ftrace: add checks on ret stack in function graph

Import: robustness checks

Add more checks in the function graph code to detect errors and
perhaps print out better information if a bug happens.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 17 insertions, 0 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index d278ad2ebda2..f98c4076a170 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -420,6 +420,15 @@ static void pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
         int index;
 
         index = current->curr_ret_stack;
+
+        if (unlikely(index < 0)) {
+                ftrace_graph_stop();
+                WARN_ON(1);
+                /* Might as well panic, otherwise we have no where to go */
+                *ret = (unsigned long)panic;
+                return;
+        }
+
         *ret = current->ret_stack[index].ret;
         trace->func = current->ret_stack[index].func;
         trace->calltime = current->ret_stack[index].calltime;
@@ -427,6 +436,7 @@ static void pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
         trace->depth = index;
         barrier();
         current->curr_ret_stack--;
+
 }
 
 /*
@@ -442,6 +452,13 @@ unsigned long ftrace_return_to_handler(void)
         trace.rettime = cpu_clock(raw_smp_processor_id());
         ftrace_graph_return(&trace);
 
+        if (unlikely(!ret)) {
+                ftrace_graph_stop();
+                WARN_ON(1);
+                /* Might as well panic. What else to do? */
+                ret = (unsigned long)panic;
+        }
+
         return ret;
 }