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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 39 40 #include <linux/kernel.h> 41 #include <linux/errno.h> 42 #include <linux/uio.h> 43 #include <linux/notifier.h> 44 #include <linux/wait.h> 45 #include <linux/fs.h> 46 #include <linux/poll.h> 47 #include <linux/mutex.h> 48 #include <linux/sched.h> 49 #include <linux/spinlock.h> 50 #include <linux/mount.h> 51 #include <linux/pagemap.h> 52 #include <linux/uaccess.h> 53 #include <linux/init.h> 54 #include <linux/namei.h> 55 #include <linux/string.h> 56 #include <linux/slab.h> 57 #include <linux/miscdevice.h> 58 #include <linux/module.h> 59 60 #include "xenbus_comms.h" 61 62 #include <xen/xenbus.h> 63 #include <xen/xen.h> 64 #include <asm/xen/hypervisor.h> 65 66 MODULE_LICENSE("GPL"); 67 68 /* 69 * An element of a list of outstanding transactions, for which we're 70 * still waiting a reply. 71 */ 72 struct xenbus_transaction_holder { 73 struct list_head list; 74 struct xenbus_transaction handle; 75 }; 76 77 /* 78 * A buffer of data on the queue. 79 */ 80 struct read_buffer { 81 struct list_head list; 82 unsigned int cons; 83 unsigned int len; 84 char msg[]; 85 }; 86 87 struct xenbus_file_priv { 88 /* 89 * msgbuffer_mutex is held while partial requests are built up 90 * and complete requests are acted on. It therefore protects 91 * the "transactions" and "watches" lists, and the partial 92 * request length and buffer. 93 * 94 * reply_mutex protects the reply being built up to return to 95 * usermode. It nests inside msgbuffer_mutex but may be held 96 * alone during a watch callback. 97 */ 98 struct mutex msgbuffer_mutex; 99 100 /* In-progress transactions */ 101 struct list_head transactions; 102 103 /* Active watches. */ 104 struct list_head watches; 105 106 /* Partial request. */ 107 unsigned int len; 108 union { 109 struct xsd_sockmsg msg; 110 char buffer[XENSTORE_PAYLOAD_MAX]; 111 } u; 112 113 /* Response queue. */ 114 struct mutex reply_mutex; 115 struct list_head read_buffers; 116 wait_queue_head_t read_waitq; 117 118 }; 119 120 /* Read out any raw xenbus messages queued up. */ 121 static ssize_t xenbus_file_read(struct file *filp, 122 char __user *ubuf, 123 size_t len, loff_t *ppos) 124 { 125 struct xenbus_file_priv *u = filp->private_data; 126 struct read_buffer *rb; 127 unsigned i; 128 int ret; 129 130 mutex_lock(&u->reply_mutex); 131 again: 132 while (list_empty(&u->read_buffers)) { 133 mutex_unlock(&u->reply_mutex); 134 if (filp->f_flags & O_NONBLOCK) 135 return -EAGAIN; 136 137 ret = wait_event_interruptible(u->read_waitq, 138 !list_empty(&u->read_buffers)); 139 if (ret) 140 return ret; 141 mutex_lock(&u->reply_mutex); 142 } 143 144 rb = list_entry(u->read_buffers.next, struct read_buffer, list); 145 i = 0; 146 while (i < len) { 147 unsigned sz = min((unsigned)len - i, rb->len - rb->cons); 148 149 ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz); 150 151 i += sz - ret; 152 rb->cons += sz - ret; 153 154 if (ret != 0) { 155 if (i == 0) 156 i = -EFAULT; 157 goto out; 158 } 159 160 /* Clear out buffer if it has been consumed */ 161 if (rb->cons == rb->len) { 162 list_del(&rb->list); 163 kfree(rb); 164 if (list_empty(&u->read_buffers)) 165 break; 166 rb = list_entry(u->read_buffers.next, 167 struct read_buffer, list); 168 } 169 } 170 if (i == 0) 171 goto again; 172 173 out: 174 mutex_unlock(&u->reply_mutex); 175 return i; 176 } 177 178 /* 179 * Add a buffer to the queue. Caller must hold the appropriate lock 180 * if the queue is not local. (Commonly the caller will build up 181 * multiple queued buffers on a temporary local list, and then add it 182 * to the appropriate list under lock once all the buffers have een 183 * successfully allocated.) 