[apple/xnu.git] / bsd / kern / kern_exit.c

/*
 * Copyright (c) 2000-2007 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995, 1997 Apple Computer, Inc. All Rights Reserved */
/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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 8.7 (Berkeley) 2/12/94
 */
/*
 * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */
 
#include <machine/reg.h>
#include <machine/psl.h>

#include "compat_43.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/ioctl.h>
#include <sys/proc_internal.h>
#include <sys/proc.h>
#include <sys/kauth.h>
#include <sys/tty.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/kernel.h>
#include <sys/wait.h>
#include <sys/file_internal.h>
#include <sys/vnode_internal.h>
#include <sys/syslog.h>
#include <sys/malloc.h>
#include <sys/resourcevar.h>
#include <sys/ptrace.h>
#include <sys/user.h>
#include <sys/aio_kern.h>
#include <sys/sysproto.h>
#include <sys/signalvar.h>
#include <sys/kdebug.h>
#include <sys/filedesc.h>       /* fdfree */
#if SYSV_SHM
#include <sys/shm_internal.h>   /* shmexit */
#endif
#include <sys/acct.h>           /* acct_process */

#include <security/audit/audit.h>
#include <bsm/audit_kevents.h>

#include <mach/mach_types.h>

#include <kern/kern_types.h>
#include <kern/kalloc.h>
#include <kern/task.h>
#include <kern/thread.h>
#include <kern/thread_call.h>
#include <kern/sched_prim.h>
#include <kern/assert.h>
#include <sys/codesign.h>

#if CONFIG_DTRACE
/* Do not include dtrace.h, it redefines kmem_[alloc/free] */
extern void (*dtrace_fasttrap_exit_ptr)(proc_t);
extern void (*dtrace_helpers_cleanup)(proc_t);
extern void dtrace_lazy_dofs_destroy(proc_t);

#include <sys/dtrace_ptss.h>
#endif

#if CONFIG_MACF
#include <security/mac.h>
#include <sys/syscall.h>
#endif

#include <mach/mach_types.h>
#include <mach/task.h>
#include <mach/thread_act.h>

#include <sys/sdt.h>

extern char init_task_failure_data[];
void proc_prepareexit(proc_t p, int rv);
void vfork_exit(proc_t p, int rv);
void vproc_exit(proc_t p);
__private_extern__ void munge_user64_rusage(struct rusage *a_rusage_p, struct user64_rusage *a_user_rusage_p);
__private_extern__ void munge_user32_rusage(struct rusage *a_rusage_p, struct user32_rusage *a_user_rusage_p);
static int reap_child_locked(proc_t parent, proc_t child, int deadparent, int locked, int droplock);

/*
 * Things which should have prototypes in headers, but don't
 */
void    *get_bsduthreadarg(thread_t);
void    proc_exit(proc_t p);
int     wait1continue(int result);
int     waitidcontinue(int result);
int     *get_bsduthreadrval(thread_t);
kern_return_t sys_perf_notify(thread_t thread, int pid);
kern_return_t abnormal_exit_notify(mach_exception_data_type_t code, 
                mach_exception_data_type_t subcode);
void    delay(int);
                        
/*
 * NOTE: Source and target may *NOT* overlap!
 * XXX Should share code with bsd/dev/ppc/unix_signal.c
 */
static void
siginfo_user_to_user32(user_siginfo_t *in, user32_siginfo_t *out)
{
        out->si_signo   = in->si_signo;
        out->si_errno   = in->si_errno;
        out->si_code    = in->si_code;
        out->si_pid     = in->si_pid;
        out->si_uid     = in->si_uid;
        out->si_status  = in->si_status;
        out->si_addr    = CAST_DOWN_EXPLICIT(user32_addr_t,in->si_addr);
        /* following cast works for sival_int because of padding */
        out->si_value.sival_ptr = CAST_DOWN_EXPLICIT(user32_addr_t,in->si_value.sival_ptr);
        out->si_band    = in->si_band;                  /* range reduction */
}

static void
siginfo_user_to_user64(user_siginfo_t *in, user64_siginfo_t *out)
{
        out->si_signo   = in->si_signo;
        out->si_errno   = in->si_errno;
        out->si_code    = in->si_code;
        out->si_pid     = in->si_pid;
        out->si_uid     = in->si_uid;
        out->si_status  = in->si_status;
        out->si_addr    = in->si_addr;
        /* following cast works for sival_int because of padding */
        out->si_value.sival_ptr = in->si_value.sival_ptr;
        out->si_band    = in->si_band;                  /* range reduction */
}

/*
 * exit --
 *      Death of process.
 */
void
exit(proc_t p, struct exit_args *uap, int *retval)
{
        exit1(p, W_EXITCODE(uap->rval, 0), retval);

        /* drop funnel before we return */
        thread_exception_return();
        /* NOTREACHED */
        while (TRUE)
                thread_block(THREAD_CONTINUE_NULL);
        /* NOTREACHED */
}

/*
 * 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.
 */
int
exit1(proc_t p, int rv, int *retval)
{
        thread_t self = current_thread();
        struct task *task = p->task;
        struct uthread *ut;

        /*
         * If a thread in this task has already
         * called exit(), then halt any others
         * right here.
         */

         ut = get_bsdthread_info(self);
         if (ut->uu_flag & UT_VFORK) {
                        vfork_exit(p, rv);
                        vfork_return(p , retval, p->p_pid);
                        unix_syscall_return(0);
                        /* NOT REACHED */
         }

        /* 
         * The parameter list of audit_syscall_exit() was augmented to
         * take the Darwin syscall number as the first parameter,
         * which is currently required by mac_audit_postselect().
         */

        /* 
         * The BSM 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, WEXITSTATUS(rv), 0);
        AUDIT_SYSCALL_EXIT(SYS_exit, p, ut, 0); /* Exit is always successfull */

        DTRACE_PROC1(exit, int, CLD_EXITED);

        proc_lock(p);
        proc_transstart(p, 1);
        while (p->exit_thread != self) {
                if (sig_try_locked(p) <= 0) {
                        proc_transend(p, 1);
                        if (get_threadtask(self) != task) {
                                proc_unlock(p);
                                return(0);
                        }
                        proc_unlock(p);
                        thread_terminate(self);
                        thread_exception_return();
                        /* NOTREACHED */
                }
                sig_lock_to_exit(p);
        }
        if (p == initproc) {
                proc_unlock(p);
                printf("pid 1 exited (signal %d, exit %d)",
                    WTERMSIG(rv), WEXITSTATUS(rv));
                panic("%s died\nState at Last Exception:\n\n%s", 
                                                        (p->p_comm[0] != '\0' ?
                                                                p->p_comm :
                                                                "launchd"),
                                                        init_task_failure_data);
        }

        p->p_lflag |= P_LEXIT;
        p->p_xstat = rv;

        proc_transend(p, 1);
        proc_unlock(p);

        proc_prepareexit(p, rv);

        /* Last thread to terminate will call proc_exit() */
        task_terminate_internal(task);

        return(0);
}

void
proc_prepareexit(proc_t p, int rv) 
{
        mach_exception_data_type_t code, subcode;
        struct uthread *ut;
        thread_t self = current_thread();
        ut = get_bsdthread_info(self);

        /* If a core should be generated, notify crash reporter */
        if (hassigprop(WTERMSIG(rv), SA_CORE) || ((p->p_csflags & CS_KILLED) != 0)) {
                /* 
                 * Workaround for processes checking up on PT_DENY_ATTACH:
                 * should be backed out post-Leopard (details in 5431025).
                 */
                if ((SIGSEGV == WTERMSIG(rv)) && 
                                (p->p_pptr->p_lflag & P_LNOATTACH)) {
                        goto skipcheck;
                }

                /*
                 * Crash Reporter looks for the signal value, original exception
                 * type, and low 20 bits of the original code in code[0] 
                 * (8, 4, and 20 bits respectively). code[1] is unmodified. 
                 */
                code = ((WTERMSIG(rv) & 0xff) << 24) |
                        ((ut->uu_exception & 0x0f) << 20) | 
                        ((int)ut->uu_code & 0xfffff);
                subcode = ut->uu_subcode;
                (void) abnormal_exit_notify(code, subcode);
        }

skipcheck:
        /* Notify the perf server */
        (void)sys_perf_notify(self, p->p_pid);

