Re: Improving GDB for multicore and embedded system!

["Ulrich Weigand" <uweigand@de.ibm.com>]

Daniel Jacobowitz wrote:
> On Fri, Mar 02, 2007 at 10:08:55AM +0100, Denis PILAT wrote:
> > Today multicore debugging means multiple instance of gdb running at the 
> > same time. I don't know how possible it is to enhance gdb so that it can 
> > handle multiple programs running on different architecture.
> > I guess Daniel should have a good vision on that.
> 
> No one has ever convinced me that there's a good reason to do this,
> rather than wire up things like DSF to drive multiple GDB's, if the
> cores are not all running the same architecture and program image.  If
> they are, we generally present them as threads, and that works very
> well.
> 
> However, I have relatively little experience with non-symmetric
> multicore debugging - I have a board lab at home but it doesn't
> include any multicore targets, and we haven't done much with them at
> my job, either.  I'm always interested in learning more about new
> debugging models, or having an opportunity to do work on them.

We have a version of GDB that supports multi-architecture debugging
(PowerPC + SPU) on Linux for the Cell BE.  This is currently not
merged upstream (and the code isn't really in a mergeable state).
[ If you're interested, a GDB source RPM including those patches is
available at http://www.bsc.es/projects/deepcomputing/linuxoncell/ ]

However, we do intend to work on common GDB infrastructure with
the goal of having mainline GDB support multi-architure debugging.
The plan here basically is:

- Complete GDB's multi-arch transition (get rid of tm.h files)
  --> This will allow multiple architectures to be compiled into
      a single GDB executable

- Switch from the global current_gdbarch to per-frame gdbarch
  --> This should allow use of multiple architectures 
      concurrently within a single inferior process

None of that is really news; GDB has been moving into that
direction for a long time.  It does look like with a bit of
additional effort (which we'd be willing to help put in), it
should be possible to complete those transitions in the
not-too-distant future.

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  GNU Toolchain for Linux on System z and Cell BE
  Ulrich.Weigand@de.ibm.com