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=-6.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 15BC3C433E7 for ; Fri, 28 Aug 2020 18:13:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB96220936 for ; Fri, 28 Aug 2020 18:13:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="KXRzfuly" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727056AbgH1SNw (ORCPT ); Fri, 28 Aug 2020 14:13:52 -0400 Received: from mail.skyhub.de ([5.9.137.197]:32984 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726010AbgH1SNw (ORCPT ); Fri, 28 Aug 2020 14:13:52 -0400 Received: from zn.tnic (p200300ec2f0ba60078cbaf9a215c2e9d.dip0.t-ipconnect.de [IPv6:2003:ec:2f0b:a600:78cb:af9a:215c:2e9d]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id EFDBB1EC03E3; Fri, 28 Aug 2020 20:13:49 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1598638430; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=/jYI5IHuv43D+ZADrXsFhwBXIJnV8i1FIyxJtyua/Yg=; b=KXRzfulyqoFzRZ+dj+HluE21PJnj0cjQ69UGDcWcPA264jRdoC9l65vRds3AZNoIGQLiw/ etQ7GAfkKPIWNnJokkDlepYsvcxMPquvY19el5NfnOAs2br3nC3Vjryk/KQaFohIqhnVUW NNFAZll3B7FQ4406XApoT0w5nSGLFcY= Date: Fri, 28 Aug 2020 20:13:46 +0200 From: Borislav Petkov To: Joerg Roedel Cc: x86@kernel.org, Joerg Roedel , Kees Cook , hpa@zytor.com, Andy Lutomirski , Dave Hansen , Peter Zijlstra , Jiri Slaby , Dan Williams , Tom Lendacky , Juergen Gross , David Rientjes , Cfir Cohen , Erdem Aktas , Masami Hiramatsu , Mike Stunes , Sean Christopherson , Martin Radev , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v6 31/76] x86/head/64: Setup MSR_GS_BASE before calling into C code Message-ID: <20200828181346.GB19342@zn.tnic> References: <20200824085511.7553-1-joro@8bytes.org> <20200824085511.7553-32-joro@8bytes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200824085511.7553-32-joro@8bytes.org> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Aug 24, 2020 at 10:54:26AM +0200, Joerg Roedel wrote: > diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S > index 2b2e91627221..800053219054 100644 > --- a/arch/x86/kernel/head_64.S > +++ b/arch/x86/kernel/head_64.S > @@ -78,6 +78,14 @@ SYM_CODE_START_NOALIGN(startup_64) > call startup_64_setup_env > popq %rsi > > + /* > + * Setup %gs here already to make stack-protector work - it needs to be > + * setup again after the switch to kernel addresses. The address read > + * from initial_gs is a kernel address, so it needs to be adjusted first > + * for the identity mapping. > + */ > + movl $MSR_GS_BASE,%ecx I'm confused: is this missing those three lines: movl initial_gs(%rip),%eax movl initial_gs+4(%rip),%edx wrmsr as it is done in secondary_startup_64 ? Or why would you otherwise put 0xc0000101 in %ecx and not do anything with it... -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette