lib: don't depend on linux headers being installed.
[muen/linux.git] / 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 modorder-target := $(obj)/modules.order
67
68 # We keep a list of all modules in $(MODVERDIR)
69
70 __build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y)) \
71          $(if $(KBUILD_MODULES),$(obj-m) $(modorder-target)) \
72          $(subdir-ym) $(always)
73         @:
74
75 # Linus' kernel sanity checking tool
76 ifeq ($(KBUILD_CHECKSRC),1)
77   quiet_cmd_checksrc       = CHECK   $<
78         cmd_checksrc       = $(CHECK) $(CHECKFLAGS) $(c_flags) $< ;
79 else ifeq ($(KBUILD_CHECKSRC),2)
80   quiet_cmd_force_checksrc = CHECK   $<
81         cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $< ;
82 endif
83
84 ifneq ($(KBUILD_ENABLE_EXTRA_GCC_CHECKS),)
85   cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $< ;
86 endif
87
88 # Do section mismatch analysis for each module/built-in.a
89 ifdef CONFIG_DEBUG_SECTION_MISMATCH
90   cmd_secanalysis = ; scripts/mod/modpost $@
91 endif
92
93 # Compile C sources (.c)
94 # ---------------------------------------------------------------------------
95
96 # Default is built-in, unless we know otherwise
97 modkern_cflags =                                          \
98         $(if $(part-of-module),                           \
99                 $(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE), \
100                 $(KBUILD_CFLAGS_KERNEL) $(CFLAGS_KERNEL))
101 quiet_modtag := $(empty)   $(empty)
102
103 $(real-obj-m)        : part-of-module := y
104 $(real-obj-m:.o=.i)  : part-of-module := y
105 $(real-obj-m:.o=.s)  : part-of-module := y
106 $(real-obj-m:.o=.lst): part-of-module := y
107
108 $(real-obj-m)        : quiet_modtag := [M]
109 $(real-obj-m:.o=.i)  : quiet_modtag := [M]
110 $(real-obj-m:.o=.s)  : quiet_modtag := [M]
111 $(real-obj-m:.o=.lst): quiet_modtag := [M]
112
113 $(obj-m)             : quiet_modtag := [M]
114
115 quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@
116 cmd_cc_s_c       = $(CC) $(c_flags) $(DISABLE_LTO) -fverbose-asm -S -o $@ $<
117
118 $(obj)/%.s: $(src)/%.c FORCE
119         $(call if_changed_dep,cc_s_c)
120
121 quiet_cmd_cpp_i_c = CPP $(quiet_modtag) $@
122 cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
123
124 $(obj)/%.i: $(src)/%.c FORCE
125         $(call if_changed_dep,cpp_i_c)
126
127 # These mirror gensymtypes_S and co below, keep them in synch.
128 cmd_gensymtypes_c =                                                         \
129     $(CPP) -D__GENKSYMS__ $(c_flags) $< |                                   \
130     $(GENKSYMS) $(if $(1), -T $(2))                                         \
131      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
132      $(if $(KBUILD_PRESERVE),-p)                                            \
133      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
134
135 quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
136 cmd_cc_symtypes_c =                                                         \
137     set -e;                                                                 \
138     $(call cmd_gensymtypes_c,true,$@) >/dev/null;                           \
139     test -s $@ || rm -f $@
140
141 $(obj)/%.symtypes : $(src)/%.c FORCE
142         $(call cmd,cc_symtypes_c)
143
144 # LLVM assembly
145 # Generate .ll files from .c
146 quiet_cmd_cc_ll_c = CC $(quiet_modtag)  $@
147       cmd_cc_ll_c = $(CC) $(c_flags) -emit-llvm -S -o $@ $<
148
149 $(obj)/%.ll: $(src)/%.c FORCE
150         $(call if_changed_dep,cc_ll_c)
151
152 # C (.c) files
153 # The C file is compiled and updated dependency information is generated.
154 # (See cmd_cc_o_c + relevant part of rule_cc_o_c)
155
156 quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
157
158 ifndef CONFIG_MODVERSIONS
159 cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
160
161 else
162 # When module versioning is enabled the following steps are executed:
163 # o compile a .tmp_<file>.o from <file>.c
164 # o if .tmp_<file>.o doesn't contain a __ksymtab version, i.e. does
165 #   not export symbols, we just rename .tmp_<file>.o to <file>.o and
166 #   are done.
