![Tracey Dent](/assets/img/avatar_default.png)
Minor cleanups that consist of removal of a whitespace and make file_operations const. Signed-off-by: Tracey Dent <tdent48227@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
753 lines
18 KiB
C
753 lines
18 KiB
C
/* mm/ashmem.c
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**
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** Anonymous Shared Memory Subsystem, ashmem
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**
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** Copyright (C) 2008 Google, Inc.
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**
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** Robert Love <rlove@google.com>
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**
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** This software is licensed under the terms of the GNU General Public
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** License version 2, as published by the Free Software Foundation, and
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** may be copied, distributed, and modified under those terms.
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**
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** This program is distributed in the hope that it will be useful,
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** but WITHOUT ANY WARRANTY; without even the implied warranty of
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** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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** GNU General Public License for more details.
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*/
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#include <linux/module.h>
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/miscdevice.h>
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#include <linux/security.h>
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#include <linux/mm.h>
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#include <linux/mman.h>
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#include <linux/uaccess.h>
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#include <linux/personality.h>
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#include <linux/bitops.h>
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#include <linux/mutex.h>
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#include <linux/shmem_fs.h>
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#include "ashmem.h"
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#define ASHMEM_NAME_PREFIX "dev/ashmem/"
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#define ASHMEM_NAME_PREFIX_LEN (sizeof(ASHMEM_NAME_PREFIX) - 1)
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#define ASHMEM_FULL_NAME_LEN (ASHMEM_NAME_LEN + ASHMEM_NAME_PREFIX_LEN)
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/*
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* ashmem_area - anonymous shared memory area
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* Lifecycle: From our parent file's open() until its release()
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* Locking: Protected by `ashmem_mutex'
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* Big Note: Mappings do NOT pin this structure; it dies on close()
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*/
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struct ashmem_area {
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char name[ASHMEM_FULL_NAME_LEN]; /* optional name in /proc/pid/maps */
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struct list_head unpinned_list; /* list of all ashmem areas */
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struct file *file; /* the shmem-based backing file */
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size_t size; /* size of the mapping, in bytes */
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unsigned long prot_mask; /* allowed prot bits, as vm_flags */
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};
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/*
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* ashmem_range - represents an interval of unpinned (evictable) pages
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* Lifecycle: From unpin to pin
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* Locking: Protected by `ashmem_mutex'
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*/
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struct ashmem_range {
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struct list_head lru; /* entry in LRU list */
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struct list_head unpinned; /* entry in its area's unpinned list */
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struct ashmem_area *asma; /* associated area */
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size_t pgstart; /* starting page, inclusive */
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size_t pgend; /* ending page, inclusive */
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unsigned int purged; /* ASHMEM_NOT or ASHMEM_WAS_PURGED */
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};
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/* LRU list of unpinned pages, protected by ashmem_mutex */
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static LIST_HEAD(ashmem_lru_list);
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/* Count of pages on our LRU list, protected by ashmem_mutex */
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static unsigned long lru_count;
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/*
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* ashmem_mutex - protects the list of and each individual ashmem_area
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*
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* Lock Ordering: ashmex_mutex -> i_mutex -> i_alloc_sem
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*/
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static DEFINE_MUTEX(ashmem_mutex);
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static struct kmem_cache *ashmem_area_cachep __read_mostly;
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static struct kmem_cache *ashmem_range_cachep __read_mostly;
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#define range_size(range) \
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((range)->pgend - (range)->pgstart + 1)
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#define range_on_lru(range) \
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((range)->purged == ASHMEM_NOT_PURGED)
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#define page_range_subsumes_range(range, start, end) \
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(((range)->pgstart >= (start)) && ((range)->pgend <= (end)))
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#define page_range_subsumed_by_range(range, start, end) \
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(((range)->pgstart <= (start)) && ((range)->pgend >= (end)))
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#define page_in_range(range, page) \
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(((range)->pgstart <= (page)) && ((range)->pgend >= (page)))
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#define page_range_in_range(range, start, end) \
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(page_in_range(range, start) || page_in_range(range, end) || \
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page_range_subsumes_range(range, start, end))
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#define range_before_page(range, page) \
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((range)->pgend < (page))
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#define PROT_MASK (PROT_EXEC | PROT_READ | PROT_WRITE)
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static inline void lru_add(struct ashmem_range *range)
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{
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list_add_tail(&range->lru, &ashmem_lru_list);
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lru_count += range_size(range);
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}
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static inline void lru_del(struct ashmem_range *range)
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{
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list_del(&range->lru);
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lru_count -= range_size(range);
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}
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/*
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* range_alloc - allocate and initialize a new ashmem_range structure
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*
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* 'asma' - associated ashmem_area
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* 'prev_range' - the previous ashmem_range in the sorted asma->unpinned list
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* 'purged' - initial purge value (ASMEM_NOT_PURGED or ASHMEM_WAS_PURGED)
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* 'start' - starting page, inclusive
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* 'end' - ending page, inclusive
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*
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* Caller must hold ashmem_mutex.
