CS 635

PROJECT 5		                Due Date: Noon Friday 05/09/2003

     The purpose of this project is to construct a tool for studying the
mapping of virtual memory areas and to acquaint students with details of
of the processor's paging mechanism for virtual address translations.


                        PROJECT STATEMENT

     Write an enhanced version of the 'vma.c' module (named 'vmaplus.c')
that will display the physical address to which each virtual memory area
has been mapped, together with that virtual memory area's size expressed
as a hexadecimal number of bytes.  Use the 'mmstudy1.cpp' program (found
on our class website) to test your enhanced module:

-----------------------------  SAMPLE OUTPUT  -----------------------------

List of the Virtual Memory Areas for task 'mmstudy1' (pid=882)

  1  vm_start=08048000  vm_end=08049000  r-xp  base=1D2FA000  size=00001000 
  2  vm_start=08049000  vm_end=0804A000  rw-p  base=1CDDA000  size=00001000 
  3  vm_start=0804A000  vm_end=0804B000  rwxp  base=00000000  size=00001000 
  4  vm_start=40000000  vm_end=40012000  r-xp  base=1FC87000  size=00012000 
  5  vm_start=40012000  vm_end=40013000  rw-p  base=1D2EA000  size=00001000 
				...........
---------------------------------------------------------------------------

                                METHODOLOGY

     Linux provides several kernel functions to help systems programmers 
manipulate the paging structures in a manner which is independent of the 
particular underlying cpu architecture:

	struct mm_struct	*mmp = vma->vm_mm;
	pgd_t	*pgd = pgd_offset( mmp, virt_address );
	pmd_t	*pmd = pmd_offset( pgd, virt_address );
	pte_t	*pte = pte_offset( pmd, virt_address );
	unsigned long	page_base = pte->pte_low & PAGE_MASK;
	unsigned long	page_part = virt_address % PAGE_SIZE;
	unsigned long	phys_address = page_base + page_part;

Alternatively, you may write your own code that directly manipulates the
Pentium progessor's Page Directory and Page Tables (which is instructive
as an exercise in itself, to clarify the operation of these structures).

	struct mm_struct	*mmp = vma->vm_mm;
	unsigned long		*dir = (unsigned long*)mmp->pgd;
	unsigned long		dir_index = virt_address >> 22;
	unsigned long		*tbl = dir[ dir_index ] & PAGE_MASK;
	unsigned long		tbl_index = virt_address >> 12;
	unsigned long		*frm = tbl[ dir_index ] & PAGE_MASK;
	unsigned long		page_base = (unsigned long)frm;
	unsigned long		page_part = virt_address % PAGE_SIZE;
	unsigned long		phys_address = page_base + page_part;

________________________________________________________________________
(C) Allan B. Cruse        University of San Francisco        Spring 2003