[sparc] Stalingrad for kbuild army.

Documentation/sparc/README-2.5

+BTFIXUP
+-------
+
+To build new kernels you have to issue "make image". The ready kernel
+in ELF format is placed in arch/sparc/boot/image. Explanation is below.
+
+BTFIXUP is a unique feature of Linux/sparc among other architectures,
+developed by Jakub Jelinek (I think... Obviously David S. Miller took
+part, too). It allows to boot the same kernel at different 
+sub-architectures, such as sun4c, sun4m, sun4d, where SunOS uses
+different kernels. This feature is convinient for people who you move
+disks between boxes and for distrution builders.
+
+To function, BTFIXUP must link the kernel "in the draft" first,
+analyze the result, write a special stub code based on that, and
+build the final kernel with the stub (btfix.o).
+
+Kai Germaschewski improved the build system of the kernel in the 2.5 series
+significantly. Unfortunately, the traditional way of running the draft
+linking from architecture specific Makefile before the actual linking
+by generic Makefile is nearly impossible to support properly in the
+new build system. Therefore, the way we integrate BTFIXUP with the
+build system was changed in 2.5.40. Now, generic Makefile performs
+the draft linking and stores the result in file vmlinux. Architecture
+specific post-processing invokes BTFIXUP machinery and final linking
+in the same way as other architectures do bootstraps.
+
+Implications of that change are as follows.
+
+1. Hackers must type "make image" now, instead of just "make", in the same
+   way as s390 people do now. It is analogous to "make bzImage" on i386.
+   This does NOT affect sparc64, you continue to use "make" to build sparc64
+   kernels.
+
+2. vmlinux is not the final kernel, so RPM builders have to adjust
+   their spec files (if they delivered vmlinux for debugging).
+   System.map generated for vmlinux is still valid.
+
+3. Scripts that produce a.out images have to be changed. First, if they
+   invoke make, they have to use "make image". Second, they have to pick up
+   the new kernel in arch/sparc/boot/image instead of vmlinux.
+
+4. Since we are compliant with Kai's build system now, make -j is permitted.
+
+-- Pete Zaitcev
+zaitcev@yahoo.com

arch/sparc/Makefile

@@ -31,21 +31,22 @@ CFLAGS := $(CFLAGS) -m32 -pipe -mno-fpu -fcall-used-g5 -fcall-used-g7
 endif
 
 #LDFLAGS_vmlinux = -N -Ttext 0xf0004000
+#  Since 2.5.40, the first stage is left not btfix-ed.
+#  Actual linking is done with "make image".
+LDFLAGS_vmlinux = -r
 
 HEAD := arch/sparc/kernel/head.o arch/sparc/kernel/init_task.o
 
 core-y += arch/sparc/kernel/ arch/sparc/mm/ arch/sparc/math-emu/
 libs-y += arch/sparc/prom/ arch/sparc/lib/
 
-# This one has to come last
-SUBDIRS += arch/sparc/boot
-CORE_FILES_NO_BTFIX := $(addsuffix built-in.o,$(core-y))
-CORE_FILES += arch/sparc/boot/btfix.o
-
 # Export what is needed by arch/sparc/boot/Makefile
-export	CORE_FILES_NO_BTFIX
+export CORE_FILES
 export INIT
 
+image: vmlinux
+	$(MAKE) -C arch/sparc/boot image
+
 archclean:
 	rm -f $(TOPDIR)/vmlinux.aout
 	-$(MAKE) -C arch/sparc/boot clean

arch/sparc/boot/Makefile

@@ -20,25 +20,23 @@ btfixupprep: btfixupprep.c
 	$(HOSTCC) $(HOSTCFLAGS) -o btfixupprep btfixupprep.c
 
 clean:
-	rm -f btfixupprep piggyback tftpboot.img btfix.o btfix.s
+	rm -f btfixupprep piggyback tftpboot.img btfix.o btfix.s image
 
-#BTOBJS := $(HEAD) init/main.o init/version.o
 BTOBJS := $(HEAD) $(INIT)
-BTLIBS := $(CORE_FILES_NO_BTFIX) $(LIBS) \
+BTLIBS := $(CORE_FILES) $(LIBS) \
 	$(DRIVERS) $(NETWORKS)
 
-# I wanted to make this depend upon BTOBJS so that a parallel
-# build would work, but this fails because $(HEAD) cannot work
-# properly as it will cause head.o to be built with the implicit
-# rules not the ones in kernel/Makefile.  Someone please fix. --DaveM
-vmlinux.o: FORCE
-	$(LD) $(LDFLAGS) -r $(patsubst %,$(TOPDIR)/%,$(BTOBJS)) \
+# Actual linking
+image: btfix.o
+	$(LD) $(LDFLAGS) -T ../vmlinux.lds.s \
+		$(patsubst %,$(TOPDIR)/%,$(BTOBJS)) \
 		--start-group \
 		$(patsubst %,$(TOPDIR)/%,$(BTLIBS)) \
-		--end-group -o vmlinux.o
+		btfix.o \
+		--end-group -o image
 
-btfix.s: btfixupprep vmlinux.o
-	$(OBJDUMP) -x vmlinux.o | ./btfixupprep > btfix.s
+btfix.s: btfixupprep $(TOPDIR)/vmlinux
+	$(OBJDUMP) -x $(TOPDIR)/vmlinux | ./btfixupprep > btfix.s
 
 btfix.o: btfix.s
 	$(CC) -c -o btfix.o btfix.s