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 #include <linux/cleanup.h> 11 12 #ifdef CONFIG_PREEMPT_RT 13 #include <linux/rcuwait.h> 14 #endif 15 16 #include <asm/futex.h> 17 18 /* 19 * Futex flags used to encode options to functions and preserve them across 20 * restarts. 21 */ 22 #define FLAGS_SIZE_8 0x0000 23 #define FLAGS_SIZE_16 0x0001 24 #define FLAGS_SIZE_32 0x0002 25 #define FLAGS_SIZE_64 0x0003 26 27 #define FLAGS_SIZE_MASK 0x0003 28 29 #ifdef CONFIG_MMU 30 # define FLAGS_SHARED 0x0010 31 #else 32 /* 33 * NOMMU does not have per process address space. Let the compiler optimize 34 * code away. 35 */ 36 # define FLAGS_SHARED 0x0000 37 #endif 38 #define FLAGS_CLOCKRT 0x0020 39 #define FLAGS_HAS_TIMEOUT 0x0040 40 #define FLAGS_NUMA 0x0080 41 #define FLAGS_STRICT 0x0100 42 #define FLAGS_MPOL 0x0200 43 44 /* FUTEX_ to FLAGS_ */ 45 static inline unsigned int futex_to_flags(unsigned int op) 46 { 47 unsigned int flags = FLAGS_SIZE_32; 48 49 if (!(op & FUTEX_PRIVATE_FLAG)) 50 flags |= FLAGS_SHARED; 51 52 if (op & FUTEX_CLOCK_REALTIME) 53 flags |= FLAGS_CLOCKRT; 54 55 return flags; 56 } 57 58 #define FUTEX2_VALID_MASK (FUTEX2_SIZE_MASK | FUTEX2_NUMA | FUTEX2_MPOL | FUTEX2_PRIVATE) 59 60 /* FUTEX2_ to FLAGS_ */ 61 static inline unsigned int futex2_to_flags(unsigned int flags2) 62 { 63 unsigned int flags = flags2 & FUTEX2_SIZE_MASK; 64 65 if (!(flags2 & FUTEX2_PRIVATE)) 66 flags |= FLAGS_SHARED; 67 68 if (flags2 & FUTEX2_NUMA) 69 flags |= FLAGS_NUMA; 70 71 if (flags2 & FUTEX2_MPOL) 72 flags |= FLAGS_MPOL; 73 74 return flags; 75 } 76 77 static inline unsigned int futex_size(unsigned int flags) 78 { 79 return 1 << (flags & FLAGS_SIZE_MASK); 80 } 81 82 static inline bool futex_flags_valid(unsigned int flags) 83 { 84 /* Only 64bit futexes for 64bit code */ 85 if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) { 86 if ((flags & FLAGS_SIZE_MASK) == FLAGS_SIZE_64) 87 return false; 88 } 89 90 /* Only 32bit futexes are implemented -- for now */ 91 if ((flags & FLAGS_SIZE_MASK) != FLAGS_SIZE_32) 92 return false; 93 94 /* 95 * Must be able to represent both FUTEX_NO_NODE and every valid nodeid 96 * in a futex word. 97 */ 98 if (flags & FLAGS_NUMA) { 99 int bits = 8 * futex_size(flags); 100 u64 max = ~0ULL; 101 102 max >>= 64 - bits; 103 if (nr_node_ids >= max) 104 return false; 105 } 106 107 return true; 108 } 109 110 static inline bool futex_validate_input(unsigned int flags, u64 val) 111 { 112 int bits = 8 * futex_size(flags); 113 114 if (bits < 64 && (val >> bits)) 115 return false; 116 117 return true; 118 } 119 120 #ifdef CONFIG_FAIL_FUTEX 121 extern bool should_fail_futex(bool fshared); 122 #else 123 static inline bool should_fail_futex(bool fshared) 124 { 125 return false; 126 } 127 #endif 128 129 /* 130 * Hash buckets are shared by all the futex_keys that hash to the same 131 * location. Each key may have multiple futex_q structures, one for each task 132 * waiting on a futex. 