Hi Rafal,
On Wednesday 02 January 2008, Rafal Jaworowski wrote:
Currently do_bootelf() disables data cache just before passing control to the entry point:
/* * QNX images require the data cache is disabled. * Data cache is already flushed, so just turn it off. */ if (dcache_status ()) dcache_disable ();With this piece of code present I'm seeing strange effects (corrupt data access, hangs) in standalone apps running from the ELF envelope.
What platform are you testing on? PPC? If yes, which one?
A pure binary made of this same ELF works without problems. Contrary to the comment above, there's no quarantee in do_bootelf() code flow that all data cache has been flushed and it seems there needs to be flush_data_cache() executed before the disable.
dcache_disable() should flush the dcache itself before disabling it. At least this is the implementation I have seen on 405 and IIRC other PPC platforms.
- Does it really hold true that QNX requires d-cache disabled upon passing
control to it?
- If so, this is a custom QNX thing that belongs to do_bootm_qnxelf() and
should be handled there and not at the common ELF handling level.
Hmmm. I think that calling applications and especially OS'es is more safe with caches disabled then with caches enabled.
Any objections to pushing this down to do_bootm_qnxelf()? I can provide a patch, but cannot test it with any QNX system. Is there anyone with such setup that would give this a try?
It's possible that other OS'es rely on caches being disabled too. I'm not sure here, but VxWorks could be one of those. Does anybody know for sure?
Thanks.
Best regards, Stefan
===================================================================== DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: +49-8142-66989-0 Fax: +49-8142-66989-80 Email: office@denx.de =====================================================================