  Performance/security trade-off is widely noticed in CFI research, however, we
observe that not every CFI scheme is subject to the trade-off. Motivated by the
key observation, we ask three questions. Although the three questions probably
cannot be directly answered, they are inspiring. We find that a deeper
understanding of the nature of the trade-off will help answer the three
questions. Accordingly, we proposed the GPT conjecture to pinpoint the
trade-off in designing CFI schemes, which says that at most two out of three
properties (fine granularity, acceptable performance, and preventive
protection) could be achieved.
