xref: /freebsd/sys/compat/linux/linux_futex.c (revision f856af0466c076beef4ea9b15d088e1119a945b8) 
1 /*	$NetBSD: linux_futex.c,v 1.5 2005/11/23 16:14:57 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 1.5 2005/11/23 16:14:57 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, args->val);
122 #endif
123 
124 	switch (args->op) {
125 	case LINUX_FUTEX_WAIT:
126 	   	FUTEX_SYSTEM_LOCK;
127 
128 		if ((error = copyin(args->uaddr,
129 		    &val, sizeof(val))) != 0) {
130 		   	FUTEX_SYSTEM_UNLOCK;
131 			return error;
132 		}
133 
134 		if (val != args->val) {
135 		   	FUTEX_SYSTEM_UNLOCK;
136 			return EWOULDBLOCK;
137 		}
138 
139 		if (args->timeout != NULL) {
140 			if ((error = copyin(args->timeout,
141 			    &timeout, sizeof(timeout))) != 0) {
142 			  	FUTEX_SYSTEM_UNLOCK;
143 				return error;
144 			}
145 		}
146 
147 #ifdef DEBUG
148 		if (ldebug(sys_futex))
149    			printf("FUTEX_WAIT %d: val = %d, uaddr = %p, "
150 		    		"*uaddr = %d, timeout = %d.%09lu\n",
151 		    		td->td_proc->p_pid, args->val,
152 		    		args->uaddr, val, timeout.tv_sec,
153 				(unsigned long)timeout.tv_nsec);
154 #endif
155 		tv.tv_usec = timeout.tv_sec * 1000000 + timeout.tv_nsec / 1000;
156 		timeout_hz = tvtohz(&tv);
157 
158 		if (timeout.tv_sec == 0 && timeout.tv_nsec == 0)
159 		   	timeout_hz = 0;
160       		/*
161                  * If the user process requests a non null timeout,
162                  * make sure we do not turn it into an infinite
163                  * timeout because timeout_hz gets null.
164                  *
165                  * We use a minimal timeout of 1/hz. Maybe it would
166                  * make sense to just return ETIMEDOUT without sleeping.
167                  */
168                 if (((timeout.tv_sec != 0) || (timeout.tv_nsec != 0)) &&
169                     (timeout_hz == 0))
170                         timeout_hz = 1;
171 
172 
173 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
174 		ret = futex_sleep(f, td, timeout_hz);
175 		futex_put(f);
176 
177 #ifdef DEBUG
178 		if (ldebug(sys_futex))
179    			printf("FUTEX_WAIT %d: uaddr = %p, "
180 		    		"ret = %d\n", td->td_proc->p_pid, args->uaddr, ret);
181 #endif
182 
183 		FUTEX_SYSTEM_UNLOCK;
184 		switch (ret) {
185 		case EWOULDBLOCK:	/* timeout */
186 			return ETIMEDOUT;
187 			break;
188 		case EINTR:		/* signal */
189 			return EINTR;
190 			break;
191 		case 0:			/* FUTEX_WAKE received */
192 #ifdef DEBUG
193 			if (ldebug(sys_futex))
194 				printf("FUTEX_WAIT %d: uaddr = %p, got FUTEX_WAKE\n",
195 			    		td->td_proc->p_pid, args->uaddr);
196 #endif
197 			return 0;
198 			break;
199 		default:
200 #ifdef DEBUG
201 			if (ldebug(sys_futex))
202    				printf("FUTEX_WAIT: unexpected ret = %d\n", ret);
203 #endif
204 			break;
205 		}
206 
207 		/* NOTREACHED */
208 		break;
209 
210 	case LINUX_FUTEX_WAKE:
211 		FUTEX_SYSTEM_LOCK;
212 
213 		/*
214 		 * XXX: Linux is able cope with different addresses
215 		 * corresponding to the same mapped memory in the sleeping
216 		 * and the waker process.
