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 :=
  19 always-y :=
  20 always-m :=
  21 targets :=
  22 subdir-y :=
  23 subdir-m :=
  24 EXTRA_AFLAGS   :=
  25 EXTRA_CFLAGS   :=
  26 EXTRA_CPPFLAGS :=
  27 EXTRA_LDFLAGS  :=
  28 asflags-y  :=
  29 ccflags-y  :=
  30 cppflags-y :=
  31 ldflags-y  :=
  32
  33 subdir-asflags-y :=
  34 subdir-ccflags-y :=
  35
  36 # Read auto.conf if it exists, otherwise ignore
  37 -include include/config/auto.conf
  38
  39 include scripts/Kbuild.include
  40
  41 # The filename Kbuild has precedence over Makefile
  42 kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
  43 kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
  44 include $(kbuild-file)
  45
  46 include scripts/Makefile.lib
  47
  48 # Do not include host rules unless needed
  49 ifneq ($(hostprogs)$(hostcxxlibs-y)$(hostcxxlibs-m),)
  50 include scripts/Makefile.host
  51 endif
  52
  53 # Do not include userprogs rules unless needed.
  54 userprogs := $(sort $(userprogs))
  55 ifneq ($(userprogs),)
  56 include scripts/Makefile.userprogs
  57 endif
  58
  59 ifndef obj
  60 $(warning kbuild: Makefile.build is included improperly)
  61 endif
  62
  63 ifeq ($(need-modorder),)
  64 ifneq ($(obj-m),)
  65 $(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
  66 $(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
  67 endif
  68 endif
  69
  70 # ===========================================================================
  71
  72 # subdir-builtin and subdir-modorder may contain duplications. Use $(sort ...)
  73 subdir-builtin := $(sort $(filter %/built-in.a, $(real-obj-y)))
  74 subdir-modorder := $(sort $(filter %/modules.order, $(obj-m)))
  75
  76 targets-for-builtin := $(extra-y)
  77
  78 ifneq ($(strip $(lib-y) $(lib-m) $(lib-)),)
  79 targets-for-builtin += $(obj)/lib.a
  80 endif
  81
  82 ifdef need-builtin
  83 targets-for-builtin += $(obj)/built-in.a
  84 endif
  85
  86 targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
  87
  88 ifdef need-modorder
  89 targets-for-modules += $(obj)/modules.order
  90 endif
  91
  92 targets += $(targets-for-builtin) $(targets-for-modules)
  93
  94 # Linus' kernel sanity checking tool
  95 ifeq ($(KBUILD_CHECKSRC),1)
  96   quiet_cmd_checksrc       = CHECK   $<
  97         cmd_checksrc       = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
  98 else ifeq ($(KBUILD_CHECKSRC),2)
  99   quiet_cmd_force_checksrc = CHECK   $<
 100         cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
 101 endif
 102
 103 ifneq ($(KBUILD_EXTRA_WARN),)
 104   cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $<
 105 endif
 106
 107 # Compile C sources (.c)
 108 # ---------------------------------------------------------------------------
 109
 110 quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@
 111       cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) $(DISABLE_LTO) -fverbose-asm -S -o $@ $<
 112
 113 $(obj)/%.s: $(src)/%.c FORCE
 114         $(call if_changed_dep,cc_s_c)
 115
 116 quiet_cmd_cpp_i_c = CPP $(quiet_modtag) $@
 117 cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
 118
 119 $(obj)/%.i: $(src)/%.c FORCE
 120         $(call if_changed_dep,cpp_i_c)
 121
 122 # These mirror gensymtypes_S and co below, keep them in synch.
