1 // SPDX-License-Identifier: GPL-2.0
4 * Anonymous Shared Memory Subsystem, ashmem
6 * Copyright (C) 2008 Google, Inc.
8 * Robert Love <rlove@google.com>
11 #define pr_fmt(fmt) "ashmem: " fmt
13 #include <linux/init.h>
14 #include <linux/export.h>
15 #include <linux/file.h>
17 #include <linux/falloc.h>
18 #include <linux/miscdevice.h>
19 #include <linux/security.h>
21 #include <linux/mman.h>
22 #include <linux/uaccess.h>
23 #include <linux/personality.h>
24 #include <linux/bitops.h>
25 #include <linux/mutex.h>
26 #include <linux/shmem_fs.h>
29 #define ASHMEM_NAME_PREFIX "dev/ashmem/"
30 #define ASHMEM_NAME_PREFIX_LEN (sizeof(ASHMEM_NAME_PREFIX) - 1)
31 #define ASHMEM_FULL_NAME_LEN (ASHMEM_NAME_LEN + ASHMEM_NAME_PREFIX_LEN)
34 * struct ashmem_area - The anonymous shared memory area
35 * @name: The optional name in /proc/pid/maps
36 * @unpinned_list: The list of all ashmem areas
37 * @file: The shmem-based backing file
38 * @size: The size of the mapping, in bytes
39 * @prot_mask: The allowed protection bits, as vm_flags
41 * The lifecycle of this structure is from our parent file's open() until
42 * its release(). It is also protected by 'ashmem_mutex'
44 * Warning: Mappings do NOT pin this structure; It dies on close()
47 char name[ASHMEM_FULL_NAME_LEN];
48 struct list_head unpinned_list;
51 unsigned long prot_mask;
55 * struct ashmem_range - A range of unpinned/evictable pages
56 * @lru: The entry in the LRU list
57 * @unpinned: The entry in its area's unpinned list
58 * @asma: The associated anonymous shared memory area.
59 * @pgstart: The starting page (inclusive)
60 * @pgend: The ending page (inclusive)
61 * @purged: The purge status (ASHMEM_NOT or ASHMEM_WAS_PURGED)
63 * The lifecycle of this structure is from unpin to pin.
64 * It is protected by 'ashmem_mutex'
68 struct list_head unpinned;
69 struct ashmem_area *asma;
75 /* LRU list of unpinned pages, protected by ashmem_mutex */
76 static LIST_HEAD(ashmem_lru_list);
78 static atomic_t ashmem_shrink_inflight = ATOMIC_INIT(0);
79 static DECLARE_WAIT_QUEUE_HEAD(ashmem_shrink_wait);
82 * long lru_count - The count of pages on our LRU list.
84 * This is protected by ashmem_mutex.
86 static unsigned long lru_count;
89 * ashmem_mutex - protects the list of and each individual ashmem_area
91 * Lock Ordering: ashmex_mutex -> i_mutex -> i_alloc_sem
93 static DEFINE_MUTEX(ashmem_mutex);
95 static struct kmem_cache *ashmem_area_cachep __read_mostly;
96 static struct kmem_cache *ashmem_range_cachep __read_mostly;
99 * A separate lockdep class for the backing shmem inodes to resolve the lockdep
100 * warning about the race between kswapd taking fs_reclaim before inode_lock
101 * and write syscall taking inode_lock and then fs_reclaim.
102 * Note that such race is impossible because ashmem does not support write
103 * syscalls operating on the backing shmem.
105 static struct lock_class_key backing_shmem_inode_class;
107 static inline unsigned long range_size(struct ashmem_range *range)
109 return range->pgend - range->pgstart + 1;
112 static inline bool range_on_lru(struct ashmem_range *range)
114 return range->purged == ASHMEM_NOT_PURGED;
117 static inline bool page_range_subsumes_range(struct ashmem_range *range,
118 size_t start, size_t end)
120 return (range->pgstart >= start) && (range->pgend <= end);
123 static inline bool page_range_subsumed_by_range(struct ashmem_range *range,
124 size_t start, size_t end)
126 return (range->pgstart <= start) && (range->pgend >= end);
129 static inline bool page_in_range(struct ashmem_range *range, size_t page)
131 return (range->pgstart <= page) && (range->pgend >= page);
134 static inline bool page_range_in_range(struct ashmem_range *range,
135 size_t start, size_t end)
137 return page_in_range(range, start) || page_in_range(range, end) ||
138 page_range_subsumes_range(range, start, end);
141 static inline bool range_before_page(struct ashmem_range *range,
144 return range->pgend < page;
147 #define PROT_MASK (PROT_EXEC | PROT_READ | PROT_WRITE)
150 * lru_add() - Adds a range of memory to the LRU list
151 * @range: The memory range being added.
