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![David Gibson](/assets/img/avatar_default.png)
The code for FUTEX_WAKE_OP calls an arch callback, futex_atomic_op_inuser(). That callback can return an error code, but currently the caller assumes any error is EFAULT, and will try various things to resolve the fault before eventually giving up with EFAULT (regardless of the original error code). This is not a theoretical case - arch callbacks currently return -ENOSYS if the opcode they are given is bogus. This patch alters the code to detect non-EFAULT errors and return them directly to the user. Of course, whether -ENOSYS is the correct return value for the bogus opcode case, or whether EINVAL would be more appropriate is another question. Signed-off-by: David Gibson <dwg@au1.ibm.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Ingo Molnar <mingo@elte.hu> Cc: Jamie Lokier <jamie@shareable.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
915 lines
22 KiB
C
915 lines
22 KiB
C
/*
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* Fast Userspace Mutexes (which I call "Futexes!").
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* (C) Rusty Russell, IBM 2002
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*
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* Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
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* (C) Copyright 2003 Red Hat Inc, All Rights Reserved
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*
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* Removed page pinning, fix privately mapped COW pages and other cleanups
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* (C) Copyright 2003, 2004 Jamie Lokier
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*
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* Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
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* enough at me, Linus for the original (flawed) idea, Matthew
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* Kirkwood for proof-of-concept implementation.
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*
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* "The futexes are also cursed."
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* "But they come in a choice of three flavours!"
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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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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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/slab.h>
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#include <linux/poll.h>
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/jhash.h>
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#include <linux/init.h>
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#include <linux/futex.h>
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#include <linux/mount.h>
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#include <linux/pagemap.h>
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#include <linux/syscalls.h>
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#include <linux/signal.h>
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#include <asm/futex.h>
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#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
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/*
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* Futexes are matched on equal values of this key.
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* The key type depends on whether it's a shared or private mapping.
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* Don't rearrange members without looking at hash_futex().
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*
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* offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
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* We set bit 0 to indicate if it's an inode-based key.
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*/
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union futex_key {
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struct {
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unsigned long pgoff;
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struct inode *inode;
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int offset;
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} shared;
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struct {
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unsigned long uaddr;
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struct mm_struct *mm;
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int offset;
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} private;
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struct {
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unsigned long word;
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void *ptr;
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int offset;
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} both;
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};
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/*
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* We use this hashed waitqueue instead of a normal wait_queue_t, so
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* we can wake only the relevant ones (hashed queues may be shared).
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*
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* A futex_q has a woken state, just like tasks have TASK_RUNNING.
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* It is considered woken when list_empty(&q->list) || q->lock_ptr == 0.
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* The order of wakup is always to make the first condition true, then
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* wake up q->waiters, then make the second condition true.
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*/
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struct futex_q {
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struct list_head list;
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wait_queue_head_t waiters;
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/* Which hash list lock to use. */
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spinlock_t *lock_ptr;
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/* Key which the futex is hashed on. */
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union futex_key key;
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/* For fd, sigio sent using these. */
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int fd;
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struct file *filp;
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};
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/*
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* Split the global futex_lock into every hash list lock.
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*/
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struct futex_hash_bucket {
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spinlock_t lock;
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struct list_head chain;
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};
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static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
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/* Futex-fs vfsmount entry: */
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static struct vfsmount *futex_mnt;
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/*
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* We hash on the keys returned from get_futex_key (see below).
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*/
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static struct futex_hash_bucket *hash_futex(union futex_key *key)
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{
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u32 hash = jhash2((u32*)&key->both.word,
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(sizeof(key->both.word)+sizeof(key->both.ptr))/4,
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key->both.offset);
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return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
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}
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/*
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* Return 1 if two futex_keys are equal, 0 otherwise.
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*/
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static inline int match_futex(union futex_key *key1, union futex_key *key2)
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{
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return (key1->both.word == key2->both.word
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&& key1->both.ptr == key2->both.ptr
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&& key1->both.offset == key2->both.offset);
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}
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/*
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* Get parameters which are the keys for a futex.
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*
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* For shared mappings, it's (page->index, vma->vm_file->f_dentry->d_inode,
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* offset_within_page). For private mappings, it's (uaddr, current->mm).
