Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

72 files changed, 17883 insertions, 0 deletions

diff --git a/arch/um/drivers/Kconfig b/arch/um/drivers/Kconfig
new file mode 100644
index 000000000..fe0210eaf
--- /dev/null
+++ b/arch/um/drivers/Kconfig
@@ -0,0 +1,384 @@
+# SPDX-License-Identifier: GPL-2.0
+
+menu "UML Character Devices"
+
+config STDERR_CONSOLE
+	bool "stderr console"
+	default y
+	help
+	  console driver which dumps all printk messages to stderr.
+
+config SSL
+	bool "Virtual serial line"
+	help
+	  The User-Mode Linux environment allows you to create virtual serial
+	  lines on the UML that are usually made to show up on the host as
+	  ttys or ptys.
+
+	  See <http://user-mode-linux.sourceforge.net/old/input.html> for more
+	  information and command line examples of how to use this facility.
+
+	  Unless you have a specific reason for disabling this, say Y.
+
+config NULL_CHAN
+	bool "null channel support"
+	help
+	  This option enables support for attaching UML consoles and serial
+	  lines to a device similar to /dev/null.  Data written to it disappears
+	  and there is never any data to be read.
+
+config PORT_CHAN
+	bool "port channel support"
+	help
+	  This option enables support for attaching UML consoles and serial
+	  lines to host portals.  They may be accessed with 'telnet <host>
+	  <port number>'.  Any number of consoles and serial lines may be
+	  attached to a single portal, although what UML device you get when
+	  you telnet to that portal will be unpredictable.
+	  It is safe to say 'Y' here.
+
+config PTY_CHAN
+	bool "pty channel support"
+	help
+	  This option enables support for attaching UML consoles and serial
+	  lines to host pseudo-terminals.  Access to both traditional
+	  pseudo-terminals (/dev/pty*) and pts pseudo-terminals are controlled
+	  with this option.  The assignment of UML devices to host devices
+	  will be announced in the kernel message log.
+	  It is safe to say 'Y' here.
+
+config TTY_CHAN
+	bool "tty channel support"
+	help
+	  This option enables support for attaching UML consoles and serial
+	  lines to host terminals.  Access to both virtual consoles
+	  (/dev/tty*) and the slave side of pseudo-terminals (/dev/ttyp* and
+	  /dev/pts/*) are controlled by this option.
+	  It is safe to say 'Y' here.
+
+config XTERM_CHAN
+	bool "xterm channel support"
+	help
+	  This option enables support for attaching UML consoles and serial
+	  lines to xterms.  Each UML device so assigned will be brought up in
+	  its own xterm.
+	  It is safe to say 'Y' here.
+
+config XTERM_CHAN_DEFAULT_EMULATOR
+	string "xterm channel default terminal emulator"
+	depends on XTERM_CHAN
+	default "xterm"
+	help
+	  This option allows changing the default terminal emulator.
+
+config NOCONFIG_CHAN
+	bool
+	default !(XTERM_CHAN && TTY_CHAN && PTY_CHAN && PORT_CHAN && NULL_CHAN)
+
+config CON_ZERO_CHAN
+	string "Default main console channel initialization"
+	default "fd:0,fd:1"
+	help
+	  This is the string describing the channel to which the main console
+	  will be attached by default.  This value can be overridden from the
+	  command line.  The default value is "fd:0,fd:1", which attaches the
+	  main console to stdin and stdout.
+	  It is safe to leave this unchanged.
+
+config CON_CHAN
+	string "Default console channel initialization"
+	default "xterm"
+	help
+	  This is the string describing the channel to which all consoles
+	  except the main console will be attached by default.  This value can
+	  be overridden from the command line.  The default value is "xterm",
+	  which brings them up in xterms.
+	  It is safe to leave this unchanged, although you may wish to change
+	  this if you expect the UML that you build to be run in environments
+	  which don't have X or xterm available.
+
+config SSL_CHAN
+	string "Default serial line channel initialization"
+	default "pty"
+	help
+	  This is the string describing the channel to which the serial lines
+	  will be attached by default.  This value can be overridden from the
+	  command line.  The default value is "pty", which attaches them to
+	  traditional pseudo-terminals.
+	  It is safe to leave this unchanged, although you may wish to change
+	  this if you expect the UML that you build to be run in environments
+	  which don't have a set of /dev/pty* devices.
+
+config UML_SOUND
+	tristate "Sound support"
+	depends on SOUND
+	select SOUND_OSS_CORE
+	help
+	  This option enables UML sound support.  If enabled, it will pull in
+	  the UML hostaudio relay, which acts as a intermediary
+	  between the host's dsp and mixer devices and the UML sound system.
+	  It is safe to say 'Y' here.
+
+endmenu
+
+menu "UML Network Devices"
+	depends on NET
+
+# UML virtual driver
+config UML_NET
+	bool "Virtual network device"
+	help
+	  While the User-Mode port cannot directly talk to any physical
+	  hardware devices, this choice and the following transport options
+	  provide one or more virtual network devices through which the UML
+	  kernels can talk to each other, the host, and with the host's help,
+	  machines on the outside world.
+
+	  For more information, including explanations of the networking and
+	  sample configurations, see
+	  <http://user-mode-linux.sourceforge.net/old/networking.html>.
+
+	  If you'd like to be able to enable networking in the User-Mode
+	  linux environment, say Y; otherwise say N.  Note that you must
+	  enable at least one of the following transport options to actually
+	  make use of UML networking.
+
+config UML_NET_ETHERTAP
+	bool "Ethertap transport (obsolete)"
+	depends on UML_NET
+	help
+	  The Ethertap User-Mode Linux network transport allows a single
+	  running UML to exchange packets with its host over one of the
+	  host's Ethertap devices, such as /dev/tap0.  Additional running
+	  UMLs can use additional Ethertap devices, one per running UML.
+	  While the UML believes it's on a (multi-device, broadcast) virtual
+	  Ethernet network, it's in fact communicating over a point-to-point
+	  link with the host.
+
+	  To use this, your host kernel must have support for Ethertap
+	  devices.  Also, if your host kernel is 2.4.x, it must have
+	  CONFIG_NETLINK_DEV configured as Y or M.
+
+	  For more information, see
+	  <http://user-mode-linux.sourceforge.net/old/networking.html>  That site
+	  has examples of the UML command line to use to enable Ethertap
+	  networking.
+
+	  NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
+	  migrate to UML_NET_VECTOR.
+
+	  If unsure, say N.
+
+config UML_NET_TUNTAP
+	bool "TUN/TAP transport (obsolete)"
+	depends on UML_NET
+	help
+	  The UML TUN/TAP network transport allows a UML instance to exchange
+	  packets with the host over a TUN/TAP device.  This option will only
+	  work with a 2.4 host, unless you've applied the TUN/TAP patch to
+	  your 2.2 host kernel.
+
+	  To use this transport, your host kernel must have support for TUN/TAP
+	  devices, either built-in or as a module.
+
+	  NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
+	  migrate to UML_NET_VECTOR.
+
+	  If unsure, say N.
+
+config UML_NET_SLIP
+	bool "SLIP transport (obsolete)"
+	depends on UML_NET
+	help
+	  The slip User-Mode Linux network transport allows a running UML to
+	  network with its host over a point-to-point link.  Unlike Ethertap,
+	  which can carry any Ethernet frame (and hence even non-IP packets),
+	  the slip transport can only carry IP packets.
+
+	  To use this, your host must support slip devices.
+
+	  For more information, see
+	  <http://user-mode-linux.sourceforge.net/old/networking.html>.
+	  has examples of the UML command line to use to enable slip
+	  networking, and details of a few quirks with it.
+
+	  NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
+	  migrate to UML_NET_VECTOR.
+
+	  If unsure, say N.
+
+config UML_NET_DAEMON
+	bool "Daemon transport (obsolete)"
+	depends on UML_NET
+	help
+	  This User-Mode Linux network transport allows one or more running
+	  UMLs on a single host to communicate with each other, but not to
+	  the host.
+
+	  To use this form of networking, you'll need to run the UML
+	  networking daemon on the host.
+
+	  For more information, see
+	  <http://user-mode-linux.sourceforge.net/old/networking.html>  That site
+	  has examples of the UML command line to use to enable Daemon
+	  networking.
+
+	  NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
+	  migrate to UML_NET_VECTOR.
+
+	  If unsure, say N.
+
+config UML_NET_DAEMON_DEFAULT_SOCK
+	string "Default socket for daemon transport"
+	default "/tmp/uml.ctl"
+	depends on UML_NET_DAEMON
+	help
+	  This option allows setting the default socket for the daemon
+	  transport, normally it defaults to /tmp/uml.ctl.
+
+config UML_NET_VECTOR
+	bool "Vector I/O high performance network devices"
+	depends on UML_NET
+	select MAY_HAVE_RUNTIME_DEPS
+	help
+	  This User-Mode Linux network driver uses multi-message send
+	  and receive functions. The host running the UML guest must have
+	  a linux kernel version above 3.0 and a libc version > 2.13.
+	  This driver provides tap, raw, gre and l2tpv3 network transports
+	  with up to 4 times higher network throughput than the UML network
+	  drivers.
+
+config UML_NET_VDE
+	bool "VDE transport (obsolete)"
+	depends on UML_NET
+	select MAY_HAVE_RUNTIME_DEPS
+	help
+	  This User-Mode Linux network transport allows one or more running
+	  UMLs on a single host to communicate with each other and also
+	  with the rest of the world using Virtual Distributed Ethernet,
+	  an improved fork of uml_switch.
+
+	  You must have libvdeplug installed in order to build the vde
+	  transport into UML.
+
+	  To use this form of networking, you will need to run vde_switch
+	  on the host.
+
+	  For more information, see <http://wiki.virtualsquare.org/>
+	  That site has a good overview of what VDE is and also examples
+	  of the UML command line to use to enable VDE networking.
+
+	  NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
+	  migrate to UML_NET_VECTOR.
+
+	  If unsure, say N.
+
+config UML_NET_MCAST
+	bool "Multicast transport (obsolete)"
+	depends on UML_NET
+	help
+	  This Multicast User-Mode Linux network transport allows multiple
+	  UMLs (even ones running on different host machines!) to talk to
+	  each other over a virtual ethernet network.  However, it requires
+	  at least one UML with one of the other transports to act as a
+	  bridge if any of them need to be able to talk to their hosts or any
+	  other IP machines.
+
+	  To use this, your host kernel(s) must support IP Multicasting.
+
+	  For more information, see
+	  <http://user-mode-linux.sourceforge.net/old/networking.html>  That site
+	  has examples of the UML command line to use to enable Multicast
+	  networking, and notes about the security of this approach.
+
+	  NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
+	  migrate to UML_NET_VECTOR.
+
+	  If unsure, say N.
+
+config UML_NET_PCAP
+	bool "pcap transport (obsolete)"
+	depends on UML_NET
+	select MAY_HAVE_RUNTIME_DEPS
+	help
+	  The pcap transport makes a pcap packet stream on the host look
+	  like an ethernet device inside UML.  This is useful for making
+	  UML act as a network monitor for the host.  You must have libcap
+	  installed in order to build the pcap transport into UML.
+
+	  For more information, see
+	  <http://user-mode-linux.sourceforge.net/old/networking.html>  That site
+	  has examples of the UML command line to use to enable this option.
+
+	  NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
+	  migrate to UML_NET_VECTOR.
+
+	  If unsure, say N.
+
+config UML_NET_SLIRP
+	bool "SLiRP transport (obsolete)"
+	depends on UML_NET
+	help
+	  The SLiRP User-Mode Linux network transport allows a running UML
+	  to network by invoking a program that can handle SLIP encapsulated
+	  packets.  This is commonly (but not limited to) the application
+	  known as SLiRP, a program that can re-socket IP packets back onto
+	  he host on which it is run.  Only IP packets are supported,
+	  unlike other network transports that can handle all Ethernet
+	  frames.  In general, slirp allows the UML the same IP connectivity
+	  to the outside world that the host user is permitted, and unlike
+	  other transports, SLiRP works without the need of root level
+	  privileges, setuid binaries, or SLIP devices on the host.  This
+	  also means not every type of connection is possible, but most
+	  situations can be accommodated with carefully crafted slirp
+	  commands that can be passed along as part of the network device's
+	  setup string.  The effect of this transport on the UML is similar
+	  that of a host behind a firewall that masquerades all network
+	  connections passing through it (but is less secure).
+
+	  NOTE: THIS TRANSPORT IS DEPRECATED AND WILL BE REMOVED SOON!!! Please
+	  migrate to UML_NET_VECTOR.
+
+	  If unsure, say N.
+
+	  Startup example: "eth0=slirp,FE:FD:01:02:03:04,/usr/local/bin/slirp"
+
+endmenu
+
+config VIRTIO_UML
+	bool "UML driver for virtio devices"
+	select VIRTIO
+	help
+	  This driver provides support for virtio based paravirtual device
+	  drivers over vhost-user sockets.
+
+config UML_RTC
+	bool "UML RTC driver"
+	depends on RTC_CLASS
+	# there's no use in this if PM_SLEEP isn't enabled ...
+	depends on PM_SLEEP
+	help
+	  When PM_SLEEP is configured, it may be desirable to wake up using
+	  rtcwake, especially in time-travel mode. This driver enables that
+	  by providing a fake RTC clock that causes a wakeup at the right
+	  time.
+
+config UML_PCI_OVER_VIRTIO
+	bool "Enable PCI over VIRTIO device simulation"
+	# in theory, just VIRTIO is enough, but that causes recursion
+	depends on VIRTIO_UML
+	select FORCE_PCI
+	select UML_IOMEM_EMULATION
+	select UML_DMA_EMULATION
+	select PCI_MSI
+	select PCI_MSI_IRQ_DOMAIN
+	select PCI_LOCKLESS_CONFIG
+
+config UML_PCI_OVER_VIRTIO_DEVICE_ID
+	int "set the virtio device ID for PCI emulation"
+	default -1
+	depends on UML_PCI_OVER_VIRTIO
+	help
+	  There's no official device ID assigned (yet), set the one you
+	  wish to use for experimentation here. The default of -1 is
+	  not valid and will cause the driver to fail at probe.
diff --git a/arch/um/drivers/Makefile b/arch/um/drivers/Makefile
new file mode 100644
index 000000000..079556ec0
--- /dev/null
+++ b/arch/um/drivers/Makefile
@@ -0,0 +1,77 @@
+# SPDX-License-Identifier: GPL-2.0
+# 
+# Copyright (C) 2000, 2002, 2003 Jeff Dike (jdike@karaya.com)
+#
+
+# pcap is broken in 2.5 because kbuild doesn't allow pcap.a to be linked
+# in to pcap.o
+
+slip-objs := slip_kern.o slip_user.o
+slirp-objs := slirp_kern.o slirp_user.o
+daemon-objs := daemon_kern.o daemon_user.o
+vector-objs := vector_kern.o vector_user.o vector_transports.o
+umcast-objs := umcast_kern.o umcast_user.o
+net-objs := net_kern.o net_user.o
+mconsole-objs := mconsole_kern.o mconsole_user.o
+hostaudio-objs := hostaudio_kern.o
+ubd-objs := ubd_kern.o ubd_user.o
+port-objs := port_kern.o port_user.o
+harddog-objs := harddog_kern.o
+harddog-builtin-$(CONFIG_UML_WATCHDOG) := harddog_user.o harddog_user_exp.o
+rtc-objs := rtc_kern.o rtc_user.o
+
+LDFLAGS_pcap.o = $(shell $(CC) $(KBUILD_CFLAGS) -print-file-name=libpcap.a)
+
+LDFLAGS_vde.o = $(shell $(CC) $(CFLAGS) -print-file-name=libvdeplug.a)
+
+targets := pcap_kern.o pcap_user.o vde_kern.o vde_user.o
+
+$(obj)/pcap.o: $(obj)/pcap_kern.o $(obj)/pcap_user.o
+	$(LD) -r -dp -o $@ $^ $(ld_flags)
+
+$(obj)/vde.o: $(obj)/vde_kern.o $(obj)/vde_user.o
+	$(LD) -r -dp -o $@ $^ $(ld_flags)
+
+#XXX: The call below does not work because the flags are added before the
+# object name, so nothing from the library gets linked.
+#$(call if_changed,ld)
+
+# When the above is fixed, don't forget to add this too!
+#targets += $(obj)/pcap.o
+
+obj-y := stdio_console.o fd.o chan_kern.o chan_user.o line.o
+obj-$(CONFIG_SSL) += ssl.o
+obj-$(CONFIG_STDERR_CONSOLE) += stderr_console.o
+
+obj-$(CONFIG_UML_NET_SLIP) += slip.o slip_common.o
+obj-$(CONFIG_UML_NET_SLIRP) += slirp.o slip_common.o
+obj-$(CONFIG_UML_NET_DAEMON) += daemon.o 
+obj-$(CONFIG_UML_NET_VECTOR) += vector.o
+obj-$(CONFIG_UML_NET_VDE) += vde.o
+obj-$(CONFIG_UML_NET_MCAST) += umcast.o
+obj-$(CONFIG_UML_NET_PCAP) += pcap.o
+obj-$(CONFIG_UML_NET) += net.o 
+obj-$(CONFIG_MCONSOLE) += mconsole.o
+obj-$(CONFIG_MMAPPER) += mmapper_kern.o 
+obj-$(CONFIG_BLK_DEV_UBD) += ubd.o 
+obj-$(CONFIG_UML_SOUND) += hostaudio.o
+obj-$(CONFIG_NULL_CHAN) += null.o 
+obj-$(CONFIG_PORT_CHAN) += port.o
+obj-$(CONFIG_PTY_CHAN) += pty.o
+obj-$(CONFIG_TTY_CHAN) += tty.o 
+obj-$(CONFIG_XTERM_CHAN) += xterm.o xterm_kern.o
+obj-$(CONFIG_UML_WATCHDOG) += harddog.o
+obj-y += $(harddog-builtin-y) $(harddog-builtin-m)
+obj-$(CONFIG_BLK_DEV_COW_COMMON) += cow_user.o
+obj-$(CONFIG_UML_RANDOM) += random.o
+obj-$(CONFIG_VIRTIO_UML) += virtio_uml.o
+obj-$(CONFIG_UML_RTC) += rtc.o
+obj-$(CONFIG_UML_PCI_OVER_VIRTIO) += virt-pci.o
+
+# pcap_user.o must be added explicitly.
+USER_OBJS := fd.o null.o pty.o tty.o xterm.o slip_common.o pcap_user.o vde_user.o vector_user.o
+CFLAGS_null.o = -DDEV_NULL=$(DEV_NULL_PATH)
+
+CFLAGS_xterm.o += '-DCONFIG_XTERM_CHAN_DEFAULT_EMULATOR="$(CONFIG_XTERM_CHAN_DEFAULT_EMULATOR)"'
+
+include arch/um/scripts/Makefile.rules
diff --git a/arch/um/drivers/chan.h b/arch/um/drivers/chan.h
new file mode 100644
index 000000000..3fec3b840
--- /dev/null
+++ b/arch/um/drivers/chan.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* 
+ * Copyright (C) 2000, 2001 Jeff Dike (jdike@karaya.com)
+ */
+
+#ifndef __CHAN_KERN_H__
+#define __CHAN_KERN_H__
+
+#include <linux/tty.h>
+#include <linux/list.h>
+#include <linux/console.h>
+#include "chan_user.h"
+#include "line.h"
+
+struct chan {
+	struct list_head list;
+	struct list_head free_list;
+	struct line *line;
+	char *dev;
+	unsigned int primary:1;
+	unsigned int input:1;
+	unsigned int output:1;
+	unsigned int opened:1;
+	unsigned int enabled:1;
+	int fd;
+	const struct chan_ops *ops;
+	void *data;
+};
+
+extern void chan_interrupt(struct line *line, int irq);
+extern int parse_chan_pair(char *str, struct line *line, int device,
+			   const struct chan_opts *opts, char **error_out);
+extern int write_chan(struct chan *chan, const char *buf, int len,
+			     int write_irq);
+extern int console_write_chan(struct chan *chan, const char *buf, 
+			      int len);
+extern int console_open_chan(struct line *line, struct console *co);
+extern void deactivate_chan(struct chan *chan, int irq);
+extern void chan_enable_winch(struct chan *chan, struct tty_port *port);
+extern int enable_chan(struct line *line);
+extern void close_chan(struct line *line);
+extern int chan_window_size(struct line *line, 
+			     unsigned short *rows_out, 
+			     unsigned short *cols_out);
+extern int chan_config_string(struct line *line, char *str, int size,
+			      char **error_out);
+
+#endif
diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
new file mode 100644
index 000000000..26a702a06
--- /dev/null
+++ b/arch/um/drivers/chan_kern.c
@@ -0,0 +1,570 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
+ */
+
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include "chan.h"
+#include <os.h>
+#include <irq_kern.h>
+
+#ifdef CONFIG_NOCONFIG_CHAN
+static void *not_configged_init(char *str, int device,
+				const struct chan_opts *opts)
+{
+	printk(KERN_ERR "Using a channel type which is configured out of "
+	       "UML\n");
+	return NULL;
+}
+
+static int not_configged_open(int input, int output, int primary, void *data,
+			      char **dev_out)
+{
+	printk(KERN_ERR "Using a channel type which is configured out of "
+	       "UML\n");
+	return -ENODEV;
+}
+
+static void not_configged_close(int fd, void *data)
+{
+	printk(KERN_ERR "Using a channel type which is configured out of "
+	       "UML\n");
+}
+
+static int not_configged_read(int fd, char *c_out, void *data)
+{
+	printk(KERN_ERR "Using a channel type which is configured out of "
+	       "UML\n");
+	return -EIO;
+}
+
+static int not_configged_write(int fd, const char *buf, int len, void *data)
+{
+	printk(KERN_ERR "Using a channel type which is configured out of "
+	       "UML\n");
+	return -EIO;
+}
+
+static int not_configged_console_write(int fd, const char *buf, int len)
+{
+	printk(KERN_ERR "Using a channel type which is configured out of "
+	       "UML\n");
+	return -EIO;
+}
+
+static int not_configged_window_size(int fd, void *data, unsigned short *rows,
+				     unsigned short *cols)
+{
+	printk(KERN_ERR "Using a channel type which is configured out of "
+	       "UML\n");
+	return -ENODEV;
+}
+
+static void not_configged_free(void *data)
+{
+	printk(KERN_ERR "Using a channel type which is configured out of "
+	       "UML\n");
+}
+
+static const struct chan_ops not_configged_ops = {
+	.init		= not_configged_init,
+	.open		= not_configged_open,
+	.close		= not_configged_close,
+	.read		= not_configged_read,
+	.write		= not_configged_write,
+	.console_write	= not_configged_console_write,
+	.window_size	= not_configged_window_size,
+	.free		= not_configged_free,
+	.winch		= 0,
+};
+#endif /* CONFIG_NOCONFIG_CHAN */
+
+static int open_one_chan(struct chan *chan)
+{
+	int fd, err;
+
+	if (chan->opened)
+		return 0;
+
+	if (chan->ops->open == NULL)
+		fd = 0;
+	else fd = (*chan->ops->open)(chan->input, chan->output, chan->primary,
+				     chan->data, &chan->dev);
+	if (fd < 0)
+		return fd;
+
+	err = os_set_fd_block(fd, 0);
+	if (err) {
+		(*chan->ops->close)(fd, chan->data);
+		return err;
+	}
+
+	chan->fd = fd;
+
+	chan->opened = 1;
+	return 0;
+}
+
+static int open_chan(struct list_head *chans)
+{
+	struct list_head *ele;
+	struct chan *chan;
+	int ret, err = 0;
+
+	list_for_each(ele, chans) {
+		chan = list_entry(ele, struct chan, list);
+		ret = open_one_chan(chan);
+		if (chan->primary)
+			err = ret;
+	}
+	return err;
+}
+
+void chan_enable_winch(struct chan *chan, struct tty_port *port)
+{
+	if (chan && chan->primary && chan->ops->winch)
+		register_winch(chan->fd, port);
+}
+
+static void line_timer_cb(struct work_struct *work)
+{
+	struct line *line = container_of(work, struct line, task.work);
+
+	if (!line->throttled)
+		chan_interrupt(line, line->read_irq);
+}
+
+int enable_chan(struct line *line)
+{
+	struct list_head *ele;
+	struct chan *chan;
+	int err;
+
+	INIT_DELAYED_WORK(&line->task, line_timer_cb);
+
+	list_for_each(ele, &line->chan_list) {
+		chan = list_entry(ele, struct chan, list);
+		err = open_one_chan(chan);
+		if (err) {
+			if (chan->primary)
+				goto out_close;
+
+			continue;
+		}
+
+		if (chan->enabled)
+			continue;
+		err = line_setup_irq(chan->fd, chan->input, chan->output, line,
+				     chan);
+		if (err)
+			goto out_close;
+
+		chan->enabled = 1;
+	}
+
+	return 0;
+
+ out_close:
+	close_chan(line);
+	return err;
+}
+
+/* Items are added in IRQ context, when free_irq can't be called, and
+ * removed in process context, when it can.
+ * This handles interrupt sources which disappear, and which need to
+ * be permanently disabled.  This is discovered in IRQ context, but
+ * the freeing of the IRQ must be done later.
+ */
+static DEFINE_SPINLOCK(irqs_to_free_lock);
+static LIST_HEAD(irqs_to_free);
+
+void free_irqs(void)
+{
+	struct chan *chan;
+	LIST_HEAD(list);
+	struct list_head *ele;
+	unsigned long flags;
+
+	spin_lock_irqsave(&irqs_to_free_lock, flags);
+	list_splice_init(&irqs_to_free, &list);
+	spin_unlock_irqrestore(&irqs_to_free_lock, flags);
+
+	list_for_each(ele, &list) {
+		chan = list_entry(ele, struct chan, free_list);
+
+		if (chan->input && chan->enabled)
+			um_free_irq(chan->line->read_irq, chan);
+		if (chan->output && chan->enabled)
+			um_free_irq(chan->line->write_irq, chan);
+		chan->enabled = 0;
+	}
+}
+
+static void close_one_chan(struct chan *chan, int delay_free_irq)
+{
+	unsigned long flags;
+
+	if (!chan->opened)
+		return;
+
+	if (delay_free_irq) {
+		spin_lock_irqsave(&irqs_to_free_lock, flags);
+		list_add(&chan->free_list, &irqs_to_free);
+		spin_unlock_irqrestore(&irqs_to_free_lock, flags);
+	} else {
+		if (chan->input && chan->enabled)
+			um_free_irq(chan->line->read_irq, chan);
+		if (chan->output && chan->enabled)
+			um_free_irq(chan->line->write_irq, chan);
+		chan->enabled = 0;
+	}
+	if (chan->ops->close != NULL)
+		(*chan->ops->close)(chan->fd, chan->data);
+
+	chan->opened = 0;
+	chan->fd = -1;
+}
+
+void close_chan(struct line *line)
+{
+	struct chan *chan;
+
+	/* Close in reverse order as open in case more than one of them
+	 * refers to the same device and they save and restore that device's
+	 * state.  Then, the first one opened will have the original state,
+	 * so it must be the last closed.
+	 */
+	list_for_each_entry_reverse(chan, &line->chan_list, list) {
+		close_one_chan(chan, 0);
+	}
+}
+
+void deactivate_chan(struct chan *chan, int irq)
+{
+	if (chan && chan->enabled)
+		deactivate_fd(chan->fd, irq);
+}
+
+int write_chan(struct chan *chan, const char *buf, int len,
+	       int write_irq)
+{
+	int n, ret = 0;
+
+	if (len == 0 || !chan || !chan->ops->write)
+		return 0;
+
+	n = chan->ops->write(chan->fd, buf, len, chan->data);
+	if (chan->primary) {
+		ret = n;
+	}
+	return ret;
+}
+
+int console_write_chan(struct chan *chan, const char *buf, int len)
+{
+	int n, ret = 0;
+
+	if (!chan || !chan->ops->console_write)
+		return 0;
+
+	n = chan->ops->console_write(chan->fd, buf, len);
+	if (chan->primary)
+		ret = n;
+	return ret;
+}
+
+int console_open_chan(struct line *line, struct console *co)
+{
+	int err;
+
+	err = open_chan(&line->chan_list);
+	if (err)
+		return err;
+
+	printk(KERN_INFO "Console initialized on /dev/%s%d\n", co->name,
+	       co->index);
+	return 0;
+}
+
+int chan_window_size(struct line *line, unsigned short *rows_out,
+		      unsigned short *cols_out)
+{
+	struct chan *chan;
+
+	chan = line->chan_in;
+	if (chan && chan->primary) {
+		if (chan->ops->window_size == NULL)
+			return 0;
+		return chan->ops->window_size(chan->fd, chan->data,
+					      rows_out, cols_out);
+	}
+	chan = line->chan_out;
+	if (chan && chan->primary) {
+		if (chan->ops->window_size == NULL)
+			return 0;
+		return chan->ops->window_size(chan->fd, chan->data,
+					      rows_out, cols_out);
+	}
+	return 0;
+}
+
+static void free_one_chan(struct chan *chan)
+{
+	list_del(&chan->list);
+
+	close_one_chan(chan, 0);
+
+	if (chan->ops->free != NULL)
+		(*chan->ops->free)(chan->data);
+
+	if (chan->primary && chan->output)
+		ignore_sigio_fd(chan->fd);
+	kfree(chan);
+}
+
+static void free_chan(struct list_head *chans)
+{
+	struct list_head *ele, *next;
+	struct chan *chan;
+
+	list_for_each_safe(ele, next, chans) {
+		chan = list_entry(ele, struct chan, list);
+		free_one_chan(chan);
+	}
+}
+
+static int one_chan_config_string(struct chan *chan, char *str, int size,
+				  char **error_out)
+{
+	int n = 0;
+
+	if (chan == NULL) {
+		CONFIG_CHUNK(str, size, n, "none", 1);
+		return n;
+	}
+
+	CONFIG_CHUNK(str, size, n, chan->ops->type, 0);
+
+	if (chan->dev == NULL) {
+		CONFIG_CHUNK(str, size, n, "", 1);
+		return n;
+	}
+
+	CONFIG_CHUNK(str, size, n, ":", 0);
+	CONFIG_CHUNK(str, size, n, chan->dev, 0);
+
+	return n;
+}
+
+static int chan_pair_config_string(struct chan *in, struct chan *out,
+				   char *str, int size, char **error_out)
+{
+	int n;
+
+	n = one_chan_config_string(in, str, size, error_out);
+	str += n;
+	size -= n;
+
+	if (in == out) {
+		CONFIG_CHUNK(str, size, n, "", 1);
+		return n;
+	}
+
+	CONFIG_CHUNK(str, size, n, ",", 1);
+	n = one_chan_config_string(out, str, size, error_out);
+	str += n;
+	size -= n;
+	CONFIG_CHUNK(str, size, n, "", 1);
+
+	return n;
+}
+
+int chan_config_string(struct line *line, char *str, int size,
+		       char **error_out)
+{
+	struct chan *in = line->chan_in, *out = line->chan_out;
+
+	if (in && !in->primary)
+		in = NULL;
+	if (out && !out->primary)
+		out = NULL;
+
+	return chan_pair_config_string(in, out, str, size, error_out);
+}
+
+struct chan_type {
+	char *key;
+	const struct chan_ops *ops;
+};
+
+static const struct chan_type chan_table[] = {
+	{ "fd", &fd_ops },
+
+#ifdef CONFIG_NULL_CHAN
+	{ "null", &null_ops },
+#else
+	{ "null", &not_configged_ops },
+#endif
+
+#ifdef CONFIG_PORT_CHAN
+	{ "port", &port_ops },
+#else
+	{ "port", &not_configged_ops },
+#endif
+
+#ifdef CONFIG_PTY_CHAN
+	{ "pty", &pty_ops },
+	{ "pts", &pts_ops },
+#else
+	{ "pty", &not_configged_ops },
+	{ "pts", &not_configged_ops },
+#endif
+
+#ifdef CONFIG_TTY_CHAN
+	{ "tty", &tty_ops },
+#else
+	{ "tty", &not_configged_ops },
+#endif
+
+#ifdef CONFIG_XTERM_CHAN
+	{ "xterm", &xterm_ops },
+#else
+	{ "xterm", &not_configged_ops },
+#endif
+};
+
+static struct chan *parse_chan(struct line *line, char *str, int device,
+			       const struct chan_opts *opts, char **error_out)
+{
+	const struct chan_type *entry;
+	const struct chan_ops *ops;
+	struct chan *chan;
+	void *data;
+	int i;
+
+	ops = NULL;
+	data = NULL;
+	for(i = 0; i < ARRAY_SIZE(chan_table); i++) {
+		entry = &chan_table[i];
+		if (!strncmp(str, entry->key, strlen(entry->key))) {
+			ops = entry->ops;
+			str += strlen(entry->key);
+			break;
+		}
+	}
+	if (ops == NULL) {
+		*error_out = "No match for configured backends";
+		return NULL;
+	}
+
+	data = (*ops->init)(str, device, opts);
+	if (data == NULL) {
+		*error_out = "Configuration failed";
+		return NULL;
+	}
+
+	chan = kmalloc(sizeof(*chan), GFP_ATOMIC);
+	if (chan == NULL) {
+		*error_out = "Memory allocation failed";
+		return NULL;
+	}
+	*chan = ((struct chan) { .list	 	= LIST_HEAD_INIT(chan->list),
+				 .free_list 	=
+				 	LIST_HEAD_INIT(chan->free_list),
+				 .line		= line,
+				 .primary	= 1,
+				 .input		= 0,
+				 .output 	= 0,
+				 .opened  	= 0,
+				 .enabled  	= 0,
+				 .fd 		= -1,
+				 .ops 		= ops,
+				 .data 		= data });
+	return chan;
+}
+
+int parse_chan_pair(char *str, struct line *line, int device,
+		    const struct chan_opts *opts, char **error_out)
+{
+	struct list_head *chans = &line->chan_list;
+	struct chan *new;
+	char *in, *out;
+
+	if (!list_empty(chans)) {
+		line->chan_in = line->chan_out = NULL;
+		free_chan(chans);
+		INIT_LIST_HEAD(chans);
+	}
+
+	if (!str)
+		return 0;
+
+	out = strchr(str, ',');
+	if (out != NULL) {
+		in = str;
+		*out = '\0';
+		out++;
+		new = parse_chan(line, in, device, opts, error_out);
+		if (new == NULL)
+			return -1;
+
+		new->input = 1;
+		list_add(&new->list, chans);
+		line->chan_in = new;
+
+		new = parse_chan(line, out, device, opts, error_out);
+		if (new == NULL)
+			return -1;
+
+		list_add(&new->list, chans);
+		new->output = 1;
+		line->chan_out = new;
+	}
+	else {
+		new = parse_chan(line, str, device, opts, error_out);
+		if (new == NULL)
+			return -1;
+
+		list_add(&new->list, chans);
+		new->input = 1;
+		new->output = 1;
+		line->chan_in = line->chan_out = new;
+	}
+	return 0;
+}
+
+void chan_interrupt(struct line *line, int irq)
+{
+	struct tty_port *port = &line->port;
+	struct chan *chan = line->chan_in;
+	int err;
+	char c;
+
+	if (!chan || !chan->ops->read)
+		goto out;
+
+	do {
+		if (!tty_buffer_request_room(port, 1)) {
+			schedule_delayed_work(&line->task, 1);
+			goto out;
+		}
+		err = chan->ops->read(chan->fd, &c, chan->data);
+		if (err > 0)
+			tty_insert_flip_char(port, c, TTY_NORMAL);
+	} while (err > 0);
+
+	if (err == -EIO) {
+		if (chan->primary) {
+			tty_port_tty_hangup(&line->port, false);
+			if (line->chan_out != chan)
+				close_one_chan(line->chan_out, 1);
+		}
+		close_one_chan(chan, 1);
+		if (chan->primary)
+			return;
+	}
+ out:
+	tty_flip_buffer_push(port);
+}
diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c
new file mode 100644
index 000000000..25727ed64
--- /dev/null
+++ b/arch/um/drivers/chan_user.c
@@ -0,0 +1,303 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
+ */
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sched.h>
+#include <signal.h>
+#include <termios.h>
+#include <sys/ioctl.h>
+#include "chan_user.h"
+#include <os.h>
+#include <um_malloc.h>
+
+void generic_close(int fd, void *unused)
+{
+	close(fd);
+}
+
+int generic_read(int fd, char *c_out, void *unused)
+{
+	int n;
+
+	n = read(fd, c_out, sizeof(*c_out));
+	if (n > 0)
+		return n;
+	else if (n == 0)
+		return -EIO;
+	else if (errno == EAGAIN)
+		return 0;
+	return -errno;
+}
+
+/* XXX Trivial wrapper around write */
+
+int generic_write(int fd, const char *buf, int n, void *unused)
+{
+	int err;
+
+	err = write(fd, buf, n);
+	if (err > 0)
+		return err;
+	else if (errno == EAGAIN)
+		return 0;
+	else if (err == 0)
+		return -EIO;
+	return -errno;
+}
+
+int generic_window_size(int fd, void *unused, unsigned short *rows_out,
+			unsigned short *cols_out)
+{
+	struct winsize size;
+	int ret;
+
+	if (ioctl(fd, TIOCGWINSZ, &size) < 0)
+		return -errno;
+
+	ret = ((*rows_out != size.ws_row) || (*cols_out != size.ws_col));
+
+	*rows_out = size.ws_row;
+	*cols_out = size.ws_col;
+
+	return ret;
+}
+
+void generic_free(void *data)
+{
+	kfree(data);
+}
+
+int generic_console_write(int fd, const char *buf, int n)
+{
+	sigset_t old, no_sigio;
+	struct termios save, new;
+	int err;
+
+	if (isatty(fd)) {
+		sigemptyset(&no_sigio);
+		sigaddset(&no_sigio, SIGIO);
+		if (sigprocmask(SIG_BLOCK, &no_sigio, &old))
+			goto error;
+
+		CATCH_EINTR(err = tcgetattr(fd, &save));
+		if (err)
+			goto error;
+		new = save;
+		/*
+		 * The terminal becomes a bit less raw, to handle \n also as
+		 * "Carriage Return", not only as "New Line". Otherwise, the new
+		 * line won't start at the first column.
+		 */
+		new.c_oflag |= OPOST;
+		CATCH_EINTR(err = tcsetattr(fd, TCSAFLUSH, &new));
+		if (err)
+			goto error;
+	}
+	err = generic_write(fd, buf, n, NULL);
+	/*
+	 * Restore raw mode, in any case; we *must* ignore any error apart
+	 * EINTR, except for debug.
+	 */
+	if (isatty(fd)) {
+		CATCH_EINTR(tcsetattr(fd, TCSAFLUSH, &save));
+		sigprocmask(SIG_SETMASK, &old, NULL);
+	}
+
+	return err;
+error:
+	return -errno;
+}
+
+/*
+ * UML SIGWINCH handling
+ *
+ * The point of this is to handle SIGWINCH on consoles which have host
+ * ttys and relay them inside UML to whatever might be running on the
+ * console and cares about the window size (since SIGWINCH notifies
+ * about terminal size changes).
+ *
+ * So, we have a separate thread for each host tty attached to a UML
+ * device (side-issue - I'm annoyed that one thread can't have
+ * multiple controlling ttys for the purpose of handling SIGWINCH, but
+ * I imagine there are other reasons that doesn't make any sense).
+ *
+ * SIGWINCH can't be received synchronously, so you have to set up to
+ * receive it as a signal.  That being the case, if you are going to
+ * wait for it, it is convenient to sit in sigsuspend() and wait for
+ * the signal to bounce you out of it (see below for how we make sure
+ * to exit only on SIGWINCH).
+ */
+
+static void winch_handler(int sig)
+{
+}
+
+struct winch_data {
+	int pty_fd;
+	int pipe_fd;
+};
+
+static int winch_thread(void *arg)
+{
+	struct winch_data *data = arg;
+	sigset_t sigs;
+	int pty_fd, pipe_fd;
+	int count;
+	char c = 1;
+
+	pty_fd = data->pty_fd;
+	pipe_fd = data->pipe_fd;
+	count = write(pipe_fd, &c, sizeof(c));
+	if (count != sizeof(c))
+		printk(UM_KERN_ERR "winch_thread : failed to write "
+		       "synchronization byte, err = %d\n", -count);
+
+	/*
+	 * We are not using SIG_IGN on purpose, so don't fix it as I thought to
+	 * do! If using SIG_IGN, the sigsuspend() call below would not stop on
+	 * SIGWINCH.
+	 */
+
+	signal(SIGWINCH, winch_handler);
+	sigfillset(&sigs);
+	/* Block all signals possible. */
+	if (sigprocmask(SIG_SETMASK, &sigs, NULL) < 0) {
+		printk(UM_KERN_ERR "winch_thread : sigprocmask failed, "
+		       "errno = %d\n", errno);
+		exit(1);
+	}
+	/* In sigsuspend(), block anything else than SIGWINCH. */
+	sigdelset(&sigs, SIGWINCH);
+
+	if (setsid() < 0) {
+		printk(UM_KERN_ERR "winch_thread : setsid failed, errno = %d\n",
+		       errno);
+		exit(1);
+	}
+
+	if (ioctl(pty_fd, TIOCSCTTY, 0) < 0) {
+		printk(UM_KERN_ERR "winch_thread : TIOCSCTTY failed on "
+		       "fd %d err = %d\n", pty_fd, errno);
+		exit(1);
+	}
+
+	if (tcsetpgrp(pty_fd, os_getpid()) < 0) {
+		printk(UM_KERN_ERR "winch_thread : tcsetpgrp failed on "
+		       "fd %d err = %d\n", pty_fd, errno);
+		exit(1);
+	}
+
+	/*
+	 * These are synchronization calls between various UML threads on the
+	 * host - since they are not different kernel threads, we cannot use
+	 * kernel semaphores. We don't use SysV semaphores because they are
+	 * persistent.
+	 */
+	count = read(pipe_fd, &c, sizeof(c));
+	if (count != sizeof(c))
+		printk(UM_KERN_ERR "winch_thread : failed to read "
+		       "synchronization byte, err = %d\n", errno);
+
+	while(1) {
+		/*
+		 * This will be interrupted by SIGWINCH only, since
+		 * other signals are blocked.
+		 */
+		sigsuspend(&sigs);
+
+		count = write(pipe_fd, &c, sizeof(c));
+		if (count != sizeof(c))
+			printk(UM_KERN_ERR "winch_thread : write failed, "
+			       "err = %d\n", errno);
+	}
+}
+
+static int winch_tramp(int fd, struct tty_port *port, int *fd_out,
+		       unsigned long *stack_out)
+{
+	struct winch_data data;
+	int fds[2], n, err, pid;
+	char c;
+
+	err = os_pipe(fds, 1, 1);
+	if (err < 0) {
+		printk(UM_KERN_ERR "winch_tramp : os_pipe failed, err = %d\n",
+		       -err);
+		goto out;
+	}
+
+	data = ((struct winch_data) { .pty_fd 		= fd,
+				      .pipe_fd 		= fds[1] } );
+	/*
+	 * CLONE_FILES so this thread doesn't hold open files which are open
+	 * now, but later closed in a different thread.  This is a
+	 * problem with /dev/net/tun, which if held open by this
+	 * thread, prevents the TUN/TAP device from being reused.
+	 */
+	pid = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out);
+	if (pid < 0) {
+		err = pid;
+		printk(UM_KERN_ERR "fork of winch_thread failed - errno = %d\n",
+		       -err);
+		goto out_close;
+	}
+
+	*fd_out = fds[0];
+	n = read(fds[0], &c, sizeof(c));
+	if (n != sizeof(c)) {
+		printk(UM_KERN_ERR "winch_tramp : failed to read "
+		       "synchronization byte\n");
+		printk(UM_KERN_ERR "read failed, err = %d\n", errno);
+		printk(UM_KERN_ERR "fd %d will not support SIGWINCH\n", fd);
+		err = -EINVAL;
+		goto out_close;
+	}
+
+	err = os_set_fd_block(*fd_out, 0);
+	if (err) {
+		printk(UM_KERN_ERR "winch_tramp: failed to set thread_fd "
+		       "non-blocking.\n");
+		goto out_close;
+	}
+
+	return pid;
+
+ out_close:
+	close(fds[1]);
+	close(fds[0]);
+ out:
+	return err;
+}
+
+void register_winch(int fd, struct tty_port *port)
+{
+	unsigned long stack;
+	int pid, thread, count, thread_fd = -1;
+	char c = 1;
+
+	if (!isatty(fd))
+		return;
+
+	pid = tcgetpgrp(fd);
+	if (is_skas_winch(pid, fd, port)) {
+		register_winch_irq(-1, fd, -1, port, 0);
+		return;
+	}
+
+	if (pid == -1) {
+		thread = winch_tramp(fd, port, &thread_fd, &stack);
+		if (thread < 0)
+			return;
+
+		register_winch_irq(thread_fd, fd, thread, port, stack);
+
+		count = write(thread_fd, &c, sizeof(c));
+		if (count != sizeof(c))
+			printk(UM_KERN_ERR "register_winch : failed to write "
+			       "synchronization byte, err = %d\n", errno);
+	}
+}
diff --git a/arch/um/drivers/chan_user.h b/arch/um/drivers/chan_user.h
new file mode 100644
index 000000000..4e51b85e2
--- /dev/null
+++ b/arch/um/drivers/chan_user.h
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2000, 2001 Jeff Dike (jdike@karaya.com)
+ */
+
+#ifndef __CHAN_USER_H__
+#define __CHAN_USER_H__
+
+#include <init.h>
+
+struct chan_opts {
+	void (*const announce)(char *dev_name, int dev);
+	char *xterm_title;
+	int raw;
+};
+
+struct chan_ops {
+	char *type;
+	void *(*init)(char *, int, const struct chan_opts *);
+	int (*open)(int, int, int, void *, char **);
+	void (*close)(int, void *);
+	int (*read)(int, char *, void *);
+	int (*write)(int, const char *, int, void *);
+	int (*console_write)(int, const char *, int);
+	int (*window_size)(int, void *, unsigned short *, unsigned short *);
+	void (*free)(void *);
+	int winch;
+};
+
+extern const struct chan_ops fd_ops, null_ops, port_ops, pts_ops, pty_ops,
+	tty_ops, xterm_ops;
+
+extern void generic_close(int fd, void *unused);
+extern int generic_read(int fd, char *c_out, void *unused);
+extern int generic_write(int fd, const char *buf, int n, void *unused);
+extern int generic_console_write(int fd, const char *buf, int n);
+extern int generic_window_size(int fd, void *unused, unsigned short *rows_out,
+			       unsigned short *cols_out);
+extern void generic_free(void *data);
+
+struct tty_port;
+extern void register_winch(int fd,  struct tty_port *port);
+extern void register_winch_irq(int fd, int tty_fd, int pid,
+			       struct tty_port *port, unsigned long stack);
+
+#define __channel_help(fn, prefix) \
+__uml_help(fn, prefix "[0-9]*=<channel description>\n" \
+"    Attach a console or serial line to a host channel.  See\n" \
+"    http://user-mode-linux.sourceforge.net/old/input.html for a complete\n" \
+"    description of this switch.\n\n" \
+);
+
+#endif
diff --git a/arch/um/drivers/cow.h b/arch/um/drivers/cow.h
new file mode 100644
index 000000000..9a67c0170
--- /dev/null
+++ b/arch/um/drivers/cow.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __COW_H__
+#define __COW_H__
+
+#include <asm/types.h>
+
+extern int init_cow_file(int fd, char *cow_file, char *backing_file,
+			 int sectorsize, int alignment, int *bitmap_offset_out,
+			 unsigned long *bitmap_len_out, int *data_offset_out);
+
+extern int file_reader(__u64 offset, char *buf, int len, void *arg);
+extern int read_cow_header(int (*reader)(__u64, char *, int, void *),
+			   void *arg, __u32 *version_out,
+			   char **backing_file_out, long long *mtime_out,
+			   unsigned long long *size_out, int *sectorsize_out,
+			   __u32 *align_out, int *bitmap_offset_out);
+
+extern int write_cow_header(char *cow_file, int fd, char *backing_file,
+			    int sectorsize, int alignment,
+			    unsigned long long *size);
+
+extern void cow_sizes(int version, __u64 size, int sectorsize, int align,
+		      int bitmap_offset, unsigned long *bitmap_len_out,
+		      int *data_offset_out);
+
+#endif
diff --git a/arch/um/drivers/cow_sys.h b/arch/um/drivers/cow_sys.h
new file mode 100644
index 000000000..916811ef5
--- /dev/null
+++ b/arch/um/drivers/cow_sys.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __COW_SYS_H__
+#define __COW_SYS_H__
+
+#include <kern_util.h>
+#include <os.h>
+#include <um_malloc.h>
+
+static inline void *cow_malloc(int size)
+{
+	return uml_kmalloc(size, UM_GFP_KERNEL);
+}
+
+static inline void cow_free(void *ptr)
+{
+	kfree(ptr);
+}
+
+#define cow_printf printk
+
+static inline char *cow_strdup(char *str)
+{
+	return uml_strdup(str);
+}
+
+static inline int cow_seek_file(int fd, __u64 offset)
+{
+	return os_seek_file(fd, offset);
+}
+
+static inline int cow_file_size(char *file, unsigned long long *size_out)
+{
+	return os_file_size(file, size_out);
+}
+
+static inline int cow_write_file(int fd, void *buf, int size)
+{
+	return os_write_file(fd, buf, size);
+}
+
+#endif
diff --git a/arch/um/drivers/cow_user.c b/arch/um/drivers/cow_user.c
new file mode 100644
index 000000000..29b46581d
--- /dev/null
+++ b/arch/um/drivers/cow_user.c
@@ -0,0 +1,444 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
+ */
+
+/*
+ * _XOPEN_SOURCE is needed for pread, but we define _GNU_SOURCE, which defines
+ * that.
+ */
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <arpa/inet.h>
+#include <endian.h>
+#include "cow.h"
+#include "cow_sys.h"
+
+#define PATH_LEN_V1 256
+
+/* unsigned time_t works until year 2106 */
+typedef __u32 time32_t;
+
+struct cow_header_v1 {
+	__s32 magic;
+	__s32 version;
+	char backing_file[PATH_LEN_V1];
+	time32_t mtime;
+	__u64 size;
+	__s32 sectorsize;
+} __attribute__((packed));
+
+/*
+ * Define PATH_LEN_V3 as the usual value of MAXPATHLEN, just hard-code it in
+ * case other systems have different values for MAXPATHLEN.
+ *
+ * The same must hold for V2 - we want file format compatibility, not anything
+ * else.
+ */
+#define PATH_LEN_V3 4096
+#define PATH_LEN_V2 PATH_LEN_V3
+
+struct cow_header_v2 {
+	__u32 magic;
+	__u32 version;
+	char backing_file[PATH_LEN_V2];
+	time32_t mtime;
+	__u64 size;
+	__s32 sectorsize;
+} __attribute__((packed));
+
+/*
+ * Changes from V2 -
+ *	PATH_LEN_V3 as described above
+ *	Explicitly specify field bit lengths for systems with different
+ *		lengths for the usual C types.  Not sure whether char or
+ *		time_t should be changed, this can be changed later without
+ *		breaking compatibility
+ *	Add alignment field so that different alignments can be used for the
+ *		bitmap and data
+ * 	Add cow_format field to allow for the possibility of different ways
+ *		of specifying the COW blocks.  For now, the only value is 0,
+ * 		for the traditional COW bitmap.
+ *	Move the backing_file field to the end of the header.  This allows
+ *		for the possibility of expanding it into the padding required
+ *		by the bitmap alignment.
+ * 	The bitmap and data portions of the file will be aligned as specified
+ * 		by the alignment field.  This is to allow COW files to be
+ *		put on devices with restrictions on access alignments, such as
+ *		/dev/raw, with a 512 byte alignment restriction.  This also
+ *		allows the data to be more aligned more strictly than on
+ *		sector boundaries.  This is needed for ubd-mmap, which needs
+ *		the data to be page aligned.
+ *	Fixed (finally!) the rounding bug
+ */
+
+/*
+ * Until Dec2005, __attribute__((packed)) was left out from the below
+ * definition, leading on 64-bit systems to 4 bytes of padding after mtime, to
+ * align size to 8-byte alignment.  This shifted all fields above (no padding
+ * was present on 32-bit, no other padding was added).
+ *
+ * However, this _can be detected_: it means that cow_format (always 0 until
+ * now) is shifted onto the first 4 bytes of backing_file, where it is otherwise
+ * impossible to find 4 zeros. -bb */
+
+struct cow_header_v3 {
+	__u32 magic;
+	__u32 version;
+	__u32 mtime;
+	__u64 size;
+	__u32 sectorsize;
+	__u32 alignment;
+	__u32 cow_format;
+	char backing_file[PATH_LEN_V3];
+} __attribute__((packed));
+
+/* This is the broken layout used by some 64-bit binaries. */
+struct cow_header_v3_broken {
+	__u32 magic;
+	__u32 version;
+	__s64 mtime;
+	__u64 size;
+	__u32 sectorsize;
+	__u32 alignment;
+	__u32 cow_format;
+	char backing_file[PATH_LEN_V3];
+};
+
+/* COW format definitions - for now, we have only the usual COW bitmap */
+#define COW_BITMAP 0
+
+union cow_header {
+	struct cow_header_v1 v1;
+	struct cow_header_v2 v2;
+	struct cow_header_v3 v3;
+	struct cow_header_v3_broken v3_b;
+};
+
+#define COW_MAGIC 0x4f4f4f4d  /* MOOO */
+#define COW_VERSION 3
+
+#define DIV_ROUND(x, len) (((x) + (len) - 1) / (len))
+#define ROUND_UP(x, align) DIV_ROUND(x, align) * (align)
+
+void cow_sizes(int version, __u64 size, int sectorsize, int align,
+	       int bitmap_offset, unsigned long *bitmap_len_out,
+	       int *data_offset_out)
+{
+	if (version < 3) {
+		*bitmap_len_out = (size + sectorsize - 1) / (8 * sectorsize);
+
+		*data_offset_out = bitmap_offset + *bitmap_len_out;
+		*data_offset_out = (*data_offset_out + sectorsize - 1) /
+			sectorsize;
+		*data_offset_out *= sectorsize;
+	}
+	else {
+		*bitmap_len_out = DIV_ROUND(size, sectorsize);
+		*bitmap_len_out = DIV_ROUND(*bitmap_len_out, 8);
+
+		*data_offset_out = bitmap_offset + *bitmap_len_out;
+		*data_offset_out = ROUND_UP(*data_offset_out, align);
+	}
+}
+
+static int absolutize(char *to, int size, char *from)
+{
+	char save_cwd[256], *slash;
+	int remaining;
+
+	if (getcwd(save_cwd, sizeof(save_cwd)) == NULL) {
+		cow_printf("absolutize : unable to get cwd - errno = %d\n",
+			   errno);
+		return -1;
+	}
+	slash = strrchr(from, '/');
+	if (slash != NULL) {
+		*slash = '\0';
+		if (chdir(from)) {
+			*slash = '/';
+			cow_printf("absolutize : Can't cd to '%s' - "
+				   "errno = %d\n", from, errno);
+			return -1;
+		}
+		*slash = '/';
+		if (getcwd(to, size) == NULL) {
+			cow_printf("absolutize : unable to get cwd of '%s' - "
+			       "errno = %d\n", from, errno);
+			return -1;
+		}
+		remaining = size - strlen(to);
+		if (strlen(slash) + 1 > remaining) {
+			cow_printf("absolutize : unable to fit '%s' into %d "
+			       "chars\n", from, size);
+			return -1;
+		}
+		strcat(to, slash);
+	}
+	else {
+		if (strlen(save_cwd) + 1 + strlen(from) + 1 > size) {
+			cow_printf("absolutize : unable to fit '%s' into %d "
+			       "chars\n", from, size);
+			return -1;
+		}
+		strcpy(to, save_cwd);
+		strcat(to, "/");
+		strcat(to, from);
+	}
+	if (chdir(save_cwd)) {
+		cow_printf("absolutize : Can't cd to '%s' - "
+			   "errno = %d\n", save_cwd, errno);
+		return -1;
+	}
+	return 0;
+}
+
+int write_cow_header(char *cow_file, int fd, char *backing_file,
+		     int sectorsize, int alignment, unsigned long long *size)
+{
+	struct cow_header_v3 *header;
+	long long modtime;
+	int err;
+
+	err = cow_seek_file(fd, 0);
+	if (err < 0) {
+		cow_printf("write_cow_header - lseek failed, err = %d\n", -err);
+		goto out;
+	}
+
+	err = -ENOMEM;
+	header = cow_malloc(sizeof(*header));
+	if (header == NULL) {
+		cow_printf("write_cow_header - failed to allocate COW V3 "
+			   "header\n");
+		goto out;
+	}
+	header->magic = htobe32(COW_MAGIC);
+	header->version = htobe32(COW_VERSION);
+
+	err = -EINVAL;
+	if (strlen(backing_file) > sizeof(header->backing_file) - 1) {
+		/* Below, %zd is for a size_t value */
+		cow_printf("Backing file name \"%s\" is too long - names are "
+			   "limited to %zd characters\n", backing_file,
+			   sizeof(header->backing_file) - 1);
+		goto out_free;
+	}
+
+	if (absolutize(header->backing_file, sizeof(header->backing_file),
+		      backing_file))
+		goto out_free;
+
+	err = os_file_modtime(header->backing_file, &modtime);
+	if (err < 0) {
+		cow_printf("write_cow_header - backing file '%s' mtime "
+			   "request failed, err = %d\n", header->backing_file,
+			   -err);
+		goto out_free;
+	}
+
+	err = cow_file_size(header->backing_file, size);
+	if (err < 0) {
+		cow_printf("write_cow_header - couldn't get size of "
+			   "backing file '%s', err = %d\n",
+			   header->backing_file, -err);
+		goto out_free;
+	}
+
+	header->mtime = htobe32(modtime);
+	header->size = htobe64(*size);
+	header->sectorsize = htobe32(sectorsize);
+	header->alignment = htobe32(alignment);
+	header->cow_format = COW_BITMAP;
+
+	err = cow_write_file(fd, header, sizeof(*header));
+	if (err != sizeof(*header)) {
+		cow_printf("write_cow_header - write of header to "
+			   "new COW file '%s' failed, err = %d\n", cow_file,
+			   -err);
+		goto out_free;
+	}
+	err = 0;
+ out_free:
+	cow_free(header);
+ out:
+	return err;
+}
+
+int file_reader(__u64 offset, char *buf, int len, void *arg)
+{
+	int fd = *((int *) arg);
+
+	return pread(fd, buf, len, offset);
+}
+
+/* XXX Need to sanity-check the values read from the header */
+
+int read_cow_header(int (*reader)(__u64, char *, int, void *), void *arg,
+		    __u32 *version_out, char **backing_file_out,
+		    long long *mtime_out, unsigned long long *size_out,
+		    int *sectorsize_out, __u32 *align_out,
+		    int *bitmap_offset_out)
+{
+	union cow_header *header;
+	char *file;
+	int err, n;
+	unsigned long version, magic;
+
+	header = cow_malloc(sizeof(*header));
+	if (header == NULL) {
+	        cow_printf("read_cow_header - Failed to allocate header\n");
+		return -ENOMEM;
+	}
+	err = -EINVAL;
+	n = (*reader)(0, (char *) header, sizeof(*header), arg);
+	if (n < offsetof(typeof(header->v1), backing_file)) {
+		cow_printf("read_cow_header - short header\n");
+		goto out;
+	}
+
+	magic = header->v1.magic;
+	if (magic == COW_MAGIC)
+		version = header->v1.version;
+	else if (magic == be32toh(COW_MAGIC))
+		version = be32toh(header->v1.version);
+	/* No error printed because the non-COW case comes through here */
+	else goto out;
+
+	*version_out = version;
+
+	if (version == 1) {
+		if (n < sizeof(header->v1)) {
+			cow_printf("read_cow_header - failed to read V1 "
+				   "header\n");
+			goto out;
+		}
+		*mtime_out = header->v1.mtime;
+		*size_out = header->v1.size;
+		*sectorsize_out = header->v1.sectorsize;
+		*bitmap_offset_out = sizeof(header->v1);
+		*align_out = *sectorsize_out;
+		file = header->v1.backing_file;
+	}
+	else if (version == 2) {
+		if (n < sizeof(header->v2)) {
+			cow_printf("read_cow_header - failed to read V2 "
+				   "header\n");
+			goto out;
+		}
+		*mtime_out = be32toh(header->v2.mtime);
+		*size_out = be64toh(header->v2.size);
+		*sectorsize_out = be32toh(header->v2.sectorsize);
+		*bitmap_offset_out = sizeof(header->v2);
+		*align_out = *sectorsize_out;
+		file = header->v2.backing_file;
+	}
+	/* This is very subtle - see above at union cow_header definition */
+	else if (version == 3 && (*((int*)header->v3.backing_file) != 0)) {
+		if (n < sizeof(header->v3)) {
+			cow_printf("read_cow_header - failed to read V3 "
+				   "header\n");
+			goto out;
+		}
+		*mtime_out = be32toh(header->v3.mtime);
+		*size_out = be64toh(header->v3.size);
+		*sectorsize_out = be32toh(header->v3.sectorsize);
+		*align_out = be32toh(header->v3.alignment);
+		if (*align_out == 0) {
+			cow_printf("read_cow_header - invalid COW header, "
+				   "align == 0\n");
+		}
+		*bitmap_offset_out = ROUND_UP(sizeof(header->v3), *align_out);
+		file = header->v3.backing_file;
+	}
+	else if (version == 3) {
+		cow_printf("read_cow_header - broken V3 file with"
+			   " 64-bit layout - recovering content.\n");
+
+		if (n < sizeof(header->v3_b)) {
+			cow_printf("read_cow_header - failed to read V3 "
+				   "header\n");
+			goto out;
+		}
+
+		/*
+		 * this was used until Dec2005 - 64bits are needed to represent
+		 * 2106+. I.e. we can safely do this truncating cast.
+		 *
+		 * Additionally, we must use be32toh() instead of be64toh(), since
+		 * the program used to use the former (tested - I got mtime
+		 * mismatch "0 vs whatever").
+		 *
+		 * Ever heard about bug-to-bug-compatibility ? ;-) */
+		*mtime_out = (time32_t) be32toh(header->v3_b.mtime);
+
+		*size_out = be64toh(header->v3_b.size);
+		*sectorsize_out = be32toh(header->v3_b.sectorsize);
+		*align_out = be32toh(header->v3_b.alignment);
+		if (*align_out == 0) {
+			cow_printf("read_cow_header - invalid COW header, "
+				   "align == 0\n");
+		}
+		*bitmap_offset_out = ROUND_UP(sizeof(header->v3_b), *align_out);
+		file = header->v3_b.backing_file;
+	}
+	else {
+		cow_printf("read_cow_header - invalid COW version\n");
+		goto out;
+	}
+	err = -ENOMEM;
+	*backing_file_out = cow_strdup(file);
+	if (*backing_file_out == NULL) {
+		cow_printf("read_cow_header - failed to allocate backing "
+			   "file\n");
+		goto out;
+	}
+	err = 0;
+ out:
+	cow_free(header);
+	return err;
+}
+
+int init_cow_file(int fd, char *cow_file, char *backing_file, int sectorsize,
+		  int alignment, int *bitmap_offset_out,
+		  unsigned long *bitmap_len_out, int *data_offset_out)
+{
+	unsigned long long size, offset;
+	char zero = 0;
+	int err;
+
+	err = write_cow_header(cow_file, fd, backing_file, sectorsize,
+			       alignment, &size);
+	if (err)
+		goto out;
+
+	*bitmap_offset_out = ROUND_UP(sizeof(struct cow_header_v3), alignment);
+	cow_sizes(COW_VERSION, size, sectorsize, alignment, *bitmap_offset_out,
+		  bitmap_len_out, data_offset_out);
+
+	offset = *data_offset_out + size - sizeof(zero);
+	err = cow_seek_file(fd, offset);
+	if (err < 0) {
+		cow_printf("cow bitmap lseek failed : err = %d\n", -err);
+		goto out;
+	}
+
+	/*
+	 * does not really matter how much we write it is just to set EOF
+	 * this also sets the entire COW bitmap
+	 * to zero without having to allocate it
+	 */
+	err = cow_write_file(fd, &zero, sizeof(zero));
+	if (err != sizeof(zero)) {
+		cow_printf("Write of bitmap to new COW file '%s' failed, "
+			   "err = %d\n", cow_file, -err);
+		if (err >= 0)
+			err = -EINVAL;
+		goto out;
+	}
+
+	return 0;
+ out:
+	return err;
+}
diff --git a/arch/um/drivers/daemon.h b/arch/um/drivers/daemon.h
new file mode 100644
index 000000000..1509cc7eb
--- /dev/null
+++ b/arch/um/drivers/daemon.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#ifndef __DAEMON_H__
+#define __DAEMON_H__
+
+#include <net_user.h>
+
+#define SWITCH_VERSION 3
+
+struct daemon_data {
+	char *sock_type;
+	char *ctl_sock;
+	void *ctl_addr;
+	void *data_addr;
+	void *local_addr;
+	int fd;
+	int control;
+	void *dev;
+};
+
+extern const struct net_user_info daemon_user_info;
+
+extern int daemon_user_write(int fd, void *buf, int len,
+			     struct daemon_data *pri);
+
+#endif
diff --git a/arch/um/drivers/daemon_kern.c b/arch/um/drivers/daemon_kern.c
new file mode 100644
index 000000000..afde1e82c
--- /dev/null
+++ b/arch/um/drivers/daemon_kern.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org) and
+ * James Leu (jleu@mindspring.net).
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Copyright (C) 2001 by various other people who didn't put their name here.
+ */
+
+#include <linux/init.h>
+#include <linux/netdevice.h>
+#include <net_kern.h>
+#include "daemon.h"
+
+struct daemon_init {
+	char *sock_type;
+	char *ctl_sock;
+};
+
+static void daemon_init(struct net_device *dev, void *data)
+{
+	struct uml_net_private *pri;
+	struct daemon_data *dpri;
+	struct daemon_init *init = data;
+
+	pri = netdev_priv(dev);
+	dpri = (struct daemon_data *) pri->user;
+	dpri->sock_type = init->sock_type;
+	dpri->ctl_sock = init->ctl_sock;
+	dpri->fd = -1;
+	dpri->control = -1;
+	dpri->dev = dev;
+	/* We will free this pointer. If it contains crap we're burned. */
+	dpri->ctl_addr = NULL;
+	dpri->data_addr = NULL;
+	dpri->local_addr = NULL;
+
+	printk("daemon backend (uml_switch version %d) - %s:%s",
+	       SWITCH_VERSION, dpri->sock_type, dpri->ctl_sock);
+	printk("\n");
+}
+
+static int daemon_read(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	return net_recvfrom(fd, skb_mac_header(skb),
+			    skb->dev->mtu + ETH_HEADER_OTHER);
+}
+
+static int daemon_write(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	return daemon_user_write(fd, skb->data, skb->len,
+				 (struct daemon_data *) &lp->user);
+}
+
+static const struct net_kern_info daemon_kern_info = {
+	.init			= daemon_init,
+	.protocol		= eth_protocol,
+	.read			= daemon_read,
+	.write			= daemon_write,
+};
+
+static int daemon_setup(char *str, char **mac_out, void *data)
+{
+	struct daemon_init *init = data;
+	char *remain;
+
+	*init = ((struct daemon_init)
+		{ .sock_type 		= "unix",
+		  .ctl_sock 		= CONFIG_UML_NET_DAEMON_DEFAULT_SOCK });
+
+	remain = split_if_spec(str, mac_out, &init->sock_type, &init->ctl_sock,
+			       NULL);
+	if (remain != NULL)
+		printk(KERN_WARNING "daemon_setup : Ignoring data socket "
+		       "specification\n");
+
+	return 1;
+}
+
+static struct transport daemon_transport = {
+	.list 		= LIST_HEAD_INIT(daemon_transport.list),
+	.name 		= "daemon",
+	.setup  	= daemon_setup,
+	.user 		= &daemon_user_info,
+	.kern 		= &daemon_kern_info,
+	.private_size 	= sizeof(struct daemon_data),
+	.setup_size 	= sizeof(struct daemon_init),
+};
+
+static int register_daemon(void)
+{
+	register_transport(&daemon_transport);
+	return 0;
+}
+
+late_initcall(register_daemon);
diff --git a/arch/um/drivers/daemon_user.c b/arch/um/drivers/daemon_user.c
new file mode 100644
index 000000000..785baedc3
--- /dev/null
+++ b/arch/um/drivers/daemon_user.c
@@ -0,0 +1,194 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org) and
+ * James Leu (jleu@mindspring.net).
+ * Copyright (C) 2001 by various other people who didn't put their name here.
