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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 9AF4CC433E0 for ; Mon, 1 Jun 2020 09:14:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 71BFE206E2 for ; Mon, 1 Jun 2020 09:14:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726017AbgFAJOp (ORCPT ); Mon, 1 Jun 2020 05:14:45 -0400 Received: from foss.arm.com ([217.140.110.172]:35244 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725778AbgFAJOp (ORCPT ); Mon, 1 Jun 2020 05:14:45 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CE0E21FB; Mon, 1 Jun 2020 02:14:44 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B12293F305; Mon, 1 Jun 2020 02:14:43 -0700 (PDT) Date: Mon, 1 Jun 2020 10:14:41 +0100 From: Dave Martin To: Keno Fischer Cc: Will Deacon , Kyle Huey , Catalin Marinas , Linux Kernel Mailing List , Oleg Nesterov , linux-arm-kernel@lists.infradead.org Subject: Re: arm64: Register modification during syscall entry/exit stop Message-ID: <20200601091441.GW5031@arm.com> References: <20200519081551.GA9980@willie-the-truck> <20200520174149.GB27629@willie-the-truck> <20200527095528.GC11111@willie-the-truck> <20200527101929.GT5031@arm.com> <20200531093320.GA30204@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 31, 2020 at 12:13:18PM -0400, Keno Fischer wrote: > > Keno -- are you planning to send out a patch? You previously spoke about > > implementing this using PTRACE_SETOPTIONS. > > Yes, I'll have a patch for you. Though I've come to the conclusion > that introducing a new regset is probably a better way to solve it. > We can then also expose orig_x0 at the same time and give it sane semantics > (there's some problems with the way it works currently - I'll write it up > together with the patch). I'd worry that having a new ptrace option would be useless bug- compatibility that is just going to bitrot. Can you explain why userspace would write a changed value for x7 but at the same time need that new to be thrown away? That sounds like a nonsensical thing for userspace to be doing. Cheers ---Dave