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 always-y :=
  20 always-m :=
  21 targets :=
  22 subdir-y :=
  23 subdir-m :=
  24 EXTRA_AFLAGS   :=
  25 EXTRA_CFLAGS   :=
  26 EXTRA_CPPFLAGS :=
  27 EXTRA_LDFLAGS  :=
  28 asflags-y  :=
  29 ccflags-y  :=
  30 cppflags-y :=
  31 ldflags-y  :=
  32
  33 subdir-asflags-y :=
  34 subdir-ccflags-y :=
  35
  36 # Read auto.conf if it exists, otherwise ignore
  37 -include include/config/auto.conf
  38
  39 include scripts/Kbuild.include
  40
  41 # The filename Kbuild has precedence over Makefile
  42 kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
  43 kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
  44 include $(kbuild-file)
  45
  46 include scripts/Makefile.lib
  47
  48 # Do not include hostprogs rules unless needed.
  49 # $(sort ...) is used here to remove duplicated words and excessive spaces.
  50 hostprogs := $(sort $(hostprogs))
  51 ifneq ($(hostprogs),)
  52 include scripts/Makefile.host
  53 endif
  54
  55 # Do not include userprogs rules unless needed.
  56 # $(sort ...) is used here to remove duplicated words and excessive spaces.
  57 userprogs := $(sort $(userprogs))
  58 ifneq ($(userprogs),)
  59 include scripts/Makefile.userprogs
  60 endif
  61
  62 ifndef obj
  63 $(warning kbuild: Makefile.build is included improperly)
  64 endif
  65
  66 ifeq ($(need-modorder),)
  67 ifneq ($(obj-m),)
  68 $(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
  69 $(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
  70 endif
  71 endif
  72
  73 # ===========================================================================
  74
  75 # subdir-builtin and subdir-modorder may contain duplications. Use $(sort ...)
  76 subdir-builtin := $(sort $(filter %/built-in.a, $(real-obj-y)))
  77 subdir-modorder := $(sort $(filter %/modules.order, $(obj-m)))
  78
  79 targets-for-builtin := $(extra-y)
  80
  81 ifneq ($(strip $(lib-y) $(lib-m) $(lib-)),)
  82 targets-for-builtin += $(obj)/lib.a
  83 endif
  84
  85 ifdef need-builtin
  86 targets-for-builtin += $(obj)/built-in.a
  87 endif
  88
  89 targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
  90
  91 ifdef need-modorder
  92 targets-for-modules += $(obj)/modules.order
  93 endif
  94
  95 targets += $(targets-for-builtin) $(targets-for-modules)
  96
  97 # Linus' kernel sanity checking tool
  98 ifeq ($(KBUILD_CHECKSRC),1)
  99   quiet_cmd_checksrc       = CHECK   $<
 100         cmd_checksrc       = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
 101 else ifeq ($(KBUILD_CHECKSRC),2)
 102   quiet_cmd_force_checksrc = CHECK   $<
 103         cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
 104 endif
 105
 106 ifneq ($(KBUILD_EXTRA_WARN),)
 107   cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $<
 108 endif
 109
 110 # Compile C sources (.c)
 111 # ---------------------------------------------------------------------------
 112
 113 quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@
 114       cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS) $(CC_FLAGS_LTO), $(c_flags)) -fverbose-asm -S -o $@ $<
 115
 116 $(obj)/%.s: $(src)/%.c FORCE
 117         $(call if_changed_dep,cc_s_c)
 118
 119 quiet_cmd_cpp_i_c = CPP $(quiet_modtag) $@
 120 cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
 121
 122 $(obj)/%.i: $(src)/%.c FORCE
 123         $(call if_changed_dep,cpp_i_c)
 124
 125 # These mirror gensymtypes_S and co below, keep them in synch.
