From owner-freebsd-questions  Wed Dec  1 11: 4: 0 1999
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Date: Wed, 1 Dec 1999 17:02:45 -0200 (EDT)
From: Carlos Antonio Ruggiero <toto@if.sc.usp.br>
Message-Id: <199912011902.RAA09268@ultra3000.if.sc.usp.br>
To: freebsd-questions@freebsd.org, sarig@bezeqint.net
Subject: Re: Hello World in Assembler
Sender: owner-freebsd-questions@FreeBSD.ORG
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>>    I am trying to write a "hello world" program in assembler, but
can't get
>> it right. The code is (based on The Assembly HOW-TO)
>>
>> section .data
>>
>> msg db "Hello World!"
>> len equ $ - msg
>>
>> section .text
>>
>> global _start
>>
>> _start:
>>
>> mov eax,4
>> mov ebx,1
>> mov ecx,msg
>> mov edx,len
>> int 0x80
>>
>> mov eax,1
>> xor ebx,ebx
>> int 0x80

>Ahem, wouldn't this be simpler?
>
>section .data
>msg db "Hello, World!"
>section .text
>global _start
>_start:
>push word msg
>call printf
>
>and build with:
>nasm -f elf -o hello.o hello.asm
>ld -lc -o hello hello.o
>
> (I didn't try this, but I think it should work)

>--
>Oren Sarig
>sarig@bezeqint.net

	You see, this is the point! I want to use freebsd for assembly
language classes and would like to avoid C as much as possible. You
are right that a code like yours should work. This one is fine:


section	.data
msg	db "Hello World",0x0A
len	equ	$ - msg
	
section	.text
	extern	write

	global	main
	
main:	push	ebp
	mov	ebp,esp
	push	long len
	push	long msg
	push	long 1
	call    write
	add	esp, 12
	leave
	ret

And if you compile and run...

toto@atm3:ttyp1 ~/cursos (156)> nasm -f elf -o hello.o hello.asm
toto@atm3:ttyp1 ~/cursos (157)> gcc -v -o hello hello.o
gcc version 2.7.2.1

 /usr/libexec/elf/ld -m elf_i386 -dynamic-linker
 /usr/libexec/ld-elf.so.1 -o hello /usr/lib/crt1.o /usr/lib/crti.o
 /usr/lib/crtbegin.o -L/usr/libdata/gcc hello.o /usr/lib/libgcc.a -lc
 /usr/lib/libgcc.a /usr/lib/crtend.o /usr/lib/crtn.o

toto@atm3:ttyp1 ~/cursos (158)> ./hello
Hello World
toto@atm3:ttyp1 ~/cursos (159)>

However, the link command is quite something! There is too much of
extra code like crt1.o, crti.o crtbegin.o libgcc, etc which I would
like to avoid.

Students tend to think this is "cheating"! They will say:
"this code is easier"
main()
{
  write(1,"Hello World\n",12);
}                          

Any other suggestions?

Toto
toto@ifsc.sc.usp.br




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