PR c++/21581
[official-gcc.git] / libssp / ssp.c
blob9576be445b2256bfc4a809ccb983188beb4b88a8
1 /* Stack protector support.
2 Copyright (C) 2005 Free Software Foundation, Inc.
4 This file is part of GCC.
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 2, or (at your option) any later
9 version.
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.)
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.
25 You should have received a copy of the GNU General Public License
26 along with GCC; see the file COPYING. If not, write to the Free
27 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
28 02110-1301, USA. */
30 /* As a special exception, if you link this library with files compiled with
31 GCC to produce an executable, this does not cause the resulting executable
32 to be covered by the GNU General Public License. This exception does not
33 however invalidate any other reasons why the executable file might be
34 covered by the GNU General Public License. */
36 #include "config.h"
37 #ifdef HAVE_ALLOCA_H
38 # include <alloca.h>
39 #endif
40 #ifdef HAVE_STRING_H
41 # include <string.h>
42 #endif
43 #ifdef HAVE_UNISTD_H
44 # include <unistd.h>
45 #endif
46 #ifdef HAVE_FCNTL_H
47 # include <fcntl.h>
48 #endif
49 #ifdef HAVE_PATHS_H
50 # include <paths.h>
51 #endif
52 #ifndef _PATH_TTY
53 # define _PATH_TTY "/dev/tty"
54 #endif
55 #ifdef HAVE_SYSLOG_H
56 # include <syslog.h>
57 #endif
59 void *__stack_chk_guard = 0;
61 static void __attribute__ ((constructor))
62 __guard_setup (void)
64 unsigned char *p;
65 int fd;
67 if (__stack_chk_guard != 0)
68 return;
70 fd = open ("/dev/urandom", O_RDONLY);
71 if (fd != -1)
73 ssize_t size = read (fd, &__stack_chk_guard,
74 sizeof (__stack_chk_guard));
75 close (fd);
76 if (size == sizeof(__stack_chk_guard) && __stack_chk_guard != 0)
77 return;
80 /* If a random generator can't be used, the protector switches the guard
81 to the "terminator canary". */
82 p = (unsigned char *) &__stack_chk_guard;
83 p[sizeof(__stack_chk_guard)-1] = 255;
84 p[sizeof(__stack_chk_guard)-2] = '\n';
85 p[0] = 0;
88 static void
89 fail (const char *msg1, size_t msg1len, const char *msg3)
91 #ifdef __GNU_LIBRARY__
92 extern char * __progname;
93 #else
94 static const char __progname[] = "";
95 #endif
96 int fd;
98 /* Print error message directly to the tty. This avoids Bad Things
99 happening if stderr is redirected. */
100 fd = open (_PATH_TTY, O_WRONLY);
101 if (fd != -1)
103 static const char msg2[] = " terminated\n";
104 size_t progname_len, len;
105 char *buf, *p;
107 progname_len = strlen (__progname);
108 len = msg1len + progname_len + sizeof(msg2)-1 + 1;
109 p = buf = alloca (len);
111 memcpy (p, msg1, msg1len);
112 p += msg1len;
113 memcpy (p, __progname, progname_len);
114 p += progname_len;
115 memcpy (p, msg2, sizeof(msg2));
117 while (len > 0)
119 ssize_t wrote = write (fd, buf, len);
120 if (wrote < 0)
121 break;
122 buf += wrote;
123 len -= wrote;
125 close (fd);
128 #ifdef HAVE_SYSLOG_H
129 /* Only send the error to syslog if there was no tty available. */
130 else
131 syslog (LOG_CRIT, msg3);
132 #endif /* HAVE_SYSLOG_H */
134 /* Try very hard to exit. Note that signals may be blocked preventing
135 the first two options from working. The use of volatile is here to
136 prevent optimizers from "knowing" that __builtin_trap is called first,
137 and that it doesn't return, and so "obviously" the rest of the code
138 is dead. */
140 volatile int state;
141 for (state = 0; ; state++)
142 switch (state)
144 case 0:
145 __builtin_trap ();
146 break;
147 case 1:
148 *(volatile int *)-1L = 0;
149 break;
150 case 2:
151 _exit (127);
152 break;
157 void
158 __stack_chk_fail (void)
160 const char *msg = "*** stack smashing detected ***: ";
161 fail (msg, strlen (msg), "stack smashing detected: terminated");
164 void
165 __chk_fail (void)
167 const char *msg = "*** buffer overflow detected ***: ";
168 fail (msg, strlen (msg), "buffer overflow detected: terminated");
171 #ifdef HAVE_HIDDEN_VISIBILITY
172 void
173 __attribute__((visibility ("hidden")))
174 __stack_chk_fail_local (void)
176 __stack_chk_fail ();
178 #endif