kbuild: asm offset generation for x86_64

Switch to a new way of generating a header file defining the offsets
into C structs for use in assembler code.

This method will hopefully be shared by all archs in the future.

The way to do handle things is taken from (or at least inspired by) 
Keith Owens' kbuild-2.5, so credit for this and the following patches
goes to him ;)

Makefile

@@ -420,8 +420,8 @@ $(patsubst %, _modinst_%, $(SUBDIRS)) :
 
 else # CONFIG_MODULES
 
-# ---------------------------------------------------------------------------
 # Modules not configured
+# ---------------------------------------------------------------------------
 
 modules modules_install: FORCE
 	@echo
@@ -433,6 +433,25 @@ modules modules_install: FORCE
 
 endif # CONFIG_MODULES
 
+# Generate asm-offsets.h 
+# ---------------------------------------------------------------------------
+
+define generate-asm-offsets.h
+	(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
+
 # RPM target
 # ---------------------------------------------------------------------------
 

arch/x86_64/Makefile

@@ -54,7 +54,7 @@ CFLAGS += -finline-limit=2000
 
 HEAD := arch/x86_64/kernel/head.o arch/x86_64/kernel/head64.o arch/x86_64/kernel/init_task.o
 
-SUBDIRS := arch/x86_64/tools $(SUBDIRS) arch/x86_64/kernel arch/x86_64/mm arch/x86_64/lib
+SUBDIRS += arch/x86_64/kernel arch/x86_64/mm arch/x86_64/lib
 CORE_FILES := arch/x86_64/kernel/kernel.o $(CORE_FILES)
 CORE_FILES +=  arch/x86_64/mm/mm.o
 LIBS := $(TOPDIR)/arch/x86_64/lib/lib.a $(LIBS)
@@ -78,36 +78,44 @@ vmlinux: arch/x86_64/vmlinux.lds
 .PHONY: zImage bzImage compressed zlilo bzlilo zdisk bzdisk install \
 		clean archclean archmrproper archdep checkoffset
 
-checkoffset: FORCE include/asm
-	make -C arch/$(ARCH)/tools $(TOPDIR)/include/asm-x86_64/offset.h
-
-bzImage: checkoffset vmlinux
+bzImage: vmlinux
 	@$(MAKEBOOT) bzImage
 
-bzImage-padded: checkoffset vmlinux
+bzImage-padded: vmlinux
 	@$(MAKEBOOT) bzImage-padded
 
 tmp:
 	@$(MAKEBOOT) BOOTIMAGE=bzImage zlilo
 
-bzlilo: checkoffset vmlinux
+bzlilo: vmlinux
 	@$(MAKEBOOT) BOOTIMAGE=bzImage zlilo
 
-bzdisk: checkoffset vmlinux
+bzdisk: vmlinux
 	@$(MAKEBOOT) BOOTIMAGE=bzImage zdisk
 
-install: checkoffset vmlinux
+install: vmlinux
 	@$(MAKEBOOT) BOOTIMAGE=bzImage install
 
 archclean:
 	@$(MAKEBOOT) clean
-	@$(MAKE) -C $(TOPDIR)/arch/x86_64/tools clean
 
 archmrproper:
-	rm -f $(TOPDIR)/arch/x86_64/tools/offset.h
-	rm -f $(TOPDIR)/arch/x86_64/tools/offset.tmp
-	rm -f $(TOPDIR)/include/asm-x86_64/offset.h
 
 archdep:
-	@$(MAKE) -C $(TOPDIR)/arch/x86_64/tools all
 	@$(MAKEBOOT) dep
+
+
+prepare: include/asm-$(ARCH)/offset.h
+
+arch/$(ARCH)/kernel/asm-offsets.s: include/asm include/linux/version.h \
+				   include/config/MARKER
+
+include/asm-$(ARCH)/offset.h.tmp: arch/$(ARCH)/kernel/asm-offsets.s
+	@$(generate-asm-offsets.h) < $< > $@
+
+include/asm-$(ARCH)/offset.h: include/asm-$(ARCH)/offset.h.tmp
+	@echo -n '  Generating $@'
+	@$(update-if-changed)
+
+CLEAN_FILES += include/asm-$(ARCH)/offset.h.tmp \
+	       include/asm-$(ARCH)/offset.h
\ No newline at end of file