        /*
         * Remove proc from allproc queue and from pidhash chain.
         * Need to do this before we do anything that can block.
         * Not doing causes things like mount() find this on allproc
         * in partially cleaned state.
         */

        proc_list_lock();

        LIST_REMOVE(p, p_list);
        LIST_INSERT_HEAD(&zombproc, p, p_list); /* Place onto zombproc. */
        /* will not be visible via proc_find */
        p->p_listflag |= P_LIST_EXITED;

        proc_list_unlock();


#ifdef PGINPROF
        vmsizmon();
#endif
        /*
         * If parent is waiting for us to exit or exec,
         * P_LPPWAIT is set; we will wakeup the parent below.
         */
        proc_lock(p);
        p->p_lflag &= ~(P_LTRACED | P_LPPWAIT);
        p->p_sigignore = ~(sigcantmask);
        ut->uu_siglist = 0;
        proc_unlock(p);
}

void 
proc_exit(proc_t p)
{
        proc_t q;
        proc_t pp;
        struct task *task = p->task;
        vnode_t tvp = NULLVP;
        struct pgrp * pg;
        struct session *sessp;
        struct uthread * uth;
        pid_t pid;
        int exitval;

        uth = (struct uthread *)get_bsdthread_info(current_thread());

        proc_lock(p);
        proc_transstart(p, 1);
        if( !(p->p_lflag & P_LEXIT)) {
                /*
                 * This can happen if a thread_terminate() occurs
                 * in a single-threaded process.
                 */
                p->p_lflag |= P_LEXIT;
                proc_transend(p, 1);
                proc_unlock(p);
                proc_prepareexit(p, 0); 
                (void) task_terminate_internal(task);
                proc_lock(p);
        } else {
                proc_transend(p, 1);
        }

        p->p_lflag |= P_LPEXIT;

        /*
         * Other kernel threads may be in the middle of signalling this process.
         * Wait for those threads to wrap it up before making the process
         * disappear on them.
         */
        if ((p->p_lflag & P_LINSIGNAL) || (p->p_sigwaitcnt > 0)) {
                p->p_sigwaitcnt++;
                while ((p->p_lflag & P_LINSIGNAL) || (p->p_sigwaitcnt > 1)) 
                        msleep(&p->p_sigmask, &p->p_mlock, PWAIT, "proc_sigdrain", NULL);
                p->p_sigwaitcnt--;
        }

        proc_unlock(p);
        pid = p->p_pid;
        exitval = p->p_xstat;
        KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_PROC, BSD_PROC_EXIT) | DBG_FUNC_START,
                                              pid, exitval, 0, 0, 0);

#if CONFIG_DTRACE
        /*
         * Free any outstanding lazy dof entries. It is imperative we
         * always call dtrace_lazy_dofs_destroy, rather than null check
         * and call if !NULL. If we NULL test, during lazy dof faulting
         * we can race with the faulting code and proceed from here to
         * beyond the helpers cleanup. The lazy dof faulting will then
         * install new helpers which will never be cleaned up, and leak.
         */
        dtrace_lazy_dofs_destroy(p);

        /*
         * Clean up any DTrace helper actions or probes for the process.
         */
        if (p->p_dtrace_helpers != NULL) {
                (*dtrace_helpers_cleanup)(p);
        }

        /*
         * Clean up any DTrace probes associated with this process.
         */
        /*
         * APPLE NOTE: We release ptss pages/entries in dtrace_fasttrap_exit_ptr(),
         * call this after dtrace_helpers_cleanup()
         */
        proc_lock(p);
        if (p->p_dtrace_probes && dtrace_fasttrap_exit_ptr) {
                (*dtrace_fasttrap_exit_ptr)(p);
        }
        proc_unlock(p);
#endif

        /* XXX Zombie allocation may fail, in which case stats get lost */
        MALLOC_ZONE(p->p_ru, struct rusage *,
                        sizeof (*p->p_ru), M_ZOMBIE, M_WAITOK);

        nspace_proc_exit(p);

        /*
         * need to cancel async IO requests that can be cancelled and wait for those
         * already active.  MAY BLOCK!
         */
        
        proc_refdrain(p);

        workqueue_mark_exiting(p);
        workqueue_exit(p);

        _aio_exit( p );

        /*
         * Close open files and release open-file table.
         * This may block!
         */
        fdfree(p);

        if (uth->uu_lowpri_window) {
                /*
                 * task is marked as a low priority I/O type
                 * and the I/O we issued while in flushing files on close
                 * collided with normal I/O operations...
                 * no need to throttle this thread since its going away
                 * but we do need to update our bookeeping w/r to throttled threads
                 */
                throttle_lowpri_io(FALSE);
        }

#if SYSV_SHM
        /* Close ref SYSV Shared memory*/
        if (p->vm_shm)
                shmexit(p);
#endif
#if SYSV_SEM
        /* Release SYSV semaphores */
        semexit(p);
#endif
        
#if PSYNCH
        pth_proc_hashdelete(p);
#endif /* PSYNCH */

        sessp = proc_session(p);
        if (SESS_LEADER(p, sessp)) {

                if (sessp->s_ttyvp != NULLVP) {
                        struct vnode *ttyvp;
                        int ttyvid;
                        struct vfs_context context;
                        struct tty * tp;


                        /*
                         * Controlling process.
                         * Signal foreground pgrp,
                         * drain controlling terminal
                         * and revoke access to controlling terminal.
                         */
                        tp = SESSION_TP(sessp);

                        if ((tp != TTY_NULL) && (tp->t_session == sessp)) {
                                tty_pgsignal(tp, SIGHUP, 1);

                                session_lock(sessp);
                                /* reget potentially tp due to revocation */
                                tp = SESSION_TP(sessp);
                                ttyvp = sessp->s_ttyvp;
                                ttyvid = sessp->s_ttyvid;
                                sessp->s_ttyvp = NULLVP;
                                sessp->s_ttyvid = 0;
                                sessp->s_ttyp = TTY_NULL;
                                sessp->s_ttypgrpid = NO_PID;
                                session_unlock(sessp);

                                if ((ttyvp != NULLVP) && (vnode_getwithvid(ttyvp, ttyvid) == 0)) {

                                        if (tp != TTY_NULL) {
                                                tty_lock(tp);
                                                (void) ttywait(tp);
                                                tty_unlock(tp);
                                        }
                                        context.vc_thread = proc_thread(p); /* XXX */
                                        context.vc_ucred = kauth_cred_proc_ref(p);
                                        VNOP_REVOKE(ttyvp, REVOKEALL, &context);
                                        vnode_put(ttyvp);
                                        kauth_cred_unref(&context.vc_ucred);
                                }
                        } else {
                                session_lock(sessp);
                                /* reget potentially tp due to revocation */
                                tp = SESSION_TP(sessp);
                                ttyvp = sessp->s_ttyvp;
                                sessp->s_ttyvp = NULLVP;
                                sessp->s_ttyvid = 0;
                                sessp->s_ttyp = TTY_NULL;
                                sessp->s_ttypgrpid = NO_PID;
                                session_unlock(sessp);
                        }
                        if (ttyvp)
                                vnode_rele(ttyvp);
                        /*
                         * s_ttyp is not zero'd; we use this to indicate
                         * that the session once had a controlling terminal.
                         * (for logging and informational purposes)
                         */
                }
                
                session_lock(sessp);
                sessp->s_leader = NULL;
                session_unlock(sessp);
        }
        session_rele(sessp);

        pg = proc_pgrp(p);
        fixjobc(p, pg, 0);
        pg_rele(pg);

        p->p_rlimit[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
        (void)acct_process(p);

        proc_list_lock();

        if ((p->p_listflag & P_LIST_EXITCOUNT) == P_LIST_EXITCOUNT) {
                p->p_listflag &= ~P_LIST_EXITCOUNT;
                proc_shutdown_exitcount--;
                if (proc_shutdown_exitcount == 0)
                        wakeup(&proc_shutdown_exitcount);
        }

