Summary: The author only attempt to prove the performance overhead optimization using Intel PT for online verification. They claim to verify the enforcement policy for both backward and forward indirect control transfer with different strictness of policy when they completely discard the discussion regarding how they achieve these policies to verify with.
Design: To efficiently extract the information from Intel PT trace log, they propose a fast lookup design. The basic block to derefered pointer lookup is basically a mechanism similar to a cache. They hardly describe anything related their Coarse-grained and Fine-grained policy, but as they only trace TIP packet in Intel PT trace, they at-most can use indirect control transfer information based policy. They simply omit enough discussion on stateful policy for forward control transfer by mentioning they use a similar approach to PathArmor.
Advantage: They briefed about advanced topics like how to handle context switch, process fork etc. when they omit much needed basic discussion.
Disadvantage: The writing is a complete hide and seek game. It misses much of the basic discussion. It completely discards anything about how they get the policies. However, they put enforcement in a parallel process and enforce strict restriction in sensitive syscall entry. This overall concise the whole idea of control flow integrity. Hence, it is not meaningful how the performance overhead they achieve.
Discussion: An offline debugging hardware should not be considered for online verification, it will be just a waste of time.