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[[Category:SPO600 Labs]][[Category:Assembly Language]]
{{Admon/lab|Purpose of this Lab|In this lab, you will experiment with assembler on the x86_64 and aarch64 platforms.}}
{{Admon/tip|SPO600 Servers|Perform this lab on [[SPO600 Servers]] (you may use your own x86_64 systems if they are of the right architecture and appropriately configured).}}
== Lab 5 4 ==
=== Code Examples ===
The code examples for this lab are available in the file <code>/public/spo600-assembler-lab-examples.tgz</code> on each of the [[SPO600 Servers]].
Unpacking the archive in your home directory will produce the following directory structure:
spo600
Throughout this lab, take advantage of1. Review, build, and run the x86_64 assembly language programs. Take a look at the code using <code>objdump -d '''objectfile'''</code> and compare it to the source code. Notice the absence of other code (compared to the C ''hello'' binary, which has a lot of extra code). 2. Build and run the three C versions of the program for aarch64. Verify that you can disassemble the object code in the ELF binary using <code>objdump -d '''objectfile'''</code> and take a look at the code. Take advantage of ''[[make and Makefiles|make]]'' whenever possible.
=== Resources ===
* [[Assembler Basics]](includes instructions on how to use the GNU Assembler)
* [[Syscalls]]
* [[x86_64 Register and Instruction Quick Start]]
* [[aarch64 Register and Instruction Quick Start]]
=== Group Lab Tasks Optional Investigation === 1. Build and run the three C versions of the program for x86_64 and aarch64, using <code>make</code>. Take a look at the differences in the code. 2. Use the <code>objdump -d</code> command to dump (print) the object code (machine code) and disassemble it into assembler for each of the binaries. Find the <code><nowiki><main></nowiki></code> section and take a look at the code. Also notice the total amount of code. 3. Review, build, and run the x86_64 assembly language programs using <code>make</code>, taking note of the commands that are executed to assemble and link the code. Take a look at the code using <code>objdump -d '''objectfile'''</code> and compare it to the source code. Notice the absence of other code (compared to the C binary, which had a lot of extra code).
4. Build and run the assembly language version of the program for aarch64 using <code>make</code>, taking note of the commands that are executed to assemble and link the code. Verify that you can disassemble the object code in the ELF binary using <code>objdump -d ''objectfile''</code> and take a look at the code. === Lab Tasks === <!-- {{Admon/tip|ShortcutAnswers in the Video!|To save lab time '''your group can decide''' The answers to do the first three steps 1below are contained in the associated [https://web.microsoftstream.com/video/8c3c1353-2 as individual homework after the lab5729-4217-b1ba-371410f14ad4 lecture video.]}} -->
1. Review, build, and run the aarch64 assembly language programs. Take a look at the code using <code>objdump -d '''objectfile'''</code> and compare it to the source code.
min = 0 /* starting value for the loop index; '''note that this is a symbol (constant)''', not a variable */
max = 30 10 /* loop exits when the index hits this number (loop condition is i<max) */
_start:
{{Admon/tip|Character conversion|In order to print the loop index value, you will need to convert from an integer to digit character. In ASCII/ISO-8859-1/Unicode UTF-8, the digit characters are in the range 48-57 (0x30-0x39). You will also need to assemble the message to be printed for each line - you can do this by writing the digit into the message buffer before outputting it to stdout, which is probably the best approach, or you can perform a sequence of writes for the thee parts of the message ('Loop: ', number, '\n'). You may want to refer to the manpage for <code>ascii</code>.}}
{{Admon/tip|6502 Implementation|For reference, here is a [[6502 Counting Loop Example|6502 implementation of this loop]].}}
3. Repeat the previous step for x86_64.
4. Extend the AArch64 code to loop from 00-30, printing each value as a 2-digit decimal number.
{{Admon/tip|2-Digit Conversion|You will need to take the loop index and convert it to a 2-digit decimal number by dividing by 10. To do this, use Read the description of the <code>div</code> division instruction, which takes the dividend from rax and the divisor from register supplied as an argument. The quotient will be placed in rax and the remainder will be placed in rdxcarefully.}} 5. Repeat the previous step for On x86_64. === Optional Investigation (Recommended) === 1. Build and run the three C versions of the program for x86_64 and aarch64. Take a look at the differences in the code. 2. Use the <code>objdump -d</code> command , you need to dump (print) the object code (machine code) and disassemble it into assembler for each of the binaries. Find the <code><nowiki><main></nowiki></code> section and take set up specific registers before performing a look at the codedivision. Also notice the total amount of code. 3. ReviewOn AArch64, build, and run the x86_64 assembly language programs. Take you will need to use a look at the code using <code>objdump -d '''objectfile'''</code> and compare it second instruction to find the source code. Notice the absence of other code (compared to the C binary, which had remainder after a lot of extra code). 4. Build and run the three assembly language versions of the program for aarch64. Verify that you can disassemble the object code in the ELF binary using <code>objdump -d '''objectfile'''</code> and take a look at the codedivision.}}
5. Change the code as needed to suppress the leading zero (printing 0-30 instead of 00-30).
5. Repeat the previous two steps for x86_64.
=== Deliverables ===
1. Complete the group lab section, above. 2. Extend the assembler programs (both x86_64 and aarch64) to suppress the high digit when it is 0. In other words, the printed values should progress from 0-30 instead of from 00-30. It is OK to output a space in place of the suppressed digit (this will cause the numbers to be aligned vertically in the output).
=== Optional Challenge ===
