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

/*
 * Copyright (c) 2000-2004 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This 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 OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_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_fork.c 8.8 (Berkeley) 2/14/95
 */

#include <kern/assert.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/user.h>
#include <sys/resourcevar.h>
#include <sys/vnode_internal.h>
#include <sys/file_internal.h>
#include <sys/acct.h>
#if KTRACE
#include <sys/ktrace.h>
#endif

#include <bsm/audit_kernel.h>

#include <mach/mach_types.h>
#include <kern/kern_types.h>
#include <kern/kalloc.h>
#include <kern/mach_param.h>
#include <kern/task.h>
#include <kern/zalloc.h>

#include <machine/spl.h>

#include <vm/vm_protos.h>       // for vm_map_commpage64

thread_t cloneproc(struct proc *, int); 
struct proc * forkproc(struct proc *, int);
thread_t procdup(struct proc *child, struct proc *parent);

#define DOFORK  0x1     /* fork() system call */
#define DOVFORK 0x2     /* vfork() system call */
static int fork1(struct proc *, long, register_t *);

/*
 * fork system call.
 */
int
fork(struct proc *p, __unused void *uap, register_t *retval)
{
        return (fork1(p, (long)DOFORK, retval));
}

/*
 * vfork system call
 */
int
vfork(struct proc *p, void *uap, register_t *retval)
{
        register struct proc * newproc;
        register uid_t uid;
        thread_t cur_act = (thread_t)current_thread();
        int count;
        task_t t;
        uthread_t ut;

        /*
         * Although process entries are dynamically created, we still keep
         * a global limit on the maximum number we will create.  Don't allow
         * a nonprivileged user to use the last process; don't let root
         * exceed the limit. The variable nprocs is the current number of
         * processes, maxproc is the limit.
         */
        uid = kauth_cred_get()->cr_ruid;
        if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) {
                tablefull("proc");
                retval[1] = 0;
                return (EAGAIN);
        }

        /*
         * Increment the count of procs running with this uid. Don't allow
         * a nonprivileged user to exceed their current limit.
         */
        count = chgproccnt(uid, 1);
        if (uid != 0 && count > p->p_rlimit[RLIMIT_NPROC].rlim_cur) {
                (void)chgproccnt(uid, -1);
                return (EAGAIN);
        }

        ut = (struct uthread *)get_bsdthread_info(cur_act);
        if (ut->uu_flag & UT_VFORK) {
                printf("vfork called recursively by %s\n", p->p_comm);
                (void)chgproccnt(uid, -1);
                return (EINVAL);
        }
        p->p_flag  |= P_VFORK;
        p->p_vforkcnt++;

        /* The newly created process comes with signal lock held */
        newproc = (struct proc *)forkproc(p,1);

        AUDIT_ARG(pid, newproc->p_pid);

        LIST_INSERT_AFTER(p, newproc, p_pglist);
        newproc->p_pptr = p;
        newproc->task = p->task;
        LIST_INSERT_HEAD(&p->p_children, newproc, p_sibling);
        LIST_INIT(&newproc->p_children);
        LIST_INSERT_HEAD(&allproc, newproc, p_list);
        LIST_INSERT_HEAD(PIDHASH(newproc->p_pid), newproc, p_hash);
        TAILQ_INIT(& newproc->p_evlist);
        newproc->p_stat = SRUN;
        newproc->p_flag  |= P_INVFORK;
        newproc->p_vforkact = cur_act;

        ut->uu_flag |= UT_VFORK;
        ut->uu_proc = newproc;
        ut->uu_userstate = (void *)act_thread_csave();
        ut->uu_vforkmask = ut->uu_sigmask;

        /* temporarily drop thread-set-id state */
        if (ut->uu_flag & UT_SETUID) {
                ut->uu_flag |= UT_WASSETUID;
                ut->uu_flag &= ~UT_SETUID;
        }
        
        thread_set_child(cur_act, newproc->p_pid);

        microtime(&newproc->p_stats->p_start);
        newproc->p_acflag = AFORK;

        /*
         * Preserve synchronization semantics of vfork.  If waiting for
         * child to exec or exit, set P_PPWAIT on child, and sleep on our
         * proc (in case of exit).
         */
        newproc->p_flag |= P_PPWAIT;

