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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8DAACC001B5 for ; Fri, 2 Sep 2022 17:13:24 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4MK4Hk5xzjz3c4K for ; Sat, 3 Sep 2022 03:13:22 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lists.ozlabs.org (Postfix) with ESMTP id 4MK4HJ24R9z2xt3 for ; Sat, 3 Sep 2022 03:12:59 +1000 (AEST) 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 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 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Zhouyi Zhou , "linuxppc-dev@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" , Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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