drivers/xen/evtchn.c

   1 /******************************************************************************
   2  * evtchn.c
   3  *
   4  * Driver for receiving and demuxing event-channel signals.
   5  *
   6  * Copyright (c) 2004-2005, K A Fraser
   7  * Multi-process extensions Copyright (c) 2004, Steven Smith
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License version 2
  11  * as published by the Free Software Foundation; or, when distributed
  12  * separately from the Linux kernel or incorporated into other
  13  * software packages, subject to the following license:
  14  *
  15  * Permission is hereby granted, free of charge, to any person obtaining a copy
  16  * of this source file (the "Software"), to deal in the Software without
  17  * restriction, including without limitation the rights to use, copy, modify,
  18  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  19  * and to permit persons to whom the Software is furnished to do so, subject to
  20  * the following conditions:
  21  *
  22  * The above copyright notice and this permission notice shall be included in
  23  * all copies or substantial portions of the Software.
  24  *
  25  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  26  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  27  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  28  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  29  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  30  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  31  * IN THE SOFTWARE.
  32  */
  33
  34 #include <linux/module.h>
  35 #include <linux/kernel.h>
  36 #include <linux/sched.h>
  37 #include <linux/slab.h>
  38 #include <linux/string.h>
  39 #include <linux/errno.h>
  40 #include <linux/fs.h>
  41 #include <linux/miscdevice.h>
  42 #include <linux/major.h>
  43 #include <linux/proc_fs.h>
  44 #include <linux/stat.h>
  45 #include <linux/poll.h>
  46 #include <linux/irq.h>
  47 #include <linux/init.h>
  48 #include <linux/mutex.h>
  49 #include <linux/cpu.h>
  50
  51 #include <xen/xen.h>
  52 #include <xen/events.h>
  53 #include <xen/evtchn.h>
  54 #include <asm/xen/hypervisor.h>
  55
  56 struct per_user_data {
  57         struct mutex bind_mutex; /* serialize bind/unbind operations */
  58
  59         /* Notification ring, accessed via /dev/xen/evtchn. */
  60 #define EVTCHN_RING_SIZE     (PAGE_SIZE / sizeof(evtchn_port_t))
  61 #define EVTCHN_RING_MASK(_i) ((_i)&(EVTCHN_RING_SIZE-1))
  62         evtchn_port_t *ring;
  63         unsigned int ring_cons, ring_prod, ring_overflow;
  64         struct mutex ring_cons_mutex; /* protect against concurrent readers */
  65
  66         /* Processes wait on this queue when ring is empty. */
  67         wait_queue_head_t evtchn_wait;
  68         struct fasync_struct *evtchn_async_queue;
  69         const char *name;
  70 };
  71
  72 /* Who's bound to each port? */
  73 static struct per_user_data *port_user[NR_EVENT_CHANNELS];
  74 static DEFINE_SPINLOCK(port_user_lock); /* protects port_user[] and ring_prod */
  75
  76 irqreturn_t evtchn_interrupt(int irq, void *data)
  77 {
  78         unsigned int port = (unsigned long)data;
  79         struct per_user_data *u;
  80
  81         spin_lock(&port_user_lock);
  82
  83         u = port_user[port];
  84
  85         disable_irq_nosync(irq);
  86
  87         if ((u->ring_prod - u->ring_cons) < EVTCHN_RING_SIZE) {
  88                 u->ring[EVTCHN_RING_MASK(u->ring_prod)] = port;
  89                 wmb(); /* Ensure ring contents visible */
  90                 if (u->ring_cons == u->ring_prod++) {
  91                         wake_up_interruptible(&u->evtchn_wait);
  92                         kill_fasync(&u->evtchn_async_queue,
  93                                     SIGIO, POLL_IN);
  94                 }
  95         } else {
  96                 u->ring_overflow = 1;
  97         }
  98
  99         spin_unlock(&port_user_lock);
 100
 101         return IRQ_HANDLED;
 102 }
 103
 104 static ssize_t evtchn_read(struct file *file, char __user *buf,
 105                            size_t count, loff_t *ppos)
