libsyscall/wrappers/__commpage_gettimeofday.c

   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
  28 int __commpage_gettimeofday(struct timeval *);
  29
  30 __attribute__((visibility("hidden")))
  31 int __commpage_gettimeofday_internal(struct timeval *tp, uint64_t *tbr_out);
  32
  33 #if   defined(__x86_64__) || defined(__i386__)
  34
  35 // XXX: must be kept in sync with __commpage_gettimeofday.s
  36 int
  37 __commpage_gettimeofday_internal(struct timeval *tp, uint64_t *tbr_out)
  38 {
  39         volatile uint32_t *gtod_generation_p = _COMM_PAGE_GTOD_GENERATION;
  40         volatile uint64_t *gtod_sec_base_p = _COMM_PAGE_GTOD_SEC_BASE;
  41         volatile uint64_t *gtod_ns_base_p = _COMM_PAGE_GTOD_NS_BASE;
  42
  43         uint64_t tbr, gen, tod_secs, tod_nsecs, elapsed;
  44         while(1) {
  45                 gen = *gtod_generation_p;
  46                 tbr = mach_absolute_time();
  47                 tod_secs = *gtod_sec_base_p;
  48                 tod_nsecs = *gtod_ns_base_p;
  49                 uint64_t gen2 = *gtod_generation_p;
  50                 if(__builtin_expect(gen, gen2) == gen2)
  51                         break;
  52         }
  53         if (gen == 0) return KERN_FAILURE;
  54         elapsed = tbr - tod_nsecs;
  55
  56         unsigned long secs;
  57         uint32_t nsec;
  58 #if defined(__x86_64__)
  59         secs = elapsed/NSEC_PER_SEC;
  60         nsec = elapsed % NSEC_PER_SEC;
  61 #elif defined(__i386__)
  62         uint32_t secs1, secs2;
  63         secs1 = elapsed >> 32;
  64         secs2 = elapsed;
  65         __asm__ (
  66           "divl %4"
  67           : "=a" (secs), "=d" (nsec)
  68           : "0" (secs2), "1" (secs1), "rm" (NSEC_PER_SEC)
  69         );
  70 #endif /* __i386 or __x86_64__ */
  71         tp->tv_sec = tod_secs + secs;
  72         tp->tv_usec = nsec / NSEC_PER_USEC;
  73
  74         if (tbr_out) *tbr_out = tbr;
  75
  76         return KERN_SUCCESS;
  77 }
  78
  79 #endif