linux/drivers/xen/evtchn.c
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   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
  56struct 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/*
  73 * Who's bound to each port?  This is logically an array of struct
  74 * per_user_data *, but we encode the current enabled-state in bit 0.
  75 */
  76static unsigned long *port_user;
  77static DEFINE_SPINLOCK(port_user_lock); /* protects port_user[] and ring_prod */
  78
  79static inline struct per_user_data *get_port_user(unsigned port)
  80{
  81        return (struct per_user_data *)(port_user[port] & ~1);
  82}
  83
  84static inline void set_port_user(unsigned port, struct per_user_data *u)
  85{
  86        port_user[port] = (unsigned long)u;
  87}
  88
  89static inline bool get_port_enabled(unsigned port)
  90{
  91        return port_user[port] & 1;
  92}
  93
  94static inline void set_port_enabled(unsigned port, bool enabled)
  95{
  96        if (enabled)
  97                port_user[port] |= 1;
  98        else
  99                port_user[port] &= ~1;
 100}
 101
 102static irqreturn_t evtchn_interrupt(int irq, void *data)
 103{
 104        unsigned int port = (unsigned long)data;
 105        struct per_user_data *u;
 106
 107        spin_lock(&port_user_lock);
 108
 109        u = get_port_user(port);
 110
 111        WARN(!get_port_enabled(port),
 112             "Interrupt for port %d, but apparently not enabled; per-user %p\n",
 113             port, u);
 114
 115        disable_irq_nosync(irq);
 116        set_port_enabled(port, false);
 117
 118        if ((u->ring_prod - u->ring_cons) < EVTCHN_RING_SIZE) {
 119                u->ring[EVTCHN_RING_MASK(u->ring_prod)] = port;
 120                wmb(); /* Ensure ring contents visible */
 121                if (u->ring_cons == u->ring_prod++) {
 122                        wake_up_interruptible(&u->evtchn_wait);
 123                        kill_fasync(&u->evtchn_async_queue,
 124                                    SIGIO, POLL_IN);
 125                }
 126        } else
 127                u->ring_overflow = 1;
 128
 129        spin_unlock(&port_user_lock);
 130
 131        return IRQ_HANDLED;
 132}
 133
 134static ssize_t evtchn_read(struct file *file, char __user *buf,
 135                           size_t count, loff_t *ppos)
 136{
 137        int rc;
 138        unsigned int c, p, bytes1 = 0, bytes2 = 0;
 139        struct per_user_data *u = file->private_data;
 140
 141        /* Whole number of ports. */
 142        count &= ~(sizeof(evtchn_port_t)-1);
 143
 144        if (count == 0)
 145                return 0;
 146
 147        if (count > PAGE_SIZE)
 148                count = PAGE_SIZE;
 149
 150        for (;;) {
 151                mutex_lock(&u->ring_cons_mutex);
 152
 153                rc = -EFBIG;
 154                if (u->ring_overflow)
 155                        goto unlock_out;
 156
 157                c = u->ring_cons;
 158                p = u->ring_prod;
 159                if (c != p)
 160                        break;
 161
 162                mutex_unlock(&u->ring_cons_mutex);
 163
 164                if (file->f_flags & O_NONBLOCK)
 165                        return -EAGAIN;
 166
 167                rc = wait_event_interruptible(u->evtchn_wait,
 168                                              u->ring_cons != u->ring_prod);
 169                if (rc)
 170                        return rc;
 171        }
 172
 173        /* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
 174        if (((c ^ p) & EVTCHN_RING_SIZE) != 0) {
 175                bytes1 = (EVTCHN_RING_SIZE - EVTCHN_RING_MASK(c)) *
 176                        sizeof(evtchn_port_t);
 177                bytes2 = EVTCHN_RING_MASK(p) * sizeof(evtchn_port_t);
 178        } else {
 179                bytes1 = (p - c) * sizeof(evtchn_port_t);
 180                bytes2 = 0;
 181        }
 182
 183        /* Truncate chunks according to caller's maximum byte count. */
 184        if (bytes1 > count) {
 185                bytes1 = count;
 186                bytes2 = 0;
 187        } else if ((bytes1 + bytes2) > count) {
 188                bytes2 = count - bytes1;
 189        }
 190
 191        rc = -EFAULT;
 192        rmb(); /* Ensure that we see the port before we copy it. */
 193        if (copy_to_user(buf, &u->ring[EVTCHN_RING_MASK(c)], bytes1) ||
 194            ((bytes2 != 0) &&
 195             copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
 196                goto unlock_out;
 197
 198        u->ring_cons += (bytes1 + bytes2) / sizeof(evtchn_port_t);
 199        rc = bytes1 + bytes2;
 200
 201 unlock_out:
 202        mutex_unlock(&u->ring_cons_mutex);
 203        return rc;
 204}
 205
 206static ssize_t evtchn_write(struct file *file, const char __user *buf,
 207                            size_t count, loff_t *ppos)
 208{
 209        int rc, i;
 210        evtchn_port_t *kbuf = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
 211        struct per_user_data *u = file->private_data;
 212
 213        if (kbuf == NULL)
 214                return -ENOMEM;
 215
 216        /* Whole number of ports. */
 217        count &= ~(sizeof(evtchn_port_t)-1);
 218
 219        rc = 0;
 220        if (count == 0)
 221                goto out;
 222
 223        if (count > PAGE_SIZE)
 224                count = PAGE_SIZE;
 225
 226        rc = -EFAULT;
 227        if (copy_from_user(kbuf, buf, count) != 0)
 228                goto out;
 229
 230        spin_lock_irq(&port_user_lock);
 231
 232        for (i = 0; i < (count/sizeof(evtchn_port_t)); i++) {
 233                unsigned port = kbuf[i];
 234
 235                if (port < NR_EVENT_CHANNELS &&
 236                    get_port_user(port) == u &&
 237                    !get_port_enabled(port)) {
 238                        set_port_enabled(port, true);
 239                        enable_irq(irq_from_evtchn(port));
 240                }
 241        }
 242
 243        spin_unlock_irq(&port_user_lock);
 244
 245        rc = count;
 246
 247 out:
 248        free_page((unsigned long)kbuf);
 249        return rc;
 250}
 251
 252static int evtchn_bind_to_user(struct per_user_data *u, int port)
 253{
 254        int rc = 0;
 255
 256        /*
 257         * Ports are never reused, so every caller should pass in a
 258         * unique port.
 259         *
 260         * (Locking not necessary because we haven't registered the
 261         * interrupt handler yet, and our caller has already
 262         * serialized bind operations.)
 263         */
 264        BUG_ON(get_port_user(port) != NULL);
 265        set_port_user(port, u);
 266        set_port_enabled(port, true); /* start enabled */
 267
 268        rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
 269                                       u->name, (void *)(unsigned long)port);
 270        if (rc >= 0)
 271                rc = evtchn_make_refcounted(port);
 272
 273        return rc;
 274}
 275
 276static void evtchn_unbind_from_user(struct per_user_data *u, int port)
 277{
 278        int irq = irq_from_evtchn(port);
 279
 280        unbind_from_irqhandler(irq, (void *)(unsigned long)port);
 281
 282        set_port_user(port, NULL);
 283}
 284
 285static long evtchn_ioctl(struct file *file,
 286                         unsigned int cmd, unsigned long arg)
 287{
 288        int rc;
 289        struct per_user_data *u = file->private_data;
 290        void __user *uarg = (void __user *) arg;
 291
 292        /* Prevent bind from racing with unbind */
 293        mutex_lock(&u->bind_mutex);
 294
 295        switch (cmd) {
 296        case IOCTL_EVTCHN_BIND_VIRQ: {
 297                struct ioctl_evtchn_bind_virq bind;
 298                struct evtchn_bind_virq bind_virq;
 299
 300                rc = -EFAULT;
 301                if (copy_from_user(&bind, uarg, sizeof(bind)))
 302                        break;
 303
 304                bind_virq.virq = bind.virq;
 305                bind_virq.vcpu = 0;
 306                rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
 307                                                 &bind_virq);
 308                if (rc != 0)
 309                        break;
 310
