| // SPDX-License-Identifier: GPL-2.0 |
| /* mm/ashmem.c |
| * |
| * Anonymous Shared Memory Subsystem, ashmem |
| * |
| * Copyright (C) 2008 Google, Inc. |
| * |
| * Robert Love <rlove@google.com> |
| */ |
| |
| #define pr_fmt(fmt) "ashmem: " fmt |
| |
| #include <linux/init.h> |
| #include <linux/export.h> |
| #include <linux/file.h> |
| #include <linux/fs.h> |
| #include <linux/falloc.h> |
| #include <linux/miscdevice.h> |
| #include <linux/security.h> |
| #include <linux/mm.h> |
| #include <linux/mman.h> |
| #include <linux/uaccess.h> |
| #include <linux/personality.h> |
| #include <linux/bitops.h> |
| #include <linux/mutex.h> |
| #include <linux/shmem_fs.h> |
| #include "ashmem.h" |
| |
| #define ASHMEM_NAME_PREFIX "dev/ashmem/" |
| #define ASHMEM_NAME_PREFIX_LEN (sizeof(ASHMEM_NAME_PREFIX) - 1) |
| #define ASHMEM_FULL_NAME_LEN (ASHMEM_NAME_LEN + ASHMEM_NAME_PREFIX_LEN) |
| |
| /** |
| * struct ashmem_area - The anonymous shared memory area |
| * @name: The optional name in /proc/pid/maps |
| * @unpinned_list: The list of all ashmem areas |
| * @file: The shmem-based backing file |
| * @size: The size of the mapping, in bytes |
| * @prot_mask: The allowed protection bits, as vm_flags |
| * |
| * The lifecycle of this structure is from our parent file's open() until |
| * its release(). It is also protected by 'ashmem_mutex' |
| * |
| * Warning: Mappings do NOT pin this structure; It dies on close() |
| */ |
| struct ashmem_area { |
| char name[ASHMEM_FULL_NAME_LEN]; |
| struct list_head unpinned_list; |
| struct file *file; |
| size_t size; |
| unsigned long prot_mask; |
| }; |
| |
| /** |
| * struct ashmem_range - A range of unpinned/evictable pages |
| * @lru: The entry in the LRU list |
| * @unpinned: The entry in its area's unpinned list |
| * @asma: The associated anonymous shared memory area. |
| * @pgstart: The starting page (inclusive) |
| * @pgend: The ending page (inclusive) |
| * @purged: The purge status (ASHMEM_NOT or ASHMEM_WAS_PURGED) |
| * |
| * The lifecycle of this structure is from unpin to pin. |
| * It is protected by 'ashmem_mutex' |
| */ |
| struct ashmem_range { |
| struct list_head lru; |
| struct list_head unpinned; |
| struct ashmem_area *asma; |
| size_t pgstart; |
| size_t pgend; |
| unsigned int purged; |
| }; |
| |
| /* LRU list of unpinned pages, protected by ashmem_mutex */ |
| static LIST_HEAD(ashmem_lru_list); |
| |
| static atomic_t ashmem_shrink_inflight = ATOMIC_INIT(0); |
| static DECLARE_WAIT_QUEUE_HEAD(ashmem_shrink_wait); |
| |
| /* |
| * long lru_count - The count of pages on our LRU list. |
| * |
| * This is protected by ashmem_mutex. |
| */ |
| static unsigned long lru_count; |
| |
| /* |
| * ashmem_mutex - protects the list of and each individual ashmem_area |
| * |
| * Lock Ordering: ashmex_mutex -> i_mutex -> i_alloc_sem |
| */ |
| static DEFINE_MUTEX(ashmem_mutex); |
| |
| static struct kmem_cache *ashmem_area_cachep __read_mostly; |
| static struct kmem_cache *ashmem_range_cachep __read_mostly; |
| |
| /* |
| * A separate lockdep class for the backing shmem inodes to resolve the lockdep |
| * warning about the race between kswapd taking fs_reclaim before inode_lock |
| * and write syscall taking inode_lock and then fs_reclaim. |
| * Note that such race is impossible because ashmem does not support write |
| * syscalls operating on the backing shmem. |
| */ |
| static struct lock_class_key backing_shmem_inode_class; |
| |
| static inline unsigned long range_size(struct ashmem_range *range) |
