--- 7.1 header-y
--- 7.2 objhdr-y
--- 7.3 destination-y
- --- 7.4 unifdef-y (deprecated)
=== 8 Kbuild Variables
=== 9 Makefile language
#drivers/isdn/i4l/Makefile
# Makefile for the kernel ISDN subsystem and device drivers.
# Each configuration option enables a list of files.
- obj-$(CONFIG_ISDN) += isdn.o
+ obj-$(CONFIG_ISDN_I4L) += isdn.o
obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o
--- 3.3 Loadable module goals - obj-m
Note: In this example $(CONFIG_ISDN_PPP_BSDCOMP) evaluates to 'm'
If a kernel module is built from several source files, you specify
- that you want to build a module in the same way as above.
-
- Kbuild needs to know which the parts that you want to build your
- module from, so you have to tell it by setting an
- $(<module_name>-objs) variable.
+ that you want to build a module in the same way as above; however,
+ kbuild needs to know which object files you want to build your
+ module from, so you have to tell it by setting a $(<module_name>-y)
+ variable.
Example:
#drivers/isdn/i4l/Makefile
- obj-$(CONFIG_ISDN) += isdn.o
- isdn-objs := isdn_net_lib.o isdn_v110.o isdn_common.o
+ obj-$(CONFIG_ISDN_I4L) += isdn.o
+ isdn-y := isdn_net_lib.o isdn_v110.o isdn_common.o
In this example, the module name will be isdn.o. Kbuild will
- compile the objects listed in $(isdn-objs) and then run
+ compile the objects listed in $(isdn-y) and then run
"$(LD) -r" on the list of these files to generate isdn.o.
- Kbuild recognises objects used for composite objects by the suffix
- -objs, and the suffix -y. This allows the Makefiles to use
- the value of a CONFIG_ symbol to determine if an object is part
- of a composite object.
+ Due to kbuild recognizing $(<module_name>-y) for composite objects,
+ you can use the value of a CONFIG_ symbol to optionally include an
+ object file as part of a composite object.
Example:
#fs/ext2/Makefile
- obj-$(CONFIG_EXT2_FS) += ext2.o
- ext2-y := balloc.o bitmap.o
- ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o
+ obj-$(CONFIG_EXT2_FS) += ext2.o
+ ext2-y := balloc.o dir.o file.o ialloc.o inode.o ioctl.o \
+ namei.o super.o symlink.o
+ ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o xattr_user.o \
+ xattr_trusted.o
- In this example, xattr.o is only part of the composite object
- ext2.o if $(CONFIG_EXT2_FS_XATTR) evaluates to 'y'.
+ In this example, xattr.o, xattr_user.o and xattr_trusted.o are only
+ part of the composite object ext2.o if $(CONFIG_EXT2_FS_XATTR)
+ evaluates to 'y'.
Note: Of course, when you are building objects into the kernel,
the syntax above will also work. So, if you have CONFIG_EXT2_FS=y,
may contain both a built-in.o and a lib.a file.
Example:
- #arch/i386/lib/Makefile
- lib-y := checksum.o delay.o
+ #arch/x86/lib/Makefile
+ lib-y := delay.o
- This will create a library lib.a based on checksum.o and delay.o.
- For kbuild to actually recognize that there is a lib.a being built,
- the directory shall be listed in libs-y.
+ This will create a library lib.a based on delay.o. For kbuild to
+ actually recognize that there is a lib.a being built, the directory
+ shall be listed in libs-y.
See also "6.3 List directories to visit when descending".
Use of lib-y is normally restricted to lib/ and arch/*/lib.
--- 3.7 Compilation flags
ccflags-y, asflags-y and ldflags-y
- The three flags listed above applies only to the kbuild makefile
- where they are assigned. They are used for all the normal
- cc, as and ld invocation happenign during a recursive build.
+ These three flags apply only to the kbuild makefile in which they
+ are assigned. They are used for all the normal cc, as and ld
+ invocations happening during a recursive build.
