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 18 static 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 32 static struct cn_msg *prealloced_cn_msg; 33 static struct dm_ulog_request *prealloced_ulog_tfr; 34 35 static struct cb_id ulog_cn_id = { 36 .idx = CN_IDX_DM, 37 .val = CN_VAL_DM_USERSPACE_LOG 38 }; 39 40 static DEFINE_MUTEX(dm_ulog_lock); 41 42 struct 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 53 static DEFINE_SPINLOCK(receiving_list_lock); 54 static struct list_head receiving_list; 55 56 static 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 */ 82 static 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 */ 133 static 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 **/ 170 int 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 size_t dummy = 0; 176 int overhead_size = sizeof(struct dm_ulog_request) + sizeof(struct cn_msg); 177 struct dm_ulog_request *tfr = prealloced_ulog_tfr; 178 struct receiving_pkg pkg; 179 180 /* 181 * Given the space needed to hold the 'struct cn_msg' and 182 * 'struct dm_ulog_request' - do we have enough payload 183 * space remaining? 184 */ 185 if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) { 186 DMINFO("Size of tfr exceeds preallocated size"); 187 return -EINVAL; 188 } 189 190 if (!rdata_size) 191 rdata_size = &dummy; 192 resend: 193 /* 194 * We serialize the sending of requests so we can 195 * use the preallocated space. 196 */ 197 mutex_lock(&dm_ulog_lock); 198 199 memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg)); 200 memcpy(tfr->uuid, uuid, DM_UUID_LEN); 201 tfr->version = DM_ULOG_REQUEST_VERSION; 202 tfr->luid = luid; 203 tfr->seq = dm_ulog_seq++; 204 205 /* 206 * Must be valid request type (all other bits set to 207 * zero). This reserves other bits for possible future 208 * use. 209 */ 210 tfr->request_type = request_type & DM_ULOG_REQUEST_MASK; 211 212 tfr->data_size = data_size; 213 if (data && data_size) 214 memcpy(tfr->data, data, data_size); 215 216 memset(&pkg, 0, sizeof(pkg)); 217 init_completion(&pkg.complete); 218 pkg.seq = tfr->seq; 219 pkg.data_size = rdata_size; 220 pkg.data = rdata; 221 spin_lock(&receiving_list_lock); 222 list_add(&(pkg.list), &receiving_list); 223 spin_unlock(&receiving_list_lock); 224 225 r = dm_ulog_sendto_server(tfr); 226 227 mutex_unlock(&dm_ulog_lock); 228 229 if (r) { 230 DMERR("Unable to send log request [%u] to userspace: %d", 231 request_type, r); 232 spin_lock(&receiving_list_lock); 233 list_del_init(&(pkg.list)); 234 spin_unlock(&receiving_list_lock); 235 236 goto out; 237 } 238 239 r = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT); 240 spin_lock(&receiving_list_lock); 241 list_del_init(&(pkg.list)); 242 spin_unlock(&receiving_list_lock); 243 if (!r) { 244 DMWARN("[%s] Request timed out: [%u/%u] - retrying", 245 (strlen(uuid) > 8) ? 246 (uuid + (strlen(uuid) - 8)) : (uuid), 247 request_type, pkg.seq); 248 goto resend; 249 } 250 251 r = pkg.error; 252 if (r == -EAGAIN) 253 goto resend; 254 255 out: 256 return r; 257 } 258 259 int dm_ulog_tfr_init(void) 260 { 261 int r; 262 void *prealloced; 263 264 INIT_LIST_HEAD(&receiving_list); 265 266 prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL); 267 if (!prealloced) 268 return -ENOMEM; 269 270 prealloced_cn_msg = prealloced; 271 prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg); 272 273 r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback); 274 if (r) { 275 kfree(prealloced_cn_msg); 276 return r; 277 } 278 279 return 0; 280 } 281 282 void dm_ulog_tfr_exit(void) 283 { 284 cn_del_callback(&ulog_cn_id); 285 kfree(prealloced_cn_msg); 286 } 287