[$] OpenBSD system-call pinning

Return-oriented programming (ROP) attacks are hard to defend against.
Partial mitigations such as address-space layout randomization, stack
canaries, and other techniques are commonly deployed to try and frustrate
ROP attacks. Now, OpenBSD is experimenting with a new
mitigation that makes it harder for attackers to make system
calls, although some security researchers have expressed doubt that it will
prove effective at stopping real-world attacks.
In his
announcement message, Theo de Raadt said that this work
'makes some specific low-level attack
methods unfeasable on OpenBSD, which will force the use of other methods.'