1 /* 2 * Driver giving user-space access to the kernel's xenbus connection 3 * to xenstore. 4 * 5 * Copyright (c) 2005, Christian Limpach 6 * Copyright (c) 2005, Rusty Russell, IBM Corporation 7 * 8 * This program is free software; you can redistribute it and/or 9 * modify it under the terms of the GNU General Public License version 2 10 * as published by the Free Software Foundation; or, when distributed 11 * separately from the Linux kernel or incorporated into other 12 * software packages, subject to the following license: 13 * 14 * Permission is hereby granted, free of charge, to any person obtaining a copy 15 * of this source file (the "Software"), to deal in the Software without 16 * restriction, including without limitation the rights to use, copy, modify, 17 * merge, publish, distribute, sublicense, and/or sell copies of the Software, 18 * and to permit persons to whom the Software is furnished to do so, subject to 19 * the following conditions: 20 * 21 * The above copyright notice and this permission notice shall be included in 22 * all copies or substantial portions of the Software. 23 * 24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 25 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 26 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 27 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 28 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 29 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 30 * IN THE SOFTWARE. 31 * 32 * Changes: 33 * 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem 34 * and /proc/xen compatibility mount point. 35 * Turned xenfs into a loadable module. 36 */ 37 38 #include <linux/kernel.h> 39 #include <linux/errno.h> 40 #include <linux/uio.h> 41 #include <linux/notifier.h> 42 #include <linux/wait.h> 43 #include <linux/fs.h> 44 #include <linux/poll.h> 45 #include <linux/mutex.h> 46 #include <linux/sched.h> 47 #include <linux/spinlock.h> 48 #include <linux/mount.h> 49 #include <linux/pagemap.h> 50 #include <linux/uaccess.h> 51 #include <linux/init.h> 52 #include <linux/namei.h> 53 #include <linux/string.h> 54 #include <linux/slab.h> 55 #include <linux/miscdevice.h> 56 #include <linux/module.h> 57 58 #include "xenbus_comms.h" 59 60 #include <xen/xenbus.h> 61 #include <xen/xen.h> 62 #include <asm/xen/hypervisor.h> 63 64 MODULE_LICENSE("GPL"); 65 66 /* 67 * An element of a list of outstanding transactions, for which we're 68 * still waiting a reply. 69 */ 70 struct xenbus_transaction_holder { 71 struct list_head list; 72 struct xenbus_transaction handle; 73 }; 74 75 /* 76 * A buffer of data on the queue. 77 */ 78 struct read_buffer { 79 struct list_head list; 80 unsigned int cons; 81 unsigned int len; 82 char msg[]; 83 }; 84 85 struct xenbus_file_priv { 86 /* 87 * msgbuffer_mutex is held while partial requests are built up 88 * and complete requests are acted on. It therefore protects 89 * the "transactions" and "watches" lists, and the partial 90 * request length and buffer. 91 * 92 * reply_mutex protects the reply being built up to return to 93 * usermode. It nests inside msgbuffer_mutex but may be held 94 * alone during a watch callback. 95 */ 96 struct mutex msgbuffer_mutex; 97 98 /* In-progress transactions */ 99 struct list_head transactions; 100 101 /* Active watches. */ 102 struct list_head watches; 103 104 /* Partial request. */ 105 unsigned int len; 106 union { 107 struct xsd_sockmsg msg; 108 char buffer[XENSTORE_PAYLOAD_MAX]; 109 } u; 110 111 /* Response queue. */ 112 struct mutex reply_mutex; 113 struct list_head read_buffers; 114 wait_queue_head_t read_waitq; 115 116 }; 117 118 /* Read out any raw xenbus messages queued up. */ 119 static ssize_t xenbus_file_read(struct file *filp, 120 char __user *ubuf, 121 size_t len, loff_t *ppos) 122 { 123 struct xenbus_file_priv *u = filp->private_data; 124 struct read_buffer *rb; 125 unsigned i; 126 int ret; 127 128 mutex_lock(&u->reply_mutex); 129 again: 130 while (list_empty(&u->read_buffers)) { 131 mutex_unlock(&u->reply_mutex); 132 if (filp->f_flags & O_NONBLOCK) 133 return -EAGAIN; 134 135 ret = wait_event_interruptible(u->read_waitq, 136 !list_empty(&u->read_buffers)); 137 if (ret) 138 return ret; 139 mutex_lock(&u->reply_mutex); 140 } 141 142 rb = list_entry(u->read_buffers.next, struct read_buffer, list); 143 i = 0; 144 while (i < len) { 145 unsigned sz = min((unsigned)len - i, rb->len - rb->cons); 146 147 ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz); 148 149 i += sz - ret; 150 rb->cons += sz - ret; 151 152 if (ret != 0) { 153 if (i == 0) 154 i = -EFAULT; 155 goto out; 156 } 157 158 /* Clear out buffer if it has been consumed */ 159 if (rb->cons == rb->len) { 160 list_del(&rb->list); 161 kfree(rb); 162 if (list_empty(&u->read_buffers)) 163 break; 164 rb = list_entry(u->read_buffers.next, 165 struct read_buffer, list); 166 } 167 } 168 if (i == 0) 169 goto again; 170 171 out: 172 mutex_unlock(&u->reply_mutex); 173 return i; 174 } 175 176 /* 177 * Add a buffer to the queue. Caller must hold the appropriate lock 178 * if the queue is not local. (Commonly the caller will build up 179 * multiple queued buffers on a temporary local list, and then add it 180 * to the appropriate list under lock once all the buffers have een 181 * successfully allocated.) 182 */ 183 static int queue_reply(struct list_head *queue, const void *data, size_t len) 184 { 185 struct read_buffer *rb; 186 187 if (len == 0) 188 return 0; 189 190 rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL); 191 if (rb == NULL) 192 return -ENOMEM; 193 194 rb->cons = 0; 195 rb->len = len; 196 197 memcpy(rb->msg, data, len); 198 199 list_add_tail(&rb->list, queue); 200 return 0; 201 } 202 203 /* 204 * Free all the read_buffer s on a list. 205 * Caller must have sole reference to list. 206 */ 207 static void queue_cleanup(struct list_head *list) 208 { 209 struct read_buffer *rb; 210 211 while (!list_empty(list)) { 212 rb = list_entry(list->next, struct read_buffer, list); 213 list_del(list->next); 214 kfree(rb); 215 } 216 } 217 218 struct watch_adapter { 219 struct list_head list; 220 struct xenbus_watch watch; 221 struct xenbus_file_priv *dev_data; 222 char *token; 223 }; 224 225 static void free_watch_adapter(struct watch_adapter *watch) 226 { 227 kfree(watch->watch.node); 228 kfree(watch->token); 229 kfree(watch); 230 } 231 232 static struct watch_adapter *alloc_watch_adapter(const char *path, 233 const char *token) 234 { 235 struct watch_adapter *watch; 236 237 watch = kzalloc(sizeof(*watch), GFP_KERNEL); 238 if (watch == NULL) 239 goto out_fail; 240 241 watch->watch.node = kstrdup(path, GFP_KERNEL); 242 if (watch->watch.node == NULL) 243 goto out_free; 244 245 watch->token = kstrdup(token, GFP_KERNEL); 246 if (watch->token == NULL) 247 goto out_free; 248 249 return watch; 250 251 out_free: 252 free_watch_adapter(watch); 253 254 out_fail: 255 return NULL; 256 } 257 258 static void watch_fired(struct xenbus_watch *watch, 259 const char **vec, 260 unsigned int len) 261 { 262 struct watch_adapter *adap; 263 struct xsd_sockmsg hdr; 264 const char *path, *token; 265 int path_len, tok_len, body_len, data_len = 0; 266 int ret; 267 LIST_HEAD(staging_q); 268 269 adap = container_of(watch, struct watch_adapter, watch); 270 271 path = vec[XS_WATCH_PATH]; 272 token = adap->token; 273 274 path_len = strlen(path) + 1; 275 tok_len = strlen(token) + 1; 276 if (len > 2) 277 data_len = vec[len] - vec[2] + 1; 278 body_len = path_len + tok_len + data_len; 279 280 hdr.type = XS_WATCH_EVENT; 281 hdr.len = body_len; 282 283 mutex_lock(&adap->dev_data->reply_mutex); 284 285 ret = queue_reply(&staging_q, &hdr, sizeof(hdr)); 286 if (!ret) 287 ret = queue_reply(&staging_q, path, path_len); 288 if (!ret) 289 ret = queue_reply(&staging_q, token, tok_len); 290 if (!ret && len > 2) 291 ret = queue_reply(&staging_q, vec[2], data_len); 292 293 if (!ret) { 294 /* success: pass reply list onto watcher */ 295 list_splice_tail(&staging_q, &adap->dev_data->read_buffers); 296 wake_up(&adap->dev_data->read_waitq); 297 } else 