DCP是一种使用更加灵活的定时器，可以对任意间隔时间进行定时。DPC定时器的内部使用了一个定时器对象KTIMER，当你设定了定时器之后，从设定开始起经过这个时间之后操作系统会将一个DPC定时器的例程插入到DPC的队列，操作系统读取DPC队列的时候定时器例程就能够被执行。这里的DPC定时器例程就相当于一个定时器的回调函数。

在使用需要一些相关的初始化操作

1，初始化Timer

VOID KeInitializeTimer(PKTIMER Timer);

//参数Timer是定时器的指针

2，初始化DPC对象

VOID KeInitializeDpc(PRKDPC Dpc,PKDEFERRED_ROUTINE DeferredRoutine,PVOID DeferredContext);

//Dpc是输入参数DPC的对象指针

//DeferredRoutine是一个与DPC关联的定时器例程函数，当定时器被触发的时候这个例程函数就会被执行调用

//DeferredContext是一个传入定时器例程的参数

3，当初始化完成之后使用函数KeSetTimer函数开启定时器，

BOOLEAN KeSetTimer( PKTIMER Timer,LARGE_INTEGER DueTime,PKDPC Dpc);

//Timer是定时器对象的指针.

//DueTimer这个参数是设定的时间间隔.

//Dpc表示传入定时器例程的参数.

//返回值:BOOL类型的，表示成功或者失败.

4，取消定时器使用内核函数KeCancelTimer，

BOOLEAN KeCancelTimer(PKTIMER Timer);

在调用KeSetTimer函数之后，经过DueTime的时间，操作系统会调用一次定时器的例程，其中如果DueTime是一个正整数，则会代表绝对时间，也就是相对于1601年1月1日到触发DPC定时器的那个时刻，如果DueTime是负数，那它表示的是间隔多长时间，DueTime的单位是100ns。

示例代码：

用户层

#define IO_CONTROL_TRANSMIT_EVENT CTL_CODE(FILE_DEVICE_UNKNOWN,0x8080,METHOD_BUFFERED,FILE_ANY_ACCESS)

#define IO_CONTROL_START_TIMER CTL_CODE(FILE_DEVICE_UNKNOWN,0x8081,METHOD_BUFFERED,FILE_ANY_ACCESS)

#define IO_CONTROL_STOP_TIMER CTL_CODE(FILE_DEVICE_UNKNOWN,0x8082,METHOD_IN_DIRECT,FILE_ANY_ACCESS)

int main()

{

    HANDLE hDevice = CreateFile(L"\\\\.\\MyDeviceSymbolLinkName01", GENERIC_READ | GENERIC_WRITE, , NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

    if (hDevice == INVALID_HANDLE_VALUE)

    {

        printf("failed to obtain file handle to device with win32 error code %d ...\n", GetLastError());

        return ;

    }

    DWORD dwOutput;

    DWORD dwMircoSeconds =  *  * ;//100ns一个单位

    //发送启动定时器命令

    DeviceIoControl(hDevice, IO_CONTROL_START_TIMER, &dwMircoSeconds, sizeof(DWORD), NULL, , &dwOutput, NULL);

    Sleep();

    //发送终止定时器命令

    DeviceIoControl(hDevice, IO_CONTROL_STOP_TIMER, NULL, , NULL, , &dwOutput, NULL);

    CloseHandle(hDevice);

    return ;

}

驱动层：

//FirstDriver.h

#pragma once

#define IO_CONTROL_TRANSMIT_EVENT CTL_CODE(FILE_DEVICE_UNKNOWN,0x8080,METHOD_BUFFERED,FILE_ANY_ACCESS)

#define IO_CONTROL_START_TIMER CTL_CODE(FILE_DEVICE_UNKNOWN,0x8081,METHOD_BUFFERED,FILE_ANY_ACCESS)

#define IO_CONTROL_STOP_TIMER CTL_CODE(FILE_DEVICE_UNKNOWN,0x8082,METHOD_IN_DIRECT,FILE_ANY_ACCESS)

typedef struct _DEVICE_EXTENSION

{

    PDEVICE_OBJECT pDevObj;

    UNICODE_STRING ustrDeviceName;

    UNICODE_STRING ustrSymbolLinkName;

