From: Masahiro Yamada masahiroy@kernel.org
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 eberman@codeaurora.org Signed-off-by: Masahiro Yamada masahiroy@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/.gitignore | 1 + kernel/Makefile | 9 +++++++-- 2 files changed, 8 insertions(+), 2 deletions(-)
--- a/kernel/.gitignore +++ b/kernel/.gitignore @@ -1,4 +1,5 @@ # +/config_data # Generated files # kheaders.md5 --- 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