xref: /illumos-gate/usr/src/lib/libc/port/threads/sigaction.c (revision 306990466301759c88d84c51c57b57ca930a3635)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 /*
28  * Copyright 2022 OmniOS Community Edition (OmniOSce) Association.
29  */
30 
31 #include "lint.h"
32 #include <sys/feature_tests.h>
33 /*
34  * setcontext() really can return, if UC_CPU is not specified.
35  * Make the compiler shut up about it.
36  */
37 #if defined(__NORETURN)
38 #undef	__NORETURN
39 #endif
40 #define	__NORETURN
41 #include "thr_uberdata.h"
42 #include "asyncio.h"
43 #include <signal.h>
44 #include <siginfo.h>
45 #include <sys/systm.h>
46 
47 /* maskable signals */
48 const sigset_t maskset = {MASKSET0, MASKSET1, MASKSET2, MASKSET3};
49 
50 /*
51  * Return true if the valid signal bits in both sets are the same.
52  */
53 int
sigequalset(const sigset_t * s1,const sigset_t * s2)54 sigequalset(const sigset_t *s1, const sigset_t *s2)
55 {
56 	/*
57 	 * We only test valid signal bits, not rubbish following MAXSIG
58 	 * (for speed).  Algorithm:
59 	 * if (s1 & fillset) == (s2 & fillset) then (s1 ^ s2) & fillset == 0
60 	 */
61 /* see lib/libc/inc/thr_uberdata.h for why this must be true */
62 #if (MAXSIG > (2 * 32) && MAXSIG <= (3 * 32))
63 	return (!((s1->__sigbits[0] ^ s2->__sigbits[0]) |
64 	    (s1->__sigbits[1] ^ s2->__sigbits[1]) |
65 	    ((s1->__sigbits[2] ^ s2->__sigbits[2]) & FILLSET2)));
66 #else
67 #error "fix me: MAXSIG out of bounds"
68 #endif
69 }
70 
71 /*
72  * Common code for calling the user-specified signal handler.
73  */
74 void
call_user_handler(int sig,siginfo_t * sip,ucontext_t * ucp)75 call_user_handler(int sig, siginfo_t *sip, ucontext_t *ucp)
76 {
77 	ulwp_t *self = curthread;
78 	uberdata_t *udp = self->ul_uberdata;
79 	struct sigaction uact;
80 	volatile struct sigaction *sap;
81 
82 	/*
83 	 * If we are taking a signal while parked or about to be parked
84 	 * on __lwp_park() then remove ourself from the sleep queue so
85 	 * that we can grab locks.  The code in mutex_lock_queue() and
86 	 * cond_wait_common() will detect this and deal with it when
87 	 * __lwp_park() returns.
88 	 */
89 	unsleep_self();
90 	set_parking_flag(self, 0);
91 
92 	if (__td_event_report(self, TD_CATCHSIG, udp)) {
93 		self->ul_td_evbuf.eventnum = TD_CATCHSIG;
94 		self->ul_td_evbuf.eventdata = (void *)(intptr_t)sig;
95 		tdb_event(TD_CATCHSIG, udp);
96 	}
97 
98 	/*
99 	 * Get a self-consistent set of flags, handler, and mask
100 	 * while holding the sig's sig_lock for the least possible time.
101 	 * We must acquire the sig's sig_lock because some thread running
102 	 * in sigaction() might be establishing a new signal handler.
103 	 * The code in sigaction() acquires the writer lock; here
104 	 * we acquire the readers lock to ehance concurrency in the
105 	 * face of heavy signal traffic, such as generated by java.
106 	 *
107 	 * Locking exceptions:
108 	 * No locking for a child of vfork().
109 	 * If the signal is SIGPROF with an si_code of PROF_SIG,
110 	 * then we assume that this signal was generated by
111 	 * setitimer(ITIMER_REALPROF) set up by the dbx collector.
112 	 * If the signal is SIGEMT with an si_code of EMT_CPCOVF,
113 	 * then we assume that the signal was generated by
114 	 * a hardware performance counter overflow.
