Re: R4000 end-of-page bug

[Frank Wille <frank%phoenix.owl.de@localhost>]

Stephen M. Rumble wrote:

> We don't have a workaround for the EOP bug. It should really be  
> handled by the toolchain, but I don't think the gnu toolchain does (at  
> least, it didn't a few years ago). It's probably very easy to solve  
> for somebody familiar with that code, but that's definitely not me.

Ok, I agree that it's much easier, and less hackish, than wiring down
subsequent pages.

Unfortunately I'm also unable to do it.
Hmm... how was that solved under Linux?


> IRIX appears to work around it in the kernel by scanning potentially  
> executable pages and wiring down the next page such that the 'not  
> present in tlb' condition no longer holds. Of course, this has  
> limitations if more than a handful of pages could trigger the bug. I'm  
> pretty sure SGI fixed it in the toolchain and did this for backward  
> compatibility.

Maybe. Although I never had problems with a self-compiled gcc there.


> Have you checked the dmesg to confirm that you're running a broken  
> cpu? I think R4000's less than revision 2.2 have it.

I have a R4000 rev. 2.2. Does that mean 2.2 is not affected by EOP bugs?


> As for other R4k bugs, I have no idea. I didn't think they were quite  
> as nasty.

Ok. But just out of curiosity I will check if the -mfix-r4000 option changes
anything.


-- 
    _  Frank Wille (frank%phoenix.owl.de@localhost)
 _ //  http://sun.hasenbraten.de/~frank/
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