ashmem.c revision e5834d620d61d01444c41958f1816d688a96433c
1/* mm/ashmem.c 2 * 3 * Anonymous Shared Memory Subsystem, ashmem 4 * 5 * Copyright (C) 2008 Google, Inc. 6 * 7 * Robert Love <rlove@google.com> 8 * 9 * This software is licensed under the terms of the GNU General Public 10 * License version 2, as published by the Free Software Foundation, and 11 * may be copied, distributed, and modified under those terms. 12 * 13 * This program is distributed in the hope that it will be useful, 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 * GNU General Public License for more details. 17 */ 18 19#define pr_fmt(fmt) "ashmem: " fmt 20 21#include <linux/module.h> 22#include <linux/file.h> 23#include <linux/fs.h> 24#include <linux/falloc.h> 25#include <linux/miscdevice.h> 26#include <linux/security.h> 27#include <linux/mm.h> 28#include <linux/mman.h> 29#include <linux/uaccess.h> 30#include <linux/personality.h> 31#include <linux/bitops.h> 32#include <linux/mutex.h> 33#include <linux/shmem_fs.h> 34#include "ashmem.h" 35 36#define ASHMEM_NAME_PREFIX "dev/ashmem/" 37#define ASHMEM_NAME_PREFIX_LEN (sizeof(ASHMEM_NAME_PREFIX) - 1) 38#define ASHMEM_FULL_NAME_LEN (ASHMEM_NAME_LEN + ASHMEM_NAME_PREFIX_LEN) 39 40/* 41 * ashmem_area - anonymous shared memory area 42 * Lifecycle: From our parent file's open() until its release() 43 * Locking: Protected by `ashmem_mutex' 44 * Big Note: Mappings do NOT pin this structure; it dies on close() 45 */ 46struct ashmem_area { 47 char name[ASHMEM_FULL_NAME_LEN]; /* optional name in /proc/pid/maps */ 48 struct list_head unpinned_list; /* list of all ashmem areas */ 49 struct file *file; /* the shmem-based backing file */ 50 size_t size; /* size of the mapping, in bytes */ 51 unsigned long prot_mask; /* allowed prot bits, as vm_flags */ 52}; 53 54/* 55 * ashmem_range - represents an interval of unpinned (evictable) pages 56 * Lifecycle: From unpin to pin 57 * Locking: Protected by `ashmem_mutex' 58 */ 59struct ashmem_range { 60 struct list_head lru; /* entry in LRU list */ 61 struct list_head unpinned; /* entry in its area's unpinned list */ 62 struct ashmem_area *asma; /* associated area */ 63 size_t pgstart; /* starting page, inclusive */ 64 size_t pgend; /* ending page, inclusive */ 65 unsigned int purged; /* ASHMEM_NOT or ASHMEM_WAS_PURGED */ 66}; 67 68/* LRU list of unpinned pages, protected by ashmem_mutex */ 69static LIST_HEAD(ashmem_lru_list); 70 71/* Count of pages on our LRU list, protected by ashmem_mutex */ 72static unsigned long lru_count; 73 74/* 75 * ashmem_mutex - protects the list of and each individual ashmem_area 76 * 77 * Lock Ordering: ashmex_mutex -> i_mutex -> i_alloc_sem 78 */ 79static DEFINE_MUTEX(ashmem_mutex); 80 81static struct kmem_cache *ashmem_area_cachep __read_mostly; 82static struct kmem_cache *ashmem_range_cachep __read_mostly; 83 84#define range_size(range) \ 85 ((range)->pgend - (range)->pgstart + 1) 86 87#define range_on_lru(range) \ 88 ((range)->purged == ASHMEM_NOT_PURGED) 89 90#define page_range_subsumes_range(range, start, end) \ 91 (((range)->pgstart >= (start)) && ((range)->pgend <= (end))) 92 93#define page_range_subsumed_by_range(range, start, end) \ 94 (((range)->pgstart <= (start)) && ((range)->pgend >= (end))) 95 96#define page_in_range(range, page) \ 97 (((range)->pgstart <= (page)) && ((range)->pgend >= (page))) 98 99#define page_range_in_range(range, start, end) \ 100 (page_in_range(range, start) || page_in_range(range, end) || \ 101 page_range_subsumes_range(range, start, end)) 102 103#define range_before_page(range, page) \ 104 ((range)->pgend < (page)) 105 106#define PROT_MASK (PROT_EXEC | PROT_READ | PROT_WRITE) 107 108static inline void lru_add(struct ashmem_range *range) 109{ 110 list_add_tail(&range->lru, &ashmem_lru_list); 111 lru_count += range_size(range); 112} 113 114static inline void lru_del(struct ashmem_range *range) 115{ 116 list_del(&range->lru); 117 lru_count -= range_size(range); 118} 119 120/* 121 * range_alloc - allocate and initialize a new ashmem_range structure 122 * 123 * 'asma' - associated ashmem_area 124 * 'prev_range' - the previous ashmem_range in the sorted asma->unpinned list 125 * 'purged' - initial purge value (ASMEM_NOT_PURGED or ASHMEM_WAS_PURGED) 126 * 'start' - starting page, inclusive 127 * 'end' - ending page, inclusive 128 * 129 * Caller must hold ashmem_mutex. 130 */ 131static int range_alloc(struct ashmem_area *asma, 132 struct ashmem_range *prev_range, unsigned int purged, 133 size_t start, size_t end) 134{ 135 struct ashmem_range *range; 136 137 range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL); 138 if (unlikely(!range)) 139 return -ENOMEM; 140 141 range->asma = asma; 142 range->pgstart = start; 143 range->pgend = end; 144 range->purged = purged; 145 146 list_add_tail(&range->unpinned, &prev_range->unpinned); 147 148 if (range_on_lru(range)) 149 lru_add(range); 150 151 return 0; 152} 153 154static void range_del(struct ashmem_range *range) 155{ 156 list_del(&range->unpinned); 157 if (range_on_lru(range)) 158 lru_del(range); 159 kmem_cache_free(ashmem_range_cachep, range); 160} 161 162/* 163 * range_shrink - shrinks a range 164 * 165 * Caller must hold ashmem_mutex. 166 */ 167static inline void range_shrink(struct ashmem_range *range, 168 size_t start, size_t end) 169{ 170 size_t pre = range_size(range); 171 172 range->pgstart = start; 173 range->pgend = end; 174 175 if (range_on_lru(range)) 176 lru_count -= pre - range_size(range); 177} 178 179static int ashmem_open(struct inode *inode, struct file *file) 180{ 181 struct ashmem_area *asma; 182 int ret; 183 184 ret = generic_file_open(inode, file); 185 if (unlikely(ret)) 186 return ret; 187 188 asma = kmem_cache_zalloc(ashmem_area_cachep, GFP_KERNEL); 189 if (unlikely(!asma)) 190 return -ENOMEM; 191 192 INIT_LIST_HEAD(&asma->unpinned_list); 193 memcpy(asma->name, ASHMEM_NAME_PREFIX, ASHMEM_NAME_PREFIX_LEN); 194 asma->prot_mask = PROT_MASK; 195 file->private_data = asma; 196 197 return 0; 198} 199 200static int ashmem_release(struct inode *ignored, struct file *file) 201{ 202 struct ashmem_area *asma = file->private_data; 203 struct ashmem_range *range, *next; 204 205 mutex_lock(&ashmem_mutex); 206 list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) 207 range_del(range); 208 mutex_unlock(&ashmem_mutex); 209 210 if (asma->file) 211 fput(asma->file); 212 kmem_cache_free(ashmem_area_cachep, asma); 213 214 return 0; 215} 216 217static ssize_t ashmem_read(struct file *file, char __user *buf, 218 size_t len, loff_t *pos) 219{ 220 struct ashmem_area *asma = file->private_data; 221 int ret = 0; 222 223 mutex_lock(&ashmem_mutex); 224 225 /* If size is not set, or set to 0, always return EOF. */ 226 if (asma->size == 0) 227 goto out; 228 229 if (!asma->file) { 230 ret = -EBADF; 231 goto out; 232 } 233 234 ret = asma->file->f_op->read(asma->file, buf, len, pos); 235 if (ret < 0) 236 goto out; 237 238 /** Update backing file pos, since f_ops->read() doesn't */ 239 asma->file->f_pos = *pos; 240 241out: 242 mutex_unlock(&ashmem_mutex); 243 return ret; 244} 245 246static loff_t ashmem_llseek(struct file *file, loff_t offset, int origin) 