//-------------------------------------------------------------------
//	tasklist.c
//
//	This module creates an entry in the '/proc' filesystem that
//	allows the user to display a list of all the current tasks.
//
//	NOTE: Developed and tested with Linux kernel version 2.4.26
//
//	programmer: ALLAN CRUSE
//	written on: 09 SEP 2004
//-------------------------------------------------------------------

#include <linux/module.h>	// for init_module() 
#include <linux/proc_fs.h>	// for create_proc_read_entry()

static char modname[] = "tasklist";

static char report[ 8192 ];

static int my_read_proc( char *page, char **start, off_t offset, 
				int count, int *eof, void *data )
{
	struct	task_struct	*tsk;
	static	int		len = 0;
	int			tasks, nbytes, i;

	if ( offset == 0 )
		{
		//--------------------------------------------
		// count the number of tasks on the task-list
		//--------------------------------------------
		tsk = &init_task;
		tasks = 0;
		do	{
			++tasks;
			tsk = tsk->next_task;
			}
		while ( tsk != &init_task );
		len = sprintf( report, "\nNumber of tasks = %d \n", tasks );
		//-----------------------------------
		// print information about each task
		//-----------------------------------
		tsk = &init_task;
		for (i = 0; i < tasks; i++)
			{
			char	ch = ( ( i % 3 ) == 0 ) ? '\n' : ' ';
			char	st = tsk->state | '0';
			len += sprintf( report+len, "%c", ch );
			len += sprintf( report+len, "%5d ", tsk->pid );
			len += sprintf( report+len, "%c ", st );
			len += sprintf( report+len, "%-15s  ", tsk->comm );
			tsk = tsk->next_task;
			}
		len += sprintf( report+len, "\n\n" );
		}
	
	//--------------------------------------------------
	// must not allow reading beyond the end-of-message
	//-------------------------------------------------- 
	if ( offset >= len ) { *eof = 1; return 0; }

	//--------------------------------------------------
	// must not deliver more bytes than 'page' can hold
	//-------------------------------------------------- 
	if ( offset + count < len ) nbytes = count;
	else	nbytes = len - offset;

	//---------------------------------------------------
	// transfer at most 'count' bytes into 'page' buffer
	//--------------------------------------------------- 
	memcpy( page, report+offset, nbytes );
	*start = page;	// tell kernel where to find our data
	return	nbytes;	//  and how many bytes we put there
}

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


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

MODULE_LICENSE("GPL");