[U-Boot] gd_t/bd_t on ARM

[Daniel Mack <daniel@caiaq.de>]

Hi Remy,

On Fri, Nov 28, 2008 at 10:39:49PM +0100, Remy Bohmer wrote:
> > I'm hunting weird behaviours with the gd_t global data pointer on my
> > PXA300 board board. The pointer gets set up fine in lib_arm/boot.c and
> > gd->bd is filled in my board specific code. However, after the tftp
> > download is finished, the content of these structures have been
> > destroyed and overwritten with garbage.
> >
> > I suspect a stack corruption to be the culprit, an overflow or overlap,
> > as it seems to happen randomly, after a while and some function calls.
> > Any hints about that?
> 
> Hook up a JTAG (or preferable an ETM) debugger and start tracing?

I did that for a couple of hours now and got somehow stuck with it.
However, I believe it's not related to my board specific code, so I
wanted to ask whether anyone else had similar trouble with the cutting
edge source tree.

> > Also, I wonder why the pointer to this struct is not placed *after*
> > U-Boot's own code as shown in the patch below. This works fine for me
> > now. Any oppinion on that?
> 
> Aren't you just hiding the symptoms here?
> It seems that there is something really wrong and by moving the global
> structures probably a different memory area is overwritten, but the
> problem should still be there...

Of course. That wasn't meant to be the fix for the other problem, I was
just curious as this other location makes more sense to me and also does
not require CONFIG_SYS_GBL_DATA_SIZE anymore. If I got that right, this
variable has to be set to something at least sizeof(gd_t)+sizeof(bd_t).
Right?

Best regards,
Daniel