External modules with O=... (was: Re: [PATCH] kbuild: Fix include path in scripts/Makefile.modpost)

External modules with O=... (was: Re: [PATCH] kbuild: Fix include path in scripts/Makefile.modpost)

[Lucas De Marchi]

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@zju.edu.cn> wrote:
>>
>> From: Jing Leng <jleng@ambarella.com>
>>
>> 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@ambarella.com>
>> ---
>>  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.

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

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

Re: External modules with O=... (was: Re: [PATCH] kbuild: Fix include path in scripts/Makefile.modpost)

[Jing Leng]

> -----Original Messages-----
> From: "Lucas De Marchi" <lucas.demarchi@intel.com>
> Send time:Tuesday, 09/10/2024 22:00:29
> To: "Masahiro Yamada" <masahiroy@kernel.org>
> Cc: 3090101217@zju.edu.cn, "Michal Marek" <michal.lkml@markovi.net>, "Nick
>  Desaulniers" <ndesaulniers@google.com>, "Linux Kbuild mailing list" <linux-kbuild@vger.kernel.org>, "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>, "Jing Leng" <jleng@ambarella.com>
> 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@zju.edu.cn> wrote:
> >>
> >> From: Jing Leng <jleng@ambarella.com>
> >>
> >> 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@ambarella.com>
> >> ---
> >>  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=$(PWD)" is the official way,
> >but this patch is a clean up.
> 
> I tried what is in this patch and also tried to find an official way in
> the docs.
> 
> In kmod's testsuite we build dummy kernel modules to exercise the API.
> https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git/tree/testsuite/module-playground
> 
> This works:
> 	make -C /lib/modules/$(uname -r)/build M=$PWD
> 
> This doesn't:
> 	make -C /lib/modules/$(uname -r)/build M=$PWD O=/tmp/kmod_test_modules
> 
> 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 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

You also can refer to:
    https://github.com/lengjingzju/cbuild-ng/blob/main/scripts/core/inc.mod.mk 
1. The complete command is as follows:
    make -C <Linux kernel source code directory> O=<Linux kernel compilation output directory> src=<Current driver module source code directory> M=<Current driver module compilation output directory>
2. If the <Linux kernel source code directory> and the <Linux kernel compilation output directory> are the same, <O=xxx> can be omitted:
    make -C <Linux kernel source code directory> src=<Current driver module source code directory> M=<Current driver module compilation output directory>
2. If the <Current driver module source code directory> and the <Current driver module compilation output directory> are the same, <src=xxx> can be omitted:
    make -C <Linux kernel source code directory> O=<Linux kernel compilation output directory> M=<Current driver module source code directory>

Best Regards!
Jing Leng

Re: External modules with O=... (was: Re: [PATCH] kbuild: Fix include path in scripts/Makefile.modpost)

[Lucas De Marchi]

On Wed, Sep 11, 2024 at 09:10:09AM GMT, Jing Leng wrote:
>> -----Original Messages-----
>> From: "Lucas De Marchi" <lucas.demarchi@intel.com>
>> Send time:Tuesday, 09/10/2024 22:00:29
>> To: "Masahiro Yamada" <masahiroy@kernel.org>
>> Cc: 3090101217@zju.edu.cn, "Michal Marek" <michal.lkml@markovi.net>, "Nick
>>  Desaulniers" <ndesaulniers@google.com>, "Linux Kbuild mailing list" <linux-kbuild@vger.kernel.org>, "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>, "Jing Leng" <jleng@ambarella.com>
>> 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@zju.edu.cn> wrote:
>> >>
>> >> From: Jing Leng <jleng@ambarella.com>
>> >>
>> >> 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@ambarella.com>
>> >> ---
>> >>  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=$(PWD)" is the official way,
>> >but this patch is a clean up.
>>
>> I tried what is in this patch and also tried to find an official way in
>> the docs.
>>
>> In kmod's testsuite we build dummy kernel modules to exercise the API.
>> https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git/tree/testsuite/module-playground
>>
>> This works:
>> 	make -C /lib/modules/$(uname -r)/build M=$PWD
>>
>> This doesn't:
>> 	make -C /lib/modules/$(uname -r)/build M=$PWD O=/tmp/kmod_test_modules
>>
>> 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.

