xnu-201.tar.gz

[apple/xnu.git] / osfmk / ipc / ipc_port.c

/*
 * Copyright (c) 2000 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@
 */
/*
 * @OSF_FREE_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1991,1990,1989 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 */
/*
 *      File:   ipc/ipc_port.c
 *      Author: Rich Draves
 *      Date:   1989
 *
 *      Functions to manipulate IPC ports.
 */

#include <norma_vm.h>
#include <mach_kdb.h>
#include <zone_debug.h>
#include <mach_assert.h>

#include <mach/port.h>
#include <mach/kern_return.h>
#include <kern/lock.h>
#include <kern/ipc_kobject.h>
#include <kern/ipc_subsystem.h>
#include <kern/thread.h>
#include <kern/thread_pool.h>
#include <kern/misc_protos.h>
#include <kern/wait_queue.h>
#include <ipc/ipc_entry.h>
#include <ipc/ipc_space.h>
#include <ipc/ipc_object.h>
#include <ipc/ipc_port.h>
#include <ipc/ipc_pset.h>
#include <ipc/ipc_kmsg.h>
#include <ipc/ipc_mqueue.h>
#include <ipc/ipc_notify.h>
#include <ipc/ipc_print.h>
#include <ipc/ipc_table.h>

#if     MACH_KDB
#include <machine/db_machdep.h>
#include <ddb/db_command.h>
#include <ddb/db_expr.h>
#endif  /* MACH_KDB */

#include <string.h>

decl_mutex_data(,       ipc_port_multiple_lock_data)
decl_mutex_data(,       ipc_port_timestamp_lock_data)
ipc_port_timestamp_t    ipc_port_timestamp_data;

#if     MACH_ASSERT
void    ipc_port_init_debug(
                ipc_port_t      port);
#endif  /* MACH_ASSERT */

#if     MACH_KDB && ZONE_DEBUG
/* Forwards */
void    print_type_ports(unsigned, unsigned);
void    print_ports(void);
#endif  /* MACH_KDB && ZONE_DEBUG */

/*
 *      Routine:        ipc_port_timestamp
 *      Purpose:
 *              Retrieve a timestamp value.
 */

ipc_port_timestamp_t
ipc_port_timestamp(void)
{
        ipc_port_timestamp_t timestamp;

        ipc_port_timestamp_lock();
        timestamp = ipc_port_timestamp_data++;
        ipc_port_timestamp_unlock();

        return timestamp;
}

/*
 *      Routine:        ipc_port_dnrequest
 *      Purpose:
 *              Try to allocate a dead-name request slot.
 *              If successful, returns the request index.
 *              Otherwise returns zero.
 *      Conditions:
 *              The port is locked and active.
 *      Returns:
 *              KERN_SUCCESS            A request index was found.
 *              KERN_NO_SPACE           No index allocated.
 */

kern_return_t
ipc_port_dnrequest(
        ipc_port_t                      port,
        mach_port_name_t                name,
        ipc_port_t                      soright,
        ipc_port_request_index_t        *indexp)
{
        ipc_port_request_t ipr, table;
        ipc_port_request_index_t index;

        assert(ip_active(port));
        assert(name != MACH_PORT_NULL);
        assert(soright != IP_NULL);

        table = port->ip_dnrequests;
        if (table == IPR_NULL)
                return KERN_NO_SPACE;

        index = table->ipr_next;
        if (index == 0)
                return KERN_NO_SPACE;

        ipr = &table[index];
        assert(ipr->ipr_name == MACH_PORT_NULL);

        table->ipr_next = ipr->ipr_next;
        ipr->ipr_name = name;
        ipr->ipr_soright = soright;

        *indexp = index;
        return KERN_SUCCESS;
}

/*
 *      Routine:        ipc_port_dngrow
 *      Purpose:
 *              Grow a port's table of dead-name requests.
 *      Conditions:
 *              The port must be locked and active.
 *              Nothing else locked; will allocate memory.
 *              Upon return the port is unlocked.
 *      Returns:
 *              KERN_SUCCESS            Grew the table.
 *              KERN_SUCCESS            Somebody else grew the table.
 *              KERN_SUCCESS            The port died.
 *              KERN_RESOURCE_SHORTAGE  Couldn't allocate new table.
 *              KERN_NO_SPACE           Couldn't grow to desired size
 */

kern_return_t
ipc_port_dngrow(
        ipc_port_t      port,
        int             target_size)
{
        ipc_table_size_t its;
        ipc_port_request_t otable, ntable;

        assert(ip_active(port));

        otable = port->ip_dnrequests;
        if (otable == IPR_NULL)
                its = &ipc_table_dnrequests[0];
        else
                its = otable->ipr_size + 1;

        if (target_size != ITS_SIZE_NONE) {
                if ((otable != IPR_NULL) &&
                    (target_size <= otable->ipr_size->its_size)) {
                        ip_unlock(port);
                        return KERN_SUCCESS;
                }
                while ((its->its_size) && (its->its_size < target_size)) {
                        its++;
                }
                if (its->its_size == 0) {
                        ip_unlock(port);
                        return KERN_NO_SPACE;
                }
        }

        ip_reference(port);
        ip_unlock(port);

        if ((its->its_size == 0) ||
            ((ntable = it_dnrequests_alloc(its)) == IPR_NULL)) {
                ipc_port_release(port);
                return KERN_RESOURCE_SHORTAGE;
        }

        ip_lock(port);
        ip_release(port);

        /*
         *      Check that port is still active and that nobody else
         *      has slipped in and grown the table on us.  Note that
         *      just checking port->ip_dnrequests == otable isn't
         *      sufficient; must check ipr_size.
         */

        if (ip_active(port) &&
            (port->ip_dnrequests == otable) &&
            ((otable == IPR_NULL) || (otable->ipr_size+1 == its))) {
                ipc_table_size_t oits;
                ipc_table_elems_t osize, nsize;
                ipc_port_request_index_t free, i;

                /* copy old table to new table */

                if (otable != IPR_NULL) {
                        oits = otable->ipr_size;
                        osize = oits->its_size;
                        free = otable->ipr_next;

                        (void) memcpy((void *)(ntable + 1),
                              (const void *)(otable + 1),
                              (osize - 1) * sizeof(struct ipc_port_request));
                } else {
                        osize = 1;
                        free = 0;
                }

                nsize = its->its_size;
                assert(nsize > osize);

                /* add new elements to the new table's free list */

                for (i = osize; i < nsize; i++) {
                        ipc_port_request_t ipr = &ntable[i];