 311                rc = evtchn_bind_to_user(u, bind_virq.port);
 312                if (rc == 0)
 313                        rc = bind_virq.port;
 314                break;
 315        }
 316
 317        case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
 318                struct ioctl_evtchn_bind_interdomain bind;
 319                struct evtchn_bind_interdomain bind_interdomain;
 320
 321                rc = -EFAULT;
 322                if (copy_from_user(&bind, uarg, sizeof(bind)))
 323                        break;
 324
 325                bind_interdomain.remote_dom  = bind.remote_domain;
 326                bind_interdomain.remote_port = bind.remote_port;
 327                rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
 328                                                 &bind_interdomain);
 329                if (rc != 0)
 330                        break;
 331
 332                rc = evtchn_bind_to_user(u, bind_interdomain.local_port);
 333                if (rc == 0)
 334                        rc = bind_interdomain.local_port;
 335                break;
 336        }
 337
 338        case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
 339                struct ioctl_evtchn_bind_unbound_port bind;
 340                struct evtchn_alloc_unbound alloc_unbound;
 341
 342                rc = -EFAULT;
 343                if (copy_from_user(&bind, uarg, sizeof(bind)))
 344                        break;
 345
 346                alloc_unbound.dom        = DOMID_SELF;
 347                alloc_unbound.remote_dom = bind.remote_domain;
 348                rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
 349                                                 &alloc_unbound);
 350                if (rc != 0)
 351                        break;
 352
 353                rc = evtchn_bind_to_user(u, alloc_unbound.port);
 354                if (rc == 0)
 355                        rc = alloc_unbound.port;
 356                break;
 357        }
 358
 359        case IOCTL_EVTCHN_UNBIND: {
 360                struct ioctl_evtchn_unbind unbind;
 361
 362                rc = -EFAULT;
 363                if (copy_from_user(&unbind, uarg, sizeof(unbind)))
 364                        break;
 365
 366                rc = -EINVAL;
 367                if (unbind.port >= NR_EVENT_CHANNELS)
 368                        break;
 369
 370                spin_lock_irq(&port_user_lock);
 371
 372                rc = -ENOTCONN;
 373                if (get_port_user(unbind.port) != u) {
 374                        spin_unlock_irq(&port_user_lock);
 375                        break;
 376                }
 377
 378                disable_irq(irq_from_evtchn(unbind.port));
 379
 380                spin_unlock_irq(&port_user_lock);
 381
 382                evtchn_unbind_from_user(u, unbind.port);
 383
 384                rc = 0;
 385                break;
 386        }
 387
 388        case IOCTL_EVTCHN_NOTIFY: {
 389                struct ioctl_evtchn_notify notify;
 390
 391                rc = -EFAULT;
 392                if (copy_from_user(&notify, uarg, sizeof(notify)))
 393                        break;
 394
 395                if (notify.port >= NR_EVENT_CHANNELS) {
 396                        rc = -EINVAL;
 397                } else if (get_port_user(notify.port) != u) {
 398                        rc = -ENOTCONN;
 399                } else {
 400                        notify_remote_via_evtchn(notify.port);
 401                        rc = 0;
 402                }
 403                break;
 404        }
 405
 406        case IOCTL_EVTCHN_RESET: {
 407                /* Initialise the ring to empty. Clear errors. */
 408                mutex_lock(&u->ring_cons_mutex);
 409                spin_lock_irq(&port_user_lock);
 410                u->ring_cons = u->ring_prod = u->ring_overflow = 0;
 411                spin_unlock_irq(&port_user_lock);
 412                mutex_unlock(&u->ring_cons_mutex);
 413                rc = 0;
 414                break;
 415        }
 416
 417        default:
 418                rc = -ENOSYS;
 419                break;
