1 files changed, 53 insertions, 3 deletions

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index b5c09242683d..e08c030b8f38 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -114,16 +114,37 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
                 return -EBUSY;
         }
 
+        /*
+         * The curr_ret_stack is an index to ftrace return stack of
+         * current task.  Its value should be in [0, FTRACE_RETFUNC_
+         * DEPTH) when the function graph tracer is used.  To support
+         * filtering out specific functions, it makes the index
+         * negative by subtracting huge value (FTRACE_NOTRACE_DEPTH)
+         * so when it sees a negative index the ftrace will ignore
+         * the record.  And the index gets recovered when returning
+         * from the filtered function by adding the FTRACE_NOTRACE_
+         * DEPTH and then it'll continue to record functions normally.
+         *
+         * The curr_ret_stack is initialized to -1 and get increased
+         * in this function.  So it can be less than -1 only if it was
+         * filtered out via ftrace_graph_notrace_addr() which can be
+         * set from set_graph_notrace file in debugfs by user.
+         */
+        if (current->curr_ret_stack < -1)
+                return -EBUSY;
+
         calltime = trace_clock_local();
 
         index = ++current->curr_ret_stack;
+        if (ftrace_graph_notrace_addr(func))
+                current->curr_ret_stack -= FTRACE_NOTRACE_DEPTH;
         barrier();
         current->ret_stack[index].ret = ret;
         current->ret_stack[index].func = func;
         current->ret_stack[index].calltime = calltime;
         current->ret_stack[index].subtime = 0;
         current->ret_stack[index].fp = frame_pointer;
-        *depth = index;
+        *depth = current->curr_ret_stack;
 
         return 0;
 }
@@ -137,7 +158,17 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
 
         index = current->curr_ret_stack;
 
-        if (unlikely(index < 0)) {
+        /*
+         * A negative index here means that it's just returned from a
+         * notrace'd function.  Recover index to get an original
+         * return address.  See ftrace_push_return_trace().
+         *
+         * TODO: Need to check whether the stack gets corrupted.
+         */
+        if (index < 0)
+                index += FTRACE_NOTRACE_DEPTH;
+
+        if (unlikely(index < 0 || index >= FTRACE_RETFUNC_DEPTH)) {
                 ftrace_graph_stop();
                 WARN_ON(1);
                 /* Might as well panic, otherwise we have no where to go */
@@ -193,6 +224,15 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
         trace.rettime = trace_clock_local();
         barrier();
         current->curr_ret_stack--;
+        /*
+         * The curr_ret_stack can be less than -1 only if it was
+         * filtered out and it's about to return from the function.
+         * Recover the index and continue to trace normal functions.
+         */
+        if (current->curr_ret_stack < -1) {
+                current->curr_ret_stack += FTRACE_NOTRACE_DEPTH;
+                return ret;
+        }
 
         /*
          * The trace should run after decrementing the ret counter
@@ -259,10 +299,20 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
 
         /* trace it when it is-nested-in or is a function enabled. */
         if ((!(trace->depth || ftrace_graph_addr(trace->func)) ||
-             ftrace_graph_ignore_irqs()) ||
+             ftrace_graph_ignore_irqs()) || (trace->depth < 0) ||
             (max_depth && trace->depth >= max_depth))
                 return 0;
 
+        /*
+         * Do not trace a function if it's filtered by set_graph_notrace.
+         * Make the index of ret stack negative to indicate that it should
+         * ignore further functions.  But it needs its own ret stack entry
+         * to recover the original index in order to continue tracing after
+         * returning from the function.
+         */
+        if (ftrace_graph_notrace_addr(trace->func))
+                return 1;
+
         local_irq_save(flags);
         cpu = raw_smp_processor_id();
         data = per_cpu_ptr(tr->trace_buffer.data, cpu);