3 * Anonymous Shared Memory Subsystem, ashmem
5 * Copyright (C) 2008 Google, Inc.
7 * Robert Love <rlove@google.com>
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.
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.
19 #define pr_fmt(fmt) "ashmem: " fmt
21 #include <linux/init.h>
22 #include <linux/export.h>
23 #include <linux/file.h>
25 #include <linux/falloc.h>
26 #include <linux/miscdevice.h>
27 #include <linux/security.h>
29 #include <linux/mman.h>
30 #include <linux/uaccess.h>
31 #include <linux/personality.h>
32 #include <linux/bitops.h>
33 #include <linux/mutex.h>
34 #include <linux/shmem_fs.h>
37 #define ASHMEM_NAME_PREFIX "dev/ashmem/"
38 #define ASHMEM_NAME_PREFIX_LEN (sizeof(ASHMEM_NAME_PREFIX) - 1)
39 #define ASHMEM_FULL_NAME_LEN (ASHMEM_NAME_LEN + ASHMEM_NAME_PREFIX_LEN)
42 * struct ashmem_area - The anonymous shared memory area
43 * @name: The optional name in /proc/pid/maps
44 * @unpinned_list: The list of all ashmem areas
45 * @file: The shmem-based backing file
46 * @size: The size of the mapping, in bytes
47 * @prot_mask: The allowed protection bits, as vm_flags
49 * The lifecycle of this structure is from our parent file's open() until
50 * its release(). It is also protected by 'ashmem_mutex'
52 * Warning: Mappings do NOT pin this structure; It dies on close()
55 char name
[ASHMEM_FULL_NAME_LEN
];
56 struct list_head unpinned_list
;
59 unsigned long prot_mask
;
63 * struct ashmem_range - A range of unpinned/evictable pages
64 * @lru: The entry in the LRU list
65 * @unpinned: The entry in its area's unpinned list
66 * @asma: The associated anonymous shared memory area.
67 * @pgstart: The starting page (inclusive)
68 * @pgend: The ending page (inclusive)
69 * @purged: The purge status (ASHMEM_NOT or ASHMEM_WAS_PURGED)
71 * The lifecycle of this structure is from unpin to pin.
72 * It is protected by 'ashmem_mutex'
76 struct list_head unpinned
;
77 struct ashmem_area
*asma
;
83 /* LRU list of unpinned pages, protected by ashmem_mutex */
84 static LIST_HEAD(ashmem_lru_list
);
87 * long lru_count - The count of pages on our LRU list.
89 * This is protected by ashmem_mutex.
91 static unsigned long lru_count
;
94 * ashmem_mutex - protects the list of and each individual ashmem_area
96 * Lock Ordering: ashmex_mutex -> i_mutex -> i_alloc_sem
98 static DEFINE_MUTEX(ashmem_mutex
);
100 static struct kmem_cache
*ashmem_area_cachep __read_mostly
;
101 static struct kmem_cache
*ashmem_range_cachep __read_mostly
;
103 static inline unsigned long range_size(struct ashmem_range
*range
)
105 return range
->pgend
- range
->pgstart
+ 1;
108 static inline bool range_on_lru(struct ashmem_range
*range
)
110 return range
->purged
== ASHMEM_NOT_PURGED
;
113 static inline bool page_range_subsumes_range(struct ashmem_range
*range
,
114 size_t start
, size_t end
)
116 return (range
->pgstart
>= start
) && (range
->pgend
<= end
);
119 static inline bool page_range_subsumed_by_range(struct ashmem_range
*range
,
120 size_t start
, size_t end
)
122 return (range
->pgstart
<= start
) && (range
->pgend
>= end
);
125 static inline bool page_in_range(struct ashmem_range
*range
, size_t page
)
127 return (range
->pgstart
<= page
) && (range
->pgend
>= page
);
130 static inline bool page_range_in_range(struct ashmem_range
*range
,
131 size_t start
, size_t end
)
133 return page_in_range(range
, start
) || page_in_range(range
, end
) ||
134 page_range_subsumes_range(range
, start
, end
);
137 static inline bool range_before_page(struct ashmem_range
*range
, size_t page
)
139 return range
->pgend
< page
;
142 #define PROT_MASK (PROT_EXEC | PROT_READ | PROT_WRITE)
145 * lru_add() - Adds a range of memory to the LRU list
146 * @range: The memory range being added.
148 * The range is first added to the end (tail) of the LRU list.
149 * After this, the size of the range is added to @lru_count
151 static inline void lru_add(struct ashmem_range
*range
)
153 list_add_tail(&range
->lru
, &ashmem_lru_list
);
154 lru_count
+= range_size(range
);
158 * lru_del() - Removes a range of memory from the LRU list
159 * @range: The memory range being removed
161 * The range is first deleted from the LRU list.
162 * After this, the size of the range is removed from @lru_count
164 static inline void lru_del(struct ashmem_range
*range
)
166 list_del(&range
->lru
);
167 lru_count
-= range_size(range
);
171 * range_alloc() - Allocates and initializes a new ashmem_range structure
172 * @asma: The associated ashmem_area
173 * @prev_range: The previous ashmem_range in the sorted asma->unpinned list
174 * @purged: Initial purge status (ASMEM_NOT_PURGED or ASHMEM_WAS_PURGED)
175 * @start: The starting page (inclusive)
176 * @end: The ending page (inclusive)
178 * This function is protected by ashmem_mutex.
180 * Return: 0 if successful, or -ENOMEM if there is an error
182 static int range_alloc(struct ashmem_area
*asma
,
183 struct ashmem_range
*prev_range
, unsigned int purged
,
184 size_t start
, size_t end
)
186 struct ashmem_range
*range
;
188 range
= kmem_cache_zalloc(ashmem_range_cachep
, GFP_KERNEL
);
189 if (unlikely(!range
))
193 range
->pgstart
= start
;
195 range
->purged
= purged
;
197 list_add_tail(&range
->unpinned
, &prev_range
->unpinned
);
199 if (range_on_lru(range
))
206 * range_del() - Deletes and dealloctes 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
);
298 * ashmem_read() - Reads a set of bytes from an Ashmem-enabled file
299 * @file: The associated backing file.
300 * @buf: The buffer of data being written to
301 * @len: The number of bytes being read
302 * @pos: The position of the first byte to read.
304 * Return: 0 if successful, or another return code if not.
306 static ssize_t
ashmem_read(struct file
*file
, char __user
*buf
,
307 size_t len
, loff_t
*pos
)
309 struct ashmem_area
*asma
= file
->private_data
;
312 mutex_lock(&ashmem_mutex
);
314 /* If size is not set, or set to 0, always return EOF. */
323 mutex_unlock(&ashmem_mutex
);
326 * asma and asma->file are used outside the lock here. We assume
327 * once asma->file is set it will never be changed, and will not
328 * be destroyed until all references to the file are dropped and
329 * ashmem_release is called.
331 ret
= __vfs_read(asma
->file
, buf
, len
, pos
);
333 /** Update backing file pos, since f_ops->read() doesn't */
334 asma
->file
->f_pos
= *pos
;
338 mutex_unlock(&ashmem_mutex
);
342 static loff_t
ashmem_llseek(struct file
*file
, loff_t offset
, int origin
)
344 struct ashmem_area
*asma
= file
->private_data
;
347 mutex_lock(&ashmem_mutex
);
349 if (asma
->size
== 0) {
359 ret
= vfs_llseek(asma
->file
, offset
, origin
);
363 /** Copy f_pos from backing file, since f_ops->llseek() sets it */
364 file
->f_pos
= asma
->file
->f_pos
;
367 mutex_unlock(&ashmem_mutex
);
371 static inline vm_flags_t
calc_vm_may_flags(unsigned long prot
)
373 return _calc_vm_trans(prot
, PROT_READ
, VM_MAYREAD
) |
374 _calc_vm_trans(prot
, PROT_WRITE
, VM_MAYWRITE
) |
375 _calc_vm_trans(prot
, PROT_EXEC
, VM_MAYEXEC
);
378 static int ashmem_mmap(struct file
*file
, struct vm_area_struct
*vma
)
380 struct ashmem_area
*asma
= file
->private_data
;
383 mutex_lock(&ashmem_mutex
);
385 /* user needs to SET_SIZE before mapping */
386 if (unlikely(!asma
->size
)) {
391 /* requested protection bits must match our allowed protection mask */
392 if (unlikely((vma
->vm_flags
& ~calc_vm_prot_bits(asma
->prot_mask
, 0)) &
393 calc_vm_prot_bits(PROT_MASK
, 0))) {
397 vma
->vm_flags
&= ~calc_vm_may_flags(~asma
->prot_mask
);
400 char *name
= ASHMEM_NAME_DEF
;
403 if (asma
->name
[ASHMEM_NAME_PREFIX_LEN
] != '\0')
406 /* ... and allocate the backing shmem file */
407 vmfile
= shmem_file_setup(name
, asma
->size
, vma
->vm_flags
);
408 if (IS_ERR(vmfile
)) {
409 ret
= PTR_ERR(vmfile
);
414 get_file(asma
->file
);
417 * XXX - Reworked to use shmem_zero_setup() instead of
418 * shmem_set_file while we're in staging. -jstultz
420 if (vma
->vm_flags
& VM_SHARED
) {
421 ret
= shmem_zero_setup(vma
);
430 vma
->vm_file
= asma
->file
;
433 mutex_unlock(&ashmem_mutex
);
438 * ashmem_shrink - our cache shrinker, called from mm/vmscan.c
440 * 'nr_to_scan' is the number of objects to scan for freeing.