167 # o otherwise, we calculate symbol versions using the good old
168 #   genksyms on the preprocessed source and postprocess them in a way
169 #   that they are usable as a linker script
170 # o generate <file>.o from .tmp_<file>.o using the linker to
171 #   replace the unresolved symbols __crc_exported_symbol with
172 #   the actual value of the checksum generated by genksyms
173
174 cmd_cc_o_c = $(CC) $(c_flags) -c -o $(@D)/.tmp_$(@F) $<
175
176 cmd_modversions_c =                                                             \
177         if $(OBJDUMP) -h $(@D)/.tmp_$(@F) | grep -q __ksymtab; then             \
178                 $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
179                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
180                                                                                 \
181                 $(LD) $(KBUILD_LDFLAGS) -r -o $@ $(@D)/.tmp_$(@F)               \
182                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
183                 rm -f $(@D)/.tmp_$(@F) $(@D)/.tmp_$(@F:.o=.ver);                \
184         else                                                                    \
185                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
186         fi;
187 endif
188
189 ifdef CONFIG_FTRACE_MCOUNT_RECORD
190 ifndef CC_USING_RECORD_MCOUNT
191 # compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
192 ifdef BUILD_C_RECORDMCOUNT
193 ifeq ("$(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 = set -e ; 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 := $(srctree)/scripts/recordmcount.pl
214 endif # BUILD_C_RECORDMCOUNT
215 cmd_record_mcount =                                             \
216         if [ "$(findstring $(CC_FLAGS_FTRACE),$(_c_flags))" =   \
217              "$(CC_FLAGS_FTRACE)" ]; then                       \
218                 $(sub_cmd_record_mcount)                        \
219         fi;
220 endif # CC_USING_RECORD_MCOUNT
221 endif # CONFIG_FTRACE_MCOUNT_RECORD
222
223 ifdef CONFIG_STACK_VALIDATION
224 ifneq ($(SKIP_STACK_VALIDATION),1)
225
226 __objtool_obj := $(objtree)/tools/objtool/objtool
227
228 objtool_args = $(if $(CONFIG_UNWINDER_ORC),orc generate,check)
229
230 objtool_args += $(if $(part-of-module), --module,)
231
232 ifndef CONFIG_FRAME_POINTER
233 objtool_args += --no-fp
234 endif
235 ifdef CONFIG_GCOV_KERNEL
236 objtool_args += --no-unreachable
237 endif
238 ifdef CONFIG_RETPOLINE
239   objtool_args += --retpoline
240 endif
241
242
243 ifdef CONFIG_MODVERSIONS
244 objtool_o = $(@D)/.tmp_$(@F)
245 else
246 objtool_o = $(@)
247 endif
248
249 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
250 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
251 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
252 cmd_objtool = $(if $(patsubst y%,, \
253         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
254         $(__objtool_obj) $(objtool_args) "$(objtool_o)";)
255 objtool_obj = $(if $(patsubst y%,, \
256         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
257         $(__objtool_obj))
258
259 endif # SKIP_STACK_VALIDATION
260 endif # CONFIG_STACK_VALIDATION
261
262 # Rebuild all objects when objtool changes, or is enabled/disabled.
263 objtool_dep = $(objtool_obj)                                    \
264               $(wildcard include/config/orc/unwinder.h          \
265                          include/config/stack/validation.h)
266
267 define rule_cc_o_c
268         $(call echo-cmd,checksrc) $(cmd_checksrc)                         \
269         $(call cmd_and_fixdep,cc_o_c)                                     \
270         $(cmd_checkdoc)                                                   \
271         $(call echo-cmd,objtool) $(cmd_objtool)                           \
272         $(cmd_modversions_c)                                              \
273         $(call echo-cmd,record_mcount) $(cmd_record_mcount)
274 endef
275
276 define rule_as_o_S
277         $(call cmd_and_fixdep,as_o_S)                                     \
278         $(call echo-cmd,objtool) $(cmd_objtool)                           \
279         $(cmd_modversions_S)
280 endef
281
282 # List module undefined symbols (or empty line if not enabled)
283 ifdef CONFIG_TRIM_UNUSED_KSYMS
284 cmd_undef_syms = $(NM) $@ | sed -n 's/^  *U //p' | xargs echo
285 else
286 cmd_undef_syms = echo
287 endif
288
289 # Built-in and composite module parts
290 $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
291         $(call cmd,force_checksrc)
292         $(call if_changed_rule,cc_o_c)
293
294 # Single-part modules are special since we need to mark them in $(MODVERDIR)
295
296 $(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
297         $(call cmd,force_checksrc)
298         $(call if_changed_rule,cc_o_c)
299         @{ echo $(@:.o=.ko); echo $@; \
300            $(cmd_undef_syms); } > $(MODVERDIR)/$(@F:.o=.mod)
301
302 quiet_cmd_cc_lst_c = MKLST   $@
303       cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
304                      $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
305                                      System.map $(OBJDUMP) > $@
306
307 $(obj)/%.lst: $(src)/%.c FORCE
308         $(call if_changed_dep,cc_lst_c)
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     $(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     set -e;                                                                 \
344     $(call cmd_gensymtypes_S,true,$@) >/dev/null;                           \
345     test -s $@ || rm -f $@
346
347 $(obj)/%.symtypes : $(src)/%.S FORCE
348         $(call cmd,cc_symtypes_S)
349
350
351 quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
352 cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
353
354 $(obj)/%.s: $(src)/%.S FORCE
355         $(call if_changed_dep,cpp_s_S)
356
357 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
358
359 ifndef CONFIG_MODVERSIONS
360 cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
361
362 else
363
364 ASM_PROTOTYPES := $(wildcard $(srctree)/arch/$(SRCARCH)/include/asm/asm-prototypes.h)
365
366 ifeq ($(ASM_PROTOTYPES),)
367 cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
368
369 else
370
371 # versioning matches the C process described above, with difference that
372 # we parse asm-prototypes.h C header to get function definitions.
373
374 cmd_as_o_S = $(CC) $(a_flags) -c -o $(@D)/.tmp_$(@F) $<
375
376 cmd_modversions_S =                                                             \
377         if $(OBJDUMP) -h $(@D)/.tmp_$(@F) | grep -q __ksymtab; then             \
378                 $(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
379                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
380                                                                                 \
381                 $(LD) $(KBUILD_LDFLAGS) -r -o $@ $(@D)/.tmp_$(@F)               \
382                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
383                 rm -f $(@D)/.tmp_$(@F) $(@D)/.tmp_$(@F:.o=.ver);                \
384         else                                                                    \
385                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
386         fi;
387 endif
388 endif
389
390 $(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
391         $(call if_changed_rule,as_o_S)
392
393 targets += $(filter-out $(subdir-obj-y), $(real-obj-y)) $(real-obj-m) $(lib-y)
394 targets += $(extra-y) $(MAKECMDGOALS) $(always)
395
396 # Linker scripts preprocessor (.lds.S -> .lds)
397 # ---------------------------------------------------------------------------
398 quiet_cmd_cpp_lds_S = LDS     $@
399       cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
400                              -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
401
402 $(obj)/%.lds: $(src)/%.lds.S FORCE
403         $(call if_changed_dep,cpp_lds_S)
404
405 # ASN.1 grammar
406 # ---------------------------------------------------------------------------
407 quiet_cmd_asn1_compiler = ASN.1   $@
408       cmd_asn1_compiler = $(objtree)/scripts/asn1_compiler $< \
409                                 $(subst .h,.c,$@) $(subst .c,.h,$@)
410
411 $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
412         $(call cmd,asn1_compiler)
413
414 # Build the compiled-in targets
415 # ---------------------------------------------------------------------------
416
417 # To build objects in subdirs, we need to descend into the directories
418 $(sort $(subdir-obj-y)): $(subdir-ym) ;
419
420 #
421 # Rule to compile a set of .o files into one .o file
422 #
423 ifdef builtin-target
424
425 # built-in.a archives are made with no symbol table or index which
426 # makes them small and fast, but unable to be used by the linker.
427 # scripts/link-vmlinux.sh builds an aggregate built-in.a with a symbol
428 # table and index.
