Laboratory: Computer Organization

Transcription

1 Laboratory: Computer Organization Software Engineering (International Program) International College King Mongkutś Institute of Technology Ladkrabang

2 Contents I Contents 1 Introduction to Raspberry Pi Hardware Hardware Assembly Heat Sink Assembly Raspberry Pi 3 Case Assembly Software Installation Format the MicroSD Card NOOBS Installation Preparing the Raspberry Pi Installing an Operating System on the Raspberry Pi Setting up Wi-Fi via Graphical Interface VIM Installation Some Useful Terminal Commands First Assembly Program Assembly Programming (Part 1) Secure Shell (SSH) Setup SSH for Raspberry Pi 3 Using Linux or MAC OS SSH for Raspberry Pi 3 Using Windows Creating Makefiles Rule of Makefiles A Simple Makefile (For C Language) Creating Your Own Makefile

3 CONTENTS II Assignments Assembly Programming for ARM The ARM architecture Assembler Language Arithmetic-Logic Instructions Branch Instructions Assignments Load/Store Instruction Assembly Programming (Part 2) ARM Registers General Purpose Register Register Accesses Hello World Keyboard Input Assignment Looping First Looping Current Program Status Register Conditional Programming Second Looping Assignment Barrel Shifter Assignment

4 CONTENTS III 4 Assembly Programming (Part 3) A GDB Debugger Debugging the Assembly Program Memory Storage Loading Data from Memory Address Loading Address to the Register Reading from the List in Memory Stack Pointer Programming of Stack Pointer

5 1 Introduction to Raspberry Pi 1 Date: 04/08/2016 Name: ID: Name: ID: 1 Introduction to Raspberry Pi The Raspberry Pi is a credit card-sized computer designed and manufactured in the UK with the initial intention of providing a cheap computing device for education. However, its applications grown beyond academic area. The Raspberry Pi s initial commercial release was in February Since then, the board has gone through a number of revisions with two models available; Model A and Model B. The Model A device is the cheaper and simpler of the two computers whereas the Model B is more powerful, including support for Ethernet connectivity.the Raspberry Pi 2 Model B was released in February 2015 while the recent one is the Raspberry Pi 3 Model B (using in this lab). Figure 1.1: Raspberry Pi 3 Model B The Raspberry Pi 3 Model B is the third generation Raspberry Pi. It can be used in various applications and supersedes the original Raspberry Pi Model B+ and Raspberry Pi 2 Model B. Whilst maintaining the popular board format the Raspberry Pi 3 Model B brings you a more powerful processer, 10x faster than the first generation Raspberry Pi. Additionally it adds wireless LAN Bluetooth connectivity making it the ideal solution for powerful connected designs.

6 1 Introduction to Raspberry Pi Hardware Raspberry Pi 3 s layout is shown in the following figure. Figure 1.2: Layout of Raspberry Pi 3 Model B The characterisitcs of Raspberry Pi 3 Model B concerning specifications, connectors, key benefits, and key applications are shown as in the following table.

7 1 Introduction to Raspberry Pi 3 Specifications Processor GPU Memory Operating System Broadcom BCM2837 chipset 1.2 GHz Quad-Core ARM Cortex-A b/g/h Wireless LAN and Bluetooth 4.1 (Bluetooth Classic and LE) Dual Core VideoCore IVR Multimedia Co-Processor, Provides Open GL ES 2.0, hardware-accelerated OpenVG and 1080p30 H.264 high-profile decode Capable of 1 Gpixel/s, 1.5 Gtexel/s or 24GFLOPs with texure filtering and DMA infrastructure 1 GB LPDDR2 Boots from Micro SD card, running a version of the Linux operating system or Windows 10 IoT 85 x 56 x 17 mm Dimensions Power Micro USB socket 5V1, 2.5A Connectors Ethernet 10/100 BaseT Ethernet socket Video Output HDMI (rev 1.3 & 1.4) Composite RCA (PAL and NTSC) Audio Output Audio Output 3.5 mm jack, HDMI USB 4 x USB 2.0 Connector GPIO Connector Camera Connector Display Connector Memory Card Slot Key Benefits 40-pin 2.54 mm(100 mil) expansion header: 2x20 strip Providing 27 GPIO pins as well as +3.3V, +5V and GND supply lines 15-pin MIPI Camera Serial Interface (CSI-2) Display Serial Interface (DSI) 15 way flat flex cable connector with two data lanes and a clock lane Push/Pull MicroSDIO Low cost 10x faster processing Consistent board format Added connectivity

8 1 Introduction to Raspberry Pi 4 Key Applications Low cost PC/tablet/laptop Media center Industrial/Home automation Print server Web camera Wireless access point Environmental sensing/monitoring IoT applications Robotics Server/cloud server Security monitoring Gaming 1.2 Hardware Assembly The Raspberry Pi 3 toolkit comes with various devices. Please check the following items inside the toolkit box. Figure 1.3: Layout of Raspberry Pi 3 Model B

9 1 Introduction to Raspberry Pi 5 No. Descriptions Qty. Yes/No 1 Raspberry Pi 3 Model B 1GB 1 2 Adapter Power Supply 5.1VDC 2.5A (USB Micro-B) 1 3 HDMI Cable 1 4 Breadboard 830 points 1 5 Raspberry Pi GPIO Extension Board for Rasp Pi B+/2 1 6 GPIO Ribbon Cable 40 pins for Raspberry Pi Model B+/2 1 7 Heat sink for Raspberry Pi 1 8 Scandisk MicroSD Ultra 16GB 1 9 Raspberry Pi Acrylic case (Model RPi3) x20 Extra Tall Stacking Header 1 11 Female to Female cable 40 pins 1 12 Male to Male cable 40 pins 1 13 VGA to HDMI adapter 1 Instructor s signature Heat Sink Assembly There are two sizes of heat sink which come with the toolkit. The larger one is used for the CPU whereas the other is used for the chipset for USB 2.0 hub and 10/100 ethernet controller. Follow the instruction in order to install the heat sink. 1. Get the larger heat sink 2. Peel of the paper to expose the glue underneath 3. Attach the heat sink on the CPU (position A) 4. Get the smaller heat sink 5. Peel of the paper to expose the glue underneath 6. Attach the heat sink on the USB 2.0 hub and 10/100 ethernet controller (position B) Instructor s signature

10 1 Introduction to Raspberry Pi 6 Figure 1.4: Raspberry Pi 3 with heat sinks Raspberry Pi 3 Case Assembly Raspberry Pi 3 toolkit comes with a case. The case consists of five pieces (see the following figure) 1. Assemble the Raspberry Pi 3 case as shown in the Figure Use screws to tighten them with the Raspberry Pi 3 board. 3. Install the 2x20 tall stacking header. The board should look like Figure 1.7 when finish Instructor s signature 1.3 Software Installation efore you can start installing Raspbian, the OS for Raspberry Pi, you will have to get the installer setup on a microsd card. Follow the steps below to prepare your microsd Card by formatting it, and then installing the NOOBS software. Regardless of which operating system you are using, begin with inserting the

11 1 Introduction to Raspberry Pi 7 Figure 1.5: Raspberry Pi 3 case Figure 1.6: A Raspberry Pi 3 with case microsd card to your computer. After that, you will have to begin by formatting the card. Follow along with the section below that matches your OS.

12 1 Introduction to Raspberry Pi 8 Figure 1.7: Raspberry Pi 3 case with 2x20 tall stack header Format the MicroSD Card Windows: Figure 1.8: SDCard formatting (Windows) 1. Download SDFormatter for Window from this link: Unzip it, and run Setup.exe. Follow along with the installshield Wizard to install SDFormatter

13 1 Introduction to Raspberry Pi 9 2. Open SDFormatter 3. Click Option and set FORMAT SIZE ADJUSTMENT to ON 4. Select your card from the Drive dropdown menu (if it wasn t selected automatically). CHECK and DOUBLE-CHECK that the drive letter is correct 5. Click Format, then click OK a couple times. You should get a Drive Format complete! pop up shortly. Mac OS X: 1. Download SDFormatter for Mac from the this link: 2. Open SDFormatter (it should be in your application folder) 3. Select Overwrite Format as the format option Figure 1.9: SDCard formatting (Mac OS X) 4. Select your card from the top dropdown menu (if it wasn t selected automatically). Make sure it s correct! 5. Click Format, and watch the progress bar slowly crawl across the bottom of the window. A Card Format complete! message should appear once successful.

14 1 Introduction to Raspberry Pi NOOBS Installation Windows: 1. Download Raspberry Pi s New Out of Box Software (NOOBS) from the this link: 2. Extract the ZIP folder and place the contents at the top level of your SD card. 3. Once unzipped, the directory structure should look similar to the Figure 1.10 Figure 1.10: Unzipped NOOBS file for Windows 4. Remove the microsd Card from the card reader. Mac OS X: 1. Download Raspberry Pi s New Out of Box Software (NOOBS) from the this link: 2. Extract the zip file, to a folder, by double-click the downloaded zip file 3. Locate the contents of the extracted NOOBS folder and copy all of the files of the NOOBS folder to the root SD card. The directory structure should look similar to the Figure 1.11 Remark: DO NOT copy the NOOBS folder itselft. Instead, copy the contents of the NOOBS folder to the root of the SD card.

15 1 Introduction to Raspberry Pi 11 Figure 1.11: Unzipped NOOBS file for Mac OS X 4. Once everything is complete eject the microsd card from your computer. Instructor s signature

16 1 Introduction to Raspberry Pi Preparing the Raspberry Pi 1. Connect HDMI to VGA adapter from the Raspberry Pi to a monitor. 2. Connect mouse and keyboard to USB ports. Figure 1.12: Connect HDMI to VGA adapter, mouse and keyboard to the Raspberry Pi 3. Insert microsd card into the Raspberry Pi Figure 1.13: Insert microsd card to the Raspberry Pi 4. Connect the power cable to the Raspberry Pi

17 1 Introduction to Raspberry Pi 13 Figure 1.14: Power cable connection Installing an Operating System on the Raspberry Pi 1. Check that a newly created microsd card into the Raspberry Pi and the power cable is connected 2. NOOBS will run automatically, first resizing the FAT partition and formatting the stteing partition, then launching into a graphical user interface 3. Choose to install Raspbian by clicking to place an X in the adjacent box. Then click Install 4. You will be advised and prompted when the operating system has finished installing. Click OK and the Raspberry Pi will reboot into the Raspberry Pi Software Configuration Tool (raspi-config) 5. Leave the configuration as its default 6. If you do not change the user passward, the login for your Pi will default to the username pi with the password raspberry 7. The graphical user interface will be launched. Raspbian can be started from the command line, type startx Instructor s signature

18 1 Introduction to Raspberry Pi 14 Figure 1.15: Install Raspbian Operating System Figure 1.16: Graphical User Interface of Raspbian

19 1 Introduction to Raspberry Pi Setting up Wi-Fi via Graphical Interface 1. In the Desktop environment locate the network icon in the top right hand side and click on the icon to see the list of available Wi-Fi networks to connect (see Figure 1.17) Figure 1.17: List of available Wi-Fi networks 2. Select your Wi-Fi SSID in the drop down list (see Figure 1.18) Figure 1.18: List of available Wi-Fi networks

