Re: [hatari-devel] Linux user-space crashes (was: SCU/VME register access)

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 17/06/2024 à 16:33, Eero Tamminen a écrit :
> > Is that what you mean with "User-space programs crash when data-cache 
> > emulation is enabled" or is this another scenario ?
>
> Yes, it's that scenario.  The exact issues have changed from one Hatari 
> version to another, but the Busybox/Glibc one has never behaved 
> correctly when data-cache is enabled (with MMU, without which Linux does 
> not work).
>
> It could be something related to switching between kernel & user-space 
> on each syscall (of which Glibc does a lot), and everything that happens 
> then:
> - MMU mapping changes
> - register content restoration
> (- exceptions)
>
> Because all Busybox tools do not crash, mostly just things that deal 
> with HW IO like disk, it could be Hatari bugs in its IO cache flushing.

Hi

I made some tries with --ide-master bb-rootfs.img (CPU MMU is enabled in 
all cases) :

 - no prefetch, no CE, no data cache : 'ls' works, no segfault

 - prefetch, no CE, no data cache : segfault

 - CE, no data cache : segfault

 - no prefetch, no CE, data cache ON : no segfault

This looks different to what you wrote "has never behaved correctly when 
data-cache is enabled", because in my tests I see that it works with 
data cache and the cause of the segfault would be related to the 
difference between normal and prefetch (as CE also includes prefetch we 
can leave it on the side for now)

Could you check if you still get segfault with data cache on and no 
prefetch / no CE ?

Nicolas