/*      $NetBSD: kern_exit.c,v 1.300 2025/03/16 15:52:18 riastradh Exp $        */

/*-
 * Copyright (c) 1998, 1999, 2006, 2007, 2008, 2020, 2023
 *     The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
 * NASA Ames Research Center, and by Andrew Doran.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

/*
 * 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.
 *
 *      @(#)kern_exit.c 8.10 (Berkeley) 2/23/95
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_exit.c,v 1.300 2025/03/16 15:52:18 riastradh Exp $");

#include "opt_ktrace.h"
#include "opt_dtrace.h"
#include "opt_sysv.h"

#include <sys/param.h>
#include <sys/types.h>

#include <sys/acct.h>
#include <sys/atomic.h>
#include <sys/buf.h>
#include <sys/cpu.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/fstrans.h>
#include <sys/ioctl.h>
#include <sys/kauth.h>
#include <sys/kernel.h>
#include <sys/ktrace.h>
#include <sys/lock.h>
#include <sys/lockdebug.h>
#include <sys/lwpctl.h>
#include <sys/mount.h>
#include <sys/pool.h>
#include <sys/proc.h>
#include <sys/psref.h>
#include <sys/ptrace.h>
#include <sys/ras.h>
#include <sys/resource.h>
#include <sys/sched.h>
#include <sys/sdt.h>
#include <sys/signalvar.h>
#include <sys/sleepq.h>
#include <sys/syscallargs.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#include <sys/time.h>
#include <sys/tty.h>
#include <sys/uidinfo.h>
#include <sys/vnode.h>
#include <sys/wait.h>

#include <uvm/uvm_extern.h>

#ifdef DEBUG_EXIT
int debug_exit = 0;
#define DPRINTF(x) if (debug_exit) printf x
#else
#define DPRINTF(x)
#endif

static int find_stopped_child(struct proc *, idtype_t, id_t, int,
    struct proc **, struct wrusage *, siginfo_t *);
static void proc_free(struct proc *, struct wrusage *);

/*
 * DTrace SDT provider definitions
 */
SDT_PROVIDER_DECLARE(proc);
SDT_PROBE_DEFINE1(proc, kernel, , exit, "int");

/*
 * Fill in the appropriate signal information, and signal the parent.
 */
/* XXX noclone works around a gcc 4.5 bug on arm */
static void __noclone
exit_psignal(struct proc *p, struct proc *pp, ksiginfo_t *ksi)
{

        KSI_INIT(ksi);
        if ((ksi->ksi_signo = P_EXITSIG(p)) == SIGCHLD) {
                if (p->p_xsig) {
                        if (p->p_sflag & PS_COREDUMP)
                                ksi->ksi_code = CLD_DUMPED;
                        else
                                ksi->ksi_code = CLD_KILLED;
                        ksi->ksi_status = p->p_xsig;
                } else {
                        ksi->ksi_code = CLD_EXITED;
                        ksi->ksi_status = p->p_xexit;
                }
        } else {
                ksi->ksi_code = SI_USER;
                ksi->ksi_status = p->p_xsig;
        }
        /*
         * We fill those in, even for non-SIGCHLD.
         * It's safe to access p->p_cred unlocked here.
         */
        ksi->ksi_pid = p->p_pid;
        ksi->ksi_uid = kauth_cred_geteuid(p->p_cred);
        /* XXX: is this still valid? */
        ksi->ksi_utime = p->p_stats->p_ru.ru_utime.tv_sec;
        ksi->ksi_stime = p->p_stats->p_ru.ru_stime.tv_sec;
}

/*
 * exit --
 *      Death of process.
 */
int
sys_exit(struct lwp *l, const struct sys_exit_args *uap, register_t *retval)
{
        /* {
                syscallarg(int) rval;
        } */
        struct proc *p = l->l_proc;

        /* Don't call exit1() multiple times in the same process. */
        mutex_enter(p->p_lock);
        if (p->p_sflag & PS_WEXIT) {
                mutex_exit(p->p_lock);
                lwp_exit(l);
        }

        /* exit1() will release the mutex. */
        exit1(l, SCARG(uap, rval), 0);
        /* NOTREACHED */
        return (0);
}

/*
 * 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.
 *
 * Must be called with p->p_lock held.  Does not return.
 */
void
exit1(struct lwp *l, int exitcode, int signo)
{
        struct proc     *p, *child, *next_child, *old_parent, *new_parent;
        struct pgrp     *pgrp;
        ksiginfo_t      ksi;
        ksiginfoq_t     kq;
        int             wakeinit;

        p = l->l_proc;

        /* Verify that we hold no locks other than p->p_lock. */
        LOCKDEBUG_BARRIER(p->p_lock, 0);

