ePMP question for entry priority rule.

[marvin-hc-liu]

Base on the pmp priority rule, the entries are statically prioritized. It means higher priority result can override lower priority entry. In this scenario, MML is set, and higher priority is S/U mode only and low priority is M mode only. The code can be tampered, and pmpcfg modified to OFF or pmpaddr modified size to change higher priority entry region. It could cause M-Mode execute new code even MML set. I must misunderstand something, this situation should be forbidden. ePMP chapter3.2, mentions : “Since PMP rules with a higher priority override rules with a lower priority, locked rules must precede non-locked rules.” It means, the priority rule has to change, and the locked entry will get higher priority even using entry 15? In above case, the address of overlap entry, the epmp result is based on M-mode property?

[jahanzebkhalid-10Xe]

No it does not mean that you locked entry will get the higher priority even if it is in the last entry.

Since PMP rules with a higher priority override rules with a lower priority, locked rules must precede non-locked rules

It means that software should always write locked rules in the entries preceding the entries with non-locked rules which also means that if software does not follow it the non-locked rule in the preceding entry will priority over locked rules which is not supposed to happen.
I hope you get my answer