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概要：
此篇文章次要介绍 Android ota 包（Android L）的编译制作过程，侧重于 Makefile 中编译 ota 的流程，从指定 target 到编译 cmd 等流程。
次要流程：
源码剖析：
build/core/Makefile：
.PHONY: otapackageotapackage: $(INTERNAL_OTA_PACKAGE_TARGET)otapackage 伪命令，即执行 make otapackage 时，将编译$(INTERNAL_OTA_PACKAGE_TARGET)指标
$(INTERNAL_OTA_PACKAGE_TARGET): $(BUILT_TARGET_FILES_PACKAGE) $(DISTTOOLS) @echo "Package OTA: $@"ifneq ($(TARGET_USERIMAGES_USE_UBIFS),true) ifeq (yes, $(filter $(TRUSTONIC_TEE_SUPPORT) $(MTK_ATF_SUPPORT),yes)) $(hide) MTK_SECURITY_SW_SUPPORT=$(MTK_SECURITY_SW_SUPPORT) MKBOOTIMG=$(MKBOOTIMG) \ ./build/tools/releasetools/ota_from_target_files -v \ --block \ -p $(HOST_OUT) \ -k $(KEY_CERT_PAIR) \ -z $(PRODUCT_OUT)/trustzone.bin \ $(if $(OEM_OTA_CONFIG), -o $(OEM_OTA_CONFIG)) \ $(BUILT_TARGET_FILES_PACKAGE) $@ else $(hide) MTK_SECURITY_SW_SUPPORT=$(MTK_SECURITY_SW_SUPPORT) MKBOOTIMG=$(MKBOOTIMG) \ ./build/tools/releasetools/ota_from_target_files -v \ --block \ -p $(HOST_OUT) \ -k $(KEY_CERT_PAIR) \ $(if $(OEM_OTA_CONFIG), -o $(OEM_OTA_CONFIG)) \ $(BUILT_TARGET_FILES_PACKAGE) $@ endifelse $(hide) MTK_SECURITY_SW_SUPPORT=$(MTK_SECURITY_SW_SUPPORT) ./build/tools/releasetools/ota_from_target_files -v \ -n \ -g \ -p $(HOST_OUT) \ -k $(KEY_CERT_PAIR) \ $(BUILT_TARGET_FILES_PACKAGE) $@endififeq ($(strip $(MTK_FW_UPGRADE)), yes)# @echo "Package FWUpgradePackage"# bash $(FWUPGRADEPACKAGE_SH) $(PRODUCT_OUT) $(KEY_CERT_PAIR)endif依赖两局部：
$(BUILT_TARGET_FILES_PACKAGE)$(DISTTOOLS)而后先找$(BUILT_TARGET_FILES_PACKAGE)。BUILT_TARGET_FILES_PACKAGE:= (intermediates)/(intermediates)/(intermediates)/(name).zip 理论为：full_p92s_hd-target_files-eng.wan.zip
# -----------------------------------------------------------------# A zip of the directories that map to the target filesystem.# This zip can be used to create an OTA package or filesystem image# as a post-build step.#name := $(TARGET_PRODUCT)ifeq ($(TARGET_BUILD_TYPE),debug) name := $(name)_debugendifname := $(name)-target_files-$(FILE_NAME_TAG)以上这些步骤次要确定 name 变量名称 name:=(project−name)−targetfiles−(project-name)-target_files-(project−name)−targetfiles−(FILE_NAME_TAG) ,假如 project-name=p92 FILE_NAME_TAG=eng , 则：
name := p92-target_files-engintermediates := $(call intermediates-dir-for,PACKAGING,target_files)此处调用了一个函数：intermediates-dir-for，咱们来解读一下它的定义，就晓得这句话的意思了。它定义在build/core/definitions.mk 中，如下：
$(1): target class, like "APPS" $(2): target name, like "NotePad" $(3): if non-empty, this is a HOST target. $(4): if non-empty, force the intermediates to be COMMON $(5): if non-empty, force the intermedistes to be for the 2ndarchdefine intermediates-dir-for$(strip \ $(eval _idfClass :=$(strip $(1))) \ $(if $(_idfClass),, \ $(error$(LOCAL_PATH): Class not defined in call to intermediates-dir-for)) \ $(eval _idfName :=$(strip $(2))) \ $(if $(_idfName),, \ $(error$(LOCAL_PATH): Name not defined in call to intermediates-dir-for)) \ $(eval _idfPrefix :=$(if $(strip $(3)),HOST,TARGET)) \ $(eval_idf2ndArchPrefix := $(if $(strip $(5)),$(TARGET_2ND_ARCH_VAR_PREFIX))) \ $(if $(filter$(_idfPrefix)-$(_idfClass),$(COMMON_MODULE_CLASSES))$(4), \ $(eval _idfIntBase:= $($(_idfPrefix)_OUT_COMMON_INTERMEDIATES)) \ ,$(if $(filter$(_idfClass),SHARED_LIBRARIES STATIC_LIBRARIES EXECUTABLES GYP),\ $(eval_idfIntBase := $($(_idf2ndArchPrefix)$(_idfPrefix)_OUT_INTERMEDIATES)) \ ,$(eval _idfIntBase:= $($(_idfPrefix)_OUT_INTERMEDIATES)) \ ) \ ) \ $(_idfIntBase)/$(_idfClass)/$(_idfName)_intermediates \)endif传入的参数：$1= PACKAGING , $2=target-files, $3及当前的参数为空。
所以执行下来：
- _idfClass := PACKAGING - _idfName := target_files - _idfPrefix := TARGET (认为$3为空，所以if函数走到else part 为TARGET) - _idfIntBase := TARGET_OUT_INTERMEDIATES 因为这个宏在 build/core/envsetup.mk 中有定义：
TARGET_OUT_INTERMEDIATES := (PRODUCTOUT)/obj(out/target/product/(PRODUCT_OUT)/obj (out/target/product/(PRODUCTOUT)/obj(out/target/product/(project)/obj)执行后果：
out/target/product/$(project)/obj/PACKAGING/target_files_intermediates所以这个函数调用之后：intermediates := out/target/product/$(project)/obj/PACKAGING/target-files_intermeidates
BUILT_TARGET_FILES_PACKAGE := $(intermediates)/$(name).zip$(BUILT_TARGET_FILES_PACKAGE): intermediates := $(intermediates)$(BUILT_TARGET_FILES_PACKAGE): \ zip_root := $(intermediates)/$(name)以上几句同样是对指标等变量赋值：
BUILT_TARGET_FILES_PACKAGE := out/target/product/$(project)/obj/PACKAGING/target-files_intermeidates/p92-target_files-eng.zip (这个即是将要生成的指标文件)
而后设定两个指标指定变量：intermediates和zip_root，即这两个变量只在 BUILT_TARGET_FILES_PACKAGE 这个指标上下文无效（相似于C语言的局部变量）Intermediates:= out/target/product/$(project)/obj/PACKAGING/target-files_intermeidateszip_root := out/target/product/$(project)/obj/PACKAGING/target-files_intermeidates/p92-target_files-eng
# $(1): Directory to copy# $(2): Location to copy it to# The "ls -A" is to prevent "acp s/* d" from failing if s is empty.define package_files-copy-root if [ -d "$(strip $(1))" -a "$$(ls -A $(1))" ]; then \ mkdir -p $(2) && \ $(ACP) -rd $(strip $(1))/* $(2); \ fiendef以上定义了一个 copy 文件的函数，有两个参数 $1,$2，把 $1 中的内容拷到 $2 中。
built_ota_tools := \ $(call intermediates-dir-for,EXECUTABLES,applypatch)/applypatch \ $(call intermediates-dir-for,EXECUTABLES,applypatch_static)/applypatch_static \ $(call intermediates-dir-for,EXECUTABLES,check_prereq)/check_prereq \ $(call intermediates-dir-for,EXECUTABLES,sqlite3)/sqlite3ifeq ($(TARGET_ARCH),arm64) built_ota_tools += $(call intermediates-dir-for,EXECUTABLES,updater,,,t)/updaterelse built_ota_tools += $(call intermediates-dir-for,EXECUTABLES,updater)/updaterendif以上次要做两件事件：