133 */ 134 struct futex_hash_bucket { 135 atomic_t waiters; 136 spinlock_t lock; 137 struct plist_head chain; 138 struct futex_private_hash *priv; 139 } ____cacheline_aligned_in_smp; 140 141 /* 142 * Priority Inheritance state: 143 */ 144 struct futex_pi_state { 145 /* 146 * list of 'owned' pi_state instances - these have to be 147 * cleaned up in do_exit() if the task exits prematurely: 148 */ 149 struct list_head list; 150 151 /* 152 * The PI object: 153 */ 154 struct rt_mutex_base pi_mutex; 155 156 struct task_struct *owner; 157 refcount_t refcount; 158 159 union futex_key key; 160 } __randomize_layout; 161 162 struct futex_q; 163 typedef void (futex_wake_fn)(struct wake_q_head *wake_q, struct futex_q *q); 164 165 /** 166 * struct futex_q - The hashed futex queue entry, one per waiting task 167 * @list: priority-sorted list of tasks waiting on this futex 168 * @task: the task waiting on the futex 169 * @lock_ptr: the hash bucket lock 170 * @wake: the wake handler for this queue 171 * @wake_data: data associated with the wake handler 172 * @key: the key the futex is hashed on 173 * @pi_state: optional priority inheritance state 174 * @rt_waiter: rt_waiter storage for use with requeue_pi 175 * @requeue_pi_key: the requeue_pi target futex key 176 * @bitset: bitset for the optional bitmasked wakeup 177 * @requeue_state: State field for futex_requeue_pi() 178 * @drop_hb_ref: Waiter should drop the extra hash bucket reference if true 179 * @requeue_wait: RCU wait for futex_requeue_pi() (RT only) 180 * 181 * We use this hashed waitqueue, instead of a normal wait_queue_entry_t, so 182 * we can wake only the relevant ones (hashed queues may be shared). 183 * 184 * A futex_q has a woken state, just like tasks have TASK_RUNNING. 185 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. 186 * The order of wakeup is always to make the first condition true, then 187 * the second. 188 * 189 * PI futexes are typically woken before they are removed from the hash list via 190 * the rt_mutex code. See futex_unqueue_pi(). 191 */ 192 struct futex_q { 193 struct plist_node list; 194 195 struct task_struct *task; 196 spinlock_t *lock_ptr; 197 futex_wake_fn *wake; 198 void *wake_data; 199 union futex_key key; 200 struct futex_pi_state *pi_state; 201 struct rt_mutex_waiter *rt_waiter; 202 union futex_key *requeue_pi_key; 203 u32 bitset; 204 atomic_t requeue_state; 205 bool drop_hb_ref; 206 #ifdef CONFIG_PREEMPT_RT 207 struct rcuwait requeue_wait; 208 #endif 209 } __randomize_layout; 210 211 extern const struct futex_q futex_q_init; 212 213 enum futex_access { 214 FUTEX_READ, 215 FUTEX_WRITE 216 }; 217 218 extern int get_futex_key(u32 __user *uaddr, unsigned int flags, union futex_key *key, 219 enum futex_access rw); 220 extern void futex_q_lockptr_lock(struct futex_q *q); 221 extern struct hrtimer_sleeper * 222 futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout, 223 int flags, u64 range_ns); 224 225 extern struct futex_hash_bucket *futex_hash(union futex_key *key); 226 #ifdef CONFIG_FUTEX_PRIVATE_HASH 227 extern void futex_hash_get(struct futex_hash_bucket *hb); 228 extern void futex_hash_put(struct futex_hash_bucket *hb); 229 230 extern struct futex_private_hash *futex_private_hash(void); 231 extern void futex_private_hash_put(struct futex_private_hash *fph); 232 233 #else /* !CONFIG_FUTEX_PRIVATE_HASH */ 234 static inline void futex_hash_get(struct futex_hash_bucket *hb) { } 235 static inline void futex_hash_put(struct futex_hash_bucket *hb) { } 236 static inline struct futex_private_hash *futex_private_hash(void) { return NULL; } 237 static inline void futex_private_hash_put(struct futex_private_hash *fph) { } 238 #endif 239 240 DEFINE_CLASS(hb, struct futex_hash_bucket *, 241 if (_T) futex_hash_put(_T), 242 futex_hash(key), union futex_key *key); 243 244 DEFINE_CLASS(private_hash, struct futex_private_hash *, 245 if (_T) futex_private_hash_put(_T), 246 futex_private_hash(), void); 247 248 /** 249 * futex_match - Check whether two futex keys are equal 250 * @key1: Pointer to key1 251 * @key2: Pointer to key2 252 * 253 * Return 1 if two futex_keys are equal, 0 otherwise. 