153 * The range is first added to the end (tail) of the LRU list.
154 * After this, the size of the range is added to @lru_count
156 static inline void lru_add(struct ashmem_range *range)
158 list_add_tail(&range->lru, &ashmem_lru_list);
159 lru_count += range_size(range);
163 * lru_del() - Removes a range of memory from the LRU list
164 * @range: The memory range being removed
166 * The range is first deleted from the LRU list.
167 * After this, the size of the range is removed from @lru_count
169 static inline void lru_del(struct ashmem_range *range)
171 list_del(&range->lru);
172 lru_count -= range_size(range);
176 * range_alloc() - Allocates and initializes a new ashmem_range structure
177 * @asma: The associated ashmem_area
178 * @prev_range: The previous ashmem_range in the sorted asma->unpinned list
179 * @purged: Initial purge status (ASMEM_NOT_PURGED or ASHMEM_WAS_PURGED)
180 * @start: The starting page (inclusive)
181 * @end: The ending page (inclusive)
182 * @new_range: The placeholder for the new range
184 * This function is protected by ashmem_mutex.
186 static void range_alloc(struct ashmem_area *asma,
187 struct ashmem_range *prev_range, unsigned int purged,
188 size_t start, size_t end,
189 struct ashmem_range **new_range)
191 struct ashmem_range *range = *new_range;
195 range->pgstart = start;
197 range->purged = purged;
199 list_add_tail(&range->unpinned, &prev_range->unpinned);
201 if (range_on_lru(range))
206 * range_del() - Deletes and deallocates an ashmem_range structure
207 * @range: The associated ashmem_range that has previously been allocated
209 static void range_del(struct ashmem_range *range)
211 list_del(&range->unpinned);
212 if (range_on_lru(range))
214 kmem_cache_free(ashmem_range_cachep, range);
218 * range_shrink() - Shrinks an ashmem_range
219 * @range: The associated ashmem_range being shrunk
220 * @start: The starting byte of the new range
221 * @end: The ending byte of the new range
223 * This does not modify the data inside the existing range in any way - It
224 * simply shrinks the boundaries of the range.
226 * Theoretically, with a little tweaking, this could eventually be changed
227 * to range_resize, and expand the lru_count if the new range is larger.
229 static inline void range_shrink(struct ashmem_range *range,
230 size_t start, size_t end)
232 size_t pre = range_size(range);
234 range->pgstart = start;
237 if (range_on_lru(range))
238 lru_count -= pre - range_size(range);
242 * ashmem_open() - Opens an Anonymous Shared Memory structure
243 * @inode: The backing file's index node(?)
244 * @file: The backing file
246 * Please note that the ashmem_area is not returned by this function - It is
247 * instead written to "file->private_data".
249 * Return: 0 if successful, or another code if unsuccessful.
251 static int ashmem_open(struct inode *inode, struct file *file)
253 struct ashmem_area *asma;
256 ret = generic_file_open(inode, file);
260 asma = kmem_cache_zalloc(ashmem_area_cachep, GFP_KERNEL);
264 INIT_LIST_HEAD(&asma->unpinned_list);
265 memcpy(asma->name, ASHMEM_NAME_PREFIX, ASHMEM_NAME_PREFIX_LEN);
266 asma->prot_mask = PROT_MASK;
267 file->private_data = asma;
273 * ashmem_release() - Releases an Anonymous Shared Memory structure
274 * @ignored: The backing file's Index Node(?) - It is ignored here.
