malloc/mcheck.c

   1 /* Standard debugging hooks for `malloc'.
   2    Copyright (C) 1990,91,92,93,94,95,96,97 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 #include <string.h>
  53 #define flood memset
  54 #else
  55 static void flood __P ((__ptr_t, int, __malloc_size_t));
  56 static void
  57 flood (ptr, val, size)
  58      __ptr_t ptr;
  59      int val;
  60      __malloc_size_t size;
  61 {
  62   char *cp = ptr;
  63   while (size--)
  64     *cp++ = val;
  65 }
  66 #endif
  67
  68 static enum mcheck_status checkhdr __P ((const struct hdr *));
  69 static enum mcheck_status
  70 checkhdr (hdr)
  71      const struct hdr *hdr;
  72 {
  73   enum mcheck_status status;
  74   switch (hdr->magic)
  75     {
  76     default:
  77       status = MCHECK_HEAD;
  78       break;
  79     case MAGICFREE:
  80       status = MCHECK_FREE;
  81       break;
  82     case MAGICWORD:
  83       if (((char *) &hdr[1])[hdr->size] != MAGICBYTE)
  84         status = MCHECK_TAIL;
  85       else
  86         status = MCHECK_OK;
  87       break;
  88     }
  89   if (status != MCHECK_OK)
  90     (*abortfunc) (status);
  91   return status;
  92 }
  93
  94 static void freehook __P ((__ptr_t));
  95 static void
  96 freehook (ptr)
  97      __ptr_t ptr;
  98 {
  99   if (ptr)
 100     {
 101       struct hdr *hdr = ((struct hdr *) ptr) - 1;
 102       checkhdr (hdr);
 103       hdr->magic = MAGICFREE;
 104       flood (ptr, FREEFLOOD, hdr->size);
 105       ptr = (__ptr_t) hdr;
 106     }
 107   __free_hook = old_free_hook;
 108   free (ptr);
 109   __free_hook = freehook;
 110 }
 111
 112 static __ptr_t mallochook __P ((__malloc_size_t));
 113 static __ptr_t
 114 mallochook (size)
 115      __malloc_size_t size;
 116 {
 117   struct hdr *hdr;
 118
 119   __malloc_hook = old_malloc_hook;
 120   hdr = (struct hdr *) malloc (sizeof (struct hdr) + size + 1);
 121   __malloc_hook = mallochook;
 122   if (hdr == NULL)
 123     return NULL;
 124
 125   hdr->size = size;
 126   hdr->magic = MAGICWORD;
 127   ((char *) &hdr[1])[size] = MAGICBYTE;
 128   flood ((__ptr_t) (hdr + 1), MALLOCFLOOD, size);
 129   return (__ptr_t) (hdr + 1);
 130 }
 131
 132 static __ptr_t reallochook __P ((__ptr_t, __malloc_size_t));
 133 static __ptr_t
 134 reallochook (ptr, size)
 135      __ptr_t ptr;
 136      __malloc_size_t size;
 137 {
 138   struct hdr *hdr;
 139   __malloc_size_t osize;
 140
 141   if (ptr)
 142     {
 143       hdr = ((struct hdr *) ptr) - 1;
 144       osize = hdr->size;
 145
 146       checkhdr (hdr);
 147       if (size < osize)
 148         flood ((char *) ptr + size, FREEFLOOD, osize - size);
 149     }
 150   else
 151     {
 152       osize = 0;
 153       hdr = NULL;
 154     }
 155   __free_hook = old_free_hook;
 156   __malloc_hook = old_malloc_hook;
 157   __realloc_hook = old_realloc_hook;
 158   hdr = (struct hdr *) realloc ((__ptr_t) hdr, sizeof (struct hdr) + size + 1);
 159   __free_hook = freehook;
 160   __malloc_hook = mallochook;
 161   __realloc_hook = reallochook;
 162   if (hdr == NULL)
 163     return NULL;
 164
 165   hdr->size = size;
 166   hdr->magic = MAGICWORD;
 167   ((char *) &hdr[1])[size] = MAGICBYTE;
 168   if (size > osize)
 169     flood ((char *) (hdr + 1) + osize, MALLOCFLOOD, size - osize);
 170   return (__ptr_t) (hdr + 1);
 171 }
 172
 173 static void mabort __P ((enum mcheck_status status));
 174 static void
 175 mabort (status)
 176      enum mcheck_status status;
 177 {
 178   const char *msg;
 179   switch (status)
 180     {
 181     case MCHECK_OK:
 182       msg = _("memory is consistent, library is buggy");
 183       break;
 184     case MCHECK_HEAD:
 185       msg = _("memory clobbered before allocated block");
 186       break;
 187     case MCHECK_TAIL:
 188       msg = _("memory clobbered past end of allocated block");
 189       break;
 190     case MCHECK_FREE:
 191       msg = _("block freed twice");
 192       break;
 193     default:
 194       msg = _("bogus mcheck_status, library is buggy");
 195       break;
 196     }
 197 #ifdef _LIBC
 198   __libc_fatal (msg);
 199 #else
 200   fprintf (stderr, "mcheck: %s\n", msg);
 201   fflush (stderr);
 202   abort ();
 203 #endif
 204 }
 205
 206 static int mcheck_used = 0;
 207
 208 int
 209 mcheck (func)
 210      void (*func) __P ((enum mcheck_status));
 211 {
 212   abortfunc = (func != NULL) ? func : &mabort;
 213
 214   /* These hooks may not be safely inserted if malloc is already in use.  */
 215   if (!__malloc_initialized && !mcheck_used)
 216     {
 217       old_free_hook = __free_hook;
 218       __free_hook = freehook;
 219       old_malloc_hook = __malloc_hook;
 220       __malloc_hook = mallochook;
 221       old_realloc_hook = __realloc_hook;
 222       __realloc_hook = reallochook;
 223       mcheck_used = 1;
 224     }
 225
 226   return mcheck_used ? 0 : -1;
 227 }
 228
 229 enum mcheck_status
 230 mprobe (__ptr_t ptr)
 231 {
 232   return mcheck_used ? checkhdr (ptr) : MCHECK_DISABLED;
 233 }