ashmem.c revision aa5af974127d317071d6225a0f3678c5f520e7ce 
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#include <linux/module.h>
20#include <linux/file.h>
21#include <linux/fs.h>
22#include <linux/miscdevice.h>
23#include <linux/security.h>
24#include <linux/mm.h>
25#include <linux/mman.h>
26#include <linux/uaccess.h>
27#include <linux/personality.h>
28#include <linux/bitops.h>
29#include <linux/mutex.h>
30#include <linux/shmem_fs.h>
31#include "ashmem.h"
32
33#define ASHMEM_NAME_PREFIX "dev/ashmem/"
34#define ASHMEM_NAME_PREFIX_LEN (sizeof(ASHMEM_NAME_PREFIX) - 1)
35#define ASHMEM_FULL_NAME_LEN (ASHMEM_NAME_LEN + ASHMEM_NAME_PREFIX_LEN)
36
37/*
38 * ashmem_area - anonymous shared memory area
39 * Lifecycle: From our parent file's open() until its release()
40 * Locking: Protected by `ashmem_mutex'
41 * Big Note: Mappings do NOT pin this structure; it dies on close()
42 */
43struct ashmem_area {
44	char name[ASHMEM_FULL_NAME_LEN]; /* optional name in /proc/pid/maps */
45	struct list_head unpinned_list;	 /* list of all ashmem areas */
46	struct file *file;		 /* the shmem-based backing file */
47	size_t size;			 /* size of the mapping, in bytes */
48	unsigned long prot_mask;	 /* allowed prot bits, as vm_flags */
49};
50
51/*
52 * ashmem_range - represents an interval of unpinned (evictable) pages
53 * Lifecycle: From unpin to pin
54 * Locking: Protected by `ashmem_mutex'
55 */
56struct ashmem_range {
57	struct list_head lru;		/* entry in LRU list */
58	struct list_head unpinned;	/* entry in its area's unpinned list */
59	struct ashmem_area *asma;	/* associated area */
60	size_t pgstart;			/* starting page, inclusive */
61	size_t pgend;			/* ending page, inclusive */
62	unsigned int purged;		/* ASHMEM_NOT or ASHMEM_WAS_PURGED */
63};
64
65/* LRU list of unpinned pages, protected by ashmem_mutex */
66static LIST_HEAD(ashmem_lru_list);
67
68/* Count of pages on our LRU list, protected by ashmem_mutex */
69static unsigned long lru_count;
70
71/*
72 * ashmem_mutex - protects the list of and each individual ashmem_area
73 *
74 * Lock Ordering: ashmex_mutex -> i_mutex -> i_alloc_sem
75 */
76static DEFINE_MUTEX(ashmem_mutex);
77
78static struct kmem_cache *ashmem_area_cachep __read_mostly;
79static struct kmem_cache *ashmem_range_cachep __read_mostly;
80
81#define range_size(range) \
82	((range)->pgend - (range)->pgstart + 1)
83
84#define range_on_lru(range) \
85	((range)->purged == ASHMEM_NOT_PURGED)
86
87#define page_range_subsumes_range(range, start, end) \
88	(((range)->pgstart >= (start)) && ((range)->pgend <= (end)))
89
90#define page_range_subsumed_by_range(range, start, end) \
91	(((range)->pgstart <= (start)) && ((range)->pgend >= (end)))
92
93#define page_in_range(range, page) \
94	(((range)->pgstart <= (page)) && ((range)->pgend >= (page)))
95
96#define page_range_in_range(range, start, end) \
97	(page_in_range(range, start) || page_in_range(range, end) || \
98		page_range_subsumes_range(range, start, end))
99
100#define range_before_page(range, page) \
101	((range)->pgend < (page))
102
103#define PROT_MASK		(PROT_EXEC | PROT_READ | PROT_WRITE)
104
105static inline void lru_add(struct ashmem_range *range)
106{
107	list_add_tail(&range->lru, &ashmem_lru_list);
108	lru_count += range_size(range);
109}
110
111static inline void lru_del(struct ashmem_range *range)
112{
113	list_del(&range->lru);
114	lru_count -= range_size(range);
115}
116
117/*
118 * range_alloc - allocate and initialize a new ashmem_range structure
119 *
120 * 'asma' - associated ashmem_area
121 * 'prev_range' - the previous ashmem_range in the sorted asma->unpinned list
122 * 'purged' - initial purge value (ASMEM_NOT_PURGED or ASHMEM_WAS_PURGED)
123 * 'start' - starting page, inclusive
124 * 'end' - ending page, inclusive
125 *
126 * Caller must hold ashmem_mutex.
