This commit is contained in:
2025-10-10 22:16:15 -04:00
parent 33175e2c19
commit 5709c50700
3 changed files with 17 additions and 33 deletions

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@@ -1,6 +1,7 @@
.PHONY: all clean
SRC := $(wildcard *.asm)
SRC := $(filter-out functions.asm, $(SRC))
OBJDIR := build
OBJS := $(SRC:%.asm=$(OBJDIR)/%.o)
BINS := $(SRC:%.asm=$(OBJDIR)/%)

0
functions.asm Normal file
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@@ -1,39 +1,22 @@
; Hello World Program - asmtutor.com
; Compile with: nasm -f elf helloworld.asm
; Link with (64 bit systems require elf_i386 option): ld -m elf_i386 helloworld.o -o helloworld
; Run with: ./helloworld
; %include 'functions.asm'
SECTION .data
msg db 'Hello, brave new world!', 0Ah ; assign msg variable with your message string
SYS_EXIT equ 1
SYS_WRITE equ 4
STDOUT equ 1
SECTION .text
global _start
section .data
msg db "Hello, world!", 0Ah
section .text
global _start
_start:
mov eax, msg
call strlen
mov edx, eax ; our function leaves the result in EAX
mov edx, 14
mov ecx, msg
mov ebx, 1 ; STDOUT
mov eax, 4 ; SYS_WRITE
int 80h
mov ebx, STDOUT
mov eax, SYS_WRITE
int 0x80
mov ebx, 0 ; return 0
mov eax, 1 ; SYS_EXIT
int 80h
strlen:
push ebx ; preserve EBX while we use in this function
mov ebx, eax ; move the address in EAX into EBX
nextchar:
cmp byte [eax], 0 ; compare the byte pointed to by EAX at this address against zero (Zero is an end of string delimiter)
jz finished ; jump (if the zero flagged has been set) to the point in the code labeled 'finished'
inc eax ; increment the address in EAX by one byte (if the zero flagged has NOT been set)
jmp nextchar ; jump to the point in the code labeled 'nextchar'
finished:
sub eax, ebx
pop ebx
ret
mov ebx, 0
mov eax, SYS_EXIT
int 0x80