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=-1.0 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 7430DC43219 for ; Tue, 30 Apr 2019 09:24:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4900E20835 for ; Tue, 30 Apr 2019 09:24:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726865AbfD3JYb (ORCPT ); Tue, 30 Apr 2019 05:24:31 -0400 Received: from mx2.suse.de ([195.135.220.15]:38526 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726119AbfD3JYa (ORCPT ); Tue, 30 Apr 2019 05:24:30 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 5D9C7AC52; Tue, 30 Apr 2019 09:24:27 +0000 (UTC) From: Nicolai Stange To: Steven Rostedt Cc: Linus Torvalds , Peter Zijlstra , 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 , Andy Lutomirski , Joerg Roedel , Linux List Kernel Mailing , live-patching@vger.kernel.org, "open list\:KERNEL SELFTEST FRAMEWORK" Subject: Re: [PATCH 3/4] x86/ftrace: make ftrace_int3_handler() not to skip fops invocation References: <20190427100639.15074-1-nstange@suse.de> <20190427100639.15074-4-nstange@suse.de> <20190427102657.GF2623@hirez.programming.kicks-ass.net> <20190428133826.3e142cfd@oasis.local.home> <20190429145250.1a5da6ed@gandalf.local.home> <20190429150724.6e501d27@gandalf.local.home> <20190429163043.535f4272@gandalf.local.home> <20190429180733.3f25d8b9@gandalf.local.home> Date: Tue, 30 Apr 2019 11:24:23 +0200 In-Reply-To: <20190429180733.3f25d8b9@gandalf.local.home> (Steven Rostedt's message of "Mon, 29 Apr 2019 18:07:33 -0400") Message-ID: <87imuv977c.fsf@suse.de> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Steven Rostedt writes: > On Mon, 29 Apr 2019 14:38:35 -0700 > Linus Torvalds wrote: > >> On Mon, Apr 29, 2019 at 1:30 PM Steven Rostedt wrote: >> > >> > The update from "call custom_trampoline" to "call iterator_trampoline" >> > is where we have an issue. >> >> So it has never worked. Just tell people that they have two chocies: > > The custom call to iterator translation never worked. One option is to > always call the iterator, and just take the hit. There's another > solution to to make permanent updates that would handle the live > patching case, but not for the tracing case. It is more critical for > live patching than tracing (missed traced function is not as critical > as running buggy code unexpectedly). I could look to work on that > instead. Making the live patching case permanent would disable tracing of live patched functions though? For unconditionally calling the iterator: I don't have numbers, but would expect that always searching through something like 50-70 live patching ftrace_ops from some hot path will be noticeable. > If Nicolai has time, perhaps he can try out the method you suggest and > see if we can move this forward. You mean making ftrace handle call->call transitions one by one in non-batch mode, right? Sure, I can do that. Another question though: is there anything that prevents us from calling ftrace_ops_list_func() directly from ftrace_int3_handler()? We don't have parent_ip, but if that is used for reporting only, maybe setting it to some ftrace_is_in_int3_and_doesnt_now_the_parent() will work? Graph tracing entries would still be lost, but well... Thanks, Nicolai