217 		 */
218 #ifdef DEBUG
219 		if (ldebug(sys_futex))
220    			printf("FUTEX_WAKE %d: uaddr = %p, val = %d\n",
221 		   		 td->td_proc->p_pid, args->uaddr, args->val);
222 #endif
223 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
224 		td->td_retval[0] = futex_wake(f, args->val, NULL);
225 		futex_put(f);
226 
227 		FUTEX_SYSTEM_UNLOCK;
228 		break;
229 
230 	case LINUX_FUTEX_CMP_REQUEUE:
231 		FUTEX_SYSTEM_LOCK;
232 
233 		if ((error = copyin(args->uaddr,
234 		    &val, sizeof(val))) != 0) {
235 		   	FUTEX_SYSTEM_UNLOCK;
236 			return error;
237 		}
238 
239 		if (val != args->val3) {
240 		   	FUTEX_SYSTEM_UNLOCK;
241 			return EAGAIN;
242 		}
243 
244 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
245 		newf = futex_get(args->uaddr2, FUTEX_UNLOCKED);
246 		td->td_retval[0] = futex_wake(f, args->val, newf);
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 		futex_put(f);
260 		futex_put(newf);
261 
262 		FUTEX_SYSTEM_UNLOCK;
263 		break;
264 
265 	case LINUX_FUTEX_FD:
266 		printf("linux_sys_futex: unimplemented op %d\n",
267 		    args->op);
268 		break;
269 
270 	case LINUX_FUTEX_WAKE_OP:
271 #ifdef	__i386__
272 		FUTEX_SYSTEM_LOCK;
273 #ifdef DEBUG
274 		if (ldebug(sys_futex))
275    		   	printf("FUTEX_WAKE_OP: %d: uaddr = %p, op = %d, val = %d, uaddr2 = %p, val3 = %d\n",
276 		      		td->td_proc->p_pid, args->uaddr, args->op, args->val, args->uaddr2, args->val3);
277 #endif
278 		f = futex_get(args->uaddr, FUTEX_UNLOCKED);
279 		f2 = futex_get(args->uaddr2, FUTEX_UNLOCKED);
280 
281 		/* This function returns positive number as results
282 		 * and negative as errors
283 		 */
284 		op_ret = futex_atomic_op(td, args->val3, args->uaddr2);
285 		if (op_ret < 0) {
286 
287 		   	/* XXX: we dont handle the EFAULT yet */
288 		   	if (op_ret != -EFAULT) {
289 			   	futex_put(f);
290 			   	futex_put(f2);
291 				FUTEX_SYSTEM_UNLOCK;
292 			   	return (-op_ret);
293 			}
294 
295 			futex_put(f);
296 			futex_put(f2);
297 
298 		   	FUTEX_SYSTEM_UNLOCK;
299 			return (EFAULT);
300 
301 		}
302 
303 		ret = futex_wake(f, args->val, NULL);
304 		futex_put(f);
305 		if (op_ret > 0) {
306 		   	op_ret = 0;
307 		   	/*
308 			 * Linux uses the address of the timespec parameter
309 			 * as the number of retries, so any large number will
310 			 * be ok.
311 			 */
312    		   	op_ret += futex_wake(f2, 0x7fffffff, NULL);
313 			ret += op_ret;
314 		}
315 		futex_put(f2);
316 		td->td_retval[0] = ret;
317 
318 		FUTEX_SYSTEM_UNLOCK;
319 #else
320 		printf("linux_sys_futex: wake_op not implemented");
321 #endif
322 	   	break;
323 
324 	default:
325 		printf("linux_sys_futex: unknown op %d\n",
326 		    args->op);
327 		break;
328 	}
329 	return 0;
330 }
331 
332 static struct futex *
333 futex_get(void *uaddr, int locked)
334 {
335 	struct futex *f;
336 
337 	if (locked == FUTEX_UNLOCKED)
338    	   	FUTEX_LOCK;
339 	LIST_FOREACH(f, &futex_list, f_list) {
340 		if (f->f_uaddr == uaddr) {
341 			f->f_refcount++;
342 			if (locked == FUTEX_UNLOCKED)
343    			   	FUTEX_UNLOCK;
344 			return f;
345 		}
346 	}
347 
348 	f = malloc(sizeof(*f), M_LINUX, M_WAITOK);
349 	f->f_uaddr = uaddr;
350 	f->f_refcount = 1;
351 	TAILQ_INIT(&f->f_waiting_proc);
352 	LIST_INSERT_HEAD(&futex_list, f, f_list);
353 	if (locked == FUTEX_UNLOCKED)
354    	   	FUTEX_UNLOCK;
355 
356 	return f;
357 }
358 
359 static void
360 futex_put(f)
361 	struct futex *f;
362 {
363    	FUTEX_LOCK;
364    	f->f_refcount--;
365 	if (f->f_refcount == 0) {
366 		LIST_REMOVE(f, f_list);
367 		free(f, M_LINUX);
368 	}
369 	FUTEX_UNLOCK;
370 
371 	return;
372 }
373 
374 static int
375 futex_sleep(struct futex *f, struct thread *td, unsigned long timeout)
376 {
377 	struct waiting_proc *wp;
378 	int ret;
379 
380 	wp = malloc(sizeof(*wp), M_LINUX, M_WAITOK);
381 	wp->wp_t = td;
382 	wp->wp_new_futex = NULL;
383 	FUTEX_LOCK;
384 	TAILQ_INSERT_TAIL(&f->f_waiting_proc, wp, wp_list);
385 	FUTEX_UNLOCK;
386 
387 #ifdef DEBUG
388 	if (ldebug(sys_futex))
389    		printf("FUTEX --> %d tlseep timeout = %ld\n", td->td_proc->p_pid,
390 	  	      timeout);
391 #endif
392 	ret = tsleep(wp, PCATCH|PZERO, "linuxfutex", timeout);
393 
394 	FUTEX_LOCK;
395 	TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
396 	FUTEX_UNLOCK;
397 
398 	if ((ret == 0) && (wp->wp_new_futex != NULL)) {
399 		ret = futex_sleep(wp->wp_new_futex, td, timeout);
400 		futex_put(wp->wp_new_futex); /* futex_get called in wakeup */
401 	}
402 
403 	free(wp, M_LINUX);
404 
405 	return ret;
406 }
407 
408 static int
409 futex_wake(struct futex *f, int n, struct futex *newf)
410 {
411 	struct waiting_proc *wp;
412 	int count = 0;
413 
414 	FUTEX_LOCK;
415 	TAILQ_FOREACH(wp, &f->f_waiting_proc, wp_list) {
416 		if (count <= n) {
417 			wakeup_one(wp);
418 			count++;
419 		} else {
420 			if (newf != NULL) {
421 				/* futex_put called after tsleep */
422 				wp->wp_new_futex = futex_get(newf->f_uaddr, FUTEX_LOCKED);
423 				wakeup_one(wp);
424 			}
425 		}
426 	}
427 	FUTEX_UNLOCK;
428 
429 	return count;
430 }
431 
432 #ifdef __i386__
433 static int
434 futex_atomic_op(struct thread *td, int encoded_op, caddr_t uaddr)
435 {
436    	int op = (encoded_op >> 28) & 7;
437         int cmp = (encoded_op >> 24) & 15;
438         int oparg = (encoded_op << 8) >> 20;
439         int cmparg = (encoded_op << 20) >> 20;
440         int oldval = 0, ret;
441 
442 	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
443 	   	oparg = 1 << oparg;
444 
445 #ifdef DEBUG
446 	printf("futex_atomic_op: op = %d, cmp = %d, oparg = %d, cmparg = %d, uaddr = %p\n",
447 	      op, cmp, oparg, cmparg, uaddr);
448 #endif
449 	/* XXX: linux verifies access here and returns EFAULT */
450 
451 	critical_enter();
452 
453 	switch (op) {
454 	   	case FUTEX_OP_SET:
455 		   	ret = futex_xchgl(oparg, uaddr, &oldval);
456 			break;
457 		case FUTEX_OP_ADD:
458 			ret = futex_addl(oparg, uaddr, &oldval);
459 			break;
460 		case FUTEX_OP_OR:
461 			ret = futex_orl(oparg, uaddr, &oldval);
462 			break;
463 		case FUTEX_OP_ANDN:
464 			ret = futex_andnl(oparg, uaddr, &oldval);
465 			break;
466 		case FUTEX_OP_XOR:
467 			ret = futex_xorl(oparg, uaddr, &oldval);
468 			break;
469 		default:
470 			ret = -ENOSYS;
471 	}
472 
473 	critical_exit();
474 
475 	if (!ret)
476 	   	switch (cmp) {
477 		      case FUTEX_OP_CMP_EQ:
478 			 	ret = (oldval == cmparg);
479 				break;
480 		      case FUTEX_OP_CMP_NE:
481 				ret = (oldval != cmparg);
482 				break;
483 		      case FUTEX_OP_CMP_LT:
484 				ret = (oldval < cmparg);
485 				break;
486 		      case FUTEX_OP_CMP_GE:
487 				ret = (oldval >= cmparg);
488 				break;
489 		      case FUTEX_OP_CMP_LE:
490 				ret = (oldval <= cmparg);
491 				break;
492 		      case FUTEX_OP_CMP_GT:
493 				ret = (oldval > cmparg);
494 				break;
495 		      default: ret = -ENOSYS;
496 		}
497 
498 	return (ret);
499 }
500 #endif
501