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