summaryrefslogtreecommitdiff
path: root/malloc/hooks.c
blob: 996111a7e3b2f1373d888c7a1a4740bcaa6dee4d (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
/* Malloc implementation for multiple threads without lock contention.
   Copyright (C) 2001-2014 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Wolfram Gloger <wg@malloc.de>, 2001.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If
   not, see <http://www.gnu.org/licenses/>.  */

/* What to do if the standard debugging hooks are in place and a
   corrupt pointer is detected: do nothing (0), print an error message
   (1), or call abort() (2). */

/* Hooks for debugging versions.  The initial hooks just call the
   initialization routine, then do the normal work. */

static void *
malloc_hook_ini (size_t sz, const void *caller)
{
  __malloc_hook = NULL;
  ptmalloc_init ();
  return __libc_malloc (sz);
}

static void *
realloc_hook_ini (void *ptr, size_t sz, const void *caller)
{
  __malloc_hook = NULL;
  __realloc_hook = NULL;
  ptmalloc_init ();
  return __libc_realloc (ptr, sz);
}

static void *
memalign_hook_ini (size_t alignment, size_t sz, const void *caller)
{
  __memalign_hook = NULL;
  ptmalloc_init ();
  return __libc_memalign (alignment, sz);
}

/* Whether we are using malloc checking.  */
static int using_malloc_checking;

/* A flag that is set by malloc_set_state, to signal that malloc checking
   must not be enabled on the request from the user (via the MALLOC_CHECK_
   environment variable).  It is reset by __malloc_check_init to tell
   malloc_set_state that the user has requested malloc checking.

   The purpose of this flag is to make sure that malloc checking is not
   enabled when the heap to be restored was constructed without malloc
   checking, and thus does not contain the required magic bytes.
   Otherwise the heap would be corrupted by calls to free and realloc.  If
   it turns out that the heap was created with malloc checking and the
   user has requested it malloc_set_state just calls __malloc_check_init
   again to enable it.  On the other hand, reusing such a heap without
   further malloc checking is safe.  */
static int disallow_malloc_check;

/* Activate a standard set of debugging hooks. */
void
__malloc_check_init (void)
{
  if (disallow_malloc_check)
    {
      disallow_malloc_check = 0;
      return;
    }
  using_malloc_checking = 1;
  __malloc_hook = malloc_check;
  __free_hook = free_check;
  __realloc_hook = realloc_check;
  __memalign_hook = memalign_check;
}

/* A simple, standard set of debugging hooks.  Overhead is `only' one
   byte per chunk; still this will catch most cases of double frees or
   overruns.  The goal here is to avoid obscure crashes due to invalid
   usage, unlike in the MALLOC_DEBUG code. */

#define MAGICBYTE(p) ((((size_t) p >> 3) ^ ((size_t) p >> 11)) & 0xFF)

/* Visualize the chunk as being partitioned into blocks of 255 bytes from the
   highest address of the chunk, downwards.  The end of each block tells us
   the size of that block, up to the actual size of the requested memory.
   The last block has a length of zero and is followed by the magic byte.
   Our magic byte is right at the end of the requested size.  If we don't
   reach it with this iteration we have witnessed a memory corruption.  */
static size_t
malloc_check_get_size (mchunkptr p)
{
  size_t total_sz, size;
  unsigned char c;
  unsigned char magic = MAGICBYTE (p);

  assert (using_malloc_checking == 1);

  /* Validate the length-byte chain.  */
  total_sz = chunksize (p) + (chunk_is_mmapped (p) ? 0 : SIZE_SZ);
  for (size = total_sz - 1;
       (c = ((unsigned char *) p)[size]) != 0;
       size -= c)
    {
      if (size <= c + 2 * SIZE_SZ)
	break;
    }
  if (c != 0 || ((unsigned char *) p)[--size] != magic)
    {
      malloc_printerr (check_action, "malloc_check_get_size: memory corruption",
		       chunk2mem (p));
      return 0;
    }

  /* chunk2mem size.  */
  return size - 2 * SIZE_SZ;
}

/* Instrument a chunk with overrun detector byte(s) and convert it
   into a user pointer with requested size sz. */

static void *
internal_function
mem2mem_check (void *ptr, size_t sz)
{
  mchunkptr p;
  unsigned char *m_ptr = ptr;
  size_t user_sz, block_sz, i;

  if (!ptr)
    return ptr;

  p = mem2chunk (ptr);
  user_sz = chunksize (p) + (chunk_is_mmapped (p) ? 0 : SIZE_SZ);
  user_sz -= 2 * SIZE_SZ;
  for (i = user_sz - 1; i > sz; i -= block_sz)
    {
      block_sz = i - (sz + 1);
      if (block_sz > 0xff)
	block_sz = 0xff;

      m_ptr[i] = (unsigned char) block_sz;

      if (block_sz == 0)
	break;
    }
  m_ptr[sz] = MAGICBYTE (p);
  return (void *) m_ptr;
}

