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=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 55A36C10F14 for ; Tue, 15 Oct 2019 16:09:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C22020873 for ; Tue, 15 Oct 2019 16:09:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571155762; bh=lymXH+CPJkzOEgsYwzTlX/oqBJpN6j+gCshs086u74w=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Dzc9nPSN7HmXglfkuzbsuKc16KAyYILOIXV66C80lwv4wYzO44aCqR6kpdPnhpgwR HPmZLu4KkgWCYvktg3/TrD2XbqWxJVWrPu0cafUvW4nALtwRbmnkL8+iNXqHnHzAsR YV3HdGQrarmMLRjMacVnffJRYvQK1q/gNlvWJzm8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727643AbfJOQJV (ORCPT ); Tue, 15 Oct 2019 12:09:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:43090 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726333AbfJOQJU (ORCPT ); Tue, 15 Oct 2019 12:09:20 -0400 Received: from linux-8ccs (ip5f5adbbb.dynamic.kabel-deutschland.de [95.90.219.187]) (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 3C99720640; Tue, 15 Oct 2019 16:09:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571155759; bh=lymXH+CPJkzOEgsYwzTlX/oqBJpN6j+gCshs086u74w=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=keT8Xy6ws5k0dTABCEb/07xm4QdknpNXD7BlPsuKOrr5mu1hvDUp+kNr0xR/HbDAV QXm9pJmMjmHPQOVe/NQe13Zw2/KClK+0q8wj/hWA7sTgTTbs+lQg+esvwuvWpj7UUG WAjTjWb+5Bi/Q9WAv/m2pFZPL94VohATMMdvYaqo= Date: Tue, 15 Oct 2019 18:09:13 +0200 From: Jessica Yu To: Steven Rostedt Cc: Peter Zijlstra , 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 Subject: Re: [PATCH v3 5/6] x86/ftrace: Use text_poke() Message-ID: <20191015160912.GB21110@linux-8ccs> References: <20191007081945.10951536.8@infradead.org> <20191008104335.6fcd78c9@gandalf.local.home> <20191009224135.2dcf7767@oasis.local.home> <20191010092054.GR2311@hirez.programming.kicks-ass.net> <20191010091956.48fbcf42@gandalf.local.home> <20191010140513.GT2311@hirez.programming.kicks-ass.net> <20191010115449.22044b53@gandalf.local.home> <20191010172819.GS2328@hirez.programming.kicks-ass.net> <20191011125903.GN2359@hirez.programming.kicks-ass.net> <20191015092802.5c9aea5e@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20191015092802.5c9aea5e@gandalf.local.home> X-OS: Linux linux-8ccs 4.12.14-lp150.12.28-default x86_64 User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +++ Steven Rostedt [15/10/19 09:28 -0400]: >On Fri, 11 Oct 2019 14:59:03 +0200 >Peter Zijlstra wrote: > >> On Thu, Oct 10, 2019 at 07:28:19PM +0200, Peter Zijlstra wrote: >> >> > Really the best solution is to move all the poking into >> > ftrace_module_init(), before we mark it RO+X. That's what I'm going to >> > do for jump_label and static_call as well, I just need to add that extra >> > notifier callback. >> >> OK, so I started writing that patch... or rather, I wrote the patch and >> started on the Changelog when I ran into trouble describing why we need >> it. >> >> That is, I'm struggling to explain why we cannot flip >> prepare_coming_module() and complete_formation(). >> >> Yes, it breaks ftrace, but I'm thinking that is all it breaks. So let me >> see if we can cure that. > >You are mainly worried about making text that is executable into >read-write again. What if we kept my one patch that just changed the >module in ftrace_module_enable() from read-only to read-write, but >before we ever set it executable. > >Jessica, would this patch break anything? > >It moves the setting of the module execution to after calling both >ftrace_module_enable() and klp_module_coming(). > >This would make it possible to do the module code and still keep with >the no executable code becoming writable. > >-- Steve > >diff --git a/kernel/module.c b/kernel/module.c >index ff2d7359a418..6e2fd40a6ed9 100644 >--- a/kernel/module.c >+++ b/kernel/module.c >@@ -3728,7 +3728,6 @@ static int complete_formation(struct module *mod, struct load_info *info) > > module_enable_ro(mod, false); > module_enable_nx(mod); >- module_enable_x(mod); > > /* Mark state as coming so strong_try_module_get() ignores us, > * but kallsyms etc. can see us. */ >@@ -3751,6 +3750,11 @@ static int prepare_coming_module(struct module *mod) > if (err) > return err; > >+ /* Make module executable after ftrace is enabled */ >+ mutex_lock(&module_mutex); >+ module_enable_x(mod); >+ mutex_unlock(&module_mutex); >+ > blocking_notifier_call_chain(&module_notify_list, > MODULE_STATE_COMING, mod); > return 0; As long as we enable x before parse_args(), which this patch does, then I don't think this change would break anything.