298 queue_cleanup(&staging_q); 299 300 mutex_unlock(&adap->dev_data->reply_mutex); 301 } 302 303 static int xenbus_write_transaction(unsigned msg_type, 304 struct xenbus_file_priv *u) 305 { 306 int rc; 307 void *reply; 308 struct xenbus_transaction_holder *trans = NULL; 309 LIST_HEAD(staging_q); 310 311 if (msg_type == XS_TRANSACTION_START) { 312 trans = kmalloc(sizeof(*trans), GFP_KERNEL); 313 if (!trans) { 314 rc = -ENOMEM; 315 goto out; 316 } 317 } 318 319 reply = xenbus_dev_request_and_reply(&u->u.msg); 320 if (IS_ERR(reply)) { 321 kfree(trans); 322 rc = PTR_ERR(reply); 323 goto out; 324 } 325 326 if (msg_type == XS_TRANSACTION_START) { 327 trans->handle.id = simple_strtoul(reply, NULL, 0); 328 329 list_add(&trans->list, &u->transactions); 330 } else if (msg_type == XS_TRANSACTION_END) { 331 list_for_each_entry(trans, &u->transactions, list) 332 if (trans->handle.id == u->u.msg.tx_id) 333 break; 334 BUG_ON(&trans->list == &u->transactions); 335 list_del(&trans->list); 336 337 kfree(trans); 338 } 339 340 mutex_lock(&u->reply_mutex); 341 rc = queue_reply(&staging_q, &u->u.msg, sizeof(u->u.msg)); 342 if (!rc) 343 rc = queue_reply(&staging_q, reply, u->u.msg.len); 344 if (!rc) { 345 list_splice_tail(&staging_q, &u->read_buffers); 346 wake_up(&u->read_waitq); 347 } else { 348 queue_cleanup(&staging_q); 349 } 350 mutex_unlock(&u->reply_mutex); 351 352 kfree(reply); 353 354 out: 355 return rc; 356 } 357 358 static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u) 359 { 360 struct watch_adapter *watch, *tmp_watch; 361 char *path, *token; 362 int err, rc; 363 LIST_HEAD(staging_q); 364 365 path = u->u.buffer + sizeof(u->u.msg); 366 token = memchr(path, 0, u->u.msg.len); 367 if (token == NULL) { 368 rc = -EILSEQ; 369 goto out; 370 } 371 token++; 372 if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) { 373 rc = -EILSEQ; 374 goto out; 375 } 376 377 if (msg_type == XS_WATCH) { 378 watch = alloc_watch_adapter(path, token); 379 if (watch == NULL) { 380 rc = -ENOMEM; 381 goto out; 382 } 383 384 watch->watch.callback = watch_fired; 385 watch->dev_data = u; 386 387 err = register_xenbus_watch(&watch->watch); 388 if (err) { 389 free_watch_adapter(watch); 390 rc = err; 391 goto out; 392 } 393 list_add(&watch->list, &u->watches); 394 } else { 395 list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) { 396 if (!strcmp(watch->token, token) && 397 !strcmp(watch->watch.node, path)) { 398 unregister_xenbus_watch(&watch->watch); 399 list_del(&watch->list); 400 free_watch_adapter(watch); 401 break; 402 } 403 } 404 } 405 406 /* Success. Synthesize a reply to say all is OK. */ 407 { 408 struct { 409 struct xsd_sockmsg hdr; 410 char body[3]; 411 } __packed reply = { 412 { 413 .type = msg_type, 414 .len = sizeof(reply.body) 415 }, 416 "OK" 417 }; 418 419 mutex_lock(&u->reply_mutex); 420 rc = queue_reply(&u->read_buffers, &reply, sizeof(reply)); 421 wake_up(&u->read_waitq); 422 mutex_unlock(&u->reply_mutex); 423 } 424 425 out: 426 return rc; 427 } 428 429 static ssize_t xenbus_file_write(struct file *filp, 430 const char __user *ubuf, 431 size_t len, loff_t *ppos) 432 { 433 struct xenbus_file_priv *u = filp->private_data; 434 uint32_t msg_type; 435 int rc = len; 436 int ret; 437 LIST_HEAD(staging_q); 438 439 /* 440 * We're expecting usermode to be writing properly formed 441 * xenbus messages. If they write an incomplete message we 442 * buffer it up. Once it is complete, we act on it. 443 */ 444 445 /* 446 * Make sure concurrent writers can't stomp all over each 447 * other's messages and make a mess of our partial message 448 * buffer. We don't make any attemppt to stop multiple 449 * writers from making a mess of each other's incomplete 450 * messages; we're just trying to guarantee our own internal 451 * consistency and make sure that single writes are handled 452 * atomically. 