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* We can usually work out the index without swapping in the page.
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*
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* Returns: 0, or negative error code.
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* The key words are stored in *key on success.
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*
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* Should be called with ¤t->mm->mmap_sem but NOT any spinlocks.
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*/
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static int get_futex_key(unsigned long uaddr, union futex_key *key)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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struct page *page;
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int err;
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/*
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* The futex address must be "naturally" aligned.
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*/
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key->both.offset = uaddr % PAGE_SIZE;
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if (unlikely((key->both.offset % sizeof(u32)) != 0))
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return -EINVAL;
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uaddr -= key->both.offset;
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/*
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* The futex is hashed differently depending on whether
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* it's in a shared or private mapping. So check vma first.
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*/
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vma = find_extend_vma(mm, uaddr);
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if (unlikely(!vma))
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return -EFAULT;
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/*
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* Permissions.
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*/
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if (unlikely((vma->vm_flags & (VM_IO|VM_READ)) != VM_READ))
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return (vma->vm_flags & VM_IO) ? -EPERM : -EACCES;
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/*
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* Private mappings are handled in a simple way.
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*
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* NOTE: When userspace waits on a MAP_SHARED mapping, even if
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* it's a read-only handle, it's expected that futexes attach to
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* the object not the particular process. Therefore we use
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* VM_MAYSHARE here, not VM_SHARED which is restricted to shared
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* mappings of _writable_ handles.
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*/
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if (likely(!(vma->vm_flags & VM_MAYSHARE))) {
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key->private.mm = mm;
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key->private.uaddr = uaddr;
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return 0;
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}
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/*
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* Linear file mappings are also simple.
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*/
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key->shared.inode = vma->vm_file->f_dentry->d_inode;
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key->both.offset++; /* Bit 0 of offset indicates inode-based key. */
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if (likely(!(vma->vm_flags & VM_NONLINEAR))) {
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key->shared.pgoff = (((uaddr - vma->vm_start) >> PAGE_SHIFT)
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+ vma->vm_pgoff);
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return 0;
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}
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/*
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* We could walk the page table to read the non-linear
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* pte, and get the page index without fetching the page
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* from swap. But that's a lot of code to duplicate here
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* for a rare case, so we simply fetch the page.
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*/
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/*
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* Do a quick atomic lookup first - this is the fastpath.
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*/
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page = follow_page(mm, uaddr, FOLL_TOUCH|FOLL_GET);
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if (likely(page != NULL)) {
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key->shared.pgoff =
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page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
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put_page(page);
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return 0;
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}
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/*
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* Do it the general way.
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*/
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err = get_user_pages(current, mm, uaddr, 1, 0, 0, &page, NULL);
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if (err >= 0) {
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key->shared.pgoff =
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page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
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put_page(page);
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return 0;
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}
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return err;
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}
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/*
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* Take a reference to the resource addressed by a key.
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* Can be called while holding spinlocks.
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*
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* NOTE: mmap_sem MUST be held between get_futex_key() and calling this
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* function, if it is called at all. mmap_sem keeps key->shared.inode valid.
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*/
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static inline void get_key_refs(union futex_key *key)
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{
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if (key->both.ptr != 0) {
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if (key->both.offset & 1)
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atomic_inc(&key->shared.inode->i_count);
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else
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atomic_inc(&key->private.mm->mm_count);
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}
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}
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/*
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* Drop a reference to the resource addressed by a key.
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* The hash bucket spinlock must not be held.
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*/
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static void drop_key_refs(union futex_key *key)
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{
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if (key->both.ptr != 0) {
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if (key->both.offset & 1)
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iput(key->shared.inode);
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else
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mmdrop(key->private.mm);
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}
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}
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static inline int get_futex_value_locked(int *dest, int __user *from)
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{
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int ret;
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inc_preempt_count();
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ret = __copy_from_user_inatomic(dest, from, sizeof(int));
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dec_preempt_count();
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return ret ? -EFAULT : 0;
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}
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/*
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* The hash bucket lock must be held when this is called.
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* Afterwards, the futex_q must not be accessed.
