v4.19.13 snapshot.
diff --git a/arch/um/drivers/random.c b/arch/um/drivers/random.c
new file mode 100644
index 0000000..778a0e5
--- /dev/null
+++ b/arch/um/drivers/random.c
@@ -0,0 +1,176 @@
+/* Copyright (C) 2005 - 2008 Jeff Dike <jdike@{linux.intel,addtoit}.com> */
+
+/* Much of this ripped from drivers/char/hw_random.c, see there for other
+ * copyright.
+ *
+ * This software may be used and distributed according to the terms
+ * of the GNU General Public License, incorporated herein by reference.
+ */
+#include <linux/sched/signal.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/interrupt.h>
+#include <linux/miscdevice.h>
+#include <linux/delay.h>
+#include <linux/uaccess.h>
+#include <init.h>
+#include <irq_kern.h>
+#include <os.h>
+
+/*
+ * core module and version information
+ */
+#define RNG_VERSION "1.0.0"
+#define RNG_MODULE_NAME "hw_random"
+
+#define RNG_MISCDEV_MINOR 183 /* official */
+
+/* Changed at init time, in the non-modular case, and at module load
+ * time, in the module case. Presumably, the module subsystem
+ * protects against a module being loaded twice at the same time.
+ */
+static int random_fd = -1;
+static DECLARE_WAIT_QUEUE_HEAD(host_read_wait);
+
+static int rng_dev_open (struct inode *inode, struct file *filp)
+{
+ /* enforce read-only access to this chrdev */
+ if ((filp->f_mode & FMODE_READ) == 0)
+ return -EINVAL;
+ if ((filp->f_mode & FMODE_WRITE) != 0)
+ return -EINVAL;
+
+ return 0;
+}
+
+static atomic_t host_sleep_count = ATOMIC_INIT(0);
+
+static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
+ loff_t *offp)
+{
+ u32 data;
+ int n, ret = 0, have_data;
+
+ while (size) {
+ n = os_read_file(random_fd, &data, sizeof(data));
+ if (n > 0) {
+ have_data = n;
+ while (have_data && size) {
+ if (put_user((u8) data, buf++)) {
+ ret = ret ? : -EFAULT;
+ break;
+ }
+ size--;
+ ret++;
+ have_data--;
+ data >>= 8;
+ }
+ }
+ else if (n == -EAGAIN) {
+ DECLARE_WAITQUEUE(wait, current);
+
+ if (filp->f_flags & O_NONBLOCK)
+ return ret ? : -EAGAIN;
+
+ atomic_inc(&host_sleep_count);
+ reactivate_fd(random_fd, RANDOM_IRQ);
+ add_sigio_fd(random_fd);
+
+ add_wait_queue(&host_read_wait, &wait);
+ set_current_state(TASK_INTERRUPTIBLE);
+
+ schedule();
+ remove_wait_queue(&host_read_wait, &wait);
+
+ if (atomic_dec_and_test(&host_sleep_count)) {
+ ignore_sigio_fd(random_fd);
+ deactivate_fd(random_fd, RANDOM_IRQ);
+ }
+ }
+ else
+ return n;
+
+ if (signal_pending (current))
+ return ret ? : -ERESTARTSYS;
+ }
+ return ret;
+}
+
+static const struct file_operations rng_chrdev_ops = {
+ .owner = THIS_MODULE,
+ .open = rng_dev_open,
+ .read = rng_dev_read,
+ .llseek = noop_llseek,
+};
+
+/* rng_init shouldn't be called more than once at boot time */
+static struct miscdevice rng_miscdev = {
+ RNG_MISCDEV_MINOR,
+ RNG_MODULE_NAME,
+ &rng_chrdev_ops,
+};
+
+static irqreturn_t random_interrupt(int irq, void *data)
+{
+ wake_up(&host_read_wait);
+
+ return IRQ_HANDLED;
+}
+
+/*
+ * rng_init - initialize RNG module
+ */
+static int __init rng_init (void)
+{
+ int err;
+
+ err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0);
+ if (err < 0)
+ goto out;
+
+ random_fd = err;
+
+ err = um_request_irq(RANDOM_IRQ, random_fd, IRQ_READ, random_interrupt,
+ 0, "random", NULL);
+ if (err)
+ goto err_out_cleanup_hw;
+
+ sigio_broken(random_fd, 1);
+
+ err = misc_register (&rng_miscdev);
+ if (err) {
+ printk (KERN_ERR RNG_MODULE_NAME ": misc device register "
+ "failed\n");
+ goto err_out_cleanup_hw;
+ }
+out:
+ return err;
+
+err_out_cleanup_hw:
+ os_close_file(random_fd);
+ random_fd = -1;
+ goto out;
+}
+
+/*
+ * rng_cleanup - shutdown RNG module
+ */
+
+static void cleanup(void)
+{
+ free_irq_by_fd(random_fd);
+ os_close_file(random_fd);
+}
+
+static void __exit rng_cleanup(void)
+{
+ os_close_file(random_fd);
+ misc_deregister (&rng_miscdev);
+}
+
+module_init (rng_init);
+module_exit (rng_cleanup);
+__uml_exitcall(cleanup);
+
+MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
+MODULE_LICENSE("GPL");