 123 cmd_gensymtypes_c =                                                         \
 124     $(CPP) -D__GENKSYMS__ $(c_flags) $< |                                   \
 125     scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
 126      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
 127      $(if $(KBUILD_PRESERVE),-p)                                            \
 128      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 129
 130 quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
 131 cmd_cc_symtypes_c =                                                         \
 132     $(call cmd_gensymtypes_c,true,$@) >/dev/null;                           \
 133     test -s $@ || rm -f $@
 134
 135 $(obj)/%.symtypes : $(src)/%.c FORCE
 136         $(call cmd,cc_symtypes_c)
 137
 138 # LLVM assembly
 139 # Generate .ll files from .c
 140 quiet_cmd_cc_ll_c = CC $(quiet_modtag)  $@
 141       cmd_cc_ll_c = $(CC) $(c_flags) -emit-llvm -S -o $@ $<
 142
 143 $(obj)/%.ll: $(src)/%.c FORCE
 144         $(call if_changed_dep,cc_ll_c)
 145
 146 # C (.c) files
 147 # The C file is compiled and updated dependency information is generated.
 148 # (See cmd_cc_o_c + relevant part of rule_cc_o_c)
 149
 150 quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
 151       cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
 152
 153 ifdef CONFIG_MODVERSIONS
 154 # When module versioning is enabled the following steps are executed:
 155 # o compile a <file>.o from <file>.c
 156 # o if <file>.o doesn't contain a __ksymtab version, i.e. does
 157 #   not export symbols, it's done.
 158 # o otherwise, we calculate symbol versions using the good old
 159 #   genksyms on the preprocessed source and postprocess them in a way
 160 #   that they are usable as a linker script
 161 # o generate .tmp_<file>.o from <file>.o using the linker to
 162 #   replace the unresolved symbols __crc_exported_symbol with
 163 #   the actual value of the checksum generated by genksyms
 164 # o remove .tmp_<file>.o to <file>.o
 165
 166 cmd_modversions_c =                                                             \
 167         if $(OBJDUMP) -h $@ | grep -q __ksymtab; then                           \
 168                 $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 169                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
 170                                                                                 \
 171                 $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@               \
 172                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
 173                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
 174                 rm -f $(@D)/.tmp_$(@F:.o=.ver);                                 \
 175         fi
 176 endif
 177
 178 ifdef CONFIG_FTRACE_MCOUNT_RECORD
 179 ifndef CC_USING_RECORD_MCOUNT
 180 # compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
 181 ifdef BUILD_C_RECORDMCOUNT
 182 ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
 183   RECORDMCOUNT_FLAGS = -w
 184 endif
 185 # Due to recursion, we must skip empty.o.
 186 # The empty.o file is created in the make process in order to determine
 187 # the target endianness and word size. It is made before all other C
 188 # files, including recordmcount.
 189 sub_cmd_record_mcount =                                 \
 190         if [ $(@) != "scripts/mod/empty.o" ]; then      \
 191                 $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)";   \
 192         fi;
 193 recordmcount_source := $(srctree)/scripts/recordmcount.c \
 194                     $(srctree)/scripts/recordmcount.h
 195 else
 196 sub_cmd_record_mcount = perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
 197         "$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \
 198         "$(if $(CONFIG_64BIT),64,32)" \
 199         "$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS)" \
 200         "$(LD) $(KBUILD_LDFLAGS)" "$(NM)" "$(RM)" "$(MV)" \
 201         "$(if $(part-of-module),1,0)" "$(@)";
 202 recordmcount_source := $(srctree)/scripts/recordmcount.pl
 203 endif # BUILD_C_RECORDMCOUNT
 204 cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)), \
 205         $(sub_cmd_record_mcount))
 206 endif # CC_USING_RECORD_MCOUNT
 207 endif # CONFIG_FTRACE_MCOUNT_RECORD
 208
 209 ifdef CONFIG_STACK_VALIDATION
 210 ifneq ($(SKIP_STACK_VALIDATION),1)
 211
 212 __objtool_obj := $(objtree)/tools/objtool/objtool
 213
 214 objtool_args = $(if $(CONFIG_UNWINDER_ORC),orc generate,check)
 215
 216 objtool_args += $(if $(part-of-module), --module,)
 217
 218 ifndef CONFIG_FRAME_POINTER
 219 objtool_args += --no-fp
 220 endif
 221 ifdef CONFIG_GCOV_KERNEL
 222 objtool_args += --no-unreachable
 223 endif
 224 ifdef CONFIG_RETPOLINE
 225   objtool_args += --retpoline
 226 endif
 227 ifdef CONFIG_X86_SMAP
 228   objtool_args += --uaccess
 229 endif
 230
 231 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
 232 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
 233 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
 234 cmd_objtool = $(if $(patsubst y%,, \
 235         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 236         $(__objtool_obj) $(objtool_args) $@)
 237 objtool_obj = $(if $(patsubst y%,, \
 238         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 239         $(__objtool_obj))
 240
 241 endif # SKIP_STACK_VALIDATION
 242 endif # CONFIG_STACK_VALIDATION
 243
 244 # Rebuild all objects when objtool changes, or is enabled/disabled.
