[apple/xnu.git] / osfmk / ipc / mach_msg.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_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.
 * Copyright (c) 2005 SPARTA, Inc.
 */
/*
 */
/*
 *      File:   ipc/mach_msg.c
 *      Author: Rich Draves
 *      Date:   1989
 *
 *      Exported message traps.  See mach/message.h.
 */

#include <mach/mach_types.h>
#include <mach/kern_return.h>
#include <mach/port.h>
#include <mach/message.h>
#include <mach/mig_errors.h>
#include <mach/mach_traps.h>

#include <kern/kern_types.h>
#include <kern/assert.h>
#include <kern/cpu_number.h>
#include <kern/ipc_kobject.h>
#include <kern/ipc_mig.h>
#include <kern/task.h>
#include <kern/thread.h>
#include <kern/sched_prim.h>
#include <kern/exception.h>
#include <kern/misc_protos.h>
#include <kern/processor.h>
#include <kern/syscall_subr.h>
#include <kern/policy_internal.h>
#include <kern/mach_filter.h>

#include <vm/vm_map.h>

#include <ipc/port.h>
#include <ipc/ipc_types.h>
#include <ipc/ipc_kmsg.h>
#include <ipc/ipc_mqueue.h>
#include <ipc/ipc_object.h>
#include <ipc/ipc_notify.h>
#include <ipc/ipc_port.h>
#include <ipc/ipc_pset.h>
#include <ipc/ipc_space.h>
#include <ipc/ipc_entry.h>
#include <ipc/ipc_importance.h>
#include <ipc/ipc_voucher.h>

#include <machine/machine_routines.h>
#include <security/mac_mach_internal.h>

#include <sys/kdebug.h>

#ifndef offsetof
#define offsetof(type, member)  ((size_t)(&((type *)0)->member))
#endif /* offsetof */

/*
 * Forward declarations - kernel internal routines
 */

mach_msg_return_t mach_msg_send(
        mach_msg_header_t       *msg,
        mach_msg_option_t       option,
        mach_msg_size_t         send_size,
        mach_msg_timeout_t      send_timeout,
        mach_port_name_t        notify);

mach_msg_return_t mach_msg_receive(
        mach_msg_header_t       *msg,
        mach_msg_option_t       option,
        mach_msg_size_t         rcv_size,
        mach_port_name_t        rcv_name,
        mach_msg_timeout_t      rcv_timeout,
        void                    (*continuation)(mach_msg_return_t),
        mach_msg_size_t         slist_size);


mach_msg_return_t msg_receive_error(
        ipc_kmsg_t              kmsg,
        mach_msg_option_t       option,
        mach_vm_address_t       rcv_addr,
        mach_msg_size_t         rcv_size,
        mach_port_seqno_t       seqno,
        ipc_space_t             space,
        mach_msg_size_t         *out_size);

static mach_msg_return_t
mach_msg_rcv_link_special_reply_port(
        ipc_port_t special_reply_port,
        mach_port_name_t dest_name_port);

void
mach_msg_receive_results_complete(ipc_object_t object);

const security_token_t KERNEL_SECURITY_TOKEN = KERNEL_SECURITY_TOKEN_VALUE;
const audit_token_t KERNEL_AUDIT_TOKEN = KERNEL_AUDIT_TOKEN_VALUE;

const mach_msg_max_trailer_t trailer_template = {
        .msgh_trailer_type = MACH_MSG_TRAILER_FORMAT_0,
        .msgh_trailer_size = MACH_MSG_TRAILER_MINIMUM_SIZE,
        .msgh_sender = KERNEL_SECURITY_TOKEN_VALUE,
        .msgh_audit = KERNEL_AUDIT_TOKEN_VALUE
};

