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Commit 1cdf25d7 authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
Browse files

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: default avatarSam Ravnborg <sam@ravnborg.org>
Signed-off-by: default avatarChristoph 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 308c05e3

Kbuild

+48 −8
Original line number Diff line number Diff line 
#

# 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))

kernel/bounds.c

0 → 100644
+19 −0
Original line number Diff line number Diff line 
/*

 * 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 */

}