drivers: dma-coherent: Account dma_pfn_offset when used with device tree
[sfrench/cifs-2.6.git] / scripts / Makefile.build
1 # ==========================================================================
2 # Building
3 # ==========================================================================
4
5 src := $(obj)
6
7 PHONY := __build
8 __build:
9
10 # Init all relevant variables used in kbuild files so
11 # 1) they have correct type
12 # 2) they do not inherit any value from the environment
13 obj-y :=
14 obj-m :=
15 lib-y :=
16 lib-m :=
17 always :=
18 targets :=
19 subdir-y :=
20 subdir-m :=
21 EXTRA_AFLAGS   :=
22 EXTRA_CFLAGS   :=
23 EXTRA_CPPFLAGS :=
24 EXTRA_LDFLAGS  :=
25 asflags-y  :=
26 ccflags-y  :=
27 cppflags-y :=
28 ldflags-y  :=
29
30 subdir-asflags-y :=
31 subdir-ccflags-y :=
32
33 # Read auto.conf if it exists, otherwise ignore
34 -include include/config/auto.conf
35
36 include scripts/Kbuild.include
37
38 # For backward compatibility check that these variables do not change
39 save-cflags := $(CFLAGS)
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 $(kbuild-file)
45
46 # If the save-* variables changed error out
47 ifeq ($(KBUILD_NOPEDANTIC),)
48         ifneq ("$(save-cflags)","$(CFLAGS)")
49                 $(error CFLAGS was changed in "$(kbuild-file)". Fix it to use ccflags-y)
50         endif
51 endif
52
53 include scripts/Makefile.lib
54
55 ifdef host-progs
56 ifneq ($(hostprogs-y),$(host-progs))
57 $(warning kbuild: $(obj)/Makefile - Usage of host-progs is deprecated. Please replace with hostprogs-y!)
58 hostprogs-y += $(host-progs)
59 endif
60 endif
61
62 # Do not include host rules unless needed
63 ifneq ($(hostprogs-y)$(hostprogs-m)$(hostlibs-y)$(hostlibs-m)$(hostcxxlibs-y)$(hostcxxlibs-m),)
64 include scripts/Makefile.host
65 endif
66
67 ifneq ($(KBUILD_SRC),)
68 # Create output directory if not already present
69 _dummy := $(shell [ -d $(obj) ] || mkdir -p $(obj))
70
71 # Create directories for object files if directory does not exist
72 # Needed when obj-y := dir/file.o syntax is used
73 _dummy := $(foreach d,$(obj-dirs), $(shell [ -d $(d) ] || mkdir -p $(d)))
74 endif
75
76 ifndef obj
77 $(warning kbuild: Makefile.build is included improperly)
78 endif
79
80 # ===========================================================================
81
82 ifneq ($(strip $(lib-y) $(lib-m) $(lib-)),)
83 lib-target := $(obj)/lib.a
84 obj-y += $(obj)/lib-ksyms.o
85 endif
86
87 ifneq ($(strip $(obj-y) $(obj-m) $(obj-) $(subdir-m) $(lib-target)),)
88 builtin-target := $(obj)/built-in.o
89 endif
90
91 modorder-target := $(obj)/modules.order
92
93 # We keep a list of all modules in $(MODVERDIR)
94
95 __build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y)) \
96          $(if $(KBUILD_MODULES),$(obj-m) $(modorder-target)) \
97          $(subdir-ym) $(always)
98         @:
99
100 # Linus' kernel sanity checking tool
101 ifneq ($(KBUILD_CHECKSRC),0)
102   ifeq ($(KBUILD_CHECKSRC),2)
103     quiet_cmd_force_checksrc = CHECK   $<
104           cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $< ;
105   else
106       quiet_cmd_checksrc     = CHECK   $<
107             cmd_checksrc     = $(CHECK) $(CHECKFLAGS) $(c_flags) $< ;
108   endif
109 endif
110
111 # Do section mismatch analysis for each module/built-in.o
112 ifdef CONFIG_DEBUG_SECTION_MISMATCH
113   cmd_secanalysis = ; scripts/mod/modpost $@
114 endif
115
116 # Compile C sources (.c)
117 # ---------------------------------------------------------------------------
118
119 # Default is built-in, unless we know otherwise
