debug/strcpy_chk.c

   1 /* Copyright (C) 1991, 1997, 2000, 2003, 2004 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <stddef.h>
  20 #include <string.h>
  21 #include <memcopy.h>
  22
  23 #undef strcpy
  24
  25 /* Copy SRC to DEST with checking of destination buffer overflow.  */
  26 char *
  27 __strcpy_chk (dest, src, destlen)
  28      char *dest;
  29      const char *src;
  30      size_t destlen;
  31 {
  32   reg_char c;
  33   char *s = (char *) src;
  34   const ptrdiff_t off = dest - s;
  35
  36   while (__builtin_expect (destlen >= 4, 0))
  37     {
  38       c = s[0];
  39       s[off] = c;
  40       if (c == '\0')
  41         return dest;
  42       c = s[1];
  43       s[off + 1] = c;
  44       if (c == '\0')
  45         return dest;
  46       c = s[2];
  47       s[off + 2] = c;
  48       if (c == '\0')
  49         return dest;
  50       c = s[3];
  51       s[off + 3] = c;
  52       if (c == '\0')
  53         return dest;
  54       destlen -= 4;
  55       s += 4;
  56     }
  57
  58   do
  59     {
  60       if (__builtin_expect (destlen-- == 0, 0))
  61         __chk_fail ();
  62       c = *s;
  63       *(s++ + off) = c;
  64     }
  65   while (c != '\0');
  66
  67   return dest;
  68 }