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[netbsd-mini2440.git] / sys / kern / kern_exit.c

/*      $NetBSD: kern_exit.c,v 1.224 2009/11/01 21:05:30 rmind Exp $    */

/*-
 * Copyright (c) 1998, 1999, 2006, 2007, 2008 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 1.224 2009/11/01 21:05:30 rmind Exp $");

#include "opt_ktrace.h"
#include "opt_perfctrs.h"
#include "opt_sa.h"
#include "opt_sysv.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/ioctl.h>
#include <sys/tty.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/buf.h>
#include <sys/wait.h>
#include <sys/file.h>
#include <sys/vnode.h>
#include <sys/syslog.h>
#include <sys/pool.h>
#include <sys/uidinfo.h>
#if defined(PERFCTRS)
#include <sys/pmc.h>
#endif
#include <sys/ptrace.h>
#include <sys/acct.h>
#include <sys/filedesc.h>
#include <sys/ras.h>
#include <sys/signalvar.h>
#include <sys/sched.h>
#include <sys/sa.h>
#include <sys/savar.h>
#include <sys/mount.h>
#include <sys/syscallargs.h>
#include <sys/kauth.h>
#include <sys/sleepq.h>
#include <sys/lockdebug.h>
#include <sys/ktrace.h>
#include <sys/cpu.h>
#include <sys/lwpctl.h>
#include <sys/atomic.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 *, pid_t, int, struct proc **, int *);
static void proc_free(struct proc *, struct rusage *);

/*
 * Fill in the appropriate signal information, and signal the parent.
 */
static void
exit_psignal(struct proc *p, struct proc *pp, ksiginfo_t *ksi)
{

        KSI_INIT(ksi);
        if ((ksi->ksi_signo = P_EXITSIG(p)) == SIGCHLD) {
                if (WIFSIGNALED(p->p_xstat)) {
                        if (WCOREDUMP(p->p_xstat))
                                ksi->ksi_code = CLD_DUMPED;
                        else
                                ksi->ksi_code = CLD_KILLED;
                } else {
                        ksi->ksi_code = CLD_EXITED;
                }
        }
        /*
         * 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);
        ksi->ksi_status = p->p_xstat;
        /* 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, W_EXITCODE(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 rv)
{
        struct proc     *p, *q, *nq;
        struct pgrp     *pgrp;
        ksiginfo_t      ksi;
        ksiginfoq_t     kq;
        int             wakeinit, sa;

        p = l->l_proc;

        KASSERT(mutex_owned(p->p_lock));

        if (__predict_false(p == initproc))
                panic("init died (signal %d, exit %d)",
                    WTERMSIG(rv), WEXITSTATUS(rv));

        /*
         * Disable scheduler activation upcalls.  We're trying to get out of
         * here.
         */
        sa = 0;
#ifdef KERN_SA
        if ((p->p_sa != NULL)) {
                l->l_pflag |= LP_SA_NOBLOCK;
                sa = 1;
        }
#endif

        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 (sa || 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)) {
                KERNEL_UNLOCK_ALL(l, &l->l_biglocks);
                sigclearall(p, &contsigmask, &kq);
                p->p_waited = 0;
                membar_producer();
                p->p_stat = SSTOP;
                lwp_lock(l);
                p->p_nrlwps--;
                l->l_stat = LSSTOP;
                mutex_exit(p->p_lock);
                mi_switch(l);
                KERNEL_LOCK(l->l_biglocks, 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;
        mutex_exit(p->p_lock);
        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(("exit1: %d.%d exiting.\n", p->p_pid, l->l_lid));

        timers_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

        /*
         * 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)
         */
        p->p_xstat = rv;
        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.
         */
        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) {
                p->p_lflag &= ~PL_PPWAIT;
                cv_broadcast(&p->p_pptr->p_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);

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

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

#if PERFCTRS
        /*
         * Save final PMC information in parent process & clean up.
         */
        if (PMC_ENABLED(p)) {
                pmc_save_context(p);
                pmc_accumulate(p->p_pptr, p);
                pmc_process_exit(p);
        }
#endif

        /*
         * 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)) {
                PROCLIST_FOREACH(q, &allproc) {
                        if ((q->p_flag & PK_MARKER) != 0)
                                continue;
                        if (q->p_opptr == p)
                                q->p_opptr = NULL;
                }
        }

