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Commit	Line	Data
	1	/*
	2	* Copyright (c) 2008 Apple Inc. All rights reserved.
	3	*
	4	* @APPLE_LICENSE_HEADER_START@
	5	*
	6	* This file contains Original Code and/or Modifications of Original Code
	7	* as defined in and that are subject to the Apple Public Source License
	8	* Version 2.0 (the 'License'). You may not use this file except in
	9	* compliance with the License. Please obtain a copy of the License at
	10	* http://www.opensource.apple.com/apsl/ and read it before using this
	11	* file.
	12	*
	13	* The Original Code and all software distributed under the License are
	14	* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
	15	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
	16	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
	17	* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
	18	* Please see the License for the specific language governing rights and
	19	* limitations under the License.
	20	*
	21	* @APPLE_LICENSE_HEADER_END@
	22	*/
	23
	24	#include <sys/time.h>
	25	#include <mach/mach_time.h>
	26	#include <machine/cpu_capabilities.h>
	27	#include <os/overflow.h>
	28	#include <kern/arithmetic_128.h>
	29
	30	int __commpage_gettimeofday(struct timeval *);
	31
	32	__attribute__((visibility("hidden")))
	33	int __commpage_gettimeofday_internal(struct timeval tp, uint64_t tbr_out);
	34
	35	int
	36	__commpage_gettimeofday(struct timeval *tp)
	37	{
	38	return __commpage_gettimeofday_internal(tp, NULL);
	39	}
	40
	41	int
	42	__commpage_gettimeofday_internal(struct timeval tp, uint64_t tbr_out)
	43	{
	44	uint64_t now, over;
	45	uint64_t delta, frac;
	46	uint64_t TimeStamp_tick;
	47	uint64_t TimeStamp_sec;
	48	uint64_t TimeStamp_frac;
	49	uint64_t Tick_scale;
	50	uint64_t Ticks_per_sec;
	51
	52	volatile uint64_t *gtod_TimeStamp_tick_p;
	53	volatile uint64_t *gtod_TimeStamp_sec_p;
	54	volatile uint64_t *gtod_TimeStamp_frac_p;
	55	volatile uint64_t *gtod_Ticks_scale_p;
	56	volatile uint64_t *gtod_Ticks_per_sec_p;
	57
	58	COMM_PAGE_SLOT_TYPE(new_commpage_timeofday_data_t) commpage_timeofday_datap =
	59	COMM_PAGE_SLOT(new_commpage_timeofday_data_t, NEWTIMEOFDAY_DATA);
	60
	61	gtod_TimeStamp_tick_p = &commpage_timeofday_datap->TimeStamp_tick;
	62	gtod_TimeStamp_sec_p = &commpage_timeofday_datap->TimeStamp_sec;
	63	gtod_TimeStamp_frac_p = &commpage_timeofday_datap->TimeStamp_frac;
	64	gtod_Ticks_scale_p = &commpage_timeofday_datap->Ticks_scale;
	65	gtod_Ticks_per_sec_p = &commpage_timeofday_datap->Ticks_per_sec;
	66
	67	do {
	68	TimeStamp_tick = *gtod_TimeStamp_tick_p;
	69	/*
	70	* This call contains an instruction barrier which will ensure that the
	71	* second read of the abs time isn't speculated above the reads of the
	72	* other values above
	73	*/
	74	now = mach_absolute_time();
	75	TimeStamp_sec = *gtod_TimeStamp_sec_p;
	76	TimeStamp_frac = *gtod_TimeStamp_frac_p;
	77	Tick_scale = *gtod_Ticks_scale_p;
	78	Ticks_per_sec = *gtod_Ticks_per_sec_p;
	79	/*
	80	* This barrier prevents the reordering of the second read of gtod_TimeStamp_tick_p
	81	* w.r.t the values read just after mach_absolute_time is invoked.
	82	*/
	83	#if (__ARM_ARCH__ >= 7)
	84	__asm__ volatile ("dmb ishld" ::: "memory");
	85	#endif
	86	} while (TimeStamp_tick != *gtod_TimeStamp_tick_p);
	87
	88	if (TimeStamp_tick == 0) {
	89	return 1;
	90	}
	91
	92	delta = now - TimeStamp_tick;
	93
	94	/* If more than one second force a syscall */
	95	if (delta >= Ticks_per_sec) {
	96	return 1;
	97	}
	98
	99	if (TimeStamp_sec > __LONG_MAX__) {
	100	return 1;
	101	}
	102
	103	tp->tv_sec = (__darwin_time_t)TimeStamp_sec;
	104
	105	over = multi_overflow(Tick_scale, delta);
	106	if (over) {
	107	tp->tv_sec += over;
	108	}
	109
	110	/* Sum scaledelta to TimeStamp_frac, if it overflows increment sec /
	111	frac = TimeStamp_frac;
	112	frac += Tick_scale * delta;
	113	if (TimeStamp_frac > frac) {
	114	tp->tv_sec++;
	115	}
	116
	117	/*
	118	* Convert frac (64 bit frac of a sec) to usec
	119	* usec = frac * USEC_PER_SEC / 2^64
	120	*/
	121	tp->tv_usec = ((uint64_t)1000000 * (uint32_t)(frac >> 32)) >> 32;
	122
	123	if (tbr_out) {
	124	*tbr_out = now;
	125	}
	126
	127	return 0;
	128	}