1 files changed, 54 insertions, 0 deletions
diff --git a/lib/once.c b/lib/once.c
new file mode 100644
index 000000000000..2d5a7de17aba
--- /dev/null
+++ b/lib/once.c
@@ -0,0 +1,54 @@
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/once.h>
+#include <linux/random.h>
+
+struct __random_once_work {
+	struct work_struct work;
+	struct static_key *key;
+};
+
+static void __random_once_deferred(struct work_struct *w)
+{
+	struct __random_once_work *work;
+
+	work = container_of(w, struct __random_once_work, work);
+	BUG_ON(!static_key_enabled(work->key));
+	static_key_slow_dec(work->key);
+	kfree(work);
+}
+
+static void __random_once_disable_jump(struct static_key *key)
+{
+	struct __random_once_work *w;
+
+	w = kmalloc(sizeof(*w), GFP_ATOMIC);
+	if (!w)
+		return;
+
+	INIT_WORK(&w->work, __random_once_deferred);
+	w->key = key;
+	schedule_work(&w->work);
+}
+
+bool __get_random_once(void *buf, int nbytes, bool *done,
+		       struct static_key *once_key)
+{
+	static DEFINE_SPINLOCK(lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&lock, flags);
+	if (*done) {
+		spin_unlock_irqrestore(&lock, flags);
+		return false;
+	}
+
+	get_random_bytes(buf, nbytes);
+	*done = true;
+	spin_unlock_irqrestore(&lock, flags);
+
+	__random_once_disable_jump(once_key);
+
+	return true;
+}
+EXPORT_SYMBOL(__get_random_once);