[apple/xnu.git] / osfmk / atm / atm.c

/*
 * Copyright (c) 2012-2013 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@
 */

#include <atm/atm_internal.h>
#include <mach/mach_types.h>
#include <mach/kern_return.h>
#include <ipc/ipc_port.h>
#include <mach/mach_vm.h>
#include <mach/vm_map.h>
#include <vm/vm_map.h>
#include <atm/atm_notification.h>
#include <mach/host_priv.h>
#include <mach/host_special_ports.h>
#include <kern/host.h>
#include <kern/kalloc.h>

#define MAX_ATM_VALUES         (2 * 4096)
#define MAX_TRACE_BUFFER_SIZE  (0x40000000)  /* Restrict to 1GB per task */
#define MAX_MAILBOX_SIZE       (8 * 4096)

#define ATM_VALUE_TO_HANDLE(x) (CAST_DOWN(atm_voucher_id_t, (x)))
#define HANDLE_TO_ATM_VALUE(x) (CAST_DOWN(atm_value_t, (x)))

#define ATM_MAX_HASH_TABLE_SIZE (256)
#define AID_HASH_MASK (0xFF)
#define AID_TO_HASH(x) ((x) & (AID_HASH_MASK))

#define ATM_LIST_DEAD_MAX 15

#define AID_ARRAY_COUNT_MAX (256)

struct atm_value_hash atm_value_hash_table[ATM_MAX_HASH_TABLE_SIZE];
extern int maxproc;

/* Global flag to disable ATM. ATM get value and memory registration will return error. */
boolean_t disable_atm = FALSE;

#if DEVELOPMENT || DEBUG
queue_head_t atm_descriptors_list;
queue_head_t atm_values_list;
#endif

ipc_voucher_attr_control_t  voucher_attr_control;    /* communication channel from ATM to voucher system */
static zone_t atm_value_zone, atm_descriptors_zone, atm_link_objects_zone;

static aid_t get_aid();
static atm_value_t atm_value_alloc_init();
static void atm_value_dealloc(atm_value_t atm_value);
static void atm_hash_table_init();
static void atm_value_hash_table_insert(atm_value_t new_atm_value);
static void atm_value_hash_table_delete(atm_value_t atm_value);
static atm_value_t get_atm_value_from_aid(aid_t aid);
static void atm_value_get_ref(atm_value_t atm_value);
static kern_return_t atm_listener_insert(atm_value_t atm_value, atm_task_descriptor_t task_descriptor, mailbox_offset_t mailbox_offset);
static void atm_listener_delete_all(atm_value_t atm_value);
static atm_task_descriptor_t atm_task_descriptor_alloc_init(mach_port_t trace_buffer,uint64_t buffer_size, void *mailbox_addr, uint64_t mailbox_array_size, __assert_only task_t task);
static void atm_descriptor_get_reference(atm_task_descriptor_t task_descriptor);
static void atm_task_descriptor_dealloc(atm_task_descriptor_t task_descriptor);
static mach_atm_subaid_t atm_get_min_sub_aid(atm_value_t atm_value);
static void
atm_get_min_sub_aid_array(aid_t *aid_array, mach_atm_subaid_t *subaid_array, uint32_t count) __unused;
static kern_return_t atm_value_unregister(atm_value_t atm_value, atm_task_descriptor_t task_descriptor, mailbox_offset_t mailbox_offset);
static kern_return_t atm_listener_delete(atm_value_t atm_value, atm_task_descriptor_t task_descriptor, mailbox_offset_t mailbox_offset);
static void atm_link_get_reference(atm_link_object_t link_object);
static void atm_link_dealloc(atm_link_object_t link_object);
kern_return_t atm_invoke_collection(atm_value_t atm_value, uint64_t sub_activity_id, uint32_t flags);
kern_return_t atm_send_user_notification(aid_t aid, uint64_t subaid, mach_port_t *buffers_array, uint64_t *sizes_array, mach_msg_type_number_t count, uint32_t flags);

kern_return_t
atm_release_value(
        ipc_voucher_attr_manager_t __assert_only manager,
        mach_voucher_attr_key_t __assert_only key,
        mach_voucher_attr_value_handle_t value,
        mach_voucher_attr_value_reference_t sync);

kern_return_t
atm_get_value(
        ipc_voucher_attr_manager_t __assert_only manager,
        mach_voucher_attr_key_t __assert_only key,
        mach_voucher_attr_recipe_command_t command,
        mach_voucher_attr_value_handle_array_t prev_values,
        mach_msg_type_number_t __assert_only prev_value_count,
        mach_voucher_attr_content_t recipe,
        mach_voucher_attr_content_size_t recipe_size,
        mach_voucher_attr_value_handle_t *out_value,
        ipc_voucher_t *out_value_voucher);

kern_return_t
atm_extract_content(
        ipc_voucher_attr_manager_t __assert_only manager,
        mach_voucher_attr_key_t __assert_only key,
        mach_voucher_attr_value_handle_array_t values,
        mach_msg_type_number_t value_count,
        mach_voucher_attr_recipe_command_t *out_command,
        mach_voucher_attr_content_t out_recipe,
        mach_voucher_attr_content_size_t *in_out_recipe_size);

kern_return_t
atm_command(
        ipc_voucher_attr_manager_t __assert_only manager,
        mach_voucher_attr_key_t __assert_only key,
        mach_voucher_attr_value_handle_array_t values,
        mach_msg_type_number_t value_count,
        mach_voucher_attr_command_t command,
        mach_voucher_attr_content_t in_content,
        mach_voucher_attr_content_size_t in_content_size,
        mach_voucher_attr_content_t out_content,
        mach_voucher_attr_content_size_t *in_out_content_size);

void
atm_release(ipc_voucher_attr_manager_t __assert_only manager);

/*
 * communication channel from voucher system to ATM
 */
struct ipc_voucher_attr_manager atm_manager = {
        .ivam_release_value    = atm_release_value,
        .ivam_get_value        = atm_get_value,
        .ivam_extract_content  = atm_extract_content,
        .ivam_command          = atm_command,
        .ivam_release          = atm_release,
};

#if DEVELOPMENT || DEBUG
decl_lck_mtx_data(, atm_descriptors_list_lock);
decl_lck_mtx_data(, atm_values_list_lock);

lck_grp_t               atm_dev_lock_grp;
lck_attr_t              atm_dev_lock_attr;
lck_grp_attr_t          atm_dev_lock_grp_attr;
#endif

extern vm_map_t kernel_map;
/*
 * Global aid. Incremented on each get_aid.
 */
aid_t global_aid;