184 */ 185 static int queue_reply(struct list_head *queue, const void *data, size_t len) 186 { 187 struct read_buffer *rb; 188 189 if (len == 0) 190 return 0; 191 192 rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL); 193 if (rb == NULL) 194 return -ENOMEM; 195 196 rb->cons = 0; 197 rb->len = len; 198 199 memcpy(rb->msg, data, len); 200 201 list_add_tail(&rb->list, queue); 202 return 0; 203 } 204 205 /* 206 * Free all the read_buffer s on a list. 207 * Caller must have sole reference to list. 208 */ 209 static void queue_cleanup(struct list_head *list) 210 { 211 struct read_buffer *rb; 212 213 while (!list_empty(list)) { 214 rb = list_entry(list->next, struct read_buffer, list); 215 list_del(list->next); 216 kfree(rb); 217 } 218 } 219 220 struct watch_adapter { 221 struct list_head list; 222 struct xenbus_watch watch; 223 struct xenbus_file_priv *dev_data; 224 char *token; 225 }; 226 227 static void free_watch_adapter(struct watch_adapter *watch) 228 { 229 kfree(watch->watch.node); 230 kfree(watch->token); 231 kfree(watch); 232 } 233 234 static struct watch_adapter *alloc_watch_adapter(const char *path, 235 const char *token) 236 { 237 struct watch_adapter *watch; 238 239 watch = kzalloc(sizeof(*watch), GFP_KERNEL); 240 if (watch == NULL) 241 goto out_fail; 242 243 watch->watch.node = kstrdup(path, GFP_KERNEL); 244 if (watch->watch.node == NULL) 245 goto out_free; 246 247 watch->token = kstrdup(token, GFP_KERNEL); 248 if (watch->token == NULL) 249 goto out_free; 250 251 return watch; 252 253 out_free: 254 free_watch_adapter(watch); 255 256 out_fail: 257 return NULL; 258 } 259 260 static void watch_fired(struct xenbus_watch *watch, 261 const char **vec, 262 unsigned int len) 263 { 264 struct watch_adapter *adap; 265 struct xsd_sockmsg hdr; 266 const char *path, *token; 267 int path_len, tok_len, body_len, data_len = 0; 268 int ret; 269 LIST_HEAD(staging_q); 270 271 adap = container_of(watch, struct watch_adapter, watch); 272 273 path = vec[XS_WATCH_PATH]; 274 token = adap->token; 275 276 path_len = strlen(path) + 1; 277 tok_len = strlen(token) + 1; 278 if (len > 2) 279 data_len = vec[len] - vec[2] + 1; 280 body_len = path_len + tok_len + data_len; 281 282 hdr.type = XS_WATCH_EVENT; 283 hdr.len = body_len; 284 285 mutex_lock(&adap->dev_data->reply_mutex); 286 287 ret = queue_reply(&staging_q, &hdr, sizeof(hdr)); 288 if (!ret) 289 ret = queue_reply(&staging_q, path, path_len); 290 if (!ret) 291 ret = queue_reply(&staging_q, token, tok_len); 292 if (!ret && len > 2) 293 ret = queue_reply(&staging_q, vec[2], data_len); 294 295 if (!ret) { 296 /* success: pass reply list onto watcher */ 297 list_splice_tail(&staging_q, &adap->dev_data->read_buffers); 298 wake_up(&adap->dev_data->read_waitq); 299 } else 300 queue_cleanup(&staging_q); 301 302 mutex_unlock(&adap->dev_data->reply_mutex); 303 } 304 305 static int xenbus_write_transaction(unsigned msg_type, 306 struct xenbus_file_priv *u) 307 { 308 int rc; 309 void *reply; 310 struct xenbus_transaction_holder *trans = NULL; 311 LIST_HEAD(staging_q); 312 313 if (msg_type == XS_TRANSACTION_START) { 314 trans = kmalloc(sizeof(*trans), GFP_KERNEL); 315 if (!trans) { 316 rc = -ENOMEM; 317 goto out; 318 } 319 } 320 321 reply = xenbus_dev_request_and_reply(&u->u.msg); 322 if (IS_ERR(reply)) { 323 kfree(trans); 324 rc = PTR_ERR(reply); 325 goto out; 326 } 327 328 if (msg_type == XS_TRANSACTION_START) { 329 if (u->u.msg.type == XS_ERROR) 330 kfree(trans); 331 else { 332 trans->handle.id = simple_strtoul(reply, NULL, 0); 333 list_add(&trans->list, &u->transactions); 