247{ 248 struct ashmem_area *asma = file->private_data; 249 int ret; 250 251 mutex_lock(&ashmem_mutex); 252 253 if (asma->size == 0) { 254 ret = -EINVAL; 255 goto out; 256 } 257 258 if (!asma->file) { 259 ret = -EBADF; 260 goto out; 261 } 262 263 ret = asma->file->f_op->llseek(asma->file, offset, origin); 264 if (ret < 0) 265 goto out; 266 267 /** Copy f_pos from backing file, since f_ops->llseek() sets it */ 268 file->f_pos = asma->file->f_pos; 269 270out: 271 mutex_unlock(&ashmem_mutex); 272 return ret; 273} 274 275static inline vm_flags_t calc_vm_may_flags(unsigned long prot) 276{ 277 return _calc_vm_trans(prot, PROT_READ, VM_MAYREAD) | 278 _calc_vm_trans(prot, PROT_WRITE, VM_MAYWRITE) | 279 _calc_vm_trans(prot, PROT_EXEC, VM_MAYEXEC); 280} 281 282static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) 283{ 284 struct ashmem_area *asma = file->private_data; 285 int ret = 0; 286 287 mutex_lock(&ashmem_mutex); 288 289 /* user needs to SET_SIZE before mapping */ 290 if (unlikely(!asma->size)) { 291 ret = -EINVAL; 292 goto out; 293 } 294 295 /* requested protection bits must match our allowed protection mask */ 296 if (unlikely((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask)) & 297 calc_vm_prot_bits(PROT_MASK))) { 298 ret = -EPERM; 299 goto out; 300 } 301 vma->vm_flags &= ~calc_vm_may_flags(~asma->prot_mask); 302 303 if (!asma->file) { 304 char *name = ASHMEM_NAME_DEF; 305 struct file *vmfile; 306 307 if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') 308 name = asma->name; 309 310 /* ... and allocate the backing shmem file */ 311 vmfile = shmem_file_setup(name, asma->size, vma->vm_flags); 312 if (unlikely(IS_ERR(vmfile))) { 313 ret = PTR_ERR(vmfile); 314 goto out; 315 } 316 asma->file = vmfile; 317 } 318 get_file(asma->file); 319 320 /* 321 * XXX - Reworked to use shmem_zero_setup() instead of 322 * shmem_set_file while we're in staging. -jstultz 323 */ 324 if (vma->vm_flags & VM_SHARED) { 325 ret = shmem_zero_setup(vma); 326 if (ret) { 327 fput(asma->file); 328 goto out; 329 } 330 } 331 332 if (vma->vm_file) 333 fput(vma->vm_file); 334 vma->vm_file = asma->file; 335 336out: 337 mutex_unlock(&ashmem_mutex); 338 return ret; 339} 340 341/* 342 * ashmem_shrink - our cache shrinker, called from mm/vmscan.c :: shrink_slab 343 * 344 * 'nr_to_scan' is the number of objects (pages) to prune, or 0 to query how 345 * many objects (pages) we have in total. 346 * 347 * 'gfp_mask' is the mask of the allocation that got us into this mess. 348 * 349 * Return value is the number of objects (pages) remaining, or -1 if we cannot 350 * proceed without risk of deadlock (due to gfp_mask). 351 * 352 * We approximate LRU via least-recently-unpinned, jettisoning unpinned partial 353 * chunks of ashmem regions LRU-wise one-at-a-time until we hit 'nr_to_scan' 354 * pages freed. 355 */ 356static int ashmem_shrink(struct shrinker *s, struct shrink_control *sc) 357{ 358 struct ashmem_range *range, *next; 359 360 /* We might recurse into filesystem code, so bail out if necessary */ 361 if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS)) 362 return -1; 363 if (!sc->nr_to_scan) 364 return lru_count; 365 366 mutex_lock(&ashmem_mutex); 367 list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) { 368 loff_t start = range->pgstart * PAGE_SIZE; 369 loff_t end = (range->pgend + 1) * PAGE_SIZE; 370 371 do_fallocate(range->asma->file, 372 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 373 start, end - start); 374 range->purged = ASHMEM_WAS_PURGED; 375 lru_del(range); 376 377 sc->nr_to_scan -= range_size(range); 