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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 86793CA9EC3 for ; Thu, 31 Oct 2019 09:02:48 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 523BC2083E for ; Thu, 31 Oct 2019 09:02:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="NXlld0Bw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 523BC2083E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=kgaJPORx9lFDkXOPZmNPDPliq1gbxTG0d/YrgsVoWus=; b=NXlld0Bwxrdd2+ J3Koa6DKnjXbwYNc8Mstcu8dibN5T52IUsg7UBeMm1qC9ZX/k9FT9dl7xifoDoipgRH5gwM8kwFLC XZr+rexCD6VKw4EBycuYjGhc7AnP+xm78NWlSW0EHslqDCPofCu3OT7/I16lWD9/V9aHgIghmTgVf 5w40r1YMX5IeDQYNyGFx5WC+HMtrzd0FCSdJ+o5gna0iJYHF1oI02B1nXHfcdr39bUtOek7WIwp5W Hty9V24U7SxtuOtGi2hWtXmpZV81SMWvUZH/IsujfVkULJ5iHROlb8VpPcxuokqSuTbuKbnf3MTJr Ni0JLBf194r82sw0u7OQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iQ6Lv-0000W5-0W; Thu, 31 Oct 2019 09:02:47 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iQ6Lr-0000Us-G4 for linux-arm-kernel@lists.infradead.org; Thu, 31 Oct 2019 09:02:45 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DE80531F; Thu, 31 Oct 2019 02:02:41 -0700 (PDT) Received: from blommer (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 627483F71E; Thu, 31 Oct 2019 02:02:37 -0700 (PDT) Date: Thu, 31 Oct 2019 09:02:32 +0000 From: Mark Rutland To: Torsten Duwe Subject: Re: [PATCHv2 2/8] module/ftrace: handle patchable-function-entry Message-ID: <20191031090231.GA3340@blommer> References: <20191029165832.33606-1-mark.rutland@arm.com> <20191029165832.33606-3-mark.rutland@arm.com> <20191030150302.GA965@suse.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191030150302.GA965@suse.de> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191031_020243_625102_2AF3D50A X-CRM114-Status: GOOD ( 22.15 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jthierry@redhat.com, linux-parisc@vger.kernel.org, peterz@infradead.org, catalin.marinas@arm.com, Helge Deller , jpoimboe@redhat.com, linux-kernel@vger.kernel.org, rostedt@goodmis.org, "James E.J. Bottomley" , takahiro.akashi@linaro.org, will@kernel.org, mingo@redhat.com, james.morse@arm.com, Jessica Yu , amit.kachhap@arm.com, svens@stackframe.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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: > > When using patchable-function-entry, the compiler will record the > > callsites into a section named "__patchable_function_entries" rather > > than "__mcount_loc". Let's abstract this difference behind a new > > FTRACE_CALLSITE_SECTION, so that architectures don't have to handle this > > explicitly (e.g. with custom module linker scripts). > > > > As parisc currently handles this explicitly, it is fixed up accordingly, > > with its custom linker script removed. Since FTRACE_CALLSITE_SECTION is > > only defined when DYNAMIC_FTRACE is selected, the parisc module loading > > code is updated to only use the definition in that case. When > > DYNAMIC_FTRACE is not selected, modules shouldn't have this section, so > > this removes some redundant work in that case. > > > > 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. For modules the kernel's ELF loader looks for the ELF ection, not the __{start,stop}_mcount_loc symbols that we use for the main kernel image. FWIW, when building a module, I see the following linker operations: | [mark@blommer:~/src/linux]% toolchain korg gcc-8.1.0-nolibc make V=1 ARCH=arm64 CROSS_COMPILE=aarch64-linux- arch/arm64/crypto/sha512-ce.ko | grep aarch64-linux-ld | aarch64-linux-ld -EL -maarch64elf -r -o arch/arm64/crypto/sha512-ce.o arch/arm64/crypto/sha512-ce-glue.o arch/arm64/crypto/sha512-ce-core.o | aarch64-linux-ld -r -EL -maarch64elf --build-id -T ./scripts/module-common.lds -T ./arch/arm64/kernel/module.lds -o arch/arm64/crypto/sha512-ce.ko arch/arm64/crypto/sha512-ce.o arch/arm64/crypto/sha512-ce.mod.o; true > Maybe you want to tackle that as well? I suggest to have at least one > FTRACE_CALLSITE_SECTION definition without double quotes. Alternatively, my > earlier solution just kept both sections, in case either one or both are > present. > > KEEP(*(__patchable_function_entries)) \ > KEEP(*(__mcount_loc)) \ 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? Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel