Import the slab allocator

As it is intended to completely replace the zone allocator, remove it on
the way. So long to the venerable code !

* Makefrag.am (libkernel_a_SOURCES): Add kern/slab.{c,h}, remove kern/kalloc.c
and kern/zalloc.{c,h}.
* configfrag.ac (SLAB_VERIFY, SLAB_USE_CPU_POOLS): Add defines.
* i386/Makefrag.am (libkernel_a_SOURCES): Remove i386/i386/zalloc.h.
* i386/configfrag.ac (CPU_L1_SHIFT): Remove define.
* include/mach_debug/slab_info.h: New file.
* kern/slab.c: Likewise.
* kern/slab.h: Likewise.
* i386/i386/zalloc.h: Remove file.
* include/mach_debug/zone_info.h: Likewise.
* kern/kalloc.c: Likewise.
* kern/zalloc.c: Likewise.
* kern/zalloc.h: Likewise.

1 files changed, 1576 insertions, 0 deletions

diff --git a/kern/slab.c b/kern/slab.c
new file mode 100644
index 0000000..38413e8
--- /dev/null
+++ b/kern/slab.c
@@ -0,0 +1,1576 @@
+/*
+ * Copyright (c) 2009, 2010, 2011 Richard Braun.
+ * Copyright (c) 2011 Maksym Planeta.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/*
+ * Object caching and general purpose memory allocator.
+ *
+ * This allocator is based on the paper "The Slab Allocator: An Object-Caching
+ * Kernel Memory Allocator" by Jeff Bonwick.
+ *
+ * It allows the allocation of objects (i.e. fixed-size typed buffers) from
+ * caches and is efficient in both space and time. This implementation follows
+ * many of the indications from the paper mentioned. The most notable
+ * differences are outlined below.
+ *
+ * The per-cache self-scaling hash table for buffer-to-bufctl conversion,
+ * described in 3.2.3 "Slab Layout for Large Objects", has been replaced by
+ * a red-black tree storing slabs, sorted by address. The use of a
+ * self-balancing tree for buffer-to-slab conversions provides a few advantages
+ * over a hash table. Unlike a hash table, a BST provides a "lookup nearest"
+ * operation, so obtaining the slab data (whether it is embedded in the slab or
+ * off slab) from a buffer address simply consists of a "lookup nearest towards
+ * 0" tree search. Storing slabs instead of buffers also considerably reduces
+ * the number of elements to retain. Finally, a self-balancing tree is a true
+ * self-scaling data structure, whereas a hash table requires periodic
+ * maintenance and complete resizing, which is expensive. The only drawback is
+ * that releasing a buffer to the slab layer takes logarithmic time instead of
+ * constant time. But as the data set size is kept reasonable (because slabs
+ * are stored instead of buffers) and because the CPU pool layer services most
+ * requests, avoiding many accesses to the slab layer, it is considered an
+ * acceptable tradeoff.
+ *
+ * This implementation uses per-cpu pools of objects, which service most
+ * allocation requests. These pools act as caches (but are named differently
+ * to avoid confusion with CPU caches) that reduce contention on multiprocessor
+ * systems. When a pool is empty and cannot provide an object, it is filled by
+ * transferring multiple objects from the slab layer. The symmetric case is
+ * handled likewise.
+ */
+
+#include <string.h>
+#include <kern/assert.h>
+#include <kern/mach_clock.h>
+#include <kern/printf.h>
+#include <kern/slab.h>
+#include <kern/kalloc.h>
+#include <kern/cpu_number.h>
+#include <mach/vm_param.h>
+#include <mach/machine/vm_types.h>
+#include <vm/vm_kern.h>
+#include <vm/vm_types.h>
+#include <sys/types.h>
+
+#ifdef MACH_DEBUG
+#include <mach_debug/slab_info.h>
+#endif
+
+/*
+ * Utility macros.
+ */
+#define ARRAY_SIZE(x)   (sizeof(x) / sizeof((x)[0]))
+#define P2ALIGNED(x, a) (((x) & ((a) - 1)) == 0)
+#define ISP2(x)         P2ALIGNED(x, x)
+#define P2ALIGN(x, a)   ((x) & -(a))
+#define P2ROUND(x, a)   (-(-(x) & -(a)))
+#define P2END(x, a)     (-(~(x) & -(a)))
+#define likely(expr)    __builtin_expect(!!(expr), 1)
+#define unlikely(expr)  __builtin_expect(!!(expr), 0)
+
+/*
+ * Minimum required alignment.
+ */
+#define KMEM_ALIGN_MIN 8
+
+/*
+ * Minimum number of buffers per slab.
+ *
+ * This value is ignored when the slab size exceeds a threshold.
+ */
+#define KMEM_MIN_BUFS_PER_SLAB 8
+
+/*
+ * Special slab size beyond which the minimum number of buffers per slab is
+ * ignored when computing the slab size of a cache.
+ */
+#define KMEM_SLAB_SIZE_THRESHOLD (8 * PAGE_SIZE)
+
+/*
+ * Special buffer size under which slab data is unconditionnally allocated
+ * from its associated slab.
+ */
+#define KMEM_BUF_SIZE_THRESHOLD (PAGE_SIZE / 8)
+
+/*
+ * Time (in seconds) between two garbage collection operations.
+ */
+#define KMEM_GC_INTERVAL (1 * hz)
+
+/*
+ * The transfer size of a CPU pool is computed by dividing the pool size by
+ * this value.
+ */
+#define KMEM_CPU_POOL_TRANSFER_RATIO 2
+
+/*
+ * Redzone guard word.
+ */
+#ifdef __LP64__
+#if _HOST_BIG_ENDIAN
+#define KMEM_REDZONE_WORD 0xfeedfacefeedfaceUL
+#else /* _HOST_BIG_ENDIAN */
+#define KMEM_REDZONE_WORD 0xcefaedfecefaedfeUL
+#endif /* _HOST_BIG_ENDIAN */
+#else /* __LP64__ */
+#if _HOST_BIG_ENDIAN
+#define KMEM_REDZONE_WORD 0xfeedfaceUL
+#else /* _HOST_BIG_ENDIAN */
+#define KMEM_REDZONE_WORD 0xcefaedfeUL
+#endif /* _HOST_BIG_ENDIAN */
+#endif /* __LP64__ */
+
+/*
+ * Redzone byte for padding.
+ */
+#define KMEM_REDZONE_BYTE 0xbb
+
+/*
+ * Size of the VM submap from which default backend functions allocate.
+ */
+#define KMEM_MAP_SIZE (64 * 1024 * 1024)
+
+/*
+ * Shift for the first kalloc cache size.
+ */
+#define KALLOC_FIRST_SHIFT 5
+
+/*
+ * Number of caches backing general purpose allocations.
+ */
+#define KALLOC_NR_CACHES 13
+
+/*
+ * Size of the VM submap for general purpose allocations.
+ */
+#define KALLOC_MAP_SIZE (64 * 1024 * 1024)
+
+/*
+ * Values the buftag state member can take.
