xnu-2050.24.15.tar.gz

[apple/xnu.git] / osfmk / ipc / ipc_port.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@
 */
/*
 * @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.
 */
/*
 * NOTICE: This file was modified by McAfee Research in 2004 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.
 */
/*
 */
/*
 *      File:   ipc/ipc_port.c
 *      Author: Rich Draves
 *      Date:   1989
 *
 *      Functions to manipulate IPC ports.
 */

#include <norma_vm.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/thread.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_table.h>

#include <security/mac_mach_internal.h>

#include <string.h>

decl_lck_mtx_data(,     ipc_port_multiple_lock_data)
lck_mtx_ext_t   ipc_port_multiple_lock_data_ext;
ipc_port_timestamp_t    ipc_port_timestamp_data;
int ipc_portbt;

#if     MACH_ASSERT
void    ipc_port_init_debug(
                ipc_port_t      port,
                natural_t       *callstack,
                unsigned int    callstack_max);

void    ipc_port_callstack_init_debug(
                natural_t       *callstack,
                unsigned int    callstack_max);
        
#endif  /* MACH_ASSERT */

void
ipc_port_release(ipc_port_t port)
{
        ip_release(port);
}

void
ipc_port_reference(ipc_port_t port)
{
        ip_reference(port);
}

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

ipc_port_timestamp_t
ipc_port_timestamp(void)
{
        return OSIncrementAtomic(&ipc_port_timestamp_data);
}

/*
 *      Routine:        ipc_port_request_alloc
 *      Purpose:
 *              Try to allocate a 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_request_alloc(
        ipc_port_t                      port,
        mach_port_name_t                name,
        ipc_port_t                      soright,
        boolean_t                       send_possible,
        boolean_t                       immediate,
        ipc_port_request_index_t        *indexp)
{
        ipc_port_request_t ipr, table;
        ipc_port_request_index_t index;
        uintptr_t mask = 0;

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

        table = port->ip_requests;

        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;
        
        if (send_possible) {
                mask |= IPR_SOR_SPREQ_MASK;
                if (immediate) {
                        mask |= IPR_SOR_SPARM_MASK;
                        port->ip_sprequests = TRUE;
                }
        }
        ipr->ipr_soright = IPR_SOR_MAKE(soright, mask);

        *indexp = index;

        return KERN_SUCCESS;
}

/*
 *      Routine:        ipc_port_request_grow
 *      Purpose:
 *              Grow a port's table of 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_request_grow(
        ipc_port_t              port,
        ipc_table_elems_t       target_size)
{
        ipc_table_size_t its;
        ipc_port_request_t otable, ntable;

        assert(ip_active(port));

        otable = port->ip_requests;
        if (otable == IPR_NULL)
                its = &ipc_table_requests[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_requests_alloc(its)) == IPR_NULL)) {
                ip_release(port);
                return KERN_RESOURCE_SHORTAGE;
        }

        ip_lock(port);

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

        if (ip_active(port) && (port->ip_requests == 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;
                        oits = 0;
                        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_requests = ntable;
                ip_unlock(port);
                ip_release(port);

                if (otable != IPR_NULL) {
                        it_requests_free(oits, otable);
                }
        } else {
                ip_unlock(port);
                ip_release(port);
                it_requests_free(its, ntable);
        }

        return KERN_SUCCESS;
}
 
/*
 *      Routine:        ipc_port_request_sparm
 *      Purpose:
 *              Arm delayed send-possible request.
 *      Conditions:
 *              The port must be locked and active.
 */

void
ipc_port_request_sparm(
        ipc_port_t                      port,
        __assert_only mach_port_name_t  name,
        ipc_port_request_index_t        index)
{
        if (index != IE_REQ_NONE) {
                ipc_port_request_t ipr, table;

                assert(ip_active(port));
        
                table = port->ip_requests;
                assert(table != IPR_NULL);

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

                if (IPR_SOR_SPREQ(ipr->ipr_soright)) {
                        ipr->ipr_soright = IPR_SOR_MAKE(ipr->ipr_soright, IPR_SOR_SPARM_MASK);
                        port->ip_sprequests = TRUE;
                }
        }
}

