mprotect_fail.cpp

#include <iostream>
#include <cstdlib>
#include <cstdlib>
#include <sys/mman.h>
#include <unistd.h>
#include <iomanip>

int
main( int argc, char **argv )
{
   int *a( nullptr );
   const auto page_size( sysconf( _SC_PAGESIZE ) );
   static const auto length( 100 );
   const auto size( length * sizeof( int ) );

   posix_memalign( reinterpret_cast< void** >( &a ), page_size, page_size * 2 );
   std::cout << "start address: " << std::hex 
      << reinterpret_cast< std::uintptr_t >( a ) << "\n";
   /** make sure it's writeable **/
   for( auto index( 0 ); index < length; index ++ )
   {
      a[ index ] = 5;
   }
   auto *last_page( 
      reinterpret_cast< void* >( 
         reinterpret_cast< std::uintptr_t >( a ) + page_size ) );
   std::cout << "last page start: " << std::hex << 
      reinterpret_cast< std::uintptr_t >( last_page ) << "\n";
   mprotect( last_page, page_size , PROT_NONE );
   std::cout << "protected page starting at: " << 
      std::hex << reinterpret_cast< std::uintptr_t >( last_page ) << "\n";
   std::cout << "calling free on: " << std::hex <<
      reinterpret_cast< std::uintptr_t >( a ) << "\n";
   std::free( a );
   return( EXIT_SUCCESS );
}