| { |
| return range->pgend - range->pgstart + 1; |
| } |
| |
| static inline bool range_on_lru(struct ashmem_range *range) |
| { |
| return range->purged == ASHMEM_NOT_PURGED; |
| } |
| |
| static inline bool page_range_subsumes_range(struct ashmem_range *range, |
| size_t start, size_t end) |
| { |
| return (range->pgstart >= start) && (range->pgend <= end); |
| } |
| |
| static inline bool page_range_subsumed_by_range(struct ashmem_range *range, |
| size_t start, size_t end) |
| { |
| return (range->pgstart <= start) && (range->pgend >= end); |
| } |
| |
| static inline bool page_in_range(struct ashmem_range *range, size_t page) |
| { |
| return (range->pgstart <= page) && (range->pgend >= page); |
| } |
| |
| static inline bool page_range_in_range(struct ashmem_range *range, |
| size_t start, size_t end) |
| { |
| return page_in_range(range, start) || page_in_range(range, end) || |
| page_range_subsumes_range(range, start, end); |
| } |
| |
| static inline bool range_before_page(struct ashmem_range *range, |
| size_t page) |
| { |
| return range->pgend < page; |
| } |
| |
| #define PROT_MASK (PROT_EXEC | PROT_READ | PROT_WRITE) |
| |
| /** |
| * lru_add() - Adds a range of memory to the LRU list |
| * @range: The memory range being added. |
| * |
| * The range is first added to the end (tail) of the LRU list. |
| * After this, the size of the range is added to @lru_count |
| */ |
| static inline void lru_add(struct ashmem_range *range) |
| { |
| list_add_tail(&range->lru, &ashmem_lru_list); |
| lru_count += range_size(range); |
| } |
| |
| /** |
| * lru_del() - Removes a range of memory from the LRU list |
| * @range: The memory range being removed |
| * |
| * The range is first deleted from the LRU list. |
| * After this, the size of the range is removed from @lru_count |
| */ |
| static inline void lru_del(struct ashmem_range *range) |
| { |
| list_del(&range->lru); |
| lru_count -= range_size(range); |
| } |
| |
| /** |
| * range_alloc() - Allocates and initializes a new ashmem_range structure |
| * @asma: The associated ashmem_area |
| * @prev_range: The previous ashmem_range in the sorted asma->unpinned list |
| * @purged: Initial purge status (ASMEM_NOT_PURGED or ASHMEM_WAS_PURGED) |
| * @start: The starting page (inclusive) |
| * @end: The ending page (inclusive) |
| * |
| * This function is protected by ashmem_mutex. |
| */ |
| static void range_alloc(struct ashmem_area *asma, |
| struct ashmem_range *prev_range, unsigned int purged, |
| size_t start, size_t end, |
| struct ashmem_range **new_range) |
| { |
| struct ashmem_range *range = *new_range; |
| |
| *new_range = NULL; |
| range->asma = asma; |
| range->pgstart = start; |
| range->pgend = end; |
| range->purged = purged; |
| |
| list_add_tail(&range->unpinned, &prev_range->unpinned); |
| |
| if (range_on_lru(range)) |
| lru_add(range); |
| } |
| |
| /** |
| * range_del() - Deletes and deallocates an ashmem_range structure |
| * @range: The associated ashmem_range that has previously been allocated |
| */ |
| static void range_del(struct ashmem_range *range) |
| { |
| list_del(&range->unpinned); |
| if (range_on_lru(range)) |
| lru_del(range); |
| kmem_cache_free(ashmem_range_cachep, range); |
| } |
| |
| /** |
| * range_shrink() - Shrinks an ashmem_range |
| * @range: The associated ashmem_range being shrunk |
| * @start: The starting byte of the new range |
| * @end: The ending byte of the new range |
| * |
