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