kbuild: allow to use GCC toolchain not in Clang search path

commit ef8c4ed9db80261f397f0c0bf723684601ae3b52 upstream.

When using a GCC cross toolchain which is not in a compiled in
Clang search path, Clang reverts to the system assembler and
linker. This leads to assembler or linker errors, depending on
which tool is first used for a given architecture.

It seems that Clang is not searching $PATH for a matching
assembler or linker.

Make sure that Clang picks up the correct assembler or linker by
passing the cross compilers bin directory as search path.

This allows to use Clang provided by distributions with GCC
toolchains not in /usr/bin.

Change-Id: Ia5683ef2a9def6122219bb38d834ad45e2d204c2
Link: https://github.com/ClangBuiltLinux/linux/issues/78
Signed-off-by: Stefan Agner <stefan@agner.ch>
Reviewed-and-tested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
[nc: Adjust context]
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Makefile b/Makefile
index 3f16de6bb90ecf4a44459819270dc6dd29289f82..31c528e7a91eb227a9cf4680a53126522732e97f 100755 (executable)
--- a/Makefile
+++ b/Makefile
@@ -737,13 +737,15 @@ ifeq ($(cc-name),clang)
 ifneq ($(CROSS_COMPILE),)
 CLANG_TRIPLE    ?= $(CROSS_COMPILE)
 CLANG_TARGET   := --target=$(notdir $(CLANG_TRIPLE:%-=%))
-GCC_TOOLCHAIN  := $(realpath $(dir $(shell which $(LD)))/..)
+GCC_TOOLCHAIN_DIR := $(dir $(shell which $(LD)))
+CLANG_PREFIX   := --prefix=$(GCC_TOOLCHAIN_DIR)
+GCC_TOOLCHAIN  := $(realpath $(GCC_TOOLCHAIN_DIR)/..)
 endif
 ifneq ($(GCC_TOOLCHAIN),)
 CLANG_GCC_TC   := --gcc-toolchain=$(GCC_TOOLCHAIN)
 endif
-KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC)
-KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC)
+KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) $(CLANG_PREFIX)
+KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) $(CLANG_PREFIX)
 KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
 KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
 KBUILD_CFLAGS += $(call cc-disable-warning, gnu)