        /* XXX Temporary: something is leaking kernel_lock. */
        KERNEL_UNLOCK_ALL(l, NULL);

        KASSERT(mutex_owned(p->p_lock));
        KASSERT(p->p_vmspace != NULL);

        if (__predict_false(p == initproc)) {
                panic("init died (signal %d, exit %d)", signo, exitcode);
        }

        p->p_sflag |= PS_WEXIT;

        /*
         * Force all other LWPs to exit before we do.  Only then can we
         * begin to tear down the rest of the process state.
         */
        if (p->p_nlwps > 1) {
                exit_lwps(l);
        }

        ksiginfo_queue_init(&kq);

        /*
         * If we have been asked to stop on exit, do so now.
         */
        if (__predict_false(p->p_sflag & PS_STOPEXIT)) {
                KASSERT(l->l_blcnt == 0);
                sigclearall(p, &contsigmask, &kq);

                if (!mutex_tryenter(&proc_lock)) {
                        mutex_exit(p->p_lock);
                        mutex_enter(&proc_lock);
                        mutex_enter(p->p_lock);
                }
                p->p_waited = 0;
                p->p_pptr->p_nstopchild++;
                p->p_stat = SSTOP;
                mutex_exit(&proc_lock);
                lwp_lock(l);
                p->p_nrlwps--;
                l->l_stat = LSSTOP;
                lwp_unlock(l);
                mutex_exit(p->p_lock);
                lwp_lock(l);
                spc_lock(l->l_cpu);
                mi_switch(l);
                mutex_enter(p->p_lock);
        }

        /*
         * Bin any remaining signals and mark the process as dying so it will
         * not be found for, e.g. signals.
         */
        sigfillset(&p->p_sigctx.ps_sigignore);
        sigclearall(p, NULL, &kq);
        p->p_stat = SDYING;

        /*
         * Perform any required thread cleanup.  Do this early so
         * anyone wanting to look us up by our global thread ID
         * will fail to find us.
         *
         * N.B. this will unlock p->p_lock on our behalf.
         */
        lwp_thread_cleanup(l);

        ksiginfo_queue_drain(&kq);

        /* Destroy any lwpctl info. */
        if (p->p_lwpctl != NULL)
                lwp_ctl_exit();

        /*
         * Drain all remaining references that procfs, ptrace and others may
         * have on the process.
         */
        rw_enter(&p->p_reflock, RW_WRITER);

        DPRINTF(("%s: %d.%d exiting.\n", __func__, p->p_pid, l->l_lid));

        ptimers_free(p, TIMERS_ALL);
#if defined(__HAVE_RAS)
        ras_purgeall();
#endif

        /*
         * Close open files, release open-file table and free signal
         * actions.  This may block!
         */
        fd_free();
        cwdfree(p->p_cwdi);
        p->p_cwdi = NULL;
        doexithooks(p);
        sigactsfree(p->p_sigacts);

        /*
         * Write out accounting data.
         */
        (void)acct_process(l);

#ifdef KTRACE
        /*
         * Release trace file.
         */
        if (p->p_tracep != NULL) {
                mutex_enter(&ktrace_lock);
                ktrderef(p);
                mutex_exit(&ktrace_lock);
        }
#endif

        p->p_xexit = exitcode;
        p->p_xsig = signo;

        /*
         * If emulation has process exit hook, call it now.
         * Set the exit status now so that the exit hook has
         * an opportunity to tweak it (COMPAT_LINUX requires
         * this for thread group emulation)
         */
        if (p->p_emul->e_proc_exit)
                (*p->p_emul->e_proc_exit)(p);

        /*
         * Free the VM resources we're still holding on to.
         * We must do this from a valid thread because doing
         * so may block. This frees vmspace, which we don't
         * need anymore. The only remaining lwp is the one
         * we run at this moment, nothing runs in userland
         * anymore.
         */
        ruspace(p);     /* Update our vm resource use */
        uvm_proc_exit(p);

        /*
         * Stop profiling.
         */
        if (__predict_false((p->p_stflag & PST_PROFIL) != 0)) {
                mutex_spin_enter(&p->p_stmutex);
                stopprofclock(p);
                mutex_spin_exit(&p->p_stmutex);
        }

