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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55E49C43381 for ; Fri, 15 Mar 2019 17:12:10 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6DF5820854 for ; Fri, 15 Mar 2019 17:12:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="Oc3VaVNu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6DF5820854 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 44LXF30XdxzDqVK for ; Sat, 16 Mar 2019 04:12:07 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=c-s.fr (client-ip=93.17.236.30; helo=pegase1.c-s.fr; envelope-from=christophe.leroy@c-s.fr; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=c-s.fr header.i=@c-s.fr header.b="Oc3VaVNu"; dkim-atps=neutral Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 44LXCH2hB8zDqRK for ; Sat, 16 Mar 2019 04:10:32 +1100 (AEDT) Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 44LXC53qPQz9vRZ6; Fri, 15 Mar 2019 18:10:25 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=Oc3VaVNu; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id OzzGINJKl5bb; Fri, 15 Mar 2019 18:10:25 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 44LXC52PCxz9vRZ4; Fri, 15 Mar 2019 18:10:25 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1552669825; bh=DTpkMMnmyCbch9WEaOwGg3QC2RDJmW8WfDx/v6uiciw=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=Oc3VaVNuEDMncYSYltoif0ICV83+rMperfRrgJ0VV4qL/LperHnV4u+5WAVi8MLff 7SmvgxCovcueIJw15FgNHORwUdAUxP72eYuYexx/+iFM/a5tkWenSsqipLJ7W3k+8T mEU9kLC4G499zSvW09PWA5JRS5biH99sNIl0Ysi0= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id F13268BF64; Fri, 15 Mar 2019 18:10:26 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id ZUCd-WtY_sPc; Fri, 15 Mar 2019 18:10:26 +0100 (CET) Received: from po16846vm.idsi0.si.c-s.fr (po15451.idsi0.si.c-s.fr [172.25.231.2]) by messagerie.si.c-s.fr (Postfix) with ESMTP id BB18E8BF48; Fri, 15 Mar 2019 18:10:26 +0100 (CET) Subject: Re: [RFC/WIP] powerpc: Fix 32-bit handling of MSR_EE on exceptions To: Michael Ellerman , Benjamin Herrenschmidt , "linuxppc-dev@lists.ozlabs.org" References:

<5a97253c-0ec4-d61f-fa9e-ea5da8590f32@c-s.fr> <87pns6mtqe.fsf@concordia.ellerman.id.au> From: Christophe Leroy Message-ID: Date: Fri, 15 Mar 2019 17:10:24 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <87pns6mtqe.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit 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: Diana Craciun , Scott Wood , Nick Piggin , Laurentiu Tudor Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 02/05/2019 10:10 AM, Michael Ellerman wrote: > Christophe Leroy writes: >> Le 20/12/2018 à 23:35, Benjamin Herrenschmidt a écrit : >>> >>>>> /* >>>>> * MSR_KERNEL is > 0x10000 on 4xx/Book-E since it include MSR_CE. >>>>> @@ -205,20 +208,46 @@ transfer_to_handler_cont: >>>>> mflr r9 >>>>> lwz r11,0(r9) /* virtual address of handler */ >>>>> lwz r9,4(r9) /* where to go when done */ >>>>> +#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS) >>>>> + mtspr SPRN_NRI, r0 >>>>> +#endif >>>> >>>> That's not part of your patch, it's already in the tree. >>> >>> Yup rebase glitch. >>> >>> .../... >>> >>>> I tested it on the 8xx with the below changes in addition. No issue seen >>>> so far. >>> >>> Thanks ! >>> >>> I'll merge that in. >> >> I'm currently working on a refactorisation and simplification of >> exception and syscall entry on ppc32. >> >> I plan to take your patch in my serie as it helps quite a bit. I hope >> you don't mind. I expect to come out with a series this week. > > Ben's AFK so go ahead and pull it in to your series if that helps you. > >>> The main obscure area is that business with the irqsoff tracer and thus >>> the need to create stack frames around calls to trace_hardirqs_* ... we >>> do it in some places and not others, but I've not managed to make it >>> crash either. I need to get to the bottom of that, and possibly provide >>> proper macro helpers like ppc64 has to do it. >> >> I can't see anything special around this in ppc32 code. As far as I >> understand, a stack frame is put in place when there is a need to >> save and restore some volatile registers. At the places where nothing >> needs to be saved, nothing is done. I think that's the normal way for >> any function call, isn't it ? > > The concern was that the irqsoff tracer was doing > __builtin_return_address(1) (or some number > 0) and that crashes if > there aren't sufficiently many stack frames available. > > See ftrace_return_address. > > Possibly the answer is that we don't have CONFIG_FRAME_POINTER and so we > get the empty version of that. > Yes indeed, ftrace_return_address(1) is not __builtin_return_address(1) but 0ul as CONFIG_FRAME_POINTER is not defined. So the crash can't be due to that as it would then crash regardless of whether we set a stack frame or not. And anyway, as far as I understand, if the stack is properly initialised, __builtin_return_address(X) returns NULL and don't crash when the top of backtrace is reached. Do you have more details about the said crash ? I think we should file an issue for it in our issue databse. For the time being, I'll get rid of that unneccessary stack frame in entry_32.S as part of my syscall prolog optimising series. Christophe