runtime/vm/code_patcher.h

// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
// Class for patching compiled code.

#ifndef VM_CODE_PATCHER_H_
#define VM_CODE_PATCHER_H_

#include "vm/allocation.h"

namespace dart {

// Forward declaration.
class Array;
class Code;
class ExternalLabel;
class Function;
class ICData;
class RawArray;
class RawFunction;
class RawICData;
class RawObject;
class String;


// Stack-allocated class to create a scope where the specified region
// [address, addresss + size] has write access enabled. This is used
// when patching generated code. Access is reset to read-execute in
// the destructor of this scope.
class WritableInstructionsScope : public ValueObject {
 public:
  WritableInstructionsScope(uword address, intptr_t size);
  ~WritableInstructionsScope();

 private:
  const uword address_;
  const intptr_t size_;
};


class CodePatcher : public AllStatic {
 public:
  // Dart static calls have a distinct, machine-dependent code pattern.

  // Patch static call before return_address in given code to the new target.
  static void PatchStaticCallAt(uword return_address,
                                const Code& code,
                                uword new_target_address);

  // Patch instance call before return_address in given code to the new target.
  static void PatchInstanceCallAt(uword return_address,
                                  const Code& code,
                                  uword new_target_address);

  // Patch entry point with a jump as specified in the code's patch region.
  static void PatchEntry(const Code& code);

  // Restore entry point with original code (i.e., before patching).
  static void RestoreEntry(const Code& code);

  // Has the entry been patched?
  static bool IsEntryPatched(const Code& code);

  // Returns true if the code can be patched with a jump at beginning (checks
  // that there are no conflicts with object pointers). Used in ASSERTs.
  static bool CodeIsPatchable(const Code& code);

  // Return the target address of the static call before return_address
  // in given code.
  static uword GetStaticCallTargetAt(uword return_address, const Code& code);

  // Get instance call information.  Returns the call target and sets each
  // of the output parameters ic_data and arguments_descriptor if they are
  // non-NULL.
  static uword GetInstanceCallAt(uword return_address,
                                 const Code& code,
                                 ICData* ic_data);

  // Return target of an unoptimized static call and its ICData object
  // (calls target via a stub).
  static RawFunction* GetUnoptimizedStaticCallAt(uword return_address,
                                                 const Code& code,
                                                 ICData* ic_data);

  // Return the arguments descriptor array of the closure call
  // before the given return address.
  static RawArray* GetClosureArgDescAt(uword return_address,
                                       const Code& code);

  static intptr_t InstanceCallSizeInBytes();

  static void InsertCallAt(uword start, uword target);

  static RawObject* GetEdgeCounterAt(uword pc, const Code& code);
#if defined(TARGET_ARCH_IA32)
  static int32_t EdgeCounterIncrementSizeInBytes();
#endif  // TARGET_ARCH_IA32

  static int32_t GetPoolOffsetAt(uword return_address);
  static void SetPoolOffsetAt(uword return_address, int32_t offset);
};

}  // namespace dart

#endif  // VM_CODE_PATCHER_H_