//-------------------------------------------------------------------
//	vma.c
//
//	This module creates a '/proc' pseudo file which allows users
//	to view information about the process memory map for a task.  
//	This Linux kernel structure lists the various virtual memory 
//	areas that are associated with the particular task. 
//
//	programmer: ALLAN CRUSE
//	written on: 20 FEB 2003
//	revised on: 26 APR 2003 -- to also show VM_SHARED (1=s, 0=p) 
//	revised on: 20 SEP 2004 -- for Linux kernel version 2.4.26
//-------------------------------------------------------------------

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

static int my_proc_read( char *buf, char **start, off_t off,
				int count, int *eof, void *data )
{
	struct task_struct	*tsk = current;
	struct vm_area_struct	*vma;
	unsigned long 		ptdb;
	int			i = 0, len = 0;
	
	// display title
	len += sprintf( buf+len, "\n\nList of the Virtual Memory Areas " );
	len += sprintf( buf+len, "for task \'%s\' ", tsk->comm );
	len += sprintf( buf+len, "(pid=%d)\n", tsk->pid );

	// loop to traverse the list of the task's vm_area_structs
	vma = tsk->mm->mmap;
	while ( vma )
		{
		char	ch;	
		len += sprintf( buf+len, "\n%3d ", ++i );
		len += sprintf( buf+len, " vm_start=%08X ", vma->vm_start );
		len += sprintf( buf+len, " vm_end=%08X  ", vma->vm_end );

		ch = ( vma->vm_flags & VM_READ ) ? 'r' : '-';
		len += sprintf( buf+len, "%c", ch );
		
		ch = ( vma->vm_flags & VM_WRITE ) ? 'w' : '-';
		len += sprintf( buf+len, "%c", ch );
		
		ch = ( vma->vm_flags & VM_EXEC ) ? 'x' : '-';
		len += sprintf( buf+len, "%c", ch );

		ch = ( vma->vm_flags & VM_SHARED ) ? 's' : 'p';
		len += sprintf( buf+len, "%c", ch );
		
		vma = vma->vm_next;
		}
	len += sprintf( buf+len, "\n" );

	// display additional information about tsk->mm
	asm(" movl %%cr3, %%eax \n movl %%eax, %0 " : "=m" (ptdb) );
	len += sprintf( buf+len, "\nCR3=%08X ", ptdb );
	len += sprintf( buf+len, " mm->pgd=%08X ", tsk->mm->pgd );
	len += sprintf( buf+len, " mm->map_count=%d ", tsk->mm->map_count );
	len += sprintf( buf+len, "\n\n" );
	return	len;
}


void cleanup_module( void )
{
	remove_proc_entry( "vma", NULL );
}


int init_module( void )
{
	create_proc_read_entry( "vma", 0, NULL, my_proc_read, NULL );
	return	0; // SUCCESS
}

MODULE_LICENSE("GPL");