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) $(CC_FLAGS_LTO), $(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 ifdef CONFIG_LTO_CLANG
 169 # Generate .o.symversions files for each .o with exported symbols, and link these
 170 # to the kernel and/or modules at the end.
 171 cmd_modversions_c =                                                             \
 172         if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then                       \
 173                 $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 174                     > $@.symversions;                                           \
 175         fi;
 176 else
 177 cmd_modversions_c =                                                             \
 178         if $(OBJDUMP) -h $@ | grep -q __ksymtab; then                           \
 179                 $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 180                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
 181                                                                                 \
 182                 $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@               \
 183                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
 184                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
 185                 rm -f $(@D)/.tmp_$(@F:.o=.ver);                                 \
 186         fi
 187 endif
 188 endif
 189
 190 ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
 191 # compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
 192 ifdef BUILD_C_RECORDMCOUNT
 193 ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
 194   RECORDMCOUNT_FLAGS = -w
 195 endif
 196 # Due to recursion, we must skip empty.o.
 197 # The empty.o file is created in the make process in order to determine
 198 # the target endianness and word size. It is made before all other C
 199 # files, including recordmcount.
 200 sub_cmd_record_mcount =                                 \
 201         if [ $(@) != "scripts/mod/empty.o" ]; then      \
 202                 $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)";   \
 203         fi;
 204 recordmcount_source := $(srctree)/scripts/recordmcount.c \
 205                     $(srctree)/scripts/recordmcount.h
 206 else
 207 sub_cmd_record_mcount = perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
 208         "$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \
 209         "$(if $(CONFIG_64BIT),64,32)" \
 210         "$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS)" \
 211         "$(LD) $(KBUILD_LDFLAGS)" "$(NM)" "$(RM)" "$(MV)" \
 212         "$(if $(part-of-module),1,0)" "$(@)";
 213 recordmcount_source := $(srctree)/scripts/recordmcount.pl
 214 endif # BUILD_C_RECORDMCOUNT
 215 cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)), \
 216         $(sub_cmd_record_mcount))
 217 endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
 218
 219 ifdef CONFIG_STACK_VALIDATION
 220 ifndef CONFIG_LTO_CLANG
 221 ifneq ($(SKIP_STACK_VALIDATION),1)
 222
 223 __objtool_obj := $(objtree)/tools/objtool/objtool
 224
 225 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
 226 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
 227 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
 228 cmd_objtool = $(if $(patsubst y%,, \
 229         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 230         $(__objtool_obj) $(objtool_args) $@)
 231 objtool_obj = $(if $(patsubst y%,, \
 232         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 233         $(__objtool_obj))
 234
 235 endif # SKIP_STACK_VALIDATION
 236 endif # CONFIG_LTO_CLANG
 237 endif # CONFIG_STACK_VALIDATION
 238
 239 # Rebuild all objects when objtool changes, or is enabled/disabled.
