Add low level support for ftrace return tracing

index f8173ed..bf574b3 100644
@@ -20,4 +20,30 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
 #endif /* __ASSEMBLY__ */
 #endif /* CONFIG_FUNCTION_TRACER */
 
+#ifdef CONFIG_FTRACE_RETURN
+#define FTRACE_RET_STACK_SIZE 20
+
+#ifndef __ASSEMBLY__
+
+/*
+ * Stack of return addresses for functions
+ * of a thread.
+ * Used in struct thread_info
+ */
+struct ftrace_ret_stack {
+	unsigned long ret;
+	unsigned long func;
+	unsigned long long calltime;
+};
+
+/*
+ * Primary handler of a function return.
+ * It relays on ftrace_return_to_handler.
+ * Defined in entry32.S
+ */
+extern void return_to_handler(void);
+
+#endif /* __ASSEMBLY__ */
+#endif /* CONFIG_FTRACE_RETURN */
+
 #endif /* _ASM_X86_FTRACE_H */

index e44d379..8b9b3e2 100644
@@ -20,6 +20,7 @@
 struct task_struct;
 struct exec_domain;
 #include <asm/processor.h>
+#include <asm/ftrace.h>
 
 struct thread_info {
 	struct task_struct	*task;		/* main task structure */

@@ -38,8 +39,30 @@ struct thread_info {
 						*/
 	__u8			supervisor_stack[0];
 #endif
+
+#ifdef CONFIG_FTRACE_RETURN
+	/* Index of current stored adress in ret_stack */
+	int		curr_ret_stack;
+	/* Stack of return addresses for return function tracing */
+	struct ftrace_ret_stack	ret_stack[FTRACE_RET_STACK_SIZE];
+#endif
 };
 
+#ifdef CONFIG_FTRACE_RETURN
+#define INIT_THREAD_INFO(tsk)			\
+{						\
+	.task		= &tsk,			\
+	.exec_domain	= &default_exec_domain,	\
+	.flags		= 0,			\
+	.cpu		= 0,			\
+	.preempt_count	= 1,			\
+	.addr_limit	= KERNEL_DS,		\
+	.restart_block = {			\
+		.fn = do_no_restart_syscall,	\
+	},					\
+	.curr_ret_stack = -1,\
+}
+#else
 #define INIT_THREAD_INFO(tsk)			\
 {						\
 	.task		= &tsk,			\

@@ -52,6 +75,7 @@ struct thread_info {
 		.fn = do_no_restart_syscall,	\
 	},					\
 }
+#endif
 
 #define init_thread_info	(init_thread_union.thread_info)
 #define init_stack		(init_thread_union.stack)

210 lines not on this page · raw message

index 1f5608c..76faccd 100644
@@ -268,6 +268,26 @@ ftrace_init_module(unsigned long *start, unsigned long *end) { }
 
 
 /*
+ * Structure that defines a return function trace.
+ */
+struct ftrace_retfunc {
+	unsigned long ret; /* Return address */
+	unsigned long func; /* Current function */
+	unsigned long long calltime;
+	unsigned long long rettime;
+};
+
+#ifdef CONFIG_FTRACE_RETURN
+/* Type of a callback handler of tracing return function */
+typedef void (*trace_function_return_t)(struct ftrace_retfunc *);
+
+extern void register_ftrace_return(trace_function_return_t func);
+/* The current handler in use */
+extern trace_function_return_t ftrace_function_return;
+extern void unregister_ftrace_return(void);
+#endif
+
+/*
  * Structure which defines the trace of an initcall.
  * You don't have to fill the func field since it is
  * only used internally by the tracer.

index b1299d6..e47e432 100644
@@ -2,7 +2,7 @@
 #define _LINUX_FTRACE_IRQ_H
 
 
-#ifdef CONFIG_DYNAMIC_FTRACE
+#if defined(CONFIG_DYNAMIC_FTRACE) || defined(CONFIG_FTRACE_RETURN)
 extern void ftrace_nmi_enter(void);
 extern void ftrace_nmi_exit(void);
 #else

index 51ad5af..05dd4b4 100644
@@ -2004,6 +2004,17 @@ static inline void setup_thread_stack(struct task_struct *p, struct task_struct
 {
 	*task_thread_info(p) = *task_thread_info(org);
 	task_thread_info(p)->task = p;
+
+#ifdef CONFIG_FTRACE_RETURN
+	/*
+	 * When fork() creates a child process, this function is called.
+	 * But the child task may not inherit the return adresses traced
+	 * by the return function tracer because it will directly execute
+	 * in userspace and will not return to kernel functions its parent
+	 * used.
+	 */
+	task_thread_info(p)->curr_ret_stack = -1;
+#endif
 }
 
 static inline unsigned long *end_of_stack(struct task_struct *p)