From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.110.172]:44750 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726426AbgIBSul (ORCPT ); Wed, 2 Sep 2020 14:50:41 -0400 Date: Wed, 2 Sep 2020 19:50:27 +0100 From: Mark Rutland Subject: Re: [PATCH v2 3/3] arm64: stacktrace: Convert to ARCH_STACKWALK Message-ID: <20200902184935.GA5875@C02TD0UTHF1T.local> References: <20200819124913.37261-1-broonie@kernel.org> <20200819124913.37261-4-broonie@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-s390-owner@vger.kernel.org List-ID: To: Miroslav Benes , Mark Brown Cc: Catalin Marinas , Will Deacon , Vasily Gorbik , Heiko Carstens , Borislav Petkov , Thomas Gleixner , "H. Peter Anvin" , Christian Borntraeger , Ingo Molnar , Jiri Slaby , x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org On Wed, Sep 02, 2020 at 11:32:13AM +0200, Miroslav Benes wrote: > Hi, > > it could be a silly question, but better to ask... > > > + if (regs) > > + start_backtrace(&frame, regs->regs[29], regs->pc); > > + else > > + start_backtrace(&frame, thread_saved_fp(task), > > + thread_saved_pc(task)); > > Would this also work for task == current? Given that the original code had > > > - start_backtrace(&frame, > > - (unsigned long)__builtin_frame_address(0), > > - (unsigned long)__save_stack_trace); Oh whoops; I'm annoyed I didn't spot that. With that gone this cannot work for (task == current && regs == NULL), as we'll erroneously use stale values from the task struct. It looks like the LKDTM tests only trigger cases with non-NULL regs, but IIUC this should show up with show_stack(NULL, NULL, KERN_INFO), as drivers/tty/sysrq.c does for other cpus. Thanks, Mark.