GNU Linux-libre 5.10.219-gnu1
[releases.git] / drivers / hv / hv_utils_transport.c
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 struct list_head hvt_list = LIST_HEAD_INIT(hvt_list);
17
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
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
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
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
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         }
133         else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
134                 /*
135                  * We're switching from netlink communication to using char
136                  * device. Issue the reset first.
137                  */
138                 issue_reset = true;
139                 hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
140         } else {
141                 ret = -EBUSY;
142         }
143
144         if (issue_reset)
145                 hvt_reset(hvt);
146
147         mutex_unlock(&hvt->lock);
148
149         return ret;
150 }
151
152 static void hvt_transport_free(struct hvutil_transport *hvt)
153 {
154         misc_deregister(&hvt->mdev);
155         kfree(hvt->outmsg);
156         kfree(hvt);
157 }
158
159 static int hvt_op_release(struct inode *inode, struct file *file)
160 {
161         struct hvutil_transport *hvt;
162         int mode_old;
163
164         hvt = container_of(file->f_op, struct hvutil_transport, fops);
165
166         mutex_lock(&hvt->lock);
167         mode_old = hvt->mode;
168         if (hvt->mode != HVUTIL_TRANSPORT_DESTROY)
169                 hvt->mode = HVUTIL_TRANSPORT_INIT;
170         /*
171          * Cleanup message buffers to avoid spurious messages when the daemon
172          * connects back.
173          */
174         hvt_reset(hvt);
175
176         if (mode_old == HVUTIL_TRANSPORT_DESTROY)
177                 complete(&hvt->release);
178
179         mutex_unlock(&hvt->lock);
180
181         return 0;
182 }
183
184 static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
185 {
186         struct hvutil_transport *hvt, *hvt_found = NULL;
187
188         spin_lock(&hvt_list_lock);
189         list_for_each_entry(hvt, &hvt_list, list) {
190                 if (hvt->cn_id.idx == msg->id.idx &&
191                     hvt->cn_id.val == msg->id.val) {
192                         hvt_found = hvt;
193                         break;
194                 }
195         }
196         spin_unlock(&hvt_list_lock);
197         if (!hvt_found) {
198                 pr_warn("hvt_cn_callback: spurious message received!\n");
199                 return;
200         }
201
202         /*
203          * Switching to NETLINK mode. Switching to CHARDEV happens when someone
204          * opens the device.
205          */
206         mutex_lock(&hvt->lock);
207         if (hvt->mode == HVUTIL_TRANSPORT_INIT)
208                 hvt->mode = HVUTIL_TRANSPORT_NETLINK;
209
210         if (hvt->mode == HVUTIL_TRANSPORT_NETLINK)
211                 hvt_found->on_msg(msg->data, msg->len);
212         else
213                 pr_warn("hvt_cn_callback: unexpected netlink message!\n");
214         mutex_unlock(&hvt->lock);
215 }
216
217 int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len,
218                           void (*on_read_cb)(void))
219 {
220         struct cn_msg *cn_msg;
221         int ret = 0;
222
223         if (hvt->mode == HVUTIL_TRANSPORT_INIT ||
224             hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
225                 return -EINVAL;
226         } else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
227                 cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
228                 if (!cn_msg)
229                         return -ENOMEM;
230                 cn_msg->id.idx = hvt->cn_id.idx;
231                 cn_msg->id.val = hvt->cn_id.val;
232                 cn_msg->len = len;
233                 memcpy(cn_msg->data, msg, len);
234                 ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC);
235                 kfree(cn_msg);
236                 /*
237                  * We don't know when netlink messages are delivered but unlike
238                  * in CHARDEV mode we're not blocked and we can send next
239                  * messages right away.
240                  */
241                 if (on_read_cb)
242                         on_read_cb();
243                 return ret;
244         }
245         /* HVUTIL_TRANSPORT_CHARDEV */
246         mutex_lock(&hvt->lock);
247         if (hvt->mode != HVUTIL_TRANSPORT_CHARDEV) {
248                 ret = -EINVAL;
249                 goto out_unlock;
250         }
251
252         if (hvt->outmsg) {
253                 /* Previous message wasn't received */
254                 ret = -EFAULT;
255                 goto out_unlock;
256         }
257         hvt->outmsg = kzalloc(len, GFP_KERNEL);
258         if (hvt->outmsg) {
259                 memcpy(hvt->outmsg, msg, len);
260                 hvt->outmsg_len = len;
261                 hvt->on_read = on_read_cb;
262                 wake_up_interruptible(&hvt->outmsg_q);
263         } else
264                 ret = -ENOMEM;
265 out_unlock:
266         mutex_unlock(&hvt->lock);
267         return ret;
268 }
269
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
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 }