120 modkern_cflags =                                          \
121         $(if $(part-of-module),                           \
122                 $(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE), \
123                 $(KBUILD_CFLAGS_KERNEL) $(CFLAGS_KERNEL))
124 quiet_modtag := $(empty)   $(empty)
125
126 $(real-objs-m)        : part-of-module := y
127 $(real-objs-m:.o=.i)  : part-of-module := y
128 $(real-objs-m:.o=.s)  : part-of-module := y
129 $(real-objs-m:.o=.lst): part-of-module := y
130
131 $(real-objs-m)        : quiet_modtag := [M]
132 $(real-objs-m:.o=.i)  : quiet_modtag := [M]
133 $(real-objs-m:.o=.s)  : quiet_modtag := [M]
134 $(real-objs-m:.o=.lst): quiet_modtag := [M]
135
136 $(obj-m)              : quiet_modtag := [M]
137
138 # Default for not multi-part modules
139 modname = $(basetarget)
140
141 $(multi-objs-m)         : modname = $(modname-multi)
142 $(multi-objs-m:.o=.i)   : modname = $(modname-multi)
143 $(multi-objs-m:.o=.s)   : modname = $(modname-multi)
144 $(multi-objs-m:.o=.lst) : modname = $(modname-multi)
145 $(multi-objs-y)         : modname = $(modname-multi)
146 $(multi-objs-y:.o=.i)   : modname = $(modname-multi)
147 $(multi-objs-y:.o=.s)   : modname = $(modname-multi)
148 $(multi-objs-y:.o=.lst) : modname = $(modname-multi)
149
150 quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@
151 cmd_cc_s_c       = $(CC) $(c_flags) $(DISABLE_LTO) -fverbose-asm -S -o $@ $<
152
153 $(obj)/%.s: $(src)/%.c FORCE
154         $(call if_changed_dep,cc_s_c)
155
156 quiet_cmd_cpp_i_c = CPP $(quiet_modtag) $@
157 cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
158
159 $(obj)/%.i: $(src)/%.c FORCE
160         $(call if_changed_dep,cpp_i_c)
161
162 # These mirror gensymtypes_S and co below, keep them in synch.
163 cmd_gensymtypes_c =                                                         \
164     $(CPP) -D__GENKSYMS__ $(c_flags) $< |                                   \
165     $(GENKSYMS) $(if $(1), -T $(2))                                         \
166      $(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX))             \
167      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
168      $(if $(KBUILD_PRESERVE),-p)                                            \
169      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
170
171 quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
172 cmd_cc_symtypes_c =                                                         \
173     set -e;                                                                 \
174     $(call cmd_gensymtypes_c,true,$@) >/dev/null;                           \
175     test -s $@ || rm -f $@
176
177 $(obj)/%.symtypes : $(src)/%.c FORCE
178         $(call cmd,cc_symtypes_c)
179
180 # LLVM assembly
181 # Generate .ll files from .c
182 quiet_cmd_cc_ll_c = CC $(quiet_modtag)  $@
183       cmd_cc_ll_c = $(CC) $(c_flags) -emit-llvm -S -o $@ $<
184
185 $(obj)/%.ll: $(src)/%.c FORCE
186         $(call if_changed_dep,cc_ll_c)
187
188 # C (.c) files
189 # The C file is compiled and updated dependency information is generated.
190 # (See cmd_cc_o_c + relevant part of rule_cc_o_c)
191
192 quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
193
194 ifndef CONFIG_MODVERSIONS
195 cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
196
197 else
198 # When module versioning is enabled the following steps are executed:
199 # o compile a .tmp_<file>.o from <file>.c
200 # o if .tmp_<file>.o doesn't contain a __ksymtab version, i.e. does
201 #   not export symbols, we just rename .tmp_<file>.o to <file>.o and
202 #   are done.
