6 files changed, 211 insertions, 155 deletions

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index f9762114983..74defe21ba4 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1190,7 +1190,7 @@ ENTRY(mcount)
 	jnz trace
 #ifdef CONFIG_FUNCTION_RET_TRACER
 	cmpl $ftrace_stub, ftrace_function_return
-	jnz trace_return
+	jnz ftrace_return_caller
 #endif
 .globl ftrace_stub
 ftrace_stub:
@@ -1211,9 +1211,15 @@ trace:
 	popl %ecx
 	popl %eax
 	jmp ftrace_stub
+END(mcount)
+#endif /* CONFIG_DYNAMIC_FTRACE */
+#endif /* CONFIG_FUNCTION_TRACER */
 
 #ifdef CONFIG_FUNCTION_RET_TRACER
-trace_return:
+ENTRY(ftrace_return_caller)
+	cmpl $0, function_trace_stop
+	jne ftrace_stub
+
 	pushl %eax
 	pushl %ecx
 	pushl %edx
@@ -1223,7 +1229,8 @@ trace_return:
 	popl %edx
 	popl %ecx
 	popl %eax
-	jmp ftrace_stub
+	ret
+END(ftrace_return_caller)
 
 .globl return_to_handler
 return_to_handler:
@@ -1237,10 +1244,7 @@ return_to_handler:
 	popl %ecx
 	popl %eax
 	ret
-#endif /* CONFIG_FUNCTION_RET_TRACER */
-END(mcount)
-#endif /* CONFIG_DYNAMIC_FTRACE */
-#endif /* CONFIG_FUNCTION_TRACER */
+#endif
 
 .section .rodata,"a"
 #include "syscall_table_32.S"
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index d98b5a8ecf4..924153edd97 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -24,134 +24,6 @@
 #include <asm/nmi.h>
 
