1/*
2 * Copyright (C) 2013 Google Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are
6 * met:
7 *
8 *     * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *     * Redistributions in binary form must reproduce the above
11 * copyright notice, this list of conditions and the following disclaimer
12 * in the documentation and/or other materials provided with the
13 * distribution.
14 *     * Neither the name of Google Inc. nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#ifndef WTF_PageAllocator_h
32#define WTF_PageAllocator_h
33
34#include "wtf/Assertions.h"
35#include "wtf/CPU.h"
36#include "wtf/WTFExport.h"
37#include <stdint.h>
38
39namespace WTF {
40
41#if OS(WIN)
42static const size_t kPageAllocationGranularityShift = 16; // 64KB
43#else
44static const size_t kPageAllocationGranularityShift = 12; // 4KB
45#endif
46static const size_t kPageAllocationGranularity = 1 << kPageAllocationGranularityShift;
47static const size_t kPageAllocationGranularityOffsetMask = kPageAllocationGranularity - 1;
48static const size_t kPageAllocationGranularityBaseMask = ~kPageAllocationGranularityOffsetMask;
49
50// All Blink-supported systems have 4096 sized system pages and can handle
51// permissions and commit / decommit at this granularity.
52static const size_t kSystemPageSize = 4096;
53static const size_t kSystemPageOffsetMask = kSystemPageSize - 1;
54static const size_t kSystemPageBaseMask = ~kSystemPageOffsetMask;
55
56// Allocate one or more pages. Addresses in the range will be readable and
57// writeable but not executable.
58// The requested address is just a hint; the actual address returned may
59// differ. The returned address will be aligned at least to align bytes.
60// len is in bytes, and must be a multiple of kPageAllocationGranularity.
61// align is in bytes, and must be a power-of-two multiple of
62// kPageAllocationGranularity.
63// If addr is null, then a suitable and randomized address will be chosen
64// automatically.
65// This call will return null if the allocation cannot be satisfied.
66WTF_EXPORT void* allocPages(void* addr, size_t len, size_t align);
67
68// Free one or more pages.
69// addr and len must match a previous call to allocPages().
70WTF_EXPORT void freePages(void* addr, size_t len);
71
72// Mark one or more system pages as being inaccessible.
73// Subsequently accessing any address in the range will fault, and the
74// addresses will not be re-used by future allocations.
75// len must be a multiple of kSystemPageSize bytes.
76WTF_EXPORT void setSystemPagesInaccessible(void* addr, size_t len);
77
78// Mark one or more system pages as being accessible.
79// The pages will be readable and writeable.
80// len must be a multiple of kSystemPageSize bytes.
81WTF_EXPORT void setSystemPagesAccessible(void* addr, size_t len);
82
83// Decommit one or more system pages. Decommitted means that the physical memory
84// is released to the system, but the virtual address space remains reserved.
85// System pages are re-committed by calling recommitSystemPages(). Touching
86// a decommitted page _may_ fault.
87// Clients should not make any assumptions about the contents of decommitted
88// system pages, before or after they write to the page. The only guarantee
89// provided is that the contents of the system page will be deterministic again
90// after recommitting and writing to it. In particlar note that system pages are// not guaranteed to be zero-filled upon re-commit.
91// len must be a multiple of kSystemPageSize bytes.
92WTF_EXPORT void decommitSystemPages(void* addr, size_t len);
93
94// Recommit one or more system pages. Decommitted system pages must be
95// recommitted before they are read are written again.
96// Note that this operation may be a no-op on some platforms.
97// len must be a multiple of kSystemPageSize bytes.
98WTF_EXPORT void recommitSystemPages(void* addr, size_t len);
99
100} // namespace WTF
101
102#endif // WTF_PageAllocator_h
103