        /* wait till parentrefs are dropped and grant no more */
        proc_childdrainstart(p);
        while ((q = p->p_children.lh_first) != NULL) {
                q->p_listflag |= P_LIST_DEADPARENT;
                if (q->p_stat == SZOMB) {
                        if (p != q->p_pptr)
                                panic("parent child linkage broken");
                        /* check for sysctl zomb lookup */
                        while ((q->p_listflag & P_LIST_WAITING) == P_LIST_WAITING) {
                                msleep(&q->p_stat, proc_list_mlock, PWAIT, "waitcoll", 0);
                        }
                        q->p_listflag |= P_LIST_WAITING;
                        /*
                         * This is a named reference and it is not granted
                         * if the reap is already in progress. So we get
                         * the reference here exclusively and their can be
                         * no waiters. So there is no need for a wakeup
                         * after we are done.  Also the reap frees the structure
                         * and the proc struct cannot be used for wakeups as well. 
                         * It is safe to use q here as this is system reap
                         */
                        (void)reap_child_locked(p, q, 1, 1, 0);
                } else {
                        proc_reparentlocked(q, initproc, 0, 1);
                        /*
                        * Traced processes are killed
                        * since their existence means someone is messing up.
                        */
                        if (q->p_lflag & P_LTRACED) {
                                /*
                                 * Take a reference on the child process to
                                 * ensure it doesn't exit and disappear between
                                 * the time we drop the list_lock and attempt
                                 * to acquire its proc_lock.
                                 */
                                if (proc_ref_locked(q) != q)
                                        continue;

                                proc_list_unlock();
                                proc_lock(q);
                                q->p_lflag &= ~P_LTRACED;
                                if (q->sigwait_thread) {
                                        thread_t thread = q->sigwait_thread;

                                        proc_unlock(q);
                                        /*
                                        * The sigwait_thread could be stopped at a
                                        * breakpoint. Wake it up to kill.
                                        * Need to do this as it could be a thread which is not
                                        * the first thread in the task. So any attempts to kill
                                        * the process would result into a deadlock on q->sigwait.
                                        */
                                        thread_resume(thread);
                                        clear_wait(thread, THREAD_INTERRUPTED);
                                        threadsignal(thread, SIGKILL, 0);
                                } else {
                                        proc_unlock(q);
                                }

                                psignal(q, SIGKILL);
                                proc_list_lock();
                                proc_rele_locked(q);
                        }
                }
        }

        proc_childdrainend(p);
        proc_list_unlock();

        /*
         * Release reference to text vnode
         */
        tvp = p->p_textvp;
        p->p_textvp = NULL;
        if (tvp != NULLVP) {
                vnode_rele(tvp);
        }

        /*
         * Save exit status and final rusage info, adding in child rusage
         * info and self times.  If we were unable to allocate a zombie
         * structure, this information is lost.
         */
        /* No need for locking here as no one than this thread can access this */
        if (p->p_ru != NULL) {
            calcru(p, &p->p_stats->p_ru.ru_utime, &p->p_stats->p_ru.ru_stime, NULL);
            *p->p_ru = p->p_stats->p_ru;

            ruadd(p->p_ru, &p->p_stats->p_cru);
        }

        /*
         * Free up profiling buffers.
         */
        {
                struct uprof *p0 = &p->p_stats->p_prof, *p1, *pn;

                p1 = p0->pr_next;
                p0->pr_next = NULL;
                p0->pr_scale = 0;

                for (; p1 != NULL; p1 = pn) {
                        pn = p1->pr_next;
                        kfree(p1, sizeof *p1);
                }
        }

        proc_spinlock(p);
        if (thread_call_cancel(p->p_rcall))
                p->p_ractive--;

        while (p->p_ractive > 0) {
                proc_spinunlock(p);
                
                delay(1);

                proc_spinlock(p);
        }
        proc_spinunlock(p);

        thread_call_free(p->p_rcall);
        p->p_rcall = NULL;

        /*
         * Other substructures are freed from wait().
         */
        FREE_ZONE(p->p_stats, sizeof *p->p_stats, M_PSTATS);
        p->p_stats = NULL;

        FREE_ZONE(p->p_sigacts, sizeof *p->p_sigacts, M_SIGACTS);
        p->p_sigacts = NULL;

        proc_limitdrop(p, 1);
        p->p_limit = NULL;


        /*
         * Finish up by terminating the task
         * and halt this thread (only if a
         * member of the task exiting).
         */
        p->task = TASK_NULL;
        set_bsdtask_info(task, NULL);

        /* exit status will be seen  by parent process */
        proc_knote(p, NOTE_EXIT | (p->p_xstat & 0xffff));

        /* mark the thread as the one that is doing proc_exit
         * no need to hold proc lock in uthread_free
         */
        uth->uu_flag |= UT_PROCEXIT;
        /*
         * Notify parent that we're gone.
         */
        pp = proc_parent(p);
        if (pp->p_flag & P_NOCLDWAIT) {

#if 3839178
                /*
                 * If the parent is ignoring SIGCHLD, then POSIX requires
                 * us to not add the resource usage to the parent process -
                 * we are only going to hand it off to init to get reaped.
                 * We should contest the standard in this case on the basis
                 * of RLIMIT_CPU.
                 */
#else   /* !3839178 */
                /*
                 * Add child resource usage to parent before giving
                 * zombie to init.  If we were unable to allocate a
                 * zombie structure, this information is lost.
                 */
                if (p->p_ru != NULL) {
                        proc_lock(pp);
                        ruadd(&pp->p_stats->p_cru, p->p_ru);
                        proc_unlock(pp);
                }
#endif  /* !3839178 */

                /* kernel can reap this one, no need to move it to launchd */
                proc_list_lock();
                p->p_listflag |= P_LIST_DEADPARENT;
                proc_list_unlock();
        }
        if ((p->p_listflag & P_LIST_DEADPARENT) == 0) {
                if (pp != initproc) {
                        proc_lock(pp);
                        pp->si_pid = p->p_pid;
                        pp->si_status = p->p_xstat;
                        pp->si_code = CLD_EXITED;
                        /*
                         * p_ucred usage is safe as it is an exiting process
                         * and reference is dropped in reap
                         */
                        pp->si_uid = kauth_cred_getruid(p->p_ucred);
                        proc_unlock(pp);
                }
                /* mark as a zombie */
                /* No need to take proc lock as all refs are drained and
                 * no one except parent (reaping ) can look at this.
                 * The write is to an int and is coherent. Also parent is
                 *  keyed off of list lock for reaping
                 */
                KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_PROC, BSD_PROC_EXIT) | DBG_FUNC_END,
                                              pid, exitval, 0, 0, 0);
                p->p_stat = SZOMB;
                /* 
                 * The current process can be reaped so, no one
                 * can depend on this
                 */

                psignal(pp, SIGCHLD);
        
                /* and now wakeup the parent */
                proc_list_lock();
                wakeup((caddr_t)pp);
                proc_list_unlock();
        } else {
                /* should be fine as parent proc would be initproc */
                /* mark as a zombie */
                /* No need to take proc lock as all refs are drained and
                 * no one except parent (reaping ) can look at this.
                 * The write is to an int and is coherent. Also parent is
                 *  keyed off of list lock for reaping
                 */
                proc_list_lock();
                KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_PROC, BSD_PROC_EXIT) | DBG_FUNC_END,
                                              pid, exitval, 0, 0, 0);
                /* check for sysctl zomb lookup */
                while ((p->p_listflag & P_LIST_WAITING) == P_LIST_WAITING) {
                        msleep(&p->p_stat, proc_list_mlock, PWAIT, "waitcoll", 0);
                }
                /* safe to use p as this is a system reap */
                p->p_stat = SZOMB;
                p->p_listflag |= P_LIST_WAITING;