        /*
         * If parent is waiting for us to exit or exec, PL_PPWAIT is set; we
         * wake up the parent early to avoid deadlock.  We can do this once
         * the VM resources are released.
         */
        mutex_enter(&proc_lock);
        if (p->p_lflag & PL_PPWAIT) {
                lwp_t *lp;

                l->l_lwpctl = NULL; /* was on loan from blocked parent */
                p->p_lflag &= ~PL_PPWAIT;

                lp = p->p_vforklwp;
                p->p_vforklwp = NULL;
                lp->l_vforkwaiting = false;
                cv_broadcast(&lp->l_waitcv);
        }

        if (SESS_LEADER(p)) {
                struct vnode *vprele = NULL, *vprevoke = NULL;
                struct session *sp = p->p_session;
                struct tty *tp;

                if (sp->s_ttyvp) {
                        /*
                         * Controlling process.
                         * Signal foreground pgrp,
                         * drain controlling terminal
                         * and revoke access to controlling terminal.
                         */
                        tp = sp->s_ttyp;
                        mutex_spin_enter(&tty_lock);
                        if (tp->t_session == sp) {
                                /* we can't guarantee the revoke will do this */
                                pgrp = tp->t_pgrp;
                                tp->t_pgrp = NULL;
                                tp->t_session = NULL;
                                mutex_spin_exit(&tty_lock);
                                if (pgrp != NULL) {
                                        pgsignal(pgrp, SIGHUP, 1);
                                }
                                mutex_exit(&proc_lock);
                                (void) ttywait(tp);
                                mutex_enter(&proc_lock);

                                /* The tty could have been revoked. */
                                vprevoke = sp->s_ttyvp;
                        } else
                                mutex_spin_exit(&tty_lock);
                        vprele = sp->s_ttyvp;
                        sp->s_ttyvp = NULL;
                        /*
                         * s_ttyp is not zero'd; we use this to indicate
                         * that the session once had a controlling terminal.
                         * (for logging and informational purposes)
                         */
                }
                sp->s_leader = NULL;

                if (vprevoke != NULL || vprele != NULL) {
                        if (vprevoke != NULL) {
                                /* Releases proc_lock. */
                                proc_sessrele(sp);
                                VOP_REVOKE(vprevoke, REVOKEALL);
                        } else
                                mutex_exit(&proc_lock);
                        if (vprele != NULL)
                                vrele(vprele);
                        mutex_enter(&proc_lock);
                }
        }
        fixjobc(p, p->p_pgrp, 0);

        /* Release fstrans private data. */
        fstrans_lwp_dtor(l);

        /*
         * Finalize the last LWP's specificdata, as well as the
         * specificdata for the proc itself.
         */
        lwp_finispecific(l);
        proc_finispecific(p);

        /*
         * Reset p_opptr pointer of all former children which got
         * traced by another process and were reparented. We reset
         * it to NULL here; the trace detach code then reparents
         * the child to initproc. We only check allproc list, since
         * eventual former children on zombproc list won't reference
         * p_opptr anymore.
         */
        if (__predict_false(p->p_slflag & PSL_CHTRACED)) {
                struct proc *q;
                PROCLIST_FOREACH(q, &allproc) {
                        if (q->p_opptr == p)
                                q->p_opptr = NULL;
                }
                PROCLIST_FOREACH(q, &zombproc) {
                        if (q->p_opptr == p)
                                q->p_opptr = NULL;
                }
        }

        /*
         * Give orphaned children to init(8).
         */
        child = LIST_FIRST(&p->p_children);
        wakeinit = (child != NULL);
        for (; child != NULL; child = next_child) {
                next_child = LIST_NEXT(child, p_sibling);

                /*
                 * Traced processes are killed since their existence
                 * means someone is screwing up. Since we reset the
                 * trace flags, the logic in sys_wait4() would not be
                 * triggered to reparent the process to its
                 * original parent, so we must do this here.
                 */
                if (__predict_false(child->p_slflag & PSL_TRACED)) {
                        mutex_enter(p->p_lock);
                        child->p_slflag &=
                            ~(PSL_TRACED|PSL_SYSCALL);
                        mutex_exit(p->p_lock);
                        if (child->p_opptr != child->p_pptr) {
                                struct proc *t = child->p_opptr;
                                proc_reparent(child, t ? t : initproc);
                                child->p_opptr = NULL;
                        } else
                                proc_reparent(child, initproc);
                        killproc(child, "orphaned traced process");
                } else
                        proc_reparent(child, initproc);
        }

        /*
         * Move proc from allproc to zombproc, it's now nearly ready to be
         * collected by parent.
         */
        LIST_REMOVE(l, l_list);
        LIST_REMOVE(p, p_list);
        LIST_INSERT_HEAD(&zombproc, p, p_list);

        /*
         * Mark the process as dead.  We must do this before we signal
         * the parent.
         */
        p->p_stat = SDEAD;

        /*
         * Let anyone watching this DTrace probe know what we're
         * on our way out.
         */
        SDT_PROBE(proc, kernel, , exit,
                ((p->p_sflag & PS_COREDUMP) ? CLD_DUMPED :
                 (p->p_xsig ? CLD_KILLED : CLD_EXITED)),
                0,0,0,0);

        /* Put in front of parent's sibling list for parent to collect it */
        old_parent = p->p_pptr;
        old_parent->p_nstopchild++;
        if (LIST_FIRST(&old_parent->p_children) != p) {
                /* Put child where it can be found quickly */
                LIST_REMOVE(p, p_sibling);
                LIST_INSERT_HEAD(&old_parent->p_children, p, p_sibling);
        }

        /*
         * Notify parent that we're gone.  If parent has the P_NOCLDWAIT
         * flag set, notify init instead (and hope it will handle
         * this situation).
         */
        if (old_parent->p_flag & (PK_NOCLDWAIT|PK_CLDSIGIGN)) {
                proc_reparent(p, initproc);
                wakeinit = 1;

                /*
                 * If this was the last child of our parent, notify
                 * parent, so in case he was wait(2)ing, he will
                 * continue.
                 */
                if (LIST_FIRST(&old_parent->p_children) == NULL)
                        cv_broadcast(&old_parent->p_waitcv);
        }

        /* Reload parent pointer, since p may have been reparented above */
        new_parent = p->p_pptr;

        if (__predict_false(p->p_exitsig != 0)) {
                exit_psignal(p, new_parent, &ksi);
                kpsignal(new_parent, &ksi, NULL);
        }

        /* Calculate the final rusage info.  */
        calcru(p, &p->p_stats->p_ru.ru_utime, &p->p_stats->p_ru.ru_stime,
            NULL, NULL);

        callout_destroy(&l->l_timeout_ch);

        /*
         * Release any PCU resources before becoming a zombie.
         */
        pcu_discard_all(l);

        /*
         * Notify other processes tracking us with a knote that
         * we're exiting.
         *
         * N.B. we do this here because the process is now SDEAD,
         * and thus cannot have any more knotes attached.  Also,
         * knote_proc_exit() expects that p->p_lock is already
         * held (and will assert so).
         */
        mutex_enter(p->p_lock);
        if (!SLIST_EMPTY(&p->p_klist)) {
                knote_proc_exit(p);
        }

        /* Free the LWP ID */
        proc_free_lwpid(p, l->l_lid);
        lwp_drainrefs(l);
        lwp_lock(l);
        l->l_prflag &= ~LPR_DETACHED;
        l->l_stat = LSZOMB;
        lwp_unlock(l);
        KASSERT(curlwp == l);
        KASSERT(p->p_nrlwps == 1);
        KASSERT(p->p_nlwps == 1);
        p->p_stat = SZOMB;
        p->p_nrlwps--;
        p->p_nzlwps++;
        p->p_ndlwps = 0;
        mutex_exit(p->p_lock);

        /*
         * Signal the parent to collect us, and drop the proclist lock.
         * Drop debugger/procfs lock; no new references can be gained.
         */
        rw_exit(&p->p_reflock);
        cv_broadcast(&p->p_pptr->p_waitcv);
        mutex_exit(&proc_lock);
        if (wakeinit)
                cv_broadcast(&initproc->p_waitcv);

        /*
         * NOTE: WE ARE NO LONGER ALLOWED TO SLEEP!
         */

        /*
         * Give machine-dependent code a chance to free any MD LWP
         * resources.  This must be done before uvm_lwp_exit(), in
         * case these resources are in the PCB.
         */
        cpu_lwp_free(l, 1);

        /* Switch away into oblivion. */
        lwp_lock(l);
        spc_lock(l->l_cpu);
        mi_switch(l);
        panic("exit1");
}

void
exit_lwps(struct lwp *l)
{
        proc_t *p = l->l_proc;
        lwp_t *l2;

retry:
        KASSERT(mutex_owned(p->p_lock));

        /*
         * Interrupt LWPs in interruptable sleep, unsuspend suspended
         * LWPs and then wait for everyone else to finish.
         */
        LIST_FOREACH(l2, &p->p_lwps, l_sibling) {
                if (l2 == l)
                        continue;
                lwp_lock(l2);
                l2->l_flag |= LW_WEXIT;
                lwp_need_userret(l2);
                if ((l2->l_stat == LSSLEEP && (l2->l_flag & LW_SINTR)) ||
                    l2->l_stat == LSSUSPENDED || l2->l_stat == LSSTOP) {
                        l2->l_flag &= ~LW_DBGSUSPEND;
                        /* setrunnable() will release the lock. */
                        setrunnable(l2);
                        continue;
                }
                lwp_unlock(l2);
        }

        /*
         * Wait for every LWP to exit.  Note: LWPs can get suspended/slept
         * behind us or there may even be new LWPs created.  Therefore, a
         * full retry is required on error.
         */
        while (p->p_nlwps > 1) {
                if (lwp_wait(l, 0, NULL, true)) {
                        goto retry;
                }
        }

        KASSERT(p->p_nlwps == 1);
}

int
do_sys_waitid(idtype_t idtype, id_t id, int *pid, int *status, int options,
    struct wrusage *wru, siginfo_t *si)
{
        proc_t *child;
        int error;


        if (wru != NULL)
                memset(wru, 0, sizeof(*wru));
        if (si != NULL)
                memset(si, 0, sizeof(*si));

        mutex_enter(&proc_lock);
        error = find_stopped_child(curproc, idtype, id, options, &child,
            wru, si);
        if (child == NULL) {
                mutex_exit(&proc_lock);
                *pid = 0;
                *status = 0;
                return error;
        }
        *pid = child->p_pid;

        if (child->p_stat == SZOMB) {
                /* Child is exiting */
                *status = P_WAITSTATUS(child);
                /* proc_free() will release the proc_lock. */
                if (options & WNOWAIT) {
                        mutex_exit(&proc_lock);
                } else {
                        proc_free(child, wru);
                }
        } else {
                /* Don't mark SIGCONT if we are being stopped */
                *status = (child->p_xsig == SIGCONT && child->p_stat != SSTOP) ?
                    W_CONTCODE() : W_STOPCODE(child->p_xsig);
                mutex_exit(&proc_lock);
        }
        return 0;
}

int
do_sys_wait(int *pid, int *status, int options, struct rusage *ru)
{
        idtype_t idtype;
        id_t id;
        int ret;
        struct wrusage wru;

        /*
         * Translate the special pid values into the (idtype, pid)
         * pair for wait6. The WAIT_MYPGRP case is handled by
         * find_stopped_child() 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;
        }
        options |= WEXITED | WTRAPPED;
        ret = do_sys_waitid(idtype, id, pid, status, options, ru ? &wru : NULL,
            NULL);
        if (ru)
                *ru = wru.wru_self;
        return ret;
}

int
sys___wait450(struct lwp *l, const struct sys___wait450_args *uap,
    register_t *retval)
{
        /* {
                syscallarg(int)                 pid;
                syscallarg(int *)               status;
                syscallarg(int)                 options;
                syscallarg(struct rusage *)     rusage;
        } */
        int error, status, pid = SCARG(uap, pid);
        struct rusage ru;

        error = do_sys_wait(&pid, &status, SCARG(uap, options),
            SCARG(uap, rusage) != NULL ? &ru : NULL);

        retval[0] = pid;
        if (pid == 0) {
                return error;
        }
        if (SCARG(uap, status)) {
                error = copyout(&status, SCARG(uap, status), sizeof(status));
        }
        if (SCARG(uap, rusage) && error == 0) {
                error = copyout(&ru, SCARG(uap, rusage), sizeof(ru));
        }
        return error;
}

int
sys_wait6(struct lwp *l, const struct sys_wait6_args *uap, register_t *retval)
{
        /* {
                syscallarg(idtype_t)            idtype;
                syscallarg(id_t)                id;
                syscallarg(int *)               status;
                syscallarg(int)                 options;
                syscallarg(struct wrusage *)    wru;
                syscallarg(siginfo_t *)         si;
        } */
        struct wrusage wru, *wrup;
        siginfo_t si, *sip;
        idtype_t idtype;
        int pid;
        id_t id;
        int error, status;

        idtype = SCARG(uap, idtype);
        id = SCARG(uap, id);

        if (SCARG(uap, wru) != NULL)
                wrup = &wru;
        else
                wrup = NULL;

        if (SCARG(uap, info) != NULL)
                sip = &si;
        else
                sip = NULL;

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

        retval[0] = pid;        /* tell userland who it was */

#if 0
        /*
         * should we copyout if there was no process, hence no useful data?
         * We don't for an old style wait4() (etc) but I believe
         * FreeBSD does for wait6(), so a tossup...  Go with FreeBSD for now.
         */
        if (pid == 0)
                return error;
#endif

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


/*
 * Find a process that matches the provided criteria, and fill siginfo
 * and resources if found.
 * Returns:
 *      -1:     Not found, abort early
 *       0:     Not matched
 *       1:     Matched, there might be more matches
 *       2:     This is the only match
 */
static int
match_process(const struct proc *pp, struct proc **q, idtype_t idtype, id_t id,
    int options, struct wrusage *wrusage, siginfo_t *siginfo)
{
        struct rusage *rup;
        struct proc *p = *q;
        int rv = 1;

