runtime/vm/code_patcher_ia32.cc

// 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.

#include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
#if defined(TARGET_ARCH_IA32)

#include "vm/code_patcher.h"
#include "vm/compiler/assembler/assembler.h"
#include "vm/compiler/backend/flow_graph_compiler.h"
#include "vm/cpu.h"
#include "vm/dart_entry.h"
#include "vm/instructions.h"
#include "vm/object.h"
#include "vm/raw_object.h"

namespace dart {

// The expected pattern of a Dart unoptimized call (static and instance):
//  mov ECX, ic-data
//  mov EDI, target-code-object
//  call target_address (stub)
//  <- return address
class UnoptimizedCall : public ValueObject {
 public:
  explicit UnoptimizedCall(uword return_address)
      : start_(return_address - kPatternSize) {
    ASSERT(IsValid());
  }

  RawObject* ic_data() const {
    return *reinterpret_cast<RawObject**>(start_ + 1);
  }

  static const int kMovInstructionSize = 5;
  static const int kCallInstructionSize = 3;
  static const int kPatternSize =
      2 * kMovInstructionSize + kCallInstructionSize;

 private:
  bool IsValid() {
    uint8_t* code_bytes = reinterpret_cast<uint8_t*>(start_);
    return (code_bytes[0] == 0xB9) &&
           (code_bytes[2 * kMovInstructionSize] == 0xFF);
  }

  uword return_address() const { return start_ + kPatternSize; }

  uword call_address() const { return start_ + 2 * kMovInstructionSize; }

 protected:
  uword start_;

 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(UnoptimizedCall);
};

class NativeCall : public UnoptimizedCall {
 public:
  explicit NativeCall(uword return_address) : UnoptimizedCall(return_address) {}

  NativeFunction native_function() const {
    return *reinterpret_cast<NativeFunction*>(start_ + 1);
  }

  void set_native_function(NativeFunction func) const {
    WritableInstructionsScope writable(start_ + 1, sizeof(func));
    *reinterpret_cast<NativeFunction*>(start_ + 1) = func;
  }

 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(NativeCall);
};

class InstanceCall : public UnoptimizedCall {
 public:
  explicit InstanceCall(uword return_address)
      : UnoptimizedCall(return_address) {
#if defined(DEBUG)
    ICData& test_ic_data = ICData::Handle();
    test_ic_data ^= ic_data();
    ASSERT(test_ic_data.NumArgsTested() > 0);
#endif  // DEBUG
  }

 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(InstanceCall);
};

class UnoptimizedStaticCall : public UnoptimizedCall {
 public:
  explicit UnoptimizedStaticCall(uword return_address)
      : UnoptimizedCall(return_address) {
#if defined(DEBUG)
    ICData& test_ic_data = ICData::Handle();
    test_ic_data ^= ic_data();
    ASSERT(test_ic_data.NumArgsTested() >= 0);
#endif  // DEBUG
  }

 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(UnoptimizedStaticCall);
};

// The expected pattern of a dart static call:
//  mov EDX, arguments_descriptor_array (optional in polymorphic calls)
//  mov EDI, Immediate(code_object)
//  call [EDI + entry_point_offset]
//  <- return address
class StaticCall : public ValueObject {
 public:
  explicit StaticCall(uword return_address)
      : start_(return_address - (kMovInstructionSize + kCallInstructionSize)) {
    ASSERT(IsValid());
  }

  bool IsValid() {
    uint8_t* code_bytes = reinterpret_cast<uint8_t*>(start_);
    return (code_bytes[0] == 0xBF) && (code_bytes[5] == 0xFF);
  }

  RawCode* target() const {
    const uword imm = *reinterpret_cast<uword*>(start_ + 1);
    return reinterpret_cast<RawCode*>(imm);
  }

  void set_target(const Code& target) const {
    uword* target_addr = reinterpret_cast<uword*>(start_ + 1);
    uword imm = reinterpret_cast<uword>(target.raw());
    *target_addr = imm;
    CPU::FlushICache(start_ + 1, sizeof(imm));
  }

  static const int kMovInstructionSize = 5;
  static const int kCallInstructionSize = 3;

 private:
  uword return_address() const {
    return start_ + kMovInstructionSize + kCallInstructionSize;
  }

  uword call_address() const { return start_ + kMovInstructionSize; }

  uword start_;

  DISALLOW_IMPLICIT_CONSTRUCTORS(StaticCall);
};

RawCode* CodePatcher::GetStaticCallTargetAt(uword return_address,
                                            const Code& code) {
  ASSERT(code.ContainsInstructionAt(return_address));
  StaticCall call(return_address);
  return call.target();
}

void CodePatcher::PatchStaticCallAt(uword return_address,
                                    const Code& code,
                                    const Code& new_target) {
  const Instructions& instrs = Instructions::Handle(code.instructions());
  WritableInstructionsScope writable(instrs.PayloadStart(), instrs.Size());
  ASSERT(code.ContainsInstructionAt(return_address));
  StaticCall call(return_address);
  call.set_target(new_target);
}

void CodePatcher::InsertDeoptimizationCallAt(uword start) {
  UNREACHABLE();
}

RawCode* CodePatcher::GetInstanceCallAt(uword return_address,
                                        const Code& code,
                                        ICData* ic_data) {
  ASSERT(code.ContainsInstructionAt(return_address));
  InstanceCall call(return_address);
  if (ic_data != NULL) {
    *ic_data ^= call.ic_data();
  }
  return Code::null();
}

RawFunction* CodePatcher::GetUnoptimizedStaticCallAt(uword return_address,
                                                     const Code& code,
                                                     ICData* ic_data_result) {
  ASSERT(code.ContainsInstructionAt(return_address));
  UnoptimizedStaticCall static_call(return_address);
  ICData& ic_data = ICData::Handle();
  ic_data ^= static_call.ic_data();
  if (ic_data_result != NULL) {
    *ic_data_result = ic_data.raw();
  }
  return ic_data.GetTargetAt(0);
}

void CodePatcher::PatchSwitchableCallAt(uword return_address,
                                        const Code& caller_code,
                                        const Object& data,
                                        const Code& target) {
  // Switchable instance calls only generated for precompilation.
  UNREACHABLE();
}

RawCode* CodePatcher::GetSwitchableCallTargetAt(uword return_address,
                                                const Code& caller_code) {
  // Switchable instance calls only generated for precompilation.
  UNREACHABLE();
  return Code::null();
}

RawObject* CodePatcher::GetSwitchableCallDataAt(uword return_address,
                                                const Code& caller_code) {
  // Switchable instance calls only generated for precompilation.
  UNREACHABLE();
  return Object::null();
}

void CodePatcher::PatchNativeCallAt(uword return_address,
                                    const Code& code,
                                    NativeFunction target,
                                    const Code& trampoline) {
  UNREACHABLE();
}

RawCode* CodePatcher::GetNativeCallAt(uword return_address,
                                      const Code& code,
                                      NativeFunction* target) {
  UNREACHABLE();
  return NULL;
}

}  // namespace dart

#endif  // defined TARGET_ARCH_IA32