        /*
         * Give orphaned children to init(8).
         */
        q = LIST_FIRST(&p->p_children);
        wakeinit = (q != NULL);
        for (; q != NULL; q = nq) {
                nq = LIST_NEXT(q, 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(q->p_slflag & PSL_TRACED)) {
                        mutex_enter(p->p_lock);
                        q->p_slflag &= ~(PSL_TRACED|PSL_FSTRACE|PSL_SYSCALL);
                        mutex_exit(p->p_lock);
                        if (q->p_opptr != q->p_pptr) {
                                struct proc *t = q->p_opptr;
                                proc_reparent(q, t ? t : initproc);
                                q->p_opptr = NULL;
                        } else
                                proc_reparent(q, initproc);
                        killproc(q, "orphaned traced process");
                } else
                        proc_reparent(q, 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;

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

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

        if (__predict_false((p->p_slflag & PSL_FSTRACE) == 0 && 
            p->p_exitsig != 0)) {
                exit_psignal(p, q, &ksi);
                kpsignal(q, &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);

        if (wakeinit)
                cv_broadcast(&initproc->p_waitcv);

        callout_destroy(&l->l_timeout_ch);

        /*
         * Remaining lwp resources will be freed in lwp_exit2() once we've
         * switch to idle context; at that point, we will be marked as a
         * full blown zombie.
         */
        mutex_enter(p->p_lock);
        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.
         */
        cv_broadcast(&p->p_pptr->p_waitcv);
        rw_exit(&p->p_reflock);
        mutex_exit(proc_lock);

        /* Verify that we hold no locks other than the kernel lock. */
        LOCKDEBUG_BARRIER(&kernel_lock, 0);

        /*
         * 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);
        pmap_deactivate(l);

        /* This process no longer needs to hold the kernel lock. */
#ifdef notyet
        /* XXXSMP hold in lwp_userret() */
        KERNEL_UNLOCK_LAST(l);
#else
        KERNEL_UNLOCK_ALL(l, NULL);
#endif

        lwp_exit_switchaway(l);
}

void
exit_lwps(struct lwp *l)
{
        struct proc *p;
        struct lwp *l2;
        int error;
        lwpid_t waited;
        int nlocks;

        KERNEL_UNLOCK_ALL(l, &nlocks);

        p = l->l_proc;
        KASSERT(mutex_owned(p->p_lock));

#ifdef KERN_SA
        if (p->p_sa != NULL) {
                struct sadata_vp *vp;
                SLIST_FOREACH(vp, &p->p_sa->sa_vps, savp_next) {
                        /*
                         * Make SA-cached LWPs normal process interruptable
                         * so that the exit code can wake them. Locking
                         * savp_mutex locks all the lwps on this vp that
                         * we need to adjust.
                         */
                        mutex_enter(&vp->savp_mutex);
                        DPRINTF(("exit_lwps: Making cached LWPs of %d on "
                            "VP %d interruptable: ", p->p_pid, vp->savp_id));
                        TAILQ_FOREACH(l2, &vp->savp_lwpcache, l_sleepchain) {
                                l2->l_flag |= LW_SINTR;
                                DPRINTF(("%d ", l2->l_lid));
                        }
                        DPRINTF(("\n"));

                        DPRINTF(("exit_lwps: Making unblocking LWPs of %d on "
                            "VP %d interruptable: ", p->p_pid, vp->savp_id));
                        TAILQ_FOREACH(l2, &vp->savp_woken, l_sleepchain) {
                                vp->savp_woken_count--;
                                l2->l_flag |= LW_SINTR;
                                DPRINTF(("%d ", l2->l_lid));
                        }
                        DPRINTF(("\n"));
                        mutex_exit(&vp->savp_mutex);
                }
        }
#endif

 retry:
        /*
         * 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_SA;
                l2->l_flag |= LW_WEXIT;
                if ((l2->l_stat == LSSLEEP && (l2->l_flag & LW_SINTR)) ||
                    l2->l_stat == LSSUSPENDED || l2->l_stat == LSSTOP) {
                        /* setrunnable() will release the lock. */
                        setrunnable(l2);
                        DPRINTF(("exit_lwps: Made %d.%d runnable\n",
                            p->p_pid, l2->l_lid));
                        continue;
                }
                lwp_unlock(l2);
        }
        while (p->p_nlwps > 1) {
                DPRINTF(("exit_lwps: waiting for %d LWPs (%d zombies)\n",
                    p->p_nlwps, p->p_nzlwps));
                error = lwp_wait1(l, 0, &waited, LWPWAIT_EXITCONTROL);
                if (p->p_nlwps == 1)
                        break;
                if (error == EDEADLK) {
                        /*
                         * LWPs can get suspended/slept behind us.
                         * (eg. sa_setwoken)
                         * kick them again and retry.
                         */
                        goto retry;
                }
                if (error)
                        panic("exit_lwps: lwp_wait1 failed with error %d",
                            error);
                DPRINTF(("exit_lwps: Got LWP %d from lwp_wait1()\n", waited));
        }

