xref: /netbsd-src/sys/compat/linux/common/linux_signal.c (revision df0caa2637da0538ecdf6b878c4d08e684b43d8f)
1 /*	$NetBSD: linux_signal.c,v 1.47 2005/05/20 01:06:50 mrg Exp $	*/
2 /*-
3  * Copyright (c) 1995, 1998 The NetBSD Foundation, Inc.
4  * All rights reserved.
5  *
6  * This code is derived from software contributed to The NetBSD Foundation
7  * by Frank van der Linden and Eric Haszlakiewicz.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  * 3. All advertising materials mentioning features or use of this software
18  *    must display the following acknowledgement:
19  *	This product includes software developed by the NetBSD
20  *	Foundation, Inc. and its contributors.
21  * 4. Neither the name of The NetBSD Foundation nor the names of its
22  *    contributors may be used to endorse or promote products derived
23  *    from this software without specific prior written permission.
24  *
25  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
26  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
27  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
28  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
29  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
30  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
31  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
32  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
33  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
34  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
35  * POSSIBILITY OF SUCH DAMAGE.
36  */
37 /*
38  * heavily from: svr4_signal.c,v 1.7 1995/01/09 01:04:21 christos Exp
39  */
40 
41 /*
42  *   Functions in multiarch:
43  *	linux_sys_signal	: linux_sig_notalpha.c
44  *	linux_sys_siggetmask	: linux_sig_notalpha.c
45  *	linux_sys_sigsetmask	: linux_sig_notalpha.c
46  *	linux_sys_pause		: linux_sig_notalpha.c
47  *	linux_sys_sigaction	: linux_sigaction.c
48  *
49  */
50 
51 /*
52  *   Unimplemented:
53  *	linux_sys_rt_sigtimedwait	: sigsuspend w/timeout.
54  */
55 
56 #include <sys/cdefs.h>
57 __KERNEL_RCSID(0, "$NetBSD: linux_signal.c,v 1.47 2005/05/20 01:06:50 mrg Exp $");
58 
59 #define COMPAT_LINUX 1
60 
61 #include <sys/param.h>
62 #include <sys/systm.h>
63 #include <sys/namei.h>
64 #include <sys/proc.h>
65 #include <sys/filedesc.h>
66 #include <sys/ioctl.h>
67 #include <sys/mount.h>
68 #include <sys/kernel.h>
69 #include <sys/signal.h>
70 #include <sys/signalvar.h>
71 #include <sys/malloc.h>
72 
73 #include <sys/sa.h>
74 #include <sys/syscallargs.h>
75 
76 #include <compat/linux/common/linux_types.h>
77 #include <compat/linux/common/linux_signal.h>
78 #include <compat/linux/common/linux_siginfo.h>
79 #include <compat/linux/common/linux_sigevent.h>
80 #include <compat/linux/common/linux_util.h>
81 
82 #include <compat/linux/linux_syscallargs.h>
83 
84 /* Locally used defines (in bsd<->linux conversion functions): */
85 #define	linux_sigemptyset(s)	memset((s), 0, sizeof(*(s)))
86 #define	linux_sigismember(s, n)	((s)->sig[((n) - 1) / LINUX__NSIG_BPW]	\
87 					& (1 << ((n) - 1) % LINUX__NSIG_BPW))
88 #define	linux_sigaddset(s, n)	((s)->sig[((n) - 1) / LINUX__NSIG_BPW]	\
89 					|= (1 << ((n) - 1) % LINUX__NSIG_BPW))
90 
91 #ifdef DEBUG_LINUX
92 #define DPRINTF(a)	uprintf a
93 #else
94 #define DPRINTF(a)
95 #endif
96 
97 extern const int native_to_linux_signo[];
98 extern const int linux_to_native_signo[];
99 
100 /*
101  * Convert between Linux and BSD signal sets.
102  */
103 #if LINUX__NSIG_WORDS > 1
104 void
105 linux_old_extra_to_native_sigset(bss, lss, extra)
106 	sigset_t *bss;
107 	const linux_old_sigset_t *lss;
108 	const unsigned long *extra;
109 {
110 	linux_sigset_t lsnew;
111 
112 	/* convert old sigset to new sigset */
113 	linux_sigemptyset(&lsnew);
114 	lsnew.sig[0] = *lss;
115 	if (extra)
116 		memcpy(&lsnew.sig[1], extra,
117 		    sizeof(linux_sigset_t) - sizeof(linux_old_sigset_t));
118 
119 	linux_to_native_sigset(bss, &lsnew);
120 }
121 
122 void
123 native_to_linux_old_extra_sigset(lss, extra, bss)
124 	linux_old_sigset_t *lss;
125 	unsigned long *extra;
126 	const sigset_t *bss;
127 {
128 	linux_sigset_t lsnew;
129 
130 	native_to_linux_sigset(&lsnew, bss);
131 
132 	/* convert new sigset to old sigset */
133 	*lss = lsnew.sig[0];
134 	if (extra)
135 		memcpy(extra, &lsnew.sig[1],
136 		    sizeof(linux_sigset_t) - sizeof(linux_old_sigset_t));
137 }
138 #endif /* LINUX__NSIG_WORDS > 1 */
139 
140 void
141 linux_to_native_sigset(bss, lss)
142 	sigset_t *bss;
143 	const linux_sigset_t *lss;
144 {
145 	int i, newsig;
146 
147 	sigemptyset(bss);
148 	for (i = 1; i < LINUX__NSIG; i++) {
149 		if (linux_sigismember(lss, i)) {
150 			newsig = linux_to_native_signo[i];
151 			if (newsig)
152 				sigaddset(bss, newsig);
153 		}
154 	}
155 }
156 
157 void
158 native_to_linux_sigset(lss, bss)
159 	linux_sigset_t *lss;
160 	const sigset_t *bss;
161 {
162 	int i, newsig;
163 
164 	linux_sigemptyset(lss);
165 	for (i = 1; i < NSIG; i++) {
166 		if (sigismember(bss, i)) {
167 			newsig = native_to_linux_signo[i];
168 			if (newsig)
169 				linux_sigaddset(lss, newsig);
170 		}
171 	}
172 }
173 
174 unsigned int
175 native_to_linux_sigflags(bsf)
176 	const int bsf;
177 {
178 	unsigned int lsf = 0;
179 	if ((bsf & SA_NOCLDSTOP) != 0)
180 		lsf |= LINUX_SA_NOCLDSTOP;
181 	if ((bsf & SA_NOCLDWAIT) != 0)
182 		lsf |= LINUX_SA_NOCLDWAIT;
183 	if ((bsf & SA_ONSTACK) != 0)
184 		lsf |= LINUX_SA_ONSTACK;
185 	if ((bsf & SA_RESTART) != 0)
186 		lsf |= LINUX_SA_RESTART;
187 	if ((bsf & SA_NODEFER) != 0)
188 		lsf |= LINUX_SA_NOMASK;
189 	if ((bsf & SA_RESETHAND) != 0)
190 		lsf |= LINUX_SA_ONESHOT;
191 	if ((bsf & SA_SIGINFO) != 0)
192 		lsf |= LINUX_SA_SIGINFO;
193 	return lsf;
194 }
195 
196 int
197 linux_to_native_sigflags(lsf)
198 	const unsigned long lsf;
199 {
200 	int bsf = 0;
201 	if ((lsf & LINUX_SA_NOCLDSTOP) != 0)
202 		bsf |= SA_NOCLDSTOP;
203 	if ((lsf & LINUX_SA_NOCLDWAIT) != 0)
204 		bsf |= SA_NOCLDWAIT;
205 	if ((lsf & LINUX_SA_ONSTACK) != 0)
206 		bsf |= SA_ONSTACK;
207 	if ((lsf & LINUX_SA_RESTART) != 0)
208 		bsf |= SA_RESTART;
209 	if ((lsf & LINUX_SA_ONESHOT) != 0)
210 		bsf |= SA_RESETHAND;
211 	if ((lsf & LINUX_SA_NOMASK) != 0)
212 		bsf |= SA_NODEFER;
213 	if ((lsf & LINUX_SA_SIGINFO) != 0)
214 		bsf |= SA_SIGINFO;
215 	if ((lsf & ~LINUX_SA_ALLBITS) != 0)
216 		DPRINTF(("linux_old_to_native_sigflags: "
217 		    "%lx extra bits ignored\n", lsf));
218 	return bsf;
219 }
220 
221 /*
222  * Convert between Linux and BSD sigaction structures.
223  */
224 void
225 linux_old_to_native_sigaction(bsa, lsa)
226 	struct sigaction *bsa;
227 	const struct linux_old_sigaction *lsa;
228 {
229 	bsa->sa_handler = lsa->linux_sa_handler;
230 	linux_old_to_native_sigset(&bsa->sa_mask, &lsa->linux_sa_mask);
231 	bsa->sa_flags = linux_to_native_sigflags(lsa->linux_sa_flags);
232 }
233 
234 void
235 native_to_linux_old_sigaction(lsa, bsa)
236 	struct linux_old_sigaction *lsa;
237 	const struct sigaction *bsa;
238 {
239 	lsa->linux_sa_handler = bsa->sa_handler;
240 	native_to_linux_old_sigset(&lsa->linux_sa_mask, &bsa->sa_mask);
241 	lsa->linux_sa_flags = native_to_linux_sigflags(bsa->sa_flags);
242 #ifndef __alpha__
243 	lsa->linux_sa_restorer = NULL;
244 #endif
245 }
246 
247 /* ...and the new sigaction conversion funcs. */
248 void
249 linux_to_native_sigaction(bsa, lsa)
250 	struct sigaction *bsa;
251 	const struct linux_sigaction *lsa;
252 {
253 	bsa->sa_handler = lsa->linux_sa_handler;
254 	linux_to_native_sigset(&bsa->sa_mask, &lsa->linux_sa_mask);
255 	bsa->sa_flags = linux_to_native_sigflags(lsa->linux_sa_flags);
256 }
257 
258 void
259 native_to_linux_sigaction(lsa, bsa)
260 	struct linux_sigaction *lsa;
261 	const struct sigaction *bsa;
262 {
263 	lsa->linux_sa_handler = bsa->sa_handler;
264 	native_to_linux_sigset(&lsa->linux_sa_mask, &bsa->sa_mask);
265 	lsa->linux_sa_flags = native_to_linux_sigflags(bsa->sa_flags);
266 #ifndef __alpha__
267 	lsa->linux_sa_restorer = NULL;
268 #endif
269 }
270 
271 /* ----------------------------------------------------------------------- */
272 
273 /*
274  * The Linux sigaction() system call. Do the usual conversions,
275  * and just call sigaction(). Some flags and values are silently
276  * ignored (see above).
277  */
278 int
279 linux_sys_rt_sigaction(l, v, retval)
280 	struct lwp *l;
281 	void *v;
282 	register_t *retval;
283 {
284 	struct linux_sys_rt_sigaction_args /* {
285 		syscallarg(int) signum;
286 		syscallarg(const struct linux_sigaction *) nsa;
287 		syscallarg(struct linux_sigaction *) osa;
288 		syscallarg(size_t) sigsetsize;
289 	} */ *uap = v;
290 	struct proc *p = l->l_proc;
291 	struct linux_sigaction nlsa, olsa;
292 	struct sigaction nbsa, obsa;
293 	int error, sig;
294 	void *tramp = NULL;
295 	int vers = 0;
296 #if defined __amd64__
297 	struct sigacts *ps = p->p_sigacts;
298 #endif
299 
300 	if (SCARG(uap, sigsetsize) != sizeof(linux_sigset_t))
301 		return (EINVAL);
302 
303 	if (SCARG(uap, nsa)) {
304 		error = copyin(SCARG(uap, nsa), &nlsa, sizeof(nlsa));
305 		if (error)
306 			return (error);
307 		linux_to_native_sigaction(&nbsa, &nlsa);
308 	}
309 
310 	sig = SCARG(uap, signum);
311 	if (sig < 0 || sig >= LINUX__NSIG)
312 		return (EINVAL);
313 	if (sig > 0 && !linux_to_native_signo[sig]) {
314 		/* Pretend that we did something useful for unknown signals. */
