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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 68E45ECE58F for ; Tue, 15 Oct 2019 13:42:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 38AEF2064A for ; Tue, 15 Oct 2019 13:42:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ExujiklK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732106AbfJONmq (ORCPT ); Tue, 15 Oct 2019 09:42:46 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:41254 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728880AbfJONmq (ORCPT ); Tue, 15 Oct 2019 09:42:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=AKETJ2nfkH7uXxWCCj7sIia2rz/qZRIp9whr7XMbtYg=; b=ExujiklKpYGQs5qRdMBD1a134 Io09hhIpCZcfSrkebxinrJhEMRP+SHPdb0jWNRW6sGNTbTfztGeppICDkSMA4E5R1LlggR9VAic45 DJg+Vw/PUMqHiIPnlVsCFqgYBXHhGrjeFGRaTcYLKBhPP11NcAkuMyveJjpmdN47pSlu89YKdkd4f rDRMNWT4q8U/o0P/Gi6FRxGqpFDLihfrJXyLSNEwy8YPsTFVTFT0r6j/cOju27NlcVrLk8JXiJvwc /kGAS1QjBKxvOZMc6Dyj3Y88fGeMwU+o8pE4pGgqS0ELEDycU/nlAFAMziEwerHdUdKkWvMDZWk+/ i+ntNiW7w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iKN5r-0006TP-Lk; Tue, 15 Oct 2019 13:42:31 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 28005300B8D; Tue, 15 Oct 2019 15:41:34 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 870A720B972E4; Tue, 15 Oct 2019 15:42:28 +0200 (CEST) Date: Tue, 15 Oct 2019 15:42:28 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: 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, jeyu@kernel.org Subject: Re: [PATCH v3 5/6] x86/ftrace: Use text_poke() Message-ID: <20191015134228.GJ2328@hirez.programming.kicks-ass.net> 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 Content-Disposition: inline In-Reply-To: <20191015092802.5c9aea5e@gandalf.local.home> 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 On Tue, Oct 15, 2019 at 09:28:02AM -0400, Steven Rostedt wrote: > 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. This still flips the protections back and forth, which is still really ugly. And afaict the only reason this is required is that set_all_modules_text_*() stuff. So please, instead of tinkering around, lets just kill that horrible interface and be done with it. There's only 2 users left, fixing those can't be too hard.