        KERNEL_LOCK(nlocks, l);
        KASSERT(p->p_nlwps == 1);
}

int
do_sys_wait(int *pid, int *status, int options, struct rusage *ru)
{
        proc_t *child;
        int error;

        if (ru != NULL) {
                memset(ru, 0, sizeof(*ru));
        }
        mutex_enter(proc_lock);
        error = find_stopped_child(curproc, *pid, options, &child, status);
        if (child == NULL) {
                mutex_exit(proc_lock);
                *pid = 0;
                return error;
        }
        *pid = child->p_pid;

        if (child->p_stat == SZOMB) {
                /* proc_free() will release the proc_lock. */
                if (options & WNOWAIT) {
                        mutex_exit(proc_lock);
                } else {
                        proc_free(child, ru);
                }
        } else {
                /* Child state must have been SSTOP. */
                mutex_exit(proc_lock);
                *status = W_STOPCODE(*status);
        }
        return 0;
}

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;
}

/*
 * 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, pid_t pid, int options,
                   struct proc **child_p, int *status_p)
{
        struct proc *child, *dead;
        int error;

        KASSERT(mutex_owned(proc_lock));

        if (options & ~(WUNTRACED|WNOHANG|WALTSIG|WALLSIG)
            && !(options & WOPTSCHECKED)) {
                *child_p = NULL;
                return EINVAL;
        }

        if (pid == 0 && !(options & WOPTSCHECKED))
                pid = -parent->p_pgid;

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

                LIST_FOREACH(child, &parent->p_children, p_sibling) {
                        if (pid >= 0) {
                                if (child->p_pid != pid) {
                                        child = p_find(pid, PFIND_ZOMBIE |
                                            PFIND_LOCKED);
                                        if (child == NULL ||
                                            child->p_pptr != parent) {
                                                child = NULL;
                                                break;
                                        }
                                }
                        } else if (pid != WAIT_ANY && child->p_pgid != -pid) {
                                /* Child not in correct pgrp */
                                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 (child->p_pid == pid) {
                                        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
                                         * immediatley before the child
                                         * process is zombified.  The wait
                                         * will be short, so avoid returning
                                         * to userspace.
                                         */
                                        dead = child;
                                }
                        }

                        if (child->p_stat == SSTOP &&
                            child->p_waited == 0 &&
                            (child->p_slflag & PSL_TRACED ||
                            options & WUNTRACED)) {
                                if ((options & WNOWAIT) == 0) {
                                        child->p_waited = 1;
                                        parent->p_nstopchild--;
                                }
                                break;
                        }
                        if (parent->p_nstopchild == 0 || child->p_pid == pid) {
                                child = NULL;
                                break;
                        }
                }

                if (child != NULL || error != 0 ||
                    ((options & WNOHANG) != 0 && dead == NULL)) {
                        if (child != NULL) {
                                *status_p = child->p_xstat;
                        }
                        *child_p = child;
                        return 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 rusage *ru)
{
        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_FSTRACE|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);
        p->p_stats->p_ru.ru_nvcsw += (l->l_ncsw - l->l_nivcsw);
        p->p_stats->p_ru.ru_nivcsw += l->l_nivcsw;
        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 (ru != NULL)
                *ru = p->p_stats->p_ru;
        p->p_xstat = 0;

        /* Release any SA state. */
#ifdef KERN_SA
        if (p->p_sa)
                sa_release(p);
#endif

        /*
         * 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);

        /*
         * 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.
         */

        limfree(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);

        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);
}

/*
 * 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 == SSTOP && !child->p_waited)) {
                child->p_pptr->p_nstopchild--;
                parent->p_nstopchild++;
        }
        if (parent == initproc)
                child->p_exitsig = SIGCHLD;

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