malloc/mcheck.c

   1 /* Standard debugging hooks for `malloc'.
   2    Copyright (C) 1990-1997,1999,2000-2002,2007 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Written May 1989 by Mike Haertel.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #ifndef _MALLOC_INTERNAL
  22 # define _MALLOC_INTERNAL
  23 # include <malloc.h>
  24 # include <mcheck.h>
  25 # include <stdint.h>
  26 # include <stdio.h>
  27 # include <libintl.h>
  28 #endif
  29
  30 /* Old hook values.  */
  31 static void (*old_free_hook) (__ptr_t ptr, __const __ptr_t);
  32 static __ptr_t (*old_malloc_hook) (__malloc_size_t size, const __ptr_t);
  33 static __ptr_t (*old_memalign_hook) (__malloc_size_t alignment,
  34                                      __malloc_size_t size,
  35                                      const __ptr_t);
  36 static __ptr_t (*old_realloc_hook) (__ptr_t ptr, __malloc_size_t size,
  37                                     __const __ptr_t);
  38
  39 /* Function to call when something awful happens.  */
  40 static void (*abortfunc) (enum mcheck_status);
  41
  42 /* Arbitrary magical numbers.  */
  43 #define MAGICWORD       0xfedabeeb
  44 #define MAGICFREE       0xd8675309
  45 #define MAGICBYTE       ((char) 0xd7)
  46 #define MALLOCFLOOD     ((char) 0x93)
  47 #define FREEFLOOD       ((char) 0x95)
  48
  49 struct hdr
  50   {
  51     __malloc_size_t size;       /* Exact size requested by user.  */
  52     unsigned long int magic;    /* Magic number to check header integrity.  */
  53     struct hdr *prev;
  54     struct hdr *next;
  55     __ptr_t block;              /* Real block allocated, for memalign.  */
  56     unsigned long int magic2;   /* Extra, keeps us doubleword aligned.  */
  57   };
  58
  59 /* This is the beginning of the list of all memory blocks allocated.
  60    It is only constructed if the pedantic testing is requested.  */
  61 static struct hdr *root;
  62
  63 static int mcheck_used;
  64
  65 /* Nonzero if pedentic checking of all blocks is requested.  */
  66 static int pedantic;
  67
  68 #if defined _LIBC || defined STDC_HEADERS || defined USG
  69 # include <string.h>
  70 # define flood memset
  71 #else
  72 static void flood (__ptr_t, int, __malloc_size_t);
  73 static void
  74 flood (ptr, val, size)
  75      __ptr_t ptr;
  76      int val;
  77      __malloc_size_t size;
  78 {
  79   char *cp = ptr;
  80   while (size--)
  81     *cp++ = val;
  82 }
  83 #endif
  84
  85 static enum mcheck_status
  86 checkhdr (const struct hdr *hdr)
  87 {
  88   enum mcheck_status status;
  89
  90   if (!mcheck_used)
  91     /* Maybe the mcheck used is disabled?  This happens when we find
  92        an error and report it.  */
  93     return MCHECK_OK;
  94
  95   switch (hdr->magic ^ ((uintptr_t) hdr->prev + (uintptr_t) hdr->next))
  96     {
  97     default:
  98       status = MCHECK_HEAD;
  99       break;
 100     case MAGICFREE:
 101       status = MCHECK_FREE;
 102       break;
 103     case MAGICWORD:
 104       if (((char *) &hdr[1])[hdr->size] != MAGICBYTE)
 105         status = MCHECK_TAIL;
 106       else if ((hdr->magic2 ^ (uintptr_t) hdr->block) != MAGICWORD)
 107         status = MCHECK_HEAD;
 108       else
 109         status = MCHECK_OK;
 110       break;
 111     }
 112   if (status != MCHECK_OK)
 113     {
 114       mcheck_used = 0;
 115       (*abortfunc) (status);
 116       mcheck_used = 1;
 117     }
 118   return status;
 119 }
 120
 121 void
 122 mcheck_check_all (void)
 123 {
 124   /* Walk through all the active blocks and test whether they were tempered
 125      with.  */
 126   struct hdr *runp = root;
 127
 128   /* Temporarily turn off the checks.  */
 129   pedantic = 0;
 130
 131   while (runp != NULL)
 132     {
 133       (void) checkhdr (runp);
 134
 135       runp = runp->next;
 136     }
 137
 138   /* Turn checks on again.  */
 139   pedantic = 1;
 140 }
 141 #ifdef _LIBC
 142 libc_hidden_def (mcheck_check_all)
 143 #endif
 144
 145 static void
 146 unlink_blk (struct hdr *ptr)
 147 {
 148   if (ptr->next != NULL)
 149     {
 150       ptr->next->prev = ptr->prev;
 151       ptr->next->magic = MAGICWORD ^ ((uintptr_t) ptr->next->prev
 152                                       + (uintptr_t) ptr->next->next);
 153     }
 154   if (ptr->prev != NULL)
 155     {
 156       ptr->prev->next = ptr->next;
 157       ptr->prev->magic = MAGICWORD ^ ((uintptr_t) ptr->prev->prev
 158                                       + (uintptr_t) ptr->prev->next);
 159     }
 160   else
 161     root = ptr->next;
 162 }
 163
 164 static void
 165 link_blk (struct hdr *hdr)
 166 {
 167   hdr->prev = NULL;
 168   hdr->next = root;
 169   root = hdr;
 170   hdr->magic = MAGICWORD ^ (uintptr_t) hdr->next;
 171
 172   /* And the next block.  */
 173   if (hdr->next != NULL)
 174     {
 175       hdr->next->prev = hdr;
 176       hdr->next->magic = MAGICWORD ^ ((uintptr_t) hdr
 177                                       + (uintptr_t) hdr->next->next);
 178     }
 179 }
 180 static void
 181 freehook (__ptr_t ptr, const __ptr_t caller)
 182 {
 183   if (pedantic)
 184     mcheck_check_all ();
 185   if (ptr)
 186     {
 187       struct hdr *hdr = ((struct hdr *) ptr) - 1;
 188       checkhdr (hdr);
 189       hdr->magic = MAGICFREE;
 190       hdr->magic2 = MAGICFREE;
 191       unlink_blk (hdr);
 192       hdr->prev = hdr->next = NULL;
 193       flood (ptr, FREEFLOOD, hdr->size);
 194       ptr = hdr->block;
 195     }
 196   __free_hook = old_free_hook;
 197   if (old_free_hook != NULL)
 198     (*old_free_hook) (ptr, caller);
 199   else
 200     free (ptr);
 201   __free_hook = freehook;
 202 }
 203
 204 static __ptr_t
 205 mallochook (__malloc_size_t size, const __ptr_t caller)
 206 {
 207   struct hdr *hdr;
 208
 209   if (pedantic)
 210     mcheck_check_all ();
 211
 212   __malloc_hook = old_malloc_hook;
 213   if (old_malloc_hook != NULL)
 214     hdr = (struct hdr *) (*old_malloc_hook) (sizeof (struct hdr) + size + 1,
 215                                              caller);
 216   else
 217     hdr = (struct hdr *) malloc (sizeof (struct hdr) + size + 1);
 218   __malloc_hook = mallochook;
 219   if (hdr == NULL)
 220     return NULL;
 221
 222   hdr->size = size;
 223   link_blk (hdr);
 224   hdr->block = hdr;
 225   hdr->magic2 = (uintptr_t) hdr ^ MAGICWORD;
 226   ((char *) &hdr[1])[size] = MAGICBYTE;
 227   flood ((__ptr_t) (hdr + 1), MALLOCFLOOD, size);
 228   return (__ptr_t) (hdr + 1);
 229 }
 230
 231 static __ptr_t
 232 memalignhook (__malloc_size_t alignment, __malloc_size_t size,
 233               const __ptr_t caller)
 234 {
 235   struct hdr *hdr;
 236   __malloc_size_t slop;
 237   char *block;
 238
 239   if (pedantic)
 240     mcheck_check_all ();
 241
 242   slop = (sizeof *hdr + alignment - 1) & -alignment;
 243
 244   __memalign_hook = old_memalign_hook;
 245   if (old_memalign_hook != NULL)
 246     block = (*old_memalign_hook) (alignment, slop + size + 1, caller);
 247   else
 248     block = memalign (alignment, slop + size + 1);
 249   __memalign_hook = memalignhook;
 250   if (block == NULL)
 251     return NULL;
 252
 253   hdr = ((struct hdr *) (block + slop)) - 1;
 254
 255   hdr->size = size;
 256   link_blk (hdr);
 257   hdr->block = (__ptr_t) block;
 258   hdr->magic2 = (uintptr_t) block ^ MAGICWORD;
 259   ((char *) &hdr[1])[size] = MAGICBYTE;
 260   flood ((__ptr_t) (hdr + 1), MALLOCFLOOD, size);
 261   return (__ptr_t) (hdr + 1);
 262 }
 263
 264 static __ptr_t
