2018-09-19 2:16 GMT+09:00 Nick Desaulniers <ndesaulniers@xxxxxxxxxx>: > On Mon, Sep 17, 2018 at 7:32 PM Stefan Agner <stefan@xxxxxxxx> wrote: >> >> 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. > > Yes, Clang uses what's called a sysroot, which is meant to be more > hygenic than $PATH, IIUC. This is surprising to folks familiar with > $PATH, but really helps include the correct headers and use the > correct toolchain when cross compiling, at the cost of freedom to put > the cross toolchain wherever in the filesystem. (this is my > understanding of sysroot, I just learned about it yesterday, so take > this with a grain of salt). > >> >> Make sure that Clang picks up the correct assembler or linker by >> passing the cross compilers bin directory as search path. >> >> This allows to use Clang provided by distributions with GCC >> toolchains not in /usr/bin. > > IIUC, its just utilities in binutils we're using (as, bfd.ld, > objcopy), not GCC, but maybe that's just being pedantic. > >> >> Link: https://github.com/ClangBuiltLinux/linux/issues/78 >> Signed-off-by: Stefan Agner <stefan@xxxxxxxx> >> --- >> Nick, I removed your Reviewed-by since I had to change variable >> assignment slightly... > > Yes, thank you, that's the right thing to do. > >> >> Makefile | 8 +++++--- >> 1 file changed, 5 insertions(+), 3 deletions(-) >> >> diff --git a/Makefile b/Makefile >> index 4d5c883a98e5..d5de2db4b549 100644 >> --- a/Makefile >> +++ b/Makefile >> @@ -495,13 +495,15 @@ endif >> ifeq ($(cc-name),clang) >> ifneq ($(CROSS_COMPILE),) >> CLANG_TARGET := --target=$(notdir $(CROSS_COMPILE:%-=%)) >> -GCC_TOOLCHAIN := $(realpath $(dir $(shell which $(LD)))/..) >> +GCC_TOOLCHAIN_DIR := $(dir $(shell which $(LD))) >> +CLANG_PREFIX := --prefix=$(GCC_TOOLCHAIN_DIR) > > Yep: https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-b-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_CFLAGS += $(call cc-option, -no-integrated-as) >> KBUILD_AFLAGS += $(call cc-option, -no-integrated-as) >> endif >> -- >> 2.19.0 >> > > Thanks for this patch Stefan. > Reviewed-and-tested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > -- > Thanks, > ~Nick Desaulniers Applied to linux-kbuild/fixes. Thanks! -- Best Regards Masahiro Yamada