                        ipr->ipr_name = MACH_PORT_NULL;
                        ipr->ipr_next = free;
                        free = i;
                }

                ntable->ipr_next = free;
                ntable->ipr_size = its;
                port->ip_dnrequests = ntable;
                ip_unlock(port);

                if (otable != IPR_NULL) {
                        it_dnrequests_free(oits, otable);
                }
        } else {
                ip_check_unlock(port);
                it_dnrequests_free(its, ntable);
        }

        return KERN_SUCCESS;
}
 
/*
 *      Routine:        ipc_port_dncancel
 *      Purpose:
 *              Cancel a dead-name request and return the send-once right.
 *      Conditions:
 *              The port must locked and active.
 */

ipc_port_t
ipc_port_dncancel(
        ipc_port_t                      port,
        mach_port_name_t                name,
        ipc_port_request_index_t        index)
{
        ipc_port_request_t ipr, table;
        ipc_port_t dnrequest;

        assert(ip_active(port));
        assert(name != MACH_PORT_NULL);
        assert(index != 0);

        table = port->ip_dnrequests;
        assert(table != IPR_NULL);

        ipr = &table[index];
        dnrequest = ipr->ipr_soright;
        assert(ipr->ipr_name == name);

        /* return ipr to the free list inside the table */

        ipr->ipr_name = MACH_PORT_NULL;
        ipr->ipr_next = table->ipr_next;
        table->ipr_next = index;

        return dnrequest;
}

/*
 *      Routine:        ipc_port_pdrequest
 *      Purpose:
 *              Make a port-deleted request, returning the
 *              previously registered send-once right.
 *              Just cancels the previous request if notify is IP_NULL.
 *      Conditions:
 *              The port is locked and active.  It is unlocked.
 *              Consumes a ref for notify (if non-null), and
 *              returns previous with a ref (if non-null).
 */

void
ipc_port_pdrequest(
        ipc_port_t      port,
        ipc_port_t      notify,
        ipc_port_t      *previousp)
{
        ipc_port_t previous;

        assert(ip_active(port));

        previous = port->ip_pdrequest;
        port->ip_pdrequest = notify;
        ip_unlock(port);

        *previousp = previous;
}

/*
 *      Routine:        ipc_port_nsrequest
 *      Purpose:
 *              Make a no-senders request, returning the
 *              previously registered send-once right.
 *              Just cancels the previous request if notify is IP_NULL.
 *      Conditions:
 *              The port is locked and active.  It is unlocked.
 *              Consumes a ref for notify (if non-null), and
 *              returns previous with a ref (if non-null).
 */

void
ipc_port_nsrequest(
        ipc_port_t              port,
        mach_port_mscount_t     sync,
        ipc_port_t              notify,
        ipc_port_t              *previousp)
{
        ipc_port_t previous;
        mach_port_mscount_t mscount;

        assert(ip_active(port));

        previous = port->ip_nsrequest;
        mscount = port->ip_mscount;

        if ((port->ip_srights == 0) && (sync <= mscount) &&
            (notify != IP_NULL)) {
                port->ip_nsrequest = IP_NULL;
                ip_unlock(port);
                ipc_notify_no_senders(notify, mscount);
        } else {
                port->ip_nsrequest = notify;
                ip_unlock(port);
        }

        *previousp = previous;
}


/*
 *      Routine:        ipc_port_clear_receiver
 *      Purpose:
 *              Prepares a receive right for transmission/destruction.
 *      Conditions:
 *              The port is locked and active.
 */

void
ipc_port_clear_receiver(
        ipc_port_t      port)
{
        spl_t           s;

        assert(ip_active(port));

        /*
         * pull ourselves from any sets.
         */
        if (port->ip_pset_count != 0) {
                ipc_pset_remove_all(port);
                port->ip_pset_count = 0;
        }

        /*
         * Send anyone waiting on the port's queue directly away.
         * Also clear the mscount and seqno.
         */
        s = splsched();
        imq_lock(&port->ip_messages);
        ipc_mqueue_changed(&port->ip_messages);
        ipc_port_set_mscount(port, 0);
        port->ip_messages.imq_seqno = 0;
        imq_unlock(&port->ip_messages);
        splx(s);
}

/*
 *      Routine:        ipc_port_init
 *      Purpose:
 *              Initializes a newly-allocated port.
 *              Doesn't touch the ip_object fields.
 */

void
ipc_port_init(
        ipc_port_t              port,
        ipc_space_t             space,
        mach_port_name_t        name)
{
        /* port->ip_kobject doesn't have to be initialized */

        port->ip_receiver = space;
        port->ip_receiver_name = name;

        port->ip_mscount = 0;
        port->ip_srights = 0;
        port->ip_sorights = 0;

        port->ip_nsrequest = IP_NULL;
        port->ip_pdrequest = IP_NULL;
        port->ip_dnrequests = IPR_NULL;

        port->ip_pset_count = 0;
        port->ip_premsg = IKM_NULL;

        thread_pool_init(&port->ip_thread_pool);

        port->ip_subsystem = RPC_SUBSYSTEM_NULL;
        
#if     MACH_ASSERT
        ipc_port_init_debug(port);
#endif  /* MACH_ASSERT */

        ipc_mqueue_init(&port->ip_messages, FALSE /* set */);
}

/*
 *      Routine:        ipc_port_alloc
 *      Purpose:
 *              Allocate a port.
 *      Conditions:
 *              Nothing locked.  If successful, the port is returned
 *              locked.  (The caller doesn't have a reference.)
 *      Returns:
 *              KERN_SUCCESS            The port is allocated.
 *              KERN_INVALID_TASK       The space is dead.
 *              KERN_NO_SPACE           No room for an entry in the space.
 *              KERN_RESOURCE_SHORTAGE  Couldn't allocate memory.
 */

kern_return_t
ipc_port_alloc(
        ipc_space_t             space,
        mach_port_name_t        *namep,
        ipc_port_t              *portp)
{
        ipc_port_t port;
        mach_port_name_t name;
        kern_return_t kr;

        kr = ipc_object_alloc(space, IOT_PORT,
                              MACH_PORT_TYPE_RECEIVE, 0,
                              &name, (ipc_object_t *) &port);
        if (kr != KERN_SUCCESS)
                return kr;

        /* port is locked */

        ipc_port_init(port, space, name);

        *namep = name;
        *portp = port;

        return KERN_SUCCESS;
}

/*
 *      Routine:        ipc_port_alloc_name
 *      Purpose:
 *              Allocate a port, with a specific name.
 *      Conditions:
 *              Nothing locked.  If successful, the port is returned
 *              locked.  (The caller doesn't have a reference.)
 *      Returns:
 *              KERN_SUCCESS            The port is allocated.
 *              KERN_INVALID_TASK       The space is dead.
 *              KERN_NAME_EXISTS        The name already denotes a right.
 *              KERN_RESOURCE_SHORTAGE  Couldn't allocate memory.
 */

kern_return_t
ipc_port_alloc_name(
        ipc_space_t             space,
        mach_port_name_t        name,
        ipc_port_t              *portp)
{
        ipc_port_t port;
        kern_return_t kr;

        kr = ipc_object_alloc_name(space, IOT_PORT,
                                   MACH_PORT_TYPE_RECEIVE, 0,
                                   name, (ipc_object_t *) &port);
        if (kr != KERN_SUCCESS)
                return kr;

