breakpoint extension for remote protocol

[J.T. Conklin]

> > Here is the protocol elements that I'm currently working with:
> >
> >     Insert Breakpoint:     B<type>,<address>[,<length>]
> >     returns:               ??   - A cookie representing the breakpoint
> >                            EX   - breakpoint type not supported
> >                                 - no breakpoint contexts available
> >                                 - invalid/unsupported address
> >                                 - invalid/unsupported length
> 
> FYI, there is already a semi-official use of `B' as a generic remote
> breakpoint operation.  The syntax is:
> 
>     B<address>,S    Set a breakpoint
>     B<address>,C    Clear a breakpoint
> 
> When using this, GDB assumes the target can handle all breakpoints.

Umm... I checked the current (98/11/21) GDB snapshot's remote.c, all
of the sample stubs, and remote.texi and could find no evidence of a
breakpoint command, much less a 'semi-official' one.  So I went back
to a design Stu described to me some years ago as the foundation of my
current work.

I think the refined proposal I sent to the list yesterday is far
superior to the the one described above, as that would require yet
another set of commands for hardware break/watchpoints.

> With regard to the general question of extending the remote-gdb protocol
> so that it supports a generic hardware breakpoint mechanism.  I agree it
> is needed.  It is a missing part of the overall toolkit.  

> Did you know that some targets actually implement hardware
> breakpoints by poking the registers directly?

I saw that.  Yuck.


	--jtc