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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _FUTEX_H
3#define _FUTEX_H
4
5#include <linux/futex.h>
6#include <linux/rtmutex.h>
7#include <linux/sched/wake_q.h>
8#include <linux/compat.h>
9#include <linux/uaccess.h>
10
11#ifdef CONFIG_PREEMPT_RT
12#include <linux/rcuwait.h>
13#endif
14
15#include <asm/futex.h>
16
17/*
18 * Futex flags used to encode options to functions and preserve them across
19 * restarts.
20 */
21#define FLAGS_SIZE_8 0x0000
22#define FLAGS_SIZE_16 0x0001
23#define FLAGS_SIZE_32 0x0002
24#define FLAGS_SIZE_64 0x0003
25
26#define FLAGS_SIZE_MASK 0x0003
27
28#ifdef CONFIG_MMU
29# define FLAGS_SHARED 0x0010
30#else
31/*
32 * NOMMU does not have per process address space. Let the compiler optimize
33 * code away.
34 */
35# define FLAGS_SHARED 0x0000
36#endif
37#define FLAGS_CLOCKRT 0x0020
38#define FLAGS_HAS_TIMEOUT 0x0040
39#define FLAGS_NUMA 0x0080
40#define FLAGS_STRICT 0x0100
41
42/* FUTEX_ to FLAGS_ */
43static inline unsigned int futex_to_flags(unsigned int op)
44{
45 unsigned int flags = FLAGS_SIZE_32;
46
47 if (!(op & FUTEX_PRIVATE_FLAG))
48 flags |= FLAGS_SHARED;
49
50 if (op & FUTEX_CLOCK_REALTIME)
51 flags |= FLAGS_CLOCKRT;
52
53 return flags;
54}
55
56#define FUTEX2_VALID_MASK (FUTEX2_SIZE_MASK | FUTEX2_PRIVATE)
57
58/* FUTEX2_ to FLAGS_ */
59static inline unsigned int futex2_to_flags(unsigned int flags2)
60{
61 unsigned int flags = flags2 & FUTEX2_SIZE_MASK;
62
63 if (!(flags2 & FUTEX2_PRIVATE))
64 flags |= FLAGS_SHARED;
65
66 if (flags2 & FUTEX2_NUMA)
67 flags |= FLAGS_NUMA;
68
69 return flags;
70}
71
72static inline unsigned int futex_size(unsigned int flags)
73{
74 return 1 << (flags & FLAGS_SIZE_MASK);
75}
76
77static inline bool futex_flags_valid(unsigned int flags)
78{
79 /* Only 64bit futexes for 64bit code */
80 if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) {
81 if ((flags & FLAGS_SIZE_MASK) == FLAGS_SIZE_64)
82 return false;
83 }
84
85 /* Only 32bit futexes are implemented -- for now */
86 if ((flags & FLAGS_SIZE_MASK) != FLAGS_SIZE_32)
87 return false;
88
89 return true;
90}
91
92static inline bool futex_validate_input(unsigned int flags, u64 val)
93{
94 int bits = 8 * futex_size(flags);
95
96 if (bits < 64 && (val >> bits))
97 return false;
98
99 return true;
100}
101
102#ifdef CONFIG_FAIL_FUTEX
103extern bool should_fail_futex(bool fshared);
104#else
105static inline bool should_fail_futex(bool fshared)
106{
107 return false;
108}
109#endif
110
111/*
112 * Hash buckets are shared by all the futex_keys that hash to the same
113 * location. Each key may have multiple futex_q structures, one for each task
114 * waiting on a futex.
115 */
116struct futex_hash_bucket {
117 atomic_t waiters;
118 spinlock_t lock;
119 struct plist_head chain;
120} ____cacheline_aligned_in_smp;
121
122/*
123 * Priority Inheritance state:
124 */
125struct futex_pi_state {
126 /*
127 * list of 'owned' pi_state instances - these have to be
128 * cleaned up in do_exit() if the task exits prematurely:
129 */
130 struct list_head list;
131
132 /*
133 * The PI object:
134 */
135 struct rt_mutex_base pi_mutex;
136
137 struct task_struct *owner;
138 refcount_t refcount;
139
140 union futex_key key;
141} __randomize_layout;
142
143struct futex_q;
144typedef void (futex_wake_fn)(struct wake_q_head *wake_q, struct futex_q *q);
145
146/**
147 * struct futex_q - The hashed futex queue entry, one per waiting task
148 * @list: priority-sorted list of tasks waiting on this futex
149 * @task: the task waiting on the futex
150 * @lock_ptr: the hash bucket lock
151 * @wake: the wake handler for this queue
152 * @wake_data: data associated with the wake handler
153 * @key: the key the futex is hashed on
154 * @pi_state: optional priority inheritance state
155 * @rt_waiter: rt_waiter storage for use with requeue_pi
156 * @requeue_pi_key: the requeue_pi target futex key
157 * @bitset: bitset for the optional bitmasked wakeup
158 * @requeue_state: State field for futex_requeue_pi()
159 * @requeue_wait: RCU wait for futex_requeue_pi() (RT only)
160 *
161 * We use this hashed waitqueue, instead of a normal wait_queue_entry_t, so
162 * we can wake only the relevant ones (hashed queues may be shared).
