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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);