        /* drop the signal lock on the child */
        signal_unlock(newproc);

        retval[0] = newproc->p_pid;
        retval[1] = 1;                  /* mark child */

        return (0);
}

/*
 * Return to parent vfork ehread()
 */
void
vfork_return(__unused thread_t th_act, struct proc *p, struct proc *p2,
        register_t *retval)
{
        thread_t cur_act = (thread_t)current_thread();
        uthread_t ut;
        
        ut = (struct uthread *)get_bsdthread_info(cur_act);

        act_thread_catt(ut->uu_userstate);

        /* Make sure only one at this time */
        p->p_vforkcnt--;
        if (p->p_vforkcnt <0)
                panic("vfork cnt is -ve");
        if (p->p_vforkcnt <=0)
                p->p_flag  &= ~P_VFORK;
        ut->uu_userstate = 0;
        ut->uu_flag &= ~UT_VFORK;
        /* restore thread-set-id state */
        if (ut->uu_flag & UT_WASSETUID) {
                ut->uu_flag |= UT_SETUID;
                ut->uu_flag &= UT_WASSETUID;
        }
        ut->uu_proc = 0;
        ut->uu_sigmask = ut->uu_vforkmask;
        p2->p_flag  &= ~P_INVFORK;
        p2->p_vforkact = (void *)0;

        thread_set_parent(cur_act, p2->p_pid);

        if (retval) {
                retval[0] = p2->p_pid;
                retval[1] = 0;                  /* mark parent */
        }

        return;
}

thread_t
procdup(struct proc *child, struct proc *parent)
{
        thread_t                thread;
        task_t                  task;
        kern_return_t   result;

        if (parent->task == kernel_task)
                result = task_create_internal(TASK_NULL, FALSE, FALSE, &task);
        else
                result = task_create_internal(parent->task, TRUE, (parent->p_flag & P_LP64), &task);
        if (result != KERN_SUCCESS)
            printf("fork/procdup: task_create failed. Code: 0x%x\n", result);
        child->task = task;
        /* task->proc = child; */
        set_bsdtask_info(task, child);
        if (parent->p_flag & P_LP64) {
                task_set_64bit(task, TRUE);
                vm_map_set_64bit(get_task_map(task));
                child->p_flag |= P_LP64;
                /* LP64todo - clean up this hacked mapping of commpage */
                pmap_map_sharedpage(task, get_map_pmap(get_task_map(task)));
                vm_map_commpage64(get_task_map(task));
        } else {
                task_set_64bit(task, FALSE);
                vm_map_set_32bit(get_task_map(task));
                child->p_flag &= ~P_LP64;
#ifdef __i386__
                /*
                 * On Intel, the comm page doesn't get mapped automatically
                 * because it goes beyond the end of the VM map in the current
                 * 3GB/1GB address space model.
                 * XXX This explicit mapping will probably become unnecessary
                 * when we switch to the new 4GB/4GB address space model.
                 */
                vm_map_commpage32(get_task_map(task));
#endif  /* __i386__ */
        }
        if (child->p_nice != 0)
                resetpriority(child);
                
        result = thread_create(task, &thread);
        if (result != KERN_SUCCESS)
            printf("fork/procdup: thread_create failed. Code: 0x%x\n", result);

        return(thread);
}


static int
fork1(p1, flags, retval)
        struct proc *p1;
        long flags;
        register_t *retval;
{
        register struct proc *p2;
        register uid_t uid;
        thread_t newth;
        int count;
        task_t t;

        /*
         * Although process entries are dynamically created, we still keep
         * a global limit on the maximum number we will create.  Don't allow
         * a nonprivileged user to use the last process; don't let root
         * exceed the limit. The variable nprocs is the current number of
         * processes, maxproc is the limit.
         */
        uid = kauth_cred_get()->cr_ruid;
        if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) {
                tablefull("proc");
                retval[1] = 0;
                return (EAGAIN);
        }

        /*
         * Increment the count of procs running with this uid. Don't allow
         * a nonprivileged user to exceed their current limit.
         */
        count = chgproccnt(uid, 1);
        if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) {
                (void)chgproccnt(uid, -1);
                return (EAGAIN);
        }

        /* The newly created process comes with signal lock held */
        newth = cloneproc(p1, 1);
        thread_dup(newth);
        /* p2 = newth->task->proc; */
        p2 = (struct proc *)(get_bsdtask_info(get_threadtask(newth)));
        set_security_token(p2);         /* propagate change of PID */

