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=-15.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL 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 BF907C433E0 for ; Fri, 22 Jan 2021 21:45:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9213223ACA for ; Fri, 22 Jan 2021 21:45:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729821AbhAVVph (ORCPT ); Fri, 22 Jan 2021 16:45:37 -0500 Received: from linux.microsoft.com ([13.77.154.182]:43716 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729322AbhAVVpR (ORCPT ); Fri, 22 Jan 2021 16:45:17 -0500 Received: from [192.168.254.32] (unknown [47.187.219.45]) by linux.microsoft.com (Postfix) with ESMTPSA id DBC8A20B7192; Fri, 22 Jan 2021 13:44:35 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com DBC8A20B7192 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1611351876; bh=geh+hCTtjutzehHxzhcv4bTi/qNORksnmBQi0+Nv/1s=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=jBujqEnpeGP8xwMuai3OpICq6dba6Y6FnMrQX0k/3qGa1kEu9oXnQw7zaZA+Q7OYi ONuz424856s5wNjf/3HgofM7gmBvyCAdU5uQ8jCtiSX/2EOTopOT68MKYePxgWNrpp xkmbNj55Bn0rG95YgVF4+/0sUgWLxANIlK995gus= Subject: Re: [RFC PATCH 00/17] objtool: add base support for arm64 To: Ard Biesheuvel Cc: Mark Brown , Josh Poimboeuf , Mark Rutland , Michal Marek , Julien Thierry , Peter Zijlstra , Catalin Marinas , Masahiro Yamada , Linux Kernel Mailing List , linux-efi , linux-hardening@vger.kernel.org, live-patching@vger.kernel.org, Will Deacon , Linux ARM , Kees Cook References: <20210120173800.1660730-1-jthierry@redhat.com> <186bb660-6e70-6bbf-4e96-1894799c79ce@redhat.com> <20210121185452.fxoz4ehqfv75bdzq@treble> <20210122174342.GG6391@sirena.org.uk> From: "Madhavan T. Venkataraman" Message-ID: Date: Fri, 22 Jan 2021 15:44:35 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org On 1/22/21 3:43 PM, Ard Biesheuvel wrote: > On Fri, 22 Jan 2021 at 22:15, Madhavan T. Venkataraman > wrote: >> >> >> >> On 1/22/21 11:43 AM, Mark Brown wrote: >>> On Thu, Jan 21, 2021 at 12:54:52PM -0600, Josh Poimboeuf wrote: >>> >>>> 2) The shadow stack idea sounds promising -- how hard would it be to >>>> make a prototype reliable unwinder? >>> >>> In theory it doesn't look too hard and I can't see a particular reason >>> not to try doing this - there's going to be edge cases but hopefully for >>> reliable stack trace they're all in areas where we would be happy to >>> just decide the stack isn't reliable anyway, things like nesting which >>> allocates separate shadow stacks for each nested level for example. >>> I'll take a look. >>> >> >> I am a new comer to this discussion and I am learning. Just have some >> questions. Pardon me if they are obvious or if they have already been >> asked and answered. >> >> Doesn't Clang already have support for a shadow stack implementation for ARM64? >> We could take a look at how Clang does it. >> >> Will there not be a significant performance hit? May be, some of it can be >> mitigated by using a parallel shadow stack rather than a compact one. >> >> Are there any longjmp style situations in the kernel where the stack is >> unwound by several frames? In these cases, the shadow stack must be unwound >> accordingly. >> > > Hello Madhavan, > > Let's discuss the details of shadow call stacks on a separate thread, > instead of further hijacking Julien's series. > OK. Sounds good.