kbuild: full dependency check on asm-offsets.h

Building asm-offsets.h has been moved to a seperate Kbuild file
located in the top-level directory. This allow us to share the
functionality across the architectures.

The old rules in architecture specific Makefiles will die
in subsequent patches.

Furhtermore the usual kbuild dependency tracking is now used
when deciding to rebuild asm-offsets.s. So we no longer risk
to fail a rebuild caused by asm-offsets.c dependencies being touched.

With this common rule-set we now force the same name across
all architectures. Following patches will fix the rest.

Signed-off-by: Sam Ravnborg <[e-mail]>

Kbuild

···
+#
+# Kbuild for top-level directory of the kernel
+# This file takes care of the following:
+# 1) Generate asm-offsets.h
+
+#####
+# 1) Generate asm-offsets.h 
+#
+
+offsets-file := include/asm-$(ARCH)/asm-offsets.h
+
+always  := $(offsets-file)
+targets := $(offsets-file)
+targets += arch/$(ARCH)/kernel/asm-offsets.s
+
+quiet_cmd_offsets = GEN     $@
+define cmd_offsets
+	cat $< | \
+	(set -e; \
+	 echo "#ifndef __ASM_OFFSETS_H__"; \
+	 echo "#define __ASM_OFFSETS_H__"; \
+	 echo "/*"; \
+	 echo " * DO NOT MODIFY."; \
+	 echo " *"; \
+	 echo " * This file was generated by $(srctree)/Kbuild"; \
+	 echo " *"; \
+	 echo " */"; \
+	 echo ""; \
+	 sed -ne "/^->/{s:^->\([^ ]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:; s:->::; p;}"; \
+	 echo ""; \
+	 echo "#endif" ) > $@
+endef
+
+# We use internal kbuild rules to avoid the "is up to date" message from make
+arch/$(ARCH)/kernel/asm-offsets.s: arch/$(ARCH)/kernel/asm-offsets.c FORCE
+	$(Q)mkdir -p $(dir $@)
+	$(call if_changed_dep,cc_s_c)
+
+$(srctree)/$(offsets-file): arch/$(ARCH)/kernel/asm-offsets.s Kbuild
+	$(call cmd,offsets)
+

Makefile

···
 # A multi level approach is used. prepare1 is updated first, then prepare0.
 # prepare-all is the collection point for the prepare targets.
 
-.PHONY: prepare-all prepare prepare0 prepare1 prepare2
+.PHONY: prepare-all prepare prepare0 prepare1 prepare2 prepare3
 
-# prepare2 is used to check if we are building in a separate output directory,
+# prepare3 is used to check if we are building in a separate output directory,
 # and if so do:
 # 1) Check that make has not been executed in the kernel src $(srctree)
 # 2) Create the include2 directory, used for the second asm symlink
 
-prepare2:
+prepare3:
 ifneq ($(KBUILD_SRC),)
 	@echo '  Using $(srctree) as source for kernel'
 	$(Q)if [ -f $(srctree)/.config ]; then \
···
 	$(Q)ln -fsn $(srctree)/include/asm-$(ARCH) include2/asm
 endif
 
-# prepare1 creates a makefile if using a separate output directory
-prepare1: prepare2 outputmakefile
+# prepare2 creates a makefile if using a separate output directory
+prepare2: prepare3 outputmakefile
 
-prepare0: prepare1 include/linux/version.h include/asm \
+prepare1: prepare2 include/linux/version.h include/asm \
                    include/config/MARKER
 ifneq ($(KBUILD_MODULES),)
 	$(Q)rm -rf $(MODVERDIR)
 	$(Q)mkdir -p $(MODVERDIR)
 endif
 
+prepare0: prepare prepare1 FORCE
+	$(Q)$(MAKE) $(build)=$(srctree)
+
 # All the preparing..
-prepare-all: prepare0 prepare
+prepare-all: prepare0
 
 #	Leave this as default for preprocessing vmlinux.lds.S, which is now
 #	done in arch/$(ARCH)/kernel/Makefile
···
 
 endif # CONFIG_MODULES
 
-# Generate asm-offsets.h 
-# ---------------------------------------------------------------------------
-
-define filechk_gen-asm-offsets
-	(set -e; \
-	 echo "#ifndef __ASM_OFFSETS_H__"; \
-	 echo "#define __ASM_OFFSETS_H__"; \
-	 echo "/*"; \
-	 echo " * DO NOT MODIFY."; \
-	 echo " *"; \
-	 echo " * This file was generated by arch/$(ARCH)/Makefile"; \
-	 echo " *"; \
-	 echo " */"; \
-	 echo ""; \
-	 sed -ne "/^->/{s:^->\([^ ]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:; s:->::; p;}"; \
-	 echo ""; \
-	 echo "#endif" )
-endef
-
-
 ###
 # Cleaning is done on three levels.
 # make clean     Delete most generated files
···
 #
 clean: rm-dirs  := $(CLEAN_DIRS)
 clean: rm-files := $(CLEAN_FILES)
-clean-dirs      := $(addprefix _clean_,$(vmlinux-alldirs))
+clean-dirs      := $(addprefix _clean_,$(srctree) $(vmlinux-alldirs))
 
 .PHONY: $(clean-dirs) clean archclean
 $(clean-dirs):

arch/i386/Makefile

···
 install kernel_install:
 	$(Q)$(MAKE) $(build)=$(boot) BOOTIMAGE=$(KBUILD_IMAGE) install
 
-prepare: include/asm-$(ARCH)/asm_offsets.h
-CLEAN_FILES += include/asm-$(ARCH)/asm_offsets.h
-
-arch/$(ARCH)/kernel/asm-offsets.s: include/asm include/linux/version.h \
-				   include/config/MARKER
-
-include/asm-$(ARCH)/asm_offsets.h: arch/$(ARCH)/kernel/asm-offsets.s
-	$(call filechk,gen-asm-offsets)
-
 archclean:
 	$(Q)$(MAKE) $(clean)=arch/i386/boot
 

arch/i386/kernel/head.S

···
 #include <asm/desc.h>
 #include <asm/cache.h>
 #include <asm/thread_info.h>
-#include <asm/asm_offsets.h>
+#include <asm/asm-offsets.h>
 #include <asm/setup.h>
 
 /*

arch/i386/kernel/vsyscall-sigreturn.S

···
  */
 
 #include <asm/unistd.h>
-#include <asm/asm_offsets.h>
+#include <asm/asm-offsets.h>
 
 
 /* XXX

arch/i386/kernel/vsyscall.lds.S

···
  * object prelinked to its virtual address, and with only one read-only
  * segment (that fits in one page).  This script controls its layout.
  */
-#include <asm/asm_offsets.h>
+#include <asm/asm-offsets.h>
 
 SECTIONS
 {

arch/i386/power/swsusp.S

···
 #include <linux/linkage.h>
 #include <asm/segment.h>
 #include <asm/page.h>
-#include <asm/asm_offsets.h>
+#include <asm/asm-offsets.h>
 
 	.text
 

include/asm-i386/thread_info.h

···
 
 #else /* !__ASSEMBLY__ */
 
-#include <asm/asm_offsets.h>
+#include <asm/asm-offsets.h>
 
 #endif