1 files changed, 34 insertions, 45 deletions

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 3f3449624..8abf1ba18 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -18,12 +18,6 @@
 
 #define STACK_TRACE_ENTRIES 500
 
-#ifdef CC_USING_FENTRY
-# define fentry		1
-#else
-# define fentry		0
-#endif
-
 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
 	 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
 static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
@@ -35,7 +29,7 @@ static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
  */
 static struct stack_trace max_stack_trace = {
 	.max_entries		= STACK_TRACE_ENTRIES - 1,
-	.entries		= &stack_dump_trace[1],
+	.entries		= &stack_dump_trace[0],
 };
 
 static unsigned long max_stack_size;
@@ -55,7 +49,7 @@ static inline void print_max_stack(void)
 
 	pr_emerg("        Depth    Size   Location    (%d entries)\n"
 			   "        -----    ----   --------\n",
-			   max_stack_trace.nr_entries - 1);
+			   max_stack_trace.nr_entries);
 
 	for (i = 0; i < max_stack_trace.nr_entries; i++) {
 		if (stack_dump_trace[i] == ULONG_MAX)
@@ -77,7 +71,7 @@ check_stack(unsigned long ip, unsigned long *stack)
 	unsigned long this_size, flags; unsigned long *p, *top, *start;
 	static int tracer_frame;
 	int frame_size = ACCESS_ONCE(tracer_frame);
-	int i;
+	int i, x;
 
 	this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
 	this_size = THREAD_SIZE - this_size;
@@ -91,9 +85,19 @@ check_stack(unsigned long ip, unsigned long *stack)
 	if (!object_is_on_stack(stack))
 		return;
 
+	/* Can't do this from NMI context (can cause deadlocks) */
+	if (in_nmi())
+		return;
+
 	local_irq_save(flags);
 	arch_spin_lock(&max_stack_lock);
 
+	/*
+	 * RCU may not be watching, make it see us.
+	 * The stack trace code uses rcu_sched.
+	 */
+	rcu_irq_enter();
+
 	/* In case another CPU set the tracer_frame on us */
 	if (unlikely(!frame_size))
 		this_size -= tracer_frame;
@@ -105,26 +109,20 @@ check_stack(unsigned long ip, unsigned long *stack)
 	max_stack_size = this_size;
 
 	max_stack_trace.nr_entries = 0;
-
-	if (using_ftrace_ops_list_func())
-		max_stack_trace.skip = 4;
-	else
-		max_stack_trace.skip = 3;
+	max_stack_trace.skip = 3;
 
 	save_stack_trace(&max_stack_trace);
 
-	/*
-	 * Add the passed in ip from the function tracer.
-	 * Searching for this on the stack will skip over
-	 * most of the overhead from the stack tracer itself.
-	 */
-	stack_dump_trace[0] = ip;
-	max_stack_trace.nr_entries++;
+	/* Skip over the overhead of the stack tracer itself */
+	for (i = 0; i < max_stack_trace.nr_entries; i++) {
+		if (stack_dump_trace[i] == ip)
+			break;
+	}
 
 	/*
 	 * Now find where in the stack these are.
 	 */
-	i = 0;
+	x = 0;
 	start = stack;
 	top = (unsigned long *)
 		(((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
@@ -139,12 +137,15 @@ check_stack(unsigned long ip, unsigned long *stack)
 	while (i < max_stack_trace.nr_entries) {
 		int found = 0;
 
-		stack_dump_index[i] = this_size;
+		stack_dump_index[x] = this_size;
 		p = start;
 
 		for (; p < top && i < max_stack_trace.nr_entries; p++) {
+			if (stack_dump_trace[i] == ULONG_MAX)
+				break;
 			if (*p == stack_dump_trace[i]) {
-				this_size = stack_dump_index[i++] =
+				stack_dump_trace[x] = stack_dump_trace[i++];
+				this_size = stack_dump_index[x++] =
 					(top - p) * sizeof(unsigned long);
 				found = 1;
 				/* Start the search from here */
@@ -156,7 +157,7 @@ check_stack(unsigned long ip, unsigned long *stack)
 				 * out what that is, then figure it out
 				 * now.
 				 */
-				if (unlikely(!tracer_frame) && i == 1) {
+				if (unlikely(!tracer_frame)) {
 					tracer_frame = (p - stack) *
 						sizeof(unsigned long);
 					max_stack_size -= tracer_frame;
@@ -168,12 +169,17 @@ check_stack(unsigned long ip, unsigned long *stack)
 			i++;
 	}
 
+	max_stack_trace.nr_entries = x;
+	for (; x < i; x++)
+		stack_dump_trace[x] = ULONG_MAX;
+
 	if (task_stack_end_corrupted(current)) {
 		print_max_stack();
 		BUG();
 	}
 
  out:
+	rcu_irq_exit();
 	arch_spin_unlock(&max_stack_lock);
 	local_irq_restore(flags);
 }
@@ -192,24 +198,7 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip,
 	if (per_cpu(trace_active, cpu)++ != 0)
 		goto out;
 
-	/*
-	 * When fentry is used, the traced function does not get
-	 * its stack frame set up, and we lose the parent.
-	 * The ip is pretty useless because the function tracer
-	 * was called before that function set up its stack frame.
-	 * In this case, we use the parent ip.
-	 *
-	 * By adding the return address of either the parent ip
-	 * or the current ip we can disregard most of the stack usage
-	 * caused by the stack tracer itself.
-	 *
-	 * The function tracer always reports the address of where the
-	 * mcount call was, but the stack will hold the return address.
-	 */
-	if (fentry)
-		ip = parent_ip;
-	else
-		ip += MCOUNT_INSN_SIZE;
+	ip += MCOUNT_INSN_SIZE;
 
 	check_stack(ip, &stack);
 
@@ -284,7 +273,7 @@ __next(struct seq_file *m, loff_t *pos)
 {
 	long n = *pos - 1;
 
-	if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
+	if (n > max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
 		return NULL;
 
 	m->private = (void *)n;
@@ -354,7 +343,7 @@ static int t_show(struct seq_file *m, void *v)
 		seq_printf(m, "        Depth    Size   Location"
 			   "    (%d entries)\n"
 			   "        -----    ----   --------\n",
-			   max_stack_trace.nr_entries - 1);
+			   max_stack_trace.nr_entries);
 
 		if (!stack_tracer_enabled && !max_stack_size)
 			print_disabled(m);