// soon as you call IoCompleteRequest.
    //

    ntStatus = Irp->IoStatus.Status;

    IoCompleteRequest(Irp, IO_NO_INCREMENT);

    //
    // We never have pending operation so always return the status code.
    //

    return ntStatus;
}

VOID
MapMemUnload(
    IN PDRIVER_OBJECT pDriverObject
    )
/*++

Routine Description:

    Just delete the associated device & return.

Arguments:

    DriverObject - pointer to a driver object

Return Value:


--*/
{
    WCHAR                  deviceLinkBuffer[]  = L"\\DosDevices\\MAPMEM";
    UNICODE_STRING         deviceLinkUnicodeString;

    //
    // Free any resources
    //

    //
    // Delete the symbolic link
    //

    RtlInitUnicodeString (&deviceLinkUnicodeString,
                          deviceLinkBuffer
                          );

    IoDeleteSymbolicLink (&deviceLinkUnicodeString);

    //
    // Delete the device object
    //

    MapMemKdPrint (("MAPMEM.SYS: unloading\n"));

    IoDeleteDevice (pDriverObject->DeviceObject);
}

NTSTATUS
MapMemMapTheMemory(
    IN PDEVICE_OBJECT DeviceObject,
    IN OUT PVOID      IoBuffer,
    IN ULONG          InputBufferLength,
    IN ULONG          OutputBufferLength
    )
/*++

Routine Description:

    Given a physical address, maps this address into a user mode process's
    address space

Arguments:

    DeviceObject       - pointer to a device object

    IoBuffer           - pointer to the I/O buffer

    InputBufferLength  - input buffer length

    OutputBufferLength - output buffer length

Return Value:

    STATUS_SUCCESS if sucessful, otherwise
    STATUS_UNSUCCESSFUL,
    STATUS_INSUFFICIENT_RESOURCES,
    (other STATUS_* as returned by kernel APIs)

--*/
{

    PPHYSICAL_MEMORY_INFO ppmi = (PPHYSICAL_MEMORY_INFO) IoBuffer;

    INTERFACE_TYPE     interfaceType;
    ULONG              busNumber;
    PHYSICAL_ADDRESS   physicalAddress;
    ULONG              length;
    UNICODE_STRING     physicalMemoryUnicodeString;
    OBJECT_ATTRIBUTES  objectAttributes;
    HANDLE             physicalMemoryHandle  = NULL;
    PVOID              PhysicalMemorySection = NULL;
    ULONG              inIoSpace, inIoSpace2;
    NTSTATUS           ntStatus;
    PHYSICAL_ADDRESS   physicalAddressBase;
    PHYSICAL_ADDRESS   physicalAddressEnd;
    PHYSICAL_ADDRESS   viewBase;
    PHYSICAL_ADDRESS   mappedLength;
    BOOLEAN            translateBaseAddress;
    BOOLEAN            translateEndAddress;
    PVOID              virtualAddress;

    if ( ( InputBufferLength  < sizeof (PHYSICAL_MEMORY_INFO) ) ||
         ( OutputBufferLength < sizeof (PVOID) ) )
    {
       MapMemKdPrint (("MAPMEM.SYS: Insufficient input or output buffer\n"));

       ntStatus = STATUS_INSUFFICIENT_RESOURCES;

       goto done;
    }

    interfaceType          = ppmi->InterfaceType;
    busNumber              = ppmi->BusNumber;
    physicalAddress        = ppmi->BusAddress;
    inIoSpace = inIoSpace2 = ppmi->AddressSpace;
    length                 = ppmi->Length;


    //
    // Get a pointer to physical memory...
    //
    // - Create the name
    // - Initialize the data to find the object
    // - Open a handle to the oject and check the status
    // - Get a pointer to the object
    // - Free the handle
    //

    RtlInitUnicodeString (&physicalMemoryUnicodeString,
                          L"\\Device\\PhysicalMemory");

    InitializeObjectAttributes (&objectAttributes,
                                &physicalMemoryUnicodeString,
                                OBJ_CASE_INSENSITIVE,
                                (HANDLE) NULL,
                                (PSECURITY_DESCRIPTOR) NULL);

    ntStatus = ZwOpenSection (&physicalMemoryHandle,
                              SECTION_ALL_ACCESS,
                              &objectAttributes);

    if (!NT_SUCCESS(ntStatus))
    {
        MapMemKdPrint (("MAPMEM.SYS: ZwOpenSection failed\n"));

        goto done;
    }

    ntStatus = ObReferenceObjectByHandle (physicalMemoryHandle,
                                          SECTION_ALL_ACCESS,
                                          (POBJECT_TYPE) NULL,
                                          KernelMode,
                                          &PhysicalMemorySection,
                                          (POBJECT_HANDLE_INFORMATION) NULL);

    if (!NT_SUCCESS(ntStatus))
    {
        MapMemKdPrint (("MAPMEM.SYS: ObReferenceObjectByHandle failed\n"));

        goto close_handle;
    }

    //
    // Initialize the physical addresses that will be translated
    //

    physicalAddressEnd = RtlLargeIntegerAdd (physicalAddress,
                                             RtlConvertUlongToLargeInteger(
                                             length));

    //
    // Translate the physical addresses.
    //

    translateBaseAddress =
        HalTranslateBusAddress (interfaceType,
                                busNumber,
                                physicalAddress,
                                &inIoSpace,
                                &physicalAddressBase);

    translateEndAddress =
        HalTranslateBusAddress (interfaceType,
                                busNumber,
                                physicalAddressEnd,
                                &inIoSpace2,
                                &physicalAddressEnd);

    if ( !(translateBaseAddress && translateEndAddress) ) {
        MapMemKdPrint (("MAPMEM.SYS: HalTranslatephysicalAddress failed\n"));

        ntStatus = STATUS_UNSUCCESSFUL;

        goto close_handle;
    }

    //
    // Calculate the length of the memory to be mapped
    //

    mappedLength = RtlLargeIntegerSubtract (physicalAddressEnd,
                                            physicalAddressBase);
    //
    // If the mappedlength is zero, somthing very weird happened in the HAL
    // since the Length was checked against zero.
    //

    if (mappedLength.LowPart == 0) {
        MapMemKdPrint (("MAPMEM.SYS: mappedLength.LowPart == 0\n"));

        ntStatus = STATUS_UNSUCCESSFUL;

        goto close_handle;
    }

    length = mappedLength.LowPart;

    //
    // If the address is in io space, just return the address, otherwise
    // go through the mapping mechanism
    //

    if (inIoSpace) {
        *((PVOID *) IoBuffer) = (PVOID) physicalAddressBase.LowPart;
    } else {
        //
        // initialize view base that will receive the physical mapped
        // address after the MapViewOfSection call.
        //

        viewBase = physicalAddressBase;

        //
        // Let ZwMapViewOfSection pick an address
        //

        virtualAddress = NULL;

        //
        // Map the section
        //

        ntStatus = ZwMapViewOfSection (physicalMemoryHandle,
                                       (HANDLE) -1,
                                       &virtualAddress,
                                       0L,
                                       length,
                                       &viewBase,
                                       &length,
                                       ViewShare,
                                       0,
                                       PAGE_READWRITE | PAGE_NOCACHE);

        if (!NT_SUCCESS(ntStatus))
        {
            MapMemKdPrint (("MAPMEM.SYS: ZwMapViewOfSection failed\n"));

            goto close_handle;
        }

        //
        // Mapping the section above rounded the physical address down to the
        // nearest 64 K boundary. Now return a virtual address that sits where
        // we want by adding in the offset from the beginning of the section.
        //

        (ULONG) virtualAddress += (ULONG)physicalAddressBase.LowPart -
                                  (ULONG)viewBase.LowPart;

        *((PVOID *) IoBuffer) = virtualAddress;

    }

    ntStatus = STATUS_SUCCESS;

close_handle:
    ZwClose (physicalMemoryHandle);

done:
    return ntStatus;
}