+ */
+
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/time.h>
+#include <sys/un.h>
+#include "daemon.h"
+#include <net_user.h>
+#include <os.h>
+#include <um_malloc.h>
+
+enum request_type { REQ_NEW_CONTROL };
+
+#define SWITCH_MAGIC 0xfeedface
+
+struct request_v3 {
+	uint32_t magic;
+	uint32_t version;
+	enum request_type type;
+	struct sockaddr_un sock;
+};
+
+static struct sockaddr_un *new_addr(void *name, int len)
+{
+	struct sockaddr_un *sun;
+
+	sun = uml_kmalloc(sizeof(struct sockaddr_un), UM_GFP_KERNEL);
+	if (sun == NULL) {
+		printk(UM_KERN_ERR "new_addr: allocation of sockaddr_un "
+		       "failed\n");
+		return NULL;
+	}
+	sun->sun_family = AF_UNIX;
+	memcpy(sun->sun_path, name, len);
+	return sun;
+}
+
+static int connect_to_switch(struct daemon_data *pri)
+{
+	struct sockaddr_un *ctl_addr = pri->ctl_addr;
+	struct sockaddr_un *local_addr = pri->local_addr;
+	struct sockaddr_un *sun;
+	struct request_v3 req;
+	int fd, n, err;
+
+	pri->control = socket(AF_UNIX, SOCK_STREAM, 0);
+	if (pri->control < 0) {
+		err = -errno;
+		printk(UM_KERN_ERR "daemon_open : control socket failed, "
+		       "errno = %d\n", -err);
+		return err;
+	}
+
+	if (connect(pri->control, (struct sockaddr *) ctl_addr,
+		   sizeof(*ctl_addr)) < 0) {
+		err = -errno;
+		printk(UM_KERN_ERR "daemon_open : control connect failed, "
+		       "errno = %d\n", -err);
+		goto out;
+	}
+
+	fd = socket(AF_UNIX, SOCK_DGRAM, 0);
+	if (fd < 0) {
+		err = -errno;
+		printk(UM_KERN_ERR "daemon_open : data socket failed, "
+		       "errno = %d\n", -err);
+		goto out;
+	}
+	if (bind(fd, (struct sockaddr *) local_addr, sizeof(*local_addr)) < 0) {
+		err = -errno;
+		printk(UM_KERN_ERR "daemon_open : data bind failed, "
+		       "errno = %d\n", -err);
+		goto out_close;
+	}
+
+	sun = uml_kmalloc(sizeof(struct sockaddr_un), UM_GFP_KERNEL);
+	if (sun == NULL) {
+		printk(UM_KERN_ERR "new_addr: allocation of sockaddr_un "
+		       "failed\n");
+		err = -ENOMEM;
+		goto out_close;
+	}
+
+	req.magic = SWITCH_MAGIC;
+	req.version = SWITCH_VERSION;
+	req.type = REQ_NEW_CONTROL;
+	req.sock = *local_addr;
+	n = write(pri->control, &req, sizeof(req));
+	if (n != sizeof(req)) {
+		printk(UM_KERN_ERR "daemon_open : control setup request "
+		       "failed, err = %d\n", -errno);
+		err = -ENOTCONN;
+		goto out_free;
+	}
+
+	n = read(pri->control, sun, sizeof(*sun));
+	if (n != sizeof(*sun)) {
+		printk(UM_KERN_ERR "daemon_open : read of data socket failed, "
+		       "err = %d\n", -errno);
+		err = -ENOTCONN;
+		goto out_free;
+	}
+
+	pri->data_addr = sun;
+	return fd;
+
+ out_free:
+	kfree(sun);
+ out_close:
+	close(fd);
+ out:
+	close(pri->control);
+	return err;
+}
+
+static int daemon_user_init(void *data, void *dev)
+{
+	struct daemon_data *pri = data;
+	struct timeval tv;
+	struct {
+		char zero;
+		int pid;
+		int usecs;
+	} name;
+
+	if (!strcmp(pri->sock_type, "unix"))
+		pri->ctl_addr = new_addr(pri->ctl_sock,
+					 strlen(pri->ctl_sock) + 1);
+	name.zero = 0;
+	name.pid = os_getpid();
+	gettimeofday(&tv, NULL);
+	name.usecs = tv.tv_usec;
+	pri->local_addr = new_addr(&name, sizeof(name));
+	pri->dev = dev;
+	pri->fd = connect_to_switch(pri);
+	if (pri->fd < 0) {
+		kfree(pri->local_addr);
+		pri->local_addr = NULL;
+		return pri->fd;
+	}
+
+	return 0;
+}
+
+static int daemon_open(void *data)
+{
+	struct daemon_data *pri = data;
+	return pri->fd;
+}
+
+static void daemon_remove(void *data)
+{
+	struct daemon_data *pri = data;
+
+	close(pri->fd);
+	pri->fd = -1;
+	close(pri->control);
+	pri->control = -1;
+
+	kfree(pri->data_addr);
+	pri->data_addr = NULL;
+	kfree(pri->ctl_addr);
+	pri->ctl_addr = NULL;
+	kfree(pri->local_addr);
+	pri->local_addr = NULL;
+}
+
+int daemon_user_write(int fd, void *buf, int len, struct daemon_data *pri)
+{
+	struct sockaddr_un *data_addr = pri->data_addr;
+
+	return net_sendto(fd, buf, len, data_addr, sizeof(*data_addr));
+}
+
+const struct net_user_info daemon_user_info = {
+	.init		= daemon_user_init,
+	.open		= daemon_open,
+	.close	 	= NULL,
+	.remove	 	= daemon_remove,
+	.add_address	= NULL,
+	.delete_address = NULL,
+	.mtu		= ETH_MAX_PACKET,
+	.max_packet	= ETH_MAX_PACKET + ETH_HEADER_OTHER,
+};
diff --git a/arch/um/drivers/fd.c b/arch/um/drivers/fd.c
new file mode 100644
index 000000000..082d739dc
--- /dev/null
+++ b/arch/um/drivers/fd.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <termios.h>
+#include "chan_user.h"
+#include <os.h>
+#include <um_malloc.h>
+
+struct fd_chan {
+	int fd;
+	int raw;
+	struct termios tt;
+	char str[sizeof("1234567890\0")];
+};
+
+static void *fd_init(char *str, int device, const struct chan_opts *opts)
+{
+	struct fd_chan *data;
+	char *end;
+	int n;
+
+	if (*str != ':') {
+		printk(UM_KERN_ERR "fd_init : channel type 'fd' must specify a "
+		       "file descriptor\n");
+		return NULL;
+	}
+	str++;
+	n = strtoul(str, &end, 0);
+	if ((*end != '\0') || (end == str)) {
+		printk(UM_KERN_ERR "fd_init : couldn't parse file descriptor "
+		       "'%s'\n", str);
+		return NULL;
+	}
+
+	data = uml_kmalloc(sizeof(*data), UM_GFP_KERNEL);
+	if (data == NULL)
+		return NULL;
+
+	*data = ((struct fd_chan) { .fd  	= n,
+				    .raw  	= opts->raw });
+	return data;
+}
+
+static int fd_open(int input, int output, int primary, void *d, char **dev_out)
+{
+	struct fd_chan *data = d;
+	int err;
+
+	if (data->raw && isatty(data->fd)) {
+		CATCH_EINTR(err = tcgetattr(data->fd, &data->tt));
+		if (err)
+			return err;
+
+		err = raw(data->fd);
+		if (err)
+			return err;
+	}
+	sprintf(data->str, "%d", data->fd);
+	*dev_out = data->str;
+	return data->fd;
+}
+
+static void fd_close(int fd, void *d)
+{
+	struct fd_chan *data = d;
+	int err;
+
+	if (!data->raw || !isatty(fd))
+		return;
+
+	CATCH_EINTR(err = tcsetattr(fd, TCSAFLUSH, &data->tt));
+	if (err)
+		printk(UM_KERN_ERR "Failed to restore terminal state - "
+		       "errno = %d\n", -err);
+	data->raw = 0;
+}
+
+const struct chan_ops fd_ops = {
+	.type		= "fd",
+	.init		= fd_init,
+	.open		= fd_open,
+	.close		= fd_close,
+	.read		= generic_read,
+	.write		= generic_write,
+	.console_write	= generic_console_write,
+	.window_size	= generic_window_size,
+	.free		= generic_free,
+	.winch		= 1,
+};
diff --git a/arch/um/drivers/harddog.h b/arch/um/drivers/harddog.h
new file mode 100644
index 000000000..6d9ea60e7
--- /dev/null
+++ b/arch/um/drivers/harddog.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef UM_WATCHDOG_H
+#define UM_WATCHDOG_H
+
+int start_watchdog(int *in_fd_ret, int *out_fd_ret, char *sock);
+void stop_watchdog(int in_fd, int out_fd);
+int ping_watchdog(int fd);
+
+#endif /* UM_WATCHDOG_H */
diff --git a/arch/um/drivers/harddog_kern.c b/arch/um/drivers/harddog_kern.c
new file mode 100644
index 000000000..60d1c6cab
--- /dev/null
+++ b/arch/um/drivers/harddog_kern.c
@@ -0,0 +1,174 @@
+/* UML hardware watchdog, shamelessly stolen from:
+ *
+ *	SoftDog	0.05:	A Software Watchdog Device
+ *
+ *	(c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
+ *				http://www.redhat.com
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ *
+ *	Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
+ *	warranty for any of this software. This material is provided
+ *	"AS-IS" and at no charge.
+ *
+ *	(c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
+ *
+ *	Software only watchdog driver. Unlike its big brother the WDT501P
+ *	driver this won't always recover a failed machine.
+ *
+ *  03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
+ *	Modularised.
+ *	Added soft_margin; use upon insmod to change the timer delay.
+ *	NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
+ *	    minors.
+ *
+ *  19980911 Alan Cox
+ *	Made SMP safe for 2.3.x
+ *
+ *  20011127 Joel Becker (jlbec@evilplan.org>
+ *	Added soft_noboot; Allows testing the softdog trigger without
+ *	requiring a recompile.
+ *	Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/miscdevice.h>
+#include <linux/watchdog.h>
+#include <linux/reboot.h>
+#include <linux/mutex.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include "mconsole.h"
+#include "harddog.h"
+
+MODULE_LICENSE("GPL");
+
+static DEFINE_MUTEX(harddog_mutex);
+static DEFINE_SPINLOCK(lock);
+static int timer_alive;
+static int harddog_in_fd = -1;
+static int harddog_out_fd = -1;
+
+/*
+ *	Allow only one person to hold it open
+ */
+
+static int harddog_open(struct inode *inode, struct file *file)
+{
+	int err = -EBUSY;
+	char *sock = NULL;
+
+	mutex_lock(&harddog_mutex);
+	spin_lock(&lock);
+	if(timer_alive)
+		goto err;
+#ifdef CONFIG_WATCHDOG_NOWAYOUT
+	__module_get(THIS_MODULE);
+#endif
+
+#ifdef CONFIG_MCONSOLE
+	sock = mconsole_notify_socket();
+#endif
+	err = start_watchdog(&harddog_in_fd, &harddog_out_fd, sock);
+	if(err)
+		goto err;
+
+	timer_alive = 1;
+	spin_unlock(&lock);
+	mutex_unlock(&harddog_mutex);
+	return stream_open(inode, file);
+err:
+	spin_unlock(&lock);
+	mutex_unlock(&harddog_mutex);
+	return err;
+}
+
+static int harddog_release(struct inode *inode, struct file *file)
+{
+	/*
+	 *	Shut off the timer.
+	 */
+
+	spin_lock(&lock);
+
+	stop_watchdog(harddog_in_fd, harddog_out_fd);
+	harddog_in_fd = -1;
+	harddog_out_fd = -1;
+
+	timer_alive=0;
+	spin_unlock(&lock);
+
+	return 0;
+}
+
+static ssize_t harddog_write(struct file *file, const char __user *data, size_t len,
+			     loff_t *ppos)
+{
+	/*
+	 *	Refresh the timer.
+	 */
+	if(len)
+		return ping_watchdog(harddog_out_fd);
+	return 0;
+}
+
+static int harddog_ioctl_unlocked(struct file *file,
+				  unsigned int cmd, unsigned long arg)
+{
+	void __user *argp= (void __user *)arg;
+	static struct watchdog_info ident = {
+		WDIOC_SETTIMEOUT,
+		0,
+		"UML Hardware Watchdog"
+	};
+	switch (cmd) {
+		default:
+			return -ENOTTY;
+		case WDIOC_GETSUPPORT:
+			if(copy_to_user(argp, &ident, sizeof(ident)))
+				return -EFAULT;
+			return 0;
+		case WDIOC_GETSTATUS:
+		case WDIOC_GETBOOTSTATUS:
+			return put_user(0,(int __user *)argp);
+		case WDIOC_KEEPALIVE:
+			return ping_watchdog(harddog_out_fd);
+	}
+}
+
+static long harddog_ioctl(struct file *file,
+			  unsigned int cmd, unsigned long arg)
+{
+	long ret;
+
+	mutex_lock(&harddog_mutex);
+	ret = harddog_ioctl_unlocked(file, cmd, arg);
+	mutex_unlock(&harddog_mutex);
+
+	return ret;
+}
+
+static const struct file_operations harddog_fops = {
+	.owner		= THIS_MODULE,
+	.write		= harddog_write,
+	.unlocked_ioctl	= harddog_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+	.open		= harddog_open,
+	.release	= harddog_release,
+	.llseek		= no_llseek,
+};
+
+static struct miscdevice harddog_miscdev = {
+	.minor		= WATCHDOG_MINOR,
+	.name		= "watchdog",
+	.fops		= &harddog_fops,
+};
+module_misc_device(harddog_miscdev);
diff --git a/arch/um/drivers/harddog_user.c b/arch/um/drivers/harddog_user.c
new file mode 100644
index 000000000..9ed893049
--- /dev/null
+++ b/arch/um/drivers/harddog_user.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <os.h>
+#include "harddog.h"
+
+struct dog_data {
+	int stdin_fd;
+	int stdout_fd;
+	int close_me[2];
+};
+
+static void pre_exec(void *d)
+{
+	struct dog_data *data = d;
+
+	dup2(data->stdin_fd, 0);
+	dup2(data->stdout_fd, 1);
+	dup2(data->stdout_fd, 2);
+	close(data->stdin_fd);
+	close(data->stdout_fd);
+	close(data->close_me[0]);
+	close(data->close_me[1]);
+}
+
+int start_watchdog(int *in_fd_ret, int *out_fd_ret, char *sock)
+{
+	struct dog_data data;
+	int in_fds[2], out_fds[2], pid, n, err;
+	char pid_buf[sizeof("nnnnnnn\0")], c;
+	char *pid_args[] = { "/usr/bin/uml_watchdog", "-pid", pid_buf, NULL };
+	char *mconsole_args[] = { "/usr/bin/uml_watchdog", "-mconsole", NULL,
+				  NULL };
+	char **args = NULL;
+
+	err = os_pipe(in_fds, 1, 0);
+	if (err < 0) {
+		printk("harddog_open - os_pipe failed, err = %d\n", -err);
+		goto out;
+	}
+
+	err = os_pipe(out_fds, 1, 0);
+	if (err < 0) {
+		printk("harddog_open - os_pipe failed, err = %d\n", -err);
+		goto out_close_in;
+	}
+
+	data.stdin_fd = out_fds[0];
+	data.stdout_fd = in_fds[1];
+	data.close_me[0] = out_fds[1];
+	data.close_me[1] = in_fds[0];
+
+	if (sock != NULL) {
+		mconsole_args[2] = sock;
+		args = mconsole_args;
+	}
+	else {
+		/* XXX The os_getpid() is not SMP correct */
+		sprintf(pid_buf, "%d", os_getpid());
+		args = pid_args;
+	}
+
+	pid = run_helper(pre_exec, &data, args);
+
+	close(out_fds[0]);
+	close(in_fds[1]);
+
+	if (pid < 0) {
+		err = -pid;
+		printk("harddog_open - run_helper failed, errno = %d\n", -err);
+		goto out_close_out;
+	}
+
+	n = read(in_fds[0], &c, sizeof(c));
+	if (n == 0) {
+		printk("harddog_open - EOF on watchdog pipe\n");
+		helper_wait(pid);
+		err = -EIO;
+		goto out_close_out;
+	}
+	else if (n < 0) {
+		printk("harddog_open - read of watchdog pipe failed, "
+		       "err = %d\n", errno);
+		helper_wait(pid);
+		err = n;
+		goto out_close_out;
+	}
+	*in_fd_ret = in_fds[0];
+	*out_fd_ret = out_fds[1];
+	return 0;
+
+ out_close_in:
+	close(in_fds[0]);
+	close(in_fds[1]);
+ out_close_out:
+	close(out_fds[0]);
+	close(out_fds[1]);
+ out:
+	return err;
+}
+
+void stop_watchdog(int in_fd, int out_fd)
+{
+	close(in_fd);
+	close(out_fd);
+}
+
+int ping_watchdog(int fd)
+{
+	int n;
+	char c = '\n';
+
+	n = write(fd, &c, sizeof(c));
+	if (n != sizeof(c)) {
+		printk("ping_watchdog - write failed, ret = %d, err = %d\n",
+		       n, errno);
+		if (n < 0)
+			return n;
+		return -EIO;
+	}
+	return 1;
+
+}
diff --git a/arch/um/drivers/harddog_user_exp.c b/arch/um/drivers/harddog_user_exp.c
new file mode 100644
index 000000000..c74d4b815
--- /dev/null
+++ b/arch/um/drivers/harddog_user_exp.c
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/export.h>
+#include "harddog.h"
+
+#if IS_MODULE(CONFIG_UML_WATCHDOG)
+EXPORT_SYMBOL(start_watchdog);
+EXPORT_SYMBOL(stop_watchdog);
+EXPORT_SYMBOL(ping_watchdog);
+#endif
diff --git a/arch/um/drivers/hostaudio_kern.c b/arch/um/drivers/hostaudio_kern.c
new file mode 100644
index 000000000..5b064d360
--- /dev/null
+++ b/arch/um/drivers/hostaudio_kern.c
@@ -0,0 +1,353 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2002 Steve Schmidtke
+ */
+
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sound.h>
+#include <linux/soundcard.h>
+#include <linux/mutex.h>
+#include <linux/uaccess.h>
+#include <init.h>
+#include <os.h>
+
+struct hostaudio_state {
+	int fd;
+};
+
+struct hostmixer_state {
+	int fd;
+};
+
+#define HOSTAUDIO_DEV_DSP "/dev/sound/dsp"
+#define HOSTAUDIO_DEV_MIXER "/dev/sound/mixer"
+
+/*
+ * Changed either at boot time or module load time.  At boot, this is
+ * single-threaded; at module load, multiple modules would each have
+ * their own copy of these variables.
+ */
+static char *dsp = HOSTAUDIO_DEV_DSP;
+static char *mixer = HOSTAUDIO_DEV_MIXER;
+
+#define DSP_HELP \
+"    This is used to specify the host dsp device to the hostaudio driver.\n" \
+"    The default is \"" HOSTAUDIO_DEV_DSP "\".\n\n"
+
+#define MIXER_HELP \
+"    This is used to specify the host mixer device to the hostaudio driver.\n"\
+"    The default is \"" HOSTAUDIO_DEV_MIXER "\".\n\n"
+
+module_param(dsp, charp, 0644);
+MODULE_PARM_DESC(dsp, DSP_HELP);
+module_param(mixer, charp, 0644);
+MODULE_PARM_DESC(mixer, MIXER_HELP);
+
+#ifndef MODULE
+static int set_dsp(char *name, int *add)
+{
+	dsp = name;
+	return 0;
+}
+
+__uml_setup("dsp=", set_dsp, "dsp=<dsp device>\n" DSP_HELP);
+
+static int set_mixer(char *name, int *add)
+{
+	mixer = name;
+	return 0;
+}
+
+__uml_setup("mixer=", set_mixer, "mixer=<mixer device>\n" MIXER_HELP);
+#endif
+
+static DEFINE_MUTEX(hostaudio_mutex);
+
+/* /dev/dsp file operations */
+
+static ssize_t hostaudio_read(struct file *file, char __user *buffer,
+			      size_t count, loff_t *ppos)
+{
+	struct hostaudio_state *state = file->private_data;
+	void *kbuf;
+	int err;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "hostaudio: read called, count = %d\n", count);
+#endif
+
+	kbuf = kmalloc(count, GFP_KERNEL);
+	if (kbuf == NULL)
+		return -ENOMEM;
+
+	err = os_read_file(state->fd, kbuf, count);
+	if (err < 0)
+		goto out;
+
+	if (copy_to_user(buffer, kbuf, err))
+		err = -EFAULT;
+
+out:
+	kfree(kbuf);
+	return err;
+}
+
+static ssize_t hostaudio_write(struct file *file, const char __user *buffer,
+			       size_t count, loff_t *ppos)
+{
+	struct hostaudio_state *state = file->private_data;
+	void *kbuf;
+	int err;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "hostaudio: write called, count = %d\n", count);
+#endif
+
+	kbuf = memdup_user(buffer, count);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
+
+	err = os_write_file(state->fd, kbuf, count);
+	if (err < 0)
+		goto out;
+	*ppos += err;
+
+ out:
+	kfree(kbuf);
+	return err;
+}
+
+static __poll_t hostaudio_poll(struct file *file,
+				struct poll_table_struct *wait)
+{
+#ifdef DEBUG
+	printk(KERN_DEBUG "hostaudio: poll called (unimplemented)\n");
+#endif
+
+	return 0;
+}
+
+static long hostaudio_ioctl(struct file *file,
+			   unsigned int cmd, unsigned long arg)
+{
+	struct hostaudio_state *state = file->private_data;
+	unsigned long data = 0;
+	int err;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "hostaudio: ioctl called, cmd = %u\n", cmd);
+#endif
+	switch(cmd){
+	case SNDCTL_DSP_SPEED:
+	case SNDCTL_DSP_STEREO:
+	case SNDCTL_DSP_GETBLKSIZE:
+	case SNDCTL_DSP_CHANNELS:
+	case SNDCTL_DSP_SUBDIVIDE:
+	case SNDCTL_DSP_SETFRAGMENT:
+		if (get_user(data, (int __user *) arg))
+			return -EFAULT;
+		break;
+	default:
+		break;
+	}
+
+	err = os_ioctl_generic(state->fd, cmd, (unsigned long) &data);
+
+	switch(cmd){
+	case SNDCTL_DSP_SPEED:
+	case SNDCTL_DSP_STEREO:
+	case SNDCTL_DSP_GETBLKSIZE:
+	case SNDCTL_DSP_CHANNELS:
+	case SNDCTL_DSP_SUBDIVIDE:
+	case SNDCTL_DSP_SETFRAGMENT:
+		if (put_user(data, (int __user *) arg))
+			return -EFAULT;
+		break;
+	default:
+		break;
+	}
+
+	return err;
+}
+
+static int hostaudio_open(struct inode *inode, struct file *file)
+{
+	struct hostaudio_state *state;
+	int r = 0, w = 0;
+	int ret;
+
+#ifdef DEBUG
+	kernel_param_lock(THIS_MODULE);
+	printk(KERN_DEBUG "hostaudio: open called (host: %s)\n", dsp);
+	kernel_param_unlock(THIS_MODULE);
+#endif
+
+	state = kmalloc(sizeof(struct hostaudio_state), GFP_KERNEL);
+	if (state == NULL)
+		return -ENOMEM;
+
+	if (file->f_mode & FMODE_READ)
+		r = 1;
+	if (file->f_mode & FMODE_WRITE)
+		w = 1;
+
+	kernel_param_lock(THIS_MODULE);
+	mutex_lock(&hostaudio_mutex);
+	ret = os_open_file(dsp, of_set_rw(OPENFLAGS(), r, w), 0);
+	mutex_unlock(&hostaudio_mutex);
+	kernel_param_unlock(THIS_MODULE);
+
+	if (ret < 0) {
+		kfree(state);
+		return ret;
+	}
+	state->fd = ret;
+	file->private_data = state;
+	return 0;
+}
+
+static int hostaudio_release(struct inode *inode, struct file *file)
+{
+	struct hostaudio_state *state = file->private_data;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "hostaudio: release called\n");
+#endif
+	os_close_file(state->fd);
+	kfree(state);
+
+	return 0;
+}
+
+/* /dev/mixer file operations */
+
+static long hostmixer_ioctl_mixdev(struct file *file,
+				  unsigned int cmd, unsigned long arg)
+{
+	struct hostmixer_state *state = file->private_data;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "hostmixer: ioctl called\n");
+#endif
+
+	return os_ioctl_generic(state->fd, cmd, arg);
+}
+
+static int hostmixer_open_mixdev(struct inode *inode, struct file *file)
+{
+	struct hostmixer_state *state;
+	int r = 0, w = 0;
+	int ret;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "hostmixer: open called (host: %s)\n", mixer);
+#endif
+
+	state = kmalloc(sizeof(struct hostmixer_state), GFP_KERNEL);
+	if (state == NULL)
+		return -ENOMEM;
+
+	if (file->f_mode & FMODE_READ)
+		r = 1;
+	if (file->f_mode & FMODE_WRITE)
+		w = 1;
+
+	kernel_param_lock(THIS_MODULE);
+	mutex_lock(&hostaudio_mutex);
+	ret = os_open_file(mixer, of_set_rw(OPENFLAGS(), r, w), 0);
+	mutex_unlock(&hostaudio_mutex);
+	kernel_param_unlock(THIS_MODULE);
+
+	if (ret < 0) {
+		kernel_param_lock(THIS_MODULE);
+		printk(KERN_ERR "hostaudio_open_mixdev failed to open '%s', "
+		       "err = %d\n", dsp, -ret);
+		kernel_param_unlock(THIS_MODULE);
+		kfree(state);
+		return ret;
+	}
+
+	file->private_data = state;
+	return 0;
+}
+
+static int hostmixer_release(struct inode *inode, struct file *file)
+{
+	struct hostmixer_state *state = file->private_data;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "hostmixer: release called\n");
+#endif
+
+	os_close_file(state->fd);
+	kfree(state);
+
+	return 0;
+}
+
+/* kernel module operations */
+
+static const struct file_operations hostaudio_fops = {
+	.owner          = THIS_MODULE,
+	.llseek         = no_llseek,
+	.read           = hostaudio_read,
+	.write          = hostaudio_write,
+	.poll           = hostaudio_poll,
+	.unlocked_ioctl	= hostaudio_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+	.mmap           = NULL,
+	.open           = hostaudio_open,
+	.release        = hostaudio_release,
+};
+
+static const struct file_operations hostmixer_fops = {
+	.owner          = THIS_MODULE,
+	.llseek         = no_llseek,
+	.unlocked_ioctl	= hostmixer_ioctl_mixdev,
+	.open           = hostmixer_open_mixdev,
+	.release        = hostmixer_release,
+};
+
+struct {
+	int dev_audio;
+	int dev_mixer;
+} module_data;
+
+MODULE_AUTHOR("Steve Schmidtke");
+MODULE_DESCRIPTION("UML Audio Relay");
+MODULE_LICENSE("GPL");
+
+static int __init hostaudio_init_module(void)
+{
+	kernel_param_lock(THIS_MODULE);
+	printk(KERN_INFO "UML Audio Relay (host dsp = %s, host mixer = %s)\n",
+	       dsp, mixer);
+	kernel_param_unlock(THIS_MODULE);
+
+	module_data.dev_audio = register_sound_dsp(&hostaudio_fops, -1);
+	if (module_data.dev_audio < 0) {
+		printk(KERN_ERR "hostaudio: couldn't register DSP device!\n");
+		return -ENODEV;
+	}
+
+	module_data.dev_mixer = register_sound_mixer(&hostmixer_fops, -1);
+	if (module_data.dev_mixer < 0) {
+		printk(KERN_ERR "hostmixer: couldn't register mixer "
+		       "device!\n");
+		unregister_sound_dsp(module_data.dev_audio);
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static void __exit hostaudio_cleanup_module (void)
+{
+	unregister_sound_mixer(module_data.dev_mixer);
+	unregister_sound_dsp(module_data.dev_audio);
+}
+
+module_init(hostaudio_init_module);
+module_exit(hostaudio_cleanup_module);
diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
new file mode 100644
index 000000000..02b0befd6
--- /dev/null
+++ b/arch/um/drivers/line.c
@@ -0,0 +1,764 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <linux/irqreturn.h>
+#include <linux/kd.h>
+#include <linux/sched/signal.h>
+#include <linux/slab.h>
+
+#include "chan.h"
+#include <irq_kern.h>
+#include <irq_user.h>
+#include <kern_util.h>
+#include <os.h>
+
+#define LINE_BUFSIZE 4096
+
+static irqreturn_t line_interrupt(int irq, void *data)
+{
+	struct chan *chan = data;
+	struct line *line = chan->line;
+
+	if (line)
+		chan_interrupt(line, irq);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * Returns the free space inside the ring buffer of this line.
+ *
+ * Should be called while holding line->lock (this does not modify data).
+ */
+static unsigned int write_room(struct line *line)
+{
+	int n;
+
+	if (line->buffer == NULL)
+		return LINE_BUFSIZE - 1;
+
+	/* This is for the case where the buffer is wrapped! */
+	n = line->head - line->tail;
+
+	if (n <= 0)
+		n += LINE_BUFSIZE; /* The other case */
+	return n - 1;
+}
+
+unsigned int line_write_room(struct tty_struct *tty)
+{
+	struct line *line = tty->driver_data;
+	unsigned long flags;
+	unsigned int room;
+
+	spin_lock_irqsave(&line->lock, flags);
+	room = write_room(line);
+	spin_unlock_irqrestore(&line->lock, flags);
+
+	return room;
+}
+
+unsigned int line_chars_in_buffer(struct tty_struct *tty)
+{
+	struct line *line = tty->driver_data;
+	unsigned long flags;
+	unsigned int ret;
+
+	spin_lock_irqsave(&line->lock, flags);
+	/* write_room subtracts 1 for the needed NULL, so we readd it.*/
+	ret = LINE_BUFSIZE - (write_room(line) + 1);
+	spin_unlock_irqrestore(&line->lock, flags);
+
+	return ret;
+}
+
+/*
+ * This copies the content of buf into the circular buffer associated with
+ * this line.
+ * The return value is the number of characters actually copied, i.e. the ones
+ * for which there was space: this function is not supposed to ever flush out
+ * the circular buffer.
+ *
+ * Must be called while holding line->lock!
+ */
+static int buffer_data(struct line *line, const char *buf, int len)
+{
+	int end, room;
+
+	if (line->buffer == NULL) {
+		line->buffer = kmalloc(LINE_BUFSIZE, GFP_ATOMIC);
+		if (line->buffer == NULL) {
+			printk(KERN_ERR "buffer_data - atomic allocation "
+			       "failed\n");
+			return 0;
+		}
+		line->head = line->buffer;
+		line->tail = line->buffer;
+	}
+
+	room = write_room(line);
+	len = (len > room) ? room : len;
+
+	end = line->buffer + LINE_BUFSIZE - line->tail;
+
+	if (len < end) {
+		memcpy(line->tail, buf, len);
+		line->tail += len;
+	}
+	else {
+		/* The circular buffer is wrapping */
+		memcpy(line->tail, buf, end);
+		buf += end;
+		memcpy(line->buffer, buf, len - end);
+		line->tail = line->buffer + len - end;
+	}
+
+	return len;
+}
+
+/*
+ * Flushes the ring buffer to the output channels. That is, write_chan is
+ * called, passing it line->head as buffer, and an appropriate count.
+ *
+ * On exit, returns 1 when the buffer is empty,
+ * 0 when the buffer is not empty on exit,
+ * and -errno when an error occurred.
+ *
+ * Must be called while holding line->lock!*/
+static int flush_buffer(struct line *line)
+{
+	int n, count;
+
+	if ((line->buffer == NULL) || (line->head == line->tail))
+		return 1;
+
+	if (line->tail < line->head) {
+		/* line->buffer + LINE_BUFSIZE is the end of the buffer! */
+		count = line->buffer + LINE_BUFSIZE - line->head;
+
+		n = write_chan(line->chan_out, line->head, count,
+			       line->write_irq);
+		if (n < 0)
+			return n;
+		if (n == count) {
+			/*
+			 * We have flushed from ->head to buffer end, now we
+			 * must flush only from the beginning to ->tail.
+			 */
+			line->head = line->buffer;
+		} else {
+			line->head += n;
+			return 0;
+		}
+	}
+
+	count = line->tail - line->head;
+	n = write_chan(line->chan_out, line->head, count,
+		       line->write_irq);
+
+	if (n < 0)
+		return n;
+
+	line->head += n;
+	return line->head == line->tail;
+}
+
+void line_flush_buffer(struct tty_struct *tty)
+{
+	struct line *line = tty->driver_data;
+	unsigned long flags;
+
+	spin_lock_irqsave(&line->lock, flags);
+	flush_buffer(line);
+	spin_unlock_irqrestore(&line->lock, flags);
+}
+
+/*
+ * We map both ->flush_chars and ->put_char (which go in pair) onto
+ * ->flush_buffer and ->write. Hope it's not that bad.
+ */
+void line_flush_chars(struct tty_struct *tty)
+{
+	line_flush_buffer(tty);
+}
+
+int line_write(struct tty_struct *tty, const unsigned char *buf, int len)
+{
+	struct line *line = tty->driver_data;
+	unsigned long flags;
+	int n, ret = 0;
+
+	spin_lock_irqsave(&line->lock, flags);
+	if (line->head != line->tail)
+		ret = buffer_data(line, buf, len);
+	else {
+		n = write_chan(line->chan_out, buf, len,
+			       line->write_irq);
+		if (n < 0) {
+			ret = n;
+			goto out_up;
+		}
+
+		len -= n;
+		ret += n;
+		if (len > 0)
+			ret += buffer_data(line, buf + n, len);
+	}
+out_up:
+	spin_unlock_irqrestore(&line->lock, flags);
+	return ret;
+}
+
+void line_throttle(struct tty_struct *tty)
+{
+	struct line *line = tty->driver_data;
+
+	deactivate_chan(line->chan_in, line->read_irq);
+	line->throttled = 1;
+}
+
+void line_unthrottle(struct tty_struct *tty)
+{
+	struct line *line = tty->driver_data;
+
+	line->throttled = 0;
+	chan_interrupt(line, line->read_irq);
+}
+
+static irqreturn_t line_write_interrupt(int irq, void *data)
+{
+	struct chan *chan = data;
+	struct line *line = chan->line;
+	int err;
+
+	/*
+	 * Interrupts are disabled here because genirq keep irqs disabled when
+	 * calling the action handler.
+	 */
+
+	spin_lock(&line->lock);
+	err = flush_buffer(line);
+	if (err == 0) {
+		spin_unlock(&line->lock);
+		return IRQ_NONE;
+	} else if ((err < 0) && (err != -EAGAIN)) {
+		line->head = line->buffer;
+		line->tail = line->buffer;
+	}
+	spin_unlock(&line->lock);
+
+	tty_port_tty_wakeup(&line->port);
+
+	return IRQ_HANDLED;
+}
+
+int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
+{
+	const struct line_driver *driver = line->driver;
+	int err;
+
+	if (input) {
+		err = um_request_irq(UM_IRQ_ALLOC, fd, IRQ_READ,
+				     line_interrupt, 0,
+				     driver->read_irq_name, data);
+		if (err < 0)
+			return err;
+
+		line->read_irq = err;
+	}
+
+	if (output) {
+		err = um_request_irq(UM_IRQ_ALLOC, fd, IRQ_WRITE,
+				     line_write_interrupt, 0,
+				     driver->write_irq_name, data);
+		if (err < 0)
+			return err;
+
+		line->write_irq = err;
+	}
+
+	return 0;
+}
+
+static int line_activate(struct tty_port *port, struct tty_struct *tty)
+{
+	int ret;
+	struct line *line = tty->driver_data;
+
+	ret = enable_chan(line);
+	if (ret)
+		return ret;
+
+	if (!line->sigio) {
+		chan_enable_winch(line->chan_out, port);
+		line->sigio = 1;
+	}
+
+	chan_window_size(line, &tty->winsize.ws_row,
+		&tty->winsize.ws_col);
+
+	return 0;
+}
+
+static void unregister_winch(struct tty_struct *tty);
+
+static void line_destruct(struct tty_port *port)
+{
+	struct tty_struct *tty = tty_port_tty_get(port);
+	struct line *line = tty->driver_data;
+
+	if (line->sigio) {
+		unregister_winch(tty);
+		line->sigio = 0;
+	}
+}
+
+static const struct tty_port_operations line_port_ops = {
+	.activate = line_activate,
+	.destruct = line_destruct,
+};
+
+int line_open(struct tty_struct *tty, struct file *filp)
+{
+	struct line *line = tty->driver_data;
+
+	return tty_port_open(&line->port, tty, filp);
+}
+
+int line_install(struct tty_driver *driver, struct tty_struct *tty,
+		 struct line *line)
+{
+	int ret;
+
+	ret = tty_standard_install(driver, tty);
+	if (ret)
+		return ret;
+
+	tty->driver_data = line;
+
+	return 0;
+}
+
+void line_close(struct tty_struct *tty, struct file * filp)
+{
+	struct line *line = tty->driver_data;
+
+	tty_port_close(&line->port, tty, filp);
+}
+
+void line_hangup(struct tty_struct *tty)
+{
+	struct line *line = tty->driver_data;
+
+	tty_port_hangup(&line->port);
+}
+
+void close_lines(struct line *lines, int nlines)
+{
+	int i;
+
+	for(i = 0; i < nlines; i++)
+		close_chan(&lines[i]);
+}
+
+int setup_one_line(struct line *lines, int n, char *init,
+		   const struct chan_opts *opts, char **error_out)
+{
+	struct line *line = &lines[n];
+	struct tty_driver *driver = line->driver->driver;
+	int err = -EINVAL;
+
+	if (line->port.count) {
+		*error_out = "Device is already open";
+		goto out;
+	}
+
+	if (!strcmp(init, "none")) {
+		if (line->valid) {
+			line->valid = 0;
+			kfree(line->init_str);
+			tty_unregister_device(driver, n);
+			parse_chan_pair(NULL, line, n, opts, error_out);
+			err = 0;
+		}
+	} else {
+		char *new = kstrdup(init, GFP_KERNEL);
+		if (!new) {
+			*error_out = "Failed to allocate memory";
+			return -ENOMEM;
+		}
+		if (line->valid) {
+			tty_unregister_device(driver, n);
+			kfree(line->init_str);
+		}
+		line->init_str = new;
+		line->valid = 1;
+		err = parse_chan_pair(new, line, n, opts, error_out);
+		if (!err) {
+			struct device *d = tty_port_register_device(&line->port,
+					driver, n, NULL);
+			if (IS_ERR(d)) {
+				*error_out = "Failed to register device";
+				err = PTR_ERR(d);
+				parse_chan_pair(NULL, line, n, opts, error_out);
+			}
+		}
+		if (err) {
+			line->init_str = NULL;
+			line->valid = 0;
+			kfree(new);
+		}
+	}
+out:
+	return err;
+}
+
+/*
+ * Common setup code for both startup command line and mconsole initialization.
+ * @lines contains the array (of size @num) to modify;
+ * @init is the setup string;
+ * @error_out is an error string in the case of failure;
+ */
+
+int line_setup(char **conf, unsigned int num, char **def,
+	       char *init, char *name)
+{
+	char *error;
+
+	if (*init == '=') {
+		/*
+		 * We said con=/ssl= instead of con#=, so we are configuring all
+		 * consoles at once.
+		 */
+		*def = init + 1;
+	} else {
+		char *end;
+		unsigned n = simple_strtoul(init, &end, 0);
+
+		if (*end != '=') {
+			error = "Couldn't parse device number";
+			goto out;
+		}
+		if (n >= num) {
+			error = "Device number out of range";
+			goto out;
+		}
+		conf[n] = end + 1;
+	}
+	return 0;
+
+out:
+	printk(KERN_ERR "Failed to set up %s with "
+	       "configuration string \"%s\" : %s\n", name, init, error);
+	return -EINVAL;
+}
+
+int line_config(struct line *lines, unsigned int num, char *str,
+		const struct chan_opts *opts, char **error_out)
+{
+	char *end;
+	int n;
+
+	if (*str == '=') {
+		*error_out = "Can't configure all devices from mconsole";
+		return -EINVAL;
+	}
+
+	n = simple_strtoul(str, &end, 0);
+	if (*end++ != '=') {
+		*error_out = "Couldn't parse device number";
+		return -EINVAL;
+	}
+	if (n >= num) {
+		*error_out = "Device number out of range";
+		return -EINVAL;
+	}
+
+	return setup_one_line(lines, n, end, opts, error_out);
+}
+
+int line_get_config(char *name, struct line *lines, unsigned int num, char *str,
+		    int size, char **error_out)
+{
+	struct line *line;
+	char *end;
+	int dev, n = 0;
+
+	dev = simple_strtoul(name, &end, 0);
+	if ((*end != '\0') || (end == name)) {
+		*error_out = "line_get_config failed to parse device number";
+		return 0;
+	}
+
+	if ((dev < 0) || (dev >= num)) {
+		*error_out = "device number out of range";
+		return 0;
+	}
+
+	line = &lines[dev];
+
+	if (!line->valid)
+		CONFIG_CHUNK(str, size, n, "none", 1);
+	else {
+		struct tty_struct *tty = tty_port_tty_get(&line->port);
+		if (tty == NULL) {
+			CONFIG_CHUNK(str, size, n, line->init_str, 1);
+		} else {
+			n = chan_config_string(line, str, size, error_out);
+			tty_kref_put(tty);
+		}
+	}
+
+	return n;
+}
+
+int line_id(char **str, int *start_out, int *end_out)
+{
+	char *end;
+	int n;
+
+	n = simple_strtoul(*str, &end, 0);
+	if ((*end != '\0') || (end == *str))
+		return -1;
+
+	*str = end;
+	*start_out = n;
+	*end_out = n;
+	return n;
+}
+
+int line_remove(struct line *lines, unsigned int num, int n, char **error_out)
+{
+	if (n >= num) {
+		*error_out = "Device number out of range";
+		return -EINVAL;
+	}
+	return setup_one_line(lines, n, "none", NULL, error_out);
+}
+
+int register_lines(struct line_driver *line_driver,
+		   const struct tty_operations *ops,
+		   struct line *lines, int nlines)
+{
+	struct tty_driver *driver;
+	int err;
+	int i;
+
+	driver = tty_alloc_driver(nlines, TTY_DRIVER_REAL_RAW |
+			TTY_DRIVER_DYNAMIC_DEV);
+	if (IS_ERR(driver))
+		return PTR_ERR(driver);
+
+	driver->driver_name = line_driver->name;
+	driver->name = line_driver->device_name;
+	driver->major = line_driver->major;
+	driver->minor_start = line_driver->minor_start;
+	driver->type = line_driver->type;
+	driver->subtype = line_driver->subtype;
+	driver->init_termios = tty_std_termios;
+
+	for (i = 0; i < nlines; i++) {
+		tty_port_init(&lines[i].port);
+		lines[i].port.ops = &line_port_ops;
+		spin_lock_init(&lines[i].lock);
+		lines[i].driver = line_driver;
+		INIT_LIST_HEAD(&lines[i].chan_list);
+	}
+	tty_set_operations(driver, ops);
+
+	err = tty_register_driver(driver);
+	if (err) {
+		printk(KERN_ERR "register_lines : can't register %s driver\n",
+		       line_driver->name);
+		tty_driver_kref_put(driver);
+		for (i = 0; i < nlines; i++)
+			tty_port_destroy(&lines[i].port);
+		return err;
+	}
+
+	line_driver->driver = driver;
+	mconsole_register_dev(&line_driver->mc);
+	return 0;
+}
+
+static DEFINE_SPINLOCK(winch_handler_lock);
+static LIST_HEAD(winch_handlers);
+
+struct winch {
+	struct list_head list;
+	int fd;
+	int tty_fd;
+	int pid;
+	struct tty_port *port;
+	unsigned long stack;
+	struct work_struct work;
+};
+
+static void __free_winch(struct work_struct *work)
+{
+	struct winch *winch = container_of(work, struct winch, work);
+	um_free_irq(WINCH_IRQ, winch);
+
+	if (winch->pid != -1)
+		os_kill_process(winch->pid, 1);
+	if (winch->stack != 0)
+		free_stack(winch->stack, 0);
+	kfree(winch);
+}
+
+static void free_winch(struct winch *winch)
+{
+	int fd = winch->fd;
+	winch->fd = -1;
+	if (fd != -1)
+		os_close_file(fd);
+	__free_winch(&winch->work);
+}
+
+static irqreturn_t winch_interrupt(int irq, void *data)
+{
+	struct winch *winch = data;
+	struct tty_struct *tty;
+	struct line *line;
+	int fd = winch->fd;
+	int err;
+	char c;
+	struct pid *pgrp;
+
+	if (fd != -1) {
+		err = generic_read(fd, &c, NULL);
+		if (err < 0) {
+			if (err != -EAGAIN) {
+				winch->fd = -1;
+				list_del(&winch->list);
+				os_close_file(fd);
+				printk(KERN_ERR "winch_interrupt : "
+				       "read failed, errno = %d\n", -err);
+				printk(KERN_ERR "fd %d is losing SIGWINCH "
+				       "support\n", winch->tty_fd);
+				INIT_WORK(&winch->work, __free_winch);
+				schedule_work(&winch->work);
+				return IRQ_HANDLED;
+			}
+			goto out;
+		}
+	}
+	tty = tty_port_tty_get(winch->port);
+	if (tty != NULL) {
+		line = tty->driver_data;
+		if (line != NULL) {
+			chan_window_size(line, &tty->winsize.ws_row,
+					 &tty->winsize.ws_col);
+			pgrp = tty_get_pgrp(tty);
+			if (pgrp)
+				kill_pgrp(pgrp, SIGWINCH, 1);
+			put_pid(pgrp);
+		}
+		tty_kref_put(tty);
+	}
+ out:
+	return IRQ_HANDLED;
+}
+
+void register_winch_irq(int fd, int tty_fd, int pid, struct tty_port *port,
+			unsigned long stack)
+{
+	struct winch *winch;
+
+	winch = kmalloc(sizeof(*winch), GFP_KERNEL);
+	if (winch == NULL) {
+		printk(KERN_ERR "register_winch_irq - kmalloc failed\n");
+		goto cleanup;
+	}
+
+	*winch = ((struct winch) { .list  	= LIST_HEAD_INIT(winch->list),
+				   .fd  	= fd,
+				   .tty_fd 	= tty_fd,
+				   .pid  	= pid,
+				   .port 	= port,
+				   .stack	= stack });
+
+	if (um_request_irq(WINCH_IRQ, fd, IRQ_READ, winch_interrupt,
+			   IRQF_SHARED, "winch", winch) < 0) {
+		printk(KERN_ERR "register_winch_irq - failed to register "
+		       "IRQ\n");
+		goto out_free;
+	}
+
+	spin_lock(&winch_handler_lock);
+	list_add(&winch->list, &winch_handlers);
+	spin_unlock(&winch_handler_lock);
+
+	return;
+
+ out_free:
+	kfree(winch);
+ cleanup:
+	os_kill_process(pid, 1);
+	os_close_file(fd);
+	if (stack != 0)
+		free_stack(stack, 0);
+}
+
+static void unregister_winch(struct tty_struct *tty)
+{
+	struct list_head *ele, *next;
+	struct winch *winch;
+	struct tty_struct *wtty;
+
+	spin_lock(&winch_handler_lock);
+
+	list_for_each_safe(ele, next, &winch_handlers) {
+		winch = list_entry(ele, struct winch, list);
+		wtty = tty_port_tty_get(winch->port);
+		if (wtty == tty) {
+			list_del(&winch->list);
+			spin_unlock(&winch_handler_lock);
+			free_winch(winch);
+			break;
+		}
+		tty_kref_put(wtty);
+	}
+	spin_unlock(&winch_handler_lock);
+}
+
+static void winch_cleanup(void)
+{
+	struct winch *winch;
+
+	spin_lock(&winch_handler_lock);
+	while ((winch = list_first_entry_or_null(&winch_handlers,
+						 struct winch, list))) {
+		list_del(&winch->list);
+		spin_unlock(&winch_handler_lock);
+
+		free_winch(winch);
+
+		spin_lock(&winch_handler_lock);
+	}
+
+	spin_unlock(&winch_handler_lock);
+}
+__uml_exitcall(winch_cleanup);
+
+char *add_xterm_umid(char *base)
+{
+	char *umid, *title;
+	int len;
+
+	umid = get_umid();
+	if (*umid == '\0')
+		return base;
+
+	len = strlen(base) + strlen(" ()") + strlen(umid) + 1;
+	title = kmalloc(len, GFP_KERNEL);
+	if (title == NULL) {
+		printk(KERN_ERR "Failed to allocate buffer for xterm title\n");
+		return base;
+	}
+
+	snprintf(title, len, "%s (%s)", base, umid);
+	return title;
+}
diff --git a/arch/um/drivers/line.h b/arch/um/drivers/line.h
new file mode 100644
index 000000000..f15be75a3
--- /dev/null
+++ b/arch/um/drivers/line.h
@@ -0,0 +1,97 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* 
+ * Copyright (C) 2001, 2002 Jeff Dike (jdike@karaya.com)
+ */
+
+#ifndef __LINE_H__
+#define __LINE_H__
+
+#include <linux/list.h>
+#include <linux/workqueue.h>
+#include <linux/tty.h>
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+#include "chan_user.h"
+#include "mconsole_kern.h"
+
+/* There's only two modifiable fields in this - .mc.list and .driver */
+struct line_driver {
+	const char *name;
+	const char *device_name;
+	const short major;
+	const short minor_start;
+	const short type;
+	const short subtype;
+	const char *read_irq_name;
+	const char *write_irq_name;
+	struct mc_device mc;
+	struct tty_driver *driver;
+};
+
+struct line {
+	struct tty_port port;
+	int valid;
+
+	int read_irq, write_irq;
+
+	char *init_str;
+	struct list_head chan_list;
+	struct chan *chan_in, *chan_out;
+
+	/*This lock is actually, mostly, local to*/
+	spinlock_t lock;
+	int throttled;
+	/* Yes, this is a real circular buffer.
+	 * XXX: And this should become a struct kfifo!
+	 *
+	 * buffer points to a buffer allocated on demand, of length
+	 * LINE_BUFSIZE, head to the start of the ring, tail to the end.*/
+	char *buffer;
+	char *head;
+	char *tail;
+
+	int sigio;
+	struct delayed_work task;
+	const struct line_driver *driver;
+};
+
+extern void line_close(struct tty_struct *tty, struct file * filp);
+extern int line_open(struct tty_struct *tty, struct file *filp);
+extern int line_install(struct tty_driver *driver, struct tty_struct *tty,
+	struct line *line);
+extern void line_cleanup(struct tty_struct *tty);
+extern void line_hangup(struct tty_struct *tty);
+extern int line_setup(char **conf, unsigned nlines, char **def,
+		      char *init, char *name);
+extern int line_write(struct tty_struct *tty, const unsigned char *buf,
+		      int len);
+extern unsigned int line_chars_in_buffer(struct tty_struct *tty);
+extern void line_flush_buffer(struct tty_struct *tty);
+extern void line_flush_chars(struct tty_struct *tty);
+extern unsigned int line_write_room(struct tty_struct *tty);
+extern void line_throttle(struct tty_struct *tty);
+extern void line_unthrottle(struct tty_struct *tty);
+
+extern char *add_xterm_umid(char *base);
+extern int line_setup_irq(int fd, int input, int output, struct line *line,
+			  void *data);
+extern void line_close_chan(struct line *line);
+extern int register_lines(struct line_driver *line_driver,
+			  const struct tty_operations *driver,
+			  struct line *lines, int nlines);
+extern int setup_one_line(struct line *lines, int n, char *init,
+			  const struct chan_opts *opts, char **error_out);
+extern void close_lines(struct line *lines, int nlines);
+
+extern int line_config(struct line *lines, unsigned int sizeof_lines,
+		       char *str, const struct chan_opts *opts,
+		       char **error_out);
+extern int line_id(char **str, int *start_out, int *end_out);
+extern int line_remove(struct line *lines, unsigned int sizeof_lines, int n,
+		       char **error_out);
+extern int line_get_config(char *dev, struct line *lines,
+			   unsigned int sizeof_lines, char *str,
+			   int size, char **error_out);
+
+#endif
diff --git a/arch/um/drivers/mconsole.h b/arch/um/drivers/mconsole.h
new file mode 100644
index 000000000..635637830
--- /dev/null
+++ b/arch/um/drivers/mconsole.h
@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org)
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#ifndef __MCONSOLE_H__
+#define __MCONSOLE_H__
+
+#ifdef __UM_HOST__
+#include <stdint.h>
+#define u32 uint32_t
+#endif
+
+#include <sysdep/ptrace.h>
+
+#define MCONSOLE_MAGIC (0xcafebabe)
+#define MCONSOLE_MAX_DATA (512)
+#define MCONSOLE_VERSION 2
+
+struct mconsole_request {
+	u32 magic;
+	u32 version;
+	u32 len;
+	char data[MCONSOLE_MAX_DATA];
+};
+
+struct mconsole_reply {
+	u32 err;
+	u32 more;
+	u32 len;
+	char data[MCONSOLE_MAX_DATA];
+};
+
+struct mconsole_notify {
+	u32 magic;
+	u32 version;
+	enum { MCONSOLE_SOCKET, MCONSOLE_PANIC, MCONSOLE_HANG,
+	       MCONSOLE_USER_NOTIFY } type;
+	u32 len;
+	char data[MCONSOLE_MAX_DATA];
+};
+
+struct mc_request;
+
+enum mc_context { MCONSOLE_INTR, MCONSOLE_PROC };
+
+struct mconsole_command
+{
+	char *command;
+	void (*handler)(struct mc_request *req);
+	enum mc_context context;
+};
+
+struct mc_request
+{
+	int len;
+	int as_interrupt;
+
+	int originating_fd;
+	unsigned int originlen;
+	unsigned char origin[128];			/* sockaddr_un */
+
+	struct mconsole_request request;
+	struct mconsole_command *cmd;
+	struct uml_pt_regs regs;
+};
+
+extern char mconsole_socket_name[];
+
+extern int mconsole_unlink_socket(void);
+extern int mconsole_reply_len(struct mc_request *req, const char *reply,
+			      int len, int err, int more);
+extern int mconsole_reply(struct mc_request *req, const char *str, int err,
+			  int more);
+
+extern void mconsole_version(struct mc_request *req);
+extern void mconsole_help(struct mc_request *req);
+extern void mconsole_halt(struct mc_request *req);
+extern void mconsole_reboot(struct mc_request *req);
+extern void mconsole_config(struct mc_request *req);
+extern void mconsole_remove(struct mc_request *req);
+extern void mconsole_sysrq(struct mc_request *req);
+extern void mconsole_cad(struct mc_request *req);
+extern void mconsole_stop(struct mc_request *req);
+extern void mconsole_go(struct mc_request *req);
+extern void mconsole_log(struct mc_request *req);
+extern void mconsole_proc(struct mc_request *req);
+extern void mconsole_stack(struct mc_request *req);
+
+extern int mconsole_get_request(int fd, struct mc_request *req);
+extern int mconsole_notify(char *sock_name, int type, const void *data,
+			   int len);
+extern char *mconsole_notify_socket(void);
+extern void lock_notify(void);
+extern void unlock_notify(void);
+
+#endif
diff --git a/arch/um/drivers/mconsole_kern.c b/arch/um/drivers/mconsole_kern.c
new file mode 100644
index 000000000..5026e7b9a
--- /dev/null
+++ b/arch/um/drivers/mconsole_kern.c
@@ -0,0 +1,871 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org)
+ * Copyright (C) 2001 - 2008 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <linux/console.h>
+#include <linux/ctype.h>
+#include <linux/string.h>
+#include <linux/interrupt.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/panic_notifier.h>
+#include <linux/reboot.h>
+#include <linux/sched/debug.h>
+#include <linux/proc_fs.h>
+#include <linux/slab.h>
+#include <linux/syscalls.h>
+#include <linux/utsname.h>
+#include <linux/socket.h>
+#include <linux/un.h>
+#include <linux/workqueue.h>
+#include <linux/mutex.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/file.h>
+#include <linux/uaccess.h>
+#include <asm/switch_to.h>
+
+#include <init.h>
+#include <irq_kern.h>
+#include <irq_user.h>
+#include <kern_util.h>
+#include "mconsole.h"
+#include "mconsole_kern.h"
+#include <os.h>
+
+static struct vfsmount *proc_mnt = NULL;
+
+static int do_unlink_socket(struct notifier_block *notifier,
+			    unsigned long what, void *data)
+{
+	return mconsole_unlink_socket();
+}
+
+
+static struct notifier_block reboot_notifier = {
+	.notifier_call		= do_unlink_socket,
+	.priority		= 0,
+};
+
+/* Safe without explicit locking for now.  Tasklets provide their own
+ * locking, and the interrupt handler is safe because it can't interrupt
+ * itself and it can only happen on CPU 0.
+ */
+
+static LIST_HEAD(mc_requests);
+
+static void mc_work_proc(struct work_struct *unused)
+{
+	struct mconsole_entry *req;
+	unsigned long flags;
+
+	while (!list_empty(&mc_requests)) {
+		local_irq_save(flags);
+		req = list_entry(mc_requests.next, struct mconsole_entry, list);
+		list_del(&req->list);
+		local_irq_restore(flags);
+		req->request.cmd->handler(&req->request);
+		kfree(req);
+	}
+}
+
+static DECLARE_WORK(mconsole_work, mc_work_proc);
+
+static irqreturn_t mconsole_interrupt(int irq, void *dev_id)
+{
+	/* long to avoid size mismatch warnings from gcc */
+	long fd;
+	struct mconsole_entry *new;
+	static struct mc_request req;	/* that's OK */
+
+	fd = (long) dev_id;
+	while (mconsole_get_request(fd, &req)) {
+		if (req.cmd->context == MCONSOLE_INTR)
+			(*req.cmd->handler)(&req);
+		else {
+			new = kmalloc(sizeof(*new), GFP_NOWAIT);
+			if (new == NULL)
+				mconsole_reply(&req, "Out of memory", 1, 0);
+			else {
+				new->request = req;
+				new->request.regs = get_irq_regs()->regs;
+				list_add(&new->list, &mc_requests);
+			}
+		}
+	}
+	if (!list_empty(&mc_requests))
+		schedule_work(&mconsole_work);
+	return IRQ_HANDLED;
+}
+
+void mconsole_version(struct mc_request *req)
+{
+	char version[256];
+
+	sprintf(version, "%s %s %s %s %s", utsname()->sysname,
+		utsname()->nodename, utsname()->release, utsname()->version,
+		utsname()->machine);
+	mconsole_reply(req, version, 0, 0);
+}
+
+void mconsole_log(struct mc_request *req)
+{
+	int len;
+	char *ptr = req->request.data;
+
+	ptr += strlen("log ");
+
+	len = req->len - (ptr - req->request.data);
+	printk(KERN_WARNING "%.*s", len, ptr);
+	mconsole_reply(req, "", 0, 0);
+}
+
+void mconsole_proc(struct mc_request *req)
+{
+	struct vfsmount *mnt = proc_mnt;
+	char *buf;
+	int len;
+	struct file *file;
+	int first_chunk = 1;
+	char *ptr = req->request.data;
+	loff_t pos = 0;
+
+	ptr += strlen("proc");
+	ptr = skip_spaces(ptr);
+
+	if (!mnt) {
+		mconsole_reply(req, "Proc not available", 1, 0);
+		goto out;
+	}
+	file = file_open_root_mnt(mnt, ptr, O_RDONLY, 0);
+	if (IS_ERR(file)) {
+		mconsole_reply(req, "Failed to open file", 1, 0);
+		printk(KERN_ERR "open /proc/%s: %ld\n", ptr, PTR_ERR(file));
+		goto out;
+	}
+
+	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (buf == NULL) {
+		mconsole_reply(req, "Failed to allocate buffer", 1, 0);
+		goto out_fput;
+	}
+
+	do {
+		len = kernel_read(file, buf, PAGE_SIZE - 1, &pos);
+		if (len < 0) {
+			mconsole_reply(req, "Read of file failed", 1, 0);
+			goto out_free;
+		}
+		/* Begin the file content on his own line. */
+		if (first_chunk) {
+			mconsole_reply(req, "\n", 0, 1);
+			first_chunk = 0;
+		}
+		buf[len] = '\0';
+		mconsole_reply(req, buf, 0, (len > 0));
+	} while (len > 0);
+ out_free:
+	kfree(buf);
+ out_fput:
+	fput(file);
+ out: ;
+}
+
+#define UML_MCONSOLE_HELPTEXT \
+"Commands: \n\
+    version - Get kernel version \n\
+    help - Print this message \n\
+    halt - Halt UML \n\
+    reboot - Reboot UML \n\
+    config <dev>=<config> - Add a new device to UML;  \n\
+	same syntax as command line \n\
+    config <dev> - Query the configuration of a device \n\
+    remove <dev> - Remove a device from UML \n\
+    sysrq <letter> - Performs the SysRq action controlled by the letter \n\
+    cad - invoke the Ctrl-Alt-Del handler \n\
+    stop - pause the UML; it will do nothing until it receives a 'go' \n\
+    go - continue the UML after a 'stop' \n\
+    log <string> - make UML enter <string> into the kernel log\n\
+    proc <file> - returns the contents of the UML's /proc/<file>\n\
+    stack <pid> - returns the stack of the specified pid\n\
+"
+
+void mconsole_help(struct mc_request *req)
+{
+	mconsole_reply(req, UML_MCONSOLE_HELPTEXT, 0, 0);
+}
+
+void mconsole_halt(struct mc_request *req)
+{
+	mconsole_reply(req, "", 0, 0);
+	machine_halt();
+}
+
+void mconsole_reboot(struct mc_request *req)
+{
+	mconsole_reply(req, "", 0, 0);
+	machine_restart(NULL);
+}
+
+void mconsole_cad(struct mc_request *req)
+{
+	mconsole_reply(req, "", 0, 0);
+	ctrl_alt_del();
+}
+
+void mconsole_go(struct mc_request *req)
+{
+	mconsole_reply(req, "Not stopped", 1, 0);
+}
+
+void mconsole_stop(struct mc_request *req)
+{
+	block_signals();
+	os_set_fd_block(req->originating_fd, 1);
+	mconsole_reply(req, "stopped", 0, 0);
+	for (;;) {
+		if (!mconsole_get_request(req->originating_fd, req))
+			continue;
+		if (req->cmd->handler == mconsole_go)
+			break;
+		if (req->cmd->handler == mconsole_stop) {
+			mconsole_reply(req, "Already stopped", 1, 0);
+			continue;
+		}
+		if (req->cmd->handler == mconsole_sysrq) {
+			struct pt_regs *old_regs;
+			old_regs = set_irq_regs((struct pt_regs *)&req->regs);
+			mconsole_sysrq(req);
+			set_irq_regs(old_regs);
+			continue;
+		}
+		(*req->cmd->handler)(req);
+	}
+	os_set_fd_block(req->originating_fd, 0);
+	mconsole_reply(req, "", 0, 0);
+	unblock_signals();
+}
+
+static DEFINE_SPINLOCK(mc_devices_lock);
+static LIST_HEAD(mconsole_devices);
+
+void mconsole_register_dev(struct mc_device *new)
+{
+	spin_lock(&mc_devices_lock);
+	BUG_ON(!list_empty(&new->list));
+	list_add(&new->list, &mconsole_devices);
+	spin_unlock(&mc_devices_lock);
+}
+
+static struct mc_device *mconsole_find_dev(char *name)
+{
+	struct list_head *ele;
+	struct mc_device *dev;
+
+	list_for_each(ele, &mconsole_devices) {
+		dev = list_entry(ele, struct mc_device, list);
+		if (!strncmp(name, dev->name, strlen(dev->name)))
+			return dev;
+	}
+	return NULL;
+}
+
+#define UNPLUGGED_PER_PAGE \
+	((PAGE_SIZE - sizeof(struct list_head)) / sizeof(unsigned long))
+
+struct unplugged_pages {
+	struct list_head list;
+	void *pages[UNPLUGGED_PER_PAGE];
+};
+
+static DEFINE_MUTEX(plug_mem_mutex);
+static unsigned long long unplugged_pages_count;
+static LIST_HEAD(unplugged_pages);
+static int unplug_index = UNPLUGGED_PER_PAGE;
+
+static int mem_config(char *str, char **error_out)
+{
+	unsigned long long diff;
+	int err = -EINVAL, i, add;
+	char *ret;
+
+	if (str[0] != '=') {
+		*error_out = "Expected '=' after 'mem'";
+		goto out;
+	}
+
+	str++;
+	if (str[0] == '-')
+		add = 0;
+	else if (str[0] == '+') {
+		add = 1;
+	}
+	else {
+		*error_out = "Expected increment to start with '-' or '+'";
+		goto out;
+	}
+
+	str++;
+	diff = memparse(str, &ret);
+	if (*ret != '\0') {
+		*error_out = "Failed to parse memory increment";
+		goto out;
+	}
+
+	diff /= PAGE_SIZE;
+
+	mutex_lock(&plug_mem_mutex);
+	for (i = 0; i < diff; i++) {
+		struct unplugged_pages *unplugged;
+		void *addr;
+
+		if (add) {
+			if (list_empty(&unplugged_pages))
+				break;
+
+			unplugged = list_entry(unplugged_pages.next,
+					       struct unplugged_pages, list);
+			if (unplug_index > 0)
+				addr = unplugged->pages[--unplug_index];
+			else {
+				list_del(&unplugged->list);
+				addr = unplugged;
+				unplug_index = UNPLUGGED_PER_PAGE;
+			}
+
+			free_page((unsigned long) addr);
+			unplugged_pages_count--;
+		}
+		else {
+			struct page *page;
+
+			page = alloc_page(GFP_ATOMIC);
+			if (page == NULL)
+				break;
+
+			unplugged = page_address(page);
+			if (unplug_index == UNPLUGGED_PER_PAGE) {
+				list_add(&unplugged->list, &unplugged_pages);
+				unplug_index = 0;
+			}
+			else {
+				struct list_head *entry = unplugged_pages.next;
+				addr = unplugged;
+
+				unplugged = list_entry(entry,
+						       struct unplugged_pages,
+						       list);
+				err = os_drop_memory(addr, PAGE_SIZE);
+				if (err) {
+					printk(KERN_ERR "Failed to release "
+					       "memory - errno = %d\n", err);
+					*error_out = "Failed to release memory";
+					goto out_unlock;
+				}
+				unplugged->pages[unplug_index++] = addr;
+			}
+
+			unplugged_pages_count++;
+		}
+	}
+
+	err = 0;
+out_unlock:
+	mutex_unlock(&plug_mem_mutex);
+out:
+	return err;
+}
+
+static int mem_get_config(char *name, char *str, int size, char **error_out)
+{
+	char buf[sizeof("18446744073709551615")];
+	int len = 0;
+
+	sprintf(buf, "%ld", uml_physmem);
+	CONFIG_CHUNK(str, size, len, buf, 1);
+
+	return len;
+}
+
+static int mem_id(char **str, int *start_out, int *end_out)
+{
+	*start_out = 0;
+	*end_out = 0;
+
+	return 0;
+}
+
+static int mem_remove(int n, char **error_out)
+{
+	*error_out = "Memory doesn't support the remove operation";
+	return -EBUSY;
+}
+
+static struct mc_device mem_mc = {
+	.list		= LIST_HEAD_INIT(mem_mc.list),
+	.name		= "mem",
+	.config		= mem_config,
+	.get_config	= mem_get_config,
+	.id		= mem_id,
+	.remove		= mem_remove,
+};
+
+static int __init mem_mc_init(void)
+{
+	if (can_drop_memory())
+		mconsole_register_dev(&mem_mc);
+	else printk(KERN_ERR "Can't release memory to the host - memory "
+		    "hotplug won't be supported\n");
+	return 0;
+}
+
+__initcall(mem_mc_init);
+
+#define CONFIG_BUF_SIZE 64
+
+static void mconsole_get_config(int (*get_config)(char *, char *, int,
+						  char **),
+				struct mc_request *req, char *name)
+{
+	char default_buf[CONFIG_BUF_SIZE], *error, *buf;
+	int n, size;
+
+	if (get_config == NULL) {
+		mconsole_reply(req, "No get_config routine defined", 1, 0);
+		return;
+	}
+
+	error = NULL;
+	size = ARRAY_SIZE(default_buf);
+	buf = default_buf;
+
+	while (1) {
+		n = (*get_config)(name, buf, size, &error);
+		if (error != NULL) {
+			mconsole_reply(req, error, 1, 0);
+			goto out;
+		}
+
+		if (n <= size) {
+			mconsole_reply(req, buf, 0, 0);
+			goto out;
+		}
+
+		if (buf != default_buf)
+			kfree(buf);
+
+		size = n;
+		buf = kmalloc(size, GFP_KERNEL);
+		if (buf == NULL) {
+			mconsole_reply(req, "Failed to allocate buffer", 1, 0);
+			return;
+		}
+	}
+ out:
+	if (buf != default_buf)
+		kfree(buf);
+}
+
+void mconsole_config(struct mc_request *req)
+{
+	struct mc_device *dev;
+	char *ptr = req->request.data, *name, *error_string = "";
+	int err;
+
+	ptr += strlen("config");
+	ptr = skip_spaces(ptr);
+	dev = mconsole_find_dev(ptr);
+	if (dev == NULL) {
+		mconsole_reply(req, "Bad configuration option", 1, 0);
+		return;
+	}
+
+	name = &ptr[strlen(dev->name)];
+	ptr = name;
+	while ((*ptr != '=') && (*ptr != '\0'))
+		ptr++;
+
+	if (*ptr == '=') {
+		err = (*dev->config)(name, &error_string);
+		mconsole_reply(req, error_string, err, 0);
+	}
+	else mconsole_get_config(dev->get_config, req, name);
+}
+
+void mconsole_remove(struct mc_request *req)
+{
+	struct mc_device *dev;
+	char *ptr = req->request.data, *err_msg = "";
+	char error[256];
+	int err, start, end, n;
+
+	ptr += strlen("remove");
+	ptr = skip_spaces(ptr);
+	dev = mconsole_find_dev(ptr);
+	if (dev == NULL) {
+		mconsole_reply(req, "Bad remove option", 1, 0);
+		return;
+	}
+
+	ptr = &ptr[strlen(dev->name)];
+
+	err = 1;
+	n = (*dev->id)(&ptr, &start, &end);
+	if (n < 0) {
+		err_msg = "Couldn't parse device number";
+		goto out;
+	}
+	else if ((n < start) || (n > end)) {
+		sprintf(error, "Invalid device number - must be between "
+			"%d and %d", start, end);
+		err_msg = error;
+		goto out;
+	}
+
+	err_msg = NULL;
+	err = (*dev->remove)(n, &err_msg);
+	switch(err) {
+	case 0:
+		err_msg = "";
+		break;
+	case -ENODEV:
+		if (err_msg == NULL)
+			err_msg = "Device doesn't exist";
+		break;
+	case -EBUSY:
+		if (err_msg == NULL)
+			err_msg = "Device is currently open";
+		break;
+	default:
+		break;
+	}
+out:
+	mconsole_reply(req, err_msg, err, 0);
+}
+
+struct mconsole_output {
+	struct list_head list;
+	struct mc_request *req;
+};
+
+static DEFINE_SPINLOCK(client_lock);
+static LIST_HEAD(clients);
+static char console_buf[MCONSOLE_MAX_DATA];
+
+static void console_write(struct console *console, const char *string,
+			  unsigned int len)
+{
+	struct list_head *ele;
+	int n;
+
+	if (list_empty(&clients))
+		return;
+
+	while (len > 0) {
+		n = min((size_t) len, ARRAY_SIZE(console_buf));
+		strncpy(console_buf, string, n);
+		string += n;
+		len -= n;
+
+		list_for_each(ele, &clients) {
+			struct mconsole_output *entry;
+
+			entry = list_entry(ele, struct mconsole_output, list);
+			mconsole_reply_len(entry->req, console_buf, n, 0, 1);
+		}
+	}
+}
+
+static struct console mc_console = { .name	= "mc",
+				     .write	= console_write,
+				     .flags	= CON_ENABLED,
+				     .index	= -1 };
+
+static int mc_add_console(void)
+{
+	register_console(&mc_console);
+	return 0;
+}
+
+late_initcall(mc_add_console);
+
+static void with_console(struct mc_request *req, void (*proc)(void *),
+			 void *arg)
+{
+	struct mconsole_output entry;
+	unsigned long flags;
+
+	entry.req = req;
+	spin_lock_irqsave(&client_lock, flags);
+	list_add(&entry.list, &clients);
+	spin_unlock_irqrestore(&client_lock, flags);
+
+	(*proc)(arg);
+
+	mconsole_reply_len(req, "", 0, 0, 0);
+
+	spin_lock_irqsave(&client_lock, flags);
+	list_del(&entry.list);
+	spin_unlock_irqrestore(&client_lock, flags);
+}
+
+#ifdef CONFIG_MAGIC_SYSRQ
+
+#include <linux/sysrq.h>
+
+static void sysrq_proc(void *arg)
+{
+	char *op = arg;
+	handle_sysrq(*op);
+}
+
+void mconsole_sysrq(struct mc_request *req)
+{
+	char *ptr = req->request.data;
+
+	ptr += strlen("sysrq");
+	ptr = skip_spaces(ptr);
+
+	/*
+	 * With 'b', the system will shut down without a chance to reply,
+	 * so in this case, we reply first.
