Re: [PATCH 0/8] gdb/s390: Add regular and fast tracepoint support.

Marcin Kościelnicki
2016-01-25T16:03:57Z

On 25/01/16 16:56, Pedro Alves wrote:
> On 01/25/2016 02:28 PM, Marcin KoÅ›cielnicki wrote:
>> On 25/01/16 14:56, Pedro Alves wrote:
>>> On 01/24/2016 12:12 PM, Marcin KoÅ›cielnicki wrote:
>>>
>>>> 1. Target independent: tfile format doesn't contain target information
>>>> (tdesc). While this affects all platforms with multiple tdescs
>>>> (eg. x86_64 is unable to pull AVX registers from tfile for that
>>>> reason), it horribly breaks 31-bit s390 with high GPRs - it has
>>>> a completely different GPR layout from plain 31-bit s390, so the
>>>> collected registers will be garbled. I suppose the proper fix to
>>>> that would be to add tdesc information to tfile format.
>>>
>>> Yes, I think so too.
>>>
>>>> Unfortunately, I don't see a way to extend it in a backwards-compatible way.
>>>
>>> The trace file header is just a list of newline-terminated lines.
>>> We're free to add more header lines - older gdb's just warn about
>>> unknown lines. See tfile_interp_line.
>>>
>>> Thanks,
>>> Pedro Alves
>>>
>>
>> Very well.
>>
>> I was thinking of just stuffing the XML in the header. We can avoid
>> embedded newlines through hex-encoding it (or just stripping them,
>> shouldn't hurt XML...), and copy it straight from the target. That
>> would fail for targets that don't get tdesc from XML, but I'm not sure
>> we should worry about it. An alternative would be to invent some
>> serialization format for tdesc in tfile, but why do that when we already
>> have a perfectly good one...
>>
>> Should be quite simple, really. Does that sound OK?
>
> Yes.
>
> Thanks,
> Pedro Alves
>

Alright, I'm getting started on it, then.