I wrote this patch set to cater to some reports: - Bernd Edlinger reports false positive check of libelf once CONFIG_UNWINDER_ORC is enabled. https://lore.kernel.org/patchwork/patch/960411/ - Borislav Petkov reports the build fails very late if CONFIG_KERNEL_LZ4 is enabled but lz4 is missing. https://patchwork.kernel.org/patch/10635381/ >From the discussion https://patchwork.kernel.org/patch/10516049/ people like to see a build error when some host tools are missing. So, we need to check host tools in makefiles. (Or, do not check at all. The build will fail anyway, but the error message might not be clear enough in some cases.) A problem is people check host tools in random places in the top Makefile. This does not work because the top Makefile is parsed twice when the include/config/auto.config is updated. Once with a stale auto.config, and once again with a new auto.conf. This will cause false positive build error. One solution is to provide a systematic way to do host-tool checks. I added small macros in scripts/Makefile.toolcheck to describe tool checks in a Kbuild-ish taste. Masahiro Yamada (3): kbuild: provide a new place to check necessary host tools objtool: move libelf check out of top Makefile kbuild: check the presence of lzo and lz4 tools when necessary Makefile | 22 ++++----------------- scripts/Makefile.build | 2 -- scripts/Makefile.toolcheck | 48 ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 52 insertions(+), 20 deletions(-) create mode 100644 scripts/Makefile.toolcheck -- 2.7.4