1 # SPDX-License-Identifier: GPL-2.0
6 NAME = Kleptomaniac Octopus
9 # To see a list of typical targets execute "make help"
10 # More info can be located in ./README
11 # Comments in this file are targeted only to the developer, do not
12 # expect to learn how to build the kernel reading this file.
14 $(if $(filter __%, $(MAKECMDGOALS)), \
15 $(error targets prefixed with '__' are only for internal use))
17 # That's our default target when none is given on the command line
21 # We are using a recursive build, so we need to do a little thinking
22 # to get the ordering right.
24 # Most importantly: sub-Makefiles should only ever modify files in
25 # their own directory. If in some directory we have a dependency on
26 # a file in another dir (which doesn't happen often, but it's often
27 # unavoidable when linking the built-in.a targets which finally
28 # turn into vmlinux), we will call a sub make in that other dir, and
29 # after that we are sure that everything which is in that other dir
32 # The only cases where we need to modify files which have global
33 # effects are thus separated out and done before the recursive
34 # descending is started. They are now explicitly listed as the
37 ifneq ($(sub_make_done),1)
39 # Do not use make's built-in rules and variables
40 # (this increases performance and avoids hard-to-debug behaviour)
43 # Avoid funny character set dependencies
47 export LC_COLLATE LC_NUMERIC
49 # Avoid interference with shell env settings
53 # ---------------------------------------------------------------------------
55 # Normally, we echo the whole command before executing it. By making
56 # that echo $($(quiet)$(cmd)), we now have the possibility to set
57 # $(quiet) to choose other forms of output instead, e.g.
59 # quiet_cmd_cc_o_c = Compiling $(RELDIR)/$@
60 # cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
62 # If $(quiet) is empty, the whole command will be printed.
63 # If it is set to "quiet_", only the short version will be printed.
64 # If it is set to "silent_", nothing will be printed at all, since
65 # the variable $(silent_cmd_cc_o_c) doesn't exist.
67 # A simple variant is to prefix commands with $(Q) - that's useful
68 # for commands that shall be hidden in non-verbose mode.
72 # If KBUILD_VERBOSE equals 0 then the above command will be hidden.
73 # If KBUILD_VERBOSE equals 1 then the above command is displayed.
74 # If KBUILD_VERBOSE equals 2 then give the reason why each target is rebuilt.
76 # To put more focus on warnings, be less verbose as default
77 # Use 'make V=1' to see the full commands
79 ifeq ("$(origin V)", "command line")
86 ifeq ($(KBUILD_VERBOSE),1)
94 # If the user is running make -s (silent mode), suppress echoing of
97 ifneq ($(findstring s,$(filter-out --%,$(MAKEFLAGS))),)
101 export quiet Q KBUILD_VERBOSE
103 # Kbuild will save output files in the current working directory.
104 # This does not need to match to the root of the kernel source tree.
106 # For example, you can do this:
108 # cd /dir/to/store/output/files; make -f /dir/to/kernel/source/Makefile
110 # If you want to save output files in a different location, there are
111 # two syntaxes to specify it.
114 # Use "make O=dir/to/store/output/files/"
116 # 2) Set KBUILD_OUTPUT
117 # Set the environment variable KBUILD_OUTPUT to point to the output directory.
118 # export KBUILD_OUTPUT=dir/to/store/output/files/; make
120 # The O= assignment takes precedence over the KBUILD_OUTPUT environment
123 # Do we want to change the working directory?
124 ifeq ("$(origin O)", "command line")
125 KBUILD_OUTPUT := $(O)
128 ifneq ($(KBUILD_OUTPUT),)
129 # Make's built-in functions such as $(abspath ...), $(realpath ...) cannot
130 # expand a shell special character '~'. We use a somewhat tedious way here.
131 abs_objtree := $(shell mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) && pwd)
132 $(if $(abs_objtree),, \
133 $(error failed to create output directory "$(KBUILD_OUTPUT)"))
135 # $(realpath ...) resolves symlinks
136 abs_objtree := $(realpath $(abs_objtree))
138 abs_objtree := $(CURDIR)
139 endif # ifneq ($(KBUILD_OUTPUT),)
141 ifeq ($(abs_objtree),$(CURDIR))
142 # Suppress "Entering directory ..." unless we are changing the work directory.
143 MAKEFLAGS += --no-print-directory
148 abs_srctree := $(realpath $(dir $(lastword $(MAKEFILE_LIST))))
150 ifneq ($(words $(subst :, ,$(abs_srctree))), 1)
151 $(error source directory cannot contain spaces or colons)
154 ifneq ($(abs_srctree),$(abs_objtree))
155 # Look for make include files relative to root of kernel src
157 # This does not become effective immediately because MAKEFLAGS is re-parsed
158 # once after the Makefile is read. We need to invoke sub-make.
159 MAKEFLAGS += --include-dir=$(abs_srctree)
163 this-makefile := $(lastword $(MAKEFILE_LIST))
165 ifneq ($(filter 3.%,$(MAKE_VERSION)),)
166 # 'MAKEFLAGS += -rR' does not immediately become effective for GNU Make 3.x
167 # We need to invoke sub-make to avoid implicit rules in the top Makefile.
169 # Cancel implicit rules for this Makefile.
173 export abs_srctree abs_objtree
174 export sub_make_done := 1
176 ifeq ($(need-sub-make),1)
178 PHONY += $(MAKECMDGOALS) __sub-make
180 $(filter-out $(this-makefile), $(MAKECMDGOALS)) __all: __sub-make
183 # Invoke a second make in the output directory, passing relevant variables
185 $(Q)$(MAKE) -C $(abs_objtree) -f $(abs_srctree)/Makefile $(MAKECMDGOALS)
187 endif # need-sub-make
188 endif # sub_make_done
190 # We process the rest of the Makefile if this is the final invocation of make
191 ifeq ($(need-sub-make),)
193 # Do not print "Entering directory ...",
194 # but we want to display it when entering to the output directory
195 # so that IDEs/editors are able to understand relative filenames.
196 MAKEFLAGS += --no-print-directory
198 # Call a source code checker (by default, "sparse") as part of the
201 # Use 'make C=1' to enable checking of only re-compiled files.
202 # Use 'make C=2' to enable checking of *all* source files, regardless
203 # of whether they are re-compiled or not.
205 # See the file "Documentation/dev-tools/sparse.rst" for more details,
206 # including where to get the "sparse" utility.
208 ifeq ("$(origin C)", "command line")
209 KBUILD_CHECKSRC = $(C)
211 ifndef KBUILD_CHECKSRC
215 # Use make M=dir or set the environment variable KBUILD_EXTMOD to specify the
216 # directory of external module to build. Setting M= takes precedence.
217 ifeq ("$(origin M)", "command line")
218 KBUILD_EXTMOD := $(M)
221 $(if $(word 2, $(KBUILD_EXTMOD)), \
222 $(error building multiple external modules is not supported))
224 export KBUILD_CHECKSRC KBUILD_EXTMOD
226 extmod-prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
228 ifeq ($(abs_srctree),$(abs_objtree))
229 # building in the source tree
231 building_out_of_srctree :=
233 ifeq ($(abs_srctree)/,$(dir $(abs_objtree)))
234 # building in a subdirectory of the source tree
237 srctree := $(abs_srctree)
239 building_out_of_srctree := 1
242 ifneq ($(KBUILD_ABS_SRCTREE),)
243 srctree := $(abs_srctree)
249 export building_out_of_srctree srctree objtree VPATH
251 # To make sure we do not include .config for any of the *config targets
252 # catch them early, and hand them over to scripts/kconfig/Makefile
253 # It is allowed to specify more targets when calling make, including
254 # mixing *config targets and build targets.
255 # For example 'make oldconfig all'.
256 # Detect when mixed targets is specified, and make a second invocation
257 # of make so .config is not included in this case either (for *config).