20 1 Introduction to Raspberry Pi You will be prompted to enter the selected WI-Fi password into the text box, so go ahead and do so (see Figure 1.19) Figure 1.19: List of available Wi-Fi networks 4. Finally, click OK and you should be connected to Wi-Fi. The signal strength should be displayed on the upper task bar on the right (see Figure 1.20) Figure 1.20: List of available Wi-Fi networks 5. It is preferable to update the cache of apt-get repository. In order to do so, start the terminal and type in sudo apt-get update in the terminal

21 1 Introduction to Raspberry Pi 17 Assignments Several commands can be used for diagnostic tests in order to obtain basic information from the Raspberry Pi. The following table shows the list of these commands. No. Commands Descriptions 1 cat /proc/cpuinfo CPU information 2 cat /proc/version OS version information 3 cat /proc/meminfo Memory information 4 cat /proc/partitions microsd Card partition 5 vcgencmd measure_temp Checking the temperature 6 vcgencmd measure_volts core Checking for the core voltage 7 vcgencmd measure_volts sdram_c Checking for the SD-RAM core voltage 8 vcgencmd measure_volts sdram_i Checking for the SD-RAM I/O voltage 9 vcgencmd measure_volts sdram_p Checking for the SD-RAM PHY voltage Answer the following questions How many core(s) does your Raspberry Pi has? What is the model of the CPU of the Raspberry Pi? Give the version of the operating system.

22 1 Introduction to Raspberry Pi 18 Give the temperature of the device. Give the voltage of SD-RAM I/O. Instructor s signature

23 1 Introduction to Raspberry Pi VIM Installation 1. Start the terminal 2. Run the following command to install Vim via the package manager sudo apt-get install vim Further information for Vim can be found at this website: Some Useful Terminal Commands The following table shows some useful terminal commands. No. Descriptions Commands 1 Move file mv <source_file> <destination_file> Ex.: mv source.c destination.c mv can also be used for renaming 2 Copy file cp <source_file> <destination_file> Ex.: cp source.c destination.c 3 Change directory cd <destination> Ex.: cd /User/Admin/Document / means start from root directory./ means start from current directory../ means start from parent directory 4 List file/directory ls <parameter> Ex.: ls -a list all files and directory including hidden files/directory Ex.: ls -l list all files and directories in long format(including permission Ex.: ls -la list all files and directories with long format(including permission) including hidden files/directories 5 Create an empty File touch <file_name> Ex.: touch test.txt creat an empty file name text.txt 6 Current directory pwd Ex.: pwd Find out which directory are you in 7 Create new directory mkdir <directory_name> Ex.: mkdir /home/lab Creat a new directory Lab under the path /home 8 Interface configuration: Show config- ifconfig <parameter> uration of all interfaces. In addition, specific interface can be specified Ex.: ifconfig wlan0 show all configuration of wlan0

24 1 Introduction to Raspberry Pi 20 Assignments Create a new directory under /home/pi user as AssemblyLabs Create a new directory under /AssemblyLabs as Lab1 Create a new empty file name TestLab1.txt List to see the file(s) in the current directory Change directory back to the root Instructor s signature

25 1 Introduction to Raspberry Pi First Assembly Program 1. Create a new directory under the pi user, i.e. /home/pi/assemblylabs/lab1 2. Naavigate to such directory such that when you type in pwd command you should be on the directory /home/pi/assemblylabs/lab1 3. Create a new assembly file using vim; type in vim Lab1.s 4. In order to edit in Vim you need to change into Insert mode. This can be done by pressing key I. 5. Add the following code in exactly manner including spacing..text.global _start _start: MOV R0, #65 MOV R7, #1 SWI 0 6. Press Esc key to change into Command mode in Vim. 7. Type in :wq to save and quit program 8. In the terminal, compile the program by typing as -o Lab1.o Lab1.s 9. Make an executable file by typing ld -o Lab1 Lab1.o 10. Run the program and see the result by typing./lab1 ; echo $?

26 1 Introduction to Raspberry Pi 22 Assignment Record the result of the previous program Change to code such that the result of the program shows 100 Instructor s signature

27 2 Assembly Programming (Part 1) 23 Date: 04/08/2016 Name: ID: Name: ID: 2 Assembly Programming (Part 1) This laboratory session discusses about Secure Shell Setup and Assembly Programming. The students should be able to do the followings: Setup SSH Create makefile Assembly programming 2.1 Secure Shell (SSH) Setup Secure Shell (SSH) is a network protocol that provides adminstrators with a secure way to access a remote computer. SSH provides strong authentication and secure encripted data communications between two computers connecting over an insecure network such as internet. SSH is widely used by network administrators for managing systems and applications remotely, allowing them to log in to another computer over a network, execute commands and move files from one computer to another. In case you are using MAC OS or Linx operating system continue to otherwise proceed to SSH for Raspberry Pi 3 Using Linux or MAC OS SSH can be used to connect to the Raspberry Pi from a Linux computer or Mac (or from another Raspberry Pi) from the terminal, without installing additional software. Follow the instruction to setup SSH. 1. Open terminal in the Raspberry Pi 2. Identify your Raspberry Pi s IP address in order to connect to it by typing the following command. hostname -I

28 2 Assembly Programming (Part 1) Write down the IP address 4. Use the following command in the terminal to connect to the Raspberry Pi from a DIFFERENT computer. ssh pi@<ip> 5. In case you receive a connection timed out error, it is likely that you have entered the wrong IP address for the Raspberry Pi. 6. When the connection works, a security/authenticity warning message will appear. Type yes to continue. This warning will be shown only for the first time you connect. 7. You will be prompted for the password for the pi login: on Raspbian. The default password is raspberry 8. Show that you can access the Raspberry Pi from DIFFERENT computer SSH for Raspberry Pi 3 Using Windows 1. Open terminal in the Raspberry Pi 2. Identify your Raspberry Pi s IP address in order to connect to it by typing the following command. hostname -I 3. Write down the IP address 4. Download SSH client called PuTTY from Look for putty.exe under the heading For Windows on Intel x86 5. Run putty.exe. The configuration screen will be shown (see Figure 2.1) 6. Type the IP address of the Raspberry Pi into the Host Name field and click Open button.

