kbuild: Add better clang cross build support

commit 785f11aa59 upstream.

Add cross target to CC if using clang. Also add custom gcc toolchain
path for fallback gcc tools.

Clang will fallback to using things like ld, as, and libgcc if
(respectively) one of the llvm linkers isn't available, the integrated
assembler is turned off, or an appropriately cross-compiled version of
compiler-rt isn't available. To this end, you can specify the path to
this fallback gcc toolchain with GCC_TOOLCHAIN.

Signed-off-by: Behan Webster <behanw@converseincode.com>
Reviewed-by: Jan-Simon Möller <dl9pf@gmx.de>
Reviewed-by: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Behan Webster 2017-04-21 11:20:01 -07:00 committed by Greg Kroah-Hartman
parent 3d26b729dd
commit 7135c75e00

View file

@ -704,6 +704,15 @@ endif
KBUILD_CFLAGS += $(stackp-flag)
ifeq ($(cc-name),clang)
ifneq ($(CROSS_COMPILE),)
CLANG_TARGET := -target $(notdir $(CROSS_COMPILE:%-=%))
GCC_TOOLCHAIN := $(realpath $(dir $(shell which $(LD)))/..)
endif
ifneq ($(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_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
KBUILD_CPPFLAGS += $(call cc-option,-Wno-unknown-warning-option,)
KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable)