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 |
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 memory |
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 virtual |
39 | memory without committing physical memory pages using PageReservation::reserve. |
40 | Following a call to reserve all memory in the region is in a decommited state, |
41 | in which the memory should not be used (accessing the memory may cause a fault). |
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 the |
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 that 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 reservation |
49 | is deallocated. Values in memory may not be retained accross a pair of calls 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 protection |
53 | is changed on memory while it is committed it should be returned to the orignal |
54 | protection before decommit is called. |
55 | */ |
56 | |
57 | class : private PageBlock { |
58 | public: |
59 | () |
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 incorrectly emits an access |
73 | // control warning when a client tries to use operator bool exposed above via "using PageBlock::operator bool". |
74 | () const { return PageBlock::operator bool(); } |
75 | #endif |
76 | |
77 | void (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, writable: m_writable, executable: m_executable); |
86 | } |
87 | |
88 | void (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 () |
100 | { |
101 | return m_committed; |
102 | } |
103 | |
104 | static PageReservation (size_t size, OSAllocator::Usage usage = OSAllocator::UnknownUsage, bool writable = true, bool executable = false) |
105 | { |
106 | ASSERT(isPageAligned(size)); |
107 | return PageReservation(OSAllocator::reserveUncommitted(size, usage, writable, executable), size, writable, executable); |
108 | } |
109 | |
110 | void () |
111 | { |
112 | ASSERT(!m_committed); |
113 | |
114 | // Clear base & size before calling release; if this is *inside* allocation |
115 | // then we won't be able to clear then after deallocating the memory. |
116 | PageReservation tmp; |
117 | std::swap(a&: tmp, b&: *this); |
118 | |
119 | ASSERT(tmp); |
120 | ASSERT(!*this); |
121 | |
122 | OSAllocator::releaseDecommitted(tmp.realBase(), tmp.realSize()); |
123 | } |
124 | |
125 | private: |
126 | (void* base, size_t size, bool writable, bool executable) |
127 | : PageBlock(base, size, false) |
128 | , m_committed(0) |
129 | , m_writable(writable) |
130 | , m_executable(executable) |
131 | { |
132 | } |
133 | |
134 | size_t ; |
135 | bool ; |
136 | bool ; |
137 | }; |
138 | |
139 | } |
140 | |
141 | using WTF::PageReservation; |
142 | |
143 | #endif // PageReservation_h |
144 | |