futex: catch certain assymetric (get|put)_futex_key calls
[linux-2.6.git] / kernel / futex.c
1 /*
2  *  Fast Userspace Mutexes (which I call "Futexes!").
3  *  (C) Rusty Russell, IBM 2002
4  *
5  *  Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
6  *  (C) Copyright 2003 Red Hat Inc, All Rights Reserved
7  *
8  *  Removed page pinning, fix privately mapped COW pages and other cleanups
9  *  (C) Copyright 2003, 2004 Jamie Lokier
10  *
11  *  Robust futex support started by Ingo Molnar
12  *  (C) Copyright 2006 Red Hat Inc, All Rights Reserved
13  *  Thanks to Thomas Gleixner for suggestions, analysis and fixes.
14  *
15  *  PI-futex support started by Ingo Molnar and Thomas Gleixner
16  *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
17  *  Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
18  *
19  *  PRIVATE futexes by Eric Dumazet
20  *  Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com>
21  *
22  *  Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
23  *  enough at me, Linus for the original (flawed) idea, Matthew
24  *  Kirkwood for proof-of-concept implementation.
25  *
26  *  "The futexes are also cursed."
27  *  "But they come in a choice of three flavours!"
28  *
29  *  This program is free software; you can redistribute it and/or modify
30  *  it under the terms of the GNU General Public License as published by
31  *  the Free Software Foundation; either version 2 of the License, or
32  *  (at your option) any later version.
33  *
34  *  This program is distributed in the hope that it will be useful,
35  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
36  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
37  *  GNU General Public License for more details.
38  *
39  *  You should have received a copy of the GNU General Public License
40  *  along with this program; if not, write to the Free Software
41  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
42  */
43 #include <linux/slab.h>
44 #include <linux/poll.h>
45 #include <linux/fs.h>
46 #include <linux/file.h>
47 #include <linux/jhash.h>
48 #include <linux/init.h>
49 #include <linux/futex.h>
50 #include <linux/mount.h>
51 #include <linux/pagemap.h>
52 #include <linux/syscalls.h>
53 #include <linux/signal.h>
54 #include <linux/module.h>
55 #include <linux/magic.h>
56 #include <linux/pid.h>
57 #include <linux/nsproxy.h>
58
59 #include <asm/futex.h>
60
61 #include "rtmutex_common.h"
62
63 int __read_mostly futex_cmpxchg_enabled;
64
65 #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
66
67 /*
68  * Priority Inheritance state:
69  */
70 struct futex_pi_state {
71         /*
72          * list of 'owned' pi_state instances - these have to be
73          * cleaned up in do_exit() if the task exits prematurely:
74          */
75         struct list_head list;
76
77         /*
78          * The PI object:
79          */
80         struct rt_mutex pi_mutex;
81
82         struct task_struct *owner;
83         atomic_t refcount;
84
85         union futex_key key;
86 };
87
88 /*
89  * We use this hashed waitqueue instead of a normal wait_queue_t, so
90  * we can wake only the relevant ones (hashed queues may be shared).
91  *
92  * A futex_q has a woken state, just like tasks have TASK_RUNNING.
93  * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
94  * The order of wakup is always to make the first condition true, then
95  * wake up q->waiter, then make the second condition true.
96  */
97 struct futex_q {
98         struct plist_node list;
99         /* There can only be a single waiter */
100         wait_queue_head_t waiter;
101
102         /* Which hash list lock to use: */
103         spinlock_t *lock_ptr;
104
105         /* Key which the futex is hashed on: */
106         union futex_key key;
107
108         /* Optional priority inheritance state: */
109         struct futex_pi_state *pi_state;
110         struct task_struct *task;
111
112         /* Bitset for the optional bitmasked wakeup */
113         u32 bitset;
114 };
115
116 /*
117  * Split the global futex_lock into every hash list lock.
118  */
119 struct futex_hash_bucket {
120         spinlock_t lock;
121         struct plist_head chain;
122 };
123
124 static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
125
126 /*
127  * We hash on the keys returned from get_futex_key (see below).
128  */
129 static struct futex_hash_bucket *hash_futex(union futex_key *key)
130 {
131         u32 hash = jhash2((u32*)&key->both.word,
132                           (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
133                           key->both.offset);
134         return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
135 }
136
137 /*
138  * Return 1 if two futex_keys are equal, 0 otherwise.
139  */
140 static inline int match_futex(union futex_key *key1, union futex_key *key2)
141 {
142         return (key1->both.word == key2->both.word
143                 && key1->both.ptr == key2->both.ptr
144                 && key1->both.offset == key2->both.offset);
145 }
146
147 /*
148  * Take a reference to the resource addressed by a key.
149  * Can be called while holding spinlocks.
150  *
151  */
152 static void get_futex_key_refs(union futex_key *key)
153 {
154         if (!key->both.ptr)
155                 return;
156
157         switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
158         case FUT_OFF_INODE:
159                 atomic_inc(&key->shared.inode->i_count);
160                 break;
161         case FUT_OFF_MMSHARED:
162                 atomic_inc(&key->private.mm->mm_count);
163                 break;
164         }
165 }
166
167 /*
168  * Drop a reference to the resource addressed by a key.
169  * The hash bucket spinlock must not be held.
170  */
171 static void drop_futex_key_refs(union futex_key *key)
172 {
173         if (!key->both.ptr) {
174                 /* If we're here then we tried to put a key we failed to get */
175                 WARN_ON_ONCE(1);
176                 return;
177         }
178
179         switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
180         case FUT_OFF_INODE:
181                 iput(key->shared.inode);
182                 break;
183         case FUT_OFF_MMSHARED:
184                 mmdrop(key->private.mm);
185                 break;
186         }
187 }
188
189 /**
190  * get_futex_key - Get parameters which are the keys for a futex.
191  * @uaddr: virtual address of the futex
192  * @shared: NULL for a PROCESS_PRIVATE futex,
193  *      &current->mm->mmap_sem for a PROCESS_SHARED futex
194  * @key: address where result is stored.
195  *
196  * Returns a negative error code or 0
197  * The key words are stored in *key on success.
198  *
199  * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
200  * offset_within_page).  For private mappings, it's (uaddr, current->mm).
201  * We can usually work out the index without swapping in the page.
202  *
203  * fshared is NULL for PROCESS_PRIVATE futexes
204  * For other futexes, it points to &current->mm->mmap_sem and
205  * caller must have taken the reader lock. but NOT any spinlocks.
206  */
207 static int get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key)
208 {
209         unsigned long address = (unsigned long)uaddr;
210         struct mm_struct *mm = current->mm;
211         struct page *page;
212         int err;
213
214         /*
215          * The futex address must be "naturally" aligned.
216          */
217         key->both.offset = address % PAGE_SIZE;
218         if (unlikely((address % sizeof(u32)) != 0))
219                 return -EINVAL;
220         address -= key->both.offset;
221
222         /*
223          * PROCESS_PRIVATE futexes are fast.
224          * As the mm cannot disappear under us and the 'key' only needs
225          * virtual address, we dont even have to find the underlying vma.
226          * Note : We do have to check 'uaddr' is a valid user address,
227          *        but access_ok() should be faster than find_vma()
228          */
229         if (!fshared) {
230                 if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))))
231                         return -EFAULT;
232                 key->private.mm = mm;
233                 key->private.address = address;
234                 get_futex_key_refs(key);
235                 return 0;
236         }
237
238 again:
239         err = get_user_pages_fast(address, 1, 0, &page);
240         if (err < 0)
241                 return err;
242
243         lock_page(page);
244         if (!page->mapping) {
245                 unlock_page(page);
246                 put_page(page);
247                 goto again;
248         }
249
250         /*
251          * Private mappings are handled in a simple way.
252          *
253          * NOTE: When userspace waits on a MAP_SHARED mapping, even if
254          * it's a read-only handle, it's expected that futexes attach to
255          * the object not the particular process.
