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 */