xnu-3789.51.2.tar.gz

[apple/xnu.git] / osfmk / kern / zalloc.c

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 * Copyright (c) 2000-2016 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
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 * 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
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 * may not be used to create, or enable the creation or redistribution of,
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 * Please obtain a copy of the License at
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/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 */
/*
 *      File:   kern/zalloc.c
 *      Author: Avadis Tevanian, Jr.
 *
 *      Zone-based memory allocator.  A zone is a collection of fixed size
 *      data blocks for which quick allocation/deallocation is possible.
 */
#include <zone_debug.h>

#include <mach/mach_types.h>
#include <mach/vm_param.h>
#include <mach/kern_return.h>
#include <mach/mach_host_server.h>
#include <mach/task_server.h>
#include <mach/machine/vm_types.h>
#include <mach_debug/zone_info.h>
#include <mach/vm_map.h>

#include <kern/kern_types.h>
#include <kern/assert.h>
#include <kern/backtrace.h>
#include <kern/host.h>
#include <kern/macro_help.h>
#include <kern/sched.h>
#include <kern/locks.h>
#include <kern/sched_prim.h>
#include <kern/misc_protos.h>
#include <kern/thread_call.h>
#include <kern/zalloc.h>
#include <kern/kalloc.h>

#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_kern.h>
#include <vm/vm_page.h>

#include <pexpert/pexpert.h>

#include <machine/machparam.h>
#include <machine/machine_routines.h>  /* ml_cpu_get_info */

#include <libkern/OSDebug.h>
#include <libkern/OSAtomic.h>
#include <sys/kdebug.h>

/*
 *  ZONE_ALIAS_ADDR (deprecated)
 */

#define from_zone_map(addr, size) \
        ((vm_offset_t)(addr)             >= zone_map_min_address && \
        ((vm_offset_t)(addr) + size - 1) <  zone_map_max_address )

/*
 * Zone Corruption Debugging
 *
 * We use three techniques to detect modification of a zone element
 * after it's been freed.
 *
 * (1) Check the freelist next pointer for sanity.
 * (2) Store a backup of the next pointer at the end of the element,
 *     and compare it to the primary next pointer when the element is allocated
 *     to detect corruption of the freelist due to use-after-free bugs.
 *     The backup pointer is also XORed with a per-boot random cookie.
 * (3) Poison the freed element by overwriting it with 0xdeadbeef,
 *     and check for that value when the element is being reused to make sure
 *     no part of the element has been modified while it was on the freelist.
 *     This will also help catch read-after-frees, as code will now dereference
 *     0xdeadbeef instead of a valid but freed pointer.
 *
 * (1) and (2) occur for every allocation and free to a zone.
 * This is done to make it slightly more difficult for an attacker to
 * manipulate the freelist to behave in a specific way.
 *
 * Poisoning (3) occurs periodically for every N frees (counted per-zone)
 * and on every free for zones smaller than a cacheline.  If -zp
 * is passed as a boot arg, poisoning occurs for every free.
 *
 * Performance slowdown is inversely proportional to the frequency of poisoning,
 * with a 4-5% hit around N=1, down to ~0.3% at N=16 and just "noise" at N=32
 * and higher. You can expect to find a 100% reproducible bug in an average of
 * N tries, with a standard deviation of about N, but you will want to set
 * "-zp" to always poison every free if you are attempting to reproduce
 * a known bug.
 *
 * For a more heavyweight, but finer-grained method of detecting misuse
 * of zone memory, look up the "Guard mode" zone allocator in gzalloc.c.
 *
 * Zone Corruption Logging
 *
 * You can also track where corruptions come from by using the boot-arguments
 * "zlog=<zone name to log> -zc". Search for "Zone corruption logging" later
 * in this document for more implementation and usage information.
 *
 * Zone Leak Detection
 *
 * To debug leaks of zone memory, use the zone leak detection tool 'zleaks'
 * found later in this file via the showtopztrace and showz* macros in kgmacros,
 * or use zlog without the -zc argument.
 *
 */

/* Returns TRUE if we rolled over the counter at factor */
static inline boolean_t
sample_counter(volatile uint32_t * count_p, uint32_t factor)
{
        uint32_t old_count, new_count;
        boolean_t rolled_over;

        do {
                new_count = old_count = *count_p;

                if (++new_count >= factor) {
                        rolled_over = TRUE;
                        new_count = 0;
                } else {
                        rolled_over = FALSE;
                }

        } while (!OSCompareAndSwap(old_count, new_count, count_p));

        return rolled_over;
}

#if defined(__LP64__)
#define ZP_POISON       0xdeadbeefdeadbeef
#else
#define ZP_POISON       0xdeadbeef
#endif

#define ZP_DEFAULT_SAMPLING_FACTOR 16
#define ZP_DEFAULT_SCALE_FACTOR 4

/*
 *  A zp_factor of 0 indicates zone poisoning is disabled,
 *  however, we still poison zones smaller than zp_tiny_zone_limit (a cacheline).
 *  Passing the -no-zp boot-arg disables even this behavior.
 *  In all cases, we record and check the integrity of a backup pointer.
 */

/* set by zp-factor=N boot arg, zero indicates non-tiny poisoning disabled */
uint32_t        zp_factor               = 0;

/* set by zp-scale=N boot arg, scales zp_factor by zone size */
uint32_t        zp_scale                = 0;

/* set in zp_init, zero indicates -no-zp boot-arg */
vm_size_t       zp_tiny_zone_limit      = 0;

/* initialized to a per-boot random value in zp_init */
uintptr_t       zp_poisoned_cookie      = 0;
uintptr_t       zp_nopoison_cookie      = 0;


/*
 * initialize zone poisoning
 * called from zone_bootstrap before any allocations are made from zalloc
 */
static inline void
zp_init(void)
{
        char temp_buf[16];

        /*
         * Initialize backup pointer random cookie for poisoned elements
         * Try not to call early_random() back to back, it may return
         * the same value if mach_absolute_time doesn't have sufficient time
         * to tick over between calls.  <rdar://problem/11597395>
         * (This is only a problem on embedded devices)
         */
        zp_poisoned_cookie = (uintptr_t) early_random();

        /*
         * Always poison zones smaller than a cacheline,
         * because it's pretty close to free
         */
        ml_cpu_info_t cpu_info;
        ml_cpu_get_info(&cpu_info);
        zp_tiny_zone_limit = (vm_size_t) cpu_info.cache_line_size;

        zp_factor = ZP_DEFAULT_SAMPLING_FACTOR;
        zp_scale  = ZP_DEFAULT_SCALE_FACTOR;

        //TODO: Bigger permutation?
        /*
         * Permute the default factor +/- 1 to make it less predictable
         * This adds or subtracts ~4 poisoned objects per 1000 frees.
         */
        if (zp_factor != 0) {
                uint32_t rand_bits = early_random() & 0x3;

                if (rand_bits == 0x1)
                        zp_factor += 1;
                else if (rand_bits == 0x2)
                        zp_factor -= 1;
                /* if 0x0 or 0x3, leave it alone */
        }

        /* -zp: enable poisoning for every alloc and free */
        if (PE_parse_boot_argn("-zp", temp_buf, sizeof(temp_buf))) {
                zp_factor = 1;
        }

        /* -no-zp: disable poisoning completely even for tiny zones */
        if (PE_parse_boot_argn("-no-zp", temp_buf, sizeof(temp_buf))) {
                zp_factor          = 0;
                zp_tiny_zone_limit = 0;
                printf("Zone poisoning disabled\n");
        }

        /* zp-factor=XXXX: override how often to poison freed zone elements */
        if (PE_parse_boot_argn("zp-factor", &zp_factor, sizeof(zp_factor))) {
                printf("Zone poisoning factor override: %u\n", zp_factor);
        }

        /* zp-scale=XXXX: override how much zone size scales zp-factor by */
        if (PE_parse_boot_argn("zp-scale", &zp_scale, sizeof(zp_scale))) {
                printf("Zone poisoning scale factor override: %u\n", zp_scale);
        }

        /* Initialize backup pointer random cookie for unpoisoned elements */
        zp_nopoison_cookie = (uintptr_t) early_random();

#if MACH_ASSERT
        if (zp_poisoned_cookie == zp_nopoison_cookie)
                panic("early_random() is broken: %p and %p are not random\n",
                      (void *) zp_poisoned_cookie, (void *) zp_nopoison_cookie);
#endif

        /*
         * Use the last bit in the backup pointer to hint poisoning state
         * to backup_ptr_mismatch_panic. Valid zone pointers are aligned, so
         * the low bits are zero.
         */
        zp_poisoned_cookie |=   (uintptr_t)0x1ULL;
        zp_nopoison_cookie &= ~((uintptr_t)0x1ULL);

#if defined(__LP64__)
        /*
         * Make backup pointers more obvious in GDB for 64 bit
         * by making OxFFFFFF... ^ cookie = 0xFACADE...
         * (0xFACADE = 0xFFFFFF ^ 0x053521)
         * (0xC0FFEE = 0xFFFFFF ^ 0x3f0011)
         * The high 3 bytes of a zone pointer are always 0xFFFFFF, and are checked
         * by the sanity check, so it's OK for that part of the cookie to be predictable.
         *
         * TODO: Use #defines, xors, and shifts
         */

        zp_poisoned_cookie &= 0x000000FFFFFFFFFF;
        zp_poisoned_cookie |= 0x0535210000000000; /* 0xFACADE */

        zp_nopoison_cookie &= 0x000000FFFFFFFFFF;
        zp_nopoison_cookie |= 0x3f00110000000000; /* 0xC0FFEE */
#endif
}

/*
 * These macros are used to keep track of the number
 * of pages being used by the zone currently. The
 * z->page_count is protected by the zone lock.
 */
#define ZONE_PAGE_COUNT_INCR(z, count)          \
{                                               \
        OSAddAtomic64(count, &(z->page_count)); \
}

#define ZONE_PAGE_COUNT_DECR(z, count)                  \
{                                                       \
        OSAddAtomic64(-count, &(z->page_count));        \
}

vm_map_t        zone_map = VM_MAP_NULL;

/* for is_sane_zone_element and garbage collection */

vm_offset_t     zone_map_min_address = 0;  /* initialized in zone_init */
vm_offset_t     zone_map_max_address = 0;

/* Globals for random boolean generator for elements in free list */
#define MAX_ENTROPY_PER_ZCRAM           4
#define RANDOM_BOOL_GEN_SEED_COUNT      4
static unsigned int bool_gen_seed[RANDOM_BOOL_GEN_SEED_COUNT];
static unsigned int bool_gen_global = 0;
decl_simple_lock_data(, bool_gen_lock)

/* VM region for all metadata structures */
vm_offset_t     zone_metadata_region_min = 0;
vm_offset_t     zone_metadata_region_max = 0;
decl_lck_mtx_data(static ,zone_metadata_region_lck)
lck_attr_t      zone_metadata_lock_attr;
lck_mtx_ext_t   zone_metadata_region_lck_ext; 

/* Helpful for walking through a zone's free element list. */
struct zone_free_element {
        struct zone_free_element *next;
        /* ... */
        /* void *backup_ptr; */
};

/*
 *      Protects num_zones, zone_array and zone_array_index
 */
decl_simple_lock_data(, all_zones_lock)
unsigned int            num_zones;

#define MAX_ZONES       256
struct zone             zone_array[MAX_ZONES];
static int              zone_array_index = 0;

#define MULTIPAGE_METADATA_MAGIC                (0xff)

#define PAGE_METADATA_GET_ZINDEX(page_meta)                     \
        (page_meta->zindex)

#define PAGE_METADATA_GET_ZONE(page_meta)                               \
        (&(zone_array[page_meta->zindex]))

#define PAGE_METADATA_SET_ZINDEX(page_meta, index)              \
        page_meta->zindex = (index);

struct zone_page_metadata {
        queue_chain_t           pages; /* linkage pointer for metadata lists */

        /* Union for maintaining start of element free list and real metadata (for multipage allocations) */
        union {
                /* 
                 * The start of the freelist can be maintained as a 32-bit offset instead of a pointer because 
                 * the free elements would be at max ZONE_MAX_ALLOC_SIZE bytes away from the metadata. Offset 
                 * from start of the allocation chunk to free element list head.
                 */
                uint32_t                freelist_offset;
                /* 
                 * This field is used to lookup the real metadata for multipage allocations, where we mark the 
                 * metadata for all pages except the first as "fake" metadata using MULTIPAGE_METADATA_MAGIC. 
                 * Offset from this fake metadata to real metadata of allocation chunk (-ve offset).
                 */
                uint32_t                real_metadata_offset;  
        };

        /* 
         * For the first page in the allocation chunk, this represents the total number of free elements in 
         * the chunk. 
         * For all other pages, it represents the number of free elements on that page (used 
         * for garbage collection of zones with large multipage allocation size)
         */
        uint16_t                        free_count;
        uint8_t                         zindex;         /* Zone index within the zone_array */
        uint8_t                         page_count; /* Count of pages within the allocation chunk */
};

/* Macro to get page index (within zone_map) of page containing element */
#define PAGE_INDEX_FOR_ELEMENT(element)                         \
        (((vm_offset_t)trunc_page(element) - zone_map_min_address) / PAGE_SIZE)

/* Macro to get metadata structure given a page index in zone_map */
#define PAGE_METADATA_FOR_PAGE_INDEX(index)                     \
        (zone_metadata_region_min + ((index) * sizeof(struct zone_page_metadata)))

/* Macro to get index (within zone_map) for given metadata */
#define PAGE_INDEX_FOR_METADATA(page_meta)                      \
        (((vm_offset_t)page_meta - zone_metadata_region_min) / sizeof(struct zone_page_metadata))

/* Macro to get page for given page index in zone_map */
#define PAGE_FOR_PAGE_INDEX(index)                              \
        (zone_map_min_address + (PAGE_SIZE * (index))) 

/* Macro to get the actual metadata for a given address */
#define PAGE_METADATA_FOR_ELEMENT(element)              \
        (struct zone_page_metadata *)(PAGE_METADATA_FOR_PAGE_INDEX(PAGE_INDEX_FOR_ELEMENT(element)))

/* Magic value to indicate empty element free list */
#define PAGE_METADATA_EMPTY_FREELIST            ((uint32_t)(~0))

static inline void *
page_metadata_get_freelist(struct zone_page_metadata *page_meta)
{
        assert(PAGE_METADATA_GET_ZINDEX(page_meta) != MULTIPAGE_METADATA_MAGIC);
        if (page_meta->freelist_offset == PAGE_METADATA_EMPTY_FREELIST)
                return NULL;
        else {
                if (from_zone_map(page_meta, sizeof(struct zone_page_metadata)))
                        return (void *)(PAGE_FOR_PAGE_INDEX(PAGE_INDEX_FOR_METADATA(page_meta)) + page_meta->freelist_offset);
                else
                        return (void *)((vm_offset_t)page_meta + page_meta->freelist_offset);
        }
}

static inline void
page_metadata_set_freelist(struct zone_page_metadata *page_meta, void *addr)
{
        assert(PAGE_METADATA_GET_ZINDEX(page_meta) != MULTIPAGE_METADATA_MAGIC);
        if (addr == NULL)
                page_meta->freelist_offset = PAGE_METADATA_EMPTY_FREELIST;
        else {
                if (from_zone_map(page_meta, sizeof(struct zone_page_metadata)))
                        page_meta->freelist_offset = (uint32_t)((vm_offset_t)(addr) - PAGE_FOR_PAGE_INDEX(PAGE_INDEX_FOR_METADATA(page_meta)));
                else
                        page_meta->freelist_offset = (uint32_t)((vm_offset_t)(addr) - (vm_offset_t)page_meta);
        }
}

static inline struct zone_page_metadata *
page_metadata_get_realmeta(struct zone_page_metadata *page_meta)
{
        assert(PAGE_METADATA_GET_ZINDEX(page_meta) == MULTIPAGE_METADATA_MAGIC);
        return (struct zone_page_metadata *)((vm_offset_t)page_meta - page_meta->real_metadata_offset);
}

static inline void 
page_metadata_set_realmeta(struct zone_page_metadata *page_meta, struct zone_page_metadata *real_meta)
{
                assert(PAGE_METADATA_GET_ZINDEX(page_meta) == MULTIPAGE_METADATA_MAGIC);
                assert(PAGE_METADATA_GET_ZINDEX(real_meta) != MULTIPAGE_METADATA_MAGIC);
                assert((vm_offset_t)page_meta > (vm_offset_t)real_meta);
                vm_offset_t offset = (vm_offset_t)page_meta - (vm_offset_t)real_meta;
                assert(offset <= UINT32_MAX);
                page_meta->real_metadata_offset = (uint32_t)offset;
}

