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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 6CF90C64EB8 for ; Tue, 9 Oct 2018 15:06:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3A57C214C4 for ; Tue, 9 Oct 2018 15:06:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3A57C214C4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zytor.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726976AbeJIWXh (ORCPT ); Tue, 9 Oct 2018 18:23:37 -0400 Received: from terminus.zytor.com ([198.137.202.136]:59127 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726563AbeJIWXh (ORCPT ); Tue, 9 Oct 2018 18:23:37 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id w99F5tGP1083804 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Tue, 9 Oct 2018 08:05:55 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w99F5sGt1083801; Tue, 9 Oct 2018 08:05:54 -0700 Date: Tue, 9 Oct 2018 08:05:54 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Dave Hansen Message-ID: Cc: peterz@infradead.org, mingo@kernel.org, tglx@linutronix.de, dave.hansen@linux.intel.com, jannh@google.com, linux-kernel@vger.kernel.org, hpa@zytor.com, luto@kernel.org, sean.j.christopherson@intel.com Reply-To: tglx@linutronix.de, dave.hansen@linux.intel.com, sean.j.christopherson@intel.com, jannh@google.com, linux-kernel@vger.kernel.org, hpa@zytor.com, luto@kernel.org, peterz@infradead.org, mingo@kernel.org In-Reply-To: <20180928160231.243A0D6A@viggo.jf.intel.com> References: <20180928160231.243A0D6A@viggo.jf.intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/mm] x86/mm: Remove spurious fault pkey check Git-Commit-ID: 367e3f1d3fc9bbf1e626da7aea527f40babf8079 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 367e3f1d3fc9bbf1e626da7aea527f40babf8079 Gitweb: https://git.kernel.org/tip/367e3f1d3fc9bbf1e626da7aea527f40babf8079 Author: Dave Hansen AuthorDate: Fri, 28 Sep 2018 09:02:31 -0700 Committer: Peter Zijlstra CommitDate: Tue, 9 Oct 2018 16:51:16 +0200 x86/mm: Remove spurious fault pkey check Spurious faults only ever occur in the kernel's address space. They are also constrained specifically to faults with one of these error codes: X86_PF_WRITE | X86_PF_PROT X86_PF_INSTR | X86_PF_PROT So, it's never even possible to reach spurious_kernel_fault_check() with X86_PF_PK set. In addition, the kernel's address space never has pages with user-mode protections. Protection Keys are only enforced on pages with user-mode protection. This gives us lots of reasons to not check for protection keys in our sprurious kernel fault handling. But, let's also add some warnings to ensure that these assumptions about protection keys hold true. Cc: x86@kernel.org Cc: Jann Horn Cc: Sean Christopherson Cc: Thomas Gleixner Cc: Andy Lutomirski Signed-off-by: Dave Hansen Signed-off-by: Peter Zijlstra (Intel) Link: http://lkml.kernel.org/r/20180928160231.243A0D6A@viggo.jf.intel.com --- arch/x86/mm/fault.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 7e0fa7e24168..a16652982f98 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1037,12 +1037,6 @@ static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte) if ((error_code & X86_PF_INSTR) && !pte_exec(*pte)) return 0; - /* - * Note: We do not do lazy flushing on protection key - * changes, so no spurious fault will ever set X86_PF_PK. - */ - if ((error_code & X86_PF_PK)) - return 1; return 1; } @@ -1217,6 +1211,13 @@ static void do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code, unsigned long address) { + /* + * Protection keys exceptions only happen on user pages. We + * have no user pages in the kernel portion of the address + * space, so do not expect them here. + */ + WARN_ON_ONCE(hw_error_code & X86_PF_PK); + /* * We can fault-in kernel-space virtual memory on-demand. The * 'reference' page table is init_mm.pgd.