From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Wed, 01 Feb 2006 19:19:20 +0000 (GMT) Received: from nevyn.them.org ([66.93.172.17]:479 "EHLO nevyn.them.org") by ftp.linux-mips.org with ESMTP id S3458570AbWBATTC (ORCPT ); Wed, 1 Feb 2006 19:19:02 +0000 Received: from drow by nevyn.them.org with local (Exim 4.54) id 1F4NaG-00033X-MM; Wed, 01 Feb 2006 14:24:04 -0500 Date: Wed, 1 Feb 2006 14:24:04 -0500 From: Daniel Jacobowitz To: Michael Uhler Cc: "'Maciej W. Rozycki'" , 'Johannes Stezenbach' , linux-mips@linux-mips.org Subject: Re: gdb vs. gdbserver with -mips3 / 32bitmode userspace Message-ID: <20060201192404.GA11719@nevyn.them.org> References: <20060201164423.GA4891@nevyn.them.org> <005901c62754$b414dc80$bb14a8c0@MIPS.COM> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <005901c62754$b414dc80$bb14a8c0@MIPS.COM> User-Agent: Mutt/1.5.8i Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 10290 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: dan@debian.org Precedence: bulk X-list: linux-mips On Wed, Feb 01, 2006 at 09:26:57AM -0800, Michael Uhler wrote: > Daniel, > > The O/S maybe doing something different, but the architecture has 3 bits in > Status: KX, SX, and UX that enable access to the address space above 32 > bits. With these bits off, an attempt to access these addresses causes an > exception. So while 32-bit apps have the full 64-bit address space, most of > it is inaccessible to the 32-bit app. That's not actually what I was referring to: there's at least one MIPS implementation where the results of 32-bit arithmetic operations are not just architecturally unpredictable but actually wrong if the upper bits are not properly sign extended (I might be misremembering, but I think I'm talking about the SB-1). That's the sort of thing that can be basically impossible to track down if your debugger doesn't show you the whole register. -- Daniel Jacobowitz CodeSourcery