1 // relro_test.cc -- test -z relro for gold
2
3 // Copyright (C) 2008-2016 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
5
6 // This file is part of gold.
7
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
12
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
17
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
22
23 #include <cassert>
24 #include <csignal>
25 #include <cstdio>
26 #include <cstdlib>
27 #include <exception>
28 #include <stdint.h>
29 #include <unistd.h>
30
31 // This tests we were linked with a script. If we were linked with a
32 // script, relro currently does not work.
33
34 extern char using_script[] __attribute__ ((weak));
35
36 // This code is put into a shared library linked with -z relro.
37
38 // i1 and i2 are not relro variables.
39 int i1 = 1;
40 static int i2 = 2;
41
42 // P1 is a global relro variable.
43 int* const p1 __attribute__ ((aligned(64))) = &i1;
44
45 // P2 is a local relro variable.
46 int* const p2 __attribute__ ((aligned(64))) = &i2;
47
48 // Add a TLS variable to make sure -z relro works correctly with TLS.
49 __thread int i3 = 1;
50
51 // Test symbol addresses.
52
53 bool
t1()54 t1()
55 {
56 if (using_script)
57 return true;
58
59 void* i1addr = static_cast<void*>(&i1);
60 void* i2addr = static_cast<void*>(&i2);
61 const void* p1addr = static_cast<const void*>(&p1);
62 const void* p2addr = static_cast<const void*>(&p2);
63
64 // The relro variables should precede the non-relro variables in the
65 // memory image.
66 assert(i1addr > p1addr);
67 assert(i1addr > p2addr);
68 assert(i2addr > p1addr);
69 assert(i2addr > p2addr);
70
71 // The relro variables should not be on the same page as the
72 // non-relro variables.
73 const size_t page_size = getpagesize();
74 uintptr_t i1page = reinterpret_cast<uintptr_t>(i1addr) & ~ (page_size - 1);
75 uintptr_t i2page = reinterpret_cast<uintptr_t>(i2addr) & ~ (page_size - 1);
76 uintptr_t p1page = reinterpret_cast<uintptr_t>(p1addr) & ~ (page_size - 1);
77 uintptr_t p2page = reinterpret_cast<uintptr_t>(p2addr) & ~ (page_size - 1);
78 assert(i1page != p1page);
79 assert(i1page != p2page);
80 assert(i2page != p1page);
81 assert(i2page != p2page);
82 assert(i3 == 1);
83
84 return true;
85 }
86
87 // Tell terminate handler that we are throwing from a signal handler.
88
89 static bool throwing;
90
91 // A signal handler for SIGSEGV.
92
93 extern "C"
94 void
sigsegv_handler(int)95 sigsegv_handler(int)
96 {
97 throwing = true;
98 throw 0;
99 }
100
101 // The original terminate handler.
102
103 std::terminate_handler orig_terminate;
104
105 // Throwing an exception out of a signal handler doesn't always work
106 // reliably. When that happens the program will call terminate. We
107 // set a terminate handler to indicate that the test probably passed.
108
109 void
terminate_handler()110 terminate_handler()
111 {
112 if (!throwing)
113 {
114 orig_terminate();
115 ::exit(EXIT_FAILURE);
116 }
117 fprintf(stderr,
118 "relro_test: terminate called due to failure to throw through signal handler\n");
119 fprintf(stderr, "relro_test: assuming test succeeded\n");
120 ::exit(EXIT_SUCCESS);
121 }
122
123 // Use a separate function to throw the exception, so that we don't
124 // need to use -fnon-call-exceptions.
125
126 void f2() __attribute__ ((noinline));
127 void
f2()128 f2()
129 {
130 int** pp1 = const_cast<int**>(&p1);
131 *pp1 = &i2;
132
133 // We shouldn't get here--the assignment to *pp1 should write to
134 // memory which the dynamic linker marked as read-only, giving us a
135 // SIGSEGV, causing sigsegv_handler to be invoked, to throw past us.
136 assert(0);
137 }
138
139 // Changing a relro variable should give us a SIGSEGV.
140
141 bool
t2()142 t2()
143 {
144 if (using_script)
145 return true;
146
147 signal(SIGSEGV, sigsegv_handler);
148 orig_terminate = std::set_terminate(terminate_handler);
149
150 try
151 {
152 f2();
153 return false;
154 }
155 catch (int i)
156 {
157 assert(i == 0);
158 return true;
159 }
160 }
161