/* The backup pointer is stored in the last pointer-sized location in an element. */
static inline vm_offset_t *
get_backup_ptr(vm_size_t  elem_size,
               vm_offset_t *element)
{
        return (vm_offset_t *) ((vm_offset_t)element + elem_size - sizeof(vm_offset_t));
}

/* 
 * Routine to populate a page backing metadata in the zone_metadata_region.
 * Must be called without the zone lock held as it might potentially block. 
 */
static inline void
zone_populate_metadata_page(struct zone_page_metadata *page_meta) 
{
        vm_offset_t page_metadata_begin = trunc_page(page_meta);
        vm_offset_t page_metadata_end = trunc_page((vm_offset_t)page_meta + sizeof(struct zone_page_metadata));
        
        for(;page_metadata_begin <= page_metadata_end; page_metadata_begin += PAGE_SIZE) {
                if (pmap_find_phys(kernel_pmap, (vm_map_address_t)page_metadata_begin))
                        continue;
                /* All updates to the zone_metadata_region are done under the zone_metadata_region_lck */
                lck_mtx_lock(&zone_metadata_region_lck);
                if (0 == pmap_find_phys(kernel_pmap, (vm_map_address_t)page_metadata_begin)) {
                        kernel_memory_populate(zone_map, 
                                       page_metadata_begin,
                                       PAGE_SIZE,
                                       KMA_KOBJECT,
                                       VM_KERN_MEMORY_OSFMK);
                }
                lck_mtx_unlock(&zone_metadata_region_lck);
        }
        return;
}

static inline uint16_t
get_metadata_alloc_count(struct zone_page_metadata *page_meta)
{
                assert(PAGE_METADATA_GET_ZINDEX(page_meta) != MULTIPAGE_METADATA_MAGIC);
                struct zone *z = PAGE_METADATA_GET_ZONE(page_meta);
                return ((page_meta->page_count * PAGE_SIZE) / z->elem_size);
}

/* 
 * Routine to lookup metadata for any given address. 
 * If init is marked as TRUE, this should be called without holding the zone lock
 * since the initialization might block.
 */
static inline struct zone_page_metadata *
get_zone_page_metadata(struct zone_free_element *element, boolean_t init)
{
        struct zone_page_metadata *page_meta = 0;

        if (from_zone_map(element, sizeof(struct zone_free_element))) { 
                page_meta = (struct zone_page_metadata *)(PAGE_METADATA_FOR_ELEMENT(element));
                if (init)
                        zone_populate_metadata_page(page_meta);
        } else {
                page_meta = (struct zone_page_metadata *)(trunc_page((vm_offset_t)element));
        }
        if (init)
                bzero((char *)page_meta, sizeof(struct zone_page_metadata));
        return ((PAGE_METADATA_GET_ZINDEX(page_meta) != MULTIPAGE_METADATA_MAGIC) ? page_meta : page_metadata_get_realmeta(page_meta));
}

/* Routine to get the page for a given metadata */
static inline vm_offset_t
get_zone_page(struct zone_page_metadata *page_meta)
{
        if (from_zone_map(page_meta, sizeof(struct zone_page_metadata)))
                return (vm_offset_t)(PAGE_FOR_PAGE_INDEX(PAGE_INDEX_FOR_METADATA(page_meta)));
        else
                return (vm_offset_t)(trunc_page(page_meta));
}

/* Routine to get the size of a zone allocated address. If the address doesnt belong to the 
 * zone_map, returns 0.
 */
vm_size_t
zone_element_size(void *addr, zone_t *z)
{
        struct zone *src_zone;
        if (from_zone_map(addr, sizeof(void *))) {
                struct zone_page_metadata *page_meta = get_zone_page_metadata((struct zone_free_element *)addr, FALSE);
                src_zone = PAGE_METADATA_GET_ZONE(page_meta);
                if (z) {
                        *z = src_zone;
                }
                return (src_zone->elem_size);
        } else {
#if CONFIG_GZALLOC
                vm_size_t gzsize;
                if (gzalloc_element_size(addr, z, &gzsize)) {
                        return gzsize;
                }
#endif /* CONFIG_GZALLOC */

                return 0;
        }
}

/*
 * Zone checking helper function.
 * A pointer that satisfies these conditions is OK to be a freelist next pointer
 * A pointer that doesn't satisfy these conditions indicates corruption
 */
static inline boolean_t
is_sane_zone_ptr(zone_t         zone,
                 vm_offset_t    addr,
                 size_t         obj_size)
{
        /*  Must be aligned to pointer boundary */
        if (__improbable((addr & (sizeof(vm_offset_t) - 1)) != 0))
                return FALSE;

        /*  Must be a kernel address */
        if (__improbable(!pmap_kernel_va(addr)))
                return FALSE;

        /*  Must be from zone map if the zone only uses memory from the zone_map */
        /*
         *  TODO: Remove the zone->collectable check when every
         *  zone using foreign memory is properly tagged with allows_foreign
         */
        if (zone->collectable && !zone->allows_foreign) {
                /*  check if addr is from zone map */
                if (addr                 >= zone_map_min_address &&
                   (addr + obj_size - 1) <  zone_map_max_address )
                        return TRUE;

                return FALSE;
        }

        return TRUE;
}

static inline boolean_t
is_sane_zone_page_metadata(zone_t       zone,
                           vm_offset_t  page_meta)
{
        /* NULL page metadata structures are invalid */
        if (page_meta == 0)
                return FALSE;
        return is_sane_zone_ptr(zone, page_meta, sizeof(struct zone_page_metadata));
}

static inline boolean_t
is_sane_zone_element(zone_t      zone,
                     vm_offset_t addr)
{
        /*  NULL is OK because it indicates the tail of the list */
        if (addr == 0)
                return TRUE;
        return is_sane_zone_ptr(zone, addr, zone->elem_size);
}
        
/* Someone wrote to freed memory. */
static inline void /* noreturn */
zone_element_was_modified_panic(zone_t        zone,
                                vm_offset_t   element,
                                vm_offset_t   found,
                                vm_offset_t   expected,
                                vm_offset_t   offset)
{
        panic("a freed zone element has been modified in zone %s: expected %p but found %p, bits changed %p, at offset %d of %d in element %p, cookies %p %p",
                         zone->zone_name,
              (void *)   expected,
              (void *)   found,
              (void *)   (expected ^ found),
              (uint32_t) offset,
              (uint32_t) zone->elem_size,
              (void *)   element,
              (void *)   zp_nopoison_cookie,
              (void *)   zp_poisoned_cookie);
}

/*
 * The primary and backup pointers don't match.
 * Determine which one was likely the corrupted pointer, find out what it
 * probably should have been, and panic.
 * I would like to mark this as noreturn, but panic() isn't marked noreturn.
 */
static void /* noreturn */
backup_ptr_mismatch_panic(zone_t        zone,
                          vm_offset_t   element,
                          vm_offset_t   primary,
                          vm_offset_t   backup)
{
        vm_offset_t likely_backup;
        vm_offset_t likely_primary;

        likely_primary = primary ^ zp_nopoison_cookie;
        boolean_t   sane_backup;
        boolean_t   sane_primary = is_sane_zone_element(zone, likely_primary);
        boolean_t   element_was_poisoned = (backup & 0x1) ? TRUE : FALSE;

#if defined(__LP64__)
        /* We can inspect the tag in the upper bits for additional confirmation */
        if ((backup & 0xFFFFFF0000000000) == 0xFACADE0000000000)
                element_was_poisoned = TRUE;
        else if ((backup & 0xFFFFFF0000000000) == 0xC0FFEE0000000000)
                element_was_poisoned = FALSE;
#endif

        if (element_was_poisoned) {
                likely_backup = backup ^ zp_poisoned_cookie;
                sane_backup = is_sane_zone_element(zone, likely_backup);
        } else {
                likely_backup = backup ^ zp_nopoison_cookie;
                sane_backup = is_sane_zone_element(zone, likely_backup);
        }

        /* The primary is definitely the corrupted one */
        if (!sane_primary && sane_backup)
                zone_element_was_modified_panic(zone, element, primary, (likely_backup ^ zp_nopoison_cookie), 0);

        /* The backup is definitely the corrupted one */
        if (sane_primary && !sane_backup)
                zone_element_was_modified_panic(zone, element, backup,
                                                (primary ^ (element_was_poisoned ? zp_poisoned_cookie : zp_nopoison_cookie)),
                                                zone->elem_size - sizeof(vm_offset_t));

        /*
         * Not sure which is the corrupted one.
         * It's less likely that the backup pointer was overwritten with
         * ( (sane address) ^ (valid cookie) ), so we'll guess that the
         * primary pointer has been overwritten with a sane but incorrect address.
         */
        if (sane_primary && sane_backup)
                zone_element_was_modified_panic(zone, element, primary, likely_backup, 0);

        /* Neither are sane, so just guess. */
        zone_element_was_modified_panic(zone, element, primary, likely_backup, 0);
}

/*
 * Adds the element to the head of the zone's free list
 * Keeps a backup next-pointer at the end of the element
 */
static inline void
free_to_zone(zone_t      zone,
             vm_offset_t element,
             boolean_t   poison)
{
        vm_offset_t old_head;
        struct zone_page_metadata *page_meta;

        vm_offset_t *primary  = (vm_offset_t *) element;
        vm_offset_t *backup   = get_backup_ptr(zone->elem_size, primary);

        page_meta = get_zone_page_metadata((struct zone_free_element *)element, FALSE);
        assert(PAGE_METADATA_GET_ZONE(page_meta) == zone);
        old_head = (vm_offset_t)page_metadata_get_freelist(page_meta);

#if MACH_ASSERT
        if (__improbable(!is_sane_zone_element(zone, old_head)))
                panic("zfree: invalid head pointer %p for freelist of zone %s\n",
                      (void *) old_head, zone->zone_name);
#endif

        if (__improbable(!is_sane_zone_element(zone, element)))
                panic("zfree: freeing invalid pointer %p to zone %s\n",
                      (void *) element, zone->zone_name);

        /*
         * Always write a redundant next pointer
         * So that it is more difficult to forge, xor it with a random cookie
         * A poisoned element is indicated by using zp_poisoned_cookie
         * instead of zp_nopoison_cookie
         */

        *backup = old_head ^ (poison ? zp_poisoned_cookie : zp_nopoison_cookie);

        /* 
         * Insert this element at the head of the free list. We also xor the 
         * primary pointer with the zp_nopoison_cookie to make sure a free 
         * element does not provide the location of the next free element directly.
         */
        *primary             = old_head ^ zp_nopoison_cookie;
        page_metadata_set_freelist(page_meta, (struct zone_free_element *)element);
        page_meta->free_count++;
        if (zone->allows_foreign && !from_zone_map(element, zone->elem_size)) {
                if (page_meta->free_count == 1) {
                        /* first foreign element freed on page, move from all_used */
                        re_queue_tail(&zone->pages.any_free_foreign, &(page_meta->pages));
                } else {
                        /* no other list transitions */
                }
        } else if (page_meta->free_count == get_metadata_alloc_count(page_meta)) {
                /* whether the page was on the intermediate or all_used, queue, move it to free */
                re_queue_tail(&zone->pages.all_free, &(page_meta->pages));
                zone->count_all_free_pages += page_meta->page_count;
        } else if (page_meta->free_count == 1) {
                /* first free element on page, move from all_used */
                re_queue_tail(&zone->pages.intermediate, &(page_meta->pages));
        }
        zone->count--;
        zone->countfree++;
}


/*
 * Removes an element from the zone's free list, returning 0 if the free list is empty.
 * Verifies that the next-pointer and backup next-pointer are intact,
 * and verifies that a poisoned element hasn't been modified.
 */
static inline vm_offset_t
try_alloc_from_zone(zone_t zone,
                    boolean_t* check_poison)
{
        vm_offset_t  element;
        struct zone_page_metadata *page_meta;

        *check_poison = FALSE;

        /* if zone is empty, bail */
        if (zone->allows_foreign && !queue_empty(&zone->pages.any_free_foreign))
                page_meta = (struct zone_page_metadata *)queue_first(&zone->pages.any_free_foreign);
        else if (!queue_empty(&zone->pages.intermediate))
                page_meta = (struct zone_page_metadata *)queue_first(&zone->pages.intermediate);
        else if (!queue_empty(&zone->pages.all_free)) {
                page_meta = (struct zone_page_metadata *)queue_first(&zone->pages.all_free);
                assert(zone->count_all_free_pages >= page_meta->page_count);
                zone->count_all_free_pages -= page_meta->page_count;
        } else {
                return 0;
        }
        /* Check if page_meta passes is_sane_zone_element */
        if (__improbable(!is_sane_zone_page_metadata(zone, (vm_offset_t)page_meta)))
                panic("zalloc: invalid metadata structure %p for freelist of zone %s\n",
                        (void *) page_meta, zone->zone_name);
        assert(PAGE_METADATA_GET_ZONE(page_meta) == zone);
        element = (vm_offset_t)page_metadata_get_freelist(page_meta);

        if (__improbable(!is_sane_zone_ptr(zone, element, zone->elem_size)))
                panic("zfree: invalid head pointer %p for freelist of zone %s\n",
                      (void *) element, zone->zone_name);

        vm_offset_t *primary = (vm_offset_t *) element;
        vm_offset_t *backup  = get_backup_ptr(zone->elem_size, primary);

        /* 
         * Since the primary next pointer is xor'ed with zp_nopoison_cookie
         * for obfuscation, retrieve the original value back
         */
        vm_offset_t  next_element          = *primary ^ zp_nopoison_cookie;
        vm_offset_t  next_element_primary  = *primary;
        vm_offset_t  next_element_backup   = *backup;

        /*
         * backup_ptr_mismatch_panic will determine what next_element
         * should have been, and print it appropriately
         */
        if (__improbable(!is_sane_zone_element(zone, next_element)))
                backup_ptr_mismatch_panic(zone, element, next_element_primary, next_element_backup);

        /* Check the backup pointer for the regular cookie */
        if (__improbable(next_element != (next_element_backup ^ zp_nopoison_cookie))) {

                /* Check for the poisoned cookie instead */
                if (__improbable(next_element != (next_element_backup ^ zp_poisoned_cookie)))
                        /* Neither cookie is valid, corruption has occurred */
                        backup_ptr_mismatch_panic(zone, element, next_element_primary, next_element_backup);

                /*
                 * Element was marked as poisoned, so check its integrity before using it.
                 */
                *check_poison = TRUE;
        }

        /* Make sure the page_meta is at the correct offset from the start of page */
        if (__improbable(page_meta != get_zone_page_metadata((struct zone_free_element *)element, FALSE)))
                panic("zalloc: Incorrect metadata %p found in zone %s page queue. Expected metadata: %p\n",
                        page_meta, zone->zone_name, get_zone_page_metadata((struct zone_free_element *)element, FALSE));

        /* Make sure next_element belongs to the same page as page_meta */
        if (next_element) {
                if (__improbable(page_meta != get_zone_page_metadata((struct zone_free_element *)next_element, FALSE)))
                        panic("zalloc: next element pointer %p for element %p points to invalid element for zone %s\n",
                                (void *)next_element, (void *)element, zone->zone_name);
        }

        /* Remove this element from the free list */
        page_metadata_set_freelist(page_meta, (struct zone_free_element *)next_element);
        page_meta->free_count--;

        if (page_meta->free_count == 0) {
                /* move to all used */
                re_queue_tail(&zone->pages.all_used, &(page_meta->pages));
        } else {
                if (!zone->allows_foreign || from_zone_map(element, zone->elem_size)) {
                        if (get_metadata_alloc_count(page_meta) == page_meta->free_count + 1) {
                                /* remove from free, move to intermediate */
                                re_queue_tail(&zone->pages.intermediate, &(page_meta->pages));
                        }
                }
        }
        zone->countfree--;
        zone->count++;
        zone->sum_count++;

        return element;
}

/*
 * End of zone poisoning
 */

/*
 * Zone info options
 */
#define ZINFO_SLOTS     MAX_ZONES               /* for now */

void            zone_display_zprint(void);

zone_t          zone_find_largest(void);

/* 
 * Async allocation of zones 
 * This mechanism allows for bootstrapping an empty zone which is setup with 
 * non-blocking flags. The first call to zalloc_noblock() will kick off a thread_call
 * to zalloc_async. We perform a zalloc() (which may block) and then an immediate free. 
 * This will prime the zone for the next use.
 *
 * Currently the thread_callout function (zalloc_async) will loop through all zones
 * looking for any zone with async_pending set and do the work for it. 
 * 
 * NOTE: If the calling thread for zalloc_noblock is lower priority than thread_call,
 * then zalloc_noblock to an empty zone may succeed. 
 */
void            zalloc_async(
                                thread_call_param_t     p0,  
                                thread_call_param_t     p1);

static thread_call_data_t call_async_alloc;

/*
 * Align elements that use the zone page list to 32 byte boundaries.
 */
#define ZONE_ELEMENT_ALIGNMENT 32

#define zone_wakeup(zone) thread_wakeup((event_t)(zone))
#define zone_sleep(zone)                                \
        (void) lck_mtx_sleep(&(zone)->lock, LCK_SLEEP_SPIN, (event_t)(zone), THREAD_UNINT);

/*
 *      The zone_locks_grp allows for collecting lock statistics.
 *      All locks are associated to this group in zinit.
 *      Look at tools/lockstat for debugging lock contention.
 */

lck_grp_t       zone_locks_grp;
lck_grp_attr_t  zone_locks_grp_attr;

#define lock_zone_init(zone)                            \
MACRO_BEGIN                                             \
        lck_attr_setdefault(&(zone)->lock_attr);                        \
        lck_mtx_init_ext(&(zone)->lock, &(zone)->lock_ext,              \
            &zone_locks_grp, &(zone)->lock_attr);                       \
MACRO_END

#define lock_try_zone(zone)     lck_mtx_try_lock_spin(&zone->lock)

/*
 *      Exclude more than one concurrent garbage collection
 */
decl_lck_mtx_data(, zone_gc_lock)

lck_attr_t      zone_gc_lck_attr;
lck_grp_t       zone_gc_lck_grp;
lck_grp_attr_t  zone_gc_lck_grp_attr;
lck_mtx_ext_t   zone_gc_lck_ext;

boolean_t zone_gc_allowed = TRUE;
boolean_t panic_include_zprint = FALSE;

vm_offset_t panic_kext_memory_info = 0;
vm_size_t panic_kext_memory_size = 0;

#define ZALLOC_DEBUG_ZONEGC             0x00000001
#define ZALLOC_DEBUG_ZCRAM              0x00000002
uint32_t zalloc_debug = 0;

/*
 * Zone leak debugging code
 *
 * When enabled, this code keeps a log to track allocations to a particular zone that have not
 * yet been freed.  Examining this log will reveal the source of a zone leak.  The log is allocated
 * only when logging is enabled, so there is no effect on the system when it's turned off.  Logging is
 * off by default.
 *
 * Enable the logging via the boot-args. Add the parameter "zlog=<zone>" to boot-args where <zone>
 * is the name of the zone you wish to log.  
 *
 * This code only tracks one zone, so you need to identify which one is leaking first.
 * Generally, you'll know you have a leak when you get a "zalloc retry failed 3" panic from the zone
 * garbage collector.  Note that the zone name printed in the panic message is not necessarily the one
 * containing the leak.  So do a zprint from gdb and locate the zone with the bloated size.  This
 * is most likely the problem zone, so set zlog in boot-args to this zone name, reboot and re-run the test.  The
 * next time it panics with this message, examine the log using the kgmacros zstack, findoldest and countpcs.
 * See the help in the kgmacros for usage info.
 *
 *
 * Zone corruption logging
 *
 * Logging can also be used to help identify the source of a zone corruption.  First, identify the zone
 * that is being corrupted, then add "-zc zlog=<zone name>" to the boot-args.  When -zc is used in conjunction
 * with zlog, it changes the logging style to track both allocations and frees to the zone.  So when the
 * corruption is detected, examining the log will show you the stack traces of the callers who last allocated
 * and freed any particular element in the zone.  Use the findelem kgmacro with the address of the element that's been
 * corrupted to examine its history.  This should lead to the source of the corruption.
 */

static boolean_t log_records_init = FALSE;
static int log_records; /* size of the log, expressed in number of records */

#define MAX_NUM_ZONES_ALLOWED_LOGGING   5 /* Maximum 5 zones can be logged at once */

static int  max_num_zones_to_log = MAX_NUM_ZONES_ALLOWED_LOGGING;
static int  num_zones_logged = 0;

#define MAX_ZONE_NAME   32      /* max length of a zone name we can take from the boot-args */

static char zone_name_to_log[MAX_ZONE_NAME] = "";       /* the zone name we're logging, if any */

/* Log allocations and frees to help debug a zone element corruption */
boolean_t       corruption_debug_flag    = FALSE;    /* enabled by "-zc" boot-arg */
/* Making pointer scanning leaks detection possible for all zones */

#if DEBUG || DEVELOPMENT
boolean_t       leak_scan_debug_flag     = FALSE;    /* enabled by "-zl" boot-arg */
#endif /* DEBUG || DEVELOPMENT */


/*
 * The number of records in the log is configurable via the zrecs parameter in boot-args.  Set this to 
 * the number of records you want in the log.  For example, "zrecs=10" sets it to 10 records. Since this
 * is the number of stacks suspected of leaking, we don't need many records.
 */

#if     defined(__LP64__)
#define ZRECORDS_MAX            2560            /* Max records allowed in the log */
#else
#define ZRECORDS_MAX            1536            /* Max records allowed in the log */
#endif
#define ZRECORDS_DEFAULT        1024            /* default records in log if zrecs is not specificed in boot-args */

/*
 * Each record in the log contains a pointer to the zone element it refers to,
 * and a small array to hold the pc's from the stack trace.  A
 * record is added to the log each time a zalloc() is done in the zone_of_interest.  For leak debugging,
 * the record is cleared when a zfree() is done.  For corruption debugging, the log tracks both allocs and frees.
 * If the log fills, old records are replaced as if it were a circular buffer.
 */


/*
 * Opcodes for the btlog operation field:
 */

#define ZOP_ALLOC       1
#define ZOP_FREE        0

/*
 * Decide if we want to log this zone by doing a string compare between a zone name and the name
 * of the zone to log. Return true if the strings are equal, false otherwise.  Because it's not
 * possible to include spaces in strings passed in via the boot-args, a period in the logname will
 * match a space in the zone name.
 */

static int
log_this_zone(const char *zonename, const char *logname) 
{
        int len;
        const char *zc = zonename;
        const char *lc = logname;

        /*
         * Compare the strings.  We bound the compare by MAX_ZONE_NAME.
         */

        for (len = 1; len <= MAX_ZONE_NAME; zc++, lc++, len++) {

                /*
                 * If the current characters don't match, check for a space in
                 * in the zone name and a corresponding period in the log name.
                 * If that's not there, then the strings don't match.
                 */

                if (*zc != *lc && !(*zc == ' ' && *lc == '.')) 
                        break;

                /*
                 * The strings are equal so far.  If we're at the end, then it's a match.
                 */

                if (*zc == '\0')
                        return TRUE;
        }

        return FALSE;
}


/*
 * Test if we want to log this zalloc/zfree event.  We log if this is the zone we're interested in and
 * the buffer for the records has been allocated.
 */

#define DO_LOGGING(z)           (z->zone_logging == TRUE && z->zlog_btlog)

extern boolean_t kmem_alloc_ready;

#if CONFIG_ZLEAKS
#pragma mark -
#pragma mark Zone Leak Detection

/* 
 * The zone leak detector, abbreviated 'zleak', keeps track of a subset of the currently outstanding
 * allocations made by the zone allocator.  Every zleak_sample_factor allocations in each zone, we capture a
 * backtrace.  Every free, we examine the table and determine if the allocation was being tracked, 
 * and stop tracking it if it was being tracked.
 *
 * We track the allocations in the zallocations hash table, which stores the address that was returned from 
 * the zone allocator.  Each stored entry in the zallocations table points to an entry in the ztraces table, which
 * stores the backtrace associated with that allocation.  This provides uniquing for the relatively large
 * backtraces - we don't store them more than once.
 *
 * Data collection begins when the zone map is 50% full, and only occurs for zones that are taking up
 * a large amount of virtual space.
 */
#define ZLEAK_STATE_ENABLED             0x01    /* Zone leak monitoring should be turned on if zone_map fills up. */
#define ZLEAK_STATE_ACTIVE              0x02    /* We are actively collecting traces. */
#define ZLEAK_STATE_ACTIVATING          0x04    /* Some thread is doing setup; others should move along. */
#define ZLEAK_STATE_FAILED              0x08    /* Attempt to allocate tables failed.  We will not try again. */
uint32_t        zleak_state = 0;                /* State of collection, as above */

boolean_t       panic_include_ztrace    = FALSE;        /* Enable zleak logging on panic */
vm_size_t       zleak_global_tracking_threshold;        /* Size of zone map at which to start collecting data */
vm_size_t       zleak_per_zone_tracking_threshold;      /* Size a zone will have before we will collect data on it */
unsigned int    zleak_sample_factor     = 1000;         /* Allocations per sample attempt */

/*
 * Counters for allocation statistics.
 */ 

/* Times two active records want to occupy the same spot */
unsigned int z_alloc_collisions = 0;
unsigned int z_trace_collisions = 0;

/* Times a new record lands on a spot previously occupied by a freed allocation */
unsigned int z_alloc_overwrites = 0;
unsigned int z_trace_overwrites = 0;

/* Times a new alloc or trace is put into the hash table */
unsigned int z_alloc_recorded   = 0;
unsigned int z_trace_recorded   = 0;

/* Times zleak_log returned false due to not being able to acquire the lock */
unsigned int z_total_conflicts  = 0;


#pragma mark struct zallocation
/*
 * Structure for keeping track of an allocation
 * An allocation bucket is in use if its element is not NULL
 */
struct zallocation {
        uintptr_t               za_element;             /* the element that was zalloc'ed or zfree'ed, NULL if bucket unused */
        vm_size_t               za_size;                        /* how much memory did this allocation take up? */
        uint32_t                za_trace_index; /* index into ztraces for backtrace associated with allocation */
        /* TODO: #if this out */
        uint32_t                za_hit_count;           /* for determining effectiveness of hash function */
};

/* Size must be a power of two for the zhash to be able to just mask off bits instead of mod */
uint32_t zleak_alloc_buckets = CONFIG_ZLEAK_ALLOCATION_MAP_NUM;
uint32_t zleak_trace_buckets = CONFIG_ZLEAK_TRACE_MAP_NUM;

vm_size_t zleak_max_zonemap_size;

/* Hashmaps of allocations and their corresponding traces */
static struct zallocation*      zallocations;
static struct ztrace*           ztraces;

/* not static so that panic can see this, see kern/debug.c */
struct ztrace*                          top_ztrace;

/* Lock to protect zallocations, ztraces, and top_ztrace from concurrent modification. */
static lck_spin_t                       zleak_lock;
static lck_attr_t                       zleak_lock_attr;
static lck_grp_t                        zleak_lock_grp;
static lck_grp_attr_t                   zleak_lock_grp_attr;

/*
 * Initializes the zone leak monitor.  Called from zone_init()
 */
static void 
zleak_init(vm_size_t max_zonemap_size) 
{
        char                    scratch_buf[16];
        boolean_t               zleak_enable_flag = FALSE;

        zleak_max_zonemap_size = max_zonemap_size;
        zleak_global_tracking_threshold = max_zonemap_size / 2; 
        zleak_per_zone_tracking_threshold = zleak_global_tracking_threshold / 8;

        /* -zleakoff (flag to disable zone leak monitor) */
        if (PE_parse_boot_argn("-zleakoff", scratch_buf, sizeof(scratch_buf))) {
                zleak_enable_flag = FALSE;
                printf("zone leak detection disabled\n");
        } else {
                zleak_enable_flag = TRUE;
                printf("zone leak detection enabled\n");
        }
        
        /* zfactor=XXXX (override how often to sample the zone allocator) */
        if (PE_parse_boot_argn("zfactor", &zleak_sample_factor, sizeof(zleak_sample_factor))) {
                printf("Zone leak factor override: %u\n", zleak_sample_factor);
        }

        /* zleak-allocs=XXXX (override number of buckets in zallocations) */
        if (PE_parse_boot_argn("zleak-allocs", &zleak_alloc_buckets, sizeof(zleak_alloc_buckets))) {
                printf("Zone leak alloc buckets override: %u\n", zleak_alloc_buckets);
                /* uses 'is power of 2' trick: (0x01000 & 0x00FFF == 0) */
                if (zleak_alloc_buckets == 0 || (zleak_alloc_buckets & (zleak_alloc_buckets-1))) {
                        printf("Override isn't a power of two, bad things might happen!\n");
                }
        }
        
        /* zleak-traces=XXXX (override number of buckets in ztraces) */
        if (PE_parse_boot_argn("zleak-traces", &zleak_trace_buckets, sizeof(zleak_trace_buckets))) {
                printf("Zone leak trace buckets override: %u\n", zleak_trace_buckets);
                /* uses 'is power of 2' trick: (0x01000 & 0x00FFF == 0) */
                if (zleak_trace_buckets == 0 || (zleak_trace_buckets & (zleak_trace_buckets-1))) {
                        printf("Override isn't a power of two, bad things might happen!\n");
                }
        }
        
        /* allocate the zleak_lock */
        lck_grp_attr_setdefault(&zleak_lock_grp_attr);
        lck_grp_init(&zleak_lock_grp, "zleak_lock", &zleak_lock_grp_attr);
        lck_attr_setdefault(&zleak_lock_attr);
        lck_spin_init(&zleak_lock, &zleak_lock_grp, &zleak_lock_attr);
        
        if (zleak_enable_flag) {
                zleak_state = ZLEAK_STATE_ENABLED;
        }
}

#if CONFIG_ZLEAKS

/*
 * Support for kern.zleak.active sysctl - a simplified
 * version of the zleak_state variable.
 */
int
get_zleak_state(void)
{
        if (zleak_state & ZLEAK_STATE_FAILED)
                return (-1);
        if (zleak_state & ZLEAK_STATE_ACTIVE)
                return (1);
        return (0);
}