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*/
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static int range_alloc(struct ashmem_area *asma,
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struct ashmem_range *prev_range, unsigned int purged,
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size_t start, size_t end)
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{
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struct ashmem_range *range;
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range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL);
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if (unlikely(!range))
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return -ENOMEM;
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range->asma = asma;
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range->pgstart = start;
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range->pgend = end;
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range->purged = purged;
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list_add_tail(&range->unpinned, &prev_range->unpinned);
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if (range_on_lru(range))
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lru_add(range);
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return 0;
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}
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static void range_del(struct ashmem_range *range)
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{
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list_del(&range->unpinned);
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if (range_on_lru(range))
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lru_del(range);
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kmem_cache_free(ashmem_range_cachep, range);
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}
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/*
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* range_shrink - shrinks a range
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*
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* Caller must hold ashmem_mutex.
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*/
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static inline void range_shrink(struct ashmem_range *range,
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size_t start, size_t end)
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{
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size_t pre = range_size(range);
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range->pgstart = start;
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range->pgend = end;
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if (range_on_lru(range))
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lru_count -= pre - range_size(range);
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}
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static int ashmem_open(struct inode *inode, struct file *file)
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{
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struct ashmem_area *asma;
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int ret;
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ret = generic_file_open(inode, file);
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if (unlikely(ret))
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return ret;
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asma = kmem_cache_zalloc(ashmem_area_cachep, GFP_KERNEL);
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if (unlikely(!asma))
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return -ENOMEM;
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INIT_LIST_HEAD(&asma->unpinned_list);
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memcpy(asma->name, ASHMEM_NAME_PREFIX, ASHMEM_NAME_PREFIX_LEN);
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asma->prot_mask = PROT_MASK;
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file->private_data = asma;
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return 0;
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}
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static int ashmem_release(struct inode *ignored, struct file *file)
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{
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struct ashmem_area *asma = file->private_data;
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struct ashmem_range *range, *next;
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mutex_lock(&ashmem_mutex);
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list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned)
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range_del(range);
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mutex_unlock(&ashmem_mutex);
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if (asma->file)
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fput(asma->file);
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kmem_cache_free(ashmem_area_cachep, asma);
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return 0;
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}
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static ssize_t ashmem_read(struct file *file, char __user *buf,
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size_t len, loff_t *pos)
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{
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struct ashmem_area *asma = file->private_data;
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int ret = 0;
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mutex_lock(&ashmem_mutex);
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/* If size is not set, or set to 0, always return EOF. */
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if (asma->size == 0)
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goto out;
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if (!asma->file) {
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ret = -EBADF;
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goto out;
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}
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ret = asma->file->f_op->read(asma->file, buf, len, pos);
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if (ret < 0)
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goto out;
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/** Update backing file pos, since f_ops->read() doesn't */
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asma->file->f_pos = *pos;
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out:
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mutex_unlock(&ashmem_mutex);
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return ret;
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}
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static loff_t ashmem_llseek(struct file *file, loff_t offset, int origin)
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{