259 version_h := include/generated/uapi/linux/version.h
260 old_version_h := include/linux/version.h
262 clean-targets := %clean mrproper cleandocs
263 no-dot-config-targets := $(clean-targets) \
264 cscope gtags TAGS tags help% %docs check% coccicheck \
265 $(version_h) headers headers_% archheaders archscripts \
266 %asm-generic kernelversion %src-pkg dt_binding_check \
268 no-sync-config-targets := $(no-dot-config-targets) %install kernelrelease
269 single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.s %.symtypes %/
277 ifneq ($(filter $(no-dot-config-targets), $(MAKECMDGOALS)),)
278 ifeq ($(filter-out $(no-dot-config-targets), $(MAKECMDGOALS)),)
283 ifneq ($(filter $(no-sync-config-targets), $(MAKECMDGOALS)),)
284 ifeq ($(filter-out $(no-sync-config-targets), $(MAKECMDGOALS)),)
289 ifneq ($(KBUILD_EXTMOD),)
293 ifeq ($(KBUILD_EXTMOD),)
294 ifneq ($(filter %config,$(MAKECMDGOALS)),)
296 ifneq ($(words $(MAKECMDGOALS)),1)
302 # We cannot build single targets and the others at the same time
303 ifneq ($(filter $(single-targets), $(MAKECMDGOALS)),)
305 ifneq ($(filter-out $(single-targets), $(MAKECMDGOALS)),)
310 # For "make -j clean all", "make -j mrproper defconfig all", etc.
311 ifneq ($(filter $(clean-targets),$(MAKECMDGOALS)),)
312 ifneq ($(filter-out $(clean-targets),$(MAKECMDGOALS)),)
317 # install and modules_install need also be processed one by one
318 ifneq ($(filter install,$(MAKECMDGOALS)),)
319 ifneq ($(filter modules_install,$(MAKECMDGOALS)),)
325 # ===========================================================================
326 # We're called with mixed targets (*config and build targets).
327 # Handle them one by one.
329 PHONY += $(MAKECMDGOALS) __build_one_by_one
331 $(MAKECMDGOALS): __build_one_by_one
336 for i in $(MAKECMDGOALS); do \
337 $(MAKE) -f $(srctree)/Makefile $$i; \
342 include scripts/Kbuild.include
344 # Read KERNELRELEASE from include/config/kernel.release (if it exists)
345 KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
346 KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
347 export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASE KERNELVERSION
349 include scripts/subarch.include
351 # Cross compiling and selecting different set of gcc/bin-utils
352 # ---------------------------------------------------------------------------
354 # When performing cross compilation for other architectures ARCH shall be set
355 # to the target architecture. (See arch/* for the possibilities).
356 # ARCH can be set during invocation of make:
358 # Another way is to have ARCH set in the environment.
359 # The default ARCH is the host where make is executed.
361 # CROSS_COMPILE specify the prefix used for all executables used
362 # during compilation. Only gcc and related bin-utils executables
363 # are prefixed with $(CROSS_COMPILE).
364 # CROSS_COMPILE can be set on the command line
365 # make CROSS_COMPILE=ia64-linux-
366 # Alternatively CROSS_COMPILE can be set in the environment.
367 # Default value for CROSS_COMPILE is not to prefix executables
368 # Note: Some architectures assign CROSS_COMPILE in their arch/*/Makefile
371 # Architecture as present in compile.h
372 UTS_MACHINE := $(ARCH)
375 # Additional ARCH settings for x86
379 ifeq ($(ARCH),x86_64)
383 # Additional ARCH settings for sparc
384 ifeq ($(ARCH),sparc32)
387 ifeq ($(ARCH),sparc64)
391 # Additional ARCH settings for sh
396 KCONFIG_CONFIG ?= .config
397 export KCONFIG_CONFIG
399 # Default file for 'make defconfig'. This may be overridden by arch-Makefile.
400 export KBUILD_DEFCONFIG := defconfig
402 # SHELL used by kbuild
405 HOST_LFS_CFLAGS := $(shell getconf LFS_CFLAGS 2>/dev/null)
406 HOST_LFS_LDFLAGS := $(shell getconf LFS_LDFLAGS 2>/dev/null)
407 HOST_LFS_LIBS := $(shell getconf LFS_LIBS 2>/dev/null)
417 export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
418 -O2 -fomit-frame-pointer -std=gnu89
419 export KBUILD_USERLDFLAGS :=
421 KBUILD_HOSTCFLAGS := $(KBUILD_USERCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
422 KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
423 KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
424 KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS)
426 # Make variables (CC, etc...)
433 OBJCOPY = llvm-objcopy
434 OBJDUMP = llvm-objdump
435 READELF = llvm-readelf
439 CC = $(CROSS_COMPILE)gcc
440 LD = $(CROSS_COMPILE)ld
441 AR = $(CROSS_COMPILE)ar
442 NM = $(CROSS_COMPILE)nm
443 OBJCOPY = $(CROSS_COMPILE)objcopy
444 OBJDUMP = $(CROSS_COMPILE)objdump
445 READELF = $(CROSS_COMPILE)readelf
446 OBJSIZE = $(CROSS_COMPILE)size
447 STRIP = $(CROSS_COMPILE)strip
450 RESOLVE_BTFIDS = $(objtree)/tools/bpf/resolve_btfids/resolve_btfids
454 INSTALLKERNEL := installkernel
455 DEPMOD = /sbin/depmod
469 CHECKFLAGS := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
470 -Wbitwise -Wno-return-void -Wno-unknown-attribute $(CF)
479 # Use USERINCLUDE when you must reference the UAPI directories only.
481 -I$(srctree)/arch/$(SRCARCH)/include/uapi \
482 -I$(objtree)/arch/$(SRCARCH)/include/generated/uapi \
483 -I$(srctree)/include/uapi \
484 -I$(objtree)/include/generated/uapi \
485 -include $(srctree)/include/linux/kconfig.h
487 # Use LINUXINCLUDE when you must reference the include/ directory.
488 # Needed to be compatible with the O= option
490 -I$(srctree)/arch/$(SRCARCH)/include \
491 -I$(objtree)/arch/$(SRCARCH)/include/generated \
492 $(if $(building_out_of_srctree),-I$(srctree)/include) \
493 -I$(objtree)/include \
496 KBUILD_AFLAGS := -D__ASSEMBLY__ -fno-PIE
497 KBUILD_CFLAGS := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs \
498 -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE \
499 -Werror=implicit-function-declaration -Werror=implicit-int \
500 -Wno-format-security \
502 KBUILD_CPPFLAGS := -D__KERNEL__
503 KBUILD_AFLAGS_KERNEL :=
504 KBUILD_CFLAGS_KERNEL :=
505 KBUILD_AFLAGS_MODULE := -DMODULE
506 KBUILD_CFLAGS_MODULE := -DMODULE
507 KBUILD_LDFLAGS_MODULE :=
508 export KBUILD_LDS_MODULE := $(srctree)/scripts/module-common.lds
512 export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC
513 export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE READELF PAHOLE RESOLVE_BTFIDS LEX YACC AWK INSTALLKERNEL
514 export PERL PYTHON PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
515 export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD
516 export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
518 export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS
519 export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
520 export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE CFLAGS_UBSAN CFLAGS_KCSAN
521 export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
522 export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
523 export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
525 # Files to ignore in find ... statements
527 export RCS_FIND_IGNORE := \( -name SCCS -o -name BitKeeper -o -name .svn -o \
528 -name CVS -o -name .pc -o -name .hg -o -name .git \) \
530 export RCS_TAR_IGNORE := --exclude SCCS --exclude BitKeeper --exclude .svn \
531 --exclude CVS --exclude .pc --exclude .hg --exclude .git
533 # ===========================================================================
534 # Rules shared between *config targets and build targets
536 # Basic helpers built in scripts/basic/
537 PHONY += scripts_basic
539 $(Q)$(MAKE) $(build)=scripts/basic
540 $(Q)rm -f .tmp_quiet_recordmcount
542 PHONY += outputmakefile
543 # Before starting out-of-tree build, make sure the source tree is clean.
544 # outputmakefile generates a Makefile in the output directory, if using a
545 # separate output directory. This allows convenient use of make in the
547 # At the same time when output Makefile generated, generate .gitignore to
548 # ignore whole output directory
550 ifdef building_out_of_srctree
551 $(Q)if [ -f $(srctree)/.config -o \
552 -d $(srctree)/include/config -o \
553 -d $(srctree)/arch/$(SRCARCH)/include/generated ]; then \
555 echo >&2 "*** The source tree is not clean, please run 'make$(if $(findstring command line, $(origin ARCH)), ARCH=$(ARCH)) mrproper'"; \
556 echo >&2 "*** in $(abs_srctree)";\
560 $(Q)ln -fsn $(srctree) source
561 $(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkmakefile $(srctree)
562 $(Q)test -e .gitignore || \
563 { echo "# this is build directory, ignore it"; echo "*"; } > .gitignore
566 ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),)
567 ifneq ($(CROSS_COMPILE),)
568 CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
569 GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
570 CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
571 GCC_TOOLCHAIN := $(realpath $(GCC_TOOLCHAIN_DIR)/..)
573 ifneq ($(GCC_TOOLCHAIN),)
574 CLANG_FLAGS += --gcc-toolchain=$(GCC_TOOLCHAIN)
576 ifneq ($(LLVM_IAS),1)
577 CLANG_FLAGS += -no-integrated-as
579 CLANG_FLAGS += -Werror=unknown-warning-option
580 KBUILD_CFLAGS += $(CLANG_FLAGS)
581 KBUILD_AFLAGS += $(CLANG_FLAGS)
585 # The expansion should be delayed until arch/$(SRCARCH)/Makefile is included.
