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
 25static DEFINE_SPINLOCK(hvt_list_lock);
 26static struct list_head hvt_list = LIST_HEAD_INIT(hvt_list);
 27
 28static 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
 37static 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	if (hvt->on_read)
 76		hvt->on_read();
 77	hvt->on_read = NULL;
 78
 79out_unlock:
 80	mutex_unlock(&hvt->lock);
 81	return ret;
 82}
 83
 84static ssize_t hvt_op_write(struct file *file, const char __user *buf,
 85			    size_t count, loff_t *ppos)
 86{
 87	struct hvutil_transport *hvt;
 88	u8 *inmsg;
 89	int ret;
 90
 91	hvt = container_of(file->f_op, struct hvutil_transport, fops);
 92
 93	inmsg = memdup_user(buf, count);
 94	if (IS_ERR(inmsg))
 95		return PTR_ERR(inmsg);
 96
 97	if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
 98		ret = -EBADF;
 99	else
100		ret = hvt->on_msg(inmsg, count);
101
102	kfree(inmsg);
103
104	return ret ? ret : count;
105}
106
107static unsigned int hvt_op_poll(struct file *file, poll_table *wait)
108{
109	struct hvutil_transport *hvt;
110
111	hvt = container_of(file->f_op, struct hvutil_transport, fops);
112
113	poll_wait(file, &hvt->outmsg_q, wait);
114
115	if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
116		return POLLERR | POLLHUP;
117
118	if (hvt->outmsg_len > 0)
119		return POLLIN | POLLRDNORM;
120
121	return 0;
122}
123
124static int hvt_op_open(struct inode *inode, struct file *file)
125{
126	struct hvutil_transport *hvt;
127	int ret = 0;
128	bool issue_reset = false;
129
130	hvt = container_of(file->f_op, struct hvutil_transport, fops);
131
132	mutex_lock(&hvt->lock);
133
134	if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
135		ret = -EBADF;
136	} else if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
137		/*
138		 * Switching to CHARDEV mode. We switch bach to INIT when
139		 * device gets released.
140		 */
141		hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
142	}
143	else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
144		/*
145		 * We're switching from netlink communication to using char
146		 * device. Issue the reset first.
147		 */
148		issue_reset = true;
149		hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
150	} else {
151		ret = -EBUSY;
152	}
153
154	if (issue_reset)
155		hvt_reset(hvt);
156
157	mutex_unlock(&hvt->lock);
158
159	return ret;
160}
161
162static void hvt_transport_free(struct hvutil_transport *hvt)
163{
164	misc_deregister(&hvt->mdev);
165	kfree(hvt->outmsg);
166	kfree(hvt);
167}
168
169static int hvt_op_release(struct inode *inode, struct file *file)
170{
171	struct hvutil_transport *hvt;
172	int mode_old;
173
174	hvt = container_of(file->f_op, struct hvutil_transport, fops);
175
176	mutex_lock(&hvt->lock);
177	mode_old = hvt->mode;
178	if (hvt->mode != HVUTIL_TRANSPORT_DESTROY)
179		hvt->mode = HVUTIL_TRANSPORT_INIT;
180	/*
181	 * Cleanup message buffers to avoid spurious messages when the daemon
182	 * connects back.
183	 */
184	hvt_reset(hvt);
185	mutex_unlock(&hvt->lock);
186
187	if (mode_old == HVUTIL_TRANSPORT_DESTROY)
188		hvt_transport_free(hvt);
189
190	return 0;
191}
192
193static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
194{
195	struct hvutil_transport *hvt, *hvt_found = NULL;
196
197	spin_lock(&hvt_list_lock);
198	list_for_each_entry(hvt, &hvt_list, list) {
199		if (hvt->cn_id.idx == msg->id.idx &&
200		    hvt->cn_id.val == msg->id.val) {
201			hvt_found = hvt;
202			break;
203		}
204	}
205	spin_unlock(&hvt_list_lock);
206	if (!hvt_found) {
207		pr_warn("hvt_cn_callback: spurious message received!\n");
208		return;
209	}
210
211	/*
212	 * Switching to NETLINK mode. Switching to CHARDEV happens when someone
213	 * opens the device.
