Windows驱动开发-设备读写方式

pDevObj->Flags |= DO_BUFFERED_IO

UCHAR OutputBuffer[10];
DWORD RetLen = 0;
readfile(hDevice,OutputBuffer,sizeof(OutputBuffer),&RetLen,NULL);

UCHAR* OutputBuffer= (UCHAR*)pIrp->AssociatedIrp.SystemBuffer;

//得到当前堆栈
PIO_STACK_LOCATION stack = IoGetCurrentIrpStackLocation(pIrp);
//得到readfile缓冲区大小
ULONG cbread = stack->Parameters..Read.Length;
//得到writefile缓冲区大小
ULONG cbwrite = stack->Parameters.Write.Length;

UCHAR* OutputBuffer= (UCHAR*)pIrp->AssociatedIrp.SystemBuffer;
ULONG cbread = stack->Parameters..Read.Length;
memcpy(OutputBuffer,0xBB,cbread);

NTSTATUS DispatchRead(IN PDEVICE_OBJECT pDevObj, IN PIRP pIrp) 
{
    KdPrint(("Enter DispatchRead\n"));
    //对一般IRP的简单操作，后面会介绍对IRP更复杂的操作
    NTSTATUS status = STATUS_SUCCESS;
    PIO_STACK_LOCATION stack = IoGetCurrentIrpStackLocation(pIrp);
    ULONG ulReadLength = stack->Parameters.Read.Length;    
    // 完成IRP
    //设置IRP完成状态
    pIrp->IoStatus.Status = status;
    //设置IRP操作了多少字节
    pIrp->IoStatus.Information = ulReadLength;    
    memset(pIrp->AssociatedIrp.SystemBuffer,0xAA,ulReadLength);
    //处理IRP
    IoCompleteRequest( pIrp, IO_NO_INCREMENT );
    KdPrint(("Leave DispatchRead\n"));
    return status;
}

pDevObj->Flags |= DO_DIRECT_IO

typedef struct _MDL {
  struct _MDL *Next;
  CSHORT Size;
  CSHORT MdlFlags;
  struct _EPROCESS *Process;
  PVOID MappedSystemVa;
  PVOID StartVa;               //给出了用户缓冲区的虚拟地址，第一个页地址，这个地址仅在拥有数据缓冲区的用户模式进程上下文中才有效
  ULONG ByteCount;       //是缓冲区的字节长度
  ULONG ByteOffset;       //是缓冲区起始位置在一个页帧中的偏移值，那么缓冲区的首地址是mdl->StartVa+mdl->ByteOffset
} MDL, *PMDL;

//用户模式调用readfile:
UCHAR OutputBuffer[10];
DWORD RetLen = 0;
readfile(hDevice,OutputBuffer,sizeof(OutputBuffer),&RetLen,NULL);
//内核模式得到要读取的字节数：（与以缓冲区读写方式一样）
//得到当前堆栈
PIO_STACK_LOCATION stack = IoGetCurrentIrpStackLocation(pIrp);
//得到readfile要读取的字节数
ULONG cbread = stack->Parameters..Read.Length;
//另外，通过IRP的pIrp->MdlAddress得到MDL数据结构，这个结构描述了被锁定的缓冲区的内存。

NTSTATUS DispathRead(IN PDEVICE_OBJECT pDevObj,IN PIRP pIrp) 
{
    KdPrint(("Enter DispathRead\n"));

    PDEVICE_EXTENSION pDevExt = (PDEVICE_EXTENSION)pDevObj->DeviceExtension;
    NTSTATUS status = STATUS_SUCCESS;

     PIO_STACK_LOCATION stack = IoGetCurrentIrpStackLocation(pIrp);

     ULONG ulReadLength = stack->Parameters.Read.Length;//得到读取的长度
    KdPrint(("ulReadLength:%d\n",ulReadLength));

    ULONG mdl_length = MmGetMdlByteCount(pIrp->MdlAddress);       //mdl虚拟内存的长度
    PVOID mdl_address = MmGetMdlVirtualAddress(pIrp->MdlAddress); //虚拟内存的起始地址
    ULONG mdl_offset = MmGetMdlByteOffset(pIrp->MdlAddress);      //虚拟内存首地址在第一页的偏移量
    
    KdPrint(("mdl_address:0X%08X\n",mdl_address));
    KdPrint(("mdl_length:%d\n",mdl_length));
    KdPrint(("mdl_offset:%d\n",mdl_offset));

    if (mdl_length!=ulReadLength)
    {
        //MDL的长度应该和读长度相等，否则该操作应该设为不成功
        pIrp->IoStatus.Information = 0;
        status = STATUS_UNSUCCESSFUL;
    }else
    {
        //用MmGetSystemAddressForMdlSafe得到MDL在内核模式下的映射,被映射到内核模式下的内存地址，必定在0X80000000-0XFFFFFFFF之间
        PVOID kernel_address = MmGetSystemAddressForMdlSafe(pIrp->MdlAddress,NormalPagePriority);
        KdPrint(("kernel_address:0X%08X\n",kernel_address));
        memset(kernel_address,0XAA,ulReadLength);        //对内核模式下的内存地址进行操作
        pIrp->IoStatus.Information = ulReadLength;    //设置实际操作字节数
    }
    
    pIrp->IoStatus.Status = status;
    
    IoCompleteRequest( pIrp, IO_NO_INCREMENT );
    KdPrint(("Leave DispatchRead\n"));

    return status;
}