                /*
                 * This is a named reference and it is not granted
                 * if the reap is already in progress. So we get
                 * the reference here exclusively and their can be
                 * no waiters. So there is no need for a wakeup
                 * after we are done. AlsO  the reap frees the structure
                 * and the proc struct cannot be used for wakeups as well. 
                 * It is safe to use p here as this is system reap
                 */
                (void)reap_child_locked(pp, p, 1, 1, 1);
                /* list lock dropped by reap_child_locked */
        }
        if (uth->uu_lowpri_window) {
                /*
                 * task is marked as a low priority I/O type and we've
                 * somehow picked up another throttle during exit processing...
                 * no need to throttle this thread since its going away
                 * but we do need to update our bookeeping w/r to throttled threads
                 */
                throttle_lowpri_io(FALSE);
        }

        proc_rele(pp);

}


/*
 * reap_child_locked
 *
 * Description: Given a process from which all status information needed
 *              has already been extracted, if the process is a ptrace
 *              attach process, detach it and give it back to its real
 *              parent, else recover all resources remaining associated
 *              with it.
 *
 * Parameters:  proc_t parent           Parent of process being reaped
 *              proc_t child            Process to reap
 *
 * Returns:     0                       Process was not reaped because it
 *                                      came from an attach
 *              1                       Process was reaped
 */
static int
reap_child_locked(proc_t parent, proc_t child, int deadparent, int locked, int droplock)
{
        proc_t trace_parent = PROC_NULL;        /* Traced parent process, if tracing */

        if (locked == 1)
                proc_list_unlock();
        
        /*
         * If we got the child via a ptrace 'attach',
         * we need to give it back to the old parent.
         *
         * Exception: someone who has been reparented to launchd before being
         * ptraced can simply be reaped, refer to radar 5677288
         *      p_oppid                  -> ptraced
         *      trace_parent == initproc -> away from launchd
         *      P_LIST_DEADPARENT        -> came to launchd by reparenting
         */
        if (child->p_oppid && (trace_parent = proc_find(child->p_oppid)) 
                        && !((trace_parent == initproc) && (child->p_lflag & P_LIST_DEADPARENT))) {
                proc_lock(child);
                child->p_oppid = 0;
                proc_unlock(child);
                if (trace_parent != initproc) {
                        /* 
                         * proc internal fileds  and p_ucred usage safe 
                         * here as child is dead and is not reaped or 
                         * reparented yet 
                         */
                        proc_lock(trace_parent);
                        trace_parent->si_pid = child->p_pid;
                        trace_parent->si_status = child->p_xstat;
                        trace_parent->si_code = CLD_CONTINUED;
                        trace_parent->si_uid = kauth_cred_getruid(child->p_ucred);
                        proc_unlock(trace_parent);
                }
                proc_reparentlocked(child, trace_parent, 1, 0);
                psignal(trace_parent, SIGCHLD);
                proc_list_lock();
                wakeup((caddr_t)trace_parent);
                child->p_listflag &= ~P_LIST_WAITING;
                wakeup(&child->p_stat);
                proc_list_unlock();
                proc_rele(trace_parent);
                if ((locked == 1) && (droplock == 0))
                        proc_list_lock();
                return (0);
        }
        
        if (trace_parent != PROC_NULL) {
                proc_rele(trace_parent);
        }
        
        proc_knote(child, NOTE_REAP);
        proc_knote_drain(child);

        child->p_xstat = 0;
        if (child->p_ru) {
                proc_lock(parent);
#if 3839178
                /*
                 * If the parent is ignoring SIGCHLD, then POSIX requires
                 * us to not add the resource usage to the parent process -
                 * we are only going to hand it off to init to get reaped.
                 * We should contest the standard in this case on the basis
                 * of RLIMIT_CPU.
                 */
                if (!(parent->p_flag & P_NOCLDWAIT))
#endif  /* 3839178 */
                        ruadd(&parent->p_stats->p_cru, child->p_ru);
                proc_unlock(parent);
                FREE_ZONE(child->p_ru, sizeof *child->p_ru, M_ZOMBIE);
                child->p_ru = NULL;
        } else {
                printf("Warning : lost p_ru for %s\n", child->p_comm);
        }

        AUDIT_SESSION_PROCEXIT(child);

        /*
         * Decrement the count of procs running with this uid.
         * p_ucred usage is safe here as it is an exited process.
         * and refernce is dropped after these calls down below
         * (locking protection is provided by list lock held in chgproccnt)
         */
        (void)chgproccnt(kauth_cred_getruid(child->p_ucred), -1);

#if CONFIG_LCTX
        ALLLCTX_LOCK;
        leavelctx(child);
        ALLLCTX_UNLOCK;
#endif

        /*
         * Free up credentials.
         */
        if (IS_VALID_CRED(child->p_ucred)) {
                kauth_cred_unref(&child->p_ucred);
        }

        /*  XXXX Note NOT SAFE TO USE p_ucred from this point onwards */

        /*
         * Finally finished with old proc entry.
         * Unlink it from its process group and free it.
         */
        leavepgrp(child);

        proc_list_lock();
        LIST_REMOVE(child, p_list);     /* off zombproc */
        parent->p_childrencnt--;
        LIST_REMOVE(child, p_sibling);
        /* If there are no more children wakeup parent */
        if ((deadparent != 0) && (LIST_EMPTY(&parent->p_children)))
                wakeup((caddr_t)parent);        /* with list lock held */
        child->p_listflag &= ~P_LIST_WAITING;
        wakeup(&child->p_stat);

        /* Take it out of process hash */
        LIST_REMOVE(child, p_hash);
        child->p_listflag &= ~P_LIST_INHASH;
        proc_checkdeadrefs(child);
        nprocs--;

        proc_list_unlock();

#if CONFIG_FINE_LOCK_GROUPS
        lck_mtx_destroy(&child->p_mlock, proc_mlock_grp);
        lck_mtx_destroy(&child->p_fdmlock, proc_fdmlock_grp);
#if CONFIG_DTRACE
        lck_mtx_destroy(&child->p_dtrace_sprlock, proc_lck_grp);
#endif
        lck_spin_destroy(&child->p_slock, proc_slock_grp);
#else /* CONFIG_FINE_LOCK_GROUPS */
        lck_mtx_destroy(&child->p_mlock, proc_lck_grp);
        lck_mtx_destroy(&child->p_fdmlock, proc_lck_grp);
#if CONFIG_DTRACE
        lck_mtx_destroy(&child->p_dtrace_sprlock, proc_lck_grp);
#endif
        lck_spin_destroy(&child->p_slock, proc_lck_grp);
#endif /* CONFIG_FINE_LOCK_GROUPS */
        workqueue_destroy_lock(child);

        FREE_ZONE(child, sizeof *child, M_PROC);
        if ((locked == 1) && (droplock == 0))
                proc_list_lock();

        return (1);
}


int
wait1continue(int result)
{
        void *vt;
        thread_t thread;
        int *retval;
        proc_t p;

        if (result)
                return(result);

        p = current_proc();
        thread = current_thread();
        vt = get_bsduthreadarg(thread);
        retval = get_bsduthreadrval(thread);
        return(wait4(p, (struct wait4_args *)vt, retval));
}

int
wait4(proc_t q, struct wait4_args *uap, int32_t *retval)
{
        __pthread_testcancel(1);
        return(wait4_nocancel(q, (struct wait4_nocancel_args *)uap, retval));
}

int
wait4_nocancel(proc_t q, struct wait4_nocancel_args *uap, int32_t *retval)
{
        int nfound;
        int sibling_count;
        proc_t p;
        int status, error;

        AUDIT_ARG(pid, uap->pid);

        if (uap->pid == 0)
                uap->pid = -q->p_pgrpid;

loop:
        proc_list_lock();
loop1:
        nfound = 0;
        sibling_count = 0;

        for (p = q->p_children.lh_first; p != 0; p = p->p_sibling.le_next) {
                if ( p->p_sibling.le_next != 0 )
                        sibling_count++;
                if (uap->pid != WAIT_ANY &&
                    p->p_pid != uap->pid &&
                    p->p_pgrpid != -(uap->pid))
                        continue;

                nfound++;