115 	 * In these cases, assume that we need no locking.  It is the
116 	 * monitoring program's responsibility to ensure correctness.
117 	 */
118 	sap = &udp->siguaction[sig].sig_uaction;
119 	if (self->ul_vfork ||
120 	    (sip != NULL &&
121 	    ((sig == SIGPROF && sip->si_code == PROF_SIG) ||
122 	    (sig == SIGEMT && sip->si_code == EMT_CPCOVF)))) {
123 		/* we wish this assignment could be atomic */
124 		(void) memcpy(&uact, (void *)sap, sizeof (uact));
125 	} else {
126 		rwlock_t *rwlp = &udp->siguaction[sig].sig_lock;
127 		lrw_rdlock(rwlp);
128 		(void) memcpy(&uact, (void *)sap, sizeof (uact));
129 		if ((sig == SIGCANCEL || sig == SIGAIOCANCEL) &&
130 		    (sap->sa_flags & SA_RESETHAND))
131 			sap->sa_handler = SIG_DFL;
132 		lrw_unlock(rwlp);
133 	}
134 
135 	/*
136 	 * Set the proper signal mask and call the user's signal handler.
137 	 * (We overrode the user-requested signal mask with maskset
138 	 * so we currently have all blockable signals blocked.)
139 	 *
140 	 * We would like to ASSERT() that the signal is not a member of the
141 	 * signal mask at the previous level (ucp->uc_sigmask) or the specified
142 	 * signal mask for sigsuspend() or pollsys() (self->ul_tmpmask) but
143 	 * /proc can override this via PCSSIG, so we don't bother.
144 	 *
145 	 * We would also like to ASSERT() that the signal mask at the previous
146 	 * level equals self->ul_sigmask (maskset for sigsuspend() / pollsys()),
147 	 * but /proc can change the thread's signal mask via PCSHOLD, so we
148 	 * don't bother with that either.
149 	 */
150 	ASSERT(ucp->uc_flags & UC_SIGMASK);
151 	if (self->ul_sigsuspend) {
152 		ucp->uc_sigmask = self->ul_sigmask;
153 		self->ul_sigsuspend = 0;
154 		/* the sigsuspend() or pollsys() signal mask */
155 		sigorset(&uact.sa_mask, &self->ul_tmpmask);
156 	} else {
157 		/* the signal mask at the previous level */
158 		sigorset(&uact.sa_mask, &ucp->uc_sigmask);
159 	}
160 	if (!(uact.sa_flags & SA_NODEFER))	/* add current signal */
161 		(void) sigaddset(&uact.sa_mask, sig);
162 	self->ul_sigmask = uact.sa_mask;
163 	self->ul_siglink = ucp;
164 	(void) __lwp_sigmask(SIG_SETMASK, &uact.sa_mask);
165 
166 	/*
167 	 * If this thread has been sent SIGCANCEL from the kernel
168 	 * or from pthread_cancel(), it is being asked to exit.
169 	 * The kernel may send SIGCANCEL without a siginfo struct.
170 	 * If the SIGCANCEL is process-directed (from kill() or
171 	 * sigqueue()), treat it as an ordinary signal.
172 	 */
173 	if (sig == SIGCANCEL) {
174 		if (sip == NULL || SI_FROMKERNEL(sip) ||
175 		    sip->si_code == SI_LWP) {
176 			do_sigcancel();
177 			goto out;
178 		}
179 		/* SIGCANCEL is ignored by default */
180 		if (uact.sa_handler == SIG_DFL ||
181 		    uact.sa_handler == SIG_IGN)
182 			goto out;
183 	}
184 
185 	/*
186 	 * If this thread has been sent SIGAIOCANCEL (SIGLWP) and
187 	 * we are an aio worker thread, cancel the aio request.
