62353048e2
commit a0d1c951ef 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
70 lines
1.9 KiB
Makefile
70 lines
1.9 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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include ../scripts/Makefile.include
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include ../scripts/Makefile.arch
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# always use the host compiler
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ifneq ($(LLVM),)
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HOSTAR ?= llvm-ar
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HOSTCC ?= clang
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HOSTLD ?= ld.lld
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else
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HOSTAR ?= ar
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HOSTCC ?= gcc
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HOSTLD ?= ld
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endif
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AR = $(HOSTAR)
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CC = $(HOSTCC)
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LD = $(HOSTLD)
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ifeq ($(srctree),)
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srctree := $(patsubst %/,%,$(dir $(CURDIR)))
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srctree := $(patsubst %/,%,$(dir $(srctree)))
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endif
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SUBCMD_SRCDIR = $(srctree)/tools/lib/subcmd/
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LIBSUBCMD_OUTPUT = $(if $(OUTPUT),$(OUTPUT),$(CURDIR)/)
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LIBSUBCMD = $(LIBSUBCMD_OUTPUT)libsubcmd.a
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OBJTOOL := $(OUTPUT)objtool
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OBJTOOL_IN := $(OBJTOOL)-in.o
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LIBELF_FLAGS := $(shell pkg-config libelf --cflags 2>/dev/null)
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LIBELF_LIBS := $(shell pkg-config libelf --libs 2>/dev/null || echo -lelf)
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all: $(OBJTOOL)
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INCLUDES := -I$(srctree)/tools/include \
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-I$(srctree)/tools/arch/$(HOSTARCH)/include/uapi \
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-I$(srctree)/tools/arch/$(SRCARCH)/include
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WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed
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CFLAGS := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBELF_FLAGS)
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LDFLAGS += $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS)
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# Allow old libelf to be used:
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elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(CC) $(CFLAGS) -x c -E - | grep elf_getshdr)
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CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED)
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AWK = awk
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export srctree OUTPUT CFLAGS SRCARCH AWK
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include $(srctree)/tools/build/Makefile.include
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$(OBJTOOL_IN): fixdep FORCE
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@$(MAKE) $(build)=objtool
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$(OBJTOOL): $(LIBSUBCMD) $(OBJTOOL_IN)
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@$(CONFIG_SHELL) ./sync-check.sh
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$(QUIET_LINK)$(CC) $(OBJTOOL_IN) $(LDFLAGS) -o $@
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$(LIBSUBCMD): fixdep FORCE
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$(Q)$(MAKE) -C $(SUBCMD_SRCDIR) OUTPUT=$(LIBSUBCMD_OUTPUT)
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clean:
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$(call QUIET_CLEAN, objtool) $(RM) $(OBJTOOL)
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$(Q)find $(OUTPUT) -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
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$(Q)$(RM) $(OUTPUT)arch/x86/inat-tables.c $(OUTPUT)fixdep
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FORCE:
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.PHONY: clean FORCE
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