+ */
+#ifdef __LP64__
+#if _HOST_BIG_ENDIAN
+#define KMEM_BUFTAG_ALLOC   0xa110c8eda110c8edUL
+#define KMEM_BUFTAG_FREE    0xf4eeb10cf4eeb10cUL
+#else /* _HOST_BIG_ENDIAN */
+#define KMEM_BUFTAG_ALLOC   0xedc810a1edc810a1UL
+#define KMEM_BUFTAG_FREE    0x0cb1eef40cb1eef4UL
+#endif /* _HOST_BIG_ENDIAN */
+#else /* __LP64__ */
+#if _HOST_BIG_ENDIAN
+#define KMEM_BUFTAG_ALLOC   0xa110c8edUL
+#define KMEM_BUFTAG_FREE    0xf4eeb10cUL
+#else /* _HOST_BIG_ENDIAN */
+#define KMEM_BUFTAG_ALLOC   0xedc810a1UL
+#define KMEM_BUFTAG_FREE    0x0cb1eef4UL
+#endif /* _HOST_BIG_ENDIAN */
+#endif /* __LP64__ */
+
+/*
+ * Free and uninitialized patterns.
+ *
+ * These values are unconditionnally 64-bit wide since buffers are at least
+ * 8-byte aligned.
+ */
+#if _HOST_BIG_ENDIAN
+#define KMEM_FREE_PATTERN   0xdeadbeefdeadbeefULL
+#define KMEM_UNINIT_PATTERN 0xbaddcafebaddcafeULL
+#else /* _HOST_BIG_ENDIAN */
+#define KMEM_FREE_PATTERN   0xefbeaddeefbeaddeULL
+#define KMEM_UNINIT_PATTERN 0xfecaddbafecaddbaULL
+#endif /* _HOST_BIG_ENDIAN */
+
+/*
+ * Cache flags.
+ *
+ * The flags don't change once set and can be tested without locking.
+ */
+#define KMEM_CF_NO_CPU_POOL     0x01    /* CPU pool layer disabled */
+#define KMEM_CF_SLAB_EXTERNAL   0x02    /* Slab data is off slab */
+#define KMEM_CF_NO_RECLAIM      0x04    /* Slabs are not reclaimable */
+#define KMEM_CF_VERIFY          0x08    /* Debugging facilities enabled */
+#define KMEM_CF_DIRECT          0x10    /* No buf-to-slab tree lookup */
+
+/*
+ * Options for kmem_cache_alloc_verify().
+ */
+#define KMEM_AV_NOCONSTRUCT 0
+#define KMEM_AV_CONSTRUCT   1
+
+/*
+ * Error codes for kmem_cache_error().
+ */
+#define KMEM_ERR_INVALID    0   /* Invalid address being freed */
+#define KMEM_ERR_DOUBLEFREE 1   /* Freeing already free address */
+#define KMEM_ERR_BUFTAG     2   /* Invalid buftag content */
+#define KMEM_ERR_MODIFIED   3   /* Buffer modified while free */
+#define KMEM_ERR_REDZONE    4   /* Redzone violation */
+
+#if SLAB_USE_CPU_POOLS
+/*
+ * Available CPU pool types.
+ *
+ * For each entry, the CPU pool size applies from the entry buf_size
+ * (excluded) up to (and including) the buf_size of the preceding entry.
+ *
+ * See struct kmem_cpu_pool_type for a description of the values.
+ */
+static struct kmem_cpu_pool_type kmem_cpu_pool_types[] = {
+    {  32768,   1, 0,           NULL },
+    {   4096,   8, CPU_L1_SIZE, NULL },
+    {    256,  64, CPU_L1_SIZE, NULL },
+    {      0, 128, CPU_L1_SIZE, NULL }
+};
+
+/*
+ * Caches where CPU pool arrays are allocated from.
+ */
+static struct kmem_cache kmem_cpu_array_caches[ARRAY_SIZE(kmem_cpu_pool_types)];
+#endif /* SLAB_USE_CPU_POOLS */
+
+/*
+ * Cache for off slab data.
+ */
+static struct kmem_cache kmem_slab_cache;
+
+/*
+ * General purpose caches array.
+ */
+static struct kmem_cache kalloc_caches[KALLOC_NR_CACHES];
+
+/*
+ * List of all caches managed by the allocator.
+ */
+static struct list kmem_cache_list;
+static unsigned int kmem_nr_caches;
+static simple_lock_data_t __attribute__((used)) kmem_cache_list_lock;
+
+/*
+ * VM submap for slab caches (except general purpose allocations).
+ */
+static struct vm_map kmem_map_store;
+vm_map_t kmem_map = &kmem_map_store;
+
+/*
+ * VM submap for general purpose allocations.
+ */
+static struct vm_map kalloc_map_store;
+vm_map_t kalloc_map = &kalloc_map_store;
+
+/*
+ * Time of the last memory reclaim, in clock ticks.
+ */
+static unsigned int kmem_gc_last_tick;
+
+#define kmem_error(format, ...)                         \
+    printf("mem: error: %s(): " format "\n", __func__,  \
+           ## __VA_ARGS__)
+
+#define kmem_warn(format, ...)                              \
+    printf("mem: warning: %s(): " format "\n", __func__,    \
+           ## __VA_ARGS__)
+
+#define kmem_print(format, ...) \
+    printf(format "\n", ## __VA_ARGS__)
+
+static void kmem_cache_error(struct kmem_cache *cache, void *buf, int error,
+                             void *arg);
+static void * kmem_cache_alloc_from_slab(struct kmem_cache *cache);
+static void kmem_cache_free_to_slab(struct kmem_cache *cache, void *buf);
+
+static void * kmem_buf_verify_bytes(void *buf, void *pattern, size_t size)
+{
+    char *ptr, *pattern_ptr, *end;
+
+    end = buf + size;
+
+    for (ptr = buf, pattern_ptr = pattern; ptr < end; ptr++, pattern_ptr++)
+        if (*ptr != *pattern_ptr)
+            return ptr;
+
+    return NULL;
+}
+
+static void * kmem_buf_verify(void *buf, uint64_t pattern, vm_size_t size)
+{
+    uint64_t *ptr, *end;
+
+    assert(P2ALIGNED((unsigned long)buf, sizeof(uint64_t)));
+    assert(P2ALIGNED(size, sizeof(uint64_t)));
+
+    end = buf + size;
+
+    for (ptr = buf; ptr < end; ptr++)
+        if (*ptr != pattern)
+            return kmem_buf_verify_bytes(ptr, &pattern, sizeof(pattern));
+
+    return NULL;
+}
+
+static void kmem_buf_fill(void *buf, uint64_t pattern, size_t size)
+{
+    uint64_t *ptr, *end;
+
+    assert(P2ALIGNED((unsigned long)buf, sizeof(uint64_t)));
+    assert(P2ALIGNED(size, sizeof(uint64_t)));
+
+    end = buf + size;
+
+    for (ptr = buf; ptr < end; ptr++)
+        *ptr = pattern;
+}
+
+static void * kmem_buf_verify_fill(void *buf, uint64_t old, uint64_t new,
+                                   size_t size)
+{
+    uint64_t *ptr, *end;
+
+    assert(P2ALIGNED((unsigned long)buf, sizeof(uint64_t)));
+    assert(P2ALIGNED(size, sizeof(uint64_t)));
+
+    end = buf + size;
+
+    for (ptr = buf; ptr < end; ptr++) {
+        if (*ptr != old)
+            return kmem_buf_verify_bytes(ptr, &old, sizeof(old));
+
+        *ptr = new;
+    }
+
+    return NULL;
+}
+
+static inline union kmem_bufctl *
+kmem_buf_to_bufctl(void *buf, struct kmem_cache *cache)
+{
+    return (union kmem_bufctl *)(buf + cache->bufctl_dist);
+}
+
+static inline struct kmem_buftag *
+kmem_buf_to_buftag(void *buf, struct kmem_cache *cache)
+{
+    return (struct kmem_buftag *)(buf + cache->buftag_dist);
+}
+
+static inline void * kmem_bufctl_to_buf(union kmem_bufctl *bufctl,
+                                        struct kmem_cache *cache)
+{
+    return (void *)bufctl - cache->bufctl_dist;
+}
+
+static vm_offset_t kmem_pagealloc(vm_size_t size)
+{
+    vm_offset_t addr;
+    kern_return_t kr;
+
+    kr = kmem_alloc_wired(kmem_map, &addr, size);
+
+    if (kr != KERN_SUCCESS)
+        return 0;
+
+    return addr;
+}
+
+static void kmem_pagefree(vm_offset_t ptr, vm_size_t size)
+{
+    kmem_free(kmem_map, ptr, size);
+}
+
+static void kmem_slab_create_verify(struct kmem_slab *slab,
+                                    struct kmem_cache *cache)
+{
+    struct kmem_buftag *buftag;
+    size_t buf_size;
+    unsigned long buffers;
+    void *buf;
+
+    buf_size = cache->buf_size;
+    buf = slab->addr;
+    buftag = kmem_buf_to_buftag(buf, cache);
+
+    for (buffers = cache->bufs_per_slab; buffers != 0; buffers--) {
+        kmem_buf_fill(buf, KMEM_FREE_PATTERN, cache->bufctl_dist);
+        buftag->state = KMEM_BUFTAG_FREE;
+        buf += buf_size;
+        buftag = kmem_buf_to_buftag(buf, cache);
+    }
+}
+
+/*
+ * Create an empty slab for a cache.
