Example #1
0
  /**
   * Analyzes the given method.
   *
   * @param owner the internal name of the class to which the method belongs.
   * @param m the method to be analyzed.
   * @return the symbolic state of the execution stack frame at each bytecode instruction of the
   *     method. The size of the returned array is equal to the number of instructions (and labels)
   *     of the method. A given frame is <tt>null</tt> if and only if the corresponding instruction
   *     cannot be reached (dead code).
   * @throws AnalyzerException if a problem occurs during the analysis.
   */
  public Frame[] analyze(final String owner, final MethodNode m) throws AnalyzerException {
    if ((m.access & (ACC_ABSTRACT | ACC_NATIVE)) != 0) {
      frames = new Frame[0];
      return frames;
    }
    n = m.instructions.size();
    insns = m.instructions;
    handlers = new List[n];
    frames = new Frame[n];
    subroutines = new Subroutine[n];
    queued = new boolean[n];
    queue = new int[n];
    top = 0;

    // computes exception handlers for each instruction
    for (int i = 0; i < m.tryCatchBlocks.size(); ++i) {
      TryCatchBlockNode tcb = (TryCatchBlockNode) m.tryCatchBlocks.get(i);
      int begin = insns.indexOf(tcb.start);
      int end = insns.indexOf(tcb.end);
      for (int j = begin; j < end; ++j) {
        List insnHandlers = handlers[j];
        if (insnHandlers == null) {
          insnHandlers = new ArrayList();
          handlers[j] = insnHandlers;
        }
        insnHandlers.add(tcb);
      }
    }

    // computes the subroutine for each instruction:
    Subroutine main = new Subroutine(null, m.maxLocals, null);
    List subroutineCalls = new ArrayList();
    Map subroutineHeads = new HashMap();
    findSubroutine(0, main, subroutineCalls);
    while (!subroutineCalls.isEmpty()) {
      JumpInsnNode jsr = (JumpInsnNode) subroutineCalls.remove(0);
      Subroutine sub = (Subroutine) subroutineHeads.get(jsr.label);
      if (sub == null) {
        sub = new Subroutine(jsr.label, m.maxLocals, jsr);
        subroutineHeads.put(jsr.label, sub);
        findSubroutine(insns.indexOf(jsr.label), sub, subroutineCalls);
      } else {
        sub.callers.add(jsr);
      }
    }
    for (int i = 0; i < n; ++i) {
      if (subroutines[i] != null && subroutines[i].start == null) {
        subroutines[i] = null;
      }
    }

    // initializes the data structures for the control flow analysis
    Frame current = newFrame(m.maxLocals, m.maxStack);
    Frame handler = newFrame(m.maxLocals, m.maxStack);
    Type[] args = Type.getArgumentTypes(m.desc);
    int local = 0;
    if ((m.access & ACC_STATIC) == 0) {
      Type ctype = Type.getObjectType(owner);
      current.setLocal(local++, interpreter.newValue(ctype));
    }
    for (int i = 0; i < args.length; ++i) {
      current.setLocal(local++, interpreter.newValue(args[i]));
      if (args[i].getSize() == 2) {
        current.setLocal(local++, interpreter.newValue(null));
      }
    }
    while (local < m.maxLocals) {
      current.setLocal(local++, interpreter.newValue(null));
    }
    merge(0, current, null);

    // control flow analysis
    while (top > 0) {
      int insn = queue[--top];
      Frame f = frames[insn];
      Subroutine subroutine = subroutines[insn];
      queued[insn] = false;

      try {
        AbstractInsnNode insnNode = m.instructions.get(insn);
        int insnOpcode = insnNode.getOpcode();
        int insnType = insnNode.getType();

        if (insnType == AbstractInsnNode.LABEL
            || insnType == AbstractInsnNode.LINE
            || insnType == AbstractInsnNode.FRAME) {
          merge(insn + 1, f, subroutine);
          newControlFlowEdge(insn, insn + 1);
        } else {
          current.init(f).execute(insnNode, interpreter);
          subroutine = subroutine == null ? null : subroutine.copy();