/* Convert a pointer to be free()d or realloc()ed to a valid chunk
   pointer.  If the provided pointer is not valid, return NULL. */

static mchunkptr
internal_function
mem2chunk_check (void *mem, unsigned char **magic_p)
{
  mchunkptr p;
  INTERNAL_SIZE_T sz, c;
  unsigned char magic;

  if (!aligned_OK (mem))
    return NULL;

  p = mem2chunk (mem);
  sz = chunksize (p);
  magic = MAGICBYTE (p);
  if (!chunk_is_mmapped (p))
    {
      /* Must be a chunk in conventional heap memory. */
      int contig = contiguous (&main_arena);
      if ((contig &&
           ((char *) p < mp_.sbrk_base ||
            ((char *) p + sz) >= (mp_.sbrk_base + main_arena.system_mem))) ||
          sz < MINSIZE || sz & MALLOC_ALIGN_MASK || !inuse (p) ||
          (!prev_inuse (p) && (p->prev_size & MALLOC_ALIGN_MASK ||
                               (contig && (char *) prev_chunk (p) < mp_.sbrk_base) ||
                               next_chunk (prev_chunk (p)) != p)))
        return NULL;

      for (sz += SIZE_SZ - 1; (c = ((unsigned char *) p)[sz]) != 0; sz -= c)
        {
	  if (sz <= c + 2 * SIZE_SZ)
	    break;
        }
      if (c != 0 || ((unsigned char *) p)[--sz] != magic)
	return NULL;
    }
  else
    {
      unsigned long offset, page_mask = GLRO (dl_pagesize) - 1;

      /* mmap()ed chunks have MALLOC_ALIGNMENT or higher power-of-two
         alignment relative to the beginning of a page.  Check this
         first. */
      offset = (unsigned long) mem & page_mask;
      if ((offset != MALLOC_ALIGNMENT && offset != 0 && offset != 0x10 &&
           offset != 0x20 && offset != 0x40 && offset != 0x80 && offset != 0x100 &&
           offset != 0x200 && offset != 0x400 && offset != 0x800 && offset != 0x1000 &&
           offset < 0x2000) ||
          !chunk_is_mmapped (p) || (p->size & PREV_INUSE) ||
          ((((unsigned long) p - p->prev_size) & page_mask) != 0) ||
          ((p->prev_size + sz) & page_mask) != 0)
        return NULL;

      for (sz -= 1; (c = ((unsigned char *) p)[sz]) != 0; sz -= c)
        {
	  if (sz <= c + 2 * SIZE_SZ)
	    break;
        }
      if (c != 0 || ((unsigned char *) p)[--sz] != magic)
	return NULL;
    }
  ((unsigned char *) p)[sz] ^= 0xFF;
  if (magic_p)
    *magic_p = (unsigned char *) p + sz;
  return p;
}

/* Check for corruption of the top chunk, and try to recover if
   necessary. */

static int
internal_function
top_check (void)
{
  mchunkptr t = top (&main_arena);
  char *brk, *new_brk;
  INTERNAL_SIZE_T front_misalign, sbrk_size;
  unsigned long pagesz = GLRO (dl_pagesize);

  if (t == initial_top (&main_arena) ||
      (!chunk_is_mmapped (t) &&
       chunksize (t) >= MINSIZE &&
       prev_inuse (t) &&
       (!contiguous (&main_arena) ||
        (char *) t + chunksize (t) == mp_.sbrk_base + main_arena.system_mem)))
    return 0;

  malloc_printerr (check_action, "malloc: top chunk is corrupt", t);

