Re: [PATCH] gdbserver gnu/linux: stepping over breakpoint

[Pedro Alves <palves at redhat dot com>]

On 04/09/2015 04:22 PM, Pedro Alves wrote:
> On 04/09/2015 04:06 PM, Yao Qi wrote:
>> Pedro Alves <palves@redhat.com> writes:
>>
>>> even reached.  The test isn't even threaded.  It sounds like
>>> gdbserver is trying to step over the breakpoint at "foo"?  Didn't
>>> gdb itself step over it?  How come that was reached in gdbserver?
>>> Did we mishandle the breakpoint's reference count in gdbserver?
>>
>> Shouldn't GDBserver step over breakpoint when the target side condition
>> is false?
> 
> Oh, this is stepping past an hardware breakpoint, not software
> breakpoint.  Yes, GDBserver should be stepping past such
> breakpoints.  But, given GDBserver's software single-step
> support is really really really really too simple:
> 
> /* We only place breakpoints in empty marker functions, and thread locking
>    is outside of the function.  So rather than importing software single-step,
>    we can just run until exit.  */
> static CORE_ADDR
> arm_reinsert_addr (void)
> {
>   struct regcache *regcache = get_thread_regcache (current_thread, 1);
>   unsigned long pc;
>   collect_register_by_name (regcache, "lr", &pc);
>   return pc;
> }
> 
> ... we should probably disable target side conditions on software
> single-step gdbserver ports.  E.g., try "si" through this function:

Sorry, "si" probably works as gdb steps over the breakpoint
itself.  Try "step" or "next" instead, which kick in the range
stepping support, which then causes gdbserver to handle the
step-over itself.

> 
>    void
>    function ()
>    {
>      i = 0;
>      i = 0; // set cond breakpoint that evals false here
>      i = 0;
>    }
> 
> I'd guess the "si" over the breakpoint ends in the caller
> of "function"...

Thanks,
Pedro Alves