1// SPDX-License-Identifier: GPL-2.0
  2/* mm/ashmem.c
  3 *
  4 * Anonymous Shared Memory Subsystem, ashmem
  5 *
  6 * Copyright (C) 2008 Google, Inc.
  7 *
  8 * Robert Love <rlove@google.com>
  9 */
 10
 11#define pr_fmt(fmt) "ashmem: " fmt
 12
 13#include <linux/init.h>
 14#include <linux/export.h>
 15#include <linux/file.h>
 16#include <linux/fs.h>
 17#include <linux/falloc.h>
 18#include <linux/miscdevice.h>
 19#include <linux/security.h>
 20#include <linux/mm.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>
 27#include "ashmem.h"
 28
 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)
 32
 33/**
 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
 40 *
 41 * The lifecycle of this structure is from our parent file's open() until
 42 * its release(). It is also protected by 'ashmem_mutex'
 43 *
 44 * Warning: Mappings do NOT pin this structure; It dies on close()
 45 */
 46struct ashmem_area {
 47	char name[ASHMEM_FULL_NAME_LEN];
 48	struct list_head unpinned_list;
 49	struct file *file;
 50	size_t size;
 51	unsigned long prot_mask;
 52};
 53
 54/**
 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)
 62 *
 63 * The lifecycle of this structure is from unpin to pin.
 64 * It is protected by 'ashmem_mutex'
 65 */
 66struct ashmem_range {
 67	struct list_head lru;
 68	struct list_head unpinned;
 69	struct ashmem_area *asma;
 70	size_t pgstart;
 71	size_t pgend;
 72	unsigned int purged;
 73};
 74
 75/* LRU list of unpinned pages, protected by ashmem_mutex */
 76static LIST_HEAD(ashmem_lru_list);
 77
 78static atomic_t ashmem_shrink_inflight = ATOMIC_INIT(0);
 79static DECLARE_WAIT_QUEUE_HEAD(ashmem_shrink_wait);
 80
 81/*
 82 * long lru_count - The count of pages on our LRU list.
 83 *
 84 * This is protected by ashmem_mutex.
 85 */
 86static unsigned long lru_count;
 87
 88/*
 89 * ashmem_mutex - protects the list of and each individual ashmem_area
 90 *
 91 * Lock Ordering: ashmex_mutex -> i_mutex -> i_alloc_sem
 92 */
 93static DEFINE_MUTEX(ashmem_mutex);
 94
 95static struct kmem_cache *ashmem_area_cachep __read_mostly;
 96static struct kmem_cache *ashmem_range_cachep __read_mostly;
 97
 98/*
 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.
104 */
105static struct lock_class_key backing_shmem_inode_class;
106
107static inline unsigned long range_size(struct ashmem_range *range)
108{
109	return range->pgend - range->pgstart + 1;
110}
111
112static inline bool range_on_lru(struct ashmem_range *range)
113{
114	return range->purged == ASHMEM_NOT_PURGED;
115}
116
117static inline bool page_range_subsumes_range(struct ashmem_range *range,
118					     size_t start, size_t end)
119{
120	return (range->pgstart >= start) && (range->pgend <= end);
121}
122
123static inline bool page_range_subsumed_by_range(struct ashmem_range *range,
124						size_t start, size_t end)
125{
126	return (range->pgstart <= start) && (range->pgend >= end);
127}
128
129static inline bool page_in_range(struct ashmem_range *range, size_t page)
130{
131	return (range->pgstart <= page) && (range->pgend >= page);
132}
133
134static inline bool page_range_in_range(struct ashmem_range *range,
135				       size_t start, size_t end)
136{
137	return page_in_range(range, start) || page_in_range(range, end) ||
138		page_range_subsumes_range(range, start, end);
139}
140
141static inline bool range_before_page(struct ashmem_range *range,
142				     size_t page)
143{
144	return range->pgend < page;
145}
146
147#define PROT_MASK		(PROT_EXEC | PROT_READ | PROT_WRITE)
148
149/**
150 * lru_add() - Adds a range of memory to the LRU list
151 * @range:     The memory range being added.
152 *
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
155 */
156static inline void lru_add(struct ashmem_range *range)
157{
158	list_add_tail(&range->lru, &ashmem_lru_list);
159	lru_count += range_size(range);
160}
161
162/**
163 * lru_del() - Removes a range of memory from the LRU list
164 * @range:     The memory range being removed
165 *
166 * The range is first deleted from the LRU list.
167 * After this, the size of the range is removed from @lru_count
168 */
169static inline void lru_del(struct ashmem_range *range)
170{
171	list_del(&range->lru);
172	lru_count -= range_size(range);
173}
174
175/**
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 *
183 * This function is protected by ashmem_mutex.
184 */
185static void range_alloc(struct ashmem_area *asma,
186			struct ashmem_range *prev_range, unsigned int purged,
187			size_t start, size_t end,
188			struct ashmem_range **new_range)
189{
190	struct ashmem_range *range = *new_range;
191
192	*new_range = NULL;
193	range->asma = asma;
194	range->pgstart = start;
195	range->pgend = end;
196	range->purged = purged;
197
198	list_add_tail(&range->unpinned, &prev_range->unpinned);
199
200	if (range_on_lru(range))
201		lru_add(range);
202}
203
204/**
205 * range_del() - Deletes and deallocates an ashmem_range structure
206 * @range:	 The associated ashmem_range that has previously been allocated
207 */
208static void range_del(struct ashmem_range *range)
209{
210	list_del(&range->unpinned);
211	if (range_on_lru(range))
212		lru_del(range);
213	kmem_cache_free(ashmem_range_cachep, range);
214}
215
216/**
217 * range_shrink() - Shrinks an ashmem_range
218 * @range:	    The associated ashmem_range being shrunk
219 * @start:	    The starting byte of the new range
220 * @end:	    The ending byte of the new range
221 *
222 * This does not modify the data inside the existing range in any way - It
223 * simply shrinks the boundaries of the range.
224 *
225 * Theoretically, with a little tweaking, this could eventually be changed
226 * to range_resize, and expand the lru_count if the new range is larger.
227 */
228static inline void range_shrink(struct ashmem_range *range,
229				size_t start, size_t end)
230{
231	size_t pre = range_size(range);
232
233	range->pgstart = start;
234	range->pgend = end;
235
236	if (range_on_lru(range))
237		lru_count -= pre - range_size(range);
238}
239
240/**
241 * ashmem_open() - Opens an Anonymous Shared Memory structure
242 * @inode:	   The backing file's index node(?)
243 * @file:	   The backing file
244 *
245 * Please note that the ashmem_area is not returned by this function - It is
246 * instead written to "file->private_data".
247 *
248 * Return: 0 if successful, or another code if unsuccessful.
249 */
250static int ashmem_open(struct inode *inode, struct file *file)
251{
252	struct ashmem_area *asma;
253	int ret;
254
255	ret = generic_file_open(inode, file);
256	if (ret)
257		return ret;
258
259	asma = kmem_cache_zalloc(ashmem_area_cachep, GFP_KERNEL);
260	if (!asma)
261		return -ENOMEM;
262
263	INIT_LIST_HEAD(&asma->unpinned_list);
264	memcpy(asma->name, ASHMEM_NAME_PREFIX, ASHMEM_NAME_PREFIX_LEN);
265	asma->prot_mask = PROT_MASK;
266	file->private_data = asma;
267
268	return 0;
269}
270
271/**
272 * ashmem_release() - Releases an Anonymous Shared Memory structure
273 * @ignored:	      The backing file's Index Node(?) - It is ignored here.
274 * @file:	      The backing file
275 *
276 * Return: 0 if successful. If it is anything else, go have a coffee and
277 * try again.
278 */
279static int ashmem_release(struct inode *ignored, struct file *file)
280{
281	struct ashmem_area *asma = file->private_data;
282	struct ashmem_range *range, *next;
283
284	mutex_lock(&ashmem_mutex);
285	list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned)
286		range_del(range);
287	mutex_unlock(&ashmem_mutex);
288
289	if (asma->file)
290		fput(asma->file);
291	kmem_cache_free(ashmem_area_cachep, asma);
292
293	return 0;
294}
295
296static ssize_t ashmem_read_iter(struct kiocb *iocb, struct iov_iter *iter)
297{
298	struct ashmem_area *asma = iocb->ki_filp->private_data;
299	int ret = 0;
300
301	mutex_lock(&ashmem_mutex);
302
303	/* If size is not set, or set to 0, always return EOF. */
304	if (asma->size == 0)
305		goto out_unlock;
306
307	if (!asma->file) {
308		ret = -EBADF;
309		goto out_unlock;
310	}
311
312	/*
313	 * asma and asma->file are used outside the lock here.  We assume
314	 * once asma->file is set it will never be changed, and will not
315	 * be destroyed until all references to the file are dropped and
316	 * ashmem_release is called.
