[SOLVED] Cda 4205l lab #1: introduction to risc-v and rars

Welcome to CDA 4205L Lab #1! The purpose of this lab is to introduce you to (or refresh your memory of)
RISC-V assembly and a RISC-V Assembler and Runtime Simulator (RARS).
Prelab
RISC-V is an open-source instruction set architecture (ISA). It was initially developed by UC Berkeley, but
in the past decade, many other groups have contributed to the project, and several companies have
started deploying physical processors that use the standard. In the lecture portion of this course, we will
go over the principles of ISA design and important tradeoffs. In the lab portion of this course, we will go
over practical implementation details.
Two very important tools for any ISA are the assembler and the runtime simulator. The assembler takes
human-readable code and translates it into machine code, represented in binary or hexadecimal. The
runtime simulator is a platform for executing machine instructions and provides insight into the state of
the processor at any given time. A simulator can also provide an environment for doing things like file
reads/writes, printing text to the console, or inputting values to your program. These are called “system
calls” or “environment calls” depending on the platform, and are shortened to “syscalls” or “ecalls”.
In this lab, you will become familiar with one particular RISC-V assembler and runtime simulator called
RARS, and experiment with some important ecalls provided by the platform.
Lab
1. Download and install RARS, which can be found here: https://github.com/TheThirdOne/rars. Note
that you will need the Java runtime installed as well.
2. Download the HelloRISCV.asm code from Canvas (in Files > Labs > Lab 01 directory), and open the
file in RARS. You should see something like this:
3. Click the “Assemble” button (marked with the green arrow). From here, you will be able to run
the code to completion (the “play” button next to the “assemble” button) or, alternatively, step
through the code line by line and see values change in the memory window (the smaller “play”
button with the number 1).
4. Modify the code so that it prints your name instead of “Hello World!”. Re-assemble, and re-run
the code.
5. Observe that the provided code uses two ecalls: 4 and 10. The documentation for the ecalls is
available here: https://github.com/TheThirdOne/rars/wiki/Environment-Calls.
6. Modify the code so that, in addition to your name, it prints “This is CDA4205L Lab 1”
a. Declare a new string in the .data section of the code. This string should be “
This is
CDA4205L Lab “ (without lab number for now). You can label this string “msg2”.
b. Print this string using the appropriate ecall.
c. Refer to the ecall documentation. Find the ecall number for “PrintInt”. Use this to print
the lab number.
d. The console output should look like this (but instead of “Hello, World!” it should print
your name).
7. Instead of hard coding the lab number into the program, modify the code so that the user can
input this number at runtime.
a. First, enable the setting in RARS “Popup dialog for input syscalls (5, 6, 7, 8, 12)”. Terms
syscall and ecall are used interchangeably. If your program uses one of these syscalls, you
should get a popup at runtime where you can enter the desired value.
b. Refer again to the ecall documentation. Find the ecall number for “ReadInt”. Use this to
read the lab number from the user, then use PrintInt to print this value to the console.
T1: Take a screenshot of the RARS console output. Include this in your report.
T2: What do ecalls 4 and 10 do? What is the purpose of register a7 and a0?
T3: Take a screenshot of the RARS console output. Include this in your report.
T4: Take a screenshot of the RARS console output. Include this in your report.
In-class work – Complete at least Task 1, show it to the TA for review and submit it on Canvas before the
lab session ends. Submit your in-class work as a Word document (.docx) format.
Final-Report – Submit your report pdf with answers to all questions and screenshots. Also, submit the
final assembly file(s). Combine these in a .zip file. It is due in 1 week, before the next lab.