378 if (sc->nr_to_scan <= 0) 379 break; 380 } 381 mutex_unlock(&ashmem_mutex); 382 383 return lru_count; 384} 385 386static struct shrinker ashmem_shrinker = { 387 .shrink = ashmem_shrink, 388 .seeks = DEFAULT_SEEKS * 4, 389}; 390 391static int set_prot_mask(struct ashmem_area *asma, unsigned long prot) 392{ 393 int ret = 0; 394 395 mutex_lock(&ashmem_mutex); 396 397 /* the user can only remove, not add, protection bits */ 398 if (unlikely((asma->prot_mask & prot) != prot)) { 399 ret = -EINVAL; 400 goto out; 401 } 402 403 /* does the application expect PROT_READ to imply PROT_EXEC? */ 404 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) 405 prot |= PROT_EXEC; 406 407 asma->prot_mask = prot; 408 409out: 410 mutex_unlock(&ashmem_mutex); 411 return ret; 412} 413 414static int set_name(struct ashmem_area *asma, void __user *name) 415{ 416 int ret = 0; 417 char local_name[ASHMEM_NAME_LEN]; 418 419 /* 420 * Holding the ashmem_mutex while doing a copy_from_user might cause 421 * an data abort which would try to access mmap_sem. If another 422 * thread has invoked ashmem_mmap then it will be holding the 423 * semaphore and will be waiting for ashmem_mutex, there by leading to 424 * deadlock. We'll release the mutex and take the name to a local 425 * variable that does not need protection and later copy the local 426 * variable to the structure member with lock held. 427 */ 428 if (copy_from_user(local_name, name, ASHMEM_NAME_LEN)) 429 return -EFAULT; 430 431 mutex_lock(&ashmem_mutex); 432 /* cannot change an existing mapping's name */ 433 if (unlikely(asma->file)) { 434 ret = -EINVAL; 435 goto out; 436 } 437 memcpy(asma->name + ASHMEM_NAME_PREFIX_LEN, 438 local_name, ASHMEM_NAME_LEN); 439 asma->name[ASHMEM_FULL_NAME_LEN-1] = '\0'; 440out: 441 mutex_unlock(&ashmem_mutex); 442 443 return ret; 444} 445 446static int get_name(struct ashmem_area *asma, void __user *name) 447{ 448 int ret = 0; 449 size_t len; 450 /* 451 * Have a local variable to which we'll copy the content 452 * from asma with the lock held. Later we can copy this to the user 453 * space safely without holding any locks. So even if we proceed to 454 * wait for mmap_sem, it won't lead to deadlock. 455 */ 456 char local_name[ASHMEM_NAME_LEN]; 457 458 mutex_lock(&ashmem_mutex); 459 if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') { 460 461 /* 462 * Copying only `len', instead of ASHMEM_NAME_LEN, bytes 463 * prevents us from revealing one user's stack to another. 464 */ 465 len = strlen(asma->name + ASHMEM_NAME_PREFIX_LEN) + 1; 466 memcpy(local_name, asma->name + ASHMEM_NAME_PREFIX_LEN, len); 467 } else { 468 len = sizeof(ASHMEM_NAME_DEF); 469 memcpy(local_name, ASHMEM_NAME_DEF, len); 470 } 471 mutex_unlock(&ashmem_mutex); 472 473 /* 474 * Now we are just copying from the stack variable to userland 475 * No lock held 476 */ 477 if (unlikely(copy_to_user(name, local_name, len))) 478 ret = -EFAULT; 479 return ret; 480} 481 482/* 483 * ashmem_pin - pin the given ashmem region, returning whether it was 484 * previously purged (ASHMEM_WAS_PURGED) or not (ASHMEM_NOT_PURGED). 485 * 486 * Caller must hold ashmem_mutex. 487 */ 488static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend) 489{ 490 struct ashmem_range *range, *next; 491 int ret = ASHMEM_NOT_PURGED; 492 493 list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) { 494 /* moved past last applicable page; we can short circuit */ 495 if (range_before_page(range, pgstart)) 496 break; 497 498 /* 499 * The user can ask us to pin pages that span multiple ranges, 500 * or to pin pages that aren't even unpinned, so this is messy. 