442 * 'gfp_mask' is the mask of the allocation that got us into this mess.
444 * Return value is the number of objects freed or -1 if we cannot
445 * proceed without risk of deadlock (due to gfp_mask).
447 * We approximate LRU via least-recently-unpinned, jettisoning unpinned partial
448 * chunks of ashmem regions LRU-wise one-at-a-time until we hit 'nr_to_scan'
452 ashmem_shrink_scan(struct shrinker
*shrink
, struct shrink_control
*sc
)
454 struct ashmem_range
*range
, *next
;
455 unsigned long freed
= 0;
457 /* We might recurse into filesystem code, so bail out if necessary */
458 if (!(sc
->gfp_mask
& __GFP_FS
))
461 if (!mutex_trylock(&ashmem_mutex
))
464 list_for_each_entry_safe(range
, next
, &ashmem_lru_list
, lru
) {
465 loff_t start
= range
->pgstart
* PAGE_SIZE
;
466 loff_t end
= (range
->pgend
+ 1) * PAGE_SIZE
;
468 vfs_fallocate(range
->asma
->file
,
469 FALLOC_FL_PUNCH_HOLE
| FALLOC_FL_KEEP_SIZE
,
471 range
->purged
= ASHMEM_WAS_PURGED
;
474 freed
+= range_size(range
);
475 if (--sc
->nr_to_scan
<= 0)
478 mutex_unlock(&ashmem_mutex
);
483 ashmem_shrink_count(struct shrinker
*shrink
, struct shrink_control
*sc
)
486 * note that lru_count is count of pages on the lru, not a count of
487 * objects on the list. This means the scan function needs to return the
488 * number of pages freed, not the number of objects scanned.
493 static struct shrinker ashmem_shrinker
= {
494 .count_objects
= ashmem_shrink_count
,
495 .scan_objects
= ashmem_shrink_scan
,
497 * XXX (dchinner): I wish people would comment on why they need on
498 * significant changes to the default value here
500 .seeks
= DEFAULT_SEEKS
* 4,
503 static int set_prot_mask(struct ashmem_area
*asma
, unsigned long prot
)
507 mutex_lock(&ashmem_mutex
);
509 /* the user can only remove, not add, protection bits */
510 if (unlikely((asma
->prot_mask
& prot
) != prot
)) {
515 /* does the application expect PROT_READ to imply PROT_EXEC? */
516 if ((prot
& PROT_READ
) && (current
->personality
& READ_IMPLIES_EXEC
))
519 asma
->prot_mask
= prot
;
522 mutex_unlock(&ashmem_mutex
);
526 static int set_name(struct ashmem_area
*asma
, void __user
*name
)
530 char local_name
[ASHMEM_NAME_LEN
];
533 * Holding the ashmem_mutex while doing a copy_from_user might cause
534 * an data abort which would try to access mmap_sem. If another
535 * thread has invoked ashmem_mmap then it will be holding the
536 * semaphore and will be waiting for ashmem_mutex, there by leading to
537 * deadlock. We'll release the mutex and take the name to a local
538 * variable that does not need protection and later copy the local
539 * variable to the structure member with lock held.
541 len
= strncpy_from_user(local_name
, name
, ASHMEM_NAME_LEN
);
544 if (len
== ASHMEM_NAME_LEN
)
545 local_name
[ASHMEM_NAME_LEN
- 1] = '\0';
546 mutex_lock(&ashmem_mutex
);
547 /* cannot change an existing mapping's name */
548 if (unlikely(asma
->file
))
551 strcpy(asma
->name
+ ASHMEM_NAME_PREFIX_LEN
, local_name
);
553 mutex_unlock(&ashmem_mutex
);
557 static int get_name(struct ashmem_area
*asma
, void __user
*name
)
562 * Have a local variable to which we'll copy the content
563 * from asma with the lock held. Later we can copy this to the user
564 * space safely without holding any locks. So even if we proceed to
565 * wait for mmap_sem, it won't lead to deadlock.