          if (insnNode instanceof JumpInsnNode) {
            JumpInsnNode j = (JumpInsnNode) insnNode;
            if (insnOpcode != GOTO && insnOpcode != JSR) {
              merge(insn + 1, current, subroutine);
              newControlFlowEdge(insn, insn + 1);
            }
            int jump = insns.indexOf(j.label);
            if (insnOpcode == JSR) {
              merge(jump, current, new Subroutine(j.label, m.maxLocals, j));
            } else {
              merge(jump, current, subroutine);
            }
            newControlFlowEdge(insn, jump);
          } else if (insnNode instanceof LookupSwitchInsnNode) {
            LookupSwitchInsnNode lsi = (LookupSwitchInsnNode) insnNode;
            int jump = insns.indexOf(lsi.dflt);
            merge(jump, current, subroutine);
            newControlFlowEdge(insn, jump);
            for (int j = 0; j < lsi.labels.size(); ++j) {
              LabelNode label = (LabelNode) lsi.labels.get(j);
              jump = insns.indexOf(label);
              merge(jump, current, subroutine);
              newControlFlowEdge(insn, jump);
            }
          } else if (insnNode instanceof TableSwitchInsnNode) {
            TableSwitchInsnNode tsi = (TableSwitchInsnNode) insnNode;
            int jump = insns.indexOf(tsi.dflt);
            merge(jump, current, subroutine);
            newControlFlowEdge(insn, jump);
            for (int j = 0; j < tsi.labels.size(); ++j) {
              LabelNode label = (LabelNode) tsi.labels.get(j);
              jump = insns.indexOf(label);
              merge(jump, current, subroutine);
              newControlFlowEdge(insn, jump);
            }
          } else if (insnOpcode == RET) {
            if (subroutine == null) {
              throw new AnalyzerException("RET instruction outside of a sub routine");
            }
            for (int i = 0; i < subroutine.callers.size(); ++i) {
              Object caller = subroutine.callers.get(i);
              int call = insns.indexOf((AbstractInsnNode) caller);
              if (frames[call] != null) {
                merge(call + 1, frames[call], current, subroutines[call], subroutine.access);
                newControlFlowEdge(insn, call + 1);
              }
            }
          } else if (insnOpcode != ATHROW && (insnOpcode < IRETURN || insnOpcode > RETURN)) {
            if (subroutine != null) {
              if (insnNode instanceof VarInsnNode) {
                int var = ((VarInsnNode) insnNode).var;
                subroutine.access[var] = true;
                if (insnOpcode == LLOAD
                    || insnOpcode == DLOAD
                    || insnOpcode == LSTORE
                    || insnOpcode == DSTORE) {
                  subroutine.access[var + 1] = true;
                }
              } else if (insnNode instanceof IincInsnNode) {
                int var = ((IincInsnNode) insnNode).var;
                subroutine.access[var] = true;
              }
            }
            merge(insn + 1, current, subroutine);
            newControlFlowEdge(insn, insn + 1);
          }
        }

        List insnHandlers = handlers[insn];
        if (insnHandlers != null) {
          for (int i = 0; i < insnHandlers.size(); ++i) {
            TryCatchBlockNode tcb = (TryCatchBlockNode) insnHandlers.get(i);
            Type type;
            if (tcb.type == null) {
              type = Type.getObjectType("java/lang/Throwable");
            } else {
              type = Type.getObjectType(tcb.type);
            }
            int jump = insns.indexOf(tcb.handler);
            if (newControlFlowExceptionEdge(insn, jump)) {
              handler.init(f);
              handler.clearStack();
              handler.push(interpreter.newValue(type));
              merge(jump, handler, subroutine);
            }
          }
        }
      } catch (AnalyzerException e) {
        throw new AnalyzerException("Error at instruction " + insn + ": " + e.getMessage(), e);
      } catch (Exception e) {
        throw new AnalyzerException("Error at instruction " + insn + ": " + e.getMessage(), e);
      }
    }

    return frames;
  }
Example #2
0
  private void findSubroutine(int insn, final Subroutine sub, final List calls)
      throws AnalyzerException {
    while (true) {
      if (insn < 0 || insn >= n) {
        throw new AnalyzerException("Execution can fall off end of the code");
      }
      if (subroutines[insn] != null) {
        return;
      }
      subroutines[insn] = sub.copy();
      AbstractInsnNode node = insns.get(insn);

      // calls findSubroutine recursively on normal successors
      if (node instanceof JumpInsnNode) {
        if (node.getOpcode() == JSR) {
          // do not follow a JSR, it leads to another subroutine!
          calls.add(node);
        } else {
          JumpInsnNode jnode = (JumpInsnNode) node;
          findSubroutine(insns.indexOf(jnode.label), sub, calls);
        }
      } else if (node instanceof TableSwitchInsnNode) {
        TableSwitchInsnNode tsnode = (TableSwitchInsnNode) node;
        findSubroutine(insns.indexOf(tsnode.dflt), sub, calls);
        for (int i = tsnode.labels.size() - 1; i >= 0; --i) {
          LabelNode l = (LabelNode) tsnode.labels.get(i);
          findSubroutine(insns.indexOf(l), sub, calls);
        }
      } else if (node instanceof LookupSwitchInsnNode) {
        LookupSwitchInsnNode lsnode = (LookupSwitchInsnNode) node;
        findSubroutine(insns.indexOf(lsnode.dflt), sub, calls);
        for (int i = lsnode.labels.size() - 1; i >= 0; --i) {
          LabelNode l = (LabelNode) lsnode.labels.get(i);
          findSubroutine(insns.indexOf(l), sub, calls);
        }
      }

      // calls findSubroutine recursively on exception handler successors
      List insnHandlers = handlers[insn];
      if (insnHandlers != null) {
        for (int i = 0; i < insnHandlers.size(); ++i) {
          TryCatchBlockNode tcb = (TryCatchBlockNode) insnHandlers.get(i);
          findSubroutine(insns.indexOf(tcb.handler), sub, calls);
        }
      }

      // if insn does not falls through to the next instruction, return.
      switch (node.getOpcode()) {
        case GOTO:
        case RET:
        case TABLESWITCH:
        case LOOKUPSWITCH:
        case IRETURN:
        case LRETURN:
        case FRETURN:
        case DRETURN:
        case ARETURN:
        case RETURN:
        case ATHROW:
          return;
      }
      insn++;
    }
  }