From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (from majordomo@localhost) by oss.sgi.com (8.11.3/8.11.3) id f4ONjQG11182 for linux-mips-outgoing; Thu, 24 May 2001 16:45:26 -0700 Received: from nevyn.them.org (gateway-1237.mvista.com [12.44.186.158]) by oss.sgi.com (8.11.3/8.11.3) with ESMTP id f4ONjQF11179 for ; Thu, 24 May 2001 16:45:26 -0700 Received: from drow by nevyn.them.org with local (Exim 3.22 #1 (Debian)) id 1534mp-0005ie-00; Thu, 24 May 2001 16:44:59 -0700 Date: Thu, 24 May 2001 16:44:59 -0700 From: Daniel Jacobowitz To: "Maciej W. Rozycki" Cc: linux-mips@oss.sgi.com Subject: Re: [PATCH] incorrect asm constraints for ll/sc constructs Message-ID: <20010524164459.A19466@nevyn.them.org> References: <20010523145257.A13013@nevyn.them.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.16i In-Reply-To: ; from macro@ds2.pg.gda.pl on Thu, May 24, 2001 at 03:42:56PM +0200 Sender: owner-linux-mips@oss.sgi.com Precedence: bulk On Thu, May 24, 2001 at 03:42:56PM +0200, Maciej W. Rozycki wrote: > On Wed, 23 May 2001, Daniel Jacobowitz wrote: > > > The ll/sc constructs in the kernel use ".set noat" to inhibit use of $at, > > and proceed to use it themselves. This is fine, except for one problem: the > > constraints on memory operands are "o" and "=o", which means offsettable > > memory references. If I'm not mistaken, the assembler will (always?) > > turn these into uses of $at if the offset is not 0 - at least, it certainly > > seems to do that here (gcc 2.95.3, binutils 2.10.91.0.2). Just being honest > > with the compiler and asking for a real memory reference does the trick. > > Both "m" and "o" seem to be incorrect here as both are the same for MIPS; > "R" seems to be appropriate, OTOH. Still gcc 2.95.3 doesn't handle "R" > fine for all cases, but it works most of the time and emits a warning > otherwise. I can't comment on 3.0. They aren't the same for MIPS, though. I exhibit as evidence the fact that my patch fixed the problem I was seeing. I didn't know about 'R'; I suppose that it is more correct. 'm' at least is closer than 'o', though. If 'R' will behave correctly, could that be applied to CVS, then? > Note that if noat is in effect and at is to be used, gas should bail out > with an error. There is a bug, if it doesn't. It issues a warning, currently (2.10.91.0.2 - I think 2.11 behaves the same). -- Daniel Jacobowitz Debian GNU/Linux Developer Monta Vista Software Debian Security Team