diff options
Diffstat (limited to 'kernel/futex.c')
| -rw-r--r-- | kernel/futex.c | 2758 |
1 files changed, 0 insertions, 2758 deletions
diff --git a/kernel/futex.c b/kernel/futex.c deleted file mode 100644 index c3a1a55a5214..000000000000 --- a/kernel/futex.c +++ /dev/null @@ -1,2758 +0,0 @@ -/* - * Fast Userspace Mutexes (which I call "Futexes!"). - * (C) Rusty Russell, IBM 2002 - * - * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar - * (C) Copyright 2003 Red Hat Inc, All Rights Reserved - * - * Removed page pinning, fix privately mapped COW pages and other cleanups - * (C) Copyright 2003, 2004 Jamie Lokier - * - * Robust futex support started by Ingo Molnar - * (C) Copyright 2006 Red Hat Inc, All Rights Reserved - * Thanks to Thomas Gleixner for suggestions, analysis and fixes. - * - * PI-futex support started by Ingo Molnar and Thomas Gleixner - * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> - * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> - * - * PRIVATE futexes by Eric Dumazet - * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com> - * - * Requeue-PI support by Darren Hart <dvhltc@us.ibm.com> - * Copyright (C) IBM Corporation, 2009 - * Thanks to Thomas Gleixner for conceptual design and careful reviews. - * - * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly - * enough at me, Linus for the original (flawed) idea, Matthew - * Kirkwood for proof-of-concept implementation. - * - * "The futexes are also cursed." - * "But they come in a choice of three flavours!" - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA - */ -#include <linux/slab.h> -#include <linux/poll.h> -#include <linux/fs.h> -#include <linux/file.h> -#include <linux/jhash.h> -#include <linux/init.h> -#include <linux/futex.h> -#include <linux/mount.h> -#include <linux/pagemap.h> -#include <linux/syscalls.h> -#include <linux/signal.h> -#include <linux/export.h> -#include <linux/magic.h> -#include <linux/pid.h> -#include <linux/nsproxy.h> -#include <linux/ptrace.h> -#include <linux/sched/rt.h> -#include <linux/hugetlb.h> -#include <linux/freezer.h> - -#include <asm/futex.h> - -#include "rtmutex_common.h" - -int __read_mostly futex_cmpxchg_enabled; - -#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8) - -/* - * Futex flags used to encode options to functions and preserve them across - * restarts. - */ -#define FLAGS_SHARED 0x01 -#define FLAGS_CLOCKRT 0x02 -#define FLAGS_HAS_TIMEOUT 0x04 - -/* - * Priority Inheritance state: - */ -struct futex_pi_state { - /* - * list of 'owned' pi_state instances - these have to be - * cleaned up in do_exit() if the task exits prematurely: - */ - struct list_head list; - - /* - * The PI object: - */ - struct rt_mutex pi_mutex; - - struct task_struct *owner; - atomic_t refcount; - - union futex_key key; -}; - -/** - * struct futex_q - The hashed futex queue entry, one per waiting task - * @list: priority-sorted list of tasks waiting on this futex - * @task: the task waiting on the futex - * @lock_ptr: the hash bucket lock - * @key: the key the futex is hashed on - * @pi_state: optional priority inheritance state - * @rt_waiter: rt_waiter storage for use with requeue_pi - * @requeue_pi_key: the requeue_pi target futex key - * @bitset: bitset for the optional bitmasked wakeup - * - * We use this hashed waitqueue, instead of a normal wait_queue_t, so - * we can wake only the relevant ones (hashed queues may be shared). - * - * A futex_q has a woken state, just like tasks have TASK_RUNNING. - * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. - * The order of wakeup is always to make the first condition true, then - * the second. - * - * PI futexes are typically woken before they are removed from the hash list via - * the rt_mutex code. See unqueue_me_pi(). - */ -struct futex_q { - struct plist_node list; - - struct task_struct *task; - spinlock_t *lock_ptr; - union futex_key key; - struct futex_pi_state *pi_state; - struct rt_mutex_waiter *rt_waiter; - union futex_key *requeue_pi_key; - u32 bitset; -}; - -static const struct futex_q futex_q_init = { - /* list gets initialized in queue_me()*/ - .key = FUTEX_KEY_INIT, - .bitset = FUTEX_BITSET_MATCH_ANY -}; - -/* - * Hash buckets are shared by all the futex_keys that hash to the same - * location. Each key may have multiple futex_q structures, one for each task - * waiting on a futex. - */ -struct futex_hash_bucket { - spinlock_t lock; - struct plist_head chain; -}; - -static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS]; - -/* - * We hash on the keys returned from get_futex_key (see below). - */ -static struct futex_hash_bucket *hash_futex(union futex_key *key) -{ - u32 hash = jhash2((u32*)&key->both.word, - (sizeof(key->both.word)+sizeof(key->both.ptr))/4, - key->both.offset); - return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)]; -} - -/* - * Return 1 if two futex_keys are equal, 0 otherwise. - */ -static inline int match_futex(union futex_key *key1, union futex_key *key2) -{ - return (key1 && key2 - && key1->both.word == key2->both.word - && key1->both.ptr == key2->both.ptr - && key1->both.offset == key2->both.offset); -} - -/* - * Take a reference to the resource addressed by a key. - * Can be called while holding spinlocks. - * - */ -static void get_futex_key_refs(union futex_key *key) -{ - if (!key->both.ptr) - return; - - switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { - case FUT_OFF_INODE: - ihold(key->shared.inode); - break; - case FUT_OFF_MMSHARED: - atomic_inc(&key->private.mm->mm_count); - break; - } -} - -/* - * Drop a reference to the resource addressed by a key. - * The hash bucket spinlock must not be held. - */ -static void drop_futex_key_refs(union futex_key *key) -{ - if (!key->both.ptr) { - /* If we're here then we tried to put a key we failed to get */ - WARN_ON_ONCE(1); - return; - } - - switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { - case FUT_OFF_INODE: - iput(key->shared.inode); - break; - case FUT_OFF_MMSHARED: - mmdrop(key->private.mm); - break; - } -} - -/** - * get_futex_key() - Get parameters which are the keys for a futex - * @uaddr: virtual address of the futex - * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED - * @key: address where result is stored. - * @rw: mapping needs to be read/write (values: VERIFY_READ, - * VERIFY_WRITE) - * - * Return: a negative error code or 0 - * - * The key words are stored in *key on success. - * - * For shared mappings, it's (page->index, file_inode(vma->vm_file), - * offset_within_page). For private mappings, it's (uaddr, current->mm). - * We can usually work out the index without swapping in the page. - * - * lock_page() might sleep, the caller should not hold a spinlock. - */ -static int -get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) -{ - unsigned long address = (unsigned long)uaddr; - struct mm_struct *mm = current->mm; - struct page *page, *page_head; - int err, ro = 0; - - /* - * The futex address must be "naturally" aligned. - */ - key->both.offset = address % PAGE_SIZE; - if (unlikely((address % sizeof(u32)) != 0)) - return -EINVAL; - address -= key->both.offset; - - /* - * PROCESS_PRIVATE futexes are fast. - * As the mm cannot disappear under us and the 'key' only needs - * virtual address, we dont even have to find the underlying vma. - * Note : We do have to check 'uaddr' is a valid user address, - * but access_ok() should be faster than find_vma() - */ - if (!fshared) { - if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))) - return -EFAULT; - key->private.mm = mm; - key->private.address = address; - get_futex_key_refs(key); - return 0; - } - -again: - err = get_user_pages_fast(address, 1, 1, &page); - /* - * If write access is not required (eg. FUTEX_WAIT), try - * and get read-only access. - */ - if (err == -EFAULT && rw == VERIFY_READ) { - err = get_user_pages_fast(address, 1, 0, &page); - ro = 1; - } - if (err < 0) - return err; - else - err = 0; - -#ifdef CONFIG_TRANSPARENT_HUGEPAGE - page_head = page; - if (unlikely(PageTail(page))) { - put_page(page); - /* serialize against __split_huge_page_splitting() */ - local_irq_disable(); - if (likely(__get_user_pages_fast(address, 1, 1, &page) == 1)) { - page_head = compound_head(page); - /* - * page_head is valid pointer but we must pin - * it before taking the PG_lock and/or - * PG_compound_lock. The moment we re-enable - * irqs __split_huge_page_splitting() can - * return and the head page can be freed from - * under us. We can't take the PG_lock and/or - * PG_compound_lock on a page that could be - * freed from under us. - */ - if (page != page_head) { - get_page(page_head); - put_page(page); - } - local_irq_enable(); - } else { - local_irq_enable(); - goto again; - } - } -#else - page_head = compound_head(page); - if (page != page_head) { - get_page(page_head); - put_page(page); - } -#endif - - lock_page(page_head); - - /* - * If page_head->mapping is NULL, then it cannot be a PageAnon - * page; but it might be the ZERO_PAGE or in the gate area or - * in a special mapping (all cases which we are happy to fail); - * or it may have been a good file page when get_user_pages_fast - * found it, but truncated or holepunched or subjected to - * invalidate_complete_page2 before we got the page lock (also - * cases which we are happy to fail). And we hold a reference, - * so refcount care in invalidate_complete_page's remove_mapping - * prevents drop_caches from setting mapping to NULL beneath us. - * - * The case we do have to guard against is when memory pressure made - * shmem_writepage move it from filecache to swapcache beneath us: - * an unlikely race, but we do need to retry for page_head->mapping. - */ - if (!page_head->mapping) { - int shmem_swizzled = PageSwapCache(page_head); - unlock_page(page_head); - put_page(page_head); - if (shmem_swizzled) - goto again; - return -EFAULT; - } - - /* - * Private mappings are handled in a simple way. - * - * NOTE: When userspace waits on a MAP_SHARED mapping, even if - * it's a read-only handle, it's expected that futexes attach to - * the object not the particular process. - */ - if (PageAnon(page_head)) { - /* - * A RO anonymous page will never change and thus doesn't make - * sense for futex operations. - */ - if (ro) { - err = -EFAULT; - goto out; - } - - key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ - key->private.mm = mm; - key->private.address = address; - } else { - key->both.offset |= FUT_OFF_INODE; /* inode-based key */ - key->shared.inode = page_head->mapping->host; - key->shared.pgoff = basepage_index(page); - } - - get_futex_key_refs(key); - -out: - unlock_page(page_head); - put_page(page_head); - return err; -} - -static inline void put_futex_key(union futex_key *key) -{ - drop_futex_key_refs(key); -} - -/** - * fault_in_user_writeable() - Fault in user address and verify RW access - * @uaddr: pointer to faulting user space address - * - * Slow path to fixup the fault we just took in the atomic write - * access to @uaddr. - * - * We have no generic implementation of a non-destructive write to the - * user address. We know that we faulted in the atomic pagefault - * disabled section so we can as well avoid the #PF overhead by - * calling get_user_pages() right away. - */ -static int fault_in_user_writeable(u32 __user *uaddr) -{ - struct mm_struct *mm = current->mm; - int ret; - - down_read(&mm->mmap_sem); - ret = fixup_user_fault(current, mm, (unsigned long)uaddr, - FAULT_FLAG_WRITE); - up_read(&mm->mmap_sem); - - return ret < 0 ? ret : 0; -} - -/** - * futex_top_waiter() - Return the highest priority waiter on a futex - * @hb: the hash bucket the futex_q's reside in - * @key: the futex key (to distinguish it from other futex futex_q's) - * - * Must be called with the hb lock held. - */ -static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, - union futex_key *key) -{ - struct futex_q *this; - - plist_for_each_entry(this, &hb->chain, list) { - if (match_futex(&this->key, key)) - return this; - } - return NULL; -} - -static int cmpxchg_futex_value_locked(u32 *curval, u32 __user *uaddr, - u32 uval, u32 newval) -{ - int ret; - - pagefault_disable(); - ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval); - pagefault_enable(); - - return ret; -} - -static int get_futex_value_locked(u32 *dest, u32 __user *from) -{ - int ret; - - pagefault_disable(); - ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); - pagefault_enable(); - - return ret ? -EFAULT : 0; -} - - -/* - * PI code: - */ -static int refill_pi_state_cache(void) -{ - struct futex_pi_state *pi_state; - - if (likely(current->pi_state_cache)) - return 0; - - pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); - - if (!pi_state) - return -ENOMEM; - - INIT_LIST_HEAD(&pi_state->list); - /* pi_mutex gets initialized later */ - pi_state->owner = NULL; - atomic_set(&pi_state->refcount, 1); - pi_state->key = FUTEX_KEY_INIT; - - current->pi_state_cache = pi_state; - - return 0; -} - -static struct futex_pi_state * alloc_pi_state(void) -{ - struct futex_pi_state *pi_state = current->pi_state_cache; - - WARN_ON(!pi_state); - current->pi_state_cache = NULL; - - return pi_state; -} - -static void free_pi_state(struct futex_pi_state *pi_state) -{ - if (!atomic_dec_and_test(&pi_state->refcount)) - return; - - /* - * If pi_state->owner is NULL, the owner is most probably dying - * and has cleaned up the pi_state already - */ - if (pi_state->owner) { - raw_spin_lock_irq(&pi_state->owner->pi_lock); - list_del_init(&pi_state->list); - raw_spin_unlock_irq(&pi_state->owner->pi_lock); - - rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); - } - - if (current->pi_state_cache) - kfree(pi_state); - else { - /* - * pi_state->list is already empty. - * clear pi_state->owner. - * refcount is at 0 - put it back to 1. - */ - pi_state->owner = NULL; - atomic_set(&pi_state->refcount, 1); - current->pi_state_cache = pi_state; - } -} - -/* - * Look up the task based on what TID userspace gave us. - * We dont trust it. - */ -static struct task_struct * futex_find_get_task(pid_t pid) -{ - struct task_struct *p; - - rcu_read_lock(); - p = find_task_by_vpid(pid); - if (p) - get_task_struct(p); - - rcu_read_unlock(); - - return p; -} - -/* - * This task is holding PI mutexes at exit time => bad. - * Kernel cleans up PI-state, but userspace is likely hosed. - * (Robust-futex cleanup is separate and might save the day for userspace.) - */ -void exit_pi_state_list(struct task_struct *curr) -{ - struct list_head *next, *head = &curr->pi_state_list; - struct futex_pi_state *pi_state; - struct futex_hash_bucket *hb; - union futex_key key = FUTEX_KEY_INIT; - - if (!futex_cmpxchg_enabled) - return; - /* - * We are a ZOMBIE and nobody can enqueue itself on - * pi_state_list anymore, but we have to be careful - * versus waiters unqueueing themselves: - */ - raw_spin_lock_irq(&curr->pi_lock); - while (!list_empty(head)) { - - next = head->next; - pi_state = list_entry(next, struct futex_pi_state, list); - key = pi_state->key; - hb = hash_futex(&key); - raw_spin_unlock_irq(&curr->pi_lock); - - spin_lock(&hb->lock); - - raw_spin_lock_irq(&curr->pi_lock); - /* - * We dropped the pi-lock, so re-check whether this - * task still owns the PI-state: - */ - if (head->next != next) { - spin_unlock(&hb->lock); - continue; - } - - WARN_ON(pi_state->owner != curr); - WARN_ON(list_empty(&pi_state->list)); - list_del_init(&pi_state->list); - pi_state->owner = NULL; - raw_spin_unlock_irq(&curr->pi_lock); - - rt_mutex_unlock(&pi_state->pi_mutex); - - spin_unlock(&hb->lock); - - raw_spin_lock_irq(&curr->pi_lock); - } - raw_spin_unlock_irq(&curr->pi_lock); -} - -static int -lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, - union futex_key *key, struct futex_pi_state **ps) -{ - struct futex_pi_state *pi_state = NULL; - struct futex_q *this, *next; - struct plist_head *head; - struct task_struct *p; - pid_t pid = uval & FUTEX_TID_MASK; - - head = &hb->chain; - - plist_for_each_entry_safe(this, next, head, list) { - if (match_futex(&this->key, key)) { - /* - * Another waiter already exists - bump up - * the refcount and return its pi_state: - */ - pi_state = this->pi_state; - /* - * Userspace might have messed up non-PI and PI futexes - */ - if (unlikely(!pi_state)) - return -EINVAL; - - WARN_ON(!atomic_read(&pi_state->refcount)); - - /* - * When pi_state->owner is NULL then the owner died - * and another waiter is on the fly. pi_state->owner - * is fixed up by the task which acquires - * pi_state->rt_mutex. - * - * We do not check for pid == 0 which can happen when - * the owner died and robust_list_exit() cleared the - * TID. - */ - if (pid && pi_state->owner) { - /* - * Bail out if user space manipulated the - * futex value. - */ - if (pid != task_pid_vnr(pi_state->owner)) - return -EINVAL; - } - - atomic_inc(&pi_state->refcount); - *ps = pi_state; - - return 0; - } - } - - /* - * We are the first waiter - try to look up the real owner and attach - * the new pi_state to it, but bail out when TID = 0 - */ - if (!pid) - return -ESRCH; - p = futex_find_get_task(pid); - if (!p) - return -ESRCH; - - /* - * We need to look at the task state flags to figure out, - * whether the task is exiting. To protect against the do_exit - * change of the task flags, we do this protected by - * p->pi_lock: - */ - raw_spin_lock_irq(&p->pi_lock); - if (unlikely(p->flags & PF_EXITING)) { - /* - * The task is on the way out. When PF_EXITPIDONE is - * set, we know that the task has finished the - * cleanup: - */ - int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; - - raw_spin_unlock_irq(&p->pi_lock); - put_task_struct(p); - return ret; - } - - pi_state = alloc_pi_state(); - - /* - * Initialize the pi_mutex in locked state and make 'p' - * the owner of it: - */ - rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); - - /* Store the key for possible exit cleanups: */ - pi_state->key = *key; - - WARN_ON(!list_empty(&pi_state->list)); - list_add(&pi_state->list, &p->pi_state_list); - pi_state->owner = p; - raw_spin_unlock_irq(&p->pi_lock); - - put_task_struct(p); - - *ps = pi_state; - - return 0; -} - -/** - * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex - * @uaddr: the pi futex user address - * @hb: the pi futex hash bucket - * @key: the futex key associated with uaddr and hb - * @ps: the pi_state pointer where we store the result of the - * lookup - * @task: the task to perform the atomic lock work for. This will - * be "current" except in the case of requeue pi. - * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) - * - * Return: - * 0 - ready to wait; - * 1 - acquired the lock; - * <0 - error - * - * The hb->lock and futex_key refs shall be held by the caller. - */ -static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, - union futex_key *key, - struct futex_pi_state **ps, - struct task_struct *task, int set_waiters) -{ - int lock_taken, ret, force_take = 0; - u32 uval, newval, curval, vpid = task_pid_vnr(task); - -retry: - ret = lock_taken = 0; - - /* - * To avoid races, we attempt to take the lock here again - * (by doing a 0 -> TID atomic cmpxchg), while holding all - * the locks. It will most likely not succeed. - */ - newval = vpid; - if (set_waiters) - newval |= FUTEX_WAITERS; - - if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, 0, newval))) - return -EFAULT; - - /* - * Detect deadlocks. - */ - if ((unlikely((curval & FUTEX_TID_MASK) == vpid))) - return -EDEADLK; - - /* - * Surprise - we got the lock. Just return to userspace: - */ - if (unlikely(!curval)) - return 1; - - uval = curval; - - /* - * Set the FUTEX_WAITERS flag, so the owner will know it has someone - * to wake at the next unlock. - */ - newval = curval | FUTEX_WAITERS; - - /* - * Should we force take the futex? See below. - */ - if (unlikely(force_take)) { - /* - * Keep the OWNER_DIED and the WAITERS bit and set the - * new TID value. - */ - newval = (curval & ~FUTEX_TID_MASK) | vpid; - force_take = 0; - lock_taken = 1; - } - - if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))) - return -EFAULT; - if (unlikely(curval != uval)) - goto retry; - - /* - * We took the lock due to forced take over. - */ - if (unlikely(lock_taken)) - return 1; - - /* - * We dont have the lock. Look up the PI state (or create it if - * we are the first waiter): - */ - ret = lookup_pi_state(uval, hb, key, ps); - - if (unlikely(ret)) { - switch (ret) { - case -ESRCH: - /* - * We failed to find an owner for this - * futex. So we have no pi_state to block - * on. This can happen in two cases: - * - * 1) The owner died - * 2) A stale FUTEX_WAITERS bit - * - * Re-read the futex value. - */ - if (get_futex_value_locked(&curval, uaddr)) - return -EFAULT; - - /* - * If the owner died or we have a stale - * WAITERS bit the owner TID in the user space - * futex is 0. - */ - if (!(curval & FUTEX_TID_MASK)) { - force_take = 1; - goto retry; - } - default: - break; - } - } - - return ret; -} - -/** - * __unqueue_futex() - Remove the futex_q from its futex_hash_bucket - * @q: The futex_q to unqueue - * - * The q->lock_ptr must not be NULL and must be held by the caller. - */ -static void __unqueue_futex(struct futex_q *q) -{ - struct futex_hash_bucket *hb; - - if (WARN_ON_SMP(!q->lock_ptr || !spin_is_locked(q->lock_ptr)) - || WARN_ON(plist_node_empty(&q->list))) - return; - - hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock); - plist_del(&q->list, &hb->chain); -} - -/* - * The hash bucket lock must be held when this is called. - * Afterwards, the futex_q must not be accessed. - */ -static void wake_futex(struct futex_q *q) -{ - struct task_struct *p = q->task; - - if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n")) - return; - - /* - * We set q->lock_ptr = NULL _before_ we wake up the task. If - * a non-futex wake up happens on another CPU then the task - * might exit and p would dereference a non-existing task - * struct. Prevent this by holding a reference on p across the - * wake up. - */ - get_task_struct(p); - - __unqueue_futex(q); - /* - * The waiting task can free the futex_q as soon as - * q->lock_ptr = NULL is written, without taking any locks. A - * memory barrier is required here to prevent the following - * store to lock_ptr from getting ahead of the plist_del. - */ - smp_wmb(); - q->lock_ptr = NULL; - - wake_up_state(p, TASK_NORMAL); - put_task_struct(p); -} - -static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) -{ - struct task_struct *new_owner; - struct futex_pi_state *pi_state = this->pi_state; - u32 uninitialized_var(curval), newval; - - if (!pi_state) - return -EINVAL; - - /* - * If current does not own the pi_state then the futex is - * inconsistent and user space fiddled with the futex value. - */ - if (pi_state->owner != current) - return -EINVAL; - - raw_spin_lock(&pi_state->pi_mutex.wait_lock); - new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); - - /* - * It is possible that the next waiter (the one that brought - * this owner to the kernel) timed out and is no longer - * waiting on the lock. - */ - if (!new_owner) - new_owner = this->task; - - /* - * We pass it to the next owner. (The WAITERS bit is always - * kept enabled while there is PI state around. We must also - * preserve the owner died bit.) - */ - if (!(uval & FUTEX_OWNER_DIED)) { - int ret = 0; - - newval = FUTEX_WAITERS | task_pid_vnr(new_owner); - - if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) - ret = -EFAULT; - else if (curval != uval) - ret = -EINVAL; - if (ret) { - raw_spin_unlock(&pi_state->pi_mutex.wait_lock); - return ret; - } - } - - raw_spin_lock_irq(&pi_state->owner->pi_lock); - WARN_ON(list_empty(&pi_state->list)); - list_del_init(&pi_state->list); - raw_spin_unlock_irq(&pi_state->owner->pi_lock); - - raw_spin_lock_irq(&new_owner->pi_lock); - WARN_ON(!list_empty(&pi_state->list)); - list_add(&pi_state->list, &new_owner->pi_state_list); - pi_state->owner = new_owner; - raw_spin_unlock_irq(&new_owner->pi_lock); - - raw_spin_unlock(&pi_state->pi_mutex.wait_lock); - rt_mutex_unlock(&pi_state->pi_mutex); - - return 0; -} - -static int unlock_futex_pi(u32 __user *uaddr, u32 uval) -{ - u32 uninitialized_var(oldval); - - /* - * There is no waiter, so we unlock the futex. The owner died - * bit has not to be preserved here. We are the owner: - */ - if (cmpxchg_futex_value_locked(&oldval, uaddr, uval, 0)) - return -EFAULT; - if (oldval != uval) - return -EAGAIN; - - return 0; -} - -/* - * Express the locking dependencies for lockdep: - */ -static inline void -double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) -{ - if (hb1 <= hb2) { - spin_lock(&hb1->lock); - if (hb1 < hb2) - spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); - } else { /* hb1 > hb2 */ - spin_lock(&hb2->lock); - spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); - } -} - -static inline void -double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) -{ - spin_unlock(&hb1->lock); - if (hb1 != hb2) - spin_unlock(&hb2->lock); -} - -/* - * Wake up waiters matching bitset queued on this futex (uaddr). - */ -static int -futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset) -{ - struct futex_hash_bucket *hb; - struct futex_q *this, *next; - struct plist_head *head; - union futex_key key = FUTEX_KEY_INIT; - int ret; - - if (!bitset) - return -EINVAL; - - ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_READ); - if (unlikely(ret != 0)) - goto out; - - hb = hash_futex(&key); - spin_lock(&hb->lock); - head = &hb->chain; - - plist_for_each_entry_safe(this, next, head, list) { - if (match_futex (&this->key, &key)) { - if (this->pi_state || this->rt_waiter) { - ret = -EINVAL; - break; - } - - /* Check if one of the bits is set in both bitsets */ - if (!(this->bitset & bitset)) - continue; - - wake_futex(this); - if (++ret >= nr_wake) - break; - } - } - - spin_unlock(&hb->lock); - put_futex_key(&key); -out: - return ret; -} - -/* - * Wake up all waiters hashed on the physical page that is mapped - * to this virtual address: - */ -static int -futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2, - int nr_wake, int nr_wake2, int op) -{ - union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; - struct futex_hash_bucket *hb1, *hb2; - struct plist_head *head; - struct futex_q *this, *next; - int ret, op_ret; - -retry: - ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); - if (unlikely(ret != 0)) - goto out; - ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); - if (unlikely(ret != 0)) - goto out_put_key1; - - hb1 = hash_futex(&key1); - hb2 = hash_futex(&key2); - -retry_private: - double_lock_hb(hb1, hb2); - op_ret = futex_atomic_op_inuser(op, uaddr2); - if (unlikely(op_ret < 0)) { - - double_unlock_hb(hb1, hb2); - -#ifndef CONFIG_MMU - /* - * we don't get EFAULT from MMU faults if we don't have an MMU, - * but we might get them from range checking - */ - ret = op_ret; - goto out_put_keys; -#endif - - if (unlikely(op_ret != -EFAULT)) { - ret = op_ret; - goto out_put_keys; - } - - ret = fault_in_user_writeable(uaddr2); - if (ret) - goto out_put_keys; - - if (!