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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 C5873C35247 for ; Wed, 5 Feb 2020 18:22:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8D6D0217F4 for ; Wed, 5 Feb 2020 18:22:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727880AbgBESWD (ORCPT ); Wed, 5 Feb 2020 13:22:03 -0500 Received: from mga14.intel.com ([192.55.52.115]:20940 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727779AbgBESU2 (ORCPT ); Wed, 5 Feb 2020 13:20:28 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Feb 2020 10:20:26 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,406,1574150400"; d="scan'208";a="279447778" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by FMSMGA003.fm.intel.com with ESMTP; 05 Feb 2020 10:20:26 -0800 From: Yu-cheng Yu 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 , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , x86-patch-review@intel.com Cc: Yu-cheng Yu Subject: [RFC PATCH v9 09/27] x86/mm: Introduce _PAGE_DIRTY_SW Date: Wed, 5 Feb 2020 10:19:17 -0800 Message-Id: <20200205181935.3712-10-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20200205181935.3712-1-yu-cheng.yu@intel.com> References: <20200205181935.3712-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org When Shadow Stack (SHSTK) is introduced, a R/O and Dirty PTE exists in the following cases: (a) A modified, copy-on-write (COW) page; (b) A R/O page that has been COW'ed; (c) A SHSTK page. To separate non-SHSTK memory from SHSTK, introduce a spare bit of the 64-bit PTE as _PAGE_BIT_DIRTY_SW and use that for case (a) and (b). This results in the following possible settings: Modified PTE: (R/W + DIRTY_HW) Modified and COW PTE: (R/O + DIRTY_SW) R/O PTE COW'ed: (R/O + DIRTY_SW) SHSTK PTE: (R/O + DIRTY_HW) SHSTK shared PTE[1]: (R/O + DIRTY_SW) SHSTK PTE COW'ed: (R/O + DIRTY_HW) [1] When a SHSTK page is being shared among threads, its PTE is cleared of _PAGE_DIRTY_HW, so the next SHSTK access causes a fault, and the page is duplicated and _PAGE_DIRTY_HW is set again. With this, in pte_wrprotect(), if SHSTK is active, use _PAGE_DIRTY_SW for the Dirty bit, and in pte_mkwrite() use _PAGE_DIRTY_HW. The same changes apply to pmd and pud. When this patch is applied, there are six free bits left in the 64-bit PTE. There are no more free bits in the 32-bit PTE (except for PAE) and SHSTK is not implemented for the 32-bit kernel. v9: - Remove pte_move_flags() etc. and put the logic directly in pte_wrprotect()/pte_mkwrite() etc. - Change compile-time conditionals to run-time checks. - Split out pte_modify()/pmd_modify() to a new patch. - Update comments. Signed-off-by: Yu-cheng Yu --- arch/x86/include/asm/pgtable.h | 111 ++++++++++++++++++++++++--- arch/x86/include/asm/pgtable_types.h | 31 +++++++- 2 files changed, 131 insertions(+), 11 deletions(-) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index ab50d25f9afc..62aeb118bc36 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -120,9 +120,9 @@ extern pmdval_t early_pmd_flags; * The following only work if pte_present() is true. * Undefined behaviour if not.. */ -static inline int pte_dirty(pte_t pte) +static inline bool pte_dirty(pte_t pte) { - return pte_flags(pte) & _PAGE_DIRTY_HW; + return pte_flags(pte) & _PAGE_DIRTY_BITS; } @@ -159,9 +159,9 @@ static inline int pte_young(pte_t pte) return pte_flags(pte) & _PAGE_ACCESSED; } -static inline int pmd_dirty(pmd_t pmd) +static inline bool pmd_dirty(pmd_t pmd) { - return pmd_flags(pmd) & _PAGE_DIRTY_HW; + return