/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1982, 1986, 1989, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "opt_ddb.h"
#include "opt_ktrace.h"

#define EXTERR_CATEGORY EXTERR_CAT_PROCEXIT
#include <sys/systm.h>
#include <sys/acct.h>           /* for acct_process() function prototype */
#include <sys/capsicum.h>
#include <sys/eventhandler.h>
#include <sys/exterrvar.h>
#include <sys/filedesc.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/procdesc.h>
#include <sys/ptrace.h>
#include <sys/racct.h>
#include <sys/resourcevar.h>
#include <sys/sbuf.h>
#include <sys/sched.h>
#include <sys/sdt.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <sys/signalvar.h>
#include <sys/sx.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/syslog.h>
#include <sys/sysproto.h>
#include <sys/timers.h>
#include <sys/tty.h>
#include <sys/umtxvar.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>
#include <sys/wait.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif

#include <security/audit/audit.h>
#include <security/mac/mac_framework.h>

#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_page.h>
#include <vm/uma.h>

#ifdef KDTRACE_HOOKS
#include <sys/dtrace_bsd.h>
dtrace_execexit_func_t  dtrace_fasttrap_exit;
#endif

SDT_PROVIDER_DECLARE(proc);
SDT_PROBE_DEFINE1(proc, , , exit, "int");

static int kern_kill_on_dbg_exit = 1;
SYSCTL_INT(_kern, OID_AUTO, kill_on_debugger_exit, CTLFLAG_RWTUN,
    &kern_kill_on_dbg_exit, 0,
    "Kill ptraced processes when debugger exits");

static bool kern_wait_dequeue_sigchld = 1;
SYSCTL_BOOL(_kern, OID_AUTO, wait_dequeue_sigchld, CTLFLAG_RWTUN,
    &kern_wait_dequeue_sigchld, 0,
    "Dequeue SIGCHLD on wait(2) for live process");

struct proc *
proc_realparent(struct proc *child)
{
        struct proc *p, *parent;

        sx_assert(&proctree_lock, SX_LOCKED);
        if ((child->p_treeflag & P_TREE_ORPHANED) == 0)
                return (child->p_pptr->p_pid == child->p_oppid ?
                    child->p_pptr : child->p_reaper);
        for (p = child; (p->p_treeflag & P_TREE_FIRST_ORPHAN) == 0;) {
                /* Cannot use LIST_PREV(), since the list head is not known. */
                p = __containerof(p->p_orphan.le_prev, struct proc,
                    p_orphan.le_next);
                KASSERT((p->p_treeflag & P_TREE_ORPHANED) != 0,
                    ("missing P_ORPHAN %p", p));
        }
        parent = __containerof(p->p_orphan.le_prev, struct proc,
            p_orphans.lh_first);
        KASSERT(child->p_pptr != parent,
            ("proc %d %p orphaned but parent %d %p is realparent",
            child->p_pid, child, parent->p_pid, parent));
        return (parent);
}

static void
reaper_clear(struct proc *p, struct proc *rp)
{
        struct proc *p1;
        bool clear;

        sx_assert(&proctree_lock, SX_XLOCKED);
        LIST_REMOVE(p, p_reapsibling);
        if (p->p_reapsubtree == 1)
                return;
        clear = true;
        LIST_FOREACH(p1, &rp->p_reaplist, p_reapsibling) {
                if (p1->p_reapsubtree == p->p_reapsubtree) {
                        clear = false;
                        break;
                }
        }
        if (clear)
                proc_id_clear(PROC_ID_REAP, p->p_reapsubtree);
}

void
reaper_abandon_children(struct proc *p, bool exiting)
{
        struct proc *p1, *p2, *ptmp;

        sx_assert(&proctree_lock, SX_XLOCKED);
        KASSERT(p != initproc, ("reaper_abandon_children for initproc"));
        if ((p->p_treeflag & P_TREE_REAPER) == 0)
                return;
        p1 = p->p_reaper;
        LIST_FOREACH_SAFE(p2, &p->p_reaplist, p_reapsibling, ptmp) {
                reaper_clear(p2, p);
                p2->p_reaper = p1;
                p2->p_reapsubtree = p->p_reapsubtree;
                LIST_INSERT_HEAD(&p1->p_reaplist, p2, p_reapsibling);
                if (exiting && p2->p_pptr == p) {
                        PROC_LOCK(p2);
                        proc_reparent(p2, p1, true);
                        PROC_UNLOCK(p2);
                }
        }
        KASSERT(LIST_EMPTY(&p->p_reaplist), ("p_reaplist not empty"));
        p->p_treeflag &= ~P_TREE_REAPER;
}

void
proc_clear_orphan(struct proc *p)
{
        struct proc *p1;

        sx_assert(&proctree_lock, SA_XLOCKED);
        if ((p->p_treeflag & P_TREE_ORPHANED) == 0)
                return;
        if ((p->p_treeflag & P_TREE_FIRST_ORPHAN) != 0) {
                p1 = LIST_NEXT(p, p_orphan);
                if (p1 != NULL)
                        p1->p_treeflag |= P_TREE_FIRST_ORPHAN;
                p->p_treeflag &= ~P_TREE_FIRST_ORPHAN;
        }
        LIST_REMOVE(p, p_orphan);
        p->p_treeflag &= ~P_TREE_ORPHANED;
}

void
exit_onexit(struct proc *p)
{
        MPASS(p->p_numthreads == 1);
        umtx_thread_exit(FIRST_THREAD_IN_PROC(p));
}

/*
 * exit -- death of process.
 */
int
sys__exit(struct thread *td, struct _exit_args *uap)
{
        kern_exit(td, uap->rval, 0);
        return (0);
}

void
proc_set_p2_wexit(struct proc *p)
{
        PROC_LOCK_ASSERT(p, MA_OWNED);
        p->p_flag2 |= P2_WEXIT;
}

static void
ast_async_exit(struct thread *td, int asts)
{
        struct proc *p;

        p = td->td_proc;
        if ((p->p_flag & P_ASYNC_EXIT) != 0)
                exit1(td, p->p_xexit, p->p_asig);
}

/*
 * The variation on exit1() intended to be used in the syscall
 * handlers.  Unlike exit1(), it might delay the current process exit
 * to ast.  This is needed e.g. when _exit(2) is executed due to the
 * ptrace(PT_SC_REMOTERQ), which must do more work after the syscall
 * handler call.
 */
void
kern_exit(struct thread *td, int rval, int signo)
{
        struct proc *p;

