/******************************************************************************
* evtchn.c
*
* Driver for receiving and demuxing event-channel signals.
*
* Copyright (c) 2004-2005, K A Fraser
* Multi-process extensions Copyright (c) 2004, Steven Smith
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation; or, when distributed
* separately from the Linux kernel or incorporated into other
* software packages, subject to the following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this source file (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify,
* merge, publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/major.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/poll.h>
#include <linux/irq.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <linux/cpu.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <xen/xen.h>
#include <xen/events.h>
#include <xen/evtchn.h>
#include <xen/xen-ops.h>
#include <asm/xen/hypervisor.h>
struct per_user_data {
struct mutex bind_mutex; /* serialize bind/unbind operations */
struct rb_root evtchns;
unsigned int nr_evtchns;
/* Notification ring, accessed via /dev/xen/evtchn. */
unsigned int ring_size;
evtchn_port_t *ring;
unsigned int ring_cons, ring_prod, ring_overflow;
struct mutex ring_cons_mutex; /* protect against concurrent readers */
spinlock_t ring_prod_lock; /* product against concurrent interrupts */
/* Processes wait on this queue when ring is empty. */
wait_queue_head_t evtchn_wait;
struct fasync_struct *evtchn_async_queue;
const char *name;
domid_t restrict_domid;
};
#define UNRESTRICTED_DOMID ((domid_t)-1)
struct user_evtchn {
struct rb_node node;
struct per_user_data *user;
evtchn_port_t port;
bool enabled;
bool unbinding;
};
static void evtchn_free_ring(evtchn_port_t *ring)
{
kvfree(ring);
}
static unsigned int evtchn_ring_offset(struct per_user_data *u,
unsigned int idx)
{
return idx & (u->ring_size - 1);
}
static evtchn_port_t *evtchn_ring_entry(struct per_user_data *u,
unsigned int idx)
{
return u->ring + evtchn_ring_offset(u, idx);
}
static int add_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
{
struct rb_node **new = &(u->evtchns.rb_node), *parent = NULL;
u->nr_evtchns++;
while (*new) {
struct user_evtchn *this;
this = rb_entry(*new, struct user_evtchn, node);
parent = *new;
if (this->port < evtchn->port)
new = &((*new)->rb_left);
else if (this->port > evtchn->port)
new = &((*new)->rb_right);
else
return -EEXIST;
}
/* Add new node and rebalance tree. */
rb_link_node(&evtchn->node, parent, new);
rb_insert_color(&evtchn->node, &u->evtchns);
return 0;
}
static void del_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
{
u->nr_evtchns--;
rb_erase(&evtchn->node, &u->evtchns);
kfree(evtchn);
}
static struct user_evtchn *find_evtchn(struct per_user_data *u,
evtchn_port_t port)
{
struct rb_node *node = u->evtchns.rb_node;
while (node) {
struct user_evtchn *evtchn;
evtchn = rb_entry(node, struct user_evtchn, node);
if (evtchn->port < port)
node = node->rb_left;
else if (evtchn->port > port)
node = node->rb_right;
else
return evtchn;
}
return NULL;
}
static irqreturn_t evtchn_interrupt(int irq, void *data)
{
struct user_evtchn *evtchn = data;
struct per_user_data *u = evtchn->user;
unsigned int prod, cons;
/* Handler might be called when tearing down the IRQ. */
if (evtchn->unbinding)
return IRQ_HANDLED;
WARN(!evtchn->enabled,
"Interrupt for port %u, but apparently not enabled; per-user %p\n",
evtchn->port, u);
evtchn->enabled = false;
spin_lock(&u->ring_prod_lock);
prod = READ_ONCE(u->ring_prod);
cons = READ_ONCE(u->ring_cons);
if ((prod - cons) < u->ring_size) {
*evtchn_ring_entry(u, prod) = evtchn->port;
smp_wmb(); /* Ensure ring contents visible */
WRITE_ONCE(u->ring_prod, prod + 1);
if (cons == prod) {
wake_up_interruptible(&u->evtchn_wait);
kill_fasync(&u->evtchn_async_queue,
SIGIO, POLL_IN);
}
} else
u->ring_overflow = 1;
spin_unlock(&u->ring_prod_lock);
return IRQ_HANDLED;
}
static ssize_t evtchn_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
int rc;
unsigned int c, p, bytes1 = 0, bytes2 = 0;
struct per_user_data *u = file->private_data;
/* Whole number of ports. */
count &= ~(sizeof(evtchn_port_t)-1);
if (count == 0)
return 0;
if (count > PAGE_SIZE)
count = PAGE_SIZE;
for (;;) {
mutex_lock(&u->ring_cons_mutex);
rc = -EFBIG;
if (u->ring_overflow)
goto unlock_out;
c = READ_ONCE(u->ring_cons);
p = READ_ONCE(u->ring_prod);
if (c != p)
break;
mutex_unlock(&u->ring_cons_mutex);
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;
rc = wait_event_interruptible(u->evtchn_wait,
READ_ONCE(u->ring_cons) != READ_ONCE(u->ring_prod));
if (rc)
return rc;
}
/* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
if (((c ^ p) & u->ring_size) != 0) {
bytes1 = (u->ring_size - evtchn_ring_offset(u, c)) *
sizeof(evtchn_port_t);
bytes2 = evtchn_ring_offset(u, p) * sizeof(evtchn_port_t);
} else {
bytes1 = (p - c) * sizeof(evtchn_port_t);
bytes2 = 0;
}
/* Truncate chunks according to caller's maximum byte count. */
if (bytes1 > count) {
bytes1 = count;
bytes2 = 0;
} else if ((bytes1 + bytes2) > count) {
bytes2 = count - bytes1;
}
rc = -EFAULT;
smp_rmb(); /* Ensure that we see the port before we copy it. */
if (copy_to_user(buf, evtchn_ring_entry(u, c), bytes1) ||
((bytes2 != 0) &&
copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
goto unlock_out;
WRITE_ONCE(u->ring_cons, c + (bytes1 + bytes2) / sizeof(evtchn_port_t));
rc = bytes1 + bytes2;
unlock_out:
mutex_unlock(&u->ring_cons_mutex);
return rc;
}
static ssize_t evtchn_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
int rc, i;
evtchn_port_t *kbuf = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
struct per_user_data *u = file->private_data;
if (kbuf == NULL)
return -ENOMEM;
/* Whole number of ports. */
count &= ~(sizeof(evtchn_port_t)-1);
rc = 0;
if (count == 0)
goto out;
if (count > PAGE_SIZE)
count = PAGE_SIZE;
rc = -EFAULT;
if (copy_from_user(kbuf, buf, count) != 0)
goto out;
mutex_lock(&u->bind_mutex);
for (i = 0; i < (count/sizeof(evtchn_port_t)); i++) {
evtchn_port_t port = kbuf[i];
struct user_evtchn *evtchn;
evtchn = find_evtchn(u, port);
if (evtchn && !evtchn->enabled) {
evtchn->enabled = true;
xen_irq_lateeoi(irq_from_evtchn(port), 0);
}
}
mutex_unlock(&u->bind_mutex);
rc = count;
out:
free_page((unsigned long)kbuf);
return rc;
}
static int evtchn_resize_ring(struct per_user_data *u)
{
unsigned int new_size;
evtchn_port_t *new_ring, *old_ring;
/*
* Ensure the ring is large enough to capture all possible
* events. i.e., one free slot for each bound event.
*/
if (u->nr_evtchns <= u->ring_size)
return 0;
if (u->ring_size == 0)
new_size = 64;
else
new_size = 2 * u->ring_size;
new_ring = kvmalloc_array(new_size, sizeof(*new_ring), GFP_KERNEL);
if (!new_ring)
return -ENOMEM;
old_ring = u->ring;
/*
* Access to the ring contents is serialized by either the
* prod /or/ cons lock so take both when resizing.
*/
mutex_lock(&u->ring_cons_mutex);
spin_lock_irq(&u->ring_prod_lock);
/*
* Copy the old ring contents to the new ring.
*
* To take care of wrapping, a full ring, and the new index
* pointing into the second half, simply copy the old contents
* twice.
*
* +---------+ +------------------+
* |34567 12| -> |34567 1234567 12|
* +-----p-c-+ +-------c------p---+
*/
memcpy(new_ring, old_ring, u->ring_size * sizeof(*u->ring));
memcpy(new_ring + u->ring_size, old_ring,
u->ring_size * sizeof(*u->ring));
u->ring = new_ring;
u->ring_size = new_size;
spin_unlock_irq(&u->ring_prod_lock);
mutex_unlock(&u->ring_cons_mutex);
evtchn_free_ring(old_ring);
return 0;
}
static int evtchn_bind_to_user(struct per_user_data *u, evtchn_port_t port,
bool is_static)
{
struct user_evtchn *evtchn;
int rc = 0;
/*
* Ports are never reused, so every caller should pass in a
* unique port.
