about summary refs log tree commit diff
path: root/malloc/mcheck-impl.c
blob: 729e94cd0f94982269267ecc3a1fb19caa6671ad (plain) (blame)
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
/* mcheck debugging hooks for malloc.
   Copyright (C) 1990-2021 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   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; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <malloc-internal.h>
#include <mcheck.h>
#include <libintl.h>
#include <stdint.h>
#include <stdio.h>

/* Arbitrary magical numbers.  */
#define MAGICWORD       0xfedabeeb
#define MAGICFREE       0xd8675309
#define MAGICBYTE       ((char) 0xd7)
#define MALLOCFLOOD     ((char) 0x93)
#define FREEFLOOD       ((char) 0x95)

/* Function to call when something awful happens.  */
static void (*abortfunc) (enum mcheck_status);

struct hdr
{
  size_t size;                  /* Exact size requested by user.  */
  unsigned long int magic;      /* Magic number to check header integrity.  */
  struct hdr *prev;
  struct hdr *next;
  void *block;                  /* Real block allocated, for memalign.  */
  unsigned long int magic2;     /* Extra, keeps us doubleword aligned.  */
} __attribute__ ((aligned (MALLOC_ALIGNMENT)));

/* This is the beginning of the list of all memory blocks allocated.
   It is only constructed if the pedantic testing is requested.  */
static struct hdr *root;

/* Nonzero if pedentic checking of all blocks is requested.  */
static bool pedantic;

#if defined _LIBC || defined STDC_HEADERS || defined USG
# include <string.h>
# define flood memset
#else
static void flood (void *, int, size_t);
static void
flood (void *ptr, int val, size_t size)
{
  char *cp = ptr;
  while (size--)
    *cp++ = val;
}
#endif

static enum mcheck_status
checkhdr (const struct hdr *hdr)
{
  enum mcheck_status status;
  bool mcheck_used = __is_malloc_debug_enabled (MALLOC_MCHECK_HOOK);

  if (!mcheck_used)
    /* Maybe the mcheck used is disabled?  This happens when we find
       an error and report it.  */
    return MCHECK_OK;

  switch (hdr->magic ^ ((uintptr_t) hdr->prev + (uintptr_t) hdr->next))
    {
    default:
      status = MCHECK_HEAD;
      break;
    case MAGICFREE:
      status = MCHECK_FREE;
      break;
    case MAGICWORD:
      if (((char *) &hdr[1])[hdr->size] != MAGICBYTE)
	status = MCHECK_TAIL;
      else if ((hdr->magic2 ^ (uintptr_t) hdr->block) != MAGICWORD)
	status = MCHECK_HEAD;
      else
	status = MCHECK_OK;
      break;
    }
  if (status != MCHECK_OK)
    {
      mcheck_used = 0;
      (*abortfunc) (status);
      mcheck_used = 1;
    }
  return status;
}

static enum mcheck_status
__mcheck_checkptr (const void *ptr)
{
  if (!__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK))
      return MCHECK_DISABLED;

  if (ptr != NULL)
    return checkhdr (((struct hdr *) ptr) - 1);

  /* Walk through all the active blocks and test whether they were tampered
     with.  */
  struct hdr *runp = root;

  /* Temporarily turn off the checks.  */
  pedantic = false;

  while (runp != NULL)
    {
      (void) checkhdr (runp);

      runp = runp->next;
    }

  /* Turn checks on again.  */
  pedantic = true;

  return MCHECK_OK;
}

static void
unlink_blk (struct hdr *ptr)
{
  if (ptr->next != NULL)
    {
      ptr->next->prev = ptr->prev;
      ptr->next->magic = MAGICWORD ^ ((uintptr_t) ptr->next->prev
                                      + (uintptr_t) ptr->next->next);
    }
  if (ptr->prev != NULL)
    {
      ptr->prev->next = ptr->next;
      ptr->prev->magic = MAGICWORD ^ ((uintptr_t) ptr->prev->prev
                                      + (uintptr_t) ptr->prev->next);
    }
  else
    root = ptr->next;
}

static void
link_blk (struct hdr *hdr)
{
  hdr->prev = NULL;
  hdr->next = root;
  root = hdr;
  hdr->magic = MAGICWORD ^ (uintptr_t) hdr->next;

  /* And the next block.  */
  if (hdr->next != NULL)
    {
      hdr->next->prev = hdr;
      hdr->next->magic = MAGICWORD ^ ((uintptr_t) hdr
                                      + (uintptr_t) hdr->next->next);
    }
}

static void *
free_mcheck (void *ptr)
{
  if (pedantic)
    __mcheck_checkptr (NULL);
  if (ptr)
    {
      struct hdr *hdr = ((struct hdr *) ptr) - 1;
      checkhdr (hdr);
      hdr->magic = MAGICFREE;
      hdr->magic2 = MAGICFREE;
      unlink_blk (hdr);
      hdr->prev = hdr->next = NULL;
      flood (ptr, FREEFLOOD, hdr->size);
      ptr = hdr->block;
    }
  return ptr;
}

static bool
malloc_mcheck_before (size_t *sizep, void **victimp)
{
  size_t size = *sizep;

  if (pedantic)
    __mcheck_checkptr (NULL);

  if (size > ~((size_t) 0) - (sizeof (struct hdr) + 1))
    {
      __set_errno (ENOMEM);
      *victimp = NULL;
      return true;
    }

