[rep_lodsb]

It has nothing to do with being unable to run 16-bit code, that's a myth.

https://man7.org/linux/man-pages/man2/modify_ldt.2.html

Set seg_32bit=0 and you can create 16-bit code and data segments. Still works on 64 bit. What's missing is V86 mode, which emulates the real mode segmentation model.

[anthk]

That can be trapped for sure.