xref: /freebsd/sys/kern/kern_exit.c (revision c6989859ae9388eeb46a24fe88f9b8d07101c710)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (c) 1982, 1986, 1989, 1991, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  * (c) UNIX System Laboratories, Inc.
7  * All or some portions of this file are derived from material licensed
8  * to the University of California by American Telephone and Telegraph
9  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
10  * the permission of UNIX System Laboratories, Inc.
11  *
12  * Redistribution and use in source and binary forms, with or without
13  * modification, are permitted provided that the following conditions
14  * are met:
15  * 1. Redistributions of source code must retain the above copyright
16  *    notice, this list of conditions and the following disclaimer.
17  * 2. Redistributions in binary form must reproduce the above copyright
18  *    notice, this list of conditions and the following disclaimer in the
19  *    documentation and/or other materials provided with the distribution.
20  * 3. Neither the name of the University nor the names of its contributors
21  *    may be used to endorse or promote products derived from this software
22  *    without specific prior written permission.
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34  * SUCH DAMAGE.
35  *
36  *	@(#)kern_exit.c	8.7 (Berkeley) 2/12/94
37  */
38 
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
41 
42 #include "opt_ktrace.h"
43 
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/sysproto.h>
47 #include <sys/capsicum.h>
48 #include <sys/eventhandler.h>
49 #include <sys/kernel.h>
50 #include <sys/ktr.h>
51 #include <sys/malloc.h>
52 #include <sys/lock.h>
53 #include <sys/mutex.h>
54 #include <sys/proc.h>
55 #include <sys/procdesc.h>
56 #include <sys/jail.h>
57 #include <sys/tty.h>
58 #include <sys/wait.h>
59 #include <sys/vmmeter.h>
60 #include <sys/vnode.h>
61 #include <sys/racct.h>
62 #include <sys/resourcevar.h>
63 #include <sys/sbuf.h>
64 #include <sys/signalvar.h>
65 #include <sys/sched.h>
66 #include <sys/sx.h>
67 #include <sys/syscallsubr.h>
68 #include <sys/syslog.h>
69 #include <sys/ptrace.h>
70 #include <sys/acct.h>		/* for acct_process() function prototype */
71 #include <sys/filedesc.h>
72 #include <sys/sdt.h>
73 #include <sys/shm.h>
74 #include <sys/sem.h>
75 #include <sys/umtx.h>
76 #ifdef KTRACE
77 #include <sys/ktrace.h>
78 #endif
79 
80 #include <security/audit/audit.h>
81 #include <security/mac/mac_framework.h>
82 
83 #include <vm/vm.h>
84 #include <vm/vm_extern.h>
85 #include <vm/vm_param.h>
86 #include <vm/pmap.h>
87 #include <vm/vm_map.h>
88 #include <vm/vm_page.h>
89 #include <vm/uma.h>
90 
91 #ifdef KDTRACE_HOOKS
92 #include <sys/dtrace_bsd.h>
93 dtrace_execexit_func_t	dtrace_fasttrap_exit;
94 #endif
95 
96 SDT_PROVIDER_DECLARE(proc);
97 SDT_PROBE_DEFINE1(proc, , , exit, "int");
98 
99 struct proc *
100 proc_realparent(struct proc *child)
101 {
102 	struct proc *p, *parent;
103 
104 	sx_assert(&proctree_lock, SX_LOCKED);
105 	if ((child->p_treeflag & P_TREE_ORPHANED) == 0)
106 		return (child->p_pptr->p_pid == child->p_oppid ?
107 		    child->p_pptr : child->p_reaper);
108 	for (p = child; (p->p_treeflag & P_TREE_FIRST_ORPHAN) == 0;) {
109 		/* Cannot use LIST_PREV(), since the list head is not known. */
110 		p = __containerof(p->p_orphan.le_prev, struct proc,
111 		    p_orphan.le_next);
112 		KASSERT((p->p_treeflag & P_TREE_ORPHANED) != 0,
113 		    ("missing P_ORPHAN %p", p));
114 	}
115 	parent = __containerof(p->p_orphan.le_prev, struct proc,
116 	    p_orphans.lh_first);
117 	return (parent);
118 }
119 
120 void
121 reaper_abandon_children(struct proc *p, bool exiting)
122 {
123 	struct proc *p1, *p2, *ptmp;
124 
125 	sx_assert(&proctree_lock, SX_LOCKED);
126 	KASSERT(p != initproc, ("reaper_abandon_children for initproc"));
127 	if ((p->p_treeflag & P_TREE_REAPER) == 0)
128 		return;
129 	p1 = p->p_reaper;
130 	LIST_FOREACH_SAFE(p2, &p->p_reaplist, p_reapsibling, ptmp) {
131 		LIST_REMOVE(p2, p_reapsibling);
132 		p2->p_reaper = p1;
133 		p2->p_reapsubtree = p->p_reapsubtree;
134 		LIST_INSERT_HEAD(&p1->p_reaplist, p2, p_reapsibling);
135 		if (exiting && p2->p_pptr == p) {
136 			PROC_LOCK(p2);
137 			proc_reparent(p2, p1, true);
138 			PROC_UNLOCK(p2);
139 		}
140 	}
141 	KASSERT(LIST_EMPTY(&p->p_reaplist), ("p_reaplist not empty"));
142 	p->p_treeflag &= ~P_TREE_REAPER;
143 }
144 
145 static void
146 reaper_clear(struct proc *p)
147 {
148 	struct proc *p1;
149 	bool clear;
150 
151 	sx_assert(&proctree_lock, SX_LOCKED);
152 	LIST_REMOVE(p, p_reapsibling);
153 	if (p->p_reapsubtree == 1)
154 		return;
155 	clear = true;
156 	LIST_FOREACH(p1, &p->p_reaper->p_reaplist, p_reapsibling) {
157 		if (p1->p_reapsubtree == p->p_reapsubtree) {
158 			clear = false;
159 			break;
160 		}
161 	}
162 	if (clear)
163 		proc_id_clear(PROC_ID_REAP, p->p_reapsubtree);
164 }
165 
166 void
167 proc_clear_orphan(struct proc *p)
168 {
169 	struct proc *p1;
170 
171 	sx_assert(&proctree_lock, SA_XLOCKED);
172 	if ((p->p_treeflag & P_TREE_ORPHANED) == 0)
173 		return;
174 	if ((p->p_treeflag & P_TREE_FIRST_ORPHAN) != 0) {
175 		p1 = LIST_NEXT(p, p_orphan);
176 		if (p1 != NULL)
177 			p1->p_treeflag |= P_TREE_FIRST_ORPHAN;
178 		p->p_treeflag &= ~P_TREE_FIRST_ORPHAN;
179 	}
180 	LIST_REMOVE(p, p_orphan);
181 	p->p_treeflag &= ~P_TREE_ORPHANED;
182 }
183 
184 /*
185  * exit -- death of process.