        /* port is locked */

        ipc_port_init(port, space, name);

        *portp = port;

        return KERN_SUCCESS;
}

/*
 * Generate dead name notifications.  Called from ipc_port_destroy.
 * Port is unlocked but still has reference(s);
 * dnrequests was taken from port while the port
 * was locked but the port now has port->ip_dnrequests set to IPR_NULL.
 */
void
ipc_port_dnnotify(
        ipc_port_t              port,
        ipc_port_request_t      dnrequests)
{
        ipc_table_size_t        its = dnrequests->ipr_size;
        ipc_table_elems_t       size = its->its_size;
        ipc_port_request_index_t index;

        for (index = 1; index < size; index++) {
                ipc_port_request_t      ipr = &dnrequests[index];
                mach_port_name_t                name = ipr->ipr_name;
                ipc_port_t              soright;

                if (name == MACH_PORT_NULL)
                        continue;

                soright = ipr->ipr_soright;
                assert(soright != IP_NULL);

                ipc_notify_dead_name(soright, name);
        }

        it_dnrequests_free(its, dnrequests);
}

/*
 *      Routine:        ipc_port_destroy
 *      Purpose:
 *              Destroys a port.  Cleans up queued messages.
 *
 *              If the port has a backup, it doesn't get destroyed,
 *              but is sent in a port-destroyed notification to the backup.
 *      Conditions:
 *              The port is locked and alive; nothing else locked.
 *              The caller has a reference, which is consumed.
 *              Afterwards, the port is unlocked and dead.
 */

void
ipc_port_destroy(
        ipc_port_t      port)
{
        ipc_port_t pdrequest, nsrequest;
        ipc_mqueue_t mqueue;
        ipc_kmsg_queue_t kmqueue;
        ipc_kmsg_t kmsg;
        ipc_port_request_t dnrequests;
        thread_pool_t thread_pool;

        assert(ip_active(port));
        /* port->ip_receiver_name is garbage */
        /* port->ip_receiver/port->ip_destination is garbage */
        assert(port->ip_pset_count == 0);
        assert(port->ip_mscount == 0);

        /* first check for a backup port */

        pdrequest = port->ip_pdrequest;
        if (pdrequest != IP_NULL) {
                /* we assume the ref for pdrequest */
                port->ip_pdrequest = IP_NULL;

                /* make port be in limbo */
                port->ip_receiver_name = MACH_PORT_NULL;
                port->ip_destination = IP_NULL;
                ip_unlock(port);

                if (!ipc_port_check_circularity(port, pdrequest)) {
                        /* consumes our refs for port and pdrequest */
                        ipc_notify_port_destroyed(pdrequest, port);
                        return;
                } else {
                        /* consume pdrequest and destroy port */
                        ipc_port_release_sonce(pdrequest);
                }

                ip_lock(port);
                assert(ip_active(port));
                assert(port->ip_pset_count == 0);
                assert(port->ip_mscount == 0);
                assert(port->ip_pdrequest == IP_NULL);
                assert(port->ip_receiver_name == MACH_PORT_NULL);
                assert(port->ip_destination == IP_NULL);

                /* fall through and destroy the port */
        }

        /* once port is dead, we don't need to keep it locked */

        port->ip_object.io_bits &= ~IO_BITS_ACTIVE;
        port->ip_timestamp = ipc_port_timestamp();

        /* save for later */
        dnrequests = port->ip_dnrequests;
        port->ip_dnrequests = IPR_NULL;

        /*
         * If the port has a preallocated message buffer and that buffer
         * is not inuse, free it.  If it has and inuse one, then the kmsg
         * free will detect that we freed the association and it can free it
         * like a normal buffer.
         */
        if (IP_PREALLOC(port)) {
                kmsg = port->ip_premsg;
                assert(kmsg != IKM_NULL);
                if (!ikm_prealloc_inuse(kmsg)) {
                        ikm_prealloc_clear_inuse(kmsg, port);
                        IP_CLEAR_PREALLOC(port, kmsg);
                        ipc_kmsg_free(kmsg);
                } else {
                        assert(ikm_prealloc_inuse_port(kmsg) == port);
                        ikm_prealloc_clear_inuse(kmsg, port);
                        IP_CLEAR_PREALLOC(port, kmsg);
                }
        }

        ip_unlock(port);

        /* wakeup any threads waiting on this pool port for an activation */
        if ((thread_pool = &port->ip_thread_pool) != THREAD_POOL_NULL)
                thread_pool_wakeup(thread_pool);

        /* throw away no-senders request */

        nsrequest = port->ip_nsrequest;
        if (nsrequest != IP_NULL)
                ipc_notify_send_once(nsrequest); /* consumes ref */

        /* destroy any queued messages */
        mqueue = &port->ip_messages;
        ipc_mqueue_destroy(mqueue);

        /* generate dead-name notifications */
        if (dnrequests != IPR_NULL) {
                ipc_port_dnnotify(port, dnrequests);
        }

        ipc_kobject_destroy(port);

        if (port->ip_subsystem != RPC_SUBSYSTEM_NULL) {
                subsystem_deallocate((subsystem_t) port->ip_kobject);
        }

        /* XXXX Perhaps should verify that ip_thread_pool is empty! */

        ipc_port_release(port); /* consume caller's ref */
}

/*
 *      Routine:        ipc_port_check_circularity
 *      Purpose:
 *              Check if queueing "port" in a message for "dest"
 *              would create a circular group of ports and messages.
 *
 *              If no circularity (FALSE returned), then "port"
 *              is changed from "in limbo" to "in transit".
 *
 *              That is, we want to set port->ip_destination == dest,
 *              but guaranteeing that this doesn't create a circle
 *              port->ip_destination->ip_destination->... == port
 *      Conditions:
 *              No ports locked.  References held for "port" and "dest".
 */

boolean_t
ipc_port_check_circularity(
        ipc_port_t      port,
        ipc_port_t      dest)
{
        ipc_port_t base;

        assert(port != IP_NULL);
        assert(dest != IP_NULL);

        if (port == dest)
                return TRUE;
        base = dest;

        /*
         *      First try a quick check that can run in parallel.
         *      No circularity if dest is not in transit.
         */

        ip_lock(port);
        if (ip_lock_try(dest)) {
                if (!ip_active(dest) ||
                    (dest->ip_receiver_name != MACH_PORT_NULL) ||
                    (dest->ip_destination == IP_NULL))
                        goto not_circular;

