| | 1 | /* |
| | 2 | * Copyright (c) 2010-2012 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 | * @OSF_COPYRIGHT@ |
| | 30 | */ |
| | 31 | /* |
| | 32 | * @APPLE_FREE_COPYRIGHT@ |
| | 33 | */ |
| | 34 | /* |
| | 35 | * File: rtclock_asm_native.h |
| | 36 | * Purpose: Native routines for reading nanotime |
| | 37 | */ |
| | 38 | |
| | 39 | #ifndef _PAL_RTCLOCK_ASM_NATIVE_H_ |
| | 40 | #define _PAL_RTCLOCK_ASM_NATIVE_H_ |
| | 41 | |
| | 42 | /* |
| | 43 | * Assembly snippet included in exception handlers and rtc_nanotime_read() |
| | 44 | * |
| | 45 | * |
| | 46 | * Warning! There are several copies of this code in the trampolines found in |
| | 47 | * osfmk/x86_64/idt64.s, coming from the various TIMER macros in rtclock_asm.h. |
| | 48 | * They're all kept in sync by using the RTC_NANOTIME_READ() macro. |
| | 49 | * |
| | 50 | * The algorithm we use is: |
| | 51 | * |
| | 52 | * ns = ((((rdtsc - rnt_tsc_base)<<rnt_shift)*rnt_tsc_scale) / 2**32) + rnt_ns_base; |
| | 53 | * |
| | 54 | * rnt_shift, a constant computed during initialization, is the smallest value for which: |
| | 55 | * |
| | 56 | * (tscFreq << rnt_shift) > SLOW_TSC_THRESHOLD |
| | 57 | * |
| | 58 | * Where SLOW_TSC_THRESHOLD is about 10e9. Since most processor's tscFreqs are greater |
| | 59 | * than 1GHz, rnt_shift is usually 0. rnt_tsc_scale is also a 32-bit constant: |
| | 60 | * |
| | 61 | * rnt_tsc_scale = (10e9 * 2**32) / (tscFreq << rnt_shift); |
| | 62 | * |
| | 63 | * %rdi points to nanotime info struct. |
| | 64 | * %rax returns nanotime |
| | 65 | */ |
| | 66 | #define PAL_RTC_NANOTIME_READ_FAST() \ |
| | 67 | 0: movl RNT_GENERATION(%rdi),%esi ; \ |
| | 68 | test %esi,%esi /* info updating? */ ; \ |
| | 69 | jz 0b /* - wait if so */ ; \ |
| | 70 | lfence ; \ |
| | 71 | rdtsc ; \ |
| | 72 | lfence ; \ |
| | 73 | shlq $32,%rdx ; \ |
| | 74 | movl RNT_SHIFT(%rdi),%ecx ; \ |
| | 75 | orq %rdx,%rax /* %rax := tsc */ ; \ |
| | 76 | subq RNT_TSC_BASE(%rdi),%rax /* tsc - tsc_base */ ; \ |
| | 77 | shlq %cl,%rax ; \ |
| | 78 | movl RNT_SCALE(%rdi),%ecx ; \ |
| | 79 | mulq %rcx /* delta * scale */ ; \ |
| | 80 | shrdq $32,%rdx,%rax /* %rdx:%rax >>= 32 */ ; \ |
| | 81 | addq RNT_NS_BASE(%rdi),%rax /* add ns_base */ ; \ |
| | 82 | cmpl RNT_GENERATION(%rdi),%esi /* repeat if changed */ ; \ |
| | 83 | jne 0b |
| | 84 | |
| | 85 | #endif /* _PAL_RTCLOCK_ASM_NATIVE_H_ */ |
projects / apple / xnu.git / blame_incremental