1 /*
2  * Kernel/userspace transport abstraction for Hyper-V util driver.
3  *
4  * Copyright (C) 2015, Vitaly Kuznetsov <vkuznets@redhat.com>
5  *
6  * This program is free software; you can redistribute it and/or modify it
7  * under the terms of the GNU General Public License version 2 as published
8  * by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful, but
11  * WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
13  * NON INFRINGEMENT.  See the GNU General Public License for more
14  * details.
15  *
16  */
17 
18 #include <linux/slab.h>
19 #include <linux/fs.h>
20 #include <linux/poll.h>
21 
22 #include "hyperv_vmbus.h"
23 #include "hv_utils_transport.h"
24 
25 static DEFINE_SPINLOCK(hvt_list_lock);
26 static struct list_head hvt_list = LIST_HEAD_INIT(hvt_list);
27 
28 static void hvt_reset(struct hvutil_transport *hvt)
29 {
30 	kfree(hvt->outmsg);
31 	hvt->outmsg = NULL;
32 	hvt->outmsg_len = 0;
33 	if (hvt->on_reset)
34 		hvt->on_reset();
35 }
36 
37 static ssize_t hvt_op_read(struct file *file, char __user *buf,
38 			   size_t count, loff_t *ppos)
39 {
40 	struct hvutil_transport *hvt;
41 	int ret;
42 
43 	hvt = container_of(file->f_op, struct hvutil_transport, fops);
44 
45 	if (wait_event_interruptible(hvt->outmsg_q, hvt->outmsg_len > 0 ||
46 				     hvt->mode != HVUTIL_TRANSPORT_CHARDEV))
47 		return -EINTR;
48 
49 	mutex_lock(&hvt->lock);
50 
51 	if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
52 		ret = -EBADF;
53 		goto out_unlock;
54 	}
55 
56 	if (!hvt->outmsg) {
57 		ret = -EAGAIN;
58 		goto out_unlock;
59 	}
60 
61 	if (count < hvt->outmsg_len) {
62 		ret = -EINVAL;
63 		goto out_unlock;
64 	}
65 
66 	if (!copy_to_user(buf, hvt->outmsg, hvt->outmsg_len))
67 		ret = hvt->outmsg_len;
68 	else
69 		ret = -EFAULT;
70 
71 	kfree(hvt->outmsg);
72 	hvt->outmsg = NULL;
73 	hvt->outmsg_len = 0;
74 
75 out_unlock:
76 	mutex_unlock(&hvt->lock);
77 	return ret;
78 }
79 
80 static ssize_t hvt_op_write(struct file *file, const char __user *buf,
81 			    size_t count, loff_t *ppos)
82 {
83 	struct hvutil_transport *hvt;
84 	u8 *inmsg;
85 	int ret;
86 
87 	hvt = container_of(file->f_op, struct hvutil_transport, fops);
88 
89 	inmsg = memdup_user(buf, count);
90 	if (IS_ERR(inmsg))
91 		return PTR_ERR(inmsg);
92 
93 	if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
94 		ret = -EBADF;
95 	else
96 		ret = hvt->on_msg(inmsg, count);
97 
98 	kfree(inmsg);
99 
100 	return ret ? ret : count;
101 }
102 
103 static unsigned int hvt_op_poll(struct file *file, poll_table *wait)
104 {
105 	struct hvutil_transport *hvt;
106 
107 	hvt = container_of(file->f_op, struct hvutil_transport, fops);
108 
109 	poll_wait(file, &hvt->outmsg_q, wait);
110 
111 	if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
112 		return POLLERR | POLLHUP;
113 
114 	if (hvt->outmsg_len > 0)
115 		return POLLIN | POLLRDNORM;
116 
117 	return 0;
118 }
119 
120 static int hvt_op_open(struct inode *inode, struct file *file)
121 {
122 	struct hvutil_transport *hvt;
123 	int ret = 0;
124 	bool issue_reset = false;
125 
126 	hvt = container_of(file->f_op, struct hvutil_transport, fops);
127 
128 	mutex_lock(&hvt->lock);
129 
130 	if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
131 		ret = -EBADF;
132 	} else if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
133 		/*
134 		 * Switching to CHARDEV mode. We switch bach to INIT when
135 		 * device gets released.