334 } 335 } else if (u->u.msg.type == XS_TRANSACTION_END) { 336 list_for_each_entry(trans, &u->transactions, list) 337 if (trans->handle.id == u->u.msg.tx_id) 338 break; 339 BUG_ON(&trans->list == &u->transactions); 340 list_del(&trans->list); 341 342 kfree(trans); 343 } 344 345 mutex_lock(&u->reply_mutex); 346 rc = queue_reply(&staging_q, &u->u.msg, sizeof(u->u.msg)); 347 if (!rc) 348 rc = queue_reply(&staging_q, reply, u->u.msg.len); 349 if (!rc) { 350 list_splice_tail(&staging_q, &u->read_buffers); 351 wake_up(&u->read_waitq); 352 } else { 353 queue_cleanup(&staging_q); 354 } 355 mutex_unlock(&u->reply_mutex); 356 357 kfree(reply); 358 359 out: 360 return rc; 361 } 362 363 static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u) 364 { 365 struct watch_adapter *watch, *tmp_watch; 366 char *path, *token; 367 int err, rc; 368 LIST_HEAD(staging_q); 369 370 path = u->u.buffer + sizeof(u->u.msg); 371 token = memchr(path, 0, u->u.msg.len); 372 if (token == NULL) { 373 rc = -EILSEQ; 374 goto out; 375 } 376 token++; 377 if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) { 378 rc = -EILSEQ; 379 goto out; 380 } 381 382 if (msg_type == XS_WATCH) { 383 watch = alloc_watch_adapter(path, token); 384 if (watch == NULL) { 385 rc = -ENOMEM; 386 goto out; 387 } 388 389 watch->watch.callback = watch_fired; 390 watch->dev_data = u; 391 392 err = register_xenbus_watch(&watch->watch); 393 if (err) { 394 free_watch_adapter(watch); 395 rc = err; 396 goto out; 397 } 398 list_add(&watch->list, &u->watches); 399 } else { 400 list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) { 401 if (!strcmp(watch->token, token) && 402 !strcmp(watch->watch.node, path)) { 403 unregister_xenbus_watch(&watch->watch); 404 list_del(&watch->list); 405 free_watch_adapter(watch); 406 break; 407 } 408 } 409 } 410 411 /* Success. Synthesize a reply to say all is OK. */ 412 { 413 struct { 414 struct xsd_sockmsg hdr; 415 char body[3]; 416 } __packed reply = { 417 { 418 .type = msg_type, 419 .len = sizeof(reply.body) 420 }, 421 "OK" 422 }; 423 424 mutex_lock(&u->reply_mutex); 425 rc = queue_reply(&u->read_buffers, &reply, sizeof(reply)); 426 wake_up(&u->read_waitq); 427 mutex_unlock(&u->reply_mutex); 428 } 429 430 out: 431 return rc; 432 } 433 434 static ssize_t xenbus_file_write(struct file *filp, 435 const char __user *ubuf, 436 size_t len, loff_t *ppos) 437 { 438 struct xenbus_file_priv *u = filp->private_data; 439 uint32_t msg_type; 440 int rc = len; 441 int ret; 442 LIST_HEAD(staging_q); 443 444 /* 445 * We're expecting usermode to be writing properly formed 446 * xenbus messages. If they write an incomplete message we 447 * buffer it up. Once it is complete, we act on it. 448 */ 449 450 /* 451 * Make sure concurrent writers can't stomp all over each 452 * other's messages and make a mess of our partial message 453 * buffer. We don't make any attemppt to stop multiple 454 * writers from making a mess of each other's incomplete 455 * messages; we're just trying to guarantee our own internal 456 * consistency and make sure that single writes are handled 457 * atomically. 