/*
 * Lock group attributes for atm sub system.
 */
lck_grp_t               atm_lock_grp;
lck_attr_t              atm_lock_attr;
lck_grp_attr_t          atm_lock_grp_attr;


/*
 * Routine: atm_init
 * Purpose: Initialize the atm subsystem.
 * Returns: None.
 */
void
atm_init()
{
        kern_return_t kr = KERN_SUCCESS;
        char temp_buf[20];

        /* Disable atm if disable_atm present in device-tree properties or in boot-args */
        if ((PE_get_default("kern.disable_atm", temp_buf, sizeof(temp_buf))) || 
            (PE_parse_boot_argn("-disable_atm", temp_buf, sizeof(temp_buf)))) {
                disable_atm = TRUE;
        }

        /* setup zones for descriptors, values and link objects */
        atm_value_zone       = zinit(sizeof(struct atm_value),
                               MAX_ATM_VALUES * sizeof(struct atm_value),
                               sizeof(struct atm_value),
                               "atm_values");

        atm_descriptors_zone = zinit(sizeof(struct atm_task_descriptor),
                               MAX_ATM_VALUES * sizeof(struct atm_task_descriptor),
                               sizeof(struct atm_task_descriptor),
                               "atm_task_descriptors");

        atm_link_objects_zone = zinit(sizeof(struct atm_link_object),
                                MAX_ATM_VALUES * sizeof(struct atm_link_object),
                                sizeof(struct atm_link_object),
                                "atm_link_objects");

        /* Initialize atm lock group and lock attributes. */
        lck_grp_attr_setdefault(&atm_lock_grp_attr);
        lck_grp_init(&atm_lock_grp, "atm_lock", &atm_lock_grp_attr);
        lck_attr_setdefault(&atm_lock_attr);

        global_aid = 1;
        atm_hash_table_init();

#if DEVELOPMENT || DEBUG
        /* Initialize global atm development lock group and lock attributes. */
        lck_grp_attr_setdefault(&atm_dev_lock_grp_attr);
        lck_grp_init(&atm_dev_lock_grp, "atm_dev_lock", &atm_dev_lock_grp_attr);
        lck_attr_setdefault(&atm_dev_lock_attr);

        lck_mtx_init(&atm_descriptors_list_lock, &atm_dev_lock_grp, &atm_dev_lock_attr);
        lck_mtx_init(&atm_values_list_lock, &atm_dev_lock_grp, &atm_dev_lock_attr);

        queue_init(&atm_descriptors_list);
        queue_init(&atm_values_list);
#endif

        /* Register the atm manager with the Vouchers sub system. */
        kr = ipc_register_well_known_mach_voucher_attr_manager(
                        &atm_manager,
                        0,
                        MACH_VOUCHER_ATTR_KEY_ATM,
                        &voucher_attr_control);
        if (kr != KERN_SUCCESS )
                panic("ATM subsystem initialization failed");

        kprintf("ATM subsystem is initialized\n");
        return ;
}


/*
 * ATM Resource Manager Routines.
 */


/*
 * Routine: atm_release_value
 * Purpose: Release a value, if sync matches the sync count in value.
 * Returns: KERN_SUCCESS: on Successful deletion.
 *          KERN_FAILURE: if sync value does not matches.
 */
kern_return_t
atm_release_value(
        ipc_voucher_attr_manager_t              __assert_only manager,
        mach_voucher_attr_key_t                 __assert_only key,
        mach_voucher_attr_value_handle_t                      value,
        mach_voucher_attr_value_reference_t               sync)
{
        atm_value_t atm_value = ATM_VALUE_NULL;

        assert(MACH_VOUCHER_ATTR_KEY_ATM == key);
        assert(manager == &atm_manager);

        atm_value = HANDLE_TO_ATM_VALUE(value);
        if (atm_value == VAM_DEFAULT_VALUE) {
                /* Return success for default value */
                return KERN_SUCCESS;
        }

        if (atm_value->sync != sync) {
                return KERN_FAILURE;
        }

        /* Deallocate the atm value. */
        atm_value_hash_table_delete(atm_value);
        atm_value_dealloc(atm_value);
        return KERN_SUCCESS;
}


/*
 * Routine: atm_get_value
 */
kern_return_t
atm_get_value(
        ipc_voucher_attr_manager_t              __assert_only manager,
        mach_voucher_attr_key_t                 __assert_only key,
        mach_voucher_attr_recipe_command_t                command,
        mach_voucher_attr_value_handle_array_t        prev_values,
        mach_msg_type_number_t                  __assert_only prev_value_count,
        mach_voucher_attr_content_t          __unused recipe,
        mach_voucher_attr_content_size_t     __unused recipe_size,
        mach_voucher_attr_value_handle_t             *out_value,
        ipc_voucher_t                                            *out_value_voucher)
{
        atm_value_t atm_value = ATM_VALUE_NULL;
        mach_voucher_attr_value_handle_t atm_handle;
        atm_task_descriptor_t task_descriptor = ATM_TASK_DESCRIPTOR_NULL;
        task_t task;
        mailbox_offset_t mailbox_offset;
        natural_t i;
        kern_return_t kr = KERN_SUCCESS;

        assert(MACH_VOUCHER_ATTR_KEY_ATM == key);
        assert(manager == &atm_manager);

        /* never an out voucher */
        *out_value_voucher = IPC_VOUCHER_NULL;

        if (disable_atm)
                return KERN_NOT_SUPPORTED;

        switch (command) {

        case MACH_VOUCHER_ATTR_ATM_REGISTER:

                for (i = 0; i < prev_value_count; i++) {
                        atm_handle = prev_values[i];
                        atm_value = HANDLE_TO_ATM_VALUE(atm_handle);

                        if (atm_value == VAM_DEFAULT_VALUE)
                                continue;

                        task = current_task();
                        task_descriptor = task->atm_context;
                        if (task_descriptor != ATM_TASK_DESCRIPTOR_NULL) {
                                if (recipe_size != sizeof(mailbox_offset_t)) {
                                        kr = KERN_INVALID_ARGUMENT;
                                        break;
                                }
                                memcpy(&mailbox_offset, recipe, sizeof(mailbox_offset_t));
                                if (mailbox_offset > task_descriptor->mailbox_array_size) {
                                        kr = KERN_INVALID_ARGUMENT;
                                        break;
                                }

