1/*
2 * Copyright (c) 2006 Apple Computer, 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
24#include <stdbool.h>
25#include <stdint.h>
26#include <stdio.h>
27#include <sys/types.h>
28#include <unistd.h>
29#include <mach/mach.h>
30
31struct page
32{
33	struct page*	other;
34	char			pad[4096-sizeof(void*)];
35};
36
37
38struct page p1 = { &p1 };
39struct page p2 = { &p1 };
40struct page p3 = { &p1 };
41struct page p4 = { &p1 };
42struct page p5 = { &p1 };
43struct page p6 = { &p1 };
44struct page p7 = { &p1 };
45struct page p8 = { &p1 };
46struct page p9 = { &p1 };
47struct page p10 = { &p1 };
48
49//
50// This dylib has 10 pages of data and each page will be adjusted
51// by dyld if this dylib is not loaded at its preferred address.
52//
53bool checkRebasing()
54{
55	int dirtyPageCount = 0;
56	vm_address_t start = (((uintptr_t)&p1) + 4095) & (-4096);
57	vm_address_t end = (((uintptr_t)&p10) + 4095) & (-4096);
58	task_port_t task;
59	task_for_pid(mach_task_self(), getpid(), &task);
60
61	for (vm_address_t addr = start; addr < end; addr += 4096) {
62		integer_t disposition = 0;
63		integer_t ref_count = 0;
64		vm_map_page_query(task, start, &disposition, &ref_count);
65		if ( disposition & VM_PAGE_QUERY_PAGE_DIRTY )
66			++dirtyPageCount;
67	}
68
69	//fprintf(stderr, "dirtyPageCount=%d\n", dirtyPageCount);
70
71	// if there are too many dirty pages, then dyld is inefficient
72	return ( dirtyPageCount < 2 );
73}
74
75
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79