203 # o otherwise, we calculate symbol versions using the good old
204 #   genksyms on the preprocessed source and postprocess them in a way
205 #   that they are usable as a linker script
206 # o generate <file>.o from .tmp_<file>.o using the linker to
207 #   replace the unresolved symbols __crc_exported_symbol with
208 #   the actual value of the checksum generated by genksyms
209
210 cmd_cc_o_c = $(CC) $(c_flags) -c -o $(@D)/.tmp_$(@F) $<
211
212 cmd_modversions_c =                                                             \
213         if $(OBJDUMP) -h $(@D)/.tmp_$(@F) | grep -q __ksymtab; then             \
214                 $(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
215                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
216                                                                                 \
217                 $(LD) $(LDFLAGS) -r -o $@ $(@D)/.tmp_$(@F)                      \
218                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
219                 rm -f $(@D)/.tmp_$(@F) $(@D)/.tmp_$(@F:.o=.ver);                \
220         else                                                                    \
221                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
222         fi;
223 endif
224
225 ifdef CONFIG_FTRACE_MCOUNT_RECORD
226 ifdef BUILD_C_RECORDMCOUNT
227 ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
228   RECORDMCOUNT_FLAGS = -w
229 endif
230 # Due to recursion, we must skip empty.o.
231 # The empty.o file is created in the make process in order to determine
232 #  the target endianness and word size. It is made before all other C
233 #  files, including recordmcount.
234 sub_cmd_record_mcount =                                 \
235         if [ $(@) != "scripts/mod/empty.o" ]; then      \
236                 $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)";   \
237         fi;
238 recordmcount_source := $(srctree)/scripts/recordmcount.c \
239                     $(srctree)/scripts/recordmcount.h
240 else
241 sub_cmd_record_mcount = set -e ; perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
242         "$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \
243         "$(if $(CONFIG_64BIT),64,32)" \
244         "$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CFLAGS)" \
245         "$(LD)" "$(NM)" "$(RM)" "$(MV)" \
246         "$(if $(part-of-module),1,0)" "$(@)";
247 recordmcount_source := $(srctree)/scripts/recordmcount.pl
248 endif
249 cmd_record_mcount =                                             \
250         if [ "$(findstring $(CC_FLAGS_FTRACE),$(_c_flags))" =   \
251              "$(CC_FLAGS_FTRACE)" ]; then                       \
252                 $(sub_cmd_record_mcount)                        \
253         fi;
254 endif
255
256 ifdef CONFIG_STACK_VALIDATION
257 ifneq ($(SKIP_STACK_VALIDATION),1)
258
259 __objtool_obj := $(objtree)/tools/objtool/objtool
260
261 objtool_args = check
262 ifndef CONFIG_FRAME_POINTER
263 objtool_args += --no-fp
264 endif
265
266 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
267 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
268 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
269 cmd_objtool = $(if $(patsubst y%,, \
270         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
271         $(__objtool_obj) $(objtool_args) "$(@)";)
272 objtool_obj = $(if $(patsubst y%,, \
273         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
274         $(__objtool_obj))
275
276 endif # SKIP_STACK_VALIDATION
277 endif # CONFIG_STACK_VALIDATION
278
279 define rule_cc_o_c
280         $(call echo-cmd,checksrc) $(cmd_checksrc)                         \
281         $(call cmd_and_fixdep,cc_o_c)                                     \
282         $(cmd_modversions_c)                                              \
283         $(call echo-cmd,objtool) $(cmd_objtool)                           \
284         $(call echo-cmd,record_mcount) $(cmd_record_mcount)
285 endef
286
287 define rule_as_o_S
288         $(call cmd_and_fixdep,as_o_S)                                     \
289         $(cmd_modversions_S)                                              \
290         $(call echo-cmd,objtool) $(cmd_objtool)
