kbuild: Generalize adding of additional sections to vmlinux

kallsyms needs to actually have a final vmlinux to extract the symbols,
and then add this information as a new section to the final vmlinux.

Currently, we basically just do the vmlinux link twice, adding
.tmp_kallsyms.o the second time. However, it's actually possible to just
link together the temporary vmlinux generated the first time and the
new object file directly without going back to all the single parts
that the temporary vmlinux was linked from.

This mechanism should be useful for sparc as well, where the btfix
mechanism needs an already linked vmlinux, too.

IMPORTANT: This does only work as desired if the link script can be
used recursively, i.e.

ld <flags> -T arch/$(ARCH)/vmlinux.lds.s -o vmlinux.test vmlinux

generates a vmlinux.test which is identical to vmlinux.
arch/i386/vmlinux.lds.S needed a little tweaking, so probably the
other archs do as well.

Makefile

@@ -285,8 +285,8 @@ export MODLIB
 
 vmlinux-objs := $(HEAD) $(init-y) $(core-y) $(libs-y) $(drivers-y) $(net-y)
 
-quiet_cmd_link_vmlinux = LD      $@
-define cmd_link_vmlinux
+quiet_cmd_ld_tmp_vmlinux = LD      $@
+define cmd_ld_tmp_vmlinux
 	$(LD) $(LDFLAGS) $(LDFLAGS_vmlinux) $(HEAD) $(init-y) \
 	--start-group \
 	$(core-y) \
@@ -294,21 +294,19 @@ define cmd_link_vmlinux
 	$(drivers-y) \
 	$(net-y) \
 	--end-group \
-	$(filter $(kallsyms.o),$^) \
 	-o $@
 endef
 
 #	set -e makes the rule exit immediately on error
 
-define rule_vmlinux
+define rule_ld_tmp_vmlinux
 	set -e
 	echo '  Generating build number'
 	. scripts/mkversion > .tmp_version
 	mv -f .tmp_version .version
 	+$(call descend,init,)
-	$(call cmd,link_vmlinux)
-	echo 'cmd_$@ := $(cmd_link_vmlinux)' > $(@D)/.$(@F).cmd
-	$(NM) $@ | grep -v '\(compiled\)\|\(\.o$$\)\|\( [aUw] \)\|\(\.\.ng$$\)\|\(LASH[RL]DI\)' | sort > System.map
+	$(call cmd,ld_tmp_vmlinux)
+	echo 'cmd_$@ := $(cmd_ld_tmp_vmlinux)' > $(@D)/.$(@F).cmd
 endef
 
 LDFLAGS_vmlinux += -T arch/$(ARCH)/vmlinux.lds.s
@@ -317,33 +315,42 @@ LDFLAGS_vmlinux += -T arch/$(ARCH)/vmlinux.lds.s
 
 ifdef CONFIG_KALLSYMS
 
-kallsyms.o := .tmp_kallsyms.o
+final-objs += .tmp_kallsyms.o
 
 quiet_cmd_kallsyms = KSYM    $@
-cmd_kallsyms = $(KALLSYMS) $< > $@
+define cmd_kallsyms
+	$(KALLSYMS) $< > $@
+endef
 
 .tmp_kallsyms.o: .tmp_vmlinux
 	$(call cmd,kallsyms)
 
-# 	After generating .tmp_vmlinux just like vmlinux, decrement the version
-#	number again, so the final vmlinux gets the same one.
-#	Ignore return value of 'expr'.
+endif
 
-define rule_.tmp_vmlinux
-	$(rule_vmlinux)
-	if expr 0`cat .version` - 1 > .tmp_version; then true; fi
-	mv -f .tmp_version .version
-endef
+#	Link a temporary vmlinux for postprocessing
+#	(e.g. kallsyms)
 
 .tmp_vmlinux: $(vmlinux-objs) arch/$(ARCH)/vmlinux.lds.s FORCE
-	$(call if_changed_rule,.tmp_vmlinux)
-
-endif
+	$(call if_changed_rule,ld_tmp_vmlinux)
 
 #	Finally the vmlinux rule
 
-vmlinux: $(vmlinux-objs) $(kallsyms.o) arch/$(ARCH)/vmlinux.lds.s FORCE
-	$(call if_changed_rule,vmlinux)
+quiet_cmd_ld_vmlinux = LD      $(echo_target)
+cmd_ld_vmlinux = $(LD) $(LDFLAGS) $(LDFLAGS_$(@F)) \
+	       $(filter-out FORCE,$^) -o $@
+
+define rule_ld_vmlinux
+	set -e
+	$(call cmd,ld_vmlinux)
+	echo 'cmd_$@ := $(cmd_ld_vmlinux)' > $(@D)/.$(@F).cmd
+	$(NM) $@ | grep -v '\(compiled\)\|\(\.o$$\)\|\( [aUw] \)\|\(\.\.ng$$\)\|\(LASH[RL]DI\)' | sort > System.map
+endef
+
+#	Link the actual vmlinux, which is temporary one from above,
+#	and possibly additional sections given in $(final-objs)
+
+vmlinux: .tmp_vmlinux $(final-objs) arch/$(ARCH)/vmlinux.lds.s FORCE
+	$(call if_changed_rule,ld_vmlinux)
 
 #	The actual objects are generated when descending, 
 #	make sure no implicit rule kicks in
@@ -861,6 +868,17 @@ ifneq ($(cmd_files),)
   include $(cmd_files)
 endif
 
+# function to only execute the passed command if necessary
+
+if_changed = $(if $(strip $? \
+		          $(filter-out $(cmd_$(1)),$(cmd_$@))\
+			  $(filter-out $(cmd_$@),$(cmd_$(1)))),\
+	@set -e; \
+	$(if $($(quiet)cmd_$(1)),echo '  $($(quiet)cmd_$(1))';) \
+	$(cmd_$(1)); \
+	echo 'cmd_$@ := $(cmd_$(1))' > $(@D)/.$(@F).cmd)
+
+
 # execute the command and also postprocess generated .d dependencies
 # file
 

arch/i386/vmlinux.lds.S

@@ -49,6 +49,7 @@ SECTIONS
   __setup_end = .;
   __initcall_start = .;
   .initcall.init : {
+	*(.initcall.init)
 	*(.initcall1.init) 
 	*(.initcall2.init) 
 	*(.initcall3.init) 
@@ -72,7 +73,7 @@ SECTIONS
   __nosave_end = .;
 
   . = ALIGN(4096);
-  .data.page_aligned : { *(.data.idt) }
+  .data.page_aligned : {  *(.data.page_aligned) *(.data.idt) }
 
   . = ALIGN(32);
   .data.cacheline_aligned : { *(.data.cacheline_aligned) }