                                kr = atm_listener_insert(atm_value, task_descriptor, mailbox_offset);
                                if (kr != KERN_SUCCESS) {
                                        break;
                                }
                        }

                        /* Increment sync value. */
                        lck_mtx_lock(&atm_value->listener_lock);
                        atm_value->sync++;
                        lck_mtx_unlock(&atm_value->listener_lock);

                        *out_value = atm_handle;
                        return kr;
                }

                *out_value = ATM_VALUE_TO_HANDLE(VAM_DEFAULT_VALUE);
                break;

        case MACH_VOUCHER_ATTR_ATM_CREATE:

                /* Allocate a new atm value. */
                atm_value = atm_value_alloc_init();
                atm_value_hash_table_insert(atm_value);

                if (atm_value == ATM_VALUE_NULL) {
                        return KERN_RESOURCE_SHORTAGE;
                }

                *out_value = ATM_VALUE_TO_HANDLE(atm_value);
                break;

        case MACH_VOUCHER_ATTR_ATM_NULL:
        default:
                kr = KERN_INVALID_ARGUMENT;
                break;
        }

        return kr;
}


/*
 * Routine: atm_extract_content
 * Purpose: Extract a set of aid from an array of voucher values.
 * Returns: KERN_SUCCESS: on Success.
 *          KERN_FAILURE: one of the value is not present in the hash.
 *          KERN_NO_SPACE: insufficeint buffer provided to fill an array of aid.
 */
kern_return_t
atm_extract_content(
        ipc_voucher_attr_manager_t      __assert_only manager,
        mach_voucher_attr_key_t         __assert_only key,
        mach_voucher_attr_value_handle_array_t        values,
        mach_msg_type_number_t                                value_count,
        mach_voucher_attr_recipe_command_t           *out_command,
        mach_voucher_attr_content_t                   out_recipe,
        mach_voucher_attr_content_size_t             *in_out_recipe_size)
{
        atm_value_t atm_value;
        mach_voucher_attr_value_handle_t atm_handle;
        natural_t i;

        assert(MACH_VOUCHER_ATTR_KEY_ATM == key);
        assert(manager == &atm_manager);

        for (i = 0; i < value_count; i++) {
                atm_handle = values[i];
                atm_value = HANDLE_TO_ATM_VALUE(atm_handle);
                if (atm_value == VAM_DEFAULT_VALUE)
                        continue;

                if (( sizeof(aid_t)) > *in_out_recipe_size) {
                        *in_out_recipe_size = 0;
                        return KERN_NO_SPACE;
                }

                memcpy(&out_recipe[0], &atm_value->aid, sizeof(aid_t));
                *out_command = MACH_VOUCHER_ATTR_ATM_NULL;
                *in_out_recipe_size = sizeof(aid_t);
                return KERN_SUCCESS;
        }

        *in_out_recipe_size = 0;
        return KERN_SUCCESS;
}

/*
 * Routine: atm_command
 * Purpose: Execute a command against a set of ATM values.
 * Returns: KERN_SUCCESS: On successful execution of command.
            KERN_FAILURE: On failure.
 */
kern_return_t
atm_command(
        ipc_voucher_attr_manager_t                 __assert_only manager,
        mach_voucher_attr_key_t                    __assert_only key,
        mach_voucher_attr_value_handle_array_t  values,
        mach_msg_type_number_t                     value_count,
        mach_voucher_attr_command_t                command,
        mach_voucher_attr_content_t        in_content,
        mach_voucher_attr_content_size_t   in_content_size,
        mach_voucher_attr_content_t        out_content,
        mach_voucher_attr_content_size_t   *out_content_size)
{
        assert(MACH_VOUCHER_ATTR_KEY_ATM == key);
        assert(manager == &atm_manager);
        atm_value_t atm_value = ATM_VALUE_NULL;
        natural_t i = 0;
        aid_t *aid_array = NULL;
        mach_atm_subaid_t *subaid_array = NULL;
        uint32_t aid_array_count = 0;
        atm_task_descriptor_t task_descriptor = ATM_TASK_DESCRIPTOR_NULL;
        task_t task;
        uint32_t collection_flags = ATM_ACTION_LOGFAIL;
        kern_return_t kr = KERN_SUCCESS;
        
        switch (command) {
        case ATM_ACTION_COLLECT:
                collection_flags = ATM_ACTION_COLLECT;
                /* Fall through */

        case ATM_ACTION_LOGFAIL: {
                mach_atm_subaid_t sub_aid = 0;

                /* find the first non-default atm_value */
                for (i = 0; i < value_count; i++) {
                        atm_value = HANDLE_TO_ATM_VALUE(values[i]);
                        if (atm_value != VAM_DEFAULT_VALUE)
                                break;
                }
                
                /* if we are not able to find any atm values
                 * in stack then this call was made in error
                 */
                if (atm_value == NULL) {
                        return KERN_FAILURE;
                }
                if (in_content == NULL || in_content_size < sizeof(mach_atm_subaid_t) ){
                        return KERN_INVALID_ARGUMENT;
                }

                sub_aid = *(mach_atm_subaid_t *)(void *)in_content;
                *out_content_size = 0;
                kr = atm_invoke_collection(atm_value, sub_aid, collection_flags);
                break;
        }

        case ATM_FIND_MIN_SUB_AID:
                if ((in_content_size/sizeof(aid_t)) > (*out_content_size/sizeof(mach_atm_subaid_t)))
                        return KERN_FAILURE;

                aid_array_count = in_content_size / sizeof(aid_t);
                if (aid_array_count > AID_ARRAY_COUNT_MAX)
                        return KERN_FAILURE;

                aid_array = (aid_t *) kalloc(aid_array_count * sizeof(aid_t));
                if (aid_array == NULL)
                        return KERN_NO_SPACE;

                subaid_array = (mach_atm_subaid_t *) kalloc(aid_array_count * sizeof(mach_atm_subaid_t));
                if (subaid_array == NULL) {
                        kfree(aid_array, aid_array_count * sizeof(aid_t));
                        return KERN_NO_SPACE;
                }

                memcpy(aid_array, in_content, aid_array_count * sizeof(aid_t));
                atm_get_min_sub_aid_array(aid_array, subaid_array, aid_array_count);
                
                memcpy(out_content, subaid_array, aid_array_count * sizeof(mach_atm_subaid_t));
                *out_content_size = aid_array_count * sizeof(mach_atm_subaid_t);

                kfree(aid_array, aid_array_count * sizeof(aid_t));
                kfree(subaid_array, aid_array_count * sizeof(mach_atm_subaid_t));
                kr = KERN_SUCCESS;

                break;

        case ATM_ACTION_UNREGISTER:
                /* find the first non-default atm_value */
                for (i = 0; i < value_count; i++) {
                        atm_value = HANDLE_TO_ATM_VALUE(values[i]);
                        if (atm_value != VAM_DEFAULT_VALUE)
                                break;
                }