291 endef
292
293 # List module undefined symbols (or empty line if not enabled)
294 ifdef CONFIG_TRIM_UNUSED_KSYMS
295 cmd_undef_syms = $(NM) $@ | sed -n 's/^ \+U //p' | xargs echo
296 else
297 cmd_undef_syms = echo
298 endif
299
300 # Built-in and composite module parts
301 $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
302         $(call cmd,force_checksrc)
303         $(call if_changed_rule,cc_o_c)
304
305 # Single-part modules are special since we need to mark them in $(MODVERDIR)
306
307 $(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
308         $(call cmd,force_checksrc)
309         $(call if_changed_rule,cc_o_c)
310         @{ echo $(@:.o=.ko); echo $@; \
311            $(cmd_undef_syms); } > $(MODVERDIR)/$(@F:.o=.mod)
312
313 quiet_cmd_cc_lst_c = MKLST   $@
314       cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
315                      $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
316                                      System.map $(OBJDUMP) > $@
317
318 $(obj)/%.lst: $(src)/%.c FORCE
319         $(call if_changed_dep,cc_lst_c)
320
321 # Compile assembler sources (.S)
322 # ---------------------------------------------------------------------------
323
324 modkern_aflags := $(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL)
325
326 $(real-objs-m)      : modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
327 $(real-objs-m:.o=.s): modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
328
329 # .S file exports must have their C prototypes defined in asm/asm-prototypes.h
330 # or a file that it includes, in order to get versioned symbols. We build a
331 # dummy C file that includes asm-prototypes and the EXPORT_SYMBOL lines from
332 # the .S file (with trailing ';'), and run genksyms on that, to extract vers.
333 #
334 # This is convoluted. The .S file must first be preprocessed to run guards and
335 # expand names, then the resulting exports must be constructed into plain
336 # EXPORT_SYMBOL(symbol); to build our dummy C file, and that gets preprocessed
337 # to make the genksyms input.
338 #
339 # These mirror gensymtypes_c and co above, keep them in synch.
340 cmd_gensymtypes_S =                                                         \
341     (echo "\#include <linux/kernel.h>" ;                                    \
342      echo "\#include <asm/asm-prototypes.h>" ;                              \
343     $(CPP) $(a_flags) $< |                                                  \
344      grep "\<___EXPORT_SYMBOL\>" |                                          \
345      sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ) | \
346     $(CPP) -D__GENKSYMS__ $(c_flags) -xc - |                                \
347     $(GENKSYMS) $(if $(1), -T $(2))                                         \
348      $(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX))             \
349      $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
350      $(if $(KBUILD_PRESERVE),-p)                                            \
351      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
352
353 quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
354 cmd_cc_symtypes_S =                                                         \
355     set -e;                                                                 \
356     $(call cmd_gensymtypes_S,true,$@) >/dev/null;                           \
357     test -s $@ || rm -f $@
358
359 $(obj)/%.symtypes : $(src)/%.S FORCE
360         $(call cmd,cc_symtypes_S)
361
362
363 quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
364 cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
365
366 $(obj)/%.s: $(src)/%.S FORCE
367         $(call if_changed_dep,cpp_s_S)
368
369 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
370
371 ifndef CONFIG_MODVERSIONS
372 cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
373
374 else
375
376 ASM_PROTOTYPES := $(wildcard $(srctree)/arch/$(SRCARCH)/include/asm/asm-prototypes.h)
377
378 ifeq ($(ASM_PROTOTYPES),)
379 cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
380
381 else
382
383 # versioning matches the C process described above, with difference that
384 # we parse asm-prototypes.h C header to get function definitions.
