xnu-4903.270.47.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@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
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 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
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 *
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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/vm_map.h>
#include <mach/sdt.h>

#include <kern/bits.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 <prng/random.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 <libkern/section_keywords.h>
#include <sys/kdebug.h>

#include <san/kasan.h>

/*
 *      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;

/*
 *  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

boolean_t zfree_poison_element(zone_t zone, vm_offset_t elem);
void zalloc_poison_element(boolean_t check_poison, zone_t zone, vm_offset_t addr);

#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 */
#if DEBUG
#define DEFAULT_ZP_FACTOR (1)
#else
#define DEFAULT_ZP_FACTOR (0)
#endif
uint32_t        zp_factor               = DEFAULT_ZP_FACTOR;

/* 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;

#if VM_MAX_TAG_ZONES
boolean_t       zone_tagging_on;
#endif /* VM_MAX_TAG_ZONES */

SECURITY_READ_ONLY_LATE(boolean_t) copyio_zalloc_check = TRUE;
static struct bool_gen zone_bool_gen;

/*
 * 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 not 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

/* 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; */
};

#if CONFIG_ZCACHE

#if !CONFIG_GZALLOC
bool use_caching = TRUE;
#else
bool use_caching = FALSE;
#endif /* !CONFIG_GZALLOC */

/*
 * Decides whether per-cpu zone caching is to be enabled for all zones.
 * Can be set to TRUE via the boot-arg '-zcache_all'.
 */
bool cache_all_zones = FALSE;

/*
 * Specifies a single zone to enable CPU caching for.
 * Can be set using boot-args: zcc_enable_for_zone_name=<zone>
 */
static char cache_zone_name[MAX_ZONE_NAME];

static inline bool
zone_caching_enabled(zone_t z)
{
        return z->cpu_cache_enabled && !z->tags && !z->zleak_on;
}

#endif /* CONFIG_ZCACHE */

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

#define MAX_ZONES       320
struct zone             zone_array[MAX_ZONES];

/* Used to keep track of empty slots in the zone_array */
bitmap_t zone_empty_bitmap[BITMAP_LEN(MAX_ZONES)];

#if DEBUG || DEVELOPMENT
/*
 * Used for sysctl kern.run_zone_test which is not thread-safe. Ensure only one thread goes through at a time.
 * Or we can end up with multiple test zones (if a second zinit() comes through before zdestroy()),  which could lead us to
 * run out of zones.
 */
decl_simple_lock_data(, zone_test_lock)
static boolean_t zone_test_running = FALSE;
static zone_t test_zone_ptr = NULL;
#endif /* DEBUG || DEVELOPMENT */

#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.
         */
        uint16_t                        free_count;
        unsigned                        zindex     : ZINDEX_BITS;    /* Zone index within the zone_array */
        unsigned                        page_count : PAGECOUNT_BITS; /* 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))

vm_map_copy_t create_vm_map_copy(vm_offset_t start_addr, vm_size_t total_size, vm_size_t used_size);
boolean_t get_zone_info(zone_t z, mach_zone_name_t *zn, mach_zone_info_t *zi);
boolean_t is_zone_map_nearing_exhaustion(void);
extern void vm_pageout_garbage_collect(int collect);

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 !KASAN
                /*
                 * This can race with another thread doing a populate on the same metadata
                 * page, where we see an updated pmap but unmapped KASan shadow, causing a
                 * fault in the shadow when we first access the metadata page. Avoid this
                 * by always synchronizing on the zone_metadata_region lock with KASan.
                 */
                if (pmap_find_phys(kernel_pmap, (vm_map_address_t)page_metadata_begin)) {
                        continue;
                }
#endif
                /* 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)) {
                        kern_return_t __assert_only ret = kernel_memory_populate(zone_map,
                            page_metadata_begin,
                            PAGE_SIZE,
                            KMA_KOBJECT,
                            VM_KERN_MEMORY_OSFMK);

                        /* should not fail with the given arguments */
                        assert(ret == KERN_SUCCESS);
                }
                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));
        }
}

/*
 * ZTAGS
 */

#if VM_MAX_TAG_ZONES

// for zones with tagging enabled:

// calculate a pointer to the tag base entry,
// holding either a uint32_t the first tag offset for a page in the zone map,
// or two uint16_t tags if the page can only hold one or two elements

#define ZTAGBASE(zone, element) \
    (&((uint32_t *)zone_tagbase_min)[atop((element) - zone_map_min_address)])

// pointer to the tag for an element
#define ZTAG(zone, element)                                     \
    ({                                                          \
        vm_tag_t * result;                                      \
        if ((zone)->tags_inline) {                              \
            result = (vm_tag_t *) ZTAGBASE((zone), (element));  \
            if ((page_mask & element) >= (zone)->elem_size) result++;    \
        } else {                                                \
            result =  &((vm_tag_t *)zone_tags_min)[ZTAGBASE((zone), (element))[0] + ((element) & page_mask) / (zone)->elem_size];   \
        }                                                       \
        result;                                                 \
    })


static vm_offset_t  zone_tagbase_min;
static vm_offset_t  zone_tagbase_max;
static vm_offset_t  zone_tagbase_map_size;
static vm_map_t     zone_tagbase_map;

static vm_offset_t  zone_tags_min;
static vm_offset_t  zone_tags_max;
static vm_offset_t  zone_tags_map_size;
static vm_map_t     zone_tags_map;

// simple heap allocator for allocating the tags for new memory

decl_lck_mtx_data(, ztLock)    /* heap lock */
enum{
        ztFreeIndexCount = 8,
        ztFreeIndexMax   = (ztFreeIndexCount - 1),
        ztTagsPerBlock   = 4
};

struct ztBlock {
#if __LITTLE_ENDIAN__
        uint64_t free:1,
            next:21,
            prev:21,
            size:21;
#else
// ztBlock needs free bit least significant
#error !__LITTLE_ENDIAN__
#endif
};
typedef struct ztBlock ztBlock;

static ztBlock * ztBlocks;
static uint32_t  ztBlocksCount;
static uint32_t  ztBlocksFree;

static uint32_t
ztLog2up(uint32_t size)
{
        if (1 == size) {
                size = 0;
        } else {
                size = 32 - __builtin_clz(size - 1);
        }
        return size;
}

static uint32_t
ztLog2down(uint32_t size)
{
        size = 31 - __builtin_clz(size);
        return size;
}

static void
ztFault(vm_map_t map, const void * address, size_t size, uint32_t flags)
{
        vm_map_offset_t addr = (vm_map_offset_t) address;
        vm_map_offset_t page, end;

        page = trunc_page(addr);
        end  = round_page(addr + size);

        for (; page < end; page += page_size) {
                if (!pmap_find_phys(kernel_pmap, page)) {
                        kern_return_t __unused
                        ret = kernel_memory_populate(map, page, PAGE_SIZE,
                            KMA_KOBJECT | flags, VM_KERN_MEMORY_DIAG);
                        assert(ret == KERN_SUCCESS);
                }
        }
}

static boolean_t
ztPresent(const void * address, size_t size)
{
        vm_map_offset_t addr = (vm_map_offset_t) address;
        vm_map_offset_t page, end;
        boolean_t       result;

        page = trunc_page(addr);
        end  = round_page(addr + size);
        for (result = TRUE; (page < end); page += page_size) {
                result = pmap_find_phys(kernel_pmap, page);
                if (!result) {
                        break;
                }
        }
        return result;
}


void __unused
ztDump(boolean_t sanity);
void __unused
ztDump(boolean_t sanity)
{
        uint32_t q, cq, p;

        for (q = 0; q <= ztFreeIndexMax; q++) {
                p = q;
                do{
                        if (sanity) {
                                cq = ztLog2down(ztBlocks[p].size);
                                if (cq > ztFreeIndexMax) {
                                        cq = ztFreeIndexMax;
                                }
                                if (!ztBlocks[p].free
                                    || ((p != q) && (q != cq))
                                    || (ztBlocks[ztBlocks[p].next].prev != p)
                                    || (ztBlocks[ztBlocks[p].prev].next != p)) {
                                        kprintf("zterror at %d", p);
                                        ztDump(FALSE);
                                        kprintf("zterror at %d", p);
                                        assert(FALSE);
                                }
                                continue;
                        }
                        kprintf("zt[%03d]%c %d, %d, %d\n",
                            p, ztBlocks[p].free ? 'F' : 'A',
                            ztBlocks[p].next, ztBlocks[p].prev,
                            ztBlocks[p].size);
                        p = ztBlocks[p].next;
                        if (p == q) {
                                break;
                        }
                }while (p != q);
                if (!sanity) {
                        printf("\n");
                }
        }
        if (!sanity) {
                printf("-----------------------\n");
        }
}