315 		obsa.sa_handler = SIG_IGN;
316 		sigemptyset(&obsa.sa_mask);
317 		obsa.sa_flags = 0;
318 	} else {
319 #if defined __amd64__
320 		if (nlsa.linux_sa_flags & LINUX_SA_RESTORER) {
321 			if ((tramp = nlsa.linux_sa_restorer) != NULL)
322 				vers = 2; /* XXX arch dependant */
323 		}
324 #endif
325 
326 		error = sigaction1(p, linux_to_native_signo[sig],
327 		    SCARG(uap, nsa) ? &nbsa : NULL,
328 		    SCARG(uap, osa) ? &obsa : NULL,
329 		    tramp, vers);
330 		if (error)
331 			return (error);
332 	}
333 	if (SCARG(uap, osa)) {
334 		native_to_linux_sigaction(&olsa, &obsa);
335 
336 #if defined __amd64__
337 		if (ps->sa_sigdesc[sig].sd_vers != 0) {
338 			olsa.linux_sa_restorer = ps->sa_sigdesc[sig].sd_tramp;
339 			olsa.linux_sa_flags |= LINUX_SA_RESTORER;
340 		}
341 #endif
342 
343 		error = copyout(&olsa, SCARG(uap, osa), sizeof(olsa));
344 		if (error)
345 			return (error);
346 	}
347 	return (0);
348 }
349 
350 int
351 linux_sigprocmask1(p, how, set, oset)
352 	struct proc *p;
353 	int how;
354 	const linux_old_sigset_t *set;
355 	linux_old_sigset_t *oset;
356 {
357 	linux_old_sigset_t nlss, olss;
358 	sigset_t nbss, obss;
359 	int error;
360 
361 	switch (how) {
362 	case LINUX_SIG_BLOCK:
363 		how = SIG_BLOCK;
364 		break;
365 	case LINUX_SIG_UNBLOCK:
366 		how = SIG_UNBLOCK;
367 		break;
368 	case LINUX_SIG_SETMASK:
369 		how = SIG_SETMASK;
370 		break;
371 	default:
372 		return (EINVAL);
373 	}
374 
375 	if (set) {
376 		error = copyin(set, &nlss, sizeof(nlss));
377 		if (error)
378 			return (error);
379 		linux_old_to_native_sigset(&nbss, &nlss);
380 	}
381 	error = sigprocmask1(p, how,
382 	    set ? &nbss : NULL, oset ? &obss : NULL);
383 	if (error)
384 		return (error);
385 	if (oset) {
386 		native_to_linux_old_sigset(&olss, &obss);
387 		error = copyout(&olss, oset, sizeof(olss));
388 		if (error)
389 			return (error);
390 	}
391 	return (error);
392 }
393 
394 int
395 linux_sys_rt_sigprocmask(l, v, retval)
396 	struct lwp *l;
397 	void *v;
398 	register_t *retval;
399 {
400 	struct linux_sys_rt_sigprocmask_args /* {
401 		syscallarg(int) how;
402 		syscallarg(const linux_sigset_t *) set;
403 		syscallarg(linux_sigset_t *) oset;
404 		syscallarg(size_t) sigsetsize;
405 	} */ *uap = v;
406 	struct proc *p = l->l_proc;
407 	linux_sigset_t nlss, olss, *oset;
408 	const linux_sigset_t *set;
409 	sigset_t nbss, obss;
410 	int error, how;
411 
412 	if (SCARG(uap, sigsetsize) != sizeof(linux_sigset_t))
413 		return (EINVAL);
414 
415 	switch (SCARG(uap, how)) {
416 	case LINUX_SIG_BLOCK:
417 		how = SIG_BLOCK;
418 		break;
419 	case LINUX_SIG_UNBLOCK:
420 		how = SIG_UNBLOCK;
421 		break;
422 	case LINUX_SIG_SETMASK:
423 		how = SIG_SETMASK;
424 		break;
425 	default:
426 		return (EINVAL);
427 	}
428 
429 	set = SCARG(uap, set);
430 	oset = SCARG(uap, oset);
431 
432 	if (set) {
433 		error = copyin(set, &nlss, sizeof(nlss));
434 		if (error)
435 			return (error);
436 		linux_to_native_sigset(&nbss, &nlss);
437 	}
438 	error = sigprocmask1(p, how,
439 	    set ? &nbss : NULL, oset ? &obss : NULL);
440 	if (!error && oset) {
441 		native_to_linux_sigset(&olss, &obss);
442 		error = copyout(&olss, oset, sizeof(olss));
443 	}
444 	return (error);
445 }
446 
447 int
448 linux_sys_rt_sigpending(l, v, retval)
449 	struct lwp *l;
450 	void *v;
451 	register_t *retval;
452 {
453 	struct linux_sys_rt_sigpending_args /* {
454 		syscallarg(linux_sigset_t *) set;
455 		syscallarg(size_t) sigsetsize;
456 	} */ *uap = v;
457 	struct proc *p = l->l_proc;
458 	sigset_t bss;
459 	linux_sigset_t lss;
460 
461 	if (SCARG(uap, sigsetsize) != sizeof(linux_sigset_t))
462 		return (EINVAL);
463 
464 	sigpending1(p, &bss);
465 	native_to_linux_sigset(&lss, &bss);
466 	return copyout(&lss, SCARG(uap, set), sizeof(lss));
467 }
468 
469 #ifndef __amd64__
470 int
471 linux_sys_sigpending(l, v, retval)
472 	struct lwp *l;
473 	void *v;
474 	register_t *retval;
475 {
476 	struct linux_sys_sigpending_args /* {
477 		syscallarg(linux_old_sigset_t *) mask;
478 	} */ *uap = v;
479 	struct proc *p = l->l_proc;
480 	sigset_t bss;
481 	linux_old_sigset_t lss;
482 
483 	sigpending1(p, &bss);
484 	native_to_linux_old_sigset(&lss, &bss);
485 	return copyout(&lss, SCARG(uap, set), sizeof(lss));
486 }
487 
488 int
489 linux_sys_sigsuspend(l, v, retval)
490 	struct lwp *l;
491 	void *v;
492 	register_t *retval;
493 {
494 	struct linux_sys_sigsuspend_args /* {
495 		syscallarg(caddr_t) restart;
496 		syscallarg(int) oldmask;
497 		syscallarg(int) mask;
498 	} */ *uap = v;
499 	struct proc *p = l->l_proc;
500 	linux_old_sigset_t lss;
501 	sigset_t bss;
502 
503 	lss = SCARG(uap, mask);
504 	linux_old_to_native_sigset(&bss, &lss);
505 	return (sigsuspend1(p, &bss));
506 }
507 #endif /* __amd64__ */
508 
509 int
510 linux_sys_rt_sigsuspend(l, v, retval)
511 	struct lwp *l;
512 	void *v;
513 	register_t *retval;
514 {
515 	struct linux_sys_rt_sigsuspend_args /* {
516 		syscallarg(linux_sigset_t *) unewset;
517 		syscallarg(size_t) sigsetsize;
518 	} */ *uap = v;
519 	struct proc *p = l->l_proc;
520 	linux_sigset_t lss;
521 	sigset_t bss;
522 	int error;
523 
524 	if (SCARG(uap, sigsetsize) != sizeof(linux_sigset_t))
525 		return (EINVAL);
526 
527 	error = copyin(SCARG(uap, unewset), &lss, sizeof(linux_sigset_t));
528 	if (error)
529 		return (error);
530 
531 	linux_to_native_sigset(&bss, &lss);
532 
533 	return (sigsuspend1(p, &bss));
534 }
535 
536 /*
537  * Once more: only a signal conversion is needed.
538  * Note: also used as sys_rt_queueinfo.  The info field is ignored.