254 */ 255 static inline int futex_match(union futex_key *key1, union futex_key *key2) 256 { 257 return (key1 && key2 258 && key1->both.word == key2->both.word 259 && key1->both.ptr == key2->both.ptr 260 && key1->both.offset == key2->both.offset); 261 } 262 263 extern int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags, 264 struct futex_q *q, union futex_key *key2, 265 struct task_struct *task); 266 extern void futex_do_wait(struct futex_q *q, struct hrtimer_sleeper *timeout); 267 extern bool __futex_wake_mark(struct futex_q *q); 268 extern void futex_wake_mark(struct wake_q_head *wake_q, struct futex_q *q); 269 270 extern int fault_in_user_writeable(u32 __user *uaddr); 271 extern struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, union futex_key *key); 272 273 static inline int futex_cmpxchg_value_locked(u32 *curval, u32 __user *uaddr, u32 uval, u32 newval) 274 { 275 int ret; 276 277 pagefault_disable(); 278 ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval); 279 pagefault_enable(); 280 281 return ret; 282 } 283 284 /* Read from user memory with pagefaults disabled */ 285 static inline int futex_get_value_locked(u32 *dest, u32 __user *from) 286 { 287 guard(pagefault)(); 288 return get_user_inline(*dest, from); 289 } 290 291 extern void __futex_unqueue(struct futex_q *q); 292 extern void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb, 293 struct task_struct *task); 294 extern int futex_unqueue(struct futex_q *q); 295 296 /** 297 * futex_queue() - Enqueue the futex_q on the futex_hash_bucket 298 * @q: The futex_q to enqueue 299 * @hb: The destination hash bucket 300 * @task: Task queueing this futex 301 * 302 * The hb->lock must be held by the caller, and is released here. A call to 303 * futex_queue() is typically paired with exactly one call to futex_unqueue(). The 304 * exceptions involve the PI related operations, which may use futex_unqueue_pi() 305 * or nothing if the unqueue is done as part of the wake process and the unqueue 306 * state is implicit in the state of woken task (see futex_wait_requeue_pi() for 307 * an example). 308 * 309 * Note that @task may be NULL, for async usage of futexes. 310 */ 311 static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb, 312 struct task_struct *task) 313 __releases(&hb->lock) 314 { 315 __futex_queue(q, hb, task); 316 spin_unlock(&hb->lock); 317 } 318 319 extern void futex_unqueue_pi(struct futex_q *q); 320 321 extern void wait_for_owner_exiting(int ret, struct task_struct *exiting); 322 323 /* 324 * Reflects a new waiter being added to the waitqueue. 325 */ 326 static inline void futex_hb_waiters_inc(struct futex_hash_bucket *hb) 327 { 328 #ifdef CONFIG_SMP 329 atomic_inc(&hb->waiters); 330 /* 331 * Full barrier (A), see the ordering comment above. 332 */ 333 smp_mb__after_atomic(); 334 #endif 335 } 336 337 /* 338 * Reflects a waiter being removed from the waitqueue by wakeup 339 * paths. 