From nobody Fri Dec 19 20:12:25 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6DDDC74A5B for ; Sun, 19 Mar 2023 00:16:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229866AbjCSAQP (ORCPT ); Sat, 18 Mar 2023 20:16:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229621AbjCSAQB (ORCPT ); Sat, 18 Mar 2023 20:16:01 -0400 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D0BBF28D00; Sat, 18 Mar 2023 17:15:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1679184959; x=1710720959; h=from:to:cc:subject:date:message-id:in-reply-to: references; bh=DZhiQrXgICtOhDgJWbiC3iTfdlJMOxEjzVm3FJAu0Gg=; b=lSLXACX8JY2WT5mXqxNuhMpj9NUzFJADeZLBQ1jDnMg1DrGM7xG1eyi2 uMwghvB1FflLCvh0LdaQw+B5E3vsN2P8cb6+MdMT3hBzN2mNlQYU8jcJx nQaCYgdsG5b05CVPx6LlxkeBys0qI6kTGfsATRAayM+wI1Iz5xpLriaTX MUwovQAgUlYuvOQkGwU7Y6j2T3m3VWBmhuPIn353xsAQlnBnnJ+HdTrmt /kPwU7AkTRjpN0aQBYhtgtnGJsux1SuZ3zsVkTJQOWEPITkB9jyzE2jWR Kk7bGAzVERKyYeGZHyE7iCyTQrOM71qOjtKLPgfNuMivtIZj9/u/G6iRo g==; X-IronPort-AV: E=McAfee;i="6600,9927,10653"; a="338490778" X-IronPort-AV: E=Sophos;i="5.98,272,1673942400"; d="scan'208";a="338490778" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Mar 2023 17:15:59 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10653"; a="749672776" X-IronPort-AV: E=Sophos;i="5.98,272,1673942400"; d="scan'208";a="749672776" Received: from bmahatwo-mobl1.gar.corp.intel.com (HELO rpedgeco-desk.amr.corp.intel.com) ([10.135.34.5]) by fmsmga004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Mar 2023 17:15:57 -0700 From: Rick Edgecombe To: x86@kernel.org, "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com, david@redhat.com, debug@rivosinc.com, szabolcs.nagy@arm.com Cc: rick.p.edgecombe@intel.com, Yu-cheng Yu Subject: [PATCH v8 03/40] x86/cpufeatures: Add CPU feature flags for shadow stacks Date: Sat, 18 Mar 2023 17:14:58 -0700 Message-Id: <20230319001535.23210-4-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20230319001535.23210-1-rick.p.edgecombe@intel.com> References: <20230319001535.23210-1-rick.p.edgecombe@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" The Control-Flow Enforcement Technology contains two related features, one of which is Shadow Stacks. Future patches will utilize this feature for shadow stack support in KVM, so add a CPU feature flags for Shadow Stacks (CPUID.(EAX=3D7,ECX=3D0):ECX[bit 7]). To protect shadow stack state from malicious modification, the registers are only accessible in supervisor mode. This implementation context-switches the registers with XSAVES. Make X86_FEATURE_SHSTK depend on XSAVES. The shadow stack feature, enumerated by the CPUID bit described above, encompasses both supervisor and userspace support for shadow stack. In near future patches, only userspace shadow stack will be enabled. In expectation of future supervisor shadow stack support, create a software CPU capability to enumerate kernel utilization of userspace shadow stack support. This user shadow stack bit should depend on the HW "shstk" capability and that logic will be implemented in future patches. Co-developed-by: Yu-cheng Yu Signed-off-by: Yu-cheng Yu Signed-off-by: Rick Edgecombe