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