Merge tag 'uml-for-linux-6.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux

Pull UML updates from Johannes Berg:
"The only really new thing is the long-standing seccomp work
(originally from 2021!). Wven if it still isn't enabled by default due
to security concerns it can still be used e.g. for tests.

- remove obsolete network transports

- remove PCI IO port support

- start adding seccomp-based process handling instead of ptrace"

* tag 'uml-for-linux-6.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux: (29 commits)
um: remove "extern" from implementation of sigchld_handler
um: fix unused variable warning
um: fix SECCOMP 32bit xstate register restore
um: pass FD for memory operations when needed
um: Add SECCOMP support detection and initialization
um: Implement kernel side of SECCOMP based process handling
um: Track userspace children dying in SECCOMP mode
um: Add helper functions to get/set state for SECCOMP
um: Add stub side of SECCOMP/futex based process handling
um: Move faultinfo extraction into userspace routine
um: vector: Use mac_pton() for MAC address parsing
um: vector: Clean up and modernize log messages
um: chan_kern: use raw spinlock for irqs_to_free_lock
MAINTAINERS: remove obsolete file entry in TUN/TAP DRIVER
um: Fix tgkill compile error on old host OSes
um: stop using PCI port I/O
um: Remove legacy network transport infrastructure
um: vector: Eliminate the dependency on uml_net
um: Remove obsolete legacy network transports
um/asm: Replace "REP; NOP" with PAUSE mnemonic
...

Documentation/virt/uml/user_mode_linux_howto_v2.rst

···
 are creating its image. It is a good idea to change that to avoid
 "Oh, bummer, I rebooted the wrong machine".
 
-UML supports two classes of network devices - the older uml_net ones
-which are scheduled for obsoletion. These are called ethX. It also
-supports the newer vector IO devices which are significantly faster
-and have support for some standard virtual network encapsulations like
-Ethernet over GRE and Ethernet over L2TPv3. These are called vec0.
+UML supports vector I/O high performance network devices which have
+support for some standard virtual network encapsulations like
+Ethernet over GRE and Ethernet over L2TPv3. These are called vecX.
 
-Depending on which one is in use, ``/etc/network/interfaces`` will
-need entries like::
-
-   # legacy UML network devices
-   auto eth0
-   iface eth0 inet dhcp
+When vector network devices are in use, ``/etc/network/interfaces``
+will need entries like::
 
    # vector UML network devices
    auto vec0
···
 +-----------+--------+------------------------------------+------------+
 | vde       | vector | dep. on VDE VPN: Virt.Net Locator  | varies     |
 +-----------+--------+------------------------------------+------------+
-| tuntap    | legacy | none                               | ~ 500Mbit  |
-+-----------+--------+------------------------------------+------------+
-| daemon    | legacy | none                               | ~ 450Mbit  |
-+-----------+--------+------------------------------------+------------+
-| socket    | legacy | none                               | ~ 450Mbit  |
-+-----------+--------+------------------------------------+------------+
-| ethertap  | legacy | obsolete                           | ~ 500Mbit  |
-+-----------+--------+------------------------------------+------------+
-| vde       | legacy | obsolete                           | ~ 500Mbit  |
-+-----------+--------+------------------------------------+------------+
 
 * All transports which have tso and checksum offloads can deliver speeds
   approaching 10G on TCP streams.
···
 * All transports which have multi-packet rx and/or tx can deliver pps
   rates of up to 1Mps or more.
 
-* All legacy transports are generally limited to ~600-700MBit and 0.05Mps.
-
 * GRE and L2TPv3 allow connections to all of: local machine, remote
   machines, remote network devices and remote UML instances.
-
-* Socket allows connections only between UML instances.
-
-* Daemon and bess require running a local switch. This switch may be
-  connected to the host as well.
 
 
 Network configuration privileges
 ================================
 
 The majority of the supported networking modes need ``root`` privileges.
-For example, in the legacy tuntap networking mode, users were required
-to be part of the group associated with the tunnel device.
-
-For newer network drivers like the vector transports, ``root`` privilege
-is required to fire an ioctl to setup the tun interface and/or use
-raw sockets where needed.
+For example, for vector transports, ``root`` privilege is required to fire
+an ioctl to setup the tun interface and/or use raw sockets where needed.
 
 This can be achieved by granting the user a particular capability instead
 of running UML as root.  In case of vector transport, a user can add the
···
 connect to a local area cloud (all the UML nodes using the same
 multicast address running on hosts in the same multicast domain (LAN)
 will be automagically connected together to a virtual LAN.
-
-Configuring Legacy transports
-=============================
-
-Legacy transports are now considered obsolete. Please use the vector
-versions.
 
 ***********
 Running UML

MAINTAINERS

···
 S:	Orphan
 F:	drivers/net/ethernet/dec/tulip/
 
-TUN/TAP driver
+TUN/TAP DRIVER
 M:	Willem de Bruijn <[e-mail]>
 M:	Jason Wang <[e-mail]>
 S:	Maintained
 W:	http://vtun.sourceforge.net/tun
 F:	Documentation/networking/tuntap.rst
-F:	arch/um/os-Linux/drivers/
 F:	drivers/net/tap.c
 F:	drivers/net/tun*
 

arch/um/Kconfig

···
 config UML_IOMEM_EMULATION
 	bool
 	select INDIRECT_IOMEM
-	select HAS_IOPORT
 	select GENERIC_PCI_IOMAP
-	select GENERIC_IOMAP
-	select NO_GENERIC_PCI_IOPORT_MAP
-
-config NO_IOPORT_MAP
-	def_bool !UML_IOMEM_EMULATION
 
 config ISA
 	bool

arch/um/configs/i386_defconfig

···
 CONFIG_UNIX=y
 CONFIG_INET=y
 # CONFIG_IPV6 is not set
-CONFIG_UML_NET=y
-CONFIG_UML_NET_ETHERTAP=y
-CONFIG_UML_NET_TUNTAP=y
-CONFIG_UML_NET_SLIP=y
-CONFIG_UML_NET_DAEMON=y
-CONFIG_UML_NET_MCAST=y
-CONFIG_UML_NET_SLIRP=y
 CONFIG_EXT4_FS=y
 CONFIG_QUOTA=y
 CONFIG_AUTOFS_FS=m

arch/um/configs/x86_64_defconfig

···
 CONFIG_UNIX=y
 CONFIG_INET=y
 # CONFIG_IPV6 is not set
-CONFIG_UML_NET=y
-CONFIG_UML_NET_ETHERTAP=y
-CONFIG_UML_NET_TUNTAP=y
-CONFIG_UML_NET_SLIP=y
-CONFIG_UML_NET_DAEMON=y
-CONFIG_UML_NET_MCAST=y
-CONFIG_UML_NET_SLIRP=y
 CONFIG_EXT4_FS=y
 CONFIG_QUOTA=y
 CONFIG_AUTOFS_FS=m

arch/um/drivers/Kconfig

···
 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.
+	  This driver provides tap, raw, gre and l2tpv3 network transports.
 
-config UML_NET_VDE
-	bool "VDE transport (obsolete)"
-	depends on UML_NET
-	depends on !MODVERSIONS
-	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_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"
+	  For more information, including explanations of the networking
+	  and sample configurations, see
+	  <file:Documentation/virt/uml/user_mode_linux_howto_v2.rst>.
 
 endmenu
 
···
 	  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.
+
+config UML_PCI_OVER_VFIO
+	bool "Enable VFIO-based PCI passthrough"
+	select UML_PCI
+	help
+	  This driver provides support for VFIO-based PCI passthrough.
+	  Currently, only MSI-X capable devices are supported, and it
+	  is assumed that drivers will use MSI-X.

arch/um/drivers/Makefile

···
 # 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
···
 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_vde.o = $(shell $(CC) $(CFLAGS) -print-file-name=libvdeplug.a)
-
-targets := vde_kern.o vde_user.o
-
-$(obj)/vde.o: $(obj)/vde_kern.o $(obj)/vde_user.o
-	$(LD) -r -dp -o $@ $^ $(ld_flags)
+vfio_uml-objs := vfio_kern.o vfio_user.o
 
 #XXX: The call below does not work because the flags are added before the
 # object name, so nothing from the library gets linked.
···
 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-$(CONFIG_UML_NET) += net.o 
 obj-$(CONFIG_MCONSOLE) += mconsole.o
 obj-$(CONFIG_MMAPPER) += mmapper_kern.o 
 obj-$(CONFIG_BLK_DEV_UBD) += ubd.o 
···
 obj-$(CONFIG_UML_RTC) += rtc.o
 obj-$(CONFIG_UML_PCI) += virt-pci.o
 obj-$(CONFIG_UML_PCI_OVER_VIRTIO) += virtio_pcidev.o
+obj-$(CONFIG_UML_PCI_OVER_VFIO) += vfio_uml.o
 
 # pcap_user.o must be added explicitly.
-USER_OBJS := fd.o null.o pty.o tty.o xterm.o slip_common.o vde_user.o vector_user.o
+USER_OBJS := fd.o null.o pty.o tty.o xterm.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)"'

arch/um/drivers/chan_kern.c

···
  * 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 DEFINE_RAW_SPINLOCK(irqs_to_free_lock);
 static LIST_HEAD(irqs_to_free);
 
 void free_irqs(void)
···
 	struct list_head *ele;
 	unsigned long flags;
 
-	spin_lock_irqsave(&irqs_to_free_lock, flags);
+	raw_spin_lock_irqsave(&irqs_to_free_lock, flags);
 	list_splice_init(&irqs_to_free, &list);
-	spin_unlock_irqrestore(&irqs_to_free_lock, flags);
+	raw_spin_unlock_irqrestore(&irqs_to_free_lock, flags);
 
 	list_for_each(ele, &list) {
 		chan = list_entry(ele, struct chan, free_list);
···
 		return;
 
 	if (delay_free_irq) {
-		spin_lock_irqsave(&irqs_to_free_lock, flags);
+		raw_spin_lock_irqsave(&irqs_to_free_lock, flags);
 		list_add(&chan->free_list, &irqs_to_free);
-		spin_unlock_irqrestore(&irqs_to_free_lock, flags);
+		raw_spin_unlock_irqrestore(&irqs_to_free_lock, flags);
 	} else {
 		if (chan->input && chan->enabled)
 			um_free_irq(chan->line->read_irq, chan);

arch/um/drivers/daemon.h

···
-/* 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

arch/um/drivers/daemon_kern.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (C) 2001 Lennert Buytenhek ([e-mail]) and
- * James Leu ([e-mail]).
- * 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);

arch/um/drivers/daemon_user.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- * Copyright (C) 2001 Lennert Buytenhek ([e-mail]) and
- * James Leu ([e-mail]).
- * 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,
-};

arch/um/drivers/net_kern.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- * Copyright (C) 2001 Lennert Buytenhek ([e-mail]) and
- * James Leu ([e-mail]).
- * 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 netdev_tx_t 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);
-}
-
-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 = container_of(dev, struct uml_net, pdev.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_or_panic(sizeof(*new), SMP_CACHE_BYTES);
-
-	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);
-}

arch/um/drivers/net_user.c

···
-// 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;
-}

arch/um/drivers/slip.h

···
-/* 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

arch/um/drivers/slip_common.c

···
-// 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;
-}

arch/um/drivers/slip_common.h

···
-/* 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

arch/um/drivers/slip_kern.c

···
-// 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);

arch/um/drivers/slip_user.c

···
-// 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,
-};

arch/um/drivers/slirp.h

···
-/* 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

arch/um/drivers/slirp_kern.c

···
-// 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... */
-};
-
-static 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);

arch/um/drivers/slirp_user.c

···
-// 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], 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;
-	}
-
-	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,
-};

arch/um/drivers/umcast.h

···
-/* 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

arch/um/drivers/umcast_kern.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- * user-mode-linux networking multicast transport
- * Copyright (C) 2001 by Harald Welte <[e-mail]>
- * 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 ([e-mail]) and
- * James Leu ([e-mail]).
- * 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);

arch/um/drivers/umcast_user.c

···
-// 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 <[e-mail]>
- *
- * based on the existing uml-networking code, which is
- * Copyright (C) 2001 Lennert Buytenhek ([e-mail]) and
- * James Leu ([e-mail]).
- * 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,
-};

arch/um/drivers/vde.h

···
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Copyright (C) 2007 Luca Bigliardi ([e-mail]).
- */
-
-#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

arch/um/drivers/vde_kern.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (C) 2007 Luca Bigliardi ([e-mail]).
- *
- * 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);

arch/um/drivers/vde_user.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (C) 2007 Luca Bigliardi ([e-mail]).
- */
-
-#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);
-}
-

arch/um/drivers/vector_kern.c

···
  * Copyright (C) 2001 by various other people who didn't put their name here.
  */
 
+#define pr_fmt(fmt) "uml-vector: " fmt
+
 #include <linux/memblock.h>
 #include <linux/etherdevice.h>
 #include <linux/ethtool.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"
···
 	napi_schedule(&vp->napi);
 }
 
+static void vector_setup_etheraddr(struct net_device *dev, char *str)
+{
+	u8 addr[ETH_ALEN];
 
+	if (str == NULL)
+		goto random;
+
+	if (!mac_pton(str, addr)) {
+		netdev_err(dev,
+			"Failed to parse '%s' as an ethernet address\n", str);
+		goto random;
+	}
+	if (is_multicast_ether_addr(addr)) {
+		netdev_err(dev,
+			"Attempt to assign a multicast ethernet address to a device disallowed\n");
+		goto random;
+	}
+	if (!is_valid_ether_addr(addr)) {
+		netdev_err(dev,
+			"Attempt to assign an invalid ethernet address to a device disallowed\n");
+		goto random;
+	}
+	if (!is_local_ether_addr(addr)) {
+		netdev_warn(dev, "Warning: Assigning a globally valid ethernet address to a device\n");
+		netdev_warn(dev, "You should set the 2nd rightmost bit in the first byte of the MAC,\n");
+		netdev_warn(dev, "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:
+	netdev_info(dev, "Choosing a random ethernet address\n");
+	eth_hw_addr_random(dev);
+}
 
 static void vector_eth_configure(
 		int n,
···
 
 	device = kzalloc(sizeof(*device), GFP_KERNEL);
 	if (device == NULL) {
-		printk(KERN_ERR "eth_configure failed to allocate struct "
-				 "vector_device\n");
+		pr_err("Failed to allocate struct vector_device for vec%d\n", 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);
+		pr_err("Failed to allocate struct net_device for vec%d\n", n);
 		goto out_free_device;
 	}
 
···
 	 * and fail.
 	 */
 	snprintf(dev->name, sizeof(dev->name), "vec%d", n);
-	uml_net_setup_etheraddr(dev, uml_vector_fetch_arg(def, "mac"));
+	vector_setup_etheraddr(dev, uml_vector_fetch_arg(def, "mac"));
 	vp = netdev_priv(dev);
 
 	/* sysfs register */
···
 
 	err = vector_parse(str, &n, &str, &error);
 	if (err) {
-		printk(KERN_ERR "vector_setup - Couldn't parse '%s' : %s\n",
-				 str, error);
+		pr_err("Couldn't parse '%s': %s\n", str, error);
 		return 1;
 	}
 	new = memblock_alloc_or_panic(sizeof(*new), SMP_CACHE_BYTES);

