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 
dummy_clock_read(struct clocksource * cs)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 
tk_normalize_xtime(struct timekeeper * tk)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 
tk_xtime(const struct timekeeper * tk)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 
tk_set_xtime(struct timekeeper * tk,const struct timespec64 * ts)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 
tk_xtime_add(struct timekeeper * tk,const struct timespec64 * ts)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 
tk_set_wall_to_mono(struct timekeeper * tk,struct timespec64 wtm)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 
tk_update_sleep_time(struct timekeeper * tk,ktime_t delta)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  */
tk_clock_read(const struct tk_read_base * tkr)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 
timekeeping_check_update(struct timekeeper * tk,u64 offset)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 
timekeeping_get_delta(const struct tk_read_base * tkr)240 static inline u64 timekeeping_get_delta(const struct tk_read_base *tkr)
241 {
242 	struct timekeeper *tk = &tk_core.timekeeper;
243 	u64 now, last, mask, max, delta;
244 	unsigned int seq;
245 
246 	/*
247 	 * Since we're called holding a seqcount, the data may shift
248 	 * under us while we're doing the calculation. This can cause
249 	 * false positives, since we'd note a problem but throw the
250 	 * results away. So nest another seqcount here to atomically
251 	 * grab the points we are checking with.
252 	 */
253 	do {
254 		seq = read_seqcount_begin(&tk_core.seq);
255 		now = tk_clock_read(tkr);
256 		last = tkr->cycle_last;
257 		mask = tkr->mask;
258 		max = tkr->clock->max_cycles;
259 	} while (read_seqcount_retry(&tk_core.seq, seq));
260 
261 	delta = clocksource_delta(now, last, mask);
262 
263 	/*
264 	 * Try to catch underflows by checking if we are seeing small
265 	 * mask-relative negative values.
266 	 */
267 	if (unlikely((~delta & mask) < (mask >> 3))) {
268 		tk->underflow_seen = 1;
269 		delta = 0;
270 	}
271 
272 	/* Cap delta value to the max_cycles values to avoid mult overflows */
273 	if (unlikely(delta > max)) {
274 		tk->overflow_seen = 1;
275 		delta = tkr->clock->max_cycles;
276 	}
277 
278 	return delta;
279 }
280 #else
timekeeping_check_update(struct timekeeper * tk,u64 offset)281 static inline void timekeeping_check_update(struct timekeeper *tk, u64 offset)
282 {
283 }
timekeeping_get_delta(const struct tk_read_base * tkr)284 static inline u64 timekeeping_get_delta(const struct tk_read_base *tkr)
285 {
286 	u64 cycle_now, delta;
287 
288 	/* read clocksource */
289 	cycle_now = tk_clock_read(tkr);
290 
291 	/* calculate the delta since the last update_wall_time */
292 	delta = clocksource_delta(cycle_now, tkr->cycle_last, tkr->mask);
293 
294 	return delta;
295 }
296 #endif
297 
298 /**
299  * tk_setup_internals - Set up internals to use clocksource clock.
300  *
301  * @tk:		The target timekeeper to setup.
302  * @clock:		Pointer to clocksource.
303  *
304  * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
305  * pair and interval request.
306  *
307  * Unless you're the timekeeping code, you should not be using this!
308  */
tk_setup_internals(struct timekeeper * tk,struct clocksource * clock)309 static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
310 {
311 	u64 interval;
312 	u64 tmp, ntpinterval;
313 	struct clocksource *old_clock;
314 
315 	++tk->cs_was_changed_seq;
316 	old_clock = tk->tkr_mono.clock;
317 	tk->tkr_mono.clock = clock;
318 	tk->tkr_mono.mask = clock->mask;
319 	tk->tkr_mono.cycle_last = tk_clock_read(&tk->tkr_mono);
320 
321 	tk->tkr_raw.clock = clock;
322 	tk->tkr_raw.mask = clock->mask;
323 	tk->tkr_raw.cycle_last = tk->tkr_mono.cycle_last;
324 
325 	/* Do the ns -> cycle conversion first, using original mult */
326 	tmp = NTP_INTERVAL_LENGTH;
327 	tmp <<= clock->shift;
328 	ntpinterval = tmp;
329 	tmp += clock->mult/2;
330 	do_div(tmp, clock->mult);
331 	if (tmp == 0)
332 		tmp = 1;
333 
334 	interval = (u64) tmp;
335 	tk->cycle_interval = interval;
336 
337 	/* Go back from cycles -> shifted ns */
338 	tk->xtime_interval = interval * clock->mult;
339 	tk->xtime_remainder = ntpinterval - tk->xtime_interval;
340 	tk->raw_interval = interval * clock->mult;
341 
342 	 /* if changing clocks, convert xtime_nsec shift units */
343 	if (old_clock) {
344 		int shift_change = clock->shift - old_clock->shift;
345 		if (shift_change < 0) {
346 			tk->tkr_mono.xtime_nsec >>= -shift_change;
347 			tk->tkr_raw.xtime_nsec >>= -shift_change;
348 		} else {
349 			tk->tkr_mono.xtime_nsec <<= shift_change;
350 			tk->tkr_raw.xtime_nsec <<= shift_change;
351 		}
352 	}
353 
354 	tk->tkr_mono.shift = clock->shift;
355 	tk->tkr_raw.shift = clock->shift;
356 
357 	tk->ntp_error = 0;
358 	tk->ntp_error_shift = NTP_SCALE_SHIFT - clock->shift;
359 	tk->ntp_tick = ntpinterval << tk->ntp_error_shift;
360 
361 	/*
362 	 * The timekeeper keeps its own mult values for the currently
363 	 * active clocksource. These value will be adjusted via NTP
364 	 * to counteract clock drifting.
365 	 */
366 	tk->tkr_mono.mult = clock->mult;
367 	tk->tkr_raw.mult = clock->mult;
368 	tk->ntp_err_mult = 0;
369 	tk->skip_second_overflow = 0;
370 }
371 
372 /* Timekeeper helper functions. */
373 
timekeeping_delta_to_ns(const struct tk_read_base * tkr,u64 delta)374 static inline u64 timekeeping_delta_to_ns(const struct tk_read_base *tkr, u64 delta)
375 {
376 	u64 nsec;
377 
378 	nsec = delta * tkr->mult + tkr->xtime_nsec;
379 	nsec >>= tkr->shift;
380 
381 	return nsec;
382 }
383 
timekeeping_get_ns(const struct tk_read_base * tkr)384 static inline u64 timekeeping_get_ns(const struct tk_read_base *tkr)
385 {
386 	u64 delta;
387 
388 	delta = timekeeping_get_delta(tkr);
389 	return timekeeping_delta_to_ns(tkr, delta);
390 }
391 
timekeeping_cycles_to_ns(const struct tk_read_base * tkr,u64 cycles)392 static inline u64 timekeeping_cycles_to_ns(const struct tk_read_base *tkr, u64 cycles)
393 {
394 	u64 delta;
395 
396 	/* calculate the delta since the last update_wall_time */
397 	delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
398 	return timekeeping_delta_to_ns(tkr, delta);
399 }
400 
401 /**
402  * update_fast_timekeeper - Update the fast and NMI safe monotonic timekeeper.
403  * @tkr: Timekeeping readout base from which we take the update
404  * @tkf: Pointer to NMI safe timekeeper
405  *
406  * We want to use this from any context including NMI and tracing /
407  * instrumenting the timekeeping code itself.
408  *
409  * Employ the latch technique; see @raw_write_seqcount_latch.
410  *
411  * So if a NMI hits the update of base[0] then it will use base[1]
412  * which is still consistent. In the worst case this can result is a
413  * slightly wrong timestamp (a few nanoseconds). See
414  * @ktime_get_mono_fast_ns.
415  */
update_fast_timekeeper(const struct tk_read_base * tkr,struct tk_fast * tkf)416 static void update_fast_timekeeper(const struct tk_read_base *tkr,
417 				   struct tk_fast *tkf)
418 {
419 	struct tk_read_base *base = tkf->base;
420 
421 	/* Force readers off to base[1] */
422 	raw_write_seqcount_latch(&tkf->seq);
423 
424 	/* Update base[0] */
425 	memcpy(base, tkr, sizeof(*base));
426 
427 	/* Force readers back to base[0] */
428 	raw_write_seqcount_latch(&tkf->seq);
429 
430 	/* Update base[1] */
431 	memcpy(base + 1, base, sizeof(*base));
432 }
433 
fast_tk_get_delta_ns(struct tk_read_base * tkr)434 static __always_inline u64 fast_tk_get_delta_ns(struct tk_read_base *tkr)
435 {
436 	u64 delta, cycles = tk_clock_read(tkr);
437 
438 	delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
439 	return timekeeping_delta_to_ns(tkr, delta);
440 }
441 
__ktime_get_fast_ns(struct tk_fast * tkf)442 static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
443 {
444 	struct tk_read_base *tkr;
445 	unsigned int seq;
446 	u64 now;
447 
448 	do {
449 		seq = raw_read_seqcount_latch(&tkf->seq);
450 		tkr = tkf->base + (seq & 0x01);
451 		now = ktime_to_ns(tkr->base);
452 		now += fast_tk_get_delta_ns(tkr);
453 	} while (raw_read_seqcount_latch_retry(&tkf->seq, seq));
454 
455 	return now;
456 }
457 
458 /**
459  * ktime_get_mono_fast_ns - Fast NMI safe access to clock monotonic
460  *
461  * This timestamp is not guaranteed to be monotonic across an update.
462  * The timestamp is calculated by:
463  *
464  *	now = base_mono + clock_delta * slope
465  *
466  * So if the update lowers the slope, readers who are forced to the
467  * not yet updated second array are still using the old steeper slope.
468  *
469  * tmono
470  * ^
471  * |    o  n
472  * |   o n
473  * |  u
474  * | o
475  * |o
476  * |12345678---> reader order
477  *
478  * o = old slope
479  * u = update
480  * n = new slope
481  *
482  * So reader 6 will observe time going backwards versus reader 5.
483  *
484  * While other CPUs are likely to be able to observe that, the only way
485  * for a CPU local observation is when an NMI hits in the middle of
486  * the update. Timestamps taken from that NMI context might be ahead
487  * of the following timestamps. Callers need to be aware of that and
488  * deal with it.
489  */
ktime_get_mono_fast_ns(void)490 u64 notrace ktime_get_mono_fast_ns(void)
491 {
492 	return __ktime_get_fast_ns(&tk_fast_mono);
493 }
494 EXPORT_SYMBOL_GPL(ktime_get_mono_fast_ns);
495 
496 /**
497  * ktime_get_raw_fast_ns - Fast NMI safe access to clock monotonic raw
498  *
499  * Contrary to ktime_get_mono_fast_ns() this is always correct because the
500  * conversion factor is not affected by NTP/PTP correction.
501  */
ktime_get_raw_fast_ns(void)502 u64 notrace ktime_get_raw_fast_ns(void)
503 {
504 	return __ktime_get_fast_ns(&tk_fast_raw);
505 }
506 EXPORT_SYMBOL_GPL(ktime_get_raw_fast_ns);
507 
508 /**
509  * ktime_get_boot_fast_ns - NMI safe and fast access to boot clock.
510  *
511  * To keep it NMI safe since we're accessing from tracing, we're not using a
512  * separate timekeeper with updates to monotonic clock and boot offset
513  * protected with seqcounts. This has the following minor side effects:
514  *
515  * (1) Its possible that a timestamp be taken after the boot offset is updated
516  * but before the timekeeper is updated. If this happens, the new boot offset
517  * is added to the old timekeeping making the clock appear to update slightly
518  * earlier:
519  *    CPU 0                                        CPU 1
520  *    timekeeping_inject_sleeptime64()
521  *    __timekeeping_inject_sleeptime(tk, delta);
522  *                                                 timestamp();
523  *    timekeeping_update(tk, TK_CLEAR_NTP...);
524  *
525  * (2) On 32-bit systems, the 64-bit boot offset (tk->offs_boot) may be
526  * partially updated.  Since the tk->offs_boot update is a rare event, this
527  * should be a rare occurrence which postprocessing should be able to handle.