#define ZTBDEQ(idx)                                                 \
    ztBlocks[ztBlocks[(idx)].prev].next = ztBlocks[(idx)].next;     \
    ztBlocks[ztBlocks[(idx)].next].prev = ztBlocks[(idx)].prev;

static void
ztFree(zone_t zone __unused, uint32_t index, uint32_t count)
{
        uint32_t q, w, p, size, merge;

        assert(count);
        ztBlocksFree += count;

        // merge with preceding
        merge = (index + count);
        if ((merge < ztBlocksCount)
            && ztPresent(&ztBlocks[merge], sizeof(ztBlocks[merge]))
            && ztBlocks[merge].free) {
                ZTBDEQ(merge);
                count += ztBlocks[merge].size;
        }

        // merge with following
        merge = (index - 1);
        if ((merge > ztFreeIndexMax)
            && ztPresent(&ztBlocks[merge], sizeof(ztBlocks[merge]))
            && ztBlocks[merge].free) {
                size = ztBlocks[merge].size;
                count += size;
                index -= size;
                ZTBDEQ(index);
        }

        q = ztLog2down(count);
        if (q > ztFreeIndexMax) {
                q = ztFreeIndexMax;
        }
        w = q;
        // queue in order of size
        while (TRUE) {
                p = ztBlocks[w].next;
                if (p == q) {
                        break;
                }
                if (ztBlocks[p].size >= count) {
                        break;
                }
                w = p;
        }
        ztBlocks[p].prev = index;
        ztBlocks[w].next = index;

        // fault in first
        ztFault(zone_tags_map, &ztBlocks[index], sizeof(ztBlocks[index]), 0);

        // mark first & last with free flag and size
        ztBlocks[index].free = TRUE;
        ztBlocks[index].size = count;
        ztBlocks[index].prev = w;
        ztBlocks[index].next = p;
        if (count > 1) {
                index += (count - 1);
                // fault in last
                ztFault(zone_tags_map, &ztBlocks[index], sizeof(ztBlocks[index]), 0);
                ztBlocks[index].free = TRUE;
                ztBlocks[index].size = count;
        }
}

static uint32_t
ztAlloc(zone_t zone, uint32_t count)
{
        uint32_t q, w, p, leftover;

        assert(count);

        q = ztLog2up(count);
        if (q > ztFreeIndexMax) {
                q = ztFreeIndexMax;
        }
        do{
                w = q;
                while (TRUE) {
                        p = ztBlocks[w].next;
                        if (p == q) {
                                break;
                        }
                        if (ztBlocks[p].size >= count) {
                                // dequeue, mark both ends allocated
                                ztBlocks[w].next = ztBlocks[p].next;
                                ztBlocks[ztBlocks[p].next].prev = w;
                                ztBlocks[p].free = FALSE;
                                ztBlocksFree -= ztBlocks[p].size;
                                if (ztBlocks[p].size > 1) {
                                        ztBlocks[p + ztBlocks[p].size - 1].free = FALSE;
                                }

                                // fault all the allocation
                                ztFault(zone_tags_map, &ztBlocks[p], count * sizeof(ztBlocks[p]), 0);
                                // mark last as allocated
                                if (count > 1) {
                                        ztBlocks[p + count - 1].free = FALSE;
                                }
                                // free remainder
                                leftover = ztBlocks[p].size - count;
                                if (leftover) {
                                        ztFree(zone, p + ztBlocks[p].size - leftover, leftover);
                                }

                                return p;
                        }
                        w = p;
                }
                q++;
        }while (q <= ztFreeIndexMax);

        return -1U;
}

static void
ztInit(vm_size_t max_zonemap_size, lck_grp_t * group)
{
        kern_return_t         ret;
        vm_map_kernel_flags_t vmk_flags;
        uint32_t              idx;

        lck_mtx_init(&ztLock, group, LCK_ATTR_NULL);

        // allocate submaps VM_KERN_MEMORY_DIAG

        zone_tagbase_map_size = atop(max_zonemap_size) * sizeof(uint32_t);
        vmk_flags = VM_MAP_KERNEL_FLAGS_NONE;
        vmk_flags.vmkf_permanent = TRUE;
        ret = kmem_suballoc(kernel_map, &zone_tagbase_min, zone_tagbase_map_size,
            FALSE, VM_FLAGS_ANYWHERE, vmk_flags, VM_KERN_MEMORY_DIAG,
            &zone_tagbase_map);

        if (ret != KERN_SUCCESS) {
                panic("zone_init: kmem_suballoc failed");
        }
        zone_tagbase_max = zone_tagbase_min + round_page(zone_tagbase_map_size);

        zone_tags_map_size = 2048 * 1024 * sizeof(vm_tag_t);
        vmk_flags = VM_MAP_KERNEL_FLAGS_NONE;
        vmk_flags.vmkf_permanent = TRUE;
        ret = kmem_suballoc(kernel_map, &zone_tags_min, zone_tags_map_size,
            FALSE, VM_FLAGS_ANYWHERE, vmk_flags, VM_KERN_MEMORY_DIAG,
            &zone_tags_map);

        if (ret != KERN_SUCCESS) {
                panic("zone_init: kmem_suballoc failed");
        }
        zone_tags_max = zone_tags_min + round_page(zone_tags_map_size);

        ztBlocks = (ztBlock *) zone_tags_min;
        ztBlocksCount = (uint32_t)(zone_tags_map_size / sizeof(ztBlock));

        // initialize the qheads
        lck_mtx_lock(&ztLock);

        ztFault(zone_tags_map, &ztBlocks[0], sizeof(ztBlocks[0]), 0);
        for (idx = 0; idx < ztFreeIndexCount; idx++) {
                ztBlocks[idx].free = TRUE;
                ztBlocks[idx].next = idx;
                ztBlocks[idx].prev = idx;
                ztBlocks[idx].size = 0;
        }
        // free remaining space
        ztFree(NULL, ztFreeIndexCount, ztBlocksCount - ztFreeIndexCount);

        lck_mtx_unlock(&ztLock);
}

static void
ztMemoryAdd(zone_t zone, vm_offset_t mem, vm_size_t size)
{
        uint32_t * tagbase;
        uint32_t   count, block, blocks, idx;
        size_t     pages;

        pages = atop(size);
        tagbase = ZTAGBASE(zone, mem);

        lck_mtx_lock(&ztLock);

        // fault tagbase
        ztFault(zone_tagbase_map, tagbase, pages * sizeof(uint32_t), 0);

        if (!zone->tags_inline) {
                // allocate tags
                count = (uint32_t)(size / zone->elem_size);
                blocks = ((count + ztTagsPerBlock - 1) / ztTagsPerBlock);
                block = ztAlloc(zone, blocks);
                if (-1U == block) {
                        ztDump(false);
                }
                assert(-1U != block);
        }

        lck_mtx_unlock(&ztLock);

        if (!zone->tags_inline) {
                // set tag base for each page
                block *= ztTagsPerBlock;
                for (idx = 0; idx < pages; idx++) {
                        tagbase[idx] = block + (uint32_t)((ptoa(idx) + (zone->elem_size - 1)) / zone->elem_size);
                }
        }
}

static void
ztMemoryRemove(zone_t zone, vm_offset_t mem, vm_size_t size)
{
        uint32_t * tagbase;
        uint32_t   count, block, blocks, idx;
        size_t     pages;

        // set tag base for each page
        pages = atop(size);
        tagbase = ZTAGBASE(zone, mem);
        block = tagbase[0];
        for (idx = 0; idx < pages; idx++) {
                tagbase[idx] = 0xFFFFFFFF;
        }

        lck_mtx_lock(&ztLock);
        if (!zone->tags_inline) {
                count = (uint32_t)(size / zone->elem_size);
                blocks = ((count + ztTagsPerBlock - 1) / ztTagsPerBlock);
                assert(block != 0xFFFFFFFF);
                block /= ztTagsPerBlock;
                ztFree(NULL /* zone is unlocked */, block, blocks);
        }

        lck_mtx_unlock(&ztLock);
}

uint32_t
zone_index_from_tag_index(uint32_t tag_zone_index, vm_size_t * elem_size)
{
        zone_t z;
        uint32_t idx;

        simple_lock(&all_zones_lock, &zone_locks_grp);

        for (idx = 0; idx < num_zones; idx++) {
                z = &(zone_array[idx]);
                if (!z->tags) {
                        continue;
                }
                if (tag_zone_index != z->tag_zone_index) {
                        continue;
                }
                *elem_size = z->elem_size;
                break;
        }

        simple_unlock(&all_zones_lock);

        if (idx == num_zones) {
                idx = -1U;
        }

        return idx;
}

#endif /* VM_MAX_TAG_ZONES */

/* 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;
        }
}

#if DEBUG || DEVELOPMENT

vm_size_t
zone_element_info(void *addr, vm_tag_t * ptag)
{
        vm_size_t     size = 0;
        vm_tag_t      tag = VM_KERN_MEMORY_NONE;
        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 VM_MAX_TAG_ZONES
                if (__improbable(src_zone->tags)) {
                        tag = (ZTAG(src_zone, (vm_offset_t) addr)[0] >> 1);
                }
#endif /* VM_MAX_TAG_ZONES */
                size = src_zone->elem_size;
        } else {
#if CONFIG_GZALLOC
                gzalloc_element_size(addr, NULL, &size);
#endif /* CONFIG_GZALLOC */
        }
        *ptag = tag;
        return size;
}

