Re: [pushed] gdbserver: redo stepping over breakpoint that was on top of a permanent breakpoint

[Antoine Tremblay <antoine.tremblay@ericsson.com>]

On 09/24/2015 09:21 AM, Yao Qi wrote:
> Antoine Tremblay <antoine.tremblay@ericsson.com> writes:
>
>> Indeed I have a fix for this see :
>> https://sourceware.org/ml/gdb-patches/2015-09/msg00222.html
>>
>
> Ah, I did read your patch, but I forget it when I am fixing this problem.
>

Np, I think that patch is valid with the scenario you mention below, 
however since it won't work properly as reinsert_addr doesn't work at 
this stage I think it may be better to introduce it when I post the 
single stepping support ?

> It can be triggered when GDBserver steps over its breakpoints, what I
> did is to pass 1 to thread_db_init, so that GDBserver will insert
> breakpoint on __nptl_create_event.  Once a new thread is created, and
> hits this breakpoint, GDBserver will step over this breakpoint.
>

Haa I had missed that scenario!

>--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -3010,7 +3010,8 @@ linux_wait_1 (ptid_t ptid,
       Advance the PC manually past the breakpoint, otherwise the
       program would keep trapping the permanent breakpoint forever.  */
    if (!ptid_equal (step_over_bkpt, null_ptid)
-      && event_child->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT)
+      && event_child->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT
+      && gdb_breakpoint_here (event_child->stop_pc))
      {
        int increment_pc = 0;
        CORE_ADDR stop_pc = event_child->stop_pc;

This won't work as that single step breakpoint is not a gdb breakpoint 
we need to check for a reinsert breakpoint like the patch I mentioned.

I tested the scenario with my patch and the issue is solved.

Note however I'm a bit concerted about the hack to remote_check_symbols. 
  I need to dig into it to understand that one should we expect it to 
work without this hack ?