How to flag opcodes as known/unknown?

I'm curious: Where in the code, or in any configuration file, do opcodes get flagged as "known" or "unknown"?

I'd like to turn on logging for unknown opcodes, but I keep getting spam for very common opcodes (0x012A, 0x009C, and so on). I'd like to mark these as known, so that they will no longer appear in the unknown-log.

Also, is there any interest in my patch to fix a (rare) crash bug? I posted earlier about it but didn't get any response.

Thanks!