Re: due to kconfig changes kernel config file is no longer sufficient for configuring the kernel

[Masahiro Yamada <yamada.masahiro@socionext.com>]

Hi,


2018-08-21 6:33 GMT+09:00 Michal Suchánek <msuchanek@suse.de>:
> Hello,
>
> On Tue, 21 Aug 2018 03:15:12 +0900
> Masahiro Yamada <yamada.masahiro@socionext.com> wrote:
>
>> 2018-08-07 3:07 GMT+09:00 Michal Suchánek <msuchanek@suse.de>:
>> > On Mon, 30 Jul 2018 17:02:42 +0900
>> > Masahiro Yamada <yamada.masahiro@socionext.com> wrote:
>> >
>> >> 2018-06-28 18:16 GMT+09:00 Michal Suchánek <msuchanek@suse.de>:
>> >> > On Wed, 27 Jun 2018 23:07:21 +0900
>> >> > Masahiro Yamada <yamada.masahiro@socionext.com> wrote:
>> >> >
>
>> >>
>> >>
>> >>
>> >> >>
>> >> >> out-of-tree modules are built with exactly the same
>> >> >> configuration as used for the kernel.
>> >> >
>> >> > It is not true. And that is the problem. You need the config file
>> >> > and dump of the environment passed to the make command at
>> >> > configuration time to get the exact same configuration. The
>> >> > environment is not saved anywhere, though.
>> >>
>> >>
>> >> Why dump of the environment?
>> >>
>> >>
>> >> If you are building external modules natively
>> >> your distribution provides /lib/modules/$(uname -r)/build,
>> >> which contains files enough for building external modules.
>> >>
>> >> You can pass the directory path to M=... parameter.  That's it.
>> >
>> > No, that's not it. Since passing ARCH=i386 is the de-facto standard
>> > to configure a 32bit kernel and the result of passing that was not
>> > saved you need to pass it to make as well.
>>
>>
>> If you pass ARCH= for the configuration phase,
>> you need to pass the same ARCH= in the build phase.
>>
>>
>>
>>
>> What I can suggest for you is:
>>
>>
>> $ make ARCH=i386 defconfig
>> $ make ARCH=i386
>>
>>    OR
>>
>> $ make i386_defconfig
>> $ make
>
> Maybe you missed that but I do not want to build the defconfig. I want
> to build a *particular* config which has been saved in a file
> beforehand.
>>
>> > And you need to patch a number of
>> > 3rd party build scripts that build a kernel module as part of a
>> > bigger project.
>>
>>
>> You do not need to patch a number of scripts.
>>
>> Just one liner fix.
>> Add 'export ARCH=i386' in the top level script.
>
> And that does not work because there is no toplevel script. rpm has
> three toplevel scripts - prep, build and install.


OK, I understood real problem cases.

I wrote patches to support non-interactive .config updates.

For package building like rpm, deb, etc.
the target ARCH is determined when creating a source package.
If so, it would not hurt to hard-code to record ARCH in the spec file.


> Building out-of-tree module is another toplevel script.


As I said before, the .config is not reconfigured
when building out-of-tree modules.

Out-of-tree modules are built with the .config
that has been used to build vmlinux
regardless of whether you pass ARCH=i386, ARCH=x86_64, or nothing.

If rpmbuild is given target option like 'rpmbuild --target i386 ...",
it think it makes sense to propagate it to ARCH=.


> And it does not suffice to 'export ARCH=i386'. What if it was a 64bit
> config? How do I tell?
>
> With more and more options left out of the config that depend on
> compiler features, environment variables, phase of the moon or whatnot
> you can't even tell what kind of kernel the user is running by looking
> at the config.


I added non-interactive .config update.

Please try it.




-- 
Best Regards
Masahiro Yamada