xref: /freebsd/sys/compat/linux/linux_futex.c (revision 2b743a9e9ddc6736208dc8ca1ce06ce64ad20a19) 
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 *);
92 #ifdef __i386__
93 static int futex_atomic_op(struct thread *td, int encoded_op, caddr_t uaddr);
94 #endif
95 
96 /* support.s */
97 int futex_xchgl(int oparg, caddr_t uaddr, int *oldval);
98 int futex_addl(int oparg, caddr_t uaddr, int *oldval);
99 int futex_orl(int oparg, caddr_t uaddr, int *oldval);
100 int futex_andnl(int oparg, caddr_t uaddr, int *oldval);
101 int futex_xorl(int oparg, caddr_t uaddr, int *oldval);
102 
103 int
104 linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
105 {
106 	int val;
107 	int ret;
108 	struct l_timespec timeout = {0, 0};
109 	int error = 0;
110 	struct futex *f;
111 	struct futex *newf;
112 	int timeout_hz;
113 	struct timeval tv = {0, 0};
114 #ifdef __i386__
115 	struct futex *f2;
116 	int op_ret;
117 #endif
118 
119 #ifdef	DEBUG
120 	if (ldebug(sys_futex))
121 		printf(ARGS(futex, "%p, %i, %i"), args->uaddr, args->op,
122 		    args->val);
123 #endif
124 
125 	switch (args->op) {
126 	case LINUX_FUTEX_WAIT:
127 		FUTEX_SYSTEM_LOCK;
128 
129 		if ((error = copyin(args->uaddr,
130 		    &val, sizeof(val))) != 0) {
131 			FUTEX_SYSTEM_UNLOCK;
132 			return error;
133 		}
134 
135 		if (val != args->val) {
136 			FUTEX_SYSTEM_UNLOCK;
137 			return EWOULDBLOCK;
138 		}
139 
140 		if (args->timeout != NULL) {
141 			if ((error = copyin(args->timeout,
142 			    &timeout, sizeof(timeout))) != 0) {
143 				FUTEX_SYSTEM_UNLOCK;
144 				return error;
145 			}
146 		}
147 
148 #ifdef DEBUG
149 		if (ldebug(sys_futex))
150 			printf("FUTEX_WAIT %d: val = %d, uaddr = %p, "
151 			    "*uaddr = %d, timeout = %d.%09lu\n",
152 			    td->td_proc->p_pid, args->val,
153 			    args->uaddr, val, timeout.tv_sec,
154 			    (unsigned long)timeout.tv_nsec);
155 #endif
156 		tv.tv_usec = timeout.tv_sec * 1000000 + timeout.tv_nsec / 1000;
157 		timeout_hz = tvtohz(&tv);
158 
159 		if (timeout.tv_sec == 0 && timeout.tv_nsec == 0)
160 			timeout_hz = 0;
161 		/*
162 		 * If the user process requests a non null timeout,
163 		 * make sure we do not turn it into an infinite
164 		 * timeout because timeout_hz gets null.
165 		 *
166 		 * We use a minimal timeout of 1/hz. Maybe it would
167 		 * make sense to just return ETIMEDOUT without sleeping.
168 		 */
169 		if (((timeout.tv_sec != 0) || (timeout.tv_nsec != 0)) &&
170 		    (timeout_hz == 0))
171 			timeout_hz = 1;
172 
173 
174 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
175 		ret = futex_sleep(f, td, timeout_hz);
176 		futex_put(f);
177 
178 #ifdef DEBUG
179 		if (ldebug(sys_futex))
180 			printf("FUTEX_WAIT %d: uaddr = %p, "
181 			    "ret = %d\n", td->td_proc->p_pid, args->uaddr, ret);
182 #endif
183 
184 		FUTEX_SYSTEM_UNLOCK;
185 		switch (ret) {
186 		case EWOULDBLOCK:	/* timeout */
187 			return ETIMEDOUT;
188 			break;
189 		case EINTR:		/* signal */
190 			return EINTR;
191 			break;
192 		case 0:		/* FUTEX_WAKE received */
193 #ifdef DEBUG
194 			if (ldebug(sys_futex))
195 				printf("FUTEX_WAIT %d: uaddr = %p, got FUTEX_WAKE\n",
196 				    td->td_proc->p_pid, args->uaddr);
197 #endif
198 			return 0;
199 			break;
200 		default:
201 #ifdef DEBUG
202 			if (ldebug(sys_futex))
203 				printf("FUTEX_WAIT: unexpected ret = %d\n", ret);
204 #endif
205 			break;
206 		}
207 
208 		/* NOTREACHED */
209 		break;
210 
211 	case LINUX_FUTEX_WAKE:
212 		FUTEX_SYSTEM_LOCK;
213 
214 		/*
215 		 * XXX: Linux is able cope with different addresses
216 		 * corresponding to the same mapped memory in the sleeping
217 		 * and the waker process.