    KDPC pollingDPC;

    KTIMER pollingTimer;

    LARGE_INTEGER pollingInterVal;

}DEVICE_EXTENSION, * PDEVICE_EXTENSION;

NTSTATUS unload(PDRIVER_OBJECT driver);

NTSTATUS DemoDeviceControlDispatch(PDEVICE_OBJECT pDeviceObject, PIRP pIrp);

NTSTATUS DeviceCreate(PDEVICE_OBJECT pDeviceObject, PIRP pIrp);

NTSTATUS DeviceClose(PDEVICE_OBJECT pDeviceObject, PIRP pIrp);

NTSTATUS DemoCreateDevice(PDRIVER_OBJECT pDriver, PCWSTR devName, PCWSTR devSymName);
//FirstDriver.c

#include <ntddk.h>

#include "FirstDriver.h"

NTSTATUS DriverEntry(PDRIVER_OBJECT driver, PUNICODE_STRING reg_path)

{

    NTSTATUS ntstatus = STATUS_SUCCESS;

    driver->DriverUnload = unload;

    driver->MajorFunction[IRP_MJ_CREATE] = DeviceCreate;//创建

    driver->MajorFunction[IRP_MJ_CLOSE] = DeviceClose;//关闭

    driver->MajorFunction[IRP_MJ_DEVICE_CONTROL] = DemoDeviceControlDispatch;

    ntstatus = DemoCreateDevice(driver, L"\\Device\\MyDevice01", L"\\??\\MyDeviceSymbolLinkName01");

    if (!NT_SUCCESS(ntstatus))

    {

        DbgPrint("IoCreateDevice Failed");

        return ntstatus;

    }

    DbgPrint("%ws", reg_path->Buffer);

    DbgPrint("driver load success...");

    return STATUS_SUCCESS;

}

VOID PollingTimerDPC(PKDPC pDpc, PVOID pContext,  PVOID SysArg1, PVOID SysArg2)

{

    PDEVICE_OBJECT pDevObj = (PDEVICE_OBJECT)pContext;

    PDEVICE_EXTENSION pdx = (PDEVICE_EXTENSION)pDevObj->DeviceExtension;

    KeSetTimer(&pdx->pollingTimer, pdx->pollingInterVal, &pdx->pollingDPC);

    KdPrint(("PollingTimerDpc\n"));

    //检验是运行在任意线程上下文

    PEPROCESS pEProcess = IoGetCurrentProcess();

    PTSTR ProcessName = (PTSTR)((LONGLONG)pEProcess + 0x174);

    DbgPrint("多余参数 %d , %d , %d", pDpc->Number, SysArg1, SysArg2);

    DbgPrint("%s\n", ProcessName);

}

NTSTATUS DemoDeviceControlDispatch(PDEVICE_OBJECT pDeviceObject, PIRP pIrp)

{

    NTSTATUS ntstatus = STATUS_SUCCESS;

    DbgPrint("enter DemoDeviceControlDispatch ...\n");

    PIO_STACK_LOCATION stack = IoGetCurrentIrpStackLocation(pIrp);

    //ULONG cbin = stack->Parameters.DeviceIoControl.InputBufferLength;

    //ULONG cbout = stack->Parameters.DeviceIoControl.OutputBufferLength;

    ULONG ctlCode = stack->Parameters.DeviceIoControl.IoControlCode;

    PDEVICE_EXTENSION pDevExt = (PDEVICE_EXTENSION)pDeviceObject->DeviceExtension;

    ULONG info = ;

    switch (ctlCode)

    {

    case IO_CONTROL_START_TIMER:

    {

        KdPrint(("IOCTL_START_TIMER!\n"));

        //从用户模式传进来的超时

        ULONG ulMircoSeconds = *(PULONG)pIrp->AssociatedIrp.SystemBuffer;

        pDevExt->pollingInterVal = RtlConvertLongToLargeInteger(ulMircoSeconds * -);

        KeSetTimer(&pDevExt->pollingTimer, pDevExt->pollingInterVal, &pDevExt->pollingDPC);

        break;

    }

    case IO_CONTROL_STOP_TIMER:

    {

        KdPrint(("IOCTL_STOP_TIMER!\n"));

