| 1 | // relro_test.cc -- test -z relro for gold |
| 2 | |
| 3 | // Copyright (C) 2008-2019 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 | } |