Information Technology Reference
In-Depth Information
executable
image
instructions
and
data
compiler
edits
source
code
Operating System
Copy
machine
instructions
machine
instructions
Data
Heap Stack
Data
Heap Stack
Operating System Kernel
Process
Physical Memory
Figure2.2: A user edits, compiles, and runs a user program. Other programs
can also be stored in physical memory, including the operating system itself.
times completely untrusted.
Protection raises several important questions which we will answer in the
rest of the chapter:
The process abstraction. What is a process and how does it differ from
a program?
Dual-mode operation. How does the operating system implement pro-
cesses? What hardware is needed for ecient restricted execution?
Safe control transfer: exceptions, interrupts, and system calls.
How do we switch safely across the boundary between processes at user-
level and the kernel?
Booting the kernel. What steps are needed to start running an oper-
ating system kernel, up to the point where it can create a process?
