[okl4-developer] root task

[Geoffrey Lee]

On Tue, Apr 22, 2008 at 11:59:53AM +0200, Charles.VANWITTENBERGHE at fr.thalesgroup.com wrote:
> Hello, 
> 

Hi

> I have a two questions dealing with my debugging work :
> 
> 1 - What is the function of the root task ? Does it make something  vital
> for the kernel mechanism ?

Threads in the root task can issue privileged system calls, while
threads in subsequently created address spaces cannot.  Hence the 
root task acts as a sort o proxy for these types of operations.  There
is currently no way to delegate privileged operations to other
non-privileged threads at run-time.

> 
> 2 - The macro OFS_TCB_PREEMPTION_CONTINUATION makes currently the function
> mips_restore_user jump to the tcb.utcb_location address. I would have
> thought that it should jump to the tcb.arch.context.epc which contains the
> instruction pointer. Is that right or did I misunderstood the mechanism ?


the epc is the saved instruction pointer of the user thread in user
context.  When you take a preemption continuation is supposed to jump to a
continuation function in the kernel context.

> 
> 
> Thanks,
> Charles.

	-gl

> 
> 
> ----
> 
> Charles Van Wittenberghe
> Stagiaire service SES
> THALES COMMUNICATION 
> 110 Avenue du Maréchal Leclerc
> BP 70942- 49309 CHOLET
> tel : 06.84.12.45.87
> charles.vanwittenberghe at fr.thalesgroup.com
> 
> 
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