IoCallDriver源码剖析

IoCallDriver是一个宏：

#define IoCallDriver(a,b)   \
        IofCallDriver(a,b)

显然用的是IofCallDriver();

IofCallDriver()代码如下：

NTSTATUS
FASTCALL
IofCallDriver(
    IN PDEVICE_OBJECT DeviceObject,
    IN OUT PIRP Irp
    )
{
    if (pIofCallDriver != NULL) {

        //
        // This routine will either jump immediately to IovCallDriver or
        // IoPerfCallDriver.
        //
        return pIofCallDriver(DeviceObject, Irp, _ReturnAddress());
    }

    return IopfCallDriver(DeviceObject, Irp);
}

pIofCallDriver 好像是(在头文件定义)

extern PIO_CALL_DRIVER        pIofCallDriver;

PIO_CALL_DRIVER则是一个函数指针

typedef
NTSTATUS
(FASTCALL *PIO_CALL_DRIVER) (
    IN      PDEVICE_OBJECT  DeviceObject,
    IN OUT  PIRP            Irp,
    IN      PVOID           ReturnAddress
    );

再来说IopfCallDriver

NTSTATUS
FORCEINLINE
IopfCallDriver(
    IN PDEVICE_OBJECT DeviceObject,
    IN OUT PIRP Irp
    )

/*++

Routine Description:

    This routine is invoked to pass an I/O Request Packet (IRP) to another
    driver at its dispatch routine.

Arguments:

    DeviceObject - Pointer to device object to which the IRP should be passed.

    Irp - Pointer to IRP for request.

Return Value:

    Return status from driver's dispatch routine.

--*/

{
    PIO_STACK_LOCATION irpSp;
    PDRIVER_OBJECT driverObject;
    NTSTATUS status;

    //
    // Ensure that this is really an I/O Request Packet.
    //

    ASSERT( Irp->Type == IO_TYPE_IRP );

    //
    // Update the IRP stack to point to the next location.
　　//可见Irp的那个数组标号越大表示越顶层设备
    //
    Irp->CurrentLocation--;

    if (Irp->CurrentLocation <= 0) {
        KiBugCheck3( NO_MORE_IRP_STACK_LOCATIONS, (ULONG_PTR) Irp, 0, 0 );
    }

    irpSp = IoGetNextIrpStackLocation( Irp );
    Irp->Tail.Overlay.CurrentStackLocation = irpSp;

    //
    // Save a pointer to the device object for this request so that it can
    // be used later in completion.
    //

    irpSp->DeviceObject = DeviceObject;


    //
    // Invoke the driver at its dispatch routine entry point.
    //

    driverObject = DeviceObject->DriverObject;
　　
    //
    // Prevent the driver from unloading.
    // 用给定的驱动对象进行调用

　　
    status = driverObject->MajorFunction[irpSp->MajorFunction]( DeviceObject,
                                                              Irp );

    return status;
}