xref: /linux/drivers/usb/mon/mon_main.c (revision 72adaa962741e8e910300b66bb123b1a9c31a8a8) 
1 /*
2  * The USB Monitor, inspired by Dave Harding's USBMon.
3  *
4  * mon_main.c: Main file, module initiation and exit, registrations, etc.
5  *
6  * Copyright (C) 2005 Pete Zaitcev (zaitcev@redhat.com)
7  */
8 
9 #include <linux/kernel.h>
10 #include <linux/module.h>
11 #include <linux/usb.h>
12 #include <linux/debugfs.h>
13 #include <linux/smp_lock.h>
14 #include <linux/notifier.h>
15 
16 #include "usb_mon.h"
17 #include "../core/hcd.h"
18 
19 static void mon_submit(struct usb_bus *ubus, struct urb *urb);
20 static void mon_complete(struct usb_bus *ubus, struct urb *urb);
21 static void mon_stop(struct mon_bus *mbus);
22 static void mon_dissolve(struct mon_bus *mbus, struct usb_bus *ubus);
23 static void mon_bus_drop(struct kref *r);
24 static void mon_bus_init(struct dentry *mondir, struct usb_bus *ubus);
25 
26 DECLARE_MUTEX(mon_lock);
27 
28 static struct dentry *mon_dir;		/* /dbg/usbmon */
29 static LIST_HEAD(mon_buses);		/* All buses we know: struct mon_bus */
30 
31 /*
32  * Link a reader into the bus.
33  *
34  * This must be called with mon_lock taken because of mbus->ref.
35  */
36 void mon_reader_add(struct mon_bus *mbus, struct mon_reader *r)
37 {
38 	unsigned long flags;
39 	struct usb_bus *ubus;
40 
41 	spin_lock_irqsave(&mbus->lock, flags);
42 	if (mbus->nreaders == 0) {
43 		ubus = mbus->u_bus;
44 		if (ubus->monitored) {
45 			/*
46 			 * Something is really broken, refuse to go on and
47 			 * possibly corrupt ops pointers or worse.
48 			 */
49 			printk(KERN_ERR TAG ": bus %d is already monitored\n",
50 			    ubus->busnum);
51 			spin_unlock_irqrestore(&mbus->lock, flags);
52 			return;
53 		}
54 		ubus->monitored = 1;
55 	}
56 	mbus->nreaders++;
57 	list_add_tail(&r->r_link, &mbus->r_list);
58 	spin_unlock_irqrestore(&mbus->lock, flags);
59 
60 	kref_get(&mbus->ref);
61 }
62 
63 /*
64  * Unlink reader from the bus.
65  *
66  * This is called with mon_lock taken, so we can decrement mbus->ref.
67  */
68 void mon_reader_del(struct mon_bus *mbus, struct mon_reader *r)
69 {
70 	unsigned long flags;
71 
72 	spin_lock_irqsave(&mbus->lock, flags);
73 	list_del(&r->r_link);
74 	--mbus->nreaders;
75 	if (mbus->nreaders == 0)
76 		mon_stop(mbus);
77 	spin_unlock_irqrestore(&mbus->lock, flags);
78 
79 	kref_put(&mbus->ref, mon_bus_drop);
80 }
81 
82 /*
83  */
84 static void mon_submit(struct usb_bus *ubus, struct urb *urb)
85 {
86 	struct mon_bus *mbus;
87 	unsigned long flags;
88 	struct list_head *pos;
89 	struct mon_reader *r;
90 
91 	mbus = ubus->mon_bus;
92 	if (mbus == NULL)
93 		goto out_unlocked;
94 
95 	spin_lock_irqsave(&mbus->lock, flags);
96 	if (mbus->nreaders == 0)
97 		goto out_locked;
98 
99 	list_for_each (pos, &mbus->r_list) {
100 		r = list_entry(pos, struct mon_reader, r_link);
101 		r->rnf_submit(r->r_data, urb);
102 	}
103 
104 	spin_unlock_irqrestore(&mbus->lock, flags);
105 	return;
106 
107 out_locked:
108 	spin_unlock_irqrestore(&mbus->lock, flags);
109 out_unlocked:
110 	return;
111 }
112 
113 /*
114  */
115 static void mon_submit_error(struct usb_bus *ubus, struct urb *urb, int err)
116 {
117 	struct mon_bus *mbus;
118 
119 	mbus = ubus->mon_bus;
120 	if (mbus == NULL)
121 		goto out_unlocked;
122 
123 	/*
124 	 * XXX Capture the error code and the 'E' event.