 126 cmd_gensymtypes_c =                                                         \
 127     $(CPP) -D__GENKSYMS__ $(c_flags) $< |                                   \
 128     scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
 129      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
 130      $(if $(KBUILD_PRESERVE),-p)                                            \
 131      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 132
 133 quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
 134 cmd_cc_symtypes_c =                                                         \
 135     $(call cmd_gensymtypes_c,true,$@) >/dev/null;                           \
 136     test -s $@ || rm -f $@
 137
 138 $(obj)/%.symtypes : $(src)/%.c FORCE
 139         $(call cmd,cc_symtypes_c)
 140
 141 # LLVM assembly
 142 # Generate .ll files from .c
 143 quiet_cmd_cc_ll_c = CC $(quiet_modtag)  $@
 144       cmd_cc_ll_c = $(CC) $(c_flags) -emit-llvm -S -o $@ $<
 145
 146 $(obj)/%.ll: $(src)/%.c FORCE
 147         $(call if_changed_dep,cc_ll_c)
 148
 149 # C (.c) files
 150 # The C file is compiled and updated dependency information is generated.
 151 # (See cmd_cc_o_c + relevant part of rule_cc_o_c)
 152
 153 quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
 154       cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
 155
 156 ifdef CONFIG_MODVERSIONS
 157 # When module versioning is enabled the following steps are executed:
 158 # o compile a <file>.o from <file>.c
 159 # o if <file>.o doesn't contain a __ksymtab version, i.e. does
 160 #   not export symbols, it's done.
 161 # o otherwise, we calculate symbol versions using the good old
 162 #   genksyms on the preprocessed source and postprocess them in a way
 163 #   that they are usable as a linker script
 164 # o generate .tmp_<file>.o from <file>.o using the linker to
 165 #   replace the unresolved symbols __crc_exported_symbol with
 166 #   the actual value of the checksum generated by genksyms
 167 # o remove .tmp_<file>.o to <file>.o
 168
 169 ifdef CONFIG_LTO_CLANG
 170 # Generate .o.symversions files for each .o with exported symbols, and link these
 171 # to the kernel and/or modules at the end.
 172 cmd_modversions_c =                                                             \
 173         if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then                       \
 174                 $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 175                     > $@.symversions;                                           \
 176         fi;
 177 else
 178 cmd_modversions_c =                                                             \
 179         if $(OBJDUMP) -h $@ | grep -q __ksymtab; then                           \
 180                 $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
 181                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
 182                                                                                 \
 183                 $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@               \
 184                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
 185                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
 186                 rm -f $(@D)/.tmp_$(@F:.o=.ver);                                 \
 187         fi
 188 endif
 189 endif
 190
 191 ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
 192 # compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
 193 ifdef BUILD_C_RECORDMCOUNT
 194 ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
 195   RECORDMCOUNT_FLAGS = -w
 196 endif
 197 # Due to recursion, we must skip empty.o.
 198 # The empty.o file is created in the make process in order to determine
 199 # the target endianness and word size. It is made before all other C
 200 # files, including recordmcount.
 201 sub_cmd_record_mcount =                                 \
 202         if [ $(@) != "scripts/mod/empty.o" ]; then      \
 203                 $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)";   \
 204         fi;
 205 recordmcount_source := $(srctree)/scripts/recordmcount.c \
 206                     $(srctree)/scripts/recordmcount.h
 207 else
 208 sub_cmd_record_mcount = perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
 209         "$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \
 210         "$(if $(CONFIG_64BIT),64,32)" \
 211         "$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS)" \
 212         "$(LD) $(KBUILD_LDFLAGS)" "$(NM)" "$(RM)" "$(MV)" \
 213         "$(if $(part-of-module),1,0)" "$(@)";
 214 recordmcount_source := $(srctree)/scripts/recordmcount.pl
 215 endif # BUILD_C_RECORDMCOUNT
 216 cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)), \
 217         $(sub_cmd_record_mcount))
 218 endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
 219
 220 ifdef CONFIG_STACK_VALIDATION
 221 ifneq ($(SKIP_STACK_VALIDATION),1)
 222
 223 __objtool_obj := $(objtree)/tools/objtool/objtool
 224
 225 objtool_args = $(if $(CONFIG_UNWINDER_ORC),orc generate,check)
 226
 227 objtool_args += $(if $(part-of-module), --module,)
 228
 229 ifndef CONFIG_FRAME_POINTER
 230 objtool_args += --no-fp
 231 endif
 232 ifdef CONFIG_GCOV_KERNEL
 233 objtool_args += --no-unreachable
 234 endif
 235 ifdef CONFIG_RETPOLINE
 236   objtool_args += --retpoline
 237 endif
 238 ifdef CONFIG_X86_SMAP
 239   objtool_args += --uaccess
 240 endif
 241
 242 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
 243 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
 244 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
 245 cmd_objtool = $(if $(patsubst y%,, \
 246         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 247         $(__objtool_obj) $(objtool_args) $@)
 248 objtool_obj = $(if $(patsubst y%,, \
 249         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 250         $(__objtool_obj))
 251
 252 endif # SKIP_STACK_VALIDATION
 253 endif # CONFIG_STACK_VALIDATION
 254
 255 # Rebuild all objects when objtool changes, or is enabled/disabled.
