linux/scripts/Makefile.build
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   1# SPDX-License-Identifier: GPL-2.0
   2# ==========================================================================
   3# Building
   4# ==========================================================================
   5
   6src := $(obj)
   7
   8PHONY := __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
  14obj-y :=
  15obj-m :=
  16lib-y :=
  17lib-m :=
  18always :=
  19targets :=
  20subdir-y :=
  21subdir-m :=
  22EXTRA_AFLAGS   :=
  23EXTRA_CFLAGS   :=
  24EXTRA_CPPFLAGS :=
  25EXTRA_LDFLAGS  :=
  26asflags-y  :=
  27ccflags-y  :=
  28cppflags-y :=
  29ldflags-y  :=
  30
  31subdir-asflags-y :=
  32subdir-ccflags-y :=
  33
  34# Read auto.conf if it exists, otherwise ignore
  35-include include/config/auto.conf
  36
  37include scripts/Kbuild.include
  38
  39# The filename Kbuild has precedence over Makefile
  40kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
  41kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
  42include $(kbuild-file)
  43
  44include scripts/Makefile.lib
  45
  46# Do not include host rules unless needed
  47ifneq ($(hostprogs-y)$(hostprogs-m)$(hostlibs-y)$(hostlibs-m)$(hostcxxlibs-y)$(hostcxxlibs-m),)
  48include scripts/Makefile.host
  49endif
  50
  51ifndef obj
  52$(warning kbuild: Makefile.build is included improperly)
  53endif
  54
  55ifeq ($(MAKECMDGOALS)$(need-modorder),)
  56ifneq ($(obj-m),)
  57$(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
  58$(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
  59endif
  60endif
  61
  62# ===========================================================================
  63
  64ifneq ($(strip $(lib-y) $(lib-m) $(lib-)),)
  65lib-target := $(obj)/lib.a
  66real-obj-y += $(obj)/lib-ksyms.o
  67endif
  68
  69ifneq ($(strip $(real-obj-y) $(need-builtin)),)
  70builtin-target := $(obj)/built-in.a
  71endif
  72
  73ifeq ($(CONFIG_MODULES)$(need-modorder),y1)
  74modorder-target := $(obj)/modules.order
  75endif
  76
  77mod-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) $(always)
  82        @:
  83
  84# Linus' kernel sanity checking tool
  85ifeq ($(KBUILD_CHECKSRC),1)
  86  quiet_cmd_checksrc       = CHECK   $<
  87        cmd_checksrc       = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
  88else ifeq ($(KBUILD_CHECKSRC),2)
  89  quiet_cmd_force_checksrc = CHECK   $<
  90        cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
  91endif
  92
  93ifneq ($(KBUILD_ENABLE_EXTRA_GCC_CHECKS),)
  94  cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $<
  95endif
  96
  97# Compile C sources (.c)
  98# ---------------------------------------------------------------------------
  99
 100# Default is built-in, unless we know otherwise
 101$(foreach x, i ll lst o s symtypes, $(patsubst %.o,%.$(x),$(real-obj-m))): \
 102        part-of-module := y
 103
 104modkern_cflags =                                          \
 105        $(if $(part-of-module),                           \
 106                $(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE), \
 107                $(KBUILD_CFLAGS_KERNEL) $(CFLAGS_KERNEL))
 108quiet_modtag = $(if $(part-of-module),[M],   )
 109
 110quiet_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
 116quiet_cmd_cpp_i_c = CPP $(quiet_modtag) $@
 117cmd_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.
 123cmd_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
 130quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
 131cmd_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
 140quiet_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
 150quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
 151      cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
 152
 153ifdef 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
 166cmd_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
 176endif
 177
 178ifdef CONFIG_FTRACE_MCOUNT_RECORD
 179ifndef CC_USING_RECORD_MCOUNT
 180# compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
 181ifdef BUILD_C_RECORDMCOUNT
 182ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
 183  RECORDMCOUNT_FLAGS = -w
 184endif
 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.
 189sub_cmd_record_mcount =                                 \
 190        if [ $(@) != "scripts/mod/empty.o" ]; then      \
 191                $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)";   \
 192        fi;
 193recordmcount_source := $(srctree)/scripts/recordmcount.c \
 194                    $(srctree)/scripts/recordmcount.h
 195else
 196sub_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 $(part-of-module),1,0)" "$(@)";
 202recordmcount_source := $(srctree)/scripts/recordmcount.pl
 203endif # BUILD_C_RECORDMCOUNT
 204cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)), \
 205        $(sub_cmd_record_mcount))
 206endif # CC_USING_RECORD_MCOUNT
 207endif # CONFIG_FTRACE_MCOUNT_RECORD
 208
 209ifdef CONFIG_STACK_VALIDATION
 210ifneq ($(SKIP_STACK_VALIDATION),1)
 211
 212__objtool_obj := $(objtree)/tools/objtool/objtool
 213
 214objtool_args = $(if $(CONFIG_UNWINDER_ORC),orc generate,check)
 215
 216objtool_args += $(if $(part-of-module), --module,)
 217
 218ifndef CONFIG_FRAME_POINTER
 219objtool_args += --no-fp
 220endif
 221ifdef CONFIG_GCOV_KERNEL
 222objtool_args += --no-unreachable
 223endif
 224ifdef CONFIG_RETPOLINE
 225  objtool_args += --retpoline
 226endif
 227ifdef CONFIG_X86_SMAP
 228  objtool_args += --uaccess
 229endif
 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
 234cmd_objtool = $(if $(patsubst y%,, \
 235        $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 236        $(__objtool_obj) $(objtool_args) $@)
 237objtool_obj = $(if $(patsubst y%,, \
 238        $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 239        $(__objtool_obj))
 240
 241endif # SKIP_STACK_VALIDATION
 242endif # CONFIG_STACK_VALIDATION
 243
 244# Rebuild all objects when objtool changes, or is enabled/disabled.
