1// SPDX-License-Identifier: GPL-2.0
2/*
3 * The USB Monitor, inspired by Dave Harding's USBMon.
4 *
5 * mon_main.c: Main file, module initiation and exit, registrations, etc.
6 *
7 * Copyright (C) 2005 Pete Zaitcev (zaitcev@redhat.com)
8 */
9
10#include <linux/kernel.h>
11#include <linux/module.h>
12#include <linux/usb.h>
13#include <linux/usb/hcd.h>
14#include <linux/slab.h>
15#include <linux/notifier.h>
16#include <linux/mutex.h>
17
18#include "usb_mon.h"
19
20
21static void mon_stop(struct mon_bus *mbus);
22static void mon_dissolve(struct mon_bus *mbus, struct usb_bus *ubus);
23static void mon_bus_drop(struct kref *r);
24static void mon_bus_init(struct usb_bus *ubus);
25
26DEFINE_MUTEX(mon_lock);
27
28struct mon_bus mon_bus0;		/* Pseudo bus meaning "all buses" */
29static 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 */
36void mon_reader_add(struct mon_bus *mbus, struct mon_reader *r)
37{
38	unsigned long flags;
39	struct list_head *p;
40
41	spin_lock_irqsave(&mbus->lock, flags);
42	if (mbus->nreaders == 0) {
43		if (mbus == &mon_bus0) {
44			list_for_each (p, &mon_buses) {
45				struct mon_bus *m1;
46				m1 = list_entry(p, struct mon_bus, bus_link);
47				m1->u_bus->monitored = 1;
48			}
49		} else {
50			mbus->u_bus->monitored = 1;
51		}
52	}
53	mbus->nreaders++;
54	list_add_tail(&r->r_link, &mbus->r_list);
55	spin_unlock_irqrestore(&mbus->lock, flags);
56
57	kref_get(&mbus->ref);
58}
59
60/*
61 * Unlink reader from the bus.
62 *
63 * This is called with mon_lock taken, so we can decrement mbus->ref.
64 */
65void mon_reader_del(struct mon_bus *mbus, struct mon_reader *r)
66{
67	unsigned long flags;
68
69	spin_lock_irqsave(&mbus->lock, flags);
70	list_del(&r->r_link);
71	--mbus->nreaders;
72	if (mbus->nreaders == 0)
73		mon_stop(mbus);
74	spin_unlock_irqrestore(&mbus->lock, flags);
75
76	kref_put(&mbus->ref, mon_bus_drop);
77}
78
79/*
80 */
81static void mon_bus_submit(struct mon_bus *mbus, struct urb *urb)
82{
83	unsigned long flags;
84	struct mon_reader *r;
85
86	spin_lock_irqsave(&mbus->lock, flags);
87	mbus->cnt_events++;
88	list_for_each_entry(r, &mbus->r_list, r_link)
89		r->rnf_submit(r->r_data, urb);
90	spin_unlock_irqrestore(&mbus->lock, flags);
91}
92
93static void mon_submit(struct usb_bus *ubus, struct urb *urb)
94{
95	struct mon_bus *mbus;
96
97	mbus = ubus->mon_bus;
98	if (mbus != NULL)
99		mon_bus_submit(mbus, urb);
100	mon_bus_submit(&mon_bus0, urb);
101}
102
103/*
104 */
105static void mon_bus_submit_error(struct mon_bus *mbus, struct urb *urb, int error)
106{
107	unsigned long flags;
108	struct mon_reader *r;
109
110	spin_lock_irqsave(&mbus->lock, flags);
111	mbus->cnt_events++;
112	list_for_each_entry(r, &mbus->r_list, r_link)
113		r->rnf_error(r->r_data, urb, error);
114	spin_unlock_irqrestore(&mbus->lock, flags);
115}
116
117static void mon_submit_error(struct usb_bus *ubus, struct urb *urb, int error)
118{
119	struct mon_bus *mbus;
120
121	mbus = ubus->mon_bus;
122	if (mbus != NULL)
123		mon_bus_submit_error(mbus, urb, error);
124	mon_bus_submit_error(&mon_bus0, urb, error);
125}
126
127/*
128 */
129static void mon_bus_complete(struct mon_bus *mbus, struct urb *urb, int status)
130{
131	unsigned long flags;
132	struct mon_reader *r;
133
134	spin_lock_irqsave(&mbus->lock, flags);
135	mbus->cnt_events++;
136	list_for_each_entry(r, &mbus->r_list, r_link)
137		r->rnf_complete(r->r_data, urb, status);
138	spin_unlock_irqrestore(&mbus->lock, flags);
139}
140
141static void mon_complete(struct usb_bus *ubus, struct urb *urb, int status)
142{
143	struct mon_bus *mbus;
144
145	mbus = ubus->mon_bus;
146	if (mbus != NULL)
147		mon_bus_complete(mbus, urb, status);
148	mon_bus_complete(&mon_bus0, urb, status);
149}
150
151/* int (*unlink_urb) (struct urb *urb, int status); */
152
153/*
154 * Stop monitoring.