+ *
+ * The caller must drop all locks before calling this function.
+ */
+static struct kmem_slab * kmem_slab_create(struct kmem_cache *cache,
+                                           size_t color)
+{
+    struct kmem_slab *slab;
+    union kmem_bufctl *bufctl;
+    size_t buf_size;
+    unsigned long buffers;
+    void *slab_buf;
+
+    if (cache->slab_alloc_fn == NULL)
+        slab_buf = (void *)kmem_pagealloc(cache->slab_size);
+    else
+        slab_buf = (void *)cache->slab_alloc_fn(cache->slab_size);
+
+    if (slab_buf == NULL)
+        return NULL;
+
+    if (cache->flags & KMEM_CF_SLAB_EXTERNAL) {
+        assert(!(cache->flags & KMEM_CF_NO_RECLAIM));
+        slab = (struct kmem_slab *)kmem_cache_alloc(&kmem_slab_cache);
+
+        if (slab == NULL) {
+            if (cache->slab_free_fn == NULL)
+                kmem_pagefree((vm_offset_t)slab_buf, cache->slab_size);
+            else
+                cache->slab_free_fn((vm_offset_t)slab_buf, cache->slab_size);
+
+            return NULL;
+        }
+    } else {
+        slab = (struct kmem_slab *)(slab_buf + cache->slab_size) - 1;
+    }
+
+    list_node_init(&slab->list_node);
+    rbtree_node_init(&slab->tree_node);
+    slab->nr_refs = 0;
+    slab->first_free = NULL;
+    slab->addr = slab_buf + color;
+
+    buf_size = cache->buf_size;
+    bufctl = kmem_buf_to_bufctl(slab->addr, cache);
+
+    for (buffers = cache->bufs_per_slab; buffers != 0; buffers--) {
+        bufctl->next = slab->first_free;
+        slab->first_free = bufctl;
+        bufctl = (union kmem_bufctl *)((void *)bufctl + buf_size);
+    }
+
+    if (cache->flags & KMEM_CF_VERIFY)
+        kmem_slab_create_verify(slab, cache);
+
+    return slab;
+}
+
+static void kmem_slab_destroy_verify(struct kmem_slab *slab,
+                                     struct kmem_cache *cache)
+{
+    struct kmem_buftag *buftag;
+    size_t buf_size;
+    unsigned long buffers;
+    void *buf, *addr;
+
+    buf_size = cache->buf_size;
+    buf = slab->addr;
+    buftag = kmem_buf_to_buftag(buf, cache);
+
+    for (buffers = cache->bufs_per_slab; buffers != 0; buffers--) {
+        if (buftag->state != KMEM_BUFTAG_FREE)
+            kmem_cache_error(cache, buf, KMEM_ERR_BUFTAG, buftag);
+
+        addr = kmem_buf_verify(buf, KMEM_FREE_PATTERN, cache->bufctl_dist);
+
+        if (addr != NULL)
+            kmem_cache_error(cache, buf, KMEM_ERR_MODIFIED, addr);
+
+        buf += buf_size;
+        buftag = kmem_buf_to_buftag(buf, cache);
+    }
+}
+
+/*
+ * Destroy a slab.
+ *
+ * The caller must drop all locks before calling this function.
+ */
+static void kmem_slab_destroy(struct kmem_slab *slab, struct kmem_cache *cache)
+{
+    vm_offset_t slab_buf;
+
+    assert(slab->nr_refs == 0);
+    assert(slab->first_free != NULL);
+    assert(!(cache->flags & KMEM_CF_NO_RECLAIM));
+
+    if (cache->flags & KMEM_CF_VERIFY)
+        kmem_slab_destroy_verify(slab, cache);
+
+    slab_buf = (vm_offset_t)P2ALIGN((unsigned long)slab->addr, PAGE_SIZE);
+
+    if (cache->slab_free_fn == NULL)
+        kmem_pagefree(slab_buf, cache->slab_size);
+    else
+        cache->slab_free_fn(slab_buf, cache->slab_size);
+
+    if (cache->flags & KMEM_CF_SLAB_EXTERNAL)
+        kmem_cache_free(&kmem_slab_cache, (vm_offset_t)slab);
+}
+
+static inline int kmem_slab_use_tree(int flags)
+{
+    return !(flags & KMEM_CF_DIRECT) || (flags & KMEM_CF_VERIFY);
+}
+
+static inline int kmem_slab_cmp_lookup(const void *addr,
+                                       const struct rbtree_node *node)
+{
+    struct kmem_slab *slab;
+
+    slab = rbtree_entry(node, struct kmem_slab, tree_node);
+
+    if (addr == slab->addr)
+        return 0;
+    else if (addr < slab->addr)
+        return -1;
+    else
+        return 1;
+}
+
+static inline int kmem_slab_cmp_insert(const struct rbtree_node *a,
+                                       const struct rbtree_node *b)
+{
+    struct kmem_slab *slab;
+
+    slab = rbtree_entry(a, struct kmem_slab, tree_node);
+    return kmem_slab_cmp_lookup(slab->addr, b);
+}
+
+#if SLAB_USE_CPU_POOLS
+static void kmem_cpu_pool_init(struct kmem_cpu_pool *cpu_pool,
+                               struct kmem_cache *cache)
+{
+    simple_lock_init(&cpu_pool->lock);
+    cpu_pool->flags = cache->flags;
+    cpu_pool->size = 0;
+    cpu_pool->transfer_size = 0;
+    cpu_pool->nr_objs = 0;
+    cpu_pool->array = NULL;
+}
+
+/*
+ * Return a CPU pool.