586 # Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.
587 # CC_VERSION_TEXT is referenced from Kconfig (so it needs export),
588 # and from include/config/auto.conf.cmd to detect the compiler upgrade.
589 CC_VERSION_TEXT = $(shell $(CC) --version 2>/dev/null | head -n 1)
592 # ===========================================================================
593 # *config targets only - make sure prerequisites are updated, and descend
594 # in scripts/kconfig to make the *config target
596 # Read arch specific Makefile to set KBUILD_DEFCONFIG as needed.
597 # KBUILD_DEFCONFIG may point out an alternative default configuration
598 # used for 'make defconfig'
599 include arch/$(SRCARCH)/Makefile
600 export KBUILD_DEFCONFIG KBUILD_KCONFIG CC_VERSION_TEXT
602 config: outputmakefile scripts_basic FORCE
603 $(Q)$(MAKE) $(build)=scripts/kconfig $@
605 %config: outputmakefile scripts_basic FORCE
606 $(Q)$(MAKE) $(build)=scripts/kconfig $@
609 # ===========================================================================
610 # Build targets only - this includes vmlinux, arch specific targets, clean
611 # targets and others. In general all targets except *config targets.
613 # If building an external module we do not care about the all: rule
614 # but instead __all depend on modules
616 ifeq ($(KBUILD_EXTMOD),)
622 # Decide whether to build built-in, modular, or both.
623 # Normally, just do built-in.
628 # If we have only "make modules", don't compile built-in objects.
629 ifeq ($(MAKECMDGOALS),modules)
633 # If we have "make <whatever> modules", compile modules
634 # in addition to whatever we do anyway.
635 # Just "make" or "make all" shall build modules as well
637 ifneq ($(filter all modules nsdeps,$(MAKECMDGOALS)),)
641 ifeq ($(MAKECMDGOALS),)
645 export KBUILD_MODULES KBUILD_BUILTIN
648 include include/config/auto.conf
651 ifeq ($(KBUILD_EXTMOD),)
652 # Objects we will link into vmlinux / subdirs we need to visit
654 drivers-y := drivers/ sound/
655 drivers-$(CONFIG_SAMPLES) += samples/
656 drivers-y += net/ virt/
658 endif # KBUILD_EXTMOD
660 # The all: target is the default when no target is given on the
662 # This allow a user to issue only 'make' to build a kernel including modules
663 # Defaults to vmlinux, but the arch makefile usually adds further targets
666 CFLAGS_GCOV := -fprofile-arcs -ftest-coverage \
667 $(call cc-option,-fno-tree-loop-im) \
668 $(call cc-disable-warning,maybe-uninitialized,)
671 # The arch Makefiles can override CC_FLAGS_FTRACE. We may also append it later.
672 ifdef CONFIG_FUNCTION_TRACER
673 CC_FLAGS_FTRACE := -pg
676 RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register
677 RETPOLINE_VDSO_CFLAGS_GCC := -mindirect-branch=thunk-inline -mindirect-branch-register
678 RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk
679 RETPOLINE_VDSO_CFLAGS_CLANG := -mretpoline
680 RETPOLINE_CFLAGS := $(call cc-option,$(RETPOLINE_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_CFLAGS_CLANG)))
681 RETPOLINE_VDSO_CFLAGS := $(call cc-option,$(RETPOLINE_VDSO_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_VDSO_CFLAGS_CLANG)))
682 export RETPOLINE_CFLAGS
683 export RETPOLINE_VDSO_CFLAGS
685 include arch/$(SRCARCH)/Makefile
688 ifdef may-sync-config
689 # Read in dependencies to all Kconfig* files, make sure to run syncconfig if
690 # changes are detected. This should be included after arch/$(SRCARCH)/Makefile
691 # because some architectures define CROSS_COMPILE there.
692 include include/config/auto.conf.cmd
696 @echo >&2 '*** Configuration file "$@" not found!'
698 @echo >&2 '*** Please run some configurator (e.g. "make oldconfig" or'
699 @echo >&2 '*** "make menuconfig" or "make xconfig").'
703 # The actual configuration files used during the build are stored in
704 # include/generated/ and include/config/. Update them if .config is newer than
705 # include/config/auto.conf (which mirrors .config).
707 # This exploits the 'multi-target pattern rule' trick.
708 # The syncconfig should be executed only once to make all the targets.
709 # (Note: use the grouped target '&:' when we bump to GNU Make 4.3)
710 %/config/auto.conf %/config/auto.conf.cmd %/generated/autoconf.h: $(KCONFIG_CONFIG)
711 $(Q)$(MAKE) -f $(srctree)/Makefile syncconfig
712 else # !may-sync-config
713 # External modules and some install targets need include/generated/autoconf.h
714 # and include/config/auto.conf but do not care if they are up-to-date.
715 # Use auto.conf to trigger the test
716 PHONY += include/config/auto.conf
718 include/config/auto.conf:
719 $(Q)test -e include/generated/autoconf.h -a -e $@ || ( \
721 echo >&2 " ERROR: Kernel configuration is invalid."; \
722 echo >&2 " include/generated/autoconf.h or $@ are missing.";\
723 echo >&2 " Run 'make oldconfig && make prepare' on kernel src to fix it."; \
727 endif # may-sync-config
730 KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks,)
731 KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
732 KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
733 KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
734 KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
736 ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
738 else ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3
740 else ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
744 # Tell gcc to never replace conditional load with a non-conditional one
745 KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0)
746 KBUILD_CFLAGS += $(call cc-option,-fno-allow-store-data-races)
748 ifdef CONFIG_READABLE_ASM
749 # Disable optimizations that make assembler listings hard to read.
750 # reorder blocks reorders the control in the function
751 # ipa clone creates specialized cloned functions
752 # partial inlining inlines only parts of functions
753 KBUILD_CFLAGS += $(call cc-option,-fno-reorder-blocks,) \
754 $(call cc-option,-fno-ipa-cp-clone,) \
755 $(call cc-option,-fno-partial-inlining)
758 ifneq ($(CONFIG_FRAME_WARN),0)
759 KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
762 stackp-flags-y := -fno-stack-protector
763 stackp-flags-$(CONFIG_STACKPROTECTOR) := -fstack-protector
764 stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG) := -fstack-protector-strong
766 KBUILD_CFLAGS += $(stackp-flags-y)
768 ifdef CONFIG_CC_IS_CLANG
769 KBUILD_CPPFLAGS += -Qunused-arguments
770 KBUILD_CFLAGS += -Wno-format-invalid-specifier
771 KBUILD_CFLAGS += -Wno-gnu
772 # CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
773 # source of a reference will be _MergedGlobals and not on of the whitelisted names.
774 # See modpost pattern 2
775 KBUILD_CFLAGS += -mno-global-merge
778 # These warnings generated too much noise in a regular build.
779 # Use make W=1 to enable them (see scripts/Makefile.extrawarn)
780 KBUILD_CFLAGS += -Wno-unused-but-set-variable
782 # Warn about unmarked fall-throughs in switch statement.
783 # Disabled for clang while comment to attribute conversion happens and
784 # https://github.com/ClangBuiltLinux/linux/issues/636 is discussed.
785 KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough,)
788 KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
789 ifdef CONFIG_FRAME_POINTER
790 KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
792 # Some targets (ARM with Thumb2, for example), can't be built with frame
793 # pointers. For those, we don't have FUNCTION_TRACER automatically
794 # select FRAME_POINTER. However, FUNCTION_TRACER adds -pg, and this is
795 # incompatible with -fomit-frame-pointer with current GCC, so we don't use
796 # -fomit-frame-pointer with FUNCTION_TRACER.