256          */
257         if (PageAnon(page)) {
258                 key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
259                 key->private.mm = mm;
260                 key->private.address = address;
261         } else {
262                 key->both.offset |= FUT_OFF_INODE; /* inode-based key */
263                 key->shared.inode = page->mapping->host;
264                 key->shared.pgoff = page->index;
265         }
266
267         get_futex_key_refs(key);
268
269         unlock_page(page);
270         put_page(page);
271         return 0;
272 }
273
274 static inline
275 void put_futex_key(int fshared, union futex_key *key)
276 {
277         drop_futex_key_refs(key);
278 }
279
280 static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
281 {
282         u32 curval;
283
284         pagefault_disable();
285         curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
286         pagefault_enable();
287
288         return curval;
289 }
290
291 static int get_futex_value_locked(u32 *dest, u32 __user *from)
292 {
293         int ret;
294
295         pagefault_disable();
296         ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
297         pagefault_enable();
298
299         return ret ? -EFAULT : 0;
300 }
301
302 /*
303  * Fault handling.
304  */
305 static int futex_handle_fault(unsigned long address, int attempt)
306 {
307         struct vm_area_struct * vma;
308         struct mm_struct *mm = current->mm;
309         int ret = -EFAULT;
310
311         if (attempt > 2)
312                 return ret;
313
314         down_read(&mm->mmap_sem);
315         vma = find_vma(mm, address);
316         if (vma && address >= vma->vm_start &&
317             (vma->vm_flags & VM_WRITE)) {
318                 int fault;
319                 fault = handle_mm_fault(mm, vma, address, 1);
320                 if (unlikely((fault & VM_FAULT_ERROR))) {
321 #if 0
322                         /* XXX: let's do this when we verify it is OK */
323                         if (ret & VM_FAULT_OOM)
324                                 ret = -ENOMEM;
325 #endif
326                 } else {
327                         ret = 0;
328                         if (fault & VM_FAULT_MAJOR)
329                                 current->maj_flt++;
330                         else
331                                 current->min_flt++;
332                 }
333         }
334         up_read(&mm->mmap_sem);
335         return ret;
336 }
337
338 /*
339  * PI code:
340  */
341 static int refill_pi_state_cache(void)
342 {
343         struct futex_pi_state *pi_state;
344
345         if (likely(current->pi_state_cache))
346                 return 0;
347
348         pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);
349
350         if (!pi_state)
351                 return -ENOMEM;
352
353         INIT_LIST_HEAD(&pi_state->list);
354         /* pi_mutex gets initialized later */
355         pi_state->owner = NULL;
356         atomic_set(&pi_state->refcount, 1);
357         pi_state->key = FUTEX_KEY_INIT;
358
359         current->pi_state_cache = pi_state;
360
361         return 0;
362 }
363
364 static struct futex_pi_state * alloc_pi_state(void)
365 {
366         struct futex_pi_state *pi_state = current->pi_state_cache;
367
368         WARN_ON(!pi_state);
369         current->pi_state_cache = NULL;
370
371         return pi_state;
372 }
373
374 static void free_pi_state(struct futex_pi_state *pi_state)
375 {
376         if (!atomic_dec_and_test(&pi_state->refcount))
377                 return;
378
379         /*
380          * If pi_state->owner is NULL, the owner is most probably dying
381          * and has cleaned up the pi_state already
382          */
383         if (pi_state->owner) {
384                 spin_lock_irq(&pi_state->owner->pi_lock);
385                 list_del_init(&pi_state->list);
386                 spin_unlock_irq(&pi_state->owner->pi_lock);
387
388                 rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
389         }
390
391         if (current->pi_state_cache)
392                 kfree(pi_state);
393         else {
394                 /*
395                  * pi_state->list is already empty.
396                  * clear pi_state->owner.
397                  * refcount is at 0 - put it back to 1.
398                  */
399                 pi_state->owner = NULL;
400                 atomic_set(&pi_state->refcount, 1);
401                 current->pi_state_cache = pi_state;
402         }
403 }
404
405 /*
406  * Look up the task based on what TID userspace gave us.
407  * We dont trust it.
408  */
409 static struct task_struct * futex_find_get_task(pid_t pid)
410 {
411         struct task_struct *p;
412
413         rcu_read_lock();
414         p = find_task_by_vpid(pid);
415         if (!p || ((current->euid != p->euid) && (current->euid != p->uid)))
416                 p = ERR_PTR(-ESRCH);
417         else
418                 get_task_struct(p);
419
420         rcu_read_unlock();
421
422         return p;
423 }
424
425 /*
426  * This task is holding PI mutexes at exit time => bad.
427  * Kernel cleans up PI-state, but userspace is likely hosed.
428  * (Robust-futex cleanup is separate and might save the day for userspace.)
429  */
430 void exit_pi_state_list(struct task_struct *curr)
431 {
432         struct list_head *next, *head = &curr->pi_state_list;
433         struct futex_pi_state *pi_state;
434         struct futex_hash_bucket *hb;
435         union futex_key key = FUTEX_KEY_INIT;
436
437         if (!futex_cmpxchg_enabled)
438                 return;
439         /*
440          * We are a ZOMBIE and nobody can enqueue itself on
441          * pi_state_list anymore, but we have to be careful
442          * versus waiters unqueueing themselves:
443          */
444         spin_lock_irq(&curr->pi_lock);
445         while (!list_empty(head)) {
446
447                 next = head->next;
448                 pi_state = list_entry(next, struct futex_pi_state, list);
449                 key = pi_state->key;
450                 hb = hash_futex(&key);
451                 spin_unlock_irq(&curr->pi_lock);
452
453                 spin_lock(&hb->lock);
454
455                 spin_lock_irq(&curr->pi_lock);
456                 /*
457                  * We dropped the pi-lock, so re-check whether this
458                  * task still owns the PI-state:
459                  */
460                 if (head->next != next) {
461                         spin_unlock(&hb->lock);
462                         continue;
463                 }
464
465                 WARN_ON(pi_state->owner != curr);
466                 WARN_ON(list_empty(&pi_state->list));
467                 list_del_init(&pi_state->list);
468                 pi_state->owner = NULL;
469                 spin_unlock_irq(&curr->pi_lock);
470
471                 rt_mutex_unlock(&pi_state->pi_mutex);
472
473                 spin_unlock(&hb->lock);
474
475                 spin_lock_irq(&curr->pi_lock);
476         }
477         spin_unlock_irq(&curr->pi_lock);
478 }
479
480 static int
481 lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
482                 union futex_key *key, struct futex_pi_state **ps)
483 {
484         struct futex_pi_state *pi_state = NULL;
485         struct futex_q *this, *next;
486         struct plist_head *head;
487         struct task_struct *p;
488         pid_t pid = uval & FUTEX_TID_MASK;
489
490         head = &hb->chain;
491
492         plist_for_each_entry_safe(this, next, head, list) {
493                 if (match_futex(&this->key, key)) {
494                         /*
495                          * Another waiter already exists - bump up
496                          * the refcount and return its pi_state:
497                          */
498                         pi_state = this->pi_state;
499                         /*
500                          * Userspace might have messed up non PI and PI futexes
501                          */
502                         if (unlikely(!pi_state))
503                                 return -EINVAL;
504
505                         WARN_ON(!atomic_read(&pi_state->refcount));
506                         WARN_ON(pid && pi_state->owner &&
507                                 pi_state->owner->pid != pid);
508
509                         atomic_inc(&pi_state->refcount);
510                         *ps = pi_state;
511
512                         return 0;
513                 }
514         }
515
516         /*
517          * We are the first waiter - try to look up the real owner and attach
518          * the new pi_state to it, but bail out when TID = 0
519          */
520         if (!pid)
521                 return -ESRCH;
522         p = futex_find_get_task(pid);
523         if (IS_ERR(p))
524                 return PTR_ERR(p);
525
526         /*
527          * We need to look at the task state flags to figure out,
528          * whether the task is exiting. To protect against the do_exit
529          * change of the task flags, we do this protected by
530          * p->pi_lock:
531          */
532         spin_lock_irq(&p->pi_lock);
533         if (unlikely(p->flags & PF_EXITING)) {
534                 /*
535                  * The task is on the way out. When PF_EXITPIDONE is
536                  * set, we know that the task has finished the
537                  * cleanup:
538                  */
539                 int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN;
540
541                 spin_unlock_irq(&p->pi_lock);
542                 put_task_struct(p);
543                 return ret;
544         }
545
546         pi_state = alloc_pi_state();
547
548         /*
549          * Initialize the pi_mutex in locked state and make 'p'
550          * the owner of it:
551          */
552         rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
553
554         /* Store the key for possible exit cleanups: */
555         pi_state->key = *key;
556
557         WARN_ON(!list_empty(&pi_state->list));
558         list_add(&pi_state->list, &p->pi_state_list);
559         pi_state->owner = p;
560         spin_unlock_irq(&p->pi_lock);
561
562         put_task_struct(p);
563
564         *ps = pi_state;
565
566         return 0;
567 }
568
569 /*
570  * The hash bucket lock must be held when this is called.
571  * Afterwards, the futex_q must not be accessed.
572  */
573 static void wake_futex(struct futex_q *q)
574 {
575         plist_del(&q->list, &q->list.plist);
576         /*
577          * The lock in wake_up_all() is a crucial memory barrier after the
578          * plist_del() and also before assigning to q->lock_ptr.
579          */
580         wake_up(&q->waiter);
581         /*
582          * The waiting task can free the futex_q as soon as this is written,
583          * without taking any locks.  This must come last.
584          *
585          * A memory barrier is required here to prevent the following store
586          * to lock_ptr from getting ahead of the wakeup. Clearing the lock
587          * at the end of wake_up_all() does not prevent this store from
588          * moving.
589          */
590         smp_wmb();
591         q->lock_ptr = NULL;
592 }
593
594 static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
595 {
596         struct task_struct *new_owner;
597         struct futex_pi_state *pi_state = this->pi_state;
598         u32 curval, newval;
599
600         if (!pi_state)
601                 return -EINVAL;
602
603         spin_lock(&pi_state->pi_mutex.wait_lock);
604         new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
605
606         /*
607          * This happens when we have stolen the lock and the original
608          * pending owner did not enqueue itself back on the rt_mutex.
609          * Thats not a tragedy. We know that way, that a lock waiter
610          * is on the fly. We make the futex_q waiter the pending owner.
611          */
612         if (!new_owner)
613                 new_owner = this->task;
614
615         /*
616          * We pass it to the next owner. (The WAITERS bit is always
617          * kept enabled while there is PI state around. We must also
618          * preserve the owner died bit.)
619          */
620         if (!(uval & FUTEX_OWNER_DIED)) {
621                 int ret = 0;
622
623                 newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
624
625                 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
626
627                 if (curval == -EFAULT)
628                         ret = -EFAULT;
629                 else if (curval != uval)
630                         ret = -EINVAL;
631                 if (ret) {
632                         spin_unlock(&pi_state->pi_mutex.wait_lock);
633                         return ret;
634                 }
635         }
636
637         spin_lock_irq(&pi_state->owner->pi_lock);
638         WARN_ON(list_empty(&pi_state->list));
639         list_del_init(&pi_state->list);
640         spin_unlock_irq(&pi_state->owner->pi_lock);
641
642         spin_lock_irq(&new_owner->pi_lock);
643         WARN_ON(!list_empty(&pi_state->list));
644         list_add(&pi_state->list, &new_owner->pi_state_list);
645         pi_state->owner = new_owner;
646         spin_unlock_irq(&new_owner->pi_lock);
647
648         spin_unlock(&pi_state->pi_mutex.wait_lock);
649         rt_mutex_unlock(&pi_state->pi_mutex);
650
651         return 0;
652 }
653
654 static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
655 {
656         u32 oldval;
657
658         /*
659          * There is no waiter, so we unlock the futex. The owner died
660          * bit has not to be preserved here. We are the owner:
661          */
662         oldval = cmpxchg_futex_value_locked(uaddr, uval, 0);
663
664         if (oldval == -EFAULT)
665                 return oldval;
666         if (oldval != uval)
667                 return -EAGAIN;
668
669         return 0;
670 }
671
672 /*
673  * Express the locking dependencies for lockdep:
674  */
675 static inline void
676 double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
677 {
678         if (hb1 <= hb2) {
679                 spin_lock(&hb1->lock);
680                 if (hb1 < hb2)
681                         spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
682         } else { /* hb1 > hb2 */
683                 spin_lock(&hb2->lock);
684                 spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
685         }
686 }
687
688 /*
689  * Wake up all waiters hashed on the physical page that is mapped
690  * to this virtual address:
691  */
692 static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
693 {
694         struct futex_hash_bucket *hb;
695         struct futex_q *this, *next;
696         struct plist_head *head;
697         union futex_key key = FUTEX_KEY_INIT;
698         int ret;
699
700         if (!bitset)
701                 return -EINVAL;
702
703         ret = get_futex_key(uaddr, fshared, &key);
704         if (unlikely(ret != 0))
705                 goto out;
706
707         hb = hash_futex(&key);
708         spin_lock(&hb->lock);
709         head = &hb->chain;
710
711         plist_for_each_entry_safe(this, next, head, list) {
712                 if (match_futex (&this->key, &key)) {
713                         if (this->pi_state) {
714                                 ret = -EINVAL;
715                                 break;
716                         }
717
718                         /* Check if one of the bits is set in both bitsets */
719                         if (!(this->bitset & bitset))
720                                 continue;
721
722                         wake_futex(this);
723                         if (++ret >= nr_wake)
724                                 break;
725                 }
726         }
727
728         spin_unlock(&hb->lock);
729         put_futex_key(fshared, &key);
730 out:
731         return ret;
732 }
733
734 /*
735  * Wake up all waiters hashed on the physical page that is mapped
736  * to this virtual address:
737  */
738 static int
739 futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
740               int nr_wake, int nr_wake2, int op)
741 {
742         union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
743         struct futex_hash_bucket *hb1, *hb2;
744         struct plist_head *head;
745         struct futex_q *this, *next;
746         int ret, op_ret, attempt = 0;
747
748 retryfull:
749         ret = get_futex_key(uaddr1, fshared, &key1);
750         if (unlikely(ret != 0))
751                 goto out;
752         ret = get_futex_key(uaddr2, fshared, &key2);
753         if (unlikely(ret != 0))
754                 goto out_put_key1;
755
756         hb1 = hash_futex(&key1);
757         hb2 = hash_futex(&key2);
758
759 retry:
760         double_lock_hb(hb1, hb2);
761
762         op_ret = futex_atomic_op_inuser(op, uaddr2);
763         if (unlikely(op_ret < 0)) {
764                 u32 dummy;
765
766                 spin_unlock(&hb1->lock);
767                 if (hb1 != hb2)
768                         spin_unlock(&hb2->lock);
769
770 #ifndef CONFIG_MMU
771                 /*
772                  * we don't get EFAULT from MMU faults if we don't have an MMU,
773                  * but we might get them from range checking
774                  */
775                 ret = op_ret;
776                 goto out_put_keys;
777 #endif
778
779                 if (unlikely(op_ret != -EFAULT)) {
780                         ret = op_ret;
781                         goto out_put_keys;
782                 }
783
784                 /*
785                  * futex_atomic_op_inuser needs to both read and write
786                  * *(int __user *)uaddr2, but we can't modify it
787                  * non-atomically.  Therefore, if get_user below is not
788                  * enough, we need to handle the fault ourselves, while
789                  * still holding the mmap_sem.