218 		 */
219 #ifdef DEBUG
220 		if (ldebug(sys_futex))
221 			printf("FUTEX_WAKE %d: uaddr = %p, val = %d\n",
222 			    td->td_proc->p_pid, args->uaddr, args->val);
223 #endif
224 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
225 		td->td_retval[0] = futex_wake(f, args->val, NULL);
226 		futex_put(f);
227 
228 		FUTEX_SYSTEM_UNLOCK;
229 		break;
230 
231 	case LINUX_FUTEX_CMP_REQUEUE:
232 		FUTEX_SYSTEM_LOCK;
233 
234 		if ((error = copyin(args->uaddr,
235 		    &val, sizeof(val))) != 0) {
236 			FUTEX_SYSTEM_UNLOCK;
237 			return error;
238 		}
239 
240 		if (val != args->val3) {
241 			FUTEX_SYSTEM_UNLOCK;
242 			return EAGAIN;
243 		}
244 
245 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
246 		newf = futex_get(args->uaddr2, FUTEX_UNLOCKED);
247 		td->td_retval[0] = futex_wake(f, args->val, newf);
248 		futex_put(f);
249 		futex_put(newf);
250 
251 		FUTEX_SYSTEM_UNLOCK;
252 		break;
253 
254 	case LINUX_FUTEX_REQUEUE:
255 		FUTEX_SYSTEM_LOCK;
256 
257 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
258 		newf = futex_get(args->uaddr2, FUTEX_UNLOCKED);
259 		td->td_retval[0] = futex_wake(f, args->val, newf);
260 		futex_put(f);
261 		futex_put(newf);
262 
263 		FUTEX_SYSTEM_UNLOCK;
264 		break;
265 
266 	case LINUX_FUTEX_FD:
267 		printf("linux_sys_futex: unimplemented op %d\n",
268 		    args->op);
269 		break;
270 
271 	case LINUX_FUTEX_WAKE_OP:
272 #ifdef	__i386__
273 		FUTEX_SYSTEM_LOCK;
274 #ifdef DEBUG
275 		if (ldebug(sys_futex))
276 			printf("FUTEX_WAKE_OP: %d: uaddr = %p, op = %d, val = %d, uaddr2 = %p, val3 = %d\n",
277 			    td->td_proc->p_pid, args->uaddr, args->op, args->val,
278 			    args->uaddr2, args->val3);
279 #endif
280 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
281 		f2 = futex_get(args->uaddr2, FUTEX_UNLOCKED);
282 
283 		/*
284 		 * This function returns positive number as results and
285 		 * negative as errors
286 		 */
287 		op_ret = futex_atomic_op(td, args->val3, args->uaddr2);
288 		if (op_ret < 0) {
289 
290 			/* XXX: we dont handle the EFAULT yet */
291 			if (op_ret != -EFAULT) {
292 				futex_put(f);
293 				futex_put(f2);
294 				FUTEX_SYSTEM_UNLOCK;
295 				return (-op_ret);
296 			}
297 
298 			futex_put(f);
299 			futex_put(f2);
300 
301 			FUTEX_SYSTEM_UNLOCK;
302 			return (EFAULT);
303 
304 		}
305 
306 		ret = futex_wake(f, args->val, NULL);
307 		futex_put(f);
308 		if (op_ret > 0) {
309 		   	op_ret = 0;
310 		   	/*
311 			 * Linux uses the address of the timespec parameter
312 			 * as the number of retries, so any large number will
313 			 * be ok.
