#
  # Building vDSO images for x86.
  #
  
  VDSO64-$(CONFIG_X86_64)		:= y
  VDSOX32-$(CONFIG_X86_X32_ABI)	:= y
  VDSO32-$(CONFIG_X86_32)		:= y
  VDSO32-$(CONFIG_COMPAT)		:= y
  
  vdso-install-$(VDSO64-y)	+= vdso.so
  vdso-install-$(VDSOX32-y)	+= vdsox32.so
  vdso-install-$(VDSO32-y)	+= $(vdso32-images)
  
  
  # files to link into the vdso
  vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o
  
  vobjs-$(VDSOX32-y) += $(vobjx32s-compat)
  
  # Filter out x32 objects.
  vobj64s := $(filter-out $(vobjx32s-compat),$(vobjs-y))
  
  # files to link into kernel
  obj-$(VDSO64-y)			+= vma.o vdso.o
  obj-$(VDSOX32-y)		+= vdsox32.o
  obj-$(VDSO32-y)			+= vdso32.o vdso32-setup.o
  
  vobjs := $(foreach F,$(vobj64s),$(obj)/$F)
  
  $(obj)/vdso.o: $(obj)/vdso.so
  
  targets += vdso.so vdso.so.dbg vdso.lds $(vobjs-y)
  
  export CPPFLAGS_vdso.lds += -P -C
  
  VDSO_LDFLAGS_vdso.lds = -m64 -Wl,-soname=linux-vdso.so.1 \
  			-Wl,--no-undefined \
  		      	-Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096
  
  $(obj)/vdso.o: $(src)/vdso.S $(obj)/vdso.so
  
  $(obj)/vdso.so.dbg: $(src)/vdso.lds $(vobjs) FORCE
  	$(call if_changed,vdso)
  
  $(obj)/%.so: OBJCOPYFLAGS := -S
  $(obj)/%.so: $(obj)/%.so.dbg FORCE
  	$(call if_changed,objcopy)
  
  #
  # Don't omit frame pointers for ease of userspace debugging, but do
  # optimize sibling calls.
  #
  CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
         $(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
         -fno-omit-frame-pointer -foptimize-sibling-calls
  
  $(vobjs): KBUILD_CFLAGS += $(CFL)
  
  #
  # vDSO code runs in userspace and -pg doesn't help with profiling anyway.
  #
  CFLAGS_REMOVE_vdso-note.o = -pg
  CFLAGS_REMOVE_vclock_gettime.o = -pg
  CFLAGS_REMOVE_vgetcpu.o = -pg
  CFLAGS_REMOVE_vvar.o = -pg
  
  targets += vdso-syms.lds
  obj-$(VDSO64-y)			+= vdso-syms.lds
  
  #
  # Match symbols in the DSO that look like VDSO*; produce a file of constants.
  #
  sed-vdsosym := -e 's/^00*/0/' \
  	-e 's/^\([0-9a-fA-F]*\) . \(VDSO[a-zA-Z0-9_]*\)$$/\2 = 0x\1;/p'
  quiet_cmd_vdsosym = VDSOSYM $@
  define cmd_vdsosym
  	$(NM) $< | LC_ALL=C sed -n $(sed-vdsosym) | LC_ALL=C sort > $@
  endef
  
  $(obj)/%-syms.lds: $(obj)/%.so.dbg FORCE
  	$(call if_changed,vdsosym)
  
  #
  # X32 processes use x32 vDSO to access 64bit kernel data.
  #
  # Build x32 vDSO image:
  # 1. Compile x32 vDSO as 64bit.
  # 2. Convert object files to x32.
  # 3. Build x32 VDSO image with x32 objects, which contains 64bit codes
  # so that it can reach 64bit address space with 64bit pointers.
  #
  
  targets += vdsox32-syms.lds
  obj-$(VDSOX32-y)		+= vdsox32-syms.lds
  
  CPPFLAGS_vdsox32.lds = $(CPPFLAGS_vdso.lds)
  VDSO_LDFLAGS_vdsox32.lds = -Wl,-m,elf32_x86_64 \
  			   -Wl,-soname=linux-vdso.so.1 \
  			   -Wl,-z,max-page-size=4096 \
  			   -Wl,-z,common-page-size=4096
  
  vobjx32s-y := $(vobj64s:.o=-x32.o)
  vobjx32s := $(foreach F,$(vobjx32s-y),$(obj)/$F)
  
  # Convert 64bit object file to x32 for x32 vDSO.
  quiet_cmd_x32 = X32     $@
        cmd_x32 = $(OBJCOPY) -O elf32-x86-64 $< $@
  
