xref: /freebsd/lib/libc/gen/sysconf.c (revision 2ca7a12a81a5376ef17d3a3ea70f7000c025c579)
1 /*-
2  * Copyright (c) 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * This code is derived from software contributed to Berkeley by
6  * Sean Eric Fagan of Cygnus Support.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  * 4. Neither the name of the University nor the names of its contributors
17  *    may be used to endorse or promote products derived from this software
18  *    without specific prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30  * SUCH DAMAGE.
31  */
32 
33 #if defined(LIBC_SCCS) && !defined(lint)
34 static char sccsid[] = "@(#)sysconf.c	8.2 (Berkeley) 3/20/94";
35 #endif /* LIBC_SCCS and not lint */
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
38 
39 #include <sys/param.h>
40 #include <sys/time.h>
41 #include <sys/sysctl.h>
42 #include <sys/resource.h>
43 #include <sys/socket.h>
44 
45 #include <errno.h>
46 #include <limits.h>
47 #include <paths.h>
48 #include <pthread.h>		/* we just need the limits */
49 #include <time.h>
50 #include <unistd.h>
51 
52 #include "../stdlib/atexit.h"
53 #include "../stdtime/tzfile.h"
54 
55 #define	_PATH_ZONEINFO	TZDIR	/* from tzfile.h */
56 
57 /*
58  * sysconf --
59  *	get configurable system variables.
60  *
61  * XXX
62  * POSIX 1003.1 (ISO/IEC 9945-1, 4.8.1.3) states that the variable values
63  * not change during the lifetime of the calling process.  This would seem
64  * to require that any change to system limits kill all running processes.
65  * A workaround might be to cache the values when they are first retrieved
66  * and then simply return the cached value on subsequent calls.  This is
67  * less useful than returning up-to-date values, however.
68  */
69 long
70 sysconf(name)
71 	int name;
72 {
73 	struct rlimit rl;
74 	size_t len;
75 	int mib[2], sverrno, value;
76 	long lvalue, defaultresult;
77 	const char *path;
78 
79 	defaultresult = -1;
80 
81 	switch (name) {
82 	case _SC_ARG_MAX:
83 		mib[0] = CTL_KERN;
84 		mib[1] = KERN_ARGMAX;
85 		break;
86 	case _SC_CHILD_MAX:
87 		if (getrlimit(RLIMIT_NPROC, &rl) != 0)
88 			return (-1);
89 		if (rl.rlim_cur == RLIM_INFINITY)
90 			return (-1);
91 		if (rl.rlim_cur > LONG_MAX) {
92 			errno = EOVERFLOW;
93 			return (-1);
94 		}
95 		return ((long)rl.rlim_cur);
96 	case _SC_CLK_TCK:
97 		return (CLK_TCK);
98 	case _SC_NGROUPS_MAX:
99 		mib[0] = CTL_KERN;
100 		mib[1] = KERN_NGROUPS;
101 		break;
102 	case _SC_OPEN_MAX:
103 	case _SC_STREAM_MAX:	/* assume fds run out before memory does */
104 		if (getrlimit(RLIMIT_NOFILE, &rl) != 0)
105 			return (-1);
106 		if (rl.rlim_cur == RLIM_INFINITY)
107 			return (-1);
108 		if (rl.rlim_cur > LONG_MAX) {
109 			errno = EOVERFLOW;
110 			return (-1);
111 		}
112 		return ((long)rl.rlim_cur);
113 	case _SC_JOB_CONTROL:
114 		return (_POSIX_JOB_CONTROL);
115 	case _SC_SAVED_IDS:
116 		/* XXX - must be 1 */
117 		mib[0] = CTL_KERN;
118 		mib[1] = KERN_SAVED_IDS;
119 		goto yesno;
120 	case _SC_VERSION:
121 		mib[0] = CTL_KERN;
122 		mib[1] = KERN_POSIX1;
123 		break;
124 	case _SC_BC_BASE_MAX:
125 		return (BC_BASE_MAX);
126 	case _SC_BC_DIM_MAX:
127 		return (BC_DIM_MAX);
128 	case _SC_BC_SCALE_MAX:
129 		return (BC_SCALE_MAX);
130 	case _SC_BC_STRING_MAX:
131 		return (BC_STRING_MAX);
132 	case _SC_COLL_WEIGHTS_MAX:
133 		return (COLL_WEIGHTS_MAX);
134 	case _SC_EXPR_NEST_MAX:
135 		return (EXPR_NEST_MAX);
136 	case _SC_LINE_MAX:
137 		return (LINE_MAX);
138 	case _SC_RE_DUP_MAX:
139 		return (RE_DUP_MAX);
140 	case _SC_2_VERSION:
141 		/*
142 		 * This is something of a lie, but it would be silly at
143 		 * this point to try to deduce this from the contents
144 		 * of the filesystem.