539  */
540 int
541 linux_sys_rt_queueinfo(l, v, retval)
542 	struct lwp *l;
543 	void *v;
544 	register_t *retval;
545 {
546 	/* XXX XAX This isn't this really int, int, siginfo_t *, is it? */
547 #if 0
548 	struct linux_sys_rt_queueinfo_args /* {
549 		syscallarg(int) pid;
550 		syscallarg(int) signum;
551 		syscallarg(siginfo_t *) uinfo;
552 	} */ *uap = v;
553 #endif
554 
555 	/* XXX To really implement this we need to	*/
556 	/* XXX keep a list of queued signals somewhere.	*/
557 	return (linux_sys_kill(l, v, retval));
558 }
559 
560 int
561 linux_sys_kill(l, v, retval)
562 	struct lwp *l;
563 	void *v;
564 	register_t *retval;
565 {
566 	struct linux_sys_kill_args /* {
567 		syscallarg(int) pid;
568 		syscallarg(int) signum;
569 	} */ *uap = v;
570 
571 	struct sys_kill_args ka;
572 	int sig;
573 
574 	SCARG(&ka, pid) = SCARG(uap, pid);
575 	sig = SCARG(uap, signum);
576 	if (sig < 0 || sig >= LINUX__NSIG)
577 		return (EINVAL);
578 	SCARG(&ka, signum) = linux_to_native_signo[sig];
579 	return sys_kill(l, &ka, retval);
580 }
581 
582 #ifdef LINUX_SS_ONSTACK
583 static void linux_to_native_sigaltstack __P((struct sigaltstack *,
584     const struct linux_sigaltstack *));
585 
586 static void
587 linux_to_native_sigaltstack(bss, lss)
588 	struct sigaltstack *bss;
589 	const struct linux_sigaltstack *lss;
590 {
591 	bss->ss_sp = lss->ss_sp;
592 	bss->ss_size = lss->ss_size;
593 	if (lss->ss_flags & LINUX_SS_ONSTACK)
594 	    bss->ss_flags = SS_ONSTACK;
595 	else if (lss->ss_flags & LINUX_SS_DISABLE)
596 	    bss->ss_flags = SS_DISABLE;
597 	else
598 	    bss->ss_flags = 0;
599 }
600 
601 void
602 native_to_linux_sigaltstack(lss, bss)
603 	struct linux_sigaltstack *lss;
604 	const struct sigaltstack *bss;
605 {
606 	lss->ss_sp = bss->ss_sp;
607 	lss->ss_size = bss->ss_size;
608 	if (bss->ss_flags & SS_ONSTACK)
609 	    lss->ss_flags = LINUX_SS_ONSTACK;
610 	else if (bss->ss_flags & SS_DISABLE)
611 	    lss->ss_flags = LINUX_SS_DISABLE;
612 	else
613 	    lss->ss_flags = 0;
614 }
615 
616 int
617 linux_sys_sigaltstack(l, v, retval)
618 	struct lwp *l;
619 	void *v;
620 	register_t *retval;
621 {
622 	struct linux_sys_sigaltstack_args /* {
623 		syscallarg(const struct linux_sigaltstack *) ss;
624 		syscallarg(struct linux_sigaltstack *) oss;
625 	} */ *uap = v;
626 	struct proc *p = l->l_proc;
627 	struct linux_sigaltstack ss;
628 	struct sigaltstack nss, oss;
629 	int error;
630 
631 	if (SCARG(uap, ss) != NULL) {
632 		if ((error = copyin(SCARG(uap, ss), &ss, sizeof(ss))) != 0)
633 			return error;
634 		linux_to_native_sigaltstack(&nss, &ss);
635 	}
636 
637 	error = sigaltstack1(p,
638 	    SCARG(uap, ss) ? &nss : NULL, SCARG(uap, oss) ? &oss : NULL);
639 	if (error)
640 		return error;
641 
642 	if (SCARG(uap, oss) != NULL) {
643 		native_to_linux_sigaltstack(&ss, &oss);
644 		if ((error = copyout(&ss, SCARG(uap, oss), sizeof(ss))) != 0)
645 			return error;
646 	}
647 	return 0;
648 }
649 #endif /* LINUX_SS_ONSTACK */
650