Note: Flags with the same behaviour were previously named:
EXTRA_CFLAGS, EXTRA_AFLAGS and EXTRA_LDFLAGS.
- They are yet supported but their use are deprecated.
+ They are still supported but their usage is deprecated.
- ccflags-y specifies options for compiling C files with $(CC).
+ ccflags-y specifies options for compiling with $(CC).
Example:
- # drivers/sound/emu10k1/Makefile
- ccflags-y += -I$(obj)
- ccflags-$(DEBUG) += -DEMU10K1_DEBUG
-
+ # drivers/acpi/Makefile
+ ccflags-y := -Os
+ ccflags-$(CONFIG_ACPI_DEBUG) += -DACPI_DEBUG_OUTPUT
This variable is necessary because the top Makefile owns the
variable $(KBUILD_CFLAGS) and uses it for compilation flags for the
entire tree.
- asflags-y is a similar string for per-directory options
- when compiling assembly language source.
+ asflags-y specifies options for assembling with $(AS).
Example:
- #arch/x86_64/kernel/Makefile
- asflags-y := -traditional
+ #arch/sparc/kernel/Makefile
+ asflags-y := -ansi
-
- ldflags-y is a string for per-directory options to $(LD).
+ ldflags-y specifies options for linking with $(LD).
Example:
- #arch/m68k/fpsp040/Makefile
- ldflags-y := -x
+ #arch/cris/boot/compressed/Makefile
+ ldflags-y += -T $(srctree)/$(src)/decompress_$(arch-y).lds
subdir-ccflags-y, subdir-asflags-y
- The two flags listed above are similar to ccflags-y and as-falgs-y.
- The difference is that the subdir- variants has effect for the kbuild
- file where tey are present and all subdirectories.
+ The two flags listed above are similar to ccflags-y and asflags-y.
+ The difference is that the subdir- variants have effect for the kbuild
+ file where they are present and all subdirectories.
Options specified using subdir-* are added to the commandline before
the options specified using the non-subdir variants.
CFLAGS_aha152x.o = -DAHA152X_STAT -DAUTOCONF
CFLAGS_gdth.o = # -DDEBUG_GDTH=2 -D__SERIAL__ -D__COM2__ \
-DGDTH_STATISTICS
- CFLAGS_seagate.o = -DARBITRATE -DPARITY -DSEAGATE_USE_ASM
- These three lines specify compilation flags for aha152x.o,
- gdth.o, and seagate.o
+ These two lines specify compilation flags for aha152x.o and gdth.o.
$(AFLAGS_$@) is a similar feature for source files in assembly
languages.
Example:
# arch/arm/kernel/Makefile
- AFLAGS_head-armv.o := -DTEXTADDR=$(TEXTADDR) -traditional
- AFLAGS_head-armo.o := -DTEXTADDR=$(TEXTADDR) -traditional
+ AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
+ AFLAGS_crunch-bits.o := -Wa,-mcpu=ep9312
+ AFLAGS_iwmmxt.o := -Wa,-mcpu=iwmmxt
+
--- 3.9 Dependency tracking
=== 7 Kbuild syntax for exported headers
The kernel include a set of headers that is exported to userspace.
-Many headers can be exported as-is but other headers requires a
+Many headers can be exported as-is but other headers require a
minimal pre-processing before they are ready for user-space.
The pre-processing does:
- drop kernel specific annotations
- drop include of compiler.h
-- drop all sections that is kernel internat (guarded by ifdef __KERNEL__)
+- drop all sections that are kernel internal (guarded by ifdef __KERNEL__)
-Each relevant directory contain a file name "Kbuild" which specify the
+Each relevant directory contains a file name "Kbuild" which specifies the
headers to be exported.
See subsequent chapter for the syntax of the Kbuild file.
will be located in the directory "include/linux" when exported.
- --- 7.4 unifdef-y (deprecated)
-
- unifdef-y is deprecated. A direct replacement is header-y.
-
-
=== 8 Kbuild Variables
The top Makefile exports the following variables:
projects / cascardo / linux.git / blobdiff