From b3d8ffe52f8f11f7af93b176f679c7dcf7f669c3 Mon Sep 17 00:00:00 2001 From: Nick Desaulniers Date: Mon, 2 Aug 2021 11:39:09 -0700 Subject: [PATCH] BACKPORT: Makefile: infer --target from ARCH for CC=clang We get constant feedback that the command line invocation of make is too long when compiling with LLVM. CROSS_COMPILE is helpful when a toolchain has a prefix of the target triple, or is an absolute path outside of $PATH. Since a Clang binary is generally multi-targeted, we can infer a given target from SRCARCH/ARCH. If CROSS_COMPILE is not set, simply set --target= for CLANG_FLAGS, KBUILD_CFLAGS, and KBUILD_AFLAGS based on $SRCARCH. Previously, we'd cross compile via: $ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make LLVM=1 LLVM_IAS=1 Now: $ ARCH=arm64 make LLVM=1 LLVM_IAS=1 For native builds (not involving cross compilation) we now explicitly specify a target triple rather than rely on the implicit host triple. Link: https://github.com/ClangBuiltLinux/linux/issues/1399 Suggested-by: Arnd Bergmann Suggested-by: Linus Torvalds Suggested-by: Masahiro Yamada Suggested-by: Nathan Chancellor Acked-by: Arnd Bergmann Reviewed-by: Nathan Chancellor Signed-off-by: Nick Desaulniers Acked-by: Miguel Ojeda Signed-off-by: Masahiro Yamada Bug: 209655537 (cherry picked from commit 231ad7f409f16b9f9505f69e058dff488a7e6bde) Change-Id: I6f61a4937e6af22deda66eeaac6c667c889dc683 --- Makefile | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) diff --git a/Makefile b/Makefile index 53f5a70bc5c6..41821aa6c947 100644 --- a/Makefile +++ b/Makefile @@ -560,9 +560,30 @@ endif CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1 | sed 's/\#//g') ifneq ($(findstring clang,$(CC_VERSION_TEXT)),) -ifneq ($(CROSS_COMPILE),) +# Individual arch/{arch}/Makefiles should use -EL/-EB to set intended +# endianness and -m32/-m64 to set word size based on Kconfigs instead of +# relying on the target triple. +CLANG_TARGET_FLAGS_arm := arm-linux-gnueabi +CLANG_TARGET_FLAGS_arm64 := aarch64-linux-gnu +CLANG_TARGET_FLAGS_hexagon := hexagon-linux-musl +CLANG_TARGET_FLAGS_m68k := m68k-linux-gnu +CLANG_TARGET_FLAGS_mips := mipsel-linux-gnu +CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu +CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu +CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu +CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu +CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH)) + +ifeq ($(CROSS_COMPILE),) +ifeq ($(CLANG_TARGET_FLAGS),) +$(error Specify CROSS_COMPILE or add '--target=' option to Makefile) +else +CLANG_FLAGS += --target=$(CLANG_TARGET_FLAGS) +endif # CLANG_TARGET_FLAGS +else CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) -endif +endif # CROSS_COMPILE + ifneq ($(LLVM_IAS),1) CLANG_FLAGS += -no-integrated-as GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))