From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17030 invoked by alias); 12 Dec 2006 17:34:53 -0000 Received: (qmail 17021 invoked by uid 22791); 12 Dec 2006 17:34:53 -0000 X-Spam-Check-By: sourceware.org Received: from smtp-vbr13.xs4all.nl (HELO smtp-vbr13.xs4all.nl) (194.109.24.33) by sourceware.org (qpsmtpd/0.31) with ESMTP; Tue, 12 Dec 2006 17:34:43 +0000 Received: from webmail.xs4all.nl (dovemail10.xs4all.nl [194.109.26.12]) by smtp-vbr13.xs4all.nl (8.13.8/8.13.8) with ESMTP id kBCHYJ5J090766; Tue, 12 Dec 2006 18:34:19 +0100 (CET) (envelope-from mark.kettenis@xs4all.nl) Received: from 82.92.89.47 (SquirrelMail authenticated user sibelius) by webmail.xs4all.nl with HTTP; Tue, 12 Dec 2006 18:34:20 +0100 (CET) Message-ID: <14038.82.92.89.47.1165944860.squirrel@webmail.xs4all.nl> In-Reply-To: <17790.57726.696229.240657@zebedee.pink> References: <20061211190300.GA4372@host0.dyn.jankratochvil.net> <17790.46246.634400.638852@zebedee.pink> <22844.82.92.89.47.1165935102.squirrel@webmail.xs4all.nl> <17790.50417.668957.495292@zebedee.pink> <17790.57726.696229.240657@zebedee.pink> Date: Tue, 12 Dec 2006 17:34:00 -0000 Subject: Re: Unwinding CFI gcc practice of assumed `same value' regs From: "Mark Kettenis" To: "Andrew Haley" Cc: "Ian Lance Taylor" , "Mark Kettenis" , "Jan Kratochvil" , gcc@gcc.gnu.org, libc-alpha@sources.redhat.com, gdb@sourceware.org, "Jakub Jelinek" , "Richard Henderson" User-Agent: SquirrelMail/1.4.8 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-8859-1 Content-Transfer-Encoding: 8bit Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org X-SW-Source: 2006-12/txt/msg00106.txt.bz2 > Ian Lance Taylor writes: > > Andrew Haley writes: > > > > > In practice, %ebp either points to a call frame -- not necessarily > the > > > most recent one -- or is null. I don't think that having an optional > > > frame pointer mees you can use %ebp for anything random at all, but > we > > > need to make a clarification request of the ABI. > > > > I don't see that as feasible. If %ebp/%rbp may be used as a general > > callee-saved register, then it can hold any value. > > Sure, we already know that, as has been clear. The question is *if* > %rbp may be used as a general callee-saved register that can hold any > value. The amd64 ABI is specifically *designed* to allow this. Mark