1// relro_test.cc -- test -z relro for gold
2
3// Copyright (C) 2008-2020 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
34extern 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.
39int i1 = 1;
40static int i2 = 2;
41
42// P1 is a global relro variable.
43int* const p1 __attribute__ ((aligned(64))) = &i1;
44
45// P2 is a local relro variable.
46int* 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
53bool
54t1()
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
89static bool throwing;
90
91// A signal handler for SIGSEGV.
92
93extern "C"
94void
95sigsegv_handler(int)
96{
97  throwing = true;
98  throw 0;
99}
100
101// The original terminate handler.
102
103std::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
109void
110terminate_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
126void f2() __attribute__ ((noinline));
127void
128f2()
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
141bool
142t2()
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