From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756842AbaJ1LPf (ORCPT ); Tue, 28 Oct 2014 07:15:35 -0400 Received: from terminus.zytor.com ([198.137.202.10]:51393 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752758AbaJ1LPc (ORCPT ); Tue, 28 Oct 2014 07:15:32 -0400 Date: Tue, 28 Oct 2014 04:15:22 -0700 From: tip-bot for Andy Lutomirski Message-ID: Cc: tglx@linutronix.de, mingo@kernel.org, linux-kernel@vger.kernel.org, luto@amacapital.net, hpa@zytor.com Reply-To: mingo@kernel.org, tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org, luto@amacapital.net In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/vdso] x86/vdso: Make the PER_CPU segment start out accessed Git-Commit-ID: 9c0080ef93bce34db130db6dc3bd946348e6a203 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 9c0080ef93bce34db130db6dc3bd946348e6a203 Gitweb: http://git.kernel.org/tip/9c0080ef93bce34db130db6dc3bd946348e6a203 Author: Andy Lutomirski AuthorDate: Tue, 23 Sep 2014 10:50:54 -0700 Committer: Ingo Molnar CommitDate: Tue, 28 Oct 2014 11:22:11 +0100 x86/vdso: Make the PER_CPU segment start out accessed The first userspace attempt to read or write the PER_CPU segment will write the accessed bit to the GDT. This is visible to userspace using the LAR instruction, and it also pointlessly dirties a cache line. Set the segment's accessed bit at boot to prevent userspace access to segments from having side effects. Signed-off-by: Andy Lutomirski Link: http://lkml.kernel.org/r/ac63814ca4c637a08ec2fd0360d67ca67560a9ee.1411494540.git.luto@amacapital.net Signed-off-by: Ingo Molnar --- arch/x86/vdso/vma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c index 261b134..0c799746 100644 --- a/arch/x86/vdso/vma.c +++ b/arch/x86/vdso/vma.c @@ -264,7 +264,7 @@ static void vsyscall_set_cpu(int cpu) d = (struct desc_struct) { .limit0 = cpu | ((node & 0xf) << 12), .limit = node >> 4, - .type = 4, /* RO data, expand down */ + .type = 5, /* RO data, expand down, accessed */ .dpl = 3, /* Visible to user code */ .s = 1, /* Not a system segment */ .p = 1, /* Present */