- 把
applypatch … sqlite3等可执行文件（obj/EXECUTABLES/…目录下）赋值给built_ota_tools 把
updater可执行文件追加赋值给built_ota_tools。这里值得注意的是updater的调用参数：(EXECUTABLES,updater,,,t)，存在 $5 ,联合上文对intermediates-dir-for函数剖析可失去：$(eval_idfIntBase := ((((_idf2ndArchPrefix)$(_idfPrefix)_OUT_INTERMEDIATES)) 可失去：idfIntBase :=$(TARGET_2ND_ARCH_VAR_PREFIX)TARGET_OUT_INTERMEDIATES:= $(PRODUCT_OUT)/obj_$(TARGET_2ND_ARCH) :=out/target/product/$(project)/obj_arm
所以最初返回：out/target/product/$(project)/obj_arm/updater_intermediates/(updater)
可发现调用intermediates-dir-for此函数，如果存在参数 $5，并且 _idfClass 在 SHARED_LIBRARIES STATIC_LIBRARIES EXECUTABLES GYP 中，则 idfIntBase := out/target/product/$(project)/obj_arm (而非obj)。最终 built_ota_tools := applypatchapplypatch_static check_prereq sqlite3 updater 这几支文件（目录疏忽）
$(BUILT_TARGET_FILES_PACKAGE): PRIVATE_OTA_TOOLS := $(built_ota_tools)$(BUILT_TARGET_FILES_PACKAGE): PRIVATE_RECOVERY_API_VERSION := $(RECOVERY_API_VERSION)$(BUILT_TARGET_FILES_PACKAGE): PRIVATE_RECOVERY_FSTAB_VERSION := $(RECOVERY_FSTAB_VERSION)ifeq ($(TARGET_RELEASETOOLS_EXTENSIONS),)# default to common dir for device vendor$(BUILT_TARGET_FILES_PACKAGE): tool_extensions := $(TARGET_DEVICE_DIR)/../commonelse$(BUILT_TARGET_FILES_PACKAGE): tool_extensions := $(TARGET_RELEASETOOLS_EXTENSIONS)endif- 把
built_ota_tools赋值给指标制订变量PRIVATE_OTA_TOOLS 别离对
PRIVATE_RECOVERY_API_VERSION,PRIVATE_RECOVERY_FSTAB_VERSION赋值，其中RECOVERY_API_VERSION,RECOVERY_FSTAB_VERSION这两个变量在bootable/recovery/Android.mk中有定义：RECOVERY_API_VERSION:= 3RECOVERY_FSTAB_VERSION:= 2- 对
tool_extensions赋值
# Depending on the various images guarantees that the underlying# directories are up-to-date.$(BUILT_TARGET_FILES_PACKAGE): \ $(INSTALLED_BOOTIMAGE_TARGET) \ $(INSTALLED_RADIOIMAGE_TARGET) \ $(INSTALLED_RECOVERYIMAGE_TARGET) \ $(INSTALLED_SYSTEMIMAGE) \ $(INSTALLED_USERDATAIMAGE_TARGET) \ $(INSTALLED_CACHEIMAGE_TARGET) \ $(INSTALLED_VENDORIMAGE_TARGET) \ $(INSTALLED_ANDROID_INFO_TXT_TARGET) \ $(SELINUX_FC) \ $(built_ota_tools) \ $(APKCERTS_FILE) \ $(HOST_OUT_EXECUTABLES)/fs_config \ | $(ACP)为指标添（out/…/obj/PACKAGING/ target-files_intermeidates/p92-target_files-eng.zip）加依赖，分为两种依赖，“|”前为一般依赖，即这些依赖 INSTALLED_BOOTIMAGE_TARGET 产生扭转，maketarget时指标也要从新构建；“|”后为 order-only 依赖，示意 ACP 这个变量若产生扭转，而 target 曾经存在时则不须要被重建，若第一次生成则须要重建。
ifeq ($(TARGET_USERIMAGES_USE_EXT4),true)$(BUILT_TARGET_FILES_PACKAGE): $(INSTALLED_CACHEIMAGE_TARGET)Endif持续增加依赖 $(INSTALLED_CACHEIMAGE_TARGET)
@echo "Package target files: $@" $(hide) rm -rf $@ $(zip_root) $(hide) mkdir -p $(dir $@) $(zip_root) @# Components of the recovery image $(hide) mkdir -p $(zip_root)/RECOVERY $(hide) $(call package_files-copy-root, \ $(TARGET_RECOVERY_ROOT_OUT),$(zip_root)/RECOVERY/RAMDISK)ifdef INSTALLED_KERNEL_TARGET $(hide) $(ACP) $(INSTALLED_KERNEL_TARGET) $(zip_root)/RECOVERY/kernel $(hide) $(ACP) $(recovery_ramdisk) $(zip_root)/RECOVERY/ramdiskifeq ($(MTK_HEADER_SUPPORT),yes) $(hide) $(ACP) $(recovery_ramdisk_bthdr) $(zip_root)/RECOVERY/ramdisk-bthdrendifendififdef INSTALLED_2NDBOOTLOADER_TARGET $(hide) $(ACP) \ $(INSTALLED_2NDBOOTLOADER_TARGET) $(zip_root)/RECOVERY/secondendififdef BOARD_KERNEL_CMDLINE $(hide) echo "$(BOARD_KERNEL_CMDLINE)" > $(zip_root)/RECOVERY/cmdlineendififdef BOARD_KERNEL_BASE $(hide) echo "$(BOARD_KERNEL_BASE)" > $(zip_root)/RECOVERY/baseendififdef BOARD_KERNEL_PAGESIZE $(hide) echo "$(BOARD_KERNEL_PAGESIZE)" > $(zip_root)/RECOVERY/pagesizeendififdef BOARD_RAMDISK_OFFSET $(hide) echo "$(BOARD_RAMDISK_OFFSET)" > $(zip_root)/RECOVERY/ramdisk_offsetendififdef BOARD_KERNEL_OFFSET $(hide) echo "$(BOARD_KERNEL_OFFSET)" > $(zip_root)/RECOVERY/kernel_offsetendififdef BOARD_TAGS_OFFSET $(hide) echo "$(BOARD_TAGS_OFFSET)" > $(zip_root)/RECOVERY/tags_offsetendif $(hide) if [ -f $(PRODUCT_OUT)/custom_build_verno ]; then \ cat $(PRODUCT_OUT)/custom_build_verno > $(zip_root)/RECOVERY/board; \ fi @# Components of the boot image $(hide) mkdir -p $(zip_root)/BOOT $(hide) $(call package_files-copy-root, \ $(TARGET_ROOT_OUT),$(zip_root)/BOOT/RAMDISK)ifdef INSTALLED_KERNEL_TARGET $(hide) $(ACP) $(INSTALLED_KERNEL_TARGET) $(zip_root)/BOOT/kernel $(hide) $(ACP) $(INSTALLED_RAMDISK_TARGET) $(zip_root)/BOOT/ramdiskendififdef INSTALLED_2NDBOOTLOADER_TARGET $(hide) $(ACP) \ $(INSTALLED_2NDBOOTLOADER_TARGET) $(zip_root)/BOOT/secondendififdef BOARD_KERNEL_CMDLINE $(hide) echo "$(BOARD_KERNEL_CMDLINE)" > $(zip_root)/BOOT/cmdlineendififdef BOARD_KERNEL_BASE $(hide) echo "$(BOARD_KERNEL_BASE)" > $(zip_root)/BOOT/baseendififdef BOARD_RAMDISK_OFFSET $(hide) echo "$(BOARD_RAMDISK_OFFSET)" > $(zip_root)/BOOT/ramdisk_offsetendififdef BOARD_KERNEL_OFFSET $(hide) echo "$(BOARD_KERNEL_OFFSET)" > $(zip_root)/BOOT/kernel_offsetendififdef BOARD_TAGS_OFFSET $(hide) echo "$(BOARD_TAGS_OFFSET)" > $(zip_root)/BOOT/tags_offsetendififdef BOARD_KERNEL_PAGESIZE $(hide) echo "$(BOARD_KERNEL_PAGESIZE)" > $(zip_root)/BOOT/pagesizeendif $(hide) if [ -f $(PRODUCT_OUT)/custom_build_verno ]; then \ cat $(PRODUCT_OUT)/custom_build_verno > $(zip_root)/BOOT/board; \ fi $(hide) $(foreach t,$(INSTALLED_RADIOIMAGE_TARGET),\ mkdir -p $(zip_root)/RADIO; \ $(ACP) $(t) $(zip_root)/RADIO/$(notdir $(t));) @# Contents of the system image $(hide) $(call package_files-copy-root, \ $(SYSTEMIMAGE_SOURCE_DIR),$(zip_root)/SYSTEM) @# Contents of the data image $(hide) $(call