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=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 472A2C04AB5 for ; Mon, 3 Jun 2019 11:24:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 21881259F0 for ; Mon, 3 Jun 2019 11:24:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728281AbfFCLYG (ORCPT ); Mon, 3 Jun 2019 07:24:06 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:49266 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728033AbfFCLYG (ORCPT ); Mon, 3 Jun 2019 07:24:06 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BB85DA78; Mon, 3 Jun 2019 04:24:05 -0700 (PDT) Received: from fuggles.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C56CF3F5AF; Mon, 3 Jun 2019 04:24:02 -0700 (PDT) Date: Mon, 3 Jun 2019 12:23:54 +0100 From: Will Deacon To: Ravi Bangoria Cc: Peter Zijlstra , Young Xiao <92siuyang@gmail.com>, linux@armlinux.org.uk, mark.rutland@arm.com, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, kan.liang@linux.intel.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, ravi.bangoria@linux.vnet.ibm.com, mpe@ellerman.id.au, acme@redhat.com, eranian@google.com, fweisbec@gmail.com, jolsa@redhat.com Subject: Re: [PATCH] perf: Fix oops when kthread execs user process Message-ID: <20190603112346.GA28296@fuggles.cambridge.arm.com> References: <20190528140103.GT2623@hirez.programming.kicks-ass.net> <20190528153224.GE20758@fuggles.cambridge.arm.com> <20190528173228.GW2623@hirez.programming.kicks-ass.net> <20190529091733.GA4485@fuggles.cambridge.arm.com> <20190529101042.GN2623@hirez.programming.kicks-ass.net> <20190529102022.GC4485@fuggles.cambridge.arm.com> <20190529125557.GU2623@hirez.programming.kicks-ass.net> <8b55f79a-c324-0701-e85f-c7797a60a708@linux.ibm.com> <20190531153703.GA21288@fuggles.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190531153703.GA21288@fuggles.cambridge.arm.com> User-Agent: Mutt/1.11.1+86 (6f28e57d73f2) () Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 31, 2019 at 04:37:15PM +0100, Will Deacon wrote: > Oh, nice! I think this happens because Power doesn't actually initialise > the regs after a kthread execs() until late in start_thread(). But the plot > thickens somewhat, since current_pt_regs() is different to > task_pt_regs(current) on Power (the former cannot return NULL). > > So a really hideous hack on top of Peter's patch might be: > > diff --git a/arch/arm64/kernel/perf_regs.c b/arch/arm64/kernel/perf_regs.c > index 0bbac612146e..5bde866024b6 100644 > --- a/arch/arm64/kernel/perf_regs.c > +++ b/arch/arm64/kernel/perf_regs.c > @@ -57,6 +57,6 @@ void perf_get_regs_user(struct perf_regs *regs_user, > struct pt_regs *regs, > struct pt_regs *regs_user_copy) > { > - regs_user->regs = task_pt_regs(current); > + regs_user->regs = current_pt_regs(); > regs_user->abi = perf_reg_abi(current); ^^^ Bah, this was clearly supposed to be a change in the powerpc code, but you get the idea. Will