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,URIBL_BLOCKED,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 9D5F5C433DB for ; Fri, 22 Jan 2021 21:18:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6BC9923AF8 for ; Fri, 22 Jan 2021 21:18:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730538AbhAVVSV (ORCPT ); Fri, 22 Jan 2021 16:18:21 -0500 Received: from linux.microsoft.com ([13.77.154.182]:40154 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729865AbhAVVRL (ORCPT ); Fri, 22 Jan 2021 16:17:11 -0500 Received: from [192.168.254.32] (unknown [47.187.219.45]) by linux.microsoft.com (Postfix) with ESMTPSA id 4884C20B6C40; Fri, 22 Jan 2021 13:16:29 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 4884C20B6C40 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1611350190; bh=LmVa0B7QKVLtgYQ+R0kakMd+3Q+60r35qr0JwnFm7VU=; h=From:Subject:To:Cc:References:Date:In-Reply-To:From; b=FwpsQhKGbt6L+aq2cJ4Vst/Kqkhxev74xZv9rJNJo0ofXaqmQbSqGFApLbJxj3lDF qHHygKBTPq/Lu1CF1HSa2kBg6c7GFsoOLW3AbJQZPI5dA4iEOFh1pV5HesqlHF6g26 vnmYb0GZw3479dSXUqrAZ+GmXjbEFoabQ1TdfXLg= From: "Madhavan T. Venkataraman" Subject: Re: [RFC PATCH 00/17] objtool: add base support for arm64 To: Mark Brown , Josh Poimboeuf Cc: 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 , Ard Biesheuvel , 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> Message-ID: <718f8021-f423-2fc8-da70-300b19942ea8@linux.microsoft.com> Date: Fri, 22 Jan 2021 15:16:28 -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: <20210122174342.GG6391@sirena.org.uk> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Madhavan > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >