1/*
2 * Copyright (C) 2006-2009 Red Hat, Inc.
3 *
4 * This file is released under the LGPL.
5 */
6
7#include <linux/kernel.h>
8#include <linux/module.h>
9#include <linux/slab.h>
10#include <net/sock.h>
11#include <linux/workqueue.h>
12#include <linux/connector.h>
13#include <linux/device-mapper.h>
14#include <linux/dm-log-userspace.h>
15
16#include "dm-log-userspace-transfer.h"
17
18static uint32_t dm_ulog_seq;
19
20/*
21 * Netlink/Connector is an unreliable protocol.  How long should
22 * we wait for a response before assuming it was lost and retrying?
23 * (If we do receive a response after this time, it will be discarded
24 * and the response to the resent request will be waited for.
25 */
26#define DM_ULOG_RETRY_TIMEOUT (15 * HZ)
27
28/*
29 * Pre-allocated space for speed
30 */
31#define DM_ULOG_PREALLOCED_SIZE 512
32static struct cn_msg *prealloced_cn_msg;
33static struct dm_ulog_request *prealloced_ulog_tfr;
34
35static struct cb_id ulog_cn_id = {
36	.idx = CN_IDX_DM,
37	.val = CN_VAL_DM_USERSPACE_LOG
38};
39
40static DEFINE_MUTEX(dm_ulog_lock);
41
42struct receiving_pkg {
43	struct list_head list;
44	struct completion complete;
45
46	uint32_t seq;
47
48	int error;
49	size_t *data_size;
50	char *data;
51};
52
53static DEFINE_SPINLOCK(receiving_list_lock);
54static struct list_head receiving_list;
55
56static int dm_ulog_sendto_server(struct dm_ulog_request *tfr)
57{
58	int r;
59	struct cn_msg *msg = prealloced_cn_msg;
60
61	memset(msg, 0, sizeof(struct cn_msg));
62
63	msg->id.idx = ulog_cn_id.idx;
64	msg->id.val = ulog_cn_id.val;
65	msg->ack = 0;
66	msg->seq = tfr->seq;
67	msg->len = sizeof(struct dm_ulog_request) + tfr->data_size;
68
69	r = cn_netlink_send(msg, 0, 0, gfp_any());
70
71	return r;
72}
73
74/*
75 * Parameters for this function can be either msg or tfr, but not
76 * both.  This function fills in the reply for a waiting request.
77 * If just msg is given, then the reply is simply an ACK from userspace
78 * that the request was received.
79 *
80 * Returns: 0 on success, -ENOENT on failure
81 */
82static int fill_pkg(struct cn_msg *msg, struct dm_ulog_request *tfr)
83{
84	uint32_t rtn_seq = (msg) ? msg->seq : (tfr) ? tfr->seq : 0;
85	struct receiving_pkg *pkg;
86
87	/*
88	 * The 'receiving_pkg' entries in this list are statically
89	 * allocated on the stack in 'dm_consult_userspace'.
90	 * Each process that is waiting for a reply from the user
91	 * space server will have an entry in this list.
92	 *
93	 * We are safe to do it this way because the stack space
94	 * is unique to each process, but still addressable by
95	 * other processes.
96	 */
97	list_for_each_entry(pkg, &receiving_list, list) {
98		if (rtn_seq != pkg->seq)
99			continue;
100
101		if (msg) {
102			pkg->error = -msg->ack;
103			/*
104			 * If we are trying again, we will need to know our
105			 * storage capacity.  Otherwise, along with the
106			 * error code, we make explicit that we have no data.
107			 */
108			if (pkg->error != -EAGAIN)
109				*(pkg->data_size) = 0;
110		} else if (tfr->data_size > *(pkg->data_size)) {
111			DMERR("Insufficient space to receive package [%u] "
112			      "(%u vs %zu)", tfr->request_type,
113			      tfr->data_size, *(pkg->data_size));
114
115			*(pkg->data_size) = 0;
116			pkg->error = -ENOSPC;
117		} else {
118			pkg->error = tfr->error;
119			memcpy(pkg->data, tfr->data, tfr->data_size);
120			*(pkg->data_size) = tfr->data_size;
121		}
122		complete(&pkg->complete);
123		return 0;
124	}
125
126	return -ENOENT;
127}
128
129/*
130 * This is the connector callback that delivers data
131 * that was sent from userspace.
