7 files changed, 24 insertions, 7 deletions

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 826682abed1d..43ceb3f454bf 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1196,6 +1196,9 @@ ENTRY(mcount)
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
         cmpl $ftrace_stub, ftrace_graph_return
         jnz ftrace_graph_caller
+
+        cmpl $ftrace_graph_entry_stub, ftrace_graph_entry
+        jnz ftrace_graph_caller
 #endif
 .globl ftrace_stub
 ftrace_stub:
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 9060ba6497e2..54e0bbdccb99 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -120,6 +120,9 @@ ENTRY(mcount)
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
         cmpq $ftrace_stub, ftrace_graph_return
         jnz ftrace_graph_caller
+
+        cmpq $ftrace_graph_entry_stub, ftrace_graph_entry
+        jnz ftrace_graph_caller
 #endif
 
 .globl ftrace_stub
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index adba8e9a427c..d278ad2ebda2 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -425,6 +425,7 @@ static void pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
         trace->calltime = current->ret_stack[index].calltime;
         trace->overrun = atomic_read(&current->trace_overrun);
         trace->depth = index;
+        barrier();
         current->curr_ret_stack--;
 }
 
@@ -506,7 +507,11 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
         }
 
         trace.func = self_addr;
-        ftrace_graph_entry(&trace);
 
+        /* Only trace if the calling function expects to */
+        if (!ftrace_graph_entry(&trace)) {
+                current->curr_ret_stack--;
+                *parent = old;
+        }
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 58ca1c3a3f4d..469ceb3e85ba 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -371,7 +371,7 @@ struct ftrace_graph_ret {
 #define FTRACE_RETSTACK_ALLOC_SIZE 32
 /* Type of the callback handlers for tracing function graph*/
 typedef void (*trace_func_graph_ret_t)(struct ftrace_graph_ret *); /* return */
-typedef void (*trace_func_graph_ent_t)(struct ftrace_graph_ent *); /* entry */
+typedef int (*trace_func_graph_ent_t)(struct ftrace_graph_ent *); /* entry */
 
 extern int register_ftrace_graph(trace_func_graph_ret_t retfunc,
                                 trace_func_graph_ent_t entryfunc);
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index a44af05ae2d0..65b9e863056b 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1636,11 +1636,15 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 
 static atomic_t ftrace_graph_active;
 
+int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace)
+{
+        return 0;
+}
+
 /* The callbacks that hook a function */
 trace_func_graph_ret_t ftrace_graph_return =
                         (trace_func_graph_ret_t)ftrace_stub;
-trace_func_graph_ent_t ftrace_graph_entry =
-                        (trace_func_graph_ent_t)ftrace_stub;
+trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub;
 
 /* Try to assign a return stack array on FTRACE_RETSTACK_ALLOC_SIZE tasks. */
 static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
@@ -1738,7 +1742,7 @@ void unregister_ftrace_graph(void)
 
         atomic_dec(&ftrace_graph_active);
         ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;
-        ftrace_graph_entry = (trace_func_graph_ent_t)ftrace_stub;
+        ftrace_graph_entry = ftrace_graph_entry_stub;
         ftrace_shutdown(FTRACE_STOP_FUNC_RET);
 
         mutex_unlock(&ftrace_sysctl_lock);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 380de630ebce..8b6409a62b54 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1200,7 +1200,7 @@ function_trace_call(unsigned long ip, unsigned long parent_ip)
 }
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
-void trace_graph_entry(struct ftrace_graph_ent *trace)
+int trace_graph_entry(struct ftrace_graph_ent *trace)
 {
         struct trace_array *tr = &global_trace;
         struct trace_array_cpu *data;
@@ -1219,6 +1219,8 @@ void trace_graph_entry(struct ftrace_graph_ent *trace)
         }
         atomic_dec(&data->disabled);
         local_irq_restore(flags);
+
+        return 1;
 }
 
 void trace_graph_return(struct ftrace_graph_ret *trace)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f96f4e787ff3..0565ae9a2210 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -412,7 +412,7 @@ void trace_function(struct trace_array *tr,
                     unsigned long flags, int pc);
 
 void trace_graph_return(struct ftrace_graph_ret *trace);
-void trace_graph_entry(struct ftrace_graph_ent *trace);
+int trace_graph_entry(struct ftrace_graph_ent *trace);
 void trace_bts(struct trace_array *tr,
                unsigned long from,
                unsigned long to);