Thanks
Lucas De Marchi

>
>You also can refer to:
>    https://github.com/lengjingzju/cbuild-ng/blob/main/scripts/core/inc.mod.mk
>1. The complete command is as follows:
>    make -C <Linux kernel source code directory> O=<Linux kernel compilation output directory> src=<Current driver module source code directory> M=<Current driver module compilation output directory>
>2. If the <Linux kernel source code directory> and the <Linux kernel compilation output directory> are the same, <O=xxx> can be omitted:
>    make -C <Linux kernel source code directory> src=<Current driver module source code directory> M=<Current driver module compilation output directory>
>2. If the <Current driver module source code directory> and the <Current driver module compilation output directory> are the same, <src=xxx> can be omitted:
>    make -C <Linux kernel source code directory> O=<Linux kernel compilation output directory> M=<Current driver module source code directory>
>
>Best Regards!
>Jing Leng

Re: External modules with O=... (was: Re: [PATCH] kbuild: Fix include path in scripts/Makefile.modpost)

[Lucas De Marchi]

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@intel.com>
>>>Send time:Tuesday, 09/10/2024 22:00:29
>>>To: "Masahiro Yamada" <masahiroy@kernel.org>
>>>Cc: 3090101217@zju.edu.cn, "Michal Marek" <michal.lkml@markovi.net>, "Nick
>>> Desaulniers" <ndesaulniers@google.com>, "Linux Kbuild mailing list" <linux-kbuild@vger.kernel.org>, "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>, "Jing Leng" <jleng@ambarella.com>
>>>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@zju.edu.cn> wrote:
>>>>>
>>>>> From: Jing Leng <jleng@ambarella.com>
>>>>>
>>>>> 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@ambarella.com>
>>>>> ---
>>>>>  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=$(PWD)" is the official way,
>>>>but this patch is a clean up.
>>>
>>>I tried what is in this patch and also tried to find an official way in
>>>the docs.
>>>
>>>In kmod's testsuite we build dummy kernel modules to exercise the API.
>>>https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git/tree/testsuite/module-playground
>>>
>>>This works:
>>>	make -C /lib/modules/$(uname -r)/build M=$PWD
>>>
>>>This doesn't:
>>>	make -C /lib/modules/$(uname -r)/build M=$PWD O=/tmp/kmod_test_modules
>>>
>>>I also tried the variants above with setting src, but all of them give
>>>me errors - I used 6.10 and 6.11-rc7 for these tests.
>>>
>>>Is there a way to do this?
>>>
>>>thanks
>>>Lucas De Marchi
>>>
>>>>
>>>>Applied to linux-kbuild. Thanks.
>>>>
>>>>
>>>>--
>>>>Best Regards
>>>>Masahiro Yamada
>>
>>Hi Masahiro,
>
>I guess you meant Lucas :)
>
>>
>>I think your intention is to separate the source code from the compiled output.
>>The correct command should be:
>>   make -C /lib/modules/$(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")

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'

Lucas De Marchi

>
>Thanks
>Lucas De Marchi
>
>>
>>You also can refer to:
>>   https://github.com/lengjingzju/cbuild-ng/blob/main/scripts/core/inc.mod.mk
>>1. The complete command is as follows:
>>   make -C <Linux kernel source code directory> O=<Linux kernel compilation output directory> src=<Current driver module source code directory> M=<Current driver module compilation output directory>
>>2. If the <Linux kernel source code directory> and the <Linux kernel compilation output directory> are the same, <O=xxx> can be omitted:
>>   make -C <Linux kernel source code directory> src=<Current driver module source code directory> M=<Current driver module compilation output directory>
>>2. If the <Current driver module source code directory> and the <Current driver module compilation output directory> are the same, <src=xxx> can be omitted:
>>   make -C <Linux kernel source code directory> O=<Linux kernel compilation output directory> M=<Current driver module source code directory>
>>
>>Best Regards!
>>Jing Leng