 
-
-#ifdef CONFIG_FUNCTION_RET_TRACER
-
-/*
- * These functions are picked from those used on
- * this page for dynamic ftrace. They have been
- * simplified to ignore all traces in NMI context.
- */
-static atomic_t in_nmi;
-
-void ftrace_nmi_enter(void)
-{
-	atomic_inc(&in_nmi);
-}
-
-void ftrace_nmi_exit(void)
-{
-	atomic_dec(&in_nmi);
-}
-
-/* Add a function return address to the trace stack on thread info.*/
-static int push_return_trace(unsigned long ret, unsigned long long time,
-				unsigned long func)
-{
-	int index;
-	struct thread_info *ti = current_thread_info();
-
-	/* The return trace stack is full */
-	if (ti->curr_ret_stack == FTRACE_RET_STACK_SIZE - 1)
-		return -EBUSY;
-
-	index = ++ti->curr_ret_stack;
-	barrier();
-	ti->ret_stack[index].ret = ret;
-	ti->ret_stack[index].func = func;
-	ti->ret_stack[index].calltime = time;
-
-	return 0;
-}
-
-/* Retrieve a function return address to the trace stack on thread info.*/
-static void pop_return_trace(unsigned long *ret, unsigned long long *time,
-				unsigned long *func)
-{
-	int index;
-
-	struct thread_info *ti = current_thread_info();
-	index = ti->curr_ret_stack;
-	*ret = ti->ret_stack[index].ret;
-	*func = ti->ret_stack[index].func;
-	*time = ti->ret_stack[index].calltime;
-	ti->curr_ret_stack--;
-}
-
-/*
- * Send the trace to the ring-buffer.
- * @return the original return address.
- */
-unsigned long ftrace_return_to_handler(void)
-{
-	struct ftrace_retfunc trace;
-	pop_return_trace(&trace.ret, &trace.calltime, &trace.func);
-	trace.rettime = cpu_clock(raw_smp_processor_id());
-	ftrace_function_return(&trace);
-
-	return trace.ret;
-}
-
-/*
- * Hook the return address and push it in the stack of return addrs
- * in current thread info.
- */
-void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
-{
-	unsigned long old;
-	unsigned long long calltime;
-	int faulted;
-	unsigned long return_hooker = (unsigned long)
-				&return_to_handler;
-
-	/* Nmi's are currently unsupported */
-	if (atomic_read(&in_nmi))
-		return;
-
-	/*
-	 * Protect against fault, even if it shouldn't
-	 * happen. This tool is too much intrusive to
-	 * ignore such a protection.
-	 */
-	asm volatile(
-		"1: movl (%[parent_old]), %[old]\n"
-		"2: movl %[return_hooker], (%[parent_replaced])\n"
-		"   movl $0, %[faulted]\n"
-
-		".section .fixup, \"ax\"\n"
-		"3: movl $1, %[faulted]\n"
-		".previous\n"
-
-		".section __ex_table, \"a\"\n"
-		"   .long 1b, 3b\n"
-		"   .long 2b, 3b\n"
-		".previous\n"
-
-		: [parent_replaced] "=r" (parent), [old] "=r" (old),
-		  [faulted] "=r" (faulted)
-		: [parent_old] "0" (parent), [return_hooker] "r" (return_hooker)
-		: "memory"
-	);
-
-	if (WARN_ON(faulted)) {
-		unregister_ftrace_return();
-		return;
-	}
-
-	if (WARN_ON(!__kernel_text_address(old))) {
-		unregister_ftrace_return();
-		*parent = old;
-		return;
-	}
-
-	calltime = cpu_clock(raw_smp_processor_id());
-
-	if (push_return_trace(old, calltime, self_addr) == -EBUSY)
-		*parent = old;
-}
-
-#endif
-
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 union ftrace_code_union {
@@ -450,3 +322,133 @@ int __init ftrace_dyn_arch_init(void *data)
 	return 0;
 }
 #endif
+
+#ifdef CONFIG_FUNCTION_RET_TRACER
+
+#ifndef CONFIG_DYNAMIC_FTRACE
+
+/*
+ * These functions are picked from those used on
+ * this page for dynamic ftrace. They have been
+ * simplified to ignore all traces in NMI context.
+ */
+static atomic_t in_nmi;
+
+void ftrace_nmi_enter(void)
+{
+	atomic_inc(&in_nmi);
+}
+
+void ftrace_nmi_exit(void)
+{
+	atomic_dec(&in_nmi);
+}
+#endif /* !CONFIG_DYNAMIC_FTRACE */
+
+/* Add a function return address to the trace stack on thread info.*/
+static int push_return_trace(unsigned long ret, unsigned long long time,
+				unsigned long func)
+{
+	int index;
+	struct thread_info *ti = current_thread_info();
+
+	/* The return trace stack is full */
+	if (ti->curr_ret_stack == FTRACE_RET_STACK_SIZE - 1)
+		return -EBUSY;
+
+	index = ++ti->curr_ret_stack;
+	barrier();
+	ti->ret_stack[index].ret = ret;
+	ti->ret_stack[index].func = func;
+	ti->ret_stack[index].calltime = time;
+
+	return 0;
+}
+
+/* Retrieve a function return address to the trace stack on thread info.*/
+static void pop_return_trace(unsigned long *ret, unsigned long long *time,
+				unsigned long *func)
+{
+	int index;
+
+	struct thread_info *ti = current_thread_info();
+	index = ti->curr_ret_stack;
+	*ret = ti->ret_stack[index].ret;
+	*func = ti->ret_stack[index].func;
+	*time = ti->ret_stack[index].calltime;
+	ti->curr_ret_stack--;
+}
+
+/*
+ * Send the trace to the ring-buffer.
+ * @return the original return address.
+ */
+unsigned long ftrace_return_to_handler(void)
+{
+	struct ftrace_retfunc trace;
+	pop_return_trace(&trace.ret, &trace.calltime, &trace.func);
+	trace.rettime = cpu_clock(raw_smp_processor_id());
+	ftrace_function_return(&trace);
+
+	return trace.ret;
+}
+
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in current thread info.
+ */
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
+{
+	unsigned long old;
+	unsigned long long calltime;
+	int faulted;
+	unsigned long return_hooker = (unsigned long)
+				&return_to_handler;
+
+	/* Nmi's are currently unsupported */
+	if (atomic_read(&in_nmi))
+		return;
+
+	/*
+	 * Protect against fault, even if it shouldn't
+	 * happen. This tool is too much intrusive to
+	 * ignore such a protection.
+	 */
+	asm volatile(
+		"1: movl (%[parent_old]), %[old]\n"
+		"2: movl %[return_hooker], (%[parent_replaced])\n"
+		"   movl $0, %[faulted]\n"
+
+		".section .fixup, \"ax\"\n"
+		"3: movl $1, %[faulted]\n"
+		".previous\n"
+
+		".section __ex_table, \"a\"\n"
+		"   .long 1b, 3b\n"
+		"   .long 2b, 3b\n"
+		".previous\n"
+
+		: [parent_replaced] "=r" (parent), [old] "=r" (old),
+		  [faulted] "=r" (faulted)
+		: [parent_old] "0" (parent), [return_hooker] "r" (return_hooker)
+		: "memory"
+	);
+
+	if (WARN_ON(faulted)) {
+		unregister_ftrace_return();
+		return;
+	}
+
+	if (WARN_ON(!__kernel_text_address(old))) {
+		unregister_ftrace_return();
+		*parent = old;
+		return;
+	}
+
+	calltime = cpu_clock(raw_smp_processor_id());
+
+	if (push_return_trace(old, calltime, self_addr) == -EBUSY)
+		*parent = old;
+}
+
+#endif /* CONFIG_FUNCTION_RET_TRACER */
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 166a2070ef6..f1af1aab00e 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -25,6 +25,17 @@ struct ftrace_ops {
 
