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