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

[Yao Qi <qiyaoltc@gmail.com>]

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.

> But I thought it would not trigger until conditional breakpoints are
> implemented thus I had not included it in this patchset.
>
> Could you share how exactly you get GDBServer to insert an internal
> breakpoint, I'm unfamiliar with :  "I force GDBserver to use thread
> event breakpoint" ?

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.

-- 
Yao (齐尧)

diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 9fb83a8..0d88694 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -5501,7 +5501,7 @@ linux_look_up_symbols (void)
   /* If the kernel supports tracing clones, then we don't need to
      use the magic thread event breakpoint to learn about
      threads.  */
-  thread_db_init (!linux_supports_traceclone ());
+  thread_db_init (1/*!linux_supports_traceclone ()*/);
 #endif
 }
 
diff --git a/gdb/remote.c b/gdb/remote.c
index b9dc4af..f1dec19 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -4157,6 +4157,13 @@ remote_check_symbols (void)
 							 sym_addr,
 							 &current_target);
 
+	  /* Hack for arm gdbserver when the thread library is compiled in
+	     thumb mode.  Set the LSB of address of __nptl_create_event so
+	     that GDBserver can choose the right breakpoint instruction to
+	     set on it.  */
+	  if (strcmp ("__nptl_create_event", msg) == 0)
+	    sym_addr |= 1;
+
 	  xsnprintf (msg, get_remote_packet_size (), "qSymbol:%s:%s",
 		     phex_nz (sym_addr, addr_size), &reply[8]);
 	}