From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from conssluserg-03.nifty.com ([210.131.2.82]:42031 "EHLO conssluserg-03.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754324AbdJIQ0g (ORCPT ); Mon, 9 Oct 2017 12:26:36 -0400 MIME-Version: 1.0 In-Reply-To: <20171002105004.32426-1-jonas.gorski@gmail.com> References: <20171002105004.32426-1-jonas.gorski@gmail.com> From: Masahiro Yamada Date: Tue, 10 Oct 2017 01:25:38 +0900 Message-ID: Subject: Re: [PATCH] kbuild: allow making undefined symbols fatal for external modules Content-Type: text/plain; charset="UTF-8" Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Jonas Gorski Cc: Linux Kbuild mailing list , Linux Kernel Mailing List , Michal Marek , Sam Ravnborg 2017-10-02 19:50 GMT+09:00 Jonas Gorski : > By passing appropriate values in KBUILD_EXTRA_SYMBOLS it is possible to > make modpost be able to resolve all symbols for external modules, even > between to other external modules. > > Because of this, it might be desirable to make unresolved symbols an > error on external module builds as well, to catch missing exports there > as well. > > So add a new flag KBUILD_MODPOST_ERROR which can be set to enable this > behaviour. It has no effect on non external module builds. > > Signed-off-by: Jonas Gorski > --- > The main target is to allow distributions (like LEDE) that make use of > kernel backports and other out of tree drivers to be able to catch > errors like missing EXPORT_SYMBOLs in the kernel early. > > scripts/Makefile.modpost | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost > index 16923ba4b5b1..29f787bf8c3a 100644 > --- a/scripts/Makefile.modpost > +++ b/scripts/Makefile.modpost > @@ -34,6 +34,8 @@ > > # KBUILD_MODPOST_WARN can be set to avoid error out in case of undefined > # symbols in the final module linking stage > +# KBUILD_MODPOST_ERROR can be set to error out in case of undefined > +# symbols in the final module linking stage for external modules > # KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules. > # This is solely useful to speed up test compiles > PHONY := _modpost > @@ -49,6 +51,8 @@ ifneq ($(KBUILD_EXTMOD),) > obj := $(KBUILD_EXTMOD) > src := $(obj) > > +KBUILD_MODPOST_WARN = $(if $(KBUILD_MODPOST_ERROR),,1) > + > # Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS > include $(if $(wildcard $(KBUILD_EXTMOD)/Kbuild), \ > $(KBUILD_EXTMOD)/Kbuild, $(KBUILD_EXTMOD)/Makefile) > @@ -78,7 +82,7 @@ modpost = scripts/mod/modpost \ > $(if $(KBUILD_EXTMOD),-o $(modulesymfile)) \ > $(if $(CONFIG_DEBUG_SECTION_MISMATCH),,-S) \ > $(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E) \ > - $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w) > + $(if $(KBUILD_MODPOST_WARN),-w) > > MODPOST_OPT=$(subst -i,-n,$(filter -i,$(MAKEFLAGS))) > The motivation looks reasonable to me, but having both KBUILD_MODPOST_WARN and KBUILD_MODPOST_ERROR is a bit confusing, I think. (Some people may wonder what would happen if both are set...) So, here is my suggestion. We have only KBUILD_MODPOST_WARN. The default value is 1 for external module building. 0 for kernel building. If you want to change the default behavior, you can specify KBUILD_MODPOST_WARN=1 when building kernel, or KBUILD_MODPOST_WARN=0 when building external module from the command line. Also, you need to update Documentation/kbuild/kbuild.txt -- Best Regards Masahiro Yamada