317	 */
318	mutex_unlock(&ashmem_mutex);
319	ret = vfs_iter_read(asma->file, iter, &iocb->ki_pos, 0);
320	mutex_lock(&ashmem_mutex);
321	if (ret > 0)
322		asma->file->f_pos = iocb->ki_pos;
323out_unlock:
324	mutex_unlock(&ashmem_mutex);
325	return ret;
326}
327
328static loff_t ashmem_llseek(struct file *file, loff_t offset, int origin)
329{
330	struct ashmem_area *asma = file->private_data;
331	loff_t ret;
332
333	mutex_lock(&ashmem_mutex);
334
335	if (asma->size == 0) {
336		mutex_unlock(&ashmem_mutex);
337		return -EINVAL;
338	}
339
340	if (!asma->file) {
341		mutex_unlock(&ashmem_mutex);
342		return -EBADF;
343	}
344
345	mutex_unlock(&ashmem_mutex);
346
347	ret = vfs_llseek(asma->file, offset, origin);
348	if (ret < 0)
349		return ret;
350
351	/** Copy f_pos from backing file, since f_ops->llseek() sets it */
352	file->f_pos = asma->file->f_pos;
353	return ret;
354}
355
356static inline vm_flags_t calc_vm_may_flags(unsigned long prot)
357{
358	return _calc_vm_trans(prot, PROT_READ,  VM_MAYREAD) |
359	       _calc_vm_trans(prot, PROT_WRITE, VM_MAYWRITE) |
360	       _calc_vm_trans(prot, PROT_EXEC,  VM_MAYEXEC);
361}
362
363static int ashmem_vmfile_mmap(struct file *file, struct vm_area_struct *vma)
364{
365	/* do not allow to mmap ashmem backing shmem file directly */
366	return -EPERM;
367}
368
369static unsigned long
370ashmem_vmfile_get_unmapped_area(struct file *file, unsigned long addr,
371				unsigned long len, unsigned long pgoff,
372				unsigned long flags)
373{
374	return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
375}
376
377static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
378{
379	static struct file_operations vmfile_fops;
380	struct ashmem_area *asma = file->private_data;
381	int ret = 0;
382
383	mutex_lock(&ashmem_mutex);
384
385	/* user needs to SET_SIZE before mapping */
386	if (!asma->size) {
387		ret = -EINVAL;
388		goto out;
389	}
390
391	/* requested mapping size larger than object size */
392	if (vma->vm_end - vma->vm_start > PAGE_ALIGN(asma->size)) {
393		ret = -EINVAL;
394		goto out;
395	}
396
397	/* requested protection bits must match our allowed protection mask */
398	if ((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask, 0)) &
399	    calc_vm_prot_bits(PROT_MASK, 0)) {
400		ret = -EPERM;
401		goto out;
402	}
403	vma->vm_flags &= ~calc_vm_may_flags(~asma->prot_mask);
404
405	if (!asma->file) {
406		char *name = ASHMEM_NAME_DEF;
407		struct file *vmfile;
408		struct inode *inode;
409
410		if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0')
411			name = asma->name;
412
413		/* ... and allocate the backing shmem file */
414		vmfile = shmem_file_setup(name, asma->size, vma->vm_flags);
415		if (IS_ERR(vmfile)) {
416			ret = PTR_ERR(vmfile);
417			goto out;
418		}
419		vmfile->f_mode |= FMODE_LSEEK;
420		inode = file_inode(vmfile);
421		lockdep_set_class(&inode->i_rwsem, &backing_shmem_inode_class);
422		asma->file = vmfile;
423		/*
424		 * override mmap operation of the vmfile so that it can't be
425		 * remapped which would lead to creation of a new vma with no
426		 * asma permission checks. Have to override get_unmapped_area
427		 * as well to prevent VM_BUG_ON check for f_ops modification.