429 quiet_cmd_ar_builtin = AR      $@
430       cmd_ar_builtin = rm -f $@; \
431                      $(AR) rcSTP$(KBUILD_ARFLAGS) $@ $(filter $(real-obj-y), $^)
432
433 $(builtin-target): $(real-obj-y) FORCE
434         $(call if_changed,ar_builtin)
435
436 targets += $(builtin-target)
437 endif # builtin-target
438
439 #
440 # Rule to create modules.order file
441 #
442 # Create commands to either record .ko file or cat modules.order from
443 # a subdirectory
444 modorder-cmds =                                         \
445         $(foreach m, $(modorder),                       \
446                 $(if $(filter %/modules.order, $m),     \
447                         cat $m;, echo kernel/$m;))
448
449 $(modorder-target): $(subdir-ym) FORCE
450         $(Q)(cat /dev/null; $(modorder-cmds)) > $@
451
452 #
453 # Rule to compile a set of .o files into one .a file
454 #
455 ifdef lib-target
456 quiet_cmd_link_l_target = AR      $@
457
458 # lib target archives do get a symbol table and index
459 cmd_link_l_target = rm -f $@; $(AR) rcsTP$(KBUILD_ARFLAGS) $@ $(lib-y)
460
461 $(lib-target): $(lib-y) FORCE
462         $(call if_changed,link_l_target)
463
464 targets += $(lib-target)
465
466 dummy-object = $(obj)/.lib_exports.o
467 ksyms-lds = $(dot-target).lds
468
469 quiet_cmd_export_list = EXPORTS $@
470 cmd_export_list = $(OBJDUMP) -h $< | \
471         sed -ne '/___ksymtab/s/.*+\([^ ]*\).*/EXTERN(\1)/p' >$(ksyms-lds);\
472         rm -f $(dummy-object);\
473         echo | $(CC) $(a_flags) -c -o $(dummy-object) -x assembler -;\
474         $(LD) $(ld_flags) -r -o $@ -T $(ksyms-lds) $(dummy-object);\
475         rm $(dummy-object) $(ksyms-lds)
476
477 $(obj)/lib-ksyms.o: $(lib-target) FORCE
478         $(call if_changed,export_list)
479
480 targets += $(obj)/lib-ksyms.o
481
482 endif
483
484 quiet_cmd_link_multi-m = LD [M]  $@
485 cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^) $(cmd_secanalysis)
486
487 $(multi-used-m): FORCE
488         $(call if_changed,link_multi-m)
489         @{ echo $(@:.o=.ko); echo $(filter %.o,$^); \
490            $(cmd_undef_syms); } > $(MODVERDIR)/$(@F:.o=.mod)
491 $(call multi_depend, $(multi-used-m), .o, -objs -y -m)
492
493 targets += $(multi-used-m)
494 targets := $(filter-out $(PHONY), $(targets))
495
496 # Add intermediate targets:
497 # When building objects with specific suffix patterns, add intermediate
498 # targets that the final targets are derived from.
499 intermediate_targets = $(foreach sfx, $(2), \
500                                 $(patsubst %$(strip $(1)),%$(sfx), \
501                                         $(filter %$(strip $(1)), $(targets))))
502 # %.asn1.o <- %.asn1.[ch] <- %.asn1
503 # %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
504 # %.lex.o <- %.lex.c <- %.l
505 # %.tab.o <- %.tab.[ch] <- %.y
506 targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
507            $(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
508            $(call intermediate_targets, .lex.o, .lex.c) \
509            $(call intermediate_targets, .tab.o, .tab.c .tab.h)
510
511 # Descending
512 # ---------------------------------------------------------------------------
513
514 PHONY += $(subdir-ym)
515 $(subdir-ym):
516         $(Q)$(MAKE) $(build)=$@ need-builtin=$(if $(findstring $@,$(subdir-obj-y)),1)
517
518 # Add FORCE to the prequisites of a target to force it to be always rebuilt.
519 # ---------------------------------------------------------------------------
520
521 PHONY += FORCE
522
523 FORCE:
524
525 # Read all saved command lines and dependencies for the $(targets) we
526 # may be building above, using $(if_changed{,_dep}). As an
527 # optimization, we don't need to read them if the target does not
528 # exist, we will rebuild anyway in that case.
529
530 cmd_files := $(wildcard $(foreach f,$(sort $(targets)),$(dir $(f)).$(notdir $(f)).cmd))
531
532 ifneq ($(cmd_files),)
533   include $(cmd_files)
534 endif
535
536 ifneq ($(KBUILD_SRC),)
537 # Create directories for object files if they do not exist
538 obj-dirs := $(sort $(obj) $(patsubst %/,%, $(dir $(targets))))
539 # If cmd_files exist, their directories apparently exist.  Skip mkdir.
540 exist-dirs := $(sort $(patsubst %/,%, $(dir $(cmd_files))))
541 obj-dirs := $(strip $(filter-out $(exist-dirs), $(obj-dirs)))
542 ifneq ($(obj-dirs),)
543 $(shell mkdir -p $(obj-dirs))
544 endif
545 endif
546
547 # Some files contained in $(targets) are intermediate artifacts.
548 # We never want them to be removed automatically.
549 .SECONDARY: $(targets)
550
551 .PHONY: $(PHONY)