790                  */
791                 if (attempt++) {
792                         ret = futex_handle_fault((unsigned long)uaddr2,
793                                                  attempt);
794                         if (ret)
795                                 goto out_put_keys;
796                         goto retry;
797                 }
798
799                 ret = get_user(dummy, uaddr2);
800                 if (ret)
801                         return ret;
802
803                 goto retryfull;
804         }
805
806         head = &hb1->chain;
807
808         plist_for_each_entry_safe(this, next, head, list) {
809                 if (match_futex (&this->key, &key1)) {
810                         wake_futex(this);
811                         if (++ret >= nr_wake)
812                                 break;
813                 }
814         }
815
816         if (op_ret > 0) {
817                 head = &hb2->chain;
818
819                 op_ret = 0;
820                 plist_for_each_entry_safe(this, next, head, list) {
821                         if (match_futex (&this->key, &key2)) {
822                                 wake_futex(this);
823                                 if (++op_ret >= nr_wake2)
824                                         break;
825                         }
826                 }
827                 ret += op_ret;
828         }
829
830         spin_unlock(&hb1->lock);
831         if (hb1 != hb2)
832                 spin_unlock(&hb2->lock);
833 out_put_keys:
834         put_futex_key(fshared, &key2);
835 out_put_key1:
836         put_futex_key(fshared, &key1);
837 out:
838         return ret;
839 }
840
841 /*
842  * Requeue all waiters hashed on one physical page to another
843  * physical page.
844  */
845 static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
846                          int nr_wake, int nr_requeue, u32 *cmpval)
847 {
848         union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
849         struct futex_hash_bucket *hb1, *hb2;
850         struct plist_head *head1;
851         struct futex_q *this, *next;
852         int ret, drop_count = 0;
853
854 retry:
855         ret = get_futex_key(uaddr1, fshared, &key1);
856         if (unlikely(ret != 0))
857                 goto out;
858         ret = get_futex_key(uaddr2, fshared, &key2);
859         if (unlikely(ret != 0))
860                 goto out_put_key1;
861
862         hb1 = hash_futex(&key1);
863         hb2 = hash_futex(&key2);
864
865         double_lock_hb(hb1, hb2);
866
867         if (likely(cmpval != NULL)) {
868                 u32 curval;
869
870                 ret = get_futex_value_locked(&curval, uaddr1);
871
872                 if (unlikely(ret)) {
873                         spin_unlock(&hb1->lock);
874                         if (hb1 != hb2)
875                                 spin_unlock(&hb2->lock);
876
877                         ret = get_user(curval, uaddr1);
878
879                         if (!ret)
880                                 goto retry;
881
882                         goto out_put_keys;
883                 }
884                 if (curval != *cmpval) {
885                         ret = -EAGAIN;
886                         goto out_unlock;
887                 }
888         }
889
890         head1 = &hb1->chain;
891         plist_for_each_entry_safe(this, next, head1, list) {
892                 if (!match_futex (&this->key, &key1))
893                         continue;
894                 if (++ret <= nr_wake) {
895                         wake_futex(this);
896                 } else {
897                         /*
898                          * If key1 and key2 hash to the same bucket, no need to
899                          * requeue.
900                          */
901                         if (likely(head1 != &hb2->chain)) {
902                                 plist_del(&this->list, &hb1->chain);
903                                 plist_add(&this->list, &hb2->chain);
904                                 this->lock_ptr = &hb2->lock;
905 #ifdef CONFIG_DEBUG_PI_LIST
906                                 this->list.plist.lock = &hb2->lock;
907 #endif
908                         }
909                         this->key = key2;
910                         get_futex_key_refs(&key2);
911                         drop_count++;
912
913                         if (ret - nr_wake >= nr_requeue)
914                                 break;
915                 }
916         }
917
918 out_unlock:
919         spin_unlock(&hb1->lock);
920         if (hb1 != hb2)
921                 spin_unlock(&hb2->lock);
922
923         /* drop_futex_key_refs() must be called outside the spinlocks. */
924         while (--drop_count >= 0)
925                 drop_futex_key_refs(&key1);
926
927 out_put_keys:
928         put_futex_key(fshared, &key2);
929 out_put_key1:
930         put_futex_key(fshared, &key1);
931 out:
932         return ret;
933 }
934
935 /* The key must be already stored in q->key. */
936 static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
937 {
938         struct futex_hash_bucket *hb;
939
940         init_waitqueue_head(&q->waiter);
941
942         get_futex_key_refs(&q->key);
943         hb = hash_futex(&q->key);
944         q->lock_ptr = &hb->lock;
945
946         spin_lock(&hb->lock);
947         return hb;
948 }
949
950 static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
951 {
952         int prio;
953
954         /*
955          * The priority used to register this element is
956          * - either the real thread-priority for the real-time threads
957          * (i.e. threads with a priority lower than MAX_RT_PRIO)
958          * - or MAX_RT_PRIO for non-RT threads.
959          * Thus, all RT-threads are woken first in priority order, and
960          * the others are woken last, in FIFO order.
961          */
962         prio = min(current->normal_prio, MAX_RT_PRIO);
963
964         plist_node_init(&q->list, prio);
965 #ifdef CONFIG_DEBUG_PI_LIST
966         q->list.plist.lock = &hb->lock;
967 #endif
968         plist_add(&q->list, &hb->chain);
969         q->task = current;
970         spin_unlock(&hb->lock);
971 }
972
973 static inline void
974 queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
975 {
976         spin_unlock(&hb->lock);
977         drop_futex_key_refs(&q->key);
978 }
979
980 /*
981  * queue_me and unqueue_me must be called as a pair, each
982  * exactly once.  They are called with the hashed spinlock held.
983  */
984
985 /* Return 1 if we were still queued (ie. 0 means we were woken) */
986 static int unqueue_me(struct futex_q *q)
987 {
988         spinlock_t *lock_ptr;
989         int ret = 0;
990
991         /* In the common case we don't take the spinlock, which is nice. */
992 retry:
993         lock_ptr = q->lock_ptr;
994         barrier();
995         if (lock_ptr != NULL) {
996                 spin_lock(lock_ptr);
997                 /*
998                  * q->lock_ptr can change between reading it and
999                  * spin_lock(), causing us to take the wrong lock.  This
1000                  * corrects the race condition.
1001                  *
1002                  * Reasoning goes like this: if we have the wrong lock,
1003                  * q->lock_ptr must have changed (maybe several times)
1004                  * between reading it and the spin_lock().  It can
1005                  * change again after the spin_lock() but only if it was
1006                  * already changed before the spin_lock().  It cannot,
1007                  * however, change back to the original value.  Therefore
1008                  * we can detect whether we acquired the correct lock.
1009                  */
1010                 if (unlikely(lock_ptr != q->lock_ptr)) {
1011                         spin_unlock(lock_ptr);
1012                         goto retry;
1013                 }
1014                 WARN_ON(plist_node_empty(&q->list));
1015                 plist_del(&q->list, &q->list.plist);
1016
1017                 BUG_ON(q->pi_state);
1018
1019                 spin_unlock(lock_ptr);
1020                 ret = 1;
1021         }
1022
1023         drop_futex_key_refs(&q->key);
1024         return ret;
1025 }
1026
1027 /*
1028  * PI futexes can not be requeued and must remove themself from the
1029  * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
1030  * and dropped here.
1031  */
1032 static void unqueue_me_pi(struct futex_q *q)
1033 {
1034         WARN_ON(plist_node_empty(&q->list));
1035         plist_del(&q->list, &q->list.plist);
1036
1037         BUG_ON(!q->pi_state);
1038         free_pi_state(q->pi_state);
1039         q->pi_state = NULL;
1040
1041         spin_unlock(q->lock_ptr);
1042
1043         drop_futex_key_refs(&q->key);
1044 }
1045
1046 /*
1047  * Fixup the pi_state owner with the new owner.
1048  *
1049  * Must be called with hash bucket lock held and mm->sem held for non
1050  * private futexes.
1051  */
1052 static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
1053                                 struct task_struct *newowner, int fshared)
1054 {
1055         u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
1056         struct futex_pi_state *pi_state = q->pi_state;
1057         struct task_struct *oldowner = pi_state->owner;
1058         u32 uval, curval, newval;
1059         int ret, attempt = 0;
1060
1061         /* Owner died? */
1062         if (!pi_state->owner)
1063                 newtid |= FUTEX_OWNER_DIED;
1064
1065         /*
1066          * We are here either because we stole the rtmutex from the
1067          * pending owner or we are the pending owner which failed to
1068          * get the rtmutex. We have to replace the pending owner TID
1069          * in the user space variable. This must be atomic as we have
1070          * to preserve the owner died bit here.