136 		 */
137 		hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
138 	}
139 	else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
140 		/*
141 		 * We're switching from netlink communication to using char
142 		 * device. Issue the reset first.
143 		 */
144 		issue_reset = true;
145 		hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
146 	} else {
147 		ret = -EBUSY;
148 	}
149 
150 	if (issue_reset)
151 		hvt_reset(hvt);
152 
153 	mutex_unlock(&hvt->lock);
154 
155 	return ret;
156 }
157 
158 static void hvt_transport_free(struct hvutil_transport *hvt)
159 {
160 	misc_deregister(&hvt->mdev);
161 	kfree(hvt->outmsg);
162 	kfree(hvt);
163 }
164 
165 static int hvt_op_release(struct inode *inode, struct file *file)
166 {
167 	struct hvutil_transport *hvt;
168 	int mode_old;
169 
170 	hvt = container_of(file->f_op, struct hvutil_transport, fops);
171 
172 	mutex_lock(&hvt->lock);
173 	mode_old = hvt->mode;
174 	if (hvt->mode != HVUTIL_TRANSPORT_DESTROY)
175 		hvt->mode = HVUTIL_TRANSPORT_INIT;
176 	/*
177 	 * Cleanup message buffers to avoid spurious messages when the daemon
178 	 * connects back.
179 	 */
180 	hvt_reset(hvt);
181 	mutex_unlock(&hvt->lock);
182 
183 	if (mode_old == HVUTIL_TRANSPORT_DESTROY)
184 		hvt_transport_free(hvt);
185 
186 	return 0;
187 }
188 
189 static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
190 {
191 	struct hvutil_transport *hvt, *hvt_found = NULL;
192 
193 	spin_lock(&hvt_list_lock);
194 	list_for_each_entry(hvt, &hvt_list, list) {
195 		if (hvt->cn_id.idx == msg->id.idx &&
196 		    hvt->cn_id.val == msg->id.val) {
197 			hvt_found = hvt;
198 			break;
199 		}
200 	}
201 	spin_unlock(&hvt_list_lock);
202 	if (!hvt_found) {
203 		pr_warn("hvt_cn_callback: spurious message received!\n");
204 		return;
205 	}
206 
207 	/*
208 	 * Switching to NETLINK mode. Switching to CHARDEV happens when someone
209 	 * opens the device.
210 	 */
211 	mutex_lock(&hvt->lock);
212 	if (hvt->mode == HVUTIL_TRANSPORT_INIT)
213 		hvt->mode = HVUTIL_TRANSPORT_NETLINK;
214 
215 	if (hvt->mode == HVUTIL_TRANSPORT_NETLINK)
216 		hvt_found->on_msg(msg->data, msg->len);
217 	else
218 		pr_warn("hvt_cn_callback: unexpected netlink message!\n");
219 	mutex_unlock(&hvt->lock);
220 }
221 
222 int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len)
223 {
224 	struct cn_msg *cn_msg;
225 	int ret = 0;
226 
227 	if (hvt->mode == HVUTIL_TRANSPORT_INIT ||
228 	    hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
229 		return -EINVAL;
230 	} else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
231 		cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
232 		if (!cn_msg)
233 			return -ENOMEM;
234 		cn_msg->id.idx = hvt->cn_id.idx;
235 		cn_msg->id.val = hvt->cn_id.val;
236 		cn_msg->len = len;
237 		memcpy(cn_msg->data, msg, len);
