[SeaBIOS] [BUG?] Doesn't retrieve control after coreboot payload return

[Antonello Dettori]

On 02/08/16 16:39, Kevin O'Connor wrote:
> On Tue, Aug 02, 2016 at 03:37:44PM +0200, Antonello Dettori wrote:
>> Hi everyone.
>>
>> I'm currently working on coreboot but I stumbled on a strange SeaBIOS
>> behaviour.
>> After executing a payload and returning control to the caller SeaBIOS
>> crashes.
>>
>> The problem is currently solved by rebooting before the payload returns but
>> doing so also makes chaining multiple payloads impossible so I'm trying to
>> look into a solution.
> The SeaBIOS payload support was not designed to robustly handle
> returns from a payload.  It will crash if the payload alters the GDT,
> overwrite the stack, or otherwise messes up the SeaBIOS state.  As far
> as I know, payloads in general aren't designed to handle returns to
> their caller.
Some payloads can handle returns to the previous caller/payload.
Would it be possible in theory to re-design the payload support so as to 
make it work (i.e. restoring the SeaBIOS state after returning)?
Are there any reasons why it would be unfeasible?
>> I tried to increment the debug level to 8 to get more information and the
>> attached log is what I got.
> That log isn't from SeaBIOS.  It's unclear what hardware you have.  In
> general, a serial port is the most robust way of obtaining a log.  See
> also: http://www.seabios.org/Debugging
>
> -Kevin
I run the image on QEMU, didn't realise that SeaBIOS probably doesn't 
support QEMU debug port output.
I'll try on a hardware target later.