kbuild

Makefile

Makefile 語法簡介
Makefile 語法筆記

KBuild

modules
kbuild 參數 list

Pre require

• prebuilt kernel
• kernel 設定可載入 module
• 可能是 CONFIG_PROC_KCORE and CONFIG_DEBUG_INFO

2 語法

基本語法

make -C <path_to_kernel_src> M=$PWD

使用運行中的 kernel

make -C /lib/modules/`uname -r`/build M=$PWD

通用使用法

make -C $KDIR M=$PWD [target]

target

• modules
  預設 target(不輸入時)，產出物會在本目錄下
• modules_install
  安裝到 /lib/modules/<kernel_release>/extra/
  INSTALL_MOD_PATH
• clean
  移除本目錄下的產出物
• help

3 Creating a Kbuild File for an External Module

新版 kernel 會先去掃過一遍 Kbuild

include object file as blob，需要將檔案命名成 <filename>_shipped，如 8123_bin.o_shipped

分離 Kbuild Makefile，且向前相容

include to module

8123_if.c
8123_if.h
8123_pci.c
8123_bin.o_shipped  <= Binary blob

Kbuild

obj-m  := 8123.o
8123-y := 8123_if.o 8123_pci.o 8123_bin.o

Makefile

ifneq ($(KERNELRELEASE),)
# kbuild part of makefile
include Kbuild

else
# normal makefile
KDIR ?= /lib/modules/`uname -r`/build

default:
    $(MAKE) -C $(KDIR) M=$$PWD

# Module specific targets
genbin:
    echo "X" > 8123_bin.o_shipped

endif

Building Multiple Modules

obj-m := foo.o bar.o
foo-y := <foo_srcs> # foo.ko
bar-y := <bar_srcs> # bar.ko

4 Header file

include/linux/
arch/$(ARCH)/include/

Kbuildz

# .
# |__ src
# |   |__ complex_main.c
# |   |__ hal
# |   |__ hardwareif.c
# |   |__ include
# |       |__ hardwareif.h
# |__ include
#     |__ complex.h
obj-m := complex.o
complex-y := src/complex_main.o
complex-y += src/hal/hardwareif.o

ccflags-y := -I$(src)/include
ccflags-y += -I$(src)/src/hal/include

5 skip

6 Symbol

build 過程中，會產生 Module.symvers，它包含所有 compiled module 的全部 exported symbols。

Module.symvers

<CRC>       <Symbol>           <module>

0x2d036834  scsi_remove_host   drivers/scsi/scsi_mod

For a kernel build without CONFIG_MODVERSIONS enabled, the CRC would read 0x00000000.

Module.symvers serves two purposes:

1) It lists all exported symbols from vmlinux and all modules.
2) It lists the CRC if CONFIG_MODVERSIONS is enabled.