1 files changed, 29 insertions, 4 deletions

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index dc02e29d8255..ea28e4b0ed58 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -20,13 +20,27 @@
 
 #define STACK_TRACE_ENTRIES 500
 
+/*
+ * If fentry is used, then the function being traced will
+ * jump to fentry directly before it sets up its stack frame.
+ * We need to ignore that one and record the parent. Since
+ * the stack frame for the traced function wasn't set up yet,
+ * the stack_trace wont see the parent. That needs to be added
+ * manually to stack_dump_trace[] as the first element.
+ */
+#ifdef CC_USING_FENTRY
+# define add_func       1
+#else
+# define add_func       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];
 
 static struct stack_trace max_stack_trace = {
-        .max_entries            = STACK_TRACE_ENTRIES,
-        .entries                = stack_dump_trace,
+        .max_entries            = STACK_TRACE_ENTRIES - add_func,
+        .entries                = &stack_dump_trace[add_func],
 };
 
 static unsigned long max_stack_size;
@@ -40,7 +54,7 @@ int stack_tracer_enabled;
 static int last_stack_tracer_enabled;
 
 static inline void
-check_stack(unsigned long *stack)
+check_stack(unsigned long ip, unsigned long *stack)
 {
         unsigned long this_size, flags;
         unsigned long *p, *top, *start;
@@ -71,6 +85,17 @@ check_stack(unsigned long *stack)
         save_stack_trace(&max_stack_trace);
 
         /*
+         * When fentry is used, the traced function does not get
+         * its stack frame set up, and we lose the parent.
+         * Add that one in manally. We set up save_stack_trace()
+         * to not touch the first element in this case.
+         */
+        if (add_func) {
+                stack_dump_trace[0] = ip;
+                max_stack_trace.nr_entries++;
+        }
+
+        /*
          * Now find where in the stack these are.
          */
         i = 0;
@@ -124,7 +149,7 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip,
         if (per_cpu(trace_active, cpu)++ != 0)
                 goto out;
 
-        check_stack(&stack);
+        check_stack(parent_ip, &stack);
 
  out:
         per_cpu(trace_active, cpu)--;