797 ifndef CONFIG_FUNCTION_TRACER
798 KBUILD_CFLAGS += -fomit-frame-pointer
802 # Initialize all stack variables with a 0xAA pattern.
803 ifdef CONFIG_INIT_STACK_ALL_PATTERN
804 KBUILD_CFLAGS += -ftrivial-auto-var-init=pattern
807 # Initialize all stack variables with a zero value.
808 ifdef CONFIG_INIT_STACK_ALL_ZERO
809 # Future support for zero initialization is still being debated, see
810 # https://bugs.llvm.org/show_bug.cgi?id=45497. These flags are subject to being
811 # renamed or dropped.
812 KBUILD_CFLAGS += -ftrivial-auto-var-init=zero
813 KBUILD_CFLAGS += -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
816 DEBUG_CFLAGS := $(call cc-option, -fno-var-tracking-assignments)
818 ifdef CONFIG_DEBUG_INFO
819 ifdef CONFIG_DEBUG_INFO_SPLIT
820 DEBUG_CFLAGS += -gsplit-dwarf
824 KBUILD_AFLAGS += -Wa,-gdwarf-2
826 ifdef CONFIG_DEBUG_INFO_DWARF4
827 DEBUG_CFLAGS += -gdwarf-4
830 ifdef CONFIG_DEBUG_INFO_REDUCED
831 DEBUG_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \
832 $(call cc-option,-fno-var-tracking)
835 ifdef CONFIG_DEBUG_INFO_COMPRESSED
836 DEBUG_CFLAGS += -gz=zlib
837 KBUILD_AFLAGS += -gz=zlib
838 KBUILD_LDFLAGS += --compress-debug-sections=zlib
841 KBUILD_CFLAGS += $(DEBUG_CFLAGS)
844 ifdef CONFIG_FUNCTION_TRACER
845 ifdef CONFIG_FTRACE_MCOUNT_RECORD
846 # gcc 5 supports generating the mcount tables directly
847 ifeq ($(call cc-option-yn,-mrecord-mcount),y)
848 CC_FLAGS_FTRACE += -mrecord-mcount
849 export CC_USING_RECORD_MCOUNT := 1
851 ifdef CONFIG_HAVE_NOP_MCOUNT
852 ifeq ($(call cc-option-yn, -mnop-mcount),y)
853 CC_FLAGS_FTRACE += -mnop-mcount
854 CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT
858 ifdef CONFIG_HAVE_FENTRY
859 ifeq ($(call cc-option-yn, -mfentry),y)
860 CC_FLAGS_FTRACE += -mfentry
861 CC_FLAGS_USING += -DCC_USING_FENTRY
864 export CC_FLAGS_FTRACE
865 KBUILD_CFLAGS += $(CC_FLAGS_FTRACE) $(CC_FLAGS_USING)
866 KBUILD_AFLAGS += $(CC_FLAGS_USING)
867 ifdef CONFIG_DYNAMIC_FTRACE
868 ifdef CONFIG_HAVE_C_RECORDMCOUNT
869 BUILD_C_RECORDMCOUNT := y
870 export BUILD_C_RECORDMCOUNT
875 # We trigger additional mismatches with less inlining
876 ifdef CONFIG_DEBUG_SECTION_MISMATCH
877 KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
880 ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
881 KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
882 LDFLAGS_vmlinux += --gc-sections
885 ifdef CONFIG_SHADOW_CALL_STACK
886 CC_FLAGS_SCS := -fsanitize=shadow-call-stack
887 KBUILD_CFLAGS += $(CC_FLAGS_SCS)
891 ifdef CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_32B
892 KBUILD_CFLAGS += -falign-functions=32
895 # arch Makefile may override CC so keep this after arch Makefile is included
896 NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
898 # warn about C99 declaration after statement
899 KBUILD_CFLAGS += -Wdeclaration-after-statement
901 # Variable Length Arrays (VLAs) should not be used anywhere in the kernel
902 KBUILD_CFLAGS += -Wvla
904 # disable pointer signed / unsigned warnings in gcc 4.0
905 KBUILD_CFLAGS += -Wno-pointer-sign
907 # disable stringop warnings in gcc 8+
908 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
910 # We'll want to enable this eventually, but it's not going away for 5.7 at least
911 KBUILD_CFLAGS += $(call cc-disable-warning, zero-length-bounds)
912 KBUILD_CFLAGS += $(call cc-disable-warning, array-bounds)
913 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
915 # Another good warning that we'll want to enable eventually
916 KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
918 # Enabled with W=2, disabled by default as noisy
919 KBUILD_CFLAGS += $(call cc-disable-warning, maybe-uninitialized)
921 # disable invalid "can't wrap" optimizations for signed / pointers
922 KBUILD_CFLAGS += $(call cc-option,-fno-strict-overflow)
924 # Make sure -fstack-check isn't enabled (like gentoo apparently did)
925 KBUILD_CFLAGS += $(call cc-option,-fno-stack-check,)
927 # conserve stack if available
928 KBUILD_CFLAGS += $(call cc-option,-fconserve-stack)
930 # Prohibit date/time macros, which would make the build non-deterministic
931 KBUILD_CFLAGS += $(call cc-option,-Werror=date-time)
933 # enforce correct pointer usage
934 KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
936 # Require designated initializers for all marked structures
937 KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
939 # change __FILE__ to the relative path from the srctree
940 KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
942 # ensure -fcf-protection is disabled when using retpoline as it is
943 # incompatible with -mindirect-branch=thunk-extern
944 ifdef CONFIG_RETPOLINE
945 KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
948 # include additional Makefiles when needed
949 include-y := scripts/Makefile.extrawarn
950 include-$(CONFIG_KASAN) += scripts/Makefile.kasan
951 include-$(CONFIG_KCSAN) += scripts/Makefile.kcsan
952 include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan
953 include-$(CONFIG_KCOV) += scripts/Makefile.kcov
954 include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins
956 include $(addprefix $(srctree)/, $(include-y))
958 # scripts/Makefile.gcc-plugins is intentionally included last.
959 # Do not add $(call cc-option,...) below this line. When you build the kernel
960 # from the clean source tree, the GCC plugins do not exist at this point.
962 # Add user supplied CPPFLAGS, AFLAGS and CFLAGS as the last assignments
963 KBUILD_CPPFLAGS += $(KCPPFLAGS)
964 KBUILD_AFLAGS += $(KAFLAGS)
965 KBUILD_CFLAGS += $(KCFLAGS)
967 KBUILD_LDFLAGS_MODULE += --build-id
968 LDFLAGS_vmlinux += --build-id
970 ifeq ($(CONFIG_STRIP_ASM_SYMS),y)
971 LDFLAGS_vmlinux += $(call ld-option, -X,)
974 ifeq ($(CONFIG_RELR),y)
975 LDFLAGS_vmlinux += --pack-dyn-relocs=relr
978 # Align the bit size of userspace programs with the kernel
979 KBUILD_USERCFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))
980 KBUILD_USERLDFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))
982 # make the checker run with the right architecture
983 CHECKFLAGS += --arch=$(ARCH)
985 # insure the checker run with the right endianness
986 CHECKFLAGS += $(if $(CONFIG_CPU_BIG_ENDIAN),-mbig-endian,-mlittle-endian)
988 # the checker needs the correct machine size
989 CHECKFLAGS += $(if $(CONFIG_64BIT),-m64,-m32)
991 # Default kernel image to build when no specific target is given.
992 # KBUILD_IMAGE may be overruled on the command line or
993 # set in the environment
994 # Also any assignments in arch/$(ARCH)/Makefile take precedence over
996 export KBUILD_IMAGE ?= vmlinux
999 # INSTALL_PATH specifies where to place the updated kernel and system map
1000 # images. Default is /boot, but you can set it to other values
1001 export INSTALL_PATH ?= /boot
1004 # INSTALL_DTBS_PATH specifies a prefix for relocations required by build roots.
1005 # Like INSTALL_MOD_PATH, it isn't defined in the Makefile, but can be passed as
1006 # an argument if needed. Otherwise it defaults to the kernel install path
1008 export INSTALL_DTBS_PATH ?= $(INSTALL_PATH)/dtbs/$(KERNELRELEASE)
1011 # INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory
1012 # relocations required by build roots. This is not defined in the
1013 # makefile but the argument can be passed to make if needed.
