Re: [Prex-devel] Educational use?

[Andrew D. <and...@gm...>]

Replying to the list too...

On 12 February 2011 14:48, Peter Desnoyers <pj...@cc...> wrote:
> On 02/11/2011 07:27 PM, Andrew Dennison wrote:
>> On 11 February 2011 14:46, Peter Desnoyers <pj...@cc...> wrote:
>>> I'm  using Prex in an operating systems class this term, and was
>>> wondering if anyone else had tried this.
>>>
>>> I was also wondering whether the project has gone dead, as there are
>>> very few messages on this list since last July.
>>
>> This sounds like a very good use of Prex, as it has a fairly clean
>> structure and good abstraction of the architecture specific
>> components.
>
> Yes, as a matter of fact my class just came up with a very good list of
> possible projects this morning.
>
> By the way, do you know if anyone has a good solution to debugging
> user-space code on MMU systems? It should be straightforward on NOMMU,
> but gdb e.g. through the QEMU stub is justifiably confused by the re-use
> of the same address space in every task. If there isn't anything, we
> have some ideas for a gdb stub that could be linked with an executable,
> and a couple of extensions to sys_debug.

Normally you would maintain a debug context for each process, and swap
the debug context as part of the task switch - the OS needs to
cooperate in this exercise. I've done this for some simple debug
support using the hardware debug support in our target processor: I'll
setup a gdb stub one day.
I haven't played with qemu debug - I've only used qemu for some basic
sanity checking that I haven't broken the architectures I don't have
hardware for.

>
>>
>> We haven't heard from Kohsuke for a while but I'm sure he is working
>> away adding some interesting features.
>
> At this point I've already committed to Prex for this term, but the
> development model is making me nervous. In particular, I'm worried that
> any effort I put in will be wasted, or else I'll be stuck using an old
> version just like you are.

That is currently one of the challenges - I think it has scared off a
few other users. I started maintaining a public git tree based on
0.8.1 to fill this void, but the large changes in the 0.9 tarball
stalled that effort.

Kohsuke mentioned setting up a public repository a few years ago and
it would be fantastic if he took that step. There are a few of us who
would like to contribute to Prex on a regular basis.

Andrew