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 $(warning kbuild: Makefile.build is included improperly)
  53 endif
  54
  55 ifeq ($(MAKECMDGOALS)$(need-modorder),)
  56 ifneq ($(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 __build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y)) \
  80          $(if $(KBUILD_MODULES),$(obj-m) $(mod-targets) $(modorder-target)) \
  81          $(subdir-ym) $(always)
  82         @:
  83
  84 # Linus' kernel sanity checking tool
  85 ifeq ($(KBUILD_CHECKSRC),1)
  86   quiet_cmd_checksrc       = CHECK   $<
  87         cmd_checksrc       = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
  88 else ifeq ($(KBUILD_CHECKSRC),2)
  89   quiet_cmd_force_checksrc = CHECK   $<
  90         cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
  91 endif
  92
  93 ifneq ($(KBUILD_ENABLE_EXTRA_GCC_CHECKS),)
  94   cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $<
  95 endif
  96
  97 # Compile C sources (.c)
  98 # ---------------------------------------------------------------------------
  99
 100 # Default is built-in, unless we know otherwise
 101 $(foreach x, i ll lst o s symtypes, $(patsubst %.o,%.$(x),$(real-obj-m))): \
 102         part-of-module := y
 103
 104 modkern_cflags =                                          \
 105         $(if $(part-of-module),                           \
 106                 $(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE), \
 107                 $(KBUILD_CFLAGS_KERNEL) $(CFLAGS_KERNEL))
 108 quiet_modtag = $(if $(part-of-module),[M],   )
 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 targets += $(mod-targets)
 292
 293 quiet_cmd_cc_lst_c = MKLST   $@
 294       cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
 295                      $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
 296                                      System.map $(OBJDUMP) > $@
 297
 298 $(obj)/%.lst: $(src)/%.c FORCE
 299         $(call if_changed_dep,cc_lst_c)
 300
 301 # header test (header-test-y, header-test-m target)
 302 # ---------------------------------------------------------------------------
 303
 304 quiet_cmd_cc_s_h = CC      $@
 305       cmd_cc_s_h = $(CC) $(c_flags) -S -o $@ -x c /dev/null -include $<
 306
 307 $(obj)/%.h.s: $(src)/%.h FORCE
 308         $(call if_changed_dep,cc_s_h)
 309
 310 # Compile assembler sources (.S)
 311 # ---------------------------------------------------------------------------
 312
 313 modkern_aflags := $(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL)
 314
 315 $(real-obj-m)      : modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
 316 $(real-obj-m:.o=.s): modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
 317
 318 # .S file exports must have their C prototypes defined in asm/asm-prototypes.h
 319 # or a file that it includes, in order to get versioned symbols. We build a
 320 # dummy C file that includes asm-prototypes and the EXPORT_SYMBOL lines from
 321 # the .S file (with trailing ';'), and run genksyms on that, to extract vers.
 322 #
 323 # This is convoluted. The .S file must first be preprocessed to run guards and
 324 # expand names, then the resulting exports must be constructed into plain
 325 # EXPORT_SYMBOL(symbol); to build our dummy C file, and that gets preprocessed
 326 # to make the genksyms input.
 327 #
 328 # These mirror gensymtypes_c and co above, keep them in synch.
 329 cmd_gensymtypes_S =                                                         \
 330    { echo "\#include <linux/kernel.h>" ;                                    \
 331      echo "\#include <asm/asm-prototypes.h>" ;                              \
 332     $(CPP) $(a_flags) $< |                                                  \
 333      grep "\<___EXPORT_SYMBOL\>" |                                          \
 334      sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ; } | \
 335     $(CPP) -D__GENKSYMS__ $(c_flags) -xc - |                                \
 336     scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
 337      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
 338      $(if $(KBUILD_PRESERVE),-p)                                            \
 339      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 340
 341 quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
 342 cmd_cc_symtypes_S =                                                         \
 343     $(call cmd_gensymtypes_S,true,$@) >/dev/null;                           \
 344     test -s $@ || rm -f $@
 345
 346 $(obj)/%.symtypes : $(src)/%.S FORCE
 347         $(call cmd,cc_symtypes_S)
 348
 349
 350 quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
 351 cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
 352
 353 $(obj)/%.s: $(src)/%.S FORCE
 354         $(call if_changed_dep,cpp_s_S)
 355
 356 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
 357       cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
 358
 359 ifdef CONFIG_MODVERSIONS
 360
 361 ASM_PROTOTYPES := $(wildcard $(srctree)/arch/$(SRCARCH)/include/asm/asm-prototypes.h)
 362
 363 ifneq ($(ASM_PROTOTYPES),)
 364
 365 # versioning matches the C process described above, with difference that
 366 # we parse asm-prototypes.h C header to get function definitions.
 367
 368 cmd_modversions_S =                                                             \
 369         if $(OBJDUMP) -h $@ | grep -q __ksymtab; then                           \
 370                 $(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 371                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
 372                                                                                 \
 373                 $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@               \
 374                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
 375                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
 376                 rm -f $(@D)/.tmp_$(@F:.o=.ver);                                 \
 377         fi
 378 endif
 379 endif
 380
 381 $(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
 382         $(call if_changed_rule,as_o_S)
 383
 384 targets += $(filter-out $(subdir-obj-y), $(real-obj-y)) $(real-obj-m) $(lib-y)
 385 targets += $(extra-y) $(MAKECMDGOALS) $(always)
 386
 387 # Linker scripts preprocessor (.lds.S -> .lds)
 388 # ---------------------------------------------------------------------------
 389 quiet_cmd_cpp_lds_S = LDS     $@
 390       cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
 391                              -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
 392
 393 $(obj)/%.lds: $(src)/%.lds.S FORCE
 394         $(call if_changed_dep,cpp_lds_S)
 395
 396 # ASN.1 grammar
 397 # ---------------------------------------------------------------------------
 398 quiet_cmd_asn1_compiler = ASN.1   $@
 399       cmd_asn1_compiler = $(objtree)/scripts/asn1_compiler $< \
 400                                 $(subst .h,.c,$@) $(subst .c,.h,$@)
 401
 402 $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
 403         $(call cmd,asn1_compiler)
 404
 405 # Build the compiled-in targets
 406 # ---------------------------------------------------------------------------
 407
 408 # To build objects in subdirs, we need to descend into the directories
 409 $(sort $(subdir-obj-y)): $(subdir-ym) ;
 410
 411 #
 412 # Rule to compile a set of .o files into one .a file (without symbol table)
 413 #
 414 ifdef builtin-target
 415
 416 quiet_cmd_ar_builtin = AR      $@
 417       cmd_ar_builtin = rm -f $@; $(AR) rcSTP$(KBUILD_ARFLAGS) $@ $(real-prereqs)
 418
 419 $(builtin-target): $(real-obj-y) FORCE
 420         $(call if_changed,ar_builtin)
 421
 422 targets += $(builtin-target)
 423 endif # builtin-target
 424
 425 #
 426 # Rule to create modules.order file
 427 #
 428 # Create commands to either record .ko file or cat modules.order from
 429 # a subdirectory
 430 $(modorder-target): $(subdir-ym) FORCE
 431         $(Q){ $(foreach m, $(modorder), \
 432         $(if $(filter %/modules.order, $m), cat $m, echo $m);) :; } \
 433         | $(AWK) '!x[$$0]++' - > $@
 434
 435 #
 436 # Rule to compile a set of .o files into one .a file (with symbol table)
 437 #
 438 ifdef lib-target
 439
 440 $(lib-target): $(lib-y) FORCE
 441         $(call if_changed,ar)
 442
 443 targets += $(lib-target)
 444
 445 dummy-object = $(obj)/.lib_exports.o
 446 ksyms-lds = $(dot-target).lds
 447
 448 quiet_cmd_export_list = EXPORTS $@
 449 cmd_export_list = $(OBJDUMP) -h $< | \
 450         sed -ne '/___ksymtab/s/.*+\([^ ]*\).*/EXTERN(\1)/p' >$(ksyms-lds);\
 451         rm -f $(dummy-object);\
 452         echo | $(CC) $(a_flags) -c -o $(dummy-object) -x assembler -;\
 453         $(LD) $(ld_flags) -r -o $@ -T $(ksyms-lds) $(dummy-object);\
 454         rm $(dummy-object) $(ksyms-lds)
 455
 456 $(obj)/lib-ksyms.o: $(lib-target) FORCE
 457         $(call if_changed,export_list)
 458
 459 targets += $(obj)/lib-ksyms.o
 460
 461 endif
 462
 463 # NOTE:
 464 # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
 465 # module is turned into a multi object module, $^ will contain header file
 466 # dependencies recorded in the .*.cmd file.
 467 quiet_cmd_link_multi-m = LD [M]  $@
 468       cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
 469
 470 $(multi-used-m): FORCE
 471         $(call if_changed,link_multi-m)
 472 $(call multi_depend, $(multi-used-m), .o, -objs -y -m)
 473
 474 targets += $(multi-used-m)
 475 targets := $(filter-out $(PHONY), $(targets))
 476
 477 # Add intermediate targets:
 478 # When building objects with specific suffix patterns, add intermediate
 479 # targets that the final targets are derived from.
 480 intermediate_targets = $(foreach sfx, $(2), \
 481                                 $(patsubst %$(strip $(1)),%$(sfx), \
 482                                         $(filter %$(strip $(1)), $(targets))))
 483 # %.asn1.o <- %.asn1.[ch] <- %.asn1
 484 # %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
 485 # %.lex.o <- %.lex.c <- %.l
 486 # %.tab.o <- %.tab.[ch] <- %.y
 487 targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
 488            $(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
 489            $(call intermediate_targets, .lex.o, .lex.c) \
 490            $(call intermediate_targets, .tab.o, .tab.c .tab.h)
 491
 492 # Descending
 493 # ---------------------------------------------------------------------------
 494
 495 PHONY += $(subdir-ym)
 496 $(subdir-ym):
 497         $(Q)$(MAKE) $(build)=$@ \
 498         need-builtin=$(if $(filter $@/built-in.a, $(subdir-obj-y)),1) \
 499         need-modorder=$(if $(need-modorder),$(if $(filter $@/modules.order, $(modorder)),1))
 500
 501 # Add FORCE to the prequisites of a target to force it to be always rebuilt.
 502 # ---------------------------------------------------------------------------
 503
 504 PHONY += FORCE
 505
 506 FORCE:
 507
 508 # Read all saved command lines and dependencies for the $(targets) we
 509 # may be building above, using $(if_changed{,_dep}). As an
 510 # optimization, we don't need to read them if the target does not
 511 # exist, we will rebuild anyway in that case.
 512
 513 existing-targets := $(wildcard $(sort $(targets)))
 514
 515 -include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
 516
 517 ifdef building_out_of_srctree
 518 # Create directories for object files if they do not exist
 519 obj-dirs := $(sort $(obj) $(patsubst %/,%, $(dir $(targets))))
 520 # If targets exist, their directories apparently exist. Skip mkdir.
 521 existing-dirs := $(sort $(patsubst %/,%, $(dir $(existing-targets))))
 522 obj-dirs := $(strip $(filter-out $(existing-dirs), $(obj-dirs)))
 523 ifneq ($(obj-dirs),)
 524 $(shell mkdir -p $(obj-dirs))
 525 endif
 526 endif
 527
 528 .PHONY: $(PHONY)