Re: [hatari-devel] 030 exceptions on auto-increment instructions

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 13/04/2019 à 01:08, Eero Tamminen a écrit :
> Hi Toni,
>
> While mailing about some issue I was hitting with m68k Linux, it
> was noticed that Linux fault handler gives different register
> values under Hatari than under real 030.
>
> Faulting instruction is:
>      $00249f5a : 0e98 2000  moves.l   (a0)+,d2
>
> A0 reg content is struct member offset address, but struct was NULL.
>
> Under Hatari Falcon emulation, Linux fault handler reg dump showed A0
> value to be 0x04, whereas with under real 030 Mac it showed 0x08.
>
> Environments weren't completely identical, so it's not 100% sure
> this is WinAUE CPU core issue, but I think it warrants checking.
>
>
> If you can have recent Linux version (5.x or slightly older, with
> SYSRQ config option enabled) under WinUAE and real m68k HW, this
> is easy to trigger.  Just do:
>      # echo t > /proc/sysrq-trigger

Hi

hard to tell without the context of this instruction, what is the value 
of SFC before the MOVES ?

Something must be missing also, because if A0=0 before MOVES, then 
"MOVES.L (A0)+,D2" can increment or not A0 before the exception trigger 
(depending on the microcode order for this instruction, I didn't check).

But in the end A0 will be either 0 or 4, but I don't see how it could be 
8, or it would mean that a 2nd (A0)+ instruction could be executed under 
030 Mac.

It would be better to compare a real 030 falcon with Hatari (remember 
that under Atari's the lowest 0x800 bytes of RAM require supervisor 
access, maybe this makes a difference).

Nicolas