Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 20a468b5 authored by Sam Ravnborg's avatar Sam Ravnborg
Browse files

kbuild: make cc-version available in kbuild files 



Move $(CC) support functions to Kbuild.include so they are available
in the kbuild files.
In addition the following was done:
	o as-option documented in Documentation/kbuild/makefiles.txt
	o Moved documentation to new section to match
	  new scope of functions
	o added cc-ifversion used to conditionally select a text string
	  dependent on actual $(CC) version
	o documented cc-ifversion
	o change so Kbuild.include is read before the kbuild file

Signed-off-by: default avatarSam Ravnborg <sam@ravnborg.org>
parent b39927cf

Documentation/kbuild/makefiles.txt

+97 −69
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ This document describes the Linux kernel Makefiles. 
	   --- 3.8 Command line dependency

	   --- 3.9 Dependency tracking

	   --- 3.10 Special Rules

	   --- 3.11 $(CC) support functions



	=== 4 Host Program support

	   --- 4.1 Simple Host Program
@@ -38,7 +39,6 @@ This document describes the Linux kernel Makefiles. 
	   --- 6.6 Commands useful for building a boot image

	   --- 6.7 Custom kbuild commands

	   --- 6.8 Preprocessing linker scripts

	   --- 6.9 $(CC) support functions



	=== 7 Kbuild Variables

	=== 8 Makefile language
@@ -385,6 +385,102 @@ more details, with real examples. 
	to prerequisites are referenced with $(src) (because they are not

	generated files).



--- 3.11 $(CC) support functions



	The kernel may be build with several different versions of

	$(CC), each supporting a unique set of features and options.

	kbuild provide basic support to check for valid options for $(CC).

	$(CC) is useally the gcc compiler, but other alternatives are

	available.



    as-option

    	as-option is used to check if $(CC) when used to compile

	assembler (*.S) files supports the given option. An optional

	second option may be specified if first option are not supported.



	Example:

		#arch/sh/Makefile

		cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),)



	In the above example cflags-y will be assinged the the option

	-Wa$(comma)-isa=$(isa-y) if it is supported by $(CC).

	The second argument is optional, and if supplied will be used

	if first argument is not supported.



    cc-option

	cc-option is used to check if $(CC) support a given option, and not

	supported to use an optional second option.



	Example:

		#arch/i386/Makefile

		cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)



	In the above example cflags-y will be assigned the option

	-march=pentium-mmx if supported by $(CC), otherwise -march-i586.

	The second argument to cc-option is optional, and if omitted

	cflags-y will be assigned no value if first option is not supported.



   cc-option-yn

   	cc-option-yn is used to check if gcc supports a given option

	and return 'y' if supported, otherwise 'n'.



	Example:

		#arch/ppc/Makefile

		biarch := $(call cc-option-yn, -m32)

		aflags-$(biarch) += -a32

		cflags-$(biarch) += -m32

	

	In the above example $(biarch) is set to y if $(CC) supports the -m32

	option. When $(biarch) equals to y the expanded variables $(aflags-y)

	and $(cflags-y) will be assigned the values -a32 and -m32.



    cc-option-align

	gcc version >= 3.0 shifted type of options used to speify

	alignment of functions, loops etc. $(cc-option-align) whrn used

	as prefix to the align options will select the right prefix:

	gcc < 3.00

		cc-option-align = -malign

	gcc >= 3.00

		cc-option-align = -falign

	

	Example:

		CFLAGS += $(cc-option-align)-functions=4



	In the above example the option -falign-functions=4 is used for

	gcc >= 3.00. For gcc < 3.00 -malign-functions=4 is used.

	

    cc-version

	cc-version return a numerical version of the $(CC) compiler version.

	The format is <major><minor> where both are two digits. So for example

	gcc 3.41 would return 0341.

	cc-version is useful when a specific $(CC) version is faulty in one

	area, for example the -mregparm=3 were broken in some gcc version

	even though the option was accepted by gcc.



	Example:

		#arch/i386/Makefile

		cflags-y += $(shell \

		if [ $(call cc-version) -ge 0300 ] ; then \

			echo "-mregparm=3"; fi ;)



	In the above example -mregparm=3 is only used for gcc version greater

	than or equal to gcc 3.0.



    cc-ifversion

	cc-ifversion test the version of $(CC) and equals last argument if

	version expression is true.



	Example:

		#fs/reiserfs/Makefile

		EXTRA_CFLAGS := $(call cc-ifversion, -lt, 0402, -O1)



	In this example EXTRA_CFLAGS will be assigned the value -O1 if the

	$(CC) version is less than 4.2.

	cc-ifversion takes all the shell operators: 

	-eq, -ne, -lt, -le, -gt, and -ge

	The third parameter may be a text as in this example, but it may also

	be an expanded variable or a macro.





=== 4 Host Program support
@@ -973,74 +1069,6 @@ When kbuild executes the following steps are followed (roughly): 
	architecture specific files.





--- 6.9 $(CC) support functions



	The kernel may be build with several different versions of

	$(CC), each supporting a unique set of features and options.

	kbuild provide basic support to check for valid options for $(CC).

	$(CC) is useally the gcc compiler, but other alternatives are

	available.



    cc-option

	cc-option is used to check if $(CC) support a given option, and not

	supported to use an optional second option.



	Example:

		#arch/i386/Makefile

		cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)



	In the above example cflags-y will be assigned the option

	-march=pentium-mmx if supported by $(CC), otherwise -march-i586.