 245 objtool_dep = $(objtool_obj)                                    \
 246               $(wildcard include/config/orc/unwinder.h          \
 247                          include/config/stack/validation.h)
 248
 249 ifdef CONFIG_TRIM_UNUSED_KSYMS
 250 cmd_gen_ksymdeps = \
 251         $(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd
 252 endif
 253
 254 define rule_cc_o_c
 255         $(call cmd,checksrc)
 256         $(call cmd_and_fixdep,cc_o_c)
 257         $(call cmd,gen_ksymdeps)
 258         $(call cmd,checkdoc)
 259         $(call cmd,objtool)
 260         $(call cmd,modversions_c)
 261         $(call cmd,record_mcount)
 262 endef
 263
 264 define rule_as_o_S
 265         $(call cmd_and_fixdep,as_o_S)
 266         $(call cmd,gen_ksymdeps)
 267         $(call cmd,objtool)
 268         $(call cmd,modversions_S)
 269 endef
 270
 271 # List module undefined symbols (or empty line if not enabled)
 272 ifdef CONFIG_TRIM_UNUSED_KSYMS
 273 cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | xargs echo
 274 else
 275 cmd_undef_syms = echo
 276 endif
 277
 278 # Built-in and composite module parts
 279 $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
 280         $(call cmd,force_checksrc)
 281         $(call if_changed_rule,cc_o_c)
 282
 283 cmd_mod = { \
 284         echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \
 285         $(cmd_undef_syms); \
 286         } > $@
 287
 288 $(obj)/%.mod: $(obj)/%.o FORCE
 289         $(call if_changed,mod)
 290
 291 quiet_cmd_cc_lst_c = MKLST   $@
 292       cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
 293                      $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
 294                                      System.map $(OBJDUMP) > $@
 295
 296 $(obj)/%.lst: $(src)/%.c FORCE
 297         $(call if_changed_dep,cc_lst_c)
 298
 299 # Compile assembler sources (.S)
 300 # ---------------------------------------------------------------------------
 301
 302 # .S file exports must have their C prototypes defined in asm/asm-prototypes.h
 303 # or a file that it includes, in order to get versioned symbols. We build a
 304 # dummy C file that includes asm-prototypes and the EXPORT_SYMBOL lines from
 305 # the .S file (with trailing ';'), and run genksyms on that, to extract vers.
 306 #
 307 # This is convoluted. The .S file must first be preprocessed to run guards and
 308 # expand names, then the resulting exports must be constructed into plain
 309 # EXPORT_SYMBOL(symbol); to build our dummy C file, and that gets preprocessed
 310 # to make the genksyms input.
 311 #
 312 # These mirror gensymtypes_c and co above, keep them in synch.
 313 cmd_gensymtypes_S =                                                         \
 314    { echo "\#include <linux/kernel.h>" ;                                    \
 315      echo "\#include <asm/asm-prototypes.h>" ;                              \
 316     $(CPP) $(a_flags) $< |                                                  \
 317      grep "\<___EXPORT_SYMBOL\>" |                                          \
 318      sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ; } | \
 319     $(CPP) -D__GENKSYMS__ $(c_flags) -xc - |                                \
 320     scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
 321      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
 322      $(if $(KBUILD_PRESERVE),-p)                                            \
 323      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 324
 325 quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
 326 cmd_cc_symtypes_S =                                                         \
 327     $(call cmd_gensymtypes_S,true,$@) >/dev/null;                           \
 328     test -s $@ || rm -f $@
 329
 330 $(obj)/%.symtypes : $(src)/%.S FORCE
 331         $(call cmd,cc_symtypes_S)
 332
 333
 334 quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
 335 cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
 336
 337 $(obj)/%.s: $(src)/%.S FORCE
 338         $(call if_changed_dep,cpp_s_S)
 339
 340 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
 341       cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
 342
 343 ifdef CONFIG_ASM_MODVERSIONS
 344
 345 # versioning matches the C process described above, with difference that
 346 # we parse asm-prototypes.h C header to get function definitions.