188 	 */
189 	if (sig == SIGAIOCANCEL) {
190 		aio_worker_t *aiowp = pthread_getspecific(_aio_key);
191 
192 		if (sip != NULL && sip->si_code == SI_LWP && aiowp != NULL)
193 			siglongjmp(aiowp->work_jmp_buf, 1);
194 		/* SIGLWP is ignored by default */
195 		if (uact.sa_handler == SIG_DFL ||
196 		    uact.sa_handler == SIG_IGN)
197 			goto out;
198 	}
199 
200 	if (!(uact.sa_flags & SA_SIGINFO))
201 		sip = NULL;
202 	__sighndlr(sig, sip, ucp, uact.sa_sigaction);
203 
204 #if defined(sparc) || defined(__sparc)
205 	/*
206 	 * If this is a floating point exception and the queue
207 	 * is non-empty, pop the top entry from the queue.  This
208 	 * is to maintain expected behavior.
209 	 */
210 	if (sig == SIGFPE && ucp->uc_mcontext.fpregs.fpu_qcnt) {
211 		fpregset_t *fp = &ucp->uc_mcontext.fpregs;
212 
213 		if (--fp->fpu_qcnt > 0) {
214 			unsigned char i;
215 			struct _fq *fqp;
216 
217 			fqp = fp->fpu_q;
218 			for (i = 0; i < fp->fpu_qcnt; i++)
219 				fqp[i] = fqp[i+1];
220 		}
221 	}
222 #endif	/* sparc */
223 
224 out:
225 	(void) setcontext(ucp);
226 	thr_panic("call_user_handler(): setcontext() returned");
227 }
228 
229 /*
230  * take_deferred_signal() is called when ul_critical and ul_sigdefer become
231  * zero and a deferred signal has been recorded on the current thread.
232  * We are out of the critical region and are ready to take a signal.
233  * The kernel has all signals blocked on this lwp, but our value of
234  * ul_sigmask is the correct signal mask for the previous context.
235  *
236  * We call __sigresend() to atomically restore the signal mask and
237  * cause the signal to be sent again with the remembered siginfo.
238  * We will not return successfully from __sigresend() until the
239  * application's signal handler has been run via sigacthandler().
240  */
241 void
take_deferred_signal(int sig)242 take_deferred_signal(int sig)
243 {
244 	extern int __sigresend(int, siginfo_t *, sigset_t *);
245 	ulwp_t *self = curthread;
246 	siguaction_t *suap = &self->ul_uberdata->siguaction[sig];
247 	siginfo_t *sip;
248 	int error;
249 
250 	ASSERT((self->ul_critical | self->ul_sigdefer | self->ul_cursig) == 0);
251 
252 	/*
253 	 * If the signal handler was established with SA_RESETHAND,
254 	 * the kernel has reset the handler to SIG_DFL, so we have
255 	 * to reestablish the handler now so that it will be entered
256 	 * again when we call __sigresend(), below.
257 	 *
258 	 * Logically, we should acquire and release the signal's
259 	 * sig_lock around this operation to protect the integrity
260 	 * of the signal action while we copy it, as is done below
261 	 * in _libc_sigaction().  However, we may be on a user-level
262 	 * sleep queue at this point and lrw_wrlock(&suap->sig_lock)
263 	 * might attempt to sleep on a different sleep queue and
264 	 * that would corrupt the entire sleep queue mechanism.
265 	 *
266 	 * If we are on a sleep queue we will remove ourself from
267 	 * it in call_user_handler(), called from sigacthandler(),
268 	 * before entering the application's signal handler.
269 	 * In the meantime, we must not acquire any locks.
270 	 */
271 	if (suap->sig_uaction.sa_flags & SA_RESETHAND) {
272 		struct sigaction tact = suap->sig_uaction;
273 		tact.sa_flags &= ~SA_NODEFER;
274 		tact.sa_sigaction = self->ul_uberdata->sigacthandler;
275 		tact.sa_mask = maskset;
276 		(void) __sigaction(sig, &tact, NULL);
277 	}
278 
279 	if (self->ul_siginfo.si_signo == 0)
280 		sip = NULL;
281 	else
282 		sip = &self->ul_siginfo;
283 
284 	/* EAGAIN can happen only for a pending SIGSTOP signal */
285 	while ((error = __sigresend(sig, sip, &self->ul_sigmask)) == EAGAIN)
286 		continue;
287 	if (error)
288 		thr_panic("take_deferred_signal(): __sigresend() failed");
289 }
290 
291 void
sigacthandler(int sig,siginfo_t * sip,void * uvp)292 sigacthandler(int sig, siginfo_t *sip, void *uvp)
293 {
294 	ucontext_t *ucp = uvp;
295 	ulwp_t *self = curthread;
296 
297 	/*
298 	 * Do this in case we took a signal while in a cancelable system call.
