RlwimiGenerator.java

/*
Copyright 2011-2016 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package com.google.security.zynamics.reil.translators.ppc;

import com.google.security.zynamics.reil.OperandSize;
import com.google.security.zynamics.reil.ReilHelpers;
import com.google.security.zynamics.reil.ReilInstruction;
import com.google.security.zynamics.reil.translators.ITranslationEnvironment;
import com.google.security.zynamics.reil.translators.InternalTranslationException;
import com.google.security.zynamics.reil.translators.TranslationHelpers;
import com.google.security.zynamics.zylib.disassembly.IInstruction;
import com.google.security.zynamics.zylib.disassembly.IOperandTreeNode;

import java.util.List;


public class RlwimiGenerator {
  public static void generate(long baseOffset, final ITranslationEnvironment environment,
      final IInstruction instruction, final List<ReilInstruction> instructions,
      final String mnemonic, final boolean isSimplified, final boolean setCr)
      throws InternalTranslationException {
    TranslationHelpers.checkTranslationArguments(environment, instruction, instructions, mnemonic);

    final IOperandTreeNode registerOperand1 =
        instruction.getOperands().get(0).getRootNode().getChildren().get(0);
    final IOperandTreeNode registerOperand2 =
        instruction.getOperands().get(1).getRootNode().getChildren().get(0);
    final IOperandTreeNode integerOperand1 =
        instruction.getOperands().get(2).getRootNode().getChildren().get(0);
    final IOperandTreeNode integerOperand2 =
        (instruction.getOperands().size() >= 4) ? instruction.getOperands().get(3).getRootNode()
            .getChildren().get(0) : null;
    final IOperandTreeNode integerOperand3 =
        (instruction.getOperands().size() == 5) ? instruction.getOperands().get(4).getRootNode()
            .getChildren().get(0) : null;

    final String targetRegister = registerOperand1.getValue();
    final String sourceRegister = registerOperand2.getValue();

    String SH = "";
    String MB = "";
    String ME = "";

    if (isSimplified) {
      if (instruction.getMnemonic().equals("inslwi") || instruction.getMnemonic().equals("inslwi.")) {
        // rlwimi rA,rS,32 - b,b,b + n - 1
        SH = String.valueOf(32 - Integer.decode(integerOperand2.getValue()));
        MB = integerOperand2.getValue();
        ME =
            String.valueOf((Integer.decode(integerOperand1.getValue()) + Integer
                .decode(integerOperand2.getValue())) - 1);
      } else if (instruction.getMnemonic().equals("insrwi")
          || instruction.getMnemonic().equals("insrwi.")) {
        // rlwimi rA,rS,32 - (b + n),b, (b + n) - 1
        SH =
            String.valueOf(32 - (Integer.decode(integerOperand2.getValue()) + Integer
                .decode(integerOperand1.getValue())));
        MB = integerOperand2.getValue();
        ME =
            String.valueOf((Integer.decode(integerOperand2.getValue()) + Integer
                .decode(integerOperand1.getValue())) - 1);
      } else {
        SH = integerOperand1.getValue();
        MB = integerOperand2.getValue();
      }
    } else {
      SH = integerOperand1.getValue();
      MB = integerOperand2.getValue();
      ME = integerOperand3.getValue();
    }
    final String crTemp = environment.getNextVariableString();

    final String rotateVar1 = environment.getNextVariableString();
    final String rotateVar2 = environment.getNextVariableString();
    final String rotateVar3 = environment.getNextVariableString();
    final String rotateVar4 = environment.getNextVariableString();

    final String normalMask =
        (instruction.getOperands().size() == 4) && !isSimplified ? integerOperand2.getValue()
            : Helpers.getRotateMask(MB, ME);
    final String inverseMask = environment.getNextVariableString();

    final String maskVar1 = environment.getNextVariableString();
    final String maskVar2 = environment.getNextVariableString();

    final OperandSize dw = OperandSize.DWORD;

    /**
     * rlwimi rA,rS,SH,MB,ME (Rc = 0) rlwimi. rA,rS,SH,MB,ME (Rc = 1)
     * 
     * 
     * n <- SH r <- ROTL(rS, n) m <- MASK(MB, ME) rA <- (r & m) | (rA & !m)
     * 
     * Simplified:
     * 
     * inslwi rA,rS,n,b equivalent to rlwimi rA,rS,32 - b,b,b + n - 1 insrwi rA,rS,n,b (n >
     * 0)equivalent to rlwimi rA,rS,32 - (b + n),b, (b + n) - 1
     * 
     */

    // generate rotate through shift
    instructions.add(ReilHelpers
        .createBsh(baseOffset++, dw, sourceRegister, dw, SH, dw, rotateVar1));
    instructions.add(ReilHelpers.createBsh(baseOffset++, dw, sourceRegister, dw,
        String.valueOf(-(32 - Integer.decode(SH))), dw, rotateVar2));
    instructions.add(ReilHelpers.createOr(baseOffset++, dw, rotateVar1, dw, rotateVar2, dw,
        rotateVar3));
    instructions.add(ReilHelpers.createAnd(baseOffset++, dw, rotateVar3, dw,
        String.valueOf(0xFFFFFFFFL), dw, rotateVar4));

    // apply normal mask
    instructions.add(ReilHelpers.createAnd(baseOffset++, dw, rotateVar4, dw, normalMask, dw,
        maskVar1));

    // generate inverse mask
    instructions.add(ReilHelpers.createXor(baseOffset++, dw, normalMask, dw,
        String.valueOf(0xFFFFFFFFL), dw, inverseMask));

    // apply inverse mask
    instructions.add(ReilHelpers.createAnd(baseOffset++, dw, targetRegister, dw, inverseMask, dw,
        maskVar2));

    // combine the results in the target register
    instructions.add(ReilHelpers.createOr(baseOffset++, dw, maskVar1, dw, maskVar2, dw,
        targetRegister));

    if (setCr) {
      // EQ CR0
      instructions.add(ReilHelpers.createBisz(baseOffset++, OperandSize.DWORD, targetRegister,
          OperandSize.BYTE, Helpers.CR0_EQUAL));

      // LT CR0
      instructions.add(ReilHelpers.createBsh(baseOffset++, OperandSize.DWORD, targetRegister,
          OperandSize.WORD, "-31", OperandSize.BYTE, Helpers.CR0_LESS_THEN));

      // GT CR0
      instructions.add(ReilHelpers.createOr(baseOffset++, OperandSize.BYTE, Helpers.CR0_EQUAL,
          OperandSize.BYTE, Helpers.CR0_LESS_THEN, OperandSize.BYTE, crTemp));
      instructions.add(ReilHelpers.createBisz(baseOffset++, OperandSize.BYTE, crTemp,
          OperandSize.BYTE, Helpers.CR0_GREATER_THEN));

      // SO CR0
      instructions.add(ReilHelpers.createStr(baseOffset, OperandSize.BYTE,
          Helpers.XER_SUMMARY_OVERFLOW, OperandSize.BYTE, Helpers.CRO_SUMMARY_OVERFLOW));
    }

  }
}