385
386 cmd_as_o_S = $(CC) $(a_flags) -c -o $(@D)/.tmp_$(@F) $<
387
388 cmd_modversions_S =                                                             \
389         if $(OBJDUMP) -h $(@D)/.tmp_$(@F) | grep -q __ksymtab; then             \
390                 $(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))  \
391                     > $(@D)/.tmp_$(@F:.o=.ver);                                 \
392                                                                                 \
393                 $(LD) $(LDFLAGS) -r -o $@ $(@D)/.tmp_$(@F)                      \
394                         -T $(@D)/.tmp_$(@F:.o=.ver);                            \
395                 rm -f $(@D)/.tmp_$(@F) $(@D)/.tmp_$(@F:.o=.ver);                \
396         else                                                                    \
397                 mv -f $(@D)/.tmp_$(@F) $@;                                      \
398         fi;
399 endif
400 endif
401
402 $(obj)/%.o: $(src)/%.S $(objtool_obj) FORCE
403         $(call if_changed_rule,as_o_S)
404
405 targets += $(real-objs-y) $(real-objs-m) $(lib-y)
406 targets += $(extra-y) $(MAKECMDGOALS) $(always)
407
408 # Linker scripts preprocessor (.lds.S -> .lds)
409 # ---------------------------------------------------------------------------
410 quiet_cmd_cpp_lds_S = LDS     $@
411       cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -C -U$(ARCH) \
412                              -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
413
414 $(obj)/%.lds: $(src)/%.lds.S FORCE
415         $(call if_changed_dep,cpp_lds_S)
416
417 # ASN.1 grammar
418 # ---------------------------------------------------------------------------
419 quiet_cmd_asn1_compiler = ASN.1   $@
420       cmd_asn1_compiler = $(objtree)/scripts/asn1_compiler $< \
421                                 $(subst .h,.c,$@) $(subst .c,.h,$@)
422
423 .PRECIOUS: $(objtree)/$(obj)/%-asn1.c $(objtree)/$(obj)/%-asn1.h
424
425 $(obj)/%-asn1.c $(obj)/%-asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
426         $(call cmd,asn1_compiler)
427
428 # Build the compiled-in targets
429 # ---------------------------------------------------------------------------
430
431 # To build objects in subdirs, we need to descend into the directories
432 $(sort $(subdir-obj-y)): $(subdir-ym) ;
433
434 #
435 # Rule to compile a set of .o files into one .o file
436 #
437 ifdef builtin-target
438
439 ifdef CONFIG_THIN_ARCHIVES
440   cmd_make_builtin = rm -f $@; $(AR) rcST$(KBUILD_ARFLAGS)
441   cmd_make_empty_builtin = rm -f $@; $(AR) rcST$(KBUILD_ARFLAGS)
442   quiet_cmd_link_o_target = AR      $@
443 else
444   cmd_make_builtin = $(LD) $(ld_flags) -r -o
445   cmd_make_empty_builtin = rm -f $@; $(AR) rcs$(KBUILD_ARFLAGS)
446   quiet_cmd_link_o_target = LD      $@
447 endif
448
449 # If the list of objects to link is empty, just create an empty built-in.o
450 cmd_link_o_target = $(if $(strip $(obj-y)),\
451                       $(cmd_make_builtin) $@ $(filter $(obj-y), $^) \
452                       $(cmd_secanalysis),\
453                       $(cmd_make_empty_builtin) $@)
454
455 $(builtin-target): $(obj-y) FORCE
456         $(call if_changed,link_o_target)
457
458 targets += $(builtin-target)
459 endif # builtin-target
460
461 #
462 # Rule to create modules.order file
463 #
464 # Create commands to either record .ko file or cat modules.order from
465 # a subdirectory
466 modorder-cmds =                                         \
467         $(foreach m, $(modorder),                       \
468                 $(if $(filter %/modules.order, $m),     \
469                         cat $m;, echo kernel/$m;))
470
471 $(modorder-target): $(subdir-ym) FORCE
472         $(Q)(cat /dev/null; $(modorder-cmds)) > $@
