Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754172AbbGIR6C (ORCPT ); Thu, 9 Jul 2015 13:58:02 -0400 Received: from mail-la0-f50.google.com ([209.85.215.50]:34023 "EHLO mail-la0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754084AbbGIR5Z (ORCPT ); Thu, 9 Jul 2015 13:57:25 -0400 MIME-Version: 1.0 In-Reply-To: <20150709090327.GA16677@amd> References: <23d4709cee2fe92c32d41b99c7a3c1823725925a.1436312944.git.luto@kernel.org> <559C8BFE.6050604@linux.intel.com> <20150709090327.GA16677@amd> From: Andy Lutomirski Date: Thu, 9 Jul 2015 10:57:03 -0700 Message-ID: Subject: Re: [PATCH] x86/kconfig/32: Mark CONFIG_VM86 as BROKEN To: Pavel Machek Cc: Thomas Gleixner , Kees Cook , Borislav Petkov , Arjan van de Ven , Oleg Nesterov , LKML , X86 ML , Linus Torvalds , Peter Zijlstra Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2924 Lines: 69 On Jul 9, 2015 2:03 AM, "Pavel Machek" wrote: > > On Wed 2015-07-08 16:00:48, Thomas Gleixner wrote: > > On Tue, 7 Jul 2015, Arjan van de Ven wrote: > > > > > On 7/7/2015 6:25 PM, Andy Lutomirski wrote: > > > > VM86 is entirely broken if ptrace, syscall auditing, or NOHZ_FULL is > > > > in use. The code is a big undocumented mess, it's a real PITA to > > > > test, and it looks like a big chunk of vm86_32.c is dead code. It > > > > also plays awful games with the entry asm. > > > > > > > > No one should be using it anyway. Use DOSBOX or KVM instead. > > > > > > > > Mark it BROKEN. I want to remove some (obviously incorrect) exit > > > > asm that it depends on, and I don't want to figure out how to run > > > > severely obsolete programs just to test something that no one uses > > > > for anything other than exploits anyway. > > > > > > > > > > while it is never great to deprecate features, in this case I am not sure > > > there is another choice unless someone steps up to seriously revamp this code. > > > (and look at it from a PREEMPT, NO_HZ etc etc angle) > > > > Aside of being broken in so many aspects it's even more obsolete than > > 386 support, we should just remove it right away. > > Bad news for you: > > vbetool-0.5/lrmi.c:#include > vbetool-0.5/lrmi.c:#include > vbetool-0.5/lrmi.c:#include > vbetool-0.5/lrmi.c: struct vm86_struct vm; > vbetool-0.5/lrmi.c: struct vm86_init_args init; > ... > vbetool-0.5/lrmi.c:lrmi_vm86(struct vm86_struct *vm) > vbetool-0.5/lrmi.c:#define lrmi_vm86 vm86 > vbetool-0.5/lrmi.c: fputs("vm86() failed\n", stderr); > vbetool-0.5/lrmi.c:run_vm86(void) > vbetool-0.5/lrmi.c: vret = lrmi_vm86(&context.vm); > vbetool-0.5/lrmi.c:vm86_callback(int sig, int code, struct sigcontext > *sc) > vbetool-0.5/lrmi.c:vm86_callback(int sig, int code, struct sigcontext > *sc) > vbetool-0.5/lrmi.c:run_vm86(void) > vbetool-0.5/lrmi.c: fprintf(stderr, "run_vm86: callback > already installed\n"); > > vbetool depends on it, and s2ram depends on vbetool. When we get > proper kernel drivers, this one will be solved, but it is not "more > obsolete than 386". > vmetool has an x86 emulator. As far as I know, it's been there for a long time, and I'd be surprised if it doesn't work on CONFIG_VM86=n kernels. That being said, the code is kind of tangled and it's not quite clear to me what's going on. See: http://www.codon.org.uk/~mjg59/libx86/ Perhaps we should instead move CONFIG_VM86 out of EXPERT, default it to n, and suggest that everyone running a reasonably modern distro (2006 and up?) turn it off. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/