Windows NT Driver >> C/C++ >> Timer

DPC

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參考資訊：
1. Source Code

由於I/O Timer的Timer間隔固定為一秒，如果使用者想要可以彈性設定的Timer間隔，則需要使用DPC Timer，使用的步驟：
1. KeInitializeTimer()
2. KeInitializeDpc()
3. KeSetTimer()
4. KeCancelTimer()

DPC Timer如果使用KeSetTimer()做設定時，其Timer為一次性，也就是Callback僅會被呼叫一次，如果要使用週期性Timer，則需要改用KeSetTimerEx()，KeSetTimerEx()宣告如下：

BOOLEAN KeSetTimerEx(PKTIMER Timer, LARGE_INTEGER DueTime, LONG Period, PKDPC Dpc);

DueTime是第一次Timer的間隔，之後的間隔則使用Period數值。

main.c

#include <wdm.h>

#define IOCTL_START CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_BUFFERED, FILE_ANY_ACCESS)
#define IOCTL_STOP  CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_BUFFERED, FILE_ANY_ACCESS)

#define DEV_NAME L"\\Device\\MyDriver"
#define SYM_NAME L"\\DosDevices\\MyDriver"


ULONG dwTimerCnt=0;
KDPC stTimerDPC={0};
KTIMER stTimerObj={0};

VOID OnTimer(struct _KDPC *Dpc, PVOID DeferredContext, PVOID SystemArgument1, PVOID SystemArgument2)
{
  dwTimerCnt+= 1;
  DbgPrint("DpcTimer: %d\n", dwTimerCnt);
}

void Unload(PDRIVER_OBJECT pOurDriver)
{
  UNICODE_STRING usSymboName;
             
  RtlInitUnicodeString(&usSymboName, L"\\DosDevices\\MyDriver");
  IoDeleteSymbolicLink(&usSymboName);
  IoDeleteDevice(pOurDriver->DeviceObject);
}

NTSTATUS IrpIOCTL(PDEVICE_OBJECT pOurDevice, PIRP pIrp)
{
  LARGE_INTEGER stTimeCnt;
  PIO_STACK_LOCATION psk = IoGetCurrentIrpStackLocation(pIrp);

  switch(psk->Parameters.DeviceIoControl.IoControlCode){
  case IOCTL_START:
    DbgPrint("IOCTL_START");
    dwTimerCnt = 0;
    stTimeCnt.HighPart|= -1;
    stTimeCnt.LowPart = -10000000;
    KeSetTimerEx(&stTimerObj, stTimeCnt, 1000, &stTimerDPC);
    break;
  case IOCTL_STOP:
    DbgPrint("IOCTL_STOP");
    KeCancelTimer(&stTimerObj);
    break;
  }
  pIrp->IoStatus.Information = 0;
  pIrp->IoStatus.Status = STATUS_SUCCESS;
  IoCompleteRequest(pIrp, IO_NO_INCREMENT);
  return STATUS_SUCCESS;
}

NTSTATUS IrpFile(PDEVICE_OBJECT pOurDevice, PIRP pIrp)
{
  PIO_STACK_LOCATION psk = IoGetCurrentIrpStackLocation(pIrp);

  switch(psk->MajorFunction){
  case IRP_MJ_CREATE:
    DbgPrint("IRP_MJ_CREATE");
    break;
  case IRP_MJ_CLOSE:
    DbgPrint("IRP_MJ_CLOSE");
    break;
  }
  IoCompleteRequest(pIrp, IO_NO_INCREMENT);
  return STATUS_SUCCESS;
}

NTSTATUS DriverEntry(PDRIVER_OBJECT pOurDriver, PUNICODE_STRING pOurRegistry)
{
  PDEVICE_OBJECT pOurDevice=NULL;
  UNICODE_STRING usDeviceName;
  UNICODE_STRING usSymboName;
        
  pOurDriver->MajorFunction[IRP_MJ_CREATE] =
  pOurDriver->MajorFunction[IRP_MJ_CLOSE] = IrpFile;
  pOurDriver->MajorFunction[IRP_MJ_DEVICE_CONTROL] = IrpIOCTL;
  pOurDriver->DriverUnload = Unload;
          
  RtlInitUnicodeString(&usDeviceName, L"\\Device\\MyDriver");
  IoCreateDevice(pOurDriver, 0, &usDeviceName, FILE_DEVICE_UNKNOWN, 0, FALSE, &pOurDevice);
  RtlInitUnicodeString(&usSymboName, L"\\DosDevices\\MyDriver");
  KeInitializeTimer(&stTimerObj);
  KeInitializeDpc(&stTimerDPC, OnTimer, pOurDevice);
  IoCreateSymbolicLink(&usSymboName, &usDeviceName);
  pOurDevice->Flags&= ~DO_DEVICE_INITIALIZING;
  pOurDevice->Flags|= DO_BUFFERED_IO;
  return STATUS_SUCCESS;
}

DriverEntry()初始化Timer以及DPC Object
IrpIOCTL()啟動或停止DPC Timer
OnTimer()僅列印訊息，其餘事情不做

app.c

#define INITGUID
#include <windows.h>
#include <winioctl.h>
#include <strsafe.h>
#include <setupapi.h>
#include <stdio.h>
#include <stdlib.h>

#define IOCTL_START CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_BUFFERED, FILE_ANY_ACCESS)
#define IOCTL_STOP  CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_BUFFERED, FILE_ANY_ACCESS)

int __cdecl main(int argc, char* argv[])
{
  HANDLE hFile = NULL;
  DWORD dwRet = 0;

  hFile = CreateFile("\\\\.\\MyDriver", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
  if (hFile == INVALID_HANDLE_VALUE) {
    printf("failed to open mydriver\n");
    return -1;
  }
  DeviceIoControl(hFile, IOCTL_START, NULL, 0, NULL, 0, &dwRet, NULL);
  Sleep(3000);
  DeviceIoControl(hFile, IOCTL_STOP, NULL, 0, NULL, 0, &dwRet, NULL);
  CloseHandle(hFile);
  return 0;
}

結果

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