malloc/mcheck.c

   1 /* Standard debugging hooks for `malloc'.
   2    Copyright (C) 1990-2014 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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef _MALLOC_INTERNAL
  21 # define _MALLOC_INTERNAL
  22 # include <malloc.h>
  23 # include <mcheck.h>
  24 # include <stdint.h>
  25 # include <stdio.h>
  26 # include <libintl.h>
  27 # include <errno.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) (size_t size, const __ptr_t);
  33 static __ptr_t (*old_memalign_hook) (size_t alignment, size_t size,
  34                                      const __ptr_t);
  35 static __ptr_t (*old_realloc_hook) (__ptr_t ptr, size_t size,
  36                                     const __ptr_t);
  37
  38 /* Function to call when something awful happens.  */
  39 static void (*abortfunc) (enum mcheck_status);
  40
  41 /* Arbitrary magical numbers.  */
  42 #define MAGICWORD       0xfedabeeb
  43 #define MAGICFREE       0xd8675309
  44 #define MAGICBYTE       ((char) 0xd7)
  45 #define MALLOCFLOOD     ((char) 0x93)
  46 #define FREEFLOOD       ((char) 0x95)
  47
  48 struct hdr
  49   {
  50     size_t size;                /* Exact size requested by user.  */
  51     unsigned long int magic;    /* Magic number to check header integrity.  */
  52     struct hdr *prev;
  53     struct hdr *next;
  54     __ptr_t block;              /* Real block allocated, for memalign.  */
  55     unsigned long int magic2;   /* Extra, keeps us doubleword aligned.  */
  56   };
  57
  58 /* This is the beginning of the list of all memory blocks allocated.
  59    It is only constructed if the pedantic testing is requested.  */
  60 static struct hdr *root;
  61
  62 static int mcheck_used;
  63
  64 /* Nonzero if pedentic checking of all blocks is requested.  */
  65 static int pedantic;
  66
  67 #if defined _LIBC || defined STDC_HEADERS || defined USG
  68 # include <string.h>
  69 # define flood memset
  70 #else
  71 static void flood (__ptr_t, int, size_t);
  72 static void
  73 flood (ptr, val, size)
  74      __ptr_t ptr;
  75      int val;
  76      size_t size;
  77 {
  78   char *cp = ptr;
  79   while (size--)
  80     *cp++ = val;
  81 }
  82 #endif
  83
  84 static enum mcheck_status
  85 checkhdr (const struct hdr *hdr)
  86 {
  87   enum mcheck_status status;
  88
  89   if (!mcheck_used)
  90     /* Maybe the mcheck used is disabled?  This happens when we find
  91        an error and report it.  */
  92     return MCHECK_OK;
  93
  94   switch (hdr->magic ^ ((uintptr_t) hdr->prev + (uintptr_t) hdr->next))
  95     {
  96     default:
  97       status = MCHECK_HEAD;
  98       break;
  99     case MAGICFREE:
 100       status = MCHECK_FREE;
 101       break;
 102     case MAGICWORD:
 103       if (((char *) &hdr[1])[hdr->size] != MAGICBYTE)
 104         status = MCHECK_TAIL;
 105       else if ((hdr->magic2 ^ (uintptr_t) hdr->block) != MAGICWORD)
 106         status = MCHECK_HEAD;
 107       else
 108         status = MCHECK_OK;
 109       break;
 110     }
 111   if (status != MCHECK_OK)
 112     {
 113       mcheck_used = 0;
 114       (*abortfunc) (status);
 115       mcheck_used = 1;
 116     }
 117   return status;
 118 }
 119
 120 void
 121 mcheck_check_all (void)
 122 {
 123   /* Walk through all the active blocks and test whether they were tampered
 124      with.  */
 125   struct hdr *runp = root;
 126
 127   /* Temporarily turn off the checks.  */
 128   pedantic = 0;
 129
 130   while (runp != NULL)
 131     {
 132       (void) checkhdr (runp);
 133
 134       runp = runp->next;
 135     }
 136
 137   /* Turn checks on again.  */
 138   pedantic = 1;
 139 }
 140 #ifdef _LIBC
 141 libc_hidden_def (mcheck_check_all)
 142 #endif
 143
 144 static void
 145 unlink_blk (struct hdr *ptr)
 146 {
 147   if (ptr->next != NULL)
 148     {
 149       ptr->next->prev = ptr->prev;
