_get_mono_fast_ns - Fast NMI safe access to clock monotonic
457  *
458  * This timestamp is not guaranteed to be monotonic across an update.
459  * The timestamp is calculated by:
460  *
461  *	now = base_mono + clock_delta * slope
462  *
463  * So if the update lowers the slope, readers who are forced to the
464  * not yet updated second array are still using the old steeper slope.
465  *
466  * tmono
467  * ^
468  * |    o  n
469  * |   o n
470  * |  u
471  * | o
472  * |o
473  * |12345678---> reader order
474  *
475  * o = old slope
476  * u = update
477  * n = new slope
478  *
479  * So reader 6 will observe time going backwards versus reader 5.
480  *
481  * While other CPUs are likely to be able to observe that, the only way
482  * for a CPU local observation is when an NMI hits in the middle of
483  * the update. Timestamps taken from that NMI context might be ahead
484  * of the following timestamps. Callers need to be aware of that and
485  * deal with it.
486  */
487 u64 notrace ktime_get_mono_fast_ns(void)
488 {
489 	return __ktime_get_fast_ns(&tk_fast_mono);
490 }
491 EXPORT_SYMBOL_GPL(ktime_get_mono_fast_ns);
492 
493 /**
494  * ktime_get_raw_fast_ns - Fast NMI safe access to clock monotonic raw
495  *
496  * Contrary to ktime_get_mono_fast_ns() this is always correct because the
497  * conversion factor is not affected by NTP/PTP correction.
498  */
499 u64 notrace ktime_get_raw_fast_ns(void)
500 {
501 	return __ktime_get_fast_ns(&tk_fast_raw);
502 }
503 EXPORT_SYMBOL_GPL(ktime_get_raw_fast_ns);
504 
505 /**
506  * ktime_get_boot_fast_ns - NMI safe and fast access to boot clock.
507  *
508  * To keep it NMI safe since we're accessing from tracing, we're not using a
509  * separate timekeeper with updates to monotonic clock and boot offset
510  * protected with seqcounts. This has the following minor side effects:
511  *
512  * (1) Its possible that a timestamp be taken after the boot offset is updated
513  * but before the timekeeper is updated. If this happens, the new boot offset
514  * is added to the old timekeeping making the clock appear to update slightly
515  * earlier:
516  *    CPU 0                                        CPU 1
517  *    timekeeping_inject_sleeptime64()
518  *    __timekeeping_inject_sleeptime(tk, delta);
519  *                                                 timestamp();
520  *    timekeeping_update(tk, TK_CLEAR_NTP...);
521  *
522  * (2) On 32-bit systems, the 64-bit boot offset (tk->offs_boot) may be
523  * partially updated.  Since the tk->offs_boot update is a rare event, this
524  * should be a rare occurrence which postprocessing should be able to handle.
525  *
526  * The caveats vs. timestamp ordering as documented for ktime_get_mono_fast_ns()
527  * apply as well.
528  */
529 u64 notrace ktime_get_boot_fast_ns(void)
530 {
531 	struct timekeeper *tk = &tk_core.timekeeper;
532 
533 	return (ktime_get_mono_fast_ns() + ktime_to_ns(data_race(tk->offs_boot)));
534 }
535 EXPORT_SYMBOL_GPL(ktime_get_boot_fast_ns);
536 
537 /**
538  * ktime_get_tai_fast_ns - NMI safe and fast access to tai clock.
539  *
540  * The same limitations as described for ktime_get_boot_fast_ns() apply. The
541  * mono time and the TAI offset are not read atomically which may yield wrong
542  * readouts. However, an update of the TAI offset is an rare event e.g., caused
543  * by settime or adjtimex with an offset. The user of this function has to deal
544  * with the possibility of wrong timestamps in post processing.
545  */
546 u64 notrace ktime_get_tai_fast_ns(void)
547 {
548 	struct timekeeper *tk = &tk_core.timekeeper;
549 
550 	return (ktime_get_mono_fast_ns() + ktime_to_ns(data_race(tk->offs_tai)));
551 }
552 EXPORT_SYMBOL_GPL(ktime_get_tai_fast_ns);
553 
554 static __always_inline u64 __ktime_get_real_fast(struct tk_fast *tkf, u64 *mono)
555 {
556 	struct tk_read_base *tkr;
557 	u64 basem, baser, delta;
558 	unsigned int seq;
559 
560 	do {
561 		seq = raw_read_seqcount_latch(&tkf->seq);
562 		tkr = tkf->base + (seq & 0x01);
563 		basem = ktime_to_ns(tkr->base);
564 		baser = ktime_to_ns(tkr->base_real);
565 		delta = __timekeeping_get_ns(tkr);
566 	} while (raw_read_seqcount_latch_retry(&tkf->seq, seq));
567 
568 	if (mono)
569 		*mono = basem + delta;
570 	return baser + delta;
571 }
572 
573 /**
574  * ktime_get_real_fast_ns: - NMI safe and fast access to clock realtime.
575  *
576  * See ktime_get_mono_fast_ns() for documentation of the time stamp ordering.
577  */
578 u64 ktime_get_real_fast_ns(void)
579 {
580 	return __ktime_get_real_fast(&tk_fast_mono, NULL);
581 }
582 EXPORT_SYMBOL_GPL(ktime_get_real_fast_ns);
583 
584 /**
585  * ktime_get_fast_timestamps: - NMI safe timestamps
586  * @snapshot:	Pointer to timestamp storage
587  *
588  * Stores clock monotonic, boottime and realtime timestamps.
589  *
590  * Boot time is a racy access on 32bit systems if the sleep time injection
591  * happens late during resume and not in timekeeping_resume(). That could
592  * be avoided by expanding struct tk_read_base with boot offset for 32bit
593  * and adding more overhead to the update. As this is a hard to observe
594  * once per resume event which can be filtered with reasonable effort using
595  * the accurate mono/real timestamps, it's probably not worth the trouble.
596  *
597  * Aside of that it might be possible on 32 and 64 bit to observe the
598  * following when the sleep time injection happens late:
599  *
600  * CPU 0				CPU 1
601  * timekeeping_resume()
602  * ktime_get_fast_timestamps()
603  *	mono, real = __ktime_get_real_fast()
604  *					inject_sleep_time()
605  *					   update boot offset
606  *	boot = mono + bootoffset;
607  *
608  * That means that boot time already has the sleep time adjustment, but
609  * real time does not. On the next readout both are in sync again.
610  *
611  * Preventing this for 64bit is not really feasible without destroying the
612  * careful cache layout of the timekeeper because the sequence count and
613  * struct tk_read_base would then need two cache lines instead of one.
614  *
615  * Access to the time keeper clock source is disabled across the innermost
616  * steps of suspend/resume. The accessors still work, but the timestamps
617  * are frozen until time keeping is resumed which happens very early.
618  *
619  * For regular suspend/resume there is no observable difference vs. sched
620  * clock, but it might affect some of the nasty low level debug printks.
621  *
622  * OTOH, access to sched clock is not guaranteed across suspend/resume on
623  * all systems either so it depends on the hardware in use.
624  *
625  * If that turns out to be a real problem then this could be mitigated by
626  * using sched clock in a similar way as during early boot. But it's not as
627  * trivial as on early boot because it needs some careful protection
628  * against the clock monotonic timestamp jumping backwards on resume.
629  */
630 void ktime_get_fast_timestamps(struct ktime_timestamps *snapshot)
631 {
632 	struct timekeeper *tk = &tk_core.timekeeper;
633 
634 	snapshot->real = __ktime_get_real_fast(&tk_fast_mono, &snapshot->mono);
635 	snapshot->boot = snapshot->mono + ktime_to_ns(data_race(tk->offs_boot));
636 }
637 
638 /**
639  * halt_fast_timekeeper - Prevent fast timekeeper from accessing clocksource.
640  * @tk: Timekeeper to snapshot.
641  *
642  * It generally is unsafe to access the clocksource after timekeeping has been
643  * suspended, so take a snapshot of the readout base of @tk and use it as the
644  * fast timekeeper's readout base while suspended.  It will return the same
645  * number of cycles every time until timekeeping is resumed at which time the
646  * proper readout base for the fast timekeeper will be restored automatically.
647  */
648 static void halt_fast_timekeeper(const struct timekeeper *tk)
649 {
650 	static struct tk_read_base tkr_dummy;
651 	const struct tk_read_base *tkr = &tk->tkr_mono;
652 
653 	memcpy(&tkr_dummy, tkr, sizeof(tkr_dummy));
654 	cycles_at_suspend = tk_clock_read(tkr);
655 	tkr_dummy.clock = &dummy_clock;
656 	tkr_dummy.base_real = tkr->base + tk->offs_real;
657 	update_fast_timekeeper(&tkr_dummy, &tk_fast_mono);
658 
659 	tkr = &tk->tkr_raw;
660 	memcpy(&tkr_dummy, tkr, sizeof(tkr_dummy));
661 	tkr_dummy.clock = &dummy_clock;
662 	update_fast_timekeeper(&tkr_dummy, &tk_fast_raw);
663 }
664 
665 static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);
666 
667 static void update_pvclock_gtod(struct timekeeper *tk, bool was_set)
668 {
669 	raw_notifier_call_chain(&pvclock_gtod_chain, was_set, tk);
670 }
671 
672 /**
673  * pvclock_gtod_register_notifier - register a pvclock timedata update listener
674  * @nb: Pointer to the notifier block to register
675  */
676 int pvclock_gtod_register_notifier(struct notifier_block *nb)
677 {
678 	struct timekeeper *tk = &tk_core.timekeeper;
679 	unsigned long flags;
680 	int ret;
681 
682 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
683 	ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);
684 	update_pvclock_gtod(tk, true);
685 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
686 
687 	return ret;
688 }
689 EXPORT_SYMBOL_GPL(pvclock_gtod_register_notifier);
690 
691 /**
692  * pvclock_gtod_unregister_notifier - unregister a pvclock
693  * timedata update listener
694  * @nb: Pointer to the notifier block to unregister
695  */
696 int pvclock_gtod_unregister_notifier(struct notifier_block *nb)
697 {
698 	unsigned long flags;
699 	int ret;
700 
701 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
702 	ret = raw_notifier_chain_unregister(&pvclock_gtod_chain, nb);
703 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
704 
705 	return ret;
706 }
707 EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);
708 
709 /*
710  * tk_update_leap_state - helper to update the next_leap_ktime
711  */
712 static inline void tk_update_leap_state(struct timekeeper *tk)
713 {
714 	tk->next_leap_ktime = ntp_get_next_leap();
715 	if (tk->next_leap_ktime != KTIME_MAX)
716 		/* Convert to monotonic time */
717 		tk->next_leap_ktime = ktime_sub(tk->next_leap_ktime, tk->offs_real);
718 }
719 
720 /*
721  * Update the ktime_t based scalar nsec members of the timekeeper
722  */
723 static inline void tk_update_ktime_data(struct timekeeper *tk)
724 {
725 	u64 seconds;
726 	u32 nsec;
727 
728 	/*
729 	 * The xtime based monotonic readout is:
730 	 *	nsec = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec + now();
731 	 * The ktime based monotonic readout is:
732 	 *	nsec = base_mono + now();
733 	 * ==> base_mono = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec
734 	 */
735 	seconds = (u64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec);
736 	nsec = (u32) tk->wall_to_monotonic.tv_nsec;
737 	tk->tkr_mono.base = ns_to_ktime(seconds * NSEC_PER_SEC + nsec);
738 
739 	/*
740 	 * The sum of the nanoseconds portions of xtime and
741 	 * wall_to_monotonic can be greater/equal one second. Take
742 	 * this into account before updating tk->ktime_sec.
743 	 */
744 	nsec += (u32)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
745 	if (nsec >= NSEC_PER_SEC)
746 		seconds++;
747 	tk->ktime_sec = seconds;
748 
749 	/* Update the monotonic raw base */
750 	tk->tkr_raw.base = ns_to_ktime(tk->raw_sec * NSEC_PER_SEC);
751 }
752 
753 /* must hold timekeeper_lock */
754 static void timekeeping_update(struct timekeeper *tk, unsigned int action)
755 {
756 	if (action & TK_CLEAR_NTP) {
757 		tk->ntp_error = 0;
758 		ntp_clear();
759 	}
760 
761 	tk_update_leap_state(tk);
762 	tk_update_ktime_data(tk);
763 
764 	update_vsyscall(tk);
765 	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
766 
767 	tk->tkr_mono.base_real = tk->tkr_mono.base + tk->offs_real;
768 	update_fast_timekeeper(&tk->tkr_mono, &tk_fast_mono);
769 	update_fast_timekeeper(&tk->tkr_raw,  &tk_fast_raw);
770 
771 	if (action & TK_CLOCK_WAS_SET)
772 		tk->clock_was_set_seq++;
773 	/*
774 	 * The mirroring of the data to the shadow-timekeeper needs
775 	 * to happen last here to ensure we don't over-write the
776 	 * timekeeper structure on the next update with stale data
777 	 */
778 	if (action & TK_MIRROR)
779 		memcpy(&shadow_timekeeper, &tk_core.timekeeper,
780 		       sizeof(tk_core.timekeeper));
781 }
782 
783 /**
784  * timekeeping_forward_now - update clock to the current time
785  * @tk:		Pointer to the timekeeper to update
786  *
787  * Forward the current clock to update its state since the last call to
788  * update_wall_time(). This is useful before significant clock changes,
789  * as it avoids having to deal with this time offset explicitly.
790  */
791 static void timekeeping_forward_now(struct timekeeper *tk)
792 {
793 	u64 cycle_now, delta;
794 
795 	cycle_now = tk_clock_read(&tk->tkr_mono);
796 	delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
797 	tk->tkr_mono.cycle_last = cycle_now;
798 	tk->tkr_raw.cycle_last  = cycle_now;
799 
800 	while (delta > 0) {
801 		u64 max = tk->tkr_mono.clock->max_cycles;
802 		u64 incr = delta < max ? delta : max;
803 
804 		tk->tkr_mono.xtime_nsec += incr * tk->tkr_mono.mult;
805 		tk->tkr_raw.xtime_nsec += incr * tk->tkr_raw.mult;
806 		tk_normalize_xtime(tk);
807 		delta -= incr;
808 	}
809 }
810 
811 /**
812  * ktime_get_real_ts64 - Returns the time of day in a timespec64.
813  * @ts:		pointer to the timespec to be set
814  *
815  * Returns the time of day in a timespec64 (WARN if suspended).
816  */
817 void ktime_get_real_ts64(struct timespec64 *ts)
818 {
819 	struct timekeeper *tk = &tk_core.timekeeper;
820 	unsigned int seq;
821 	u64 nsecs;
822 
823 	WARN_ON(timekeeping_suspended);
824 
825 	do {
826 		seq = read_seqcount_begin(&tk_core.seq);
827 
828 		ts->tv_sec = tk->xtime_sec;
829 		nsecs = timekeeping_get_ns(&tk->tkr_mono);
830 
831 	} while (read_seqcount_retry(&tk_core.seq, seq));
832 
833 	ts->tv_nsec = 0;
834 	timespec64_add_ns(ts, nsecs);
835 }
836 EXPORT_SYMBOL(ktime_get_real_ts64);
837 
838 ktime_t ktime_get(void)
839 {
840 	struct timekeeper *tk = &tk_core.timekeeper;
841 	unsigned int seq;
842 	ktime_t base;
843 	u64 nsecs;
844 
845 	WARN_ON(timekeeping_suspended);
846 
847 	do {
848 		seq = read_seqcount_begin(&tk_core.seq);
849 		base = tk->tkr_mono.base;
850 		nsecs = timekeeping_get_ns(&tk->tkr_mono);
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);
857 
858 u32 ktime_get_resolution_ns(void)
859 {
860 	struct timekeeper *tk = &tk_core.timekeeper;
861 	unsigned int seq;
862 	u32 nsecs;
863 
864 	WARN_ON(timekeeping_suspended);
865 
866 	do {
867 		seq = read_seqcount_begin(&tk_core.seq);
868 		nsecs = tk->tkr_mono.mult >> tk->tkr_mono.shift;
869 	} while (read_seqcount_retry(&tk_core.seq, seq));
870 
871 	return nsecs;
872 }
873 EXPORT_SYMBOL_GPL(ktime_get_resolution_ns);
874 
875 static ktime_t *offsets[TK_OFFS_MAX] = {
876 	[TK_OFFS_REAL]	= &tk_core.timekeeper.offs_real,
877 	[TK_OFFS_BOOT]	= &tk_core.timekeeper.offs_boot,
878 	[TK_OFFS_TAI]	= &tk_core.timekeeper.offs_tai,
879 };
880 
881 ktime_t ktime_get_with_offset(enum tk_offsets offs)
882 {
883 	struct timekeeper *tk = &tk_core.timekeeper;
884 	unsigned int seq;
885 	ktime_t base, *offset = offsets[offs];
886 	u64 nsecs;
887 
888 	WARN_ON(timekeeping_suspended);
889 
890 	do {
891 		seq = read_seqcount_begin(&tk_core.seq);
892 		base = ktime_add(tk->tkr_mono.base, *offset);
893 		nsecs = timekeeping_get_ns(&tk->tkr_mono);
894 
895 	} while (read_seqcount_retry(&tk_core.seq, seq));
896 
897 	return ktime_add_ns(base, nsecs);
898 
899 }
900 EXPORT_SYMBOL_GPL(ktime_get_with_offset);
901 
902 ktime_t ktime_get_coarse_with_offset(enum tk_offsets offs)
903 {
904 	struct timekeeper *tk = &tk_core.timekeeper;
905 	unsigned int seq;
906 	ktime_t base, *offset = offsets[offs];
907 	u64 nsecs;
908 
909 	WARN_ON(timekeeping_suspended);
910 
911 	do {
912 		seq = read_seqcount_begin(&tk_core.seq);
913 		base = ktime_add(tk->tkr_mono.base, *offset);
914 		nsecs = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
915 
916 	} while (read_seqcount_retry(&tk_core.seq, seq));
917 
918 	return ktime_add_ns(base, nsecs);
919 }
920 EXPORT_SYMBOL_GPL(ktime_get_coarse_with_offset);
921 
922 /**
923  * ktime_mono_to_any() - convert monotonic time to any other time
924  * @tmono:	time to convert.
925  * @offs:	which offset to use
926  */
927 ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs)
928 {
929 	ktime_t *offset = offsets[offs];
930 	unsigned int seq;
931 	ktime_t tconv;
932 
933 	do {
934 		seq = read_seqcount_begin(&tk_core.seq);
935 		tconv = ktime_add(tmono, *offset);
936 	} while (read_seqcount_retry(&tk_core.seq, seq));
937 
938 	return tconv;
939 }
940 EXPORT_SYMBOL_GPL(ktime_mono_to_any);
941 
942 /**
943  * ktime_get_raw - Returns the raw monotonic time in ktime_t format
944  */
945 ktime_t ktime_get_raw(void)
946 {
947 	struct timekeeper *tk = &tk_core.timekeeper;
948 	unsigned int seq;
949 	ktime_t base;
950 	u64 nsecs;
951 
952 	do {
953 		seq = read_seqcount_begin(&tk_core.seq);
954 		base = tk->tkr_raw.base;
955 		nsecs = timekeeping_get_ns(&tk->tkr_raw);
956 
957 	} while (read_seqcount_retry(&tk_core.seq, seq));
958 
959 	return ktime_add_ns(base, nsecs);
960 }
961 EXPORT_SYMBOL_GPL(ktime_get_raw);
962 
963 /**
964  * ktime_get_ts64 - get the monotonic clock in timespec64 format
965  * @ts:		pointer to timespec variable
966  *
967  * The function calculates the monotonic clock from the realtime
968  * clock and the wall_to_monotonic offset and stores the result
969  * in normalized timespec64 format in the variable pointed to by @ts.