	The second argument to cc-option is optional, and if omitted

	cflags-y will be assigned no value if first option is not supported.



   cc-option-yn

   	cc-option-yn is used to check if gcc supports a given option

	and return 'y' if supported, otherwise 'n'.



	Example:

		#arch/ppc/Makefile

		biarch := $(call cc-option-yn, -m32)

		aflags-$(biarch) += -a32

		cflags-$(biarch) += -m32

	

	In the above example $(biarch) is set to y if $(CC) supports the -m32

	option. When $(biarch) equals to y the expanded variables $(aflags-y)

	and $(cflags-y) will be assigned the values -a32 and -m32.



    cc-option-align

	gcc version >= 3.0 shifted type of options used to speify

	alignment of functions, loops etc. $(cc-option-align) whrn used

	as prefix to the align options will select the right prefix:

	gcc < 3.00

		cc-option-align = -malign

	gcc >= 3.00

		cc-option-align = -falign

	

	Example:

		CFLAGS += $(cc-option-align)-functions=4



	In the above example the option -falign-functions=4 is used for

	gcc >= 3.00. For gcc < 3.00 -malign-functions=4 is used.

	

    cc-version

	cc-version return a numerical version of the $(CC) compiler version.

	The format is <major><minor> where both are two digits. So for example

	gcc 3.41 would return 0341.

	cc-version is useful when a specific $(CC) version is faulty in one

	area, for example the -mregparm=3 were broken in some gcc version

	even though the option was accepted by gcc.



	Example:

		#arch/i386/Makefile

		cflags-y += $(shell \

		if [ $(call cc-version) -ge 0300 ] ; then \

			echo "-mregparm=3"; fi ;)



	In the above example -mregparm=3 is only used for gcc version greater

	than or equal to gcc 3.0.

	



=== 7 Kbuild Variables



The top Makefile exports the following variables:

Makefile

+0 −32
Original line number Diff line number Diff line
@@ -258,38 +258,6 @@ endif 


export quiet Q KBUILD_VERBOSE



######

# cc support functions to be used (only) in arch/$(ARCH)/Makefile

# See documentation in Documentation/kbuild/makefiles.txt



# as-option

# Usage: cflags-y += $(call as-option, -Wa$(comma)-isa=foo,)



as-option = $(shell if $(CC) $(CFLAGS) $(1) -Wa,-Z -c -o /dev/null \

	     -xassembler /dev/null > /dev/null 2>&1; then echo "$(1)"; \

	     else echo "$(2)"; fi ;)



# cc-option

# Usage: cflags-y += $(call cc-option, -march=winchip-c6, -march=i586)



cc-option = $(shell if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null \

             > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)



# cc-option-yn

# Usage: flag := $(call cc-option-yn, -march=winchip-c6)

cc-option-yn = $(shell if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null \

                > /dev/null 2>&1; then echo "y"; else echo "n"; fi;)



# cc-option-align

# Prefix align with either -falign or -malign

cc-option-align = $(subst -functions=0,,\

	$(call cc-option,-falign-functions=0,-malign-functions=0))



# cc-version

# Usage gcc-ver := $(call cc-version $(CC))

cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh \

              $(if $(1), $(1), $(CC)))





# Look for make include files relative to root of kernel src

MAKEFLAGS += --include-dir=$(srctree)

scripts/Kbuild.include

+37 −0
Original line number Diff line number Diff line
@@ -44,6 +44,43 @@ define filechk 
	fi

endef



######

# cc support functions to be used (only) in arch/$(ARCH)/Makefile

# See documentation in Documentation/kbuild/makefiles.txt



# as-option

# Usage: cflags-y += $(call as-option, -Wa$(comma)-isa=foo,)



as-option = $(shell if $(CC) $(CFLAGS) $(1) -Wa,-Z -c -o /dev/null \

	     -xassembler /dev/null > /dev/null 2>&1; then echo "$(1)"; \

	     else echo "$(2)"; fi ;)



# cc-option

# Usage: cflags-y += $(call cc-option, -march=winchip-c6, -march=i586)



cc-option = $(shell if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null \

             > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)



# cc-option-yn

# Usage: flag := $(call cc-option-yn, -march=winchip-c6)

cc-option-yn = $(shell if $(CC) $(CFLAGS) $(1) -S -o /dev/null -xc /dev/null \

                > /dev/null 2>&1; then echo "y"; else echo "n"; fi;)



# cc-option-align

# Prefix align with either -falign or -malign

cc-option-align = $(subst -functions=0,,\

	$(call cc-option,-falign-functions=0,-malign-functions=0))



# cc-version

# Usage gcc-ver := $(call cc-version, $(CC))

cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh \

              $(if $(1), $(1), $(CC)))



# cc-ifversion

# Usage:  EXTRA_CFLAGS += $(call cc-ifversion, -lt, 0402, -O1)

cc-ifversion = $(shell if [ $(call cc-version, $(CC)) $(1) $(2) ]; then \

                       echo $(3); fi;)



###

# Shorthand for $(Q)$(MAKE) -f scripts/Makefile.build obj=

# Usage:

scripts/Makefile.build

+2 −1
Original line number Diff line number Diff line
@@ -10,11 +10,12 @@ __build: 
# Read .config if it exist, otherwise ignore

-include .config



include scripts/Kbuild.include



# The filename Kbuild has precedence over Makefile

kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))

include $(if $(wildcard $(kbuild-dir)/Kbuild), $(kbuild-dir)/Kbuild, $(kbuild-dir)/Makefile)



include scripts/Kbuild.include

include scripts/Makefile.lib



ifdef host-progs