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RE: eCos Code at address 0x000? (MPC8270)


Gary Thomas wrote:
>
> On Tue, 2004-05-18 at 11:44, Tim Sohacki wrote:
> > Hello,
> >  
> > On the MPC8270, it appears that eCos has some code running at (or 
> > near) address 0. I suspect this is eCos specific because the first
PPC 
> > interrupt vector stub is at 0x100.
> >  
> > What is this code?  It appears to be executed at runtime, because if

> > it is trampled, the target will crash. Is it a NULL pointer write 
> > detector?
>
> It's just a place holder - in this case, your code will just hang
there 
> if you did a jump (or function call) to 0x0.
> 
> What do you mean "trampled" and how does the problem show up?  That
code 
> should never be executed - if it does, your program would just stop.



Interesting.  Does that suggest that someone may be calling 
a NULL function pointer?  Where is the code for this stub? 

We've seen some crashes at address 0x4.  Dumping that area, 
it appeared that the values around 0 had been written to 
(trampled), because they no longer matched the power up 
values.

Later, I manually "trampled" the area around 0 with a debug 
command, and the target crashed shortly afterwards. 

Cheers,
Tim.



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