 347
 348 cmd_modversions_S =                                                             \
 349         if $(OBJDUMP) -h $@ | grep -q __ksymtab; then                           \
 350                 $(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 351                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
 352                                                                                 \
 353                 $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@               \
 354                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
 355                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
 356                 rm -f $(@D)/.tmp_$(@F:.o=.ver);                                 \
 357         fi
 358 endif
 359
 360 $(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
 361         $(call if_changed_rule,as_o_S)
 362
 363 targets += $(filter-out $(subdir-builtin), $(real-obj-y))
 364 targets += $(filter-out $(subdir-modorder), $(real-obj-m))
 365 targets += $(lib-y) $(always-y) $(MAKECMDGOALS)
 366
 367 # Linker scripts preprocessor (.lds.S -> .lds)
 368 # ---------------------------------------------------------------------------
 369 quiet_cmd_cpp_lds_S = LDS     $@
 370       cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
 371                              -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
 372
 373 $(obj)/%.lds: $(src)/%.lds.S FORCE
 374         $(call if_changed_dep,cpp_lds_S)
 375
 376 # ASN.1 grammar
 377 # ---------------------------------------------------------------------------
 378 quiet_cmd_asn1_compiler = ASN.1   $(basename $@).[ch]
 379       cmd_asn1_compiler = $(objtree)/scripts/asn1_compiler $< \
 380                                 $(basename $@).c $(basename $@).h
 381
 382 $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
 383         $(call cmd,asn1_compiler)
 384
 385 # Build the compiled-in targets
 386 # ---------------------------------------------------------------------------
 387
 388 # To build objects in subdirs, we need to descend into the directories
 389 $(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ;
 390 $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
 391
 392 #
 393 # Rule to compile a set of .o files into one .a file (without symbol table)
 394 #
 395
 396 quiet_cmd_ar_builtin = AR      $@
 397       cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
 398
 399 $(obj)/built-in.a: $(real-obj-y) FORCE
 400         $(call if_changed,ar_builtin)
 401
 402 #
 403 # Rule to create modules.order file
 404 #
 405 # Create commands to either record .ko file or cat modules.order from
 406 # a subdirectory
 407 # Add $(obj-m) as the prerequisite to avoid updating the timestamp of
 408 # modules.order unless contained modules are updated.
 409
 410 cmd_modules_order = { $(foreach m, $(real-prereqs), \
 411         $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.o,%.ko,$m));) :; } \
 412         | $(AWK) '!x[$$0]++' - > $@
 413
 414 $(obj)/modules.order: $(obj-m) FORCE
 415         $(call if_changed,modules_order)
 416
 417 #
 418 # Rule to compile a set of .o files into one .a file (with symbol table)
 419 #
 420 $(obj)/lib.a: $(lib-y) FORCE
 421         $(call if_changed,ar)
 422
 423 # NOTE:
 424 # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
 425 # module is turned into a multi object module, $^ will contain header file
 426 # dependencies recorded in the .*.cmd file.
 427 quiet_cmd_link_multi-m = LD [M]  $@
 428       cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
 429
 430 $(multi-used-m): FORCE
 431         $(call if_changed,link_multi-m)
 432 $(call multi_depend, $(multi-used-m), .o, -objs -y -m)
 433
 434 targets += $(multi-used-m)
 435 targets := $(filter-out $(PHONY), $(targets))
 436
 437 # Add intermediate targets:
 438 # When building objects with specific suffix patterns, add intermediate
 439 # targets that the final targets are derived from.
