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 targets :=
  20 subdir-y :=
  21 subdir-m :=
  22 EXTRA_AFLAGS   :=
  23 EXTRA_CFLAGS   :=
  24 EXTRA_CPPFLAGS :=
  25 EXTRA_LDFLAGS  :=
  26 asflags-y  :=
  27 ccflags-y  :=
  28 cppflags-y :=
  29 ldflags-y  :=
  30
  31 subdir-asflags-y :=
  32 subdir-ccflags-y :=
  33
  34 # Read auto.conf if it exists, otherwise ignore
  35 -include include/config/auto.conf
  36
  37 include scripts/Kbuild.include
  38
  39 # The filename Kbuild has precedence over Makefile
  40 kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
  41 kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
  42 include $(kbuild-file)
  43
  44 include scripts/Makefile.lib
  45
  46 # Do not include host rules unless needed
  47 ifneq ($(hostprogs-y)$(hostprogs-m)$(hostlibs-y)$(hostlibs-m)$(hostcxxlibs-y)$(hostcxxlibs-m),)
  48 include scripts/Makefile.host
  49 endif
  50
  51 ifndef obj
  52 $(warning kbuild: Makefile.build is included improperly)
  53 endif
  54
  55 ifeq ($(need-modorder),)
  56 ifneq ($(obj-m),)
  57 $(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
  58 $(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
  59 endif
  60 endif
  61
  62 # ===========================================================================
  63
  64 ifneq ($(strip $(lib-y) $(lib-m) $(lib-)),)
  65 lib-target := $(obj)/lib.a
  66 real-obj-y += $(obj)/lib-ksyms.o
  67 endif
  68
  69 ifneq ($(strip $(real-obj-y) $(need-builtin)),)
  70 builtin-target := $(obj)/built-in.a
  71 endif
  72
  73 ifeq ($(CONFIG_MODULES)$(need-modorder),y1)
  74 modorder-target := $(obj)/modules.order
  75 endif
  76
  77 mod-targets := $(patsubst %.o, %.mod, $(obj-m))
  78
  79 # Linus' kernel sanity checking tool
  80 ifeq ($(KBUILD_CHECKSRC),1)
  81   quiet_cmd_checksrc       = CHECK   $<
  82         cmd_checksrc       = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
  83 else ifeq ($(KBUILD_CHECKSRC),2)
  84   quiet_cmd_force_checksrc = CHECK   $<
  85         cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
  86 endif
  87
  88 ifneq ($(KBUILD_EXTRA_WARN),)
  89   cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $<
  90 endif
  91
  92 # Compile C sources (.c)
  93 # ---------------------------------------------------------------------------
  94
  95 quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@
  96       cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) $(DISABLE_LTO) -fverbose-asm -S -o $@ $<
  97
  98 $(obj)/%.s: $(src)/%.c FORCE
  99         $(call if_changed_dep,cc_s_c)
 100
 101 quiet_cmd_cpp_i_c = CPP $(quiet_modtag) $@
 102 cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
 103
 104 $(obj)/%.i: $(src)/%.c FORCE
 105         $(call if_changed_dep,cpp_i_c)
 106
 107 # These mirror gensymtypes_S and co below, keep them in synch.
 108 cmd_gensymtypes_c =                                                         \
 109     $(CPP) -D__GENKSYMS__ $(c_flags) $< |                                   \
 110     scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
 111      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
 112      $(if $(KBUILD_PRESERVE),-p)                                            \
 113      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 114
 115 quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
 116 cmd_cc_symtypes_c =                                                         \
 117     $(call cmd_gensymtypes_c,true,$@) >/dev/null;                           \
 118     test -s $@ || rm -f $@
 119
 120 $(obj)/%.symtypes : $(src)/%.c FORCE
 121         $(call cmd,cc_symtypes_c)
 122
 123 # LLVM assembly
 124 # Generate .ll files from .c
 125 quiet_cmd_cc_ll_c = CC $(quiet_modtag)  $@
 126       cmd_cc_ll_c = $(CC) $(c_flags) -emit-llvm -S -o $@ $<
 127
 128 $(obj)/%.ll: $(src)/%.c FORCE
 129         $(call if_changed_dep,cc_ll_c)
 130
 131 # C (.c) files
 132 # The C file is compiled and updated dependency information is generated.