 150       ptr->next->magic = MAGICWORD ^ ((uintptr_t) ptr->next->prev
 151                                       + (uintptr_t) ptr->next->next);
 152     }
 153   if (ptr->prev != NULL)
 154     {
 155       ptr->prev->next = ptr->next;
 156       ptr->prev->magic = MAGICWORD ^ ((uintptr_t) ptr->prev->prev
 157                                       + (uintptr_t) ptr->prev->next);
 158     }
 159   else
 160     root = ptr->next;
 161 }
 162
 163 static void
 164 link_blk (struct hdr *hdr)
 165 {
 166   hdr->prev = NULL;
 167   hdr->next = root;
 168   root = hdr;
 169   hdr->magic = MAGICWORD ^ (uintptr_t) hdr->next;
 170
 171   /* And the next block.  */
 172   if (hdr->next != NULL)
 173     {
 174       hdr->next->prev = hdr;
 175       hdr->next->magic = MAGICWORD ^ ((uintptr_t) hdr
 176                                       + (uintptr_t) hdr->next->next);
 177     }
 178 }
 179 static void
 180 freehook (__ptr_t ptr, const __ptr_t caller)
 181 {
 182   if (pedantic)
 183     mcheck_check_all ();
 184   if (ptr)
 185     {
 186       struct hdr *hdr = ((struct hdr *) ptr) - 1;
 187       checkhdr (hdr);
 188       hdr->magic = MAGICFREE;
 189       hdr->magic2 = MAGICFREE;
 190       unlink_blk (hdr);
 191       hdr->prev = hdr->next = NULL;
 192       flood (ptr, FREEFLOOD, hdr->size);
 193       ptr = hdr->block;
 194     }
 195   __free_hook = old_free_hook;
 196   if (old_free_hook != NULL)
 197     (*old_free_hook) (ptr, caller);
 198   else
 199     free (ptr);
 200   __free_hook = freehook;
 201 }
 202
 203 static __ptr_t
 204 mallochook (size_t size, const __ptr_t caller)
 205 {
 206   struct hdr *hdr;
 207
 208   if (pedantic)
 209     mcheck_check_all ();
 210
 211   if (size > ~((size_t) 0) - (sizeof (struct hdr) + 1))
 212     {
 213       __set_errno (ENOMEM);
 214       return NULL;
 215     }
 216
 217   __malloc_hook = old_malloc_hook;
 218   if (old_malloc_hook != NULL)
 219     hdr = (struct hdr *) (*old_malloc_hook) (sizeof (struct hdr) + size + 1,
 220                                              caller);
 221   else
 222     hdr = (struct hdr *) malloc (sizeof (struct hdr) + size + 1);
 223   __malloc_hook = mallochook;
 224   if (hdr == NULL)
 225     return NULL;
 226
 227   hdr->size = size;
 228   link_blk (hdr);
 229   hdr->block = hdr;
 230   hdr->magic2 = (uintptr_t) hdr ^ MAGICWORD;
 231   ((char *) &hdr[1])[size] = MAGICBYTE;
 232   flood ((__ptr_t) (hdr + 1), MALLOCFLOOD, size);
 233   return (__ptr_t) (hdr + 1);
 234 }
 235
 236 static __ptr_t
 237 memalignhook (size_t alignment, size_t size,
 238               const __ptr_t caller)
 239 {
 240   struct hdr *hdr;
 241   size_t slop;
 242   char *block;
 243
 244   if (pedantic)
 245     mcheck_check_all ();
 246
 247   slop = (sizeof *hdr + alignment - 1) & -alignment;
 248
 249   if (size > ~((size_t) 0) - (slop + 1))
 250     {
 251       __set_errno (ENOMEM);
 252       return NULL;
 253     }
 254
 255   __memalign_hook = old_memalign_hook;
 256   if (old_memalign_hook != NULL)
 257     block = (*old_memalign_hook) (alignment, slop + size + 1, caller);
 258   else
 259     block = memalign (alignment, slop + size + 1);
 260   __memalign_hook = memalignhook;
 261   if (block == NULL)
 262     return NULL;
 263
 264   hdr = ((struct hdr *) (block + slop)) - 1;
 265
 266   hdr->size = size;
 267   link_blk (hdr);
 268   hdr->block = (__ptr_t) block;
 269   hdr->magic2 = (uintptr_t) block ^ MAGICWORD;
 270   ((char *) &hdr[1])[size] = MAGICBYTE;
 271   flood ((__ptr_t) (hdr + 1), MALLOCFLOOD, size);
 272   return (__ptr_t) (hdr + 1);
 273 }
 274
 275 static __ptr_t
 276 reallochook (__ptr_t ptr, size_t size, const __ptr_t caller)
 277 {
 278   if (size == 0)
 279     {
 280       freehook (ptr, caller);
 281       return NULL;
 282     }
 283
 284   struct hdr *hdr;
 285   size_t osize;
 286
 287   if (pedantic)
 288     mcheck_check_all ();
 289
 290   if (size > ~((size_t) 0) - (sizeof (struct hdr) + 1))
 291     {
 292       __set_errno (ENOMEM);
 293       return NULL;
 294     }
 295
 296   if (ptr)
 297     {
 298       hdr = ((struct hdr *) ptr) - 1;
 299       osize = hdr->size;
 300
 301       checkhdr (hdr);
 302       unlink_blk (hdr);
 303       if (size < osize)
 304         flood ((char *) ptr + size, FREEFLOOD, osize - size);
 305     }
 306   else
 307     {
 308       osize = 0;
 309       hdr = NULL;
 310     }
 311   __free_hook = old_free_hook;
 312   __malloc_hook = old_malloc_hook;
 313   __memalign_hook = old_memalign_hook;
 314   __realloc_hook = old_realloc_hook;
 315   if (old_realloc_hook != NULL)
 316     hdr = (struct hdr *) (*old_realloc_hook) ((__ptr_t) hdr,
 317                                               sizeof (struct hdr) + size + 1,
 318                                               caller);
 319   else
 320     hdr = (struct hdr *) realloc ((__ptr_t) hdr,
 321                                   sizeof (struct hdr) + size + 1);
 322   __free_hook = freehook;
 323   __malloc_hook = mallochook;
 324   __memalign_hook = memalignhook;
 325   __realloc_hook = reallochook;
 326   if (hdr == NULL)
 327     return NULL;
 328
 329   hdr->size = size;
 330   link_blk (hdr);
 331   hdr->block = hdr;
 332   hdr->magic2 = (uintptr_t) hdr ^ MAGICWORD;
 333   ((char *) &hdr[1])[size] = MAGICBYTE;
 334   if (size > osize)
 335     flood ((char *) (hdr + 1) + osize, MALLOCFLOOD, size - osize);
 336   return (__ptr_t) (hdr + 1);
 337 }
 338
 339 __attribute__ ((noreturn))
 340 static void
 341 mabort (enum mcheck_status status)
 342 {
 343   const char *msg;
 344   switch (status)
 345     {
 346     case MCHECK_OK:
 347       msg = _("memory is consistent, library is buggy\n");
 348       break;
 349     case MCHECK_HEAD:
 350       msg = _("memory clobbered before allocated block\n");
 351       break;
 352     case MCHECK_TAIL:
 353       msg = _("memory clobbered past end of allocated block\n");
 354       break;
 355     case MCHECK_FREE:
 356       msg = _("block freed twice\n");
 357       break;
 358     default:
 359       msg = _("bogus mcheck_status, library is buggy\n");
 360       break;
 361     }
 362 #ifdef _LIBC
 363   __libc_fatal (msg);
 364 #else
 365   fprintf (stderr, "mcheck: %s", msg);
 366   fflush (stderr);
 367   abort ();
 368 #endif
 369 }
 370
 371 /* Memory barrier so that GCC does not optimize out the argument.  */
 372 #define malloc_opt_barrier(x) \
 373 ({ __typeof (x) __x = x; __asm ("" : "+m" (__x)); __x; })
 374
 375 int
 376 mcheck (func)
 377      void (*func) (enum mcheck_status);
 378 {
 379   abortfunc = (func != NULL) ? func : &mabort;
 380
 381   /* These hooks may not be safely inserted if malloc is already in use.  */
 382   if (__malloc_initialized <= 0 && !mcheck_used)
 383     {
 384       /* We call malloc() once here to ensure it is initialized.  */
 385       void *p = malloc (0);
 386       /* GCC might optimize out the malloc/free pair without a barrier.  */
 387       p = malloc_opt_barrier (p);
 388       free (p);
 389
 390       old_free_hook = __free_hook;
 391       __free_hook = freehook;
 392       old_malloc_hook = __malloc_hook;
 393       __malloc_hook = mallochook;
 394       old_memalign_hook = __memalign_hook;
 395       __memalign_hook = memalignhook;
 396       old_realloc_hook = __realloc_hook;
 397       __realloc_hook = reallochook;
 398       mcheck_used = 1;
 399     }
 400
 401   return mcheck_used ? 0 : -1;
 402 }
 403 #ifdef _LIBC
 404 libc_hidden_def (mcheck)
 405 #endif
 406
 407 int
 408 mcheck_pedantic (func)
 409       void (*func) (enum mcheck_status);
 410 {
 411   int res = mcheck (func);
 412   if (res == 0)
 413     pedantic = 1;
 414   return res;
 415 }
 416
 417 enum mcheck_status
 418 mprobe (__ptr_t ptr)
 419 {
 420   return mcheck_used ? checkhdr (((struct hdr *) ptr) - 1) : MCHECK_DISABLED;
 421 }