From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760017Ab2FURiA (ORCPT ); Thu, 21 Jun 2012 13:38:00 -0400 Received: from terminus.zytor.com ([198.137.202.10]:51367 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760000Ab2FURh6 (ORCPT ); Thu, 21 Jun 2012 13:37:58 -0400 Date: Thu, 21 Jun 2012 10:37:45 -0700 From: "tip-bot for H. Peter Anvin" Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, tglx@linutronix.de In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/reboot] x86-64, reboot: Be more paranoid in 64-bit reboot =bios Git-Commit-ID: 9751d7627582fc1cc64625d63bde9528c14f1544 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 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.6 (terminus.zytor.com [127.0.0.1]); Thu, 21 Jun 2012 10:37:51 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 9751d7627582fc1cc64625d63bde9528c14f1544 Gitweb: http://git.kernel.org/tip/9751d7627582fc1cc64625d63bde9528c14f1544 Author: H. Peter Anvin AuthorDate: Thu, 21 Jun 2012 10:25:03 -0700 Committer: H. Peter Anvin CommitDate: Thu, 21 Jun 2012 10:25:03 -0700 x86-64, reboot: Be more paranoid in 64-bit reboot=bios Be a bit more paranoid in the transition back to 16-bit mode. In particular, in case the kernel is residing above the 4 GiB mark, switch to the trampoline GDT, and make the jump after turning off paging a far jump. In theory, none of this should matter, but it is exactly the kind of things that broken SMM or virtualization software could trip up on. Signed-off-by: H. Peter Anvin Link: http://lkml.kernel.org/r/tip-jopx7y6g6dbcx4tpal8q0jlr@git.kernel.org --- arch/x86/realmode/rm/reboot.S | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/realmode/rm/reboot.S b/arch/x86/realmode/rm/reboot.S index 6bf8fea..f932ea6 100644 --- a/arch/x86/realmode/rm/reboot.S +++ b/arch/x86/realmode/rm/reboot.S @@ -22,14 +22,18 @@ ENTRY(machine_real_restart_asm) #ifdef CONFIG_X86_64 + /* Switch to trampoline GDT as it is guaranteed < 4 GiB */ + movl $__KERNEL_DS, %eax + movl %eax, %ds + lgdtl pa_tr_gdt /* Disable paging to drop us out of long mode */ movl %cr0, %eax andl $~X86_CR0_PG, %eax movl %eax, %cr0 - jmp 1f /* "A branch" may be needed here, assume near is OK */ + ljmpl $__KERNEL32_CS, $pa_machine_real_restart_paging_off -1: +GLOBAL(machine_real_restart_paging_off) xorl %eax, %eax xorl %edx, %edx movl $MSR_EFER, %ecx