+++ /dev/null
-/* mm/ashmem.c
-**
-** Anonymous Shared Memory Subsystem, ashmem
-**
-** Copyright (C) 2008 Google, Inc.
-**
-** Robert Love <rlove@google.com>
-**
-** This software is licensed under the terms of the GNU General Public
-** License version 2, as published by the Free Software Foundation, and
-** may be copied, distributed, and modified under those terms.
-**
-** This program is distributed in the hope that it will be useful,
-** but WITHOUT ANY WARRANTY; without even the implied warranty of
-** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-** GNU General Public License for more details.
-*/
-
-#include <linux/module.h>
-#include <linux/file.h>
-#include <linux/fs.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 <linux/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)
-
-/*
- * ashmem_area - anonymous shared memory area
- * Lifecycle: From our parent file's open() until its release()
- * Locking: Protected by `ashmem_mutex'
- * Big Note: Mappings do NOT pin this structure; it dies on close()
- */
-struct ashmem_area {
- char name[ASHMEM_FULL_NAME_LEN];/* optional name for /proc/pid/maps */
- struct list_head unpinned_list; /* list of all ashmem areas */
- struct file *file; /* the shmem-based backing file */
- size_t size; /* size of the mapping, in bytes */
- unsigned long prot_mask; /* allowed prot bits, as vm_flags */
-};
-
-/*
- * ashmem_range - represents an interval of unpinned (evictable) pages
- * Lifecycle: From unpin to pin
- * Locking: Protected by `ashmem_mutex'
- */
-struct ashmem_range {
- struct list_head lru; /* entry in LRU list */
- struct list_head unpinned; /* entry in its area's unpinned list */
- struct ashmem_area *asma; /* associated area */
- size_t pgstart; /* starting page, inclusive */
- size_t pgend; /* ending page, inclusive */
- unsigned int purged; /* ASHMEM_NOT or ASHMEM_WAS_PURGED */
-};
-
-/* LRU list of unpinned pages, protected by ashmem_mutex */
-static LIST_HEAD(ashmem_lru_list);
-
-/* Count of pages on our LRU list, 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;
-
-#define range_size(range) \
- ((range)->pgend - (range)->pgstart + 1)
-
-#define range_on_lru(range) \
- ((range)->purged == ASHMEM_NOT_PURGED)
-
-#define page_range_subsumes_range(range, start, end) \
- (((range)->pgstart >= (start)) && ((range)->pgend <= (end)))
-
-#define page_range_subsumed_by_range(range, start, end) \
- (((range)->pgstart <= (start)) && ((range)->pgend >= (end)))
-
-#define page_in_range(range, page) \
- (((range)->pgstart <= (page)) && ((range)->pgend >= (page)))
-
-#define page_range_in_range(range, start, end) \
- (page_in_range(range, start) || page_in_range(range, end) || \
- page_range_subsumes_range(range, start, end))
-
-#define range_before_page(range, page) \
- ((range)->pgend < (page))
-
-#define PROT_MASK (PROT_EXEC | PROT_READ | PROT_WRITE)
-
-static inline void lru_add(struct ashmem_range *range)
-{
- list_add_tail(&range->lru, &ashmem_lru_list);
- lru_count += range_size(range);
-}
-
-static inline void lru_del(struct ashmem_range *range)
-{
- list_del(&range->lru);
- lru_count -= range_size(range);
-}
-
-/*
- * range_alloc - allocate and initialize a new ashmem_range structure
- *
- * 'asma' - associated ashmem_area
- * 'prev_range' - the previous ashmem_range in the sorted asma->unpinned list
- * 'purged' - initial purge value (ASMEM_NOT_PURGED or ASHMEM_WAS_PURGED)
- * 'start' - starting page, inclusive
- * 'end' - ending page, inclusive
- *
- * Caller must hold ashmem_mutex.
- */
-static int range_alloc(struct ashmem_area *asma,
- struct ashmem_range *prev_range, unsigned int purged,
- size_t start, size_t end)
-{
- struct ashmem_range *range;
-
- range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL);
- if (unlikely(!range))
- return -ENOMEM;
-
- 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);
-
- return 0;
-}
-
-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 a range
- *
- * Caller must hold ashmem_mutex.
