Re: [PATCH] Fix exception unwinding for ARM Cortex-M

James-Adam Renquinha Henri
2019-06-10T21:25:05Z

Hi everyone in this thread, (not many as I see)

We could take another shot at integrating some changes to GDB so it
works correctly, but that may only happen if there are the least amount
of useless bike-shedding and that the right people in the mailing list
contribute.

Basically, we must 1) make *very* clear the fact that Cortex-M devices
are used typically in a bare-metal system with no OS (read: Linux)
whatsoever, only possibly a tiny scheduler and that's all. That means we
don't have to be concerned about "user visible" registers and whatnot,
they are all visible anyway, and if the spec says that a register
exists, *it is visible*, period. Other thing though, 2) my patch
achieved its goal in a rather weaselly way, and the correct way is
indeed to have it integrated into target features. But I need more info
on the matter, and I'm a bit clueless about what to do with those
"target features", how they are handled by GDB and how I can test the
new configuration in isolation, without being "altered" by e.g. OpenOCD,
which handily provides a target description that I can use as I did before.

I sure can figure it out all by myself, but that might be only after
pouring an rather big amount of time into the matter that I cannot
afford to do now. I need active collaboration and answers.

Here, let that message be in the mailing list for everyone to see.

James-Adam Renquinha Henri, Ing. jr
IngÃ©nieur d'application
CIMEQ INC.

On 19-06-02 03 h 31, Fredrik Hederstierna wrote:
> Hi Yao, Adam,
>
>
> Some years back there was done some work done on unwinding on Cortex-M.
>
> Only the very first start of the chain of patches was completed (new
> function arm_m_pc_is_magic()).
>
>
> The actual real patch work with code work by me/Adam for cortex-M4F
> MSP/PSP and unwinding did never reached the repo.
>
>
> What do you think of making another attempt to fix the stuff, I guess
> all paper-work etc is in place, so we can try do a retake on this?
>
>
> Thanks, Best Regards, Fredrik
>
> ------------------------------------------------------------------------
> *From:* Yao Qi <qiyaoltc@gmail.com>
> *Sent:* Tuesday, September 27, 2016 3:38 AM
> *To:* Adam Renquinha
> *Cc:* Fredrik Hederstierna; gdb-patches@sourceware.org
> *Subject:* Re: [PATCH] Fix exception unwinding for ARM Cortex-M
> On Mon, Sep 26, 2016 at 3:26 PM, Adam Renquinha <arenquinha@cimeq.qc.ca>
> wrote:
>> That looks correct.
>>
>
> Patch is pushed into master and 7.12.Â  The rest of your original
> patch is still welcome!
>
> --
> Yao (é½å°§)