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 <stdint.h>
  26 #include <unistd.h>
  27
  28 // This code is put into a shared library linked with -z relro.
  29
  30 // i1 and i2 are not relro variables.
  31 int i1 = 1;
  32 static int i2 = 2;
  33
  34 // P1 is a global relro variable.
  35 int* const p1 = &i1;
  36
  37 // P2 is a local relro variable.
  38 int* const p2 = &i2;
  39
  40 // Test symbol addresses.
  41
  42 bool
  43 t1()
  44 {
  45   void* i1addr = static_cast<void*>(&i1);
  46   void* i2addr = static_cast<void*>(&i2);
  47   const void* p1addr = static_cast<const void*>(&p1);
  48   const void* p2addr = static_cast<const void*>(&p2);
  49
  50   // The relro variables should precede the non-relro variables in the
  51   // memory image.
  52   assert(i1addr > p1addr);
  53   assert(i1addr > p2addr);
  54   assert(i2addr > p1addr);
  55   assert(i2addr > p2addr);
  56
  57   // The relro variables should not be on the same page as the
  58   // non-relro variables.
  59   const size_t page_size = getpagesize();
  60   uintptr_t i1page = reinterpret_cast<uintptr_t>(i1addr) & ~ (page_size - 1);
  61   uintptr_t i2page = reinterpret_cast<uintptr_t>(i2addr) & ~ (page_size - 1);
  62   uintptr_t p1page = reinterpret_cast<uintptr_t>(p1addr) & ~ (page_size - 1);
  63   uintptr_t p2page = reinterpret_cast<uintptr_t>(p2addr) & ~ (page_size - 1);
  64   assert(i1page != p1page);
  65   assert(i1page != p2page);
  66   assert(i2page != p1page);
  67   assert(i2page != p2page);
  68
  69   return true;
  70 }
  71
  72 // A signal handler for SIGSEGV.
  73
  74 extern "C"
  75 void
  76 sigsegv_handler(int)
  77 {
  78   throw 0;
  79 }
  80
  81 // Use a separate function to throw the exception, so that we don't
  82 // need to use -fnon-call-exceptions.
  83
  84 void f2() __attribute__ ((noinline));
  85 void
  86 f2()
  87 {
  88   int** pp1 = const_cast<int**>(&p1);
  89   *pp1 = &i2;
  90
  91   // We shouldn't get here--the assignment to *pp1 should write to
  92   // memory which the dynamic linker marked as read-only, giving us a
  93   // SIGSEGV, causing sigsegv_handler to be invoked, to throw past us.
  94   assert(0);
  95 }
  96
  97 // Changing a relro variable should give us a SIGSEGV.
  98
  99 bool
 100 t2()
 101 {
 102   signal(SIGSEGV, sigsegv_handler);
 103
 104   try
 105     {
 106       f2();
 107       return false;
 108     }
 109   catch (int i)
 110     {
 111       assert(i == 0);
 112       return true;
 113     }
 114 }