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
 75out_unlock:
 76	mutex_unlock(&hvt->lock);
 77	return ret;
 78}
 79
 80static 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
103static 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
120static 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
158static void hvt_transport_free(struct hvutil_transport *hvt)
159{
160	misc_deregister(&hvt->mdev);
161	kfree(hvt->outmsg);
162	kfree(hvt);
163}
164
165static 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
189static 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
222int 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;
261out_unlock:
262	mutex_unlock(&hvt->lock);
263	return ret;
264}
265
266struct 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
312err_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
320void 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}