127 */
128static int range_alloc(struct ashmem_area *asma,
129		       struct ashmem_range *prev_range, unsigned int purged,
130		       size_t start, size_t end)
131{
132	struct ashmem_range *range;
133
134	range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL);
135	if (unlikely(!range))
136		return -ENOMEM;
137
138	range->asma = asma;
139	range->pgstart = start;
140	range->pgend = end;
141	range->purged = purged;
142
143	list_add_tail(&range->unpinned, &prev_range->unpinned);
144
145	if (range_on_lru(range))
146		lru_add(range);
147
148	return 0;
149}
150
151static void range_del(struct ashmem_range *range)
152{
153	list_del(&range->unpinned);
154	if (range_on_lru(range))
155		lru_del(range);
156	kmem_cache_free(ashmem_range_cachep, range);
157}
158
159/*
160 * range_shrink - shrinks a range
161 *
162 * Caller must hold ashmem_mutex.
163 */
164static inline void range_shrink(struct ashmem_range *range,
165				size_t start, size_t end)
166{
167	size_t pre = range_size(range);
168
169	range->pgstart = start;
170	range->pgend = end;
171
172	if (range_on_lru(range))
173		lru_count -= pre - range_size(range);
174}
175
176static int ashmem_open(struct inode *inode, struct file *file)
177{
178	struct ashmem_area *asma;
179	int ret;
180
181	ret = generic_file_open(inode, file);
182	if (unlikely(ret))
183		return ret;
184
185	asma = kmem_cache_zalloc(ashmem_area_cachep, GFP_KERNEL);
186	if (unlikely(!asma))
187		return -ENOMEM;
188
189	INIT_LIST_HEAD(&asma->unpinned_list);
190	memcpy(asma->name, ASHMEM_NAME_PREFIX, ASHMEM_NAME_PREFIX_LEN);
191	asma->prot_mask = PROT_MASK;
192	file->private_data = asma;
193
194	return 0;
195}
196
197static int ashmem_release(struct inode *ignored, struct file *file)
198{
199	struct ashmem_area *asma = file->private_data;
200	struct ashmem_range *range, *next;
201
202	mutex_lock(&ashmem_mutex);
203	list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned)
204		range_del(range);
205	mutex_unlock(&ashmem_mutex);
206
207	if (asma->file)
208		fput(asma->file);
209	kmem_cache_free(ashmem_area_cachep, asma);
210
211	return 0;
212}
213
214static ssize_t ashmem_read(struct file *file, char __user *buf,
215			   size_t len, loff_t *pos)
216{
217	struct ashmem_area *asma = file->private_data;
218	int ret = 0;
219
220	mutex_lock(&ashmem_mutex);
221
222	/* If size is not set, or set to 0, always return EOF. */
223	if (asma->size == 0)
224		goto out;
225
226	if (!asma->file) {
227		ret = -EBADF;
228		goto out;
229	}
230
231	ret = asma->file->f_op->read(asma->file, buf, len, pos);
232	if (ret < 0)
233		goto out;
234
235	/** Update backing file pos, since f_ops->read() doesn't */
236	asma->file->f_pos = *pos;
237
238out:
239	mutex_unlock(&ashmem_mutex);
240	return ret;
241}
242
243static loff_t ashmem_llseek(struct file *file, loff_t offset, int origin)
244{
245	struct ashmem_area *asma = file->private_data;
246	int ret;
247
248	mutex_lock(&ashmem_mutex);
249
250	if (asma->size == 0) {
251		ret = -EINVAL;
252		goto out;
253	}
254
255	if (!asma->file) {
256		ret = -EBADF;
257		goto out;
258	}
259
260	ret = asma->file->f_op->llseek(asma->file, offset, origin);
261	if (ret < 0)
262		goto out;
263
264	/** Copy f_pos from backing file, since f_ops->llseek() sets it */
265	file->f_pos = asma->file->f_pos;
266
267out:
268	mutex_unlock(&ashmem_mutex);
269	return ret;
270}
271
272static inline unsigned long calc_vm_may_flags(unsigned long prot)
273{
274	return _calc_vm_trans(prot, PROT_READ,  VM_MAYREAD) |
275	       _calc_vm_trans(prot, PROT_WRITE, VM_MAYWRITE) |
276	       _calc_vm_trans(prot, PROT_EXEC,  VM_MAYEXEC);
277}
278
279static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
280{
281	struct ashmem_area *asma = file->private_data;
282	int ret = 0;
283
284	mutex_lock(&ashmem_mutex);
285
286	/* user needs to SET_SIZE before mapping */
287	if (unlikely(!asma->size)) {
288		ret = -EINVAL;
289		goto out;
290	}
291
292	/* requested protection bits must match our allowed protection mask */
293	if (unlikely((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask)) &
294		     calc_vm_prot_bits(PROT_MASK))) {
295		ret = -EPERM;
296		goto out;
297	}
298	vma->vm_flags &= ~calc_vm_may_flags(~asma->prot_mask);
299
300	if (!asma->file) {
301		char *name = ASHMEM_NAME_DEF;
302		struct file *vmfile;
303
304		if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0')
305			name = asma->name;
306
307		/* ... and allocate the backing shmem file */
308		vmfile = shmem_file_setup(name, asma->size, vma->vm_flags);
309		if (unlikely(IS_ERR(vmfile))) {
310			ret = PTR_ERR(vmfile);
311			goto out;
312		}
313		asma->file = vmfile;
314	}
315	get_file(asma->file);
316
317	/*
318	 * XXX - Reworked to use shmem_zero_setup() instead of
319	 * shmem_set_file while we're in staging. -jstultz
320	 */
321	if (vma->vm_flags & VM_SHARED) {
322		ret = shmem_zero_setup(vma);
323		if (ret) {
324			fput(asma->file);
325			goto out;
326		}
327	}
328
329	if (vma->vm_file)
330		fput(vma->vm_file);
331	vma->vm_file = asma->file;
332	vma->vm_flags |= VM_CAN_NONLINEAR;
333
334out:
335	mutex_unlock(&ashmem_mutex);
336	return ret;
337}
338
339/*
340 * ashmem_shrink - our cache shrinker, called from mm/vmscan.c :: shrink_slab
341 *
342 * 'nr_to_scan' is the number of objects (pages) to prune, or 0 to query how
343 * many objects (pages) we have in total.
344 *
345 * 'gfp_mask' is the mask of the allocation that got us into this mess.
346 *
347 * Return value is the number of objects (pages) remaining, or -1 if we cannot
348 * proceed without risk of deadlock (due to gfp_mask).
349 *
350 * We approximate LRU via least-recently-unpinned, jettisoning unpinned partial
351 * chunks of ashmem regions LRU-wise one-at-a-time until we hit 'nr_to_scan'
352 * pages freed.