 420        }
 421        mutex_unlock(&u->bind_mutex);
 422
 423        return rc;
 424}
 425
 426static unsigned int evtchn_poll(struct file *file, poll_table *wait)
 427{
 428        unsigned int mask = POLLOUT | POLLWRNORM;
 429        struct per_user_data *u = file->private_data;
 430
 431        poll_wait(file, &u->evtchn_wait, wait);
 432        if (u->ring_cons != u->ring_prod)
 433                mask |= POLLIN | POLLRDNORM;
 434        if (u->ring_overflow)
 435                mask = POLLERR;
 436        return mask;
 437}
 438
 439static int evtchn_fasync(int fd, struct file *filp, int on)
 440{
 441        struct per_user_data *u = filp->private_data;
 442        return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
 443}
 444
 445static int evtchn_open(struct inode *inode, struct file *filp)
 446{
 447        struct per_user_data *u;
 448
 449        u = kzalloc(sizeof(*u), GFP_KERNEL);
 450        if (u == NULL)
 451                return -ENOMEM;
 452
 453        u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
 454        if (u->name == NULL) {
 455                kfree(u);
 456                return -ENOMEM;
 457        }
 458
 459        init_waitqueue_head(&u->evtchn_wait);
 460
 461        u->ring = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
 462        if (u->ring == NULL) {
 463                kfree(u->name);
 464                kfree(u);
 465                return -ENOMEM;
 466        }
 467
 468        mutex_init(&u->bind_mutex);
 469        mutex_init(&u->ring_cons_mutex);
 470
 471        filp->private_data = u;
 472
 473        return nonseekable_open(inode, filp);
 474}
 475
 476static int evtchn_release(struct inode *inode, struct file *filp)
 477{
 478        int i;
 479        struct per_user_data *u = filp->private_data;
 480
 481        spin_lock_irq(&port_user_lock);
 482
 483        free_page((unsigned long)u->ring);
 484
 485        for (i = 0; i < NR_EVENT_CHANNELS; i++) {
 486                if (get_port_user(i) != u)
 487                        continue;
 488
 489                disable_irq(irq_from_evtchn(i));
 490        }
 491
 492        spin_unlock_irq(&port_user_lock);
 493
 494        for (i = 0; i < NR_EVENT_CHANNELS; i++) {
 495                if (get_port_user(i) != u)
 496                        continue;
 497
 498                evtchn_unbind_from_user(get_port_user(i), i);
 499        }
 500
 501        kfree(u->name);
 502        kfree(u);
 503
 504        return 0;
 505}
 506
 507static const struct file_operations evtchn_fops = {
 508        .owner   = THIS_MODULE,
 509        .read    = evtchn_read,
 510        .write   = evtchn_write,
 511        .unlocked_ioctl = evtchn_ioctl,
 512        .poll    = evtchn_poll,
 513        .fasync  = evtchn_fasync,
 514        .open    = evtchn_open,
 515        .release = evtchn_release,
 516        .llseek  = no_llseek,
 517};
 518
 519static struct miscdevice evtchn_miscdev = {
 520        .minor        = MISC_DYNAMIC_MINOR,
 521        .name         = "xen/evtchn",
 522        .fops         = &evtchn_fops,
 523};
 524static int __init evtchn_init(void)
 525{
 526        int err;
 527
 528        if (!xen_domain())
 529                return -ENODEV;
 530
 531        port_user = kcalloc(NR_EVENT_CHANNELS, sizeof(*port_user), GFP_KERNEL);
 532        if (port_user == NULL)
 533                return -ENOMEM;
 534
 535        spin_lock_init(&port_user_lock);
 536
 537        /* Create '/dev/misc/evtchn'. */
 538        err = misc_register(&evtchn_miscdev);
 539        if (err != 0) {
 540                printk(KERN_ALERT "Could not register /dev/misc/evtchn\n");
 541                return err;
 542        }
 543
 544        printk(KERN_INFO "Event-channel device installed.\n");
 545
 546        return 0;
 547}
 548
 549static void __exit evtchn_cleanup(void)
 550{
 551        kfree(port_user);
 552        port_user = NULL;
 553
 554        misc_deregister(&evtchn_miscdev);
 555}
 556
 557module_init(evtchn_init);
 558module_exit(evtchn_cleanup);
 559
 560MODULE_LICENSE("GPL");
 561
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