  /* Try to set up a new top chunk. */
  brk = MORECORE (0);
  front_misalign = (unsigned long) chunk2mem (brk) & MALLOC_ALIGN_MASK;
  if (front_misalign > 0)
    front_misalign = MALLOC_ALIGNMENT - front_misalign;
  sbrk_size = front_misalign + mp_.top_pad + MINSIZE;
  sbrk_size += pagesz - ((unsigned long) (brk + sbrk_size) & (pagesz - 1));
  new_brk = (char *) (MORECORE (sbrk_size));
  if (new_brk == (char *) (MORECORE_FAILURE))
    {
      __set_errno (ENOMEM);
      return -1;
    }
  /* Call the `morecore' hook if necessary.  */
  void (*hook) (void) = atomic_forced_read (__after_morecore_hook);
  if (hook)
    (*hook)();
  main_arena.system_mem = (new_brk - mp_.sbrk_base) + sbrk_size;

  top (&main_arena) = (mchunkptr) (brk + front_misalign);
  set_head (top (&main_arena), (sbrk_size - front_misalign) | PREV_INUSE);

  return 0;
}

static void *
malloc_check (size_t sz, const void *caller)
{
  void *victim;

  if (sz + 1 == 0)
    {
      __set_errno (ENOMEM);
      return NULL;
    }

  (void) mutex_lock (&main_arena.mutex);
  victim = (top_check () >= 0) ? _int_malloc (&main_arena, sz + 1) : NULL;
  (void) mutex_unlock (&main_arena.mutex);
  return mem2mem_check (victim, sz);
}

static void
free_check (void *mem, const void *caller)
{
  mchunkptr p;

  if (!mem)
    return;

  (void) mutex_lock (&main_arena.mutex);
  p = mem2chunk_check (mem, NULL);
  if (!p)
    {
      (void) mutex_unlock (&main_arena.mutex);

      malloc_printerr (check_action, "free(): invalid pointer", mem);
      return;
    }
  if (chunk_is_mmapped (p))
    {
      (void) mutex_unlock (&main_arena.mutex);
      munmap_chunk (p);
      return;
    }
  _int_free (&main_arena, p, 1);
  (void) mutex_unlock (&main_arena.mutex);
}

static void *
realloc_check (void *oldmem, size_t bytes, const void *caller)
{
  INTERNAL_SIZE_T nb;
  void *newmem = 0;
  unsigned char *magic_p;

  if (bytes + 1 == 0)
    {
      __set_errno (ENOMEM);
      return NULL;
    }
  if (oldmem == 0)
    return malloc_check (bytes, NULL);

  if (bytes == 0)
    {
      free_check (oldmem, NULL);
      return NULL;
    }
  (void) mutex_lock (&main_arena.mutex);
  const mchunkptr oldp = mem2chunk_check (oldmem, &magic_p);
  (void) mutex_unlock (&main_arena.mutex);
  if (!oldp)
    {
      malloc_printerr (check_action, "realloc(): invalid pointer", oldmem);
      return malloc_check (bytes, NULL);
    }
  const INTERNAL_SIZE_T oldsize = chunksize (oldp);

  checked_request2size (bytes + 1, nb);
  (void) mutex_lock (&main_arena.mutex);

  if (chunk_is_mmapped (oldp))
    {
#if HAVE_MREMAP
      mchunkptr newp = mremap_chunk (oldp, nb);
      if (newp)
        newmem = chunk2mem (newp);
      else
#endif
      {
        /* Note the extra SIZE_SZ overhead. */
        if (oldsize - SIZE_SZ >= nb)
          newmem = oldmem; /* do nothing */
        else
          {
            /* Must alloc, copy, free. */
            if (top_check () >= 0)
              newmem = _int_malloc (&main_arena, bytes + 1);
            if (newmem)
              {
                memcpy (newmem, oldmem, oldsize - 2 * SIZE_SZ);
                munmap_chunk (oldp);
              }
          }
      }
    }
  else
    {
      if (top_check () >= 0)
        {
          INTERNAL_SIZE_T nb;
          checked_request2size (bytes + 1, nb);
          newmem = _int_realloc (&main_arena, oldp, oldsize, nb);
        }
    }

  /* mem2chunk_check changed the magic byte in the old chunk.
     If newmem is NULL, then the old chunk will still be used though,
     so we need to invert that change here.  */
  if (newmem == NULL)
    *magic_p ^= 0xFF;

  (void) mutex_unlock (&main_arena.mutex);

  return mem2mem_check (newmem, bytes);
}

static void *
memalign_check (size_t alignment, size_t bytes, const void *caller)
{
  void *mem;

  if (alignment <= MALLOC_ALIGNMENT)
    return malloc_check (bytes, NULL);

  if (alignment < MINSIZE)
    alignment = MINSIZE;

  /* If the alignment is greater than SIZE_MAX / 2 + 1 it cannot be a
     power of 2 and will cause overflow in the check below.  */
  if (alignment > SIZE_MAX / 2 + 1)
    {
      __set_errno (EINVAL);
      return 0;
    }

  /* Check for overflow.  */
  if (bytes > SIZE_MAX - alignment - MINSIZE)
    {
      __set_errno (ENOMEM);
      return 0;
    }

  /* Make sure alignment is power of 2.  */
  if (!powerof2 (alignment))
    {
      size_t a = MALLOC_ALIGNMENT * 2;
      while (a < alignment)
        a <<= 1;
      alignment = a;
    }

  (void) mutex_lock (&main_arena.mutex);
  mem = (top_check () >= 0) ? _int_memalign (&main_arena, alignment, bytes + 1) :
        NULL;
  (void) mutex_unlock (&main_arena.mutex);
  return mem2mem_check (mem, bytes);
}


/* Get/set state: malloc_get_state() records the current state of all
   malloc variables (_except_ for the actual heap contents and `hook'
   function pointers) in a system dependent, opaque data structure.
   This data structure is dynamically allocated and can be free()d
   after use.  malloc_set_state() restores the state of all malloc
   variables to the previously obtained state.  This is especially
   useful when using this malloc as part of a shared library, and when
   the heap contents are saved/restored via some other method.  The
   primary example for this is GNU Emacs with its `dumping' procedure.
   `Hook' function pointers are never saved or restored by these
   functions, with two exceptions: If malloc checking was in use when
   malloc_get_state() was called, then malloc_set_state() calls
   __malloc_check_init() if possible; if malloc checking was not in
   use in the recorded state but the user requested malloc checking,
   then the hooks are reset to 0.  */

#define MALLOC_STATE_MAGIC   0x444c4541l
#define MALLOC_STATE_VERSION (0 * 0x100l + 4l) /* major*0x100 + minor */

struct malloc_save_state
{
  long magic;
  long version;
  mbinptr av[NBINS * 2 + 2];
  char *sbrk_base;
  int sbrked_mem_bytes;
  unsigned long trim_threshold;
  unsigned long top_pad;
  unsigned int n_mmaps_max;
  unsigned long mmap_threshold;
  int check_action;
  unsigned long max_sbrked_mem;
  unsigned long max_total_mem;
  unsigned int n_mmaps;
  unsigned int max_n_mmaps;
  unsigned long mmapped_mem;
  unsigned long max_mmapped_mem;
  int using_malloc_checking;
  unsigned long max_fast;
  unsigned long arena_test;
  unsigned long arena_max;
  unsigned long narenas;
};

void *
__malloc_get_state (void)
{
  struct malloc_save_state *ms;
  int i;
  mbinptr b;

  ms = (struct malloc_save_state *) __libc_malloc (sizeof (*ms));
  if (!ms)
    return 0;

  (void) mutex_lock (&main_arena.mutex);
  malloc_consolidate (&main_arena);
  ms->magic = MALLOC_STATE_MAGIC;
  ms->version = MALLOC_STATE_VERSION;
  ms->av[0] = 0;
  ms->av[1] = 0; /* used to be binblocks, now no longer used */
  ms->av[2] = top (&main_arena);
  ms->av[3] = 0; /* used to be undefined */
  for (i = 1; i < NBINS; i++)
    {
      b = bin_at (&main_arena, i);
      if (first (b) == b)
        ms->av[2 * i + 2] = ms->av[2 * i + 3] = 0; /* empty bin */
      else
        {
          ms->av[2 * i + 2] = first (b);
          ms->av[2 * i + 3] = last (b);
        }
    }
  ms->sbrk_base = mp_.sbrk_base;
  ms->sbrked_mem_bytes = main_arena.system_mem;
  ms->trim_threshold = mp_.trim_threshold;
  ms->top_pad = mp_.top_pad;
  ms->n_mmaps_max = mp_.n_mmaps_max;
  ms->mmap_threshold = mp_.mmap_threshold;
  ms->check_action = check_action;
  ms->max_sbrked_mem = main_arena.max_system_mem;
  ms->max_total_mem = 0;
  ms->n_mmaps = mp_.n_mmaps;
  ms->max_n_mmaps = mp_.max_n_mmaps;
  ms->mmapped_mem = mp_.mmapped_mem;
  ms->max_mmapped_mem = mp_.max_mmapped_mem;
  ms->using_malloc_checking = using_malloc_checking;
  ms->max_fast = get_max_fast ();
  ms->arena_test = mp_.arena_test;
  ms->arena_max = mp_.arena_max;
  ms->narenas = narenas;
  (void) mutex_unlock (&main_arena.mutex);
  return (void *) ms;
}

int
__malloc_set_state (void *msptr)
{
  struct malloc_save_state *ms = (struct malloc_save_state *) msptr;
  size_t i;
  mbinptr b;

  disallow_malloc_check = 1;
  ptmalloc_init ();
  if (ms->magic != MALLOC_STATE_MAGIC)
    return -1;

