7aaf09fd5c
commit a0d1c951ef08ed24f35129267e3595d86f57f5d3 upstream. 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> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> [nd: conflict in exported vars list from not backporting commit e83b9f55448a ("kbuild: add ability to generate BTF type info for vmlinux")] [nd: hunk against Documentation/kbuild/kbuild.rst dropped due to not backporting commit cd238effefa2 ("docs: kbuild: convert docs to ReST and rename to *.rst")] Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
73 lines
2 KiB
Makefile
73 lines
2 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
|
|
include ../scripts/Makefile.include
|
|
include ../scripts/Makefile.arch
|
|
|
|
ifeq ($(ARCH),x86_64)
|
|
ARCH := x86
|
|
endif
|
|
|
|
# always use the host compiler
|
|
ifneq ($(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$(srctree)/tools/objtool/arch/$(ARCH)/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/lib/inat-tables.c $(OUTPUT)fixdep
|
|
|
|
FORCE:
|
|
|
|
.PHONY: clean FORCE
|