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
 15static DEFINE_SPINLOCK(hvt_list_lock);
 16static LIST_HEAD(hvt_list);
 17
 18static 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
 27static 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
 69out_unlock:
 70	mutex_unlock(&hvt->lock);
 71	return ret;
 72}
 73
 74static 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
 97static __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
114static 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
151static void hvt_transport_free(struct hvutil_transport *hvt)
152{
153	misc_deregister(&hvt->mdev);
154	kfree(hvt->outmsg);
155	kfree(hvt);
156}
157
158static 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
183static 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
216int 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	}
265out_unlock:
266	mutex_unlock(&hvt->lock);
267	return ret;
268}
269
270struct 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
317err_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
325void 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}