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=-7.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 B745DC433E2 for ; Fri, 11 Sep 2020 16:15:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D9E720731 for ; Fri, 11 Sep 2020 16:15:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=deltatee.com header.i=@deltatee.com header.b="aowX1kkd" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726546AbgIKQPN (ORCPT ); Fri, 11 Sep 2020 12:15:13 -0400 Received: from ale.deltatee.com ([204.191.154.188]:35644 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726600AbgIKQOw (ORCPT ); Fri, 11 Sep 2020 12:14:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=deltatee.com; s=20200525; h=Subject:Content-Transfer-Encoding:Content-Type: In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To:Sender: Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender :Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=MwrdSe8WFHXr29NOm/NiXpeNHwXZYZQa5mCvsCZ9j68=; b=aowX1kkdsr5U5Csum1KHk6yTp8 2VG0op7gcgZpd5VO7EXE1bRDVSaYGpz+SC57u/bqwv0nLMH5GBcH+xn3TN05tgvDhTARVywdR3WKH OkislVwCqPfjFN0A0V3q3BOfAIGpu9ZxMF+/9LzVS3f/eWcgwLXZp3K0p/qdEvX26n5vaMSZbF0pw EWXUba0PdX5Imh0zgUDxQMBkQIObtG3A3TAuG7Bhohx3SIBVuxdb2M9Y+zr5eKGiEjqRE52AxEpKP 0gFPmq/4BcM/oZMOl2gmQyVwEoyjF1gtly9ndGgjvR5+5CC1HuCrx6HUuOQ3n7KqHPdVjOKbXHqLe cGI1B0MQ==; Received: from guinness.priv.deltatee.com ([172.16.1.162]) by ale.deltatee.com with esmtp (Exim 4.92) (envelope-from ) id 1kGlhF-0001q3-UN; Fri, 11 Sep 2020 10:14:46 -0600 To: Josh Poimboeuf Cc: LKML , x86@kernel.org, Thomas Gleixner , Ingo Molnar , Andy Lutomirski , Naresh Kamboju , Borislav Petkov References: <20200911160053.w66xit3imcqsn33g@treble> From: Logan Gunthorpe Message-ID: <5a66f512-960b-7f24-068a-01c043ca9877@deltatee.com> Date: Fri, 11 Sep 2020 10:14:41 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200911160053.w66xit3imcqsn33g@treble> Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.16.1.162 X-SA-Exim-Rcpt-To: bp@alien8.de, naresh.kamboju@linaro.org, luto@kernel.org, mingo@kernel.org, tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org, jpoimboe@redhat.com X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: WARNING: Kernel stack regs has bad 'bp' value X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-09-11 10:00 a.m., Josh Poimboeuf wrote: > Hi Logan, > > Thanks for the bug report. (Sorry I missed the first one, Naresh.) > > The problem is that ret_from_fork() is no longer in .entry.text, so the > following check in the FP unwinder doesn't work when ret_from_fork() > gets interrupted. > > /* > * Don't warn if the unwinder got lost due to an interrupt in entry > * code or in the C handler before the first frame pointer got set up: > */ > if (state->got_irq && in_entry_code(state->ip)) > goto the_end; > > If you have the ability to recreate, can you try the following patch? Sorry, but I can not reliably hit this bug. I hit it randomly twice last week however, despite doing a bunch more runs this week, I haven't hit it again. I can add the patch to my testing next week but I ca not give you a definitive answer on whether this fixes the bug. Perhaps Naresh's test is a better reproducer. Thanks! Logan