428		 */
429		if (!vmfile_fops.mmap) {
430			vmfile_fops = *vmfile->f_op;
431			vmfile_fops.mmap = ashmem_vmfile_mmap;
432			vmfile_fops.get_unmapped_area =
433					ashmem_vmfile_get_unmapped_area;
434		}
435		vmfile->f_op = &vmfile_fops;
436	}
437	get_file(asma->file);
438
439	/*
440	 * XXX - Reworked to use shmem_zero_setup() instead of
441	 * shmem_set_file while we're in staging. -jstultz
442	 */
443	if (vma->vm_flags & VM_SHARED) {
444		ret = shmem_zero_setup(vma);
445		if (ret) {
446			fput(asma->file);
447			goto out;
448		}
449	} else {
450		vma_set_anonymous(vma);
451	}
452
453	if (vma->vm_file)
454		fput(vma->vm_file);
455	vma->vm_file = asma->file;
456
457out:
458	mutex_unlock(&ashmem_mutex);
459	return ret;
460}
461
462/*
463 * ashmem_shrink - our cache shrinker, called from mm/vmscan.c
464 *
465 * 'nr_to_scan' is the number of objects to scan for freeing.
466 *
467 * 'gfp_mask' is the mask of the allocation that got us into this mess.
468 *
469 * Return value is the number of objects freed or -1 if we cannot
470 * proceed without risk of deadlock (due to gfp_mask).
471 *
472 * We approximate LRU via least-recently-unpinned, jettisoning unpinned partial
473 * chunks of ashmem regions LRU-wise one-at-a-time until we hit 'nr_to_scan'
474 * pages freed.
475 */
476static unsigned long
477ashmem_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
478{
479	unsigned long freed = 0;
480
481	/* We might recurse into filesystem code, so bail out if necessary */
482	if (!(sc->gfp_mask & __GFP_FS))
483		return SHRINK_STOP;
484
485	if (!mutex_trylock(&ashmem_mutex))
486		return -1;
487
488	while (!list_empty(&ashmem_lru_list)) {
489		struct ashmem_range *range =
490			list_first_entry(&ashmem_lru_list, typeof(*range), lru);
491		loff_t start = range->pgstart * PAGE_SIZE;
492		loff_t end = (range->pgend + 1) * PAGE_SIZE;
493		struct file *f = range->asma->file;
494
495		get_file(f);
496		atomic_inc(&ashmem_shrink_inflight);
497		range->purged = ASHMEM_WAS_PURGED;
498		lru_del(range);
499
500		freed += range_size(range);
501		mutex_unlock(&ashmem_mutex);
502		f->f_op->fallocate(f,
503				   FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
504				   start, end - start);
505		fput(f);
506		if (atomic_dec_and_test(&ashmem_shrink_inflight))
507			wake_up_all(&ashmem_shrink_wait);
508		if (!mutex_trylock(&ashmem_mutex))
509			goto out;
510		if (--sc->nr_to_scan <= 0)
511			break;
512	}
513	mutex_unlock(&ashmem_mutex);
514out:
515	return freed;
516}
517
518static unsigned long
519ashmem_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
520{
521	/*
522	 * note that lru_count is count of pages on the lru, not a count of
523	 * objects on the list. This means the scan function needs to return the
524	 * number of pages freed, not the number of objects scanned.
525	 */
526	return lru_count;
527}
528
529static struct shrinker ashmem_shrinker = {
530	.count_objects = ashmem_shrink_count,
531	.scan_objects = ashmem_shrink_scan,
532	/*
533	 * XXX (dchinner): I wish people would comment on why they need on
534	 * significant changes to the default value here
535	 */
536	.seeks = DEFAULT_SEEKS * 4,
537};
538
539static int set_prot_mask(struct ashmem_area *asma, unsigned long prot)
540{
541	int ret = 0;
542
543	mutex_lock(&ashmem_mutex);
544
545	/* the user can only remove, not add, protection bits */
546	if ((asma->prot_mask & prot) != prot) {
547		ret = -EINVAL;
548		goto out;
549	}
550
551	/* does the application expect PROT_READ to imply PROT_EXEC? */
552	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
553		prot |= PROT_EXEC;
554
555	asma->prot_mask = prot;
556
557out:
558	mutex_unlock(&ashmem_mutex);
559	return ret;
560}
561
562static int set_name(struct ashmem_area *asma, void __user *name)
563{
564	int len;
565	int ret = 0;
566	char local_name[ASHMEM_NAME_LEN];
567
568	/*
569	 * Holding the ashmem_mutex while doing a copy_from_user might cause
570	 * an data abort which would try to access mmap_lock. If another
571	 * thread has invoked ashmem_mmap then it will be holding the
572	 * semaphore and will be waiting for ashmem_mutex, there by leading to
573	 * deadlock. We'll release the mutex and take the name to a local
574	 * variable that does not need protection and later copy the local
575	 * variable to the structure member with lock held.