  *sizep = sizeof (struct hdr) + size + 1;
  return false;
}

static void *
malloc_mcheck_after (void *mem, size_t size)
{
  struct hdr *hdr = mem;

  if (hdr == NULL)
    return NULL;

  hdr->size = size;
  link_blk (hdr);
  hdr->block = hdr;
  hdr->magic2 = (uintptr_t) hdr ^ MAGICWORD;
  ((char *) &hdr[1])[size] = MAGICBYTE;
  flood ((void *) (hdr + 1), MALLOCFLOOD, size);
  return (void *) (hdr + 1);
}

static bool
memalign_mcheck_before (size_t alignment, size_t *sizep, void **victimp)
{
  struct hdr *hdr;
  size_t slop, size = *sizep;

  /* Punt to malloc to avoid double headers.  */
  if (alignment <= MALLOC_ALIGNMENT)
    {
      *victimp = __debug_malloc (size);
      return true;
    }

  if (pedantic)
    __mcheck_checkptr (NULL);

  slop = (sizeof *hdr + alignment - 1) & - alignment;

  if (size > ~((size_t) 0) - (slop + 1))
    {
      __set_errno (ENOMEM);
      *victimp = NULL;
      return true;
    }

  *sizep = slop + size + 1;
  return false;
}

static void *
memalign_mcheck_after (void *block, size_t alignment, size_t size)
{
  if (block == NULL)
    return NULL;

  /* This was served by __debug_malloc, so return as is.  */
  if (alignment <= MALLOC_ALIGNMENT)
    return block;

  size_t slop = (sizeof (struct hdr) + alignment - 1) & - alignment;
  struct hdr *hdr = ((struct hdr *) (block + slop)) - 1;

  hdr->size = size;
  link_blk (hdr);
  hdr->block = (void *) block;
  hdr->magic2 = (uintptr_t) block ^ MAGICWORD;
  ((char *) &hdr[1])[size] = MAGICBYTE;
  flood ((void *) (hdr + 1), MALLOCFLOOD, size);
  return (void *) (hdr + 1);
}

static bool
realloc_mcheck_before (void **ptrp, size_t *sizep, size_t *oldsize,
		       void **victimp)
{
  size_t size = *sizep;
  void *ptr = *ptrp;

  if (ptr == NULL)
    {
      *victimp = __debug_malloc (size);
      *oldsize = 0;
      return true;
    }

  if (size == 0)
    {
      __debug_free (ptr);
      *victimp = NULL;
      return true;
    }

  if (size > ~((size_t) 0) - (sizeof (struct hdr) + 1))
    {
      __set_errno (ENOMEM);
      *victimp = NULL;
      *oldsize = 0;
      return true;
    }

  if (pedantic)
    __mcheck_checkptr (NULL);

  struct hdr *hdr;
  size_t osize;

  /* Update the oldptr for glibc realloc.  */
  *ptrp = hdr = ((struct hdr *) ptr) - 1;

  osize = hdr->size;

  checkhdr (hdr);
  unlink_blk (hdr);
  if (size < osize)
    flood ((char *) ptr + size, FREEFLOOD, osize - size);

  *oldsize = osize;
  *sizep = sizeof (struct hdr) + size + 1;
  return false;
}

static void *
realloc_mcheck_after (void *ptr, void *oldptr, size_t size, size_t osize)
{
  struct hdr *hdr = ptr;

  if (hdr == NULL)
    return NULL;

  /* Malloc already added the header so don't tamper with it.  */
  if (oldptr == NULL)
    return ptr;

  hdr->size = size;
  link_blk (hdr);
  hdr->block = hdr;
  hdr->magic2 = (uintptr_t) hdr ^ MAGICWORD;
  ((char *) &hdr[1])[size] = MAGICBYTE;
  if (size > osize)
    flood ((char *) (hdr + 1) + osize, MALLOCFLOOD, size - osize);
  return (void *) (hdr + 1);
}

__attribute__ ((noreturn))
static void
mabort (enum mcheck_status status)
{
  const char *msg;
  switch (status)
    {
    case MCHECK_OK:
      msg = _ ("memory is consistent, library is buggy\n");
      break;
    case MCHECK_HEAD:
      msg = _ ("memory clobbered before allocated block\n");
      break;
    case MCHECK_TAIL:
      msg = _ ("memory clobbered past end of allocated block\n");
      break;
    case MCHECK_FREE:
      msg = _ ("block freed twice\n");
      break;
    default:
      msg = _ ("bogus mcheck_status, library is buggy\n");
      break;
    }
#ifdef _LIBC
  __libc_fatal (msg);
#else
  fprintf (stderr, "mcheck: %s", msg);
  fflush (stderr);
  abort ();
#endif
}

/* Memory barrier so that GCC does not optimize out the argument.  */
#define malloc_opt_barrier(x) \
  ({ __typeof (x) __x = x; __asm ("" : "+m" (__x)); __x; })

static int
__mcheck_initialize (void (*func) (enum mcheck_status), bool in_pedantic)
{
  abortfunc = (func != NULL) ? func : &mabort;

  switch (debug_initialized)
    {
    case -1:
      /* Called before the first malloc was called.  */
      __debug_free (__debug_malloc (0));
      /* FALLTHROUGH */
    case 0:
      /* Called through the initializer hook.  */
      __malloc_debug_enable (MALLOC_MCHECK_HOOK);
      break;
    case 1:
    default:
      /* Malloc was already called.  Fail.  */
      return -1;
    }

  pedantic = in_pedantic;
  return 0;
}

static int
mcheck_usable_size (struct hdr *h)
{
  return (h - 1)->size;
}