From owner-freebsd-hackers@FreeBSD.ORG  Tue Mar  2 11:52:23 2004
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id D9C3E16A4CE
	for <hackers@freebsd.org>; Tue,  2 Mar 2004 11:52:23 -0800 (PST)
Received: from lilzmailso01.liwest.at (lilzmailso01.liwest.at [212.33.55.23])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 6D6CF43D2D
	for <hackers@freebsd.org>; Tue,  2 Mar 2004 11:52:23 -0800 (PST)
	(envelope-from dgw@liwest.at)
Received: from cm58-27.liwest.at ([212.33.58.27])
	by lilzmailso01.liwest.at with esmtp (Exim 4.24)
	id 1AyFwD-0001jg-LF
	for hackers@freebsd.org; Tue, 02 Mar 2004 20:52:21 +0100
From: Daniela <dgw@liwest.at>
To: hackers@freebsd.org
Date: Tue, 2 Mar 2004 20:46:22 +0000
User-Agent: KMail/1.5.3
MIME-Version: 1.0
Content-Type: text/plain;
  charset="us-ascii"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Message-Id: <200403022046.22882.dgw@liwest.at>
Subject: Strange behaviour in assembly language program
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 02 Mar 2004 19:52:24 -0000

Hi!

I'm already a bit experienced with assembly, and started to enter my 
executables directly in the hexeditor (for educational purpose only; I know 
this is poor programming style).
I do not yet fully understand all aspects of the ELF header, but I managed to 
somehow write working ELF executables. I tried first a program that exits 
with status 1, and it works. But then I tried other values, and found out 
that it always exits with 1 no matter what I enter. I don't think I made a 
stupid mistake, because the Linux version (exit value given in EBX and 
ELF_OSABI = 03) runs perfectly in emulation mode. The first strange thing is, 
that it doesn't run on a real Linux system (tells me it doesn't have enough 
core memory for a 96 byte program).

Second strange thing:
Finally I came up with the simplest ASM program that reproduces the error.
Here it is:

.text
.global _start
_start:
	pushl	$0
	movl	$1, %eax
	int	$0x80

I looked everywhere (Developer's handbook, Google, ...) to find the solution, 
but all resources I consulted tell me this is the right way to do it.
This program, however, always exits with 1 regardless of the value I push.

Please, can someone tell me that I made a really stupid error? I'm already 
pulling my hair out.

Thanks for your time.

Daniela