155 */
156static void mon_stop(struct mon_bus *mbus)
157{
158	struct usb_bus *ubus;
159
160	if (mbus == &mon_bus0) {
161		list_for_each_entry(mbus, &mon_buses, bus_link) {
162			/*
163			 * We do not change nreaders here, so rely on mon_lock.
164			 */
165			if (mbus->nreaders == 0 && (ubus = mbus->u_bus) != NULL)
166				ubus->monitored = 0;
167		}
168	} else {
169		/*
170		 * A stop can be called for a dissolved mon_bus in case of
171		 * a reader staying across an rmmod foo_hcd, so test ->u_bus.
172		 */
173		if (mon_bus0.nreaders == 0 && (ubus = mbus->u_bus) != NULL) {
174			ubus->monitored = 0;
175			mb();
176		}
177	}
178}
179
180/*
181 * Add a USB bus (usually by a modprobe foo-hcd)
182 *
183 * This does not return an error code because the core cannot care less
184 * if monitoring is not established.
185 */
186static void mon_bus_add(struct usb_bus *ubus)
187{
188	mon_bus_init(ubus);
189	mutex_lock(&mon_lock);
190	if (mon_bus0.nreaders != 0)
191		ubus->monitored = 1;
192	mutex_unlock(&mon_lock);
193}
194
195/*
196 * Remove a USB bus (either from rmmod foo-hcd or from a hot-remove event).
197 */
198static void mon_bus_remove(struct usb_bus *ubus)
199{
200	struct mon_bus *mbus = ubus->mon_bus;
201
202	mutex_lock(&mon_lock);
203	list_del(&mbus->bus_link);
204	if (mbus->text_inited)
205		mon_text_del(mbus);
206	if (mbus->bin_inited)
207		mon_bin_del(mbus);
208
209	mon_dissolve(mbus, ubus);
210	kref_put(&mbus->ref, mon_bus_drop);
211	mutex_unlock(&mon_lock);
212}
213
214static int mon_notify(struct notifier_block *self, unsigned long action,
215		      void *dev)
216{
217	switch (action) {
218	case USB_BUS_ADD:
219		mon_bus_add(dev);
220		break;
221	case USB_BUS_REMOVE:
222		mon_bus_remove(dev);
223	}
224	return NOTIFY_OK;
225}
226
227static struct notifier_block mon_nb = {
228	.notifier_call = 	mon_notify,
229};
230
231/*
232 * Ops
233 */
234static const struct usb_mon_operations mon_ops_0 = {
235	.urb_submit =	mon_submit,
236	.urb_submit_error = mon_submit_error,
237	.urb_complete =	mon_complete,
238};
239
240/*
241 * Tear usb_bus and mon_bus apart.
242 */
243static void mon_dissolve(struct mon_bus *mbus, struct usb_bus *ubus)
244{
245
246	if (ubus->monitored) {
247		ubus->monitored = 0;
248		mb();
249	}
250
251	ubus->mon_bus = NULL;
252	mbus->u_bus = NULL;
253	mb();
254
255	/* We want synchronize_irq() here, but that needs an argument. */
256}
257
258/*
259 */
260static void mon_bus_drop(struct kref *r)
261{
262	struct mon_bus *mbus = container_of(r, struct mon_bus, ref);
263	kfree(mbus);
264}
265
266/*
267 * Initialize a bus for us:
268 *  - allocate mon_bus
269 *  - refcount USB bus struct
270 *  - link
271 */
272static void mon_bus_init(struct usb_bus *ubus)
273{
274	struct mon_bus *mbus;
275
276	mbus = kzalloc(sizeof(struct mon_bus), GFP_KERNEL);
277	if (mbus == NULL)
278		goto err_alloc;
279	kref_init(&mbus->ref);
280	spin_lock_init(&mbus->lock);
281	INIT_LIST_HEAD(&mbus->r_list);
282
283	/*
284	 * We don't need to take a reference to ubus, because we receive
285	 * a notification if the bus is about to be removed.