29 2 Assembly Programming (Part 1) 25 Figure 2.1: PuTTY Configuration Screen 7. If nothing happens when you click the Open button, and you eventually see a message saying Network error: Connection timed out. It is likely that you have entered the wrong IP address for the Raspberry Pi 8. When the connection works you will see the security warning as shown in Figure 2.2. Figure 2.2: PuTTY Security Alert Screen 9. Click Yes button. This screen will be shown only for the first time when PuTTY connects to the Raspberry Pi that it has never seen before.

30 2 Assembly Programming (Part 1) You should have the usual login prompt. Log in with the same username and password as if you would use on the Raspberry Pi itself. 11. The default login for Raspbian is pi with the password raspberry 12. Show that you can access the Raspberry Pi from DIFFERENT computer. 13. You can type exit to close PuTTY window Instructor s signature

31 2 Assembly Programming (Part 1) Creating Makefiles A makefile is a file created to tell make command what to do. Most often, the makefile tells make how to compile and link a program Rule of Makefiles A simple makefile consits of rules with the following shape target... : prerequisites... recipe A target is usually the name of a file that is generated by a program; examples of targets are executable or object files. A target can also be the name of an action to carry out, such as clean. A prerequisite is a file that is used as input to create the target. A target often depends on several files. A recipe is an action that make carries out. A recipe may have more than one command, either on the same line or each on its own line. Note that you need to put a tab character at the beginning of every recipe line. Usually a recipe is in a rule with prerequisites and serves to create a target file if any of the prerequisites change. However, the rule that specifies a recipe for the target need not have prerequisites. A rule explains how and when to remake certain files which are the targets of the particular rule. make carries out the recipe on the prerequisites to create or update the target. A rule can also explain how and when to carry out an action A Simple Makefile (For C Language) The following makefile describes the way an executable file called edit depends on eight object files, which in turn, depend on eigh C source and three header files.

32 2 Assembly Programming (Part 1) 28 edit : main.o kbd.o command.o display.o \ insert.o search.o files.o utils.o cc -o edit main.o kbd.o command.o display.o \ insert.o search.o files.o utils.o main.o : main.c defs.h cc -c main.c kbd.o : kbd.c defs.h command.h cc -c kbd.c command.o : command.c defs.h command.h cc -c command.c display.o : display.c defs.h buffer.h cc -c display.c insert.o : insert.c defs.h buffer.h cc -c insert.c search.o : search.c defs.h buffer.h cc -c search.c files.o : files.c defs.h buffer.h command.h cc -c files.c utils.o : utils.c defs.h cc -c utils.c clean : rm edit main.o kbd.o command.o display.o \ insert.o search.o files.o utils.o Here the \ refers to newline. To use this make file to create the executable file called edit, type: make To use makefile to delete the executable file and all the objects files from the directory, type: make clean In this example makefile, the targets include the executable file edit, and the object files main.o and kbd.o. The prerequisites are files such as main.c and defs.h. In fact, each.o fils is both a target and a prerequisite. Recipes include cc -c main.c and cc -c kbd.c When a target is a file, it needs to be recompiled or relinked if any of its prerequisites change. In addition, any requisites that are themselves automatically generated should be updated first. In this example, edit depends on each of the eight object files; the object file main.odepends on the source file main.c and on the header file defs.h A recipe may follow each line that contains a target and prerequisites. These

33 2 Assembly Programming (Part 1) 29 recipes say how to update the target file. A tab character (or whatever character is specified by the.recipeprefix) variable) must come at the beginning of every line in the recipe to distinguish recipes from other lines in the makefile. Note that make does not know anything about how the recipes work. It is up to the developer to supply recipes that will update the target file properly. All make does is execute the recipe that have specified when the target file needs to be updated. The target clean is not a file, but merely the name of an action. Since you normally do not want to carry out the actions in this rule, clean is not a prerequisite of any other rule. Consequently, make never does anything with it unless you tell it specifically. Thus, the only purpose of the rule is to run the specified recipe. Targets that do not refer to files but are just actions are called phony targets Creating Your Own Makefile 1. Navigate to the directory /home/pi/assemblylabs/lab1 2. Type in pwd command and be assure that you are on the directory /home/pi/assemblylabs/lab1 3. Create a new assembly file name makefile using vim 4. Enter Insert mode and put in the code as shown in the following: Lab1: Lab1.o ld -o Lab1 Lab1.o Lab1.o: Lab1.s as -o Lab1.o Lab1.s clean: rm *.o Lab1 Remarks: DO NOT forget to hit a tab key before entering the recipes. 5. Press esc key. Save and quit by typing :wq 6. Execute the makefile by typing make. Record the result shown from the terminal screen.

34 2 Assembly Programming (Part 1) Modify the code of Lab1.s to be as follows Instructor s signature.global _start _start: MOV R0, #100 MOV R7, #1 SWI 0 8. Save and exit Lab1.s. Execute the makefile again and record the result shown from the terminal screen.

35 2 Assembly Programming (Part 1) Explain why do you get different results shown in the terminal. 10. Type./Lab1 ; echo $? and record the result. 11. Type in command ls and see the list of the file within the current directory. 12. Type in make clean. Record the result shown in the terminal screen and explain the operation of this command. Instructor s signature Assignments 1. Modify the code of Lab1.s by replacing all _start with start. Save and run the make file. Record the result shown in the termimal screen. Explain this result.