(flags & FLAGS_SHARED)) - goto retry_private; - - put_futex_key(&key2); - put_futex_key(&key1); - goto retry; - } - - head = &hb1->chain; - - plist_for_each_entry_safe(this, next, head, list) { - if (match_futex (&this->key, &key1)) { - if (this->pi_state || this->rt_waiter) { - ret = -EINVAL; - goto out_unlock; - } - wake_futex(this); - if (++ret >= nr_wake) - break; - } - } - - if (op_ret > 0) { - head = &hb2->chain; - - op_ret = 0; - plist_for_each_entry_safe(this, next, head, list) { - if (match_futex (&this->key, &key2)) { - if (this->pi_state || this->rt_waiter) { - ret = -EINVAL; - goto out_unlock; - } - wake_futex(this); - if (++op_ret >= nr_wake2) - break; - } - } - ret += op_ret; - } - -out_unlock: - double_unlock_hb(hb1, hb2); -out_put_keys: - put_futex_key(&key2); -out_put_key1: - put_futex_key(&key1); -out: - return ret; -} - -/** - * requeue_futex() - Requeue a futex_q from one hb to another - * @q: the futex_q to requeue - * @hb1: the source hash_bucket - * @hb2: the target hash_bucket - * @key2: the new key for the requeued futex_q - */ -static inline -void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, - struct futex_hash_bucket *hb2, union futex_key *key2) -{ - - /* - * If key1 and key2 hash to the same bucket, no need to - * requeue. - */ - if (likely(&hb1->chain != &hb2->chain)) { - plist_del(&q->list, &hb1->chain); - plist_add(&q->list, &hb2->chain); - q->lock_ptr = &hb2->lock; - } - get_futex_key_refs(key2); - q->key = *key2; -} - -/** - * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue - * @q: the futex_q - * @key: the key of the requeue target futex - * @hb: the hash_bucket of the requeue target futex - * - * During futex_requeue, with requeue_pi=1, it is possible to acquire the - * target futex if it is uncontended or via a lock steal. Set the futex_q key - * to the requeue target futex so the waiter can detect the wakeup on the right - * futex, but remove it from the hb and NULL the rt_waiter so it can detect - * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock - * to protect access to the pi_state to fixup the owner later. Must be called - * with both q->lock_ptr and hb->lock held. - */ -static inline -void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key, - struct futex_hash_bucket *hb) -{ - get_futex_key_refs(key); - q->key = *key; - - __unqueue_futex(q); - - WARN_ON(!q->rt_waiter); - q->rt_waiter = NULL; - - q->lock_ptr = &hb->lock; - - wake_up_state(q->task, TASK_NORMAL); -} - -/** - * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter - * @pifutex: the user address of the to futex - * @hb1: the from futex hash bucket, must be locked by the caller - * @hb2: the to futex hash bucket, must be locked by the caller - * @key1: the from futex key - * @key2: the to futex key - * @ps: address to store the pi_state pointer - * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) - * - * Try and get the lock on behalf of the top waiter if we can do it atomically. - * Wake the top waiter if we succeed. If the caller specified set_waiters, - * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit. - * hb1 and hb2 must be held by the caller. - * - * Return: - * 0 - failed to acquire the lock atomically; - * 1 - acquired the lock; - * <0 - error - */ -static int futex_proxy_trylock_atomic(u32 __user *pifutex, - struct futex_hash_bucket *hb1, - struct futex_hash_bucket *hb2, - union futex_key *key1, union futex_key *key2, - struct futex_pi_state **ps, int set_waiters) -{ - struct futex_q *top_waiter = NULL; - u32 curval; - int ret; - - if (get_futex_value_locked(&curval, pifutex)) - return -EFAULT; - - /* - * Find the top_waiter and determine if there are additional waiters. - * If the caller intends to requeue more than 1 waiter to pifutex, - * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now, - * as we have means to handle the possible fault. If not, don't set - * the bit unecessarily as it will force the subsequent unlock to enter - * the kernel. - */ - top_waiter = futex_top_waiter(hb1, key1); - - /* There are no waiters, nothing for us to do. */ - if (!top_waiter) - return 0; - - /* Ensure we requeue to the expected futex. */ - if (!match_futex(top_waiter->requeue_pi_key, key2)) - return -EINVAL; - - /* - * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in - * the contended case or if set_waiters is 1. The pi_state is returned - * in ps in contended cases. - */ - ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task, - set_waiters); - if (ret == 1) - requeue_pi_wake_futex(top_waiter, key2, hb2); - - return ret; -} - -/** - * futex_requeue() - Requeue waiters from uaddr1 to uaddr2 - * @uaddr1: source futex user address - * @flags: futex flags (FLAGS_SHARED, etc.) - * @uaddr2: target futex user address - * @nr_wake: number of waiters to wake (must be 1 for requeue_pi) - * @nr_requeue: number of waiters to requeue (0-INT_MAX) - * @cmpval: @uaddr1 expected value (or %NULL) - * @requeue_pi: if we are attempting to requeue from a non-pi futex to a - * pi futex (pi to pi requeue is not supported) - * - * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire - * uaddr2 atomically on behalf of the top waiter. - * - * Return: - * >=0 - on success, the number of tasks requeued or woken; - * <0 - on error - */ -static int futex_requeue(u32 __user *uaddr1, unsigned int flags, - u32 __user *uaddr2, int nr_wake, int nr_requeue, - u32 *cmpval, int requeue_pi) -{ - union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; - int drop_count = 0, task_count = 0, ret; - struct futex_pi_state *pi_state = NULL; - struct futex_hash_bucket *hb1, *hb2; - struct plist_head *head1; - struct futex_q *this, *next; - u32 curval2; - - if (requeue_pi) { - /* - * requeue_pi requires a pi_state, try to allocate it now - * without any locks in case it fails. - */ - if (refill_pi_state_cache()) - return -ENOMEM; - /* - * requeue_pi must wake as many tasks as it can, up to nr_wake - * + nr_requeue, since it acquires the rt_mutex prior to - * returning to userspace, so as to not leave the rt_mutex with - * waiters and no owner. However, second and third wake-ups - * cannot be predicted as they involve race conditions with the - * first wake and a fault while looking up the pi_state. Both - * pthread_cond_signal() and pthread_cond_broadcast() should - * use nr_wake=1. - */ - if (nr_wake != 1) - return -EINVAL; - } - -retry: - if (pi_state != NULL) { - /* - * We will have to lookup the pi_state again, so free this one - * to keep the accounting correct. - */ - free_pi_state(pi_state); - pi_state = NULL; - } - - ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); - if (unlikely(ret != 0)) - goto out; - ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, - requeue_pi ? VERIFY_WRITE : VERIFY_READ); - if (unlikely(ret != 0)) - goto out_put_key1; - - hb1 = hash_futex(&key1); - hb2 = hash_futex(&key2); - -retry_private: - double_lock_hb(hb1, hb2); - - if (likely(cmpval != NULL)) { - u32 curval; - - ret = get_futex_value_locked(&curval, uaddr1); - - if (unlikely(ret)) { - double_unlock_hb(hb1, hb2); - - ret = get_user(curval, uaddr1); - if (ret) - goto out_put_keys; - - if (!(flags & FLAGS_SHARED)) - goto retry_private; - - put_futex_key(&key2); - put_futex_key(&key1); - goto retry; - } - if (curval != *cmpval) { - ret = -EAGAIN; - goto out_unlock; - } - } - - if (requeue_pi && (task_count - nr_wake < nr_requeue)) { - /* - * Attempt to acquire uaddr2 and wake the top waiter. If we - * intend to requeue waiters, force setting the FUTEX_WAITERS - * bit. We force this here where we are able to easily handle - * faults rather in the requeue loop below. - */ - ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1, - &key2, &pi_state, nr_requeue); - - /* - * At this point the top_waiter has either taken uaddr2 or is - * waiting on it. If the former, then the pi_state will not - * exist yet, look it up one more time to ensure we have a - * reference to it. - */ - if (ret == 1) { - WARN_ON(pi_state); - drop_count++; - task_count++; - ret = get_futex_value_locked(&curval2, uaddr2); - if (!ret) - ret = lookup_pi_state(curval2, hb2, &key2, - &pi_state); - } - - switch (ret) { - case 0: - break; - case -EFAULT: - double_unlock_hb(hb1, hb2); - put_futex_key(&key2); - put_futex_key(&key1); - ret = fault_in_user_writeable(uaddr2); - if (!ret) - goto retry; - goto out; - case -EAGAIN: - /* The owner was exiting, try again. */ - double_unlock_hb(hb1, hb2); - put_futex_key(&key2); - put_futex_key(&key1); - cond_resched(); - goto retry; - default: - goto out_unlock; - } - } - - head1 = &hb1->chain; - plist_for_each_entry_safe(this, next, head1, list) { - if (task_count - nr_wake >= nr_requeue) - break; - - if (!match_futex(&this->key, &key1)) - continue; - - /* - * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always - * be paired with each other and no other futex ops. - * - * We should never be requeueing a futex_q with a pi_state, - * which is awaiting a futex_unlock_pi(). - */ - if ((requeue_pi && !this->rt_waiter) || - (!requeue_pi && this->rt_waiter) || - this->pi_state) { - ret = -EINVAL; - break; - } - - /* - * Wake nr_wake waiters. For requeue_pi, if we acquired the - * lock, we already woke the top_waiter. If not, it will be - * woken by futex_unlock_pi(). - */ - if (++task_count <= nr_wake && !requeue_pi) { - wake_futex(this); - continue; - } - - /* Ensure we requeue to the expected futex for requeue_pi. */ - if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) { - ret = -EINVAL; - break; - } - - /* - * Requeue nr_requeue waiters and possibly one more in the case - * of requeue_pi if we couldn't acquire the lock atomically. - */ - if (requeue_pi) { - /* Prepare the waiter to take the rt_mutex. */ - atomic_inc(&pi_state->refcount); - this->pi_state = pi_state; - ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex, - this->rt_waiter, - this->task, 1); - if (ret == 1) { - /* We got the lock. */ - requeue_pi_wake_futex(this, &key2, hb2); - drop_count++; - continue; - } else if (ret) { - /* -EDEADLK */ - this->pi_state = NULL; - free_pi_state(pi_state); - goto out_unlock; - } - } - requeue_futex(this, hb1, hb2, &key2); - drop_count++; - } - -out_unlock: - double_unlock_hb(hb1, hb2); - - /* - * drop_futex_key_refs() must be called outside the spinlocks. During - * the requeue we moved futex_q's from the hash bucket at key1 to the - * one at key2 and updated their key pointer. We no longer need to - * hold the references to key1. - */ - while (--drop_count >= 0) - drop_futex_key_refs(&key1); - -out_put_keys: - put_futex_key(&key2); -out_put_key1: - put_futex_key(&key1); -out: - if (pi_state != NULL) - free_pi_state(pi_state); - return ret ? ret : task_count; -} - -/* The key must be already stored in q->key. */ -static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) - __acquires(&hb->lock) -{ - struct futex_hash_bucket *hb; - - hb = hash_futex(&q->key); - q->lock_ptr = &hb->lock; - - spin_lock(&hb->lock); - return hb; -} - -static inline void -queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) - __releases(&hb->lock) -{ - spin_unlock(&hb->lock); -} - -/** - * queue_me() - Enqueue the futex_q on the futex_hash_bucket - * @q: The futex_q to enqueue - * @hb: The destination hash bucket - * - * The hb->lock must be held by the caller, and is released here. A call to - * queue_me() is typically paired with exactly one call to unqueue_me(). The - * exceptions involve the PI related operations, which may use unqueue_me_pi() - * or nothing if the unqueue is done as part of the wake process and the unqueue - * state is implicit in the state of woken task (see futex_wait_requeue_pi() for - * an example). - */ -static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) - __releases(&hb->lock) -{ - int prio; - - /* - * The priority used to register this element is - * - either the real thread-priority for the real-time threads - * (i.e. threads with a priority lower than MAX_RT_PRIO) - * - or MAX_RT_PRIO for non-RT threads. - * Thus, all RT-threads are woken first in priority order, and - * the others are woken last, in FIFO order. - */ - prio = min(current->normal_prio, MAX_RT_PRIO); - - plist_node_init(&q->list, prio); - plist_add(&q->list, &hb->chain); - q->task = current; - spin_unlock(&hb->lock); -} - -/** - * unqueue_me() - Remove the futex_q from its futex_hash_bucket - * @q: The futex_q to unqueue - * - * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must - * be paired with exactly one earlier call to queue_me(). - * - * Return: - * 1 - if the futex_q was still queued (and we removed unqueued it); - * 0 - if the futex_q was already removed by the waking thread - */ -static int unqueue_me(struct futex_q *q) -{ - spinlock_t *lock_ptr; - int ret = 0; - - /* In the common case we don't take the spinlock, which is nice. */ -retry: - lock_ptr = q->lock_ptr; - barrier(); - if (lock_ptr != NULL) { - 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; - } - __unqueue_futex(q); - - BUG_ON(q->pi_state); - - spin_unlock(lock_ptr); - ret = 1; - } - - drop_futex_key_refs(&q->key); - return ret; -} - -/* - * PI futexes can not be requeued and must remove themself from the - * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry - * and dropped here. - */ -static void unqueue_me_pi(struct futex_q *q) - __releases(q->lock_ptr) -{ - __unqueue_futex(q); - - BUG_ON(!q->pi_state); - free_pi_state(q->pi_state); - q->pi_state = NULL; - - spin_unlock(q->lock_ptr); -} - -/* - * Fixup the pi_state owner with the new owner. - * - * Must be called with hash bucket lock held and mm->sem held for non - * private futexes. - */ -static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, - struct task_struct *newowner) -{ - u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; - struct futex_pi_state *pi_state = q->pi_state; - struct task_struct *oldowner = pi_state->owner; - u32 uval, uninitialized_var(curval), newval; - int ret; - - /* Owner died? */ - if (!pi_state->owner) - newtid |= FUTEX_OWNER_DIED; - - /* - * We are here either because we stole the rtmutex from the - * previous highest priority waiter or we are the highest priority - * waiter but failed to get the rtmutex the first time. - * We have to replace the newowner TID in the user space variable. - * This must be atomic as we have to preserve the owner died bit here. - * - * Note: We write the user space value _before_ changing the pi_state - * because we can fault here. Imagine swapped out pages or a fork - * that marked all the anonymous memory readonly for cow. - * - * Modifying pi_state _before_ the user space value would - * leave the pi_state in an inconsistent state when we fault - * here, because we need to drop the hash bucket lock to - * handle the fault. This might be observed in the PID check - * in lookup_pi_state. - */ -retry: - if (get_futex_value_locked(&uval, uaddr)) - goto handle_fault; - - while (1) { - newval = (uval & FUTEX_OWNER_DIED) | newtid; - - if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) - goto handle_fault; - if (curval == uval) - break; - uval = curval; - } - - /* - * We fixed up user space. Now we need to fix the pi_state - * itself. - */ - if (pi_state->owner != NULL) { - raw_spin_lock_irq(&pi_state->owner->pi_lock); - WARN_ON(list_empty(&pi_state->list)); - list_del_init(&pi_state->list); - raw_spin_unlock_irq(&pi_state->owner->pi_lock); - } - - pi_state->owner = newowner; - - raw_spin_lock_irq(&newowner->pi_lock); - WARN_ON(!list_empty(&pi_state->list)); - list_add(&pi_state->list, &newowner->pi_state_list); - raw_spin_unlock_irq(&newowner->pi_lock); - return 0; - - /* - * To handle the page fault we need to drop the hash bucket - * lock here. That gives the other task (either the highest priority - * waiter itself or the task which stole the rtmutex) the - * chance to try the fixup of the pi_state. So once we are - * back from handling the fault we need to check the pi_state - * after reacquiring the hash bucket lock and before trying to - * do another fixup. When the fixup has been done already we - * simply return. - */ -handle_fault: - spin_unlock(q->lock_ptr); - - ret = fault_in_user_writeable(uaddr); - - spin_lock(q->lock_ptr); - - /* - * Check if someone else fixed it for us: - */ - if (pi_state->owner != oldowner) - return 0; - - if (ret) - return ret; - - goto retry; -} - -static long futex_wait_restart(struct restart_block *restart); - -/** - * fixup_owner() - Post lock pi_state and corner case management - * @uaddr: user address of the futex - * @q: futex_q (contains pi_state and access to the rt_mutex) - * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0) - * - * After attempting to lock an rt_mutex, this function is called to cleanup - * the pi_state owner as well as handle race conditions that may allow us to - * acquire the lock. Must be called with the hb lock held. - * - * Return: - * 1 - success, lock taken; - * 0 - success, lock not taken; - * <0 - on error (-EFAULT) - */ -static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked) -{ - struct task_struct *owner; - int ret = 0; - - if (locked) { - /* - * Got the lock. We might not be the anticipated owner if we - * did a lock-steal - fix up the PI-state in that case: - */ - if (q->pi_state->owner != current) - ret = fixup_pi_state_owner(uaddr, q, current); - goto out; - } - - /* - * Catch the rare case, where the lock was released when we were on the - * way back before we locked the hash bucket. - */ - if (q->pi_state->owner == current) { - /* - * Try to get the rt_mutex now. This might fail as some other - * task acquired the rt_mutex after we removed ourself from the - * rt_mutex waiters list. - */ - if (rt_mutex_trylock(&q->pi_state->pi_mutex)) { - locked = 1; - goto out; - } - - /* - * pi_state is incorrect, some other task did a lock steal and - * we returned due to timeout or signal without taking the - * rt_mutex. Too late. - */ - raw_spin_lock(&q->pi_state->pi_mutex.wait_lock); - owner = rt_mutex_owner(&q->pi_state->pi_mutex); - if (!owner) - owner = rt_mutex_next_owner(&q->pi_state->pi_mutex); - raw_spin_unlock(&q->pi_state->pi_mutex.wait_lock); - ret = fixup_pi_state_owner(uaddr, q, owner); - goto out; - } - - /* - * Paranoia check. If we did not take the lock, then we should not be - * the owner of the rt_mutex. - */ - if (rt_mutex_owner(&q->pi_state->pi_mutex) == current) - printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p " - "pi-state %p\n", ret, - q->pi_state->pi_mutex.owner, - q->pi_state->owner); - -out: - return ret ? ret : locked; -} - -/** - * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal - * @hb: the futex hash bucket, must be locked by the caller - * @q: the futex_q to queue up on - * @timeout: the prepared hrtimer_sleeper, or null for no timeout - */ -static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q, - struct hrtimer_sleeper *timeout) -{ - /* - * The task state is guaranteed to be set before another task can - * wake it. set_current_state() is implemented using set_mb() and - * queue_me() calls spin_unlock() upon completion, both serializing - * access to the hash list and forcing another memory barrier. - */ - set_current_state(TASK_INTERRUPTIBLE); - queue_me(q, hb); - - /* Arm the timer */ - if (timeout) { - hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); - if (!hrtimer_active(&timeout->timer)) - timeout->task = NULL; - } - - /* - * If we have been removed from the hash list, then another task - * has tried to wake us, and we can skip the call to schedule(). - */ - if (likely(!plist_node_empty(&q->list))) { - /* - * If the timer has already expired, current will already be - * flagged for rescheduling. Only call schedule if there - * is no timeout, or if it has yet to expire. - */ - if (!timeout || timeout->task) - freezable_schedule(); - } - __set_current_state(TASK_RUNNING); -} - -/** - * futex_wait_setup() - Prepare to wait on a futex - * @uaddr: the futex userspace address - * @val: the expected value - * @flags: futex flags (FLAGS_SHARED, etc.) - * @q: the associated futex_q - * @hb: storage for hash_bucket pointer to be returned to caller - * - * Setup the futex_q and locate the hash_bucket. Get the futex value and - * compare it with the expected value. Handle atomic faults internally. - * Return with the hb lock held and a q.key reference on success, and unlocked - * with no q.key reference on failure. - * - * Return: - * 0 - uaddr contains val and hb has been locked; - * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked - */ -static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags, - struct futex_q *q, struct futex_hash_bucket **hb) -{ - u32 uval; - int ret; - - /* - * Access the page AFTER the hash-bucket is locked. - * 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 locked the hash-bucket after testing *uaddr, that - * would open a race condition where we could block indefinitely with - * cond(var) false, which would violate the guarantee. - * - * On the other hand, we insert q and release the hash-bucket only - * after testing *uaddr. This guarantees that futex_wait() will NOT - * absorb a wakeup if *uaddr does not match the desired values - * while the syscall executes. - */ -retry: - ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key, VERIFY_READ); - if (unlikely(ret != 0)) - return ret; - -retry_private: - *hb = queue_lock(q); - - ret = get_futex_value_locked(&uval, uaddr); - - if (ret) { - queue_unlock(q, *hb); - - ret = get_user(uval, uaddr); - if (ret) - goto out; - - if (!(flags & FLAGS_SHARED)) - goto retry_private; - - put_futex_key(&q->key); - goto retry; - } - - if (uval != val) { - queue_unlock(q, *hb); - ret = -EWOULDBLOCK; - } - -out: - if (ret) - put_futex_key(&q->key); - return ret; -} - -static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, - ktime_t *abs_time, u32 bitset) -{ - struct hrtimer_sleeper timeout, *to = NULL; - struct restart_block *restart; - struct futex_hash_bucket *hb; - struct futex_q q = futex_q_init; - int ret; - - if (!bitset) - return -EINVAL; - q.bitset = bitset; - - if (abs_time) { - to = &timeout; - - hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? - CLOCK_REALTIME : CLOCK_MONOTONIC, - HRTIMER_MODE_ABS); - hrtimer_init_sleeper(to, current); - hrtimer_set_expires_range_ns(&to->timer, *abs_time, - current->timer_slack_ns); - } - -retry: - /* - * Prepare to wait on uaddr. On success, holds hb lock and increments - * q.key refs. - */ - ret = futex_wait_setup(uaddr, val, flags, &q, &hb); - if (ret) - goto out; - - /* queue_me and wait for wakeup, timeout, or a signal. */ - futex_wait_queue_me(hb, &q, to); - - /* If we were woken (and unqueued), we succeeded, whatever. */ - ret = 0; - /* unqueue_me() drops q.key ref */ - if (!unqueue_me(&q)) - goto out; - ret = -ETIMEDOUT; - if (to && !to->task) - goto out; - - /* - * We expect signal_pending(current), but we might be the - * victim of a spurious wakeup as well. - */ - if (!signal_pending(current)) - goto retry; - - ret = -ERESTARTSYS; - if (!abs_time) - goto out; - - restart = ¤t_thread_info()->restart_block; - restart->fn = futex_wait_restart; - restart->futex.uaddr = uaddr; - restart->futex.val = val; - restart->futex.time = abs_time->tv64; - restart->futex.bitset = bitset; - restart->futex.flags = flags | FLAGS_HAS_TIMEOUT; - - ret = -ERESTART_RESTARTBLOCK; - -out: - if (to) { - hrtimer_cancel(&to->timer); - destroy_hrtimer_on_stack(&to->timer); - } - return ret; -} - - -static long futex_wait_restart(struct restart_block *restart) -{ - u32 __user *uaddr = restart->futex.uaddr; - ktime_t t, *tp = NULL; - - if (restart->futex.flags & FLAGS_HAS_TIMEOUT) { - t.tv64 = restart->futex.time; - tp = &t; - } - restart->fn = do_no_restart_syscall; - - return (long)futex_wait(uaddr, restart->futex.flags, - restart->futex.val, tp, restart->futex.bitset); -} - - -/* - * Userspace tried a 0 -> TID atomic transition of the futex value - * and failed. The kernel side here does the whole locking operation: - * if there are waiters then it will block, it does PI, etc. (Due to - * races the kernel might see a 0 value of the futex too.) - */ -static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect, - ktime_t *time, int trylock) -{ - struct hrtimer_sleeper timeout, *to = NULL; - struct futex_hash_bucket *hb; - struct futex_q q = futex_q_init; - int res, ret; - - if (refill_pi_state_cache()) - return -ENOMEM; - - if (time) { - to = &timeout; - hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, - HRTIMER_MODE_ABS); - hrtimer_init_sleeper(to, current); - hrtimer_set_expires(&to->timer, *time); - } - -retry: - ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, VERIFY_WRITE); - if (unlikely(ret != 0)) - goto out; - -retry_private: - hb = queue_lock(&q); - - ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0); - if (unlikely(ret)) { - switch (ret) { - case 1: - /* We got the lock. */ - ret = 0; - goto out_unlock_put_key; - case -EFAULT: - goto uaddr_faulted; - case -EAGAIN: - /* - * Task is exiting and we just wait for the - * exit to complete. - */ - queue_unlock(&q, hb); - put_futex_key(&q.key); - cond_resched(); - goto retry; - default: - goto out_unlock_put_key; - } - } - - /* - * Only actually queue now that the atomic ops are done: - */ - queue_me(&q, hb); - - WARN_ON(!q.pi_state); - /* - * Block on the PI mutex: - */ - if (!trylock) - ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); - else { - ret = rt_mutex_trylock(&q.pi_state->pi_mutex); - /* Fixup the trylock return value: */ - ret = ret ? 0 : -EWOULDBLOCK; - } - - spin_lock(q.lock_ptr); - /* - * Fixup the pi_state owner and possibly acquire the lock if we - * haven't already. - */ - res = fixup_owner(uaddr, &q, !ret); - /* - * If fixup_owner() returned an error, proprogate that. If it acquired - * the lock, clear our -ETIMEDOUT or -EINTR. - */ - if (res) - ret = (res < 0) ? res : 0; - - /* - * If fixup_owner() faulted and was unable to handle the fault, unlock - * it and return the fault to userspace. - */ - if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) - rt_mutex_unlock(&q.pi_state->pi_mutex); - - /* Unqueue and drop the lock */ - unqueue_me_pi(&q); - - goto out_put_key; - -out_unlock_put_key: - queue_unlock(&q, hb); - -out_put_key: - put_futex_key(&q.key); -out: - if (to) - destroy_hrtimer_on_stack(&to->timer); - return ret != -EINTR ? ret : -ERESTARTNOINTR; - -uaddr_faulted: - queue_unlock(&q, hb); - - ret = fault_in_user_writeable(uaddr); - if (ret) - goto out_put_key; - - if (!