NTSTATUS
NTAPI
IoCallDriver(IN PDEVICE_OBJECT DeviceObject,
             IN PIRP Irp)
{
    /* Call fastcall */
    return IofCallDriver(DeviceObject, Irp);
}
NTSTATUS
FASTCALL
IofCallDriver(IN PDEVICE_OBJECT DeviceObject,
              IN PIRP Irp)
{
    PDRIVER_OBJECT DriverObject;
    PIO_STACK_LOCATION StackPtr;

    /* Make sure this is a valid IRP */
    ASSERT(Irp->Type == IO_TYPE_IRP);

    /* Get the Driver Object */
    DriverObject = DeviceObject->DriverObject;

    /* Decrease the current location and check if */
    Irp->CurrentLocation--;
    if (Irp->CurrentLocation <= 0)
    {
        /* This IRP ran out of stack, bugcheck */
        KeBugCheckEx(NO_MORE_IRP_STACK_LOCATIONS, (ULONG_PTR)Irp, 0, 0, 0);
    }

    /*将当前I/O堆栈的指针下移*/
    StackPtr = IoGetNextIrpStackLocation(Irp);
    Irp->Tail.Overlay.CurrentStackLocation = StackPtr;

    /* Get the Device Object */
    StackPtr->DeviceObject = DeviceObject;

    /* Call it */
    return DriverObject->MajorFunction[StackPtr->MajorFunction](DeviceObject,
                                                                Irp);
}

但有的时候，当前设备堆栈不对IRP做任何处理，而IoCallDriver会将当前I/O堆栈向下移动一个单位，此时可以调用IoSkipCurrentIrpStackLocation对设备堆栈的移动会实现平衡，它的作用就是将I/O堆栈往回移动一个单位。这时IoCallDriver调用的低一层驱动所用到的I/O堆栈和上一层用到的是同一个。
为什么要用上层设备的IO堆栈数据，因为上层IO堆栈有我们想要的数据，如果低一层驱动想要用上层的IO数据，也可以用IoCopyCurrentIrpStackLocationToNext。
如图，当DeviceB不对IRP做任何处理时候，向下层设备(DeviceA)转发IRP时，调用IoCallDriver内核函数会将IRP的当前指针下移，指向下一个IO_STACK_LOCATION指针，所以在调用IoCallDriver之前应该调用IoSkipCurrentIrpStackLocation，使IO堆栈上移，从而使IO_STACK_LOCATION(B)中的数据能够正确被DeviceA所使用

另一种情况，当IRP被本层驱动(DeviceB)设备使用，但需要向下(DeviceA)转发IRP时，调用IoCopyCurrentIrpStackLocationToNext来复制当前I/O堆栈(IO_STACK_LOCATION(B))参数到下一层(IO_STACK_LOCATION(A))，然后调用IoCallDriver。
几个重要的函数实现

#define IoSkipCurrentIrpStackLocation( Irp ) \
    (Irp)->CurrentLocation++; \
    (Irp)->Tail.Overlay.CurrentStackLocation++;

#define IoGetNextIrpStackLocation( Irp ) (\
    (Irp)->Tail.Overlay.CurrentStackLocation - 1 )

FORCEINLINE
VOID
IoCopyCurrentIrpStackLocationToNext(
    _Inout_ PIRP Irp)
{
    PIO_STACK_LOCATION irpSp;
    PIO_STACK_LOCATION nextIrpSp;
    irpSp = IoGetCurrentIrpStackLocation(Irp);
    nextIrpSp = IoGetNextIrpStackLocation(Irp);
    RtlCopyMemory(nextIrpSp, irpSp, FIELD_OFFSET(IO_STACK_LOCATION, CompletionRoutine));
    nextIrpSp->Control = 0;
}