On Wed, Sep 11, 2024 at 10:38:58AM -0500, Lucas De Marchi wrote: > On Wed, Sep 11, 2024 at 04:28:30PM GMT, Masahiro Yamada wrote: > > On Wed, Sep 11, 2024 at 1:36 PM Lucas De Marchi > > <lucas.demarchi@xxxxxxxxx> wrote: > > > > > > On Tue, Sep 10, 2024 at 09:43:14PM GMT, Lucas De Marchi wrote: > > > >On Wed, Sep 11, 2024 at 09:10:09AM GMT, Jing Leng wrote: > > > >>>-----Original Messages----- > > > >>>From: "Lucas De Marchi" <lucas.demarchi@xxxxxxxxx> > > > >>>Send time:Tuesday, 09/10/2024 22:00:29 > > > >>>To: "Masahiro Yamada" <masahiroy@xxxxxxxxxx> > > > >>>Cc: 3090101217@xxxxxxxxxx, "Michal Marek" <michal.lkml@xxxxxxxxxxx>, "Nick > > > >>> Desaulniers" <ndesaulniers@xxxxxxxxxx>, "Linux Kbuild mailing list" <linux-kbuild@xxxxxxxxxxxxxxx>, "Linux Kernel Mailing List" <linux-kernel@xxxxxxxxxxxxxxx>, "Jing Leng" <jleng@xxxxxxxxxxxxx> > > > >>>Subject: External modules with O=... (was: Re: [PATCH] kbuild: Fix include path in scripts/Makefile.modpost) > > > >>> > > > >>>Hi, I was pointed to this thread since I'm trying something similar > > > >>>in kmod's testsuite. See below. > > > >>> > > > >>>On Tue, May 24, 2022 at 02:52:45AM GMT, Masahiro Yamada wrote: > > > >>>>On Tue, May 17, 2022 at 7:51 PM <3090101217@xxxxxxxxxx> wrote: > > > >>>>> > > > >>>>> From: Jing Leng <jleng@xxxxxxxxxxxxx> > > > >>>>> > > > >>>>> When building an external module, if users don't need to separate the > > > >>>>> compilation output and source code, they run the following command: > > > >>>>> "make -C $(LINUX_SRC_DIR) M=$(PWD)". At this point, "$(KBUILD_EXTMOD)" > > > >>>>> and "$(src)" are the same. > > > >>>>> > > > >>>>> If they need to separate them, they run "make -C $(KERNEL_SRC_DIR) > > > >>>>> O=$(KERNEL_OUT_DIR) M=$(OUT_DIR) src=$(PWD)". Before running the > > > >>>>> command, they need to copy "Kbuild" or "Makefile" to "$(OUT_DIR)" to > > > >>>>> prevent compilation failure. > > > >>>>> > > > >>>>> So the kernel should change the included path to avoid the copy operation. > > > >>>>> > > > >>>>> Signed-off-by: Jing Leng <jleng@xxxxxxxxxxxxx> > > > >>>>> --- > > > >>>>> scripts/Makefile.modpost | 3 +-- > > > >>>>> 1 file changed, 1 insertion(+), 2 deletions(-) > > > >>>>> > > > >>>>> diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost > > > >>>>> index 48585c4d04ad..0273bf7375e2 100644 > > > >>>>> --- a/scripts/Makefile.modpost > > > >>>>> +++ b/scripts/Makefile.modpost > > > >>>>> @@ -87,8 +87,7 @@ obj := $(KBUILD_EXTMOD) > > > >>>>> src := $(obj) > > > >>>>> > > > >>>>> # Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS > > > >>>>> -include $(if $(wildcard $(KBUILD_EXTMOD)/Kbuild), \ > > > >>>>> - $(KBUILD_EXTMOD)/Kbuild, $(KBUILD_EXTMOD)/Makefile) > > > >>>>> +include $(if $(wildcard $(src)/Kbuild), $(src)/Kbuild, $(src)/Makefile) > > > >>>>> > > > >>>>> # modpost option for external modules > > > >>>>> MODPOST += -e > > > >>>>> -- > > > >>>>> 2.17.1 > > > >>>>> > > > >>>> > > > >>>> > > > >>>>I do not think "M=$(OUT_DIR) src=$(PWD)" is the official way, > > > >>>>but this patch is a clean up. > > > >>> > > > >>>I tried what is in this patch and also tried to find an official way in > > > >>>the docs. > > > > > > There is no official way. > > > > > >>> > > > >>>In kmod's testsuite we build dummy kernel modules to exercise the