[PATCH] tracing: Fix oops caused by graph notrace filter

* [PATCH] tracing: Fix oops caused by graph notrace filter
@ 2016-06-21 10:57 Chunyu Hu
  2016-06-21 12:22 ` kbuild test robot
                   ` (2 more replies)
  0 siblings, 3 replies; 9+ messages in thread
From: Chunyu Hu @ 2016-06-21 10:57 UTC (permalink / raw)
  To: rostedt; +Cc: linux-kernel

wakeup tracer can use function_graph trace when display_graph trace
option is setup by user via tracefs, and bypass the set_graph_function
and set_graph_notrace. But the bypass of set_graph_notrace is not clean.
Although wakeup_graph_entry does most of the bypass, and both the enry
and exit event will be submitted to the trace ring buffer, the ret_stack
index, which will be assigned to depth field of graph enrty event is not
handled. The issue is that the depth is used as the array index of
fgraph_cpu_data and can cause an oops when it's negative. irqsoff tracer
has same issue. To see the oops:

echo 1 > options/display_graph
echo schedule > set_graph_notrace
echo wakeup > current_tracer
cat trace
cat trace

Making ftrace_graph_notrace_addr always return false when tracers need
to bypass it is a proposed fix.

Signed-off-by: Chunyu Hu <chuhu@redhat.com>
---
 kernel/trace/ftrace.c                | 1 +
 kernel/trace/trace.h                 | 4 ++++
 kernel/trace/trace_functions_graph.c | 2 ++
 kernel/trace/trace_irqsoff.c         | 7 +++++++
 kernel/trace/trace_sched_wakeup.c    | 8 ++++++++
 5 files changed, 22 insertions(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index a680482..bb06828 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4471,6 +4471,7 @@ static DEFINE_MUTEX(graph_lock);
 
 int ftrace_graph_count;
 int ftrace_graph_notrace_count;
+int ftrace_graph_ignore_notrace;
 unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS] __read_mostly;
 unsigned long ftrace_graph_notrace_funcs[FTRACE_GRAPH_MAX_FUNCS] __read_mostly;
 
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 5167c36..b089e04 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -757,6 +757,7 @@ extern void __trace_graph_return(struct trace_array *tr,
 extern int ftrace_graph_count;
 extern unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS];
 extern int ftrace_graph_notrace_count;
+extern int ftrace_graph_ignore_notrace;
 extern unsigned long ftrace_graph_notrace_funcs[FTRACE_GRAPH_MAX_FUNCS];
 
 static inline int ftrace_graph_addr(unsigned long addr)
@@ -791,6 +792,9 @@ static inline int ftrace_graph_notrace_addr(unsigned long addr)
 	if (!ftrace_graph_notrace_count)
 		return 0;
 
+	if (unlikely(ftrace_graph_ignore_notrace))
+		return 0;
+
 	for (i = 0; i < ftrace_graph_notrace_count; i++) {
 		if (addr == ftrace_graph_notrace_funcs[i])
 			return 1;
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 3a0244f..24d92f0 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -822,6 +822,8 @@ print_graph_entry_nested(struct trace_iterator *iter,
 		cpu_data = per_cpu_ptr(data->cpu_data, cpu);
 		cpu_data->depth = call->depth;
 
+		WARN(call->depth < 0, "call->depth = %d\n", call->depth);
+
 		/* Save this function pointer to see if the exit matches */
 		if (call->depth < FTRACE_RETFUNC_DEPTH)
 			cpu_data->enter_funcs[call->depth] = call->func;
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 03cdff8..3d76e0f 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -32,6 +32,8 @@ static int trace_type __read_mostly;
 
 static int save_flags;
 
+extern int ftrace_graph_ignore_notrace;
+
 static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
 static int start_irqsoff_tracer(struct trace_array *tr, int graph);
 
@@ -629,6 +631,9 @@ static int __irqsoff_tracer_init(struct trace_array *tr)
 
 	ftrace_init_array_ops(tr, irqsoff_tracer_call);
 
+	/* bypass function_graph notrace filter */
+	ftrace_graph_ignore_notrace = 1;
+
 	/* Only toplevel instance supports graph tracing */
 	if (start_irqsoff_tracer(tr, (tr->flags & TRACE_ARRAY_FL_GLOBAL &&
 				      is_graph(tr))))
@@ -650,6 +655,8 @@ static void irqsoff_tracer_reset(struct trace_array *tr)
 	ftrace_reset_array_ops(tr);
 
 	irqsoff_busy = false;
+
+	ftrace_graph_ignore_notrace = 0;
 }
 
 static void irqsoff_tracer_start(struct trace_array *tr)
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 9d4399b..81dd566 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -37,6 +37,8 @@ static void __wakeup_reset(struct trace_array *tr);
 
 static int save_flags;
 
+extern int ftrace_graph_ignore_notrace;
+
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 static int wakeup_display_graph(struct trace_array *tr, int set);
 # define is_graph(tr) ((tr)->trace_flags & TRACE_ITER_DISPLAY_GRAPH)
@@ -672,6 +674,10 @@ static int __wakeup_tracer_init(struct trace_array *tr)
 	tr->max_latency = 0;
 	wakeup_trace = tr;
 	ftrace_init_array_ops(tr, wakeup_tracer_call);
+
+	/* bypass function_graph notrace filter */
+	ftrace_graph_ignore_notrace = 1;
+
 	start_wakeup_tracer(tr);
 
 	wakeup_busy = true;
@@ -721,6 +727,8 @@ static void wakeup_tracer_reset(struct trace_array *tr)
 	set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
 	ftrace_reset_array_ops(tr);
 	wakeup_busy = false;
+
+	ftrace_graph_ignore_notrace = 0;
 }
 
 static void wakeup_tracer_start(struct trace_array *tr)
-- 
1.8.3.1

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