Worksheet 4

Learning Goals

Sept. 24 Quiz will check:

• I understand the difference between static and shared library, the advantage and disadvtange of each approach, and in which scenario they are used. (Linking)
• I understand the role of CPU modes (user vs. kernel) and why only trusted code can run in kernel mode.
• I understand the purpose of system calls
• I understand what an address space is: stack, heap, code. (Address Space)
• I understand the step-by-step process of a system call (saving registers, trapping to the kernel, switching to the kernel stack, validating arguments, running kernel functions, and returning to user mode). And how system call is different from function call
• I understand what CPU exceptions are (trap, interrupt, fault, abort)
• I understand why context switching is necessary for CPU time sharing
• I understand the difference between fast and slow system calls
• I understand how vDSO can bypass mode switching to improve performance.
• I understand the importance of input validation for platform providers and error checking for platform users in system programming.
• I understand why running as root is dangerous if privileges are not dropped and how this leads to privilege escalation vulnerabilities. (Path Traversal)
• I understand the Principle of Least Privilege and how dropping privileges prevents unintended access to protected files. (Path Traversal)