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