scripts/Makefile.build

   1 # SPDX-License-Identifier: GPL-2.0
   2 # ==========================================================================
   3 # Building
   4 # ==========================================================================
   5
   6 src := $(obj)
   7
   8 PHONY := __build
   9 __build:
  10
  11 # Init all relevant variables used in kbuild files so
  12 # 1) they have correct type
  13 # 2) they do not inherit any value from the environment
  14 obj-y :=
  15 obj-m :=
  16 lib-y :=
  17 lib-m :=
  18 always-y :=
  19 always-m :=
  20 targets :=
  21 subdir-y :=
  22 subdir-m :=
  23 EXTRA_AFLAGS   :=
  24 EXTRA_CFLAGS   :=
  25 EXTRA_CPPFLAGS :=
  26 EXTRA_LDFLAGS  :=
  27 asflags-y  :=
  28 ccflags-y  :=
  29 cppflags-y :=
  30 ldflags-y  :=
  31
  32 subdir-asflags-y :=
  33 subdir-ccflags-y :=
  34
  35 # Read auto.conf if it exists, otherwise ignore
  36 -include include/config/auto.conf
  37
  38 include scripts/Kbuild.include
  39
  40 # The filename Kbuild has precedence over Makefile
  41 kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
  42 kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
  43 include $(kbuild-file)
  44
  45 include scripts/Makefile.lib
  46
  47 # Do not include hostprogs rules unless needed.
  48 # $(sort ...) is used here to remove duplicated words and excessive spaces.
  49 hostprogs := $(sort $(hostprogs))
  50 ifneq ($(hostprogs),)
  51 include scripts/Makefile.host
  52 endif
  53
  54 # Do not include userprogs rules unless needed.
  55 # $(sort ...) is used here to remove duplicated words and excessive spaces.
  56 userprogs := $(sort $(userprogs))
  57 ifneq ($(userprogs),)
  58 include scripts/Makefile.userprogs
  59 endif
  60
  61 ifndef obj
  62 $(warning kbuild: Makefile.build is included improperly)
  63 endif
  64
  65 ifeq ($(need-modorder),)
  66 ifneq ($(obj-m),)
  67 $(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
  68 $(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
  69 endif
  70 endif
  71
  72 # ===========================================================================
  73
  74 # subdir-builtin and subdir-modorder may contain duplications. Use $(sort ...)
  75 subdir-builtin := $(sort $(filter %/built-in.a, $(real-obj-y)))
  76 subdir-modorder := $(sort $(filter %/modules.order, $(obj-m)))
  77
  78 targets-for-builtin := $(extra-y)
  79
  80 ifneq ($(strip $(lib-y) $(lib-m) $(lib-)),)
  81 targets-for-builtin += $(obj)/lib.a
  82 endif
  83
  84 ifdef need-builtin
  85 targets-for-builtin += $(obj)/built-in.a
  86 endif
  87
  88 targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
  89
  90 ifdef need-modorder
  91 targets-for-modules += $(obj)/modules.order
  92 endif
  93
  94 targets += $(targets-for-builtin) $(targets-for-modules)
  95
  96 # Linus' kernel sanity checking tool
  97 ifeq ($(KBUILD_CHECKSRC),1)
  98   quiet_cmd_checksrc       = CHECK   $<
  99         cmd_checksrc       = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
 100 else ifeq ($(KBUILD_CHECKSRC),2)
 101   quiet_cmd_force_checksrc = CHECK   $<
 102         cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
 103 endif
 104
 105 ifneq ($(KBUILD_EXTRA_WARN),)
 106   cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $<
 107 endif
 108
 109 # Compile C sources (.c)
 110 # ---------------------------------------------------------------------------
 111
 112 quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@
 113       cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) -fverbose-asm -S -o $@ $<
 114
 115 $(obj)/%.s: $(src)/%.c FORCE
 116         $(call if_changed_dep,cc_s_c)
 117
 118 quiet_cmd_cpp_i_c = CPP $(quiet_modtag) $@
 119 cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
 120
 121 $(obj)/%.i: $(src)/%.c FORCE
 122         $(call if_changed_dep,cpp_i_c)
 123
 124 # These mirror gensymtypes_S and co below, keep them in synch.
 125 cmd_gensymtypes_c =                                                         \
 126     $(CPP) -D__GENKSYMS__ $(c_flags) $< |                                   \
 127     scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
 128      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
 129      $(if $(KBUILD_PRESERVE),-p)                                            \
 130      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 131
 132 quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
 133 cmd_cc_symtypes_c =                                                         \
 134     $(call cmd_gensymtypes_c,true,$@) >/dev/null;                           \
 135     test -s $@ || rm -f $@
 136
 137 $(obj)/%.symtypes : $(src)/%.c FORCE
 138         $(call cmd,cc_symtypes_c)
 139
 140 # LLVM assembly
 141 # Generate .ll files from .c
 142 quiet_cmd_cc_ll_c = CC $(quiet_modtag)  $@
 143       cmd_cc_ll_c = $(CC) $(c_flags) -emit-llvm -S -o $@ $<
 144
 145 $(obj)/%.ll: $(src)/%.c FORCE
 146         $(call if_changed_dep,cc_ll_c)
 147
 148 # C (.c) files
 149 # The C file is compiled and updated dependency information is generated.
 150 # (See cmd_cc_o_c + relevant part of rule_cc_o_c)
 151
 152 quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
 153       cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
 154
 155 ifdef CONFIG_MODVERSIONS
 156 # When module versioning is enabled the following steps are executed:
 157 # o compile a <file>.o from <file>.c
 158 # o if <file>.o doesn't contain a __ksymtab version, i.e. does
 159 #   not export symbols, it's done.
 160 # o otherwise, we calculate symbol versions using the good old
 161 #   genksyms on the preprocessed source and postprocess them in a way
 162 #   that they are usable as a linker script
 163 # o generate .tmp_<file>.o from <file>.o using the linker to
 164 #   replace the unresolved symbols __crc_exported_symbol with
 165 #   the actual value of the checksum generated by genksyms
 166 # o remove .tmp_<file>.o to <file>.o
 167
 168 cmd_modversions_c =                                                             \
 169         if $(OBJDUMP) -h $@ | grep -q __ksymtab; then                           \
 170                 $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 171                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
 172                                                                                 \
 173                 $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@               \
 174                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
 175                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
 176                 rm -f $(@D)/.tmp_$(@F:.o=.ver);                                 \
 177         fi
 178 endif
 179
 180 ifdef CONFIG_FTRACE_MCOUNT_RECORD
 181 ifndef CC_USING_RECORD_MCOUNT
 182 # compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
 183 ifdef BUILD_C_RECORDMCOUNT
 184 ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
 185   RECORDMCOUNT_FLAGS = -w
 186 endif
 187 # Due to recursion, we must skip empty.o.
 188 # The empty.o file is created in the make process in order to determine
 189 # the target endianness and word size. It is made before all other C
 190 # files, including recordmcount.
 191 sub_cmd_record_mcount =                                 \
 192         if [ $(@) != "scripts/mod/empty.o" ]; then      \
 193                 $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)";   \
 194         fi;
 195 recordmcount_source := $(srctree)/scripts/recordmcount.c \
 196                     $(srctree)/scripts/recordmcount.h
 197 else
 198 sub_cmd_record_mcount = perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
 199         "$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \
 200         "$(if $(CONFIG_64BIT),64,32)" \
 201         "$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS)" \
 202         "$(LD) $(KBUILD_LDFLAGS)" "$(NM)" "$(RM)" "$(MV)" \
 203         "$(if $(part-of-module),1,0)" "$(@)";
 204 recordmcount_source := $(srctree)/scripts/recordmcount.pl
 205 endif # BUILD_C_RECORDMCOUNT
 206 cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)), \
 207         $(sub_cmd_record_mcount))
 208 endif # CC_USING_RECORD_MCOUNT
 209 endif # CONFIG_FTRACE_MCOUNT_RECORD
 210
 211 ifdef CONFIG_STACK_VALIDATION
 212 ifneq ($(SKIP_STACK_VALIDATION),1)
 213
 214 __objtool_obj := $(objtree)/tools/objtool/objtool
 215
 216 objtool_args = $(if $(CONFIG_UNWINDER_ORC),orc generate,check)
 217
 218 objtool_args += $(if $(part-of-module), --module,)
 219
 220 ifndef CONFIG_FRAME_POINTER
 221 objtool_args += --no-fp
 222 endif
 223 ifdef CONFIG_GCOV_KERNEL
 224 objtool_args += --no-unreachable
 225 endif
 226 ifdef CONFIG_RETPOLINE
 227   objtool_args += --retpoline
 228 endif
 229 ifdef CONFIG_X86_SMAP
 230   objtool_args += --uaccess
 231 endif
 232
 233 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
 234 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
 235 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
 236 cmd_objtool = $(if $(patsubst y%,, \
 237         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 238         $(__objtool_obj) $(objtool_args) $@)
 239 objtool_obj = $(if $(patsubst y%,, \
 240         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 241         $(__objtool_obj))
 242
 243 endif # SKIP_STACK_VALIDATION
 244 endif # CONFIG_STACK_VALIDATION
 245
 246 # Rebuild all objects when objtool changes, or is enabled/disabled.
