This is paxctl for controlling PaX flags on a per binary basis. PaX
is an intrusion prevention system that provides the best protection
mechanisms against memory corruption bugs. Some applications are not
compatible with certain features (due to design or bad engineering)
and therefore they have to be exempted from certain enforcements. It
is also possible to use PaX in soft mode where none of the protection
mechanisms are active by default - here paxctl can be used to turn
them on for selected programs (e.g., network daemons, programs that
process network data such as mail clients, web browsers, etc).

PaX is provided by a separate kernel patch, that you need to install 
manually. You can get it from: https://grsecurity.net/