 245objtool_dep = $(objtool_obj)                                    \
 246              $(wildcard include/config/orc/unwinder.h          \
 247                         include/config/stack/validation.h)
 248
 249ifdef CONFIG_TRIM_UNUSED_KSYMS
 250cmd_gen_ksymdeps = \
 251        $(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd
 252endif
 253
 254define 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)
 262endef
 263
 264define 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)
 269endef
 270
 271# List module undefined symbols (or empty line if not enabled)
 272ifdef CONFIG_TRIM_UNUSED_KSYMS
 273cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | xargs echo
 274else
 275cmd_undef_syms = echo
 276endif
 277
 278# Built-in and composite module parts
 279$(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
 280        $(call cmd,force_checksrc)
 281        $(call if_changed_rule,cc_o_c)
 282
 283cmd_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
 291targets += $(mod-targets)
 292
 293quiet_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
 304quiet_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
 313modkern_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.
 329cmd_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
 341quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
 342cmd_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
 350quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
 351cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
 352
 353$(obj)/%.s: $(src)/%.S FORCE
 354        $(call if_changed_dep,cpp_s_S)
 355
 356quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
 357      cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
 358
 359ifdef CONFIG_MODVERSIONS
 360
 361ASM_PROTOTYPES := $(wildcard $(srctree)/arch/$(SRCARCH)/include/asm/asm-prototypes.h)
 362
 363ifneq ($(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
 368cmd_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
 378endif
 379endif
 380
 381$(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
 382        $(call if_changed_rule,as_o_S)
 383
 384targets += $(filter-out $(subdir-obj-y), $(real-obj-y)) $(real-obj-m) $(lib-y)
 385targets += $(extra-y) $(MAKECMDGOALS) $(always)
 386
 387# Linker scripts preprocessor (.lds.S -> .lds)
 388# ---------------------------------------------------------------------------
 389quiet_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# ---------------------------------------------------------------------------
 398quiet_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#
 414ifdef builtin-target
 415
 416quiet_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
 422targets += $(builtin-target)
 423endif # builtin-target
 424
 425#
 426# Rule to create modules.order file
 427#
 428# Create commands to either record .ko file or cat modules.order from
 429# a subdirectory
 430$(modorder-target): $(subdir-ym) FORCE
 431        $(Q){ $(foreach m, $(modorder), \
 432        $(if $(filter %/modules.order, $m), cat $m, echo $m);) :; } \
 433        | $(AWK) '!x[$$0]++' - > $@
 434
 435#
 436# Rule to compile a set of .o files into one .a file (with symbol table)
 437#
 438ifdef lib-target
 439
 440$(lib-target): $(lib-y) FORCE
 441        $(call if_changed,ar)
 442
 443targets += $(lib-target)
 444
 445dummy-object = $(obj)/.lib_exports.o
 446ksyms-lds = $(dot-target).lds
 447
 448quiet_cmd_export_list = EXPORTS $@
 449cmd_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
 459targets += $(obj)/lib-ksyms.o
 460
 461endif
 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.
 467quiet_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
 474targets += $(multi-used-m)
 475targets := $(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.
 480intermediate_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
 487targets += $(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
 495PHONY += $(subdir-ym)
 496$(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
 504PHONY += FORCE
 505
 506FORCE:
 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
 513existing-targets := $(wildcard $(sort $(targets)))
 514
 515-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
 516
 517ifdef building_out_of_srctree
 518# Create directories for object files if they do not exist
 519obj-dirs := $(sort $(obj) $(patsubst %/,%, $(dir $(targets))))
 520# If targets exist, their directories apparently exist. Skip mkdir.
 521existing-dirs := $(sort $(patsubst %/,%, $(dir $(existing-targets))))
 522obj-dirs := $(strip $(filter-out $(existing-dirs), $(obj-dirs)))
 523ifneq ($(obj-dirs),)
 524$(shell mkdir -p $(obj-dirs))
 525endif
 526endif
 527
 528.PHONY: $(PHONY)
 529