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 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",
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 }
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