pmd_flags(pmd) & _PAGE_DIRTY_BITS; } static inline int pmd_young(pmd_t pmd) @@ -169,9 +169,9 @@ static inline int pmd_young(pmd_t pmd) return pmd_flags(pmd) & _PAGE_ACCESSED; } -static inline int pud_dirty(pud_t pud) +static inline bool pud_dirty(pud_t pud) { - return pud_flags(pud) & _PAGE_DIRTY_HW; + return pud_flags(pud) & _PAGE_DIRTY_BITS; } static inline int pud_young(pud_t pud) @@ -312,7 +312,7 @@ static inline pte_t pte_clear_flags(pte_t pte, pteval_t clear) static inline pte_t pte_mkclean(pte_t pte) { - return pte_clear_flags(pte, _PAGE_DIRTY_HW); + return pte_clear_flags(pte, _PAGE_DIRTY_BITS); } static inline pte_t pte_mkold(pte_t pte) @@ -322,6 +322,17 @@ static inline pte_t pte_mkold(pte_t pte) static inline pte_t pte_wrprotect(pte_t pte) { + /* + * Use _PAGE_DIRTY_SW on a R/O PTE to set it apart from + * a Shadow Stack PTE, which is R/O + _PAGE_DIRTY_HW. + */ + if (static_cpu_has(X86_FEATURE_SHSTK)) { + if (pte_flags(pte) & _PAGE_DIRTY_HW) { + pte = pte_clear_flags(pte, _PAGE_DIRTY_HW); + pte = pte_set_flags(pte, _PAGE_DIRTY_SW); + } + } + return pte_clear_flags(pte, _PAGE_RW); } @@ -332,9 +343,25 @@ static inline pte_t pte_mkexec(pte_t pte) static inline pte_t pte_mkdirty(pte_t pte) { + pteval_t dirty = _PAGE_DIRTY_HW; + + if (static_cpu_has(X86_FEATURE_SHSTK) && !pte_write(pte)) + dirty = _PAGE_DIRTY_SW; + + return pte_set_flags(pte, dirty | _PAGE_SOFT_DIRTY); +} + +static inline pte_t pte_mkdirty_shstk(pte_t pte) +{ + pte = pte_clear_flags(pte, _PAGE_DIRTY_SW); return pte_set_flags(pte, _PAGE_DIRTY_HW | _PAGE_SOFT_DIRTY); } +static inline bool pte_dirty_hw(pte_t pte) +{ + return pte_flags(pte) & _PAGE_DIRTY_HW; +} + static inline pte_t pte_mkyoung(pte_t pte) { return pte_set_flags(pte, _PAGE_ACCESSED); @@ -342,6 +369,13 @@ static inline pte_t pte_mkyoung(pte_t pte) static inline pte_t pte_mkwrite(pte_t pte) { + if (static_cpu_has(X86_FEATURE_SHSTK)) { + if (pte_flags(pte) & _PAGE_DIRTY_SW) { + pte = pte_clear_flags(pte, _PAGE_DIRTY_SW); + pte = pte_set_flags(pte, _PAGE_DIRTY_HW); + } + } + return pte_set_flags(pte, _PAGE_RW); } @@ -396,19 +430,46 @@ static inline pmd_t pmd_mkold(pmd_t pmd) static inline pmd_t pmd_mkclean(pmd_t pmd) { - return pmd_clear_flags(pmd, _PAGE_DIRTY_HW); + return pmd_clear_flags(pmd, _PAGE_DIRTY_BITS); } static inline pmd_t pmd_wrprotect(pmd_t pmd) { + /* + * Use _PAGE_DIRTY_SW on a R/O PMD to set it apart from + * a Shadow Stack PTE, which is R/O + _PAGE_DIRTY_HW. + */ + if (static_cpu_has(X86_FEATURE_SHSTK)) { + if (pmd_flags(pmd) & _PAGE_DIRTY_HW) { + pmd = pmd_clear_flags(pmd, _PAGE_DIRTY_HW); + pmd = pmd_set_flags(pmd, _PAGE_DIRTY_SW); + } + } + return pmd_clear_flags(pmd, _PAGE_RW); } static inline pmd_t pmd_mkdirty(pmd_t pmd) { + pmdval_t dirty = _PAGE_DIRTY_HW; + + if (static_cpu_has(X86_FEATURE_SHSTK) && !(pmd_flags(pmd) & _PAGE_RW)) + dirty = _PAGE_DIRTY_SW; + + return pmd_set_flags(pmd, dirty | _PAGE_SOFT_DIRTY); +} + +static inline pmd_t pmd_mkdirty_shstk(pmd_t pmd) +{ + pmd = pmd_clear_flags(pmd, _PAGE_DIRTY_SW); return pmd_set_flags(pmd, _PAGE_DIRTY_HW | _PAGE_SOFT_DIRTY); } +static inline bool pmd_dirty_hw(pmd_t pmd) +{ + return pmd_flags(pmd) & _PAGE_DIRTY_HW; +} + static inline pmd_t pmd_mkdevmap(pmd_t pmd) { return pmd_set_flags(pmd, _PAGE_DEVMAP); @@ -426,6 +487,13 @@ static inline pmd_t pmd_mkyoung(pmd_t pmd) static inline pmd_t pmd_mkwrite(pmd_t pmd) { + if (static_cpu_has(X86_FEATURE_SHSTK)) { + if (pmd_flags(pmd) & _PAGE_DIRTY_SW) { + pmd = pmd_clear_flags(pmd, _PAGE_DIRTY_SW); + pmd = pmd_set_flags(pmd, _PAGE_DIRTY_HW); + } + } + return pmd_set_flags(pmd, _PAGE_RW); } @@ -450,17 +518,33 @@ static inline pud_t pud_mkold(pud_t pud) static inline pud_t pud_mkclean(pud_t pud) { - return pud_clear_flags(pud, _PAGE_DIRTY_HW); + return pud_clear_flags(pud, _PAGE_DIRTY_BITS); } static inline pud_t pud_wrprotect(pud_t pud) { + /* + * Use _PAGE_DIRTY_SW on a R/O PUD to set it apart from + * a Shadow Stack PTE, which is R/O + _PAGE_DIRTY_HW. + */ + if (static_cpu_has(X86_FEATURE_SHSTK)) { + if (pud_flags(pud) & _PAGE_DIRTY_HW) { + pud = pud_clear_flags(pud, _PAGE_DIRTY_HW); + pud = pud_set_flags(pud, _PAGE_DIRTY_SW); + } + } + return pud_clear_flags(pud, _PAGE_RW); } static inline pud_t pud_mkdirty(pud_t pud) { - return pud_set_flags(pud, _PAGE_DIRTY_HW | _PAGE_SOFT_DIRTY); + pudval_t dirty = _PAGE_DIRTY_HW; + + if (static_cpu_has(X86_FEATURE_SHSTK) && !(pud_flags(pud) & _PAGE_RW)) + dirty = _PAGE_DIRTY_SW; + + return pud_set_flags(pud, dirty | _PAGE_SOFT_DIRTY); } static inline pud_t pud_mkdevmap(pud_t pud) @@ -480,6 +564,13 @@ static inline pud_t pud_mkyoung(pud_t pud) static inline pud_t pud_mkwrite(pud_t pud) { + if (static_cpu_has(X86_FEATURE_SHSTK)) { + if (pud_flags(pud) & _PAGE_DIRTY_SW) { + pud = pud_clear_flags(pud, _PAGE_DIRTY_SW); + pud = pud_set_flags(pud, _PAGE_DIRTY_HW); + } + } + return pud_set_flags(pud, _PAGE_RW); } diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h index e647e3c75578..826823df917f 100644 --- a/arch/x86/include/asm/pgtable_types.h +++ b/arch/x86/include/asm/pgtable_types.h @@ -23,7 +23,8 @@ #define _PAGE_BIT_SOFTW2 10 /* " */ #define _PAGE_BIT_SOFTW3 11 /* " */ #define _PAGE_BIT_PAT_LARGE 12 /* On 2MB or 1GB pages */ -#define _PAGE_BIT_SOFTW4 58 /* available for programmer */ +#define _PAGE_BIT_SOFTW4 57 /* available for programmer */ +#define _PAGE_BIT_SOFTW5 58 /* available for programmer */ #define _PAGE_BIT_PKEY_BIT0 59 /* Protection Keys, bit 1/4 */ #define _PAGE_BIT_PKEY_BIT1 60 /* Protection Keys, bit 2/4 */ #define _PAGE_BIT_PKEY_BIT2 61 /* Protection Keys, bit 3/4 */ @@ -35,6 +36,12 @@ #define _PAGE_BIT_SOFT_DIRTY _PAGE_BIT_SOFTW3 /* software dirty tracking */ #define _PAGE_BIT_DEVMAP _PAGE_BIT_SOFTW4 +/* + * This bit indicates a copy-on-write page, and is different from + * _PAGE_BIT_SOFT_DIRTY, which tracks which pages a task writes to. + */ +#define _PAGE_BIT_DIRTY_SW _PAGE_BIT_SOFTW5 /* was written to */ + /* If _PAGE_BIT_PRESENT is clear, we use these: */ /* - if the user mapped it with PROT_NONE; pte_present gives true */ #define _PAGE_BIT_PROTNONE _PAGE_BIT_GLOBAL @@ -108,6 +115,28 @@ #define _PAGE_DEVMAP (_AT(pteval_t, 0)) #endif +/* A R/O and dirty PTE exists in the following cases: + * (a) A modified, copy-on-write (COW) page; + * (b) A R/O page that has been COW'ed; + * (c) A SHSTK page. + * _PAGE_DIRTY_SW is used to separate case (c) from others. + * This results in the following settings: + * + * Modified PTE: (R/W + DIRTY_HW) + * Modified and COW PTE: (R/O + DIRTY_SW) + * R/O PTE COW'ed: (R/O + DIRTY_SW) + * SHSTK PTE: (R/O + DIRTY_HW) + * SHSTK PTE COW'ed: (R/O + DIRTY_HW) + * SHSTK PTE being shared among threads: (R/O + DIRTY_SW) + */ +#ifdef CONFIG_X86_INTEL_SHADOW_STACK_USER +#define _PAGE_DIRTY_SW (_AT(pteval_t, 1) << _PAGE_BIT_DIRTY_SW) +#else +#define _PAGE_DIRTY_SW (_AT(pteval_t, 0)) +#endif + +#define _PAGE_DIRTY_BITS (_PAGE_DIRTY_HW | _PAGE_DIRTY_SW) + #define _PAGE_PROTNONE (_AT(pteval_t, 1) << _PAGE_BIT_PROTNONE) #define _PAGE_TABLE_NOENC (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER |\ -- 2.21.0