163 *
164 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
165 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
166 * The order of wakeup is always to make the first condition true, then
167 * the second.
168 *
169 * PI futexes are typically woken before they are removed from the hash list via
170 * the rt_mutex code. See futex_unqueue_pi().
171 */
172struct futex_q {
173 struct plist_node list;
174
175 struct task_struct *task;
176 spinlock_t *lock_ptr;
177 futex_wake_fn *wake;
178 void *wake_data;
179 union futex_key key;
180 struct futex_pi_state *pi_state;
181 struct rt_mutex_waiter *rt_waiter;
182 union futex_key *requeue_pi_key;
183 u32 bitset;
184 atomic_t requeue_state;
185#ifdef CONFIG_PREEMPT_RT
186 struct rcuwait requeue_wait;
187#endif
188} __randomize_layout;
189
190extern const struct futex_q futex_q_init;
191
192enum futex_access {
193 FUTEX_READ,
194 FUTEX_WRITE
195};
196
197extern int get_futex_key(u32 __user *uaddr, unsigned int flags, union futex_key *key,
198 enum futex_access rw);
199
200extern struct hrtimer_sleeper *
201futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
202 int flags, u64 range_ns);
203
204extern struct futex_hash_bucket *futex_hash(union futex_key *key);
205
206/**
207 * futex_match - Check whether two futex keys are equal
208 * @key1: Pointer to key1
209 * @key2: Pointer to key2
210 *
211 * Return 1 if two futex_keys are equal, 0 otherwise.
212 */
213static inline int futex_match(union futex_key *key1, union futex_key *key2)
214{
215 return (key1 && key2
216 && key1->both.word == key2->both.word
217 && key1->both.ptr == key2->both.ptr
218 && key1->both.offset == key2->both.offset);
219}
220
221extern int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
222 struct futex_q *q, struct futex_hash_bucket **hb);
223extern void futex_wait_queue(struct futex_hash_bucket *hb, struct futex_q *q,
224 struct hrtimer_sleeper *timeout);
225extern bool __futex_wake_mark(struct futex_q *q);
226extern void futex_wake_mark(struct wake_q_head *wake_q, struct futex_q *q);
227
228extern int fault_in_user_writeable(u32 __user *uaddr);
229extern struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, union futex_key *key);
230
231static inline int futex_cmpxchg_value_locked(u32 *curval, u32 __user *uaddr, u32 uval, u32 newval)
232{
233 int ret;
234
235 pagefault_disable();
236 ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval);
237 pagefault_enable();
238
239 return ret;
240}
241
242/*
243 * This does a plain atomic user space read, and the user pointer has
244 * already been verified earlier by get_futex_key() to be both aligned
245 * and actually in user space, just like futex_atomic_cmpxchg_inatomic().
246 *
247 * We still want to avoid any speculation, and while __get_user() is
248 * the traditional model for this, it's actually slower than doing
249 * this manually these days.
250 *
251 * We could just have a per-architecture special function for it,
252 * the same way we do futex_atomic_cmpxchg_inatomic(), but rather
253 * than force everybody to do that, write it out long-hand using
254 * the low-level user-access infrastructure.
255 *
256 * This looks a bit overkill, but generally just results in a couple
257 * of instructions.
258 */
259static __always_inline int futex_read_inatomic(u32 *dest, u32 __user *from)
260{
261 u32 val;
262
263 if (can_do_masked_user_access())
264 from = masked_user_access_begin(from);
265 else if (!user_read_access_begin(from, sizeof(*from)))
266 return -EFAULT;
267 unsafe_get_user(val, from, Efault);
268 user_read_access_end();
269 *dest = val;
270 return 0;
271Efault:
272 user_read_access_end();
273 return -EFAULT;
274}
275
276static inline int futex_get_value_locked(u32 *dest, u32 __user *from)
277{
278 int ret;
279
280 pagefault_disable();
281 ret = futex_read_inatomic(dest, from);
282 pagefault_enable();
283
284 return ret;
285}
286
287extern void __futex_unqueue(struct futex_q *q);
288extern void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb);
289extern int futex_unqueue(struct futex_q *q);
290
291/**
292 * futex_queue() - Enqueue the futex_q on the futex_hash_bucket
293 * @q: The futex_q to enqueue
294 * @hb: The destination hash bucket
295 *
296 * The hb->lock must be held by the caller, and is released here. A call to
297 * futex_queue() is typically paired with exactly one call to futex_unqueue(). The
298 * exceptions involve the PI related operations, which may use futex_unqueue_pi()
299 * or nothing if the unqueue is done as part of the wake process and the unqueue
300 * state is implicit in the state of woken task (see futex_wait_requeue_pi() for
301 * an example).
