| 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., 59 Temple Place - Suite 330, |
| 20 | Boston, MA 02111-1307, 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 "mmprivate.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 (unsigned int) 0xfedabeeb /* Active chunk */ |
| 36 | #define MAGICWORDFREE (unsigned int) 0xdeadbeef /* 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 | static void checkhdr PARAMS ((struct mdesc *, CONST struct hdr *)); |
| 55 | static void mfree_check PARAMS ((PTR, PTR)); |
| 56 | static PTR mmalloc_check PARAMS ((PTR, size_t)); |
| 57 | static PTR mrealloc_check PARAMS ((PTR, PTR, size_t)); |
| 58 | |
| 59 | /* Check the magicword and magicbyte, and if either is corrupted then |
| 60 | call the emergency abort function specified for the heap in use. */ |
| 61 | |
| 62 | static void |
| 63 | checkhdr (mdp, hdr) |
| 64 | struct mdesc *mdp; |
| 65 | CONST struct hdr *hdr; |
| 66 | { |
| 67 | if (hdr -> magic != MAGICWORD || |
| 68 | ((char *) &hdr[1])[hdr -> size] != MAGICBYTE) |
| 69 | { |
| 70 | (*mdp -> abortfunc)(); |
| 71 | } |
| 72 | } |
| 73 | |
| 74 | static void |
| 75 | mfree_check (md, ptr) |
| 76 | PTR md; |
| 77 | PTR ptr; |
| 78 | { |
| 79 | struct hdr *hdr = ((struct hdr *) ptr) - 1; |
| 80 | struct mdesc *mdp; |
| 81 | |
| 82 | mdp = MD_TO_MDP (md); |
| 83 | checkhdr (mdp, hdr); |
| 84 | hdr -> magic = MAGICWORDFREE; |
| 85 | mdp -> mfree_hook = NULL; |
| 86 | mfree (md, (PTR)hdr); |
| 87 | mdp -> mfree_hook = mfree_check; |
| 88 | } |
| 89 | |
| 90 | static PTR |
| 91 | mmalloc_check (md, size) |
| 92 | PTR md; |
| 93 | size_t size; |
| 94 | { |
| 95 | struct hdr *hdr; |
| 96 | struct mdesc *mdp; |
| 97 | size_t nbytes; |
| 98 | |
| 99 | mdp = MD_TO_MDP (md); |
| 100 | mdp -> mmalloc_hook = NULL; |
| 101 | nbytes = sizeof (struct hdr) + size + 1; |
| 102 | hdr = (struct hdr *) mmalloc (md, nbytes); |
| 103 | mdp -> mmalloc_hook = mmalloc_check; |
| 104 | if (hdr != NULL) |
| 105 | { |
| 106 | hdr -> size = size; |
| 107 | hdr -> magic = MAGICWORD; |
| 108 | hdr++; |
| 109 | *((char *) hdr + size) = MAGICBYTE; |
| 110 | } |
| 111 | return ((PTR) hdr); |
| 112 | } |
| 113 | |
| 114 | static PTR |
| 115 | mrealloc_check (md, ptr, size) |
| 116 | PTR md; |
| 117 | PTR ptr; |
| 118 | size_t size; |
| 119 | { |
| 120 | struct hdr *hdr = ((struct hdr *) ptr) - 1; |
| 121 | struct mdesc *mdp; |
| 122 | size_t nbytes; |
| 123 | |
| 124 | mdp = MD_TO_MDP (md); |
| 125 | checkhdr (mdp, hdr); |
| 126 | mdp -> mfree_hook = NULL; |
| 127 | mdp -> mmalloc_hook = NULL; |
| 128 | mdp -> mrealloc_hook = NULL; |
| 129 | nbytes = sizeof (struct hdr) + size + 1; |
| 130 | hdr = (struct hdr *) mrealloc (md, (PTR) hdr, nbytes); |
| 131 | mdp -> mfree_hook = mfree_check; |
| 132 | mdp -> mmalloc_hook = mmalloc_check; |
| 133 | mdp -> mrealloc_hook = mrealloc_check; |
| 134 | if (hdr != NULL) |
| 135 | { |
| 136 | hdr -> size = size; |
| 137 | hdr++; |
| 138 | *((char *) hdr + size) = MAGICBYTE; |
| 139 | } |
| 140 | return ((PTR) hdr); |
| 141 | } |
| 142 | |
| 143 | /* Turn on default checking for mmalloc/mrealloc/mfree, for the heap specified |
| 144 | by MD. If FUNC is non-NULL, it is a pointer to the function to call |
| 145 | to abort whenever memory corruption is detected. By default, this is the |
| 146 | standard library function abort(). |
