From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753456AbdKXJQG (ORCPT ); Fri, 24 Nov 2017 04:16:06 -0500 Received: from mail-wm0-f65.google.com ([74.125.82.65]:43711 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753346AbdKXJPt (ORCPT ); Fri, 24 Nov 2017 04:15:49 -0500 X-Google-Smtp-Source: AGs4zMa/joVgIXnWpp/saJ5Kbro4e886hFXyxT7+7rjNL4RH7jXO9Wu7gH2udc+1dZHtOz5PqIhmIg== From: Ingo Molnar To: linux-kernel@vger.kernel.org Cc: Dave Hansen , Andy Lutomirski , Thomas Gleixner , "H . Peter Anvin" , Peter Zijlstra , Borislav Petkov , Linus Torvalds Subject: [PATCH 30/43] x86/mm/kaiser: Map espfix structures Date: Fri, 24 Nov 2017 10:14:35 +0100 Message-Id: <20171124091448.7649-31-mingo@kernel.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20171124091448.7649-1-mingo@kernel.org> References: <20171124091448.7649-1-mingo@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Hansen There is some rather arcane code to help when an IRET returns to 16-bit segments. It is referred to as the "espfix" code. This consists of a few per-cpu variables: espfix_stack: tells us where the stack is allocated (the bottom) espfix_waddr: tells us to where %rsp may be pointed (the top) These are in addition to the stack itself. All three things must be mapped for the espfix code to function. Note: the espfix code runs with a kernel GSBASE, but user (shadow) page tables. A switch to the kernel page tables could be performed instead of mapping these structures, but mapping them is simpler and less likely to break the assembly. To switch over to the kernel copy, additional temporary storage would be required which is in short supply in this context. The original KAISER patch missed this case. Signed-off-by: Dave Hansen Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Daniel Gruss Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Hugh Dickins Cc: Josh Poimboeuf Cc: Kees Cook Cc: Linus Torvalds Cc: Michael Schwarz Cc: Moritz Lipp Cc: Peter Zijlstra Cc: Richard Fellner Cc: Thomas Gleixner Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20171123003457.EB854D0D@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/espfix_64.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c index 4780dba2cc59..8bb116d73aaa 100644 --- a/arch/x86/kernel/espfix_64.c +++ b/arch/x86/kernel/espfix_64.c @@ -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 @@ void init_espfix_ap(int cpu) 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); } -- 2.14.1