        KASSERT(rval == 0 || signo == 0,
            ("kern_exit rv %d sig %d", rval, signo));

        p = td->td_proc;
        if ((td->td_dbgflags & TDB_SCREMOTEREQ) != 0) {
                PROC_LOCK(p);
                p->p_xexit = rval;
                p->p_asig = signo;
                p->p_flag |= P_ASYNC_EXIT;
                ast_sched(td, TDA_ASYNC_EXIT);
                PROC_UNLOCK(p);
                return;
        }
        if ((p->p_flag & P_ASYNC_EXIT) != 0) {
                rval = p->p_xexit;
                signo = p->p_asig;
        }
        exit1(td, rval, signo);
}

/*
 * Exit: deallocate address space and other resources, change proc state to
 * zombie, and unlink proc from allproc and parent's lists.  Save exit status
 * and rusage for wait().  Check for child processes and orphan them.
 */
void
exit1(struct thread *td, int rval, int signo)
{
        struct proc *p, *nq, *q, *t;
        struct thread *tdt;
        ksiginfo_t *ksi, *ksi1;
        int signal_parent;

        mtx_assert(&Giant, MA_NOTOWNED);
        KASSERT(rval == 0 || signo == 0, ("exit1 rv %d sig %d", rval, signo));
        MPASS((td->td_dbgflags & TDB_SCREMOTEREQ) == 0);
        TSPROCEXIT(td->td_proc->p_pid);

        p = td->td_proc;
        /*
         * In case we're rebooting we just let init die in order to
         * work around an issues where pid 1 might get a fatal signal.
         * For instance, if network interface serving NFS root is
         * going down due to reboot, page-in requests for text are
         * failing.
         */
        if (p == initproc && rebooting == 0) {
                printf("init died (signal %d, exit %d)\n", signo, rval);
                panic("Going nowhere without my init!");
        }

        /*
         * Process deferred operations, designated with ASTF_KCLEAR.
         * For instance, we need to deref SU mp, since the thread does
         * not return to userspace, and wait for geom to stabilize.
         */
        ast_kclear(td);

        /*
         * MUST abort all other threads before proceeding past here.
         */
        PROC_LOCK(p);
        proc_set_p2_wexit(p);

        /*
         * First check if some other thread or external request got
         * here before us.  If so, act appropriately: exit or suspend.
         * We must ensure that stop requests are handled before we set
         * P_WEXIT.
         */
        thread_suspend_check(0);
        while (p->p_flag & P_HADTHREADS) {
                /*
                 * Kill off the other threads. This requires
                 * some co-operation from other parts of the kernel
                 * so it may not be instantaneous.  With this state set
                 * any thread attempting to interruptibly
                 * sleep will return immediately with EINTR or EWOULDBLOCK
                 * which will hopefully force them to back out to userland
                 * freeing resources as they go.  Any thread attempting
                 * to return to userland will thread_exit() from ast().
                 * thread_exit() will unsuspend us when the last of the
                 * other threads exits.
                 * If there is already a thread singler after resumption,
                 * calling thread_single() will fail; in that case, we just
                 * re-check all suspension request, the thread should
                 * either be suspended there or exit.
                 */
                if (!thread_single(p, SINGLE_EXIT))
                        /*
                         * All other activity in this process is now
                         * stopped.  Threading support has been turned
                         * off.
                         */
                        break;
                /*
                 * Recheck for new stop or suspend requests which
                 * might appear while process lock was dropped in
                 * thread_single().
                 */
                thread_suspend_check(0);
        }
        KASSERT(p->p_numthreads == 1,
            ("exit1: proc %p exiting with %d threads", p, p->p_numthreads));
        racct_sub(p, RACCT_NTHR, 1);

        /* Let event handler change exit status */
        p->p_xexit = rval;
        p->p_xsig = signo;

        /*
         * Ignore any pending request to stop due to a stop signal.
         * Once P_WEXIT is set, future requests will be ignored as
         * well.
         */
        p->p_flag &= ~P_STOPPED_SIG;
        KASSERT(!P_SHOULDSTOP(p), ("exiting process is stopped"));

        /* Note that we are exiting. */
        p->p_flag |= P_WEXIT;

        /*
         * Wait for any processes that have a hold on our vmspace to
         * release their reference.
         */
        while (p->p_lock > 0)
                msleep(&p->p_lock, &p->p_mtx, PWAIT, "exithold", 0);

        MPASS(p->p_execblock == 0);
        PROC_UNLOCK(p);
        /* Drain the limit callout while we don't have the proc locked */
        callout_drain(&p->p_limco);

#ifdef AUDIT
        /*
         * The Sun BSM exit token contains two components: an exit status as
         * passed to exit(), and a return value to indicate what sort of exit
         * it was.  The exit status is WEXITSTATUS(rv), but it's not clear
         * what the return value is.
         */
        AUDIT_ARG_EXIT(rval, 0);
        AUDIT_SYSCALL_EXIT(0, td);
#endif

        /* Are we a task leader with peers? */
        if (p->p_peers != NULL && p == p->p_leader) {
                mtx_lock(&ppeers_lock);
                q = p->p_peers;
                while (q != NULL) {
                        PROC_LOCK(q);
                        kern_psignal(q, SIGKILL);
                        PROC_UNLOCK(q);
                        q = q->p_peers;
                }
                while (p->p_peers != NULL)
                        msleep(p, &ppeers_lock, PWAIT, "exit1", 0);
                mtx_unlock(&ppeers_lock);
        }

        itimers_exit(p);

        /*
         * Check if any loadable modules need anything done at process exit.
         * E.g. SYSV IPC stuff.
         * Event handler could change exit status.
         * XXX what if one of these generates an error?
         */
        EVENTHANDLER_DIRECT_INVOKE(process_exit, p);

        /*
         * If parent is waiting for us to exit or exec,
         * P_PPWAIT is set; we will wakeup the parent below.
         */
        PROC_LOCK(p);
        stopprofclock(p);
        p->p_ptevents = 0;

        /*
         * Stop the real interval timer.  If the handler is currently
         * executing, prevent it from rearming itself and let it finish.
         */
        p->p_flag2 &= ~P2_ITSTOPPED;
        if (timevalisset(&p->p_realtimer.it_value) &&
            callout_stop(&p->p_itcallout) == 0) {
                timevalclear(&p->p_realtimer.it_interval);
                PROC_UNLOCK(p);
                callout_drain(&p->p_itcallout);
        } else {
                PROC_UNLOCK(p);
        }

        if (p->p_sysent->sv_onexit != NULL)
                p->p_sysent->sv_onexit(p);
        seltdfini(td);