275 * @file: The backing file
277 * Return: 0 if successful. If it is anything else, go have a coffee and
280 static int ashmem_release(struct inode *ignored, struct file *file)
282 struct ashmem_area *asma = file->private_data;
283 struct ashmem_range *range, *next;
285 mutex_lock(&ashmem_mutex);
286 list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned)
288 mutex_unlock(&ashmem_mutex);
292 kmem_cache_free(ashmem_area_cachep, asma);
297 static ssize_t ashmem_read_iter(struct kiocb *iocb, struct iov_iter *iter)
299 struct ashmem_area *asma = iocb->ki_filp->private_data;
302 mutex_lock(&ashmem_mutex);
304 /* If size is not set, or set to 0, always return EOF. */
314 * asma and asma->file are used outside the lock here. We assume
315 * once asma->file is set it will never be changed, and will not
316 * be destroyed until all references to the file are dropped and
317 * ashmem_release is called.
319 mutex_unlock(&ashmem_mutex);
320 ret = vfs_iter_read(asma->file, iter, &iocb->ki_pos, 0);
321 mutex_lock(&ashmem_mutex);
323 asma->file->f_pos = iocb->ki_pos;
325 mutex_unlock(&ashmem_mutex);
329 static loff_t ashmem_llseek(struct file *file, loff_t offset, int origin)
331 struct ashmem_area *asma = file->private_data;
334 mutex_lock(&ashmem_mutex);
336 if (asma->size == 0) {
337 mutex_unlock(&ashmem_mutex);
342 mutex_unlock(&ashmem_mutex);
346 mutex_unlock(&ashmem_mutex);
348 ret = vfs_llseek(asma->file, offset, origin);
352 /** Copy f_pos from backing file, since f_ops->llseek() sets it */
353 file->f_pos = asma->file->f_pos;
357 static inline vm_flags_t calc_vm_may_flags(unsigned long prot)
359 return _calc_vm_trans(prot, PROT_READ, VM_MAYREAD) |
360 _calc_vm_trans(prot, PROT_WRITE, VM_MAYWRITE) |
361 _calc_vm_trans(prot, PROT_EXEC, VM_MAYEXEC);
364 static int ashmem_vmfile_mmap(struct file *file, struct vm_area_struct *vma)
366 /* do not allow to mmap ashmem backing shmem file directly */
371 ashmem_vmfile_get_unmapped_area(struct file *file, unsigned long addr,
372 unsigned long len, unsigned long pgoff,
375 return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
378 static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
380 static struct file_operations vmfile_fops;
381 struct ashmem_area *asma = file->private_data;
384 mutex_lock(&ashmem_mutex);
386 /* user needs to SET_SIZE before mapping */
392 /* requested mapping size larger than object size */
393 if (vma->vm_end - vma->vm_start > PAGE_ALIGN(asma->size)) {
398 /* requested protection bits must match our allowed protection mask */
399 if ((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask, 0)) &
400 calc_vm_prot_bits(PROT_MASK, 0)) {
404 vma->vm_flags &= ~calc_vm_may_flags(~asma->prot_mask);
407 char *name = ASHMEM_NAME_DEF;
411 if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0')
414 /* ... and allocate the backing shmem file */
415 vmfile = shmem_file_setup(name, asma->size, vma->vm_flags);
416 if (IS_ERR(vmfile)) {
417 ret = PTR_ERR(vmfile);
420 vmfile->f_mode |= FMODE_LSEEK;
421 inode = file_inode(vmfile);
422 lockdep_set_class(&inode->i_rwsem, &backing_shmem_inode_class);
425 * override mmap operation of the vmfile so that it can't be
426 * remapped which would lead to creation of a new vma with no
427 * asma permission checks. Have to override get_unmapped_area
428 * as well to prevent VM_BUG_ON check for f_ops modification.
430 if (!vmfile_fops.mmap) {
431 vmfile_fops = *vmfile->f_op;
432 vmfile_fops.mmap = ashmem_vmfile_mmap;
433 vmfile_fops.get_unmapped_area =
434 ashmem_vmfile_get_unmapped_area;
436 vmfile->f_op = &vmfile_fops;
438 get_file(asma->file);
441 * XXX - Reworked to use shmem_zero_setup() instead of
442 * shmem_set_file while we're in staging. -jstultz
444 if (vma->vm_flags & VM_SHARED) {
445 ret = shmem_zero_setup(vma);
451 vma_set_anonymous(vma);
454 vma_set_file(vma, asma->file);
455 /* XXX: merge this with the get_file() above if possible */
459 mutex_unlock(&ashmem_mutex);
464 * ashmem_shrink - our cache shrinker, called from mm/vmscan.c
466 * 'nr_to_scan' is the number of objects to scan for freeing.