#endif /* DEBUG || DEVELOPMENT */

/*
 * 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,
                    (likely_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 ^ zp_nopoison_cookie), 0);
        }

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

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

        if (__improbable(old_head == element)) {
                panic("zfree: double free of %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++;

#if KASAN_ZALLOC
        kasan_poison_range(element, zone->elem_size, ASAN_HEAP_FREED);
#endif
}


/*
 * 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,
    vm_tag_t tag __unused,
    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++;

#if VM_MAX_TAG_ZONES
        if (__improbable(zone->tags)) {
                // set the tag with b0 clear so the block remains inuse
                ZTAG(zone, element)[0] = (tag << 1);
        }
#endif /* VM_MAX_TAG_ZONES */


#if KASAN_ZALLOC
        kasan_poison_range(element, zone->elem_size, ASAN_VALID);
#endif

        return element;
}

/*
 * End of zone poisoning
 */

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

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_ALWAYS, (event_t)(zone), THREAD_UNINT);


#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;

mach_memory_info_t *panic_kext_memory_info = NULL;
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   10 /* Maximum 10 zones can be logged at once */

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

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    = DEBUG;    /* 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.
 */


/*
 * 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.
 */

int
track_this_zone(const char *zonename, const char *logname)
{
        unsigned 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;

#if CONFIG_EMBEDDED
        if (PE_parse_boot_argn("-zleakon", scratch_buf, sizeof(scratch_buf))) {
                zleak_enable_flag = TRUE;
                printf("zone leak detection enabled\n");
        } else {
                zleak_enable_flag = FALSE;
                printf("zone leak detection disabled\n");
        }
#else /* CONFIG_EMBEDDED */
        /* -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");
        }
#endif /* CONFIG_EMBEDDED */

        /* 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)

/* Used to manage copying in of new zone names */
static vm_offset_t zone_names_start;
static vm_offset_t zone_names_next;

static vm_size_t
compute_element_size(vm_size_t requested_size)
{
        vm_size_t element_size = requested_size;

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

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

        return element_size;
}

#if KASAN_ZALLOC

/*
 * Called from zinit().
 *
 * Fixes up the zone's element size to incorporate the redzones.
 */
static void
kasan_update_element_size_for_redzone(
        zone_t          zone,           /* the zone that needs to be updated */
        vm_size_t       *size,          /* requested zone element size */
        vm_size_t       *max,           /* maximum memory to use */
        const char      *name)          /* zone name */
{
        /* Expand the zone allocation size to include the redzones. For page-multiple
         * zones add a full guard page because they likely require alignment. kalloc
         * and fakestack handles its own KASan state, so ignore those zones. */
        /* XXX: remove this when zinit_with_options() is a thing */
        const char *kalloc_name = "kalloc.";
        const char *fakestack_name = "fakestack.";
        if (strncmp(name, kalloc_name, strlen(kalloc_name)) == 0) {
                zone->kasan_redzone = 0;
        } else if (strncmp(name, fakestack_name, strlen(fakestack_name)) == 0) {
                zone->kasan_redzone = 0;
        } else {
                if ((*size % PAGE_SIZE) != 0) {
                        zone->kasan_redzone = KASAN_GUARD_SIZE;
                } else {
                        zone->kasan_redzone = PAGE_SIZE;
                }
                *max = (*max / *size) * (*size + zone->kasan_redzone * 2);
                *size += zone->kasan_redzone * 2;
        }
}

/*
 * Called from zalloc_internal() to fix up the address of the newly
 * allocated element.
 *
 * Returns the element address skipping over the redzone on the left.
 */
static vm_offset_t
kasan_fixup_allocated_element_address(
        zone_t                  zone,   /* the zone the element belongs to */
        vm_offset_t             addr)   /* address of the element, including the redzone */
{
        /* Fixup the return address to skip the redzone */
        if (zone->kasan_redzone) {
                addr = kasan_alloc(addr, zone->elem_size,
                    zone->elem_size - 2 * zone->kasan_redzone, zone->kasan_redzone);
        }
        return addr;
}

/*
 * Called from zfree() to add the element being freed to the KASan quarantine.
 *
 * Returns true if the newly-freed element made it into the quarantine without
 * displacing another, false otherwise. In the latter case, addrp points to the
 * address of the displaced element, which will be freed by the zone.
 */
static bool
kasan_quarantine_freed_element(
        zone_t          *zonep,         /* the zone the element is being freed to */
        void            **addrp)        /* address of the element being freed */
{
        zone_t zone = *zonep;
        void *addr = *addrp;

        /*
         * Resize back to the real allocation size and hand off to the KASan
         * quarantine. `addr` may then point to a different allocation, if the
         * current element replaced another in the quarantine. The zone then
         * takes ownership of the swapped out free element.
         */
        vm_size_t usersz = zone->elem_size - 2 * zone->kasan_redzone;
        vm_size_t sz = usersz;

        if (addr && zone->kasan_redzone) {
                kasan_check_free((vm_address_t)addr, usersz, KASAN_HEAP_ZALLOC);
                addr = (void *)kasan_dealloc((vm_address_t)addr, &sz);
                assert(sz == zone->elem_size);
        }
        if (addr && zone->kasan_quarantine) {
                kasan_free(&addr, &sz, KASAN_HEAP_ZALLOC, zonep, usersz, true);
                if (!addr) {
                        return TRUE;
                }
        }
        *addrp = addr;
        return FALSE;
}

#endif /* KASAN_ZALLOC */

/*
 *      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;

        size = compute_element_size(size);

        simple_lock(&all_zones_lock, &zone_locks_grp);

        assert(num_zones < MAX_ZONES);
        assert(num_zones_in_use <= num_zones);

        /* If possible, find a previously zdestroy'ed zone in the zone_array that we can reuse instead of initializing a new zone. */
        for (int index = bitmap_first(zone_empty_bitmap, MAX_ZONES);
            index >= 0 && index < (int)num_zones;
            index = bitmap_next(zone_empty_bitmap, index)) {
                z = &(zone_array[index]);

                /*
                 * If the zone name and the element size are the same, we can just reuse the old zone struct.
                 * Otherwise hand out a new zone from the zone_array.
                 */
                if (!strcmp(z->zone_name, name)) {
                        vm_size_t old_size = z->elem_size;
#if KASAN_ZALLOC
                        old_size -= z->kasan_redzone * 2;
#endif
                        if (old_size == size) {
                                /* Clear the empty bit for this zone, increment num_zones_in_use, and mark the zone as valid again. */
                                bitmap_clear(zone_empty_bitmap, index);
                                num_zones_in_use++;
                                z->zone_valid = TRUE;

                                /* All other state is already set up since the zone was previously in use. Return early. */
                                simple_unlock(&all_zones_lock);
                                return z;
                        }
                }
        }

        /* If we're here, it means we didn't find a zone above that we could simply reuse. Set up a new zone. */

        /* Clear the empty bit for the new zone */
        bitmap_clear(zone_empty_bitmap, num_zones);

        z = &(zone_array[num_zones]);
        z->index = num_zones;

        num_zones++;
        num_zones_in_use++;

        /*
         * Initialize the zone lock here before dropping the all_zones_lock. Otherwise we could race with
         * zalloc_async() and try to grab the zone lock before it has been initialized, causing a panic.
         */
        lock_zone_init(z);

        simple_unlock(&all_zones_lock);

#if KASAN_ZALLOC
        kasan_update_element_size_for_redzone(z, &size, &max, name);
#endif

        max = round_page(max);

        vm_size_t best_alloc = PAGE_SIZE;

        if ((size % PAGE_SIZE) == 0) {
                /* zero fragmentation by definition */
                best_alloc = size;
        } else {
                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->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;
        z->kasan_quarantine = TRUE;
        z->zone_valid = TRUE;
        z->cpu_cache_enabled = FALSE;

