From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752910AbdKHTrq (ORCPT ); Wed, 8 Nov 2017 14:47:46 -0500 Received: from mga11.intel.com ([192.55.52.93]:22725 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752852AbdKHTrj (ORCPT ); Wed, 8 Nov 2017 14:47:39 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,365,1505804400"; d="scan'208";a="173401961" Subject: [PATCH 14/30] x86, kaiser: map espfix structures To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, dave.hansen@linux.intel.com, moritz.lipp@iaik.tugraz.at, daniel.gruss@iaik.tugraz.at, michael.schwarz@iaik.tugraz.at, richard.fellner@student.tugraz.at, luto@kernel.org, torvalds@linux-foundation.org, keescook@google.com, hughd@google.com, x86@kernel.org From: Dave Hansen Date: Wed, 08 Nov 2017 11:47:11 -0800 References: <20171108194646.907A1942@viggo.jf.intel.com> In-Reply-To: <20171108194646.907A1942@viggo.jf.intel.com> Message-Id: <20171108194711.7939CA37@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Hansen We have some rather arcane code to help when we IRET to 16-bit segments: the "espfix" code. This consists of a few per-cpu variables: espfix_stack: tells us where we allocated the stack (the bottom) espfix_waddr: tells us where we can actually point %rsp and the stack itself. We need all three things mapped for this to work. Note: the espfix code runs with a kernel GSBASE, but user (shadow) page tables. We could switch to the kernel page tables here and then not have to map any of this, but just user-pagetable-mapping is simpler. To switch over to the kernel copy, we would need some temporary storage which is in short supply at this point. The original KAISER patch missed this case. Signed-off-by: Dave Hansen Cc: Moritz Lipp Cc: Daniel Gruss Cc: Michael Schwarz Cc: Richard Fellner Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Kees Cook Cc: Hugh Dickins Cc: x86@kernel.org --- b/arch/x86/kernel/espfix_64.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff -puN arch/x86/kernel/espfix_64.c~kaiser-user-map-espfix arch/x86/kernel/espfix_64.c --- a/arch/x86/kernel/espfix_64.c~kaiser-user-map-espfix 2017-11-08 10:45:33.465681385 -0800 +++ b/arch/x86/kernel/espfix_64.c 2017-11-08 10:45:33.469681385 -0800 @@ -33,6 +33,7 @@ #include #include +#include #include #include #include @@ -41,7 +42,6 @@ #include #include #include -#include /* * Note: we only need 6*8 = 48 bytes for the espfix stack, but round @@ -61,8 +61,8 @@ #define PGALLOC_GFP (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO) /* This contains the *bottom* address of the espfix stack */ -DEFINE_PER_CPU_READ_MOSTLY(unsigned long, espfix_stack); -DEFINE_PER_CPU_READ_MOSTLY(unsigned long, espfix_waddr); +DEFINE_PER_CPU_USER_MAPPED(unsigned long, espfix_stack); +DEFINE_PER_CPU_USER_MAPPED(unsigned long, espfix_waddr); /* Initialization mutex - should this be a spinlock? */ static DEFINE_MUTEX(espfix_init_mutex); @@ -225,4 +225,10 @@ done: per_cpu(espfix_stack, cpu) = addr; per_cpu(espfix_waddr, cpu) = (unsigned long)stack_page + (addr & ~PAGE_MASK); + /* + * _PAGE_GLOBAL is not really required. This is not a hot + * path, but we do it here for consistency. + */ + kaiser_add_mapping((unsigned long)stack_page, PAGE_SIZE, + __PAGE_KERNEL | _PAGE_GLOBAL); } _