xref: /freebsd/sys/compat/linux/linux_futex.c (revision 4fd2d3b6927878771635a3628ae1623daf810d39) 
1 /*	$NetBSD: linux_futex.c,v 1.7 2006/07/24 19:01:49 manu Exp $ */
2 
3 /*-
4  * Copyright (c) 2005 Emmanuel Dreyfus, all rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. All advertising materials mentioning features or use of this software
15  *    must display the following acknowledgement:
16  *	This product includes software developed by Emmanuel Dreyfus
17  * 4. The name of the author may not be used to endorse or promote
18  *    products derived from this software without specific prior written
19  *    permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE THE AUTHOR AND CONTRIBUTORS ``AS IS''
22  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
23  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
24  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
25  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
26  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
27  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
28  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
29  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
30  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
31  * POSSIBILITY OF SUCH DAMAGE.
32  */
33 
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
36 #if 0
37 __KERNEL_RCSID(1, "$NetBSD: linux_futex.c,v 1.7 2006/07/24 19:01:49 manu Exp $");
38 #endif
39 
40 #include "opt_compat.h"
41 
42 #include <sys/param.h>
43 #include <sys/types.h>
44 #include <sys/time.h>
45 #include <sys/systm.h>
46 #include <sys/proc.h>
47 #include <sys/queue.h>
48 #include <sys/lock.h>
49 #include <sys/mutex.h>
50 #include <sys/sx.h>
51 #include <sys/malloc.h>
52 
53 #ifdef COMPAT_LINUX32
54 #include <machine/../linux32/linux.h>
55 #include <machine/../linux32/linux32_proto.h>
56 #else
57 #include <machine/../linux/linux.h>
58 #include <machine/../linux/linux_proto.h>
59 #endif
60 #include <compat/linux/linux_futex.h>
61 
62 struct futex;
63 
64 struct waiting_proc {
65 	struct thread *wp_t;
66 	struct futex *wp_new_futex;
67 	TAILQ_ENTRY(waiting_proc) wp_list;
68 };
69 struct futex {
70 	void   *f_uaddr;
71 	int	f_refcount;
72 	LIST_ENTRY(futex) f_list;
73 	TAILQ_HEAD(lf_waiting_proc, waiting_proc) f_waiting_proc;
74 };
75 
76 LIST_HEAD(futex_list, futex) futex_list;
77 struct sx futex_sx;		/* this protects the LIST of futexes */
78 
79 #define FUTEX_LOCK sx_xlock(&futex_sx)
80 #define FUTEX_UNLOCK sx_xunlock(&futex_sx)
81 
82 #define FUTEX_LOCKED	1
83 #define FUTEX_UNLOCKED	0
84 
85 #define FUTEX_SYSTEM_LOCK mtx_lock(&Giant)
86 #define FUTEX_SYSTEM_UNLOCK mtx_unlock(&Giant)
87 
88 static struct futex	*futex_get(void *, int);
89 static void futex_put(struct futex *);
90 static int futex_sleep(struct futex *, struct thread *, unsigned long);
91 static int futex_wake(struct futex *, int, struct futex *, int);
92 static int futex_atomic_op(struct thread *td, int encoded_op, caddr_t uaddr);
93 
94 /* support.s */
95 int futex_xchgl(int oparg, caddr_t uaddr, int *oldval);
96 int futex_addl(int oparg, caddr_t uaddr, int *oldval);
97 int futex_orl(int oparg, caddr_t uaddr, int *oldval);
98 int futex_andl(int oparg, caddr_t uaddr, int *oldval);
99 int futex_xorl(int oparg, caddr_t uaddr, int *oldval);
100 
101 int
102 linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
103 {
104 	int val;
105 	int ret;
106 	struct l_timespec timeout = {0, 0};
107 	int error = 0;
108 	struct futex *f;
109 	struct futex *newf;
110 	int timeout_hz;
111 	struct timeval tv = {0, 0};
112 	struct futex *f2;
113 	int op_ret;
114 
115 #ifdef	DEBUG
116 	if (ldebug(sys_futex))
117 		printf(ARGS(futex, "%p, %i, %i, *, %p, %i"), args->uaddr, args->op,
118 		    args->val, args->uaddr2, args->val3);
119 #endif
120 
121 	switch (args->op) {
122 	case LINUX_FUTEX_WAIT:
123 		FUTEX_SYSTEM_LOCK;
124 
125 		if ((error = copyin(args->uaddr,
126 		    &val, sizeof(val))) != 0) {
127 			FUTEX_SYSTEM_UNLOCK;
128 			return error;
129 		}
130 
131 		if (val != args->val) {
132 			FUTEX_SYSTEM_UNLOCK;
133 			return EWOULDBLOCK;
134 		}
135 
136 		if (args->timeout != NULL) {
137 			if ((error = copyin(args->timeout,
138 			    &timeout, sizeof(timeout))) != 0) {
139 				FUTEX_SYSTEM_UNLOCK;
140 				return error;
141 			}
142 		}
143 
144 #ifdef DEBUG
145 		if (ldebug(sys_futex))
146 			printf("FUTEX_WAIT %d: val = %d, uaddr = %p, "
147 			    "*uaddr = %d, timeout = %d.%09lu\n",
148 			    td->td_proc->p_pid, args->val,
149 			    args->uaddr, val, timeout.tv_sec,
150 			    (unsigned long)timeout.tv_nsec);
151 #endif
152 		tv.tv_usec = timeout.tv_sec * 1000000 + timeout.tv_nsec / 1000;
153 		timeout_hz = tvtohz(&tv);
154 
155 		if (timeout.tv_sec == 0 && timeout.tv_nsec == 0)
156 			timeout_hz = 0;
157 		/*
158 		 * If the user process requests a non null timeout,
159 		 * make sure we do not turn it into an infinite
160 		 * timeout because timeout_hz gets null.
