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=-8.3 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 714AFC34056 for ; Wed, 19 Feb 2020 20:12:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 40FFD24654 for ; Wed, 19 Feb 2020 20:12:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="KZjz6JeV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726851AbgBSUMe (ORCPT ); Wed, 19 Feb 2020 15:12:34 -0500 Received: from mail-vk1-f195.google.com ([209.85.221.195]:42281 "EHLO mail-vk1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726634AbgBSUMe (ORCPT ); Wed, 19 Feb 2020 15:12:34 -0500 Received: by mail-vk1-f195.google.com with SMTP id c15so509822vko.9 for ; Wed, 19 Feb 2020 12:12:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=42MaK4n6+CrelpQTjPFZO9NB2S0O1OTsWCtSJ9pIv6o=; b=KZjz6JeV1vFYXt8q0wyrdwBhXZ/8rzg3LVXGgnEjLp0yccOlrd9L+Ok9CSnmEDAScF 5DXgdCokxyl/DepQSJRvQZcSN+CE8Kcr0SWpEfzBMCL7WlKU8JPwmUJCsE2rI7Vb7lKV bgQULZyhEbb7MwpvmgaQHsqZa8CaNOAvokqUXRgGKlW538y3zdoMMZdFUy60Yhv2WJdn xOhNioYtaDA8ydHmJeTzDTHNO8vInpQ9cb9Ph5Mu9jvt5hFURbjsN43FQ7NZbkVfeBb2 LHRWZWKArxzLHQPRZfP/szxqEcv4AqpjRJQcw8TGu10OvO3/JnOO2GhuCUA9yjJvEBPV ehWg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=42MaK4n6+CrelpQTjPFZO9NB2S0O1OTsWCtSJ9pIv6o=; b=Z8BhsKge4kFfCpHTxFnaYFm30Z1SnWHzVIPCHHNXPl9EXvQppcGvBILGM3DhwQIGPl RVbLuYoHKEm6+ZJhBXv6OUYDIB+Gw/8/pgWCFqO8gMlyhP7j2TFvzl97NWpcZUPnGXW5 1A3cMi5ZsreplbhzGVjIA0zkfcgbAkCzNV35gZauzjQKjZ7BrB089mkdDjVhPBhrEkjB pUGrcSs5auicTgMRS7Jv+E7MX3/Dw+PiZbaCvnzBMb/YyqlmRIF5Gcsfbfr8Phy96/2g jf+zVPbcDXuwOxLkYT/DDDSc89r3EjZAH5L5DiEGDja9y7aUuE1AbX5qnfbs40g7kj41 /APA== X-Gm-Message-State: APjAAAX+IZrAR8pUqZgGgYYoNGLnrjD5nS6YqNbNFvkefwOsky5M5/72 Aot86DSTWe2hLlbMeZ4p+6M3yLGReDuuNnc9KoYqEg== X-Google-Smtp-Source: APXvYqyTw52gSQ4jw8pztzOwndZ0sk6pyQFwXTfytaf2zPfg719bU3sRcZ3Xjk3tkUfVqd3npa2/1rrBf+K/+C8JeGQ= X-Received: by 2002:a1f:4541:: with SMTP id s62mr12216061vka.59.1582143153200; Wed, 19 Feb 2020 12:12:33 -0800 (PST) MIME-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20200219000817.195049-1-samitolvanen@google.com> <0386ecad-f3d6-f1dc-90da-7f05b2793839@arm.com> In-Reply-To: <0386ecad-f3d6-f1dc-90da-7f05b2793839@arm.com> From: Sami Tolvanen Date: Wed, 19 Feb 2020 12:12:21 -0800 Message-ID: Subject: Re: [PATCH v8 00/12] add support for Clang's Shadow Call Stack To: James Morse Cc: Marc Zyngier , Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Mark Rutland , Dave Martin , Kees Cook , Laura Abbott , Nick Desaulniers , Jann Horn , Miguel Ojeda , Masahiro Yamada , clang-built-linux , Kernel Hardening , linux-arm-kernel , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 19, 2020 at 10:38 AM James Morse wrote: > This looks like reserving x18 is causing Clang to not-inline the __kern_hyp_va() calls, > losing the vitally important section information. (I can see why the compiler thinks this > is fair) Thanks for catching this. This doesn't appear to be caused by reserving x18, it looks like SCS itself is causing clang to avoid inlining these. If I add __noscs to __kern_hyp_va(), clang inlines the function again. __always_inline also works, as you pointed out. > Is this a known, er, thing, with clang-9? I can reproduce this with ToT clang as well. > I suspect repainting all KVM's 'inline' with __always_inline will fix it. (yuck!) I'll try > tomorrow. I think switching to __always_inline is the correct solution here. Sami