From owner-freebsd-hackers  Wed Dec 13 14:21:49 2000
From owner-freebsd-hackers@FreeBSD.ORG  Wed Dec 13 14:21:47 2000
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from chopper.Poohsticks.ORG (chopper.poohsticks.org [63.227.60.73])
	by hub.freebsd.org (Postfix) with ESMTP id 6E37937B402
	for <freebsd-hackers@FreeBSD.ORG>; Wed, 13 Dec 2000 14:21:46 -0800 (PST)
Received: from chopper.Poohsticks.ORG (drew@localhost.poohsticks.org [127.0.0.1])
	by chopper.Poohsticks.ORG (8.10.1/8.10.1) with ESMTP id eBDMLdh28943;
	Wed, 13 Dec 2000 15:21:39 -0700
Message-Id: <200012132221.eBDMLdh28943@chopper.Poohsticks.ORG>
To: Alfred Perlstein <bright@wintelcom.net>
Cc: Marc Tardif <intmktg@CAM.ORG>, freebsd-hackers@FreeBSD.ORG
Subject: Re: syscall assembly 
In-reply-to: Your message of "Wed, 13 Dec 2000 14:10:23 PST."
             <20001213141023.O16205@fw.wintelcom.net> 
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <28939.976746099.1@chopper.Poohsticks.ORG>
Date: Wed, 13 Dec 2000 15:21:39 -0700
From: Drew Eckhardt <drew@PoohSticks.ORG>
Sender: drew@chopper.Poohsticks.ORG
Sender: owner-freebsd-hackers@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG

In message <20001213141023.O16205@fw.wintelcom.net>, bright@wintelcom.net write
s:
>>         subl $8,%esp
>>         addl $-8,%esp

>> What is the purpose of the subl and addl
>> instructions? On Linux, they are simply
>> unexistent..
>
>FreeBSD passes syscall args on the stack, Linux uses registers.

The 'C' compiler doesn't know open is a syscall, and treats it like
any other code.

The pushls put the arguments on the stack.

The subl/addl are there because your version of GCC is broken.


To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-hackers" in the body of the message