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[176.74.128.122]) by smtp.gmail.com with ESMTPSA id ci20sm3540303ejc.26.2020.12.17.04.04.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Dec 2020 04:04:44 -0800 (PST) Date: Thu, 17 Dec 2020 13:04:43 +0100 From: Artem Savkov To: Masahiro Yamada Cc: Joe Lawrence , WANG Chao , Linux Kernel Mailing List , Linux Kbuild mailing list Subject: Re: [PATCH] kbuild: add extra-y to targets-for-modules Message-ID: <20201217120443.GA739639@sparkplug.usersys.redhat.com> References: <20201103054425.59251-1-chao.wang@ucloud.cn> <20201123150452.GA68187@MacBook-Pro-2> <20201208092035.GA96434@MacBook-Pro-2.local> <20201208143117.GA3333762@wtfbox.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 17, 2020 at 05:26:07PM +0900, Masahiro Yamada wrote: > On Thu, Dec 17, 2020 at 8:04 AM Joe Lawrence wrote: > > > > On 12/16/20 1:14 AM, Masahiro Yamada wrote: > > > On Tue, Dec 8, 2020 at 11:31 PM Artem Savkov wrote: > > >> > > >> On Tue, Dec 08, 2020 at 05:20:35PM +0800, WANG Chao wrote: > > >>> Sorry for the late reply. > > >>> > > >>> On 11/25/20 at 10:42P, Masahiro Yamada wrote: > > >>>> On Tue, Nov 24, 2020 at 12:05 AM WANG Chao wrote: > > >>>>> > > >>>>> On 11/23/20 at 02:23P, Masahiro Yamada wrote: > > >>>>>> On Tue, Nov 3, 2020 at 3:23 PM WANG Chao wrote: > > >>>>>>> > > >>>>>>> extra-y target doesn't build for 'make M=...' since commit 6212804f2d78 > > >>>>>>> ("kbuild: do not create built-in objects for external module builds"). > > >>>>>>> > > >>>>>>> This especially breaks kpatch, which is using 'extra-y := kpatch.lds' > > >>>>>>> and 'make M=...' to build livepatch patch module. > > >>>>>>> > > >>>>>>> Add extra-y to targets-for-modules so that such kind of build works > > >>>>>>> properly. > > >>>>>>> > > >>>>>>> Signed-off-by: WANG Chao > > >>>>>>> --- > > >>>>>>> scripts/Makefile.build | 2 +- > > >>>>>>> 1 file changed, 1 insertion(+), 1 deletion(-) > > >>>>>>> > > >>>>>>> diff --git a/scripts/Makefile.build b/scripts/Makefile.build > > >>>>>>> index ae647379b579..0113a042d643 100644 > > >>>>>>> --- a/scripts/Makefile.build > > >>>>>>> +++ b/scripts/Makefile.build > > >>>>>>> @@ -86,7 +86,7 @@ ifdef need-builtin > > >>>>>>> targets-for-builtin += $(obj)/built-in.a > > >>>>>>> endif > > >>>>>>> > > >>>>>>> -targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m))) > > >>>>>>> +targets-for-modules := $(extra-y) $(patsubst %.o, %.mod, $(filter %.o, $(obj-m))) > > >>>>>>> > > >>>>>>> ifdef need-modorder > > >>>>>>> targets-for-modules += $(obj)/modules.order > > >>>>>>> -- > > >>>>>>> 2.29.1 > > >>>>>>> > > >>>>>> > > >>>>>> NACK. > > >>>>>> > > >>>>>> Please fix your Makefile. > > >>>>>> > > >>>>>> Hint: > > >>>>>> https://patchwork.kernel.org/project/linux-kbuild/patch/20201123045403.63402-6-masahiroy@kernel.org/ > > >>>>>> > > >>>>>> > > >>>>>> Probably what you should use is 'targets'. > > >>>>> > > >>>>> I tried with 'targets' and 'always-y'. Both doesn't work for me. > > >>>>> > > >>>>> I narraw it down to the following example: > > >>>>> > > >>>>> cat > Makefile << _EOF_ > > >>>>> obj-m += foo.o > > >>>>> > > >>>>> ldflags-y += -T $(src)/kpatch.lds > > >>>>> always-y += kpatch.lds > > >>>>> > > >>>>> foo-objs += bar.o > > >>>>> > > >>>>> all: > > >>>>> make -C /lib/modules/$(shell uname -r)/build M=$(PWD) > > >>>>> clean: > > >>>>> make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean > > >>>>> _EOF_ > > >>>>> > > >>>>> Take a look into scripts/Makefile.build:488: > > >>>>> > > >>>>> __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \ > > >>>>> $(if $(KBUILD_MODULES), $(targets-for-modules)) \ > > >>>>> $(subdir-ym) $(always-y) > > >>>>> @: > > >>>>> > > >>>>> 'always-y' is built after 'targets-for-modules'. This makes > > >>>>> 'targets-for-modules' fails because kpatch.lds isn't there. > > >>>> > > >>>> > > >>>> Heh, you rely on the targets built from left to right, > > >>>> and you have never thought Make supports the parallel option -j. > > >>> > > >>> You're right. I missed that. > > >>> > > >>>> > > >>>> > > >>>> You need to specify the dependency if you expect objects > > >>>> are built in the particular order. > > >>>> > > >>>> However, in this case, using ldflags-y looks wrong > > >>>> in the first place. > > >>>> > > >>>> The linker script is used when combining the object > > >>>> as well as the final link of *.ko > > >> > > >> We want linker script to be used on both those steps, otherwise modpost > > >> fails. > > > > > > > > > In that case, does the following work? > > > (untested) > > > > > > > > > > > > diff --git a/kmod/patch/Makefile b/kmod/patch/Makefile > > > index e017b17..02d4c66 100644 > > > --- a/kmod/patch/Makefile > > > +++ b/kmod/patch/Makefile > > > @@ -12,7 +12,9 @@ endif > > > > > > obj-m += $(KPATCH_NAME).o > > > ldflags-y += -T $(src)/kpatch.lds > > > -extra-y := kpatch.lds > > > +targets += kpatch.lds > > > + > > > +$(obj)/$(KPATCH_NAME).o: $(obj)/kpatch.lds > > > > > > $(KPATCH_NAME)-objs += patch-hook.o output.o > > > > > > > Hi Masahiro, > > > > Yeah this is more or less what Artem came up with: > > https://github.com/dynup/kpatch/pull/1149 > > > > though we hadn't added kpatch.lds to targets. Is there documentation > > somewhere on what effect "targets" has for out-of-tree builds? > > > > Thanks, > > > > -- Joe > > > > > Please try the rebuild without changing any source code. > > If kpatch.lds is needlessly rebuilt, you need to add > it to 'targets'. > > > In linux-next, this is documented. > > Documentation/kbuild/makefile.rst: > > Any target that utilizes if_changed must be listed in $(targets), > otherwise the command line check will fail, and the target will > always be built. Ah yes, it did rebuild every time. Thank you for the pointer. -- Artem