Here comes a patch to enable exceptions after exceptions vector code is copied (i.e after relocation). I tested it with my board (PPC 405), I also changed 440 and IOP480 target but without testing...
I run the MAKEALL script : there are no errors, warnings was not due to this patch.
CHANGELOG : * cpu/ppc4xx/start.S : exceptions are enabled after relocation.
About XMD, as I thought the spurious exception comes infinitely... So there is no easy way to fix it. If you apply this patch (this is an easy way to detect this spurious exception), you should add at the end of doc/README.ml300 : ======================== 6. Warning ----------
It was reported that XMD makes (sometimes) a spurious "Machine Check Exception". When debugging, if you are sure that this exception doesn't come from your system, comment this line into cpu/ppc4xx/start.S :
addi r7,r0,0x1000 /* set ME bit (Machine Exceptions) */
========================
Regards, Cedric VINCENT