567 char local_name
[ASHMEM_NAME_LEN
];
569 mutex_lock(&ashmem_mutex
);
570 if (asma
->name
[ASHMEM_NAME_PREFIX_LEN
] != '\0') {
572 * Copying only `len', instead of ASHMEM_NAME_LEN, bytes
573 * prevents us from revealing one user's stack to another.
575 len
= strlen(asma
->name
+ ASHMEM_NAME_PREFIX_LEN
) + 1;
576 memcpy(local_name
, asma
->name
+ ASHMEM_NAME_PREFIX_LEN
, len
);
578 len
= sizeof(ASHMEM_NAME_DEF
);
579 memcpy(local_name
, ASHMEM_NAME_DEF
, len
);
581 mutex_unlock(&ashmem_mutex
);
584 * Now we are just copying from the stack variable to userland
587 if (unlikely(copy_to_user(name
, local_name
, len
)))
593 * ashmem_pin - pin the given ashmem region, returning whether it was
594 * previously purged (ASHMEM_WAS_PURGED) or not (ASHMEM_NOT_PURGED).
596 * Caller must hold ashmem_mutex.
598 static int ashmem_pin(struct ashmem_area
*asma
, size_t pgstart
, size_t pgend
)
600 struct ashmem_range
*range
, *next
;
601 int ret
= ASHMEM_NOT_PURGED
;
603 list_for_each_entry_safe(range
, next
, &asma
->unpinned_list
, unpinned
) {
604 /* moved past last applicable page; we can short circuit */
605 if (range_before_page(range
, pgstart
))
609 * The user can ask us to pin pages that span multiple ranges,
610 * or to pin pages that aren't even unpinned, so this is messy.
613 * 1. The requested range subsumes an existing range, so we
614 * just remove the entire matching range.
615 * 2. The requested range overlaps the start of an existing
616 * range, so we just update that range.
617 * 3. The requested range overlaps the end of an existing
618 * range, so we just update that range.
619 * 4. The requested range punches a hole in an existing range,
620 * so we have to update one side of the range and then
621 * create a new range for the other side.
623 if (page_range_in_range(range
, pgstart
, pgend
)) {
624 ret
|= range
->purged
;
626 /* Case #1: Easy. Just nuke the whole thing. */
627 if (page_range_subsumes_range(range
, pgstart
, pgend
)) {
632 /* Case #2: We overlap from the start, so adjust it */
633 if (range
->pgstart
>= pgstart
) {
634 range_shrink(range
, pgend
+ 1, range
->pgend
);
638 /* Case #3: We overlap from the rear, so adjust it */
639 if (range
->pgend
<= pgend
) {
640 range_shrink(range
, range
->pgstart
,
646 * Case #4: We eat a chunk out of the middle. A bit
647 * more complicated, we allocate a new range for the
648 * second half and adjust the first chunk's endpoint.
650 range_alloc(asma
, range
, range
->purged
,
651 pgend
+ 1, range
->pgend
);
652 range_shrink(range
, range
->pgstart
, pgstart
- 1);
661 * ashmem_unpin - unpin the given range of pages. Returns zero on success.
663 * Caller must hold ashmem_mutex.
665 static int ashmem_unpin(struct ashmem_area
*asma
, size_t pgstart
, size_t pgend
)
667 struct ashmem_range
*range
, *next
;
668 unsigned int purged
= ASHMEM_NOT_PURGED
;
671 list_for_each_entry_safe(range
, next
, &asma
->unpinned_list
, unpinned
) {
672 /* short circuit: this is our insertion point */
673 if (range_before_page(range
, pgstart
))
677 * The user can ask us to unpin pages that are already entirely
678 * or partially pinned. We handle those two cases here.
680 if (page_range_subsumed_by_range(range
, pgstart
, pgend
))
682 if (page_range_in_range(range
, pgstart
, pgend
)) {
683 pgstart
= min(range
->pgstart
, pgstart
);
684 pgend
= max(range
->pgend
, pgend
);
685 purged
|= range
->purged
;
691 return range_alloc(asma
, range
, purged
, pgstart
, pgend
);
695 * ashmem_get_pin_status - Returns ASHMEM_IS_UNPINNED if _any_ pages in the
696 * given interval are unpinned and ASHMEM_IS_PINNED otherwise.
698 * Caller must hold ashmem_mutex.
