android androidkernel.mk,高通kernel顶层目录下的AndroidKernel.mk文件

高通kernel顶层目录下的AndroidKernel.mk文件高通kernel顶层目录下的AndroidKernel.mk文件是Android的编译系统的一部分，用来编译kernel。它的位置是在aosp/kernel目录下。文件层级结构12345678910111213141516定义变量【第一处】ifeq ($(TARGET_PREBUILT_KERNEL),)定义变量【第二处】ifeq (

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高通kernel顶层目录下的AndroidKernel.mk文件

高通kernel顶层目录下的AndroidKernel.mk文件是Android的编译系统的一部分，用来编译kernel。

它的位置是在aosp/kernel目录下。

文件层级结构

16定义变量【第一处】

ifeq ($(TARGET_PREBUILT_KERNEL),)

定义变量【第二处】

ifeq ($(KERNEL_DEFCONFIG)$(wildcard $(KERNEL_CONFIG)),)

$(error Kernel configuration not defined, cannot build kernel)

else

定义变量【第三处】

定义一些目标和依赖

endif

文件具体内容(带注释)

定义变量【第一处】

PERL变量

2#Android makefile to build kernel as a part of Android Build

PERL = perl

KERNEL_TARGET 和 INSTALLED_KERNEL_TARGET 变量

4KERNEL_TARGET := $(strip $(INSTALLED_KERNEL_TARGET))

ifeq ($(KERNEL_TARGET),)

INSTALLED_KERNEL_TARGET := $(PRODUCT_OUT)/kernel

endif

在build/core/Makefile文件中，定义了INSTALLED_KERNEL_TARGET变量

5ifneq ($(strip $(TARGET_NO_KERNEL)),true)

INSTALLED_KERNEL_TARGET := $(PRODUCT_OUT)/kernel

else

INSTALLED_KERNEL_TARGET :=

endif

TARGET_NO_KERNEL是在device/厂商/产品名/BoardConfig.mk中定义的

1TARGET_NO_KERNEL := false

Makefile中， ifeq关键字用来判断参数是否相等， ifneq的关键字是用来判断参数是否不相等，格式为：

5ifneq (ARG1, ARG2) / ifneq (ARG1, ARG2)

ifneq 'ARG1' 'ARG2' / ifneq 'ARG1' 'ARG2'

ifneq "ARG1" "ARG2" / ifneq "ARG1" "ARG2"

ifneq "ARG1" 'ARG2' / ifneq "ARG1" 'ARG2'

ifneq 'ARG1' "ARG2" / ifneq 'ARG1' "ARG2"

综上所述可知，不论TARGET_NO_KERNEL为false还是true，则KERNEL_TARGET和INSTALLED_KERNEL_TARGET的值都为$(PRODUCT_OUT)/kernel。

TARGET_KERNEL_ARCH 和 KERNEL_ARCH 变量

6TARGET_KERNEL_ARCH := $(strip $(TARGET_KERNEL_ARCH))

ifeq ($(TARGET_KERNEL_ARCH),)

KERNEL_ARCH := arm

else

KERNEL_ARCH := $(TARGET_KERNEL_ARCH)

endif

TARGET_KERNEL_ARCH是在device/厂商/产品名/BoardConfig.mk中定义的。如果已经定义为某值(如arm64)，KERNEL_ARCH就设定为该值(如arm64)。反之，则设定为默认值arm

TARGET_KERNEL_HEADER_ARCH 和 KERNEL_HEADER_ARCH 变量

7TARGET_KERNEL_HEADER_ARCH := $(strip $(TARGET_KERNEL_HEADER_ARCH))

ifeq ($(TARGET_KERNEL_HEADER_ARCH),)

KERNEL_HEADER_ARCH := $(KERNEL_ARCH)

else

$(warning Forcing kernel header generation only for '$(TARGET_KERNEL_HEADER_ARCH)')

KERNEL_HEADER_ARCH := $(TARGET_KERNEL_HEADER_ARCH)

endif

TARGET_KERNEL_ARCH是在device/厂商/产品名/BoardConfig.mk中定义的。如果TARGET_KERNEL_HEADER_ARCH为空，KERNEL_HEADER_ARCH就设定为KERNEL_ARCH的值。反之，则警告并将KERNEL_HEADER_ARCH设定为TARGET_KERNEL_HEADER_ARCH

KERNEL_HEADER_DEFCONFIG 变量

4KERNEL_HEADER_DEFCONFIG := $(strip $(KERNEL_HEADER_DEFCONFIG))

ifeq ($(KERNEL_HEADER_DEFCONFIG),)

KERNEL_HEADER_DEFCONFIG := $(KERNEL_DEFCONFIG)

endif

KERNEL_DEFCONFIG是在device/厂商/产品名/AndroidBoard.mk中定义的。 KERNEL_HEADER_DEFCONFIG未找到定义的地方。当KERNEL_HEADER_DEFCONFIG为空，则被赋值为KERNEL_DEFCONFIG。

binder

6# Force 32-bit binder IPC for 64bit kernel with 32bit userspace

ifeq ($(KERNEL_ARCH),arm64)

ifeq ($(TARGET_ARCH),arm)

KERNEL_CONFIG_OVERRIDE := CONFIG_ANDROID_BINDER_IPC_32BIT=y

endif

通过条件判断，是否让32-bit的binder IPC(进程间通信机制) 强制运行于64bit的kernel的32bit用户空间。

TARGET_KERNEL_CROSS_COMPILE_PREFIX 和 KERNEL_CROSS_COMPILE 变量

6TARGET_KERNEL_CROSS_COMPILE_PREFIX := $(strip $(TARGET_KERNEL_CROSS_COMPILE_PREFIX))

ifeq ($(TARGET_KERNEL_CROSS_COMPILE_PREFIX),)

KERNEL_CROSS_COMPILE := arm-eabi-

else

KERNEL_CROSS_COMPILE := $(TARGET_KERNEL_CROSS_COMPILE_PREFIX)

endif

TARGET_KERNEL_CROSS_COMPILE_PREFIX是在device/厂商/产品名/AndroidBoard.mk中定义的。例：TARGET_KERNEL_CROSS_COMPILE_PREFIX := aarch64-linux-android-

定义变量【第二处】

KERNEL_CFLAGS变量

4KERNEL_GCC_NOANDROID_CHK := $(shell (echo "int main() {return 0;}" | $(KERNEL_CROSS_COMPILE)gcc -E -mno-android - > /dev/null 2>&1 ; echo $$?))

ifeq ($(strip $(KERNEL_GCC_NOANDROID_CHK)),0)

KERNEL_CFLAGS := KCFLAGS=-mno-android

endif

KERNEL_GCC_NOANDROID_CHK 变量如果为0，则定义KERNEL_CFLAGS为KCFLAGS=-mno-android

mkfile_path变量

1mkfile_path := $(abspath $(lastword $(MAKEFILE_LIST)))

获得mk文件路径

current_dir变量

1current_dir := $(notdir $(patsubst %/,%,$(dir $(mkfile_path))))

TARGET_KERNEL_VERSION变量

3ifeq ($(TARGET_KERNEL_VERSION),)

TARGET_KERNEL_VERSION := 3.18

endif

TARGET_KERNEL变量

1TARGET_KERNEL := msm-$(TARGET_KERNEL_VERSION)

通过TARGET_KERNEL变量，定义KERNEL_OUT等变量

14ifeq ($(TARGET_KERNEL),$(current_dir))

# New style, kernel/msm-version

BUILD_ROOT_LOC := ../../

TARGET_KERNEL_SOURCE := kernel/$(TARGET_KERNEL)

KERNEL_OUT := $(TARGET_OUT_INTERMEDIATES)/kernel/$(TARGET_KERNEL)

KERNEL_SYMLINK := $(TARGET_OUT_INTERMEDIATES)/KERNEL_OBJ

KERNEL_USR := $(KERNEL_SYMLINK)/usr

else

# Legacy style, kernel source directly under kernel

KERNEL_LEGACY_DIR := true

BUILD_ROOT_LOC := ../

TARGET_KERNEL_SOURCE := kernel

KERNEL_OUT := $(TARGET_OUT_INTERMEDIATES)/KERNEL_OBJ

endif

KERNEL_CONFIG变量

1KERNEL_CONFIG := $(KERNEL_OUT)/.config

定义变量【第三处】

TARGET_PREBUILT_INT_KERNEL变量

10ifeq ($(TARGET_USES_UNCOMPRESSED_KERNEL),true)

$(info Using uncompressed kernel)

TARGET_PREBUILT_INT_KERNEL := $(KERNEL_OUT)/arch/$(KERNEL_ARCH)/boot/Image

else

ifeq ($(KERNEL_ARCH),arm64)

TARGET_PREBUILT_INT_KERNEL := $(KERNEL_OUT)/arch/$(KERNEL_ARCH)/boot/Image.gz

else

TARGET_PREBUILT_INT_KERNEL := $(KERNEL_OUT)/arch/$(KERNEL_ARCH)/boot/zImage

endif

依据TARGET_KERNEL_APPEND_DTB变量，定义TARGET_PREBUILT_INT_KERNEL变量

4ifeq ($(TARGET_KERNEL_APPEND_DTB), true)