468 * 'gfp_mask' is the mask of the allocation that got us into this mess.
470 * Return value is the number of objects freed or -1 if we cannot
471 * proceed without risk of deadlock (due to gfp_mask).
473 * We approximate LRU via least-recently-unpinned, jettisoning unpinned partial
474 * chunks of ashmem regions LRU-wise one-at-a-time until we hit 'nr_to_scan'
478 ashmem_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
480 unsigned long freed = 0;
482 /* We might recurse into filesystem code, so bail out if necessary */
483 if (!(sc->gfp_mask & __GFP_FS))
486 if (!mutex_trylock(&ashmem_mutex))
489 while (!list_empty(&ashmem_lru_list)) {
490 struct ashmem_range *range =
491 list_first_entry(&ashmem_lru_list, typeof(*range), lru);
492 loff_t start = range->pgstart * PAGE_SIZE;
493 loff_t end = (range->pgend + 1) * PAGE_SIZE;
494 struct file *f = range->asma->file;
497 atomic_inc(&ashmem_shrink_inflight);
498 range->purged = ASHMEM_WAS_PURGED;
501 freed += range_size(range);
502 mutex_unlock(&ashmem_mutex);
503 f->f_op->fallocate(f,
504 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
507 if (atomic_dec_and_test(&ashmem_shrink_inflight))
508 wake_up_all(&ashmem_shrink_wait);
509 if (!mutex_trylock(&ashmem_mutex))
511 if (--sc->nr_to_scan <= 0)
514 mutex_unlock(&ashmem_mutex);
520 ashmem_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
523 * note that lru_count is count of pages on the lru, not a count of
524 * objects on the list. This means the scan function needs to return the
525 * number of pages freed, not the number of objects scanned.
530 static struct shrinker ashmem_shrinker = {
531 .count_objects = ashmem_shrink_count,
532 .scan_objects = ashmem_shrink_scan,
534 * XXX (dchinner): I wish people would comment on why they need on
535 * significant changes to the default value here
537 .seeks = DEFAULT_SEEKS * 4,
540 static int set_prot_mask(struct ashmem_area *asma, unsigned long prot)
544 mutex_lock(&ashmem_mutex);
546 /* the user can only remove, not add, protection bits */
547 if ((asma->prot_mask & prot) != prot) {
552 /* does the application expect PROT_READ to imply PROT_EXEC? */
553 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
556 asma->prot_mask = prot;
559 mutex_unlock(&ashmem_mutex);
563 static int set_name(struct ashmem_area *asma, void __user *name)
567 char local_name[ASHMEM_NAME_LEN];
570 * Holding the ashmem_mutex while doing a copy_from_user might cause
571 * an data abort which would try to access mmap_lock. If another
572 * thread has invoked ashmem_mmap then it will be holding the
573 * semaphore and will be waiting for ashmem_mutex, there by leading to
574 * deadlock. We'll release the mutex and take the name to a local
575 * variable that does not need protection and later copy the local
576 * variable to the structure member with lock held.
578 len = strncpy_from_user(local_name, name, ASHMEM_NAME_LEN);
582 mutex_lock(&ashmem_mutex);
583 /* cannot change an existing mapping's name */
587 strscpy(asma->name + ASHMEM_NAME_PREFIX_LEN, local_name,
590 mutex_unlock(&ashmem_mutex);
594 static int get_name(struct ashmem_area *asma, void __user *name)
599 * Have a local variable to which we'll copy the content
600 * from asma with the lock held. Later we can copy this to the user
601 * space safely without holding any locks. So even if we proceed to
602 * wait for mmap_lock, it won't lead to deadlock.
604 char local_name[ASHMEM_NAME_LEN];
606 mutex_lock(&ashmem_mutex);
607 if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') {
609 * Copying only `len', instead of ASHMEM_NAME_LEN, bytes
610 * prevents us from revealing one user's stack to another.
612 len = strlen(asma->name + ASHMEM_NAME_PREFIX_LEN) + 1;
613 memcpy(local_name, asma->name + ASHMEM_NAME_PREFIX_LEN, len);
615 len = sizeof(ASHMEM_NAME_DEF);
616 memcpy(local_name, ASHMEM_NAME_DEF, len);
618 mutex_unlock(&ashmem_mutex);
621 * Now we are just copying from the stack variable to userland
624 if (copy_to_user(name, local_name, len))
630 * ashmem_pin - pin the given ashmem region, returning whether it was
631 * previously purged (ASHMEM_WAS_PURGED) or not (ASHMEM_NOT_PURGED).
