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