299 	 * It does no harm if we were not in such a system call.
300 	 */
301 	self->ul_sp = 0;
302 	if (sig != SIGCANCEL)
303 		self->ul_cancel_async = self->ul_save_async;
304 
305 	/*
306 	 * If this thread has performed a longjmp() from a signal handler
307 	 * back to main level some time in the past, it has left the kernel
308 	 * thinking that it is still in the signal context.  We repair this
309 	 * possible damage by setting ucp->uc_link to NULL if we know that
310 	 * we are actually executing at main level (self->ul_siglink == NULL).
311 	 * See the code for setjmp()/longjmp() for more details.
312 	 */
313 	if (self->ul_siglink == NULL)
314 		ucp->uc_link = NULL;
315 
316 	/*
317 	 * If we are not in a critical region and are
318 	 * not deferring signals, take the signal now.
319 	 */
320 	if ((self->ul_critical + self->ul_sigdefer) == 0) {
321 		call_user_handler(sig, sip, ucp);
322 		/*
323 		 * On the surface, the following call seems redundant
324 		 * because call_user_handler() cannot return. However,
325 		 * we don't want to return from here because the compiler
326 		 * might recycle our frame. We want to keep it on the
327 		 * stack to assist debuggers such as pstack in identifying
328 		 * signal frames. The call to thr_panic() serves to prevent
329 		 * tail-call optimisation here.
330 		 */
331 		thr_panic("sigacthandler(): call_user_handler() returned");
332 	}
333 
334 	/*
335 	 * We are in a critical region or we are deferring signals.  When
336 	 * we emerge from the region we will call take_deferred_signal().
337 	 */
338 	ASSERT(self->ul_cursig == 0);
339 	self->ul_cursig = (char)sig;
340 	if (sip != NULL)
341 		(void) memcpy(&self->ul_siginfo,
342 		    sip, sizeof (siginfo_t));
343 	else
344 		self->ul_siginfo.si_signo = 0;
345 
346 	/*
347 	 * Make sure that if we return to a call to __lwp_park()
348 	 * or ___lwp_cond_wait() that it returns right away
349 	 * (giving us a spurious wakeup but not a deadlock).
350 	 */
351 	set_parking_flag(self, 0);
352 
353 	/*
354 	 * Return to the previous context with all signals blocked.
355 	 * We will restore the signal mask in take_deferred_signal().
356 	 * Note that we are calling the system call trap here, not
357 	 * the setcontext() wrapper.  We don't want to change the
358 	 * thread's ul_sigmask by this operation.
359 	 */
360 	ucp->uc_sigmask = maskset;
361 	(void) __setcontext(ucp);
362 	thr_panic("sigacthandler(): __setcontext() returned");
363 }
364 
365 #pragma weak _sigaction = sigaction
366 int
sigaction(int sig,const struct sigaction * nact,struct sigaction * oact)367 sigaction(int sig, const struct sigaction *nact, struct sigaction *oact)
368 {
369 	ulwp_t *self = curthread;
370 	uberdata_t *udp = self->ul_uberdata;
371 	struct sigaction oaction;
372 	struct sigaction tact;
373 	struct sigaction *tactp = NULL;
374 	int rv;
375 
376 	if (sig <= 0 || sig >= NSIG) {
377 		errno = EINVAL;
378 		return (-1);
379 	}
380 
381 	if (!self->ul_vfork)
382 		lrw_wrlock(&udp->siguaction[sig].sig_lock);
383 
384 	oaction = udp->siguaction[sig].sig_uaction;
385 
386 	if (nact != NULL) {
387 		tact = *nact;	/* make a copy so we can modify it */
388 		tactp = &tact;
389 		delete_reserved_signals(&tact.sa_mask);
390 
391 #if !defined(_LP64)
392 		tact.sa_resv[0] = tact.sa_resv[1] = 0;	/* cleanliness */
393 #endif
394 		/*
395 		 * To be compatible with the behavior of SunOS 4.x:
396 		 * If the new signal handler is SIG_IGN or SIG_DFL, do
397 		 * not change the signal's entry in the siguaction array.
398 		 * This allows a child of vfork(2) to set signal handlers
399 		 * to SIG_IGN or SIG_DFL without affecting the parent.
400 		 *
401 		 * This also covers a race condition with some thread
402 		 * setting the signal action to SIG_DFL or SIG_IGN
403 		 * when the thread has also received and deferred
404 		 * that signal.  When the thread takes the deferred
405 		 * signal, even though it has set the action to SIG_DFL
406 		 * or SIG_IGN, it will execute the old signal handler
407 		 * anyway.  This is an inherent signaling race condition
408 		 * and is not a bug.
409 		 *
410 		 * A child of vfork() is not allowed to change signal
411 		 * handlers to anything other than SIG_DFL or SIG_IGN.
412 		 */
413 		if (self->ul_vfork) {
414 			if (tact.sa_handler != SIG_IGN)
415 				tact.sa_handler = SIG_DFL;
416 		} else if (sig == SIGCANCEL || sig == SIGAIOCANCEL) {
417 			/*
418 			 * Always catch these signals.
419 			 * We need SIGCANCEL for pthread_cancel() to work.
420 			 * We need SIGAIOCANCEL for aio_cancel() to work.
421 			 */
422 			udp->siguaction[sig].sig_uaction = tact;
423 			if (tact.sa_handler == SIG_DFL ||
424 			    tact.sa_handler == SIG_IGN)
425 				tact.sa_flags = SA_SIGINFO;
426 			else {
427 				tact.sa_flags |= SA_SIGINFO;
428 				tact.sa_flags &=
429 				    ~(SA_NODEFER | SA_RESETHAND | SA_RESTART);
430 			}
431 			tact.sa_sigaction = udp->sigacthandler;
432 			tact.sa_mask = maskset;
433 		} else if (tact.sa_handler != SIG_DFL &&
434 		    tact.sa_handler != SIG_IGN) {
435 			udp->siguaction[sig].sig_uaction = tact;
436 			tact.sa_flags &= ~SA_NODEFER;
437 			tact.sa_sigaction = udp->sigacthandler;
438 			tact.sa_mask = maskset;
439 		}
440 	}
441 
442 	if ((rv = __sigaction(sig, tactp, oact)) != 0)
443 		udp->siguaction[sig].sig_uaction = oaction;
444 	else if (oact != NULL &&
445 	    oact->sa_handler != SIG_DFL &&
446 	    oact->sa_handler != SIG_IGN)
447 		*oact = oaction;
448 
449 	/*
450 	 * We detect setting the disposition of SIGIO just to set the
451 	 * _sigio_enabled flag for the asynchronous i/o (aio) code.
452 	 */
453 	if (sig == SIGIO && rv == 0 && tactp != NULL) {
454 		_sigio_enabled =
455 		    (tactp->sa_handler != SIG_DFL &&
456 		    tactp->sa_handler != SIG_IGN);
457 	}
458 
459 	if (!self->ul_vfork)
460 		lrw_unlock(&udp->siguaction[sig].sig_lock);
461 	return (rv);
462 }
463 
464 /*
465  * This is a private interface for the linux brand interface.
466  */
467 void
setsigacthandler(void (* nsigacthandler)(int,siginfo_t *,void *),void (** osigacthandler)(int,siginfo_t *,void *))468 setsigacthandler(void (*nsigacthandler)(int, siginfo_t *, void *),
469     void (**osigacthandler)(int, siginfo_t *, void *))
470 {
471 	ulwp_t *self = curthread;
472 	uberdata_t *udp = self->ul_uberdata;
473 
474 	if (osigacthandler != NULL)
475 		*osigacthandler = udp->sigacthandler;
476 
477 	udp->sigacthandler = nsigacthandler;
478 }
479 
480 /*
481  * Tell the kernel to block all signals.
