//-------------------------------------------------------------------
//	showvmap.cpp
//
//	This program shows a map of the virtual memory space, based
//	on information in the task_struct's 'mm->pgd[]' array which 
//	is obtained by reading the '/proc/vmap' pseudo-file.  (Note
//	that the 'vmap.o' module must be in the current directory.)   
//
//	programmer: ALLAN CRUSE
//	written on: 03 OCT 2004
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for read(), close() 

char filename[] = "/proc/vmap";

int main( int argc, char **argv )
{
	//------------------------------------
	// install the required kernel module
	//------------------------------------ 
	system( "/sbin/insmod vmap.o" );
	
	//----------------------------------
	// open the pseudo-file for reading
	//---------------------------------- 
	int	fd = open( filename, O_RDONLY );
	if ( fd < 0 ) { perror( filename ); exit(1); }

	//------------------------------
	// read the array of characters
	//------------------------------
	char	buffer[ 1024 ];
	int	nbytes = read( fd, buffer, 1024 );
	if ( nbytes < 1024 ) { perror( "read" ); exit(1); }

	//----------------------------------------------------
	// close the pseudo-file and unload the kernel module
	//----------------------------------------------------
	close( fd );
	system( "/sbin/rmmod vmap" );

	//--------------------------------------------------
	// display a nicely formatted map of virtual memory
	//--------------------------------------------------
	printf( "\n\t\t\tMap of virtual memory-space\n" );
	for (int i = 0; i < 1024; i++)
		{
		if ( ( i % 64 ) == 0 ) printf( "\n   " );
		if ( ( i % 16 ) == 0 ) printf( " " );
		int	ch = ( buffer[i] & 7 ) | 0x30;
		if ( ch == '0' ) ch = '.';
		printf( "%c", ch );
		}	
	printf( "\n\n" );
}