1071          *
1072          * Note: We write the user space value _before_ changing the
1073          * pi_state because we can fault here. Imagine swapped out
1074          * pages or a fork, which was running right before we acquired
1075          * mmap_sem, that marked all the anonymous memory readonly for
1076          * cow.
1077          *
1078          * Modifying pi_state _before_ the user space value would
1079          * leave the pi_state in an inconsistent state when we fault
1080          * here, because we need to drop the hash bucket lock to
1081          * handle the fault. This might be observed in the PID check
1082          * in lookup_pi_state.
1083          */
1084 retry:
1085         if (get_futex_value_locked(&uval, uaddr))
1086                 goto handle_fault;
1087
1088         while (1) {
1089                 newval = (uval & FUTEX_OWNER_DIED) | newtid;
1090
1091                 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
1092
1093                 if (curval == -EFAULT)
1094                         goto handle_fault;
1095                 if (curval == uval)
1096                         break;
1097                 uval = curval;
1098         }
1099
1100         /*
1101          * We fixed up user space. Now we need to fix the pi_state
1102          * itself.
1103          */
1104         if (pi_state->owner != NULL) {
1105                 spin_lock_irq(&pi_state->owner->pi_lock);
1106                 WARN_ON(list_empty(&pi_state->list));
1107                 list_del_init(&pi_state->list);
1108                 spin_unlock_irq(&pi_state->owner->pi_lock);
1109         }
1110
1111         pi_state->owner = newowner;
1112
1113         spin_lock_irq(&newowner->pi_lock);
1114         WARN_ON(!list_empty(&pi_state->list));
1115         list_add(&pi_state->list, &newowner->pi_state_list);
1116         spin_unlock_irq(&newowner->pi_lock);
1117         return 0;
1118
1119         /*
1120          * To handle the page fault we need to drop the hash bucket
1121          * lock here. That gives the other task (either the pending
1122          * owner itself or the task which stole the rtmutex) the
1123          * chance to try the fixup of the pi_state. So once we are
1124          * back from handling the fault we need to check the pi_state
1125          * after reacquiring the hash bucket lock and before trying to
1126          * do another fixup. When the fixup has been done already we
1127          * simply return.
1128          */
1129 handle_fault:
1130         spin_unlock(q->lock_ptr);
1131
1132         ret = futex_handle_fault((unsigned long)uaddr, attempt++);
1133
1134         spin_lock(q->lock_ptr);
1135
1136         /*
1137          * Check if someone else fixed it for us:
1138          */
1139         if (pi_state->owner != oldowner)
1140                 return 0;
1141
1142         if (ret)
1143                 return ret;
1144
1145         goto retry;
1146 }
1147
1148 /*
1149  * In case we must use restart_block to restart a futex_wait,
1150  * we encode in the 'flags' shared capability
1151  */
1152 #define FLAGS_SHARED            0x01
1153 #define FLAGS_CLOCKRT           0x02
1154
1155 static long futex_wait_restart(struct restart_block *restart);
1156
1157 static int futex_wait(u32 __user *uaddr, int fshared,
1158                       u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
1159 {
1160         struct task_struct *curr = current;
1161         DECLARE_WAITQUEUE(wait, curr);
1162         struct futex_hash_bucket *hb;
1163         struct futex_q q;
1164         u32 uval;
1165         int ret;
1166         struct hrtimer_sleeper t;
1167         int rem = 0;
1168
1169         if (!bitset)
1170                 return -EINVAL;
1171
1172         q.pi_state = NULL;
1173         q.bitset = bitset;
1174 retry:
1175         q.key = FUTEX_KEY_INIT;
1176         ret = get_futex_key(uaddr, fshared, &q.key);
1177         if (unlikely(ret != 0))
1178                 goto out;
1179
1180         hb = queue_lock(&q);
1181
1182         /*
1183          * Access the page AFTER the futex is queued.
1184          * Order is important:
1185          *
1186          *   Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1187          *   Userspace waker:  if (cond(var)) { var = new; futex_wake(&var); }
1188          *
1189          * The basic logical guarantee of a futex is that it blocks ONLY
1190          * if cond(var) is known to be true at the time of blocking, for
1191          * any cond.  If we queued after testing *uaddr, that would open
1192          * a race condition where we could block indefinitely with
1193          * cond(var) false, which would violate the guarantee.
1194          *
1195          * A consequence is that futex_wait() can return zero and absorb
1196          * a wakeup when *uaddr != val on entry to the syscall.  This is
1197          * rare, but normal.
1198          *
1199          * for shared futexes, we hold the mmap semaphore, so the mapping
1200          * cannot have changed since we looked it up in get_futex_key.
1201          */
1202         ret = get_futex_value_locked(&uval, uaddr);
1203
1204         if (unlikely(ret)) {
1205                 queue_unlock(&q, hb);
1206                 put_futex_key(fshared, &q.key);
1207
1208                 ret = get_user(uval, uaddr);
1209
1210                 if (!ret)
1211                         goto retry;
1212                 return ret;
1213         }
1214         ret = -EWOULDBLOCK;
1215         if (uval != val)
1216                 goto out_unlock_put_key;
1217
1218         /* Only actually queue if *uaddr contained val.  */
1219         queue_me(&q, hb);
1220
1221         /*
1222          * There might have been scheduling since the queue_me(), as we
1223          * cannot hold a spinlock across the get_user() in case it
1224          * faults, and we cannot just set TASK_INTERRUPTIBLE state when
1225          * queueing ourselves into the futex hash.  This code thus has to
1226          * rely on the futex_wake() code removing us from hash when it
1227          * wakes us up.
1228          */
1229
1230         /* add_wait_queue is the barrier after __set_current_state. */
1231         __set_current_state(TASK_INTERRUPTIBLE);
1232         add_wait_queue(&q.waiter, &wait);
1233         /*
1234          * !plist_node_empty() is safe here without any lock.
1235          * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
1236          */
1237         if (likely(!plist_node_empty(&q.list))) {
1238                 if (!abs_time)
1239                         schedule();
1240                 else {
1241                         unsigned long slack;
1242                         slack = current->timer_slack_ns;
1243                         if (rt_task(current))
1244                                 slack = 0;
1245                         hrtimer_init_on_stack(&t.timer,
1246                                               clockrt ? CLOCK_REALTIME :
1247                                               CLOCK_MONOTONIC,
1248                                               HRTIMER_MODE_ABS);
1249                         hrtimer_init_sleeper(&t, current);
1250                         hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack);
1251
1252                         hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS);
1253                         if (!hrtimer_active(&t.timer))
1254                                 t.task = NULL;
1255
1256                         /*
1257                          * the timer could have already expired, in which
1258                          * case current would be flagged for rescheduling.
1259                          * Don't bother calling schedule.
1260                          */
1261                         if (likely(t.task))
1262                                 schedule();
1263
1264                         hrtimer_cancel(&t.timer);
1265
1266                         /* Flag if a timeout occured */
1267                         rem = (t.task == NULL);
1268
1269                         destroy_hrtimer_on_stack(&t.timer);
1270                 }
1271         }
1272         __set_current_state(TASK_RUNNING);
1273
1274         /*
1275          * NOTE: we don't remove ourselves from the waitqueue because
1276          * we are the only user of it.
1277          */
1278
1279         /* If we were woken (and unqueued), we succeeded, whatever. */
1280         if (!unqueue_me(&q))
1281                 return 0;
1282         if (rem)
1283                 return -ETIMEDOUT;
1284
1285         /*
1286          * We expect signal_pending(current), but another thread may
1287          * have handled it for us already.