145 		 */
146 		return (_POSIX2_VERSION);
147 	case _SC_2_C_BIND:
148 		return (_POSIX2_C_BIND);
149 	case _SC_2_C_DEV:
150 		return (_POSIX2_C_DEV);
151 	case _SC_2_CHAR_TERM:
152 		return (_POSIX2_CHAR_TERM);
153 	case _SC_2_FORT_DEV:
154 		return (_POSIX2_FORT_DEV);
155 	case _SC_2_FORT_RUN:
156 		return (_POSIX2_FORT_RUN);
157 	case _SC_2_LOCALEDEF:
158 		return (_POSIX2_LOCALEDEF);
159 	case _SC_2_SW_DEV:
160 		return (_POSIX2_SW_DEV);
161 	case _SC_2_UPE:
162 		return (_POSIX2_UPE);
163 	case _SC_TZNAME_MAX:
164 		path = _PATH_ZONEINFO;
165 do_NAME_MAX:
166 		sverrno = errno;
167 		errno = 0;
168 		lvalue = pathconf(path, _PC_NAME_MAX);
169 		if (lvalue == -1 && errno != 0)
170 			return (-1);
171 		errno = sverrno;
172 		return (lvalue);
173 
174 	case _SC_ASYNCHRONOUS_IO:
175 #if _POSIX_ASYNCHRONOUS_IO == 0
176 		mib[0] = CTL_P1003_1B;
177 		mib[1] = CTL_P1003_1B_ASYNCHRONOUS_IO;
178 		break;
179 #else
180 		return (_POSIX_ASYNCHRONOUS_IO);
181 #endif
182 	case _SC_MAPPED_FILES:
183 		return (_POSIX_MAPPED_FILES);
184 	case _SC_MEMLOCK:
185 		return (_POSIX_MEMLOCK);
186 	case _SC_MEMLOCK_RANGE:
187 		return (_POSIX_MEMLOCK_RANGE);
188 	case _SC_MEMORY_PROTECTION:
189 		return (_POSIX_MEMORY_PROTECTION);
190 	case _SC_MESSAGE_PASSING:
191 #if _POSIX_MESSAGE_PASSING == 0
192 		mib[0] = CTL_P1003_1B;
193 		mib[1] = CTL_P1003_1B_MESSAGE_PASSING;
194 		goto yesno;
195 #else
196 		return (_POSIX_MESSAGE_PASSING);
197 #endif
198 	case _SC_PRIORITIZED_IO:
199 #if _POSIX_PRIORITIZED_IO == 0
200 		mib[0] = CTL_P1003_1B;
201 		mib[1] = CTL_P1003_1B_PRIORITIZED_IO;
202 		goto yesno;
203 #else
204 		return (_POSIX_PRIORITIZED_IO);
205 #endif
206 	case _SC_PRIORITY_SCHEDULING:
207 #if _POSIX_PRIORITY_SCHEDULING == 0
208 		mib[0] = CTL_P1003_1B;
209 		mib[1] = CTL_P1003_1B_PRIORITY_SCHEDULING;
210 		goto yesno;
211 #else
212 		return (_POSIX_PRIORITY_SCHEDULING);
213 #endif
214 	case _SC_REALTIME_SIGNALS:
215 #if _POSIX_REALTIME_SIGNALS == 0
216 		mib[0] = CTL_P1003_1B;
217 		mib[1] = CTL_P1003_1B_REALTIME_SIGNALS;
218 		goto yesno;
219 #else
220 		return (_POSIX_REALTIME_SIGNALS);
221 #endif
222 	case _SC_SEMAPHORES:
223 #if _POSIX_SEMAPHORES == 0
224 		mib[0] = CTL_P1003_1B;
225 		mib[1] = CTL_P1003_1B_SEMAPHORES;
226 		goto yesno;
227 #else
228 		return (_POSIX_SEMAPHORES);
229 #endif
230 	case _SC_FSYNC:
231 		return (_POSIX_FSYNC);
