Kernel Mode Driver Framework >> C/C++ (PNP) >> IOCTL

METHOD_BUFFERED

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參考資訊：
1. Source Code

METHOD_BUFFERED的處理手法就是I/O Manager會在Kernel配置一塊跟User Buffer一樣大小的記憶體，Driver只能對該配置的記憶體做讀寫的操作，而讀寫的操作都會同步回User Buffer，也因為結果都需要整塊複製回User Buffer，因此，METHOD_BUFFERED的方式會消耗比較大的資源，速度也比較慢。

記憶體指標：

	Buffer	Length
Input	Step 1. WdfRequestRetrieveInputMemory() Step 2. WdfMemoryGetBuffer()	傳入的第四個參數
Output	Step 1. WdfRequestRetrieveOutputMemory() Step 2. WdfMemoryGetBuffer()	傳入的第三個參數

main.c

#include <ntddk.h>
#include <wdf.h>

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

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

char szBuffer[255]={0};

void IrpFileCreate(WDFDEVICE Device, WDFREQUEST Request, WDFFILEOBJECT FileObject)
{  
  DbgPrint("IrpFieCreate");
  WdfRequestComplete(Request, STATUS_SUCCESS);
}

void IrpFileClose(WDFFILEOBJECT FileObject)
{
  DbgPrint("IrpFieClose");
}

void IrpIOCTL(WDFQUEUE Queue, WDFREQUEST Request, size_t OutputBufferLength, size_t InputBufferLength, ULONG IoControlCode)
{
  ULONG len;
  WDFMEMORY memory;
  
  switch(IoControlCode){
  case IOCTL_SET:
    DbgPrint("IOCTL_SET");
    WdfRequestRetrieveInputMemory(Request, &memory);
    WdfMemoryCopyToBuffer(memory, 0, szBuffer, InputBufferLength);
    DbgPrint("Buffer: %s, Length:%d", szBuffer, InputBufferLength);
    WdfRequestSetInformation(Request, InputBufferLength);
    break;
  case IOCTL_GET:
    DbgPrint("IOCTL_GET");
    WdfRequestRetrieveOutputMemory(Request, &memory);
    WdfMemoryCopyFromBuffer(memory, 0, szBuffer, OutputBufferLength);
    len = strlen(szBuffer) + 1;
    WdfRequestSetInformation(Request, len);
    break;
  }
  WdfRequestComplete(Request, STATUS_SUCCESS);
}

NTSTATUS AddDevice(WDFDRIVER Driver, PWDFDEVICE_INIT pDeviceInit)
{
  WDFDEVICE device;
  UNICODE_STRING suDevName;
  UNICODE_STRING szSymName;
  WDF_FILEOBJECT_CONFIG file_cfg;
  WDF_IO_QUEUE_CONFIG ioqueue_cfg;
  
  RtlInitUnicodeString(&suDevName, DEV_NAME);
  RtlInitUnicodeString(&szSymName, SYM_NAME);
  WdfDeviceInitAssignName(pDeviceInit, &suDevName);
  
  WdfDeviceInitSetIoType(pDeviceInit, WdfDeviceIoBuffered);
  WDF_FILEOBJECT_CONFIG_INIT(&file_cfg, IrpFileCreate, IrpFileClose, NULL);
  WdfDeviceInitSetFileObjectConfig(pDeviceInit, &file_cfg, WDF_NO_OBJECT_ATTRIBUTES);
  WdfDeviceCreate(&pDeviceInit, WDF_NO_OBJECT_ATTRIBUTES, &device);
  WdfDeviceCreateSymbolicLink(device, &szSymName);
  
  WDF_IO_QUEUE_CONFIG_INIT_DEFAULT_QUEUE(&ioqueue_cfg, WdfIoQueueDispatchSequential);
  ioqueue_cfg.EvtIoDeviceControl = IrpIOCTL;
  return WdfIoQueueCreate(device, &ioqueue_cfg, WDF_NO_OBJECT_ATTRIBUTES, WDF_NO_HANDLE);
}

NTSTATUS DriverEntry(PDRIVER_OBJECT pOurDriver, PUNICODE_STRING pRegistry)
{
  WDF_DRIVER_CONFIG config;

  WDF_DRIVER_CONFIG_INIT(&config, AddDevice);
  return WdfDriverCreate(pOurDriver, pRegistry, WDF_NO_OBJECT_ATTRIBUTES, &config, WDF_NO_HANDLE);
}

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。

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_BUFFERED, FILE_ANY_ACCESS)
#define IOCTL_GET CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_BUFFERED, 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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