Windows NT Driver >> C/C++ >> IOCTL

METHOD_NEITHER

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參考資訊：
1. Source Code

Neither I/O(METHOD_NEITHER)的意思就是Neither Buffered Nor Direct I/O，使用這種方式時，I/O Manager會將User Buffer的指標，透過操作後，傳遞給驅動程式使用，因此，驅動程式可以直接存取User Buffer的資料，所以存取速度可以得到很大的改善，對於有速度要求的驅動程式來說，建議使用Neither的方式，不過，關於User Buffer指標的存取問題上，會遇到更多需要面對的問題，如：指標的有效性以及多次存取的同步問題，因此，在選擇使用上，更需要考量到這些額外付出的代價是否值得使用，因為，驅動程式以及User Application雙方都需要很嚴謹的看待這塊共用的Buffer。

Microsoft的說明網頁：
using-neither-buffered-nor-direct-i-o

記憶體指標：

	Buffer	Length
Input	(IrpStack) Parameters.DeviceIoControl.Type3InputBuffer	(IrpStack) Parameters.DeviceIoControl.InputBufferLength
Output	(Irp) UserBuffer	(IrpStack) Parameters.DeviceIoControl.OutputBufferLength

main.c

#include <wdm.h>

#define IOCTL_SET CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_NEITHER, FILE_ANY_ACCESS)
#define IOCTL_GET CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_NEITHER, FILE_ANY_ACCESS)

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

char szBuffer[255]={0};

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)
{
  ULONG Len=0;
  PIO_STACK_LOCATION psk = IoGetCurrentIrpStackLocation(pIrp);

  switch(psk->Parameters.DeviceIoControl.IoControlCode){
  case IOCTL_SET:
    DbgPrint("IOCTL_SET");
    Len = psk->Parameters.DeviceIoControl.InputBufferLength;
    memcpy(szBuffer, psk->Parameters.DeviceIoControl.Type3InputBuffer, Len);
    DbgPrint("Buffer: %s, Length: %d", szBuffer, Len);
    break;
  case IOCTL_GET:
    DbgPrint("IOCTL_GET");
    Len = strlen(szBuffer)+1;
    memcpy(pIrp->UserBuffer, szBuffer, Len);
    break;
  }
  pIrp->IoStatus.Status = STATUS_SUCCESS;
  pIrp->IoStatus.Information = Len;
  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");
  IoCreateSymbolicLink(&usSymboName, &usDeviceName);
  pOurDevice->Flags&= ~DO_DEVICE_INITIALIZING;
  pOurDevice->Flags|= DO_BUFFERED_IO;
  return STATUS_SUCCESS;
}

IrpIOCTL()收到IOCTL_SET時，Driver複製User Buffer的內容到szBuffer，而收到IOCTL_GET時，將szBuffer內容又複製回User Buffer，完成暫存的功能，IoStatus.Information的數值就是OutBufferSize回傳的長度。

app.c

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

#define IOCTL_SET CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_NEITHER, FILE_ANY_ACCESS)
#define IOCTL_GET CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_NEITHER, FILE_ANY_ACCESS)

int __cdecl main(int argc, char* argv[])
{
  DWORD dwRet = 0;
  HANDLE hFile = NULL;
  char szBuffer[255]={"I am error"};

  hFile = CreateFile("\\\\.\\MyDriver", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
  if (hFile == INVALID_HANDLE_VALUE) {
    printf("failed to open mydriver");
    return 1;
  }
  printf("SET: %s, %d\n", szBuffer, strlen(szBuffer)+1);
  DeviceIoControl(hFile, IOCTL_SET, szBuffer, strlen(szBuffer)+1, NULL, 0, &dwRet, NULL);
  memset(szBuffer, 0, sizeof(szBuffer));
  DeviceIoControl(hFile, IOCTL_GET, NULL, 0, szBuffer, sizeof(szBuffer), &dwRet, NULL);
  printf("GET: %s, %d\n", szBuffer, dwRet);
  CloseHandle(hFile);
  return 0;
}

結果

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