186  */
187 void
188 sys_sys_exit(struct thread *td, struct sys_exit_args *uap)
189 {
190 
191 	exit1(td, uap->rval, 0);
192 	/* NOTREACHED */
193 }
194 
195 /*
196  * Exit: deallocate address space and other resources, change proc state to
197  * zombie, and unlink proc from allproc and parent's lists.  Save exit status
198  * and rusage for wait().  Check for child processes and orphan them.
199  */
200 void
201 exit1(struct thread *td, int rval, int signo)
202 {
203 	struct proc *p, *nq, *q, *t;
204 	struct thread *tdt;
205 	ksiginfo_t *ksi, *ksi1;
206 	int signal_parent;
207 
208 	mtx_assert(&Giant, MA_NOTOWNED);
209 	KASSERT(rval == 0 || signo == 0, ("exit1 rv %d sig %d", rval, signo));
210 
211 	p = td->td_proc;
212 	/*
213 	 * XXX in case we're rebooting we just let init die in order to
214 	 * work around an unsolved stack overflow seen very late during
215 	 * shutdown on sparc64 when the gmirror worker process exists.
216 	 * XXX what to do now that sparc64 is gone... remove if?
217 	 */
218 	if (p == initproc && rebooting == 0) {
219 		printf("init died (signal %d, exit %d)\n", signo, rval);
220 		panic("Going nowhere without my init!");
221 	}
222 
223 	/*
224 	 * Deref SU mp, since the thread does not return to userspace.
225 	 */
226 	td_softdep_cleanup(td);
227 
228 	/*
229 	 * MUST abort all other threads before proceeding past here.
230 	 */
231 	PROC_LOCK(p);
232 	/*
233 	 * First check if some other thread or external request got
234 	 * here before us.  If so, act appropriately: exit or suspend.
235 	 * We must ensure that stop requests are handled before we set
236 	 * P_WEXIT.
237 	 */
238 	thread_suspend_check(0);
239 	while (p->p_flag & P_HADTHREADS) {
240 		/*
241 		 * Kill off the other threads. This requires
242 		 * some co-operation from other parts of the kernel
243 		 * so it may not be instantaneous.  With this state set
244 		 * any thread entering the kernel from userspace will
245 		 * thread_exit() in trap().  Any thread attempting to
246 		 * sleep will return immediately with EINTR or EWOULDBLOCK
247 		 * which will hopefully force them to back out to userland
248 		 * freeing resources as they go.  Any thread attempting
249 		 * to return to userland will thread_exit() from userret().
250 		 * thread_exit() will unsuspend us when the last of the
251 		 * other threads exits.
252 		 * If there is already a thread singler after resumption,
253 		 * calling thread_single will fail; in that case, we just
254 		 * re-check all suspension request, the thread should
255 		 * either be suspended there or exit.
256 		 */
257 		if (!thread_single(p, SINGLE_EXIT))
258 			/*
259 			 * All other activity in this process is now
260 			 * stopped.  Threading support has been turned
261 			 * off.
262 			 */
263 			break;
264 		/*
265 		 * Recheck for new stop or suspend requests which
266 		 * might appear while process lock was dropped in
267 		 * thread_single().
268 		 */
269 		thread_suspend_check(0);
270 	}
271 	KASSERT(p->p_numthreads == 1,
272 	    ("exit1: proc %p exiting with %d threads", p, p->p_numthreads));
273 	racct_sub(p, RACCT_NTHR, 1);
274 
275 	/* Let event handler change exit status */
276 	p->p_xexit = rval;
277 	p->p_xsig = signo;
278 
279 	/*
280 	 * Ignore any pending request to stop due to a stop signal.
281 	 * Once P_WEXIT is set, future requests will be ignored as
282 	 * well.
283 	 */
284 	p->p_flag &= ~P_STOPPED_SIG;
285 	KASSERT(!P_SHOULDSTOP(p), ("exiting process is stopped"));
286 
287 	/* Note that we are exiting. */
288 	p->p_flag |= P_WEXIT;
289 
290 	/*
291 	 * Wait for any processes that have a hold on our vmspace to
292 	 * release their reference.
293 	 */
294 	while (p->p_lock > 0)
295 		msleep(&p->p_lock, &p->p_mtx, PWAIT, "exithold", 0);
296 
297 	PROC_UNLOCK(p);
298 	/* Drain the limit callout while we don't have the proc locked */
299 	callout_drain(&p->p_limco);
300 
301 #ifdef AUDIT
302 	/*
303 	 * The Sun BSM exit token contains two components: an exit status as
304 	 * passed to exit(), and a return value to indicate what sort of exit
305 	 * it was.  The exit status is WEXITSTATUS(rv), but it's not clear
306 	 * what the return value is.
307 	 */
308 	AUDIT_ARG_EXIT(rval, 0);
309 	AUDIT_SYSCALL_EXIT(0, td);
310 #endif
311 
312 	/* Are we a task leader with peers? */
313 	if (p->p_peers != NULL && p == p->p_leader) {
314 		mtx_lock(&ppeers_lock);
315 		q = p->p_peers;
316 		while (q != NULL) {
317 			PROC_LOCK(q);
318 			kern_psignal(q, SIGKILL);
319 			PROC_UNLOCK(q);
320 			q = q->p_peers;
321 		}
322 		while (p->p_peers != NULL)
323 			msleep(p, &ppeers_lock, PWAIT, "exit1", 0);
324 		mtx_unlock(&ppeers_lock);
325 	}
326 
327 	/*
328 	 * Check if any loadable modules need anything done at process exit.
329 	 * E.g. SYSV IPC stuff.
330 	 * Event handler could change exit status.
331 	 * XXX what if one of these generates an error?
332 	 */
333 	EVENTHANDLER_DIRECT_INVOKE(process_exit, p);
334 
335 	/*
336 	 * If parent is waiting for us to exit or exec,
337 	 * P_PPWAIT is set; we will wakeup the parent below.
338 	 */
339 	PROC_LOCK(p);
340 	stopprofclock(p);
341 	p->p_ptevents = 0;
342 
343 	/*
344 	 * Stop the real interval timer.  If the handler is currently
345 	 * executing, prevent it from rearming itself and let it finish.
346 	 */
347 	if (timevalisset(&p->p_realtimer.it_value) &&
348 	    _callout_stop_safe(&p->p_itcallout, CS_EXECUTING, NULL) == 0) {
349 		timevalclear(&p->p_realtimer.it_interval);
350 		msleep(&p->p_itcallout, &p->p_mtx, PWAIT, "ritwait", 0);
351 		KASSERT(!timevalisset(&p->p_realtimer.it_value),
352 		    ("realtime timer is still armed"));
353 	}
354 
355 	PROC_UNLOCK(p);
356 
357 	umtx_thread_exit(td);
358 
359 	/*
360 	 * Reset any sigio structures pointing to us as a result of
361 	 * F_SETOWN with our pid.
362 	 */
363 	funsetownlst(&p->p_sigiolst);
364 
365 	/*
366 	 * Close open files and release open-file table.
367 	 * This may block!
368 	 */
369 	fdescfree(td);
370 
371 	/*
372 	 * If this thread tickled GEOM, we need to wait for the giggling to
373 	 * stop before we return to userland
374 	 */
375 	if (td->td_pflags & TDP_GEOM)
376 		g_waitidle();
377 
378 	/*
379 	 * Remove ourself from our leader's peer list and wake our leader.
380 	 */
381 	if (p->p_leader->p_peers != NULL) {
382 		mtx_lock(&ppeers_lock);
383 		if (p->p_leader->p_peers != NULL) {
384 			q = p->p_leader;
385 			while (q->p_peers != p)
386 				q = q->p_peers;
387 			q->p_peers = p->p_peers;
388 			wakeup(p->p_leader);
389 		}
390 		mtx_unlock(&ppeers_lock);
391 	}
392 
393 	vmspace_exit(td);
394 	(void)acct_process(td);
395 
396 #ifdef KTRACE
397 	ktrprocexit(td);
398 #endif
399 	/*
400 	 * Release reference to text vnode
401 	 */
402 	if (p->p_textvp != NULL) {
403 		vrele(p->p_textvp);
404 		p->p_textvp = NULL;
405 	}
406 
407 	/*
408 	 * Release our limits structure.
409 	 */
410 	lim_free(p->p_limit);
411 	p->p_limit = NULL;
412 
413 	tidhash_remove(td);
414 
415 	/*
416 	 * Call machine-dependent code to release any
417 	 * machine-dependent resources other than the address space.
418 	 * The address space is released by "vmspace_exitfree(p)" in
419 	 * vm_waitproc().
420 	 */
421 	cpu_exit(td);
422 
423 	WITNESS_WARN(WARN_PANIC, NULL, "process (pid %d) exiting", p->p_pid);
424 
425 	/*
426 	 * Remove from allproc. It still sits in the hash.
427 	 */
428 	sx_xlock(&allproc_lock);
429 	LIST_REMOVE(p, p_list);
430 	sx_xunlock(&allproc_lock);
431 
432 	sx_xlock(&proctree_lock);
433 	PROC_LOCK(p);
434 	p->p_flag &= ~(P_TRACED | P_PPWAIT | P_PPTRACE);
435 	PROC_UNLOCK(p);
436 
437 	/*
438 	 * killjobc() might drop and re-acquire proctree_lock to
439 	 * revoke control tty if exiting process was a session leader.
440 	 */
441 	killjobc();
442 
443 	/*
444 	 * Reparent all children processes:
445 	 * - traced ones to the original parent (or init if we are that parent)
446 	 * - the rest to init
447 	 */
448 	q = LIST_FIRST(&p->p_children);
449 	if (q != NULL)		/* only need this if any child is S_ZOMB */
450 		wakeup(q->p_reaper);
451 	for (; q != NULL; q = nq) {
452 		nq = LIST_NEXT(q, p_sibling);
453 		ksi = ksiginfo_alloc(TRUE);
454 		PROC_LOCK(q);
455 		q->p_sigparent = SIGCHLD;
456 
457 		if ((q->p_flag & P_TRACED) == 0) {
458 			proc_reparent(q, q->p_reaper, true);
459 			if (q->p_state == PRS_ZOMBIE) {
460 				/*
461 				 * Inform reaper about the reparented
462 				 * zombie, since wait(2) has something
463 				 * new to report.  Guarantee queueing
464 				 * of the SIGCHLD signal, similar to
465 				 * the _exit() behaviour, by providing
466 				 * our ksiginfo.  Ksi is freed by the
467 				 * signal delivery.
468 				 */
469 				if (q->p_ksi == NULL) {
470 					ksi1 = NULL;
471 				} else {
472 					ksiginfo_copy(q->p_ksi, ksi);
473 					ksi->ksi_flags |= KSI_INS;
474 					ksi1 = ksi;
475 					ksi = NULL;
476 				}
477 				PROC_LOCK(q->p_reaper);
478 				pksignal(q->p_reaper, SIGCHLD, ksi1);
479 				PROC_UNLOCK(q->p_reaper);
480 			} else if (q->p_pdeathsig > 0) {
481 				/*
482 				 * The child asked to received a signal
483 				 * when we exit.
484 				 */
485 				kern_psignal(q, q->p_pdeathsig);
486 			}
487 		} else {
488 			/*
489 			 * Traced processes are killed since their existence
490 			 * means someone is screwing up.
491 			 */
492 			t = proc_realparent(q);
493 			if (t == p) {
494 				proc_reparent(q, q->p_reaper, true);
495 			} else {
496 				PROC_LOCK(t);
497 				proc_reparent(q, t, true);
498 				PROC_UNLOCK(t);
499 			}
500 			/*
501 			 * Since q was found on our children list, the
502 			 * proc_reparent() call moved q to the orphan
503 			 * list due to present P_TRACED flag. Clear
504 			 * orphan link for q now while q is locked.
505 			 */
506 			proc_clear_orphan(q);
507 			q->p_flag &= ~(P_TRACED | P_STOPPED_TRACE);
508 			q->p_flag2 &= ~P2_PTRACE_FSTP;
509 			q->p_ptevents = 0;
510 			FOREACH_THREAD_IN_PROC(q, tdt) {
511 				tdt->td_dbgflags &= ~(TDB_SUSPEND | TDB_XSIG |
512 				    TDB_FSTP);
513 			}
514 			kern_psignal(q, SIGKILL);
515 		}
516 		PROC_UNLOCK(q);
517 		if (ksi != NULL)
518 			ksiginfo_free(ksi);
519 	}
520 
521 	/*
522 	 * Also get rid of our orphans.