arch/um/drivers/vfio_kern.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2025 Ant Group
+ * Author: Tiwei Bie <[e-mail]>
+ */
+
+#define pr_fmt(fmt) "vfio-uml: " fmt
+
+#include <linux/module.h>
+#include <linux/logic_iomem.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/string.h>
+#include <linux/unaligned.h>
+#include <irq_kern.h>
+#include <init.h>
+#include <os.h>
+
+#include "virt-pci.h"
+#include "vfio_user.h"
+
+#define to_vdev(_pdev) container_of(_pdev, struct uml_vfio_device, pdev)
+
+struct uml_vfio_intr_ctx {
+	struct uml_vfio_device *dev;
+	int irq;
+};
+
+struct uml_vfio_device {
+	const char *name;
+	int group;
+
+	struct um_pci_device pdev;
+	struct uml_vfio_user_device udev;
+	struct uml_vfio_intr_ctx *intr_ctx;
+
+	int msix_cap;
+	int msix_bar;
+	int msix_offset;
+	int msix_size;
+	u32 *msix_data;
+
+	struct list_head list;
+};
+
+struct uml_vfio_group {
+	int id;
+	int fd;
+	int users;
+	struct list_head list;
+};
+
+static struct {
+	int fd;
+	int users;
+} uml_vfio_container = { .fd = -1 };
+static DEFINE_MUTEX(uml_vfio_container_mtx);
+
+static LIST_HEAD(uml_vfio_groups);
+static DEFINE_MUTEX(uml_vfio_groups_mtx);
+
+static LIST_HEAD(uml_vfio_devices);
+
+static int uml_vfio_set_container(int group_fd)
+{
+	int err;
+
+	guard(mutex)(&uml_vfio_container_mtx);
+
+	err = uml_vfio_user_set_container(uml_vfio_container.fd, group_fd);
+	if (err)
+		return err;
+
+	uml_vfio_container.users++;
+	if (uml_vfio_container.users > 1)
+		return 0;
+
+	err = uml_vfio_user_setup_iommu(uml_vfio_container.fd);
+	if (err) {
+		uml_vfio_user_unset_container(uml_vfio_container.fd, group_fd);
+		uml_vfio_container.users--;
+	}
+	return err;
+}
+
+static void uml_vfio_unset_container(int group_fd)
+{
+	guard(mutex)(&uml_vfio_container_mtx);
+
+	uml_vfio_user_unset_container(uml_vfio_container.fd, group_fd);
+	uml_vfio_container.users--;
+}
+
+static int uml_vfio_open_group(int group_id)
+{
+	struct uml_vfio_group *group;
+	int err;
+
+	guard(mutex)(&uml_vfio_groups_mtx);
+
+	list_for_each_entry(group, &uml_vfio_groups, list) {
+		if (group->id == group_id) {
+			group->users++;
+			return group->fd;
+		}
+	}
+
+	group = kzalloc(sizeof(*group), GFP_KERNEL);
+	if (!group)
+		return -ENOMEM;
+
+	group->fd = uml_vfio_user_open_group(group_id);
+	if (group->fd < 0) {
+		err = group->fd;
+		goto free_group;
+	}
+
+	err = uml_vfio_set_container(group->fd);
+	if (err)
+		goto close_group;
+
+	group->id = group_id;
+	group->users = 1;
+
+	list_add(&group->list, &uml_vfio_groups);
+
+	return group->fd;
+
+close_group:
+	os_close_file(group->fd);
+free_group:
+	kfree(group);
+	return err;
+}
+
+static int uml_vfio_release_group(int group_fd)
+{
+	struct uml_vfio_group *group;
+
+	guard(mutex)(&uml_vfio_groups_mtx);
+
+	list_for_each_entry(group, &uml_vfio_groups, list) {
+		if (group->fd == group_fd) {
+			group->users--;
+			if (group->users == 0) {
+				uml_vfio_unset_container(group_fd);
+				os_close_file(group_fd);
+				list_del(&group->list);
+				kfree(group);
+			}
+			return 0;
+		}
+	}
+
+	return -ENOENT;
+}
+
+static irqreturn_t uml_vfio_interrupt(int unused, void *opaque)
+{
+	struct uml_vfio_intr_ctx *ctx = opaque;
+	struct uml_vfio_device *dev = ctx->dev;
+	int index = ctx - dev->intr_ctx;
+	int irqfd = dev->udev.irqfd[index];
+	int irq = dev->msix_data[index];
+	uint64_t v;
+	int r;
+
+	do {
+		r = os_read_file(irqfd, &v, sizeof(v));
+		if (r == sizeof(v))
+			generic_handle_irq(irq);
+	} while (r == sizeof(v) || r == -EINTR);
+	WARN(r != -EAGAIN, "read returned %d\n", r);
+
+	return IRQ_HANDLED;
+}
+
+static int uml_vfio_activate_irq(struct uml_vfio_device *dev, int index)
+{
+	struct uml_vfio_intr_ctx *ctx = &dev->intr_ctx[index];
+	int err, irqfd;
+
+	if (ctx->irq >= 0)
+		return 0;
+
+	irqfd = uml_vfio_user_activate_irq(&dev->udev, index);
+	if (irqfd < 0)
+		return irqfd;
+
+	ctx->irq = um_request_irq(UM_IRQ_ALLOC, irqfd, IRQ_READ,
+				  uml_vfio_interrupt, 0,
+				  "vfio-uml", ctx);
+	if (ctx->irq < 0) {
+		err = ctx->irq;
+		goto deactivate;
+	}
+
+	err = add_sigio_fd(irqfd);
+	if (err)
+		goto free_irq;
+
+	return 0;
+
+free_irq:
+	um_free_irq(ctx->irq, ctx);
+	ctx->irq = -1;
+deactivate:
+	uml_vfio_user_deactivate_irq(&dev->udev, index);
+	return err;
+}
+
+static int uml_vfio_deactivate_irq(struct uml_vfio_device *dev, int index)
+{
+	struct uml_vfio_intr_ctx *ctx = &dev->intr_ctx[index];
+
+	if (ctx->irq >= 0) {
+		ignore_sigio_fd(dev->udev.irqfd[index]);
+		um_free_irq(ctx->irq, ctx);
+		uml_vfio_user_deactivate_irq(&dev->udev, index);
+		ctx->irq = -1;
+	}
+	return 0;
+}
+
+static int uml_vfio_update_msix_cap(struct uml_vfio_device *dev,
+				    unsigned int offset, int size,
+				    unsigned long val)
+{
+	/*
+	 * Here, we handle only the operations we care about,
+	 * ignoring the rest.
+	 */
+	if (size == 2 && offset == dev->msix_cap + PCI_MSIX_FLAGS) {
+		switch (val & ~PCI_MSIX_FLAGS_QSIZE) {
+		case PCI_MSIX_FLAGS_ENABLE:
+		case 0:
+			return uml_vfio_user_update_irqs(&dev->udev);
+		}
+	}
+	return 0;
+}
+
+static int uml_vfio_update_msix_table(struct uml_vfio_device *dev,
+				      unsigned int offset, int size,
+				      unsigned long val)
+{
+	int index;
+
+	/*
+	 * Here, we handle only the operations we care about,
+	 * ignoring the rest.
+	 */
+	offset -= dev->msix_offset + PCI_MSIX_ENTRY_DATA;
+
+	if (size != 4 || offset % PCI_MSIX_ENTRY_SIZE != 0)
+		return 0;
+
+	index = offset / PCI_MSIX_ENTRY_SIZE;
+	if (index >= dev->udev.irq_count)
+		return -EINVAL;
+
+	dev->msix_data[index] = val;
+
+	return val ? uml_vfio_activate_irq(dev, index) :
+		uml_vfio_deactivate_irq(dev, index);
+}
+
+static unsigned long __uml_vfio_cfgspace_read(struct uml_vfio_device *dev,
+					      unsigned int offset, int size)
+{
+	u8 data[8];
+
+	memset(data, 0xff, sizeof(data));
+
+	if (uml_vfio_user_cfgspace_read(&dev->udev, offset, data, size))
+		return ULONG_MAX;
+
+	switch (size) {
+	case 1:
+		return data[0];
+	case 2:
+		return le16_to_cpup((void *)data);
+	case 4:
+		return le32_to_cpup((void *)data);
+#ifdef CONFIG_64BIT
+	case 8:
+		return le64_to_cpup((void *)data);
+#endif
+	default:
+		return ULONG_MAX;
+	}
+}
+
+static unsigned long uml_vfio_cfgspace_read(struct um_pci_device *pdev,
+					    unsigned int offset, int size)
+{
+	struct uml_vfio_device *dev = to_vdev(pdev);
+
+	return __uml_vfio_cfgspace_read(dev, offset, size);
+}
+
+static void __uml_vfio_cfgspace_write(struct uml_vfio_device *dev,
+				      unsigned int offset, int size,
+				      unsigned long val)
+{
+	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
+	}
+
+	WARN_ON(uml_vfio_user_cfgspace_write(&dev->udev, offset, data, size));
+}
+
+static void uml_vfio_cfgspace_write(struct um_pci_device *pdev,
+				    unsigned int offset, int size,
+				    unsigned long val)
+{
+	struct uml_vfio_device *dev = to_vdev(pdev);
+
+	if (offset < dev->msix_cap + PCI_CAP_MSIX_SIZEOF &&
+	    offset + size > dev->msix_cap)
+		WARN_ON(uml_vfio_update_msix_cap(dev, offset, size, val));
+
+	__uml_vfio_cfgspace_write(dev, offset, size, val);
+}
+
+static void uml_vfio_bar_copy_from(struct um_pci_device *pdev, int bar,
+				   void *buffer, unsigned int offset, int size)
+{
+	struct uml_vfio_device *dev = to_vdev(pdev);
+
+	memset(buffer, 0xff, size);
+	uml_vfio_user_bar_read(&dev->udev, bar, offset, buffer, size);
+}
+
+static unsigned long uml_vfio_bar_read(struct um_pci_device *pdev, int bar,
+				       unsigned int offset, int size)
+{
+	u8 data[8];
+
+	uml_vfio_bar_copy_from(pdev, bar, data, offset, size);
+
+	switch (size) {
+	case 1:
+		return data[0];
+	case 2:
+		return le16_to_cpup((void *)data);
+	case 4:
+		return le32_to_cpup((void *)data);
+#ifdef CONFIG_64BIT
+	case 8:
+		return le64_to_cpup((void *)data);
+#endif
+	default:
+		return ULONG_MAX;
+	}
+}
+
+static void uml_vfio_bar_copy_to(struct um_pci_device *pdev, int bar,
+				 unsigned int offset, const void *buffer,
+				 int size)
+{
+	struct uml_vfio_device *dev = to_vdev(pdev);
+
+	uml_vfio_user_bar_write(&dev->udev, bar, offset, buffer, size);
+}
+
+static void uml_vfio_bar_write(struct um_pci_device *pdev, int bar,
+			       unsigned int offset, int size,
+			       unsigned long val)
+{
+	struct uml_vfio_device *dev = to_vdev(pdev);
+	u8 data[8];
+
+	if (bar == dev->msix_bar && offset + size > dev->msix_offset &&
+	    offset < dev->msix_offset + dev->msix_size)
+		WARN_ON(uml_vfio_update_msix_table(dev, offset, size, val));
+
+	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
+	}
+
+	uml_vfio_bar_copy_to(pdev, bar, offset, data, size);
+}
+
+static void uml_vfio_bar_set(struct um_pci_device *pdev, int bar,
+			     unsigned int offset, u8 value, int size)
+{
+	struct uml_vfio_device *dev = to_vdev(pdev);
+	int i;
+
+	for (i = 0; i < size; i++)
+		uml_vfio_user_bar_write(&dev->udev, bar, offset + i, &value, 1);
+}
+
+static const struct um_pci_ops uml_vfio_um_pci_ops = {
+	.cfgspace_read	= uml_vfio_cfgspace_read,
+	.cfgspace_write	= uml_vfio_cfgspace_write,
+	.bar_read	= uml_vfio_bar_read,
+	.bar_write	= uml_vfio_bar_write,
+	.bar_copy_from	= uml_vfio_bar_copy_from,
+	.bar_copy_to	= uml_vfio_bar_copy_to,
+	.bar_set	= uml_vfio_bar_set,
+};
+
+static u8 uml_vfio_find_capability(struct uml_vfio_device *dev, u8 cap)
+{
+	u8 id, pos;
+	u16 ent;
+	int ttl = 48; /* PCI_FIND_CAP_TTL */
+
+	pos = __uml_vfio_cfgspace_read(dev, PCI_CAPABILITY_LIST, sizeof(pos));
+
+	while (pos && ttl--) {
+		ent = __uml_vfio_cfgspace_read(dev, pos, sizeof(ent));
+
+		id = ent & 0xff;
+		if (id == 0xff)
+			break;
+		if (id == cap)
+			return pos;
+
+		pos = ent >> 8;
+	}
+
+	return 0;
+}
+
+static int uml_vfio_read_msix_table(struct uml_vfio_device *dev)
+{
+	unsigned int off;
+	u16 flags;
+	u32 tbl;
+
+	off = uml_vfio_find_capability(dev, PCI_CAP_ID_MSIX);
+	if (!off)
+		return -ENOTSUPP;
+
+	dev->msix_cap = off;
+
+	tbl = __uml_vfio_cfgspace_read(dev, off + PCI_MSIX_TABLE, sizeof(tbl));
+	flags = __uml_vfio_cfgspace_read(dev, off + PCI_MSIX_FLAGS, sizeof(flags));
+
+	dev->msix_bar = tbl & PCI_MSIX_TABLE_BIR;
+	dev->msix_offset = tbl & PCI_MSIX_TABLE_OFFSET;
+	dev->msix_size = ((flags & PCI_MSIX_FLAGS_QSIZE) + 1) * PCI_MSIX_ENTRY_SIZE;
+
+	dev->msix_data = kzalloc(dev->msix_size, GFP_KERNEL);
+	if (!dev->msix_data)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void uml_vfio_open_device(struct uml_vfio_device *dev)
+{
+	struct uml_vfio_intr_ctx *ctx;
+	int err, group_id, i;
+
+	group_id = uml_vfio_user_get_group_id(dev->name);
+	if (group_id < 0) {
+		pr_err("Failed to get group id (%s), error %d\n",
+		       dev->name, group_id);
+		goto free_dev;
+	}
+
+	dev->group = uml_vfio_open_group(group_id);
+	if (dev->group < 0) {
+		pr_err("Failed to open group %d (%s), error %d\n",
+		       group_id, dev->name, dev->group);
+		goto free_dev;
+	}
+
+	err = uml_vfio_user_setup_device(&dev->udev, dev->group, dev->name);
+	if (err) {
+		pr_err("Failed to setup device (%s), error %d\n",
+		       dev->name, err);
+		goto release_group;
+	}
+
+	err = uml_vfio_read_msix_table(dev);
+	if (err) {
+		pr_err("Failed to read MSI-X table (%s), error %d\n",
+		       dev->name, err);
+		goto teardown_udev;
+	}
+
+	dev->intr_ctx = kmalloc_array(dev->udev.irq_count,
+				      sizeof(struct uml_vfio_intr_ctx),
+				      GFP_KERNEL);
+	if (!dev->intr_ctx) {
+		pr_err("Failed to allocate interrupt context (%s)\n",
+		       dev->name);
+		goto free_msix;
+	}
+
+	for (i = 0; i < dev->udev.irq_count; i++) {
+		ctx = &dev->intr_ctx[i];
+		ctx->dev = dev;
+		ctx->irq = -1;
+	}
+
+	dev->pdev.ops = &uml_vfio_um_pci_ops;
+
+	err = um_pci_device_register(&dev->pdev);
+	if (err) {
+		pr_err("Failed to register UM PCI device (%s), error %d\n",
+		       dev->name, err);
+		goto free_intr_ctx;
+	}
+
+	return;
+
+free_intr_ctx:
+	kfree(dev->intr_ctx);
+free_msix:
+	kfree(dev->msix_data);
+teardown_udev:
+	uml_vfio_user_teardown_device(&dev->udev);
+release_group:
+	uml_vfio_release_group(dev->group);
+free_dev:
+	list_del(&dev->list);
+	kfree(dev->name);
+	kfree(dev);
+}
+
+static void uml_vfio_release_device(struct uml_vfio_device *dev)
+{
+	int i;
+
+	for (i = 0; i < dev->udev.irq_count; i++)
+		uml_vfio_deactivate_irq(dev, i);
+	uml_vfio_user_update_irqs(&dev->udev);
+
+	um_pci_device_unregister(&dev->pdev);
+	kfree(dev->intr_ctx);
+	kfree(dev->msix_data);
+	uml_vfio_user_teardown_device(&dev->udev);
+	uml_vfio_release_group(dev->group);
+	list_del(&dev->list);
+	kfree(dev->name);
+	kfree(dev);
+}
+
+static int uml_vfio_cmdline_set(const char *device, const struct kernel_param *kp)
+{
+	struct uml_vfio_device *dev;
+	int fd;
+
+	if (uml_vfio_container.fd < 0) {
+		fd = uml_vfio_user_open_container();
+		if (fd < 0)
+			return fd;
+		uml_vfio_container.fd = fd;
+	}
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	dev->name = kstrdup(device, GFP_KERNEL);
+	if (!dev->name) {
+		kfree(dev);
+		return -ENOMEM;
+	}
+
+	list_add_tail(&dev->list, &uml_vfio_devices);
+	return 0;
+}
+
+static int uml_vfio_cmdline_get(char *buffer, const struct kernel_param *kp)
+{
+	return 0;
+}
+
+static const struct kernel_param_ops uml_vfio_cmdline_param_ops = {
+	.set = uml_vfio_cmdline_set,
+	.get = uml_vfio_cmdline_get,
+};
+
+device_param_cb(device, &uml_vfio_cmdline_param_ops, NULL, 0400);
+__uml_help(uml_vfio_cmdline_param_ops,
+"vfio_uml.device=<domain:bus:slot.function>\n"
+"    Pass through a PCI device to UML via VFIO. Currently, only MSI-X\n"
+"    capable devices are supported, and it is assumed that drivers will\n"
+"    use MSI-X. This parameter can be specified multiple times to pass\n"
+"    through multiple PCI devices to UML.\n\n"
+);
+
+static int __init uml_vfio_init(void)
+{
+	struct uml_vfio_device *dev, *n;
+
+	sigio_broken();
+
+	/* If the opening fails, the device will be released. */
+	list_for_each_entry_safe(dev, n, &uml_vfio_devices, list)
+		uml_vfio_open_device(dev);
+
+	return 0;
+}
+late_initcall(uml_vfio_init);
+
+static void __exit uml_vfio_exit(void)
+{
+	struct uml_vfio_device *dev, *n;
+
+	list_for_each_entry_safe(dev, n, &uml_vfio_devices, list)
+		uml_vfio_release_device(dev);
+
+	if (uml_vfio_container.fd >= 0)
+		os_close_file(uml_vfio_container.fd);
+}
+module_exit(uml_vfio_exit);

arch/um/drivers/vfio_user.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2025 Ant Group
+ * Author: Tiwei Bie <[e-mail]>
+ */
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/eventfd.h>
+#include <linux/limits.h>
+#include <linux/vfio.h>
+#include <linux/pci_regs.h>
+#include <as-layout.h>
+#include <um_malloc.h>
+
+#include "vfio_user.h"
+
+int uml_vfio_user_open_container(void)
+{
+	int r, fd;
+
+	fd = open("/dev/vfio/vfio", O_RDWR);
+	if (fd < 0)
+		return -errno;
+
+	r = ioctl(fd, VFIO_GET_API_VERSION);
+	if (r != VFIO_API_VERSION) {
+		r = r < 0 ? -errno : -EINVAL;
+		goto error;
+	}
+
+	r = ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_TYPE1_IOMMU);
+	if (r <= 0) {
+		r = r < 0 ? -errno : -EINVAL;
+		goto error;
+	}
+
+	return fd;
+
+error:
+	close(fd);
+	return r;
+}
+
+int uml_vfio_user_setup_iommu(int container)
+{
+	/*
+	 * This is a bit tricky. See the big comment in
+	 * vhost_user_set_mem_table() in virtio_uml.c.
+	 */
+	unsigned long reserved = uml_reserved - uml_physmem;
+	struct vfio_iommu_type1_dma_map dma_map = {
+		.argsz = sizeof(dma_map),
+		.flags = VFIO_DMA_MAP_FLAG_READ | VFIO_DMA_MAP_FLAG_WRITE,
+		.vaddr = uml_reserved,
+		.iova = reserved,
+		.size = physmem_size - reserved,
+	};
+
+	if (ioctl(container, VFIO_SET_IOMMU, VFIO_TYPE1_IOMMU) < 0)
+		return -errno;
+
+	if (ioctl(container, VFIO_IOMMU_MAP_DMA, &dma_map) < 0)
+		return -errno;
+
+	return 0;
+}
+
+int uml_vfio_user_get_group_id(const char *device)
+{
+	char *path, *buf, *end;
+	const char *name;
+	int r;
+
+	path = uml_kmalloc(PATH_MAX, UM_GFP_KERNEL);
+	if (!path)
+		return -ENOMEM;
+
+	sprintf(path, "/sys/bus/pci/devices/%s/iommu_group", device);
+
+	buf = uml_kmalloc(PATH_MAX + 1, UM_GFP_KERNEL);
+	if (!buf) {
+		r = -ENOMEM;
+		goto free_path;
+	}
+
+	r = readlink(path, buf, PATH_MAX);
+	if (r < 0) {
+		r = -errno;
+		goto free_buf;
+	}
+	buf[r] = '\0';
+
+	name = basename(buf);
+
+	r = strtoul(name, &end, 10);
+	if (*end != '\0' || end == name) {
+		r = -EINVAL;
+		goto free_buf;
+	}
+
+free_buf:
+	kfree(buf);
+free_path:
+	kfree(path);
+	return r;
+}
+
+int uml_vfio_user_open_group(int group_id)
+{
+	char *path;
+	int fd;
+
+	path = uml_kmalloc(PATH_MAX, UM_GFP_KERNEL);
+	if (!path)
+		return -ENOMEM;
+
+	sprintf(path, "/dev/vfio/%d", group_id);
+
+	fd = open(path, O_RDWR);
+	if (fd < 0) {
+		fd = -errno;
+		goto out;
+	}
+
+out:
+	kfree(path);
+	return fd;
+}
+
+int uml_vfio_user_set_container(int container, int group)
+{
+	if (ioctl(group, VFIO_GROUP_SET_CONTAINER, &container) < 0)
+		return -errno;
+	return 0;
+}
+
+int uml_vfio_user_unset_container(int container, int group)
+{
+	if (ioctl(group, VFIO_GROUP_UNSET_CONTAINER, &container) < 0)
+		return -errno;
+	return 0;
+}
+
+static int vfio_set_irqs(int device, int start, int count, int *irqfd)
+{
+	struct vfio_irq_set *irq_set;
+	int argsz = sizeof(*irq_set) + sizeof(*irqfd) * count;
+	int err = 0;
+
+	irq_set = uml_kmalloc(argsz, UM_GFP_KERNEL);
+	if (!irq_set)
+		return -ENOMEM;
+
+	irq_set->argsz = argsz;
+	irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD | VFIO_IRQ_SET_ACTION_TRIGGER;
+	irq_set->index = VFIO_PCI_MSIX_IRQ_INDEX;
+	irq_set->start = start;
+	irq_set->count = count;
+	memcpy(irq_set->data, irqfd, sizeof(*irqfd) * count);
+
+	if (ioctl(device, VFIO_DEVICE_SET_IRQS, irq_set) < 0) {
+		err = -errno;
+		goto out;
+	}
+
+out:
+	kfree(irq_set);
+	return err;
+}
+
+int uml_vfio_user_setup_device(struct uml_vfio_user_device *dev,
+			       int group, const char *device)
+{
+	struct vfio_device_info device_info = { .argsz = sizeof(device_info) };
+	struct vfio_irq_info irq_info = { .argsz = sizeof(irq_info) };
+	int err, i;
+
+	dev->device = ioctl(group, VFIO_GROUP_GET_DEVICE_FD, device);
+	if (dev->device < 0)
+		return -errno;
+
+	if (ioctl(dev->device, VFIO_DEVICE_GET_INFO, &device_info) < 0) {
+		err = -errno;
+		goto close_device;
+	}
+
+	dev->num_regions = device_info.num_regions;
+	if (dev->num_regions > VFIO_PCI_CONFIG_REGION_INDEX + 1)
+		dev->num_regions = VFIO_PCI_CONFIG_REGION_INDEX + 1;
+
+	dev->region = uml_kmalloc(sizeof(*dev->region) * dev->num_regions,
+				  UM_GFP_KERNEL);
+	if (!dev->region) {
+		err = -ENOMEM;
+		goto close_device;
+	}
+
+	for (i = 0; i < dev->num_regions; i++) {
+		struct vfio_region_info region = {
+			.argsz = sizeof(region),
+			.index = i,
+		};
+		if (ioctl(dev->device, VFIO_DEVICE_GET_REGION_INFO, &region) < 0) {
+			err = -errno;
+			goto free_region;
+		}
+		dev->region[i].size = region.size;
+		dev->region[i].offset = region.offset;
+	}
+
+	/* Only MSI-X is supported currently. */
+	irq_info.index = VFIO_PCI_MSIX_IRQ_INDEX;
+	if (ioctl(dev->device, VFIO_DEVICE_GET_IRQ_INFO, &irq_info) < 0) {
+		err = -errno;
+		goto free_region;
+	}
+
+	dev->irq_count = irq_info.count;
+
+	dev->irqfd = uml_kmalloc(sizeof(int) * dev->irq_count, UM_GFP_KERNEL);
+	if (!dev->irqfd) {
+		err = -ENOMEM;
+		goto free_region;
+	}
+
+	memset(dev->irqfd, -1, sizeof(int) * dev->irq_count);
+
+	err = vfio_set_irqs(dev->device, 0, dev->irq_count, dev->irqfd);
+	if (err)
+		goto free_irqfd;
+
+	return 0;
+
+free_irqfd:
+	kfree(dev->irqfd);
+free_region:
+	kfree(dev->region);
+close_device:
+	close(dev->device);
+	return err;
+}
+
+void uml_vfio_user_teardown_device(struct uml_vfio_user_device *dev)
+{
+	kfree(dev->irqfd);
+	kfree(dev->region);
+	close(dev->device);
+}
+
+int uml_vfio_user_activate_irq(struct uml_vfio_user_device *dev, int index)
+{
+	int irqfd;
+
+	irqfd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
+	if (irqfd < 0)
+		return -errno;
+
+	dev->irqfd[index] = irqfd;
+	return irqfd;
+}
+
+void uml_vfio_user_deactivate_irq(struct uml_vfio_user_device *dev, int index)
+{
+	close(dev->irqfd[index]);
+	dev->irqfd[index] = -1;
+}
+
+int uml_vfio_user_update_irqs(struct uml_vfio_user_device *dev)
+{
+	return vfio_set_irqs(dev->device, 0, dev->irq_count, dev->irqfd);
+}
+
+static int vfio_region_read(struct uml_vfio_user_device *dev, unsigned int index,
+			    uint64_t offset, void *buf, uint64_t size)
+{
+	if (index >= dev->num_regions || offset + size > dev->region[index].size)
+		return -EINVAL;
+
+	if (pread(dev->device, buf, size, dev->region[index].offset + offset) < 0)
+		return -errno;
+
+	return 0;
+}
+
+static int vfio_region_write(struct uml_vfio_user_device *dev, unsigned int index,
+			     uint64_t offset, const void *buf, uint64_t size)
+{
+	if (index >= dev->num_regions || offset + size > dev->region[index].size)
+		return -EINVAL;
+
+	if (pwrite(dev->device, buf, size, dev->region[index].offset + offset) < 0)
+		return -errno;
+
+	return 0;
+}
+
+int uml_vfio_user_cfgspace_read(struct uml_vfio_user_device *dev,
+				unsigned int offset, void *buf, int size)
+{
+	return vfio_region_read(dev, VFIO_PCI_CONFIG_REGION_INDEX,
+				offset, buf, size);
+}
+
+int uml_vfio_user_cfgspace_write(struct uml_vfio_user_device *dev,
+				 unsigned int offset, const void *buf, int size)
+{
+	return vfio_region_write(dev, VFIO_PCI_CONFIG_REGION_INDEX,
+				 offset, buf, size);
+}
+
+int uml_vfio_user_bar_read(struct uml_vfio_user_device *dev, int bar,
+			   unsigned int offset, void *buf, int size)
+{
+	return vfio_region_read(dev, bar, offset, buf, size);
+}
+
+int uml_vfio_user_bar_write(struct uml_vfio_user_device *dev, int bar,
+			    unsigned int offset, const void *buf, int size)
+{
+	return vfio_region_write(dev, bar, offset, buf, size);
+}

