[tip:tracing/urgent] tracing: Fix infinite recursion in ftrace_update_pid_func()

tip-bot for Matt Fleming
2009-10-01T06:49:15Z

Commit-ID: 33974093c024f08caadd2fc71a83bd811ed1831d
Gitweb: http://git.kernel.org/tip/33974093c024f08caadd2fc71a83bd811ed1831d
Author: Matt Fleming <matthew.fleming@imgtec.com>
AuthorDate: Mon, 28 Sep 2009 16:43:01 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Thu, 1 Oct 2009 08:19:24 +0200

tracing: Fix infinite recursion in ftrace_update_pid_func()

When CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST is enabled
__ftrace_trace_function contains the current trace function, not
ftrace_trace_function.

In ftrace_update_pid_func() we currently incorrectly assign the
value of ftrace_trace_function to __ftrace_trace_funcion before
returning.

Without this patch it is possible to execute an infinite recursion
whereby ftrace_test_stop_func() calls __ftrace_trace_function,
which was assigned ftrace_test_stop_func() in
ftrace_update_pid_func().

Signed-off-by: Matt Fleming <matthew.fleming@imgtec.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1254152581-18347-1-git-send-email-matt@console-pimps.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
kernel/trace/ftrace.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 46592fe..3724756 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -225,7 +225,11 @@ static void ftrace_update_pid_func(void)
if (ftrace_trace_function == ftrace_stub)
return;

+#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
func = ftrace_trace_function;
+#else
+ func = __ftrace_trace_function;
+#endif

if (ftrace_pid_trace) {
set_ftrace_pid_function(func);