        AUDIT_ARG(pid, p2->p_pid);

        thread_set_child(newth, p2->p_pid);

        microtime(&p2->p_stats->p_start);
        p2->p_acflag = AFORK;

        /*
         * Preserve synchronization semantics of vfork.  If waiting for
         * child to exec or exit, set P_PPWAIT on child, and sleep on our
         * proc (in case of exit).
         */
        if (flags == DOVFORK)
                p2->p_flag |= P_PPWAIT;
        /* drop the signal lock on the child */
        signal_unlock(p2);

        (void) thread_resume(newth);

        /* drop the extra references we got during the creation */
        if ((t = (task_t)get_threadtask(newth)) != NULL) {
                task_deallocate(t);
        }
        thread_deallocate(newth);

        KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);

        while (p2->p_flag & P_PPWAIT)
                tsleep(p1, PWAIT, "ppwait", 0);

        retval[0] = p2->p_pid;
        retval[1] = 0;                  /* mark parent */

        return (0);
}

/*
 * cloneproc()
 *
 * Create a new process from a specified process.
 * On return newly created child process has signal
 * lock held to block delivery of signal to it if called with
 * lock set. fork() code needs to explicity remove this lock 
 * before signals can be delivered
 */
thread_t
cloneproc(p1, lock)
        register struct proc *p1;
        register int lock;
{
        register struct proc *p2;
        thread_t th;

        p2 = (struct proc *)forkproc(p1,lock);


        th = procdup(p2, p1);   /* child, parent */

        LIST_INSERT_AFTER(p1, p2, p_pglist);
        p2->p_pptr = p1;
        LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling);
        LIST_INIT(&p2->p_children);
        LIST_INSERT_HEAD(&allproc, p2, p_list);
        LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
        TAILQ_INIT(&p2->p_evlist);
        /*
         * Make child runnable, set start time.
         */
        p2->p_stat = SRUN;

        return(th);
}

struct proc *
forkproc(p1, lock)
        register struct proc *p1;
        register int lock;
{
        register struct proc *p2, *newproc;
        static int nextpid = 0, pidchecked = 0;

        /* Allocate new proc. */
        MALLOC_ZONE(newproc, struct proc *,
                        sizeof *newproc, M_PROC, M_WAITOK);
        if (newproc == NULL)
                panic("forkproc: M_PROC zone exhausted");
        MALLOC_ZONE(newproc->p_stats, struct pstats *,
                        sizeof *newproc->p_stats, M_SUBPROC, M_WAITOK);
        if (newproc->p_stats == NULL)
                panic("forkproc: M_SUBPROC zone exhausted (p_stats)");
        MALLOC_ZONE(newproc->p_sigacts, struct sigacts *,
                        sizeof *newproc->p_sigacts, M_SUBPROC, M_WAITOK);
        if (newproc->p_sigacts == NULL)
                panic("forkproc: M_SUBPROC zone exhausted (p_sigacts)");

        /*
         * Find an unused process ID.  We remember a range of unused IDs
         * ready to use (from nextpid+1 through pidchecked-1).
         */
        nextpid++;
retry:
        /*
         * If the process ID prototype has wrapped around,
         * restart somewhat above 0, as the low-numbered procs
         * tend to include daemons that don't exit.
         */
        if (nextpid >= PID_MAX) {
                nextpid = 100;
                pidchecked = 0;
        }
        if (nextpid >= pidchecked) {
                int doingzomb = 0;

                pidchecked = PID_MAX;
                /*
                 * Scan the active and zombie procs to check whether this pid
                 * is in use.  Remember the lowest pid that's greater
                 * than nextpid, so we can avoid checking for a while.
                 */
                p2 = allproc.lh_first;
again:
                for (; p2 != 0; p2 = p2->p_list.le_next) {
                        while (p2->p_pid == nextpid ||
                            p2->p_pgrp->pg_id == nextpid ||
                                p2->p_session->s_sid == nextpid) {
                                nextpid++;
                                if (nextpid >= pidchecked)
                                        goto retry;
                        }
                        if (p2->p_pid > nextpid && pidchecked > p2->p_pid)
                                pidchecked = p2->p_pid;
                        if (p2->p_pgrp && p2->p_pgrp->pg_id > nextpid && 
                            pidchecked > p2->p_pgrp->pg_id)
                                pidchecked = p2->p_pgrp->pg_id;
                        if (p2->p_session->s_sid > nextpid &&
                                pidchecked > p2->p_session->s_sid)
                                pidchecked = p2->p_session->s_sid;
                }
                if (!doingzomb) {
                        doingzomb = 1;
                        p2 = zombproc.lh_first;
                        goto again;
                }
        }

        nprocs++;
        p2 = newproc;
        p2->p_stat = SIDL;
        p2->p_shutdownstate = 0;
        p2->p_pid = nextpid;

