contrib/gcc-4.4/libssp/ssp.c

   1 /* Stack protector support.
   2    Copyright (C) 2005, 2009 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 In addition to the permissions in the GNU General Public License, the
  12 Free Software Foundation gives you unlimited permission to link the
  13 compiled version of this file into combinations with other programs,
  14 and to distribute those combinations without any restriction coming
  15 from the use of this file.  (The General Public License restrictions
  16 do apply in other respects; for example, they cover modification of
  17 the file, and distribution when not linked into a combine
  18 executable.)
  19
  20 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  21 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  22 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  23 for more details.
  24
  25 Under Section 7 of GPL version 3, you are granted additional
  26 permissions described in the GCC Runtime Library Exception, version
  27 3.1, as published by the Free Software Foundation.
  28
  29 You should have received a copy of the GNU General Public License and
  30 a copy of the GCC Runtime Library Exception along with this program;
  31 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  32 <http://www.gnu.org/licenses/>.  */
  33
  34
  35 #include "config.h"
  36 #ifdef HAVE_ALLOCA_H
  37 # include <alloca.h>
  38 #endif
  39 #ifdef HAVE_STRING_H
  40 # include <string.h>
  41 #endif
  42 #ifdef HAVE_UNISTD_H
  43 # include <unistd.h>
  44 #endif
  45 #ifdef HAVE_FCNTL_H
  46 # include <fcntl.h>
  47 #endif
  48 #ifdef HAVE_PATHS_H
  49 # include <paths.h>
  50 #endif
  51 #ifndef _PATH_TTY
  52 /* Native win32 apps don't know about /dev/tty but can print directly
  53    to the console using  "CONOUT$"   */
  54 #if defined (_WIN32) && !defined (__CYGWIN__)
  55 # define _PATH_TTY "CONOUT$"
  56 #else
  57 # define _PATH_TTY "/dev/tty"
  58 #endif
  59 #endif
  60 #ifdef HAVE_SYSLOG_H
  61 # include <syslog.h>
  62 #endif
  63
  64 void *__stack_chk_guard = 0;
  65
  66 static void __attribute__ ((constructor))
  67 __guard_setup (void)
  68 {
  69   unsigned char *p;
  70   int fd;
  71
  72   if (__stack_chk_guard != 0)
  73     return;
  74
  75   fd = open ("/dev/urandom", O_RDONLY);
  76   if (fd != -1)
  77     {
  78       ssize_t size = read (fd, &__stack_chk_guard,
  79                            sizeof (__stack_chk_guard));
  80       close (fd);
  81       if (size == sizeof(__stack_chk_guard) && __stack_chk_guard != 0)
  82         return;
  83     }
  84
  85   /* If a random generator can't be used, the protector switches the guard
  86      to the "terminator canary".  */
  87   p = (unsigned char *) &__stack_chk_guard;
  88   p[sizeof(__stack_chk_guard)-1] = 255;
  89   p[sizeof(__stack_chk_guard)-2] = '\n';
  90   p[0] = 0;
  91 }
  92
  93 static void
  94 fail (const char *msg1, size_t msg1len, const char *msg3)
  95 {
  96 #ifdef __GNU_LIBRARY__
  97   extern char * __progname;
  98 #else
  99   static const char __progname[] = "";
 100 #endif
 101   int fd;
 102
 103   /* Print error message directly to the tty.  This avoids Bad Things
 104      happening if stderr is redirected.  */
 105   fd = open (_PATH_TTY, O_WRONLY);
 106   if (fd != -1)
 107     {
 108       static const char msg2[] = " terminated\n";
 109       size_t progname_len, len;
 110       char *buf, *p;
 111
 112       progname_len = strlen (__progname);
 113       len = msg1len + progname_len + sizeof(msg2)-1 + 1;
 114       p = buf = alloca (len);
 115
 116       memcpy (p, msg1, msg1len);
 117       p += msg1len;
 118       memcpy (p, __progname, progname_len);
 119       p += progname_len;
 120       memcpy (p, msg2, sizeof(msg2));
 121
 122       while (len > 0)
 123         {
 124           ssize_t wrote = write (fd, buf, len);
 125           if (wrote < 0)
 126             break;
 127           buf += wrote;
 128           len -= wrote;
 129         }
 130       close (fd);
 131     }
 132
 133 #ifdef HAVE_SYSLOG_H
 134   /* Only send the error to syslog if there was no tty available.  */
 135   else
 136     syslog (LOG_CRIT, msg3);
 137 #endif /* HAVE_SYSLOG_H */
 138
 139   /* Try very hard to exit.  Note that signals may be blocked preventing
 140      the first two options from working.  The use of volatile is here to
 141      prevent optimizers from "knowing" that __builtin_trap is called first,
 142      and that it doesn't return, and so "obviously" the rest of the code
 143      is dead.  */
 144   {
 145     volatile int state;
 146     for (state = 0; ; state++)
 147       switch (state)
 148         {
 149         case 0:
 150           __builtin_trap ();
 151           break;
 152         case 1:
 153           *(volatile int *)-1L = 0;
 154           break;
 155         case 2:
 156           _exit (127);
 157           break;
 158         }
 159   }
 160 }
 161
 162 void
 163 __stack_chk_fail (void)
 164 {
 165   const char *msg = "*** stack smashing detected ***: ";
 166   fail (msg, strlen (msg), "stack smashing detected: terminated");
 167 }
 168
 169 void
 170 __chk_fail (void)
 171 {
 172   const char *msg = "*** buffer overflow detected ***: ";
 173   fail (msg, strlen (msg), "buffer overflow detected: terminated");
 174 }
 175
 176 #ifdef HAVE_HIDDEN_VISIBILITY
 177 void
 178 __attribute__((visibility ("hidden")))
 179 __stack_chk_fail_local (void)
 180 {
 181   __stack_chk_fail ();
 182 }
 183 #endif