I believe that what Matthew Garrett is talking about is mostly different from SELinux and AppArmor and so on. Those are all kernel features to harden user-level

I believe that what Matthew Garrett is talking about is mostly different from SELinux and AppArmor and so on. Those are all kernel features to harden user-level software in the face of vulnerabilities. Garrett is (mostly?) talking about internal kernel features to limit the damage of kernel vulnerabilities. (Many of the grsecurity changes are kernel hardening, for instance; they don't directly affect user level code.)