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
__commpage_gettimeofday(struct timeval * tp)36 __commpage_gettimeofday(struct timeval *tp)
37 {
38 return __commpage_gettimeofday_internal(tp, NULL);
39 }
40
41 int
__commpage_gettimeofday_internal(struct timeval * tp,uint64_t * tbr_out)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 scale*delta 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 }
129