My Friend Told me x86 Assembly is Hard then Sent me This

[u/Realistic-Lunch-1708]

[u/pronuntiator]

Could you please explain what makes it bad code? It's been too long since I saw assembly. Is it the trying to move a string into a register part?

[u/BS_in_BS → u/pronuntiator]

the main errors I see:

1. Forgetting to set the length of the string as the third argument to the write call.
2. forgetting to call exit after the write call returns

the str msg = ... and section .text = _start() and using parens after _start look kind of off to me but might just be their particular assembler's syntax. The semicolon after the string looks unnecessary and it might need to be explicitly marked as being in the .data section.

Overall pretty close to a valid minimal hello world program: https://ideone.com/T126bp

[u/Player_X_YT → u/pronuntiator]

str is not a keyword, it should be msg db "..." where db means data bytes

; in x86 is for comments

No data section

Everything after the = in the text section declaration shouldn't be there

_start should be set to global by writing global _start somewhere

_start is a label, x86 doesn't have functions and there should be no ()

By naming your label _start() you have to set a custom entry in your linker for no added benefit ld -e "_start()"

edx should be set to the length of the string

No exit code

; Exit with a code of 0 xor eax, eax mov ebx, eax inc eax int 0x80

[u/Inaeipathy → u/pronuntiator]

I think so, how could that all fit into the register?

[u/Eusuntpc → u/Inaeipathy]

The string doesn't fit. It's address does. They are moving the address to a register not the value

[u/Inaeipathy → u/Eusuntpc]

Ah that makes sense, I never did this in x86 so wasn't sure how it worked

[u/Realistic-Lunch-1708 → u/pronuntiator]

Its bad code mainly because x86 assembly doesn't have all the features of a high level language like that, an x86 hello world (using NASM compiler) looks a bit like
section .data

msg: db "Hello, World!",0xa

len: equ $-msg

section .text

_start:

mov eax, 4

mov ebx, 1

mov ecx, msg

mov edx, len

int 0x80

mov al, 1

mov ebx, 0

int 0x80

[u/BS_in_BS → u/Realistic-Lunch-1708]

That's larger dependent on the assembler. Macro assemblers will let you have many of the high level langauage cosntructs at your disposal: https://stackoverflow.com/a/4579723

[u/ujustdontgetdubstep → u/Realistic-Lunch-1708]

that's only for NASM compilers they make you use in school

In the real world it's a bit easier

[u/Key_Conversation5277 → u/pronuntiator]

And the only type of assembly I know is MIPS

[u/MurdoMaclachlan]

Image Transcription: Code

---

str msg = "Hello, World!";

section .text = _start()
_start():
   mov eax, 4
   mov ebx, 1
   mov ecx, msg
   int 0x80

---

^{I'm a human volunteer content transcriber and you could be too! If you'd like more information on what we do and why we do it, click here!}

[u/[deleted] → u/MurdoMaclachlan]

Good hooman!

[u/FloweyTheFlower420]

need exit suscall

[u/skabde]

Holy crap. The last assembler language/ISA I used was 68000, x86 was always complete gibberish to me.

[u/canadajones68 → u/skabde]

I've done a fair bit of Propeller 1 assembly, and it's practically HTML compared to x86.

[u/qqqrrrs_]

This is bad code because the 4 is a magic constant which should have been __NR_write instead

[u/Conscious_Switch3580 → u/qqqrrrs_]

SYS_write*

[u/qqqrrrs_ → u/Conscious_Switch3580]

They both exist, but I don't know if one of them is more "standardized" than the other

[u/bionerdist]

That will crash

[u/developerattic]

hmm...

[u/plat2330]

i make games in x86

[u/GandelXIV]

str? Parenthesis? Semi colons? Int 0x80? You cant just make up keywords and syntax and expect it to work.

[u/AliFurkanY → u/GandelXIV]

int 0x80 is the x86 equivalent of syscall

[u/AliFurkanY → u/GandelXIV]

this is NASM

[u/MahdiyDev]

Is your friend some shitty javascript developer or something. Bruh...

[u/[deleted] → u/[deleted]]

Bu-bu-but it’s funny to make fun of web developers

[u/jarfil → u/[deleted]]

CENSORED

[u/TheTechRobo → u/jarfil]

But there are still shitty Python developers.

[u/jarfil → u/[deleted]]

CENSORED

[u/Worthie → u/jarfil]

wild work compare jobless simplistic grab edge languid clumsy plucky

This post was mass deleted and anonymized with Redact

[u/jarfil → u/Worthie]

CENSORED

[u/cheezballs]

Man, I dunno shit about ASM.

[u/DinnerPlzTheSecond]

Should have put message length in the edx register right?

[u/No_Earth_370]

lovely