1288          */
1289         if (!abs_time)
1290                 return -ERESTARTSYS;
1291         else {
1292                 struct restart_block *restart;
1293                 restart = &current_thread_info()->restart_block;
1294                 restart->fn = futex_wait_restart;
1295                 restart->futex.uaddr = (u32 *)uaddr;
1296                 restart->futex.val = val;
1297                 restart->futex.time = abs_time->tv64;
1298                 restart->futex.bitset = bitset;
1299                 restart->futex.flags = 0;
1300
1301                 if (fshared)
1302                         restart->futex.flags |= FLAGS_SHARED;
1303                 if (clockrt)
1304                         restart->futex.flags |= FLAGS_CLOCKRT;
1305                 return -ERESTART_RESTARTBLOCK;
1306         }
1307
1308 out_unlock_put_key:
1309         queue_unlock(&q, hb);
1310         put_futex_key(fshared, &q.key);
1311
1312 out:
1313         return ret;
1314 }
1315
1316
1317 static long futex_wait_restart(struct restart_block *restart)
1318 {
1319         u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
1320         int fshared = 0;
1321         ktime_t t;
1322
1323         t.tv64 = restart->futex.time;
1324         restart->fn = do_no_restart_syscall;
1325         if (restart->futex.flags & FLAGS_SHARED)
1326                 fshared = 1;
1327         return (long)futex_wait(uaddr, fshared, restart->futex.val, &t,
1328                                 restart->futex.bitset,
1329                                 restart->futex.flags & FLAGS_CLOCKRT);
1330 }
1331
1332
1333 /*
1334  * Userspace tried a 0 -> TID atomic transition of the futex value
1335  * and failed. The kernel side here does the whole locking operation:
1336  * if there are waiters then it will block, it does PI, etc. (Due to
1337  * races the kernel might see a 0 value of the futex too.)
1338  */
1339 static int futex_lock_pi(u32 __user *uaddr, int fshared,
1340                          int detect, ktime_t *time, int trylock)
1341 {
1342         struct hrtimer_sleeper timeout, *to = NULL;
1343         struct task_struct *curr = current;
1344         struct futex_hash_bucket *hb;
1345         u32 uval, newval, curval;
1346         struct futex_q q;
1347         int ret, lock_taken, ownerdied = 0, attempt = 0;
1348
1349         if (refill_pi_state_cache())
1350                 return -ENOMEM;
1351
1352         if (time) {
1353                 to = &timeout;
1354                 hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME,
1355                                       HRTIMER_MODE_ABS);
1356                 hrtimer_init_sleeper(to, current);
1357                 hrtimer_set_expires(&to->timer, *time);
1358         }
1359
1360         q.pi_state = NULL;
1361 retry:
1362         q.key = FUTEX_KEY_INIT;
1363         ret = get_futex_key(uaddr, fshared, &q.key);
1364         if (unlikely(ret != 0))
1365                 goto out;
1366
1367 retry_unlocked:
1368         hb = queue_lock(&q);
1369
1370 retry_locked:
1371         ret = lock_taken = 0;
1372
1373         /*
1374          * To avoid races, we attempt to take the lock here again
1375          * (by doing a 0 -> TID atomic cmpxchg), while holding all
1376          * the locks. It will most likely not succeed.
1377          */
1378         newval = task_pid_vnr(current);
1379
1380         curval = cmpxchg_futex_value_locked(uaddr, 0, newval);
1381
1382         if (unlikely(curval == -EFAULT))
1383                 goto uaddr_faulted;
1384
1385         /*
1386          * Detect deadlocks. In case of REQUEUE_PI this is a valid
1387          * situation and we return success to user space.
1388          */
1389         if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) {
1390                 ret = -EDEADLK;
1391                 goto out_unlock_put_key;
1392         }
1393
1394         /*
1395          * Surprise - we got the lock. Just return to userspace:
1396          */
1397         if (unlikely(!curval))
1398                 goto out_unlock_put_key;
1399
1400         uval = curval;
1401
1402         /*
1403          * Set the WAITERS flag, so the owner will know it has someone
1404          * to wake at next unlock
1405          */
1406         newval = curval | FUTEX_WAITERS;
1407
1408         /*
1409          * There are two cases, where a futex might have no owner (the
1410          * owner TID is 0): OWNER_DIED. We take over the futex in this
1411          * case. We also do an unconditional take over, when the owner
1412          * of the futex died.
1413          *
1414          * This is safe as we are protected by the hash bucket lock !
1415          */
1416         if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
1417                 /* Keep the OWNER_DIED bit */
1418                 newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current);
1419                 ownerdied = 0;
1420                 lock_taken = 1;
1421         }
1422
1423         curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
1424
1425         if (unlikely(curval == -EFAULT))
1426                 goto uaddr_faulted;
1427         if (unlikely(curval != uval))
1428                 goto retry_locked;
1429
1430         /*
1431          * We took the lock due to owner died take over.
1432          */
1433         if (unlikely(lock_taken))
1434                 goto out_unlock_put_key;
1435
1436         /*
1437          * We dont have the lock. Look up the PI state (or create it if
1438          * we are the first waiter):
1439          */
1440         ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state);
1441
1442         if (unlikely(ret)) {
1443                 switch (ret) {
1444
1445                 case -EAGAIN:
1446                         /*
1447                          * Task is exiting and we just wait for the
1448                          * exit to complete.
1449                          */
1450                         queue_unlock(&q, hb);
1451                         cond_resched();
1452                         goto retry;
1453
1454                 case -ESRCH:
1455                         /*
1456                          * No owner found for this futex. Check if the
1457                          * OWNER_DIED bit is set to figure out whether
1458                          * this is a robust futex or not.
1459                          */
1460                         if (get_futex_value_locked(&curval, uaddr))
1461                                 goto uaddr_faulted;
1462
1463                         /*
1464                          * We simply start over in case of a robust
1465                          * futex. The code above will take the futex
1466                          * and return happy.
1467                          */
1468                         if (curval & FUTEX_OWNER_DIED) {
1469                                 ownerdied = 1;
1470                                 goto retry_locked;
1471                         }
1472                 default:
1473                         goto out_unlock_put_key;
1474                 }
1475         }
1476
1477         /*
1478          * Only actually queue now that the atomic ops are done:
1479          */
1480         queue_me(&q, hb);
1481
1482         WARN_ON(!q.pi_state);
1483         /*
1484          * Block on the PI mutex:
1485          */
1486         if (!trylock)
1487                 ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1);
1488         else {
1489                 ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
1490                 /* Fixup the trylock return value: */
1491                 ret = ret ? 0 : -EWOULDBLOCK;
1492         }
1493
1494         spin_lock(q.lock_ptr);
1495
1496         if (!ret) {
1497                 /*
1498                  * Got the lock. We might not be the anticipated owner
1499                  * if we did a lock-steal - fix up the PI-state in
1500                  * that case:
1501                  */
1502                 if (q.pi_state->owner != curr)
1503                         ret = fixup_pi_state_owner(uaddr, &q, curr, fshared);
1504         } else {
1505                 /*
1506                  * Catch the rare case, where the lock was released
1507                  * when we were on the way back before we locked the
1508                  * hash bucket.
1509                  */
1510                 if (q.pi_state->owner == curr) {
1511                         /*
1512                          * Try to get the rt_mutex now. This might
1513                          * fail as some other task acquired the
1514                          * rt_mutex after we removed ourself from the
1515                          * rt_mutex waiters list.
1516                          */
1517                         if (rt_mutex_trylock(&q.pi_state->pi_mutex))
1518                                 ret = 0;
1519                         else {
1520                                 /*
1521                                  * pi_state is incorrect, some other
1522                                  * task did a lock steal and we
1523                                  * returned due to timeout or signal
1524                                  * without taking the rt_mutex. Too
1525                                  * late. We can access the
1526                                  * rt_mutex_owner without locking, as
1527                                  * the other task is now blocked on
1528                                  * the hash bucket lock. Fix the state
1529                                  * up.