528  *
529  * The caveats vs. timestamp ordering as documented for ktime_get_mono_fast_ns()
530  * apply as well.
531  */
ktime_get_boot_fast_ns(void)532 u64 notrace ktime_get_boot_fast_ns(void)
533 {
534 	struct timekeeper *tk = &tk_core.timekeeper;
535 
536 	return (ktime_get_mono_fast_ns() + ktime_to_ns(data_race(tk->offs_boot)));
537 }
538 EXPORT_SYMBOL_GPL(ktime_get_boot_fast_ns);
539 
540 /**
541  * ktime_get_tai_fast_ns - NMI safe and fast access to tai clock.
542  *
543  * The same limitations as described for ktime_get_boot_fast_ns() apply. The
544  * mono time and the TAI offset are not read atomically which may yield wrong
545  * readouts. However, an update of the TAI offset is an rare event e.g., caused
546  * by settime or adjtimex with an offset. The user of this function has to deal
547  * with the possibility of wrong timestamps in post processing.
548  */
ktime_get_tai_fast_ns(void)549 u64 notrace ktime_get_tai_fast_ns(void)
550 {
551 	struct timekeeper *tk = &tk_core.timekeeper;
552 
553 	return (ktime_get_mono_fast_ns() + ktime_to_ns(data_race(tk->offs_tai)));
554 }
555 EXPORT_SYMBOL_GPL(ktime_get_tai_fast_ns);
556 
__ktime_get_real_fast(struct tk_fast * tkf,u64 * mono)557 static __always_inline u64 __ktime_get_real_fast(struct tk_fast *tkf, u64 *mono)
558 {
559 	struct tk_read_base *tkr;
560 	u64 basem, baser, delta;
561 	unsigned int seq;
562 
563 	do {
564 		seq = raw_read_seqcount_latch(&tkf->seq);
565 		tkr = tkf->base + (seq & 0x01);
566 		basem = ktime_to_ns(tkr->base);
567 		baser = ktime_to_ns(tkr->base_real);
568 		delta = fast_tk_get_delta_ns(tkr);
569 	} while (raw_read_seqcount_latch_retry(&tkf->seq, seq));
570 
571 	if (mono)
572 		*mono = basem + delta;
573 	return baser + delta;
574 }
575 
576 /**
577  * ktime_get_real_fast_ns: - NMI safe and fast access to clock realtime.
578  *
579  * See ktime_get_mono_fast_ns() for documentation of the time stamp ordering.
580  */
ktime_get_real_fast_ns(void)581 u64 ktime_get_real_fast_ns(void)
582 {
583 	return __ktime_get_real_fast(&tk_fast_mono, NULL);
584 }
585 EXPORT_SYMBOL_GPL(ktime_get_real_fast_ns);
586 
587 /**
588  * ktime_get_fast_timestamps: - NMI safe timestamps
589  * @snapshot:	Pointer to timestamp storage
590  *
591  * Stores clock monotonic, boottime and realtime timestamps.
592  *
593  * Boot time is a racy access on 32bit systems if the sleep time injection
594  * happens late during resume and not in timekeeping_resume(). That could
595  * be avoided by expanding struct tk_read_base with boot offset for 32bit
596  * and adding more overhead to the update. As this is a hard to observe
597  * once per resume event which can be filtered with reasonable effort using
598  * the accurate mono/real timestamps, it's probably not worth the trouble.
599  *
600  * Aside of that it might be possible on 32 and 64 bit to observe the
601  * following when the sleep time injection happens late:
602  *
603  * CPU 0				CPU 1
604  * timekeeping_resume()
605  * ktime_get_fast_timestamps()
606  *	mono, real = __ktime_get_real_fast()
607  *					inject_sleep_time()
608  *					   update boot offset
609  *	boot = mono + bootoffset;
610  *
611  * That means that boot time already has the sleep time adjustment, but
612  * real time does not. On the next readout both are in sync again.
613  *
614  * Preventing this for 64bit is not really feasible without destroying the
615  * careful cache layout of the timekeeper because the sequence count and
616  * struct tk_read_base would then need two cache lines instead of one.
617  *
618  * Access to the time keeper clock source is disabled across the innermost
619  * steps of suspend/resume. The accessors still work, but the timestamps
620  * are frozen until time keeping is resumed which happens very early.
621  *
622  * For regular suspend/resume there is no observable difference vs. sched
623  * clock, but it might affect some of the nasty low level debug printks.
624  *
625  * OTOH, access to sched clock is not guaranteed across suspend/resume on
626  * all systems either so it depends on the hardware in use.
627  *
628  * If that turns out to be a real problem then this could be mitigated by
629  * using sched clock in a similar way as during early boot. But it's not as
630  * trivial as on early boot because it needs some careful protection
631  * against the clock monotonic timestamp jumping backwards on resume.
632  */
ktime_get_fast_timestamps(struct ktime_timestamps * snapshot)633 void ktime_get_fast_timestamps(struct ktime_timestamps *snapshot)
634 {
635 	struct timekeeper *tk = &tk_core.timekeeper;
636 
637 	snapshot->real = __ktime_get_real_fast(&tk_fast_mono, &snapshot->mono);
638 	snapshot->boot = snapshot->mono + ktime_to_ns(data_race(tk->offs_boot));
639 }
640 
641 /**
642  * halt_fast_timekeeper - Prevent fast timekeeper from accessing clocksource.
643  * @tk: Timekeeper to snapshot.
644  *
645  * It generally is unsafe to access the clocksource after timekeeping has been
646  * suspended, so take a snapshot of the readout base of @tk and use it as the
647  * fast timekeeper's readout base while suspended.  It will return the same
648  * number of cycles every time until timekeeping is resumed at which time the
649  * proper readout base for the fast timekeeper will be restored automatically.
650  */
halt_fast_timekeeper(const struct timekeeper * tk)651 static void halt_fast_timekeeper(const struct timekeeper *tk)
652 {
653 	static struct tk_read_base tkr_dummy;
654 	const struct tk_read_base *tkr = &tk->tkr_mono;
655 
656 	memcpy(&tkr_dummy, tkr, sizeof(tkr_dummy));
657 	cycles_at_suspend = tk_clock_read(tkr);
658 	tkr_dummy.clock = &dummy_clock;
659 	tkr_dummy.base_real = tkr->base + tk->offs_real;
660 	update_fast_timekeeper(&tkr_dummy, &tk_fast_mono);
661 
662 	tkr = &tk->tkr_raw;
663 	memcpy(&tkr_dummy, tkr, sizeof(tkr_dummy));
664 	tkr_dummy.clock = &dummy_clock;
665 	update_fast_timekeeper(&tkr_dummy, &tk_fast_raw);
666 }
667 
668 static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);
669 
update_pvclock_gtod(struct timekeeper * tk,bool was_set)670 static void update_pvclock_gtod(struct timekeeper *tk, bool was_set)
671 {
672 	raw_notifier_call_chain(&pvclock_gtod_chain, was_set, tk);
673 }
674 
675 /**
676  * pvclock_gtod_register_notifier - register a pvclock timedata update listener
677  * @nb: Pointer to the notifier block to register
678  */
pvclock_gtod_register_notifier(struct notifier_block * nb)679 int pvclock_gtod_register_notifier(struct notifier_block *nb)
680 {
681 	struct timekeeper *tk = &tk_core.timekeeper;
682 	unsigned long flags;
683 	int ret;
684 
685 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
686 	ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);
687 	update_pvclock_gtod(tk, true);
688 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
689 
690 	return ret;
691 }
692 EXPORT_SYMBOL_GPL(pvclock_gtod_register_notifier);
693 
694 /**
695  * pvclock_gtod_unregister_notifier - unregister a pvclock
696  * timedata update listener
697  * @nb: Pointer to the notifier block to unregister
698  */
pvclock_gtod_unregister_notifier(struct notifier_block * nb)699 int pvclock_gtod_unregister_notifier(struct notifier_block *nb)
700 {
701 	unsigned long flags;
702 	int ret;
703 
704 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
705 	ret = raw_notifier_chain_unregister(&pvclock_gtod_chain, nb);
706 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
707 
708 	return ret;
709 }
710 EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);
711 
712 /*
713  * tk_update_leap_state - helper to update the next_leap_ktime
714  */
tk_update_leap_state(struct timekeeper * tk)715 static inline void tk_update_leap_state(struct timekeeper *tk)
716 {
717 	tk->next_leap_ktime = ntp_get_next_leap();
718 	if (tk->next_leap_ktime != KTIME_MAX)
719 		/* Convert to monotonic time */
720 		tk->next_leap_ktime = ktime_sub(tk->next_leap_ktime, tk->offs_real);
721 }
722 
723 /*
724  * Update the ktime_t based scalar nsec members of the timekeeper
725  */
tk_update_ktime_data(struct timekeeper * tk)726 static inline void tk_update_ktime_data(struct timekeeper *tk)
727 {
728 	u64 seconds;
729 	u32 nsec;
730 
731 	/*
732 	 * The xtime based monotonic readout is:
733 	 *	nsec = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec + now();
734 	 * The ktime based monotonic readout is:
735 	 *	nsec = base_mono + now();
736 	 * ==> base_mono = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec
737 	 */
738 	seconds = (u64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec);
739 	nsec = (u32) tk->wall_to_monotonic.tv_nsec;
740 	tk->tkr_mono.base = ns_to_ktime(seconds * NSEC_PER_SEC + nsec);
741 
742 	/*
743 	 * The sum of the nanoseconds portions of xtime and
744 	 * wall_to_monotonic can be greater/equal one second. Take
745 	 * this into account before updating tk->ktime_sec.
746 	 */
747 	nsec += (u32)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
748 	if (nsec >= NSEC_PER_SEC)
749 		seconds++;
750 	tk->ktime_sec = seconds;
751 
752 	/* Update the monotonic raw base */
753 	tk->tkr_raw.base = ns_to_ktime(tk->raw_sec * NSEC_PER_SEC);
754 }
755 
756 /* must hold timekeeper_lock */
timekeeping_update(struct timekeeper * tk,unsigned int action)757 static void timekeeping_update(struct timekeeper *tk, unsigned int action)
758 {
759 	if (action & TK_CLEAR_NTP) {
760 		tk->ntp_error = 0;
761 		ntp_clear();
762 	}
763 
764 	tk_update_leap_state(tk);
765 	tk_update_ktime_data(tk);
766 
767 	update_vsyscall(tk);
768 	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
769 
770 	tk->tkr_mono.base_real = tk->tkr_mono.base + tk->offs_real;
771 	update_fast_timekeeper(&tk->tkr_mono, &tk_fast_mono);
772 	update_fast_timekeeper(&tk->tkr_raw,  &tk_fast_raw);
773 
774 	if (action & TK_CLOCK_WAS_SET)
775 		tk->clock_was_set_seq++;
776 	/*
777 	 * The mirroring of the data to the shadow-timekeeper needs
778 	 * to happen last here to ensure we don't over-write the
779 	 * timekeeper structure on the next update with stale data
780 	 */
781 	if (action & TK_MIRROR)
782 		memcpy(&shadow_timekeeper, &tk_core.timekeeper,
783 		       sizeof(tk_core.timekeeper));
784 }
785 
786 /**
787  * timekeeping_forward_now - update clock to the current time
788  * @tk:		Pointer to the timekeeper to update
789  *
790  * Forward the current clock to update its state since the last call to
791  * update_wall_time(). This is useful before significant clock changes,
792  * as it avoids having to deal with this time offset explicitly.
