Re: [Qemu-devel] vexpress-a9: coreboot is unable to push any data on stack

[Peter Maydell]

On 15 August 2014 19:02, Piotr Król <address@hidden> wrote:
> On Fri, Aug 15, 2014 at 05:10:04PM +0100, Peter Maydell wrote:
>> For your stack issues, it looks like your code is trying to
>> use the area which is the flash as the stack. Since flash
>> isn't writeable, we ignore the writes and it's not very
>> useful for stack. It looks like your code is assuming that
>> the low memory is RAM, not flash -- so how does your
>> code work on real hardware? Do you try to use the
>> software controllable remapping to copy from the flash
>> into RAM before using the stack, or something else?
>
> Peter thanks for your reply. I'm not coreboot developer so cannot
> advocate for their decision.

I'm not looking for advocacy, just for an explanation of
what it's doing, and in particular whether anybody's
ever tested this on real hardware. (Running guest code
only on QEMU is a recipe for bugs, because our emulation
is often not very accurate and if you only test on QEMU
you can end up accidentally relying on our bugs.)

> Bootblock that I sent is from build
> targeted on qemu and developer who initially wrote the code suggest
> using it with '-kernel' parameter. I would like to fix this code
> according to correct memory map.
>
> Comment in hw/arm/vexpress.c say that, as you wrote below, Versatile
> Express got two possible memory maps. Can you point me to exact
> documentation that you use as reference for vexpress implementation ?

The common motherboard docs:
http://infocenter.arm.com/help/topic/com.arm.doc.dui0447j/index.html
A9 daughterboard docs:
http://infocenter.arm.com/help/topic/com.arm.doc.dui0448h/index.html
A15 daughterboard docs:
http://infocenter.arm.com/help/topic/com.arm.doc.dui0604e/index.html

thanks
-- PMM