 247 objtool_dep = $(objtool_obj)                                    \
 248               $(wildcard include/config/orc/unwinder.h          \
 249                          include/config/stack/validation.h)
 250
 251 ifdef CONFIG_TRIM_UNUSED_KSYMS
 252 cmd_gen_ksymdeps = \
 253         $(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd
 254
 255 # List module undefined symbols
 256 undefined_syms = $(NM) $< | $(AWK) '$$1 == "U" { printf("%s%s", x++ ? " " : "", $$2) }';
 257 endif
 258
 259 define rule_cc_o_c
 260         $(call cmd_and_fixdep,cc_o_c)
 261         $(call cmd,gen_ksymdeps)
 262         $(call cmd,checksrc)
 263         $(call cmd,checkdoc)
 264         $(call cmd,objtool)
 265         $(call cmd,modversions_c)
 266         $(call cmd,record_mcount)
 267 endef
 268
 269 define rule_as_o_S
 270         $(call cmd_and_fixdep,as_o_S)
 271         $(call cmd,gen_ksymdeps)
 272         $(call cmd,objtool)
 273         $(call cmd,modversions_S)
 274 endef
 275
 276 # Built-in and composite module parts
 277 $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
 278         $(call if_changed_rule,cc_o_c)
 279         $(call cmd,force_checksrc)
 280
 281 cmd_mod = { \
 282         echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \
 283         $(undefined_syms) echo; \
 284         } > $@
 285
 286 $(obj)/%.mod: $(obj)/%.o FORCE
 287         $(call if_changed,mod)
 288
 289 quiet_cmd_cc_lst_c = MKLST   $@
 290       cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
 291                      $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
 292                                      System.map $(OBJDUMP) > $@
 293
 294 $(obj)/%.lst: $(src)/%.c FORCE
 295         $(call if_changed_dep,cc_lst_c)
 296
 297 # Compile assembler sources (.S)
 298 # ---------------------------------------------------------------------------
 299
 300 # .S file exports must have their C prototypes defined in asm/asm-prototypes.h
 301 # or a file that it includes, in order to get versioned symbols. We build a
 302 # dummy C file that includes asm-prototypes and the EXPORT_SYMBOL lines from
 303 # the .S file (with trailing ';'), and run genksyms on that, to extract vers.
 304 #
 305 # This is convoluted. The .S file must first be preprocessed to run guards and
 306 # expand names, then the resulting exports must be constructed into plain
 307 # EXPORT_SYMBOL(symbol); to build our dummy C file, and that gets preprocessed
 308 # to make the genksyms input.
 309 #
 310 # These mirror gensymtypes_c and co above, keep them in synch.
