Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964843AbVL1PQ7 (ORCPT ); Wed, 28 Dec 2005 10:16:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964848AbVL1PQ7 (ORCPT ); Wed, 28 Dec 2005 10:16:59 -0500 Received: from 167.imtp.Ilyichevsk.Odessa.UA ([195.66.192.167]:52362 "HELO ilport.com.ua") by vger.kernel.org with SMTP id S964843AbVL1PQ6 (ORCPT ); Wed, 28 Dec 2005 10:16:58 -0500 From: Denis Vlasenko To: "linux-os \(Dick Johnson\)" Subject: Re: 4k stacks Date: Wed, 28 Dec 2005 17:16:42 +0200 User-Agent: KMail/1.8.2 Cc: "Linux kernel" References: <200512241403.38482.vda@ilport.com.ua> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200512281716.43089.vda@ilport.com.ua> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 938 Lines: 25 On Wednesday 28 December 2005 15:14, linux-os (Dick Johnson) wrote: > >> Anyway, getting down to 20 bytes of stack-space available > >> seems to be pretty scary. > > > > + movl %esp, %edi > > + movl %edi, %ecx > > + andl $~0x1000, %edi > > + subl %edi, %ecx > > > > ecx will be equal to ? > > Whatever the stack was minus that value ANDed with NOT 0x1000, > i.e. 0x1000 minus the stack already in use. The code assumes > that the stack starts and ends on a 0x1000 (page) boundary. > If that's not true, then all bets are off. Hmm. I must be thick today. (esp - (esp & 0xffffefff)) is always equal to (esp & 0x00001000). Which is either 0 or 0x1000. -- vda - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/