- */
-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);
-}
-
-static int ashmem_open(struct inode *inode, struct file *file)
-{
- struct ashmem_area *asma;
- int ret;
-
- ret = nonseekable_open(inode, file);
- if (unlikely(ret))
- return ret;
-
- asma = kmem_cache_zalloc(ashmem_area_cachep, GFP_KERNEL);
- if (unlikely(!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;
-}
-
-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 int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
-{
- struct ashmem_area *asma = file->private_data;
- int ret = 0;
-
- mutex_lock(&ashmem_mutex);
-
- /* user needs to SET_SIZE before mapping */
- if (unlikely(!asma->size)) {
- ret = -EINVAL;
- goto out;
- }
-
- /* requested protection bits must match our allowed protection mask */
- if (unlikely((vma->vm_flags & ~asma->prot_mask) & PROT_MASK)) {
- ret = -EPERM;
- goto out;
- }
-
- if (!asma->file) {
- char *name = ASHMEM_NAME_DEF;
- struct file *vmfile;
-
- 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 (unlikely(IS_ERR(vmfile))) {
- ret = PTR_ERR(vmfile);
- goto out;
- }
- asma->file = vmfile;
- }
- get_file(asma->file);
-
- if (vma->vm_flags & VM_SHARED)
- shmem_set_file(vma, asma->file);
- else {
- if (vma->vm_file)
- fput(vma->vm_file);
- vma->vm_file = asma->file;
- }
- vma->vm_flags |= VM_CAN_NONLINEAR;
-
-out:
- mutex_unlock(&ashmem_mutex);
- return ret;
-}
-
-/*
- * ashmem_shrink - our cache shrinker, called from mm/vmscan.c :: shrink_slab
- *
- * 'nr_to_scan' is the number of objects (pages) to prune, or 0 to query how
- * many objects (pages) we have in total.
- *
- * 'gfp_mask' is the mask of the allocation that got us into this mess.
- *
- * Return value is the number of objects (pages) remaining, 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 int ashmem_shrink(int nr_to_scan, gfp_t gfp_mask)
-{
- struct ashmem_range *range, *next;
-
- /* We might recurse into filesystem code, so bail out if necessary */
- if (nr_to_scan && !(gfp_mask & __GFP_FS))
- return -1;
- if (!nr_to_scan)
- return lru_count;
-
- mutex_lock(&ashmem_mutex);
- list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) {
- struct inode *inode = range->asma->file->f_dentry->d_inode;
- loff_t start = range->pgstart * PAGE_SIZE;
- loff_t end = (range->pgend + 1) * PAGE_SIZE - 1;
-
- vmtruncate_range(inode, start, end);
- range->purged = ASHMEM_WAS_PURGED;
- lru_del(range);
-
- nr_to_scan -= range_size(range);
- if (nr_to_scan <= 0)
- break;
- }
- mutex_unlock(&ashmem_mutex);
-
- return lru_count;
-}
-
-static struct shrinker ashmem_shrinker = {
- .shrink = ashmem_shrink,
- .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 (unlikely((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 ret = 0;
-
- mutex_lock(&ashmem_mutex);
-
- /* cannot change an existing mapping's name */
- if (unlikely(asma->file)) {
- ret = -EINVAL;
- goto out;
- }
-
- if (unlikely(copy_from_user(asma->name + ASHMEM_NAME_PREFIX_LEN,
- name, ASHMEM_NAME_LEN)))
- ret = -EFAULT;
- asma->name[ASHMEM_FULL_NAME_LEN-1] = '\0';
-
-out:
- mutex_unlock(&ashmem_mutex);
-
- return ret;
-}
-
-static int get_name(struct ashmem_area *asma, void __user *name)
-{
- int ret = 0;
-
- mutex_lock(&ashmem_mutex);
- if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') {
- size_t len;
-
- /*
- * 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;
- if (unlikely(copy_to_user(name,
- asma->name + ASHMEM_NAME_PREFIX_LEN, len)))
- ret = -EFAULT;