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*/
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static void wake_futex(struct futex_q *q)
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{
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list_del_init(&q->list);
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if (q->filp)
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send_sigio(&q->filp->f_owner, q->fd, POLL_IN);
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/*
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* The lock in wake_up_all() is a crucial memory barrier after the
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* list_del_init() and also before assigning to q->lock_ptr.
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*/
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wake_up_all(&q->waiters);
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/*
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* The waiting task can free the futex_q as soon as this is written,
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* without taking any locks. This must come last.
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*/
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q->lock_ptr = NULL;
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}
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/*
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* Wake up all waiters hashed on the physical page that is mapped
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* to this virtual address:
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*/
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static int futex_wake(unsigned long uaddr, int nr_wake)
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{
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union futex_key key;
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struct futex_hash_bucket *bh;
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struct list_head *head;
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struct futex_q *this, *next;
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int ret;
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down_read(¤t->mm->mmap_sem);
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ret = get_futex_key(uaddr, &key);
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if (unlikely(ret != 0))
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goto out;
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bh = hash_futex(&key);
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spin_lock(&bh->lock);
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head = &bh->chain;
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list_for_each_entry_safe(this, next, head, list) {
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if (match_futex (&this->key, &key)) {
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wake_futex(this);
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if (++ret >= nr_wake)
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break;
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}
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}
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spin_unlock(&bh->lock);
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out:
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up_read(¤t->mm->mmap_sem);
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return ret;
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}
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/*
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* Wake up all waiters hashed on the physical page that is mapped
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* to this virtual address:
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*/
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static int futex_wake_op(unsigned long uaddr1, unsigned long uaddr2, int nr_wake, int nr_wake2, int op)
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{
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union futex_key key1, key2;
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struct futex_hash_bucket *bh1, *bh2;
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struct list_head *head;
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struct futex_q *this, *next;
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int ret, op_ret, attempt = 0;
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retryfull:
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down_read(¤t->mm->mmap_sem);
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ret = get_futex_key(uaddr1, &key1);
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if (unlikely(ret != 0))
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goto out;
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ret = get_futex_key(uaddr2, &key2);
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if (unlikely(ret != 0))
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goto out;
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bh1 = hash_futex(&key1);
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bh2 = hash_futex(&key2);
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retry:
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if (bh1 < bh2)
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spin_lock(&bh1->lock);
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spin_lock(&bh2->lock);
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if (bh1 > bh2)
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spin_lock(&bh1->lock);
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op_ret = futex_atomic_op_inuser(op, (int __user *)uaddr2);
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if (unlikely(op_ret < 0)) {
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int dummy;
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spin_unlock(&bh1->lock);
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if (bh1 != bh2)
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spin_unlock(&bh2->lock);
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if (unlikely(op_ret != -EFAULT)) {
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ret = op_ret;
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goto out;
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}
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/* futex_atomic_op_inuser needs to both read and write
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* *(int __user *)uaddr2, but we can't modify it
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* non-atomically. Therefore, if get_user below is not
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* enough, we need to handle the fault ourselves, while
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* still holding the mmap_sem. */
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if (attempt++) {
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struct vm_area_struct * vma;
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struct mm_struct *mm = current->mm;
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ret = -EFAULT;
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if (attempt >= 2 ||
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!(vma = find_vma(mm, uaddr2)) ||
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vma->vm_start > uaddr2 ||
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!(vma->vm_flags & VM_WRITE))
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goto out;
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switch (handle_mm_fault(mm, vma, uaddr2, 1)) {
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case VM_FAULT_MINOR:
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current->min_flt++;
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break;
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case VM_FAULT_MAJOR:
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current->maj_flt++;
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break;
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default:
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goto out;
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}
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goto retry;
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}
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/* If we would have faulted, release mmap_sem,
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* fault it in and start all over again. */
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up_read(¤t->mm->mmap_sem);
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ret = get_user(dummy, (int __user *)uaddr2);
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if (ret)
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return ret;
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goto retryfull;
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}
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head = &bh1->chain;
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list_for_each_entry_safe(this, next, head, list) {
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if (match_futex (&this->key, &key1)) {
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wake_futex(this);
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if (++ret >= nr_wake)
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break;
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}
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}
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if (op_ret > 0) {
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head = &bh2->chain;
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op_ret = 0;
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list_for_each_entry_safe(this, next, head, list) {
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if (match_futex (&this->key, &key2)) {
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wake_futex(this);
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if (++op_ret >= nr_wake2)
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break;
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}
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}
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ret += op_ret;
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}
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spin_unlock(&bh1->lock);
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if (bh1 != bh2)
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spin_unlock(&bh2->lock);
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out:
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up_read(¤t->mm->mmap_sem);
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return ret;
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}
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/*
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* Requeue all waiters hashed on one physical page to another
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* physical page.
