osfmk/x86_64/machine_remote_time.c

   1 /*
   2  * Copyright (c) 2017 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_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. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 #include <kern/misc_protos.h>
  29 #include <x86_64/machine_remote_time.h>
  30 #include <machine/atomic.h>
  31 #include <kern/locks.h>
  32 #include <kern/clock.h>
  33 #include <kern/remote_time.h>
  34
  35 void mach_bridge_send_timestamp(uint64_t timestamp);
  36
  37 extern _Atomic uint32_t bt_init_flag;
  38 extern uint32_t bt_enable_flag;
  39
  40 /*
  41  * Delay sending timestamps by certain interval to
  42  * avoid overwriting sentinel values
  43  */
  44 #define DELAY_INTERVAL_NS (50 * NSEC_PER_MSEC)
  45 static uint64_t bt_delay_timestamp = 0;
  46 static mach_bridge_regwrite_timestamp_func_t bridge_regwrite_timestamp_callback = NULL;
  47
  48 /*
  49  * This function should only be called by the kext
  50  * responsible for sending timestamps across the link
  51  */
  52 void
  53 mach_bridge_register_regwrite_timestamp_callback(mach_bridge_regwrite_timestamp_func_t func)
  54 {
  55         static uint64_t delay_amount = 0;
  56
  57         if (!os_atomic_load(&bt_init_flag, relaxed)) {
  58                 nanoseconds_to_absolutetime(DELAY_INTERVAL_NS, &delay_amount);
  59                 os_atomic_store(&bt_init_flag, 1, release);
  60         }
  61
  62         lck_spin_lock(&bt_maintenance_lock);
  63         bridge_regwrite_timestamp_callback = func;
  64         bt_enable_flag = (func != NULL) ? 1 : 0;
  65         bt_delay_timestamp = mach_absolute_time() + delay_amount;
  66         lck_spin_unlock(&bt_maintenance_lock);
  67 }
  68
  69 void
  70 mach_bridge_send_timestamp(uint64_t timestamp)
  71 {
  72         LCK_SPIN_ASSERT(&bt_maintenance_lock, LCK_ASSERT_OWNED);
  73
  74         if (bt_delay_timestamp > 0) {
  75                 uint64_t now = mach_absolute_time();
  76                 if (now < bt_delay_timestamp) {
  77                         return;
  78                 }
  79                 bt_delay_timestamp = 0;
  80         }
  81
  82         if (bridge_regwrite_timestamp_callback) {
  83                 bridge_regwrite_timestamp_callback(timestamp);
  84         }
  85 }