1016 MODLIB = $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)
1020 # INSTALL_MOD_STRIP, if defined, will cause modules to be
1021 # stripped after they are installed. If INSTALL_MOD_STRIP is '1', then
1022 # the default option --strip-debug will be used. Otherwise,
1023 # INSTALL_MOD_STRIP value will be used as the options to the strip command.
1025 ifdef INSTALL_MOD_STRIP
1026 ifeq ($(INSTALL_MOD_STRIP),1)
1027 mod_strip_cmd = $(STRIP) --strip-debug
1029 mod_strip_cmd = $(STRIP) $(INSTALL_MOD_STRIP)
1030 endif # INSTALL_MOD_STRIP=1
1032 mod_strip_cmd = true
1033 endif # INSTALL_MOD_STRIP
1034 export mod_strip_cmd
1036 # CONFIG_MODULE_COMPRESS, if defined, will cause module to be compressed
1037 # after they are installed in agreement with CONFIG_MODULE_COMPRESS_GZIP
1038 # or CONFIG_MODULE_COMPRESS_XZ.
1040 mod_compress_cmd = true
1041 ifdef CONFIG_MODULE_COMPRESS
1042 ifdef CONFIG_MODULE_COMPRESS_GZIP
1043 mod_compress_cmd = $(KGZIP) -n -f
1044 endif # CONFIG_MODULE_COMPRESS_GZIP
1045 ifdef CONFIG_MODULE_COMPRESS_XZ
1046 mod_compress_cmd = $(XZ) -f
1047 endif # CONFIG_MODULE_COMPRESS_XZ
1048 endif # CONFIG_MODULE_COMPRESS
1049 export mod_compress_cmd
1051 ifdef CONFIG_MODULE_SIG_ALL
1052 $(eval $(call config_filename,MODULE_SIG_KEY))
1054 mod_sign_cmd = scripts/sign-file $(CONFIG_MODULE_SIG_HASH) $(MODULE_SIG_KEY_SRCPREFIX)$(CONFIG_MODULE_SIG_KEY) certs/signing_key.x509
1060 HOST_LIBELF_LIBS = $(shell pkg-config libelf --libs 2>/dev/null || echo -lelf)
1062 has_libelf = $(call try-run,\
1063 echo "int main() {}" | $(HOSTCC) -xc -o /dev/null $(HOST_LIBELF_LIBS) -,1,0)
1065 ifdef CONFIG_STACK_VALIDATION
1066 ifeq ($(has_libelf),1)
1067 objtool_target := tools/objtool FORCE
1069 SKIP_STACK_VALIDATION := 1
1070 export SKIP_STACK_VALIDATION
1074 ifdef CONFIG_DEBUG_INFO_BTF
1075 ifeq ($(has_libelf),1)
1076 resolve_btfids_target := tools/bpf/resolve_btfids FORCE
1078 ERROR_RESOLVE_BTFIDS := 1
1084 export MODORDER := $(extmod-prefix)modules.order
1085 export MODULES_NSDEPS := $(extmod-prefix)modules.nsdeps
1087 ifeq ($(KBUILD_EXTMOD),)
1088 core-y += kernel/ certs/ mm/ fs/ ipc/ security/ crypto/ block/
1090 vmlinux-dirs := $(patsubst %/,%,$(filter %/, \
1091 $(core-y) $(core-m) $(drivers-y) $(drivers-m) \
1092 $(libs-y) $(libs-m)))
1094 vmlinux-alldirs := $(sort $(vmlinux-dirs) Documentation \
1095 $(patsubst %/,%,$(filter %/, $(core-) \
1096 $(drivers-) $(libs-))))
1098 subdir-modorder := $(addsuffix modules.order,$(filter %/, \
1099 $(core-y) $(core-m) $(libs-y) $(libs-m) \
1100 $(drivers-y) $(drivers-m)))
1102 build-dirs := $(vmlinux-dirs)
1103 clean-dirs := $(vmlinux-alldirs)
1105 # Externally visible symbols (used by link-vmlinux.sh)
1106 KBUILD_VMLINUX_OBJS := $(head-y) $(patsubst %/,%/built-in.a, $(core-y))
1107 KBUILD_VMLINUX_OBJS += $(addsuffix built-in.a, $(filter %/, $(libs-y)))
1108 ifdef CONFIG_MODULES
1109 KBUILD_VMLINUX_OBJS += $(patsubst %/, %/lib.a, $(filter %/, $(libs-y)))
1110 KBUILD_VMLINUX_LIBS := $(filter-out %/, $(libs-y))
1112 KBUILD_VMLINUX_LIBS := $(patsubst %/,%/lib.a, $(libs-y))
1114 KBUILD_VMLINUX_OBJS += $(patsubst %/,%/built-in.a, $(drivers-y))
1116 export KBUILD_VMLINUX_OBJS KBUILD_VMLINUX_LIBS
1117 export KBUILD_LDS := arch/$(SRCARCH)/kernel/vmlinux.lds
1118 # used by scripts/Makefile.package
1119 export KBUILD_ALLDIRS := $(sort $(filter-out arch/%,$(vmlinux-alldirs)) LICENSES arch include scripts tools)
1121 vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_OBJS) $(KBUILD_VMLINUX_LIBS)
1123 # Recurse until adjust_autoksyms.sh is satisfied
1124 PHONY += autoksyms_recursive
1125 ifdef CONFIG_TRIM_UNUSED_KSYMS
1126 # For the kernel to actually contain only the needed exported symbols,
1127 # we have to build modules as well to determine what those symbols are.
1128 # (this can be evaluated only once include/config/auto.conf has been included)
1131 autoksyms_recursive: descend modules.order
1132 $(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh \
1133 "$(MAKE) -f $(srctree)/Makefile vmlinux"
1136 autoksyms_h := $(if $(CONFIG_TRIM_UNUSED_KSYMS), include/generated/autoksyms.h)
1138 quiet_cmd_autoksyms_h = GEN $@
1139 cmd_autoksyms_h = mkdir -p $(dir $@); \
1140 $(CONFIG_SHELL) $(srctree)/scripts/gen_autoksyms.sh $@
1143 $(call cmd,autoksyms_h)
1145 ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
1147 # Final link of vmlinux with optional arch pass after final link
1148 cmd_link-vmlinux = \
1149 $(CONFIG_SHELL) $< "$(LD)" "$(KBUILD_LDFLAGS)" "$(LDFLAGS_vmlinux)"; \
1150 $(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
1152 vmlinux: scripts/link-vmlinux.sh autoksyms_recursive $(vmlinux-deps) FORCE
1153 +$(call if_changed,link-vmlinux)
1157 # The actual objects are generated when descending,
1158 # make sure no implicit rule kicks in
1159 $(sort $(vmlinux-deps) $(subdir-modorder)): descend ;
1161 filechk_kernel.release = \
1162 echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))"
1164 # Store (new) KERNELRELEASE string in include/config/kernel.release
1165 include/config/kernel.release: FORCE
1166 $(call filechk,kernel.release)
1168 # Additional helpers built in scripts/
1169 # Carefully list dependencies so we do not try to build scripts twice
1172 scripts: scripts_basic scripts_dtc
1173 $(Q)$(MAKE) $(build)=$(@)
1175 # Things we need to do before we recursively start building the kernel
1176 # or the modules are listed in "prepare".
1177 # A multi level approach is used. prepareN is processed before prepareN-1.
1178 # archprepare is used in arch Makefiles and when processed asm symlink,
1179 # version.h and scripts_basic is processed / created.
1181 PHONY += prepare archprepare
1183 archprepare: outputmakefile archheaders archscripts scripts include/config/kernel.release \
1184 asm-generic $(version_h) $(autoksyms_h) include/generated/utsrelease.h \
1185 include/generated/autoconf.h
1187 prepare0: archprepare
1188 $(Q)$(MAKE) $(build)=scripts/mod
1189 $(Q)$(MAKE) $(build)=.
1191 # All the preparing..
