Re: [PATCH bpf-next v6 5/8] kbuild: Sync kconfig when PAHOLE_VERSION changes

[Nicolas Schier]

On Thu, Dec 18, 2025 at 06:00:03PM -0800, Ihor Solodrai wrote:
> This patch implements kconfig re-sync when the pahole version changes
> between builds, similar to how it happens for compiler version change
> via CC_VERSION_TEXT.
> 
> Define PAHOLE_VERSION in the top-level Makefile and export it for
> config builds. Set CONFIG_PAHOLE_VERSION default to the exported
> variable.
> 
> Kconfig records the PAHOLE_VERSION value in
> include/config/auto.conf.cmd [1].
> 
> The Makefile includes auto.conf.cmd, so if PAHOLE_VERSION changes
> between builds, make detects a dependency change and triggers
> syncconfig to update the kconfig [2].
> 
> For external module builds, add a warning message in the prepare
> target, similar to the existing compiler version mismatch warning.
> 
> Note that if pahole is not installed or available, PAHOLE_VERSION is
> set to 0 by pahole-version.sh, so the (un)installation of pahole is
> treated as a version change.
> 
> See previous discussions for context [3].
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/kconfig/preprocess.c?h=v6.18#n91
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile?h=v6.18#n815
> [3] https://lore.kernel.org/bpf/8f946abf-dd88-4fac-8bb4-84fcd8d81cf0@xxxxxxxxxx/
> 
> Signed-off-by: Ihor Solodrai <ihor.solodrai@xxxxxxxxx>
> ---
>  Makefile     | 9 ++++++++-
>  init/Kconfig | 2 +-
>  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index e404e4767944..9b90a2a2218e 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -713,6 +713,7 @@ endif
>  # upgrade.
>  CC_VERSION_TEXT = $(subst $(pound),,$(shell LC_ALL=C $(CC) --version 2>/dev/null | head -n 1))
>  RUSTC_VERSION_TEXT = $(subst $(pound),,$(shell $(RUSTC) --version 2>/dev/null))
> +PAHOLE_VERSION = $(shell $(srctree)/scripts/pahole-version.sh $(PAHOLE))

As PAHOLE_VERSION is handled in the same way as CC_VERSION_TEXT and
RUSTC_VERSION_TEXT at line 736/737: could you please add it to the
comment above, too?

Patch looks good to me, thanks!

Reviewed-by: Nicolas Schier <nsc@xxxxxxxxxx>
Tested-by: Nicolas Schier <nsc@xxxxxxxxxx>