linking: link bootblock.elf with .data and .bss sections again

Currently coreboot expects the loader to clear the bss section
for all stages. i.e. stages don't clear their own bss. On ARM
SoCs the BootROM would be responsible for this. To do that
one needs to include the bss section data (all zeros) in the
bootblock.bin file. This was previously being attempted by
keeping the .bss info in the .data section because objcopy
happened zero out non-file allocated data section data.

Instead go back to linking bootblock with the bss section
but mark the bss section as loadable allocatable data. That
way it will be included in the binary properly when objcopy
-O binary is emplyed. Also do the same for the data section
in the case of no non-zero object values are in the data
section.

Without this change the trick of including .bss in .data
was not working when there wasn't a non-zero value object
in the data section.

BUG=None
BRANCH=None
TEST=Built emulation/qemu-armv7 and noted bootblock.bin contains
     the cleared bss.

Change-Id: I94bd404c2c4a8b9332393e6224e98940a9cad4a2
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/11680
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

Makefile.inc

@@ -531,10 +531,19 @@ find-substr = $(word 1,$(subst _, ,$(1)))
 # and remove .x the next time and finally return romstage
 find-class = $(if $(filter $(1),$(basename $(1))),$(if $(CC_$(1)), $(1), $(call find-substr,$(1))),$(call find-class,$(basename $(1))))
 
-$(objcbfs)/%.bin: $(objcbfs)/%.elf
-	$(eval class := $(call find-class,$(@F)))
-	@printf "    OBJCOPY    $(subst $(obj)/,,$(@))\n"
-	$(OBJCOPY_$(class)) -O binary $< $@
+# Bootblocks are not CBFS stages. coreboot is currently expecting the bss to
+# be cleared by the loader of the stage. For ARM SoCs that means one needs to
+# include the bss section in the binary so the BootROM clears the bss on
+# loading of the bootblock stage. Achieve this by marking the bss section
+# loadable,allocatable, and data. Do the same for the .data section in case
+# it's marked as NOBITS.
+$(objcbfs)/bootblock.raw.bin: $(objcbfs)/bootblock.elf
+	@printf "    OBJCOPY    $(notdir $(@))\n"
+	$(OBJCOPY_bootblock) --set-section-flags .bss=load,alloc,data --set-section-flags .data=load,alloc,data $< $<.tmp
+	$(OBJCOPY_bootblock) -O binary $<.tmp $@
+
+$(objcbfs)/%.bin: $(objcbfs)/%.raw.bin
+	cp $< $@
 
 $(objcbfs)/%.elf: $(objcbfs)/%.debug
 	$(eval class := $(call find-class,$(@F)))