1530                                  */
1531                                 struct task_struct *owner;
1532                                 int res;
1533
1534                                 owner = rt_mutex_owner(&q.pi_state->pi_mutex);
1535                                 res = fixup_pi_state_owner(uaddr, &q, owner,
1536                                                            fshared);
1537
1538                                 /* propagate -EFAULT, if the fixup failed */
1539                                 if (res)
1540                                         ret = res;
1541                         }
1542                 } else {
1543                         /*
1544                          * Paranoia check. If we did not take the lock
1545                          * in the trylock above, then we should not be
1546                          * the owner of the rtmutex, neither the real
1547                          * nor the pending one:
1548                          */
1549                         if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr)
1550                                 printk(KERN_ERR "futex_lock_pi: ret = %d "
1551                                        "pi-mutex: %p pi-state %p\n", ret,
1552                                        q.pi_state->pi_mutex.owner,
1553                                        q.pi_state->owner);
1554                 }
1555         }
1556
1557         /* Unqueue and drop the lock */
1558         unqueue_me_pi(&q);
1559
1560         if (to)
1561                 destroy_hrtimer_on_stack(&to->timer);
1562         return ret != -EINTR ? ret : -ERESTARTNOINTR;
1563
1564 out_unlock_put_key:
1565         queue_unlock(&q, hb);
1566
1567 out_put_key:
1568         put_futex_key(fshared, &q.key);
1569 out:
1570         if (to)
1571                 destroy_hrtimer_on_stack(&to->timer);
1572         return ret;
1573
1574 uaddr_faulted:
1575         /*
1576          * We have to r/w  *(int __user *)uaddr, and we have to modify it
1577          * atomically.  Therefore, if we continue to fault after get_user()
1578          * below, we need to handle the fault ourselves, while still holding
1579          * the mmap_sem.  This can occur if the uaddr is under contention as
1580          * we have to drop the mmap_sem in order to call get_user().
1581          */
1582         queue_unlock(&q, hb);
1583
1584         if (attempt++) {
1585                 ret = futex_handle_fault((unsigned long)uaddr, attempt);
1586                 if (ret)
1587                         goto out_put_key;
1588                 goto retry_unlocked;
1589         }
1590
1591         ret = get_user(uval, uaddr);
1592         if (!ret)
1593                 goto retry;
1594
1595         if (to)
1596                 destroy_hrtimer_on_stack(&to->timer);
1597         return ret;
1598 }
1599
1600 /*
1601  * Userspace attempted a TID -> 0 atomic transition, and failed.
1602  * This is the in-kernel slowpath: we look up the PI state (if any),
1603  * and do the rt-mutex unlock.
1604  */
1605 static int futex_unlock_pi(u32 __user *uaddr, int fshared)
1606 {
1607         struct futex_hash_bucket *hb;
1608         struct futex_q *this, *next;
1609         u32 uval;
1610         struct plist_head *head;
1611         union futex_key key = FUTEX_KEY_INIT;
1612         int ret, attempt = 0;
1613
1614 retry:
1615         if (get_user(uval, uaddr))
1616                 return -EFAULT;
1617         /*
1618          * We release only a lock we actually own:
1619          */
1620         if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
1621                 return -EPERM;
1622
1623         ret = get_futex_key(uaddr, fshared, &key);
1624         if (unlikely(ret != 0))
1625                 goto out;
1626
1627         hb = hash_futex(&key);
1628 retry_unlocked:
1629         spin_lock(&hb->lock);
1630
1631         /*
1632          * To avoid races, try to do the TID -> 0 atomic transition
1633          * again. If it succeeds then we can return without waking
1634          * anyone else up:
1635          */
1636         if (!(uval & FUTEX_OWNER_DIED))
1637                 uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0);
1638
1639
1640         if (unlikely(uval == -EFAULT))
1641                 goto pi_faulted;
1642         /*
1643          * Rare case: we managed to release the lock atomically,
1644          * no need to wake anyone else up:
1645          */
1646         if (unlikely(uval == task_pid_vnr(current)))
1647                 goto out_unlock;
1648
1649         /*
1650          * Ok, other tasks may need to be woken up - check waiters
1651          * and do the wakeup if necessary:
1652          */
1653         head = &hb->chain;
1654
1655         plist_for_each_entry_safe(this, next, head, list) {
1656                 if (!match_futex (&this->key, &key))
1657                         continue;
1658                 ret = wake_futex_pi(uaddr, uval, this);
1659                 /*
1660                  * The atomic access to the futex value
1661                  * generated a pagefault, so retry the
1662                  * user-access and the wakeup:
1663                  */
1664                 if (ret == -EFAULT)
1665                         goto pi_faulted;
1666                 goto out_unlock;
1667         }
1668         /*
1669          * No waiters - kernel unlocks the futex:
1670          */
1671         if (!(uval & FUTEX_OWNER_DIED)) {
1672                 ret = unlock_futex_pi(uaddr, uval);
1673                 if (ret == -EFAULT)
1674                         goto pi_faulted;
1675         }
1676
1677 out_unlock:
1678         spin_unlock(&hb->lock);
1679         put_futex_key(fshared, &key);
1680
1681 out:
1682         return ret;
1683
1684 pi_faulted:
1685         /*
1686          * We have to r/w  *(int __user *)uaddr, and we have to modify it
1687          * atomically.  Therefore, if we continue to fault after get_user()
1688          * below, we need to handle the fault ourselves, while still holding
1689          * the mmap_sem.  This can occur if the uaddr is under contention as
1690          * we have to drop the mmap_sem in order to call get_user().
1691          */
1692         spin_unlock(&hb->lock);
1693
1694         if (attempt++) {
1695                 ret = futex_handle_fault((unsigned long)uaddr, attempt);
1696                 if (ret)
1697                         goto out;
1698                 uval = 0;
1699                 goto retry_unlocked;
1700         }
1701
1702         ret = get_user(uval, uaddr);
1703         if (!ret)
1704                 goto retry;
1705
1706         return ret;
1707 }
1708
1709 /*
1710  * Support for robust futexes: the kernel cleans up held futexes at
1711  * thread exit time.
1712  *
1713  * Implementation: user-space maintains a per-thread list of locks it
1714  * is holding. Upon do_exit(), the kernel carefully walks this list,
1715  * and marks all locks that are owned by this thread with the
1716  * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
1717  * always manipulated with the lock held, so the list is private and
1718  * per-thread. Userspace also maintains a per-thread 'list_op_pending'
1719  * field, to allow the kernel to clean up if the thread dies after
1720  * acquiring the lock, but just before it could have added itself to
1721  * the list. There can only be one such pending lock.
1722  */
1723
1724 /**
1725  * sys_set_robust_list - set the robust-futex list head of a task
1726  * @head: pointer to the list-head
1727  * @len: length of the list-head, as userspace expects
1728  */
1729 asmlinkage long
1730 sys_set_robust_list(struct robust_list_head __user *head,
1731                     size_t len)
1732 {
1733         if (!futex_cmpxchg_enabled)
1734                 return -ENOSYS;
1735         /*
1736          * The kernel knows only one size for now:
1737          */
1738         if (unlikely(len != sizeof(*head)))
1739                 return -EINVAL;
1740
1741         current->robust_list = head;
1742
1743         return 0;
1744 }
1745
1746 /**
1747  * sys_get_robust_list - get the robust-futex list head of a task
1748  * @pid: pid of the process [zero for current task]
1749  * @head_ptr: pointer to a list-head pointer, the kernel fills it in
1750  * @len_ptr: pointer to a length field, the kernel fills in the header size
1751  */
1752 asmlinkage long
1753 sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr,
1754                     size_t __user *len_ptr)
1755 {
1756         struct robust_list_head __user *head;
1757         unsigned long ret;
1758
1759         if (!futex_cmpxchg_enabled)
1760                 return -ENOSYS;
1761
1762         if (!pid)
1763                 head = current->robust_list;
1764         else {
1765                 struct task_struct *p;
1766
1767                 ret = -ESRCH;
1768                 rcu_read_lock();
1769                 p = find_task_by_vpid(pid);
1770                 if (!p)
1771                         goto err_unlock;
1772                 ret = -EPERM;
1773                 if ((current->euid != p->euid) && (current->euid != p->uid) &&
1774                                 !capable(CAP_SYS_PTRACE))
1775                         goto err_unlock;
1776                 head = p->robust_list;
1777                 rcu_read_unlock();
1778         }
1779
1780         if (put_user(sizeof(*head), len_ptr))
1781                 return -EFAULT;
1782         return put_user(head, head_ptr);
1783
1784 err_unlock:
1785         rcu_read_unlock();
1786
1787         return ret;
1788 }
1789
1790 /*
1791  * Process a futex-list entry, check whether it's owned by the
1792  * dying task, and do notification if so:
1793  */
1794 int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
1795 {
1796         u32 uval, nval, mval;
1797
1798 retry:
1799         if (get_user(uval, uaddr))
1800                 return -1;
1801
1802         if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
1803                 /*
1804                  * Ok, this dying thread is truly holding a futex
1805                  * of interest. Set the OWNER_DIED bit atomically
1806                  * via cmpxchg, and if the value had FUTEX_WAITERS
1807                  * set, wake up a waiter (if any). (We have to do a
1808                  * futex_wake() even if OWNER_DIED is already set -
1809                  * to handle the rare but possible case of recursive
1810                  * thread-death.) The rest of the cleanup is done in
1811                  * userspace.
