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