From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932718AbdC2STf (ORCPT ); Wed, 29 Mar 2017 14:19:35 -0400 Received: from mail-pg0-f48.google.com ([74.125.83.48]:36329 "EHLO mail-pg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753003AbdC2SQX (ORCPT ); Wed, 29 Mar 2017 14:16:23 -0400 From: Kees Cook To: kernel-hardening@lists.openwall.com Cc: Kees Cook , Mark Rutland , Andy Lutomirski , Hoeun Ryu , PaX Team , Emese Revfy , Russell King , x86@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Date: Wed, 29 Mar 2017 11:15:56 -0700 Message-Id: <1490811363-93944-5-git-send-email-keescook@chromium.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1490811363-93944-1-git-send-email-keescook@chromium.org> References: <1490811363-93944-1-git-send-email-keescook@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Based on PaX's x86 pax_{open,close}_kernel() implementation, this allows HAVE_ARCH_RARE_WRITE to work on x86. There is missing work to sort out some header file issues where preempt.h is missing, though it can't be included in pg_table.h unconditionally... some other solution will be needed, perhaps an entirely separate header file for rare_write()-related defines... This patch is also missing paravirt support. Signed-off-by: Kees Cook --- arch/x86/Kconfig | 1 + arch/x86/include/asm/pgtable.h | 31 +++++++++++++++++++++++++++++++ 2 files changed, 32 insertions(+) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index cc98d5a294ee..2d1d707aa036 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -106,6 +106,7 @@ config X86 select HAVE_ARCH_KMEMCHECK select HAVE_ARCH_MMAP_RND_BITS if MMU select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT + select HAVE_ARCH_RARE_WRITE select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_TRACEHOOK select HAVE_ARCH_TRANSPARENT_HUGEPAGE diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 1cfb36b8c024..2e6bf661bb84 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -91,6 +91,37 @@ extern struct mm_struct *pgd_page_get_mm(struct page *page); #endif /* CONFIG_PARAVIRT */ +/* TODO: Bad hack to deal with preempt macros being missing sometimes. */ +#ifndef preempt_disable +#include +#endif + +static __always_inline unsigned long __arch_rare_write_begin(void) +{ + unsigned long cr0; + + preempt_disable(); + barrier(); + cr0 = read_cr0() ^ X86_CR0_WP; + BUG_ON(cr0 & X86_CR0_WP); + write_cr0(cr0); + barrier(); + return cr0 ^ X86_CR0_WP; +} + +static __always_inline unsigned long __arch_rare_write_end(void) +{ + unsigned long cr0; + + barrier(); + cr0 = read_cr0() ^ X86_CR0_WP; + BUG_ON(!(cr0 & X86_CR0_WP)); + write_cr0(cr0); + barrier(); + preempt_enable_no_resched(); + return cr0 ^ X86_CR0_WP; +} + /* * The following only work if pte_present() is true. * Undefined behaviour if not.. -- 2.7.4