[[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).}}
== Lab 4 ==
=== Code Examples ===
{{Admon/caution|Not Updated|This page contains outdated information. It will be updated with new information The code examples for Fall 2014.}}{{Admon/lab|Purpose of this Lab|In this lab, you will experiment with assembler on are available in the x86_64 and aarch64 platforms.}}{{Admonfile <code>/public/tip|Ireland|Perform this spo600-assembler-lab on ireland.proximity-examples.tgz</code> oneach of the [[SPO600 Servers]].ca.}}
== Lab 3 ==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
=== Ireland - Configuration ===Throughout this lab, take advantage of ''[[make and Makefiles|make]]'' whenever possible.
The host ''Ireland'' === Resources ===* [[Assembler Basics]] (ireland.proximity.includes instructions on.cahow to use the GNU Assembler) has been set up so that you can use it normally as an * [[Syscalls]]* [[x86_64 host, or Register and Instruction Quick Start]]* [[SPO600 aarch64 QEMU on Ireland|use an emulation environment to build Register and run aarch64 binariesInstruction Quick Start]].
The directory <code>~/arm64/spo600/examples</code>, which is also accessible as <code>~/spo600-examples</code>, contains these files:=== Optional Investigation ===
── hello # 'hello world' example programs ├── assembler │ ├── aarch64 # aarch64 assembler version │ │ ├── hello1.s │ │ └── Makefile │ └── Build and run the three C versions of the program for x86_64 # x86_64 assembler versions │ ├── hello-gas.s # 64-bit instructions with AT&T/gnu assembler syntax (called 'gas'and aarch64, using <code>make</usr/bin/as) │ ├── hello-nasmcode>.s # 32-bit instructions with Intel/nasm assembler syntax (/usr/bin/nasm) │ └── Makefile └── c ├── hello2.c # C version using Take a look at the differences in the write() syscall wrapper ├── hellocode.c # C version using printf() └── Makefile
Throughout this lab, 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 advantage a look at the code. Also notice the total amount of ''[[make and Makefiles|make]]'' whenever possiblecode.
=== Group Lab Tasks ===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).
14. Build and run the C versions assembly language version of the program for x86_64aarch64 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.
2. Review, build, and run the x86_64 assembler programs. Make sure you understand the code.=== Lab Tasks ===
4. Build and run <!-- {{Admon/tip|Answers in the Video!|The answers to the C versions of first three steps below are contained in the program for aarch64 (noteassociated [https: you may need to <code>make clean</code>)/web.microsoftstream.com/video/8c3c1353-5729-4217-b1ba-371410f14ad4 lecture video. Verify that you can disassemble the object code in the ELF binary using <code>objdump ]}} --d</code>
51. Review, build, and run the aarch64 assembler assembly language programs. Make sure you understand Take a look at the code using <code>objdump -d '''objectfile'''</code> and compare it to the source code.
62. Here is a basic loop in x86_64 AArch64 assembler - this loops from 0 to 9, using r15 r19 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 $startx19,%r15 /* loop index */min
loop:
/* ... do something useful here ... */
inc %r15 /* increment index '''... body of the loop ... do something useful here ...''' */ add x19, x19, 1 cmp $x19, max,%r15 /* see if we're done */ jne loop /* b.ne loop if we're not */
mov $x0, 0,%rdi /* exit status -> 0 */ mov $60x8,%rax 93 /* exit is syscall sys_exit #93 */ svc 0 /* invoke syscall*/ This code doesn't actually do anything while looping, because the body of the 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: Loop Loop Loop Loop Loop Loop Loop Loop Loop Loop
Extend this code, combining it with code from Then modify the "Hello World" example, message so that it prints includes the loop index values, showing each digit from 0 to 9 like this:
Loop: 0
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-99598859-1/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. For reference, here is the loop code in x86_64 assembler:
7 . Repeat step 6 text .globl _start min = 0 /* starting value for aarch64the 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 $min,%r15 /* loop index */ loop: /* '''... body of the loop ... do something useful here ...''' */ inc %r15 /* increment index */ cmp $max,%r15 /* see if we're done */ jne loop /* loop if we're not */ mov $0,%rdi /* exit status */ mov $60,%rax /* syscall sys_exit */ syscall 4. Extend the AArch64 code to loop from 00-30, printing each value as a 2-digit decimal number.
8. Extend {{Admon/tip|2-Digit Conversion|You will need to take the code loop index and convert it to loop from 00-30, printing each value as a 2-digit decimal numberby dividing by 10. Read 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.}}
{{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 105. To do this, use Change the <code>div</code> instruction, which takes the dividend from rax and the divisor from register supplied as an argument. The quotient will be placed in rax and needed to suppress the remainder will be placed in rdxleading zero (printing 0-30 instead of 00-30).}}
95. Repeat step 8 the previous two steps for aarch64x86_64.
=== Deliverables ===
1. Complete the group lab section, above.
2. Extend Blog about the programs you've written. Describe the experience of writing and debugging in assembler programs (both , as compared to writing in other languages. Contrast x86_64 and aarch64) to suppress the high digit when it is 0. In other wordsassembler, your experience with each, the printed values should progress from 0-30 instead and your opinions of from 00-30each. It is OK Include links to output a space in place the source code for each of the suppressed digit (this will cause the numbers to be aligned vertically in the printout)your assembler programs.
3. Blog about the programs 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, your experience with each, and your opinions of each. Include links to the source code for both of your assembler programs.=== Optional Challenge ===
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. The output could look something like this: 1 x 1 = 1 2 x 1 = 2 3 x 1 = 3 4 x 1 = 4 5 x 1 = 5 6 x 1 = 6 7 x 1 = 7 8 x 1 = 8 9 x 1 = 9 10 x 1 = 10 11 x 1 = 11 12 x 1 = 12 ------------- 1 x 2 = 2 2 x 2 = 4 3 x 2 = References 6 4 x 2 = 8 5 x 2 = 10 ''' ''...lines snipped for space...'' ''' 11 x 12 =132* [[Assembler Basics]] -------------** [[x86_64 Register and Instruction Quick Start]] 1 x 12 = 12 2 x 12 = 24 3 x 12 = 36 4 x 12 = 48 5 x 12 = 60 6 x 12 = 72 7 x 12 = 84 8 x 12 = 96 9 x 12 = 108 10 x 12 = 120 11 x 12 = 132** [[aarch64 Register and Instruction Quick Start]] 12 x 12 = 144