contrib/gcc-4.7/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_MALLOC_H
  40 # include <malloc.h>
  41 #else
  42 # include <stdlib.h>
  43 #endif
  44 #ifdef HAVE_STRING_H
  45 # include <string.h>
  46 #endif
  47 #ifdef HAVE_UNISTD_H
  48 # include <unistd.h>
  49 #endif
  50 #ifdef HAVE_FCNTL_H
  51 # include <fcntl.h>
  52 #endif
  53 #ifdef HAVE_PATHS_H
  54 # include <paths.h>
  55 #endif
  56 #ifndef _PATH_TTY
  57 /* Native win32 apps don't know about /dev/tty but can print directly
  58    to the console using  "CONOUT$"   */
  59 #if defined (_WIN32) && !defined (__CYGWIN__)
  60 # define _PATH_TTY "CONOUT$"
  61 #else
  62 # define _PATH_TTY "/dev/tty"
  63 #endif
  64 #endif
  65 #ifdef HAVE_SYSLOG_H
  66 # include <syslog.h>
  67 #endif
  68
  69 void *__stack_chk_guard = 0;
  70
  71 static void __attribute__ ((constructor))
  72 __guard_setup (void)
  73 {
  74   unsigned char *p;
  75   int fd;
  76
  77   if (__stack_chk_guard != 0)
  78     return;
  79
  80   fd = open ("/dev/urandom", O_RDONLY);
  81   if (fd != -1)
  82     {
  83       ssize_t size = read (fd, &__stack_chk_guard,
  84                            sizeof (__stack_chk_guard));
  85       close (fd);
  86       if (size == sizeof(__stack_chk_guard) && __stack_chk_guard != 0)
  87         return;
  88     }
  89
  90   /* If a random generator can't be used, the protector switches the guard
  91      to the "terminator canary".  */
  92   p = (unsigned char *) &__stack_chk_guard;
  93   p[sizeof(__stack_chk_guard)-1] = 255;
  94   p[sizeof(__stack_chk_guard)-2] = '\n';
  95   p[0] = 0;
  96 }
  97
  98 static void
  99 fail (const char *msg1, size_t msg1len, const char *msg3)
 100 {
 101 #ifdef __GNU_LIBRARY__
 102   extern char * __progname;
 103 #else
 104   static const char __progname[] = "";
 105 #endif
 106   int fd;
 107
 108   /* Print error message directly to the tty.  This avoids Bad Things
 109      happening if stderr is redirected.  */
 110   fd = open (_PATH_TTY, O_WRONLY);
 111   if (fd != -1)
 112     {
 113       static const char msg2[] = " terminated\n";
 114       size_t progname_len, len;
 115       char *buf, *p;
 116
 117       progname_len = strlen (__progname);
 118       len = msg1len + progname_len + sizeof(msg2)-1 + 1;
 119       p = buf = alloca (len);
 120
 121       memcpy (p, msg1, msg1len);
 122       p += msg1len;
 123       memcpy (p, __progname, progname_len);
 124       p += progname_len;
 125       memcpy (p, msg2, sizeof(msg2));
 126
 127       while (len > 0)
 128         {
 129           ssize_t wrote = write (fd, buf, len);
 130           if (wrote < 0)
 131             break;
 132           buf += wrote;
 133           len -= wrote;
 134         }
 135       close (fd);
 136     }
 137
 138 #ifdef HAVE_SYSLOG_H
 139   /* Only send the error to syslog if there was no tty available.  */
 140   else
 141     syslog (LOG_CRIT, msg3);
 142 #endif /* HAVE_SYSLOG_H */
 143
 144   /* Try very hard to exit.  Note that signals may be blocked preventing
 145      the first two options from working.  The use of volatile is here to
 146      prevent optimizers from "knowing" that __builtin_trap is called first,
 147      and that it doesn't return, and so "obviously" the rest of the code
 148      is dead.  */
 149   {
 150     volatile int state;
 151     for (state = 0; ; state++)
 152       switch (state)
 153         {
 154         case 0:
 155           __builtin_trap ();
 156           break;
 157         case 1:
 158           *(volatile int *)-1L = 0;
 159           break;
 160         case 2:
 161           _exit (127);
 162           break;
 163         }
 164   }
 165 }
 166
 167 void
 168 __stack_chk_fail (void)
 169 {
 170   const char *msg = "*** stack smashing detected ***: ";
 171   fail (msg, strlen (msg), "stack smashing detected: terminated");
 172 }
 173
 174 void
 175 __chk_fail (void)
 176 {
 177   const char *msg = "*** buffer overflow detected ***: ";
 178   fail (msg, strlen (msg), "buffer overflow detected: terminated");
 179 }
 180
 181 #ifdef HAVE_HIDDEN_VISIBILITY
 182 void
 183 __attribute__((visibility ("hidden")))
 184 __stack_chk_fail_local (void)
 185 {
 186   __stack_chk_fail ();
 187 }
 188 #endif