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

METHOD_IN_DIRECT、METHOD_OUT_DIRECT

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參考資訊：
1. Source Code

METHOD_IN_DIRECT、METHOD_OUT_DIRECT的概念就是直接Mapping User Buffer，然後驅動程式使用該Mapped的MDL(Memory Description List)操作，相較於METHOD_BUFFERED，因為不須I/O Manager更新回User Buffer>，因此，效率會比較好，而相比File的DO_DIRECT_IO，IOCTL細分成IN和OUT兩種，這是因為IOCTL有區分Input和Output Buffer的緣故，因此，會有方向性的考量，Microsoft針對這部份的描述，僅說明MDL描述會有讀>寫存取方向的區分，但是司徒實際測試，發現DeviceIoControl()的Input和Output Buffer是可以混用的，意思就是Input Buffer可以充當Input或Output Buffer使用，而Output Buffer也可以充當Input或Output Buffer使用，只要驅動程式跟User Application定義好即可，當然，METHOD_IN_DIRECT和METHOD_OUT_DIRECT也是可以混用的，關於這部份的細節，有興趣的使用者可以研讀WRK代碼，不過，深怕未知問題可能發生，建議還是依照Microsoft規定去撰寫驅動程式會比較保險。

Microsoft針對I/O部份的說明：
buffer-descriptions-for-i-o-control-codes

記憶體指標：

	Buffer	Length
Input	(Irp) AssociatedIrp.SystemBuffer	(IrpStack) Parameters.DeviceIoControl.InputBufferLength
Output	(MDL) MmGetSystemAddressForMdlSafe	(IrpStack) Parameters.DeviceIoControl.OutputBufferLength

main.c

#include <wdm.h>

#define IOCTL_SET CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_IN_DIRECT, FILE_ANY_ACCESS)
#define IOCTL_GET CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_OUT_DIRECT, 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;
  PUCHAR pBuf;
  PIO_STACK_LOCATION psk = IoGetCurrentIrpStackLocation(pIrp);

  switch(psk->Parameters.DeviceIoControl.IoControlCode){
  case IOCTL_SET:
    DbgPrint("IOCTL_SET");
    Len = psk->Parameters.DeviceIoControl.InputBufferLength;
    memcpy(szBuffer, pIrp->AssociatedIrp.SystemBuffer, Len);
    DbgPrint("Buffer: %s, Length: %d", szBuffer, Len);
    break;
  case IOCTL_GET:
    DbgPrint("IOCTL_GET");
    pBuf = MmGetSystemAddressForMdlSafe(pIrp->MdlAddress, LowPagePriority);
    Len = strlen(szBuffer)+1;
    memcpy(pBuf, 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_IN_DIRECT, FILE_ANY_ACCESS)
#define IOCTL_GET CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_OUT_DIRECT, 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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