#endif


kern_return_t
zleak_activate(void)
{
        kern_return_t retval;
        vm_size_t z_alloc_size = zleak_alloc_buckets * sizeof(struct zallocation);
        vm_size_t z_trace_size = zleak_trace_buckets * sizeof(struct ztrace);
        void *allocations_ptr = NULL;
        void *traces_ptr = NULL;

        /* Only one thread attempts to activate at a time */
        if (zleak_state & (ZLEAK_STATE_ACTIVE | ZLEAK_STATE_ACTIVATING | ZLEAK_STATE_FAILED)) {
                return KERN_SUCCESS;
        }

        /* Indicate that we're doing the setup */
        lck_spin_lock(&zleak_lock);
        if (zleak_state & (ZLEAK_STATE_ACTIVE | ZLEAK_STATE_ACTIVATING | ZLEAK_STATE_FAILED)) {
                lck_spin_unlock(&zleak_lock);
                return KERN_SUCCESS;
        }

        zleak_state |= ZLEAK_STATE_ACTIVATING;
        lck_spin_unlock(&zleak_lock);

        /* Allocate and zero tables */
        retval = kmem_alloc_kobject(kernel_map, (vm_offset_t*)&allocations_ptr, z_alloc_size, VM_KERN_MEMORY_OSFMK);
        if (retval != KERN_SUCCESS) {
                goto fail;
        }

        retval = kmem_alloc_kobject(kernel_map, (vm_offset_t*)&traces_ptr, z_trace_size, VM_KERN_MEMORY_OSFMK);
        if (retval != KERN_SUCCESS) {
                goto fail;
        }

        bzero(allocations_ptr, z_alloc_size);
        bzero(traces_ptr, z_trace_size);

        /* Everything's set.  Install tables, mark active. */
        zallocations = allocations_ptr;
        ztraces = traces_ptr;

        /*
         * Initialize the top_ztrace to the first entry in ztraces, 
         * so we don't have to check for null in zleak_log
         */
        top_ztrace = &ztraces[0];

        /*
         * Note that we do need a barrier between installing
         * the tables and setting the active flag, because the zfree()
         * path accesses the table without a lock if we're active.
         */
        lck_spin_lock(&zleak_lock);
        zleak_state |= ZLEAK_STATE_ACTIVE;
        zleak_state &= ~ZLEAK_STATE_ACTIVATING;
        lck_spin_unlock(&zleak_lock);
        
        return 0;

fail:   
        /*
         * If we fail to allocate memory, don't further tax
         * the system by trying again.
         */
        lck_spin_lock(&zleak_lock);
        zleak_state |= ZLEAK_STATE_FAILED;
        zleak_state &= ~ZLEAK_STATE_ACTIVATING;
        lck_spin_unlock(&zleak_lock);

        if (allocations_ptr != NULL) {
                kmem_free(kernel_map, (vm_offset_t)allocations_ptr, z_alloc_size);
        }

        if (traces_ptr != NULL) {
                kmem_free(kernel_map, (vm_offset_t)traces_ptr, z_trace_size);
        }

        return retval;
}

/*
 * TODO: What about allocations that never get deallocated, 
 * especially ones with unique backtraces? Should we wait to record
 * until after boot has completed?  
 * (How many persistent zallocs are there?)
 */

/*
 * This function records the allocation in the allocations table, 
 * and stores the associated backtrace in the traces table 
 * (or just increments the refcount if the trace is already recorded)
 * If the allocation slot is in use, the old allocation is replaced with the new allocation, and
 * the associated trace's refcount is decremented.
 * If the trace slot is in use, it returns.
 * The refcount is incremented by the amount of memory the allocation consumes.
 * The return value indicates whether to try again next time.
 */
static boolean_t
zleak_log(uintptr_t* bt,
                  uintptr_t addr,
                  uint32_t depth,
                  vm_size_t allocation_size) 
{
        /* Quit if there's someone else modifying the hash tables */
        if (!lck_spin_try_lock(&zleak_lock)) {
                z_total_conflicts++;
                return FALSE;
        }
        
        struct zallocation* allocation  = &zallocations[hashaddr(addr, zleak_alloc_buckets)];
        
        uint32_t trace_index = hashbacktrace(bt, depth, zleak_trace_buckets);
        struct ztrace* trace = &ztraces[trace_index];
        
        allocation->za_hit_count++;
        trace->zt_hit_count++;
        
        /* 
         * If the allocation bucket we want to be in is occupied, and if the occupier
         * has the same trace as us, just bail.  
         */
        if (allocation->za_element != (uintptr_t) 0 && trace_index == allocation->za_trace_index) {
                z_alloc_collisions++;
                
                lck_spin_unlock(&zleak_lock);
                return TRUE;
        }
        
        /* STEP 1: Store the backtrace in the traces array. */
        /* A size of zero indicates that the trace bucket is free. */
        
        if (trace->zt_size > 0 && bcmp(trace->zt_stack, bt, (depth * sizeof(uintptr_t))) != 0 ) {
                /* 
                 * Different unique trace with same hash!
                 * Just bail - if we're trying to record the leaker, hopefully the other trace will be deallocated
                 * and get out of the way for later chances
                 */
                trace->zt_collisions++;
                z_trace_collisions++;
                
                lck_spin_unlock(&zleak_lock);
                return TRUE;
        } else if (trace->zt_size > 0) {
                /* Same trace, already added, so increment refcount */
                trace->zt_size += allocation_size;
        } else {
                /* Found an unused trace bucket, record the trace here! */
                if (trace->zt_depth != 0) /* if this slot was previously used but not currently in use */
                        z_trace_overwrites++;
                
                z_trace_recorded++;
                trace->zt_size                  = allocation_size;
                memcpy(trace->zt_stack, bt, (depth * sizeof(uintptr_t)) );
                
                trace->zt_depth         = depth;
                trace->zt_collisions    = 0;
        }
        
        /* STEP 2: Store the allocation record in the allocations array. */
        
        if (allocation->za_element != (uintptr_t) 0) {
                /* 
                 * Straight up replace any allocation record that was there.  We don't want to do the work
                 * to preserve the allocation entries that were there, because we only record a subset of the 
                 * allocations anyways.
                 */
                
                z_alloc_collisions++;
                
                struct ztrace* associated_trace = &ztraces[allocation->za_trace_index];
                /* Knock off old allocation's size, not the new allocation */
                associated_trace->zt_size -= allocation->za_size;
        } else if (allocation->za_trace_index != 0) {
                /* Slot previously used but not currently in use */
                z_alloc_overwrites++;
        }

        allocation->za_element          = addr;
        allocation->za_trace_index      = trace_index;
        allocation->za_size             = allocation_size;
        
        z_alloc_recorded++;
        
        if (top_ztrace->zt_size < trace->zt_size)
                top_ztrace = trace;
        
        lck_spin_unlock(&zleak_lock);
        return TRUE;
}

/*
 * Free the allocation record and release the stacktrace.
 * This should be as fast as possible because it will be called for every free.
 */
static void
zleak_free(uintptr_t addr,
                   vm_size_t allocation_size) 
{
        if (addr == (uintptr_t) 0)
                return;
        
        struct zallocation* allocation = &zallocations[hashaddr(addr, zleak_alloc_buckets)];
        
        /* Double-checked locking: check to find out if we're interested, lock, check to make
         * sure it hasn't changed, then modify it, and release the lock.
         */
        
        if (allocation->za_element == addr && allocation->za_trace_index < zleak_trace_buckets) {
                /* if the allocation was the one, grab the lock, check again, then delete it */
                lck_spin_lock(&zleak_lock);
                
                if (allocation->za_element == addr && allocation->za_trace_index < zleak_trace_buckets) {
                        struct ztrace *trace;

                        /* allocation_size had better match what was passed into zleak_log - otherwise someone is freeing into the wrong zone! */
                        if (allocation->za_size != allocation_size) {
                                panic("Freeing as size %lu memory that was allocated with size %lu\n", 
                                                (uintptr_t)allocation_size, (uintptr_t)allocation->za_size);
                        }
                        
                        trace = &ztraces[allocation->za_trace_index];
                        
                        /* size of 0 indicates trace bucket is unused */
                        if (trace->zt_size > 0) {
                                trace->zt_size -= allocation_size;
                        }
                        
                        /* A NULL element means the allocation bucket is unused */
                        allocation->za_element = 0;
                }
                lck_spin_unlock(&zleak_lock);
        }
}

#endif /* CONFIG_ZLEAKS */

/*  These functions outside of CONFIG_ZLEAKS because they are also used in
 *  mbuf.c for mbuf leak-detection.  This is why they lack the z_ prefix.
 */

/* "Thomas Wang's 32/64 bit mix functions."  http://www.concentric.net/~Ttwang/tech/inthash.htm */
uintptr_t
hash_mix(uintptr_t x)
{
#ifndef __LP64__
        x += ~(x << 15);
        x ^=  (x >> 10);
        x +=  (x << 3 );
        x ^=  (x >> 6 );
        x += ~(x << 11);
        x ^=  (x >> 16);
#else
        x += ~(x << 32);
        x ^=  (x >> 22);
        x += ~(x << 13);
        x ^=  (x >> 8 );
        x +=  (x << 3 );
        x ^=  (x >> 15);
        x += ~(x << 27);
        x ^=  (x >> 31);
#endif
        return x;
}

uint32_t
hashbacktrace(uintptr_t* bt, uint32_t depth, uint32_t max_size)
{

        uintptr_t hash = 0;
        uintptr_t mask = max_size - 1;

        while (depth) {
                hash += bt[--depth];
        }

        hash = hash_mix(hash) & mask;

        assert(hash < max_size);

        return (uint32_t) hash;
}

/*
 *  TODO: Determine how well distributed this is
 *      max_size must be a power of 2. i.e 0x10000 because 0x10000-1 is 0x0FFFF which is a great bitmask
 */
uint32_t
hashaddr(uintptr_t pt, uint32_t max_size)
{
        uintptr_t hash = 0;
        uintptr_t mask = max_size - 1;

        hash = hash_mix(pt) & mask;

        assert(hash < max_size);

        return (uint32_t) hash;
}

/* End of all leak-detection code */
#pragma mark -

#define ZONE_MAX_ALLOC_SIZE     (32 * 1024) 
#define ZONE_ALLOC_FRAG_PERCENT(alloc_size, ele_size) (((alloc_size % ele_size) * 100) / alloc_size)

/*
 *      zinit initializes a new zone.  The zone data structures themselves
 *      are stored in a zone, which is initially a static structure that
 *      is initialized by zone_init.
 */
zone_t
zinit(
        vm_size_t       size,           /* the size of an element */
        vm_size_t       max,            /* maximum memory to use */
        vm_size_t       alloc,          /* allocation size */
        const char      *name)          /* a name for the zone */
{
        zone_t          z;

        simple_lock(&all_zones_lock);
        z = &(zone_array[zone_array_index]);
        zone_array_index++;
        assert(zone_array_index != MAX_ZONES);
        simple_unlock(&all_zones_lock);

        /* Zone elements must fit both a next pointer and a backup pointer */
        vm_size_t  minimum_element_size = sizeof(vm_offset_t) * 2;
        if (size < minimum_element_size)
                size = minimum_element_size;

        /*
         *  Round element size to a multiple of sizeof(pointer)
         *  This also enforces that allocations will be aligned on pointer boundaries
         */
        size = ((size-1) + sizeof(vm_offset_t)) -
               ((size-1) % sizeof(vm_offset_t));

        if (alloc == 0)
                alloc = PAGE_SIZE;

        alloc = round_page(alloc);
        max   = round_page(max);

        vm_size_t best_alloc = PAGE_SIZE;
        vm_size_t alloc_size;
        for (alloc_size = (2 * PAGE_SIZE); alloc_size <= ZONE_MAX_ALLOC_SIZE; alloc_size += PAGE_SIZE) {
                if (ZONE_ALLOC_FRAG_PERCENT(alloc_size, size) < ZONE_ALLOC_FRAG_PERCENT(best_alloc, size)) {
                        best_alloc = alloc_size;
                }
        }
        alloc = best_alloc;
        if (max && (max < alloc))
                max = alloc;

        z->free_elements = NULL;
        queue_init(&z->pages.any_free_foreign);
        queue_init(&z->pages.all_free);
        queue_init(&z->pages.intermediate);
        queue_init(&z->pages.all_used);
        z->cur_size = 0;
        z->page_count = 0;
        z->max_size = max;
        z->elem_size = size;
        z->alloc_size = alloc;
        z->zone_name = name;
        z->count = 0;
        z->countfree = 0;
        z->count_all_free_pages = 0;
        z->sum_count = 0LL;
        z->doing_alloc_without_vm_priv = FALSE;
        z->doing_alloc_with_vm_priv = FALSE;
        z->exhaustible = FALSE;
        z->collectable = TRUE;
        z->allows_foreign = FALSE;
        z->expandable  = TRUE;
        z->waiting = FALSE;
        z->async_pending = FALSE;
        z->caller_acct = TRUE;
        z->noencrypt = FALSE;
        z->no_callout = FALSE;
        z->async_prio_refill = FALSE;
        z->gzalloc_exempt = FALSE;
        z->alignment_required = FALSE;
        z->zone_replenishing = FALSE;
        z->prio_refill_watermark = 0;
        z->zone_replenish_thread = NULL;
        z->zp_count = 0;

#if CONFIG_ZLEAKS
        z->zleak_capture = 0;
        z->zleak_on = FALSE;
#endif /* CONFIG_ZLEAKS */

        lock_zone_init(z);

        /*
         *      Add the zone to the all-zones list.
         */
        simple_lock(&all_zones_lock);
        z->index = num_zones;
        num_zones++;
        simple_unlock(&all_zones_lock);

        /*
         * Check for and set up zone leak detection if requested via boot-args.  We recognized two
         * boot-args:
         *
         *      zlog=<zone_to_log>
         *      zrecs=<num_records_in_log>
         *
         * The zlog arg is used to specify the zone name that should be logged, and zrecs is used to
         * control the size of the log.  If zrecs is not specified, a default value is used.
         */

        if (num_zones_logged < max_num_zones_to_log) {

                int             i = 1; /* zlog0 isn't allowed. */
                boolean_t       zone_logging_enabled = FALSE;
                char            zlog_name[MAX_ZONE_NAME] = ""; /* Temp. buffer to create the strings zlog1, zlog2 etc... */

                while (i <= max_num_zones_to_log) {

                        snprintf(zlog_name, MAX_ZONE_NAME, "zlog%d", i);

                        if (PE_parse_boot_argn(zlog_name, zone_name_to_log, sizeof(zone_name_to_log)) == TRUE) {
                                if (log_this_zone(z->zone_name, zone_name_to_log)) {
                                        z->zone_logging = TRUE;
                                        zone_logging_enabled = TRUE;
                                        num_zones_logged++;
                                        break;
                                }
                        }
                        i++;
                }

                if (zone_logging_enabled == FALSE) {
                        /* 
                         * Backwards compat. with the old boot-arg used to specify single zone logging i.e. zlog
                         * Needs to happen after the newer zlogn checks because the prefix will match all the zlogn
                         * boot-args.
                         */
                        if (PE_parse_boot_argn("zlog", zone_name_to_log, sizeof(zone_name_to_log)) == TRUE) {
                                if (log_this_zone(z->zone_name, zone_name_to_log)) {
                                                z->zone_logging = TRUE;
                                                zone_logging_enabled = TRUE;
                                                num_zones_logged++;
                                }
                        }
                }

                if (log_records_init == FALSE && zone_logging_enabled == TRUE) {
                    if (PE_parse_boot_argn("zrecs", &log_records, sizeof(log_records)) == TRUE) {
                                /*
                                 * Don't allow more than ZRECORDS_MAX records even if the user asked for more.
                                 * This prevents accidentally hogging too much kernel memory and making the system
                                 * unusable.
                                 */

