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

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

[Dmitry Voytik]

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@gmail.com>
---
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@gmail.com/
---
 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)
 		;;
 
 	*)
-- 
2.55.0

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

[Nicolas Schier]

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 ${KBUILD_OUTPUT}/.config
> to be updated.
> The problem can be worked around with --file, but this is easy to miss,
> and is inconsistent with how the Makefile and other tools work
> (e.g., scripts/diffconfig).
> 
> How to reproduce the issue:
> 	rm .config
> 	export KBUILD_OUTPUT=.out
> 	make defconfig
> 	./scripts/config \
> 	       -e CONFIG_UBSAN
> 	grep: .config: No such file or directory
> 
> Signed-off-by: Dmitry Voytik <voytikd@gmail.com>
> ---
> v3:
>  - Added an example in the commit message how to reproduce the issue
> v2:
>  - Addressed comments by sashiko:
>    - https://sashiko.dev/#/patchset/20260920064350.17999-1-voytikd%40gmail.com
>    - use basename when --refresh is used
>    - remove echo which can be misleading when --file is passed
> v1:
>  - https://lore.kernel.org/all/20260920064350.17999-1-voytikd@gmail.com/
> ---
>  scripts/config | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/config b/scripts/config
> index 32428ea909c2..cdee67157fe1 100755
> --- a/scripts/config
> +++ b/scripts/config
> @@ -130,6 +130,10 @@ on_exit() {
>  trap on_exit EXIT
>  
>  FN=.config
> +if [ -n "${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.

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.

-- 
Nicolas

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@kernel.org> 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 ${KBUILD_OUTPUT}/.config
> > to be updated.
> > The problem can be worked around with --file, but this is easy to miss,
> > and is inconsistent with how the Makefile and other tools work
> > (e.g., scripts/diffconfig).
> >
> > How to reproduce the issue:
> >       rm .config
> >       export KBUILD_OUTPUT=.out
> >       make defconfig
> >       ./scripts/config \
> >              -e CONFIG_UBSAN
> >       grep: .config: No such file or directory
> >
> > Signed-off-by: Dmitry Voytik <voytikd@gmail.com>
> > ---
> > v3:
> >  - Added an example in the commit message how to reproduce the issue
> > v2:
> >  - Addressed comments by sashiko:
> >    - https://sashiko.dev/#/patchset/20260920064350.17999-1-voytikd%40gmail.com
> >    - use basename when --refresh is used
> >    - remove echo which can be misleading when --file is passed
> > v1:
> >  - https://lore.kernel.org/all/20260920064350.17999-1-voytikd@gmail.com/
> > ---
> >  scripts/config | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/scripts/config b/scripts/config
> > index 32428ea909c2..cdee67157fe1 100755
> > --- a/scripts/config
> > +++ b/scripts/config
> > @@ -130,6 +130,10 @@ on_exit() {
> >  trap on_exit EXIT
> >
> >  FN=.config
> > +if [ -n "${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.

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

[Nicolas Schier]

On Tue, Sep 29, 2026 at 09:15:28PM +0200, Dmitry Voytik wrote:
> Hi Nicolas,
> 
> Thank you for taking your time and reviewing the patch.
> 
> On Tue, Sep 29, 2026 at 2:05 PM Nicolas Schier <nsc@kernel.org> 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 ${KBUILD_OUTPUT}/.config
> > > to be updated.
> > > The problem can be worked around with --file, but this is easy to miss,
> > > and is inconsistent with how the Makefile and other tools work
> > > (e.g., scripts/diffconfig).
> > >
> > > How to reproduce the issue:
> > >       rm .config
> > >       export KBUILD_OUTPUT=.out
> > >       make defconfig
> > >       ./scripts/config \
> > >              -e CONFIG_UBSAN
> > >       grep: .config: No such file or directory
> > >
> > > Signed-off-by: Dmitry Voytik <voytikd@gmail.com>
> > > ---
> > > v3:
> > >  - Added an example in the commit message how to reproduce the issue
> > > v2:
> > >  - Addressed comments by sashiko:
> > >    - https://sashiko.dev/#/patchset/20260920064350.17999-1-voytikd%40gmail.com
> > >    - use basename when --refresh is used
> > >    - remove echo which can be misleading when --file is passed
> > > v1:
> > >  - https://lore.kernel.org/all/20260920064350.17999-1-voytikd@gmail.com/
> > > ---
> > >  scripts/config | 6 +++++-
> > >  1 file changed, 5 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/scripts/config b/scripts/config
> > > index 32428ea909c2..cdee67157fe1 100755
> > > --- a/scripts/config
> > > +++ b/scripts/config
> > > @@ -130,6 +130,10 @@ on_exit() {
> > >  trap on_exit EXIT
> > >
> > >  FN=.config
> > > +if [ -n "${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

This one shows one of the problems with scripts/config: while the script
itself handles relative paths to --file FILE from the current working
directory, a call of Kbuild changes the working directory to
$(KBUILD_OUTOUT) and realtive paths in KCONFIG_CONFIG are resolved from
there.

I don't have a solution in mind, that fits it all.  But I think it's
important to not make things worse (or more unexpected) than before, by
accident.

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

yeah, please send a v4 and then let's see what we'll do with it, ok?

Thanks and kind regards,
Nicolas

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

[Dmitry Voytik]

Hi Nicolas,

Thanks for the review!

On Thu, Oct 1, 2026 at 5:06 PM Nicolas Schier <nsc@kernel.org> wrote:
>
> On Tue, Sep 29, 2026 at 09:15:28PM +0200, Dmitry Voytik wrote:
> > Hi Nicolas,
> >
> > Thank you for taking your time and reviewing the patch.
> >
> > On Tue, Sep 29, 2026 at 2:05 PM Nicolas Schier <nsc@kernel.org> 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 ${KBUILD_OUTPUT}/.config
> > > > to be updated.
> > > > The problem can be worked around with --file, but this is easy to miss,
> > > > and is inconsistent with how the Makefile and other tools work
> > > > (e.g., scripts/diffconfig).
> > > >
> > > > How to reproduce the issue:
> > > >       rm .config
> > > >       export KBUILD_OUTPUT=.out
> > > >       make defconfig
> > > >       ./scripts/config \
> > > >              -e CONFIG_UBSAN
> > > >       grep: .config: No such file or directory
> > > >
> > > > Signed-off-by: Dmitry Voytik <voytikd@gmail.com>
> > > > ---
> > > > v3:
> > > >  - Added an example in the commit message how to reproduce the issue
> > > > v2:
> > > >  - Addressed comments by sashiko:
> > > >    - https://sashiko.dev/#/patchset/20260920064350.17999-1-voytikd%40gmail.com
> > > >    - use basename when --refresh is used
> > > >    - remove echo which can be misleading when --file is passed
> > > > v1:
> > > >  - https://lore.kernel.org/all/20260920064350.17999-1-voytikd@gmail.com/
> > > > ---
> > > >  scripts/config | 6 +++++-
> > > >  1 file changed, 5 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/scripts/config b/scripts/config
> > > > index 32428ea909c2..cdee67157fe1 100755
> > > > --- a/scripts/config
> > > > +++ b/scripts/config
> > > > @@ -130,6 +130,10 @@ on_exit() {
> > > >  trap on_exit EXIT
> > > >
> > > >  FN=.config
> > > > +if [ -n "${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
>
> This one shows one of the problems with scripts/config: while the script
> itself handles relative paths to --file FILE from the current working
> directory, a call of Kbuild changes the working directory to
> $(KBUILD_OUTOUT) and realtive paths in KCONFIG_CONFIG are resolved from
> there.

Indeed, with the patch, if I pass a relative path,
it creates the config file in an unexpected place:

       make mrproper
       export KBUILD_OUTPUT=.out
       make defconfig
       mkdir .out2
       cp .out/.config .out2/.my_config
       ./scripts/config --file .out2/.my_config \
              --refresh \
              -e CONFIG_UBSAN
       ls .out/.out2/.my_config

Also, apparently, the following test case with --refresh misbehaves:
       ./scripts/config --refresh \
              -e CONFIG_UBSAN
It creates .out/.out/.config :)

I decided to always enforce converting $FN to the absolute path:

       diff --git a/scripts/config b/scripts/config
       index 4e29c3084fec..0b28fc498195 100755
       --- a/scripts/config
       +++ b/scripts/config
       @@ -147,6 +147,7 @@ while [[ $# -gt 0 ]]; do
       shift
       fi
       done
       +FN=$(realpath "$FN")

       set -- "${CMDS[@]}"
       if [ "$1" = "" ] ; then

With this change, all tests pass, no side effects as it seems.

> I don't have a solution in mind, that fits it all.  But I think it's
> important to not make things worse (or more unexpected) than before, by
> accident.
>
> > If you are fine with the above, I can send v4 with adding the above
> > testing steps into the commit message.
>
> yeah, please send a v4 and then let's see what we'll do with it, ok?

I'll send a v4 patch.
Thanks for the review!

> Thanks and kind regards,
> Nicolas

Best Regards,
Dmitry Voytik.