214	 */
215	mutex_lock(&hvt->lock);
216	if (hvt->mode == HVUTIL_TRANSPORT_INIT)
217		hvt->mode = HVUTIL_TRANSPORT_NETLINK;
218
219	if (hvt->mode == HVUTIL_TRANSPORT_NETLINK)
220		hvt_found->on_msg(msg->data, msg->len);
221	else
222		pr_warn("hvt_cn_callback: unexpected netlink message!\n");
223	mutex_unlock(&hvt->lock);
224}
225
226int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len,
227			  void (*on_read_cb)(void))
228{
229	struct cn_msg *cn_msg;
230	int ret = 0;
231
232	if (hvt->mode == HVUTIL_TRANSPORT_INIT ||
233	    hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
234		return -EINVAL;
235	} else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
236		cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
237		if (!cn_msg)
238			return -ENOMEM;
239		cn_msg->id.idx = hvt->cn_id.idx;
240		cn_msg->id.val = hvt->cn_id.val;
241		cn_msg->len = len;
242		memcpy(cn_msg->data, msg, len);
243		ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC);
244		kfree(cn_msg);
245		/*
246		 * We don't know when netlink messages are delivered but unlike
247		 * in CHARDEV mode we're not blocked and we can send next
248		 * messages right away.
249		 */
250		if (on_read_cb)
251			on_read_cb();
252		return ret;
253	}
254	/* HVUTIL_TRANSPORT_CHARDEV */
255	mutex_lock(&hvt->lock);
256	if (hvt->mode != HVUTIL_TRANSPORT_CHARDEV) {
257		ret = -EINVAL;
258		goto out_unlock;
259	}
260
261	if (hvt->outmsg) {
262		/* Previous message wasn't received */
263		ret = -EFAULT;
264		goto out_unlock;
265	}
266	hvt->outmsg = kzalloc(len, GFP_KERNEL);
267	if (hvt->outmsg) {
268		memcpy(hvt->outmsg, msg, len);
269		hvt->outmsg_len = len;
270		hvt->on_read = on_read_cb;
271		wake_up_interruptible(&hvt->outmsg_q);
272	} else
273		ret = -ENOMEM;
274out_unlock:
275	mutex_unlock(&hvt->lock);
276	return ret;
277}
278
279struct hvutil_transport *hvutil_transport_init(const char *name,
280					       u32 cn_idx, u32 cn_val,
281					       int (*on_msg)(void *, int),
282					       void (*on_reset)(void))
283{
284	struct hvutil_transport *hvt;
285
286	hvt = kzalloc(sizeof(*hvt), GFP_KERNEL);
287	if (!hvt)
288		return NULL;
289
290	hvt->cn_id.idx = cn_idx;
291	hvt->cn_id.val = cn_val;
292
293	hvt->mdev.minor = MISC_DYNAMIC_MINOR;
294	hvt->mdev.name = name;
295
296	hvt->fops.owner = THIS_MODULE;
297	hvt->fops.read = hvt_op_read;
298	hvt->fops.write = hvt_op_write;
299	hvt->fops.poll = hvt_op_poll;
300	hvt->fops.open = hvt_op_open;
301	hvt->fops.release = hvt_op_release;
302
303	hvt->mdev.fops = &hvt->fops;
304
305	init_waitqueue_head(&hvt->outmsg_q);
306	mutex_init(&hvt->lock);
307
308	spin_lock(&hvt_list_lock);
309	list_add(&hvt->list, &hvt_list);
310	spin_unlock(&hvt_list_lock);
311
312	hvt->on_msg = on_msg;
313	hvt->on_reset = on_reset;
314
315	if (misc_register(&hvt->mdev))
316		goto err_free_hvt;
317
318	/* Use cn_id.idx/cn_id.val to determine if we need to setup netlink */
319	if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0 &&
320	    cn_add_callback(&hvt->cn_id, name, hvt_cn_callback))
321		goto err_free_hvt;
322
323	return hvt;
324
325err_free_hvt:
326	spin_lock(&hvt_list_lock);
327	list_del(&hvt->list);
328	spin_unlock(&hvt_list_lock);
329	kfree(hvt);
330	return NULL;
331}
332
333void hvutil_transport_destroy(struct hvutil_transport *hvt)
334{
335	int mode_old;
336
337	mutex_lock(&hvt->lock);
338	mode_old = hvt->mode;
339	hvt->mode = HVUTIL_TRANSPORT_DESTROY;
340	wake_up_interruptible(&hvt->outmsg_q);
341	mutex_unlock(&hvt->lock);
342
343	/*
344	 * In case we were in 'chardev' mode we still have an open fd so we
345	 * have to defer freeing the device. Netlink interface can be freed
346	 * now.
347	 */
348	spin_lock(&hvt_list_lock);
349	list_del(&hvt->list);
350	spin_unlock(&hvt_list_lock);
351	if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0)
352		cn_del_callback(&hvt->cn_id);
353
354	if (mode_old != HVUTIL_TRANSPORT_CHARDEV)
355		hvt_transport_free(hvt);
356}