//-------------------------------------------------------------------
//	codesize.c	(solution for Question VI, Midterm Exam I)
//
//	This module creates a pseudo-file (named '/proc/codesize')
//	which reports the total amount of userspace memory devoted
//	to the Virtual Memory Areas that contain 'executable' code
//	for any task presently belonging to the kernel's tasklist.
//
//	NOTE: Written and tested with Linux kernel version 2.6.10.  
//
//	programmer: ALLAN CRUSE
//	written on: 15 FEB 2005
//-------------------------------------------------------------------

#include <linux/module.h>	// for init_module() 
#include <linux/proc_fs.h>	// for create_proc_info_entry() 
#include <linux/mm.h>		// for 'vm_area_struct'

static char modname[] = "codesize";

static int my_get_info( char *buf, char **start, off_t off, int count )
{
	struct task_struct	*task;
	struct vm_area_struct	*vma;
	unsigned int		areasize, codesize, totalcode;
	int			len = 0;

	// show the explanatory title
	len += sprintf( buf+len, "\nList of userspace code-footprints " );
	len += sprintf( buf+len, "(by task)\n\n" );

	// outer-loop iterates over all the 'task_struct' objects
	totalcode = 0;
	task = &init_task;	
	do	{	
		if ( task->mm != NULL )     // can omit if a 'kernel-thread' 
			{
			// inner-loop iterates over all the 'vm_area_struct' 
			// objects that are associated with a specific task
			codesize = 0;
			vma = task->mm->mmap;
			while ( vma != NULL )
				{
				areasize = vma->vm_end - vma->vm_start;
				if ( vma->vm_flags & VM_EXEC ) 
					codesize += areasize;
				vma = vma->vm_next;
				}
			totalcode += codesize;
			len += sprintf( buf+len, " pid=%-5d ", task->pid );
			len += sprintf( buf+len, " codesize=%08X ", codesize );
			len += sprintf( buf+len, " %-15s \n", task->comm );
			}
		task = next_task( task );
		}
	while ( task != &init_task );

	// show the total size of userspace code
	len += sprintf( buf+len, "\nTotal size of userspace code " );
	len += sprintf( buf+len, "is 0x%08X bytes \n\n", totalcode );
	return	len;
}


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


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

MODULE_LICENSE("GPL");