482  * Use the schedctl interface, or failing that, use __lwp_sigmask().
483  * This action can be rescinded only by making a system call that
484  * sets the signal mask:
485  *	__lwp_sigmask(), __sigprocmask(), __setcontext(),
486  *	__sigsuspend() or __pollsys().
487  * In particular, this action cannot be reversed by assigning
488  * scp->sc_sigblock = 0.  That would be a way to lose signals.
489  * See the definition of restore_signals(self).
490  */
491 void
block_all_signals(ulwp_t * self)492 block_all_signals(ulwp_t *self)
493 {
494 	volatile sc_shared_t *scp;
495 
496 	enter_critical(self);
497 	if ((scp = self->ul_schedctl) != NULL ||
498 	    (scp = setup_schedctl()) != NULL)
499 		scp->sc_sigblock = 1;
500 	else
501 		(void) __lwp_sigmask(SIG_SETMASK, &maskset);
502 	exit_critical(self);
503 }
504 
505 /*
506  * setcontext() has code that forcibly restores the curthread
507  * pointer in a context passed to the setcontext(2) syscall.
508  *
509  * Certain processes may need to disable this feature, so these routines
510  * provide the mechanism to do so.
511  *
512  * (As an example, branded 32-bit x86 processes may use %gs for their own
513  * purposes, so they need to be able to specify a %gs value to be restored
514  * on return from a signal handler via the passed ucontext_t.)
515  */
516 static int setcontext_enforcement = 1;
517 
518 void
set_setcontext_enforcement(int on)519 set_setcontext_enforcement(int on)
520 {
521 	setcontext_enforcement = on;
522 }
523 
524 #pragma weak _setcontext = setcontext
525 int
setcontext(const ucontext_t * ucp)526 setcontext(const ucontext_t *ucp)
527 {
528 	ulwp_t *self = curthread;
529 	int ret;
530 	ucontext_t uc;
531 
532 	/*
533 	 * Returning from the main context (uc_link == NULL) causes
534 	 * the thread to exit.  See setcontext(2) and makecontext(3C).
535 	 */
536 	if (ucp == NULL)
537 		thr_exit(NULL);
538 	(void) memcpy(&uc, ucp, sizeof (uc));
539 
540 	/*
541 	 * Restore previous signal mask and context link.
542 	 */
543 	if (uc.uc_flags & UC_SIGMASK) {
544 		block_all_signals(self);
545 		delete_reserved_signals(&uc.uc_sigmask);
546 		self->ul_sigmask = uc.uc_sigmask;
547 		if (self->ul_cursig) {
548 			/*
549 			 * We have a deferred signal present.
550 			 * The signal mask will be set when the
551 			 * signal is taken in take_deferred_signal().
552 			 */
553 			ASSERT(self->ul_critical + self->ul_sigdefer != 0);
554 			uc.uc_flags &= ~UC_SIGMASK;
555 		}
556 	}
557 	self->ul_siglink = uc.uc_link;
558 
559 	/*
560 	 * We don't know where this context structure has been.
561 	 * Preserve the curthread pointer, at least.
562 	 *
563 	 * Allow this feature to be disabled if a particular process
564 	 * requests it.
565 	 */
566 	if (setcontext_enforcement) {
567 #if defined(__sparc)
568 		uc.uc_mcontext.gregs[REG_G7] = (greg_t)self;
569 #elif defined(__amd64)
570 		/*
571 		 * 64-bit processes must have a selector value of zero for %fs
572 		 * in order to use the 64-bit fs_base (the full 64-bit address
573 		 * range cannot be expressed in a long mode descriptor).