                /* if we are not able to find any atm values
                 * in stack then this call was made in error
                 */
                if (atm_value == NULL) {
                        return KERN_FAILURE;
                }
                if (in_content == NULL || in_content_size != sizeof(mailbox_offset_t)){
                        return KERN_INVALID_ARGUMENT;
                }

                mailbox_offset_t mailbox_offset;
                memcpy(&mailbox_offset, in_content, sizeof(mailbox_offset_t));
                task = current_task();
                task_descriptor = task->atm_context;

                kr = atm_value_unregister(atm_value, task_descriptor, mailbox_offset);

                break;

        default:
                kr = KERN_INVALID_ARGUMENT;
                break;
        }

        return kr;
}


void
atm_release(
        ipc_voucher_attr_manager_t              __assert_only manager)
{
        assert(manager == &atm_manager);
}


/*
 * Routine: atm_invoke_collection
 * Purpose: Sends a notification with array of memory buffer.
 * Note: may block till user daemon responds.
 */
kern_return_t
atm_invoke_collection(
        atm_value_t atm_value,
        subaid_t sub_activity_id,
        uint32_t flags)
{
        aid_t aid = atm_value->aid;
        kern_return_t kr = KERN_SUCCESS;
        uint32_t array_count = 0, i = 0, requestor_index = 0;
        uint64_t *sizes_array = NULL;
        atm_link_object_t link_object = NULL;
        mach_port_t *mem_array = NULL;
        boolean_t need_swap_first = FALSE;
        atm_task_descriptor_t requesting_descriptor = current_task()->atm_context;

        lck_mtx_lock(&atm_value->listener_lock);
        array_count = atm_value->listener_count;
        lck_mtx_unlock(&atm_value->listener_lock);

        if (array_count == 0){
                return KERN_SUCCESS;
        }

        mem_array = kalloc(sizeof(mach_port_t) * array_count);
        if (mem_array == NULL){
                return KERN_NO_SPACE;
        }

        sizes_array = kalloc(sizeof(uint64_t) * array_count);
        if (sizes_array == NULL){
                kfree(mem_array, sizeof(mach_port_t) * array_count);
                return KERN_NO_SPACE;
        }

        lck_mtx_lock(&atm_value->listener_lock);
        queue_iterate(&atm_value->listeners, link_object, atm_link_object_t, listeners_element) {
                if (i >= array_count){
                        break;
                }

                if (!need_swap_first && requesting_descriptor == link_object->descriptor){
                        assert(requesting_descriptor != NULL);
                        requestor_index = i;
                        need_swap_first = TRUE;
                }

                sizes_array[i] = link_object->descriptor->trace_buffer_size;
                mem_array[i] = ipc_port_copy_send(link_object->descriptor->trace_buffer);
                if (!IPC_PORT_VALID(mem_array[i])){
                        mem_array[i] = NULL;
                }
                i++;
        }
        lck_mtx_unlock(&atm_value->listener_lock);

        /*
         * Swap the position of requesting task ahead, diagnostics can 
         * process its buffers the first.
         */
        if (need_swap_first && requestor_index != 0){
                assert(requestor_index < array_count);
                mach_port_t tmp_port = mem_array[0];
                uint64_t tmp_size = sizes_array[0];
                mem_array[0] = mem_array[requestor_index];
                sizes_array[0] = sizes_array[requestor_index];
                mem_array[requestor_index] = tmp_port;
                sizes_array[requestor_index] = tmp_size;
        }

        if (i > 0) {
                kr = atm_send_user_notification(aid, sub_activity_id, mem_array, sizes_array, i, flags);
        }

        kfree(mem_array, sizeof(mach_port_t) * array_count);
        kfree(sizes_array, sizeof(uint64_t) * array_count);

        return kr;
}

/*
 * Routine: atm_send_user_notification
 * Purpose: Make an upcall to user space daemon if its listening for atm notifications.
 * Returns: KERN_SUCCESS for successful delivery.
 *                      KERN_FAILURE if port is dead or NULL.
 */
kern_return_t
atm_send_user_notification(
        aid_t aid,
        subaid_t subaid,
        mach_port_t *buffers_array,
        uint64_t *sizes_array,
        mach_msg_type_number_t count,
        uint32_t flags)
{
        mach_port_t user_port;
        int                     error;
        error = host_get_atm_notification_port(host_priv_self(), &user_port);
        if ((error != KERN_SUCCESS) || !IPC_PORT_VALID(user_port)) {
                return KERN_FAILURE;
        }

        return atm_collect_trace_info(user_port, aid, subaid, flags, buffers_array, count, sizes_array, count);
}

/*
 * Routine: atm_send_proc_inspect_notification
 * Purpose: Make an upcall to user space daemon if its listening for trace 
 *          notifications for per process inspection.
 * Returns: KERN_SUCCESS for successful delivery.
 *                      KERN_FAILURE if port is dead or NULL.
 */

kern_return_t
atm_send_proc_inspect_notification(
        task_t task,
        int32_t traced_pid,
        uint64_t traced_uniqueid)
{
        mach_port_t user_port = MACH_PORT_NULL;
        mach_port_t memory_port = MACH_PORT_NULL;
        atm_task_descriptor_t task_descriptor = ATM_TASK_DESCRIPTOR_NULL;
        uint64_t buffer_size = 0;
        int                     error;

        /* look for the requested memory in target task */
        if (!task)
                return KERN_INVALID_TASK;

        task_lock(task);
        if (task->atm_context){
                task_descriptor = task->atm_context;
                atm_descriptor_get_reference(task_descriptor);
        }
        task_unlock(task);

        if (task_descriptor == ATM_TASK_DESCRIPTOR_NULL){
                return KERN_FAILURE;
        }

        memory_port = ipc_port_copy_send(task_descriptor->trace_buffer);
        buffer_size =  task_descriptor->trace_buffer_size;
        atm_task_descriptor_dealloc(task_descriptor);