arch/um/drivers/vfio_user.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_VFIO_USER_H
+#define __UM_VFIO_USER_H
+
+struct uml_vfio_user_device {
+	int device;
+
+	struct {
+		uint64_t size;
+		uint64_t offset;
+	} *region;
+	int num_regions;
+
+	int32_t *irqfd;
+	int irq_count;
+};
+
+int uml_vfio_user_open_container(void);
+int uml_vfio_user_setup_iommu(int container);
+
+int uml_vfio_user_get_group_id(const char *device);
+int uml_vfio_user_open_group(int group_id);
+int uml_vfio_user_set_container(int container, int group);
+int uml_vfio_user_unset_container(int container, int group);
+
+int uml_vfio_user_setup_device(struct uml_vfio_user_device *dev,
+			       int group, const char *device);
+void uml_vfio_user_teardown_device(struct uml_vfio_user_device *dev);
+
+int uml_vfio_user_activate_irq(struct uml_vfio_user_device *dev, int index);
+void uml_vfio_user_deactivate_irq(struct uml_vfio_user_device *dev, int index);
+int uml_vfio_user_update_irqs(struct uml_vfio_user_device *dev);
+
+int uml_vfio_user_cfgspace_read(struct uml_vfio_user_device *dev,
+				unsigned int offset, void *buf, int size);
+int uml_vfio_user_cfgspace_write(struct uml_vfio_user_device *dev,
+				 unsigned int offset, const void *buf, int size);
+
+int uml_vfio_user_bar_read(struct uml_vfio_user_device *dev, int bar,
+			   unsigned int offset, void *buf, int size);
+int uml_vfio_user_bar_write(struct uml_vfio_user_device *dev, int bar,
+			    unsigned int offset, const void *buf, int size);
+
+#endif /* __UM_VFIO_USER_H */

arch/um/drivers/virt-pci.c

···
 
 static int __init um_pci_init(void)
 {
-	struct irq_domain_info inner_domain_info = {
-		.size		= MAX_MSI_VECTORS,
-		.hwirq_max	= MAX_MSI_VECTORS,
-		.ops		= &um_pci_inner_domain_ops,
-	};
 	int err, i;
 
 	WARN_ON(logic_iomem_add_region(&virt_cfgspace_resource,
···
 		goto free;
 	}
 
-	inner_domain_info.fwnode = um_pci_fwnode;
-	um_pci_inner_domain = irq_domain_instantiate(&inner_domain_info);
-	if (IS_ERR(um_pci_inner_domain)) {
-		err = PTR_ERR(um_pci_inner_domain);
+	um_pci_inner_domain = irq_domain_create_linear(um_pci_fwnode, MAX_MSI_VECTORS,
+						       &um_pci_inner_domain_ops, NULL);
+	if (!um_pci_inner_domain) {
+		err = -ENOMEM;
 		goto free;
 	}
 
···
 	return 0;
 
 free:
-	if (!IS_ERR_OR_NULL(um_pci_inner_domain))
+	if (um_pci_inner_domain)
 		irq_domain_remove(um_pci_inner_domain);
 	if (um_pci_fwnode)
 		irq_domain_free_fwnode(um_pci_fwnode);

arch/um/drivers/xterm.c

···
 "    '<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"
+"    Values for gnome-terminal are 'xterm=gnome-terminal,-t,--'.\n\n"
 );
 
 static int xterm_open(int input, int output, int primary, void *d,
···
 	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");
+	/* Ensure we are running on Xorg or Wayland. */
+	if (!getenv("DISPLAY") && !getenv("WAYLAND_DISPLAY")) {
+		printk(UM_KERN_ERR "xterm_open : neither $DISPLAY nor $WAYLAND_DISPLAY is set.\n");
 		return -ENODEV;
 	}
 

arch/um/include/asm/asm-prototypes.h

···
 #include <asm-generic/asm-prototypes.h>
+#include <asm/checksum.h>
+
+#ifdef CONFIG_UML_X86
+extern void cmpxchg8b_emu(void);
+#endif

arch/um/include/asm/irq.h

···
 #define TELNETD_IRQ 		8
 #define XTERM_IRQ 		9
 #define RANDOM_IRQ 		10
+#define SIGCHLD_IRQ		11
 
 #ifdef CONFIG_UML_NET_VECTOR
 
-#define VECTOR_BASE_IRQ		(RANDOM_IRQ + 1)
+#define VECTOR_BASE_IRQ		(SIGCHLD_IRQ + 1)
 #define VECTOR_IRQ_SPACE	8
 
 #define UM_FIRST_DYN_IRQ (VECTOR_IRQ_SPACE + VECTOR_BASE_IRQ)
 
 #else
 
-#define UM_FIRST_DYN_IRQ (RANDOM_IRQ + 1)
+#define UM_FIRST_DYN_IRQ (SIGCHLD_IRQ + 1)
 
 #endif
 

arch/um/include/asm/mmu.h

···
 #ifndef __ARCH_UM_MMU_H
 #define __ARCH_UM_MMU_H
 
+#include "linux/types.h"
 #include <mm_id.h>
 
 typedef struct mm_context {
 	struct mm_id id;
+
+	struct list_head list;
 
 	/* Address range in need of a TLB sync */
 	unsigned long sync_tlb_range_from;

arch/um/include/shared/common-offsets.h

···
 
 DEFINE(UM_NSEC_PER_SEC, NSEC_PER_SEC);
 DEFINE(UM_NSEC_PER_USEC, NSEC_PER_USEC);
+
+DEFINE(UM_KERN_GDT_ENTRY_TLS_ENTRIES, GDT_ENTRY_TLS_ENTRIES);
+
+DEFINE(UM_SECCOMP_ARCH_NATIVE, SECCOMP_ARCH_NATIVE);

arch/um/include/shared/irq_user.h

···
 struct siginfo;
 extern void sigio_handler(int sig, struct siginfo *unused_si,
 			  struct uml_pt_regs *regs, void *mc);
+extern void sigchld_handler(int sig, struct siginfo *unused_si,
+			   struct uml_pt_regs *regs, void *mc);
 void sigio_run_timetravel_handlers(void);
 extern void free_irq_by_fd(int fd);
 extern void deactivate_fd(int fd, int irqnum);

arch/um/include/shared/net_kern.h

···
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Copyright (C) 2002 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- */
-
-#ifndef __UM_NET_KERN_H
-#define __UM_NET_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/workqueue.h>
-
-struct uml_net {
-	struct list_head list;
-	struct net_device *dev;
-	struct platform_device pdev;
-	int index;
-};
-
-struct uml_net_private {
-	struct list_head list;
-	spinlock_t lock;
-	struct net_device *dev;
-	struct timer_list tl;
-
-	struct work_struct work;
-	int fd;
-	unsigned char mac[ETH_ALEN];
-	int max_packet;
-	unsigned short (*protocol)(struct sk_buff *);
-	int (*open)(void *);
-	void (*close)(int, void *);
-	void (*remove)(void *);
-	int (*read)(int, struct sk_buff *skb, struct uml_net_private *);
-	int (*write)(int, struct sk_buff *skb, struct uml_net_private *);
-
-	void (*add_address)(unsigned char *, unsigned char *, void *);
-	void (*delete_address)(unsigned char *, unsigned char *, void *);
-	char user[];
-};
-
-struct net_kern_info {
-	void (*init)(struct net_device *, void *);
-	unsigned short (*protocol)(struct sk_buff *);
-	int (*read)(int, struct sk_buff *skb, struct uml_net_private *);
-	int (*write)(int, struct sk_buff *skb, struct uml_net_private *);
-};
-
-struct transport {
-	struct list_head list;
-	const char *name;
-	int (* const setup)(char *, char **, void *);
-	const struct net_user_info *user;
-	const struct net_kern_info *kern;
-	const int private_size;
-	const int setup_size;
-};
-
-extern int tap_setup_common(char *str, char *type, char **dev_name,
-			    char **mac_out, char **gate_addr);
-extern void register_transport(struct transport *new);
-extern unsigned short eth_protocol(struct sk_buff *skb);
-extern void uml_net_setup_etheraddr(struct net_device *dev, char *str);
-
-
-#endif

arch/um/include/shared/net_user.h

···
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- */
-
-#ifndef __UM_NET_USER_H__
-#define __UM_NET_USER_H__
-
-#define ETH_ADDR_LEN (6)
-#define ETH_HEADER_ETHERTAP (16)
-#define ETH_HEADER_OTHER (26) /* 14 for ethernet + VLAN + MPLS for crazy people */
-#define ETH_MAX_PACKET (1500)
-
-#define UML_NET_VERSION (4)
-
-struct net_user_info {
-	int (*init)(void *, void *);
-	int (*open)(void *);
-	void (*close)(int, void *);
-	void (*remove)(void *);
-	void (*add_address)(unsigned char *, unsigned char *, void *);
-	void (*delete_address)(unsigned char *, unsigned char *, void *);
-	int max_packet;
-	int mtu;
-};
-
-extern void iter_addresses(void *d, void (*cb)(unsigned char *,
-					       unsigned char *, void *),
-			   void *arg);
-
-extern void *get_output_buffer(int *len_out);
-extern void free_output_buffer(void *buffer);
-
-extern int tap_open_common(void *dev, char *gate_addr);
-extern void tap_check_ips(char *gate_addr, unsigned char *eth_addr);
-
-extern void read_output(int fd, char *output_out, int len);
-
-extern int net_read(int fd, void *buf, int len);
-extern int net_recvfrom(int fd, void *buf, int len);
-extern int net_write(int fd, void *buf, int len);
-extern int net_send(int fd, void *buf, int len);
-extern int net_sendto(int fd, void *buf, int len, void *to, int sock_len);
-
-extern void open_addr(unsigned char *addr, unsigned char *netmask, void *arg);
-extern void close_addr(unsigned char *addr, unsigned char *netmask, void *arg);
-
-extern char *split_if_spec(char *str, ...);
-
-extern int dev_netmask(void *d, void *m);
-
-#endif

arch/um/include/shared/os.h

···
 extern int os_set_exec_close(int fd);
 extern int os_ioctl_generic(int fd, unsigned int cmd, unsigned long arg);
 extern int os_get_ifname(int fd, char *namebuf);
-extern int os_set_slip(int fd);
 extern int os_mode_fd(int fd, int mode);
 
 extern int os_seek_file(int fd, unsigned long long offset);
···
 extern void report_enomem(void);
 
 /* process.c */
+pid_t os_reap_child(void);
 extern void os_alarm_process(int pid);
 extern void os_kill_process(int pid, int reap_child);
 extern void os_kill_ptraced_process(int pid, int reap_child);
···
 
 /* skas/process.c */
 extern int is_skas_winch(int pid, int fd, void *data);
-extern int start_userspace(unsigned long stub_stack);
+extern int start_userspace(struct mm_id *mm_id);
 extern void userspace(struct uml_pt_regs *regs);
 extern void new_thread(void *stack, jmp_buf *buf, void (*handler)(void));
 extern void switch_threads(jmp_buf *me, jmp_buf *you);

arch/um/include/shared/skas/mm_id.h

···
 #ifndef __MM_ID_H
 #define __MM_ID_H
 
+#define STUB_MAX_FDS 4
+
 struct mm_id {
 	int pid;
 	unsigned long stack;
 	int syscall_data_len;
+
+	/* Only used with SECCOMP mode */
+	int sock;
+	int syscall_fd_num;
+	int syscall_fd_map[STUB_MAX_FDS];
 };
 
 void __switch_mm(struct mm_id *mm_idp);
+
+void notify_mm_kill(int pid);
 
 #endif

arch/um/include/shared/skas/skas.h

···
 
 #include <sysdep/ptrace.h>
 
+extern int using_seccomp;
 extern int userspace_pid[];
 
 extern void new_thread_handler(void);

arch/um/include/shared/skas/stub-data.h

···
 #include <linux/compiler_types.h>
 #include <as-layout.h>
 #include <sysdep/tls.h>
+#include <sysdep/stub-data.h>
+#include <mm_id.h>
+
+#define FUTEX_IN_CHILD 0
+#define FUTEX_IN_KERN 1
 
 struct stub_init_data {
+	int seccomp;
+
 	unsigned long stub_start;
 
 	int stub_code_fd;
···
 	int stub_data_fd;
 	unsigned long stub_data_offset;
 
-	unsigned long segv_handler;
+	unsigned long signal_handler;
+	unsigned long signal_restorer;
 };
 
 #define STUB_NEXT_SYSCALL(s) \
···
 	int syscall_data_len;
 	/* 128 leaves enough room for additional fields in the struct */
 	struct stub_syscall syscall_data[(UM_KERN_PAGE_SIZE - 128) / sizeof(struct stub_syscall)] __aligned(16);
+
+	/* data shared with signal handler (only used in seccomp mode) */
+	short restart_wait;
+	unsigned int futex;
+	int signal;
+	unsigned short si_offset;
+	unsigned short mctx_offset;
+
+	/* seccomp architecture specific state restore */
+	struct stub_data_arch arch_data;
 
 	/* Stack for our signal handlers and for calling into . */
 	unsigned char sigstack[UM_KERN_PAGE_SIZE] __aligned(UM_KERN_PAGE_SIZE);

arch/um/kernel/Makefile

···
 obj-$(CONFIG_OF) += dtb.o
 obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
 obj-$(CONFIG_STACKTRACE) += stacktrace.o
-obj-$(CONFIG_GENERIC_PCI_IOMAP) += ioport.o
 
 USER_OBJS := config.o
 

arch/um/kernel/ioport.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (C) 2021 Intel Corporation
- * Author: Johannes Berg <[e-mail]>
- */
-#include <asm/iomap.h>
-#include <asm-generic/pci_iomap.h>
-
-void __iomem *__pci_ioport_map(struct pci_dev *dev, unsigned long port,
-			       unsigned int nr)
-{
-	return NULL;
-}

arch/um/kernel/irq.c

···
 	/* Initialize EPOLL Loop */
 	os_setup_epoll();
 }
+
+void sigchld_handler(int sig, struct siginfo *unused_si,
+		     struct uml_pt_regs *regs, void *mc)
+{
+	do_IRQ(SIGCHLD_IRQ, regs);
+}

arch/um/kernel/skas/mmu.c

···
 #include <linux/sched/signal.h>
 #include <linux/slab.h>
 
+#include <shared/irq_kern.h>
 #include <asm/pgalloc.h>
 #include <asm/sections.h>
 #include <asm/mmu_context.h>
···
 
 /* Ensure the stub_data struct covers the allocated area */
 static_assert(sizeof(struct stub_data) == STUB_DATA_PAGES * UM_KERN_PAGE_SIZE);
+
+spinlock_t mm_list_lock;
+struct list_head mm_list;
 
 int init_new_context(struct task_struct *task, struct mm_struct *mm)
 {
···
 
 	new_id->stack = stack;
 
-	block_signals_trace();
-	new_id->pid = start_userspace(stack);
-	unblock_signals_trace();
-
-	if (new_id->pid < 0) {
-		ret = new_id->pid;
-		goto out_free;
+	scoped_guard(spinlock_irqsave, &mm_list_lock) {
+		/* Insert into list, used for lookups when the child dies */
+		list_add(&mm->context.list, &mm_list);
 	}
+
+	ret = start_userspace(new_id);
+	if (ret < 0)
+		goto out_free;
 