1192 prepare: prepare0 prepare-objtool prepare-resolve_btfids
1194 # Support for using generic headers in asm-generic
1195 asm-generic := -f $(srctree)/scripts/Makefile.asm-generic obj
1197 PHONY += asm-generic uapi-asm-generic
1198 asm-generic: uapi-asm-generic
1199 $(Q)$(MAKE) $(asm-generic)=arch/$(SRCARCH)/include/generated/asm \
1200 generic=include/asm-generic
1202 $(Q)$(MAKE) $(asm-generic)=arch/$(SRCARCH)/include/generated/uapi/asm \
1203 generic=include/uapi/asm-generic
1205 PHONY += prepare-objtool prepare-resolve_btfids
1206 prepare-objtool: $(objtool_target)
1207 ifeq ($(SKIP_STACK_VALIDATION),1)
1208 ifdef CONFIG_UNWINDER_ORC
1209 @echo "error: Cannot generate ORC metadata for CONFIG_UNWINDER_ORC=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2
1212 @echo "warning: Cannot use CONFIG_STACK_VALIDATION=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2
1216 prepare-resolve_btfids: $(resolve_btfids_target)
1217 ifeq ($(ERROR_RESOLVE_BTFIDS),1)
1218 @echo "error: Cannot resolve BTF IDs for CONFIG_DEBUG_INFO_BTF, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2
1221 # Generate some files
1222 # ---------------------------------------------------------------------------
1224 # KERNELRELEASE can change from a few different places, meaning version.h
1225 # needs to be updated, so this check is forced on all builds
1228 define filechk_utsrelease.h
1229 if [ `echo -n "$(KERNELRELEASE)" | wc -c ` -gt $(uts_len) ]; then \
1230 echo '"$(KERNELRELEASE)" exceeds $(uts_len) characters' >&2; \
1233 echo \#define UTS_RELEASE \"$(KERNELRELEASE)\"
1236 define filechk_version.h
1237 echo \#define LINUX_VERSION_CODE $(shell \
1238 expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
1239 echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
1243 $(call filechk,version.h)
1244 $(Q)rm -f $(old_version_h)
1246 include/generated/utsrelease.h: include/config/kernel.release FORCE
1247 $(call filechk,utsrelease.h)
1251 $(Q)find $(srctree)/include/ -name '*.h' | xargs --max-args 1 \
1252 $(srctree)/scripts/headerdep.pl -I$(srctree)/include
1254 # ---------------------------------------------------------------------------
1257 #Default location for installed headers
1258 export INSTALL_HDR_PATH = $(objtree)/usr
1260 quiet_cmd_headers_install = INSTALL $(INSTALL_HDR_PATH)/include
1261 cmd_headers_install = \
1262 mkdir -p $(INSTALL_HDR_PATH); \
1263 rsync -mrl --include='*/' --include='*\.h' --exclude='*' \
1264 usr/include $(INSTALL_HDR_PATH)
1266 PHONY += headers_install
1267 headers_install: headers
1268 $(call cmd,headers_install)
1270 PHONY += archheaders archscripts
1272 hdr-inst := -f $(srctree)/scripts/Makefile.headersinst obj
1275 headers: $(version_h) scripts_unifdef uapi-asm-generic archheaders archscripts
1276 $(if $(wildcard $(srctree)/arch/$(SRCARCH)/include/uapi/asm/Kbuild),, \
1277 $(error Headers not exportable for the $(SRCARCH) architecture))
1278 $(Q)$(MAKE) $(hdr-inst)=include/uapi
1279 $(Q)$(MAKE) $(hdr-inst)=arch/$(SRCARCH)/include/uapi
1281 # Deprecated. It is no-op now.
1282 PHONY += headers_check
1286 ifdef CONFIG_HEADERS_INSTALL
1290 PHONY += scripts_unifdef
1291 scripts_unifdef: scripts_basic
1292 $(Q)$(MAKE) $(build)=scripts scripts/unifdef
1294 # ---------------------------------------------------------------------------
1299 $(Q)$(MAKE) -C $(srctree)/tools/testing/selftests run_tests
1302 $(Q)$(MAKE) -C $(srctree)/tools/testing/selftests $*
1304 PHONY += kselftest-merge
1306 $(if $(wildcard $(objtree)/.config),, $(error No .config exists, config your kernel first!))
1307 $(Q)find $(srctree)/tools/testing/selftests -name config | \
1308 xargs $(srctree)/scripts/kconfig/merge_config.sh -m $(objtree)/.config
1309 $(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig
1311 # ---------------------------------------------------------------------------
1314 ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/boot/dts/),)
1315 dtstree := arch/$(SRCARCH)/boot/dts
1320 %.dtb: include/config/kernel.release scripts_dtc
1321 $(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
1323 PHONY += dtbs dtbs_install dtbs_check
1324 dtbs: include/config/kernel.release scripts_dtc
1325 $(Q)$(MAKE) $(build)=$(dtstree)
1327 ifneq ($(filter dtbs_check, $(MAKECMDGOALS)),)
1329 dtbs: dt_binding_check
1335 $(Q)$(MAKE) $(dtbinst)=$(dtstree) dst=$(INSTALL_DTBS_PATH)
1337 ifdef CONFIG_OF_EARLY_FLATTREE
1343 PHONY += scripts_dtc
1344 scripts_dtc: scripts_basic
1345 $(Q)$(MAKE) $(build)=scripts/dtc
1347 ifneq ($(filter dt_binding_check, $(MAKECMDGOALS)),)
1348 export CHECK_DT_BINDING=y
1351 PHONY += dt_binding_check
1352 dt_binding_check: scripts_dtc
1353 $(Q)$(MAKE) $(build)=Documentation/devicetree/bindings
1355 # ---------------------------------------------------------------------------
1358 ifdef CONFIG_MODULES
1360 # By default, build modules as well
1364 # When we're building modules with modversions, we need to consider
1365 # the built-in objects during the descend as well, in order to
1366 # make sure the checksums are up to date before we record them.
1367 ifdef CONFIG_MODVERSIONS
1373 # A module can be listed more than once in obj-m resulting in
1374 # duplicate lines in modules.order files. Those are removed
1375 # using awk while concatenating to the final file.
1378 modules: $(if $(KBUILD_BUILTIN),vmlinux) modules_check
1379 $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
1381 PHONY += modules_check
1382 modules_check: modules.order
1383 $(Q)$(CONFIG_SHELL) $(srctree)/scripts/modules-check.sh $<
1385 cmd_modules_order = $(AWK) '!x[$$0]++' $(real-prereqs) > $@
1387 modules.order: $(subdir-modorder) FORCE
1388 $(call if_changed,modules_order)
1390 targets += modules.order
1392 # Target to prepare building external modules
1393 PHONY += modules_prepare
1394 modules_prepare: prepare
1396 # Target to install modules
1397 PHONY += modules_install
1398 modules_install: _modinst_ _modinst_post
1402 @rm -rf $(MODLIB)/kernel
1403 @rm -f $(MODLIB)/source
1404 @mkdir -p $(MODLIB)/kernel
1405 @ln -s $(abspath $(srctree)) $(MODLIB)/source
1406 @if [ ! $(objtree) -ef $(MODLIB)/build ]; then \
1407 rm -f $(MODLIB)/build ; \
1408 ln -s $(CURDIR) $(MODLIB)/build ; \
1410 @sed 's:^:kernel/:' modules.order > $(MODLIB)/modules.order
1411 @cp -f modules.builtin $(MODLIB)/
1412 @cp -f $(objtree)/modules.builtin.modinfo $(MODLIB)/
1413 $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modinst
1415 # This depmod is only for convenience to give the initial
1416 # boot a modules.dep even before / is mounted read-write. However the
1417 # boot script depmod is the master version.
1418 PHONY += _modinst_post
1419 _modinst_post: _modinst_
1422 ifeq ($(CONFIG_MODULE_SIG), y)
1423 PHONY += modules_sign
1425 $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modsign
1428 else # CONFIG_MODULES
1430 # Modules not configured
1431 # ---------------------------------------------------------------------------
1433 PHONY += modules modules_install
1434 modules modules_install:
1436 @echo >&2 "The present kernel configuration has modules disabled."
1437 @echo >&2 "Type 'make config' and enable loadable module support."
1438 @echo >&2 "Then build a kernel with module support enabled."
1442 endif # CONFIG_MODULES
1445 # Cleaning is done on three levels.
