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

[Marcin KoÅcielnicki <koriakin at 0x04 dot net>]

On 25/01/16 14:56, Pedro Alves wrote:
> On 01/24/2016 12:12 PM, Marcin KoÅcielnicki 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 KoÅcielnicki