458 */ 459 mutex_lock(&u->msgbuffer_mutex); 460 461 /* Get this out of the way early to avoid confusion */ 462 if (len == 0) 463 goto out; 464 465 /* Can't write a xenbus message larger we can buffer */ 466 if (len > sizeof(u->u.buffer) - u->len) { 467 /* On error, dump existing buffer */ 468 u->len = 0; 469 rc = -EINVAL; 470 goto out; 471 } 472 473 ret = copy_from_user(u->u.buffer + u->len, ubuf, len); 474 475 if (ret != 0) { 476 rc = -EFAULT; 477 goto out; 478 } 479 480 /* Deal with a partial copy. */ 481 len -= ret; 482 rc = len; 483 484 u->len += len; 485 486 /* Return if we haven't got a full message yet */ 487 if (u->len < sizeof(u->u.msg)) 488 goto out; /* not even the header yet */ 489 490 /* If we're expecting a message that's larger than we can 491 possibly send, dump what we have and return an error. */ 492 if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) { 493 rc = -E2BIG; 494 u->len = 0; 495 goto out; 496 } 497 498 if (u->len < (sizeof(u->u.msg) + u->u.msg.len)) 499 goto out; /* incomplete data portion */ 500 501 /* 502 * OK, now we have a complete message. Do something with it. 503 */ 504 505 msg_type = u->u.msg.type; 506 507 switch (msg_type) { 508 case XS_WATCH: 509 case XS_UNWATCH: 510 /* (Un)Ask for some path to be watched for changes */ 511 ret = xenbus_write_watch(msg_type, u); 512 break; 513 514 default: 515 /* Send out a transaction */ 516 ret = xenbus_write_transaction(msg_type, u); 517 break; 518 } 519 if (ret != 0) 520 rc = ret; 521 522 /* Buffered message consumed */ 523 u->len = 0; 524 525 out: 526 mutex_unlock(&u->msgbuffer_mutex); 527 return rc; 528 } 529 530 static int xenbus_file_open(struct inode *inode, struct file *filp) 531 { 532 struct xenbus_file_priv *u; 533 534 if (xen_store_evtchn == 0) 535 return -ENOENT; 536 537 nonseekable_open(inode, filp); 538 539 u = kzalloc(sizeof(*u), GFP_KERNEL); 540 if (u == NULL) 541 return -ENOMEM; 542 543 INIT_LIST_HEAD(&u->transactions); 544 INIT_LIST_HEAD(&u->watches); 545 INIT_LIST_HEAD(&u->read_buffers); 546 init_waitqueue_head(&u->read_waitq); 547 548 mutex_init(&u->reply_mutex); 549 mutex_init(&u->msgbuffer_mutex); 550 551 filp->private_data = u; 552 553 return 0; 554 } 555 556 static int xenbus_file_release(struct inode *inode, struct file *filp) 557 { 558 struct xenbus_file_priv *u = filp->private_data; 559 struct xenbus_transaction_holder *trans, *tmp; 560 struct watch_adapter *watch, *tmp_watch; 561 struct read_buffer *rb, *tmp_rb; 562 563 /* 564 * No need for locking here because there are no other users, 565 * by definition. 566 */ 567 568 list_for_each_entry_safe(trans, tmp, &u->transactions, list) { 569 xenbus_transaction_end(trans->handle, 1); 570 list_del(&trans->list); 571 kfree(trans); 572 } 573 574 list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) { 575 unregister_xenbus_watch(&watch->watch); 576 list_del(&watch->list); 577 free_watch_adapter(watch); 578 } 579 580 list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) { 581 list_del(&rb->list); 582 kfree(rb); 583 } 584 kfree(u); 585 586 return 0; 587 } 588 589 static unsigned int xenbus_file_poll(struct file *file, poll_table *wait) 590 { 591 struct xenbus_file_priv *u = file->private_data; 592 593 poll_wait(file, &u->read_waitq, wait); 594 if (!list_empty(&u->read_buffers)) 595 return POLLIN | POLLRDNORM; 596 return 0; 597 } 598 599 const struct file_operations xen_xenbus_fops = { 600 .read = xenbus_file_read, 601 .write = xenbus_file_write, 602 .open = xenbus_file_open, 603 .release = xenbus_file_release, 604 .poll = xenbus_file_poll, 605 .llseek = no_llseek, 606 }; 607 EXPORT_SYMBOL_GPL(xen_xenbus_fops); 608 609 static struct miscdevice xenbus_dev = { 610 .minor = MISC_DYNAMIC_MINOR, 611 .name = "xen/xenbus", 612 .fops = &xen_xenbus_fops, 613 }; 614 615 static int __init xenbus_init(void) 616 { 617 int err; 618 619 if (!xen_domain()) 620 return -ENODEV; 621 622 err = misc_register(&xenbus_dev); 623 if (err) 624 pr_err("Could not register xenbus frontend device\n"); 625 return err; 626 } 627 628 static void __exit xenbus_exit(void) 629 { 630 misc_deregister(&xenbus_dev); 631 } 632 633 module_init(xenbus_init); 634 module_exit(xenbus_exit); 635