Lab 3

 

Lab 3

Getting Started: Unpacking the Examples

To begin, I unpacked the provided example files on the SPO600 servers:

cd ~
tar xvf /public/spo600-assembler-lab-examples.tgz

This produced the following directory structure:

spo600
└── examples
    └── hello
        ├── assembler
        │   ├── aarch64
        │   │   ├── hello.s
        │   │   └── Makefile
        │   ├── Makefile
        │   └── x86_64
        │       ├── hello-gas.s
        │       ├── hello-nasm.s
        │       └── Makefile
        └── c
            ├── hello2.c
            ├── hello3.c
            ├── hello.c
            └── Makefile


I first built and ran the C versions of the "Hello World" program:
cd ~/spo600/examples/hello/c
make
./hello
./hello2
./hello3

Next, I used objdump to disassemble the binaries and inspect the <main> section:
objdump -d hello
objdump -d hello2
objdump -d hello3

I navigated to the x86_64 directory to review and build the assembly language programs:
cd ~/spo600/examples/hello/assembler/x86_64
make
./hello-gas
./hello-nasm
Disassembling the object code:
objdump -d hello-gas
objdump -d hello-nasm
This showed a more concise code compared to the C binaries, with fewer additional instructions.
Building and Running
Similarly, I built and ran the AArch64 assembly language program:
cd ~/spo600/examples/hello/assembler/aarch64
make
./hello
Disassembling the object code:
objdump -d hello


.text
.globl _start
min = 0
max = 10

_start:
    mov     x19, min
loop:
    ldr     x0, =msg
    bl      puts

    add     x19, x19, 1
    cmp     x19, max
    b.ne    loop

    mov     x0, 0
    mov     x8, 93
    svc     0

msg:
    .asciz  "Loop"


.text
.globl _start
min = 0
max = 10

_start:
    mov     x19, min
loop:
    add     x0, x19, '0'
    bl      putchar

    mov     x0, '\n'
    bl      putchar

    add     x19, x19, 1
    cmp     x19, max
    b.ne    loop

    mov     x0, 0
    mov     x8, 93
    svc     0

putchar:
    mov     x8, 64
    svc     0
    ret



Optional Challenge 

.text
.globl _start

_start:
    mov x20, 1       /* Multiplier */
    mov x21, 1       /* Multiplicand */

table:
    mov x0, x20
    bl print_number
    mov x0, ' x '
    bl print_string
    mov x0, x21
    bl print_number
    mov x0, ' = '
    bl print_string
    mul x0, x20, x21
    bl print_number
    mov x0, '\n'
    bl putchar

    add x21, x21, 1
    cmp x21, 13
    b.eq next_table
    b table

next_table:
    mov x21, 1
    add x20, x20, 1
    cmp x20, 13
    b.ne table

    /* Exit */
    mov x0, 0
    mov x8, 93
    svc 0

print_number:
    ret

print_string:
    ret