633 * Caller must hold ashmem_mutex.
635 static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend,
636 struct ashmem_range **new_range)
638 struct ashmem_range *range, *next;
639 int ret = ASHMEM_NOT_PURGED;
641 list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) {
642 /* moved past last applicable page; we can short circuit */
643 if (range_before_page(range, pgstart))
647 * The user can ask us to pin pages that span multiple ranges,
648 * or to pin pages that aren't even unpinned, so this is messy.
651 * 1. The requested range subsumes an existing range, so we
652 * just remove the entire matching range.
653 * 2. The requested range overlaps the start of an existing
654 * range, so we just update that range.
655 * 3. The requested range overlaps the end of an existing
656 * range, so we just update that range.
657 * 4. The requested range punches a hole in an existing range,
658 * so we have to update one side of the range and then
659 * create a new range for the other side.
661 if (page_range_in_range(range, pgstart, pgend)) {
662 ret |= range->purged;
664 /* Case #1: Easy. Just nuke the whole thing. */
665 if (page_range_subsumes_range(range, pgstart, pgend)) {
670 /* Case #2: We overlap from the start, so adjust it */
671 if (range->pgstart >= pgstart) {
672 range_shrink(range, pgend + 1, range->pgend);
676 /* Case #3: We overlap from the rear, so adjust it */
677 if (range->pgend <= pgend) {
678 range_shrink(range, range->pgstart,
684 * Case #4: We eat a chunk out of the middle. A bit
685 * more complicated, we allocate a new range for the
686 * second half and adjust the first chunk's endpoint.
688 range_alloc(asma, range, range->purged,
689 pgend + 1, range->pgend, new_range);
690 range_shrink(range, range->pgstart, pgstart - 1);
699 * ashmem_unpin - unpin the given range of pages. Returns zero on success.
701 * Caller must hold ashmem_mutex.
703 static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend,
704 struct ashmem_range **new_range)
706 struct ashmem_range *range, *next;
707 unsigned int purged = ASHMEM_NOT_PURGED;
710 list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) {
711 /* short circuit: this is our insertion point */
712 if (range_before_page(range, pgstart))
716 * The user can ask us to unpin pages that are already entirely
717 * or partially pinned. We handle those two cases here.
719 if (page_range_subsumed_by_range(range, pgstart, pgend))
721 if (page_range_in_range(range, pgstart, pgend)) {
722 pgstart = min(range->pgstart, pgstart);
723 pgend = max(range->pgend, pgend);
724 purged |= range->purged;
730 range_alloc(asma, range, purged, pgstart, pgend, new_range);
735 * ashmem_get_pin_status - Returns ASHMEM_IS_UNPINNED if _any_ pages in the
736 * given interval are unpinned and ASHMEM_IS_PINNED otherwise.
738 * Caller must hold ashmem_mutex.
740 static int ashmem_get_pin_status(struct ashmem_area *asma, size_t pgstart,
743 struct ashmem_range *range;
744 int ret = ASHMEM_IS_PINNED;
746 list_for_each_entry(range, &asma->unpinned_list, unpinned) {
747 if (range_before_page(range, pgstart))
749 if (page_range_in_range(range, pgstart, pgend)) {
750 ret = ASHMEM_IS_UNPINNED;
758 static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd,
761 struct ashmem_pin pin;
762 size_t pgstart, pgend;
764 struct ashmem_range *range = NULL;
766 if (copy_from_user(&pin, p, sizeof(pin)))
769 if (cmd == ASHMEM_PIN || cmd == ASHMEM_UNPIN) {
770 range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL);
775 mutex_lock(&ashmem_mutex);
