4 files changed, 106 insertions, 2 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 35c8ec2ba03a..b9d446329da1 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -47,6 +47,7 @@
 #include <linux/task_io_accounting_ops.h>
 #include <linux/tracehook.h>
 #include <trace/sched.h>
+#include <linux/ftrace.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -1127,7 +1128,9 @@ NORET_TYPE void do_exit(long code)
         preempt_disable();
         /* causes final put_task_struct in finish_task_switch(). */
         tsk->state = TASK_DEAD;
-
+#ifdef CONFIG_FUNCTION_RET_TRACER
+        ftrace_retfunc_exit_task(tsk);
+#endif
         schedule();
         BUG();
         /* Avoid "noreturn function does return".  */
diff --git a/kernel/fork.c b/kernel/fork.c
index ac62f43ee430..d1eb30e69ccc 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -47,6 +47,7 @@
 #include <linux/mount.h>
 #include <linux/audit.h>
 #include <linux/memcontrol.h>
+#include <linux/ftrace.h>
 #include <linux/profile.h>
 #include <linux/rmap.h>
 #include <linux/acct.h>
@@ -1269,6 +1270,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         total_forks++;
         spin_unlock(&current->sighand->siglock);
         write_unlock_irq(&tasklist_lock);
+#ifdef CONFIG_FUNCTION_RET_TRACER
+        ftrace_retfunc_init_task(p);
+#endif
         proc_fork_connector(p);
         cgroup_post_fork(p);
         return p;
diff --git a/kernel/sched.c b/kernel/sched.c
index 4de56108c86f..fb17205950de 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5901,6 +5901,9 @@ void __cpuinit init_idle(struct task_struct *idle, int cpu)
          * The idle tasks have their own, simple scheduling class:
          */
         idle->sched_class = &idle_sched_class;
+#ifdef CONFIG_FUNCTION_RET_TRACER
+        ftrace_retfunc_init_task(idle);
+#endif
 }
 
 /*
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f212da486689..90d99fb02ae4 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1498,10 +1498,77 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 
 #ifdef CONFIG_FUNCTION_RET_TRACER
 
+static atomic_t ftrace_retfunc_active;
+
 /* The callback that hooks the return of a function */
 trace_function_return_t ftrace_function_return =
                         (trace_function_return_t)ftrace_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)
+{
+        int i;
+        int ret = 0;
+        unsigned long flags;
+        int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE;
+        struct task_struct *g, *t;
+
+        for (i = 0; i < FTRACE_RETSTACK_ALLOC_SIZE; i++) {
+                ret_stack_list[i] = kmalloc(FTRACE_RETFUNC_DEPTH
+                                        * sizeof(struct ftrace_ret_stack),
+                                        GFP_KERNEL);
+                if (!ret_stack_list[i]) {
+                        start = 0;
+                        end = i;
+                        ret = -ENOMEM;
+                        goto free;
+                }
+        }
+
+        read_lock_irqsave(&tasklist_lock, flags);
+        do_each_thread(g, t) {
+                if (start == end) {
+                        ret = -EAGAIN;
+                        goto unlock;
+                }
+
+                if (t->ret_stack == NULL) {
+                        t->ret_stack = ret_stack_list[start++];
+                        t->curr_ret_stack = -1;
+                        atomic_set(&t->trace_overrun, 0);
+                }
+        } while_each_thread(g, t);
+
+unlock:
+        read_unlock_irqrestore(&tasklist_lock, flags);
+free:
+        for (i = start; i < end; i++)
+                kfree(ret_stack_list[i]);
+        return ret;
+}
+
+/* Allocate a return stack for each task */
+static int start_return_tracing(void)
+{
+        struct ftrace_ret_stack **ret_stack_list;
+        int ret;
+
+        ret_stack_list = kmalloc(FTRACE_RETSTACK_ALLOC_SIZE *
+                                sizeof(struct ftrace_ret_stack *),
+                                GFP_KERNEL);
+
+        if (!ret_stack_list)
+                return -ENOMEM;
+
+        do {
+                ret = alloc_retstack_tasklist(ret_stack_list);
+        } while (ret == -EAGAIN);
+
+        kfree(ret_stack_list);
+        return ret;
+}
+
 int register_ftrace_return(trace_function_return_t func)
 {
         int ret = 0;
@@ -1516,7 +1583,12 @@ int register_ftrace_return(trace_function_return_t func)
                 ret = -EBUSY;
                 goto out;
         }
-
+        atomic_inc(&ftrace_retfunc_active);
+        ret = start_return_tracing();
+        if (ret) {
+                atomic_dec(&ftrace_retfunc_active);
+                goto out;
+        }
         ftrace_tracing_type = FTRACE_TYPE_RETURN;
         ftrace_function_return = func;
         ftrace_startup();
@@ -1530,6 +1602,7 @@ void unregister_ftrace_return(void)
 {
         mutex_lock(&ftrace_sysctl_lock);
 
+        atomic_dec(&ftrace_retfunc_active);
         ftrace_function_return = (trace_function_return_t)ftrace_stub;
         ftrace_shutdown();
         /* Restore normal tracing type */
@@ -1537,6 +1610,27 @@ void unregister_ftrace_return(void)
 
         mutex_unlock(&ftrace_sysctl_lock);
 }
+
+/* Allocate a return stack for newly created task */
+void ftrace_retfunc_init_task(struct task_struct *t)
+{
+        if (atomic_read(&ftrace_retfunc_active)) {
+                t->ret_stack = kmalloc(FTRACE_RETFUNC_DEPTH
+                                * sizeof(struct ftrace_ret_stack),
+                                GFP_KERNEL);
+                if (!t->ret_stack)
+                        return;
+                t->curr_ret_stack = -1;
+                atomic_set(&t->trace_overrun, 0);
+        } else
+                t->ret_stack = NULL;
+}
+
+void ftrace_retfunc_exit_task(struct task_struct *t)
+{
+        kfree(t->ret_stack);
+        t->ret_stack = NULL;
+}
 #endif