                                log_records = MIN(ZRECORDS_MAX, log_records);
                                log_records_init = TRUE;
                        } else {
                                log_records = ZRECORDS_DEFAULT;
                                log_records_init = TRUE;
                        }
                }

                /*
                 * If we want to log a zone, see if we need to allocate buffer space for the log.  Some vm related zones are
                 * zinit'ed before we can do a kmem_alloc, so we have to defer allocation in that case.  kmem_alloc_ready is set to
                 * TRUE once enough of the VM system is up and running to allow a kmem_alloc to work.  If we want to log one
                 * of the VM related zones that's set up early on, we will skip allocation of the log until zinit is called again
                 * later on some other zone.  So note we may be allocating a buffer to log a zone other than the one being initialized
                 * right now.
                 */
                if (kmem_alloc_ready) {

                        zone_t curr_zone = NULL;
                        unsigned int max_zones = 0, zone_idx = 0;

                        simple_lock(&all_zones_lock);
                        max_zones = num_zones;
                        simple_unlock(&all_zones_lock);

                        for (zone_idx = 0; zone_idx < max_zones; zone_idx++) {

                                curr_zone = &(zone_array[zone_idx]);

                                /*
                                 * We work with the zone unlocked here because we could end up needing the zone lock to
                                 * enable logging for this zone e.g. need a VM object to allocate memory to enable logging for the
                                 * VM objects zone.
                                 *
                                 * We don't expect these zones to be needed at this early a time in boot and so take this chance.
                                 */
                                if (curr_zone->zone_logging && curr_zone->zlog_btlog == NULL) {

                                        curr_zone->zlog_btlog = btlog_create(log_records, MAX_ZTRACE_DEPTH, (corruption_debug_flag == FALSE) /* caller_will_remove_entries_for_element? */);

                                        if (curr_zone->zlog_btlog) {

                                                printf("zone: logging started for zone %s\n", curr_zone->zone_name);
                                        } else {
                                                printf("zone: couldn't allocate memory for zrecords, turning off zleak logging\n");
                                                curr_zone->zone_logging = FALSE;
                                        }
                                }

                        }
                }
        }

#if     CONFIG_GZALLOC  
        gzalloc_zone_init(z);
#endif
        return(z);
}
unsigned        zone_replenish_loops, zone_replenish_wakeups, zone_replenish_wakeups_initiated, zone_replenish_throttle_count;

static void zone_replenish_thread(zone_t);

/* High priority VM privileged thread used to asynchronously refill a designated
 * zone, such as the reserved VM map entry zone.
 */
__attribute__((noreturn))
static void
zone_replenish_thread(zone_t z)
{
        vm_size_t free_size;
        current_thread()->options |= TH_OPT_VMPRIV;

        for (;;) {
                lock_zone(z);
                z->zone_replenishing = TRUE;
                assert(z->prio_refill_watermark != 0);
                while ((free_size = (z->cur_size - (z->count * z->elem_size))) < (z->prio_refill_watermark * z->elem_size)) {
                        assert(z->doing_alloc_without_vm_priv == FALSE);
                        assert(z->doing_alloc_with_vm_priv == FALSE);
                        assert(z->async_prio_refill == TRUE);

                        unlock_zone(z);
                        int     zflags = KMA_KOBJECT|KMA_NOPAGEWAIT;
                        vm_offset_t space, alloc_size;
                        kern_return_t kr;
                                
                        if (vm_pool_low())
                                alloc_size = round_page(z->elem_size);
                        else
                                alloc_size = z->alloc_size;
                                
                        if (z->noencrypt)
                                zflags |= KMA_NOENCRYPT;
                                
                        kr = kernel_memory_allocate(zone_map, &space, alloc_size, 0, zflags, VM_KERN_MEMORY_ZONE);

                        if (kr == KERN_SUCCESS) {
                                zcram(z, space, alloc_size);
                        } else if (kr == KERN_RESOURCE_SHORTAGE) {
                                VM_PAGE_WAIT();
                        } else if (kr == KERN_NO_SPACE) {
                                kr = kernel_memory_allocate(kernel_map, &space, alloc_size, 0, zflags, VM_KERN_MEMORY_ZONE);
                                if (kr == KERN_SUCCESS) {
                                        zcram(z, space, alloc_size);
                                } else {
                                        assert_wait_timeout(&z->zone_replenish_thread, THREAD_UNINT, 1, 100 * NSEC_PER_USEC);
                                        thread_block(THREAD_CONTINUE_NULL);
                                }
                        }

                        lock_zone(z);
                        zone_replenish_loops++;
                }

                z->zone_replenishing = FALSE;
                /* Signal any potential throttled consumers, terminating
                 * their timer-bounded waits.
                 */
                thread_wakeup(z);

                assert_wait(&z->zone_replenish_thread, THREAD_UNINT);
                unlock_zone(z);
                thread_block(THREAD_CONTINUE_NULL);
                zone_replenish_wakeups++;
        }
}

void
zone_prio_refill_configure(zone_t z, vm_size_t low_water_mark) {
        z->prio_refill_watermark = low_water_mark;

        z->async_prio_refill = TRUE;
        OSMemoryBarrier();
        kern_return_t tres = kernel_thread_start_priority((thread_continue_t)zone_replenish_thread, z, MAXPRI_KERNEL, &z->zone_replenish_thread);

        if (tres != KERN_SUCCESS) {
                panic("zone_prio_refill_configure, thread create: 0x%x", tres);
        }

        thread_deallocate(z->zone_replenish_thread);
}

/* Initialize the metadata for an allocation chunk */
static inline void
zcram_metadata_init(vm_offset_t newmem, vm_size_t size, struct zone_page_metadata *chunk_metadata)
{
        struct zone_page_metadata *page_metadata;

        /* The first page is the real metadata for this allocation chunk. We mark the others as fake metadata */
        size -= PAGE_SIZE;
        newmem += PAGE_SIZE;

        for (; size > 0; newmem += PAGE_SIZE, size -= PAGE_SIZE) {
                page_metadata = get_zone_page_metadata((struct zone_free_element *)newmem, TRUE);
                assert(page_metadata != chunk_metadata);
                PAGE_METADATA_SET_ZINDEX(page_metadata, MULTIPAGE_METADATA_MAGIC);
                page_metadata_set_realmeta(page_metadata, chunk_metadata);
                page_metadata->free_count = 0;
        }
        return;
}


/*
 * Boolean Random Number Generator for generating booleans to randomize 
 * the order of elements in newly zcram()'ed memory. The algorithm is a 
 * modified version of the KISS RNG proposed in the paper:
 * http://stat.fsu.edu/techreports/M802.pdf
 * The modifications have been documented in the technical paper 
 * paper from UCL:
 * http://www0.cs.ucl.ac.uk/staff/d.jones/GoodPracticeRNG.pdf 
 */

static void random_bool_gen_entropy(
                int     *buffer,
                int     count)
{

        int i, t;
        simple_lock(&bool_gen_lock);
        for (i = 0; i < count; i++) {
                bool_gen_seed[1] ^= (bool_gen_seed[1] << 5);
                bool_gen_seed[1] ^= (bool_gen_seed[1] >> 7);
                bool_gen_seed[1] ^= (bool_gen_seed[1] << 22);
                t = bool_gen_seed[2] + bool_gen_seed[3] + bool_gen_global;
                bool_gen_seed[2] = bool_gen_seed[3];
                bool_gen_global = t < 0;
                bool_gen_seed[3] = t &2147483647;
                bool_gen_seed[0] += 1411392427;
                buffer[i] = (bool_gen_seed[0] + bool_gen_seed[1] + bool_gen_seed[3]);
        }
        simple_unlock(&bool_gen_lock);
}

static boolean_t random_bool_gen(
                int     *buffer,
                int     index,
                int     bufsize)
{
        int valindex, bitpos;
        valindex = (index / (8 * sizeof(int))) % bufsize;
        bitpos = index % (8 * sizeof(int));
        return (boolean_t)(buffer[valindex] & (1 << bitpos));
} 

static void 
random_free_to_zone(
                        zone_t          zone,
                        vm_offset_t     newmem,
                        vm_offset_t     first_element_offset,
                        int             element_count,
                        int             *entropy_buffer)
{
        vm_offset_t     last_element_offset;
        vm_offset_t     element_addr;
        vm_size_t       elem_size;
        int             index;  

        elem_size = zone->elem_size;
        last_element_offset = first_element_offset + ((element_count * elem_size) - elem_size);
        for (index = 0; index < element_count; index++) {
                assert(first_element_offset <= last_element_offset);
                if (
#if DEBUG || DEVELOPMENT
                leak_scan_debug_flag ||
#endif /* DEBUG || DEVELOPMENT */
                random_bool_gen(entropy_buffer, index, MAX_ENTROPY_PER_ZCRAM)) {
                        element_addr = newmem + first_element_offset;
                        first_element_offset += elem_size;
                } else {
                        element_addr = newmem + last_element_offset;
                        last_element_offset -= elem_size;
                }
                if (element_addr != (vm_offset_t)zone) {
                        zone->count++;  /* compensate for free_to_zone */
                        free_to_zone(zone, element_addr, FALSE);
                }
                zone->cur_size += elem_size;
        }
}

/*
 *      Cram the given memory into the specified zone. Update the zone page count accordingly.
 */
void
zcram(
        zone_t          zone,
        vm_offset_t                     newmem,
        vm_size_t               size)
{
        vm_size_t       elem_size;
        boolean_t   from_zm = FALSE;
        int element_count;
        int entropy_buffer[MAX_ENTROPY_PER_ZCRAM];

        /* Basic sanity checks */
        assert(zone != ZONE_NULL && newmem != (vm_offset_t)0);
        assert(!zone->collectable || zone->allows_foreign
                || (from_zone_map(newmem, size)));

        elem_size = zone->elem_size;

        KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_ZALLOC, ZALLOC_ZCRAM) | DBG_FUNC_START, VM_KERNEL_ADDRPERM(zone), size, 0, 0, 0);

        if (from_zone_map(newmem, size))
                from_zm = TRUE;

        if (!from_zm) {
                /* We cannot support elements larger than page size for foreign memory because we 
                 * put metadata on the page itself for each page of foreign memory. We need to do 
                 * this in order to be able to reach the metadata when any element is freed 
                 */
                assert((zone->allows_foreign == TRUE) && (zone->elem_size <= (PAGE_SIZE - sizeof(struct zone_page_metadata))));
        } 

        if (zalloc_debug & ZALLOC_DEBUG_ZCRAM)
                kprintf("zcram(%p[%s], 0x%lx%s, 0x%lx)\n", zone, zone->zone_name,
                                (unsigned long)newmem, from_zm ? "" : "[F]", (unsigned long)size);

        ZONE_PAGE_COUNT_INCR(zone, (size / PAGE_SIZE));

        random_bool_gen_entropy(entropy_buffer, MAX_ENTROPY_PER_ZCRAM);
        
        /* 
         * Initialize the metadata for all pages. We dont need the zone lock 
         * here because we are not manipulating any zone related state yet.
         */

        struct zone_page_metadata *chunk_metadata;
        size_t zone_page_metadata_size = sizeof(struct zone_page_metadata);

        assert((newmem & PAGE_MASK) == 0);
        assert((size & PAGE_MASK) == 0);

        chunk_metadata = get_zone_page_metadata((struct zone_free_element *)newmem, TRUE);
        chunk_metadata->pages.next = NULL;
        chunk_metadata->pages.prev = NULL;
        page_metadata_set_freelist(chunk_metadata, 0);
        PAGE_METADATA_SET_ZINDEX(chunk_metadata, zone->index);
        chunk_metadata->free_count = 0;
        chunk_metadata->page_count = (size / PAGE_SIZE);

        zcram_metadata_init(newmem, size, chunk_metadata);

        lock_zone(zone);
        enqueue_tail(&zone->pages.all_used, &(chunk_metadata->pages));

        if (!from_zm) {
                /* We cannot support elements larger than page size for foreign memory because we 
                 * put metadata on the page itself for each page of foreign memory. We need to do 
                 * this in order to be able to reach the metadata when any element is freed 
                 */

                for (; size > 0; newmem += PAGE_SIZE, size -= PAGE_SIZE) {
                        vm_offset_t first_element_offset = 0;
                        if (zone_page_metadata_size % ZONE_ELEMENT_ALIGNMENT == 0){
                                first_element_offset = zone_page_metadata_size;
                        } else {
                                first_element_offset = zone_page_metadata_size + (ZONE_ELEMENT_ALIGNMENT - (zone_page_metadata_size % ZONE_ELEMENT_ALIGNMENT));
                        }
                        element_count = (int)((PAGE_SIZE - first_element_offset) / elem_size);
                        random_free_to_zone(zone, newmem, first_element_offset, element_count, entropy_buffer);                         
                }
        } else {
                element_count = (int)(size / elem_size);
                random_free_to_zone(zone, newmem, 0, element_count, entropy_buffer);    
        }
        unlock_zone(zone);
        
        KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_ZALLOC, ZALLOC_ZCRAM) | DBG_FUNC_END, VM_KERNEL_ADDRPERM(zone), 0, 0, 0, 0);

}

/*
 * Fill a zone with enough memory to contain at least nelem elements.
 * Memory is obtained with kmem_alloc_kobject from the kernel_map.
 * Return the number of elements actually put into the zone, which may
 * be more than the caller asked for since the memory allocation is
 * rounded up to a full page.
 */
int
zfill(
        zone_t  zone,
        int     nelem)
{
        kern_return_t   kr;
        vm_size_t       size;
        vm_offset_t     memory;
        int             nalloc;

        assert(nelem > 0);
        if (nelem <= 0)
                return 0;
        size = nelem * zone->elem_size;
        size = round_page(size);
        kr = kmem_alloc_kobject(kernel_map, &memory, size, VM_KERN_MEMORY_ZONE);
        if (kr != KERN_SUCCESS)
                return 0;

        zone_change(zone, Z_FOREIGN, TRUE);
        zcram(zone, memory, size);
        nalloc = (int)(size / zone->elem_size);
        assert(nalloc >= nelem);

        return nalloc;
}

/*
 *      Initialize the "zone of zones" which uses fixed memory allocated
 *      earlier in memory initialization.  zone_bootstrap is called
 *      before zone_init.
 */
void
zone_bootstrap(void)
{
        char temp_buf[16];
        unsigned int i;

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

        /* Set up zone element poisoning */
        zp_init();

        /* Seed the random boolean generator for elements in zone free list */
        for (i = 0; i < RANDOM_BOOL_GEN_SEED_COUNT; i++) {
                bool_gen_seed[i] = (unsigned int)early_random();
        }
        simple_lock_init(&bool_gen_lock, 0);

        /* should zlog log to debug zone corruption instead of leaks? */
        if (PE_parse_boot_argn("-zc", temp_buf, sizeof(temp_buf))) {
                corruption_debug_flag = TRUE;
        }       

#if DEBUG || DEVELOPMENT
        /* disable element location randomization in a page */
        if (PE_parse_boot_argn("-zl", temp_buf, sizeof(temp_buf))) {
                leak_scan_debug_flag = TRUE;
        }
#endif

        simple_lock_init(&all_zones_lock, 0);

        num_zones = 0;
        thread_call_setup(&call_async_alloc, zalloc_async, NULL);

        /* initializing global lock group for zones */
        lck_grp_attr_setdefault(&zone_locks_grp_attr);
        lck_grp_init(&zone_locks_grp, "zone_locks", &zone_locks_grp_attr);

        lck_attr_setdefault(&zone_metadata_lock_attr); 
        lck_mtx_init_ext(&zone_metadata_region_lck, &zone_metadata_region_lck_ext, &zone_locks_grp, &zone_metadata_lock_attr);
}

/* Global initialization of Zone Allocator.
 * Runs after zone_bootstrap.
 */
void
zone_init(
        vm_size_t max_zonemap_size)
{
        kern_return_t   retval;
        vm_offset_t     zone_min;
        vm_offset_t     zone_max;
        vm_offset_t     zone_metadata_space;
        unsigned int    zone_pages;

        retval = kmem_suballoc(kernel_map, &zone_min, max_zonemap_size,
                               FALSE, VM_FLAGS_ANYWHERE | VM_FLAGS_PERMANENT | VM_MAKE_TAG(VM_KERN_MEMORY_ZONE),
                               &zone_map);

        if (retval != KERN_SUCCESS)
                panic("zone_init: kmem_suballoc failed");
        zone_max = zone_min + round_page(max_zonemap_size);
#if     CONFIG_GZALLOC
        gzalloc_init(max_zonemap_size);
#endif
        /*
         * Setup garbage collection information:
         */
        zone_map_min_address = zone_min;
        zone_map_max_address = zone_max;

        zone_pages = (unsigned int)atop_kernel(zone_max - zone_min);
        zone_metadata_space = round_page(zone_pages * sizeof(struct zone_page_metadata));
        retval = kernel_memory_allocate(zone_map, &zone_metadata_region_min, zone_metadata_space,
                                        0, KMA_KOBJECT | KMA_VAONLY | KMA_PERMANENT, VM_KERN_MEMORY_OSFMK);
        if (retval != KERN_SUCCESS)
                panic("zone_init: zone_metadata_region initialization failed!");
        zone_metadata_region_max = zone_metadata_region_min + zone_metadata_space;

#if defined(__LP64__)
        /*
         * ensure that any vm_page_t that gets created from
         * the vm_page zone can be packed properly (see vm_page.h
         * for the packing requirements
         */
        if ((vm_page_t)(VM_PAGE_UNPACK_PTR(VM_PAGE_PACK_PTR(zone_metadata_region_max))) != (vm_page_t)zone_metadata_region_max)
                panic("VM_PAGE_PACK_PTR failed on zone_metadata_region_max - %p", (void *)zone_metadata_region_max);

        if ((vm_page_t)(VM_PAGE_UNPACK_PTR(VM_PAGE_PACK_PTR(zone_map_max_address))) != (vm_page_t)zone_map_max_address)
                panic("VM_PAGE_PACK_PTR failed on zone_map_max_address - %p", (void *)zone_map_max_address);
#endif

        lck_grp_attr_setdefault(&zone_gc_lck_grp_attr);
        lck_grp_init(&zone_gc_lck_grp, "zone_gc", &zone_gc_lck_grp_attr);
        lck_attr_setdefault(&zone_gc_lck_attr);
        lck_mtx_init_ext(&zone_gc_lock, &zone_gc_lck_ext, &zone_gc_lck_grp, &zone_gc_lck_attr);
        
#if CONFIG_ZLEAKS
        /*
         * Initialize the zone leak monitor
         */
        zleak_init(max_zonemap_size);
#endif /* CONFIG_ZLEAKS */
}

extern volatile SInt32 kfree_nop_count;

#pragma mark -
#pragma mark zalloc_canblock

/*
 *      zalloc returns an element from the specified zone.
 */
static void *
zalloc_internal(
        zone_t  zone,
        boolean_t canblock,
        boolean_t nopagewait)
{
        vm_offset_t     addr = 0;
        kern_return_t   retval;
        uintptr_t       zbt[MAX_ZTRACE_DEPTH];  /* used in zone leak logging and zone leak detection */
        int             numsaved = 0;
        boolean_t       zone_replenish_wakeup = FALSE, zone_alloc_throttle = FALSE;
#if     CONFIG_GZALLOC
        boolean_t       did_gzalloc = FALSE;
#endif
        thread_t thr = current_thread();
        boolean_t       check_poison = FALSE;
        boolean_t       set_doing_alloc_with_vm_priv = FALSE;

#if CONFIG_ZLEAKS
        uint32_t        zleak_tracedepth = 0;  /* log this allocation if nonzero */
#endif /* CONFIG_ZLEAKS */

        assert(zone != ZONE_NULL);

#if     CONFIG_GZALLOC
        addr = gzalloc_alloc(zone, canblock);
        did_gzalloc = (addr != 0);
#endif

        /*
         * If zone logging is turned on and this is the zone we're tracking, grab a backtrace.
         */
        if (__improbable(DO_LOGGING(zone)))
                numsaved = OSBacktrace((void*) zbt, MAX_ZTRACE_DEPTH);

#if CONFIG_ZLEAKS
        /*
         * Zone leak detection: capture a backtrace every zleak_sample_factor
         * allocations in this zone.
         */
        if (__improbable(zone->zleak_on && sample_counter(&zone->zleak_capture, zleak_sample_factor) == TRUE)) {
                /* Avoid backtracing twice if zone logging is on */
                if (numsaved == 0)
                        zleak_tracedepth = backtrace(zbt, MAX_ZTRACE_DEPTH);
                else
                        zleak_tracedepth = numsaved;
        }
#endif /* CONFIG_ZLEAKS */

        lock_zone(zone);

        if (zone->async_prio_refill && zone->zone_replenish_thread) {
                    do {
                            vm_size_t zfreec = (zone->cur_size - (zone->count * zone->elem_size));
                            vm_size_t zrefillwm = zone->prio_refill_watermark * zone->elem_size;
                            zone_replenish_wakeup = (zfreec < zrefillwm);
                            zone_alloc_throttle = (zfreec < (zrefillwm / 2)) && ((thr->options & TH_OPT_VMPRIV) == 0);

                            if (zone_replenish_wakeup) {
                                    zone_replenish_wakeups_initiated++;
                                    /* Signal the potentially waiting
                                     * refill thread.
                                     */
                                    thread_wakeup(&zone->zone_replenish_thread);
                                    unlock_zone(zone);
                                    /* Scheduling latencies etc. may prevent
                                     * the refill thread from keeping up
                                     * with demand. Throttle consumers
                                     * when we fall below half the
                                     * watermark, unless VM privileged
                                     */
                                    if (zone_alloc_throttle) {
                                            zone_replenish_throttle_count++;
                                            assert_wait_timeout(zone, THREAD_UNINT, 1, NSEC_PER_MSEC);
                                            thread_block(THREAD_CONTINUE_NULL);
                                    }
                                    lock_zone(zone);
                            }
                    } while (zone_alloc_throttle == TRUE);
        }
        
        if (__probable(addr == 0))
                addr = try_alloc_from_zone(zone, &check_poison);


        while ((addr == 0) && canblock) {
                /*
                 * zone is empty, try to expand it
                 * 
                 * Note that we now allow up to 2 threads (1 vm_privliged and 1 non-vm_privliged)
                 * to expand the zone concurrently...  this is necessary to avoid stalling
                 * vm_privileged threads running critical code necessary to continue compressing/swapping
                 * pages (i.e. making new free pages) from stalling behind non-vm_privileged threads
                 * waiting to acquire free pages when the vm_page_free_count is below the
                 * vm_page_free_reserved limit.
                 */
                if ((zone->doing_alloc_without_vm_priv || zone->doing_alloc_with_vm_priv) &&
                    (((thr->options & TH_OPT_VMPRIV) == 0) || zone->doing_alloc_with_vm_priv)) {
                        /*
                         * This is a non-vm_privileged thread and a non-vm_privileged or
                         * a vm_privileged thread is already expanding the zone...
                         *    OR
                         * this is a vm_privileged thread and a vm_privileged thread is
                         * already expanding the zone...
                         *
                         * In either case wait for a thread to finish, then try again.
                         */
                        zone->waiting = TRUE;
                        zone_sleep(zone);
                } else {
                        vm_offset_t space;
                        vm_size_t alloc_size;
                        int retry = 0;

                        if ((zone->cur_size + zone->elem_size) >
                            zone->max_size) {
                                if (zone->exhaustible)
                                        break;
                                if (zone->expandable) {
                                        /*
                                         * We're willing to overflow certain
                                         * zones, but not without complaining.
                                         *
                                         * This is best used in conjunction
                                         * with the collectable flag. What we
                                         * want is an assurance we can get the
                                         * memory back, assuming there's no
                                         * leak. 
                                         */
                                        zone->max_size += (zone->max_size >> 1);
                                } else {
                                        unlock_zone(zone);

                                        panic_include_zprint = TRUE;
#if CONFIG_ZLEAKS
                                        if (zleak_state & ZLEAK_STATE_ACTIVE)
                                                panic_include_ztrace = TRUE;
#endif /* CONFIG_ZLEAKS */
                                        panic("zalloc: zone \"%s\" empty.", zone->zone_name);
                                }
                        }
                        /* 
                         * It is possible that a BG thread is refilling/expanding the zone
                         * and gets pre-empted during that operation. That blocks all other
                         * threads from making progress leading to a watchdog timeout. To
                         * avoid that, boost the thread priority using the rwlock boost
                         */
                        set_thread_rwlock_boost();
                        
                        if ((thr->options & TH_OPT_VMPRIV)) {
                                zone->doing_alloc_with_vm_priv = TRUE;
                                set_doing_alloc_with_vm_priv = TRUE;
                        } else {
                                zone->doing_alloc_without_vm_priv = TRUE;
                        }
                        unlock_zone(zone);

                        for (;;) {
                                int     zflags = KMA_KOBJECT|KMA_NOPAGEWAIT;

                                if (vm_pool_low() || retry >= 1)
                                        alloc_size = 
                                                round_page(zone->elem_size);
                                else
                                        alloc_size = zone->alloc_size;
                                
                                if (zone->noencrypt)
                                        zflags |= KMA_NOENCRYPT;
                                
                                retval = kernel_memory_allocate(zone_map, &space, alloc_size, 0, zflags, VM_KERN_MEMORY_ZONE);
                                if (retval == KERN_SUCCESS) {
#if CONFIG_ZLEAKS
                                        if ((zleak_state & (ZLEAK_STATE_ENABLED | ZLEAK_STATE_ACTIVE)) == ZLEAK_STATE_ENABLED) {
                                                if (zone_map->size >= zleak_global_tracking_threshold) {
                                                        kern_return_t kr;
                                                        
                                                        kr = zleak_activate();
                                                        if (kr != KERN_SUCCESS) {
                                                                printf("Failed to activate live zone leak debugging (%d).\n", kr);
                                                        }
                                                }
                                        }
                                        
                                        if ((zleak_state & ZLEAK_STATE_ACTIVE) && !(zone->zleak_on)) {
                                                if (zone->cur_size > zleak_per_zone_tracking_threshold) {
                                                        zone->zleak_on = TRUE;
                                                }       
                                        }
#endif /* CONFIG_ZLEAKS */
                                        zcram(zone, space, alloc_size);
                                        
                                        break;
                                } else if (retval != KERN_RESOURCE_SHORTAGE) {
                                        retry++;
                                        
                                        if (retry == 2) {
                                                zone_gc();
                                                printf("zalloc did gc\n");
                                                zone_display_zprint();
                                        }
                                        if (retry == 3) {
                                                panic_include_zprint = TRUE;
#if CONFIG_ZLEAKS
                                                if ((zleak_state & ZLEAK_STATE_ACTIVE)) {
                                                        panic_include_ztrace = TRUE;
                                                }
#endif /* CONFIG_ZLEAKS */              
                                                if (retval == KERN_NO_SPACE) {
                                                        zone_t zone_largest = zone_find_largest();
                                                        panic("zalloc: zone map exhausted while allocating from zone %s, likely due to memory leak in zone %s (%lu total bytes, %d elements allocated)",
                                                        zone->zone_name, zone_largest->zone_name,
                                                        (unsigned long)zone_largest->cur_size, zone_largest->count);

                                                }
                                                panic("zalloc: \"%s\" (%d elements) retry fail %d, kfree_nop_count: %d", zone->zone_name, zone->count, retval, (int)kfree_nop_count);
                                        }
                                } else {
                                        break;
                                }
                        }
                        lock_zone(zone);

                        if (set_doing_alloc_with_vm_priv == TRUE)
                                zone->doing_alloc_with_vm_priv = FALSE;
                        else
                                zone->doing_alloc_without_vm_priv = FALSE; 
                        
                        if (zone->waiting) {
                                zone->waiting = FALSE;
                                zone_wakeup(zone);
                        }
                        clear_thread_rwlock_boost();

                        addr = try_alloc_from_zone(zone, &check_poison);
                        if (addr == 0 &&
                            retval == KERN_RESOURCE_SHORTAGE) {
                                if (nopagewait == TRUE)
                                        break;  /* out of the main while loop */
                                unlock_zone(zone);

                                VM_PAGE_WAIT();
                                lock_zone(zone);
                        }
                }
                if (addr == 0)
                        addr = try_alloc_from_zone(zone, &check_poison);
        }

#if CONFIG_ZLEAKS
        /* Zone leak detection:
         * If we're sampling this allocation, add it to the zleaks hash table. 
         */
        if (addr && zleak_tracedepth > 0)  {
                /* Sampling can fail if another sample is happening at the same time in a different zone. */
                if (!zleak_log(zbt, addr, zleak_tracedepth, zone->elem_size)) {
                        /* If it failed, roll back the counter so we sample the next allocation instead. */
                        zone->zleak_capture = zleak_sample_factor;
                }
        }
#endif /* CONFIG_ZLEAKS */                      
                        
                        
        if ((addr == 0) && (!canblock || nopagewait) && (zone->async_pending == FALSE) && (zone->no_callout == FALSE) && (zone->exhaustible == FALSE) && (!vm_pool_low())) {
                zone->async_pending = TRUE;
                unlock_zone(zone);
                thread_call_enter(&call_async_alloc);
                lock_zone(zone);
                addr = try_alloc_from_zone(zone, &check_poison);
        }

        vm_offset_t     inner_size = zone->elem_size;

        unlock_zone(zone);

        if (__improbable(DO_LOGGING(zone) && addr)) {
                btlog_add_entry(zone->zlog_btlog, (void *)addr, ZOP_ALLOC, (void **)zbt, numsaved);
        }

        if (__improbable(check_poison && addr)) {
                vm_offset_t *element_cursor  = ((vm_offset_t *) addr) + 1;
                vm_offset_t *backup  = get_backup_ptr(inner_size, (vm_offset_t *) addr);

                for ( ; element_cursor < backup ; element_cursor++)
                        if (__improbable(*element_cursor != ZP_POISON))
                                zone_element_was_modified_panic(zone,
                                                                addr,
                                                                *element_cursor,
                                                                ZP_POISON,
                                                                ((vm_offset_t)element_cursor) - addr);
        }

        if (addr) {
                /*
                 * Clear out the old next pointer and backup to avoid leaking the cookie
                 * and so that only values on the freelist have a valid cookie
                 */

                vm_offset_t *primary  = (vm_offset_t *) addr;
                vm_offset_t *backup   = get_backup_ptr(inner_size, primary);

                *primary = ZP_POISON;
                *backup  = ZP_POISON;

#if DEBUG || DEVELOPMENT
                if (__improbable(leak_scan_debug_flag && !(zone->elem_size & (sizeof(uintptr_t) - 1)))) {
                        int count, idx;
                        /* Fill element, from tail, with backtrace in reverse order */
                        if (numsaved == 0) numsaved = backtrace(zbt, MAX_ZTRACE_DEPTH);
                        count = (int) (zone->elem_size / sizeof(uintptr_t));
                        if (count >= numsaved) count = numsaved - 1;
                        for (idx = 0; idx < count; idx++) ((uintptr_t *)addr)[count - 1 - idx] = zbt[idx + 1];
                }
#endif /* DEBUG || DEVELOPMENT */
        }

