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. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "config.h"
27#include <wtf/OSAllocator.h>
28
29#include <errno.h>
30#include <sys/mman.h>
31#include <wtf/Assertions.h>
32#include <wtf/PageAllocation.h>
33
34namespace WTF {
35
36void* OSAllocator::reserveUncommitted(size_t bytes, Usage usage, bool writable, bool executable, bool includesGuardPages)
37{
38#if OS(LINUX)
39 UNUSED_PARAM(usage);
40 UNUSED_PARAM(writable);
41 UNUSED_PARAM(executable);
42 UNUSED_PARAM(includesGuardPages);
43
44 void* result = mmap(0, bytes, PROT_NONE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0);
45 if (result == MAP_FAILED)
46 CRASH();
47 madvise(result, bytes, MADV_DONTNEED);
48#else
49 void* result = reserveAndCommit(bytes, usage, writable, executable, includesGuardPages);
50#if HAVE(MADV_FREE_REUSE)
51 if (result) {
52 // To support the "reserve then commit" model, we have to initially decommit.
53 while (madvise(result, bytes, MADV_FREE_REUSABLE) == -1 && errno == EAGAIN) { }
54 }
55#endif
56
57#endif
58
59 return result;
60}
61
62void* OSAllocator::reserveAndCommit(size_t bytes, Usage usage, bool writable, bool executable, bool includesGuardPages)
63{
64 // All POSIX reservations start out logically committed.
65 int protection = PROT_READ;
66 if (writable)
67 protection |= PROT_WRITE;
68 if (executable)
69 protection |= PROT_EXEC;
70
71 int flags = MAP_PRIVATE | MAP_ANON;
72#if OS(DARWIN)
73 if (executable)
74 flags |= MAP_JIT;
75#endif
76
77#if OS(DARWIN)
78 int fd = usage;
79#else
80 UNUSED_PARAM(usage);
81 int fd = -1;
82#endif
83
84 void* result = 0;
85#if (OS(DARWIN) && CPU(X86_64))
86 if (executable) {
87 ASSERT(includesGuardPages);
88 // Cook up an address to allocate at, using the following recipe:
89 // 17 bits of zero, stay in userspace kids.
90 // 26 bits of randomness for ASLR.
91 // 21 bits of zero, at least stay aligned within one level of the pagetables.
92 //
93 // But! - as a temporary workaround for some plugin problems (rdar://problem/6812854),
94 // for now instead of 2^26 bits of ASLR lets stick with 25 bits of randomization plus
95 // 2^24, which should put up somewhere in the middle of userspace (in the address range
96 // 0x200000000000 .. 0x5fffffffffff).
97 intptr_t randomLocation = 0;
98 randomLocation = arc4random() & ((1 << 25) - 1);
99 randomLocation += (1 << 24);
100 randomLocation <<= 21;
101 result = reinterpret_cast<void*>(randomLocation);
102 }
103#endif
104
105 result = mmap(result, bytes, protection, flags, fd, 0);
106 if (result == MAP_FAILED) {
107 if (executable)
108 result = 0;
109 else
110 CRASH();
111 }
112 if (result && includesGuardPages) {
113 // We use mmap to remap the guardpages rather than using mprotect as
114 // mprotect results in multiple references to the code region. This
115 // breaks the madvise based mechanism we use to return physical memory
116 // to the OS.
117 mmap(result, pageSize(), PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANON, fd, 0);
118 mmap(static_cast<char*>(result) + bytes - pageSize(), pageSize(), PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANON, fd, 0);
119 }
120 return result;
121}
122
123void OSAllocator::commit(void* address, size_t bytes, bool writable, bool executable)
124{
125#if OS(LINUX)
126 int protection = PROT_READ;
127 if (writable)
128 protection |= PROT_WRITE;
129 if (executable)
130 protection |= PROT_EXEC;
131 if (mprotect(address, bytes, protection))
132 CRASH();
133 madvise(address, bytes, MADV_WILLNEED);
134#elif HAVE(MADV_FREE_REUSE)
135 UNUSED_PARAM(writable);
136 UNUSED_PARAM(executable);
137 while (madvise(address, bytes, MADV_FREE_REUSE) == -1 && errno == EAGAIN) { }
138#else
139 // Non-MADV_FREE_REUSE reservations automatically commit on demand.
140 UNUSED_PARAM(address);
141 UNUSED_PARAM(bytes);
142 UNUSED_PARAM(writable);
143 UNUSED_PARAM(executable);
144#endif
145}
146
147void OSAllocator::decommit(void* address, size_t bytes)
148{
149#if OS(LINUX)
150 madvise(address, bytes, MADV_DONTNEED);
151 if (mprotect(address, bytes, PROT_NONE))
152 CRASH();
153#elif HAVE(MADV_FREE_REUSE)
154 while (madvise(address, bytes, MADV_FREE_REUSABLE) == -1 && errno == EAGAIN) { }
155#elif HAVE(MADV_FREE)
156 while (madvise(address, bytes, MADV_FREE) == -1 && errno == EAGAIN) { }
157#elif HAVE(MADV_DONTNEED)
158 while (madvise(address, bytes, MADV_DONTNEED) == -1 && errno == EAGAIN) { }
159#else
160 UNUSED_PARAM(address);
161 UNUSED_PARAM(bytes);
162#endif
163}
164
165void OSAllocator::hintMemoryNotNeededSoon(void* address, size_t bytes)
166{
167#if HAVE(MADV_DONTNEED)
168 while (madvise(address, bytes, MADV_DONTNEED) == -1 && errno == EAGAIN) { }
169#else
170 UNUSED_PARAM(address);
171 UNUSED_PARAM(bytes);
172#endif
173}
174
175void OSAllocator::releaseDecommitted(void* address, size_t bytes)
176{
177 int result = munmap(address, bytes);
178 if (result == -1)
179 CRASH();
180}
181
182} // namespace WTF
183