 133 # (See cmd_cc_o_c + relevant part of rule_cc_o_c)
 134
 135 quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
 136       cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
 137
 138 ifdef CONFIG_MODVERSIONS
 139 # When module versioning is enabled the following steps are executed:
 140 # o compile a <file>.o from <file>.c
 141 # o if <file>.o doesn't contain a __ksymtab version, i.e. does
 142 #   not export symbols, it's done.
 143 # o otherwise, we calculate symbol versions using the good old
 144 #   genksyms on the preprocessed source and postprocess them in a way
 145 #   that they are usable as a linker script
 146 # o generate .tmp_<file>.o from <file>.o using the linker to
 147 #   replace the unresolved symbols __crc_exported_symbol with
 148 #   the actual value of the checksum generated by genksyms
 149 # o remove .tmp_<file>.o to <file>.o
 150
 151 cmd_modversions_c =                                                             \
 152         if $(OBJDUMP) -h $@ | grep -q __ksymtab; then                           \
 153                 $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 154                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
 155                                                                                 \
 156                 $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@               \
 157                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
 158                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
 159                 rm -f $(@D)/.tmp_$(@F:.o=.ver);                                 \
 160         fi
 161 endif
 162
 163 ifdef CONFIG_FTRACE_MCOUNT_RECORD
 164 ifndef CC_USING_RECORD_MCOUNT
 165 # compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
 166 ifdef BUILD_C_RECORDMCOUNT
 167 ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
 168   RECORDMCOUNT_FLAGS = -w
 169 endif
 170 # Due to recursion, we must skip empty.o.
 171 # The empty.o file is created in the make process in order to determine
 172 # the target endianness and word size. It is made before all other C
 173 # files, including recordmcount.
 174 sub_cmd_record_mcount =                                 \
 175         if [ $(@) != "scripts/mod/empty.o" ]; then      \
 176                 $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)";   \
 177         fi;
 178 recordmcount_source := $(srctree)/scripts/recordmcount.c \
 179                     $(srctree)/scripts/recordmcount.h
 180 else
 181 sub_cmd_record_mcount = perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
 182         "$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \
 183         "$(if $(CONFIG_64BIT),64,32)" \
 184         "$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS)" \
 185         "$(LD) $(KBUILD_LDFLAGS)" "$(NM)" "$(RM)" "$(MV)" \
 186         "$(if $(part-of-module),1,0)" "$(@)";
 187 recordmcount_source := $(srctree)/scripts/recordmcount.pl
 188 endif # BUILD_C_RECORDMCOUNT
 189 cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)), \
 190         $(sub_cmd_record_mcount))
 191 endif # CC_USING_RECORD_MCOUNT
 192 endif # CONFIG_FTRACE_MCOUNT_RECORD
 193
 194 ifdef CONFIG_STACK_VALIDATION
 195 ifneq ($(SKIP_STACK_VALIDATION),1)
 196
 197 __objtool_obj := $(objtree)/tools/objtool/objtool
 198
 199 objtool_args = $(if $(CONFIG_UNWINDER_ORC),orc generate,check)
 200
 201 objtool_args += $(if $(part-of-module), --module,)
 202
 203 ifndef CONFIG_FRAME_POINTER
 204 objtool_args += --no-fp
 205 endif
 206 ifdef CONFIG_GCOV_KERNEL
 207 objtool_args += --no-unreachable
 208 endif
 209 ifdef CONFIG_RETPOLINE
 210   objtool_args += --retpoline
 211 endif
 212 ifdef CONFIG_X86_SMAP
 213   objtool_args += --uaccess
 214 endif
 215
 216 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
 217 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
 218 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
 219 cmd_objtool = $(if $(patsubst y%,, \
 220         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 221         $(__objtool_obj) $(objtool_args) $@)
 222 objtool_obj = $(if $(patsubst y%,, \
 223         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 224         $(__objtool_obj))
 225
 226 endif # SKIP_STACK_VALIDATION
 227 endif # CONFIG_STACK_VALIDATION
 228
 229 # Rebuild all objects when objtool changes, or is enabled/disabled.
 230 objtool_dep = $(objtool_obj)                                    \
 231               $(wildcard include/config/orc/unwinder.h          \
 232                          include/config/stack/validation.h)
 233
 234 ifdef CONFIG_TRIM_UNUSED_KSYMS
 235 cmd_gen_ksymdeps = \
 236         $(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd
 237 endif
 238
 239 define rule_cc_o_c
 240         $(call cmd,checksrc)
 241         $(call cmd_and_fixdep,cc_o_c)
 242         $(call cmd,gen_ksymdeps)
 243         $(call cmd,checkdoc)
 244         $(call cmd,objtool)
 245         $(call cmd,modversions_c)
 246         $(call cmd,record_mcount)
 247 endef
 248
 249 define rule_as_o_S
 250         $(call cmd_and_fixdep,as_o_S)
 251         $(call cmd,gen_ksymdeps)
 252         $(call cmd,objtool)
 253         $(call cmd,modversions_S)
 254 endef
 255
 256 # List module undefined symbols (or empty line if not enabled)
 257 ifdef CONFIG_TRIM_UNUSED_KSYMS
 258 cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | xargs echo
 259 else
 260 cmd_undef_syms = echo
 261 endif
 262
 263 # Built-in and composite module parts
 264 $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
 265         $(call cmd,force_checksrc)
 266         $(call if_changed_rule,cc_o_c)
 267
 268 cmd_mod = { \
 269         echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \
 270         $(cmd_undef_syms); \
 271         } > $@
 272
 273 $(obj)/%.mod: $(obj)/%.o FORCE
 274         $(call if_changed,mod)
 275
 276 targets += $(mod-targets)
 277
 278 quiet_cmd_cc_lst_c = MKLST   $@
 279       cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
 280                      $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
 281                                      System.map $(OBJDUMP) > $@
 282
 283 $(obj)/%.lst: $(src)/%.c FORCE
 284         $(call if_changed_dep,cc_lst_c)
 285
 286 # header test (header-test-y, header-test-m target)
 287 # ---------------------------------------------------------------------------
 288
 289 quiet_cmd_cc_s_h = CC      $@
 290       cmd_cc_s_h = $(CC) $(c_flags) -S -o $@ -x c /dev/null -include $<
 291
 292 $(obj)/%.h.s: $(src)/%.h FORCE
 293         $(call if_changed_dep,cc_s_h)
 294
 295 # Compile assembler sources (.S)
 296 # ---------------------------------------------------------------------------
 297
 298 # .S file exports must have their C prototypes defined in asm/asm-prototypes.h
 299 # or a file that it includes, in order to get versioned symbols. We build a
 300 # dummy C file that includes asm-prototypes and the EXPORT_SYMBOL lines from
 301 # the .S file (with trailing ';'), and run genksyms on that, to extract vers.
 302 #
 303 # This is convoluted. The .S file must first be preprocessed to run guards and
 304 # expand names, then the resulting exports must be constructed into plain
 305 # EXPORT_SYMBOL(symbol); to build our dummy C file, and that gets preprocessed
 306 # to make the genksyms input.
 307 #
 308 # These mirror gensymtypes_c and co above, keep them in synch.
 309 cmd_gensymtypes_S =                                                         \
 310    { echo "\#include <linux/kernel.h>" ;                                    \
 311      echo "\#include <asm/asm-prototypes.h>" ;                              \
 312     $(CPP) $(a_flags) $< |                                                  \
 313      grep "\<___EXPORT_SYMBOL\>" |                                          \
 314      sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ; } | \
 315     $(CPP) -D__GENKSYMS__ $(c_flags) -xc - |                                \
 316     scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
 317      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
 318      $(if $(KBUILD_PRESERVE),-p)                                            \
 319      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 320
 321 quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
 322 cmd_cc_symtypes_S =                                                         \
 323     $(call cmd_gensymtypes_S,true,$@) >/dev/null;                           \
 324     test -s $@ || rm -f $@
 325
 326 $(obj)/%.symtypes : $(src)/%.S FORCE
 327         $(call cmd,cc_symtypes_S)
 328
 329
 330 quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
 331 cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
 332
 333 $(obj)/%.s: $(src)/%.S FORCE
 334         $(call if_changed_dep,cpp_s_S)
 335
 336 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
 337       cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
 338
 339 ifdef CONFIG_ASM_MODVERSIONS
 340
 341 # versioning matches the C process described above, with difference that
 342 # we parse asm-prototypes.h C header to get function definitions.
