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#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
35
36#include <linux/module.h>
37#include <linux/kernel.h>
38#include <linux/sched.h>
39#include <linux/slab.h>
40#include <linux/string.h>
41#include <linux/errno.h>
42#include <linux/fs.h>
43#include <linux/miscdevice.h>
44#include <linux/major.h>
45#include <linux/proc_fs.h>
46#include <linux/stat.h>
47#include <linux/poll.h>
48#include <linux/irq.h>
49#include <linux/init.h>
50#include <linux/mutex.h>
51#include <linux/cpu.h>
52#include <linux/mm.h>
53#include <linux/vmalloc.h>
54
55#include <xen/xen.h>
56#include <xen/events.h>
57#include <xen/evtchn.h>
58#include <xen/xen-ops.h>
59#include <asm/xen/hypervisor.h>
60
61struct per_user_data {
62 struct mutex bind_mutex; /* serialize bind/unbind operations */
63 struct rb_root evtchns;
64 unsigned int nr_evtchns;
65
66 /* Notification ring, accessed via /dev/xen/evtchn. */
67 unsigned int ring_size;
68 evtchn_port_t *ring;
69 unsigned int ring_cons, ring_prod, ring_overflow;
70 struct mutex ring_cons_mutex; /* protect against concurrent readers */
71 spinlock_t ring_prod_lock; /* product against concurrent interrupts */
72
73 /* Processes wait on this queue when ring is empty. */
74 wait_queue_head_t evtchn_wait;
75 struct fasync_struct *evtchn_async_queue;
76 const char *name;
77
78 domid_t restrict_domid;
79};
80
81#define UNRESTRICTED_DOMID ((domid_t)-1)
82
83struct user_evtchn {
84 struct rb_node node;
85 struct per_user_data *user;
86 unsigned port;
87 bool enabled;
88};
89
90static void evtchn_free_ring(evtchn_port_t *ring)
91{
92 kvfree(ring);
93}
94
95static unsigned int evtchn_ring_offset(struct per_user_data *u,
96 unsigned int idx)
97{
98 return idx & (u->ring_size - 1);
99}
100
101static evtchn_port_t *evtchn_ring_entry(struct per_user_data *u,
102 unsigned int idx)
103{
104 return u->ring + evtchn_ring_offset(u, idx);
105}
106
107static int add_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
108{
109 struct rb_node **new = &(u->evtchns.rb_node), *parent = NULL;
110
111 u->nr_evtchns++;
112
113 while (*new) {
114 struct user_evtchn *this;
115
116 this = rb_entry(*new, struct user_evtchn, node);
117
118 parent = *new;
119 if (this->port < evtchn->port)
120 new = &((*new)->rb_left);
121 else if (this->port > evtchn->port)
122 new = &((*new)->rb_right);
123 else
124 return -EEXIST;
125 }
126
127 /* Add new node and rebalance tree. */
128 rb_link_node(&evtchn->node, parent, new);
129 rb_insert_color(&evtchn->node, &u->evtchns);
130
131 return 0;
132}
133
134static void del_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
135{
136 u->nr_evtchns--;
137 rb_erase(&evtchn->node, &u->evtchns);
138 kfree(evtchn);
139}
140
141static struct user_evtchn *find_evtchn(struct per_user_data *u, unsigned port)
142{
143 struct rb_node *node = u->evtchns.rb_node;
144
145 while (node) {
146 struct user_evtchn *evtchn;
147
148 evtchn = rb_entry(node, struct user_evtchn, node);
149
150 if (evtchn->port < port)
151 node = node->rb_left;
152 else if (evtchn->port > port)
153 node = node->rb_right;
154 else
155 return evtchn;
156 }
157 return NULL;
158}
159
160static irqreturn_t evtchn_interrupt(int irq, void *data)
161{
162 struct user_evtchn *evtchn = data;
163 struct per_user_data *u = evtchn->user;
164
165 WARN(!evtchn->enabled,
166 "Interrupt for port %d, but apparently not enabled; per-user %p\n",
167 evtchn->port, u);
168
169 disable_irq_nosync(irq);
170 evtchn->enabled = false;
171