| * This does not modify the data inside the existing range in any way - It |
| * simply shrinks the boundaries of the range. |
| * |
| * Theoretically, with a little tweaking, this could eventually be changed |
| * to range_resize, and expand the lru_count if the new range is larger. |
| */ |
| static inline void range_shrink(struct ashmem_range *range, |
| size_t start, size_t end) |
| { |
| size_t pre = range_size(range); |
| |
| range->pgstart = start; |
| range->pgend = end; |
| |
| if (range_on_lru(range)) |
| lru_count -= pre - range_size(range); |
| } |
| |
| /** |
| * ashmem_open() - Opens an Anonymous Shared Memory structure |
| * @inode: The backing file's index node(?) |
| * @file: The backing file |
| * |
| * Please note that the ashmem_area is not returned by this function - It is |
| * instead written to "file->private_data". |
| * |
| * Return: 0 if successful, or another code if unsuccessful. |
| */ |
| static int ashmem_open(struct inode *inode, struct file *file) |
| { |
| struct ashmem_area *asma; |
| int ret; |
| |
| ret = generic_file_open(inode, file); |
| if (ret) |
| return ret; |
| |
| asma = kmem_cache_zalloc(ashmem_area_cachep, GFP_KERNEL); |
| if (!asma) |
| return -ENOMEM; |
| |
| INIT_LIST_HEAD(&asma->unpinned_list); |
| memcpy(asma->name, ASHMEM_NAME_PREFIX, ASHMEM_NAME_PREFIX_LEN); |
| asma->prot_mask = PROT_MASK; |
| file->private_data = asma; |
| |
| return 0; |
| } |
| |
| /** |
| * ashmem_release() - Releases an Anonymous Shared Memory structure |
| * @ignored: The backing file's Index Node(?) - It is ignored here. |
| * @file: The backing file |
| * |
| * Return: 0 if successful. If it is anything else, go have a coffee and |
| * try again. |
| */ |
| static int ashmem_release(struct inode *ignored, struct file *file) |
| { |
| struct ashmem_area *asma = file->private_data; |
| struct ashmem_range *range, *next; |
| |
| mutex_lock(&ashmem_mutex); |
| list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) |
| range_del(range); |
| mutex_unlock(&ashmem_mutex); |
| |
| if (asma->file) |
| fput(asma->file); |
| kmem_cache_free(ashmem_area_cachep, asma); |
| |
| return 0; |
| } |
| |
| static ssize_t ashmem_read_iter(struct kiocb *iocb, struct iov_iter *iter) |
| { |
| struct ashmem_area *asma = iocb->ki_filp->private_data; |
| int ret = 0; |
| |
| mutex_lock(&ashmem_mutex); |
| |
| /* If size is not set, or set to 0, always return EOF. */ |
| if (asma->size == 0) |
| goto out_unlock; |
| |
| if (!asma->file) { |
| ret = -EBADF; |
| goto out_unlock; |
| } |
| |
| /* |
| * asma and asma->file are used outside the lock here. We assume |
| * once asma->file is set it will never be changed, and will not |
| * be destroyed until all references to the file are dropped and |
| * ashmem_release is called. |
| */ |
| mutex_unlock(&ashmem_mutex); |
| ret = vfs_iter_read(asma->file, iter, &iocb->ki_pos, 0); |
| mutex_lock(&ashmem_mutex); |
| if (ret > 0) |
| asma->file->f_pos = iocb->ki_pos; |
| out_unlock: |
| mutex_unlock(&ashmem_mutex); |
| return ret; |
| } |
| |
| static loff_t ashmem_llseek(struct file *file, loff_t offset, int origin) |
| { |
| struct ashmem_area *asma = file->private_data; |
| loff_t ret; |
| |
| mutex_lock(&ashmem_mutex); |
| |
| if (asma->size == 0) { |
| mutex_unlock(&ashmem_mutex); |
| return -EINVAL; |
| } |
| |
| if (!asma->file) { |
| mutex_unlock(&ashmem_mutex); |
| return -EBADF; |
| } |
| |
| mutex_unlock(&ashmem_mutex); |
| |
| ret = vfs_llseek(asma->file, offset, origin); |
