Randomizing the KUSER_SHARED_DATA Structure on Windows

Windows 10 made a lot of improvements in Kernel Address Space Layout Randomization (KASLR) that increases the cost of exploitation, particularly for remote code execution exploits. Many kernel virtual address space (VAS) locations including kernel stacks, pools, system PTEs etc. are randomized. A well-known exception to this is the KUSER_SHARED_DATA structure which is a page of memory that has always been traditionally mapped at a fixed virtual address in the kernel.