353 */
354static int ashmem_shrink(struct shrinker *s, struct shrink_control *sc)
355{
356	struct ashmem_range *range, *next;
357
358	/* We might recurse into filesystem code, so bail out if necessary */
359	if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS))
360		return -1;
361	if (!sc->nr_to_scan)
362		return lru_count;
363
364	mutex_lock(&ashmem_mutex);
365	list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) {
366		struct inode *inode = range->asma->file->f_dentry->d_inode;
367		loff_t start = range->pgstart * PAGE_SIZE;
368		loff_t end = (range->pgend + 1) * PAGE_SIZE - 1;
369
370		vmtruncate_range(inode, start, end);
371		range->purged = ASHMEM_WAS_PURGED;
372		lru_del(range);
373
374		sc->nr_to_scan -= range_size(range);
375		if (sc->nr_to_scan <= 0)
376			break;
377	}
378	mutex_unlock(&ashmem_mutex);
379
380	return lru_count;
381}
382
383static struct shrinker ashmem_shrinker = {
384	.shrink = ashmem_shrink,
385	.seeks = DEFAULT_SEEKS * 4,
386};
387
388static int set_prot_mask(struct ashmem_area *asma, unsigned long prot)
389{
390	int ret = 0;
391
392	mutex_lock(&ashmem_mutex);
393
394	/* the user can only remove, not add, protection bits */
395	if (unlikely((asma->prot_mask & prot) != prot)) {
396		ret = -EINVAL;
397		goto out;
398	}
399
400	/* does the application expect PROT_READ to imply PROT_EXEC? */
401	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
402		prot |= PROT_EXEC;
403
404	asma->prot_mask = prot;
405
406out:
407	mutex_unlock(&ashmem_mutex);
408	return ret;
409}
410
411static int set_name(struct ashmem_area *asma, void __user *name)
412{
413	int ret = 0;
414
415	mutex_lock(&ashmem_mutex);
416
417	/* cannot change an existing mapping's name */
418	if (unlikely(asma->file)) {
419		ret = -EINVAL;
420		goto out;
421	}
422
423	if (unlikely(copy_from_user(asma->name + ASHMEM_NAME_PREFIX_LEN,
424				    name, ASHMEM_NAME_LEN)))
425		ret = -EFAULT;
426	asma->name[ASHMEM_FULL_NAME_LEN-1] = '\0';
427
428out:
429	mutex_unlock(&ashmem_mutex);
430
431	return ret;
432}
433
434static int get_name(struct ashmem_area *asma, void __user *name)
435{
436	int ret = 0;
437
438	mutex_lock(&ashmem_mutex);
439	if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') {
440		size_t len;
441
442		/*
443		 * Copying only `len', instead of ASHMEM_NAME_LEN, bytes
444		 * prevents us from revealing one user's stack to another.
445		 */
446		len = strlen(asma->name + ASHMEM_NAME_PREFIX_LEN) + 1;
447		if (unlikely(copy_to_user(name,
448				asma->name + ASHMEM_NAME_PREFIX_LEN, len)))
449			ret = -EFAULT;
450	} else {
451		if (unlikely(copy_to_user(name, ASHMEM_NAME_DEF,
452					  sizeof(ASHMEM_NAME_DEF))))
453			ret = -EFAULT;
454	}
455	mutex_unlock(&ashmem_mutex);
456
457	return ret;
458}
459
460/*
461 * ashmem_pin - pin the given ashmem region, returning whether it was
462 * previously purged (ASHMEM_WAS_PURGED) or not (ASHMEM_NOT_PURGED).
463 *
464 * Caller must hold ashmem_mutex.
465 */
466static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend)
467{
468	struct ashmem_range *range, *next;
469	int ret = ASHMEM_NOT_PURGED;
470
471	list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) {
472		/* moved past last applicable page; we can short circuit */
473		if (range_before_page(range, pgstart))
474			break;
475
476		/*
477		 * The user can ask us to pin pages that span multiple ranges,
478		 * or to pin pages that aren't even unpinned, so this is messy.
479		 *
480		 * Four cases:
481		 * 1. The requested range subsumes an existing range, so we
482		 *    just remove the entire matching range.
483		 * 2. The requested range overlaps the start of an existing
484		 *    range, so we just update that range.
485		 * 3. The requested range overlaps the end of an existing
486		 *    range, so we just update that range.
487		 * 4. The requested range punches a hole in an existing range,
488		 *    so we have to update one side of the range and then
489		 *    create a new range for the other side.