 106 {
 107         int rc;
 108         unsigned int c, p, bytes1 = 0, bytes2 = 0;
 109         struct per_user_data *u = file->private_data;
 110
 111         /* Whole number of ports. */
 112         count &= ~(sizeof(evtchn_port_t)-1);
 113
 114         if (count == 0)
 115                 return 0;
 116
 117         if (count > PAGE_SIZE)
 118                 count = PAGE_SIZE;
 119
 120         for (;;) {
 121                 mutex_lock(&u->ring_cons_mutex);
 122
 123                 rc = -EFBIG;
 124                 if (u->ring_overflow)
 125                         goto unlock_out;
 126
 127                 c = u->ring_cons;
 128                 p = u->ring_prod;
 129                 if (c != p)
 130                         break;
 131
 132                 mutex_unlock(&u->ring_cons_mutex);
 133
 134                 if (file->f_flags & O_NONBLOCK)
 135                         return -EAGAIN;
 136
 137                 rc = wait_event_interruptible(u->evtchn_wait,
 138                                               u->ring_cons != u->ring_prod);
 139                 if (rc)
 140                         return rc;
 141         }
 142
 143         /* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
 144         if (((c ^ p) & EVTCHN_RING_SIZE) != 0) {
 145                 bytes1 = (EVTCHN_RING_SIZE - EVTCHN_RING_MASK(c)) *
 146                         sizeof(evtchn_port_t);
 147                 bytes2 = EVTCHN_RING_MASK(p) * sizeof(evtchn_port_t);
 148         } else {
 149                 bytes1 = (p - c) * sizeof(evtchn_port_t);
 150                 bytes2 = 0;
 151         }
 152
 153         /* Truncate chunks according to caller's maximum byte count. */
 154         if (bytes1 > count) {
 155                 bytes1 = count;
 156                 bytes2 = 0;
 157         } else if ((bytes1 + bytes2) > count) {
 158                 bytes2 = count - bytes1;
 159         }
 160
 161         rc = -EFAULT;
 162         rmb(); /* Ensure that we see the port before we copy it. */
 163         if (copy_to_user(buf, &u->ring[EVTCHN_RING_MASK(c)], bytes1) ||
 164             ((bytes2 != 0) &&
 165              copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
 166                 goto unlock_out;
 167
 168         u->ring_cons += (bytes1 + bytes2) / sizeof(evtchn_port_t);
 169         rc = bytes1 + bytes2;
 170
 171  unlock_out:
 172         mutex_unlock(&u->ring_cons_mutex);
 173         return rc;
 174 }
 175
 176 static ssize_t evtchn_write(struct file *file, const char __user *buf,
 177                             size_t count, loff_t *ppos)
 178 {
 179         int rc, i;
 180         evtchn_port_t *kbuf = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
 181         struct per_user_data *u = file->private_data;
 182
 183         if (kbuf == NULL)
 184                 return -ENOMEM;
 185
 186         /* Whole number of ports. */
 187         count &= ~(sizeof(evtchn_port_t)-1);
 188
 189         rc = 0;
 190         if (count == 0)
 191                 goto out;
 192
 193         if (count > PAGE_SIZE)
 194                 count = PAGE_SIZE;
 195
 196         rc = -EFAULT;
 197         if (copy_from_user(kbuf, buf, count) != 0)
 198                 goto out;
 199
 200         spin_lock_irq(&port_user_lock);
 201         for (i = 0; i < (count/sizeof(evtchn_port_t)); i++)
 202                 if ((kbuf[i] < NR_EVENT_CHANNELS) && (port_user[kbuf[i]] == u))
 203                         enable_irq(irq_from_evtchn(kbuf[i]));
 204         spin_unlock_irq(&port_user_lock);
 205
 206         rc = count;
 207
 208  out:
 209         free_page((unsigned long)kbuf);
 210         return rc;
 211 }
 212
 213 static int evtchn_bind_to_user(struct per_user_data *u, int port)
 214 {
 215         int rc = 0;
 216
 217         /*
 218          * Ports are never reused, so every caller should pass in a
 219          * unique port.
 220          *
 221          * (Locking not necessary because we haven't registered the
 222          * interrupt handler yet, and our caller has already
 223          * serialized bind operations.)