970  */
971 void ktime_get_ts64(struct timespec64 *ts)
972 {
973 	struct timekeeper *tk = &tk_core.timekeeper;
974 	struct timespec64 tomono;
975 	unsigned int seq;
976 	u64 nsec;
977 
978 	WARN_ON(timekeeping_suspended);
979 
980 	do {
981 		seq = read_seqcount_begin(&tk_core.seq);
982 		ts->tv_sec = tk->xtime_sec;
983 		nsec = timekeeping_get_ns(&tk->tkr_mono);
984 		tomono = tk->wall_to_monotonic;
985 
986 	} while (read_seqcount_retry(&tk_core.seq, seq));
987 
988 	ts->tv_sec += tomono.tv_sec;
989 	ts->tv_nsec = 0;
990 	timespec64_add_ns(ts, nsec + tomono.tv_nsec);
991 }
992 EXPORT_SYMBOL_GPL(ktime_get_ts64);
993 
994 /**
995  * ktime_get_seconds - Get the seconds portion of CLOCK_MONOTONIC
996  *
997  * Returns the seconds portion of CLOCK_MONOTONIC with a single non
998  * serialized read. tk->ktime_sec is of type 'unsigned long' so this
999  * works on both 32 and 64 bit systems. On 32 bit systems the readout
1000  * covers ~136 years of uptime which should be enough to prevent
1001  * premature wrap arounds.
1002  */
1003 time64_t ktime_get_seconds(void)
1004 {
1005 	struct timekeeper *tk = &tk_core.timekeeper;
1006 
1007 	WARN_ON(timekeeping_suspended);
1008 	return tk->ktime_sec;
1009 }
1010 EXPORT_SYMBOL_GPL(ktime_get_seconds);
1011 
1012 /**
1013  * ktime_get_real_seconds - Get the seconds portion of CLOCK_REALTIME
1014  *
1015  * Returns the wall clock seconds since 1970.
1016  *
1017  * For 64bit systems the fast access to tk->xtime_sec is preserved. On
1018  * 32bit systems the access must be protected with the sequence
1019  * counter to provide "atomic" access to the 64bit tk->xtime_sec
1020  * value.
1021  */
1022 time64_t ktime_get_real_seconds(void)
1023 {
1024 	struct timekeeper *tk = &tk_core.timekeeper;
1025 	time64_t seconds;
1026 	unsigned int seq;
1027 
1028 	if (IS_ENABLED(CONFIG_64BIT))
1029 		return tk->xtime_sec;
1030 
1031 	do {
1032 		seq = read_seqcount_begin(&tk_core.seq);
1033 		seconds = tk->xtime_sec;
1034 
1035 	} while (read_seqcount_retry(&tk_core.seq, seq));
1036 
1037 	return seconds;
1038 }
1039 EXPORT_SYMBOL_GPL(ktime_get_real_seconds);
1040 
1041 /**
1042  * __ktime_get_real_seconds - The same as ktime_get_real_seconds
1043  * but without the sequence counter protect. This internal function
1044  * is called just when timekeeping lock is already held.
1045  */
1046 noinstr time64_t __ktime_get_real_seconds(void)
1047 {
1048 	struct timekeeper *tk = &tk_core.timekeeper;
1049 
1050 	return tk->xtime_sec;
1051 }
1052 
1053 /**
1054  * ktime_get_snapshot - snapshots the realtime/monotonic raw clocks with counter
1055  * @systime_snapshot:	pointer to struct receiving the system time snapshot
1056  */
1057 void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
1058 {
1059 	struct timekeeper *tk = &tk_core.timekeeper;
1060 	unsigned int seq;
1061 	ktime_t base_raw;
1062 	ktime_t base_real;
1063 	u64 nsec_raw;
1064 	u64 nsec_real;
1065 	u64 now;
1066 
1067 	WARN_ON_ONCE(timekeeping_suspended);
1068 
1069 	do {
1070 		seq = read_seqcount_begin(&tk_core.seq);
1071 		now = tk_clock_read(&tk->tkr_mono);
1072 		systime_snapshot->cs_id = tk->tkr_mono.clock->id;
1073 		systime_snapshot->cs_was_changed_seq = tk->cs_was_changed_seq;
1074 		systime_snapshot->clock_was_set_seq = tk->clock_was_set_seq;
1075 		base_real = ktime_add(tk->tkr_mono.base,
1076 				      tk_core.timekeeper.offs_real);
1077 		base_raw = tk->tkr_raw.base;
1078 		nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, now);
1079 		nsec_raw  = timekeeping_cycles_to_ns(&tk->tkr_raw, now);
1080 	} while (read_seqcount_retry(&tk_core.seq, seq));
1081 
1082 	systime_snapshot->cycles = now;
1083 	systime_snapshot->real = ktime_add_ns(base_real, nsec_real);
1084 	systime_snapshot->raw = ktime_add_ns(base_raw, nsec_raw);
1085 }
1086 EXPORT_SYMBOL_GPL(ktime_get_snapshot);
1087 
1088 /* Scale base by mult/div checking for overflow */
1089 static int scale64_check_overflow(u64 mult, u64 div, u64 *base)
1090 {
1091 	u64 tmp, rem;
1092 
1093 	tmp = div64_u64_rem(*base, div, &rem);
1094 
1095 	if (((int)sizeof(u64)*8 - fls64(mult) < fls64(tmp)) ||
1096 	    ((int)sizeof(u64)*8 - fls64(mult) < fls64(rem)))
1097 		return -EOVERFLOW;
1098 	tmp *= mult;
1099 
1100 	rem = div64_u64(rem * mult, div);
1101 	*base = tmp + rem;
1102 	return 0;
1103 }
1104 
1105 /**
1106  * adjust_historical_crosststamp - adjust crosstimestamp previous to current interval
1107  * @history:			Snapshot representing start of history
1108  * @partial_history_cycles:	Cycle offset into history (fractional part)
1109  * @total_history_cycles:	Total history length in cycles
1110  * @discontinuity:		True indicates clock was set on history period
1111  * @ts:				Cross timestamp that should be adjusted using
1112  *	partial/total ratio
1113  *
1114  * Helper function used by get_device_system_crosststamp() to correct the
1115  * crosstimestamp corresponding to the start of the current interval to the
1116  * system counter value (timestamp point) provided by the driver. The
1117  * total_history_* quantities are the total history starting at the provided
1118  * reference point and ending at the start of the current interval. The cycle
1119  * count between the driver timestamp point and the start of the current
1120  * interval is partial_history_cycles.
1121  */
1122 static int adjust_historical_crosststamp(struct system_time_snapshot *history,
1123 					 u64 partial_history_cycles,
1124 					 u64 total_history_cycles,
1125 					 bool discontinuity,
1126 					 struct system_device_crosststamp *ts)
1127 {
1128 	struct timekeeper *tk = &tk_core.timekeeper;
1129 	u64 corr_raw, corr_real;
1130 	bool interp_forward;
1131 	int ret;
1132 
1133 	if (total_history_cycles == 0 || partial_history_cycles == 0)
1134 		return 0;
1135 
1136 	/* Interpolate shortest distance from beginning or end of history */
1137 	interp_forward = partial_history_cycles > total_history_cycles / 2;
1138 	partial_history_cycles = interp_forward ?
1139 		total_history_cycles - partial_history_cycles :
1140 		partial_history_cycles;
1141 
1142 	/*
1143 	 * Scale the monotonic raw time delta by:
1144 	 *	partial_history_cycles / total_history_cycles
1145 	 */
1146 	corr_raw = (u64)ktime_to_ns(
1147 		ktime_sub(ts->sys_monoraw, history->raw));
1148 	ret = scale64_check_overflow(partial_history_cycles,
1149 				     total_history_cycles, &corr_raw);
1150 	if (ret)
1151 		return ret;
1152 
1153 	/*
1154 	 * If there is a discontinuity in the history, scale monotonic raw
1155 	 *	correction by:
1156 	 *	mult(real)/mult(raw) yielding the realtime correction
1157 	 * Otherwise, calculate the realtime correction similar to monotonic
1158 	 *	raw calculation
1159 	 */
1160 	if (discontinuity) {
1161 		corr_real = mul_u64_u32_div
1162 			(corr_raw, tk->tkr_mono.mult, tk->tkr_raw.mult);
1163 	} else {
1164 		corr_real = (u64)ktime_to_ns(
1165 			ktime_sub(ts->sys_realtime, history->real));
1166 		ret = scale64_check_overflow(partial_history_cycles,
1167 					     total_history_cycles, &corr_real);
1168 		if (ret)
1169 			return ret;
1170 	}
1171 
1172 	/* Fixup monotonic raw and real time time values */
1173 	if (interp_forward) {
1174 		ts->sys_monoraw = ktime_add_ns(history->raw, corr_raw);
1175 		ts->sys_realtime = ktime_add_ns(history->real, corr_real);
1176 	} else {
1177 		ts->sys_monoraw = ktime_sub_ns(ts->sys_monoraw, corr_raw);
1178 		ts->sys_realtime = ktime_sub_ns(ts->sys_realtime, corr_real);
1179 	}
1180 
1181 	return 0;
1182 }
1183 
1184 /*
1185  * timestamp_in_interval - true if ts is chronologically in [start, end]
1186  *
1187  * True if ts occurs chronologically at or after start, and before or at end.