523 	 */
524 	while ((q = LIST_FIRST(&p->p_orphans)) != NULL) {
525 		PROC_LOCK(q);
526 		KASSERT(q->p_oppid == p->p_pid,
527 		    ("orphan %p of %p has unexpected oppid %d", q, p,
528 		    q->p_oppid));
529 		q->p_oppid = q->p_reaper->p_pid;
530 
531 		/*
532 		 * If we are the real parent of this process
533 		 * but it has been reparented to a debugger, then
534 		 * check if it asked for a signal when we exit.
535 		 */
536 		if (q->p_pdeathsig > 0)
537 			kern_psignal(q, q->p_pdeathsig);
538 		CTR2(KTR_PTRACE, "exit: pid %d, clearing orphan %d", p->p_pid,
539 		    q->p_pid);
540 		proc_clear_orphan(q);
541 		PROC_UNLOCK(q);
542 	}
543 
544 #ifdef KDTRACE_HOOKS
545 	if (SDT_PROBES_ENABLED()) {
546 		int reason = CLD_EXITED;
547 		if (WCOREDUMP(signo))
548 			reason = CLD_DUMPED;
549 		else if (WIFSIGNALED(signo))
550 			reason = CLD_KILLED;
551 		SDT_PROBE1(proc, , , exit, reason);
552 	}
553 #endif
554 
555 	/* Save exit status. */
556 	PROC_LOCK(p);
557 	p->p_xthread = td;
558 
559 #ifdef KDTRACE_HOOKS
560 	/*
561 	 * Tell the DTrace fasttrap provider about the exit if it
562 	 * has declared an interest.
563 	 */
564 	if (dtrace_fasttrap_exit)
565 		dtrace_fasttrap_exit(p);
566 #endif
567 
568 	/*
569 	 * Notify interested parties of our demise.
570 	 */
571 	KNOTE_LOCKED(p->p_klist, NOTE_EXIT);
572 
573 	/*
574 	 * If this is a process with a descriptor, we may not need to deliver
575 	 * a signal to the parent.  proctree_lock is held over
576 	 * procdesc_exit() to serialize concurrent calls to close() and
577 	 * exit().
578 	 */
579 	signal_parent = 0;
580 	if (p->p_procdesc == NULL || procdesc_exit(p)) {
581 		/*
582 		 * Notify parent that we're gone.  If parent has the
583 		 * PS_NOCLDWAIT flag set, or if the handler is set to SIG_IGN,
584 		 * notify process 1 instead (and hope it will handle this
585 		 * situation).
586 		 */
587 		PROC_LOCK(p->p_pptr);
588 		mtx_lock(&p->p_pptr->p_sigacts->ps_mtx);
589 		if (p->p_pptr->p_sigacts->ps_flag &
590 		    (PS_NOCLDWAIT | PS_CLDSIGIGN)) {
591 			struct proc *pp;
592 
593 			mtx_unlock(&p->p_pptr->p_sigacts->ps_mtx);
594 			pp = p->p_pptr;
595 			PROC_UNLOCK(pp);
596 			proc_reparent(p, p->p_reaper, true);
597 			p->p_sigparent = SIGCHLD;
598 			PROC_LOCK(p->p_pptr);
599 
600 			/*
601 			 * Notify parent, so in case he was wait(2)ing or
602 			 * executing waitpid(2) with our pid, he will
603 			 * continue.
604 			 */
605 			wakeup(pp);
606 		} else
607 			mtx_unlock(&p->p_pptr->p_sigacts->ps_mtx);
608 
609 		if (p->p_pptr == p->p_reaper || p->p_pptr == initproc) {
610 			signal_parent = 1;
611 		} else if (p->p_sigparent != 0) {
612 			if (p->p_sigparent == SIGCHLD) {
613 				signal_parent = 1;
614 			} else { /* LINUX thread */
615 				signal_parent = 2;
616 			}
617 		}
618 	} else
619 		PROC_LOCK(p->p_pptr);
620 	sx_xunlock(&proctree_lock);
621 
622 	if (signal_parent == 1) {
623 		childproc_exited(p);
624 	} else if (signal_parent == 2) {
625 		kern_psignal(p->p_pptr, p->p_sigparent);
626 	}
627 
628 	/* Tell the prison that we are gone. */
629 	prison_proc_free(p->p_ucred->cr_prison);
630 
631 	/*
632 	 * The state PRS_ZOMBIE prevents other proesses from sending
633 	 * signal to the process, to avoid memory leak, we free memory
634 	 * for signal queue at the time when the state is set.
635 	 */
636 	sigqueue_flush(&p->p_sigqueue);
637 	sigqueue_flush(&td->td_sigqueue);
638 
639 	/*
640 	 * We have to wait until after acquiring all locks before
641 	 * changing p_state.  We need to avoid all possible context
642 	 * switches (including ones from blocking on a mutex) while
643 	 * marked as a zombie.  We also have to set the zombie state
644 	 * before we release the parent process' proc lock to avoid
645 	 * a lost wakeup.  So, we first call wakeup, then we grab the
646 	 * sched lock, update the state, and release the parent process'
647 	 * proc lock.
648 	 */
649 	wakeup(p->p_pptr);
650 	cv_broadcast(&p->p_pwait);
651 	sched_exit(p->p_pptr, td);
652 	PROC_SLOCK(p);
653 	p->p_state = PRS_ZOMBIE;
654 	PROC_UNLOCK(p->p_pptr);
655 
656 	/*
657 	 * Save our children's rusage information in our exit rusage.
658 	 */
659 	PROC_STATLOCK(p);
660 	ruadd(&p->p_ru, &p->p_rux, &p->p_stats->p_cru, &p->p_crux);
661 	PROC_STATUNLOCK(p);
662 
663 	/*
664 	 * Make sure the scheduler takes this thread out of its tables etc.
665 	 * This will also release this thread's reference to the ucred.
666 	 * Other thread parts to release include pcb bits and such.
667 	 */
668 	thread_exit();
669 }
670 
671 #ifndef _SYS_SYSPROTO_H_
672 struct abort2_args {
673 	char *why;
674 	int nargs;
675 	void **args;
676 };
677 #endif
678 
679 int
680 sys_abort2(struct thread *td, struct abort2_args *uap)
681 {
682 	struct proc *p = td->td_proc;
683 	struct sbuf *sb;
684 	void *uargs[16];
685 	int error, i, sig;
686 
687 	/*
688 	 * Do it right now so we can log either proper call of abort2(), or
689 	 * note, that invalid argument was passed. 512 is big enough to
690 	 * handle 16 arguments' descriptions with additional comments.
