CSE 120 -- Homework #1
- Chapter 2, Section 2.6: 1, 3, 11
- Chapter 3, Section 3.15: 1, 3, 14, 16, 31
- Which of the following instructions are privileged?
- Set value of timer
- Read the clock
- Clear memory
- Turn off interrupts
- Switch from user to kernel mode
- Protecting the operating system is crucial to ensuring that the
computer system operates correctly. Provision of this protection is
the reason behind user/kernel operation, memory protection, and the
timer. To allow maximum flexibility, however, we would also like to
place minimal constraints on the user. The following is a list of
operations that are normally protected. What is the minimal set
of instructions that must be protected?
- Change to user mode.
- Change to kernel mode.
- Read from kernel memory.
- Write into kernel memory.
- Fetch an instruction from kernel memory.
- Turn on timer interrupt.
- Turn off timer interrupt.