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

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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>
This commit is contained in:
Christoph Lameter 2008-04-28 02:12:44 -07:00 committed by Linus Torvalds
parent 308c05e35e
commit 1cdf25d704
2 changed files with 67 additions and 8 deletions
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56
Kbuild
View file

@ -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))

19
kernel/bounds.c Normal file
View file

@ -0,0 +1,19 @@
/*
* Generate definitions needed by the preprocessor.
* This code generates raw asm output which is post-processed
* to extract and format the required data.
*/
#define __GENERATING_BOUNDS_H
/* Include headers that define the enum constants of interest */
#define DEFINE(sym, val) \
asm volatile("\n->" #sym " %0 " #val : : "i" (val))
#define BLANK() asm volatile("\n->" : : )
void foo(void)
{
/* The enum constants to put into include/linux/bounds.h */
/* End of constants */
}