501 * 502 * Four cases: 503 * 1. The requested range subsumes an existing range, so we 504 * just remove the entire matching range. 505 * 2. The requested range overlaps the start of an existing 506 * range, so we just update that range. 507 * 3. The requested range overlaps the end of an existing 508 * range, so we just update that range. 509 * 4. The requested range punches a hole in an existing range, 510 * so we have to update one side of the range and then 511 * create a new range for the other side. 512 */ 513 if (page_range_in_range(range, pgstart, pgend)) { 514 ret |= range->purged; 515 516 /* Case #1: Easy. Just nuke the whole thing. */ 517 if (page_range_subsumes_range(range, pgstart, pgend)) { 518 range_del(range); 519 continue; 520 } 521 522 /* Case #2: We overlap from the start, so adjust it */ 523 if (range->pgstart >= pgstart) { 524 range_shrink(range, pgend + 1, range->pgend); 525 continue; 526 } 527 528 /* Case #3: We overlap from the rear, so adjust it */ 529 if (range->pgend <= pgend) { 530 range_shrink(range, range->pgstart, pgstart-1); 531 continue; 532 } 533 534 /* 535 * Case #4: We eat a chunk out of the middle. A bit 536 * more complicated, we allocate a new range for the 537 * second half and adjust the first chunk's endpoint. 538 */ 539 range_alloc(asma, range, range->purged, 540 pgend + 1, range->pgend); 541 range_shrink(range, range->pgstart, pgstart - 1); 542 break; 543 } 544 } 545 546 return ret; 547} 548 549/* 550 * ashmem_unpin - unpin the given range of pages. Returns zero on success. 551 * 552 * Caller must hold ashmem_mutex. 553 */ 554static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend) 555{ 556 struct ashmem_range *range, *next; 557 unsigned int purged = ASHMEM_NOT_PURGED; 558 559restart: 560 list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) { 561 /* short circuit: this is our insertion point */ 562 if (range_before_page(range, pgstart)) 563 break; 564 565 /* 566 * The user can ask us to unpin pages that are already entirely 567 * or partially pinned. We handle those two cases here. 568 */ 569 if (page_range_subsumed_by_range(range, pgstart, pgend)) 570 return 0; 571 if (page_range_in_range(range, pgstart, pgend)) { 572 pgstart = min_t(size_t, range->pgstart, pgstart), 573 pgend = max_t(size_t, range->pgend, pgend); 574 purged |= range->purged; 575 range_del(range); 576 goto restart; 577 } 578 } 579 580 return range_alloc(asma, range, purged, pgstart, pgend); 581} 582 583/* 584 * ashmem_get_pin_status - Returns ASHMEM_IS_UNPINNED if _any_ pages in the 585 * given interval are unpinned and ASHMEM_IS_PINNED otherwise. 586 * 587 * Caller must hold ashmem_mutex. 588 */ 589static int ashmem_get_pin_status(struct ashmem_area *asma, size_t pgstart, 590 size_t pgend) 591{ 592 struct ashmem_range *range; 593 int ret = ASHMEM_IS_PINNED; 594 595 list_for_each_entry(range, &asma->unpinned_list, unpinned) { 596 if (range_before_page(range, pgstart)) 597 break; 598 if (page_range_in_range(range, pgstart, pgend)) { 599 ret = ASHMEM_IS_UNPINNED; 600 break; 601 } 602 } 603 604 return ret; 605} 606 607static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, 608 void __user *p) 609{ 610 struct ashmem_pin pin; 611 size_t pgstart, pgend; 612 int ret = -EINVAL; 613 614 if (unlikely(!asma->file)) 615 return -EINVAL; 616 617 if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) 618 return -EFAULT; 619 620 /* per custom, you can pass zero for len to mean "everything onward" */ 621 if (!pin.len) 622 pin.len = PAGE_ALIGN(asma->size) - pin.offset; 623 624 if (unlikely((pin.offset | pin.len) & ~PAGE_MASK)) 625 return -EINVAL; 626 627 if (unlikely(((__u32) -1) - pin.offset < pin.len)) 628 return -EINVAL; 629 630 if (unlikely(PAGE_ALIGN(asma->size) < pin.offset + pin.len)) 631 return -EINVAL; 632 633 pgstart = pin.offset / PAGE_SIZE; 634 pgend = pgstart + (pin.len / PAGE_SIZE) - 1; 635 636 mutex_lock(&ashmem_mutex); 637 638 switch (cmd) { 639 case ASHMEM_PIN: 640 ret = ashmem_pin(asma, pgstart, pgend); 641 break; 642 case ASHMEM_UNPIN: 643 ret = ashmem_unpin(asma, pgstart, pgend); 644 break; 645 case ASHMEM_GET_PIN_STATUS: 646 ret = ashmem_get_pin_status(asma, pgstart, pgend); 647 break; 648 } 649 650 mutex_unlock(&ashmem_mutex); 651 652 return ret; 653} 654 655static long ashmem_ioctl(struct file *file, unsigned int cmd, unsigned long arg) 656{ 657 struct ashmem_area *asma = file->private_data; 658 long ret = -ENOTTY; 659 660 switch (cmd) { 661 case ASHMEM_SET_NAME: 662 ret = set_name(asma, (void __user *) arg); 663 break; 664 case ASHMEM_GET_NAME: 665 ret = get_name(asma, (void __user *) arg); 666 break; 667 case ASHMEM_SET_SIZE: 668 ret = -EINVAL; 669 if (!asma->file) { 670 ret = 0; 671 asma->size = (size_t) arg; 672 } 673 break; 674 case ASHMEM_GET_SIZE: 675 ret = asma->size; 676 break; 677 case ASHMEM_SET_PROT_MASK: 678 ret = set_prot_mask(asma, arg); 679 break; 680 case ASHMEM_GET_PROT_MASK: 681 ret = asma->prot_mask; 682 break; 683 case ASHMEM_PIN: 684 case ASHMEM_UNPIN: 685 case ASHMEM_GET_PIN_STATUS: 686 ret = ashmem_pin_unpin(asma, cmd, (void __user *) arg); 687 break; 688 case ASHMEM_PURGE_ALL_CACHES: 689 ret = -EPERM; 690 if (capable(CAP_SYS_ADMIN)) { 691 struct shrink_control sc = { 692 .gfp_mask = GFP_KERNEL, 693 .nr_to_scan = 0, 694 }; 695 ret = ashmem_shrink(&ashmem_shrinker, &sc); 696 sc.nr_to_scan = ret; 697 ashmem_shrink(&ashmem_shrinker, &sc); 698 } 699 break; 700 } 701 702 return ret; 703} 704 705static const struct file_operations ashmem_fops = { 706 .owner = THIS_MODULE, 707 .open = ashmem_open, 708 .release = ashmem_release, 709 .read = ashmem_read, 710 .llseek = ashmem_llseek, 711 .mmap = ashmem_mmap, 712 .unlocked_ioctl = ashmem_ioctl, 713 .compat_ioctl = ashmem_ioctl, 714}; 715 716static struct miscdevice ashmem_misc = { 717 .minor = MISC_DYNAMIC_MINOR, 718 .name = "ashmem", 719 .fops = &ashmem_fops, 720}; 721 722static int __init ashmem_init(void) 723{ 724 int ret; 725 726 ashmem_area_cachep = kmem_cache_create("ashmem_area_cache", 727 sizeof(struct ashmem_area), 728 0, 0, NULL); 729 if (unlikely(!ashmem_area_cachep)) { 730 pr_err("failed to create slab cache\n"); 731 return -ENOMEM; 732 } 733 734 ashmem_range_cachep = kmem_cache_create("ashmem_range_cache", 735 sizeof(struct ashmem_range), 736 0, 0, NULL); 737 if (unlikely(!ashmem_range_cachep)) { 738 pr_err("failed to create slab cache\n"); 739 return -ENOMEM; 740 } 741 742 ret = misc_register(&ashmem_misc); 743 if (unlikely(ret)) { 744 pr_err("failed to register misc device!\n"); 745 return ret; 746 } 747 748 register_shrinker(&ashmem_shrinker); 749 750 pr_info("initialized\n"); 751 752 return 0; 753} 754 755static void __exit ashmem_exit(void) 756{ 757 int ret; 758 759 unregister_shrinker(&ashmem_shrinker); 760 761 ret = misc_deregister(&ashmem_misc); 762 if (unlikely(ret)) 763 pr_err("failed to unregister misc device!\n"); 764 765 kmem_cache_destroy(ashmem_range_cachep); 766 kmem_cache_destroy(ashmem_area_cachep); 767 768 pr_info("unloaded\n"); 769} 770 771module_init(ashmem_init); 772module_exit(ashmem_exit); 773 774MODULE_LICENSE("GPL"); 775