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*/
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static int futex_requeue(unsigned long uaddr1, unsigned long uaddr2,
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int nr_wake, int nr_requeue, int *valp)
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{
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union futex_key key1, key2;
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struct futex_hash_bucket *bh1, *bh2;
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struct list_head *head1;
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struct futex_q *this, *next;
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int ret, drop_count = 0;
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retry:
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down_read(¤t->mm->mmap_sem);
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ret = get_futex_key(uaddr1, &key1);
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if (unlikely(ret != 0))
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goto out;
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ret = get_futex_key(uaddr2, &key2);
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if (unlikely(ret != 0))
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goto out;
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bh1 = hash_futex(&key1);
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bh2 = hash_futex(&key2);
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if (bh1 < bh2)
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spin_lock(&bh1->lock);
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spin_lock(&bh2->lock);
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if (bh1 > bh2)
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spin_lock(&bh1->lock);
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if (likely(valp != NULL)) {
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int curval;
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ret = get_futex_value_locked(&curval, (int __user *)uaddr1);
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if (unlikely(ret)) {
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spin_unlock(&bh1->lock);
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if (bh1 != bh2)
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spin_unlock(&bh2->lock);
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/* If we would have faulted, release mmap_sem, fault
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* it in and start all over again.
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*/
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up_read(¤t->mm->mmap_sem);
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ret = get_user(curval, (int __user *)uaddr1);
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if (!ret)
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goto retry;
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return ret;
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}
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if (curval != *valp) {
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ret = -EAGAIN;
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goto out_unlock;
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}
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}
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head1 = &bh1->chain;
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list_for_each_entry_safe(this, next, head1, list) {
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if (!match_futex (&this->key, &key1))
|
|
continue;
|
|
if (++ret <= nr_wake) {
|
|
wake_futex(this);
|
|
} else {
|
|
list_move_tail(&this->list, &bh2->chain);
|
|
this->lock_ptr = &bh2->lock;
|
|
this->key = key2;
|
|
get_key_refs(&key2);
|
|
drop_count++;
|
|
|
|
if (ret - nr_wake >= nr_requeue)
|
|
break;
|
|
/* Make sure to stop if key1 == key2 */
|
|
if (head1 == &bh2->chain && head1 != &next->list)
|
|
head1 = &this->list;
|
|
}
|
|
}
|
|
|
|
out_unlock:
|
|
spin_unlock(&bh1->lock);
|
|
if (bh1 != bh2)
|
|
spin_unlock(&bh2->lock);
|
|
|
|
/* drop_key_refs() must be called outside the spinlocks. */
|
|
while (--drop_count >= 0)
|
|
drop_key_refs(&key1);
|
|
|
|
out:
|
|
up_read(¤t->mm->mmap_sem);
|
|
return ret;
|
|
}
|
|
|
|
/* The key must be already stored in q->key. */
|
|
static inline struct futex_hash_bucket *
|
|
queue_lock(struct futex_q *q, int fd, struct file *filp)
|
|
{
|
|
struct futex_hash_bucket *bh;
|
|
|
|
q->fd = fd;
|
|
q->filp = filp;
|
|
|
|
init_waitqueue_head(&q->waiters);
|
|
|
|
get_key_refs(&q->key);
|
|
bh = hash_futex(&q->key);
|
|
q->lock_ptr = &bh->lock;
|
|
|
|
spin_lock(&bh->lock);
|
|
return bh;
|
|
}
|
|
|
|
static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *bh)
|
|
{
|
|
list_add_tail(&q->list, &bh->chain);
|
|
spin_unlock(&bh->lock);
|
|
}
|
|
|
|
static inline void
|
|
queue_unlock(struct futex_q *q, struct futex_hash_bucket *bh)
|
|
{
|
|
spin_unlock(&bh->lock);
|
|
drop_key_refs(&q->key);
|
|
}
|
|
|
|
/*
|
|
* queue_me and unqueue_me must be called as a pair, each
|
|
* exactly once. They are called with the hashed spinlock held.