 343
 344 cmd_modversions_S =                                                             \
 345         if $(OBJDUMP) -h $@ | grep -q __ksymtab; then                           \
 346                 $(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 347                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
 348                                                                                 \
 349                 $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@               \
 350                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
 351                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
 352                 rm -f $(@D)/.tmp_$(@F:.o=.ver);                                 \
 353         fi
 354 endif
 355
 356 $(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
 357         $(call if_changed_rule,as_o_S)
 358
 359 targets += $(filter-out $(subdir-obj-y), $(real-obj-y)) $(real-obj-m) $(lib-y)
 360 targets += $(extra-y) $(MAKECMDGOALS) $(always)
 361
 362 # Linker scripts preprocessor (.lds.S -> .lds)
 363 # ---------------------------------------------------------------------------
 364 quiet_cmd_cpp_lds_S = LDS     $@
 365       cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
 366                              -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
 367
 368 $(obj)/%.lds: $(src)/%.lds.S FORCE
 369         $(call if_changed_dep,cpp_lds_S)
 370
 371 # ASN.1 grammar
 372 # ---------------------------------------------------------------------------
 373 quiet_cmd_asn1_compiler = ASN.1   $(basename $@).[ch]
 374       cmd_asn1_compiler = $(objtree)/scripts/asn1_compiler $< \
 375                                 $(basename $@).c $(basename $@).h
 376
 377 $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
 378         $(call cmd,asn1_compiler)
 379
 380 # Build the compiled-in targets
 381 # ---------------------------------------------------------------------------
 382
 383 # To build objects in subdirs, we need to descend into the directories
 384 $(sort $(subdir-obj-y)): $(subdir-ym) ;
 385
 386 #
 387 # Rule to compile a set of .o files into one .a file (without symbol table)
 388 #
 389 ifdef builtin-target
 390
 391 quiet_cmd_ar_builtin = AR      $@
 392       cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
 393
 394 $(builtin-target): $(real-obj-y) FORCE
 395         $(call if_changed,ar_builtin)
 396
 397 targets += $(builtin-target)
 398 endif # builtin-target
 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 $(modorder-target): $(subdir-ym) FORCE
 406         $(Q){ $(foreach m, $(modorder), \
 407         $(if $(filter %/modules.order, $m), cat $m, echo $m);) :; } \
 408         | $(AWK) '!x[$$0]++' - > $@
 409
 410 #
 411 # Rule to compile a set of .o files into one .a file (with symbol table)
 412 #
 413 ifdef lib-target
 414
 415 $(lib-target): $(lib-y) FORCE
 416         $(call if_changed,ar)
 417
 418 targets += $(lib-target)
 419
 420 dummy-object = $(obj)/.lib_exports.o
 421 ksyms-lds = $(dot-target).lds
 422
 423 quiet_cmd_export_list = EXPORTS $@
 424 cmd_export_list = $(OBJDUMP) -h $< | \
 425         sed -ne '/___ksymtab/s/.*+\([^ ]*\).*/EXTERN(\1)/p' >$(ksyms-lds);\
 426         rm -f $(dummy-object);\
 427         echo | $(CC) $(a_flags) -c -o $(dummy-object) -x assembler -;\
 428         $(LD) $(ld_flags) -r -o $@ -T $(ksyms-lds) $(dummy-object);\
 429         rm $(dummy-object) $(ksyms-lds)
 430
 431 $(obj)/lib-ksyms.o: $(lib-target) FORCE
 432         $(call if_changed,export_list)
 433
 434 targets += $(obj)/lib-ksyms.o
 435
 436 endif
 437
 438 # NOTE:
 439 # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
 440 # module is turned into a multi object module, $^ will contain header file
 441 # dependencies recorded in the .*.cmd file.
 442 quiet_cmd_link_multi-m = LD [M]  $@
 443       cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
 444
 445 $(multi-used-m): FORCE
 446         $(call if_changed,link_multi-m)
 447 $(call multi_depend, $(multi-used-m), .o, -objs -y -m)
 448
 449 targets += $(multi-used-m)
 450 targets := $(filter-out $(PHONY), $(targets))
 451
 452 # Add intermediate targets:
 453 # When building objects with specific suffix patterns, add intermediate
 454 # targets that the final targets are derived from.
 455 intermediate_targets = $(foreach sfx, $(2), \
 456                                 $(patsubst %$(strip $(1)),%$(sfx), \
 457                                         $(filter %$(strip $(1)), $(targets))))
 458 # %.asn1.o <- %.asn1.[ch] <- %.asn1
 459 # %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
 460 # %.lex.o <- %.lex.c <- %.l
 461 # %.tab.o <- %.tab.[ch] <- %.y
 462 targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
 463            $(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
 464            $(call intermediate_targets, .lex.o, .lex.c) \
 465            $(call intermediate_targets, .tab.o, .tab.c .tab.h)
 466
 467 # Build
 468 # ---------------------------------------------------------------------------
 469
 470 ifdef single-build
 471
 472 curdir-single := $(sort $(foreach x, $(KBUILD_SINGLE_TARGETS), \
 473                         $(if $(filter $(x) $(basename $(x)).o, $(targets)), $(x))))
 474
 475 # Handle single targets without any rule: show "Nothing to be done for ..." or
 476 # "No rule to make target ..." depending on whether the target exists.
 477 unknown-single := $(filter-out $(addsuffix /%, $(subdir-ym)), \
 478                         $(filter $(obj)/%, \
 479                                 $(filter-out $(curdir-single), \
 480                                         $(KBUILD_SINGLE_TARGETS))))
 481
 482 __build: $(curdir-single) $(subdir-ym)
 483 ifneq ($(unknown-single),)
 484         $(Q)$(MAKE) -f /dev/null $(unknown-single)
 485 endif
 486         @:
 487
 488 ifeq ($(curdir-single),)
 489 # Nothing to do in this directory. Do not include any .*.cmd file for speed-up
 490 targets :=
 491 else
 492 targets += $(curdir-single)
 493 endif
 494
 495 else
 496
 497 __build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y)) \
 498          $(if $(KBUILD_MODULES),$(obj-m) $(mod-targets) $(modorder-target)) \
 499          $(subdir-ym) $(always)
 500         @:
 501
 502 endif
 503
 504 # Descending
 505 # ---------------------------------------------------------------------------
 506
 507 PHONY += $(subdir-ym)
 508 $(subdir-ym):
 509         $(Q)$(MAKE) $(build)=$@ \
 510         $(if $(filter $@/, $(KBUILD_SINGLE_TARGETS)),single-build=) \
 511         need-builtin=$(if $(filter $@/built-in.a, $(subdir-obj-y)),1) \
 512         need-modorder=$(if $(need-modorder),$(if $(filter $@/modules.order, $(modorder)),1))
 513
 514 # Add FORCE to the prequisites of a target to force it to be always rebuilt.
 515 # ---------------------------------------------------------------------------
 516
 517 PHONY += FORCE
 518
 519 FORCE:
 520
 521 # Read all saved command lines and dependencies for the $(targets) we
 522 # may be building above, using $(if_changed{,_dep}). As an
 523 # optimization, we don't need to read them if the target does not
 524 # exist, we will rebuild anyway in that case.
 525
 526 existing-targets := $(wildcard $(sort $(targets)))
 527
 528 -include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
 529
 530 ifdef building_out_of_srctree
 531 # Create directories for object files if they do not exist
 532 obj-dirs := $(sort $(obj) $(patsubst %/,%, $(dir $(targets))))
 533 # If targets exist, their directories apparently exist. Skip mkdir.
 534 existing-dirs := $(sort $(patsubst %/,%, $(dir $(existing-targets))))
 535 obj-dirs := $(strip $(filter-out $(existing-dirs), $(obj-dirs)))
 536 ifneq ($(obj-dirs),)
 537 $(shell mkdir -p $(obj-dirs))
 538 endif
 539 endif
 540
 541 .PHONY: $(PHONY)