[OpenBIOS] memory corruption with "read" $call-method (sparc32)

[Artyom Tarasenko]

2010/4/9 Mark Cave-Ayland <mark.cave-ayland at siriusit.co.uk>:
> Artyom Tarasenko wrote:
>
>> Yes, it's a bunch of reads.  The first 9 reads (f00890ec-f00a10ec) don't
>>  do any visible harm, but  f00a30ec is lethal. Under OBP there is more
>> than 30 reads after this point. Didn't count them after this point.
>
> Well given that the same disk code for SPARC64 is reading in several megs at
> a time without any problems now, I think if there was an issue then it could
> be in one of the hardware drivers or possibly the MMU.
>
> Wait a minute. I've just noticed that arch/sparc32 hasn't been updated to
> use the new libopenbios/ofmem_common.c API which will handle the physical
> memory allocation, virtual memory allocation and mappings for you. And this
> would explain why CONFIG_DEBUG_OFMEM wouldn't have actually output anything
> :(
>
> I'd suggest a good starting point for you would be to first switch over to
> the libopenbios/ofmem_common.c API in arch/sparc32/lib.c using
> arch/sparc64/lib.c as a reference, and then similarly update
> arch/sparc32/romvec.c where appropriate.

If they are so similar, why isn't the code located somewhere in sparc-common?

>I also seem to recall that Blue had
> a compile time #define in Qemu that would dump the page table contents and
> so you can use this to verify that the OpenBIOS code is correct. With these
> two things in place, then you have all the debugging information you need :D

Within the next months I only have time to test, not to develop/refactor.

A quick analysis has shown that obp_dumb_memalloc is probably too dumb:
it maps f00aXXXX to 0104xxxx (which seems to be already mapped to 0104xxxx).

totmap[0].num_bytes is always initialized with value 2088960. Is it the size
of already mappED memory? Then why does obp_dumb_memalloc decrease
this amount? If it is mappABLE, then the value 2088960 seems to be quite small.

-- 
Regards,
Artyom Tarasenko

solaris/sparc under qemu blog: http://tyom.blogspot.com/