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01fb5bca1c
hooks and set up to enforce the requirements. However, we still allow unconditional installation until some complications are resolved.
197 lines
5.9 KiB
C
197 lines
5.9 KiB
C
/* Standard debugging hooks for `mmalloc'.
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Copyright 1990, 1991, 1992 Free Software Foundation
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Written May 1989 by Mike Haertel.
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Heavily modified Mar 1992 by Fred Fish (fnf@cygnus.com)
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, USA.
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The author may be reached (Email) at the address mike@ai.mit.edu,
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or (US mail) as Mike Haertel c/o Free Software Foundation. */
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#include "mmalloc.h"
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/* Default function to call when something awful happens. The application
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can specify an alternate function to be called instead (and probably will
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want to). */
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extern void abort PARAMS ((void));
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/* Arbitrary magical numbers. */
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#define MAGICWORD 0xfedabeeb /* Magic word for active chunk */
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#define MAGICWORDFREE 0xdeadbeef /* Magic word for inactive chunk */
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#define MAGICBYTE ((char) 0xd7)
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/* Each memory allocation is bounded by a header structure and a trailer
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byte. I.E.
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<size><magicword><user's allocation><magicbyte>
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The pointer returned to the user points to the first byte in the
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user's allocation area. The magic word can be tested to detect
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buffer underruns and the magic byte can be tested to detect overruns. */
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struct hdr
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{
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size_t size; /* Exact size requested by user. */
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unsigned long int magic; /* Magic number to check header integrity. */
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};
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/* Check the magicword and magicbyte, and if either is corrupted then
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call the emergency abort function specified for the heap in use. */
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static void
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checkhdr (mdp, hdr)
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struct mdesc *mdp;
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CONST struct hdr *hdr;
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{
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if (hdr -> magic != MAGICWORD ||
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((char *) &hdr[1])[hdr -> size] != MAGICBYTE)
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{
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(*mdp -> abortfunc)();
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}
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}
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static void
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mfree_check (md, ptr)
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PTR md;
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PTR ptr;
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{
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struct hdr *hdr = ((struct hdr *) ptr) - 1;
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struct mdesc *mdp;
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mdp = MD_TO_MDP (md);
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checkhdr (mdp, hdr);
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hdr -> magic = MAGICWORDFREE;
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mdp -> mfree_hook = NULL;
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mfree (md, hdr);
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mdp -> mfree_hook = mfree_check;
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}
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static PTR
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mmalloc_check (md, size)
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PTR md;
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size_t size;
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{
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struct hdr *hdr;
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struct mdesc *mdp;
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size_t nbytes;
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mdp = MD_TO_MDP (md);
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mdp -> mmalloc_hook = NULL;
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nbytes = sizeof (struct hdr) + size + 1;
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hdr = (struct hdr *) mmalloc (md, nbytes);
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mdp -> mmalloc_hook = mmalloc_check;
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if (hdr != NULL)
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{
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hdr -> size = size;
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hdr -> magic = MAGICWORD;
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hdr++;
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*((char *) hdr + size) = MAGICBYTE;
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}
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return ((PTR) hdr);
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}
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static PTR
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mrealloc_check (md, ptr, size)
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PTR md;
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PTR ptr;
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size_t size;
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{
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struct hdr *hdr = ((struct hdr *) ptr) - 1;
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struct mdesc *mdp;
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size_t nbytes;
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mdp = MD_TO_MDP (md);
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checkhdr (mdp, hdr);
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mdp -> mfree_hook = NULL;
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mdp -> mmalloc_hook = NULL;
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mdp -> mrealloc_hook = NULL;
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nbytes = sizeof (struct hdr) + size + 1;
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hdr = (struct hdr *) mrealloc (md, (PTR) hdr, nbytes);
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mdp -> mfree_hook = mfree_check;
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mdp -> mmalloc_hook = mmalloc_check;
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mdp -> mrealloc_hook = mrealloc_check;
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if (hdr != NULL)
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{
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hdr -> size = size;
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hdr++;
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*((char *) hdr + size) = MAGICBYTE;
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}
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return ((PTR) hdr);
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}
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/* Turn on default checking for mmalloc/mrealloc/mfree, for the heap specified
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by MD. If FUNC is non-NULL, it is a pointer to the function to call
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to abort whenever memory corruption is detected. By default, this is the
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standard library function abort().
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Note that we disallow installation of initial checking hooks if mmalloc
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has been called at any time for this particular heap, since if any region
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that is allocated prior to installation of the hooks is subsequently
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reallocated or freed after installation of the hooks, it is guaranteed
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to trigger a memory corruption error. We do this by checking the state
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of the MMALLOC_INITIALIZED flag.
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However, we can call this function at any time after the initial call,
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to update the function pointers to the checking routines and to the
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user defined corruption handler routine, as long as these function pointers
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have been previously extablished by the initial call. Note that we
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do this automatically when remapping an previously used heap, to ensure
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that the hooks get updated to the correct values, although the corruption
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handler pointer gets set back to the default. The application can then
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call mmcheck to use a different corruption handler if desired.
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Returns non-zero if checking is successfully enabled, zero otherwise. */
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int
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mmcheck (md, func)
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PTR md;
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void (*func) PARAMS ((void));
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{
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struct mdesc *mdp;
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int rtnval;
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mdp = MD_TO_MDP (md);
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/* We can safely set or update the abort function at any time, regardless
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of whether or not we successfully do anything else. */
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mdp -> abortfunc = (func != NULL ? func : abort);
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/* If we haven't yet called mmalloc the first time for this heap, or if we
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have hooks that were previously installed, then allow the hooks to be
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initialized or updated. */
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if (1 /* FIXME: Always allow installation for now. */ ||
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!(mdp -> flags & MMALLOC_INITIALIZED) ||
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(mdp -> mfree_hook != NULL))
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{
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mdp -> mfree_hook = mfree_check;
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mdp -> mmalloc_hook = mmalloc_check;
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mdp -> mrealloc_hook = mrealloc_check;
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mdp -> flags |= MMALLOC_MMCHECK_USED;
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rtnval = 1;
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}
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else
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{
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rtnval = 0;
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}
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return (rtnval);
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}
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