  $(obj)/%-x32.o: $(obj)/%.o FORCE
  	$(call if_changed,x32)
  
  targets += vdsox32.so vdsox32.so.dbg vdsox32.lds $(vobjx32s-y)
  
  $(obj)/vdsox32.o: $(src)/vdsox32.S $(obj)/vdsox32.so
  
  $(obj)/vdsox32.so.dbg: $(src)/vdsox32.lds $(vobjx32s) FORCE
  	$(call if_changed,vdso)
  
  #
  # Build multiple 32-bit vDSO images to choose from at boot time.
  #
  obj-$(VDSO32-y)			+= vdso32-syms.lds
  vdso32.so-$(VDSO32-y)		+= int80
  vdso32.so-$(CONFIG_COMPAT)	+= syscall
  vdso32.so-$(VDSO32-y)		+= sysenter
  
  vdso32-images			= $(vdso32.so-y:%=vdso32-%.so)
  
  CPPFLAGS_vdso32.lds = $(CPPFLAGS_vdso.lds)
  VDSO_LDFLAGS_vdso32.lds = -m32 -Wl,-soname=linux-gate.so.1
  
  # This makes sure the $(obj) subdirectory exists even though vdso32/
  # is not a kbuild sub-make subdirectory.
  override obj-dirs = $(dir $(obj)) $(obj)/vdso32/
  
  targets += vdso32/vdso32.lds
  targets += $(vdso32-images) $(vdso32-images:=.dbg)
  targets += vdso32/note.o $(vdso32.so-y:%=vdso32/%.o)
  
  extra-y	+= $(vdso32-images)
  
  $(obj)/vdso32.o: $(vdso32-images:%=$(obj)/%)
  
  KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS))
  $(vdso32-images:%=$(obj)/%.dbg): KBUILD_AFLAGS = $(KBUILD_AFLAGS_32)
  $(vdso32-images:%=$(obj)/%.dbg): asflags-$(CONFIG_X86_64) += -m32
  
  $(vdso32-images:%=$(obj)/%.dbg): $(obj)/vdso32-%.so.dbg: FORCE \
  				 $(obj)/vdso32/vdso32.lds \
  				 $(obj)/vdso32/note.o \
  				 $(obj)/vdso32/%.o
  	$(call if_changed,vdso)
  
  # Make vdso32-*-syms.lds from each image, and then make sure they match.
  # The only difference should be that some do not define VDSO32_SYSENTER_RETURN.
  
  targets += vdso32-syms.lds $(vdso32.so-y:%=vdso32-%-syms.lds)
  
  quiet_cmd_vdso32sym = VDSOSYM $@
  define cmd_vdso32sym
  	if LC_ALL=C sort -u $(filter-out FORCE,$^) > $(@D)/.tmp_$(@F) && \
  	   $(foreach H,$(filter-out FORCE,$^),\
  		     if grep -q VDSO32_SYSENTER_RETURN $H; \
  		     then diff -u $(@D)/.tmp_$(@F) $H; \
  		     else sed /VDSO32_SYSENTER_RETURN/d $(@D)/.tmp_$(@F) | \
  			  diff -u - $H; fi &&) : ;\
  	then mv -f $(@D)/.tmp_$(@F) $@; \
  	else rm -f $(@D)/.tmp_$(@F); exit 1; \
  	fi
  endef
  
  $(obj)/vdso32-syms.lds: $(vdso32.so-y:%=$(obj)/vdso32-%-syms.lds) FORCE
  	$(call if_changed,vdso32sym)
  
  #
  # The DSO images are built using a special linker script.
  #
  quiet_cmd_vdso = VDSO    $@
        cmd_vdso = $(CC) -nostdlib -o $@ \
  		       $(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \
  		       -Wl,-T,$(filter %.lds,$^) $(filter %.o,$^) && \
  		 sh $(srctree)/$(src)/checkundef.sh '$(NM)' '$@'
  
  VDSO_LDFLAGS = -fPIC -shared $(call cc-ldoption, -Wl$(comma)--hash-style=sysv)
  GCOV_PROFILE := n
  
  #
  # Install the unstripped copy of vdso*.so listed in $(vdso-install-y).
  #
  quiet_cmd_vdso_install = INSTALL $@
        cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
  $(vdso-install-y): %.so: $(obj)/%.so.dbg FORCE
  	@mkdir -p $(MODLIB)/vdso
  	$(call cmd,vdso_install)
  
  PHONY += vdso_install $(vdso-install-y)
  vdso_install: $(vdso-install-y)
  
  clean-files := vdso32-syscall* vdso32-sysenter* vdso32-int80*