 224          */
 225         BUG_ON(port_user[port] != NULL);
 226         port_user[port] = u;
 227
 228         rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
 229                                        u->name, (void *)(unsigned long)port);
 230         if (rc >= 0)
 231                 rc = 0;
 232
 233         return rc;
 234 }
 235
 236 static void evtchn_unbind_from_user(struct per_user_data *u, int port)
 237 {
 238         int irq = irq_from_evtchn(port);
 239
 240         unbind_from_irqhandler(irq, (void *)(unsigned long)port);
 241
 242         /* make sure we unbind the irq handler before clearing the port */
 243         barrier();
 244
 245         port_user[port] = NULL;
 246 }
 247
 248 static long evtchn_ioctl(struct file *file,
 249                          unsigned int cmd, unsigned long arg)
 250 {
 251         int rc;
 252         struct per_user_data *u = file->private_data;
 253         void __user *uarg = (void __user *) arg;
 254
 255         /* Prevent bind from racing with unbind */
 256         mutex_lock(&u->bind_mutex);
 257
 258         switch (cmd) {
 259         case IOCTL_EVTCHN_BIND_VIRQ: {
 260                 struct ioctl_evtchn_bind_virq bind;
 261                 struct evtchn_bind_virq bind_virq;
 262
 263                 rc = -EFAULT;
 264                 if (copy_from_user(&bind, uarg, sizeof(bind)))
 265                         break;
 266
 267                 bind_virq.virq = bind.virq;
 268                 bind_virq.vcpu = 0;
 269                 rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
 270                                                  &bind_virq);
 271                 if (rc != 0)
 272                         break;
 273
 274                 rc = evtchn_bind_to_user(u, bind_virq.port);
 275                 if (rc == 0)
 276                         rc = bind_virq.port;
 277                 break;
 278         }
 279
 280         case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
 281                 struct ioctl_evtchn_bind_interdomain bind;
 282                 struct evtchn_bind_interdomain bind_interdomain;
 283
 284                 rc = -EFAULT;
 285                 if (copy_from_user(&bind, uarg, sizeof(bind)))
 286                         break;
 287
 288                 bind_interdomain.remote_dom  = bind.remote_domain;
 289                 bind_interdomain.remote_port = bind.remote_port;
 290                 rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
 291                                                  &bind_interdomain);
 292                 if (rc != 0)
 293                         break;
 294
 295                 rc = evtchn_bind_to_user(u, bind_interdomain.local_port);
 296                 if (rc == 0)
 297                         rc = bind_interdomain.local_port;
 298                 break;
 299         }
 300
 301         case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
 302                 struct ioctl_evtchn_bind_unbound_port bind;
 303                 struct evtchn_alloc_unbound alloc_unbound;
 304
 305                 rc = -EFAULT;
 306                 if (copy_from_user(&bind, uarg, sizeof(bind)))
 307                         break;
 308
 309                 alloc_unbound.dom        = DOMID_SELF;
 310                 alloc_unbound.remote_dom = bind.remote_domain;
 311                 rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
 312                                                  &alloc_unbound);
 313                 if (rc != 0)
 314                         break;
 315
 316                 rc = evtchn_bind_to_user(u, alloc_unbound.port);
 317                 if (rc == 0)
 318                         rc = alloc_unbound.port;
 319                 break;
 320         }
 321
 322         case IOCTL_EVTCHN_UNBIND: {
 323                 struct ioctl_evtchn_unbind unbind;
 324
 325                 rc = -EFAULT;
 326                 if (copy_from_user(&unbind, uarg, sizeof(unbind)))
 327                         break;
 328
 329                 rc = -EINVAL;
 330                 if (unbind.port >= NR_EVENT_CHANNELS)
 331                         break;
 332
 333                 spin_lock_irq(&port_user_lock);
 334
 335                 rc = -ENOTCONN;
 336                 if (port_user[unbind.port] != u) {
 337                         spin_unlock_irq(&port_user_lock);
 338                         break;
 339                 }
 340
 341                 evtchn_unbind_from_user(u, unbind.port);
 342
 343                 spin_unlock_irq(&port_user_lock);
 344
 345                 rc = 0;
 346                 break;
 347         }
 348
 349         case IOCTL_EVTCHN_NOTIFY: {
 350                 struct ioctl_evtchn_notify notify;
 351
 352                 rc = -EFAULT;