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

        /*
         * If the VM is ready to handle kmem_alloc requests, copy the zone name passed in.
         *
         * Else simply maintain a pointer to the name string. The only zones we'll actually have
         * to do this for would be the VM-related zones that are created very early on before any
         * kexts can be loaded (unloaded). So we should be fine with just a pointer in this case.
         */
        if (kmem_alloc_ready) {
                size_t len = MIN(strlen(name) + 1, MACH_ZONE_NAME_MAX_LEN);

                if (zone_names_start == 0 || ((zone_names_next - zone_names_start) + len) > PAGE_SIZE) {
                        printf("zalloc: allocating memory for zone names buffer\n");
                        kern_return_t retval = kmem_alloc_kobject(kernel_map, &zone_names_start,
                            PAGE_SIZE, VM_KERN_MEMORY_OSFMK);
                        if (retval != KERN_SUCCESS) {
                                panic("zalloc: zone_names memory allocation failed");
                        }
                        bzero((char *)zone_names_start, PAGE_SIZE);
                        zone_names_next = zone_names_start;
                }

                strlcpy((char *)zone_names_next, name, len);
                z->zone_name = (char *)zone_names_next;
                zone_names_next += len;
        } else {
                z->zone_name = name;
        }

        /*
         * 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 (track_this_zone(z->zone_name, zone_name_to_log)) {
                                        if (z->zone_valid) {
                                                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 (track_this_zone(z->zone_name, zone_name_to_log)) {
                                        if (z->zone_valid) {
                                                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, &zone_locks_grp);
                        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]);

                                if (!curr_zone->zone_valid) {
                                        continue;
                                }

                                /*
                                 * 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

#if     CONFIG_ZCACHE
        /* Check if boot-arg specified it should have a cache */
        if (cache_all_zones || track_this_zone(name, cache_zone_name)) {
                zone_change(z, Z_CACHING_ENABLED, TRUE);
        }
#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);
                assert(z->zone_valid);
                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;
                        }

                        /* Trigger jetsams via the vm_pageout_garbage_collect thread if we're running out of zone memory */
                        if (is_zone_map_nearing_exhaustion()) {
                                thread_wakeup((event_t) &vm_pageout_garbage_collect);
                        }

                        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);
                        assert(z->zone_valid);
                        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);
}

void
zdestroy(zone_t z)
{
        unsigned int zindex;

        assert(z != NULL);

        lock_zone(z);
        assert(z->zone_valid);

        /* Assert that the zone does not have any allocations in flight */
        assert(z->doing_alloc_without_vm_priv == FALSE);
        assert(z->doing_alloc_with_vm_priv == FALSE);
        assert(z->async_pending == FALSE);
        assert(z->waiting == FALSE);
        assert(z->async_prio_refill == FALSE);

#if !KASAN_ZALLOC
        /*
         * Unset the valid bit. We'll hit an assert failure on further operations on this zone, until zinit() is called again.
         * Leave the zone valid for KASan as we will see zfree's on quarantined free elements even after the zone is destroyed.
         */
        z->zone_valid = FALSE;
#endif
        unlock_zone(z);

#if CONFIG_ZCACHE
        /* Drain the per-cpu caches if caching is enabled for the zone. */
        if (zone_caching_enabled(z)) {
                panic("zdestroy: Zone caching enabled for zone %s", z->zone_name);
        }
#endif /* CONFIG_ZCACHE */

        /* Dump all the free elements */
        drop_free_elements(z);

#if     CONFIG_GZALLOC
        /* If the zone is gzalloc managed dump all the elements in the free cache */
        gzalloc_empty_free_cache(z);
#endif

        lock_zone(z);

#if !KASAN_ZALLOC
        /* Assert that all counts are zero */
        assert(z->count == 0);
        assert(z->countfree == 0);
        assert(z->cur_size == 0);
        assert(z->page_count == 0);
        assert(z->count_all_free_pages == 0);

        /* Assert that all queues except the foreign queue are empty. The zone allocator doesn't know how to free up foreign memory. */
        assert(queue_empty(&z->pages.all_used));
        assert(queue_empty(&z->pages.intermediate));
        assert(queue_empty(&z->pages.all_free));
#endif

        zindex = z->index;

        unlock_zone(z);

        simple_lock(&all_zones_lock, &zone_locks_grp);

        assert(!bitmap_test(zone_empty_bitmap, zindex));
        /* Mark the zone as empty in the bitmap */
        bitmap_set(zone_empty_bitmap, zindex);
        num_zones_in_use--;
        assert(num_zones_in_use > 0);

        simple_unlock(&all_zones_lock);
}

/* 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;
}


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

        assert(element_count && element_count <= ZONE_CHUNK_MAXELEMENTS);
        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 || __improbable(zone->tags) ||
#endif /* DEBUG || DEVELOPMENT */
                        random_bool_gen_bits(&zone_bool_gen, entropy_buffer, MAX_ENTROPY_PER_ZCRAM, 1)) {
                        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;
        unsigned int entropy_buffer[MAX_ENTROPY_PER_ZCRAM] = { 0 };

        /* 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;

        KDBG(MACHDBG_CODE(DBG_MACH_ZALLOC, ZALLOC_ZCRAM) | DBG_FUNC_START, zone->index, size);

        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));

        /*
         * 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;
        assert((size / PAGE_SIZE) <= ZONE_CHUNK_MAXPAGES);
        chunk_metadata->page_count = (unsigned)(size / PAGE_SIZE);

        zcram_metadata_init(newmem, size, chunk_metadata);

#if VM_MAX_TAG_ZONES
        if (__improbable(zone->tags)) {
                assert(from_zm);
                ztMemoryAdd(zone, newmem, size);
        }
#endif /* VM_MAX_TAG_ZONES */

        lock_zone(zone);
        assert(zone->zone_valid);
        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 = (unsigned int)((PAGE_SIZE - first_element_offset) / elem_size);
                        random_free_to_zone(zone, newmem, first_element_offset, element_count, entropy_buffer);
                }
        } else {
                element_count = (unsigned int)(size / elem_size);
                random_free_to_zone(zone, newmem, 0, element_count, entropy_buffer);
        }
        unlock_zone(zone);

        KDBG(MACHDBG_CODE(DBG_MACH_ZALLOC, ZALLOC_ZCRAM) | DBG_FUNC_END, zone->index);
}

/*
 * Fill a zone with enough memory to contain at least nelem elements.
 * 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 the next zone allocation size.
 */
int
zfill(
        zone_t  zone,
        int     nelem)
{
        kern_return_t kr;
        vm_offset_t     memory;

        vm_size_t alloc_size = zone->alloc_size;
        vm_size_t elem_per_alloc = alloc_size / zone->elem_size;
        vm_size_t nalloc = (nelem + elem_per_alloc - 1) / elem_per_alloc;

        /* Don't mix-and-match zfill with foreign memory */
        assert(!zone->allows_foreign);

        /* Trigger jetsams via the vm_pageout_garbage_collect thread if we're running out of zone memory */
        if (is_zone_map_nearing_exhaustion()) {
                thread_wakeup((event_t) &vm_pageout_garbage_collect);
        }

        kr = kernel_memory_allocate(zone_map, &memory, nalloc * alloc_size, 0, KMA_KOBJECT, VM_KERN_MEMORY_ZONE);
        if (kr != KERN_SUCCESS) {
                printf("%s: kernel_memory_allocate() of %lu bytes failed\n",
                    __func__, (unsigned long)(nalloc * alloc_size));
                return 0;
        }

        for (vm_size_t i = 0; i < nalloc; i++) {
                zcram(zone, memory + i * alloc_size, alloc_size);
        }

        return (int)(nalloc * elem_per_alloc);
}

/*
 *      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];

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

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

        random_bool_init(&zone_bool_gen);

        /* 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
        /* should perform zone element size checking in copyin/copyout? */
        if (PE_parse_boot_argn("-no-copyio-zalloc-check", temp_buf, sizeof(temp_buf))) {
                copyio_zalloc_check = FALSE;
        }
#if VM_MAX_TAG_ZONES
        /* enable tags for zones that ask for  */
        if (PE_parse_boot_argn("-zt", temp_buf, sizeof(temp_buf))) {
                zone_tagging_on = TRUE;
        }
#endif /* VM_MAX_TAG_ZONES */
        /* 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_in_use = 0;
        num_zones = 0;
        /* Mark all zones as empty */
        bitmap_full(zone_empty_bitmap, BITMAP_LEN(MAX_ZONES));
        zone_names_next = zone_names_start = 0;

#if DEBUG || DEVELOPMENT
        simple_lock_init(&zone_test_lock, 0);
#endif /* DEBUG || DEVELOPMENT */

        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);

#if     CONFIG_ZCACHE
        /* zcc_enable_for_zone_name=<zone>: enable per-cpu zone caching for <zone>. */
        if (PE_parse_boot_arg_str("zcc_enable_for_zone_name", cache_zone_name, sizeof(cache_zone_name))) {
                printf("zcache: caching enabled for zone %s\n", cache_zone_name);
        }

        /* -zcache_all: enable per-cpu zone caching for all zones, overrides 'zcc_enable_for_zone_name'. */
        if (PE_parse_boot_argn("-zcache_all", temp_buf, sizeof(temp_buf))) {
                cache_all_zones = TRUE;
                printf("zcache: caching enabled for all zones\n");
        }
#endif /* CONFIG_ZCACHE */
}

/*
 * We're being very conservative here and picking a value of 95%. We might need to lower this if
 * we find that we're not catching the problem and are still hitting zone map exhaustion panics.
 */
#define ZONE_MAP_JETSAM_LIMIT_DEFAULT 95

/*
 * Trigger zone-map-exhaustion jetsams if the zone map is X% full, where X=zone_map_jetsam_limit.
 * Can be set via boot-arg "zone_map_jetsam_limit". Set to 95% by default.
 */
unsigned int zone_map_jetsam_limit = ZONE_MAP_JETSAM_LIMIT_DEFAULT;

/*
 * Returns pid of the task with the largest number of VM map entries.
 */
extern pid_t find_largest_process_vm_map_entries(void);

/*
 * Callout to jetsam. If pid is -1, we wake up the memorystatus thread to do asynchronous kills.
 * For any other pid we try to kill that process synchronously.
 */
boolean_t memorystatus_kill_on_zone_map_exhaustion(pid_t pid);

void
get_zone_map_size(uint64_t *current_size, uint64_t *capacity)
{
        *current_size = zone_map->size;
        *capacity = vm_map_max(zone_map) - vm_map_min(zone_map);
}

void
get_largest_zone_info(char *zone_name, size_t zone_name_len, uint64_t *zone_size)
{
        zone_t largest_zone = zone_find_largest();
        strlcpy(zone_name, largest_zone->zone_name, zone_name_len);
        *zone_size = largest_zone->cur_size;
}

boolean_t
is_zone_map_nearing_exhaustion(void)
{
        uint64_t size = zone_map->size;
        uint64_t capacity = vm_map_max(zone_map) - vm_map_min(zone_map);
        if (size > ((capacity * zone_map_jetsam_limit) / 100)) {
                return TRUE;
        }
        return FALSE;
}

extern zone_t vm_map_entry_zone;
extern zone_t vm_object_zone;

#define VMENTRY_TO_VMOBJECT_COMPARISON_RATIO 98

/*
 * Tries to kill a single process if it can attribute one to the largest zone. If not, wakes up the memorystatus thread
 * to walk through the jetsam priority bands and kill processes.
 */
static void
kill_process_in_largest_zone(void)
{
        pid_t pid = -1;
        zone_t largest_zone = zone_find_largest();

        printf("zone_map_exhaustion: Zone map size %lld, capacity %lld [jetsam limit %d%%]\n", (uint64_t)zone_map->size,
            (uint64_t)(vm_map_max(zone_map) - vm_map_min(zone_map)), zone_map_jetsam_limit);
        printf("zone_map_exhaustion: Largest zone %s, size %lu\n", largest_zone->zone_name, (uintptr_t)largest_zone->cur_size);

        /*
         * We want to make sure we don't call this function from userspace. Or we could end up trying to synchronously kill the process
         * whose context we're in, causing the system to hang.
         */
        assert(current_task() == kernel_task);

        /*
         * If vm_object_zone is the largest, check to see if the number of elements in vm_map_entry_zone is comparable. If so, consider
         * vm_map_entry_zone as the largest. This lets us target a specific process to jetsam to quickly recover from the zone map bloat.
         */
        if (largest_zone == vm_object_zone) {
                unsigned int vm_object_zone_count = vm_object_zone->count;
                unsigned int vm_map_entry_zone_count = vm_map_entry_zone->count;
                /* Is the VM map entries zone count >= 98% of the VM objects zone count? */
                if (vm_map_entry_zone_count >= ((vm_object_zone_count * VMENTRY_TO_VMOBJECT_COMPARISON_RATIO) / 100)) {
                        largest_zone = vm_map_entry_zone;
                        printf("zone_map_exhaustion: Picking VM map entries as the zone to target, size %lu\n", (uintptr_t)largest_zone->cur_size);
                }
        }

        /* TODO: Extend this to check for the largest process in other zones as well. */
        if (largest_zone == vm_map_entry_zone) {
                pid = find_largest_process_vm_map_entries();
        } else {
                printf("zone_map_exhaustion: Nothing to do for the largest zone [%s]. Waking up memorystatus thread.\n", largest_zone->zone_name);
        }
        if (!memorystatus_kill_on_zone_map_exhaustion(pid)) {
                printf("zone_map_exhaustion: Call to memorystatus failed, victim pid: %d\n", pid);
        }
}

/* 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;
        vm_map_kernel_flags_t vmk_flags;

#if VM_MAX_TAG_ZONES
        if (zone_tagging_on) {
                ztInit(max_zonemap_size, &zone_locks_grp);
        }
#endif

        vmk_flags = VM_MAP_KERNEL_FLAGS_NONE;
        vmk_flags.vmkf_permanent = TRUE;
        retval = kmem_suballoc(kernel_map, &zone_min, max_zonemap_size,
            FALSE, VM_FLAGS_ANYWHERE, vmk_flags, 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 */

#if VM_MAX_TAG_ZONES
        if (zone_tagging_on) {
                vm_allocation_zones_init();
        }
#endif

        int jetsam_limit_temp = 0;
        if (PE_parse_boot_argn("zone_map_jetsam_limit", &jetsam_limit_temp, sizeof(jetsam_limit_temp)) &&
            jetsam_limit_temp > 0 && jetsam_limit_temp <= 100) {
                zone_map_jetsam_limit = jetsam_limit_temp;
        }
}

#pragma mark -
#pragma mark zalloc_canblock

extern boolean_t early_boot_complete;

void
zalloc_poison_element(boolean_t check_poison, zone_t zone, vm_offset_t addr)
{
        vm_offset_t     inner_size = zone->elem_size;
        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;
        }
}

/*
 *      zalloc returns an element from the specified zone.
 */
static void *
zalloc_internal(
        zone_t  zone,
        boolean_t canblock,
        boolean_t nopagewait,
        vm_size_t
#if !VM_MAX_TAG_ZONES
        __unused
#endif
        reqsize,
        vm_tag_t  tag)
{
        vm_offset_t     addr = 0;
        kern_return_t   retval;
        uintptr_t       zbt[MAX_ZTRACE_DEPTH];  /* used in zone leak logging and zone leak detection */
        unsigned int            numsaved = 0;
        boolean_t       zone_replenish_wakeup = FALSE, zone_alloc_throttle = FALSE;
        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 */

#if KASAN
        /*
         * KASan uses zalloc() for fakestack, which can be called anywhere. However,
         * we make sure these calls can never block.
         */
        boolean_t irq_safe = FALSE;
        const char *fakestack_name = "fakestack.";
        if (strncmp(zone->zone_name, fakestack_name, strlen(fakestack_name)) == 0) {
                irq_safe = TRUE;
        }
#elif MACH_ASSERT
        /* In every other case, zalloc() from interrupt context is unsafe. */
        const boolean_t irq_safe = FALSE;
#endif

        assert(zone != ZONE_NULL);
        assert(irq_safe || ml_get_interrupts_enabled() || ml_is_quiescing() || debug_mode_active() || !early_boot_complete);

#if     CONFIG_GZALLOC
        addr = gzalloc_alloc(zone, canblock);
#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 */

#if VM_MAX_TAG_ZONES
        if (__improbable(zone->tags)) {
                vm_tag_will_update_zone(tag, zone->tag_zone_index);
        }
#endif /* VM_MAX_TAG_ZONES */

#if CONFIG_ZCACHE
        if (__probable(addr == 0)) {
                if (zone_caching_enabled(zone)) {
                        addr = zcache_alloc_from_cpu_cache(zone);
                        if (addr) {
#if KASAN_ZALLOC
                                addr = kasan_fixup_allocated_element_address(zone, addr);
#endif
                                DTRACE_VM2(zalloc, zone_t, zone, void*, addr);
                                return (void *)addr;
                        }
                }
        }
#endif /* CONFIG_ZCACHE */

        lock_zone(zone);
        assert(zone->zone_valid);

        if (zone->async_prio_refill && zone->zone_replenish_thread) {
                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)) || (zfreec == 0));

                do {
                        if (zone_replenish_wakeup) {
                                zone_replenish_wakeups_initiated++;
                                /* Signal the potentially waiting
                                 * refill thread.
                                 */
                                thread_wakeup(&zone->zone_replenish_thread);

                                /* We don't want to wait around for zone_replenish_thread to bump up the free count
                                 * if we're in zone_gc(). This keeps us from deadlocking with zone_replenish_thread.
                                 */
                                if (thr->options & TH_OPT_ZONE_GC) {
                                        break;
                                }

                                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);
                                assert(zone->zone_valid);
                        }

                        zfreec = (zone->cur_size - (zone->count * zone->elem_size));
                        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)) || (zfreec == 0));
                } while (zone_alloc_throttle == TRUE);
        }

        if (__probable(addr == 0)) {
                addr = try_alloc_from_zone(zone, tag, &check_poison);
        }

        /* If we're here because of zone_gc(), we didn't wait for zone_replenish_thread to finish.
         * So we need to ensure that we did successfully grab an element. And we only need to assert
         * this for zones that have a replenish thread configured (in this case, the Reserved VM map
         * entries zone).
         */
        if (thr->options & TH_OPT_ZONE_GC && zone->async_prio_refill) {
                assert(addr != 0);
        }

        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;
                                }

                                /* Trigger jetsams via the vm_pageout_garbage_collect thread if we're running out of zone memory */
                                if (is_zone_map_nearing_exhaustion()) {
                                        thread_wakeup((event_t) &vm_pageout_garbage_collect);
                                }

                                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 == 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", zone->zone_name, zone->count, retval);
                                        }
                                } else {
                                        break;
                                }
                        }
                        lock_zone(zone);
                        assert(zone->zone_valid);

                        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, tag, &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);
                                assert(zone->zone_valid);
                        }
                }
                if (addr == 0) {
                        addr = try_alloc_from_zone(zone, tag, &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);
                assert(zone->zone_valid);
                addr = try_alloc_from_zone(zone, tag, &check_poison);
        }

#if VM_MAX_TAG_ZONES
        if (__improbable(zone->tags) && addr) {
                if (reqsize) {
                        reqsize = zone->elem_size - reqsize;
                }
                vm_tag_update_zone_size(tag, zone->tag_zone_index, zone->elem_size, reqsize);
        }
#endif /* VM_MAX_TAG_ZONES */

        unlock_zone(zone);

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

        zalloc_poison_element(check_poison, zone, addr);

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


#if KASAN_ZALLOC
        addr = kasan_fixup_allocated_element_address(zone, addr);
#endif

        DTRACE_VM2(zalloc, zone_t, zone, void*, addr);

        return (void *)addr;
}

void *
zalloc(zone_t zone)
{
        return zalloc_internal(zone, TRUE, FALSE, 0, VM_KERN_MEMORY_NONE);
}

void *
zalloc_noblock(zone_t zone)
{
        return zalloc_internal(zone, FALSE, FALSE, 0, VM_KERN_MEMORY_NONE);
}

void *
zalloc_nopagewait(zone_t zone)
{
        return zalloc_internal(zone, TRUE, TRUE, 0, VM_KERN_MEMORY_NONE);
}

void *
zalloc_canblock_tag(zone_t zone, boolean_t canblock, vm_size_t reqsize, vm_tag_t tag)
{
        return zalloc_internal(zone, canblock, FALSE, reqsize, tag);
}

void *
zalloc_canblock(zone_t zone, boolean_t canblock)
{
        return zalloc_internal(zone, canblock, FALSE, 0, VM_KERN_MEMORY_NONE);
}

void *
zalloc_attempt(zone_t zone)
{
        boolean_t check_poison = FALSE;
        vm_offset_t addr = try_alloc_from_zone(zone, VM_KERN_MEMORY_NONE, &check_poison);
        zalloc_poison_element(check_poison, zone, addr);
        return (void *)addr;
}

void
zfree_direct(zone_t zone, vm_offset_t elem)
{
        boolean_t       poison = zfree_poison_element(zone, elem);
        free_to_zone(zone, elem, poison);
}


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, &zone_locks_grp);
        max_zones = num_zones;
        simple_unlock(&all_zones_lock);
        for (i = 0; i < max_zones; i++) {
                current_z = &(zone_array[i]);

                if (current_z->no_callout == TRUE) {
                        /* async_pending will never be set */
                        continue;
                }

                lock_zone(current_z);
                if (current_z->zone_valid && current_z->async_pending == TRUE) {
                        current_z->async_pending = FALSE;
                        pending = TRUE;
                }
                unlock_zone(current_z);

                if (pending == TRUE) {
                        elt = zalloc_canblock_tag(current_z, TRUE, 0, VM_KERN_MEMORY_OSFMK);
                        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, 0, VM_KERN_MEMORY_NONE);
}

/* 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");
                        }
                }
        }
}

boolean_t
zfree_poison_element(zone_t zone, vm_offset_t elem)
{
        boolean_t       poison = FALSE;
        if (zp_factor != 0 || zp_tiny_zone_limit != 0) {
                /*
                 * 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;
                        }
                }
        }
        return poison;
}
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 */
        unsigned int            numsaved = 0;
        boolean_t       gzfreed = FALSE;
        boolean_t       poison = FALSE;
#if VM_MAX_TAG_ZONES
        vm_tag_t tag;
#endif /* VM_MAX_TAG_ZONES */

        assert(zone != ZONE_NULL);
        DTRACE_VM2(zfree, zone_t, zone, void*, addr);
#if KASAN_ZALLOC
        if (kasan_quarantine_freed_element(&zone, &addr)) {
                return;
        }
        elem = (vm_offset_t)addr;
#endif

        /*
         * 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 (!gzfreed) {
                poison = zfree_poison_element(zone, elem);
        }

        /*
         * 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);
                }
        }

#if CONFIG_ZCACHE
        if (zone_caching_enabled(zone)) {
                int __assert_only ret = zcache_free_to_cpu_cache(zone, addr);
                assert(ret != FALSE);
                return;
        }
#endif /* CONFIG_ZCACHE */

        lock_zone(zone);
        assert(zone->zone_valid);

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

        if (__probable(!gzfreed)) {
#if VM_MAX_TAG_ZONES
                if (__improbable(zone->tags)) {
                        tag = (ZTAG(zone, elem)[0] >> 1);
                        // set the tag with b0 clear so the block remains inuse
                        ZTAG(zone, elem)[0] = 0xFFFE;
                }
#endif /* VM_MAX_TAG_ZONES */
                free_to_zone(zone, elem, poison);
        }

        if (__improbable(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);
        }

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

#if VM_MAX_TAG_ZONES
        if (__improbable(zone->tags) && __probable(!gzfreed)) {
                vm_tag_update_zone_size(tag, zone->tag_zone_index, -((int64_t)zone->elem_size), 0);
        }
#endif /* VM_MAX_TAG_ZONES */

        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_TAGS_ENABLED:
#if VM_MAX_TAG_ZONES
                {
                        static int tag_zone_index;
                        zone->tags = TRUE;
                        zone->tags_inline = (((page_size + zone->elem_size - 1) / zone->elem_size) <= (sizeof(uint32_t) / sizeof(uint16_t)));
                        zone->tag_zone_index = OSAddAtomic(1, &tag_zone_index);
                }
#endif /* VM_MAX_TAG_ZONES */
                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 KASAN_ZALLOC
                if (zone->kasan_redzone == KASAN_GUARD_SIZE) {
                        /* Don't disturb alignment with the redzone for zones with
                         * specific alignment requirements. */
                        zone->elem_size -= zone->kasan_redzone * 2;
                        zone->kasan_redzone = 0;
                }
#endif
#if     CONFIG_GZALLOC
                gzalloc_reconfigure(zone);
#endif
                break;
        case Z_KASAN_QUARANTINE:
                zone->kasan_quarantine = value;
                break;
        case Z_CACHING_ENABLED:
#if     CONFIG_ZCACHE
                if (value == TRUE && use_caching) {
                        if (zcache_ready()) {
                                zcache_init(zone);
                        } else {
                                zone->cpu_cache_enable_when_ready = TRUE;
                        }
                }
#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;
}