793  */
timekeeping_forward_now(struct timekeeper * tk)794 static void timekeeping_forward_now(struct timekeeper *tk)
795 {
796 	u64 cycle_now, delta;
797 
798 	cycle_now = tk_clock_read(&tk->tkr_mono);
799 	delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
800 	tk->tkr_mono.cycle_last = cycle_now;
801 	tk->tkr_raw.cycle_last  = cycle_now;
802 
803 	tk->tkr_mono.xtime_nsec += delta * tk->tkr_mono.mult;
804 	tk->tkr_raw.xtime_nsec += delta * tk->tkr_raw.mult;
805 
806 	tk_normalize_xtime(tk);
807 }
808 
809 /**
810  * ktime_get_real_ts64 - Returns the time of day in a timespec64.
811  * @ts:		pointer to the timespec to be set
812  *
813  * Returns the time of day in a timespec64 (WARN if suspended).
814  */
ktime_get_real_ts64(struct timespec64 * ts)815 void ktime_get_real_ts64(struct timespec64 *ts)
816 {
817 	struct timekeeper *tk = &tk_core.timekeeper;
818 	unsigned int seq;
819 	u64 nsecs;
820 
821 	WARN_ON(timekeeping_suspended);
822 
823 	do {
824 		seq = read_seqcount_begin(&tk_core.seq);
825 
826 		ts->tv_sec = tk->xtime_sec;
827 		nsecs = timekeeping_get_ns(&tk->tkr_mono);
828 
829 	} while (read_seqcount_retry(&tk_core.seq, seq));
830 
831 	ts->tv_nsec = 0;
832 	timespec64_add_ns(ts, nsecs);
833 }
834 EXPORT_SYMBOL(ktime_get_real_ts64);
835 
ktime_get(void)836 ktime_t ktime_get(void)
837 {
838 	struct timekeeper *tk = &tk_core.timekeeper;
839 	unsigned int seq;
840 	ktime_t base;
841 	u64 nsecs;
842 
843 	WARN_ON(timekeeping_suspended);
844 
845 	do {
846 		seq = read_seqcount_begin(&tk_core.seq);
847 		base = tk->tkr_mono.base;
848 		nsecs = timekeeping_get_ns(&tk->tkr_mono);
849 
850 	} while (read_seqcount_retry(&tk_core.seq, seq));
851 
852 	return ktime_add_ns(base, nsecs);
853 }
854 EXPORT_SYMBOL_GPL(ktime_get);
855 
ktime_get_resolution_ns(void)856 u32 ktime_get_resolution_ns(void)
857 {
858 	struct timekeeper *tk = &tk_core.timekeeper;
859 	unsigned int seq;
860 	u32 nsecs;
861 
862 	WARN_ON(timekeeping_suspended);
863 
864 	do {
865 		seq = read_seqcount_begin(&tk_core.seq);
866 		nsecs = tk->tkr_mono.mult >> tk->tkr_mono.shift;
867 	} while (read_seqcount_retry(&tk_core.seq, seq));
868 
869 	return nsecs;
870 }
871 EXPORT_SYMBOL_GPL(ktime_get_resolution_ns);
872 
873 static ktime_t *offsets[TK_OFFS_MAX] = {
874 	[TK_OFFS_REAL]	= &tk_core.timekeeper.offs_real,
875 	[TK_OFFS_BOOT]	= &tk_core.timekeeper.offs_boot,
876 	[TK_OFFS_TAI]	= &tk_core.timekeeper.offs_tai,
877 };
878 
ktime_get_with_offset(enum tk_offsets offs)879 ktime_t ktime_get_with_offset(enum tk_offsets offs)
880 {
881 	struct timekeeper *tk = &tk_core.timekeeper;
882 	unsigned int seq;
883 	ktime_t base, *offset = offsets[offs];
884 	u64 nsecs;
885 
886 	WARN_ON(timekeeping_suspended);
887 
888 	do {
889 		seq = read_seqcount_begin(&tk_core.seq);
890 		base = ktime_add(tk->tkr_mono.base, *offset);
891 		nsecs = timekeeping_get_ns(&tk->tkr_mono);
892 
893 	} while (read_seqcount_retry(&tk_core.seq, seq));
894 
895 	return ktime_add_ns(base, nsecs);
896 
897 }
898 EXPORT_SYMBOL_GPL(ktime_get_with_offset);
899 
ktime_get_coarse_with_offset(enum tk_offsets offs)900 ktime_t ktime_get_coarse_with_offset(enum tk_offsets offs)
901 {
902 	struct timekeeper *tk = &tk_core.timekeeper;
903 	unsigned int seq;
904 	ktime_t base, *offset = offsets[offs];
905 	u64 nsecs;
906 
907 	WARN_ON(timekeeping_suspended);
908 
909 	do {
910 		seq = read_seqcount_begin(&tk_core.seq);
911 		base = ktime_add(tk->tkr_mono.base, *offset);
912 		nsecs = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
913 
914 	} while (read_seqcount_retry(&tk_core.seq, seq));
915 
916 	return ktime_add_ns(base, nsecs);
917 }
918 EXPORT_SYMBOL_GPL(ktime_get_coarse_with_offset);
919 
920 /**
921  * ktime_mono_to_any() - convert monotonic time to any other time
922  * @tmono:	time to convert.
923  * @offs:	which offset to use
924  */
ktime_mono_to_any(ktime_t tmono,enum tk_offsets offs)925 ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs)
926 {
927 	ktime_t *offset = offsets[offs];
928 	unsigned int seq;
929 	ktime_t tconv;
930 
931 	do {
932 		seq = read_seqcount_begin(&tk_core.seq);
933 		tconv = ktime_add(tmono, *offset);
934 	} while (read_seqcount_retry(&tk_core.seq, seq));
935 
936 	return tconv;
937 }
938 EXPORT_SYMBOL_GPL(ktime_mono_to_any);
939 
940 /**
941  * ktime_get_raw - Returns the raw monotonic time in ktime_t format
942  */
ktime_get_raw(void)943 ktime_t ktime_get_raw(void)
944 {
945 	struct timekeeper *tk = &tk_core.timekeeper;
946 	unsigned int seq;
947 	ktime_t base;
948 	u64 nsecs;
949 
950 	do {
951 		seq = read_seqcount_begin(&tk_core.seq);
952 		base = tk->tkr_raw.base;
953 		nsecs = timekeeping_get_ns(&tk->tkr_raw);
954 
955 	} while (read_seqcount_retry(&tk_core.seq, seq));
956 
957 	return ktime_add_ns(base, nsecs);
958 }
959 EXPORT_SYMBOL_GPL(ktime_get_raw);
960 
961 /**
962  * ktime_get_ts64 - get the monotonic clock in timespec64 format
963  * @ts:		pointer to timespec variable
964  *
965  * The function calculates the monotonic clock from the realtime
966  * clock and the wall_to_monotonic offset and stores the result
967  * in normalized timespec64 format in the variable pointed to by @ts.
968  */
ktime_get_ts64(struct timespec64 * ts)969 void ktime_get_ts64(struct timespec64 *ts)
970 {
971 	struct timekeeper *tk = &tk_core.timekeeper;
972 	struct timespec64 tomono;
973 	unsigned int seq;
974 	u64 nsec;
975 
976 	WARN_ON(timekeeping_suspended);
977 
978 	do {
979 		seq = read_seqcount_begin(&tk_core.seq);
980 		ts->tv_sec = tk->xtime_sec;
981 		nsec = timekeeping_get_ns(&tk->tkr_mono);
982 		tomono = tk->wall_to_monotonic;
983 
984 	} while (read_seqcount_retry(&tk_core.seq, seq));
985 
986 	ts->tv_sec += tomono.tv_sec;
987 	ts->tv_nsec = 0;
988 	timespec64_add_ns(ts, nsec + tomono.tv_nsec);
989 }
990 EXPORT_SYMBOL_GPL(ktime_get_ts64);
991 
992 /**
993  * ktime_get_seconds - Get the seconds portion of CLOCK_MONOTONIC
994  *
995  * Returns the seconds portion of CLOCK_MONOTONIC with a single non
996  * serialized read. tk->ktime_sec is of type 'unsigned long' so this
997  * works on both 32 and 64 bit systems. On 32 bit systems the readout
998  * covers ~136 years of uptime which should be enough to prevent
999  * premature wrap arounds.
1000  */
ktime_get_seconds(void)1001 time64_t ktime_get_seconds(void)
1002 {
1003 	struct timekeeper *tk = &tk_core.timekeeper;
1004 
1005 	WARN_ON(timekeeping_suspended);
1006 	return tk->ktime_sec;
1007 }
1008 EXPORT_SYMBOL_GPL(ktime_get_seconds);
1009 
1010 /**
1011  * ktime_get_real_seconds - Get the seconds portion of CLOCK_REALTIME
1012  *
1013  * Returns the wall clock seconds since 1970.
1014  *
1015  * For 64bit systems the fast access to tk->xtime_sec is preserved. On
1016  * 32bit systems the access must be protected with the sequence
1017  * counter to provide "atomic" access to the 64bit tk->xtime_sec
1018  * value.
1019  */
ktime_get_real_seconds(void)1020 time64_t ktime_get_real_seconds(void)
1021 {
1022 	struct timekeeper *tk = &tk_core.timekeeper;
1023 	time64_t seconds;
1024 	unsigned int seq;
1025 
1026 	if (IS_ENABLED(CONFIG_64BIT))
1027 		return tk->xtime_sec;
1028 
1029 	do {
1030 		seq = read_seqcount_begin(&tk_core.seq);
1031 		seconds = tk->xtime_sec;
1032 
1033 	} while (read_seqcount_retry(&tk_core.seq, seq));
1034 
1035 	return seconds;
1036 }
1037 EXPORT_SYMBOL_GPL(ktime_get_real_seconds);
1038 
1039 /**
1040  * __ktime_get_real_seconds - The same as ktime_get_real_seconds
1041  * but without the sequence counter protect. This internal function
1042  * is called just when timekeeping lock is already held.
1043  */
__ktime_get_real_seconds(void)1044 noinstr time64_t __ktime_get_real_seconds(void)
1045 {
1046 	struct timekeeper *tk = &tk_core.timekeeper;
1047 
1048 	return tk->xtime_sec;
1049 }
1050 
1051 /**
1052  * ktime_get_snapshot - snapshots the realtime/monotonic raw clocks with counter
1053  * @systime_snapshot:	pointer to struct receiving the system time snapshot
1054  */
ktime_get_snapshot(struct system_time_snapshot * systime_snapshot)1055 void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
1056 {
1057 	struct timekeeper *tk = &tk_core.timekeeper;
1058 	unsigned int seq;
1059 	ktime_t base_raw;
1060 	ktime_t base_real;
1061 	u64 nsec_raw;
1062 	u64 nsec_real;
1063 	u64 now;
1064 
1065 	WARN_ON_ONCE(timekeeping_suspended);
1066 
1067 	do {
1068 		seq = read_seqcount_begin(&tk_core.seq);
1069 		now = tk_clock_read(&tk->tkr_mono);
1070 		systime_snapshot->cs_id = tk->tkr_mono.clock->id;
1071 		systime_snapshot->cs_was_changed_seq = tk->cs_was_changed_seq;
1072 		systime_snapshot->clock_was_set_seq = tk->clock_was_set_seq;
1073 		base_real = ktime_add(tk->tkr_mono.base,
1074 				      tk_core.timekeeper.offs_real);
1075 		base_raw = tk->tkr_raw.base;
1076 		nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, now);
1077 		nsec_raw  = timekeeping_cycles_to_ns(&tk->tkr_raw, now);
1078 	} while (read_seqcount_retry(&tk_core.seq, seq));
1079 
1080 	systime_snapshot->cycles = now;
1081 	systime_snapshot->real = ktime_add_ns(base_real, nsec_real);
1082 	systime_snapshot->raw = ktime_add_ns(base_raw, nsec_raw);
1083 }
1084 EXPORT_SYMBOL_GPL(ktime_get_snapshot);
1085 
1086 /* Scale base by mult/div checking for overflow */
scale64_check_overflow(u64 mult,u64 div,u64 * base)1087 static int scale64_check_overflow(u64 mult, u64 div, u64 *base)
1088 {
1089 	u64 tmp, rem;
1090 
1091 	tmp = div64_u64_rem(*base, div, &rem);
1092 
1093 	if (((int)sizeof(u64)*8 - fls64(mult) < fls64(tmp)) ||
1094 	    ((int)sizeof(u64)*8 - fls64(mult) < fls64(rem)))
1095 		return -EOVERFLOW;
1096 	tmp *= mult;
1097 
1098 	rem = div64_u64(rem * mult, div);
1099 	*base = tmp + rem;
1100 	return 0;
1101 }
1102 
1103 /**
1104  * adjust_historical_crosststamp - adjust crosstimestamp previous to current interval
1105  * @history:			Snapshot representing start of history
1106  * @partial_history_cycles:	Cycle offset into history (fractional part)
1107  * @total_history_cycles:	Total history length in cycles
1108  * @discontinuity:		True indicates clock was set on history period
1109  * @ts:				Cross timestamp that should be adjusted using
1110  *	partial/total ratio
1111  *
1112  * Helper function used by get_device_system_crosststamp() to correct the
1113  * crosstimestamp corresponding to the start of the current interval to the
1114  * system counter value (timestamp point) provided by the driver. The
1115  * total_history_* quantities are the total history starting at the provided
1116  * reference point and ending at the start of the current interval. The cycle
1117  * count between the driver timestamp point and the start of the current
1118  * interval is partial_history_cycles.
1119  */
adjust_historical_crosststamp(struct system_time_snapshot * history,u64 partial_history_cycles,u64 total_history_cycles,bool discontinuity,struct system_device_crosststamp * ts)1120 static int adjust_historical_crosststamp(struct system_time_snapshot *history,
1121 					 u64 partial_history_cycles,
1122 					 u64 total_history_cycles,
1123 					 bool discontinuity,
1124 					 struct system_device_crosststamp *ts)
1125 {
1126 	struct timekeeper *tk = &tk_core.timekeeper;
1127 	u64 corr_raw, corr_real;
1128 	bool interp_forward;
1129 	int ret;
1130 
1131 	if (total_history_cycles == 0 || partial_history_cycles == 0)
1132 		return 0;
1133 
1134 	/* Interpolate shortest distance from beginning or end of history */
1135 	interp_forward = partial_history_cycles > total_history_cycles / 2;
1136 	partial_history_cycles = interp_forward ?
1137 		total_history_cycles - partial_history_cycles :
1138 		partial_history_cycles;
1139 
1140 	/*
1141 	 * Scale the monotonic raw time delta by:
1142 	 *	partial_history_cycles / total_history_cycles
1143 	 */
1144 	corr_raw = (u64)ktime_to_ns(
1145 		ktime_sub(ts->sys_monoraw, history->raw));
1146 	ret = scale64_check_overflow(partial_history_cycles,
1147 				     total_history_cycles, &corr_raw);
1148 	if (ret)
1149 		return ret;
1150 
1151 	/*
1152 	 * If there is a discontinuity in the history, scale monotonic raw
1153 	 *	correction by:
1154 	 *	mult(real)/mult(raw) yielding the realtime correction
1155 	 * Otherwise, calculate the realtime correction similar to monotonic
1156 	 *	raw calculation
1157 	 */
1158 	if (discontinuity) {
1159 		corr_real = mul_u64_u32_div
1160 			(corr_raw, tk->tkr_mono.mult, tk->tkr_raw.mult);
1161 	} else {
1162 		corr_real = (u64)ktime_to_ns(
1163 			ktime_sub(ts->sys_realtime, history->real));
1164 		ret = scale64_check_overflow(partial_history_cycles,
1165 					     total_history_cycles, &corr_real);
1166 		if (ret)
1167 			return ret;
1168 	}
1169 
1170 	/* Fixup monotonic raw and real time time values */
1171 	if (interp_forward) {
1172 		ts->sys_monoraw = ktime_add_ns(history->raw, corr_raw);
1173 		ts->sys_realtime = ktime_add_ns(history->real, corr_real);
1174 	} else {
1175 		ts->sys_monoraw = ktime_sub_ns(ts->sys_monoraw, corr_raw);
1176 		ts->sys_realtime = ktime_sub_ns(ts->sys_realtime, corr_real);
1177 	}
1178 
1179 	return 0;
1180 }
1181 
1182 /*
1183  * cycle_between - true if test occurs chronologically between before and after
1184  */
cycle_between(u64 before,u64 test,u64 after)1185 static bool cycle_between(u64 before, u64 test, u64 after)
1186 {
1187 	if (test > before && test < after)
1188 		return true;
1189 	if (test < before && before > after)
1190 		return true;
1191 	return false;
1192 }
1193 
1194 /**
1195  * get_device_system_crosststamp - Synchronously capture system/device timestamp
1196  * @get_time_fn:	Callback to get simultaneous device time and
1197  *	system counter from the device driver
1198  * @ctx:		Context passed to get_time_fn()
1199  * @history_begin:	Historical reference point used to interpolate system
1200  *	time when counter provided by the driver is before the current interval
1201  * @xtstamp:		Receives simultaneously captured system and device time
1202  *
1203  * Reads a timestamp from a device and correlates it to system time
1204  */
get_device_system_crosststamp(int (* get_time_fn)(ktime_t * device_time,struct system_counterval_t * sys_counterval,void * ctx),void * ctx,struct system_time_snapshot * history_begin,struct system_device_crosststamp * xtstamp)1205 int get_device_system_crosststamp(int (*get_time_fn)
1206 				  (ktime_t *device_time,
1207 				   struct system_counterval_t *sys_counterval,
1208 				   void *ctx),
1209 				  void *ctx,
1210 				  struct system_time_snapshot *history_begin,
1211 				  struct system_device_crosststamp *xtstamp)
1212 {
1213 	struct system_counterval_t system_counterval;
1214 	struct timekeeper *tk = &tk_core.timekeeper;
1215 	u64 cycles, now, interval_start;
1216 	unsigned int clock_was_set_seq = 0;
1217 	ktime_t base_real, base_raw;
1218 	u64 nsec_real, nsec_raw;
1219 	u8 cs_was_changed_seq;
1220 	unsigned int seq;
1221 	bool do_interp;
1222 	int ret;
1223 
1224 	do {
1225 		seq = read_seqcount_begin(&tk_core.seq);
1226 		/*
1227 		 * Try to synchronously capture device time and a system
1228 		 * counter value calling back into the device driver
1229 		 */
1230 		ret = get_time_fn(&xtstamp->device, &system_counterval, ctx);
1231 		if (ret)
1232 			return ret;
1233 
1234 		/*
1235 		 * Verify that the clocksource associated with the captured
1236 		 * system counter value is the same as the currently installed
1237 		 * timekeeper clocksource
1238 		 */
1239 		if (tk->tkr_mono.clock != system_counterval.cs)
1240 			return -ENODEV;
1241 		cycles = system_counterval.cycles;
1242 
1243 		/*
1244 		 * Check whether the system counter value provided by the
1245 		 * device driver is on the current timekeeping interval.
1246 		 */
1247 		now = tk_clock_read(&tk->tkr_mono);
1248 		interval_start = tk->tkr_mono.cycle_last;
1249 		if (!cycle_between(interval_start, cycles, now)) {
1250 			clock_was_set_seq = tk->clock_was_set_seq;
1251 			cs_was_changed_seq = tk->cs_was_changed_seq;
1252 			cycles = interval_start;
1253 			do_interp = true;
1254 		} else {
1255 			do_interp = false;
1256 		}
1257 
1258 		base_real = ktime_add(tk->tkr_mono.base,
1259 				      tk_core.timekeeper.offs_real);
1260 		base_raw = tk->tkr_raw.base;
1261 
1262 		nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono,
1263 						     system_counterval.cycles);
1264 		nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw,
1265 						    system_counterval.cycles);
1266 	} while (read_seqcount_retry(&tk_core.seq, seq));
1267 
1268 	xtstamp->sys_realtime = ktime_add_ns(base_real, nsec_real);
1269 	xtstamp->sys_monoraw = ktime_add_ns(base_raw, nsec_raw);
1270 
1271 	/*
1272 	 * Interpolate if necessary, adjusting back from the start of the
1273 	 * current interval
1274 	 */
1275 	if (do_interp) {
1276 		u64 partial_history_cycles, total_history_cycles;
1277 		bool discontinuity;
1278 
1279 		/*
1280 		 * Check that the counter value occurs after the provided
1281 		 * history reference and that the history doesn't cross a
1282 		 * clocksource change
1283 		 */
1284 		if (!history_begin ||
1285 		    !cycle_between(history_begin->cycles,
1286 				   system_counterval.cycles, cycles) ||
1287 		    history_begin->cs_was_changed_seq != cs_was_changed_seq)
1288 			return -EINVAL;
1289 		partial_history_cycles = cycles - system_counterval.cycles;
1290 		total_history_cycles = cycles - history_begin->cycles;
1291 		discontinuity =
1292 			history_begin->clock_was_set_seq != clock_was_set_seq;
1293 
1294 		ret = adjust_historical_crosststamp(history_begin,
1295 						    partial_history_cycles,
1296 						    total_history_cycles,
1297 						    discontinuity, xtstamp);
1298 		if (ret)
1299 			return ret;
1300 	}
1301 
1302 	return 0;
1303 }
1304 EXPORT_SYMBOL_GPL(get_device_system_crosststamp);
1305 
1306 /**
1307  * do_settimeofday64 - Sets the time of day.
1308  * @ts:     pointer to the timespec64 variable containing the new time
1309  *
1310  * Sets the time of day to the new time and update NTP and notify hrtimers
1311  */
do_settimeofday64(const struct timespec64 * ts)1312 int do_settimeofday64(const struct timespec64 *ts)
1313 {
1314 	struct timekeeper *tk = &tk_core.timekeeper;
1315 	struct timespec64 ts_delta, xt;
1316 	unsigned long flags;
1317 	int ret = 0;
1318 
1319 	if (!timespec64_valid_settod(ts))
1320 		return -EINVAL;
1321 
1322 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1323 	write_seqcount_begin(&tk_core.seq);
1324 
1325 	timekeeping_forward_now(tk);
1326 
1327 	xt = tk_xtime(tk);
1328 	ts_delta = timespec64_sub(*ts, xt);
1329 
1330 	if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) {
1331 		ret = -EINVAL;
1332 		goto out;
1333 	}
1334 
1335 	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta));
1336 
1337 	tk_set_xtime(tk, ts);
1338 out:
1339 	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1340 
1341 	write_seqcount_end(&tk_core.seq);
1342 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1343 
1344 	/* Signal hrtimers about time change */
1345 	clock_was_set(CLOCK_SET_WALL);
1346 
1347 	if (!ret) {
1348 		audit_tk_injoffset(ts_delta);
1349 		add_device_randomness(ts, sizeof(*ts));
1350 	}
1351 
1352 	return ret;
1353 }
1354 EXPORT_SYMBOL(do_settimeofday64);
1355 
1356 /**
1357  * timekeeping_inject_offset - Adds or subtracts from the current time.