| 147 | |
| 148 | Note that we disallow installation of initial checking hooks if mmalloc |
| 149 | has been called at any time for this particular heap, since if any region |
| 150 | that is allocated prior to installation of the hooks is subsequently |
| 151 | reallocated or freed after installation of the hooks, it is guaranteed |
| 152 | to trigger a memory corruption error. We do this by checking the state |
| 153 | of the MMALLOC_INITIALIZED flag. If the FORCE argument is non-zero, this |
| 154 | checking is disabled and it is allowed to install the checking hooks at any |
| 155 | time. This is useful on systems where the C runtime makes one or more |
| 156 | malloc calls before the user code had a chance to call mmcheck or mmcheckf, |
| 157 | but never calls free with these values. Thus if we are certain that only |
| 158 | values obtained from mallocs after an mmcheck/mmcheckf will ever be passed |
| 159 | to free(), we can go ahead and force installation of the useful checking |
| 160 | hooks. |
| 161 | |
| 162 | However, we can call this function at any time after the initial call, |
| 163 | to update the function pointers to the checking routines and to the |
| 164 | user defined corruption handler routine, as long as these function pointers |
| 165 | have been previously extablished by the initial call. Note that we |
| 166 | do this automatically when remapping a previously used heap, to ensure |
| 167 | that the hooks get updated to the correct values, although the corruption |
| 168 | handler pointer gets set back to the default. The application can then |
| 169 | call mmcheck to use a different corruption handler if desired. |
| 170 | |
| 171 | Returns non-zero if checking is successfully enabled, zero otherwise. */ |
| 172 | |
| 173 | int |
| 174 | mmcheckf (md, func, force) |
| 175 | PTR md; |
| 176 | void (*func) PARAMS ((void)); |
| 177 | int force; |
| 178 | { |
| 179 | struct mdesc *mdp; |
| 180 | int rtnval; |
| 181 | |
| 182 | mdp = MD_TO_MDP (md); |
| 183 | |
| 184 | /* We can safely set or update the abort function at any time, regardless |
| 185 | of whether or not we successfully do anything else. */ |
| 186 | |
| 187 | mdp -> abortfunc = (func != NULL ? func : abort); |
| 188 | |
| 189 | /* If we haven't yet called mmalloc the first time for this heap, or if we |
| 190 | have hooks that were previously installed, then allow the hooks to be |
| 191 | initialized or updated. */ |
| 192 | |
| 193 | if (force || |
| 194 | !(mdp -> flags & MMALLOC_INITIALIZED) || |
| 195 | (mdp -> mfree_hook != NULL)) |
| 196 | { |
| 197 | mdp -> mfree_hook = mfree_check; |
| 198 | mdp -> mmalloc_hook = mmalloc_check; |
| 199 | mdp -> mrealloc_hook = mrealloc_check; |
| 200 | mdp -> flags |= MMALLOC_MMCHECK_USED; |
| 201 | rtnval = 1; |
| 202 | } |
| 203 | else |
| 204 | { |
| 205 | rtnval = 0; |
| 206 | } |
| 207 | |
| 208 | return (rtnval); |
| 209 | } |
| 210 | |
| 211 | /* This routine is for backwards compatibility only, in case there are |
| 212 | still callers to the original mmcheck function. */ |
| 213 | |
| 214 | int |
| 215 | mmcheck (md, func) |
| 216 | PTR md; |
| 217 | void (*func) PARAMS ((void)); |
| 218 | { |
| 219 | int rtnval; |
| 220 | |
| 221 | rtnval = mmcheckf (md, func, 0); |
| 222 | return (rtnval); |
| 223 | } |