[ECOS] Leon mode in eCos

Eric Donnat e.donnat@silicomp.fr
Thu Apr 1 22:18:00 GMT 2004


On Thu, 1 Apr 2004 15:51:07 +0200
"Michele Portolan" <michele.Portolan@imag.fr> wrote:

> Hi, I am working on eCos on Leon and I have a few questions about
> user/supervisor modes: how are they used inside that OS?
> I usually thought that in any OS threads where executed in user mode (S=0 in
> PSR register), while all kernel function like scheduling where in supervisor
> mode (S=1). Or, at least, that is what I have been taught.
> Anyway debugging with cygwin/ddd on the "twothreads" example (two threads
> are runned with the scheduler) I always find S=1. both in the kernel (I put
> a breakpoint just before context-switch) and in the threads (breakpoints
> during execution).
> Can I safely assume that the processor is always in supervisor mode?
> Thanks,
> 
> Michele

eCos est un RTOS minimaliste tres similaire a Nucleus, pSos, et parfois VxWorks. La cible reste principalement l'embarque enfui (en dessous du Mo de resources et sur des processeur ne possedant pas de MMU). Donc la
plupart des ports tournent en superviseur et sans aucune forme de protection memoire. C'est la regle pour les sources de l'arbre RedHat.

Certains ont essaye d'ajouter un semblant de personnalite UNIX (eCos-M3) ou de protection memoire (Cf. mailing liste), mais quoiqu'il en soit les
instances fondatrices (redhat, ecoscentric) ont deja largement donner leur avis clair et net de continuer l'arbre eCos officiel dans cet etat de fait. Donc sauf exception tout tourne en mode "dieu".

-- 
Eric DONNAT

Silicomp Research Institute
38330 Montbonnot-St-Martin (France)
http://www.ri.silicomp.com

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