xref: /openbmc/linux/scripts/Makefile.build (revision 1e70d57e) 
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-y :=
19always-m :=
20targets :=
21subdir-y :=
22subdir-m :=
23EXTRA_AFLAGS   :=
24EXTRA_CFLAGS   :=
25EXTRA_CPPFLAGS :=
26EXTRA_LDFLAGS  :=
27asflags-y  :=
28ccflags-y  :=
29cppflags-y :=
30ldflags-y  :=
31
32subdir-asflags-y :=
33subdir-ccflags-y :=
34
35# Read auto.conf if it exists, otherwise ignore
36-include include/config/auto.conf
37
38include $(srctree)/scripts/Kbuild.include
39include $(srctree)/scripts/Makefile.compiler
40
41# The filename Kbuild has precedence over Makefile
42kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
43include $(or $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Makefile)
44
45include $(srctree)/scripts/Makefile.lib
46
47# Do not include hostprogs rules unless needed.
48# $(sort ...) is used here to remove duplicated words and excessive spaces.
49hostprogs := $(sort $(hostprogs))
50ifneq ($(hostprogs),)
51include $(srctree)/scripts/Makefile.host
52endif
53
54# Do not include userprogs rules unless needed.
55# $(sort ...) is used here to remove duplicated words and excessive spaces.
56userprogs := $(sort $(userprogs))
57ifneq ($(userprogs),)
58include $(srctree)/scripts/Makefile.userprogs
59endif
60
61ifndef obj
62$(warning kbuild: Makefile.build is included improperly)
63endif
64
65ifeq ($(need-modorder),)
66ifneq ($(obj-m),)
67$(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
68$(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
69endif
70endif
71
72# ===========================================================================
73
74# subdir-builtin and subdir-modorder may contain duplications. Use $(sort ...)
75subdir-builtin := $(sort $(filter %/built-in.a, $(real-obj-y)))
76subdir-modorder := $(sort $(filter %/modules.order, $(obj-m)))
77
78targets-for-builtin := $(extra-y)
79
80ifneq ($(strip $(lib-y) $(lib-m) $(lib-)),)
81targets-for-builtin += $(obj)/lib.a
82endif
83
84ifdef need-builtin
85targets-for-builtin += $(obj)/built-in.a
86endif
87
88targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
89
90ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
91targets-for-modules += $(patsubst %.o, %.prelink.o, $(filter %.o, $(obj-m)))
92endif
93
94ifdef need-modorder
95targets-for-modules += $(obj)/modules.order
96endif
97
98targets += $(targets-for-builtin) $(targets-for-modules)
99
100# Linus' kernel sanity checking tool
101ifeq ($(KBUILD_CHECKSRC),1)
102  quiet_cmd_checksrc       = CHECK   $<
103        cmd_checksrc       = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
104else ifeq ($(KBUILD_CHECKSRC),2)
105  quiet_cmd_force_checksrc = CHECK   $<
106        cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
107endif
108
109ifneq ($(KBUILD_EXTRA_WARN),)
110  cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $<
111endif
112
113# Compile C sources (.c)
114# ---------------------------------------------------------------------------
115
116quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@
117      cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS) $(CC_FLAGS_LTO), $(c_flags)) -fverbose-asm -S -o $@ $<
118
119$(obj)/%.s: $(src)/%.c FORCE
120	$(call if_changed_dep,cc_s_c)
121
122quiet_cmd_cpp_i_c = CPP $(quiet_modtag) $@
123cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
124
125$(obj)/%.i: $(src)/%.c FORCE
126	$(call if_changed_dep,cpp_i_c)
127
128# These mirror gensymtypes_S and co below, keep them in synch.
129cmd_gensymtypes_c =                                                         \
130    $(CPP) -D__GENKSYMS__ $(c_flags) $< |                                   \
131    scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
132     $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
133     $(if $(KBUILD_PRESERVE),-p)                                            \
134     -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
135
136quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
137cmd_cc_symtypes_c =                                                         \
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
146quiet_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
156quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
157      cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $< $(cmd_objtool)
158
159ifdef CONFIG_MODVERSIONS
160# When module versioning is enabled the following steps are executed:
161# o compile a <file>.o from <file>.c
162# o if <file>.o doesn't contain a __ksymtab version, i.e. does
163#   not export symbols, it's done.