package_files-copy-root, \ $(TARGET_OUT_DATA),$(zip_root)/DATA) @# Contents of the apd image $(hide) $(call package_files-copy-root, \ $(TARGET_OUT_APD),$(zip_root)/APD)ifdef BOARD_VENDORIMAGE_FILE_SYSTEM_TYPE @# Contents of the vendor image $(hide) $(call package_files-copy-root, \ $(TARGET_OUT_VENDOR),$(zip_root)/VENDOR)endif#wschen 2012-11-07 $(if $(BOARD_CUSTOMIMAGE_PARTITION_SIZE), \ $(hide) $(call package_files-copy-root, \ $(TARGET_CUSTOM_OUT),$(zip_root)/CUSTOM)) @# Extra contents of the OTA package $(hide) mkdir -p $(zip_root)/OTA/bin $(hide) $(ACP) $(INSTALLED_ANDROID_INFO_TXT_TARGET) $(zip_root)/OTA/ $(hide) $(ACP) $(PRIVATE_OTA_TOOLS) $(zip_root)/OTA/bin/下面内容次要是在 zip_root 目录下创立相应降级分区须要的目录，并把 out 目录下对应的文件 copy 到相应目录下。如果须要增加一个新分区到 ota 中，则须要在下面做一些批改，可参考 apd 分区。
@# Security information of the OTA package @echo "[SEC OTA] Adding Security information to OTA package" @echo "[SEC OTA] path : vendor/mediatek/proprietary/custom/$(MTK_BASE_PROJECT)/security/recovery/SEC_VER.txt" $(hide) $(ACP) vendor/mediatek/proprietary/custom/$(MTK_BASE_PROJECT)/security/recovery/SEC_VER.txt $(zip_root)/OTA/ -$(hide) $(ACP) $(PRODUCT_OUT)/trustzone.bin $(zip_root)/OTA/ @# Files that do not end up in any images, but are necessary to @# build them. $(hide) mkdir -p $(zip_root)/META $(hide) $(ACP) $(APKCERTS_FILE) $(zip_root)/META/apkcerts.txt $(hide) if test -e $(tool_extensions)/releasetools.py; then $(ACP) $(tool_extensions)/releasetools.py $(zip_root)/META/; fi $(hide) echo "$(PRODUCT_OTA_PUBLIC_KEYS)" > $(zip_root)/META/otakeys.txt $(hide) echo "recovery_api_version=$(PRIVATE_RECOVERY_API_VERSION)" > $(zip_root)/META/misc_info.txt $(hide) echo "fstab_version=$(PRIVATE_RECOVERY_FSTAB_VERSION)" >> $(zip_root)/META/misc_info.txtfdef BOARD_FLASH_BLOCK_SIZE $(hide) echo "blocksize=$(BOARD_FLASH_BLOCK_SIZE)" >> $(zip_root)/META/misc_info.txtendififdef BOARD_BOOTIMAGE_PARTITION_SIZE $(hide) echo "boot_size=$(BOARD_BOOTIMAGE_PARTITION_SIZE)" >> $(zip_root)/META/misc_info.txtendififdef BOARD_RECOVERYIMAGE_PARTITION_SIZE $(hide) echo "recovery_size=$(BOARD_RECOVERYIMAGE_PARTITION_SIZE)" >> $(zip_root)/META/misc_info.txtendififdef TARGET_RECOVERY_FSTYPE_MOUNT_OPTIONS @# TARGET_RECOVERY_FSTYPE_MOUNT_OPTIONS can be empty to indicate that nothing but defaults should be used. $(hide) echo "recovery_mount_options=$(TARGET_RECOVERY_FSTYPE_MOUNT_OPTIONS)" >> $(zip_root)/META/misc_info.txtelse $(hide) echo "recovery_mount_options=$(DEFAULT_TARGET_RECOVERY_FSTYPE_MOUNT_OPTIONS)" >> $(zip_root)/META/misc_info.txtendif $(hide) echo "tool_extensions=$(tool_extensions)" >> $(zip_root)/META/misc_info.txt $(hide) echo "default_system_dev_certificate=$(DEFAULT_KEY_CERT_PAIR)" >> $(zip_root)/META/misc_info.txtifdef