                /* dest is in transit; further checking necessary */

                ip_unlock(dest);
        }
        ip_unlock(port);

        ipc_port_multiple_lock(); /* massive serialization */

        /*
         *      Search for the end of the chain (a port not in transit),
         *      acquiring locks along the way.
         */

        for (;;) {
                ip_lock(base);

                if (!ip_active(base) ||
                    (base->ip_receiver_name != MACH_PORT_NULL) ||
                    (base->ip_destination == IP_NULL))
                        break;

                base = base->ip_destination;
        }

        /* all ports in chain from dest to base, inclusive, are locked */

        if (port == base) {
                /* circularity detected! */

                ipc_port_multiple_unlock();

                /* port (== base) is in limbo */

                assert(ip_active(port));
                assert(port->ip_receiver_name == MACH_PORT_NULL);
                assert(port->ip_destination == IP_NULL);

                while (dest != IP_NULL) {
                        ipc_port_t next;

                        /* dest is in transit or in limbo */

                        assert(ip_active(dest));
                        assert(dest->ip_receiver_name == MACH_PORT_NULL);

                        next = dest->ip_destination;
                        ip_unlock(dest);
                        dest = next;
                }

                return TRUE;
        }

        /*
         *      The guarantee:  lock port while the entire chain is locked.
         *      Once port is locked, we can take a reference to dest,
         *      add port to the chain, and unlock everything.
         */

        ip_lock(port);
        ipc_port_multiple_unlock();

    not_circular:

        /* port is in limbo */

        assert(ip_active(port));
        assert(port->ip_receiver_name == MACH_PORT_NULL);
        assert(port->ip_destination == IP_NULL);

        ip_reference(dest);
        port->ip_destination = dest;

        /* now unlock chain */

        while (port != base) {
                ipc_port_t next;

                /* port is in transit */

                assert(ip_active(port));
                assert(port->ip_receiver_name == MACH_PORT_NULL);
                assert(port->ip_destination != IP_NULL);

                next = port->ip_destination;
                ip_unlock(port);
                port = next;
        }

        /* base is not in transit */

        assert(!ip_active(base) ||
               (base->ip_receiver_name != MACH_PORT_NULL) ||
               (base->ip_destination == IP_NULL));
        ip_unlock(base);

        return FALSE;
}

/*
 *      Routine:        ipc_port_lookup_notify
 *      Purpose:
 *              Make a send-once notify port from a receive right.
 *              Returns IP_NULL if name doesn't denote a receive right.
 *      Conditions:
 *              The space must be locked (read or write) and active.
 *              Being the active space, we can rely on thread server_id
 *              context to give us the proper server level sub-order
 *              within the space.
 */

ipc_port_t
ipc_port_lookup_notify(
        ipc_space_t             space,
        mach_port_name_t        name)
{
        ipc_port_t port;
        ipc_entry_t entry;

        assert(space->is_active);

        entry = ipc_entry_lookup(space, name);
        if (entry == IE_NULL)
                return IP_NULL;
        if ((entry->ie_bits & MACH_PORT_TYPE_RECEIVE) == 0)
                return IP_NULL;

        port = (ipc_port_t) entry->ie_object;
        assert(port != IP_NULL);

        ip_lock(port);
        assert(ip_active(port));
        assert(port->ip_receiver_name == name);
        assert(port->ip_receiver == space);

        ip_reference(port);
        port->ip_sorights++;
        ip_unlock(port);

        return port;
}

/*
 *      Routine:        ipc_port_make_send_locked
 *      Purpose:
 *              Make a naked send right from a receive right.
 *
 *      Conditions:
 *              port locked and active.
 */
ipc_port_t
ipc_port_make_send_locked(
        ipc_port_t      port)
{
        assert(ip_active(port));
        port->ip_mscount++;
        port->ip_srights++;
        ip_reference(port);
        ip_unlock(port);
        return port;
}

/*
 *      Routine:        ipc_port_make_send
 *      Purpose:
 *              Make a naked send right from a receive right.
 */

ipc_port_t
ipc_port_make_send(
        ipc_port_t      port)
{
        
        if (!IP_VALID(port))
                return port;

        ip_lock(port);
        if (ip_active(port)) {
                port->ip_mscount++;
                port->ip_srights++;
                ip_reference(port);
                ip_unlock(port);
                return port;
        }
        ip_unlock(port);
        return IP_DEAD;
}

/*
 *      Routine:        ipc_port_copy_send
 *      Purpose:
 *              Make a naked send right from another naked send right.
 *                      IP_NULL         -> IP_NULL
 *                      IP_DEAD         -> IP_DEAD
 *                      dead port       -> IP_DEAD
 *                      live port       -> port + ref
 *      Conditions:
 *              Nothing locked except possibly a space.
 */

ipc_port_t
ipc_port_copy_send(
        ipc_port_t      port)
{
        ipc_port_t sright;

        if (!IP_VALID(port))
                return port;

        ip_lock(port);
        if (ip_active(port)) {
                assert(port->ip_srights > 0);

                ip_reference(port);
                port->ip_srights++;
                sright = port;
        } else
                sright = IP_DEAD;
        ip_unlock(port);

        return sright;
}

/*
 *      Routine:        ipc_port_copyout_send
 *      Purpose:
 *              Copyout a naked send right (possibly null/dead),
 *              or if that fails, destroy the right.
 *      Conditions:
 *              Nothing locked.
 */

mach_port_name_t
ipc_port_copyout_send(
        ipc_port_t      sright,
        ipc_space_t     space)
{
        mach_port_name_t name;

        if (IP_VALID(sright)) {
                kern_return_t kr;

                kr = ipc_object_copyout(space, (ipc_object_t) sright,
                                        MACH_MSG_TYPE_PORT_SEND, TRUE, &name);
                if (kr != KERN_SUCCESS) {
                        ipc_port_release_send(sright);

                        if (kr == KERN_INVALID_CAPABILITY)
                                name = MACH_PORT_DEAD;
                        else
                                name = MACH_PORT_NULL;
                }
        } else
                name = (mach_port_name_t) sright;

        return name;
}

/*
 *      Routine:        ipc_port_release_send
 *      Purpose:
 *              Release a (valid) naked send right.
 *              Consumes a ref for the port.
 *      Conditions:
 *              Nothing locked.
 */

void
ipc_port_release_send(
        ipc_port_t      port)
{
        ipc_port_t nsrequest = IP_NULL;
        mach_port_mscount_t mscount;

        assert(IP_VALID(port));

        ip_lock(port);
        ip_release(port);

        if (!ip_active(port)) {
                ip_check_unlock(port);
                return;
        }

        assert(port->ip_srights > 0);

        if (--port->ip_srights == 0 &&
            port->ip_nsrequest != IP_NULL) {
                nsrequest = port->ip_nsrequest;
                port->ip_nsrequest = IP_NULL;
                mscount = port->ip_mscount;
                ip_unlock(port);
                ipc_notify_no_senders(nsrequest, mscount);
                /*
                 * Check that there are no other locks taken, because
                 * [norma_]ipc_notify_no_senders routines may block.
                 */
                check_simple_locks();
        } else
                ip_unlock(port);
}

