/DRIVER (Windows NT Kernel Mode Driver)
Use this linker option to build a Windows NT kernel mode driver. The linker will perform some special optimizations if this option is selected. The UPONLY keyword causes the linker to add the IMAGE_FILE_UP_SYSTEM_ONLY bit to the characteristics in the output header to specify that it is a uniprocessor (UP) driver. The operating system will refuse to load a UP driver on a multiprocessor (MP) system.