[[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 systems if they are of the right architecture and appropriately configured).}}
{{Admon/lab|Purpose of this == Lab|In this lab, you will experiment with assembler on the x86_64 and aarch64 platforms.}}4 =={{Admon/tip|Australia and Red|Perform this lab on <code>australia.proximity.on.ca</code> (for x86_64) and red (for aarch64, accessed via port 2222 on <code>iraq.proximity.on.ca</code>).}}=== Code Examples ===
== Lab 3 ==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 └── examples └── hello # "hello world" example programs ├── assembler │ ├── aarch64 # aarch64 gas assembly language version │ │ ├── hello.s │ │ └── Makefile │ ├── Makefile │ └── x86_64 # x86_64 assembly language versions │ ├── hello-gas.s # ... gas syntax │ ├── hello-nasm.s # ... nasm syntax │ └── Makefile └── c # Portable C versions ├── hello2.c # ... using write() ├── hello3.c # ... using syscall() ├── hello.c # ... using printf() └── Makefile
### THIS COMMENTED-OUT SECTION DESCRIBES THE ### CONFIGURATION USED FOR THE WINTER 2014 ### OFFERING OF THE SPO600 COURSEThroughout this lab, WHERE THE### AARCH64 WORK WAS DONE IN EMULATION ALONGSIDE### THE X86_64 WORK ON THE INTEL HOST "IRELAND".### IN FALL 2014, AARCH64 HARDWARE WAS AVAILABLE,### AND IRELAND HAD FAILED, SO WE SWITCHED TO### THOSE HOSTStake advantage of ''[[make and Makefiles|make]]'' whenever possible.
=== Ireland - Configuration 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]]
The host ''Ireland'' (ireland.proximity.on.ca) has been set up so that you can use it normally as an x86_64 host, or [[SPO600 aarch64 QEMU on Ireland|use an emulation environment to build and run aarch64 binaries]].=== Optional Investigation ===
The directory 1. Build and run the three C versions of the program for x86_64 and aarch64, using <code>~/arm64/spo600/examplesmake</code>, which is also accessible as <. Take a look at the differences in the code>~/spo600-examples</code>, contains these files:.
── hello # 'hello world' example programs ├── assembler │ ├── aarch64 # aarch64 assembler version │ │ ├── hello2.s │ │ └── Makefile │ └── x86_64 # x86_64 assembler versions │ ├── helloUse the <code>objdump -gas.s # 64-bit instructions with AT&Td</gnu assembler syntax code> command to dump (print) the object code (called 'gas', /usr/bin/asmachine code) │ ├── hello-nasmand disassemble it into assembler for each of the binaries.s # 32-bit instructions with IntelFind the <code><nowiki><main></nasm assembler syntax (nowiki></usr/bin/nasm) │ └── Makefile └── c ├── hello2code> section and take a look at the code.c # C version using Also notice the write() syscall wrapper ├── hellototal amount of code.c # C version using printf() └── Makefile
Throughout this lab3. Review, take advantage 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'[[make and Makefiles|make]]'' whenever possible</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.
=== Code Examples Lab Tasks ===
<!-- {{Admon/tip|Answers in the Video!|The code examples for this lab answers to the first three steps below are available at this link: httpcontained in the associated [https://englandweb.proximitymicrosoftstream.on.cacom/spo600video/spo6008c3c1353-lab35729-examples4217-b1ba-371410f14ad4 lecture video.tgz]}} -->
Please download this archive to your accounts on Australia and Red1. Review, build, and unpack run the archive on both systemsaarch64 assembly language programs. Do all of the work for Take a look at the x86_64 architecture on Australia, code using <code>objdump -d '''objectfile'''</code> and all of compare it to the work on the aarch64 architecture on Redsource code.
Unpacking the archive 2. Here is a basic loop in your home directory will produce AArch64 assembler - this loops from 0 to 9, using r19 as the following directory structureindex (loop control) counter:
spo600.text .globl _start min = 0 /* starting value for the loop index; '''note that this is a symbol (constant)''', not a variable */ max = 10 /* loop exits when the index hits this number (loop condition is i<max) */ `-- examples `-- hello # "hello world" example programs _start: |-- assembler | |-- aarch64 # aarch64 gas assembly language version mov x19, min | | |-- hello.s | | `-- Makefile loop: | `-- x86_64 # x86_64 assembly language versions | |-- hello-gas /* '''...s # body of the loop ... gas syntax | |-- hello-nasmdo something useful here .s # ..''' */ add x19, x19, 1 cmp x19, max b. nasm syntaxne loop | `-- Makefile ` mov x0, 0 /* status -- c # Portable C versions> 0 */ |-- hello2.c mov x8, 93 # /* exit is syscall wrapper version |-- hello.c # printf version93 */ `-- Makefile svc 0 /* invoke syscall */
Throughout this labThis code doesn't actually do anything while looping, take advantage because the body of ''[[make and Makefiles|make]]'' whenever possiblethe loop is empty.On an AArch64 machine, combine this code with code from the "Hello World" assembley-language example, so that it prints a word each time it loops:
=== References === Loop* [[Assembler Basics]] Loop** [[x86_64 Register and Instruction Quick Start]] Loop** [[aarch64 Register and Instruction Quick Start]] Loop Loop Loop Loop Loop Loop Loop
=== Group Lab Tasks ===Then modify the message so that it includes the loop index values, showing each digit from 0 to 9 like this:
Loop: 0 Loop: 1. Build and run the C versions of the program for x86_64. Loop: 2 Loop: 3 Loop: 4 Loop: 5 Loop: 6 Loop: 7 Loop: 8 Loop: 9
2{{Admon/tip|Character conversion|In order to print the loop index value, you will need to convert from an integer to digit character. ReviewIn 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, buildwhich is probably the best approach, and run or you can perform a sequence of writes for the x86_64 assembler programsthee parts of the message ('Loop: ', number, '\n'). Make sure you understand You may want to refer to the manpage for <code>ascii</code>.}}
4. Build and run the C versions {{Admon/tip|6502 Implementation|For reference, here is a [[6502 Counting Loop Example|6502 implementation of the program for aarch64this loop]]. Verify that you can disassemble the object code in the ELF binary using <code>objdump -d</code>}}
53. Review, build, and run Repeat the aarch64 assembler programs. Make sure you understand the codeprevious step for x86_64.
6. Here For reference, here is a basic the loop code in x86_64 assembler - this loops from 0 to 9, using r15 as the index (loop control) counter:
.text
.globl _start
start min = 0 /* starting value for the loop index ; '''note that this is a symbol (constant)''', not a variable */
max = 10 /* loop exits when the index hits this number (loop condition is i<max) */
_start:
mov $startmin,%r15 /* loop index */
loop:
/* '''... body of the loop ... do something useful here ... ''' */
inc %r15 /* increment index */
syscall
4. Extend this code, combining it with the AArch64 code from the "Hello World" example, so that it prints each digit from 0 to 9 like this: Loop: 0 Loop: 1 Loop: 2 Loop: 3 Loop: 4 Loop: 5 Loop: 6 Loop: 7 Loop: 8 Loop: 9 {{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-9959-1/Unicode UTF00-830, the digit characters are in the range 48-57 (0x30-0x39). You will also need to assemble the message to be printed for printing each line value as a 2- you can do this by writing the digit into the message buffer before outputting it to stdout, or you can perform a sequence of writes for the thee parts of the message ('Loop: ', decimal number, '\n').}}
7{{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. Repeat step 6 for aarch64Read the description of the division instruction carefully.On x86_64, you need to set up specific registers before performing a division. On AArch64, you will need to use a second instruction to find the remainder after a division.}}
85. Extend Change the code as needed to loop from suppress the leading zero (printing 0-30 instead of 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 the <code>div</code> instruction, which takes the dividend from rax and the divisor from register supplied as an argument5. The quotient will be placed in rax and Repeat the remainder will be placed in rdxprevious two steps for x86_64.}}
9. Repeat step 8 for aarch64.=== Deliverables ===
=== Deliverables ===1. Complete the lab section, above.
12. Complete Blog about the group lab sectionprograms you've written. Describe the experience of writing and debugging in assembler, as compared to writing in other languages. Contrast x86_64 and aarch64 assembler, aboveyour experience with each, and your opinions of each. Include links to the source code for each of your assembler programs.
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 ===
3. Blog about the programs you've written. Describe the experience of writing and debugging Write a program in assembler, as compared aarch64 assembly language to writing in other languagesprint the times tables from 1-12 ("1 x 1 = 1" through "12 x 12 = 144"). Contrast x86_64 and aarch64 assembler, your experience with Add a spacer between eachtable, and your opinions of each. Include links use a function/subroutine to format the source code for both of your assembler programsnumbers with leading-zero suppression.
=== Optional Challenge ===The output could look something like this:
Write a program in aarch64 assembly language to print the times tables from 1-12 ("1 x 1 = 1' through '12 x 12 = 144'). Add a spacer between each table, and use a function/subroutine to format the numbers with leading-zero suppression.
1 x 1 = 1
2 x 1 = 2