malloc/mcheck.c

   1 /* Standard debugging hooks for `malloc'.
   2    Copyright (C) 1990,91,92,93,94,95,96 Free Software Foundation, Inc.
   3    Written May 1989 by Mike Haertel.
   4
   5    This library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    This library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with this library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.
  19
  20    The author may be reached (Email) at the address mike@ai.mit.edu,
  21    or (US mail) as Mike Haertel c/o Free Software Foundation.  */
  22
  23 #ifndef _MALLOC_INTERNAL
  24 #define _MALLOC_INTERNAL
  25 #include <malloc.h>
  26 #include <mcheck.h>
  27 #include <stdio.h>
  28 #endif
  29
  30 /* Old hook values.  */
  31 static void (*old_free_hook) __P ((__ptr_t ptr));
  32 static __ptr_t (*old_malloc_hook) __P ((__malloc_size_t size));
  33 static __ptr_t (*old_realloc_hook) __P ((__ptr_t ptr, __malloc_size_t size));
  34
  35 /* Function to call when something awful happens.  */
  36 static void (*abortfunc) __P ((enum mcheck_status));
  37
  38 /* Arbitrary magical numbers.  */
  39 #define MAGICWORD       0xfedabeeb
  40 #define MAGICFREE       0xd8675309
  41 #define MAGICBYTE       ((char) 0xd7)
  42 #define MALLOCFLOOD     ((char) 0x93)
  43 #define FREEFLOOD       ((char) 0x95)
  44
  45 struct hdr
  46   {
  47     __malloc_size_t size;               /* Exact size requested by user.  */
  48     unsigned long int magic;    /* Magic number to check header integrity.  */
  49   };
  50
  51 #if     defined(_LIBC) || defined(STDC_HEADERS) || defined(USG)
  52 #define flood memset
  53 #else
  54 static void flood __P ((__ptr_t, int, __malloc_size_t));
  55 static void
  56 flood (ptr, val, size)
  57      __ptr_t ptr;
  58      int val;
  59      __malloc_size_t size;
  60 {
  61   char *cp = ptr;
  62   while (size--)
  63     *cp++ = val;
  64 }
  65 #endif
  66
  67 static enum mcheck_status checkhdr __P ((const struct hdr *));
  68 static enum mcheck_status
  69 checkhdr (hdr)
  70      const struct hdr *hdr;
  71 {
  72   enum mcheck_status status;
  73   switch (hdr->magic)
  74     {
  75     default:
  76       status = MCHECK_HEAD;
  77       break;
  78     case MAGICFREE:
  79       status = MCHECK_FREE;
  80       break;
  81     case MAGICWORD:
  82       if (((char *) &hdr[1])[hdr->size] != MAGICBYTE)
  83         status = MCHECK_TAIL;
  84       else
  85         status = MCHECK_OK;
  86       break;
  87     }
  88   if (status != MCHECK_OK)
  89     (*abortfunc) (status);
  90   return status;
  91 }
  92
  93 static void freehook __P ((__ptr_t));
  94 static void
  95 freehook (ptr)
  96      __ptr_t ptr;
  97 {
  98   if (ptr)
  99     {
 100       struct hdr *hdr = ((struct hdr *) ptr) - 1;
 101       checkhdr (hdr);
 102       hdr->magic = MAGICFREE;
 103       flood (ptr, FREEFLOOD, hdr->size);
 104       ptr = (__ptr_t) hdr;
 105     }
 106   __free_hook = old_free_hook;
 107   free (ptr);
 108   __free_hook = freehook;
 109 }
 110
 111 static __ptr_t mallochook __P ((__malloc_size_t));
 112 static __ptr_t
 113 mallochook (size)
 114      __malloc_size_t size;
 115 {
 116   struct hdr *hdr;
 117
