7 files changed, 51 insertions, 9 deletions

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index a71158369fd..e90e81ef6ab 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -21,6 +21,7 @@ struct task_struct;
 struct exec_domain;
 #include <asm/processor.h>
 #include <asm/ftrace.h>
+#include <asm/atomic.h>
 
 struct thread_info {
 	struct task_struct	*task;		/* main task structure */
@@ -45,6 +46,11 @@ struct thread_info {
 	int		curr_ret_stack;
 	/* Stack of return addresses for return function tracing */
 	struct ftrace_ret_stack	ret_stack[FTRACE_RET_STACK_SIZE];
+	/*
+	 * Number of functions that haven't been traced
+	 * because of depth overrun.
+	 */
+	atomic_t	trace_overrun;
 #endif
 };
 
@@ -61,6 +67,7 @@ struct thread_info {
 		.fn = do_no_restart_syscall,	\
 	},					\
 	.curr_ret_stack = -1,\
+	.trace_overrun	= ATOMIC_INIT(0)	\
 }
 #else
 #define INIT_THREAD_INFO(tsk)			\
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 924153edd97..356bb1eb6e9 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -353,8 +353,10 @@ static int push_return_trace(unsigned long ret, unsigned long long time,
 	struct thread_info *ti = current_thread_info();
 
 	/* The return trace stack is full */
-	if (ti->curr_ret_stack == FTRACE_RET_STACK_SIZE - 1)
+	if (ti->curr_ret_stack == FTRACE_RET_STACK_SIZE - 1) {
+		atomic_inc(&ti->trace_overrun);
 		return -EBUSY;
+	}
 
 	index = ++ti->curr_ret_stack;
 	barrier();
@@ -367,7 +369,7 @@ static int push_return_trace(unsigned long ret, unsigned long long time,
 
 /* 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)
+				unsigned long *func, unsigned long *overrun)
 {
 	int index;
 
@@ -376,6 +378,7 @@ static void pop_return_trace(unsigned long *ret, unsigned long long *time,
 	*ret = ti->ret_stack[index].ret;
 	*func = ti->ret_stack[index].func;
 	*time = ti->ret_stack[index].calltime;
+	*overrun = atomic_read(&ti->trace_overrun);
 	ti->curr_ret_stack--;
 }
 
@@ -386,7 +389,8 @@ static void pop_return_trace(unsigned long *ret, unsigned long long *time,
 unsigned long ftrace_return_to_handler(void)
 {
 	struct ftrace_retfunc trace;
-	pop_return_trace(&trace.ret, &trace.calltime, &trace.func);
+	pop_return_trace(&trace.ret, &trace.calltime, &trace.func,
+			&trace.overrun);
 	trace.rettime = cpu_clock(raw_smp_processor_id());
 	ftrace_function_return(&trace);
 
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index f1af1aab00e..f7ba4ea5e12 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -318,6 +318,8 @@ struct ftrace_retfunc {
 	unsigned long func; /* Current function */
 	unsigned long long calltime;
 	unsigned long long rettime;
+	/* Number of functions that overran the depth limit for current task */
+	unsigned long overrun;
 };
 
 #ifdef CONFIG_FUNCTION_RET_TRACER
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 61c8cc36028..c8e0db46420 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2016,6 +2016,7 @@ static inline void setup_thread_stack(struct task_struct *p, struct task_struct
 	 * used.
 	 */
 	task_thread_info(p)->curr_ret_stack = -1;
+	atomic_set(&task_thread_info(p)->trace_overrun, 0);
 #endif
 }
 
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 9531fddcfb8..e97c29a6e7b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -853,6 +853,7 @@ static void __trace_function_return(struct trace_array *tr,
 	entry->parent_ip	= trace->ret;
 	entry->rettime		= trace->rettime;
 	entry->calltime		= trace->calltime;
+	entry->overrun		= trace->overrun;
 	ring_buffer_unlock_commit(global_trace.buffer, event, irq_flags);
 }
 #endif
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 9d22618bf99..2cb12fd98f6 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -60,6 +60,7 @@ struct ftrace_ret_entry {
 	unsigned long		parent_ip;
 	unsigned long long	calltime;
 	unsigned long long	rettime;
+	unsigned long		overrun;
 };
 extern struct tracer boot_tracer;
 
diff --git a/kernel/trace/trace_functions_return.c b/kernel/trace/trace_functions_return.c
index a68564af022..e00d64509c9 100644
--- a/kernel/trace/trace_functions_return.c
+++ b/kernel/trace/trace_functions_return.c
@@ -14,6 +14,19 @@
 #include "trace.h"
 
 
+#define TRACE_RETURN_PRINT_OVERRUN	0x1
+static struct tracer_opt trace_opts[] = {
+	/* Display overruns or not */
+	{ TRACER_OPT(overrun, TRACE_RETURN_PRINT_OVERRUN) },
+	{ } /* Empty entry */
+};
+
+static struct tracer_flags tracer_flags = {
+	.val = 0, /* Don't display overruns by default */
+	.opts = trace_opts
+};
+
+
 static int return_trace_init(struct trace_array *tr)
 {
 	int cpu;
@@ -42,26 +55,39 @@ print_return_function(struct trace_iterator *iter)
 		ret = trace_seq_printf(s, "%pF -> ", (void *)field->parent_ip);
 		if (!ret)
 			return TRACE_TYPE_PARTIAL_LINE;
+
 		ret = seq_print_ip_sym(s, field->ip,
 					trace_flags & TRACE_ITER_SYM_MASK);
 		if (!ret)
 			return TRACE_TYPE_PARTIAL_LINE;
-		ret = trace_seq_printf(s, " (%llu ns)\n",
+
+		ret = trace_seq_printf(s, " (%llu ns)",
 					field->rettime - field->calltime);
 		if (!ret)
 			return TRACE_TYPE_PARTIAL_LINE;
-		else
-			return TRACE_TYPE_HANDLED;
+
+		if (tracer_flags.val & TRACE_RETURN_PRINT_OVERRUN) {
+			ret = trace_seq_printf(s, " (Overruns: %lu)",
+						field->overrun);
+			if (!ret)
+				return TRACE_TYPE_PARTIAL_LINE;
+		}
+
+		ret = trace_seq_printf(s, "\n");
+		if (!ret)
+			return TRACE_TYPE_PARTIAL_LINE;
+
+		return TRACE_TYPE_HANDLED;
 	}
 	return TRACE_TYPE_UNHANDLED;
 }
 
-static struct tracer return_trace __read_mostly =
-{
+static struct tracer return_trace __read_mostly = {
 	.name	     = "return",
 	.init	     = return_trace_init,
 	.reset	     = return_trace_reset,
-	.print_line = print_return_function
+	.print_line = print_return_function,
+	.flags		= &tracer_flags,
 };
 
 static __init int init_return_trace(void)