+	 */
+	if (*ptr == 'b')
+		mconsole_reply(req, "", 0, 0);
+
+	with_console(req, sysrq_proc, ptr);
+}
+#else
+void mconsole_sysrq(struct mc_request *req)
+{
+	mconsole_reply(req, "Sysrq not compiled in", 1, 0);
+}
+#endif
+
+static void stack_proc(void *arg)
+{
+	struct task_struct *task = arg;
+
+	show_stack(task, NULL, KERN_INFO);
+}
+
+/*
+ * Mconsole stack trace
+ *  Added by Allan Graves, Jeff Dike
+ *  Dumps a stacks registers to the linux console.
+ *  Usage stack <pid>.
+ */
+void mconsole_stack(struct mc_request *req)
+{
+	char *ptr = req->request.data;
+	int pid_requested= -1;
+	struct task_struct *to = NULL;
+
+	/*
+	 * Would be nice:
+	 * 1) Send showregs output to mconsole.
+	 * 2) Add a way to stack dump all pids.
+	 */
+
+	ptr += strlen("stack");
+	ptr = skip_spaces(ptr);
+
+	/*
+	 * Should really check for multiple pids or reject bad args here
+	 */
+	/* What do the arguments in mconsole_reply mean? */
+	if (sscanf(ptr, "%d", &pid_requested) == 0) {
+		mconsole_reply(req, "Please specify a pid", 1, 0);
+		return;
+	}
+
+	to = find_task_by_pid_ns(pid_requested, &init_pid_ns);
+	if ((to == NULL) || (pid_requested == 0)) {
+		mconsole_reply(req, "Couldn't find that pid", 1, 0);
+		return;
+	}
+	with_console(req, stack_proc, to);
+}
+
+static int __init mount_proc(void)
+{
+	struct file_system_type *proc_fs_type;
+	struct vfsmount *mnt;
+
+	proc_fs_type = get_fs_type("proc");
+	if (!proc_fs_type)
+		return -ENODEV;
+
+	mnt = kern_mount(proc_fs_type);
+	put_filesystem(proc_fs_type);
+	if (IS_ERR(mnt))
+		return PTR_ERR(mnt);
+
+	proc_mnt = mnt;
+	return 0;
+}
+
+/*
+ * Changed by mconsole_setup, which is __setup, and called before SMP is
+ * active.
+ */
+static char *notify_socket = NULL;
+
+static int __init mconsole_init(void)
+{
+	/* long to avoid size mismatch warnings from gcc */
+	long sock;
+	int err;
+	char file[UNIX_PATH_MAX];
+
+	mount_proc();
+
+	if (umid_file_name("mconsole", file, sizeof(file)))
+		return -1;
+	snprintf(mconsole_socket_name, sizeof(file), "%s", file);
+
+	sock = os_create_unix_socket(file, sizeof(file), 1);
+	if (sock < 0) {
+		printk(KERN_ERR "Failed to initialize management console\n");
+		return 1;
+	}
+	if (os_set_fd_block(sock, 0))
+		goto out;
+
+	register_reboot_notifier(&reboot_notifier);
+
+	err = um_request_irq(MCONSOLE_IRQ, sock, IRQ_READ, mconsole_interrupt,
+			     IRQF_SHARED, "mconsole", (void *)sock);
+	if (err < 0) {
+		printk(KERN_ERR "Failed to get IRQ for management console\n");
+		goto out;
+	}
+
+	if (notify_socket != NULL) {
+		notify_socket = kstrdup(notify_socket, GFP_KERNEL);
+		if (notify_socket != NULL)
+			mconsole_notify(notify_socket, MCONSOLE_SOCKET,
+					mconsole_socket_name,
+					strlen(mconsole_socket_name) + 1);
+		else printk(KERN_ERR "mconsole_setup failed to strdup "
+			    "string\n");
+	}
+
+	printk(KERN_INFO "mconsole (version %d) initialized on %s\n",
+	       MCONSOLE_VERSION, mconsole_socket_name);
+	return 0;
+
+ out:
+	os_close_file(sock);
+	return 1;
+}
+
+__initcall(mconsole_init);
+
+static ssize_t mconsole_proc_write(struct file *file,
+		const char __user *buffer, size_t count, loff_t *pos)
+{
+	char *buf;
+
+	buf = memdup_user_nul(buffer, count);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	mconsole_notify(notify_socket, MCONSOLE_USER_NOTIFY, buf, count);
+	kfree(buf);
+	return count;
+}
+
+static const struct proc_ops mconsole_proc_ops = {
+	.proc_write	= mconsole_proc_write,
+	.proc_lseek	= noop_llseek,
+};
+
+static int create_proc_mconsole(void)
+{
+	struct proc_dir_entry *ent;
+
+	if (notify_socket == NULL)
+		return 0;
+
+	ent = proc_create("mconsole", 0200, NULL, &mconsole_proc_ops);
+	if (ent == NULL) {
+		printk(KERN_INFO "create_proc_mconsole : proc_create failed\n");
+		return 0;
+	}
+	return 0;
+}
+
+static DEFINE_SPINLOCK(notify_spinlock);
+
+void lock_notify(void)
+{
+	spin_lock(&notify_spinlock);
+}
+
+void unlock_notify(void)
+{
+	spin_unlock(&notify_spinlock);
+}
+
+__initcall(create_proc_mconsole);
+
+#define NOTIFY "notify:"
+
+static int mconsole_setup(char *str)
+{
+	if (!strncmp(str, NOTIFY, strlen(NOTIFY))) {
+		str += strlen(NOTIFY);
+		notify_socket = str;
+	}
+	else printk(KERN_ERR "mconsole_setup : Unknown option - '%s'\n", str);
+	return 1;
+}
+
+__setup("mconsole=", mconsole_setup);
+
+__uml_help(mconsole_setup,
+"mconsole=notify:<socket>\n"
+"    Requests that the mconsole driver send a message to the named Unix\n"
+"    socket containing the name of the mconsole socket.  This also serves\n"
+"    to notify outside processes when UML has booted far enough to respond\n"
+"    to mconsole requests.\n\n"
+);
+
+static int notify_panic(struct notifier_block *self, unsigned long unused1,
+			void *ptr)
+{
+	char *message = ptr;
+
+	if (notify_socket == NULL)
+		return 0;
+
+	mconsole_notify(notify_socket, MCONSOLE_PANIC, message,
+			strlen(message) + 1);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block panic_exit_notifier = {
+	.notifier_call	= notify_panic,
+	.priority	= INT_MAX, /* run as soon as possible */
+};
+
+static int add_notifier(void)
+{
+	atomic_notifier_chain_register(&panic_notifier_list,
+			&panic_exit_notifier);
+	return 0;
+}
+
+__initcall(add_notifier);
+
+char *mconsole_notify_socket(void)
+{
+	return notify_socket;
+}
+
+EXPORT_SYMBOL(mconsole_notify_socket);
diff --git a/arch/um/drivers/mconsole_kern.h b/arch/um/drivers/mconsole_kern.h
new file mode 100644
index 000000000..56d8d6a3f
--- /dev/null
+++ b/arch/um/drivers/mconsole_kern.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2001, 2002 Jeff Dike (jdike@karaya.com)
+ */
+
+#ifndef __MCONSOLE_KERN_H__
+#define __MCONSOLE_KERN_H__
+
+#include <linux/list.h>
+#include "mconsole.h"
+
+struct mconsole_entry {
+	struct list_head list;
+	struct mc_request request;
+};
+
+/* All these methods are called in process context. */
+struct mc_device {
+	struct list_head list;
+	char *name;
+	int (*config)(char *, char **);
+	int (*get_config)(char *, char *, int, char **);
+	int (*id)(char **, int *, int *);
+	int (*remove)(int, char **);
+};
+
+#define CONFIG_CHUNK(str, size, current, chunk, end) \
+do { \
+	current += strlen(chunk); \
+	if(current >= size) \
+		str = NULL; \
+	if(str != NULL){ \
+		strcpy(str, chunk); \
+		str += strlen(chunk); \
+	} \
+	if(end) \
+		current++; \
+} while(0)
+
+#ifdef CONFIG_MCONSOLE
+
+extern void mconsole_register_dev(struct mc_device *new);
+
+#else
+
+static inline void mconsole_register_dev(struct mc_device *new)
+{
+}
+
+#endif
+
+#endif
diff --git a/arch/um/drivers/mconsole_user.c b/arch/um/drivers/mconsole_user.c
new file mode 100644
index 000000000..e24298a73
--- /dev/null
+++ b/arch/um/drivers/mconsole_user.c
@@ -0,0 +1,219 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org)
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+#include <sys/un.h>
+#include "mconsole.h"
+
+static struct mconsole_command commands[] = {
+	/*
+	 * With uts namespaces, uts information becomes process-specific, so
+	 * we need a process context.  If we try handling this in interrupt
+	 * context, we may hit an exiting process without a valid uts
+	 * namespace.
+	 */
+	{ "version", mconsole_version, MCONSOLE_PROC },
+	{ "halt", mconsole_halt, MCONSOLE_PROC },
+	{ "reboot", mconsole_reboot, MCONSOLE_PROC },
+	{ "config", mconsole_config, MCONSOLE_PROC },
+	{ "remove", mconsole_remove, MCONSOLE_PROC },
+	{ "sysrq", mconsole_sysrq, MCONSOLE_INTR },
+	{ "help", mconsole_help, MCONSOLE_INTR },
+	{ "cad", mconsole_cad, MCONSOLE_INTR },
+	{ "stop", mconsole_stop, MCONSOLE_PROC },
+	{ "go", mconsole_go, MCONSOLE_INTR },
+	{ "log", mconsole_log, MCONSOLE_INTR },
+	{ "proc", mconsole_proc, MCONSOLE_PROC },
+	{ "stack", mconsole_stack, MCONSOLE_INTR },
+};
+
+/* Initialized in mconsole_init, which is an initcall */
+char mconsole_socket_name[256];
+
+static int mconsole_reply_v0(struct mc_request *req, char *reply)
+{
+	struct iovec iov;
+	struct msghdr msg;
+
+	iov.iov_base = reply;
+	iov.iov_len = strlen(reply);
+
+	msg.msg_name = &(req->origin);
+	msg.msg_namelen = req->originlen;
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+	msg.msg_control = NULL;
+	msg.msg_controllen = 0;
+	msg.msg_flags = 0;
+
+	return sendmsg(req->originating_fd, &msg, 0);
+}
+
+static struct mconsole_command *mconsole_parse(struct mc_request *req)
+{
+	struct mconsole_command *cmd;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(commands); i++) {
+		cmd = &commands[i];
+		if (!strncmp(req->request.data, cmd->command,
+			    strlen(cmd->command))) {
+			return cmd;
+		}
+	}
+	return NULL;
+}
+
+#define MIN(a,b) ((a)<(b) ? (a):(b))
+
+#define STRINGX(x) #x
+#define STRING(x) STRINGX(x)
+
+int mconsole_get_request(int fd, struct mc_request *req)
+{
+	int len;
+
+	req->originlen = sizeof(req->origin);
+	req->len = recvfrom(fd, &req->request, sizeof(req->request), 0,
+			    (struct sockaddr *) req->origin, &req->originlen);
+	if (req->len < 0)
+		return 0;
+
+	req->originating_fd = fd;
+
+	if (req->request.magic != MCONSOLE_MAGIC) {
+		/* Unversioned request */
+		len = MIN(sizeof(req->request.data) - 1,
+			  strlen((char *) &req->request));
+		memmove(req->request.data, &req->request, len);
+		req->request.data[len] = '\0';
+
+		req->request.magic = MCONSOLE_MAGIC;
+		req->request.version = 0;
+		req->request.len = len;
+
+		mconsole_reply_v0(req, "ERR Version 0 mconsole clients are "
+				  "not supported by this driver");
+		return 0;
+	}
+
+	if (req->request.len >= MCONSOLE_MAX_DATA) {
+		mconsole_reply(req, "Request too large", 1, 0);
+		return 0;
+	}
+	if (req->request.version != MCONSOLE_VERSION) {
+		mconsole_reply(req, "This driver only supports version "
+			       STRING(MCONSOLE_VERSION) " clients", 1, 0);
+	}
+
+	req->request.data[req->request.len] = '\0';
+	req->cmd = mconsole_parse(req);
+	if (req->cmd == NULL) {
+		mconsole_reply(req, "Unknown command", 1, 0);
+		return 0;
+	}
+
+	return 1;
+}
+
+int mconsole_reply_len(struct mc_request *req, const char *str, int total,
+		       int err, int more)
+{
+	/*
+	 * XXX This is a stack consumption problem.  It'd be nice to
+	 * make it global and serialize access to it, but there are a
+	 * ton of callers to this function.
+	 */
+	struct mconsole_reply reply;
+	int len, n;
+
+	do {
+		reply.err = err;
+
+		/* err can only be true on the first packet */
+		err = 0;
+
+		len = MIN(total, MCONSOLE_MAX_DATA - 1);
+
+		if (len == total) reply.more = more;
+		else reply.more = 1;
+
+		memcpy(reply.data, str, len);
+		reply.data[len] = '\0';
+		total -= len;
+		str += len;
+		reply.len = len + 1;
+
+		len = sizeof(reply) + reply.len - sizeof(reply.data);
+
+		n = sendto(req->originating_fd, &reply, len, 0,
+			   (struct sockaddr *) req->origin, req->originlen);
+
+		if (n < 0)
+			return -errno;
+	} while (total > 0);
+	return 0;
+}
+
+int mconsole_reply(struct mc_request *req, const char *str, int err, int more)
+{
+	return mconsole_reply_len(req, str, strlen(str), err, more);
+}
+
+
+int mconsole_unlink_socket(void)
+{
+	unlink(mconsole_socket_name);
+	return 0;
+}
+
+static int notify_sock = -1;
+
+int mconsole_notify(char *sock_name, int type, const void *data, int len)
+{
+	struct sockaddr_un target;
+	struct mconsole_notify packet;
+	int n, err = 0;
+
+	lock_notify();
+	if (notify_sock < 0) {
+		notify_sock = socket(PF_UNIX, SOCK_DGRAM, 0);
+		if (notify_sock < 0) {
+			err = -errno;
+			printk(UM_KERN_ERR "mconsole_notify - socket failed, "
+			       "errno = %d\n", errno);
+		}
+	}
+	unlock_notify();
+
+	if (err)
+		return err;
+
+	target.sun_family = AF_UNIX;
+	strcpy(target.sun_path, sock_name);
+
+	packet.magic = MCONSOLE_MAGIC;
+	packet.version = MCONSOLE_VERSION;
+	packet.type = type;
+	len = (len > sizeof(packet.data)) ? sizeof(packet.data) : len;
+	packet.len = len;
+	memcpy(packet.data, data, len);
+
+	err = 0;
+	len = sizeof(packet) + packet.len - sizeof(packet.data);
+	n = sendto(notify_sock, &packet, len, 0, (struct sockaddr *) &target,
+		   sizeof(target));
+	if (n < 0) {
+		err = -errno;
+		printk(UM_KERN_ERR "mconsole_notify - sendto failed, "
+		       "errno = %d\n", errno);
+	}
+	return err;
+}
diff --git a/arch/um/drivers/mmapper_kern.c b/arch/um/drivers/mmapper_kern.c
new file mode 100644
index 000000000..807cd3358
--- /dev/null
+++ b/arch/um/drivers/mmapper_kern.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * arch/um/drivers/mmapper_kern.c
+ *
+ * BRIEF MODULE DESCRIPTION
+ *
+ * Copyright (C) 2000 RidgeRun, Inc.
+ * Author: RidgeRun, Inc.
+ *         Greg Lonnon glonnon@ridgerun.com or info@ridgerun.com
+ *
+ */
+
+#include <linux/stddef.h>
+#include <linux/types.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+
+#include <linux/uaccess.h>
+#include <mem_user.h>
+
+/* These are set in mmapper_init, which is called at boot time */
+static unsigned long mmapper_size;
+static unsigned long p_buf;
+static char *v_buf;
+
+static ssize_t mmapper_read(struct file *file, char __user *buf, size_t count,
+			    loff_t *ppos)
+{
+	return simple_read_from_buffer(buf, count, ppos, v_buf, mmapper_size);
+}
+
+static ssize_t mmapper_write(struct file *file, const char __user *buf,
+			     size_t count, loff_t *ppos)
+{
+	if (*ppos > mmapper_size)
+		return -EINVAL;
+
+	return simple_write_to_buffer(v_buf, mmapper_size, ppos, buf, count);
+}
+
+static long mmapper_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	return -ENOIOCTLCMD;
+}
+
+static int mmapper_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	int ret = -EINVAL;
+	int size;
+
+	if (vma->vm_pgoff != 0)
+		goto out;
+
+	size = vma->vm_end - vma->vm_start;
+	if (size > mmapper_size)
+		return -EFAULT;
+
+	/*
+	 * XXX A comment above remap_pfn_range says it should only be
+	 * called when the mm semaphore is held
+	 */
+	if (remap_pfn_range(vma, vma->vm_start, p_buf >> PAGE_SHIFT, size,
+			    vma->vm_page_prot))
+		goto out;
+	ret = 0;
+out:
+	return ret;
+}
+
+static int mmapper_open(struct inode *inode, struct file *file)
+{
+	return 0;
+}
+
+static int mmapper_release(struct inode *inode, struct file *file)
+{
+	return 0;
+}
+
+static const struct file_operations mmapper_fops = {
+	.owner		= THIS_MODULE,
+	.read		= mmapper_read,
+	.write		= mmapper_write,
+	.unlocked_ioctl	= mmapper_ioctl,
+	.mmap		= mmapper_mmap,
+	.open		= mmapper_open,
+	.release	= mmapper_release,
+	.llseek		= default_llseek,
+};
+
+/*
+ * No locking needed - only used (and modified) by below initcall and exitcall.
+ */
+static struct miscdevice mmapper_dev = {
+	.minor		= MISC_DYNAMIC_MINOR,
+	.name		= "mmapper",
+	.fops		= &mmapper_fops
+};
+
+static int __init mmapper_init(void)
+{
+	int err;
+
+	printk(KERN_INFO "Mapper v0.1\n");
+
+	v_buf = (char *) find_iomem("mmapper", &mmapper_size);
+	if (mmapper_size == 0) {
+		printk(KERN_ERR "mmapper_init - find_iomem failed\n");
+		return -ENODEV;
+	}
+	p_buf = __pa(v_buf);
+
+	err = misc_register(&mmapper_dev);
+	if (err) {
+		printk(KERN_ERR "mmapper - misc_register failed, err = %d\n",
+		       err);
+		return err;
+	}
+	return 0;
+}
+
+static void __exit mmapper_exit(void)
+{
+	misc_deregister(&mmapper_dev);
+}
+
+module_init(mmapper_init);
+module_exit(mmapper_exit);
+
+MODULE_AUTHOR("Greg Lonnon <glonnon@ridgerun.com>");
+MODULE_DESCRIPTION("DSPLinux simulator mmapper driver");
+MODULE_LICENSE("GPL");
diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c
new file mode 100644
index 000000000..3d7836c46
--- /dev/null
+++ b/arch/um/drivers/net_kern.c
@@ -0,0 +1,892 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org) and
+ * James Leu (jleu@mindspring.net).
+ * Copyright (C) 2001 by various other people who didn't put their name here.
+ */
+
+#include <linux/memblock.h>
+#include <linux/etherdevice.h>
+#include <linux/ethtool.h>
+#include <linux/inetdevice.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/netdevice.h>
+#include <linux/platform_device.h>
+#include <linux/rtnetlink.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <init.h>
+#include <irq_kern.h>
+#include <irq_user.h>
+#include "mconsole_kern.h"
+#include <net_kern.h>
+#include <net_user.h>
+
+#define DRIVER_NAME "uml-netdev"
+
+static DEFINE_SPINLOCK(opened_lock);
+static LIST_HEAD(opened);
+
+/*
+ * The drop_skb is used when we can't allocate an skb.  The
+ * packet is read into drop_skb in order to get the data off the
+ * connection to the host.
+ * It is reallocated whenever a maximum packet size is seen which is
+ * larger than any seen before.  update_drop_skb is called from
+ * eth_configure when a new interface is added.
+ */
+static DEFINE_SPINLOCK(drop_lock);
+static struct sk_buff *drop_skb;
+static int drop_max;
+
+static int update_drop_skb(int max)
+{
+	struct sk_buff *new;
+	unsigned long flags;
+	int err = 0;
+
+	spin_lock_irqsave(&drop_lock, flags);
+
+	if (max <= drop_max)
+		goto out;
+
+	err = -ENOMEM;
+	new = dev_alloc_skb(max);
+	if (new == NULL)
+		goto out;
+
+	skb_put(new, max);
+
+	kfree_skb(drop_skb);
+	drop_skb = new;
+	drop_max = max;
+	err = 0;
+out:
+	spin_unlock_irqrestore(&drop_lock, flags);
+
+	return err;
+}
+
+static int uml_net_rx(struct net_device *dev)
+{
+	struct uml_net_private *lp = netdev_priv(dev);
+	int pkt_len;
+	struct sk_buff *skb;
+
+	/* If we can't allocate memory, try again next round. */
+	skb = dev_alloc_skb(lp->max_packet);
+	if (skb == NULL) {
+		drop_skb->dev = dev;
+		/* Read a packet into drop_skb and don't do anything with it. */
+		(*lp->read)(lp->fd, drop_skb, lp);
+		dev->stats.rx_dropped++;
+		return 0;
+	}
+
+	skb->dev = dev;
+	skb_put(skb, lp->max_packet);
+	skb_reset_mac_header(skb);
+	pkt_len = (*lp->read)(lp->fd, skb, lp);
+
+	if (pkt_len > 0) {
+		skb_trim(skb, pkt_len);
+		skb->protocol = (*lp->protocol)(skb);
+
+		dev->stats.rx_bytes += skb->len;
+		dev->stats.rx_packets++;
+		netif_rx(skb);
+		return pkt_len;
+	}
+
+	kfree_skb(skb);
+	return pkt_len;
+}
+
+static void uml_dev_close(struct work_struct *work)
+{
+	struct uml_net_private *lp =
+		container_of(work, struct uml_net_private, work);
+	dev_close(lp->dev);
+}
+
+static irqreturn_t uml_net_interrupt(int irq, void *dev_id)
+{
+	struct net_device *dev = dev_id;
+	struct uml_net_private *lp = netdev_priv(dev);
+	int err;
+
+	if (!netif_running(dev))
+		return IRQ_NONE;
+
+	spin_lock(&lp->lock);
+	while ((err = uml_net_rx(dev)) > 0) ;
+	if (err < 0) {
+		printk(KERN_ERR
+		       "Device '%s' read returned %d, shutting it down\n",
+		       dev->name, err);
+		/* dev_close can't be called in interrupt context, and takes
+		 * again lp->lock.
+		 * And dev_close() can be safely called multiple times on the
+		 * same device, since it tests for (dev->flags & IFF_UP). So
+		 * there's no harm in delaying the device shutdown.
+		 * Furthermore, the workqueue will not re-enqueue an already
+		 * enqueued work item. */
+		schedule_work(&lp->work);
+		goto out;
+	}
+out:
+	spin_unlock(&lp->lock);
+	return IRQ_HANDLED;
+}
+
+static int uml_net_open(struct net_device *dev)
+{
+	struct uml_net_private *lp = netdev_priv(dev);
+	int err;
+
+	if (lp->fd >= 0) {
+		err = -ENXIO;
+		goto out;
+	}
+
+	lp->fd = (*lp->open)(&lp->user);
+	if (lp->fd < 0) {
+		err = lp->fd;
+		goto out;
+	}
+
+	err = um_request_irq(dev->irq, lp->fd, IRQ_READ, uml_net_interrupt,
+			     IRQF_SHARED, dev->name, dev);
+	if (err < 0) {
+		printk(KERN_ERR "uml_net_open: failed to get irq(%d)\n", err);
+		err = -ENETUNREACH;
+		goto out_close;
+	}
+
+	netif_start_queue(dev);
+
+	/* clear buffer - it can happen that the host side of the interface
+	 * is full when we get here.  In this case, new data is never queued,
+	 * SIGIOs never arrive, and the net never works.
+	 */
+	while ((err = uml_net_rx(dev)) > 0) ;
+
+	spin_lock(&opened_lock);
+	list_add(&lp->list, &opened);
+	spin_unlock(&opened_lock);
+
+	return 0;
+out_close:
+	if (lp->close != NULL) (*lp->close)(lp->fd, &lp->user);
+	lp->fd = -1;
+out:
+	return err;
+}
+
+static int uml_net_close(struct net_device *dev)
+{
+	struct uml_net_private *lp = netdev_priv(dev);
+
+	netif_stop_queue(dev);
+
+	um_free_irq(dev->irq, dev);
+	if (lp->close != NULL)
+		(*lp->close)(lp->fd, &lp->user);
+	lp->fd = -1;
+
+	spin_lock(&opened_lock);
+	list_del(&lp->list);
+	spin_unlock(&opened_lock);
+
+	return 0;
+}
+
+static int uml_net_start_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct uml_net_private *lp = netdev_priv(dev);
+	unsigned long flags;
+	int len;
+
+	netif_stop_queue(dev);
+
+	spin_lock_irqsave(&lp->lock, flags);
+
+	len = (*lp->write)(lp->fd, skb, lp);
+	skb_tx_timestamp(skb);
+
+	if (len == skb->len) {
+		dev->stats.tx_packets++;
+		dev->stats.tx_bytes += skb->len;
+		netif_trans_update(dev);
+		netif_start_queue(dev);
+
+		/* this is normally done in the interrupt when tx finishes */
+		netif_wake_queue(dev);
+	}
+	else if (len == 0) {
+		netif_start_queue(dev);
+		dev->stats.tx_dropped++;
+	}
+	else {
+		netif_start_queue(dev);
+		printk(KERN_ERR "uml_net_start_xmit: failed(%d)\n", len);
+	}
+
+	spin_unlock_irqrestore(&lp->lock, flags);
+
+	dev_consume_skb_any(skb);
+
+	return NETDEV_TX_OK;
+}
+
+static void uml_net_set_multicast_list(struct net_device *dev)
+{
+	return;
+}
+
+static void uml_net_tx_timeout(struct net_device *dev, unsigned int txqueue)
+{
+	netif_trans_update(dev);
+	netif_wake_queue(dev);
+}
+
+#ifdef CONFIG_NET_POLL_CONTROLLER
+static void uml_net_poll_controller(struct net_device *dev)
+{
+	disable_irq(dev->irq);
+	uml_net_interrupt(dev->irq, dev);
+	enable_irq(dev->irq);
+}
+#endif
+
+static void uml_net_get_drvinfo(struct net_device *dev,
+				struct ethtool_drvinfo *info)
+{
+	strscpy(info->driver, DRIVER_NAME, sizeof(info->driver));
+}
+
+static const struct ethtool_ops uml_net_ethtool_ops = {
+	.get_drvinfo	= uml_net_get_drvinfo,
+	.get_link	= ethtool_op_get_link,
+	.get_ts_info	= ethtool_op_get_ts_info,
+};
+
+void uml_net_setup_etheraddr(struct net_device *dev, char *str)
+{
+	u8 addr[ETH_ALEN];
+	char *end;
+	int i;
+
+	if (str == NULL)
+		goto random;
+
+	for (i = 0; i < 6; i++) {
+		addr[i] = simple_strtoul(str, &end, 16);
+		if ((end == str) ||
+		   ((*end != ':') && (*end != ',') && (*end != '\0'))) {
+			printk(KERN_ERR
+			       "setup_etheraddr: failed to parse '%s' "
+			       "as an ethernet address\n", str);
+			goto random;
+		}
+		str = end + 1;
+	}
+	if (is_multicast_ether_addr(addr)) {
+		printk(KERN_ERR
+		       "Attempt to assign a multicast ethernet address to a "
+		       "device disallowed\n");
+		goto random;
+	}
+	if (!is_valid_ether_addr(addr)) {
+		printk(KERN_ERR
+		       "Attempt to assign an invalid ethernet address to a "
+		       "device disallowed\n");
+		goto random;
+	}
+	if (!is_local_ether_addr(addr)) {
+		printk(KERN_WARNING
+		       "Warning: Assigning a globally valid ethernet "
+		       "address to a device\n");
+		printk(KERN_WARNING "You should set the 2nd rightmost bit in "
+		       "the first byte of the MAC,\n");
+		printk(KERN_WARNING "i.e. %02x:%02x:%02x:%02x:%02x:%02x\n",
+		       addr[0] | 0x02, addr[1], addr[2], addr[3], addr[4],
+		       addr[5]);
+	}
+	eth_hw_addr_set(dev, addr);
+	return;
+
+random:
+	printk(KERN_INFO
+	       "Choosing a random ethernet address for device %s\n", dev->name);
+	eth_hw_addr_random(dev);
+}
+
+static DEFINE_SPINLOCK(devices_lock);
+static LIST_HEAD(devices);
+
+static struct platform_driver uml_net_driver = {
+	.driver = {
+		.name  = DRIVER_NAME,
+	},
+};
+
+static void net_device_release(struct device *dev)
+{
+	struct uml_net *device = dev_get_drvdata(dev);
+	struct net_device *netdev = device->dev;
+	struct uml_net_private *lp = netdev_priv(netdev);
+
+	if (lp->remove != NULL)
+		(*lp->remove)(&lp->user);
+	list_del(&device->list);
+	kfree(device);
+	free_netdev(netdev);
+}
+
+static const struct net_device_ops uml_netdev_ops = {
+	.ndo_open 		= uml_net_open,
+	.ndo_stop 		= uml_net_close,
+	.ndo_start_xmit 	= uml_net_start_xmit,
+	.ndo_set_rx_mode	= uml_net_set_multicast_list,
+	.ndo_tx_timeout 	= uml_net_tx_timeout,
+	.ndo_set_mac_address	= eth_mac_addr,
+	.ndo_validate_addr	= eth_validate_addr,
+#ifdef CONFIG_NET_POLL_CONTROLLER
+	.ndo_poll_controller = uml_net_poll_controller,
+#endif
+};
+
+/*
+ * Ensures that platform_driver_register is called only once by
+ * eth_configure.  Will be set in an initcall.
+ */
+static int driver_registered;
+
+static void eth_configure(int n, void *init, char *mac,
+			  struct transport *transport, gfp_t gfp_mask)
+{
+	struct uml_net *device;
+	struct net_device *dev;
+	struct uml_net_private *lp;
+	int err, size;
+
+	size = transport->private_size + sizeof(struct uml_net_private);
+
+	device = kzalloc(sizeof(*device), gfp_mask);
+	if (device == NULL) {
+		printk(KERN_ERR "eth_configure failed to allocate struct "
+		       "uml_net\n");
+		return;
+	}
+
+	dev = alloc_etherdev(size);
+	if (dev == NULL) {
+		printk(KERN_ERR "eth_configure: failed to allocate struct "
+		       "net_device for eth%d\n", n);
+		goto out_free_device;
+	}
+
+	INIT_LIST_HEAD(&device->list);
+	device->index = n;
+
+	/* If this name ends up conflicting with an existing registered
+	 * netdevice, that is OK, register_netdev{,ice}() will notice this
+	 * and fail.
+	 */
+	snprintf(dev->name, sizeof(dev->name), "eth%d", n);
+
+	uml_net_setup_etheraddr(dev, mac);
+
+	printk(KERN_INFO "Netdevice %d (%pM) : ", n, dev->dev_addr);
+
+	lp = netdev_priv(dev);
+	/* This points to the transport private data. It's still clear, but we
+	 * must memset it to 0 *now*. Let's help the drivers. */
+	memset(lp, 0, size);
+	INIT_WORK(&lp->work, uml_dev_close);
+
+	/* sysfs register */
+	if (!driver_registered) {
+		platform_driver_register(&uml_net_driver);
+		driver_registered = 1;
+	}
+	device->pdev.id = n;
+	device->pdev.name = DRIVER_NAME;
+	device->pdev.dev.release = net_device_release;
+	dev_set_drvdata(&device->pdev.dev, device);
+	if (platform_device_register(&device->pdev))
+		goto out_free_netdev;
+	SET_NETDEV_DEV(dev,&device->pdev.dev);
+
+	device->dev = dev;
+
+	/*
+	 * These just fill in a data structure, so there's no failure
+	 * to be worried about.
+	 */
+	(*transport->kern->init)(dev, init);
+
+	*lp = ((struct uml_net_private)
+		{ .list  		= LIST_HEAD_INIT(lp->list),
+		  .dev 			= dev,
+		  .fd 			= -1,
+		  .mac 			= { 0xfe, 0xfd, 0x0, 0x0, 0x0, 0x0},
+		  .max_packet		= transport->user->max_packet,
+		  .protocol 		= transport->kern->protocol,
+		  .open 		= transport->user->open,
+		  .close 		= transport->user->close,
+		  .remove 		= transport->user->remove,
+		  .read 		= transport->kern->read,
+		  .write 		= transport->kern->write,
+		  .add_address 		= transport->user->add_address,
+		  .delete_address  	= transport->user->delete_address });
+
+	spin_lock_init(&lp->lock);
+	memcpy(lp->mac, dev->dev_addr, sizeof(lp->mac));
+
+	if ((transport->user->init != NULL) &&
+	    ((*transport->user->init)(&lp->user, dev) != 0))
+		goto out_unregister;
+
+	dev->mtu = transport->user->mtu;
+	dev->netdev_ops = &uml_netdev_ops;
+	dev->ethtool_ops = &uml_net_ethtool_ops;
+	dev->watchdog_timeo = (HZ >> 1);
+	dev->irq = UM_ETH_IRQ;
+
+	err = update_drop_skb(lp->max_packet);
+	if (err)
+		goto out_undo_user_init;
+
+	rtnl_lock();
+	err = register_netdevice(dev);
+	rtnl_unlock();
+	if (err)
+		goto out_undo_user_init;
+
+	spin_lock(&devices_lock);
+	list_add(&device->list, &devices);
+	spin_unlock(&devices_lock);
+
+	return;
+
+out_undo_user_init:
+	if (transport->user->remove != NULL)
+		(*transport->user->remove)(&lp->user);
+out_unregister:
+	platform_device_unregister(&device->pdev);
+	return; /* platform_device_unregister frees dev and device */
+out_free_netdev:
+	free_netdev(dev);
+out_free_device:
+	kfree(device);
+}
+
+static struct uml_net *find_device(int n)
+{
+	struct uml_net *device;
+	struct list_head *ele;
+
+	spin_lock(&devices_lock);
+	list_for_each(ele, &devices) {
+		device = list_entry(ele, struct uml_net, list);
+		if (device->index == n)
+			goto out;
+	}
+	device = NULL;
+ out:
+	spin_unlock(&devices_lock);
+	return device;
+}
+
+static int eth_parse(char *str, int *index_out, char **str_out,
+		     char **error_out)
+{
+	char *end;
+	int n, err = -EINVAL;
+
+	n = simple_strtoul(str, &end, 0);
+	if (end == str) {
+		*error_out = "Bad device number";
+		return err;
+	}
+
+	str = end;
+	if (*str != '=') {
+		*error_out = "Expected '=' after device number";
+		return err;
+	}
+
+	str++;
+	if (find_device(n)) {
+		*error_out = "Device already configured";
+		return err;
+	}
+
+	*index_out = n;
+	*str_out = str;
+	return 0;
+}
+
+struct eth_init {
+	struct list_head list;
+	char *init;
+	int index;
+};
+
+static DEFINE_SPINLOCK(transports_lock);
+static LIST_HEAD(transports);
+
+/* Filled in during early boot */
+static LIST_HEAD(eth_cmd_line);
+
+static int check_transport(struct transport *transport, char *eth, int n,
+			   void **init_out, char **mac_out, gfp_t gfp_mask)
+{
+	int len;
+
+	len = strlen(transport->name);
+	if (strncmp(eth, transport->name, len))
+		return 0;
+
+	eth += len;
+	if (*eth == ',')
+		eth++;
+	else if (*eth != '\0')
+		return 0;
+
+	*init_out = kmalloc(transport->setup_size, gfp_mask);
+	if (*init_out == NULL)
+		return 1;
+
+	if (!transport->setup(eth, mac_out, *init_out)) {
+		kfree(*init_out);
+		*init_out = NULL;
+	}
+	return 1;
+}
+
+void register_transport(struct transport *new)
+{
+	struct list_head *ele, *next;
+	struct eth_init *eth;
+	void *init;
+	char *mac = NULL;
+	int match;
+
+	spin_lock(&transports_lock);
+	BUG_ON(!list_empty(&new->list));
+	list_add(&new->list, &transports);
+	spin_unlock(&transports_lock);
+
+	list_for_each_safe(ele, next, &eth_cmd_line) {
+		eth = list_entry(ele, struct eth_init, list);
+		match = check_transport(new, eth->init, eth->index, &init,
+					&mac, GFP_KERNEL);
+		if (!match)
+			continue;
+		else if (init != NULL) {
+			eth_configure(eth->index, init, mac, new, GFP_KERNEL);
+			kfree(init);
+		}
+		list_del(&eth->list);
+	}
+}
+
+static int eth_setup_common(char *str, int index)
+{
+	struct list_head *ele;
+	struct transport *transport;
+	void *init;
+	char *mac = NULL;
+	int found = 0;
+
+	spin_lock(&transports_lock);
+	list_for_each(ele, &transports) {
+		transport = list_entry(ele, struct transport, list);
+	        if (!check_transport(transport, str, index, &init,
+					&mac, GFP_ATOMIC))
+			continue;
+		if (init != NULL) {
+			eth_configure(index, init, mac, transport, GFP_ATOMIC);
+			kfree(init);
+		}
+		found = 1;
+		break;
+	}
+
+	spin_unlock(&transports_lock);
+	return found;
+}
+
+static int __init eth_setup(char *str)
+{
+	struct eth_init *new;
+	char *error;
+	int n, err;
+
+	err = eth_parse(str, &n, &str, &error);
+	if (err) {
+		printk(KERN_ERR "eth_setup - Couldn't parse '%s' : %s\n",
+		       str, error);
+		return 1;
+	}
+
+	new = memblock_alloc(sizeof(*new), SMP_CACHE_BYTES);
+	if (!new)
+		panic("%s: Failed to allocate %zu bytes\n", __func__,
+		      sizeof(*new));
+
+	INIT_LIST_HEAD(&new->list);
+	new->index = n;
+	new->init = str;
+
+	list_add_tail(&new->list, &eth_cmd_line);
+	return 1;
+}
+
+__setup("eth", eth_setup);
+__uml_help(eth_setup,
+"eth[0-9]+=<transport>,<options>\n"
+"    Configure a network device.\n\n"
+);
+
+static int net_config(char *str, char **error_out)
+{
+	int n, err;
+
+	err = eth_parse(str, &n, &str, error_out);
+	if (err)
+		return err;
+
+	/* This string is broken up and the pieces used by the underlying
+	 * driver.  So, it is freed only if eth_setup_common fails.
+	 */
+	str = kstrdup(str, GFP_KERNEL);
+	if (str == NULL) {
+	        *error_out = "net_config failed to strdup string";
+		return -ENOMEM;
+	}
+	err = !eth_setup_common(str, n);
+	if (err)
+		kfree(str);
+	return err;
+}
+
+static int net_id(char **str, int *start_out, int *end_out)
+{
+	char *end;
+	int n;
+
+	n = simple_strtoul(*str, &end, 0);
+	if ((*end != '\0') || (end == *str))
+		return -1;
+
+	*start_out = n;
+	*end_out = n;
+	*str = end;
+	return n;
+}
+
+static int net_remove(int n, char **error_out)
+{
+	struct uml_net *device;
+	struct net_device *dev;
+	struct uml_net_private *lp;
+
+	device = find_device(n);
+	if (device == NULL)
+		return -ENODEV;
+
+	dev = device->dev;
+	lp = netdev_priv(dev);
+	if (lp->fd > 0)
+		return -EBUSY;
+	unregister_netdev(dev);
+	platform_device_unregister(&device->pdev);
+
+	return 0;
+}
+
+static struct mc_device net_mc = {
+	.list		= LIST_HEAD_INIT(net_mc.list),
+	.name		= "eth",
+	.config		= net_config,
+	.get_config	= NULL,
+	.id		= net_id,
+	.remove		= net_remove,
+};
+
+#ifdef CONFIG_INET
+static int uml_inetaddr_event(struct notifier_block *this, unsigned long event,
+			      void *ptr)
+{
+	struct in_ifaddr *ifa = ptr;
+	struct net_device *dev = ifa->ifa_dev->dev;
+	struct uml_net_private *lp;
+	void (*proc)(unsigned char *, unsigned char *, void *);
+	unsigned char addr_buf[4], netmask_buf[4];
+
+	if (dev->netdev_ops->ndo_open != uml_net_open)
+		return NOTIFY_DONE;
+
+	lp = netdev_priv(dev);
+
+	proc = NULL;
+	switch (event) {
+	case NETDEV_UP:
+		proc = lp->add_address;
+		break;
+	case NETDEV_DOWN:
+		proc = lp->delete_address;
+		break;
+	}
+	if (proc != NULL) {
+		memcpy(addr_buf, &ifa->ifa_address, sizeof(addr_buf));
+		memcpy(netmask_buf, &ifa->ifa_mask, sizeof(netmask_buf));
+		(*proc)(addr_buf, netmask_buf, &lp->user);
+	}
+	return NOTIFY_DONE;
+}
+
+/* uml_net_init shouldn't be called twice on two CPUs at the same time */
+static struct notifier_block uml_inetaddr_notifier = {
+	.notifier_call		= uml_inetaddr_event,
+};
+
+static void inet_register(void)
+{
+	struct list_head *ele;
+	struct uml_net_private *lp;
+	struct in_device *ip;
+	struct in_ifaddr *in;
+
+	register_inetaddr_notifier(&uml_inetaddr_notifier);
+
+	/* Devices may have been opened already, so the uml_inetaddr_notifier
+	 * didn't get a chance to run for them.  This fakes it so that
+	 * addresses which have already been set up get handled properly.
+	 */
+	spin_lock(&opened_lock);
+	list_for_each(ele, &opened) {
+		lp = list_entry(ele, struct uml_net_private, list);
+		ip = lp->dev->ip_ptr;
+		if (ip == NULL)
+			continue;
+		in = ip->ifa_list;
+		while (in != NULL) {
+			uml_inetaddr_event(NULL, NETDEV_UP, in);
+			in = in->ifa_next;
+		}
+	}
+	spin_unlock(&opened_lock);
+}
+#else
+static inline void inet_register(void)
+{
+}
+#endif
+
+static int uml_net_init(void)
+{
+	mconsole_register_dev(&net_mc);
+	inet_register();
+	return 0;
+}
+
+__initcall(uml_net_init);
+
+static void close_devices(void)
+{
+	struct list_head *ele;
+	struct uml_net_private *lp;
+
+	spin_lock(&opened_lock);
+	list_for_each(ele, &opened) {
+		lp = list_entry(ele, struct uml_net_private, list);
+		um_free_irq(lp->dev->irq, lp->dev);
+		if ((lp->close != NULL) && (lp->fd >= 0))
+			(*lp->close)(lp->fd, &lp->user);
+		if (lp->remove != NULL)
+			(*lp->remove)(&lp->user);
+	}
+	spin_unlock(&opened_lock);
+}
+
+__uml_exitcall(close_devices);
+
+void iter_addresses(void *d, void (*cb)(unsigned char *, unsigned char *,
+					void *),
+		    void *arg)
+{
+	struct net_device *dev = d;
+	struct in_device *ip = dev->ip_ptr;
+	struct in_ifaddr *in;
+	unsigned char address[4], netmask[4];
+
+	if (ip == NULL) return;
+	in = ip->ifa_list;
+	while (in != NULL) {
+		memcpy(address, &in->ifa_address, sizeof(address));
+		memcpy(netmask, &in->ifa_mask, sizeof(netmask));
+		(*cb)(address, netmask, arg);
+		in = in->ifa_next;
+	}
+}
+
+int dev_netmask(void *d, void *m)
+{
+	struct net_device *dev = d;
+	struct in_device *ip = dev->ip_ptr;
+	struct in_ifaddr *in;
+	__be32 *mask_out = m;
+
+	if (ip == NULL)
+		return 1;
+
+	in = ip->ifa_list;
+	if (in == NULL)
+		return 1;
+
+	*mask_out = in->ifa_mask;
+	return 0;
+}
+
+void *get_output_buffer(int *len_out)
+{
+	void *ret;
+
+	ret = (void *) __get_free_pages(GFP_KERNEL, 0);
+	if (ret) *len_out = PAGE_SIZE;
+	else *len_out = 0;
+	return ret;
+}
+
+void free_output_buffer(void *buffer)
+{
+	free_pages((unsigned long) buffer, 0);
+}
+
+int tap_setup_common(char *str, char *type, char **dev_name, char **mac_out,
+		     char **gate_addr)
+{
+	char *remain;
+
+	remain = split_if_spec(str, dev_name, mac_out, gate_addr, NULL);
+	if (remain != NULL) {
+		printk(KERN_ERR "tap_setup_common - Extra garbage on "
+		       "specification : '%s'\n", remain);
+		return 1;
+	}
+
+	return 0;
+}
+
+unsigned short eth_protocol(struct sk_buff *skb)
+{
+	return eth_type_trans(skb, skb->dev);
+}
diff --git a/arch/um/drivers/net_user.c b/arch/um/drivers/net_user.c
new file mode 100644
index 000000000..4c9576452
--- /dev/null
+++ b/arch/um/drivers/net_user.c
@@ -0,0 +1,271 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdarg.h>
+#include <errno.h>
+#include <stddef.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <net_user.h>
+#include <os.h>
+#include <um_malloc.h>
+
+int tap_open_common(void *dev, char *gate_addr)
+{
+	int tap_addr[4];
+
+	if (gate_addr == NULL)
+		return 0;
+	if (sscanf(gate_addr, "%d.%d.%d.%d", &tap_addr[0],
+		  &tap_addr[1], &tap_addr[2], &tap_addr[3]) != 4) {
+		printk(UM_KERN_ERR "Invalid tap IP address - '%s'\n",
+		       gate_addr);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+void tap_check_ips(char *gate_addr, unsigned char *eth_addr)
+{
+	int tap_addr[4];
+
+	if ((gate_addr != NULL) &&
+	    (sscanf(gate_addr, "%d.%d.%d.%d", &tap_addr[0],
+		    &tap_addr[1], &tap_addr[2], &tap_addr[3]) == 4) &&
+	    (eth_addr[0] == tap_addr[0]) &&
+	    (eth_addr[1] == tap_addr[1]) &&
+	    (eth_addr[2] == tap_addr[2]) &&
+	    (eth_addr[3] == tap_addr[3])) {
+		printk(UM_KERN_ERR "The tap IP address and the UML eth IP "
+		       "address must be different\n");
+	}
+}
+
+/* Do reliable error handling as this fails frequently enough. */
+void read_output(int fd, char *output, int len)
+{
+	int remain, ret, expected;
+	char c;
+	char *str;
+
+	if (output == NULL) {
+		output = &c;
+		len = sizeof(c);
+	}
+
+	*output = '\0';
+	ret = read(fd, &remain, sizeof(remain));
+
+	if (ret != sizeof(remain)) {
+		if (ret < 0)
+			ret = -errno;
+		expected = sizeof(remain);
+		str = "length";
+		goto err;
+	}
+
+	while (remain != 0) {
+		expected = (remain < len) ? remain : len;
+		ret = read(fd, output, expected);
+		if (ret != expected) {
+			if (ret < 0)
+				ret = -errno;
+			str = "data";
+			goto err;
+		}
+		remain -= ret;
+	}
+
+	return;
+
+err:
+	if (ret < 0)
+		printk(UM_KERN_ERR "read_output - read of %s failed, "
+		       "errno = %d\n", str, -ret);
+	else
+		printk(UM_KERN_ERR "read_output - read of %s failed, read only "
+		       "%d of %d bytes\n", str, ret, expected);
+}
+
+int net_read(int fd, void *buf, int len)
+{
+	int n;
+
+	n = read(fd,  buf,  len);
+
+	if ((n < 0) && (errno == EAGAIN))
+		return 0;
+	else if (n == 0)
+		return -ENOTCONN;
+	return n;
+}
+
+int net_recvfrom(int fd, void *buf, int len)
+{
+	int n;
+
+	CATCH_EINTR(n = recvfrom(fd,  buf,  len, 0, NULL, NULL));
+	if (n < 0) {
+		if (errno == EAGAIN)
+			return 0;
+		return -errno;
+	}
+	else if (n == 0)
+		return -ENOTCONN;
+	return n;
+}
+
+int net_write(int fd, void *buf, int len)
+{
+	int n;
+
+	n = write(fd, buf, len);
+
+	if ((n < 0) && (errno == EAGAIN))
+		return 0;
+	else if (n == 0)
+		return -ENOTCONN;
+	return n;
+}
+
+int net_send(int fd, void *buf, int len)
+{
+	int n;
+
+	CATCH_EINTR(n = send(fd, buf, len, 0));
+	if (n < 0) {
+		if (errno == EAGAIN)
+			return 0;
+		return -errno;
+	}
+	else if (n == 0)
+		return -ENOTCONN;
+	return n;
+}
+
+int net_sendto(int fd, void *buf, int len, void *to, int sock_len)
+{
+	int n;
+
+	CATCH_EINTR(n = sendto(fd, buf, len, 0, (struct sockaddr *) to,
+			       sock_len));
+	if (n < 0) {
+		if (errno == EAGAIN)
+			return 0;
+		return -errno;
+	}
+	else if (n == 0)
+		return -ENOTCONN;
+	return n;
+}
+
+struct change_pre_exec_data {
+	int close_me;
+	int stdout_fd;
+};
+
+static void change_pre_exec(void *arg)
+{
+	struct change_pre_exec_data *data = arg;
+
+	close(data->close_me);
+	dup2(data->stdout_fd, 1);
+}
+
+static int change_tramp(char **argv, char *output, int output_len)
+{
+	int pid, fds[2], err;
+	struct change_pre_exec_data pe_data;
+
+	err = os_pipe(fds, 1, 0);
+	if (err < 0) {
+		printk(UM_KERN_ERR "change_tramp - pipe failed, err = %d\n",
+		       -err);
+		return err;
+	}
+	pe_data.close_me = fds[0];
+	pe_data.stdout_fd = fds[1];
+	pid = run_helper(change_pre_exec, &pe_data, argv);
+
+	if (pid > 0)	/* Avoid hang as we won't get data in failure case. */
+		read_output(fds[0], output, output_len);
+
+	close(fds[0]);
+	close(fds[1]);
+
+	if (pid > 0)
+		helper_wait(pid);
+	return pid;
+}
+
+static void change(char *dev, char *what, unsigned char *addr,
+		   unsigned char *netmask)
+{
+	char addr_buf[sizeof("255.255.255.255\0")];
+	char netmask_buf[sizeof("255.255.255.255\0")];
+	char version[sizeof("nnnnn\0")];
+	char *argv[] = { "uml_net", version, what, dev, addr_buf,
+			 netmask_buf, NULL };
+	char *output;
+	int output_len, pid;
+
+	sprintf(version, "%d", UML_NET_VERSION);
+	sprintf(addr_buf, "%d.%d.%d.%d", addr[0], addr[1], addr[2], addr[3]);
+	sprintf(netmask_buf, "%d.%d.%d.%d", netmask[0], netmask[1],
+		netmask[2], netmask[3]);
+
+	output_len = UM_KERN_PAGE_SIZE;
+	output = uml_kmalloc(output_len, UM_GFP_KERNEL);
+	if (output == NULL)
+		printk(UM_KERN_ERR "change : failed to allocate output "
+		       "buffer\n");
+
+	pid = change_tramp(argv, output, output_len);
+	if (pid < 0) {
+		kfree(output);
+		return;
+	}
+
+	if (output != NULL) {
+		printk("%s", output);
+		kfree(output);
+	}
+}
+
+void open_addr(unsigned char *addr, unsigned char *netmask, void *arg)
+{
+	change(arg, "add", addr, netmask);
+}
+
+void close_addr(unsigned char *addr, unsigned char *netmask, void *arg)
+{
+	change(arg, "del", addr, netmask);
+}
+
+char *split_if_spec(char *str, ...)
+{
+	char **arg, *end, *ret = NULL;
+	va_list ap;
+
+	va_start(ap, str);
+	while ((arg = va_arg(ap, char **)) != NULL) {
+		if (*str == '\0')
+			goto out;
+		end = strchr(str, ',');
+		if (end != str)
+			*arg = str;
+		if (end == NULL)
+			goto out;
+		*end++ = '\0';
+		str = end;
+	}
+	ret = str;
+out:
+	va_end(ap);
+	return ret;
+}
diff --git a/arch/um/drivers/null.c b/arch/um/drivers/null.c
new file mode 100644
index 000000000..87087763a
--- /dev/null
+++ b/arch/um/drivers/null.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
+ */
+
+#include <stddef.h>
+#include <errno.h>
+#include <fcntl.h>
+#include "chan_user.h"
+#include <os.h>
+
+/* This address is used only as a unique identifier */
+static int null_chan;
+
+static void *null_init(char *str, int device, const struct chan_opts *opts)
+{
+	return &null_chan;
+}
+
+static int null_open(int input, int output, int primary, void *d,
+		     char **dev_out)
+{
+	int fd;
+
+	*dev_out = NULL;
+
+	fd = open(DEV_NULL, O_RDWR);
+	return (fd < 0) ? -errno : fd;
+}
+
+static int null_read(int fd, char *c_out, void *unused)
+{
+	return -ENODEV;
+}
+
+static void null_free(void *data)
+{
+}
+
+const struct chan_ops null_ops = {
+	.type		= "null",
+	.init		= null_init,
+	.open		= null_open,
+	.close		= generic_close,
+	.read		= null_read,
+	.write		= generic_write,
+	.console_write	= generic_console_write,
+	.window_size	= generic_window_size,
+	.free		= null_free,
+	.winch		= 0,
+};
diff --git a/arch/um/drivers/pcap_kern.c b/arch/um/drivers/pcap_kern.c
new file mode 100644
index 000000000..cfe4cb176
--- /dev/null
+++ b/arch/um/drivers/pcap_kern.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <linux/init.h>
+#include <linux/netdevice.h>
+#include <net_kern.h>
+#include "pcap_user.h"
+
+struct pcap_init {
+	char *host_if;
+	int promisc;
+	int optimize;
+	char *filter;
+};
+
+void pcap_init(struct net_device *dev, void *data)
+{
+	struct uml_net_private *pri;
+	struct pcap_data *ppri;
+	struct pcap_init *init = data;
+
+	pri = netdev_priv(dev);
+	ppri = (struct pcap_data *) pri->user;
+	ppri->host_if = init->host_if;
+	ppri->promisc = init->promisc;
+	ppri->optimize = init->optimize;
+	ppri->filter = init->filter;
+
+	printk("pcap backend, host interface %s\n", ppri->host_if);
+}
+
+static int pcap_read(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	return pcap_user_read(fd, skb_mac_header(skb),
+			      skb->dev->mtu + ETH_HEADER_OTHER,
+			      (struct pcap_data *) &lp->user);
+}
+
+static int pcap_write(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	return -EPERM;
+}
+
+static const struct net_kern_info pcap_kern_info = {
+	.init			= pcap_init,
+	.protocol		= eth_protocol,
+	.read			= pcap_read,
+	.write			= pcap_write,
+};
+
+int pcap_setup(char *str, char **mac_out, void *data)
+{
+	struct pcap_init *init = data;
+	char *remain, *host_if = NULL, *options[2] = { NULL, NULL };
+	int i;
+
+	*init = ((struct pcap_init)
+		{ .host_if 	= "eth0",
+		  .promisc 	= 1,
+		  .optimize 	= 0,
+		  .filter 	= NULL });
+
+	remain = split_if_spec(str, &host_if, &init->filter,
+			       &options[0], &options[1], mac_out, NULL);
+	if (remain != NULL) {
+		printk(KERN_ERR "pcap_setup - Extra garbage on "
+		       "specification : '%s'\n", remain);
+		return 0;
+	}
+
+	if (host_if != NULL)
+		init->host_if = host_if;
+
+	for (i = 0; i < ARRAY_SIZE(options); i++) {
+		if (options[i] == NULL)
+			continue;
+		if (!strcmp(options[i], "promisc"))
+			init->promisc = 1;
+		else if (!strcmp(options[i], "nopromisc"))
+			init->promisc = 0;
+		else if (!strcmp(options[i], "optimize"))
+			init->optimize = 1;
+		else if (!strcmp(options[i], "nooptimize"))
+			init->optimize = 0;
+		else {
+			printk(KERN_ERR "pcap_setup : bad option - '%s'\n",
+			       options[i]);
+			return 0;
+		}
+	}
+
+	return 1;
+}
+
+static struct transport pcap_transport = {
+	.list 		= LIST_HEAD_INIT(pcap_transport.list),
+	.name 		= "pcap",
+	.setup  	= pcap_setup,
+	.user 		= &pcap_user_info,
+	.kern 		= &pcap_kern_info,
+	.private_size 	= sizeof(struct pcap_data),
+	.setup_size 	= sizeof(struct pcap_init),
+};
+
+static int register_pcap(void)
+{
+	register_transport(&pcap_transport);
+	return 0;
+}
+
+late_initcall(register_pcap);
diff --git a/arch/um/drivers/pcap_user.c b/arch/um/drivers/pcap_user.c
new file mode 100644
index 000000000..52ddda3e3
--- /dev/null
+++ b/arch/um/drivers/pcap_user.c
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <errno.h>
+#include <pcap.h>
+#include <string.h>
+#include <asm/types.h>
+#include <net_user.h>
+#include "pcap_user.h"
+#include <um_malloc.h>
+
+#define PCAP_FD(p) (*(int *)(p))
+
+static int pcap_user_init(void *data, void *dev)
+{
+	struct pcap_data *pri = data;
+	pcap_t *p;
+	char errors[PCAP_ERRBUF_SIZE];
+
+	p = pcap_open_live(pri->host_if, ETH_MAX_PACKET + ETH_HEADER_OTHER,
+			   pri->promisc, 0, errors);
+	if (p == NULL) {
+		printk(UM_KERN_ERR "pcap_user_init : pcap_open_live failed - "
+		       "'%s'\n", errors);
+		return -EINVAL;
+	}
+
+	pri->dev = dev;
+	pri->pcap = p;
+	return 0;
+}
+
+static int pcap_user_open(void *data)
+{
+	struct pcap_data *pri = data;
+	__u32 netmask;
+	int err;
+
+	if (pri->pcap == NULL)
+		return -ENODEV;
+
+	if (pri->filter != NULL) {
+		err = dev_netmask(pri->dev, &netmask);
+		if (err < 0) {
+			printk(UM_KERN_ERR "pcap_user_open : dev_netmask failed\n");
+			return -EIO;
+		}
+
+		pri->compiled = uml_kmalloc(sizeof(struct bpf_program),
+					UM_GFP_KERNEL);
+		if (pri->compiled == NULL) {
+			printk(UM_KERN_ERR "pcap_user_open : kmalloc failed\n");
+			return -ENOMEM;
+		}
+
+		err = pcap_compile(pri->pcap,
+				   (struct bpf_program *) pri->compiled,
+				   pri->filter, pri->optimize, netmask);
+		if (err < 0) {
+			printk(UM_KERN_ERR "pcap_user_open : pcap_compile failed - "
+			       "'%s'\n", pcap_geterr(pri->pcap));
+			goto out;
+		}
+
+		err = pcap_setfilter(pri->pcap, pri->compiled);
+		if (err < 0) {
+			printk(UM_KERN_ERR "pcap_user_open : pcap_setfilter "
+			       "failed - '%s'\n", pcap_geterr(pri->pcap));
+			goto out;
+		}
+	}
+
+	return PCAP_FD(pri->pcap);
+
+ out:
+	kfree(pri->compiled);
+	return -EIO;
+}
+
+static void pcap_remove(void *data)
+{
+	struct pcap_data *pri = data;
+
+	if (pri->compiled != NULL)
+		pcap_freecode(pri->compiled);
+
+	if (pri->pcap != NULL)
+		pcap_close(pri->pcap);
+}
+
+struct pcap_handler_data {
+	char *buffer;
+	int len;
+};
+
+static void handler(u_char *data, const struct pcap_pkthdr *header,
+		    const u_char *packet)
+{
+	int len;
+
+	struct pcap_handler_data *hdata = (struct pcap_handler_data *) data;
+
+	len = hdata->len < header->caplen ? hdata->len : header->caplen;
+	memcpy(hdata->buffer, packet, len);
+	hdata->len = len;
+}
+
+int pcap_user_read(int fd, void *buffer, int len, struct pcap_data *pri)
+{
+	struct pcap_handler_data hdata = ((struct pcap_handler_data)
+		                          { .buffer  	= buffer,
+					    .len 	= len });
+	int n;
+
+	n = pcap_dispatch(pri->pcap, 1, handler, (u_char *) &hdata);
+	if (n < 0) {
+		printk(UM_KERN_ERR "pcap_dispatch failed - %s\n",
+		       pcap_geterr(pri->pcap));
+		return -EIO;
+	}
+	else if (n == 0)
+		return 0;
+	return hdata.len;
+}
+
+const struct net_user_info pcap_user_info = {
+	.init		= pcap_user_init,
+	.open		= pcap_user_open,
+	.close	 	= NULL,
+	.remove	 	= pcap_remove,
+	.add_address	= NULL,
+	.delete_address = NULL,
+	.mtu		= ETH_MAX_PACKET,
+	.max_packet	= ETH_MAX_PACKET + ETH_HEADER_OTHER,
+};
diff --git a/arch/um/drivers/pcap_user.h b/arch/um/drivers/pcap_user.h
new file mode 100644
index 000000000..216246f5f
--- /dev/null
+++ b/arch/um/drivers/pcap_user.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* 
+ * Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
+ */
+
+#include <net_user.h>
+
+struct pcap_data {
+	char *host_if;
+	int promisc;
+	int optimize;
+	char *filter;
+	void *compiled;
+	void *pcap;
+	void *dev;
+};
+
+extern const struct net_user_info pcap_user_info;
+
+extern int pcap_user_read(int fd, void *buf, int len, struct pcap_data *pri);
+
diff --git a/arch/um/drivers/port.h b/arch/um/drivers/port.h
new file mode 100644
index 000000000..9085b336e
--- /dev/null
+++ b/arch/um/drivers/port.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* 
+ * Copyright (C) 2001 Jeff Dike (jdike@karaya.com)
+ */
+
+#ifndef __PORT_H__
+#define __PORT_H__
+
+extern void *port_data(int port);
+extern int port_wait(void *data);
+extern void port_kern_close(void *d);
+extern int port_connection(int fd, int *socket_out, int *pid_out);
+extern int port_listen_fd(int port);
+extern void port_read(int fd, void *data);
+extern void port_kern_free(void *d);
+extern int port_rcv_fd(int fd);
+extern void port_remove_dev(void *d);
+
+#endif
+
diff --git a/arch/um/drivers/port_kern.c b/arch/um/drivers/port_kern.c
new file mode 100644
index 000000000..efa8b7304
--- /dev/null
+++ b/arch/um/drivers/port_kern.c
@@ -0,0 +1,303 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
+ */
+
+#include <linux/completion.h>
+#include <linux/interrupt.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include <asm/atomic.h>
+#include <init.h>
+#include <irq_kern.h>
+#include <os.h>
+#include "port.h"
+
+struct port_list {
+	struct list_head list;
+	atomic_t wait_count;
+	int has_connection;
+	struct completion done;
+	int port;
+	int fd;
+	spinlock_t lock;
+	struct list_head pending;
+	struct list_head connections;
+};
+
+struct port_dev {
+	struct port_list *port;
+	int helper_pid;
+	int telnetd_pid;
+};
+
+struct connection {
+	struct list_head list;
+	int fd;
+	int helper_pid;
+	int socket[2];
+	int telnetd_pid;
+	struct port_list *port;
+};
+
+static irqreturn_t pipe_interrupt(int irq, void *data)
+{
+	struct connection *conn = data;
+	int fd;
+
+	fd = os_rcv_fd(conn->socket[0], &conn->helper_pid);
+	if (fd < 0) {
+		if (fd == -EAGAIN)
+			return IRQ_NONE;
+
+		printk(KERN_ERR "pipe_interrupt : os_rcv_fd returned %d\n",
+		       -fd);
+		os_close_file(conn->fd);
+	}
+
+	list_del(&conn->list);
+
+	conn->fd = fd;
+	list_add(&conn->list, &conn->port->connections);
+
+	complete(&conn->port->done);
+	return IRQ_HANDLED;
+}
+
+#define NO_WAITER_MSG \
+    "****\n" \
+    "There are currently no UML consoles waiting for port connections.\n" \
+    "Either disconnect from one to make it available or activate some more\n" \
+    "by enabling more consoles in the UML /etc/inittab.\n" \
+    "****\n"
+
+static int port_accept(struct port_list *port)
+{
+	struct connection *conn;
+	int fd, socket[2], pid;
+
+	fd = port_connection(port->fd, socket, &pid);
+	if (fd < 0) {
+		if (fd != -EAGAIN)
+			printk(KERN_ERR "port_accept : port_connection "
+			       "returned %d\n", -fd);
+		goto out;
+	}
+
+	conn = kmalloc(sizeof(*conn), GFP_ATOMIC);
+	if (conn == NULL) {
+		printk(KERN_ERR "port_accept : failed to allocate "
+		       "connection\n");
+		goto out_close;
+	}
+	*conn = ((struct connection)
+		{ .list 	= LIST_HEAD_INIT(conn->list),
+		  .fd 		= fd,
+		  .socket  	= { socket[0], socket[1] },
+		  .telnetd_pid 	= pid,
+		  .port 	= port });
+
+	if (um_request_irq(TELNETD_IRQ, socket[0], IRQ_READ, pipe_interrupt,
+			  IRQF_SHARED, "telnetd", conn) < 0) {
+		printk(KERN_ERR "port_accept : failed to get IRQ for "
+		       "telnetd\n");
+		goto out_free;
+	}
+
+	if (atomic_read(&port->wait_count) == 0) {
+		os_write_file(fd, NO_WAITER_MSG, sizeof(NO_WAITER_MSG));
+		printk(KERN_ERR "No one waiting for port\n");
+	}
+	list_add(&conn->list, &port->pending);
+	return 1;
+
+ out_free:
+	kfree(conn);
+ out_close:
+	os_close_file(fd);
+	os_kill_process(pid, 1);
+ out:
+	return 0;
+}
+
+static DEFINE_MUTEX(ports_mutex);
+static LIST_HEAD(ports);
+
+static void port_work_proc(struct work_struct *unused)
+{
+	struct port_list *port;
+	struct list_head *ele;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	list_for_each(ele, &ports) {
+		port = list_entry(ele, struct port_list, list);
+		if (!port->has_connection)
+			continue;
+
+		while (port_accept(port))
+			;
+		port->has_connection = 0;
+	}
+	local_irq_restore(flags);
+}
+
+DECLARE_WORK(port_work, port_work_proc);
+
+static irqreturn_t port_interrupt(int irq, void *data)
+{
+	struct port_list *port = data;
+
+	port->has_connection = 1;
+	schedule_work(&port_work);
+	return IRQ_HANDLED;
+}
+
+void *port_data(int port_num)
+{
+	struct list_head *ele;
+	struct port_list *port;
+	struct port_dev *dev = NULL;
+	int fd;
+
+	mutex_lock(&ports_mutex);
+	list_for_each(ele, &ports) {
+		port = list_entry(ele, struct port_list, list);
+		if (port->port == port_num)
+			goto found;
+	}
+	port = kmalloc(sizeof(struct port_list), GFP_KERNEL);
+	if (port == NULL) {
+		printk(KERN_ERR "Allocation of port list failed\n");
+		goto out;
+	}
+
+	fd = port_listen_fd(port_num);
+	if (fd < 0) {
+		printk(KERN_ERR "binding to port %d failed, errno = %d\n",
+		       port_num, -fd);
+		goto out_free;
+	}
+
+	if (um_request_irq(ACCEPT_IRQ, fd, IRQ_READ, port_interrupt,
+			  IRQF_SHARED, "port", port) < 0) {
+		printk(KERN_ERR "Failed to get IRQ for port %d\n", port_num);
+		goto out_close;
+	}
+
+	*port = ((struct port_list)
+		{ .list 	 	= LIST_HEAD_INIT(port->list),
+		  .wait_count		= ATOMIC_INIT(0),
+		  .has_connection 	= 0,
+		  .port 	 	= port_num,
+		  .fd  			= fd,
+		  .pending 		= LIST_HEAD_INIT(port->pending),
+		  .connections 		= LIST_HEAD_INIT(port->connections) });
+	spin_lock_init(&port->lock);
+	init_completion(&port->done);
+	list_add(&port->list, &ports);
+
+ found:
+	dev = kmalloc(sizeof(struct port_dev), GFP_KERNEL);
+	if (dev == NULL) {
+		printk(KERN_ERR "Allocation of port device entry failed\n");
+		goto out;
+	}
+
+	*dev = ((struct port_dev) { .port  		= port,
+				    .helper_pid  	= -1,
+				    .telnetd_pid  	= -1 });
+	goto out;
+
+ out_close:
+	os_close_file(fd);
+ out_free:
+	kfree(port);
+ out:
+	mutex_unlock(&ports_mutex);
+	return dev;
+}
+
+int port_wait(void *data)
+{
+	struct port_dev *dev = data;
+	struct connection *conn;
+	struct port_list *port = dev->port;
+	int fd;
+
+	atomic_inc(&port->wait_count);
+	while (1) {
+		fd = -ERESTARTSYS;
+		if (wait_for_completion_interruptible(&port->done))
+			goto out;
+
+		spin_lock(&port->lock);
+
+		conn = list_entry(port->connections.next, struct connection,
+				  list);
+		list_del(&conn->list);
+		spin_unlock(&port->lock);
+
+		os_shutdown_socket(conn->socket[0], 1, 1);
+		os_close_file(conn->socket[0]);
+		os_shutdown_socket(conn->socket[1], 1, 1);
+		os_close_file(conn->socket[1]);
+
+		/* This is done here because freeing an IRQ can't be done
+		 * within the IRQ handler.  So, pipe_interrupt always ups
+		 * the semaphore regardless of whether it got a successful
+		 * connection.  Then we loop here throwing out failed
+		 * connections until a good one is found.
