//-------------------------------------------------------------------
//	findvmlist.c
//
//	This module demonstrates use of 'vmalloc()' and 'vfree()'
//	to allocate a temporeary memory buffer in kernel-space.
//	It also shows how the address of a kernel symbol that was
//	not exported can be extracted from the 'System.map' file.
//
//	NOTE: This module was written and tested using the kernel
//	version 2.4.18-14smp, which exported the names of system-
//	call functions; it is left as an exercise for the student 
//	to revise this module so it works with our 2.4.20 kernel.
//
//	programmer: ALLAN CRUSE
//	written on: 04 MAR 2003
//-------------------------------------------------------------------

#define	__KERNEL__
#define	  MODULE  

#include <linux/module.h>	// for init_module() 
#include <linux/proc_fs.h>	// for create_proc_read_entry() 
#include <linux/vmalloc.h>	// for vmalloc(), vfree()
#include <linux/fs.h>		// for sys_open(), sys_read(), etc
#include <asm/uaccess.h>	// for set_fs(), get_ds()

#define	SUCCESS	0
#define BASE_16 16

static char modname[] = "findvmlist";
static char mapfile[] = "/boot/System.map-2.4.18-14smp";
static struct vm_struct **vmlistp;


static int my_proc_read( char *buf, char **start, off_t off,
			int count, int *eof, void *data )
{
	struct vm_struct	*vm;
	int			i = 0, len;

	len = sprintf( buf, "\nLinked-list of 'vm_struct' objects\n" );
	vm = *vmlistp;
	while ( vm )
		{
		++i;
		len += sprintf( buf+len, "\n#%d:\t", i );
		len += sprintf( buf+len, "addr=%08X  ", vm->addr );
		len += sprintf( buf+len, "size=%08X  ", vm->size );
		len += sprintf( buf+len, "flags=%08X  ", vm->flags );
		len += sprintf( buf+len, "next=%08X  ", vm->next );
		vm = vm->next;
		}
	len += sprintf( buf+len, "\n\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 )
{
	int	fd, filesize, nbytes;
	char	*data, *cp;
	
	printk( "<1>\nInstalling \'%s\' module\n", modname );

	set_fs( get_ds() );	// allow system-calls from this module

	// open the 'System.map' file
	fd = sys_open( mapfile, O_RDONLY, 0 );
	if ( fd < 0 ) return -EINVAL;

	// determine the size of the file
	filesize = sys_lseek( fd, 0, 2 );
	printk( "<1>  filename: \'%s\' \n", mapfile );
	printk( "<1>  filesize: %d bytes \n", filesize );

	// allocate enough memory for file contents
	data = (char *)vmalloc( filesize );
	if ( !data ) return -ENOMEM;
	
	// rewind, then read the entire 'System.map' file
	sys_lseek( fd, 0, 0 );
	nbytes = sys_read( fd, data, filesize );
	if ( nbytes == filesize ) sys_close( fd );
	else	{ vfree( data ); return -EFAULT; }
	
	// search line-by-line for the 'vmlist' symbol
	cp = strtok( data, "\n" );
	while ( cp < data + filesize )
		{
		if ( strstr( cp, "B vmlist" ) ) break;
		cp = strtok( NULL, "\n" );
		if ( cp == NULL ) break;
		}
	if ( !cp ) { vfree( data ); return -ESRCH; }

	// extract the kernel address of the 'vmlist' variable
	vmlistp = (struct vm_struct**)simple_strtol( cp, NULL, BASE_16 );
	vfree( data );
	printk( "<1>  address of \'vmlist\': %08X \n", vmlistp );
	
	create_proc_read_entry( modname, 0, NULL, my_proc_read, NULL );
	return	SUCCESS;
}

MODULE_LICENSE("GPL");