232 
233 	case _SC_SHARED_MEMORY_OBJECTS:
234 		return (_POSIX_SHARED_MEMORY_OBJECTS);
235 	case _SC_SYNCHRONIZED_IO:
236 #if _POSIX_SYNCHRONIZED_IO == 0
237 		mib[0] = CTL_P1003_1B;
238 		mib[1] = CTL_P1003_1B_SYNCHRONIZED_IO;
239 		goto yesno;
240 #else
241 		return (_POSIX_SYNCHRONIZED_IO);
242 #endif
243 	case _SC_TIMERS:
244 #if _POSIX_TIMERS == 0
245 		mib[0] = CTL_P1003_1B;
246 		mib[1] = CTL_P1003_1B_TIMERS;
247 		goto yesno;
248 #else
249 		return (_POSIX_TIMERS);
250 #endif
251 	case _SC_AIO_LISTIO_MAX:
252 		mib[0] = CTL_P1003_1B;
253 		mib[1] = CTL_P1003_1B_AIO_LISTIO_MAX;
254 		break;
255 	case _SC_AIO_MAX:
256 		mib[0] = CTL_P1003_1B;
257 		mib[1] = CTL_P1003_1B_AIO_MAX;
258 		break;
259 	case _SC_AIO_PRIO_DELTA_MAX:
260 		mib[0] = CTL_P1003_1B;
261 		mib[1] = CTL_P1003_1B_AIO_PRIO_DELTA_MAX;
262 		break;
263 	case _SC_DELAYTIMER_MAX:
264 		mib[0] = CTL_P1003_1B;
265 		mib[1] = CTL_P1003_1B_DELAYTIMER_MAX;
266 		goto yesno;
267 	case _SC_MQ_OPEN_MAX:
268 		mib[0] = CTL_P1003_1B;
269 		mib[1] = CTL_P1003_1B_MQ_OPEN_MAX;
270 		goto yesno;
271 	case _SC_PAGESIZE:
272 		defaultresult = getpagesize();
273 		mib[0] = CTL_P1003_1B;
274 		mib[1] = CTL_P1003_1B_PAGESIZE;
275 		goto yesno;
276 	case _SC_RTSIG_MAX:
277 		mib[0] = CTL_P1003_1B;
278 		mib[1] = CTL_P1003_1B_RTSIG_MAX;
279 		goto yesno;
280 	case _SC_SEM_NSEMS_MAX:
281 		mib[0] = CTL_P1003_1B;
282 		mib[1] = CTL_P1003_1B_SEM_NSEMS_MAX;
283 		goto yesno;
284 	case _SC_SEM_VALUE_MAX:
285 		mib[0] = CTL_P1003_1B;
286 		mib[1] = CTL_P1003_1B_SEM_VALUE_MAX;
287 		goto yesno;
288 	case _SC_SIGQUEUE_MAX:
289 		mib[0] = CTL_P1003_1B;
290 		mib[1] = CTL_P1003_1B_SIGQUEUE_MAX;
291 		goto yesno;
292 	case _SC_TIMER_MAX:
293 		mib[0] = CTL_P1003_1B;
294 		mib[1] = CTL_P1003_1B_TIMER_MAX;
295 yesno:
296 		len = sizeof(value);
297 		if (sysctl(mib, 2, &value, &len, NULL, 0) == -1)
298 			return (-1);
299 		if (value == 0)
300 			return (defaultresult);
301 		return ((long)value);
302 
303 	case _SC_2_PBS:
304 	case _SC_2_PBS_ACCOUNTING:
305 	case _SC_2_PBS_CHECKPOINT:
306 	case _SC_2_PBS_LOCATE:
307 	case _SC_2_PBS_MESSAGE:
308 	case _SC_2_PBS_TRACK:
309 #if _POSIX2_PBS == 0
310 #error "don't know how to determine _SC_2_PBS"
311 		/*
312 		 * This probably requires digging through the filesystem
313 		 * to see if the appropriate package has been installed.