1188  */
1189 static bool timestamp_in_interval(u64 start, u64 end, u64 ts)
1190 {
1191 	if (ts >= start && ts <= end)
1192 		return true;
1193 	if (start > end && (ts >= start || ts <= end))
1194 		return true;
1195 	return false;
1196 }
1197 
1198 /**
1199  * get_device_system_crosststamp - Synchronously capture system/device timestamp
1200  * @get_time_fn:	Callback to get simultaneous device time and
1201  *	system counter from the device driver
1202  * @ctx:		Context passed to get_time_fn()
1203  * @history_begin:	Historical reference point used to interpolate system
1204  *	time when counter provided by the driver is before the current interval
1205  * @xtstamp:		Receives simultaneously captured system and device time
1206  *
1207  * Reads a timestamp from a device and correlates it to system time
1208  */
1209 int get_device_system_crosststamp(int (*get_time_fn)
1210 				  (ktime_t *device_time,
1211 				   struct system_counterval_t *sys_counterval,
1212 				   void *ctx),
1213 				  void *ctx,
1214 				  struct system_time_snapshot *history_begin,
1215 				  struct system_device_crosststamp *xtstamp)
1216 {
1217 	struct system_counterval_t system_counterval;
1218 	struct timekeeper *tk = &tk_core.timekeeper;
1219 	u64 cycles, now, interval_start;
1220 	unsigned int clock_was_set_seq = 0;
1221 	ktime_t base_real, base_raw;
1222 	u64 nsec_real, nsec_raw;
1223 	u8 cs_was_changed_seq;
1224 	unsigned int seq;
1225 	bool do_interp;
1226 	int ret;
1227 
1228 	do {
1229 		seq = read_seqcount_begin(&tk_core.seq);
1230 		/*
1231 		 * Try to synchronously capture device time and a system
1232 		 * counter value calling back into the device driver
1233 		 */
1234 		ret = get_time_fn(&xtstamp->device, &system_counterval, ctx);
1235 		if (ret)
1236 			return ret;
1237 
1238 		/*
1239 		 * Verify that the clocksource ID associated with the captured
1240 		 * system counter value is the same as for the currently
1241 		 * installed timekeeper clocksource
1242 		 */
1243 		if (system_counterval.cs_id == CSID_GENERIC ||
1244 		    tk->tkr_mono.clock->id != system_counterval.cs_id)
1245 			return -ENODEV;
1246 		cycles = system_counterval.cycles;
1247 
1248 		/*
1249 		 * Check whether the system counter value provided by the
1250 		 * device driver is on the current timekeeping interval.
1251 		 */
1252 		now = tk_clock_read(&tk->tkr_mono);
1253 		interval_start = tk->tkr_mono.cycle_last;
1254 		if (!timestamp_in_interval(interval_start, now, cycles)) {
1255 			clock_was_set_seq = tk->clock_was_set_seq;
1256 			cs_was_changed_seq = tk->cs_was_changed_seq;
1257 			cycles = interval_start;
1258 			do_interp = true;
1259 		} else {
1260 			do_interp = false;
1261 		}
1262 
1263 		base_real = ktime_add(tk->tkr_mono.base,
1264 				      tk_core.timekeeper.offs_real);
1265 		base_raw = tk->tkr_raw.base;
1266 
1267 		nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, cycles);
1268 		nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw, cycles);
1269 	} while (read_seqcount_retry(&tk_core.seq, seq));
1270 
1271 	xtstamp->sys_realtime = ktime_add_ns(base_real, nsec_real);
1272 	xtstamp->sys_monoraw = ktime_add_ns(base_raw, nsec_raw);
1273 
1274 	/*
1275 	 * Interpolate if necessary, adjusting back from the start of the
1276 	 * current interval
1277 	 */
1278 	if (do_interp) {
1279 		u64 partial_history_cycles, total_history_cycles;
1280 		bool discontinuity;
1281 
1282 		/*
1283 		 * Check that the counter value is not before the provided
1284 		 * history reference and that the history doesn't cross a
1285 		 * clocksource change
1286 		 */
1287 		if (!history_begin ||
1288 		    !timestamp_in_interval(history_begin->cycles,
1289 					   cycles, system_counterval.cycles) ||
1290 		    history_begin->cs_was_changed_seq != cs_was_changed_seq)
1291 			return -EINVAL;
1292 		partial_history_cycles = cycles - system_counterval.cycles;
1293 		total_history_cycles = cycles - history_begin->cycles;
1294 		discontinuity =
1295 			history_begin->clock_was_set_seq != clock_was_set_seq;
1296 
1297 		ret = adjust_historical_crosststamp(history_begin,
1298 						    partial_history_cycles,
1299 						    total_history_cycles,
1300 						    discontinuity, xtstamp);
1301 		if (ret)
1302 			return ret;
1303 	}
1304 
1305 	return 0;
1306 }
1307 EXPORT_SYMBOL_GPL(get_device_system_crosststamp);
1308 
1309 /**
1310  * do_settimeofday64 - Sets the time of day.
1311  * @ts:     pointer to the timespec64 variable containing the new time
1312  *
1313  * Sets the time of day to the new time and update NTP and notify hrtimers
1314  */
1315 int do_settimeofday64(const struct timespec64 *ts)
1316 {
1317 	struct timekeeper *tk = &tk_core.timekeeper;
1318 	struct timespec64 ts_delta, xt;
1319 	unsigned long flags;
1320 	int ret = 0;
1321 
1322 	if (!timespec64_valid_settod(ts))
1323 		return -EINVAL;
1324 
1325 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1326 	write_seqcount_begin(&tk_core.seq);
1327 
1328 	timekeeping_forward_now(tk);
1329 
1330 	xt = tk_xtime(tk);
1331 	ts_delta = timespec64_sub(*ts, xt);
1332 
1333 	if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) {
1334 		ret = -EINVAL;
1335 		goto out;
1336 	}
1337 
1338 	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta));
1339 
1340 	tk_set_xtime(tk, ts);
1341 out:
1342 	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1343 
1344 	write_seqcount_end(&tk_core.seq);
1345 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1346 
1347 	/* Signal hrtimers about time change */
1348 	clock_was_set(CLOCK_SET_WALL);
1349 
1350 	if (!ret) {
1351 		audit_tk_injoffset(ts_delta);
1352 		add_device_randomness(ts, sizeof(*ts));
1353 	}
1354 
1355 	return ret;
1356 }
1357 EXPORT_SYMBOL(do_settimeofday64);
1358 
1359 /**
1360  * timekeeping_inject_offset - Adds or subtracts from the current time.
1361  * @ts:		Pointer to the timespec variable containing the offset
1362  *
1363  * Adds or subtracts an offset value from the current time.
1364  */
1365 static int timekeeping_inject_offset(const struct timespec64 *ts)
1366 {
1367 	struct timekeeper *tk = &tk_core.timekeeper;
1368 	unsigned long flags;
1369 	struct timespec64 tmp;
1370 	int ret = 0;
1371 
1372 	if (ts->tv_nsec < 0 || ts->tv_nsec >= NSEC_PER_SEC)
1373 		return -EINVAL;
1374 
1375 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1376 	write_seqcount_begin(&tk_core.seq);
1377 
1378 	timekeeping_forward_now(tk);
1379 
1380 	/* Make sure the proposed value is valid */
1381 	tmp = timespec64_add(tk_xtime(tk), *ts);
1382 	if (timespec64_compare(&tk->wall_to_monotonic, ts) > 0 ||
1383 	    !timespec64_valid_settod(&tmp)) {
1384 		ret = -EINVAL;
1385 		goto error;
1386 	}
1387 
1388 	tk_xtime_add(tk, ts);
1389 	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *ts));
1390 
1391 error: /* even if we error out, we forwarded the time, so call update */
1392 	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1393 
1394 	write_seqcount_end(&tk_core.seq);
1395 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1396 
1397 	/* Signal hrtimers about time change */
1398 	clock_was_set(CLOCK_SET_WALL);
1399 
1400 	return ret;
1401 }
1402 
1403 /*
1404  * Indicates if there is an offset between the system clock and the hardware
1405  * clock/persistent clock/rtc.
1406  */
1407 int persistent_clock_is_local;
1408 
1409 /*
1410  * Adjust the time obtained from the CMOS to be UTC time instead of
1411  * local time.
1412  *
1413  * This is ugly, but preferable to the alternatives.  Otherwise we
1414  * would either need to write a program to do it in /etc/rc (and risk
1415  * confusion if the program gets run more than once; it would also be
1416  * hard to make the program warp the clock precisely n hours)  or
1417  * compile in the timezone information into the kernel.  Bad, bad....
1418  *
1419  *						- TYT, 1992-01-01
1420  *
1421  * The best thing to do is to keep the CMOS clock in universal time (UTC)
1422  * as real UNIX machines always do it. This avoids all headaches about
1423  * daylight saving times and warping kernel clocks.
1424  */
1425 void timekeeping_warp_clock(void)
1426 {
1427 	if (sys_tz.tz_minuteswest != 0) {
1428 		struct timespec64 adjust;
1429 
1430 		persistent_clock_is_local = 1;
1431 		adjust.tv_sec = sys_tz.tz_minuteswest * 60;
1432 		adjust.tv_nsec = 0;
1433 		timekeeping_inject_offset(&adjust);
1434 	}
1435 }
1436 
1437 /*
1438  * __timekeeping_set_tai_offset - Sets the TAI offset from UTC and monotonic
1439  */
1440 static void __timekeeping_set_tai_offset(struct timekeeper *tk, s32 tai_offset)
1441 {
1442 	tk->tai_offset = tai_offset;
1443 	tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tai_offset, 0));
1444 }
1445 
1446 /*
1447  * change_clocksource - Swaps clocksources if a new one is available
1448  *
1449  * Accumulates current time interval and initializes new clocksource
1450  */
1451 static int change_clocksource(void *data)
1452 {
1453 	struct timekeeper *tk = &tk_core.timekeeper;
1454 	struct clocksource *new, *old = NULL;
1455 	unsigned long flags;
1456 	bool change = false;
1457 
1458 	new = (struct clocksource *) data;
1459 
1460 	/*
1461 	 * If the cs is in module, get a module reference. Succeeds
1462 	 * for built-in code (owner == NULL) as well.
1463 	 */
1464 	if (try_module_get(new->owner)) {
1465 		if (!new->enable || new->enable(new) == 0)
1466 			change = true;
1467 		else
1468 			module_put(new->owner);
1469 	}
1470 
1471 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1472 	write_seqcount_begin(&tk_core.seq);
1473 
1474 	timekeeping_forward_now(tk);
1475 
1476 	if (change) {
1477 		old = tk->tkr_mono.clock;
1478 		tk_setup_internals(tk, new);
1479 	}
1480 
1481 	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1482 
1483 	write_seqcount_end(&tk_core.seq);
1484 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1485 
1486 	if (old) {
1487 		if (old->disable)
1488 			old->disable(old);
1489 
1490 		module_put(old->owner);
1491 	}
1492 
1493 	return 0;
1494 }
1495 
1496 /**
1497  * timekeeping_notify - Install a new clock source
1498  * @clock:		pointer to the clock source
1499  *
1500  * This function is called from clocksource.c after a new, better clock
1501  * source has been registered. The caller holds the clocksource_mutex.
