Re: GDB 13 release -- 2023-01-21 Update

[Luis Machado <luis.machado@arm.com>]

On 1/31/23 13:57, Luis Machado wrote:
> Hi Joel,
> 
> On 1/31/23 07:03, Joel Brobecker wrote:
>> Hi Luis,
>>
>> On Mon, Jan 30, 2023 at 11:23:06AM +0000, Luis Machado wrote:
>>> On 1/29/23 11:52, Joel Brobecker wrote:
>>>>>>>>       - With that said, the patch appears to simply add a cache,
>>>>>>>>         so the logic of it all doesn't appear to be extremely
>>>>>>>>         complicated. So I would rate the risk to be low.
>>>>>>>
>>>>>>> That's what it seems to me.
>>>>>>>
>>>>>>> I think another round of testing would be a good step to make sure there are no hidden bugs.
>>>>>> My understanding is that the problem was making debugging borderline
>>>>>> impossible.  Or at least, really, really unpleasant.  So I think it
>>>>>> qualifies as a bug fix, and that the benefit is worth the risk.
>>>>>
>>>>> Right. Past a short number of frames, unwinding got really really slow.
>>>>
>>>> The part that I haven't been clear on is whether this affected everyone
>>>> on Arm-32bit, or everyone on both Arm and AArch64, or just a subset
>>>> of the users?
>>>
>>> Just a subset.
>>>
>>> It affects 32-bit m-profile Arm targets that report the additional stack pointers.  This is either
>>> the org.gnu.gdb.arm.m-system feature or the org.gnu.gdb.arm.secext feature.
>>>
>>> I'm fairly sure these features are only reported by emulators and bare-metal targets.
>>>
>>> Now, a 64-bit gdb can debug 32-bit Arm as well, so you could have a 64-bit gdb running into this too
>>> if the target is a 32-bit m-profile Arm. But the target is still 32-bit Arm.
>>>
>>> This doesn't affect AArch64 at all.
>>
>> Thanks for the extra effort explaining the impact. This is much clear
>> for me, now. With your permission, I'd like to copy the text above
>> as a comment in the PR. Would that be OK?> 
> 
> Yes, that's fine. Let me know if you want me to do it.
> 
>>>> Regardless of the above, I agree we can backport. To avoid confusion,
>>>> can I leave this to you, Luis, to confirm that the two patches I identified
>>>> previously are the only two patches that need to be backported, and
>>>> can you backport those for us, with a round of testing if you haven't
>>>> done so already, just to double-check?
>>>
>>> Sure. I gave it a try with master and the test results look the same with or without the patches.
>>>
>>> Unfortunately the 32-bit Arm test results are not too clean as there is quite a bit of noise from
>>> failing watchpoints tests.
>>>
>>> I'll try with GDB 13 just to be sure.
>>
>> Thank you. Once you've finished testing, whatever that might be,
>> you can go ahead and push the patches. As disussed earlier, we all
>> agree the risk of bad impact is very low.
>>
>> Let me know when this is done. It's starting to look like we might
>> have a pre-release created this weekend! Maybe earlier, if I can
>> carve some time out of my work schedule.
>>
> 
> I ran checks with the gdb 13 branch and the results look the same for a patched gdb compared to
> an unpatched one.
> 
> I'll cherry-pick both commits to gdb 13 once sourceware is back up.

Done now.