1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Kernel/userspace transport abstraction for Hyper-V util driver.
4 *
5 * Copyright (C) 2015, Vitaly Kuznetsov <vkuznets@redhat.com>
6 */
7
8 #include <linux/slab.h>
9 #include <linux/fs.h>
10 #include <linux/poll.h>
11
12 #include "hyperv_vmbus.h"
13 #include "hv_utils_transport.h"
14
15 static DEFINE_SPINLOCK(hvt_list_lock);
16 static LIST_HEAD(hvt_list);
17
hvt_reset(struct hvutil_transport * hvt)18 static void hvt_reset(struct hvutil_transport *hvt)
19 {
20 kfree(hvt->outmsg);
21 hvt->outmsg = NULL;
22 hvt->outmsg_len = 0;
23 if (hvt->on_reset)
24 hvt->on_reset();
25 }
26
hvt_op_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)27 static ssize_t hvt_op_read(struct file *file, char __user *buf,
28 size_t count, loff_t *ppos)
29 {
30 struct hvutil_transport *hvt;
31 int ret;
32
33 hvt = container_of(file->f_op, struct hvutil_transport, fops);
34
35 if (wait_event_interruptible(hvt->outmsg_q, hvt->outmsg_len > 0 ||
36 hvt->mode != HVUTIL_TRANSPORT_CHARDEV))
37 return -EINTR;
38
39 mutex_lock(&hvt->lock);
40
41 if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
42 ret = -EBADF;
43 goto out_unlock;
44 }
45
46 if (!hvt->outmsg) {
47 ret = -EAGAIN;
48 goto out_unlock;
49 }
50
51 if (count < hvt->outmsg_len) {
52 ret = -EINVAL;
53 goto out_unlock;
54 }
55
56 if (!copy_to_user(buf, hvt->outmsg, hvt->outmsg_len))
57 ret = hvt->outmsg_len;
58 else
59 ret = -EFAULT;
60
61 kfree(hvt->outmsg);
62 hvt->outmsg = NULL;
63 hvt->outmsg_len = 0;
64
65 if (hvt->on_read)
66 hvt->on_read();
67 hvt->on_read = NULL;
68
69 out_unlock:
70 mutex_unlock(&hvt->lock);
71 return ret;
72 }
73
hvt_op_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)74 static ssize_t hvt_op_write(struct file *file, const char __user *buf,
75 size_t count, loff_t *ppos)
76 {
77 struct hvutil_transport *hvt;
78 u8 *inmsg;
79 int ret;
80
81 hvt = container_of(file->f_op, struct hvutil_transport, fops);
82
83 inmsg = memdup_user(buf, count);
84 if (IS_ERR(inmsg))
85 return PTR_ERR(inmsg);
86
87 if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
88 ret = -EBADF;
89 else
90 ret = hvt->on_msg(inmsg, count);
91
92 kfree(inmsg);
93
94 return ret ? ret : count;
95 }
96
hvt_op_poll(struct file * file,poll_table * wait)97 static __poll_t hvt_op_poll(struct file *file, poll_table *wait)
98 {
99 struct hvutil_transport *hvt;
100
101 hvt = container_of(file->f_op, struct hvutil_transport, fops);
102
103 poll_wait(file, &hvt->outmsg_q, wait);
104
105 if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
106 return EPOLLERR | EPOLLHUP;
107
108 if (hvt->outmsg_len > 0)
109 return EPOLLIN | EPOLLRDNORM;
110
111 return 0;
112 }
113
hvt_op_open(struct inode * inode,struct file * file)114 static int hvt_op_open(struct inode *inode, struct file *file)
115 {
116 struct hvutil_transport *hvt;
117 int ret = 0;
118 bool issue_reset = false;
119
120 hvt = container_of(file->f_op, struct hvutil_transport, fops);
121
122 mutex_lock(&hvt->lock);
123
124 if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
125 ret = -EBADF;
126 } else if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
127 /*
128 * Switching to CHARDEV mode. We switch bach to INIT when
129 * device gets released.
