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 f4U0I8915983 for linux-mips-outgoing; Tue, 29 May 2001 17:18:08 -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 SMTP id f4U0Hkh15975; Tue, 29 May 2001 17:17:52 -0700 Received: from drow by nevyn.them.org with local (Exim 3.22 #1 (Debian)) id 154tgK-0001yQ-00; Tue, 29 May 2001 17:17:48 -0700 Date: Tue, 29 May 2001 17:17:48 -0700 From: Daniel Jacobowitz To: Ralf Baechle Cc: linux-mips@oss.sgi.com Subject: Re: [PATCH] incorrect asm constraints for ll/sc constructs Message-ID: <20010529171748.A7362@nevyn.them.org> References: <20010523145257.A13013@nevyn.them.org> <20010525172746.B6578@bacchus.dhis.org> <20010525134909.A26065@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: <20010525134909.A26065@nevyn.them.org>; from dan@debian.org on Fri, May 25, 2001 at 01:49:09PM -0700 Sender: owner-linux-mips@oss.sgi.com Precedence: bulk On Fri, May 25, 2001 at 01:49:09PM -0700, Daniel Jacobowitz wrote: > On Fri, May 25, 2001 at 05:27:46PM -0300, Ralf Baechle wrote: > > On Thu, May 24, 2001 at 03:42:56PM +0200, Maciej W. Rozycki 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. Back to quibbling - that's just not true. For one thing, from the info documentation: `R' Memory reference that can be loaded with one instruction (`m' is preferable for `asm' statements) For another, using the patch I posted below, I get inconsistent constraint errors. I'm not entirely sure why. Is there any reason not to use the "m" version? I can't see any case in which it would not behave correctly. -- Daniel Jacobowitz Debian GNU/Linux Developer Monta Vista Software Debian Security Team