314 		 * Since we don't currently support this option at all,
315 		 * it's not worth the effort to write the code now.
316 		 * Figuring out which of the sub-options are supported
317 		 * would be even more difficult, so it's probably easier
318 		 * to always say ``no''.
319 		 */
320 #else
321 		return (_POSIX2_PBS);
322 #endif
323 	case _SC_ADVISORY_INFO:
324 #if _POSIX_ADVISORY_INFO == 0
325 #error "_POSIX_ADVISORY_INFO"
326 #else
327 		return (_POSIX_ADVISORY_INFO);
328 #endif
329 	case _SC_BARRIERS:
330 #if _POSIX_BARRIERS == 0
331 #error "_POSIX_BARRIERS"
332 #else
333 		return (_POSIX_BARRIERS);
334 #endif
335 	case _SC_CLOCK_SELECTION:
336 #if _POSIX_CLOCK_SELECTION == 0
337 #error "_POSIX_CLOCK_SELECTION"
338 #else
339 		return (_POSIX_CLOCK_SELECTION);
340 #endif
341 	case _SC_CPUTIME:
342 #if _POSIX_CPUTIME == 0
343 #error "_POSIX_CPUTIME"
344 #else
345 		return (_POSIX_CPUTIME);
346 #endif
347 #ifdef notdef
348 	case _SC_FILE_LOCKING:
349 		/*
350 		 * XXX - The standard doesn't tell us how to define
351 		 * _POSIX_FILE_LOCKING, so we can't answer this one.
352 		 */
353 #endif
354 #if _POSIX_THREAD_SAFE_FUNCTIONS > -1
355 	case _SC_GETGR_R_SIZE_MAX:
356 	case _SC_GETPW_R_SIZE_MAX:
357 #error "somebody needs to implement this"
358 #endif
359 	case _SC_HOST_NAME_MAX:
360 		return (MAXHOSTNAMELEN - 1); /* does not include \0 */
361 	case _SC_LOGIN_NAME_MAX:
362 		return (MAXLOGNAME);
363 	case _SC_MONOTONIC_CLOCK:
364 #if _POSIX_MONOTONIC_CLOCK == 0
365 #error "_POSIX_MONOTONIC_CLOCK"
366 #else
367 		return (_POSIX_MONOTONIC_CLOCK);
368 #endif
369 #if _POSIX_MESSAGE_PASSING > -1
370 	case _SC_MQ_PRIO_MAX:
371 		return (MQ_PRIO_MAX);
372 #endif
373 	case _SC_READER_WRITER_LOCKS:
374 		return (_POSIX_READER_WRITER_LOCKS);
375 	case _SC_REGEXP:
376 		return (_POSIX_REGEXP);
377 	case _SC_SHELL:
378 		return (_POSIX_SHELL);
379 	case _SC_SPAWN:
380 		return (_POSIX_SPAWN);
381 	case _SC_SPIN_LOCKS:
382 		return (_POSIX_SPIN_LOCKS);
383 	case _SC_SPORADIC_SERVER:
384 #if _POSIX_SPORADIC_SERVER == 0
385 #error "_POSIX_SPORADIC_SERVER"
386 #else
387 		return (_POSIX_SPORADIC_SERVER);
388 #endif
389 	case _SC_THREAD_ATTR_STACKADDR:
390 		return (_POSIX_THREAD_ATTR_STACKADDR);
391 	case _SC_THREAD_ATTR_STACKSIZE:
392 		return (_POSIX_THREAD_ATTR_STACKSIZE);
393 	case _SC_THREAD_CPUTIME:
394 		return (_POSIX_THREAD_CPUTIME);
395 	case _SC_THREAD_DESTRUCTOR_ITERATIONS:
396 		return (PTHREAD_DESTRUCTOR_ITERATIONS);
397 	case _SC_THREAD_KEYS_MAX:
398 		return (PTHREAD_KEYS_MAX);
399 	case _SC_THREAD_PRIO_INHERIT:
400 		return (_POSIX_THREAD_PRIO_INHERIT);
401 	case _SC_THREAD_PRIO_PROTECT:
