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
  34 void mach_bridge_send_timestamp(uint64_t timestamp);
  35
  36 extern _Atomic uint32_t bt_init_flag;
  37 extern lck_spin_t *bt_maintenance_lock;
  38 extern void mach_bridge_timer_init(void);
  39 extern uint32_t bt_enable_flag;
  40
  41 /*
  42  * Delay sending timestamps by certain interval to
  43  * avoid overwriting sentinel values
  44  */
  45 #define DELAY_INTERVAL_NS (50 * NSEC_PER_MSEC)
  46 static uint64_t bt_delay_timestamp = 0;
  47 static mach_bridge_regwrite_timestamp_func_t bridge_regwrite_timestamp_callback = NULL;
  48
  49 /*
  50  * This function should only be called by the kext
  51  * responsible for sending timestamps across the link
  52  */
  53 void
  54 mach_bridge_register_regwrite_timestamp_callback(mach_bridge_regwrite_timestamp_func_t func)
  55 {
  56         static uint64_t delay_amount = 0;
  57
  58         if (!os_atomic_load(&bt_init_flag, relaxed)) {
  59                 mach_bridge_timer_init();
  60                 nanoseconds_to_absolutetime(DELAY_INTERVAL_NS, &delay_amount);
  61                 os_atomic_store(&bt_init_flag, 1, release);
  62         }
  63
  64         lck_spin_lock(bt_maintenance_lock);
  65         bridge_regwrite_timestamp_callback = func;
  66         bt_enable_flag = (func != NULL) ? 1 : 0;
  67         bt_delay_timestamp = mach_absolute_time() + delay_amount;
  68         lck_spin_unlock(bt_maintenance_lock);
  69 }
  70
  71 void
  72 mach_bridge_send_timestamp(uint64_t timestamp)
  73 {
  74         LCK_SPIN_ASSERT(bt_maintenance_lock, LCK_ASSERT_OWNED);
  75
  76         if (bt_delay_timestamp > 0) {
  77                 uint64_t now = mach_absolute_time();
  78                 if (now < bt_delay_timestamp) {
  79                         return;
  80                 }
  81                 bt_delay_timestamp = 0;
  82         }
  83
  84         if (bridge_regwrite_timestamp_callback) {
  85                 bridge_regwrite_timestamp_callback(timestamp);
  86         }
  87 }