ftrace: Add default recursion protection for function tracing
As more users of the function tracer utility are being added, they do
not always add the necessary recursion protection. To protect from
function recursion due to tracing, if the callback ftrace_ops does not
specifically specify that it protects against recursion (by setting
the FTRACE_OPS_FL_RECURSION_SAFE flag), the list operation will be
called by the mcount trampoline which adds recursion protection.
If the flag is set, then the function will be called directly with no
extra protection.
Note, the list operation is called if more than one function callback
is registered, or if the arch does not support all of the function
tracer features.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c55f7e2..ad765b4 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -66,6 +66,7 @@
static struct ftrace_ops ftrace_list_end __read_mostly = {
.func = ftrace_stub,
+ .flags = FTRACE_OPS_FL_RECURSION_SAFE,
};
/* ftrace_enabled is a method to turn ftrace on or off */
@@ -221,12 +222,13 @@
/*
* If we are at the end of the list and this ops is
- * not dynamic and the arch supports passing ops, then have the
- * mcount trampoline call the function directly.
+ * recursion safe and not dynamic and the arch supports passing ops,
+ * then have the mcount trampoline call the function directly.
*/
if (ftrace_ops_list == &ftrace_list_end ||
(ftrace_ops_list->next == &ftrace_list_end &&
!(ftrace_ops_list->flags & FTRACE_OPS_FL_DYNAMIC) &&
+ (ftrace_ops_list->flags & FTRACE_OPS_FL_RECURSION_SAFE) &&
!FTRACE_FORCE_LIST_FUNC)) {
/* Set the ftrace_ops that the arch callback uses */
if (ftrace_ops_list == &global_ops)
@@ -867,6 +869,7 @@
#else
static struct ftrace_ops ftrace_profile_ops __read_mostly = {
.func = function_profile_call,
+ .flags = FTRACE_OPS_FL_RECURSION_SAFE,
};
static int register_ftrace_profiler(void)
@@ -1049,6 +1052,7 @@
.func = ftrace_stub,
.notrace_hash = EMPTY_HASH,
.filter_hash = EMPTY_HASH,
+ .flags = FTRACE_OPS_FL_RECURSION_SAFE,
};
static DEFINE_MUTEX(ftrace_regex_lock);
@@ -3967,6 +3971,7 @@
static struct ftrace_ops global_ops = {
.func = ftrace_stub,
+ .flags = FTRACE_OPS_FL_RECURSION_SAFE,
};
static int __init ftrace_nodyn_init(void)
@@ -4023,6 +4028,7 @@
static struct ftrace_ops control_ops = {
.func = ftrace_ops_control_func,
+ .flags = FTRACE_OPS_FL_RECURSION_SAFE,
};
static inline void