 256 objtool_dep = $(objtool_obj)                                    \
 257               $(wildcard include/config/orc/unwinder.h          \
 258                          include/config/stack/validation.h)
 259
 260 ifdef CONFIG_TRIM_UNUSED_KSYMS
 261 cmd_gen_ksymdeps = \
 262         $(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd
 263
 264 # List module undefined symbols
 265 undefined_syms = $(NM) $< | $(AWK) '$$1 == "U" { printf("%s%s", x++ ? " " : "", $$2) }';
 266 endif
 267
 268 define rule_cc_o_c
 269         $(call cmd_and_fixdep,cc_o_c)
 270         $(call cmd,gen_ksymdeps)
 271         $(call cmd,checksrc)
 272         $(call cmd,checkdoc)
 273         $(call cmd,objtool)
 274         $(call cmd,modversions_c)
 275         $(call cmd,record_mcount)
 276 endef
 277
 278 define rule_as_o_S
 279         $(call cmd_and_fixdep,as_o_S)
 280         $(call cmd,gen_ksymdeps)
 281         $(call cmd,objtool)
 282         $(call cmd,modversions_S)
 283 endef
 284
 285 # Built-in and composite module parts
 286 $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
 287         $(call if_changed_rule,cc_o_c)
 288         $(call cmd,force_checksrc)
 289
 290 cmd_mod = { \
 291         echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \
 292         $(undefined_syms) echo; \
 293         } > $@
 294
 295 $(obj)/%.mod: $(obj)/%.o FORCE
 296         $(call if_changed,mod)
 297
 298 quiet_cmd_cc_lst_c = MKLST   $@
 299       cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
 300                      $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
 301                                      System.map $(OBJDUMP) > $@
 302
 303 $(obj)/%.lst: $(src)/%.c FORCE
 304         $(call if_changed_dep,cc_lst_c)
 305
 306 # Compile assembler sources (.S)
 307 # ---------------------------------------------------------------------------
 308
 309 # .S file exports must have their C prototypes defined in asm/asm-prototypes.h
 310 # or a file that it includes, in order to get versioned symbols. We build a
 311 # dummy C file that includes asm-prototypes and the EXPORT_SYMBOL lines from
 312 # the .S file (with trailing ';'), and run genksyms on that, to extract vers.
 313 #
 314 # This is convoluted. The .S file must first be preprocessed to run guards and
 315 # expand names, then the resulting exports must be constructed into plain
 316 # EXPORT_SYMBOL(symbol); to build our dummy C file, and that gets preprocessed
 317 # to make the genksyms input.
 318 #
 319 # These mirror gensymtypes_c and co above, keep them in synch.
