return VM_Memory.mprotect(start, VM_Extent.fromInt(size),
return VM_Memory.mprotect(start, VM_Extent.fromIntZeroExtend(size),
  public static boolean munprotect(VM_Address start, int size) {    return VM_Memory.mprotect(start, VM_Extent.fromInt(size),                              VM_Memory.PROT_READ | VM_Memory.PROT_WRITE | VM_Memory.PROT_EXEC);  }