fgraph: Add new fgraph_ops structure to enable function graph hooks

Currently the registering of function graph is to pass in a entry and return
function. We need to have a way to associate those functions together where
the entry can determine to run the return hook. Having a structure that
contains both functions will facilitate the process of converting the code
to be able to do such.

This is similar to the way function hooks are enabled (it passes in
ftrace_ops). Instead of passing in the functions to use, a single structure
is passed in to the registering function.

The unregister function is now passed in the fgraph_ops handle. When we
allow more than one callback to the function graph hooks, this will let the
system know which one to remove.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 11 insertions, 10 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 98625f10d982..21c80491ccde 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -749,6 +749,11 @@ typedef int (*trace_func_graph_ent_t)(struct ftrace_graph_ent *); /* entry */
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
+struct fgraph_ops {
+	trace_func_graph_ent_t		entryfunc;
+	trace_func_graph_ret_t		retfunc;
+};
+
 /*
  * Stack of return addresses for functions
  * of a thread.
@@ -792,8 +797,9 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
 
 #define FTRACE_RETFUNC_DEPTH 50
 #define FTRACE_RETSTACK_ALLOC_SIZE 32
-extern int register_ftrace_graph(trace_func_graph_ret_t retfunc,
-				trace_func_graph_ent_t entryfunc);
+
+extern int register_ftrace_graph(struct fgraph_ops *ops);
+extern void unregister_ftrace_graph(struct fgraph_ops *ops);
 
 extern bool ftrace_graph_is_dead(void);
 extern void ftrace_graph_stop(void);
@@ -802,8 +808,6 @@ extern void ftrace_graph_stop(void);
 extern trace_func_graph_ret_t ftrace_graph_return;
 extern trace_func_graph_ent_t ftrace_graph_entry;
 
-extern void unregister_ftrace_graph(void);
-
 extern void ftrace_graph_init_task(struct task_struct *t);
 extern void ftrace_graph_exit_task(struct task_struct *t);
 extern void ftrace_graph_init_idle_task(struct task_struct *t, int cpu);
@@ -825,12 +829,9 @@ static inline void ftrace_graph_init_task(struct task_struct *t) { }
 static inline void ftrace_graph_exit_task(struct task_struct *t) { }
 static inline void ftrace_graph_init_idle_task(struct task_struct *t, int cpu) { }
 
-static inline int register_ftrace_graph(trace_func_graph_ret_t retfunc,
-			  trace_func_graph_ent_t entryfunc)
-{
-	return -1;
-}
-static inline void unregister_ftrace_graph(void) { }
+/* Define as macros as fgraph_ops may not be defined */
+#define register_ftrace_graph(ops) ({ -1; })
+#define unregister_ftrace_graph(ops) do { } while (0)
 
 static inline unsigned long
 ftrace_graph_ret_addr(struct task_struct *task, int *idx, unsigned long ret,