[PATCH v2 3/4] libtracefs: Implement tracefs_kprobe_clear() to remove all kprobes

[Steven Rostedt <rostedt@goodmis.org>]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

A call to tracefs_kprobe_clear() will attempt to disable all kprobes. If
any kprobe is set, and the @force parameter is set, it will fail with
errno set to EBUSY. If @force is set, then it will attempt to disable all
the defined kprobe events and then clear it.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/tracefs.h     |   2 +-
 src/tracefs-kprobes.c | 116 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 117 insertions(+), 1 deletion(-)

diff --git a/include/tracefs.h b/include/tracefs.h
index bc504bcb0188..19b9b49d2dae 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -217,5 +217,5 @@ void tracefs_trace_pipe_stop(struct tracefs_instance *instance);
 
 int tracefs_kprobe_raw(const char *system, const char *event,
 		       const char *addr, const char *format);
-
+int tracefs_kprobe_clear(bool force);
 #endif /* _TRACE_FS_H */
diff --git a/src/tracefs-kprobes.c b/src/tracefs-kprobes.c
index e4b28cff9f08..a6faf69fc010 100644
--- a/src/tracefs-kprobes.c
+++ b/src/tracefs-kprobes.c
@@ -68,3 +68,119 @@ int tracefs_kprobe_raw(const char *system, const char *event,
 
 	return ret < 0 ? ret : 0;
 }
+
+struct instance_list {
+	struct instance_list	*next;
+	struct tracefs_instance	*instance;
+};
+
+static void disable_events(const char *system, const char *event,
+			   char **list)
+{
+	struct tracefs_instance *instance;
+	int i;
+
+	/*
+	 * Note, this will not fail even on error.
+	 * That is because even if something fails, it may still
+	 * work enough to clear the kprobes. If that's the case
+	 * the clearing after the loop will succeed and the function
+	 * is a success, even though other parts had failed. If
+	 * one of the kprobe events is enabled in one of the
+	 * instances that fail, then the clearing will fail too
+	 * and the function will return an error.
+	 */
+
+	tracefs_event_disable(NULL, system, event);
+	/* No need to test results */
+
+	if (!list)
+		return;
+
+	for (i = 0; list[i]; i++) {
+		instance = tracefs_instance_alloc(NULL, list[i]);
+		/* If this fails, try the next one */
+		if (!instance)
+			continue;
+		tracefs_event_disable(instance, system, event);
+		tracefs_instance_free(instance);
+	}
+	return;
+}
+
+/**
+ * tracefs_kprobe_clear - clear kprobe events
+ * @force: Will attempt to disable all kprobe events and clear them
+ *
+ * Will remove all defined kprobe events. If any of them are enabled,
+ * and @force is not set, then it will error with -1 and errno to be
+ * EBUSY. If @force is set, then it will attempt to disable all the kprobe
+ * events in all instances, and try again.
+ *
+ * Returns zero on success, -1 otherwise.
+ */
+int tracefs_kprobe_clear(bool force)
+{
+	char **instance_list;
+	char *content;
+	char *saveptr;
+	char *system;
+	char *event;
+	char *p;
+	int ret;
+
+	ret = tracefs_instance_file_clear(NULL, KPROBE_EVENTS);
+	if (!ret)
+		return 0;
+
+	if (!force)
+		return -1;
+
+	/* Attempt to disable all kprobe events */
+	content = tracefs_instance_file_read(NULL, KPROBE_EVENTS, NULL);
+	if (!content)
+		return -1;
+
+	instance_list = tracefs_instances(NULL);
+	/*
+	 * Even if the above failed and instance_list is NULL,
+	 * keep going, as the enabled event may simply be in the
+	 * top level.
+	 */
+
+	ret = -1;
+	p = strtok_r(content, ":", &saveptr);
+	if (!p)
+		goto out;
+
+	for (;;) {
+		p = strtok_r(NULL, "/", &saveptr);
+		if (!p)
+			goto out;
+
+		system = p;
+
+		p = strtok_r(NULL," ", &saveptr);
+		if (!p)
+			goto out;
+		event = p;
+
+		disable_events(system, event, instance_list);
+
+		ret = tracefs_instance_file_clear(NULL, KPROBE_EVENTS);
+		/* On success stop the loop */
+		if (!ret)
+			goto out;
+
+		ret = -1;
+		p = strtok_r(NULL, "\n", &saveptr);
+		if (!p)
+			goto out;
+
+		p = strtok_r(NULL, ":", &saveptr);
+	}
+ out:
+	tracefs_list_free(instance_list);
+	free(content);
+	return ret;
+}
-- 
2.30.2