This is a collection of drivers that demonstrate how to allocate memory differently in the linux kernel. Additionally, some drivers also demonstrate how to share those virtual mappings between user and kernel.
The get_user_pages driver demonstrates the useage of that API. This driver shows that user memory can be mapped into kernel space. Additionally, demonstrate that these pages will never be swapped. This interface is GPL'd, and should not be used in proprietary software.
The vmap driver demonstrates how to remap 2 separately allocated pages (using alloc_page) into a single virtually contiguous block.
The vmalloc driver demonstrates how to get (struct page*) from a vmalloc allocation, so that it can be used with mmap.
The mmap driver demonstrates how to allow user programs to allocate memory backed by pages allocated by the driver with alloc_struct. You can even replace existing mappings with driver memory if you want to avoid additional memory dererefences.
The shared_memory driver demonstrates a combination of vmap and mmap driver, such that a virtually contiguous range of memory can be shared between user and kernel mode in a friendly manner.