+		 */
+		um_free_irq(TELNETD_IRQ, conn);
+
+		if (conn->fd >= 0)
+			break;
+		os_close_file(conn->fd);
+		kfree(conn);
+	}
+
+	fd = conn->fd;
+	dev->helper_pid = conn->helper_pid;
+	dev->telnetd_pid = conn->telnetd_pid;
+	kfree(conn);
+ out:
+	atomic_dec(&port->wait_count);
+	return fd;
+}
+
+void port_remove_dev(void *d)
+{
+	struct port_dev *dev = d;
+
+	if (dev->helper_pid != -1)
+		os_kill_process(dev->helper_pid, 0);
+	if (dev->telnetd_pid != -1)
+		os_kill_process(dev->telnetd_pid, 1);
+	dev->helper_pid = -1;
+	dev->telnetd_pid = -1;
+}
+
+void port_kern_free(void *d)
+{
+	struct port_dev *dev = d;
+
+	port_remove_dev(dev);
+	kfree(dev);
+}
+
+static void free_port(void)
+{
+	struct list_head *ele;
+	struct port_list *port;
+
+	list_for_each(ele, &ports) {
+		port = list_entry(ele, struct port_list, list);
+		free_irq_by_fd(port->fd);
+		os_close_file(port->fd);
+	}
+}
+
+__uml_exitcall(free_port);
diff --git a/arch/um/drivers/port_user.c b/arch/um/drivers/port_user.c
new file mode 100644
index 000000000..3c62ae81d
--- /dev/null
+++ b/arch/um/drivers/port_user.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <termios.h>
+#include <unistd.h>
+#include <netinet/in.h>
+#include "chan_user.h"
+#include <os.h>
+#include "port.h"
+#include <um_malloc.h>
+
+struct port_chan {
+	int raw;
+	struct termios tt;
+	void *kernel_data;
+	char dev[sizeof("32768\0")];
+};
+
+static void *port_init(char *str, int device, const struct chan_opts *opts)
+{
+	struct port_chan *data;
+	void *kern_data;
+	char *end;
+	int port;
+
+	if (*str != ':') {
+		printk(UM_KERN_ERR "port_init : channel type 'port' must "
+		       "specify a port number\n");
+		return NULL;
+	}
+	str++;
+	port = strtoul(str, &end, 0);
+	if ((*end != '\0') || (end == str)) {
+		printk(UM_KERN_ERR "port_init : couldn't parse port '%s'\n",
+		       str);
+		return NULL;
+	}
+
+	kern_data = port_data(port);
+	if (kern_data == NULL)
+		return NULL;
+
+	data = uml_kmalloc(sizeof(*data), UM_GFP_KERNEL);
+	if (data == NULL)
+		goto err;
+
+	*data = ((struct port_chan) { .raw  		= opts->raw,
+				      .kernel_data 	= kern_data });
+	sprintf(data->dev, "%d", port);
+
+	return data;
+ err:
+	port_kern_free(kern_data);
+	return NULL;
+}
+
+static void port_free(void *d)
+{
+	struct port_chan *data = d;
+
+	port_kern_free(data->kernel_data);
+	kfree(data);
+}
+
+static int port_open(int input, int output, int primary, void *d,
+		     char **dev_out)
+{
+	struct port_chan *data = d;
+	int fd, err;
+
+	fd = port_wait(data->kernel_data);
+	if ((fd >= 0) && data->raw) {
+		CATCH_EINTR(err = tcgetattr(fd, &data->tt));
+		if (err)
+			return err;
+
+		err = raw(fd);
+		if (err)
+			return err;
+	}
+	*dev_out = data->dev;
+	return fd;
+}
+
+static void port_close(int fd, void *d)
+{
+	struct port_chan *data = d;
+
+	port_remove_dev(data->kernel_data);
+	os_close_file(fd);
+}
+
+const struct chan_ops port_ops = {
+	.type		= "port",
+	.init		= port_init,
+	.open		= port_open,
+	.close		= port_close,
+	.read	        = generic_read,
+	.write		= generic_write,
+	.console_write	= generic_console_write,
+	.window_size	= generic_window_size,
+	.free		= port_free,
+	.winch		= 1,
+};
+
+int port_listen_fd(int port)
+{
+	struct sockaddr_in addr;
+	int fd, err, arg;
+
+	fd = socket(PF_INET, SOCK_STREAM, 0);
+	if (fd == -1)
+		return -errno;
+
+	arg = 1;
+	if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &arg, sizeof(arg)) < 0) {
+		err = -errno;
+		goto out;
+	}
+
+	addr.sin_family = AF_INET;
+	addr.sin_port = htons(port);
+	addr.sin_addr.s_addr = htonl(INADDR_ANY);
+	if (bind(fd, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
+		err = -errno;
+		goto out;
+	}
+
+	if (listen(fd, 1) < 0) {
+		err = -errno;
+		goto out;
+	}
+
+	err = os_set_fd_block(fd, 0);
+	if (err < 0)
+		goto out;
+
+	return fd;
+ out:
+	close(fd);
+	return err;
+}
+
+struct port_pre_exec_data {
+	int sock_fd;
+	int pipe_fd;
+};
+
+static void port_pre_exec(void *arg)
+{
+	struct port_pre_exec_data *data = arg;
+
+	dup2(data->sock_fd, 0);
+	dup2(data->sock_fd, 1);
+	dup2(data->sock_fd, 2);
+	close(data->sock_fd);
+	dup2(data->pipe_fd, 3);
+	shutdown(3, SHUT_RD);
+	close(data->pipe_fd);
+}
+
+int port_connection(int fd, int *socket, int *pid_out)
+{
+	int new, err;
+	char *env;
+	char *argv[] = { "in.telnetd", "-L",
+			 OS_LIB_PATH "/uml/port-helper", NULL };
+	struct port_pre_exec_data data;
+
+	if ((env = getenv("UML_PORT_HELPER")))
+		argv[2] = env;
+
+	new = accept(fd, NULL, 0);
+	if (new < 0)
+		return -errno;
+
+	err = os_access(argv[2], X_OK);
+	if (err < 0) {
+		printk(UM_KERN_ERR "port_connection : error accessing port-helper "
+		       "executable at %s: %s\n", argv[2], strerror(-err));
+		if (env == NULL)
+			printk(UM_KERN_ERR "Set UML_PORT_HELPER environment "
+				"variable to path to uml-utilities port-helper "
+				"binary\n");
+		goto out_close;
+	}
+
+	err = os_pipe(socket, 0, 0);
+	if (err < 0)
+		goto out_close;
+
+	data = ((struct port_pre_exec_data)
+		{ .sock_fd  		= new,
+		  .pipe_fd 		= socket[1] });
+
+	err = run_helper(port_pre_exec, &data, argv);
+	if (err < 0)
+		goto out_shutdown;
+
+	*pid_out = err;
+	return new;
+
+ out_shutdown:
+	shutdown(socket[0], SHUT_RDWR);
+	close(socket[0]);
+	shutdown(socket[1], SHUT_RDWR);
+	close(socket[1]);
+ out_close:
+	close(new);
+	return err;
+}
diff --git a/arch/um/drivers/pty.c b/arch/um/drivers/pty.c
new file mode 100644
index 000000000..39c60068c
--- /dev/null
+++ b/arch/um/drivers/pty.c
@@ -0,0 +1,165 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <termios.h>
+#include <sys/stat.h>
+#include "chan_user.h"
+#include <os.h>
+#include <um_malloc.h>
+
+struct pty_chan {
+	void (*announce)(char *dev_name, int dev);
+	int dev;
+	int raw;
+	struct termios tt;
+	char dev_name[sizeof("/dev/pts/0123456\0")];
+};
+
+static void *pty_chan_init(char *str, int device, const struct chan_opts *opts)
+{
+	struct pty_chan *data;
+
+	data = uml_kmalloc(sizeof(*data), UM_GFP_KERNEL);
+	if (data == NULL)
+		return NULL;
+
+	*data = ((struct pty_chan) { .announce  	= opts->announce,
+				     .dev  		= device,
+				     .raw  		= opts->raw });
+	return data;
+}
+
+static int pts_open(int input, int output, int primary, void *d,
+		    char **dev_out)
+{
+	struct pty_chan *data = d;
+	char *dev;
+	int fd, err;
+
+	fd = get_pty();
+	if (fd < 0) {
+		err = -errno;
+		printk(UM_KERN_ERR "open_pts : Failed to open pts\n");
+		return err;
+	}
+
+	if (data->raw) {
+		CATCH_EINTR(err = tcgetattr(fd, &data->tt));
+		if (err)
+			goto out_close;
+
+		err = raw(fd);
+		if (err)
+			goto out_close;
+	}
+
+	dev = ptsname(fd);
+	sprintf(data->dev_name, "%s", dev);
+	*dev_out = data->dev_name;
+
+	if (data->announce)
+		(*data->announce)(dev, data->dev);
+
+	return fd;
+
+out_close:
+	close(fd);
+	return err;
+}
+
+static int getmaster(char *line)
+{
+	struct stat buf;
+	char *pty, *bank, *cp;
+	int master, err;
+
+	pty = &line[strlen("/dev/ptyp")];
+	for (bank = "pqrs"; *bank; bank++) {
+		line[strlen("/dev/pty")] = *bank;
+		*pty = '0';
+		/* Did we hit the end ? */
+		if ((stat(line, &buf) < 0) && (errno == ENOENT))
+			break;
+
+		for (cp = "0123456789abcdef"; *cp; cp++) {
+			*pty = *cp;
+			master = open(line, O_RDWR);
+			if (master >= 0) {
+				char *tp = &line[strlen("/dev/")];
+
+				/* verify slave side is usable */
+				*tp = 't';
+				err = access(line, R_OK | W_OK);
+				*tp = 'p';
+				if (!err)
+					return master;
+				close(master);
+			}
+		}
+	}
+
+	printk(UM_KERN_ERR "getmaster - no usable host pty devices\n");
+	return -ENOENT;
+}
+
+static int pty_open(int input, int output, int primary, void *d,
+		    char **dev_out)
+{
+	struct pty_chan *data = d;
+	int fd, err;
+	char dev[sizeof("/dev/ptyxx\0")] = "/dev/ptyxx";
+
+	fd = getmaster(dev);
+	if (fd < 0)
+		return fd;
+
+	if (data->raw) {
+		err = raw(fd);
+		if (err) {
+			close(fd);
+			return err;
+		}
+	}
+
+	if (data->announce)
+		(*data->announce)(dev, data->dev);
+
+	sprintf(data->dev_name, "%s", dev);
+	*dev_out = data->dev_name;
+
+	return fd;
+}
+
+const struct chan_ops pty_ops = {
+	.type		= "pty",
+	.init		= pty_chan_init,
+	.open		= pty_open,
+	.close		= generic_close,
+	.read		= generic_read,
+	.write		= generic_write,
+	.console_write	= generic_console_write,
+	.window_size	= generic_window_size,
+	.free		= generic_free,
+	.winch		= 0,
+};
+
+const struct chan_ops pts_ops = {
+	.type		= "pts",
+	.init		= pty_chan_init,
+	.open		= pts_open,
+	.close		= generic_close,
+	.read		= generic_read,
+	.write		= generic_write,
+	.console_write	= generic_console_write,
+	.window_size	= generic_window_size,
+	.free		= generic_free,
+	.winch		= 0,
+};
diff --git a/arch/um/drivers/random.c b/arch/um/drivers/random.c
new file mode 100644
index 000000000..32b3341fe
--- /dev/null
+++ b/arch/um/drivers/random.c
@@ -0,0 +1,122 @@
+/* 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/hw_random.h>
+#include <linux/delay.h>
+#include <linux/uaccess.h>
+#include <init.h>
+#include <irq_kern.h>
+#include <os.h>
+
+/*
+ * core module information
+ */
+#define RNG_MODULE_NAME "hw_random"
+
+/* 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 struct hwrng hwrng;
+static DECLARE_COMPLETION(have_data);
+
+static int rng_dev_read(struct hwrng *rng, void *buf, size_t max, bool block)
+{
+	int ret;
+
+	for (;;) {
+		ret = os_read_file(random_fd, buf, max);
+		if (block && ret == -EAGAIN) {
+			add_sigio_fd(random_fd);
+
+			ret = wait_for_completion_killable(&have_data);
+
+			ignore_sigio_fd(random_fd);
+			deactivate_fd(random_fd, RANDOM_IRQ);
+
+			if (ret < 0)
+				break;
+		} else {
+			break;
+		}
+	}
+
+	return ret != -EAGAIN ? ret : 0;
+}
+
+static irqreturn_t random_interrupt(int irq, void *data)
+{
+	complete(&have_data);
+
+	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 < 0)
+		goto err_out_cleanup_hw;
+
+	sigio_broken(random_fd);
+	hwrng.name = RNG_MODULE_NAME;
+	hwrng.read = rng_dev_read;
+	hwrng.quality = 1024;
+
+	err = hwrng_register(&hwrng);
+	if (err) {
+		pr_err(RNG_MODULE_NAME " registering failed (%d)\n", err);
+		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)
+{
+	hwrng_unregister(&hwrng);
+	os_close_file(random_fd);
+}
+
+module_init (rng_init);
+module_exit (rng_cleanup);
+__uml_exitcall(cleanup);
+
+MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
+MODULE_LICENSE("GPL");
diff --git a/arch/um/drivers/rtc.h b/arch/um/drivers/rtc.h
new file mode 100644
index 000000000..95e41c7d3
--- /dev/null
+++ b/arch/um/drivers/rtc.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 Intel Corporation
+ * Author: Johannes Berg <johannes@sipsolutions.net>
+ */
+#ifndef __UM_RTC_H__
+#define __UM_RTC_H__
+
+int uml_rtc_start(bool timetravel);
+int uml_rtc_enable_alarm(unsigned long long delta_seconds);
+void uml_rtc_disable_alarm(void);
+void uml_rtc_stop(bool timetravel);
+void uml_rtc_send_timetravel_alarm(void);
+
+#endif /* __UM_RTC_H__ */
diff --git a/arch/um/drivers/rtc_kern.c b/arch/um/drivers/rtc_kern.c
new file mode 100644
index 000000000..97ceb205c
--- /dev/null
+++ b/arch/um/drivers/rtc_kern.c
@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Intel Corporation
+ * Author: Johannes Berg <johannes@sipsolutions.net>
+ */
+#include <linux/platform_device.h>
+#include <linux/time-internal.h>
+#include <linux/suspend.h>
+#include <linux/err.h>
+#include <linux/rtc.h>
+#include <kern_util.h>
+#include <irq_kern.h>
+#include <os.h>
+#include "rtc.h"
+
+static time64_t uml_rtc_alarm_time;
+static bool uml_rtc_alarm_enabled;
+static struct rtc_device *uml_rtc;
+static int uml_rtc_irq_fd, uml_rtc_irq;
+
+#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+
+static void uml_rtc_time_travel_alarm(struct time_travel_event *ev)
+{
+	uml_rtc_send_timetravel_alarm();
+}
+
+static struct time_travel_event uml_rtc_alarm_event = {
+	.fn = uml_rtc_time_travel_alarm,
+};
+#endif
+
+static int uml_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct timespec64 ts;
+
+	/* Use this to get correct time in time-travel mode */
+	read_persistent_clock64(&ts);
+	rtc_time64_to_tm(timespec64_to_ktime(ts) / NSEC_PER_SEC, tm);
+
+	return 0;
+}
+
+static int uml_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	rtc_time64_to_tm(uml_rtc_alarm_time, &alrm->time);
+	alrm->enabled = uml_rtc_alarm_enabled;
+
+	return 0;
+}
+
+static int uml_rtc_alarm_irq_enable(struct device *dev, unsigned int enable)
+{
+	unsigned long long secs;
+
+	if (!enable && !uml_rtc_alarm_enabled)
+		return 0;
+
+	uml_rtc_alarm_enabled = enable;
+
+	secs = uml_rtc_alarm_time - ktime_get_real_seconds();
+
+	if (time_travel_mode == TT_MODE_OFF) {
+		if (!enable) {
+			uml_rtc_disable_alarm();
+			return 0;
+		}
+
+		/* enable or update */
+		return uml_rtc_enable_alarm(secs);
+	} else {
+		time_travel_del_event(&uml_rtc_alarm_event);
+
+		if (enable)
+			time_travel_add_event_rel(&uml_rtc_alarm_event,
+						  secs * NSEC_PER_SEC);
+	}
+
+	return 0;
+}
+
+static int uml_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	uml_rtc_alarm_irq_enable(dev, 0);
+	uml_rtc_alarm_time = rtc_tm_to_time64(&alrm->time);
+	uml_rtc_alarm_irq_enable(dev, alrm->enabled);
+
+	return 0;
+}
+
+static const struct rtc_class_ops uml_rtc_ops = {
+	.read_time = uml_rtc_read_time,
+	.read_alarm = uml_rtc_read_alarm,
+	.alarm_irq_enable = uml_rtc_alarm_irq_enable,
+	.set_alarm = uml_rtc_set_alarm,
+};
+
+static irqreturn_t uml_rtc_interrupt(int irq, void *data)
+{
+	unsigned long long c = 0;
+
+	/* alarm triggered, it's now off */
+	uml_rtc_alarm_enabled = false;
+
+	os_read_file(uml_rtc_irq_fd, &c, sizeof(c));
+	WARN_ON(c == 0);
+
+	pm_system_wakeup();
+	rtc_update_irq(uml_rtc, 1, RTC_IRQF | RTC_AF);
+
+	return IRQ_HANDLED;
+}
+
+static int uml_rtc_setup(void)
+{
+	int err;
+
+	err = uml_rtc_start(time_travel_mode != TT_MODE_OFF);
+	if (WARN(err < 0, "err = %d\n", err))
+		return err;
+
+	uml_rtc_irq_fd = err;
+
+	err = um_request_irq(UM_IRQ_ALLOC, uml_rtc_irq_fd, IRQ_READ,
+			     uml_rtc_interrupt, 0, "rtc", NULL);
+	if (err < 0) {
+		uml_rtc_stop(time_travel_mode != TT_MODE_OFF);
+		return err;
+	}
+
+	irq_set_irq_wake(err, 1);
+
+	uml_rtc_irq = err;
+	return 0;
+}
+
+static void uml_rtc_cleanup(void)
+{
+	um_free_irq(uml_rtc_irq, NULL);
+	uml_rtc_stop(time_travel_mode != TT_MODE_OFF);
+}
+
+static int uml_rtc_probe(struct platform_device *pdev)
+{
+	int err;
+
+	err = uml_rtc_setup();
+	if (err)
+		return err;
+
+	uml_rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(uml_rtc)) {
+		err = PTR_ERR(uml_rtc);
+		goto cleanup;
+	}
+
+	uml_rtc->ops = &uml_rtc_ops;
+
+	device_init_wakeup(&pdev->dev, 1);
+
+	err = devm_rtc_register_device(uml_rtc);
+	if (err)
+		goto cleanup;
+
+	return 0;
+cleanup:
+	uml_rtc_cleanup();
+	return err;
+}
+
+static int uml_rtc_remove(struct platform_device *pdev)
+{
+	device_init_wakeup(&pdev->dev, 0);
+	uml_rtc_cleanup();
+	return 0;
+}
+
+static struct platform_driver uml_rtc_driver = {
+	.probe = uml_rtc_probe,
+	.remove = uml_rtc_remove,
+	.driver = {
+		.name = "uml-rtc",
+	},
+};
+
+static int __init uml_rtc_init(void)
+{
+	struct platform_device *pdev;
+	int err;
+
+	err = platform_driver_register(&uml_rtc_driver);
+	if (err)
+		return err;
+
+	pdev = platform_device_alloc("uml-rtc", 0);
+	if (!pdev) {
+		err = -ENOMEM;
+		goto unregister;
+	}
+
+	err = platform_device_add(pdev);
+	if (err)
+		goto unregister;
+	return 0;
+
+unregister:
+	platform_device_put(pdev);
+	platform_driver_unregister(&uml_rtc_driver);
+	return err;
+}
+device_initcall(uml_rtc_init);
diff --git a/arch/um/drivers/rtc_user.c b/arch/um/drivers/rtc_user.c
new file mode 100644
index 000000000..7c3cec4c6
--- /dev/null
+++ b/arch/um/drivers/rtc_user.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Intel Corporation
+ * Author: Johannes Berg <johannes@sipsolutions.net>
+ */
+#include <stdbool.h>
+#include <os.h>
+#include <errno.h>
+#include <sched.h>
+#include <unistd.h>
+#include <kern_util.h>
+#include <sys/select.h>
+#include <stdio.h>
+#include <sys/timerfd.h>
+#include "rtc.h"
+
+static int uml_rtc_irq_fds[2];
+
+void uml_rtc_send_timetravel_alarm(void)
+{
+	unsigned long long c = 1;
+
+	CATCH_EINTR(write(uml_rtc_irq_fds[1], &c, sizeof(c)));
+}
+
+int uml_rtc_start(bool timetravel)
+{
+	int err;
+
+	if (timetravel) {
+		int err = os_pipe(uml_rtc_irq_fds, 1, 1);
+		if (err)
+			goto fail;
+	} else {
+		uml_rtc_irq_fds[0] = timerfd_create(CLOCK_REALTIME, TFD_CLOEXEC);
+		if (uml_rtc_irq_fds[0] < 0) {
+			err = -errno;
+			goto fail;
+		}
+
+		/* apparently timerfd won't send SIGIO, use workaround */
+		sigio_broken(uml_rtc_irq_fds[0]);
+		err = add_sigio_fd(uml_rtc_irq_fds[0]);
+		if (err < 0) {
+			close(uml_rtc_irq_fds[0]);
+			goto fail;
+		}
+	}
+
+	return uml_rtc_irq_fds[0];
+fail:
+	uml_rtc_stop(timetravel);
+	return err;
+}
+
+int uml_rtc_enable_alarm(unsigned long long delta_seconds)
+{
+	struct itimerspec it = {
+		.it_value = {
+			.tv_sec = delta_seconds,
+		},
+	};
+
+	if (timerfd_settime(uml_rtc_irq_fds[0], 0, &it, NULL))
+		return -errno;
+	return 0;
+}
+
+void uml_rtc_disable_alarm(void)
+{
+	uml_rtc_enable_alarm(0);
+}
+
+void uml_rtc_stop(bool timetravel)
+{
+	if (timetravel)
+		os_close_file(uml_rtc_irq_fds[1]);
+	else
+		ignore_sigio_fd(uml_rtc_irq_fds[0]);
+	os_close_file(uml_rtc_irq_fds[0]);
+}
diff --git a/arch/um/drivers/slip.h b/arch/um/drivers/slip.h
new file mode 100644
index 000000000..0f3b7ca99
--- /dev/null
+++ b/arch/um/drivers/slip.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_SLIP_H
+#define __UM_SLIP_H
+
+#include "slip_common.h"
+
+struct slip_data {
+	void *dev;
+	char name[sizeof("slnnnnn\0")];
+	char *addr;
+	char *gate_addr;
+	int slave;
+	struct slip_proto slip;
+};
+
+extern const struct net_user_info slip_user_info;
+
+extern int slip_user_read(int fd, void *buf, int len, struct slip_data *pri);
+extern int slip_user_write(int fd, void *buf, int len, struct slip_data *pri);
+
+#endif
diff --git a/arch/um/drivers/slip_common.c b/arch/um/drivers/slip_common.c
new file mode 100644
index 000000000..20fe4f427
--- /dev/null
+++ b/arch/um/drivers/slip_common.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <string.h>
+#include "slip_common.h"
+#include <net_user.h>
+
+int slip_proto_read(int fd, void *buf, int len, struct slip_proto *slip)
+{
+	int i, n, size, start;
+
+	if(slip->more > 0){
+		i = 0;
+		while(i < slip->more){
+			size = slip_unesc(slip->ibuf[i++], slip->ibuf,
+					  &slip->pos, &slip->esc);
+			if(size){
+				memcpy(buf, slip->ibuf, size);
+				memmove(slip->ibuf, &slip->ibuf[i],
+					slip->more - i);
+				slip->more = slip->more - i;
+				return size;
+			}
+		}
+		slip->more = 0;
+	}
+
+	n = net_read(fd, &slip->ibuf[slip->pos],
+		     sizeof(slip->ibuf) - slip->pos);
+	if(n <= 0)
+		return n;
+
+	start = slip->pos;
+	for(i = 0; i < n; i++){
+		size = slip_unesc(slip->ibuf[start + i], slip->ibuf,&slip->pos,
+				  &slip->esc);
+		if(size){
+			memcpy(buf, slip->ibuf, size);
+			memmove(slip->ibuf, &slip->ibuf[start+i+1],
+				n - (i + 1));
+			slip->more = n - (i + 1);
+			return size;
+		}
+	}
+	return 0;
+}
+
+int slip_proto_write(int fd, void *buf, int len, struct slip_proto *slip)
+{
+	int actual, n;
+
+	actual = slip_esc(buf, slip->obuf, len);
+	n = net_write(fd, slip->obuf, actual);
+	if(n < 0)
+		return n;
+	else return len;
+}
diff --git a/arch/um/drivers/slip_common.h b/arch/um/drivers/slip_common.h
new file mode 100644
index 000000000..d3798b5ca
--- /dev/null
+++ b/arch/um/drivers/slip_common.h
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_SLIP_COMMON_H
+#define __UM_SLIP_COMMON_H
+
+#define BUF_SIZE 1500
+ /* two bytes each for a (pathological) max packet of escaped chars +  *
+  * terminating END char + initial END char                            */
+#define ENC_BUF_SIZE (2 * BUF_SIZE + 2)
+
+/* SLIP protocol characters. */
+#define SLIP_END             0300	/* indicates end of frame	*/
+#define SLIP_ESC             0333	/* indicates byte stuffing	*/
+#define SLIP_ESC_END         0334	/* ESC ESC_END means END 'data'	*/
+#define SLIP_ESC_ESC         0335	/* ESC ESC_ESC means ESC 'data'	*/
+
+static inline int slip_unesc(unsigned char c, unsigned char *buf, int *pos,
+                             int *esc)
+{
+	int ret;
+
+	switch(c){
+	case SLIP_END:
+		*esc = 0;
+		ret=*pos;
+		*pos=0;
+		return(ret);
+	case SLIP_ESC:
+		*esc = 1;
+		return(0);
+	case SLIP_ESC_ESC:
+		if(*esc){
+			*esc = 0;
+			c = SLIP_ESC;
+		}
+		break;
+	case SLIP_ESC_END:
+		if(*esc){
+			*esc = 0;
+			c = SLIP_END;
+		}
+		break;
+	}
+	buf[(*pos)++] = c;
+	return(0);
+}
+
+static inline int slip_esc(unsigned char *s, unsigned char *d, int len)
+{
+	unsigned char *ptr = d;
+	unsigned char c;
+
+	/*
+	 * Send an initial END character to flush out any
+	 * data that may have accumulated in the receiver
+	 * due to line noise.
+	 */
+
+	*ptr++ = SLIP_END;
+
+	/*
+	 * For each byte in the packet, send the appropriate
+	 * character sequence, according to the SLIP protocol.
+	 */
+
+	while (len-- > 0) {
+		switch(c = *s++) {
+		case SLIP_END:
+			*ptr++ = SLIP_ESC;
+			*ptr++ = SLIP_ESC_END;
+			break;
+		case SLIP_ESC:
+			*ptr++ = SLIP_ESC;
+			*ptr++ = SLIP_ESC_ESC;
+			break;
+		default:
+			*ptr++ = c;
+			break;
+		}
+	}
+	*ptr++ = SLIP_END;
+	return (ptr - d);
+}
+
+struct slip_proto {
+	unsigned char ibuf[ENC_BUF_SIZE];
+	unsigned char obuf[ENC_BUF_SIZE];
+	int more; /* more data: do not read fd until ibuf has been drained */
+	int pos;
+	int esc;
+};
+
+static inline void slip_proto_init(struct slip_proto * slip)
+{
+	memset(slip->ibuf, 0, sizeof(slip->ibuf));
+	memset(slip->obuf, 0, sizeof(slip->obuf));
+	slip->more = 0;
+	slip->pos = 0;
+	slip->esc = 0;
+}
+
+extern int slip_proto_read(int fd, void *buf, int len,
+			   struct slip_proto *slip);
+extern int slip_proto_write(int fd, void *buf, int len,
+			    struct slip_proto *slip);
+
+#endif
diff --git a/arch/um/drivers/slip_kern.c b/arch/um/drivers/slip_kern.c
new file mode 100644
index 000000000..c58ccdcc1
--- /dev/null
+++ b/arch/um/drivers/slip_kern.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <linux/if_arp.h>
+#include <linux/init.h>
+#include <linux/netdevice.h>
+#include <net_kern.h>
+#include "slip.h"
+
+struct slip_init {
+	char *gate_addr;
+};
+
+static void slip_init(struct net_device *dev, void *data)
+{
+	struct uml_net_private *private;
+	struct slip_data *spri;
+	struct slip_init *init = data;
+
+	private = netdev_priv(dev);
+	spri = (struct slip_data *) private->user;
+
+	memset(spri->name, 0, sizeof(spri->name));
+	spri->addr = NULL;
+	spri->gate_addr = init->gate_addr;
+	spri->slave = -1;
+	spri->dev = dev;
+
+	slip_proto_init(&spri->slip);
+
+	dev->hard_header_len = 0;
+	dev->header_ops = NULL;
+	dev->addr_len = 0;
+	dev->type = ARPHRD_SLIP;
+	dev->tx_queue_len = 256;
+	dev->flags = IFF_NOARP;
+	printk("SLIP backend - SLIP IP = %s\n", spri->gate_addr);
+}
+
+static unsigned short slip_protocol(struct sk_buff *skbuff)
+{
+	return htons(ETH_P_IP);
+}
+
+static int slip_read(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	return slip_user_read(fd, skb_mac_header(skb), skb->dev->mtu,
+			      (struct slip_data *) &lp->user);
+}
+
+static int slip_write(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	return slip_user_write(fd, skb->data, skb->len,
+			       (struct slip_data *) &lp->user);
+}
+
+static const struct net_kern_info slip_kern_info = {
+	.init			= slip_init,
+	.protocol		= slip_protocol,
+	.read			= slip_read,
+	.write			= slip_write,
+};
+
+static int slip_setup(char *str, char **mac_out, void *data)
+{
+	struct slip_init *init = data;
+
+	*init = ((struct slip_init) { .gate_addr = NULL });
+
+	if (str[0] != '\0')
+		init->gate_addr = str;
+	return 1;
+}
+
+static struct transport slip_transport = {
+	.list 		= LIST_HEAD_INIT(slip_transport.list),
+	.name 		= "slip",
+	.setup  	= slip_setup,
+	.user 		= &slip_user_info,
+	.kern 		= &slip_kern_info,
+	.private_size 	= sizeof(struct slip_data),
+	.setup_size 	= sizeof(struct slip_init),
+};
+
+static int register_slip(void)
+{
+	register_transport(&slip_transport);
+	return 0;
+}
+
+late_initcall(register_slip);
diff --git a/arch/um/drivers/slip_user.c b/arch/um/drivers/slip_user.c
new file mode 100644
index 000000000..7334019c9
--- /dev/null
+++ b/arch/um/drivers/slip_user.c
@@ -0,0 +1,252 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <termios.h>
+#include <sys/wait.h>
+#include <net_user.h>
+#include <os.h>
+#include "slip.h"
+#include <um_malloc.h>
+
+static int slip_user_init(void *data, void *dev)
+{
+	struct slip_data *pri = data;
+
+	pri->dev = dev;
+	return 0;
+}
+
+static int set_up_tty(int fd)
+{
+	int i;
+	struct termios tios;
+
+	if (tcgetattr(fd, &tios) < 0) {
+		printk(UM_KERN_ERR "could not get initial terminal "
+		       "attributes\n");
+		return -1;
+	}
+
+	tios.c_cflag = CS8 | CREAD | HUPCL | CLOCAL;
+	tios.c_iflag = IGNBRK | IGNPAR;
+	tios.c_oflag = 0;
+	tios.c_lflag = 0;
+	for (i = 0; i < NCCS; i++)
+		tios.c_cc[i] = 0;
+	tios.c_cc[VMIN] = 1;
+	tios.c_cc[VTIME] = 0;
+
+	cfsetospeed(&tios, B38400);
+	cfsetispeed(&tios, B38400);
+
+	if (tcsetattr(fd, TCSAFLUSH, &tios) < 0) {
+		printk(UM_KERN_ERR "failed to set terminal attributes\n");
+		return -1;
+	}
+	return 0;
+}
+
+struct slip_pre_exec_data {
+	int stdin_fd;
+	int stdout_fd;
+	int close_me;
+};
+
+static void slip_pre_exec(void *arg)
+{
+	struct slip_pre_exec_data *data = arg;
+
+	if (data->stdin_fd >= 0)
+		dup2(data->stdin_fd, 0);
+	dup2(data->stdout_fd, 1);
+	if (data->close_me >= 0)
+		close(data->close_me);
+}
+
+static int slip_tramp(char **argv, int fd)
+{
+	struct slip_pre_exec_data pe_data;
+	char *output;
+	int pid, fds[2], err, output_len;
+
+	err = os_pipe(fds, 1, 0);
+	if (err < 0) {
+		printk(UM_KERN_ERR "slip_tramp : pipe failed, err = %d\n",
+		       -err);
+		goto out;
+	}
+
+	err = 0;
+	pe_data.stdin_fd = fd;
+	pe_data.stdout_fd = fds[1];
+	pe_data.close_me = fds[0];
+	err = run_helper(slip_pre_exec, &pe_data, argv);
+	if (err < 0)
+		goto out_close;
+	pid = err;
+
+	output_len = UM_KERN_PAGE_SIZE;
+	output = uml_kmalloc(output_len, UM_GFP_KERNEL);
+	if (output == NULL) {
+		printk(UM_KERN_ERR "slip_tramp : failed to allocate output "
+		       "buffer\n");
+		os_kill_process(pid, 1);
+		err = -ENOMEM;
+		goto out_close;
+	}
+
+	close(fds[1]);
+	read_output(fds[0], output, output_len);
+	printk("%s", output);
+
+	err = helper_wait(pid);
+	close(fds[0]);
+
+	kfree(output);
+	return err;
+
+out_close:
+	close(fds[0]);
+	close(fds[1]);
+out:
+	return err;
+}
+
+static int slip_open(void *data)
+{
+	struct slip_data *pri = data;
+	char version_buf[sizeof("nnnnn\0")];
+	char gate_buf[sizeof("nnn.nnn.nnn.nnn\0")];
+	char *argv[] = { "uml_net", version_buf, "slip", "up", gate_buf,
+			 NULL };
+	int sfd, mfd, err;
+
+	err = get_pty();
+	if (err < 0) {
+		printk(UM_KERN_ERR "slip-open : Failed to open pty, err = %d\n",
+		       -err);
+		goto out;
+	}
+	mfd = err;
+
+	err = open(ptsname(mfd), O_RDWR, 0);
+	if (err < 0) {
+		printk(UM_KERN_ERR "Couldn't open tty for slip line, "
+		       "err = %d\n", -err);
+		goto out_close;
+	}
+	sfd = err;
+
+	err = set_up_tty(sfd);
+	if (err)
+		goto out_close2;
+
+	pri->slave = sfd;
+	pri->slip.pos = 0;
+	pri->slip.esc = 0;
+	if (pri->gate_addr != NULL) {
+		sprintf(version_buf, "%d", UML_NET_VERSION);
+		strcpy(gate_buf, pri->gate_addr);
+
+		err = slip_tramp(argv, sfd);
+
+		if (err < 0) {
+			printk(UM_KERN_ERR "slip_tramp failed - err = %d\n",
+			       -err);
+			goto out_close2;
+		}
+		err = os_get_ifname(pri->slave, pri->name);
+		if (err < 0) {
+			printk(UM_KERN_ERR "get_ifname failed, err = %d\n",
+			       -err);
+			goto out_close2;
+		}
+		iter_addresses(pri->dev, open_addr, pri->name);
+	}
+	else {
+		err = os_set_slip(sfd);
+		if (err < 0) {
+			printk(UM_KERN_ERR "Failed to set slip discipline "
+			       "encapsulation - err = %d\n", -err);
+			goto out_close2;
+		}
+	}
+	return mfd;
+out_close2:
+	close(sfd);
+out_close:
+	close(mfd);
+out:
+	return err;
+}
+
+static void slip_close(int fd, void *data)
+{
+	struct slip_data *pri = data;
+	char version_buf[sizeof("nnnnn\0")];
+	char *argv[] = { "uml_net", version_buf, "slip", "down", pri->name,
+			 NULL };
+	int err;
+
+	if (pri->gate_addr != NULL)
+		iter_addresses(pri->dev, close_addr, pri->name);
+
+	sprintf(version_buf, "%d", UML_NET_VERSION);
+
+	err = slip_tramp(argv, pri->slave);
+
+	if (err != 0)
+		printk(UM_KERN_ERR "slip_tramp failed - errno = %d\n", -err);
+	close(fd);
+	close(pri->slave);
+	pri->slave = -1;
+}
+
+int slip_user_read(int fd, void *buf, int len, struct slip_data *pri)
+{
+	return slip_proto_read(fd, buf, len, &pri->slip);
+}
+
+int slip_user_write(int fd, void *buf, int len, struct slip_data *pri)
+{
+	return slip_proto_write(fd, buf, len, &pri->slip);
+}
+
+static void slip_add_addr(unsigned char *addr, unsigned char *netmask,
+			  void *data)
+{
+	struct slip_data *pri = data;
+
+	if (pri->slave < 0)
+		return;
+	open_addr(addr, netmask, pri->name);
+}
+
+static void slip_del_addr(unsigned char *addr, unsigned char *netmask,
+			    void *data)
+{
+	struct slip_data *pri = data;
+
+	if (pri->slave < 0)
+		return;
+	close_addr(addr, netmask, pri->name);
+}
+
+const struct net_user_info slip_user_info = {
+	.init		= slip_user_init,
+	.open		= slip_open,
+	.close	 	= slip_close,
+	.remove	 	= NULL,
+	.add_address	= slip_add_addr,
+	.delete_address = slip_del_addr,
+	.mtu		= BUF_SIZE,
+	.max_packet	= BUF_SIZE,
+};
diff --git a/arch/um/drivers/slirp.h b/arch/um/drivers/slirp.h
new file mode 100644
index 000000000..4aef2b882
--- /dev/null
+++ b/arch/um/drivers/slirp.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_SLIRP_H
+#define __UM_SLIRP_H
+
+#include "slip_common.h"
+
+#define SLIRP_MAX_ARGS 100
+/*
+ * XXX this next definition is here because I don't understand why this
+ * initializer doesn't work in slirp_kern.c:
+ *
+ *   argv :  { init->argv[ 0 ... SLIRP_MAX_ARGS-1 ] },
+ *
+ * or why I can't typecast like this:
+ *
+ *   argv :  (char* [SLIRP_MAX_ARGS])(init->argv), 
+ */
+struct arg_list_dummy_wrapper { char *argv[SLIRP_MAX_ARGS]; };
+
+struct slirp_data {
+	void *dev;
+	struct arg_list_dummy_wrapper argw;
+	int pid;
+	int slave;
+	struct slip_proto slip;
+};
+
+extern const struct net_user_info slirp_user_info;
+
+extern int slirp_user_read(int fd, void *buf, int len, struct slirp_data *pri);
+extern int slirp_user_write(int fd, void *buf, int len,
+			    struct slirp_data *pri);
+
+#endif
diff --git a/arch/um/drivers/slirp_kern.c b/arch/um/drivers/slirp_kern.c
new file mode 100644
index 000000000..2d9769237
--- /dev/null
+++ b/arch/um/drivers/slirp_kern.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <linux/if_arp.h>
+#include <linux/init.h>
+#include <linux/netdevice.h>
+#include <linux/string.h>
+#include <net_kern.h>
+#include <net_user.h>
+#include "slirp.h"
+
+struct slirp_init {
+	struct arg_list_dummy_wrapper argw;  /* XXX should be simpler... */
+};
+
+void slirp_init(struct net_device *dev, void *data)
+{
+	struct uml_net_private *private;
+	struct slirp_data *spri;
+	struct slirp_init *init = data;
+	int i;
+
+	private = netdev_priv(dev);
+	spri = (struct slirp_data *) private->user;
+
+	spri->argw = init->argw;
+	spri->pid = -1;
+	spri->slave = -1;
+	spri->dev = dev;
+
+	slip_proto_init(&spri->slip);
+
+	dev->hard_header_len = 0;
+	dev->header_ops = NULL;
+	dev->addr_len = 0;
+	dev->type = ARPHRD_SLIP;
+	dev->tx_queue_len = 256;
+	dev->flags = IFF_NOARP;
+	printk("SLIRP backend - command line:");
+	for (i = 0; spri->argw.argv[i] != NULL; i++)
+		printk(" '%s'",spri->argw.argv[i]);
+	printk("\n");
+}
+
+static unsigned short slirp_protocol(struct sk_buff *skbuff)
+{
+	return htons(ETH_P_IP);
+}
+
+static int slirp_read(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	return slirp_user_read(fd, skb_mac_header(skb), skb->dev->mtu,
+			       (struct slirp_data *) &lp->user);
+}
+
+static int slirp_write(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	return slirp_user_write(fd, skb->data, skb->len,
+				(struct slirp_data *) &lp->user);
+}
+
+const struct net_kern_info slirp_kern_info = {
+	.init			= slirp_init,
+	.protocol		= slirp_protocol,
+	.read			= slirp_read,
+	.write			= slirp_write,
+};
+
+static int slirp_setup(char *str, char **mac_out, void *data)
+{
+	struct slirp_init *init = data;
+	int i=0;
+
+	*init = ((struct slirp_init) { .argw = { { "slirp", NULL  } } });
+
+	str = split_if_spec(str, mac_out, NULL);
+
+	if (str == NULL) /* no command line given after MAC addr */
+		return 1;
+
+	do {
+		if (i >= SLIRP_MAX_ARGS - 1) {
+			printk(KERN_WARNING "slirp_setup: truncating slirp "
+			       "arguments\n");
+			break;
+		}
+		init->argw.argv[i++] = str;
+		while(*str && *str!=',') {
+			if (*str == '_')
+				*str=' ';
+			str++;
+		}
+		if (*str != ',')
+			break;
+		*str++ = '\0';
+	} while (1);
+
+	init->argw.argv[i] = NULL;
+	return 1;
+}
+
+static struct transport slirp_transport = {
+	.list 		= LIST_HEAD_INIT(slirp_transport.list),
+	.name 		= "slirp",
+	.setup  	= slirp_setup,
+	.user 		= &slirp_user_info,
+	.kern 		= &slirp_kern_info,
+	.private_size 	= sizeof(struct slirp_data),
+	.setup_size 	= sizeof(struct slirp_init),
+};
+
+static int register_slirp(void)
+{
+	register_transport(&slirp_transport);
+	return 0;
+}
+
+late_initcall(register_slirp);
diff --git a/arch/um/drivers/slirp_user.c b/arch/um/drivers/slirp_user.c
new file mode 100644
index 000000000..8f633e2e5
--- /dev/null
+++ b/arch/um/drivers/slirp_user.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <net_user.h>
+#include <os.h>
+#include "slirp.h"
+
+static int slirp_user_init(void *data, void *dev)
+{
+	struct slirp_data *pri = data;
+
+	pri->dev = dev;
+	return 0;
+}
+
+struct slirp_pre_exec_data {
+	int stdin_fd;
+	int stdout_fd;
+};
+
+static void slirp_pre_exec(void *arg)
+{
+	struct slirp_pre_exec_data *data = arg;
+
+	if (data->stdin_fd != -1)
+		dup2(data->stdin_fd, 0);
+	if (data->stdout_fd != -1)
+		dup2(data->stdout_fd, 1);
+}
+
+static int slirp_tramp(char **argv, int fd)
+{
+	struct slirp_pre_exec_data pe_data;
+	int pid;
+
+	pe_data.stdin_fd = fd;
+	pe_data.stdout_fd = fd;
+	pid = run_helper(slirp_pre_exec, &pe_data, argv);
+
+	return pid;
+}
+
+static int slirp_open(void *data)
+{
+	struct slirp_data *pri = data;
+	int fds[2], pid, err;
+
+	err = os_pipe(fds, 1, 1);
+	if (err)
+		return err;
+
+	err = slirp_tramp(pri->argw.argv, fds[1]);
+	if (err < 0) {
+		printk(UM_KERN_ERR "slirp_tramp failed - errno = %d\n", -err);
+		goto out;
+	}
+	pid = err;
+
+	pri->slave = fds[1];
+	pri->slip.pos = 0;
+	pri->slip.esc = 0;
+	pri->pid = err;
+
+	return fds[0];
+out:
+	close(fds[0]);
+	close(fds[1]);
+	return err;
+}
+
+static void slirp_close(int fd, void *data)
+{
+	struct slirp_data *pri = data;
+	int err;
+
+	close(fd);
+	close(pri->slave);
+
+	pri->slave = -1;
+
+	if (pri->pid<1) {
+		printk(UM_KERN_ERR "slirp_close: no child process to shut "
+		       "down\n");
+		return;
+	}
+
+#if 0
+	if (kill(pri->pid, SIGHUP)<0) {
+		printk(UM_KERN_ERR "slirp_close: sending hangup to %d failed "
+		       "(%d)\n", pri->pid, errno);
+	}
+#endif
+	err = helper_wait(pri->pid);
+	if (err < 0)
+		return;
+
+	pri->pid = -1;
+}
+
+int slirp_user_read(int fd, void *buf, int len, struct slirp_data *pri)
+{
+	return slip_proto_read(fd, buf, len, &pri->slip);
+}
+
+int slirp_user_write(int fd, void *buf, int len, struct slirp_data *pri)
+{
+	return slip_proto_write(fd, buf, len, &pri->slip);
+}
+
+const struct net_user_info slirp_user_info = {
+	.init		= slirp_user_init,
+	.open		= slirp_open,
+	.close	 	= slirp_close,
+	.remove	 	= NULL,
+	.add_address	= NULL,
+	.delete_address = NULL,
+	.mtu		= BUF_SIZE,
+	.max_packet	= BUF_SIZE,
+};
diff --git a/arch/um/drivers/ssl.c b/arch/um/drivers/ssl.c
new file mode 100644
index 000000000..277cea3d3
--- /dev/null
+++ b/arch/um/drivers/ssl.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0
+/* 
+ * Copyright (C) 2000, 2002 Jeff Dike (jdike@karaya.com)
+ */
+
+#include <linux/fs.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/major.h>
+#include <linux/mm.h>
+#include <linux/init.h>
+#include <linux/console.h>
+#include <asm/termbits.h>
+#include <asm/irq.h>
+#include "chan.h"
+#include <init.h>
+#include <irq_user.h>
+#include "mconsole_kern.h"
+
+static const int ssl_version = 1;
+
+#define NR_PORTS 64
+
+static void ssl_announce(char *dev_name, int dev)
+{
+	printk(KERN_INFO "Serial line %d assigned device '%s'\n", dev,
+	       dev_name);
+}
+
+/* Almost const, except that xterm_title may be changed in an initcall */
+static struct chan_opts opts = {
+	.announce 	= ssl_announce,
+	.xterm_title	= "Serial Line #%d",
+	.raw		= 1,
+};
+
+static int ssl_config(char *str, char **error_out);
+static int ssl_get_config(char *dev, char *str, int size, char **error_out);
+static int ssl_remove(int n, char **error_out);
+
+
+/* Const, except for .mc.list */
+static struct line_driver driver = {
+	.name 			= "UML serial line",
+	.device_name 		= "ttyS",
+	.major 			= TTY_MAJOR,
+	.minor_start 		= 64,
+	.type 		 	= TTY_DRIVER_TYPE_SERIAL,
+	.subtype 	 	= 0,
+	.read_irq_name 		= "ssl",
+	.write_irq_name 	= "ssl-write",
+	.mc  = {
+		.list		= LIST_HEAD_INIT(driver.mc.list),
+		.name  		= "ssl",
+		.config 	= ssl_config,
+		.get_config 	= ssl_get_config,
+		.id		= line_id,
+		.remove 	= ssl_remove,
+	},
+};
+
+/* The array is initialized by line_init, at initcall time.  The
+ * elements are locked individually as needed.
+ */
+static char *conf[NR_PORTS];
+static char *def_conf = CONFIG_SSL_CHAN;
+static struct line serial_lines[NR_PORTS];
+
+static int ssl_config(char *str, char **error_out)
+{
+	return line_config(serial_lines, ARRAY_SIZE(serial_lines), str, &opts,
+			   error_out);
+}
+
+static int ssl_get_config(char *dev, char *str, int size, char **error_out)
+{
+	return line_get_config(dev, serial_lines, ARRAY_SIZE(serial_lines), str,
+			       size, error_out);
+}
+
+static int ssl_remove(int n, char **error_out)
+{
+	return line_remove(serial_lines, ARRAY_SIZE(serial_lines), n,
+			   error_out);
+}
+
+static int ssl_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	return line_install(driver, tty, &serial_lines[tty->index]);
+}
+
+static const struct tty_operations ssl_ops = {
+	.open 	 		= line_open,
+	.close 	 		= line_close,
+	.write 	 		= line_write,
+	.write_room		= line_write_room,
+	.chars_in_buffer 	= line_chars_in_buffer,
+	.flush_buffer 		= line_flush_buffer,
+	.flush_chars 		= line_flush_chars,
+	.throttle 		= line_throttle,
+	.unthrottle 		= line_unthrottle,
+	.install		= ssl_install,
+	.hangup			= line_hangup,
+};
+
+/* Changed by ssl_init and referenced by ssl_exit, which are both serialized
+ * by being an initcall and exitcall, respectively.
+ */
+static int ssl_init_done;
+
+static void ssl_console_write(struct console *c, const char *string,
+			      unsigned len)
+{
+	struct line *line = &serial_lines[c->index];
+	unsigned long flags;
+
+	spin_lock_irqsave(&line->lock, flags);
+	console_write_chan(line->chan_out, string, len);
+	spin_unlock_irqrestore(&line->lock, flags);
+}
+
+static struct tty_driver *ssl_console_device(struct console *c, int *index)
+{
+	*index = c->index;
+	return driver.driver;
+}
+
+static int ssl_console_setup(struct console *co, char *options)
+{
+	struct line *line = &serial_lines[co->index];
+
+	return console_open_chan(line, co);
+}
+
+/* No locking for register_console call - relies on single-threaded initcalls */
+static struct console ssl_cons = {
+	.name		= "ttyS",
+	.write		= ssl_console_write,
+	.device		= ssl_console_device,
+	.setup		= ssl_console_setup,
+	.flags		= CON_PRINTBUFFER|CON_ANYTIME,
+	.index		= -1,
+};
+
+static int ssl_init(void)
+{
+	char *new_title;
+	int err;
+	int i;
+
+	printk(KERN_INFO "Initializing software serial port version %d\n",
+	       ssl_version);
+
+	err = register_lines(&driver, &ssl_ops, serial_lines,
+				    ARRAY_SIZE(serial_lines));
+	if (err)
+		return err;
+
+	new_title = add_xterm_umid(opts.xterm_title);
+	if (new_title != NULL)
+		opts.xterm_title = new_title;
+
+	for (i = 0; i < NR_PORTS; i++) {
+		char *error;
+		char *s = conf[i];
+		if (!s)
+			s = def_conf;
+		if (setup_one_line(serial_lines, i, s, &opts, &error))
+			printk(KERN_ERR "setup_one_line failed for "
+			       "device %d : %s\n", i, error);
+	}
+
+	ssl_init_done = 1;
+	register_console(&ssl_cons);
+	return 0;
+}
+late_initcall(ssl_init);
+
+static void ssl_exit(void)
+{
+	if (!ssl_init_done)
+		return;
+	close_lines(serial_lines, ARRAY_SIZE(serial_lines));
+}
+__uml_exitcall(ssl_exit);
+
+static int ssl_chan_setup(char *str)
+{
+	line_setup(conf, NR_PORTS, &def_conf, str, "serial line");
+	return 1;
+}
+
+__setup("ssl", ssl_chan_setup);
+__channel_help(ssl_chan_setup, "ssl");
+
+static int ssl_non_raw_setup(char *str)
+{
+	opts.raw = 0;
+	return 1;
+}
+__setup("ssl-non-raw", ssl_non_raw_setup);
+__channel_help(ssl_non_raw_setup, "set serial lines to non-raw mode");
diff --git a/arch/um/drivers/stderr_console.c b/arch/um/drivers/stderr_console.c
new file mode 100644
index 000000000..ecc3a5814
--- /dev/null
+++ b/arch/um/drivers/stderr_console.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/console.h>
+
+#include "chan_user.h"
+
+/* ----------------------------------------------------------------------------- */
+/* trivial console driver -- simply dump everything to stderr                    */
+
+/*
+ * Don't register by default -- as this registers very early in the
+ * boot process it becomes the default console.
+ *
+ * Initialized at init time.
+ */
+static int use_stderr_console = 0;
+
+static void stderr_console_write(struct console *console, const char *string,
+				 unsigned len)
+{
+	generic_write(2 /* stderr */, string, len, NULL);
+}
+
+static struct console stderr_console = {
+	.name		= "stderr",
+	.write		= stderr_console_write,
+	.flags		= CON_PRINTBUFFER,
+};
+
+static int __init stderr_console_init(void)
+{
+	if (use_stderr_console)
+		register_console(&stderr_console);
+	return 0;
+}
+console_initcall(stderr_console_init);
+
+static int stderr_setup(char *str)
+{
+	if (!str)
+		return 0;
+	use_stderr_console = simple_strtoul(str,&str,0);
+	return 1;
+}
+__setup("stderr=", stderr_setup);
+
+/* The previous behavior of not unregistering led to /dev/console being
+ * impossible to open.  My FC5 filesystem started having init die, and the
+ * system panicing because of this.  Unregistering causes the real
+ * console to become the default console, and /dev/console can then be
+ * opened.  Making this an initcall makes this happen late enough that
+ * there is no added value in dumping everything to stderr, and the
+ * normal console is good enough to show you all available output.
+ */
+static int __init unregister_stderr(void)
+{
+	unregister_console(&stderr_console);
+
+	return 0;
+}
+
+__initcall(unregister_stderr);
diff --git a/arch/um/drivers/stdio_console.c b/arch/um/drivers/stdio_console.c
new file mode 100644
index 000000000..1c239737d
--- /dev/null
+++ b/arch/um/drivers/stdio_console.c
@@ -0,0 +1,198 @@
+// SPDX-License-Identifier: GPL-2.0
+/* 
+ * Copyright (C) 2000, 2001 Jeff Dike (jdike@karaya.com)
+ */
+
+#include <linux/posix_types.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/types.h>
+#include <linux/major.h>
+#include <linux/kdev_t.h>
+#include <linux/console.h>
+#include <linux/string.h>
+#include <linux/sched.h>
+#include <linux/list.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+#include <linux/hardirq.h>
+#include <asm/current.h>
+#include <asm/irq.h>
+#include "stdio_console.h"
+#include "chan.h"
+#include <irq_user.h>
+#include "mconsole_kern.h"
+#include <init.h>
+
+#define MAX_TTYS (16)
+
+static void stdio_announce(char *dev_name, int dev)
+{
+	printk(KERN_INFO "Virtual console %d assigned device '%s'\n", dev,
+	       dev_name);
+}
+
+/* Almost const, except that xterm_title may be changed in an initcall */
+static struct chan_opts opts = {
+	.announce 	= stdio_announce,
+	.xterm_title	= "Virtual Console #%d",
+	.raw		= 1,
+};
+
+static int con_config(char *str, char **error_out);
+static int con_get_config(char *dev, char *str, int size, char **error_out);
+static int con_remove(int n, char **con_remove);
+
+
+/* Const, except for .mc.list */
+static struct line_driver driver = {
+	.name 			= "UML console",
+	.device_name 		= "tty",
+	.major 			= TTY_MAJOR,
+	.minor_start 		= 0,
+	.type 		 	= TTY_DRIVER_TYPE_CONSOLE,
+	.subtype 	 	= SYSTEM_TYPE_CONSOLE,
+	.read_irq_name 		= "console",
+	.write_irq_name 	= "console-write",
+	.mc  = {
+		.list		= LIST_HEAD_INIT(driver.mc.list),
+		.name  		= "con",
+		.config 	= con_config,
+		.get_config 	= con_get_config,
+		.id		= line_id,
+		.remove 	= con_remove,
+	},
+};
+
+/* The array is initialized by line_init, at initcall time.  The
+ * elements are locked individually as needed.
+ */
+static char *vt_conf[MAX_TTYS];
+static char *def_conf;
+static struct line vts[MAX_TTYS];
+
+static int con_config(char *str, char **error_out)
+{
+	return line_config(vts, ARRAY_SIZE(vts), str, &opts, error_out);
+}
+
+static int con_get_config(char *dev, char *str, int size, char **error_out)
+{
+	return line_get_config(dev, vts, ARRAY_SIZE(vts), str, size, error_out);
+}
+
+static int con_remove(int n, char **error_out)
+{
+	return line_remove(vts, ARRAY_SIZE(vts), n, error_out);
+}
+
+/* Set in an initcall, checked in an exitcall */
+static int con_init_done;
+
+static int con_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	return line_install(driver, tty, &vts[tty->index]);
+}
+
+static const struct tty_operations console_ops = {
+	.open 	 		= line_open,
+	.install		= con_install,
+	.close 	 		= line_close,
+	.write 	 		= line_write,
+	.write_room		= line_write_room,
+	.chars_in_buffer 	= line_chars_in_buffer,
+	.flush_buffer 		= line_flush_buffer,
+	.flush_chars 		= line_flush_chars,
+	.throttle 		= line_throttle,
+	.unthrottle 		= line_unthrottle,
+	.hangup			= line_hangup,
+};
+
+static void uml_console_write(struct console *console, const char *string,
+			      unsigned len)
+{
+	struct line *line = &vts[console->index];
+	unsigned long flags;
+
+	spin_lock_irqsave(&line->lock, flags);
+	console_write_chan(line->chan_out, string, len);
+	spin_unlock_irqrestore(&line->lock, flags);
+}
+
+static struct tty_driver *uml_console_device(struct console *c, int *index)
+{
+	*index = c->index;
+	return driver.driver;
+}
+
+static int uml_console_setup(struct console *co, char *options)
+{
+	struct line *line = &vts[co->index];
+
+	return console_open_chan(line, co);
+}
+
+/* No locking for register_console call - relies on single-threaded initcalls */
+static struct console stdiocons = {
+	.name		= "tty",
+	.write		= uml_console_write,
+	.device		= uml_console_device,
+	.setup		= uml_console_setup,
+	.flags		= CON_PRINTBUFFER|CON_ANYTIME,
+	.index		= -1,
+};
+
+static int stdio_init(void)
+{
+	char *new_title;
+	int err;
+	int i;
+
+	err = register_lines(&driver, &console_ops, vts,
+					ARRAY_SIZE(vts));
+	if (err)
+		return err;
+
+	printk(KERN_INFO "Initialized stdio console driver\n");
+
+	new_title = add_xterm_umid(opts.xterm_title);
+	if(new_title != NULL)
+		opts.xterm_title = new_title;
+
+	for (i = 0; i < MAX_TTYS; i++) {
+		char *error;
+		char *s = vt_conf[i];
+		if (!s)
+			s = def_conf;
+		if (!s)
+			s = i ? CONFIG_CON_CHAN : CONFIG_CON_ZERO_CHAN;
+		if (setup_one_line(vts, i, s, &opts, &error))
+			printk(KERN_ERR "setup_one_line failed for "
+			       "device %d : %s\n", i, error);
+	}
+
+	con_init_done = 1;
+	register_console(&stdiocons);
+	return 0;
+}
+late_initcall(stdio_init);
+
+static void console_exit(void)
+{
+	if (!con_init_done)
+		return;
+	close_lines(vts, ARRAY_SIZE(vts));
+}
+__uml_exitcall(console_exit);
+
+static int console_chan_setup(char *str)
+{
+	if (!strncmp(str, "sole=", 5))	/* console= option specifies tty */
+		return 0;
+
+	line_setup(vt_conf, MAX_TTYS, &def_conf, str, "console");
+	return 1;
+}
+__setup("con", console_chan_setup);
+__channel_help(console_chan_setup, "con");
diff --git a/arch/um/drivers/stdio_console.h b/arch/um/drivers/stdio_console.h
new file mode 100644
index 000000000..3a409ec23
--- /dev/null
+++ b/arch/um/drivers/stdio_console.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* 
+ * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
+ */
+
+#ifndef __STDIO_CONSOLE_H
+#define __STDIO_CONSOLE_H
+
+extern void save_console_flags(void);
+#endif
+
diff --git a/arch/um/drivers/tty.c b/arch/um/drivers/tty.c
new file mode 100644
index 000000000..884a762d2
--- /dev/null
+++ b/arch/um/drivers/tty.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <termios.h>
+#include "chan_user.h"
+#include <os.h>
+#include <um_malloc.h>
+
+struct tty_chan {
+	char *dev;
+	int raw;
+	struct termios tt;
+};
+
+static void *tty_chan_init(char *str, int device, const struct chan_opts *opts)
+{
+	struct tty_chan *data;
+
+	if (*str != ':') {
+		printk(UM_KERN_ERR "tty_init : channel type 'tty' must specify "
+		       "a device\n");
+		return NULL;
+	}
+	str++;
+
+	data = uml_kmalloc(sizeof(*data), UM_GFP_KERNEL);
+	if (data == NULL)
+		return NULL;
+	*data = ((struct tty_chan) { .dev 	= str,
+				     .raw 	= opts->raw });
+
+	return data;
+}
+
+static int tty_open(int input, int output, int primary, void *d,
+		    char **dev_out)
+{
+	struct tty_chan *data = d;
+	int fd, err, mode = 0;
+
+	if (input && output)
+		mode = O_RDWR;
+	else if (input)
+		mode = O_RDONLY;
+	else if (output)
+		mode = O_WRONLY;
+
+	fd = open(data->dev, mode);
+	if (fd < 0)
+		return -errno;
+
+	if (data->raw) {
+		CATCH_EINTR(err = tcgetattr(fd, &data->tt));
+		if (err)
+			return err;
+
+		err = raw(fd);
+		if (err)
+			return err;
+	}
+
+	*dev_out = data->dev;
+	return fd;
+}
+
+const struct chan_ops tty_ops = {
+	.type		= "tty",
+	.init		= tty_chan_init,
+	.open		= tty_open,
+	.close		= generic_close,
+	.read		= generic_read,
+	.write		= generic_write,
+	.console_write	= generic_console_write,
+	.window_size	= generic_window_size,
+	.free		= generic_free,
+	.winch		= 0,
+};
diff --git a/arch/um/drivers/ubd.h b/arch/um/drivers/ubd.h
new file mode 100644
index 000000000..f016fe154
--- /dev/null
+++ b/arch/um/drivers/ubd.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* 
+ * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
+ * Copyright (C) 2001 RidgeRun, Inc (glonnon@ridgerun.com)
+ */
+
+#ifndef __UM_UBD_USER_H
+#define __UM_UBD_USER_H
+
+extern int start_io_thread(unsigned long sp, int *fds_out);
+extern int io_thread(void *arg);
+extern int kernel_fd;
+
+extern int ubd_read_poll(int timeout);
+extern int ubd_write_poll(int timeout);
+
+#define UBD_REQ_BUFFER_SIZE 64
+
+#endif
+
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
new file mode 100644
index 000000000..f4c1e6e97
--- /dev/null
+++ b/arch/um/drivers/ubd_kern.c
@@ -0,0 +1,1607 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018 Cambridge Greys Ltd
+ * Copyright (C) 2015-2016 Anton Ivanov (aivanov@brocade.com)
+ * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
+ */
+
+/* 2001-09-28...2002-04-17
+ * Partition stuff by James_McMechan@hotmail.com
+ * old style ubd by setting UBD_SHIFT to 0
+ * 2002-09-27...2002-10-18 massive tinkering for 2.5
+ * partitions have changed in 2.5
+ * 2003-01-29 more tinkering for 2.5.59-1
+ * This should now address the sysfs problems and has
+ * the symlink for devfs to allow for booting with
+ * the common /dev/ubd/discX/... names rather than
+ * only /dev/ubdN/discN this version also has lots of
+ * clean ups preparing for ubd-many.