        /* get the communication port */
        error = host_get_atm_notification_port(host_priv_self(), &user_port);
        if ((error != KERN_SUCCESS) || !IPC_PORT_VALID(user_port)) {
                ipc_port_release_send(memory_port);
                return KERN_FAILURE;
        }

        return atm_inspect_process_buffer(user_port, traced_pid, traced_uniqueid, buffer_size, memory_port);
}

/*
 * Routine: atm_value_alloc_init
 * Purpose: Allocates an atm value struct and initialize it.
 * Returns: atm_value_t: On Success with a sync count on atm_value.
 *          ATM_VALUE_NULL: On failure.
 */
static atm_value_t
atm_value_alloc_init()
{
        atm_value_t new_atm_value = ATM_VALUE_NULL;

        new_atm_value = (atm_value_t) zalloc(atm_value_zone);
        if (new_atm_value == ATM_VALUE_NULL)
                panic("Ran out of ATM values structure.\n\n");

        new_atm_value->aid = get_aid();
        queue_init(&new_atm_value->listeners);
        new_atm_value->sync = 1;
        new_atm_value->listener_count = 0;
        new_atm_value->reference_count = 1;
        lck_mtx_init(&new_atm_value->listener_lock, &atm_lock_grp, &atm_lock_attr);

#if DEVELOPMENT || DEBUG
        lck_mtx_lock(&atm_values_list_lock);
        queue_enter(&atm_values_list, new_atm_value, atm_value_t, value_elt);
        lck_mtx_unlock(&atm_values_list_lock);
#endif
        return new_atm_value;
}


/*
 * Routine: get_aid
 * Purpose: Increment the global aid counter and return it.
 * Returns: aid
 */
static aid_t
get_aid()
{
        aid_t aid;
        aid = (aid_t)OSIncrementAtomic64((SInt64 *)&global_aid);
        return aid;
}


/*
 * Routine: atm_value_dealloc
 * Purpose: Drops the reference on atm value and deallocates.
 *          Deletes all the listeners on deallocation.
 * Returns: None.
 */
static void
atm_value_dealloc(atm_value_t atm_value)
{
        lck_mtx_lock(&atm_value->listener_lock);

        atm_value->reference_count--;
        assert(atm_value->reference_count >= 0);

        if (atm_value->reference_count > 0) {
                lck_mtx_unlock(&atm_value->listener_lock);
                return;
        }

        lck_mtx_unlock(&atm_value->listener_lock);

        /* Free up the atm value and also remove all the listeners. */
        atm_listener_delete_all(atm_value);

        lck_mtx_destroy(&atm_value->listener_lock, &atm_lock_grp);

#if DEVELOPMENT || DEBUG
        lck_mtx_lock(&atm_values_list_lock);
        queue_remove(&atm_values_list, atm_value, atm_value_t, value_elt);
        lck_mtx_unlock(&atm_values_list_lock);
#endif
        zfree(atm_value_zone, atm_value);
        return;
}


/*
 * Routine: atm_hash_table_init
 * Purpose: Initialize the atm aid hash table.
 * Returns: None.
 */
static void
atm_hash_table_init()
{
        int i;

        for (i = 0; i < ATM_MAX_HASH_TABLE_SIZE; i++) {
                queue_init(&atm_value_hash_table[i].hash_list);
                lck_mtx_init(&atm_value_hash_table[i].hash_list_lock, &atm_lock_grp, &atm_lock_attr);
        }
}


/*
 * Routine: atm_value_hash_table_insert
 * Purpose: Insert an atm value in the hash table.
 * Returns: None.
 */
static void
atm_value_hash_table_insert(atm_value_t new_atm_value)
{
        int hash_index;
        atm_value_hash_t hash_list_head;
        aid_t aid = new_atm_value->aid;

        hash_index = AID_TO_HASH(aid);
        hash_list_head = &atm_value_hash_table[hash_index];

        lck_mtx_lock(&hash_list_head->hash_list_lock);
        queue_enter(&hash_list_head->hash_list, new_atm_value, atm_value_t, vid_hash_elt);
        lck_mtx_unlock(&hash_list_head->hash_list_lock);
}


/*
 * Routine: atm_value_hash_table_delete
 * Purpose: Delete the atm value from the hash table.
 * Returns: None.
 */
static void
atm_value_hash_table_delete(atm_value_t atm_value)
{
        int hash_index;
        atm_value_hash_t hash_list_head;
        aid_t aid = atm_value->aid;

        hash_index = AID_TO_HASH(aid);
        hash_list_head = &atm_value_hash_table[hash_index];

        lck_mtx_lock(&hash_list_head->hash_list_lock);
        queue_remove(&hash_list_head->hash_list, atm_value, atm_value_t, vid_hash_elt);
        lck_mtx_unlock(&hash_list_head->hash_list_lock);
}


/*
 * Routine: get_atm_value_from_aid
 * Purpose: Search a given aid in atm value hash table and
 *          return the atm value stucture.
 * Returns: atm value structure if aid found.
 *          ATM_VALUE_NULL: If aid not found in atm value hash table.
 */
static atm_value_t
get_atm_value_from_aid(aid_t aid)
{
        int hash_index;
        atm_value_hash_t hash_list_head;
        atm_value_t next;

        hash_index = AID_TO_HASH(aid);
        hash_list_head = &atm_value_hash_table[hash_index];

        /* Lock the atm list and search for the aid. */
        lck_mtx_lock(&hash_list_head->hash_list_lock);

        queue_iterate(&hash_list_head->hash_list, next, atm_value_t, vid_hash_elt) {
                if (next->aid == aid) {
                        /*
                         * Aid found. Incerease ref count and return
                         * the atm value structure.
                         */
                        atm_value_get_ref(next);
                        lck_mtx_unlock(&hash_list_head->hash_list_lock);
                        return (next);
                }
        }
        lck_mtx_unlock(&hash_list_head->hash_list_lock);
        return ATM_VALUE_NULL;
}


/*
 * Routine: atm_value_get_ref
 * Purpose: Get a reference on atm value.
 * Returns: None.
 */
static void
atm_value_get_ref(atm_value_t atm_value)
{
        lck_mtx_lock(&atm_value->listener_lock);
        atm_value->reference_count++;
        lck_mtx_unlock(&atm_value->listener_lock);
}