1358  * @ts:		Pointer to the timespec variable containing the offset
1359  *
1360  * Adds or subtracts an offset value from the current time.
1361  */
timekeeping_inject_offset(const struct timespec64 * ts)1362 static int timekeeping_inject_offset(const struct timespec64 *ts)
1363 {
1364 	struct timekeeper *tk = &tk_core.timekeeper;
1365 	unsigned long flags;
1366 	struct timespec64 tmp;
1367 	int ret = 0;
1368 
1369 	if (ts->tv_nsec < 0 || ts->tv_nsec >= NSEC_PER_SEC)
1370 		return -EINVAL;
1371 
1372 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1373 	write_seqcount_begin(&tk_core.seq);
1374 
1375 	timekeeping_forward_now(tk);
1376 
1377 	/* Make sure the proposed value is valid */
1378 	tmp = timespec64_add(tk_xtime(tk), *ts);
1379 	if (timespec64_compare(&tk->wall_to_monotonic, ts) > 0 ||
1380 	    !timespec64_valid_settod(&tmp)) {
1381 		ret = -EINVAL;
1382 		goto error;
1383 	}
1384 
1385 	tk_xtime_add(tk, ts);
1386 	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *ts));
1387 
1388 error: /* even if we error out, we forwarded the time, so call update */
1389 	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1390 
1391 	write_seqcount_end(&tk_core.seq);
1392 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1393 
1394 	/* Signal hrtimers about time change */
1395 	clock_was_set(CLOCK_SET_WALL);
1396 
1397 	return ret;
1398 }
1399 
1400 /*
1401  * Indicates if there is an offset between the system clock and the hardware
1402  * clock/persistent clock/rtc.
1403  */
1404 int persistent_clock_is_local;
1405 
1406 /*
1407  * Adjust the time obtained from the CMOS to be UTC time instead of
1408  * local time.
1409  *
1410  * This is ugly, but preferable to the alternatives.  Otherwise we
1411  * would either need to write a program to do it in /etc/rc (and risk
1412  * confusion if the program gets run more than once; it would also be
1413  * hard to make the program warp the clock precisely n hours)  or
1414  * compile in the timezone information into the kernel.  Bad, bad....
1415  *
1416  *						- TYT, 1992-01-01
1417  *
1418  * The best thing to do is to keep the CMOS clock in universal time (UTC)
1419  * as real UNIX machines always do it. This avoids all headaches about
1420  * daylight saving times and warping kernel clocks.
1421  */
timekeeping_warp_clock(void)1422 void timekeeping_warp_clock(void)
1423 {
1424 	if (sys_tz.tz_minuteswest != 0) {
1425 		struct timespec64 adjust;
1426 
1427 		persistent_clock_is_local = 1;
1428 		adjust.tv_sec = sys_tz.tz_minuteswest * 60;
1429 		adjust.tv_nsec = 0;
1430 		timekeeping_inject_offset(&adjust);
1431 	}
1432 }
1433 
1434 /*
1435  * __timekeeping_set_tai_offset - Sets the TAI offset from UTC and monotonic
1436  */
__timekeeping_set_tai_offset(struct timekeeper * tk,s32 tai_offset)1437 static void __timekeeping_set_tai_offset(struct timekeeper *tk, s32 tai_offset)
1438 {
1439 	tk->tai_offset = tai_offset;
1440 	tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tai_offset, 0));
1441 }
1442 
1443 /*
1444  * change_clocksource - Swaps clocksources if a new one is available
1445  *
1446  * Accumulates current time interval and initializes new clocksource
1447  */
change_clocksource(void * data)1448 static int change_clocksource(void *data)
1449 {
1450 	struct timekeeper *tk = &tk_core.timekeeper;
1451 	struct clocksource *new, *old = NULL;
1452 	unsigned long flags;
1453 	bool change = false;
1454 
1455 	new = (struct clocksource *) data;
1456 
1457 	/*
1458 	 * If the cs is in module, get a module reference. Succeeds
1459 	 * for built-in code (owner == NULL) as well.
1460 	 */
1461 	if (try_module_get(new->owner)) {
1462 		if (!new->enable || new->enable(new) == 0)
1463 			change = true;
1464 		else
1465 			module_put(new->owner);
1466 	}
1467 
1468 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1469 	write_seqcount_begin(&tk_core.seq);
1470 
1471 	timekeeping_forward_now(tk);
1472 
1473 	if (change) {
1474 		old = tk->tkr_mono.clock;
1475 		tk_setup_internals(tk, new);
1476 	}
1477 
1478 	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1479 
1480 	write_seqcount_end(&tk_core.seq);
1481 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1482 
1483 	if (old) {
1484 		if (old->disable)
1485 			old->disable(old);
1486 
1487 		module_put(old->owner);
1488 	}
1489 
1490 	return 0;
1491 }
1492 
1493 /**
1494  * timekeeping_notify - Install a new clock source
1495  * @clock:		pointer to the clock source
1496  *
1497  * This function is called from clocksource.c after a new, better clock
1498  * source has been registered. The caller holds the clocksource_mutex.
1499  */
timekeeping_notify(struct clocksource * clock)1500 int timekeeping_notify(struct clocksource *clock)
1501 {
1502 	struct timekeeper *tk = &tk_core.timekeeper;
1503 
1504 	if (tk->tkr_mono.clock == clock)
1505 		return 0;
1506 	stop_machine(change_clocksource, clock, NULL);
1507 	tick_clock_notify();
1508 	return tk->tkr_mono.clock == clock ? 0 : -1;
1509 }
1510 
1511 /**
1512  * ktime_get_raw_ts64 - Returns the raw monotonic time in a timespec
1513  * @ts:		pointer to the timespec64 to be set
1514  *
1515  * Returns the raw monotonic time (completely un-modified by ntp)
1516  */
ktime_get_raw_ts64(struct timespec64 * ts)1517 void ktime_get_raw_ts64(struct timespec64 *ts)
1518 {
1519 	struct timekeeper *tk = &tk_core.timekeeper;
1520 	unsigned int seq;
1521 	u64 nsecs;
1522 
1523 	do {
1524 		seq = read_seqcount_begin(&tk_core.seq);
1525 		ts->tv_sec = tk->raw_sec;
1526 		nsecs = timekeeping_get_ns(&tk->tkr_raw);
1527 
1528 	} while (read_seqcount_retry(&tk_core.seq, seq));
1529 
1530 	ts->tv_nsec = 0;
1531 	timespec64_add_ns(ts, nsecs);
1532 }
1533 EXPORT_SYMBOL(ktime_get_raw_ts64);
1534 
1535 
1536 /**
1537  * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
1538  */
timekeeping_valid_for_hres(void)1539 int timekeeping_valid_for_hres(void)
1540 {
1541 	struct timekeeper *tk = &tk_core.timekeeper;
1542 	unsigned int seq;
1543 	int ret;
1544 
1545 	do {
1546 		seq = read_seqcount_begin(&tk_core.seq);
1547 
1548 		ret = tk->tkr_mono.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
1549 
1550 	} while (read_seqcount_retry(&tk_core.seq, seq));
1551 
1552 	return ret;
1553 }
1554 
1555 /**
1556  * timekeeping_max_deferment - Returns max time the clocksource can be deferred
1557  */
timekeeping_max_deferment(void)1558 u64 timekeeping_max_deferment(void)
1559 {
1560 	struct timekeeper *tk = &tk_core.timekeeper;
1561 	unsigned int seq;
1562 	u64 ret;
1563 
1564 	do {
1565 		seq = read_seqcount_begin(&tk_core.seq);
1566 
1567 		ret = tk->tkr_mono.clock->max_idle_ns;
1568 
1569 	} while (read_seqcount_retry(&tk_core.seq, seq));
1570 
1571 	return ret;
1572 }
1573 
1574 /**
1575  * read_persistent_clock64 -  Return time from the persistent clock.
1576  * @ts: Pointer to the storage for the readout value
1577  *
1578  * Weak dummy function for arches that do not yet support it.
1579  * Reads the time from the battery backed persistent clock.
1580  * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
1581  *
1582  *  XXX - Do be sure to remove it once all arches implement it.
1583  */
read_persistent_clock64(struct timespec64 * ts)1584 void __weak read_persistent_clock64(struct timespec64 *ts)
1585 {
1586 	ts->tv_sec = 0;
1587 	ts->tv_nsec = 0;
1588 }
1589 
1590 /**
1591  * read_persistent_wall_and_boot_offset - Read persistent clock, and also offset
1592  *                                        from the boot.
1593  * @wall_time:	  current time as returned by persistent clock
1594  * @boot_offset:  offset that is defined as wall_time - boot_time
1595  *
1596  * Weak dummy function for arches that do not yet support it.
1597  *
1598  * The default function calculates offset based on the current value of
1599  * local_clock(). This way architectures that support sched_clock() but don't
1600  * support dedicated boot time clock will provide the best estimate of the
1601  * boot time.
1602  */
1603 void __weak __init
read_persistent_wall_and_boot_offset(struct timespec64 * wall_time,struct timespec64 * boot_offset)1604 read_persistent_wall_and_boot_offset(struct timespec64 *wall_time,
1605 				     struct timespec64 *boot_offset)
1606 {
1607 	read_persistent_clock64(wall_time);
1608 	*boot_offset = ns_to_timespec64(local_clock());
1609 }
1610 
1611 /*
1612  * Flag reflecting whether timekeeping_resume() has injected sleeptime.
1613  *
1614  * The flag starts of false and is only set when a suspend reaches
1615  * timekeeping_suspend(), timekeeping_resume() sets it to false when the
1616  * timekeeper clocksource is not stopping across suspend and has been
1617  * used to update sleep time. If the timekeeper clocksource has stopped
1618  * then the flag stays true and is used by the RTC resume code to decide
1619  * whether sleeptime must be injected and if so the flag gets false then.
1620  *
1621  * If a suspend fails before reaching timekeeping_resume() then the flag
1622  * stays false and prevents erroneous sleeptime injection.
1623  */
1624 static bool suspend_timing_needed;
1625 
1626 /* Flag for if there is a persistent clock on this platform */
1627 static bool persistent_clock_exists;
1628 
1629 /*
1630  * timekeeping_init - Initializes the clocksource and common timekeeping values
1631  */
timekeeping_init(void)1632 void __init timekeeping_init(void)
1633 {
1634 	struct timespec64 wall_time, boot_offset, wall_to_mono;
1635 	struct timekeeper *tk = &tk_core.timekeeper;
1636 	struct clocksource *clock;
1637 	unsigned long flags;
1638 
1639 	read_persistent_wall_and_boot_offset(&wall_time, &boot_offset);
1640 	if (timespec64_valid_settod(&wall_time) &&
1641 	    timespec64_to_ns(&wall_time) > 0) {
1642 		persistent_clock_exists = true;
1643 	} else if (timespec64_to_ns(&wall_time) != 0) {
1644 		pr_warn("Persistent clock returned invalid value");
1645 		wall_time = (struct timespec64){0};
1646 	}
1647 
1648 	if (timespec64_compare(&wall_time, &boot_offset) < 0)
1649 		boot_offset = (struct timespec64){0};
1650 
1651 	/*
1652 	 * We want set wall_to_mono, so the following is true:
1653 	 * wall time + wall_to_mono = boot time
1654 	 */
1655 	wall_to_mono = timespec64_sub(boot_offset, wall_time);
1656 
1657 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1658 	write_seqcount_begin(&tk_core.seq);
1659 	ntp_init();
1660 
1661 	clock = clocksource_default_clock();
1662 	if (clock->enable)
1663 		clock->enable(clock);
1664 	tk_setup_internals(tk, clock);
1665 
1666 	tk_set_xtime(tk, &wall_time);
1667 	tk->raw_sec = 0;
1668 
1669 	tk_set_wall_to_mono(tk, wall_to_mono);
1670 
1671 	timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
1672 
1673 	write_seqcount_end(&tk_core.seq);
1674 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1675 }
1676 
1677 /* time in seconds when suspend began for persistent clock */
1678 static struct timespec64 timekeeping_suspend_time;
1679 
1680 /**
1681  * __timekeeping_inject_sleeptime - Internal function to add sleep interval
1682  * @tk:		Pointer to the timekeeper to be updated
1683  * @delta:	Pointer to the delta value in timespec64 format
1684  *
1685  * Takes a timespec offset measuring a suspend interval and properly
1686  * adds the sleep offset to the timekeeping variables.
