v4.19.13 snapshot.
diff --git a/include/linux/start_kernel.h b/include/linux/start_kernel.h
new file mode 100644
index 0000000..4b268d8
--- /dev/null
+++ b/include/linux/start_kernel.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_START_KERNEL_H
+#define _LINUX_START_KERNEL_H
+
+#include <linux/linkage.h>
+#include <linux/init.h>
+
+/* Define the prototype for start_kernel here, rather than cluttering
+ up something else. */
+
+extern asmlinkage void __init start_kernel(void);
+
+#endif /* _LINUX_START_KERNEL_H */