Changes

{{Admon/tip|Australia and RedSPO600 Servers|Perform this lab on [[SPO600_Servers#AArch64:_Australia|AustraliaSPO600 Servers]] or (you may use your own x86_64 system (for x86_64) and on [[SPO600_Servers#if desired, along with the AArch64:_Red|Red]] (for Aarch64server).}}

The code examples for this lab are available at this link: http://england.proximity.on.cain the file <code>/spo600public/spo600-lab5assembler-lab-examples.tgz Please download this archive to your accounts </code> on the x86_64 and Aarch64 systems, and unpack the archive on both systems[[SPO600 Servers]].

|-- hello2.c # write() version |-- hello3.c # syscall () wrapper version |-- hello.c # printf () version

=== References Resources ===

*[[Syscalls]]* [[x86_64 Register and Instruction Quick Start]]** [[aarch64 Register and Instruction Quick Start]]

{{Admon/tip|Shortcut|To save lab time '''your group can decide''' to do steps 1-4 as individual homework after the lab.}} 1. Build and run the two three C versions of the program for x86_64. Take a look at the differences in the code.

2. Review, build, 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 run take a look at the x86_64 assembly language programscode. Make sure you understand Notice the total amount of code.

43. Build Review, build, and run the C versions of the program for aarch64x86_64 assembly language programs. Verify that you can disassemble Take a look at the object code in the ELF binary 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).

54. Review, build, Build and run the three C versions of the program for aarch64 assembly language programs. Make sure Verify that you understand can disassemble the object code in the ELF binary using <code>objdump -d '''objectfile'''</code> and take a look at the code.

5. 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. 6. 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:

.globl _start

start min = 0 /* starting value for the loop index ; '''note that this is a symbol (constant)''', not a variable */ max = 10 30 /* loop exits when the index hits this number (loop condition is i<max) */

mov $startx19,%r15 /* loop index */min

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:

{{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>.}} 7. Repeat step 6 for x86_64.

7For reference, here is the loop code in x86_64 assembler:  . 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

8. Extend the AArch64 code to loop from 00-30, printing each value as a 2-digit decimal number.

9. Repeat step 8 for aarch64x86_64.