691 	 */
692 	sb = sbuf_new(NULL, NULL, 512, SBUF_FIXEDLEN);
693 	sbuf_clear(sb);
694 	sbuf_printf(sb, "%s(pid %d uid %d) aborted: ",
695 	    p->p_comm, p->p_pid, td->td_ucred->cr_uid);
696 	/*
697 	 * Since we can't return from abort2(), send SIGKILL in cases, where
698 	 * abort2() was called improperly
699 	 */
700 	sig = SIGKILL;
701 	/* Prevent from DoSes from user-space. */
702 	if (uap->nargs < 0 || uap->nargs > 16)
703 		goto out;
704 	if (uap->nargs > 0) {
705 		if (uap->args == NULL)
706 			goto out;
707 		error = copyin(uap->args, uargs, uap->nargs * sizeof(void *));
708 		if (error != 0)
709 			goto out;
710 	}
711 	/*
712 	 * Limit size of 'reason' string to 128. Will fit even when
713 	 * maximal number of arguments was chosen to be logged.
714 	 */
715 	if (uap->why != NULL) {
716 		error = sbuf_copyin(sb, uap->why, 128);
717 		if (error < 0)
718 			goto out;
719 	} else {
720 		sbuf_printf(sb, "(null)");
721 	}
722 	if (uap->nargs > 0) {
723 		sbuf_printf(sb, "(");
724 		for (i = 0;i < uap->nargs; i++)
725 			sbuf_printf(sb, "%s%p", i == 0 ? "" : ", ", uargs[i]);
726 		sbuf_printf(sb, ")");
727 	}
728 	/*
729 	 * Final stage: arguments were proper, string has been
730 	 * successfully copied from userspace, and copying pointers
731 	 * from user-space succeed.
732 	 */
733 	sig = SIGABRT;
734 out:
735 	if (sig == SIGKILL) {
736 		sbuf_trim(sb);
737 		sbuf_printf(sb, " (Reason text inaccessible)");
738 	}
739 	sbuf_cat(sb, "\n");
740 	sbuf_finish(sb);
741 	log(LOG_INFO, "%s", sbuf_data(sb));
742 	sbuf_delete(sb);
743 	exit1(td, 0, sig);
744 	return (0);
745 }
746 
747 #ifdef COMPAT_43
748 /*
749  * The dirty work is handled by kern_wait().
750  */
751 int
752 owait(struct thread *td, struct owait_args *uap __unused)
753 {
754 	int error, status;
755 
756 	error = kern_wait(td, WAIT_ANY, &status, 0, NULL);
757 	if (error == 0)
758 		td->td_retval[1] = status;
759 	return (error);
760 }
761 #endif /* COMPAT_43 */
762 
763 /*
764  * The dirty work is handled by kern_wait().
765  */
766 int
767 sys_wait4(struct thread *td, struct wait4_args *uap)
768 {
769 	struct rusage ru, *rup;
770 	int error, status;
771 
772 	if (uap->rusage != NULL)
773 		rup = &ru;
774 	else
775 		rup = NULL;
776 	error = kern_wait(td, uap->pid, &status, uap->options, rup);
777 	if (uap->status != NULL && error == 0 && td->td_retval[0] != 0)
778 		error = copyout(&status, uap->status, sizeof(status));
779 	if (uap->rusage != NULL && error == 0 && td->td_retval[0] != 0)
780 		error = copyout(&ru, uap->rusage, sizeof(struct rusage));
781 	return (error);
782 }
783 
784 int
785 sys_wait6(struct thread *td, struct wait6_args *uap)
786 {
787 	struct __wrusage wru, *wrup;
788 	siginfo_t si, *sip;
789 	idtype_t idtype;
790 	id_t id;
791 	int error, status;
792 
793 	idtype = uap->idtype;
794 	id = uap->id;
795 
796 	if (uap->wrusage != NULL)
797 		wrup = &wru;
798 	else
799 		wrup = NULL;
800 
801 	if (uap->info != NULL) {
802 		sip = &si;
803 		bzero(sip, sizeof(*sip));
804 	} else
805 		sip = NULL;
806 
807 	/*
808 	 *  We expect all callers of wait6() to know about WEXITED and
809 	 *  WTRAPPED.
810 	 */
811 	error = kern_wait6(td, idtype, id, &status, uap->options, wrup, sip);
812 
813 	if (uap->status != NULL && error == 0 && td->td_retval[0] != 0)
814 		error = copyout(&status, uap->status, sizeof(status));
815 	if (uap->wrusage != NULL && error == 0 && td->td_retval[0] != 0)
816 		error = copyout(&wru, uap->wrusage, sizeof(wru));
817 	if (uap->info != NULL && error == 0)
818 		error = copyout(&si, uap->info, sizeof(si));
819 	return (error);
820 }
821 
822 /*
823  * Reap the remains of a zombie process and optionally return status and
824  * rusage.  Asserts and will release both the proctree_lock and the process
825  * lock as part of its work.
826  */
827 void
828 proc_reap(struct thread *td, struct proc *p, int *status, int options)
829 {
830 	struct proc *q, *t;
831 
832 	sx_assert(&proctree_lock, SA_XLOCKED);
833 	PROC_LOCK_ASSERT(p, MA_OWNED);
834 	KASSERT(p->p_state == PRS_ZOMBIE, ("proc_reap: !PRS_ZOMBIE"));
835 
836 	mtx_spin_wait_unlocked(&p->p_slock);
837 
838 	q = td->td_proc;
839 
840 	if (status)
841 		*status = KW_EXITCODE(p->p_xexit, p->p_xsig);
842 	if (options & WNOWAIT) {
843 		/*
844 		 *  Only poll, returning the status.  Caller does not wish to
845 		 * release the proc struct just yet.
846 		 */
847 		PROC_UNLOCK(p);
848 		sx_xunlock(&proctree_lock);
849 		return;
850 	}
851 
852 	PROC_LOCK(q);
853 	sigqueue_take(p->p_ksi);
854 	PROC_UNLOCK(q);
855 
856 	/*
857 	 * If we got the child via a ptrace 'attach', we need to give it back
858 	 * to the old parent.
859 	 */
860 	if (p->p_oppid != p->p_pptr->p_pid) {
861 		PROC_UNLOCK(p);
862 		t = proc_realparent(p);
863 		PROC_LOCK(t);
864 		PROC_LOCK(p);
865 		CTR2(KTR_PTRACE,
866 		    "wait: traced child %d moved back to parent %d", p->p_pid,
867 		    t->p_pid);
868 		proc_reparent(p, t, false);
869 		PROC_UNLOCK(p);
870 		pksignal(t, SIGCHLD, p->p_ksi);
871 		wakeup(t);
872 		cv_broadcast(&p->p_pwait);
873 		PROC_UNLOCK(t);
874 		sx_xunlock(&proctree_lock);
875 		return;
876 	}
877 	PROC_UNLOCK(p);
878 
879 	/*
880 	 * Remove other references to this process to ensure we have an
881 	 * exclusive reference.