 240 objtool_dep = $(objtool_obj)                                    \
 241               $(wildcard include/config/orc/unwinder.h          \
 242                          include/config/stack/validation.h)
 243
 244 ifdef CONFIG_TRIM_UNUSED_KSYMS
 245 cmd_gen_ksymdeps = \
 246         $(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd
 247
 248 # List module undefined symbols
 249 undefined_syms = $(NM) $< | $(AWK) '$$1 == "U" { printf("%s%s", x++ ? " " : "", $$2) }';
 250 endif
 251
 252 define rule_cc_o_c
 253         $(call cmd_and_fixdep,cc_o_c)
 254         $(call cmd,gen_ksymdeps)
 255         $(call cmd,checksrc)
 256         $(call cmd,checkdoc)
 257         $(call cmd,objtool)
 258         $(call cmd,modversions_c)
 259         $(call cmd,record_mcount)
 260 endef
 261
 262 define rule_as_o_S
 263         $(call cmd_and_fixdep,as_o_S)
 264         $(call cmd,gen_ksymdeps)
 265         $(call cmd,objtool)
 266         $(call cmd,modversions_S)
 267 endef
 268
 269 # Built-in and composite module parts
 270 $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
 271         $(call if_changed_rule,cc_o_c)
 272         $(call cmd,force_checksrc)
 273
 274 cmd_mod = { \
 275         echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \
 276         $(undefined_syms) echo; \
 277         } > $@
 278
 279 $(obj)/%.mod: $(obj)/%.o FORCE
 280         $(call if_changed,mod)
 281
 282 quiet_cmd_cc_lst_c = MKLST   $@
 283       cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
 284                      $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
 285                                      System.map $(OBJDUMP) > $@
 286
 287 $(obj)/%.lst: $(src)/%.c FORCE
 288         $(call if_changed_dep,cc_lst_c)
 289
 290 # Compile assembler sources (.S)
 291 # ---------------------------------------------------------------------------
 292
 293 # .S file exports must have their C prototypes defined in asm/asm-prototypes.h
 294 # or a file that it includes, in order to get versioned symbols. We build a
 295 # dummy C file that includes asm-prototypes and the EXPORT_SYMBOL lines from
 296 # the .S file (with trailing ';'), and run genksyms on that, to extract vers.
 297 #
 298 # This is convoluted. The .S file must first be preprocessed to run guards and
 299 # expand names, then the resulting exports must be constructed into plain
 300 # EXPORT_SYMBOL(symbol); to build our dummy C file, and that gets preprocessed
 301 # to make the genksyms input.
 302 #
 303 # These mirror gensymtypes_c and co above, keep them in synch.
 304 cmd_gensymtypes_S =                                                         \
 305    { echo "\#include <linux/kernel.h>" ;                                    \
 306      echo "\#include <asm/asm-prototypes.h>" ;                              \
 307     $(CPP) $(a_flags) $< |                                                  \
 308      grep "\<___EXPORT_SYMBOL\>" |                                          \
 309      sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ; } | \
 310     $(CPP) -D__GENKSYMS__ $(c_flags) -xc - |                                \
 311     scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
 312      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
 313      $(if $(KBUILD_PRESERVE),-p)                                            \
 314      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 315
 316 quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
 317 cmd_cc_symtypes_S =                                                         \
 318     $(call cmd_gensymtypes_S,true,$@) >/dev/null;                           \
 319     test -s $@ || rm -f $@
 320
 321 $(obj)/%.symtypes : $(src)/%.S FORCE
 322         $(call cmd,cc_symtypes_S)
 323
 324
 325 quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
 326 cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
 327
 328 $(obj)/%.s: $(src)/%.S FORCE
 329         $(call if_changed_dep,cpp_s_S)
 330
 331 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
 332       cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
 333
 334 ifdef CONFIG_ASM_MODVERSIONS
 335
 336 # versioning matches the C process described above, with difference that
 337 # we parse asm-prototypes.h C header to get function definitions.
