From 1431d9de00d212b08aa8b77134e9a261c9dab0c7 Mon Sep 17 00:00:00 2001 From: Sultan Alsawaf Date: Fri, 29 Jan 2021 20:38:03 -0800 Subject: [PATCH] ashmem: Rewrite to improve clarity and performance 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 Signed-off-by: Forenche --- drivers/staging/android/ashmem.c | 779 +++++-------------------------- 1 file changed, 113 insertions(+), 666 deletions(-) diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c index 7b1c3843176a..6a17c3cd86a5 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -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 - * - * 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 . */ #define pr_fmt(fmt) "ashmem: " fmt -#include -#include -#include -#include -#include #include -#include -#include #include -#include -#include -#include -#include #include #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; + static DEFINE_SPINLOCK(vmfile_fops_lock); + struct file *vmfile; - mutex_lock(&ashmem_mutex); + vmfile = shmem_file_setup(ASHMEM_NAME_DEF, size, vma->vm_flags); + if (IS_ERR(vmfile)) + return PTR_ERR(vmfile); - /* 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; - 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 (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. - */ + /* + * 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; + ashmem_vmfile_get_unmapped_area; + WRITE_ONCE(vmfile_fops.mmap, ashmem_vmfile_mmap); } - vmfile->f_op = &vmfile_fops; + 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)) - 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; + WRITE_ONCE(asma->prot_mask, prot); + return 0; } 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: