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RE: eCos Code at address 0x000? (MPC8270)
- From: Gary Thomas <gary at mlbassoc dot com>
- To: Tim Sohacki <tsohacki at telesyn dot com>
- Cc: 'eCos Discussion' <ecos-discuss at ecos dot sourceware dot org>
- Date: Tue, 18 May 2004 12:52:26 -0600
- Subject: RE: [ECOS] eCos Code at address 0x000? (MPC8270)
- Organization: MLB Associates
- References: <014001c43d08$96a00a40$490810ac@telesyn.corp>
On Tue, 2004-05-18 at 12:47, Tim Sohacki wrote:
> 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?
>
Look at "hal_reserved_vector_0000" in
hal/powerpc/mpc8xxx/current/include/variant.inc
> 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.
Then there's probably something else wrong with your code - eCos neither
uses nor relies on anything in this chunk of memory (0x0..0x100)
--
Gary Thomas <gary@mlbassoc.com>
MLB Associates
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