From: Zhaolei <zhaolei@cn.fujitsu.com>
Date: Wed, 25 Mar 2009 04:06:05 +0000 (+0800)
Subject: ftrace: Using FTRACE_WARN_ON() to check "freed record" in ftrace_release()
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=2a4efa42450762cbfa5c5712aa4cc9f06924c9fd;p=linux-2.6-omap-h63xx.git

ftrace: Using FTRACE_WARN_ON() to check "freed record" in ftrace_release()

 "Because when we call ftrace_free_rec we change the rec->ip to point to the
  next record in the chain. Something is very wrong if rec->ip >= s &&
  rec->ip < e and the record is already free."

 "Note, use FTRACE_WARN_ON() macro. This way it shuts down ftrace if it is
  hit and helps to avoid further damage later."
                   -- Steven Rostedt <rostedt@goodmis.org>

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7b8722baf15..1752a63f37c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -358,9 +358,14 @@ void ftrace_release(void *start, unsigned long size)
 
 	mutex_lock(&ftrace_lock);
 	do_for_each_ftrace_rec(pg, rec) {
-		if ((rec->ip >= s) && (rec->ip < e) &&
-		    !(rec->flags & FTRACE_FL_FREE))
+		if ((rec->ip >= s) && (rec->ip < e)) {
+			/*
+			 * rec->ip is changed in ftrace_free_rec()
+			 * It should not between s and e if record was freed.
+			 */
+			FTRACE_WARN_ON(rec->flags & FTRACE_FL_FREE);
 			ftrace_free_rec(rec);
+		}
 	} while_for_each_ftrace_rec();
 	mutex_unlock(&ftrace_lock);
 }