Initial import

1 files changed, 883 insertions, 0 deletions

diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
new file mode 100644
index 000000000..82effc8b4
--- /dev/null
+++ b/drivers/staging/android/ashmem.c
@@ -0,0 +1,883 @@
+/* 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.
+ */
+
+#define pr_fmt(fmt) "ashmem: " fmt
+
+#include <linux/module.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_masks:		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);
+
+/**
+ * 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;
+
+#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)
+
+/**
+ * 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.
+ *
+ * Return: 0 if successful, or -ENOMEM if there is an error
+ */
+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;
+}
+
+/**
+ * range_del() - Deletes and dealloctes 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 (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;
+}
+
+/**
+ * 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;
+}
+
+/**
+ * ashmem_read() - Reads a set of bytes from an Ashmem-enabled file
+ * @file:	   The associated backing file.
+ * @buf:	   The buffer of data being written to
+ * @len:	   The number of bytes being read
+ * @pos:	   The position of the first byte to read.
+ *
+ * Return: 0 if successful, or another return code if not.
+ */
+static ssize_t ashmem_read(struct file *file, char __user *buf,
+			   size_t len, loff_t *pos)
+{
+	struct ashmem_area *asma = file->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;
+	}
+
+	mutex_unlock(&ashmem_mutex);
+
+	/*
+	 * 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.
+	 */
+	ret = __vfs_read(asma->file, buf, len, pos);
+	if (ret >= 0) {
+		/** Update backing file pos, since f_ops->read() doesn't */
+		asma->file->f_pos = *pos;
+	}
+	return ret;
+
+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;
+	int ret;
+
+	mutex_lock(&ashmem_mutex);
+
+	if (asma->size == 0) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (!asma->file) {
+		ret = -EBADF;
+		goto out;
+	}
+
+	ret = vfs_llseek(asma->file, offset, origin);
+	if (ret < 0)
+		goto out;
+
+	/** Copy f_pos from backing file, since f_ops->llseek() sets it */
+	file->f_pos = asma->file->f_pos;
+
+out:
+	mutex_unlock(&ashmem_mutex);
+	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_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 & ~calc_vm_prot_bits(asma->prot_mask)) &
+		     calc_vm_prot_bits(PROT_MASK))) {
+		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;
+
+		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, 0);
+		if (unlikely(IS_ERR(vmfile))) {
+			ret = PTR_ERR(vmfile);
+			goto out;
+		}
+		asma->file = vmfile;
+	}
+	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;
+		}
+	}
+
+	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)
+{
+	struct ashmem_range *range, *next;
+	unsigned long freed = 0;
+
+	/* We might recurse into filesystem code, so bail out if necessary */
+	if (!(sc->gfp_mask & __GFP_FS))
+		return SHRINK_STOP;
+
+	mutex_lock(&ashmem_mutex);
+	list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) {
+		loff_t start = range->pgstart * PAGE_SIZE;
+		loff_t end = (range->pgend + 1) * PAGE_SIZE;
+
+		vfs_fallocate(range->asma->file,
+			      FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+			      start, end - start);
+		range->purged = ASHMEM_WAS_PURGED;
+		lru_del(range);
+
+		freed += range_size(range);
+		if (--sc->nr_to_scan <= 0)
+			break;
+	}
+	mutex_unlock(&ashmem_mutex);
+	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 (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 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 (unlikely(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 (unlikely(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 *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)) {
+			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
+
+static const struct file_operations ashmem_fops = {
+	.owner = THIS_MODULE,
+	.open = ashmem_open,
+	.release = ashmem_release,
+	.read = ashmem_read,
+	.llseek = ashmem_llseek,
+	.mmap = ashmem_mmap,
+	.unlocked_ioctl = ashmem_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = compat_ashmem_ioctl,
+#endif
+};
+
+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)) {
+		pr_err("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)) {
+		pr_err("failed to create slab cache\n");
+		return -ENOMEM;
+	}
+
+	ret = misc_register(&ashmem_misc);
+	if (unlikely(ret)) {
+		pr_err("failed to register misc device!\n");
+		return ret;
+	}
+
+	register_shrinker(&ashmem_shrinker);
+
+	pr_info("initialized\n");
+
+	return 0;
+}
+
+static void __exit ashmem_exit(void)
+{
+	int ret;
+
+	unregister_shrinker(&ashmem_shrinker);
+
+	ret = misc_deregister(&ashmem_misc);
+	if (unlikely(ret))
+		pr_err("failed to unregister misc device!\n");
+
+	kmem_cache_destroy(ashmem_range_cachep);
+	kmem_cache_destroy(ashmem_area_cachep);
+
+	pr_info("unloaded\n");
+}
+
+module_init(ashmem_init);
+module_exit(ashmem_exit);
+
+MODULE_LICENSE("GPL");