summaryrefslogtreecommitdiff
path: root/kern/slab.c
blob: e8451a8a3bb84b501dc2b444db33cfa4c43c3495 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
/*
 * Copyright (c) 2011 Free Software Foundation.
 *
 * 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.
 */

/*
 * Copyright (c) 2010, 2011 Richard Braun.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *
 * 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 ticks) between two garbage collection operations.
 */
#define KMEM_GC_INTERVAL (5 * 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 (96 * 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

/*
 * 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.
 */
static struct vm_map kmem_map_store;
vm_map_t kmem_map = &kmem_map_store;

/*
 * Time of the last memory reclaim, in clock ticks.
 */
static unsigned long kmem_gc_last_tick;

#define kmem_error(format, ...)                         \
    panic("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)
{
    kmem_cache_ctor_t ctor;
    void *buf;
    int i;

    ctor = (cpu_pool->flags & KMEM_CF_VERIFY) ? NULL : cache->ctor;

    simple_lock(&cache->lock);

    for (i = 0; i < cpu_pool->transfer_size; i++) {
        buf = kmem_cache_alloc_from_slab(cache);

        if (buf == NULL)
            break;

        if (ctor != NULL)
            ctor(buf);

        kmem_cpu_pool_push(cpu_pool, buf);
    }

    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_warn("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 = 0;

    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_head(&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;
    unsigned long nr_free_slabs;

    if (cache->flags & KMEM_CF_NO_RECLAIM)
        return;

    simple_lock(&cache->lock);
    list_set_head(&dead_slabs, &cache->free_slabs);
    list_init(&cache->free_slabs);
    nr_free_slabs = cache->nr_free_slabs;
    cache->nr_bufs -= cache->bufs_per_slab * nr_free_slabs;
    cache->nr_slabs -= nr_free_slabs;
    cache->nr_free_slabs = 0;
    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);
        nr_free_slabs--;
    }

    assert(nr_free_slabs == 0);
}

/*
 * 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++;

    if (slab->nr_refs == cache->bufs_per_slab) {
        /* The slab has become complete */
        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. Insert the new slab at the end of
         * the list to reduce fragmentation.
         */
        list_remove(&slab->list_node);
        list_insert_tail(&cache->partial_slabs, &slab->list_node);
        cache->nr_free_slabs--;
    }

    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--;

    if (slab->nr_refs == 0) {
        /* The slab has become free */

        if (kmem_slab_use_tree(cache->flags))
            rbtree_remove(&cache->active_slabs, &slab->tree_node);

        if (cache->bufs_per_slab > 1)
            list_remove(&slab->list_node);

        list_insert_head(&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_head(&cache->partial_slabs, &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);
            simple_lock(&cpu_pool->lock);
            goto fast_free;
        }

        kmem_cpu_pool_build(cpu_pool, cache, array);
        goto fast_free;
    }

slab_free:
#endif /* SLAB_USE_CPU_POOLS */

    simple_lock(&cache->lock);
    kmem_cache_free_to_slab(cache, (void *)obj);
    simple_unlock(&cache->lock);
}

void slab_collect(void)
{
    struct kmem_cache *cache;

    if (elapsed_ticks <= (kmem_gc_last_tick + KMEM_GC_INTERVAL))
        return;

    kmem_gc_last_tick = elapsed_ticks;

    simple_lock(&kmem_cache_list_lock);

    list_for_each_entry(&kmem_cache_list, cache, node)
        kmem_cache_reap(cache);

    simple_unlock(&kmem_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(kmem_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(kmem_map, ptr, size);
}

void kalloc_init(void)
{
    char name[KMEM_CACHE_NAME_SIZE];
    size_t i, size;

    size = 1 << KALLOC_FIRST_SHIFT;

    for (i = 0; i < ARRAY_SIZE(kalloc_caches); i++) {
        sprintf(name, "kalloc_%lu", 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);
    }
}

void slab_info(void)
{
    struct kmem_cache *cache;
    vm_size_t mem_usage, mem_reclaimable;

    printf("cache                  obj slab  bufs   objs   bufs "
           "   total reclaimable\n"
           "name                  size size /slab  usage  count "
           "  memory      memory\n");

    simple_lock(&kmem_cache_list_lock);

    list_for_each_entry(&kmem_cache_list, cache, node) {
        simple_lock(&cache->lock);

        mem_usage = (cache->nr_slabs * cache->slab_size) >> 10;
        mem_reclaimable = (cache->nr_free_slabs * cache->slab_size) >> 10;

        printf("%-19s %6lu %3luk  %4lu %6lu %6lu %7uk %10uk\n",
               cache->name, cache->obj_size, cache->slab_size >> 10,
               cache->bufs_per_slab, cache->nr_objs, cache->nr_bufs,
               mem_usage, mem_reclaimable);

        simple_unlock(&cache->lock);
    }

    simple_unlock(&kmem_cache_list_lock);
}

#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 = 0;
    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(&kmem_cache_list_lock);
    nr_caches = kmem_nr_caches;
    simple_unlock(&kmem_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 */