关于串口监视程序！

我仿照网友提供的文件系统监视程序（filesrc.zip），编写了一个串口监视程序，但总是在钩子处理例程中的IoCallDriver()处死机。
源代码如下，那位高手帮我看一看有什么问题？
（其它部分略）
BOOLEAN
HookSerial(
    IN PDRIVER_OBJECT DriverObject,
    FILE_SYSTEM_TYPE FsType
    )
{
    IO_STATUS_BLOCK     ioStatus;
    HANDLE              ntFileHandle;  
    OBJECT_ATTRIBUTES   objectAttributes;
    PDEVICE_OBJECT      fileSysDevice;
    PDEVICE_OBJECT      topAttachDevice;
    PDEVICE_OBJECT      hookDevice;
    UNICODE_STRING      fileNameUnicodeString;
    WCHAR               Com1Filename[] = L"\\Device\\Serial0";
    WCHAR               Com2Filename[] = L"\\Device\\Serial1";
    NTSTATUS            ntStatus;
    ULONG               i;
    PFILE_OBJECT        fileObject;
    PHOOK_EXTENSION     hookExtension;

    //
    // If we've already hooked it, just return success
    //
    if( FsType == COM1 && COM1HookDevice ) return TRUE;
    if( FsType == COM2 && COM2HookDevice ) return TRUE;
    
    //
    // We have to figure out what device to hook - first open the volume's
    // root directory
    //
    if( FsType == COM1 ) RtlInitUnicodeString( &fileNameUnicodeString, Com1Filename );
    else                 RtlInitUnicodeString( &fileNameUnicodeString, Com2Filename );
    InitializeObjectAttributes( &objectAttributes, &fileNameUnicodeString,
                                OBJ_CASE_INSENSITIVE, NULL, NULL );
    ntStatus = ZwCreateFile( &ntFileHandle, /*SYNCHRONIZE|FILE_ANY_ACCESS*/FILE_READ_DATA,
                             &objectAttributes, &ioStatus, NULL, 0, FILE_SHARE_READ/*|FILE_SHARE_WRITE*/,
                             FILE_OPEN,
                             /*FILE_SYNCHRONOUS_IO_NONALERT|*/FILE_NON_DIRECTORY_FILE,
                             NULL, 0 );
    if( !NT_SUCCESS( ntStatus ) ) {

        DbgPrint(("Filemon: Could not open %s\n", FsType == COM1 ? "COM1" : "COM2", ntStatus ));

        return FALSE;
    }

    DbgPrint(("Filemon:  opened the root directory!!! handle: %x\n", ntFileHandle));  

    //
    // Got the file handle, so now look-up the file-object it refers to
    //
    ntStatus = ObReferenceObjectByHandle( ntFileHandle, FILE_READ_DATA,
                                          NULL, KernelMode, &fileObject, NULL );
    if( !NT_SUCCESS( ntStatus )) {

        DbgPrint(("Filemon: Could not get fileobject from %s handle: %x\n",
                  FsType == COM1 ? "COM1" : "COM2", ntStatus ));
        ZwClose( ntFileHandle );

        return FALSE;
    }

    //  
    // Next, find out what device is associated with the file object by getting its related
    // device object
    //
    fileSysDevice = IoGetRelatedDeviceObject( fileObject );

    if( ! fileSysDevice ) {

        DbgPrint(("Filemon: Could not get related device object for %s: %x\n",
                  FsType == COM1 ? "COM1" : "COM2", ntStatus ));

        ObDereferenceObject( fileObject );
        ZwClose( ntFileHandle );

        return FALSE;
    }

    //
    // The file system's device hasn't been hooked already, so make a hooking device
    //  object that will be attached to it.
    //
    ntStatus = IoCreateDevice( DriverObject,
                               sizeof(HOOK_EXTENSION),
                               NULL,
                               fileSysDevice->DeviceType,
                               0,
                               FALSE,
                               &hookDevice );
    if( !NT_SUCCESS(ntStatus) ) {

        DbgPrint(("Filemon: failed to create associated device %s: %x\n",
                  FsType == COM1 ? "COM1" : "COM2", ntStatus ));

        ObDereferenceObject( fileObject );
        ZwClose( ntFileHandle );

        return FALSE;
    }

    //
    // Clear the device's init flag as per NT DDK KB article on creating device
    // objects from a dispatch routine
    //
    hookDevice->Flags &= ~DO_DEVICE_INITIALIZING;

    //
    // Finally, attach to the device. The second we're successfully attached, we may
    // start receiving IRPs targetted at the device we've hooked.
    //
    topAttachDevice = IoAttachDeviceToDeviceStack( hookDevice, fileSysDevice );
    if( !topAttachDevice )  {

        //
        // Couldn' attach for some reason
        //
        DbgPrint(("Filemon: Connect with Filesystem failed: %s (%x) =>%x\n",
                  FsType == COM1 ? "COM1" : "COM2", fileSysDevice, ntStatus ));

        //
        // Derefence the object and get out
        //
        ObDereferenceObject( fileObject );
        ZwClose( ntFileHandle );

        return FALSE;

    } else {

        DbgPrint(("Filemon: Successfully connected to Filesystem device %s\n",
                  FsType == COM1 ? "COM1" : "COM2" ));
    }

    //
    // Setup the device extensions. The drive letter and file system object are stored
    // in the extension.
    //
    hookExtension = hookDevice->DeviceExtension;
    hookExtension->LogicalDrive = '\\';
    hookExtension->FileSystem   = topAttachDevice;
    hookExtension->Hooked       = TRUE;
    hookExtension->Type = FsType;
    
    //
    // Close the file and update the hooked drive list by entering a
    // pointer to the hook device object in it.
    //
    ObDereferenceObject( fileObject );
    ZwClose( ntFileHandle );

    if( FsType == COM1 ) COM1HookDevice = hookDevice;
    else                 COM2HookDevice  = hookDevice;

    return TRUE;
}

NTSTATUS
FilemonHookRoutine(
    PDEVICE_OBJECT HookDevice,
    IN PIRP Irp
    )
{
    .....
    .....
    return IoCallDriver( hookExt->FileSystem, Irp );
}

   你的问题正好也是我想问的！！，那位大虾要是能够解决，也要
通知我一声啊，这个问题很特别，希望各位高手不吝赐教

    my mail :nicexu@yahoo.com.cn