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 <stddef.h>
24 #include <stdbool.h>
25 #include <sys/types.h>
26 #include <machine/cpu_capabilities.h>
27 #include <mach/mach_time.h>
28
29 __attribute__((visibility("hidden")))
30 uint64_t
_mach_continuous_time_base(void)31 _mach_continuous_time_base(void)
32 {
33 #if !defined(__x86_64__) && !defined(__arm64__)
34 // Deal with the lack of 64-bit loads on arm32 (see mach_approximate_time.s)
35 while (1) {
36 volatile uint64_t *base_ptr = (volatile uint64_t*)_COMM_PAGE_CONT_TIMEBASE;
37 uint64_t read1, read2;
38 read1 = *base_ptr;
39 #if defined(__arm__)
40 __asm__ volatile ("dsb sy" ::: "memory");
41 #elif defined(__i386__)
42 __asm__ volatile ("lfence" ::: "memory");
43 #else
44 #error "unsupported arch"
45 #endif
46 read2 = *base_ptr;
47
48 if (__builtin_expect((read1 == read2), 1)) {
49 return read1;
50 }
51 }
52 #else // 64-bit
53 return *(volatile uint64_t*)_COMM_PAGE_CONT_TIMEBASE;
54 #endif // 64-bit
55 }
56
57 #define CNTVCTSS_EL0 "S3_3_c14_c0_6"
58
59 __attribute__((visibility("hidden")))
60 kern_return_t
_mach_continuous_hwclock(uint64_t * cont_time __unused)61 _mach_continuous_hwclock(uint64_t *cont_time __unused)
62 {
63 #if defined(__arm64__)
64 #define ISB_SY 0xf
65 uint8_t cont_hwclock = *((uint8_t*)_COMM_PAGE_CONT_HWCLOCK);
66 if (cont_hwclock) {
67 volatile uint64_t *base_ptr = (volatile uint64_t*)_COMM_PAGE_CONT_HW_TIMEBASE;
68
69 boolean_t has_cntvctss_el0 = *((uint8_t*)_COMM_PAGE_USER_TIMEBASE) == USER_TIMEBASE_NOSPEC;
70 if (has_cntvctss_el0) {
71 *cont_time = __builtin_arm_rsr64(CNTVCTSS_EL0) + *base_ptr;
72 return KERN_SUCCESS;
73 }
74
75
76 __builtin_arm_isb(ISB_SY);
77 *cont_time = __builtin_arm_rsr64("CNTVCT_EL0") + *base_ptr;
78 return KERN_SUCCESS;
79 }
80 #endif
81 return KERN_NOT_SUPPORTED;
82 }
83
84 __attribute__((visibility("hidden")))
85 kern_return_t
_mach_continuous_time(uint64_t * absolute_time,uint64_t * cont_time)86 _mach_continuous_time(uint64_t* absolute_time, uint64_t* cont_time)
87 {
88 volatile uint64_t *base_ptr = (volatile uint64_t*)_COMM_PAGE_CONT_TIMEBASE;
89 volatile uint64_t read1, read2;
90 volatile uint64_t absolute;
91
92 do {
93 read1 = *base_ptr;
94 absolute = mach_absolute_time();
95 #if defined(__arm__) || defined(__arm64__)
96 /*
97 * mach_absolute_time() contains an instruction barrier which will
98 * prevent the speculation of read2 above this point, so we don't
99 * need another barrier here.
100 */
101 #endif
102 read2 = *base_ptr;
103 } while (__builtin_expect((read1 != read2), 0));
104
105 if (absolute_time) {
106 *absolute_time = absolute;
107 }
108 if (cont_time) {
109 *cont_time = absolute + read1;
110 }
111
112 return KERN_SUCCESS;
113 }
114
115 uint64_t
mach_continuous_time(void)116 mach_continuous_time(void)
117 {
118 uint64_t cont_time;
119 if (_mach_continuous_hwclock(&cont_time) != KERN_SUCCESS) {
120 _mach_continuous_time(NULL, &cont_time);
121 }
122 return cont_time;
123 }
124
125 uint64_t
mach_continuous_approximate_time(void)126 mach_continuous_approximate_time(void)
127 {
128 /*
129 * No retry loop here because if we use a slightly too old timebase that's
130 * okay, we are approximate time anyway.
131 */
132 volatile register uint64_t time_base = _mach_continuous_time_base();
133 return time_base + mach_approximate_time();
134 }
135