/*
* Copyright (c) 2018 Apple Inc. All rights reserved.
*
* @APPLE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this
* file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_LICENSE_HEADER_END@
*/
#include <sys/types.h>
#include <machine/cpu_capabilities.h>
#include <kern/remote_time.h>
#include <mach/mach_time.h>
#include "strings.h"
#include <TargetConditionals.h>
#define BT_RESET_SENTINEL_TS (~3ULL) /* from machine/machine_remote_time.h */
extern uint64_t __mach_bridge_remote_time(uint64_t local_time);
#if TARGET_OS_BRIDGE && defined(__arm64__)
static uint64_t
absolutetime_to_nanoseconds(uint64_t abs_time)
{
mach_timebase_info_data_t info;
mach_timebase_info(&info);
uint64_t time_in_ns = (uint64_t)(((double)info.numer / (double)info.denom) * abs_time);
return time_in_ns;
}
uint64_t
mach_bridge_remote_time(__unused uint64_t local_time)
{
uint64_t remote_time = 0;
uint64_t local_time_ns = 0;
uint64_t now = 0;
struct bt_params params = {};
COMM_PAGE_SLOT_TYPE(struct bt_params) commpage_bt_params_p =
COMM_PAGE_SLOT(struct bt_params, REMOTETIME_PARAMS);
volatile uint64_t *base_local_ts_p = &commpage_bt_params_p->base_local_ts;
volatile uint64_t *base_remote_ts_p = &commpage_bt_params_p->base_remote_ts;
volatile double *rate_p = &commpage_bt_params_p->rate;
do {
params.base_local_ts = *base_local_ts_p;
if (*base_local_ts_p == BT_RESET_SENTINEL_TS) {
return 0;
}
/*
* This call contains an instruction barrier that ensures the second read of
* base_local_ts is not speculated above the first read of base_local_ts.
*/
now = mach_absolute_time();
params.base_remote_ts = *base_remote_ts_p;
params.rate = *rate_p;
/*
* This barrier prevents the second read of base_local_ts from being reordered
* w.r.t the reads of other values in bt_params.
*/
__asm__ volatile ("dmb ishld" ::: "memory");
} while (params.base_local_ts && (params.base_local_ts != commpage_bt_params_p->base_local_ts));
if (!local_time) {
local_time = now;
}
local_time_ns = absolutetime_to_nanoseconds(local_time);
if (local_time_ns < params.base_local_ts) {
remote_time = __mach_bridge_remote_time(local_time);
} else {
remote_time = mach_bridge_compute_timestamp(local_time_ns, ¶ms);
}
return remote_time;
}
#endif /* TARGET_OS_BRIDGE && defined(__arm64__) */