402 		return (_POSIX_THREAD_PRIO_PROTECT);
403 	case _SC_THREAD_PRIORITY_SCHEDULING:
404 		return (_POSIX_THREAD_PRIORITY_SCHEDULING);
405 	case _SC_THREAD_PROCESS_SHARED:
406 		return (_POSIX_THREAD_PROCESS_SHARED);
407 	case _SC_THREAD_SAFE_FUNCTIONS:
408 		return (_POSIX_THREAD_SAFE_FUNCTIONS);
409 	case _SC_THREAD_STACK_MIN:
410 		return (PTHREAD_STACK_MIN);
411 	case _SC_THREAD_THREADS_MAX:
412 		return (PTHREAD_THREADS_MAX); /* XXX wrong type! */
413 	case _SC_TIMEOUTS:
414 		return (_POSIX_TIMEOUTS);
415 	case _SC_THREADS:
416 		return (_POSIX_THREADS);
417 	case _SC_TRACE:
418 #if _POSIX_TRACE == 0
419 #error "_POSIX_TRACE"
420 		/* While you're implementing this, also do the ones below. */
421 #else
422 		return (_POSIX_TRACE);
423 #endif
424 #if _POSIX_TRACE > -1
425 	case _SC_TRACE_EVENT_FILTER:
426 		return (_POSIX_TRACE_EVENT_FILTER);
427 	case _SC_TRACE_INHERIT:
428 		return (_POSIX_TRACE_INHERIT);
429 	case _SC_TRACE_LOG:
430 		return (_POSIX_TRACE_LOG);
431 #endif
432 	case _SC_TTY_NAME_MAX:
433 		path = _PATH_DEV;
434 		goto do_NAME_MAX;
435 	case _SC_TYPED_MEMORY_OBJECTS:
436 #if _POSIX_TYPED_MEMORY_OBJECTS == 0
437 #error "_POSIX_TYPED_MEMORY_OBJECTS"
438 #else
439 		return (_POSIX_TYPED_MEMORY_OBJECTS);
440 #endif
441 	case _SC_V6_ILP32_OFF32:
442 #if _V6_ILP32_OFF32 == 0
443 		if (sizeof(int) * CHAR_BIT == 32 &&
444 		    sizeof(int) == sizeof(long) &&
445 		    sizeof(long) == sizeof(void *) &&
446 		    sizeof(void *) == sizeof(off_t))
447 			return 1;
448 		else
449 			return -1;
450 #else
451 		return (_V6_ILP32_OFF32);
452 #endif
453 	case _SC_V6_ILP32_OFFBIG:
454 #if _V6_ILP32_OFFBIG == 0
455 		if (sizeof(int) * CHAR_BIT == 32 &&
456 		    sizeof(int) == sizeof(long) &&
457 		    sizeof(long) == sizeof(void *) &&
458 		    sizeof(off_t) * CHAR_BIT >= 64)
459 			return 1;
460 		else
461 			return -1;
462 #else
463 		return (_V6_ILP32_OFFBIG);
464 #endif
465 	case _SC_V6_LP64_OFF64:
466 #if _V6_LP64_OFF64 == 0
467 		if (sizeof(int) * CHAR_BIT == 32 &&
468 		    sizeof(long) * CHAR_BIT == 64 &&
469 		    sizeof(long) == sizeof(void *) &&
470 		    sizeof(void *) == sizeof(off_t))
471 			return 1;
472 		else
473 			return -1;
474 #else
475 		return (_V6_LP64_OFF64);
476 #endif
477 	case _SC_V6_LPBIG_OFFBIG:
478 #if _V6_LPBIG_OFFBIG == 0
479 		if (sizeof(int) * CHAR_BIT >= 32 &&
480 		    sizeof(long) * CHAR_BIT >= 64 &&
481 		    sizeof(void *) * CHAR_BIT >= 64 &&
482 		    sizeof(off_t) * CHAR_BIT >= 64)
483 			return 1;
484 		else
485 			return -1;
486 #else
487 		return (_V6_LPBIG_OFFBIG);
488 #endif
489 	case _SC_ATEXIT_MAX:
490 		return (ATEXIT_SIZE);
