Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752588AbbGMShK (ORCPT ); Mon, 13 Jul 2015 14:37:10 -0400 Received: from mail-la0-f52.google.com ([209.85.215.52]:35980 "EHLO mail-la0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751853AbbGMShI (ORCPT ); Mon, 13 Jul 2015 14:37:08 -0400 MIME-Version: 1.0 In-Reply-To: References: <1436591360-16210-1-git-send-email-brgerst@gmail.com> <1436591360-16210-2-git-send-email-brgerst@gmail.com> From: Andy Lutomirski Date: Mon, 13 Jul 2015 11:36:47 -0700 Message-ID: Subject: Re: [PATCH 1/5] x86/vm86: Move userspace accesses to do_sys_vm86() To: Brian Gerst Cc: X86 ML , "linux-kernel@vger.kernel.org" , Ingo Molnar , "H. Peter Anvin" , Denys Vlasenko , Linus Torvalds 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: 2141 Lines: 49 On Mon, Jul 13, 2015 at 9:45 AM, Brian Gerst wrote: > On Sat, Jul 11, 2015 at 12:37 PM, Andy Lutomirski wrote: >> On Fri, Jul 10, 2015 at 10:09 PM, Brian Gerst wrote: >>> Move the userspace accesses down into the common function in >>> preparation for the next set of patches. >>> >> >> One thing I don't like about the current code that makes these patches >> harder to review is the bizarre approach to copying. If you changed >> this: >> >>> - tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs, >>> - offsetof(struct kernel_vm86_struct, vm86plus) - >>> - sizeof(info.regs)); >> >> into a normal field-by-field get_user / copy_from_user (the latter for >> the big regs struct) then it would be clear what the ABI is and it >> would be much easier to read the patches and confirm that you aren't >> accidentally changing the ABI. >> >> You could also get rid of the constraint that certain fields in >> apparently kernel-internal structs had to be in a certain order. >> >> Other than that, patches 1-4 look good on cursory inspection. I'll >> look more carefully later. I need to think about patch 5 more. >> >> --Andy > > Any other comments before I start working on v2? > Nothing major. I'm a bit nervous about leaving ds, es, fs, and gs in pt_regs more or less undefined until save_v86_state happens, but it's unlikely that there's any ABI to break there. The results from perf might be a bit odd with your patches applied. Of course, they're probably useless without your patch. It might also be worth renaming save_v86_state in patch 5. Do your patches pass my upgraded entry_from_vm86 test? You're changing handle_vm86_trap so it always returns, which may have unexpected side effects (or I missed something in your patch). --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/