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struct ashmem_area *asma = file->private_data;
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int ret;
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mutex_lock(&ashmem_mutex);
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if (asma->size == 0) {
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ret = -EINVAL;
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goto out;
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}
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if (!asma->file) {
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ret = -EBADF;
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goto out;
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}
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ret = asma->file->f_op->llseek(asma->file, offset, origin);
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if (ret < 0)
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goto out;
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/** Copy f_pos from backing file, since f_ops->llseek() sets it */
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file->f_pos = asma->file->f_pos;
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out:
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mutex_unlock(&ashmem_mutex);
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return ret;
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}
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static inline unsigned long calc_vm_may_flags(unsigned long prot)
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{
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return _calc_vm_trans(prot, PROT_READ, VM_MAYREAD) |
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_calc_vm_trans(prot, PROT_WRITE, VM_MAYWRITE) |
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_calc_vm_trans(prot, PROT_EXEC, VM_MAYEXEC);
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}
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static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
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{
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struct ashmem_area *asma = file->private_data;
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int ret = 0;
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mutex_lock(&ashmem_mutex);
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/* user needs to SET_SIZE before mapping */
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if (unlikely(!asma->size)) {
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ret = -EINVAL;
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goto out;
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}
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/* requested protection bits must match our allowed protection mask */
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if (unlikely((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask)) &
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calc_vm_prot_bits(PROT_MASK))) {
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ret = -EPERM;
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goto out;
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}
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vma->vm_flags &= ~calc_vm_may_flags(~asma->prot_mask);
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if (!asma->file) {
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char *name = ASHMEM_NAME_DEF;
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struct file *vmfile;
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if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0')
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name = asma->name;
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/* ... and allocate the backing shmem file */
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vmfile = shmem_file_setup(name, asma->size, vma->vm_flags);
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if (unlikely(IS_ERR(vmfile))) {
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ret = PTR_ERR(vmfile);
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goto out;
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}
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asma->file = vmfile;
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}
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get_file(asma->file);
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/*
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* XXX - Reworked to use shmem_zero_setup() instead of
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* shmem_set_file while we're in staging. -jstultz
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*/
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if (vma->vm_flags & VM_SHARED) {
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ret = shmem_zero_setup(vma);
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if (ret) {
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fput(asma->file);
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goto out;
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}
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}
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if (vma->vm_file)
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fput(vma->vm_file);
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vma->vm_file = asma->file;
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vma->vm_flags |= VM_CAN_NONLINEAR;
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out:
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mutex_unlock(&ashmem_mutex);
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return ret;
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}
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/*
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* ashmem_shrink - our cache shrinker, called from mm/vmscan.c :: shrink_slab
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*
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* 'nr_to_scan' is the number of objects (pages) to prune, or 0 to query how
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* many objects (pages) we have in total.
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*
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* 'gfp_mask' is the mask of the allocation that got us into this mess.
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*
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* Return value is the number of objects (pages) remaining, or -1 if we cannot
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* proceed without risk of deadlock (due to gfp_mask).
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*
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* We approximate LRU via least-recently-unpinned, jettisoning unpinned partial
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* chunks of ashmem regions LRU-wise one-at-a-time until we hit 'nr_to_scan'
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* pages freed.
