+/*
+ * 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 = {};
+
+ volatile struct bt_params *commpage_bt_params_p = (struct bt_params *)_COMM_PAGE_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__) */
projects / apple / xnu.git / commitdiff
