Are there any tools to make C drivers written for 32 bit linux, work in 64bit linux?

I am contracting for a company and we are attempting to port a 32-bit Linux driver to a 64-bit Linux system. Are there any tools that are capable of doing this conversion for us, or will it need to be manually ported? If it must be manually done, do 64-bit Linux systems support the use of C++ in a kernel module build format?

Thanks in advance for your help!