POWER Gets SMAP-Like Functionality, 32-bit KASAN Support On Linux 5.2

Not only has the Linux 5.2 kernel been exciting on the x86_64 and ARM front, but there is also a fair amount of new IBM POWER architecture updates that landed for this summer 2019 kernel update.

First up, POWER is now supporting a kernel user-space access/execution prevention technology. This feature is similar to Intel's SMAP (Supervisor Mode Access Prevention) and similar SMEP / PAN / PXN technologies. This feature will prevent the kernel from accidentally accessing user-space outside of certain calls or ever executing user-space.

Also on the security front but for 32-bit POWER is support for the Kernel Address Sanitizer (KASAN). This Linux 5.2 merge window has also brought a rewrite of more code into C around their idle handling bits, a fast path entry for syscalls on 32-bit CPUs yielding a 12~17% improvement in a syscall benchmark, and various other low-level improvements.

More details on this new material via this Git merge.