1502  */
1503 int timekeeping_notify(struct clocksource *clock)
1504 {
1505 	struct timekeeper *tk = &tk_core.timekeeper;
1506 
1507 	if (tk->tkr_mono.clock == clock)
1508 		return 0;
1509 	stop_machine(change_clocksource, clock, NULL);
1510 	tick_clock_notify();
1511 	return tk->tkr_mono.clock == clock ? 0 : -1;
1512 }
1513 
1514 /**
1515  * ktime_get_raw_ts64 - Returns the raw monotonic time in a timespec
1516  * @ts:		pointer to the timespec64 to be set
1517  *
1518  * Returns the raw monotonic time (completely un-modified by ntp)
1519  */
1520 void ktime_get_raw_ts64(struct timespec64 *ts)
1521 {
1522 	struct timekeeper *tk = &tk_core.timekeeper;
1523 	unsigned int seq;
1524 	u64 nsecs;
1525 
1526 	do {
1527 		seq = read_seqcount_begin(&tk_core.seq);
1528 		ts->tv_sec = tk->raw_sec;
1529 		nsecs = timekeeping_get_ns(&tk->tkr_raw);
1530 
1531 	} while (read_seqcount_retry(&tk_core.seq, seq));
1532 
1533 	ts->tv_nsec = 0;
1534 	timespec64_add_ns(ts, nsecs);
1535 }
1536 EXPORT_SYMBOL(ktime_get_raw_ts64);
1537 
1538 
1539 /**
1540  * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
1541  */
1542 int timekeeping_valid_for_hres(void)
1543 {
1544 	struct timekeeper *tk = &tk_core.timekeeper;
1545 	unsigned int seq;
1546 	int ret;
1547 
1548 	do {
1549 		seq = read_seqcount_begin(&tk_core.seq);
1550 
1551 		ret = tk->tkr_mono.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
1552 
1553 	} while (read_seqcount_retry(&tk_core.seq, seq));
1554 
1555 	return ret;
1556 }
1557 
1558 /**
1559  * timekeeping_max_deferment - Returns max time the clocksource can be deferred
1560  */
1561 u64 timekeeping_max_deferment(void)
1562 {
1563 	struct timekeeper *tk = &tk_core.timekeeper;
1564 	unsigned int seq;
1565 	u64 ret;
1566 
1567 	do {
1568 		seq = read_seqcount_begin(&tk_core.seq);
1569 
1570 		ret = tk->tkr_mono.clock->max_idle_ns;
1571 
1572 	} while (read_seqcount_retry(&tk_core.seq, seq));
1573 
1574 	return ret;
1575 }
1576 
1577 /**
1578  * read_persistent_clock64 -  Return time from the persistent clock.
1579  * @ts: Pointer to the storage for the readout value
1580  *
1581  * Weak dummy function for arches that do not yet support it.
1582  * Reads the time from the battery backed persistent clock.
1583  * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
1584  *
1585  *  XXX - Do be sure to remove it once all arches implement it.
1586  */
1587 void __weak read_persistent_clock64(struct timespec64 *ts)
1588 {
1589 	ts->tv_sec = 0;
1590 	ts->tv_nsec = 0;
1591 }
1592 
1593 /**
1594  * read_persistent_wall_and_boot_offset - Read persistent clock, and also offset
1595  *                                        from the boot.
1596  * @wall_time:	  current time as returned by persistent clock
1597  * @boot_offset:  offset that is defined as wall_time - boot_time
1598  *
1599  * Weak dummy function for arches that do not yet support it.
1600  *
1601  * The default function calculates offset based on the current value of
1602  * local_clock(). This way architectures that support sched_clock() but don't
1603  * support dedicated boot time clock will provide the best estimate of the
1604  * boot time.
1605  */
1606 void __weak __init
1607 read_persistent_wall_and_boot_offset(struct timespec64 *wall_time,
1608 				     struct timespec64 *boot_offset)
1609 {
1610 	read_persistent_clock64(wall_time);
1611 	*boot_offset = ns_to_timespec64(local_clock());
1612 }
1613 
1614 /*
1615  * Flag reflecting whether timekeeping_resume() has injected sleeptime.
1616  *
1617  * The flag starts of false and is only set when a suspend reaches
1618  * timekeeping_suspend(), timekeeping_resume() sets it to false when the
1619  * timekeeper clocksource is not stopping across suspend and has been
1620  * used to update sleep time. If the timekeeper clocksource has stopped
1621  * then the flag stays true and is used by the RTC resume code to decide
1622  * whether sleeptime must be injected and if so the flag gets false then.
1623  *
1624  * If a suspend fails before reaching timekeeping_resume() then the flag
1625  * stays false and prevents erroneous sleeptime injection.
1626  */
1627 static bool suspend_timing_needed;
1628 
1629 /* Flag for if there is a persistent clock on this platform */
1630 static bool persistent_clock_exists;
1631 
1632 /*
1633  * timekeeping_init - Initializes the clocksource and common timekeeping values
1634  */
1635 void __init timekeeping_init(void)
1636 {
1637 	struct timespec64 wall_time, boot_offset, wall_to_mono;
1638 	struct timekeeper *tk = &tk_core.timekeeper;
1639 	struct clocksource *clock;
1640 	unsigned long flags;
1641 
1642 	read_persistent_wall_and_boot_offset(&wall_time, &boot_offset);
1643 	if (timespec64_valid_settod(&wall_time) &&
1644 	    timespec64_to_ns(&wall_time) > 0) {
1645 		persistent_clock_exists = true;
1646 	} else if (timespec64_to_ns(&wall_time) != 0) {
1647 		pr_warn("Persistent clock returned invalid value");
1648 		wall_time = (struct timespec64){0};
1649 	}
1650 
1651 	if (timespec64_compare(&wall_time, &boot_offset) < 0)
1652 		boot_offset = (struct timespec64){0};
1653 
1654 	/*
1655 	 * We want set wall_to_mono, so the following is true:
1656 	 * wall time + wall_to_mono = boot time
1657 	 */
1658 	wall_to_mono = timespec64_sub(boot_offset, wall_time);
1659 
1660 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1661 	write_seqcount_begin(&tk_core.seq);
1662 	ntp_init();
1663 
1664 	clock = clocksource_default_clock();
1665 	if (clock->enable)
1666 		clock->enable(clock);
1667 	tk_setup_internals(tk, clock);
1668 
1669 	tk_set_xtime(tk, &wall_time);
1670 	tk->raw_sec = 0;
1671 
1672 	tk_set_wall_to_mono(tk, wall_to_mono);
1673 
1674 	timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
1675 
1676 	write_seqcount_end(&tk_core.seq);
1677 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1678 }
1679 
1680 /* time in seconds when suspend began for persistent clock */
1681 static struct timespec64 timekeeping_suspend_time;
1682 
1683 /**
1684  * __timekeeping_inject_sleeptime - Internal function to add sleep interval
1685  * @tk:		Pointer to the timekeeper to be updated
1686  * @delta:	Pointer to the delta value in timespec64 format
1687  *
1688  * Takes a timespec offset measuring a suspend interval and properly
1689  * adds the sleep offset to the timekeeping variables.
1690  */
1691 static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
1692 					   const struct timespec64 *delta)
1693 {
1694 	if (!timespec64_valid_strict(delta)) {
1695 		printk_deferred(KERN_WARNING
1696 				"__timekeeping_inject_sleeptime: Invalid "
1697 				"sleep delta value!\n");
1698 		return;
1699 	}
1700 	tk_xtime_add(tk, delta);
1701 	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *delta));
1702 	tk_update_sleep_time(tk, timespec64_to_ktime(*delta));
1703 	tk_debug_account_sleep_time(delta);
1704 }
1705 
1706 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
1707 /*
1708  * We have three kinds of time sources to use for sleep time
1709  * injection, the preference order is:
1710  * 1) non-stop clocksource
1711  * 2) persistent clock (ie: RTC accessible when irqs are off)
1712  * 3) RTC
1713  *
1714  * 1) and 2) are used by timekeeping, 3) by RTC subsystem.
1715  * If system has neither 1) nor 2), 3) will be used finally.
1716  *
1717  *
1718  * If timekeeping has injected sleeptime via either 1) or 2),
1719  * 3) becomes needless, so in this case we don't need to call
1720  * rtc_resume(), and this is what timekeeping_rtc_skipresume()
1721  * means.
1722  */
1723 bool timekeeping_rtc_skipresume(void)
1724 {
1725 	return !suspend_timing_needed;
1726 }
1727 
1728 /*
1729  * 1) can be determined whether to use or not only when doing
1730  * timekeeping_resume() which is invoked after rtc_suspend(),
1731  * so we can't skip rtc_suspend() surely if system has 1).
1732  *
1733  * But if system has 2), 2) will definitely be used, so in this
1734  * case we don't need to call rtc_suspend(), and this is what
1735  * timekeeping_rtc_skipsuspend() means.
1736  */
1737 bool timekeeping_rtc_skipsuspend(void)
1738 {
1739 	return persistent_clock_exists;
1740 }
1741 
1742 /**
1743  * timekeeping_inject_sleeptime64 - Adds suspend interval to timeekeeping values
1744  * @delta: pointer to a timespec64 delta value
1745  *
1746  * This hook is for architectures that cannot support read_persistent_clock64
1747  * because their RTC/persistent clock is only accessible when irqs are enabled.
1748  * and also don't have an effective nonstop clocksource.
1749  *
1750  * This function should only be called by rtc_resume(), and allows
1751  * a suspend offset to be injected into the timekeeping values.