/*
 *      Routine:        ipc_port_make_sonce
 *      Purpose:
 *              Make a naked send-once right from a receive right.
 *      Conditions:
 *              The port is not locked but it is active.
 */

ipc_port_t
ipc_port_make_sonce(
        ipc_port_t      port)
{
        assert(IP_VALID(port));

        ip_lock(port);
        assert(ip_active(port));
        port->ip_sorights++;
        ip_reference(port);
        ip_unlock(port);

        return port;
}

/*
 *      Routine:        ipc_port_release_sonce
 *      Purpose:
 *              Release a naked send-once right.
 *              Consumes a ref for the port.
 *
 *              In normal situations, this is never used.
 *              Send-once rights are only consumed when
 *              a message (possibly a send-once notification)
 *              is sent to them.
 *      Conditions:
 *              Nothing locked except possibly a space.
 */

void
ipc_port_release_sonce(
        ipc_port_t      port)
{
        assert(IP_VALID(port));

        ip_lock(port);

        assert(port->ip_sorights > 0);

        port->ip_sorights--;

        ip_release(port);

        if (!ip_active(port)) {
                ip_check_unlock(port);
                return;
        }

        ip_unlock(port);
}

/*
 *      Routine:        ipc_port_release_receive
 *      Purpose:
 *              Release a naked (in limbo or in transit) receive right.
 *              Consumes a ref for the port; destroys the port.
 *      Conditions:
 *              Nothing locked.
 */

void
ipc_port_release_receive(
        ipc_port_t      port)
{
        ipc_port_t dest;

        assert(IP_VALID(port));

        ip_lock(port);
        assert(ip_active(port));
        assert(port->ip_receiver_name == MACH_PORT_NULL);
        dest = port->ip_destination;

        ipc_port_destroy(port); /* consumes ref, unlocks */

        if (dest != IP_NULL)
                ipc_port_release(dest);
}

/*
 *      Routine:        ipc_port_alloc_special
 *      Purpose:
 *              Allocate a port in a special space.
 *              The new port is returned with one ref.
 *              If unsuccessful, IP_NULL is returned.
 *      Conditions:
 *              Nothing locked.
 */

ipc_port_t
ipc_port_alloc_special(
        ipc_space_t     space)
{
        ipc_port_t port;

        port = (ipc_port_t) io_alloc(IOT_PORT);
        if (port == IP_NULL)
                return IP_NULL;

        bzero((char *)port, sizeof(*port));
        io_lock_init(&port->ip_object);
        port->ip_references = 1;
        port->ip_object.io_bits = io_makebits(TRUE, IOT_PORT, 0);

        ipc_port_init(port, space, 1);

        return port;
}

/*
 *      Routine:        ipc_port_dealloc_special
 *      Purpose:
 *              Deallocate a port in a special space.
 *              Consumes one ref for the port.
 *      Conditions:
 *              Nothing locked.
 */

void
ipc_port_dealloc_special(
        ipc_port_t      port,
        ipc_space_t     space)
{
        ip_lock(port);
        assert(ip_active(port));
        assert(port->ip_receiver_name != MACH_PORT_NULL);
        assert(port->ip_receiver == space);

        /*
         *      We clear ip_receiver_name and ip_receiver to simplify
         *      the ipc_space_kernel check in ipc_mqueue_send.
         */

        port->ip_receiver_name = MACH_PORT_NULL;
        port->ip_receiver = IS_NULL;

        /* relevant part of ipc_port_clear_receiver */
        ipc_port_set_mscount(port, 0);
        port->ip_messages.imq_seqno = 0;

        ipc_port_destroy(port);
}


#if     MACH_ASSERT
/*
 *      Keep a list of all allocated ports.
 *      Allocation is intercepted via ipc_port_init;
 *      deallocation is intercepted via io_free.
 */
queue_head_t    port_alloc_queue;
decl_mutex_data(,port_alloc_queue_lock)

unsigned long   port_count = 0;
unsigned long   port_count_warning = 20000;
unsigned long   port_timestamp = 0;

void            db_port_stack_trace(
                        ipc_port_t      port);
void            db_ref(
                        int             refs);
int             db_port_walk(
                        unsigned int    verbose,
                        unsigned int    display,
                        unsigned int    ref_search,
                        unsigned int    ref_target);

/*
 *      Initialize global state needed for run-time
 *      port debugging.
 */
void
ipc_port_debug_init(void)
{
        queue_init(&port_alloc_queue);
        mutex_init(&port_alloc_queue_lock, ETAP_IPC_PORT_ALLOCQ);
}


/*
 *      Initialize all of the debugging state in a port.
 *      Insert the port into a global list of all allocated ports.
 */
void
ipc_port_init_debug(
        ipc_port_t      port)
{
        unsigned int    i;

        port->ip_thread = (unsigned long) current_thread();
        port->ip_timetrack = port_timestamp++;
        for (i = 0; i < IP_CALLSTACK_MAX; ++i)
                port->ip_callstack[i] = 0;
        for (i = 0; i < IP_NSPARES; ++i)
                port->ip_spares[i] = 0;

        /*
         *      Machine-dependent routine to fill in an
         *      array with up to IP_CALLSTACK_MAX levels
         *      of return pc information.
         */
        machine_callstack(&port->ip_callstack[0], IP_CALLSTACK_MAX);

#if 0
        mutex_lock(&port_alloc_queue_lock);
        ++port_count;
        if (port_count_warning > 0 && port_count >= port_count_warning)
                assert(port_count < port_count_warning);
        queue_enter(&port_alloc_queue, port, ipc_port_t, ip_port_links);
        mutex_unlock(&port_alloc_queue_lock);
#endif
}


/*
 *      Remove a port from the queue of allocated ports.
 *      This routine should be invoked JUST prior to
 *      deallocating the actual memory occupied by the port.
 */
void
ipc_port_track_dealloc(
        ipc_port_t      port)
{
#if 0
        mutex_lock(&port_alloc_queue_lock);
        assert(port_count > 0);
        --port_count;
        queue_remove(&port_alloc_queue, port, ipc_port_t, ip_port_links);
        mutex_unlock(&port_alloc_queue_lock);
#endif
}

#endif  /* MACH_ASSERT */


#if     MACH_KDB

#include <ddb/db_output.h>
#include <ddb/db_print.h>

#define printf  kdbprintf
extern int db_indent;

int
db_port_queue_print(
        ipc_port_t      port);

/*
 * ipc_entry_print - pretty-print an ipc_entry
 */
static void ipc_entry_print(struct ipc_entry *, char *); /* forward */

static void ipc_entry_print(struct ipc_entry *iep, char *tag)
{
        ipc_entry_bits_t bits = iep->ie_bits;

        iprintf("%s @", tag);
        printf(" 0x%x, bits=%x object=%x\n", iep, bits, iep->ie_object);
        db_indent += 2;
        iprintf("urefs=%x ", IE_BITS_UREFS(bits));
        printf("type=%x gen=%x\n", IE_BITS_TYPE(bits), IE_BITS_GEN(bits));
        db_indent -= 2;
}

