malloc/mcheck.c

   1 /* Standard debugging hooks for `malloc'.
   2    Copyright (C) 1990-1997, 1999, 2000, 2001 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) __P ((__ptr_t ptr, __const __ptr_t));
  32 static __ptr_t (*old_malloc_hook) __P ((__malloc_size_t size, const __ptr_t));
  33 static __ptr_t (*old_realloc_hook) __P ((__ptr_t ptr, __malloc_size_t size,
  34                                          __const __ptr_t));
  35
  36 /* Function to call when something awful happens.  */
  37 static void (*abortfunc) __P ((enum mcheck_status));
  38
  39 /* Arbitrary magical numbers.  */
  40 #define MAGICWORD       0xfedabeeb
  41 #define MAGICFREE       0xd8675309
  42 #define MAGICBYTE       ((char) 0xd7)
  43 #define MALLOCFLOOD     ((char) 0x93)
  44 #define FREEFLOOD       ((char) 0x95)
  45
  46 struct hdr
  47   {
  48     __malloc_size_t size;       /* Exact size requested by user.  */
  49     unsigned long int magic;    /* Magic number to check header integrity.  */
  50     struct hdr *prev;
  51     struct hdr *next;
  52   };
  53
  54 /* This is the beginning of the list of all memory blocks allocated.
  55    It is only constructed if the pedantic testing is requested.  */
  56 static struct hdr *root;
  57
  58 static int mcheck_used;
  59
  60 /* Nonzero if pedentic checking of all blocks is requested.  */
  61 static int pedantic;
  62
  63 #if defined _LIBC || defined STDC_HEADERS || defined USG
  64 # include <string.h>
  65 # define flood memset
  66 #else
  67 static void flood __P ((__ptr_t, int, __malloc_size_t));
  68 static void
  69 flood (ptr, val, size)
  70      __ptr_t ptr;
  71      int val;
  72      __malloc_size_t size;
  73 {
  74   char *cp = ptr;
  75   while (size--)
  76     *cp++ = val;
  77 }
  78 #endif
  79
  80 static enum mcheck_status checkhdr __P ((const struct hdr *));
  81 static enum mcheck_status
  82 checkhdr (hdr)
  83      const struct hdr *hdr;
  84 {
  85   enum mcheck_status status;
  86
  87   if (!mcheck_used)
  88     /* Maybe the mcheck used is disabled?  This happens when we find
  89        an error and report it.  */
  90     return MCHECK_OK;
  91
  92   switch (hdr->magic ^ ((uintptr_t) hdr->prev + (uintptr_t) hdr->next))
  93     {
  94     default:
  95       status = MCHECK_HEAD;
  96       break;
  97     case MAGICFREE:
  98       status = MCHECK_FREE;
  99       break;
 100     case MAGICWORD:
 101       if (((char *) &hdr[1])[hdr->size] != MAGICBYTE)
 102         status = MCHECK_TAIL;
 103       else
 104         status = MCHECK_OK;
 105       break;
 106     }
 107   if (status != MCHECK_OK)
 108     {
 109       mcheck_used = 0;
 110       (*abortfunc) (status);
 111       mcheck_used = 1;
 112     }
 113   return status;
 114 }
 115
 116 void
 117 mcheck_check_all ()
 118 {
 119   /* Walk through all the active blocks and test whether they were tempered
 120      with.  */
 121   struct hdr *runp = root;
 122
 123   /* Temporarily turn off the checks.  */
 124   pedantic = 0;
 125
 126   while (runp != NULL)
 127     {
 128       (void) checkhdr (runp);
 129
 130       runp = runp->next;
 131     }
 132
 133   /* Turn checks on again.  */
 134   pedantic = 1;
 135 }
 136
 137 static void unlink_blk __P ((struct hdr *ptr));
 138 static void
 139 unlink_blk (ptr)
 140      struct hdr *ptr;
 141 {
 142   if (ptr->next != NULL)
 143     {
 144       ptr->next->prev = ptr->prev;
 145       ptr->next->magic = MAGICWORD ^ ((uintptr_t) ptr->next->prev
 146                                       + (uintptr_t) ptr->next->next);
 147     }
 148   if (ptr->prev != NULL)
 149     {
 150       ptr->prev->next = ptr->next;
 151       ptr->prev->magic = MAGICWORD ^ ((uintptr_t) ptr->prev->prev
 152                                       + (uintptr_t) ptr->prev->next);
 153     }
 154   else
 155     root = ptr->next;
 156 }
 157
 158 static void link_blk  __P ((struct hdr *ptr));
 159 static void
 160 link_blk (hdr)
 161      struct hdr *hdr;
 162 {
 163   hdr->prev = NULL;
 164   hdr->next = root;
 165   root = hdr;
 166   hdr->magic = MAGICWORD ^ (uintptr_t) hdr->next;
 167
 168   /* And the next block.  */
 169   if (hdr->next != NULL)
 170     {
 171       hdr->next->prev = hdr;
 172       hdr->next->magic = MAGICWORD ^ ((uintptr_t) hdr
 173                                       + (uintptr_t) hdr->next->next);
 174     }
 175 }
 176
 177 static void freehook __P ((__ptr_t, const __ptr_t));
 178 static void
 179 freehook (ptr, caller)
 180      __ptr_t ptr;
 181      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       unlink_blk (hdr);