340 */ 341 static inline void futex_hb_waiters_dec(struct futex_hash_bucket *hb) 342 { 343 #ifdef CONFIG_SMP 344 atomic_dec(&hb->waiters); 345 #endif 346 } 347 348 static inline int futex_hb_waiters_pending(struct futex_hash_bucket *hb) 349 { 350 #ifdef CONFIG_SMP 351 /* 352 * Full barrier (B), see the ordering comment above. 353 */ 354 smp_mb(); 355 return atomic_read(&hb->waiters); 356 #else 357 return 1; 358 #endif 359 } 360 361 extern void futex_q_lock(struct futex_q *q, struct futex_hash_bucket *hb); 362 extern void futex_q_unlock(struct futex_hash_bucket *hb); 363 364 365 extern int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, 366 union futex_key *key, 367 struct futex_pi_state **ps, 368 struct task_struct *task, 369 struct task_struct **exiting, 370 int set_waiters); 371 372 extern int refill_pi_state_cache(void); 373 extern void get_pi_state(struct futex_pi_state *pi_state); 374 extern void put_pi_state(struct futex_pi_state *pi_state); 375 extern int fixup_pi_owner(u32 __user *uaddr, struct futex_q *q, int locked); 376 377 /* 378 * Express the locking dependencies for lockdep: 379 */ 380 static inline void 381 double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) 382 { 383 if (hb1 > hb2) 384 swap(hb1, hb2); 385 386 spin_lock(&hb1->lock); 387 if (hb1 != hb2) 388 spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); 389 } 390 391 static inline void 392 double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) 393 { 394 spin_unlock(&hb1->lock); 395 if (hb1 != hb2) 396 spin_unlock(&hb2->lock); 397 } 398 399 /* syscalls */ 400 401 extern int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, u32 402 val, ktime_t *abs_time, u32 bitset, u32 __user 403 *uaddr2); 404 405 extern int futex_requeue(u32 __user *uaddr1, unsigned int flags1, 406 u32 __user *uaddr2, unsigned int flags2, 407 int nr_wake, int nr_requeue, 408 u32 *cmpval, int requeue_pi); 409 410 extern int __futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, 411 struct hrtimer_sleeper *to, u32 bitset); 412 413 extern int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, 414 ktime_t *abs_time, u32 bitset); 415 416 /** 417 * struct futex_vector - Auxiliary struct for futex_waitv() 418 * @w: Userspace provided data 419 * @q: Kernel side data 420 * 421 * Struct used to build an array with all data need for futex_waitv() 422 */ 423 struct futex_vector { 424 struct futex_waitv w; 425 struct futex_q q; 426 }; 427 428 extern int futex_parse_waitv(struct futex_vector *futexv, 429 struct futex_waitv __user *uwaitv, 430 unsigned int nr_futexes, futex_wake_fn *wake, 431 void *wake_data); 432 433 extern int futex_wait_multiple_setup(struct futex_vector *vs, int count, 434 int *woken); 435 436 extern int futex_unqueue_multiple(struct futex_vector *v, int count); 437 438 extern int futex_wait_multiple(struct futex_vector *vs, unsigned int count, 439 struct hrtimer_sleeper *to); 440 441 extern int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset); 442 443 extern int futex_wake_op(u32 __user *uaddr1, unsigned int flags, 444 u32 __user *uaddr2, int nr_wake, int nr_wake2, int op); 445 446 extern int futex_unlock_pi(u32 __user *uaddr, unsigned int flags); 447 448 extern int futex_lock_pi(u32 __user *uaddr, unsigned int flags, ktime_t *time, int trylock); 449 450 #endif /* _FUTEX_H */ 451