From patchwork Wed Jul 7 18:14:51 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brijesh Singh X-Patchwork-Id: 470883 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=-18.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, MSGID_FROM_MTA_HEADER, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 BF734C07E9B for ; Wed, 7 Jul 2021 18:17:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A92E361CB0 for ; Wed, 7 Jul 2021 18:17:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231893AbhGGSTz (ORCPT ); Wed, 7 Jul 2021 14:19:55 -0400 Received: from mail-bn8nam12on2067.outbound.protection.outlook.com ([40.107.237.67]:45063 "EHLO NAM12-BN8-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S232136AbhGGSTe (ORCPT ); Wed, 7 Jul 2021 14:19:34 -0400 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=QHdhl9ptc/8r1x5fIIkIsryWS7GfKLbKbTs6iVWLP9pNE6+ISTqWtBSpH4NiHiZ6PgoZc64t7YRg7Zr487tuIJKQNl/w0pQNgUUJ6jMaX3IWcNJCxnsiXWGa/GptbI6788JdM6MfSLgYQLzs2sv1rDNytE3nju8GYBmAk1Cn4UkAsXV1ArWWDz3fEfu7jT27ZK34Jvnnesr6w8GcS+KGuawSaCczlZBao8Lt7CkShyQTpD+G4qCmJg6MY1H50q65iLTgiDVNyKhJpAn3bLCnn5RvdyIxOAdl3knJxN8OECvDLfr4o0ThSmNHuEswvYoki0Q9vLHOVIzL86gD7x6NeQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=fx2WDBdjGaBF/g6x3agK+7pQ+o9Ag8h7WcyLfaEPrfQ=; b=GiGE7epdlK9IW5SQWb3Ar4TR88+QZV2vmtu5CL6UiWHFhtKdjc/27yS1BQCdEDbqeteYq1dGNN2GSIFI+H3LFmnovRLirhc9gIn6n6NgIfvP65FpuNFpyNuqJp6u3MqTEeN0RLfuLwBQAAzCkSfZAUsKk5UMoj2e+H61ujfMB2jcYAf+e6YhveuusUg33dgf7+OoezcnH45WwIbZbOembhZxWXld7iF+quRJY9QCh8bpwFQdoFaq052T8xQxQHkqSP25fT+LScpuBKu56MnOf7AzTRmfYjQKxUcHQ2suSufGgWAcMNcSAkeR/txSzYCm5K6/vcWjhF8TImkPZB4feA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=amd.com; dmarc=pass action=none header.from=amd.com; dkim=pass header.d=amd.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=fx2WDBdjGaBF/g6x3agK+7pQ+o9Ag8h7WcyLfaEPrfQ=; b=NjOBBCtyjfX4X0LsD7Mdc2VDsL9qsplL74aaFOahWim2QmQZEesyE1UXDMxLg4WzpXehf6gd7O+xIA7CWzTVHLljuDpaIfD+oMevb9/Ry9lHLpmhVHmTWCnzpv0xKtell9fyXxowX4elwwWyaV/AchBSFCUNpbib5VNuhKsSMBw= Authentication-Results: kernel.org; dkim=none (message not signed) header.d=none; kernel.org; dmarc=none action=none header.from=amd.com; Received: from BYAPR12MB2711.namprd12.prod.outlook.com (2603:10b6:a03:63::10) by BY5PR12MB5016.namprd12.prod.outlook.com (2603:10b6:a03:1c5::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4308.20; Wed, 7 Jul 2021 18:16:22 +0000 Received: from BYAPR12MB2711.namprd12.prod.outlook.com ([fe80::40e3:aade:9549:4bed]) by BYAPR12MB2711.namprd12.prod.outlook.com ([fe80::40e3:aade:9549:4bed%7]) with mapi id 15.20.4287.033; Wed, 7 Jul 2021 18:16:22 +0000 From: Brijesh Singh To: x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org Cc: Thomas Gleixner , Ingo Molnar , Joerg Roedel , Tom Lendacky , "H. Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Gonda , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Borislav Petkov , Michael Roth , Vlastimil Babka , tony.luck@intel.com, npmccallum@redhat.com, brijesh.ksingh@gmail.com, Brijesh Singh Subject: [PATCH Part1 RFC v4 21/36] x86/head/64: set up a startup %gs for stack protector Date: Wed, 7 Jul 2021 13:14:51 -0500 Message-Id: <20210707181506.30489-22-brijesh.singh@amd.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210707181506.30489-1-brijesh.singh@amd.com> References: <20210707181506.30489-1-brijesh.singh@amd.com> X-ClientProxiedBy: SA0PR11CA0104.namprd11.prod.outlook.com (2603:10b6:806:d1::19) To BYAPR12MB2711.namprd12.prod.outlook.com (2603:10b6:a03:63::10) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from sbrijesh-desktop.amd.com (165.204.77.1) by SA0PR11CA0104.namprd11.prod.outlook.com (2603:10b6:806:d1::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4308.19 via Frontend Transport; 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While sufficient for that case, this will still cause issues if we attempt to call out to any external functions that were compiled with stack protection enabled that in-turn make stack-protected calls, or if the exception handlers set up by set_bringup_idt_handler() make calls to stack-protected functions. Subsequent patches for SEV-SNP CPUID validation support will introduce both such cases. Attempting to disable stack protection for everything in scope to address that is prohibitive since much of the code, like SEV-ES #VC handler, is shared code that remains in use after boot and could benefit from having stack protection enabled. Attempting to inline calls is brittle and can quickly balloon out to library/helper code where that's not really an option. Instead, set up %gs to point a buffer that stack protector can use for canary values when needed. In doing so, it's likely we can stop using -no-stack-protector for head64.c, but that hasn't been tested yet, and head32.c would need a similar solution to be safe, so that is left as a potential follow-up. Signed-off-by: Michael Roth Signed-off-by: Brijesh Singh --- arch/x86/kernel/head64.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index f4c3e632345a..8615418f98f1 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -74,6 +74,9 @@ static struct desc_struct startup_gdt[GDT_ENTRIES] = { [GDT_ENTRY_KERNEL_DS] = GDT_ENTRY_INIT(0xc093, 0, 0xfffff), }; +/* For use by stack protector code before switching to virtual addresses */ +static char startup_gs_area[64]; + /* * Address needs to be set at runtime because it references the startup_gdt * while the kernel still uses a direct mapping. @@ -598,6 +601,8 @@ void early_setup_idt(void) */ void __head startup_64_setup_env(unsigned long physbase) { + u64 gs_area = (u64)fixup_pointer(startup_gs_area, physbase); + /* Load GDT */ startup_gdt_descr.address = (unsigned long)fixup_pointer(startup_gdt, physbase); native_load_gdt(&startup_gdt_descr); @@ -605,7 +610,18 @@ void __head startup_64_setup_env(unsigned long physbase) /* New GDT is live - reload data segment registers */ asm volatile("movl %%eax, %%ds\n" "movl %%eax, %%ss\n" - "movl %%eax, %%es\n" : : "a"(__KERNEL_DS) : "memory"); + "movl %%eax, %%es\n" + "movl %%eax, %%gs\n" : : "a"(__KERNEL_DS) : "memory"); + + /* + * GCC stack protection needs a place to store canary values. The + * default is %gs:0x28, which is what the kernel currently uses. + * Point GS base to a buffer that can be used for this purpose. + * Note that newer GCCs now allow this location to be configured, + * so if we change from the default in the future we need to ensure + * that this buffer overlaps whatever address ends up being used. + */ + native_wrmsr(MSR_GS_BASE, gs_area, gs_area >> 32); startup_64_load_idt(physbase); }