[PATCH v6 6/7] Enable software single stepping for while-stepping actions in GDBServer.

Antoine Tremblay
2015-12-04T18:47:00Z

This patch enables software single stepping if the targets support 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 | 48 ++++++++++++++++++++++++++++++-----------------
1 file changed, 31 insertions(+), 17 deletions(-)

diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 8a3c438..9ddcf92 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -3977,6 +3977,33 @@ install_software_single_step_breakpoints (struct lwp_info *lwp)
do_cleanups (old_chain);
}

+/* 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. */

@@ -4124,13 +4151,13 @@ 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 (thread->while_stepping != NULL)
{
if (debug_threads)
debug_printf ("lwp %ld has a while-stepping action -> forcing step.\n",
lwpid_of (thread));
- step = 1;
+
+ step = single_step (lwp);
}

if (proc->tdesc != NULL && the_low_target.get_pc != NULL)
@@ -4536,20 +4563,7 @@ 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;

--
2.6.3