 extern int function_trace_stop;
 
+/*
+ * Type of the current tracing.
+ */
+enum ftrace_tracing_type_t {
+	FTRACE_TYPE_ENTER = 0, /* Hook the call of the function */
+	FTRACE_TYPE_RETURN,	/* Hook the return of the function */
+};
+
+/* Current tracing type, default is FTRACE_TYPE_ENTER */
+extern enum ftrace_tracing_type_t ftrace_tracing_type;
+
 /**
  * ftrace_stop - stop function tracer.
  *
@@ -104,6 +115,9 @@ extern int ftrace_update_ftrace_func(ftrace_func_t func);
 extern void ftrace_caller(void);
 extern void ftrace_call(void);
 extern void mcount_call(void);
+#ifdef CONFIG_FUNCTION_RET_TRACER
+extern void ftrace_return_caller(void);
+#endif
 
 /**
  * ftrace_make_nop - convert code into top
@@ -310,7 +324,7 @@ struct ftrace_retfunc {
 /* 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);
+extern int 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);
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 9c89526b6b7..b8378fad29a 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -59,7 +59,6 @@ config FUNCTION_TRACER
 
 config FUNCTION_RET_TRACER
 	bool "Kernel Function return Tracer"
-	depends on !DYNAMIC_FTRACE
 	depends on HAVE_FUNCTION_RET_TRACER
 	depends on FUNCTION_TRACER
 	help
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index b42ec1de546..2f78a45aac1 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -50,6 +50,9 @@ static int last_ftrace_enabled;
 /* Quick disabling of function tracer. */
 int function_trace_stop;
 
+/* By default, current tracing type is normal tracing. */
+enum ftrace_tracing_type_t ftrace_tracing_type = FTRACE_TYPE_ENTER;
+
 /*
  * ftrace_disabled is set when an anomaly is discovered.
  * ftrace_disabled is much stronger than ftrace_enabled.
@@ -385,12 +388,21 @@ static void ftrace_bug(int failed, unsigned long ip)
 	}
 }
 