/*
 * Routine: atm_listener_insert
 * Purpose: Insert a listener to an atm value.
 * Returns: KERN_SUCCESS on success.
 *          KERN_FAILURE if the task is already present as a listener.
 */
static kern_return_t
atm_listener_insert(
        atm_value_t             atm_value,
        atm_task_descriptor_t   task_descriptor,
        mailbox_offset_t        mailbox_offset)
{
        atm_link_object_t new_link_object;
        atm_link_object_t next;
        void *mailbox = (void *)((char *)task_descriptor->mailbox_kernel_addr + mailbox_offset);

        new_link_object = (atm_link_object_t) zalloc(atm_link_objects_zone);
        new_link_object->descriptor = task_descriptor;
        new_link_object->reference_count = 1;
        new_link_object->flags = 0;
        new_link_object->mailbox = mailbox;

        /* Get a reference on the task descriptor */
        atm_descriptor_get_reference(task_descriptor);

        /* Check if the task mailbox is already on the listener list */
        lck_mtx_lock(&atm_value->listener_lock);
        queue_iterate(&atm_value->listeners, next, atm_link_object_t, listeners_element) {
                if (next->descriptor == task_descriptor) {
                        /* 
                         * Replace the mailbox with the new one, the old mailbox is anyways on unregister path.
                         * There is a race when get_min_sub_aid would cache the mailbox, and this function will
                         * replace it. It would just behave as if the get value call happened after get_min_sub_aid
                         * was already completed.
                         */
                        next->mailbox = mailbox;
                        lck_mtx_unlock(&atm_value->listener_lock);
                        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (ATM_CODE(ATM_GETVALUE_INFO, (ATM_VALUE_REPLACED))) | DBG_FUNC_NONE,
                                atm_value, atm_value->aid, mailbox_offset, 0, 0);

                        /* Drop the extra reference on task descriptor taken by this function. */
                        atm_task_descriptor_dealloc(task_descriptor);
                        zfree(atm_link_objects_zone, new_link_object);
                        return KERN_SUCCESS;
                }
        }
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (ATM_CODE(ATM_GETVALUE_INFO, (ATM_VALUE_ADDED))) | DBG_FUNC_NONE,
                                atm_value, atm_value->aid, mailbox_offset, 0, 0);

        queue_enter(&atm_value->listeners, new_link_object, atm_link_object_t, listeners_element);
        atm_value->listener_count++;
        lck_mtx_unlock(&atm_value->listener_lock);
        return KERN_SUCCESS;
}


/*
 * Routine: atm_listener_delete_all
 * Purpose: Deletes all the listeners for an atm value.
 * Returns: None.
 */
static void
atm_listener_delete_all(atm_value_t atm_value)
{
        atm_link_object_t next;

        while(!queue_empty(&atm_value->listeners)) {
                queue_remove_first(&atm_value->listeners, next, atm_link_object_t, listeners_element);

                /* Drops the reference on the link object */
                atm_link_dealloc(next);
        }
}


/*
 * Routine: atm_listener_delete
 * Purpose: Deletes a listerner for an atm value.
 * Returns: KERN_SUCCESS on successful unregister.
 *          KERN_INVALID_VALUE on finding a different mailbox.
 *          KERN_FAILURE on failure.
 */
static kern_return_t
atm_listener_delete(
        atm_value_t atm_value,
        atm_task_descriptor_t task_descriptor,
        mailbox_offset_t mailbox_offset)
{
        queue_head_t free_listeners;
        atm_link_object_t next, elem;
        void *mailbox = (void *)((char *)task_descriptor->mailbox_kernel_addr + mailbox_offset);
        kern_return_t kr = KERN_FAILURE;

        queue_init(&free_listeners);

        lck_mtx_lock(&atm_value->listener_lock);

        next = (atm_link_object_t)(void *) queue_first(&atm_value->listeners);
        while (!queue_end(&atm_value->listeners, (queue_entry_t)next)) {
                elem = next;
                next = (atm_link_object_t)(void *) queue_next(&next->listeners_element);

                if (elem->descriptor == task_descriptor) {
                        if (elem->mailbox == mailbox) {
                                KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (ATM_CODE(ATM_UNREGISTER_INFO,
                                        (ATM_VALUE_UNREGISTERED))) | DBG_FUNC_NONE,
                                        atm_value, atm_value->aid, mailbox_offset, 0, 0);
                                queue_remove(&atm_value->listeners, elem, atm_link_object_t, listeners_element);
                                queue_enter(&free_listeners, elem, atm_link_object_t, listeners_element);
                                atm_value->listener_count--;
                                kr = KERN_SUCCESS;
                                break;
                        } else {
                                KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (ATM_CODE(ATM_UNREGISTER_INFO,
                                        (ATM_VALUE_DIFF_MAILBOX))) | DBG_FUNC_NONE,
                                        atm_value, atm_value->aid, 0, 0, 0);
                                kr = KERN_INVALID_VALUE;
                                break;
                        }
                }
        }
        lck_mtx_unlock(&atm_value->listener_lock);

        while(!queue_empty(&free_listeners)) {
                queue_remove_first(&free_listeners, next, atm_link_object_t, listeners_element);
        
                /* Drops the reference on the link object */
                atm_link_dealloc(next);
        }
        return kr;
}


/*
 * Routine: atm_descriptor_alloc_init
 * Purpose: Allocate an atm task descriptor and initialize it and takes a reference.
 * Returns: atm task descriptor: On success.
 *          NULL: on error.
 */
static atm_task_descriptor_t
atm_task_descriptor_alloc_init(
        mach_port_t             trace_buffer,
        uint64_t                buffer_size,
        void *                  mailbox_addr,
        uint64_t                mailbox_array_size,
        task_t                  __assert_only task)
{
        atm_task_descriptor_t new_task_descriptor;

        new_task_descriptor = (atm_task_descriptor_t) zalloc(atm_descriptors_zone);

        new_task_descriptor->trace_buffer = trace_buffer;
        new_task_descriptor->trace_buffer_size = buffer_size;
        new_task_descriptor->mailbox_array_size = mailbox_array_size;
        new_task_descriptor->mailbox_kernel_addr = mailbox_addr;
        new_task_descriptor->reference_count = 1;
        new_task_descriptor->flags = 0;
        lck_mtx_init(&new_task_descriptor->lock, &atm_lock_grp, &atm_lock_attr);

#if DEVELOPMENT || DEBUG
        new_task_descriptor->task = task;
        lck_mtx_lock(&atm_descriptors_list_lock);
        queue_enter(&atm_descriptors_list, new_task_descriptor, atm_task_descriptor_t, descriptor_elt);
        lck_mtx_unlock(&atm_descriptors_list_lock);
#endif

        return new_task_descriptor;
}


/*
 * Routine: atm_descriptor_get_reference
 * Purpose: Get a reference count on task descriptor.
 * Returns: None.
 */
static void
atm_descriptor_get_reference(atm_task_descriptor_t task_descriptor)
{
        lck_mtx_lock(&task_descriptor->lock);
        task_descriptor->reference_count++;
        lck_mtx_unlock(&task_descriptor->lock);
}


