Memory protection was Re: change log for rtems (2011-10-21)

[Sebastian Huber]

On 10/25/2011 10:18 PM, Joel Sherrill wrote:
> On 10/24/2011 08:55 AM, Sebastian Huber wrote:
>> We are (at the moment) not interested in a general MPU or MMU API.  Currently
>> we use a Nios II specific API to do the low level stuff.
> Eventually this would result in 15+ APIs in RTEMS.  After suffering
> through a few IRQ APIs that were related but different, I would
> expect you to feel a cold chill and shudder about now.

We already have these 1+ APIs.  Just look at the PowerPC MMU/BAT stuff.  In the 
long run it is better to use one general API, but someone has to invent one.

>>   We are interested in
>> thread stack protection.  This means that stack overflows are detected and
>> access to other thread stacks is prohibited.
>
> Stack overflow detection is OK.
>
> Stack protection is likely to result in a violation of the POSIX
> process/thread model.  RTEMS is best compared to a thread
> implementation in a user space library in POSIX process terms.

Yes, it violates the POSIX thread model.  Everything has its cost.

-- 
Sebastian Huber, embedded brains GmbH

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