libsyscall/wrappers/mach_get_times.c

   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
  39 mach_get_times(uint64_t* absolute_time, uint64_t* cont_time, struct timespec *tp) {
  40         if (tp == NULL) {
  41                 return _mach_continuous_time(absolute_time, cont_time);
  42         }
  43
  44         uint64_t continuous_time_base_prior = -1, continuous_time_base_post = -1;
  45         uint64_t tbr;
  46         struct timeval tv;
  47
  48         do {
  49                 /*
  50                  * We need to capture the result of gettimeofday without our continuous
  51                  * time base changing.  Once we have that, and the value for absolute
  52                  * time that was used to compute the timespec, we can just add the base
  53                  * to get the accompanying continuous time.
  54                  */
  55                 continuous_time_base_prior = _mach_continuous_time_base();
  56
  57                 /*
  58                  * This call has the necessary memory barriers for this retry loop,
  59                  * since it is implemented with a retry loop of its own.
  60                  */
  61                 if (__commpage_gettimeofday_internal(&tv, &tbr)) {
  62                         tbr = 0;
  63                         if (__gettimeofday_with_mach(&tv, NULL, &tbr) < 0) {
  64                                 return KERN_FAILURE;
  65                         } else if (tbr == 0) {
  66 #if !TARGET_OS_EMBEDDED
  67                                 // On an old kernel, likely chroot'ed. (remove next year)
  68                                 tbr = mach_absolute_time();
  69 #else
  70                                 __builtin_trap();
  71 #endif
  72                         }
  73                 }
  74
  75                 continuous_time_base_post = _mach_continuous_time_base();
  76         } while (__builtin_expect(continuous_time_base_prior != continuous_time_base_post, 0));
  77
  78         if (absolute_time) *absolute_time = tbr;
  79         if (cont_time) *cont_time = continuous_time_base_prior + tbr;
  80         tp->tv_sec = tv.tv_sec;
  81         tp->tv_nsec = tv.tv_usec * NSEC_PER_USEC;
  82
  83         return KERN_SUCCESS;
  84 }