gdb remote stubs

C. M. Heard/VVNET, Inc.
Thu Feb 5 15:54:00 GMT 1998

On Thu, 5 Feb 1998, Joel Sherrill wrote:

[ ... ]

> > I'm currently trying to learn enough to write such a stub.  Any pointers?
> Other than whatever source and documentation is included with gdb, I do
> not know of anything.  gdb 4.16 has remote stubs for i386, m68k, and the
> sparc.  The last gdb snapshot I looked at also included stubs for the sh
> and m32r.  It also included support for a much wider variety of ROM
> monitors.

There is also one for the IDT R4600 (a MIPS 4000-series machine) available
by anonymous ftp from

or, with slightly updated porting hints, at

There is also a README file available at

This stub differs from the ones in the gdb distribution in that it runs
stand-alone in ROM.  I wrote it, in fact, for initial board bring-up (a
logic analyzer was used to debug the stub :-).

> The pc stub over a com port should not be THAT difficult.  There is
> already an i386 stub included in the current gdb so it should be a matter
> of doing the IO and integrating it.  Then give the world instructions and
> the code. :)
> Providing a stub for CPUs like the PowerPC would be more challenging but
> the protocol is well-defined and starting with an example for a cpu you
> understand would help.  I suspect many folks would start with the m68k or
> i386. :)

When I wrote the R4600 stub I looked over the all the stubs bundled with
gdb-4.16, especially the i386 stub because I knew that CPU, but decided
in the end to start from the sh stub even though I did not know that CPU
at all.  I did so because the sh stub seemed to me to be by far and away
the best organized and easiest to understand.

> I hope this helps.

Likewise ...

> --joel

C. M. Heard/VVNET, Inc.

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