-#define FTRACE_ADDR ((long)(ftrace_caller))
 
 static int
 __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
 {
 	unsigned long ip, fl;
+	unsigned long ftrace_addr;
+
+#ifdef CONFIG_FUNCTION_RET_TRACER
+	if (ftrace_tracing_type == FTRACE_TYPE_ENTER)
+		ftrace_addr = (unsigned long)ftrace_caller;
+	else
+		ftrace_addr = (unsigned long)ftrace_return_caller;
+#else
+	ftrace_addr = (unsigned long)ftrace_caller;
+#endif
 
 	ip = rec->ip;
 
@@ -450,9 +462,9 @@ __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
 	}
 
 	if (rec->flags & FTRACE_FL_ENABLED)
-		return ftrace_make_call(rec, FTRACE_ADDR);
+		return ftrace_make_call(rec, ftrace_addr);
 	else
-		return ftrace_make_nop(NULL, rec, FTRACE_ADDR);
+		return ftrace_make_nop(NULL, rec, ftrace_addr);
 }
 
 static void ftrace_replace_code(int enable)
@@ -1405,10 +1417,17 @@ int register_ftrace_function(struct ftrace_ops *ops)
 		return -1;
 
 	mutex_lock(&ftrace_sysctl_lock);
+
+	if (ftrace_tracing_type == FTRACE_TYPE_RETURN) {
+		ret = -EBUSY;
+		goto out;
+	}
+
 	ret = __register_ftrace_function(ops);
 	ftrace_startup();
-	mutex_unlock(&ftrace_sysctl_lock);
 
+out:
+	mutex_unlock(&ftrace_sysctl_lock);
 	return ret;
 }
 
@@ -1474,16 +1493,45 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 }
 
 #ifdef CONFIG_FUNCTION_RET_TRACER
+
+/* The callback that hooks the return of a function */
 trace_function_return_t ftrace_function_return =
 			(trace_function_return_t)ftrace_stub;
-void register_ftrace_return(trace_function_return_t func)
+
+int register_ftrace_return(trace_function_return_t func)
 {
+	int ret = 0;
+
+	mutex_lock(&ftrace_sysctl_lock);
+
+	/*
+	 * Don't launch return tracing if normal function
+	 * tracing is already running.
+	 */
+	if (ftrace_trace_function != ftrace_stub) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	ftrace_tracing_type = FTRACE_TYPE_RETURN;
 	ftrace_function_return = func;
+	ftrace_startup();
+
+out:
+	mutex_unlock(&ftrace_sysctl_lock);
+	return ret;
 }
 
 void unregister_ftrace_return(void)
 {
+	mutex_lock(&ftrace_sysctl_lock);
+
 	ftrace_function_return = (trace_function_return_t)ftrace_stub;
+	ftrace_shutdown();
+	/* Restore normal tracing type */
+	ftrace_tracing_type = FTRACE_TYPE_ENTER;
+
+	mutex_unlock(&ftrace_sysctl_lock);
 }
 #endif
 
diff --git a/kernel/trace/trace_functions_return.c b/kernel/trace/trace_functions_return.c
index 61185f756a1..a68564af022 100644
--- a/kernel/trace/trace_functions_return.c
+++ b/kernel/trace/trace_functions_return.c
@@ -14,29 +14,18 @@
 #include "trace.h"
 
 
-static void start_return_trace(struct trace_array *tr)
-{
-	register_ftrace_return(&trace_function_return);
-}
-
-static void stop_return_trace(struct trace_array *tr)
-{
-	unregister_ftrace_return();
-}
-
 static int return_trace_init(struct trace_array *tr)
 {
 	int cpu;
 	for_each_online_cpu(cpu)
 		tracing_reset(tr, cpu);
 
-	start_return_trace(tr);
-	return 0;
+	return register_ftrace_return(&trace_function_return);
 }
 
 static void return_trace_reset(struct trace_array *tr)
 {
-		stop_return_trace(tr);
+		unregister_ftrace_return();
 }