                /* XXX This is racy because we don't get the lock!!!! */

                if (p->p_listflag & P_LIST_WAITING) {
                        (void)msleep(&p->p_stat, proc_list_mlock, PWAIT, "waitcoll", 0);
                        goto loop1;
                }
                p->p_listflag |= P_LIST_WAITING;   /* only allow single thread to wait() */


                if (p->p_stat == SZOMB) {
                        proc_list_unlock();
#if CONFIG_MACF
                        if ((error = mac_proc_check_wait(q, p)) != 0)
                                goto out;
#endif
                        retval[0] = p->p_pid;
                        if (uap->status) {
                                /* Legacy apps expect only 8 bits of status */
                                status = 0xffff & p->p_xstat;   /* convert to int */
                                error = copyout((caddr_t)&status,
                                                        uap->status,
                                                    sizeof(status));
                                if (error) 
                                        goto out;
                        }
                        if (uap->rusage) {
                                if (p->p_ru == NULL) {
                                        error = ENOMEM;
                                } else {
                                        if (IS_64BIT_PROCESS(q)) {
                                                struct user64_rusage    my_rusage;
                                                munge_user64_rusage(p->p_ru, &my_rusage);
                                                error = copyout((caddr_t)&my_rusage,
                                                        uap->rusage,
                                                        sizeof (my_rusage));
                                        }
                                        else {
                                                struct user32_rusage    my_rusage;
                                                munge_user32_rusage(p->p_ru, &my_rusage);
                                                error = copyout((caddr_t)&my_rusage,
                                                        uap->rusage,
                                                        sizeof (my_rusage));
                                        }
                                }
                                /* information unavailable? */
                                if (error) 
                                        goto out;
                        }

                        /* Conformance change for 6577252.
                         * When SIGCHLD is blocked and wait() returns because the status
                         * of a child process is available and there are no other 
                         * children processes, then any pending SIGCHLD signal is cleared.
                         */
                        if ( sibling_count == 0 ) {
                                int mask = sigmask(SIGCHLD);
                                uthread_t uth = (struct uthread *)get_bsdthread_info(current_thread());

                                if ( (uth->uu_sigmask & mask) != 0 ) {
                                        /* we are blocking SIGCHLD signals.  clear any pending SIGCHLD.
                                         * This locking looks funny but it is protecting access to the 
                                         * thread via p_uthlist.
                                         */
                                        proc_lock(q); 
                                        uth->uu_siglist &= ~mask;       /* clear pending signal */
                                        proc_unlock(q);
                                }
                        }
                        
                        /* Clean up */
                        (void)reap_child_locked(q, p, 0, 0, 0);

                        return (0);
                }
                if (p->p_stat == SSTOP && (p->p_lflag & P_LWAITED) == 0 &&
                    (p->p_lflag & P_LTRACED || uap->options & WUNTRACED)) {
                        proc_list_unlock();
#if CONFIG_MACF
                        if ((error = mac_proc_check_wait(q, p)) != 0)
                                goto out;
#endif
                        proc_lock(p);
                        p->p_lflag |= P_LWAITED;
                        proc_unlock(p);
                        retval[0] = p->p_pid;
                        if (uap->status) {
                                status = W_STOPCODE(p->p_xstat);
                                error = copyout((caddr_t)&status,
                                        uap->status,
                                    sizeof(status));
                        } else
                                error = 0;
                        goto out;
                }
                /*
                 * If we are waiting for continued processses, and this
                 * process was continued
                 */
                if ((uap->options & WCONTINUED) &&
                    (p->p_flag & P_CONTINUED)) {
                        proc_list_unlock();
#if CONFIG_MACF
                        if ((error = mac_proc_check_wait(q, p)) != 0)
                                goto out;
#endif

                        /* Prevent other process for waiting for this event */
                        OSBitAndAtomic(~((uint32_t)P_CONTINUED), &p->p_flag);
                        retval[0] = p->p_pid;
                        if (uap->status) {
                                status = W_STOPCODE(SIGCONT);
                                error = copyout((caddr_t)&status,
                                        uap->status,
                                    sizeof(status));
                        } else
                                error = 0;
                        goto out;
                }
                p->p_listflag &= ~P_LIST_WAITING;
                wakeup(&p->p_stat);
        }
        /* list lock is held when we get here any which way */
        if (nfound == 0) {
                proc_list_unlock();
                return (ECHILD);
        }

        if (uap->options & WNOHANG) {
                retval[0] = 0;
                proc_list_unlock();
                return (0);
        }

        if ((error = msleep0((caddr_t)q, proc_list_mlock, PWAIT | PCATCH | PDROP, "wait", 0, wait1continue)))
                return (error);

        goto loop;
out:
        proc_list_lock();
        p->p_listflag &= ~P_LIST_WAITING;
        wakeup(&p->p_stat);
        proc_list_unlock();
        return (error);
}


int
waitidcontinue(int result)
{
        void *vt;
        thread_t thread;
        int *retval;

        if (result)
                return(result);

        thread = current_thread();
        vt = get_bsduthreadarg(thread);
        retval = get_bsduthreadrval(thread);
        return(waitid(current_proc(), (struct waitid_args *)vt, retval));
}

/*
 * Description: Suspend the calling thread until one child of the process
 *              containing the calling thread changes state.
 *
 * Parameters:  uap->idtype             one of P_PID, P_PGID, P_ALL
 *              uap->id                 pid_t or gid_t or ignored
 *              uap->infop              Address of signinfo_t struct in
 *                                      user space into which to return status
 *              uap->options            flag values
 *
 * Returns:     0                       Success
 *              !0                      Error returning status to user space
 */
int
waitid(proc_t q, struct waitid_args *uap, int32_t *retval)
{
        __pthread_testcancel(1);
        return(waitid_nocancel(q, (struct waitid_nocancel_args *)uap, retval));
}

int
waitid_nocancel(proc_t q, struct waitid_nocancel_args *uap, __unused int32_t *retval)
{
        user_siginfo_t  collect64;      /* siginfo data to return to caller */

        int nfound;
        proc_t p;
        int error;

        /*
         * Forced validation of options for T.waitpid 21; should be a TSD!
         * This will pass the test, but note that we have more bits than the
         * standard specifies that we will allow in, in this case.  The test
         * passes because they light all the bits, not just the ones we allow,
         * and so the following check returns EINVAL like the test wants.
         */
        if (((uap->options & (WNOHANG|WNOWAIT|WCONTINUED|WUNTRACED|WSTOPPED|WEXITED)) != uap->options) ||
            (uap->options == 0))
                return (EINVAL);        /* bits set that aren't recognized */

        /*
         * Overly critical options checking, per POSIX
         */
        switch(uap->idtype) {
        case P_PID:     /* child with process ID equal to... */
        case P_PGID:    /* child with process group ID equal to... */
                if (((int)uap->id) < 0)
                        return (EINVAL);
                break;
        case P_ALL:     /* any child */
                break;
        }

loop:
        proc_list_lock();
loop1:
        nfound = 0;
        for (p = q->p_children.lh_first; p != 0; p = p->p_sibling.le_next) {
                switch(uap->idtype) {
                case P_PID:     /* child with process ID equal to... */
                        if (p->p_pid != (pid_t)uap->id)
                                continue;
                        break;
                case P_PGID:    /* child with process group ID equal to... */
                        if (p->p_pgrpid != (pid_t)uap->id)
                                continue;
                        break;
                case P_ALL:     /* any child */
                        break;
                }

                /* XXX This is racy because we don't get the lock!!!! */

                /*
                 * Wait collision; go to sleep and restart; used to maintain
                 * the single return for waited process guarantee.
                 */
                if (p->p_listflag & P_LIST_WAITING) {
                        (void)msleep(&p->p_stat, proc_list_mlock, PWAIT, "waitidcoll", 0);
                        goto loop1;
                }
                p->p_listflag |= P_LIST_WAITING;                /* mark busy */

                nfound++;