 118   __malloc_hook = old_malloc_hook;
 119   hdr = (struct hdr *) malloc (sizeof (struct hdr) + size + 1);
 120   __malloc_hook = mallochook;
 121   if (hdr == NULL)
 122     return NULL;
 123
 124   hdr->size = size;
 125   hdr->magic = MAGICWORD;
 126   ((char *) &hdr[1])[size] = MAGICBYTE;
 127   flood ((__ptr_t) (hdr + 1), MALLOCFLOOD, size);
 128   return (__ptr_t) (hdr + 1);
 129 }
 130
 131 static __ptr_t reallochook __P ((__ptr_t, __malloc_size_t));
 132 static __ptr_t
 133 reallochook (ptr, size)
 134      __ptr_t ptr;
 135      __malloc_size_t size;
 136 {
 137   struct hdr *hdr;
 138   __malloc_size_t osize;
 139
 140   if (ptr)
 141     {
 142       hdr = ((struct hdr *) ptr) - 1;
 143       osize = hdr->size;
 144
 145       checkhdr (hdr);
 146       if (size < osize)
 147         flood ((char *) ptr + size, FREEFLOOD, osize - size);
 148     }
 149   else
 150     {
 151       osize = 0;
 152       hdr = NULL;
 153     }
 154   __free_hook = old_free_hook;
 155   __malloc_hook = old_malloc_hook;
 156   __realloc_hook = old_realloc_hook;
 157   hdr = (struct hdr *) realloc ((__ptr_t) hdr, sizeof (struct hdr) + size + 1);
 158   __free_hook = freehook;
 159   __malloc_hook = mallochook;
 160   __realloc_hook = reallochook;
 161   if (hdr == NULL)
 162     return NULL;
 163
 164   hdr->size = size;
 165   hdr->magic = MAGICWORD;
 166   ((char *) &hdr[1])[size] = MAGICBYTE;
 167   if (size > osize)
 168     flood ((char *) (hdr + 1) + osize, MALLOCFLOOD, size - osize);
 169   return (__ptr_t) (hdr + 1);
 170 }
 171
 172 static void mabort __P ((enum mcheck_status status));
 173 static void
 174 mabort (status)
 175      enum mcheck_status status;
 176 {
 177   const char *msg;
 178   switch (status)
 179     {
 180     case MCHECK_OK:
 181       msg = _("memory is consistent, library is buggy");
 182       break;
 183     case MCHECK_HEAD:
 184       msg = _("memory clobbered before allocated block");
 185       break;
 186     case MCHECK_TAIL:
 187       msg = _("memory clobbered past end of allocated block");
 188       break;
 189     case MCHECK_FREE:
 190       msg = _("block freed twice");
 191       break;
 192     default:
 193       msg = _("bogus mcheck_status, library is buggy");
 194       break;
 195     }
 196 #ifdef _LIBC
 197   __libc_fatal (msg);
 198 #else
 199   fprintf (stderr, "mcheck: %s\n", msg);
 200   fflush (stderr);
 201   abort ();
 202 #endif
 203 }
 204
 205 static int mcheck_used = 0;
 206
 207 int
 208 mcheck (func)
 209      void (*func) __P ((enum mcheck_status));
 210 {
 211   abortfunc = (func != NULL) ? func : &mabort;
 212
 213   /* These hooks may not be safely inserted if malloc is already in use.  */
 214   if (!__malloc_initialized && !mcheck_used)
 215     {
 216       old_free_hook = __free_hook;
 217       __free_hook = freehook;
 218       old_malloc_hook = __malloc_hook;
 219       __malloc_hook = mallochook;
 220       old_realloc_hook = __realloc_hook;
 221       __realloc_hook = reallochook;
 222       mcheck_used = 1;
 223     }
 224
 225   return mcheck_used ? 0 : -1;
 226 }
 227
 228 enum mcheck_status
 229 mprobe (__ptr_t ptr)
 230 {
 231   return mcheck_used ? checkhdr (ptr) : MCHECK_DISABLED;
 232 }