        /*
         * Reset any sigio structures pointing to us as a result of
         * F_SETOWN with our pid.  The P_WEXIT flag interlocks with fsetown().
         */
        funsetownlst(&p->p_sigiolst);

        /*
         * Close open files and release open-file table.
         * This may block!
         */
        pdescfree(td);
        fdescfree(td);

        /*
         * Remove ourself from our leader's peer list and wake our leader.
         */
        if (p->p_leader->p_peers != NULL) {
                mtx_lock(&ppeers_lock);
                if (p->p_leader->p_peers != NULL) {
                        q = p->p_leader;
                        while (q->p_peers != p)
                                q = q->p_peers;
                        q->p_peers = p->p_peers;
                        wakeup(p->p_leader);
                }
                mtx_unlock(&ppeers_lock);
        }

        exec_free_abi_mappings(p);
        vmspace_exit(td);
        (void)acct_process(td);

#ifdef KTRACE
        ktrprocexit(td);
#endif
        /*
         * Release reference to text vnode etc
         */
        if (p->p_textvp != NULL) {
                vrele(p->p_textvp);
                p->p_textvp = NULL;
        }
        if (p->p_textdvp != NULL) {
                vrele(p->p_textdvp);
                p->p_textdvp = NULL;
        }
        if (p->p_binname != NULL) {
                free(p->p_binname, M_PARGS);
                p->p_binname = NULL;
        }

        /*
         * Release our limits structure.
         */
        lim_free(p->p_limit);
        p->p_limit = NULL;

        tidhash_remove(td);

        /*
         * Call machine-dependent code to release any
         * machine-dependent resources other than the address space.
         * The address space is released by "vmspace_exitfree(p)" in
         * vm_waitproc().
         */
        cpu_exit(td);

        WITNESS_WARN(WARN_PANIC, NULL, "process (pid %d) exiting", p->p_pid);

        /*
         * Remove from allproc. It still sits in the hash.
         */
        sx_xlock(&allproc_lock);
        LIST_REMOVE(p, p_list);

#ifdef DDB
        /*
         * Used by ddb's 'ps' command to find this process via the
         * pidhash.
         */
        p->p_list.le_prev = NULL;
#endif
        prison_proc_unlink(p->p_ucred->cr_prison, p);
        sx_xunlock(&allproc_lock);

        sx_xlock(&proctree_lock);
        if ((p->p_flag & (P_TRACED | P_PPWAIT | P_PPTRACE)) != 0) {
                PROC_LOCK(p);
                p->p_flag &= ~(P_TRACED | P_PPWAIT | P_PPTRACE);
                PROC_UNLOCK(p);
        }

        /*
         * killjobc() might drop and re-acquire proctree_lock to
         * revoke control tty if exiting process was a session leader.
         */
        killjobc();

        /*
         * Reparent all children processes:
         * - traced ones to the original parent (or init if we are that parent)
         * - the rest to init
         */
        q = LIST_FIRST(&p->p_children);
        if (q != NULL)          /* only need this if any child is S_ZOMB */
                wakeup(q->p_reaper);
        for (; q != NULL; q = nq) {
                nq = LIST_NEXT(q, p_sibling);
                ksi = ksiginfo_alloc(M_WAITOK);
                PROC_LOCK(q);
                q->p_sigparent = SIGCHLD;

                if ((q->p_flag & P_TRACED) == 0) {
                        proc_reparent(q, q->p_reaper, true);
                        if (q->p_state == PRS_ZOMBIE) {
                                /*
                                 * Inform reaper about the reparented
                                 * zombie, since wait(2) has something
                                 * new to report.  Guarantee queueing
                                 * of the SIGCHLD signal, similar to
                                 * the _exit() behaviour, by providing
                                 * our ksiginfo.  Ksi is freed by the
                                 * signal delivery.
                                 */
                                if (q->p_ksi == NULL) {
                                        ksi1 = NULL;
                                } else {
                                        ksiginfo_copy(q->p_ksi, ksi);
                                        ksi->ksi_flags |= KSI_INS;
                                        ksi1 = ksi;
                                        ksi = NULL;
                                }
                                PROC_LOCK(q->p_reaper);
                                pksignal(q->p_reaper, SIGCHLD, ksi1);
                                PROC_UNLOCK(q->p_reaper);
                        } else if (q->p_pdeathsig > 0) {
                                /*
                                 * The child asked to received a signal
                                 * when we exit.
                                 */
                                kern_psignal(q, q->p_pdeathsig);
                        }
                } else {
                        /*
                         * Traced processes are killed by default
                         * since their existence means someone is
                         * screwing up.
                         */
                        t = proc_realparent(q);
                        if (t == p) {
                                proc_reparent(q, q->p_reaper, true);
                        } else {
                                PROC_LOCK(t);
                                proc_reparent(q, t, true);
                                PROC_UNLOCK(t);
                        }
                        /*
                         * Since q was found on our children list, the
                         * proc_reparent() call moved q to the orphan
                         * list due to present P_TRACED flag. Clear
                         * orphan link for q now while q is locked.
                         */
                        proc_clear_orphan(q);
                        q->p_flag &= ~P_TRACED;
                        q->p_flag2 &= ~P2_PTRACE_FSTP;
                        q->p_ptevents = 0;
                        p->p_xthread = NULL;
                        FOREACH_THREAD_IN_PROC(q, tdt) {
                                tdt->td_dbgflags &= ~(TDB_SUSPEND | TDB_XSIG |
                                    TDB_FSTP);
                                tdt->td_xsig = 0;
                        }
                        if (kern_kill_on_dbg_exit) {
                                q->p_flag &= ~P_STOPPED_TRACE;
                                kern_psignal(q, SIGKILL);
                        } else if ((q->p_flag & (P_STOPPED_TRACE |
                            P_STOPPED_SIG)) != 0) {
                                sigqueue_delete_proc(q, SIGTRAP);
                                ptrace_unsuspend(q);
                        }
                }
                PROC_UNLOCK(q);
                if (ksi != NULL)
                        ksiginfo_free(ksi);
        }

        /*
         * Also get rid of our orphans.
         */
        while ((q = LIST_FIRST(&p->p_orphans)) != NULL) {
                PROC_LOCK(q);
                KASSERT(q->p_oppid == p->p_pid,
                    ("orphan %p of %p has unexpected oppid %d", q, p,
                    q->p_oppid));
                q->p_oppid = q->p_reaper->p_pid;

                /*
                 * If we are the real parent of this process
                 * but it has been reparented to a debugger, then
                 * check if it asked for a signal when we exit.
                 */
                if (q->p_pdeathsig > 0)
                        kern_psignal(q, q->p_pdeathsig);
                CTR2(KTR_PTRACE, "exit: pid %d, clearing orphan %d", p->p_pid,
                    q->p_pid);
                proc_clear_orphan(q);
                PROC_UNLOCK(q);
        }

