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 <ihor.solodrai@linux.dev>
---
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 $(PAHOLE))
ifneq ($(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 fa79feb8fe57..317f3c0b13ad 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
--
2.52.0On Wed, 2025-12-17 at 16:33 -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@oracle.com/
>
> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
> ---
When building BPF selftest modules the pahole version change was
detected, but it seems that BTF rebuild was not triggered:
$ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
make[1]: Entering directory '/home/ezingerman/bpf-next'
make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
CC [M] bpf_testmod.o
CC [M] bpf_test_no_cfi.o
CC [M] bpf_test_modorder_x.o
CC [M] bpf_test_modorder_y.o
CC [M] bpf_test_rqspinlock.o
MODPOST Module.symvers
CC [M] bpf_testmod.mod.o
CC [M] .module-common.o
CC [M] bpf_test_no_cfi.mod.o
CC [M] bpf_test_modorder_x.mod.o
CC [M] bpf_test_modorder_y.mod.o
CC [M] bpf_test_rqspinlock.mod.o
LD [M] bpf_test_modorder_x.ko
LD [M] bpf_testmod.ko
LD [M] bpf_test_modorder_y.ko
LD [M] bpf_test_no_cfi.ko
BTF [M] bpf_test_modorder_x.ko
LD [M] bpf_test_rqspinlock.ko
BTF bpf_test_modorder_x.ko
BTF [M] bpf_test_no_cfi.ko
BTF [M] bpf_test_modorder_y.ko
BTF [M] bpf_testmod.ko
BTF bpf_test_no_cfi.ko
BTF bpf_test_modorder_y.ko
BTF [M] bpf_test_rqspinlock.ko
BTF bpf_testmod.ko
BTF bpf_test_rqspinlock.ko
BTFIDS bpf_test_modorder_x.ko
BTFIDS bpf_test_modorder_y.ko
BTFIDS bpf_test_no_cfi.ko
BTFIDS bpf_testmod.ko
OBJCOPY bpf_test_modorder_x.ko.BTF
BTFIDS bpf_test_rqspinlock.ko
OBJCOPY bpf_test_no_cfi.ko.BTF
OBJCOPY bpf_test_modorder_y.ko.BTF
OBJCOPY bpf_testmod.ko.BTF
OBJCOPY bpf_test_rqspinlock.ko.BTF
make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
make[1]: Leaving directory '/home/ezingerman/bpf-next'
[~/bpf-next]
$ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
make[1]: Entering directory '/home/ezingerman/bpf-next'
make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
make[1]: Leaving directory '/home/ezingerman/bpf-next'
... update pahole from version 131 to 132 ...
[~/bpf-next]
$ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j)
make[1]: Entering directory '/home/ezingerman/bpf-next'
make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
warning: pahole version differs from the one used to build the kernel
The kernel was built with: 131
You are using: 132
make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods'
make[1]: Leaving directory '/home/ezingerman/bpf-next'
Is this an expected behavior?
On 12/18/25 11:21 AM, Eduard Zingerman wrote: > On Wed, 2025-12-17 at 16:33 -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@oracle.com/ >> >> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev> >> --- > > When building BPF selftest modules the pahole version change was > detected, but it seems that BTF rebuild was not triggered: > > $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j) > make[1]: Entering directory '/home/ezingerman/bpf-next' > make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > CC [M] bpf_testmod.o > CC [M] bpf_test_no_cfi.o > CC [M] bpf_test_modorder_x.o > CC [M] bpf_test_modorder_y.o > CC [M] bpf_test_rqspinlock.o > MODPOST Module.symvers > CC [M] bpf_testmod.mod.o > CC [M] .module-common.o > CC [M] bpf_test_no_cfi.mod.o > CC [M] bpf_test_modorder_x.mod.o > CC [M] bpf_test_modorder_y.mod.o > CC [M] bpf_test_rqspinlock.mod.o > LD [M] bpf_test_modorder_x.ko > LD [M] bpf_testmod.ko > LD [M] bpf_test_modorder_y.ko > LD [M] bpf_test_no_cfi.ko > BTF [M] bpf_test_modorder_x.ko > LD [M] bpf_test_rqspinlock.ko > BTF bpf_test_modorder_x.ko > BTF [M] bpf_test_no_cfi.ko > BTF [M] bpf_test_modorder_y.ko > BTF [M] bpf_testmod.ko > BTF bpf_test_no_cfi.ko > BTF bpf_test_modorder_y.ko > BTF [M] bpf_test_rqspinlock.ko > BTF bpf_testmod.ko > BTF bpf_test_rqspinlock.ko > BTFIDS bpf_test_modorder_x.ko > BTFIDS bpf_test_modorder_y.ko > BTFIDS bpf_test_no_cfi.ko > BTFIDS bpf_testmod.ko > OBJCOPY bpf_test_modorder_x.ko.BTF > BTFIDS bpf_test_rqspinlock.ko > OBJCOPY bpf_test_no_cfi.ko.BTF > OBJCOPY bpf_test_modorder_y.ko.BTF > OBJCOPY bpf_testmod.ko.BTF > OBJCOPY bpf_test_rqspinlock.ko.BTF > make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > make[1]: Leaving directory '/home/ezingerman/bpf-next' > [~/bpf-next] > $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j) > make[1]: Entering directory '/home/ezingerman/bpf-next' > make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > make[1]: Leaving directory '/home/ezingerman/bpf-next' > > ... update pahole from version 131 to 132 ... > > [~/bpf-next] > $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j) > make[1]: Entering directory '/home/ezingerman/bpf-next' > make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > warning: pahole version differs from the one used to build the kernel > The kernel was built with: 131 > You are using: 132 > make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > make[1]: Leaving directory '/home/ezingerman/bpf-next' > > Is this an expected behavior? Yes, it's expected. I simply repeated the logic used for compiler version change: for external modules only the warning is printed. See https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile?h=v6.18#n1857
On Thu, 2025-12-18 at 13:33 -0800, Ihor Solodrai wrote: > On 12/18/25 11:21 AM, Eduard Zingerman wrote: > > On Wed, 2025-12-17 at 16:33 -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@oracle.com/ > > > > > > Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev> > > > --- > > > > When building BPF selftest modules the pahole version change was > > detected, but it seems that BTF rebuild was not triggered: > > > > $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j) > > make[1]: Entering directory '/home/ezingerman/bpf-next' > > make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > > CC [M] bpf_testmod.o > > CC [M] bpf_test_no_cfi.o > > CC [M] bpf_test_modorder_x.o > > CC [M] bpf_test_modorder_y.o > > CC [M] bpf_test_rqspinlock.o > > MODPOST Module.symvers > > CC [M] bpf_testmod.mod.o > > CC [M] .module-common.o > > CC [M] bpf_test_no_cfi.mod.o > > CC [M] bpf_test_modorder_x.mod.o > > CC [M] bpf_test_modorder_y.mod.o > > CC [M] bpf_test_rqspinlock.mod.o > > LD [M] bpf_test_modorder_x.ko > > LD [M] bpf_testmod.ko > > LD [M] bpf_test_modorder_y.ko > > LD [M] bpf_test_no_cfi.ko > > BTF [M] bpf_test_modorder_x.ko > > LD [M] bpf_test_rqspinlock.ko > > BTF bpf_test_modorder_x.ko > > BTF [M] bpf_test_no_cfi.ko > > BTF [M] bpf_test_modorder_y.ko > > BTF [M] bpf_testmod.ko > > BTF bpf_test_no_cfi.ko > > BTF bpf_test_modorder_y.ko > > BTF [M] bpf_test_rqspinlock.ko > > BTF bpf_testmod.ko > > BTF bpf_test_rqspinlock.ko > > BTFIDS bpf_test_modorder_x.ko > > BTFIDS bpf_test_modorder_y.ko > > BTFIDS bpf_test_no_cfi.ko > > BTFIDS bpf_testmod.ko > > OBJCOPY bpf_test_modorder_x.ko.BTF > > BTFIDS bpf_test_rqspinlock.ko > > OBJCOPY bpf_test_no_cfi.ko.BTF > > OBJCOPY bpf_test_modorder_y.ko.BTF > > OBJCOPY bpf_testmod.ko.BTF > > OBJCOPY bpf_test_rqspinlock.ko.BTF > > make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > > make[1]: Leaving directory '/home/ezingerman/bpf-next' > > [~/bpf-next] > > $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j) > > make[1]: Entering directory '/home/ezingerman/bpf-next' > > make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > > make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > > make[1]: Leaving directory '/home/ezingerman/bpf-next' > > > > ... update pahole from version 131 to 132 ... > > > > [~/bpf-next] > > $ (cd ./tools/testing/selftests/bpf/test_kmods/; make -j) > > make[1]: Entering directory '/home/ezingerman/bpf-next' > > make[2]: Entering directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > > warning: pahole version differs from the one used to build the kernel > > The kernel was built with: 131 > > You are using: 132 > > make[2]: Leaving directory '/home/ezingerman/bpf-next/tools/testing/selftests/bpf/test_kmods' > > make[1]: Leaving directory '/home/ezingerman/bpf-next' > > > > Is this an expected behavior? > > Yes, it's expected. > > I simply repeated the logic used for compiler version change: for > external modules only the warning is printed. > > See https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile?h=v6.18#n1857 > Ok, it does rebuild BTF for the kernel itself. Tested-by: Eduard Zingerman <eddyz87@gmail.com>
On Wed, Dec 17, 2025 at 4:34 PM Ihor Solodrai <ihor.solodrai@linux.dev> 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@oracle.com/ > > Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev> > --- > Makefile | 9 ++++++++- > init/Kconfig | 2 +- > 2 files changed, 9 insertions(+), 2 deletions(-) > This is great, we should have done that a long time ago :) [...]
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