/*
 * Routine: atm_task_descriptor_dealloc
 * Prupose: Drops the reference on atm descriptor.
 * Returns: None.
 */
static void
atm_task_descriptor_dealloc(atm_task_descriptor_t task_descriptor)
{
        lck_mtx_lock(&task_descriptor->lock);
        task_descriptor->reference_count--;
        assert(task_descriptor->reference_count >= 0);
        if (task_descriptor->reference_count > 0) {
                lck_mtx_unlock(&task_descriptor->lock);
                return;
        }

#if DEVELOPMENT || DEBUG
        lck_mtx_lock(&atm_descriptors_list_lock);
        queue_remove(&atm_descriptors_list, task_descriptor, atm_task_descriptor_t, descriptor_elt);
        lck_mtx_unlock(&atm_descriptors_list_lock);
#endif
        mach_vm_deallocate(kernel_map, (mach_vm_address_t)task_descriptor->mailbox_kernel_addr,
                task_descriptor->mailbox_array_size);
        task_descriptor->mailbox_kernel_addr = NULL;
        task_descriptor->mailbox_array_size = 0;
        /* release the send right for the named memory entry */
        ipc_port_release_send(task_descriptor->trace_buffer);
        lck_mtx_unlock(&task_descriptor->lock);
        lck_mtx_destroy(&task_descriptor->lock, &atm_lock_grp);
        zfree(atm_descriptors_zone, task_descriptor);
        return;
}


/*
 * Routine: atm_link_get_reference
 * Purpose: Get a reference count on atm link object.
 * Returns: None.
 */
static void
atm_link_get_reference(atm_link_object_t link_object)
{
        atm_link_object_reference_internal(link_object);
}


/*
 * Routine: atm_link_dealloc
 * Prupose: Drops the reference on link object.
 * Returns: None.
 */
static void
atm_link_dealloc(atm_link_object_t link_object)
{
        if (0 < atm_link_object_release_internal(link_object)) {
                return;
        }

        assert(link_object->reference_count == 0);

        /* Drop the reference on atm task descriptor. */
        atm_task_descriptor_dealloc(link_object->descriptor);
        zfree(atm_link_objects_zone, link_object);
}


/*
 * Routine: atm_register_trace_memory
 * Purpose: Registers trace memory for a task.
 * Returns: KERN_SUCCESS: on Success.
 *          KERN_FAILURE: on Error.
 */
kern_return_t
atm_register_trace_memory(
        task_t                  task,
        uint64_t                trace_buffer_address,
        uint64_t                buffer_size,
        uint64_t                mailbox_array_size)
{
        atm_task_descriptor_t task_descriptor;
        mach_port_t trace_buffer = MACH_PORT_NULL;
        mach_vm_offset_t mailbox_kernel_ptr = 0;
        kern_return_t kr = KERN_SUCCESS;

        if (disable_atm)
                return KERN_NOT_SUPPORTED;

        if (task != current_task())
                return KERN_INVALID_ARGUMENT;

        if (task->atm_context != NULL
            || (void *)trace_buffer_address == NULL
            || buffer_size == 0
            || (buffer_size & PAGE_MASK) != 0
            || buffer_size > MAX_TRACE_BUFFER_SIZE
            || mailbox_array_size == 0
            || mailbox_array_size >= buffer_size
            || mailbox_array_size > MAX_MAILBOX_SIZE
            || mailbox_array_size & PAGE_MIN_MASK) {
                return KERN_INVALID_ARGUMENT;
        }

        vm_map_t map = current_map();
        memory_object_size_t mo_size = (memory_object_size_t) buffer_size;
        kr = mach_make_memory_entry_64(map,
                                          &mo_size,
                                          (mach_vm_offset_t)trace_buffer_address,
                                          VM_PROT_READ,
                                          &trace_buffer,
                                          NULL);
        if (kr != KERN_SUCCESS)
                return kr;

        kr = mach_vm_map(kernel_map,
                                 &mailbox_kernel_ptr,
                                 mailbox_array_size,
                                 0,
                                 VM_FLAGS_ANYWHERE,
                                 trace_buffer,
                                 0,
                                 FALSE,
                                 VM_PROT_READ,
                                 VM_PROT_READ,
                                 VM_INHERIT_NONE
                                 );

        if (kr != KERN_SUCCESS){
                ipc_port_release_send(trace_buffer);
                return kr;
        }

        task_descriptor = atm_task_descriptor_alloc_init(trace_buffer, buffer_size, (void *)mailbox_kernel_ptr, mailbox_array_size, task);
        if (task_descriptor == ATM_TASK_DESCRIPTOR_NULL) {
                ipc_port_release_send(trace_buffer);
                mach_vm_deallocate(kernel_map, (mach_vm_address_t)mailbox_kernel_ptr, mailbox_array_size);
                return KERN_NO_SPACE;
        }

        task_lock(task);
        if (task->atm_context == NULL) {
                task->atm_context = task_descriptor;
                kr = KERN_SUCCESS;
        } else {
                kr = KERN_FAILURE;
        }
        task_unlock(task);

        if (kr != KERN_SUCCESS) {
                /* undo the mapping and allocations since we failed to hook descriptor to task */
                atm_task_descriptor_dealloc(task_descriptor);
        }
        return KERN_SUCCESS;
}


/*
 * Routine: atm_get_min_sub_aid_array
 * Purpose: For an array of aid, lookup the atm value and fill the minimum subaid.
 * Returns: None.
 */
static void
atm_get_min_sub_aid_array(
        aid_t                           *aid_array,
        mach_atm_subaid_t       *subaid_array,
        uint32_t                        count)
{
        atm_value_t atm_value;
        uint32_t i;

        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (ATM_CODE(ATM_SUBAID_INFO, (ATM_MIN_CALLED))) | DBG_FUNC_START,
                        0, 0, 0, 0, 0);

        for (i = 0; i < count; i++) {
                atm_value = get_atm_value_from_aid(aid_array[i]);
                if (atm_value == ATM_VALUE_NULL) {
                        subaid_array[i] = ATM_SUBAID32_MAX;
                        continue;
                }
                subaid_array[i] = atm_get_min_sub_aid(atm_value);
                atm_value_dealloc(atm_value);
        }

        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (ATM_CODE(ATM_SUBAID_INFO, (ATM_MIN_CALLED))) | DBG_FUNC_END,
                        count, 0, 0, 0, 0);

}


/*
 * Routine: atm_get_min_sub_aid
 * Purpose: Walk the list of listeners and get the min sub-aid for an activity id.
 * Returns: Minimum sub-aid to keep.
 * Note: Unlock the listener lock before accessing the mailbox, since it may page fault and
 *       might take long time. Also cleans the listeners list for the tasks which are dead 
 *       and atm_task_descriptors do not hold any useful data.
 */
static mach_atm_subaid_t
atm_get_min_sub_aid(atm_value_t atm_value)
{
        int32_t i = 0, j, freed_count = 0, dead_but_not_freed = 0;
        int32_t listener_count;
        atm_subaid32_t min_subaid = ATM_SUBAID32_MAX, subaid, max_subaid;
        atm_link_object_t *link_object_array = NULL;
        atm_link_object_t next, elem;
        queue_head_t free_listeners;

        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (ATM_CODE(ATM_SUBAID_INFO, (ATM_MIN_LINK_LIST))) | DBG_FUNC_START,
                        0, 0, 0, 0, 0);

        lck_mtx_lock(&atm_value->listener_lock);
        listener_count = atm_value->listener_count;
        lck_mtx_unlock(&atm_value->listener_lock);

        /* separate memory access from locked iterate since memory read may fault */
        link_object_array = (atm_link_object_t *) kalloc(sizeof(atm_link_object_t) * listener_count);
        if (link_object_array == NULL) {
                return 0;
        }

        /* Iterate the list and take a ref on link objects and store it in an array */ 
        lck_mtx_lock(&atm_value->listener_lock);
        queue_iterate(&atm_value->listeners, next, atm_link_object_t, listeners_element) {
                /* Additional listener are added between the allocation of array and iterating the list */
                if (i >= listener_count)
                        break;

                /* Get a ref on the link object */
                atm_link_get_reference(next);
                link_object_array[i] = (atm_link_object_t)next;
                i++;
        }
        lck_mtx_unlock(&atm_value->listener_lock);
        j = i;

        /* Iterate the array to find the min */
        for (i = 0; i < j; i++) {
                /* Ignore the min value of the dead processes. */
                if (link_object_array[i]->descriptor->flags == ATM_TASK_DEAD)
                        continue;
                /* Dereference the mailbox to get the min subaid */
                subaid = *((atm_subaid32_t *)link_object_array[i]->mailbox);
                if (subaid < min_subaid)
                        min_subaid = subaid;
        }

        /*
         * Mark the link object that can be freed, and release the ref on the link object
         * Mark the link object of dead task free after the dead task descriptor count
         * increases than ATM_LIST_DEAD_MAX.
         */
        for (i = j - 1; i >= 0; i--) {
                if (link_object_array[i]->descriptor->flags == ATM_TASK_DEAD) {
                        if (dead_but_not_freed > ATM_LIST_DEAD_MAX) {
                                link_object_array[i]->flags = ATM_LINK_REMOVE;
                                freed_count++;
                        } else {
                                max_subaid = *(((atm_subaid32_t *)link_object_array[i]->mailbox) + 1);
                                if (max_subaid < min_subaid) {
                                        link_object_array[i]->flags = ATM_LINK_REMOVE;
                                        freed_count++;
                                } else {
                                        dead_but_not_freed++;
                                }
                        }
                }
                atm_link_dealloc(link_object_array[i]);
                link_object_array[i] = NULL;
        }

        /* Check if the number of live entries in list is less than maxproc */
        assert((j - (freed_count + dead_but_not_freed)) <= maxproc);

        kfree(link_object_array, (sizeof(atm_link_object_t) * listener_count));

        /* Remove the marked link objects from the list */
        lck_mtx_lock(&atm_value->listener_lock);
        
        queue_init(&free_listeners);
        next = (atm_link_object_t)(void *) queue_first(&atm_value->listeners);
        while (!queue_end(&atm_value->listeners, (queue_entry_t)next)) {
                elem = next;
                next = (atm_link_object_t)(void *) queue_next(&next->listeners_element);

                if (elem->flags == ATM_LINK_REMOVE) {
                        queue_remove(&atm_value->listeners, elem, atm_link_object_t, listeners_element);
                        queue_enter(&free_listeners, elem, atm_link_object_t, listeners_element);
                        atm_value->listener_count--;
                }
        }
        lck_mtx_unlock(&atm_value->listener_lock);

        /* Free the link objects */
        while(!queue_empty(&free_listeners)) {
                queue_remove_first(&free_listeners, next, atm_link_object_t, listeners_element);
        
                /* Drops the reference on the link object */
                atm_link_dealloc(next);
        }
        
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, (ATM_CODE(ATM_SUBAID_INFO, (ATM_MIN_LINK_LIST))) | DBG_FUNC_END,
                        j, freed_count, dead_but_not_freed, 0, 0);

        /* explicitly upgrade uint32_t to 64 bit mach size */
        return CAST_DOWN(mach_atm_subaid_t, min_subaid);
}


/*
 * Routine: atm_value_unregister
 * Purpose: Unregisters a process from an activity id.
 * Returns: KERN_SUCCESS on successful unregister.
 *          KERN_INVALID_VALUE on finding a diff mailbox.
 *          KERN_FAILURE on failure.
 */
static kern_return_t
atm_value_unregister(
        atm_value_t atm_value,
        atm_task_descriptor_t task_descriptor,
        mailbox_offset_t mailbox_offset)
{
        kern_return_t kr;

        if (task_descriptor == ATM_TASK_DESCRIPTOR_NULL)
                return KERN_INVALID_ARGUMENT;
        if (mailbox_offset > task_descriptor->mailbox_array_size)
                return KERN_INVALID_ARGUMENT;
        
        kr = atm_listener_delete(atm_value, task_descriptor, mailbox_offset);
        return kr;
}

void
atm_task_descriptor_destroy(atm_task_descriptor_t task_descriptor)
{
        /* Mark the task dead in the task descriptor to make task descriptor eligible for cleanup. */
        lck_mtx_lock(&task_descriptor->lock);
        task_descriptor->flags = ATM_TASK_DEAD;
        lck_mtx_unlock(&task_descriptor->lock);

        atm_task_descriptor_dealloc(task_descriptor);
}