CS 315-01 Lecture/Lab Meeting Summary — Fall 2025

• Date: Sep 09, 2025
• Time: 08:08 AM Pacific
• Meeting ID: 886 4953 2573

Quick Recap

The session focused on: - Technical setup for RISC-V development, including software installation and VM management with QEMU and UTM. - SSH configuration for VMs and GitHub access. - Assembly language concepts: function calling conventions, arrays, pointers, control flow, and memory access. - GDB debugging techniques. - Auto-grader setup and workflow for assignments. - Upcoming lab sessions on functions.

Action Items (Next Steps)

• Gillian:
• Finalize UTM setup instructions for the RISC-V VM and resolve the driver issue.
• Greg:
• Follow up on Beagle lab machine home directories not mounting.
• Follow up on the submitted legal issue report.
• Update assembly code examples with proper type annotations.
• Students:
• Set up local RISC-V VM environments following the demonstrated steps.
• Complete Lab 3.
• Download UTM (App Store or the free download from the UTM website).
• Follow the setup instructions for the Ubuntu VM using the provided image.
• Create a user account on the VM using the CS Labs username.
• Set up SSH keys for passwordless login and GitHub access.
• Visit Greg during office hours if experiencing VM installation problems.

Detailed Summary

RISC-V Software Setup

• Overview of installing and configuring required tools across operating systems.
• Noted issues with Beagle lab machines (home directories not mounting); students encouraged to use local environments.
• Guidance provided on QEMU and UTM; a UTM link was shared on campus Wire.
• The provided Ubuntu image for UTM includes necessary tooling to simplify setup.

SSH Setup on Virtual Machines

• Demonstrated:
• Creating a new user on the VM.
• Configuring SSH keys for passwordless login and Git operations.
• Copying a public key to the VM’s authorized_keys.
• Recommended using a terminal and a window manager (e.g., UTM) for better workflow.

VM Configuration and Editor Settings

• Walkthrough of local VM setup, addressing driver configuration and editor color scheme issues.
• Encouraged consistent environment setup to avoid common tooling issues.

Assembly Language: Functions and Calling Conventions

• Reviewed the add3 function and how arguments map to registers.
• Emphasized:
• Using labels for control flow.
• Returning values in a0 (which may overwrite inputs—callers must preserve values if needed).
• Leaf functions (functions that do not call other functions) and constraints: use A and T registers, ≤ 8 arguments.

Control Structures in Assembly

• Implementing if-else and loops using branch instructions and labels.
• Accessing arrays via load word instructions (lw) from memory addresses passed as arguments.
• Encouraged practice with GDB to understand instruction flow.

Arrays and Pointers in C (for Assembly Preparation)

• Explained equivalence between array indexing and pointer arithmetic.
• Converted array access to pointer-based implementations to bridge C and assembly.
• Assigned a challenge: implement C array access with pointers, then translate to assembly.

Array Access in Assembly

• Demonstrated:
• Calculating offsets (index * element size).
• Adding base addresses and offsets.
• Loading values with lw and updating values with sw.
• Stressed:
• Use of temporary registers.
• Clear, correct code over optimization.
• Direction of data flow: lw loads from memory; sw stores to memory.

GDB Debugging Techniques

• Showed how to:
• Set breakpoints and step through code.
• Inspect registers and memory.
• Use the x command to examine memory with specific formats and lengths.
• Highlighted the utility of memory inspection for values that may not be visible in general output.

Auto-Grader Setup and Usage

• Demonstrated:
• Exporting the auto-grader profile.
• Setting paths and configuring the test repository.
• Emphasized:
• Frequent commits and pushes to GitHub.
• Beagle lab machines are expected to be restored; office hours are available for help.
• Next lab will focus on functions.