gold/testsuite/relro_test.cc

   1 // relro_test.cc -- test -z relro for gold
   2
   3 // Copyright (C) 2008-2022 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 }