 320 cmd_gensymtypes_S =                                                         \
 321    { echo "\#include <linux/kernel.h>" ;                                    \
 322      echo "\#include <asm/asm-prototypes.h>" ;                              \
 323     $(CPP) $(a_flags) $< |                                                  \
 324      grep "\<___EXPORT_SYMBOL\>" |                                          \
 325      sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ; } | \
 326     $(CPP) -D__GENKSYMS__ $(c_flags) -xc - |                                \
 327     scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
 328      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
 329      $(if $(KBUILD_PRESERVE),-p)                                            \
 330      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 331
 332 quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
 333 cmd_cc_symtypes_S =                                                         \
 334     $(call cmd_gensymtypes_S,true,$@) >/dev/null;                           \
 335     test -s $@ || rm -f $@
 336
 337 $(obj)/%.symtypes : $(src)/%.S FORCE
 338         $(call cmd,cc_symtypes_S)
 339
 340
 341 quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
 342 cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
 343
 344 $(obj)/%.s: $(src)/%.S FORCE
 345         $(call if_changed_dep,cpp_s_S)
 346
 347 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
 348       cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
 349
 350 ifdef CONFIG_ASM_MODVERSIONS
 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
 367 $(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
 368         $(call if_changed_rule,as_o_S)
 369
 370 targets += $(filter-out $(subdir-builtin), $(real-obj-y))
 371 targets += $(filter-out $(subdir-modorder), $(real-obj-m))
 372 targets += $(lib-y) $(always-y) $(MAKECMDGOALS)
 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   $(basename $@).[ch]
 386       cmd_asn1_compiler = $(objtree)/scripts/asn1_compiler $< \
 387                                 $(basename $@).c $(basename $@).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 $(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ;
 397 $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
 398
 399 # combine symversions for later processing
 400 quiet_cmd_update_lto_symversions = SYMVER  $@
 401 ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
 402       cmd_update_lto_symversions =                                      \
 403         rm -f $@.symversions                                            \
 404         $(foreach n, $(filter-out FORCE,$^),                            \
 405                 $(if $(wildcard $(n).symversions),                      \
 406                         ; cat $(n).symversions >> $@.symversions))
 407 else
 408       cmd_update_lto_symversions = echo >/dev/null
 409 endif
 410
 411 #
 412 # Rule to compile a set of .o files into one .a file (without symbol table)
 413 #
 414
 415 quiet_cmd_ar_builtin = AR      $@
 416       cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
 417
 418 quiet_cmd_ar_and_symver = AR      $@
 419       cmd_ar_and_symver = $(cmd_update_lto_symversions); $(cmd_ar_builtin)
 420
 421 $(obj)/built-in.a: $(real-obj-y) FORCE
 422         $(call if_changed,ar_and_symver)
 423
 424 #
 425 # Rule to create modules.order file
 426 #
 427 # Create commands to either record .ko file or cat modules.order from
 428 # a subdirectory
 429 # Add $(obj-m) as the prerequisite to avoid updating the timestamp of
 430 # modules.order unless contained modules are updated.
 431
 432 cmd_modules_order = { $(foreach m, $(real-prereqs), \
 433         $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.o,%.ko,$m));) :; } \
 434         | $(AWK) '!x[$$0]++' - > $@
 435
 436 $(obj)/modules.order: $(obj-m) FORCE
 437         $(call if_changed,modules_order)
 438
 439 #
 440 # Rule to compile a set of .o files into one .a file (with symbol table)
 441 #
 442 quiet_cmd_ar_lib = AR      $@
 443       cmd_ar_lib = $(cmd_update_lto_symversions); $(cmd_ar)
 444
 445 $(obj)/lib.a: $(lib-y) FORCE
 446         $(call if_changed,ar_lib)
 447
 448 # NOTE:
 449 # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
 450 # module is turned into a multi object module, $^ will contain header file
 451 # dependencies recorded in the .*.cmd file.
 452 ifdef CONFIG_LTO_CLANG
 453 quiet_cmd_link_multi-m = AR [M]  $@
 454 cmd_link_multi-m =                                              \
 455         $(cmd_update_lto_symversions);                          \
 456         rm -f $@;                                               \
 457         $(AR) cDPrsT $@ $(filter %.o,$^)
 458 else
 459 quiet_cmd_link_multi-m = LD [M]  $@
 460       cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
 461 endif
 462
 463 $(multi-used-m): FORCE
 464         $(call if_changed,link_multi-m)
 465 $(call multi_depend, $(multi-used-m), .o, -objs -y -m)
 466
 467 targets += $(multi-used-m)
 468 targets := $(filter-out $(PHONY), $(targets))
 469
 470 # Add intermediate targets:
 471 # When building objects with specific suffix patterns, add intermediate
 472 # targets that the final targets are derived from.