- } else {
- if (unlikely(copy_to_user(name, ASHMEM_NAME_DEF,
- sizeof(ASHMEM_NAME_DEF))))
- ret = -EFAULT;
- }
- mutex_unlock(&ashmem_mutex);
-
- 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 *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);
- 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 *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_t(size_t, range->pgstart, pgstart),
- pgend = max_t(size_t, range->pgend, pgend);
- purged |= range->purged;
- range_del(range);
- goto restart;
- }
- }
-
- return range_alloc(asma, range, purged, pgstart, pgend);
-}
-
-/*
- * 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;
-
- if (unlikely(!asma->file))
- return -EINVAL;
-
- if (unlikely(copy_from_user(&pin, p, sizeof(pin))))
- return -EFAULT;
-
- /* per custom, you can pass zero for len to mean "everything onward" */
- if (!pin.len)
- pin.len = PAGE_ALIGN(asma->size) - pin.offset;
-
- if (unlikely((pin.offset | pin.len) & ~PAGE_MASK))
- return -EINVAL;
-
- if (unlikely(((__u32) -1) - pin.offset < pin.len))
- return -EINVAL;
-
- if (unlikely(PAGE_ALIGN(asma->size) < pin.offset + pin.len))
- return -EINVAL;
-
- pgstart = pin.offset / PAGE_SIZE;
- pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
-
- mutex_lock(&ashmem_mutex);
-
- switch (cmd) {
- case ASHMEM_PIN:
- ret = ashmem_pin(asma, pgstart, pgend);
- break;
- case ASHMEM_UNPIN:
- ret = ashmem_unpin(asma, pgstart, pgend);
- break;
- case ASHMEM_GET_PIN_STATUS:
- ret = ashmem_get_pin_status(asma, pgstart, pgend);
- break;
- }
-
- mutex_unlock(&ashmem_mutex);
-
- 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;
- if (!asma->file) {
- ret = 0;
- asma->size = (size_t) arg;
- }
- 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)) {
- ret = ashmem_shrink(0, GFP_KERNEL);
- ashmem_shrink(ret, GFP_KERNEL);
- }
- break;
- }
-
- return ret;
-}
-
-static struct file_operations ashmem_fops = {
- .owner = THIS_MODULE,
- .open = ashmem_open,
- .release = ashmem_release,
- .mmap = ashmem_mmap,
- .unlocked_ioctl = ashmem_ioctl,
- .compat_ioctl = ashmem_ioctl,
-};
-
-static struct miscdevice ashmem_misc = {
- .minor = MISC_DYNAMIC_MINOR,
- .name = "ashmem",
- .fops = &ashmem_fops,
-};
-
-static int __init ashmem_init(void)
-{
- int ret;
-
- ashmem_area_cachep = kmem_cache_create("ashmem_area_cache",
- sizeof(struct ashmem_area),
- 0, 0, NULL);
- if (unlikely(!ashmem_area_cachep)) {
- printk(KERN_ERR "ashmem: failed to create slab cache\n");
- return -ENOMEM;
- }
-
- ashmem_range_cachep = kmem_cache_create("ashmem_range_cache",
- sizeof(struct ashmem_range),
- 0, 0, NULL);
- if (unlikely(!ashmem_range_cachep)) {
- printk(KERN_ERR "ashmem: failed to create slab cache\n");
- return -ENOMEM;
- }
-
- ret = misc_register(&ashmem_misc);
- if (unlikely(ret)) {
- printk(KERN_ERR "ashmem: failed to register misc device!\n");
- return ret;
- }
-
- register_shrinker(&ashmem_shrinker);
-
- printk(KERN_INFO "ashmem: initialized\n");
-
- return 0;
-}
-
-static void __exit ashmem_exit(void)
-{
- int ret;
-
- unregister_shrinker(&ashmem_shrinker);
-
- ret = misc_deregister(&ashmem_misc);
- if (unlikely(ret))
- printk(KERN_ERR "ashmem: failed to unregister misc device!\n");
-
- kmem_cache_destroy(ashmem_range_cachep);
- kmem_cache_destroy(ashmem_area_cachep);
-
- printk(KERN_INFO "ashmem: unloaded\n");
-}
-
-module_init(ashmem_init);
-module_exit(ashmem_exit);
-
-MODULE_LICENSE("GPL");
projects / firefly-linux-kernel-4.4.55.git / commitdiff