| 1 | /* Standard debugging hooks for `mmalloc'. |
| 2 | Copyright 1990, 1991, 1992 Free Software Foundation |
| 3 | |
| 4 | Written May 1989 by Mike Haertel. |
| 5 | Heavily modified Mar 1992 by Fred Fish (fnf@cygnus.com) |
| 6 | |
| 7 | The GNU C Library is free software; you can redistribute it and/or |
| 8 | modify it under the terms of the GNU Library General Public License as |
| 9 | published by the Free Software Foundation; either version 2 of the |
| 10 | License, or (at your option) any later version. |
| 11 | |
| 12 | The GNU C Library is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 15 | Library General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU Library General Public |
| 18 | License along with the GNU C Library; see the file COPYING.LIB. If |
| 19 | not, write to the Free Software Foundation, Inc., 675 Mass Ave, |
| 20 | Cambridge, MA 02139, USA. |
| 21 | |
| 22 | The author may be reached (Email) at the address mike@ai.mit.edu, |
| 23 | or (US mail) as Mike Haertel c/o Free Software Foundation. */ |
| 24 | |
| 25 | #include "mmalloc.h" |
| 26 | |
| 27 | /* Default function to call when something awful happens. The application |
| 28 | can specify an alternate function to be called instead (and probably will |
| 29 | want to). */ |
| 30 | |
| 31 | extern void abort PARAMS ((void)); |
| 32 | |
| 33 | /* Arbitrary magical numbers. */ |
| 34 | |
| 35 | #define MAGICWORD 0xfedabeeb /* Magic word for active chunk */ |
| 36 | #define MAGICWORDFREE 0xdeadbeef /* Magic word for inactive chunk */ |
| 37 | #define MAGICBYTE ((char) 0xd7) |
| 38 | |
| 39 | /* Each memory allocation is bounded by a header structure and a trailer |
| 40 | byte. I.E. |
| 41 | |
| 42 | <size><magicword><user's allocation><magicbyte> |
| 43 | |
| 44 | The pointer returned to the user points to the first byte in the |
| 45 | user's allocation area. The magic word can be tested to detect |
| 46 | buffer underruns and the magic byte can be tested to detect overruns. */ |
| 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 | }; |
| 53 | |
| 54 | /* Check the magicword and magicbyte, and if either is corrupted then |
| 55 | call the emergency abort function specified for the heap in use. */ |
| 56 | |
| 57 | static void |
| 58 | checkhdr (mdp, hdr) |
| 59 | struct mdesc *mdp; |
| 60 | CONST struct hdr *hdr; |
| 61 | { |
| 62 | if (hdr -> magic != MAGICWORD || |
| 63 | ((char *) &hdr[1])[hdr -> size] != MAGICBYTE) |
| 64 | { |
| 65 | (*mdp -> abortfunc)(); |
| 66 | } |
| 67 | } |
| 68 | |
| 69 | static void |
| 70 | mfree_check (md, ptr) |
| 71 | PTR md; |
| 72 | PTR ptr; |
| 73 | { |
| 74 | struct hdr *hdr = ((struct hdr *) ptr) - 1; |
| 75 | struct mdesc *mdp; |
| 76 | |
| 77 | mdp = MD_TO_MDP (md); |
| 78 | checkhdr (mdp, hdr); |
| 79 | hdr -> magic = MAGICWORDFREE; |
| 80 | mdp -> mfree_hook = NULL; |
| 81 | mfree (md, hdr); |
| 82 | mdp -> mfree_hook = mfree_check; |
| 83 | } |
| 84 | |
| 85 | static PTR |
| 86 | mmalloc_check (md, size) |
| 87 | PTR md; |
| 88 | size_t size; |
| 89 | { |
| 90 | struct hdr *hdr; |
| 91 | struct mdesc *mdp; |
| 92 | size_t nbytes; |
| 93 | |
| 94 | mdp = MD_TO_MDP (md); |
| 95 | mdp -> mmalloc_hook = NULL; |
| 96 | nbytes = sizeof (struct hdr) + size + 1; |
| 97 | hdr = (struct hdr *) mmalloc (md, nbytes); |
| 98 | mdp -> mmalloc_hook = mmalloc_check; |
| 99 | if (hdr != NULL) |
| 100 | { |
| 101 | hdr -> size = size; |
| 102 | hdr -> magic = MAGICWORD; |
| 103 | hdr++; |
| 104 | *((char *) hdr + size) = MAGICBYTE; |
| 105 | } |
| 106 | return ((PTR) hdr); |
| 107 | } |
| 108 | |
| 109 | static PTR |
| 110 | mrealloc_check (md, ptr, size) |
| 111 | PTR md; |
| 112 | PTR ptr; |
| 113 | size_t size; |
| 114 | { |
| 115 | struct hdr *hdr = ((struct hdr *) ptr) - 1; |
| 116 | struct mdesc *mdp; |
| 117 | size_t nbytes; |
| 118 | |
| 119 | mdp = MD_TO_MDP (md); |
| 120 | checkhdr (mdp, hdr); |
| 121 | mdp -> mfree_hook = NULL; |
| 122 | mdp -> mmalloc_hook = NULL; |
| 123 | mdp -> mrealloc_hook = NULL; |
| 124 | nbytes = sizeof (struct hdr) + size + 1; |
| 125 | hdr = (struct hdr *) mrealloc (md, (PTR) hdr, nbytes); |
| 126 | mdp -> mfree_hook = mfree_check; |
| 127 | mdp -> mmalloc_hook = mmalloc_check; |
| 128 | mdp -> mrealloc_hook = mrealloc_check; |
| 129 | if (hdr != NULL) |
| 130 | { |
| 131 | hdr -> size = size; |
| 132 | hdr++; |
| 133 | *((char *) hdr + size) = MAGICBYTE; |
| 134 | } |
| 135 | return ((PTR) hdr); |
| 136 | } |
| 137 | |
| 138 | /* Turn on default checking for mmalloc/mrealloc/mfree, for the heap specified |
| 139 | by MD. If FUNC is non-NULL, it is a pointer to the function to call |
| 140 | to abort whenever memory corruption is detected. By default, this is the |
| 141 | standard library function abort(). |
| 142 | |
| 143 | Note that we disallow installation of initial checking hooks if mmalloc |
| 144 | has been called at any time for this particular heap, since if any region |
| 145 | that is allocated prior to installation of the hooks is subsequently |
| 146 | reallocated or freed after installation of the hooks, it is guaranteed |
| 147 | to trigger a memory corruption error. We do this by checking the state |
| 148 | of the MMALLOC_INITIALIZED flag. |
| 149 | |
| 150 | However, we can call this function at any time after the initial call, |
| 151 | to update the function pointers to the checking routines and to the |
| 152 | user defined corruption handler routine, as long as these function pointers |
| 153 | have been previously extablished by the initial call. Note that we |
| 154 | do this automatically when remapping an previously used heap, to ensure |
| 155 | that the hooks get updated to the correct values, although the corruption |
| 156 | handler pointer gets set back to the default. The application can then |
| 157 | call mmcheck to use a different corruption handler if desired. |
| 158 | |
| 159 | Returns non-zero if checking is successfully enabled, zero otherwise. */ |
| 160 | |
| 161 | int |
| 162 | mmcheck (md, func) |
| 163 | PTR md; |
| 164 | void (*func) PARAMS ((void)); |
| 165 | { |
| 166 | struct mdesc *mdp; |
| 167 | int rtnval; |
| 168 | |
| 169 | mdp = MD_TO_MDP (md); |
| 170 | |
| 171 | /* We can safely set or update the abort function at any time, regardless |
| 172 | of whether or not we successfully do anything else. */ |
| 173 | |
| 174 | mdp -> abortfunc = (func != NULL ? func : abort); |
| 175 | |
| 176 | /* If we haven't yet called mmalloc the first time for this heap, or if we |
| 177 | have hooks that were previously installed, then allow the hooks to be |
| 178 | initialized or updated. */ |
| 179 | |
| 180 | if (1 /* FIXME: Always allow installation for now. */ || |
| 181 | !(mdp -> flags & MMALLOC_INITIALIZED) || |
| 182 | (mdp -> mfree_hook != NULL)) |
| 183 | { |
| 184 | mdp -> mfree_hook = mfree_check; |
| 185 | mdp -> mmalloc_hook = mmalloc_check; |
| 186 | mdp -> mrealloc_hook = mrealloc_check; |
| 187 | mdp -> flags |= MMALLOC_MMCHECK_USED; |
| 188 | rtnval = 1; |
| 189 | } |
| 190 | else |
| 191 | { |
| 192 | rtnval = 0; |
| 193 | } |
| 194 | |
| 195 | return (rtnval); |
| 196 | } |