161 		 *
162 		 * We use a minimal timeout of 1/hz. Maybe it would
163 		 * make sense to just return ETIMEDOUT without sleeping.
164 		 */
165 		if (((timeout.tv_sec != 0) || (timeout.tv_nsec != 0)) &&
166 		    (timeout_hz == 0))
167 			timeout_hz = 1;
168 
169 
170 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
171 		ret = futex_sleep(f, td, timeout_hz);
172 		futex_put(f);
173 
174 #ifdef DEBUG
175 		if (ldebug(sys_futex))
176 			printf("FUTEX_WAIT %d: uaddr = %p, "
177 			    "ret = %d\n", td->td_proc->p_pid, args->uaddr, ret);
178 #endif
179 
180 		FUTEX_SYSTEM_UNLOCK;
181 		switch (ret) {
182 		case EWOULDBLOCK:	/* timeout */
183 			return ETIMEDOUT;
184 			break;
185 		case EINTR:		/* signal */
186 			return EINTR;
187 			break;
188 		case 0:		/* FUTEX_WAKE received */
189 #ifdef DEBUG
190 			if (ldebug(sys_futex))
191 				printf("FUTEX_WAIT %d: uaddr = %p, "
192 				    "got FUTEX_WAKE\n",
193 				    td->td_proc->p_pid, args->uaddr);
194 #endif
195 			return 0;
196 			break;
197 		default:
198 #ifdef DEBUG
199 			if (ldebug(sys_futex))
200 				printf("FUTEX_WAIT: unexpected ret = %d\n",
201 				    ret);
202 #endif
203 			break;
204 		}
205 
206 		/* NOTREACHED */
207 		break;
208 
209 	case LINUX_FUTEX_WAKE:
210 		FUTEX_SYSTEM_LOCK;
211 
212 		/*
213 		 * XXX: Linux is able to cope with different addresses
214 		 * corresponding to the same mapped memory in the sleeping
215 		 * and waker process(es).
