From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 2 Sep 2015 02:27:35 +0000 (-0400)
Subject: Fix: non-enabler events should be disabled by default
X-Git-Tag: v2.8.0-rc1~83
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=a0493bef1367458230b0319401f8533b0400cea2;p=lttng-modules.git

Fix: non-enabler events should be disabled by default

The session daemon expects that all events (enablers and events) are
disabled when created, so we can attach a filter before enabling them.

Also fix the kretprobe to ensure we can enable/disable both the entry
and return probe (--function instrumentation).

Fixes: #926

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/lttng-events.c b/lttng-events.c
index c49174dd..bd7b4efe 100644
--- a/lttng-events.c
+++ b/lttng-events.c
@@ -329,8 +329,23 @@ int lttng_event_enable(struct lttng_event *event)
 		ret = -EEXIST;
 		goto end;
 	}
-	ACCESS_ONCE(event->enabled) = 1;
-	lttng_session_sync_enablers(event->chan->session);
+	switch (event->instrumentation) {
+	case LTTNG_KERNEL_TRACEPOINT:
+	case LTTNG_KERNEL_SYSCALL:
+		ret = -EINVAL;
+		break;
+	case LTTNG_KERNEL_KPROBE:
+	case LTTNG_KERNEL_FUNCTION:
+	case LTTNG_KERNEL_NOOP:
+		ACCESS_ONCE(event->enabled) = 1;
+		break;
+	case LTTNG_KERNEL_KRETPROBE:
+		ret = lttng_kretprobes_event_enable_state(event, 1);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		ret = -EINVAL;
+	}
 end:
 	mutex_unlock(&sessions_mutex);
 	return ret;
@@ -349,8 +364,23 @@ int lttng_event_disable(struct lttng_event *event)
 		ret = -EEXIST;
 		goto end;
 	}
-	ACCESS_ONCE(event->enabled) = 0;
-	lttng_session_sync_enablers(event->chan->session);
+	switch (event->instrumentation) {
+	case LTTNG_KERNEL_TRACEPOINT:
+	case LTTNG_KERNEL_SYSCALL:
+		ret = -EINVAL;
+		break;
+	case LTTNG_KERNEL_KPROBE:
+	case LTTNG_KERNEL_FUNCTION:
+	case LTTNG_KERNEL_NOOP:
+		ACCESS_ONCE(event->enabled) = 0;
+		break;
+	case LTTNG_KERNEL_KRETPROBE:
+		ret = lttng_kretprobes_event_enable_state(event, 0);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		ret = -EINVAL;
+	}
 end:
 	mutex_unlock(&sessions_mutex);
 	return ret;
@@ -538,7 +568,11 @@ struct lttng_event *_lttng_event_create(struct lttng_channel *chan,
 		smp_wmb();
 		break;
 	case LTTNG_KERNEL_KPROBE:
-		event->enabled = 1;
+		/*
+		 * Needs to be explicitly enabled after creation, since
+		 * we may want to apply filters.
+		 */
+		event->enabled = 0;
 		event->registered = 1;
 		/*
 		 * Populate lttng_event structure before event
@@ -562,7 +596,11 @@ struct lttng_event *_lttng_event_create(struct lttng_channel *chan,
 		struct lttng_event *event_return;
 
 		/* kretprobe defines 2 events */
-		event->enabled = 1;
+		/*
+		 * Needs to be explicitly enabled after creation, since
+		 * we may want to apply filters.
+		 */
+		event->enabled = 0;
 		event->registered = 1;
 		event_return =
 			kmem_cache_zalloc(event_cache, GFP_KERNEL);
@@ -573,7 +611,7 @@ struct lttng_event *_lttng_event_create(struct lttng_channel *chan,
 		event_return->chan = chan;
 		event_return->filter = filter;
 		event_return->id = chan->free_event_id++;
-		event_return->enabled = 1;
+		event_return->enabled = 0;
 		event_return->registered = 1;
 		event_return->instrumentation = itype;
 		/*
@@ -608,7 +646,11 @@ struct lttng_event *_lttng_event_create(struct lttng_channel *chan,
 		break;
 	}
 	case LTTNG_KERNEL_FUNCTION:
-		event->enabled = 1;
+		/*
+		 * Needs to be explicitly enabled after creation, since
+		 * we may want to apply filters.
+		 */
+		event->enabled = 0;
 		event->registered = 1;
 		/*
 		 * Populate lttng_event structure before event
@@ -626,7 +668,11 @@ struct lttng_event *_lttng_event_create(struct lttng_channel *chan,
 		break;
 	case LTTNG_KERNEL_NOOP:
 	case LTTNG_KERNEL_SYSCALL:
-		event->enabled = 1;
+		/*
+		 * Needs to be explicitly enabled after creation, since
+		 * we may want to apply filters.
+		 */
+		event->enabled = 0;
 		event->registered = 0;
 		event->desc = event_desc;
 		if (!event->desc) {
diff --git a/lttng-events.h b/lttng-events.h
index b3e94a0c..82b88e85 100644
--- a/lttng-events.h
+++ b/lttng-events.h
@@ -681,6 +681,8 @@ int lttng_kretprobes_register(const char *name,
 		struct lttng_event *event_exit);
 void lttng_kretprobes_unregister(struct lttng_event *event);
 void lttng_kretprobes_destroy_private(struct lttng_event *event);
+int lttng_kretprobes_event_enable_state(struct lttng_event *event,
+	int enable);
 #else
 static inline
 int lttng_kretprobes_register(const char *name,
@@ -702,6 +704,13 @@ static inline
 void lttng_kretprobes_destroy_private(struct lttng_event *event)
 {
 }
+
+static inline
+int lttng_kretprobes_event_enable_state(struct lttng_event *event,
+	int enable)
+{
+	return -ENOSYS;
+}
 #endif
 
 #ifdef CONFIG_DYNAMIC_FTRACE
diff --git a/probes/lttng-kretprobes.c b/probes/lttng-kretprobes.c
index d71090a2..52b3f781 100644
--- a/probes/lttng-kretprobes.c
+++ b/probes/lttng-kretprobes.c
@@ -285,6 +285,26 @@ void lttng_kretprobes_destroy_private(struct lttng_event *event)
 }
 EXPORT_SYMBOL_GPL(lttng_kretprobes_destroy_private);
 
+int lttng_kretprobes_event_enable_state(struct lttng_event *event,
+		int enable)
+{
+	struct lttng_event *event_return;
+	struct lttng_krp *lttng_krp;
+
+	if (event->instrumentation != LTTNG_KERNEL_KRETPROBE) {
+		return -EINVAL;
+	}
+	if (event->enabled == enable) {
+		return -EBUSY;
+	}
+	lttng_krp = event->u.kretprobe.lttng_krp;
+	event_return = lttng_krp->event[EVENT_RETURN];
+	ACCESS_ONCE(event->enabled) = enable;
+	ACCESS_ONCE(event_return->enabled) = enable;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(lttng_kretprobes_event_enable_state);
+
 MODULE_LICENSE("GPL and additional rights");
 MODULE_AUTHOR("Mathieu Desnoyers");
 MODULE_DESCRIPTION("Linux Trace Toolkit Kretprobes Support");