a0d1c951ef
As Documentation/kbuild/llvm.rst implies, building the kernel with a full set of LLVM tools gets very verbose and unwieldy. Provide a single switch LLVM=1 to use Clang and LLVM tools instead of GCC and Binutils. You can pass it from the command line or as an environment variable. Please note LLVM=1 does not turn on the integrated assembler. You need to pass LLVM_IAS=1 to use it. When the upstream kernel is ready for the integrated assembler, I think we can make it default. We discussed what we need, and we agreed to go with a simple boolean flag that switches both target and host tools: https://lkml.org/lkml/2020/3/28/494 https://lkml.org/lkml/2020/4/3/43 Some items discussed, but not adopted: - LLVM_DIR When multiple versions of LLVM are installed, I just thought supporting LLVM_DIR=/path/to/my/llvm/bin/ might be useful. CC = $(LLVM_DIR)clang LD = $(LLVM_DIR)ld.lld ... However, we can handle this by modifying PATH. So, we decided to not do this. - LLVM_SUFFIX Some distributions (e.g. Debian) package specific versions of LLVM with naming conventions that use the version as a suffix. CC = clang$(LLVM_SUFFIX) LD = ld.lld(LLVM_SUFFIX) ... will allow a user to pass LLVM_SUFFIX=-11 to use clang-11 etc., but the suffixed versions in /usr/bin/ are symlinks to binaries in /usr/lib/llvm-#/bin/, so this can also be handled by PATH. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Tested-by: Nathan Chancellor <natechancellor@gmail.com> # build Tested-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
1.9 KiB
SPDX-License-Identifier: GPL-2.0
include ../scripts/Makefile.include include ../scripts/Makefile.arch
always use the host compiler
ifneq ($(LLVM),) HOSTAR ?= llvm-ar HOSTCC ?= clang HOSTLD ?= ld.lld else HOSTAR ?= ar HOSTCC ?= gcc HOSTLD ?= ld endif AR = $(HOSTAR) CC = $(HOSTCC) LD = $(HOSTLD)
ifeq ($(srctree),) srctree := $(patsubst %/,%,$(dir $(CURDIR))) srctree := $(patsubst %/,%,$(dir $(srctree))) endif
SUBCMD_SRCDIR = $(srctree)/tools/lib/subcmd/ LIBSUBCMD_OUTPUT = $(if $(OUTPUT),$(OUTPUT),$(CURDIR)/) LIBSUBCMD = $(LIBSUBCMD_OUTPUT)libsubcmd.a
OBJTOOL := $(OUTPUT)objtool OBJTOOL_IN := $(OBJTOOL)-in.o
LIBELF_FLAGS := $(shell pkg-config libelf --cflags 2>/dev/null) LIBELF_LIBS := $(shell pkg-config libelf --libs 2>/dev/null || echo -lelf)
all: $(OBJTOOL)
INCLUDES := -I$(srctree)/tools/include
-I$(srctree)/tools/arch/$(HOSTARCH)/include/uapi
-I$(srctree)/tools/arch/$(SRCARCH)/include
WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed
CFLAGS := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBELF_FLAGS)
LDFLAGS += $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS)
Allow old libelf to be used:
elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(CC) $(CFLAGS) -x c -E - | grep elf_getshdr) CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED)
AWK = awk export srctree OUTPUT CFLAGS SRCARCH AWK include $(srctree)/tools/build/Makefile.include
$(OBJTOOL_IN): fixdep FORCE @$(MAKE) $(build)=objtool
$(OBJTOOL): $(LIBSUBCMD) $(OBJTOOL_IN) @$(CONFIG_SHELL) ./sync-check.sh $(QUIET_LINK)$(CC) $(OBJTOOL_IN) $(LDFLAGS) -o $@
$(LIBSUBCMD): fixdep FORCE $(Q)$(MAKE) -C $(SUBCMD_SRCDIR) OUTPUT=$(LIBSUBCMD_OUTPUT)
clean: $(call QUIET_CLEAN, objtool) $(RM) $(OBJTOOL) $(Q)find $(OUTPUT) -name '.o' -delete -o -name '..cmd' -delete -o -name '.*.d' -delete $(Q)$(RM) $(OUTPUT)arch/x86/inat-tables.c $(OUTPUT)fixdep
FORCE:
.PHONY: clean FORCE