+ *
+ * This function will generally return the pool matching the CPU running the
+ * calling thread. Because of context switches and thread migration, the
+ * caller might be running on another processor after this function returns.
+ * Although not optimal, this should rarely happen, and it doesn't affect the
+ * allocator operations in any other way, as CPU pools are always valid, and
+ * their access is serialized by a lock.
+ */
+static inline struct kmem_cpu_pool * kmem_cpu_pool_get(struct kmem_cache *cache)
+{
+    return &cache->cpu_pools[cpu_number()];
+}
+
+static inline void kmem_cpu_pool_build(struct kmem_cpu_pool *cpu_pool,
+                                       struct kmem_cache *cache, void **array)
+{
+    cpu_pool->size = cache->cpu_pool_type->array_size;
+    cpu_pool->transfer_size = (cpu_pool->size
+                               + KMEM_CPU_POOL_TRANSFER_RATIO - 1)
+                              / KMEM_CPU_POOL_TRANSFER_RATIO;
+    cpu_pool->array = array;
+}
+
+static inline void * kmem_cpu_pool_pop(struct kmem_cpu_pool *cpu_pool)
+{
+    cpu_pool->nr_objs--;
+    return cpu_pool->array[cpu_pool->nr_objs];
+}
+
+static inline void kmem_cpu_pool_push(struct kmem_cpu_pool *cpu_pool, void *obj)
+{
+    cpu_pool->array[cpu_pool->nr_objs] = obj;
+    cpu_pool->nr_objs++;
+}
+
+static int kmem_cpu_pool_fill(struct kmem_cpu_pool *cpu_pool,
+                              struct kmem_cache *cache)
+{
+    void *obj;
+    int i;
+
+    simple_lock(&cache->lock);
+
+    for (i = 0; i < cpu_pool->transfer_size; i++) {
+        obj = kmem_cache_alloc_from_slab(cache);
+
+        if (obj == NULL)
+            break;
+
+        kmem_cpu_pool_push(cpu_pool, obj);
+    }
+
+    simple_unlock(&cache->lock);
+
+    return i;
+}
+
+static void kmem_cpu_pool_drain(struct kmem_cpu_pool *cpu_pool,
+                                struct kmem_cache *cache)
+{
+    void *obj;
+    int i;
+
+    simple_lock(&cache->lock);
+
+    for (i = cpu_pool->transfer_size; i > 0; i--) {
+        obj = kmem_cpu_pool_pop(cpu_pool);
+        kmem_cache_free_to_slab(cache, obj);
+    }
+
+    simple_unlock(&cache->lock);
+}
+#endif /* SLAB_USE_CPU_POOLS */
+
+static void kmem_cache_error(struct kmem_cache *cache, void *buf, int error,
+                             void *arg)
+{
+    struct kmem_buftag *buftag;
+
+    kmem_error("cache: %s, buffer: %p", cache->name, (void *)buf);
+
+    switch(error) {
+    case KMEM_ERR_INVALID:
+        kmem_error("freeing invalid address");
+        break;
+    case KMEM_ERR_DOUBLEFREE:
+        kmem_error("attempting to free the same address twice");
+        break;
+    case KMEM_ERR_BUFTAG:
+        buftag = arg;
+        kmem_error("invalid buftag content, buftag state: %p",
+                   (void *)buftag->state);
+        break;
+    case KMEM_ERR_MODIFIED:
+        kmem_error("free buffer modified, fault address: %p, "
+                   "offset in buffer: %td", arg, arg - buf);
+        break;
+    case KMEM_ERR_REDZONE:
+        kmem_error("write beyond end of buffer, fault address: %p, "
+                   "offset in buffer: %td", arg, arg - buf);
+        break;
+    default:
+        kmem_error("unknown error");
+    }
+
+    /*
+     * Never reached.
+     */
+}
+
+/*
+ * Compute an appropriate slab size for the given cache.
+ *
+ * Once the slab size is known, this function sets the related properties
+ * (buffers per slab and maximum color). It can also set the KMEM_CF_DIRECT
+ * and/or KMEM_CF_SLAB_EXTERNAL flags depending on the resulting layout.
+ */
+static void kmem_cache_compute_sizes(struct kmem_cache *cache, int flags)
+{
+    size_t i, buffers, buf_size, slab_size, free_slab_size, optimal_size;
+    size_t waste, waste_min;
+    int embed, optimal_embed = optimal_embed;
+
+    buf_size = cache->buf_size;
+
+    if (buf_size < KMEM_BUF_SIZE_THRESHOLD)
+        flags |= KMEM_CACHE_NOOFFSLAB;
+
+    i = 0;
+    waste_min = (size_t)-1;
+
+    do {
+        i++;
+        slab_size = P2ROUND(i * buf_size, PAGE_SIZE);
+        free_slab_size = slab_size;
+
+        if (flags & KMEM_CACHE_NOOFFSLAB)
+            free_slab_size -= sizeof(struct kmem_slab);
+
+        buffers = free_slab_size / buf_size;
+        waste = free_slab_size % buf_size;
+
+        if (buffers > i)
+            i = buffers;
+
+        if (flags & KMEM_CACHE_NOOFFSLAB)
+            embed = 1;
+        else if (sizeof(struct kmem_slab) <= waste) {
+            embed = 1;
+            waste -= sizeof(struct kmem_slab);
+        } else {
+            embed = 0;
+        }
+
+        if (waste <= waste_min) {
+            waste_min = waste;
+            optimal_size = slab_size;
+            optimal_embed = embed;
+        }
+    } while ((buffers < KMEM_MIN_BUFS_PER_SLAB)
+             && (slab_size < KMEM_SLAB_SIZE_THRESHOLD));
+
+    assert(!(flags & KMEM_CACHE_NOOFFSLAB) || optimal_embed);
+
+    cache->slab_size = optimal_size;
+    slab_size = cache->slab_size - (optimal_embed
+                ? sizeof(struct kmem_slab)
+                : 0);
+    cache->bufs_per_slab = slab_size / buf_size;
+    cache->color_max = slab_size % buf_size;
+
+    if (cache->color_max >= PAGE_SIZE)
+        cache->color_max = PAGE_SIZE - 1;
+
+    if (optimal_embed) {
+        if (cache->slab_size == PAGE_SIZE)
+            cache->flags |= KMEM_CF_DIRECT;
+    } else {
+        cache->flags |= KMEM_CF_SLAB_EXTERNAL;
+    }
+}
+
+void kmem_cache_init(struct kmem_cache *cache, const char *name,
+                     size_t obj_size, size_t align, kmem_cache_ctor_t ctor,
+                     kmem_slab_alloc_fn_t slab_alloc_fn,
+                     kmem_slab_free_fn_t slab_free_fn, int flags)
+{
+#if SLAB_USE_CPU_POOLS
+    struct kmem_cpu_pool_type *cpu_pool_type;
+    size_t i;
+#endif /* SLAB_USE_CPU_POOLS */