| if (ret < 0) |
| return ret; |
| |
| /** Copy f_pos from backing file, since f_ops->llseek() sets it */ |
| file->f_pos = asma->file->f_pos; |
| return ret; |
| } |
| |
| static inline vm_flags_t calc_vm_may_flags(unsigned long prot) |
| { |
| return _calc_vm_trans(prot, PROT_READ, VM_MAYREAD) | |
| _calc_vm_trans(prot, PROT_WRITE, VM_MAYWRITE) | |
| _calc_vm_trans(prot, PROT_EXEC, VM_MAYEXEC); |
| } |
| |
| static int ashmem_vmfile_mmap(struct file *file, struct vm_area_struct *vma) |
| { |
| /* do not allow to mmap ashmem backing shmem file directly */ |
| return -EPERM; |
| } |
| |
| static unsigned long |
| ashmem_vmfile_get_unmapped_area(struct file *file, unsigned long addr, |
| unsigned long len, unsigned long pgoff, |
| unsigned long flags) |
| { |
| return current->mm->get_unmapped_area(file, addr, len, pgoff, flags); |
| } |
| |
| static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) |
| { |
| static struct file_operations vmfile_fops; |
| struct ashmem_area *asma = file->private_data; |
| int ret = 0; |
| |
| mutex_lock(&ashmem_mutex); |
| |
| /* user needs to SET_SIZE before mapping */ |
| if (!asma->size) { |
| ret = -EINVAL; |
| goto out; |
| } |
| |
| /* requested mapping size larger than object size */ |
| if (vma->vm_end - vma->vm_start > PAGE_ALIGN(asma->size)) { |
| ret = -EINVAL; |
| goto out; |
| } |
| |
| /* requested protection bits must match our allowed protection mask */ |
| if ((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask, 0)) & |
| calc_vm_prot_bits(PROT_MASK, 0)) { |
| ret = -EPERM; |
| goto out; |
| } |
| vma->vm_flags &= ~calc_vm_may_flags(~asma->prot_mask); |
| |
| if (!asma->file) { |
| char *name = ASHMEM_NAME_DEF; |
| struct file *vmfile; |
| struct inode *inode; |
| |
| if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') |
| name = asma->name; |
| |
| /* ... and allocate the backing shmem file */ |
| vmfile = shmem_file_setup(name, asma->size, vma->vm_flags); |
| if (IS_ERR(vmfile)) { |
| ret = PTR_ERR(vmfile); |
| goto out; |
| } |
| vmfile->f_mode |= FMODE_LSEEK; |
| inode = file_inode(vmfile); |
| lockdep_set_class(&inode->i_rwsem, &backing_shmem_inode_class); |
| asma->file = vmfile; |
| /* |
| * override mmap operation of the vmfile so that it can't be |
| * remapped which would lead to creation of a new vma with no |
| * asma permission checks. Have to override get_unmapped_area |
| * as well to prevent VM_BUG_ON check for f_ops modification. |
| */ |
| if (!vmfile_fops.mmap) { |
| vmfile_fops = *vmfile->f_op; |
| vmfile_fops.mmap = ashmem_vmfile_mmap; |
| vmfile_fops.get_unmapped_area = |
| ashmem_vmfile_get_unmapped_area; |
| } |
| vmfile->f_op = &vmfile_fops; |
| } |
| get_file(asma->file); |
| |
| /* |
| * XXX - Reworked to use shmem_zero_setup() instead of |
| * shmem_set_file while we're in staging. -jstultz |
| */ |
| if (vma->vm_flags & VM_SHARED) { |
| ret = shmem_zero_setup(vma); |
| if (ret) { |
| fput(asma->file); |
| goto out; |
| } |
| } else { |
| vma_set_anonymous(vma); |
| } |
| |
| if (vma->vm_file) |
| fput(vma->vm_file); |
| vma->vm_file = asma->file; |
| |
| out: |
| mutex_unlock(&ashmem_mutex); |
| return ret; |
| } |
| |
| /* |
| * ashmem_shrink - our cache shrinker, called from mm/vmscan.c |
| * |
| * 'nr_to_scan' is the number of objects to scan for freeing. |
| * |
| * 'gfp_mask' is the mask of the allocation that got us into this mess. |
| * |
| * Return value is the number of objects freed or -1 if we cannot |