arch/x86_64/tools/offset.c → arch/x86_64/kernel/asm-offsets.c

-/* Written 2000 by Andi Kleen */
-/* This program is never executed, just its assembly is examined for offsets 
-   (this trick is needed to get cross compiling right) */  
-/* $Id: offset.c,v 1.13 2002/01/08 15:19:57 ak Exp $ */
-#define ASM_OFFSET_H 1
-#ifndef __KERNEL__
-#define __KERNEL__ 
-#endif
+/*
+ * Generate definitions needed by assembly language modules.
+ * This code generates raw asm output which is post-processed to extract
+ * and format the required data.
+ */
+
 #include <linux/sched.h> 
 #include <linux/stddef.h>
 #include <linux/errno.h> 
@@ -15,26 +13,26 @@
 #include <asm/segment.h>
 #include <asm/thread_info.h>
 
-#define output(x) asm volatile ("--- " x)
-#define outconst(x,y) asm volatile ("--- " x : : "i" (y)) 
+#define DEFINE(sym, val) \
+        asm volatile("\n->" #sym " %0 " #val : : "i" (val))
 
-int main(void) 
-{ 
-	output("/* Auto generated by arch/../tools/offset.c at " __DATE__ ". Do not edit. */\n"); 
-	output("#ifndef ASM_OFFSET_H\n");
-	output("#define ASM_OFFSET_H 1\n"); 
+#define BLANK() asm volatile("\n->" : : )
 
-#define ENTRY(entry) outconst("#define tsk_" #entry " %0", offsetof(struct task_struct, entry))
+int main(void)
+{
+#define ENTRY(entry) DEFINE(tsk_ ## entry, offsetof(struct task_struct, entry))
 	ENTRY(state);
 	ENTRY(flags); 
 	ENTRY(thread); 
+	BLANK();
 #undef ENTRY
-#define ENTRY(entry) outconst("#define threadinfo_" #entry " %0", offsetof(struct thread_info, entry))
+#define ENTRY(entry) DEFINE(threadinfo__ ## entry, offsetof(struct thread_info, entry))
 	ENTRY(flags);
 	ENTRY(addr_limit);
 	ENTRY(preempt_count);
+	BLANK();
 #undef ENTRY
-#define ENTRY(entry) outconst("#define pda_" #entry " %0", offsetof(struct x8664_pda, entry))
+#define ENTRY(entry) DEFINE(pda__ ## entry, offsetof(struct x8664_pda, entry))
 	ENTRY(kernelstack); 
 	ENTRY(oldrsp); 
 	ENTRY(pcurrent); 
@@ -42,8 +40,7 @@ int main(void)
 	ENTRY(irqcount);
 	ENTRY(cpunumber);
 	ENTRY(irqstackptr);
+	BLANK();
 #undef ENTRY
-	output("#endif\n"); 
-
-	return(0); 
-} 
+	return 0;
+}

arch/x86_64/tools/Makefile

-
-TARGET = $(TOPDIR)/include/asm-x86_64/offset.h
-
-all: 
-
-mrproper:
-
-fastdep: $(TARGET)
-
-.PHONY: all
-
-$(TARGET): offset.h
-	cmp -s $^ $@ || (cp $^ $(TARGET).new && mv $(TARGET).new $(TARGET))
-
-.PHONY : offset.h all modules modules_install
-
-offset.h: offset.sed offset.c FORCE
-	$(CC) $(CFLAGS) -S -o offset.tmp offset.c
-	sed -n -f offset.sed < offset.tmp > offset.h   
-
-clean:
-	rm -f offset.[hs] $(TARGET).new offset.tmp
-
-mrproper:	
-	rm -f offset.[hs] $(TARGET)
-	rm -f $(TARGET)
-
-include $(TOPDIR)/Rules.make
-

arch/x86_64/tools/offset.sed

-/---/ {
-	s/---//
-	s/\$//
-	s/^	//
-	s/^ //
-	p
-}