• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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 
39 namespace WTF {
40 
41 #if OS(WIN)
42 static const size_t kPageAllocationGranularityShift = 16; // 64KB
43 #else
44 static const size_t kPageAllocationGranularityShift = 12; // 4KB
45 #endif
46 static const size_t kPageAllocationGranularity = 1 << kPageAllocationGranularityShift;
47 static const size_t kPageAllocationGranularityOffsetMask = kPageAllocationGranularity - 1;
48 static 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.
52 static const size_t kSystemPageSize = 4096;
53 static const size_t kSystemPageOffsetMask = kSystemPageSize - 1;
54 static 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.
66 WTF_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().
70 WTF_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.
76 WTF_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.
81 WTF_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.
92 WTF_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.
98 WTF_EXPORT void recommitSystemPages(void* addr, size_t len);
99 
100 } // namespace WTF
101 
102 #endif // WTF_PageAllocator_h
103