|
|
*/
|
|
|
|
/* The key must be already stored in q->key. */
|
|
static void queue_me(struct futex_q *q, int fd, struct file *filp)
|
|
{
|
|
struct futex_hash_bucket *bh;
|
|
bh = queue_lock(q, fd, filp);
|
|
__queue_me(q, bh);
|
|
}
|
|
|
|
/* Return 1 if we were still queued (ie. 0 means we were woken) */
|
|
static int unqueue_me(struct futex_q *q)
|
|
{
|
|
int ret = 0;
|
|
spinlock_t *lock_ptr;
|
|
|
|
/* In the common case we don't take the spinlock, which is nice. */
|
|
retry:
|
|
lock_ptr = q->lock_ptr;
|
|
if (lock_ptr != 0) {
|
|
spin_lock(lock_ptr);
|
|
/*
|
|
* q->lock_ptr can change between reading it and
|
|
* spin_lock(), causing us to take the wrong lock. This
|
|
* corrects the race condition.
|
|
*
|
|
* Reasoning goes like this: if we have the wrong lock,
|
|
* q->lock_ptr must have changed (maybe several times)
|
|
* between reading it and the spin_lock(). It can
|
|
* change again after the spin_lock() but only if it was
|
|
* already changed before the spin_lock(). It cannot,
|
|
* however, change back to the original value. Therefore
|
|
* we can detect whether we acquired the correct lock.
|
|
*/
|
|
if (unlikely(lock_ptr != q->lock_ptr)) {
|
|
spin_unlock(lock_ptr);
|
|
goto retry;
|
|
}
|
|
WARN_ON(list_empty(&q->list));
|
|
list_del(&q->list);
|
|
spin_unlock(lock_ptr);
|
|
ret = 1;
|
|
}
|
|
|
|
drop_key_refs(&q->key);
|
|
return ret;
|
|
}
|
|
|
|
static int futex_wait(unsigned long uaddr, int val, unsigned long time)
|
|
{
|
|
DECLARE_WAITQUEUE(wait, current);
|
|
int ret, curval;
|
|
struct futex_q q;
|
|
struct futex_hash_bucket *bh;
|
|
|
|
retry:
|
|
down_read(¤t->mm->mmap_sem);
|
|
|
|
ret = get_futex_key(uaddr, &q.key);
|
|
if (unlikely(ret != 0))
|
|
goto out_release_sem;
|
|
|
|
bh = queue_lock(&q, -1, NULL);
|
|
|
|
/*
|
|
* Access the page AFTER the futex is queued.
|
|
* Order is important:
|
|
*
|
|
* Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
|
|
* Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
|
|
*
|
|
* The basic logical guarantee of a futex is that it blocks ONLY
|
|
* if cond(var) is known to be true at the time of blocking, for
|
|
* any cond. If we queued after testing *uaddr, that would open
|
|
* a race condition where we could block indefinitely with
|
|
* cond(var) false, which would violate the guarantee.
|
|
*
|
|
* A consequence is that futex_wait() can return zero and absorb
|
|
* a wakeup when *uaddr != val on entry to the syscall. This is
|
|
* rare, but normal.
|
|
*
|
|
* We hold the mmap semaphore, so the mapping cannot have changed
|
|
* since we looked it up in get_futex_key.
|
|
*/
|
|
|
|
ret = get_futex_value_locked(&curval, (int __user *)uaddr);
|
|
|
|
if (unlikely(ret)) {
|
|
queue_unlock(&q, bh);
|
|
|
|
/* If we would have faulted, release mmap_sem, fault it in and
|
|
* start all over again.
|
|
*/
|
|
up_read(¤t->mm->mmap_sem);
|
|
|
|
ret = get_user(curval, (int __user *)uaddr);
|
|
|
|
if (!ret)
|
|
goto retry;
|
|
return ret;
|
|
}
|
|
if (curval != val) {
|
|
ret = -EWOULDBLOCK;
|
|
queue_unlock(&q, bh);
|
|
goto out_release_sem;
|
|
}
|
|
|
|
/* Only actually queue if *uaddr contained val. */
|
|
__queue_me(&q, bh);
|
|
|
|
/*
|
|
* Now the futex is queued and we have checked the data, we
|
|
* don't want to hold mmap_sem while we sleep.
