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

Marcin Kościelnicki
2016-01-25T14:28:42Z

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?

Marcin KoÅ›cielnicki