882 	 */
883 	sx_xlock(PIDHASHLOCK(p->p_pid));
884 	LIST_REMOVE(p, p_hash);
885 	sx_xunlock(PIDHASHLOCK(p->p_pid));
886 	LIST_REMOVE(p, p_sibling);
887 	reaper_abandon_children(p, true);
888 	reaper_clear(p);
889 	PROC_LOCK(p);
890 	proc_clear_orphan(p);
891 	PROC_UNLOCK(p);
892 	leavepgrp(p);
893 	if (p->p_procdesc != NULL)
894 		procdesc_reap(p);
895 	sx_xunlock(&proctree_lock);
896 
897 	proc_id_clear(PROC_ID_PID, p->p_pid);
898 
899 	PROC_LOCK(p);
900 	knlist_detach(p->p_klist);
901 	p->p_klist = NULL;
902 	PROC_UNLOCK(p);
903 
904 	/*
905 	 * Removal from allproc list and process group list paired with
906 	 * PROC_LOCK which was executed during that time should guarantee
907 	 * nothing can reach this process anymore. As such further locking
908 	 * is unnecessary.
909 	 */
910 	p->p_xexit = p->p_xsig = 0;		/* XXX: why? */
911 
912 	PROC_LOCK(q);
913 	ruadd(&q->p_stats->p_cru, &q->p_crux, &p->p_ru, &p->p_rux);
914 	PROC_UNLOCK(q);
915 
916 	/*
917 	 * Decrement the count of procs running with this uid.
918 	 */
919 	(void)chgproccnt(p->p_ucred->cr_ruidinfo, -1, 0);
920 
921 	/*
922 	 * Destroy resource accounting information associated with the process.
923 	 */
924 #ifdef RACCT
925 	if (racct_enable) {
926 		PROC_LOCK(p);
927 		racct_sub(p, RACCT_NPROC, 1);
928 		PROC_UNLOCK(p);
929 	}
930 #endif
931 	racct_proc_exit(p);
932 
933 	/*
934 	 * Free credentials, arguments, and sigacts.
935 	 */
936 	proc_unset_cred(p);
937 	pargs_drop(p->p_args);
938 	p->p_args = NULL;
939 	sigacts_free(p->p_sigacts);
940 	p->p_sigacts = NULL;
941 
942 	/*
943 	 * Do any thread-system specific cleanups.
944 	 */
945 	thread_wait(p);
946 
947 	/*
948 	 * Give vm and machine-dependent layer a chance to free anything that
949 	 * cpu_exit couldn't release while still running in process context.
950 	 */
951 	vm_waitproc(p);
952 #ifdef MAC
953 	mac_proc_destroy(p);
954 #endif
955 
956 	KASSERT(FIRST_THREAD_IN_PROC(p),
957 	    ("proc_reap: no residual thread!"));
958 	uma_zfree(proc_zone, p);
959 	atomic_add_int(&nprocs, -1);
960 }
961 
962 static int
963 proc_to_reap(struct thread *td, struct proc *p, idtype_t idtype, id_t id,
964     int *status, int options, struct __wrusage *wrusage, siginfo_t *siginfo,
965     int check_only)
966 {
967 	struct rusage *rup;
968 
969 	sx_assert(&proctree_lock, SA_XLOCKED);
970 
971 	PROC_LOCK(p);
972 
973 	switch (idtype) {
974 	case P_ALL:
975 		if (p->p_procdesc == NULL ||
976 		   (p->p_pptr == td->td_proc &&
977 		   (p->p_flag & P_TRACED) != 0)) {
978 			break;
979 		}
980 
981 		PROC_UNLOCK(p);
982 		return (0);
983 	case P_PID:
984 		if (p->p_pid != (pid_t)id) {
985 			PROC_UNLOCK(p);
986 			return (0);
987 		}
988 		break;
989 	case P_PGID:
990 		if (p->p_pgid != (pid_t)id) {
991 			PROC_UNLOCK(p);
992 			return (0);
993 		}
994 		break;
995 	case P_SID:
996 		if (p->p_session->s_sid != (pid_t)id) {
997 			PROC_UNLOCK(p);
998 			return (0);
999 		}
1000 		break;
1001 	case P_UID:
1002 		if (p->p_ucred->cr_uid != (uid_t)id) {
1003 			PROC_UNLOCK(p);
1004 			return (0);
1005 		}
1006 		break;
1007 	case P_GID:
1008 		if (p->p_ucred->cr_gid != (gid_t)id) {
1009 			PROC_UNLOCK(p);
1010 			return (0);
1011 		}
1012 		break;
1013 	case P_JAILID:
1014 		if (p->p_ucred->cr_prison->pr_id != (int)id) {
1015 			PROC_UNLOCK(p);
1016 			return (0);
1017 		}
1018 		break;
1019 	/*
1020 	 * It seems that the thread structures get zeroed out
1021 	 * at process exit.  This makes it impossible to
1022 	 * support P_SETID, P_CID or P_CPUID.
1023 	 */
1024 	default:
1025 		PROC_UNLOCK(p);
1026 		return (0);
1027 	}
1028 
1029 	if (p_canwait(td, p)) {
1030 		PROC_UNLOCK(p);
1031 		return (0);
1032 	}
1033 
1034 	if (((options & WEXITED) == 0) && (p->p_state == PRS_ZOMBIE)) {
1035 		PROC_UNLOCK(p);
1036 		return (0);
1037 	}
1038 
1039 	/*
1040 	 * This special case handles a kthread spawned by linux_clone
1041 	 * (see linux_misc.c).  The linux_wait4 and linux_waitpid
1042 	 * functions need to be able to distinguish between waiting
1043 	 * on a process and waiting on a thread.  It is a thread if
1044 	 * p_sigparent is not SIGCHLD, and the WLINUXCLONE option
1045 	 * signifies we want to wait for threads and not processes.
1046 	 */
1047 	if ((p->p_sigparent != SIGCHLD) ^
1048 	    ((options & WLINUXCLONE) != 0)) {
1049 		PROC_UNLOCK(p);
1050 		return (0);
1051 	}
1052 
1053 	if (siginfo != NULL) {
1054 		bzero(siginfo, sizeof(*siginfo));
1055 		siginfo->si_errno = 0;
1056 
1057 		/*
1058 		 * SUSv4 requires that the si_signo value is always
1059 		 * SIGCHLD. Obey it despite the rfork(2) interface
1060 		 * allows to request other signal for child exit
1061 		 * notification.
