Hi,
It appeard that on my mpc862 target I had also this problem. I am using
ELDK3.1.1 which includes a 2.4.25 kernel.
The symptoms however were:
Large application (20MB c++, mostly shared-libs) crashes (sigseg) at
startup BEFORE main() is called.
Attempts to debug the application also fail: the debugger crashes
also (sigseg).
I didn't change the C-lib, I took the 2.4.30/arch/ppc/kernel/head_8xx.S
file and copied this over the 2.4.25 head_8xx.S file.
In the 2.4.30 version there is a piece of code mentioning the dcbX
instruction problems.
Has anyone an idea why only this large application failed? busybox_1.0
and more applications work fine.
system is a: mcp862/32Mb SDRAM started from u-boot 0.4.1,
kernel enhanced with atm/utopia driver.
This driver causes the CPM sometimes to hang when performing a memset,
can this be caused by the same problem?
(CPM stops responding, console buffers are not flused anymore and
kernel stops waiting for buffers)
Greetings,
Theo Gjaltema
Yuli Barcohen schreef:
>>>>>>Marcelo Tosatti writes:
>>>>>>
>>>>>>
>
> Yuli> [...deleted...]
>
> Jason> Ha. Funny. The glibc powerpc maintainer doesn't want any
> Jason> embedded fixes in the mainline. Last I checked, that was for
> Jason> 'the tools vendors' to fix.
>
> Jason> "We won't work around processor bugs" is their philosophy.
>
> Yuli> [...deleted...]
>
> Yuli> I investigated the problem a bit when I had trouble with a
> Yuli> self-compiled glibc a year or so ago. IIRC, I found bug in the
> Yuli> memset code, not in the chip. The code was just wrong for
> Yuli> cache line sizes not equal to 32. So memset.S is good for 60x
> Yuli> series (PQII included) but for 8xx it fails.
>
> Marcelo> I suppose you didnt actually use dcbz for userspace memset
> Marcelo> on 8xx?
>
>Standard glibc did. After the fix, it doesn't do it any more on our
>systems.
>
> Yuli> We use dcbX instructions in some kernel drivers and since we
> Yuli> never had any problems with those drivers I'm a bit surprised
> Yuli> to hear that all 8xx chips have got that bug.
>
> Marcelo> The problem is that the DAR register is correctly unset (it
> Marcelo> comes as NULL IIRC) on pagefaults for the dcbz
> Marcelo> instruction. The dcbz instructions you issue are probably
> Marcelo> always works on kernel addresses whose pagetables are
> Marcelo> present?
>
>It's not dcbz, it's dcbi/dcbf. And yes, they work on kernel addresses. I
>never investigated if the page tables are present or not because there
>were no problems.
>
> Marcelo> Joakim has developed a workaround for the
> Marcelo> problem... although I promised him several times to test it
> Marcelo> I never managed to get dcbz to work on the kernel copying
> Marcelo> functions. :(
>
>[...patch deleted...]
>
>Well, if I manage to find time, I'll try it. No timetables though. I'm
>not sure if using dcbz in user-space memset is such a great
>optimisation. It well can be an example of over-engineering.
>
>
>
