kbuild: create a way to create preprocessor constants from C expressions

The use of enums create constants that are not available to the preprocessor
when building the kernel (f.e.  MAX_NR_ZONES).

Arch code already has a way to export constants calculated to the preprocessor
through the asm-offsets.c file.  Generate something similar for the core
kernel through kbuild.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 48 insertions, 8 deletions

diff --git a/Kbuild b/Kbuild
index 1570d248ad92..7136de7b6fcb 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))
+