Enforcing Modularity

1
Enforcing Modularity

• Junehwa Song
• CS
• KAIST

2
How to run multiple modules?
X server
Emacs
Mail Reader
File Server
3
Can multiple Modules share MM?

• Partition MM space?
• Intentional/unintentional intrusion
• LOAD
• STORE

Emacs
Mail



X server
4
Then, What Can We Do???
Address
Main Memory
PROCESSOR
Read/Write
Data
Virtual Address
Physical Address
Main Memory
Virtual Address Manager
PROCESSOR
Read/Write
Read/Write
Data
5
Address Translation

• Page Map (Page Table)
• Virtual Address Space
• Segmentation
• int PageTablesize
• int translate(int virtual)

6
Address Translation
Virtual address
Page
Byte Offset
Block
Page Map (Page Table)
Block
Byte Offset
BTW, where do you want to put Page Map?
Physical address
7
Can multiple Modules share MM?
0
Page 10 (VM1)
Physical Address
100
Virtual Address
Page 10 (VM1)
Page
Offset
Block
Offset
Virtual Address Manager
Page 12 (VM2)
PROCESSOR
200
Read/Write
Read/Write
Unused block
300
300
10
100
Data
Page Map of VM1
Page Map Address Register
11
400
12
0
400
Page 11 (VM1)
Thus, a Page Map defines an address space
500
Page Map of VM2
12
100
13
800
8
What do we further need to do?

• Create/Delete an address space
• Grow an address space
• Map a device to an address space
• Switch an address space to another

9
Q/A

• Isnt it too slow doing address translation?
• MMU
• TLB
• Do we want to see the details of a PageMap?