 473 intermediate_targets = $(foreach sfx, $(2), \
 474                                 $(patsubst %$(strip $(1)),%$(sfx), \
 475                                         $(filter %$(strip $(1)), $(targets))))
 476 # %.asn1.o <- %.asn1.[ch] <- %.asn1
 477 # %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
 478 # %.lex.o <- %.lex.c <- %.l
 479 # %.tab.o <- %.tab.[ch] <- %.y
 480 targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
 481            $(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
 482            $(call intermediate_targets, .lex.o, .lex.c) \
 483            $(call intermediate_targets, .tab.o, .tab.c .tab.h)
 484
 485 # Build
 486 # ---------------------------------------------------------------------------
 487
 488 ifdef single-build
 489
 490 KBUILD_SINGLE_TARGETS := $(filter $(obj)/%, $(KBUILD_SINGLE_TARGETS))
 491
 492 curdir-single := $(sort $(foreach x, $(KBUILD_SINGLE_TARGETS), \
 493                         $(if $(filter $(x) $(basename $(x)).o, $(targets)), $(x))))
 494
 495 # Handle single targets without any rule: show "Nothing to be done for ..." or
 496 # "No rule to make target ..." depending on whether the target exists.
 497 unknown-single := $(filter-out $(addsuffix /%, $(subdir-ym)), \
 498                         $(filter-out $(curdir-single), $(KBUILD_SINGLE_TARGETS)))
 499
 500 single-subdirs := $(foreach d, $(subdir-ym), \
 501                         $(if $(filter $(d)/%, $(KBUILD_SINGLE_TARGETS)), $(d)))
 502
 503 __build: $(curdir-single) $(single-subdirs)
 504 ifneq ($(unknown-single),)
 505         $(Q)$(MAKE) -f /dev/null $(unknown-single)
 506 endif
 507         @:
 508
 509 ifeq ($(curdir-single),)
 510 # Nothing to do in this directory. Do not include any .*.cmd file for speed-up
 511 targets :=
 512 else
 513 targets += $(curdir-single)
 514 endif
 515
 516 else
 517
 518 __build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
 519          $(if $(KBUILD_MODULES), $(targets-for-modules)) \
 520          $(subdir-ym) $(always-y)
 521         @:
 522
 523 endif
 524
 525 # Descending
 526 # ---------------------------------------------------------------------------
 527
 528 PHONY += $(subdir-ym)
 529 $(subdir-ym):
 530         $(Q)$(MAKE) $(build)=$@ \
 531         $(if $(filter $@/, $(KBUILD_SINGLE_TARGETS)),single-build=) \
 532         need-builtin=$(if $(filter $@/built-in.a, $(subdir-builtin)),1) \
 533         need-modorder=$(if $(filter $@/modules.order, $(subdir-modorder)),1)
 534
 535 # Add FORCE to the prequisites of a target to force it to be always rebuilt.
 536 # ---------------------------------------------------------------------------
 537
 538 PHONY += FORCE
 539
 540 FORCE:
 541
 542 # Read all saved command lines and dependencies for the $(targets) we
 543 # may be building above, using $(if_changed{,_dep}). As an
 544 # optimization, we don't need to read them if the target does not
 545 # exist, we will rebuild anyway in that case.
 546
 547 existing-targets := $(wildcard $(sort $(targets)))
 548
 549 -include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
 550
 551 # Create directories for object files if they do not exist
 552 obj-dirs := $(sort $(patsubst %/,%, $(dir $(targets))))
 553 # If targets exist, their directories apparently exist. Skip mkdir.
 554 existing-dirs := $(sort $(patsubst %/,%, $(dir $(existing-targets))))
 555 obj-dirs := $(strip $(filter-out $(existing-dirs), $(obj-dirs)))
 556 ifneq ($(obj-dirs),)
 557 $(shell mkdir -p $(obj-dirs))
 558 endif
 559
 560 .PHONY: $(PHONY)