From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935256Ab1JEVk4 (ORCPT ); Wed, 5 Oct 2011 17:40:56 -0400 Received: from filtteri1.pp.htv.fi ([213.243.153.184]:33247 "EHLO filtteri1.pp.htv.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754579Ab1JEVkz (ORCPT ); Wed, 5 Oct 2011 17:40:55 -0400 Date: Thu, 6 Oct 2011 00:40:47 +0300 From: Adrian Bunk To: Andrew Lutomirski , "H. Peter Anvin" Cc: Thomas Gleixner , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org, Andrew Morton Subject: [3.1 patch] x86: default to vsyscall=native Message-ID: <20111005214047.GE14406@localhost.pp.htv.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After upgrading a kernel the existing userspace should just work (assuming it did work before ;-) ), but when I upgraded my kernel from 3.0.4 to 3.1.0-rc8 a UML instance didn't come up properly. dmesg said: linux-2.6.30.1[3800] vsyscall fault (exploit attempt?) ip:ffffffffff600000 cs:33 sp:7fbfb9c498 ax:ffffffffff600000 si:0 di:606790 linux-2.6.30.1[3856] vsyscall fault (exploit attempt?) ip:ffffffffff600000 cs:33 sp:7fbfb13168 ax:ffffffffff600000 si:0 di:606790 Looking throught the changelog I ended up at commit 3ae36655 ("x86-64: Rework vsyscall emulation and add vsyscall= parameter"). Linus suggested in https://lkml.org/lkml/2011/8/9/376 to default to vsyscall=native. That sounds reasonable to me, and fixes the problem for me. Signed-off-by: Adrian Bunk Acked-by: Andrew Lutomirski --- Documentation/kernel-parameters.txt | 7 ++++--- arch/x86/kernel/vsyscall_64.c | 2 +- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 854ed5ca..d6e6724 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2706,10 +2706,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. functions are at fixed addresses, they make nice targets for exploits that can control RIP. - emulate [default] Vsyscalls turn into traps and are - emulated reasonably safely. + emulate Vsyscalls turn into traps and are emulated + reasonably safely. - native Vsyscalls are native syscall instructions. + native [default] Vsyscalls are native syscall + instructions. This is a little bit faster than trapping and makes a few dynamic recompilers work better than they would in emulation mode. diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c index 18ae83d..b56c65de 100644 --- a/arch/x86/kernel/vsyscall_64.c +++ b/arch/x86/kernel/vsyscall_64.c @@ -56,7 +56,7 @@ DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data) = .lock = __SEQLOCK_UNLOCKED(__vsyscall_gtod_data.lock), }; -static enum { EMULATE, NATIVE, NONE } vsyscall_mode = EMULATE; +static enum { EMULATE, NATIVE, NONE } vsyscall_mode = NATIVE; static int __init vsyscall_setup(char *str) { -- 1.7.6.3