How does execute only memory disable privileged access never memory? The bigger problem I expect is the overhead of loosing PC-relative loads unless the hardware still allows these as instruction fetching related? Would you have to dedicated one of your 31 GPRs as the table of contents pointer similar to PowerPC’s ABI (e.g. sizeof(void()(void)) == 2sizeof(void *))?
https://blog.siguza.net/PAN/ has a nice summary of the PAN issue. Also, you can't load data under execute-only but you can execute it (e.g. by jumping there). If you are compiling under this scheme you need to tell your compiler that this is the case.