 	/* Ensure the new MM is clean and nothing unwanted is mapped */
 	unmap(new_id, 0, STUB_START);
···
 	 * zero, resulting in a kill(0), which will result in the
 	 * whole UML suddenly dying.  Also, cover negative and
 	 * 1 cases, since they shouldn't happen either.
+	 *
+	 * Negative cases happen if the child died unexpectedly.
 	 */
-	if (mmu->id.pid < 2) {
+	if (mmu->id.pid >= 0 && mmu->id.pid < 2) {
 		printk(KERN_ERR "corrupt mm_context - pid = %d\n",
 		       mmu->id.pid);
 		return;
 	}
-	os_kill_ptraced_process(mmu->id.pid, 1);
+
+	if (mmu->id.pid > 0) {
+		os_kill_ptraced_process(mmu->id.pid, 1);
+		mmu->id.pid = -1;
+	}
+
+	if (using_seccomp && mmu->id.sock)
+		os_close_file(mmu->id.sock);
 
 	free_pages(mmu->id.stack, ilog2(STUB_DATA_PAGES));
+
+	guard(spinlock_irqsave)(&mm_list_lock);
+
+	list_del(&mm->context.list);
 }
+
+static irqreturn_t mm_sigchld_irq(int irq, void* dev)
+{
+	struct mm_context *mm_context;
+	pid_t pid;
+
+	guard(spinlock)(&mm_list_lock);
+
+	while ((pid = os_reap_child()) > 0) {
+		/*
+		* A child died, check if we have an MM with the PID. This is
+		* only relevant in SECCOMP mode (as ptrace will fail anyway).
+		*
+		* See wait_stub_done_seccomp for more details.
+		*/
+		list_for_each_entry(mm_context, &mm_list, list) {
+			if (mm_context->id.pid == pid) {
+				struct stub_data *stub_data;
+				printk("Unexpectedly lost MM child! Affected tasks will segfault.");
+
+				/* Marks the MM as dead */
+				mm_context->id.pid = -1;
+
+				/*
+				 * NOTE: If SMP is implemented, a futex_wake
+				 * needs to be added here.
+				 */
+				stub_data = (void *)mm_context->id.stack;
+				stub_data->futex = FUTEX_IN_KERN;
+
+				/*
+				 * NOTE: Currently executing syscalls by
+				 * affected tasks may finish normally.
+				 */
+				break;
+			}
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int __init init_child_tracking(void)
+{
+	int err;
+
+	spin_lock_init(&mm_list_lock);
+	INIT_LIST_HEAD(&mm_list);
+
+	err = request_irq(SIGCHLD_IRQ, mm_sigchld_irq, 0, "SIGCHLD", NULL);
+	if (err < 0)
+		panic("Failed to register SIGCHLD IRQ: %d", err);
+
+	return 0;
+}
+early_initcall(init_child_tracking)

arch/um/kernel/skas/stub.c

···
 
 #include <sysdep/stub.h>
 
-static __always_inline int syscall_handler(struct stub_data *d)
+#include <linux/futex.h>
+#include <sys/socket.h>
+#include <errno.h>
+
+/*
+ * Known security issues
+ *
+ * Userspace can jump to this address to execute *any* syscall that is
+ * permitted by the stub. As we will return afterwards, it can do
+ * whatever it likes, including:
+ * - Tricking the kernel into handing out the memory FD
+ * - Using this memory FD to read/write all physical memory
+ * - Running in parallel to the kernel processing a syscall
+ *   (possibly creating data races?)
+ * - Blocking e.g. SIGALRM to avoid time based scheduling
+ *
+ * To avoid this, the permitted location for each syscall needs to be
+ * checked for in the SECCOMP filter (which is reasonably simple). Also,
+ * more care will need to go into considerations how the code might be
+ * tricked by using a prepared stack (or even modifying the stack from
+ * another thread in case SMP support is added).
+ *
+ * As for the SIGALRM, the best counter measure will be to check in the
+ * kernel that the process is reporting back the SIGALRM in a timely
+ * fashion.
+ */
+static __always_inline int syscall_handler(int fd_map[STUB_MAX_FDS])
 {
+	struct stub_data *d = get_stub_data();
 	int i;
 	unsigned long res;
+	int fd;
 
 	for (i = 0; i < d->syscall_data_len; i++) {
 		struct stub_syscall *sc = &d->syscall_data[i];
 
 		switch (sc->syscall) {
 		case STUB_SYSCALL_MMAP:
+			if (fd_map)
+				fd = fd_map[sc->mem.fd];
+			else
+				fd = sc->mem.fd;
+
 			res = stub_syscall6(STUB_MMAP_NR,
 					    sc->mem.addr, sc->mem.length,
 					    sc->mem.prot,
 					    MAP_SHARED | MAP_FIXED,
-					    sc->mem.fd, sc->mem.offset);
+					    fd, sc->mem.offset);
 			if (res != sc->mem.addr) {
 				d->err = res;
 				d->syscall_data_len = i;
···
 void __section(".__syscall_stub")
 stub_syscall_handler(void)
 {
-	struct stub_data *d = get_stub_data();
-
-	syscall_handler(d);
+	syscall_handler(NULL);
 
 	trap_myself();
+}
+
+void __section(".__syscall_stub")
+stub_signal_interrupt(int sig, siginfo_t *info, void *p)
+{
+	struct stub_data *d = get_stub_data();
+	char rcv_data;
+	union {
+		char data[CMSG_SPACE(sizeof(int) * STUB_MAX_FDS)];
+		struct cmsghdr align;
+	} ctrl = {};
+	struct iovec iov = {
+		.iov_base = &rcv_data,
+		.iov_len = 1,
+	};
+	struct msghdr msghdr = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+		.msg_control = &ctrl,
+		.msg_controllen = sizeof(ctrl),
+	};
+	ucontext_t *uc = p;
+	struct cmsghdr *fd_msg;
+	int *fd_map;
+	int num_fds;
+	long res;
+
+	d->signal = sig;
+	d->si_offset = (unsigned long)info - (unsigned long)&d->sigstack[0];
+	d->mctx_offset = (unsigned long)&uc->uc_mcontext - (unsigned long)&d->sigstack[0];
+
+restart_wait:
+	d->futex = FUTEX_IN_KERN;
+	do {
+		res = stub_syscall3(__NR_futex, (unsigned long)&d->futex,
+				    FUTEX_WAKE, 1);
+	} while (res == -EINTR);
+
+	do {
+		res = stub_syscall4(__NR_futex, (unsigned long)&d->futex,
+				    FUTEX_WAIT, FUTEX_IN_KERN, 0);
+	} while (res == -EINTR || d->futex == FUTEX_IN_KERN);
+
+	if (res < 0 && res != -EAGAIN)
+		stub_syscall1(__NR_exit_group, 1);
+
+	if (d->syscall_data_len) {
+		/* Read passed FDs (if any) */
+		do {
+			res = stub_syscall3(__NR_recvmsg, 0, (unsigned long)&msghdr, 0);
+		} while (res == -EINTR);
+
+		/* We should never have a receive error (other than -EAGAIN) */
+		if (res < 0 && res != -EAGAIN)
+			stub_syscall1(__NR_exit_group, 1);
+
+		/* Receive the FDs */
+		num_fds = 0;
+		fd_msg = msghdr.msg_control;
+		fd_map = (void *)&CMSG_DATA(fd_msg);
+		if (res == iov.iov_len && msghdr.msg_controllen > sizeof(struct cmsghdr))
+			num_fds = (fd_msg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
+
+		/* Try running queued syscalls. */
+		res = syscall_handler(fd_map);
+
+		while (num_fds)
+			stub_syscall2(__NR_close, fd_map[--num_fds], 0);
+	} else {
+		res = 0;
+	}
+
+	if (res < 0 || d->restart_wait) {
+		/* Report SIGSYS if we restart. */
+		d->signal = SIGSYS;
+		d->restart_wait = 0;
+
+		goto restart_wait;
+	}
+
+	/* Restore arch dependent state that is not part of the mcontext */
+	stub_seccomp_restore_state(&d->arch_data);
+
+	/* Return so that the host modified mcontext is restored. */
+}
+
+void __section(".__syscall_stub")
+stub_signal_restorer(void)
+{
+	/* We must not have anything on the stack when doing rt_sigreturn */
+	stub_syscall0(__NR_rt_sigreturn);
 }

arch/um/kernel/skas/stub_exe.c

···
 #include <sys/ptrace.h>
 #include <sys/prctl.h>
+#include <sys/fcntl.h>
 #include <asm/unistd.h>
 #include <sysdep/stub.h>
 #include <stub-data.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+#include <generated/asm-offsets.h>
 
 void _start(void);
 
···
 	} sa = {
 		/* Need to set SA_RESTORER (but the handler never returns) */
 		.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO | 0x04000000,
-		/* no need to mask any signals */
-		.sa_mask = 0,
 	};
 
 	/* set a nice name */
···
 	/* Make sure this process dies if the kernel dies */
 	stub_syscall2(__NR_prctl, PR_SET_PDEATHSIG, SIGKILL);
 
+	/* Needed in SECCOMP mode (and safe to do anyway) */
+	stub_syscall5(__NR_prctl, PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+
 	/* read information from STDIN and close it */
 	res = stub_syscall3(__NR_read, 0,
 			    (unsigned long)&init_data, sizeof(init_data));
 	if (res != sizeof(init_data))
 		stub_syscall1(__NR_exit, 10);
 
-	stub_syscall1(__NR_close, 0);
+	/* In SECCOMP mode, FD 0 is a socket and is later used for FD passing */
+	if (!init_data.seccomp)
+		stub_syscall1(__NR_close, 0);
+	else
+		stub_syscall3(__NR_fcntl, 0, F_SETFL, O_NONBLOCK);
 
 	/* map stub code + data */
 	res = stub_syscall6(STUB_MMAP_NR,
···
 	if (res != init_data.stub_start + UM_KERN_PAGE_SIZE)
 		stub_syscall1(__NR_exit, 12);
 
+	/* In SECCOMP mode, we only need the signalling FD from now on */
+	if (init_data.seccomp) {
+		res = stub_syscall3(__NR_close_range, 1, ~0U, 0);
+		if (res != 0)
+			stub_syscall1(__NR_exit, 13);
+	}
+
 	/* setup signal stack inside stub data */
 	stack.ss_sp = (void *)init_data.stub_start + UM_KERN_PAGE_SIZE;
 	stub_syscall2(__NR_sigaltstack, (unsigned long)&stack, 0);
 
-	/* register SIGSEGV handler */
-	sa.sa_handler_ = (void *) init_data.segv_handler;
-	res = stub_syscall4(__NR_rt_sigaction, SIGSEGV, (unsigned long)&sa, 0,
-			    sizeof(sa.sa_mask));
-	if (res != 0)
-		stub_syscall1(__NR_exit, 13);
+	/* register signal handlers */
+	sa.sa_handler_ = (void *) init_data.signal_handler;
+	sa.sa_restorer = (void *) init_data.signal_restorer;
+	if (!init_data.seccomp) {
+		/* In ptrace mode, the SIGSEGV handler never returns */
+		sa.sa_mask = 0;
 
-	stub_syscall4(__NR_ptrace, PTRACE_TRACEME, 0, 0, 0);
+		res = stub_syscall4(__NR_rt_sigaction, SIGSEGV,
+				    (unsigned long)&sa, 0, sizeof(sa.sa_mask));
+		if (res != 0)
+			stub_syscall1(__NR_exit, 14);
+	} else {
+		/* SECCOMP mode uses rt_sigreturn, need to mask all signals */
+		sa.sa_mask = ~0ULL;
 
-	stub_syscall2(__NR_kill, stub_syscall0(__NR_getpid), SIGSTOP);
+		res = stub_syscall4(__NR_rt_sigaction, SIGSEGV,
+				    (unsigned long)&sa, 0, sizeof(sa.sa_mask));
+		if (res != 0)
+			stub_syscall1(__NR_exit, 15);
 
-	stub_syscall1(__NR_exit, 14);
+		res = stub_syscall4(__NR_rt_sigaction, SIGSYS,
+				    (unsigned long)&sa, 0, sizeof(sa.sa_mask));
+		if (res != 0)
+			stub_syscall1(__NR_exit, 16);
+
+		res = stub_syscall4(__NR_rt_sigaction, SIGALRM,
+				    (unsigned long)&sa, 0, sizeof(sa.sa_mask));
+		if (res != 0)
+			stub_syscall1(__NR_exit, 17);
+
+		res = stub_syscall4(__NR_rt_sigaction, SIGTRAP,
+				    (unsigned long)&sa, 0, sizeof(sa.sa_mask));
+		if (res != 0)
+			stub_syscall1(__NR_exit, 18);
+
+		res = stub_syscall4(__NR_rt_sigaction, SIGILL,
+				    (unsigned long)&sa, 0, sizeof(sa.sa_mask));
+		if (res != 0)
+			stub_syscall1(__NR_exit, 19);
+
+		res = stub_syscall4(__NR_rt_sigaction, SIGFPE,
+				    (unsigned long)&sa, 0, sizeof(sa.sa_mask));
+		if (res != 0)
+			stub_syscall1(__NR_exit, 20);
+	}
+
+	/*
+	 * If in seccomp mode, install the SECCOMP filter and trigger a syscall.
+	 * Otherwise set PTRACE_TRACEME and do a SIGSTOP.
+	 */
+	if (init_data.seccomp) {
+		struct sock_filter filter[] = {
+#if __BITS_PER_LONG > 32
+			/* [0] Load upper 32bit of instruction pointer from seccomp_data */
+			BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
+				 (offsetof(struct seccomp_data, instruction_pointer) + 4)),
+
+			/* [1] Jump forward 3 instructions if the upper address is not identical */
+			BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, (init_data.stub_start) >> 32, 0, 3),
+#endif
+			/* [2] Load lower 32bit of instruction pointer from seccomp_data */
+			BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
+				 (offsetof(struct seccomp_data, instruction_pointer))),
+
+			/* [3] Mask out lower bits */
+			BPF_STMT(BPF_ALU | BPF_AND | BPF_K, 0xfffff000),
+
+			/* [4] Jump to [6] if the lower bits are not on the expected page */
+			BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, (init_data.stub_start) & 0xfffff000, 1, 0),
+
+			/* [5] Trap call, allow */
+			BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_TRAP),
+
+			/* [6,7] Check architecture */
+			BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
+				 offsetof(struct seccomp_data, arch)),
+			BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K,
+				 UM_SECCOMP_ARCH_NATIVE, 1, 0),
+
+			/* [8] Kill (for architecture check) */
+			BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_KILL_PROCESS),
+
+			/* [9] Load syscall number */
+			BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
+				 offsetof(struct seccomp_data, nr)),
+
+			/* [10-16] Check against permitted syscalls */
+			BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_futex,
+				 7, 0),
+			BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K,__NR_recvmsg,
+				 6, 0),
+			BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K,__NR_close,
+				 5, 0),
+			BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, STUB_MMAP_NR,
+				 4, 0),
+			BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_munmap,
+				 3, 0),
+#ifdef __i386__
+			BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_set_thread_area,
+				 2, 0),
+#else
+			BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_arch_prctl,
+				 2, 0),
+#endif
+			BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_rt_sigreturn,
+				 1, 0),
+
+			/* [17] Not one of the permitted syscalls */
+			BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_KILL_PROCESS),
+
+			/* [18] Permitted call for the stub */
+			BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
+		};
+		struct sock_fprog prog = {
+			.len = sizeof(filter) / sizeof(filter[0]),
+			.filter = filter,
+		};
+
+		if (stub_syscall3(__NR_seccomp, SECCOMP_SET_MODE_FILTER,
+				  SECCOMP_FILTER_FLAG_TSYNC,
+				  (unsigned long)&prog) != 0)
+			stub_syscall1(__NR_exit, 21);
+
+		/* Fall through, the exit syscall will cause SIGSYS */
+	} else {
+		stub_syscall4(__NR_ptrace, PTRACE_TRACEME, 0, 0, 0);
+
+		stub_syscall2(__NR_kill, stub_syscall0(__NR_getpid), SIGSTOP);
+	}
+
+	stub_syscall1(__NR_exit, 30);
 
 	__builtin_unreachable();
 }

arch/um/kernel/time.c

···
 
 static irqreturn_t um_timer(int irq, void *dev)
 {
-	if (get_current()->mm != NULL)
-	{
-        /* userspace - relay signal, results in correct userspace timers */
+	/*
+	 * Interrupt the (possibly) running userspace process, technically this
+	 * should only happen if userspace is currently executing.
+	 * With infinite CPU time-travel, we can only get here when userspace
+	 * is not executing. Do not notify there and avoid spurious scheduling.
+	 */
+	if (time_travel_mode != TT_MODE_INFCPU &&
+	    time_travel_mode != TT_MODE_EXTERNAL &&
+	    get_current()->mm)
 		os_alarm_process(get_current()->mm->context.id.pid);
-	}
 
 	(*timer_clockevent.event_handler)(&timer_clockevent);
 

arch/um/kernel/trap.c

···
 #include <kern_util.h>
 #include <os.h>
 #include <skas.h>
-#include <arch.h>
+
+/*
+ * NOTE: UML does not have exception tables. As such, this is almost a copy
+ * of the code in mm/memory.c, only adjusting the logic to simply check whether
+ * we are coming from the kernel instead of doing an additional lookup in the
+ * exception table.
+ * We can do this simplification because we never get here if the exception was
+ * fixable.
+ */
+static inline bool get_mmap_lock_carefully(struct mm_struct *mm, bool is_user)
+{
+	if (likely(mmap_read_trylock(mm)))
+		return true;
+
+	if (!is_user)
+		return false;
+
+	return !mmap_read_lock_killable(mm);
+}
+
+static inline bool mmap_upgrade_trylock(struct mm_struct *mm)
+{
+	/*
+	 * We don't have this operation yet.
+	 *
+	 * It should be easy enough to do: it's basically a
+	 *    atomic_long_try_cmpxchg_acquire()
+	 * from RWSEM_READER_BIAS -> RWSEM_WRITER_LOCKED, but
+	 * it also needs the proper lockdep magic etc.
+	 */
+	return false;
+}
+
+static inline bool upgrade_mmap_lock_carefully(struct mm_struct *mm, bool is_user)
+{
+	mmap_read_unlock(mm);
+	if (!is_user)
+		return false;
+
+	return !mmap_write_lock_killable(mm);
+}
+
+/*
+ * Helper for page fault handling.
+ *
+ * This is kind of equivalend to "mmap_read_lock()" followed
+ * by "find_extend_vma()", except it's a lot more careful about
+ * the locking (and will drop the lock on failure).
+ *
+ * For example, if we have a kernel bug that causes a page
+ * fault, we don't want to just use mmap_read_lock() to get
+ * the mm lock, because that would deadlock if the bug were
+ * to happen while we're holding the mm lock for writing.
+ *
+ * So this checks the exception tables on kernel faults in
+ * order to only do this all for instructions that are actually
+ * expected to fault.
+ *
+ * We can also actually take the mm lock for writing if we
+ * need to extend the vma, which helps the VM layer a lot.
+ */
+static struct vm_area_struct *
+um_lock_mm_and_find_vma(struct mm_struct *mm,
+			unsigned long addr, bool is_user)
+{
+	struct vm_area_struct *vma;
+
+	if (!get_mmap_lock_carefully(mm, is_user))
+		return NULL;
+
+	vma = find_vma(mm, addr);
+	if (likely(vma && (vma->vm_start <= addr)))
+		return vma;
+
+	/*
+	 * Well, dang. We might still be successful, but only
+	 * if we can extend a vma to do so.
+	 */
+	if (!vma || !(vma->vm_flags & VM_GROWSDOWN)) {
+		mmap_read_unlock(mm);
+		return NULL;
+	}
+
+	/*
+	 * We can try to upgrade the mmap lock atomically,
+	 * in which case we can continue to use the vma
+	 * we already looked up.
+	 *
+	 * Otherwise we'll have to drop the mmap lock and
+	 * re-take it, and also look up the vma again,
+	 * re-checking it.
+	 */
+	if (!mmap_upgrade_trylock(mm)) {
+		if (!upgrade_mmap_lock_carefully(mm, is_user))
+			return NULL;
+
+		vma = find_vma(mm, addr);
+		if (!vma)
+			goto fail;
+		if (vma->vm_start <= addr)
+			goto success;
+		if (!(vma->vm_flags & VM_GROWSDOWN))
+			goto fail;
+	}
+
+	if (expand_stack_locked(vma, addr))
+		goto fail;
+
+success:
+	mmap_write_downgrade(mm);
+	return vma;
+
+fail:
+	mmap_write_unlock(mm);
+	return NULL;
+}
 
 /*
  * Note this is constrained to return 0, -EFAULT, -EACCES, -ENOMEM by
···
 	if (is_user)
 		flags |= FAULT_FLAG_USER;
 retry:
-	mmap_read_lock(mm);
-	vma = find_vma(mm, address);
-	if (!vma)
-		goto out;
-	if (vma->vm_start <= address)
-		goto good_area;
-	if (!(vma->vm_flags & VM_GROWSDOWN))
-		goto out;
-	if (is_user && !ARCH_IS_STACKGROW(address))
-		goto out;
-	vma = expand_stack(mm, address);
+	vma = um_lock_mm_and_find_vma(mm, address, is_user);
 	if (!vma)
 		goto out_nosemaphore;
 
-good_area:
 	*code_out = SEGV_ACCERR;
 	if (is_write) {
 		if (!(vma->vm_flags & VM_WRITE))

arch/um/os-Linux/Makefile

···
 
 obj-y = execvp.o file.o helper.o irq.o main.o mem.o process.o \
 	registers.o sigio.o signal.o start_up.o time.o tty.o \
-	umid.o user_syms.o util.o drivers/ skas/
+	umid.o user_syms.o util.o skas/
 
