Re: [PATCH v5] scripts/config: honor $KBUILD_OUTPUT by default

[Nathan Chancellor]

Hi Dmitry,

> 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.
> Handle properly if the config file is a relative path.
> 
> 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
> 
> How the patch was tested:
> 	make mrproper
> 	export KBUILD_OUTPUT=.out
> 	make defconfig
> 	grep "CONFIG_UBSAN=y" $KBUILD_OUTPUT/.config || echo "OK"
> 
> Test the basic usage:
> 	./scripts/config -e CONFIG_UBSAN
> 	grep "CONFIG_UBSAN=y" $KBUILD_OUTPUT/.config && echo "OK"
> 
> Test --refresh picks up correct config file by using $KBUILD_OUTPUT:
> 	./scripts/config -d CONFIG_UBSAN
> 	./scripts/config --refresh -e CONFIG_UBSAN
> 	grep "CONFIG_UBSAN=y" $KBUILD_OUTPUT/.config && echo "OK"
> 
> Test --file takes precedence over $KBUILD_OUTPUT and a relative
> path is handled properly:
> 	./scripts/config -d CONFIG_UBSAN
> 	mkdir .out2
> 	cp .out/.config .out2/.my_config
> 	grep "CONFIG_UBSAN=y" .out2/.my_config
> 	./scripts/config --file .out2/.my_config --refresh \
> 	       -e CONFIG_UBSAN
> 	grep "CONFIG_UBSAN=y" .out2/.my_config && echo "OK"
> 	ls .out/.out2 || echo "OK"
> 	ls .out/.out || echo "OK"
> 
> Test --file can accept files with hyphen:
> 	./scripts/config -d CONFIG_UBSAN
> 	cp .out/.config -- -my_config
> 	grep "CONFIG_UBSAN=y" -- -my_config || echo "OK"
> 	./scripts/config  --refresh \
> 	       -e CONFIG_UBSAN --file -my_config
> 	grep "CONFIG_UBSAN=y" -- -my_config && echo "OK"
> 
> Signed-off-by: Dmitry Voytik <voytikd@xxxxxxxxx>
> ---
> v5:
>  - Per Nathan Chancellor's suggestion, improved handling $FN path by
>    realpath
>  - https://lore.kernel.org/lkml/179097210878.309835.10523307262544578337.b4-review@b4/
>  - Documented the new test scenario in the git commit message
> v4:
>  - Addressed Nicolas Schier's comments - dropped the change how '--refresh'
>    is handled
>  - Implemented conversion of $FN to the absolute path which helps with
>    '--refresh' and relative paths
>  - Documented testing steps in the commit message
> v3:
>  - Added an example in the commit message how to reproduce the issue
> v2:
>  - Addressed comments by sashiko:
>    - https://sashiko.dev/#/patchset/20260920064350.17999-1-voytikd%40gmail.com
>    - use basename when --refresh is used
>    - remove echo which can be misleading when --file is passed
> v1:
>  - https://lore.kernel.org/all/20260920064350.17999-1-voytikd@xxxxxxxxx/
> ---
>  scripts/config | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/scripts/config b/scripts/config
> index 32428ea909c2..7e84c3d4e621 100755
> --- a/scripts/config
> +++ b/scripts/config
> @@ -130,6 +130,10 @@ on_exit() {
>  trap on_exit EXIT
>  
>  FN=.config
> +if [ -n "${KBUILD_OUTPUT}" ]; then
> +	FN=${KBUILD_OUTPUT}/${FN}
> +fi
> +
>  CMDS=()
>  while [[ $# -gt 0 ]]; do
>  	if [ "$1" = "--file" ]; then
> @@ -143,6 +147,7 @@ while [[ $# -gt 0 ]]; do
>  		shift
>  	fi
>  done
> +FN=$(realpath -q -- "$FN" || echo "$FN")

Sashiko has some further complaints about this:

  https://sashiko.dev/#/patchset/20261002222119.393508-1-voytikd@xxxxxxxxx

Due to travel and Linux Plumbers, I am not sure I will be able to think
about the best way to resolve this before I finalize the Kbuild tree for
7.4, so this may need to be deferred until after 7.4-rc1 is released
(i.e., it will target 7.5). One option that immediately comes to mind is
requiring $KBUILD_OUTPUT to exist already and only running realpath on
$KBUILD_OUTPUT, which would leave the script unchanged for the case of
$KBUILD_OUTPUT being unset, which seems safer to me:

  if [ -n "$KBUILD_OUTPUT" ]; then
      if [ ! -d "$KBUILD_OUTPUT" ]; then
          echo "KBUILD_OUTPUT is set but does not exist or is not a directory, create it before running $myname" >&2
          exit 1
      fi
      FN=$(realpath "$KBUILD_OUTPUT")/$FN
  fi

This would leave a relative '--file' value + KBUILD_OUTPUT + '--refresh'
in a weird state still but it appears that commit f757f6011c92 ("kbuild:
fix argument parsing in scripts/config") got that wrong almost two years
ago so it doesn't feel like it is worth caring about that until someone
actually complains about it (but I might be missing something).

-- 
Cheers,
Nathan