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/*
* Copyright (C) 2009 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef LinkBuffer_h
#define LinkBuffer_h
#include <wtf/Platform.h>
#if ENABLE(ASSEMBLER)
#include <MacroAssembler.h>
#include <wtf/Noncopyable.h>
namespace JSC {
// LinkBuffer:
//
// This class assists in linking code generated by the macro assembler, once code generation
// has been completed, and the code has been copied to is final location in memory. At this
// time pointers to labels within the code may be resolved, and relative offsets to external
// addresses may be fixed.
//
// Specifically:
// * Jump objects may be linked to external targets,
// * The address of Jump objects may taken, such that it can later be relinked.
// * The return address of a Call may be acquired.
// * The address of a Label pointing into the code may be resolved.
// * The value referenced by a DataLabel may be set.
//
class LinkBuffer : public Noncopyable {
typedef MacroAssemblerCodeRef CodeRef;
typedef MacroAssembler::Label Label;
typedef MacroAssembler::Jump Jump;
typedef MacroAssembler::JumpList JumpList;
typedef MacroAssembler::Call Call;
typedef MacroAssembler::DataLabel32 DataLabel32;
typedef MacroAssembler::DataLabelPtr DataLabelPtr;
public:
// Note: Initialization sequence is significant, since executablePool is a PassRefPtr.
// First, executablePool is copied into m_executablePool, then the initialization of
// m_code uses m_executablePool, *not* executablePool, since this is no longer valid.
LinkBuffer(MacroAssembler* masm, PassRefPtr<ExecutablePool> executablePool)
: m_executablePool(executablePool)
, m_code(masm->m_assembler.executableCopy(m_executablePool.get()))
, m_size(masm->m_assembler.size())
#ifndef NDEBUG
, m_completed(false)
#endif
{
}
~LinkBuffer()
{
ASSERT(m_completed);
}
// These methods are used to link or set values at code generation time.
void link(Call call, FunctionPtr function)
{
ASSERT(call.isFlagSet(Call::Linkable));
MacroAssembler::linkCall(code(), call, function);
}
void link(Jump jump, CodeLocationLabel label)
{
MacroAssembler::linkJump(code(), jump, label);
}
void link(JumpList list, CodeLocationLabel label)
{
for (unsigned i = 0; i < list.m_jumps.size(); ++i)
MacroAssembler::linkJump(code(), list.m_jumps[i], label);
}
void patch(DataLabelPtr label, void* value)
{
MacroAssembler::linkPointer(code(), label.m_label, value);
}
void patch(DataLabelPtr label, CodeLocationLabel value)
{
MacroAssembler::linkPointer(code(), label.m_label, value.executableAddress());
}
// These methods are used to obtain handles to allow the code to be relinked / repatched later.
CodeLocationCall locationOf(Call call)
{
ASSERT(call.isFlagSet(Call::Linkable));
ASSERT(!call.isFlagSet(Call::Near));
return CodeLocationCall(MacroAssembler::getLinkerAddress(code(), call.m_jmp));
}
CodeLocationNearCall locationOfNearCall(Call call)
{
ASSERT(call.isFlagSet(Call::Linkable));
ASSERT(call.isFlagSet(Call::Near));
return CodeLocationNearCall(MacroAssembler::getLinkerAddress(code(), call.m_jmp));
}
CodeLocationLabel locationOf(Label label)
{
return CodeLocationLabel(MacroAssembler::getLinkerAddress(code(), label.m_label));
}
CodeLocationDataLabelPtr locationOf(DataLabelPtr label)
{
return CodeLocationDataLabelPtr(MacroAssembler::getLinkerAddress(code(), label.m_label));
}
CodeLocationDataLabel32 locationOf(DataLabel32 label)
{
return CodeLocationDataLabel32(MacroAssembler::getLinkerAddress(code(), label.m_label));
}
// This method obtains the return address of the call, given as an offset from
// the start of the code.
unsigned returnAddressOffset(Call call)
{
return MacroAssembler::getLinkerCallReturnOffset(call);
}
// Upon completion of all patching either 'finalizeCode()' or 'finalizeCodeAddendum()' should be called
// once to complete generation of the code. 'finalizeCode()' is suited to situations
// where the executable pool must also be retained, the lighter-weight 'finalizeCodeAddendum()' is
// suited to adding to an existing allocation.
CodeRef finalizeCode()
{
performFinalization();
return CodeRef(m_code, m_executablePool, m_size);
}
CodeLocationLabel finalizeCodeAddendum()
{
performFinalization();
return CodeLocationLabel(code());
}
private:
// Keep this private! - the underlying code should only be obtained externally via
// finalizeCode() or finalizeCodeAddendum().
void* code()
{
return m_code;
}
void performFinalization()
{
#ifndef NDEBUG
ASSERT(!m_completed);
m_completed = true;
#endif
ExecutableAllocator::makeExecutable(code(), m_size);
ExecutableAllocator::cacheFlush(code(), m_size);
}
RefPtr<ExecutablePool> m_executablePool;
void* m_code;
size_t m_size;
#ifndef NDEBUG
bool m_completed;
#endif
};
} // namespace JSC
#endif // ENABLE(ASSEMBLER)
#endif // LinkBuffer_h
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