                /*
                 * Types of processes we are interested in
                 *
                 * XXX Don't know what to do for WCONTINUED?!?
                 */
                switch(p->p_stat) {
                case SZOMB:             /* Exited */
                        if (!(uap->options & WEXITED))
                                break;

                        /* drop the lock and the thread is going to return */
                        proc_list_unlock();

                        /* Collect "siginfo" information for caller */
                        collect64.si_signo = SIGCHLD;
                        collect64.si_code = 0;
                        collect64.si_errno = 0;
                        collect64.si_pid = 0;
                        collect64.si_uid = 0;
                        collect64.si_addr  = 0;
                        collect64.si_status = WEXITSTATUS(p->p_xstat);
                        collect64.si_band = 0;

                        if (IS_64BIT_PROCESS(p)) {
                                user64_siginfo_t sinfo64;
                                
                                siginfo_user_to_user64(&collect64, &sinfo64);
                                
                                error = copyout((caddr_t)&sinfo64,
                                        uap->infop,
                                        sizeof(sinfo64));
                        } else {
                                user32_siginfo_t sinfo32;
                                
                                siginfo_user_to_user32(&collect64, &sinfo32);
                                
                                error = copyout((caddr_t)&sinfo32,
                                                                uap->infop,
                                                                sizeof(sinfo32));
                        }
                        /* information unavailable? */
                        if (error) 
                                goto out;

                        /* Prevent other process for waiting for this event? */
                        if (!(uap->options & WNOWAIT)) {
                                /* Clean up */
                                (void)reap_child_locked(q, p, 0, 0, 0);
                        } else {
                                proc_list_lock();
                                p->p_listflag &= ~P_LIST_WAITING;
                                proc_list_unlock();
                        }

                        return (0);

                case SSTOP:             /* Stopped */
                        /*
                         * If we are not interested in stopped processes, then
                         * ignore this one.
                         */
                        if (!(uap->options & WSTOPPED))
                                break;

                        /*
                         * If someone has already waited it, we lost a race
                         * to be the one to return status.
                         */
                        if ((p->p_lflag & P_LWAITED) != 0)
                                break;

                        /* drop the lock and the thread is going to return */
                        proc_list_unlock();

                        /* Collect "siginfo" information for caller */
                        collect64.si_signo = SIGCHLD;
                        collect64.si_code = 0;
                        collect64.si_errno = 0;
                        collect64.si_pid = 0;
                        collect64.si_uid = 0;
                        collect64.si_addr  = 0;
                        proc_lock(p);
                        collect64.si_status = p->p_xstat;
                        proc_unlock(p);
                        collect64.si_band = 0;

                        if (IS_64BIT_PROCESS(p)) {
                                user64_siginfo_t sinfo64;
                                
                                siginfo_user_to_user64(&collect64, &sinfo64);
                                
                                error = copyout((caddr_t)&sinfo64,
                                                                uap->infop,
                                                                sizeof(sinfo64));
                        } else {
                                user32_siginfo_t sinfo32;
                                
                                siginfo_user_to_user32(&collect64, &sinfo32);
                                
                                error = copyout((caddr_t)&sinfo32,
                                                                uap->infop,
                                                                sizeof(sinfo32));
                        }
                        /* information unavailable? */
                        if (error)
                                goto out;

                        /* Prevent other process for waiting for this event? */
                        if (!(uap->options & WNOWAIT)) {
                                proc_lock(p);
                                p->p_lflag |= P_LWAITED;
                                proc_unlock(p);
                        }

                        error = 0;
                        goto out;

                default:                /* All others */
                                        /* ...meaning Continued */
                        if (!(uap->options & WCONTINUED))
                                break;

                        /*
                         * If the flag isn't set, then this process has not
                         * been stopped and continued, or the status has
                         * already been reaped by another caller of waitid().
                         */
                        if ((p->p_flag & P_CONTINUED) == 0)
                                break;

                        /* drop the lock and the thread is going to return */
                        proc_list_unlock();

                        /* Collect "siginfo" information for caller */
                        proc_lock(p);
                        collect64.si_signo = SIGCHLD;
                        collect64.si_code = CLD_CONTINUED;
                        collect64.si_errno = 0;
                        collect64.si_pid = p->p_contproc;
                        collect64.si_uid = 0;
                        collect64.si_addr  = 0;
                        collect64.si_status = p->p_xstat;
                        collect64.si_band = 0;
                        proc_unlock(p);

                        if (IS_64BIT_PROCESS(p)) {
                                user64_siginfo_t sinfo64;
                                
                                siginfo_user_to_user64(&collect64, &sinfo64);
                                
                                error = copyout((caddr_t)&sinfo64,
                                                                uap->infop,
                                                                sizeof(sinfo64));
                        } else {
                                user32_siginfo_t sinfo32;
                                
                                siginfo_user_to_user32(&collect64, &sinfo32);
                                
                                error = copyout((caddr_t)&sinfo32,
                                                                uap->infop,
                                                                sizeof(sinfo32));
                        }
                        /* information unavailable? */
                        if (error)
                                goto out;

                        /* Prevent other process for waiting for this event? */
                        if (!(uap->options & WNOWAIT)) {
                                OSBitAndAtomic(~((uint32_t)P_CONTINUED), &p->p_flag);
                        }

                        error = 0;
                        goto out;
                }
                /* LIST LOCK IS HELD HERE */
                /* Not a process we are interested in; go on to next child */
                
                p->p_listflag &= ~P_LIST_WAITING;
                wakeup(&p->p_stat);
        }

        /* list lock is always held */
        /* No child processes that could possibly satisfy the request? */
        if (nfound == 0) {
                proc_list_unlock();
                return (ECHILD);
        }

        if (uap->options & WNOHANG) {
                proc_list_unlock();
                return (0);
        }

        if ((error = msleep0((caddr_t)q, proc_list_mlock, PWAIT | PCATCH | PDROP, "waitid", 0, waitidcontinue)))
                return (error);

        goto loop;
out:
        proc_list_lock();
        p->p_listflag &= ~P_LIST_WAITING;
        wakeup(&p->p_stat);
        proc_list_unlock();
        return (error);
}

/*
 * make process 'parent' the new parent of process 'child'.
 */
void
proc_reparentlocked(proc_t child, proc_t parent, int cansignal, int locked)
{
        proc_t oldparent = PROC_NULL;

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

        if (locked == 0)
                proc_list_lock();

        oldparent = child->p_pptr;
#if __PROC_INTERNAL_DEBUG
        if (oldparent == PROC_NULL)
                panic("proc_reparent: process %p does not have a parent\n", child);
#endif

        LIST_REMOVE(child, p_sibling);
#if __PROC_INTERNAL_DEBUG
        if (oldparent->p_childrencnt == 0)
                panic("process children count already 0\n");
#endif
        oldparent->p_childrencnt--;
#if __PROC_INTERNAL_DEBUG1
        if (oldparent->p_childrencnt < 0)
                panic("process children count -ve\n");
#endif
        LIST_INSERT_HEAD(&parent->p_children, child, p_sibling);
        parent->p_childrencnt++;        
        child->p_pptr = parent;
        child->p_ppid = parent->p_pid;

        proc_list_unlock();

        if ((cansignal != 0) && (initproc == parent) && (child->p_stat == SZOMB))
                psignal(initproc, SIGCHLD);
        if (locked == 1)
                proc_list_lock();
}

/*
 * 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
vfork_exit(proc_t p, int rv)
{
        vfork_exit_internal(p, rv, 0);
}

void
vfork_exit_internal(proc_t p, int rv, int forceexit)
{
        thread_t self = current_thread();
#ifdef FIXME
        struct task *task = p->task;
#endif
        struct uthread *ut;