130 */
131 hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
132 } else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
133 /*
134 * We're switching from netlink communication to using char
135 * device. Issue the reset first.
136 */
137 issue_reset = true;
138 hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
139 } else {
140 ret = -EBUSY;
141 }
142
143 if (issue_reset)
144 hvt_reset(hvt);
145
146 mutex_unlock(&hvt->lock);
147
148 return ret;
149 }
150
hvt_transport_free(struct hvutil_transport * hvt)151 static void hvt_transport_free(struct hvutil_transport *hvt)
152 {
153 misc_deregister(&hvt->mdev);
154 kfree(hvt->outmsg);
155 kfree(hvt);
156 }
157
hvt_op_release(struct inode * inode,struct file * file)158 static int hvt_op_release(struct inode *inode, struct file *file)
159 {
160 struct hvutil_transport *hvt;
161 int mode_old;
162
163 hvt = container_of(file->f_op, struct hvutil_transport, fops);
164
165 mutex_lock(&hvt->lock);
166 mode_old = hvt->mode;
167 if (hvt->mode != HVUTIL_TRANSPORT_DESTROY)
168 hvt->mode = HVUTIL_TRANSPORT_INIT;
169 /*
170 * Cleanup message buffers to avoid spurious messages when the daemon
171 * connects back.
172 */
173 hvt_reset(hvt);
174
175 if (mode_old == HVUTIL_TRANSPORT_DESTROY)
176 complete(&hvt->release);
177
178 mutex_unlock(&hvt->lock);
179
180 return 0;
181 }
182
hvt_cn_callback(struct cn_msg * msg,struct netlink_skb_parms * nsp)183 static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
184 {
185 struct hvutil_transport *hvt, *hvt_found = NULL;
186
187 spin_lock(&hvt_list_lock);
188 list_for_each_entry(hvt, &hvt_list, list) {
189 if (hvt->cn_id.idx == msg->id.idx &&
190 hvt->cn_id.val == msg->id.val) {
191 hvt_found = hvt;
192 break;
193 }
194 }
195 spin_unlock(&hvt_list_lock);
196 if (!hvt_found) {
197 pr_warn("%s: spurious message received!\n", __func__);
198 return;
199 }
200
201 /*
202 * Switching to NETLINK mode. Switching to CHARDEV happens when someone
203 * opens the device.
204 */
205 mutex_lock(&hvt->lock);
206 if (hvt->mode == HVUTIL_TRANSPORT_INIT)
207 hvt->mode = HVUTIL_TRANSPORT_NETLINK;
208
209 if (hvt->mode == HVUTIL_TRANSPORT_NETLINK)
210 hvt_found->on_msg(msg->data, msg->len);
211 else
212 pr_warn("%s: unexpected netlink message!\n", __func__);
213 mutex_unlock(&hvt->lock);
214 }
215
hvutil_transport_send(struct hvutil_transport * hvt,void * msg,int len,void (* on_read_cb)(void))216 int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len,
217 void (*on_read_cb)(void))
218 {
219 struct cn_msg *cn_msg;
220 int ret = 0;
221
222 if (hvt->mode == HVUTIL_TRANSPORT_INIT ||
223 hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
224 return -EINVAL;
225 } else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
226 cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
227 if (!cn_msg)
228 return -ENOMEM;
229 cn_msg->id.idx = hvt->cn_id.idx;
230 cn_msg->id.val = hvt->cn_id.val;
231 cn_msg->len = len;
232 memcpy(cn_msg->data, msg, len);
233 ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC);
234 kfree(cn_msg);
235 /*
236 * We don't know when netlink messages are delivered but unlike
237 * in CHARDEV mode we're not blocked and we can send next
238 * messages right away.