1752  */
1753 void timekeeping_inject_sleeptime64(const struct timespec64 *delta)
1754 {
1755 	struct timekeeper *tk = &tk_core.timekeeper;
1756 	unsigned long flags;
1757 
1758 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1759 	write_seqcount_begin(&tk_core.seq);
1760 
1761 	suspend_timing_needed = false;
1762 
1763 	timekeeping_forward_now(tk);
1764 
1765 	__timekeeping_inject_sleeptime(tk, delta);
1766 
1767 	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1768 
1769 	write_seqcount_end(&tk_core.seq);
1770 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1771 
1772 	/* Signal hrtimers about time change */
1773 	clock_was_set(CLOCK_SET_WALL | CLOCK_SET_BOOT);
1774 }
1775 #endif
1776 
1777 /**
1778  * timekeeping_resume - Resumes the generic timekeeping subsystem.
1779  */
1780 void timekeeping_resume(void)
1781 {
1782 	struct timekeeper *tk = &tk_core.timekeeper;
1783 	struct clocksource *clock = tk->tkr_mono.clock;
1784 	unsigned long flags;
1785 	struct timespec64 ts_new, ts_delta;
1786 	u64 cycle_now, nsec;
1787 	bool inject_sleeptime = false;
1788 
1789 	read_persistent_clock64(&ts_new);
1790 
1791 	clockevents_resume();
1792 	clocksource_resume();
1793 
1794 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1795 	write_seqcount_begin(&tk_core.seq);
1796 
1797 	/*
1798 	 * After system resumes, we need to calculate the suspended time and
1799 	 * compensate it for the OS time. There are 3 sources that could be
1800 	 * used: Nonstop clocksource during suspend, persistent clock and rtc
1801 	 * device.
1802 	 *
1803 	 * One specific platform may have 1 or 2 or all of them, and the
1804 	 * preference will be:
1805 	 *	suspend-nonstop clocksource -> persistent clock -> rtc
1806 	 * The less preferred source will only be tried if there is no better
1807 	 * usable source. The rtc part is handled separately in rtc core code.
1808 	 */
1809 	cycle_now = tk_clock_read(&tk->tkr_mono);
1810 	nsec = clocksource_stop_suspend_timing(clock, cycle_now);
1811 	if (nsec > 0) {
1812 		ts_delta = ns_to_timespec64(nsec);
1813 		inject_sleeptime = true;
1814 	} else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {
1815 		ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);
1816 		inject_sleeptime = true;
1817 	}
1818 
1819 	if (inject_sleeptime) {
1820 		suspend_timing_needed = false;
1821 		__timekeeping_inject_sleeptime(tk, &ts_delta);
1822 	}
1823 
1824 	/* Re-base the last cycle value */
1825 	tk->tkr_mono.cycle_last = cycle_now;
1826 	tk->tkr_raw.cycle_last  = cycle_now;
1827 
1828 	tk->ntp_error = 0;
1829 	timekeeping_suspended = 0;
1830 	timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
1831 	write_seqcount_end(&tk_core.seq);
1832 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1833 
1834 	touch_softlockup_watchdog();
1835 
1836 	/* Resume the clockevent device(s) and hrtimers */
1837 	tick_resume();
1838 	/* Notify timerfd as resume is equivalent to clock_was_set() */
1839 	timerfd_resume();
1840 }
1841 
1842 int timekeeping_suspend(void)
1843 {
1844 	struct timekeeper *tk = &tk_core.timekeeper;
1845 	unsigned long flags;
1846 	struct timespec64		delta, delta_delta;
1847 	static struct timespec64	old_delta;
1848 	struct clocksource *curr_clock;
1849 	u64 cycle_now;
1850 
1851 	read_persistent_clock64(&timekeeping_suspend_time);
1852 
1853 	/*
1854 	 * On some systems the persistent_clock can not be detected at
1855 	 * timekeeping_init by its return value, so if we see a valid
1856 	 * value returned, update the persistent_clock_exists flag.
1857 	 */
1858 	if (timekeeping_suspend_time.tv_sec || timekeeping_suspend_time.tv_nsec)
1859 		persistent_clock_exists = true;
1860 
1861 	suspend_timing_needed = true;
1862 
1863 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1864 	write_seqcount_begin(&tk_core.seq);
1865 	timekeeping_forward_now(tk);
1866 	timekeeping_suspended = 1;
1867 
1868 	/*
1869 	 * Since we've called forward_now, cycle_last stores the value
1870 	 * just read from the current clocksource. Save this to potentially
1871 	 * use in suspend timing.
1872 	 */
1873 	curr_clock = tk->tkr_mono.clock;
1874 	cycle_now = tk->tkr_mono.cycle_last;
1875 	clocksource_start_suspend_timing(curr_clock, cycle_now);
1876 
1877 	if (persistent_clock_exists) {
1878 		/*
1879 		 * To avoid drift caused by repeated suspend/resumes,
1880 		 * which each can add ~1 second drift error,
1881 		 * try to compensate so the difference in system time
1882 		 * and persistent_clock time stays close to constant.
1883 		 */
1884 		delta = timespec64_sub(tk_xtime(tk), timekeeping_suspend_time);
1885 		delta_delta = timespec64_sub(delta, old_delta);
1886 		if (abs(delta_delta.tv_sec) >= 2) {
1887 			/*
1888 			 * if delta_delta is too large, assume time correction
1889 			 * has occurred and set old_delta to the current delta.
1890 			 */
1891 			old_delta = delta;
1892 		} else {
1893 			/* Otherwise try to adjust old_system to compensate */
1894 			timekeeping_suspend_time =
1895 				timespec64_add(timekeeping_suspend_time, delta_delta);
1896 		}
1897 	}
1898 
1899 	timekeeping_update(tk, TK_MIRROR);
1900 	halt_fast_timekeeper(tk);
1901 	write_seqcount_end(&tk_core.seq);
1902 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1903 
1904 	tick_suspend();
1905 	clocksource_suspend();
1906 	clockevents_suspend();
1907 
1908 	return 0;
1909 }
1910 
1911 /* sysfs resume/suspend bits for timekeeping */
1912 static struct syscore_ops timekeeping_syscore_ops = {
1913 	.resume		= timekeeping_resume,
1914 	.suspend	= timekeeping_suspend,
1915 };
1916 
1917 static int __init timekeeping_init_ops(void)
1918 {
1919 	register_syscore_ops(&timekeeping_syscore_ops);
1920 	return 0;
1921 }
1922 device_initcall(timekeeping_init_ops);
1923 
1924 /*
1925  * Apply a multiplier adjustment to the timekeeper
1926  */
1927 static __always_inline void timekeeping_apply_adjustment(struct timekeeper *tk,
1928 							 s64 offset,
1929 							 s32 mult_adj)
1930 {
1931 	s64 interval = tk->cycle_interval;
1932 
1933 	if (mult_adj == 0) {
1934 		return;
1935 	} else if (mult_adj == -1) {
1936 		interval = -interval;
1937 		offset = -offset;
1938 	} else if (mult_adj != 1) {
1939 		interval *= mult_adj;
1940 		offset *= mult_adj;
1941 	}
1942 
1943 	/*
1944 	 * So the following can be confusing.
1945 	 *
1946 	 * To keep things simple, lets assume mult_adj == 1 for now.
1947 	 *
1948 	 * When mult_adj != 1, remember that the interval and offset values
1949 	 * have been appropriately scaled so the math is the same.
1950 	 *
1951 	 * The basic idea here is that we're increasing the multiplier
1952 	 * by one, this causes the xtime_interval to be incremented by
1953 	 * one cycle_interval. This is because:
1954 	 *	xtime_interval = cycle_interval * mult
1955 	 * So if mult is being incremented by one:
1956 	 *	xtime_interval = cycle_interval * (mult + 1)
1957 	 * Its the same as:
1958 	 *	xtime_interval = (cycle_interval * mult) + cycle_interval
1959 	 * Which can be shortened to:
1960 	 *	xtime_interval += cycle_interval
1961 	 *
1962 	 * So offset stores the non-accumulated cycles. Thus the current
1963 	 * time (in shifted nanoseconds) is:
1964 	 *	now = (offset * adj) + xtime_nsec
1965 	 * Now, even though we're adjusting the clock frequency, we have
1966 	 * to keep time consistent. In other words, we can't jump back
1967 	 * in time, and we also want to avoid jumping forward in time.
1968 	 *
1969 	 * So given the same offset value, we need the time to be the same
1970 	 * both before and after the freq adjustment.
1971 	 *	now = (offset * adj_1) + xtime_nsec_1
1972 	 *	now = (offset * adj_2) + xtime_nsec_2
1973 	 * So:
1974 	 *	(offset * adj_1) + xtime_nsec_1 =
1975 	 *		(offset * adj_2) + xtime_nsec_2
1976 	 * And we know:
1977 	 *	adj_2 = adj_1 + 1
1978 	 * So:
1979 	 *	(offset * adj_1) + xtime_nsec_1 =
1980 	 *		(offset * (adj_1+1)) + xtime_nsec_2
1981 	 *	(offset * adj_1) + xtime_nsec_1 =
1982 	 *		(offset * adj_1) + offset + xtime_nsec_2
1983 	 * Canceling the sides:
1984 	 *	xtime_nsec_1 = offset + xtime_nsec_2
1985 	 * Which gives us:
1986 	 *	xtime_nsec_2 = xtime_nsec_1 - offset
1987 	 * Which simplifies to:
1988 	 *	xtime_nsec -= offset
1989 	 */
1990 	if ((mult_adj > 0) && (tk->tkr_mono.mult + mult_adj < mult_adj)) {
1991 		/* NTP adjustment caused clocksource mult overflow */
1992 		WARN_ON_ONCE(1);
1993 		return;
1994 	}
1995 
1996 	tk->tkr_mono.mult += mult_adj;
1997 	tk->xtime_interval += interval;
1998 	tk->tkr_mono.xtime_nsec -= offset;
1999 }
2000 
2001 /*
2002  * Adjust the timekeeper's multiplier to the correct frequency
2003  * and also to reduce the accumulated error value.
2004  */
2005 static void timekeeping_adjust(struct timekeeper *tk, s64 offset)
2006 {
2007 	u32 mult;
2008 
2009 	/*
2010 	 * Determine the multiplier from the current NTP tick length.
