From 90e5b38a26529391da2d851a9cc5eb9de2ec35ca Mon Sep 17 00:00:00 2001 From: Ihor Solodrai Date: Fri, 19 Dec 2025 10:13:18 -0800 Subject: [PATCH] kbuild: Sync kconfig when PAHOLE_VERSION changes 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@oracle.com/ Signed-off-by: Ihor Solodrai Signed-off-by: Andrii Nakryiko Tested-by: Nicolas Schier Tested-by: Alan Maguire Reviewed-by: Nicolas Schier Link: https://lore.kernel.org/bpf/20251219181321.1283664-6-ihor.solodrai@linux.dev --- Makefile | 15 +++++++++++---- init/Kconfig | 2 +- 2 files changed, 12 insertions(+), 5 deletions(-) diff --git a/Makefile b/Makefile index e404e4767944e..18adf55022448 100644 --- a/Makefile +++ b/Makefile @@ -708,11 +708,12 @@ endif # The expansion should be delayed until arch/$(SRCARCH)/Makefile is included. # Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile. -# CC_VERSION_TEXT and RUSTC_VERSION_TEXT are referenced from Kconfig (so they -# need export), and from include/config/auto.conf.cmd to detect the compiler -# upgrade. +# CC_VERSION_TEXT, RUSTC_VERSION_TEXT and PAHOLE_VERSION are referenced from +# Kconfig (so they need export), and from include/config/auto.conf.cmd to +# detect the version changes between builds. 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 $(PAHOLE)) ifneq ($(findstring clang,$(CC_VERSION_TEXT)),) include $(srctree)/scripts/Makefile.clang @@ -733,7 +734,7 @@ ifdef config-build # KBUILD_DEFCONFIG may point out an alternative default configuration # used for 'make defconfig' include $(srctree)/arch/$(SRCARCH)/Makefile -export KBUILD_DEFCONFIG KBUILD_KCONFIG CC_VERSION_TEXT RUSTC_VERSION_TEXT +export KBUILD_DEFCONFIG KBUILD_KCONFIG CC_VERSION_TEXT RUSTC_VERSION_TEXT PAHOLE_VERSION config: outputmakefile scripts_basic FORCE $(Q)$(MAKE) $(build)=scripts/kconfig $@ @@ -1921,12 +1922,18 @@ clean: private rm-files := Module.symvers modules.nsdeps compile_commands.json PHONY += prepare # now expand this into a simple variable to reduce the cost of shell evaluations prepare: CC_VERSION_TEXT := $(CC_VERSION_TEXT) +prepare: PAHOLE_VERSION := $(PAHOLE_VERSION) prepare: @if [ "$(CC_VERSION_TEXT)" != "$(CONFIG_CC_VERSION_TEXT)" ]; then \ echo >&2 "warning: the compiler differs from the one used to build the kernel"; \ echo >&2 " The kernel was built by: $(CONFIG_CC_VERSION_TEXT)"; \ echo >&2 " You are using: $(CC_VERSION_TEXT)"; \ fi + @if [ "$(PAHOLE_VERSION)" != "$(CONFIG_PAHOLE_VERSION)" ]; then \ + echo >&2 "warning: pahole version differs from the one used to build the kernel"; \ + echo >&2 " The kernel was built with: $(CONFIG_PAHOLE_VERSION)"; \ + echo >&2 " You are using: $(PAHOLE_VERSION)"; \ + fi PHONY += help help: diff --git a/init/Kconfig b/init/Kconfig index fa79feb8fe57b..317f3c0b13ad2 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -171,7 +171,7 @@ config RUSTC_HAS_FILE_AS_C_STR config PAHOLE_VERSION int - default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) + default "$(PAHOLE_VERSION)" config CONSTRUCTORS bool -- 2.47.3