286	 */
287	mbus->u_bus = ubus;
288	ubus->mon_bus = mbus;
289
290	mbus->text_inited = mon_text_add(mbus, ubus);
291	mbus->bin_inited = mon_bin_add(mbus, ubus);
292
293	mutex_lock(&mon_lock);
294	list_add_tail(&mbus->bus_link, &mon_buses);
295	mutex_unlock(&mon_lock);
296	return;
297
298err_alloc:
299	return;
300}
301
302static void mon_bus0_init(void)
303{
304	struct mon_bus *mbus = &mon_bus0;
305
306	kref_init(&mbus->ref);
307	spin_lock_init(&mbus->lock);
308	INIT_LIST_HEAD(&mbus->r_list);
309
310	mbus->text_inited = mon_text_add(mbus, NULL);
311	mbus->bin_inited = mon_bin_add(mbus, NULL);
312}
313
314/*
315 * Search a USB bus by number. Notice that USB bus numbers start from one,
316 * which we may later use to identify "all" with zero.
317 *
318 * This function must be called with mon_lock held.
319 *
320 * This is obviously inefficient and may be revised in the future.
321 */
322struct mon_bus *mon_bus_lookup(unsigned int num)
323{
324	struct mon_bus *mbus;
325
326	if (num == 0) {
327		return &mon_bus0;
328	}
329	list_for_each_entry(mbus, &mon_buses, bus_link) {
330		if (mbus->u_bus->busnum == num) {
331			return mbus;
332		}
333	}
334	return NULL;
335}
336
337static int __init mon_init(void)
338{
339	struct usb_bus *ubus;
340	int rc, id;
341
342	if ((rc = mon_text_init()) != 0)
343		goto err_text;
344	if ((rc = mon_bin_init()) != 0)
345		goto err_bin;
346
347	mon_bus0_init();
348
349	if (usb_mon_register(&mon_ops_0) != 0) {
350		printk(KERN_NOTICE TAG ": unable to register with the core\n");
351		rc = -ENODEV;
352		goto err_reg;
353	}
354	// MOD_INC_USE_COUNT(which_module?);
355
356	mutex_lock(&usb_bus_idr_lock);
357	idr_for_each_entry(&usb_bus_idr, ubus, id)
358		mon_bus_init(ubus);
359	usb_register_notify(&mon_nb);
360	mutex_unlock(&usb_bus_idr_lock);
361	return 0;
362
363err_reg:
364	mon_bin_exit();
365err_bin:
366	mon_text_exit();
367err_text:
368	return rc;
369}
370
371static void __exit mon_exit(void)
372{
373	struct mon_bus *mbus;
374	struct list_head *p;
375
376	usb_unregister_notify(&mon_nb);
377	usb_mon_deregister();
378
379	mutex_lock(&mon_lock);
380
381	while (!list_empty(&mon_buses)) {
382		p = mon_buses.next;
383		mbus = list_entry(p, struct mon_bus, bus_link);
384		list_del(p);
385
386		if (mbus->text_inited)
387			mon_text_del(mbus);
388		if (mbus->bin_inited)
389			mon_bin_del(mbus);
390
391		/*
392		 * This never happens, because the open/close paths in
393		 * file level maintain module use counters and so rmmod fails
394		 * before reaching here. However, better be safe...
395		 */
396		if (mbus->nreaders) {
397			printk(KERN_ERR TAG
398			    ": Outstanding opens (%d) on usb%d, leaking...\n",
399			    mbus->nreaders, mbus->u_bus->busnum);
400			kref_get(&mbus->ref); /* Force leak */
401		}
402
403		mon_dissolve(mbus, mbus->u_bus);
404		kref_put(&mbus->ref, mon_bus_drop);
405	}
406
407	mbus = &mon_bus0;
408	if (mbus->text_inited)
409		mon_text_del(mbus);
410	if (mbus->bin_inited)
411		mon_bin_del(mbus);
412
413	mutex_unlock(&mon_lock);
414
415	mon_text_exit();
416	mon_bin_exit();
417}
418
419module_init(mon_init);
420module_exit(mon_exit);
421
422MODULE_LICENSE("GPL");
423