Enforcing Modularity

Client / Servicemodule per computer

module per Virtual computer

Kernel Virtual processor

Virtualmemory

Why VM:

-A can overwrite B’s memory

Mem

Mod A

Mod B

ST R1,B μProc.code

data

Virtual Memory

code

code code

code

Disk

AddressSpace

VA

VA VM Physical Addr

Memory

Simplified VM Hardware

LD VA, R1

pmar

VM(MMU)

μProc.

Mem VA

VA PA

PA

“page map address reg”

20 bit 12 bit 212= 4096 words 32 bit VA Page # Offset

4096bytes

Page

Page

Mem PA

Supervisory Module -Kernel

Kernel AS

pmar

μProc.

user / kernel

only kernel can change PMAR

maps

Supervisor Call -SVC

SVC gate malloc

Set U / K KSet PMAR to kernel mapSave PCPC addr gate

Kernel –Trusted intermediary

producer(put)

Consumer(get)

ES IPC Net Graphics

Graphics

AS A AS B

Lib 1 Lib 1,2

Code A

Memory

Code 1

Code B

Code 2