[$] Hardening the kernel with allocation tokens and bootpatch-SLR

There is a lot of work going into eliminating exploitable bugs from thekernel and preventing the addition of new ones. Even if this work ismaximally successful, though, there is no chance that the kernel will befree of these bugs anytime soon. Thus, there is also ongoing interest inhardening the kernel to make the existing bugs more difficult to exploit.The upcoming 7.2 kernel release will include a change to how dynamicallyallocated structures are placed in memory to make them harder to overwrite,while a project to randomize structure layout at boot time has a ratherlonger timeline.