164# o otherwise, we calculate symbol versions using the good old
165#   genksyms on the preprocessed source and postprocess them in a way
166#   that they are usable as a linker script
167# o generate .tmp_<file>.o from <file>.o using the linker to
168#   replace the unresolved symbols __crc_exported_symbol with
169#   the actual value of the checksum generated by genksyms
170# o remove .tmp_<file>.o to <file>.o
171
172ifdef CONFIG_LTO_CLANG
173# Generate .o.symversions files for each .o with exported symbols, and link these
174# to the kernel and/or modules at the end.
175cmd_modversions_c =								\
176	if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then			\
177		$(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
178		    > $@.symversions;						\
179	else									\
180		rm -f $@.symversions;						\
181	fi;
182else
183cmd_modversions_c =								\
184	if $(OBJDUMP) -h $@ | grep -q __ksymtab; then				\
185		$(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
186		    > $(@D)/.tmp_$(@F:.o=.ver);					\
187										\
188		$(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@ 		\
189			-T $(@D)/.tmp_$(@F:.o=.ver);				\
190		mv -f $(@D)/.tmp_$(@F) $@;					\
191		rm -f $(@D)/.tmp_$(@F:.o=.ver);					\
192	fi
193endif
194endif
195
196ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
197# compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
198ifdef BUILD_C_RECORDMCOUNT
199ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
200  RECORDMCOUNT_FLAGS = -w
201endif
202# Due to recursion, we must skip empty.o.
203# The empty.o file is created in the make process in order to determine
204# the target endianness and word size. It is made before all other C
205# files, including recordmcount.
206sub_cmd_record_mcount =					\
207	if [ $(@) != "scripts/mod/empty.o" ]; then	\
208		$(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)";	\
209	fi;
210recordmcount_source := $(srctree)/scripts/recordmcount.c \
211		    $(srctree)/scripts/recordmcount.h
212else
213sub_cmd_record_mcount = perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
214	"$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \
215	"$(if $(CONFIG_64BIT),64,32)" \
216	"$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS)" \
217	"$(LD) $(KBUILD_LDFLAGS)" "$(NM)" "$(RM)" "$(MV)" \
218	"$(if $(part-of-module),1,0)" "$(@)";
219recordmcount_source := $(srctree)/scripts/recordmcount.pl
220endif # BUILD_C_RECORDMCOUNT
221cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)),	\
222	$(sub_cmd_record_mcount))
223endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
224
225ifdef CONFIG_STACK_VALIDATION
226
227objtool := $(objtree)/tools/objtool/objtool
228
229objtool_args =								\
230	$(if $(CONFIG_UNWINDER_ORC),orc generate,check)			\
231	$(if $(part-of-module), --module)				\
232	$(if $(CONFIG_X86_KERNEL_IBT), --lto --ibt)			\
233	$(if $(CONFIG_FRAME_POINTER),, --no-fp)				\
234	$(if $(CONFIG_GCOV_KERNEL)$(CONFIG_LTO_CLANG), --no-unreachable)\
235	$(if $(CONFIG_RETPOLINE), --retpoline)				\
236	$(if $(CONFIG_X86_SMAP), --uaccess)				\
237	$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount)		\
238	$(if $(CONFIG_SLS), --sls)
239
240cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $@)
241cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
242
243endif # CONFIG_STACK_VALIDATION
244
245ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
246
247# Skip objtool for LLVM bitcode
248$(obj)/%.o: objtool-enabled :=
249
250else
251
252# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
253# 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
254# 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
255
256$(obj)/%.o: objtool-enabled = $(if $(filter-out y%, \
257	$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y)
258
259endif
260
261ifdef CONFIG_TRIM_UNUSED_KSYMS
262cmd_gen_ksymdeps = \
263	$(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd
264
265# List module undefined symbols
266undefined_syms = $(NM) $< | $(AWK) '$$1 == "U" { printf("%s%s", x++ ? " " : "", $$2) }';
267endif
268
269define rule_cc_o_c
270	$(call cmd_and_fixdep,cc_o_c)
271	$(call cmd,gen_ksymdeps)
272	$(call cmd,checksrc)
273	$(call cmd,checkdoc)