        TRACE_MACHLEAKS(ZALLOC_CODE, ZALLOC_CODE_2, zone->elem_size, addr);
        return((void *)addr);
}


void *
zalloc(zone_t zone)
{
        return (zalloc_internal(zone, TRUE, FALSE));
}

void *
zalloc_noblock(zone_t zone)
{
        return (zalloc_internal(zone, FALSE, FALSE));
}

void *
zalloc_nopagewait(zone_t zone)
{
        return (zalloc_internal(zone, TRUE, TRUE));
}

void *
zalloc_canblock(zone_t zone, boolean_t canblock)
{
        return (zalloc_internal(zone, canblock, FALSE));
}


void
zalloc_async(
        __unused thread_call_param_t          p0,
        __unused thread_call_param_t p1)
{
        zone_t current_z = NULL;
        unsigned int max_zones, i;
        void *elt = NULL;
        boolean_t pending = FALSE;
        
        simple_lock(&all_zones_lock);
        max_zones = num_zones;
        simple_unlock(&all_zones_lock);
        for (i = 0; i < max_zones; i++) {
                current_z = &(zone_array[i]);
                lock_zone(current_z);
                if (current_z->async_pending == TRUE) {
                        current_z->async_pending = FALSE;
                        pending = TRUE;
                }
                unlock_zone(current_z);

                if (pending == TRUE) {
                        elt = zalloc_canblock(current_z, TRUE);
                        zfree(current_z, elt);
                        pending = FALSE;
                }
        }
}

/*
 *      zget returns an element from the specified zone
 *      and immediately returns nothing if there is nothing there.
 */
void *
zget(
        zone_t  zone)
{
    return zalloc_internal(zone, FALSE, TRUE);
}

/* Keep this FALSE by default.  Large memory machine run orders of magnitude
   slower in debug mode when true.  Use debugger to enable if needed */
/* static */ boolean_t zone_check = FALSE;

static void zone_check_freelist(zone_t zone, vm_offset_t elem)
{
        struct zone_free_element *this;
        struct zone_page_metadata *thispage;

        if (zone->allows_foreign) {
                for (thispage = (struct zone_page_metadata *)queue_first(&zone->pages.any_free_foreign);
                         !queue_end(&zone->pages.any_free_foreign, &(thispage->pages));
                         thispage = (struct zone_page_metadata *)queue_next(&(thispage->pages))) {
                        for (this = page_metadata_get_freelist(thispage);
                                 this != NULL;
                                 this = this->next) {
                                if (!is_sane_zone_element(zone, (vm_address_t)this) || (vm_address_t)this == elem)
                                        panic("zone_check_freelist");
                        }
                }
        }
        for (thispage = (struct zone_page_metadata *)queue_first(&zone->pages.all_free);
                !queue_end(&zone->pages.all_free, &(thispage->pages));
                thispage = (struct zone_page_metadata *)queue_next(&(thispage->pages))) {
                for (this = page_metadata_get_freelist(thispage);
                        this != NULL;
                        this = this->next) {
                        if (!is_sane_zone_element(zone, (vm_address_t)this) || (vm_address_t)this == elem)
                                panic("zone_check_freelist");
                }
        }
        for (thispage = (struct zone_page_metadata *)queue_first(&zone->pages.intermediate);
                !queue_end(&zone->pages.intermediate, &(thispage->pages));
                thispage = (struct zone_page_metadata *)queue_next(&(thispage->pages))) {
                for (this = page_metadata_get_freelist(thispage);
                        this != NULL;
                        this = this->next) {
                        if (!is_sane_zone_element(zone, (vm_address_t)this) || (vm_address_t)this == elem)
                                panic("zone_check_freelist");
                }
        }
}

void
zfree(
        zone_t  zone,
        void            *addr)
{
        vm_offset_t     elem = (vm_offset_t) addr;
        uintptr_t       zbt[MAX_ZTRACE_DEPTH];                  /* only used if zone logging is enabled via boot-args */
        int             numsaved = 0;
        boolean_t       gzfreed = FALSE;
        boolean_t       poison = FALSE;

        assert(zone != ZONE_NULL);

        /*
         * If zone logging is turned on and this is the zone we're tracking, grab a backtrace.
         */

        if (__improbable(DO_LOGGING(zone) && corruption_debug_flag))
                numsaved = OSBacktrace((void *)zbt, MAX_ZTRACE_DEPTH);

#if MACH_ASSERT
        /* Basic sanity checks */
        if (zone == ZONE_NULL || elem == (vm_offset_t)0)
                panic("zfree: NULL");
#endif

#if     CONFIG_GZALLOC  
        gzfreed = gzalloc_free(zone, addr);
#endif

        if (!gzfreed) {
                struct zone_page_metadata *page_meta = get_zone_page_metadata((struct zone_free_element *)addr, FALSE);
                if (zone != PAGE_METADATA_GET_ZONE(page_meta)) {
                        panic("Element %p from zone %s caught being freed to wrong zone %s\n", addr, PAGE_METADATA_GET_ZONE(page_meta)->zone_name, zone->zone_name);
                }
        }

        TRACE_MACHLEAKS(ZFREE_CODE, ZFREE_CODE_2, zone->elem_size, (uintptr_t)addr);

        if (__improbable(!gzfreed && zone->collectable && !zone->allows_foreign &&
                !from_zone_map(elem, zone->elem_size))) {
                panic("zfree: non-allocated memory in collectable zone!");
        }

        if ((zp_factor != 0 || zp_tiny_zone_limit != 0) && !gzfreed) {
                /*
                 * Poison the memory before it ends up on the freelist to catch
                 * use-after-free and use of uninitialized memory
                 *
                 * Always poison tiny zones' elements (limit is 0 if -no-zp is set)
                 * Also poison larger elements periodically
                 */

                vm_offset_t     inner_size = zone->elem_size;

                uint32_t sample_factor = zp_factor + (((uint32_t)inner_size) >> zp_scale);

                if (inner_size <= zp_tiny_zone_limit)
                        poison = TRUE;
                else if (zp_factor != 0 && sample_counter(&zone->zp_count, sample_factor) == TRUE)
                        poison = TRUE;

                if (__improbable(poison)) {

                        /* memset_pattern{4|8} could help make this faster: <rdar://problem/4662004> */
                        /* Poison everything but primary and backup */
                        vm_offset_t *element_cursor  = ((vm_offset_t *) elem) + 1;
                        vm_offset_t *backup   = get_backup_ptr(inner_size, (vm_offset_t *)elem);

                        for ( ; element_cursor < backup; element_cursor++)
                                *element_cursor = ZP_POISON;
                }
        }

        /*
         * See if we're doing logging on this zone.  There are two styles of logging used depending on
         * whether we're trying to catch a leak or corruption.  See comments above in zalloc for details.
         */

        if (__improbable(DO_LOGGING(zone))) {
                if (corruption_debug_flag) {
                        /*
                         * We're logging to catch a corruption.  Add a record of this zfree operation
                         * to log.
                         */
                        btlog_add_entry(zone->zlog_btlog, (void *)addr, ZOP_FREE, (void **)zbt, numsaved);
                } else {
                        /*
                         * We're logging to catch a leak. Remove any record we might have for this
                         * element since it's being freed.  Note that we may not find it if the buffer
                         * overflowed and that's OK.  Since the log is of a limited size, old records
                         * get overwritten if there are more zallocs than zfrees.
                         */
                        btlog_remove_entries_for_element(zone->zlog_btlog, (void *)addr);
                }
        }

        lock_zone(zone);

        if (zone_check) {
                zone_check_freelist(zone, elem);
        }

        if (__probable(!gzfreed))
                free_to_zone(zone, elem, poison);

#if MACH_ASSERT
        if (zone->count < 0)
                panic("zfree: zone count underflow in zone %s while freeing element %p, possible cause: double frees or freeing memory that did not come from this zone",
                zone->zone_name, addr);
#endif
        

#if CONFIG_ZLEAKS
        /*
         * Zone leak detection: un-track the allocation 
         */
        if (zone->zleak_on) {
                zleak_free(elem, zone->elem_size);
        }
#endif /* CONFIG_ZLEAKS */
        
        unlock_zone(zone);
}


/*      Change a zone's flags.
 *      This routine must be called immediately after zinit.
 */
void
zone_change(
        zone_t          zone,
        unsigned int    item,
        boolean_t       value)
{
        assert( zone != ZONE_NULL );
        assert( value == TRUE || value == FALSE );

        switch(item){
                case Z_NOENCRYPT:
                        zone->noencrypt = value;
                        break;
                case Z_EXHAUST:
                        zone->exhaustible = value;
                        break;
                case Z_COLLECT:
                        zone->collectable = value;
                        break;
                case Z_EXPAND:
                        zone->expandable = value;
                        break;
                case Z_FOREIGN:
                        zone->allows_foreign = value;
                        break;
                case Z_CALLERACCT:
                        zone->caller_acct = value;
                        break;
                case Z_NOCALLOUT:
                        zone->no_callout = value;
                        break;
                case Z_GZALLOC_EXEMPT:
                        zone->gzalloc_exempt = value;
#if     CONFIG_GZALLOC
                        gzalloc_reconfigure(zone);
#endif
                        break;
                case Z_ALIGNMENT_REQUIRED:
                        zone->alignment_required = value;
#if     CONFIG_GZALLOC
                        gzalloc_reconfigure(zone);
#endif
                        break;
                default:
                        panic("Zone_change: Wrong Item Type!");
                        /* break; */
        }
}

/*
 * Return the expected number of free elements in the zone.
 * This calculation will be incorrect if items are zfree'd that
 * were never zalloc'd/zget'd. The correct way to stuff memory
 * into a zone is by zcram.
 */

integer_t
zone_free_count(zone_t zone)
{
        integer_t free_count;

        lock_zone(zone);
        free_count = zone->countfree;
        unlock_zone(zone);

        assert(free_count >= 0);

        return(free_count);
}

/*      Zone garbage collection
 *
 *      zone_gc will walk through all the free elements in all the
 *      zones that are marked collectable looking for reclaimable
 *      pages.  zone_gc is called by consider_zone_gc when the system
 *      begins to run out of memory.
 */
extern zone_t   vm_map_entry_reserved_zone;
uint64_t                zone_gc_bailed = 0;

void
zone_gc(void)
{
        unsigned int    max_zones;
        zone_t                  z;
        unsigned int    i;
        zone_t                  zres = vm_map_entry_reserved_zone;

        lck_mtx_lock(&zone_gc_lock);

        simple_lock(&all_zones_lock);
        max_zones = num_zones;
        simple_unlock(&all_zones_lock);

        if (zalloc_debug & ZALLOC_DEBUG_ZONEGC)
                kprintf("zone_gc() starting...\n");

        for (i = 0; i < max_zones; i++) {
                z = &(zone_array[i]);
                vm_size_t                                       elt_size, size_freed;
                int                                                     total_freed_pages = 0;
                struct zone_page_metadata       *page_meta;
                queue_head_t                            page_meta_head;

                assert(z != ZONE_NULL);

                if (!z->collectable)
                        continue;
                
                if (queue_empty(&z->pages.all_free)) {
                        continue;
                }
                
                /*
                 * Since kmem_free() might use VM entries from the reserved VM entries zone, we should bail from zone_gc() if we
                 * are below the critical threshold for that zone. Otherwise, there could be a deadlock between the zone_gc 
                 * thread and the zone_replenish thread for the VM entries zone on the zone_map lock.
                 */
                if (zres->zone_replenishing) {
                        zone_gc_bailed++;
                        break;
                }

                lock_zone(z);
                elt_size = z->elem_size;

                if (queue_empty(&z->pages.all_free)) {
                        unlock_zone(z);
                        continue;
                }

                /*
                 * Snatch all of the free elements away from the zone.
                 */
                uint64_t old_all_free_count = z->count_all_free_pages;
                queue_new_head(&z->pages.all_free, &page_meta_head, struct zone_page_metadata *, pages);
                queue_init(&z->pages.all_free);
                z->count_all_free_pages = 0;
                unlock_zone(z);

                /* Iterate through all elements to find out size and count of elements we snatched */
                size_freed = 0;
                queue_iterate(&page_meta_head, page_meta, struct zone_page_metadata *, pages) {
                        assert(from_zone_map((vm_address_t)page_meta, sizeof(*page_meta))); /* foreign elements should be in any_free_foreign */
                        size_freed += elt_size * page_meta->free_count;
                }

                /* Update the zone size and free element count */
                lock_zone(z);
                z->cur_size -= size_freed;
                z->countfree -= size_freed/elt_size;
                unlock_zone(z);

                while ((page_meta = (struct zone_page_metadata *)dequeue_head(&page_meta_head)) != NULL) {
                        vm_address_t        free_page_address;
                        if (zres->zone_replenishing)
                                break;
                        /* Free the pages for metadata and account for them */
                        free_page_address = get_zone_page(page_meta);
                        ZONE_PAGE_COUNT_DECR(z, page_meta->page_count);
                        total_freed_pages += page_meta->page_count;
                        old_all_free_count -= page_meta->page_count;
                        size_freed -= (elt_size * page_meta->free_count);
                        kmem_free(zone_map, free_page_address, (page_meta->page_count * PAGE_SIZE));
                        thread_yield_to_preemption();
                }
                if (page_meta != NULL) {
                   /* 
                        * We bailed because the VM entry reserved zone is replenishing. Put the remaining 
                        * metadata objects back on the all_free list and bail.
                        */
                        queue_entry_t qe;
                        enqueue_head(&page_meta_head, &(page_meta->pages));
                        zone_gc_bailed++;

                        lock_zone(z);
                        qe_foreach_safe(qe, &page_meta_head) {
                                re_queue_tail(&z->pages.all_free, qe);
                        }
                        z->count_all_free_pages += (int)old_all_free_count;
                        z->cur_size += size_freed;
                        z->countfree += size_freed/elt_size;
                        unlock_zone(z);
                        if (zalloc_debug & ZALLOC_DEBUG_ZONEGC)
                                kprintf("zone_gc() bailed due to VM entry zone replenishing (zone_gc_bailed: %lld)\n", zone_gc_bailed);
                        break;
                }
                
                /* We freed all the pages from the all_free list for this zone */
                assert(old_all_free_count == 0);

                if (zalloc_debug & ZALLOC_DEBUG_ZONEGC)
                        kprintf("zone_gc() of zone %s freed %lu elements, %d pages\n", z->zone_name, (unsigned long)size_freed/elt_size, total_freed_pages);
        }

        lck_mtx_unlock(&zone_gc_lock);
}

extern vm_offset_t kmapoff_kaddr;
extern unsigned int kmapoff_pgcnt;

