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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. 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);
     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);
     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
    102