# SPDX-License-Identifier: GPL-2.0ifneq ($(O),)ifeq ($(origin O), command line)	dummy := $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)	ABSOLUTE_O := $(shell cd $(PWD); cd $(O) ; pwd)	OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/)	COMMAND_O := O=$(ABSOLUTE_O)ifeq ($(objtree),)	objtree := $(O)endifendifendif # check that the output directory actually existsifneq ($(OUTPUT),)OUTDIR := $(shell cd $(OUTPUT) && pwd)$(if $(OUTDIR),, $(error output directory "$(OUTPUT)" does not exist))endif ## Include saner warnings here, which can catch bugs:#EXTRA_WARNINGS := -Wbad-function-castEXTRA_WARNINGS += -Wdeclaration-after-statementEXTRA_WARNINGS += -Wformat-securityEXTRA_WARNINGS += -Wformat-y2kEXTRA_WARNINGS += -Winit-selfEXTRA_WARNINGS += -Wmissing-declarationsEXTRA_WARNINGS += -Wmissing-prototypesEXTRA_WARNINGS += -Wnested-externsEXTRA_WARNINGS += -Wno-system-headersEXTRA_WARNINGS += -Wold-style-definitionEXTRA_WARNINGS += -WpackedEXTRA_WARNINGS += -Wredundant-declsEXTRA_WARNINGS += -Wstrict-prototypesEXTRA_WARNINGS += -Wswitch-defaultEXTRA_WARNINGS += -Wswitch-enumEXTRA_WARNINGS += -WundefEXTRA_WARNINGS += -Wwrite-stringsEXTRA_WARNINGS += -Wformat CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?) # Makefiles suck: This macro sets a default value of $(2) for the# variable named by $(1), unless the variable has been set by# environment or command line. This is necessary for CC and AR# because make sets default values, so the simpler ?= approach# won't work as expected.define allow-override  $(if $(or $(findstring environment,$(origin $(1))),\            $(findstring command line,$(origin $(1)))),,\    $(eval $(1) = $(2)))endef # Allow setting various cross-compile vars or setting CROSS_COMPILE as a prefix.$(call allow-override,CC,$(CROSS_COMPILE)gcc)$(call allow-override,AR,$(CROSS_COMPILE)ar)$(call allow-override,LD,$(CROSS_COMPILE)ld)$(call allow-override,CXX,$(CROSS_COMPILE)g++)$(call allow-override,STRIP,$(CROSS_COMPILE)strip) ifneq ($(LLVM),)HOSTAR  ?= llvm-arHOSTCC  ?= clangHOSTLD  ?= ld.lldelseHOSTAR  ?= arHOSTCC  ?= gccHOSTLD  ?= ldendif # Some tools require Clang, LLC and/or LLVM utilsCLANG		?= clangLLC		?= llcLLVM_CONFIG	?= llvm-configLLVM_OBJCOPY	?= llvm-objcopyLLVM_STRIP	?= llvm-strip ifeq ($(CC_NO_CLANG), 1)EXTRA_WARNINGS += -Wstrict-aliasing=3endif # Hack to avoid type-punned warnings on old systems such as RHEL5:# We should be changing CFLAGS and checking gcc version, but this# will do for now and keep the above -Wstrict-aliasing=3 in place# in newer systems.# Needed for the __raw_cmpxchg in tools/arch/x86/include/asm/cmpxchg.h## See https://lkml.org/lkml/2006/11/28/253 and https://gcc.gnu.org/gcc-4.8/changes.html,# that takes into account Linus's comments (search for Wshadow) for the reasoning about# -Wshadow not being interesting before gcc 4.8. ifneq ($(filter 3.%,$(MAKE_VERSION)),)  # make-3EXTRA_WARNINGS += -fno-strict-aliasingEXTRA_WARNINGS += -Wno-shadowelseEXTRA_WARNINGS += -Wshadowendif ifneq ($(findstring $(MAKEFLAGS), w),w)PRINT_DIR = --no-print-directoryelseNO_SUBDIR = :endif ifneq ($(findstring s,$(filter-out --%,$(MAKEFLAGS))),)  silent=1endif ## Define a callable command for descending to a new directory## Call by doing: $(call descend,directory[,target])#descend = \	+mkdir -p $(OUTPUT)$(1) && \	$(MAKE) $(COMMAND_O) subdir=$(if $(subdir),$(subdir)/$(1),$(1)) $(PRINT_DIR) -C $(1) $(2) QUIET_SUBDIR0  = +$(MAKE) $(COMMAND_O) -C # space to separate -C and subdirQUIET_SUBDIR1  = ifneq ($(silent),1)  ifneq ($(V),1)	QUIET_CC       = @echo '  CC       '$@;	QUIET_CC_FPIC  = @echo '  CC FPIC  '$@;	QUIET_CLANG    = @echo '  CLANG    '$@;	QUIET_AR       = @echo '  AR       '$@;	QUIET_LINK     = @echo '  LINK     '$@;	QUIET_MKDIR    = @echo '  MKDIR    '$@;	QUIET_GEN      = @echo '  GEN      '$@;	QUIET_SUBDIR0  = +@subdir=	QUIET_SUBDIR1  = ;$(NO_SUBDIR) \			  echo '  SUBDIR   '$$subdir; \			 $(MAKE) $(PRINT_DIR) -C $$subdir	QUIET_FLEX     = @echo '  FLEX     '$@;	QUIET_BISON    = @echo '  BISON    '$@;	QUIET_GENSKEL  = @echo '  GEN-SKEL '$@; 	descend = \		+@echo	       '  DESCEND  '$(1); \		mkdir -p $(OUTPUT)$(1) && \		$(MAKE) $(COMMAND_O) subdir=$(if $(subdir),$(subdir)/$(1),$(1)) $(PRINT_DIR) -C $(1) $(2) 	QUIET_CLEAN    = @printf '  CLEAN    %s\n' $1;	QUIET_INSTALL  = @printf '  INSTALL  %s\n' $1;	QUIET_UNINST   = @printf '  UNINST   %s\n' $1;  endifendif pound := \#