gold/testsuite/relro_test.cc

   1 // relro_test.cc -- test -z relro for gold
   2
   3 // Copyright 2008 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 = &i1;
  44
  45 // P2 is a local relro variable.
  46 int* const p2 = &i2;
  47
  48 // Test symbol addresses.
  49
  50 bool
  51 t1()
  52 {
  53   if (using_script)
  54     return true;
  55
  56   void* i1addr = static_cast<void*>(&i1);
  57   void* i2addr = static_cast<void*>(&i2);
  58   const void* p1addr = static_cast<const void*>(&p1);
  59   const void* p2addr = static_cast<const void*>(&p2);
  60
  61   // The relro variables should precede the non-relro variables in the
  62   // memory image.
  63   assert(i1addr > p1addr);
  64   assert(i1addr > p2addr);
  65   assert(i2addr > p1addr);
  66   assert(i2addr > p2addr);
  67
  68   // The relro variables should not be on the same page as the
  69   // non-relro variables.
  70   const size_t page_size = getpagesize();
  71   uintptr_t i1page = reinterpret_cast<uintptr_t>(i1addr) & ~ (page_size - 1);
  72   uintptr_t i2page = reinterpret_cast<uintptr_t>(i2addr) & ~ (page_size - 1);
  73   uintptr_t p1page = reinterpret_cast<uintptr_t>(p1addr) & ~ (page_size - 1);
  74   uintptr_t p2page = reinterpret_cast<uintptr_t>(p2addr) & ~ (page_size - 1);
  75   assert(i1page != p1page);
  76   assert(i1page != p2page);
  77   assert(i2page != p1page);
  78   assert(i2page != p2page);
  79
  80   return true;
  81 }
  82
  83 // Tell terminate handler that we are throwing from a signal handler.
  84
  85 static bool throwing;
  86
  87 // A signal handler for SIGSEGV.
  88
  89 extern "C"
  90 void
  91 sigsegv_handler(int)
  92 {
  93   throwing = true;
  94   throw 0;
  95 }
  96
  97 // The original terminate handler.
  98
  99 std::terminate_handler orig_terminate;
 100
 101 // Throwing an exception out of a signal handler doesn't always work
 102 // reliably.  When that happens the program will call terminate.  We
 103 // set a terminate handler to indicate that the test probably passed.
 104
 105 void
 106 terminate_handler()
 107 {
 108   if (!throwing)
 109     {
 110       orig_terminate();
 111       ::exit(EXIT_FAILURE);
 112     }
 113   fprintf(stderr,
 114           "relro_test: terminate called due to failure to throw through signal handler\n");
 115   fprintf(stderr, "relro_test: assuming test succeeded\n");
 116   ::exit(EXIT_SUCCESS);
 117 }
 118
 119 // Use a separate function to throw the exception, so that we don't
 120 // need to use -fnon-call-exceptions.
 121
 122 void f2() __attribute__ ((noinline));
 123 void
 124 f2()
 125 {
 126   int** pp1 = const_cast<int**>(&p1);
 127   *pp1 = &i2;
 128
 129   // We shouldn't get here--the assignment to *pp1 should write to
 130   // memory which the dynamic linker marked as read-only, giving us a
 131   // SIGSEGV, causing sigsegv_handler to be invoked, to throw past us.
 132   assert(0);
 133 }
 134
 135 // Changing a relro variable should give us a SIGSEGV.
 136
 137 bool
 138 t2()
 139 {
 140   if (using_script)
 141     return true;
 142
 143   signal(SIGSEGV, sigsegv_handler);
 144   orig_terminate = std::set_terminate(terminate_handler);
 145
 146   try
 147     {
 148       f2();
 149       return false;
 150     }
 151   catch (int i)
 152     {
 153       assert(i == 0);
 154       return true;
 155     }
 156 }