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Diffstat (limited to 'Documentation/kbuild/makefiles.txt')
| -rw-r--r-- | Documentation/kbuild/makefiles.txt | 127 |
1 files changed, 71 insertions, 56 deletions
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index 71c602d61680..c375313cb128 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -168,7 +168,7 @@ more details, with real examples. #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 @@ -187,34 +187,35 @@ more details, with real examples. 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, @@ -244,12 +245,12 @@ more details, with real examples. 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. @@ -284,43 +285,40 @@ more details, with real examples. --- 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. @@ -340,18 +338,18 @@ more details, with real examples. 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 @@ -923,16 +921,33 @@ When kbuild executes, the following steps are followed (roughly): The first example utilises the trick that a config option expands to 'y' when selected. - CFLAGS_KERNEL $(CC) options specific for built-in + KBUILD_AFLAGS_KERNEL $(AS) options specific for built-in + + $(KBUILD_AFLAGS_KERNEL) contains extra C compiler flags used to compile + resident kernel code. + + KBUILD_AFLAGS_MODULE Options for $(AS) when building modules + + $(KBUILD_AFLAGS_MODULE) is used to add arch specific options that + are used for $(AS). + From commandline AFLAGS_MODULE shall be used (see kbuild.txt). - $(CFLAGS_KERNEL) contains extra C compiler flags used to compile + KBUILD_CFLAGS_KERNEL $(CC) options specific for built-in + + $(KBUILD_CFLAGS_KERNEL) contains extra C compiler flags used to compile resident kernel code. - CFLAGS_MODULE $(CC) options specific for modules + KBUILD_CFLAGS_MODULE Options for $(CC) when building modules + + $(KBUILD_CFLAGS_MODULE) is used to add arch specific options that + are used for $(CC). + From commandline CFLAGS_MODULE shall be used (see kbuild.txt). - $(CFLAGS_MODULE) contains extra C compiler flags used to compile code - for loadable kernel modules. + KBUILD_LDFLAGS_MODULE Options for $(LD) when linking modules + $(KBUILD_LDFLAGS_MODULE) is used to add arch specific options + used when linking modules. This is often a linker script. + From commandline LDFLAGS_MODULE shall be used (see kbuild.txt). --- 6.2 Add prerequisites to archprepare: @@ -1176,14 +1191,14 @@ When kbuild executes, the following steps are followed (roughly): === 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. |