        /*
         * Make a proc table entry for the new process.
         * Start by zeroing the section of proc that is zero-initialized,
         * then copy the section that is copied directly from the parent.
         */
        bzero(&p2->p_startzero,
            (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero));
        bcopy(&p1->p_startcopy, &p2->p_startcopy,
            (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy));
        p2->vm_shm = (void *)NULL; /* Make sure it is zero */

        /*
         * Some flags are inherited from the parent.
         * Duplicate sub-structures as needed.
         * Increase reference counts on shared objects.
         * The p_stats and p_sigacts substructs are set in vm_fork.
         */
        p2->p_flag = (p1->p_flag & (P_LP64 | P_TRANSLATED | P_AFFINITY));
        if (p1->p_flag & P_PROFIL)
                startprofclock(p2);
        /*
         * Note that if the current thread has an assumed identity, this
         * credential will be granted to the new process.
         */
        p2->p_ucred = kauth_cred_get_with_ref();

        lck_mtx_init(&p2->p_mlock, proc_lck_grp, proc_lck_attr);
        lck_mtx_init(&p2->p_fdmlock, proc_lck_grp, proc_lck_attr);
        klist_init(&p2->p_klist);

        /* bump references to the text vnode */
        p2->p_textvp = p1->p_textvp;
        if (p2->p_textvp) {
                vnode_rele(p2->p_textvp);
        }
        /* XXX may fail to copy descriptors to child */
        p2->p_fd = fdcopy(p1);

        if (p1->vm_shm) {
                /* XXX may fail to attach shm to child */
                (void)shmfork(p1,p2);
        }
        /*
         * If p_limit is still copy-on-write, bump refcnt,
         * otherwise get a copy that won't be modified.
         * (If PL_SHAREMOD is clear, the structure is shared
         * copy-on-write.)
         */
        if (p1->p_limit->p_lflags & PL_SHAREMOD)
                p2->p_limit = limcopy(p1->p_limit);
        else {
                p2->p_limit = p1->p_limit;
                p2->p_limit->p_refcnt++;
        }

        bzero(&p2->p_stats->pstat_startzero,
            (unsigned) ((caddr_t)&p2->p_stats->pstat_endzero -
            (caddr_t)&p2->p_stats->pstat_startzero));
        bcopy(&p1->p_stats->pstat_startcopy, &p2->p_stats->pstat_startcopy,
            ((caddr_t)&p2->p_stats->pstat_endcopy -
             (caddr_t)&p2->p_stats->pstat_startcopy));

        bzero(&p2->p_stats->user_p_prof, sizeof(struct user_uprof));

        if (p1->p_sigacts != NULL)
                (void)memcpy(p2->p_sigacts,
                                p1->p_sigacts, sizeof *p2->p_sigacts);
        else
                (void)memset(p2->p_sigacts, 0, sizeof *p2->p_sigacts);

        if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
                p2->p_flag |= P_CONTROLT;

        p2->p_argslen = p1->p_argslen;
        p2->p_argc = p1->p_argc;
        p2->p_xstat = 0;
        p2->p_ru = NULL;

        p2->p_debugger = 0;     /* don't inherit */
        lockinit(&p2->signal_lock, PVM, "signal", 0, 0);
        /* block all signals to reach the process */
        if (lock)
                signal_lock(p2);
        p2->sigwait = FALSE;
        p2->sigwait_thread = NULL;
        p2->exit_thread = NULL;
        p2->user_stack = p1->user_stack;
        p2->p_vforkcnt = 0;
        p2->p_vforkact = 0;
        p2->p_lflag  = 0;
        p2->p_ladvflag  = 0;
        p2->p_internalref  = 0;
        TAILQ_INIT(&p2->p_uthlist);
        TAILQ_INIT(&p2->aio_activeq);
        TAILQ_INIT(&p2->aio_doneq);
        p2->aio_active_count = 0;
        p2->aio_done_count = 0;