453 */ 454 mutex_lock(&u->msgbuffer_mutex); 455 456 /* Get this out of the way early to avoid confusion */ 457 if (len == 0) 458 goto out; 459 460 /* Can't write a xenbus message larger we can buffer */ 461 if (len > sizeof(u->u.buffer) - u->len) { 462 /* On error, dump existing buffer */ 463 u->len = 0; 464 rc = -EINVAL; 465 goto out; 466 } 467 468 ret = copy_from_user(u->u.buffer + u->len, ubuf, len); 469 470 if (ret != 0) { 471 rc = -EFAULT; 472 goto out; 473 } 474 475 /* Deal with a partial copy. */ 476 len -= ret; 477 rc = len; 478 479 u->len += len; 480 481 /* Return if we haven't got a full message yet */ 482 if (u->len < sizeof(u->u.msg)) 483 goto out; /* not even the header yet */ 484 485 /* If we're expecting a message that's larger than we can 486 possibly send, dump what we have and return an error. */ 487 if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) { 488 rc = -E2BIG; 489 u->len = 0; 490 goto out; 491 } 492 493 if (u->len < (sizeof(u->u.msg) + u->u.msg.len)) 494 goto out; /* incomplete data portion */ 495 496 /* 497 * OK, now we have a complete message. Do something with it. 498 */ 499 500 msg_type = u->u.msg.type; 501 502 switch (msg_type) { 503 case XS_WATCH: 504 case XS_UNWATCH: 505 /* (Un)Ask for some path to be watched for changes */ 506 ret = xenbus_write_watch(msg_type, u); 507 break; 508 509 default: 510 /* Send out a transaction */ 511 ret = xenbus_write_transaction(msg_type, u); 512 break; 513 } 514 if (ret != 0) 515 rc = ret; 516 517 /* Buffered message consumed */ 518 u->len = 0; 519 520 out: 521 mutex_unlock(&u->msgbuffer_mutex); 522 return rc; 523 } 524 525 static int xenbus_file_open(struct inode *inode, struct file *filp) 526 { 527 struct xenbus_file_priv *u; 528 529 if (xen_store_evtchn == 0) 530 return -ENOENT; 531 532 nonseekable_open(inode, filp); 533 534 u = kzalloc(sizeof(*u), GFP_KERNEL); 535 if (u == NULL) 536 return -ENOMEM; 537 538 INIT_LIST_HEAD(&u->transactions); 539 INIT_LIST_HEAD(&u->watches); 540 INIT_LIST_HEAD(&u->read_buffers); 541 init_waitqueue_head(&u->read_waitq); 542 543 mutex_init(&u->reply_mutex); 544 mutex_init(&u->msgbuffer_mutex); 545 546 filp->private_data = u; 547 548 return 0; 549 } 550 551 static int xenbus_file_release(struct inode *inode, struct file *filp) 552 { 553 struct xenbus_file_priv *u = filp->private_data; 554 struct xenbus_transaction_holder *trans, *tmp; 555 struct watch_adapter *watch, *tmp_watch; 556 struct read_buffer *rb, *tmp_rb; 557 558 /* 559 * No need for locking here because there are no other users, 560 * by definition. 561 */ 562 563 list_for_each_entry_safe(trans, tmp, &u->transactions, list) { 564 xenbus_transaction_end(trans->handle, 1); 565 list_del(&trans->list); 566 kfree(trans); 567 } 568 569 list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) { 570 unregister_xenbus_watch(&watch->watch); 571 list_del(&watch->list); 572 free_watch_adapter(watch); 573 } 574 575 list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) { 576 list_del(&rb->list); 577 kfree(rb); 578 } 579 kfree(u); 580 581 return 0; 582 } 583 584 static unsigned int xenbus_file_poll(struct file *file, poll_table *wait) 585 { 586 struct xenbus_file_priv *u = file->private_data; 587 588 poll_wait(file, &u->read_waitq, wait); 589 if (!list_empty(&u->read_buffers)) 590 return POLLIN | POLLRDNORM; 591 return 0; 592 } 593 594 const struct file_operations xen_xenbus_fops = { 595 .read = xenbus_file_read, 596 .write = xenbus_file_write, 597 .open = xenbus_file_open, 598 .release = xenbus_file_release, 599 .poll = xenbus_file_poll, 600 .llseek = no_llseek, 601 }; 602 EXPORT_SYMBOL_GPL(xen_xenbus_fops); 603 604 static struct miscdevice xenbus_dev = { 605 .minor = MISC_DYNAMIC_MINOR, 606 .name = "xen/xenbus", 607 .fops = &xen_xenbus_fops, 608 }; 609 610 static int __init xenbus_init(void) 611 { 612 int err; 613 614 if (!xen_domain()) 615 return -ENODEV; 616 617 err = misc_register(&xenbus_dev); 618 if (err) 619 printk(KERN_ERR "Could not register xenbus frontend device\n"); 620 return err; 621 } 622 623 static void __exit xenbus_exit(void) 624 { 625 misc_deregister(&xenbus_dev); 626 } 627 628 module_init(xenbus_init); 629 module_exit(xenbus_exit); 630