172 spin_lock(&u->ring_prod_lock);
173
174 if ((u->ring_prod - u->ring_cons) < u->ring_size) {
175 *evtchn_ring_entry(u, u->ring_prod) = evtchn->port;
176 wmb(); /* Ensure ring contents visible */
177 if (u->ring_cons == u->ring_prod++) {
178 wake_up_interruptible(&u->evtchn_wait);
179 kill_fasync(&u->evtchn_async_queue,
180 SIGIO, POLL_IN);
181 }
182 } else
183 u->ring_overflow = 1;
184
185 spin_unlock(&u->ring_prod_lock);
186
187 return IRQ_HANDLED;
188}
189
190static ssize_t evtchn_read(struct file *file, char __user *buf,
191 size_t count, loff_t *ppos)
192{
193 int rc;
194 unsigned int c, p, bytes1 = 0, bytes2 = 0;
195 struct per_user_data *u = file->private_data;
196
197 /* Whole number of ports. */
198 count &= ~(sizeof(evtchn_port_t)-1);
199
200 if (count == 0)
201 return 0;
202
203 if (count > PAGE_SIZE)
204 count = PAGE_SIZE;
205
206 for (;;) {
207 mutex_lock(&u->ring_cons_mutex);
208
209 rc = -EFBIG;
210 if (u->ring_overflow)
211 goto unlock_out;
212
213 c = u->ring_cons;
214 p = u->ring_prod;
215 if (c != p)
216 break;
217
218 mutex_unlock(&u->ring_cons_mutex);
219
220 if (file->f_flags & O_NONBLOCK)
221 return -EAGAIN;
222
223 rc = wait_event_interruptible(u->evtchn_wait,
224 u->ring_cons != u->ring_prod);
225 if (rc)
226 return rc;
227 }
228
229 /* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
230 if (((c ^ p) & u->ring_size) != 0) {
231 bytes1 = (u->ring_size - evtchn_ring_offset(u, c)) *
232 sizeof(evtchn_port_t);
233 bytes2 = evtchn_ring_offset(u, p) * sizeof(evtchn_port_t);
234 } else {
235 bytes1 = (p - c) * sizeof(evtchn_port_t);
236 bytes2 = 0;
237 }
238
239 /* Truncate chunks according to caller's maximum byte count. */
240 if (bytes1 > count) {
241 bytes1 = count;
242 bytes2 = 0;
243 } else if ((bytes1 + bytes2) > count) {
244 bytes2 = count - bytes1;
245 }
246
247 rc = -EFAULT;
248 rmb(); /* Ensure that we see the port before we copy it. */
249 if (copy_to_user(buf, evtchn_ring_entry(u, c), bytes1) ||
250 ((bytes2 != 0) &&
251 copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
252 goto unlock_out;
253
254 u->ring_cons += (bytes1 + bytes2) / sizeof(evtchn_port_t);
255 rc = bytes1 + bytes2;
256
257 unlock_out:
258 mutex_unlock(&u->ring_cons_mutex);
259 return rc;
260}
261
262static ssize_t evtchn_write(struct file *file, const char __user *buf,
263 size_t count, loff_t *ppos)
264{
265 int rc, i;
266 evtchn_port_t *kbuf = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
267 struct per_user_data *u = file->private_data;
268
269 if (kbuf == NULL)
270 return -ENOMEM;
271
272 /* Whole number of ports. */
273 count &= ~(sizeof(evtchn_port_t)-1);
274
275 rc = 0;
276 if (count == 0)
277 goto out;
278
279 if (count > PAGE_SIZE)
280 count = PAGE_SIZE;
281
282 rc = -EFAULT;
283 if (copy_from_user(kbuf, buf, count) != 0)
284 goto out;
285
286 mutex_lock(&u->bind_mutex);
287
288 for (i = 0; i < (count/sizeof(evtchn_port_t)); i++) {
289 unsigned port = kbuf[i];
290 struct user_evtchn *evtchn;
291
292 evtchn = find_evtchn(u, port);
293 if (evtchn && !evtchn->enabled) {
294 evtchn->enabled = true;
295 enable_irq(irq_from_evtchn(port));
296 }
297 }
298
299 mutex_unlock(&u->bind_mutex);
300
301 rc = count;
302
303 out:
304 free_page((unsigned long)kbuf);
305 return rc;
306}
307
308static int evtchn_resize_ring(struct per_user_data *u)
309{
310 unsigned int new_size;
311 evtchn_port_t *new_ring, *old_ring;
312
313 /*
314 * Ensure the ring is large enough to capture all possible
315 * events. i.e., one free slot for each bound event.
316 */
317 if (u->nr_evtchns <= u->ring_size)
318 return 0;
319
320 if (u->ring_size == 0)
321 new_size = 64;
322 else
323 new_size = 2 * u->ring_size;
324
325 new_ring = kvmalloc_array(new_size, sizeof(*new_ring), GFP_KERNEL);
326 if (!new_ring)
327 return -ENOMEM;
328
329 old_ring = u->ring;
330
331 /*
332 * Access to the ring contents is serialized by either the
333 * prod /or/ cons lock so take both when resizing.
334 */
335 mutex_lock(&u->ring_cons_mutex);
336 spin_lock_irq(&u->ring_prod_lock);
337
338 /*
339 * Copy the old ring contents to the new ring.
340 *
341 * To take care of wrapping, a full ring, and the new index
342 * pointing into the second half, simply copy the old contents
343 * twice.
344 *
345 * +---------+ +------------------+
346 * |34567 12| -> |34567 1234567 12|
347 * +-----p-c-+ +-------c------p---+
348 */
349 memcpy(new_ring, old_ring, u->ring_size * sizeof(*u->ring));
350 memcpy(new_ring + u->ring_size, old_ring,
351 u->ring_size * sizeof(*u->ring));
352
353 u->ring = new_ring;
354 u->ring_size = new_size;
355
356 spin_unlock_irq(&u->ring_prod_lock);
357 mutex_unlock(&u->ring_cons_mutex);
358
359 evtchn_free_ring(old_ring);
360
361 return 0;
362}
363
364static int evtchn_bind_to_user(struct per_user_data *u, int port)
365{
366 struct user_evtchn *evtchn;
367 struct evtchn_close close;
368 int rc = 0;
369
370 /*
371 * Ports are never reused, so every caller should pass in a
372 * unique port.
373 *
374 * (Locking not necessary because we haven't registered the
375 * interrupt handler yet, and our caller has already
376 * serialized bind operations.)
377 */
378
379 evtchn = kzalloc(sizeof(*evtchn), GFP_KERNEL);
380 if (!evtchn)
381 return -ENOMEM;
382
383 evtchn->user = u;
384 evtchn->port = port;
385 evtchn->enabled = true; /* start enabled */
386
387 rc = add_evtchn(u, evtchn);
388 if (rc < 0)
389 goto err;
390
391 rc = evtchn_resize_ring(u);
392 if (rc < 0)
393 goto err;
394
395 rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, 0,
396 u->name, evtchn);
397 if (rc < 0)
398 goto err;
399
400 rc = evtchn_make_refcounted(port);
401 return rc;
402
403err:
404 /* bind failed, should close the port now */
405 close.port = port;
406 if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
407 BUG();
408 del_evtchn(u, evtchn);
409 return rc;
410}
411
412static void evtchn_unbind_from_user(struct per_user_data *u,
413 struct user_evtchn *evtchn)
414{
415 int irq = irq_from_evtchn(evtchn->port);
416
417 BUG_ON(irq < 0);
418
419 unbind_from_irqhandler(irq, evtchn);
420
421 del_evtchn(u, evtchn);
422}
423
424static DEFINE_PER_CPU(int, bind_last_selected_cpu);
425
426static void evtchn_bind_interdom_next_vcpu(int evtchn)
427{
428 unsigned int selected_cpu, irq;
429 struct irq_desc *desc;
430 unsigned long flags;
431
432 irq = irq_from_evtchn(evtchn);
433 desc = irq_to_desc(irq);
434
435 if (!desc)
436 return;
437
438 raw_spin_lock_irqsave(&desc->lock, flags);
439 selected_cpu = this_cpu_read(bind_last_selected_cpu);
440 selected_cpu = cpumask_next_and(selected_cpu,
441 desc->irq_common_data.affinity, cpu_online_mask);
442
443 if (unlikely(selected_cpu >= nr_cpu_ids))
444 selected_cpu = cpumask_first_and(desc->irq_common_data.affinity,
445 cpu_online_mask);
446
447 this_cpu_write(bind_last_selected_cpu, selected_cpu);
448
449 /* unmask expects irqs to be disabled */
450 xen_rebind_evtchn_to_cpu(evtchn, selected_cpu);