API. > > > >>>https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git/tree/testsuite/module-playground > > > >>> > > > >>>This works: > > > >>> make -C /lib/modules/$(uname -r)/build M=$PWD > > > >>> > > > >>>This doesn't: > > > >>> make -C /lib/modules/$(uname -r)/build M=$PWD O=/tmp/kmod_test_modules > > > > > > > > O= points the output directory of the kernel, > > not the output directory of the external modules. > > > > > > /lib/modules/$(uname -r)/build > > is the clean source tree. > > > > /tmp/kmod_test_modules > > contains the build artifacts of vmlinux and > > in-tree modules. > > > > Then, the command you gave would work. > > > > > > > > > > > > > > > >>> > > > >>>I also tried the variants above with setting src, but all of them give > > > >>>me errors - I used 6.10 and 6.11-rc7 for these tests. > > > >>> > > > >>>Is there a way to do this? > > > >>> > > > >>>thanks > > > >>>Lucas De Marchi > > > >>> > > > >>>> > > > >>>>Applied to linux-kbuild. Thanks. > > > >>>> > > > >>>> > > > >>>>-- > > > >>>>Best Regards > > > >>>>Masahiro Yamada > > > >> > > > >>Hi Masahiro, > > > > > > > >I guess you meant Lucas :) > > > > > > > >> > > > >>I think your intention is to separate the source code from the compiled output. > > > >>The correct command should be: > > > >> make -C /lib/modules/$(uname -r)/build src=$PWD M=/tmp/kmod_test_modules > > > > > > > >oh, looks like this works. Apparently my mistake was trying to set O= > > > >like I normally do for in-tree modules. > > > > > > spoke too early... It worked because I was in another machine pointing > > > to a 6.8 kernel. It seems like something broke between 6.9 and 6.10. > > > > > > Running a quick bisect, it's pointing to this commit: > > > 9a0ebe5011f4 ("kbuild: use $(obj)/ instead of $(src)/ for common pattern rules") > > > > > > Overriding 'src' from the command is not allowed. That's why. > > > > > > > Error like below: > > > > > > $ make -j$(nproc) -C ~/p/linux-dim/src MddPWD/build srcx=$PWD > > > make: Entering directory '/home/ldmartin/p/linux-dim/src' > > > make[2]: *** No rule to make target '/home/ldmartin/p/kmod/testsuite/module-playground/build/mod-simple.o', needed by '/home/ldmartin/p/kmod/testsuite/module-playground/build/'. Stop. > > > make[1]: *** [/home/ldmartin/p/linux-dim/src/Makefile:1922: /home/ldmartin/p/kmod/testsuite/module-playground/build] Error 2 > > > make: *** [Makefile:240: __sub-make] Error 2 > > > make: Leaving directory '/home/ldmartin/p/linux-dim/src' > > > > > > I suggested M=relative-path + VPATH= > > but I do not know what you want to achieve. > > > > https://lore.kernel.org/linux-kbuild/CAK7LNATGGibmjZzYX_A2SkJthmOPbKw2K3R7JYuHTWzgGL2Zjg@xxxxxxxxxxxxxx/ > > but that is only for in-tree modules, not external modules, right? > Quick reproducer on what I expected would work: > > git clone https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git > cd kmod/testsuite/module-playground > make -C $KDIR M=$PWD O=$PWD/build > > So... did I get the below statement right? > > There never was an official way to build external modules with > source and build in different directories. Up until 6.9 we > could pass `-C <kernel_srcdir> M=<mod_builddir> src=<mod_srcdir>` > for unofficial way. After that there's no alternative. yes, AFAICT your summary describes the situation quite precisely. Kind regards, Nicolas
