Re: earm(v5) not working on RPi

[Robert Swindells <rjs%fdy2.co.uk@localhost>]

It looks like the illegal instruction traps are being triggered by some
SWP instructions in libc.

These instructions are deprecated in ARMv6 and above.

It seems that there is a mode that ARMv7 processors can run in where
they disable these instructions and generate an exception if one is
executed.

The idea is that the kernel trap handler maps them onto LDREX and STREX
instructions. Linux does seem to have code to do this.

The SWP instructions are not in ARMv8 at all so if we want to be able to
run older arm binaries then we probably want to emulate them there.