v4.19.13 snapshot.
diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
new file mode 100644
index 0000000..3f435d7
--- /dev/null
+++ b/arch/x86/lib/usercopy.c
@@ -0,0 +1,38 @@
+/*
+ * User address space access functions.
+ *
+ * For licencing details see kernel-base/COPYING
+ */
+
+#include <linux/uaccess.h>
+#include <linux/export.h>
+
+#include <asm/tlbflush.h>
+
+/*
+ * We rely on the nested NMI work to allow atomic faults from the NMI path; the
+ * nested NMI paths are careful to preserve CR2.
+ */
+unsigned long
+copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
+{
+ unsigned long ret;
+
+ if (__range_not_ok(from, n, TASK_SIZE))
+ return n;
+
+ if (!nmi_uaccess_okay())
+ return n;
+
+ /*
+ * Even though this function is typically called from NMI/IRQ context
+ * disable pagefaults so that its behaviour is consistent even when
+ * called form other contexts.
+ */
+ pagefault_disable();
+ ret = __copy_from_user_inatomic(to, from, n);
+ pagefault_enable();
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(copy_from_user_nmi);