238 		ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC);
239 		kfree(cn_msg);
240 		return ret;
241 	}
242 	/* HVUTIL_TRANSPORT_CHARDEV */
243 	mutex_lock(&hvt->lock);
244 	if (hvt->mode != HVUTIL_TRANSPORT_CHARDEV) {
245 		ret = -EINVAL;
246 		goto out_unlock;
247 	}
248 
249 	if (hvt->outmsg) {
250 		/* Previous message wasn't received */
251 		ret = -EFAULT;
252 		goto out_unlock;
253 	}
254 	hvt->outmsg = kzalloc(len, GFP_KERNEL);
255 	if (hvt->outmsg) {
256 		memcpy(hvt->outmsg, msg, len);
257 		hvt->outmsg_len = len;
258 		wake_up_interruptible(&hvt->outmsg_q);
259 	} else
260 		ret = -ENOMEM;
261 out_unlock:
262 	mutex_unlock(&hvt->lock);
263 	return ret;
264 }
265 
266 struct hvutil_transport *hvutil_transport_init(const char *name,
267 					       u32 cn_idx, u32 cn_val,
268 					       int (*on_msg)(void *, int),
269 					       void (*on_reset)(void))
270 {
271 	struct hvutil_transport *hvt;
272 
273 	hvt = kzalloc(sizeof(*hvt), GFP_KERNEL);
274 	if (!hvt)
275 		return NULL;
276 
277 	hvt->cn_id.idx = cn_idx;
278 	hvt->cn_id.val = cn_val;
279 
280 	hvt->mdev.minor = MISC_DYNAMIC_MINOR;
281 	hvt->mdev.name = name;
282 
283 	hvt->fops.owner = THIS_MODULE;
284 	hvt->fops.read = hvt_op_read;
285 	hvt->fops.write = hvt_op_write;
286 	hvt->fops.poll = hvt_op_poll;
287 	hvt->fops.open = hvt_op_open;
288 	hvt->fops.release = hvt_op_release;
289 
290 	hvt->mdev.fops = &hvt->fops;
291 
292 	init_waitqueue_head(&hvt->outmsg_q);
293 	mutex_init(&hvt->lock);
294 
295 	spin_lock(&hvt_list_lock);
296 	list_add(&hvt->list, &hvt_list);
297 	spin_unlock(&hvt_list_lock);
298 
299 	hvt->on_msg = on_msg;
300 	hvt->on_reset = on_reset;
301 
302 	if (misc_register(&hvt->mdev))
303 		goto err_free_hvt;
304 
305 	/* Use cn_id.idx/cn_id.val to determine if we need to setup netlink */
306 	if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0 &&
307 	    cn_add_callback(&hvt->cn_id, name, hvt_cn_callback))
308 		goto err_free_hvt;
309 
310 	return hvt;
311 
312 err_free_hvt:
313 	spin_lock(&hvt_list_lock);
314 	list_del(&hvt->list);
315 	spin_unlock(&hvt_list_lock);
316 	kfree(hvt);
317 	return NULL;
318 }
319 
320 void hvutil_transport_destroy(struct hvutil_transport *hvt)
321 {
322 	int mode_old;
323 
324 	mutex_lock(&hvt->lock);
325 	mode_old = hvt->mode;
326 	hvt->mode = HVUTIL_TRANSPORT_DESTROY;
327 	wake_up_interruptible(&hvt->outmsg_q);
328 	mutex_unlock(&hvt->lock);
329 
330 	/*
331 	 * In case we were in 'chardev' mode we still have an open fd so we
332 	 * have to defer freeing the device. Netlink interface can be freed
333 	 * now.
334 	 */
335 	spin_lock(&hvt_list_lock);
336 	list_del(&hvt->list);
337 	spin_unlock(&hvt_list_lock);
338 	if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0)
339 		cn_del_callback(&hvt->cn_id);
340 
341 	if (mode_old != HVUTIL_TRANSPORT_CHARDEV)
342 		hvt_transport_free(hvt);
343 }
344