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Re: [PATCH] Fix displaced stepping for remote targets


On 03/20/2012 03:53 AM, Yao Qi wrote:
On 03/20/2012 12:38 PM, Luis Gustavo wrote:
On 03/20/2012 01:34 AM, Yao Qi wrote:
On 03/20/2012 10:02 AM, Luis Gustavo wrote:
If a target supports hw single-stepping for displaced stepping, GDB
should just send a vCont;s packet to tell the target to step a single
instruction. In my case, GDB was always sending a vCont;c instead.

On some arch, the original instruction may be translated to more than one instructions, and copied to scratch pad. So, we can't do single-step in scratch pad.

During a few tests x86 seems to do single-stepping in the scratch pad when using displaced stepping, or at least it sends the correct vCont;s packet.


GDB writes only one instruction in scratch pad on i386 and amd64. That may be the reason why no fail shows up.


Yes, most probably. I think ppc does this as well.


If a target can't use hw single-stepping to execute instructions in the scratch pad, i think it should disallow it by returning 0 in gdbarch_displaced_step_hw_singlestep. Does it make sense?

Luis


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