Memory protection in RTEMS

[Gedare Bloom]

On Thu, Apr 2, 2015 at 11:19 AM, Tomasz Gregorek
<tomasz.gregorek at gmail.com> wrote:
> Hi Gedare
>
> Thank you for your comments, they answer my question.
>
> We will look at other RTOSes this time.
>
OK, I'd be happy to hear what you find or settle on. It's a topic that
I have continued interest in working on for RTEMS.

Gedare

> Thanks
> Tomasz
>
> 2015-04-02 17:01 GMT+02:00 Gedare Bloom <gedare at rtems.org>:
>>
>> Hi Tomasz,
>>
>> It is possible to implement some memory protection between threads. As
>> you noticed, RTEMS is a SASOS with "one process" when viewed from the
>> POSIX interface. Generalizing memory protection in such a system is
>> hard. The most common approach I know of is to provide separate
>> protection domains for each thread stack. In theory, you could create
>> a protection domain for the RTEMS "kernel", but I'm not aware of
>> anyone that has tried hard to do that. You may also look for the "Zero
>> Kernel" work some folks did as a research project at Univ of Idaho I
>> think it was.
>>
>> If you want memory protection, you'd have to tailor it to your
>> specific application requirements and set-up the MMU/MPU to do it.
>> Final note: Since there is no notion of privilege in RTEMS, any thread
>> can always disable or modify the protection domains since priviliged
>> registers and instructions are available. Thus, while you may add
>> memory protection, it would not be for a complete security solution.
>>
>> Gedare
>>
>> On Thu, Apr 2, 2015 at 10:04 AM, Tomasz Gregorek
>> <tomasz.gregorek at gmail.com> wrote:
>> > Hi
>> >
>> > We are investigating possible OSes for a new product where one of the
>> > requirements is memory protection between processes.
>> >
>> > Does RTEMS supports memory protection? If not than is it planned to
>> > implement memory protection?
>> >
>> > This is what I found so far:
>> >
>> > RTEMS is single process, multiple threads and as such have everything in
>> > single memory space.
>> > http://comments.gmane.org/gmane.os.rtems.user/19858
>> >
>> > Gedare's blog with his implementation of memory protection from
>> > 2011/2012.
>> > http://gedare-csphd.blogspot.be/2011/12/rtems-memory-protection-api.html
>> > but it seems that this code didn't get to the main.
>> >
>> > Project "MMU Support" by Aanjhan Ranganathan from 6 years ago:
>> > https://devel.rtems.org/wiki/Projects/MMU_Support
>> >
>> > Source code configures MMUs but it seems it do it to enable cache only,
>> > not
>> > the memory protection. Though I did only simple search through the code.
>> > There are exception handlers for some architectures/CPUs but only for
>> > few if
>> > not for only one.
>> >
>> > Best regards
>> > Tomasz Gregorek
>> >
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>
>