A common question is “how do I lock user space memory?”. The context is usually when the memory is going to be used for DMA to or from a device.
The best way is to have user space request the memory from your driver via an mmap() on a character device files. Sometimes, however, this is not feasible. In those cases, you have two choices:
– If you have control of the user space application, use the POSIX mlock() and munlock() APIs.
_ if you only have control of the driver side, use the get_user_pages() API in the kernel. lwn.net has an excellent article on get_user_pages, and common pitfalls.
Muli Ben-Yehuda's journal 
Leave a Reply