From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757205AbcIUKcM (ORCPT ); Wed, 21 Sep 2016 06:32:12 -0400 Received: from foss.arm.com ([217.140.101.70]:45128 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757185AbcIUKcJ (ORCPT ); Wed, 21 Sep 2016 06:32:09 -0400 Date: Wed, 21 Sep 2016 11:31:47 +0100 From: Mark Rutland To: Laura Abbott Cc: linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, ard.biesheuvel@linaro.org, catalin.marinas@arm.com, james.morse@arm.com, keescook@chromium.org, linux-kernel@vger.kernel.org, lorenzo.pieralisi@arm.com, luto@kernel.org, suzuki.poulose@arm.com, takahiro.akashi@linaro.org, will.deacon@arm.com, kernel-hardening@lists.openwall.com Subject: Re: [RFC PATCH 0/8] arm64: move thread_info off of the task stack Message-ID: <20160921103147.GD18176@leverpostej> References: <1473947349-14521-1-git-send-email-mark.rutland@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 20, 2016 at 06:26:54PM -0700, Laura Abbott wrote: > On 09/15/2016 06:49 AM, Mark Rutland wrote: > >Building atop of Andy's work on x86 and generic code, these patches move > >arm64's thread_info off of the stack and into task_struct. This protects > >thread_info from corruption in the face of stack overflow, and serves as > >a step towards fully robust stack overflow handling will be addressed by > >subsequent patches. > > > >In contrast to x86, we can't place some critical data such as > >preempt_count in percpu variables, and we must store these in some > >per-task location. This, compounded with the way headers are organised > >conspires to require us to still define our own thread_info. I > >understand that the longer term plan is to kill off thread_info > >entirely, hence I'm sending this as an RFC so we can figure out if/how > >we can achieve that. > > > >These patches are based on Andy's x86/vmap_stack branch [1,2], and I've > >pushed a copy to me arm64/ti-stack-split branch [3,4]. The result of > >these patches boots happily on platforms within reach of my desk, but > >has not seen much stressing so far. > > FWIW, I used your ti-stack-split branch while running some kernel builds > and it seems to work well enough. You can take that as a Tested-by or I > can re-test with a non-RFC version. Thanks for testing, and many thanks for the offer! Based on Andy's feedback some core bits are changing, and I'm hoping to have a non-RFC version out soon once I've fixed up the remaining fallout. I'll make sure you're Cc'd! Thanks, Mark.