debug/strcpy_chk.c

   1 /* Copyright (C) 1991-2015 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, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <stddef.h>
  19 #include <string.h>
  20 #include <memcopy.h>
  21
  22 #undef strcpy
  23
  24 /* Copy SRC to DEST with checking of destination buffer overflow.  */
  25 char *
  26 __strcpy_chk (dest, src, destlen)
  27      char *dest;
  28      const char *src;
  29      size_t destlen;
  30 {
  31   char c;
  32   char *s = (char *) src;
  33   const ptrdiff_t off = dest - s;
  34
  35   while (__builtin_expect (destlen >= 4, 0))
  36     {
  37       c = s[0];
  38       s[off] = c;
  39       if (c == '\0')
  40         return dest;
  41       c = s[1];
  42       s[off + 1] = c;
  43       if (c == '\0')
  44         return dest;
  45       c = s[2];
  46       s[off + 2] = c;
  47       if (c == '\0')
  48         return dest;
  49       c = s[3];
  50       s[off + 3] = c;
  51       if (c == '\0')
  52         return dest;
  53       destlen -= 4;
  54       s += 4;
  55     }
  56
  57   do
  58     {
  59       if (__glibc_unlikely (destlen-- == 0))
  60         __chk_fail ();
  61       c = *s;
  62       *(s++ + off) = c;
  63     }
  64   while (c != '\0');
  65
  66   return dest;
  67 }