/*
 *      Routine:        ipc_port_request_type
 *      Purpose:
 *              Determine the type(s) of port requests enabled for a name.
 *      Conditions:
 *              The port must be locked or inactive (to avoid table growth).
 *              The index must not be IE_REQ_NONE and for the name in question.
 */
mach_port_type_t
ipc_port_request_type(
        ipc_port_t                      port,
        __assert_only mach_port_name_t  name,
        ipc_port_request_index_t        index)
{
        ipc_port_request_t ipr, table;
        mach_port_type_t type = 0;

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

        assert(index != IE_REQ_NONE);
        ipr = &table[index];
        assert(ipr->ipr_name == name);

        if (IP_VALID(IPR_SOR_PORT(ipr->ipr_soright))) {
                type |= MACH_PORT_TYPE_DNREQUEST;

                if (IPR_SOR_SPREQ(ipr->ipr_soright)) {
                        type |= MACH_PORT_TYPE_SPREQUEST;

                        if (!IPR_SOR_SPARMED(ipr->ipr_soright)) {
                                type |= MACH_PORT_TYPE_SPREQUEST_DELAYED;
                        }
                }
        }
        return type;
}

/*
 *      Routine:        ipc_port_request_cancel
 *      Purpose:
 *              Cancel a dead-name/send-possible request and return the send-once right.
 *      Conditions:
 *              The port must be locked and active.
 *              The index must not be IPR_REQ_NONE and must correspond with name.
 */

ipc_port_t
ipc_port_request_cancel(
        ipc_port_t                      port,
        __assert_only mach_port_name_t  name,
        ipc_port_request_index_t        index)
{
        ipc_port_request_t ipr, table;
        ipc_port_t request = IP_NULL;

        assert(ip_active(port));
        table = port->ip_requests;
        assert(table != IPR_NULL);

        assert (index != IE_REQ_NONE);
        ipr = &table[index];
        assert(ipr->ipr_name == name);
        request = IPR_SOR_PORT(ipr->ipr_soright);

        /* 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 request;
}

/*
 *      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,
        queue_t         links)
{
        spl_t           s;

        assert(ip_active(port));

        /*
         * pull ourselves from any sets.
         */
        if (port->ip_pset_count != 0) {
                ipc_pset_remove_from_all(port, links);
                assert(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_requests = IPR_NULL;

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

        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;

#if     MACH_ASSERT
        natural_t buf[IP_CALLSTACK_MAX];
        ipc_port_callstack_init_debug(&buf[0], IP_CALLSTACK_MAX);
#endif /* MACH_ASSERT */
            
        kr = ipc_object_alloc(space, IOT_PORT,
                              MACH_PORT_TYPE_RECEIVE, 0,
                              &name, (ipc_object_t *) &port);
        if (kr != KERN_SUCCESS)
                return kr;

        /* port and space are locked */
        ipc_port_init(port, space, name);

#if     MACH_ASSERT
        ipc_port_init_debug(port, &buf[0], IP_CALLSTACK_MAX);
#endif  /* MACH_ASSERT */

        /* unlock space after init */
        is_write_unlock(space);

#if CONFIG_MACF_MACH
        task_t issuer = current_task();
        tasklabel_lock2 (issuer, space->is_task);
        mac_port_label_associate(&issuer->maclabel, &space->is_task->maclabel,
                         &port->ip_label);
        tasklabel_unlock2 (issuer, space->is_task);
#endif

        *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;

#if     MACH_ASSERT
        natural_t buf[IP_CALLSTACK_MAX];
        ipc_port_callstack_init_debug(&buf[0], IP_CALLSTACK_MAX);
#endif /* MACH_ASSERT */        

        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);

#if     MACH_ASSERT
        ipc_port_init_debug(port, &buf[0], IP_CALLSTACK_MAX);
#endif  /* MACH_ASSERT */       

#if CONFIG_MACF_MACH
        task_t issuer = current_task();
        tasklabel_lock2 (issuer, space->is_task);
        mac_port_label_associate(&issuer->maclabel, &space->is_task->maclabel,
                         &port->ip_label);
        tasklabel_unlock2 (issuer, space->is_task);
#endif

        *portp = port;

        return KERN_SUCCESS;
}

/*
 *      Routine:        ipc_port_spnotify
 *      Purpose:
 *              Generate send-possible port notifications.
 *      Conditions:
 *              Nothing locked, reference held on port.
 */
void
ipc_port_spnotify(
        ipc_port_t      port)
{
        ipc_port_request_index_t index = 0;
        ipc_table_elems_t size = 0;