#if KTRACE
        /*
         * Copy traceflag and tracefile if enabled.
         * If not inherited, these were zeroed above.
         */
        if (p1->p_traceflag&KTRFAC_INHERIT) {
                p2->p_traceflag = p1->p_traceflag;
                if ((p2->p_tracep = p1->p_tracep) != NULL) {
                        vnode_ref(p2->p_tracep);
                }
        }
#endif
        return(p2);

}

void
proc_lock(proc_t p)
{
        lck_mtx_lock(&p->p_mlock);
}

void
proc_unlock(proc_t p)
{
        lck_mtx_unlock(&p->p_mlock);
}

#include <kern/zalloc.h>

struct zone     *uthread_zone;
int uthread_zone_inited = 0;

void
uthread_zone_init(void)
{
        if (!uthread_zone_inited) {
                uthread_zone = zinit(sizeof(struct uthread),
                                        THREAD_MAX * sizeof(struct uthread),
                                        THREAD_CHUNK * sizeof(struct uthread),
                                        "uthreads");
                uthread_zone_inited = 1;
        }
}

void *
uthread_alloc(task_t task, thread_t thr_act )
{
        struct proc *p;
        struct uthread *uth, *uth_parent;
        void *ut;
        boolean_t funnel_state;

        if (!uthread_zone_inited)
                uthread_zone_init();

        ut = (void *)zalloc(uthread_zone);
        bzero(ut, sizeof(struct uthread));

        p = (struct proc *) get_bsdtask_info(task);
        uth = (struct uthread *)ut;

        /*
         * Thread inherits credential from the creating thread, if both
         * are in the same task.
         *
         * If the creating thread has no credential or is from another
         * task we can leave the new thread credential NULL.  If it needs
         * one later, it will be lazily assigned from the task's process.
         */
        uth_parent = (struct uthread *)get_bsdthread_info(current_thread());
        if ((task == current_task()) && 
            (uth_parent != NULL) &&
            (uth_parent->uu_ucred != NOCRED)) {
                uth->uu_ucred = uth_parent->uu_ucred;
                kauth_cred_ref(uth->uu_ucred);
                /* the credential we just inherited is an assumed credential */
                if (uth_parent->uu_flag & UT_SETUID)
                        uth->uu_flag |= UT_SETUID;
        } else {
                uth->uu_ucred = NOCRED;
        }
        
        if (task != kernel_task) {
                
                funnel_state = thread_funnel_set(kernel_flock, TRUE);
                if (uth_parent) {
                        if (uth_parent->uu_flag & UT_SAS_OLDMASK)
                                uth->uu_sigmask = uth_parent->uu_oldmask;
                        else
                                uth->uu_sigmask = uth_parent->uu_sigmask;
                }
                uth->uu_act = thr_act;
                //signal_lock(p);
                if (p) {
                        TAILQ_INSERT_TAIL(&p->p_uthlist, uth, uu_list);
                }
                //signal_unlock(p);
                (void)thread_funnel_set(kernel_flock, funnel_state);
        }

        return (ut);
}


void
uthread_free(task_t task, void *uthread, void * bsd_info)
{
        struct _select *sel;
        struct uthread *uth = (struct uthread *)uthread;
        struct proc * p = (struct proc *)bsd_info;
        boolean_t funnel_state;

        /*
         * Per-thread audit state should never last beyond system
         * call return.  Since we don't audit the thread creation/
         * removal, the thread state pointer should never be
         * non-NULL when we get here.
         */
        assert(uth->uu_ar == NULL);

        sel = &uth->uu_select;
        /* cleanup the select bit space */
        if (sel->nbytes) {
                FREE(sel->ibits, M_TEMP);
                FREE(sel->obits, M_TEMP);
        }

        if (sel->allocsize && sel->wqset){
                kfree(sel->wqset, sel->allocsize);
                sel->count = 0;
                sel->allocsize = 0;
                sel->wqset = 0;
                sel->wql = 0;
        }

        if (uth->uu_ucred != NOCRED)
                kauth_cred_rele(uth->uu_ucred);

        if ((task != kernel_task) && p) {
                funnel_state = thread_funnel_set(kernel_flock, TRUE);
                //signal_lock(p);
                TAILQ_REMOVE(&p->p_uthlist, uth, uu_list);
                //signal_unlock(p);
                (void)thread_funnel_set(kernel_flock, funnel_state);
        }
        /* and free the uthread itself */
        zfree(uthread_zone, uthread);
}