451 raw_spin_unlock_irqrestore(&desc->lock, flags);
452}
453
454static long evtchn_ioctl(struct file *file,
455 unsigned int cmd, unsigned long arg)
456{
457 int rc;
458 struct per_user_data *u = file->private_data;
459 void __user *uarg = (void __user *) arg;
460
461 /* Prevent bind from racing with unbind */
462 mutex_lock(&u->bind_mutex);
463
464 switch (cmd) {
465 case IOCTL_EVTCHN_BIND_VIRQ: {
466 struct ioctl_evtchn_bind_virq bind;
467 struct evtchn_bind_virq bind_virq;
468
469 rc = -EACCES;
470 if (u->restrict_domid != UNRESTRICTED_DOMID)
471 break;
472
473 rc = -EFAULT;
474 if (copy_from_user(&bind, uarg, sizeof(bind)))
475 break;
476
477 bind_virq.virq = bind.virq;
478 bind_virq.vcpu = xen_vcpu_nr(0);
479 rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
480 &bind_virq);
481 if (rc != 0)
482 break;
483
484 rc = evtchn_bind_to_user(u, bind_virq.port);
485 if (rc == 0)
486 rc = bind_virq.port;
487 break;
488 }
489
490 case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
491 struct ioctl_evtchn_bind_interdomain bind;
492 struct evtchn_bind_interdomain bind_interdomain;
493
494 rc = -EFAULT;
495 if (copy_from_user(&bind, uarg, sizeof(bind)))
496 break;
497
498 rc = -EACCES;
499 if (u->restrict_domid != UNRESTRICTED_DOMID &&
500 u->restrict_domid != bind.remote_domain)
501 break;
502
503 bind_interdomain.remote_dom = bind.remote_domain;
504 bind_interdomain.remote_port = bind.remote_port;
505 rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
506 &bind_interdomain);
507 if (rc != 0)
508 break;
509
510 rc = evtchn_bind_to_user(u, bind_interdomain.local_port);
511 if (rc == 0) {
512 rc = bind_interdomain.local_port;
513 evtchn_bind_interdom_next_vcpu(rc);
514 }
515 break;
516 }
517
518 case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
519 struct ioctl_evtchn_bind_unbound_port bind;
520 struct evtchn_alloc_unbound alloc_unbound;
521
522 rc = -EACCES;
523 if (u->restrict_domid != UNRESTRICTED_DOMID)
524 break;
525
526 rc = -EFAULT;
527 if (copy_from_user(&bind, uarg, sizeof(bind)))
528 break;
529
530 alloc_unbound.dom = DOMID_SELF;
531 alloc_unbound.remote_dom = bind.remote_domain;
532 rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
533 &alloc_unbound);
534 if (rc != 0)
535 break;
536
537 rc = evtchn_bind_to_user(u, alloc_unbound.port);
538 if (rc == 0)
539 rc = alloc_unbound.port;
540 break;
541 }
542
543 case IOCTL_EVTCHN_UNBIND: {
544 struct ioctl_evtchn_unbind unbind;
545 struct user_evtchn *evtchn;
546
547 rc = -EFAULT;
548 if (copy_from_user(&unbind, uarg, sizeof(unbind)))
549 break;
550
551 rc = -EINVAL;
552 if (unbind.port >= xen_evtchn_nr_channels())
553 break;
554
555 rc = -ENOTCONN;
556 evtchn = find_evtchn(u, unbind.port);
557 if (!evtchn)
558 break;
559
560 disable_irq(irq_from_evtchn(unbind.port));
561 evtchn_unbind_from_user(u, evtchn);
562 rc = 0;
563 break;
564 }
565
566 case IOCTL_EVTCHN_NOTIFY: {
567 struct ioctl_evtchn_notify notify;
568 struct user_evtchn *evtchn;
569
570 rc = -EFAULT;
571 if (copy_from_user(&notify, uarg, sizeof(notify)))
572 break;
573
574 rc = -ENOTCONN;
575 evtchn = find_evtchn(u, notify.port);
576 if (evtchn) {
577 notify_remote_via_evtchn(notify.port);
578 rc = 0;
579 }
580 break;
581 }
582
583 case IOCTL_EVTCHN_RESET: {
584 /* Initialise the ring to empty. Clear errors. */
585 mutex_lock(&u->ring_cons_mutex);