1687  */
__timekeeping_inject_sleeptime(struct timekeeper * tk,const struct timespec64 * delta)1688 static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
1689 					   const struct timespec64 *delta)
1690 {
1691 	if (!timespec64_valid_strict(delta)) {
1692 		printk_deferred(KERN_WARNING
1693 				"__timekeeping_inject_sleeptime: Invalid "
1694 				"sleep delta value!\n");
1695 		return;
1696 	}
1697 	tk_xtime_add(tk, delta);
1698 	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *delta));
1699 	tk_update_sleep_time(tk, timespec64_to_ktime(*delta));
1700 	tk_debug_account_sleep_time(delta);
1701 }
1702 
1703 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
1704 /*
1705  * We have three kinds of time sources to use for sleep time
1706  * injection, the preference order is:
1707  * 1) non-stop clocksource
1708  * 2) persistent clock (ie: RTC accessible when irqs are off)
1709  * 3) RTC
1710  *
1711  * 1) and 2) are used by timekeeping, 3) by RTC subsystem.
1712  * If system has neither 1) nor 2), 3) will be used finally.
1713  *
1714  *
1715  * If timekeeping has injected sleeptime via either 1) or 2),
1716  * 3) becomes needless, so in this case we don't need to call
1717  * rtc_resume(), and this is what timekeeping_rtc_skipresume()
1718  * means.
1719  */
timekeeping_rtc_skipresume(void)1720 bool timekeeping_rtc_skipresume(void)
1721 {
1722 	return !suspend_timing_needed;
1723 }
1724 
1725 /*
1726  * 1) can be determined whether to use or not only when doing
1727  * timekeeping_resume() which is invoked after rtc_suspend(),
1728  * so we can't skip rtc_suspend() surely if system has 1).
1729  *
1730  * But if system has 2), 2) will definitely be used, so in this
1731  * case we don't need to call rtc_suspend(), and this is what
1732  * timekeeping_rtc_skipsuspend() means.
1733  */
timekeeping_rtc_skipsuspend(void)1734 bool timekeeping_rtc_skipsuspend(void)
1735 {
1736 	return persistent_clock_exists;
1737 }
1738 
1739 /**
1740  * timekeeping_inject_sleeptime64 - Adds suspend interval to timeekeeping values
1741  * @delta: pointer to a timespec64 delta value
1742  *
1743  * This hook is for architectures that cannot support read_persistent_clock64
1744  * because their RTC/persistent clock is only accessible when irqs are enabled.
1745  * and also don't have an effective nonstop clocksource.
1746  *
1747  * This function should only be called by rtc_resume(), and allows
1748  * a suspend offset to be injected into the timekeeping values.
1749  */
timekeeping_inject_sleeptime64(const struct timespec64 * delta)1750 void timekeeping_inject_sleeptime64(const struct timespec64 *delta)
1751 {
1752 	struct timekeeper *tk = &tk_core.timekeeper;
1753 	unsigned long flags;
1754 
1755 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1756 	write_seqcount_begin(&tk_core.seq);
1757 
1758 	suspend_timing_needed = false;
1759 
1760 	timekeeping_forward_now(tk);
1761 
1762 	__timekeeping_inject_sleeptime(tk, delta);
1763 
1764 	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
1765 
1766 	write_seqcount_end(&tk_core.seq);
1767 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1768 
1769 	/* Signal hrtimers about time change */
1770 	clock_was_set(CLOCK_SET_WALL | CLOCK_SET_BOOT);
1771 }
1772 #endif
1773 
1774 /**
1775  * timekeeping_resume - Resumes the generic timekeeping subsystem.
1776  */
timekeeping_resume(void)1777 void timekeeping_resume(void)
1778 {
1779 	struct timekeeper *tk = &tk_core.timekeeper;
1780 	struct clocksource *clock = tk->tkr_mono.clock;
1781 	unsigned long flags;
1782 	struct timespec64 ts_new, ts_delta;
1783 	u64 cycle_now, nsec;
1784 	bool inject_sleeptime = false;
1785 
1786 	read_persistent_clock64(&ts_new);
1787 
1788 	clockevents_resume();
1789 	clocksource_resume();
1790 
1791 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1792 	write_seqcount_begin(&tk_core.seq);
1793 
1794 	/*
1795 	 * After system resumes, we need to calculate the suspended time and
1796 	 * compensate it for the OS time. There are 3 sources that could be
1797 	 * used: Nonstop clocksource during suspend, persistent clock and rtc
1798 	 * device.
1799 	 *
1800 	 * One specific platform may have 1 or 2 or all of them, and the
1801 	 * preference will be:
1802 	 *	suspend-nonstop clocksource -> persistent clock -> rtc
1803 	 * The less preferred source will only be tried if there is no better
1804 	 * usable source. The rtc part is handled separately in rtc core code.
1805 	 */
1806 	cycle_now = tk_clock_read(&tk->tkr_mono);
1807 	nsec = clocksource_stop_suspend_timing(clock, cycle_now);
1808 	if (nsec > 0) {
1809 		ts_delta = ns_to_timespec64(nsec);
1810 		inject_sleeptime = true;
1811 	} else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {
1812 		ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);
1813 		inject_sleeptime = true;
1814 	}
1815 
1816 	if (inject_sleeptime) {
1817 		suspend_timing_needed = false;
1818 		__timekeeping_inject_sleeptime(tk, &ts_delta);
1819 	}
1820 
1821 	/* Re-base the last cycle value */
1822 	tk->tkr_mono.cycle_last = cycle_now;
1823 	tk->tkr_raw.cycle_last  = cycle_now;
1824 
1825 	tk->ntp_error = 0;
1826 	timekeeping_suspended = 0;
1827 	timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
1828 	write_seqcount_end(&tk_core.seq);
1829 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1830 
1831 	touch_softlockup_watchdog();
1832 
1833 	/* Resume the clockevent device(s) and hrtimers */
1834 	tick_resume();
1835 	/* Notify timerfd as resume is equivalent to clock_was_set() */
1836 	timerfd_resume();
1837 }
1838 
timekeeping_suspend(void)1839 int timekeeping_suspend(void)
1840 {
1841 	struct timekeeper *tk = &tk_core.timekeeper;
1842 	unsigned long flags;
1843 	struct timespec64		delta, delta_delta;
1844 	static struct timespec64	old_delta;
1845 	struct clocksource *curr_clock;
1846 	u64 cycle_now;
1847 
1848 	read_persistent_clock64(&timekeeping_suspend_time);
1849 
1850 	/*
1851 	 * On some systems the persistent_clock can not be detected at
1852 	 * timekeeping_init by its return value, so if we see a valid
1853 	 * value returned, update the persistent_clock_exists flag.
1854 	 */
1855 	if (timekeeping_suspend_time.tv_sec || timekeeping_suspend_time.tv_nsec)
1856 		persistent_clock_exists = true;
1857 
1858 	suspend_timing_needed = true;
1859 
1860 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
1861 	write_seqcount_begin(&tk_core.seq);
1862 	timekeeping_forward_now(tk);
1863 	timekeeping_suspended = 1;
1864 
1865 	/*
1866 	 * Since we've called forward_now, cycle_last stores the value
1867 	 * just read from the current clocksource. Save this to potentially
1868 	 * use in suspend timing.
1869 	 */
1870 	curr_clock = tk->tkr_mono.clock;
1871 	cycle_now = tk->tkr_mono.cycle_last;
1872 	clocksource_start_suspend_timing(curr_clock, cycle_now);
1873 
1874 	if (persistent_clock_exists) {
1875 		/*
1876 		 * To avoid drift caused by repeated suspend/resumes,
1877 		 * which each can add ~1 second drift error,
1878 		 * try to compensate so the difference in system time
1879 		 * and persistent_clock time stays close to constant.
1880 		 */
1881 		delta = timespec64_sub(tk_xtime(tk), timekeeping_suspend_time);
1882 		delta_delta = timespec64_sub(delta, old_delta);
1883 		if (abs(delta_delta.tv_sec) >= 2) {
1884 			/*
1885 			 * if delta_delta is too large, assume time correction
1886 			 * has occurred and set old_delta to the current delta.
1887 			 */
1888 			old_delta = delta;
1889 		} else {
1890 			/* Otherwise try to adjust old_system to compensate */
1891 			timekeeping_suspend_time =
1892 				timespec64_add(timekeeping_suspend_time, delta_delta);
1893 		}
1894 	}
1895 
1896 	timekeeping_update(tk, TK_MIRROR);
1897 	halt_fast_timekeeper(tk);
1898 	write_seqcount_end(&tk_core.seq);
1899 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
1900 
1901 	tick_suspend();
1902 	clocksource_suspend();
1903 	clockevents_suspend();
1904 
1905 	return 0;
1906 }
1907 
1908 /* sysfs resume/suspend bits for timekeeping */
1909 static struct syscore_ops timekeeping_syscore_ops = {
1910 	.resume		= timekeeping_resume,
1911 	.suspend	= timekeeping_suspend,
1912 };
1913 
timekeeping_init_ops(void)1914 static int __init timekeeping_init_ops(void)
1915 {
1916 	register_syscore_ops(&timekeeping_syscore_ops);
1917 	return 0;
1918 }
1919 device_initcall(timekeeping_init_ops);
1920 
1921 /*
1922  * Apply a multiplier adjustment to the timekeeper
1923  */
timekeeping_apply_adjustment(struct timekeeper * tk,s64 offset,s32 mult_adj)1924 static __always_inline void timekeeping_apply_adjustment(struct timekeeper *tk,
1925 							 s64 offset,
1926 							 s32 mult_adj)
1927 {
1928 	s64 interval = tk->cycle_interval;
1929 
1930 	if (mult_adj == 0) {
1931 		return;
1932 	} else if (mult_adj == -1) {
1933 		interval = -interval;
1934 		offset = -offset;
1935 	} else if (mult_adj != 1) {
1936 		interval *= mult_adj;
1937 		offset *= mult_adj;
1938 	}
1939 
1940 	/*
1941 	 * So the following can be confusing.
1942 	 *
1943 	 * To keep things simple, lets assume mult_adj == 1 for now.
1944 	 *
1945 	 * When mult_adj != 1, remember that the interval and offset values
1946 	 * have been appropriately scaled so the math is the same.
1947 	 *
1948 	 * The basic idea here is that we're increasing the multiplier
1949 	 * by one, this causes the xtime_interval to be incremented by
1950 	 * one cycle_interval. This is because:
1951 	 *	xtime_interval = cycle_interval * mult
1952 	 * So if mult is being incremented by one:
1953 	 *	xtime_interval = cycle_interval * (mult + 1)
1954 	 * Its the same as:
1955 	 *	xtime_interval = (cycle_interval * mult) + cycle_interval
1956 	 * Which can be shortened to:
1957 	 *	xtime_interval += cycle_interval
1958 	 *
1959 	 * So offset stores the non-accumulated cycles. Thus the current
1960 	 * time (in shifted nanoseconds) is:
1961 	 *	now = (offset * adj) + xtime_nsec
1962 	 * Now, even though we're adjusting the clock frequency, we have
1963 	 * to keep time consistent. In other words, we can't jump back
1964 	 * in time, and we also want to avoid jumping forward in time.