/*
 *      Routine:        ipc_port_print
 *      Purpose:
 *              Pretty-print a port for kdb.
 */
int     ipc_port_print_long = 0;        /* set for more detail */

void
ipc_port_print(
        ipc_port_t      port,
        boolean_t       have_addr,
        db_expr_t       count,
        char            *modif)
{
        extern int      db_indent;
        db_addr_t       task;
        int             task_id;
        int             nmsgs;
        int             verbose = 0;
#if     MACH_ASSERT
        int             i, needs_db_indent, items_printed;
#endif  /* MACH_ASSERT */
        
        if (db_option(modif, 'l') || db_option(modif, 'v'))
                ++verbose;

        printf("port 0x%x\n", port);

        db_indent += 2;

        ipc_object_print(&port->ip_object);

        if (ipc_port_print_long) {
                iprintf("pool=0x%x", port->ip_thread_pool);
                printf("\n");
        }

        if (!ip_active(port)) {
                iprintf("timestamp=0x%x", port->ip_timestamp);
        } else if (port->ip_receiver_name == MACH_PORT_NULL) {
                iprintf("destination=0x%x (", port->ip_destination);
                if (port->ip_destination != MACH_PORT_NULL &&
                    (task = db_task_from_space(port->ip_destination->
                                               ip_receiver, &task_id)))
                        printf("task%d at 0x%x", task_id, task);
                else
                        printf("unknown");
                printf(")");
        } else {
                iprintf("receiver=0x%x (", port->ip_receiver);
                if (port->ip_receiver == ipc_space_kernel)
                        printf("kernel");
                else if (port->ip_receiver == ipc_space_reply)
                        printf("reply");
                else if (port->ip_receiver == default_pager_space)
                        printf("default_pager");
                else if (task = db_task_from_space(port->ip_receiver, &task_id))
                        printf("task%d at 0x%x", task_id, task);
                else
                        printf("unknown");
                printf(")");
        }
        printf(", receiver_name=0x%x\n", port->ip_receiver_name);

        iprintf("mscount=%d", port->ip_mscount);
        printf(", srights=%d", port->ip_srights);
        printf(", sorights=%d\n", port->ip_sorights);

        iprintf("nsrequest=0x%x", port->ip_nsrequest);
        printf(", pdrequest=0x%x", port->ip_pdrequest);
        printf(", dnrequests=0x%x\n", port->ip_dnrequests);

        iprintf("pset_count=0x%x", port->ip_pset_count);
        printf(", seqno=%d", port->ip_messages.imq_seqno);
        printf(", msgcount=%d", port->ip_messages.imq_msgcount);
        printf(", qlimit=%d\n", port->ip_messages.imq_qlimit);

        iprintf("kmsgs=0x%x", port->ip_messages.imq_messages.ikmq_base);
        printf(", rcvrs queue=0x%x", port->ip_messages.imq_wait_queue);
        printf(", kobj=0x%x\n", port->ip_kobject);

        iprintf("premsg=0x%x", port->ip_premsg);

#if     MACH_ASSERT
        /* don't bother printing callstack or queue links */
        iprintf("ip_thread=0x%x, ip_timetrack=0x%x\n",
                port->ip_thread, port->ip_timetrack);
        items_printed = 0;
        needs_db_indent = 1;
        for (i = 0; i < IP_NSPARES; ++i) {
                if (port->ip_spares[i] != 0) {
                        if (needs_db_indent) {
                                iprintf("");
                                needs_db_indent = 0;
                        }
                        printf("%sip_spares[%d] = %d",
                               items_printed ? ", " : "", i, 
                               port->ip_spares[i]);
                        if (++items_printed >= 4) {
                                needs_db_indent = 1;
                                printf("\n");
                                items_printed = 0;
                        }
                }
        }
#endif  /* MACH_ASSERT */

        if (verbose) {
                iprintf("kmsg queue contents:\n");
                db_indent += 2;
                nmsgs = db_port_queue_print(port);
                db_indent -= 2;
                iprintf("...total kmsgs:  %d\n", nmsgs);
        }

        db_indent -=2;
}

ipc_port_t
ipc_name_to_data(
        task_t                  task,
        mach_port_name_t        name)
{
        ipc_space_t     space;
        ipc_entry_t     entry;

        if (task == TASK_NULL) {
                db_printf("port_name_to_data: task is null\n");
                return (0);
        }
        if ((space = task->itk_space) == 0) {
                db_printf("port_name_to_data: task->itk_space is null\n");
                return (0);
        }
        if (!space->is_active) {
                db_printf("port_name_to_data: task->itk_space not active\n");
                return (0);
        }
        if ((entry = ipc_entry_lookup(space, name)) == 0) {
                db_printf("port_name_to_data: lookup yields zero\n");
                return (0);
        }
        return ((ipc_port_t)entry->ie_object);
}

#if     ZONE_DEBUG
void
print_type_ports(type, dead)
        unsigned type;
        unsigned dead;
{
        ipc_port_t port;
        int n;

        n = 0;
        for (port = (ipc_port_t)first_element(ipc_object_zones[IOT_PORT]);
             port;
             port = (ipc_port_t)next_element(ipc_object_zones[IOT_PORT], 
                                             (vm_offset_t)port))
                if (ip_kotype(port) == type &&
                    (!dead || !ip_active(port))) {
                        if (++n % 5)
                                printf("0x%x\t", port);
                        else
                                printf("0x%x\n", port);
                }
        if (n % 5)
                printf("\n");
}

void
print_ports(void)
{
        ipc_port_t port;
        int total_port_count;
        int space_null_count;
        int space_kernel_count;
        int space_reply_count;
        int space_pager_count;
        int space_other_count;

        struct {
                int total_count;
                int dead_count;
        } port_types[IKOT_MAX_TYPE];

        total_port_count = 0;

        bzero((char *)&port_types[0], sizeof(port_types));
        space_null_count = 0;
        space_kernel_count = 0;
        space_reply_count = 0;
        space_pager_count = 0;
        space_other_count = 0;

        for (port = (ipc_port_t)first_element(ipc_object_zones[IOT_PORT]);
             port;
             port = (ipc_port_t)next_element(ipc_object_zones[IOT_PORT], 
                                             (vm_offset_t)port)) {
                total_port_count++;
                if (ip_kotype(port) >= IKOT_MAX_TYPE) {
                        port_types[IKOT_UNKNOWN].total_count++;
                        if (!io_active(&port->ip_object))
                                port_types[IKOT_UNKNOWN].dead_count++;
                } else {
                        port_types[ip_kotype(port)].total_count++;
                        if (!io_active(&port->ip_object))
                                port_types[ip_kotype(port)].dead_count++;
                }

                if (!port->ip_receiver)
                        space_null_count++;
                else if (port->ip_receiver == ipc_space_kernel)
                        space_kernel_count++;
                else if (port->ip_receiver == ipc_space_reply)
                        space_reply_count++;
                else if (port->ip_receiver == default_pager_space)
                        space_pager_count++;
                else
                        space_other_count++;
        }
        printf("\n%7d   total ports\n\n", total_port_count);