1812                  */
1813                 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
1814                 nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);
1815
1816                 if (nval == -EFAULT)
1817                         return -1;
1818
1819                 if (nval != uval)
1820                         goto retry;
1821
1822                 /*
1823                  * Wake robust non-PI futexes here. The wakeup of
1824                  * PI futexes happens in exit_pi_state():
1825                  */
1826                 if (!pi && (uval & FUTEX_WAITERS))
1827                         futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
1828         }
1829         return 0;
1830 }
1831
1832 /*
1833  * Fetch a robust-list pointer. Bit 0 signals PI futexes:
1834  */
1835 static inline int fetch_robust_entry(struct robust_list __user **entry,
1836                                      struct robust_list __user * __user *head,
1837                                      int *pi)
1838 {
1839         unsigned long uentry;
1840
1841         if (get_user(uentry, (unsigned long __user *)head))
1842                 return -EFAULT;
1843
1844         *entry = (void __user *)(uentry & ~1UL);
1845         *pi = uentry & 1;
1846
1847         return 0;
1848 }
1849
1850 /*
1851  * Walk curr->robust_list (very carefully, it's a userspace list!)
1852  * and mark any locks found there dead, and notify any waiters.
1853  *
1854  * We silently return on any sign of list-walking problem.
1855  */
1856 void exit_robust_list(struct task_struct *curr)
1857 {
1858         struct robust_list_head __user *head = curr->robust_list;
1859         struct robust_list __user *entry, *next_entry, *pending;
1860         unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
1861         unsigned long futex_offset;
1862         int rc;
1863
1864         if (!futex_cmpxchg_enabled)
1865                 return;
1866
1867         /*
1868          * Fetch the list head (which was registered earlier, via
1869          * sys_set_robust_list()):
1870          */
1871         if (fetch_robust_entry(&entry, &head->list.next, &pi))
1872                 return;
1873         /*
1874          * Fetch the relative futex offset:
1875          */
1876         if (get_user(futex_offset, &head->futex_offset))
1877                 return;
1878         /*
1879          * Fetch any possibly pending lock-add first, and handle it
1880          * if it exists:
1881          */
1882         if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
1883                 return;
1884
1885         next_entry = NULL;      /* avoid warning with gcc */
1886         while (entry != &head->list) {
1887                 /*
1888                  * Fetch the next entry in the list before calling
1889                  * handle_futex_death:
1890                  */
1891                 rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
1892                 /*
1893                  * A pending lock might already be on the list, so
1894                  * don't process it twice:
1895                  */
1896                 if (entry != pending)
1897                         if (handle_futex_death((void __user *)entry + futex_offset,
1898                                                 curr, pi))
1899                                 return;
1900                 if (rc)
1901                         return;
1902                 entry = next_entry;
1903                 pi = next_pi;
1904                 /*
1905                  * Avoid excessively long or circular lists:
1906                  */
1907                 if (!--limit)
1908                         break;
1909
1910                 cond_resched();
1911         }
1912
1913         if (pending)
1914                 handle_futex_death((void __user *)pending + futex_offset,
1915                                    curr, pip);
1916 }
1917
1918 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
1919                 u32 __user *uaddr2, u32 val2, u32 val3)
1920 {
1921         int clockrt, ret = -ENOSYS;
1922         int cmd = op & FUTEX_CMD_MASK;
1923         int fshared = 0;
1924
1925         if (!(op & FUTEX_PRIVATE_FLAG))
1926                 fshared = 1;
1927
1928         clockrt = op & FUTEX_CLOCK_REALTIME;
1929         if (clockrt && cmd != FUTEX_WAIT_BITSET)
1930                 return -ENOSYS;
1931
1932         switch (cmd) {
1933         case FUTEX_WAIT:
1934                 val3 = FUTEX_BITSET_MATCH_ANY;
1935         case FUTEX_WAIT_BITSET:
1936                 ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
1937                 break;
1938         case FUTEX_WAKE:
1939                 val3 = FUTEX_BITSET_MATCH_ANY;
1940         case FUTEX_WAKE_BITSET:
1941                 ret = futex_wake(uaddr, fshared, val, val3);
1942                 break;
1943         case FUTEX_REQUEUE:
1944                 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL);
1945                 break;
1946         case FUTEX_CMP_REQUEUE:
1947                 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3);
1948                 break;
1949         case FUTEX_WAKE_OP:
1950                 ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3);
1951                 break;
1952         case FUTEX_LOCK_PI:
1953                 if (futex_cmpxchg_enabled)
1954                         ret = futex_lock_pi(uaddr, fshared, val, timeout, 0);
1955                 break;
1956         case FUTEX_UNLOCK_PI:
1957                 if (futex_cmpxchg_enabled)
1958                         ret = futex_unlock_pi(uaddr, fshared);
1959                 break;
1960         case FUTEX_TRYLOCK_PI:
1961                 if (futex_cmpxchg_enabled)
1962                         ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1);
1963                 break;
1964         default:
1965                 ret = -ENOSYS;
1966         }
1967         return ret;
1968 }
1969
1970
1971 asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val,
1972                           struct timespec __user *utime, u32 __user *uaddr2,
1973                           u32 val3)
1974 {
1975         struct timespec ts;
1976         ktime_t t, *tp = NULL;
1977         u32 val2 = 0;
1978         int cmd = op & FUTEX_CMD_MASK;
1979
1980         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
1981                       cmd == FUTEX_WAIT_BITSET)) {
1982                 if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
1983                         return -EFAULT;
1984                 if (!timespec_valid(&ts))
1985                         return -EINVAL;
1986
1987                 t = timespec_to_ktime(ts);
1988                 if (cmd == FUTEX_WAIT)
1989                         t = ktime_add_safe(ktime_get(), t);
1990                 tp = &t;
1991         }
1992         /*
1993          * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE.
1994          * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
1995          */
1996         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
1997             cmd == FUTEX_WAKE_OP)
1998                 val2 = (u32) (unsigned long) utime;
1999
2000         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
2001 }
2002
2003 static int __init futex_init(void)
2004 {
2005         u32 curval;
2006         int i;
2007
2008         /*
2009          * This will fail and we want it. Some arch implementations do
2010          * runtime detection of the futex_atomic_cmpxchg_inatomic()
2011          * functionality. We want to know that before we call in any
2012          * of the complex code paths. Also we want to prevent
2013          * registration of robust lists in that case. NULL is
2014          * guaranteed to fault and we get -EFAULT on functional
2015          * implementation, the non functional ones will return
2016          * -ENOSYS.
2017          */
2018         curval = cmpxchg_futex_value_locked(NULL, 0, 0);
2019         if (curval == -EFAULT)
2020                 futex_cmpxchg_enabled = 1;
2021
2022         for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
2023                 plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock);
2024                 spin_lock_init(&futex_queues[i].lock);
2025         }
2026
2027         return 0;
2028 }
2029 __initcall(futex_init);