+ * James McMechan
+ */
+
+#define UBD_SHIFT 4
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/blkdev.h>
+#include <linux/blk-mq.h>
+#include <linux/ata.h>
+#include <linux/hdreg.h>
+#include <linux/major.h>
+#include <linux/cdrom.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/ctype.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/platform_device.h>
+#include <linux/scatterlist.h>
+#include <asm/tlbflush.h>
+#include <kern_util.h>
+#include "mconsole_kern.h"
+#include <init.h>
+#include <irq_kern.h>
+#include "ubd.h"
+#include <os.h>
+#include "cow.h"
+
+/* Max request size is determined by sector mask - 32K */
+#define UBD_MAX_REQUEST (8 * sizeof(long))
+
+struct io_desc {
+	char *buffer;
+	unsigned long length;
+	unsigned long sector_mask;
+	unsigned long long cow_offset;
+	unsigned long bitmap_words[2];
+};
+
+struct io_thread_req {
+	struct request *req;
+	int fds[2];
+	unsigned long offsets[2];
+	unsigned long long offset;
+	int sectorsize;
+	int error;
+
+	int desc_cnt;
+	/* io_desc has to be the last element of the struct */
+	struct io_desc io_desc[];
+};
+
+
+static struct io_thread_req * (*irq_req_buffer)[];
+static struct io_thread_req *irq_remainder;
+static int irq_remainder_size;
+
+static struct io_thread_req * (*io_req_buffer)[];
+static struct io_thread_req *io_remainder;
+static int io_remainder_size;
+
+
+
+static inline int ubd_test_bit(__u64 bit, unsigned char *data)
+{
+	__u64 n;
+	int bits, off;
+
+	bits = sizeof(data[0]) * 8;
+	n = bit / bits;
+	off = bit % bits;
+	return (data[n] & (1 << off)) != 0;
+}
+
+static inline void ubd_set_bit(__u64 bit, unsigned char *data)
+{
+	__u64 n;
+	int bits, off;
+
+	bits = sizeof(data[0]) * 8;
+	n = bit / bits;
+	off = bit % bits;
+	data[n] |= (1 << off);
+}
+/*End stuff from ubd_user.h*/
+
+#define DRIVER_NAME "uml-blkdev"
+
+static DEFINE_MUTEX(ubd_lock);
+static DEFINE_MUTEX(ubd_mutex); /* replaces BKL, might not be needed */
+
+static int ubd_open(struct block_device *bdev, fmode_t mode);
+static void ubd_release(struct gendisk *disk, fmode_t mode);
+static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
+		     unsigned int cmd, unsigned long arg);
+static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo);
+
+#define MAX_DEV (16)
+
+static const struct block_device_operations ubd_blops = {
+        .owner		= THIS_MODULE,
+        .open		= ubd_open,
+        .release	= ubd_release,
+        .ioctl		= ubd_ioctl,
+        .compat_ioctl	= blkdev_compat_ptr_ioctl,
+	.getgeo		= ubd_getgeo,
+};
+
+/* Protected by ubd_lock */
+static struct gendisk *ubd_gendisk[MAX_DEV];
+
+#ifdef CONFIG_BLK_DEV_UBD_SYNC
+#define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 1, .c = 0, \
+					 .cl = 1 })
+#else
+#define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 0, .c = 0, \
+					 .cl = 1 })
+#endif
+static struct openflags global_openflags = OPEN_FLAGS;
+
+struct cow {
+	/* backing file name */
+	char *file;
+	/* backing file fd */
+	int fd;
+	unsigned long *bitmap;
+	unsigned long bitmap_len;
+	int bitmap_offset;
+	int data_offset;
+};
+
+#define MAX_SG 64
+
+struct ubd {
+	/* name (and fd, below) of the file opened for writing, either the
+	 * backing or the cow file. */
+	char *file;
+	char *serial;
+	int count;
+	int fd;
+	__u64 size;
+	struct openflags boot_openflags;
+	struct openflags openflags;
+	unsigned shared:1;
+	unsigned no_cow:1;
+	unsigned no_trim:1;
+	struct cow cow;
+	struct platform_device pdev;
+	struct request_queue *queue;
+	struct blk_mq_tag_set tag_set;
+	spinlock_t lock;
+};
+
+#define DEFAULT_COW { \
+	.file =			NULL, \
+	.fd =			-1,	\
+	.bitmap =		NULL, \
+	.bitmap_offset =	0, \
+	.data_offset =		0, \
+}
+
+#define DEFAULT_UBD { \
+	.file = 		NULL, \
+	.serial =		NULL, \
+	.count =		0, \
+	.fd =			-1, \
+	.size =			-1, \
+	.boot_openflags =	OPEN_FLAGS, \
+	.openflags =		OPEN_FLAGS, \
+	.no_cow =               0, \
+	.no_trim =		0, \
+	.shared =		0, \
+	.cow =			DEFAULT_COW, \
+	.lock =			__SPIN_LOCK_UNLOCKED(ubd_devs.lock), \
+}
+
+/* Protected by ubd_lock */
+static struct ubd ubd_devs[MAX_DEV] = { [0 ... MAX_DEV - 1] = DEFAULT_UBD };
+
+static blk_status_t ubd_queue_rq(struct blk_mq_hw_ctx *hctx,
+				 const struct blk_mq_queue_data *bd);
+
+static int fake_ide_setup(char *str)
+{
+	pr_warn("The fake_ide option has been removed\n");
+	return 1;
+}
+__setup("fake_ide", fake_ide_setup);
+
+__uml_help(fake_ide_setup,
+"fake_ide\n"
+"    Obsolete stub.\n\n"
+);
+
+static int parse_unit(char **ptr)
+{
+	char *str = *ptr, *end;
+	int n = -1;
+
+	if(isdigit(*str)) {
+		n = simple_strtoul(str, &end, 0);
+		if(end == str)
+			return -1;
+		*ptr = end;
+	}
+	else if (('a' <= *str) && (*str <= 'z')) {
+		n = *str - 'a';
+		str++;
+		*ptr = str;
+	}
+	return n;
+}
+
+/* If *index_out == -1 at exit, the passed option was a general one;
+ * otherwise, the str pointer is used (and owned) inside ubd_devs array, so it
+ * should not be freed on exit.
+ */
+static int ubd_setup_common(char *str, int *index_out, char **error_out)
+{
+	struct ubd *ubd_dev;
+	struct openflags flags = global_openflags;
+	char *file, *backing_file, *serial;
+	int n, err = 0, i;
+
+	if(index_out) *index_out = -1;
+	n = *str;
+	if(n == '='){
+		str++;
+		if(!strcmp(str, "sync")){
+			global_openflags = of_sync(global_openflags);
+			return err;
+		}
+
+		pr_warn("fake major not supported any more\n");
+		return 0;
+	}
+
+	n = parse_unit(&str);
+	if(n < 0){
+		*error_out = "Couldn't parse device number";
+		return -EINVAL;
+	}
+	if(n >= MAX_DEV){
+		*error_out = "Device number out of range";
+		return 1;
+	}
+
+	err = -EBUSY;
+	mutex_lock(&ubd_lock);
+
+	ubd_dev = &ubd_devs[n];
+	if(ubd_dev->file != NULL){
+		*error_out = "Device is already configured";
+		goto out;
+	}
+
+	if (index_out)
+		*index_out = n;
+
+	err = -EINVAL;
+	for (i = 0; i < sizeof("rscdt="); i++) {
+		switch (*str) {
+		case 'r':
+			flags.w = 0;
+			break;
+		case 's':
+			flags.s = 1;
+			break;
+		case 'd':
+			ubd_dev->no_cow = 1;
+			break;
+		case 'c':
+			ubd_dev->shared = 1;
+			break;
+		case 't':
+			ubd_dev->no_trim = 1;
+			break;
+		case '=':
+			str++;
+			goto break_loop;
+		default:
+			*error_out = "Expected '=' or flag letter "
+				"(r, s, c, t or d)";
+			goto out;
+		}
+		str++;
+	}
+
+	if (*str == '=')
+		*error_out = "Too many flags specified";
+	else
+		*error_out = "Missing '='";
+	goto out;
+
+break_loop:
+	file = strsep(&str, ",:");
+	if (*file == '\0')
+		file = NULL;
+
+	backing_file = strsep(&str, ",:");
+	if (backing_file && *backing_file == '\0')
+		backing_file = NULL;
+
+	serial = strsep(&str, ",:");
+	if (serial && *serial == '\0')
+		serial = NULL;
+
+	if (backing_file && ubd_dev->no_cow) {
+		*error_out = "Can't specify both 'd' and a cow file";
+		goto out;
+	}
+
+	err = 0;
+	ubd_dev->file = file;
+	ubd_dev->cow.file = backing_file;
+	ubd_dev->serial = serial;
+	ubd_dev->boot_openflags = flags;
+out:
+	mutex_unlock(&ubd_lock);
+	return err;
+}
+
+static int ubd_setup(char *str)
+{
+	char *error;
+	int err;
+
+	err = ubd_setup_common(str, NULL, &error);
+	if(err)
+		printk(KERN_ERR "Failed to initialize device with \"%s\" : "
+		       "%s\n", str, error);
+	return 1;
+}
+
+__setup("ubd", ubd_setup);
+__uml_help(ubd_setup,
+"ubd<n><flags>=<filename>[(:|,)<filename2>][(:|,)<serial>]\n"
+"    This is used to associate a device with a file in the underlying\n"
+"    filesystem. When specifying two filenames, the first one is the\n"
+"    COW name and the second is the backing file name. As separator you can\n"
+"    use either a ':' or a ',': the first one allows writing things like;\n"
+"	ubd0=~/Uml/root_cow:~/Uml/root_backing_file\n"
+"    while with a ',' the shell would not expand the 2nd '~'.\n"
+"    When using only one filename, UML will detect whether to treat it like\n"
+"    a COW file or a backing file. To override this detection, add the 'd'\n"
+"    flag:\n"
+"	ubd0d=BackingFile\n"
+"    Usually, there is a filesystem in the file, but \n"
+"    that's not required. Swap devices containing swap files can be\n"
+"    specified like this. Also, a file which doesn't contain a\n"
+"    filesystem can have its contents read in the virtual \n"
+"    machine by running 'dd' on the device. <n> must be in the range\n"
+"    0 to 7. Appending an 'r' to the number will cause that device\n"
+"    to be mounted read-only. For example ubd1r=./ext_fs. Appending\n"
+"    an 's' will cause data to be written to disk on the host immediately.\n"
+"    'c' will cause the device to be treated as being shared between multiple\n"
+"    UMLs and file locking will be turned off - this is appropriate for a\n"
+"    cluster filesystem and inappropriate at almost all other times.\n\n"
+"    't' will disable trim/discard support on the device (enabled by default).\n\n"
+"    An optional device serial number can be exposed using the serial parameter\n"
+"    on the cmdline which is exposed as a sysfs entry. This is particularly\n"
+"    useful when a unique number should be given to the device. Note when\n"
+"    specifying a label, the filename2 must be also presented. It can be\n"
+"    an empty string, in which case the backing file is not used:\n"
+"       ubd0=File,,Serial\n"
+);
+
+static int udb_setup(char *str)
+{
+	printk("udb%s specified on command line is almost certainly a ubd -> "
+	       "udb TYPO\n", str);
+	return 1;
+}
+
+__setup("udb", udb_setup);
+__uml_help(udb_setup,
+"udb\n"
+"    This option is here solely to catch ubd -> udb typos, which can be\n"
+"    to impossible to catch visually unless you specifically look for\n"
+"    them.  The only result of any option starting with 'udb' is an error\n"
+"    in the boot output.\n\n"
+);
+
+/* Only changed by ubd_init, which is an initcall. */
+static int thread_fd = -1;
+
+/* Function to read several request pointers at a time
+* handling fractional reads if (and as) needed
+*/
+
+static int bulk_req_safe_read(
+	int fd,
+	struct io_thread_req * (*request_buffer)[],
+	struct io_thread_req **remainder,
+	int *remainder_size,
+	int max_recs
+	)
+{
+	int n = 0;
+	int res = 0;
+
+	if (*remainder_size > 0) {
+		memmove(
+			(char *) request_buffer,
+			(char *) remainder, *remainder_size
+		);
+		n = *remainder_size;
+	}
+
+	res = os_read_file(
+			fd,
+			((char *) request_buffer) + *remainder_size,
+			sizeof(struct io_thread_req *)*max_recs
+				- *remainder_size
+		);
+	if (res > 0) {
+		n += res;
+		if ((n % sizeof(struct io_thread_req *)) > 0) {
+			/*
+			* Read somehow returned not a multiple of dword
+			* theoretically possible, but never observed in the
+			* wild, so read routine must be able to handle it
+			*/
+			*remainder_size = n % sizeof(struct io_thread_req *);
+			WARN(*remainder_size > 0, "UBD IPC read returned a partial result");
+			memmove(
+				remainder,
+				((char *) request_buffer) +
+					(n/sizeof(struct io_thread_req *))*sizeof(struct io_thread_req *),
+				*remainder_size
+			);
+			n = n - *remainder_size;
+		}
+	} else {
+		n = res;
+	}
+	return n;
+}
+
+/* Called without dev->lock held, and only in interrupt context. */
+static void ubd_handler(void)
+{
+	int n;
+	int count;
+
+	while(1){
+		n = bulk_req_safe_read(
+			thread_fd,
+			irq_req_buffer,
+			&irq_remainder,
+			&irq_remainder_size,
+			UBD_REQ_BUFFER_SIZE
+		);
+		if (n < 0) {
+			if(n == -EAGAIN)
+				break;
+			printk(KERN_ERR "spurious interrupt in ubd_handler, "
+			       "err = %d\n", -n);
+			return;
+		}
+		for (count = 0; count < n/sizeof(struct io_thread_req *); count++) {
+			struct io_thread_req *io_req = (*irq_req_buffer)[count];
+
+			if ((io_req->error == BLK_STS_NOTSUPP) && (req_op(io_req->req) == REQ_OP_DISCARD)) {
+				blk_queue_max_discard_sectors(io_req->req->q, 0);
+				blk_queue_max_write_zeroes_sectors(io_req->req->q, 0);
+			}
+			blk_mq_end_request(io_req->req, io_req->error);
+			kfree(io_req);
+		}
+	}
+}
+
+static irqreturn_t ubd_intr(int irq, void *dev)
+{
+	ubd_handler();
+	return IRQ_HANDLED;
+}
+
+/* Only changed by ubd_init, which is an initcall. */
+static int io_pid = -1;
+
+static void kill_io_thread(void)
+{
+	if(io_pid != -1)
+		os_kill_process(io_pid, 1);
+}
+
+__uml_exitcall(kill_io_thread);
+
+static inline int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
+{
+	char *file;
+	int fd;
+	int err;
+
+	__u32 version;
+	__u32 align;
+	char *backing_file;
+	time64_t mtime;
+	unsigned long long size;
+	int sector_size;
+	int bitmap_offset;
+
+	if (ubd_dev->file && ubd_dev->cow.file) {
+		file = ubd_dev->cow.file;
+
+		goto out;
+	}
+
+	fd = os_open_file(ubd_dev->file, of_read(OPENFLAGS()), 0);
+	if (fd < 0)
+		return fd;
+
+	err = read_cow_header(file_reader, &fd, &version, &backing_file, \
+		&mtime, &size, &sector_size, &align, &bitmap_offset);
+	os_close_file(fd);
+
+	if(err == -EINVAL)
+		file = ubd_dev->file;
+	else
+		file = backing_file;
+
+out:
+	return os_file_size(file, size_out);
+}
+
+static int read_cow_bitmap(int fd, void *buf, int offset, int len)
+{
+	int err;
+
+	err = os_pread_file(fd, buf, len, offset);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static int backing_file_mismatch(char *file, __u64 size, time64_t mtime)
+{
+	time64_t modtime;
+	unsigned long long actual;
+	int err;
+
+	err = os_file_modtime(file, &modtime);
+	if (err < 0) {
+		printk(KERN_ERR "Failed to get modification time of backing "
+		       "file \"%s\", err = %d\n", file, -err);
+		return err;
+	}
+
+	err = os_file_size(file, &actual);
+	if (err < 0) {
+		printk(KERN_ERR "Failed to get size of backing file \"%s\", "
+		       "err = %d\n", file, -err);
+		return err;
+	}
+
+	if (actual != size) {
+		/*__u64 can be a long on AMD64 and with %lu GCC complains; so
+		 * the typecast.*/
+		printk(KERN_ERR "Size mismatch (%llu vs %llu) of COW header "
+		       "vs backing file\n", (unsigned long long) size, actual);
+		return -EINVAL;
+	}
+	if (modtime != mtime) {
+		printk(KERN_ERR "mtime mismatch (%lld vs %lld) of COW header vs "
+		       "backing file\n", mtime, modtime);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int path_requires_switch(char *from_cmdline, char *from_cow, char *cow)
+{
+	struct uml_stat buf1, buf2;
+	int err;
+
+	if (from_cmdline == NULL)
+		return 0;
+	if (!strcmp(from_cmdline, from_cow))
+		return 0;
+
+	err = os_stat_file(from_cmdline, &buf1);
+	if (err < 0) {
+		printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cmdline,
+		       -err);
+		return 0;
+	}
+	err = os_stat_file(from_cow, &buf2);
+	if (err < 0) {
+		printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cow,
+		       -err);
+		return 1;
+	}
+	if ((buf1.ust_dev == buf2.ust_dev) && (buf1.ust_ino == buf2.ust_ino))
+		return 0;
+
+	printk(KERN_ERR "Backing file mismatch - \"%s\" requested, "
+	       "\"%s\" specified in COW header of \"%s\"\n",
+	       from_cmdline, from_cow, cow);
+	return 1;
+}
+
+static int open_ubd_file(char *file, struct openflags *openflags, int shared,
+		  char **backing_file_out, int *bitmap_offset_out,
+		  unsigned long *bitmap_len_out, int *data_offset_out,
+		  int *create_cow_out)
+{
+	time64_t mtime;
+	unsigned long long size;
+	__u32 version, align;
+	char *backing_file;
+	int fd, err, sectorsize, asked_switch, mode = 0644;
+
+	fd = os_open_file(file, *openflags, mode);
+	if (fd < 0) {
+		if ((fd == -ENOENT) && (create_cow_out != NULL))
+			*create_cow_out = 1;
+		if (!openflags->w ||
+		    ((fd != -EROFS) && (fd != -EACCES)))
+			return fd;
+		openflags->w = 0;
+		fd = os_open_file(file, *openflags, mode);
+		if (fd < 0)
+			return fd;
+	}
+
+	if (shared)
+		printk(KERN_INFO "Not locking \"%s\" on the host\n", file);
+	else {
+		err = os_lock_file(fd, openflags->w);
+		if (err < 0) {
+			printk(KERN_ERR "Failed to lock '%s', err = %d\n",
+			       file, -err);
+			goto out_close;
+		}
+	}
+
+	/* Successful return case! */
+	if (backing_file_out == NULL)
+		return fd;
+
+	err = read_cow_header(file_reader, &fd, &version, &backing_file, &mtime,
+			      &size, &sectorsize, &align, bitmap_offset_out);
+	if (err && (*backing_file_out != NULL)) {
+		printk(KERN_ERR "Failed to read COW header from COW file "
+		       "\"%s\", errno = %d\n", file, -err);
+		goto out_close;
+	}
+	if (err)
+		return fd;
+
+	asked_switch = path_requires_switch(*backing_file_out, backing_file,
+					    file);
+
+	/* Allow switching only if no mismatch. */
+	if (asked_switch && !backing_file_mismatch(*backing_file_out, size,
+						   mtime)) {
+		printk(KERN_ERR "Switching backing file to '%s'\n",
+		       *backing_file_out);
+		err = write_cow_header(file, fd, *backing_file_out,
+				       sectorsize, align, &size);
+		if (err) {
+			printk(KERN_ERR "Switch failed, errno = %d\n", -err);
+			goto out_close;
+		}
+	} else {
+		*backing_file_out = backing_file;
+		err = backing_file_mismatch(*backing_file_out, size, mtime);
+		if (err)
+			goto out_close;
+	}
+
+	cow_sizes(version, size, sectorsize, align, *bitmap_offset_out,
+		  bitmap_len_out, data_offset_out);
+
+	return fd;
+ out_close:
+	os_close_file(fd);
+	return err;
+}
+
+static int create_cow_file(char *cow_file, char *backing_file,
+		    struct openflags flags,
+		    int sectorsize, int alignment, int *bitmap_offset_out,
+		    unsigned long *bitmap_len_out, int *data_offset_out)
+{
+	int err, fd;
+
+	flags.c = 1;
+	fd = open_ubd_file(cow_file, &flags, 0, NULL, NULL, NULL, NULL, NULL);
+	if (fd < 0) {
+		err = fd;
+		printk(KERN_ERR "Open of COW file '%s' failed, errno = %d\n",
+		       cow_file, -err);
+		goto out;
+	}
+
+	err = init_cow_file(fd, cow_file, backing_file, sectorsize, alignment,
+			    bitmap_offset_out, bitmap_len_out,
+			    data_offset_out);
+	if (!err)
+		return fd;
+	os_close_file(fd);
+ out:
+	return err;
+}
+
+static void ubd_close_dev(struct ubd *ubd_dev)
+{
+	os_close_file(ubd_dev->fd);
+	if(ubd_dev->cow.file == NULL)
+		return;
+
+	os_close_file(ubd_dev->cow.fd);
+	vfree(ubd_dev->cow.bitmap);
+	ubd_dev->cow.bitmap = NULL;
+}
+
+static int ubd_open_dev(struct ubd *ubd_dev)
+{
+	struct openflags flags;
+	char **back_ptr;
+	int err, create_cow, *create_ptr;
+	int fd;
+
+	ubd_dev->openflags = ubd_dev->boot_openflags;
+	create_cow = 0;
+	create_ptr = (ubd_dev->cow.file != NULL) ? &create_cow : NULL;
+	back_ptr = ubd_dev->no_cow ? NULL : &ubd_dev->cow.file;
+
+	fd = open_ubd_file(ubd_dev->file, &ubd_dev->openflags, ubd_dev->shared,
+				back_ptr, &ubd_dev->cow.bitmap_offset,
+				&ubd_dev->cow.bitmap_len, &ubd_dev->cow.data_offset,
+				create_ptr);
+
+	if((fd == -ENOENT) && create_cow){
+		fd = create_cow_file(ubd_dev->file, ubd_dev->cow.file,
+					  ubd_dev->openflags, SECTOR_SIZE, PAGE_SIZE,
+					  &ubd_dev->cow.bitmap_offset,
+					  &ubd_dev->cow.bitmap_len,
+					  &ubd_dev->cow.data_offset);
+		if(fd >= 0){
+			printk(KERN_INFO "Creating \"%s\" as COW file for "
+			       "\"%s\"\n", ubd_dev->file, ubd_dev->cow.file);
+		}
+	}
+
+	if(fd < 0){
+		printk("Failed to open '%s', errno = %d\n", ubd_dev->file,
+		       -fd);
+		return fd;
+	}
+	ubd_dev->fd = fd;
+
+	if(ubd_dev->cow.file != NULL){
+		blk_queue_max_hw_sectors(ubd_dev->queue, 8 * sizeof(long));
+
+		err = -ENOMEM;
+		ubd_dev->cow.bitmap = vmalloc(ubd_dev->cow.bitmap_len);
+		if(ubd_dev->cow.bitmap == NULL){
+			printk(KERN_ERR "Failed to vmalloc COW bitmap\n");
+			goto error;
+		}
+		flush_tlb_kernel_vm();
+
+		err = read_cow_bitmap(ubd_dev->fd, ubd_dev->cow.bitmap,
+				      ubd_dev->cow.bitmap_offset,
+				      ubd_dev->cow.bitmap_len);
+		if(err < 0)
+			goto error;
+
+		flags = ubd_dev->openflags;
+		flags.w = 0;
+		err = open_ubd_file(ubd_dev->cow.file, &flags, ubd_dev->shared, NULL,
+				    NULL, NULL, NULL, NULL);
+		if(err < 0) goto error;
+		ubd_dev->cow.fd = err;
+	}
+	if (ubd_dev->no_trim == 0) {
+		ubd_dev->queue->limits.discard_granularity = SECTOR_SIZE;
+		blk_queue_max_discard_sectors(ubd_dev->queue, UBD_MAX_REQUEST);
+		blk_queue_max_write_zeroes_sectors(ubd_dev->queue, UBD_MAX_REQUEST);
+	}
+	blk_queue_flag_set(QUEUE_FLAG_NONROT, ubd_dev->queue);
+	return 0;
+ error:
+	os_close_file(ubd_dev->fd);
+	return err;
+}
+
+static void ubd_device_release(struct device *dev)
+{
+	struct ubd *ubd_dev = dev_get_drvdata(dev);
+
+	blk_mq_free_tag_set(&ubd_dev->tag_set);
+	*ubd_dev = ((struct ubd) DEFAULT_UBD);
+}
+
+static ssize_t serial_show(struct device *dev,
+			   struct device_attribute *attr, char *buf)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+	struct ubd *ubd_dev = disk->private_data;
+
+	if (!ubd_dev)
+		return 0;
+
+	return sprintf(buf, "%s", ubd_dev->serial);
+}
+
+static DEVICE_ATTR_RO(serial);
+
+static struct attribute *ubd_attrs[] = {
+	&dev_attr_serial.attr,
+	NULL,
+};
+
+static umode_t ubd_attrs_are_visible(struct kobject *kobj,
+				     struct attribute *a, int n)
+{
+	return a->mode;
+}
+
+static const struct attribute_group ubd_attr_group = {
+	.attrs = ubd_attrs,
+	.is_visible = ubd_attrs_are_visible,
+};
+
+static const struct attribute_group *ubd_attr_groups[] = {
+	&ubd_attr_group,
+	NULL,
+};
+
+static int ubd_disk_register(int major, u64 size, int unit,
+			     struct gendisk *disk)
+{
+	disk->major = major;
+	disk->first_minor = unit << UBD_SHIFT;
+	disk->minors = 1 << UBD_SHIFT;
+	disk->fops = &ubd_blops;
+	set_capacity(disk, size / 512);
+	sprintf(disk->disk_name, "ubd%c", 'a' + unit);
+
+	ubd_devs[unit].pdev.id   = unit;
+	ubd_devs[unit].pdev.name = DRIVER_NAME;
+	ubd_devs[unit].pdev.dev.release = ubd_device_release;
+	dev_set_drvdata(&ubd_devs[unit].pdev.dev, &ubd_devs[unit]);
+	platform_device_register(&ubd_devs[unit].pdev);
+
+	disk->private_data = &ubd_devs[unit];
+	disk->queue = ubd_devs[unit].queue;
+	return device_add_disk(&ubd_devs[unit].pdev.dev, disk, ubd_attr_groups);
+}
+
+#define ROUND_BLOCK(n) ((n + (SECTOR_SIZE - 1)) & (-SECTOR_SIZE))
+
+static const struct blk_mq_ops ubd_mq_ops = {
+	.queue_rq = ubd_queue_rq,
+};
+
+static int ubd_add(int n, char **error_out)
+{
+	struct ubd *ubd_dev = &ubd_devs[n];
+	struct gendisk *disk;
+	int err = 0;
+
+	if(ubd_dev->file == NULL)
+		goto out;
+
+	err = ubd_file_size(ubd_dev, &ubd_dev->size);
+	if(err < 0){
+		*error_out = "Couldn't determine size of device's file";
+		goto out;
+	}
+
+	ubd_dev->size = ROUND_BLOCK(ubd_dev->size);
+
+	ubd_dev->tag_set.ops = &ubd_mq_ops;
+	ubd_dev->tag_set.queue_depth = 64;
+	ubd_dev->tag_set.numa_node = NUMA_NO_NODE;
+	ubd_dev->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
+	ubd_dev->tag_set.driver_data = ubd_dev;
+	ubd_dev->tag_set.nr_hw_queues = 1;
+
+	err = blk_mq_alloc_tag_set(&ubd_dev->tag_set);
+	if (err)
+		goto out;
+
+	disk = blk_mq_alloc_disk(&ubd_dev->tag_set, ubd_dev);
+	if (IS_ERR(disk)) {
+		err = PTR_ERR(disk);
+		goto out_cleanup_tags;
+	}
+	ubd_dev->queue = disk->queue;
+
+	blk_queue_write_cache(ubd_dev->queue, true, false);
+	blk_queue_max_segments(ubd_dev->queue, MAX_SG);
+	blk_queue_segment_boundary(ubd_dev->queue, PAGE_SIZE - 1);
+	err = ubd_disk_register(UBD_MAJOR, ubd_dev->size, n, disk);
+	if (err)
+		goto out_cleanup_disk;
+
+	ubd_gendisk[n] = disk;
+	return 0;
+
+out_cleanup_disk:
+	put_disk(disk);
+out_cleanup_tags:
+	blk_mq_free_tag_set(&ubd_dev->tag_set);
+out:
+	return err;
+}
+
+static int ubd_config(char *str, char **error_out)
+{
+	int n, ret;
+
+	/* This string is possibly broken up and stored, so it's only
+	 * freed if ubd_setup_common fails, or if only general options
+	 * were set.
+	 */
+	str = kstrdup(str, GFP_KERNEL);
+	if (str == NULL) {
+		*error_out = "Failed to allocate memory";
+		return -ENOMEM;
+	}
+
+	ret = ubd_setup_common(str, &n, error_out);
+	if (ret)
+		goto err_free;
+
+	if (n == -1) {
+		ret = 0;
+		goto err_free;
+	}
+
+	mutex_lock(&ubd_lock);
+	ret = ubd_add(n, error_out);
+	if (ret)
+		ubd_devs[n].file = NULL;
+	mutex_unlock(&ubd_lock);
+
+out:
+	return ret;
+
+err_free:
+	kfree(str);
+	goto out;
+}
+
+static int ubd_get_config(char *name, char *str, int size, char **error_out)
+{
+	struct ubd *ubd_dev;
+	int n, len = 0;
+
+	n = parse_unit(&name);
+	if((n >= MAX_DEV) || (n < 0)){
+		*error_out = "ubd_get_config : device number out of range";
+		return -1;
+	}
+
+	ubd_dev = &ubd_devs[n];
+	mutex_lock(&ubd_lock);
+
+	if(ubd_dev->file == NULL){
+		CONFIG_CHUNK(str, size, len, "", 1);
+		goto out;
+	}
+
+	CONFIG_CHUNK(str, size, len, ubd_dev->file, 0);
+
+	if(ubd_dev->cow.file != NULL){
+		CONFIG_CHUNK(str, size, len, ",", 0);
+		CONFIG_CHUNK(str, size, len, ubd_dev->cow.file, 1);
+	}
+	else CONFIG_CHUNK(str, size, len, "", 1);
+
+ out:
+	mutex_unlock(&ubd_lock);
+	return len;
+}
+
+static int ubd_id(char **str, int *start_out, int *end_out)
+{
+	int n;
+
+	n = parse_unit(str);
+	*start_out = 0;
+	*end_out = MAX_DEV - 1;
+	return n;
+}
+
+static int ubd_remove(int n, char **error_out)
+{
+	struct gendisk *disk = ubd_gendisk[n];
+	struct ubd *ubd_dev;
+	int err = -ENODEV;
+
+	mutex_lock(&ubd_lock);
+
+	ubd_dev = &ubd_devs[n];
+
+	if(ubd_dev->file == NULL)
+		goto out;
+
+	/* you cannot remove a open disk */
+	err = -EBUSY;
+	if(ubd_dev->count > 0)
+		goto out;
+
+	ubd_gendisk[n] = NULL;
+	if(disk != NULL){
+		del_gendisk(disk);
+		put_disk(disk);
+	}
+
+	err = 0;
+	platform_device_unregister(&ubd_dev->pdev);
+out:
+	mutex_unlock(&ubd_lock);
+	return err;
+}
+
+/* All these are called by mconsole in process context and without
+ * ubd-specific locks.  The structure itself is const except for .list.
+ */
+static struct mc_device ubd_mc = {
+	.list		= LIST_HEAD_INIT(ubd_mc.list),
+	.name		= "ubd",
+	.config		= ubd_config,
+	.get_config	= ubd_get_config,
+	.id		= ubd_id,
+	.remove		= ubd_remove,
+};
+
+static int __init ubd_mc_init(void)
+{
+	mconsole_register_dev(&ubd_mc);
+	return 0;
+}
+
+__initcall(ubd_mc_init);
+
+static int __init ubd0_init(void)
+{
+	struct ubd *ubd_dev = &ubd_devs[0];
+
+	mutex_lock(&ubd_lock);
+	if(ubd_dev->file == NULL)
+		ubd_dev->file = "root_fs";
+	mutex_unlock(&ubd_lock);
+
+	return 0;
+}
+
+__initcall(ubd0_init);
+
+/* Used in ubd_init, which is an initcall */
+static struct platform_driver ubd_driver = {
+	.driver = {
+		.name  = DRIVER_NAME,
+	},
+};
+
+static int __init ubd_init(void)
+{
+	char *error;
+	int i, err;
+
+	if (register_blkdev(UBD_MAJOR, "ubd"))
+		return -1;
+
+	irq_req_buffer = kmalloc_array(UBD_REQ_BUFFER_SIZE,
+				       sizeof(struct io_thread_req *),
+				       GFP_KERNEL
+		);
+	irq_remainder = 0;
+
+	if (irq_req_buffer == NULL) {
+		printk(KERN_ERR "Failed to initialize ubd buffering\n");
+		return -1;
+	}
+	io_req_buffer = kmalloc_array(UBD_REQ_BUFFER_SIZE,
+				      sizeof(struct io_thread_req *),
+				      GFP_KERNEL
+		);
+
+	io_remainder = 0;
+
+	if (io_req_buffer == NULL) {
+		printk(KERN_ERR "Failed to initialize ubd buffering\n");
+		return -1;
+	}
+	platform_driver_register(&ubd_driver);
+	mutex_lock(&ubd_lock);
+	for (i = 0; i < MAX_DEV; i++){
+		err = ubd_add(i, &error);
+		if(err)
+			printk(KERN_ERR "Failed to initialize ubd device %d :"
+			       "%s\n", i, error);
+	}
+	mutex_unlock(&ubd_lock);
+	return 0;
+}
+
+late_initcall(ubd_init);
+
+static int __init ubd_driver_init(void){
+	unsigned long stack;
+	int err;
+
+	/* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
+	if(global_openflags.s){
+		printk(KERN_INFO "ubd: Synchronous mode\n");
+		/* Letting ubd=sync be like using ubd#s= instead of ubd#= is
+		 * enough. So use anyway the io thread. */
+	}
+	stack = alloc_stack(0, 0);
+	io_pid = start_io_thread(stack + PAGE_SIZE, &thread_fd);
+	if(io_pid < 0){
+		printk(KERN_ERR
+		       "ubd : Failed to start I/O thread (errno = %d) - "
+		       "falling back to synchronous I/O\n", -io_pid);
+		io_pid = -1;
+		return 0;
+	}
+	err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr,
+			     0, "ubd", ubd_devs);
+	if(err < 0)
+		printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
+	return 0;
+}
+
+device_initcall(ubd_driver_init);
+
+static int ubd_open(struct block_device *bdev, fmode_t mode)
+{
+	struct gendisk *disk = bdev->bd_disk;
+	struct ubd *ubd_dev = disk->private_data;
+	int err = 0;
+
+	mutex_lock(&ubd_mutex);
+	if(ubd_dev->count == 0){
+		err = ubd_open_dev(ubd_dev);
+		if(err){
+			printk(KERN_ERR "%s: Can't open \"%s\": errno = %d\n",
+			       disk->disk_name, ubd_dev->file, -err);
+			goto out;
+		}
+	}
+	ubd_dev->count++;
+	set_disk_ro(disk, !ubd_dev->openflags.w);
+
+	/* This should no more be needed. And it didn't work anyway to exclude
+	 * read-write remounting of filesystems.*/
+	/*if((mode & FMODE_WRITE) && !ubd_dev->openflags.w){
+	        if(--ubd_dev->count == 0) ubd_close_dev(ubd_dev);
+	        err = -EROFS;
+	}*/
+out:
+	mutex_unlock(&ubd_mutex);
+	return err;
+}
+
+static void ubd_release(struct gendisk *disk, fmode_t mode)
+{
+	struct ubd *ubd_dev = disk->private_data;
+
+	mutex_lock(&ubd_mutex);
+	if(--ubd_dev->count == 0)
+		ubd_close_dev(ubd_dev);
+	mutex_unlock(&ubd_mutex);
+}
+
+static void cowify_bitmap(__u64 io_offset, int length, unsigned long *cow_mask,
+			  __u64 *cow_offset, unsigned long *bitmap,
+			  __u64 bitmap_offset, unsigned long *bitmap_words,
+			  __u64 bitmap_len)
+{
+	__u64 sector = io_offset >> SECTOR_SHIFT;
+	int i, update_bitmap = 0;
+
+	for (i = 0; i < length >> SECTOR_SHIFT; i++) {
+		if(cow_mask != NULL)
+			ubd_set_bit(i, (unsigned char *) cow_mask);
+		if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
+			continue;
+
+		update_bitmap = 1;
+		ubd_set_bit(sector + i, (unsigned char *) bitmap);
+	}
+
+	if(!update_bitmap)
+		return;
+
+	*cow_offset = sector / (sizeof(unsigned long) * 8);
+
+	/* This takes care of the case where we're exactly at the end of the
+	 * device, and *cow_offset + 1 is off the end.  So, just back it up
+	 * by one word.  Thanks to Lynn Kerby for the fix and James McMechan
+	 * for the original diagnosis.
+	 */
+	if (*cow_offset == (DIV_ROUND_UP(bitmap_len,
+					 sizeof(unsigned long)) - 1))
+		(*cow_offset)--;
+
+	bitmap_words[0] = bitmap[*cow_offset];
+	bitmap_words[1] = bitmap[*cow_offset + 1];
+
+	*cow_offset *= sizeof(unsigned long);
+	*cow_offset += bitmap_offset;
+}
+
+static void cowify_req(struct io_thread_req *req, struct io_desc *segment,
+		       unsigned long offset, unsigned long *bitmap,
+		       __u64 bitmap_offset, __u64 bitmap_len)
+{
+	__u64 sector = offset >> SECTOR_SHIFT;
+	int i;
+
+	if (segment->length > (sizeof(segment->sector_mask) * 8) << SECTOR_SHIFT)
+		panic("Operation too long");
+
+	if (req_op(req->req) == REQ_OP_READ) {
+		for (i = 0; i < segment->length >> SECTOR_SHIFT; i++) {
+			if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
+				ubd_set_bit(i, (unsigned char *)
+					    &segment->sector_mask);
+		}
+	} else {
+		cowify_bitmap(offset, segment->length, &segment->sector_mask,
+			      &segment->cow_offset, bitmap, bitmap_offset,
+			      segment->bitmap_words, bitmap_len);
+	}
+}
+
+static void ubd_map_req(struct ubd *dev, struct io_thread_req *io_req,
+			struct request *req)
+{
+	struct bio_vec bvec;
+	struct req_iterator iter;
+	int i = 0;
+	unsigned long byte_offset = io_req->offset;
+	enum req_op op = req_op(req);
+
+	if (op == REQ_OP_WRITE_ZEROES || op == REQ_OP_DISCARD) {
+		io_req->io_desc[0].buffer = NULL;
+		io_req->io_desc[0].length = blk_rq_bytes(req);
+	} else {
+		rq_for_each_segment(bvec, req, iter) {
+			BUG_ON(i >= io_req->desc_cnt);
+
+			io_req->io_desc[i].buffer = bvec_virt(&bvec);
+			io_req->io_desc[i].length = bvec.bv_len;
+			i++;
+		}
+	}
+
+	if (dev->cow.file) {
+		for (i = 0; i < io_req->desc_cnt; i++) {
+			cowify_req(io_req, &io_req->io_desc[i], byte_offset,
+				   dev->cow.bitmap, dev->cow.bitmap_offset,
+				   dev->cow.bitmap_len);
+			byte_offset += io_req->io_desc[i].length;
+		}
+
+	}
+}
+
+static struct io_thread_req *ubd_alloc_req(struct ubd *dev, struct request *req,
+					   int desc_cnt)
+{
+	struct io_thread_req *io_req;
+	int i;
+
+	io_req = kmalloc(sizeof(*io_req) +
+			 (desc_cnt * sizeof(struct io_desc)),
+			 GFP_ATOMIC);
+	if (!io_req)
+		return NULL;
+
+	io_req->req = req;
+	if (dev->cow.file)
+		io_req->fds[0] = dev->cow.fd;
+	else
+		io_req->fds[0] = dev->fd;
+	io_req->error = 0;
+	io_req->sectorsize = SECTOR_SIZE;
+	io_req->fds[1] = dev->fd;
+	io_req->offset = (u64) blk_rq_pos(req) << SECTOR_SHIFT;
+	io_req->offsets[0] = 0;
+	io_req->offsets[1] = dev->cow.data_offset;
+
+	for (i = 0 ; i < desc_cnt; i++) {
+		io_req->io_desc[i].sector_mask = 0;
+		io_req->io_desc[i].cow_offset = -1;
+	}
+
+	return io_req;
+}
+
+static int ubd_submit_request(struct ubd *dev, struct request *req)
+{
+	int segs = 0;
+	struct io_thread_req *io_req;
+	int ret;
+	enum req_op op = req_op(req);
+
+	if (op == REQ_OP_FLUSH)
+		segs = 0;
+	else if (op == REQ_OP_WRITE_ZEROES || op == REQ_OP_DISCARD)
+		segs = 1;
+	else
+		segs = blk_rq_nr_phys_segments(req);
+
+	io_req = ubd_alloc_req(dev, req, segs);
+	if (!io_req)
+		return -ENOMEM;
+
+	io_req->desc_cnt = segs;
+	if (segs)
+		ubd_map_req(dev, io_req, req);
+
+	ret = os_write_file(thread_fd, &io_req, sizeof(io_req));
+	if (ret != sizeof(io_req)) {
+		if (ret != -EAGAIN)
+			pr_err("write to io thread failed: %d\n", -ret);
+		kfree(io_req);
+	}
+	return ret;
+}
+
+static blk_status_t ubd_queue_rq(struct blk_mq_hw_ctx *hctx,
+				 const struct blk_mq_queue_data *bd)
+{
+	struct ubd *ubd_dev = hctx->queue->queuedata;
+	struct request *req = bd->rq;
+	int ret = 0, res = BLK_STS_OK;
+
+	blk_mq_start_request(req);
+
+	spin_lock_irq(&ubd_dev->lock);
+
+	switch (req_op(req)) {
+	case REQ_OP_FLUSH:
+	case REQ_OP_READ:
+	case REQ_OP_WRITE:
+	case REQ_OP_DISCARD:
+	case REQ_OP_WRITE_ZEROES:
+		ret = ubd_submit_request(ubd_dev, req);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		res = BLK_STS_NOTSUPP;
+	}
+
+	spin_unlock_irq(&ubd_dev->lock);
+
+	if (ret < 0) {
+		if (ret == -ENOMEM)
+			res = BLK_STS_RESOURCE;
+		else
+			res = BLK_STS_DEV_RESOURCE;
+	}
+
+	return res;
+}
+
+static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
+{
+	struct ubd *ubd_dev = bdev->bd_disk->private_data;
+
+	geo->heads = 128;
+	geo->sectors = 32;
+	geo->cylinders = ubd_dev->size / (128 * 32 * 512);
+	return 0;
+}
+
+static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
+		     unsigned int cmd, unsigned long arg)
+{
+	struct ubd *ubd_dev = bdev->bd_disk->private_data;
+	u16 ubd_id[ATA_ID_WORDS];
+
+	switch (cmd) {
+		struct cdrom_volctrl volume;
+	case HDIO_GET_IDENTITY:
+		memset(&ubd_id, 0, ATA_ID_WORDS * 2);
+		ubd_id[ATA_ID_CYLS]	= ubd_dev->size / (128 * 32 * 512);
+		ubd_id[ATA_ID_HEADS]	= 128;
+		ubd_id[ATA_ID_SECTORS]	= 32;
+		if(copy_to_user((char __user *) arg, (char *) &ubd_id,
+				 sizeof(ubd_id)))
+			return -EFAULT;
+		return 0;
+
+	case CDROMVOLREAD:
+		if(copy_from_user(&volume, (char __user *) arg, sizeof(volume)))
+			return -EFAULT;
+		volume.channel0 = 255;
+		volume.channel1 = 255;
+		volume.channel2 = 255;
+		volume.channel3 = 255;
+		if(copy_to_user((char __user *) arg, &volume, sizeof(volume)))
+			return -EFAULT;
+		return 0;
+	}
+	return -EINVAL;
+}
+
+static int map_error(int error_code)
+{
+	switch (error_code) {
+	case 0:
+		return BLK_STS_OK;
+	case ENOSYS:
+	case EOPNOTSUPP:
+		return BLK_STS_NOTSUPP;
+	case ENOSPC:
+		return BLK_STS_NOSPC;
+	}
+	return BLK_STS_IOERR;
+}
+
+/*
+ * Everything from here onwards *IS NOT PART OF THE KERNEL*
+ *
+ * The following functions are part of UML hypervisor code.
+ * All functions from here onwards are executed as a helper
+ * thread and are not allowed to execute any kernel functions.
+ *
+ * Any communication must occur strictly via shared memory and IPC.
+ *
+ * Do not add printks, locks, kernel memory operations, etc - it
+ * will result in unpredictable behaviour and/or crashes.
+ */
+
+static int update_bitmap(struct io_thread_req *req, struct io_desc *segment)
+{
+	int n;
+
+	if (segment->cow_offset == -1)
+		return map_error(0);
+
+	n = os_pwrite_file(req->fds[1], &segment->bitmap_words,
+			  sizeof(segment->bitmap_words), segment->cow_offset);
+	if (n != sizeof(segment->bitmap_words))
+		return map_error(-n);
+
+	return map_error(0);
+}
+
+static void do_io(struct io_thread_req *req, struct io_desc *desc)
+{
+	char *buf = NULL;
+	unsigned long len;
+	int n, nsectors, start, end, bit;
+	__u64 off;
+
+	/* FLUSH is really a special case, we cannot "case" it with others */
+
+	if (req_op(req->req) == REQ_OP_FLUSH) {
+		/* fds[0] is always either the rw image or our cow file */
+		req->error = map_error(-os_sync_file(req->fds[0]));
+		return;
+	}
+
+	nsectors = desc->length / req->sectorsize;
+	start = 0;
+	do {
+		bit = ubd_test_bit(start, (unsigned char *) &desc->sector_mask);
+		end = start;
+		while((end < nsectors) &&
+		      (ubd_test_bit(end, (unsigned char *) &desc->sector_mask) == bit))
+			end++;
+
+		off = req->offset + req->offsets[bit] +
+			start * req->sectorsize;
+		len = (end - start) * req->sectorsize;
+		if (desc->buffer != NULL)
+			buf = &desc->buffer[start * req->sectorsize];
+
+		switch (req_op(req->req)) {
+		case REQ_OP_READ:
+			n = 0;
+			do {
+				buf = &buf[n];
+				len -= n;
+				n = os_pread_file(req->fds[bit], buf, len, off);
+				if (n < 0) {
+					req->error = map_error(-n);
+					return;
+				}
+			} while((n < len) && (n != 0));
+			if (n < len) memset(&buf[n], 0, len - n);
+			break;
+		case REQ_OP_WRITE:
+			n = os_pwrite_file(req->fds[bit], buf, len, off);
+			if(n != len){
+				req->error = map_error(-n);
+				return;
+			}
+			break;
+		case REQ_OP_DISCARD:
+			n = os_falloc_punch(req->fds[bit], off, len);
+			if (n) {
+				req->error = map_error(-n);
+				return;
+			}
+			break;
+		case REQ_OP_WRITE_ZEROES:
+			n = os_falloc_zeroes(req->fds[bit], off, len);
+			if (n) {
+				req->error = map_error(-n);
+				return;
+			}
+			break;
+		default:
+			WARN_ON_ONCE(1);
+			req->error = BLK_STS_NOTSUPP;
+			return;
+		}
+
+		start = end;
+	} while(start < nsectors);
+
+	req->offset += len;
+	req->error = update_bitmap(req, desc);
+}
+
+/* Changed in start_io_thread, which is serialized by being called only
+ * from ubd_init, which is an initcall.
+ */
+int kernel_fd = -1;
+
+/* Only changed by the io thread. XXX: currently unused. */
+static int io_count;
+
+int io_thread(void *arg)
+{
+	int n, count, written, res;
+
+	os_fix_helper_signals();
+
+	while(1){
+		n = bulk_req_safe_read(
+			kernel_fd,
+			io_req_buffer,
+			&io_remainder,
+			&io_remainder_size,
+			UBD_REQ_BUFFER_SIZE
+		);
+		if (n <= 0) {
+			if (n == -EAGAIN)
+				ubd_read_poll(-1);
+
+			continue;
+		}
+
+		for (count = 0; count < n/sizeof(struct io_thread_req *); count++) {
+			struct io_thread_req *req = (*io_req_buffer)[count];
+			int i;
+
+			io_count++;
+			for (i = 0; !req->error && i < req->desc_cnt; i++)
+				do_io(req, &(req->io_desc[i]));
+
+		}
+
+		written = 0;
+
+		do {
+			res = os_write_file(kernel_fd,
+					    ((char *) io_req_buffer) + written,
+					    n - written);
+			if (res >= 0) {
+				written += res;
+			}
+			if (written < n) {
+				ubd_write_poll(-1);
+			}
+		} while (written < n);
+	}
+
+	return 0;
+}
diff --git a/arch/um/drivers/ubd_user.c b/arch/um/drivers/ubd_user.c
new file mode 100644
index 000000000..a1afe414c
--- /dev/null
+++ b/arch/um/drivers/ubd_user.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2016 Anton Ivanov (aivanov@brocade.com)
+ * Copyright (C) 2000, 2001, 2002 Jeff Dike (jdike@karaya.com)
+ * Copyright (C) 2001 Ridgerun,Inc (glonnon@ridgerun.com)
+ */
+
+#include <stddef.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sched.h>
+#include <signal.h>
+#include <string.h>
+#include <netinet/in.h>
+#include <sys/time.h>
+#include <sys/socket.h>
+#include <sys/mman.h>
+#include <sys/param.h>
+#include <endian.h>
+#include <byteswap.h>
+
+#include "ubd.h"
+#include <os.h>
+#include <poll.h>
+
+struct pollfd kernel_pollfd;
+
+int start_io_thread(unsigned long sp, int *fd_out)
+{
+	int pid, fds[2], err;
+
+	err = os_pipe(fds, 1, 1);
+	if(err < 0){
+		printk("start_io_thread - os_pipe failed, err = %d\n", -err);
+		goto out;
+	}
+
+	kernel_fd = fds[0];
+	kernel_pollfd.fd = kernel_fd;
+	kernel_pollfd.events = POLLIN;
+	*fd_out = fds[1];
+
+	err = os_set_fd_block(*fd_out, 0);
+	err = os_set_fd_block(kernel_fd, 0);
+	if (err) {
+		printk("start_io_thread - failed to set nonblocking I/O.\n");
+		goto out_close;
+	}
+
+	pid = clone(io_thread, (void *) sp, CLONE_FILES | CLONE_VM, NULL);
+	if(pid < 0){
+		err = -errno;
+		printk("start_io_thread - clone failed : errno = %d\n", errno);
+		goto out_close;
+	}
+
+	return(pid);
+
+ out_close:
+	os_close_file(fds[0]);
+	os_close_file(fds[1]);
+	kernel_fd = -1;
+	*fd_out = -1;
+ out:
+	return err;
+}
+
+int ubd_read_poll(int timeout)
+{
+	kernel_pollfd.events = POLLIN;
+	return poll(&kernel_pollfd, 1, timeout);
+}
+int ubd_write_poll(int timeout)
+{
+	kernel_pollfd.events = POLLOUT;
+	return poll(&kernel_pollfd, 1, timeout);
+}
+
diff --git a/arch/um/drivers/umcast.h b/arch/um/drivers/umcast.h
new file mode 100644
index 000000000..fe39bee1e
--- /dev/null
+++ b/arch/um/drivers/umcast.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#ifndef __DRIVERS_UMCAST_H
+#define __DRIVERS_UMCAST_H
+
+#include <net_user.h>
+
+struct umcast_data {
+	char *addr;
+	unsigned short lport;
+	unsigned short rport;
+	void *listen_addr;
+	void *remote_addr;
+	int ttl;
+	int unicast;
+	void *dev;
+};
+
+extern const struct net_user_info umcast_user_info;
+
+extern int umcast_user_write(int fd, void *buf, int len,
+			     struct umcast_data *pri);
+
+#endif
diff --git a/arch/um/drivers/umcast_kern.c b/arch/um/drivers/umcast_kern.c
new file mode 100644
index 000000000..595a54f2b
--- /dev/null
+++ b/arch/um/drivers/umcast_kern.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * user-mode-linux networking multicast transport
+ * Copyright (C) 2001 by Harald Welte <laforge@gnumonks.org>
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ *
+ * based on the existing uml-networking code, which is
+ * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org) and
+ * James Leu (jleu@mindspring.net).
+ * Copyright (C) 2001 by various other people who didn't put their name here.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/netdevice.h>
+#include "umcast.h"
+#include <net_kern.h>
+
+struct umcast_init {
+	char *addr;
+	int lport;
+	int rport;
+	int ttl;
+	bool unicast;
+};
+
+static void umcast_init(struct net_device *dev, void *data)
+{
+	struct uml_net_private *pri;
+	struct umcast_data *dpri;
+	struct umcast_init *init = data;
+
+	pri = netdev_priv(dev);
+	dpri = (struct umcast_data *) pri->user;
+	dpri->addr = init->addr;
+	dpri->lport = init->lport;
+	dpri->rport = init->rport;
+	dpri->unicast = init->unicast;
+	dpri->ttl = init->ttl;
+	dpri->dev = dev;
+
+	if (dpri->unicast) {
+		printk(KERN_INFO "ucast backend address: %s:%u listen port: "
+		       "%u\n", dpri->addr, dpri->rport, dpri->lport);
+	} else {
+		printk(KERN_INFO "mcast backend multicast address: %s:%u, "
+		       "TTL:%u\n", dpri->addr, dpri->lport, dpri->ttl);
+	}
+}
+
+static int umcast_read(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	return net_recvfrom(fd, skb_mac_header(skb),
+			    skb->dev->mtu + ETH_HEADER_OTHER);
+}
+
+static int umcast_write(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	return umcast_user_write(fd, skb->data, skb->len,
+				(struct umcast_data *) &lp->user);
+}
+
+static const struct net_kern_info umcast_kern_info = {
+	.init			= umcast_init,
+	.protocol		= eth_protocol,
+	.read			= umcast_read,
+	.write			= umcast_write,
+};
+
+static int mcast_setup(char *str, char **mac_out, void *data)
+{
+	struct umcast_init *init = data;
+	char *port_str = NULL, *ttl_str = NULL, *remain;
+	char *last;
+
+	*init = ((struct umcast_init)
+		{ .addr	= "239.192.168.1",
+		  .lport	= 1102,
+		  .ttl	= 1 });
+
+	remain = split_if_spec(str, mac_out, &init->addr, &port_str, &ttl_str,
+			       NULL);
+	if (remain != NULL) {
+		printk(KERN_ERR "mcast_setup - Extra garbage on "
+		       "specification : '%s'\n", remain);
+		return 0;
+	}
+
+	if (port_str != NULL) {
+		init->lport = simple_strtoul(port_str, &last, 10);
+		if ((*last != '\0') || (last == port_str)) {
+			printk(KERN_ERR "mcast_setup - Bad port : '%s'\n",
+			       port_str);
+			return 0;
+		}
+	}
+
+	if (ttl_str != NULL) {
+		init->ttl = simple_strtoul(ttl_str, &last, 10);
+		if ((*last != '\0') || (last == ttl_str)) {
+			printk(KERN_ERR "mcast_setup - Bad ttl : '%s'\n",
+			       ttl_str);
+			return 0;
+		}
+	}
+
+	init->unicast = false;
+	init->rport = init->lport;
+
+	printk(KERN_INFO "Configured mcast device: %s:%u-%u\n", init->addr,
+	       init->lport, init->ttl);
+
+	return 1;
+}
+
+static int ucast_setup(char *str, char **mac_out, void *data)
+{
+	struct umcast_init *init = data;
+	char *lport_str = NULL, *rport_str = NULL, *remain;
+	char *last;
+
+	*init = ((struct umcast_init)
+		{ .addr		= "",
+		  .lport	= 1102,
+		  .rport	= 1102 });
+
+	remain = split_if_spec(str, mac_out, &init->addr,
+			       &lport_str, &rport_str, NULL);
+	if (remain != NULL) {
+		printk(KERN_ERR "ucast_setup - Extra garbage on "
+		       "specification : '%s'\n", remain);
+		return 0;
+	}
+
+	if (lport_str != NULL) {
+		init->lport = simple_strtoul(lport_str, &last, 10);
+		if ((*last != '\0') || (last == lport_str)) {
+			printk(KERN_ERR "ucast_setup - Bad listen port : "
+			       "'%s'\n", lport_str);
+			return 0;
+		}
+	}
+
+	if (rport_str != NULL) {
+		init->rport = simple_strtoul(rport_str, &last, 10);
+		if ((*last != '\0') || (last == rport_str)) {
+			printk(KERN_ERR "ucast_setup - Bad remote port : "
+			       "'%s'\n", rport_str);
+			return 0;
+		}
+	}
+
+	init->unicast = true;
+
+	printk(KERN_INFO "Configured ucast device: :%u -> %s:%u\n",
+	       init->lport, init->addr, init->rport);
+
+	return 1;
+}
+
+static struct transport mcast_transport = {
+	.list	= LIST_HEAD_INIT(mcast_transport.list),
+	.name	= "mcast",
+	.setup	= mcast_setup,
+	.user	= &umcast_user_info,
+	.kern	= &umcast_kern_info,
+	.private_size	= sizeof(struct umcast_data),
+	.setup_size	= sizeof(struct umcast_init),
+};
+
+static struct transport ucast_transport = {
+	.list	= LIST_HEAD_INIT(ucast_transport.list),
+	.name	= "ucast",
+	.setup	= ucast_setup,
+	.user	= &umcast_user_info,
+	.kern	= &umcast_kern_info,
+	.private_size	= sizeof(struct umcast_data),
+	.setup_size	= sizeof(struct umcast_init),
+};
+
+static int register_umcast(void)
+{
+	register_transport(&mcast_transport);
+	register_transport(&ucast_transport);
+	return 0;
+}
+
+late_initcall(register_umcast);
diff --git a/arch/um/drivers/umcast_user.c b/arch/um/drivers/umcast_user.c
new file mode 100644
index 000000000..b50b13cff
--- /dev/null
+++ b/arch/um/drivers/umcast_user.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * user-mode-linux networking multicast transport
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Copyright (C) 2001 by Harald Welte <laforge@gnumonks.org>
+ *
+ * based on the existing uml-networking code, which is
+ * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org) and
+ * James Leu (jleu@mindspring.net).
+ * Copyright (C) 2001 by various other people who didn't put their name here.
+ *
+ *
+ */
+
+#include <unistd.h>
+#include <errno.h>
+#include <netinet/in.h>
+#include "umcast.h"
+#include <net_user.h>
+#include <um_malloc.h>
+
+static struct sockaddr_in *new_addr(char *addr, unsigned short port)
+{
+	struct sockaddr_in *sin;
+
+	sin = uml_kmalloc(sizeof(struct sockaddr_in), UM_GFP_KERNEL);
+	if (sin == NULL) {
+		printk(UM_KERN_ERR "new_addr: allocation of sockaddr_in "
+		       "failed\n");
+		return NULL;
+	}
+	sin->sin_family = AF_INET;
+	if (addr)
+		sin->sin_addr.s_addr = in_aton(addr);
+	else
+		sin->sin_addr.s_addr = INADDR_ANY;
+	sin->sin_port = htons(port);
+	return sin;
+}
+
+static int umcast_user_init(void *data, void *dev)
+{
+	struct umcast_data *pri = data;
+
+	pri->remote_addr = new_addr(pri->addr, pri->rport);
+	if (pri->unicast)
+		pri->listen_addr = new_addr(NULL, pri->lport);
+	else
+		pri->listen_addr = pri->remote_addr;
+	pri->dev = dev;
+	return 0;
+}
+
+static void umcast_remove(void *data)
+{
+	struct umcast_data *pri = data;
+
+	kfree(pri->listen_addr);
+	if (pri->unicast)
+		kfree(pri->remote_addr);
+	pri->listen_addr = pri->remote_addr = NULL;
+}
+
+static int umcast_open(void *data)
+{
+	struct umcast_data *pri = data;
+	struct sockaddr_in *lsin = pri->listen_addr;
+	struct sockaddr_in *rsin = pri->remote_addr;
+	struct ip_mreq mreq;
+	int fd, yes = 1, err = -EINVAL;
+
+
+	if ((!pri->unicast && lsin->sin_addr.s_addr == 0) ||
+	    (rsin->sin_addr.s_addr == 0) ||
+	    (lsin->sin_port == 0) || (rsin->sin_port == 0))
+		goto out;
+
+	fd = socket(AF_INET, SOCK_DGRAM, 0);
+
+	if (fd < 0) {
+		err = -errno;
+		printk(UM_KERN_ERR "umcast_open : data socket failed, "
+		       "errno = %d\n", errno);
+		goto out;
+	}
+
+	if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)) < 0) {
+		err = -errno;
+		printk(UM_KERN_ERR "umcast_open: SO_REUSEADDR failed, "
+		       "errno = %d\n", errno);
+		goto out_close;
+	}
+
+	if (!pri->unicast) {
+		/* set ttl according to config */
+		if (setsockopt(fd, SOL_IP, IP_MULTICAST_TTL, &pri->ttl,
+			       sizeof(pri->ttl)) < 0) {
+			err = -errno;
+			printk(UM_KERN_ERR "umcast_open: IP_MULTICAST_TTL "
+			       "failed, error = %d\n", errno);
+			goto out_close;
+		}
+
+		/* set LOOP, so data does get fed back to local sockets */
+		if (setsockopt(fd, SOL_IP, IP_MULTICAST_LOOP,
+			       &yes, sizeof(yes)) < 0) {
+			err = -errno;
+			printk(UM_KERN_ERR "umcast_open: IP_MULTICAST_LOOP "
+			       "failed, error = %d\n", errno);
+			goto out_close;
+		}
+	}
+
+	/* bind socket to the address */
+	if (bind(fd, (struct sockaddr *) lsin, sizeof(*lsin)) < 0) {
+		err = -errno;
+		printk(UM_KERN_ERR "umcast_open : data bind failed, "
+		       "errno = %d\n", errno);
+		goto out_close;
+	}
+
+	if (!pri->unicast) {
+		/* subscribe to the multicast group */
+		mreq.imr_multiaddr.s_addr = lsin->sin_addr.s_addr;
+		mreq.imr_interface.s_addr = 0;
+		if (setsockopt(fd, SOL_IP, IP_ADD_MEMBERSHIP,
+			       &mreq, sizeof(mreq)) < 0) {
+			err = -errno;
+			printk(UM_KERN_ERR "umcast_open: IP_ADD_MEMBERSHIP "
+			       "failed, error = %d\n", errno);
+			printk(UM_KERN_ERR "There appears not to be a "
+			       "multicast-capable network interface on the "
+			       "host.\n");
+			printk(UM_KERN_ERR "eth0 should be configured in order "
+			       "to use the multicast transport.\n");
+			goto out_close;
+		}
+	}
+
+	return fd;
+
+ out_close:
+	close(fd);
+ out:
+	return err;
+}
+
+static void umcast_close(int fd, void *data)
+{
+	struct umcast_data *pri = data;
+
+	if (!pri->unicast) {
+		struct ip_mreq mreq;
+		struct sockaddr_in *lsin = pri->listen_addr;
+
+		mreq.imr_multiaddr.s_addr = lsin->sin_addr.s_addr;
+		mreq.imr_interface.s_addr = 0;
+		if (setsockopt(fd, SOL_IP, IP_DROP_MEMBERSHIP,
+			       &mreq, sizeof(mreq)) < 0) {
+			printk(UM_KERN_ERR "umcast_close: IP_DROP_MEMBERSHIP "
+			       "failed, error = %d\n", errno);
+		}
+	}
+
+	close(fd);
+}
+
+int umcast_user_write(int fd, void *buf, int len, struct umcast_data *pri)
+{
+	struct sockaddr_in *data_addr = pri->remote_addr;
+
+	return net_sendto(fd, buf, len, data_addr, sizeof(*data_addr));
+}
+
+const struct net_user_info umcast_user_info = {
+	.init	= umcast_user_init,
+	.open	= umcast_open,
+	.close	= umcast_close,
+	.remove	= umcast_remove,
+	.add_address	= NULL,
+	.delete_address = NULL,
+	.mtu	= ETH_MAX_PACKET,
+	.max_packet	= ETH_MAX_PACKET + ETH_HEADER_OTHER,
+};
diff --git a/arch/um/drivers/vde.h b/arch/um/drivers/vde.h
new file mode 100644
index 000000000..cab0379e6
--- /dev/null
+++ b/arch/um/drivers/vde.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2007 Luca Bigliardi (shammash@artha.org).
+ */
+
+#ifndef __UM_VDE_H__
+#define __UM_VDE_H__
+
+struct vde_data {
+	char *vde_switch;
+	char *descr;
+	void *args;
+	void *conn;
+	void *dev;
+};
+
+struct vde_init {
+	char *vde_switch;
+	char *descr;
+	int port;
+	char *group;
+	int mode;
+};
+
+extern const struct net_user_info vde_user_info;
+
+extern void vde_init_libstuff(struct vde_data *vpri, struct vde_init *init);
+
+extern int vde_user_read(void *conn, void *buf, int len);
+extern int vde_user_write(void *conn, void *buf, int len);
+
+#endif
diff --git a/arch/um/drivers/vde_kern.c b/arch/um/drivers/vde_kern.c
new file mode 100644
index 000000000..bc6f22cbf
--- /dev/null
+++ b/arch/um/drivers/vde_kern.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Luca Bigliardi (shammash@artha.org).
+ *
+ * Transport usage:
+ *  ethN=vde,<vde_switch>,<mac addr>,<port>,<group>,<mode>,<description>
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/netdevice.h>
+#include <net_kern.h>
+#include <net_user.h>
+#include "vde.h"
+
+static void vde_init(struct net_device *dev, void *data)
+{
+	struct vde_init *init = data;
+	struct uml_net_private *pri;
+	struct vde_data *vpri;
+
+	pri = netdev_priv(dev);
+	vpri = (struct vde_data *) pri->user;
+
+	vpri->vde_switch = init->vde_switch;
+	vpri->descr = init->descr ? init->descr : "UML vde_transport";
+	vpri->args = NULL;
+	vpri->conn = NULL;
+	vpri->dev = dev;
+
+	printk("vde backend - %s, ", vpri->vde_switch ?
