Technique 2: Using IoIs32bitProcess

In cases where it is not practical to define separate IOCTL or FSCTL control codes for I/O requests from 32-bit and 64-bit applications, it is left to the driver to determine which type of application sent the I/O request. The 64-bit version of Microsoft Windows introduces a new kernel-mode routine, IoIs32bitProcess, that detects whether the current I/O request originated in a 32-bit user-mode process. Its prototype is:

BOOLEAN
  IoIs32bitProcess(
    _In_opt_ PIRP Irp  // NULL for fast I/O call, IRP otherwise
    );

IoIs32bitProcess returns TRUE if the originator of the current I/O request is a 32-bit user-mode application.

The following code sample shows how to use IoIs32bitProcess:

typedef UINT32 POINTER_32 PVOID32;

typedef struct _IOCTL_PARAMETERS
{
    PVOID   Addr;
    SIZE_T  Length;
    HANDLE  Handle;
} IOCTL_PARAMETERS, *PIOCTL_PARAMETERS;

typedef struct _IOCTL_PARAMETERS_32
{
    PVOID32  Addr;
    INT32    Length;
    PVOID32  Handle;
} IOCTL_PARAMETERS_32, *PIOCTL_PARAMETERS_32;

...

IOCTL_PARAMETERS LocalParam;

if (IoIs32bitProcess(Irp))
{ 
    /* 32-bit process IOCTL */
    PIOCTL_PARAMETERS_32 params32;

    params32 = (PIOCTL_PARAMETERS_32)(Irp->AssociatedIrp.SystemBuffer);
    if (irpSp->Parameters.DeviceIoControl.InputBufferLength < sizeof(IOCTL_PARAMETERS_32))
    {
        status = STATUS_INVALID_PARAMETER;
    }
    else
    {
        LocalParam.Addr = Ptr32ToPtr(params32->Addr);
        LocalParam.Handle = Handle32ToHandle(params32->Handle);
        LocalParam.Length = params32->Length;

        /* Handle the IOCTL here. */
        ...

        status = STATUS_SUCCESS;
        Irp->IoStatus.Information = 0;
    }
}
else
{  
    /* 64-bit process IOCTL */
    PIOCTL_PARAMETERS params;

    params = (PIOCTL_PARAMETERS)(Irp->AssociatedIrp.SystemBuffer);
    if (irpSp->Parameters.DeviceIoControl.InputBufferLength < sizeof(IOCTL_PARAMETERS))
    {
        status = STATUS_INVALID_PARAMETER;
    }
    else
    {
        RtlCopyMemory(&LocalParam, params, sizeof(IOCTL_PARAMETERS));

        /* Handle the IOCTL here. */
        ...

        status = STATUS_SUCCESS;
    }
    Irp->IoStatus.Information = 0;
}