274	$(call cmd,gen_objtooldep)
275	$(call cmd,modversions_c)
276	$(call cmd,record_mcount)
277endef
278
279define rule_as_o_S
280	$(call cmd_and_fixdep,as_o_S)
281	$(call cmd,gen_ksymdeps)
282	$(call cmd,gen_objtooldep)
283	$(call cmd,modversions_S)
284endef
285
286# Built-in and composite module parts
287$(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
288	$(call if_changed_rule,cc_o_c)
289	$(call cmd,force_checksrc)
290
291ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
292# Module .o files may contain LLVM bitcode, compile them into native code
293# before ELF processing
294quiet_cmd_cc_prelink_modules = LD [M]  $@
295      cmd_cc_prelink_modules =						\
296	$(LD) $(ld_flags) -r -o $@					\
297               $(shell [ -s $(@:.prelink.o=.o.symversions) ] &&		\
298                       echo -T $(@:.prelink.o=.o.symversions))		\
299		--whole-archive $(filter-out FORCE,$^)			\
300		$(cmd_objtool)
301
302# objtool was skipped for LLVM bitcode, run it now that we have compiled
303# modules into native code
304$(obj)/%.prelink.o: objtool-enabled = y
305$(obj)/%.prelink.o: part-of-module := y
306
307$(obj)/%.prelink.o: $(obj)/%.o FORCE
308	$(call if_changed,cc_prelink_modules)
309endif
310
311cmd_mod = { \
312	echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \
313	$(undefined_syms) echo; \
314	} > $@
315
316$(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE
317	$(call if_changed,mod)
318
319quiet_cmd_cc_lst_c = MKLST   $@
320      cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
321		     $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
322				     System.map $(OBJDUMP) > $@
323
324$(obj)/%.lst: $(src)/%.c FORCE
325	$(call if_changed_dep,cc_lst_c)
326
327# Compile assembler sources (.S)
328# ---------------------------------------------------------------------------
329
330# .S file exports must have their C prototypes defined in asm/asm-prototypes.h
331# or a file that it includes, in order to get versioned symbols. We build a
332# dummy C file that includes asm-prototypes and the EXPORT_SYMBOL lines from
333# the .S file (with trailing ';'), and run genksyms on that, to extract vers.
334#
335# This is convoluted. The .S file must first be preprocessed to run guards and
336# expand names, then the resulting exports must be constructed into plain
337# EXPORT_SYMBOL(symbol); to build our dummy C file, and that gets preprocessed
338# to make the genksyms input.
339#
340# These mirror gensymtypes_c and co above, keep them in synch.
341cmd_gensymtypes_S =                                                         \
342   { echo "\#include <linux/kernel.h>" ;                                    \
343     echo "\#include <asm/asm-prototypes.h>" ;                              \
344    $(CPP) $(a_flags) $< |                                                  \
345     grep "\<___EXPORT_SYMBOL\>" |                                          \
346     sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ; } | \
347    $(CPP) -D__GENKSYMS__ $(c_flags) -xc - |                                \
348    scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
349     $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
350     $(if $(KBUILD_PRESERVE),-p)                                            \
351     -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
352
353quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
354cmd_cc_symtypes_S =                                                         \
355    $(call cmd_gensymtypes_S,true,$@) >/dev/null;                           \
356    test -s $@ || rm -f $@
357
358$(obj)/%.symtypes : $(src)/%.S FORCE
359	$(call cmd,cc_symtypes_S)
360
361
362quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
363cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
364
365$(obj)/%.s: $(src)/%.S FORCE
366	$(call if_changed_dep,cpp_s_S)
367
368quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
369      cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $< $(cmd_objtool)
370
371ifdef CONFIG_ASM_MODVERSIONS
372
373# versioning matches the C process described above, with difference that
374# we parse asm-prototypes.h C header to get function definitions.