576	 */
577	len = strncpy_from_user(local_name, name, ASHMEM_NAME_LEN);
578	if (len < 0)
579		return len;
580
 
581	mutex_lock(&ashmem_mutex);
582	/* cannot change an existing mapping's name */
583	if (asma->file)
584		ret = -EINVAL;
585	else
586		strscpy(asma->name + ASHMEM_NAME_PREFIX_LEN, local_name,
587			ASHMEM_NAME_LEN);
588
589	mutex_unlock(&ashmem_mutex);
590	return ret;
591}
592
593static int get_name(struct ashmem_area *asma, void __user *name)
594{
595	int ret = 0;
596	size_t len;
597	/*
598	 * Have a local variable to which we'll copy the content
599	 * from asma with the lock held. Later we can copy this to the user
600	 * space safely without holding any locks. So even if we proceed to
601	 * wait for mmap_lock, it won't lead to deadlock.
602	 */
603	char local_name[ASHMEM_NAME_LEN];
604
605	mutex_lock(&ashmem_mutex);
606	if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') {
607		/*
608		 * Copying only `len', instead of ASHMEM_NAME_LEN, bytes
609		 * prevents us from revealing one user's stack to another.
610		 */
611		len = strlen(asma->name + ASHMEM_NAME_PREFIX_LEN) + 1;
612		memcpy(local_name, asma->name + ASHMEM_NAME_PREFIX_LEN, len);
613	} else {
614		len = sizeof(ASHMEM_NAME_DEF);
615		memcpy(local_name, ASHMEM_NAME_DEF, len);
616	}
617	mutex_unlock(&ashmem_mutex);
618
619	/*
620	 * Now we are just copying from the stack variable to userland
621	 * No lock held
622	 */
623	if (copy_to_user(name, local_name, len))
624		ret = -EFAULT;
625	return ret;
626}
627
628/*
629 * ashmem_pin - pin the given ashmem region, returning whether it was
630 * previously purged (ASHMEM_WAS_PURGED) or not (ASHMEM_NOT_PURGED).
631 *
632 * Caller must hold ashmem_mutex.
633 */
634static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend,
635		      struct ashmem_range **new_range)
636{
637	struct ashmem_range *range, *next;
638	int ret = ASHMEM_NOT_PURGED;
639
640	list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) {
641		/* moved past last applicable page; we can short circuit */
642		if (range_before_page(range, pgstart))
643			break;
644
645		/*
646		 * The user can ask us to pin pages that span multiple ranges,
647		 * or to pin pages that aren't even unpinned, so this is messy.
648		 *
649		 * Four cases:
650		 * 1. The requested range subsumes an existing range, so we
651		 *    just remove the entire matching range.
652		 * 2. The requested range overlaps the start of an existing
653		 *    range, so we just update that range.
654		 * 3. The requested range overlaps the end of an existing
655		 *    range, so we just update that range.
656		 * 4. The requested range punches a hole in an existing range,
657		 *    so we have to update one side of the range and then
658		 *    create a new range for the other side.
659		 */
660		if (page_range_in_range(range, pgstart, pgend)) {
661			ret |= range->purged;
662
663			/* Case #1: Easy. Just nuke the whole thing. */
664			if (page_range_subsumes_range(range, pgstart, pgend)) {
665				range_del(range);
666				continue;
667			}
668
669			/* Case #2: We overlap from the start, so adjust it */
670			if (range->pgstart >= pgstart) {
671				range_shrink(range, pgend + 1, range->pgend);
672				continue;
673			}
674
675			/* Case #3: We overlap from the rear, so adjust it */
676			if (range->pgend <= pgend) {
677				range_shrink(range, range->pgstart,
678					     pgstart - 1);
679				continue;
680			}
681
682			/*
683			 * Case #4: We eat a chunk out of the middle. A bit
684			 * more complicated, we allocate a new range for the
685			 * second half and adjust the first chunk's endpoint.
686			 */
687			range_alloc(asma, range, range->purged,
688				    pgend + 1, range->pgend, new_range);
689			range_shrink(range, range->pgstart, pgstart - 1);
690			break;
691		}
692	}
693
694	return ret;
695}
696
697/*
698 * ashmem_unpin - unpin the given range of pages. Returns zero on success.
