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