1446 # make clean Delete most generated files
1447 # Leave enough to build external modules
1448 # make mrproper Delete the current configuration, and all generated files
1449 # make distclean Remove editor backup files, patch leftover files and the like
1451 # Directories & files removed with 'make clean'
1452 CLEAN_FILES += include/ksym vmlinux.symvers \
1453 modules.builtin modules.builtin.modinfo modules.nsdeps
1455 # Directories & files removed with 'make mrproper'
1456 MRPROPER_FILES += include/config include/generated \
1457 arch/$(SRCARCH)/include/generated .tmp_objdiff \
1458 debian snap tar-install \
1459 .config .config.old .version \
1461 signing_key.pem signing_key.priv signing_key.x509 \
1462 x509.genkey extra_certificates signing_key.x509.keyid \
1463 signing_key.x509.signer vmlinux-gdb.py \
1466 # Directories & files removed with 'make distclean'
1467 DISTCLEAN_FILES += tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS
1469 # clean - Delete most, but leave enough to build external modules
1471 clean: rm-files := $(CLEAN_FILES)
1473 PHONY += archclean vmlinuxclean
1476 $(Q)$(CONFIG_SHELL) $(srctree)/scripts/link-vmlinux.sh clean
1477 $(Q)$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) clean)
1479 clean: archclean vmlinuxclean
1481 # mrproper - Delete all generated files, including .config
1483 mrproper: rm-files := $(wildcard $(MRPROPER_FILES))
1484 mrproper-dirs := $(addprefix _mrproper_,scripts)
1486 PHONY += $(mrproper-dirs) mrproper
1488 $(Q)$(MAKE) $(clean)=$(patsubst _mrproper_%,%,$@)
1490 mrproper: clean $(mrproper-dirs)
1495 distclean: rm-files := $(wildcard $(DISTCLEAN_FILES))
1501 @find $(srctree) $(RCS_FIND_IGNORE) \
1502 \( -name '*.orig' -o -name '*.rej' -o -name '*~' \
1503 -o -name '*.bak' -o -name '#*#' -o -name '*%' \
1504 -o -name 'core' \) \
1505 -type f -print | xargs rm -f
1508 # Packaging of the kernel to various formats
1509 # ---------------------------------------------------------------------------
1512 $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.package $@
1513 %pkg: include/config/kernel.release FORCE
1514 $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.package $@
1516 # Brief documentation of the typical targets used
1517 # ---------------------------------------------------------------------------
1519 boards := $(wildcard $(srctree)/arch/$(SRCARCH)/configs/*_defconfig)
1520 boards := $(sort $(notdir $(boards)))
1521 board-dirs := $(dir $(wildcard $(srctree)/arch/$(SRCARCH)/configs/*/*_defconfig))
1522 board-dirs := $(sort $(notdir $(board-dirs:/=)))
1526 @echo 'Cleaning targets:'
1527 @echo ' clean - Remove most generated files but keep the config and'
1528 @echo ' enough build support to build external modules'
1529 @echo ' mrproper - Remove all generated files + config + various backup files'
1530 @echo ' distclean - mrproper + remove editor backup and patch files'
1532 @echo 'Configuration targets:'
1533 @$(MAKE) -f $(srctree)/scripts/kconfig/Makefile help
1535 @echo 'Other generic targets:'
1536 @echo ' all - Build all targets marked with [*]'
1537 @echo '* vmlinux - Build the bare kernel'
1538 @echo '* modules - Build all modules'
1539 @echo ' modules_install - Install all modules to INSTALL_MOD_PATH (default: /)'
1540 @echo ' dir/ - Build all files in dir and below'
1541 @echo ' dir/file.[ois] - Build specified target only'
1542 @echo ' dir/file.ll - Build the LLVM assembly file'
1543 @echo ' (requires compiler support for LLVM assembly generation)'
1544 @echo ' dir/file.lst - Build specified mixed source/assembly target only'
1545 @echo ' (requires a recent binutils and recent build (System.map))'
1546 @echo ' dir/file.ko - Build module including final link'
1547 @echo ' modules_prepare - Set up for building external modules'
1548 @echo ' tags/TAGS - Generate tags file for editors'
1549 @echo ' cscope - Generate cscope index'
1550 @echo ' gtags - Generate GNU GLOBAL index'
1551 @echo ' kernelrelease - Output the release version string (use with make -s)'
1552 @echo ' kernelversion - Output the version stored in Makefile (use with make -s)'
1553 @echo ' image_name - Output the image name (use with make -s)'
1554 @echo ' headers_install - Install sanitised kernel headers to INSTALL_HDR_PATH'; \
1555 echo ' (default: $(INSTALL_HDR_PATH))'; \
1557 @echo 'Static analysers:'
1558 @echo ' checkstack - Generate a list of stack hogs'
1559 @echo ' namespacecheck - Name space analysis on compiled kernel'
1560 @echo ' versioncheck - Sanity check on version.h usage'
1561 @echo ' includecheck - Check for duplicate included header files'
1562 @echo ' export_report - List the usages of all exported symbols'
1563 @echo ' headerdep - Detect inclusion cycles in headers'
1564 @echo ' coccicheck - Check with Coccinelle'
1567 @echo ' nsdeps - Generate missing symbol namespace dependencies'
1569 @echo 'Kernel selftest:'
1570 @echo ' kselftest - Build and run kernel selftest'
1571 @echo ' Build, install, and boot kernel before'
1572 @echo ' running kselftest on it'
1573 @echo ' Run as root for full coverage'
1574 @echo ' kselftest-all - Build kernel selftest'
1575 @echo ' kselftest-install - Build and install kernel selftest'
1576 @echo ' kselftest-clean - Remove all generated kselftest files'
1577 @echo ' kselftest-merge - Merge all the config dependencies of'
1578 @echo ' kselftest to existing .config.'
1581 echo 'Devicetree:'; \
1582 echo '* dtbs - Build device tree blobs for enabled boards'; \
1583 echo ' dtbs_install - Install dtbs to $(INSTALL_DTBS_PATH)'; \
1584 echo ' dt_binding_check - Validate device tree binding documents'; \
1585 echo ' dtbs_check - Validate device tree source files';\
1588 @echo 'Userspace tools targets:'
1589 @echo ' use "make tools/help"'
1590 @echo ' or "cd tools; make help"'
1592 @echo 'Kernel packaging:'
1593 @$(MAKE) -f $(srctree)/scripts/Makefile.package help
1595 @echo 'Documentation targets:'
1596 @$(MAKE) -f $(srctree)/Documentation/Makefile dochelp
1598 @echo 'Architecture specific targets ($(SRCARCH)):'
1599 @$(if $(archhelp),$(archhelp),\
1600 echo ' No architecture specific help defined for $(SRCARCH)')
1603 $(foreach b, $(boards), \
1604 printf " %-27s - Build for %s\\n" $(b) $(subst _defconfig,,$(b));) \
1606 @$(if $(board-dirs), \
1607 $(foreach b, $(board-dirs), \
1608 printf " %-16s - Show %s-specific targets\\n" help-$(b) $(b);) \
1609 printf " %-16s - Show all of the above\\n" help-boards; \
1612 @echo ' make V=0|1 [targets] 0 => quiet build (default), 1 => verbose build'
1613 @echo ' make V=2 [targets] 2 => give reason for rebuild of target'
1614 @echo ' make O=dir [targets] Locate all output files in "dir", including .config'
1615 @echo ' make C=1 [targets] Check re-compiled c source with $$CHECK'
1616 @echo ' (sparse by default)'
1617 @echo ' make C=2 [targets] Force check of all c source with $$CHECK'
1618 @echo ' make RECORDMCOUNT_WARN=1 [targets] Warn about ignored mcount sections'
1619 @echo ' make W=n [targets] Enable extra build checks, n=1,2,3 where'
1620 @echo ' 1: warnings which may be relevant and do not occur too often'
1621 @echo ' 2: warnings which occur quite often but may still be relevant'
1622 @echo ' 3: more obscure warnings, can most likely be ignored'
1623 @echo ' Multiple levels can be combined with W=12 or W=123'
1625 @echo 'Execute "make" or "make all" to build all targets marked with [*] '
1626 @echo 'For further info see the ./README file'
1629 help-board-dirs := $(addprefix help-,$(board-dirs))
1631 help-boards: $(help-board-dirs)
1633 boards-per-dir = $(sort $(notdir $(wildcard $(srctree)/arch/$(SRCARCH)/configs/$*/*_defconfig)))
1635 $(help-board-dirs): help-%:
1636 @echo 'Architecture specific targets ($(SRCARCH) $*):'
1637 @$(if $(boards-per-dir), \
1638 $(foreach b, $(boards-per-dir), \
1639 printf " %-24s - Build for %s\\n" $*/$(b) $(subst _defconfig,,$(b));) \
1643 # Documentation targets
1644 # ---------------------------------------------------------------------------
1645 DOC_TARGETS := xmldocs latexdocs pdfdocs htmldocs epubdocs cleandocs \
1646 linkcheckdocs dochelp refcheckdocs
1647 PHONY += $(DOC_TARGETS)
1649 $(Q)$(MAKE) $(build)=Documentation $@
1652 # ---------------------------------------------------------------------------
1654 PHONY += scripts_gdb
1655 scripts_gdb: prepare0
1656 $(Q)$(MAKE) $(build)=scripts/gdb
1657 $(Q)ln -fsn $(abspath $(srctree)/scripts/gdb/vmlinux-gdb.py)
1659 ifdef CONFIG_GDB_SCRIPTS
1663 else # KBUILD_EXTMOD
1666 # External module support.