|
|
*/
|
|
up_read(¤t->mm->mmap_sem);
|
|
|
|
/*
|
|
* There might have been scheduling since the queue_me(), as we
|
|
* cannot hold a spinlock across the get_user() in case it
|
|
* faults, and we cannot just set TASK_INTERRUPTIBLE state when
|
|
* queueing ourselves into the futex hash. This code thus has to
|
|
* rely on the futex_wake() code removing us from hash when it
|
|
* wakes us up.
|
|
*/
|
|
|
|
/* add_wait_queue is the barrier after __set_current_state. */
|
|
__set_current_state(TASK_INTERRUPTIBLE);
|
|
add_wait_queue(&q.waiters, &wait);
|
|
/*
|
|
* !list_empty() is safe here without any lock.
|
|
* q.lock_ptr != 0 is not safe, because of ordering against wakeup.
|
|
*/
|
|
if (likely(!list_empty(&q.list)))
|
|
time = schedule_timeout(time);
|
|
__set_current_state(TASK_RUNNING);
|
|
|
|
/*
|
|
* NOTE: we don't remove ourselves from the waitqueue because
|
|
* we are the only user of it.
|
|
*/
|
|
|
|
/* If we were woken (and unqueued), we succeeded, whatever. */
|
|
if (!unqueue_me(&q))
|
|
return 0;
|
|
if (time == 0)
|
|
return -ETIMEDOUT;
|
|
/* We expect signal_pending(current), but another thread may
|
|
* have handled it for us already. */
|
|
return -EINTR;
|
|
|
|
out_release_sem:
|
|
up_read(¤t->mm->mmap_sem);
|
|
return ret;
|
|
}
|
|
|
|
static int futex_close(struct inode *inode, struct file *filp)
|
|
{
|
|
struct futex_q *q = filp->private_data;
|
|
|
|
unqueue_me(q);
|
|
kfree(q);
|
|
return 0;
|
|
}
|
|
|
|
/* This is one-shot: once it's gone off you need a new fd */
|
|
static unsigned int futex_poll(struct file *filp,
|
|
struct poll_table_struct *wait)
|
|
{
|
|
struct futex_q *q = filp->private_data;
|
|
int ret = 0;
|
|
|
|
poll_wait(filp, &q->waiters, wait);
|
|
|
|
/*
|
|
* list_empty() is safe here without any lock.
|
|
* q->lock_ptr != 0 is not safe, because of ordering against wakeup.
|
|
*/
|
|
if (list_empty(&q->list))
|
|
ret = POLLIN | POLLRDNORM;
|
|
|
|
return ret;
|
|
}
|
|
|
|
static struct file_operations futex_fops = {
|
|
.release = futex_close,
|
|
.poll = futex_poll,
|
|
};
|
|
|
|
/*
|
|
* Signal allows caller to avoid the race which would occur if they
|
|
* set the sigio stuff up afterwards.
|
|
*/
|
|
static int futex_fd(unsigned long uaddr, int signal)
|
|
{
|
|
struct futex_q *q;
|
|
struct file *filp;
|
|
int ret, err;
|
|
|
|
ret = -EINVAL;
|
|
if (!valid_signal(signal))
|
|
goto out;
|
|
|
|
ret = get_unused_fd();
|
|
if (ret < 0)
|
|
goto out;
|
|
filp = get_empty_filp();
|
|
if (!filp) {
|
|
put_unused_fd(ret);
|
|
ret = -ENFILE;
|
|
goto out;
|
|
}
|
|
filp->f_op = &futex_fops;
|
|
filp->f_vfsmnt = mntget(futex_mnt);
|
|
filp->f_dentry = dget(futex_mnt->mnt_root);
|
|
filp->f_mapping = filp->f_dentry->d_inode->i_mapping;
|
|
|
|
if (signal) {
|
|
err = f_setown(filp, current->pid, 1);
|
|
if (err < 0) {
|
|
goto error;
|
|
}
|
|
filp->f_owner.signum = signal;
|
|
}
|
|
|
|
q = kmalloc(sizeof(*q), GFP_KERNEL);
|
|
if (!q) {
|
|
err = -ENOMEM;
|
|
goto error;
|
|
}
|
|
|
|
down_read(¤t->mm->mmap_sem);
|
|
err = get_futex_key(uaddr, &q->key);
|
|
|
|
if (unlikely(err != 0)) {
|
|
up_read(¤t->mm->mmap_sem);
|
|
kfree(q);
|
|
goto error;
|
|
}
|
|
|
|
/*
|
|
* queue_me() must be called before releasing mmap_sem, because
|
|
* key->shared.inode needs to be referenced while holding it.