/*
 *      Routine:        mach_msg_send [Kernel Internal]
 *      Purpose:
 *              Routine for kernel-task threads to send a message.
 *
 *              Unlike mach_msg_send_from_kernel(), this routine
 *              looks port names up in the kernel's port namespace
 *              and copies in the kernel virtual memory (instead
 *              of taking a vm_map_copy_t pointer for OOL descriptors).
 *      Conditions:
 *              Nothing locked.
 *      Returns:
 *              MACH_MSG_SUCCESS        Sent the message.
 *              MACH_SEND_MSG_TOO_SMALL Message smaller than a header.
 *              MACH_SEND_NO_BUFFER     Couldn't allocate buffer.
 *              MACH_SEND_INVALID_DATA  Couldn't copy message data.
 *              MACH_SEND_INVALID_HEADER
 *                      Illegal value in the message header bits.
 *              MACH_SEND_INVALID_DEST  The space is dead.
 *              MACH_SEND_INVALID_NOTIFY        Bad notify port.
 *              MACH_SEND_INVALID_DEST  Can't copyin destination port.
 *              MACH_SEND_INVALID_REPLY Can't copyin reply port.
 *              MACH_SEND_TIMED_OUT     Timeout expired without delivery.
 *              MACH_SEND_INTERRUPTED   Delivery interrupted.
 */

mach_msg_return_t
mach_msg_send(
        mach_msg_header_t       *msg,
        mach_msg_option_t       option,
        mach_msg_size_t         send_size,
        mach_msg_timeout_t      send_timeout,
        mach_msg_priority_t     priority)
{
        ipc_space_t space = current_space();
        vm_map_t map = current_map();
        ipc_kmsg_t kmsg;
        mach_msg_return_t mr;
        mach_msg_size_t msg_and_trailer_size;
        mach_msg_max_trailer_t  *trailer;

        option |= MACH_SEND_KERNEL;

        if ((send_size & 3) ||
            send_size < sizeof(mach_msg_header_t) ||
            (send_size < sizeof(mach_msg_base_t) && (msg->msgh_bits & MACH_MSGH_BITS_COMPLEX))) {
                return MACH_SEND_MSG_TOO_SMALL;
        }

        if (send_size > MACH_MSG_SIZE_MAX - MAX_TRAILER_SIZE) {
                return MACH_SEND_TOO_LARGE;
        }

        KDBG(MACHDBG_CODE(DBG_MACH_IPC, MACH_IPC_KMSG_INFO) | DBG_FUNC_START);

        msg_and_trailer_size = send_size + MAX_TRAILER_SIZE;

        kmsg = ipc_kmsg_alloc(msg_and_trailer_size);

        if (kmsg == IKM_NULL) {
                KDBG(MACHDBG_CODE(DBG_MACH_IPC, MACH_IPC_KMSG_INFO) | DBG_FUNC_END, MACH_SEND_NO_BUFFER);
                return MACH_SEND_NO_BUFFER;
        }

        KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_IPC, MACH_IPC_KMSG_LINK) | DBG_FUNC_NONE,
            (uintptr_t)0,                   /* this should only be called from the kernel! */
            VM_KERNEL_ADDRPERM((uintptr_t)kmsg),
            0, 0,
            0);
        (void) memcpy((void *) kmsg->ikm_header, (const void *) msg, send_size);

        kmsg->ikm_header->msgh_size = send_size;

        /*
         * reserve for the trailer the largest space (MAX_TRAILER_SIZE)
         * However, the internal size field of the trailer (msgh_trailer_size)
         * is initialized to the minimum (sizeof(mach_msg_trailer_t)), to optimize
         * the cases where no implicit data is requested.
         */
        trailer = (mach_msg_max_trailer_t *) ((vm_offset_t)kmsg->ikm_header + send_size);
        bzero(trailer, sizeof(*trailer));
        trailer->msgh_sender = current_thread()->task->sec_token;
        trailer->msgh_audit = current_thread()->task->audit_token;
        trailer->msgh_trailer_type = MACH_MSG_TRAILER_FORMAT_0;
        trailer->msgh_trailer_size = MACH_MSG_TRAILER_MINIMUM_SIZE;

        mr = ipc_kmsg_copyin(kmsg, space, map, priority, &option);

        if (mr != MACH_MSG_SUCCESS) {
                ipc_kmsg_free(kmsg);
                KDBG(MACHDBG_CODE(DBG_MACH_IPC, MACH_IPC_KMSG_INFO) | DBG_FUNC_END, mr);
                return mr;
        }

        mr = ipc_kmsg_send(kmsg, option, send_timeout);