 338
 339 cmd_modversions_S =                                                             \
 340         if $(OBJDUMP) -h $@ | grep -q __ksymtab; then                           \
 341                 $(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 342                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
 343                                                                                 \
 344                 $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@               \
 345                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
 346                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
 347                 rm -f $(@D)/.tmp_$(@F:.o=.ver);                                 \
 348         fi
 349 endif
 350
 351 $(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
 352         $(call if_changed_rule,as_o_S)
 353
 354 targets += $(filter-out $(subdir-builtin), $(real-obj-y))
 355 targets += $(filter-out $(subdir-modorder), $(real-obj-m))
 356 targets += $(lib-y) $(always-y) $(MAKECMDGOALS)
 357
 358 # Linker scripts preprocessor (.lds.S -> .lds)
 359 # ---------------------------------------------------------------------------
 360 quiet_cmd_cpp_lds_S = LDS     $@
 361       cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
 362                              -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
 363
 364 $(obj)/%.lds: $(src)/%.lds.S FORCE
 365         $(call if_changed_dep,cpp_lds_S)
 366
 367 # ASN.1 grammar
 368 # ---------------------------------------------------------------------------
 369 quiet_cmd_asn1_compiler = ASN.1   $(basename $@).[ch]
 370       cmd_asn1_compiler = $(objtree)/scripts/asn1_compiler $< \
 371                                 $(basename $@).c $(basename $@).h
 372
 373 $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
 374         $(call cmd,asn1_compiler)
 375
 376 # Build the compiled-in targets
 377 # ---------------------------------------------------------------------------
 378
 379 # To build objects in subdirs, we need to descend into the directories
 380 $(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ;
 381 $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
 382
 383 # combine symversions for later processing
 384 quiet_cmd_update_lto_symversions = SYMVER  $@
 385 ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
 386       cmd_update_lto_symversions =                                      \
 387         rm -f $@.symversions                                            \
 388         $(foreach n, $(filter-out FORCE,$^),                            \
 389                 $(if $(wildcard $(n).symversions),                      \
 390                         ; cat $(n).symversions >> $@.symversions))
 391 else
 392       cmd_update_lto_symversions = echo >/dev/null
 393 endif
 394
 395 #
 396 # Rule to compile a set of .o files into one .a file (without symbol table)
 397 #
 398
 399 quiet_cmd_ar_builtin = AR      $@
 400       cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
 401
 402 quiet_cmd_ar_and_symver = AR      $@
 403       cmd_ar_and_symver = $(cmd_update_lto_symversions); $(cmd_ar_builtin)
 404
 405 $(obj)/built-in.a: $(real-obj-y) FORCE
 406         $(call if_changed,ar_and_symver)
 407
 408 #
 409 # Rule to create modules.order file
 410 #
 411 # Create commands to either record .ko file or cat modules.order from
 412 # a subdirectory
 413 # Add $(obj-m) as the prerequisite to avoid updating the timestamp of
 414 # modules.order unless contained modules are updated.
 415
 416 cmd_modules_order = { $(foreach m, $(real-prereqs), \
 417         $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.o,%.ko,$m));) :; } \
 418         | $(AWK) '!x[$$0]++' - > $@
 419
 420 $(obj)/modules.order: $(obj-m) FORCE
 421         $(call if_changed,modules_order)
 422
 423 #
 424 # Rule to compile a set of .o files into one .a file (with symbol table)
 425 #
 426 quiet_cmd_ar_lib = AR      $@
 427       cmd_ar_lib = $(cmd_update_lto_symversions); $(cmd_ar)
 428
 429 $(obj)/lib.a: $(lib-y) FORCE
 430         $(call if_changed,ar_lib)
 431
 432 # NOTE:
 433 # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
 434 # module is turned into a multi object module, $^ will contain header file
 435 # dependencies recorded in the .*.cmd file.
 436 ifdef CONFIG_LTO_CLANG
 437 quiet_cmd_link_multi-m = AR [M]  $@
 438 cmd_link_multi-m =                                              \
 439         $(cmd_update_lto_symversions);                          \
 440         rm -f $@;                                               \
 441         $(AR) cDPrsT $@ $(filter %.o,$^)
 442 else
 443 quiet_cmd_link_multi-m = LD [M]  $@
 444       cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
 445 endif
 446
 447 $(multi-used-m): FORCE
 448         $(call if_changed,link_multi-m)
 449 $(call multi_depend, $(multi-used-m), .o, -objs -y -m)
 450
 451 targets += $(multi-used-m)
 452 targets := $(filter-out $(PHONY), $(targets))
 453
 454 # Add intermediate targets:
 455 # When building objects with specific suffix patterns, add intermediate
 456 # targets that the final targets are derived from.