 440 intermediate_targets = $(foreach sfx, $(2), \
 441                                 $(patsubst %$(strip $(1)),%$(sfx), \
 442                                         $(filter %$(strip $(1)), $(targets))))
 443 # %.asn1.o <- %.asn1.[ch] <- %.asn1
 444 # %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
 445 # %.lex.o <- %.lex.c <- %.l
 446 # %.tab.o <- %.tab.[ch] <- %.y
 447 targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
 448            $(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
 449            $(call intermediate_targets, .lex.o, .lex.c) \
 450            $(call intermediate_targets, .tab.o, .tab.c .tab.h)
 451
 452 # Build
 453 # ---------------------------------------------------------------------------
 454
 455 ifdef single-build
 456
 457 KBUILD_SINGLE_TARGETS := $(filter $(obj)/%, $(KBUILD_SINGLE_TARGETS))
 458
 459 curdir-single := $(sort $(foreach x, $(KBUILD_SINGLE_TARGETS), \
 460                         $(if $(filter $(x) $(basename $(x)).o, $(targets)), $(x))))
 461
 462 # Handle single targets without any rule: show "Nothing to be done for ..." or
 463 # "No rule to make target ..." depending on whether the target exists.
 464 unknown-single := $(filter-out $(addsuffix /%, $(subdir-ym)), \
 465                         $(filter-out $(curdir-single), $(KBUILD_SINGLE_TARGETS)))
 466
 467 single-subdirs := $(foreach d, $(subdir-ym), \
 468                         $(if $(filter $(d)/%, $(KBUILD_SINGLE_TARGETS)), $(d)))
 469
 470 __build: $(curdir-single) $(single-subdirs)
 471 ifneq ($(unknown-single),)
 472         $(Q)$(MAKE) -f /dev/null $(unknown-single)
 473 endif
 474         @:
 475
 476 ifeq ($(curdir-single),)
 477 # Nothing to do in this directory. Do not include any .*.cmd file for speed-up
 478 targets :=
 479 else
 480 targets += $(curdir-single)
 481 endif
 482
 483 else
 484
 485 __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
 486          $(if $(KBUILD_MODULES), $(targets-for-modules)) \
 487          $(subdir-ym) $(always-y)
 488         @:
 489
 490 endif
 491
 492 # Descending
 493 # ---------------------------------------------------------------------------
 494
 495 PHONY += $(subdir-ym)
 496 $(subdir-ym):
 497         $(Q)$(MAKE) $(build)=$@ \
 498         $(if $(filter $@/, $(KBUILD_SINGLE_TARGETS)),single-build=) \
 499         need-builtin=$(if $(filter $@/built-in.a, $(subdir-builtin)),1) \
 500         need-modorder=$(if $(filter $@/modules.order, $(subdir-modorder)),1)
 501
 502 # Add FORCE to the prequisites of a target to force it to be always rebuilt.
 503 # ---------------------------------------------------------------------------
 504
 505 PHONY += FORCE
 506
 507 FORCE:
 508
 509 # Read all saved command lines and dependencies for the $(targets) we
 510 # may be building above, using $(if_changed{,_dep}). As an
 511 # optimization, we don't need to read them if the target does not
 512 # exist, we will rebuild anyway in that case.
 513
 514 existing-targets := $(wildcard $(sort $(targets)))
 515
 516 -include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
 517
 518 ifdef building_out_of_srctree
 519 # Create directories for object files if they do not exist
 520 obj-dirs := $(sort $(obj) $(patsubst %/,%, $(dir $(targets))))
 521 # If targets exist, their directories apparently exist. Skip mkdir.
 522 existing-dirs := $(sort $(patsubst %/,%, $(dir $(existing-targets))))
 523 obj-dirs := $(strip $(filter-out $(existing-dirs), $(obj-dirs)))
 524 ifneq ($(obj-dirs),)
 525 $(shell mkdir -p $(obj-dirs))
 526 endif
 527 endif
 528
 529 .PHONY: $(PHONY)