132 */
133static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
134{
135	struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1);
136
137	if (!capable(CAP_SYS_ADMIN))
138		return;
139
140	spin_lock(&receiving_list_lock);
141	if (msg->len == 0)
142		fill_pkg(msg, NULL);
143	else if (msg->len < sizeof(*tfr))
144		DMERR("Incomplete message received (expected %u, got %u): [%u]",
145		      (unsigned)sizeof(*tfr), msg->len, msg->seq);
146	else
147		fill_pkg(NULL, tfr);
148	spin_unlock(&receiving_list_lock);
149}
150
151/**
152 * dm_consult_userspace
153 * @uuid: log's universal unique identifier (must be DM_UUID_LEN in size)
154 * @luid: log's local unique identifier
155 * @request_type:  found in include/linux/dm-log-userspace.h
156 * @data: data to tx to the server
157 * @data_size: size of data in bytes
158 * @rdata: place to put return data from server
159 * @rdata_size: value-result (amount of space given/amount of space used)
160 *
161 * rdata_size is undefined on failure.
162 *
163 * Memory used to communicate with userspace is zero'ed
164 * before populating to ensure that no unwanted bits leak
165 * from kernel space to user-space.  All userspace log communications
166 * between kernel and user space go through this function.
167 *
168 * Returns: 0 on success, -EXXX on failure
169 **/
170int dm_consult_userspace(const char *uuid, uint64_t luid, int request_type,
171			 char *data, size_t data_size,
172			 char *rdata, size_t *rdata_size)
173{
174	int r = 0;
175	unsigned long tmo;
176	size_t dummy = 0;
177	int overhead_size = sizeof(struct dm_ulog_request) + sizeof(struct cn_msg);
178	struct dm_ulog_request *tfr = prealloced_ulog_tfr;
179	struct receiving_pkg pkg;
180
181	/*
182	 * Given the space needed to hold the 'struct cn_msg' and
183	 * 'struct dm_ulog_request' - do we have enough payload
184	 * space remaining?
185	 */
186	if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) {
187		DMINFO("Size of tfr exceeds preallocated size");
188		return -EINVAL;
189	}
190
191	if (!rdata_size)
192		rdata_size = &dummy;
193resend:
194	/*
195	 * We serialize the sending of requests so we can
196	 * use the preallocated space.
197	 */
198	mutex_lock(&dm_ulog_lock);
199
200	memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg));
201	memcpy(tfr->uuid, uuid, DM_UUID_LEN);
202	tfr->version = DM_ULOG_REQUEST_VERSION;
203	tfr->luid = luid;
204	tfr->seq = dm_ulog_seq++;
205
206	/*
207	 * Must be valid request type (all other bits set to
208	 * zero).  This reserves other bits for possible future
209	 * use.
210	 */
211	tfr->request_type = request_type & DM_ULOG_REQUEST_MASK;
212
213	tfr->data_size = data_size;
214	if (data && data_size)
215		memcpy(tfr->data, data, data_size);
216
217	memset(&pkg, 0, sizeof(pkg));
218	init_completion(&pkg.complete);
219	pkg.seq = tfr->seq;
220	pkg.data_size = rdata_size;
221	pkg.data = rdata;
222	spin_lock(&receiving_list_lock);
223	list_add(&(pkg.list), &receiving_list);
224	spin_unlock(&receiving_list_lock);
225
226	r = dm_ulog_sendto_server(tfr);
227
228	mutex_unlock(&dm_ulog_lock);
229
230	if (r) {
231		DMERR("Unable to send log request [%u] to userspace: %d",
232		      request_type, r);
233		spin_lock(&receiving_list_lock);
234		list_del_init(&(pkg.list));
235		spin_unlock(&receiving_list_lock);
236
237		goto out;
238	}
239
240	tmo = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT);
241	spin_lock(&receiving_list_lock);
242	list_del_init(&(pkg.list));
243	spin_unlock(&receiving_list_lock);
244	if (!tmo) {
245		DMWARN("[%s] Request timed out: [%u/%u] - retrying",
246		       (strlen(uuid) > 8) ?
247		       (uuid + (strlen(uuid) - 8)) : (uuid),
248		       request_type, pkg.seq);
249		goto resend;
250	}
251
252	r = pkg.error;
253	if (r == -EAGAIN)
254		goto resend;
255
256out:
257	return r;
258}
259
260int dm_ulog_tfr_init(void)
261{
262	int r;
263	void *prealloced;
264
265	INIT_LIST_HEAD(&receiving_list);
266
267	prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL);
268	if (!prealloced)
269		return -ENOMEM;
270
271	prealloced_cn_msg = prealloced;
272	prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg);
273
274	r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback);
275	if (r) {
276		kfree(prealloced_cn_msg);
277		return r;
278	}
279
280	return 0;
281}
282
283void dm_ulog_tfr_exit(void)
284{
285	cn_del_callback(&ulog_cn_id);
286	kfree(prealloced_cn_msg);
287}
288