        if (mr != MACH_MSG_SUCCESS) {
                mr |= ipc_kmsg_copyout_pseudo(kmsg, space, map, MACH_MSG_BODY_NULL);
                (void) memcpy((void *) msg, (const void *) kmsg->ikm_header,
                    kmsg->ikm_header->msgh_size);
                ipc_kmsg_free(kmsg);
                KDBG(MACHDBG_CODE(DBG_MACH_IPC, MACH_IPC_KMSG_INFO) | DBG_FUNC_END, mr);
        }

        return mr;
}

/*
 * message header as seen at user-space
 * (for MACH_RCV_LARGE/IDENTITY updating)
 */
typedef struct{
        mach_msg_bits_t       msgh_bits;
        mach_msg_size_t       msgh_size;
        mach_port_name_t      msgh_remote_port;
        mach_port_name_t      msgh_local_port;
        mach_msg_size_t       msgh_reserved;
        mach_msg_id_t         msgh_id;
} mach_msg_user_header_t;

/*
 *      Routine:        mach_msg_receive_results
 *      Purpose:
 *              Receive a message.
 *      Conditions:
 *              Nothing locked.
 *      Returns:
 *              MACH_MSG_SUCCESS        Received a message.
 *              MACH_RCV_INVALID_NAME   The name doesn't denote a right,
 *                      or the denoted right is not receive or port set.
 *              MACH_RCV_IN_SET         Receive right is a member of a set.
 *              MACH_RCV_TOO_LARGE      Message wouldn't fit into buffer.
 *              MACH_RCV_TIMED_OUT      Timeout expired without a message.
 *              MACH_RCV_INTERRUPTED    Reception interrupted.
 *              MACH_RCV_PORT_DIED      Port/set died while receiving.
 *              MACH_RCV_PORT_CHANGED   Port moved into set while receiving.
 *              MACH_RCV_INVALID_DATA   Couldn't copy to user buffer.
 *              MACH_RCV_INVALID_NOTIFY Bad notify port.
 *              MACH_RCV_HEADER_ERROR
 */

mach_msg_return_t
mach_msg_receive_results(
        mach_msg_size_t *sizep)
{
        thread_t          self = current_thread();
        ipc_space_t       space = current_space();
        vm_map_t          map = current_map();

        ipc_object_t      object = self->ith_object;
        mach_msg_return_t mr = self->ith_state;
        mach_vm_address_t rcv_addr = self->ith_msg_addr;
        mach_msg_size_t   rcv_size = self->ith_rsize;
        mach_msg_option_t option = self->ith_option;
        ipc_kmsg_t        kmsg = self->ith_kmsg;
        mach_port_seqno_t seqno = self->ith_seqno;

        mach_msg_trailer_size_t trailer_size;
        mach_vm_address_t context;
        mach_msg_size_t   size = 0;

        /*
         * unlink the special_reply_port before releasing reference to object.
         * get the thread's turnstile, if the thread donated it's turnstile to the port
         */
        mach_msg_receive_results_complete(object);
        io_release(object);

        if (mr != MACH_MSG_SUCCESS) {
                if (mr == MACH_RCV_TOO_LARGE) {
                        /*
                         * If the receive operation occurs with MACH_RCV_LARGE set
                         * then no message was extracted from the queue, and the size
                         * and (optionally) receiver names were the only thing captured.
                         * Just copyout the size (and optional port name) in a fake
                         * header.
                         */
                        if (option & MACH_RCV_LARGE) {
                                if ((option & MACH_RCV_STACK) == 0 &&
                                    rcv_size >= offsetof(mach_msg_user_header_t, msgh_reserved)) {
                                        /*
                                         * We need to inform the user-level code that it needs more
                                         * space.  The value for how much space was returned in the
                                         * msize save area instead of the message (which was left on
                                         * the queue).
                                         */
                                        if (option & MACH_RCV_LARGE_IDENTITY) {
                                                if (copyout((char *) &self->ith_receiver_name,
                                                    rcv_addr + offsetof(mach_msg_user_header_t, msgh_local_port),
                                                    sizeof(mach_port_name_t))) {
                                                        mr = MACH_RCV_INVALID_DATA;
                                                }
                                        }
                                        if (copyout((char *) &self->ith_msize,
                                            rcv_addr + offsetof(mach_msg_user_header_t, msgh_size),
                                            sizeof(mach_msg_size_t))) {
                                                mr = MACH_RCV_INVALID_DATA;
                                        }
                                }
                        } else {
                                /* discard importance in message */
                                ipc_importance_clean(kmsg);

                                if (msg_receive_error(kmsg, option, rcv_addr, rcv_size, seqno, space, &size)
                                    == MACH_RCV_INVALID_DATA) {
                                        mr = MACH_RCV_INVALID_DATA;
                                }
                        }
                }

                if (sizep) {
                        *sizep = size;
                }
                return mr;
        }

        /* MACH_MSG_SUCCESS */

#if IMPORTANCE_INHERITANCE

        /* adopt/transform any importance attributes carried in the message */
        ipc_importance_receive(kmsg, option);

#endif  /* IMPORTANCE_INHERITANCE */

        /* auto redeem the voucher in the message */
        ipc_voucher_receive_postprocessing(kmsg, option);

        /* Save destination port context for the trailer before copyout */
        context = kmsg->ikm_header->msgh_remote_port->ip_context;

        mr = ipc_kmsg_copyout(kmsg, space, map, MACH_MSG_BODY_NULL, option);

        trailer_size = ipc_kmsg_trailer_size(option, self);

        if (mr != MACH_MSG_SUCCESS) {
                /* already received importance, so have to undo that here */
                ipc_importance_unreceive(kmsg, option);

                /* if we had a body error copyout what we have, otherwise a simple header/trailer */
                if ((mr & ~MACH_MSG_MASK) == MACH_RCV_BODY_ERROR) {
                        ipc_kmsg_add_trailer(kmsg, space, option, self, seqno, FALSE, context);
                        if (ipc_kmsg_put(kmsg, option, rcv_addr, rcv_size, trailer_size, &size) == MACH_RCV_INVALID_DATA) {
                                mr = MACH_RCV_INVALID_DATA;
                        }
                } else {
                        if (msg_receive_error(kmsg, option, rcv_addr, rcv_size, seqno, space, &size)
                            == MACH_RCV_INVALID_DATA) {
                                mr = MACH_RCV_INVALID_DATA;
                        }
                }
        } else {
                /* capture ksmg QoS values to the thread continuation state */
                self->ith_ppriority = kmsg->ikm_ppriority;
                self->ith_qos_override = kmsg->ikm_qos_override;
                ipc_kmsg_add_trailer(kmsg, space, option, self, seqno, FALSE, context);
                mr = ipc_kmsg_put(kmsg, option, rcv_addr, rcv_size, trailer_size, &size);
        }

        if (sizep) {
                *sizep = size;
        }
        return mr;
}

/*
 *      Routine:        mach_msg_receive [Kernel Internal]
 *      Purpose:
 *              Routine for kernel-task threads to actively receive a message.
 *
 *              Unlike being dispatched to by ipc_kobject_server() or the
 *              reply part of mach_msg_rpc_from_kernel(), this routine
 *              looks up the receive port name in the kernel's port
 *              namespace and copies out received port rights to that namespace
 *              as well.  Out-of-line memory is copied out the kernel's
 *              address space (rather than just providing the vm_map_copy_t).
 *      Conditions:
 *              Nothing locked.
 *      Returns:
 *              MACH_MSG_SUCCESS        Received a message.
 *              See <mach/message.h> for list of MACH_RCV_XXX errors.
 */
mach_msg_return_t
mach_msg_receive(
        mach_msg_header_t       *msg,
        mach_msg_option_t       option,
        mach_msg_size_t         rcv_size,
        mach_port_name_t        rcv_name,
        mach_msg_timeout_t      rcv_timeout,
        void                    (*continuation)(mach_msg_return_t),
        __unused mach_msg_size_t slist_size)
{
        thread_t self = current_thread();
        ipc_space_t space = current_space();
        ipc_object_t object;
        ipc_mqueue_t mqueue;
        mach_msg_return_t mr;

        mr = ipc_mqueue_copyin(space, rcv_name, &mqueue, &object);
        if (mr != MACH_MSG_SUCCESS) {
                return mr;
        }
        /* hold ref for object */

        self->ith_msg_addr = CAST_DOWN(mach_vm_address_t, msg);
        self->ith_object = object;
        self->ith_rsize = rcv_size;
        self->ith_msize = 0;
        self->ith_option = option;
        self->ith_continuation = continuation;
        self->ith_knote = ITH_KNOTE_NULL;

