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Commit 20a468b5 authored by Sam Ravnborg's avatar Sam Ravnborg
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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
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Showing with 136 additions and 102 deletions
Documentation/kbuild/makefiles.txt
View file @ 20a468b5
......@@ -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 [ $(call cc-version) -ge 0300 ] ; then \
echo "-mregparm=3"; fi ;)
In the above example -mregparm=3 is only used for gcc version greater
than or equal to gcc 3.0.
=== 7 Kbuild Variables
The top Makefile exports the following variables:
......
Makefile
View file @ 20a468b5
......@@ -258,38 +258,6 @@ endif
export quiet Q KBUILD_VERBOSE
######
# cc support functions to be used (only) in arch/$(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
View file @ 20a468b5
......@@ -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
View file @ 20a468b5
......@@ -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
......
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