Re: [PATCH v4 1/2] Provide in-kernel headers for making it easy to extend the kernel

[Justin Capella]

Would you consider this more reliable than the make install_headers,
and am curious about DKMS applications / whether this should be
preferable to the /lib/modules/kernver/biuld symlinks

On Wed, Mar 6, 2019 at 6:48 AM Masahiro Yamada
<yamada.masahiro@xxxxxxxxxxxxx> wrote:
>
> On Mon, Mar 4, 2019 at 1:15 AM Joel Fernandes <joelaf@xxxxxxxxxx> wrote:
> >
> > This report is for an older version of the patch so ignore it. The
> > issue is already resolved.
> >
> > On Sat, Mar 2, 2019 at 2:00 PM kbuild test robot <lkp@xxxxxxxxx> wrote:
> > >
> > > Hi Joel,
> > >
> > > Thank you for the patch! Yet something to improve:
> > >
> > > [auto build test ERROR on linus/master]
> > > [also build test ERROR on v5.0-rc8]
> > > [cannot apply to next-20190301]
> > > [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> > >
> > > url:    https://github.com/0day-ci/linux/commits/Joel-Fernandes-Google/Provide-in-kernel-headers-for-making-it-easy-to-extend-the-kernel/20190303-014850
> > > config: sh-allmodconfig (attached as .config)
> > > compiler: sh4-linux-gnu-gcc (Debian 8.2.0-11) 8.2.0
> > > reproduce:
> > >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > >         chmod +x ~/bin/make.cross
> > >         # save the attached .config to linux build tree
> > >         GCC_VERSION=8.2.0 make.cross ARCH=sh
> > >
> > > All errors (new ones prefixed by >>):
> > >
> > > >> find: 'arch/sh/kernel/module.lds': No such file or directory
> > > >> find: 'arch/sh/kernel/module.lds': No such file or directory
> > >
> > > ---
> > > 0-DAY kernel test infrastructure                Open Source Technology Center
> > > https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
> > >
> > > --
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>
>
>
> Honestly speaking, I am worried about some flaws
> in this feature, but anyway I read your code.
>
> Here are just comments from the build system point of view
> in case something might be useful.
>
> Please feel free to adopt some of them if you think they are good.
>
> (I do not think you need to re-post a patch just for
> adding Reviewed-by/Tested-by tags, but anyway looks like you are
> planning to post a new version.)
>
>
>
> [1]
>
> Please do not ignore kbuild test robot.
>
> It never makes such a mistake like
> replying to a new patch about the test result from old version.
>
> The reports are really addressing this version (v4).
>
> I see the error message even on x86.
>
>
> [2]
>
> The shell script keeps running
> even when an error occurs.
>
> If any line in a shell script fails,
> probably it went already wrong.
>
> I highly recommend to add 'set -e'
> at the very beginning of your shell script.
>
> It will propagate the error to Make.
>
>
>
> [3]
>
> targets += kheaders_data.tar.xz
> targets += kheaders_data.h
> targets += kheaders.md5
>
> These three lines are unneeded because
> 'targets' is necessary just for if_changed or if_changed_rule.
>
> Instead, please add
>
> clean-files := kheaders_data.tar.xz kheaders_data.h kheaders.md5
>
>
> [4]
>
> It is pointless to pass 'ikh_file_list'
> from Makefile to the shell script.
>
>
> You can directly describe the following in gen_ikh_data.sh
>
> You do not need to use sed.
>
>
> src_file_list="
> include/
> arch/$SRCARCH/Makefile
> arch/$SRCARCH/include/
> arch/$SRCARCH/kernel/module.lds
> scripts/
> Makefile
> "
>
> obj_file_list="
> scripts/
> include/
> arch/$SRCARCH/include/
> "
>
> if grep -q "^CONFIG_STACK_VALIDATION=y" $KCONFIG_CONFIG; then
>         obj_file_list="$obj_file_list tools/objtool/objtool"
> fi
>
>
>
> Be careful about module.lds
> so that it will work for all architectures.
>
>
>
>
> [5]
> strip-comments.pl is short enough,
> and I do not assume any other user.
>
>
> IMHO, it would be cleaner to embed the one-liner perl
> into the shell script, for example, like follows:
>
> find  $cpio_dir -type f -print0 |
>  xargs -0 -P8 -n1 perl -pi -e 'BEGIN {undef $/;}; s/\/\*((?!SPDX).)*?\*\///smg;'
>
>
>
> [6]
> It might be better to move
> scripts/gen_ikh_data.sh to kernel/gen_ikh_data.sh
>
> It will make this feature self-contained in kernel/.
> And (more importantly to me), it would reduce my maintenance field.
>
>
>
> [7]
> I do not understand for what 'tarfile_md5' is used.
> Is it necessary?
>
>
>
> [8]
> Is it more efficient to pipe the header files
> to perl script like this?
>
>
>  cat (header) | perl 'do something' > (tmp directory)
>
>
> Actually, I am not sure if it is more efficient than
> stripping comments in-line. I could be wrong...
>
>
> [9]
>
> I'd prefer avoiding 'pushd && popd' if possible.
>
> Hint: Kbuild already runs at the top directory
> of objtree.
>
>
> It is OK if the change would mess up the script.
>
>
> [10]
>
> You can embed a binary directly into C file
> without producing a giant header file.
>
> I refactored kernel/configs.c
> https://lore.kernel.org/patchwork/patch/1042013/
>
> Be careful; my patch has not been merged yet into the mainline.
>
> It has been a while in linux-next,
> and I have not received any problem report.
>
> So, I am guessing it will probably be merged
> in the current MW.
>
>
>
>
> That's all from me.
>
>
> --
> Best Regards
> Masahiro Yamada