        ipc_mqueue_receive(mqueue, option, rcv_size, rcv_timeout, THREAD_ABORTSAFE);
        if ((option & MACH_RCV_TIMEOUT) && rcv_timeout == 0) {
                thread_poll_yield(self);
        }
        return mach_msg_receive_results(NULL);
}

void
mach_msg_receive_continue(void)
{
        mach_msg_return_t mr;
        thread_t self = current_thread();

        ipc_port_thread_group_unblocked();
        if (self->ith_state == MACH_PEEK_READY) {
                mr = MACH_PEEK_READY;
        } else {
                mr = mach_msg_receive_results(NULL);
        }
        (*self->ith_continuation)(mr);
}


/*
 *      Routine:        mach_msg_overwrite_trap [mach trap]
 *      Purpose:
 *              Possibly send a message; possibly receive a message.
 *      Conditions:
 *              Nothing locked.
 *      Returns:
 *              All of mach_msg_send and mach_msg_receive error codes.
 */

mach_msg_return_t
mach_msg_overwrite_trap(
        struct mach_msg_overwrite_trap_args *args)
{
        mach_vm_address_t       msg_addr = args->msg;
        mach_msg_option_t       option = args->option;
        mach_msg_size_t         send_size = args->send_size;
        mach_msg_size_t         rcv_size = args->rcv_size;
        mach_port_name_t        rcv_name = args->rcv_name;
        mach_msg_timeout_t      msg_timeout = args->timeout;
        mach_msg_priority_t     priority = args->priority;
        mach_vm_address_t       rcv_msg_addr = args->rcv_msg;
        __unused mach_port_seqno_t temp_seqno = 0;

        mach_msg_return_t  mr = MACH_MSG_SUCCESS;
        vm_map_t map = current_map();

        /* Only accept options allowed by the user */
        option &= MACH_MSG_OPTION_USER;

        if (option & MACH_SEND_MSG) {
                ipc_space_t space = current_space();
                ipc_kmsg_t kmsg;

                KDBG(MACHDBG_CODE(DBG_MACH_IPC, MACH_IPC_KMSG_INFO) | DBG_FUNC_START);

                mr = ipc_kmsg_get(msg_addr, send_size, &kmsg);

                if (mr != MACH_MSG_SUCCESS) {
                        KDBG(MACHDBG_CODE(DBG_MACH_IPC, MACH_IPC_KMSG_INFO) | DBG_FUNC_END, mr);
                        return mr;
                }

                KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_IPC, MACH_IPC_KMSG_LINK) | DBG_FUNC_NONE,
                    (uintptr_t)msg_addr,
                    VM_KERNEL_ADDRPERM((uintptr_t)kmsg),
                    0, 0,
                    0);

                mr = ipc_kmsg_copyin(kmsg, space, map, priority, &option);

                if (mr != MACH_MSG_SUCCESS) {
                        ipc_kmsg_free(kmsg);
                        KDBG(MACHDBG_CODE(DBG_MACH_IPC, MACH_IPC_KMSG_INFO) | DBG_FUNC_END, mr);
                        goto end;
                }

                mr = ipc_kmsg_send(kmsg, option, msg_timeout);

                if (mr != MACH_MSG_SUCCESS) {
                        mr |= ipc_kmsg_copyout_pseudo(kmsg, space, map, MACH_MSG_BODY_NULL);
                        (void) ipc_kmsg_put(kmsg, option, msg_addr, send_size, 0, NULL);
                        KDBG(MACHDBG_CODE(DBG_MACH_IPC, MACH_IPC_KMSG_INFO) | DBG_FUNC_END, mr);
                        goto end;
                }
        }

        if (option & MACH_RCV_MSG) {
                thread_t self = current_thread();
                ipc_space_t space = current_space();
                ipc_object_t object;
                ipc_mqueue_t mqueue;

                mr = ipc_mqueue_copyin(space, rcv_name, &mqueue, &object);
                if (mr != MACH_MSG_SUCCESS) {
                        goto end;
                }
                /* hold ref for object */