125 	 */
126 
127 	return;
128 
129 out_unlocked:
130 	return;
131 }
132 
133 /*
134  */
135 static void mon_complete(struct usb_bus *ubus, struct urb *urb)
136 {
137 	struct mon_bus *mbus;
138 	unsigned long flags;
139 	struct list_head *pos;
140 	struct mon_reader *r;
141 
142 	mbus = ubus->mon_bus;
143 	if (mbus == NULL) {
144 		/*
145 		 * This should not happen.
146 		 * At this point we do not even know the bus number...
147 		 */
148 		printk(KERN_ERR TAG ": Null mon bus in URB, pipe 0x%x\n",
149 		    urb->pipe);
150 		return;
151 	}
152 
153 	spin_lock_irqsave(&mbus->lock, flags);
154 	list_for_each (pos, &mbus->r_list) {
155 		r = list_entry(pos, struct mon_reader, r_link);
156 		r->rnf_complete(r->r_data, urb);
157 	}
158 	spin_unlock_irqrestore(&mbus->lock, flags);
159 }
160 
161 /* int (*unlink_urb) (struct urb *urb, int status); */
162 
163 /*
164  * Stop monitoring.
165  * Obviously this must be well locked, so no need to play with mb's.
166  */
167 static void mon_stop(struct mon_bus *mbus)
168 {
169 	struct usb_bus *ubus = mbus->u_bus;
170 
171 	/*
172 	 * A stop can be called for a dissolved mon_bus in case of
173 	 * a reader staying across an rmmod foo_hcd.
174 	 */
175 	if (ubus != NULL) {
176 		ubus->monitored = 0;
177 		mb();
178 	}
179 }
180 
181 /*
182  * Add a USB bus (usually by a modprobe foo-hcd)
183  *
184  * This does not return an error code because the core cannot care less
185  * if monitoring is not established.
186  */
187 static void mon_bus_add(struct usb_bus *ubus)
188 {
189 	mon_bus_init(mon_dir, ubus);
190 }
191 
192 /*
193  * Remove a USB bus (either from rmmod foo-hcd or from a hot-remove event).
194  */
195 static void mon_bus_remove(struct usb_bus *ubus)
196 {
197 	struct mon_bus *mbus = ubus->mon_bus;
198 
199 	down(&mon_lock);
200 	list_del(&mbus->bus_link);
201 	debugfs_remove(mbus->dent_t);
202 	debugfs_remove(mbus->dent_s);
203 
204 	mon_dissolve(mbus, ubus);
205 	kref_put(&mbus->ref, mon_bus_drop);
206 	up(&mon_lock);
207 }
208 
209 static int mon_notify(struct notifier_block *self, unsigned long action,
210 		      void *dev)
211 {
212 	switch (action) {
213 	case USB_BUS_ADD:
214 		mon_bus_add(dev);
215 		break;
216 	case USB_BUS_REMOVE:
217 		mon_bus_remove(dev);
218 	}
219 	return NOTIFY_OK;
220 }
221 
222 static struct notifier_block mon_nb = {
223 	.notifier_call = 	mon_notify,
224 };
225 
226 /*
227  * Ops
228  */
229 static struct usb_mon_operations mon_ops_0 = {
230 	.urb_submit =	mon_submit,
231 	.urb_submit_error = mon_submit_error,
232 	.urb_complete =	mon_complete,
233 };
234 
235 /*
236  * Tear usb_bus and mon_bus apart.
237  */
238 static void mon_dissolve(struct mon_bus *mbus, struct usb_bus *ubus)
239 {
240 
241 	/*
242 	 * Never happens, but...
243 	 */
244 	if (ubus->monitored) {
245 		printk(KERN_ERR TAG ": bus %d is dissolved while monitored\n",
246 		    ubus->busnum);
247 		ubus->monitored = 0;
248 		mb();
249 	}
250 
251 	ubus->mon_bus = NULL;
252 	mbus->u_bus = NULL;
253 	mb();
254 	// usb_bus_put(ubus);
255 }
256 
257 /*
258  */
259 static void mon_bus_drop(struct kref *r)
260 {
261 	struct mon_bus *mbus = container_of(r, struct mon_bus, ref);
262 	kfree(mbus);
263 }
264 
265 /*
266  * Initialize a bus for us:
267  *  - allocate mon_bus
268  *  - refcount USB bus struct
269  *  - link
270  */
271 static void mon_bus_init(struct dentry *mondir, struct usb_bus *ubus)
272 {
273 	struct dentry *d;
274 	struct mon_bus *mbus;
275 	enum { NAMESZ = 10 };
276 	char name[NAMESZ];
277 	int rc;
278 
279 	if ((mbus = kmalloc(sizeof(struct mon_bus), GFP_KERNEL)) == NULL)
280 		goto err_alloc;
281 	memset(mbus, 0, sizeof(struct mon_bus));
282 	kref_init(&mbus->ref);
283 	spin_lock_init(&mbus->lock);
284 	INIT_LIST_HEAD(&mbus->r_list);
285 
286 	/*
287 	 * This usb_bus_get here is superfluous, because we receive
288 	 * a notification if usb_bus is about to be removed.
289 	 */
290 	// usb_bus_get(ubus);
291 	mbus->u_bus = ubus;
292 	ubus->mon_bus = mbus;
293 
294 	rc = snprintf(name, NAMESZ, "%dt", ubus->busnum);
295 	if (rc <= 0 || rc >= NAMESZ)
296 		goto err_print_t;
297 	d = debugfs_create_file(name, 0600, mondir, mbus, &mon_fops_text);
298 	if (d == NULL)
299 		goto err_create_t;
300 	mbus->dent_t = d;
301 
302 	rc = snprintf(name, NAMESZ, "%ds", ubus->busnum);
303 	if (rc <= 0 || rc >= NAMESZ)
304 		goto err_print_s;
305 	d = debugfs_create_file(name, 0600, mondir, mbus, &mon_fops_stat);
306 	if (d == NULL)
307 		goto err_create_s;
308 	mbus->dent_s = d;
309 
310 	down(&mon_lock);
311 	list_add_tail(&mbus->bus_link, &mon_buses);
312 	up(&mon_lock);
313 	return;
314 
315 err_create_s:
316 err_print_s:
317 	debugfs_remove(mbus->dent_t);
318 err_create_t:
319 err_print_t:
320 	kfree(mbus);
321 err_alloc:
322 	return;
323 }
324 
325 static int __init mon_init(void)
326 {
327 	struct usb_bus *ubus;
328 	struct dentry *mondir;
329 
330 	mondir = debugfs_create_dir("usbmon", NULL);
331 	if (IS_ERR(mondir)) {
332 		printk(KERN_NOTICE TAG ": debugfs is not available\n");
333 		return -ENODEV;
334 	}
335 	if (mondir == NULL) {
336 		printk(KERN_NOTICE TAG ": unable to create usbmon directory\n");
337 		return -ENODEV;
338 	}
339 	mon_dir = mondir;
340 
341 	if (usb_mon_register(&mon_ops_0) != 0) {
342 		printk(KERN_NOTICE TAG ": unable to register with the core\n");
343 		debugfs_remove(mondir);
344 		return -ENODEV;
345 	}
346 	// MOD_INC_USE_COUNT(which_module?);
347 
348 	usb_register_notify(&mon_nb);
349 
350 	down(&usb_bus_list_lock);
351 	list_for_each_entry (ubus, &usb_bus_list, bus_list) {
352 		mon_bus_init(mondir, ubus);
353 	}
354 	up(&usb_bus_list_lock);
355 	return 0;
356 }
357 
358 static void __exit mon_exit(void)
359 {
360 	struct mon_bus *mbus;
361 	struct list_head *p;
362 
363 	usb_unregister_notify(&mon_nb);
364 	usb_mon_deregister();
365 
366 	down(&mon_lock);
367 	while (!list_empty(&mon_buses)) {
368 		p = mon_buses.next;
369 		mbus = list_entry(p, struct mon_bus, bus_link);
370 		list_del(p);
371 
372 		debugfs_remove(mbus->dent_t);
373 		debugfs_remove(mbus->dent_s);
374 
375 		/*
376 		 * This never happens, because the open/close paths in
377 		 * file level maintain module use counters and so rmmod fails
378 		 * before reaching here. However, better be safe...
379 		 */
380 		if (mbus->nreaders) {
381 			printk(KERN_ERR TAG
382 			    ": Outstanding opens (%d) on usb%d, leaking...\n",
383 			    mbus->nreaders, mbus->u_bus->busnum);
384 			atomic_set(&mbus->ref.refcount, 2);	/* Force leak */
385 		}
386 
387 		mon_dissolve(mbus, mbus->u_bus);
388 		kref_put(&mbus->ref, mon_bus_drop);
389 	}
390 	up(&mon_lock);
391 
392 	debugfs_remove(mon_dir);
393 }
394 
395 module_init(mon_init);
396 module_exit(mon_exit);
397 
398 MODULE_LICENSE("GPL");
399