 457 intermediate_targets = $(foreach sfx, $(2), \
 458                                 $(patsubst %$(strip $(1)),%$(sfx), \
 459                                         $(filter %$(strip $(1)), $(targets))))
 460 # %.asn1.o <- %.asn1.[ch] <- %.asn1
 461 # %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
 462 # %.lex.o <- %.lex.c <- %.l
 463 # %.tab.o <- %.tab.[ch] <- %.y
 464 targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
 465            $(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
 466            $(call intermediate_targets, .lex.o, .lex.c) \
 467            $(call intermediate_targets, .tab.o, .tab.c .tab.h)
 468
 469 # Build
 470 # ---------------------------------------------------------------------------
 471
 472 ifdef single-build
 473
 474 KBUILD_SINGLE_TARGETS := $(filter $(obj)/%, $(KBUILD_SINGLE_TARGETS))
 475
 476 curdir-single := $(sort $(foreach x, $(KBUILD_SINGLE_TARGETS), \
 477                         $(if $(filter $(x) $(basename $(x)).o, $(targets)), $(x))))
 478
 479 # Handle single targets without any rule: show "Nothing to be done for ..." or
 480 # "No rule to make target ..." depending on whether the target exists.
 481 unknown-single := $(filter-out $(addsuffix /%, $(subdir-ym)), \
 482                         $(filter-out $(curdir-single), $(KBUILD_SINGLE_TARGETS)))
 483
 484 single-subdirs := $(foreach d, $(subdir-ym), \
 485                         $(if $(filter $(d)/%, $(KBUILD_SINGLE_TARGETS)), $(d)))
 486
 487 __build: $(curdir-single) $(single-subdirs)
 488 ifneq ($(unknown-single),)
 489         $(Q)$(MAKE) -f /dev/null $(unknown-single)
 490 endif
 491         @:
 492
 493 ifeq ($(curdir-single),)
 494 # Nothing to do in this directory. Do not include any .*.cmd file for speed-up
 495 targets :=
 496 else
 497 targets += $(curdir-single)
 498 endif
 499
 500 else
 501
 502 __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
 503          $(if $(KBUILD_MODULES), $(targets-for-modules)) \
 504          $(subdir-ym) $(always-y)
 505         @:
 506
 507 endif
 508
 509 # Descending
 510 # ---------------------------------------------------------------------------
 511
 512 PHONY += $(subdir-ym)
 513 $(subdir-ym):
 514         $(Q)$(MAKE) $(build)=$@ \
 515         $(if $(filter $@/, $(KBUILD_SINGLE_TARGETS)),single-build=) \
 516         need-builtin=$(if $(filter $@/built-in.a, $(subdir-builtin)),1) \
 517         need-modorder=$(if $(filter $@/modules.order, $(subdir-modorder)),1)
 518
 519 # Add FORCE to the prequisites of a target to force it to be always rebuilt.
 520 # ---------------------------------------------------------------------------
 521
 522 PHONY += FORCE
 523
 524 FORCE:
 525
 526 # Read all saved command lines and dependencies for the $(targets) we
 527 # may be building above, using $(if_changed{,_dep}). As an
 528 # optimization, we don't need to read them if the target does not
 529 # exist, we will rebuild anyway in that case.
 530
 531 existing-targets := $(wildcard $(sort $(targets)))
 532
 533 -include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
 534
 535 # Create directories for object files if they do not exist
 536 obj-dirs := $(sort $(patsubst %/,%, $(dir $(targets))))
 537 # If targets exist, their directories apparently exist. Skip mkdir.
 538 existing-dirs := $(sort $(patsubst %/,%, $(dir $(existing-targets))))
 539 obj-dirs := $(strip $(filter-out $(existing-dirs), $(obj-dirs)))
 540 ifneq ($(obj-dirs),)
 541 $(shell mkdir -p $(obj-dirs))
 542 endif
 543
 544 .PHONY: $(PHONY)