+	       vpri->vde_switch : "(default socket)");
+
+	vde_init_libstuff(vpri, init);
+
+	printk("\n");
+}
+
+static int vde_read(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	struct vde_data *pri = (struct vde_data *) &lp->user;
+
+	if (pri->conn != NULL)
+		return vde_user_read(pri->conn, skb_mac_header(skb),
+				     skb->dev->mtu + ETH_HEADER_OTHER);
+
+	printk(KERN_ERR "vde_read - we have no VDECONN to read from");
+	return -EBADF;
+}
+
+static int vde_write(int fd, struct sk_buff *skb, struct uml_net_private *lp)
+{
+	struct vde_data *pri = (struct vde_data *) &lp->user;
+
+	if (pri->conn != NULL)
+		return vde_user_write((void *)pri->conn, skb->data,
+				      skb->len);
+
+	printk(KERN_ERR "vde_write - we have no VDECONN to write to");
+	return -EBADF;
+}
+
+static const struct net_kern_info vde_kern_info = {
+	.init			= vde_init,
+	.protocol		= eth_protocol,
+	.read			= vde_read,
+	.write			= vde_write,
+};
+
+static int vde_setup(char *str, char **mac_out, void *data)
+{
+	struct vde_init *init = data;
+	char *remain, *port_str = NULL, *mode_str = NULL, *last;
+
+	*init = ((struct vde_init)
+		{ .vde_switch		= NULL,
+		  .descr		= NULL,
+		  .port			= 0,
+		  .group		= NULL,
+		  .mode			= 0 });
+
+	remain = split_if_spec(str, &init->vde_switch, mac_out, &port_str,
+				&init->group, &mode_str, &init->descr, NULL);
+
+	if (remain != NULL)
+		printk(KERN_WARNING "vde_setup - Ignoring extra data :"
+		       "'%s'\n", remain);
+
+	if (port_str != NULL) {
+		init->port = simple_strtoul(port_str, &last, 10);
+		if ((*last != '\0') || (last == port_str)) {
+			printk(KERN_ERR "vde_setup - Bad port : '%s'\n",
+						port_str);
+			return 0;
+		}
+	}
+
+	if (mode_str != NULL) {
+		init->mode = simple_strtoul(mode_str, &last, 8);
+		if ((*last != '\0') || (last == mode_str)) {
+			printk(KERN_ERR "vde_setup - Bad mode : '%s'\n",
+						mode_str);
+			return 0;
+		}
+	}
+
+	printk(KERN_INFO "Configured vde device: %s\n", init->vde_switch ?
+	       init->vde_switch : "(default socket)");
+
+	return 1;
+}
+
+static struct transport vde_transport = {
+	.list 		= LIST_HEAD_INIT(vde_transport.list),
+	.name 		= "vde",
+	.setup  	= vde_setup,
+	.user 		= &vde_user_info,
+	.kern 		= &vde_kern_info,
+	.private_size 	= sizeof(struct vde_data),
+	.setup_size 	= sizeof(struct vde_init),
+};
+
+static int register_vde(void)
+{
+	register_transport(&vde_transport);
+	return 0;
+}
+
+late_initcall(register_vde);
diff --git a/arch/um/drivers/vde_user.c b/arch/um/drivers/vde_user.c
new file mode 100644
index 000000000..bc7dc4e1e
--- /dev/null
+++ b/arch/um/drivers/vde_user.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Luca Bigliardi (shammash@artha.org).
+ */
+
+#include <stddef.h>
+#include <errno.h>
+#include <libvdeplug.h>
+#include <net_user.h>
+#include <um_malloc.h>
+#include "vde.h"
+
+static int vde_user_init(void *data, void *dev)
+{
+	struct vde_data *pri = data;
+	VDECONN *conn = NULL;
+	int err = -EINVAL;
+
+	pri->dev = dev;
+
+	conn = vde_open(pri->vde_switch, pri->descr, pri->args);
+
+	if (conn == NULL) {
+		err = -errno;
+		printk(UM_KERN_ERR "vde_user_init: vde_open failed, "
+		       "errno = %d\n", errno);
+		return err;
+	}
+
+	printk(UM_KERN_INFO "vde backend - connection opened\n");
+
+	pri->conn = conn;
+
+	return 0;
+}
+
+static int vde_user_open(void *data)
+{
+	struct vde_data *pri = data;
+
+	if (pri->conn != NULL)
+		return vde_datafd(pri->conn);
+
+	printk(UM_KERN_WARNING "vde_open - we have no VDECONN to open");
+	return -EINVAL;
+}
+
+static void vde_remove(void *data)
+{
+	struct vde_data *pri = data;
+
+	if (pri->conn != NULL) {
+		printk(UM_KERN_INFO "vde backend - closing connection\n");
+		vde_close(pri->conn);
+		pri->conn = NULL;
+		kfree(pri->args);
+		pri->args = NULL;
+		return;
+	}
+
+	printk(UM_KERN_WARNING "vde_remove - we have no VDECONN to remove");
+}
+
+const struct net_user_info vde_user_info = {
+	.init		= vde_user_init,
+	.open		= vde_user_open,
+	.close	 	= NULL,
+	.remove	 	= vde_remove,
+	.add_address	= NULL,
+	.delete_address = NULL,
+	.mtu		= ETH_MAX_PACKET,
+	.max_packet	= ETH_MAX_PACKET + ETH_HEADER_OTHER,
+};
+
+void vde_init_libstuff(struct vde_data *vpri, struct vde_init *init)
+{
+	struct vde_open_args *args;
+
+	vpri->args = uml_kmalloc(sizeof(struct vde_open_args), UM_GFP_KERNEL);
+	if (vpri->args == NULL) {
+		printk(UM_KERN_ERR "vde_init_libstuff - vde_open_args "
+		       "allocation failed");
+		return;
+	}
+
+	args = vpri->args;
+
+	args->port = init->port;
+	args->group = init->group;
+	args->mode = init->mode ? init->mode : 0700;
+
+	args->port ?  printk("port %d", args->port) :
+		printk("undefined port");
+}
+
+int vde_user_read(void *conn, void *buf, int len)
+{
+	VDECONN *vconn = conn;
+	int rv;
+
+	if (vconn == NULL)
+		return 0;
+
+	rv = vde_recv(vconn, buf, len, 0);
+	if (rv < 0) {
+		if (errno == EAGAIN)
+			return 0;
+		return -errno;
+	}
+	else if (rv == 0)
+		return -ENOTCONN;
+
+	return rv;
+}
+
+int vde_user_write(void *conn, void *buf, int len)
+{
+	VDECONN *vconn = conn;
+
+	if (vconn == NULL)
+		return 0;
+
+	return vde_send(vconn, buf, len, 0);
+}
+
diff --git a/arch/um/drivers/vector_kern.c b/arch/um/drivers/vector_kern.c
new file mode 100644
index 000000000..131b7cb29
--- /dev/null
+++ b/arch/um/drivers/vector_kern.c
@@ -0,0 +1,1766 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017 - 2019 Cambridge Greys Limited
+ * Copyright (C) 2011 - 2014 Cisco Systems Inc
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org) and
+ * James Leu (jleu@mindspring.net).
+ * Copyright (C) 2001 by various other people who didn't put their name here.
+ */
+
+#include <linux/memblock.h>
+#include <linux/etherdevice.h>
+#include <linux/ethtool.h>
+#include <linux/inetdevice.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/netdevice.h>
+#include <linux/platform_device.h>
+#include <linux/rtnetlink.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/firmware.h>
+#include <linux/fs.h>
+#include <uapi/linux/filter.h>
+#include <init.h>
+#include <irq_kern.h>
+#include <irq_user.h>
+#include <net_kern.h>
+#include <os.h>
+#include "mconsole_kern.h"
+#include "vector_user.h"
+#include "vector_kern.h"
+
+/*
+ * Adapted from network devices with the following major changes:
+ * All transports are static - simplifies the code significantly
+ * Multiple FDs/IRQs per device
+ * Vector IO optionally used for read/write, falling back to legacy
+ * based on configuration and/or availability
+ * Configuration is no longer positional - L2TPv3 and GRE require up to
+ * 10 parameters, passing this as positional is not fit for purpose.
+ * Only socket transports are supported
+ */
+
+
+#define DRIVER_NAME "uml-vector"
+struct vector_cmd_line_arg {
+	struct list_head list;
+	int unit;
+	char *arguments;
+};
+
+struct vector_device {
+	struct list_head list;
+	struct net_device *dev;
+	struct platform_device pdev;
+	int unit;
+	int opened;
+};
+
+static LIST_HEAD(vec_cmd_line);
+
+static DEFINE_SPINLOCK(vector_devices_lock);
+static LIST_HEAD(vector_devices);
+
+static int driver_registered;
+
+static void vector_eth_configure(int n, struct arglist *def);
+static int vector_mmsg_rx(struct vector_private *vp, int budget);
+
+/* Argument accessors to set variables (and/or set default values)
+ * mtu, buffer sizing, default headroom, etc
+ */
+
+#define DEFAULT_HEADROOM 2
+#define SAFETY_MARGIN 32
+#define DEFAULT_VECTOR_SIZE 64
+#define TX_SMALL_PACKET 128
+#define MAX_IOV_SIZE (MAX_SKB_FRAGS + 1)
+
+static const struct {
+	const char string[ETH_GSTRING_LEN];
+} ethtool_stats_keys[] = {
+	{ "rx_queue_max" },
+	{ "rx_queue_running_average" },
+	{ "tx_queue_max" },
+	{ "tx_queue_running_average" },
+	{ "rx_encaps_errors" },
+	{ "tx_timeout_count" },
+	{ "tx_restart_queue" },
+	{ "tx_kicks" },
+	{ "tx_flow_control_xon" },
+	{ "tx_flow_control_xoff" },
+	{ "rx_csum_offload_good" },
+	{ "rx_csum_offload_errors"},
+	{ "sg_ok"},
+	{ "sg_linearized"},
+};
+
+#define VECTOR_NUM_STATS	ARRAY_SIZE(ethtool_stats_keys)
+
+static void vector_reset_stats(struct vector_private *vp)
+{
+	vp->estats.rx_queue_max = 0;
+	vp->estats.rx_queue_running_average = 0;
+	vp->estats.tx_queue_max = 0;
+	vp->estats.tx_queue_running_average = 0;
+	vp->estats.rx_encaps_errors = 0;
+	vp->estats.tx_timeout_count = 0;
+	vp->estats.tx_restart_queue = 0;
+	vp->estats.tx_kicks = 0;
+	vp->estats.tx_flow_control_xon = 0;
+	vp->estats.tx_flow_control_xoff = 0;
+	vp->estats.sg_ok = 0;
+	vp->estats.sg_linearized = 0;
+}
+
+static int get_mtu(struct arglist *def)
+{
+	char *mtu = uml_vector_fetch_arg(def, "mtu");
+	long result;
+
+	if (mtu != NULL) {
+		if (kstrtoul(mtu, 10, &result) == 0)
+			if ((result < (1 << 16) - 1) && (result >= 576))
+				return result;
+	}
+	return ETH_MAX_PACKET;
+}
+
+static char *get_bpf_file(struct arglist *def)
+{
+	return uml_vector_fetch_arg(def, "bpffile");
+}
+
+static bool get_bpf_flash(struct arglist *def)
+{
+	char *allow = uml_vector_fetch_arg(def, "bpfflash");
+	long result;
+
+	if (allow != NULL) {
+		if (kstrtoul(allow, 10, &result) == 0)
+			return (allow > 0);
+	}
+	return false;
+}
+
+static int get_depth(struct arglist *def)
+{
+	char *mtu = uml_vector_fetch_arg(def, "depth");
+	long result;
+
+	if (mtu != NULL) {
+		if (kstrtoul(mtu, 10, &result) == 0)
+			return result;
+	}
+	return DEFAULT_VECTOR_SIZE;
+}
+
+static int get_headroom(struct arglist *def)
+{
+	char *mtu = uml_vector_fetch_arg(def, "headroom");
+	long result;
+
+	if (mtu != NULL) {
+		if (kstrtoul(mtu, 10, &result) == 0)
+			return result;
+	}
+	return DEFAULT_HEADROOM;
+}
+
+static int get_req_size(struct arglist *def)
+{
+	char *gro = uml_vector_fetch_arg(def, "gro");
+	long result;
+
+	if (gro != NULL) {
+		if (kstrtoul(gro, 10, &result) == 0) {
+			if (result > 0)
+				return 65536;
+		}
+	}
+	return get_mtu(def) + ETH_HEADER_OTHER +
+		get_headroom(def) + SAFETY_MARGIN;
+}
+
+
+static int get_transport_options(struct arglist *def)
+{
+	char *transport = uml_vector_fetch_arg(def, "transport");
+	char *vector = uml_vector_fetch_arg(def, "vec");
+
+	int vec_rx = VECTOR_RX;
+	int vec_tx = VECTOR_TX;
+	long parsed;
+	int result = 0;
+
+	if (transport == NULL)
+		return -EINVAL;
+
+	if (vector != NULL) {
+		if (kstrtoul(vector, 10, &parsed) == 0) {
+			if (parsed == 0) {
+				vec_rx = 0;
+				vec_tx = 0;
+			}
+		}
+	}
+
+	if (get_bpf_flash(def))
+		result = VECTOR_BPF_FLASH;
+
+	if (strncmp(transport, TRANS_TAP, TRANS_TAP_LEN) == 0)
+		return result;
+	if (strncmp(transport, TRANS_HYBRID, TRANS_HYBRID_LEN) == 0)
+		return (result | vec_rx | VECTOR_BPF);
+	if (strncmp(transport, TRANS_RAW, TRANS_RAW_LEN) == 0)
+		return (result | vec_rx | vec_tx | VECTOR_QDISC_BYPASS);
+	return (result | vec_rx | vec_tx);
+}
+
+
+/* A mini-buffer for packet drop read
+ * All of our supported transports are datagram oriented and we always
+ * read using recvmsg or recvmmsg. If we pass a buffer which is smaller
+ * than the packet size it still counts as full packet read and will
+ * clean the incoming stream to keep sigio/epoll happy
+ */
+
+#define DROP_BUFFER_SIZE 32
+
+static char *drop_buffer;
+
+/* Array backed queues optimized for bulk enqueue/dequeue and
+ * 1:N (small values of N) or 1:1 enqueuer/dequeuer ratios.
+ * For more details and full design rationale see
+ * http://foswiki.cambridgegreys.com/Main/EatYourTailAndEnjoyIt
+ */
+
+
+/*
+ * Advance the mmsg queue head by n = advance. Resets the queue to
+ * maximum enqueue/dequeue-at-once capacity if possible. Called by
+ * dequeuers. Caller must hold the head_lock!
+ */
+
+static int vector_advancehead(struct vector_queue *qi, int advance)
+{
+	int queue_depth;
+
+	qi->head =
+		(qi->head + advance)
+			% qi->max_depth;
+
+
+	spin_lock(&qi->tail_lock);
+	qi->queue_depth -= advance;
+
+	/* we are at 0, use this to
+	 * reset head and tail so we can use max size vectors
+	 */
+
+	if (qi->queue_depth == 0) {
+		qi->head = 0;
+		qi->tail = 0;
+	}
+	queue_depth = qi->queue_depth;
+	spin_unlock(&qi->tail_lock);
+	return queue_depth;
+}
+
+/*	Advance the queue tail by n = advance.
+ *	This is called by enqueuers which should hold the
+ *	head lock already
+ */
+
+static int vector_advancetail(struct vector_queue *qi, int advance)
+{
+	int queue_depth;
+
+	qi->tail =
+		(qi->tail + advance)
+			% qi->max_depth;
+	spin_lock(&qi->head_lock);
+	qi->queue_depth += advance;
+	queue_depth = qi->queue_depth;
+	spin_unlock(&qi->head_lock);
+	return queue_depth;
+}
+
+static int prep_msg(struct vector_private *vp,
+	struct sk_buff *skb,
+	struct iovec *iov)
+{
+	int iov_index = 0;
+	int nr_frags, frag;
+	skb_frag_t *skb_frag;
+
+	nr_frags = skb_shinfo(skb)->nr_frags;
+	if (nr_frags > MAX_IOV_SIZE) {
+		if (skb_linearize(skb) != 0)
+			goto drop;
+	}
+	if (vp->header_size > 0) {
+		iov[iov_index].iov_len = vp->header_size;
+		vp->form_header(iov[iov_index].iov_base, skb, vp);
+		iov_index++;
+	}
+	iov[iov_index].iov_base = skb->data;
+	if (nr_frags > 0) {
+		iov[iov_index].iov_len = skb->len - skb->data_len;
+		vp->estats.sg_ok++;
+	} else
+		iov[iov_index].iov_len = skb->len;
+	iov_index++;
+	for (frag = 0; frag < nr_frags; frag++) {
+		skb_frag = &skb_shinfo(skb)->frags[frag];
+		iov[iov_index].iov_base = skb_frag_address_safe(skb_frag);
+		iov[iov_index].iov_len = skb_frag_size(skb_frag);
+		iov_index++;
+	}
+	return iov_index;
+drop:
+	return -1;
+}
+/*
+ * Generic vector enqueue with support for forming headers using transport
+ * specific callback. Allows GRE, L2TPv3, RAW and other transports
+ * to use a common enqueue procedure in vector mode
+ */
+
+static int vector_enqueue(struct vector_queue *qi, struct sk_buff *skb)
+{
+	struct vector_private *vp = netdev_priv(qi->dev);
+	int queue_depth;
+	int packet_len;
+	struct mmsghdr *mmsg_vector = qi->mmsg_vector;
+	int iov_count;
+
+	spin_lock(&qi->tail_lock);
+	spin_lock(&qi->head_lock);
+	queue_depth = qi->queue_depth;
+	spin_unlock(&qi->head_lock);
+
+	if (skb)
+		packet_len = skb->len;
+
+	if (queue_depth < qi->max_depth) {
+
+		*(qi->skbuff_vector + qi->tail) = skb;
+		mmsg_vector += qi->tail;
+		iov_count = prep_msg(
+			vp,
+			skb,
+			mmsg_vector->msg_hdr.msg_iov
+		);
+		if (iov_count < 1)
+			goto drop;
+		mmsg_vector->msg_hdr.msg_iovlen = iov_count;
+		mmsg_vector->msg_hdr.msg_name = vp->fds->remote_addr;
+		mmsg_vector->msg_hdr.msg_namelen = vp->fds->remote_addr_size;
+		queue_depth = vector_advancetail(qi, 1);
+	} else
+		goto drop;
+	spin_unlock(&qi->tail_lock);
+	return queue_depth;
+drop:
+	qi->dev->stats.tx_dropped++;
+	if (skb != NULL) {
+		packet_len = skb->len;
+		dev_consume_skb_any(skb);
+		netdev_completed_queue(qi->dev, 1, packet_len);
+	}
+	spin_unlock(&qi->tail_lock);
+	return queue_depth;
+}
+
+static int consume_vector_skbs(struct vector_queue *qi, int count)
+{
+	struct sk_buff *skb;
+	int skb_index;
+	int bytes_compl = 0;
+
+	for (skb_index = qi->head; skb_index < qi->head + count; skb_index++) {
+		skb = *(qi->skbuff_vector + skb_index);
+		/* mark as empty to ensure correct destruction if
+		 * needed
+		 */
+		bytes_compl += skb->len;
+		*(qi->skbuff_vector + skb_index) = NULL;
+		dev_consume_skb_any(skb);
+	}
+	qi->dev->stats.tx_bytes += bytes_compl;
+	qi->dev->stats.tx_packets += count;
+	netdev_completed_queue(qi->dev, count, bytes_compl);
+	return vector_advancehead(qi, count);
+}
+
+/*
+ * Generic vector deque via sendmmsg with support for forming headers
+ * using transport specific callback. Allows GRE, L2TPv3, RAW and
+ * other transports to use a common dequeue procedure in vector mode
+ */
+
+
+static int vector_send(struct vector_queue *qi)
+{
+	struct vector_private *vp = netdev_priv(qi->dev);
+	struct mmsghdr *send_from;
+	int result = 0, send_len, queue_depth = qi->max_depth;
+
+	if (spin_trylock(&qi->head_lock)) {
+		if (spin_trylock(&qi->tail_lock)) {
+			/* update queue_depth to current value */
+			queue_depth = qi->queue_depth;
+			spin_unlock(&qi->tail_lock);
+			while (queue_depth > 0) {
+				/* Calculate the start of the vector */
+				send_len = queue_depth;
+				send_from = qi->mmsg_vector;
+				send_from += qi->head;
+				/* Adjust vector size if wraparound */
+				if (send_len + qi->head > qi->max_depth)
+					send_len = qi->max_depth - qi->head;
+				/* Try to TX as many packets as possible */
+				if (send_len > 0) {
+					result = uml_vector_sendmmsg(
+						 vp->fds->tx_fd,
+						 send_from,
+						 send_len,
+						 0
+					);
+					vp->in_write_poll =
+						(result != send_len);
+				}
+				/* For some of the sendmmsg error scenarios
+				 * we may end being unsure in the TX success
+				 * for all packets. It is safer to declare
+				 * them all TX-ed and blame the network.
+				 */
+				if (result < 0) {
+					if (net_ratelimit())
+						netdev_err(vp->dev, "sendmmsg err=%i\n",
+							result);
+					vp->in_error = true;
+					result = send_len;
+				}
+				if (result > 0) {
+					queue_depth =
+						consume_vector_skbs(qi, result);
+					/* This is equivalent to an TX IRQ.
+					 * Restart the upper layers to feed us
+					 * more packets.
+					 */
+					if (result > vp->estats.tx_queue_max)
+						vp->estats.tx_queue_max = result;
+					vp->estats.tx_queue_running_average =
+						(vp->estats.tx_queue_running_average + result) >> 1;
+				}
+				netif_wake_queue(qi->dev);
+				/* if TX is busy, break out of the send loop,
+				 *  poll write IRQ will reschedule xmit for us
+				 */
+				if (result != send_len) {
+					vp->estats.tx_restart_queue++;
+					break;
+				}
+			}
+		}
+		spin_unlock(&qi->head_lock);
+	}
+	return queue_depth;
+}
+
+/* Queue destructor. Deliberately stateless so we can use
+ * it in queue cleanup if initialization fails.
+ */
+
+static void destroy_queue(struct vector_queue *qi)
+{
+	int i;
+	struct iovec *iov;
+	struct vector_private *vp = netdev_priv(qi->dev);
+	struct mmsghdr *mmsg_vector;
+
+	if (qi == NULL)
+		return;
+	/* deallocate any skbuffs - we rely on any unused to be
+	 * set to NULL.
+	 */
+	if (qi->skbuff_vector != NULL) {
+		for (i = 0; i < qi->max_depth; i++) {
+			if (*(qi->skbuff_vector + i) != NULL)
+				dev_kfree_skb_any(*(qi->skbuff_vector + i));
+		}
+		kfree(qi->skbuff_vector);
+	}
+	/* deallocate matching IOV structures including header buffs */
+	if (qi->mmsg_vector != NULL) {
+		mmsg_vector = qi->mmsg_vector;
+		for (i = 0; i < qi->max_depth; i++) {
+			iov = mmsg_vector->msg_hdr.msg_iov;
+			if (iov != NULL) {
+				if ((vp->header_size > 0) &&
+					(iov->iov_base != NULL))
+					kfree(iov->iov_base);
+				kfree(iov);
+			}
+			mmsg_vector++;
+		}
+		kfree(qi->mmsg_vector);
+	}
+	kfree(qi);
+}
+
+/*
+ * Queue constructor. Create a queue with a given side.
+ */
+static struct vector_queue *create_queue(
+	struct vector_private *vp,
+	int max_size,
+	int header_size,
+	int num_extra_frags)
+{
+	struct vector_queue *result;
+	int i;
+	struct iovec *iov;
+	struct mmsghdr *mmsg_vector;
+
+	result = kmalloc(sizeof(struct vector_queue), GFP_KERNEL);
+	if (result == NULL)
+		return NULL;
+	result->max_depth = max_size;
+	result->dev = vp->dev;
+	result->mmsg_vector = kmalloc(
+		(sizeof(struct mmsghdr) * max_size), GFP_KERNEL);
+	if (result->mmsg_vector == NULL)
+		goto out_mmsg_fail;
+	result->skbuff_vector = kmalloc(
+		(sizeof(void *) * max_size), GFP_KERNEL);
+	if (result->skbuff_vector == NULL)
+		goto out_skb_fail;
+
+	/* further failures can be handled safely by destroy_queue*/
+
+	mmsg_vector = result->mmsg_vector;
+	for (i = 0; i < max_size; i++) {
+		/* Clear all pointers - we use non-NULL as marking on
+		 * what to free on destruction
+		 */
+		*(result->skbuff_vector + i) = NULL;
+		mmsg_vector->msg_hdr.msg_iov = NULL;
+		mmsg_vector++;
+	}
+	mmsg_vector = result->mmsg_vector;
+	result->max_iov_frags = num_extra_frags;
+	for (i = 0; i < max_size; i++) {
+		if (vp->header_size > 0)
+			iov = kmalloc_array(3 + num_extra_frags,
+					    sizeof(struct iovec),
+					    GFP_KERNEL
+			);
+		else
+			iov = kmalloc_array(2 + num_extra_frags,
+					    sizeof(struct iovec),
+					    GFP_KERNEL
+			);
+		if (iov == NULL)
+			goto out_fail;
+		mmsg_vector->msg_hdr.msg_iov = iov;
+		mmsg_vector->msg_hdr.msg_iovlen = 1;
+		mmsg_vector->msg_hdr.msg_control = NULL;
+		mmsg_vector->msg_hdr.msg_controllen = 0;
+		mmsg_vector->msg_hdr.msg_flags = MSG_DONTWAIT;
+		mmsg_vector->msg_hdr.msg_name = NULL;
+		mmsg_vector->msg_hdr.msg_namelen = 0;
+		if (vp->header_size > 0) {
+			iov->iov_base = kmalloc(header_size, GFP_KERNEL);
+			if (iov->iov_base == NULL)
+				goto out_fail;
+			iov->iov_len = header_size;
+			mmsg_vector->msg_hdr.msg_iovlen = 2;
+			iov++;
+		}
+		iov->iov_base = NULL;
+		iov->iov_len = 0;
+		mmsg_vector++;
+	}
+	spin_lock_init(&result->head_lock);
+	spin_lock_init(&result->tail_lock);
+	result->queue_depth = 0;
+	result->head = 0;
+	result->tail = 0;
+	return result;
+out_skb_fail:
+	kfree(result->mmsg_vector);
+out_mmsg_fail:
+	kfree(result);
+	return NULL;
+out_fail:
+	destroy_queue(result);
+	return NULL;
+}
+
+/*
+ * We do not use the RX queue as a proper wraparound queue for now
+ * This is not necessary because the consumption via napi_gro_receive()
+ * happens in-line. While we can try using the return code of
+ * netif_rx() for flow control there are no drivers doing this today.
+ * For this RX specific use we ignore the tail/head locks and
+ * just read into a prepared queue filled with skbuffs.
+ */
+
+static struct sk_buff *prep_skb(
+	struct vector_private *vp,
+	struct user_msghdr *msg)
+{
+	int linear = vp->max_packet + vp->headroom + SAFETY_MARGIN;
+	struct sk_buff *result;
+	int iov_index = 0, len;
+	struct iovec *iov = msg->msg_iov;
+	int err, nr_frags, frag;
+	skb_frag_t *skb_frag;
+
+	if (vp->req_size <= linear)
+		len = linear;
+	else
+		len = vp->req_size;
+	result = alloc_skb_with_frags(
+		linear,
+		len - vp->max_packet,
+		3,
+		&err,
+		GFP_ATOMIC
+	);
+	if (vp->header_size > 0)
+		iov_index++;
+	if (result == NULL) {
+		iov[iov_index].iov_base = NULL;
+		iov[iov_index].iov_len = 0;
+		goto done;
+	}
+	skb_reserve(result, vp->headroom);
+	result->dev = vp->dev;
+	skb_put(result, vp->max_packet);
+	result->data_len = len - vp->max_packet;
+	result->len += len - vp->max_packet;
+	skb_reset_mac_header(result);
+	result->ip_summed = CHECKSUM_NONE;
+	iov[iov_index].iov_base = result->data;
+	iov[iov_index].iov_len = vp->max_packet;
+	iov_index++;
+
+	nr_frags = skb_shinfo(result)->nr_frags;
+	for (frag = 0; frag < nr_frags; frag++) {
+		skb_frag = &skb_shinfo(result)->frags[frag];
+		iov[iov_index].iov_base = skb_frag_address_safe(skb_frag);
+		if (iov[iov_index].iov_base != NULL)
+			iov[iov_index].iov_len = skb_frag_size(skb_frag);
+		else
+			iov[iov_index].iov_len = 0;
+		iov_index++;
+	}
+done:
+	msg->msg_iovlen = iov_index;
+	return result;
+}
+
+
+/* Prepare queue for recvmmsg one-shot rx - fill with fresh sk_buffs*/
+
+static void prep_queue_for_rx(struct vector_queue *qi)
+{
+	struct vector_private *vp = netdev_priv(qi->dev);
+	struct mmsghdr *mmsg_vector = qi->mmsg_vector;
+	void **skbuff_vector = qi->skbuff_vector;
+	int i;
+
+	if (qi->queue_depth == 0)
+		return;
+	for (i = 0; i < qi->queue_depth; i++) {
+		/* it is OK if allocation fails - recvmmsg with NULL data in
+		 * iov argument still performs an RX, just drops the packet
+		 * This allows us stop faffing around with a "drop buffer"
+		 */
+
+		*skbuff_vector = prep_skb(vp, &mmsg_vector->msg_hdr);
+		skbuff_vector++;
+		mmsg_vector++;
+	}
+	qi->queue_depth = 0;
+}
+
+static struct vector_device *find_device(int n)
+{
+	struct vector_device *device;
+	struct list_head *ele;
+
+	spin_lock(&vector_devices_lock);
+	list_for_each(ele, &vector_devices) {
+		device = list_entry(ele, struct vector_device, list);
+		if (device->unit == n)
+			goto out;
+	}
+	device = NULL;
+ out:
+	spin_unlock(&vector_devices_lock);
+	return device;
+}
+
+static int vector_parse(char *str, int *index_out, char **str_out,
+			char **error_out)
+{
+	int n, len, err;
+	char *start = str;
+
+	len = strlen(str);
+
+	while ((*str != ':') && (strlen(str) > 1))
+		str++;
+	if (*str != ':') {
+		*error_out = "Expected ':' after device number";
+		return -EINVAL;
+	}
+	*str = '\0';
+
+	err = kstrtouint(start, 0, &n);
+	if (err < 0) {
+		*error_out = "Bad device number";
+		return err;
+	}
+
+	str++;
+	if (find_device(n)) {
+		*error_out = "Device already configured";
+		return -EINVAL;
+	}
+
+	*index_out = n;
+	*str_out = str;
+	return 0;
+}
+
+static int vector_config(char *str, char **error_out)
+{
+	int err, n;
+	char *params;
+	struct arglist *parsed;
+
+	err = vector_parse(str, &n, &params, error_out);
+	if (err != 0)
+		return err;
+
+	/* This string is broken up and the pieces used by the underlying
+	 * driver. We should copy it to make sure things do not go wrong
+	 * later.
+	 */
+
+	params = kstrdup(params, GFP_KERNEL);
+	if (params == NULL) {
+		*error_out = "vector_config failed to strdup string";
+		return -ENOMEM;
+	}
+
+	parsed = uml_parse_vector_ifspec(params);
+
+	if (parsed == NULL) {
+		*error_out = "vector_config failed to parse parameters";
+		kfree(params);
+		return -EINVAL;
+	}
+
+	vector_eth_configure(n, parsed);
+	return 0;
+}
+
+static int vector_id(char **str, int *start_out, int *end_out)
+{
+	char *end;
+	int n;
+
+	n = simple_strtoul(*str, &end, 0);
+	if ((*end != '\0') || (end == *str))
+		return -1;
+
+	*start_out = n;
+	*end_out = n;
+	*str = end;
+	return n;
+}
+
+static int vector_remove(int n, char **error_out)
+{
+	struct vector_device *vec_d;
+	struct net_device *dev;
+	struct vector_private *vp;
+
+	vec_d = find_device(n);
+	if (vec_d == NULL)
+		return -ENODEV;
+	dev = vec_d->dev;
+	vp = netdev_priv(dev);
+	if (vp->fds != NULL)
+		return -EBUSY;
+	unregister_netdev(dev);
+	platform_device_unregister(&vec_d->pdev);
+	return 0;
+}
+
+/*
+ * There is no shared per-transport initialization code, so
+ * we will just initialize each interface one by one and
+ * add them to a list
+ */
+
+static struct platform_driver uml_net_driver = {
+	.driver = {
+		.name = DRIVER_NAME,
+	},
+};
+
+
+static void vector_device_release(struct device *dev)
+{
+	struct vector_device *device = dev_get_drvdata(dev);
+	struct net_device *netdev = device->dev;
+
+	list_del(&device->list);
+	kfree(device);
+	free_netdev(netdev);
+}
+
+/* Bog standard recv using recvmsg - not used normally unless the user
+ * explicitly specifies not to use recvmmsg vector RX.
+ */
+
+static int vector_legacy_rx(struct vector_private *vp)
+{
+	int pkt_len;
+	struct user_msghdr hdr;
+	struct iovec iov[2 + MAX_IOV_SIZE]; /* header + data use case only */
+	int iovpos = 0;
+	struct sk_buff *skb;
+	int header_check;
+
+	hdr.msg_name = NULL;
+	hdr.msg_namelen = 0;
+	hdr.msg_iov = (struct iovec *) &iov;
+	hdr.msg_control = NULL;
+	hdr.msg_controllen = 0;
+	hdr.msg_flags = 0;
+
+	if (vp->header_size > 0) {
+		iov[0].iov_base = vp->header_rxbuffer;
+		iov[0].iov_len = vp->header_size;
+	}
+
+	skb = prep_skb(vp, &hdr);
+
+	if (skb == NULL) {
+		/* Read a packet into drop_buffer and don't do
+		 * anything with it.
+		 */
+		iov[iovpos].iov_base = drop_buffer;
+		iov[iovpos].iov_len = DROP_BUFFER_SIZE;
+		hdr.msg_iovlen = 1;
+		vp->dev->stats.rx_dropped++;
+	}
+
+	pkt_len = uml_vector_recvmsg(vp->fds->rx_fd, &hdr, 0);
+	if (pkt_len < 0) {
+		vp->in_error = true;
+		return pkt_len;
+	}
+
+	if (skb != NULL) {
+		if (pkt_len > vp->header_size) {
+			if (vp->header_size > 0) {
+				header_check = vp->verify_header(
+					vp->header_rxbuffer, skb, vp);
+				if (header_check < 0) {
+					dev_kfree_skb_irq(skb);
+					vp->dev->stats.rx_dropped++;
+					vp->estats.rx_encaps_errors++;
+					return 0;
+				}
+				if (header_check > 0) {
+					vp->estats.rx_csum_offload_good++;
+					skb->ip_summed = CHECKSUM_UNNECESSARY;
+				}
+			}
+			pskb_trim(skb, pkt_len - vp->rx_header_size);
+			skb->protocol = eth_type_trans(skb, skb->dev);
+			vp->dev->stats.rx_bytes += skb->len;
+			vp->dev->stats.rx_packets++;
+			napi_gro_receive(&vp->napi, skb);
+		} else {
+			dev_kfree_skb_irq(skb);
+		}
+	}
+	return pkt_len;
+}
+
+/*
+ * Packet at a time TX which falls back to vector TX if the
+ * underlying transport is busy.
+ */
+
+
+
+static int writev_tx(struct vector_private *vp, struct sk_buff *skb)
+{
+	struct iovec iov[3 + MAX_IOV_SIZE];
+	int iov_count, pkt_len = 0;
+
+	iov[0].iov_base = vp->header_txbuffer;
+	iov_count = prep_msg(vp, skb, (struct iovec *) &iov);
+
+	if (iov_count < 1)
+		goto drop;
+
+	pkt_len = uml_vector_writev(
+		vp->fds->tx_fd,
+		(struct iovec *) &iov,
+		iov_count
+	);
+
+	if (pkt_len < 0)
+		goto drop;
+
+	netif_trans_update(vp->dev);
+	netif_wake_queue(vp->dev);
+
+	if (pkt_len > 0) {
+		vp->dev->stats.tx_bytes += skb->len;
+		vp->dev->stats.tx_packets++;
+	} else {
+		vp->dev->stats.tx_dropped++;
+	}
+	consume_skb(skb);
+	return pkt_len;
+drop:
+	vp->dev->stats.tx_dropped++;
+	consume_skb(skb);
+	if (pkt_len < 0)
+		vp->in_error = true;
+	return pkt_len;
+}
+
+/*
+ * Receive as many messages as we can in one call using the special
+ * mmsg vector matched to an skb vector which we prepared earlier.
+ */
+
+static int vector_mmsg_rx(struct vector_private *vp, int budget)
+{
+	int packet_count, i;
+	struct vector_queue *qi = vp->rx_queue;
+	struct sk_buff *skb;
+	struct mmsghdr *mmsg_vector = qi->mmsg_vector;
+	void **skbuff_vector = qi->skbuff_vector;
+	int header_check;
+
+	/* Refresh the vector and make sure it is with new skbs and the
+	 * iovs are updated to point to them.
+	 */
+
+	prep_queue_for_rx(qi);
+
+	/* Fire the Lazy Gun - get as many packets as we can in one go. */
+
+	if (budget > qi->max_depth)
+		budget = qi->max_depth;
+
+	packet_count = uml_vector_recvmmsg(
+		vp->fds->rx_fd, qi->mmsg_vector, qi->max_depth, 0);
+
+	if (packet_count < 0)
+		vp->in_error = true;
+
+	if (packet_count <= 0)
+		return packet_count;
+
+	/* We treat packet processing as enqueue, buffer refresh as dequeue
+	 * The queue_depth tells us how many buffers have been used and how
+	 * many do we need to prep the next time prep_queue_for_rx() is called.
+	 */
+
+	qi->queue_depth = packet_count;
+
+	for (i = 0; i < packet_count; i++) {
+		skb = (*skbuff_vector);
+		if (mmsg_vector->msg_len > vp->header_size) {
+			if (vp->header_size > 0) {
+				header_check = vp->verify_header(
+					mmsg_vector->msg_hdr.msg_iov->iov_base,
+					skb,
+					vp
+				);
+				if (header_check < 0) {
+				/* Overlay header failed to verify - discard.
+				 * We can actually keep this skb and reuse it,
+				 * but that will make the prep logic too
+				 * complex.
+				 */
+					dev_kfree_skb_irq(skb);
+					vp->estats.rx_encaps_errors++;
+					continue;
+				}
+				if (header_check > 0) {
+					vp->estats.rx_csum_offload_good++;
+					skb->ip_summed = CHECKSUM_UNNECESSARY;
+				}
+			}
+			pskb_trim(skb,
+				mmsg_vector->msg_len - vp->rx_header_size);
+			skb->protocol = eth_type_trans(skb, skb->dev);
+			/*
+			 * We do not need to lock on updating stats here
+			 * The interrupt loop is non-reentrant.
+			 */
+			vp->dev->stats.rx_bytes += skb->len;
+			vp->dev->stats.rx_packets++;
+			napi_gro_receive(&vp->napi, skb);
+		} else {
+			/* Overlay header too short to do anything - discard.
+			 * We can actually keep this skb and reuse it,
+			 * but that will make the prep logic too complex.
+			 */
+			if (skb != NULL)
+				dev_kfree_skb_irq(skb);
+		}
+		(*skbuff_vector) = NULL;
+		/* Move to the next buffer element */
+		mmsg_vector++;
+		skbuff_vector++;
+	}
+	if (packet_count > 0) {
+		if (vp->estats.rx_queue_max < packet_count)
+			vp->estats.rx_queue_max = packet_count;
+		vp->estats.rx_queue_running_average =
+			(vp->estats.rx_queue_running_average + packet_count) >> 1;
+	}
+	return packet_count;
+}
+
+static int vector_net_start_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct vector_private *vp = netdev_priv(dev);
+	int queue_depth = 0;
+
+	if (vp->in_error) {
+		deactivate_fd(vp->fds->rx_fd, vp->rx_irq);
+		if ((vp->fds->rx_fd != vp->fds->tx_fd) && (vp->tx_irq != 0))
+			deactivate_fd(vp->fds->tx_fd, vp->tx_irq);
+		return NETDEV_TX_BUSY;
+	}
+
+	if ((vp->options & VECTOR_TX) == 0) {
+		writev_tx(vp, skb);
+		return NETDEV_TX_OK;
+	}
+
+	/* We do BQL only in the vector path, no point doing it in
+	 * packet at a time mode as there is no device queue
+	 */
+
+	netdev_sent_queue(vp->dev, skb->len);
+	queue_depth = vector_enqueue(vp->tx_queue, skb);
+
+	if (queue_depth < vp->tx_queue->max_depth && netdev_xmit_more()) {
+		mod_timer(&vp->tl, vp->coalesce);
+		return NETDEV_TX_OK;
+	} else {
+		queue_depth = vector_send(vp->tx_queue);
+		if (queue_depth > 0)
+			napi_schedule(&vp->napi);
+	}
+
+	return NETDEV_TX_OK;
+}
+
+static irqreturn_t vector_rx_interrupt(int irq, void *dev_id)
+{
+	struct net_device *dev = dev_id;
+	struct vector_private *vp = netdev_priv(dev);
+
+	if (!netif_running(dev))
+		return IRQ_NONE;
+	napi_schedule(&vp->napi);
+	return IRQ_HANDLED;
+
+}
+
+static irqreturn_t vector_tx_interrupt(int irq, void *dev_id)
+{
+	struct net_device *dev = dev_id;
+	struct vector_private *vp = netdev_priv(dev);
+
+	if (!netif_running(dev))
+		return IRQ_NONE;
+	/* We need to pay attention to it only if we got
+	 * -EAGAIN or -ENOBUFFS from sendmmsg. Otherwise
+	 * we ignore it. In the future, it may be worth
+	 * it to improve the IRQ controller a bit to make
+	 * tweaking the IRQ mask less costly
+	 */
+
+	napi_schedule(&vp->napi);
+	return IRQ_HANDLED;
+
+}
+
+static int irq_rr;
+
+static int vector_net_close(struct net_device *dev)
+{
+	struct vector_private *vp = netdev_priv(dev);
+	unsigned long flags;
+
+	netif_stop_queue(dev);
+	del_timer(&vp->tl);
+
+	if (vp->fds == NULL)
+		return 0;
+
+	/* Disable and free all IRQS */
+	if (vp->rx_irq > 0) {
+		um_free_irq(vp->rx_irq, dev);
+		vp->rx_irq = 0;
+	}
+	if (vp->tx_irq > 0) {
+		um_free_irq(vp->tx_irq, dev);
+		vp->tx_irq = 0;
+	}
+	napi_disable(&vp->napi);
+	netif_napi_del(&vp->napi);
+	if (vp->fds->rx_fd > 0) {
+		if (vp->bpf)
+			uml_vector_detach_bpf(vp->fds->rx_fd, vp->bpf);
+		os_close_file(vp->fds->rx_fd);
+		vp->fds->rx_fd = -1;
+	}
+	if (vp->fds->tx_fd > 0) {
+		os_close_file(vp->fds->tx_fd);
+		vp->fds->tx_fd = -1;
+	}
+	if (vp->bpf != NULL)
+		kfree(vp->bpf->filter);
+	kfree(vp->bpf);
+	vp->bpf = NULL;
+	kfree(vp->fds->remote_addr);
+	kfree(vp->transport_data);
+	kfree(vp->header_rxbuffer);
+	kfree(vp->header_txbuffer);
+	if (vp->rx_queue != NULL)
+		destroy_queue(vp->rx_queue);
+	if (vp->tx_queue != NULL)
+		destroy_queue(vp->tx_queue);
+	kfree(vp->fds);
+	vp->fds = NULL;
+	spin_lock_irqsave(&vp->lock, flags);
+	vp->opened = false;
+	vp->in_error = false;
+	spin_unlock_irqrestore(&vp->lock, flags);
+	return 0;
+}
+
+static int vector_poll(struct napi_struct *napi, int budget)
+{
+	struct vector_private *vp = container_of(napi, struct vector_private, napi);
+	int work_done = 0;
+	int err;
+	bool tx_enqueued = false;
+
+	if ((vp->options & VECTOR_TX) != 0)
+		tx_enqueued = (vector_send(vp->tx_queue) > 0);
+	if ((vp->options & VECTOR_RX) > 0)
+		err = vector_mmsg_rx(vp, budget);
+	else {
+		err = vector_legacy_rx(vp);
+		if (err > 0)
+			err = 1;
+	}
+	if (err > 0)
+		work_done += err;
+
+	if (tx_enqueued || err > 0)
+		napi_schedule(napi);
+	if (work_done < budget)
+		napi_complete_done(napi, work_done);
+	return work_done;
+}
+
+static void vector_reset_tx(struct work_struct *work)
+{
+	struct vector_private *vp =
+		container_of(work, struct vector_private, reset_tx);
+	netdev_reset_queue(vp->dev);
+	netif_start_queue(vp->dev);
+	netif_wake_queue(vp->dev);
+}
+
+static int vector_net_open(struct net_device *dev)
+{
+	struct vector_private *vp = netdev_priv(dev);
+	unsigned long flags;
+	int err = -EINVAL;
+	struct vector_device *vdevice;
+
+	spin_lock_irqsave(&vp->lock, flags);
+	if (vp->opened) {
+		spin_unlock_irqrestore(&vp->lock, flags);
+		return -ENXIO;
+	}
+	vp->opened = true;
+	spin_unlock_irqrestore(&vp->lock, flags);
+
+	vp->bpf = uml_vector_user_bpf(get_bpf_file(vp->parsed));
+
+	vp->fds = uml_vector_user_open(vp->unit, vp->parsed);
+
+	if (vp->fds == NULL)
+		goto out_close;
+
+	if (build_transport_data(vp) < 0)
+		goto out_close;
+
+	if ((vp->options & VECTOR_RX) > 0) {
+		vp->rx_queue = create_queue(
+			vp,
+			get_depth(vp->parsed),
+			vp->rx_header_size,
+			MAX_IOV_SIZE
+		);
+		vp->rx_queue->queue_depth = get_depth(vp->parsed);
+	} else {
+		vp->header_rxbuffer = kmalloc(
+			vp->rx_header_size,
+			GFP_KERNEL
+		);
+		if (vp->header_rxbuffer == NULL)
+			goto out_close;
+	}
+	if ((vp->options & VECTOR_TX) > 0) {
+		vp->tx_queue = create_queue(
+			vp,
+			get_depth(vp->parsed),
+			vp->header_size,
+			MAX_IOV_SIZE
+		);
+	} else {
+		vp->header_txbuffer = kmalloc(vp->header_size, GFP_KERNEL);
+		if (vp->header_txbuffer == NULL)
+			goto out_close;
+	}
+
+	netif_napi_add_weight(vp->dev, &vp->napi, vector_poll,
+			      get_depth(vp->parsed));
+	napi_enable(&vp->napi);
+
+	/* READ IRQ */
+	err = um_request_irq(
+		irq_rr + VECTOR_BASE_IRQ, vp->fds->rx_fd,
+			IRQ_READ, vector_rx_interrupt,
+			IRQF_SHARED, dev->name, dev);
+	if (err < 0) {
+		netdev_err(dev, "vector_open: failed to get rx irq(%d)\n", err);
+		err = -ENETUNREACH;
+		goto out_close;
+	}
+	vp->rx_irq = irq_rr + VECTOR_BASE_IRQ;
+	dev->irq = irq_rr + VECTOR_BASE_IRQ;
+	irq_rr = (irq_rr + 1) % VECTOR_IRQ_SPACE;
+
+	/* WRITE IRQ - we need it only if we have vector TX */
+	if ((vp->options & VECTOR_TX) > 0) {
+		err = um_request_irq(
+			irq_rr + VECTOR_BASE_IRQ, vp->fds->tx_fd,
+				IRQ_WRITE, vector_tx_interrupt,
+				IRQF_SHARED, dev->name, dev);
+		if (err < 0) {
+			netdev_err(dev,
+				"vector_open: failed to get tx irq(%d)\n", err);
+			err = -ENETUNREACH;
+			goto out_close;
+		}
+		vp->tx_irq = irq_rr + VECTOR_BASE_IRQ;
+		irq_rr = (irq_rr + 1) % VECTOR_IRQ_SPACE;
+	}
+
+	if ((vp->options & VECTOR_QDISC_BYPASS) != 0) {
+		if (!uml_raw_enable_qdisc_bypass(vp->fds->rx_fd))
+			vp->options |= VECTOR_BPF;
+	}
+	if (((vp->options & VECTOR_BPF) != 0) && (vp->bpf == NULL))
+		vp->bpf = uml_vector_default_bpf(dev->dev_addr);
+
+	if (vp->bpf != NULL)
+		uml_vector_attach_bpf(vp->fds->rx_fd, vp->bpf);
+
+	netif_start_queue(dev);
+	vector_reset_stats(vp);
+
+	/* clear buffer - it can happen that the host side of the interface
+	 * is full when we get here. In this case, new data is never queued,
+	 * SIGIOs never arrive, and the net never works.
+	 */
+
+	napi_schedule(&vp->napi);
+
+	vdevice = find_device(vp->unit);
+	vdevice->opened = 1;
+
+	if ((vp->options & VECTOR_TX) != 0)
+		add_timer(&vp->tl);
+	return 0;
+out_close:
+	vector_net_close(dev);
+	return err;
+}
+
+
+static void vector_net_set_multicast_list(struct net_device *dev)
+{
+	/* TODO: - we can do some BPF games here */
+	return;
+}
+
+static void vector_net_tx_timeout(struct net_device *dev, unsigned int txqueue)
+{
+	struct vector_private *vp = netdev_priv(dev);
+
+	vp->estats.tx_timeout_count++;
+	netif_trans_update(dev);
+	schedule_work(&vp->reset_tx);
+}
+
+static netdev_features_t vector_fix_features(struct net_device *dev,
+	netdev_features_t features)
+{
+	features &= ~(NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM);
+	return features;
+}
+
+static int vector_set_features(struct net_device *dev,
+	netdev_features_t features)
+{
+	struct vector_private *vp = netdev_priv(dev);
+	/* Adjust buffer sizes for GSO/GRO. Unfortunately, there is
+	 * no way to negotiate it on raw sockets, so we can change
+	 * only our side.
+	 */
+	if (features & NETIF_F_GRO)
+		/* All new frame buffers will be GRO-sized */
+		vp->req_size = 65536;
+	else
+		/* All new frame buffers will be normal sized */
+		vp->req_size = vp->max_packet + vp->headroom + SAFETY_MARGIN;
+	return 0;
+}
+
+#ifdef CONFIG_NET_POLL_CONTROLLER
+static void vector_net_poll_controller(struct net_device *dev)
+{
+	disable_irq(dev->irq);
+	vector_rx_interrupt(dev->irq, dev);
+	enable_irq(dev->irq);
+}
+#endif
+
+static void vector_net_get_drvinfo(struct net_device *dev,
+				struct ethtool_drvinfo *info)
+{
+	strscpy(info->driver, DRIVER_NAME, sizeof(info->driver));
+}
+
+static int vector_net_load_bpf_flash(struct net_device *dev,
+				struct ethtool_flash *efl)
+{
+	struct vector_private *vp = netdev_priv(dev);
+	struct vector_device *vdevice;
+	const struct firmware *fw;
+	int result = 0;
+
+	if (!(vp->options & VECTOR_BPF_FLASH)) {
+		netdev_err(dev, "loading firmware not permitted: %s\n", efl->data);
+		return -1;
+	}
+
+	spin_lock(&vp->lock);
+
+	if (vp->bpf != NULL) {
+		if (vp->opened)
+			uml_vector_detach_bpf(vp->fds->rx_fd, vp->bpf);
+		kfree(vp->bpf->filter);
+		vp->bpf->filter = NULL;
+	} else {
+		vp->bpf = kmalloc(sizeof(struct sock_fprog), GFP_ATOMIC);
+		if (vp->bpf == NULL) {
+			netdev_err(dev, "failed to allocate memory for firmware\n");
+			goto flash_fail;
+		}
+	}
+
+	vdevice = find_device(vp->unit);
+
+	if (request_firmware(&fw, efl->data, &vdevice->pdev.dev))
+		goto flash_fail;
+
+	vp->bpf->filter = kmemdup(fw->data, fw->size, GFP_ATOMIC);
+	if (!vp->bpf->filter)
+		goto free_buffer;
+
+	vp->bpf->len = fw->size / sizeof(struct sock_filter);
+	release_firmware(fw);
+
+	if (vp->opened)
+		result = uml_vector_attach_bpf(vp->fds->rx_fd, vp->bpf);
+
+	spin_unlock(&vp->lock);
+
+	return result;
+
+free_buffer:
+	release_firmware(fw);
+
+flash_fail:
+	spin_unlock(&vp->lock);
+	if (vp->bpf != NULL)
+		kfree(vp->bpf->filter);
+	kfree(vp->bpf);
+	vp->bpf = NULL;
+	return -1;
+}
+
+static void vector_get_ringparam(struct net_device *netdev,
+				 struct ethtool_ringparam *ring,
+				 struct kernel_ethtool_ringparam *kernel_ring,
+				 struct netlink_ext_ack *extack)
+{
+	struct vector_private *vp = netdev_priv(netdev);
+
+	ring->rx_max_pending = vp->rx_queue->max_depth;
+	ring->tx_max_pending = vp->tx_queue->max_depth;
+	ring->rx_pending = vp->rx_queue->max_depth;
+	ring->tx_pending = vp->tx_queue->max_depth;
+}
+
+static void vector_get_strings(struct net_device *dev, u32 stringset, u8 *buf)
+{
+	switch (stringset) {
+	case ETH_SS_TEST:
+		*buf = '\0';
+		break;
+	case ETH_SS_STATS:
+		memcpy(buf, &ethtool_stats_keys, sizeof(ethtool_stats_keys));
+		break;
+	default:
+		WARN_ON(1);
+		break;
+	}
+}
+
+static int vector_get_sset_count(struct net_device *dev, int sset)
+{
+	switch (sset) {
+	case ETH_SS_TEST:
+		return 0;
+	case ETH_SS_STATS:
+		return VECTOR_NUM_STATS;
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static void vector_get_ethtool_stats(struct net_device *dev,
+	struct ethtool_stats *estats,
+	u64 *tmp_stats)
+{
+	struct vector_private *vp = netdev_priv(dev);
+
+	memcpy(tmp_stats, &vp->estats, sizeof(struct vector_estats));
+}
+
+static int vector_get_coalesce(struct net_device *netdev,
+			       struct ethtool_coalesce *ec,
+			       struct kernel_ethtool_coalesce *kernel_coal,
+			       struct netlink_ext_ack *extack)
+{
+	struct vector_private *vp = netdev_priv(netdev);
+
+	ec->tx_coalesce_usecs = (vp->coalesce * 1000000) / HZ;
+	return 0;
+}
+
+static int vector_set_coalesce(struct net_device *netdev,
+			       struct ethtool_coalesce *ec,
+			       struct kernel_ethtool_coalesce *kernel_coal,
+			       struct netlink_ext_ack *extack)
+{
+	struct vector_private *vp = netdev_priv(netdev);
+
+	vp->coalesce = (ec->tx_coalesce_usecs * HZ) / 1000000;
+	if (vp->coalesce == 0)
+		vp->coalesce = 1;
+	return 0;
+}
+
+static const struct ethtool_ops vector_net_ethtool_ops = {
+	.supported_coalesce_params = ETHTOOL_COALESCE_TX_USECS,
+	.get_drvinfo	= vector_net_get_drvinfo,
+	.get_link	= ethtool_op_get_link,
+	.get_ts_info	= ethtool_op_get_ts_info,
+	.get_ringparam	= vector_get_ringparam,
+	.get_strings	= vector_get_strings,
+	.get_sset_count	= vector_get_sset_count,
+	.get_ethtool_stats = vector_get_ethtool_stats,
+	.get_coalesce	= vector_get_coalesce,
+	.set_coalesce	= vector_set_coalesce,
+	.flash_device	= vector_net_load_bpf_flash,
+};
+
+
+static const struct net_device_ops vector_netdev_ops = {
+	.ndo_open		= vector_net_open,
+	.ndo_stop		= vector_net_close,
+	.ndo_start_xmit		= vector_net_start_xmit,
+	.ndo_set_rx_mode	= vector_net_set_multicast_list,
+	.ndo_tx_timeout		= vector_net_tx_timeout,
+	.ndo_set_mac_address	= eth_mac_addr,
+	.ndo_validate_addr	= eth_validate_addr,
+	.ndo_fix_features	= vector_fix_features,
+	.ndo_set_features	= vector_set_features,
+#ifdef CONFIG_NET_POLL_CONTROLLER
+	.ndo_poll_controller = vector_net_poll_controller,
+#endif
+};
+
+static void vector_timer_expire(struct timer_list *t)
+{
+	struct vector_private *vp = from_timer(vp, t, tl);
+
+	vp->estats.tx_kicks++;
+	napi_schedule(&vp->napi);
+}
+
+
+
+static void vector_eth_configure(
+		int n,
+		struct arglist *def
+	)
+{
+	struct vector_device *device;
+	struct net_device *dev;
+	struct vector_private *vp;
+	int err;
+
+	device = kzalloc(sizeof(*device), GFP_KERNEL);
+	if (device == NULL) {
+		printk(KERN_ERR "eth_configure failed to allocate struct "
+				 "vector_device\n");
+		return;
+	}
+	dev = alloc_etherdev(sizeof(struct vector_private));
+	if (dev == NULL) {
+		printk(KERN_ERR "eth_configure: failed to allocate struct "
+				 "net_device for vec%d\n", n);
+		goto out_free_device;
+	}
+
+	dev->mtu = get_mtu(def);
+
+	INIT_LIST_HEAD(&device->list);
+	device->unit = n;
+
+	/* If this name ends up conflicting with an existing registered
+	 * netdevice, that is OK, register_netdev{,ice}() will notice this
+	 * and fail.
+	 */
+	snprintf(dev->name, sizeof(dev->name), "vec%d", n);
+	uml_net_setup_etheraddr(dev, uml_vector_fetch_arg(def, "mac"));
+	vp = netdev_priv(dev);
+
+	/* sysfs register */
+	if (!driver_registered) {
+		platform_driver_register(&uml_net_driver);
+		driver_registered = 1;
+	}
+	device->pdev.id = n;
+	device->pdev.name = DRIVER_NAME;
+	device->pdev.dev.release = vector_device_release;
+	dev_set_drvdata(&device->pdev.dev, device);
+	if (platform_device_register(&device->pdev))
+		goto out_free_netdev;
+	SET_NETDEV_DEV(dev, &device->pdev.dev);
+
+	device->dev = dev;
+
+	*vp = ((struct vector_private)
+		{
+		.list			= LIST_HEAD_INIT(vp->list),
+		.dev			= dev,
+		.unit			= n,
+		.options		= get_transport_options(def),
+		.rx_irq			= 0,
+		.tx_irq			= 0,
+		.parsed			= def,
+		.max_packet		= get_mtu(def) + ETH_HEADER_OTHER,
+		/* TODO - we need to calculate headroom so that ip header
+		 * is 16 byte aligned all the time
+		 */
+		.headroom		= get_headroom(def),
+		.form_header		= NULL,
+		.verify_header		= NULL,
+		.header_rxbuffer	= NULL,
+		.header_txbuffer	= NULL,
+		.header_size		= 0,
+		.rx_header_size		= 0,
+		.rexmit_scheduled	= false,
+		.opened			= false,
+		.transport_data		= NULL,
+		.in_write_poll		= false,
+		.coalesce		= 2,
+		.req_size		= get_req_size(def),
+		.in_error		= false,
+		.bpf			= NULL
+	});
+
+	dev->features = dev->hw_features = (NETIF_F_SG | NETIF_F_FRAGLIST);
+	INIT_WORK(&vp->reset_tx, vector_reset_tx);
+
+	timer_setup(&vp->tl, vector_timer_expire, 0);
+	spin_lock_init(&vp->lock);
+
+	/* FIXME */
+	dev->netdev_ops = &vector_netdev_ops;
+	dev->ethtool_ops = &vector_net_ethtool_ops;
+	dev->watchdog_timeo = (HZ >> 1);
+	/* primary IRQ - fixme */
+	dev->irq = 0; /* we will adjust this once opened */
+
+	rtnl_lock();
+	err = register_netdevice(dev);
+	rtnl_unlock();
+	if (err)
+		goto out_undo_user_init;
+
+	spin_lock(&vector_devices_lock);
+	list_add(&device->list, &vector_devices);
+	spin_unlock(&vector_devices_lock);
+
+	return;
+
+out_undo_user_init:
+	return;
+out_free_netdev:
+	free_netdev(dev);
+out_free_device:
+	kfree(device);
+}
+
+
+
+
+/*
+ * Invoked late in the init
+ */
+
+static int __init vector_init(void)
+{
+	struct list_head *ele;
+	struct vector_cmd_line_arg *def;
+	struct arglist *parsed;
+
+	list_for_each(ele, &vec_cmd_line) {
+		def = list_entry(ele, struct vector_cmd_line_arg, list);
+		parsed = uml_parse_vector_ifspec(def->arguments);
+		if (parsed != NULL)
+			vector_eth_configure(def->unit, parsed);
+	}
+	return 0;
+}
+
+
+/* Invoked at initial argument parsing, only stores
+ * arguments until a proper vector_init is called
+ * later
+ */
+
+static int __init vector_setup(char *str)
+{
+	char *error;
+	int n, err;
+	struct vector_cmd_line_arg *new;
+
+	err = vector_parse(str, &n, &str, &error);
+	if (err) {
+		printk(KERN_ERR "vector_setup - Couldn't parse '%s' : %s\n",
+				 str, error);
+		return 1;
+	}
+	new = memblock_alloc(sizeof(*new), SMP_CACHE_BYTES);
+	if (!new)
+		panic("%s: Failed to allocate %zu bytes\n", __func__,
+		      sizeof(*new));
+	INIT_LIST_HEAD(&new->list);
+	new->unit = n;
+	new->arguments = str;
+	list_add_tail(&new->list, &vec_cmd_line);
+	return 1;
+}
+
+__setup("vec", vector_setup);
+__uml_help(vector_setup,
+"vec[0-9]+:<option>=<value>,<option>=<value>\n"
+"	 Configure a vector io network device.\n\n"
+);
+
+late_initcall(vector_init);
+
+static struct mc_device vector_mc = {
+	.list		= LIST_HEAD_INIT(vector_mc.list),
+	.name		= "vec",
+	.config		= vector_config,
+	.get_config	= NULL,
+	.id		= vector_id,
+	.remove		= vector_remove,
+};
+
+#ifdef CONFIG_INET
+static int vector_inetaddr_event(
+	struct notifier_block *this,
+	unsigned long event,
+	void *ptr)
+{
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block vector_inetaddr_notifier = {
+	.notifier_call		= vector_inetaddr_event,
+};
+
+static void inet_register(void)
+{
+	register_inetaddr_notifier(&vector_inetaddr_notifier);
+}
+#else
+static inline void inet_register(void)
+{
+}
+#endif
+
+static int vector_net_init(void)
+{
+	mconsole_register_dev(&vector_mc);
+	inet_register();
+	return 0;
+}
+
+__initcall(vector_net_init);
+
+
+
diff --git a/arch/um/drivers/vector_kern.h b/arch/um/drivers/vector_kern.h
new file mode 100644
index 000000000..2a1fa8e0f
--- /dev/null
+++ b/arch/um/drivers/vector_kern.h
@@ -0,0 +1,138 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2002 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#ifndef __UM_VECTOR_KERN_H
+#define __UM_VECTOR_KERN_H
+
+#include <linux/netdevice.h>
+#include <linux/platform_device.h>
+#include <linux/skbuff.h>
+#include <linux/socket.h>
+#include <linux/list.h>
+#include <linux/ctype.h>
+#include <linux/workqueue.h>
+#include <linux/interrupt.h>
+
+#include "vector_user.h"
+
+/* Queue structure specially adapted for multiple enqueue/dequeue
+ * in a mmsgrecv/mmsgsend context
+ */
+
+/* Dequeue method */
+
+#define QUEUE_SENDMSG 0
+#define QUEUE_SENDMMSG 1
+
+#define VECTOR_RX 1
+#define VECTOR_TX (1 << 1)
+#define VECTOR_BPF (1 << 2)
+#define VECTOR_QDISC_BYPASS (1 << 3)
+#define VECTOR_BPF_FLASH (1 << 4)
+
+#define ETH_MAX_PACKET 1500
+#define ETH_HEADER_OTHER 32 /* just in case someone decides to go mad on QnQ */
+
+#define MAX_FILTER_PROG (2 << 16)
+
+struct vector_queue {
+	struct mmsghdr *mmsg_vector;
+	void **skbuff_vector;
+	 /* backlink to device which owns us */
+	struct net_device *dev;
+	spinlock_t head_lock;
+	spinlock_t tail_lock;
+	int queue_depth, head, tail, max_depth, max_iov_frags;
+	short options;
+};
+
+struct vector_estats {
+	uint64_t rx_queue_max;
+	uint64_t rx_queue_running_average;
+	uint64_t tx_queue_max;
+	uint64_t tx_queue_running_average;
+	uint64_t rx_encaps_errors;
+	uint64_t tx_timeout_count;
+	uint64_t tx_restart_queue;
+	uint64_t tx_kicks;
+	uint64_t tx_flow_control_xon;
+	uint64_t tx_flow_control_xoff;
+	uint64_t rx_csum_offload_good;
+	uint64_t rx_csum_offload_errors;
+	uint64_t sg_ok;
+	uint64_t sg_linearized;
+};
+
+#define VERIFY_HEADER_NOK -1
+#define VERIFY_HEADER_OK 0
+#define VERIFY_CSUM_OK 1
+
+struct vector_private {
+	struct list_head list;
+	spinlock_t lock;
+	struct net_device *dev;
+	struct napi_struct		napi	____cacheline_aligned;
+
+	int unit;
+
+	/* Timeout timer in TX */
+
+	struct timer_list tl;
+
+	/* Scheduled "remove device" work */
+	struct work_struct reset_tx;
+	struct vector_fds *fds;
+
+	struct vector_queue *rx_queue;
+	struct vector_queue *tx_queue;
+
+	int rx_irq;
+	int tx_irq;
+
+	struct arglist *parsed;
+
+	void *transport_data; /* transport specific params if needed */
+
+	int max_packet;
+	int req_size; /* different from max packet - used for TSO */
+	int headroom;
+
+	int options;
+
+	/* remote address if any - some transports will leave this as null */
+
+	int header_size;
+	int rx_header_size;
+	int coalesce;
+
+	void *header_rxbuffer;
+	void *header_txbuffer;
+
+	int (*form_header)(uint8_t *header,
+		struct sk_buff *skb, struct vector_private *vp);
+	int (*verify_header)(uint8_t *header,
+		struct sk_buff *skb, struct vector_private *vp);
+
+	spinlock_t stats_lock;
+
+	bool rexmit_scheduled;
+	bool opened;
+	bool in_write_poll;
+	bool in_error;
+
+	/* guest allowed to use ethtool flash to load bpf */
+	bool bpf_via_flash;
+
+	/* ethtool stats */
+
+	struct vector_estats estats;
+	struct sock_fprog *bpf;
+
+	char user[];
+};
+
+extern int build_transport_data(struct vector_private *vp);
+
+#endif
diff --git a/arch/um/drivers/vector_transports.c b/arch/um/drivers/vector_transports.c
new file mode 100644
index 000000000..0794d23f0
--- /dev/null
+++ b/arch/um/drivers/vector_transports.c
@@ -0,0 +1,495 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017 - Cambridge Greys Limited
+ * Copyright (C) 2011 - 2014 Cisco Systems Inc
+ */
+
+#include <linux/etherdevice.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <asm/byteorder.h>
+#include <uapi/linux/ip.h>
+#include <uapi/linux/virtio_net.h>
+#include <linux/virtio_net.h>
+#include <linux/virtio_byteorder.h>
+#include <linux/netdev_features.h>
+#include "vector_user.h"
+#include "vector_kern.h"
+
+#define GOOD_LINEAR 512
+#define GSO_ERROR "Incoming GSO frames and GRO disabled on the interface"
+
+struct gre_minimal_header {
+	uint16_t header;
+	uint16_t arptype;
+};
+
+
+struct uml_gre_data {
+	uint32_t rx_key;
+	uint32_t tx_key;
+	uint32_t sequence;
+
+	bool ipv6;
+	bool has_sequence;
+	bool pin_sequence;
+	bool checksum;
+	bool key;
+	struct gre_minimal_header expected_header;
+
+	uint32_t checksum_offset;
+	uint32_t key_offset;
+	uint32_t sequence_offset;
+
+};
+
+struct uml_l2tpv3_data {
+	uint64_t rx_cookie;
+	uint64_t tx_cookie;
+	uint64_t rx_session;
+	uint64_t tx_session;
+	uint32_t counter;
+
+	bool udp;
+	bool ipv6;
+	bool has_counter;
+	bool pin_counter;
+	bool cookie;
+	bool cookie_is_64;
+
+	uint32_t cookie_offset;
+	uint32_t session_offset;
+	uint32_t counter_offset;
+};
+
+static int l2tpv3_form_header(uint8_t *header,
+	struct sk_buff *skb, struct vector_private *vp)
+{
+	struct uml_l2tpv3_data *td = vp->transport_data;
+	uint32_t *counter;
+
+	if (td->udp)
+		*(uint32_t *) header = cpu_to_be32(L2TPV3_DATA_PACKET);
+	(*(uint32_t *) (header + td->session_offset)) = td->tx_session;
+
+	if (td->cookie) {
+		if (td->cookie_is_64)
+			(*(uint64_t *)(header + td->cookie_offset)) =
+				td->tx_cookie;
+		else
+			(*(uint32_t *)(header + td->cookie_offset)) =
+				td->tx_cookie;
+	}
+	if (td->has_counter) {
+		counter = (uint32_t *)(header + td->counter_offset);
+		if (td->pin_counter) {
+			*counter = 0;
+		} else {
+			td->counter++;
+			*counter = cpu_to_be32(td->counter);
+		}
+	}
+	return 0;
+}
+
+static int gre_form_header(uint8_t *header,
+		struct sk_buff *skb, struct vector_private *vp)
+{
+	struct uml_gre_data *td = vp->transport_data;
+	uint32_t *sequence;
+	*((uint32_t *) header) = *((uint32_t *) &td->expected_header);
+	if (td->key)
+		(*(uint32_t *) (header + td->key_offset)) = td->tx_key;
+	if (td->has_sequence) {
+		sequence = (uint32_t *)(header + td->sequence_offset);
+		if (td->pin_sequence)
+			*sequence = 0;
+		else
+			*sequence = cpu_to_be32(++td->sequence);
+	}
+	return 0;
+}
+
+static int raw_form_header(uint8_t *header,
+		struct sk_buff *skb, struct vector_private *vp)
+{
+	struct virtio_net_hdr *vheader = (struct virtio_net_hdr *) header;
+
+	virtio_net_hdr_from_skb(
+		skb,
+		vheader,
+		virtio_legacy_is_little_endian(),
+		false,
+		0
+	);
+
+	return 0;
+}
+
+static int l2tpv3_verify_header(
+	uint8_t *header, struct sk_buff *skb, struct vector_private *vp)
+{
+	struct uml_l2tpv3_data *td = vp->transport_data;
+	uint32_t *session;
+	uint64_t cookie;
+
+	if ((!td->udp) && (!td->ipv6))
+		header += sizeof(struct iphdr) /* fix for ipv4 raw */;
+
+	/* we do not do a strict check for "data" packets as per
+	 * the RFC spec because the pure IP spec does not have
+	 * that anyway.