Reviewed-by: Kees Cook Acked-by: Mike Rapoport (IBM) Tested-by: Pengfei Xu Tested-by: John Allen Tested-by: Kees Cook --- v5: - Drop "shstk" from cpuinfo (Boris) - Remove capitalization on shadow stack (Boris) v3: - Add user specific shadow stack cpu cap (Andrew Cooper) - Drop reviewed-bys from Boris and Kees due to the above change. v2: - Remove IBT reference in commit log (Kees) - Describe xsaves dependency using text from (Dave) v1: - Remove IBT, can be added in a follow on IBT series. --- arch/x86/include/asm/cpufeatures.h | 2 ++ arch/x86/include/asm/disabled-features.h | 8 +++++++- arch/x86/kernel/cpu/cpuid-deps.c | 1 + 3 files changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpuf= eatures.h index 73c9672c123b..3d98ce9f41fe 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -309,6 +309,7 @@ #define X86_FEATURE_MSR_TSX_CTRL (11*32+20) /* "" MSR IA32_TSX_CTRL (Intel= ) implemented */ #define X86_FEATURE_SMBA (11*32+21) /* "" Slow Memory Bandwidth Allocatio= n */ #define X86_FEATURE_BMEC (11*32+22) /* "" Bandwidth Monitoring Event Conf= iguration */ +#define X86_FEATURE_USER_SHSTK (11*32+23) /* Shadow stack support for use= r mode applications */ =20 /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */ #define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI instructions */ @@ -378,6 +379,7 @@ #define X86_FEATURE_OSPKE (16*32+ 4) /* OS Protection Keys Enable */ #define X86_FEATURE_WAITPKG (16*32+ 5) /* UMONITOR/UMWAIT/TPAUSE Instruct= ions */ #define X86_FEATURE_AVX512_VBMI2 (16*32+ 6) /* Additional AVX512 Vector Bi= t Manipulation Instructions */ +#define X86_FEATURE_SHSTK (16*32+ 7) /* "" Shadow stack */ #define X86_FEATURE_GFNI (16*32+ 8) /* Galois Field New Instructions */ #define X86_FEATURE_VAES (16*32+ 9) /* Vector AES */ #define X86_FEATURE_VPCLMULQDQ (16*32+10) /* Carry-Less Multiplication Do= uble Quadword */ diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/as= m/disabled-features.h index 5dfa4fb76f4b..505f78ddca82 100644 --- a/arch/x86/include/asm/disabled-features.h +++ b/arch/x86/include/asm/disabled-features.h @@ -99,6 +99,12 @@ # define DISABLE_TDX_GUEST (1 << (X86_FEATURE_TDX_GUEST & 31)) #endif =20 +#ifdef CONFIG_X86_USER_SHADOW_STACK +#define DISABLE_USER_SHSTK 0 +#else +#define DISABLE_USER_SHSTK (1 << (X86_FEATURE_USER_SHSTK & 31)) +#endif + /* * Make sure to add features to the correct mask */ @@ -114,7 +120,7 @@ #define DISABLED_MASK9 (DISABLE_SGX) #define DISABLED_MASK10 0 #define DISABLED_MASK11 (DISABLE_RETPOLINE|DISABLE_RETHUNK|DISABLE_UNRET| \ - DISABLE_CALL_DEPTH_TRACKING) + DISABLE_CALL_DEPTH_TRACKING|DISABLE_USER_SHSTK) #define DISABLED_MASK12 0 #define DISABLED_MASK13 0 #define DISABLED_MASK14 0 diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-d= eps.c index f6748c8bd647..e462c1d3800a 100644 --- a/arch/x86/kernel/cpu/cpuid-deps.c +++ b/arch/x86/kernel/cpu/cpuid-deps.c @@ -81,6 +81,7 @@ static const struct cpuid_dep cpuid_deps[] =3D { { X86_FEATURE_XFD, X86_FEATURE_XSAVES }, { X86_FEATURE_XFD, X86_FEATURE_XGETBV1 }, { X86_FEATURE_AMX_TILE, X86_FEATURE_XFD }, + { X86_FEATURE_SHSTK, X86_FEATURE_XSAVES }, {} }; =20 --=20 2.17.1