From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752786AbbC0PJh (ORCPT ); Fri, 27 Mar 2015 11:09:37 -0400 Received: from mail.skyhub.de ([78.46.96.112]:55470 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752189AbbC0PJd (ORCPT ); Fri, 27 Mar 2015 11:09:33 -0400 Date: Fri, 27 Mar 2015 16:07:43 +0100 From: Borislav Petkov To: Dave Hansen Cc: linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, dave.hansen@linux.intel.com Subject: Re: [PATCH 08/17] x86, mpx: boot-time disable Message-ID: <20150327150743.GA5517@pd.tnic> References: <20150326183327.64807530@viggo.jf.intel.com> <20150326183343.F64975EC@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20150326183343.F64975EC@viggo.jf.intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 26, 2015 at 11:33:43AM -0700, Dave Hansen wrote: > > From: Dave Hansen > > MPX has the _potential_ to cause some issues. Say part of your init > system tried to protect one of its components from buffer overflows > with MPX. If there were a false positive, it's possible that MPX > could keep a system from booting. > > MPX could also potentially cause performance issues since it is > present in hot paths like the unmap path. > > Allow it to be disabled at boot time. > > Signed-off-by: Dave Hansen > --- > > b/Documentation/kernel-parameters.txt | 4 ++++ > b/arch/x86/kernel/cpu/common.c | 16 ++++++++++++++++ > 2 files changed, 20 insertions(+) > > diff -puN arch/x86/kernel/cpu/common.c~x86-mpx-disable-boot-time arch/x86/kernel/cpu/common.c > --- a/arch/x86/kernel/cpu/common.c~x86-mpx-disable-boot-time 2015-03-26 11:27:31.269400935 -0700 > +++ b/arch/x86/kernel/cpu/common.c 2015-03-26 11:27:31.275401206 -0700 > @@ -172,6 +172,22 @@ static int __init x86_xsaves_setup(char > } > __setup("noxsaves", x86_xsaves_setup); > > +static int __init x86_mpx_setup(char *s) > +{ > + /* require an exact match without trailing characters */ > + if (strlen(s)) > + return 0; > + > + /* do not emit a message if the feature is not present */ > + if (!boot_cpu_has(X86_FEATURE_MPX)) > + return 1; > + > + setup_clear_cpu_cap(X86_FEATURE_MPX); > + printk("nompx: Intel Memory Protection Extensions (MPX) disabled\n"); WARNING: printk() should include KERN_ facility level #52: FILE: arch/x86/kernel/cpu/common.c:186: + printk("nompx: Intel Memory Protection Extensions (MPX) disabled\n"); checkpatch is sometimes right. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. --