1965 	 *
1966 	 * So given the same offset value, we need the time to be the same
1967 	 * both before and after the freq adjustment.
1968 	 *	now = (offset * adj_1) + xtime_nsec_1
1969 	 *	now = (offset * adj_2) + xtime_nsec_2
1970 	 * So:
1971 	 *	(offset * adj_1) + xtime_nsec_1 =
1972 	 *		(offset * adj_2) + xtime_nsec_2
1973 	 * And we know:
1974 	 *	adj_2 = adj_1 + 1
1975 	 * So:
1976 	 *	(offset * adj_1) + xtime_nsec_1 =
1977 	 *		(offset * (adj_1+1)) + xtime_nsec_2
1978 	 *	(offset * adj_1) + xtime_nsec_1 =
1979 	 *		(offset * adj_1) + offset + xtime_nsec_2
1980 	 * Canceling the sides:
1981 	 *	xtime_nsec_1 = offset + xtime_nsec_2
1982 	 * Which gives us:
1983 	 *	xtime_nsec_2 = xtime_nsec_1 - offset
1984 	 * Which simplifies to:
1985 	 *	xtime_nsec -= offset
1986 	 */
1987 	if ((mult_adj > 0) && (tk->tkr_mono.mult + mult_adj < mult_adj)) {
1988 		/* NTP adjustment caused clocksource mult overflow */
1989 		WARN_ON_ONCE(1);
1990 		return;
1991 	}
1992 
1993 	tk->tkr_mono.mult += mult_adj;
1994 	tk->xtime_interval += interval;
1995 	tk->tkr_mono.xtime_nsec -= offset;
1996 }
1997 
1998 /*
1999  * Adjust the timekeeper's multiplier to the correct frequency
2000  * and also to reduce the accumulated error value.
2001  */
timekeeping_adjust(struct timekeeper * tk,s64 offset)2002 static void timekeeping_adjust(struct timekeeper *tk, s64 offset)
2003 {
2004 	u32 mult;
2005 
2006 	/*
2007 	 * Determine the multiplier from the current NTP tick length.
2008 	 * Avoid expensive division when the tick length doesn't change.
2009 	 */
2010 	if (likely(tk->ntp_tick == ntp_tick_length())) {
2011 		mult = tk->tkr_mono.mult - tk->ntp_err_mult;
2012 	} else {
2013 		tk->ntp_tick = ntp_tick_length();
2014 		mult = div64_u64((tk->ntp_tick >> tk->ntp_error_shift) -
2015 				 tk->xtime_remainder, tk->cycle_interval);
2016 	}
2017 
2018 	/*
2019 	 * If the clock is behind the NTP time, increase the multiplier by 1
2020 	 * to catch up with it. If it's ahead and there was a remainder in the
2021 	 * tick division, the clock will slow down. Otherwise it will stay
2022 	 * ahead until the tick length changes to a non-divisible value.
2023 	 */
2024 	tk->ntp_err_mult = tk->ntp_error > 0 ? 1 : 0;
2025 	mult += tk->ntp_err_mult;
2026 
2027 	timekeeping_apply_adjustment(tk, offset, mult - tk->tkr_mono.mult);
2028 
2029 	if (unlikely(tk->tkr_mono.clock->maxadj &&
2030 		(abs(tk->tkr_mono.mult - tk->tkr_mono.clock->mult)
2031 			> tk->tkr_mono.clock->maxadj))) {
2032 		printk_once(KERN_WARNING
2033 			"Adjusting %s more than 11%% (%ld vs %ld)\n",
2034 			tk->tkr_mono.clock->name, (long)tk->tkr_mono.mult,
2035 			(long)tk->tkr_mono.clock->mult + tk->tkr_mono.clock->maxadj);
2036 	}
2037 
2038 	/*
2039 	 * It may be possible that when we entered this function, xtime_nsec
2040 	 * was very small.  Further, if we're slightly speeding the clocksource
2041 	 * in the code above, its possible the required corrective factor to
2042 	 * xtime_nsec could cause it to underflow.
2043 	 *
2044 	 * Now, since we have already accumulated the second and the NTP
2045 	 * subsystem has been notified via second_overflow(), we need to skip
2046 	 * the next update.
2047 	 */
2048 	if (unlikely((s64)tk->tkr_mono.xtime_nsec < 0)) {
2049 		tk->tkr_mono.xtime_nsec += (u64)NSEC_PER_SEC <<
2050 							tk->tkr_mono.shift;
2051 		tk->xtime_sec--;
2052 		tk->skip_second_overflow = 1;
2053 	}
2054 }
2055 
2056 /*
2057  * accumulate_nsecs_to_secs - Accumulates nsecs into secs
2058  *
2059  * Helper function that accumulates the nsecs greater than a second
2060  * from the xtime_nsec field to the xtime_secs field.
2061  * It also calls into the NTP code to handle leapsecond processing.
2062  */
accumulate_nsecs_to_secs(struct timekeeper * tk)2063 static inline unsigned int accumulate_nsecs_to_secs(struct timekeeper *tk)
2064 {
2065 	u64 nsecps = (u64)NSEC_PER_SEC << tk->tkr_mono.shift;
2066 	unsigned int clock_set = 0;
2067 
2068 	while (tk->tkr_mono.xtime_nsec >= nsecps) {
2069 		int leap;
2070 
2071 		tk->tkr_mono.xtime_nsec -= nsecps;
2072 		tk->xtime_sec++;
2073 
2074 		/*
2075 		 * Skip NTP update if this second was accumulated before,
2076 		 * i.e. xtime_nsec underflowed in timekeeping_adjust()
2077 		 */
2078 		if (unlikely(tk->skip_second_overflow)) {
2079 			tk->skip_second_overflow = 0;
2080 			continue;
2081 		}
2082 
2083 		/* Figure out if its a leap sec and apply if needed */
2084 		leap = second_overflow(tk->xtime_sec);
2085 		if (unlikely(leap)) {
2086 			struct timespec64 ts;
2087 
2088 			tk->xtime_sec += leap;
2089 
2090 			ts.tv_sec = leap;
2091 			ts.tv_nsec = 0;
2092 			tk_set_wall_to_mono(tk,
2093 				timespec64_sub(tk->wall_to_monotonic, ts));
2094 
2095 			__timekeeping_set_tai_offset(tk, tk->tai_offset - leap);
2096 
2097 			clock_set = TK_CLOCK_WAS_SET;
2098 		}
2099 	}
2100 	return clock_set;
2101 }
2102 
2103 /*
2104  * logarithmic_accumulation - shifted accumulation of cycles
2105  *
2106  * This functions accumulates a shifted interval of cycles into
2107  * a shifted interval nanoseconds. Allows for O(log) accumulation
2108  * loop.
2109  *
2110  * Returns the unconsumed cycles.
2111  */
logarithmic_accumulation(struct timekeeper * tk,u64 offset,u32 shift,unsigned int * clock_set)2112 static u64 logarithmic_accumulation(struct timekeeper *tk, u64 offset,
2113 				    u32 shift, unsigned int *clock_set)
2114 {
2115 	u64 interval = tk->cycle_interval << shift;
2116 	u64 snsec_per_sec;
2117 
2118 	/* If the offset is smaller than a shifted interval, do nothing */
2119 	if (offset < interval)
2120 		return offset;
2121 
2122 	/* Accumulate one shifted interval */
2123 	offset -= interval;
2124 	tk->tkr_mono.cycle_last += interval;
2125 	tk->tkr_raw.cycle_last  += interval;
2126 
2127 	tk->tkr_mono.xtime_nsec += tk->xtime_interval << shift;
2128 	*clock_set |= accumulate_nsecs_to_secs(tk);
2129 
2130 	/* Accumulate raw time */
2131 	tk->tkr_raw.xtime_nsec += tk->raw_interval << shift;
2132 	snsec_per_sec = (u64)NSEC_PER_SEC << tk->tkr_raw.shift;
2133 	while (tk->tkr_raw.xtime_nsec >= snsec_per_sec) {
2134 		tk->tkr_raw.xtime_nsec -= snsec_per_sec;
2135 		tk->raw_sec++;
2136 	}
2137 
2138 	/* Accumulate error between NTP and clock interval */
2139 	tk->ntp_error += tk->ntp_tick << shift;
2140 	tk->ntp_error -= (tk->xtime_interval + tk->xtime_remainder) <<
2141 						(tk->ntp_error_shift + shift);
2142 
2143 	return offset;
2144 }
2145 
2146 /*
2147  * timekeeping_advance - Updates the timekeeper to the current time and
2148  * current NTP tick length
2149  */
timekeeping_advance(enum timekeeping_adv_mode mode)2150 static bool timekeeping_advance(enum timekeeping_adv_mode mode)
2151 {
2152 	struct timekeeper *real_tk = &tk_core.timekeeper;
2153 	struct timekeeper *tk = &shadow_timekeeper;
2154 	u64 offset;
2155 	int shift = 0, maxshift;
2156 	unsigned int clock_set = 0;
2157 	unsigned long flags;
2158 
2159 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
2160 
2161 	/* Make sure we're fully resumed: */
2162 	if (unlikely(timekeeping_suspended))
2163 		goto out;
2164 
2165 	offset = clocksource_delta(tk_clock_read(&tk->tkr_mono),
2166 				   tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
2167 
2168 	/* Check if there's really nothing to do */
2169 	if (offset < real_tk->cycle_interval && mode == TK_ADV_TICK)
2170 		goto out;
2171 
2172 	/* Do some additional sanity checking */
2173 	timekeeping_check_update(tk, offset);
2174 
2175 	/*
2176 	 * With NO_HZ we may have to accumulate many cycle_intervals
2177 	 * (think "ticks") worth of time at once. To do this efficiently,
2178 	 * we calculate the largest doubling multiple of cycle_intervals
2179 	 * that is smaller than the offset.  We then accumulate that
2180 	 * chunk in one go, and then try to consume the next smaller
2181 	 * doubled multiple.
2182 	 */
2183 	shift = ilog2(offset) - ilog2(tk->cycle_interval);
2184 	shift = max(0, shift);
2185 	/* Bound shift to one less than what overflows tick_length */
2186 	maxshift = (64 - (ilog2(ntp_tick_length())+1)) - 1;
2187 	shift = min(shift, maxshift);
2188 	while (offset >= tk->cycle_interval) {
2189 		offset = logarithmic_accumulation(tk, offset, shift,
2190 							&clock_set);
2191 		if (offset < tk->cycle_interval<<shift)
2192 			shift--;
2193 	}
2194 
2195 	/* Adjust the multiplier to correct NTP error */
2196 	timekeeping_adjust(tk, offset);
2197 
2198 	/*
2199 	 * Finally, make sure that after the rounding
2200 	 * xtime_nsec isn't larger than NSEC_PER_SEC
2201 	 */
2202 	clock_set |= accumulate_nsecs_to_secs(tk);
2203 
2204 	write_seqcount_begin(&tk_core.seq);
2205 	/*
2206 	 * Update the real timekeeper.
2207 	 *
2208 	 * We could avoid this memcpy by switching pointers, but that
2209 	 * requires changes to all other timekeeper usage sites as
2210 	 * well, i.e. move the timekeeper pointer getter into the
2211 	 * spinlocked/seqcount protected sections. And we trade this
2212 	 * memcpy under the tk_core.seq against one before we start
2213 	 * updating.