|
|
*/
|
|
filp->private_data = q;
|
|
|
|
queue_me(q, ret, filp);
|
|
up_read(¤t->mm->mmap_sem);
|
|
|
|
/* Now we map fd to filp, so userspace can access it */
|
|
fd_install(ret, filp);
|
|
out:
|
|
return ret;
|
|
error:
|
|
put_unused_fd(ret);
|
|
put_filp(filp);
|
|
ret = err;
|
|
goto out;
|
|
}
|
|
|
|
long do_futex(unsigned long uaddr, int op, int val, unsigned long timeout,
|
|
unsigned long uaddr2, int val2, int val3)
|
|
{
|
|
int ret;
|
|
|
|
switch (op) {
|
|
case FUTEX_WAIT:
|
|
ret = futex_wait(uaddr, val, timeout);
|
|
break;
|
|
case FUTEX_WAKE:
|
|
ret = futex_wake(uaddr, val);
|
|
break;
|
|
case FUTEX_FD:
|
|
/* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */
|
|
ret = futex_fd(uaddr, val);
|
|
break;
|
|
case FUTEX_REQUEUE:
|
|
ret = futex_requeue(uaddr, uaddr2, val, val2, NULL);
|
|
break;
|
|
case FUTEX_CMP_REQUEUE:
|
|
ret = futex_requeue(uaddr, uaddr2, val, val2, &val3);
|
|
break;
|
|
case FUTEX_WAKE_OP:
|
|
ret = futex_wake_op(uaddr, uaddr2, val, val2, val3);
|
|
break;
|
|
default:
|
|
ret = -ENOSYS;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
|
|
asmlinkage long sys_futex(u32 __user *uaddr, int op, int val,
|
|
struct timespec __user *utime, u32 __user *uaddr2,
|
|
int val3)
|
|
{
|
|
struct timespec t;
|
|
unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
|
|
int val2 = 0;
|
|
|
|
if ((op == FUTEX_WAIT) && utime) {
|
|
if (copy_from_user(&t, utime, sizeof(t)) != 0)
|
|
return -EFAULT;
|
|
timeout = timespec_to_jiffies(&t) + 1;
|
|
}
|
|
/*
|
|
* requeue parameter in 'utime' if op == FUTEX_REQUEUE.
|
|
*/
|
|
if (op >= FUTEX_REQUEUE)
|
|
val2 = (int) (unsigned long) utime;
|
|
|
|
return do_futex((unsigned long)uaddr, op, val, timeout,
|
|
(unsigned long)uaddr2, val2, val3);
|
|
}
|
|
|
|
static struct super_block *
|
|
futexfs_get_sb(struct file_system_type *fs_type,
|
|
int flags, const char *dev_name, void *data)
|
|
{
|
|
return get_sb_pseudo(fs_type, "futex", NULL, 0xBAD1DEA);
|
|
}
|
|
|
|
static struct file_system_type futex_fs_type = {
|
|
.name = "futexfs",
|
|
.get_sb = futexfs_get_sb,
|
|
.kill_sb = kill_anon_super,
|
|
};
|
|
|
|
static int __init init(void)
|
|
{
|
|
unsigned int i;
|
|
|
|
register_filesystem(&futex_fs_type);
|
|
futex_mnt = kern_mount(&futex_fs_type);
|
|
|
|
for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
|
|
INIT_LIST_HEAD(&futex_queues[i].chain);
|
|
spin_lock_init(&futex_queues[i].lock);
|
|
}
|
|
return 0;
|
|
}
|
|
__initcall(init);
|