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; hello.asm a first program for nasm for Linux, Intel, gcc
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;
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; assemble: nasm -f elf -l hello.lst hello.asm
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; link: gcc -o hello hello.o
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; run: hello
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; output is: Hello World
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%include "config.asm"
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%ifdef FOO
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%define RETVAL HELLO
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%endif
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SECTION .data ; data section
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msg: db "Hello World",10 ; the string to print, 10=cr
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len: equ $-msg ; "$" means "here"
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; len is a value, not an address
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SECTION .text ; code section
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global main ; make label available to linker
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main: ; standard gcc entry point
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mov edx,len ; arg3, length of string to print
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mov ecx,msg ; arg2, pointer to string
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mov ebx,1 ; arg1, where to write, screen
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mov eax,4 ; write sysout command to int 80 hex
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int 0x80 ; interrupt 80 hex, call kernel
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mov ebx,RETVAL ; exit code, 0=normal
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mov eax,1 ; exit command to kernel
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int 0x80 ; interrupt 80 hex, call kernel
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