        /*
         * If the port has no send-possible request
         * armed, don't bother to lock the port.
         */
        if (!port->ip_sprequests)
                return;

        ip_lock(port);
        if (!port->ip_sprequests) {
                ip_unlock(port);
                return;
        }
        port->ip_sprequests = FALSE;

 revalidate:
        if (ip_active(port)) {
                ipc_port_request_t requests;

                /* table may change each time port unlocked (reload) */
                requests = port->ip_requests;
                assert(requests != IPR_NULL);

                /*
                 * no need to go beyond table size when first
                 * we entered - those are future notifications.
                 */
                if (size == 0)
                        size = requests->ipr_size->its_size;

                /* no need to backtrack either */
                while (++index < size) {
                        ipc_port_request_t ipr = &requests[index];
                        mach_port_name_t name = ipr->ipr_name;
                        ipc_port_t soright = IPR_SOR_PORT(ipr->ipr_soright);
                        boolean_t armed = IPR_SOR_SPARMED(ipr->ipr_soright);

                        if (MACH_PORT_VALID(name) && armed && IP_VALID(soright)) {
                                /* claim send-once right - slot still inuse */
                                ipr->ipr_soright = IP_NULL;
                                ip_unlock(port);

                                ipc_notify_send_possible(soright, name);

                                ip_lock(port);
                                goto revalidate;
                        }
                }
        }
        ip_unlock(port);
}

/*
 *      Routine:        ipc_port_dnnotify
 *      Purpose:
 *              Generate dead name notifications for
 *              all outstanding dead-name and send-
 *              possible requests.
 *      Conditions:
 *              Nothing locked.
 *              Port must be inactive.
 *              Reference held on port.
 */
void
ipc_port_dnnotify(
        ipc_port_t      port)
{
        ipc_port_request_t requests = port->ip_requests;

        assert(!ip_active(port));
        if (requests != IPR_NULL) {
                ipc_table_size_t its = requests->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 = &requests[index];
                        mach_port_name_t name = ipr->ipr_name;
                        ipc_port_t soright = IPR_SOR_PORT(ipr->ipr_soright);

                        if (MACH_PORT_VALID(name) && IP_VALID(soright)) {
                                ipc_notify_dead_name(soright, name);
                        }
                }
        }
}


/*
 *      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_t kmsg;

        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);

                /* consumes our refs for port and pdrequest */
                ipc_notify_port_destroyed(pdrequest, port);
                return;
        }

        /* 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();

        /*
         * If the port has a preallocated message buffer and that buffer
         * is not inuse, free it.  If it has an 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)) {
                ipc_port_t inuse_port;

                kmsg = port->ip_premsg;
                assert(kmsg != IKM_NULL);
                inuse_port = ikm_prealloc_inuse_port(kmsg);
                IP_CLEAR_PREALLOC(port, kmsg);
                ip_unlock(port);
                if (inuse_port != IP_NULL) {
                        assert(inuse_port == port);
                } else {
                        ipc_kmsg_free(kmsg);
                }
        } else {
                ip_unlock(port);
        }

        /* 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 */
        ipc_port_dnnotify(port);

        ipc_kobject_destroy(port);

        ip_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(is_active(space));

        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 = CAST_MACH_PORT_TO_NAME(sright);

        return name;
}

/*
 *      Routine:        ipc_port_release_send
 *      Purpose:
 *              Release a 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;

        if (!IP_VALID(port))
                return;

        ip_lock(port);

        if (!ip_active(port)) {
                ip_unlock(port);
                ip_release(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);
                ip_release(port);
                ipc_notify_no_senders(nsrequest, mscount);
        } else {
                ip_unlock(port);
                ip_release(port);
        }
}

/*
 *      Routine:        ipc_port_make_sonce_locked
 *      Purpose:
 *              Make a naked send-once right from a receive right.
 *      Conditions:
 *              The port is locked and active.
 */

ipc_port_t
ipc_port_make_sonce_locked(
        ipc_port_t      port)
{
        assert(ip_active(port));
        port->ip_sorights++;
        ip_reference(port);
        return port;
}

