From patchwork Mon Mar 14 02:42:13 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Pitre X-Patchwork-Id: 8575241 Return-Path: X-Original-To: patchwork-linux-kbuild@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 870E5C0553 for ; Mon, 14 Mar 2016 02:43:26 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 56D7320454 for ; Mon, 14 Mar 2016 02:43:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 30B5920452 for ; Mon, 14 Mar 2016 02:43:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754605AbcCNCnS (ORCPT ); Sun, 13 Mar 2016 22:43:18 -0400 Received: from alt22.smtp-out.videotron.ca ([70.80.0.73]:43531 "EHLO alt22.smtp-out.videotron.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754558AbcCNCnG (ORCPT ); Sun, 13 Mar 2016 22:43:06 -0400 Received: from yoda.home ([96.23.157.65]) by Videotron with SMTP id fITGaLbbPde0FfITHaHtm1; Sun, 13 Mar 2016 22:43:03 -0400 X-Authority-Analysis: v=2.1 cv=K+CCZ3iI c=1 sm=1 tr=0 a=keA3yYpnlypCNW5BNWqu+w==:117 a=keA3yYpnlypCNW5BNWqu+w==:17 a=L9H7d07YOLsA:10 a=9cW_t1CCXrUA:10 a=s5jvgZ67dGcA:10 a=7OsogOcEt9IA:10 a=KKAkSRfTAAAA:8 a=Tty9oNO6AAAA:8 a=ZSXhne8G9MgRMkPpJisA:9 Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id 6485B2DA05E2; Sun, 13 Mar 2016 22:43:01 -0400 (EDT) From: Nicolas Pitre To: Michal Marek Cc: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v6 5/8] kbuild: add fine grained build dependencies for exported symbols Date: Sun, 13 Mar 2016 22:42:13 -0400 Message-Id: <1457923336-2732-6-git-send-email-nicolas.pitre@linaro.org> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1457923336-2732-1-git-send-email-nicolas.pitre@linaro.org> References: <1457923336-2732-1-git-send-email-nicolas.pitre@linaro.org> X-CMAE-Envelope: MS4wfGe7xnxyuuL1NEl1rcjdx4Uo0SyB/joAFILhnYzyh99YUIMtYWOVgjvsxhvm7Voi1K5vzQHj61BSEdoUQOpMDXxsui40F+8mCcqgyhIOmhB9Q1EidcTv YRIhYm1rvyBjgr5ZAmWkzM4lMwJQo4iR7G4Paz13vU3NEmmoyrhhclQfykfXxpcJW/t6Po/4HnMJJR/seWd/q+OjSB71iDt1OFRbcttmwRzHSszWqrgaHEfI AWP1Vn4S4WNWU1SfbfpBBg== Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Like with kconfig options, we now have the ability to compile in and out individual EXPORT_SYMBOL() declarations based on the content of include/generated/autoksyms.h. However we don't want the entire world to be rebuilt whenever that file is touched. Let's apply the same build dependency trick used for CONFIG_* symbols where the time stamp of empty files whose paths matching those symbols is used to trigger fine grained rebuilds. In our case the key is the symbol name passed to EXPORT_SYMBOL(). However, unlike config options, we cannot just use fixdep to parse the source code for EXPORT_SYMBOL(ksym) because several variants exist and parsing them all in a separate tool, and keeping it in synch, is not trivially maintainable. Furthermore, there are variants such as EXPORT_SYMBOL_GPL(pci_user_read_config_##size); that are instanciated via a macro for which we can't easily determine the actual exported symbol name(s) short of actually running the preprocessor on them. Storing the symbol name string in a special ELF section doesn't work for targets that output assembly or preprocessed source. So the best way is really to leverage the preprocessor by having it output actual symbol names anchored by a special sequence that can be easily filtered out. Then the list of symbols is simply fed to fixdep to be merged with the other dependencies. That implies the preprocessor is executed twice for each source file. A previous attempt relied on a warning pragma for each EXPORT_SYMBOL() instance that was filtered apart from stderr by the build system with a sed