/* Drops the elements in the free queue of a zone. Called by zone_gc() on each zone, and when a zone is zdestroy'ed. */
void
drop_free_elements(zone_t z)
{
        vm_size_t                                       elt_size, size_freed;
        unsigned int                                                    total_freed_pages = 0;
        uint64_t                                        old_all_free_count;
        struct zone_page_metadata       *page_meta;
        queue_head_t                            page_meta_head;

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

        /*
         * Snatch all of the free elements away from the zone.
         */
        elt_size = z->elem_size;
        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;
                /* 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;
#if KASAN_ZALLOC
                kasan_poison_range(free_page_address, page_meta->page_count * PAGE_SIZE, ASAN_VALID);
#endif
#if VM_MAX_TAG_ZONES
                if (z->tags) {
                        ztMemoryRemove(z, free_page_address, (page_meta->page_count * PAGE_SIZE));
                }
#endif /* VM_MAX_TAG_ZONES */
                kmem_free(zone_map, free_page_address, (page_meta->page_count * PAGE_SIZE));
                if (current_thread()->options & TH_OPT_ZONE_GC) {
                        thread_yield_to_preemption();
                }
        }

        /* 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);
        }
}

/*      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.
 *
 *      We should ensure that zone_gc never blocks.
 */
void
zone_gc(boolean_t consider_jetsams)
{
        unsigned int    max_zones;
        zone_t                  z;
        unsigned int    i;

        if (consider_jetsams) {
                kill_process_in_largest_zone();
                /*
                 * If we do end up jetsamming something, we need to do a zone_gc so that
                 * we can reclaim free zone elements and update the zone map size.
                 * Fall through.
                 */
        }

        lck_mtx_lock(&zone_gc_lock);

        current_thread()->options |= TH_OPT_ZONE_GC;

        simple_lock(&all_zones_lock, &zone_locks_grp);
        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]);
                assert(z != ZONE_NULL);

                if (!z->collectable) {
                        continue;
                }
#if CONFIG_ZCACHE
                if (zone_caching_enabled(z)) {
                        zcache_drain_depot(z);
                }
#endif /* CONFIG_ZCACHE */
                if (queue_empty(&z->pages.all_free)) {
                        continue;
                }

                drop_free_elements(z);
        }

        current_thread()->options &= ~TH_OPT_ZONE_GC;

        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(boolean_t consider_jetsams)
{
        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(consider_jetsams);
        }
}

/*
 * Creates a vm_map_copy_t to return to the caller of mach_* MIG calls
 * requesting zone information.
 * Frees unused pages towards the end of the region, and zero'es out unused
 * space on the last page.
 */
vm_map_copy_t
create_vm_map_copy(
        vm_offset_t             start_addr,
        vm_size_t               total_size,
        vm_size_t               used_size)
{
        kern_return_t   kr;
        vm_offset_t             end_addr;
        vm_size_t               free_size;
        vm_map_copy_t   copy;

        if (used_size != total_size) {
                end_addr = start_addr + used_size;
                free_size = total_size - (round_page(end_addr) - start_addr);

                if (free_size >= PAGE_SIZE) {
                        kmem_free(ipc_kernel_map,
                            round_page(end_addr), free_size);
                }
                bzero((char *) end_addr, round_page(end_addr) - end_addr);
        }

        kr = vm_map_copyin(ipc_kernel_map, (vm_map_address_t)start_addr,
            (vm_map_size_t)used_size, TRUE, &copy);
        assert(kr == KERN_SUCCESS);

        return copy;
}

boolean_t
get_zone_info(
        zone_t                          z,
        mach_zone_name_t        *zn,
        mach_zone_info_t        *zi)
{
        struct zone zcopy;

        assert(z != ZONE_NULL);
        lock_zone(z);
        if (!z->zone_valid) {
                unlock_zone(z);
                return FALSE;
        }
        zcopy = *z;
        unlock_zone(z);

        if (zn != NULL) {
                /* assuming here the name data is static */
                (void) __nosan_strlcpy(zn->mzn_name, zcopy.zone_name,
                    strlen(zcopy.zone_name) + 1);
        }

        if (zi != NULL) {
                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 = 0;
                if (zcopy.collectable) {
                        SET_MZI_COLLECTABLE_BYTES(zi->mzi_collectable, ((uint64_t)zcopy.count_all_free_pages * PAGE_SIZE));
                        SET_MZI_COLLECTABLE_FLAG(zi->mzi_collectable, TRUE);
                }
        }

        return TRUE;
}

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
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_info;

        unsigned int            max_zones, used_zones, i;
        mach_zone_name_t        *zn;
        mach_zone_info_t        *zi;
        kern_return_t           kr;

        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, &zone_locks_grp);
        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];

        used_zones = max_zones;
        for (i = 0; i < max_zones; i++) {
                if (!get_zone_info(&(zone_array[i]), zn, zi)) {
                        used_zones--;
                        continue;
                }
                zones_collectable_bytes += GET_MZI_COLLECTABLE_BYTES(zi->mzi_collectable);
                zn++;
                zi++;
        }

        *namesp = (mach_zone_name_t *) create_vm_map_copy(names_addr, names_size, used_zones * sizeof *names);
        *namesCntp = used_zones;

        *infop = (mach_zone_info_t *) create_vm_map_copy(info_addr, info_size, used_zones * sizeof *info);
        *infoCntp = used_zones;

        num_info = 0;
        memory_info_addr = 0;

        if (memoryInfop && memoryInfoCntp) {
                vm_map_copy_t           copy;
                num_info = vm_page_diagnose_estimate();
                memory_info_size = num_info * sizeof(*memory_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) {
                        return kr;
                }

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

                memory_info = (mach_memory_info_t *) memory_info_addr;
                vm_page_diagnose(memory_info, num_info, 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_info;
        }

        return KERN_SUCCESS;
}

kern_return_t
mach_zone_info_for_zone(
        host_priv_t                     host,
        mach_zone_name_t        name,
        mach_zone_info_t        *infop)
{
        unsigned int max_zones, i;
        zone_t zone_ptr;

        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

        if (infop == NULL) {
                return KERN_INVALID_ARGUMENT;
        }

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

        zone_ptr = ZONE_NULL;
        for (i = 0; i < max_zones; i++) {
                zone_t z = &(zone_array[i]);
                assert(z != ZONE_NULL);

                /* Find the requested zone by name */
                if (track_this_zone(z->zone_name, name.mzn_name)) {
                        zone_ptr = z;
                        break;
                }
        }

        /* No zones found with the requested zone name */
        if (zone_ptr == ZONE_NULL) {
                return KERN_INVALID_ARGUMENT;
        }

        if (get_zone_info(zone_ptr, NULL, infop)) {
                return KERN_SUCCESS;
        }
        return KERN_FAILURE;
}

kern_return_t
mach_zone_info_for_largest_zone(
        host_priv_t                     host,
        mach_zone_name_t        *namep,
        mach_zone_info_t        *infop)
{
        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

        if (namep == NULL || infop == NULL) {
                return KERN_INVALID_ARGUMENT;
        }

        if (get_zone_info(zone_find_largest(), namep, infop)) {
                return KERN_SUCCESS;
        }
        return KERN_FAILURE;
}

uint64_t
get_zones_collectable_bytes(void)
{
        unsigned int i, max_zones;
        uint64_t zones_collectable_bytes = 0;
        mach_zone_info_t zi;

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

        for (i = 0; i < max_zones; i++) {
                if (get_zone_info(&(zone_array[i]), NULL, &zi)) {
                        zones_collectable_bytes += GET_MZI_COLLECTABLE_BYTES(zi.mzi_collectable);
                }
        }

        return zones_collectable_bytes;
}

kern_return_t
mach_zone_get_zlog_zones(
        host_priv_t                             host,
        mach_zone_name_array_t  *namesp,
        mach_msg_type_number_t  *namesCntp)
{
#if DEBUG || DEVELOPMENT
        unsigned int max_zones, logged_zones, i;
        kern_return_t kr;
        zone_t zone_ptr;
        mach_zone_name_t *names;
        vm_offset_t names_addr;
        vm_size_t names_size;

        if (host == HOST_NULL) {
                return KERN_INVALID_HOST;
        }

        if (namesp == NULL || namesCntp == NULL) {
                return KERN_INVALID_ARGUMENT;
        }

        simple_lock(&all_zones_lock, &zone_locks_grp);
        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;

        zone_ptr = ZONE_NULL;
        logged_zones = 0;
        for (i = 0; i < max_zones; i++) {
                zone_t z = &(zone_array[i]);
                assert(z != ZONE_NULL);