                if ((option & MACH_RCV_SYNC_WAIT) && !(option & MACH_SEND_SYNC_OVERRIDE)) {
                        ipc_port_t special_reply_port;
                        special_reply_port = ip_object_to_port(object);
                        /* link the special reply port to the destination */
                        mr = mach_msg_rcv_link_special_reply_port(special_reply_port,
                            (mach_port_name_t)priority);
                        if (mr != MACH_MSG_SUCCESS) {
                                io_release(object);
                                goto end;
                        }
                }

                if (rcv_msg_addr != (mach_vm_address_t)0) {
                        self->ith_msg_addr = rcv_msg_addr;
                } else {
                        self->ith_msg_addr = msg_addr;
                }
                self->ith_object = object;
                self->ith_rsize = rcv_size;
                self->ith_msize = 0;
                self->ith_option = option;
                self->ith_receiver_name = MACH_PORT_NULL;
                self->ith_continuation = thread_syscall_return;
                self->ith_knote = ITH_KNOTE_NULL;

                ipc_mqueue_receive(mqueue, option, rcv_size, msg_timeout, THREAD_ABORTSAFE);
                if ((option & MACH_RCV_TIMEOUT) && msg_timeout == 0) {
                        thread_poll_yield(self);
                }
                mr = mach_msg_receive_results(NULL);
                goto end;
        }

end:
        ipc_port_thread_group_unblocked();
        return mr;
}

/*
 *      Routine:        mach_msg_rcv_link_special_reply_port
 *      Purpose:
 *              Link the special reply port(rcv right) to the
 *              other end of the sync ipc channel.
 *      Conditions:
 *              Nothing locked.
 *      Returns:
 *              None.
 */
static mach_msg_return_t
mach_msg_rcv_link_special_reply_port(
        ipc_port_t special_reply_port,
        mach_port_name_t dest_name_port)
{
        ipc_port_t dest_port = IP_NULL;
        kern_return_t kr;

        if (current_thread()->ith_special_reply_port != special_reply_port) {
                return MACH_RCV_INVALID_NOTIFY;
        }

        /* Copyin the destination port */
        if (!MACH_PORT_VALID(dest_name_port)) {
                return MACH_RCV_INVALID_NOTIFY;
        }

        kr = ipc_port_translate_send(current_space(), dest_name_port, &dest_port);
        if (kr == KERN_SUCCESS) {
                ip_reference(dest_port);
                ip_unlock(dest_port);

                /*
                 * The receive right of dest port might have gone away,
                 * do not fail the receive in that case.
                 */
                ipc_port_link_special_reply_port(special_reply_port,
                    dest_port, FALSE);

                ip_release(dest_port);
        }
        return MACH_MSG_SUCCESS;
}

/*
 *      Routine:        mach_msg_receive_results_complete
 *      Purpose:
 *              Get thread's turnstile back from the object and
 *              if object is a special reply port then reset its
 *              linkage.
 *      Condition:
 *              Nothing locked.
 *      Returns:
 *              None.
 */
void
mach_msg_receive_results_complete(ipc_object_t object)
{
        thread_t self = current_thread();
        ipc_port_t port = IPC_PORT_NULL;
        boolean_t get_turnstile = (self->turnstile == TURNSTILE_NULL);

        if (io_otype(object) == IOT_PORT) {
                port = ip_object_to_port(object);
        } else {
                assert(self->turnstile != TURNSTILE_NULL);
                return;
        }

        uint8_t flags = IPC_PORT_ADJUST_SR_ALLOW_SYNC_LINKAGE;

        /*
         * Don't clear the ip_srp_msg_sent bit if...
         */
        if (!((self->ith_state == MACH_RCV_TOO_LARGE && self->ith_option & MACH_RCV_LARGE) || //msg was too large and the next receive will get it
            self->ith_state == MACH_RCV_INTERRUPTED ||
            self->ith_state == MACH_RCV_TIMED_OUT ||
            self->ith_state == MACH_RCV_PORT_CHANGED ||
            self->ith_state == MACH_PEEK_READY)) {
                flags |= IPC_PORT_ADJUST_SR_RECEIVED_MSG;
        }

        if (port->ip_specialreply || get_turnstile) {
                ip_lock(port);
                ipc_port_adjust_special_reply_port_locked(port, NULL,
                    flags, get_turnstile);
        }
        assert(self->turnstile != TURNSTILE_NULL);
        /* thread now has a turnstile */
}

