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=-2.3 required=3.0 tests=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 101F6CA9ECE for ; Thu, 31 Oct 2019 11:42:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E373D20862 for ; Thu, 31 Oct 2019 11:42:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726843AbfJaLm1 (ORCPT ); Thu, 31 Oct 2019 07:42:27 -0400 Received: from mx2.suse.de ([195.135.220.15]:51736 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726462AbfJaLm1 (ORCPT ); Thu, 31 Oct 2019 07:42:27 -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 83BABAF7A; Thu, 31 Oct 2019 11:42:25 +0000 (UTC) Date: Thu, 31 Oct 2019 12:42:23 +0100 From: Torsten Duwe To: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, Jessica Yu , Helge Deller , "James E.J. Bottomley" , linux-kernel@vger.kernel.org, amit.kachhap@arm.com, catalin.marinas@arm.com, james.morse@arm.com, jpoimboe@redhat.com, jthierry@redhat.com, linux-parisc@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, rostedt@goodmis.org, svens@stackframe.org, takahiro.akashi@linaro.org, will@kernel.org Subject: Re: [PATCHv2 2/8] module/ftrace: handle patchable-function-entry Message-ID: <20191031114223.GA11684@suse.de> References: <20191029165832.33606-1-mark.rutland@arm.com> <20191029165832.33606-3-mark.rutland@arm.com> <20191030150302.GA965@suse.de> <20191031090231.GA3340@blommer> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191031090231.GA3340@blommer> 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 Thu, Oct 31, 2019 at 09:02:32AM +0000, Mark Rutland wrote: > On Wed, Oct 30, 2019 at 04:03:02PM +0100, Torsten Duwe wrote: > > On Tue, Oct 29, 2019 at 04:58:26PM +0000, Mark Rutland wrote: > > > > > > I built parisc generic-{32,64}bit_defconfig with DYNAMIC_FTRACE enabled, > > > and verified that the section made it into the .ko files for modules. > > > > This is because of remaining #ifdeffery in include/asm-generic/vmlinux.lds.h: > > > > #ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY > > #define MCOUNT_REC() . = ALIGN(8); \ > > __start_mcount_loc = .; \ > > KEEP(*(__patchable_function_entries)) \ > > __stop_mcount_loc = .; > > #else > > #define MCOUNT_REC() . = ALIGN(8); \ > > __start_mcount_loc = .; \ > > KEEP(*(__mcount_loc)) \ > > __stop_mcount_loc = .; > > #endif > > For modules we use a combination of scripts/module-common.lds and an > architecture's own module.lds, not vmlinux.lds.h. So I don't think the above is > relevant for modules. Sure, this is only loosely related,... > I agree that the CC_USING_PATCHABLE_FUNCTION_ENTRY ifdeffery could be > simplified, and that it would be nice to consistently use > FTRACE_CALLSITE_SECTION if we can. However, the generic linker script doesn't > include anything, and I don't see a good location for that to live. > > What I could do is add an explicit comment: > > /* > * The ftrace call sites are logged to a section whose name depends on the > * compiler option used. A given kernel image will only use one, AKA > * FTRACE_CALLSITE_SECTION. We capture all of them here to avoid header > * dependencies. > */ > #define MCOUNT_REC() \ > . = ALIGN(8); \ > __start_mcount_loc = .; \ > KEEP(*(__patchable_function_entries)) \ > KEEP(*(__mcount_loc)) \ > __stop_mcount_loc = .; > > ... which should make the dependency clear. Does that sound good to you? Beautiful. I just didn't want to miss the opportunity to have this cleaned up as well, and deemed this patch "closest" because of the definition of FTRACE_CALLSITE_SECTION. Put it where you see it fit best. Thanks, Torsten