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))
__guard_setup(void)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
fail(const char * msg1,size_t msg1len,const char * msg3)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
__stack_chk_fail(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
__chk_fail(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")))
__stack_chk_fail_local(void)184 __stack_chk_fail_local (void)
185 {
186 __stack_chk_fail ();
187 }
188 #endif
189