1 /*
2 * Copyright (c) 2015 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 #include <stdbool.h>
24 #include <sys/types.h>
25 #include <sys/time.h>
26 #include <mach/mach_time.h>
27 #include <sys/time.h>
28 #include <machine/cpu_capabilities.h>
29
30 // From __commpage_gettimeofday.c
31 extern int __commpage_gettimeofday_internal(struct timeval *tp, uint64_t *tbr_out);
32 extern kern_return_t _mach_continuous_time(uint64_t* absolute_time, uint64_t* cont_time);
33 // From mach_continuous_time.c
34 extern uint64_t _mach_continuous_time_base(void);
35 // Underlying syscall stub
36 extern int __gettimeofday_with_mach(struct timeval *, struct timezone *, uint64_t *);
37
38 kern_return_t
mach_get_times(uint64_t * absolute_time,uint64_t * cont_time,struct timespec * tp)39 mach_get_times(uint64_t* absolute_time, uint64_t* cont_time, struct timespec *tp)
40 {
41 if (tp == NULL) {
42 return _mach_continuous_time(absolute_time, cont_time);
43 }
44
45 uint64_t continuous_time_base_prior = -1, continuous_time_base_post = -1;
46 uint64_t tbr;
47 struct timeval tv;
48
49 do {
50 /*
51 * We need to capture the result of gettimeofday without our continuous
52 * time base changing. Once we have that, and the value for absolute
53 * time that was used to compute the timespec, we can just add the base
54 * to get the accompanying continuous time.
55 */
56 continuous_time_base_prior = _mach_continuous_time_base();
57
58 /*
59 * This call has the necessary memory barriers for this retry loop,
60 * since it is implemented with a retry loop of its own.
61 */
62 if (__commpage_gettimeofday_internal(&tv, &tbr)) {
63 tbr = 0;
64 if (__gettimeofday_with_mach(&tv, NULL, &tbr) < 0) {
65 return KERN_FAILURE;
66 } else if (tbr == 0) {
67 __builtin_trap();
68 }
69 }
70
71 continuous_time_base_post = _mach_continuous_time_base();
72 } while (__builtin_expect(continuous_time_base_prior != continuous_time_base_post, 0));
73
74 if (absolute_time) {
75 *absolute_time = tbr;
76 }
77 if (cont_time) {
78 *cont_time = continuous_time_base_prior + tbr;
79 }
80 tp->tv_sec = tv.tv_sec;
81 tp->tv_nsec = tv.tv_usec * NSEC_PER_USEC;
82
83 return KERN_SUCCESS;
84 }
85