490		 */
491		if (page_range_in_range(range, pgstart, pgend)) {
492			ret |= range->purged;
493
494			/* Case #1: Easy. Just nuke the whole thing. */
495			if (page_range_subsumes_range(range, pgstart, pgend)) {
496				range_del(range);
497				continue;
498			}
499
500			/* Case #2: We overlap from the start, so adjust it */
501			if (range->pgstart >= pgstart) {
502				range_shrink(range, pgend + 1, range->pgend);
503				continue;
504			}
505
506			/* Case #3: We overlap from the rear, so adjust it */
507			if (range->pgend <= pgend) {
508				range_shrink(range, range->pgstart, pgstart-1);
509				continue;
510			}
511
512			/*
513			 * Case #4: We eat a chunk out of the middle. A bit
514			 * more complicated, we allocate a new range for the
515			 * second half and adjust the first chunk's endpoint.
516			 */
517			range_alloc(asma, range, range->purged,
518				    pgend + 1, range->pgend);
519			range_shrink(range, range->pgstart, pgstart - 1);
520			break;
521		}
522	}
523
524	return ret;
525}
526
527/*
528 * ashmem_unpin - unpin the given range of pages. Returns zero on success.
529 *
530 * Caller must hold ashmem_mutex.
531 */
532static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend)
533{
534	struct ashmem_range *range, *next;
535	unsigned int purged = ASHMEM_NOT_PURGED;
536
537restart:
538	list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) {
539		/* short circuit: this is our insertion point */
540		if (range_before_page(range, pgstart))
541			break;
542
543		/*
544		 * The user can ask us to unpin pages that are already entirely
545		 * or partially pinned. We handle those two cases here.
546		 */
547		if (page_range_subsumed_by_range(range, pgstart, pgend))
548			return 0;
549		if (page_range_in_range(range, pgstart, pgend)) {
550			pgstart = min_t(size_t, range->pgstart, pgstart),
551			pgend = max_t(size_t, range->pgend, pgend);
552			purged |= range->purged;
553			range_del(range);
554			goto restart;
555		}
556	}
557
558	return range_alloc(asma, range, purged, pgstart, pgend);
559}
560
561/*
562 * ashmem_get_pin_status - Returns ASHMEM_IS_UNPINNED if _any_ pages in the
563 * given interval are unpinned and ASHMEM_IS_PINNED otherwise.
564 *
565 * Caller must hold ashmem_mutex.
566 */
567static int ashmem_get_pin_status(struct ashmem_area *asma, size_t pgstart,
568				 size_t pgend)
569{
570	struct ashmem_range *range;
571	int ret = ASHMEM_IS_PINNED;
572
573	list_for_each_entry(range, &asma->unpinned_list, unpinned) {
574		if (range_before_page(range, pgstart))
575			break;
576		if (page_range_in_range(range, pgstart, pgend)) {
577			ret = ASHMEM_IS_UNPINNED;
578			break;
579		}
580	}
581
582	return ret;
583}
584
585static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd,
586			    void __user *p)
587{
588	struct ashmem_pin pin;
589	size_t pgstart, pgend;
590	int ret = -EINVAL;
591
592	if (unlikely(!asma->file))
593		return -EINVAL;
594
595	if (unlikely(copy_from_user(&pin, p, sizeof(pin))))
596		return -EFAULT;
597
598	/* per custom, you can pass zero for len to mean "everything onward" */
599	if (!pin.len)
600		pin.len = PAGE_ALIGN(asma->size) - pin.offset;
601
602	if (unlikely((pin.offset | pin.len) & ~PAGE_MASK))
603		return -EINVAL;
604
605	if (unlikely(((__u32) -1) - pin.offset < pin.len))
606		return -EINVAL;
607
608	if (unlikely(PAGE_ALIGN(asma->size) < pin.offset + pin.len))
609		return -EINVAL;
610
611	pgstart = pin.offset / PAGE_SIZE;