216 		 */
217 #ifdef DEBUG
218 		if (ldebug(sys_futex))
219 			printf("FUTEX_WAKE %d: uaddr = %p, val = %d\n",
220 			    td->td_proc->p_pid, args->uaddr, args->val);
221 #endif
222 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
223 		td->td_retval[0] = futex_wake(f, args->val, NULL, 0);
224 		futex_put(f);
225 
226 		FUTEX_SYSTEM_UNLOCK;
227 		break;
228 
229 	case LINUX_FUTEX_CMP_REQUEUE:
230 		FUTEX_SYSTEM_LOCK;
231 
232 		if ((error = copyin(args->uaddr,
233 		    &val, sizeof(val))) != 0) {
234 			FUTEX_SYSTEM_UNLOCK;
235 			return error;
236 		}
237 
238 		if (val != args->val3) {
239 			FUTEX_SYSTEM_UNLOCK;
240 			return EAGAIN;
241 		}
242 
243 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
244 		newf = futex_get(args->uaddr2, FUTEX_UNLOCKED);
245 		td->td_retval[0] = futex_wake(f, args->val, newf,
246 		    (int)(unsigned long)args->timeout);
247 		futex_put(f);
248 		futex_put(newf);
249 
250 		FUTEX_SYSTEM_UNLOCK;
251 		break;
252 
253 	case LINUX_FUTEX_REQUEUE:
254 		FUTEX_SYSTEM_LOCK;
255 
256 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
257 		newf = futex_get(args->uaddr2, FUTEX_UNLOCKED);
258 		td->td_retval[0] = futex_wake(f, args->val, newf,
259 		    (int)(unsigned long)args->timeout);
260 		futex_put(f);
261 		futex_put(newf);
262 
263 		FUTEX_SYSTEM_UNLOCK;
264 		break;
265 
266 	case LINUX_FUTEX_FD:
267 		/* XXX: Linux plans to remove this operation */
268 		printf("linux_sys_futex: unimplemented op %d\n",
269 		    args->op);
270 		break;
271 
272 	case LINUX_FUTEX_WAKE_OP:
273 		FUTEX_SYSTEM_LOCK;
274 #ifdef DEBUG
275 		if (ldebug(sys_futex))
276 			printf("FUTEX_WAKE_OP: %d: uaddr = %p, op = %d, "
277 			    "val = %x, uaddr2 = %p, val3 = %x\n",
278 			    td->td_proc->p_pid, args->uaddr, args->op,
279 			    args->val, args->uaddr2, args->val3);
280 #endif
281 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
282 		f2 = futex_get(args->uaddr2, FUTEX_UNLOCKED);
283 
284 		/*
285 		 * This function returns positive number as results and
286 		 * negative as errors
287 		 */
288 		op_ret = futex_atomic_op(td, args->val3, args->uaddr2);
289 #ifdef DEBUG
290 		if (ldebug(sys_futex))
291 			printf("futex_atomic_op ret %d\n", op_ret);
292 #endif
293 		if (op_ret < 0) {
294 			/* XXX: We don't handle the EFAULT yet. */
295 			if (op_ret != -EFAULT) {
296 				futex_put(f);
297 				futex_put(f2);
298 				FUTEX_SYSTEM_UNLOCK;
299 				return (-op_ret);
300 			}
301 
302 			futex_put(f);
303 			futex_put(f2);
304 
305 			FUTEX_SYSTEM_UNLOCK;
306 			return (EFAULT);
307 		}
308 
309 		ret = futex_wake(f, args->val, NULL, 0);
310 		futex_put(f);
311 		if (op_ret > 0) {
312 			op_ret = 0;
313 			/*
314 			 * Linux abuses the address of the timespec parameter
315 			 * as the number of retries.
316 			 */
317 			op_ret += futex_wake(f2,
318 			    (int)(unsigned long)args->timeout, NULL, 0);
319 			ret += op_ret;
320 		}
321 		futex_put(f2);
322 		td->td_retval[0] = ret;
323 
324 		FUTEX_SYSTEM_UNLOCK;
325 		break;
326 
327 	default:
328 		printf("linux_sys_futex: unknown op %d\n",
329 		    args->op);
330 		return (ENOSYS);
331 	}
332 	return (0);
333 }
334 
335 static struct futex *
336 futex_get(void *uaddr, int locked)
337 {
338 	struct futex *f;
339 
340 	if (locked == FUTEX_UNLOCKED)
341 		FUTEX_LOCK;
342 	LIST_FOREACH(f, &futex_list, f_list) {
343 		if (f->f_uaddr == uaddr) {
344 			f->f_refcount++;
345 			if (locked == FUTEX_UNLOCKED)
346 				FUTEX_UNLOCK;
347 			return f;
348 		}
349 	}
350 
351 	f = malloc(sizeof(*f), M_LINUX, M_WAITOK);
352 	f->f_uaddr = uaddr;
353 	f->f_refcount = 1;
354 	TAILQ_INIT(&f->f_waiting_proc);
355 	LIST_INSERT_HEAD(&futex_list, f, f_list);
356 	if (locked == FUTEX_UNLOCKED)
357 		FUTEX_UNLOCK;
358 
359 	return f;
360 }
