Commit 757ee027 authored Jul 29, 2019 by Masahiro Yamada Committed by Greg Kroah-Hartman Aug 06, 2019

kbuild: initialize CLANG_FLAGS correctly in the top Makefile



commit 5241ab4cf42d3a93b933b55d3d53f43049081fa1 upstream.

CLANG_FLAGS is initialized by the following line:

  CLANG_FLAGS     := --target=$(notdir $(CROSS_COMPILE:%-=%))

..., which is run only when CROSS_COMPILE is set.

Some build targets (bindeb-pkg etc.) recurse to the top Makefile.

When you build the kernel with Clang but without CROSS_COMPILE,
the same compiler flags such as -no-integrated-as are accumulated
into CLANG_FLAGS.

If you run 'make CC=clang' and then 'make CC=clang bindeb-pkg',
Kbuild will recompile everything needlessly due to the build command
change.

Fix this by correctly initializing CLANG_FLAGS.

Fixes: 238bcbc4e07f ("kbuild: consolidate Clang compiler flags")
Cc: <stable@vger.kernel.org> # v5.0+
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent b2ca435c

Makefile

+2 −1

Original line number	Diff line number	Diff line
		@@ -400,6 +400,7 @@ KBUILD_AFLAGS_MODULE := -DMODULE
		KBUILD_CFLAGS_MODULE := -DMODULE
		KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds
		GCC_PLUGINS_CFLAGS :=
		CLANG_FLAGS :=

		# Read KERNELRELEASE from include/config/kernel.release (if it exists)
		KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
		@@ -506,7 +507,7 @@ endif

		ifeq ($(cc-name),clang)
		ifneq ($(CROSS_COMPILE),)
		CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE:%-=%))
		CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
		GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
		CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)
		GCC_TOOLCHAIN := $(realpath $(GCC_TOOLCHAIN_DIR)/..)