#define PRINT_ONE_PORT_TYPE(name) \
        printf("%7d     %s", port_types[IKOT_##name].total_count, # name); \
        if (port_types[IKOT_##name].dead_count) \
             printf(" (%d dead ports)", port_types[IKOT_##name].dead_count);\
        printf("\n");

        PRINT_ONE_PORT_TYPE(NONE);
        PRINT_ONE_PORT_TYPE(THREAD);
        PRINT_ONE_PORT_TYPE(TASK);
        PRINT_ONE_PORT_TYPE(HOST);
        PRINT_ONE_PORT_TYPE(HOST_PRIV);
        PRINT_ONE_PORT_TYPE(PROCESSOR);
        PRINT_ONE_PORT_TYPE(PSET);
        PRINT_ONE_PORT_TYPE(PSET_NAME);
        PRINT_ONE_PORT_TYPE(PAGING_REQUEST);
        PRINT_ONE_PORT_TYPE(MEMORY_OBJECT);
        PRINT_ONE_PORT_TYPE(MIG);
        PRINT_ONE_PORT_TYPE(XMM_PAGER);
        PRINT_ONE_PORT_TYPE(XMM_KERNEL);
        PRINT_ONE_PORT_TYPE(XMM_REPLY);
        PRINT_ONE_PORT_TYPE(CLOCK);
        PRINT_ONE_PORT_TYPE(CLOCK_CTRL);
        PRINT_ONE_PORT_TYPE(MASTER_DEVICE);
        PRINT_ONE_PORT_TYPE(UNKNOWN);
        printf("\nipc_space:\n\n");
        printf("NULL    KERNEL  REPLY   PAGER   OTHER\n");
        printf("%d      %d      %d      %d      %d\n",
               space_null_count,
               space_kernel_count,
               space_reply_count,
               space_pager_count,
               space_other_count
        );
}

#endif  /* ZONE_DEBUG */


/*
 *      Print out all the kmsgs in a queue.  Aggregate kmsgs with
 *      identical message ids into a single entry.  Count up the
 *      amount of inline and out-of-line data consumed by each
 *      and every kmsg.
 *
 */

#define KMSG_MATCH_FIELD(kmsg)  ((unsigned int) kmsg->ikm_header.msgh_id)
#define DKQP_LONG(kmsg) FALSE
char    *dkqp_long_format = "(%3d) <%10d> 0x%x   %10d %10d\n";
char    *dkqp_format = "(%3d) <%10d> 0x%x   %10d %10d\n";

int
db_kmsg_queue_print(
        ipc_kmsg_t      kmsg);
int
db_kmsg_queue_print(
        ipc_kmsg_t      kmsg)
{
        ipc_kmsg_t      ikmsg, first_kmsg;
        register int    icount;
        mach_msg_id_t   cur_id;
        unsigned int    inline_total, ool_total;
        int             nmsgs;

        iprintf("Count      msgh_id  kmsg addr inline bytes   ool bytes\n");
        inline_total = ool_total = (vm_size_t) 0;
        cur_id = KMSG_MATCH_FIELD(kmsg);
        for (icount = 0, nmsgs = 0, first_kmsg = ikmsg = kmsg;
             kmsg != IKM_NULL && (kmsg != first_kmsg || nmsgs == 0);
             kmsg = kmsg->ikm_next) {
                ++nmsgs;
                if (!(KMSG_MATCH_FIELD(kmsg) == cur_id)) {
                        iprintf(DKQP_LONG(kmsg) ? dkqp_long_format:dkqp_format,
                                icount, cur_id, ikmsg, inline_total,ool_total);
                        cur_id = KMSG_MATCH_FIELD(kmsg);
                        icount = 1;
                        ikmsg = kmsg;
                        inline_total = ool_total = 0;
                } else {
                        icount++;
                }
                if (DKQP_LONG(kmsg))
                        inline_total += kmsg->ikm_size;
                else
                        inline_total += kmsg->ikm_header.msgh_size;
        }
        iprintf(DKQP_LONG(kmsg) ? dkqp_long_format : dkqp_format,
                icount, cur_id, ikmsg, inline_total, ool_total);
        return nmsgs;
}


/*
 *      Process all of the messages on a port - prints out the
 *      number of occurences of each message type, and the first
 *      kmsg with a particular msgh_id.
 */
int
db_port_queue_print(
        ipc_port_t      port)
{
        ipc_kmsg_t      kmsg;

        if (ipc_kmsg_queue_empty(&port->ip_messages.imq_messages))
                return 0;
        kmsg = ipc_kmsg_queue_first(&port->ip_messages.imq_messages);
        return db_kmsg_queue_print(kmsg);
}


#if     MACH_ASSERT
#include <ddb/db_sym.h>
#include <ddb/db_access.h>

#define FUNC_NULL       ((void (*)) 0)
#define MAX_REFS        5               /* bins for tracking ref counts */

/*
 *      Translate port's cache of call stack pointers
 *      into symbolic names.
 */
void
db_port_stack_trace(
        ipc_port_t      port)
{
        unsigned int    i;

        for (i = 0; i < IP_CALLSTACK_MAX; ++i) {
                iprintf("[%d] 0x%x\t", i, port->ip_callstack[i]);
                if (port->ip_callstack[i] != 0 &&
                    DB_VALID_KERN_ADDR(port->ip_callstack[i]))
                        db_printsym(port->ip_callstack[i], DB_STGY_PROC);
                printf("\n");
        }
}


typedef struct port_item {
        unsigned long   item;
        unsigned long   count;
} port_item;


#define ITEM_MAX        400
typedef struct port_track {
        char            *name;
        unsigned long   max;
        unsigned long   warning;
        port_item       items[ITEM_MAX];
} port_track;

port_track      port_callers;           /* match against calling addresses */
port_track      port_threads;           /* match against allocating threads */
port_track      port_spaces;            /* match against ipc spaces */

void            port_track_init(
                        port_track      *trackp,
                        char            *name);
void            port_item_add(
                        port_track      *trackp,
                        unsigned long   item);
void            port_track_sort(
                        port_track      *trackp);
void            port_track_print(
                        port_track      *trackp,
                        void            (*func)(port_item *));
void            port_callers_print(
                        port_item       *p);

void
port_track_init(
        port_track      *trackp,
        char            *name)
{
        port_item       *i;

        trackp->max = trackp->warning = 0;
        trackp->name = name;
        for (i = trackp->items; i < trackp->items + ITEM_MAX; ++i)
                i->item = i->count = 0;
}


void
port_item_add(
        port_track      *trackp,
        unsigned long   item)
{
        port_item       *limit, *i;

        limit = trackp->items + trackp->max;
        for (i = trackp->items; i < limit; ++i)
                if (i->item == item) {
                        i->count++;
                        return;
                }
        if (trackp->max >= ITEM_MAX) {
                if (trackp->warning++ == 0)
                        iprintf("%s:  no room\n", trackp->name);
                return;
        }
        i->item = item;
        i->count = 1;
        trackp->max++;
}


