wtf/OSAllocator.h

   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 #ifndef OSAllocator_h
  27 #define OSAllocator_h
  28
  29 #include <wtf/UnusedParam.h>
  30 #include <wtf/VMTags.h>
  31 #include <wtf/VMTags.h>
  32
  33 namespace WTF {
  34
  35 class OSAllocator {
  36 public:
  37     enum Usage {
  38         UnknownUsage = -1,
  39         FastMallocPages = VM_TAG_FOR_TCMALLOC_MEMORY,
  40         JSGCHeapPages = VM_TAG_FOR_COLLECTOR_MEMORY,
  41         JSVMStackPages = VM_TAG_FOR_REGISTERFILE_MEMORY,
  42         JSJITCodePages = VM_TAG_FOR_EXECUTABLEALLOCATOR_MEMORY,
  43     };
  44
  45     // These methods are symmetric; reserveUncommitted allocates VM in an uncommitted state,
  46     // releaseDecommitted should be called on a region of VM allocated by a single reservation,
  47     // the memory must all currently be in a decommitted state.
  48     static void* reserveUncommitted(size_t, Usage = UnknownUsage, bool writable = true, bool executable = false, bool includesGuardPages = false);
  49     static void releaseDecommitted(void*, size_t);
  50
  51     // These methods are symmetric; they commit or decommit a region of VM (uncommitted VM should
  52     // never be accessed, since the OS may not have attached physical memory for these regions).
  53     // Clients should only call commit on uncommitted regions and decommit on committed regions.
  54     static void commit(void*, size_t, bool writable, bool executable);
  55     static void decommit(void*, size_t);
  56
  57     // These methods are symmetric; reserveAndCommit allocates VM in an committed state,
  58     // decommitAndRelease should be called on a region of VM allocated by a single reservation,
  59     // the memory must all currently be in a committed state.
  60     static void* reserveAndCommit(size_t, Usage = UnknownUsage, bool writable = true, bool executable = false, bool includesGuardPages = false);
  61     static void decommitAndRelease(void* base, size_t size);
  62
  63     // These methods are akin to reserveAndCommit/decommitAndRelease, above - however rather than
  64     // committing/decommitting the entire region additional parameters allow a subregion to be
  65     // specified.
  66     static void* reserveAndCommit(size_t reserveSize, size_t commitSize, Usage = UnknownUsage, bool writable = true, bool executable = false);
  67     static void decommitAndRelease(void* releaseBase, size_t releaseSize, void* decommitBase, size_t decommitSize);
  68 };
  69
  70 inline void* OSAllocator::reserveAndCommit(size_t reserveSize, size_t commitSize, Usage usage, bool writable, bool executable)
  71 {
  72     void* base = reserveUncommitted(reserveSize, usage, writable, executable);
  73     commit(base, commitSize, writable, executable);
  74     return base;
  75 }
  76
  77 inline void OSAllocator::decommitAndRelease(void* releaseBase, size_t releaseSize, void* decommitBase, size_t decommitSize)
  78 {
  79     ASSERT(decommitBase >= releaseBase && (static_cast<char*>(decommitBase) + decommitSize) <= (static_cast<char*>(releaseBase) + releaseSize));
  80 #if OS(WINCE) || OS(SYMBIAN)
  81     // On most platforms we can actually skip this final decommit; releasing the VM will
  82     // implicitly decommit any physical memory in the region. This is not true on WINCE.
  83     // On Symbian, this makes implementation simpler and better aligned with the RChunk API
  84     decommit(decommitBase, decommitSize);
  85 #else
  86     UNUSED_PARAM(decommitBase);
  87     UNUSED_PARAM(decommitSize);
  88 #endif
  89     releaseDecommitted(releaseBase, releaseSize);
  90 }
  91
  92 inline void OSAllocator::decommitAndRelease(void* base, size_t size)
  93 {
  94     decommitAndRelease(base, size, base, size);
  95 }
  96
  97 } // namespace WTF
  98
  99 using WTF::OSAllocator;
 100
 101 #endif // OSAllocator_h