700 static int ashmem_get_pin_status(struct ashmem_area
*asma
, size_t pgstart
,
703 struct ashmem_range
*range
;
704 int ret
= ASHMEM_IS_PINNED
;
706 list_for_each_entry(range
, &asma
->unpinned_list
, unpinned
) {
707 if (range_before_page(range
, pgstart
))
709 if (page_range_in_range(range
, pgstart
, pgend
)) {
710 ret
= ASHMEM_IS_UNPINNED
;
718 static int ashmem_pin_unpin(struct ashmem_area
*asma
, unsigned long cmd
,
721 struct ashmem_pin pin
;
722 size_t pgstart
, pgend
;
725 if (unlikely(!asma
->file
))
728 if (unlikely(copy_from_user(&pin
, p
, sizeof(pin
))))
731 /* per custom, you can pass zero for len to mean "everything onward" */
733 pin
.len
= PAGE_ALIGN(asma
->size
) - pin
.offset
;
735 if (unlikely((pin
.offset
| pin
.len
) & ~PAGE_MASK
))
738 if (unlikely(((__u32
)-1) - pin
.offset
< pin
.len
))
741 if (unlikely(PAGE_ALIGN(asma
->size
) < pin
.offset
+ pin
.len
))
744 pgstart
= pin
.offset
/ PAGE_SIZE
;
745 pgend
= pgstart
+ (pin
.len
/ PAGE_SIZE
) - 1;
747 mutex_lock(&ashmem_mutex
);
751 ret
= ashmem_pin(asma
, pgstart
, pgend
);
754 ret
= ashmem_unpin(asma
, pgstart
, pgend
);
756 case ASHMEM_GET_PIN_STATUS
:
757 ret
= ashmem_get_pin_status(asma
, pgstart
, pgend
);
761 mutex_unlock(&ashmem_mutex
);
766 static long ashmem_ioctl(struct file
*file
, unsigned int cmd
, unsigned long arg
)
768 struct ashmem_area
*asma
= file
->private_data
;
772 case ASHMEM_SET_NAME
:
773 ret
= set_name(asma
, (void __user
*)arg
);
775 case ASHMEM_GET_NAME
:
776 ret
= get_name(asma
, (void __user
*)arg
);
778 case ASHMEM_SET_SIZE
:
782 asma
->size
= (size_t)arg
;
785 case ASHMEM_GET_SIZE
:
788 case ASHMEM_SET_PROT_MASK
:
789 ret
= set_prot_mask(asma
, arg
);
791 case ASHMEM_GET_PROT_MASK
:
792 ret
= asma
->prot_mask
;
796 case ASHMEM_GET_PIN_STATUS
:
797 ret
= ashmem_pin_unpin(asma
, cmd
, (void __user
*)arg
);
799 case ASHMEM_PURGE_ALL_CACHES
:
801 if (capable(CAP_SYS_ADMIN
)) {
802 struct shrink_control sc
= {
803 .gfp_mask
= GFP_KERNEL
,
804 .nr_to_scan
= LONG_MAX
,
806 ret
= ashmem_shrink_count(&ashmem_shrinker
, &sc
);
807 ashmem_shrink_scan(&ashmem_shrinker
, &sc
);
815 /* support of 32bit userspace on 64bit platforms */
817 static long compat_ashmem_ioctl(struct file
*file
, unsigned int cmd
,
821 case COMPAT_ASHMEM_SET_SIZE
:
822 cmd
= ASHMEM_SET_SIZE
;
824 case COMPAT_ASHMEM_SET_PROT_MASK
:
825 cmd
= ASHMEM_SET_PROT_MASK
;
828 return ashmem_ioctl(file
, cmd
, arg
);
832 static const struct file_operations ashmem_fops
= {
833 .owner
= THIS_MODULE
,
835 .release
= ashmem_release
,
837 .llseek
= ashmem_llseek
,
839 .unlocked_ioctl
= ashmem_ioctl
,
841 .compat_ioctl
= compat_ashmem_ioctl
,
845 static struct miscdevice ashmem_misc
= {
846 .minor
= MISC_DYNAMIC_MINOR
,
848 .fops
= &ashmem_fops
,
851 static int __init
ashmem_init(void)
855 ashmem_area_cachep
= kmem_cache_create("ashmem_area_cache",
856 sizeof(struct ashmem_area
),
858 if (unlikely(!ashmem_area_cachep
)) {
859 pr_err("failed to create slab cache\n");
863 ashmem_range_cachep
= kmem_cache_create("ashmem_range_cache",
864 sizeof(struct ashmem_range
),
866 if (unlikely(!ashmem_range_cachep
)) {
867 pr_err("failed to create slab cache\n");
871 ret
= misc_register(&ashmem_misc
);
873 pr_err("failed to register misc device!\n");
877 register_shrinker(&ashmem_shrinker
);
879 pr_info("initialized\n");
884 kmem_cache_destroy(ashmem_range_cachep
);
886 kmem_cache_destroy(ashmem_area_cachep
);
890 device_initcall(ashmem_init
);