(flags & FLAGS_SHARED)) - goto retry_private; - - put_futex_key(&q.key); - goto retry; -} - -/* - * Userspace attempted a TID -> 0 atomic transition, and failed. - * This is the in-kernel slowpath: we look up the PI state (if any), - * and do the rt-mutex unlock. - */ -static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags) -{ - struct futex_hash_bucket *hb; - struct futex_q *this, *next; - struct plist_head *head; - union futex_key key = FUTEX_KEY_INIT; - u32 uval, vpid = task_pid_vnr(current); - int ret; - -retry: - if (get_user(uval, uaddr)) - return -EFAULT; - /* - * We release only a lock we actually own: - */ - if ((uval & FUTEX_TID_MASK) != vpid) - return -EPERM; - - ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_WRITE); - if (unlikely(ret != 0)) - goto out; - - hb = hash_futex(&key); - spin_lock(&hb->lock); - - /* - * To avoid races, try to do the TID -> 0 atomic transition - * again. If it succeeds then we can return without waking - * anyone else up: - */ - if (!(uval & FUTEX_OWNER_DIED) && - cmpxchg_futex_value_locked(&uval, uaddr, vpid, 0)) - goto pi_faulted; - /* - * Rare case: we managed to release the lock atomically, - * no need to wake anyone else up: - */ - if (unlikely(uval == vpid)) - goto out_unlock; - - /* - * Ok, other tasks may need to be woken up - check waiters - * and do the wakeup if necessary: - */ - head = &hb->chain; - - plist_for_each_entry_safe(this, next, head, list) { - if (!match_futex (&this->key, &key)) - continue; - ret = wake_futex_pi(uaddr, uval, this); - /* - * The atomic access to the futex value - * generated a pagefault, so retry the - * user-access and the wakeup: - */ - if (ret == -EFAULT) - goto pi_faulted; - goto out_unlock; - } - /* - * No waiters - kernel unlocks the futex: - */ - if (!(uval & FUTEX_OWNER_DIED)) { - ret = unlock_futex_pi(uaddr, uval); - if (ret == -EFAULT) - goto pi_faulted; - } - -out_unlock: - spin_unlock(&hb->lock); - put_futex_key(&key); - -out: - return ret; - -pi_faulted: - spin_unlock(&hb->lock); - put_futex_key(&key); - - ret = fault_in_user_writeable(uaddr); - if (!ret) - goto retry; - - return ret; -} - -/** - * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex - * @hb: the hash_bucket futex_q was original enqueued on - * @q: the futex_q woken while waiting to be requeued - * @key2: the futex_key of the requeue target futex - * @timeout: the timeout associated with the wait (NULL if none) - * - * Detect if the task was woken on the initial futex as opposed to the requeue - * target futex. If so, determine if it was a timeout or a signal that caused - * the wakeup and return the appropriate error code to the caller. Must be - * called with the hb lock held. - * - * Return: - * 0 = no early wakeup detected; - * <0 = -ETIMEDOUT or -ERESTARTNOINTR - */ -static inline -int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, - struct futex_q *q, union futex_key *key2, - struct hrtimer_sleeper *timeout) -{ - int ret = 0; - - /* - * With the hb lock held, we avoid races while we process the wakeup. - * We only need to hold hb (and not hb2) to ensure atomicity as the - * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb. - * It can't be requeued from uaddr2 to something else since we don't - * support a PI aware source futex for requeue. - */ - if (!match_futex(&q->key, key2)) { - WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr)); - /* - * We were woken prior to requeue by a timeout or a signal. - * Unqueue the futex_q and determine which it was. - */ - plist_del(&q->list, &hb->chain); - - /* Handle spurious wakeups gracefully */ - ret = -EWOULDBLOCK; - if (timeout && !timeout->task) - ret = -ETIMEDOUT; - else if (signal_pending(current)) - ret = -ERESTARTNOINTR; - } - return ret; -} - -/** - * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2 - * @uaddr: the futex we initially wait on (non-pi) - * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be - * the same type, no requeueing from private to shared, etc. - * @val: the expected value of uaddr - * @abs_time: absolute timeout - * @bitset: 32 bit wakeup bitset set by userspace, defaults to all - * @uaddr2: the pi futex we will take prior to returning to user-space - * - * The caller will wait on uaddr and will be requeued by futex_requeue() to - * uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake - * on uaddr2 and complete the acquisition of the rt_mutex prior to returning to - * userspace. This ensures the rt_mutex maintains an owner when it has waiters; - * without one, the pi logic would not know which task to boost/deboost, if - * there was a need to. - * - * We call schedule in futex_wait_queue_me() when we enqueue and return there - * via the following-- - * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue() - * 2) wakeup on uaddr2 after a requeue - * 3) signal - * 4) timeout - * - * If 3, cleanup and return -ERESTARTNOINTR. - * - * If 2, we may then block on trying to take the rt_mutex and return via: - * 5) successful lock - * 6) signal - * 7) timeout - * 8) other lock acquisition failure - * - * If 6, return -EWOULDBLOCK (restarting the syscall would do the same). - * - * If 4 or 7, we cleanup and return with -ETIMEDOUT. - * - * Return: - * 0 - On success; - * <0 - On error - */ -static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, - u32 val, ktime_t *abs_time, u32 bitset, - u32 __user *uaddr2) -{ - struct hrtimer_sleeper timeout, *to = NULL; - struct rt_mutex_waiter rt_waiter; - struct rt_mutex *pi_mutex = NULL; - struct futex_hash_bucket *hb; - union futex_key key2 = FUTEX_KEY_INIT; - struct futex_q q = futex_q_init; - int res, ret; - - if (uaddr == uaddr2) - return -EINVAL; - - if (!bitset) - return -EINVAL; - - if (abs_time) { - to = &timeout; - hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? - CLOCK_REALTIME : CLOCK_MONOTONIC, - HRTIMER_MODE_ABS); - hrtimer_init_sleeper(to, current); - hrtimer_set_expires_range_ns(&to->timer, *abs_time, - current->timer_slack_ns); - } - - /* - * The waiter is allocated on our stack, manipulated by the requeue - * code while we sleep on uaddr. - */ - debug_rt_mutex_init_waiter(&rt_waiter); - rt_waiter.task = NULL; - - ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); - if (unlikely(ret != 0)) - goto out; - - q.bitset = bitset; - q.rt_waiter = &rt_waiter; - q.requeue_pi_key = &key2; - - /* - * Prepare to wait on uaddr. On success, increments q.key (key1) ref - * count. - */ - ret = futex_wait_setup(uaddr, val, flags, &q, &hb); - if (ret) - goto out_key2; - - /* Queue the futex_q, drop the hb lock, wait for wakeup. */ - futex_wait_queue_me(hb, &q, to); - - spin_lock(&hb->lock); - ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to); - spin_unlock(&hb->lock); - if (ret) - goto out_put_keys; - - /* - * In order for us to be here, we know our q.key == key2, and since - * we took the hb->lock above, we also know that futex_requeue() has - * completed and we no longer have to concern ourselves with a wakeup - * race with the atomic proxy lock acquisition by the requeue code. The - * futex_requeue dropped our key1 reference and incremented our key2 - * reference count. - */ - - /* Check if the requeue code acquired the second futex for us. */ - if (!q.rt_waiter) { - /* - * Got the lock. We might not be the anticipated owner if we - * did a lock-steal - fix up the PI-state in that case. - */ - if (q.pi_state && (q.pi_state->owner != current)) { - spin_lock(q.lock_ptr); - ret = fixup_pi_state_owner(uaddr2, &q, current); - spin_unlock(q.lock_ptr); - } - } else { - /* - * We have been woken up by futex_unlock_pi(), a timeout, or a - * signal. futex_unlock_pi() will not destroy the lock_ptr nor - * the pi_state. - */ - WARN_ON(!q.pi_state); - pi_mutex = &q.pi_state->pi_mutex; - ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1); - debug_rt_mutex_free_waiter(&rt_waiter); - - spin_lock(q.lock_ptr); - /* - * Fixup the pi_state owner and possibly acquire the lock if we - * haven't already. - */ - res = fixup_owner(uaddr2, &q, !ret); - /* - * If fixup_owner() returned an error, proprogate that. If it - * acquired the lock, clear -ETIMEDOUT or -EINTR. - */ - if (res) - ret = (res < 0) ? res : 0; - - /* Unqueue and drop the lock. */ - unqueue_me_pi(&q); - } - - /* - * If fixup_pi_state_owner() faulted and was unable to handle the - * fault, unlock the rt_mutex and return the fault to userspace. - */ - if (ret == -EFAULT) { - if (pi_mutex && rt_mutex_owner(pi_mutex) == current) - rt_mutex_unlock(pi_mutex); - } else if (ret == -EINTR) { - /* - * We've already been requeued, but cannot restart by calling - * futex_lock_pi() directly. We could restart this syscall, but - * it would detect that the user space "val" changed and return - * -EWOULDBLOCK. Save the overhead of the restart and return - * -EWOULDBLOCK directly. - */ - ret = -EWOULDBLOCK; - } - -out_put_keys: - put_futex_key(&q.key); -out_key2: - put_futex_key(&key2); - -out: - if (to) { - hrtimer_cancel(&to->timer); - destroy_hrtimer_on_stack(&to->timer); - } - return ret; -} - -/* - * Support for robust futexes: the kernel cleans up held futexes at - * thread exit