| * proceed without risk of deadlock (due to gfp_mask). |
| * |
| * We approximate LRU via least-recently-unpinned, jettisoning unpinned partial |
| * chunks of ashmem regions LRU-wise one-at-a-time until we hit 'nr_to_scan' |
| * pages freed. |
| */ |
| static unsigned long |
| ashmem_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) |
| { |
| unsigned long freed = 0; |
| |
| /* We might recurse into filesystem code, so bail out if necessary */ |
| if (!(sc->gfp_mask & __GFP_FS)) |
| return SHRINK_STOP; |
| |
| if (!mutex_trylock(&ashmem_mutex)) |
| return -1; |
| |
| while (!list_empty(&ashmem_lru_list)) { |
| struct ashmem_range *range = |
| list_first_entry(&ashmem_lru_list, typeof(*range), lru); |
| loff_t start = range->pgstart * PAGE_SIZE; |
| loff_t end = (range->pgend + 1) * PAGE_SIZE; |
| struct file *f = range->asma->file; |
| |
| get_file(f); |
| atomic_inc(&ashmem_shrink_inflight); |
| range->purged = ASHMEM_WAS_PURGED; |
| lru_del(range); |
| |
| freed += range_size(range); |
| mutex_unlock(&ashmem_mutex); |
| f->f_op->fallocate(f, |
| FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, |
| start, end - start); |
| fput(f); |
| if (atomic_dec_and_test(&ashmem_shrink_inflight)) |
| wake_up_all(&ashmem_shrink_wait); |
| if (!mutex_trylock(&ashmem_mutex)) |
| goto out; |
| if (--sc->nr_to_scan <= 0) |
| break; |
| } |
| mutex_unlock(&ashmem_mutex); |
| out: |
| return freed; |
| } |
| |
| static unsigned long |
| ashmem_shrink_count(struct shrinker *shrink, struct shrink_control *sc) |
| { |
| /* |
| * note that lru_count is count of pages on the lru, not a count of |
| * objects on the list. This means the scan function needs to return the |
| * number of pages freed, not the number of objects scanned. |
| */ |
| return lru_count; |
| } |
| |
| static struct shrinker ashmem_shrinker = { |
| .count_objects = ashmem_shrink_count, |
| .scan_objects = ashmem_shrink_scan, |
| /* |
| * XXX (dchinner): I wish people would comment on why they need on |
| * significant changes to the default value here |
| */ |
| .seeks = DEFAULT_SEEKS * 4, |
| }; |
| |
| static int set_prot_mask(struct ashmem_area *asma, unsigned long prot) |
| { |
| int ret = 0; |
| |
| mutex_lock(&ashmem_mutex); |
| |
| /* the user can only remove, not add, protection bits */ |
| if ((asma->prot_mask & prot) != prot) { |
| ret = -EINVAL; |
| goto out; |
| } |
| |
| /* does the application expect PROT_READ to imply PROT_EXEC? */ |
| if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) |
| prot |= PROT_EXEC; |
| |
| asma->prot_mask = prot; |
| |
| out: |
| mutex_unlock(&ashmem_mutex); |
| return ret; |
| } |
| |
| static int set_name(struct ashmem_area *asma, void __user *name) |
| { |
| int len; |
| int ret = 0; |
| char local_name[ASHMEM_NAME_LEN]; |
| |
| /* |
| * Holding the ashmem_mutex while doing a copy_from_user might cause |
| * an data abort which would try to access mmap_sem. If another |
| * thread has invoked ashmem_mmap then it will be holding the |
| * semaphore and will be waiting for ashmem_mutex, there by leading to |
| * deadlock. We'll release the mutex and take the name to a local |
| * variable that does not need protection and later copy the local |
| * variable to the structure member with lock held. |
| */ |
| len = strncpy_from_user(local_name, name, ASHMEM_NAME_LEN); |
| if (len < 0) |
| return len; |
| if (len == ASHMEM_NAME_LEN) |
| local_name[ASHMEM_NAME_LEN - 1] = '\0'; |
| mutex_lock(&ashmem_mutex); |
| /* cannot change an existing mapping's name */ |
| if (asma->file) |
| ret = -EINVAL; |
| else |
| strcpy(asma->name + ASHMEM_NAME_PREFIX_LEN, local_name); |
| |
| mutex_unlock(&ashmem_mutex); |
| return ret; |
| } |
| |
| static int get_name(struct ashmem_area *asma, void __user *name) |
| { |
| int ret = 0; |
| size_t len; |
| /* |
| * Have a local variable to which we'll copy the content |
| * from asma with the lock held. Later we can copy this to the user |
| * space safely without holding any locks. So even if we proceed to |
| * wait for mmap_sem, it won't lead to deadlock. |
| */ |
| char local_name[ASHMEM_NAME_LEN]; |
| |
| mutex_lock(&ashmem_mutex); |
| if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') { |
| /* |
| * Copying only `len', instead of ASHMEM_NAME_LEN, bytes |
| * prevents us from revealing one user's stack to another. |
| */ |
| len = strlen(asma->name + ASHMEM_NAME_PREFIX_LEN) + 1; |
| memcpy(local_name, asma->name + ASHMEM_NAME_PREFIX_LEN, len); |
| } else { |
| len = sizeof(ASHMEM_NAME_DEF); |
| memcpy(local_name, ASHMEM_NAME_DEF, len); |
| } |
| mutex_unlock(&ashmem_mutex); |
| |
| /* |
| * Now we are just copying from the stack variable to userland |
| * No lock held |
| */ |
| if (copy_to_user(name, local_name, len)) |
| ret = -EFAULT; |
| return ret; |
| } |
| |
| /* |
| * ashmem_pin - pin the given ashmem region, returning whether it was |
| * previously purged (ASHMEM_WAS_PURGED) or not (ASHMEM_NOT_PURGED). |
| * |
| * Caller must hold ashmem_mutex. |
| */ |
| static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend, |
| struct ashmem_range **new_range) |
| { |
| struct ashmem_range *range, *next; |
| int ret = ASHMEM_NOT_PURGED; |
| |
| list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) { |
| /* moved past last applicable page; we can short circuit */ |
| if (range_before_page(range, pgstart)) |
| break; |
| |
| /* |
| * The user can ask us to pin pages that span multiple ranges, |
| * or to pin pages that aren't even unpinned, so this is messy. |
| * |
| * Four cases: |
| * 1. The requested range subsumes an existing range, so we |
| * just remove the entire matching range. |
| * 2. The requested range overlaps the start of an existing |
| * range, so we just update that range. |
| * 3. The requested range overlaps the end of an existing |
| * range, so we just update that range. |
| * 4. The requested range punches a hole in an existing range, |
| * so we have to update one side of the range and then |
| * create a new range for the other side. |
| */ |
| if (page_range_in_range(range, pgstart, pgend)) { |
| ret |= range->purged; |
| |
| /* Case #1: Easy. Just nuke the whole thing. */ |
| if (page_range_subsumes_range(range, pgstart, pgend)) { |
| range_del(range); |
| continue; |
| } |
| |
| /* Case #2: We overlap from the start, so adjust it */ |
| if (range->pgstart >= pgstart) { |
| range_shrink(range, pgend + 1, range->pgend); |
| continue; |
| } |
| |
| /* Case #3: We overlap from the rear, so adjust it */ |
| if (range->pgend <= pgend) { |
| range_shrink(range, range->pgstart, |
| pgstart - 1); |
| continue; |
| } |
| |
| /* |
| * Case #4: We eat a chunk out of the middle. A bit |
| * more complicated, we allocate a new range for the |
| * second half and adjust the first chunk's endpoint. |
| */ |
| range_alloc(asma, range, range->purged, |
| pgend + 1, range->pgend, new_range); |
| range_shrink(range, range->pgstart, pgstart - 1); |
| break; |
| } |
| } |
| |
