[2/2] Enable range stepping for ARM on GDBServer
Commit Message
[sigh, I am testing my arm range stepping patches today...]
On Thu, Sep 1, 2016 at 4:59 PM, Pedro Alves <palves@redhat.com> wrote:
>>>
>>>> I'm sorry I can't be more helpful at the moment but I wanted to post
>>>> this issue before I have to leave for a while.
>>>
>>> Understood. Does enabling range stepping unblock something else?
>>
>> It would unblock ARM tracepoints, as per Yao's requirements...
>
> Tracepoints make gdbserver single-step and then not report the event
> to gdb, so I do see the parallel with range-stepping. Throwing
> while-stepping into the equation would make it even more clear.
>
Range-stepping makes gdbserver single-step and then not report the event
to gdb if thread pc is within the range. It is similar to tracepoint, but much
simpler.
Both range-stepping and tracepoing needs to remove reinsert_breakpoint
when gdbserver gets an event but doesn't report it back to gdb. However,
gdbserver doesn't do so now. That is the reason I believe we need to
support range-stepping first, and I am working on this (but interrupted by
7.12 release). The draft patch attached removes reinsert_breakpoint when
gdbserver gets an event but not to report it back to gdb.
Beside "removing reinsert_breakpoint on gdbserver internal event", we'd
better to think that "each backend unwinders don't have to worry about
unavailable data". I posted a draft here
https://sourceware.org/ml/gdb-patches/2016-05/msg00060.html, I need
some review comments. Pedro,
can you take a look? This is not a hard requirement for ARM tracepoint
support.
Comments
On 09/01/2016 05:44 PM, Yao Qi wrote:
> Beside "removing reinsert_breakpoint on gdbserver internal event", we'd
> better to think that "each backend unwinders don't have to worry about
> unavailable data". I posted a draft here
> https://sourceware.org/ml/gdb-patches/2016-05/msg00060.html, I need
> some review comments. Pedro,
> can you take a look? This is not a hard requirement for ARM tracepoint
> support.
I plan to, but there a few things still blocking 7.12 that I'd like to
clear first.
Thanks,
Pedro Alves
Yao Qi writes:
> [sigh, I am testing my arm range stepping patches today...]
>
Thanks for working on this :)
> On Thu, Sep 1, 2016 at 4:59 PM, Pedro Alves <palves@redhat.com> wrote:
>>>>
>>>>> I'm sorry I can't be more helpful at the moment but I wanted to post
>>>>> this issue before I have to leave for a while.
>>>>
>>>> Understood. Does enabling range stepping unblock something else?
>>>
>>> It would unblock ARM tracepoints, as per Yao's requirements...
>>
>> Tracepoints make gdbserver single-step and then not report the event
>> to gdb, so I do see the parallel with range-stepping. Throwing
>> while-stepping into the equation would make it even more clear.
>>
>
> Range-stepping makes gdbserver single-step and then not report the event
> to gdb if thread pc is within the range. It is similar to tracepoint, but much
> simpler.
>
> Both range-stepping and tracepoing needs to remove reinsert_breakpoint
> when gdbserver gets an event but doesn't report it back to gdb. However,
> gdbserver doesn't do so now. That is the reason I believe we need to
> support range-stepping first, and I am working on this (but interrupted by
> 7.12 release). The draft patch attached removes reinsert_breakpoint when
> gdbserver gets an event but not to report it back to gdb.
>
OK
> Beside "removing reinsert_breakpoint on gdbserver internal event", we'd
> better to think that "each backend unwinders don't have to worry about
> unavailable data". I posted a draft here
> https://sourceware.org/ml/gdb-patches/2016-05/msg00060.html, I need
> some review comments. Pedro,
> can you take a look? This is not a hard requirement for ARM tracepoint
> support.
Thanks for not making this one a hard requirement!
Regards,
Antoine
@@ -3662,17 +3662,31 @@ linux_wait_1 (ptid_t ptid,
(*the_low_target.set_pc) (regcache, event_child->stop_pc);
}
- /* We may have finished stepping over a breakpoint. If so,
- we've stopped and suspended all LWPs momentarily except the
- stepping one. This is where we resume them all again. We're
- going to keep waiting, so use proceed, which handles stepping
- over the next breakpoint. */
- if (debug_threads)
- debug_printf ("proceeding all threads.\n");
-
if (step_over_finished)
- unsuspend_all_lwps (event_child);
+ {
+ /* If we have finished stepping over a breakpoint, we've
+ stopped and suspended all LWPs momentarily except the
+ stepping one. This is where we resume them all again.
+ We're going to keep waiting, so use proceed, which
+ handles stepping over the next breakpoint. */
+ unsuspend_all_lwps (event_child);
+ }
+ else
+ {
+ /* Remove the singlestep breakpoints if any. Note that
+ there isn't singlestep breakpoint if we finished stepping
+ over. */
+ if (can_software_single_step ()
+ && has_reinsert_breakpoints (current_thread))
+ {
+ stop_all_lwps (0, event_child);
+ delete_reinsert_breakpoints (current_thread);
+ unstop_all_lwps (0, event_child);
+ }
+ }
+ if (debug_threads)
+ debug_printf ("proceeding all threads.\n");
proceed_all_lwps ();
return ignore_event (ourstatus);
}