 CFLAGS_signal.o += -Wframe-larger-than=4096
 

arch/um/os-Linux/drivers/Makefile

···
-# SPDX-License-Identifier: GPL-2.0
-# 
-# Copyright (C) 2000, 2002 Jeff Dike ([e-mail])
-#
-
-ethertap-objs := ethertap_kern.o ethertap_user.o
-tuntap-objs := tuntap_kern.o tuntap_user.o
-
-obj-y = 
-obj-$(CONFIG_UML_NET_ETHERTAP) += ethertap.o
-obj-$(CONFIG_UML_NET_TUNTAP) += tuntap.o
-
-include $(srctree)/arch/um/scripts/Makefile.rules

arch/um/os-Linux/drivers/etap.h

···
-/* SPDX-License-Identifier: GPL-2.0 */
-/* 
- * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- */
-
-#ifndef __DRIVERS_ETAP_H
-#define __DRIVERS_ETAP_H
-
-#include <net_user.h>
-
-struct ethertap_data {
-	char *dev_name;
-	char *gate_addr;
-	int data_fd;
-	int control_fd;
-	void *dev;
-};
-
-extern const struct net_user_info ethertap_user_info;
-
-#endif

arch/um/os-Linux/drivers/ethertap_kern.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (C) 2001 Lennert Buytenhek ([e-mail]) and
- * James Leu ([e-mail]).
- * 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 "etap.h"
-#include <net_kern.h>
-
-struct ethertap_init {
-	char *dev_name;
-	char *gate_addr;
-};
-
-static void etap_init(struct net_device *dev, void *data)
-{
-	struct uml_net_private *pri;
-	struct ethertap_data *epri;
-	struct ethertap_init *init = data;
-
-	pri = netdev_priv(dev);
-	epri = (struct ethertap_data *) pri->user;
-	epri->dev_name = init->dev_name;
-	epri->gate_addr = init->gate_addr;
-	epri->data_fd = -1;
-	epri->control_fd = -1;
-	epri->dev = dev;
-
-	printk(KERN_INFO "ethertap backend - %s", epri->dev_name);
-	if (epri->gate_addr != NULL)
-		printk(KERN_CONT ", IP = %s", epri->gate_addr);
-	printk(KERN_CONT "\n");
-}
-
-static int etap_read(int fd, struct sk_buff *skb, struct uml_net_private *lp)
-{
-	int len;
-
-	len = net_recvfrom(fd, skb_mac_header(skb),
-			   skb->dev->mtu + 2 + ETH_HEADER_ETHERTAP);
-	if (len <= 0)
-		return(len);
-
-	skb_pull(skb, 2);
-	len -= 2;
-	return len;
-}
-
-static int etap_write(int fd, struct sk_buff *skb, struct uml_net_private *lp)
-{
-	skb_push(skb, 2);
-	return net_send(fd, skb->data, skb->len);
-}
-
-const struct net_kern_info ethertap_kern_info = {
-	.init			= etap_init,
-	.protocol		= eth_protocol,
-	.read			= etap_read,
-	.write 			= etap_write,
-};
-
-static int ethertap_setup(char *str, char **mac_out, void *data)
-{
-	struct ethertap_init *init = data;
-
-	*init = ((struct ethertap_init)
-		{ .dev_name 	= NULL,
-		  .gate_addr 	= NULL });
-	if (tap_setup_common(str, "ethertap", &init->dev_name, mac_out,
-			    &init->gate_addr))
-		return 0;
-	if (init->dev_name == NULL) {
-		printk(KERN_ERR "ethertap_setup : Missing tap device name\n");
-		return 0;
-	}
-
-	return 1;
-}
-
-static struct transport ethertap_transport = {
-	.list 		= LIST_HEAD_INIT(ethertap_transport.list),
-	.name 		= "ethertap",
-	.setup  	= ethertap_setup,
-	.user 		= &ethertap_user_info,
-	.kern 		= &ethertap_kern_info,
-	.private_size 	= sizeof(struct ethertap_data),
-	.setup_size 	= sizeof(struct ethertap_init),
-};
-
-static int register_ethertap(void)
-{
-	register_transport(&ethertap_transport);
-	return 0;
-}
-
-late_initcall(register_ethertap);

arch/um/os-Linux/drivers/ethertap_user.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- * Copyright (C) 2001 Lennert Buytenhek ([e-mail]) and
- * James Leu ([e-mail]).
- * Copyright (C) 2001 by various other people who didn't put their name here.
- */
-
-#include <stdio.h>
-#include <unistd.h>
-#include <errno.h>
-#include <string.h>
-#include <sys/socket.h>
-#include <sys/wait.h>
-#include "etap.h"
-#include <os.h>
-#include <net_user.h>
-#include <um_malloc.h>
-
-#define MAX_PACKET ETH_MAX_PACKET
-
-static int etap_user_init(void *data, void *dev)
-{
-	struct ethertap_data *pri = data;
-
-	pri->dev = dev;
-	return 0;
-}
-
-struct addr_change {
-	enum { ADD_ADDR, DEL_ADDR } what;
-	unsigned char addr[4];
-	unsigned char netmask[4];
-};
-
-static void etap_change(int op, unsigned char *addr, unsigned char *netmask,
-			int fd)
-{
-	struct addr_change change;
-	char *output;
-	int n;
-
-	change.what = op;
-	memcpy(change.addr, addr, sizeof(change.addr));
-	memcpy(change.netmask, netmask, sizeof(change.netmask));
-	CATCH_EINTR(n = write(fd, &change, sizeof(change)));
-	if (n != sizeof(change)) {
-		printk(UM_KERN_ERR "etap_change - request failed, err = %d\n",
-		       errno);
-		return;
-	}
-
-	output = uml_kmalloc(UM_KERN_PAGE_SIZE, UM_GFP_KERNEL);
-	if (output == NULL)
-		printk(UM_KERN_ERR "etap_change : Failed to allocate output "
-		       "buffer\n");
-	read_output(fd, output, UM_KERN_PAGE_SIZE);
-	if (output != NULL) {
-		printk("%s", output);
-		kfree(output);
-	}
-}
-
-static void etap_open_addr(unsigned char *addr, unsigned char *netmask,
-			   void *arg)
-{
-	etap_change(ADD_ADDR, addr, netmask, *((int *) arg));
-}
-
-static void etap_close_addr(unsigned char *addr, unsigned char *netmask,
-			    void *arg)
-{
-	etap_change(DEL_ADDR, addr, netmask, *((int *) arg));
-}
-
-struct etap_pre_exec_data {
-	int control_remote;
-	int control_me;
-	int data_me;
-};
-
-static void etap_pre_exec(void *arg)
-{
-	struct etap_pre_exec_data *data = arg;
-
-	dup2(data->control_remote, 1);
-	close(data->data_me);
-	close(data->control_me);
-}
-
-static int etap_tramp(char *dev, char *gate, int control_me,
-		      int control_remote, int data_me, int data_remote)
-{
-	struct etap_pre_exec_data pe_data;
-	int pid, err, n;
-	char version_buf[sizeof("nnnnn\0")];
-	char data_fd_buf[sizeof("nnnnnn\0")];
-	char gate_buf[sizeof("nnn.nnn.nnn.nnn\0")];
-	char *setup_args[] = { "uml_net", version_buf, "ethertap", dev,
-			       data_fd_buf, gate_buf, NULL };
-	char *nosetup_args[] = { "uml_net", version_buf, "ethertap",
-				 dev, data_fd_buf, NULL };
-	char **args, c;
-
-	sprintf(data_fd_buf, "%d", data_remote);
-	sprintf(version_buf, "%d", UML_NET_VERSION);
-	if (gate != NULL) {
-		strscpy(gate_buf, gate);
-		args = setup_args;
-	}
-	else args = nosetup_args;
-
-	err = 0;
-	pe_data.control_remote = control_remote;
-	pe_data.control_me = control_me;
-	pe_data.data_me = data_me;
-	pid = run_helper(etap_pre_exec, &pe_data, args);
-
-	if (pid < 0)
-		err = pid;
-	close(data_remote);
-	close(control_remote);
-	CATCH_EINTR(n = read(control_me, &c, sizeof(c)));
-	if (n != sizeof(c)) {
-		err = -errno;
-		printk(UM_KERN_ERR "etap_tramp : read of status failed, "
-		       "err = %d\n", -err);
-		return err;
-	}
-	if (c != 1) {
-		printk(UM_KERN_ERR "etap_tramp : uml_net failed\n");
-		err = helper_wait(pid);
-	}
-	return err;
-}
-
-static int etap_open(void *data)
-{
-	struct ethertap_data *pri = data;
-	char *output;
-	int data_fds[2], control_fds[2], err, output_len;
-
-	err = tap_open_common(pri->dev, pri->gate_addr);
-	if (err)
-		return err;
-
-	err = socketpair(AF_UNIX, SOCK_DGRAM, 0, data_fds);
-	if (err) {
-		err = -errno;
-		printk(UM_KERN_ERR "etap_open - data socketpair failed - "
-		       "err = %d\n", errno);
-		return err;
-	}
-
-	err = socketpair(AF_UNIX, SOCK_STREAM, 0, control_fds);
-	if (err) {
-		err = -errno;
-		printk(UM_KERN_ERR "etap_open - control socketpair failed - "
-		       "err = %d\n", errno);
-		goto out_close_data;
-	}
-
-	err = etap_tramp(pri->dev_name, pri->gate_addr, control_fds[0],
-			 control_fds[1], data_fds[0], data_fds[1]);
-	output_len = UM_KERN_PAGE_SIZE;
-	output = uml_kmalloc(output_len, UM_GFP_KERNEL);
-	read_output(control_fds[0], output, output_len);
-
-	if (output == NULL)
-		printk(UM_KERN_ERR "etap_open : failed to allocate output "
-		       "buffer\n");
-	else {
-		printk("%s", output);
-		kfree(output);
-	}
-
-	if (err < 0) {
-		printk(UM_KERN_ERR "etap_tramp failed - err = %d\n", -err);
-		goto out_close_control;
-	}
-
-	pri->data_fd = data_fds[0];
-	pri->control_fd = control_fds[0];
-	iter_addresses(pri->dev, etap_open_addr, &pri->control_fd);
-	return data_fds[0];
-
-out_close_control:
-	close(control_fds[0]);
-	close(control_fds[1]);
-out_close_data:
-	close(data_fds[0]);
-	close(data_fds[1]);
-	return err;
-}
-
-static void etap_close(int fd, void *data)
-{
-	struct ethertap_data *pri = data;
-
-	iter_addresses(pri->dev, etap_close_addr, &pri->control_fd);
-	close(fd);
-
-	if (shutdown(pri->data_fd, SHUT_RDWR) < 0)
-		printk(UM_KERN_ERR "etap_close - shutdown data socket failed, "
-		       "errno = %d\n", errno);
-
-	if (shutdown(pri->control_fd, SHUT_RDWR) < 0)
-		printk(UM_KERN_ERR "etap_close - shutdown control socket "
-		       "failed, errno = %d\n", errno);
-
-	close(pri->data_fd);
-	pri->data_fd = -1;
-	close(pri->control_fd);
-	pri->control_fd = -1;
-}
-
-static void etap_add_addr(unsigned char *addr, unsigned char *netmask,
-			  void *data)
-{
-	struct ethertap_data *pri = data;
-
-	tap_check_ips(pri->gate_addr, addr);
-	if (pri->control_fd == -1)
-		return;
-	etap_open_addr(addr, netmask, &pri->control_fd);
-}
-
-static void etap_del_addr(unsigned char *addr, unsigned char *netmask,
-			  void *data)
-{
-	struct ethertap_data *pri = data;
-
-	if (pri->control_fd == -1)
-		return;
-
-	etap_close_addr(addr, netmask, &pri->control_fd);
-}
-
-const struct net_user_info ethertap_user_info = {
-	.init		= etap_user_init,
-	.open		= etap_open,
-	.close	 	= etap_close,
-	.remove	 	= NULL,
-	.add_address	= etap_add_addr,
-	.delete_address = etap_del_addr,
-	.mtu		= ETH_MAX_PACKET,
-	.max_packet	= ETH_MAX_PACKET + ETH_HEADER_ETHERTAP,
-};

arch/um/os-Linux/drivers/tuntap.h

···
-/* SPDX-License-Identifier: GPL-2.0 */
-/* 
- * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- */
-
-#ifndef __UM_TUNTAP_H
-#define __UM_TUNTAP_H
-
-#include <net_user.h>
-
-struct tuntap_data {
-	char *dev_name;
-	int fixed_config;
-	char *gate_addr;
-	int fd;
-	void *dev;
-};
-
-extern const struct net_user_info tuntap_user_info;
-
-#endif

arch/um/os-Linux/drivers/tuntap_kern.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- */
-
-#include <linux/netdevice.h>
-#include <linux/init.h>
-#include <linux/skbuff.h>
-#include <asm/errno.h>
-#include <net_kern.h>
-#include "tuntap.h"
-
-struct tuntap_init {
-	char *dev_name;
-	char *gate_addr;
-};
-
-static void tuntap_init(struct net_device *dev, void *data)
-{
-	struct uml_net_private *pri;
-	struct tuntap_data *tpri;
-	struct tuntap_init *init = data;
-
-	pri = netdev_priv(dev);
-	tpri = (struct tuntap_data *) pri->user;
-	tpri->dev_name = init->dev_name;
-	tpri->fixed_config = (init->dev_name != NULL);
-	tpri->gate_addr = init->gate_addr;
-	tpri->fd = -1;
-	tpri->dev = dev;
-
-	printk(KERN_INFO "TUN/TAP backend - ");
-	if (tpri->gate_addr != NULL)
-		printk(KERN_CONT "IP = %s", tpri->gate_addr);
-	printk(KERN_CONT "\n");
-}
-
-static int tuntap_read(int fd, struct sk_buff *skb, struct uml_net_private *lp)
-{
-	return net_read(fd, skb_mac_header(skb),
-			skb->dev->mtu + ETH_HEADER_OTHER);
-}
-
-static int tuntap_write(int fd, struct sk_buff *skb, struct uml_net_private *lp)
-{
-	return net_write(fd, skb->data, skb->len);
-}
-
-const struct net_kern_info tuntap_kern_info = {
-	.init			= tuntap_init,
-	.protocol		= eth_protocol,
-	.read			= tuntap_read,
-	.write 			= tuntap_write,
-};
-
-static int tuntap_setup(char *str, char **mac_out, void *data)
-{
-	struct tuntap_init *init = data;
-
-	*init = ((struct tuntap_init)
-		{ .dev_name 	= NULL,
-		  .gate_addr 	= NULL });
-	if (tap_setup_common(str, "tuntap", &init->dev_name, mac_out,
-			    &init->gate_addr))
-		return 0;
-
-	return 1;
-}
-
-static struct transport tuntap_transport = {
-	.list 		= LIST_HEAD_INIT(tuntap_transport.list),
-	.name 		= "tuntap",
-	.setup  	= tuntap_setup,
-	.user 		= &tuntap_user_info,
-	.kern 		= &tuntap_kern_info,
-	.private_size 	= sizeof(struct tuntap_data),
-	.setup_size 	= sizeof(struct tuntap_init),
-};
-
-static int register_tuntap(void)
-{
-	register_transport(&tuntap_transport);
-	return 0;
-}
-
-late_initcall(register_tuntap);

arch/um/os-Linux/drivers/tuntap_user.c

···
-// SPDX-License-Identifier: GPL-2.0
-/* 
- * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- */
-
-#include <stdio.h>
-#include <unistd.h>
-#include <errno.h>
-#include <string.h>
-#include <linux/if_tun.h>
-#include <net/if.h>
-#include <sys/ioctl.h>
-#include <sys/socket.h>
-#include <sys/wait.h>
-#include <sys/uio.h>
-#include <kern_util.h>
-#include <os.h>
-#include "tuntap.h"
-
-static int tuntap_user_init(void *data, void *dev)
-{
-	struct tuntap_data *pri = data;
-
-	pri->dev = dev;
-	return 0;
-}
-
-static void tuntap_add_addr(unsigned char *addr, unsigned char *netmask,
-			    void *data)
-{
-	struct tuntap_data *pri = data;
-
-	tap_check_ips(pri->gate_addr, addr);
-	if ((pri->fd == -1) || pri->fixed_config)
-		return;
-	open_addr(addr, netmask, pri->dev_name);
-}
-
-static void tuntap_del_addr(unsigned char *addr, unsigned char *netmask,
-			    void *data)
-{
-	struct tuntap_data *pri = data;
-
-	if ((pri->fd == -1) || pri->fixed_config)
-		return;
-	close_addr(addr, netmask, pri->dev_name);
-}
-
-struct tuntap_pre_exec_data {
-	int stdout_fd;
-	int close_me;
-};
-
-static void tuntap_pre_exec(void *arg)
-{
-	struct tuntap_pre_exec_data *data = arg;
-
-	dup2(data->stdout_fd, 1);
-	close(data->close_me);
-}
-
-static int tuntap_open_tramp(char *gate, int *fd_out, int me, int remote,
-			     char *buffer, int buffer_len, int *used_out)
-{
-	struct tuntap_pre_exec_data data;
-	char version_buf[sizeof("nnnnn\0")];
-	char *argv[] = { "uml_net", version_buf, "tuntap", "up", gate,
-			 NULL };
-	char buf[CMSG_SPACE(sizeof(*fd_out))];
-	struct msghdr msg;
-	struct cmsghdr *cmsg;
-	struct iovec iov;
-	int pid, n, err;
-
-	sprintf(version_buf, "%d", UML_NET_VERSION);
-
-	data.stdout_fd = remote;
-	data.close_me = me;
-
-	pid = run_helper(tuntap_pre_exec, &data, argv);
-
-	if (pid < 0)
-		return pid;
-
-	close(remote);
-
-	msg.msg_name = NULL;
-	msg.msg_namelen = 0;
-	if (buffer != NULL) {
-		iov = ((struct iovec) { buffer, buffer_len });
-		msg.msg_iov = &iov;
-		msg.msg_iovlen = 1;
-	}
-	else {
-		msg.msg_iov = NULL;
-		msg.msg_iovlen = 0;
-	}
-	msg.msg_control = buf;
-	msg.msg_controllen = sizeof(buf);
-	msg.msg_flags = 0;
-	n = recvmsg(me, &msg, 0);
-	*used_out = n;
-	if (n < 0) {
-		err = -errno;
-		printk(UM_KERN_ERR "tuntap_open_tramp : recvmsg failed - "
-		       "errno = %d\n", errno);
-		return err;
-	}
-	helper_wait(pid);
-
-	cmsg = CMSG_FIRSTHDR(&msg);
-	if (cmsg == NULL) {
-		printk(UM_KERN_ERR "tuntap_open_tramp : didn't receive a "
-		       "message\n");
-		return -EINVAL;
-	}
-	if ((cmsg->cmsg_level != SOL_SOCKET) ||
-	   (cmsg->cmsg_type != SCM_RIGHTS)) {
-		printk(UM_KERN_ERR "tuntap_open_tramp : didn't receive a "
-		       "descriptor\n");
-		return -EINVAL;
-	}
-	*fd_out = ((int *) CMSG_DATA(cmsg))[0];
-	os_set_exec_close(*fd_out);
-	return 0;
-}
-
-static int tuntap_open(void *data)
-{
-	struct ifreq ifr;
-	struct tuntap_data *pri = data;
-	char *output, *buffer;
-	int err, fds[2], len, used;
-
-	err = tap_open_common(pri->dev, pri->gate_addr);
-	if (err < 0)
-		return err;
-
-	if (pri->fixed_config) {
-		pri->fd = os_open_file("/dev/net/tun",
-				       of_cloexec(of_rdwr(OPENFLAGS())), 0);
-		if (pri->fd < 0) {
-			printk(UM_KERN_ERR "Failed to open /dev/net/tun, "
-			       "err = %d\n", -pri->fd);
-			return pri->fd;
-		}
-		memset(&ifr, 0, sizeof(ifr));
-		ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
-		strscpy(ifr.ifr_name, pri->dev_name);
-		if (ioctl(pri->fd, TUNSETIFF, &ifr) < 0) {
-			err = -errno;
-			printk(UM_KERN_ERR "TUNSETIFF failed, errno = %d\n",
-			       errno);
-			close(pri->fd);
-			return err;
-		}
-	}
-	else {
-		err = socketpair(AF_UNIX, SOCK_DGRAM, 0, fds);
-		if (err) {
-			err = -errno;
-			printk(UM_KERN_ERR "tuntap_open : socketpair failed - "
-			       "errno = %d\n", errno);
-			return err;
-		}
-
-		buffer = get_output_buffer(&len);
-		if (buffer != NULL)
-			len--;
-		used = 0;
-
-		err = tuntap_open_tramp(pri->gate_addr, &pri->fd, fds[0],
-					fds[1], buffer, len, &used);
-
-		output = buffer;
-		if (err < 0) {
-			printk("%s", output);
-			free_output_buffer(buffer);
-			printk(UM_KERN_ERR "tuntap_open_tramp failed - "
-			       "err = %d\n", -err);
-			return err;
-		}
-
-		pri->dev_name = uml_strdup(buffer);
-		output += IFNAMSIZ;
-		printk("%s", output);
-		free_output_buffer(buffer);
-
-		close(fds[0]);
-		iter_addresses(pri->dev, open_addr, pri->dev_name);
-	}
-
-	return pri->fd;
-}
-
-static void tuntap_close(int fd, void *data)
-{
-	struct tuntap_data *pri = data;
-
-	if (!pri->fixed_config)
-		iter_addresses(pri->dev, close_addr, pri->dev_name);
-	close(fd);
-	pri->fd = -1;
-}
-
-const struct net_user_info tuntap_user_info = {
-	.init		= tuntap_user_init,
-	.open		= tuntap_open,
-	.close	 	= tuntap_close,
-	.remove	 	= NULL,
-	.add_address	= tuntap_add_addr,
-	.delete_address = tuntap_del_addr,
-	.mtu		= ETH_MAX_PACKET,
-	.max_packet	= ETH_MAX_PACKET + ETH_HEADER_OTHER,
-};

arch/um/os-Linux/file.c

···
 	return 0;
 }
 
-int os_set_slip(int fd)
-{
-	int disc, sencap;
-
-	disc = N_SLIP;
-	if (ioctl(fd, TIOCSETD, &disc) < 0)
-		return -errno;
-
-	sencap = 0;
-	if (ioctl(fd, SIOCSIFENCAP, &sencap) < 0)
-		return -errno;
-
-	return 0;
-}
-
 int os_mode_fd(int fd, int mode)
 {
 	int err;

arch/um/os-Linux/internal.h

···
 #ifndef __UM_OS_LINUX_INTERNAL_H
 #define __UM_OS_LINUX_INTERNAL_H
 
+#include <mm_id.h>
+#include <stub-data.h>
+
 /*
  * elf_aux.c
  */
···
  * skas/process.c
  */
 void wait_stub_done(int pid);
-
+void wait_stub_done_seccomp(struct mm_id *mm_idp, int running, int wait_sigsys);
 #endif /* __UM_OS_LINUX_INTERNAL_H */

arch/um/os-Linux/process.c

···
 #include <init.h>
 #include <longjmp.h>
 #include <os.h>
+#include <skas/skas.h>
 
 void os_alarm_process(int pid)
 {
+	if (pid <= 0)
+		return;
+
 	kill(pid, SIGALRM);
 }
 
 void os_kill_process(int pid, int reap_child)
 {
+	if (pid <= 0)
+		return;
+
+	/* Block signals until child is reaped */
+	block_signals();
+
 	kill(pid, SIGKILL);
 	if (reap_child)
 		CATCH_EINTR(waitpid(pid, NULL, __WALL));
+
+	unblock_signals();
 }
 
