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ashmem: Rewrite to improve clarity and performance

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Ashmem uses a single big mutex lock for all synchronization, and even
uses it when no synchronization issues are present. The contention from
using a single lock results in all-around poor performance.

Rewrite to use fine-grained locks and atomic constructions to eliminate
the big mutex lock, thereby improving performance greatly. In places
where locks are needed for a one-time operation, we speculatively
check if locking is needed while avoiding data races. The optional name
fields are removed as well.

Note that because asma->unpinned_list never has anything added to it,
we can remove any code using it to clean up the driver a lot and
reduce synchronization requirements. This also means that
ashmem_lru_list never gets anything added to it either, so all code
using it is dead code as well, which we can remove.

Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
Signed-off-by: Forenche <prahul2003@gmail.com>
This commit is contained in:
Sultan Alsawaf 2021-01-29 20:38:03 -08:00 committed by Forenche
parent 0e95de7e0a
commit 1431d9de00
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GPG Key ID: 1337D655BAFE85E2
1 changed files with 113 additions and 666 deletions
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759
drivers/staging/android/ashmem.c
View File

@ -1,243 +1,40 @@
/* mm/ashmem.c
*
* Anonymous Shared Memory Subsystem, ashmem
*
// SPDX-License-Identifier: GPL-2.0
/*
* 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.
* Copyright (C) 2021 Sultan Alsawaf <sultan@kerneltoast.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
* @mmap_lock: The mmap mutex lock
* @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'
* its release().
*
* 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 mutex mmap_lock;
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;
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.
*
* 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(?)
@ -257,13 +54,15 @@ static int ashmem_open(struct inode *inode, struct file *file)
if (unlikely(ret))
return ret;
asma = kmem_cache_zalloc(ashmem_area_cachep, GFP_KERNEL);
asma = kmem_cache_alloc(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;
*asma = (typeof(*asma)){
.mmap_lock = __MUTEX_INITIALIZER(asma->mmap_lock),
.prot_mask = PROT_MASK
};
file->private_data = asma;
return 0;
@ -280,12 +79,6 @@ static int ashmem_open(struct inode *inode, struct file *file)
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);
@ -297,18 +90,16 @@ static int ashmem_release(struct inode *ignored, struct file *file)
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);
struct file *vmfile;
ssize_t ret;
/* If size is not set, or set to 0, always return EOF. */
if (asma->size == 0)
goto out_unlock;
if (!READ_ONCE(asma->size))
return 0;
if (!asma->file) {
ret = -EBADF;
goto out_unlock;
}
vmfile = READ_ONCE(asma->file);
if (!vmfile)
return -EBADF;
/*
* asma and asma->file are used outside the lock here. We assume
@ -316,41 +107,31 @@ static ssize_t ashmem_read_iter(struct kiocb *iocb, struct iov_iter *iter)
* 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);
ret = vfs_iter_read(vmfile, iter, &iocb->ki_pos, 0);
if (ret > 0)
asma->file->f_pos = iocb->ki_pos;
out_unlock:
mutex_unlock(&ashmem_mutex);
vmfile->f_pos = iocb->ki_pos;
return ret;
}
static loff_t ashmem_llseek(struct file *file, loff_t offset, int origin)
{
struct ashmem_area *asma = file->private_data;
int ret;
struct file *vmfile;
loff_t ret;
mutex_lock(&ashmem_mutex);
if (asma->size == 0) {
mutex_unlock(&ashmem_mutex);
if (!READ_ONCE(asma->size))
return -EINVAL;
}
if (!asma->file) {
mutex_unlock(&ashmem_mutex);
vmfile = READ_ONCE(asma->file);
if (!vmfile)
return -EBADF;
}
mutex_unlock(&ashmem_mutex);
ret = vfs_llseek(asma->file, offset, origin);
ret = vfs_llseek(vmfile, 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;
file->f_pos = vmfile->f_pos;
return ret;
}
@ -375,457 +156,134 @@ ashmem_vmfile_get_unmapped_area(struct file *file, unsigned long addr,
return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
}
static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
static int ashmem_file_setup(struct ashmem_area *asma, size_t size,