302 */
303static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb)
304 __releases(&hb->lock)
305{
306 __futex_queue(q, hb);
307 spin_unlock(&hb->lock);
308}
309
310extern void futex_unqueue_pi(struct futex_q *q);
311
312extern void wait_for_owner_exiting(int ret, struct task_struct *exiting);
313
314/*
315 * Reflects a new waiter being added to the waitqueue.
316 */
317static inline void futex_hb_waiters_inc(struct futex_hash_bucket *hb)
318{
319#ifdef CONFIG_SMP
320 atomic_inc(&hb->waiters);
321 /*
322 * Full barrier (A), see the ordering comment above.
323 */
324 smp_mb__after_atomic();
325#endif
326}
327
328/*
329 * Reflects a waiter being removed from the waitqueue by wakeup
330 * paths.
331 */
332static inline void futex_hb_waiters_dec(struct futex_hash_bucket *hb)
333{
334#ifdef CONFIG_SMP
335 atomic_dec(&hb->waiters);
336#endif
337}
338
339static inline int futex_hb_waiters_pending(struct futex_hash_bucket *hb)
340{
341#ifdef CONFIG_SMP
342 /*
343 * Full barrier (B), see the ordering comment above.
344 */
345 smp_mb();
346 return atomic_read(&hb->waiters);
347#else
348 return 1;
349#endif
350}
351
352extern struct futex_hash_bucket *futex_q_lock(struct futex_q *q);
353extern void futex_q_unlock(struct futex_hash_bucket *hb);
354
355
356extern int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
357 union futex_key *key,
358 struct futex_pi_state **ps,
359 struct task_struct *task,
360 struct task_struct **exiting,
361 int set_waiters);
362
363extern int refill_pi_state_cache(void);
364extern void get_pi_state(struct futex_pi_state *pi_state);
365extern void put_pi_state(struct futex_pi_state *pi_state);
366extern int fixup_pi_owner(u32 __user *uaddr, struct futex_q *q, int locked);
367
368/*
369 * Express the locking dependencies for lockdep:
370 */
371static inline void
372double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
373{
374 if (hb1 > hb2)
375 swap(hb1, hb2);
376
377 spin_lock(&hb1->lock);
378 if (hb1 != hb2)
379 spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
380}
381
382static inline void
383double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
384{
385 spin_unlock(&hb1->lock);
386 if (hb1 != hb2)
387 spin_unlock(&hb2->lock);
388}
389
390/* syscalls */
391
392extern int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, u32
393 val, ktime_t *abs_time, u32 bitset, u32 __user
394 *uaddr2);
395
396extern int futex_requeue(u32 __user *uaddr1, unsigned int flags1,
397 u32 __user *uaddr2, unsigned int flags2,
398 int nr_wake, int nr_requeue,
399 u32 *cmpval, int requeue_pi);
400
401extern int __futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
402 struct hrtimer_sleeper *to, u32 bitset);
403
404extern int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
405 ktime_t *abs_time, u32 bitset);
406
407/**
408 * struct futex_vector - Auxiliary struct for futex_waitv()
409 * @w: Userspace provided data
410 * @q: Kernel side data
411 *
412 * Struct used to build an array with all data need for futex_waitv()
413 */
414struct futex_vector {
415 struct futex_waitv w;
416 struct futex_q q;
417};
418
419extern int futex_parse_waitv(struct futex_vector *futexv,
420 struct futex_waitv __user *uwaitv,
421 unsigned int nr_futexes, futex_wake_fn *wake,
422 void *wake_data);
423
424extern int futex_wait_multiple_setup(struct futex_vector *vs, int count,
425 int *woken);
426
427extern int futex_unqueue_multiple(struct futex_vector *v, int count);
428
429extern int futex_wait_multiple(struct futex_vector *vs, unsigned int count,
430 struct hrtimer_sleeper *to);
431
432extern int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset);
433
434extern int futex_wake_op(u32 __user *uaddr1, unsigned int flags,
435 u32 __user *uaddr2, int nr_wake, int nr_wake2, int op);
436
437extern int futex_unlock_pi(u32 __user *uaddr, unsigned int flags);
438
439extern int futex_lock_pi(u32 __user *uaddr, unsigned int flags, ktime_t *time, int trylock);
440
441#endif /* _FUTEX_H */