574 		 */
575 		uc.uc_mcontext.gregs[REG_FS] = (greg_t)0;
576 		uc.uc_mcontext.gregs[REG_FSBASE] = (greg_t)self;
577 #elif defined(__i386)
578 		uc.uc_mcontext.gregs[GS] = (greg_t)LWPGS_SEL;
579 #else
580 #error "none of __sparc, __amd64, __i386 defined"
581 #endif
582 	}
583 
584 	/*
585 	 * Make sure that if we return to a call to __lwp_park()
586 	 * or ___lwp_cond_wait() that it returns right away
587 	 * (giving us a spurious wakeup but not a deadlock).
588 	 */
589 	set_parking_flag(self, 0);
590 	self->ul_sp = 0;
591 	ret = __setcontext(&uc);
592 
593 	/*
594 	 * It is OK for setcontext() to return if the user has not specified
595 	 * UC_CPU.
596 	 */
597 	if (uc.uc_flags & UC_CPU)
598 		thr_panic("setcontext(): __setcontext() returned");
599 	return (ret);
600 }
601 
602 #pragma weak _thr_sigsetmask = thr_sigsetmask
603 int
thr_sigsetmask(int how,const sigset_t * set,sigset_t * oset)604 thr_sigsetmask(int how, const sigset_t *set, sigset_t *oset)
605 {
606 	ulwp_t *self = curthread;
607 	sigset_t saveset;
608 
609 	if (set == NULL) {
610 		enter_critical(self);
611 		if (oset != NULL)
612 			*oset = self->ul_sigmask;
613 		exit_critical(self);
614 	} else {
615 		switch (how) {
616 		case SIG_BLOCK:
617 		case SIG_UNBLOCK:
618 		case SIG_SETMASK:
619 			break;
620 		default:
621 			return (EINVAL);
622 		}
623 
624 		/*
625 		 * The assignments to self->ul_sigmask must be protected from
626 		 * signals.  The nuances of this code are subtle.  Be careful.
627 		 */
628 		block_all_signals(self);
629 		if (oset != NULL)
630 			saveset = self->ul_sigmask;
631 		switch (how) {
632 		case SIG_BLOCK:
633 			self->ul_sigmask.__sigbits[0] |= set->__sigbits[0];
634 			self->ul_sigmask.__sigbits[1] |= set->__sigbits[1];
635 			self->ul_sigmask.__sigbits[2] |= set->__sigbits[2];
636 			self->ul_sigmask.__sigbits[3] |= set->__sigbits[3];
637 			break;
638 		case SIG_UNBLOCK:
639 			self->ul_sigmask.__sigbits[0] &= ~set->__sigbits[0];
640 			self->ul_sigmask.__sigbits[1] &= ~set->__sigbits[1];
641 			self->ul_sigmask.__sigbits[2] &= ~set->__sigbits[2];
642 			self->ul_sigmask.__sigbits[3] &= ~set->__sigbits[3];
643 			break;
644 		case SIG_SETMASK:
645 			self->ul_sigmask.__sigbits[0] = set->__sigbits[0];
646 			self->ul_sigmask.__sigbits[1] = set->__sigbits[1];
647 			self->ul_sigmask.__sigbits[2] = set->__sigbits[2];
648 			self->ul_sigmask.__sigbits[3] = set->__sigbits[3];
649 			break;
650 		}
651 		delete_reserved_signals(&self->ul_sigmask);
652 		if (oset != NULL)
653 			*oset = saveset;
654 		restore_signals(self);
655 	}
656 
657 	return (0);
658 }
659 
660 #pragma weak _pthread_sigmask = pthread_sigmask
661 int
pthread_sigmask(int how,const sigset_t * set,sigset_t * oset)662 pthread_sigmask(int how, const sigset_t *set, sigset_t *oset)
663 {
664 	return (thr_sigsetmask(how, set, oset));
665 }
666 
667 #pragma weak _sigprocmask = sigprocmask
668 int
sigprocmask(int how,const sigset_t * set,sigset_t * oset)669 sigprocmask(int how, const sigset_t *set, sigset_t *oset)
670 {
671 	int error;
672 
673 	/*
674 	 * Guard against children of vfork().
675 	 */
676 	if (curthread->ul_vfork)
677 		return (__sigprocmask(how, set, oset));
678 
679 	if ((error = thr_sigsetmask(how, set, oset)) != 0) {
680 		errno = error;
681 		return (-1);
682 	}
683 
684 	return (0);
685 }
686 
687 /*
688  * Called at library initialization to set up signal handling.