1062 		 */
1063 		siginfo->si_signo = SIGCHLD;
1064 
1065 		/*
1066 		 *  This is still a rough estimate.  We will fix the
1067 		 *  cases TRAPPED, STOPPED, and CONTINUED later.
1068 		 */
1069 		if (WCOREDUMP(p->p_xsig)) {
1070 			siginfo->si_code = CLD_DUMPED;
1071 			siginfo->si_status = WTERMSIG(p->p_xsig);
1072 		} else if (WIFSIGNALED(p->p_xsig)) {
1073 			siginfo->si_code = CLD_KILLED;
1074 			siginfo->si_status = WTERMSIG(p->p_xsig);
1075 		} else {
1076 			siginfo->si_code = CLD_EXITED;
1077 			siginfo->si_status = p->p_xexit;
1078 		}
1079 
1080 		siginfo->si_pid = p->p_pid;
1081 		siginfo->si_uid = p->p_ucred->cr_uid;
1082 
1083 		/*
1084 		 * The si_addr field would be useful additional
1085 		 * detail, but apparently the PC value may be lost
1086 		 * when we reach this point.  bzero() above sets
1087 		 * siginfo->si_addr to NULL.
1088 		 */
1089 	}
1090 
1091 	/*
1092 	 * There should be no reason to limit resources usage info to
1093 	 * exited processes only.  A snapshot about any resources used
1094 	 * by a stopped process may be exactly what is needed.
1095 	 */
1096 	if (wrusage != NULL) {
1097 		rup = &wrusage->wru_self;
1098 		*rup = p->p_ru;
1099 		PROC_STATLOCK(p);
1100 		calcru(p, &rup->ru_utime, &rup->ru_stime);
1101 		PROC_STATUNLOCK(p);
1102 
1103 		rup = &wrusage->wru_children;
1104 		*rup = p->p_stats->p_cru;
1105 		calccru(p, &rup->ru_utime, &rup->ru_stime);
1106 	}
1107 
1108 	if (p->p_state == PRS_ZOMBIE && !check_only) {
1109 		proc_reap(td, p, status, options);
1110 		return (-1);
1111 	}
1112 	return (1);
1113 }
1114 
1115 int
1116 kern_wait(struct thread *td, pid_t pid, int *status, int options,
1117     struct rusage *rusage)
1118 {
1119 	struct __wrusage wru, *wrup;
1120 	idtype_t idtype;
1121 	id_t id;
1122 	int ret;
1123 
1124 	/*
1125 	 * Translate the special pid values into the (idtype, pid)
1126 	 * pair for kern_wait6.  The WAIT_MYPGRP case is handled by
1127 	 * kern_wait6() on its own.
1128 	 */
1129 	if (pid == WAIT_ANY) {
1130 		idtype = P_ALL;
1131 		id = 0;
1132 	} else if (pid < 0) {
1133 		idtype = P_PGID;
1134 		id = (id_t)-pid;
1135 	} else {
1136 		idtype = P_PID;
1137 		id = (id_t)pid;
1138 	}
1139 
1140 	if (rusage != NULL)
1141 		wrup = &wru;
1142 	else
1143 		wrup = NULL;
1144 
1145 	/*
1146 	 * For backward compatibility we implicitly add flags WEXITED
1147 	 * and WTRAPPED here.
1148 	 */
1149 	options |= WEXITED | WTRAPPED;
1150 	ret = kern_wait6(td, idtype, id, status, options, wrup, NULL);
1151 	if (rusage != NULL)
1152 		*rusage = wru.wru_self;
1153 	return (ret);
1154 }
1155 
1156 static void
1157 report_alive_proc(struct thread *td, struct proc *p, siginfo_t *siginfo,
1158     int *status, int options, int si_code)
1159 {
1160 	bool cont;
1161 
1162 	PROC_LOCK_ASSERT(p, MA_OWNED);
1163 	sx_assert(&proctree_lock, SA_XLOCKED);
1164 	MPASS(si_code == CLD_TRAPPED || si_code == CLD_STOPPED ||
1165 	    si_code == CLD_CONTINUED);
1166 
1167 	cont = si_code == CLD_CONTINUED;
1168 	if ((options & WNOWAIT) == 0) {
1169 		if (cont)
1170 			p->p_flag &= ~P_CONTINUED;
1171 		else
1172 			p->p_flag |= P_WAITED;
1173 		PROC_LOCK(td->td_proc);
1174 		sigqueue_take(p->p_ksi);
1175 		PROC_UNLOCK(td->td_proc);
1176 	}
1177 	sx_xunlock(&proctree_lock);
1178 	if (siginfo != NULL) {
1179 		siginfo->si_code = si_code;
1180 		siginfo->si_status = cont ? SIGCONT : p->p_xsig;
1181 	}
1182 	if (status != NULL)
1183 		*status = cont ? SIGCONT : W_STOPCODE(p->p_xsig);
1184 	PROC_UNLOCK(p);
1185 	td->td_retval[0] = p->p_pid;
1186 }
1187 
1188 int
1189 kern_wait6(struct thread *td, idtype_t idtype, id_t id, int *status,
1190     int options, struct __wrusage *wrusage, siginfo_t *siginfo)
1191 {
1192 	struct proc *p, *q;
1193 	pid_t pid;
1194 	int error, nfound, ret;
1195 	bool report;
1196 
1197 	AUDIT_ARG_VALUE((int)idtype);	/* XXX - This is likely wrong! */
1198 	AUDIT_ARG_PID((pid_t)id);	/* XXX - This may be wrong! */
1199 	AUDIT_ARG_VALUE(options);
1200 
1201 	q = td->td_proc;
1202 
1203 	if ((pid_t)id == WAIT_MYPGRP && (idtype == P_PID || idtype == P_PGID)) {
1204 		PROC_LOCK(q);
1205 		id = (id_t)q->p_pgid;
1206 		PROC_UNLOCK(q);
1207 		idtype = P_PGID;
1208 	}
1209 
1210 	/* If we don't know the option, just return. */
1211 	if ((options & ~(WUNTRACED | WNOHANG | WCONTINUED | WNOWAIT |
1212 	    WEXITED | WTRAPPED | WLINUXCLONE)) != 0)
1213 		return (EINVAL);
1214 	if ((options & (WEXITED | WUNTRACED | WCONTINUED | WTRAPPED)) == 0) {
1215 		/*
1216 		 * We will be unable to find any matching processes,
1217 		 * because there are no known events to look for.
1218 		 * Prefer to return error instead of blocking
1219 		 * indefinitely.