  /* Must fail if the major version is too high. */
  if ((ms->version & ~0xffl) > (MALLOC_STATE_VERSION & ~0xffl))
    return -2;

  (void) mutex_lock (&main_arena.mutex);
  /* There are no fastchunks.  */
  clear_fastchunks (&main_arena);
  if (ms->version >= 4)
    set_max_fast (ms->max_fast);
  else
    set_max_fast (64);  /* 64 used to be the value we always used.  */
  for (i = 0; i < NFASTBINS; ++i)
    fastbin (&main_arena, i) = 0;
  for (i = 0; i < BINMAPSIZE; ++i)
    main_arena.binmap[i] = 0;
  top (&main_arena) = ms->av[2];
  main_arena.last_remainder = 0;
  for (i = 1; i < NBINS; i++)
    {
      b = bin_at (&main_arena, i);
      if (ms->av[2 * i + 2] == 0)
        {
          assert (ms->av[2 * i + 3] == 0);
          first (b) = last (b) = b;
        }
      else
        {
          if (ms->version >= 3 &&
              (i < NSMALLBINS || (largebin_index (chunksize (ms->av[2 * i + 2])) == i &&
                                  largebin_index (chunksize (ms->av[2 * i + 3])) == i)))
            {
              first (b) = ms->av[2 * i + 2];
              last (b) = ms->av[2 * i + 3];
              /* Make sure the links to the bins within the heap are correct.  */
              first (b)->bk = b;
              last (b)->fd = b;
              /* Set bit in binblocks.  */
              mark_bin (&main_arena, i);
            }
          else
            {
              /* Oops, index computation from chunksize must have changed.
                 Link the whole list into unsorted_chunks.  */
              first (b) = last (b) = b;
              b = unsorted_chunks (&main_arena);
              ms->av[2 * i + 2]->bk = b;
              ms->av[2 * i + 3]->fd = b->fd;
              b->fd->bk = ms->av[2 * i + 3];
              b->fd = ms->av[2 * i + 2];
            }
        }
    }
  if (ms->version < 3)
    {
      /* Clear fd_nextsize and bk_nextsize fields.  */
      b = unsorted_chunks (&main_arena)->fd;
      while (b != unsorted_chunks (&main_arena))
        {
          if (!in_smallbin_range (chunksize (b)))
            {
              b->fd_nextsize = NULL;
              b->bk_nextsize = NULL;
            }
          b = b->fd;
        }
    }
  mp_.sbrk_base = ms->sbrk_base;
  main_arena.system_mem = ms->sbrked_mem_bytes;
  mp_.trim_threshold = ms->trim_threshold;
  mp_.top_pad = ms->top_pad;
  mp_.n_mmaps_max = ms->n_mmaps_max;
  mp_.mmap_threshold = ms->mmap_threshold;
  check_action = ms->check_action;
  main_arena.max_system_mem = ms->max_sbrked_mem;
  mp_.n_mmaps = ms->n_mmaps;
  mp_.max_n_mmaps = ms->max_n_mmaps;
  mp_.mmapped_mem = ms->mmapped_mem;
  mp_.max_mmapped_mem = ms->max_mmapped_mem;
  /* add version-dependent code here */
  if (ms->version >= 1)
    {
      /* Check whether it is safe to enable malloc checking, or whether
         it is necessary to disable it.  */
      if (ms->using_malloc_checking && !using_malloc_checking &&
          !disallow_malloc_check)
        __malloc_check_init ();
      else if (!ms->using_malloc_checking && using_malloc_checking)
        {
          __malloc_hook = NULL;
          __free_hook = NULL;
          __realloc_hook = NULL;
          __memalign_hook = NULL;
          using_malloc_checking = 0;
        }
    }
  if (ms->version >= 4)
    {
      mp_.arena_test = ms->arena_test;
      mp_.arena_max = ms->arena_max;
      narenas = ms->narenas;
    }
  check_malloc_state (&main_arena);

  (void) mutex_unlock (&main_arena.mutex);
  return 0;
}

/*
 * Local variables:
 * c-basic-offset: 2
 * End:
 */