        switch (idtype) {
        case P_ALL:
                mutex_enter(p->p_lock);
                break;
        case P_PID:
                if (p->p_pid != (pid_t)id) {
                        p = *q = proc_find_raw((pid_t)id);
                        if (p == NULL || p->p_stat == SIDL || p->p_pptr != pp) {
                                *q = NULL;
                                return -1;
                        }
                }
                mutex_enter(p->p_lock);
                rv++;
                break;
        case P_PGID:
                if (p->p_pgid != (pid_t)id)
                        return 0;
                mutex_enter(p->p_lock);
                break;
        case P_SID:
                if (p->p_session->s_sid != (pid_t)id)
                        return 0;
                mutex_enter(p->p_lock);
                break;
        case P_UID:
                mutex_enter(p->p_lock);
                if (kauth_cred_geteuid(p->p_cred) != (uid_t)id) {
                        mutex_exit(p->p_lock);
                        return 0;
                }
                break;
        case P_GID:
                mutex_enter(p->p_lock);
                if (kauth_cred_getegid(p->p_cred) != (gid_t)id) {
                        mutex_exit(p->p_lock);
                        return 0;
                }
                break;
        case P_CID:
        case P_PSETID:
        case P_CPUID:
                /* XXX: Implement me */
        default:
                return 0;
        }

        if ((options & WEXITED) == 0 && p->p_stat == SZOMB) {
                mutex_exit(p->p_lock);
                return 0;
        }

        if (siginfo != NULL) {
                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 (p->p_sflag & PS_COREDUMP) {
                        siginfo->si_code = CLD_DUMPED;
                        siginfo->si_status = p->p_xsig;
                } else if (p->p_xsig) {
                        siginfo->si_code = CLD_KILLED;
                        siginfo->si_status = p->p_xsig;
                } else {
                        siginfo->si_code = CLD_EXITED;
                        siginfo->si_status = p->p_xexit;
                }

                siginfo->si_pid = p->p_pid;
                siginfo->si_uid = kauth_cred_geteuid(p->p_cred);
                siginfo->si_utime = p->p_stats->p_ru.ru_utime.tv_sec;
                siginfo->si_stime = p->p_stats->p_ru.ru_stime.tv_sec;
        }

        /*
         * 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.
         */
        if (wrusage != NULL) {
                rup = &wrusage->wru_self;
                *rup = p->p_stats->p_ru;
                calcru(p, &rup->ru_utime, &rup->ru_stime, NULL, NULL);

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

        mutex_exit(p->p_lock);
        return rv;
}

/*
 * Determine if there are existing processes being debugged
 * that used to be (and sometime later will be again) children
 * of a specific parent (while matching wait criteria)
 */
static bool
debugged_child_exists(idtype_t idtype, id_t id, int options, siginfo_t *si,
    const struct proc *parent)
{
        struct proc *pp;

        /*
         * If we are searching for a specific pid, we can optimise a little
         */
        if (idtype == P_PID) {
                /*
                 * Check the specific process to see if its real parent is us
                 */
                pp = proc_find_raw((pid_t)id);
                if (pp != NULL && pp->p_stat != SIDL && pp->p_opptr == parent) {
                        /*
                         * using P_ALL here avoids match_process() doing the
                         * same work that we just did, but incorrectly for
                         * this scenario.
                         */
                        if (match_process(parent, &pp, P_ALL, id, options,
                            NULL, si))
                                return true;
                }
                return false;
        }

        /*
         * For the hard cases, just look everywhere to see if some
         * stolen (reparented) process is really our lost child.
         * Then check if that process could satisfy the wait conditions.
         */

        /*
         * XXX inefficient, but hopefully fairly rare.
         * XXX should really use a list of reparented processes.
         */
        PROCLIST_FOREACH(pp, &allproc) {
                if (pp->p_stat == SIDL)         /* XXX impossible ?? */
                        continue;
                if (pp->p_opptr == parent &&
                    match_process(parent, &pp, idtype, id, options, NULL, si))
                        return true;
        }
        PROCLIST_FOREACH(pp, &zombproc) {
                if (pp->p_stat == SIDL)         /* XXX impossible ?? */
                        continue;
                if (pp->p_opptr == parent &&
                    match_process(parent, &pp, idtype, id, options, NULL, si))
                        return true;
        }

        return false;
}

/*
 * Scan list of child processes for a child process that has stopped or
 * exited.  Used by sys_wait4 and 'compat' equivalents.
 *
 * Must be called with the proc_lock held, and may release while waiting.
 */
static int
find_stopped_child(struct proc *parent, idtype_t idtype, id_t id, int options,
    struct proc **child_p, struct wrusage *wru, siginfo_t *si)
{
        struct proc *child, *dead;
        int error;

        KASSERT(mutex_owned(&proc_lock));

        if (options & ~WALLOPTS) {
                *child_p = NULL;
                return SET_ERROR(EINVAL);
        }

        if ((options & WSELECTOPTS) == 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.
                 */
                *child_p = NULL;
                return SET_ERROR(EINVAL);
        }