1667 # When building external modules the kernel used as basis is considered
1668 # read-only, and no consistency checks are made and the make
1669 # system is not used on the basis kernel. If updates are required
1670 # in the basis kernel ordinary make commands (without M=...) must
1673 # The following are the only valid targets when building external
1675 # make M=dir clean Delete all automatically generated files
1676 # make M=dir modules Make all modules in specified dir
1677 # make M=dir Same as 'make M=dir modules'
1678 # make M=dir modules_install
1679 # Install the modules built in the module directory
1680 # Assumes install directory is already created
1682 # We are always building modules
1685 build-dirs := $(KBUILD_EXTMOD)
1688 $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
1690 PHONY += modules_install
1691 modules_install: _emodinst_ _emodinst_post
1693 install-dir := $(if $(INSTALL_MOD_DIR),$(INSTALL_MOD_DIR),extra)
1696 $(Q)mkdir -p $(MODLIB)/$(install-dir)
1697 $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modinst
1699 PHONY += _emodinst_post
1700 _emodinst_post: _emodinst_
1703 clean-dirs := $(KBUILD_EXTMOD)
1704 clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps
1708 @echo ' Building external modules.'
1709 @echo ' Syntax: make -C path/to/kernel/src M=$$PWD target'
1711 @echo ' modules - default target, build the module(s)'
1712 @echo ' modules_install - install the module'
1713 @echo ' clean - remove generated files in module directory only'
1717 endif # KBUILD_EXTMOD
1720 # ---------------------------------------------------------------------------
1721 # To build individual files in subdirectories, you can do like this:
1723 # make foo/bar/baz.s
1725 # The supported suffixes for single-target are listed in 'single-targets'
1727 # To build only under specific subdirectories, you can do like this:
1733 # .ko is special because modpost is needed
1734 single-ko := $(sort $(filter %.ko, $(MAKECMDGOALS)))
1735 single-no-ko := $(sort $(patsubst %.ko,%.mod, $(MAKECMDGOALS)))
1737 $(single-ko): single_modpost
1739 $(single-no-ko): descend
1742 ifeq ($(KBUILD_EXTMOD),)
1743 # For the single build of in-tree modules, use a temporary file to avoid
1744 # the situation of modules_install installing an invalid modules.order.
1745 MODORDER := .modules.tmp
1748 PHONY += single_modpost
1749 single_modpost: $(single-no-ko)
1750 $(Q){ $(foreach m, $(single-ko), echo $(extmod-prefix)$m;) } > $(MODORDER)
1751 $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
1755 export KBUILD_SINGLE_TARGETS := $(addprefix $(extmod-prefix), $(single-no-ko))
1757 # trim unrelated directories
1758 build-dirs := $(foreach d, $(build-dirs), \
1759 $(if $(filter $(d)/%, $(KBUILD_SINGLE_TARGETS)), $(d)))
1763 ifndef CONFIG_MODULES
1767 # Handle descending into subdirectories listed in $(build-dirs)
1768 # Preset locale variables to speed up the build process. Limit locale
1769 # tweaks to this spot to avoid wrong language settings when running
1770 # make menuconfig etc.
1771 # Error messages still appears in the original language
1772 PHONY += descend $(build-dirs)
1773 descend: $(build-dirs)
1774 $(build-dirs): prepare
1775 $(Q)$(MAKE) $(build)=$@ \
1776 single-build=$(if $(filter-out $@/, $(filter $@/%, $(KBUILD_SINGLE_TARGETS))),1) \
1777 need-builtin=1 need-modorder=1
1779 clean-dirs := $(addprefix _clean_, $(clean-dirs))
1780 PHONY += $(clean-dirs) clean
1782 $(Q)$(MAKE) $(clean)=$(patsubst _clean_%,%,$@)
1784 clean: $(clean-dirs)
1786 @find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
1787 \( -name '*.[aios]' -o -name '*.ko' -o -name '.*.cmd' \
1789 -o -name '*.dtb' -o -name '*.dtb.S' -o -name '*.dt.yaml' \
1790 -o -name '*.dwo' -o -name '*.lst' \
1791 -o -name '*.su' -o -name '*.mod' \
1792 -o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
1793 -o -name '*.lex.c' -o -name '*.tab.[ch]' \
1794 -o -name '*.asn1.[ch]' \
1795 -o -name '*.symtypes' -o -name 'modules.order' \
1796 -o -name '.tmp_*.o.*' \
1797 -o -name '*.c.[012]*.*' \
1799 -o -name '*.gcno' \) -type f -print | xargs rm -f
1801 # Generate tags for editors
1802 # ---------------------------------------------------------------------------
1803 quiet_cmd_tags = GEN $@
1804 cmd_tags = $(BASH) $(srctree)/scripts/tags.sh $@
1806 tags TAGS cscope gtags: FORCE
1809 # Script to generate missing namespace dependencies
1810 # ---------------------------------------------------------------------------
1813 nsdeps: export KBUILD_NSDEPS=1
1815 $(Q)$(CONFIG_SHELL) $(srctree)/scripts/nsdeps
1817 # Scripts to check various things for consistency
1818 # ---------------------------------------------------------------------------
1820 PHONY += includecheck versioncheck coccicheck namespacecheck export_report
1823 find $(srctree)/* $(RCS_FIND_IGNORE) \
1824 -name '*.[hcS]' -type f -print | sort \
1825 | xargs $(PERL) -w $(srctree)/scripts/checkincludes.pl
1828 find $(srctree)/* $(RCS_FIND_IGNORE) \
1829 -name '*.[hcS]' -type f -print | sort \
1830 | xargs $(PERL) -w $(srctree)/scripts/checkversion.pl
1833 $(Q)$(BASH) $(srctree)/scripts/$@
1836 $(PERL) $(srctree)/scripts/namespace.pl
1839 $(PERL) $(srctree)/scripts/export_report.pl
1841 PHONY += checkstack kernelrelease kernelversion image_name
1843 # UML needs a little special treatment here. It wants to use the host
1844 # toolchain, so needs $(SUBARCH) passed to checkstack.pl. Everyone
1845 # else wants $(ARCH), including people doing cross-builds, which means
1846 # that $(SUBARCH) doesn't work here.
1848 CHECKSTACK_ARCH := $(SUBARCH)
1850 CHECKSTACK_ARCH := $(ARCH)
1853 $(OBJDUMP) -d vmlinux $$(find . -name '*.ko') | \
1854 $(PERL) $(srctree)/scripts/checkstack.pl $(CHECKSTACK_ARCH)
1857 @echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))"
1860 @echo $(KERNELVERSION)
1863 @echo $(KBUILD_IMAGE)
1865 # Clear a bunch of variables before executing the submake
1867 ifeq ($(quiet),silent_)
1872 $(Q)mkdir -p $(objtree)/tools
1873 $(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/
1876 $(Q)mkdir -p $(objtree)/tools
1877 $(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/ $*
1879 quiet_cmd_rmfiles = $(if $(wildcard $(rm-files)),CLEAN $(wildcard $(rm-files)))
1880 cmd_rmfiles = rm -rf $(rm-files)
1882 # Run depmod only if we have System.map and depmod is executable
1883 quiet_cmd_depmod = DEPMOD $(KERNELRELEASE)
1884 cmd_depmod = $(CONFIG_SHELL) $(srctree)/scripts/depmod.sh $(DEPMOD) \
1887 # read saved command lines for existing targets
1888 existing-targets := $(wildcard $(sort $(targets)))
1890 -include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
1892 endif # config-build
1894 endif # need-sub-make
1899 # Declare the contents of the PHONY variable as phony. We keep that
1900 # information in a variable so we can use it in if_changed and friends.