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[209.132.180.67]) by mx.google.com with ESMTP id d1si15866953eds.148.2019.10.16.07.22.15; Wed, 16 Oct 2019 07:22:39 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404627AbfJPKUj (ORCPT + 99 others); Wed, 16 Oct 2019 06:20:39 -0400 Received: from mx2.suse.de ([195.135.220.15]:52764 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2392341AbfJPKUj (ORCPT ); Wed, 16 Oct 2019 06:20:39 -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 51972B01F; Wed, 16 Oct 2019 10:20:37 +0000 (UTC) Date: Wed, 16 Oct 2019 12:20:36 +0200 (CEST) From: Miroslav Benes To: Peter Zijlstra cc: Steven Rostedt , Joe Lawrence , Jessica Yu , x86@kernel.org, linux-kernel@vger.kernel.org, mhiramat@kernel.org, bristot@redhat.com, jbaron@akamai.com, torvalds@linux-foundation.org, tglx@linutronix.de, mingo@kernel.org, namit@vmware.com, hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com, live-patching@vger.kernel.org, pmladek@suse.com Subject: Re: [PATCH v3 5/6] x86/ftrace: Use text_poke() In-Reply-To: <20191016074951.GM2328@hirez.programming.kicks-ass.net> Message-ID: References: <20191010115449.22044b53@gandalf.local.home> <20191010172819.GS2328@hirez.programming.kicks-ass.net> <20191011125903.GN2359@hirez.programming.kicks-ass.net> <20191015130739.GA23565@linux-8ccs> <20191015135634.GK2328@hirez.programming.kicks-ass.net> <88bab814-ea24-ece9-2bc0-7a1e10a62f12@redhat.com> <20191015153120.GA21580@linux-8ccs> <7e9c7dd1-809e-f130-26a3-3d3328477437@redhat.com> <20191015182705.1aeec284@gandalf.local.home> <20191016074951.GM2328@hirez.programming.kicks-ass.net> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 16 Oct 2019, Peter Zijlstra wrote: > On Tue, Oct 15, 2019 at 06:27:05PM -0400, Steven Rostedt wrote: > > > (7) Seventh session, titled "klp-convert and livepatch relocations", was led > > by Joe Lawrence. > > > > Joe started the session with problem statement: accessing non exported / static > > symbols from inside the patch module. One possible workardound is manually via > > kallsyms. Second workaround is klp-convert, which actually creates proper > > relocations inside the livepatch module from the symbol database during the > > final .ko link. > > Currently module loader looks for special livepatch relocations and resolves > > those during runtime; kernel support for these relocations have so far been > > added for x86 only. Special livepatch relocations are supported and processed > > also on other architectures. Special quirks/sections are not yet supported. > > Plus klp-convert would still be needed even with late module patching update. > > vmlinux or modules could have ambiguous static symbols. > > > > It turns out that the features / bugs below have to be resolved before we > > can claim the klp-convert support for relocation complete: > > - handle all the corner cases (jump labels, static keys, ...) properly and > > have a good regression tests in place > > I suppose all the patches in this series-of-series here will make life > harder for KLP, static_call() and 2 byte jumps etc.. Yes, I think so. We'll have to deal with that once it lands. That is why we want to get rid of all this arch-specific code in livepatch and reinvent the late module patching. So it is perhaps better to start working on it sooner than later. Adding Petr, who hesitantly signed up for the task... Miroslav