239 */
240 if (on_read_cb)
241 on_read_cb();
242 return ret;
243 }
244 /* HVUTIL_TRANSPORT_CHARDEV */
245 mutex_lock(&hvt->lock);
246 if (hvt->mode != HVUTIL_TRANSPORT_CHARDEV) {
247 ret = -EINVAL;
248 goto out_unlock;
249 }
250
251 if (hvt->outmsg) {
252 /* Previous message wasn't received */
253 ret = -EFAULT;
254 goto out_unlock;
255 }
256 hvt->outmsg = kzalloc(len, GFP_KERNEL);
257 if (hvt->outmsg) {
258 memcpy(hvt->outmsg, msg, len);
259 hvt->outmsg_len = len;
260 hvt->on_read = on_read_cb;
261 wake_up_interruptible(&hvt->outmsg_q);
262 } else {
263 ret = -ENOMEM;
264 }
265 out_unlock:
266 mutex_unlock(&hvt->lock);
267 return ret;
268 }
269
hvutil_transport_init(const char * name,u32 cn_idx,u32 cn_val,int (* on_msg)(void *,int),void (* on_reset)(void))270 struct hvutil_transport *hvutil_transport_init(const char *name,
271 u32 cn_idx, u32 cn_val,
272 int (*on_msg)(void *, int),
273 void (*on_reset)(void))
274 {
275 struct hvutil_transport *hvt;
276
277 hvt = kzalloc(sizeof(*hvt), GFP_KERNEL);
278 if (!hvt)
279 return NULL;
280
281 hvt->cn_id.idx = cn_idx;
282 hvt->cn_id.val = cn_val;
283
284 hvt->mdev.minor = MISC_DYNAMIC_MINOR;
285 hvt->mdev.name = name;
286
287 hvt->fops.owner = THIS_MODULE;
288 hvt->fops.read = hvt_op_read;
289 hvt->fops.write = hvt_op_write;
290 hvt->fops.poll = hvt_op_poll;
291 hvt->fops.open = hvt_op_open;
292 hvt->fops.release = hvt_op_release;
293
294 hvt->mdev.fops = &hvt->fops;
295
296 init_waitqueue_head(&hvt->outmsg_q);
297 mutex_init(&hvt->lock);
298 init_completion(&hvt->release);
299
300 spin_lock(&hvt_list_lock);
301 list_add(&hvt->list, &hvt_list);
302 spin_unlock(&hvt_list_lock);
303
304 hvt->on_msg = on_msg;
305 hvt->on_reset = on_reset;
306
307 if (misc_register(&hvt->mdev))
308 goto err_free_hvt;
309
310 /* Use cn_id.idx/cn_id.val to determine if we need to setup netlink */
311 if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0 &&
312 cn_add_callback(&hvt->cn_id, name, hvt_cn_callback))
313 goto err_free_hvt;
314
315 return hvt;
316
317 err_free_hvt:
318 spin_lock(&hvt_list_lock);
319 list_del(&hvt->list);
320 spin_unlock(&hvt_list_lock);
321 kfree(hvt);
322 return NULL;
323 }
324
hvutil_transport_destroy(struct hvutil_transport * hvt)325 void hvutil_transport_destroy(struct hvutil_transport *hvt)
326 {
327 int mode_old;
328
329 mutex_lock(&hvt->lock);
330 mode_old = hvt->mode;
331 hvt->mode = HVUTIL_TRANSPORT_DESTROY;
332 wake_up_interruptible(&hvt->outmsg_q);
333 mutex_unlock(&hvt->lock);
334
335 /*
336 * In case we were in 'chardev' mode we still have an open fd so we
337 * have to defer freeing the device. Netlink interface can be freed
338 * now.
339 */
340 spin_lock(&hvt_list_lock);
341 list_del(&hvt->list);
342 spin_unlock(&hvt_list_lock);
343 if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0)
344 cn_del_callback(&hvt->cn_id);
345
346 if (mode_old == HVUTIL_TRANSPORT_CHARDEV)
347 wait_for_completion(&hvt->release);
348
349 hvt_transport_free(hvt);
350 }
351