From sam@ravnborg.org Thu Mar  6 12:59:38 2008
Date: Thu, 6 Mar 2008 22:00:05 +0100
From: Sam Ravnborg <sam@ravnborg.org>
To: Christoph Lameter <clameter@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, ak@suse.de, Mel Gorman <mel@csn.ul.ie>, apw@shadowen.org, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Rik van Riel <riel@redhat.com>, linux-mm@kvack.org
Subject: Re: [patch 2/8] Kbuild: Create a way to create preprocessor constants from C expressions

On Thu, Mar 06, 2008 at 12:20:17PM -0800, Christoph Lameter wrote:
> On Wed, 5 Mar 2008, Andrew Morton wrote:
> 
> > > --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> > > +++ linux-2.6/include/linux/bounds.h	2008-02-29 19:29:50.000000000 -0800
> > > @@ -0,0 +1,10 @@
> > > +#ifndef __LINUX_BOUNDS_H__
> > > +#define __LINUX_BOUNDS_H__
> > > +/*
> > > + * DO NOT MODIFY.
> > > + *
> > > + * This file was generated by Kbuild
> > > + *
> > > + */
> > > +
> > > +#endif
> > 
> > a) I'm not sure that we should check in a file which is supposed to get
> >    overwritten at build-time.
> 
> Well but it needs to be present in order to generate it. If the 
> definitions are not present then the new values of the constants cannot be 
> determined. A .config determined the value of these.

Ehh - the file above is empty.
I do not understand why we need an empty file to be present???

>  
> > b) Is this `make O=' friendly?
> 
> These are just symbol definitions. Should be handled the 
> same way as arch/x86/*/asm-offsets.* stuff 
> 
> > c)
> > 	make mrproper
> > 	make allmodconfig
> > 	make
> > 
> > In file included from include/linux/mm.h:192,
> >                  from include/linux/suspend.h:11,
> >                  from arch/x86/kernel/asm-offsets_64.c:12,
> >                  from arch/x86/kernel/asm-offsets.c:4:
> > include/linux/page-flags.h:10:26: error: linux/bounds.h: No such file or directory
> 
So asm-offset need bounds.h.
We better tell make so - updated patch below.

	Sam

diff --git a/Kbuild b/Kbuild
index 1570d24..2a52057 100644
--- a/Kbuild
+++ b/Kbuild
@@ -1,19 +1,54 @@
 #
 # Kbuild for top-level directory of the kernel
 # This file takes care of the following:
-# 1) Generate asm-offsets.h
-# 2) Check for missing system calls
+# 1) Generate bounds.h
+# 2) Generate asm-offsets.h (may need bounds.h)
+# 3) Check for missing system calls
 
 #####
-# 1) Generate asm-offsets.h
+# 1) Generate bounds.h
+
+bounds-file := include/linux/bounds.h
+
+always  := $(bounds-file)
+targets := $(bounds-file) kernel/bounds.s
+
+quiet_cmd_bounds = GEN     $@
+define cmd_bounds
+	(set -e; \
+	 echo "#ifndef __LINUX_BOUNDS_H__"; \
+	 echo "#define __LINUX_BOUNDS_H__"; \
+	 echo "/*"; \
+	 echo " * DO NOT MODIFY."; \
+	 echo " *"; \
+	 echo " * This file was generated by Kbuild"; \
+	 echo " *"; \
+	 echo " */"; \
+	 echo ""; \
+	 sed -ne $(sed-y) $<; \
+	 echo ""; \
+	 echo "#endif" ) > $@
+endef
+
+# We use internal kbuild rules to avoid the "is up to date" message from make
+kernel/bounds.s: kernel/bounds.c FORCE
+	$(Q)mkdir -p $(dir $@)
+	$(call if_changed_dep,cc_s_c)
+
+$(obj)/$(bounds-file): kernel/bounds.s Kbuild
+	$(Q)mkdir -p $(dir $@)
+	$(call cmd,bounds)
+
+#####
+# 2) Generate asm-offsets.h
 #
 
 offsets-file := include/asm-$(SRCARCH)/asm-offsets.h
 
-always  := $(offsets-file)
-targets := $(offsets-file)
+always  += $(offsets-file)
+targets += $(offsets-file)
 targets += arch/$(SRCARCH)/kernel/asm-offsets.s
-clean-files := $(addprefix $(objtree)/,$(targets))
+
 
 # Default sed regexp - multiline due to syntax constraints
 define sed-y
@@ -40,7 +75,8 @@ define cmd_offsets
 endef
 
 # We use internal kbuild rules to avoid the "is up to date" message from make
-arch/$(SRCARCH)/kernel/asm-offsets.s: arch/$(SRCARCH)/kernel/asm-offsets.c FORCE
+arch/$(SRCARCH)/kernel/asm-offsets.s: arch/$(SRCARCH)/kernel/asm-offsets.c \
+                                      $(obj)/$(bounds-file) FORCE
 	$(Q)mkdir -p $(dir $@)
 	$(call if_changed_dep,cc_s_c)
 
@@ -49,7 +85,7 @@ $(obj)/$(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s Kbuild
 	$(call cmd,offsets)
 
 #####
-# 2) Check for missing system calls
+# 3) Check for missing system calls
 #
 
 quiet_cmd_syscalls = CALL    $<
@@ -58,3 +94,7 @@ quiet_cmd_syscalls = CALL    $<
 PHONY += missing-syscalls
 missing-syscalls: scripts/checksyscalls.sh FORCE
 	$(call cmd,syscalls)
+
+# Delete all targets during make clean
+clean-files := $(addprefix $(objtree)/,$(targets))
+