36 2 Assembly Programming (Part 1) Modify the code of makefile by replacing all ld with gcc. Save and run the make file. Record the result shown in the termimal screen. Explain this result. 3. Modify the code of Lab1.s by replacing all start with main. Save and run the make file. Record the result shown in the termimal screen. Explain this result. Instructor s signature

37 2 Assembly Programming (Part 1) Assembly Programming for ARM The ARM architecture The ARM architecture is a relatively simple implementation of a load/store architecture, i.e. an architecture where main memory (RAM) access is performed through dedicated load and store instructions, while all computation (sums,products, logical operations, etc.) is performed on values held in registers. For example, ADD R4, R1, R2 will store in register R4 the sum of the values held in R1 and R2. The ARM architecture provides 16 registers, numbered from R0 to R15, of which the last three have special hardware significance. R13, also known as SP, is the stack pointer, that is it holds the address ofthe top element of the program stack. It is used automatically in the PUSH and POP instructions to manage storage and recovery of registers in the stack. R14, also known as LR is the link register, and holds the return address, that is the address of the first instruction to be executed after returning from the current function. R15, also known as PC is the program counter, and holds the address of the next instruction Assembler Language Assembly statements are structured in the following way: label: instruction Comments can be inserted for one line case and /* */ for multiple lines case. The label is optional, that is it is possible to define instructions without a label. The label is used to refer to the instruction address in the code - in particular, this is necessary to perform branch instructions. Labels can be any sequence of alphanumeric characters. The underscore(_) and dollar ($) characters can also be used, and numeric characters (digits) cannot appear as the first character of a symbol. Instructions can be divided into three different sets: Arithmetic-Logic: This group of instructions perform mathematical operations on data. They can be arithmetic (sum, subtraction, multiplication), logic (boolean operations), or relational (comparison of two values). Branch: This group of instructions change the control flow, by modifying the

38 2 Assembly Programming (Part 1) 34 value of the Program Counter (R15). They are needed to implement conditional statements, loops, and function calls. Load/Store: This group of instructions move data to and from the main memory. Since all other operations only work with immediate constant values (encoded in the instruction itself) or with values from the registers, the load/store instructions are necessary to deal with all but the smallest data sets Arithmetic-Logic Instructions Arithmetic instructions include the following (where Rd, Rn and Rm are any three registers, and #imm are 8-bit immediates): Syntax Semantics ADD Rd, Rn, Rm/#imm Rd = Rn + Rm/#imm SUB Rd, Rn, Rm/#imm Rd = Rn - Rm/#imm MUL Rd, Rn, Rm Rd = (Rn * Rm/#imm)%2 32 (truncated at 32 bits) AND Rd, Rn, Rm/#imm Rd = Rn & Rm/#imm) (bitwise AND) EOR Rd, Rn, Rm/#imm Rd = Rn ^ Rm/#imm) (bitwise XOR) ORR Rd, Rn, Rm/#imm Rd = Rn Rm/imm) (bitwise OR) MVN Rd, Rm/#imm Rd = ~Rm/#imm) (bitwise negation) CMP Rn, Rm/#imm Status comparison (<,>,==) of Rn and Rm/#imm) MOV Rd, Rm/#imm Rd = Rm/#imm) 1. Create a new directory under the pi user, i.e. /home/pi/assemblylabs/lab2 2. Naavigate to such directory such that when you type in pwd command you should be on the directory /home/pi/assemblylabs/lab2 3. Create a new assembly file vim Lab2.s using vim 4. Enter the following code:.global _start _start: MOV R0, #0 MOV R1, #2 MOV R2, #4 ORR R0, R1, R2 MOV R7, #1

39 2 Assembly Programming (Part 1) 35 SWI 0 5. Record and explain the program output. 6. Modify the code of vim Lab2.s as follows:.global _start _start: MOV R0, #0 MOV R1, #2 MOV R2, #4 ADD R3, R1, R2 SUB R0, R3, #5 MOV R7, #1 SWI 0 7. Record and explain the program output.

40 2 Assembly Programming (Part 1) Modify the code of Lab2.s by replacing SUB R0, R3, #5 by SUB R0, R3, #9 and SUB R0, R3, R1. 9. Record and explain the program output. Instructor s signature

41 2 Assembly Programming (Part 1) Branch Instructions The basic functionality of the branch instruction is to change the Program Counter by setting it to a new value (usually a constant, but not always). The set of branch instructions includes the following: Syntax B label BEQ label BNE label BGT label BLT label BGE label BLE label BL label BX Rd Semantics Jump to label (uncondition) Jump to label if previously compared values were equal Jump to label if previously compared values were different Jump to label if previously compared Rn > Rm/#imm Jump to label if previously compared Rn < Rm/#imm Jump to label if previously compared Rn >= Rm/#imm Jump to label if previously compared Rn <= Rm/#imm Function call (label is the function name/entry point) Return from function (always as BX LR) B label is the basic branch. Control is changed to run the instruction labeled with label next. BL label perform function call, which means it jumps as in B label, but also saves the value of the Program Counter in the Link Register (as by command MOV LR PC) Return from function is performed by BX LR. It is almost the same as MOV LR PC, but PC should not be manipulated explicitly by programmer, unless there is a very good reason to do so. 1. Modify the code of Lab2.s as follows:.global _start _start: MOV R0, #0x14 B other MOV R0, #0xB other: MOV R7, #1 SWI 0

42 2 Assembly Programming (Part 1) Record and explain the program output. 3. Modify the code of Lab2.s as follows:.global _start _start: CMP R4, #0 BLE else MOV R5, #1 B end else: MOV R5, #2 end: MOV R0, R5 MOV R7, #1 SWI 0 4. Record and explain the program output.

43 2 Assembly Programming (Part 1) Suppose an extra command MOV R4, #1 is added before the line CMP R4, #0 what would be the output. Explain your answer. 6. Modify the code of Lab2.s as follows:.global _start _start: MOV R5, #1 loop: CMP R4, #0 BLE end else: MOV R5, #2 end: MOV R0, R5 BX LR 7. Record and explain the program output. Instructor s signature

44 2 Assembly Programming (Part 1) Assignments 1. Modify the code of Lab2.s such that the program outputs 10 when R3 > 2 and 20 otherwise. Write down your program below and run to show the output to the instructor. Instructor s signature

45 2 Assembly Programming (Part 1) Load/Store Instruction Load and store instructions perform data transfer from memory to registers and vice versa. The following instructions allow us to work with word and byte sized data: Syntax LDR Rd [Rn, Rm/#imm] STR Rd [Rn, Rm/#imm] LDRB Rd [Rn, Rm/#imm] STRB Rd [Rn, Rm/#imm] PUSH {register list} POP {register list} Semantics Rd = mem[rn+rm/#imm] (32 bit copy) mem[rn+rm/#imm] = Rd (32 bit copy) Rd = mem[rn+rm/#imm] (8 bit copy) mem[rn+rm/#imm] = Rd (8 bit copy) Push registers onto stack Pop registers from stack In load instructions, values are read from a certain memory address and moved to register Rd, while in store instructions Rd is the source from which data is read, and the values are stored in memory. The meomory address employed is, in both cases, computed as the sum of a base Rn and an offset (Rm or a constant.) Usually, the programmer uses this capability to access arrays of data. 1. Modify the code of Lab2.s as follows:.data.balign 4 wordvar1:.word 1.text.global main main: LDR R2, wordvar1addr LDR R0, [R2] BX LR wordvar1addr:.word wordvar1 2. Record and explain the program output.

46 2 Assembly Programming (Part 1) Modify the code of Lab2.s as follows:.data.balign 4 wordvar1:.word 1.text.global main main: MOV R1, #2 LDR R2, wordvar1addr STR R1, [R2] LDR R0, [R2] BX LR wordvar1addr:.word wordvar1 4. Record and explain the program output. Instructor s signature

47 3 Assembly Programming (Part 2) 43 Date: 01/09/2016 Name: ID: Name: ID: 3 Assembly Programming (Part 2) This laboratory session discusses about Secure Shell Setup and Assembly Programming. The students should be able to do the followings: Output to the terminal Get input from key board Loop programming Barrel shifter 3.1 ARM Registers ARM processors provide general-purpose and sepcial-purpose registers. Some additional registers are available in privileged execution mode. In all ARM processors, the following registers are available and accessible in any processor mode: 13 general-purpose registers R0-R12 One Stack Pointer (SP) One Link Register (LR) One Program Counter (PC) One Appplication Program Register (APSR) General Purpose Register There are restrictions on the use of SP and LR as general-purpose registers.

48 3 Assembly Programming (Part 2) 44 With the exception of ARMv6-M and ARMv7-M based processors, there are 30 (or 32 if Security Extensions are implemented) general-purpose 32-bit registers, that include the banked SP and LR registers. Fifteen general-purpose registers are visible at any one time, depending on the current processor mode. These are R0-R12, SP, LR. The PC (R15) is not considered a general-purpose register. SP (or R13) is the stack pointer. The C and C++ compilers always use SP as the stack pointer. Use of SP as a general purpose register is discouraged. In Thumb, SP is strictly defined as the stack pointer. The instruction descriptions mention when SP and PC can be used. In User mode, LR (or R14) is used as a link register to store the return address when a subroutine call is made. It can also be used as a general-purpose register if the return address is stored on the stack. In the exception handling modes, LR holds the return address for the exception, or a subroutine return address if subroutine calls are executed within an exception. LR can be used as a general-purpose register if the return address is stored on the stack Register Accesses 16-bit Thumb instructions can access only a limited set of registers. There are also some restrictions on the use of special-purpose registers by ARM and 32-bit Thumb instructions. Most 16-bit Thumb instructions can only access R0 to R7. Only a small number of these instructions can access R8-R12, SP, LR, and PC. Registers R0 to R7 are called Lo registers. Registers R8-R12, SP, LR, and PC are called Hi registers. All 32-bit Thumb instructions can access R0 to R12, and LR. However, apart from a few designated stack manipulation instructions, most Thumb instructions cannot use SP. Except for a few specific instructions where PC is useful, most Thumb instructions cannot use PC. In ARM state, all instructions can access R0 to R12, SP, and LR, and most instructions can also access PC (R15). However, the use of the SP in an ARM instruction, in any way that is not possible in the corresponding Thumb instruction, is deprecated. Explicit use of the PC in an ARM instruction is not usually useful, and except for specific instances that are useful, such use is deprecated. Implicit use of the PC, for example in branch instructions or load (literal) instructions, is never deprecated.

49 3 Assembly Programming (Part 2) Hello World 1. Create a new directory under the pi user, i.e. /home/pi/assemblylabs/lab3 2. Naavigate to such directory such that when you type in pwd command you should be on the directory /home/pi/assemblylabs/lab3 3. Create a new assembly file vim Lab3.s using vim 4. Create a makefile to run the program Lab3.s 5. Enter the following code:.global _start _start: MOV R7, #4 MOV R0, #1 MOV R2, #12 LDR R1, =message SWI Write to the Output to the Length of output string end: MOV R7, #1 SWI Jump to the terminal.data message:.ascii Hello World\n 6. Run the makefile 7. Type.\Lab3 and record the result

50 3 Assembly Programming (Part 2) Keyboard Input 1. Modify the code of Lab3.s as follows:.global _start _start: MOV R7, #3 MOV R0, #0 MOV R2, #10 LDR R1, =message SWI System call Input from Length of input string _write: MOV R7, #4 MOV R0, #1 MOV R2, #5 LDR R1, =message SWI 0 end: MOV R7, #1 SWI Jump to the terminal.data message:.ascii 2. Run the makefile 3. Type.\Lab3 input the string and record the result Instructor s signature

51 3 Assembly Programming (Part 2) Assignment The instruction BIC has the following syntax: BIC Rd, Rn, Operand2 The BIC(Bit Clear) instruction performs an AND operation on the bits in Rn with the complements of the corresponding bits in the value of operand2 Write an assembly program that receive a lower case character from keyboard as an input, e.g. a, and output the corresponding uppercase letter to the screen, e.g. A. Hint: Use LDR and STR to load and store the value/address to the register. Use ASCII code table to see the binary code of the character. Use BIC command in uppercase transformation Instructor s signature

52 3 Assembly Programming (Part 2) Looping Performin looping in the program is one of the important ingredient in programming. In this case, the program will perform the task until the pre-set conditions are met First Looping In general, performing looping, for example a while loop, has the following structure R0 = 0 while(r0 <= 10) R0 = R0+1 This can also be done in assembly language. The following program illustrates it. 1. Modify the code of Lab3.s as follows:.global _start _start: MOV R0, #0 MOV R1, #1 B _continue_loop _loop: ADD R0, R0, R1 _continue_loop: CMP R0, #9 BLE _loop end: MOV R7, #1 SWI 0 2. Run the makefile

53 3 Assembly Programming (Part 2) Type.\Lab3 ; echo $? and record the result 4. Explain the program and the result Instructor s signature Current Program Status Register The Current Program Status Register is a 32-bit wide register used in the ARM architecture to record various pieces of information regarding the state of the program being executed by the processor and the state of the processor. This information is recorded by setting or clearing specific bits in the register. This is shown in Figure 3.1 Condition code flags The N, Z, C, and V bits are the condition code flags. They can be by arithmetic and logical operations. They can also be set by MSR and LDM instructions. The ARM processor tests these flags to determine whether to execute an instruction.

54 3 Assembly Programming (Part 2) 50 Figure 3.1: Current Program Status Register All instructions can execute conditionally in ARM state. In Thumb state, only the Branch instruction can be executed conditionally. Control bits The bottom eight bits of a PSR are known collectively as the control bits. They are the: Interrupt disable bits T bit mode bits The control bits change when an exception occurs. When the processor is operating in a privileged mode, software can manipulate these bits. Reserved bits The remaining bits in the CPSRs are unused, but are reserved. When changing a PSR flag or control bits, make sure that these reserved bits are not altered. Also, make sure that your program does not rely on reserved bits containing specific values because future processors might have these bits set to 1 or Conditional Programming The following list show the conditional code which can be used in the program in order to make the program operates according to the desired conditions.

55 3 Assembly Programming (Part 2) 51 EQ : Z Set NE : Z Not Set CS : Carry Set CC : Carry Not Set MI : Negative Set PL : Negative Not Set VS : Overflow Set VC : Overflow Not Set HI : Carry &!Zero LS : Carry & Zero GE : Negative == Overflow LT : Negative!= Overflow GT :!Zero && Negative = Overflow LE : Zero Negative!= Overflow Second Looping Now, we would like to perform the loop as shown in the following: R0 = 50 R1 = 2 while(r0 > R1) R0 -= 2 1. Modify the code of Lab3.s as follows:.global _start _start: MOV R0, #50 MOV R1, #2 B _loop _decrement: SUBGT R0, R0, R1 _loop: CMP R0, R1 BNE _decrement

56 3 Assembly Programming (Part 2) 52 end: MOV R7, #1 SWI 0 2. Run the makefile 3. Type.\Lab3 ; echo $? and record the result 4. Explain the program and the result Instructor s signature Assignment Write assembly program which add the even number from 0 to 9 and output to the screen. Instructor s signature

57 3 Assembly Programming (Part 2) Barrel Shifter The barrel shifter is a functional unit which can be used in a number of different circumstances. It provides five types of shifts and rotates which can be applied to Operand2. (These are not operations themselves in ARM mode.) Logical Shift Left (LSL) Example of Logical Shift Left by 4 is shown in Figure 3.2. This is equivalent to << in C. Figure 3.2: Logical Shift Left Logical Shift Right (LSR) Example of Logical Shift Right by 4 is shown in Figure 3.3. This is equivalent to >> in C, i.e. unsigned division by a power of 2. Figure 3.3: Logical Shift Right Arithmetic Shift Right (ASR) Example of Arithmetic Shift Right by 4, positive valueis is shown in Figure 3.4 Figure 3.4: Arithmetic Shift Right (positive value) Example of Arithmetic Shift Right by 4, negative value is shown in Figure 3.5 This is equivalent to >> in C, i.e. signed division by a power of 2. Rotate Right (ROR) Example of Rotate Right by 4 is shown in Figure 3.6. This is a bit rotation with wrap-around.