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

        for (;;) {
                error = ECHILD;
                dead = NULL;

                LIST_FOREACH(child, &parent->p_children, p_sibling) {
                        int rv = match_process(parent, &child, idtype, id,
                            options, wru, si);
                        if (rv == -1)
                                break;
                        if (rv == 0)
                                continue;

                        /*
                         * Wait for processes with p_exitsig != SIGCHLD
                         * processes only if WALTSIG is set; wait for
                         * processes with p_exitsig == SIGCHLD only
                         * if WALTSIG is clear.
                         */
                        if (((options & WALLSIG) == 0) &&
                            (options & WALTSIG ? child->p_exitsig == SIGCHLD
                                                : P_EXITSIG(child) != SIGCHLD)){
                                if (rv == 2) {
                                        child = NULL;
                                        break;
                                }
                                continue;
                        }

                        error = 0;
                        if ((options & WNOZOMBIE) == 0) {
                                if (child->p_stat == SZOMB)
                                        break;
                                if (child->p_stat == SDEAD) {
                                        /*
                                         * We may occasionally arrive here
                                         * after receiving a signal, but
                                         * immediately before the child
                                         * process is zombified.  The wait
                                         * will be short, so avoid returning
                                         * to userspace.
                                         */
                                        dead = child;
                                }
                        }

                        if ((options & WCONTINUED) != 0 &&
                            child->p_xsig == SIGCONT &&
                            (child->p_sflag & PS_CONTINUED)) {
                                if ((options & WNOWAIT) == 0) {
                                        child->p_sflag &= ~PS_CONTINUED;
                                        child->p_waited = 1;
                                        parent->p_nstopchild--;
                                }
                                if (si) {
                                        si->si_status = child->p_xsig;
                                        si->si_code = CLD_CONTINUED;
                                }
                                break;
                        }

                        if ((options & (WTRAPPED|WSTOPPED)) != 0 &&
                            child->p_stat == SSTOP &&
                            child->p_waited == 0 &&
                            ((child->p_slflag & PSL_TRACED) ||
                            options & (WUNTRACED|WSTOPPED))) {
                                if ((options & WNOWAIT) == 0) {
                                        child->p_waited = 1;
                                        parent->p_nstopchild--;
                                }
                                if (si) {
                                        si->si_status = child->p_xsig;
                                        si->si_code =
                                            (child->p_slflag & PSL_TRACED) ?
                                            CLD_TRAPPED : CLD_STOPPED;
                                }
                                break;
                        }
                        if (parent->p_nstopchild == 0 || rv == 2) {
                                child = NULL;
                                break;
                        }
                }

                /*
                 * If we found nothing, but we are the bereaved parent
                 * of a stolen child, look and see if that child (or
                 * one of them) meets our search criteria.   If so, then
                 * we cannot succeed, but we can hang (wait...), 
                 * or if WNOHANG, return 0 instead of ECHILD
                 */
                if (child == NULL && error == ECHILD && 
                    (parent->p_slflag & PSL_CHTRACED) &&
                    debugged_child_exists(idtype, id, options, si, parent))
                        error = 0;

                if (child != NULL || error != 0 ||
                    ((options & WNOHANG) != 0 && dead == NULL)) {
                        *child_p = child;
                        return SET_ERROR(error);
                }

                /*
                 * Wait for another child process to stop.
                 */
                error = cv_wait_sig(&parent->p_waitcv, &proc_lock);

                if (error != 0) {
                        *child_p = NULL;
                        return error;
                }
        }
}

/*
 * Free a process after parent has taken all the state info.  Must be called
 * with the proclist lock held, and will release before returning.
 *
 * *ru is returned to the caller, and must be freed by the caller.
 */
static void
proc_free(struct proc *p, struct wrusage *wru)
{
        struct proc *parent = p->p_pptr;
        struct lwp *l;
        ksiginfo_t ksi;
        kauth_cred_t cred1, cred2;
        uid_t uid;

        KASSERT(mutex_owned(&proc_lock));
        KASSERT(p->p_nlwps == 1);
        KASSERT(p->p_nzlwps == 1);
        KASSERT(p->p_nrlwps == 0);
        KASSERT(p->p_stat == SZOMB);