 265 reallochook (__ptr_t ptr, __malloc_size_t size, const __ptr_t caller)
 266 {
 267   if (size == 0)
 268     {
 269       freehook (ptr, caller);
 270       return NULL;
 271     }
 272
 273   struct hdr *hdr;
 274   __malloc_size_t osize;
 275
 276   if (pedantic)
 277     mcheck_check_all ();
 278
 279   if (ptr)
 280     {
 281       hdr = ((struct hdr *) ptr) - 1;
 282       osize = hdr->size;
 283
 284       checkhdr (hdr);
 285       unlink_blk (hdr);
 286       if (size < osize)
 287         flood ((char *) ptr + size, FREEFLOOD, osize - size);
 288     }
 289   else
 290     {
 291       osize = 0;
 292       hdr = NULL;
 293     }
 294   __free_hook = old_free_hook;
 295   __malloc_hook = old_malloc_hook;
 296   __memalign_hook = old_memalign_hook;
 297   __realloc_hook = old_realloc_hook;
 298   if (old_realloc_hook != NULL)
 299     hdr = (struct hdr *) (*old_realloc_hook) ((__ptr_t) hdr,
 300                                               sizeof (struct hdr) + size + 1,
 301                                               caller);
 302   else
 303     hdr = (struct hdr *) realloc ((__ptr_t) hdr,
 304                                   sizeof (struct hdr) + size + 1);
 305   __free_hook = freehook;
 306   __malloc_hook = mallochook;
 307   __memalign_hook = memalignhook;
 308   __realloc_hook = reallochook;
 309   if (hdr == NULL)
 310     return NULL;
 311
 312   hdr->size = size;
 313   link_blk (hdr);
 314   hdr->block = hdr;
 315   hdr->magic2 = (uintptr_t) hdr ^ MAGICWORD;
 316   ((char *) &hdr[1])[size] = MAGICBYTE;
 317   if (size > osize)
 318     flood ((char *) (hdr + 1) + osize, MALLOCFLOOD, size - osize);
 319   return (__ptr_t) (hdr + 1);
 320 }
 321
 322 __attribute__ ((noreturn))
 323 static void
 324 mabort (enum mcheck_status status)
 325 {
 326   const char *msg;
 327   switch (status)
 328     {
 329     case MCHECK_OK:
 330       msg = _("memory is consistent, library is buggy\n");
 331       break;
 332     case MCHECK_HEAD:
 333       msg = _("memory clobbered before allocated block\n");
 334       break;
 335     case MCHECK_TAIL:
 336       msg = _("memory clobbered past end of allocated block\n");
 337       break;
 338     case MCHECK_FREE:
 339       msg = _("block freed twice\n");
 340       break;
 341     default:
 342       msg = _("bogus mcheck_status, library is buggy\n");
 343       break;
 344     }
 345 #ifdef _LIBC
 346   __libc_fatal (msg);
 347 #else
 348   fprintf (stderr, "mcheck: %s", msg);
 349   fflush (stderr);
 350   abort ();
 351 #endif
 352 }
 353
 354 int
 355 mcheck (func)
 356      void (*func) (enum mcheck_status);
 357 {
 358   abortfunc = (func != NULL) ? func : &mabort;
 359
 360   /* These hooks may not be safely inserted if malloc is already in use.  */
 361   if (__malloc_initialized <= 0 && !mcheck_used)
 362     {
 363       /* We call malloc() once here to ensure it is initialized.  */
 364       void *p = malloc (0);
 365       free (p);
 366
 367       old_free_hook = __free_hook;
 368       __free_hook = freehook;
 369       old_malloc_hook = __malloc_hook;
 370       __malloc_hook = mallochook;
 371       old_memalign_hook = __memalign_hook;
 372       __memalign_hook = memalignhook;
 373       old_realloc_hook = __realloc_hook;
 374       __realloc_hook = reallochook;
 375       mcheck_used = 1;
 376     }
 377
 378   return mcheck_used ? 0 : -1;
 379 }
 380 #ifdef _LIBC
 381 libc_hidden_def (mcheck)
 382 #endif
 383
 384 int
 385 mcheck_pedantic (func)
 386       void (*func) (enum mcheck_status);
 387 {
 388   int res = mcheck (func);
 389   if (res == 0)
 390     pedantic = 1;
 391   return res;
 392 }
 393
 394 enum mcheck_status
 395 mprobe (__ptr_t ptr)
 396 {
 397   return mcheck_used ? checkhdr (((struct hdr *) ptr) - 1) : MCHECK_DISABLED;
 398 }