/*
 *      consider_zone_gc:
 *
 *      Called by the pageout daemon when the system needs more free pages.
 */

void
consider_zone_gc(void)
{
        if (kmapoff_kaddr != 0) {
                /*
                 * One-time reclaim of kernel_map resources we allocated in
                 * early boot.
                 */
                (void) vm_deallocate(kernel_map,
                    kmapoff_kaddr, kmapoff_pgcnt * PAGE_SIZE_64);
                kmapoff_kaddr = 0;
        }

        if (zone_gc_allowed)
                zone_gc();
}

kern_return_t
task_zone_info(
        __unused task_t                                 task,
        __unused mach_zone_name_array_t *namesp,
        __unused mach_msg_type_number_t *namesCntp,
        __unused task_zone_info_array_t *infop,
        __unused mach_msg_type_number_t *infoCntp)
{
        return KERN_FAILURE;
}

kern_return_t
mach_zone_info(
        host_priv_t             host,
        mach_zone_name_array_t  *namesp,
        mach_msg_type_number_t  *namesCntp,
        mach_zone_info_array_t  *infop,
        mach_msg_type_number_t  *infoCntp)
{
        return (mach_memory_info(host, namesp, namesCntp, infop, infoCntp, NULL, NULL));
}


kern_return_t
host_zone_info(
        host_priv_t             host,
        zone_name_array_t       *namesp,
        mach_msg_type_number_t  *namesCntp,
        zone_info_array_t       *infop,
        mach_msg_type_number_t  *infoCntp)
{
        return (mach_memory_info(host, (mach_zone_name_array_t *)namesp, namesCntp, (mach_zone_info_array_t *)infop, infoCntp, NULL, NULL));
}

kern_return_t
mach_memory_info(
        host_priv_t             host,
        mach_zone_name_array_t  *namesp,
        mach_msg_type_number_t  *namesCntp,
        mach_zone_info_array_t  *infop,
        mach_msg_type_number_t  *infoCntp,
        mach_memory_info_array_t *memoryInfop,
        mach_msg_type_number_t   *memoryInfoCntp)
{
        mach_zone_name_t        *names;
        vm_offset_t             names_addr;
        vm_size_t               names_size;

        mach_zone_info_t        *info;
        vm_offset_t             info_addr;
        vm_size_t               info_size;

        mach_memory_info_t      *memory_info;
        vm_offset_t             memory_info_addr;
        vm_size_t               memory_info_size;
        vm_size_t               memory_info_vmsize;
        unsigned int            num_sites;

        unsigned int            max_zones, i;
        zone_t                  z;
        mach_zone_name_t        *zn;
        mach_zone_info_t        *zi;
        kern_return_t           kr;
        
        vm_size_t               used;
        vm_map_copy_t           copy;
        uint64_t                zones_collectable_bytes = 0;

        if (host == HOST_NULL)
                return KERN_INVALID_HOST;
#if CONFIG_DEBUGGER_FOR_ZONE_INFO
        if (!PE_i_can_has_debugger(NULL))
                return KERN_INVALID_HOST;
#endif

        /*
         *      We assume that zones aren't freed once allocated.
         *      We won't pick up any zones that are allocated later.
         */

        simple_lock(&all_zones_lock);
        max_zones = (unsigned int)(num_zones);
        simple_unlock(&all_zones_lock);

        names_size = round_page(max_zones * sizeof *names);
        kr = kmem_alloc_pageable(ipc_kernel_map,
                                 &names_addr, names_size, VM_KERN_MEMORY_IPC);
        if (kr != KERN_SUCCESS)
                return kr;
        names = (mach_zone_name_t *) names_addr;

        info_size = round_page(max_zones * sizeof *info);
        kr = kmem_alloc_pageable(ipc_kernel_map,
                                 &info_addr, info_size, VM_KERN_MEMORY_IPC);
        if (kr != KERN_SUCCESS) {
                kmem_free(ipc_kernel_map,
                          names_addr, names_size);
                return kr;
        }
        info = (mach_zone_info_t *) info_addr;

        zn = &names[0];
        zi = &info[0];

        for (i = 0; i < max_zones; i++) {
                struct zone zcopy;
                z = &(zone_array[i]);
                assert(z != ZONE_NULL);

                lock_zone(z);
                zcopy = *z;
                unlock_zone(z);

                /* assuming here the name data is static */
                (void) strncpy(zn->mzn_name, zcopy.zone_name,
                               sizeof zn->mzn_name);
                zn->mzn_name[sizeof zn->mzn_name - 1] = '\0';

                zi->mzi_count = (uint64_t)zcopy.count;
                zi->mzi_cur_size = ptoa_64(zcopy.page_count);
                zi->mzi_max_size = (uint64_t)zcopy.max_size;
                zi->mzi_elem_size = (uint64_t)zcopy.elem_size;
                zi->mzi_alloc_size = (uint64_t)zcopy.alloc_size;
                zi->mzi_sum_size = zcopy.sum_count * zcopy.elem_size;
                zi->mzi_exhaustible = (uint64_t)zcopy.exhaustible;
                zi->mzi_collectable = (uint64_t)zcopy.collectable;
                zones_collectable_bytes += ((uint64_t)zcopy.count_all_free_pages * PAGE_SIZE);
                zn++;
                zi++;
        }

        used = max_zones * sizeof *names;
        if (used != names_size)
                bzero((char *) (names_addr + used), names_size - used);

        kr = vm_map_copyin(ipc_kernel_map, (vm_map_address_t)names_addr,
                           (vm_map_size_t)used, TRUE, &copy);
        assert(kr == KERN_SUCCESS);

        *namesp = (mach_zone_name_t *) copy;
        *namesCntp = max_zones;

        used = max_zones * sizeof *info;

        if (used != info_size)
                bzero((char *) (info_addr + used), info_size - used);

        kr = vm_map_copyin(ipc_kernel_map, (vm_map_address_t)info_addr,
                           (vm_map_size_t)used, TRUE, &copy);
        assert(kr == KERN_SUCCESS);

        *infop = (mach_zone_info_t *) copy;
        *infoCntp = max_zones;
        
        num_sites = 0;
        memory_info_addr = 0;

        if (memoryInfop && memoryInfoCntp)
        {
                num_sites = VM_KERN_MEMORY_COUNT + VM_KERN_COUNTER_COUNT;
                memory_info_size = num_sites * sizeof(*info);
                memory_info_vmsize = round_page(memory_info_size);
                kr = kmem_alloc_pageable(ipc_kernel_map,
                                         &memory_info_addr, memory_info_vmsize, VM_KERN_MEMORY_IPC);
                if (kr != KERN_SUCCESS) {
                        kmem_free(ipc_kernel_map,
                                  names_addr, names_size);
                        kmem_free(ipc_kernel_map,
                                  info_addr, info_size);
                        return kr;
                }

                kr = vm_map_wire(ipc_kernel_map, memory_info_addr, memory_info_addr + memory_info_vmsize,
                                     VM_PROT_READ|VM_PROT_WRITE|VM_PROT_MEMORY_TAG_MAKE(VM_KERN_MEMORY_IPC), FALSE);
                assert(kr == KERN_SUCCESS);

                memory_info = (mach_memory_info_t *) memory_info_addr;
                vm_page_diagnose(memory_info, num_sites, zones_collectable_bytes);

                kr = vm_map_unwire(ipc_kernel_map, memory_info_addr, memory_info_addr + memory_info_vmsize, FALSE);
                assert(kr == KERN_SUCCESS);
        
                kr = vm_map_copyin(ipc_kernel_map, (vm_map_address_t)memory_info_addr,
                                   (vm_map_size_t)memory_info_size, TRUE, &copy);
                assert(kr == KERN_SUCCESS);

                *memoryInfop = (mach_memory_info_t *) copy;
                *memoryInfoCntp = num_sites;
        }

        return KERN_SUCCESS;
}

kern_return_t
mach_zone_force_gc(
        host_t host)
{

        if (host == HOST_NULL)
                return KERN_INVALID_HOST;

        consider_zone_gc();

        return (KERN_SUCCESS);
}

extern unsigned int stack_total;
extern unsigned long long stack_allocs;

#if defined(__i386__) || defined (__x86_64__)
extern unsigned int inuse_ptepages_count;
extern long long alloc_ptepages_count;
#endif

void zone_display_zprint()
{
        unsigned int    i;
        zone_t          the_zone;

        for (i = 0; i < num_zones; i++) {
                the_zone = &(zone_array[i]);
                if(the_zone->cur_size > (1024*1024)) {
                        printf("%.20s:\t%lu\n",the_zone->zone_name,(uintptr_t)the_zone->cur_size);
                }
        }
        printf("Kernel Stacks:\t%lu\n",(uintptr_t)(kernel_stack_size * stack_total));

#if defined(__i386__) || defined (__x86_64__)
        printf("PageTables:\t%lu\n",(uintptr_t)(PAGE_SIZE * inuse_ptepages_count));
#endif

        printf("Kalloc.Large:\t%lu\n",(uintptr_t)kalloc_large_total);
}

zone_t
zone_find_largest(void)
{
        unsigned int    i;
        unsigned int    max_zones;
        zone_t          the_zone;
        zone_t          zone_largest;

        simple_lock(&all_zones_lock);
        max_zones = num_zones;
        simple_unlock(&all_zones_lock);
        
        zone_largest = &(zone_array[0]);
        for (i = 0; i < max_zones; i++) {
                the_zone = &(zone_array[i]);
                if (the_zone->cur_size > zone_largest->cur_size) {
                        zone_largest = the_zone;
                }
        }
        return zone_largest;
}

#if     ZONE_DEBUG

/* should we care about locks here ? */

#define zone_in_use(z)  ( z->count || z->free_elements \
                                                  || !queue_empty(&z->pages.all_free) \
                                                  || !queue_empty(&z->pages.intermediate) \
                                                  || (z->allows_foreign && !queue_empty(&z->pages.any_free_foreign)))


#endif  /* ZONE_DEBUG */


/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#if DEBUG || DEVELOPMENT

static uintptr_t *
zone_copy_all_allocations_inqueue(zone_t z, queue_head_t * queue, uintptr_t * elems)
{
    struct zone_page_metadata *page_meta;
    vm_offset_t free, elements;
    vm_offset_t idx, numElements, freeCount, bytesAvail, metaSize;

    queue_iterate(queue, page_meta, struct zone_page_metadata *, pages)
    {
        elements = get_zone_page(page_meta);
        bytesAvail = ptoa(page_meta->page_count);
        freeCount = 0;
        if (z->allows_foreign && !from_zone_map(elements, z->elem_size))
        {
            metaSize    = (sizeof(struct zone_page_metadata) + ZONE_ELEMENT_ALIGNMENT - 1) & ~(ZONE_ELEMENT_ALIGNMENT - 1);
            bytesAvail -= metaSize;
            elements   += metaSize;
        }
        numElements = bytesAvail / z->elem_size;
        // construct array of all possible elements
        for (idx = 0; idx < numElements; idx++)
        {
            elems[idx] = INSTANCE_PUT(elements + idx * z->elem_size);
        }
        // remove from the array all free elements
        free = (vm_offset_t)page_metadata_get_freelist(page_meta);
        while (free)
        {
            // find idx of free element
            for (idx = 0; (idx < numElements) && (elems[idx] != INSTANCE_PUT(free)); idx++)  {}
            assert(idx < numElements);
            // remove it
            bcopy(&elems[idx + 1], &elems[idx], (numElements - (idx + 1)) * sizeof(elems[0]));
            numElements--;
            freeCount++;
            // next free element
            vm_offset_t *primary = (vm_offset_t *) free;
            free = *primary ^ zp_nopoison_cookie;
        }
        elems += numElements;
    }

    return (elems);
}

kern_return_t
zone_leaks(const char * zoneName, uint32_t nameLen, leak_site_proc proc, void * refCon)
{
        uintptr_t         zbt[MAX_ZTRACE_DEPTH];
    zone_t        zone;
    uintptr_t *   array;
    uintptr_t *   next;
    uintptr_t     element, bt;
    uint32_t      idx, count, found;
    uint32_t      btidx, btcount, nobtcount, btfound;
    uint32_t      elemSize;
    uint64_t      maxElems;
    kern_return_t kr;

    for (idx = 0; idx < num_zones; idx++)
    {
        if (!strncmp(zoneName, zone_array[idx].zone_name, nameLen)) break;
    }
    if (idx >= num_zones) return (KERN_INVALID_NAME);
    zone = &zone_array[idx];

    elemSize = (uint32_t) zone->elem_size;
    maxElems = ptoa(zone->page_count) / elemSize;

    if ((zone->alloc_size % elemSize)
      && !leak_scan_debug_flag) return (KERN_INVALID_CAPABILITY);

    kr = kmem_alloc_kobject(kernel_map, (vm_offset_t *) &array,
                            maxElems * sizeof(uintptr_t), VM_KERN_MEMORY_DIAG);
    if (KERN_SUCCESS != kr) return (kr);

    lock_zone(zone);

    next = array;
    next = zone_copy_all_allocations_inqueue(zone, &zone->pages.any_free_foreign, next);
    next = zone_copy_all_allocations_inqueue(zone, &zone->pages.intermediate,     next);
    next = zone_copy_all_allocations_inqueue(zone, &zone->pages.all_used,         next);
    count = (uint32_t)(next - array);

    unlock_zone(zone);

    zone_leaks_scan(array, count, (uint32_t)zone->elem_size, &found);
    assert(found <= count);

    for (idx = 0; idx < count; idx++)
    {
        element = array[idx];
        if (kInstanceFlagReferenced & element) continue;
        element = INSTANCE_PUT(element) & ~kInstanceFlags;
    }

    if (zone->zlog_btlog && !corruption_debug_flag)
    {
        // btlog_copy_backtraces_for_elements will set kInstanceFlagReferenced on elements it found
        btlog_copy_backtraces_for_elements(zone->zlog_btlog, array, &count, elemSize, proc, refCon);
    }

    for (nobtcount = idx = 0; idx < count; idx++)
    {
        element = array[idx];
        if (!element)                          continue;
        if (kInstanceFlagReferenced & element) continue;
        element = INSTANCE_PUT(element) & ~kInstanceFlags;

        // see if we can find any backtrace left in the element
        btcount = (typeof(btcount)) (zone->elem_size / sizeof(uintptr_t));
        if (btcount >= MAX_ZTRACE_DEPTH) btcount = MAX_ZTRACE_DEPTH - 1;
        for (btfound = btidx = 0; btidx < btcount; btidx++)
        {
            bt = ((uintptr_t *)element)[btcount - 1 - btidx];
            if (!VM_KERNEL_IS_SLID(bt)) break;
            zbt[btfound++] = bt;
        }
        if (btfound) (*proc)(refCon, 1, elemSize, &zbt[0], btfound);
        else         nobtcount++;
    }
    if (nobtcount)
    {
        // fake backtrace when we found nothing
        zbt[0] = (uintptr_t) &zalloc;
        (*proc)(refCon, nobtcount, elemSize, &zbt[0], 1);
    }

    kmem_free(kernel_map, (vm_offset_t) array, maxElems * sizeof(uintptr_t));

    return (KERN_SUCCESS);
}

void
kern_wired_diagnose(void)
{
    unsigned int       count = VM_KERN_MEMORY_COUNT + VM_KERN_COUNTER_COUNT;
    mach_memory_info_t info[count];
    unsigned int       idx;
    uint64_t           total_zone, total_wired, top_wired, osfmk_wired;

    if (KERN_SUCCESS != vm_page_diagnose(info, count, 0)) return;

    total_zone = total_wired = top_wired = osfmk_wired = 0;
    for (idx = 0; idx < num_zones; idx++)
    {
        total_zone += ptoa_64(zone_array[idx].page_count);
    }
    total_wired = total_zone;

    for (idx = 0; idx < count; idx++)
    {
        if (VM_KERN_COUNT_WIRED  == info[idx].site)   top_wired   = info[idx].size;
        if (VM_KERN_MEMORY_OSFMK == info[idx].site)   osfmk_wired = info[idx].size;
        if (VM_KERN_SITE_HIDE    &  info[idx].flags)  continue;
        if (!(VM_KERN_SITE_WIRED &  info[idx].flags)) continue;
        total_wired += info[idx].size;
    }

    printf("top 0x%qx, total 0x%qx, zone 0x%qx, osfmk 0x%qx\n",
           top_wired, total_wired, total_zone, osfmk_wired);
}

boolean_t
kdp_is_in_zone(void *addr, const char *zone_name)
{
        zone_t z;
        return (zone_element_size(addr, &z) && !strcmp(z->zone_name, zone_name));
}

#endif /* DEBUG || DEVELOPMENT */