//-------------------------------------------------------------------
//	demo.c
//
//	This module creates a '/proc' pseudo-file that displays the
//	effect of executing the 'set_fs( get_ds() )' statement upon
//	the 'addr_limit' field in the task's process descriptor. 
//
//	NOTE: Written and tested with Linux kernel version 2.4.20.
//
//	programmer: ALLAN CRUSE
//	written on: 10 FEB 2003
//-------------------------------------------------------------------

#define	__KERNEL__
#define	  MODULE  

#include <linux/module.h>	// for init_module() 
#include <linux/proc_fs.h>	// for create_proc_read_entry() 
#include <asm/uaccess.h>	// for set_fs(), get_ds()

#define	SUCCESS	0

static char modname[] = "demo";

static int my_proc_read( char *buf, char **start, off_t off,
			int count, int *eof, void *data )
{
	unsigned long	*lp = (unsigned long*)current;
	int		i, len;

	len = 0;
	len += sprintf( buf+len, "\nBEFORE: \n" );
	for (i = 0; i < 5; i++) len += sprintf( buf+len, "%08X ", lp[i] );
	len += sprintf( buf+len, "\n" );

	set_fs( get_ds() );
	
	len += sprintf( buf+len, "\nAFTER: \n" );
	for (i = 0; i < 5; i++) len += sprintf( buf+len, "%08X ", lp[i] );
	len += sprintf( buf+len, "\n" );
	len += sprintf( buf+len, "\n" );

	*eof = 1;
	return	len;
}

void cleanup_module( void )
{
	remove_proc_entry( modname, NULL );
	printk( "<1>Removing \'%s\' module\n", modname );
}

int init_module( void )
{
	printk( "<1>\nInstalling \'%s\' module\n", modname );
	create_proc_read_entry( modname, 0, NULL, my_proc_read, NULL );
	return	SUCCESS;
}

MODULE_LICENSE("GPL");