361 
362 static void
363 futex_put(f)
364 	struct futex *f;
365 {
366 	FUTEX_LOCK;
367 	f->f_refcount--;
368 	if (f->f_refcount == 0) {
369 		LIST_REMOVE(f, f_list);
370 		free(f, M_LINUX);
371 	}
372 	FUTEX_UNLOCK;
373 
374 	return;
375 }
376 
377 static int
378 futex_sleep(struct futex *f, struct thread *td, unsigned long timeout)
379 {
380 	struct waiting_proc *wp;
381 	int ret;
382 
383 	wp = malloc(sizeof(*wp), M_LINUX, M_WAITOK);
384 	wp->wp_t = td;
385 	wp->wp_new_futex = NULL;
386 	FUTEX_LOCK;
387 	TAILQ_INSERT_TAIL(&f->f_waiting_proc, wp, wp_list);
388 	FUTEX_UNLOCK;
389 
390 #ifdef DEBUG
391 	if (ldebug(sys_futex))
392 		printf("FUTEX --> %d tlseep timeout = %ld\n",
393 		    td->td_proc->p_pid, timeout);
394 #endif
395 	ret = tsleep(wp, PCATCH | PZERO, "linuxfutex", timeout);
396 #ifdef DEBUG
397 	if (ldebug(sys_futex))
398 		printf("FUTEX -> %d tsleep returns %d\n",
399 		    td->td_proc->p_pid, ret);
400 #endif
401 
402 	FUTEX_LOCK;
403 	TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
404 	FUTEX_UNLOCK;
405 
406 	/* if we got woken up in futex_wake */
407 	if ((ret == 0) && (wp->wp_new_futex != NULL)) {
408 		/* suspend us on the new futex */
409 		ret = futex_sleep(wp->wp_new_futex, td, timeout);
410 		/* and release the old one */
411 		futex_put(wp->wp_new_futex);
412 	}
413 
414 	free(wp, M_LINUX);
415 
416 	return ret;
417 }
418 
419 static int
420 futex_wake(struct futex *f, int n, struct futex *newf, int n2)
421 {
422 	struct waiting_proc *wp;
423 	int count;
424 
425 	/*
426 	 * Linux is very strange it wakes up N threads for
427 	 * all operations BUT requeue ones where its N+1
428 	 * mimic this.
429 	 */
430 	count = newf ? 0 : 1;
431 
432 	FUTEX_LOCK;
433 	TAILQ_FOREACH(wp, &f->f_waiting_proc, wp_list) {
434 		if (count <= n) {
435 			wakeup_one(wp);
436 			count++;
437 		} else {
438 			if (newf != NULL) {
439 				/* futex_put called after tsleep */
440 				wp->wp_new_futex = futex_get(newf->f_uaddr,
441 				    FUTEX_LOCKED);
442 				wakeup_one(wp);
443 				if (count - n >= n2)
444 					break;
445 			}
446 		}
447 	}
448 	FUTEX_UNLOCK;
449 
450 	return count;
451 }
452 
453 static int
454 futex_atomic_op(struct thread *td, int encoded_op, caddr_t uaddr)
455 {
456 	int op = (encoded_op >> 28) & 7;
457 	int cmp = (encoded_op >> 24) & 15;
458 	int oparg = (encoded_op << 8) >> 20;
459 	int cmparg = (encoded_op << 20) >> 20;
460 	int oldval = 0, ret;
461 
462 	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
463 		oparg = 1 << oparg;
464 
465 #ifdef DEBUG
466 	if (ldebug(sys_futex))
467 		printf("futex_atomic_op: op = %d, cmp = %d, oparg = %x, "
468 		       "cmparg = %x, uaddr = %p\n",
469 		       op, cmp, oparg, cmparg, uaddr);
470 #endif
471 	/* XXX: linux verifies access here and returns EFAULT */
472 
473 	switch (op) {
474 	case FUTEX_OP_SET:
475 		ret = futex_xchgl(oparg, uaddr, &oldval);
476 		break;
477 	case FUTEX_OP_ADD:
478 		ret = futex_addl(oparg, uaddr, &oldval);
479 		break;
480 	case FUTEX_OP_OR:
481 		ret = futex_orl(oparg, uaddr, &oldval);
482 		break;
483 	case FUTEX_OP_ANDN:
484 		ret = futex_andl(~oparg, uaddr, &oldval);
485 		break;
486 	case FUTEX_OP_XOR:
487 		ret = futex_xorl(oparg, uaddr, &oldval);
488 		break;
489 	default:
490 		ret = -ENOSYS;
491 		break;
492 	}
493 
494 	if (ret)
495 		return (ret);
496 
497 	switch (cmp) {
498 	case FUTEX_OP_CMP_EQ:
499 		return (oldval == cmparg);
500 	case FUTEX_OP_CMP_NE:
501 		return (oldval != cmparg);
502 	case FUTEX_OP_CMP_LT:
503 		return (oldval < cmparg);
504 	case FUTEX_OP_CMP_GE:
505 		return (oldval >= cmparg);
506 	case FUTEX_OP_CMP_LE:
507 		return (oldval <= cmparg);
508 	case FUTEX_OP_CMP_GT:
509 		return (oldval > cmparg);
510 	default:
511 		return (-ENOSYS);
512 	}
513 }
514