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 (unlikely(!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 (unlikely((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;
static DEFINE_SPINLOCK(vmfile_fops_lock);
struct file *vmfile;
if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0')
name = asma->name;
vmfile = shmem_file_setup(ASHMEM_NAME_DEF, size, vma->vm_flags);
if (IS_ERR(vmfile))
return PTR_ERR(vmfile);
/* ... 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;
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 (!READ_ONCE(vmfile_fops.mmap)) {
spin_lock(&vmfile_fops_lock);
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;
WRITE_ONCE(vmfile_fops.mmap, ashmem_vmfile_mmap);
}
spin_unlock(&vmfile_fops_lock);
}
vmfile->f_op = &vmfile_fops;
vmfile->f_mode |= FMODE_LSEEK;
WRITE_ONCE(asma->file, vmfile);
return 0;
}
static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
{
struct ashmem_area *asma = file->private_data;
unsigned long prot_mask;
size_t size;
/* user needs to SET_SIZE before mapping */
size = READ_ONCE(asma->size);
if (unlikely(!size))
return -EINVAL;
/* requested mapping size larger than object size */
if (vma->vm_end - vma->vm_start > PAGE_ALIGN(size))
return -EINVAL;
/* requested protection bits must match our allowed protection mask */
prot_mask = READ_ONCE(asma->prot_mask);
if (unlikely((vma->vm_flags & ~calc_vm_prot_bits(prot_mask, 0)) &
calc_vm_prot_bits(PROT_MASK, 0)))
return -EPERM;
vma->vm_flags &= ~calc_vm_may_flags(~prot_mask);
if (!READ_ONCE(asma->file)) {
int ret = 0;
mutex_lock(&asma->mmap_lock);
if (!asma->file)
ret = ashmem_file_setup(asma, size, vma);
mutex_unlock(&asma->mmap_lock);
if (ret)
return ret;
}
get_file(asma->file);
if (vma->vm_flags & VM_SHARED)
if (vma->vm_flags & VM_SHARED) {
shmem_set_file(vma, asma->file);
else {
} else {
if (vma->vm_file)
fput(vma->vm_file);
vma->vm_file = asma->file;
}
out:
mutex_unlock(&ashmem_mutex);
return ret;
return 0;
}
/*
* 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;
if (!mutex_trylock(&ashmem_mutex))
return -1;
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;
range->asma->file->f_op->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;
}
if (unlikely((READ_ONCE(asma->prot_mask) & prot) != prot))
return -EINVAL;
/* 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))
WRITE_ONCE(asma->prot_mask, prot);
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;
}
}
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(copy_from_user(&pin, p, sizeof(pin))))
return -EFAULT;
mutex_lock(&ashmem_mutex);
if (unlikely(!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 (unlikely((pin.offset | pin.len) & ~PAGE_MASK))
goto out_unlock;
if (unlikely(((__u32)-1) - pin.offset < pin.len))
goto out_unlock;
if (unlikely(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);
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;
}
out_unlock:
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;
return 0;
case ASHMEM_GET_NAME:
ret = get_name(asma, (void __user *)arg);
break;
return 0;
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;
if (READ_ONCE(asma->file))
return -EINVAL;
WRITE_ONCE(asma->size, (size_t)arg);
return 0;
case ASHMEM_GET_SIZE:
ret = asma->size;
break;
return READ_ONCE(asma->size);
case ASHMEM_SET_PROT_MASK:
ret = set_prot_mask(asma, arg);
break;
return set_prot_mask(asma, arg);
case ASHMEM_GET_PROT_MASK:
ret = asma->prot_mask;
break;
return READ_ONCE(asma->prot_mask);
case ASHMEM_PIN:
return 0;
case ASHMEM_UNPIN:
return 0;
case ASHMEM_GET_PIN_STATUS:
ret = ashmem_pin_unpin(asma, cmd, (void __user *)arg);
break;
return ASHMEM_IS_PINNED;
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 capable(CAP_SYS_ADMIN) ? 0 : -EPERM;
}
return ret;
return -ENOTTY;
}
/* support of 32bit userspace on 64bit platforms */
@ -866,38 +324,27 @@ static struct miscdevice ashmem_misc = {
static int __init ashmem_init(void)
{
int ret = -ENOMEM;
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");
ret = -ENOMEM;
goto out;
}
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");
goto out_free1;
}
ret = misc_register(&ashmem_misc);
if (unlikely(ret)) {
pr_err("failed to register misc device!\n");
goto out_free2;
goto out_free1;
}
register_shrinker(&ashmem_shrinker);
pr_info("initialized\n");
return 0;
out_free2:
kmem_cache_destroy(ashmem_range_cachep);
out_free1:
kmem_cache_destroy(ashmem_area_cachep);
out: