From 79c95130a52adcf999ba5c62b638666266d43385 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sun, 25 Apr 2021 15:24:07 +0900 Subject: [PATCH] kbuild: update config_data.gz only when the content of .config is changed commit 46b41d5dd8019b264717978c39c43313a524d033 upstream. If the timestamp of the .config file is updated, config_data.gz is regenerated, then vmlinux is re-linked. This occurs even if the content of the .config has not changed at all. This issue was mitigated by commit 67424f61f813 ("kconfig: do not write .config if the content is the same"); Kconfig does not update the .config when it ends up with the identical configuration. The issue is remaining when the .config is created by *_defconfig with some config fragment(s) applied on top. This is typical for powerpc and mips, where several *_defconfig targets are constructed by using merge_config.sh. One workaround is to have the copy of the .config. The filechk rule updates the copy, kernel/config_data, by checking the content instead of the timestamp. With this commit, the second run with the same configuration avoids the needless rebuilds. $ make ARCH=mips defconfig all [ snip ] $ make ARCH=mips defconfig all *** Default configuration is based on target '32r2el_defconfig' Using ./arch/mips/configs/generic_defconfig as base Merging arch/mips/configs/generic/32r2.config Merging arch/mips/configs/generic/el.config Merging ./arch/mips/configs/generic/board-boston.config Merging ./arch/mips/configs/generic/board-ni169445.config Merging ./arch/mips/configs/generic/board-ocelot.config Merging ./arch/mips/configs/generic/board-ranchu.config Merging ./arch/mips/configs/generic/board-sead-3.config Merging ./arch/mips/configs/generic/board-xilfpga.config # # configuration written to .config # SYNC include/config/auto.conf CALL scripts/checksyscalls.sh CALL scripts/atomic/check-atomics.sh CHK include/generated/compile.h CHK include/generated/autoksyms.h Reported-by: Elliot Berman Signed-off-by: Masahiro Yamada Signed-off-by: Greg Kroah-Hartman --- kernel/.gitignore | 1 + kernel/Makefile | 9 +++++++-- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/.gitignore b/kernel/.gitignore index 34d1e77ee9df..0f0dba6c1eed 100644 --- a/kernel/.gitignore +++ b/kernel/.gitignore @@ -1,4 +1,5 @@ # +/config_data # Generated files # kheaders.md5 diff --git a/kernel/Makefile b/kernel/Makefile index 6aef13053a5c..d038b0de886e 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -122,10 +122,15 @@ KCOV_INSTRUMENT_stackleak.o := n $(obj)/configs.o: $(obj)/config_data.gz -targets += config_data.gz -$(obj)/config_data.gz: $(KCONFIG_CONFIG) FORCE +targets += config_data config_data.gz +$(obj)/config_data.gz: $(obj)/config_data FORCE $(call if_changed,gzip) +filechk_cat = cat $< + +$(obj)/config_data: $(KCONFIG_CONFIG) FORCE + $(call filechk,cat) + $(obj)/kheaders.o: $(obj)/kheaders_data.tar.xz quiet_cmd_genikh = CHK $(obj)/kheaders_data.tar.xz