2011 	 * Avoid expensive division when the tick length doesn't change.
2012 	 */
2013 	if (likely(tk->ntp_tick == ntp_tick_length())) {
2014 		mult = tk->tkr_mono.mult - tk->ntp_err_mult;
2015 	} else {
2016 		tk->ntp_tick = ntp_tick_length();
2017 		mult = div64_u64((tk->ntp_tick >> tk->ntp_error_shift) -
2018 				 tk->xtime_remainder, tk->cycle_interval);
2019 	}
2020 
2021 	/*
2022 	 * If the clock is behind the NTP time, increase the multiplier by 1
2023 	 * to catch up with it. If it's ahead and there was a remainder in the
2024 	 * tick division, the clock will slow down. Otherwise it will stay
2025 	 * ahead until the tick length changes to a non-divisible value.
2026 	 */
2027 	tk->ntp_err_mult = tk->ntp_error > 0 ? 1 : 0;
2028 	mult += tk->ntp_err_mult;
2029 
2030 	timekeeping_apply_adjustment(tk, offset, mult - tk->tkr_mono.mult);
2031 
2032 	if (unlikely(tk->tkr_mono.clock->maxadj &&
2033 		(abs(tk->tkr_mono.mult - tk->tkr_mono.clock->mult)
2034 			> tk->tkr_mono.clock->maxadj))) {
2035 		printk_once(KERN_WARNING
2036 			"Adjusting %s more than 11%% (%ld vs %ld)\n",
2037 			tk->tkr_mono.clock->name, (long)tk->tkr_mono.mult,
2038 			(long)tk->tkr_mono.clock->mult + tk->tkr_mono.clock->maxadj);
2039 	}
2040 
2041 	/*
2042 	 * It may be possible that when we entered this function, xtime_nsec
2043 	 * was very small.  Further, if we're slightly speeding the clocksource
2044 	 * in the code above, its possible the required corrective factor to
2045 	 * xtime_nsec could cause it to underflow.
2046 	 *
2047 	 * Now, since we have already accumulated the second and the NTP
2048 	 * subsystem has been notified via second_overflow(), we need to skip
2049 	 * the next update.
2050 	 */
2051 	if (unlikely((s64)tk->tkr_mono.xtime_nsec < 0)) {
2052 		tk->tkr_mono.xtime_nsec += (u64)NSEC_PER_SEC <<
2053 							tk->tkr_mono.shift;
2054 		tk->xtime_sec--;
2055 		tk->skip_second_overflow = 1;
2056 	}
2057 }
2058 
2059 /*
2060  * accumulate_nsecs_to_secs - Accumulates nsecs into secs
2061  *
2062  * Helper function that accumulates the nsecs greater than a second
2063  * from the xtime_nsec field to the xtime_secs field.
2064  * It also calls into the NTP code to handle leapsecond processing.
2065  */
2066 static inline unsigned int accumulate_nsecs_to_secs(struct timekeeper *tk)
2067 {
2068 	u64 nsecps = (u64)NSEC_PER_SEC << tk->tkr_mono.shift;
2069 	unsigned int clock_set = 0;
2070 
2071 	while (tk->tkr_mono.xtime_nsec >= nsecps) {
2072 		int leap;
2073 
2074 		tk->tkr_mono.xtime_nsec -= nsecps;
2075 		tk->xtime_sec++;
2076 
2077 		/*
2078 		 * Skip NTP update if this second was accumulated before,
2079 		 * i.e. xtime_nsec underflowed in timekeeping_adjust()
2080 		 */
2081 		if (unlikely(tk->skip_second_overflow)) {
2082 			tk->skip_second_overflow = 0;
2083 			continue;
2084 		}
2085 
2086 		/* Figure out if its a leap sec and apply if needed */
2087 		leap = second_overflow(tk->xtime_sec);
2088 		if (unlikely(leap)) {
2089 			struct timespec64 ts;
2090 
2091 			tk->xtime_sec += leap;
2092 
2093 			ts.tv_sec = leap;
2094 			ts.tv_nsec = 0;
2095 			tk_set_wall_to_mono(tk,
2096 				timespec64_sub(tk->wall_to_monotonic, ts));
2097 
2098 			__timekeeping_set_tai_offset(tk, tk->tai_offset - leap);
2099 
2100 			clock_set = TK_CLOCK_WAS_SET;
2101 		}
2102 	}
2103 	return clock_set;
2104 }
2105 
2106 /*
2107  * logarithmic_accumulation - shifted accumulation of cycles
2108  *
2109  * This functions accumulates a shifted interval of cycles into
2110  * a shifted interval nanoseconds. Allows for O(log) accumulation
2111  * loop.
2112  *
2113  * Returns the unconsumed cycles.
2114  */
2115 static u64 logarithmic_accumulation(struct timekeeper *tk, u64 offset,
2116 				    u32 shift, unsigned int *clock_set)
2117 {
2118 	u64 interval = tk->cycle_interval << shift;
2119 	u64 snsec_per_sec;
2120 
2121 	/* If the offset is smaller than a shifted interval, do nothing */
2122 	if (offset < interval)
2123 		return offset;
2124 
2125 	/* Accumulate one shifted interval */
2126 	offset -= interval;
2127 	tk->tkr_mono.cycle_last += interval;
2128 	tk->tkr_raw.cycle_last  += interval;
2129 
2130 	tk->tkr_mono.xtime_nsec += tk->xtime_interval << shift;
2131 	*clock_set |= accumulate_nsecs_to_secs(tk);
2132 
2133 	/* Accumulate raw time */
2134 	tk->tkr_raw.xtime_nsec += tk->raw_interval << shift;
2135 	snsec_per_sec = (u64)NSEC_PER_SEC << tk->tkr_raw.shift;
2136 	while (tk->tkr_raw.xtime_nsec >= snsec_per_sec) {
2137 		tk->tkr_raw.xtime_nsec -= snsec_per_sec;
2138 		tk->raw_sec++;
2139 	}
2140 
2141 	/* Accumulate error between NTP and clock interval */
2142 	tk->ntp_error += tk->ntp_tick << shift;
2143 	tk->ntp_error -= (tk->xtime_interval + tk->xtime_remainder) <<
2144 						(tk->ntp_error_shift + shift);
2145 
2146 	return offset;
2147 }
2148 
2149 /*
2150  * timekeeping_advance - Updates the timekeeper to the current time and
2151  * current NTP tick length
2152  */
2153 static bool timekeeping_advance(enum timekeeping_adv_mode mode)
2154 {
2155 	struct timekeeper *real_tk = &tk_core.timekeeper;
2156 	struct timekeeper *tk = &shadow_timekeeper;
2157 	u64 offset;
2158 	int shift = 0, maxshift;
2159 	unsigned int clock_set = 0;
2160 	unsigned long flags;
2161 
2162 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
2163 
2164 	/* Make sure we're fully resumed: */
2165 	if (unlikely(timekeeping_suspended))
2166 		goto out;
2167 
2168 	offset = clocksource_delta(tk_clock_read(&tk->tkr_mono),
2169 				   tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
2170 
2171 	/* Check if there's really nothing to do */
2172 	if (offset < real_tk->cycle_interval && mode == TK_ADV_TICK)
2173 		goto out;
2174 
2175 	/* Do some additional sanity checking */
2176 	timekeeping_check_update(tk, offset);
2177 
2178 	/*
2179 	 * With NO_HZ we may have to accumulate many cycle_intervals
2180 	 * (think "ticks") worth of time at once. To do this efficiently,
2181 	 * we calculate the largest doubling multiple of cycle_intervals
2182 	 * that is smaller than the offset.  We then accumulate that
2183 	 * chunk in one go, and then try to consume the next smaller
2184 	 * doubled multiple.
2185 	 */
2186 	shift = ilog2(offset) - ilog2(tk->cycle_interval);
2187 	shift = max(0, shift);
2188 	/* Bound shift to one less than what overflows tick_length */
2189 	maxshift = (64 - (ilog2(ntp_tick_length())+1)) - 1;
2190 	shift = min(shift, maxshift);
2191 	while (offset >= tk->cycle_interval) {
2192 		offset = logarithmic_accumulation(tk, offset, shift,
2193 							&clock_set);
2194 		if (offset < tk->cycle_interval<<shift)
2195 			shift--;
2196 	}
2197 
2198 	/* Adjust the multiplier to correct NTP error */
2199 	timekeeping_adjust(tk, offset);
2200 
2201 	/*
2202 	 * Finally, make sure that after the rounding
2203 	 * xtime_nsec isn't larger than NSEC_PER_SEC
2204 	 */
2205 	clock_set |= accumulate_nsecs_to_secs(tk);
2206 
2207 	write_seqcount_begin(&tk_core.seq);
2208 	/*
2209 	 * Update the real timekeeper.
2210 	 *
2211 	 * We could avoid this memcpy by switching pointers, but that
2212 	 * requires changes to all other timekeeper usage sites as
2213 	 * well, i.e. move the timekeeper pointer getter into the
2214 	 * spinlocked/seqcount protected sections. And we trade this
2215 	 * memcpy under the tk_core.seq against one before we start
2216 	 * updating.
2217 	 */
2218 	timekeeping_update(tk, clock_set);
2219 	memcpy(real_tk, tk, sizeof(*tk));
2220 	/* The memcpy must come last. Do not put anything here! */
2221 	write_seqcount_end(&tk_core.seq);
2222 out:
2223 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2224 
2225 	return !!clock_set;
2226 }
2227 
2228 /**
2229  * update_wall_time - Uses the current clocksource to increment the wall time
2230  *
2231  */
2232 void update_wall_time(void)
2233 {
2234 	if (timekeeping_advance(TK_ADV_TICK))
2235 		clock_was_set_delayed();
2236 }
2237 
2238 /**
2239  * getboottime64 - Return the real time of system boot.
2240  * @ts:		pointer to the timespec64 to be set
2241  *
2242  * Returns the wall-time of boot in a timespec64.
2243  *
2244  * This is based on the wall_to_monotonic offset and the total suspend
2245  * time. Calls to settimeofday will affect the value returned (which
2246  * basically means that however wrong your real time clock is at boot time,
2247  * you get the right time here).
2248  */
2249 void getboottime64(struct timespec64 *ts)
2250 {
2251 	struct timekeeper *tk = &tk_core.timekeeper;
2252 	ktime_t t = ktime_sub(tk->offs_real, tk->offs_boot);
2253 
2254 	*ts = ktime_to_timespec64(t);
2255 }
2256 EXPORT_SYMBOL_GPL(getboottime64);
2257 
2258 void ktime_get_coarse_real_ts64(struct timespec64 *ts)
2259 {
2260 	struct timekeeper *tk = &tk_core.timekeeper;
2261 	unsigned int seq;
2262 
2263 	do {
2264 		seq = read_seqcount_begin(&tk_core.seq);
2265 
2266 		*ts = tk_xtime(tk);
2267 	} while (read_seqcount_retry(&tk_core.seq, seq));
2268 }
2269 EXPORT_SYMBOL(ktime_get_coarse_real_ts64);
2270 
2271 void ktime_get_coarse_ts64(struct timespec64 *ts)
2272 {
2273 	struct timekeeper *tk = &tk_core.timekeeper;
2274 	struct timespec64 now, mono;
2275 	unsigned int seq;
2276 
2277 	do {
2278 		seq = read_seqcount_begin(&tk_core.seq);
2279 
2280 		now = tk_xtime(tk);
2281 		mono = tk->wall_to_monotonic;
2282 	} while (read_seqcount_retry(&tk_core.seq, seq));
2283 
2284 	set_normalized_timespec64(ts, now.tv_sec + mono.tv_sec,
2285 				now.tv_nsec + mono.tv_nsec);
2286 }
2287 EXPORT_SYMBOL(ktime_get_coarse_ts64);
2288 
2289 /*
2290  * Must hold jiffies_lock
2291  */
2292 void do_timer(unsigned long ticks)
2293 {
2294 	jiffies_64 += ticks;
2295 	calc_global_load();
2296 }
2297 
2298 /**
2299  * ktime_get_update_offsets_now - hrtimer helper
2300  * @cwsseq:	pointer to check and store the clock was set sequence number
2301  * @offs_real:	pointer to storage for monotonic -> realtime offset
2302  * @offs_boot:	pointer to storage for monotonic -> boottime offset
2303  * @offs_tai:	pointer to storage for monotonic -> clock tai offset
2304  *
2305  * Returns current monotonic time and updates the offsets if the
2306  * sequence number in @cwsseq and timekeeper.clock_was_set_seq are
2307  * different.
2308  *
2309  * Called from hrtimer_interrupt() or retrigger_next_event()
2310  */
2311 ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq, ktime_t *offs_real,
2312 				     ktime_t *offs_boot, ktime_t *offs_tai)
2313 {
2314 	struct timekeeper *tk = &tk_core.timekeeper;
2315 	unsigned int seq;
2316 	ktime_t base;
2317 	u64 nsecs;
2318 
2319 	do {
2320 		seq = read_seqcount_begin(&tk_core.seq);
2321 
2322 		base = tk->tkr_mono.base;
2323 		nsecs = timekeeping_get_ns(&tk->tkr_mono);
2324 		base = ktime_add_ns(base, nsecs);
2325 
2326 		if (*cwsseq != tk->clock_was_set_seq) {
2327 			*cwsseq = tk->clock_was_set_seq;
2328 			*offs_real = tk->offs_real;
2329 			*offs_boot = tk->offs_boot;
2330 			*offs_tai = tk->offs_tai;
2331 		}
2332 
2333 		/* Handle leapsecond insertion adjustments */
2334 		if (unlikely(base >= tk->next_leap_ktime))
2335 			*offs_real = ktime_sub(tk->offs_real, ktime_set(1, 0));
2336 
2337 	} while (read_seqcount_retry(&tk_core.seq, seq));
2338 
2339 	return base;
2340 }
2341 
2342 /*
2343  * timekeeping_validate_timex - Ensures the timex is ok for use in do_adjtimex
2344  */
2345 static int timekeeping_validate_timex(const struct __kernel_timex *txc)
2346 {
2347 	if (txc->modes & ADJ_ADJTIME) {
2348 		/* singleshot must not be used with any other mode bits */
2349 		if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
2350 			return -EINVAL;
2351 		if (!(txc->modes & ADJ_OFFSET_READONLY) &&
2352 		    !capable(CAP_SYS_TIME))
2353 			return -EPERM;
2354 	} else {
2355 		/* In order to modify anything, you gotta be super-user! */
2356 		if (txc->modes && !capable(CAP_SYS_TIME))
2357 			return -EPERM;
2358 		/*
2359 		 * if the quartz is off by more than 10% then
2360 		 * something is VERY wrong!
2361 		 */
2362 		if (txc->modes & ADJ_TICK &&
2363 		    (txc->tick <  900000/USER_HZ ||
2364 		     txc->tick > 1100000/USER_HZ))
2365 			return -EINVAL;
2366 	}
2367 
2368 	if (txc->modes & ADJ_SETOFFSET) {
2369 		/* In order to inject time, you gotta be super-user! */
2370 		if (!capable(CAP_SYS_TIME))
2371 			return -EPERM;
2372 
2373 		/*
2374 		 * Validate if a timespec/timeval used to inject a time
2375 		 * offset is valid.  Offsets can be positive or negative, so
2376 		 * we don't check tv_sec. The value of the timeval/timespec
2377 		 * is the sum of its fields,but *NOTE*:
2378 		 * The field tv_usec/tv_nsec must always be non-negative and
2379 		 * we can't have more nanoseconds/microseconds than a second.
2380 		 */
2381 		if (txc->time.tv_usec < 0)
2382 			return -EINVAL;
2383 
2384 		if (txc->modes & ADJ_NANO) {
2385 			if (txc->time.tv_usec >= NSEC_PER_SEC)
2386 				return -EINVAL;
2387 		} else {
2388 			if (txc->time.tv_usec >= USEC_PER_SEC)
2389 				return -EINVAL;
2390 		}
2391 	}
2392 
2393 	/*
2394 	 * Check for potential multiplication overflows that can
2395 	 * only happen on 64-bit systems:
2396 	 */
2397 	if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) {
2398 		if (LLONG_MIN / PPM_SCALE > txc->freq)
2399 			return -EINVAL;
2400 		if (LLONG_MAX / PPM_SCALE < txc->freq)
2401 			return -EINVAL;
2402 	}
2403 
2404 	return 0;
2405 }
2406 
2407 /**
2408  * random_get_entropy_fallback - Returns the raw clock source value,
2409  * used by random.c for platforms with no valid random_get_entropy().
2410  */
2411 unsigned long random_get_entropy_fallback(void)
2412 {
2413 	struct tk_read_base *tkr = &tk_core.timekeeper.tkr_mono;
2414 	struct clocksource *clock = READ_ONCE(tkr->clock);
2415 
2416 	if (unlikely(timekeeping_suspended || !clock))
2417 		return 0;
2418 	return clock->read(clock);
2419 }
2420 EXPORT_SYMBOL_GPL(random_get_entropy_fallback);
2421 
2422 /**
2423  * do_adjtimex() - Accessor function to NTP __do_adjtimex function
2424  */
2425 int do_adjtimex(struct __kernel_timex *txc)
2426 {
2427 	struct timekeeper *tk = &tk_core.timekeeper;
2428 	struct audit_ntp_data ad;
2429 	bool clock_set = false;
2430 	struct timespec64 ts;
2431 	unsigned long flags;
2432 	s32 orig_tai, tai;
2433 	int ret;
2434 
2435 	/* Validate the data before disabling interrupts */
2436 	ret = timekeeping_validate_timex(txc);
2437 	if (ret)
2438 		return ret;
2439 	add_device_randomness(txc, sizeof(*txc));
2440 
2441 	if (txc->modes & ADJ_SETOFFSET) {
2442 		struct timespec64 delta;
2443 		delta.tv_sec  = txc->time.tv_sec;
2444 		delta.tv_nsec = txc->time.tv_usec;
2445 		if (!(txc->modes & ADJ_NANO))
2446 			delta.tv_nsec *= 1000;
2447 		ret = timekeeping_inject_offset(&delta);
2448 		if (ret)
2449 			return ret;
2450 
2451 		audit_tk_injoffset(delta);
2452 	}
2453 
2454 	audit_ntp_init(&ad);
2455 
2456 	ktime_get_real_ts64(&ts);
2457 	add_device_randomness(&ts, sizeof(ts));
2458 
2459 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
2460 	write_seqcount_begin(&tk_core.seq);
2461 
2462 	orig_tai = tai = tk->tai_offset;
2463 	ret = __do_adjtimex(txc, &ts, &tai, &ad);
2464 
2465 	if (tai != orig_tai) {
2466 		__timekeeping_set_tai_offset(tk, tai);
2467 		timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
2468 		clock_set = true;
2469 	}
2470 	tk_update_leap_state(tk);
2471 
2472 	write_seqcount_end(&tk_core.seq);
2473 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2474 
2475 	audit_ntp_log(&ad);
2476 
2477 	/* Update the multiplier immediately if frequency was set directly */
2478 	if (txc->modes & (ADJ_FREQUENCY | ADJ_TICK))
2479 		clock_set |= timekeeping_advance(TK_ADV_FREQ);
2480 
2481 	if (clock_set)
2482 		clock_was_set(CLOCK_REALTIME);
2483 
2484 	ntp_notify_cmos_timer();
2485 
2486 	return ret;
2487 }
2488 
2489 #ifdef CONFIG_NTP_PPS
2490 /**
2491  * hardpps() - Accessor function to NTP __hardpps function
2492  */
2493 void hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
2494 {
2495 	unsigned long flags;
2496 
2497 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
2498 	write_seqcount_begin(&tk_core.seq);
2499 
2500 	__hardpps(phase_ts, raw_ts);
2501 
2502 	write_seqcount_end(&tk_core.seq);
2503 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2504 }
2505 EXPORT_SYMBOL(hardpps);
2506 #endif /* CONFIG_NTP_PPS */
2507