        /*
         * If we got the child via ptrace(2) or procfs, and
         * the parent is different (meaning the process was
         * attached, rather than run as a child), then we need
         * to give it back to the old parent, and send the
         * parent the exit signal.  The rest of the cleanup
         * will be done when the old parent waits on the child.
         */
        if ((p->p_slflag & PSL_TRACED) != 0 && p->p_opptr != parent) {
                mutex_enter(p->p_lock);
                p->p_slflag &= ~(PSL_TRACED|PSL_SYSCALL);
                mutex_exit(p->p_lock);
                parent = (p->p_opptr == NULL) ? initproc : p->p_opptr;
                proc_reparent(p, parent);
                p->p_opptr = NULL;
                if (p->p_exitsig != 0) {
                        exit_psignal(p, parent, &ksi);
                        kpsignal(parent, &ksi, NULL);
                }
                cv_broadcast(&parent->p_waitcv);
                mutex_exit(&proc_lock);
                return;
        }

        sched_proc_exit(parent, p);

        /*
         * Add child times of exiting process onto its own times.
         * This cannot be done any earlier else it might get done twice.
         */
        l = LIST_FIRST(&p->p_lwps);
        ruadd(&p->p_stats->p_ru, &l->l_ru);
        ruadd(&p->p_stats->p_ru, &p->p_stats->p_cru);
        ruadd(&parent->p_stats->p_cru, &p->p_stats->p_ru);
        if (wru != NULL) {
                wru->wru_self = p->p_stats->p_ru;
                wru->wru_children = p->p_stats->p_cru;
        }
        p->p_xsig = 0;
        p->p_xexit = 0;

        /*
         * At this point we are going to start freeing the final resources.
         * If anyone tries to access the proc structure after here they will
         * get a shock - bits are missing.  Attempt to make it hard!  We
         * don't bother with any further locking past this point.
         */
        p->p_stat = SIDL;               /* not even a zombie any more */
        LIST_REMOVE(p, p_list); /* off zombproc */
        parent->p_nstopchild--;
        LIST_REMOVE(p, p_sibling);

        /*
         * Let pid be reallocated.
         */
        proc_free_pid(p->p_pid);
        atomic_dec_uint(&nprocs);

        /*
         * Unlink process from its process group.
         * Releases the proc_lock.
         */
        proc_leavepgrp(p);

        /*
         * Delay release until after lwp_free.
         */
        cred2 = l->l_cred;

        /*
         * Free the last LWP's resources.
         *
         * lwp_free ensures the LWP is no longer running on another CPU.
         */
        lwp_free(l, false, true);

        /*
         * Now no one except us can reach the process p.
         */

        /*
         * Decrement the count of procs running with this uid.
         */
        cred1 = p->p_cred;
        uid = kauth_cred_getuid(cred1);
        (void)chgproccnt(uid, -1);

        /*
         * Release substructures.
         */

        lim_free(p->p_limit);
        pstatsfree(p->p_stats);
        kauth_cred_free(cred1);
        kauth_cred_free(cred2);

        /*
         * Release reference to text vnode
         */
        if (p->p_textvp)
                vrele(p->p_textvp);
        kmem_strfree(p->p_path);

        mutex_destroy(&p->p_auxlock);
        mutex_obj_free(p->p_lock);
        mutex_destroy(&p->p_stmutex);
        cv_destroy(&p->p_waitcv);
        cv_destroy(&p->p_lwpcv);
        rw_destroy(&p->p_reflock);

        proc_free_mem(p);
}

/*
 * Change the parent of a process for tracing purposes.
 */
void
proc_changeparent(struct proc *t, struct proc *p)
{
        SET(t->p_slflag, PSL_TRACED);
        t->p_opptr = t->p_pptr;
        if (t->p_pptr == p)
                return;
        struct proc *parent = t->p_pptr;

        if (parent->p_lock < t->p_lock) {
                if (!mutex_tryenter(parent->p_lock)) {
                        mutex_exit(t->p_lock);
                        mutex_enter(parent->p_lock);
                        mutex_enter(t->p_lock);
                }
        } else if (parent->p_lock > t->p_lock) {
                mutex_enter(parent->p_lock);
        }
        parent->p_slflag |= PSL_CHTRACED;
        proc_reparent(t, p);
        if (parent->p_lock != t->p_lock)
                mutex_exit(parent->p_lock);
}

/*
 * make process 'parent' the new parent of process 'child'.
 *
 * Must be called with proc_lock held.
 */
void
proc_reparent(struct proc *child, struct proc *parent)
{

        KASSERT(mutex_owned(&proc_lock));

        if (child->p_pptr == parent)
                return;

        if (child->p_stat == SZOMB || child->p_stat == SDEAD ||
            (child->p_stat == SSTOP && !child->p_waited)) {
                child->p_pptr->p_nstopchild--;
                parent->p_nstopchild++;
        }
        if (parent == initproc) {
                child->p_exitsig = SIGCHLD;
                child->p_ppid = parent->p_pid;
        }

        LIST_REMOVE(child, p_sibling);
        LIST_INSERT_HEAD(&parent->p_children, child, p_sibling);
        child->p_pptr = parent;
}