$(info Using appended DTB)

TARGET_PREBUILT_INT_KERNEL := $(TARGET_PREBUILT_INT_KERNEL)-dtb

endif

KERNEL_HEADERS_INSTALL变量

1KERNEL_HEADERS_INSTALL := $(KERNEL_OUT)/usr

KERNEL_MODULES_INSTALL变量

1KERNEL_MODULES_INSTALL :=system

KERNEL_MODULES_OUT变量

1KERNEL_MODULES_OUT := $(TARGET_OUT)/lib/modules

TARGET_PREBUILT_KERNEL变量

1TARGET_PREBUILT_KERNEL := $(TARGET_PREBUILT_INT_KERNEL)

宏mv-modules

8define mv-modules

mdpath=`find $(KERNEL_MODULES_OUT) -type f -name modules.dep`;\

if [ "$$mdpath" != "" ];then\

mpath=`dirname $$mdpath`;\

ko=`find $$mpath/kernel -type f -name *.ko`;\

for i in $$ko; do mv $$i $(KERNEL_MODULES_OUT)/; done;\

endef

宏clean-module-folder

6define clean-module-folder

mdpath=`find $(KERNEL_MODULES_OUT) -type f -name modules.dep`;\

if [ "$$mdpath" != "" ];then\

mpath=`dirname $$mdpath`; rm -rf $$mpath;\

endef

目标和依赖

ifneq ($(KERNEL_LEGACY_DIR),true)

$(KERNEL_USR): $(KERNEL_HEADERS_INSTALL)

rm -rf $(KERNEL_SYMLINK)

ln -s kernel/$(TARGET_KERNEL) $(KERNEL_SYMLINK)

$(TARGET_PREBUILT_INT_KERNEL): $(KERNEL_USR)

endif

$(KERNEL_OUT):

mkdir -p $(KERNEL_OUT)

$(KERNEL_CONFIG): $(KERNEL_OUT)

$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_DEFCONFIG)

$(hide) if [ ! -z "$(KERNEL_CONFIG_OVERRIDE)" ]; then \

echo "Overriding kernel config with '$(KERNEL_CONFIG_OVERRIDE)'"; \

echo $(KERNEL_CONFIG_OVERRIDE) >> $(KERNEL_OUT)/.config; \

$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) oldconfig; fi

$(TARGET_PREBUILT_INT_KERNEL): $(KERNEL_OUT) $(KERNEL_HEADERS_INSTALL)

$(hide) echo "Building kernel..."

$(hide) rm -rf $(KERNEL_OUT)/arch/$(KERNEL_ARCH)/boot/dts

$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_CFLAGS)

$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_CFLAGS) modules

$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) INSTALL_MOD_PATH=$(BUILD_ROOT_LOC)../$(KERNEL_MODULES_INSTALL) INSTALL_MOD_STRIP=1 ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) modules_install

$(mv-modules)

$(clean-module-folder)

$(KERNEL_HEADERS_INSTALL): $(KERNEL_OUT)

$(hide) if [ ! -z "$(KERNEL_HEADER_DEFCONFIG)" ]; then \

rm -f $(BUILD_ROOT_LOC)$(KERNEL_CONFIG); \

$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_HEADER_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_HEADER_DEFCONFIG); \

$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_HEADER_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) headers_install; fi

$(hide) if [ "$(KERNEL_HEADER_DEFCONFIG)" != "$(KERNEL_DEFCONFIG)" ]; then \

echo "Used a different defconfig for header generation"; \

rm -f $(BUILD_ROOT_LOC)$(KERNEL_CONFIG); \

$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) $(KERNEL_DEFCONFIG); fi

$(hide) if [ ! -z "$(KERNEL_CONFIG_OVERRIDE)" ]; then \

echo "Overriding kernel config with '$(KERNEL_CONFIG_OVERRIDE)'"; \

echo $(KERNEL_CONFIG_OVERRIDE) >> $(KERNEL_OUT)/.config; \

$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) oldconfig; fi

kerneltags: $(KERNEL_OUT) $(KERNEL_CONFIG)

$(MAKE) -C $(TARGET_KERNEL_SOURCE) O=$(BUILD_ROOT_LOC)$(KERNEL_OUT) ARCH=$(KERNEL_ARCH) CROSS_COMPILE=$(KERNEL_CROSS_COMPILE) tags

kernelconfig: $(KERNEL_OUT) $(KERNEL_CONFIG)

env KCONFIG_NOTIMESTAMP=true \