612	pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
613
614	mutex_lock(&ashmem_mutex);
615
616	switch (cmd) {
617	case ASHMEM_PIN:
618		ret = ashmem_pin(asma, pgstart, pgend);
619		break;
620	case ASHMEM_UNPIN:
621		ret = ashmem_unpin(asma, pgstart, pgend);
622		break;
623	case ASHMEM_GET_PIN_STATUS:
624		ret = ashmem_get_pin_status(asma, pgstart, pgend);
625		break;
626	}
627
628	mutex_unlock(&ashmem_mutex);
629
630	return ret;
631}
632
633static long ashmem_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
634{
635	struct ashmem_area *asma = file->private_data;
636	long ret = -ENOTTY;
637
638	switch (cmd) {
639	case ASHMEM_SET_NAME:
640		ret = set_name(asma, (void __user *) arg);
641		break;
642	case ASHMEM_GET_NAME:
643		ret = get_name(asma, (void __user *) arg);
644		break;
645	case ASHMEM_SET_SIZE:
646		ret = -EINVAL;
647		if (!asma->file) {
648			ret = 0;
649			asma->size = (size_t) arg;
650		}
651		break;
652	case ASHMEM_GET_SIZE:
653		ret = asma->size;
654		break;
655	case ASHMEM_SET_PROT_MASK:
656		ret = set_prot_mask(asma, arg);
657		break;
658	case ASHMEM_GET_PROT_MASK:
659		ret = asma->prot_mask;
660		break;
661	case ASHMEM_PIN:
662	case ASHMEM_UNPIN:
663	case ASHMEM_GET_PIN_STATUS:
664		ret = ashmem_pin_unpin(asma, cmd, (void __user *) arg);
665		break;
666	case ASHMEM_PURGE_ALL_CACHES:
667		ret = -EPERM;
668		if (capable(CAP_SYS_ADMIN)) {
669			struct shrink_control sc = {
670				.gfp_mask = GFP_KERNEL,
671				.nr_to_scan = 0,
672			};
673			ret = ashmem_shrink(&ashmem_shrinker, &sc);
674			sc.nr_to_scan = ret;
675			ashmem_shrink(&ashmem_shrinker, &sc);
676		}
677		break;
678	}
679
680	return ret;
681}
682
683static const struct file_operations ashmem_fops = {
684	.owner = THIS_MODULE,
685	.open = ashmem_open,
686	.release = ashmem_release,
687	.read = ashmem_read,
688	.llseek = ashmem_llseek,
689	.mmap = ashmem_mmap,
690	.unlocked_ioctl = ashmem_ioctl,
691	.compat_ioctl = ashmem_ioctl,
692};
693
694static struct miscdevice ashmem_misc = {
695	.minor = MISC_DYNAMIC_MINOR,
696	.name = "ashmem",
697	.fops = &ashmem_fops,
698};
699
700static int __init ashmem_init(void)
701{
702	int ret;
703
704	ashmem_area_cachep = kmem_cache_create("ashmem_area_cache",
705					  sizeof(struct ashmem_area),
706					  0, 0, NULL);
707	if (unlikely(!ashmem_area_cachep)) {
708		printk(KERN_ERR "ashmem: failed to create slab cache\n");
709		return -ENOMEM;
710	}
711
712	ashmem_range_cachep = kmem_cache_create("ashmem_range_cache",
713					  sizeof(struct ashmem_range),
714					  0, 0, NULL);
715	if (unlikely(!ashmem_range_cachep)) {
716		printk(KERN_ERR "ashmem: failed to create slab cache\n");
717		return -ENOMEM;
718	}
719
720	ret = misc_register(&ashmem_misc);
721	if (unlikely(ret)) {
722		printk(KERN_ERR "ashmem: failed to register misc device!\n");
723		return ret;
724	}
725
726	register_shrinker(&ashmem_shrinker);
727
728	printk(KERN_INFO "ashmem: initialized\n");
729
730	return 0;
731}
732
733static void __exit ashmem_exit(void)
734{
735	int ret;
736
737	unregister_shrinker(&ashmem_shrinker);
738
739	ret = misc_deregister(&ashmem_misc);
740	if (unlikely(ret))
741		printk(KERN_ERR "ashmem: failed to unregister misc device!\n");
742
743	kmem_cache_destroy(ashmem_range_cachep);
744	kmem_cache_destroy(ashmem_area_cachep);
745
746	printk(KERN_INFO "ashmem: unloaded\n");
747}
748
749module_init(ashmem_init);
750module_exit(ashmem_exit);
751
752MODULE_LICENSE("GPL");
753