Re: External modules with O=... (was: Re: [PATCH] kbuild: Fix include path in scripts/Makefile.modpost)

[Masahiro Yamada]

On Wed, Sep 11, 2024 at 1:36 PM Lucas De Marchi
<lucas.demarchi@intel.com> 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@intel.com>
> >>>Send time:Tuesday, 09/10/2024 22:00:29
> >>>To: "Masahiro Yamada" <masahiroy@kernel.org>
> >>>Cc: 3090101217@zju.edu.cn, "Michal Marek" <michal.lkml@markovi.net>, "Nick
> >>> Desaulniers" <ndesaulniers@google.com>, "Linux Kbuild mailing list" <linux-kbuild@vger.kernel.org>, "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>, "Jing Leng" <jleng@ambarella.com>
> >>>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@zju.edu.cn> wrote:
> >>>>>
> >>>>> From: Jing Leng <jleng@ambarella.com>
> >>>>>
> >>>>> 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@ambarella.com>
> >>>>> ---
> >>>>>  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@mail.gmail.com/







> Lucas De Marchi
>
> >
> >Thanks
> >Lucas De Marchi
> >
> >>
> >>You also can refer to:
> >>   https://github.com/lengjingzju/cbuild-ng/blob/main/scripts/core/inc.mod.mk
> >>1. The complete command is as follows:
> >>   make -C <Linux kernel source code directory> O=<Linux kernel compilation output directory> src=<Current driver module source code directory> M=<Current driver module compilation output directory>
> >>2. If the <Linux kernel source code directory> and the <Linux kernel compilation output directory> are the same, <O=xxx> can be omitted:
> >>   make -C <Linux kernel source code directory> src=<Current driver module source code directory> M=<Current driver module compilation output directory>
> >>2. If the <Current driver module source code directory> and the <Current driver module compilation output directory> are the same, <src=xxx> can be omitted:
> >>   make -C <Linux kernel source code directory> O=<Linux kernel compilation output directory> M=<Current driver module source code directory>
> >>
> >>Best Regards!
> >>Jing Leng



-- 
Best Regards
Masahiro Yamada

Re: External modules with O=... (was: Re: [PATCH] kbuild: Fix include path in scripts/Makefile.modpost)

[Lucas De Marchi]

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@intel.com> 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@intel.com>
>> >>>Send time:Tuesday, 09/10/2024 22:00:29
>> >>>To: "Masahiro Yamada" <masahiroy@kernel.org>
>> >>>Cc: 3090101217@zju.edu.cn, "Michal Marek" <michal.lkml@markovi.net>, "Nick
>> >>> Desaulniers" <ndesaulniers@google.com>, "Linux Kbuild mailing list" <linux-kbuild@vger.kernel.org>, "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>, "Jing Leng" <jleng@ambarella.com>
>> >>>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@zju.edu.cn> wrote:
>> >>>>>
>> >>>>> From: Jing Leng <jleng@ambarella.com>
>> >>>>>
>> >>>>> 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@ambarella.com>
>> >>>>> ---
>> >>>>>  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@mail.gmail.com/

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.

thanks

Lucas De Marchi

Re: External modules with O=... (was: Re: [PATCH] kbuild: Fix include path in scripts/Makefile.modpost)

[Nicolas Schier]

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@intel.com> 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@intel.com>
> > > >>>Send time:Tuesday, 09/10/2024 22:00:29
> > > >>>To: "Masahiro Yamada" <masahiroy@kernel.org>
> > > >>>Cc: 3090101217@zju.edu.cn, "Michal Marek" <michal.lkml@markovi.net>, "Nick
> > > >>> Desaulniers" <ndesaulniers@google.com>, "Linux Kbuild mailing list" <linux-kbuild@vger.kernel.org>, "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>, "Jing Leng" <jleng@ambarella.com>
> > > >>>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@zju.edu.cn> wrote:
> > > >>>>>
> > > >>>>> From: Jing Leng <jleng@ambarella.com>
> > > >>>>>
> > > >>>>> 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@ambarella.com>
> > > >>>>> ---
> > > >>>>>  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@mail.gmail.com/
> 
> 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