689  * All we really do is initialize the sig_lock rwlocks.
690  * All signal handlers are either SIG_DFL or SIG_IGN on exec().
691  * However, if any signal handlers were established on alternate
692  * link maps before the primary link map has been initialized,
693  * then inform the kernel of the new sigacthandler.
694  */
695 void
signal_init()696 signal_init()
697 {
698 	uberdata_t *udp = curthread->ul_uberdata;
699 	struct sigaction *sap;
700 	struct sigaction act;
701 	rwlock_t *rwlp;
702 	int sig;
703 
704 	for (sig = 0; sig < NSIG; sig++) {
705 		rwlp = &udp->siguaction[sig].sig_lock;
706 		rwlp->rwlock_magic = RWL_MAGIC;
707 		rwlp->mutex.mutex_flag = LOCK_INITED;
708 		rwlp->mutex.mutex_magic = MUTEX_MAGIC;
709 		sap = &udp->siguaction[sig].sig_uaction;
710 		if (sap->sa_handler != SIG_DFL &&
711 		    sap->sa_handler != SIG_IGN &&
712 		    __sigaction(sig, NULL, &act) == 0 &&
713 		    act.sa_handler != SIG_DFL &&
714 		    act.sa_handler != SIG_IGN) {
715 			act = *sap;
716 			act.sa_flags &= ~SA_NODEFER;
717 			act.sa_sigaction = udp->sigacthandler;
718 			act.sa_mask = maskset;
719 			(void) __sigaction(sig, &act, NULL);
720 		}
721 	}
722 }
723 
724 /*
725  * Common code for cancelling self in _sigcancel() and pthread_cancel().
726  * First record the fact that a cancellation is pending.
727  * Then, if cancellation is disabled or if we are holding unprotected
728  * libc locks, just return to defer the cancellation.
729  * Then, if we are at a cancellation point (ul_cancelable) just
730  * return and let _canceloff() do the exit.
731  * Else exit immediately if async mode is in effect.
732  */
733 void
do_sigcancel(void)734 do_sigcancel(void)
735 {
736 	ulwp_t *self = curthread;
737 
738 	ASSERT(self->ul_critical == 0);
739 	ASSERT(self->ul_sigdefer == 0);
740 	self->ul_cancel_pending = 1;
741 	if (self->ul_cancel_async &&
742 	    !self->ul_cancel_disabled &&
743 	    self->ul_libc_locks == 0 &&
744 	    !self->ul_cancelable)
745 		pthread_exit(PTHREAD_CANCELED);
746 	set_cancel_pending_flag(self, 0);
747 }
748 
749 /*
750  * Set up the SIGCANCEL handler for threads cancellation,
751  * needed only when we have more than one thread,
752  * or the SIGAIOCANCEL handler for aio cancellation,
753  * called when aio is initialized, in __uaio_init().
754  */
755 void
setup_cancelsig(int sig)756 setup_cancelsig(int sig)
757 {
758 	uberdata_t *udp = curthread->ul_uberdata;
759 	rwlock_t *rwlp = &udp->siguaction[sig].sig_lock;
760 	struct sigaction act;
761 
762 	ASSERT(sig == SIGCANCEL || sig == SIGAIOCANCEL);
763 	lrw_rdlock(rwlp);
764 	act = udp->siguaction[sig].sig_uaction;
765 	lrw_unlock(rwlp);
766 	if (act.sa_handler == SIG_DFL ||
767 	    act.sa_handler == SIG_IGN)
768 		act.sa_flags = SA_SIGINFO;
769 	else {
770 		act.sa_flags |= SA_SIGINFO;
771 		act.sa_flags &= ~(SA_NODEFER | SA_RESETHAND | SA_RESTART);
772 	}
773 	act.sa_sigaction = udp->sigacthandler;
774 	act.sa_mask = maskset;
775 	(void) __sigaction(sig, &act, NULL);
776 }
777