#ifdef KDTRACE_HOOKS
        if (SDT_PROBES_ENABLED()) {
                int reason = CLD_EXITED;
                if (WCOREDUMP(signo))
                        reason = CLD_DUMPED;
                else if (WIFSIGNALED(signo))
                        reason = CLD_KILLED;
                SDT_PROBE1(proc, , , exit, reason);
        }
#endif

        /* Save exit status. */
        PROC_LOCK(p);
        p->p_xthread = td;

        if (p->p_sysent->sv_ontdexit != NULL)
                p->p_sysent->sv_ontdexit(td);

#ifdef KDTRACE_HOOKS
        /*
         * Tell the DTrace fasttrap provider about the exit if it
         * has declared an interest.
         */
        if (dtrace_fasttrap_exit)
                dtrace_fasttrap_exit(p);
#endif

        /*
         * Notify interested parties of our demise.
         */
        KNOTE_LOCKED(p->p_klist, NOTE_EXIT);

        /*
         * If this is a process with a descriptor, we may not need to deliver
         * a signal to the parent.  proctree_lock is held over
         * procdesc_exit() to serialize concurrent calls to close() and
         * exit().
         */
        signal_parent = 0;
        procdesc_exit(p);
        if (p->p_procdesc == NULL) {
                /*
                 * Notify parent that we're gone.  If parent has the
                 * PS_NOCLDWAIT flag set, or if the handler is set to SIG_IGN,
                 * notify process 1 instead (and hope it will handle this
                 * situation).
                 */
                PROC_LOCK(p->p_pptr);
                mtx_lock(&p->p_pptr->p_sigacts->ps_mtx);
                if (p->p_pptr->p_sigacts->ps_flag &
                    (PS_NOCLDWAIT | PS_CLDSIGIGN)) {
                        struct proc *pp;

                        mtx_unlock(&p->p_pptr->p_sigacts->ps_mtx);
                        pp = p->p_pptr;
                        PROC_UNLOCK(pp);
                        proc_reparent(p, p->p_reaper, true);
                        p->p_sigparent = SIGCHLD;
                        PROC_LOCK(p->p_pptr);

                        /*
                         * Notify parent, so in case he was wait(2)ing or
                         * executing waitpid(2) with our pid, he will
                         * continue.
                         */
                        wakeup(pp);
                } else
                        mtx_unlock(&p->p_pptr->p_sigacts->ps_mtx);

                if (p->p_pptr == p->p_reaper || p->p_pptr == initproc) {
                        signal_parent = 1;
                } else if (p->p_sigparent != 0) {
                        if (p->p_sigparent == SIGCHLD) {
                                signal_parent = 1;
                        } else { /* LINUX thread */
                                signal_parent = 2;
                        }
                }
        } else
                PROC_LOCK(p->p_pptr);
        sx_xunlock(&proctree_lock);

        if (signal_parent == 1) {
                childproc_exited(p);
        } else if (signal_parent == 2) {
                kern_psignal(p->p_pptr, p->p_sigparent);
        }

        /* Tell the prison that we are gone. */
        prison_proc_free(p->p_ucred->cr_prison);

        /*
         * The state PRS_ZOMBIE prevents other processes from sending
         * signal to the process, to avoid memory leak, we free memory
         * for signal queue at the time when the state is set.
         */
        sigqueue_flush(&p->p_sigqueue);
        sigqueue_flush(&td->td_sigqueue);

        /*
         * We have to wait until after acquiring all locks before
         * changing p_state.  We need to avoid all possible context
         * switches (including ones from blocking on a mutex) while
         * marked as a zombie.  We also have to set the zombie state
         * before we release the parent process' proc lock to avoid
         * a lost wakeup.  So, we first call wakeup, then we grab the
         * sched lock, update the state, and release the parent process'
         * proc lock.
         */
        wakeup(p->p_pptr);
        cv_broadcast(&p->p_pwait);
        sched_exit(p->p_pptr, td);
        PROC_SLOCK(p);
        p->p_state = PRS_ZOMBIE;
        PROC_UNLOCK(p->p_pptr);

        /*
         * Save our children's rusage information in our exit rusage.
         */
        PROC_STATLOCK(p);
        ruadd(&p->p_ru, &p->p_rux, &p->p_stats->p_cru, &p->p_crux);
        PROC_STATUNLOCK(p);

        /*
         * Make sure the scheduler takes this thread out of its tables etc.
         * This will also release this thread's reference to the ucred.
         * Other thread parts to release include pcb bits and such.
         */
        thread_exit();
}

#ifndef _SYS_SYSPROTO_H_
struct abort2_args {
        char *why;
        int nargs;
        void **args;
};
#endif

int
sys_abort2(struct thread *td, struct abort2_args *uap)
{
        void *uargs[16];
        void **uargsp;
        int error, nargs;

        nargs = uap->nargs;
        if (nargs < 0 || nargs > nitems(uargs))
                nargs = -1;
        uargsp = NULL;
        if (nargs > 0) {
                if (uap->args != NULL) {
                        error = copyin(uap->args, uargs,
                            nargs * sizeof(void *));
                        if (error != 0)
                                nargs = -1;
                        else
                                uargsp = uargs;
                } else
                        nargs = -1;
        }
        return (kern_abort2(td, uap->why, nargs, uargsp));
}

/*
 * kern_abort2()
 * Arguments:
 *  why - user pointer to why
 *  nargs - number of arguments copied or -1 if an error occurred in copying
 *  args - pointer to an array of pointers in kernel format
 */
int
kern_abort2(struct thread *td, const char *why, int nargs, void **uargs)
{
        struct proc *p = td->td_proc;
        struct sbuf *sb;
        int error, i, sig;

        /*
         * Do it right now so we can log either proper call of abort2(), or
         * note, that invalid argument was passed. 512 is big enough to
         * handle 16 arguments' descriptions with additional comments.
         */
        sb = sbuf_new(NULL, NULL, 512, SBUF_FIXEDLEN);
        sbuf_clear(sb);
        sbuf_printf(sb, "%s(pid %d uid %d) aborted: ",
            p->p_comm, p->p_pid, td->td_ucred->cr_uid);
        /*
         * Since we can't return from abort2(), send SIGKILL in cases, where
         * abort2() was called improperly
         */
        sig = SIGKILL;
        /* Prevent from DoSes from user-space. */
        if (nargs == -1)
                goto out;
        KASSERT(nargs >= 0 && nargs <= 16, ("called with too many args (%d)",
            nargs));
        /*
         * Limit size of 'reason' string to 128. Will fit even when
         * maximal number of arguments was chosen to be logged.
         */
        if (why != NULL) {
                error = sbuf_copyin(sb, why, 128);
                if (error < 0)
                        goto out;
        } else {
                sbuf_cat(sb, "(null)");
        }
        if (nargs > 0) {
                sbuf_putc(sb, '(');
                for (i = 0; i < nargs; i++)
                        sbuf_printf(sb, "%s%p", i == 0 ? "" : ", ", uargs[i]);
                sbuf_putc(sb, ')');
        }
        /*
         * Final stage: arguments were proper, string has been
         * successfully copied from userspace, and copying pointers
         * from user-space succeed.
         */
        sig = SIGABRT;
out:
        if (sig == SIGKILL) {
                sbuf_trim(sb);
                sbuf_cat(sb, " (Reason text inaccessible)");
        }
        sbuf_cat(sb, "\n");
        sbuf_finish(sb);
        log(LOG_INFO, "%s", sbuf_data(sb));
        sbuf_delete(sb);
        PROC_LOCK(p);
        sigexit(td, sig);
        return (0);
}

#ifdef COMPAT_43
/*
 * The dirty work is handled by kern_wait().
 */
int
owait(struct thread *td, struct owait_args *uap __unused)
{
        int error, status;

        error = kern_wait(td, WAIT_ANY, &status, 0, NULL);
        if (error == 0)
                td->td_retval[1] = status;
        return (error);
}
#endif /* COMPAT_43 */

/*
 * The dirty work is handled by kern_wait().
 */
int
sys_wait4(struct thread *td, struct wait4_args *uap)
{
        struct rusage ru, *rup;
        int error, status;

        if (uap->rusage != NULL)
                rup = &ru;
        else
                rup = NULL;
        error = kern_wait(td, uap->pid, &status, uap->options, rup);
        if (uap->status != NULL && error == 0 && td->td_retval[0] != 0)
                error = copyout(&status, uap->status, sizeof(status));
        if (uap->rusage != NULL && error == 0 && td->td_retval[0] != 0)
                error = copyout(&ru, uap->rusage, sizeof(struct rusage));
        return (error);
}

int
sys_wait6(struct thread *td, struct wait6_args *uap)
{
        struct __wrusage wru, *wrup;
        siginfo_t si, *sip;
        idtype_t idtype;
        id_t id;
        int error, status;

        idtype = uap->idtype;
        id = uap->id;

        if (uap->wrusage != NULL)
                wrup = &wru;
        else
                wrup = NULL;

        if (uap->info != NULL) {
                sip = &si;
                bzero(sip, sizeof(*sip));
        } else
                sip = NULL;

        /*
         *  We expect all callers of wait6() to know about WEXITED and
         *  WTRAPPED.
         */
        error = kern_wait6(td, idtype, id, &status, uap->options, wrup, sip);

        if (uap->status != NULL && error == 0 && td->td_retval[0] != 0)
                error = copyout(&status, uap->status, sizeof(status));
        if (uap->wrusage != NULL && error == 0 && td->td_retval[0] != 0)
                error = copyout(&wru, uap->wrusage, sizeof(wru));
        if (uap->info != NULL && error == 0)
                error = copyout(&si, uap->info, sizeof(si));
        return (error);
}

int
sys_pdwait(struct thread *td, struct pdwait_args *uap)
{
        struct __wrusage wru, *wrup;
        siginfo_t si, *sip;
        int error, status;

        wrup = uap->wrusage != NULL ? &wru : NULL;

        if (uap->info != NULL) {
                sip = &si;
                bzero(sip, sizeof(*sip));
        } else {
                sip = NULL;
        }

        error = kern_pdwait(td, uap->fd, &status, uap->options, wrup, sip);

        if (uap->status != NULL && error == 0)
                error = copyout(&status, uap->status, sizeof(status));
        if (uap->wrusage != NULL && error == 0)
                error = copyout(&wru, uap->wrusage, sizeof(wru));
        if (uap->info != NULL && error == 0)
                error = copyout(&si, uap->info, sizeof(si));
        return (error);
}

/*
 * Reap the remains of a zombie process and optionally return status and
 * rusage.  Asserts and will release both the proctree_lock and the process
 * lock as part of its work.
 */
void
proc_reap(struct thread *td, struct proc *p, int *status, int options)
{
        struct proc *q, *t;

        sx_assert(&proctree_lock, SA_XLOCKED);
        PROC_LOCK_ASSERT(p, MA_OWNED);
        KASSERT(p->p_state == PRS_ZOMBIE, ("proc_reap: !PRS_ZOMBIE"));

        mtx_spin_wait_unlocked(&p->p_slock);

        q = td->td_proc;

        if (status != NULL)
                *status = KW_EXITCODE(p->p_xexit, p->p_xsig);
        if ((options & WNOWAIT) != 0) {
                /*
                 *  Only poll, returning the status.  Caller does not wish to
                 * release the proc struct just yet.
                 */
                PROC_UNLOCK(p);
                sx_xunlock(&proctree_lock);
                return;
        }

        PROC_LOCK(q);
        sigqueue_take(p->p_ksi);
        PROC_UNLOCK(q);

        /*
         * If we got the child via a ptrace 'attach', we need to give it back
         * to the old parent.
         */
        if (p->p_oppid != p->p_pptr->p_pid) {
                PROC_UNLOCK(p);
                t = proc_realparent(p);
                PROC_LOCK(t);
                PROC_LOCK(p);
                CTR2(KTR_PTRACE,
                    "wait: traced child %d moved back to parent %d", p->p_pid,
                    t->p_pid);
                proc_reparent(p, t, false);
                PROC_UNLOCK(p);
                pksignal(t, SIGCHLD, p->p_ksi);
                wakeup(t);
                cv_broadcast(&p->p_pwait);
                PROC_UNLOCK(t);
                sx_xunlock(&proctree_lock);
                return;
        }
        PROC_UNLOCK(p);

        /*
         * Remove other references to this process to ensure we have an
         * exclusive reference.
         */
        sx_xlock(PIDHASHLOCK(p->p_pid));
        LIST_REMOVE(p, p_hash);
        sx_xunlock(PIDHASHLOCK(p->p_pid));
        LIST_REMOVE(p, p_sibling);
        reaper_abandon_children(p, true);
        reaper_clear(p, p->p_reaper);
        PROC_LOCK(p);
        proc_clear_orphan(p);
        PROC_UNLOCK(p);
        leavepgrp(p);
        if (p->p_procdesc != NULL)
                procdesc_reap(p);
        else
                proc_id_clear(PROC_ID_PID, p->p_pid);
        sx_xunlock(&proctree_lock);

