From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753433AbbL2McH (ORCPT ); Tue, 29 Dec 2015 07:32:07 -0500 Received: from mail-ob0-f176.google.com ([209.85.214.176]:35249 "EHLO mail-ob0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753332AbbL2McD convert rfc822-to-8bit (ORCPT ); Tue, 29 Dec 2015 07:32:03 -0500 MIME-Version: 1.0 In-Reply-To: <56827B97.9060106@list.ru> References: <66cb936904b7ce56ddc1ce58119bd9683e4f3b43.1445822498.git.luto@kernel.org> <5634DD68.4090709@list.ru> <56827B97.9060106@list.ru> From: Andy Lutomirski Date: Tue, 29 Dec 2015 04:31:42 -0800 Message-ID: Subject: Re: [PATCH v2 1/4] x86/signal/64: Add a comment about sigcontext->fs and gs To: Stas Sergeev Cc: Denys Vlasenko , Borislav Petkov , Brian Gerst , "linux-kernel@vger.kernel.org" , X86 ML , Linus Torvalds Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 29, 2015 at 4:24 AM, Stas Sergeev wrote: > 08.12.2015 02:23, Andy Lutomirski пишет: >> On Oct 31, 2015 8:25 AM, "Stas Sergeev" wrote: >>> >>> 26.10.2015 04:25, Andy Lutomirski пишет: >>> >>>> These fields have a strange history. This tries to document it. >>>> >>>> This borrows from 9a036b93a344 ("x86/signal/64: Remove 'fs' and 'gs' >>>> from sigcontext"), which was reverted by ed596cde9425 ("Revert x86 >>>> sigcontext cleanups"). >>>> >>>> Signed-off-by: Andy Lutomirski >>> >>> Now the strategy about SS is to always save it to the sigcontext. >>> This is good because the syscall can clobber it, so the app had >>> to be very careful in the past trying to save it by hands. >>> How about saving also fs and gs? (without restoring yet) >>> If you do, you'll save dosemu a headache of doing any "pre-syscall" >>> work. Pre-syscall work is very nasty. >>> I haven't checked if the syscall clobber also these or only SS, >>> but perhaps saving them by the kernel won't hurt? >> >> There's a bunch of ongoing work about FS and GS. I want to wait and see. > Andy, have you postponed only this, or also the sigreturn patch? > Long time no news... > sigreturn patch would really be nice to have. Sorry, I got caught up with a bunch of other stuff, and everyone being slow with the holiday season. There's some slight chance we'll get it in for 4.5, but 4.6 is more likely. --Andy -- Andy Lutomirski AMA Capital Management, LLC