From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A46FFECAAD5 for ; Fri, 2 Sep 2022 17:14:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236320AbiIBROD (ORCPT ); Fri, 2 Sep 2022 13:14:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47508 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233264AbiIBROC (ORCPT ); Fri, 2 Sep 2022 13:14:02 -0400 Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 51F57112EED for ; Fri, 2 Sep 2022 10:14:01 -0700 (PDT) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 282HAqvu018556; Fri, 2 Sep 2022 12:10:52 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 282HApOJ018555; Fri, 2 Sep 2022 12:10:51 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Fri, 2 Sep 2022 12:10:51 -0500 From: Segher Boessenkool To: Peter Bergner Cc: Christophe Leroy , "linuxppc-dev@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" , Nicholas Piggin , Zhouyi Zhou Subject: Re: [PATCH v2] powerpc: Fix irq_soft_mask_set() and irq_soft_mask_return() with sanitizer Message-ID: <20220902171051.GU25951@gate.crashing.org> References: <7c11b659-5b8e-256c-508e-39395041fccb@csgroup.eu> <20220831224522.GX25951@gate.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 02, 2022 at 10:57:27AM -0500, Peter Bergner wrote: > On 8/31/22 5:45 PM, Segher Boessenkool wrote: > > Yes, this is guaranteed. > > Agree with Segher here. That said, there was a gcc bug a looooong time > ago where gcc copied r13 into a temporary register and used it from there. r13 is a fixed register on most of our ABIs (everything that is not AIX or Darwin, even), so this can never happen. Except if there are bugs, of course ;-) > That's ok (correctness wise, but not ideal) from user land standpoint, > but we took a context switch after the reg copy and it was restarted on > a different cpu, so differnt local_paca and r13 value. We went boom > because the copy wasn't pointing to the correct local_paca anymore. > So it is very important the compiler always use r13 when accessing > the local_paca. Yes. So we either whould use -ffixed-r13, or just not use unsupported compilers. powerpc*-linux and powerpc*-elf work fine for example :-) Segher