473
474 #
475 # Rule to compile a set of .o files into one .a file
476 #
477 ifdef lib-target
478 quiet_cmd_link_l_target = AR      $@
479
480 ifdef CONFIG_THIN_ARCHIVES
481   cmd_link_l_target = rm -f $@; $(AR) rcsT$(KBUILD_ARFLAGS) $@ $(lib-y)
482 else
483   cmd_link_l_target = rm -f $@; $(AR) rcs$(KBUILD_ARFLAGS) $@ $(lib-y)
484 endif
485
486 $(lib-target): $(lib-y) FORCE
487         $(call if_changed,link_l_target)
488
489 targets += $(lib-target)
490
491 dummy-object = $(obj)/.lib_exports.o
492 ksyms-lds = $(dot-target).lds
493 ifdef CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX
494 ref_prefix = EXTERN(_
495 else
496 ref_prefix = EXTERN(
497 endif
498
499 quiet_cmd_export_list = EXPORTS $@
500 cmd_export_list = $(OBJDUMP) -h $< | \
501         sed -ne '/___ksymtab/s/.*+\([^ ]*\).*/$(ref_prefix)\1)/p' >$(ksyms-lds);\
502         rm -f $(dummy-object);\
503         echo | $(CC) $(a_flags) -c -o $(dummy-object) -x assembler -;\
504         $(LD) $(ld_flags) -r -o $@ -T $(ksyms-lds) $(dummy-object);\
505         rm $(dummy-object) $(ksyms-lds)
506
507 $(obj)/lib-ksyms.o: $(lib-target) FORCE
508         $(call if_changed,export_list)
509
510 targets += $(obj)/lib-ksyms.o
511
512 endif
513
514 #
515 # Rule to link composite objects
516 #
517 #  Composite objects are specified in kbuild makefile as follows:
518 #    <composite-object>-objs := <list of .o files>
519 #  or
520 #    <composite-object>-y    := <list of .o files>
521 #  or
522 #    <composite-object>-m    := <list of .o files>
523 #  The -m syntax only works if <composite object> is a module
524 link_multi_deps =                     \
525 $(filter $(addprefix $(obj)/,         \
526 $($(subst $(obj)/,,$(@:.o=-objs)))    \
527 $($(subst $(obj)/,,$(@:.o=-y)))       \
528 $($(subst $(obj)/,,$(@:.o=-m)))), $^)
529
530 cmd_link_multi-link = $(LD) $(ld_flags) -r -o $@ $(link_multi_deps) $(cmd_secanalysis)
531
532 ifdef CONFIG_THIN_ARCHIVES
533   quiet_cmd_link_multi-y = AR      $@
534   cmd_link_multi-y = rm -f $@; $(AR) rcST$(KBUILD_ARFLAGS) $@ $(link_multi_deps)
535 else
536   quiet_cmd_link_multi-y = LD      $@
537   cmd_link_multi-y = $(cmd_link_multi-link)
538 endif
539
540 quiet_cmd_link_multi-m = LD [M]  $@
541 cmd_link_multi-m = $(cmd_link_multi-link)
542
543 $(multi-used-y): FORCE
544         $(call if_changed,link_multi-y)
545 $(call multi_depend, $(multi-used-y), .o, -objs -y)
546
547 $(multi-used-m): FORCE
548         $(call if_changed,link_multi-m)
549         @{ echo $(@:.o=.ko); echo $(link_multi_deps); \
550            $(cmd_undef_syms); } > $(MODVERDIR)/$(@F:.o=.mod)
551 $(call multi_depend, $(multi-used-m), .o, -objs -y -m)
552
553 targets += $(multi-used-y) $(multi-used-m)
554
555
556 # Descending
557 # ---------------------------------------------------------------------------
558
559 PHONY += $(subdir-ym)
560 $(subdir-ym):
561         $(Q)$(MAKE) $(build)=$@
562
563 # Add FORCE to the prequisites of a target to force it to be always rebuilt.
564 # ---------------------------------------------------------------------------
565
566 PHONY += FORCE
567
568 FORCE:
569
570 # Read all saved command lines and dependencies for the $(targets) we
571 # may be building above, using $(if_changed{,_dep}). As an
572 # optimization, we don't need to read them if the target does not
573 # exist, we will rebuild anyway in that case.
574
575 targets := $(wildcard $(sort $(targets)))
576 cmd_files := $(wildcard $(foreach f,$(targets),$(dir $(f)).$(notdir $(f)).cmd))
577
578 ifneq ($(cmd_files),)
579   include $(cmd_files)
580 endif
581
582 # Declare the contents of the .PHONY variable as phony.  We keep that
583 # information in a variable se we can use it in if_changed and friends.
584
585 .PHONY: $(PHONY)