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1 /* | |
2 * Copyright (C) 2010 Apple 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 | |
6 * are met: | |
7 * 1. Redistributions of source code must retain the above copyright | |
8 * notice, this list of conditions and the following disclaimer. | |
9 * 2. Redistributions in binary form must reproduce the above copyright | |
10 * notice, this list of conditions and the following disclaimer in the | |
11 * documentation and/or other materials provided with the distribution. | |
12 * | |
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY | |
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR | |
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR | |
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, | |
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, | |
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR | |
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY | |
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
24 */ | |
25 | |
26 #ifndef PageReservation_h | |
27 #define PageReservation_h | |
28 | |
29 #include <wtf/PageAllocation.h> | |
30 | |
31 namespace WTF { | |
32 | |
33 /* | |
34 PageReservation | |
35 | |
36 Like PageAllocation, the PageReservation class provides a cross-platform mem
ory | |
37 allocation interface, but with a set of capabilities more similar to that of | |
38 VirtualAlloc than posix mmap. PageReservation can be used to allocate virtu
al | |
39 memory without committing physical memory pages using PageReservation::reser
ve. | |
40 Following a call to reserve all memory in the region is in a decommited stat
e, | |
41 in which the memory should not be used (accessing the memory may cause a fau
lt). | |
42 | |
43 Before using memory it must be committed by calling commit, which is passed
start | |
44 and size values (both of which require system page size granularity). One t
he | |
45 committed memory is no longer needed 'decommit' may be called to return the | |
46 memory to its devommitted state. Commit should only be called on memory tha
t is | |
47 currently decommitted, and decommit should only be called on memory regions
that | |
48 are currently committed. All memory should be decommited before the reserva
tion | |
49 is deallocated. Values in memory may not be retained accross a pair of call
s if | |
50 the region of memory is decommitted and then committed again. | |
51 | |
52 Memory protection should not be changed on decommitted memory, and if protec
tion | |
53 is changed on memory while it is committed it should be returned to the orig
nal | |
54 protection before decommit is called. | |
55 */ | |
56 | |
57 class PageReservation : private PageBlock { | |
58 public: | |
59 PageReservation() | |
60 : m_committed(0) | |
61 , m_writable(false) | |
62 , m_executable(false) | |
63 { | |
64 } | |
65 | |
66 using PageBlock::base; | |
67 using PageBlock::size; | |
68 | |
69 #ifndef __clang__ | |
70 using PageBlock::operator bool; | |
71 #else | |
72 // FIXME: This is a workaround for <rdar://problem/8876150>, wherein Clang i
ncorrectly emits an access | |
73 // control warning when a client tries to use operator bool exposed above vi
a "using PageBlock::operator bool". | |
74 operator bool() const { return PageBlock::operator bool(); } | |
75 #endif | |
76 | |
77 void commit(void* start, size_t size) | |
78 { | |
79 ASSERT(*this); | |
80 ASSERT(isPageAligned(start)); | |
81 ASSERT(isPageAligned(size)); | |
82 ASSERT(contains(start, size)); | |
83 | |
84 m_committed += size; | |
85 OSAllocator::commit(start, size, m_writable, m_executable); | |
86 } | |
87 | |
88 void decommit(void* start, size_t size) | |
89 { | |
90 ASSERT(*this); | |
91 ASSERT(isPageAligned(start)); | |
92 ASSERT(isPageAligned(size)); | |
93 ASSERT(contains(start, size)); | |
94 | |
95 m_committed -= size; | |
96 OSAllocator::decommit(start, size); | |
97 } | |
98 | |
99 size_t committed() | |
100 { | |
101 return m_committed; | |
102 } | |
103 | |
104 static PageReservation reserve(size_t size, OSAllocator::Usage usage = OSAll
ocator::UnknownUsage, bool writable = true, bool executable = false) | |
105 { | |
106 ASSERT(isPageAligned(size)); | |
107 return PageReservation(OSAllocator::reserveUncommitted(size, usage, writ
able, executable), size, writable, executable, false); | |
108 } | |
109 | |
110 static PageReservation reserveWithGuardPages(size_t size, OSAllocator::Usage
usage = OSAllocator::UnknownUsage, bool writable = true, bool executable = fals
e) | |
111 { | |
112 ASSERT(isPageAligned(size)); | |
113 return PageReservation(OSAllocator::reserveUncommitted(size + pageSize()
* 2, usage, writable, executable, true), size, writable, executable, true); | |
114 } | |
115 | |
116 void deallocate() | |
117 { | |
118 ASSERT(!m_committed); | |
119 | |
120 // Clear base & size before calling release; if this is *inside* allocat
ion | |
121 // then we won't be able to clear then after deallocating the memory. | |
122 PageReservation tmp; | |
123 std::swap(tmp, *this); | |
124 | |
125 ASSERT(tmp); | |
126 ASSERT(!*this); | |
127 | |
128 OSAllocator::releaseDecommitted(tmp.base(), tmp.size()); | |
129 } | |
130 | |
131 private: | |
132 PageReservation(void* base, size_t size, bool writable, bool executable, boo
l hasGuardPages) | |
133 : PageBlock(base, size, hasGuardPages) | |
134 , m_committed(0) | |
135 , m_writable(writable) | |
136 , m_executable(executable) | |
137 { | |
138 } | |
139 | |
140 size_t m_committed; | |
141 bool m_writable; | |
142 bool m_executable; | |
143 }; | |
144 | |
145 } | |
146 | |
147 using WTF::PageReservation; | |
148 | |
149 #endif // PageReservation_h | |
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