        /*
         * If a thread in this task has already
         * called exit(), then halt any others
         * right here.
         */

         ut = get_bsdthread_info(self);


        proc_lock(p);
         if ((p->p_lflag & P_LPEXIT) == P_LPEXIT) {
                /* 
                * This happens when a parent exits/killed and vfork is in progress  
                * other threads. But shutdown code for ex has already called exit1()
                */
                proc_unlock(p);
                return;
        }
        p->p_lflag |= (P_LEXIT | P_LPEXIT);
        proc_unlock(p);

        if (forceexit == 0) {
                /*
                 * parent of a vfork child has already called exit() and the 
                 * thread that has vfork in proress terminates. So there is no
                 * separate address space here and it has already been marked for
                 * termination. This was never covered before and could cause problems
                 * if we block here for outside code.
                 */
                /* Notify the perf server */
                (void)sys_perf_notify(self, p->p_pid);
        }

        /*
         * Remove proc from allproc queue and from pidhash chain.
         * Need to do this before we do anything that can block.
         * Not doing causes things like mount() find this on allproc
         * in partially cleaned state.
         */

        proc_list_lock();

        LIST_REMOVE(p, p_list);
        LIST_INSERT_HEAD(&zombproc, p, p_list); /* Place onto zombproc. */
        /* will not be visible via proc_find */
        p->p_listflag |= P_LIST_EXITED;

        proc_list_unlock();

        proc_lock(p);
        p->p_xstat = rv;
        p->p_lflag &= ~(P_LTRACED | P_LPPWAIT);
        p->p_sigignore = ~0;
        proc_unlock(p);

        proc_spinlock(p);
        if (thread_call_cancel(p->p_rcall))
                p->p_ractive--;

        while (p->p_ractive > 0) {
                proc_spinunlock(p);
                
                delay(1);

                proc_spinlock(p);
        }
        proc_spinunlock(p);

        thread_call_free(p->p_rcall);
        p->p_rcall = NULL;

        ut->uu_siglist = 0;

        vproc_exit(p);
}

void 
vproc_exit(proc_t p)
{
        proc_t q;
        proc_t pp;
        
        vnode_t tvp;
#ifdef FIXME
        struct task *task = p->task;
#endif
        struct pgrp * pg;
        struct session *sessp;

        /* XXX Zombie allocation may fail, in which case stats get lost */
        MALLOC_ZONE(p->p_ru, struct rusage *,
                        sizeof (*p->p_ru), M_ZOMBIE, M_WAITOK);


        proc_refdrain(p);

        /*
         * Close open files and release open-file table.
         * This may block!
         */
        fdfree(p);

        sessp = proc_session(p);
        if (SESS_LEADER(p, sessp)) {
                
                if (sessp->s_ttyvp != NULLVP) {
                        struct vnode *ttyvp;
                        int ttyvid;
                        struct vfs_context context;
                        struct tty * tp;

                        /*
                         * Controlling process.
                         * Signal foreground pgrp,
                         * drain controlling terminal
                         * and revoke access to controlling terminal.
                         */
                        tp = SESSION_TP(sessp);

                        if ((tp != TTY_NULL) && (tp->t_session == sessp)) {
                                tty_pgsignal(tp, SIGHUP, 1);
                                tty_lock(tp);
                                (void) ttywait(tp);
                                tty_unlock(tp);
                                /*
                                 * The tty could have been revoked
                                 * if we blocked.
                                 */

                                session_lock(sessp);
                                /* reget in case of race */
                                tp = SESSION_TP(sessp);
                                ttyvp = sessp->s_ttyvp;
                                ttyvid = sessp->s_ttyvid;
                                sessp->s_ttyvp = NULL;
                                sessp->s_ttyvid = 0;
                                sessp->s_ttyp = TTY_NULL;
                                sessp->s_ttypgrpid = NO_PID;
                                session_unlock(sessp);

                               if ((ttyvp != NULLVP) && (vnode_getwithvid(ttyvp, ttyvid) == 0)) {
                                        context.vc_thread = proc_thread(p); /* XXX */
                                        context.vc_ucred = kauth_cred_proc_ref(p);
                                        VNOP_REVOKE(ttyvp, REVOKEALL, &context);
                                        vnode_put(ttyvp);
                                        kauth_cred_unref(&context.vc_ucred);
                                }
                        } else {
                                session_lock(sessp);
                                ttyvp = sessp->s_ttyvp;
                                sessp->s_ttyvp = NULL;
                                sessp->s_ttyvid = 0;
                                sessp->s_ttyp = TTY_NULL;
                                sessp->s_ttypgrpid = NO_PID;
                                session_unlock(sessp);
                        }
                        if (ttyvp) 
                                vnode_rele(ttyvp);
                        /*
                         * s_ttyp is not zero'd; we use this to indicate
                         * that the session once had a controlling terminal.
                         * (for logging and informational purposes)
                         */
                }

                session_lock(sessp);
                sessp->s_leader = NULL;
                session_unlock(sessp);
        }
        session_rele(sessp);

        pg = proc_pgrp(p);
        fixjobc(p, pg, 0);
        pg_rele(pg);

        p->p_rlimit[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;

        proc_list_lock();
        proc_childdrainstart(p);
        while ((q = p->p_children.lh_first) != NULL) {
                q->p_listflag |= P_LIST_DEADPARENT;
                if (q->p_stat == SZOMB) {
                        if (p != q->p_pptr)
                                panic("parent child linkage broken");
                        /* check for lookups by zomb sysctl */
                        while ((q->p_listflag & P_LIST_WAITING) == P_LIST_WAITING) {
                                msleep(&q->p_stat, proc_list_mlock, PWAIT, "waitcoll", 0);
                        }
                        q->p_listflag |= P_LIST_WAITING;
                        /*
                         * This is a named reference and it is not granted
                         * if the reap is already in progress. So we get
                         * the reference here exclusively and their can be
                         * no waiters. So there is no need for a wakeup
                         * after we are done. AlsO  the reap frees the structure
                         * and the proc struct cannot be used for wakeups as well. 
                         * It is safe to use q here as this is system reap
                         */
                        (void)reap_child_locked(p, q, 1, 1, 0);
                } else {
                        proc_reparentlocked(q, initproc, 0, 1);
                        /*
                        * Traced processes are killed
                        * since their existence means someone is messing up.
                        */
                        if (q->p_lflag & P_LTRACED) {
                                proc_list_unlock();
                                proc_lock(q);
                                q->p_lflag &= ~P_LTRACED;
                                if (q->sigwait_thread) {
                                        thread_t thread = q->sigwait_thread;

                                        proc_unlock(q);
                                        /*
                                        * The sigwait_thread could be stopped at a
                                        * breakpoint. Wake it up to kill.
                                        * Need to do this as it could be a thread which is not
                                        * the first thread in the task. So any attempts to kill
                                        * the process would result into a deadlock on q->sigwait.
                                        */
                                        thread_resume(thread);
                                        clear_wait(thread, THREAD_INTERRUPTED);
                                        threadsignal(thread, SIGKILL, 0);
                                } else {
                                        proc_unlock(q);
                                }

                                psignal(q, SIGKILL);
                                proc_list_lock();
                        }
                }
        }

        proc_childdrainend(p);
        proc_list_unlock();

        /*
         * Release reference to text vnode
         */
        tvp = p->p_textvp;
        p->p_textvp = NULL;
        if (tvp != NULLVP) {
                vnode_rele(tvp);
        }

        /*
         * Save exit status and final rusage info, adding in child rusage
         * info and self times.  If we were unable to allocate a zombie
         * structure, this information is lost.
         */
        /* No need for locking here as no one than this thread can access this */
        if (p->p_ru != NULL) {
            *p->p_ru = p->p_stats->p_ru;
            timerclear(&p->p_ru->ru_utime);
            timerclear(&p->p_ru->ru_stime);

