理解驱动对象（DriverObject）

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        每个驱动程序都会有唯一一个驱动对象表示，驱动对象是对驱动程序的实例化。她由Ring0层的执行体组件中的IO管理器负责加载，并且每个驱动只加载一个实例。在wdm.h头文件中。DriverObject结构如下：

typedef struct _DRIVER_OBJECT {
    CSHORT Type;
    CSHORT Size;

    //
    // The following links all of the devices created by a single driver
    // together on a list, and the Flags word provides an extensible flag
    // location for driver objects.
    //

    PDEVICE_OBJECT DeviceObject;
    ULONG Flags;

    //
    // The following section describes where the driver is loaded.  The count
    // field is used to count the number of times the driver has had its
    // registered reinitialization routine invoked.
    //

    PVOID DriverStart;
    ULONG DriverSize;
    PVOID DriverSection;
    PDRIVER_EXTENSION DriverExtension;

    //
    // The driver name field is used by the error log thread
    // determine the name of the driver that an I/O request is/was bound.
    //

    UNICODE_STRING DriverName;

    //
    // The following section is for registry support.  Thise is a pointer
    // to the path to the hardware information in the registry
    //

    PUNICODE_STRING HardwareDatabase;

    //
    // The following section contains the optional pointer to an array of
    // alternate entry points to a driver for "fast I/O" support.  Fast I/O
    // is performed by invoking the driver routine directly with separate
    // parameters, rather than using the standard IRP call mechanism.  Note
    // that these functions may only be used for synchronous I/O, and when
    // the file is cached.
    //

    PFAST_IO_DISPATCH FastIoDispatch;

    //
    // The following section describes the entry points to this particular
    // driver.  Note that the major function dispatch table must be the last
    // field in the object so that it remains extensible.
    //

    PDRIVER_INITIALIZE DriverInit;
    PDRIVER_STARTIO DriverStartIo;
    PDRIVER_UNLOAD DriverUnload;
    PDRIVER_DISPATCH MajorFunction[IRP_MJ_MAXIMUM_FUNCTION + 1];

} DRIVER_OBJECT;

DeviceObject：每个驱动会有一个或者多个设备对象。这些设备对象通过链表的方式组织。每个设备对象有一nextDevice的指针指向链表的下一个设备对象。但是注意：驱动对象里面的这个DeviceObject相当设备链表的头节点。他指向的是：本驱动程序自己创建的第一个设备对象。

DriverName:驱动的名字

DriverStartIO：处理多个irp的时候。需要这个来序列化。

DriverUnload：卸载驱动的时候的回调函数。

Driverextension：驱动的扩展。和设备的扩展差不多。

majorFunction:IRP派遣函数。这个感觉也相当于回调。只不过是向操作系统注册IRP的处理函数。

Flag：标志位。

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