+    size_t buf_size;
+
+#if SLAB_VERIFY
+    cache->flags = KMEM_CF_VERIFY;
+#else /* SLAB_VERIFY */
+    cache->flags = 0;
+#endif /* SLAB_VERIFY */
+
+    if (flags & KMEM_CACHE_NOCPUPOOL)
+        cache->flags |= KMEM_CF_NO_CPU_POOL;
+
+    if (flags & KMEM_CACHE_NORECLAIM) {
+        assert(slab_free_fn == NULL);
+        flags |= KMEM_CACHE_NOOFFSLAB;
+        cache->flags |= KMEM_CF_NO_RECLAIM;
+    }
+
+    if (flags & KMEM_CACHE_VERIFY)
+        cache->flags |= KMEM_CF_VERIFY;
+
+    if (align < KMEM_ALIGN_MIN)
+        align = KMEM_ALIGN_MIN;
+
+    assert(obj_size > 0);
+    assert(ISP2(align));
+    assert(align < PAGE_SIZE);
+
+    buf_size = P2ROUND(obj_size, align);
+
+    simple_lock_init(&cache->lock);
+    list_node_init(&cache->node);
+    list_init(&cache->partial_slabs);
+    list_init(&cache->free_slabs);
+    rbtree_init(&cache->active_slabs);
+    cache->obj_size = obj_size;
+    cache->align = align;
+    cache->buf_size = buf_size;
+    cache->bufctl_dist = buf_size - sizeof(union kmem_bufctl);
+    cache->color = 0;
+    cache->nr_objs = 0;
+    cache->nr_bufs = 0;
+    cache->nr_slabs = 0;
+    cache->nr_free_slabs = 0;
+    cache->ctor = ctor;
+    cache->slab_alloc_fn = slab_alloc_fn;
+    cache->slab_free_fn = slab_free_fn;
+    strncpy(cache->name, name, sizeof(cache->name));
+    cache->name[sizeof(cache->name) - 1] = '\0';
+    cache->buftag_dist = 0;
+    cache->redzone_pad = 0;
+
+    if (cache->flags & KMEM_CF_VERIFY) {
+        cache->bufctl_dist = buf_size;
+        cache->buftag_dist = cache->bufctl_dist + sizeof(union kmem_bufctl);
+        cache->redzone_pad = cache->bufctl_dist - cache->obj_size;
+        buf_size += sizeof(union kmem_bufctl) + sizeof(struct kmem_buftag);
+        buf_size = P2ROUND(buf_size, align);
+        cache->buf_size = buf_size;
+    }
+
+    kmem_cache_compute_sizes(cache, flags);
+
+#if SLAB_USE_CPU_POOLS
+    for (cpu_pool_type = kmem_cpu_pool_types;
+         buf_size <= cpu_pool_type->buf_size;
+         cpu_pool_type++);
+
+    cache->cpu_pool_type = cpu_pool_type;
+
+    for (i = 0; i < ARRAY_SIZE(cache->cpu_pools); i++)
+        kmem_cpu_pool_init(&cache->cpu_pools[i], cache);
+#endif /* SLAB_USE_CPU_POOLS */
+
+    simple_lock(&kmem_cache_list_lock);
+    list_insert_tail(&kmem_cache_list, &cache->node);
+    kmem_nr_caches++;
+    simple_unlock(&kmem_cache_list_lock);
+}
+
+static inline int kmem_cache_empty(struct kmem_cache *cache)
+{
+    return cache->nr_objs == cache->nr_bufs;
+}
+
+static int kmem_cache_grow(struct kmem_cache *cache)
+{
+    struct kmem_slab *slab;
+    size_t color;
+    int empty;
+
+    simple_lock(&cache->lock);
+
+    if (!kmem_cache_empty(cache)) {
+        simple_unlock(&cache->lock);
+        return 1;
+    }
+
+    color = cache->color;
+    cache->color += cache->align;
+
+    if (cache->color > cache->color_max)
+        cache->color = 0;
+
+    simple_unlock(&cache->lock);
+
+    slab = kmem_slab_create(cache, color);
+
+    simple_lock(&cache->lock);
+
+    if (slab != NULL) {
+        list_insert_tail(&cache->free_slabs, &slab->list_node);
+        cache->nr_bufs += cache->bufs_per_slab;
+        cache->nr_slabs++;
+        cache->nr_free_slabs++;
+    }
+
+    /*
+     * Even if our slab creation failed, another thread might have succeeded
+     * in growing the cache.
+     */
+    empty = kmem_cache_empty(cache);
+
+    simple_unlock(&cache->lock);
+
+    return !empty;
+}
+
+static void kmem_cache_reap(struct kmem_cache *cache)
+{
+    struct kmem_slab *slab;
+    struct list dead_slabs;
+
+    if (cache->flags & KMEM_CF_NO_RECLAIM)
+        return;
+
+    list_init(&dead_slabs);
+
+    simple_lock(&cache->lock);
+
+    while (!list_empty(&cache->free_slabs)) {
+        slab = list_first_entry(&cache->free_slabs, struct kmem_slab,
+                                list_node);
+        list_remove(&slab->list_node);
+        list_insert(&dead_slabs, &slab->list_node);
+        cache->nr_bufs -= cache->bufs_per_slab;
+        cache->nr_slabs--;
+        cache->nr_free_slabs--;
+    }
+
+    simple_unlock(&cache->lock);
+
+    while (!list_empty(&dead_slabs)) {
+        slab = list_first_entry(&dead_slabs, struct kmem_slab, list_node);
+        list_remove(&slab->list_node);
+        kmem_slab_destroy(slab, cache);
+    }
+}
+
+/*
+ * Allocate a raw (unconstructed) buffer from the slab layer of a cache.
+ *
+ * The cache must be locked before calling this function.
+ */
+static void * kmem_cache_alloc_from_slab(struct kmem_cache *cache)
+{
+    struct kmem_slab *slab;
+    union kmem_bufctl *bufctl;
+
+    if (!list_empty(&cache->partial_slabs))
+        slab = list_first_entry(&cache->partial_slabs, struct kmem_slab,
+                                list_node);
+    else if (!list_empty(&cache->free_slabs))
+        slab = list_first_entry(&cache->free_slabs, struct kmem_slab,
+                                list_node);
+    else
+        return NULL;
+
+    bufctl = slab->first_free;
+    assert(bufctl != NULL);
+    slab->first_free = bufctl->next;
+    slab->nr_refs++;
+    cache->nr_objs++;
+
+    /*
+     * The slab has become complete.
+     */
+    if (slab->nr_refs == cache->bufs_per_slab) {
+        list_remove(&slab->list_node);
+
+        if (slab->nr_refs == 1)
+            cache->nr_free_slabs--;
+    } else if (slab->nr_refs == 1) {
+        /*
+         * The slab has become partial.
+         */
+        list_remove(&slab->list_node);
+        list_insert_tail(&cache->partial_slabs, &slab->list_node);
+        cache->nr_free_slabs--;
+    } else if (!list_singular(&cache->partial_slabs)) {
+        struct list *node;
+        struct kmem_slab *tmp;
+
+        /*
+         * The slab remains partial. If there are more than one partial slabs,
+         * maintain the list sorted.