/*
 *      Routine:        mach_msg_trap [mach trap]
 *      Purpose:
 *              Possibly send a message; possibly receive a message.
 *      Conditions:
 *              Nothing locked.
 *      Returns:
 *              All of mach_msg_send and mach_msg_receive error codes.
 */

mach_msg_return_t
mach_msg_trap(
        struct mach_msg_overwrite_trap_args *args)
{
        kern_return_t kr;
        args->rcv_msg = (mach_vm_address_t)0;

        kr = mach_msg_overwrite_trap(args);
        return kr;
}


/*
 *      Routine:        msg_receive_error       [internal]
 *      Purpose:
 *              Builds a minimal header/trailer and copies it to
 *              the user message buffer.  Invoked when in the case of a
 *              MACH_RCV_TOO_LARGE or MACH_RCV_BODY_ERROR error.
 *      Conditions:
 *              Nothing locked.
 *              size - maximum buffer size on input,
 *                     actual copied-out size on output
 *      Returns:
 *              MACH_MSG_SUCCESS        minimal header/trailer copied
 *              MACH_RCV_INVALID_DATA   copyout to user buffer failed
 */

mach_msg_return_t
msg_receive_error(
        ipc_kmsg_t              kmsg,
        mach_msg_option_t       option,
        mach_vm_address_t       rcv_addr,
        mach_msg_size_t         rcv_size,
        mach_port_seqno_t       seqno,
        ipc_space_t             space,
        mach_msg_size_t         *sizep)
{
        mach_vm_address_t       context;
        mach_msg_trailer_size_t trailer_size;
        mach_msg_max_trailer_t  *trailer;
        thread_t                self = current_thread();

        context = kmsg->ikm_header->msgh_remote_port->ip_context;

        /*
         * Copy out the destination port in the message.
         * Destroy all other rights and memory in the message.
         */
        ipc_kmsg_copyout_dest(kmsg, space);

        /*
         * Build a minimal message with the requested trailer.
         */
        trailer = (mach_msg_max_trailer_t *)
            ((vm_offset_t)kmsg->ikm_header +
            mach_round_msg(sizeof(mach_msg_header_t)));
        kmsg->ikm_header->msgh_size = sizeof(mach_msg_header_t);
        bcopy((const char *)&trailer_template,
            (char *)trailer,
            sizeof(trailer_template));

        trailer_size = ipc_kmsg_trailer_size(option, self);
        ipc_kmsg_add_trailer(kmsg, space, option, self,
            seqno, TRUE, context);

        /*
         * Copy the message to user space and return the size
         * (note that ipc_kmsg_put may also adjust the actual
         * size copied out to user-space).
         */
        if (ipc_kmsg_put(kmsg, option, rcv_addr, rcv_size, trailer_size, sizep) == MACH_RCV_INVALID_DATA) {
                return MACH_RCV_INVALID_DATA;
        } else {
                return MACH_MSG_SUCCESS;
        }
}

static SECURITY_READ_ONLY_LATE(mach_msg_fetch_filter_policy_cbfunc_t) mach_msg_fetch_filter_policy_callback = NULL;

kern_return_t
mach_msg_filter_register_callback(
        const struct mach_msg_filter_callbacks *callbacks)
{
        if (callbacks == NULL) {
                return KERN_INVALID_ARGUMENT;
        }

        if (callbacks->version >= MACH_MSG_FILTER_CALLBACKS_VERSION_0) {
                if (mach_msg_fetch_filter_policy_callback != NULL) {
                        return KERN_FAILURE;
                }
                mach_msg_fetch_filter_policy_callback = callbacks->fetch_filter_policy;
        }

        return KERN_SUCCESS;
}

/* This function should only be called if the task and port allow message filtering */
boolean_t
mach_msg_fetch_filter_policy(
        void *port_label,
        mach_msg_id_t msgh_id,
        mach_msg_filter_id *fid)
{
        boolean_t ret = TRUE;

        if (mach_msg_fetch_filter_policy_callback == NULL) {
                *fid = MACH_MSG_FILTER_POLICY_ALLOW;
                return true;
        }
        ret = mach_msg_fetch_filter_policy_callback(current_task(), port_label, msgh_id, fid);

        return ret;
}