*
* (Locking not necessary because we haven't registered the
* interrupt handler yet, and our caller has already
* serialized bind operations.)
*/
evtchn = kzalloc(sizeof(*evtchn), GFP_KERNEL);
if (!evtchn)
return -ENOMEM;
evtchn->user = u;
evtchn->port = port;
evtchn->enabled = true; /* start enabled */
rc = add_evtchn(u, evtchn);
if (rc < 0)
goto err;
rc = evtchn_resize_ring(u);
if (rc < 0)
goto err;
rc = bind_evtchn_to_irqhandler_lateeoi(port, evtchn_interrupt, IRQF_SHARED,
u->name, evtchn);
if (rc < 0)
goto err;
rc = evtchn_make_refcounted(port, is_static);
return rc;
err:
/* bind failed, should close the port now */
if (!is_static)
xen_evtchn_close(port);
del_evtchn(u, evtchn);
return rc;
}
static void evtchn_unbind_from_user(struct per_user_data *u,
struct user_evtchn *evtchn)
{
int irq = irq_from_evtchn(evtchn->port);
BUG_ON(irq < 0);
evtchn->unbinding = true;
unbind_from_irqhandler(irq, evtchn);
del_evtchn(u, evtchn);
}
static long evtchn_ioctl(struct file *file,
unsigned int cmd, unsigned long arg)
{
int rc;
struct per_user_data *u = file->private_data;
void __user *uarg = (void __user *) arg;
/* Prevent bind from racing with unbind */
mutex_lock(&u->bind_mutex);
switch (cmd) {
case IOCTL_EVTCHN_BIND_VIRQ: {
struct ioctl_evtchn_bind_virq bind;
struct evtchn_bind_virq bind_virq;
rc = -EACCES;
if (u->restrict_domid != UNRESTRICTED_DOMID)
break;
rc = -EFAULT;
if (copy_from_user(&bind, uarg, sizeof(bind)))
break;
bind_virq.virq = bind.virq;
bind_virq.vcpu = xen_vcpu_nr(0);
rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
&bind_virq);
if (rc != 0)
break;
rc = evtchn_bind_to_user(u, bind_virq.port, false);
if (rc == 0)
rc = bind_virq.port;
break;
}
case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
struct ioctl_evtchn_bind_interdomain bind;
struct evtchn_bind_interdomain bind_interdomain;
rc = -EFAULT;
if (copy_from_user(&bind, uarg, sizeof(bind)))
break;
rc = -EACCES;
if (u->restrict_domid != UNRESTRICTED_DOMID &&
u->restrict_domid != bind.remote_domain)
break;
bind_interdomain.remote_dom = bind.remote_domain;
bind_interdomain.remote_port = bind.remote_port;
rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
&bind_interdomain);
if (rc != 0)
break;
rc = evtchn_bind_to_user(u, bind_interdomain.local_port, false);
if (rc == 0)
rc = bind_interdomain.local_port;
break;
}
case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
struct ioctl_evtchn_bind_unbound_port bind;
struct evtchn_alloc_unbound alloc_unbound;
rc = -EACCES;
if (u->restrict_domid != UNRESTRICTED_DOMID)
break;
rc = -EFAULT;
if (copy_from_user(&bind, uarg, sizeof(bind)))
break;
alloc_unbound.dom = DOMID_SELF;
alloc_unbound.remote_dom = bind.remote_domain;
rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
&alloc_unbound);
if (rc != 0)
break;
rc = evtchn_bind_to_user(u, alloc_unbound.port, false);
if (rc == 0)
rc = alloc_unbound.port;
break;
}
case IOCTL_EVTCHN_UNBIND: {
struct ioctl_evtchn_unbind unbind;
struct user_evtchn *evtchn;
rc = -EFAULT;
if (copy_from_user(&unbind, uarg, sizeof(unbind)))
break;
rc = -EINVAL;
if (unbind.port >= xen_evtchn_nr_channels())
break;
rc = -ENOTCONN;
evtchn = find_evtchn(u, unbind.port);
if (!evtchn)
break;
disable_irq(irq_from_evtchn(unbind.port));
evtchn_unbind_from_user(u, evtchn);
rc = 0;
break;
}
case IOCTL_EVTCHN_BIND_STATIC: {
struct ioctl_evtchn_bind bind;
struct user_evtchn *evtchn;
rc = -EFAULT;
if (copy_from_user(&bind, uarg, sizeof(bind)))
break;
rc = -EISCONN;
evtchn = find_evtchn(u, bind.port);
if (evtchn)
break;
rc = evtchn_bind_to_user(u, bind.port, true);
break;
}
case IOCTL_EVTCHN_NOTIFY: {
struct ioctl_evtchn_notify notify;
struct user_evtchn *evtchn;
rc = -EFAULT;
if (copy_from_user(¬ify, uarg, sizeof(notify)))
break;
rc = -ENOTCONN;
evtchn = find_evtchn(u, notify.port);
if (evtchn) {
notify_remote_via_evtchn(notify.port);
rc = 0;
}
break;
}
case IOCTL_EVTCHN_RESET: {
/* Initialise the ring to empty. Clear errors. */
mutex_lock(&u->ring_cons_mutex);
spin_lock_irq(&u->ring_prod_lock);
WRITE_ONCE(u->ring_cons, 0);
WRITE_ONCE(u->ring_prod, 0);
u->ring_overflow = 0;
spin_unlock_irq(&u->ring_prod_lock);
mutex_unlock(&u->ring_cons_mutex);
rc = 0;
break;
}
case IOCTL_EVTCHN_RESTRICT_DOMID: {
struct ioctl_evtchn_restrict_domid ierd;
rc = -EACCES;
if (u->restrict_domid != UNRESTRICTED_DOMID)
break;
rc = -EFAULT;
if (copy_from_user(&ierd, uarg, sizeof(ierd)))
break;
rc = -EINVAL;
if (ierd.domid == 0 || ierd.domid >= DOMID_FIRST_RESERVED)
break;
u->restrict_domid = ierd.domid;
rc = 0;
break;
}
default:
rc = -ENOSYS;
break;
}
mutex_unlock(&u->bind_mutex);
return rc;
}
static __poll_t evtchn_poll(struct file *file, poll_table *wait)
{
__poll_t mask = EPOLLOUT | EPOLLWRNORM;
struct per_user_data *u = file->private_data;
poll_wait(file, &u->evtchn_wait, wait);
if (READ_ONCE(u->ring_cons) != READ_ONCE(u->ring_prod))
mask |= EPOLLIN | EPOLLRDNORM;
if (u->ring_overflow)
mask = EPOLLERR;
return mask;
}
static int evtchn_fasync(int fd, struct file *filp, int on)
{
struct per_user_data *u = filp->private_data;
return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
}
static int evtchn_open(struct inode *inode, struct file *filp)
{
struct per_user_data *u;
u = kzalloc(sizeof(*u), GFP_KERNEL);
if (u == NULL)
return -ENOMEM;
u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
if (u->name == NULL) {
kfree(u);
return -ENOMEM;
}
init_waitqueue_head(&u->evtchn_wait);
mutex_init(&u->bind_mutex);
mutex_init(&u->ring_cons_mutex);
spin_lock_init(&u->ring_prod_lock);
u->restrict_domid = UNRESTRICTED_DOMID;
filp->private_data = u;
return stream_open(inode, filp);
}
static int evtchn_release(struct inode *inode, struct file *filp)
{
struct per_user_data *u = filp->private_data;
struct rb_node *node;
while ((node = u->evtchns.rb_node)) {
struct user_evtchn *evtchn;
evtchn = rb_entry(node, struct user_evtchn, node);
disable_irq(irq_from_evtchn(evtchn->port));
evtchn_unbind_from_user(u, evtchn);
}
evtchn_free_ring(u->ring);
kfree(u->name);
kfree(u);
return 0;
}
static const struct file_operations evtchn_fops = {
.owner = THIS_MODULE,
.read = evtchn_read,
.write = evtchn_write,
.unlocked_ioctl = evtchn_ioctl,
.poll = evtchn_poll,
.fasync = evtchn_fasync,
.open = evtchn_open,
.release = evtchn_release,
};
static struct miscdevice evtchn_miscdev = {
.minor = MISC_DYNAMIC_MINOR,
.name = "xen/evtchn",
.fops = &evtchn_fops,
};
static int __init evtchn_init(void)
{
int err;
if (!xen_domain())
return -ENODEV;
/* Create '/dev/xen/evtchn'. */
err = misc_register(&evtchn_miscdev);
if (err != 0) {
pr_err("Could not register /dev/xen/evtchn\n");
return err;
}
pr_info("Event-channel device installed\n");
return 0;
}
static void __exit evtchn_cleanup(void)
{
misc_deregister(&evtchn_miscdev);
}
module_init(evtchn_init);
module_exit(evtchn_cleanup);
MODULE_DESCRIPTION("Xen /dev/xen/evtchn device driver");
MODULE_LICENSE("GPL");
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