+         */
+
+        assert(slab->nr_refs > 1);
+
+        for (node = list_prev(&slab->list_node);
+             !list_end(&cache->partial_slabs, node);
+             node = list_prev(node)) {
+            tmp = list_entry(node, struct kmem_slab, list_node);
+
+            if (tmp->nr_refs >= slab->nr_refs)
+                break;
+        }
+
+        /*
+         * If the direct neighbor was found, the list is already sorted.
+         * If no slab was found, the slab is inserted at the head of the list.
+         */
+        if (node != list_prev(&slab->list_node)) {
+            list_remove(&slab->list_node);
+            list_insert_after(node, &slab->list_node);
+        }
+    }
+
+    if ((slab->nr_refs == 1) && kmem_slab_use_tree(cache->flags))
+        rbtree_insert(&cache->active_slabs, &slab->tree_node,
+                      kmem_slab_cmp_insert);
+
+    return kmem_bufctl_to_buf(bufctl, cache);
+}
+
+/*
+ * Release a buffer to the slab layer of a cache.
+ *
+ * The cache must be locked before calling this function.
+ */
+static void kmem_cache_free_to_slab(struct kmem_cache *cache, void *buf)
+{
+    struct kmem_slab *slab;
+    union kmem_bufctl *bufctl;
+
+    if (cache->flags & KMEM_CF_DIRECT) {
+        assert(cache->slab_size == PAGE_SIZE);
+        slab = (struct kmem_slab *)P2END((unsigned long)buf, cache->slab_size)
+               - 1;
+    } else {
+        struct rbtree_node *node;
+
+        node = rbtree_lookup_nearest(&cache->active_slabs, buf,
+                                     kmem_slab_cmp_lookup, RBTREE_LEFT);
+        assert(node != NULL);
+        slab = rbtree_entry(node, struct kmem_slab, tree_node);
+        assert((unsigned long)buf < (P2ALIGN((unsigned long)slab->addr
+                                             + cache->slab_size, PAGE_SIZE)));
+    }
+
+    assert(slab->nr_refs >= 1);
+    assert(slab->nr_refs <= cache->bufs_per_slab);
+    bufctl = kmem_buf_to_bufctl(buf, cache);
+    bufctl->next = slab->first_free;
+    slab->first_free = bufctl;
+    slab->nr_refs--;
+    cache->nr_objs--;
+
+    /*
+     * The slab has become free.
+     */
+    if (slab->nr_refs == 0) {
+        if (kmem_slab_use_tree(cache->flags))
+            rbtree_remove(&cache->active_slabs, &slab->tree_node);
+
+        /*
+         * The slab was partial.
+         */
+        if (cache->bufs_per_slab > 1)
+            list_remove(&slab->list_node);
+
+        list_insert_tail(&cache->free_slabs, &slab->list_node);
+        cache->nr_free_slabs++;
+    } else if (slab->nr_refs == (cache->bufs_per_slab - 1)) {
+        /*
+         * The slab has become partial.
+         */
+        list_insert(&cache->partial_slabs, &slab->list_node);
+    } else if (!list_singular(&cache->partial_slabs)) {
+        struct list *node;
+        struct kmem_slab *tmp;
+
+        /*
+         * The slab remains partial. If there are more than one partial slabs,
+         * maintain the list sorted.
+         */
+
+        assert(slab->nr_refs > 0);
+
+        for (node = list_next(&slab->list_node);
+             !list_end(&cache->partial_slabs, node);
+             node = list_next(node)) {
+            tmp = list_entry(node, struct kmem_slab, list_node);
+
+            if (tmp->nr_refs <= slab->nr_refs)
+                break;
+        }
+
+        /*
+         * If the direct neighbor was found, the list is already sorted.
+         * If no slab was found, the slab is inserted at the tail of the list.
+         */
+        if (node != list_next(&slab->list_node)) {
+            list_remove(&slab->list_node);
+            list_insert_before(node, &slab->list_node);
+        }
+    }
+}
+
+static void kmem_cache_alloc_verify(struct kmem_cache *cache, void *buf,
+                                    int construct)
+{
+    struct kmem_buftag *buftag;
+    union kmem_bufctl *bufctl;
+    void *addr;
+
+    buftag = kmem_buf_to_buftag(buf, cache);
+
+    if (buftag->state != KMEM_BUFTAG_FREE)
+        kmem_cache_error(cache, buf, KMEM_ERR_BUFTAG, buftag);
+
+    addr = kmem_buf_verify_fill(buf, KMEM_FREE_PATTERN, KMEM_UNINIT_PATTERN,
+                                cache->bufctl_dist);
+
+    if (addr != NULL)
+        kmem_cache_error(cache, buf, KMEM_ERR_MODIFIED, addr);
+
+    addr = buf + cache->obj_size;
+    memset(addr, KMEM_REDZONE_BYTE, cache->redzone_pad);
+
+    bufctl = kmem_buf_to_bufctl(buf, cache);
+    bufctl->redzone = KMEM_REDZONE_WORD;
+    buftag->state = KMEM_BUFTAG_ALLOC;
+
+    if (construct && (cache->ctor != NULL))
+        cache->ctor(buf);
+}
+
+vm_offset_t kmem_cache_alloc(struct kmem_cache *cache)
+{
+    int filled;
+    void *buf;
+
+#if SLAB_USE_CPU_POOLS
+    struct kmem_cpu_pool *cpu_pool;
+
+    cpu_pool = kmem_cpu_pool_get(cache);
+
+    if (cpu_pool->flags & KMEM_CF_NO_CPU_POOL)
+        goto slab_alloc;
+
+    simple_lock(&cpu_pool->lock);
+
+fast_alloc:
+    if (likely(cpu_pool->nr_objs > 0)) {
+        buf = kmem_cpu_pool_pop(cpu_pool);
+        simple_unlock(&cpu_pool->lock);
+
+        if (cpu_pool->flags & KMEM_CF_VERIFY)
+            kmem_cache_alloc_verify(cache, buf, KMEM_AV_CONSTRUCT);
+
+        return (vm_offset_t)buf;
+    }
+
+    if (cpu_pool->array != NULL) {
+        filled = kmem_cpu_pool_fill(cpu_pool, cache);
+
+        if (!filled) {
+            simple_unlock(&cpu_pool->lock);
+
+            filled = kmem_cache_grow(cache);
+
+            if (!filled)
+                return 0;
+
+            simple_lock(&cpu_pool->lock);
+        }
+
+        goto fast_alloc;
+    }
+
+    simple_unlock(&cpu_pool->lock);
+#endif /* SLAB_USE_CPU_POOLS */
+
+slab_alloc:
+    simple_lock(&cache->lock);
+    buf = kmem_cache_alloc_from_slab(cache);
+    simple_unlock(&cache->lock);
+
+    if (buf == NULL) {
+        filled = kmem_cache_grow(cache);
+
+        if (!filled)
+            return 0;
+
+        goto slab_alloc;
+    }
+
+    if (cache->flags & KMEM_CF_VERIFY)
+        kmem_cache_alloc_verify(cache, buf, KMEM_AV_NOCONSTRUCT);
+
+    if (cache->ctor != NULL)
+        cache->ctor(buf);
+
+    return (vm_offset_t)buf;
+}
+
+static void kmem_cache_free_verify(struct kmem_cache *cache, void *buf)
+{
+    struct rbtree_node *node;
+    struct kmem_buftag *buftag;
+    struct kmem_slab *slab;
+    union kmem_bufctl *bufctl;
+    unsigned char *redzone_byte;
+    unsigned long slabend;
+
+    simple_lock(&cache->lock);
+    node = rbtree_lookup_nearest(&cache->active_slabs, buf,
+                                 kmem_slab_cmp_lookup, RBTREE_LEFT);
+    simple_unlock(&cache->lock);
+
+    if (node == NULL)
+        kmem_cache_error(cache, buf, KMEM_ERR_INVALID, NULL);
+
+    slab = rbtree_entry(node, struct kmem_slab, tree_node);
+    slabend = P2ALIGN((unsigned long)slab->addr + cache->slab_size, PAGE_SIZE);
+
+    if ((unsigned long)buf >= slabend)
+        kmem_cache_error(cache, buf, KMEM_ERR_INVALID, NULL);
+
+    if ((((unsigned long)buf - (unsigned long)slab->addr) % cache->buf_size)
+        != 0)
+        kmem_cache_error(cache, buf, KMEM_ERR_INVALID, NULL);
+
+    /*
+     * As the buffer address is valid, accessing its buftag is safe.