| return ret; |
| } |
| |
| /* |
| * ashmem_unpin - unpin the given range of pages. Returns zero on success. |
| * |
| * Caller must hold ashmem_mutex. |
| */ |
| static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend, |
| struct ashmem_range **new_range) |
| { |
| struct ashmem_range *range, *next; |
| unsigned int purged = ASHMEM_NOT_PURGED; |
| |
| restart: |
| list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) { |
| /* short circuit: this is our insertion point */ |
| if (range_before_page(range, pgstart)) |
| break; |
| |
| /* |
| * The user can ask us to unpin pages that are already entirely |
| * or partially pinned. We handle those two cases here. |
| */ |
| if (page_range_subsumed_by_range(range, pgstart, pgend)) |
| return 0; |
| if (page_range_in_range(range, pgstart, pgend)) { |
| pgstart = min(range->pgstart, pgstart); |
| pgend = max(range->pgend, pgend); |
| purged |= range->purged; |
| range_del(range); |
| goto restart; |
| } |
| } |
| |
| range_alloc(asma, range, purged, pgstart, pgend, new_range); |
| return 0; |
| } |
| |
| /* |
| * ashmem_get_pin_status - Returns ASHMEM_IS_UNPINNED if _any_ pages in the |
| * given interval are unpinned and ASHMEM_IS_PINNED otherwise. |
| * |
| * Caller must hold ashmem_mutex. |
| */ |
| static int ashmem_get_pin_status(struct ashmem_area *asma, size_t pgstart, |
| size_t pgend) |
| { |
| struct ashmem_range *range; |
| int ret = ASHMEM_IS_PINNED; |
| |
| list_for_each_entry(range, &asma->unpinned_list, unpinned) { |
| if (range_before_page(range, pgstart)) |
| break; |
| if (page_range_in_range(range, pgstart, pgend)) { |
| ret = ASHMEM_IS_UNPINNED; |
| break; |
| } |
| } |
| |
| return ret; |
| } |
| |
| static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, |
| void __user *p) |
| { |
| struct ashmem_pin pin; |
| size_t pgstart, pgend; |
| int ret = -EINVAL; |
| struct ashmem_range *range = NULL; |
| |
| if (copy_from_user(&pin, p, sizeof(pin))) |
| return -EFAULT; |
| |
| if (cmd == ASHMEM_PIN || cmd == ASHMEM_UNPIN) { |
| range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL); |
| if (!range) |
| return -ENOMEM; |
| } |
| |
| mutex_lock(&ashmem_mutex); |
| wait_event(ashmem_shrink_wait, !atomic_read(&ashmem_shrink_inflight)); |
| |
| if (!asma->file) |
| goto out_unlock; |
| |
| /* per custom, you can pass zero for len to mean "everything onward" */ |
| if (!pin.len) |
| pin.len = PAGE_ALIGN(asma->size) - pin.offset; |
| |
| if ((pin.offset | pin.len) & ~PAGE_MASK) |
| goto out_unlock; |
| |
| if (((__u32)-1) - pin.offset < pin.len) |
| goto out_unlock; |
| |
| if (PAGE_ALIGN(asma->size) < pin.offset + pin.len) |
| goto out_unlock; |
| |
| pgstart = pin.offset / PAGE_SIZE; |
| pgend = pgstart + (pin.len / PAGE_SIZE) - 1; |
| |
| switch (cmd) { |
| case ASHMEM_PIN: |
| ret = ashmem_pin(asma, pgstart, pgend, &range); |
| break; |
| case ASHMEM_UNPIN: |
| ret = ashmem_unpin(asma, pgstart, pgend, &range); |
| break; |
| case ASHMEM_GET_PIN_STATUS: |
| ret = ashmem_get_pin_status(asma, pgstart, pgend); |
| break; |
| } |
| |
| out_unlock: |
| mutex_unlock(&ashmem_mutex); |
| if (range) |
| kmem_cache_free(ashmem_range_cachep, range); |
| |
| return ret; |
| } |
| |
| static long ashmem_ioctl(struct file *file, unsigned int cmd, unsigned long arg) |
| { |
| struct ashmem_area *asma = file->private_data; |
| long ret = -ENOTTY; |
| |
| switch (cmd) { |
| case ASHMEM_SET_NAME: |
| ret = set_name(asma, (void __user *)arg); |
| break; |
