v4.19.13 snapshot.
diff --git a/arch/um/drivers/xterm_kern.c b/arch/um/drivers/xterm_kern.c
new file mode 100644
index 0000000..e8f9957
--- /dev/null
+++ b/arch/um/drivers/xterm_kern.c
@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <linux/slab.h>
+#include <linux/completion.h>
+#include <linux/irqreturn.h>
+#include <asm/irq.h>
+#include <irq_kern.h>
+#include <os.h>
+
+struct xterm_wait {
+ struct completion ready;
+ int fd;
+ int pid;
+ int new_fd;
+};
+
+static irqreturn_t xterm_interrupt(int irq, void *data)
+{
+ struct xterm_wait *xterm = data;
+ int fd;
+
+ fd = os_rcv_fd(xterm->fd, &xterm->pid);
+ if (fd == -EAGAIN)
+ return IRQ_NONE;
+
+ xterm->new_fd = fd;
+ complete(&xterm->ready);
+
+ return IRQ_HANDLED;
+}
+
+int xterm_fd(int socket, int *pid_out)
+{
+ struct xterm_wait *data;
+ int err, ret;
+
+ data = kmalloc(sizeof(*data), GFP_KERNEL);
+ if (data == NULL) {
+ printk(KERN_ERR "xterm_fd : failed to allocate xterm_wait\n");
+ return -ENOMEM;
+ }
+
+ /* This is a locked semaphore... */
+ *data = ((struct xterm_wait) { .fd = socket,
+ .pid = -1,
+ .new_fd = -1 });
+ init_completion(&data->ready);
+
+ err = um_request_irq(XTERM_IRQ, socket, IRQ_READ, xterm_interrupt,
+ IRQF_SHARED, "xterm", data);
+ if (err) {
+ printk(KERN_ERR "xterm_fd : failed to get IRQ for xterm, "
+ "err = %d\n", err);
+ ret = err;
+ goto out;
+ }
+
+ /* ... so here we wait for an xterm interrupt.
+ *
+ * XXX Note, if the xterm doesn't work for some reason (eg. DISPLAY
+ * isn't set) this will hang... */
+ wait_for_completion(&data->ready);
+
+ um_free_irq(XTERM_IRQ, data);
+
+ ret = data->new_fd;
+ *pid_out = data->pid;
+ out:
+ kfree(data);
+
+ return ret;
+}