| | 1 | /* |
| | 2 | * Copyright (c) 2003-2007 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 | #include <sys/appleapiopts.h> |
| | 30 | #include <machine/cpu_capabilities.h> |
| | 31 | |
| | 32 | #if defined(__i386__) |
| | 33 | |
| | 34 | .text |
| | 35 | .align 4, 0x90 |
| | 36 | .globl _mach_approximate_time |
| | 37 | _mach_approximate_time: |
| | 38 | pushl %ebp // push a frame |
| | 39 | movl %esp, %ebp |
| | 40 | cmpb $0, _COMM_PAGE_APPROX_TIME_SUPPORTED // check commpage |
| | 41 | // "is supported" flag. |
| | 42 | je _approx_time_not_supported // if zero, fall through to |
| | 43 | // absolute_time |
| | 44 | // note the comment above for 32-bit ARM applies equally to 32-bit i386. |
| | 45 | .align 4, 0x90 |
| | 46 | _approx_time_consistency_check: |
| | 47 | movl _COMM_PAGE_APPROX_TIME+4, %edx // load high |
| | 48 | movl _COMM_PAGE_APPROX_TIME, %eax // load low |
| | 49 | lfence // avoid predictive reads that |
| | 50 | // could be invalid if |
| | 51 | // interrupted |
| | 52 | cmpl _COMM_PAGE_APPROX_TIME+4, %edx // load high and check if equal |
| | 53 | // to the first read |
| | 54 | jne _approx_time_consistency_check // if not, try again. |
| | 55 | popl %ebp |
| | 56 | ret |
| | 57 | |
| | 58 | _approx_time_not_supported: |
| | 59 | popl %ebp |
| | 60 | jmp _mach_absolute_time |
| | 61 | |
| | 62 | #endif |
projects / apple / xnu.git / blame_incremental