debug/strncat_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 <string.h>
  19
  20 #include <memcopy.h>
  21
  22
  23 char *
  24 __strncat_chk (s1, s2, n, s1len)
  25      char *s1;
  26      const char *s2;
  27      size_t n;
  28      size_t s1len;
  29 {
  30   char c;
  31   char *s = s1;
  32
  33   /* Find the end of S1.  */
  34   do
  35     {
  36       if (__glibc_unlikely (s1len-- == 0))
  37         __chk_fail ();
  38       c = *s1++;
  39     }
  40   while (c != '\0');
  41
  42   /* Make S1 point before next character, so we can increment
  43      it while memory is read (wins on pipelined cpus).  */
  44   ++s1len;
  45   s1 -= 2;
  46
  47   if (n >= 4)
  48     {
  49       size_t n4 = n >> 2;
  50       do
  51         {
  52           if (__glibc_unlikely (s1len-- == 0))
  53             __chk_fail ();
  54           c = *s2++;
  55           *++s1 = c;
  56           if (c == '\0')
  57             return s;
  58           if (__glibc_unlikely (s1len-- == 0))
  59             __chk_fail ();
  60           c = *s2++;
  61           *++s1 = c;
  62           if (c == '\0')
  63             return s;
  64           if (__glibc_unlikely (s1len-- == 0))
  65             __chk_fail ();
  66           c = *s2++;
  67           *++s1 = c;
  68           if (c == '\0')
  69             return s;
  70           if (__glibc_unlikely (s1len-- == 0))
  71             __chk_fail ();
  72           c = *s2++;
  73           *++s1 = c;
  74           if (c == '\0')
  75             return s;
  76         } while (--n4 > 0);
  77       n &= 3;
  78     }
  79
  80   while (n > 0)
  81     {
  82       if (__glibc_unlikely (s1len-- == 0))
  83         __chk_fail ();
  84       c = *s2++;
  85       *++s1 = c;
  86       if (c == '\0')
  87         return s;
  88       n--;
  89     }
  90
  91   if (c != '\0')
  92     {
  93       if (__glibc_unlikely (s1len-- == 0))
  94         __chk_fail ();
  95       *++s1 = '\0';
  96     }
  97
  98   return s;
  99 }