CHERI instruction map and differences

[trevorcarlson]

One idea, to both help with the standardization process, and help those that understand CHERI migrate to Capstone, might be to have a list of mappings from CHERI to Capstone.

In addition, we might consider having a set of instructions listed that are common between CHERI and Capstone, that could form the base of a standard that all capability systems will need. Then, implementation-specific versions can be on top.

[jasonyu1996]

We can start by adding one section specifically discussing the relationship between Capstone and CHERI. I'll think about the second suggestion of extracting a core for all capability systems. It's tricky as we don't want it to be too broad supporting every conceivable capability system as it would likely end up being useless. So it's actually gonna be opinionated regarding what features are most important for a capability system and therefore worth supporting.

[jasonyu1996]

@trevorcarlson I have added an appendix talking about this. It can be viewed here https://jason.kisp.ml/specs-revs/by-branch/cheri-cmp/

It's now an instruction mapping table and a feature matrix. I'll think about two things

• For some of the designs present in CHERI but not in Capstone, how important are they? Can they be supported on Capstone through other means? Can we easily add support for them if necessary?
• For those instructions in the mapping table, many are the basic capability manipulation instructions which will likely be part of any capability-based system. We can perhaps unify the instruction formats and mnemonics with theirs.