//-------------------------------------------------------------------
//	showrbda.cpp
//
//	This program shows the contents of the ROM-BIOS DATA AREA in
//	hexadecimal format (it employs a custom device-driver module
//	to support mapping of the relevant area of physical memory).
//
//	These preliminary steps required (to create the device-file)
//	before executing this program for the first time:
//			$ sudo mkdir /dev/dos c 86 0
//			$ sudo chmod a+rwx /dev/dos
//
//	NOTE: Developed and tested with Linux kernel version 2.4.23.	
//
//	programmer: ALLAN CRUSE
//	written on: 23 JAN 2004
//-------------------------------------------------------------------

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

#define N_WORDS 128	// number of words in ROM-BIOS DATA-AREA

char devname[] = "/dev/dos";

int main( int argc, char **argv )
{
	// install our custom device-driver module
	system( "/sbin/insmod dos.o" );

	// open the device special file for reading
	int	fd = open( devname, O_RDONLY );
	if ( fd < 0 ) { perror( devname ); exit(1); }

	// memory map the file's initial two killobytes
	int	base = 0;
	int	size = (2<<10);		// 2KB
	int	prot = PROT_READ;
	int	flag = MAP_FIXED | MAP_PRIVATE;
	void	*vm = (void*)base;
	if ( mmap( vm, size, prot, flag, fd, base ) == MAP_FAILED )
		{ perror( "mmap" ); exit(1); }

	// display the ROM-BIOS DATA AREA (0x00000400 - 0x00000500)	
	unsigned short	*wp = (unsigned short*)0x400;
	for (int i = 0; i < N_WORDS; i++)
		{
		if ( ( i % 8 ) == 0 ) printf( "\n%04X: ", &wp[i] );
		printf( "%04X ", wp[i] );	
		}
	printf( "\n\n" );
}