osfmk/kern/remote_time.h

   1 /*
   2  * Copyright (c) 2016 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
  29 #ifndef REMOTE_TIME_H
  30 #define REMOTE_TIME_H
  31
  32 #include <sys/cdefs.h>
  33 #include <stdint.h>
  34 #include <os/overflow.h>
  35
  36 __BEGIN_DECLS
  37 /* bt_params is an ABI for tracing tools */
  38 struct bt_params {
  39         double rate;
  40         uint64_t base_local_ts;
  41         uint64_t base_remote_ts;
  42 };
  43
  44 /* local_ts_ns should be in nanoseconds */
  45 static inline uint64_t
  46 mach_bridge_compute_timestamp(uint64_t local_ts_ns, struct bt_params *params)
  47 {
  48         if (!params || params->rate == 0.0) {
  49                 return 0;
  50         }
  51         /*
  52          * Formula to compute remote_timestamp
  53          * remote_timestamp = (bt_params.rate * (local_ts_ns - bt_params.base_local_ts))
  54          *       +  bt_params.base_remote_ts
  55          */
  56         int64_t remote_ts = 0;
  57         int64_t rate_prod = 0;
  58         /* To avoid precision loss due to typecasting from int64_t to double */
  59         if (params->rate != 1.0) {
  60                 rate_prod = (int64_t)(params->rate * (double)((int64_t)local_ts_ns - (int64_t)params->base_local_ts));
  61         } else {
  62                 rate_prod = (int64_t)local_ts_ns - (int64_t)params->base_local_ts;
  63         }
  64         if (os_add_overflow((int64_t)params->base_remote_ts, rate_prod, &remote_ts)) {
  65                 return 0;
  66         }
  67
  68         return (uint64_t)remote_ts;
  69 }
  70
  71 uint64_t mach_bridge_remote_time(uint64_t);
  72
  73 #if XNU_KERNEL_PRIVATE
  74 #include <kern/locks.h>
  75 extern lck_spin_t bt_maintenance_lock;
  76 extern lck_spin_t bt_spin_lock;
  77 extern lck_spin_t bt_ts_conversion_lock;
  78 #endif
  79
  80 __END_DECLS
  81
  82 #endif /* REMOTE_TIME_H */