#ifdef  FIXME
            if (task) {
                task_basic_info_data_t tinfo;
                task_thread_times_info_data_t ttimesinfo;
                int task_info_stuff, task_ttimes_stuff;
                struct timeval ut,st;

                task_info_stuff = TASK_BASIC_INFO_COUNT;
                task_info(task, TASK_BASIC_INFO,
                          &tinfo, &task_info_stuff);
                p->p_ru->ru_utime.tv_sec = tinfo.user_time.seconds;
                p->p_ru->ru_utime.tv_usec = tinfo.user_time.microseconds;
                p->p_ru->ru_stime.tv_sec = tinfo.system_time.seconds;
                p->p_ru->ru_stime.tv_usec = tinfo.system_time.microseconds;

                task_ttimes_stuff = TASK_THREAD_TIMES_INFO_COUNT;
                task_info(task, TASK_THREAD_TIMES_INFO,
                          &ttimesinfo, &task_ttimes_stuff);

                ut.tv_sec = ttimesinfo.user_time.seconds;
                ut.tv_usec = ttimesinfo.user_time.microseconds;
                st.tv_sec = ttimesinfo.system_time.seconds;
                st.tv_usec = ttimesinfo.system_time.microseconds;
                timeradd(&ut,&p->p_ru->ru_utime,&p->p_ru->ru_utime);
                        timeradd(&st,&p->p_ru->ru_stime,&p->p_ru->ru_stime);
            }
#endif /* FIXME */

            ruadd(p->p_ru, &p->p_stats->p_cru);
        }

        /*
         * Free up profiling buffers.
         */
        {
                struct uprof *p0 = &p->p_stats->p_prof, *p1, *pn;

                p1 = p0->pr_next;
                p0->pr_next = NULL;
                p0->pr_scale = 0;

                for (; p1 != NULL; p1 = pn) {
                        pn = p1->pr_next;
                        kfree(p1, sizeof *p1);
                }
        }

#if PSYNCH
        pth_proc_hashdelete(p);
#endif /* PSYNCH */

        /*
         * Other substructures are freed from wait().
         */
        FREE_ZONE(p->p_stats, sizeof *p->p_stats, M_PSTATS);
        p->p_stats = NULL;

        FREE_ZONE(p->p_sigacts, sizeof *p->p_sigacts, M_SIGACTS);
        p->p_sigacts = NULL;

        proc_limitdrop(p, 1);
        p->p_limit = NULL;

        /*
         * Finish up by terminating the task
         * and halt this thread (only if a
         * member of the task exiting).
         */
        p->task = TASK_NULL;

        /*
         * Notify parent that we're gone.
         */
        pp = proc_parent(p);
        if ((p->p_listflag & P_LIST_DEADPARENT) == 0) {
                if (pp != initproc) {
                        proc_lock(pp);
                        pp->si_pid = p->p_pid;
                        pp->si_status = p->p_xstat;
                        pp->si_code = CLD_EXITED;
                        /*
                         * p_ucred usage is safe as it is an exiting process
                         * and reference is dropped in reap
                         */
                        pp->si_uid = kauth_cred_getruid(p->p_ucred);
                        proc_unlock(pp);
                }
                /* mark as a zombie */
                /* mark as a zombie */
                /* No need to take proc lock as all refs are drained and
                 * no one except parent (reaping ) can look at this.
                 * The write is to an int and is coherent. Also parent is
                 *  keyed off of list lock for reaping
                 */
                p->p_stat = SZOMB;

                psignal(pp, SIGCHLD);

                /* and now wakeup the parent */
                proc_list_lock();
                wakeup((caddr_t)pp);
                proc_list_unlock();
        } else {
                proc_list_lock();
                /* check for lookups by zomb sysctl */
                while ((p->p_listflag & P_LIST_WAITING) == P_LIST_WAITING) {
                        msleep(&p->p_stat, proc_list_mlock, PWAIT, "waitcoll", 0);
                }
                p->p_stat = SZOMB;
                p->p_listflag |= P_LIST_WAITING;

                /*
                 * This is a named reference and it is not granted
                 * if the reap is already in progress. So we get
                 * the reference here exclusively and their can be
                 * no waiters. So there is no need for a wakeup
                 * after we are done. AlsO  the reap frees the structure
                 * and the proc struct cannot be used for wakeups as well. 
                 * It is safe to use p here as this is system reap
                 */
                (void)reap_child_locked(pp, p, 0, 1, 1);
                /* list lock dropped by reap_child_locked */
        }
        proc_rele(pp);
}

                                                
/*
 * munge_rusage
 *      LP64 support - long is 64 bits if we are dealing with a 64 bit user
 *      process.  We munge the kernel version of rusage into the
 *      64 bit version.
 */
__private_extern__  void 
munge_user64_rusage(struct rusage *a_rusage_p, struct user64_rusage *a_user_rusage_p)
{
        /* timeval changes size, so utime and stime need special handling */
        a_user_rusage_p->ru_utime.tv_sec = a_rusage_p->ru_utime.tv_sec;
        a_user_rusage_p->ru_utime.tv_usec = a_rusage_p->ru_utime.tv_usec;
        a_user_rusage_p->ru_stime.tv_sec = a_rusage_p->ru_stime.tv_sec;
        a_user_rusage_p->ru_stime.tv_usec = a_rusage_p->ru_stime.tv_usec;
        /*
         * everything else can be a direct assign, since there is no loss
         * of precision implied boing 32->64.
         */
        a_user_rusage_p->ru_maxrss = a_rusage_p->ru_maxrss;
        a_user_rusage_p->ru_ixrss = a_rusage_p->ru_ixrss;
        a_user_rusage_p->ru_idrss = a_rusage_p->ru_idrss;
        a_user_rusage_p->ru_isrss = a_rusage_p->ru_isrss;
        a_user_rusage_p->ru_minflt = a_rusage_p->ru_minflt;
        a_user_rusage_p->ru_majflt = a_rusage_p->ru_majflt;
        a_user_rusage_p->ru_nswap = a_rusage_p->ru_nswap;
        a_user_rusage_p->ru_inblock = a_rusage_p->ru_inblock;
        a_user_rusage_p->ru_oublock = a_rusage_p->ru_oublock;
        a_user_rusage_p->ru_msgsnd = a_rusage_p->ru_msgsnd;
        a_user_rusage_p->ru_msgrcv = a_rusage_p->ru_msgrcv;
        a_user_rusage_p->ru_nsignals = a_rusage_p->ru_nsignals;
        a_user_rusage_p->ru_nvcsw = a_rusage_p->ru_nvcsw;
        a_user_rusage_p->ru_nivcsw = a_rusage_p->ru_nivcsw;
}

/* For a 64-bit kernel and 32-bit userspace, munging may be needed */
__private_extern__  void 
munge_user32_rusage(struct rusage *a_rusage_p, struct user32_rusage *a_user_rusage_p)
{
        /* timeval changes size, so utime and stime need special handling */
        a_user_rusage_p->ru_utime.tv_sec = a_rusage_p->ru_utime.tv_sec;
        a_user_rusage_p->ru_utime.tv_usec = a_rusage_p->ru_utime.tv_usec;
        a_user_rusage_p->ru_stime.tv_sec = a_rusage_p->ru_stime.tv_sec;
        a_user_rusage_p->ru_stime.tv_usec = a_rusage_p->ru_stime.tv_usec;
        /*
         * everything else can be a direct assign. We currently ignore
         * the loss of precision
         */
        a_user_rusage_p->ru_maxrss = a_rusage_p->ru_maxrss;
        a_user_rusage_p->ru_ixrss = a_rusage_p->ru_ixrss;
        a_user_rusage_p->ru_idrss = a_rusage_p->ru_idrss;
        a_user_rusage_p->ru_isrss = a_rusage_p->ru_isrss;
        a_user_rusage_p->ru_minflt = a_rusage_p->ru_minflt;
        a_user_rusage_p->ru_majflt = a_rusage_p->ru_majflt;
        a_user_rusage_p->ru_nswap = a_rusage_p->ru_nswap;
        a_user_rusage_p->ru_inblock = a_rusage_p->ru_inblock;
        a_user_rusage_p->ru_oublock = a_rusage_p->ru_oublock;
        a_user_rusage_p->ru_msgsnd = a_rusage_p->ru_msgsnd;
        a_user_rusage_p->ru_msgrcv = a_rusage_p->ru_msgrcv;
        a_user_rusage_p->ru_nsignals = a_rusage_p->ru_nsignals;
        a_user_rusage_p->ru_nvcsw = a_rusage_p->ru_nvcsw;
        a_user_rusage_p->ru_nivcsw = a_rusage_p->ru_nivcsw;
}