From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 192D0C004C9 for ; Tue, 7 May 2019 16:25:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E930E20989 for ; Tue, 7 May 2019 16:25:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726522AbfEGQZP (ORCPT ); Tue, 7 May 2019 12:25:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:44470 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726197AbfEGQZP (ORCPT ); Tue, 7 May 2019 12:25:15 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B3136205C9; Tue, 7 May 2019 16:25:11 +0000 (UTC) Date: Tue, 7 May 2019 12:25:10 -0400 From: Steven Rostedt To: Linus Torvalds Cc: Peter Zijlstra , Andy Lutomirski , Linux List Kernel Mailing , Ingo Molnar , Andrew Morton , Andy Lutomirski , Nicolai Stange , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , "the arch/x86 maintainers" , Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , Shuah Khan , Konrad Rzeszutek Wilk , Tim Chen , Sebastian Andrzej Siewior , Mimi Zohar , Juergen Gross , Nick Desaulniers , Nayna Jain , Masahiro Yamada , Joerg Roedel , "open list:KERNEL SELFTEST FRAMEWORK" , stable , Masami Hiramatsu Subject: Re: [RFC][PATCH 1/2] x86: Allow breakpoints to emulate call functions Message-ID: <20190507122510.0dd37cc8@gandalf.local.home> In-Reply-To: <20190507112513.11297412@gandalf.local.home> References: <20190502181811.GY2623@hirez.programming.kicks-ass.net> <20190506162915.380993f9@gandalf.local.home> <20190506174511.2f8b696b@gandalf.local.home> <20190506210416.2489a659@oasis.local.home> <20190506215353.14a8ef78@oasis.local.home> <20190506225819.11756974@oasis.local.home> <20190506232158.13c9123b@oasis.local.home> <20190507111227.1d4268d7@gandalf.local.home> <20190507112513.11297412@gandalf.local.home> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, 7 May 2019 11:25:13 -0400 Steven Rostedt wrote: > Note, if you really are adamant on your solution, I can write them up, > test them, and get them out for this merge window. I really want a > solution for the int3 emulate calls, as there is a real bug here that > they fix. Thinking about this more, as my real motivation for getting this in (for this merge window), is to fix the live kernel patching bug. We only need to implement int3 call emulation for x86_64. We don't need to implement it for 32bit. The ftrace code can continue to just make it a nop. Live kernel patching does not support x86_32, and the only issue that happens on 32bit when we do a nop when converting a call to call, is that we might lose a trace. But that's been the case since this started, and not a critical issue. But with live kernel patching, losing a trace could crash the machine. As I need to mark all this for stable, I'm going to look into just implementing this for x86_64. Then we can continue the debate about how to do this for x86_32 if we care about loss traces. But we don't need to commit to anything yet. -- Steve