58 3 Assembly Programming (Part 2) 54 Figure 3.5: Arithmetic Shift Right (negative value) Figure 3.6: Rotate Right Rotate Right Extended (RRX) Example of Rotate Right Extended is shown in Figure 3.7. This is a 33-bit rotation with wrap-around through carry bit. Figure 3.7: Rotate Right Extended 1. Modify the code of Lab3.s as follows:.global _start _start: MOV R1, #15 MOV R0, R1, LSL #1 end: MOV R7, #1 SWI 0 2. Run the makefile

59 3 Assembly Programming (Part 2) Type.\Lab3 ; echo $? and record the result 4. Explain the program and result. Instructor s signature Assignment Write an assembly program which accepts a number n (0-9) from keyboard. The program then calculates 4 n and output to the screen using barrel shifter command. Instructor s signature Write an assembly program whcih sets R3=5 and then divide R3 by 2. Output the result to the screen. Explain the result. Instructor s signature

60 4 Assembly Programming (Part 3) 56 Date: 08/09/2016 Name: ID: Name: ID: 4 Assembly Programming (Part 3) pointer: This laboratory session discusses about debugging, memory storage, and stack Using gdb to debug the program Load and store from/to memory Stack pointer programming 4.1 A GDB Debugger A debugger is a program that runs other programs, allowing the user to exercise control over these programs, and to examine variables when problems arise. gdb is the GNU source-level debugger that is standard on the linux systems. It can be used both for programs written in highlevel languages like C and C++ and for assembly code programs. gdb will work in an ordinary terminal window, and this is fine for debugging assembly code. Here are some useful commands. Many can be abbreviated, as shown. Hitting return generally repeats the last command, sometimes advancing the current location. Syntax Descriptions h[elp][keyword] Display help information. r[un][arg] Begin program execution. If the program normally takes command-line arguments (e.g., foo hi 3), you should specify them here (e.g., run hi 3).

61 4 Assembly Programming (Part 3) 57 Syntax b[reak][address] c[ontinue] i[nfo] b[reak] d[elete] b[reakpoints] number p[rint] [/format] expr Descriptions Set a breakpoint at the specified address (or at the current address if none specified). Addresses can be given symbolically (e.g., foo) or numerically (e.g.*0x10a38). When execution reaches a breakpoint, you are thrown back into the gdb command line interpreter Continue execution after stopping at a breakpoint Display numbered list of all breakpoints currently set Delete specified breakpoint number Print the value of an expression using the specified format (decimal if unspecified). Expressions can involve program variables or registers, which are specified using a $ rather than a % sign. Useful formats include: d decimal regis- i[nfo] r[egister] ter x hexadecimal t binary f floating point i instruction c character For example to display the value of register R1 in decimal, type p/d $R1. To see the value of the current program counter, type p/x $pc. An alternative way to print the value of a register (or, if none is specified, of all registers) in hex and decimal. Specify the register without a leading %, e.g., R4.

62 4 Assembly Programming (Part 3) 58 Syntax Descriptions x/[count][format] [address] Examine the contents of a specified memory address, or the current address if none specified. If count is specified, displays specified number of words. Addresses can be symbolic (e.g., main) or numeric (e.g., 0x10a44). Formats are as for print. Particularly useful for printing the program text, e.g., x/100i foo disassembles and prints 100 instructions starting at foo. set var = expr Set specified register or memory location to value of expression. Examples:set $g4=0x456789ab or set myvar=myvar*2. s[tep]i Execute a single instruction and then return to the command line interpreter n[ext]i Like stepi, except that if the instruction is a subroutine call, the entire subroutine is executed before control returns to the interpreter. where Show current activation stack q[uit] Exit from gdb Debugging the Assembly Program 1. Navigate to the directory /home/pi/assemblylabs 2. Create a new directory Lab4 3. Navigate to the directory /home/pi/assemblylabs/lab4 4. Type in pwd command and be assure that you are on the directory /home/pi/assemblylabs/lab4 5. Create a new assembly file name Lab4 using vim 6. Enter Insert mode and put in the code as shown in the following:.global _start _start: MOV R0, #0 MOV R1, #1

63 4 Assembly Programming (Part 3) 59 B _loop: ADD _continue_loop R0, R0, R1 _continue_loop: CMP R0, #9 BLE _loop end: MOV R7, #1 SWI 0 7. To compile the program with debug add -g option as follows as -g -o Lab4.o Lab4.s ld -o Lab4 Lab4.o gdb Lab4 8. Type list after (gdb) and record the result. 9. Type q and answer y to quit. 10. Edit you makefile such that the target debug: with the code shown in the previous step is included.

64 4 Assembly Programming (Part 3) Run the makefile by typing make debug. Record and explain the result. Instructor s signature 12. The command disassemble dumps a range of memory as machine instructions. To disassemble the code attached to the label _loop type disassemble _loop. Record the result. The first number is the location in memory for the instruction. The second part is the number of bytes from the beginning of the label or function. 13. Disassemble the code attached to the label _start. What is the starting memory location of the label _start and how many bytes are b is away from the starting memory location? Instructor s signature

65 4 Assembly Programming (Part 3) By using breakpoints, you can step through your code one line at a time and see how register and flag values change. At (gdb) type b 13. This command sets a breakpoint at line 13. (d 13 to delete the breakpoint) 15. Use list command to indicate the line no of the command CMP R0, #9 in the code. Set a break point at this particular line. 16. Type run to run the program. Observe and record the result. 17. Type info r to return the current register values. Record the values of register r0, r1, sp, pc, cpsr 18. Type c to continue running the code until next breakpoint. Record the valus of the register r0, r1, sp, pc, cpsr. Explain the changes observed from these registers.

66 4 Assembly Programming (Part 3) Type c to continue running the code AGAIN until next breakpoint. Record the valus of the register r0, r1, sp, pc, cpsr. Explain the changes observed from these registers. 20. Type q to exit the gdb. Instructor s signature 4.2 Memory Storage In the previous assembly program, we have been storing data in registers for the most part. Now we will store the data in memory. In this approach, the data is stored by referring to that data address in memory. We can store an address in a register and then use that register to load and store data. The labels we have used are addresses that refer to code, but we can also use them to refer to data.