stack-register checking
https://marc.info/?l=openbsd-tech&m=152035796722258&w=2 [marc.info]
2018-03-06 23:35
How about we add another new permission! This is not a hardware permission, but a software permission. It is opportunistically enforced by the kernel.
the permission is MAP_STACK. If you want to use memory as a stack, you must mmap it with that flag bit.