        PROC_LOCK(p);
        KNOTE_LOCKED(p->p_klist, NOTE_REAP);
        knlist_detach(p->p_klist);
        p->p_klist = NULL;
        PROC_UNLOCK(p);

        /*
         * Removal from allproc list and process group list paired with
         * PROC_LOCK which was executed during that time should guarantee
         * nothing can reach this process anymore. As such further locking
         * is unnecessary.
         */
        p->p_xexit = p->p_xsig = 0;             /* XXX: why? */

        PROC_LOCK(q);
        ruadd(&q->p_stats->p_cru, &q->p_crux, &p->p_ru, &p->p_rux);
        PROC_UNLOCK(q);

        /*
         * Destroy resource accounting information associated with the process.
         */
#ifdef RACCT
        if (racct_enable) {
                PROC_LOCK(p);
                racct_sub(p, RACCT_NPROC, 1);
                PROC_UNLOCK(p);
        }
#endif
        racct_proc_exit(p);

        /*
         * Free credentials, arguments, and sigacts, and decrement the count of
         * processes running with this uid.
         */
        proc_unset_cred(p, true);
        pargs_drop(p->p_args);
        p->p_args = NULL;
        sigacts_free(p->p_sigacts);
        p->p_sigacts = NULL;

        /*
         * Do any thread-system specific cleanups.
         */
        thread_wait(p);

        /*
         * Give vm and machine-dependent layer a chance to free anything that
         * cpu_exit couldn't release while still running in process context.
         */
        vm_waitproc(p);
#ifdef MAC
        mac_proc_destroy(p);
#endif

        KASSERT(FIRST_THREAD_IN_PROC(p),
            ("proc_reap: no residual thread!"));
        PROC_TREE_UNREF(p);
        atomic_add_int(&nprocs, -1);
}

static void
wait_fill_siginfo(struct proc *p, siginfo_t *siginfo)
{
        PROC_LOCK_ASSERT(p, MA_OWNED);

        if (siginfo == NULL)
                return;

        bzero(siginfo, sizeof(*siginfo));
        siginfo->si_errno = 0;

        /*
         * SUSv4 requires that the si_signo value is always
         * SIGCHLD. Obey it despite the rfork(2) interface allows to
         * request other signal for child exit notification.
         */
        siginfo->si_signo = SIGCHLD;

        /*
         *  This is still a rough estimate.  We will fix the cases
         *  TRAPPED, STOPPED, and CONTINUED later.
         */
        if (WCOREDUMP(p->p_xsig)) {
                siginfo->si_code = CLD_DUMPED;
                siginfo->si_status = WTERMSIG(p->p_xsig);
        } else if (WIFSIGNALED(p->p_xsig)) {
                siginfo->si_code = CLD_KILLED;
                siginfo->si_status = WTERMSIG(p->p_xsig);
        } else {
                siginfo->si_code = CLD_EXITED;
                siginfo->si_status = p->p_xexit;
        }

        siginfo->si_pid = p->p_pid;
        siginfo->si_uid = p->p_ucred->cr_uid;

        /*
         * The si_addr field would be useful additional detail, but
         * apparently the PC value may be lost when we reach this
         * point.  bzero() above sets siginfo->si_addr to NULL.
         */
}

static void
wait_fill_wrusage(struct proc *p, struct __wrusage *wrusage)
{
        struct rusage *rup;

        PROC_LOCK_ASSERT(p, MA_OWNED);

        if (wrusage == NULL)
                return;

        rup = &wrusage->wru_self;
        *rup = p->p_ru;
        PROC_STATLOCK(p);
        calcru(p, &rup->ru_utime, &rup->ru_stime);
        PROC_STATUNLOCK(p);

        rup = &wrusage->wru_children;
        *rup = p->p_stats->p_cru;
        calccru(p, &rup->ru_utime, &rup->ru_stime);
}

static int
proc_to_reap(struct thread *td, struct proc *p, idtype_t idtype, id_t id,
    int *status, int options, struct __wrusage *wrusage, siginfo_t *siginfo,
    bool check_only)
{
        sx_assert(&proctree_lock, SA_XLOCKED);

        PROC_LOCK(p);

        switch (idtype) {
        case P_ALL:
                if (p->p_procdesc == NULL ||
                   (p->p_pptr == td->td_proc &&
                   (p->p_flag & P_TRACED) != 0)) {
                        break;
                }

                PROC_UNLOCK(p);
                return (0);
        case P_PID:
                if (p->p_pid != (pid_t)id) {
                        PROC_UNLOCK(p);
                        return (0);
                }
                break;
        case P_PGID:
                if (p->p_pgid != (pid_t)id) {
                        PROC_UNLOCK(p);
                        return (0);
                }
                break;
        case P_SID:
                if (p->p_session->s_sid != (pid_t)id) {
                        PROC_UNLOCK(p);
                        return (0);
                }
                break;
        case P_UID:
                if (p->p_ucred->cr_uid != (uid_t)id) {
                        PROC_UNLOCK(p);
                        return (0);
                }
                break;
        case P_GID:
                if (p->p_ucred->cr_gid != (gid_t)id) {
                        PROC_UNLOCK(p);
                        return (0);
                }
                break;
        case P_JAILID:
                if (p->p_ucred->cr_prison->pr_id != (int)id) {
                        PROC_UNLOCK(p);
                        return (0);
                }
                break;
        /*
         * It seems that the thread structures get zeroed out
         * at process exit.  This makes it impossible to
         * support P_SETID, P_CID or P_CPUID.
         */
        default:
                PROC_UNLOCK(p);
                return (0);
        }

        if (p_canwait(td, p)) {
                PROC_UNLOCK(p);
                return (0);
        }

        if ((options & WEXITED) == 0 && p->p_state == PRS_ZOMBIE) {
                PROC_UNLOCK(p);
                return (0);
        }

        /*
         * This special case handles a kthread spawned by linux_clone
         * (see linux_misc.c).  The linux_wait4 and linux_waitpid
         * functions need to be able to distinguish between waiting
         * on a process and waiting on a thread.  It is a thread if
         * p_sigparent is not SIGCHLD, and the WLINUXCLONE option
         * signifies we want to wait for threads and not processes.
         */
        if ((p->p_sigparent != SIGCHLD) ^
            ((options & WLINUXCLONE) != 0)) {
                PROC_UNLOCK(p);
                return (0);
        }

        wait_fill_siginfo(p, siginfo);

