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

[Gedare Bloom]

I envision users will configure the extra protection therefore it is
optional. My goal is to provide an rtems_api to protect memory regions
(base, bounds, permission) that libcpu (or score/cpu) and libbsp provide the
enforcement mechanism. Then higher apis can implement e.g. posix mmap
protection, task stack isolation, or users can define their own protected
regions. I have seb's approximate nios api and will consider it as I design
the middle layer between cpukit and cpu/bsp.

My code will be tracked in the gsoc-mmu svn, since I am extending that code
as my first cut.
-gedare
On Oct 26, 2011 2:43 AM, "Sebastian Huber" <
sebastian.huber at embedded-brains.de> wrote:

> 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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> E-Mail  : sebastian.huber at embedded-**brains.de<sebastian.huber at embedded-brains.de>
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>
> Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
>
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