/*
 *      Simple (and slow) bubble sort.
 */
void
port_track_sort(
        port_track      *trackp)
{
        port_item       *limit, *p;
        port_item       temp;
        boolean_t       unsorted;

        limit = trackp->items + trackp->max - 1;
        do {
                unsorted = FALSE;
                for (p = trackp->items; p < limit - 1; ++p) {
                        if (p->count < (p+1)->count) {
                                temp = *p;
                                *p = *(p+1);
                                *(p+1) = temp;
                                unsorted = TRUE;
                        }
                }
        } while (unsorted == TRUE);
}


void
port_track_print(
        port_track      *trackp,
        void            (*func)(port_item *))
{
        port_item       *limit, *p;

        limit = trackp->items + trackp->max;
        iprintf("%s:\n", trackp->name);
        for (p = trackp->items; p < limit; ++p) {
                if (func != FUNC_NULL)
                        (*func)(p);
                else
                        iprintf("0x%x\t%8d\n", p->item, p->count);
        }
}


void
port_callers_print(
        port_item       *p)
{
        iprintf("0x%x\t%8d\t", p->item, p->count);
        db_printsym(p->item, DB_STGY_PROC);
        printf("\n");
}


/*
 *      Show all ports with a given reference count.
 */
void
db_ref(
        int             refs)
{
        db_port_walk(1, 1, 1, refs);
}


/*
 *      Examine all currently allocated ports.
 *      Options:
 *              verbose         display suspicious ports
 *              display         print out each port encountered
 *              ref_search      restrict examination to ports with
 *                              a specified reference count
 *              ref_target      reference count for ref_search
 */
int
db_port_walk(
        unsigned int    verbose,
        unsigned int    display,
        unsigned int    ref_search,
        unsigned int    ref_target)
{
        ipc_port_t      port;
        unsigned int    ref_overflow, refs, i, ref_inactive_overflow;
        unsigned int    no_receiver, no_match;
        unsigned int    ref_counts[MAX_REFS];
        unsigned int    inactive[MAX_REFS];
        unsigned int    ipc_ports = 0;
        unsigned int    proxies = 0, principals = 0;

        iprintf("Allocated port count is %d\n", port_count);
        no_receiver = no_match = ref_overflow = 0;
        ref_inactive_overflow = 0;
        for (i = 0; i < MAX_REFS; ++i) {
                ref_counts[i] = 0;
                inactive[i] = 0;
        }
        port_track_init(&port_callers, "port callers");
        port_track_init(&port_threads, "port threads");
        port_track_init(&port_spaces, "port spaces");
        if (ref_search)
                iprintf("Walking ports of ref_count=%d.\n", ref_target);
        else
                iprintf("Walking all ports.\n");

        queue_iterate(&port_alloc_queue, port, ipc_port_t, ip_port_links) {
                char    *port_type;

                port_type = " IPC port";
                if (ip_active(port))
                  ipc_ports++;

                refs = port->ip_references;
                if (ref_search && refs != ref_target)
                        continue;

                if (refs >= MAX_REFS) {
                        if (ip_active(port))
                                ++ref_overflow;
                        else
                                ++ref_inactive_overflow;
                } else {
                        if (refs == 0 && verbose)
                                iprintf("%s 0x%x has ref count of zero!\n",
                                        port_type, port);
                        if (ip_active(port))
                                ref_counts[refs]++;
                        else
                                inactive[refs]++;
                }
                port_item_add(&port_threads, (unsigned long) port->ip_thread);
                for (i = 0; i < IP_CALLSTACK_MAX; ++i) {
                        if (port->ip_callstack[i] != 0 &&
                            DB_VALID_KERN_ADDR(port->ip_callstack[i]))
                                port_item_add(&port_callers,
                                              port->ip_callstack[i]);
                }
                if (!ip_active(port)) {
                        if (verbose)
                                iprintf("%s 0x%x, inactive, refcnt %d\n",
                                        port_type, port, refs);
                        continue;
                }

                if (port->ip_receiver_name == MACH_PORT_NULL) {
                        iprintf("%s  0x%x, no receiver, refcnt %d\n",
                                port, refs);
                        ++no_receiver;
                        continue;
                }
                if (port->ip_receiver == ipc_space_kernel ||
                    port->ip_receiver == ipc_space_reply ||
                    ipc_entry_lookup(port->ip_receiver,
                                        port->ip_receiver_name) 
                                        != IE_NULL) {
                        port_item_add(&port_spaces,
                                      (unsigned long)port->ip_receiver);
                        if (display) {
                                iprintf( "%s 0x%x time 0x%x ref_cnt %d\n",
                                                port_type, port,
                                                port->ip_timetrack, refs);
                        }
                        continue;
                }
                iprintf("%s 0x%x, rcvr 0x%x, name 0x%x, ref %d, no match\n",
                                port_type, port, port->ip_receiver,
                                port->ip_receiver_name, refs);
                ++no_match;
        }
        iprintf("Active port type summary:\n");
        iprintf("\tlocal  IPC %6d\n", ipc_ports);
        iprintf("summary:\tcallers %d threads %d spaces %d\n",
                port_callers.max, port_threads.max, port_spaces.max);

        iprintf("\tref_counts:\n");
        for (i = 0; i < MAX_REFS; ++i)
                iprintf("\t  ref_counts[%d] = %d\n", i, ref_counts[i]);

        iprintf("\t%d ports w/o receivers, %d w/o matches\n",
                no_receiver, no_match);

        iprintf("\tinactives:");
        if ( ref_inactive_overflow || inactive[0] || inactive[1] ||
             inactive[2] || inactive[3] || inactive[4] )
                printf(" [0]=%d [1]=%d [2]=%d [3]=%d [4]=%d [5+]=%d\n",
                        inactive[0], inactive[1], inactive[2],
                        inactive[3], inactive[4], ref_inactive_overflow);
        else
                printf(" No inactive ports.\n");

        port_track_sort(&port_spaces);
        port_track_print(&port_spaces, FUNC_NULL);
        port_track_sort(&port_threads);
        port_track_print(&port_threads, FUNC_NULL);
        port_track_sort(&port_callers);
        port_track_print(&port_callers, port_callers_print);
        return 0;
}


#endif  /* MACH_ASSERT */

#endif  /* MACH_KDB */