Re: [patch 2/8] Kbuild: Create a way to create preprocessor constants from C expressions

[Sam Ravnborg <sam@ravnborg.org>]

Hi Christoph

Sorry for getting back to you so late. Too busy with day-time job atm.

On Wed, Mar 05, 2008 at 02:38:17PM -0800, Christoph Lameter wrote:
> 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.
> 
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Christoph Lameter <clameter@sgi.com>
> 
> ---
>  Kbuild                 |   31 +++++++++++++++++++++++++++++--
>  include/linux/bounds.h |   10 ++++++++++
>  kernel/bounds.c        |   16 ++++++++++++++++
>  3 files changed, 55 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6/Kbuild
> ===================================================================
> --- linux-2.6.orig/Kbuild	2008-02-29 19:27:40.000000000 -0800
> +++ linux-2.6/Kbuild	2008-02-29 19:29:38.000000000 -0800
> @@ -9,9 +9,10 @@
>  #
>  
>  offsets-file := include/asm-$(SRCARCH)/asm-offsets.h
> +bounds := include/linux/bounds.h
>  
> -always  := $(offsets-file)
> -targets := $(offsets-file)
> +always  := $(offsets-file) $(bounds)
> +targets := $(offsets-file) $(bounds)
>  targets += arch/$(SRCARCH)/kernel/asm-offsets.s
>  clean-files := $(addprefix $(objtree)/,$(targets))

We build a bounds.s file later so it needs to be listed as
we do with asm-offsets.s:

targets += kernel/bounds.s

>  
> @@ -39,6 +40,23 @@ define cmd_offsets
>  	 echo "#endif" ) > $@
>  endef
>  
> +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" ) > $@
> +endef
> +
>  # We use internal kbuild rules to avoid the "is up to date" message from make
>  arch/$(SRCARCH)/kernel/asm-offsets.s: arch/$(SRCARCH)/kernel/asm-offsets.c FORCE
>  	$(Q)mkdir -p $(dir $@)
> @@ -48,6 +66,15 @@ $(obj)/$(offsets-file): arch/$(SRCARCH)/
>  	$(Q)mkdir -p $(dir $@)
>  	$(call cmd,offsets)
>  
> +# 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)
OK

> +
> +$(obj)/$(bounds): kernel/bounds.s Kbuild
> +	$(Q)mkdir -p $(dir $@)
> +	$(call cmd,bounds)
OK


> +
>  #####
>  # 2) Check for missing system calls
>  #
> Index: linux-2.6/kernel/bounds.c
> ===================================================================
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ linux-2.6/kernel/bounds.c	2008-02-29 19:29:38.000000000 -0800
> @@ -0,0 +1,16 @@
> +/*
> + * Generate definitions needed by the preprocessor.
> + * This code generates raw asm output which is post-processed
> + * to extract and format the required data.
> + */
> +
> +#include <linux/mm.h>
> +
> +#define DEFINE(sym, val) \
> +        asm volatile("\n->" #sym " %0 " #val : : "i" (val))
> +
> +#define BLANK() asm volatile("\n->" : : )
> +
> +void foo(void)
> +{
> +}
> Index: linux-2.6/include/linux/bounds.h
> ===================================================================
> --- /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 @@
NO NO - we do not add files to the tree we overwrite.
The kbuild stuff will take care that the file is generated before
we start the kernel build.

I have fixed it up and rearranged stuff to follow the style
of the Kbuild file.

diff --git a/Kbuild b/Kbuild
index 1570d24..0198e3f 100644
--- a/Kbuild
+++ b/Kbuild
@@ -2,7 +2,8 @@
 # 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
+# 2) Generate bounds.h
+# 3) Check for missing system calls
 
 #####
 # 1) Generate asm-offsets.h
@@ -13,7 +14,7 @@ offsets-file := include/asm-$(SRCARCH)/asm-offsets.h
 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
@@ -49,7 +50,41 @@ $(obj)/$(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s Kbuild
 	$(call cmd,offsets)
 
 #####
-# 2) Check for missing system calls
+# 2) 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)
+
+#####
+# 3) Check for missing system calls
 #
 
 quiet_cmd_syscalls = CALL    $<
@@ -58,3 +93,7 @@ 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))
+

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