 /* Kill off a ptraced child by all means available.  kill it normally first,
···
 
 void os_kill_ptraced_process(int pid, int reap_child)
 {
+	if (pid <= 0)
+		return;
+
+	/* Block signals until child is reaped */
+	block_signals();
+
 	kill(pid, SIGKILL);
 	ptrace(PTRACE_KILL, pid);
 	ptrace(PTRACE_CONT, pid);
 	if (reap_child)
 		CATCH_EINTR(waitpid(pid, NULL, __WALL));
+
+	unblock_signals();
+}
+
+pid_t os_reap_child(void)
+{
+	int status;
+
+	/* Try to reap a child */
+	return waitpid(-1, &status, WNOHANG);
 }
 
 /* Don't use the glibc version, which caches the result in TLS. It misses some
···
 	set_handler(SIGBUS);
 	signal(SIGHUP, SIG_IGN);
 	set_handler(SIGIO);
+	/* We (currently) only use the child reaper IRQ in seccomp mode */
+	if (using_seccomp)
+		set_handler(SIGCHLD);
 	signal(SIGWINCH, SIG_IGN);
 }
 

arch/um/os-Linux/registers.c

···
 
 /* This is set once at boot time and not changed thereafter */
 
-static unsigned long exec_regs[MAX_REG_NR];
-static unsigned long *exec_fp_regs;
+unsigned long exec_regs[MAX_REG_NR];
+unsigned long *exec_fp_regs;
 
 int init_pid_registers(int pid)
 {

arch/um/os-Linux/sigio.c

···
 #include <signal.h>
 #include <string.h>
 #include <sys/epoll.h>
+#include <asm/unistd.h>
 #include <kern_util.h>
 #include <init.h>
 #include <os.h>
···
 			       __func__, errno);
 		}
 
-		CATCH_EINTR(r = tgkill(pid, pid, SIGIO));
+		CATCH_EINTR(r = syscall(__NR_tgkill, pid, pid, SIGIO));
 		if (r < 0)
 			printk(UM_KERN_ERR "%s: tgkill failed, errno = %d\n",
 			       __func__, errno);

arch/um/os-Linux/signal.c

···
 	[SIGBUS]	= relay_signal,
 	[SIGSEGV]	= segv_handler,
 	[SIGIO]		= sigio_handler,
+	[SIGCHLD]	= sigchld_handler,
 };
 
 static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
···
 	}
 
 	/* enable signals if sig isn't IRQ signal */
-	if ((sig != SIGIO) && (sig != SIGWINCH))
+	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGCHLD))
 		unblock_signals_trace();
 
 	(*sig_info[sig])(sig, si, &r, mc);
···
 
 #define SIGALRM_BIT 1
 #define SIGALRM_MASK (1 << SIGALRM_BIT)
+
+#define SIGCHLD_BIT 2
+#define SIGCHLD_MASK (1 << SIGCHLD_BIT)
 
 int signals_enabled;
 #if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
···
 			sigio_run_timetravel_handlers();
 		else
 			signals_pending |= SIGIO_MASK;
+		return;
+	}
+
+	if (!enabled && (sig == SIGCHLD)) {
+		signals_pending |= SIGCHLD_MASK;
 		return;
 	}
 
···
 
 	[SIGIO] = sig_handler,
 	[SIGWINCH] = sig_handler,
+	/* SIGCHLD is only actually registered in seccomp mode. */
+	[SIGCHLD] = sig_handler,
 	[SIGALRM] = timer_alarm_handler,
 
 	[SIGUSR1] = sigusr1_handler,
···
 		 */
 		if (save_pending & SIGIO_MASK)
 			sig_handler_common(SIGIO, NULL, NULL);
+
+		if (save_pending & SIGCHLD_MASK) {
+			struct uml_pt_regs regs = {};
+
+			sigchld_handler(SIGCHLD, NULL, &regs, NULL);
+		}
 
 		/* Do not reenter the handler */
 

arch/um/os-Linux/skas/mem.c

···
 
 	print_hex_dump(UM_KERN_ERR, "    syscall data: ", 0,
 		       16, 4, sc, sizeof(*sc), 0);
+
+	if (using_seccomp) {
+		printk(UM_KERN_ERR "%s: FD map num: %d", __func__,
+		       mm_idp->syscall_fd_num);
+		print_hex_dump(UM_KERN_ERR,
+				"    FD map: ", 0, 16,
+				sizeof(mm_idp->syscall_fd_map[0]),
+				mm_idp->syscall_fd_map,
+				sizeof(mm_idp->syscall_fd_map), 0);
+	}
 }
 
 static inline unsigned long *check_init_stack(struct mm_id * mm_idp,
···
 	int n, i;
 	int err, pid = mm_idp->pid;
 
-	n = ptrace_setregs(pid, syscall_regs);
-	if (n < 0) {
-		printk(UM_KERN_ERR "Registers - \n");
-		for (i = 0; i < MAX_REG_NR; i++)
-			printk(UM_KERN_ERR "\t%d\t0x%lx\n", i, syscall_regs[i]);
-		panic("%s : PTRACE_SETREGS failed, errno = %d\n",
-		      __func__, -n);
-	}
-
 	/* Inform process how much we have filled in. */
 	proc_data->syscall_data_len = mm_idp->syscall_data_len;
 
-	err = ptrace(PTRACE_CONT, pid, 0, 0);
-	if (err)
-		panic("Failed to continue stub, pid = %d, errno = %d\n", pid,
-		      errno);
+	if (using_seccomp) {
+		proc_data->restart_wait = 1;
+		wait_stub_done_seccomp(mm_idp, 0, 1);
+	} else {
+		n = ptrace_setregs(pid, syscall_regs);
+		if (n < 0) {
+			printk(UM_KERN_ERR "Registers -\n");
+			for (i = 0; i < MAX_REG_NR; i++)
+				printk(UM_KERN_ERR "\t%d\t0x%lx\n", i, syscall_regs[i]);
+			panic("%s : PTRACE_SETREGS failed, errno = %d\n",
+			      __func__, -n);
+		}
 
-	wait_stub_done(pid);
+		err = ptrace(PTRACE_CONT, pid, 0, 0);
+		if (err)
+			panic("Failed to continue stub, pid = %d, errno = %d\n",
+			      pid, errno);
+
+		wait_stub_done(pid);
+	}
 
 	/*
-	 * proc_data->err will be non-zero if there was an (unexpected) error.
+	 * proc_data->err will be negative if there was an (unexpected) error.
 	 * In that case, syscall_data_len points to the last executed syscall,
 	 * otherwise it will be zero (but we do not need to rely on that).
 	 */
···
 	} else {
 		mm_idp->syscall_data_len = 0;
 	}
+
+	if (using_seccomp)
+		mm_idp->syscall_fd_num = 0;
 
 	return mm_idp->syscall_data_len;
 }
···
 	return NULL;
 }
 
+static int get_stub_fd(struct mm_id *mm_idp, int fd)
+{
+	int i;
+
+	/* Find an FD slot (or flush and use first) */
+	if (!using_seccomp)
+		return fd;
+
+	/* Already crashed, value does not matter */
+	if (mm_idp->syscall_data_len < 0)
+		return 0;
+
+	/* Find existing FD in map if we can allocate another syscall */
+	if (mm_idp->syscall_data_len <
+	    ARRAY_SIZE(((struct stub_data *)NULL)->syscall_data)) {
+		for (i = 0; i < mm_idp->syscall_fd_num; i++) {
+			if (mm_idp->syscall_fd_map[i] == fd)
+				return i;
+		}
+
+		if (mm_idp->syscall_fd_num < STUB_MAX_FDS) {
+			i = mm_idp->syscall_fd_num;
+			mm_idp->syscall_fd_map[i] = fd;
+
+			mm_idp->syscall_fd_num++;
+
+			return i;
+		}
+	}
+
+	/* FD map full or no syscall space available, continue after flush */
+	do_syscall_stub(mm_idp);
+	mm_idp->syscall_fd_map[0] = fd;
+	mm_idp->syscall_fd_num = 1;
+
+	return 0;
+}
+
 int map(struct mm_id *mm_idp, unsigned long virt, unsigned long len, int prot,
 	int phys_fd, unsigned long long offset)
 {
···
 
 	/* Compress with previous syscall if that is possible */
 	sc = syscall_stub_get_previous(mm_idp, STUB_SYSCALL_MMAP, virt);
-	if (sc && sc->mem.prot == prot && sc->mem.fd == phys_fd &&
+	if (sc && sc->mem.prot == prot &&
 	    sc->mem.offset == MMAP_OFFSET(offset - sc->mem.length)) {
-		sc->mem.length += len;
-		return 0;
+		int prev_fd = sc->mem.fd;
+
+		if (using_seccomp)
+			prev_fd = mm_idp->syscall_fd_map[sc->mem.fd];
+
+		if (phys_fd == prev_fd) {
+			sc->mem.length += len;
+			return 0;
+		}
 	}
+
+	phys_fd = get_stub_fd(mm_idp, phys_fd);
 
 	sc = syscall_stub_alloc(mm_idp);
 	sc->syscall = STUB_SYSCALL_MMAP;

arch/um/os-Linux/skas/process.c

···
 // SPDX-License-Identifier: GPL-2.0
 /*
+ * Copyright (C) 2021 Benjamin Berg <[e-mail]>
  * Copyright (C) 2015 Thomas Meyer ([e-mail])
  * Copyright (C) 2002- 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  */
···
 #include <sys/mman.h>
 #include <sys/wait.h>
 #include <sys/stat.h>
+#include <sys/socket.h>
 #include <asm/unistd.h>
 #include <as-layout.h>
 #include <init.h>
···
 #include <registers.h>
 #include <skas.h>
 #include <sysdep/stub.h>
+#include <sysdep/mcontext.h>
+#include <linux/futex.h>
 #include <linux/threads.h>
 #include <timetravel.h>
+#include <asm-generic/rwonce.h>
 #include "../internal.h"
 
 int is_skas_winch(int pid, int fd, void *data)
···
 	fatal_sigsegv();
 }
 
+void wait_stub_done_seccomp(struct mm_id *mm_idp, int running, int wait_sigsys)
+{
+	struct stub_data *data = (void *)mm_idp->stack;
+	int ret;
+
+	do {
+		const char byte = 0;
+		struct iovec iov = {
+			.iov_base = (void *)&byte,
+			.iov_len = sizeof(byte),
+		};
+		union {
+			char data[CMSG_SPACE(sizeof(mm_idp->syscall_fd_map))];
+			struct cmsghdr align;
+		} ctrl;
+		struct msghdr msgh = {
+			.msg_iov = &iov,
+			.msg_iovlen = 1,
+		};
+
+		if (!running) {
+			if (mm_idp->syscall_fd_num) {
+				unsigned int fds_size =
+					sizeof(int) * mm_idp->syscall_fd_num;
+				struct cmsghdr *cmsg;
+
+				msgh.msg_control = ctrl.data;
+				msgh.msg_controllen = CMSG_SPACE(fds_size);
+				cmsg = CMSG_FIRSTHDR(&msgh);
+				cmsg->cmsg_level = SOL_SOCKET;
+				cmsg->cmsg_type = SCM_RIGHTS;
+				cmsg->cmsg_len = CMSG_LEN(fds_size);
+				memcpy(CMSG_DATA(cmsg), mm_idp->syscall_fd_map,
+				       fds_size);
+
+				CATCH_EINTR(syscall(__NR_sendmsg, mm_idp->sock,
+						&msgh, 0));
+			}
+
+			data->signal = 0;
+			data->futex = FUTEX_IN_CHILD;
+			CATCH_EINTR(syscall(__NR_futex, &data->futex,
+					    FUTEX_WAKE, 1, NULL, NULL, 0));
+		}
+
+		do {
+			/*
+			 * We need to check whether the child is still alive
+			 * before and after the FUTEX_WAIT call. Before, in
+			 * case it just died but we still updated data->futex
+			 * to FUTEX_IN_CHILD. And after, in case it died while
+			 * we were waiting (and SIGCHLD woke us up, see the
+			 * IRQ handler in mmu.c).
+			 *
+			 * Either way, if PID is negative, then we have no
+			 * choice but to kill the task.
+			 */
+			if (__READ_ONCE(mm_idp->pid) < 0)
+				goto out_kill;
+
+			ret = syscall(__NR_futex, &data->futex,
+				      FUTEX_WAIT, FUTEX_IN_CHILD,
+				      NULL, NULL, 0);
+			if (ret < 0 && errno != EINTR && errno != EAGAIN) {
+				printk(UM_KERN_ERR "%s : FUTEX_WAIT failed, errno = %d\n",
+				       __func__, errno);
+				goto out_kill;
+			}
+		} while (data->futex == FUTEX_IN_CHILD);
+
+		if (__READ_ONCE(mm_idp->pid) < 0)
+			goto out_kill;
+
+		running = 0;
+
+		/* We may receive a SIGALRM before SIGSYS, iterate again. */
+	} while (wait_sigsys && data->signal == SIGALRM);
+
+	if (data->mctx_offset > sizeof(data->sigstack) - sizeof(mcontext_t)) {
+		printk(UM_KERN_ERR "%s : invalid mcontext offset", __func__);
+		goto out_kill;
+	}
+
+	if (wait_sigsys && data->signal != SIGSYS) {
+		printk(UM_KERN_ERR "%s : expected SIGSYS but got %d",
+		       __func__, data->signal);
+		goto out_kill;
+	}
+
+	return;
+
+out_kill:
+	printk(UM_KERN_ERR "%s : failed to wait for stub, pid = %d, errno = %d\n",
+	       __func__, mm_idp->pid, errno);
+	/* This is not true inside start_userspace */
+	if (current_mm_id() == mm_idp)
+		fatal_sigsegv();
+}
+
 extern unsigned long current_stub_stack(void);
 
 static void get_skas_faultinfo(int pid, struct faultinfo *fi)
···
 	memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
 }
 
-static void handle_segv(int pid, struct uml_pt_regs *regs)
-{
-	get_skas_faultinfo(pid, &regs->faultinfo);
-	segv(regs->faultinfo, 0, 1, NULL, NULL);
-}
-
 static void handle_trap(int pid, struct uml_pt_regs *regs)
 {
 	if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
···
 
 static int stub_exe_fd;
 
+struct tramp_data {
+	struct stub_data *stub_data;
+	/* 0 is inherited, 1 is the kernel side */
+	int sockpair[2];
+};
+
 #ifndef CLOSE_RANGE_CLOEXEC
 #define CLOSE_RANGE_CLOEXEC	(1U << 2)
 #endif
 
-static int userspace_tramp(void *stack)
+static int userspace_tramp(void *data)
 {
+	struct tramp_data *tramp_data = data;
 	char *const argv[] = { "uml-userspace", NULL };
-	int pipe_fds[2];
 	unsigned long long offset;
 	struct stub_init_data init_data = {
+		.seccomp = using_seccomp,
 		.stub_start = STUB_START,
-		.segv_handler = STUB_CODE +
-				(unsigned long) stub_segv_handler -
-				(unsigned long) __syscall_stub_start,
 	};
 	struct iomem_region *iomem;
 	int ret;
+
+	if (using_seccomp) {
+		init_data.signal_handler = STUB_CODE +
+					   (unsigned long) stub_signal_interrupt -
+					   (unsigned long) __syscall_stub_start;
+		init_data.signal_restorer = STUB_CODE +
+					   (unsigned long) stub_signal_restorer -
+					   (unsigned long) __syscall_stub_start;
+	} else {
+		init_data.signal_handler = STUB_CODE +
+					   (unsigned long) stub_segv_handler -
+					   (unsigned long) __syscall_stub_start;
+		init_data.signal_restorer = 0;
+	}
 
 	init_data.stub_code_fd = phys_mapping(uml_to_phys(__syscall_stub_start),
 					      &offset);
 	init_data.stub_code_offset = MMAP_OFFSET(offset);
 
-	init_data.stub_data_fd = phys_mapping(uml_to_phys(stack), &offset);
+	init_data.stub_data_fd = phys_mapping(uml_to_phys(tramp_data->stub_data),
+					      &offset);
 	init_data.stub_data_offset = MMAP_OFFSET(offset);
 
 	/*
···
 	syscall(__NR_close_range, 0, ~0U, CLOSE_RANGE_CLOEXEC);
 
 	fcntl(init_data.stub_data_fd, F_SETFD, 0);
-	for (iomem = iomem_regions; iomem; iomem = iomem->next)
-		fcntl(iomem->fd, F_SETFD, 0);
 
-	/* Create a pipe for init_data (no CLOEXEC) and dup2 to STDIN */
-	if (pipe(pipe_fds))
-		exit(2);
+	/* In SECCOMP mode, these FDs are passed when needed */
+	if (!using_seccomp) {
+		for (iomem = iomem_regions; iomem; iomem = iomem->next)
+			fcntl(iomem->fd, F_SETFD, 0);
+	}
 
-	if (dup2(pipe_fds[0], 0) < 0)
+	/* dup2 signaling FD/socket to STDIN */
+	if (dup2(tramp_data->sockpair[0], 0) < 0)
 		exit(3);
-	close(pipe_fds[0]);
+	close(tramp_data->sockpair[0]);
 
 	/* Write init_data and close write side */
-	ret = write(pipe_fds[1], &init_data, sizeof(init_data));
-	close(pipe_fds[1]);
+	ret = write(tramp_data->sockpair[1], &init_data, sizeof(init_data));
+	close(tramp_data->sockpair[1]);
 
 	if (ret != sizeof(init_data))
 		exit(4);
···
 }
 __initcall(init_stub_exe_fd);
 
+int using_seccomp;
 int userspace_pid[NR_CPUS];
 