                /* Copy out the zone name if zone logging is enabled */
                if (z->zlog_btlog) {
                        get_zone_info(z, &names[logged_zones], NULL);
                        logged_zones++;
                }
        }

        *namesp = (mach_zone_name_t *) create_vm_map_copy(names_addr, names_size, logged_zones * sizeof *names);
        *namesCntp = logged_zones;

        return KERN_SUCCESS;

#else /* DEBUG || DEVELOPMENT */
#pragma unused(host, namesp, namesCntp)
        return KERN_FAILURE;
#endif /* DEBUG || DEVELOPMENT */
}

kern_return_t
mach_zone_get_btlog_records(
        host_priv_t                             host,
        mach_zone_name_t                name,
        zone_btrecord_array_t   *recsp,
        mach_msg_type_number_t  *recsCntp)
{
#if DEBUG || DEVELOPMENT
        unsigned int max_zones, i, numrecs = 0;
        zone_btrecord_t *recs;
        kern_return_t kr;
        zone_t zone_ptr;
        vm_offset_t recs_addr;
        vm_size_t recs_size;

        if (host == HOST_NULL) {
                return KERN_INVALID_HOST;
        }

        if (recsp == NULL || recsCntp == NULL) {
                return KERN_INVALID_ARGUMENT;
        }

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

        zone_ptr = ZONE_NULL;
        for (i = 0; i < max_zones; i++) {
                zone_t z = &(zone_array[i]);
                assert(z != ZONE_NULL);

                /* Find the requested zone by name */
                if (track_this_zone(z->zone_name, name.mzn_name)) {
                        zone_ptr = z;
                        break;
                }
        }

        /* No zones found with the requested zone name */
        if (zone_ptr == ZONE_NULL) {
                return KERN_INVALID_ARGUMENT;
        }

        /* Logging not turned on for the requested zone */
        if (!DO_LOGGING(zone_ptr)) {
                return KERN_FAILURE;
        }

        /* Allocate memory for btlog records */
        numrecs = (unsigned int)(get_btlog_records_count(zone_ptr->zlog_btlog));
        recs_size = round_page(numrecs * sizeof *recs);

        kr = kmem_alloc_pageable(ipc_kernel_map, &recs_addr, recs_size, VM_KERN_MEMORY_IPC);
        if (kr != KERN_SUCCESS) {
                return kr;
        }

        /*
         * We will call get_btlog_records() below which populates this region while holding a spinlock
         * (the btlog lock). So these pages need to be wired.
         */
        kr = vm_map_wire_kernel(ipc_kernel_map, recs_addr, recs_addr + recs_size,
            VM_PROT_READ | VM_PROT_WRITE, VM_KERN_MEMORY_IPC, FALSE);
        assert(kr == KERN_SUCCESS);

        recs = (zone_btrecord_t *)recs_addr;
        get_btlog_records(zone_ptr->zlog_btlog, recs, &numrecs);

        kr = vm_map_unwire(ipc_kernel_map, recs_addr, recs_addr + recs_size, FALSE);
        assert(kr == KERN_SUCCESS);

        *recsp = (zone_btrecord_t *) create_vm_map_copy(recs_addr, recs_size, numrecs * sizeof *recs);
        *recsCntp = numrecs;

        return KERN_SUCCESS;

#else /* DEBUG || DEVELOPMENT */
#pragma unused(host, name, recsp, recsCntp)
        return KERN_FAILURE;
#endif /* DEBUG || DEVELOPMENT */
}


#if DEBUG || DEVELOPMENT

kern_return_t
mach_memory_info_check(void)
{
        mach_memory_info_t * memory_info;
        mach_memory_info_t * info;
        zone_t                       zone;
        unsigned int         idx, num_info, max_zones;
        vm_offset_t                  memory_info_addr;
        kern_return_t        kr;
        size_t               memory_info_size, memory_info_vmsize;
        uint64_t             top_wired, zonestotal, total;

        num_info = vm_page_diagnose_estimate();
        memory_info_size = num_info * sizeof(*memory_info);
        memory_info_vmsize = round_page(memory_info_size);
        kr = kmem_alloc(kernel_map, &memory_info_addr, memory_info_vmsize, VM_KERN_MEMORY_DIAG);
        assert(kr == KERN_SUCCESS);

        memory_info = (mach_memory_info_t *) memory_info_addr;
        vm_page_diagnose(memory_info, num_info, 0);

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

        top_wired = total = zonestotal = 0;
        for (idx = 0; idx < max_zones; idx++) {
                zone = &(zone_array[idx]);
                assert(zone != ZONE_NULL);
                lock_zone(zone);
                zonestotal += ptoa_64(zone->page_count);
                unlock_zone(zone);
        }
        for (idx = 0; idx < num_info; idx++) {
                info = &memory_info[idx];
                if (!info->size) {
                        continue;
                }
                if (VM_KERN_COUNT_WIRED == info->site) {
                        top_wired = info->size;
                }
                if (VM_KERN_SITE_HIDE & info->flags) {
                        continue;
                }
                if (!(VM_KERN_SITE_WIRED & info->flags)) {
                        continue;
                }
                total += info->size;
        }
        total += zonestotal;

        printf("vm_page_diagnose_check %qd of %qd, zones %qd, short 0x%qx\n", total, top_wired, zonestotal, top_wired - total);

        kmem_free(kernel_map, memory_info_addr, memory_info_vmsize);

        return kr;
}

extern boolean_t(*volatile consider_buffer_cache_collect)(int);

#endif /* DEBUG || DEVELOPMENT */

kern_return_t
mach_zone_force_gc(
        host_t host)
{
        if (host == HOST_NULL) {
                return KERN_INVALID_HOST;
        }

#if DEBUG || DEVELOPMENT
        /* Callout to buffer cache GC to drop elements in the apfs zones */
        if (consider_buffer_cache_collect != NULL) {
                (void)(*consider_buffer_cache_collect)(0);
        }
        consider_zone_gc(FALSE);
#endif /* DEBUG || DEVELOPMENT */
        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

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, &zone_locks_grp);
        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;
        unsigned int  max_zones;
        kern_return_t kr;

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

        for (idx = 0; idx < max_zones; idx++) {
                if (!strncmp(zoneName, zone_array[idx].zone_name, nameLen)) {
                        break;
                }
        }
        if (idx >= max_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;
}

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);
}

boolean_t
run_zone_test(void)
{
        unsigned int i = 0, max_iter = 5;
        void * test_ptr;
        zone_t test_zone;

        simple_lock(&zone_test_lock, &zone_locks_grp);
        if (!zone_test_running) {
                zone_test_running = TRUE;
        } else {
                simple_unlock(&zone_test_lock);
                printf("run_zone_test: Test already running.\n");
                return FALSE;
        }
        simple_unlock(&zone_test_lock);

        printf("run_zone_test: Testing zinit(), zalloc(), zfree() and zdestroy() on zone \"test_zone_sysctl\"\n");

        /* zinit() and zdestroy() a zone with the same name a bunch of times, verify that we get back the same zone each time */
        do {
                test_zone = zinit(sizeof(uint64_t), 100 * sizeof(uint64_t), sizeof(uint64_t), "test_zone_sysctl");
                if (test_zone == NULL) {
                        printf("run_zone_test: zinit() failed\n");
                        return FALSE;
                }

#if KASAN_ZALLOC
                if (test_zone_ptr == NULL && zone_free_count(test_zone) != 0) {
#else
                if (zone_free_count(test_zone) != 0) {
#endif
                        printf("run_zone_test: free count is not zero\n");
                        return FALSE;
                }

                if (test_zone_ptr == NULL) {
                        /* Stash the zone pointer returned on the fist zinit */
                        printf("run_zone_test: zone created for the first time\n");
                        test_zone_ptr = test_zone;
                } else if (test_zone != test_zone_ptr) {
                        printf("run_zone_test: old zone pointer and new zone pointer don't match\n");
                        return FALSE;
                }

                test_ptr = zalloc(test_zone);
                if (test_ptr == NULL) {
                        printf("run_zone_test: zalloc() failed\n");
                        return FALSE;
                }
                zfree(test_zone, test_ptr);

                zdestroy(test_zone);
                i++;

                printf("run_zone_test: Iteration %d successful\n", i);
        } while (i < max_iter);

        printf("run_zone_test: Test passed\n");

        simple_lock(&zone_test_lock, &zone_locks_grp);
        zone_test_running = FALSE;
        simple_unlock(&zone_test_lock);

        return TRUE;
}

#endif /* DEBUG || DEVELOPMENT */