1 /* 2 * Copyright (c) 2018 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 #include <sys/types.h> 24 #include <machine/cpu_capabilities.h> 25 #include <kern/remote_time.h> 26 #include <mach/mach_time.h> 27 #include "strings.h" 28 #include <TargetConditionals.h> 29 30 #define BT_RESET_SENTINEL_TS (~3ULL) /* from machine/machine_remote_time.h */ 31 32 extern uint64_t __mach_bridge_remote_time(uint64_t local_time); 33 34 #if TARGET_OS_BRIDGE && defined(__arm64__) 35 static uint64_t absolutetime_to_nanoseconds(uint64_t abs_time)36absolutetime_to_nanoseconds(uint64_t abs_time) 37 { 38 mach_timebase_info_data_t info; 39 mach_timebase_info(&info); 40 uint64_t time_in_ns = (uint64_t)(((double)info.numer / (double)info.denom) * abs_time); 41 42 return time_in_ns; 43 } 44 45 uint64_t mach_bridge_remote_time(__unused uint64_t local_time)46mach_bridge_remote_time(__unused uint64_t local_time) 47 { 48 uint64_t remote_time = 0; 49 uint64_t local_time_ns = 0; 50 uint64_t now = 0; 51 struct bt_params params = {}; 52 53 COMM_PAGE_SLOT_TYPE(struct bt_params) commpage_bt_params_p = 54 COMM_PAGE_SLOT(struct bt_params, REMOTETIME_PARAMS); 55 volatile uint64_t *base_local_ts_p = &commpage_bt_params_p->base_local_ts; 56 volatile uint64_t *base_remote_ts_p = &commpage_bt_params_p->base_remote_ts; 57 volatile double *rate_p = &commpage_bt_params_p->rate; 58 59 do { 60 params.base_local_ts = *base_local_ts_p; 61 if (*base_local_ts_p == BT_RESET_SENTINEL_TS) { 62 return 0; 63 } 64 /* 65 * This call contains an instruction barrier that ensures the second read of 66 * base_local_ts is not speculated above the first read of base_local_ts. 67 */ 68 now = mach_absolute_time(); 69 params.base_remote_ts = *base_remote_ts_p; 70 params.rate = *rate_p; 71 /* 72 * This barrier prevents the second read of base_local_ts from being reordered 73 * w.r.t the reads of other values in bt_params. 74 */ 75 __asm__ volatile ("dmb ishld" ::: "memory"); 76 } while (params.base_local_ts && (params.base_local_ts != commpage_bt_params_p->base_local_ts)); 77 78 if (!local_time) { 79 local_time = now; 80 } 81 local_time_ns = absolutetime_to_nanoseconds(local_time); 82 if (local_time_ns < params.base_local_ts) { 83 remote_time = __mach_bridge_remote_time(local_time); 84 } else { 85 remote_time = mach_bridge_compute_timestamp(local_time_ns, ¶ms); 86 } 87 return remote_time; 88 } 89 #endif /* TARGET_OS_BRIDGE && defined(__arm64__) */ 90