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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED 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 DDF0EC3279B for ; Wed, 4 Jul 2018 11:30:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8BE34208DC for ; Wed, 4 Jul 2018 11:30:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=agner.ch header.i=@agner.ch header.b="vdfvsELP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8BE34208DC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=agner.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933849AbeGDLac (ORCPT ); Wed, 4 Jul 2018 07:30:32 -0400 Received: from mail.kmu-office.ch ([178.209.48.109]:55214 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933214AbeGDLaa (ORCPT ); Wed, 4 Jul 2018 07:30:30 -0400 Received: from webmail.kmu-office.ch (unknown [IPv6:2a02:418:6a02::a3]) by mail.kmu-office.ch (Postfix) with ESMTPSA id C37B35C1AB3; Wed, 4 Jul 2018 13:30:28 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=agner.ch; s=dkim; t=1530703828; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=paK+ekcQTXwZyr8l9+FX56ASYP1U6b88U+lqCA3qzdU=; b=vdfvsELPSqy/wqrZ1kOO6/dBRlXBwYsDUpptBYa6aHwvmisPxLzAtDi3OGJXsf6hR/ZcJf MYbq3gNCcinM1eNRcQQ8nbLM3XPqCruLuAU73rOkHSlwteOgsxgkjcy7Ee6nWgtwEBygI6 cuEkrL1mKkEJIqw/u6W2I90g8oJzkPk= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Date: Wed, 04 Jul 2018 13:30:28 +0200 From: Stefan Agner To: Steven Rostedt Cc: LKML , linux-arm-kernel@lists.infradead.org, Russell King - ARM Linux , abelvesa@linux.com, Abhishek Sagar , Ingo Molnar Subject: Re: [PATCH] ARM: ftrace: Only set kernel memory back to read-only after boot In-Reply-To: <20180621124710.453ee0ae@gandalf.local.home> References: <20180621124710.453ee0ae@gandalf.local.home> Message-ID: <7aa5a479aa484775f492dc5251bcf5c9@agner.ch> X-Sender: stefan@agner.ch User-Agent: Roundcube Webmail/1.3.4 X-Spamd-Result: default: False [-3.10 / 15.00]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; TAGGED_RCPT(0.00)[]; MIME_GOOD(-0.10)[text/plain]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_SEVEN(0.00)[7]; FROM_EQ_ENVFROM(0.00)[]; DKIM_SIGNED(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_ZERO(0.00)[0]; ASN(0.00)[asn:29691, ipnet:2a02:418::/29, country:CH]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-3.00)[99.99%]; ARC_NA(0.00)[] Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21.06.2018 18:47, Steven Rostedt wrote: > From: Steven Rostedt (VMware) > > Dynamic ftrace requires modifying the code segments that are usually > set to read-only. To do this, a per arch function is called both before > and after the ftrace modifications are performed. The "before" function > will set kernel code text to read-write to allow for ftrace to make the > modifications, and the "after" function will set the kernel code text > back to "read-only" to keep the kernel code text protected. > > The issue happens when dynamic ftrace is tested at boot up. The test is > done before the kernel code text has been set to read-only. But the > "before" and "after" calls are still performed. The "after" call will > change the kernel code text to read-only prematurely, and other boot > code that expects this code to be read-write will fail. > > The solution is to add a variable that is set when the kernel code text > is expected to be converted to read-only, and make the ftrace "before" > and "after" calls do nothing if that variable is not yet set. This is > similar to the x86 solution from commit 162396309745 ("ftrace, x86: > make kernel text writable only for conversions"). > > Reported-by: Stefan Agner > Tested-by: Stefan Agner > Link: http://lkml.kernel.org/r/20180620212906.24b7b66e@vmware.local.home > Signed-off-by: Steven Rostedt (VMware) > --- > diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c > index c186474422f3..0cc8e04295a4 100644 > --- a/arch/arm/mm/init.c > +++ b/arch/arm/mm/init.c I guess this can be seen as reviewed? Patches touching core ARM port usually go through Russels patch tracker. You have to submit the patch here: http://www.armlinux.org.uk/developer/patches/ -- Stefan > @@ -736,20 +736,29 @@ static int __mark_rodata_ro(void *unused) > return 0; > } > > +static int kernel_set_to_readonly __read_mostly; > + > void mark_rodata_ro(void) > { > + kernel_set_to_readonly = 1; > stop_machine(__mark_rodata_ro, NULL, NULL); > debug_checkwx(); > } > > void set_kernel_text_rw(void) > { > + if (!kernel_set_to_readonly) > + return; > + > set_section_perms(ro_perms, ARRAY_SIZE(ro_perms), false, > current->active_mm); > } > > void set_kernel_text_ro(void) > { > + if (!kernel_set_to_readonly) > + return; > + > set_section_perms(ro_perms, ARRAY_SIZE(ro_perms), true, > current->active_mm); > }