 311 cmd_gensymtypes_S =                                                         \
 312    { echo "\#include <linux/kernel.h>" ;                                    \
 313      echo "\#include <asm/asm-prototypes.h>" ;                              \
 314     $(CPP) $(a_flags) $< |                                                  \
 315      grep "\<___EXPORT_SYMBOL\>" |                                          \
 316      sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ; } | \
 317     $(CPP) -D__GENKSYMS__ $(c_flags) -xc - |                                \
 318     scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
 319      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
 320      $(if $(KBUILD_PRESERVE),-p)                                            \
 321      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 322
 323 quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
 324 cmd_cc_symtypes_S =                                                         \
 325     $(call cmd_gensymtypes_S,true,$@) >/dev/null;                           \
 326     test -s $@ || rm -f $@
 327
 328 $(obj)/%.symtypes : $(src)/%.S FORCE
 329         $(call cmd,cc_symtypes_S)
 330
 331
 332 quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
 333 cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
 334
 335 $(obj)/%.s: $(src)/%.S FORCE
 336         $(call if_changed_dep,cpp_s_S)
 337
 338 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
 339       cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
 340
 341 ifdef CONFIG_ASM_MODVERSIONS
 342
 343 # versioning matches the C process described above, with difference that
 344 # we parse asm-prototypes.h C header to get function definitions.
 345
 346 cmd_modversions_S =                                                             \
 347         if $(OBJDUMP) -h $@ | grep -q __ksymtab; then                           \
 348                 $(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 349                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
 350                                                                                 \
 351                 $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@               \
 352                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
 353                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
 354                 rm -f $(@D)/.tmp_$(@F:.o=.ver);                                 \
 355         fi
 356 endif
 357
 358 $(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
 359         $(call if_changed_rule,as_o_S)
 360
 361 targets += $(filter-out $(subdir-builtin), $(real-obj-y))
 362 targets += $(filter-out $(subdir-modorder), $(real-obj-m))
 363 targets += $(lib-y) $(always-y) $(MAKECMDGOALS)
 364
 365 # Linker scripts preprocessor (.lds.S -> .lds)
 366 # ---------------------------------------------------------------------------
 367 quiet_cmd_cpp_lds_S = LDS     $@
 368       cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
 369                              -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
 370
 371 $(obj)/%.lds: $(src)/%.lds.S FORCE
 372         $(call if_changed_dep,cpp_lds_S)
 373
 374 # ASN.1 grammar
 375 # ---------------------------------------------------------------------------
 376 quiet_cmd_asn1_compiler = ASN.1   $(basename $@).[ch]
 377       cmd_asn1_compiler = $(objtree)/scripts/asn1_compiler $< \
 378                                 $(basename $@).c $(basename $@).h
 379
 380 $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
 381         $(call cmd,asn1_compiler)
 382
 383 # Build the compiled-in targets
 384 # ---------------------------------------------------------------------------
 385
 386 # To build objects in subdirs, we need to descend into the directories
 387 $(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ;
 388 $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
 389
 390 #
 391 # Rule to compile a set of .o files into one .a file (without symbol table)
 392 #
 393
 394 quiet_cmd_ar_builtin = AR      $@
 395       cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
 396
 397 $(obj)/built-in.a: $(real-obj-y) FORCE
 398         $(call if_changed,ar_builtin)
 399
 400 #
 401 # Rule to create modules.order file
 402 #
 403 # Create commands to either record .ko file or cat modules.order from
 404 # a subdirectory
 405 # Add $(obj-m) as the prerequisite to avoid updating the timestamp of
 406 # modules.order unless contained modules are updated.
 407
 408 cmd_modules_order = { $(foreach m, $(real-prereqs), \
 409         $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.o,%.ko,$m));) :; } \
 410         | $(AWK) '!x[$$0]++' - > $@
 411
 412 $(obj)/modules.order: $(obj-m) FORCE
 413         $(call if_changed,modules_order)
 414
 415 #
 416 # Rule to compile a set of .o files into one .a file (with symbol table)
 417 #
 418 $(obj)/lib.a: $(lib-y) FORCE
 419         $(call if_changed,ar)
 420
 421 # NOTE:
 422 # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
 423 # module is turned into a multi object module, $^ will contain header file
 424 # dependencies recorded in the .*.cmd file.
 425 quiet_cmd_link_multi-m = LD [M]  $@
 426       cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
 427
 428 $(multi-used-m): FORCE
 429         $(call if_changed,link_multi-m)
 430 $(call multi_depend, $(multi-used-m), .o, -objs -y -m)
 431
 432 targets += $(multi-used-m)
 433 targets := $(filter-out $(PHONY), $(targets))
 434
 435 # Add intermediate targets:
 436 # When building objects with specific suffix patterns, add intermediate
 437 # targets that the final targets are derived from.