699 *
700 * Caller must hold ashmem_mutex.
701 */
702static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend,
703			struct ashmem_range **new_range)
704{
705	struct ashmem_range *range, *next;
706	unsigned int purged = ASHMEM_NOT_PURGED;
707
708restart:
709	list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) {
710		/* short circuit: this is our insertion point */
711		if (range_before_page(range, pgstart))
712			break;
713
714		/*
715		 * The user can ask us to unpin pages that are already entirely
716		 * or partially pinned. We handle those two cases here.
717		 */
718		if (page_range_subsumed_by_range(range, pgstart, pgend))
719			return 0;
720		if (page_range_in_range(range, pgstart, pgend)) {
721			pgstart = min(range->pgstart, pgstart);
722			pgend = max(range->pgend, pgend);
723			purged |= range->purged;
724			range_del(range);
725			goto restart;
726		}
727	}
728
729	range_alloc(asma, range, purged, pgstart, pgend, new_range);
730	return 0;
731}
732
733/*
734 * ashmem_get_pin_status - Returns ASHMEM_IS_UNPINNED if _any_ pages in the
735 * given interval are unpinned and ASHMEM_IS_PINNED otherwise.
736 *
737 * Caller must hold ashmem_mutex.
738 */
739static int ashmem_get_pin_status(struct ashmem_area *asma, size_t pgstart,
740				 size_t pgend)
741{
742	struct ashmem_range *range;
743	int ret = ASHMEM_IS_PINNED;
744
745	list_for_each_entry(range, &asma->unpinned_list, unpinned) {
746		if (range_before_page(range, pgstart))
747			break;
748		if (page_range_in_range(range, pgstart, pgend)) {
749			ret = ASHMEM_IS_UNPINNED;
750			break;
751		}
752	}
753
754	return ret;
755}
756
757static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd,
758			    void __user *p)
759{
760	struct ashmem_pin pin;
761	size_t pgstart, pgend;
762	int ret = -EINVAL;
763	struct ashmem_range *range = NULL;
764
765	if (copy_from_user(&pin, p, sizeof(pin)))
766		return -EFAULT;
767
768	if (cmd == ASHMEM_PIN || cmd == ASHMEM_UNPIN) {
769		range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL);
770		if (!range)
771			return -ENOMEM;
772	}
773
774	mutex_lock(&ashmem_mutex);
775	wait_event(ashmem_shrink_wait, !atomic_read(&ashmem_shrink_inflight));
776
777	if (!asma->file)
778		goto out_unlock;
779
780	/* per custom, you can pass zero for len to mean "everything onward" */
781	if (!pin.len)
782		pin.len = PAGE_ALIGN(asma->size) - pin.offset;
783
784	if ((pin.offset | pin.len) & ~PAGE_MASK)
785		goto out_unlock;
786
787	if (((__u32)-1) - pin.offset < pin.len)
788		goto out_unlock;
789
790	if (PAGE_ALIGN(asma->size) < pin.offset + pin.len)
791		goto out_unlock;
792
793	pgstart = pin.offset / PAGE_SIZE;
794	pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
795
796	switch (cmd) {
797	case ASHMEM_PIN:
798		ret = ashmem_pin(asma, pgstart, pgend, &range);
799		break;
800	case ASHMEM_UNPIN:
801		ret = ashmem_unpin(asma, pgstart, pgend, &range);
802		break;
803	case ASHMEM_GET_PIN_STATUS:
804		ret = ashmem_get_pin_status(asma, pgstart, pgend);
805		break;
806	}
807
808out_unlock:
809	mutex_unlock(&ashmem_mutex);
810	if (range)
811		kmem_cache_free(ashmem_range_cachep, range);
812
813	return ret;
814}
815
816static long ashmem_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
817{
818	struct ashmem_area *asma = file->private_data;
819	long ret = -ENOTTY;
820
821	switch (cmd) {
822	case ASHMEM_SET_NAME:
823		ret = set_name(asma, (void __user *)arg);
824		break;
825	case ASHMEM_GET_NAME:
826		ret = get_name(asma, (void __user *)arg);