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

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

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

/*
 *      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)
{
        if (!IP_VALID(port))
                return;

        ip_lock(port);

        assert(port->ip_sorights > 0);

        port->ip_sorights--;

        ip_unlock(port);
        ip_release(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;

        if (!IP_VALID(port))
                return;

        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)
                ip_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;

#if     MACH_ASSERT
        natural_t buf[IP_CALLSTACK_MAX];
        ipc_port_callstack_init_debug(&buf[0], IP_CALLSTACK_MAX);
#endif /* MACH_ASSERT */        

        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);

#if     MACH_ASSERT
        ipc_port_init_debug(port, &buf[0], IP_CALLSTACK_MAX);
#endif  /* MACH_ASSERT */               

#if CONFIG_MACF_MACH
        /* Currently, ipc_port_alloc_special is used for two things:
         * - Reply ports for messages from the kernel
         * - Ports for communication with the kernel (e.g. task ports)
         * Since both of these would typically be labelled as kernel objects,
         * we will use a new entry point for this purpose, as current_task()
         * is often wrong (i.e. not kernel_task) or null.
         */
        mac_port_label_init(&port->ip_label);
        mac_port_label_associate_kernel(&port->ip_label, space == ipc_space_reply);
#endif

        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,
        __assert_only 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);
}

/*
 *      Routine:        ipc_port_finalize
 *      Purpose:
 *              Called on last reference deallocate to
 *              free any remaining data associated with the
 *              port.
 *      Conditions:
 *              Nothing locked.
 */
void
ipc_port_finalize(
        ipc_port_t              port)
{
        ipc_port_request_t requests = port->ip_requests;

        assert(!ip_active(port));
        if (requests != IPR_NULL) {
                ipc_table_size_t its = requests->ipr_size;
                it_requests_free(its, requests);
                port->ip_requests = IPR_NULL;
        }
        
#if     MACH_ASSERT
        ipc_port_track_dealloc(port);
#endif  /* MACH_ASSERT */

#if CONFIG_MACF_MACH
        /* Port label should have been initialized after creation. */
        mac_port_label_destroy(&port->ip_label);
#endif    
}

#if     MACH_ASSERT
#include <kern/machine.h>

/*
 *      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;
lck_spin_t      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);

        lck_spin_init(&port_alloc_queue_lock, &ipc_lck_grp, &ipc_lck_attr);

        if (!PE_parse_boot_argn("ipc_portbt", &ipc_portbt, sizeof (ipc_portbt)))
                ipc_portbt = 0;
}

#ifdef MACH_BSD
extern int proc_pid(struct proc*);
#endif /* MACH_BSD */

/*
 *      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,
        natural_t       *callstack,
        unsigned int    callstack_max)
{
        unsigned int    i;

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

#ifdef MACH_BSD
        task_t task = current_task();
        if (task != TASK_NULL) {
                struct proc* proc = (struct proc*) get_bsdtask_info(task);
                if (proc)
                        port->ip_spares[0] = proc_pid(proc);
        }
#endif /* MACH_BSD */

#if 0
        lck_spin_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);
        lck_spin_unlock(&port_alloc_queue_lock);
#endif
}

/*
 *      Routine:        ipc_port_callstack_init_debug
 *      Purpose:
 *              Calls the machine-dependent routine to
 *              fill in an array with up to IP_CALLSTACK_MAX
 *              levels of return pc information
 *      Conditions:
 *              May block (via copyin)
 */
void
ipc_port_callstack_init_debug(
        natural_t       *callstack,
        unsigned int    callstack_max)
{
        unsigned int    i;

        /* guarantee the callstack is initialized */
        for (i=0; i < callstack_max; i++)
                callstack[i] = 0;       

        if (ipc_portbt)
                machine_callstack(callstack, callstack_max);
}

/*
 *      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.
 */
#if 1
void
ipc_port_track_dealloc(
        __unused ipc_port_t     port)
{
}
#else
void
ipc_port_track_dealloc(
        ipc_port_t              port)
{
        lck_spin_lock(&port_alloc_queue_lock);
        assert(port_count > 0);
        --port_count;
        queue_remove(&port_alloc_queue, port, ipc_port_t, ip_port_links);
        lck_spin_unlock(&port_alloc_queue_lock);
}
#endif


#endif  /* MACH_ASSERT */