586 spin_lock_irq(&u->ring_prod_lock);
587 u->ring_cons = u->ring_prod = u->ring_overflow = 0;
588 spin_unlock_irq(&u->ring_prod_lock);
589 mutex_unlock(&u->ring_cons_mutex);
590 rc = 0;
591 break;
592 }
593
594 case IOCTL_EVTCHN_RESTRICT_DOMID: {
595 struct ioctl_evtchn_restrict_domid ierd;
596
597 rc = -EACCES;
598 if (u->restrict_domid != UNRESTRICTED_DOMID)
599 break;
600
601 rc = -EFAULT;
602 if (copy_from_user(&ierd, uarg, sizeof(ierd)))
603 break;
604
605 rc = -EINVAL;
606 if (ierd.domid == 0 || ierd.domid >= DOMID_FIRST_RESERVED)
607 break;
608
609 u->restrict_domid = ierd.domid;
610 rc = 0;
611
612 break;
613 }
614
615 default:
616 rc = -ENOSYS;
617 break;
618 }
619 mutex_unlock(&u->bind_mutex);
620
621 return rc;
622}
623
624static __poll_t evtchn_poll(struct file *file, poll_table *wait)
625{
626 __poll_t mask = EPOLLOUT | EPOLLWRNORM;
627 struct per_user_data *u = file->private_data;
628
629 poll_wait(file, &u->evtchn_wait, wait);
630 if (u->ring_cons != u->ring_prod)
631 mask |= EPOLLIN | EPOLLRDNORM;
632 if (u->ring_overflow)
633 mask = EPOLLERR;
634 return mask;
635}
636
637static int evtchn_fasync(int fd, struct file *filp, int on)
638{
639 struct per_user_data *u = filp->private_data;
640 return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
641}
642
643static int evtchn_open(struct inode *inode, struct file *filp)
644{
645 struct per_user_data *u;
646
647 u = kzalloc(sizeof(*u), GFP_KERNEL);
648 if (u == NULL)
649 return -ENOMEM;
650
651 u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
652 if (u->name == NULL) {
653 kfree(u);
654 return -ENOMEM;
655 }
656
657 init_waitqueue_head(&u->evtchn_wait);
658
659 mutex_init(&u->bind_mutex);
660 mutex_init(&u->ring_cons_mutex);
661 spin_lock_init(&u->ring_prod_lock);
662
663 u->restrict_domid = UNRESTRICTED_DOMID;
664
665 filp->private_data = u;
666
667 return nonseekable_open(inode, filp);
668}
669
670static int evtchn_release(struct inode *inode, struct file *filp)
671{
672 struct per_user_data *u = filp->private_data;
673 struct rb_node *node;
674
675 while ((node = u->evtchns.rb_node)) {
676 struct user_evtchn *evtchn;
677
678 evtchn = rb_entry(node, struct user_evtchn, node);
679 disable_irq(irq_from_evtchn(evtchn->port));
680 evtchn_unbind_from_user(u, evtchn);
681 }
682
683 evtchn_free_ring(u->ring);
684 kfree(u->name);
685 kfree(u);
686
687 return 0;
688}
689
690static const struct file_operations evtchn_fops = {
691 .owner = THIS_MODULE,
692 .read = evtchn_read,
693 .write = evtchn_write,
694 .unlocked_ioctl = evtchn_ioctl,
695 .poll = evtchn_poll,
696 .fasync = evtchn_fasync,
697 .open = evtchn_open,
698 .release = evtchn_release,
699 .llseek = no_llseek,
700};
701
702static struct miscdevice evtchn_miscdev = {
703 .minor = MISC_DYNAMIC_MINOR,
704 .name = "xen/evtchn",
705 .fops = &evtchn_fops,
706};
707static int __init evtchn_init(void)
708{
709 int err;
710
711 if (!xen_domain())
712 return -ENODEV;
713
714 /* Create '/dev/xen/evtchn'. */
715 err = misc_register(&evtchn_miscdev);
716 if (err != 0) {
717 pr_err("Could not register /dev/xen/evtchn\n");
718 return err;
719 }
720
721 pr_info("Event-channel device installed\n");
722
723 return 0;
724}
725
726static void __exit evtchn_cleanup(void)
727{
728 misc_deregister(&evtchn_miscdev);
729}
730
731module_init(evtchn_init);
732module_exit(evtchn_cleanup);
733
734MODULE_LICENSE("GPL");
735