776 wait_event(ashmem_shrink_wait, !atomic_read(&ashmem_shrink_inflight));
781 /* per custom, you can pass zero for len to mean "everything onward" */
783 pin.len = PAGE_ALIGN(asma->size) - pin.offset;
785 if ((pin.offset | pin.len) & ~PAGE_MASK)
788 if (((__u32)-1) - pin.offset < pin.len)
791 if (PAGE_ALIGN(asma->size) < pin.offset + pin.len)
794 pgstart = pin.offset / PAGE_SIZE;
795 pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
799 ret = ashmem_pin(asma, pgstart, pgend, &range);
802 ret = ashmem_unpin(asma, pgstart, pgend, &range);
804 case ASHMEM_GET_PIN_STATUS:
805 ret = ashmem_get_pin_status(asma, pgstart, pgend);
810 mutex_unlock(&ashmem_mutex);
812 kmem_cache_free(ashmem_range_cachep, range);
817 static long ashmem_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
819 struct ashmem_area *asma = file->private_data;
823 case ASHMEM_SET_NAME:
824 ret = set_name(asma, (void __user *)arg);
826 case ASHMEM_GET_NAME:
827 ret = get_name(asma, (void __user *)arg);
829 case ASHMEM_SET_SIZE:
831 mutex_lock(&ashmem_mutex);
834 asma->size = (size_t)arg;
836 mutex_unlock(&ashmem_mutex);
838 case ASHMEM_GET_SIZE:
841 case ASHMEM_SET_PROT_MASK:
842 ret = set_prot_mask(asma, arg);
844 case ASHMEM_GET_PROT_MASK:
845 ret = asma->prot_mask;
849 case ASHMEM_GET_PIN_STATUS:
850 ret = ashmem_pin_unpin(asma, cmd, (void __user *)arg);
852 case ASHMEM_PURGE_ALL_CACHES:
854 if (capable(CAP_SYS_ADMIN)) {
855 struct shrink_control sc = {
856 .gfp_mask = GFP_KERNEL,
857 .nr_to_scan = LONG_MAX,
859 ret = ashmem_shrink_count(&ashmem_shrinker, &sc);
860 ashmem_shrink_scan(&ashmem_shrinker, &sc);
868 /* support of 32bit userspace on 64bit platforms */
870 static long compat_ashmem_ioctl(struct file *file, unsigned int cmd,
874 case COMPAT_ASHMEM_SET_SIZE:
875 cmd = ASHMEM_SET_SIZE;
877 case COMPAT_ASHMEM_SET_PROT_MASK:
878 cmd = ASHMEM_SET_PROT_MASK;
881 return ashmem_ioctl(file, cmd, arg);
884 #ifdef CONFIG_PROC_FS
885 static void ashmem_show_fdinfo(struct seq_file *m, struct file *file)
887 struct ashmem_area *asma = file->private_data;
889 mutex_lock(&ashmem_mutex);
892 seq_printf(m, "inode:\t%ld\n", file_inode(asma->file)->i_ino);
894 if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0')
895 seq_printf(m, "name:\t%s\n",
896 asma->name + ASHMEM_NAME_PREFIX_LEN);
898 seq_printf(m, "size:\t%zu\n", asma->size);
900 mutex_unlock(&ashmem_mutex);
903 static const struct file_operations ashmem_fops = {
904 .owner = THIS_MODULE,
906 .release = ashmem_release,
907 .read_iter = ashmem_read_iter,
908 .llseek = ashmem_llseek,
910 .unlocked_ioctl = ashmem_ioctl,
912 .compat_ioctl = compat_ashmem_ioctl,
914 #ifdef CONFIG_PROC_FS
915 .show_fdinfo = ashmem_show_fdinfo,
919 static struct miscdevice ashmem_misc = {
920 .minor = MISC_DYNAMIC_MINOR,
922 .fops = &ashmem_fops,
925 static int __init ashmem_init(void)
929 ashmem_area_cachep = kmem_cache_create("ashmem_area_cache",
930 sizeof(struct ashmem_area),
932 if (!ashmem_area_cachep) {
933 pr_err("failed to create slab cache\n");
937 ashmem_range_cachep = kmem_cache_create("ashmem_range_cache",
938 sizeof(struct ashmem_range),
939 0, SLAB_RECLAIM_ACCOUNT, NULL);
940 if (!ashmem_range_cachep) {
941 pr_err("failed to create slab cache\n");
945 ret = misc_register(&ashmem_misc);
947 pr_err("failed to register misc device!\n");
951 ret = register_shrinker(&ashmem_shrinker);
953 pr_err("failed to register shrinker!\n");
957 pr_info("initialized\n");
962 misc_deregister(&ashmem_misc);
964 kmem_cache_destroy(ashmem_range_cachep);
966 kmem_cache_destroy(ashmem_area_cachep);
970 device_initcall(ashmem_init);