1220 		 */
1221 		return (EINVAL);
1222 	}
1223 
1224 loop:
1225 	if (q->p_flag & P_STATCHILD) {
1226 		PROC_LOCK(q);
1227 		q->p_flag &= ~P_STATCHILD;
1228 		PROC_UNLOCK(q);
1229 	}
1230 	sx_xlock(&proctree_lock);
1231 loop_locked:
1232 	nfound = 0;
1233 	LIST_FOREACH(p, &q->p_children, p_sibling) {
1234 		pid = p->p_pid;
1235 		ret = proc_to_reap(td, p, idtype, id, status, options,
1236 		    wrusage, siginfo, 0);
1237 		if (ret == 0)
1238 			continue;
1239 		else if (ret != 1) {
1240 			td->td_retval[0] = pid;
1241 			return (0);
1242 		}
1243 
1244 		nfound++;
1245 		PROC_LOCK_ASSERT(p, MA_OWNED);
1246 
1247 		if ((options & WTRAPPED) != 0 &&
1248 		    (p->p_flag & P_TRACED) != 0) {
1249 			PROC_SLOCK(p);
1250 			report =
1251 			    ((p->p_flag & (P_STOPPED_TRACE | P_STOPPED_SIG)) &&
1252 			    p->p_suspcount == p->p_numthreads &&
1253 			    (p->p_flag & P_WAITED) == 0);
1254 			PROC_SUNLOCK(p);
1255 			if (report) {
1256 			CTR4(KTR_PTRACE,
1257 			    "wait: returning trapped pid %d status %#x "
1258 			    "(xstat %d) xthread %d",
1259 			    p->p_pid, W_STOPCODE(p->p_xsig), p->p_xsig,
1260 			    p->p_xthread != NULL ?
1261 			    p->p_xthread->td_tid : -1);
1262 				report_alive_proc(td, p, siginfo, status,
1263 				    options, CLD_TRAPPED);
1264 				return (0);
1265 			}
1266 		}
1267 		if ((options & WUNTRACED) != 0 &&
1268 		    (p->p_flag & P_STOPPED_SIG) != 0) {
1269 			PROC_SLOCK(p);
1270 			report = (p->p_suspcount == p->p_numthreads &&
1271 			    ((p->p_flag & P_WAITED) == 0));
1272 			PROC_SUNLOCK(p);
1273 			if (report) {
1274 				report_alive_proc(td, p, siginfo, status,
1275 				    options, CLD_STOPPED);
1276 				return (0);
1277 			}
1278 		}
1279 		if ((options & WCONTINUED) != 0 &&
1280 		    (p->p_flag & P_CONTINUED) != 0) {
1281 			report_alive_proc(td, p, siginfo, status, options,
1282 			    CLD_CONTINUED);
1283 			return (0);
1284 		}
1285 		PROC_UNLOCK(p);
1286 	}
1287 
1288 	/*
1289 	 * Look in the orphans list too, to allow the parent to
1290 	 * collect it's child exit status even if child is being
1291 	 * debugged.
1292 	 *
1293 	 * Debugger detaches from the parent upon successful
1294 	 * switch-over from parent to child.  At this point due to
1295 	 * re-parenting the parent loses the child to debugger and a
1296 	 * wait4(2) call would report that it has no children to wait
1297 	 * for.  By maintaining a list of orphans we allow the parent
1298 	 * to successfully wait until the child becomes a zombie.
1299 	 */
1300 	if (nfound == 0) {
1301 		LIST_FOREACH(p, &q->p_orphans, p_orphan) {
1302 			ret = proc_to_reap(td, p, idtype, id, NULL, options,
1303 			    NULL, NULL, 1);
1304 			if (ret != 0) {
1305 				KASSERT(ret != -1, ("reaped an orphan (pid %d)",
1306 				    (int)td->td_retval[0]));
1307 				PROC_UNLOCK(p);
1308 				nfound++;
1309 				break;
1310 			}
1311 		}
1312 	}
1313 	if (nfound == 0) {
1314 		sx_xunlock(&proctree_lock);
1315 		return (ECHILD);
1316 	}
1317 	if (options & WNOHANG) {
1318 		sx_xunlock(&proctree_lock);
1319 		td->td_retval[0] = 0;
1320 		return (0);
1321 	}
1322 	PROC_LOCK(q);
1323 	if (q->p_flag & P_STATCHILD) {
1324 		q->p_flag &= ~P_STATCHILD;
1325 		PROC_UNLOCK(q);
1326 		goto loop_locked;
1327 	}
1328 	sx_xunlock(&proctree_lock);
1329 	error = msleep(q, &q->p_mtx, PWAIT | PCATCH | PDROP, "wait", 0);
1330 	if (error)
1331 		return (error);
1332 	goto loop;
1333 }
1334 
1335 void
1336 proc_add_orphan(struct proc *child, struct proc *parent)
1337 {
1338 
1339 	sx_assert(&proctree_lock, SX_XLOCKED);
1340 	KASSERT((child->p_flag & P_TRACED) != 0,
1341 	    ("proc_add_orphan: not traced"));
1342 
1343 	if (LIST_EMPTY(&parent->p_orphans)) {
1344 		child->p_treeflag |= P_TREE_FIRST_ORPHAN;
1345 		LIST_INSERT_HEAD(&parent->p_orphans, child, p_orphan);
1346 	} else {
1347 		LIST_INSERT_AFTER(LIST_FIRST(&parent->p_orphans),
1348 		    child, p_orphan);
1349 	}
1350 	child->p_treeflag |= P_TREE_ORPHANED;
1351 }
1352 
1353 /*
1354  * Make process 'parent' the new parent of process 'child'.
1355  * Must be called with an exclusive hold of proctree lock.
1356  */
1357 void
1358 proc_reparent(struct proc *child, struct proc *parent, bool set_oppid)
1359 {
1360 
1361 	sx_assert(&proctree_lock, SX_XLOCKED);
1362 	PROC_LOCK_ASSERT(child, MA_OWNED);
1363 	if (child->p_pptr == parent)
1364 		return;
1365 
1366 	PROC_LOCK(child->p_pptr);
1367 	sigqueue_take(child->p_ksi);
1368 	PROC_UNLOCK(child->p_pptr);
1369 	LIST_REMOVE(child, p_sibling);
1370 	LIST_INSERT_HEAD(&parent->p_children, child, p_sibling);
1371 
1372 	proc_clear_orphan(child);
1373 	if ((child->p_flag & P_TRACED) != 0) {
1374 		proc_add_orphan(child, child->p_pptr);
1375 	}
1376 
1377 	child->p_pptr = parent;
1378 	if (set_oppid)
1379 		child->p_oppid = parent->p_pid;
1380 }
1381