time. - * - * Implementation: user-space maintains a per-thread list of locks it - * is holding. Upon do_exit(), the kernel carefully walks this list, - * and marks all locks that are owned by this thread with the - * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is - * always manipulated with the lock held, so the list is private and - * per-thread. Userspace also maintains a per-thread 'list_op_pending' - * field, to allow the kernel to clean up if the thread dies after - * acquiring the lock, but just before it could have added itself to - * the list. There can only be one such pending lock. - */ - -/** - * sys_set_robust_list() - Set the robust-futex list head of a task - * @head: pointer to the list-head - * @len: length of the list-head, as userspace expects - */ -SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, - size_t, len) -{ - if (!futex_cmpxchg_enabled) - return -ENOSYS; - /* - * The kernel knows only one size for now: - */ - if (unlikely(len != sizeof(*head))) - return -EINVAL; - - current->robust_list = head; - - return 0; -} - -/** - * sys_get_robust_list() - Get the robust-futex list head of a task - * @pid: pid of the process [zero for current task] - * @head_ptr: pointer to a list-head pointer, the kernel fills it in - * @len_ptr: pointer to a length field, the kernel fills in the header size - */ -SYSCALL_DEFINE3(get_robust_list, int, pid, - struct robust_list_head __user * __user *, head_ptr, - size_t __user *, len_ptr) -{ - struct robust_list_head __user *head; - unsigned long ret; - struct task_struct *p; - - if (!futex_cmpxchg_enabled) - return -ENOSYS; - - rcu_read_lock(); - - ret = -ESRCH; - if (!pid) - p = current; - else { - p = find_task_by_vpid(pid); - if (!p) - goto err_unlock; - } - - ret = -EPERM; - if (!ptrace_may_access(p, PTRACE_MODE_READ)) - goto err_unlock; - - head = p->robust_list; - rcu_read_unlock(); - - if (put_user(sizeof(*head), len_ptr)) - return -EFAULT; - return put_user(head, head_ptr); - -err_unlock: - rcu_read_unlock(); - - return ret; -} - -/* - * Process a futex-list entry, check whether it's owned by the - * dying task, and do notification if so: - */ -int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) -{ - u32 uval, uninitialized_var(nval), mval; - -retry: - if (get_user(uval, uaddr)) - return -1; - - if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { - /* - * Ok, this dying thread is truly holding a futex - * of interest. Set the OWNER_DIED bit atomically - * via cmpxchg, and if the value had FUTEX_WAITERS - * set, wake up a waiter (if any). (We have to do a - * futex_wake() even if OWNER_DIED is already set - - * to handle the rare but possible case of recursive - * thread-death.) The rest of the cleanup is done in - * userspace. - */ - mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; - /* - * We are not holding a lock here, but we want to have - * the pagefault_disable/enable() protection because - * we want to handle the fault gracefully. If the - * access fails we try to fault in the futex with R/W - * verification via get_user_pages. get_user() above - * does not guarantee R/W access. If that fails we - * give up and leave the futex locked. - */ - if (cmpxchg_futex_value_locked(&nval, uaddr, uval, mval)) { - if (fault_in_user_writeable(uaddr)) - return -1; - goto retry; - } - if (nval != uval) - goto retry; - - /* - * Wake robust non-PI futexes here. The wakeup of - * PI futexes happens in exit_pi_state(): - */ - if (!pi && (uval & FUTEX_WAITERS)) - futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); - } - return 0; -} - -/* - * Fetch a robust-list pointer. Bit 0 signals PI futexes: - */ -static inline int fetch_robust_entry(struct robust_list __user **entry, - struct robust_list __user * __user *head, - unsigned int *pi) -{ - unsigned long uentry; - - if (get_user(uentry, (unsigned long __user *)head)) - return -EFAULT; - - *entry = (void __user *)(uentry & ~1UL); - *pi = uentry & 1; - - return 0; -} - -/* - * Walk curr->robust_list (very carefully, it's a userspace list!) - * and mark any locks found there dead, and notify any waiters. - * - * We silently return on any sign of list-walking problem. - */ -void exit_robust_list(struct task_struct *curr) -{ - struct robust_list_head __user *head = curr->robust_list; - struct robust_list __user *entry, *next_entry, *pending; - unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; - unsigned int uninitialized_var(next_pi); - unsigned long futex_offset; - int rc; - - if (!futex_cmpxchg_enabled) - return; - - /* - * Fetch the list head (which was registered earlier, via - * sys_set_robust_list()): - */ - if (fetch_robust_entry(&entry, &head->list.next, &pi)) - return; - /* - * Fetch the relative futex offset: - */ - if (get_user(futex_offset, &head->futex_offset)) - return; - /* - * Fetch any possibly pending lock-add first, and handle it - * if it exists: - */ - if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) - return; - - next_entry = NULL; /* avoid warning with gcc */ - while (entry != &head->list) { - /* - * Fetch the next entry in the list before calling - * handle_futex_death: - */ - rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); - /* - * A pending lock might already be on the list, so - * don't process it twice: - */ - if (entry != pending) - if (handle_futex_death((void __user *)entry + futex_offset, - curr, pi)) - return; - if (rc) - return; - entry = next_entry; - pi = next_pi; - /* - * Avoid excessively long or circular lists: - */ - if (!--limit) - break; - - cond_resched(); - } - - if (pending) - handle_futex_death((void __user *)pending + futex_offset, - curr, pip); -} - -long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, - u32 __user *uaddr2, u32 val2, u32 val3) -{ - int cmd = op & FUTEX_CMD_MASK; - unsigned int flags = 0; - - if (!(op & FUTEX_PRIVATE_FLAG)) - flags |= FLAGS_SHARED; - - if (op & FUTEX_CLOCK_REALTIME) { - flags |= FLAGS_CLOCKRT; - if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI) - return -ENOSYS; - } - - switch (cmd) { - case FUTEX_LOCK_PI: - case FUTEX_UNLOCK_PI: - case FUTEX_TRYLOCK_PI: - case FUTEX_WAIT_REQUEUE_PI: - case FUTEX_CMP_REQUEUE_PI: - if (!futex_cmpxchg_enabled) - return -ENOSYS; - } - - switch (cmd) { - case FUTEX_WAIT: - val3 = FUTEX_BITSET_MATCH_ANY; - case FUTEX_WAIT_BITSET: - return futex_wait(uaddr, flags, val, timeout, val3); - case FUTEX_WAKE: - val3 = FUTEX_BITSET_MATCH_ANY; - case FUTEX_WAKE_BITSET: - return futex_wake(uaddr, flags, val, val3); - case FUTEX_REQUEUE: - return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0); - case FUTEX_CMP_REQUEUE: - return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0); - case FUTEX_WAKE_OP: - return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3); - case FUTEX_LOCK_PI: - return futex_lock_pi(uaddr, flags, val, timeout, 0); - case FUTEX_UNLOCK_PI: - return futex_unlock_pi(uaddr, flags); - case FUTEX_TRYLOCK_PI: - return futex_lock_pi(uaddr, flags, 0, timeout, 1); - case FUTEX_WAIT_REQUEUE_PI: - val3 = FUTEX_BITSET_MATCH_ANY; - return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3, - uaddr2); - case FUTEX_CMP_REQUEUE_PI: - return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1); - } - return -ENOSYS; -} - - -SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, - struct timespec __user *, utime, u32 __user *, uaddr2, - u32, val3) -{ - struct timespec ts; - ktime_t t, *tp = NULL; - u32 val2 = 0; - int cmd = op & FUTEX_CMD_MASK; - - if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || - cmd == FUTEX_WAIT_BITSET || - cmd == FUTEX_WAIT_REQUEUE_PI)) { - if (copy_from_user(&ts, utime, sizeof(ts)) != 0) - return -EFAULT; - if (!timespec_valid(&ts)) - return -EINVAL; - - t = timespec_to_ktime(ts); - if (cmd == FUTEX_WAIT) - t = ktime_add_safe(ktime_get(), t); - tp = &t; - } - /* - * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*. - * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. - */ - if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || - cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP) - val2 = (u32) (unsigned long) utime; - - return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); -} - -static int __init futex_init(void) -{ - u32 curval; - int i; - - /* - * This will fail and we want it. Some arch implementations do - * runtime detection of the futex_atomic_cmpxchg_inatomic() - * functionality. We want to know that before we call in any - * of the complex code paths. Also we want to prevent - * registration of robust lists in that case. NULL is - * guaranteed to fault and we get -EFAULT on functional - * implementation, the non-functional ones will return - * -ENOSYS. - */ - if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT) - futex_cmpxchg_enabled = 1; - - for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { - plist_head_init(&futex_queues[i].chain); - spin_lock_init(&futex_queues[i].lock); - } - - return 0; -} -__initcall(futex_init); |