criu/pie/Makefile: simplify and fix

The way criu/pie/Makefile is currently written, ld is run twice:

 1. link $(NAME-obj-y) objects to NAME.built-in.o

 2. link NAME.built-in.o, pie.lib.a, and compel plugins
    to NAME.built-in.bin.o (with compel ldflags and linker script)

There is absolutely no need for such two-stage linking, but it was OK.
It is not OK now, as "compel ldflags" for ARM doesn't need -r, and we
can't run the first stage with -r and the second stage without it.

So, let's simplify linking using a single ld invocation. This is my
third attempt in doing it, I think I nailed it this time -- it is now
clean and (relatively) simple.

While at it:
 - fix compel linker script dependency (it was not working);
 - rearrange the Makefile so variables goes first, then rules;
 - remove a comment about mount implementation in restorer.

NOTE that compel is called with ./ prefix so the file paths it prints
are also prefixed with ./, which is needed for objectify macro to ignore
those.
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Makefile.compel

-COMPEL_BIN		:= compel/compel-host
+COMPEL_BIN		:= ./compel/compel-host
 export COMPEL_BIN
 
 COMPEL_VERSION_HEADER	:= compel/include/version.h

criu/pie/Makefile

-target		+= parasite restorer
-
-parasite-obj-y	+= parasite.o
-restorer-obj-y	+= restorer.o
-restorer-obj-y	+= ./$(ARCH_DIR)/restorer.o
-
-ifeq ($(ARCH),x86)
-        ifeq ($(CONFIG_COMPAT),y)
-                restorer-obj-y	+= ./$(ARCH_DIR)/call32.o
-                restorer-obj-y	+= ./$(ARCH_DIR)/sigaction_compat_pie.o
-        endif
-endif
-
-#
-# We can't provide proper mount implementation
-# in parasite code -- it requires run-time rellocation
-# applications, which is not the target of the
-# project.
-#
-CFLAGS		:= $(filter-out -pg $(CFLAGS-GCOV),$(CFLAGS))
-CFLAGS		:= $(filter-out $(CFLAGS-ASAN),$(CFLAGS))
+target		:= parasite restorer
 
+CFLAGS		:= $(filter-out -pg $(CFLAGS-GCOV) $(CFLAGS-ASAN),$(CFLAGS))
 ccflags-y	+= $(COMPEL_UAPI_INCLUDES)
 ccflags-y	+= -DCR_NOGLIBC
 ccflags-y	+= -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0
 ccflags-y	+= -Wp,-U_FORTIFY_SOURCE -Wp,-D_FORTIFY_SOURCE=0
 
 ifneq ($(filter-out clean mrproper,$(MAKECMDGOALS)),)
-        CFLAGS	+= $(shell $(COMPEL_BIN) cflags)
-	compel_std	:= $(shell $(COMPEL_BIN) plugins)
+	CFLAGS		+= $(shell $(COMPEL_BIN) cflags)
+	LDFLAGS		+= $(shell $(COMPEL_BIN) ldflags)
+	compel_plugins	:= $(shell $(COMPEL_BIN) plugins)
 endif
 
 ifeq ($(SRCARCH),arm)
-        ccflags-y	+= -marm
+	ccflags-y	+= -marm
 endif
 
 asflags-y	+= -D__ASSEMBLY__
 
-BLOBS		+= $(obj)/restorer-blob.h $(obj)/parasite-blob.h
 LDS		:= compel/arch/$(SRCARCH)/scripts/compel-pack.lds.S
 
-.SECONDARY:
+restorer-obj-y	+= ./$(ARCH_DIR)/restorer.o
+
+ifeq ($(ARCH),x86)
+        ifeq ($(CONFIG_COMPAT),y)
+                restorer-obj-y	+= ./$(ARCH_DIR)/call32.o
+                restorer-obj-y	+= ./$(ARCH_DIR)/sigaction_compat_pie.o
+        endif
+endif
+
+define gen-pie-rules
+$(1)-obj-y	+= $(1).o
+$(1)-obj-e	+= pie.lib.a
+$(1)-obj-e	+= $$(compel_plugins)
 
-target-name = $(patsubst criu/pie/%-blob.h,%,$(1))
+# Dependency on compel linker script, to relink if it has changed
+$$(obj)/$(1).built-in.o: $$(LDS)
 
-$(obj)/%.build-in.bin.o: $(LDS)
-$(obj)/%.built-in.bin.o: $(obj)/%.built-in.o $(obj)/pie.lib.a $(compel_std)
-	$(call msg-gen, $@)
-	$(Q) $(LD) $(shell $(COMPEL_BIN) ldflags) -o $@ $^
+$$(obj)/$(1)-blob.h: $$(obj)/$(1).built-in.o
+	$$(call msg-gen, $$@)
+	$$(Q) $$(COMPEL_BIN) hgen -f $$< -o $$@
 
-$(obj)/%-blob.h: $(obj)/%.built-in.bin.o
-	$(call msg-gen, $@)
-	$(Q) $(COMPEL_BIN) hgen -f $< -o $@
+all-y		+= $$(obj)/$(1)-blob.h
+cleanup-y	+= $$(obj)/$(1)-blob.h
+endef
 
-all-y += $(BLOBS)
-# blobs and pields are in cleanup, rather than in mrproper because
-# we want them to be re-generated after `make clean && make`
-cleanup-y += $(BLOBS)
-cleanup-y += $(obj)/*.bin
-cleanup-y += $(obj)/*.built-in.bin.o
-cleanup-y += $(obj)/*.built-in.bin
+$(foreach t,$(target),$(eval $(call gen-pie-rules,$(t))))