2214 	 */
2215 	timekeeping_update(tk, clock_set);
2216 	memcpy(real_tk, tk, sizeof(*tk));
2217 	/* The memcpy must come last. Do not put anything here! */
2218 	write_seqcount_end(&tk_core.seq);
2219 out:
2220 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2221 
2222 	return !!clock_set;
2223 }
2224 
2225 /**
2226  * update_wall_time - Uses the current clocksource to increment the wall time
2227  *
2228  */
update_wall_time(void)2229 void update_wall_time(void)
2230 {
2231 	if (timekeeping_advance(TK_ADV_TICK))
2232 		clock_was_set_delayed();
2233 }
2234 
2235 /**
2236  * getboottime64 - Return the real time of system boot.
2237  * @ts:		pointer to the timespec64 to be set
2238  *
2239  * Returns the wall-time of boot in a timespec64.
2240  *
2241  * This is based on the wall_to_monotonic offset and the total suspend
2242  * time. Calls to settimeofday will affect the value returned (which
2243  * basically means that however wrong your real time clock is at boot time,
2244  * you get the right time here).
2245  */
getboottime64(struct timespec64 * ts)2246 void getboottime64(struct timespec64 *ts)
2247 {
2248 	struct timekeeper *tk = &tk_core.timekeeper;
2249 	ktime_t t = ktime_sub(tk->offs_real, tk->offs_boot);
2250 
2251 	*ts = ktime_to_timespec64(t);
2252 }
2253 EXPORT_SYMBOL_GPL(getboottime64);
2254 
ktime_get_coarse_real_ts64(struct timespec64 * ts)2255 void ktime_get_coarse_real_ts64(struct timespec64 *ts)
2256 {
2257 	struct timekeeper *tk = &tk_core.timekeeper;
2258 	unsigned int seq;
2259 
2260 	do {
2261 		seq = read_seqcount_begin(&tk_core.seq);
2262 
2263 		*ts = tk_xtime(tk);
2264 	} while (read_seqcount_retry(&tk_core.seq, seq));
2265 }
2266 EXPORT_SYMBOL(ktime_get_coarse_real_ts64);
2267 
ktime_get_coarse_ts64(struct timespec64 * ts)2268 void ktime_get_coarse_ts64(struct timespec64 *ts)
2269 {
2270 	struct timekeeper *tk = &tk_core.timekeeper;
2271 	struct timespec64 now, mono;
2272 	unsigned int seq;
2273 
2274 	do {
2275 		seq = read_seqcount_begin(&tk_core.seq);
2276 
2277 		now = tk_xtime(tk);
2278 		mono = tk->wall_to_monotonic;
2279 	} while (read_seqcount_retry(&tk_core.seq, seq));
2280 
2281 	set_normalized_timespec64(ts, now.tv_sec + mono.tv_sec,
2282 				now.tv_nsec + mono.tv_nsec);
2283 }
2284 EXPORT_SYMBOL(ktime_get_coarse_ts64);
2285 
2286 /*
2287  * Must hold jiffies_lock
2288  */
do_timer(unsigned long ticks)2289 void do_timer(unsigned long ticks)
2290 {
2291 	jiffies_64 += ticks;
2292 	calc_global_load();
2293 }
2294 
2295 /**
2296  * ktime_get_update_offsets_now - hrtimer helper
2297  * @cwsseq:	pointer to check and store the clock was set sequence number
2298  * @offs_real:	pointer to storage for monotonic -> realtime offset
2299  * @offs_boot:	pointer to storage for monotonic -> boottime offset
2300  * @offs_tai:	pointer to storage for monotonic -> clock tai offset
2301  *
2302  * Returns current monotonic time and updates the offsets if the
2303  * sequence number in @cwsseq and timekeeper.clock_was_set_seq are
2304  * different.
2305  *
2306  * Called from hrtimer_interrupt() or retrigger_next_event()
2307  */
ktime_get_update_offsets_now(unsigned int * cwsseq,ktime_t * offs_real,ktime_t * offs_boot,ktime_t * offs_tai)2308 ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq, ktime_t *offs_real,
2309 				     ktime_t *offs_boot, ktime_t *offs_tai)
2310 {
2311 	struct timekeeper *tk = &tk_core.timekeeper;
2312 	unsigned int seq;
2313 	ktime_t base;
2314 	u64 nsecs;
2315 
2316 	do {
2317 		seq = read_seqcount_begin(&tk_core.seq);
2318 
2319 		base = tk->tkr_mono.base;
2320 		nsecs = timekeeping_get_ns(&tk->tkr_mono);
2321 		base = ktime_add_ns(base, nsecs);
2322 
2323 		if (*cwsseq != tk->clock_was_set_seq) {
2324 			*cwsseq = tk->clock_was_set_seq;
2325 			*offs_real = tk->offs_real;
2326 			*offs_boot = tk->offs_boot;
2327 			*offs_tai = tk->offs_tai;
2328 		}
2329 
2330 		/* Handle leapsecond insertion adjustments */
2331 		if (unlikely(base >= tk->next_leap_ktime))
2332 			*offs_real = ktime_sub(tk->offs_real, ktime_set(1, 0));
2333 
2334 	} while (read_seqcount_retry(&tk_core.seq, seq));
2335 
2336 	return base;
2337 }
2338 
2339 /*
2340  * timekeeping_validate_timex - Ensures the timex is ok for use in do_adjtimex
2341  */
timekeeping_validate_timex(const struct __kernel_timex * txc)2342 static int timekeeping_validate_timex(const struct __kernel_timex *txc)
2343 {
2344 	if (txc->modes & ADJ_ADJTIME) {
2345 		/* singleshot must not be used with any other mode bits */
2346 		if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
2347 			return -EINVAL;
2348 		if (!(txc->modes & ADJ_OFFSET_READONLY) &&
2349 		    !capable(CAP_SYS_TIME))
2350 			return -EPERM;
2351 	} else {
2352 		/* In order to modify anything, you gotta be super-user! */
2353 		if (txc->modes && !capable(CAP_SYS_TIME))
2354 			return -EPERM;
2355 		/*
2356 		 * if the quartz is off by more than 10% then
2357 		 * something is VERY wrong!
2358 		 */
2359 		if (txc->modes & ADJ_TICK &&
2360 		    (txc->tick <  900000/USER_HZ ||
2361 		     txc->tick > 1100000/USER_HZ))
2362 			return -EINVAL;
2363 	}
2364 
2365 	if (txc->modes & ADJ_SETOFFSET) {
2366 		/* In order to inject time, you gotta be super-user! */
2367 		if (!capable(CAP_SYS_TIME))
2368 			return -EPERM;
2369 
2370 		/*
2371 		 * Validate if a timespec/timeval used to inject a time
2372 		 * offset is valid.  Offsets can be positive or negative, so
2373 		 * we don't check tv_sec. The value of the timeval/timespec
2374 		 * is the sum of its fields,but *NOTE*:
2375 		 * The field tv_usec/tv_nsec must always be non-negative and
2376 		 * we can't have more nanoseconds/microseconds than a second.
2377 		 */
2378 		if (txc->time.tv_usec < 0)
2379 			return -EINVAL;
2380 
2381 		if (txc->modes & ADJ_NANO) {
2382 			if (txc->time.tv_usec >= NSEC_PER_SEC)
2383 				return -EINVAL;
2384 		} else {
2385 			if (txc->time.tv_usec >= USEC_PER_SEC)
2386 				return -EINVAL;
2387 		}
2388 	}
2389 
2390 	/*
2391 	 * Check for potential multiplication overflows that can
2392 	 * only happen on 64-bit systems:
2393 	 */
2394 	if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) {
2395 		if (LLONG_MIN / PPM_SCALE > txc->freq)
2396 			return -EINVAL;
2397 		if (LLONG_MAX / PPM_SCALE < txc->freq)
2398 			return -EINVAL;
2399 	}
2400 
2401 	return 0;
2402 }
2403 
2404 /**
2405  * random_get_entropy_fallback - Returns the raw clock source value,
2406  * used by random.c for platforms with no valid random_get_entropy().
2407  */
random_get_entropy_fallback(void)2408 unsigned long random_get_entropy_fallback(void)
2409 {
2410 	struct tk_read_base *tkr = &tk_core.timekeeper.tkr_mono;
2411 	struct clocksource *clock = READ_ONCE(tkr->clock);
2412 
2413 	if (unlikely(timekeeping_suspended || !clock))
2414 		return 0;
2415 	return clock->read(clock);
2416 }
2417 EXPORT_SYMBOL_GPL(random_get_entropy_fallback);
2418 
2419 /**
2420  * do_adjtimex() - Accessor function to NTP __do_adjtimex function
2421  */
do_adjtimex(struct __kernel_timex * txc)2422 int do_adjtimex(struct __kernel_timex *txc)
2423 {
2424 	struct timekeeper *tk = &tk_core.timekeeper;
2425 	struct audit_ntp_data ad;
2426 	bool clock_set = false;
2427 	struct timespec64 ts;
2428 	unsigned long flags;
2429 	s32 orig_tai, tai;
2430 	int ret;
2431 
2432 	/* Validate the data before disabling interrupts */
2433 	ret = timekeeping_validate_timex(txc);
2434 	if (ret)
2435 		return ret;
2436 	add_device_randomness(txc, sizeof(*txc));
2437 
2438 	if (txc->modes & ADJ_SETOFFSET) {
2439 		struct timespec64 delta;
2440 		delta.tv_sec  = txc->time.tv_sec;
2441 		delta.tv_nsec = txc->time.tv_usec;
2442 		if (!(txc->modes & ADJ_NANO))
2443 			delta.tv_nsec *= 1000;
2444 		ret = timekeeping_inject_offset(&delta);
2445 		if (ret)
2446 			return ret;
2447 
2448 		audit_tk_injoffset(delta);
2449 	}
2450 
2451 	audit_ntp_init(&ad);
2452 
2453 	ktime_get_real_ts64(&ts);
2454 	add_device_randomness(&ts, sizeof(ts));
2455 
2456 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
2457 	write_seqcount_begin(&tk_core.seq);
2458 
2459 	orig_tai = tai = tk->tai_offset;
2460 	ret = __do_adjtimex(txc, &ts, &tai, &ad);
2461 
2462 	if (tai != orig_tai) {
2463 		__timekeeping_set_tai_offset(tk, tai);
2464 		timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
2465 		clock_set = true;
2466 	}
2467 	tk_update_leap_state(tk);
2468 
2469 	write_seqcount_end(&tk_core.seq);
2470 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2471 
2472 	audit_ntp_log(&ad);
2473 
2474 	/* Update the multiplier immediately if frequency was set directly */
2475 	if (txc->modes & (ADJ_FREQUENCY | ADJ_TICK))
2476 		clock_set |= timekeeping_advance(TK_ADV_FREQ);
2477 
2478 	if (clock_set)
2479 		clock_was_set(CLOCK_REALTIME);
2480 
2481 	ntp_notify_cmos_timer();
2482 
2483 	return ret;
2484 }
2485 
2486 #ifdef CONFIG_NTP_PPS
2487 /**
2488  * hardpps() - Accessor function to NTP __hardpps function
2489  */
hardpps(const struct timespec64 * phase_ts,const struct timespec64 * raw_ts)2490 void hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
2491 {
2492 	unsigned long flags;
2493 
2494 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
2495 	write_seqcount_begin(&tk_core.seq);
2496 
2497 	__hardpps(phase_ts, raw_ts);
2498 
2499 	write_seqcount_end(&tk_core.seq);
2500 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
2501 }
2502 EXPORT_SYMBOL(hardpps);
2503 #endif /* CONFIG_NTP_PPS */
2504