Using XML in GDB?

[Andrew STUBBS]

Daniel Jacobowitz wrote:
> There isn't a definitive conclusion because it's evolved substantially
> once I began (re-) implementing it.  This is what I had two weeks ago:
> 
>   http://sourceware.org/ml/gdb/2005-05/msg00171.html
> 
> But it doesn't look entirely like that any more.
> 
> Registers can be generically described without hard-coded GDB
> knowledge.  Most other features can't, except for their presence or
> absence.  But the point of suggesting XML is to keep this extensible
> should someone have a bright idea :-)

That sounds good. We have been considering doing something with memory 
mapped registers (devices, exception/interrupt reason codes, etc.), and 
this might be the answer.

More generally we have been looking at ways to pass back information 
about the target to replace the GDB scripts we currently use that just 
trust that the target is as they describe - there is no check that the 
user hasn't connected to the wrong type.

You may remember that my proposal concerning a plugin interface provided 
means for the target plugin to run GDB commands. This was one way I 
planned to solve this problem.

Specifically, the data we need/want GDB to know about the target are as 
follows:
  - architecture variant (i.e. what registers and instructions are valid);
  - endian;
  - memory map (not that GDB seems to do much with this at present);
  - non-core control/information registers;
  - other features.

'Other features' includes simulator specific trace features, silicon 
specific performance measurement devices, low level jtag commands etc. 
These things are controlled through custom GDB commands that may or may 
not be available on any given target.

In general, there is a selection of GDB 'set' commands which are of 
interest to targets and for which an interface might be nice.

None of this directly addresses the question of XML, but it does 
represent the sort of thing (some) users are looking to do, and 
therefore what 'extensibility' might entail. Of course, I'm still not 
sure exactly what you envisage as the limits of the interface.

Speaking of XML, are you aware of the SPIRIT SOC definition standard 
(http://www.spiritconsortium.com) which contains some things that the 
debugger might be interested in (and much in which it is not). I've no 
idea how compatible they are, but it might be nice if GDB could pull 
relevant information out of one of these.

Thanks

Andrew Stubbs