314 			 */
315    		   	op_ret += futex_wake(f2, 0x7fffffff, NULL);
316 			ret += op_ret;
317 		}
318 		futex_put(f2);
319 		td->td_retval[0] = ret;
320 
321 		FUTEX_SYSTEM_UNLOCK;
322 #else
323 		printf("linux_sys_futex: wake_op not implemented");
324 #endif
325 	   	break;
326 
327 	default:
328 		printf("linux_sys_futex: unknown op %d\n",
329 		    args->op);
330 		break;
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", td->td_proc->p_pid,
393 		    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 ((ret == 0) && (wp->wp_new_futex != NULL)) {
407 		ret = futex_sleep(wp->wp_new_futex, td, timeout);
408 		futex_put(wp->wp_new_futex);	/* futex_get called in wakeup */
409 	}
410 
411 	free(wp, M_LINUX);
412 
413 	return ret;
414 }
415 
416 static int
417 futex_wake(struct futex *f, int n, struct futex *newf)
418 {
419 	struct waiting_proc *wp;
420 	int count = 0;
421 
422 	FUTEX_LOCK;
423 	TAILQ_FOREACH(wp, &f->f_waiting_proc, wp_list) {
424 		if (count <= n) {
425 			wakeup_one(wp);
426 			count++;
427 		} else {
428 			if (newf != NULL) {
429 				/* futex_put called after tsleep */
430 				wp->wp_new_futex = futex_get(newf->f_uaddr, FUTEX_LOCKED);
431 				wakeup_one(wp);
432 			}
433 		}
434 	}
435 	FUTEX_UNLOCK;
436 
437 	return count;
438 }
439 
440 #ifdef __i386__
441 static int
442 futex_atomic_op(struct thread *td, int encoded_op, caddr_t uaddr)
443 {
444    	int op = (encoded_op >> 28) & 7;
445         int cmp = (encoded_op >> 24) & 15;
446         int oparg = (encoded_op << 8) >> 20;
447         int cmparg = (encoded_op << 20) >> 20;
448         int oldval = 0, ret;
449 
450 	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
451 	   	oparg = 1 << oparg;
452 
453 #ifdef DEBUG
454 	printf("futex_atomic_op: op = %d, cmp = %d, oparg = %d, cmparg = %d, uaddr = %p\n",
455 	      op, cmp, oparg, cmparg, uaddr);
456 #endif
457 	/* XXX: linux verifies access here and returns EFAULT */
458 
459 	critical_enter();
460 
461 	switch (op) {
462 	   	case FUTEX_OP_SET:
463 		   	ret = futex_xchgl(oparg, uaddr, &oldval);
464 			break;
465 		case FUTEX_OP_ADD:
466 			ret = futex_addl(oparg, uaddr, &oldval);
467 			break;
468 		case FUTEX_OP_OR:
469 			ret = futex_orl(oparg, uaddr, &oldval);
470 			break;
471 		case FUTEX_OP_ANDN:
472 			ret = futex_andnl(oparg, uaddr, &oldval);
473 			break;
474 		case FUTEX_OP_XOR:
475 			ret = futex_xorl(oparg, uaddr, &oldval);
476 			break;
477 		default:
478 			ret = -ENOSYS;
479 	}
480 
481 	critical_exit();
482 
483 	if (!ret)
484 	   	switch (cmp) {
485 		      case FUTEX_OP_CMP_EQ:
486 			 	ret = (oldval == cmparg);
487 				break;
488 		      case FUTEX_OP_CMP_NE:
489 				ret = (oldval != cmparg);
490 				break;
491 		      case FUTEX_OP_CMP_LT:
492 				ret = (oldval < cmparg);
493 				break;
494 		      case FUTEX_OP_CMP_GE:
495 				ret = (oldval >= cmparg);
496 				break;
497 		      case FUTEX_OP_CMP_LE:
498 				ret = (oldval <= cmparg);
499 				break;
500 		      case FUTEX_OP_CMP_GT:
501 				ret = (oldval > cmparg);
502 				break;
503 		      default: ret = -ENOSYS;
504 		}
505 
506 	return (ret);
507 }
508 #endif
509