+     */
+    buftag = kmem_buf_to_buftag(buf, cache);
+
+    if (buftag->state != KMEM_BUFTAG_ALLOC) {
+        if (buftag->state == KMEM_BUFTAG_FREE)
+            kmem_cache_error(cache, buf, KMEM_ERR_DOUBLEFREE, NULL);
+        else
+            kmem_cache_error(cache, buf, KMEM_ERR_BUFTAG, buftag);
+    }
+
+    redzone_byte = buf + cache->obj_size;
+    bufctl = kmem_buf_to_bufctl(buf, cache);
+
+    while (redzone_byte < (unsigned char *)bufctl) {
+        if (*redzone_byte != KMEM_REDZONE_BYTE)
+            kmem_cache_error(cache, buf, KMEM_ERR_REDZONE, redzone_byte);
+
+        redzone_byte++;
+    }
+
+    if (bufctl->redzone != KMEM_REDZONE_WORD) {
+        unsigned long word;
+
+        word = KMEM_REDZONE_WORD;
+        redzone_byte = kmem_buf_verify_bytes(&bufctl->redzone, &word,
+                                             sizeof(bufctl->redzone));
+        kmem_cache_error(cache, buf, KMEM_ERR_REDZONE, redzone_byte);
+    }
+
+    kmem_buf_fill(buf, KMEM_FREE_PATTERN, cache->bufctl_dist);
+    buftag->state = KMEM_BUFTAG_FREE;
+}
+
+void kmem_cache_free(struct kmem_cache *cache, vm_offset_t obj)
+{
+#if SLAB_USE_CPU_POOLS
+    struct kmem_cpu_pool *cpu_pool;
+    void **array;
+
+    cpu_pool = kmem_cpu_pool_get(cache);
+
+    if (cpu_pool->flags & KMEM_CF_VERIFY) {
+#else /* SLAB_USE_CPU_POOLS */
+    if (cache->flags & KMEM_CF_VERIFY) {
+#endif /* SLAB_USE_CPU_POOLS */
+        kmem_cache_free_verify(cache, (void *)obj);
+    }
+
+#if SLAB_USE_CPU_POOLS
+    if (cpu_pool->flags & KMEM_CF_NO_CPU_POOL)
+        goto slab_free;
+
+    simple_lock(&cpu_pool->lock);
+
+fast_free:
+    if (likely(cpu_pool->nr_objs < cpu_pool->size)) {
+        kmem_cpu_pool_push(cpu_pool, (void *)obj);
+        simple_unlock(&cpu_pool->lock);
+        return;
+    }
+
+    if (cpu_pool->array != NULL) {
+        kmem_cpu_pool_drain(cpu_pool, cache);
+        goto fast_free;
+    }
+
+    simple_unlock(&cpu_pool->lock);
+
+    array = (void *)kmem_cache_alloc(cache->cpu_pool_type->array_cache);
+
+    if (array != NULL) {
+        simple_lock(&cpu_pool->lock);
+
+        /*
+         * Another thread may have built the CPU pool while the lock was
+         * dropped.
+         */
+        if (cpu_pool->array != NULL) {
+            simple_unlock(&cpu_pool->lock);
+            kmem_cache_free(cache->cpu_pool_type->array_cache,
+                            (vm_offset_t)array);
+            goto fast_free;
+        }
+
+        kmem_cpu_pool_build(cpu_pool, cache, array);
+        goto fast_free;
+    }
+
+slab_free:
+#endif /* SLAB_USE_CPU_POOLS */
+
+    kmem_cache_free_to_slab(cache, (void *)obj);
+}
+
+void slab_collect(void)
+{
+    struct kmem_cache *cache;
+
+    if (sched_tick <= (kmem_gc_last_tick + KMEM_GC_INTERVAL))
+        return;
+
+    kmem_gc_last_tick = sched_tick;
+
+    simple_lock(&mem_cache_list_lock);
+
+    list_for_each_entry(&kmem_cache_list, cache, node)
+        kmem_cache_reap(cache);
+
+    simple_unlock(&mem_cache_list_lock);
+}
+
+void slab_bootstrap(void)
+{
+    /* Make sure a bufctl can always be stored in a buffer */
+    assert(sizeof(union kmem_bufctl) <= KMEM_ALIGN_MIN);
+
+    list_init(&kmem_cache_list);
+    simple_lock_init(&kmem_cache_list_lock);
+}
+
+void slab_init(void)
+{
+    vm_offset_t min, max;
+
+#if SLAB_USE_CPU_POOLS
+    struct kmem_cpu_pool_type *cpu_pool_type;
+    char name[KMEM_CACHE_NAME_SIZE];
+    size_t i, size;
+#endif /* SLAB_USE_CPU_POOLS */
+
+    kmem_submap(kmem_map, kernel_map, &min, &max, KMEM_MAP_SIZE, FALSE);
+
+#if SLAB_USE_CPU_POOLS
+    for (i = 0; i < ARRAY_SIZE(kmem_cpu_pool_types); i++) {
+        cpu_pool_type = &kmem_cpu_pool_types[i];
+        cpu_pool_type->array_cache = &kmem_cpu_array_caches[i];
+        sprintf(name, "kmem_cpu_array_%d", cpu_pool_type->array_size);
+        size = sizeof(void *) * cpu_pool_type->array_size;
+        kmem_cache_init(cpu_pool_type->array_cache, name, size,
+                        cpu_pool_type->array_align, NULL, NULL, NULL, 0);
+    }
+#endif /* SLAB_USE_CPU_POOLS */
+
+    /*
+     * Prevent off slab data for the slab cache to avoid infinite recursion.
