From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964926AbWEOOTM (ORCPT ); Mon, 15 May 2006 10:19:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964936AbWEOOTM (ORCPT ); Mon, 15 May 2006 10:19:12 -0400 Received: from mailhost.tue.nl ([131.155.2.19]:61174 "EHLO mailhost.tue.nl") by vger.kernel.org with ESMTP id S964926AbWEOOTK (ORCPT ); Mon, 15 May 2006 10:19:10 -0400 Message-ID: <44688DDC.3020605@etpmod.phys.tue.nl> Date: Mon, 15 May 2006 16:19:08 +0200 From: Bart Hartgers User-Agent: Thunderbird 1.5 (X11/20060111) MIME-Version: 1.0 To: "linux-os (Dick Johnson)" Cc: Tomasz Malesinski , Andi Kleen , linux-kernel@vger.kernel.org Subject: Re: Segfault on the i386 enter instruction References: <20060512131654.GB2994@duch.mimuw.edu.pl> <20060512153139.GA4852@duch.mimuw.edu.pl> <446867C4.3070108@etpmod.phys.tue.nl> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org linux-os (Dick Johnson) wrote: > On Mon, 15 May 2006, Bart Hartgers wrote: > >> Tomasz Malesinski wrote: >>> On Fri, May 12, 2006 at 03:50:20PM +0200, Andi Kleen wrote: >>>> Handling it like you expect would require to disassemble >>>> the function in the page fault handler and it's probably not >>>> worth doing that for this weird case. >>> Does it mean that the ENTER instruction should not be used to create >>> stack frames in Linux programs? >>> >> Basically, yes. Here is a link to a relevant discussion in the 2.2.7 era: >> >> http://groups.google.co.nz/groups?selm=7i86ni%24b7n%241%40palladium.transmeta.com >> >> And perhaps x86-64 is handled different because of the red zone (some >> memory below the stack-pointer that can be accessed legally)? >> >> Groeten, >> Bart > > The enter instruction works perfectly fine. The processors were > designed to use both enter and leave. There are no prohibitions > against their use. It's just that if you play games with assembly > so you create a stack-pointer wrap situation, you can get a > bounds error. No. The assembly is fine. Also enter does what it is supposed to do. The problem is that enter can cause a pagefault on an address (far) below the %esp, and Linu[xs] considers that an error (for good reasons). Groeten, Bart -- Bart Hartgers - TUE Eindhoven - http://plasimo.phys.tue.nl/bart/contact/