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*/
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static int ashmem_shrink(struct shrinker *s, struct shrink_control *sc)
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{
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struct ashmem_range *range, *next;
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/* We might recurse into filesystem code, so bail out if necessary */
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if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS))
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return -1;
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if (!sc->nr_to_scan)
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return lru_count;
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mutex_lock(&ashmem_mutex);
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list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) {
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struct inode *inode = range->asma->file->f_dentry->d_inode;
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loff_t start = range->pgstart * PAGE_SIZE;
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loff_t end = (range->pgend + 1) * PAGE_SIZE - 1;
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vmtruncate_range(inode, start, end);
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range->purged = ASHMEM_WAS_PURGED;
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lru_del(range);
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sc->nr_to_scan -= range_size(range);
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if (sc->nr_to_scan <= 0)
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break;
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}
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mutex_unlock(&ashmem_mutex);
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return lru_count;
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}
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static struct shrinker ashmem_shrinker = {
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.shrink = ashmem_shrink,
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.seeks = DEFAULT_SEEKS * 4,
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};
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static int set_prot_mask(struct ashmem_area *asma, unsigned long prot)
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{
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int ret = 0;
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mutex_lock(&ashmem_mutex);
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/* the user can only remove, not add, protection bits */
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if (unlikely((asma->prot_mask & prot) != prot)) {
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ret = -EINVAL;
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goto out;
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}
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/* does the application expect PROT_READ to imply PROT_EXEC? */
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if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
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prot |= PROT_EXEC;
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asma->prot_mask = prot;
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out:
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mutex_unlock(&ashmem_mutex);
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return ret;
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}
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static int set_name(struct ashmem_area *asma, void __user *name)
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{
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int ret = 0;
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mutex_lock(&ashmem_mutex);
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/* cannot change an existing mapping's name */
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if (unlikely(asma->file)) {
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ret = -EINVAL;
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goto out;
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}
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if (unlikely(copy_from_user(asma->name + ASHMEM_NAME_PREFIX_LEN,
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name, ASHMEM_NAME_LEN)))
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ret = -EFAULT;
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asma->name[ASHMEM_FULL_NAME_LEN-1] = '\0';
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out:
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mutex_unlock(&ashmem_mutex);
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return ret;
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}
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static int get_name(struct ashmem_area *asma, void __user *name)
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{
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int ret = 0;
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mutex_lock(&ashmem_mutex);
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if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') {
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size_t len;
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/*
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* Copying only `len', instead of ASHMEM_NAME_LEN, bytes
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* prevents us from revealing one user's stack to another.
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*/
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len = strlen(asma->name + ASHMEM_NAME_PREFIX_LEN) + 1;
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if (unlikely(copy_to_user(name,
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asma->name + ASHMEM_NAME_PREFIX_LEN, len)))
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ret = -EFAULT;
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} else {
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if (unlikely(copy_to_user(name, ASHMEM_NAME_DEF,
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sizeof(ASHMEM_NAME_DEF))))
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ret = -EFAULT;
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}
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mutex_unlock(&ashmem_mutex);
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return ret;
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}
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/*
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* ashmem_pin - pin the given ashmem region, returning whether it was
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* previously purged (ASHMEM_WAS_PURGED) or not (ASHMEM_NOT_PURGED).
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*
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* Caller must hold ashmem_mutex.
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*/
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static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend)
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{
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struct ashmem_range *range, *next;
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int ret = ASHMEM_NOT_PURGED;
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list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) {
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/* moved past last applicable page; we can short circuit */
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if (range_before_page(range, pgstart))
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break;
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/*
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* The user can ask us to pin pages that span multiple ranges,
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* or to pin pages that aren't even unpinned, so this is messy.
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*
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* Four cases:
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* 1. The requested range subsumes an existing range, so we
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* just remove the entire matching range.
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* 2. The requested range overlaps the start of an existing
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* range, so we just update that range.
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* 3. The requested range overlaps the end of an existing
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* range, so we just update that range.
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* 4. The requested range punches a hole in an existing range,
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* so we have to update one side of the range and then
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* create a new range for the other side.
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*/
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if (page_range_in_range(range, pgstart, pgend)) {
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ret |= range->purged;
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/* Case #1: Easy. Just nuke the whole thing. */
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if (page_range_subsumes_range(range, pgstart, pgend)) {
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range_del(range);
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continue;
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}
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/* Case #2: We overlap from the start, so adjust it */
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if (range->pgstart >= pgstart) {
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range_shrink(range, pgend + 1, range->pgend);
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continue;
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}
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/* Case #3: We overlap from the rear, so adjust it */
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if (range->pgend <= pgend) {
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range_shrink(range, range->pgstart, pgstart-1);
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continue;
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}
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/*
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* Case #4: We eat a chunk out of the middle. A bit
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* more complicated, we allocate a new range for the
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* 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 = 0,
|
|
};
|
|
ret = ashmem_shrink(&ashmem_shrinker, &sc);
|
|
sc.nr_to_scan = ret;
|
|
ashmem_shrink(&ashmem_shrinker, &sc);
|
|
}
|
|
break;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
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,
|
|
.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");
|