375
376cmd_modversions_S =								\
377	if $(OBJDUMP) -h $@ | 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		mv -f $(@D)/.tmp_$(@F) $@;					\
384		rm -f $(@D)/.tmp_$(@F:.o=.ver);					\
385	fi
386endif
387
388$(obj)/%.o: $(src)/%.S FORCE
389	$(call if_changed_rule,as_o_S)
390
391targets += $(filter-out $(subdir-builtin), $(real-obj-y))
392targets += $(filter-out $(subdir-modorder), $(real-obj-m))
393targets += $(real-dtb-y) $(lib-y) $(always-y) $(MAKECMDGOALS)
394
395# Linker scripts preprocessor (.lds.S -> .lds)
396# ---------------------------------------------------------------------------
397quiet_cmd_cpp_lds_S = LDS     $@
398      cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
399	                     -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
400
401$(obj)/%.lds: $(src)/%.lds.S FORCE
402	$(call if_changed_dep,cpp_lds_S)
403
404# ASN.1 grammar
405# ---------------------------------------------------------------------------
406quiet_cmd_asn1_compiler = ASN.1   $(basename $@).[ch]
407      cmd_asn1_compiler = $(objtree)/scripts/asn1_compiler $< \
408				$(basename $@).c $(basename $@).h
409
410$(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
411	$(call cmd,asn1_compiler)
412
413# Build the compiled-in targets
414# ---------------------------------------------------------------------------
415
416# To build objects in subdirs, we need to descend into the directories
417$(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ;
418$(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
419
420# combine symversions for later processing
421ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
422      cmd_update_lto_symversions =					\
423	rm -f $@.symversions						\
424	$(foreach n, $(filter-out FORCE,$^),				\
425		$(if $(shell test -s $(n).symversions && echo y),	\
426			; cat $(n).symversions >> $@.symversions))
427else
428      cmd_update_lto_symversions = echo >/dev/null
429endif
430
431#
432# Rule to compile a set of .o files into one .a file (without symbol table)
433#
434
435quiet_cmd_ar_builtin = AR      $@
436      cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
437
438quiet_cmd_ar_and_symver = AR      $@
439      cmd_ar_and_symver = $(cmd_update_lto_symversions); $(cmd_ar_builtin)
440
441$(obj)/built-in.a: $(real-obj-y) FORCE
442	$(call if_changed,ar_and_symver)
443
444#
445# Rule to create modules.order file
446#
447# Create commands to either record .ko file or cat modules.order from
448# a subdirectory
449# Add $(obj-m) as the prerequisite to avoid updating the timestamp of
450# modules.order unless contained modules are updated.
451
452cmd_modules_order = { $(foreach m, $(real-prereqs), \
453	$(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.o,%.ko,$m));) :; } \
454	| $(AWK) '!x[$$0]++' - > $@
455
456$(obj)/modules.order: $(obj-m) FORCE
457	$(call if_changed,modules_order)
458
459#
460# Rule to compile a set of .o files into one .a file (with symbol table)
461#
462quiet_cmd_ar_lib = AR      $@
463      cmd_ar_lib = $(cmd_update_lto_symversions); $(cmd_ar)
464
465$(obj)/lib.a: $(lib-y) FORCE
466	$(call if_changed,ar_lib)
467
468# NOTE:
469# Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
470# module is turned into a multi object module, $^ will contain header file
471# dependencies recorded in the .*.cmd file.
472ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
473quiet_cmd_link_multi-m = AR [M]  $@
474cmd_link_multi-m =						\
475	$(cmd_update_lto_symversions);				\
476	rm -f $@; 						\
477	$(AR) cDPrsT $@ $(filter %.o,$^)
478else
479quiet_cmd_link_multi-m = LD [M]  $@
480      cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
481endif
482
483$(multi-obj-m): FORCE
484	$(call if_changed,link_multi-m)
485$(call multi_depend, $(multi-obj-m), .o, -objs -y -m)
486
487targets += $(multi-obj-m)
488targets := $(filter-out $(PHONY), $(targets))
489
490# Add intermediate targets:
491# When building objects with specific suffix patterns, add intermediate
492# targets that the final targets are derived from.
493intermediate_targets = $(foreach sfx, $(2), \
494				$(patsubst %$(strip $(1)),%$(sfx), \
495					$(filter %$(strip $(1)), $(targets))))
496# %.asn1.o <- %.asn1.[ch] <- %.asn1
497# %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
498# %.lex.o <- %.lex.c <- %.l
499# %.tab.o <- %.tab.[ch] <- %.y
500targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
501	   $(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
502	   $(call intermediate_targets, .lex.o, .lex.c) \
503	   $(call intermediate_targets, .tab.o, .tab.c .tab.h)
504
505# Build
506# ---------------------------------------------------------------------------
507
508ifdef single-build
509
510KBUILD_SINGLE_TARGETS := $(filter $(obj)/%, $(KBUILD_SINGLE_TARGETS))
511
512curdir-single := $(sort $(foreach x, $(KBUILD_SINGLE_TARGETS), \
513			$(if $(filter $(x) $(basename $(x)).o, $(targets)), $(x))))
514
515# Handle single targets without any rule: show "Nothing to be done for ..." or
516# "No rule to make target ..." depending on whether the target exists.
517unknown-single := $(filter-out $(addsuffix /%, $(subdir-ym)), \
518			$(filter-out $(curdir-single), $(KBUILD_SINGLE_TARGETS)))
519
520single-subdirs := $(foreach d, $(subdir-ym), \
521			$(if $(filter $(d)/%, $(KBUILD_SINGLE_TARGETS)), $(d)))
522
523__build: $(curdir-single) $(single-subdirs)
524ifneq ($(unknown-single),)
525	$(Q)$(MAKE) -f /dev/null $(unknown-single)
526endif
527	@:
528
529ifeq ($(curdir-single),)
530# Nothing to do in this directory. Do not include any .*.cmd file for speed-up
531targets :=
532else
533targets += $(curdir-single)
534endif
535
536else
537
538__build: $(if $(KBUILD_BUILTIN), $(targets-for-builtin)) \
539	 $(if $(KBUILD_MODULES), $(targets-for-modules)) \
540	 $(subdir-ym) $(always-y)
541	@:
542
543endif
544
545# Descending
546# ---------------------------------------------------------------------------
547
548PHONY += $(subdir-ym)
549$(subdir-ym):
550	$(Q)$(MAKE) $(build)=$@ \
551	$(if $(filter $@/, $(KBUILD_SINGLE_TARGETS)),single-build=) \
552	need-builtin=$(if $(filter $@/built-in.a, $(subdir-builtin)),1) \
553	need-modorder=$(if $(filter $@/modules.order, $(subdir-modorder)),1)
554
555# Add FORCE to the prequisites of a target to force it to be always rebuilt.
556# ---------------------------------------------------------------------------
557
558PHONY += FORCE
559
560FORCE:
561
562# Read all saved command lines and dependencies for the $(targets) we
563# may be building above, using $(if_changed{,_dep}). As an
564# optimization, we don't need to read them if the target does not
565# exist, we will rebuild anyway in that case.
566
567existing-targets := $(wildcard $(sort $(targets)))
568
569-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
570
571# Create directories for object files if they do not exist
572obj-dirs := $(sort $(patsubst %/,%, $(dir $(targets))))
573# If targets exist, their directories apparently exist. Skip mkdir.
574existing-dirs := $(sort $(patsubst %/,%, $(dir $(existing-targets))))
575obj-dirs := $(strip $(filter-out $(existing-dirs), $(obj-dirs)))
576ifneq ($(obj-dirs),)
577$(shell mkdir -p $(obj-dirs))
578endif
579
580.PHONY: $(PHONY)
581