+	 */
+
+	if (td->cookie) {
+		if (td->cookie_is_64)
+			cookie = *(uint64_t *)(header + td->cookie_offset);
+		else
+			cookie = *(uint32_t *)(header + td->cookie_offset);
+		if (cookie != td->rx_cookie) {
+			if (net_ratelimit())
+				netdev_err(vp->dev, "uml_l2tpv3: unknown cookie id");
+			return -1;
+		}
+	}
+	session = (uint32_t *) (header + td->session_offset);
+	if (*session != td->rx_session) {
+		if (net_ratelimit())
+			netdev_err(vp->dev, "uml_l2tpv3: session mismatch");
+		return -1;
+	}
+	return 0;
+}
+
+static int gre_verify_header(
+	uint8_t *header, struct sk_buff *skb, struct vector_private *vp)
+{
+
+	uint32_t key;
+	struct uml_gre_data *td = vp->transport_data;
+
+	if (!td->ipv6)
+		header += sizeof(struct iphdr) /* fix for ipv4 raw */;
+
+	if (*((uint32_t *) header) != *((uint32_t *) &td->expected_header)) {
+		if (net_ratelimit())
+			netdev_err(vp->dev, "header type disagreement, expecting %0x, got %0x",
+				*((uint32_t *) &td->expected_header),
+				*((uint32_t *) header)
+			);
+		return -1;
+	}
+
+	if (td->key) {
+		key = (*(uint32_t *)(header + td->key_offset));
+		if (key != td->rx_key) {
+			if (net_ratelimit())
+				netdev_err(vp->dev, "unknown key id %0x, expecting %0x",
+						key, td->rx_key);
+			return -1;
+		}
+	}
+	return 0;
+}
+
+static int raw_verify_header(
+	uint8_t *header, struct sk_buff *skb, struct vector_private *vp)
+{
+	struct virtio_net_hdr *vheader = (struct virtio_net_hdr *) header;
+
+	if ((vheader->gso_type != VIRTIO_NET_HDR_GSO_NONE) &&
+		(vp->req_size != 65536)) {
+		if (net_ratelimit())
+			netdev_err(
+				vp->dev,
+				GSO_ERROR
+		);
+	}
+	if ((vheader->flags & VIRTIO_NET_HDR_F_DATA_VALID) > 0)
+		return 1;
+
+	virtio_net_hdr_to_skb(skb, vheader, virtio_legacy_is_little_endian());
+	return 0;
+}
+
+static bool get_uint_param(
+	struct arglist *def, char *param, unsigned int *result)
+{
+	char *arg = uml_vector_fetch_arg(def, param);
+
+	if (arg != NULL) {
+		if (kstrtoint(arg, 0, result) == 0)
+			return true;
+	}
+	return false;
+}
+
+static bool get_ulong_param(
+	struct arglist *def, char *param, unsigned long *result)
+{
+	char *arg = uml_vector_fetch_arg(def, param);
+
+	if (arg != NULL) {
+		if (kstrtoul(arg, 0, result) == 0)
+			return true;
+		return true;
+	}
+	return false;
+}
+
+static int build_gre_transport_data(struct vector_private *vp)
+{
+	struct uml_gre_data *td;
+	int temp_int;
+	int temp_rx;
+	int temp_tx;
+
+	vp->transport_data = kmalloc(sizeof(struct uml_gre_data), GFP_KERNEL);
+	if (vp->transport_data == NULL)
+		return -ENOMEM;
+	td = vp->transport_data;
+	td->sequence = 0;
+
+	td->expected_header.arptype = GRE_IRB;
+	td->expected_header.header = 0;
+
+	vp->form_header = &gre_form_header;
+	vp->verify_header = &gre_verify_header;
+	vp->header_size = 4;
+	td->key_offset = 4;
+	td->sequence_offset = 4;
+	td->checksum_offset = 4;
+
+	td->ipv6 = false;
+	if (get_uint_param(vp->parsed, "v6", &temp_int)) {
+		if (temp_int > 0)
+			td->ipv6 = true;
+	}
+	td->key = false;
+	if (get_uint_param(vp->parsed, "rx_key", &temp_rx)) {
+		if (get_uint_param(vp->parsed, "tx_key", &temp_tx)) {
+			td->key = true;
+			td->expected_header.header |= GRE_MODE_KEY;
+			td->rx_key = cpu_to_be32(temp_rx);
+			td->tx_key = cpu_to_be32(temp_tx);
+			vp->header_size += 4;
+			td->sequence_offset += 4;
+		} else {
+			return -EINVAL;
+		}
+	}
+
+	td->sequence = false;
+	if (get_uint_param(vp->parsed, "sequence", &temp_int)) {
+		if (temp_int > 0) {
+			vp->header_size += 4;
+			td->has_sequence = true;
+			td->expected_header.header |= GRE_MODE_SEQUENCE;
+			if (get_uint_param(
+				vp->parsed, "pin_sequence", &temp_int)) {
+				if (temp_int > 0)
+					td->pin_sequence = true;
+			}
+		}
+	}
+	vp->rx_header_size = vp->header_size;
+	if (!td->ipv6)
+		vp->rx_header_size += sizeof(struct iphdr);
+	return 0;
+}
+
+static int build_l2tpv3_transport_data(struct vector_private *vp)
+{
+
+	struct uml_l2tpv3_data *td;
+	int temp_int, temp_rxs, temp_txs;
+	unsigned long temp_rx;
+	unsigned long temp_tx;
+
+	vp->transport_data = kmalloc(
+		sizeof(struct uml_l2tpv3_data), GFP_KERNEL);
+
+	if (vp->transport_data == NULL)
+		return -ENOMEM;
+
+	td = vp->transport_data;
+
+	vp->form_header = &l2tpv3_form_header;
+	vp->verify_header = &l2tpv3_verify_header;
+	td->counter = 0;
+
+	vp->header_size = 4;
+	td->session_offset = 0;
+	td->cookie_offset = 4;
+	td->counter_offset = 4;
+
+
+	td->ipv6 = false;
+	if (get_uint_param(vp->parsed, "v6", &temp_int)) {
+		if (temp_int > 0)
+			td->ipv6 = true;
+	}
+
+	if (get_uint_param(vp->parsed, "rx_session", &temp_rxs)) {
+		if (get_uint_param(vp->parsed, "tx_session", &temp_txs)) {
+			td->tx_session = cpu_to_be32(temp_txs);
+			td->rx_session = cpu_to_be32(temp_rxs);
+		} else {
+			return -EINVAL;
+		}
+	} else {
+		return -EINVAL;
+	}
+
+	td->cookie_is_64  = false;
+	if (get_uint_param(vp->parsed, "cookie64", &temp_int)) {
+		if (temp_int > 0)
+			td->cookie_is_64  = true;
+	}
+	td->cookie = false;
+	if (get_ulong_param(vp->parsed, "rx_cookie", &temp_rx)) {
+		if (get_ulong_param(vp->parsed, "tx_cookie", &temp_tx)) {
+			td->cookie = true;
+			if (td->cookie_is_64) {
+				td->rx_cookie = cpu_to_be64(temp_rx);
+				td->tx_cookie = cpu_to_be64(temp_tx);
+				vp->header_size += 8;
+				td->counter_offset += 8;
+			} else {
+				td->rx_cookie = cpu_to_be32(temp_rx);
+				td->tx_cookie = cpu_to_be32(temp_tx);
+				vp->header_size += 4;
+				td->counter_offset += 4;
+			}
+		} else {
+			return -EINVAL;
+		}
+	}
+
+	td->has_counter = false;
+	if (get_uint_param(vp->parsed, "counter", &temp_int)) {
+		if (temp_int > 0) {
+			td->has_counter = true;
+			vp->header_size += 4;
+			if (get_uint_param(
+				vp->parsed, "pin_counter", &temp_int)) {
+				if (temp_int > 0)
+					td->pin_counter = true;
+			}
+		}
+	}
+
+	if (get_uint_param(vp->parsed, "udp", &temp_int)) {
+		if (temp_int > 0) {
+			td->udp = true;
+			vp->header_size += 4;
+			td->counter_offset += 4;
+			td->session_offset += 4;
+			td->cookie_offset += 4;
+		}
+	}
+
+	vp->rx_header_size = vp->header_size;
+	if ((!td->ipv6) && (!td->udp))
+		vp->rx_header_size += sizeof(struct iphdr);
+
+	return 0;
+}
+
+static int build_raw_transport_data(struct vector_private *vp)
+{
+	if (uml_raw_enable_vnet_headers(vp->fds->rx_fd)) {
+		if (!uml_raw_enable_vnet_headers(vp->fds->tx_fd))
+			return -1;
+		vp->form_header = &raw_form_header;
+		vp->verify_header = &raw_verify_header;
+		vp->header_size = sizeof(struct virtio_net_hdr);
+		vp->rx_header_size = sizeof(struct virtio_net_hdr);
+		vp->dev->hw_features |= (NETIF_F_TSO | NETIF_F_GRO);
+		vp->dev->features |=
+			(NETIF_F_RXCSUM | NETIF_F_HW_CSUM |
+				NETIF_F_TSO | NETIF_F_GRO);
+		netdev_info(
+			vp->dev,
+			"raw: using vnet headers for tso and tx/rx checksum"
+		);
+	}
+	return 0;
+}
+
+static int build_hybrid_transport_data(struct vector_private *vp)
+{
+	if (uml_raw_enable_vnet_headers(vp->fds->rx_fd)) {
+		vp->form_header = &raw_form_header;
+		vp->verify_header = &raw_verify_header;
+		vp->header_size = sizeof(struct virtio_net_hdr);
+		vp->rx_header_size = sizeof(struct virtio_net_hdr);
+		vp->dev->hw_features |=
+			(NETIF_F_TSO | NETIF_F_GSO | NETIF_F_GRO);
+		vp->dev->features |=
+			(NETIF_F_RXCSUM | NETIF_F_HW_CSUM |
+				NETIF_F_TSO | NETIF_F_GSO | NETIF_F_GRO);
+		netdev_info(
+			vp->dev,
+			"tap/raw hybrid: using vnet headers for tso and tx/rx checksum"
+		);
+	} else {
+		return 0; /* do not try to enable tap too if raw failed */
+	}
+	if (uml_tap_enable_vnet_headers(vp->fds->tx_fd))
+		return 0;
+	return -1;
+}
+
+static int build_tap_transport_data(struct vector_private *vp)
+{
+	/* "Pure" tap uses the same fd for rx and tx */
+	if (uml_tap_enable_vnet_headers(vp->fds->tx_fd)) {
+		vp->form_header = &raw_form_header;
+		vp->verify_header = &raw_verify_header;
+		vp->header_size = sizeof(struct virtio_net_hdr);
+		vp->rx_header_size = sizeof(struct virtio_net_hdr);
+		vp->dev->hw_features |=
+			(NETIF_F_TSO | NETIF_F_GSO | NETIF_F_GRO);
+		vp->dev->features |=
+			(NETIF_F_RXCSUM | NETIF_F_HW_CSUM |
+				NETIF_F_TSO | NETIF_F_GSO | NETIF_F_GRO);
+		netdev_info(
+			vp->dev,
+			"tap: using vnet headers for tso and tx/rx checksum"
+		);
+		return 0;
+	}
+	return -1;
+}
+
+
+static int build_bess_transport_data(struct vector_private *vp)
+{
+	vp->form_header = NULL;
+	vp->verify_header = NULL;
+	vp->header_size = 0;
+	vp->rx_header_size = 0;
+	return 0;
+}
+
+int build_transport_data(struct vector_private *vp)
+{
+	char *transport = uml_vector_fetch_arg(vp->parsed, "transport");
+
+	if (strncmp(transport, TRANS_GRE, TRANS_GRE_LEN) == 0)
+		return build_gre_transport_data(vp);
+	if (strncmp(transport, TRANS_L2TPV3, TRANS_L2TPV3_LEN) == 0)
+		return build_l2tpv3_transport_data(vp);
+	if (strncmp(transport, TRANS_RAW, TRANS_RAW_LEN) == 0)
+		return build_raw_transport_data(vp);
+	if (strncmp(transport, TRANS_TAP, TRANS_TAP_LEN) == 0)
+		return build_tap_transport_data(vp);
+	if (strncmp(transport, TRANS_HYBRID, TRANS_HYBRID_LEN) == 0)
+		return build_hybrid_transport_data(vp);
+	if (strncmp(transport, TRANS_BESS, TRANS_BESS_LEN) == 0)
+		return build_bess_transport_data(vp);
+	return 0;
+}
+
diff --git a/arch/um/drivers/vector_user.c b/arch/um/drivers/vector_user.c
new file mode 100644
index 000000000..c650e4284
--- /dev/null
+++ b/arch/um/drivers/vector_user.c
@@ -0,0 +1,858 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdarg.h>
+#include <errno.h>
+#include <stddef.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <net/if.h>
+#include <linux/if_tun.h>
+#include <arpa/inet.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <netinet/ip.h>
+#include <linux/if_ether.h>
+#include <linux/if_packet.h>
+#include <sys/wait.h>
+#include <sys/uio.h>
+#include <linux/virtio_net.h>
+#include <netdb.h>
+#include <stdlib.h>
+#include <os.h>
+#include <limits.h>
+#include <um_malloc.h>
+#include "vector_user.h"
+
+#define ID_GRE 0
+#define ID_L2TPV3 1
+#define ID_BESS 2
+#define ID_MAX 2
+
+#define TOKEN_IFNAME "ifname"
+#define TOKEN_SCRIPT "ifup"
+
+#define TRANS_RAW "raw"
+#define TRANS_RAW_LEN strlen(TRANS_RAW)
+
+#define TRANS_FD "fd"
+#define TRANS_FD_LEN strlen(TRANS_FD)
+
+#define VNET_HDR_FAIL "could not enable vnet headers on fd %d"
+#define TUN_GET_F_FAIL "tapraw: TUNGETFEATURES failed: %s"
+#define L2TPV3_BIND_FAIL "l2tpv3_open : could not bind socket err=%i"
+#define UNIX_BIND_FAIL "unix_open : could not bind socket err=%i"
+#define BPF_ATTACH_FAIL "Failed to attach filter size %d prog %px to %d, err %d\n"
+#define BPF_DETACH_FAIL "Failed to detach filter size %d prog %px to %d, err %d\n"
+
+#define MAX_UN_LEN 107
+
+static const char padchar[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+static const char *template = "tapXXXXXX";
+
+/* This is very ugly and brute force lookup, but it is done
+ * only once at initialization so not worth doing hashes or
+ * anything more intelligent
+ */
+
+char *uml_vector_fetch_arg(struct arglist *ifspec, char *token)
+{
+	int i;
+
+	for (i = 0; i < ifspec->numargs; i++) {
+		if (strcmp(ifspec->tokens[i], token) == 0)
+			return ifspec->values[i];
+	}
+	return NULL;
+
+}
+
+struct arglist *uml_parse_vector_ifspec(char *arg)
+{
+	struct arglist *result;
+	int pos, len;
+	bool parsing_token = true, next_starts = true;
+
+	if (arg == NULL)
+		return NULL;
+	result = uml_kmalloc(sizeof(struct arglist), UM_GFP_KERNEL);
+	if (result == NULL)
+		return NULL;
+	result->numargs = 0;
+	len = strlen(arg);
+	for (pos = 0; pos < len; pos++) {
+		if (next_starts) {
+			if (parsing_token) {
+				result->tokens[result->numargs] = arg + pos;
+			} else {
+				result->values[result->numargs] = arg + pos;
+				result->numargs++;
+			}
+			next_starts = false;
+		}
+		if (*(arg + pos) == '=') {
+			if (parsing_token)
+				parsing_token = false;
+			else
+				goto cleanup;
+			next_starts = true;
+			(*(arg + pos)) = '\0';
+		}
+		if (*(arg + pos) == ',') {
+			parsing_token = true;
+			next_starts = true;
+			(*(arg + pos)) = '\0';
+		}
+	}
+	return result;
+cleanup:
+	printk(UM_KERN_ERR "vector_setup - Couldn't parse '%s'\n", arg);
+	kfree(result);
+	return NULL;
+}
+
+/*
+ * Socket/FD configuration functions. These return an structure
+ * of rx and tx descriptors to cover cases where these are not
+ * the same (f.e. read via raw socket and write via tap).
+ */
+
+#define PATH_NET_TUN "/dev/net/tun"
+
+
+static int create_tap_fd(char *iface)
+{
+	struct ifreq ifr;
+	int fd = -1;
+	int err = -ENOMEM, offload;
+
+	fd = open(PATH_NET_TUN, O_RDWR);
+	if (fd < 0) {
+		printk(UM_KERN_ERR "uml_tap: failed to open tun device\n");
+		goto tap_fd_cleanup;
+	}
+	memset(&ifr, 0, sizeof(ifr));
+	ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
+	strncpy((char *)&ifr.ifr_name, iface, sizeof(ifr.ifr_name) - 1);
+
+	err = ioctl(fd, TUNSETIFF, (void *) &ifr);
+	if (err != 0) {
+		printk(UM_KERN_ERR "uml_tap: failed to select tap interface\n");
+		goto tap_fd_cleanup;
+	}
+
+	offload = TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6;
+	ioctl(fd, TUNSETOFFLOAD, offload);
+	return fd;
+tap_fd_cleanup:
+	if (fd >= 0)
+		os_close_file(fd);
+	return err;
+}
+
+static int create_raw_fd(char *iface, int flags, int proto)
+{
+	struct ifreq ifr;
+	int fd = -1;
+	struct sockaddr_ll sock;
+	int err = -ENOMEM;
+
+	fd = socket(AF_PACKET, SOCK_RAW, flags);
+	if (fd == -1) {
+		err = -errno;
+		goto raw_fd_cleanup;
+	}
+	memset(&ifr, 0, sizeof(ifr));
+	strncpy((char *)&ifr.ifr_name, iface, sizeof(ifr.ifr_name) - 1);
+	if (ioctl(fd, SIOCGIFINDEX, (void *) &ifr) < 0) {
+		err = -errno;
+		goto raw_fd_cleanup;
+	}
+
+	sock.sll_family = AF_PACKET;
+	sock.sll_protocol = htons(proto);
+	sock.sll_ifindex = ifr.ifr_ifindex;
+
+	if (bind(fd,
+		(struct sockaddr *) &sock, sizeof(struct sockaddr_ll)) < 0) {
+		err = -errno;
+		goto raw_fd_cleanup;
+	}
+	return fd;
+raw_fd_cleanup:
+	printk(UM_KERN_ERR "user_init_raw: init failed, error %d", err);
+	if (fd >= 0)
+		os_close_file(fd);
+	return err;
+}
+
+
+static struct vector_fds *user_init_tap_fds(struct arglist *ifspec)
+{
+	int fd = -1, i;
+	char *iface;
+	struct vector_fds *result = NULL;
+	bool dynamic = false;
+	char dynamic_ifname[IFNAMSIZ];
+	char *argv[] = {NULL, NULL, NULL, NULL};
+
+	iface = uml_vector_fetch_arg(ifspec, TOKEN_IFNAME);
+	if (iface == NULL) {
+		dynamic = true;
+		iface = dynamic_ifname;
+		srand(getpid());
+	}
+
+	result = uml_kmalloc(sizeof(struct vector_fds), UM_GFP_KERNEL);
+	if (result == NULL) {
+		printk(UM_KERN_ERR "uml_tap: failed to allocate file descriptors\n");
+		goto tap_cleanup;
+	}
+	result->rx_fd = -1;
+	result->tx_fd = -1;
+	result->remote_addr = NULL;
+	result->remote_addr_size = 0;
+
+	/* TAP */
+	do {
+		if (dynamic) {
+			strcpy(iface, template);
+			for (i = 0; i < strlen(iface); i++) {
+				if (iface[i] == 'X') {
+					iface[i] = padchar[rand() % strlen(padchar)];
+				}
+			}
+		}
+		fd = create_tap_fd(iface);
+		if ((fd < 0) && (!dynamic)) {
+			printk(UM_KERN_ERR "uml_tap: failed to create tun interface\n");
+			goto tap_cleanup;
+		}
+		result->tx_fd = fd;
+		result->rx_fd = fd;
+	} while (fd < 0);
+
+	argv[0] = uml_vector_fetch_arg(ifspec, TOKEN_SCRIPT);
+	if (argv[0]) {
+		argv[1] = iface;
+		run_helper(NULL, NULL, argv);
+	}
+
+	return result;
+tap_cleanup:
+	printk(UM_KERN_ERR "user_init_tap: init failed, error %d", fd);
+	kfree(result);
+	return NULL;
+}
+
+static struct vector_fds *user_init_hybrid_fds(struct arglist *ifspec)
+{
+	char *iface;
+	struct vector_fds *result = NULL;
+	char *argv[] = {NULL, NULL, NULL, NULL};
+
+	iface = uml_vector_fetch_arg(ifspec, TOKEN_IFNAME);
+	if (iface == NULL) {
+		printk(UM_KERN_ERR "uml_tap: failed to parse interface spec\n");
+		goto hybrid_cleanup;
+	}
+
+	result = uml_kmalloc(sizeof(struct vector_fds), UM_GFP_KERNEL);
+	if (result == NULL) {
+		printk(UM_KERN_ERR "uml_tap: failed to allocate file descriptors\n");
+		goto hybrid_cleanup;
+	}
+	result->rx_fd = -1;
+	result->tx_fd = -1;
+	result->remote_addr = NULL;
+	result->remote_addr_size = 0;
+
+	/* TAP */
+
+	result->tx_fd = create_tap_fd(iface);
+	if (result->tx_fd < 0) {
+		printk(UM_KERN_ERR "uml_tap: failed to create tun interface: %i\n", result->tx_fd);
+		goto hybrid_cleanup;
+	}
+
+	/* RAW */
+
+	result->rx_fd = create_raw_fd(iface, ETH_P_ALL, ETH_P_ALL);
+	if (result->rx_fd == -1) {
+		printk(UM_KERN_ERR
+			"uml_tap: failed to create paired raw socket: %i\n", result->rx_fd);
+		goto hybrid_cleanup;
+	}
+
+	argv[0] = uml_vector_fetch_arg(ifspec, TOKEN_SCRIPT);
+	if (argv[0]) {
+		argv[1] = iface;
+		run_helper(NULL, NULL, argv);
+	}
+	return result;
+hybrid_cleanup:
+	printk(UM_KERN_ERR "user_init_hybrid: init failed");
+	kfree(result);
+	return NULL;
+}
+
+static struct vector_fds *user_init_unix_fds(struct arglist *ifspec, int id)
+{
+	int fd = -1;
+	int socktype;
+	char *src, *dst;
+	struct vector_fds *result = NULL;
+	struct sockaddr_un *local_addr = NULL, *remote_addr = NULL;
+
+	src = uml_vector_fetch_arg(ifspec, "src");
+	dst = uml_vector_fetch_arg(ifspec, "dst");
+	result = uml_kmalloc(sizeof(struct vector_fds), UM_GFP_KERNEL);
+	if (result == NULL) {
+		printk(UM_KERN_ERR "unix open:cannot allocate remote addr");
+		goto unix_cleanup;
+	}
+	remote_addr = uml_kmalloc(sizeof(struct sockaddr_un), UM_GFP_KERNEL);
+	if (remote_addr == NULL) {
+		printk(UM_KERN_ERR "unix open:cannot allocate remote addr");
+		goto unix_cleanup;
+	}
+
+	switch (id) {
+	case ID_BESS:
+		socktype = SOCK_SEQPACKET;
+		if ((src != NULL) && (strlen(src) <= MAX_UN_LEN)) {
+			local_addr = uml_kmalloc(sizeof(struct sockaddr_un), UM_GFP_KERNEL);
+			if (local_addr == NULL) {
+				printk(UM_KERN_ERR "bess open:cannot allocate local addr");
+				goto unix_cleanup;
+			}
+			local_addr->sun_family = AF_UNIX;
+			memcpy(local_addr->sun_path, src, strlen(src) + 1);
+		}
+		if ((dst == NULL) || (strlen(dst) > MAX_UN_LEN))
+			goto unix_cleanup;
+		remote_addr->sun_family = AF_UNIX;
+		memcpy(remote_addr->sun_path, dst, strlen(dst) + 1);
+		break;
+	default:
+		printk(KERN_ERR "Unsupported unix socket type\n");
+		return NULL;
+	}
+
+	fd = socket(AF_UNIX, socktype, 0);
+	if (fd == -1) {
+		printk(UM_KERN_ERR
+			"unix open: could not open socket, error = %d",
+			-errno
+		);
+		goto unix_cleanup;
+	}
+	if (local_addr != NULL) {
+		if (bind(fd, (struct sockaddr *) local_addr, sizeof(struct sockaddr_un))) {
+			printk(UM_KERN_ERR UNIX_BIND_FAIL, errno);
+			goto unix_cleanup;
+		}
+	}
+	switch (id) {
+	case ID_BESS:
+		if (connect(fd, (const struct sockaddr *) remote_addr, sizeof(struct sockaddr_un)) < 0) {
+			printk(UM_KERN_ERR "bess open:cannot connect to %s %i", remote_addr->sun_path, -errno);
+			goto unix_cleanup;
+		}
+		break;
+	}
+	result->rx_fd = fd;
+	result->tx_fd = fd;
+	result->remote_addr_size = sizeof(struct sockaddr_un);
+	result->remote_addr = remote_addr;
+	return result;
+unix_cleanup:
+	if (fd >= 0)
+		os_close_file(fd);
+	kfree(remote_addr);
+	kfree(result);
+	return NULL;
+}
+
+static int strtofd(const char *nptr)
+{
+	long fd;
+	char *endptr;
+
+	if (nptr == NULL)
+		return -1;
+
+	errno = 0;
+	fd = strtol(nptr, &endptr, 10);
+	if (nptr == endptr ||
+		errno != 0 ||
+		*endptr != '\0' ||
+		fd < 0 ||
+		fd > INT_MAX) {
+		return -1;
+	}
+	return fd;
+}
+
+static struct vector_fds *user_init_fd_fds(struct arglist *ifspec)
+{
+	int fd = -1;
+	char *fdarg = NULL;
+	struct vector_fds *result = NULL;
+
+	fdarg = uml_vector_fetch_arg(ifspec, "fd");
+	fd = strtofd(fdarg);
+	if (fd == -1) {
+		printk(UM_KERN_ERR "fd open: bad or missing fd argument");
+		goto fd_cleanup;
+	}
+
+	result = uml_kmalloc(sizeof(struct vector_fds), UM_GFP_KERNEL);
+	if (result == NULL) {
+		printk(UM_KERN_ERR "fd open: allocation failed");
+		goto fd_cleanup;
+	}
+
+	result->rx_fd = fd;
+	result->tx_fd = fd;
+	result->remote_addr_size = 0;
+	result->remote_addr = NULL;
+	return result;
+
+fd_cleanup:
+	if (fd >= 0)
+		os_close_file(fd);
+	kfree(result);
+	return NULL;
+}
+
+static struct vector_fds *user_init_raw_fds(struct arglist *ifspec)
+{
+	int rxfd = -1, txfd = -1;
+	int err = -ENOMEM;
+	char *iface;
+	struct vector_fds *result = NULL;
+	char *argv[] = {NULL, NULL, NULL, NULL};
+
+	iface = uml_vector_fetch_arg(ifspec, TOKEN_IFNAME);
+	if (iface == NULL)
+		goto raw_cleanup;
+
+	rxfd = create_raw_fd(iface, ETH_P_ALL, ETH_P_ALL);
+	if (rxfd == -1) {
+		err = -errno;
+		goto raw_cleanup;
+	}
+	txfd = create_raw_fd(iface, 0, ETH_P_IP); /* Turn off RX on this fd */
+	if (txfd == -1) {
+		err = -errno;
+		goto raw_cleanup;
+	}
+	result = uml_kmalloc(sizeof(struct vector_fds), UM_GFP_KERNEL);
+	if (result != NULL) {
+		result->rx_fd = rxfd;
+		result->tx_fd = txfd;
+		result->remote_addr = NULL;
+		result->remote_addr_size = 0;
+	}
+	argv[0] = uml_vector_fetch_arg(ifspec, TOKEN_SCRIPT);
+	if (argv[0]) {
+		argv[1] = iface;
+		run_helper(NULL, NULL, argv);
+	}
+	return result;
+raw_cleanup:
+	printk(UM_KERN_ERR "user_init_raw: init failed, error %d", err);
+	kfree(result);
+	return NULL;
+}
+
+
+bool uml_raw_enable_qdisc_bypass(int fd)
+{
+	int optval = 1;
+
+	if (setsockopt(fd,
+		SOL_PACKET, PACKET_QDISC_BYPASS,
+		&optval, sizeof(optval)) != 0) {
+		return false;
+	}
+	return true;
+}
+
+bool uml_raw_enable_vnet_headers(int fd)
+{
+	int optval = 1;
+
+	if (setsockopt(fd,
+		SOL_PACKET, PACKET_VNET_HDR,
+		&optval, sizeof(optval)) != 0) {
+		printk(UM_KERN_INFO VNET_HDR_FAIL, fd);
+		return false;
+	}
+	return true;
+}
+bool uml_tap_enable_vnet_headers(int fd)
+{
+	unsigned int features;
+	int len = sizeof(struct virtio_net_hdr);
+
+	if (ioctl(fd, TUNGETFEATURES, &features) == -1) {
+		printk(UM_KERN_INFO TUN_GET_F_FAIL, strerror(errno));
+		return false;
+	}
+	if ((features & IFF_VNET_HDR) == 0) {
+		printk(UM_KERN_INFO "tapraw: No VNET HEADER support");
+		return false;
+	}
+	ioctl(fd, TUNSETVNETHDRSZ, &len);
+	return true;
+}
+
+static struct vector_fds *user_init_socket_fds(struct arglist *ifspec, int id)
+{
+	int err = -ENOMEM;
+	int fd = -1, gairet;
+	struct addrinfo srchints;
+	struct addrinfo dsthints;
+	bool v6, udp;
+	char *value;
+	char *src, *dst, *srcport, *dstport;
+	struct addrinfo *gairesult = NULL;
+	struct vector_fds *result = NULL;
+
+
+	value = uml_vector_fetch_arg(ifspec, "v6");
+	v6 = false;
+	udp = false;
+	if (value != NULL) {
+		if (strtol((const char *) value, NULL, 10) > 0)
+			v6 = true;
+	}
+
+	value = uml_vector_fetch_arg(ifspec, "udp");
+	if (value != NULL) {
+		if (strtol((const char *) value, NULL, 10) > 0)
+			udp = true;
+	}
+	src = uml_vector_fetch_arg(ifspec, "src");
+	dst = uml_vector_fetch_arg(ifspec, "dst");
+	srcport = uml_vector_fetch_arg(ifspec, "srcport");
+	dstport = uml_vector_fetch_arg(ifspec, "dstport");
+
+	memset(&dsthints, 0, sizeof(dsthints));
+
+	if (v6)
+		dsthints.ai_family = AF_INET6;
+	else
+		dsthints.ai_family = AF_INET;
+
+	switch (id) {
+	case ID_GRE:
+		dsthints.ai_socktype = SOCK_RAW;
+		dsthints.ai_protocol = IPPROTO_GRE;
+		break;
+	case ID_L2TPV3:
+		if (udp) {
+			dsthints.ai_socktype = SOCK_DGRAM;
+			dsthints.ai_protocol = 0;
+		} else {
+			dsthints.ai_socktype = SOCK_RAW;
+			dsthints.ai_protocol = IPPROTO_L2TP;
+		}
+		break;
+	default:
+		printk(KERN_ERR "Unsupported socket type\n");
+		return NULL;
+	}
+	memcpy(&srchints, &dsthints, sizeof(struct addrinfo));
+
+	gairet = getaddrinfo(src, srcport, &dsthints, &gairesult);
+	if ((gairet != 0) || (gairesult == NULL)) {
+		printk(UM_KERN_ERR
+			"socket_open : could not resolve src, error = %s",
+			gai_strerror(gairet)
+		);
+		return NULL;
+	}
+	fd = socket(gairesult->ai_family,
+		gairesult->ai_socktype, gairesult->ai_protocol);
+	if (fd == -1) {
+		printk(UM_KERN_ERR
+			"socket_open : could not open socket, error = %d",
+			-errno
+		);
+		goto cleanup;
+	}
+	if (bind(fd,
+		(struct sockaddr *) gairesult->ai_addr,
+		gairesult->ai_addrlen)) {
+		printk(UM_KERN_ERR L2TPV3_BIND_FAIL, errno);
+		goto cleanup;
+	}
+
+	if (gairesult != NULL)
+		freeaddrinfo(gairesult);
+
+	gairesult = NULL;
+
+	gairet = getaddrinfo(dst, dstport, &dsthints, &gairesult);
+	if ((gairet != 0) || (gairesult == NULL)) {
+		printk(UM_KERN_ERR
+			"socket_open : could not resolve dst, error = %s",
+			gai_strerror(gairet)
+		);
+		return NULL;
+	}
+
+	result = uml_kmalloc(sizeof(struct vector_fds), UM_GFP_KERNEL);
+	if (result != NULL) {
+		result->rx_fd = fd;
+		result->tx_fd = fd;
+		result->remote_addr = uml_kmalloc(
+			gairesult->ai_addrlen, UM_GFP_KERNEL);
+		if (result->remote_addr == NULL)
+			goto cleanup;
+		result->remote_addr_size = gairesult->ai_addrlen;
+		memcpy(
+			result->remote_addr,
+			gairesult->ai_addr,
+			gairesult->ai_addrlen
+		);
+	}
+	freeaddrinfo(gairesult);
+	return result;
+cleanup:
+	if (gairesult != NULL)
+		freeaddrinfo(gairesult);
+	printk(UM_KERN_ERR "user_init_socket: init failed, error %d", err);
+	if (fd >= 0)
+		os_close_file(fd);
+	if (result != NULL) {
+		kfree(result->remote_addr);
+		kfree(result);
+	}
+	return NULL;
+}
+
+struct vector_fds *uml_vector_user_open(
+	int unit,
+	struct arglist *parsed
+)
+{
+	char *transport;
+
+	if (parsed == NULL) {
+		printk(UM_KERN_ERR "no parsed config for unit %d\n", unit);
+		return NULL;
+	}
+	transport = uml_vector_fetch_arg(parsed, "transport");
+	if (transport == NULL) {
+		printk(UM_KERN_ERR "missing transport for unit %d\n", unit);
+		return NULL;
+	}
+	if (strncmp(transport, TRANS_RAW, TRANS_RAW_LEN) == 0)
+		return user_init_raw_fds(parsed);
+	if (strncmp(transport, TRANS_HYBRID, TRANS_HYBRID_LEN) == 0)
+		return user_init_hybrid_fds(parsed);
+	if (strncmp(transport, TRANS_TAP, TRANS_TAP_LEN) == 0)
+		return user_init_tap_fds(parsed);
+	if (strncmp(transport, TRANS_GRE, TRANS_GRE_LEN) == 0)
+		return user_init_socket_fds(parsed, ID_GRE);
+	if (strncmp(transport, TRANS_L2TPV3, TRANS_L2TPV3_LEN) == 0)
+		return user_init_socket_fds(parsed, ID_L2TPV3);
+	if (strncmp(transport, TRANS_BESS, TRANS_BESS_LEN) == 0)
+		return user_init_unix_fds(parsed, ID_BESS);
+	if (strncmp(transport, TRANS_FD, TRANS_FD_LEN) == 0)
+		return user_init_fd_fds(parsed);
+	return NULL;
+}
+
+
+int uml_vector_sendmsg(int fd, void *hdr, int flags)
+{
+	int n;
+
+	CATCH_EINTR(n = sendmsg(fd, (struct msghdr *) hdr,  flags));
+	if ((n < 0) && (errno == EAGAIN))
+		return 0;
+	if (n >= 0)
+		return n;
+	else
+		return -errno;
+}
+
+int uml_vector_recvmsg(int fd, void *hdr, int flags)
+{
+	int n;
+	struct msghdr *msg = (struct msghdr *) hdr;
+
+	CATCH_EINTR(n = readv(fd, msg->msg_iov, msg->msg_iovlen));
+	if ((n < 0) && (errno == EAGAIN))
+		return 0;
+	if (n >= 0)
+		return n;
+	else
+		return -errno;
+}
+
+int uml_vector_writev(int fd, void *hdr, int iovcount)
+{
+	int n;
+
+	CATCH_EINTR(n = writev(fd, (struct iovec *) hdr,  iovcount));
+	if ((n < 0) && ((errno == EAGAIN) || (errno == ENOBUFS)))
+		return 0;
+	if (n >= 0)
+		return n;
+	else
+		return -errno;
+}
+
+int uml_vector_sendmmsg(
+	int fd,
+	void *msgvec,
+	unsigned int vlen,
+	unsigned int flags)
+{
+	int n;
+
+	CATCH_EINTR(n = sendmmsg(fd, (struct mmsghdr *) msgvec, vlen, flags));
+	if ((n < 0) && ((errno == EAGAIN) || (errno == ENOBUFS)))
+		return 0;
+	if (n >= 0)
+		return n;
+	else
+		return -errno;
+}
+
+int uml_vector_recvmmsg(
+	int fd,
+	void *msgvec,
+	unsigned int vlen,
+	unsigned int flags)
+{
+	int n;
+
+	CATCH_EINTR(
+		n = recvmmsg(fd, (struct mmsghdr *) msgvec, vlen, flags, 0));
+	if ((n < 0) && (errno == EAGAIN))
+		return 0;
+	if (n >= 0)
+		return n;
+	else
+		return -errno;
+}
+int uml_vector_attach_bpf(int fd, void *bpf)
+{
+	struct sock_fprog *prog = bpf;
+
+	int err = setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, bpf, sizeof(struct sock_fprog));
+
+	if (err < 0)
+		printk(KERN_ERR BPF_ATTACH_FAIL, prog->len, prog->filter, fd, -errno);
+	return err;
+}
+
+int uml_vector_detach_bpf(int fd, void *bpf)
+{
+	struct sock_fprog *prog = bpf;
+
+	int err = setsockopt(fd, SOL_SOCKET, SO_DETACH_FILTER, bpf, sizeof(struct sock_fprog));
+	if (err < 0)
+		printk(KERN_ERR BPF_DETACH_FAIL, prog->len, prog->filter, fd, -errno);
+	return err;
+}
+void *uml_vector_default_bpf(const void *mac)
+{
+	struct sock_filter *bpf;
+	uint32_t *mac1 = (uint32_t *)(mac + 2);
+	uint16_t *mac2 = (uint16_t *) mac;
+	struct sock_fprog *bpf_prog;
+
+	bpf_prog = uml_kmalloc(sizeof(struct sock_fprog), UM_GFP_KERNEL);
+	if (bpf_prog) {
+		bpf_prog->len = DEFAULT_BPF_LEN;
+		bpf_prog->filter = NULL;
+	} else {
+		return NULL;
+	}
+	bpf = uml_kmalloc(
+		sizeof(struct sock_filter) * DEFAULT_BPF_LEN, UM_GFP_KERNEL);
+	if (bpf) {
+		bpf_prog->filter = bpf;
+		/* ld	[8] */
+		bpf[0] = (struct sock_filter){ 0x20, 0, 0, 0x00000008 };
+		/* jeq	#0xMAC[2-6] jt 2 jf 5*/
+		bpf[1] = (struct sock_filter){ 0x15, 0, 3, ntohl(*mac1)};
+		/* ldh	[6] */
+		bpf[2] = (struct sock_filter){ 0x28, 0, 0, 0x00000006 };
+		/* jeq	#0xMAC[0-1] jt 4 jf 5 */
+		bpf[3] = (struct sock_filter){ 0x15, 0, 1, ntohs(*mac2)};
+		/* ret	#0 */
+		bpf[4] = (struct sock_filter){ 0x6, 0, 0, 0x00000000 };
+		/* ret	#0x40000 */
+		bpf[5] = (struct sock_filter){ 0x6, 0, 0, 0x00040000 };
+	} else {
+		kfree(bpf_prog);
+		bpf_prog = NULL;
+	}
+	return bpf_prog;
+}
+
+/* Note - this function requires a valid mac being passed as an arg */
+
+void *uml_vector_user_bpf(char *filename)
+{
+	struct sock_filter *bpf;
+	struct sock_fprog *bpf_prog;
+	struct stat statbuf;
+	int res, ffd = -1;
+
+	if (filename == NULL)
+		return NULL;
+
+	if (stat(filename, &statbuf) < 0) {
+		printk(KERN_ERR "Error %d reading bpf file", -errno);
+		return false;
+	}
+	bpf_prog = uml_kmalloc(sizeof(struct sock_fprog), UM_GFP_KERNEL);
+	if (bpf_prog == NULL) {
+		printk(KERN_ERR "Failed to allocate bpf prog buffer");
+		return NULL;
+	}
+	bpf_prog->len = statbuf.st_size / sizeof(struct sock_filter);
+	bpf_prog->filter = NULL;
+	ffd = os_open_file(filename, of_read(OPENFLAGS()), 0);
+	if (ffd < 0) {
+		printk(KERN_ERR "Error %d opening bpf file", -errno);
+		goto bpf_failed;
+	}
+	bpf = uml_kmalloc(statbuf.st_size, UM_GFP_KERNEL);
+	if (bpf == NULL) {
+		printk(KERN_ERR "Failed to allocate bpf buffer");
+		goto bpf_failed;
+	}
+	bpf_prog->filter = bpf;
+	res = os_read_file(ffd, bpf, statbuf.st_size);
+	if (res < statbuf.st_size) {
+		printk(KERN_ERR "Failed to read bpf program %s, error %d", filename, res);
+		kfree(bpf);
+		goto bpf_failed;
+	}
+	os_close_file(ffd);
+	return bpf_prog;
+bpf_failed:
+	if (ffd > 0)
+		os_close_file(ffd);
+	kfree(bpf_prog);
+	return NULL;
+}
diff --git a/arch/um/drivers/vector_user.h b/arch/um/drivers/vector_user.h
new file mode 100644
index 000000000..3a73d17a0
--- /dev/null
+++ b/arch/um/drivers/vector_user.h
@@ -0,0 +1,109 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2002 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#ifndef __UM_VECTOR_USER_H
+#define __UM_VECTOR_USER_H
+
+#define MAXVARGS	20
+
+#define TOKEN_IFNAME "ifname"
+
+#define TRANS_RAW "raw"
+#define TRANS_RAW_LEN strlen(TRANS_RAW)
+
+#define TRANS_TAP "tap"
+#define TRANS_TAP_LEN strlen(TRANS_TAP)
+
+#define TRANS_GRE "gre"
+#define TRANS_GRE_LEN strlen(TRANS_GRE)
+
+#define TRANS_L2TPV3 "l2tpv3"
+#define TRANS_L2TPV3_LEN strlen(TRANS_L2TPV3)
+
+#define TRANS_HYBRID "hybrid"
+#define TRANS_HYBRID_LEN strlen(TRANS_HYBRID)
+
+#define TRANS_BESS "bess"
+#define TRANS_BESS_LEN strlen(TRANS_BESS)
+
+#define DEFAULT_BPF_LEN 6
+
+#ifndef IPPROTO_GRE
+#define IPPROTO_GRE 0x2F
+#endif
+
+#define GRE_MODE_CHECKSUM	cpu_to_be16(8 << 12)	/* checksum */
+#define GRE_MODE_RESERVED	cpu_to_be16(4 << 12)	/* unused */
+#define GRE_MODE_KEY		cpu_to_be16(2 << 12)	/* KEY present */
+#define GRE_MODE_SEQUENCE	cpu_to_be16(1 << 12)	/* sequence */
+
+#define GRE_IRB cpu_to_be16(0x6558)
+
+#define L2TPV3_DATA_PACKET 0x30000
+
+/* IANA-assigned IP protocol ID for L2TPv3 */
+
+#ifndef IPPROTO_L2TP
+#define IPPROTO_L2TP 0x73
+#endif
+
+struct arglist {
+	int	numargs;
+	char	*tokens[MAXVARGS];
+	char	*values[MAXVARGS];
+};
+
+/* Separating read and write FDs allows us to have different
+ * rx and tx method. Example - read tap via raw socket using
+ * recvmmsg, write using legacy tap write calls
+ */
+
+struct vector_fds {
+	int rx_fd;
+	int tx_fd;
+	void *remote_addr;
+	int remote_addr_size;
+};
+
+#define VECTOR_READ	1
+#define VECTOR_WRITE	(1 < 1)
+#define VECTOR_HEADERS	(1 < 2)
+
+extern struct arglist *uml_parse_vector_ifspec(char *arg);
+
+extern struct vector_fds *uml_vector_user_open(
+	int unit,
+	struct arglist *parsed
+);
+
+extern char *uml_vector_fetch_arg(
+	struct arglist *ifspec,
+	char *token
+);
+
+extern int uml_vector_recvmsg(int fd, void *hdr, int flags);
+extern int uml_vector_sendmsg(int fd, void *hdr, int flags);
+extern int uml_vector_writev(int fd, void *hdr, int iovcount);
+extern int uml_vector_sendmmsg(
+	int fd, void *msgvec,
+	unsigned int vlen,
+	unsigned int flags
+);
+extern int uml_vector_recvmmsg(
+	int fd,
+	void *msgvec,
+	unsigned int vlen,
+	unsigned int flags
+);
+extern void *uml_vector_default_bpf(const void *mac);
+extern void *uml_vector_user_bpf(char *filename);
+extern int uml_vector_attach_bpf(int fd, void *bpf);
+extern int uml_vector_detach_bpf(int fd, void *bpf);
+extern bool uml_raw_enable_qdisc_bypass(int fd);
+extern bool uml_raw_enable_vnet_headers(int fd);
+extern bool uml_tap_enable_vnet_headers(int fd);
+
+
+#endif
diff --git a/arch/um/drivers/vhost_user.h b/arch/um/drivers/vhost_user.h
new file mode 100644
index 000000000..6f147cd3c
--- /dev/null
+++ b/arch/um/drivers/vhost_user.h
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Vhost-user protocol */
+
+#ifndef __VHOST_USER_H__
+#define __VHOST_USER_H__
+
+/* Message flags */
+#define VHOST_USER_FLAG_REPLY		BIT(2)
+#define VHOST_USER_FLAG_NEED_REPLY	BIT(3)
+/* Feature bits */
+#define VHOST_USER_F_PROTOCOL_FEATURES	30
+/* Protocol feature bits */
+#define VHOST_USER_PROTOCOL_F_REPLY_ACK			3
+#define VHOST_USER_PROTOCOL_F_SLAVE_REQ			5
+#define VHOST_USER_PROTOCOL_F_CONFIG			9
+#define VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS	14
+/* Vring state index masks */
+#define VHOST_USER_VRING_INDEX_MASK	0xff
+#define VHOST_USER_VRING_POLL_MASK	BIT(8)
+
+/* Supported version */
+#define VHOST_USER_VERSION		1
+/* Supported transport features */
+#define VHOST_USER_SUPPORTED_F		BIT_ULL(VHOST_USER_F_PROTOCOL_FEATURES)
+/* Supported protocol features */
+#define VHOST_USER_SUPPORTED_PROTOCOL_F	(BIT_ULL(VHOST_USER_PROTOCOL_F_REPLY_ACK) | \
+					 BIT_ULL(VHOST_USER_PROTOCOL_F_SLAVE_REQ) | \
+					 BIT_ULL(VHOST_USER_PROTOCOL_F_CONFIG) | \
+					 BIT_ULL(VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS))
+
+enum vhost_user_request {
+	VHOST_USER_GET_FEATURES = 1,
+	VHOST_USER_SET_FEATURES = 2,
+	VHOST_USER_SET_OWNER = 3,
+	VHOST_USER_RESET_OWNER = 4,
+	VHOST_USER_SET_MEM_TABLE = 5,
+	VHOST_USER_SET_LOG_BASE = 6,
+	VHOST_USER_SET_LOG_FD = 7,
+	VHOST_USER_SET_VRING_NUM = 8,
+	VHOST_USER_SET_VRING_ADDR = 9,
+	VHOST_USER_SET_VRING_BASE = 10,
+	VHOST_USER_GET_VRING_BASE = 11,
+	VHOST_USER_SET_VRING_KICK = 12,
+	VHOST_USER_SET_VRING_CALL = 13,
+	VHOST_USER_SET_VRING_ERR = 14,
+	VHOST_USER_GET_PROTOCOL_FEATURES = 15,
+	VHOST_USER_SET_PROTOCOL_FEATURES = 16,
+	VHOST_USER_GET_QUEUE_NUM = 17,
+	VHOST_USER_SET_VRING_ENABLE = 18,
+	VHOST_USER_SEND_RARP = 19,
+	VHOST_USER_NET_SEND_MTU = 20,
+	VHOST_USER_SET_SLAVE_REQ_FD = 21,
+	VHOST_USER_IOTLB_MSG = 22,
+	VHOST_USER_SET_VRING_ENDIAN = 23,
+	VHOST_USER_GET_CONFIG = 24,
+	VHOST_USER_SET_CONFIG = 25,
+	VHOST_USER_VRING_KICK = 35,
+};
+
+enum vhost_user_slave_request {
+	VHOST_USER_SLAVE_IOTLB_MSG = 1,
+	VHOST_USER_SLAVE_CONFIG_CHANGE_MSG = 2,
+	VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG = 3,
+	VHOST_USER_SLAVE_VRING_CALL = 4,
+};
+
+struct vhost_user_header {
+	/*
+	 * Use enum vhost_user_request for outgoing messages,
+	 * uses enum vhost_user_slave_request for incoming ones.
+	 */
+	u32 request;
+	u32 flags;
+	u32 size;
+} __packed;
+
+struct vhost_user_config {
+	u32 offset;
+	u32 size;
+	u32 flags;
+	u8 payload[]; /* Variable length */
+} __packed;
+
+struct vhost_user_vring_state {
+	u32 index;
+	u32 num;
+} __packed;
+
+struct vhost_user_vring_addr {
+	u32 index;
+	u32 flags;
+	u64 desc, used, avail, log;
+} __packed;
+
+struct vhost_user_mem_region {
+	u64 guest_addr;
+	u64 size;
+	u64 user_addr;
+	u64 mmap_offset;
+} __packed;
+
+struct vhost_user_mem_regions {
+	u32 num;
+	u32 padding;
+	struct vhost_user_mem_region regions[2]; /* Currently supporting 2 */
+} __packed;
+
+union vhost_user_payload {
+	u64 integer;
+	struct vhost_user_config config;
+	struct vhost_user_vring_state vring_state;
+	struct vhost_user_vring_addr vring_addr;
+	struct vhost_user_mem_regions mem_regions;
+};
+
+struct vhost_user_msg {
+	struct vhost_user_header header;
+	union vhost_user_payload payload;
+} __packed;
+
+#endif
diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c
new file mode 100644
index 000000000..5472b1a0a
--- /dev/null
+++ b/arch/um/drivers/virt-pci.c
@@ -0,0 +1,969 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Intel Corporation
+ * Author: Johannes Berg <johannes@sipsolutions.net>
+ */
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/logic_iomem.h>
+#include <linux/irqdomain.h>
+#include <linux/virtio_pcidev.h>
+#include <linux/virtio-uml.h>
+#include <linux/delay.h>
+#include <linux/msi.h>
+#include <asm/unaligned.h>
+#include <irq_kern.h>
+
+#define MAX_DEVICES 8
+#define MAX_MSI_VECTORS 32
+#define CFG_SPACE_SIZE 4096
+
+/* for MSI-X we have a 32-bit payload */
+#define MAX_IRQ_MSG_SIZE (sizeof(struct virtio_pcidev_msg) + sizeof(u32))
+#define NUM_IRQ_MSGS	10
+
+#define HANDLE_NO_FREE(ptr) ((void *)((unsigned long)(ptr) | 1))
+#define HANDLE_IS_NO_FREE(ptr) ((unsigned long)(ptr) & 1)
+
+struct um_pci_device {
+	struct virtio_device *vdev;
+
+	/* for now just standard BARs */
+	u8 resptr[PCI_STD_NUM_BARS];
+
+	struct virtqueue *cmd_vq, *irq_vq;
+
+#define UM_PCI_STAT_WAITING	0
+	unsigned long status;
+
+	int irq;
+};
+
+struct um_pci_device_reg {
+	struct um_pci_device *dev;
+	void __iomem *iomem;
+};
+
+static struct pci_host_bridge *bridge;
+static DEFINE_MUTEX(um_pci_mtx);
+static struct um_pci_device_reg um_pci_devices[MAX_DEVICES];
+static struct fwnode_handle *um_pci_fwnode;
+static struct irq_domain *um_pci_inner_domain;
+static struct irq_domain *um_pci_msi_domain;
+static unsigned long um_pci_msi_used[BITS_TO_LONGS(MAX_MSI_VECTORS)];
+
+#define UM_VIRT_PCI_MAXDELAY 40000
+
+struct um_pci_message_buffer {
+	struct virtio_pcidev_msg hdr;
+	u8 data[8];
+};
+
+static struct um_pci_message_buffer __percpu *um_pci_msg_bufs;
+
+static int um_pci_send_cmd(struct um_pci_device *dev,
+			   struct virtio_pcidev_msg *cmd,
+			   unsigned int cmd_size,
+			   const void *extra, unsigned int extra_size,
+			   void *out, unsigned int out_size)
+{
+	struct scatterlist out_sg, extra_sg, in_sg;
+	struct scatterlist *sgs_list[] = {
+		[0] = &out_sg,
+		[1] = extra ? &extra_sg : &in_sg,
+		[2] = extra ? &in_sg : NULL,
+	};
+	struct um_pci_message_buffer *buf;
+	int delay_count = 0;
+	int ret, len;
+	bool posted;
+
+	if (WARN_ON(cmd_size < sizeof(*cmd) || cmd_size > sizeof(*buf)))
+		return -EINVAL;
+
+	switch (cmd->op) {
+	case VIRTIO_PCIDEV_OP_CFG_WRITE:
+	case VIRTIO_PCIDEV_OP_MMIO_WRITE:
+	case VIRTIO_PCIDEV_OP_MMIO_MEMSET:
+		/* in PCI, writes are posted, so don't wait */
+		posted = !out;
+		WARN_ON(!posted);
+		break;
+	default:
+		posted = false;
+		break;
+	}
+
+	buf = get_cpu_var(um_pci_msg_bufs);
+	if (buf)
+		memcpy(buf, cmd, cmd_size);
+
+	if (posted) {
+		u8 *ncmd = kmalloc(cmd_size + extra_size, GFP_ATOMIC);
+
+		if (ncmd) {
+			memcpy(ncmd, cmd, cmd_size);
+			if (extra)
+				memcpy(ncmd + cmd_size, extra, extra_size);
+			cmd = (void *)ncmd;
+			cmd_size += extra_size;
+			extra = NULL;
+			extra_size = 0;
+		} else {
+			/* try without allocating memory */
+			posted = false;
+			cmd = (void *)buf;
+		}
+	} else {
+		cmd = (void *)buf;
+	}
+
+	sg_init_one(&out_sg, cmd, cmd_size);
+	if (extra)
+		sg_init_one(&extra_sg, extra, extra_size);
+	if (out)
+		sg_init_one(&in_sg, out, out_size);
+
+	/* add to internal virtio queue */
+	ret = virtqueue_add_sgs(dev->cmd_vq, sgs_list,
+				extra ? 2 : 1,
+				out ? 1 : 0,
+				posted ? cmd : HANDLE_NO_FREE(cmd),
+				GFP_ATOMIC);
+	if (ret) {
+		if (posted)
+			kfree(cmd);
+		goto out;
+	}
+
+	if (posted) {
+		virtqueue_kick(dev->cmd_vq);
+		ret = 0;
+		goto out;
+	}
+
+	/* kick and poll for getting a response on the queue */
+	set_bit(UM_PCI_STAT_WAITING, &dev->status);
+	virtqueue_kick(dev->cmd_vq);
+
+	while (1) {
+		void *completed = virtqueue_get_buf(dev->cmd_vq, &len);
+
+		if (completed == HANDLE_NO_FREE(cmd))
+			break;
+
+		if (completed && !HANDLE_IS_NO_FREE(completed))
+			kfree(completed);
+
+		if (WARN_ONCE(virtqueue_is_broken(dev->cmd_vq) ||
+			      ++delay_count > UM_VIRT_PCI_MAXDELAY,
+			      "um virt-pci delay: %d", delay_count)) {
+			ret = -EIO;
+			break;
+		}
+		udelay(1);
+	}
+	clear_bit(UM_PCI_STAT_WAITING, &dev->status);
+
+out:
+	put_cpu_var(um_pci_msg_bufs);
+	return ret;
+}
+
+static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
+					  int size)
+{
+	struct um_pci_device_reg *reg = priv;
+	struct um_pci_device *dev = reg->dev;
+	struct virtio_pcidev_msg hdr = {
+		.op = VIRTIO_PCIDEV_OP_CFG_READ,
+		.size = size,
+		.addr = offset,
+	};
+	/* buf->data is maximum size - we may only use parts of it */
+	struct um_pci_message_buffer *buf;
+	u8 *data;
+	unsigned long ret = ULONG_MAX;
+	size_t bytes = sizeof(buf->data);
+
+	if (!dev)
+		return ULONG_MAX;
+
+	buf = get_cpu_var(um_pci_msg_bufs);
+	data = buf->data;
+
+	if (buf)
+		memset(data, 0xff, bytes);
+
+	switch (size) {
+	case 1:
+	case 2:
+	case 4:
+#ifdef CONFIG_64BIT
+	case 8:
+#endif
+		break;
+	default:
+		WARN(1, "invalid config space read size %d\n", size);
+		goto out;
+	}
+
+	if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, data, bytes))
+		goto out;
+
+	switch (size) {
+	case 1:
+		ret = data[0];
+		break;
+	case 2:
+		ret = le16_to_cpup((void *)data);
+		break;
+	case 4:
+		ret = le32_to_cpup((void *)data);
+		break;
+#ifdef CONFIG_64BIT
+	case 8:
+		ret = le64_to_cpup((void *)data);
+		break;
+#endif
+	default:
+		break;
+	}
+
+out:
+	put_cpu_var(um_pci_msg_bufs);
+	return ret;
+}
+
+static void um_pci_cfgspace_write(void *priv, unsigned int offset, int size,
+				  unsigned long val)
+{
+	struct um_pci_device_reg *reg = priv;
+	struct um_pci_device *dev = reg->dev;
+	struct {
+		struct virtio_pcidev_msg hdr;
+		/* maximum size - we may only use parts of it */
+		u8 data[8];
+	} msg = {
+		.hdr = {
+			.op = VIRTIO_PCIDEV_OP_CFG_WRITE,
+			.size = size,
+			.addr = offset,
+		},
+	};
+
+	if (!dev)
+		return;
+
+	switch (size) {
+	case 1:
+		msg.data[0] = (u8)val;
+		break;
+	case 2:
+		put_unaligned_le16(val, (void *)msg.data);
+		break;
+	case 4:
+		put_unaligned_le32(val, (void *)msg.data);
+		break;
+#ifdef CONFIG_64BIT
+	case 8:
+		put_unaligned_le64(val, (void *)msg.data);
+		break;
+#endif
+	default:
+		WARN(1, "invalid config space write size %d\n", size);
+		return;
+	}
+
+	WARN_ON(um_pci_send_cmd(dev, &msg.hdr, sizeof(msg), NULL, 0, NULL, 0));
+}
+
+static const struct logic_iomem_ops um_pci_device_cfgspace_ops = {
+	.read = um_pci_cfgspace_read,
+	.write = um_pci_cfgspace_write,
+};
+
+static void um_pci_bar_copy_from(void *priv, void *buffer,
+				 unsigned int offset, int size)
+{
+	u8 *resptr = priv;
+	struct um_pci_device *dev = container_of(resptr - *resptr,
+						 struct um_pci_device,
+						 resptr[0]);
+	struct virtio_pcidev_msg hdr = {
+		.op = VIRTIO_PCIDEV_OP_MMIO_READ,
+		.bar = *resptr,
+		.size = size,
+		.addr = offset,
+	};
+
+	memset(buffer, 0xff, size);
+
+	um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, buffer, size);
+}
+
+static unsigned long um_pci_bar_read(void *priv, unsigned int offset,
+				     int size)
+{
+	/* buf->data is maximum size - we may only use parts of it */
+	struct um_pci_message_buffer *buf;
+	u8 *data;
+	unsigned long ret = ULONG_MAX;
+
+	buf = get_cpu_var(um_pci_msg_bufs);
+	data = buf->data;
+
+	switch (size) {
+	case 1:
+	case 2:
+	case 4:
+#ifdef CONFIG_64BIT
+	case 8:
+#endif
+		break;
+	default:
+		WARN(1, "invalid config space read size %d\n", size);
+		goto out;
+	}
+
+	um_pci_bar_copy_from(priv, data, offset, size);
+
+	switch (size) {
+	case 1:
+		ret = data[0];
+		break;
+	case 2:
+		ret = le16_to_cpup((void *)data);
+		break;
+	case 4:
+		ret = le32_to_cpup((void *)data);
+		break;
+#ifdef CONFIG_64BIT
+	case 8:
+		ret = le64_to_cpup((void *)data);
+		break;
+#endif
+	default:
+		break;
+	}
+
+out:
+	put_cpu_var(um_pci_msg_bufs);
+	return ret;
+}
+
+static void um_pci_bar_copy_to(void *priv, unsigned int offset,
+			       const void *buffer, int size)
+{
+	u8 *resptr = priv;
+	struct um_pci_device *dev = container_of(resptr - *resptr,
+						 struct um_pci_device,
+						 resptr[0]);
+	struct virtio_pcidev_msg hdr = {
+		.op = VIRTIO_PCIDEV_OP_MMIO_WRITE,
+		.bar = *resptr,
+		.size = size,
+		.addr = offset,
+	};
+
+	um_pci_send_cmd(dev, &hdr, sizeof(hdr), buffer, size, NULL, 0);
+}
+
+static void um_pci_bar_write(void *priv, unsigned int offset, int size,
+			     unsigned long val)
+{
+	/* maximum size - we may only use parts of it */
+	u8 data[8];
+
+	switch (size) {
+	case 1:
+		data[0] = (u8)val;
+		break;
+	case 2:
+		put_unaligned_le16(val, (void *)data);
+		break;
+	case 4:
+		put_unaligned_le32(val, (void *)data);
+		break;
+#ifdef CONFIG_64BIT
+	case 8:
+		put_unaligned_le64(val, (void *)data);
+		break;
+#endif
+	default:
+		WARN(1, "invalid config space write size %d\n", size);
+		return;
+	}
+
+	um_pci_bar_copy_to(priv, offset, data, size);
+}
+
+static void um_pci_bar_set(void *priv, unsigned int offset, u8 value, int size)
+{
+	u8 *resptr = priv;
+	struct um_pci_device *dev = container_of(resptr - *resptr,
+						 struct um_pci_device,
+						 resptr[0]);
+	struct {
+		struct virtio_pcidev_msg hdr;
+		u8 data;
+	} msg = {
+		.hdr = {
+			.op = VIRTIO_PCIDEV_OP_CFG_WRITE,
+			.bar = *resptr,
+			.size = size,
+			.addr = offset,
+		},
+		.data = value,
+	};
+
+	um_pci_send_cmd(dev, &msg.hdr, sizeof(msg), NULL, 0, NULL, 0);
+}
+
+static const struct logic_iomem_ops um_pci_device_bar_ops = {
+	.read = um_pci_bar_read,
+	.write = um_pci_bar_write,
+	.set = um_pci_bar_set,
+	.copy_from = um_pci_bar_copy_from,
+	.copy_to = um_pci_bar_copy_to,
+};
+
+static void __iomem *um_pci_map_bus(struct pci_bus *bus, unsigned int devfn,
+				    int where)
+{
+	struct um_pci_device_reg *dev;
+	unsigned int busn = bus->number;
+
+	if (busn > 0)
+		return NULL;
+
+	/* not allowing functions for now ... */
+	if (devfn % 8)
+		return NULL;
+
+	if (devfn / 8 >= ARRAY_SIZE(um_pci_devices))
+		return NULL;
+
+	dev = &um_pci_devices[devfn / 8];
+	if (!dev)
+		return NULL;
+
+	return (void __iomem *)((unsigned long)dev->iomem + where);
+}
+
+static struct pci_ops um_pci_ops = {
+	.map_bus = um_pci_map_bus,
+	.read = pci_generic_config_read,
+	.write = pci_generic_config_write,
+};
+
+static void um_pci_rescan(void)
+{
+	pci_lock_rescan_remove();
+	pci_rescan_bus(bridge->bus);
+	pci_unlock_rescan_remove();
+}
+
+static void um_pci_irq_vq_addbuf(struct virtqueue *vq, void *buf, bool kick)
+{
+	struct scatterlist sg[1];
+
+	sg_init_one(sg, buf, MAX_IRQ_MSG_SIZE);
+	if (virtqueue_add_inbuf(vq, sg, 1, buf, GFP_ATOMIC))
+		kfree(buf);
+	else if (kick)
+		virtqueue_kick(vq);
+}
+
+static void um_pci_handle_irq_message(struct virtqueue *vq,
+				      struct virtio_pcidev_msg *msg)
+{
+	struct virtio_device *vdev = vq->vdev;
+	struct um_pci_device *dev = vdev->priv;
+
+	/* we should properly chain interrupts, but on ARCH=um we don't care */
+
+	switch (msg->op) {
+	case VIRTIO_PCIDEV_OP_INT:
+		generic_handle_irq(dev->irq);
+		break;
+	case VIRTIO_PCIDEV_OP_MSI:
+		/* our MSI message is just the interrupt number */
+		if (msg->size == sizeof(u32))
+			generic_handle_irq(le32_to_cpup((void *)msg->data));
+		else
+			generic_handle_irq(le16_to_cpup((void *)msg->data));
+		break;
+	case VIRTIO_PCIDEV_OP_PME:
+		/* nothing to do - we already woke up due to the message */
+		break;
+	default:
+		dev_err(&vdev->dev, "unexpected virt-pci message %d\n", msg->op);
+		break;
+	}
+}
+
+static void um_pci_cmd_vq_cb(struct virtqueue *vq)
+{
+	struct virtio_device *vdev = vq->vdev;
+	struct um_pci_device *dev = vdev->priv;
+	void *cmd;
+	int len;
+
+	if (test_bit(UM_PCI_STAT_WAITING, &dev->status))
+		return;
+
+	while ((cmd = virtqueue_get_buf(vq, &len))) {
+		if (WARN_ON(HANDLE_IS_NO_FREE(cmd)))
+			continue;
+		kfree(cmd);
+	}
+}
+
+static void um_pci_irq_vq_cb(struct virtqueue *vq)
+{
+	struct virtio_pcidev_msg *msg;
+	int len;
+
+	while ((msg = virtqueue_get_buf(vq, &len))) {
+		if (len >= sizeof(*msg))
+			um_pci_handle_irq_message(vq, msg);
+
+		/* recycle the message buffer */
+		um_pci_irq_vq_addbuf(vq, msg, true);
+	}
+}
+
+static int um_pci_init_vqs(struct um_pci_device *dev)
+{
+	struct virtqueue *vqs[2];
+	static const char *const names[2] = { "cmd", "irq" };
+	vq_callback_t *cbs[2] = { um_pci_cmd_vq_cb, um_pci_irq_vq_cb };
+	int err, i;
+
+	err = virtio_find_vqs(dev->vdev, 2, vqs, cbs, names, NULL);
+	if (err)
+		return err;
+
+	dev->cmd_vq = vqs[0];
+	dev->irq_vq = vqs[1];
+
+	virtio_device_ready(dev->vdev);
+
+	for (i = 0; i < NUM_IRQ_MSGS; i++) {
+		void *msg = kzalloc(MAX_IRQ_MSG_SIZE, GFP_KERNEL);
+
+		if (msg)
+			um_pci_irq_vq_addbuf(dev->irq_vq, msg, false);
+	}
+
+	virtqueue_kick(dev->irq_vq);
+
+	return 0;
+}
+
+static int um_pci_virtio_probe(struct virtio_device *vdev)
+{
+	struct um_pci_device *dev;
+	int i, free = -1;
+	int err = -ENOSPC;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	dev->vdev = vdev;
+	vdev->priv = dev;
+
+	mutex_lock(&um_pci_mtx);
+	for (i = 0; i < MAX_DEVICES; i++) {
+		if (um_pci_devices[i].dev)
+			continue;
+		free = i;
+		break;
+	}
+
+	if (free < 0)
+		goto error;
+
+	err = um_pci_init_vqs(dev);
+	if (err)
+		goto error;
+
+	dev->irq = irq_alloc_desc(numa_node_id());
+	if (dev->irq < 0) {
+		err = dev->irq;
+		goto err_reset;
+	}
+	um_pci_devices[free].dev = dev;
+	vdev->priv = dev;
+
+	mutex_unlock(&um_pci_mtx);
+
+	device_set_wakeup_enable(&vdev->dev, true);
+
+	/*
+	 * In order to do suspend-resume properly, don't allow VQs
+	 * to be suspended.
+	 */
+	virtio_uml_set_no_vq_suspend(vdev, true);
+
+	um_pci_rescan();
+	return 0;
+err_reset:
+	virtio_reset_device(vdev);
+	vdev->config->del_vqs(vdev);
+error:
+	mutex_unlock(&um_pci_mtx);
+	kfree(dev);
+	return err;
+}
+
+static void um_pci_virtio_remove(struct virtio_device *vdev)
+{
+	struct um_pci_device *dev = vdev->priv;
+	int i;
+
+	device_set_wakeup_enable(&vdev->dev, false);
+
+	mutex_lock(&um_pci_mtx);
+	for (i = 0; i < MAX_DEVICES; i++) {
+		if (um_pci_devices[i].dev != dev)
+			continue;
+
+		um_pci_devices[i].dev = NULL;
+		irq_free_desc(dev->irq);
+
+		break;
+	}
+	mutex_unlock(&um_pci_mtx);
+
+	if (i < MAX_DEVICES) {
+		struct pci_dev *pci_dev;
+
+		pci_dev = pci_get_slot(bridge->bus, i);
+		if (pci_dev)
+			pci_stop_and_remove_bus_device_locked(pci_dev);
+	}
+
+	/* Stop all virtqueues */
+	virtio_reset_device(vdev);
+	dev->cmd_vq = NULL;
+	dev->irq_vq = NULL;
+	vdev->config->del_vqs(vdev);
+
+	kfree(dev);
+}
+
+static struct virtio_device_id id_table[] = {
+	{ CONFIG_UML_PCI_OVER_VIRTIO_DEVICE_ID, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+MODULE_DEVICE_TABLE(virtio, id_table);
+
+static struct virtio_driver um_pci_virtio_driver = {
+	.driver.name = "virtio-pci",
+	.driver.owner = THIS_MODULE,
+	.id_table = id_table,
+	.probe = um_pci_virtio_probe,
+	.remove = um_pci_virtio_remove,
+};
+
+static struct resource virt_cfgspace_resource = {
+	.name = "PCI config space",
+	.start = 0xf0000000 - MAX_DEVICES * CFG_SPACE_SIZE,
+	.end = 0xf0000000 - 1,
+	.flags = IORESOURCE_MEM,
+};
+
+static long um_pci_map_cfgspace(unsigned long offset, size_t size,
+				const struct logic_iomem_ops **ops,
+				void **priv)
+{
+	if (WARN_ON(size > CFG_SPACE_SIZE || offset % CFG_SPACE_SIZE))
+		return -EINVAL;
+
+	if (offset / CFG_SPACE_SIZE < MAX_DEVICES) {
+		*ops = &um_pci_device_cfgspace_ops;
+		*priv = &um_pci_devices[offset / CFG_SPACE_SIZE];
+		return 0;
+	}
+
+	WARN(1, "cannot map offset 0x%lx/0x%zx\n", offset, size);
+	return -ENOENT;
+}
+
+static const struct logic_iomem_region_ops um_pci_cfgspace_ops = {
+	.map = um_pci_map_cfgspace,
+};
+
+static struct resource virt_iomem_resource = {
+	.name = "PCI iomem",
+	.start = 0xf0000000,
+	.end = 0xffffffff,
+	.flags = IORESOURCE_MEM,
+};
+
+struct um_pci_map_iomem_data {
+	unsigned long offset;
+	size_t size;
+	const struct logic_iomem_ops **ops;
+	void **priv;
+	long ret;
+};
+
+static int um_pci_map_iomem_walk(struct pci_dev *pdev, void *_data)
+{
+	struct um_pci_map_iomem_data *data = _data;
+	struct um_pci_device_reg *reg = &um_pci_devices[pdev->devfn / 8];
+	struct um_pci_device *dev;
+	int i;
+
+	if (!reg->dev)
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(dev->resptr); i++) {
+		struct resource *r = &pdev->resource[i];
+
+		if ((r->flags & IORESOURCE_TYPE_BITS) != IORESOURCE_MEM)
+			continue;
+
+		/*
+		 * must be the whole or part of the resource,
+		 * not allowed to only overlap
+		 */
+		if (data->offset < r->start || data->offset > r->end)
+			continue;
+		if (data->offset + data->size - 1 > r->end)
+			continue;
+
+		dev = reg->dev;
+		*data->ops = &um_pci_device_bar_ops;
+		dev->resptr[i] = i;
+		*data->priv = &dev->resptr[i];
+		data->ret = data->offset - r->start;
+
+		/* no need to continue */
+		return 1;
+	}
+
+	return 0;
+}
+
+static long um_pci_map_iomem(unsigned long offset, size_t size,
+			     const struct logic_iomem_ops **ops,
+			     void **priv)
+{
+	struct um_pci_map_iomem_data data = {
+		/* we want the full address here */
+		.offset = offset + virt_iomem_resource.start,
+		.size = size,
+		.ops = ops,
+		.priv = priv,
+		.ret = -ENOENT,
+	};
+
+	pci_walk_bus(bridge->bus, um_pci_map_iomem_walk, &data);
+	return data.ret;
+}
+
+static const struct logic_iomem_region_ops um_pci_iomem_ops = {
+	.map = um_pci_map_iomem,
+};
+
+static void um_pci_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
+{
+	/*
+	 * This is a very low address and not actually valid 'physical' memory
+	 * in UML, so we can simply map MSI(-X) vectors to there, it cannot be
+	 * legitimately written to by the device in any other way.
+	 * We use the (virtual) IRQ number here as the message to simplify the
+	 * code that receives the message, where for now we simply trust the
+	 * device to send the correct message.
+	 */
+	msg->address_hi = 0;
+	msg->address_lo = 0xa0000;
+	msg->data = data->irq;
+}
+
+static struct irq_chip um_pci_msi_bottom_irq_chip = {
+	.name = "UM virtio MSI",
+	.irq_compose_msi_msg = um_pci_compose_msi_msg,
+};
+
+static int um_pci_inner_domain_alloc(struct irq_domain *domain,
+				     unsigned int virq, unsigned int nr_irqs,
+				     void *args)
+{
+	unsigned long bit;
+
+	WARN_ON(nr_irqs != 1);
+
+	mutex_lock(&um_pci_mtx);
+	bit = find_first_zero_bit(um_pci_msi_used, MAX_MSI_VECTORS);
+	if (bit >= MAX_MSI_VECTORS) {
+		mutex_unlock(&um_pci_mtx);
+		return -ENOSPC;
+	}
+
+	set_bit(bit, um_pci_msi_used);
+	mutex_unlock(&um_pci_mtx);
+
+	irq_domain_set_info(domain, virq, bit, &um_pci_msi_bottom_irq_chip,
+			    domain->host_data, handle_simple_irq,
+			    NULL, NULL);
+
+	return 0;
+}
+
+static void um_pci_inner_domain_free(struct irq_domain *domain,
+				     unsigned int virq, unsigned int nr_irqs)
+{
+	struct irq_data *d = irq_domain_get_irq_data(domain, virq);
+
+	mutex_lock(&um_pci_mtx);
+
+	if (!test_bit(d->hwirq, um_pci_msi_used))
+		pr_err("trying to free unused MSI#%lu\n", d->hwirq);
+	else
+		__clear_bit(d->hwirq, um_pci_msi_used);
+
+	mutex_unlock(&um_pci_mtx);
+}
+
+static const struct irq_domain_ops um_pci_inner_domain_ops = {
+	.alloc = um_pci_inner_domain_alloc,
+	.free = um_pci_inner_domain_free,
+};
+
+static struct irq_chip um_pci_msi_irq_chip = {
+	.name = "UM virtio PCIe MSI",
+	.irq_mask = pci_msi_mask_irq,
+	.irq_unmask = pci_msi_unmask_irq,
+};
+
+static struct msi_domain_info um_pci_msi_domain_info = {
+	.flags	= MSI_FLAG_USE_DEF_DOM_OPS |
+		  MSI_FLAG_USE_DEF_CHIP_OPS |
+		  MSI_FLAG_PCI_MSIX,
+	.chip	= &um_pci_msi_irq_chip,
+};
+
+static struct resource busn_resource = {
+	.name	= "PCI busn",
+	.start	= 0,
+	.end	= 0,
+	.flags	= IORESOURCE_BUS,
+};
+
+static int um_pci_map_irq(const struct pci_dev *pdev, u8 slot, u8 pin)
+{
+	struct um_pci_device_reg *reg = &um_pci_devices[pdev->devfn / 8];
+
+	if (WARN_ON(!reg->dev))
+		return -EINVAL;
+
+	/* Yes, we map all pins to the same IRQ ... doesn't matter for now. */
+	return reg->dev->irq;
+}
+
+void *pci_root_bus_fwnode(struct pci_bus *bus)
+{
+	return um_pci_fwnode;
+}
+
+static int __init um_pci_init(void)
+{
+	int err, i;
+
+	WARN_ON(logic_iomem_add_region(&virt_cfgspace_resource,
+				       &um_pci_cfgspace_ops));
+	WARN_ON(logic_iomem_add_region(&virt_iomem_resource,
+				       &um_pci_iomem_ops));
+
+	if (WARN(CONFIG_UML_PCI_OVER_VIRTIO_DEVICE_ID < 0,
+		 "No virtio device ID configured for PCI - no PCI support\n"))
+		return 0;
+
+	um_pci_msg_bufs = alloc_percpu(struct um_pci_message_buffer);
+	if (!um_pci_msg_bufs)
+		return -ENOMEM;
+
+	bridge = pci_alloc_host_bridge(0);
+	if (!bridge) {
+		err = -ENOMEM;
+		goto free;
+	}
+
+	um_pci_fwnode = irq_domain_alloc_named_fwnode("um-pci");
+	if (!um_pci_fwnode) {
+		err = -ENOMEM;
+		goto free;
+	}
+
+	um_pci_inner_domain = __irq_domain_add(um_pci_fwnode, MAX_MSI_VECTORS,
+					       MAX_MSI_VECTORS, 0,
+					       &um_pci_inner_domain_ops, NULL);
+	if (!um_pci_inner_domain) {
+		err = -ENOMEM;
+		goto free;
+	}
+
+	um_pci_msi_domain = pci_msi_create_irq_domain(um_pci_fwnode,
+						      &um_pci_msi_domain_info,
+						      um_pci_inner_domain);
+	if (!um_pci_msi_domain) {
+		err = -ENOMEM;
+		goto free;
+	}
+
+	pci_add_resource(&bridge->windows, &virt_iomem_resource);
+	pci_add_resource(&bridge->windows, &busn_resource);
+	bridge->ops = &um_pci_ops;
+	bridge->map_irq = um_pci_map_irq;
+
+	for (i = 0; i < MAX_DEVICES; i++) {
+		resource_size_t start;
+
+		start = virt_cfgspace_resource.start + i * CFG_SPACE_SIZE;
+		um_pci_devices[i].iomem = ioremap(start, CFG_SPACE_SIZE);
+		if (WARN(!um_pci_devices[i].iomem, "failed to map %d\n", i)) {
+			err = -ENOMEM;
+			goto free;
+		}
+	}
+
+	err = pci_host_probe(bridge);
+	if (err)
+		goto free;
+
+	err = register_virtio_driver(&um_pci_virtio_driver);
+	if (err)
+		goto free;
+	return 0;
+free:
+	if (um_pci_inner_domain)
+		irq_domain_remove(um_pci_inner_domain);
+	if (um_pci_fwnode)
+		irq_domain_free_fwnode(um_pci_fwnode);
+	if (bridge) {
+		pci_free_resource_list(&bridge->windows);
+		pci_free_host_bridge(bridge);
+	}
+	free_percpu(um_pci_msg_bufs);
+	return err;
+}
+module_init(um_pci_init);
+
+static void __exit um_pci_exit(void)
+{
+	unregister_virtio_driver(&um_pci_virtio_driver);
+	irq_domain_remove(um_pci_msi_domain);
+	irq_domain_remove(um_pci_inner_domain);
+	pci_free_resource_list(&bridge->windows);
+	pci_free_host_bridge(bridge);
+	free_percpu(um_pci_msg_bufs);
+}
+module_exit(um_pci_exit);
diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c
new file mode 100644
index 000000000..ddd080f6d
--- /dev/null
+++ b/arch/um/drivers/virtio_uml.c
@@ -0,0 +1,1473 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Virtio vhost-user driver
+ *
+ * Copyright(c) 2019 Intel Corporation
+ *
+ * This driver allows virtio devices to be used over a vhost-user socket.
+ *
+ * Guest devices can be instantiated by kernel module or command line
+ * parameters. One device will be created for each parameter. Syntax:
+ *
+ *		virtio_uml.device=<socket>:<virtio_id>[:<platform_id>]
+ * where:
+ *		<socket>	:= vhost-user socket path to connect
+ *		<virtio_id>	:= virtio device id (as in virtio_ids.h)
+ *		<platform_id>	:= (optional) platform device id
+ *
+ * example:
+ *		virtio_uml.device=/var/uml.socket:1
+ *
+ * Based on Virtio MMIO driver by Pawel Moll, copyright 2011-2014, ARM Ltd.
+ */
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_ring.h>
+#include <linux/time-internal.h>
+#include <linux/virtio-uml.h>
+#include <shared/as-layout.h>
+#include <irq_kern.h>
+#include <init.h>
+#include <os.h>
+#include "vhost_user.h"
+
+#define MAX_SUPPORTED_QUEUE_SIZE	256
+
+#define to_virtio_uml_device(_vdev) \
+	container_of(_vdev, struct virtio_uml_device, vdev)
+
+struct virtio_uml_platform_data {
+	u32 virtio_device_id;
+	const char *socket_path;
+	struct work_struct conn_broken_wk;
+	struct platform_device *pdev;
+};
+
+struct virtio_uml_device {
+	struct virtio_device vdev;
+	struct platform_device *pdev;
+	struct virtio_uml_platform_data *pdata;
+
+	spinlock_t sock_lock;
+	int sock, req_fd, irq;
+	u64 features;
+	u64 protocol_features;
+	u8 status;
+	u8 registered:1;
+	u8 suspended:1;
+	u8 no_vq_suspend:1;
+
+	u8 config_changed_irq:1;
+	uint64_t vq_irq_vq_map;
+	int recv_rc;
+};
+
+struct virtio_uml_vq_info {
+	int kick_fd, call_fd;
+	char name[32];
+	bool suspended;
+};
+
+extern unsigned long long physmem_size, highmem;
+
+#define vu_err(vu_dev, ...)	dev_err(&(vu_dev)->pdev->dev, ##__VA_ARGS__)
+
+/* Vhost-user protocol */
+
+static int full_sendmsg_fds(int fd, const void *buf, unsigned int len,
+			    const int *fds, unsigned int fds_num)
+{
+	int rc;
+
+	do {
+		rc = os_sendmsg_fds(fd, buf, len, fds, fds_num);
+		if (rc > 0) {
+			buf += rc;
+			len -= rc;
+			fds = NULL;
+			fds_num = 0;
+		}
+	} while (len && (rc >= 0 || rc == -EINTR));
+
+	if (rc < 0)
+		return rc;
+	return 0;
+}
+
+static int full_read(int fd, void *buf, int len, bool abortable)
+{
+	int rc;
+
+	if (!len)
+		return 0;
+
+	do {
+		rc = os_read_file(fd, buf, len);
+		if (rc > 0) {
+			buf += rc;
+			len -= rc;
+		}
+	} while (len && (rc > 0 || rc == -EINTR || (!abortable && rc == -EAGAIN)));
+
+	if (rc < 0)
+		return rc;
+	if (rc == 0)
+		return -ECONNRESET;
+	return 0;
+}
+
+static int vhost_user_recv_header(int fd, struct vhost_user_msg *msg)
+{
+	return full_read(fd, msg, sizeof(msg->header), true);
+}
+
+static int vhost_user_recv(struct virtio_uml_device *vu_dev,
+			   int fd, struct vhost_user_msg *msg,
+			   size_t max_payload_size, bool wait)
+{
+	size_t size;
+	int rc;
+
+	/*
+	 * In virtio time-travel mode, we're handling all the vhost-user
+	 * FDs by polling them whenever appropriate. However, we may get
+	 * into a situation where we're sending out an interrupt message
+	 * to a device (e.g. a net device) and need to handle a simulation
+	 * time message while doing so, e.g. one that tells us to update
+	 * our idea of how long we can run without scheduling.
+	 *
+	 * Thus, we need to not just read() from the given fd, but need
+	 * to also handle messages for the simulation time - this function
+	 * does that for us while waiting for the given fd to be readable.
+	 */
+	if (wait)
+		time_travel_wait_readable(fd);
+
+	rc = vhost_user_recv_header(fd, msg);
+
+	if (rc)
+		return rc;
+	size = msg->header.size;
+	if (size > max_payload_size)
+		return -EPROTO;
+	return full_read(fd, &msg->payload, size, false);
+}
+
+static void vhost_user_check_reset(struct virtio_uml_device *vu_dev,
+				   int rc)
+{
+	struct virtio_uml_platform_data *pdata = vu_dev->pdata;
+
+	if (rc != -ECONNRESET)
+		return;
+
+	if (!vu_dev->registered)
+		return;
+
+	vu_dev->registered = 0;
+
+	schedule_work(&pdata->conn_broken_wk);
+}
+
+static int vhost_user_recv_resp(struct virtio_uml_device *vu_dev,
+				struct vhost_user_msg *msg,
+				size_t max_payload_size)
+{
+	int rc = vhost_user_recv(vu_dev, vu_dev->sock, msg,
+				 max_payload_size, true);
+
+	if (rc) {
+		vhost_user_check_reset(vu_dev, rc);
+		return rc;
+	}
+
+	if (msg->header.flags != (VHOST_USER_FLAG_REPLY | VHOST_USER_VERSION))
+		return -EPROTO;
+
+	return 0;
+}
+
+static int vhost_user_recv_u64(struct virtio_uml_device *vu_dev,
+			       u64 *value)
+{
+	struct vhost_user_msg msg;
+	int rc = vhost_user_recv_resp(vu_dev, &msg,
+				      sizeof(msg.payload.integer));
+
+	if (rc)
+		return rc;
+	if (msg.header.size != sizeof(msg.payload.integer))
+		return -EPROTO;
+	*value = msg.payload.integer;
+	return 0;
+}
+
+static int vhost_user_recv_req(struct virtio_uml_device *vu_dev,
+			       struct vhost_user_msg *msg,
+			       size_t max_payload_size)
+{
+	int rc = vhost_user_recv(vu_dev, vu_dev->req_fd, msg,
+				 max_payload_size, false);
+
+	if (rc)
+		return rc;
+
+	if ((msg->header.flags & ~VHOST_USER_FLAG_NEED_REPLY) !=
+			VHOST_USER_VERSION)
+		return -EPROTO;
+
+	return 0;
+}
+
+static int vhost_user_send(struct virtio_uml_device *vu_dev,
+			   bool need_response, struct vhost_user_msg *msg,
+			   int *fds, size_t num_fds)
+{
+	size_t size = sizeof(msg->header) + msg->header.size;
+	unsigned long flags;
+	bool request_ack;
+	int rc;
+
+	msg->header.flags |= VHOST_USER_VERSION;
+
+	/*
+	 * The need_response flag indicates that we already need a response,
+	 * e.g. to read the features. In these cases, don't request an ACK as
+	 * it is meaningless. Also request an ACK only if supported.
+	 */
+	request_ack = !need_response;
+	if (!(vu_dev->protocol_features &
+			BIT_ULL(VHOST_USER_PROTOCOL_F_REPLY_ACK)))
+		request_ack = false;
+
+	if (request_ack)
+		msg->header.flags |= VHOST_USER_FLAG_NEED_REPLY;
+
+	spin_lock_irqsave(&vu_dev->sock_lock, flags);
+	rc = full_sendmsg_fds(vu_dev->sock, msg, size, fds, num_fds);
+	if (rc < 0)
+		goto out;
+
+	if (request_ack) {
+		uint64_t status;
+
+		rc = vhost_user_recv_u64(vu_dev, &status);
+		if (rc)
+			goto out;
+
+		if (status) {
+			vu_err(vu_dev, "slave reports error: %llu\n", status);
+			rc = -EIO;
+			goto out;
+		}
+	}
+
+out:
+	spin_unlock_irqrestore(&vu_dev->sock_lock, flags);
+	return rc;
+}
+
+static int vhost_user_send_no_payload(struct virtio_uml_device *vu_dev,
+				      bool need_response, u32 request)
+{
+	struct vhost_user_msg msg = {
+		.header.request = request,
+	};
+
+	return vhost_user_send(vu_dev, need_response, &msg, NULL, 0);
+}
+
+static int vhost_user_send_no_payload_fd(struct virtio_uml_device *vu_dev,
+					 u32 request, int fd)
+{
+	struct vhost_user_msg msg = {
+		.header.request = request,
+	};
+
+	return vhost_user_send(vu_dev, false, &msg, &fd, 1);
+}
+
+static int vhost_user_send_u64(struct virtio_uml_device *vu_dev,
+			       u32 request, u64 value)
+{
+	struct vhost_user_msg msg = {
+		.header.request = request,
+		.header.size = sizeof(msg.payload.integer),
+		.payload.integer = value,
+	};
+
+	return vhost_user_send(vu_dev, false, &msg, NULL, 0);
+}
+
+static int vhost_user_set_owner(struct virtio_uml_device *vu_dev)
+{
+	return vhost_user_send_no_payload(vu_dev, false, VHOST_USER_SET_OWNER);
+}
+
+static int vhost_user_get_features(struct virtio_uml_device *vu_dev,
+				   u64 *features)
+{
+	int rc = vhost_user_send_no_payload(vu_dev, true,
+					    VHOST_USER_GET_FEATURES);
+
+	if (rc)
+		return rc;
+	return vhost_user_recv_u64(vu_dev, features);
+}
+
+static int vhost_user_set_features(struct virtio_uml_device *vu_dev,
+				   u64 features)
+{
+	return vhost_user_send_u64(vu_dev, VHOST_USER_SET_FEATURES, features);
+}
+
+static int vhost_user_get_protocol_features(struct virtio_uml_device *vu_dev,
+					    u64 *protocol_features)
+{
+	int rc = vhost_user_send_no_payload(vu_dev, true,
+			VHOST_USER_GET_PROTOCOL_FEATURES);
+
+	if (rc)
+		return rc;
+	return vhost_user_recv_u64(vu_dev, protocol_features);
+}
+
+static int vhost_user_set_protocol_features(struct virtio_uml_device *vu_dev,
+					    u64 protocol_features)
+{
+	return vhost_user_send_u64(vu_dev, VHOST_USER_SET_PROTOCOL_FEATURES,
+				   protocol_features);
+}
+
+static void vhost_user_reply(struct virtio_uml_device *vu_dev,
+			     struct vhost_user_msg *msg, int response)
+{
+	struct vhost_user_msg reply = {
+		.payload.integer = response,
+	};
+	size_t size = sizeof(reply.header) + sizeof(reply.payload.integer);
+	int rc;
+
+	reply.header = msg->header;
+	reply.header.flags &= ~VHOST_USER_FLAG_NEED_REPLY;
+	reply.header.flags |= VHOST_USER_FLAG_REPLY;
+	reply.header.size = sizeof(reply.payload.integer);
+
+	rc = full_sendmsg_fds(vu_dev->req_fd, &reply, size, NULL, 0);
+
+	if (rc)
+		vu_err(vu_dev,
+		       "sending reply to slave request failed: %d (size %zu)\n",
+		       rc, size);
+}
+
+static irqreturn_t vu_req_read_message(struct virtio_uml_device *vu_dev,
+				       struct time_travel_event *ev)
+{
+	struct virtqueue *vq;
+	int response = 1;
+	struct {
+		struct vhost_user_msg msg;
+		u8 extra_payload[512];
+	} msg;
+	int rc;
+	irqreturn_t irq_rc = IRQ_NONE;
+
+	while (1) {
+		rc = vhost_user_recv_req(vu_dev, &msg.msg,
+					 sizeof(msg.msg.payload) +
+					 sizeof(msg.extra_payload));
+		if (rc)
+			break;
+
+		switch (msg.msg.header.request) {
+		case VHOST_USER_SLAVE_CONFIG_CHANGE_MSG:
+			vu_dev->config_changed_irq = true;
+			response = 0;
+			break;
+		case VHOST_USER_SLAVE_VRING_CALL:
+			virtio_device_for_each_vq((&vu_dev->vdev), vq) {
+				if (vq->index == msg.msg.payload.vring_state.index) {
+					response = 0;
+					vu_dev->vq_irq_vq_map |= BIT_ULL(vq->index);
+					break;
+				}
+			}
+			break;
+		case VHOST_USER_SLAVE_IOTLB_MSG:
+			/* not supported - VIRTIO_F_ACCESS_PLATFORM */
+		case VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG:
+			/* not supported - VHOST_USER_PROTOCOL_F_HOST_NOTIFIER */
+		default:
+			vu_err(vu_dev, "unexpected slave request %d\n",
+			       msg.msg.header.request);
+		}
+
+		if (ev && !vu_dev->suspended)
+			time_travel_add_irq_event(ev);
+
+		if (msg.msg.header.flags & VHOST_USER_FLAG_NEED_REPLY)
+			vhost_user_reply(vu_dev, &msg.msg, response);
+		irq_rc = IRQ_HANDLED;
+	};
+	/* mask EAGAIN as we try non-blocking read until socket is empty */
+	vu_dev->recv_rc = (rc == -EAGAIN) ? 0 : rc;
+	return irq_rc;
+}
+
+static irqreturn_t vu_req_interrupt(int irq, void *data)
+{
+	struct virtio_uml_device *vu_dev = data;
+	irqreturn_t ret = IRQ_HANDLED;
+
+	if (!um_irq_timetravel_handler_used())
+		ret = vu_req_read_message(vu_dev, NULL);
+
+	if (vu_dev->recv_rc) {
+		vhost_user_check_reset(vu_dev, vu_dev->recv_rc);
+	} else if (vu_dev->vq_irq_vq_map) {
+		struct virtqueue *vq;
+
+		virtio_device_for_each_vq((&vu_dev->vdev), vq) {
+			if (vu_dev->vq_irq_vq_map & BIT_ULL(vq->index))
+				vring_interrupt(0 /* ignored */, vq);
+		}
+		vu_dev->vq_irq_vq_map = 0;
+	} else if (vu_dev->config_changed_irq) {
+		virtio_config_changed(&vu_dev->vdev);
+		vu_dev->config_changed_irq = false;
+	}
+
+	return ret;
+}
+
+static void vu_req_interrupt_comm_handler(int irq, int fd, void *data,
+					  struct time_travel_event *ev)
+{
+	vu_req_read_message(data, ev);
+}
+
+static int vhost_user_init_slave_req(struct virtio_uml_device *vu_dev)
+{
+	int rc, req_fds[2];
+
+	/* Use a pipe for slave req fd, SIGIO is not supported for eventfd */
+	rc = os_pipe(req_fds, true, true);
+	if (rc < 0)
+		return rc;
+	vu_dev->req_fd = req_fds[0];
+
+	rc = um_request_irq_tt(UM_IRQ_ALLOC, vu_dev->req_fd, IRQ_READ,
+			       vu_req_interrupt, IRQF_SHARED,
+			       vu_dev->pdev->name, vu_dev,
+			       vu_req_interrupt_comm_handler);
+	if (rc < 0)
+		goto err_close;
+
+	vu_dev->irq = rc;
+
+	rc = vhost_user_send_no_payload_fd(vu_dev, VHOST_USER_SET_SLAVE_REQ_FD,
+					   req_fds[1]);
+	if (rc)
+		goto err_free_irq;
+
+	goto out;
+
+err_free_irq:
+	um_free_irq(vu_dev->irq, vu_dev);
+err_close:
+	os_close_file(req_fds[0]);
+out:
+	/* Close unused write end of request fds */
+	os_close_file(req_fds[1]);
+	return rc;
+}
+
+static int vhost_user_init(struct virtio_uml_device *vu_dev)
+{
+	int rc = vhost_user_set_owner(vu_dev);
+
+	if (rc)
+		return rc;
+	rc = vhost_user_get_features(vu_dev, &vu_dev->features);
+	if (rc)
+		return rc;
+
+	if (vu_dev->features & BIT_ULL(VHOST_USER_F_PROTOCOL_FEATURES)) {
+		rc = vhost_user_get_protocol_features(vu_dev,
+				&vu_dev->protocol_features);
+		if (rc)
+			return rc;
+		vu_dev->protocol_features &= VHOST_USER_SUPPORTED_PROTOCOL_F;
+		rc = vhost_user_set_protocol_features(vu_dev,
+				vu_dev->protocol_features);
+		if (rc)
+			return rc;
+	}
+
+	if (vu_dev->protocol_features &
+			BIT_ULL(VHOST_USER_PROTOCOL_F_SLAVE_REQ)) {
+		rc = vhost_user_init_slave_req(vu_dev);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
+
+static void vhost_user_get_config(struct virtio_uml_device *vu_dev,
+				  u32 offset, void *buf, u32 len)
+{
+	u32 cfg_size = offset + len;
+	struct vhost_user_msg *msg;
+	size_t payload_size = sizeof(msg->payload.config) + cfg_size;
+	size_t msg_size = sizeof(msg->header) + payload_size;
+	int rc;
+
+	if (!(vu_dev->protocol_features &
+	      BIT_ULL(VHOST_USER_PROTOCOL_F_CONFIG)))
+		return;
+
+	msg = kzalloc(msg_size, GFP_KERNEL);
+	if (!msg)
+		return;
+	msg->header.request = VHOST_USER_GET_CONFIG;
+	msg->header.size = payload_size;
+	msg->payload.config.offset = 0;
+	msg->payload.config.size = cfg_size;
+
+	rc = vhost_user_send(vu_dev, true, msg, NULL, 0);
+	if (rc) {
+		vu_err(vu_dev, "sending VHOST_USER_GET_CONFIG failed: %d\n",
+		       rc);
+		goto free;
+	}
+
+	rc = vhost_user_recv_resp(vu_dev, msg, msg_size);
+	if (rc) {
+		vu_err(vu_dev,
+		       "receiving VHOST_USER_GET_CONFIG response failed: %d\n",
+		       rc);
+		goto free;
+	}
+
+	if (msg->header.size != payload_size ||
+	    msg->payload.config.size != cfg_size) {
+		rc = -EPROTO;
+		vu_err(vu_dev,
+		       "Invalid VHOST_USER_GET_CONFIG sizes (payload %d expected %zu, config %u expected %u)\n",
+		       msg->header.size, payload_size,
+		       msg->payload.config.size, cfg_size);
+		goto free;
+	}
+	memcpy(buf, msg->payload.config.payload + offset, len);
+
+free:
+	kfree(msg);
+}
+
+static void vhost_user_set_config(struct virtio_uml_device *vu_dev,
+				  u32 offset, const void *buf, u32 len)
+{
+	struct vhost_user_msg *msg;
+	size_t payload_size = sizeof(msg->payload.config) + len;
+	size_t msg_size = sizeof(msg->header) + payload_size;
+	int rc;
+
+	if (!(vu_dev->protocol_features &
+	      BIT_ULL(VHOST_USER_PROTOCOL_F_CONFIG)))
+		return;
+
+	msg = kzalloc(msg_size, GFP_KERNEL);
+	if (!msg)
+		return;
+	msg->header.request = VHOST_USER_SET_CONFIG;
+	msg->header.size = payload_size;
+	msg->payload.config.offset = offset;
+	msg->payload.config.size = len;
+	memcpy(msg->payload.config.payload, buf, len);
+
+	rc = vhost_user_send(vu_dev, false, msg, NULL, 0);
+	if (rc)
+		vu_err(vu_dev, "sending VHOST_USER_SET_CONFIG failed: %d\n",
+		       rc);
+
+	kfree(msg);
+}
+
+static int vhost_user_init_mem_region(u64 addr, u64 size, int *fd_out,
+				      struct vhost_user_mem_region *region_out)
+{
+	unsigned long long mem_offset;
+	int rc = phys_mapping(addr, &mem_offset);
+
+	if (WARN(rc < 0, "phys_mapping of 0x%llx returned %d\n", addr, rc))
+		return -EFAULT;
+	*fd_out = rc;
+	region_out->guest_addr = addr;
+	region_out->user_addr = addr;
+	region_out->size = size;
+	region_out->mmap_offset = mem_offset;
+
+	/* Ensure mapping is valid for the entire region */
+	rc = phys_mapping(addr + size - 1, &mem_offset);
+	if (WARN(rc != *fd_out, "phys_mapping of 0x%llx failed: %d != %d\n",
+		 addr + size - 1, rc, *fd_out))
+		return -EFAULT;
+	return 0;
+}
+
+static int vhost_user_set_mem_table(struct virtio_uml_device *vu_dev)
+{
+	struct vhost_user_msg msg = {
+		.header.request = VHOST_USER_SET_MEM_TABLE,
+		.header.size = sizeof(msg.payload.mem_regions),
+		.payload.mem_regions.num = 1,
+	};
+	unsigned long reserved = uml_reserved - uml_physmem;
+	int fds[2];
+	int rc;
+
+	/*
+	 * This is a bit tricky, see also the comment with setup_physmem().
+	 *
+	 * Essentially, setup_physmem() uses a file to mmap() our physmem,
+	 * but the code and data we *already* have is omitted. To us, this
+	 * is no difference, since they both become part of our address
+	 * space and memory consumption. To somebody looking in from the
+	 * outside, however, it is different because the part of our memory
+	 * consumption that's already part of the binary (code/data) is not
+	 * mapped from the file, so it's not visible to another mmap from
+	 * the file descriptor.
+	 *
+	 * Thus, don't advertise this space to the vhost-user slave. This
+	 * means that the slave will likely abort or similar when we give
+	 * it an address from the hidden range, since it's not marked as
+	 * a valid address, but at least that way we detect the issue and
+	 * don't just have the slave read an all-zeroes buffer from the
+	 * shared memory file, or write something there that we can never
+	 * see (depending on the direction of the virtqueue traffic.)
+	 *
+	 * Since we usually don't want to use .text for virtio buffers,
+	 * this effectively means that you cannot use
+	 *  1) global variables, which are in the .bss and not in the shm
+	 *     file-backed memory
+	 *  2) the stack in some processes, depending on where they have
+	 *     their stack (or maybe only no interrupt stack?)
+	 *
+	 * The stack is already not typically valid for DMA, so this isn't
+	 * much of a restriction, but global variables might be encountered.
+	 *
+	 * It might be possible to fix it by copying around the data that's
+	 * between bss_start and where we map the file now, but it's not
+	 * something that you typically encounter with virtio drivers, so
+	 * it didn't seem worthwhile.
+	 */
+	rc = vhost_user_init_mem_region(reserved, physmem_size - reserved,
+					&fds[0],
+					&msg.payload.mem_regions.regions[0]);
+
+	if (rc < 0)
+		return rc;
+	if (highmem) {
+		msg.payload.mem_regions.num++;
+		rc = vhost_user_init_mem_region(__pa(end_iomem), highmem,
+				&fds[1], &msg.payload.mem_regions.regions[1]);
+		if (rc < 0)
+			return rc;
+	}
+
+	return vhost_user_send(vu_dev, false, &msg, fds,
+			       msg.payload.mem_regions.num);
+}
+
+static int vhost_user_set_vring_state(struct virtio_uml_device *vu_dev,
+				      u32 request, u32 index, u32 num)
+{
+	struct vhost_user_msg msg = {
+		.header.request = request,
+		.header.size = sizeof(msg.payload.vring_state),
+		.payload.vring_state.index = index,
+		.payload.vring_state.num = num,
+	};
+
+	return vhost_user_send(vu_dev, false, &msg, NULL, 0);
+}
+
+static int vhost_user_set_vring_num(struct virtio_uml_device *vu_dev,
+				    u32 index, u32 num)
+{
+	return vhost_user_set_vring_state(vu_dev, VHOST_USER_SET_VRING_NUM,
+					  index, num);
+}
+
+static int vhost_user_set_vring_base(struct virtio_uml_device *vu_dev,
+				     u32 index, u32 offset)
+{
+	return vhost_user_set_vring_state(vu_dev, VHOST_USER_SET_VRING_BASE,
+					  index, offset);
+}
+
+static int vhost_user_set_vring_addr(struct virtio_uml_device *vu_dev,
+				     u32 index, u64 desc, u64 used, u64 avail,
+				     u64 log)
+{
+	struct vhost_user_msg msg = {
+		.header.request = VHOST_USER_SET_VRING_ADDR,
+		.header.size = sizeof(msg.payload.vring_addr),
+		.payload.vring_addr.index = index,
+		.payload.vring_addr.desc = desc,
+		.payload.vring_addr.used = used,
+		.payload.vring_addr.avail = avail,
+		.payload.vring_addr.log = log,
+	};
+
+	return vhost_user_send(vu_dev, false, &msg, NULL, 0);
+}
+
+static int vhost_user_set_vring_fd(struct virtio_uml_device *vu_dev,
+				   u32 request, int index, int fd)
+{
+	struct vhost_user_msg msg = {
+		.header.request = request,
+		.header.size = sizeof(msg.payload.integer),
+		.payload.integer = index,
+	};
+
+	if (index & ~VHOST_USER_VRING_INDEX_MASK)
+		return -EINVAL;
+	if (fd < 0) {
+		msg.payload.integer |= VHOST_USER_VRING_POLL_MASK;
+		return vhost_user_send(vu_dev, false, &msg, NULL, 0);
+	}
+	return vhost_user_send(vu_dev, false, &msg, &fd, 1);
+}
+
+static int vhost_user_set_vring_call(struct virtio_uml_device *vu_dev,
+				     int index, int fd)
+{
+	return vhost_user_set_vring_fd(vu_dev, VHOST_USER_SET_VRING_CALL,
+				       index, fd);
+}
+
+static int vhost_user_set_vring_kick(struct virtio_uml_device *vu_dev,
+				     int index, int fd)
+{
+	return vhost_user_set_vring_fd(vu_dev, VHOST_USER_SET_VRING_KICK,
+				       index, fd);
+}
+
+static int vhost_user_set_vring_enable(struct virtio_uml_device *vu_dev,
+				       u32 index, bool enable)
+{
+	if (!(vu_dev->features & BIT_ULL(VHOST_USER_F_PROTOCOL_FEATURES)))
+		return 0;
+
+	return vhost_user_set_vring_state(vu_dev, VHOST_USER_SET_VRING_ENABLE,
+					  index, enable);
+}
+
+
+/* Virtio interface */
+
+static bool vu_notify(struct virtqueue *vq)
+{
+	struct virtio_uml_vq_info *info = vq->priv;
+	const uint64_t n = 1;
+	int rc;
+
+	if (info->suspended)
+		return true;
+
+	time_travel_propagate_time();
+
+	if (info->kick_fd < 0) {
+		struct virtio_uml_device *vu_dev;
+
+		vu_dev = to_virtio_uml_device(vq->vdev);
+
+		return vhost_user_set_vring_state(vu_dev, VHOST_USER_VRING_KICK,
+						  vq->index, 0) == 0;
+	}
+
+	do {
+		rc = os_write_file(info->kick_fd, &n, sizeof(n));
+	} while (rc == -EINTR);
+	return !WARN(rc != sizeof(n), "write returned %d\n", rc);
+}
+
+static irqreturn_t vu_interrupt(int irq, void *opaque)
+{
+	struct virtqueue *vq = opaque;
+	struct virtio_uml_vq_info *info = vq->priv;
+	uint64_t n;
+	int rc;
+	irqreturn_t ret = IRQ_NONE;
+
+	do {
+		rc = os_read_file(info->call_fd, &n, sizeof(n));
+		if (rc == sizeof(n))
+			ret |= vring_interrupt(irq, vq);
+	} while (rc == sizeof(n) || rc == -EINTR);
+	WARN(rc != -EAGAIN, "read returned %d\n", rc);
+	return ret;
+}
+
+
+static void vu_get(struct virtio_device *vdev, unsigned offset,
+		   void *buf, unsigned len)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+
+	vhost_user_get_config(vu_dev, offset, buf, len);
+}
+
+static void vu_set(struct virtio_device *vdev, unsigned offset,
+		   const void *buf, unsigned len)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+
+	vhost_user_set_config(vu_dev, offset, buf, len);
+}
+
+static u8 vu_get_status(struct virtio_device *vdev)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+
+	return vu_dev->status;
+}
+
+static void vu_set_status(struct virtio_device *vdev, u8 status)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+
+	vu_dev->status = status;
+}
+
+static void vu_reset(struct virtio_device *vdev)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+
+	vu_dev->status = 0;
+}
+
+static void vu_del_vq(struct virtqueue *vq)
+{
+	struct virtio_uml_vq_info *info = vq->priv;
+
+	if (info->call_fd >= 0) {
+		struct virtio_uml_device *vu_dev;
+
+		vu_dev = to_virtio_uml_device(vq->vdev);
+
+		um_free_irq(vu_dev->irq, vq);
+		os_close_file(info->call_fd);
+	}
+
+	if (info->kick_fd >= 0)
+		os_close_file(info->kick_fd);
+
+	vring_del_virtqueue(vq);
+	kfree(info);
+}
+
+static void vu_del_vqs(struct virtio_device *vdev)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+	struct virtqueue *vq, *n;
+	u64 features;
+
+	/* Note: reverse order as a workaround to a decoding bug in snabb */
+	list_for_each_entry_reverse(vq, &vdev->vqs, list)
+		WARN_ON(vhost_user_set_vring_enable(vu_dev, vq->index, false));
+
+	/* Ensure previous messages have been processed */
+	WARN_ON(vhost_user_get_features(vu_dev, &features));
+
+	list_for_each_entry_safe(vq, n, &vdev->vqs, list)
+		vu_del_vq(vq);
+}
+
+static int vu_setup_vq_call_fd(struct virtio_uml_device *vu_dev,
+			       struct virtqueue *vq)
+{
+	struct virtio_uml_vq_info *info = vq->priv;
+	int call_fds[2];
+	int rc;
+
+	/* no call FD needed/desired in this case */
+	if (vu_dev->protocol_features &
+			BIT_ULL(VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS) &&
+	    vu_dev->protocol_features &
+			BIT_ULL(VHOST_USER_PROTOCOL_F_SLAVE_REQ)) {
+		info->call_fd = -1;
+		return 0;
+	}
+
+	/* Use a pipe for call fd, since SIGIO is not supported for eventfd */
+	rc = os_pipe(call_fds, true, true);
+	if (rc < 0)
+		return rc;
+
+	info->call_fd = call_fds[0];
+	rc = um_request_irq(vu_dev->irq, info->call_fd, IRQ_READ,
+			    vu_interrupt, IRQF_SHARED, info->name, vq);
+	if (rc < 0)
+		goto close_both;
+
+	rc = vhost_user_set_vring_call(vu_dev, vq->index, call_fds[1]);
+	if (rc)
+		goto release_irq;
+
+	goto out;
+
+release_irq:
+	um_free_irq(vu_dev->irq, vq);
+close_both:
+	os_close_file(call_fds[0]);
+out:
+	/* Close (unused) write end of call fds */
+	os_close_file(call_fds[1]);
+
+	return rc;
+}
+
+static struct virtqueue *vu_setup_vq(struct virtio_device *vdev,
+				     unsigned index, vq_callback_t *callback,
+				     const char *name, bool ctx)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+	struct platform_device *pdev = vu_dev->pdev;
+	struct virtio_uml_vq_info *info;
+	struct virtqueue *vq;
+	int num = MAX_SUPPORTED_QUEUE_SIZE;
+	int rc;
+
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info) {
+		rc = -ENOMEM;
+		goto error_kzalloc;
+	}
+	snprintf(info->name, sizeof(info->name), "%s.%d-%s", pdev->name,
+		 pdev->id, name);
+
+	vq = vring_create_virtqueue(index, num, PAGE_SIZE, vdev, true, true,
+				    ctx, vu_notify, callback, info->name);
+	if (!vq) {
+		rc = -ENOMEM;
+		goto error_create;
+	}
+	vq->priv = info;
+	vq->num_max = num;
+	num = virtqueue_get_vring_size(vq);
+
+	if (vu_dev->protocol_features &
+			BIT_ULL(VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS)) {
+		info->kick_fd = -1;
+	} else {
+		rc = os_eventfd(0, 0);
+		if (rc < 0)
+			goto error_kick;
+		info->kick_fd = rc;
+	}
+
+	rc = vu_setup_vq_call_fd(vu_dev, vq);
+	if (rc)
+		goto error_call;
+
+	rc = vhost_user_set_vring_num(vu_dev, index, num);
+	if (rc)
+		goto error_setup;
+
+	rc = vhost_user_set_vring_base(vu_dev, index, 0);
+	if (rc)
+		goto error_setup;
+
+	rc = vhost_user_set_vring_addr(vu_dev, index,
+				       virtqueue_get_desc_addr(vq),
+				       virtqueue_get_used_addr(vq),
+				       virtqueue_get_avail_addr(vq),
+				       (u64) -1);
+	if (rc)
+		goto error_setup;
+
+	return vq;
+
+error_setup:
+	if (info->call_fd >= 0) {
+		um_free_irq(vu_dev->irq, vq);
+		os_close_file(info->call_fd);
+	}
+error_call:
+	if (info->kick_fd >= 0)
+		os_close_file(info->kick_fd);
+error_kick:
+	vring_del_virtqueue(vq);
+error_create:
+	kfree(info);
+error_kzalloc:
+	return ERR_PTR(rc);
+}
+
+static int vu_find_vqs(struct virtio_device *vdev, unsigned nvqs,
+		       struct virtqueue *vqs[], vq_callback_t *callbacks[],
+		       const char * const names[], const bool *ctx,
+		       struct irq_affinity *desc)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+	int i, queue_idx = 0, rc;
+	struct virtqueue *vq;
+
+	/* not supported for now */
+	if (WARN_ON(nvqs > 64))
+		return -EINVAL;
+
+	rc = vhost_user_set_mem_table(vu_dev);
+	if (rc)
+		return rc;
+
+	for (i = 0; i < nvqs; ++i) {
+		if (!names[i]) {
+			vqs[i] = NULL;
+			continue;
+		}
+
+		vqs[i] = vu_setup_vq(vdev, queue_idx++, callbacks[i], names[i],
+				     ctx ? ctx[i] : false);
+		if (IS_ERR(vqs[i])) {
+			rc = PTR_ERR(vqs[i]);
+			goto error_setup;
+		}
+	}
+
+	list_for_each_entry(vq, &vdev->vqs, list) {
+		struct virtio_uml_vq_info *info = vq->priv;
+
+		if (info->kick_fd >= 0) {
+			rc = vhost_user_set_vring_kick(vu_dev, vq->index,
+						       info->kick_fd);
+			if (rc)
+				goto error_setup;
+		}
+
+		rc = vhost_user_set_vring_enable(vu_dev, vq->index, true);
+		if (rc)
+			goto error_setup;
+	}
+
+	return 0;
+
+error_setup:
+	vu_del_vqs(vdev);
+	return rc;
+}
+
+static u64 vu_get_features(struct virtio_device *vdev)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+
+	return vu_dev->features;
+}
+
+static int vu_finalize_features(struct virtio_device *vdev)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+	u64 supported = vdev->features & VHOST_USER_SUPPORTED_F;
+
+	vring_transport_features(vdev);
+	vu_dev->features = vdev->features | supported;
+
+	return vhost_user_set_features(vu_dev, vu_dev->features);
+}
+
+static const char *vu_bus_name(struct virtio_device *vdev)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+
+	return vu_dev->pdev->name;
+}
+
+static const struct virtio_config_ops virtio_uml_config_ops = {
+	.get = vu_get,
+	.set = vu_set,
+	.get_status = vu_get_status,
+	.set_status = vu_set_status,
+	.reset = vu_reset,
+	.find_vqs = vu_find_vqs,
+	.del_vqs = vu_del_vqs,
+	.get_features = vu_get_features,
+	.finalize_features = vu_finalize_features,
+	.bus_name = vu_bus_name,
+};
+
+static void virtio_uml_release_dev(struct device *d)
+{
+	struct virtio_device *vdev =
+			container_of(d, struct virtio_device, dev);
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+
+	time_travel_propagate_time();
+
+	/* might not have been opened due to not negotiating the feature */
+	if (vu_dev->req_fd >= 0) {
+		um_free_irq(vu_dev->irq, vu_dev);
+		os_close_file(vu_dev->req_fd);
+	}
+
+	os_close_file(vu_dev->sock);
+	kfree(vu_dev);
+}
+
+void virtio_uml_set_no_vq_suspend(struct virtio_device *vdev,
+				  bool no_vq_suspend)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+
+	if (WARN_ON(vdev->config != &virtio_uml_config_ops))
+		return;
+
+	vu_dev->no_vq_suspend = no_vq_suspend;
+	dev_info(&vdev->dev, "%sabled VQ suspend\n",
+		 no_vq_suspend ? "dis" : "en");
+}
+
+static void vu_of_conn_broken(struct work_struct *wk)
+{
+	struct virtio_uml_platform_data *pdata;
+	struct virtio_uml_device *vu_dev;
+
+	pdata = container_of(wk, struct virtio_uml_platform_data, conn_broken_wk);
+
+	vu_dev = platform_get_drvdata(pdata->pdev);
+
+	virtio_break_device(&vu_dev->vdev);
+
+	/*
+	 * We can't remove the device from the devicetree so the only thing we
+	 * can do is warn.
+	 */
+	WARN_ON(1);
+}
+
+/* Platform device */
+
+static struct virtio_uml_platform_data *
+virtio_uml_create_pdata(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct virtio_uml_platform_data *pdata;
+	int ret;
+
+	if (!np)
+		return ERR_PTR(-EINVAL);
+
+	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return ERR_PTR(-ENOMEM);
+
+	INIT_WORK(&pdata->conn_broken_wk, vu_of_conn_broken);
+	pdata->pdev = pdev;
+
+	ret = of_property_read_string(np, "socket-path", &pdata->socket_path);
+	if (ret)
+		return ERR_PTR(ret);
+
+	ret = of_property_read_u32(np, "virtio-device-id",
+				   &pdata->virtio_device_id);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return pdata;
+}
+
+static int virtio_uml_probe(struct platform_device *pdev)
+{
+	struct virtio_uml_platform_data *pdata = pdev->dev.platform_data;
+	struct virtio_uml_device *vu_dev;
+	int rc;
+
+	if (!pdata) {
+		pdata = virtio_uml_create_pdata(pdev);
+		if (IS_ERR(pdata))
+			return PTR_ERR(pdata);
+	}
+
+	vu_dev = kzalloc(sizeof(*vu_dev), GFP_KERNEL);
+	if (!vu_dev)
+		return -ENOMEM;
+
+	vu_dev->pdata = pdata;
+	vu_dev->vdev.dev.parent = &pdev->dev;
+	vu_dev->vdev.dev.release = virtio_uml_release_dev;
+	vu_dev->vdev.config = &virtio_uml_config_ops;
+	vu_dev->vdev.id.device = pdata->virtio_device_id;
+	vu_dev->vdev.id.vendor = VIRTIO_DEV_ANY_ID;
+	vu_dev->pdev = pdev;
+	vu_dev->req_fd = -1;
+
+	time_travel_propagate_time();
+
+	do {
+		rc = os_connect_socket(pdata->socket_path);
+	} while (rc == -EINTR);
+	if (rc < 0)
+		goto error_free;
+	vu_dev->sock = rc;
+
+	spin_lock_init(&vu_dev->sock_lock);
+
+	rc = vhost_user_init(vu_dev);
+	if (rc)
+		goto error_init;
+
+	platform_set_drvdata(pdev, vu_dev);
+
+	device_set_wakeup_capable(&vu_dev->vdev.dev, true);
+
+	rc = register_virtio_device(&vu_dev->vdev);
+	if (rc)
+		put_device(&vu_dev->vdev.dev);
+	vu_dev->registered = 1;
+	return rc;
+
+error_init:
+	os_close_file(vu_dev->sock);
+error_free:
+	kfree(vu_dev);
+	return rc;
+}
+
+static int virtio_uml_remove(struct platform_device *pdev)
+{
+	struct virtio_uml_device *vu_dev = platform_get_drvdata(pdev);
+
+	unregister_virtio_device(&vu_dev->vdev);
+	return 0;
+}
+
+/* Command line device list */
+
+static void vu_cmdline_release_dev(struct device *d)
+{
+}
+
+static struct device vu_cmdline_parent = {
+	.init_name = "virtio-uml-cmdline",
+	.release = vu_cmdline_release_dev,
+};
+
+static bool vu_cmdline_parent_registered;
+static int vu_cmdline_id;
+
+static int vu_unregister_cmdline_device(struct device *dev, void *data)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct virtio_uml_platform_data *pdata = pdev->dev.platform_data;
+
+	kfree(pdata->socket_path);
+	platform_device_unregister(pdev);
+	return 0;
+}
+
+static void vu_conn_broken(struct work_struct *wk)
+{
+	struct virtio_uml_platform_data *pdata;
+	struct virtio_uml_device *vu_dev;
+
+	pdata = container_of(wk, struct virtio_uml_platform_data, conn_broken_wk);
+
+	vu_dev = platform_get_drvdata(pdata->pdev);
+
+	virtio_break_device(&vu_dev->vdev);
+
+	vu_unregister_cmdline_device(&pdata->pdev->dev, NULL);
+}
+
+static int vu_cmdline_set(const char *device, const struct kernel_param *kp)
+{
+	const char *ids = strchr(device, ':');
+	unsigned int virtio_device_id;
+	int processed, consumed, err;
+	char *socket_path;
+	struct virtio_uml_platform_data pdata, *ppdata;
+	struct platform_device *pdev;
+
+	if (!ids || ids == device)
+		return -EINVAL;
+
+	processed = sscanf(ids, ":%u%n:%d%n",
+			   &virtio_device_id, &consumed,
+			   &vu_cmdline_id, &consumed);
+
+	if (processed < 1 || ids[consumed])
+		return -EINVAL;
+
+	if (!vu_cmdline_parent_registered) {
+		err = device_register(&vu_cmdline_parent);
+		if (err) {
+			pr_err("Failed to register parent device!\n");
+			put_device(&vu_cmdline_parent);
+			return err;
+		}
+		vu_cmdline_parent_registered = true;
+	}
+
+	socket_path = kmemdup_nul(device, ids - device, GFP_KERNEL);
+	if (!socket_path)
+		return -ENOMEM;
+
+	pdata.virtio_device_id = (u32) virtio_device_id;
+	pdata.socket_path = socket_path;
+
+	pr_info("Registering device virtio-uml.%d id=%d at %s\n",
+		vu_cmdline_id, virtio_device_id, socket_path);
+
+	pdev = platform_device_register_data(&vu_cmdline_parent, "virtio-uml",
+					     vu_cmdline_id++, &pdata,
+					     sizeof(pdata));
+	err = PTR_ERR_OR_ZERO(pdev);
+	if (err)
+		goto free;
+
+	ppdata = pdev->dev.platform_data;
+	ppdata->pdev = pdev;
+	INIT_WORK(&ppdata->conn_broken_wk, vu_conn_broken);
+
+	return 0;
+
+free:
+	kfree(socket_path);
+	return err;
+}
+
+static int vu_cmdline_get_device(struct device *dev, void *data)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct virtio_uml_platform_data *pdata = pdev->dev.platform_data;
+	char *buffer = data;
+	unsigned int len = strlen(buffer);
+
+	snprintf(buffer + len, PAGE_SIZE - len, "%s:%d:%d\n",
+		 pdata->socket_path, pdata->virtio_device_id, pdev->id);
+	return 0;
+}
+
+static int vu_cmdline_get(char *buffer, const struct kernel_param *kp)
+{
+	buffer[0] = '\0';
+	if (vu_cmdline_parent_registered)
+		device_for_each_child(&vu_cmdline_parent, buffer,
+				      vu_cmdline_get_device);
+	return strlen(buffer) + 1;
+}
+
+static const struct kernel_param_ops vu_cmdline_param_ops = {
+	.set = vu_cmdline_set,
+	.get = vu_cmdline_get,
+};
+
+device_param_cb(device, &vu_cmdline_param_ops, NULL, S_IRUSR);
+__uml_help(vu_cmdline_param_ops,
+"virtio_uml.device=<socket>:<virtio_id>[:<platform_id>]\n"
+"    Configure a virtio device over a vhost-user socket.\n"
+"    See virtio_ids.h for a list of possible virtio device id values.\n"
+"    Optionally use a specific platform_device id.\n\n"
+);
+
+
+static void vu_unregister_cmdline_devices(void)
+{
+	if (vu_cmdline_parent_registered) {
+		device_for_each_child(&vu_cmdline_parent, NULL,
+				      vu_unregister_cmdline_device);
+		device_unregister(&vu_cmdline_parent);
+		vu_cmdline_parent_registered = false;
+	}
+}
+
+/* Platform driver */
+
+static const struct of_device_id virtio_uml_match[] = {
+	{ .compatible = "virtio,uml", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, virtio_uml_match);
+
+static int virtio_uml_suspend(struct platform_device *pdev, pm_message_t state)
+{
+	struct virtio_uml_device *vu_dev = platform_get_drvdata(pdev);
+
+	if (!vu_dev->no_vq_suspend) {
+		struct virtqueue *vq;
+
+		virtio_device_for_each_vq((&vu_dev->vdev), vq) {
+			struct virtio_uml_vq_info *info = vq->priv;
+
+			info->suspended = true;
+			vhost_user_set_vring_enable(vu_dev, vq->index, false);
+		}
+	}
+
+	if (!device_may_wakeup(&vu_dev->vdev.dev)) {
+		vu_dev->suspended = true;
+		return 0;
+	}
+
+	return irq_set_irq_wake(vu_dev->irq, 1);
+}
+
+static int virtio_uml_resume(struct platform_device *pdev)
+{
+	struct virtio_uml_device *vu_dev = platform_get_drvdata(pdev);
+
+	if (!vu_dev->no_vq_suspend) {
+		struct virtqueue *vq;
+
+		virtio_device_for_each_vq((&vu_dev->vdev), vq) {
+			struct virtio_uml_vq_info *info = vq->priv;
+
+			info->suspended = false;
+			vhost_user_set_vring_enable(vu_dev, vq->index, true);
+		}
+	}
+
+	vu_dev->suspended = false;
+
+	if (!device_may_wakeup(&vu_dev->vdev.dev))
+		return 0;
+
+	return irq_set_irq_wake(vu_dev->irq, 0);
+}
+
+static struct platform_driver virtio_uml_driver = {
+	.probe = virtio_uml_probe,
+	.remove = virtio_uml_remove,
+	.driver = {
+		.name = "virtio-uml",
+		.of_match_table = virtio_uml_match,
+	},
+	.suspend = virtio_uml_suspend,
+	.resume = virtio_uml_resume,
+};
+
+static int __init virtio_uml_init(void)
+{
+	return platform_driver_register(&virtio_uml_driver);
+}
+
+static void __exit virtio_uml_exit(void)
+{
+	platform_driver_unregister(&virtio_uml_driver);
+	vu_unregister_cmdline_devices();
+}
+
+module_init(virtio_uml_init);
+module_exit(virtio_uml_exit);
+__uml_exitcall(virtio_uml_exit);
+
+MODULE_DESCRIPTION("UML driver for vhost-user virtio devices");
+MODULE_LICENSE("GPL");
diff --git a/arch/um/drivers/xterm.c b/arch/um/drivers/xterm.c
new file mode 100644
index 000000000..6918de5e2
--- /dev/null
+++ b/arch/um/drivers/xterm.c
@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <termios.h>
+#include "chan_user.h"
+#include <os.h>
+#include <um_malloc.h>
+#include "xterm.h"
+
+struct xterm_chan {
+	int pid;
+	int helper_pid;
+	int chan_fd;
+	char *title;
+	int device;
+	int raw;
+	struct termios tt;
+};
+
+static void *xterm_init(char *str, int device, const struct chan_opts *opts)
+{
+	struct xterm_chan *data;
+
+	data = uml_kmalloc(sizeof(*data), UM_GFP_KERNEL);
+	if (data == NULL)
+		return NULL;
+	*data = ((struct xterm_chan) { .pid 		= -1,
+				       .helper_pid 	= -1,
+				       .chan_fd		= -1,
+				       .device 		= device,
+				       .title 		= opts->xterm_title,
+				       .raw  		= opts->raw } );
+	return data;
+}
+
+/* Only changed by xterm_setup, which is a setup */
+static char *terminal_emulator = CONFIG_XTERM_CHAN_DEFAULT_EMULATOR;
+static char *title_switch = "-T";
+static char *exec_switch = "-e";
+
+static int __init xterm_setup(char *line, int *add)
+{
+	*add = 0;
+	terminal_emulator = line;
+
+	line = strchr(line, ',');
+	if (line == NULL)
+		return 0;
+
+	*line++ = '\0';
+	if (*line)
+		title_switch = line;
+
+	line = strchr(line, ',');
+	if (line == NULL)
+		return 0;
+
+	*line++ = '\0';
+	if (*line)
+		exec_switch = line;
+
+	return 0;
+}
+
+__uml_setup("xterm=", xterm_setup,
+"xterm=<terminal emulator>,<title switch>,<exec switch>\n"
+"    Specifies an alternate terminal emulator to use for the debugger,\n"
+"    consoles, and serial lines when they are attached to the xterm channel.\n"
+"    The values are the terminal emulator binary, the switch it uses to set\n"
+"    its title, and the switch it uses to execute a subprocess,\n"
+"    respectively.  The title switch must have the form '<switch> title',\n"
+"    not '<switch>=title'.  Similarly, the exec switch must have the form\n"
+"    '<switch> command arg1 arg2 ...'.\n"
+"    The default values are 'xterm=" CONFIG_XTERM_CHAN_DEFAULT_EMULATOR
+     ",-T,-e'.\n"
+"    Values for gnome-terminal are 'xterm=gnome-terminal,-t,-x'.\n\n"
+);
+
+static int xterm_open(int input, int output, int primary, void *d,
+		      char **dev_out)
+{
+	struct xterm_chan *data = d;
+	int pid, fd, new, err;
+	char title[256], file[] = "/tmp/xterm-pipeXXXXXX";
+	char *argv[] = { terminal_emulator, title_switch, title, exec_switch,
+			 OS_LIB_PATH "/uml/port-helper", "-uml-socket",
+			 file, NULL };
+
+	if (access(argv[4], X_OK) < 0)
+		argv[4] = "port-helper";
+
+	/*
+	 * Check that DISPLAY is set, this doesn't guarantee the xterm
+	 * will work but w/o it we can be pretty sure it won't.
+	 */
+	if (getenv("DISPLAY") == NULL) {
+		printk(UM_KERN_ERR "xterm_open: $DISPLAY not set.\n");
+		return -ENODEV;
+	}
+
+	/*
+	 * This business of getting a descriptor to a temp file,
+	 * deleting the file and closing the descriptor is just to get
+	 * a known-unused name for the Unix socket that we really
+	 * want.
+	 */
+	fd = mkstemp(file);
+	if (fd < 0) {
+		err = -errno;
+		printk(UM_KERN_ERR "xterm_open : mkstemp failed, errno = %d\n",
+		       errno);
+		return err;
+	}
+
+	if (unlink(file)) {
+		err = -errno;
+		printk(UM_KERN_ERR "xterm_open : unlink failed, errno = %d\n",
+		       errno);
+		close(fd);
+		return err;
+	}
+	close(fd);
+
+	fd = os_create_unix_socket(file, sizeof(file), 1);
+	if (fd < 0) {
+		printk(UM_KERN_ERR "xterm_open : create_unix_socket failed, "
+		       "errno = %d\n", -fd);
+		return fd;
+	}
+
+	sprintf(title, data->title, data->device);
+	pid = run_helper(NULL, NULL, argv);
+	if (pid < 0) {
+		err = pid;
+		printk(UM_KERN_ERR "xterm_open : run_helper failed, "
+		       "errno = %d\n", -err);
+		goto out_close1;
+	}
+
+	err = os_set_fd_block(fd, 0);
+	if (err < 0) {
+		printk(UM_KERN_ERR "xterm_open : failed to set descriptor "
+		       "non-blocking, err = %d\n", -err);
+		goto out_kill;
+	}
+
+	data->chan_fd = fd;
+	new = xterm_fd(fd, &data->helper_pid);
+	if (new < 0) {
+		err = new;
+		printk(UM_KERN_ERR "xterm_open : os_rcv_fd failed, err = %d\n",
+		       -err);
+		goto out_kill;
+	}
+
+	err = os_set_fd_block(new, 0);
+	if (err) {
+		printk(UM_KERN_ERR "xterm_open : failed to set xterm "
+		       "descriptor non-blocking, err = %d\n", -err);
+		goto out_close2;
+	}
+
+	CATCH_EINTR(err = tcgetattr(new, &data->tt));
+	if (err) {
+		new = err;
+		goto out_close2;
+	}
+
+	if (data->raw) {
+		err = raw(new);
+		if (err) {
+			new = err;
+			goto out_close2;
+		}
+	}
+
+	unlink(file);
+	data->pid = pid;
+	*dev_out = NULL;
+
+	return new;
+
+ out_close2:
+	close(new);
+ out_kill:
+	os_kill_process(pid, 1);
+ out_close1:
+	close(fd);
+
+	return err;
+}
+
+static void xterm_close(int fd, void *d)
+{
+	struct xterm_chan *data = d;
+
+	if (data->pid != -1)
+		os_kill_process(data->pid, 1);
+	data->pid = -1;
+
+	if (data->helper_pid != -1)
+		os_kill_process(data->helper_pid, 0);
+	data->helper_pid = -1;
+
+	if (data->chan_fd != -1)
+		os_close_file(data->chan_fd);
+	os_close_file(fd);
+}
+
+const struct chan_ops xterm_ops = {
+	.type		= "xterm",
+	.init		= xterm_init,
+	.open		= xterm_open,
+	.close		= xterm_close,
+	.read		= generic_read,
+	.write		= generic_write,
+	.console_write	= generic_console_write,
+	.window_size	= generic_window_size,
+	.free		= generic_free,
+	.winch		= 1,
+};
diff --git a/arch/um/drivers/xterm.h b/arch/um/drivers/xterm.h
new file mode 100644
index 000000000..5968da3a6
--- /dev/null
+++ b/arch/um/drivers/xterm.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* 
+ * Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
+ */
+
+#ifndef __XTERM_H__
+#define __XTERM_H__
+
+extern int xterm_fd(int socket, int *pid_out);
+
+#endif
+
diff --git a/arch/um/drivers/xterm_kern.c b/arch/um/drivers/xterm_kern.c
new file mode 100644
index 000000000..50f11b7b4
--- /dev/null
+++ b/arch/um/drivers/xterm_kern.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0
+/* 
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#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 < 0) {
+		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;
+}