        /*
         * There should be no reason to limit resources usage info to
         * exited processes only.  A snapshot about any resources used
         * by a stopped process may be exactly what is needed.
         */
        wait_fill_wrusage(p, wrusage);

        if (p->p_state == PRS_ZOMBIE && !check_only) {
                proc_reap(td, p, status, options);
                return (-1);
        }
        return (1);
}

int
kern_wait(struct thread *td, pid_t pid, int *status, int options,
    struct rusage *rusage)
{
        struct __wrusage wru, *wrup;
        idtype_t idtype;
        id_t id;
        int ret;

        /*
         * Translate the special pid values into the (idtype, pid)
         * pair for kern_wait6.  The WAIT_MYPGRP case is handled by
         * kern_wait6() on its own.
         */
        if (pid == WAIT_ANY) {
                idtype = P_ALL;
                id = 0;
        } else if (pid < 0) {
                idtype = P_PGID;
                id = (id_t)-pid;
        } else {
                idtype = P_PID;
                id = (id_t)pid;
        }

        if (rusage != NULL)
                wrup = &wru;
        else
                wrup = NULL;

        /*
         * For backward compatibility we implicitly add flags WEXITED
         * and WTRAPPED here.
         */
        options |= WEXITED | WTRAPPED;
        ret = kern_wait6(td, idtype, id, status, options, wrup, NULL);
        if (rusage != NULL)
                *rusage = wru.wru_self;
        return (ret);
}

static void
report_alive_proc(struct thread *td, struct proc *p, siginfo_t *siginfo,
    int *status, int options, int si_code)
{
        bool cont;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        sx_assert(&proctree_lock, SA_XLOCKED);
        MPASS(si_code == CLD_TRAPPED || si_code == CLD_STOPPED ||
            si_code == CLD_CONTINUED);

        cont = si_code == CLD_CONTINUED;
        if ((options & WNOWAIT) == 0) {
                if (cont)
                        p->p_flag &= ~P_CONTINUED;
                else
                        p->p_flag |= P_WAITED;
                if (kern_wait_dequeue_sigchld &&
                    (td->td_proc->p_sysent->sv_flags & SV_SIG_WAITNDQ) == 0) {
                        PROC_LOCK(td->td_proc);
                        sigqueue_take(p->p_ksi);
                        PROC_UNLOCK(td->td_proc);
                }
        }
        sx_xunlock(&proctree_lock);
        if (siginfo != NULL) {
                siginfo->si_code = si_code;
                siginfo->si_status = cont ? SIGCONT : p->p_xsig;
        }
        if (status != NULL)
                *status = cont ? SIGCONT : W_STOPCODE(p->p_xsig);
        PROC_UNLOCK(p);
}

static int
wait6_checkopt(int options)
{
        /* If we don't know the option, just return. */
        if ((options & ~(WUNTRACED | WNOHANG | WCONTINUED | WNOWAIT |
            WEXITED | WTRAPPED | WLINUXCLONE)) != 0)
                return (EXTERROR(EINVAL, "Unknown options %#jx", options));
        if ((options & (WEXITED | WUNTRACED | WCONTINUED | WTRAPPED)) == 0) {
                /*
                 * We will be unable to find any matching processes,
                 * because there are no known events to look for.
                 * Prefer to return error instead of blocking
                 * indefinitely.
                 */
                return (EXTERROR(EINVAL,
                    "Cannot match processes %#jx", options));
        }
        return (0);
}

/*
 * Checks and reports status for alive process, according to the
 * options.  Returns true if the process fits one of the requested
 * options and its status was updated in siginfo.
 *
 * If the process was reported (the function result is true), both the
 * process and proctree locks are unlocked.
 */
static bool
wait6_check_alive(struct thread *td, int options, struct proc *p, int *status,
    siginfo_t *siginfo)
{
        bool report;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        sx_assert(&proctree_lock, SA_XLOCKED);

        if ((options & WTRAPPED) != 0 && (p->p_flag & P_TRACED) != 0) {
                PROC_SLOCK(p);
                report = (p->p_flag & (P_STOPPED_TRACE | P_STOPPED_SIG)) &&
                    p->p_suspcount == p->p_numthreads &&
                    (p->p_flag & P_WAITED) == 0;
                PROC_SUNLOCK(p);
                if (report) {
                        CTR4(KTR_PTRACE,
            "wait: returning trapped pid %d status %#x (xstat %d) xthread %d",
                            p->p_pid, W_STOPCODE(p->p_xsig), p->p_xsig,
                            p->p_xthread != NULL ?
                            p->p_xthread->td_tid : -1);
                        report_alive_proc(td, p, siginfo, status,
                            options, CLD_TRAPPED);
                        return (true);
                }
        }

        if ((options & WUNTRACED) != 0 && (p->p_flag & P_STOPPED_SIG) != 0) {
                PROC_SLOCK(p);
                report = p->p_suspcount == p->p_numthreads &&
                    (p->p_flag & P_WAITED) == 0;
                PROC_SUNLOCK(p);
                if (report) {
                        report_alive_proc(td, p, siginfo, status, options,
                            CLD_STOPPED);
                        return (true);
                }
        }

        if ((options & WCONTINUED) != 0 && (p->p_flag & P_CONTINUED) != 0) {
                report_alive_proc(td, p, siginfo, status, options,
                    CLD_CONTINUED);
                return (true);
        }

        return (false);
}

int
kern_wait6(struct thread *td, idtype_t idtype, id_t id, int *status,
    int options, struct __wrusage *wrusage, siginfo_t *siginfo)
{
        struct proc *p, *q;
        pid_t pid;
        int error, nfound, ret;

        AUDIT_ARG_VALUE((int)idtype);   /* XXX - This is likely wrong! */
        AUDIT_ARG_PID((pid_t)id);       /* XXX - This may be wrong! */
        AUDIT_ARG_VALUE(options);

        q = td->td_proc;

        if ((pid_t)id == WAIT_MYPGRP && (idtype == P_PID || idtype == P_PGID)) {
                PROC_LOCK(q);
                id = (id_t)q->p_pgid;
                PROC_UNLOCK(q);
                idtype = P_PGID;
        }

        error = wait6_checkopt(options);
        if (error != 0)
                return (error);
loop:
        if (q->p_flag & P_STATCHILD) {
                PROC_LOCK(q);
                q->p_flag &= ~P_STATCHILD;
                PROC_UNLOCK(q);
        }
        sx_xlock(&proctree_lock);
loop_locked:
        nfound = 0;
        LIST_FOREACH(p, &q->p_children, p_sibling) {
                pid = p->p_pid;
                ret = proc_to_reap(td, p, idtype, id, status, options,
                    wrusage, siginfo, false);
                if (ret == 0)
                        continue;
                else if (ret != 1) {
                        td->td_retval[0] = pid;
                        return (0);
                }

