Re: [PATCH v3] scripts/config: honor $KBUILD_OUTPUT by default

[Dmitry Voytik]

Hi Nicolas,

Thank you for taking your time and reviewing the patch.

On Tue, Sep 29, 2026 at 2:05 PM Nicolas Schier <nsc@xxxxxxxxxx> wrote:
>
> On Sun, Sep 27, 2026 at 05:41:01PM +0200, Dmitry Voytik wrote:
> > If $KBUILD_OUTPUT is set, use it by default if --file is not passed.
> >
> > Fix the issue when the script silently updates a stale .config in
> > the root directory, while the user expects ${KBUILD_OUTPUT}/.config
> > to be updated.
> > The problem can be worked around with --file, but this is easy to miss,
> > and is inconsistent with how the Makefile and other tools work
> > (e.g., scripts/diffconfig).
> >
> > How to reproduce the issue:
> >       rm .config
> >       export KBUILD_OUTPUT=.out
> >       make defconfig
> >       ./scripts/config \
> >              -e CONFIG_UBSAN
> >       grep: .config: No such file or directory
> >
> > Signed-off-by: Dmitry Voytik <voytikd@xxxxxxxxx>
> > ---
> > v3:
> >  - Added an example in the commit message how to reproduce the issue
> > v2:
> >  - Addressed comments by sashiko:
> >    - https://sashiko.dev/#/patchset/20260920064350.17999-1-voytikd%40gmail.com
> >    - use basename when --refresh is used
> >    - remove echo which can be misleading when --file is passed
> > v1:
> >  - https://lore.kernel.org/all/20260920064350.17999-1-voytikd@xxxxxxxxx/
> > ---
> >  scripts/config | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/scripts/config b/scripts/config
> > index 32428ea909c2..cdee67157fe1 100755
> > --- a/scripts/config
> > +++ b/scripts/config
> > @@ -130,6 +130,10 @@ on_exit() {
> >  trap on_exit EXIT
> >
> >  FN=.config
> > +if [ -n "${KBUILD_OUTPUT}" ]; then
> > +     FN=${KBUILD_OUTPUT}/${FN}
> > +fi
> > +
> >  CMDS=()
> >  while [[ $# -gt 0 ]]; do
> >       if [ "$1" = "--file" ]; then
> > @@ -229,7 +233,7 @@ while [ "$1" != "" ] ; do
> >               ;;
> >
> >       --refresh)
> > -             yes "" | make oldconfig KCONFIG_CONFIG=$FN
> > +             yes "" | make oldconfig KCONFIG_CONFIG=$(basename $FN)
>
> Thanks for attempting to fix the '--refresh' option.  But this way,
> this may lead to very unexpected behaviour, as it regardlessly modifies
> the path to the config file, even if it was specified via --file.
>
> If --file is given, it should take precedence over any KBUILD_OUTPUT
> (or KCONFIG_CONFIG) from the environment and not be changed unrequested.

Thanks. I misunderstood what KBUILD_OUTPUT really means. For some reason,
I thought it should be a filename and not a full path. The
documentation entry is a bit vague on it.

> It would be a tiny bit nicer to just strip the KBUILD_OUTPUT path from
> FN, e.g. (untested):
>
>                 yes "" | make oldconfig KCONFIG_CONFIG="${FN#${KBUILD_OUTPUT}/}"
>
> But I am still not feeling happy with that.

Thanks for the suggestion! So, what I did - I just completely dropped
the second change hunk, i.e. kept it as is:
      yes "" | make oldconfig KCONFIG_CONFIG=$FN

I tested the following three scenarios and it looks like it works as expected:

make mrproper
export KBUILD_OUTPUT=.out
make defconfig
grep "CONFIG_UBSAN=y" $KBUILD_OUTPUT/.config

# test basic use case:
./scripts/config \
       -e CONFIG_UBSAN
grep "CONFIG_UBSAN=y" $KBUILD_OUTPUT/.config
./scripts/config -d CONFIG_UBSAN

# test --refresh picks up correct config file by using $KBUILD_OUTPUT
./scripts/config --refresh \
       -e CONFIG_UBSAN
grep "CONFIG_UBSAN=y" $KBUILD_OUTPUT/.config
./scripts/config -d CONFIG_UBSAN

# test --file takes precedence over $KBUILD_OUTPUT
cp .out/.config .my_config
grep "CONFIG_UBSAN=y" .my_config
./scripts/config --file $(pwd)/.my_config --refresh \
       -e CONFIG_UBSAN
grep "CONFIG_UBSAN=y" .my_config

If you are fine with the above, I can send v4 with adding the above
testing steps into the commit message.
Thanks!

> --
> Nicolas

-- 
Best Regards,
Dmitry Voytik.