Windows NT Driver >> C/C++

Queue IRP


參考資訊:
1. Source Code

驅動程式作為User Application跟硬體的溝通橋樑,最常遇到的問題就是硬體處理速度不夠快,導致驅動程式需要等待硬體完成後,再繼續處理下一筆資料,但是驅動程式如果要跟User Application溝通這些同步事情,會產生額外的等待時間,因此,為了達到比較好的處理效能,一般驅動程式做會Queue Irp的動作,讓處理的間隔可以縮到最小,這也是這篇教學要說明的東西,教導使用者一些Queue Irp的基本觀念和作法。

首先要知道的就是,儲存Irp的地方在哪?在Windows驅動程式裡,可以使用List作為儲存媒介(使用者也可以使用其它方式儲存),使用步驟相當簡單,如下所示:
1. InitializeListHead()
2. InsertHeadList()
3. IsListEmpty()
4. RemoveHeadList()
首先初始化List(InitializeListHead()),接著插入(InsertHeadList())需要儲存的資料,接著判斷List是否還有資料(IsListEmpty()),假如還有資料,則取出(RemoveHeadList())處裡

Irp是處裡資料的最小單位,一個Irp通常代表處理一筆資料的訊息,因此,當硬體來不及處理資料時,驅動程式需要做Pending Irp的動作,讓User Application知道這筆資料稍後處理,Pending Irp的步驟如下:
1. IoMarkIrpPending()
2. IoCompleteRequest(STATUS_PENDING)
回傳Pending,告知I/O Manager,這筆Irp資料先Pending一下,稍後處理

接著就是User Application如何知道資料是否處理完畢或者被Pending了呢?在CreateFile()時,如果沒有用FILE_FLAG_OVERLAPPED,則代表每一筆資料都是必須完成才會回傳,此種寫法也稱為Blocking方式,如:呼叫WriteFile()後,必須等待驅動程式完成該Irp才會繼續往下,否則呼叫WriteFile()後,會卡在這個Win32 API,相反地,如果CreateFile()使用FILE_FLAG_OVERLAPPED,而呼叫WriteFile()時,驅動程式回傳Pending,則WriteFile()會馬上回傳ERROR_IO_PENDING,告知User Application,該筆資料驅動程式會稍後處裡,此種寫法也稱為Non-Blocking方式,那如何得知該筆資料處理完畢了呢?當使用Non-Blocking寫法,會在WriteFile()傳入一個OVERLAPPED參數,該參數裡面有一個Event,用來告知是否已經處理完畢了。

Queue IRP流程:
1. InsertHeadList()
2. IoMarkIrpPending()
3. IoCompleteRequest(STATUS_PENDING)
4. IsListEmpty()
5. RemoveHeadList()
6. IoCompleteRequest(STATUS_SUCCESS)

main.c

#include <wdm.h>

#define IOCTL_QUEUE   CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_BUFFERED, FILE_ANY_ACCESS)
#define IOCTL_PROCESS CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_BUFFERED, FILE_ANY_ACCESS)

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

LIST_ENTRY stQueue={0};
KDPC stTimeDPC={0};
KTIMER stTime={0};

VOID OnTimer(struct _KDPC *Dpc, PVOID DeferredContext, PVOID SystemArgument1, PVOID SystemArgument2)
{
  PIRP pIrp;
  PLIST_ENTRY plist;
  if(IsListEmpty(&stQueue) == TRUE){
    KeCancelTimer(&stTime);
    DbgPrint("Finish");
  }
  else{
    plist = RemoveHeadList(&stQueue);
    pIrp = CONTAINING_RECORD(plist, IRP, Tail.Overlay.ListEntry);
    pIrp->IoStatus.Status = STATUS_SUCCESS;
    pIrp->IoStatus.Information = 0;
    IoCompleteRequest(pIrp, IO_NO_INCREMENT);
    DbgPrint("Complete Irp");
  }
}

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 stTimePeriod;
  PIO_STACK_LOCATION psk = IoGetCurrentIrpStackLocation(pIrp);

  switch(psk->Parameters.DeviceIoControl.IoControlCode){
  case IOCTL_QUEUE:
    DbgPrint("IOCTL_QUEUE");
    InsertHeadList(&stQueue, &pIrp->Tail.Overlay.ListEntry);
    IoMarkIrpPending(pIrp);
    return STATUS_PENDING;
  case IOCTL_PROCESS:
    DbgPrint("IOCTL_PROCESS");
    stTimePeriod.HighPart|= -1;
    stTimePeriod.LowPart = -10000000;
    KeSetTimerEx(&stTime, stTimePeriod, 10, &stTimeDPC);
    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");
  InitializeListHead(&stQueue);
  KeInitializeTimer(&stTime);
  KeInitializeDpc(&stTimeDPC, OnTimer, pOurDevice);
  IoCreateSymbolicLink(&usSymboName, &usDeviceName);
  pOurDevice->Flags&= ~DO_DEVICE_INITIALIZING;
  pOurDevice->Flags|= DO_BUFFERED_IO;
  return STATUS_SUCCESS;
}

DriverEntry()初始List以及DPC Timer,DPC Timer用來定期確認List是否還有資料需要處理,當然,使用Thread檢查或許更恰當些
IrpIOCTL()IOCTL_QUEUE代表該IOCTL會被Queue起來,稍後處理,而當收到IOCTL_PROCESS時,則啟動DPC Timer開始處理那些被Queue起來的Irp
OnTimer()處理Queue裡面的Irp

app.c

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

#define IOCTL_QUEUE   CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_BUFFERED, FILE_ANY_ACCESS)
#define IOCTL_PROCESS CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_BUFFERED, FILE_ANY_ACCESS)
 
int __cdecl main(int argc, char* argv[])
{
  int i=0;
  DWORD dwRet = 0;
  HANDLE hFile = NULL;
  OVERLAPPED ov[3]={0};

  hFile = CreateFile("\\\\.\\MyDriver", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED | FILE_ATTRIBUTE_NORMAL, NULL);
  if (hFile == INVALID_HANDLE_VALUE) {
    printf("failed to open mydriver\n");
    return -1;
  }
  for(i=0; i<3; i++){
    memset(&ov[i], 0, sizeof(ov[i]));
    ov[i].hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    printf("queue event\n");
    DeviceIoControl(hFile, IOCTL_QUEUE, NULL, 0, NULL, 0, &dwRet, &ov[i]);
  }
  printf("process all of events\n");
  DeviceIoControl(hFile, IOCTL_PROCESS, NULL, 0, NULL, 0, &dwRet, NULL);
  for(i=0; i<3; i++){
    WaitForSingleObject(ov[i].hEvent, INFINITE);
    CloseHandle(ov[i].hEvent);
    printf("wait complete\n");
  }
  CloseHandle(hFile);
  return 0;
}

結果


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