From 5a9479dcba0b43d326569fa0bd48318222d23fcb Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 18 May 2011 23:57:08 -0400
Subject: [PATCH] Fix ftrace support

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 probes/lttng-ftrace.c | 13 ++++----
 wrapper/ftrace.h      | 70 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 77 insertions(+), 6 deletions(-)
 create mode 100644 wrapper/ftrace.h

diff --git a/probes/lttng-ftrace.c b/probes/lttng-ftrace.c
index 4b7be183..3ec000ae 100644
--- a/probes/lttng-ftrace.c
+++ b/probes/lttng-ftrace.c
@@ -12,10 +12,11 @@
 #include <linux/slab.h>
 #include "../ltt-events.h"
 #include "../wrapper/ringbuffer/frontend_types.h"
+#include "../wrapper/ftrace.h"
 #include "../ltt-tracer.h"
 
 static
-int lttng_ftrace_handler(unsigned long ip, unsigned long parent_ip, void **data)
+void lttng_ftrace_handler(unsigned long ip, unsigned long parent_ip, void **data)
 {
 	struct ltt_event *event = *data;
 	struct ltt_channel *chan = event->chan;
@@ -27,18 +28,18 @@ int lttng_ftrace_handler(unsigned long ip, unsigned long parent_ip, void **data)
 	int ret;
 
 	if (!ACCESS_ONCE(chan->session->active))
-		return 0;
+		return;
 	lib_ring_buffer_ctx_init(&ctx, chan->chan, NULL,
 				 sizeof(payload), ltt_alignof(payload), -1);
 	ret = chan->ops->event_reserve(&ctx);
 	if (ret < 0)
-		return 0;
+		return;
 	payload.ip = ip;
 	payload.parent_ip = parent_ip;
 	lib_ring_buffer_align_ctx(&ctx, ltt_alignof(payload));
 	chan->ops->event_write(&ctx, &payload, sizeof(payload));
 	chan->ops->event_commit(&ctx);
-	return 0;
+	return;
 }
 
 /*
@@ -108,7 +109,7 @@ int lttng_ftrace_register(const char *name,
 	if (!event->u.ftrace.symbol_name)
 		goto name_error;
 
-	ret = register_ftrace_function_probe(symbol_name,
+	ret = wrapper_register_ftrace_function_probe(event->u.ftrace.symbol_name,
 			&lttng_ftrace_ops, event);
 	if (ret)
 		goto register_error;
@@ -126,7 +127,7 @@ EXPORT_SYMBOL_GPL(lttng_ftrace_register);
 
 void lttng_ftrace_unregister(struct ltt_event *event)
 {
-	unregister_ftrace_function_probe(event->u.ftrace.symbol_name,
+	wrapper_unregister_ftrace_function_probe(event->u.ftrace.symbol_name,
 			&lttng_ftrace_ops, event);
 	kfree(event->u.ftrace.symbol_name);
 	kfree(event->desc->name);
diff --git a/wrapper/ftrace.h b/wrapper/ftrace.h
new file mode 100644
index 00000000..44014692
--- /dev/null
+++ b/wrapper/ftrace.h
@@ -0,0 +1,70 @@
+#ifndef _LTT_WRAPPER_FTRACE_H
+#define _LTT_WRAPPER_FTRACE_H
+
+/*
+ * Copyright (C) 2011 Mathieu Desnoyers (mathieu.desnoyers@efficios.com)
+ *
+ * wrapper around vmalloc_sync_all. Using KALLSYMS to get its address when
+ * available, else we need to have a kernel that exports this function to GPL
+ * modules.
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+#include <linux/ftrace.h>
+
+#ifdef CONFIG_KALLSYMS
+
+#include <linux/kallsyms.h>
+
+static inline
+int wrapper_register_ftrace_function_probe(char *glob,
+		struct ftrace_probe_ops *ops, void *data)
+{
+	int (*register_ftrace_function_probe_sym)(char *glob,
+			struct ftrace_probe_ops *ops, void *data);
+
+	register_ftrace_function_probe_sym = (void *) kallsyms_lookup_name("register_ftrace_function_probe_sym");
+	if (register_ftrace_function_probe_sym) {
+		return register_ftrace_function_probe_sym(glob, ops, data);
+	} else {
+		printk(KERN_WARNING "LTTng: register_ftrace_function_probe symbol lookup failed.\n");
+		return -EINVAL;
+	}
+}
+
+static inline
+void wrapper_unregister_ftrace_function_probe(char *glob,
+		struct ftrace_probe_ops *ops, void *data)
+{
+	void (*unregister_ftrace_function_probe_sym)(char *glob,
+			struct ftrace_probe_ops *ops, void *data);
+
+	unregister_ftrace_function_probe_sym = (void *) kallsyms_lookup_name("unregister_ftrace_function_probe_sym");
+	if (unregister_ftrace_function_probe_sym) {
+		unregister_ftrace_function_probe_sym(glob, ops, data);
+	} else {
+		printk(KERN_WARNING "LTTng: unregister_ftrace_function_probe symbol lookup failed.\n");
+		WARN_ON(1);
+	}
+}
+
+#else
+
+static inline
+int wrapper_register_ftrace_function_probe(char *glob,
+		struct ftrace_probe_ops *ops, void *data);
+
+{
+	return unregister_ftrace_function_probe();
+}
+
+static inline
+void wrapper_unregister_ftrace_function_probe(char *glob,
+		struct ftrace_probe_ops *ops, void *data);
+{
+	return unregister_ftrace_function_probe();
+}
+#endif
+
+#endif /* _LTT_WRAPPER_FTRACE_H */
-- 
2.34.1