491 	case _SC_IOV_MAX:
492 		mib[0] = CTL_KERN;
493 		mib[1] = KERN_IOV_MAX;
494 		break;
495 	case _SC_XOPEN_CRYPT:
496 		return (_XOPEN_CRYPT);
497 	case _SC_XOPEN_ENH_I18N:
498 		return (_XOPEN_ENH_I18N);
499 	case _SC_XOPEN_LEGACY:
500 		return (_XOPEN_LEGACY);
501 	case _SC_XOPEN_REALTIME:
502 #if _XOPEN_REALTIME == 0
503 		sverrno = errno;
504 		value = sysconf(_SC_ASYNCHRONOUS_IO) > 0 &&
505 			sysconf(_SC_MEMLOCK) > 0 &&
506 			sysconf(_SC_MEMLOCK_RANGE) > 0 &&
507 			sysconf(_SC_MESSAGE_PASSING) > 0 &&
508 			sysconf(_SC_PRIORITY_SCHEDULING) > 0 &&
509 			sysconf(_SC_REALTIME_SIGNALS) > 0 &&
510 			sysconf(_SC_SEMAPHORES) > 0 &&
511 			sysconf(_SC_SHARED_MEMORY_OBJECTS) > 0 &&
512 			sysconf(_SC_SYNCHRONIZED_IO) > 0 &&
513 			sysconf(_SC_TIMERS) > 0;
514 		errno = sverrno;
515 		if (value)
516 			return (200112L);
517 		else
518 			return (-1);
519 #else
520 		return (_XOPEN_REALTIME);
521 #endif
522 	case _SC_XOPEN_REALTIME_THREADS:
523 #if _XOPEN_REALTIME_THREADS == 0
524 #error "_XOPEN_REALTIME_THREADS"
525 #else
526 		return (_XOPEN_REALTIME_THREADS);
527 #endif
528 	case _SC_XOPEN_SHM:
529 		len = sizeof(lvalue);
530 		sverrno = errno;
531 		if (sysctlbyname("kern.ipc.shmmin", &lvalue, &len, NULL,
532 		    0) == -1) {
533 			errno = sverrno;
534 			return (-1);
535 		}
536 		errno = sverrno;
537 		return (1);
538 	case _SC_XOPEN_STREAMS:
539 		return (_XOPEN_STREAMS);
540 	case _SC_XOPEN_UNIX:
541 		return (_XOPEN_UNIX);
542 #ifdef _XOPEN_VERSION
543 	case _SC_XOPEN_VERSION:
544 		return (_XOPEN_VERSION);
545 #endif
546 #ifdef _XOPEN_XCU_VERSION
547 	case _SC_XOPEN_XCU_VERSION:
548 		return (_XOPEN_XCU_VERSION);
549 #endif
550 	case _SC_SYMLOOP_MAX:
551 		return (MAXSYMLINKS);
552 	case _SC_RAW_SOCKETS:
553 		return (_POSIX_RAW_SOCKETS);
554 	case _SC_IPV6:
555 #if _POSIX_IPV6 == 0
556 		sverrno = errno;
557 		value = socket(PF_INET6, SOCK_DGRAM, 0);
558 		errno = sverrno;
559 		if (value >= 0) {
560 			close(value);
561 			return (200112L);
562 		} else
563 			return (0);
564 #else
565 		return (_POSIX_IPV6);
566 #endif
567 
568 	case _SC_NPROCESSORS_CONF:
569 	case _SC_NPROCESSORS_ONLN:
570 		mib[0] = CTL_HW;
571 		mib[1] = HW_NCPU;
572 		break;
573 
574 #ifdef _SC_PHYS_PAGES
575 	case _SC_PHYS_PAGES:
576 		len = sizeof(lvalue);
577 		if (sysctlbyname("hw.availpages", &lvalue, &len, NULL, 0) == -1)
578 			return (-1);
579 		return (lvalue);
580 #endif
581 
582 	default:
583 		errno = EINVAL;
584 		return (-1);
585 	}
586 	len = sizeof(value);
587 	if (sysctl(mib, 2, &value, &len, NULL, 0) == -1)
588 		value = -1;
589 	return ((long)value);
590 }
591