                /*
                 * When running in capsicum(4) mode, make wait(2) ignore
                 * processes created with pdfork(2).  This is because one can
                 * disown them - by passing their process descriptor to another
                 * process - which means it needs to be prevented from touching
                 * them afterwards.
                 */
                if (IN_CAPABILITY_MODE(td) && p->p_procdesc != NULL) {
                        PROC_UNLOCK(p);
                        continue;
                }

                nfound++;
                PROC_LOCK_ASSERT(p, MA_OWNED);

                if (wait6_check_alive(td, options, p, status, siginfo)) {
                        td->td_retval[0] = pid;
                        return (0);
                }

                PROC_UNLOCK(p);
        }

        /*
         * Look in the orphans list too, to allow the parent to
         * collect it's child exit status even if child is being
         * debugged.
         *
         * Debugger detaches from the parent upon successful
         * switch-over from parent to child.  At this point due to
         * re-parenting the parent loses the child to debugger and a
         * wait4(2) call would report that it has no children to wait
         * for.  By maintaining a list of orphans we allow the parent
         * to successfully wait until the child becomes a zombie.
         */
        if (nfound == 0) {
                LIST_FOREACH(p, &q->p_orphans, p_orphan) {
                        ret = proc_to_reap(td, p, idtype, id, NULL, options,
                            NULL, NULL, true);
                        if (ret != 0) {
                                KASSERT(ret != -1, ("reaped an orphan (pid %d)",
                                    (int)td->td_retval[0]));
                                PROC_UNLOCK(p);
                                nfound++;
                                break;
                        }
                }
        }
        if (nfound == 0) {
                sx_xunlock(&proctree_lock);
                return (ECHILD);
        }
        if ((options & WNOHANG) != 0) {
                sx_xunlock(&proctree_lock);
                td->td_retval[0] = 0;
                return (0);
        }
        PROC_LOCK(q);
        if ((q->p_flag & P_STATCHILD) != 0) {
                q->p_flag &= ~P_STATCHILD;
                PROC_UNLOCK(q);
                goto loop_locked;
        }
        sx_xunlock(&proctree_lock);
        error = msleep(q, &q->p_mtx, PWAIT | PCATCH | PDROP, "wait", 0);
        if (error != 0)
                return (error);
        goto loop;
}

int
kern_pdwait(struct thread *td, int fd, int *status,
    int options, struct __wrusage *wrusage, siginfo_t *siginfo)
{
        struct proc *p;
        struct file *fp;
        struct procdesc *pd;
        int error;

        AUDIT_ARG_FD(fd);
        AUDIT_ARG_VALUE(options);

        error = wait6_checkopt(options);
        if (error != 0)
                return (error);

        error = fget_procdesc(td, fd, &cap_pdwait_rights, &fp, &pd, NULL);
        if (error != 0)
                goto exit_unlocked;

        for (;;) {
                sx_xlock(&proctree_lock);
                /* We own a reference on the procdesc file. */
                KASSERT(pd->pd_fpcount > 0,
                    ("closed proc %p procdesc %p pd flags %#x",
                    pd->pd_proc, pd, pd->pd_flags));

                p = pd->pd_proc;
                if (p == NULL) {
                        error = ESRCH;
                        goto exit_tree_locked;
                }
                PROC_LOCK(p);

                error = p_canwait(td, p);
                if (error != 0)
                        break;
                if ((options & WEXITED) == 0 && p->p_state == PRS_ZOMBIE) {
                        error = ESRCH;
                        break;
                }

                wait_fill_siginfo(p, siginfo);
                wait_fill_wrusage(p, wrusage);

                if (p->p_state == PRS_ZOMBIE) {
                        proc_reap(td, p, status, options);
                        goto exit_unlocked;
                }

                if (wait6_check_alive(td, options, p, status, siginfo))
                        goto exit_unlocked;

                if ((options & WNOHANG) != 0) {
                        error = EWOULDBLOCK;
                        break;
                }

                PROC_UNLOCK(p);
                error = sx_sleep(&p->p_procdesc, &proctree_lock,
                    PWAIT | PCATCH | PDROP, "pdwait", 0);
                if (error != 0)
                        goto exit_unlocked;
        }

        PROC_UNLOCK(p);
exit_tree_locked:
        sx_xunlock(&proctree_lock);
exit_unlocked:
        if (fp != NULL)
                fdrop(fp, td);
        return (error);
}

void
proc_add_orphan(struct proc *child, struct proc *parent)
{

        sx_assert(&proctree_lock, SX_XLOCKED);
        KASSERT((child->p_flag & P_TRACED) != 0,
            ("proc_add_orphan: not traced"));

        if (LIST_EMPTY(&parent->p_orphans)) {
                child->p_treeflag |= P_TREE_FIRST_ORPHAN;
                LIST_INSERT_HEAD(&parent->p_orphans, child, p_orphan);
        } else {
                LIST_INSERT_AFTER(LIST_FIRST(&parent->p_orphans),
                    child, p_orphan);
        }
        child->p_treeflag |= P_TREE_ORPHANED;
}

/*
 * Make process 'parent' the new parent of process 'child'.
 * Must be called with an exclusive hold of proctree lock.
 */
void
proc_reparent(struct proc *child, struct proc *parent, bool set_oppid)
{

        sx_assert(&proctree_lock, SX_XLOCKED);
        PROC_LOCK_ASSERT(child, MA_OWNED);
        if (child->p_pptr == parent)
                return;

        PROC_LOCK(child->p_pptr);
        sigqueue_take(child->p_ksi);
        PROC_UNLOCK(child->p_pptr);
        LIST_REMOVE(child, p_sibling);
        LIST_INSERT_HEAD(&parent->p_children, child, p_sibling);

        proc_clear_orphan(child);
        if ((child->p_flag & P_TRACED) != 0) {
                proc_add_orphan(child, child->p_pptr);
        }

        child->p_pptr = parent;
        if (set_oppid)
                child->p_oppid = parent->p_pid;
}

static void
initexit(void *dummy __unused)
{
        ast_register(TDA_ASYNC_EXIT, ASTR_ASTF_REQUIRED, 0, ast_async_exit);
}
SYSINIT(exit, SI_SUB_EXEC, SI_ORDER_ANY, initexit, NULL);