[PATCH 1/2] gdbserver: catch fetch registers error

[Pedro Alves]

On 01/19/2017 02:48 PM, Metzger, Markus T wrote:
> Hello Pedro,
> 
> Thanks for the review and the elaborate response.
> 
>> The case of trying to read registers from a thread that is
>> running is always a client bug.  GDB should know which threads
>> it resumed, and checks like the validate_registers_access
>> you found should prevent such accesses reaching the server.
> 
> That's a general misunderstanding of the design on my part, then.  I typically
> don't check if I can/should do something but instead just do it and handle errors
> in case it failed.  Like reading registers.
> 
> Let me drop this patch and instead call validate_registers_access in btrace before
> reading the PC.

We have similar checks in other places, like e.g., frame.c:has_stack_frames.
Might make sense to factor things out a bit to avoid a throw/catch.

>> So it seems to me that btrace shouldn't even be trying to be enabled
>> on running threads.
> 
> It works fine and I didn't see a reason why we would not want to allow it.

Sorry, that was bogus.  I agree -- what it shouldn't be doing
is reading registers.

Thanks,
Pedro Alves