[PATCH 4/4] trace-cruncher: Allow for detachable kprobes

["Yordan Karadzhov (VMware)" <y.karadz@gmail.com>]

If a kprobe or kretprobe is created with "detached=True", the Python
module is no longer responsible for destroying it when exiting. It is
therefore up to the user free it explicitly, or to keep it active.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 src/ftracepy-utils.c                  | 26 ++++++++++++++++----------
 tests/1_unit/test_01_ftracepy_unit.py |  9 +++++++++
 tracecruncher/ft_utils.py             |  8 ++++----
 3 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/src/ftracepy-utils.c b/src/ftracepy-utils.c
index d061817..605f7eb 100644
--- a/src/ftracepy-utils.c
+++ b/src/ftracepy-utils.c
@@ -1570,16 +1570,18 @@ bool store_new_kprobe(const char *event)
 PyObject *PyFtrace_register_kprobe(PyObject *self, PyObject *args,
 						   PyObject *kwargs)
 {
-	static char *kwlist[] = {"event", "function", "probe", NULL};
+	static char *kwlist[] = {"event", "function", "probe", "detached", NULL};
 	const char *event, *function, *probe;
+	int detached = false;
 
 	if (!PyArg_ParseTupleAndKeywords(args,
 					 kwargs,
-					 "sss",
+					 "sss|p",
 					 kwlist,
 					 &event,
 					 &function,
-					 &probe)) {
+					 &probe,
+					 &detached)) {
 		return NULL;
 	}
 
@@ -1589,8 +1591,9 @@ PyObject *PyFtrace_register_kprobe(PyObject *self, PyObject *args,
 		return NULL;
 	}
 
-	if (!store_new_kprobe(event))
-		return NULL;
+	if (!detached)
+		if (!store_new_kprobe(event))
+			return NULL;
 
 	Py_RETURN_NONE;
 }
@@ -1598,16 +1601,18 @@ PyObject *PyFtrace_register_kprobe(PyObject *self, PyObject *args,
 PyObject *PyFtrace_register_kretprobe(PyObject *self, PyObject *args,
 						      PyObject *kwargs)
 {
-	static char *kwlist[] = {"event", "function", "probe", NULL};
+	static char *kwlist[] = {"event", "function", "probe", "detached", NULL};
 	const char *event, *function, *probe = "$retval";
+	int detached = false;
 
 	if (!PyArg_ParseTupleAndKeywords(args,
 					 kwargs,
-					 "ss|s",
+					 "ss|sp",
 					 kwlist,
 					 &event,
 					 &function,
-					 &probe)) {
+					 &probe,
+					 &detached)) {
 		return NULL;
 	}
 
@@ -1617,8 +1622,9 @@ PyObject *PyFtrace_register_kretprobe(PyObject *self, PyObject *args,
 		return NULL;
 	}
 
-	if (!store_new_kprobe(event))
-		return NULL;
+	if (!detached)
+		if (!store_new_kprobe(event))
+			return NULL;
 
 	Py_RETURN_NONE;
 }
diff --git a/tests/1_unit/test_01_ftracepy_unit.py b/tests/1_unit/test_01_ftracepy_unit.py
index 0d62da2..a7a6dec 100644
--- a/tests/1_unit/test_01_ftracepy_unit.py
+++ b/tests/1_unit/test_01_ftracepy_unit.py
@@ -479,6 +479,15 @@ class KprobeTestCase(unittest.TestCase):
         all_kprobes = ft.registered_kprobes()
         self.assertEqual(len(all_kprobes), 0)
 
+        ft.register_kprobe(event=evt1, function=evt1_func,
+                           probe=evt1_prove, detached=True)
+        ft.unregister_kprobe(event='ALL')
+        all_kprobes = ft.registered_kprobes()
+        self.assertEqual(len(all_kprobes), 1)
+        ft.unregister_kprobe(event='ALL', force=True)
+        all_kprobes = ft.registered_kprobes()
+        self.assertEqual(len(all_kprobes), 0)
+
 
     def test_enable_kprobe(self):
         evt1 = 'mkdir'
diff --git a/tracecruncher/ft_utils.py b/tracecruncher/ft_utils.py
index 8c245b1..a976885 100644
--- a/tracecruncher/ft_utils.py
+++ b/tracecruncher/ft_utils.py
@@ -171,12 +171,12 @@ class kprobe(kprobe_base):
                            offset=offset,
                            size=size)
 
-    def register(self):
+    def register(self, detached=False):
         """ Register this probe to Ftrace.
         """
         probe = ' '.join('{!s}={!s}'.format(key,val) for (key, val) in self.fields.items())
 
-        ft.register_kprobe(event=self.name, function=self.func, probe=probe);
+        ft.register_kprobe(event=self.name, function=self.func, probe=probe, detached=detached);
         self.evt_id = find_event_id(system=ft.tc_event_system(), event=self.name)
 
 
@@ -203,8 +203,8 @@ class kretval_probe(kprobe_base):
         """
         super().__init__(name, func)
 
-    def register(self):
+    def register(self, detached=False):
         """ Register this probe to Ftrace.
         """
-        ft.register_kprobe(event=self.name, function=self.func);
+        ft.register_kprobe(event=self.name, function=self.func, detached=detached);
         self.evt_id = find_event_id(system=ft.tc_event_system(), event=self.name)
-- 
2.27.0