[PATCH 09/10] Enable software single stepping for while-stepping actions in GDBServer.

[Antoine Tremblay <antoine dot tremblay at ericsson dot com>]

This patch enables software single stepping if the targets supports it,
to do while-stepping actions.

No regressions, tested on ubuntu 14.04 ARMv7 and x86.
With gdbserver-{native,extended} / { -marm -mthumb }

gdb/gdbserver/ChangeLog:

	* linux-low.c (single_step): New function.
	(linux_resume_one_lwp_throw): Call single_step.
	(start_step_over): Likewise.
---
 gdb/gdbserver/linux-low.c | 59 +++++++++++++++++++++++++++++------------------
 1 file changed, 36 insertions(+), 23 deletions(-)

diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 1f423ba..d0a9c2a 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -3900,7 +3900,34 @@ install_software_single_step_breakpoints (struct lwp_info *lwp)
   VEC_free (CORE_ADDR, next_pcs.result);
 }
 
-/* Resume execution of LWP.  If STEP is nonzero, single-step it.  If
+/* Single step via hardware or software single step.
+   Return 1 if hardware single stepping, 0 if software single stepping
+   or can't single step.  */
+
+static int
+single_step (struct lwp_info* lwp)
+{
+  int step = 0;
+
+  if (can_hardware_single_step ())
+    {
+      step = 1;
+    }
+  else if (can_software_single_step ())
+    {
+      install_software_single_step_breakpoints (lwp);
+      step = 0;
+    }
+  else
+    {
+      if (debug_threads)
+	debug_printf ("stepping is not implemented on this target");
+    }
+
+  return step;
+}
+
+/* RESUME execution of LWP.  If STEP is nonzero, single-step it.  If
    SIGNAL is nonzero, give it that signal.  */
 
 static void
@@ -4045,14 +4072,13 @@ linux_resume_one_lwp_throw (struct lwp_info *lwp,
      address, continue, and carry on catching this while-stepping
      action only when that breakpoint is hit.  A future
      enhancement.  */
-  if (thread->while_stepping != NULL
-      && can_hardware_single_step ())
-    {
-      if (debug_threads)
-	debug_printf ("lwp %ld has a while-stepping action -> forcing step.\n",
-		      lwpid_of (thread));
-      step = 1;
-    }
+  if (thread->while_stepping != NULL) {
+    if (debug_threads)
+      debug_printf ("lwp %ld has a while-stepping action -> forcing step.\n",
+		    lwpid_of (thread));
+
+    step = single_step (lwp);
+  }
 
   if (proc->tdesc != NULL && the_low_target.get_pc != NULL)
     {
@@ -4457,20 +4483,7 @@ start_step_over (struct lwp_info *lwp)
   uninsert_breakpoints_at (pc);
   uninsert_fast_tracepoint_jumps_at (pc);
 
-  if (can_hardware_single_step ())
-    {
-      step = 1;
-    }
-  else if (can_software_single_step ())
-    {
-      install_software_single_step_breakpoints (lwp);
-      step = 0;
-    }
-  else
-    {
-      internal_error (__FILE__, __LINE__,
-		      "stepping is not implemented on this target");
-    }
+  step = single_step (lwp);
 
   current_thread = saved_thread;
 
-- 
1.9.1