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Re: ARM7, remote GDB, Software Breakpoints

On Wed, 12 Feb 2003, Torsten Mohr wrote:

> Hi,
> i have several questions related to the GDB remote protocol
> server i wrote ( ),
> it would be great if someone could give me some hints.
> 1. I could handle HW breakpoints, how can i tell GDB that it should
> use HW breakpoints?  Just answering requests for SW breakpoints with
> "ENN" doesn't seem to make GDB use HW breakpoints.

You have to implement commands starting with 'Z' and 'z' in order to
support hw breakpoints.

> 2. When i use SW breakpoints and download and start a program on
> the target, first the program is downloaded and then the SW
> breakpoints are set.  SW breakpoints are done by replacing the
> instruction at that address with a "breakpoint instruction".
> When the program stops on a "breakpoint instruction", and i
> then do a "step" or "continue", that original instruction is
> NOT EXECUTED, it seems i have to restore that value temporarily,
> do a "single step" and put back that "breakpoint instruction"
> again, right?
> >From watching the communication between target and server i assume
> it is like this, i just want to make sure this is the way to handle
> it and i don't miss anything.

It is very strange, because gdb works exactly this way. I am wondering do
you have 'step' command implemented?

> 3. Thumb mode is not handled at all at the moment, what do i need
> to do to handle Thumb mode?
> If GDB downloads a program into the target and sets the PC to a
> certain address, how does my server know if it should execute this
> in ARM or in Thumb mode?
> Best regards,
> Torsten.



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