+     */
+    kmem_cache_init(&kmem_slab_cache, "kmem_slab", sizeof(struct kmem_slab),
+                    0, NULL, NULL, NULL, KMEM_CACHE_NOOFFSLAB);
+}
+
+static vm_offset_t kalloc_pagealloc(vm_size_t size)
+{
+    vm_offset_t addr;
+    kern_return_t kr;
+
+    kr = kmem_alloc_wired(kalloc_map, &addr, size);
+
+    if (kr != KERN_SUCCESS)
+        return 0;
+
+    return addr;
+}
+
+static void kalloc_pagefree(vm_offset_t ptr, vm_size_t size)
+{
+    kmem_free(kalloc_map, ptr, size);
+}
+
+void kalloc_init(void)
+{
+    char name[KMEM_CACHE_NAME_SIZE];
+    size_t i, size;
+    vm_offset_t min, max;
+
+    kmem_submap(kalloc_map, kernel_map, &min, &max, KALLOC_MAP_SIZE, FALSE);
+
+    size = 1 << KALLOC_FIRST_SHIFT;
+
+    for (i = 0; i < ARRAY_SIZE(kalloc_caches); i++) {
+        sprintf(name, "kalloc_%u", size);
+        kmem_cache_init(&kalloc_caches[i], name, size, 0, NULL,
+                        kalloc_pagealloc, kalloc_pagefree, 0);
+        size <<= 1;
+    }
+}
+
+/*
+ * Return the kalloc cache index matching the given allocation size, which
+ * must be strictly greater than 0.
+ */
+static inline size_t kalloc_get_index(unsigned long size)
+{
+    assert(size != 0);
+
+    size = (size - 1) >> KALLOC_FIRST_SHIFT;
+
+    if (size == 0)
+        return 0;
+    else
+        return (sizeof(long) * 8) - __builtin_clzl(size);
+}
+
+static void kalloc_verify(struct kmem_cache *cache, void *buf, size_t size)
+{
+    size_t redzone_size;
+    void *redzone;
+
+    assert(size <= cache->obj_size);
+
+    redzone = buf + size;
+    redzone_size = cache->obj_size - size;
+    memset(redzone, KMEM_REDZONE_BYTE, redzone_size);
+}
+
+vm_offset_t kalloc(vm_size_t size)
+{
+    size_t index;
+    void *buf;
+
+    if (size == 0)
+        return 0;
+
+    index = kalloc_get_index(size);
+
+    if (index < ARRAY_SIZE(kalloc_caches)) {
+        struct kmem_cache *cache;
+
+        cache = &kalloc_caches[index];
+        buf = (void *)kmem_cache_alloc(cache);
+
+        if ((buf != 0) && (cache->flags & KMEM_CF_VERIFY))
+            kalloc_verify(cache, buf, size);
+    } else
+        buf = (void *)kalloc_pagealloc(size);
+
+    return (vm_offset_t)buf;
+}
+
+static void kfree_verify(struct kmem_cache *cache, void *buf, size_t size)
+{
+    unsigned char *redzone_byte, *redzone_end;
+
+    assert(size <= cache->obj_size);
+
+    redzone_byte = buf + size;
+    redzone_end = buf + cache->obj_size;
+
+    while (redzone_byte < redzone_end) {
+        if (*redzone_byte != KMEM_REDZONE_BYTE)
+            kmem_cache_error(cache, buf, KMEM_ERR_REDZONE, redzone_byte);
+
+        redzone_byte++;
+    }
+}
+
+void kfree(vm_offset_t data, vm_size_t size)
+{
+    size_t index;
+
+    if ((data == 0) || (size == 0))
+        return;
+
+    index = kalloc_get_index(size);
+
+    if (index < ARRAY_SIZE(kalloc_caches)) {
+        struct kmem_cache *cache;
+
+        cache = &kalloc_caches[index];
+
+        if (cache->flags & KMEM_CF_VERIFY)
+            kfree_verify(cache, (void *)data, size);
+
+        kmem_cache_free(cache, data);
+    } else {
+        kalloc_pagefree(data, size);
+    }
+}
+
+#if MACH_DEBUG
+kern_return_t host_slab_info(host_t host, cache_info_array_t *infop,
+                             unsigned int *infoCntp)
+{
+    struct kmem_cache *cache;
+    cache_info_t *info;
+    unsigned int i, nr_caches;
+    vm_size_t info_size = info_size;
+    kern_return_t kr;
+
+    if (host == HOST_NULL)
+        return KERN_INVALID_HOST;
+
+    /*
+     * Assume the cache list is unaltered once the kernel is ready.
+     */
+
+    simple_lock(&mem_cache_list_lock);
+    nr_caches = kmem_nr_caches;
+    simple_unlock(&mem_cache_list_lock);
+
+    if (nr_caches <= *infoCntp)
+        info = *infop;
+    else {
+        vm_offset_t info_addr;
+
+        info_size = round_page(nr_caches * sizeof(*info));
+        kr = kmem_alloc_pageable(ipc_kernel_map, &info_addr, info_size);
+
+        if (kr != KERN_SUCCESS)
+            return kr;
+
+        info = (cache_info_t *)info_addr;
+    }
+
+    if (info == NULL)
+        return KERN_RESOURCE_SHORTAGE;
+
+    i = 0;
+
+    list_for_each_entry(&kmem_cache_list, cache, node) {
+        simple_lock(&cache_lock);
+        info[i].flags = ((cache->flags & KMEM_CF_NO_CPU_POOL)
+                         ? CACHE_FLAGS_NO_CPU_POOL : 0)
+                        | ((cache->flags & KMEM_CF_SLAB_EXTERNAL)
+                           ? CACHE_FLAGS_SLAB_EXTERNAL : 0)
+                        | ((cache->flags & KMEM_CF_NO_RECLAIM)
+                           ? CACHE_FLAGS_NO_RECLAIM : 0)
+                        | ((cache->flags & KMEM_CF_VERIFY)
+                           ? CACHE_FLAGS_VERIFY : 0)
+                        | ((cache->flags & KMEM_CF_DIRECT)
+                           ? CACHE_FLAGS_DIRECT : 0);
+#if SLAB_USE_CPU_POOLS
+        info[i].cpu_pool_size = cache->cpu_pool_type->array_size;
+#else /* SLAB_USE_CPU_POOLS */
+        info[i].cpu_pool_size = 0;
+#endif /* SLAB_USE_CPU_POOLS */
+        info[i].obj_size = cache->obj_size;
+        info[i].align = cache->align;
+        info[i].buf_size = cache->buf_size;
+        info[i].slab_size = cache->slab_size;
+        info[i].bufs_per_slab = cache->bufs_per_slab;
+        info[i].nr_objs = cache->nr_objs;
+        info[i].nr_bufs = cache->nr_bufs;
+        info[i].nr_slabs = cache->nr_slabs;
+        info[i].nr_free_slabs = cache->nr_free_slabs;
+        strncpy(info[i].name, cache->name, sizeof(info[i].name));
+        info[i].name[sizeof(info[i].name) - 1] = '\0';
+        simple_unlock(&cache->lock);
+
+        i++;
+    }
+
+    if (info != *infop) {
+        vm_map_copy_t copy;
+        vm_size_t used;
+
+        used = nr_caches * sizeof(*info);
+
+        if (used != info_size)
+            memset((char *)info + used, 0, info_size - used);
+
+        kr = vm_map_copyin(ipc_kernel_map, (vm_offset_t)info, used, TRUE,
+                           &copy);
+
+        assert(kr == KERN_SUCCESS);
+        *infop = (cache_info_t *)copy;
+    }
+
+    *infoCntp = nr_caches;
+
+    return KERN_SUCCESS;
+}
+#endif /* MACH_DEBUG */