v4.19.13 snapshot.
diff --git a/arch/um/os-Linux/tty.c b/arch/um/os-Linux/tty.c
new file mode 100644
index 0000000..721d8af
--- /dev/null
+++ b/arch/um/os-Linux/tty.c
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <kern_util.h>
+#include <os.h>
+
+struct grantpt_info {
+ int fd;
+ int res;
+ int err;
+};
+
+static void grantpt_cb(void *arg)
+{
+ struct grantpt_info *info = arg;
+
+ info->res = grantpt(info->fd);
+ info->err = errno;
+}
+
+int get_pty(void)
+{
+ struct grantpt_info info;
+ int fd, err;
+
+ fd = open("/dev/ptmx", O_RDWR);
+ if (fd < 0) {
+ err = -errno;
+ printk(UM_KERN_ERR "get_pty : Couldn't open /dev/ptmx - "
+ "err = %d\n", errno);
+ return err;
+ }
+
+ info.fd = fd;
+ initial_thread_cb(grantpt_cb, &info);
+
+ if (info.res < 0) {
+ err = -info.err;
+ printk(UM_KERN_ERR "get_pty : Couldn't grant pty - "
+ "errno = %d\n", -info.err);
+ goto out;
+ }
+
+ if (unlockpt(fd) < 0) {
+ err = -errno;
+ printk(UM_KERN_ERR "get_pty : Couldn't unlock pty - "
+ "errno = %d\n", errno);
+ goto out;
+ }
+ return fd;
+out:
+ close(fd);
+ return err;
+}