827		break;
828	case ASHMEM_SET_SIZE:
829		ret = -EINVAL;
830		mutex_lock(&ashmem_mutex);
831		if (!asma->file) {
832			ret = 0;
833			asma->size = (size_t)arg;
834		}
835		mutex_unlock(&ashmem_mutex);
836		break;
837	case ASHMEM_GET_SIZE:
838		ret = asma->size;
839		break;
840	case ASHMEM_SET_PROT_MASK:
841		ret = set_prot_mask(asma, arg);
842		break;
843	case ASHMEM_GET_PROT_MASK:
844		ret = asma->prot_mask;
845		break;
846	case ASHMEM_PIN:
847	case ASHMEM_UNPIN:
848	case ASHMEM_GET_PIN_STATUS:
849		ret = ashmem_pin_unpin(asma, cmd, (void __user *)arg);
850		break;
851	case ASHMEM_PURGE_ALL_CACHES:
852		ret = -EPERM;
853		if (capable(CAP_SYS_ADMIN)) {
854			struct shrink_control sc = {
855				.gfp_mask = GFP_KERNEL,
856				.nr_to_scan = LONG_MAX,
857			};
858			ret = ashmem_shrink_count(&ashmem_shrinker, &sc);
859			ashmem_shrink_scan(&ashmem_shrinker, &sc);
860		}
861		break;
862	}
863
864	return ret;
865}
866
867/* support of 32bit userspace on 64bit platforms */
868#ifdef CONFIG_COMPAT
869static long compat_ashmem_ioctl(struct file *file, unsigned int cmd,
870				unsigned long arg)
871{
872	switch (cmd) {
873	case COMPAT_ASHMEM_SET_SIZE:
874		cmd = ASHMEM_SET_SIZE;
875		break;
876	case COMPAT_ASHMEM_SET_PROT_MASK:
877		cmd = ASHMEM_SET_PROT_MASK;
878		break;
879	}
880	return ashmem_ioctl(file, cmd, arg);
881}
882#endif
883#ifdef CONFIG_PROC_FS
884static void ashmem_show_fdinfo(struct seq_file *m, struct file *file)
885{
886	struct ashmem_area *asma = file->private_data;
887
888	mutex_lock(&ashmem_mutex);
889
890	if (asma->file)
891		seq_printf(m, "inode:\t%ld\n", file_inode(asma->file)->i_ino);
892
893	if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0')
894		seq_printf(m, "name:\t%s\n",
895			   asma->name + ASHMEM_NAME_PREFIX_LEN);
896
897	mutex_unlock(&ashmem_mutex);
898}
899#endif
900static const struct file_operations ashmem_fops = {
901	.owner = THIS_MODULE,
902	.open = ashmem_open,
903	.release = ashmem_release,
904	.read_iter = ashmem_read_iter,
905	.llseek = ashmem_llseek,
906	.mmap = ashmem_mmap,
907	.unlocked_ioctl = ashmem_ioctl,
908#ifdef CONFIG_COMPAT
909	.compat_ioctl = compat_ashmem_ioctl,
910#endif
911#ifdef CONFIG_PROC_FS
912	.show_fdinfo = ashmem_show_fdinfo,
913#endif
914};
915
916static struct miscdevice ashmem_misc = {
917	.minor = MISC_DYNAMIC_MINOR,
918	.name = "ashmem",
919	.fops = &ashmem_fops,
920};
921
922static int __init ashmem_init(void)
923{
924	int ret = -ENOMEM;
925
926	ashmem_area_cachep = kmem_cache_create("ashmem_area_cache",
927					       sizeof(struct ashmem_area),
928					       0, 0, NULL);
929	if (!ashmem_area_cachep) {
930		pr_err("failed to create slab cache\n");
931		goto out;
932	}
933
934	ashmem_range_cachep = kmem_cache_create("ashmem_range_cache",
935						sizeof(struct ashmem_range),
936						0, 0, NULL);
937	if (!ashmem_range_cachep) {
938		pr_err("failed to create slab cache\n");
939		goto out_free1;
940	}
941
942	ret = misc_register(&ashmem_misc);
943	if (ret) {
944		pr_err("failed to register misc device!\n");
945		goto out_free2;
946	}
947
948	ret = register_shrinker(&ashmem_shrinker);
949	if (ret) {
950		pr_err("failed to register shrinker!\n");
951		goto out_demisc;
952	}
953
954	pr_info("initialized\n");
955
956	return 0;
957
958out_demisc:
959	misc_deregister(&ashmem_misc);
960out_free2:
961	kmem_cache_destroy(ashmem_range_cachep);
962out_free1:
963	kmem_cache_destroy(ashmem_area_cachep);
964out:
965	return ret;
966}
967device_initcall(ashmem_init);