 191       hdr->prev = hdr->next = NULL;
 192       flood (ptr, FREEFLOOD, hdr->size);
 193       ptr = (__ptr_t) hdr;
 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 mallochook __P ((__malloc_size_t, const __ptr_t));
 204 static __ptr_t
 205 mallochook (size, caller)
 206      __malloc_size_t size;
 207      const __ptr_t caller;
 208 {
 209   struct hdr *hdr;
 210
 211   if (pedantic)
 212     mcheck_check_all ();
 213
 214   __malloc_hook = old_malloc_hook;
 215   if (old_malloc_hook != NULL)
 216     hdr = (struct hdr *) (*old_malloc_hook) (sizeof (struct hdr) + size + 1,
 217                                              caller);
 218   else
 219     hdr = (struct hdr *) malloc (sizeof (struct hdr) + size + 1);
 220   __malloc_hook = mallochook;
 221   if (hdr == NULL)
 222     return NULL;
 223
 224   hdr->size = size;
 225   link_blk (hdr);
 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 reallochook __P ((__ptr_t, __malloc_size_t, const __ptr_t));
 232 static __ptr_t
 233 reallochook (ptr, size, caller)
 234      __ptr_t ptr;
 235      __malloc_size_t size;
 236      const __ptr_t caller;
 237 {
 238   struct hdr *hdr;
 239   __malloc_size_t osize;
 240
 241   if (pedantic)
 242     mcheck_check_all ();
 243
 244   if (ptr)
 245     {
 246       hdr = ((struct hdr *) ptr) - 1;
 247       osize = hdr->size;
 248
 249       checkhdr (hdr);
 250       unlink_blk (hdr);
 251       if (size < osize)
 252         flood ((char *) ptr + size, FREEFLOOD, osize - size);
 253     }
 254   else
 255     {
 256       osize = 0;
 257       hdr = NULL;
 258     }
 259   __free_hook = old_free_hook;
 260   __malloc_hook = old_malloc_hook;
 261   __realloc_hook = old_realloc_hook;
 262   if (old_realloc_hook != NULL)
 263     hdr = (struct hdr *) (*old_realloc_hook) ((__ptr_t) hdr,
 264                                               sizeof (struct hdr) + size + 1,
 265                                               caller);
 266   else
 267     hdr = (struct hdr *) realloc ((__ptr_t) hdr,
 268                                   sizeof (struct hdr) + size + 1);
 269   __free_hook = freehook;
 270   __malloc_hook = mallochook;
 271   __realloc_hook = reallochook;
 272   if (hdr == NULL)
 273     return NULL;
 274
 275   hdr->size = size;
 276   link_blk (hdr);
 277   ((char *) &hdr[1])[size] = MAGICBYTE;
 278   if (size > osize)
 279     flood ((char *) (hdr + 1) + osize, MALLOCFLOOD, size - osize);
 280   return (__ptr_t) (hdr + 1);
 281 }
 282
 283 static void mabort __P ((enum mcheck_status status))
 284      __attribute__ ((noreturn));
 285 static void
 286 mabort (status)
 287      enum mcheck_status status;
 288 {
 289   const char *msg;
 290   switch (status)
 291     {
 292     case MCHECK_OK:
 293       msg = _("memory is consistent, library is buggy\n");
 294       break;
 295     case MCHECK_HEAD:
 296       msg = _("memory clobbered before allocated block\n");
 297       break;
 298     case MCHECK_TAIL:
 299       msg = _("memory clobbered past end of allocated block\n");
 300       break;
 301     case MCHECK_FREE:
 302       msg = _("block freed twice\n");
 303       break;
 304     default:
 305       msg = _("bogus mcheck_status, library is buggy\n");
 306       break;
 307     }
 308 #ifdef _LIBC
 309   __libc_fatal (msg);
 310 #else
 311   fprintf (stderr, "mcheck: %s", msg);
 312   fflush (stderr);
 313   abort ();
 314 #endif
 315 }
 316
 317 int
 318 mcheck (func)
 319      void (*func) __P ((enum mcheck_status));
 320 {
 321   abortfunc = (func != NULL) ? func : &mabort;
 322
 323   /* These hooks may not be safely inserted if malloc is already in use.  */
 324   if (__malloc_initialized <= 0 && !mcheck_used)
 325     {
 326       /* We call malloc() once here to ensure it is initialized.  */
 327       void *p = malloc (0);
 328       free (p);
 329
 330       old_free_hook = __free_hook;
 331       __free_hook = freehook;
 332       old_malloc_hook = __malloc_hook;
 333       __malloc_hook = mallochook;
 334       old_realloc_hook = __realloc_hook;
 335       __realloc_hook = reallochook;
 336       mcheck_used = 1;
 337     }
 338
 339   return mcheck_used ? 0 : -1;
 340 }
 341
 342 int
 343 mcheck_pedantic (func)
 344       void (*func) __P ((enum mcheck_status));
 345 {
 346   int res = mcheck (func);
 347   if (res == 0)
 348     pedantic = 1;
 349   return res;
 350 }
 351
 352 enum mcheck_status
 353 mprobe (__ptr_t ptr)
 354 {
 355   return mcheck_used ? checkhdr (((struct hdr *) ptr) - 1) : MCHECK_DISABLED;
 356 }