assembler/LinkBuffer.h

   1 /*
   2  * Copyright (C) 2009 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 LinkBuffer_h
  27 #define LinkBuffer_h
  28
  29 #include <wtf/Platform.h>
  30
  31 #if ENABLE(ASSEMBLER)
  32
  33 #include <MacroAssembler.h>
  34 #include <wtf/Noncopyable.h>
  35
  36 namespace JSC {
  37
  38 // LinkBuffer:
  39 //
  40 // This class assists in linking code generated by the macro assembler, once code generation
  41 // has been completed, and the code has been copied to is final location in memory.  At this
  42 // time pointers to labels within the code may be resolved, and relative offsets to external
  43 // addresses may be fixed.
  44 //
  45 // Specifically:
  46 //   * Jump objects may be linked to external targets,
  47 //   * The address of Jump objects may taken, such that it can later be relinked.
  48 //   * The return address of a Call may be acquired.
  49 //   * The address of a Label pointing into the code may be resolved.
  50 //   * The value referenced by a DataLabel may be set.
  51 //
  52 class LinkBuffer : public Noncopyable {
  53     typedef MacroAssemblerCodeRef CodeRef;
  54     typedef MacroAssembler::Label Label;
  55     typedef MacroAssembler::Jump Jump;
  56     typedef MacroAssembler::JumpList JumpList;
  57     typedef MacroAssembler::Call Call;
  58     typedef MacroAssembler::DataLabel32 DataLabel32;
  59     typedef MacroAssembler::DataLabelPtr DataLabelPtr;
  60
  61 public:
  62     // Note: Initialization sequence is significant, since executablePool is a PassRefPtr.
  63     //       First, executablePool is copied into m_executablePool, then the initialization of
  64     //       m_code uses m_executablePool, *not* executablePool, since this is no longer valid.
  65     LinkBuffer(MacroAssembler* masm, PassRefPtr<ExecutablePool> executablePool)
  66         : m_executablePool(executablePool)
  67         , m_code(masm->m_assembler.executableCopy(m_executablePool.get()))
  68         , m_size(masm->m_assembler.size())
  69 #ifndef NDEBUG
  70         , m_completed(false)
  71 #endif
  72     {
  73     }
  74
  75     ~LinkBuffer()
  76     {
  77         ASSERT(m_completed);
  78     }
  79
  80     // These methods are used to link or set values at code generation time.
  81
  82     void link(Call call, FunctionPtr function)
  83     {
  84         ASSERT(call.isFlagSet(Call::Linkable));
  85         MacroAssembler::linkCall(code(), call, function);
  86     }
  87
  88     void link(Jump jump, CodeLocationLabel label)
  89     {
  90         MacroAssembler::linkJump(code(), jump, label);
  91     }
  92
  93     void link(JumpList list, CodeLocationLabel label)
  94     {
  95         for (unsigned i = 0; i < list.m_jumps.size(); ++i)
  96             MacroAssembler::linkJump(code(), list.m_jumps[i], label);
  97     }
  98
  99     void patch(DataLabelPtr label, void* value)
 100     {
 101         MacroAssembler::linkPointer(code(), label.m_label, value);
 102     }
 103
 104     void patch(DataLabelPtr label, CodeLocationLabel value)
 105     {
 106         MacroAssembler::linkPointer(code(), label.m_label, value.executableAddress());
 107     }
 108
 109     // These methods are used to obtain handles to allow the code to be relinked / repatched later.
 110
 111     CodeLocationCall locationOf(Call call)
 112     {
 113         ASSERT(call.isFlagSet(Call::Linkable));
 114         ASSERT(!call.isFlagSet(Call::Near));
 115         return CodeLocationCall(MacroAssembler::getLinkerAddress(code(), call.m_jmp));
 116     }
 117
 118     CodeLocationNearCall locationOfNearCall(Call call)
 119     {
 120         ASSERT(call.isFlagSet(Call::Linkable));
 121         ASSERT(call.isFlagSet(Call::Near));
 122         return CodeLocationNearCall(MacroAssembler::getLinkerAddress(code(), call.m_jmp));
 123     }
 124
 125     CodeLocationLabel locationOf(Label label)
 126     {
 127         return CodeLocationLabel(MacroAssembler::getLinkerAddress(code(), label.m_label));
 128     }
 129
 130     CodeLocationDataLabelPtr locationOf(DataLabelPtr label)
 131     {
 132         return CodeLocationDataLabelPtr(MacroAssembler::getLinkerAddress(code(), label.m_label));
 133     }
 134
 135     CodeLocationDataLabel32 locationOf(DataLabel32 label)
 136     {
 137         return CodeLocationDataLabel32(MacroAssembler::getLinkerAddress(code(), label.m_label));
 138     }
 139
 140     // This method obtains the return address of the call, given as an offset from
 141     // the start of the code.
 142     unsigned returnAddressOffset(Call call)
 143     {
 144         return MacroAssembler::getLinkerCallReturnOffset(call);
 145     }
 146
 147     // Upon completion of all patching either 'finalizeCode()' or 'finalizeCodeAddendum()' should be called
 148     // once to complete generation of the code.  'finalizeCode()' is suited to situations
 149     // where the executable pool must also be retained, the lighter-weight 'finalizeCodeAddendum()' is
 150     // suited to adding to an existing allocation.
 151     CodeRef finalizeCode()
 152     {
 153         performFinalization();
 154
 155         return CodeRef(m_code, m_executablePool, m_size);
 156     }
 157     CodeLocationLabel finalizeCodeAddendum()
 158     {
 159         performFinalization();
 160
 161         return CodeLocationLabel(code());
 162     }
 163
 164 private:
 165     // Keep this private! - the underlying code should only be obtained externally via
 166     // finalizeCode() or finalizeCodeAddendum().
 167     void* code()
 168     {
 169         return m_code;
 170     }
 171
 172     void performFinalization()
 173     {
 174 #ifndef NDEBUG
 175         ASSERT(!m_completed);
 176         m_completed = true;
 177 #endif
 178
 179         ExecutableAllocator::makeExecutable(code(), m_size);
 180         ExecutableAllocator::cacheFlush(code(), m_size);
 181     }
 182
 183     RefPtr<ExecutablePool> m_executablePool;
 184     void* m_code;
 185     size_t m_size;
 186 #ifndef NDEBUG
 187     bool m_completed;
 188 #endif
 189 };
 190
 191 } // namespace JSC
 192
 193 #endif // ENABLE(ASSEMBLER)
 194
 195 #endif // LinkBuffer_h