 438 intermediate_targets = $(foreach sfx, $(2), \
 439                                 $(patsubst %$(strip $(1)),%$(sfx), \
 440                                         $(filter %$(strip $(1)), $(targets))))
 441 # %.asn1.o <- %.asn1.[ch] <- %.asn1
 442 # %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
 443 # %.lex.o <- %.lex.c <- %.l
 444 # %.tab.o <- %.tab.[ch] <- %.y
 445 targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
 446            $(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
 447            $(call intermediate_targets, .lex.o, .lex.c) \
 448            $(call intermediate_targets, .tab.o, .tab.c .tab.h)
 449
 450 # Build
 451 # ---------------------------------------------------------------------------
 452
 453 ifdef single-build
 454
 455 KBUILD_SINGLE_TARGETS := $(filter $(obj)/%, $(KBUILD_SINGLE_TARGETS))
 456
 457 curdir-single := $(sort $(foreach x, $(KBUILD_SINGLE_TARGETS), \
 458                         $(if $(filter $(x) $(basename $(x)).o, $(targets)), $(x))))
 459
 460 # Handle single targets without any rule: show "Nothing to be done for ..." or
 461 # "No rule to make target ..." depending on whether the target exists.
 462 unknown-single := $(filter-out $(addsuffix /%, $(subdir-ym)), \
 463                         $(filter-out $(curdir-single), $(KBUILD_SINGLE_TARGETS)))
 464
 465 single-subdirs := $(foreach d, $(subdir-ym), \
 466                         $(if $(filter $(d)/%, $(KBUILD_SINGLE_TARGETS)), $(d)))
 467
 468 __build: $(curdir-single) $(single-subdirs)
 469 ifneq ($(unknown-single),)
 470         $(Q)$(MAKE) -f /dev/null $(unknown-single)
 471 endif
 472         @:
 473
 474 ifeq ($(curdir-single),)
 475 # Nothing to do in this directory. Do not include any .*.cmd file for speed-up
 476 targets :=
 477 else
 478 targets += $(curdir-single)
 479 endif
 480
 481 else
 482
 483 __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
 484          $(if $(KBUILD_MODULES), $(targets-for-modules)) \
 485          $(subdir-ym) $(always-y)
 486         @:
 487
 488 endif
 489
 490 # Descending
 491 # ---------------------------------------------------------------------------
 492
 493 PHONY += $(subdir-ym)
 494 $(subdir-ym):
 495         $(Q)$(MAKE) $(build)=$@ \
 496         $(if $(filter $@/, $(KBUILD_SINGLE_TARGETS)),single-build=) \
 497         need-builtin=$(if $(filter $@/built-in.a, $(subdir-builtin)),1) \
 498         need-modorder=$(if $(filter $@/modules.order, $(subdir-modorder)),1)
 499
 500 # Add FORCE to the prequisites of a target to force it to be always rebuilt.
 501 # ---------------------------------------------------------------------------
 502
 503 PHONY += FORCE
 504
 505 FORCE:
 506
 507 # Read all saved command lines and dependencies for the $(targets) we
 508 # may be building above, using $(if_changed{,_dep}). As an
 509 # optimization, we don't need to read them if the target does not
 510 # exist, we will rebuild anyway in that case.
 511
 512 existing-targets := $(wildcard $(sort $(targets)))
 513
 514 -include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
 515
 516 # Create directories for object files if they do not exist
 517 obj-dirs := $(sort $(patsubst %/,%, $(dir $(targets))))
 518 # If targets exist, their directories apparently exist. Skip mkdir.
 519 existing-dirs := $(sort $(patsubst %/,%, $(dir $(existing-targets))))
 520 obj-dirs := $(strip $(filter-out $(existing-dirs), $(obj-dirs)))
 521 ifneq ($(obj-dirs),)
 522 $(shell mkdir -p $(obj-dirs))
 523 endif
 524
 525 .PHONY: $(PHONY)