        KeCancelTimer(&pDevExt->pollingTimer);

        break;

    }

    default:

        ntstatus = STATUS_INVALID_VARIANT;

        break;

    }

    pIrp->IoStatus.Status = ntstatus;

    pIrp->IoStatus.Information = info;

    IoCompleteRequest(pIrp, IO_NO_INCREMENT);

    DbgPrint("leave the demo device control dispatch ...");

    DbgPrint("device io control test success...%d", pDeviceObject->ActiveThreadCount);

    return ntstatus;

}

NTSTATUS DeviceCreate(PDEVICE_OBJECT pDeviceObject, PIRP pIrp)

{

    //业务代码区

    //设置返回状态

    pIrp->IoStatus.Status = STATUS_SUCCESS;

    pIrp->IoStatus.Information = ;

    IoCompleteRequest(pIrp, IO_NO_INCREMENT);

    DbgPrint("create device success...%d", pDeviceObject->ActiveThreadCount);

    return STATUS_SUCCESS;

}

NTSTATUS DeviceClose(PDEVICE_OBJECT pDeviceObject, PIRP pIrp)

{

    //业务代码区

    //设置返回状态

    pIrp->IoStatus.Status = STATUS_SUCCESS;//getLastError()得到的值

    pIrp->IoStatus.Information = ;            //返回给3环多少数据，没有填0

    IoCompleteRequest(pIrp, IO_NO_INCREMENT);

    DbgPrint("close device success...%d", pDeviceObject->ActiveThreadCount);

    return STATUS_SUCCESS;

}

NTSTATUS DemoCreateDevice(PDRIVER_OBJECT pDriver, PCWSTR devName, PCWSTR devSymName)

{

    PDEVICE_OBJECT pDevice;

    PDEVICE_EXTENSION pDevExt;

    UNICODE_STRING DeviceName;

    UNICODE_STRING SymbolLinkName;

    RtlInitUnicodeString(&DeviceName, devName);

    RtlInitUnicodeString(&SymbolLinkName, devSymName);

    NTSTATUS ntstatus = STATUS_SUCCESS;

    ntstatus = IoCreateDevice(pDriver, sizeof(DEVICE_EXTENSION), &DeviceName, FILE_DEVICE_UNKNOWN, FILE_DEVICE_SECURE_OPEN, FALSE, &pDevice);

    if (!NT_SUCCESS(ntstatus))

    {

        DbgPrint("IoCreateDevice Failed");

        return ntstatus;

    }

    ntstatus = IoCreateSymbolicLink(&SymbolLinkName, &DeviceName);

    if (!NT_SUCCESS(ntstatus))

    {

        DbgPrint("IoCreateSymbolicLink Failed");

        IoDeleteDevice(pDevice);

        return ntstatus;

    }

    pDevice->Flags |= DO_BUFFERED_IO;

    pDevExt = (PDEVICE_EXTENSION)pDevice->DeviceExtension;

    pDevExt->pDevObj = pDevice;

    pDevExt->ustrDeviceName = DeviceName;

    pDevExt->ustrSymbolLinkName = SymbolLinkName;

    KeInitializeTimer(&pDevExt->pollingTimer);

    KeInitializeDpc(&pDevExt->pollingDPC, PollingTimerDPC, (PVOID)pDevice);

    return ntstatus;

}

NTSTATUS unload(PDRIVER_OBJECT driver)

{

    PDEVICE_OBJECT pDev;

    DbgPrint("driver :%ws unload", driver->DriverName.Buffer);

    pDev = driver->DeviceObject;

    while (pDev != NULL)

    {

        PDEVICE_EXTENSION pDevExt = {  };

        pDevExt = (PDEVICE_EXTENSION)pDev->DeviceExtension;

        //删除符号链接

        UNICODE_STRING pLinkName = pDevExt->ustrSymbolLinkName;

        DbgPrint("this is the divice name : %ws", pLinkName.Buffer);

        IoDeleteSymbolicLink(&pLinkName);

        pDev = pDev->NextDevice;

        IoDeleteDevice(pDevExt->pDevObj);

    }

    DbgPrint("driver unload success...");

    return STATUS_SUCCESS;

}

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