| case ASHMEM_GET_NAME: |
| ret = get_name(asma, (void __user *)arg); |
| break; |
| case ASHMEM_SET_SIZE: |
| ret = -EINVAL; |
| mutex_lock(&ashmem_mutex); |
| if (!asma->file) { |
| ret = 0; |
| asma->size = (size_t)arg; |
| } |
| mutex_unlock(&ashmem_mutex); |
| break; |
| case ASHMEM_GET_SIZE: |
| ret = asma->size; |
| break; |
| case ASHMEM_SET_PROT_MASK: |
| ret = set_prot_mask(asma, arg); |
| break; |
| case ASHMEM_GET_PROT_MASK: |
| ret = asma->prot_mask; |
| break; |
| case ASHMEM_PIN: |
| case ASHMEM_UNPIN: |
| case ASHMEM_GET_PIN_STATUS: |
| ret = ashmem_pin_unpin(asma, cmd, (void __user *)arg); |
| break; |
| case ASHMEM_PURGE_ALL_CACHES: |
| ret = -EPERM; |
| if (capable(CAP_SYS_ADMIN)) { |
| struct shrink_control sc = { |
| .gfp_mask = GFP_KERNEL, |
| .nr_to_scan = LONG_MAX, |
| }; |
| ret = ashmem_shrink_count(&ashmem_shrinker, &sc); |
| ashmem_shrink_scan(&ashmem_shrinker, &sc); |
| } |
| break; |
| } |
| |
| return ret; |
| } |
| |
| /* support of 32bit userspace on 64bit platforms */ |
| #ifdef CONFIG_COMPAT |
| static long compat_ashmem_ioctl(struct file *file, unsigned int cmd, |
| unsigned long arg) |
| { |
| switch (cmd) { |
| case COMPAT_ASHMEM_SET_SIZE: |
| cmd = ASHMEM_SET_SIZE; |
| break; |
| case COMPAT_ASHMEM_SET_PROT_MASK: |
| cmd = ASHMEM_SET_PROT_MASK; |
| break; |
| } |
| return ashmem_ioctl(file, cmd, arg); |
| } |
| #endif |
| #ifdef CONFIG_PROC_FS |
| static void ashmem_show_fdinfo(struct seq_file *m, struct file *file) |
| { |
| struct ashmem_area *asma = file->private_data; |
| |
| mutex_lock(&ashmem_mutex); |
| |
| if (asma->file) |
| seq_printf(m, "inode:\t%ld\n", file_inode(asma->file)->i_ino); |
| |
| if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') |
| seq_printf(m, "name:\t%s\n", |
| asma->name + ASHMEM_NAME_PREFIX_LEN); |
| |
| mutex_unlock(&ashmem_mutex); |
| } |
| #endif |
| static const struct file_operations ashmem_fops = { |
| .owner = THIS_MODULE, |
| .open = ashmem_open, |
| .release = ashmem_release, |
| .read_iter = ashmem_read_iter, |
| .llseek = ashmem_llseek, |
| .mmap = ashmem_mmap, |
| .unlocked_ioctl = ashmem_ioctl, |
| #ifdef CONFIG_COMPAT |
| .compat_ioctl = compat_ashmem_ioctl, |
| #endif |
| #ifdef CONFIG_PROC_FS |
| .show_fdinfo = ashmem_show_fdinfo, |
| #endif |
| }; |
| |
| static struct miscdevice ashmem_misc = { |
| .minor = MISC_DYNAMIC_MINOR, |
| .name = "ashmem", |
| .fops = &ashmem_fops, |
| }; |
| |
| static int __init ashmem_init(void) |
| { |
| int ret = -ENOMEM; |
| |
| ashmem_area_cachep = kmem_cache_create("ashmem_area_cache", |
| sizeof(struct ashmem_area), |
| 0, 0, NULL); |
| if (!ashmem_area_cachep) { |
| pr_err("failed to create slab cache\n"); |
| goto out; |
| } |
| |
| ashmem_range_cachep = kmem_cache_create("ashmem_range_cache", |
| sizeof(struct ashmem_range), |
| 0, 0, NULL); |
| if (!ashmem_range_cachep) { |
| pr_err("failed to create slab cache\n"); |
| goto out_free1; |
| } |
| |
| ret = misc_register(&ashmem_misc); |
| if (ret) { |
| pr_err("failed to register misc device!\n"); |
| goto out_free2; |
| } |
| |
| ret = register_shrinker(&ashmem_shrinker); |
| if (ret) { |
| pr_err("failed to register shrinker!\n"); |
| goto out_demisc; |
| } |
| |
| pr_info("initialized\n"); |
| |
| return 0; |
| |
| out_demisc: |
| misc_deregister(&ashmem_misc); |
| out_free2: |
| kmem_cache_destroy(ashmem_range_cachep); |
| out_free1: |
| kmem_cache_destroy(ashmem_area_cachep); |
| out: |
| return ret; |
| } |
| device_initcall(ashmem_init); |