From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750806AbdAXSls (ORCPT ); Tue, 24 Jan 2017 13:41:48 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:33110 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750708AbdAXSlo (ORCPT ); Tue, 24 Jan 2017 13:41:44 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org CD1496084B Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=tbaicar@codeaurora.org Subject: Re: [PATCH V7 04/10] arm64: exception: handle Synchronous External Abort To: James Morse References: <1484244924-24786-1-git-send-email-tbaicar@codeaurora.org> <1484244924-24786-5-git-send-email-tbaicar@codeaurora.org> <587DF279.1010402@arm.com> <5880FD8A.2000405@arm.com> <5885D46A.7000304@arm.com> Cc: christoffer.dall@linaro.org, marc.zyngier@arm.com, pbonzini@redhat.com, rkrcmar@redhat.com, linux@armlinux.org.uk, catalin.marinas@arm.com, will.deacon@arm.com, rjw@rjwysocki.net, lenb@kernel.org, matt@codeblueprint.co.uk, robert.moore@intel.com, lv.zheng@intel.com, nkaje@codeaurora.org, zjzhang@codeaurora.org, mark.rutland@arm.com, akpm@linux-foundation.org, eun.taik.lee@samsung.com, sandeepa.s.prabhu@gmail.com, labbott@redhat.com, shijie.huang@arm.com, rruigrok@codeaurora.org, paul.gortmaker@windriver.com, tn@semihalf.com, fu.wei@linaro.org, rostedt@goodmis.org, bristot@redhat.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-efi@vger.kernel.org, devel@acpica.org, Suzuki.Poulose@arm.com, punit.agrawal@arm.com, astone@redhat.com, harba@codeaurora.org, hanjun.guo@linaro.org, john.garry@huawei.com, shiju.jose@huawei.com From: "Baicar, Tyler" Message-ID: <4ee2633d-e4a9-6237-4298-4454e7d268ad@codeaurora.org> Date: Tue, 24 Jan 2017 11:41:38 -0700 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 MIME-Version: 1.0 In-Reply-To: <5885D46A.7000304@arm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/23/2017 3:01 AM, James Morse wrote: > Hi Tyler, > > On 20/01/17 20:35, Baicar, Tyler wrote: >> On 1/19/2017 10:55 AM, James Morse wrote: >>> On 18/01/17 23:26, Baicar, Tyler wrote: >>>> On 1/17/2017 3:31 AM, James Morse wrote: >>>>> On 12/01/17 18:15, Tyler Baicar wrote: >>>>>> + info.si_addr = (void __user *)addr; >>>>> addr here was read from FAR_EL1, but for some of the classes of exception you >>>>> have listed below this register isn't updated with the faulting address. >>>>> >>>>> The ARM-ARM version 'k' in D1.10.5 "Summary of registers on faults taken to an >>>>> Exception level that is using Aarch64" has: >>>>>> The architecture permits that the FAR_ELx is UNKNOWN for Synchronous External >>>>>> Aborts other than Synchronous External Aborts on Translation Table Walks. In >>>>>> this case, the ISS.FnV bit returned in ESR_ELx indicates whether FAR_ELx is >>>>>> valid. >>>>> This is a problem if we get 'synchronous external abort' or 'synchronous parity >>>>> error' while a user space process was running. >>>> It looks like this would just cause an incorrect address to be printed in the >>>> above pr_err. >>>> Unless I'm missing something, I don't see arm64_notify_die or anything that gets >>>> called from >>>> there using the info.si_addr variable. >>> I may be misreading something here... >>> >>> This patch has: >>>> info.si_addr = (void __user *)addr; >>>> arm64_notify_die("", regs, &info, esr); >>> From arch/arm64/kernel/traps.c:arm64_notify_die(): >>>> if (user_mode(regs)) { >>>> current->thread.fault_address = 0; >>>> current->thread.fault_code = err; >>>> force_sig_info(info->si_signo, info, current); >>>> } >>> So if the SEA interrupted userspace, we put maybe-unknown addr into >>> force_sig_info() to deliver a signal to user space. User-space then gets a copy >>> of the info struct containing the maybe-unknown addr. >>> >>> I think this is an existing bug, but if we are separating the synchronous >>> external aborts from the generic do_bad handler, we should probably check the >>> FnV bit. (I think we should still print it out) >>> >>> >>>> What do you suggest I do here? The firmware should be reporting the physical and >>>> virtual >>>> address information if it is available in the HEST entry that the kernel will >>>> parse. >>> Its not just firmware that may trigger this, other SoCs may use it for parity or >>> ECC errors, and they may not always have a valid address in FAR_EL1. >>> >>> I think we should check the FnV bit in the esr variable and set info.si_addr to >>> 0 if the addr we have isn't valid: >>> 'For some implementations, the value of si_addr may be inaccurate.' [0] >> Okay, that makes sense, we don't want userspace to be notified with an incorrect >> address. >> I will add the check to verify it's valid. Which bit in the ESR is the FnV bit? >> I'm not finding >> the bit breakdown of the ISS that shows it. > The bits in ISS vary depending on the EC, so a little digging is required. > "D7.2.27 ESR_ELx, Exception Syndrome Register (ELx)" lists the EC values, from > there 'Instruction Abort' and 'Data Abort' both list FnV as bit 10. Version 'k' > of the ARM-ARM has this on pages D7-1953 to D7-1956. Got it! I'll add the check for this in my next patchset. Thanks, Tyler -- Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.