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, __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   };
  51
  52 #if defined _LIBC || defined STDC_HEADERS || defined USG
  53 # include <string.h>
  54 # define flood memset
  55 #else
  56 static void flood __P ((__ptr_t, int, __malloc_size_t));
  57 static void
  58 flood (ptr, val, size)
  59      __ptr_t ptr;
  60      int val;
  61      __malloc_size_t size;
  62 {
  63   char *cp = ptr;
  64   while (size--)
  65     *cp++ = val;
  66 }
  67 #endif
  68
  69 static enum mcheck_status checkhdr __P ((const struct hdr *));
  70 static enum mcheck_status
  71 checkhdr (hdr)
  72      const struct hdr *hdr;
  73 {
  74   enum mcheck_status status;
  75   switch (hdr->magic)
  76     {
  77     default:
  78       status = MCHECK_HEAD;
  79       break;
  80     case MAGICFREE:
  81       status = MCHECK_FREE;
  82       break;
  83     case MAGICWORD:
  84       if (((char *) &hdr[1])[hdr->size] != MAGICBYTE)
  85         status = MCHECK_TAIL;
  86       else
  87         status = MCHECK_OK;
  88       break;
  89     }
  90   if (status != MCHECK_OK)
  91     (*abortfunc) (status);
  92   return status;
  93 }
  94
  95 static void freehook __P ((__ptr_t, const __ptr_t));
  96 static void
  97 freehook (ptr, caller)
  98      __ptr_t ptr;
  99      const __ptr_t caller;
 100 {
 101   if (ptr)
 102     {
 103       struct hdr *hdr = ((struct hdr *) ptr) - 1;
 104       checkhdr (hdr);
 105       hdr->magic = MAGICFREE;
 106       flood (ptr, FREEFLOOD, hdr->size);
 107       ptr = (__ptr_t) hdr;
 108     }
 109   __free_hook = old_free_hook;
 110   if (old_free_hook != NULL)
 111     (*old_free_hook) (ptr, caller);
 112   else
 113     free (ptr);
 114   __free_hook = freehook;
 115 }
 116
 117 static __ptr_t mallochook __P ((__malloc_size_t, const __ptr_t));
 118 static __ptr_t
 119 mallochook (size, caller)
 120      __malloc_size_t size;
 121      const __ptr_t caller;
 122 {
 123   struct hdr *hdr;
 124
 125   __malloc_hook = old_malloc_hook;
 126   if (old_malloc_hook != NULL)
 127     hdr = (struct hdr *) (*old_malloc_hook) (sizeof (struct hdr) + size + 1,
 128                                              caller);
 129   else
 130     hdr = (struct hdr *) malloc (sizeof (struct hdr) + size + 1);
 131   __malloc_hook = mallochook;
 132   if (hdr == NULL)
 133     return NULL;
 134
 135   hdr->size = size;
 136   hdr->magic = MAGICWORD;
 137   ((char *) &hdr[1])[size] = MAGICBYTE;
 138   flood ((__ptr_t) (hdr + 1), MALLOCFLOOD, size);
 139   return (__ptr_t) (hdr + 1);
 140 }
 141
 142 static __ptr_t reallochook __P ((__ptr_t, __malloc_size_t, const __ptr_t));
 143 static __ptr_t
 144 reallochook (ptr, size, caller)
 145      __ptr_t ptr;
 146      __malloc_size_t size;
 147      const __ptr_t caller;
 148 {
 149   struct hdr *hdr;
 150   __malloc_size_t osize;
 151
 152   if (ptr)
 153     {
 154       hdr = ((struct hdr *) ptr) - 1;
 155       osize = hdr->size;
 156
 157       checkhdr (hdr);
 158       if (size < osize)
 159         flood ((char *) ptr + size, FREEFLOOD, osize - size);
 160     }
 161   else
 162     {
 163       osize = 0;
 164       hdr = NULL;
 165     }
 166   __free_hook = old_free_hook;
 167   __malloc_hook = old_malloc_hook;
 168   __realloc_hook = old_realloc_hook;
 169   if (old_realloc_hook != NULL)
 170     hdr = (struct hdr *) (*old_realloc_hook) ((__ptr_t) hdr,
 171                                               sizeof (struct hdr) + size + 1,
 172                                               caller);
 173   else
 174     hdr = (struct hdr *) realloc ((__ptr_t) hdr,
 175                                   sizeof (struct hdr) + size + 1);
 176   __free_hook = freehook;
 177   __malloc_hook = mallochook;
 178   __realloc_hook = reallochook;
 179   if (hdr == NULL)
 180     return NULL;
 181
 182   hdr->size = size;
 183   hdr->magic = MAGICWORD;
 184   ((char *) &hdr[1])[size] = MAGICBYTE;
 185   if (size > osize)
 186     flood ((char *) (hdr + 1) + osize, MALLOCFLOOD, size - osize);
 187   return (__ptr_t) (hdr + 1);
 188 }
 189
 190 static void mabort __P ((enum mcheck_status status));
 191 static void
 192 mabort (status)
 193      enum mcheck_status status;
 194 {
 195   const char *msg;
 196   switch (status)
 197     {
 198     case MCHECK_OK:
 199       msg = _("memory is consistent, library is buggy\n");
 200       break;
 201     case MCHECK_HEAD:
 202       msg = _("memory clobbered before allocated block\n");
 203       break;
 204     case MCHECK_TAIL:
 205       msg = _("memory clobbered past end of allocated block\n");
 206       break;
 207     case MCHECK_FREE:
 208       msg = _("block freed twice\n");
 209       break;
 210     default:
 211       msg = _("bogus mcheck_status, library is buggy\n");
 212       break;
 213     }
 214 #ifdef _LIBC
 215   __libc_fatal (msg);
 216 #else
 217   fprintf (stderr, "mcheck: %s", msg);
 218   fflush (stderr);
 219   abort ();
 220 #endif
 221 }
 222
 223 static int mcheck_used = 0;
 224
 225 int
 226 mcheck (func)
 227      void (*func) __P ((enum mcheck_status));
 228 {
 229   abortfunc = (func != NULL) ? func : &mabort;
 230
 231   /* These hooks may not be safely inserted if malloc is already in use.  */
 232   if (__malloc_initialized <= 0 && !mcheck_used)
 233     {
 234       old_free_hook = __free_hook;
 235       __free_hook = freehook;
 236       old_malloc_hook = __malloc_hook;
 237       __malloc_hook = mallochook;
 238       old_realloc_hook = __realloc_hook;
 239       __realloc_hook = reallochook;
 240       mcheck_used = 1;
 241     }
 242
 243   return mcheck_used ? 0 : -1;
 244 }
 245
 246 enum mcheck_status
 247 mprobe (__ptr_t ptr)
 248 {
 249   return mcheck_used ? checkhdr (((struct hdr *) ptr) - 1) : MCHECK_DISABLED;
 250 }