 353                 if (copy_from_user(&notify, uarg, sizeof(notify)))
 354                         break;
 355
 356                 if (notify.port >= NR_EVENT_CHANNELS) {
 357                         rc = -EINVAL;
 358                 } else if (port_user[notify.port] != u) {
 359                         rc = -ENOTCONN;
 360                 } else {
 361                         notify_remote_via_evtchn(notify.port);
 362                         rc = 0;
 363                 }
 364                 break;
 365         }
 366
 367         case IOCTL_EVTCHN_RESET: {
 368                 /* Initialise the ring to empty. Clear errors. */
 369                 mutex_lock(&u->ring_cons_mutex);
 370                 spin_lock_irq(&port_user_lock);
 371                 u->ring_cons = u->ring_prod = u->ring_overflow = 0;
 372                 spin_unlock_irq(&port_user_lock);
 373                 mutex_unlock(&u->ring_cons_mutex);
 374                 rc = 0;
 375                 break;
 376         }
 377
 378         default:
 379                 rc = -ENOSYS;
 380                 break;
 381         }
 382         mutex_unlock(&u->bind_mutex);
 383
 384         return rc;
 385 }
 386
 387 static unsigned int evtchn_poll(struct file *file, poll_table *wait)
 388 {
 389         unsigned int mask = POLLOUT | POLLWRNORM;
 390         struct per_user_data *u = file->private_data;
 391
 392         poll_wait(file, &u->evtchn_wait, wait);
 393         if (u->ring_cons != u->ring_prod)
 394                 mask |= POLLIN | POLLRDNORM;
 395         if (u->ring_overflow)
 396                 mask = POLLERR;
 397         return mask;
 398 }
 399
 400 static int evtchn_fasync(int fd, struct file *filp, int on)
 401 {
 402         struct per_user_data *u = filp->private_data;
 403         return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
 404 }
 405
 406 static int evtchn_open(struct inode *inode, struct file *filp)
 407 {
 408         struct per_user_data *u;
 409
 410         u = kzalloc(sizeof(*u), GFP_KERNEL);
 411         if (u == NULL)
 412                 return -ENOMEM;
 413
 414         u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
 415         if (u->name == NULL) {
 416                 kfree(u);
 417                 return -ENOMEM;
 418         }
 419
 420         init_waitqueue_head(&u->evtchn_wait);
 421
 422         u->ring = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
 423         if (u->ring == NULL) {
 424                 kfree(u->name);
 425                 kfree(u);
 426                 return -ENOMEM;
 427         }
 428
 429         mutex_init(&u->bind_mutex);
 430         mutex_init(&u->ring_cons_mutex);
 431
 432         filp->private_data = u;
 433
 434         return 0;
 435 }
 436
 437 static int evtchn_release(struct inode *inode, struct file *filp)
 438 {
 439         int i;
 440         struct per_user_data *u = filp->private_data;
 441
 442         spin_lock_irq(&port_user_lock);
 443
 444         free_page((unsigned long)u->ring);
 445
 446         for (i = 0; i < NR_EVENT_CHANNELS; i++) {
 447                 if (port_user[i] != u)
 448                         continue;
 449
 450                 evtchn_unbind_from_user(port_user[i], i);
 451         }
 452
 453         spin_unlock_irq(&port_user_lock);
 454
 455         kfree(u->name);
 456         kfree(u);
 457
 458         return 0;
 459 }
 460
 461 static const struct file_operations evtchn_fops = {
 462         .owner   = THIS_MODULE,
 463         .read    = evtchn_read,
 464         .write   = evtchn_write,
 465         .unlocked_ioctl = evtchn_ioctl,
 466         .poll    = evtchn_poll,
 467         .fasync  = evtchn_fasync,
 468         .open    = evtchn_open,
 469         .release = evtchn_release,
 470 };
 471
 472 static struct miscdevice evtchn_miscdev = {
 473         .minor        = MISC_DYNAMIC_MINOR,
 474         .name         = "evtchn",
 475         .fops         = &evtchn_fops,
 476 };
 477 static int __init evtchn_init(void)
 478 {
 479         int err;
 480
 481         if (!xen_domain())
 482                 return -ENODEV;
 483
 484         spin_lock_init(&port_user_lock);
 485         memset(port_user, 0, sizeof(port_user));
 486
 487         /* Create '/dev/misc/evtchn'. */
 488         err = misc_register(&evtchn_miscdev);
 489         if (err != 0) {
 490                 printk(KERN_ALERT "Could not register /dev/misc/evtchn\n");
 491                 return err;
 492         }
 493
 494         printk(KERN_INFO "Event-channel device installed.\n");
 495
 496         return 0;
 497 }
 498
 499 static void __exit evtchn_cleanup(void)
 500 {
 501         misc_deregister(&evtchn_miscdev);
 502 }
 503
 504 module_init(evtchn_init);
 505 module_exit(evtchn_cleanup);
 506
 507 MODULE_LICENSE("GPL");