Unexpected behavior when issuing ExecuteOnly permission on code

[huettenhain]

Consider the following code:

from icicle import Icicle, MemoryProtection

ic = Icicle('x86_64')
ic.mem_map(0x100, 0x20, MemoryProtection.ExecuteOnly)
ic.mem_write(0x100, B'\x90')
ic.reg_write('rip', 0x100)
status = ic.step(1)

print(F'run status      : {status}')
print(F'exception code  : {ic.exception_code}')
print(F'exception value : {hex(ic.exception_value)}')

When executing this under Python 3.12.6 on Windows, using icicle-emu==0.0.5, it produces the following output:

run status      : RunStatus.UnhandledException
exception code  : ExceptionCode.ExecViolation
exception value : 0x100

I would have expected the memory protection constant ExecuteOnly to allow execution, but executing code is only possible when the memory protection is at least ExecuteRead.

PS: I can see the argument that the code needs to be read before it can be executed, but in this case the ExecuteOnly permission seems to serve no purpose that I could think of.