 /**
  * start_userspace() - prepare a new userspace process
- * @stub_stack:	pointer to the stub stack.
+ * @mm_id: The corresponding struct mm_id
  *
  * Setups a new temporary stack page that is used while userspace_tramp() runs
  * Clones the kernel process into a new userspace process, with FDs only.
···
  *         when negative: an error number.
  * FIXME: can PIDs become negative?!
  */
-int start_userspace(unsigned long stub_stack)
+int start_userspace(struct mm_id *mm_id)
 {
+	struct stub_data *proc_data = (void *)mm_id->stack;
+	struct tramp_data tramp_data = {
+		.stub_data = proc_data,
+	};
 	void *stack;
 	unsigned long sp;
-	int pid, status, n, err;
+	int status, n, err;
 
 	/* setup a temporary stack page */
 	stack = mmap(NULL, UM_KERN_PAGE_SIZE,
···
 	/* set stack pointer to the end of the stack page, so it can grow downwards */
 	sp = (unsigned long)stack + UM_KERN_PAGE_SIZE;
 
-	/* clone into new userspace process */
-	pid = clone(userspace_tramp, (void *) sp,
-		    CLONE_VFORK | CLONE_VM | SIGCHLD,
-		    (void *)stub_stack);
-	if (pid < 0) {
+	/* socket pair for init data and SECCOMP FD passing (no CLOEXEC here) */
+	if (socketpair(AF_UNIX, SOCK_STREAM, 0, tramp_data.sockpair)) {
 		err = -errno;
-		printk(UM_KERN_ERR "%s : clone failed, errno = %d\n",
+		printk(UM_KERN_ERR "%s : socketpair failed, errno = %d\n",
 		       __func__, errno);
 		return err;
 	}
 
-	do {
-		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
-		if (n < 0) {
+	if (using_seccomp)
+		proc_data->futex = FUTEX_IN_CHILD;
+
+	mm_id->pid = clone(userspace_tramp, (void *) sp,
+		    CLONE_VFORK | CLONE_VM | SIGCHLD,
+		    (void *)&tramp_data);
+	if (mm_id->pid < 0) {
+		err = -errno;
+		printk(UM_KERN_ERR "%s : clone failed, errno = %d\n",
+		       __func__, errno);
+		goto out_close;
+	}
+
+	if (using_seccomp) {
+		wait_stub_done_seccomp(mm_id, 1, 1);
+	} else {
+		do {
+			CATCH_EINTR(n = waitpid(mm_id->pid, &status,
+						WUNTRACED | __WALL));
+			if (n < 0) {
+				err = -errno;
+				printk(UM_KERN_ERR "%s : wait failed, errno = %d\n",
+				       __func__, errno);
+				goto out_kill;
+			}
+		} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
+
+		if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
+			err = -EINVAL;
+			printk(UM_KERN_ERR "%s : expected SIGSTOP, got status = %d\n",
+			       __func__, status);
+			goto out_kill;
+		}
+
+		if (ptrace(PTRACE_SETOPTIONS, mm_id->pid, NULL,
+			   (void *) PTRACE_O_TRACESYSGOOD) < 0) {
 			err = -errno;
-			printk(UM_KERN_ERR "%s : wait failed, errno = %d\n",
+			printk(UM_KERN_ERR "%s : PTRACE_SETOPTIONS failed, errno = %d\n",
 			       __func__, errno);
 			goto out_kill;
 		}
-	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
-
-	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
-		err = -EINVAL;
-		printk(UM_KERN_ERR "%s : expected SIGSTOP, got status = %d\n",
-		       __func__, status);
-		goto out_kill;
-	}
-
-	if (ptrace(PTRACE_SETOPTIONS, pid, NULL,
-		   (void *) PTRACE_O_TRACESYSGOOD) < 0) {
-		err = -errno;
-		printk(UM_KERN_ERR "%s : PTRACE_SETOPTIONS failed, errno = %d\n",
-		       __func__, errno);
-		goto out_kill;
 	}
 
 	if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
···
 		goto out_kill;
 	}
 
-	return pid;
+	close(tramp_data.sockpair[0]);
+	if (using_seccomp)
+		mm_id->sock = tramp_data.sockpair[1];
+	else
+		close(tramp_data.sockpair[1]);
 
- out_kill:
-	os_kill_ptraced_process(pid, 1);
+	return 0;
+
+out_kill:
+	os_kill_ptraced_process(mm_id->pid, 1);
+out_close:
+	close(tramp_data.sockpair[0]);
+	close(tramp_data.sockpair[1]);
+
+	mm_id->pid = -1;
+
 	return err;
 }
 
···
 void userspace(struct uml_pt_regs *regs)
 {
 	int err, status, op, pid = userspace_pid[0];
-	siginfo_t si;
+	siginfo_t si_ptrace;
+	siginfo_t *si;
+	int sig;
 
 	/* Handle any immediate reschedules or signals */
 	interrupt_end();
···
 
 		current_mm_sync();
 
-		/* Flush out any pending syscalls */
-		err = syscall_stub_flush(current_mm_id());
-		if (err) {
-			if (err == -ENOMEM)
-				report_enomem();
+		if (using_seccomp) {
+			struct mm_id *mm_id = current_mm_id();
+			struct stub_data *proc_data = (void *) mm_id->stack;
+			int ret;
 
-			printk(UM_KERN_ERR "%s - Error flushing stub syscalls: %d",
-				__func__, -err);
-			fatal_sigsegv();
-		}
+			ret = set_stub_state(regs, proc_data, singlestepping());
+			if (ret) {
+				printk(UM_KERN_ERR "%s - failed to set regs: %d",
+				       __func__, ret);
+				fatal_sigsegv();
+			}
 
-		/*
-		 * This can legitimately fail if the process loads a
-		 * bogus value into a segment register.  It will
-		 * segfault and PTRACE_GETREGS will read that value
-		 * out of the process.  However, PTRACE_SETREGS will
-		 * fail.  In this case, there is nothing to do but
-		 * just kill the process.
-		 */
-		if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp)) {
-			printk(UM_KERN_ERR "%s - ptrace set regs failed, errno = %d\n",
-			       __func__, errno);
-			fatal_sigsegv();
-		}
+			/* Must have been reset by the syscall caller */
+			if (proc_data->restart_wait != 0)
+				panic("Programming error: Flag to only run syscalls in child was not cleared!");
 
-		if (put_fp_registers(pid, regs->fp)) {
-			printk(UM_KERN_ERR "%s - ptrace set fp regs failed, errno = %d\n",
-			       __func__, errno);
-			fatal_sigsegv();
-		}
+			/* Mark pending syscalls for flushing */
+			proc_data->syscall_data_len = mm_id->syscall_data_len;
 
-		if (singlestepping())
-			op = PTRACE_SYSEMU_SINGLESTEP;
-		else
-			op = PTRACE_SYSEMU;
+			wait_stub_done_seccomp(mm_id, 0, 0);
 
-		if (ptrace(op, pid, 0, 0)) {
-			printk(UM_KERN_ERR "%s - ptrace continue failed, op = %d, errno = %d\n",
-			       __func__, op, errno);
-			fatal_sigsegv();
-		}
+			sig = proc_data->signal;
 
-		CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
-		if (err < 0) {
-			printk(UM_KERN_ERR "%s - wait failed, errno = %d\n",
-			       __func__, errno);
-			fatal_sigsegv();
-		}
+			if (sig == SIGTRAP && proc_data->err != 0) {
+				printk(UM_KERN_ERR "%s - Error flushing stub syscalls",
+				       __func__);
+				syscall_stub_dump_error(mm_id);
+				mm_id->syscall_data_len = proc_data->err;
+				fatal_sigsegv();
+			}
 
-		regs->is_user = 1;
-		if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
-			printk(UM_KERN_ERR "%s - PTRACE_GETREGS failed, errno = %d\n",
-			       __func__, errno);
-			fatal_sigsegv();
-		}
+			mm_id->syscall_data_len = 0;
+			mm_id->syscall_fd_num = 0;
 
-		if (get_fp_registers(pid, regs->fp)) {
-			printk(UM_KERN_ERR "%s -  get_fp_registers failed, errno = %d\n",
-			       __func__, errno);
-			fatal_sigsegv();
+			ret = get_stub_state(regs, proc_data, NULL);
+			if (ret) {
+				printk(UM_KERN_ERR "%s - failed to get regs: %d",
+				       __func__, ret);
+				fatal_sigsegv();
+			}
+
+			if (proc_data->si_offset > sizeof(proc_data->sigstack) - sizeof(*si))
+				panic("%s - Invalid siginfo offset from child",
+				      __func__);
+			si = (void *)&proc_data->sigstack[proc_data->si_offset];
+
+			regs->is_user = 1;
+
+			/* Fill in ORIG_RAX and extract fault information */
+			PT_SYSCALL_NR(regs->gp) = si->si_syscall;
+			if (sig == SIGSEGV) {
+				mcontext_t *mcontext = (void *)&proc_data->sigstack[proc_data->mctx_offset];
+
+				GET_FAULTINFO_FROM_MC(regs->faultinfo, mcontext);
+			}
+		} else {
+			/* Flush out any pending syscalls */
+			err = syscall_stub_flush(current_mm_id());
+			if (err) {
+				if (err == -ENOMEM)
+					report_enomem();
+
+				printk(UM_KERN_ERR "%s - Error flushing stub syscalls: %d",
+					__func__, -err);
+				fatal_sigsegv();
+			}
+
+			/*
+			 * This can legitimately fail if the process loads a
+			 * bogus value into a segment register.  It will
+			 * segfault and PTRACE_GETREGS will read that value
+			 * out of the process.  However, PTRACE_SETREGS will
+			 * fail.  In this case, there is nothing to do but
+			 * just kill the process.
+			 */
+			if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp)) {
+				printk(UM_KERN_ERR "%s - ptrace set regs failed, errno = %d\n",
+				       __func__, errno);
+				fatal_sigsegv();
+			}
+
+			if (put_fp_registers(pid, regs->fp)) {
+				printk(UM_KERN_ERR "%s - ptrace set fp regs failed, errno = %d\n",
+				       __func__, errno);
+				fatal_sigsegv();
+			}
+
+			if (singlestepping())
+				op = PTRACE_SYSEMU_SINGLESTEP;
+			else
+				op = PTRACE_SYSEMU;
+
+			if (ptrace(op, pid, 0, 0)) {
+				printk(UM_KERN_ERR "%s - ptrace continue failed, op = %d, errno = %d\n",
+				       __func__, op, errno);
+				fatal_sigsegv();
+			}
+
+			CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
+			if (err < 0) {
+				printk(UM_KERN_ERR "%s - wait failed, errno = %d\n",
+				       __func__, errno);
+				fatal_sigsegv();
+			}
+
+			regs->is_user = 1;
+			if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
+				printk(UM_KERN_ERR "%s - PTRACE_GETREGS failed, errno = %d\n",
+				       __func__, errno);
+				fatal_sigsegv();
+			}
+
+			if (get_fp_registers(pid, regs->fp)) {
+				printk(UM_KERN_ERR "%s -  get_fp_registers failed, errno = %d\n",
+				       __func__, errno);
+				fatal_sigsegv();
+			}
+
+			if (WIFSTOPPED(status)) {
+				sig = WSTOPSIG(status);
+
+				/*
+				 * These signal handlers need the si argument
+				 * and SIGSEGV needs the faultinfo.
+				 * The SIGIO and SIGALARM handlers which constitute
+				 * the majority of invocations, do not use it.
+				 */
+				switch (sig) {
+				case SIGSEGV:
+					get_skas_faultinfo(pid,
+							   &regs->faultinfo);
+					fallthrough;
+				case SIGTRAP:
+				case SIGILL:
+				case SIGBUS:
+				case SIGFPE:
+				case SIGWINCH:
+					ptrace(PTRACE_GETSIGINFO, pid, 0,
+					       (struct siginfo *)&si_ptrace);
+					si = &si_ptrace;
+					break;
+				default:
+					si = NULL;
+					break;
+				}
+			} else {
+				sig = 0;
+			}
 		}
 
 		UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
 
-		if (WIFSTOPPED(status)) {
-			int sig = WSTOPSIG(status);
-
-			/* These signal handlers need the si argument.
-			 * The SIGIO and SIGALARM handlers which constitute the
-			 * majority of invocations, do not use it.
-			 */
+		if (sig) {
 			switch (sig) {
 			case SIGSEGV:
-			case SIGTRAP:
-			case SIGILL:
-			case SIGBUS:
-			case SIGFPE:
-			case SIGWINCH:
-				ptrace(PTRACE_GETSIGINFO, pid, 0, (struct siginfo *)&si);
-				break;
-			}
-
-			switch (sig) {
-			case SIGSEGV:
-				if (PTRACE_FULL_FAULTINFO) {
-					get_skas_faultinfo(pid,
-							   &regs->faultinfo);
-					(*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si,
+				if (using_seccomp || PTRACE_FULL_FAULTINFO)
+					(*sig_info[SIGSEGV])(SIGSEGV,
+							     (struct siginfo *)si,
 							     regs, NULL);
-				}
-				else handle_segv(pid, regs);
+				else
+					segv(regs->faultinfo, 0, 1, NULL, NULL);
+
+				break;
+			case SIGSYS:
+				handle_syscall(regs);
 				break;
 			case SIGTRAP + 0x80:
 				handle_trap(pid, regs);
 				break;
 			case SIGTRAP:
-				relay_signal(SIGTRAP, (struct siginfo *)&si, regs, NULL);
+				relay_signal(SIGTRAP, (struct siginfo *)si, regs, NULL);
 				break;
 			case SIGALRM:
 				break;
···
 			case SIGFPE:
 			case SIGWINCH:
 				block_signals_trace();
-				(*sig_info[sig])(sig, (struct siginfo *)&si, regs, NULL);
+				(*sig_info[sig])(sig, (struct siginfo *)si, regs, NULL);
 				unblock_signals_trace();
 				break;
 			default:

arch/um/os-Linux/start_up.c

···
 // SPDX-License-Identifier: GPL-2.0
 /*
+ * Copyright (C) 2021 Benjamin Berg <[e-mail]>
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  */
 
···
 #include <kern_util.h>
 #include <mem_user.h>
 #include <ptrace_user.h>
+#include <stdbool.h>
+#include <stub-data.h>
+#include <sys/prctl.h>
+#include <linux/seccomp.h>
+#include <linux/filter.h>
+#include <sysdep/mcontext.h>
+#include <sysdep/stub.h>
 #include <registers.h>
 #include <skas.h>
 #include "internal.h"
···
 	check_sysemu();
 }
 
+extern unsigned long host_fp_size;
+extern unsigned long exec_regs[MAX_REG_NR];
+extern unsigned long *exec_fp_regs;
+
+__initdata static struct stub_data *seccomp_test_stub_data;
+
+static void __init sigsys_handler(int sig, siginfo_t *info, void *p)
+{
+	ucontext_t *uc = p;
+
+	/* Stow away the location of the mcontext in the stack */
+	seccomp_test_stub_data->mctx_offset = (unsigned long)&uc->uc_mcontext -
+					      (unsigned long)&seccomp_test_stub_data->sigstack[0];
+
+	/* Prevent libc from clearing memory (mctx_offset in particular) */
+	syscall(__NR_exit, 0);
+}
+
+static int __init seccomp_helper(void *data)
+{
+	static struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
+			 offsetof(struct seccomp_data, nr)),
+		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_clock_nanosleep, 1, 0),
+		BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
+		BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_TRAP),
+	};
+	static struct sock_fprog prog = {
+		.len = ARRAY_SIZE(filter),
+		.filter = filter,
+	};
+	struct sigaction sa;
+
+	/* close_range is needed for the stub */
+	if (stub_syscall3(__NR_close_range, 1, ~0U, 0))
+		exit(1);
+
+	set_sigstack(seccomp_test_stub_data->sigstack,
+			sizeof(seccomp_test_stub_data->sigstack));
+
+	sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
+	sa.sa_sigaction = (void *) sigsys_handler;
+	sa.sa_restorer = NULL;
+	if (sigaction(SIGSYS, &sa, NULL) < 0)
+		exit(2);
+
+	prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
+	if (syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER,
+			SECCOMP_FILTER_FLAG_TSYNC, &prog) != 0)
+		exit(3);
+
+	sleep(0);
+
+	/* Never reached. */
+	_exit(4);
+}
+
+static bool __init init_seccomp(void)
+{
+	int pid;
+	int status;
+	int n;
+	unsigned long sp;
+
+	/*
+	 * We check that we can install a seccomp filter and then exit(0)
+	 * from a trapped syscall.
+	 *
+	 * Note that we cannot verify that no seccomp filter already exists
+	 * for a syscall that results in the process/thread to be killed.
+	 */
+
+	os_info("Checking that seccomp filters can be installed...");
+
+	seccomp_test_stub_data = mmap(0, sizeof(*seccomp_test_stub_data),
+				      PROT_READ | PROT_WRITE,
+				      MAP_SHARED | MAP_ANON, 0, 0);
+
+	/* Use the syscall data area as stack, we just need something */
+	sp = (unsigned long)&seccomp_test_stub_data->syscall_data +
+	     sizeof(seccomp_test_stub_data->syscall_data) -
+	     sizeof(void *);
+	pid = clone(seccomp_helper, (void *)sp, CLONE_VFORK | CLONE_VM, NULL);
+
+	if (pid < 0)
+		fatal_perror("check_seccomp : clone failed");
+
+	CATCH_EINTR(n = waitpid(pid, &status, __WCLONE));
+	if (n < 0)
+		fatal_perror("check_seccomp : waitpid failed");
+
+	if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
+		struct uml_pt_regs *regs;
+		unsigned long fp_size;
+		int r;
+
+		/* Fill in the host_fp_size from the mcontext. */
+		regs = calloc(1, sizeof(struct uml_pt_regs));
+		get_stub_state(regs, seccomp_test_stub_data, &fp_size);
+		host_fp_size = fp_size;
+		free(regs);
+
+		/* Repeat with the correct size */
+		regs = calloc(1, sizeof(struct uml_pt_regs) + host_fp_size);
+		r = get_stub_state(regs, seccomp_test_stub_data, NULL);
+
+		/* Store as the default startup registers */
+		exec_fp_regs = malloc(host_fp_size);
+		memcpy(exec_regs, regs->gp, sizeof(exec_regs));
+		memcpy(exec_fp_regs, regs->fp, host_fp_size);
+
+		munmap(seccomp_test_stub_data, sizeof(*seccomp_test_stub_data));
+
+		free(regs);
+
+		if (r) {
+			os_info("failed to fetch registers: %d\n", r);
+			return false;
+		}
+
+		os_info("OK\n");
+		return true;
+	}
+
+	if (WIFEXITED(status) && WEXITSTATUS(status) == 2)
+		os_info("missing\n");
+	else
+		os_info("error\n");
+
+	munmap(seccomp_test_stub_data, sizeof(*seccomp_test_stub_data));
+	return false;
+}
+
+
 static void __init check_coredump_limit(void)
 {
 	struct rlimit lim;
···
 	}
 }
 
+static int seccomp_config __initdata;
+
+static int __init uml_seccomp_config(char *line, int *add)
+{
+	*add = 0;
+
+	if (strcmp(line, "off") == 0)
+		seccomp_config = 0;
+	else if (strcmp(line, "auto") == 0)
+		seccomp_config = 1;
+	else if (strcmp(line, "on") == 0)
+		seccomp_config = 2;
+	else
+		fatal("Invalid seccomp option '%s', expected on/auto/off\n",
+		      line);
+
+	return 0;
+}
+
+__uml_setup("seccomp=", uml_seccomp_config,
+"seccomp=<on/auto/off>\n"
+"    Configure whether or not SECCOMP is used. With SECCOMP, userspace\n"
+"    processes work collaboratively with the kernel instead of being\n"
+"    traced using ptrace. All syscalls from the application are caught and\n"
+"    redirected using a signal. This signal handler in turn is permitted to\n"
+"    do the selected set of syscalls to communicate with the UML kernel and\n"
+"    do the required memory management.\n"
+"\n"
+"    This method is overall faster than the ptrace based userspace, primarily\n"
+"    because it reduces the number of context switches for (minor) page faults.\n"
+"\n"
+"    However, the SECCOMP filter is not (yet) restrictive enough to prevent\n"
+"    userspace from reading and writing all physical memory. Userspace\n"
+"    processes could also trick the stub into disabling SIGALRM which\n"
+"    prevents it from being interrupted for scheduling purposes.\n"
+"\n"
+"    This is insecure and should only be used with a trusted userspace\n\n"
+);
 
 void __init os_early_checks(void)
 {
···
 	/* Print out the core dump limits early */
 	check_coredump_limit();
 
-	check_ptrace();
-
 	/* Need to check this early because mmapping happens before the
 	 * kernel is running.
 	 */
 	check_tmpexec();
+
+	if (seccomp_config) {
+		if (init_seccomp()) {
+			using_seccomp = 1;
+			return;
+		}
+
+		if (seccomp_config == 2)
+			fatal("SECCOMP userspace requested but not functional!\n");
+	}
+
+	using_seccomp = 0;
+	check_ptrace();
 
 	pid = start_ptraced_child();
 	if (init_pid_registers(pid))

arch/x86/um/asm/checksum.h

···
  */
 extern __wsum csum_partial(const void *buff, int len, __wsum sum);
 
+/* Do not call this directly. Declared for export type visibility. */
+extern __visible __wsum csum_partial_copy_generic(const void *src, void *dst, int len);
+
 /**
  * csum_fold - Fold and invert a 32bit checksum.
  * sum: 32bit unfolded sum

arch/x86/um/asm/processor.h

···
 
 #include <asm/user.h>
 
-/* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */
-static __always_inline void rep_nop(void)
+/* PAUSE is a good thing to insert into busy-wait loops. */
+static __always_inline void native_pause(void)
 {
-	__asm__ __volatile__("rep;nop": : :"memory");
+	__asm__ __volatile__("pause": : :"memory");
 }
 
 static __always_inline void cpu_relax(void)
···
 	    time_travel_mode == TT_MODE_EXTERNAL)
 		time_travel_ndelay(1);
 	else
-		rep_nop();
+		native_pause();
 }
 
 #define task_pt_regs(t) (&(t)->thread.regs)

arch/x86/um/os-Linux/mcontext.c

···
 // SPDX-License-Identifier: GPL-2.0
-#include <sys/ucontext.h>
 #define __FRAME_OFFSETS
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <sys/ucontext.h>
 #include <asm/ptrace.h>
+#include <asm/sigcontext.h>
 #include <sysdep/ptrace.h>
 #include <sysdep/mcontext.h>
 #include <arch.h>
···
 	COPY2(UESP, ESP); /* sic */
 	COPY(EBX); COPY(EDX); COPY(ECX); COPY(EAX);
 	COPY(EIP); COPY_SEG_CPL3(CS); COPY(EFL); COPY_SEG_CPL3(SS);
+#undef COPY2
+#undef COPY
+#undef COPY_SEG
+#undef COPY_SEG_CPL3
 #else
 #define COPY2(X,Y) regs->gp[X/sizeof(unsigned long)] = mc->gregs[REG_##Y]
 #define COPY(X) regs->gp[X/sizeof(unsigned long)] = mc->gregs[REG_##X]
···
 	COPY2(EFLAGS, EFL);
 	COPY2(CS, CSGSFS);
 	regs->gp[SS / sizeof(unsigned long)] = mc->gregs[REG_CSGSFS] >> 48;
+#undef COPY2
+#undef COPY
 #endif
 }
 
···
 #else
 	mc->gregs[REG_RIP] = (unsigned long)target;
 #endif
+}
+
+/* Same thing, but the copy macros are turned around. */
+void get_mc_from_regs(struct uml_pt_regs *regs, mcontext_t *mc, int single_stepping)
+{
+#ifdef __i386__
+#define COPY2(X,Y) mc->gregs[REG_##Y] = regs->gp[X]
+#define COPY(X) mc->gregs[REG_##X] = regs->gp[X]
+#define COPY_SEG(X) mc->gregs[REG_##X] = regs->gp[X] & 0xffff;
+#define COPY_SEG_CPL3(X) mc->gregs[REG_##X] = (regs->gp[X] & 0xffff) | 3;
+	COPY_SEG(GS); COPY_SEG(FS); COPY_SEG(ES); COPY_SEG(DS);
+	COPY(EDI); COPY(ESI); COPY(EBP);
+	COPY2(UESP, ESP); /* sic */
+	COPY(EBX); COPY(EDX); COPY(ECX); COPY(EAX);
+	COPY(EIP); COPY_SEG_CPL3(CS); COPY(EFL); COPY_SEG_CPL3(SS);
+#else
+#define COPY2(X,Y) mc->gregs[REG_##Y] = regs->gp[X/sizeof(unsigned long)]
+#define COPY(X) mc->gregs[REG_##X] = regs->gp[X/sizeof(unsigned long)]
+	COPY(R8); COPY(R9); COPY(R10); COPY(R11);
+	COPY(R12); COPY(R13); COPY(R14); COPY(R15);
+	COPY(RDI); COPY(RSI); COPY(RBP); COPY(RBX);
+	COPY(RDX); COPY(RAX); COPY(RCX); COPY(RSP);
+	COPY(RIP);
+	COPY2(EFLAGS, EFL);
+	mc->gregs[REG_CSGSFS] = mc->gregs[REG_CSGSFS] & 0xffffffffffffl;
+	mc->gregs[REG_CSGSFS] |= (regs->gp[SS / sizeof(unsigned long)] & 0xffff) << 48;
+#endif
+
+	if (single_stepping)
+		mc->gregs[REG_EFL] |= X86_EFLAGS_TF;
+	else
+		mc->gregs[REG_EFL] &= ~X86_EFLAGS_TF;
+}
+
+#ifdef CONFIG_X86_32
+struct _xstate_64 {
+	struct _fpstate_64		fpstate;
+	struct _header			xstate_hdr;
+	struct _ymmh_state		ymmh;
+	/* New processor state extensions go here: */
+};
+
+/* Not quite the right structures as these contain more information */
+int um_i387_from_fxsr(struct _fpstate_32 *i387,
+		      const struct _fpstate_64 *fxsave);
+int um_fxsr_from_i387(struct _fpstate_64 *fxsave,
+		      const struct _fpstate_32 *from);
+#else
+#define _xstate_64 _xstate
+#endif
+
+static struct _fpstate *get_fpstate(struct stub_data *data,
+				    mcontext_t *mcontext,
+				    int *fp_size)
+{
+	struct _fpstate *res;
+
+	/* Assume floating point registers are on the same page */
+	res = (void *)(((unsigned long)mcontext->fpregs &
+			(UM_KERN_PAGE_SIZE - 1)) +
+		       (unsigned long)&data->sigstack[0]);
+
+	if ((void *)res + sizeof(struct _fpstate) >
+	    (void *)data->sigstack + sizeof(data->sigstack))
+		return NULL;
+
+	if (res->sw_reserved.magic1 != FP_XSTATE_MAGIC1) {
+		*fp_size = sizeof(struct _fpstate);
+	} else {
+		char *magic2_addr;
+
+		magic2_addr = (void *)res;
+		magic2_addr += res->sw_reserved.extended_size;
+		magic2_addr -= FP_XSTATE_MAGIC2_SIZE;
+
+		/* We still need to be within our stack */
+		if ((void *)magic2_addr >
+		    (void *)data->sigstack + sizeof(data->sigstack))
+			return NULL;
+
+		/* If we do not read MAGIC2, then we did something wrong */
+		if (*(__u32 *)magic2_addr != FP_XSTATE_MAGIC2)
+			return NULL;
+
+		/* Remove MAGIC2 from the size, we do not save/restore it */
+		*fp_size = res->sw_reserved.extended_size -
+			   FP_XSTATE_MAGIC2_SIZE;
+	}
+
+	return res;
+}
+
+int get_stub_state(struct uml_pt_regs *regs, struct stub_data *data,
+		   unsigned long *fp_size_out)
+{
+	mcontext_t *mcontext;
+	struct _fpstate *fpstate_stub;
+	struct _xstate_64 *xstate_stub;
+	int fp_size, xstate_size;
+
+	/* mctx_offset is verified by wait_stub_done_seccomp */
+	mcontext = (void *)&data->sigstack[data->mctx_offset];
+
+	get_regs_from_mc(regs, mcontext);
+
+	fpstate_stub = get_fpstate(data, mcontext, &fp_size);
+	if (!fpstate_stub)
+		return -EINVAL;
+
+#ifdef CONFIG_X86_32
+	xstate_stub = (void *)&fpstate_stub->_fxsr_env;
+	xstate_size = fp_size - offsetof(struct _fpstate_32, _fxsr_env);
+#else
+	xstate_stub = (void *)fpstate_stub;
+	xstate_size = fp_size;
+#endif
+
+	if (fp_size_out)
+		*fp_size_out = xstate_size;
+
+	if (xstate_size > host_fp_size)
+		return -ENOSPC;
+
+	memcpy(&regs->fp, xstate_stub, xstate_size);
+
+	/* We do not need to read the x86_64 FS_BASE/GS_BASE registers as
+	 * we do not permit userspace to set them directly.
+	 */
+
+#ifdef CONFIG_X86_32
+	/* Read the i387 legacy FP registers */
+	if (um_fxsr_from_i387((void *)&regs->fp, fpstate_stub))
+		return -EINVAL;
+#endif
+
+	return 0;
+}
+
+/* Copied because we cannot include regset.h here. */
+struct task_struct;
+struct user_regset;
+struct membuf {
+	void *p;
+	size_t left;
+};
+
+int fpregs_legacy_get(struct task_struct *target,
+		      const struct user_regset *regset,
+		      struct membuf to);
+
+int set_stub_state(struct uml_pt_regs *regs, struct stub_data *data,
+		   int single_stepping)
+{
+	mcontext_t *mcontext;
+	struct _fpstate *fpstate_stub;
+	struct _xstate_64 *xstate_stub;
+	int fp_size, xstate_size;
+
+	/* mctx_offset is verified by wait_stub_done_seccomp */
+	mcontext = (void *)&data->sigstack[data->mctx_offset];
+
+	if ((unsigned long)mcontext < (unsigned long)data->sigstack ||
+	    (unsigned long)mcontext >
+			(unsigned long) data->sigstack +
+			sizeof(data->sigstack) - sizeof(*mcontext))
+		return -EINVAL;
+
+	get_mc_from_regs(regs, mcontext, single_stepping);
+
+	fpstate_stub = get_fpstate(data, mcontext, &fp_size);
+	if (!fpstate_stub)
+		return -EINVAL;
+
+#ifdef CONFIG_X86_32
+	xstate_stub = (void *)&fpstate_stub->_fxsr_env;
+	xstate_size = fp_size - offsetof(struct _fpstate_32, _fxsr_env);
+#else
+	xstate_stub = (void *)fpstate_stub;
+	xstate_size = fp_size;
+#endif
+
+	memcpy(xstate_stub, &regs->fp, xstate_size);
+
+#ifdef __i386__
+	/*
+	 * On x86, the GDT entries are updated by arch_set_tls.
+	 */
+
+	/* Store the i387 legacy FP registers which the host will use */
+	if (um_i387_from_fxsr(fpstate_stub, (void *)&regs->fp))
+		return -EINVAL;
+#else
+	/*
+	 * On x86_64, we need to sync the FS_BASE/GS_BASE registers using the
+	 * arch specific data.
+	 */
+	if (data->arch_data.fs_base != regs->gp[FS_BASE / sizeof(unsigned long)]) {
+		data->arch_data.fs_base = regs->gp[FS_BASE / sizeof(unsigned long)];
+		data->arch_data.sync |= STUB_SYNC_FS_BASE;
+	}
+	if (data->arch_data.gs_base != regs->gp[GS_BASE / sizeof(unsigned long)]) {
+		data->arch_data.gs_base = regs->gp[GS_BASE / sizeof(unsigned long)];
+		data->arch_data.sync |= STUB_SYNC_GS_BASE;
+	}
+#endif
+
+	return 0;
 }

arch/x86/um/ptrace.c

···
 	return tmp;
 }
 
-static inline unsigned long twd_fxsr_to_i387(struct user_fxsr_struct *fxsave)
+static inline unsigned long
+twd_fxsr_to_i387(const struct user_fxsr_struct *fxsave)
 {
 	struct _fpxreg *st = NULL;
 	unsigned long twd = (unsigned long) fxsave->twd;
···
 	return ret;
 }
 
-/* Get/set the old 32bit i387 registers (pre-FPX) */
-static int fpregs_legacy_get(struct task_struct *target,
-			     const struct user_regset *regset,
-			     struct membuf to)
+/*
+ * Get/set the old 32bit i387 registers (pre-FPX)
+ *
+ * We provide simple wrappers for mcontext.c, they are only defined locally
+ * because mcontext.c is userspace facing and needs to a different definition
+ * of the structures.
+ */
+static int _um_i387_from_fxsr(struct membuf to,
+			      const struct user_fxsr_struct *fxsave)
 {
-	struct user_fxsr_struct *fxsave = (void *)target->thread.regs.regs.fp;
 	int i;
 
 	membuf_store(&to, (unsigned long)fxsave->cwd | 0xffff0000ul);
···
 	return 0;
 }
 
-static int fpregs_legacy_set(struct task_struct *target,
+int um_i387_from_fxsr(struct user_i387_struct *i387,
+		      const struct user_fxsr_struct *fxsave);
+
+int um_i387_from_fxsr(struct user_i387_struct *i387,
+		      const struct user_fxsr_struct *fxsave)
+{
+	struct membuf to = {
+		.p = i387,
+		.left = sizeof(*i387),
+	};
+
+	return _um_i387_from_fxsr(to, fxsave);
+}
+
+static int fpregs_legacy_get(struct task_struct *target,
 			     const struct user_regset *regset,
-			     unsigned int pos, unsigned int count,
-			     const void *kbuf, const void __user *ubuf)
+			     struct membuf to)
 {
 	struct user_fxsr_struct *fxsave = (void *)target->thread.regs.regs.fp;
-	const struct user_i387_struct *from;
-	struct user_i387_struct buf;
-	int i;
 
-	if (ubuf) {
-		if (copy_from_user(&buf, ubuf, sizeof(buf)))
-			return -EFAULT;
-		from = &buf;
-	} else {
-		from = kbuf;
-	}
+	return _um_i387_from_fxsr(to, fxsave);
+}
+
+int um_fxsr_from_i387(struct user_fxsr_struct *fxsave,
+		      const struct user_i387_struct *from);
+
+int um_fxsr_from_i387(struct user_fxsr_struct *fxsave,
+		      const struct user_i387_struct *from)
+{
+	int i;
 
 	fxsave->cwd = (unsigned short)(from->cwd & 0xffff);
 	fxsave->swd = (unsigned short)(from->swd & 0xffff);
···
 	}
 
 	return 0;
+}
+
+static int fpregs_legacy_set(struct task_struct *target,
+			     const struct user_regset *regset,
+			     unsigned int pos, unsigned int count,
+			     const void *kbuf, const void __user *ubuf)
+{
+	struct user_fxsr_struct *fxsave = (void *)target->thread.regs.regs.fp;
+	const struct user_i387_struct *from;
+	struct user_i387_struct buf;
+
+	if (ubuf) {
+		if (copy_from_user(&buf, ubuf, sizeof(buf)))
+			return -EFAULT;
+		from = &buf;
+	} else {
+		from = kbuf;
+	}
+
+	return um_fxsr_from_i387(fxsave, &buf);
 }
 #endif
 

arch/x86/um/shared/sysdep/kernel-offsets.h

···
 #include <linux/elf.h>
 #include <linux/crypto.h>
 #include <linux/kbuild.h>
+#include <linux/audit.h>
 #include <asm/mman.h>
+#include <asm/seccomp.h>
 
 /* workaround for a warning with -Wmissing-prototypes */
 void foo(void);

arch/x86/um/shared/sysdep/mcontext.h

···
 #ifndef __SYS_SIGCONTEXT_X86_H
 #define __SYS_SIGCONTEXT_X86_H
 
+#include <stub-data.h>
+
 extern void get_regs_from_mc(struct uml_pt_regs *, mcontext_t *);
+extern void get_mc_from_regs(struct uml_pt_regs *regs, mcontext_t *mc,
+			     int single_stepping);
+
+extern int get_stub_state(struct uml_pt_regs *regs, struct stub_data *data,
+			  unsigned long *fp_size_out);
+extern int set_stub_state(struct uml_pt_regs *regs, struct stub_data *data,
+			  int single_stepping);
 
 #ifdef __i386__
 

arch/x86/um/shared/sysdep/stub-data.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARCH_STUB_DATA_H
+#define __ARCH_STUB_DATA_H
+
+#ifdef __i386__
+#include <generated/asm-offsets.h>
+#include <asm/ldt.h>
+
+struct stub_data_arch {
+	int sync;
+	struct user_desc tls[UM_KERN_GDT_ENTRY_TLS_ENTRIES];
+};
+#else
+#define STUB_SYNC_FS_BASE (1 << 0)
+#define STUB_SYNC_GS_BASE (1 << 1)
+struct stub_data_arch {
+	int sync;
+	unsigned long fs_base;
+	unsigned long gs_base;
+};
+#endif
+
+#endif /* __ARCH_STUB_DATA_H */

arch/x86/um/shared/sysdep/stub.h

···
 
 extern void stub_segv_handler(int, siginfo_t *, void *);
 extern void stub_syscall_handler(void);
+extern void stub_signal_interrupt(int, siginfo_t *, void *);
+extern void stub_signal_restorer(void);

arch/x86/um/shared/sysdep/stub_32.h

···
 		"call *%%eax ;"						\
 		:: "i" ((1 + STUB_DATA_PAGES) * UM_KERN_PAGE_SIZE),	\
 		   "i" (&fn))
+
+static __always_inline void
+stub_seccomp_restore_state(struct stub_data_arch *arch)
+{
+	for (int i = 0; i < sizeof(arch->tls) / sizeof(arch->tls[0]); i++) {
+		if (arch->sync & (1 << i))
+			stub_syscall1(__NR_set_thread_area,
+				      (unsigned long) &arch->tls[i]);
+	}
+
+	arch->sync = 0;
+}
+
 #endif

arch/x86/um/shared/sysdep/stub_64.h

···
 #include <sysdep/ptrace_user.h>
 #include <generated/asm-offsets.h>
 #include <linux/stddef.h>
+#include <asm/prctl.h>
 
 #define STUB_MMAP_NR __NR_mmap
 #define MMAP_OFFSET(o) (o)
···
 		"call *%%rax ;"						\
 		:: "i" ((1 + STUB_DATA_PAGES) * UM_KERN_PAGE_SIZE),	\
 		   "i" (&fn))
+
+static __always_inline void
+stub_seccomp_restore_state(struct stub_data_arch *arch)
+{
+	/*
+	 * We could use _writefsbase_u64/_writegsbase_u64 if the host reports
+	 * support in the hwcaps (HWCAP2_FSGSBASE).
+	 */
+	if (arch->sync & STUB_SYNC_FS_BASE)
+		stub_syscall2(__NR_arch_prctl, ARCH_SET_FS, arch->fs_base);
+	if (arch->sync & STUB_SYNC_GS_BASE)
+		stub_syscall2(__NR_arch_prctl, ARCH_SET_GS, arch->gs_base);
+
+	arch->sync = 0;
+}
+
 #endif

arch/x86/um/tls_32.c

···
 #include <skas.h>
 #include <sysdep/tls.h>
 #include <asm/desc.h>
+#include <stub-data.h>
 
 /*
  * If needed we can detect when it's uninitialized.
···
 static int host_supports_tls = -1;
 int host_gdt_entry_tls_min;
 
-static int do_set_thread_area(struct user_desc *info)
+static int do_set_thread_area(struct task_struct* task, struct user_desc *info)
 {
 	int ret;
-	u32 cpu;
 
-	cpu = get_cpu();
-	ret = os_set_thread_area(info, userspace_pid[cpu]);
-	put_cpu();
+	if (info->entry_number < host_gdt_entry_tls_min ||
+	    info->entry_number >= host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES)
+		return -EINVAL;
+
+	if (using_seccomp) {
+		int idx = info->entry_number - host_gdt_entry_tls_min;
+		struct stub_data *data = (void *)task->mm->context.id.stack;
+
+		data->arch_data.tls[idx] = *info;
+		data->arch_data.sync |= BIT(idx);
+
+		return 0;
+	}
+
+	ret = os_set_thread_area(info, task->mm->context.id.pid);
 
 	if (ret)
 		printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, "
···
 		if (!(flags & O_FORCE) && curr->flushed)
 			continue;
 
-		ret = do_set_thread_area(&curr->tls);
+		ret = do_set_thread_area(current, &curr->tls);
 		if (ret)
 			goto out;
 
···
 			return -EFAULT;
 	}
 
-	ret = do_set_thread_area(&info);
+	ret = do_set_thread_area(current, &info);
 	if (ret)
 		return ret;
 	return set_tls_entry(current, &info, idx, 1);