script during the actual compilation pass. Unfortunately the preprocessor/compiler diagnostic output isn't stable between versions and this solution, although more efficient, was deemed too fragile. Because of the lowercasing performed by fixdep, there might be name collisions triggering spurious rebuilds for similar symbols. But this shouldn't be a big issue in practice. (This is the case for CONFIG_* symbols and I didn't want to be different here, whatever the original reason for doing so.) To avoid needless build overhead, the exported symbol name gathering is performed only when CONFIG_TRIM_UNUSED_KSYMS is selected. Signed-off-by: Nicolas Pitre Acked-by: Rusty Russell --- include/linux/export.h | 13 ++++++++++++- scripts/Kbuild.include | 27 +++++++++++++++++++++++++++ scripts/basic/fixdep.c | 1 + 3 files changed, 40 insertions(+), 1 deletion(-) diff --git a/include/linux/export.h b/include/linux/export.h index 77afdb2a25..2f9ccbe6a6 100644 --- a/include/linux/export.h +++ b/include/linux/export.h @@ -65,7 +65,18 @@ extern struct module __this_module; __attribute__((section("___ksymtab" sec "+" #sym), unused)) \ = { (unsigned long)&sym, __kstrtab_##sym } -#ifdef CONFIG_TRIM_UNUSED_KSYMS +#if defined(__KSYM_DEPS__) + +/* + * For fine grained build dependencies, we want to tell the build system + * about each possible exported symbol even if they're not actually exported. + * We use a string pattern that is unlikely to be valid code that the build + * system filters out from the preprocessor output (see ksym_dep_filter + * in scripts/Kbuild.include). + */ +#define __EXPORT_SYMBOL(sym, sec) === __KSYM_##sym === + +#elif defined(CONFIG_TRIM_UNUSED_KSYMS) #include #include diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index 8a257fa663..2c14a27e39 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -258,12 +258,39 @@ if_changed_dep = $(if $(strip $(any-prereq) $(arg-check) ), \ @set -e; \ $(cmd_and_fixdep)) +ifndef CONFIG_TRIM_UNUSED_KSYMS + cmd_and_fixdep = \ $(echo-cmd) $(cmd_$(1)); \ scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).tmp;\ rm -f $(depfile); \ mv -f $(dot-target).tmp $(dot-target).cmd; +else + +# Filter out exported kernel symbol names from the preprocessor output. +# See also __KSYM_DEPS__ in include/linux/export.h. +# We disable the depfile generation here, so as not to overwrite the existing +# depfile while fixdep is parsing it +flags_nodeps = $(filter-out -Wp$(comma)-M%, $($(1))) +ksym_dep_filter = \ + case "$(1)" in \ + cc_*_c) $(CPP) $(call flags_nodeps,c_flags) -D__KSYM_DEPS__ $< ;; \ + as_*_S) $(CPP) $(call flags_nodeps,a_flags) -D__KSYM_DEPS__ $< ;; \ + cpp_lds_S) : ;; \ + *) echo "Don't know how to preprocess $(1)" >&2; false ;; \ + esac | sed -rn 's/^.*=== __KSYM_(.*) ===.*$$/KSYM_\1/p' + +cmd_and_fixdep = \ + $(echo-cmd) $(cmd_$(1)); \ + $(ksym_dep_filter) | \ + scripts/basic/fixdep -e $(depfile) $@ '$(make-cmd)' \ + > $(dot-target).tmp; \ + rm -f $(depfile); \ + mv -f $(dot-target).tmp $(dot-target).cmd; + +endif + # Usage: $(call if_changed_rule,foo) # Will check if $(cmd_foo) or any of the prerequisites changed, # and if so will execute $(rule_foo). diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c index d984deb120..2dc6bf754a 100644 --- a/scripts/basic/fixdep.c +++ b/scripts/basic/fixdep.c @@ -354,6 +354,7 @@ static void parse_dep_file(void *map, size_t len) /* Ignore certain dependencies */ if (strrcmp(s, "include/generated/autoconf.h") && + strrcmp(s, "include/generated/autoksyms.h") && strrcmp(s, "arch/um/include/uml-config.h") && strrcmp(s, "include/linux/kconfig.h") && strrcmp(s, ".ver")) {