PRODUCT_EXTRA_RECOVERY_KEYS $(hide) echo "extra_recovery_keys=$(PRODUCT_EXTRA_RECOVERY_KEYS)" >> $(zip_root)/META/misc_info.txtendif $(hide) echo 'mkbootimg_args=$(BOARD_MKBOOTIMG_ARGS)' >> $(zip_root)/META/misc_info.txt $(hide) echo "use_set_metadata=1" >> $(zip_root)/META/misc_info.txt $(hide) echo "multistage_support=1" >> $(zip_root)/META/misc_info.txt $(hide) echo "update_rename_support=1" >> $(zip_root)/META/misc_info.txt $(hide) echo "blockimgdiff_versions=1,2" >> $(zip_root)/META/misc_info.txtifeq ($(MTK_HEADER_SUPPORT),yes) $(hide) echo "mtk_header_support=1" >> $(zip_root)/META/misc_info.txtendififneq ($(OEM_THUMBPRINT_PROPERTIES),) # OTA scripts are only interested in fingerprint related properties $(hide) echo "oem_fingerprint_properties=$(OEM_THUMBPRINT_PROPERTIES)" >> $(zip_root)/META/misc_info.txtendififeq ($(TARGET_USERIMAGES_USE_UBIFS),true) $(call generate-ubifs-prop-dictionary, $(zip_root)/META/misc_info.txt)endif $(call generate-userimage-prop-dictionary, $(zip_root)/META/misc_info.txt)ifeq ($(TRUSTONIC_TEE_SUPPORT),yes) $(hide) ./build/tools/releasetools/make_recovery_patch $(zip_root) $(zip_root) $(PRODUCT_OUT)else $(hide) ./build/tools/releasetools/make_recovery_patch $(zip_root) $(zip_root) $(TRUSTONIC_TEE_SUPPORT)endififeq ($(strip $(MTK_SECURITY_SW_SUPPORT)), yes) #security boot signature $(hide) $(SHELL) $(SECURITY_SIG_TOOL) $(hide) cp $(PRODUCT_OUT)/sig/boot.sig $(zip_root)/META/ $(hide) cp $(PRODUCT_OUT)/sig/recovery.sig $(zip_root)/META/ $(hide) cp $(PRODUCT_OUT)/sig/recovery.sig $(zip_root)/SYSTEM/etc/Endif持续做一些 copy 文件的动作。
@# Zip everything up, preserving symlinks $(hide) (cd $(zip_root) && zip -qry ../$(notdir $@) .) @# Run fs_config on all the system, vendor, boot ramdisk, @# and recovery ramdisk files in the zip, and save the output把 zip_root 中的内容压缩成指标压缩包 zip –qry …/p92-target_files-eng.zip 。
$(hide) zipinfo -1 $@ | awk 'BEGIN { FS="SYSTEM/" } /^SYSTEM\// {print "system/" $$2}' | $(HOST_OUT_EXECUTABLES)/fs_config -C -S $(SELINUX_FC) > $(zip_root)/META/filesystem_config.txt $(hide) zipinfo -1 $@ | awk 'BEGIN { FS="VENDOR/" } /^VENDOR\// {print "vendor/" $$2}' | $(HOST_OUT_EXECUTABLES)/fs_config -C -S $(SELINUX_FC) > $(zip_root)/META/vendor_filesystem_config.txt $(hide) zipinfo -1 $@ | awk 'BEGIN { FS="APD/" } /^APD\// {print "apd/" $$2}' | $(HOST_OUT_EXECUTABLES)/fs_config -C -S $(SELINUX_FC) > $(zip_root)/META/apd_filesystem_config.txt $(hide) zipinfo -1 $@ | awk 'BEGIN { FS="BOOT/RAMDISK/" } /^BOOT\/RAMDISK\// {print $$2}' | $(HOST_OUT_EXECUTABLES)/fs_config -C -S $(SELINUX_FC) > $(zip_root)/META/boot_filesystem_config.txt $(hide) zipinfo -1 $@ | awk 'BEGIN { FS="RECOVERY/RAMDISK/" } /^RECOVERY\/RAMDISK\// {print $$2}' | $(HOST_OUT_EXECUTABLES)/fs_config -C -S $(SELINUX_FC) > $(zip_root)/META/recovery_filesystem_config.txt#wschen 2012-11-07 $(if $(BOARD_CUSTOMIMAGE_PARTITION_SIZE), \ $(hide) zipinfo -1 $@ | awk 'BEGIN { FS="CUSTOM/" } /^CUSTOM\// {print "custom/" $$2}' | $(HOST_OUT_EXECUTABLES)/fs_config -C -S $(SELINUX_FC) > $(zip_root)/META/custom_filesystem_config.txt)为须要ota降级的分区目录及其目录下的文件增加selinux权限，并把这些权限内容输入到X_filesystem_config.txt 文件中，如meta/apd_filesystem_config.txt:
apd 0 0 755selabel=u:object_r:apd_file:s0 capabilities=0x0apd/test.ini 0 2000 777selabel=u:object_r:apd_file:s0 capabilities=0x0apd/apd.txt 0 2000 777selabel=u:object_r:apd_file:s0 capabilities=0x0apd/apd.ini 0 2000 777selabel=u:object_r:apd_file:s0 capabilities=0x0$(hide) (cd $(zip_root) && zip -q ../$(notdir $@) META/*filesystem_config.txt)把这些 *filesystem_config.txt 文件一并搁置指标压缩包中
$(hide) ./build/tools/releasetools/add_img_to_target_files -p $(HOST_OUT) $@这个文件 add_img_to_target_files.py 很重要,次要性能是生成一个 images 文件夹，寄存着生成的各种 img（包含须要增加至 ota 降级的分区），如下图。如果须要把一个新分区增加至 ota 升级包中，这个文件则须要批改，可参考 custom/vendor 分区的增加办法。
$(hide) ./build/tools/releasetools/replace_img_from_target_files.py $@ $(PRODUCT_OUT)要理解这句话的次要目标，来看一下 replace_img_from_target_files.py 文件的注解：
'''Given a target-files zipfilethat does contain images (ie, doeshave an IMAGES/ top-level subdirectory), replace the images tothe output dir.Usage: replace_img_from_target_files target_files output'''把指标压缩包 out/target/product/(project)/obj/PACKAGING/target−filesintermeidates/p92−targetfiles−eng.zip 中的images/ 门路下的各个 img 输入到 out/target/product/(project)/obj/PACKAGING/target-files_intermeidates/p92-target_files-eng.zip中的 images/ 门路下的各个 img 输入到 out/target/product/(project)/obj/PACKAGING/target−filesintermeidates/p92−targetfiles−eng.zip 中的 images/ 门路下的各个 img 输入到 out/target/product/(project-name)/ 目录下。比方替换 out… 目录下原来的 boot.img，system.img，apd.img 等。
而后来看一下另外一个依赖：
DISTTOOLS := $(HOST_OUT_EXECUTABLES)/minigzip \ $(HOST_OUT_EXECUTABLES)/mkbootfs \ $(HOST_OUT_EXECUTABLES)/mkbootimg \ $(HOST_OUT_EXECUTABLES)/fs_config \ $(HOST_OUT_EXECUTABLES)/mkyaffs2image \ $(HOST_OUT_EXECUTABLES)/zipalign \ $(HOST_OUT_EXECUTABLES)/bsdiff \ $(HOST_OUT_EXECUTABLES)/imgdiff \ $(HOST_OUT_JAVA_LIBRARIES)/dumpkey.jar \ $(HOST_OUT_JAVA_LIBRARIES)/signapk.jar \ $(HOST_OUT_EXECUTABLES)/mkuserimg.sh \ $(HOST_OUT_EXECUTABLES)/make_ext4fs \ $(HOST_OUT_EXECUTABLES)/simg2img \ $(HOST_OUT_EXECUTABLES)/e2fsck \ $(HOST_OUT_EXECUTABLES)/build_verity_tree \ $(HOST_OUT_EXECUTABLES)/verity_signer \ $(HOST_OUT_EXECUTABLES)/append2simg其实就是定义 disttools 为 out/host/ 目录下的一些可执行文件。
最初再跳到终极目标的 cmd 开始执行：
$(hide) MTK_SECURITY_SW_SUPPORT=$(MTK_SECURITY_SW_SUPPORT) MKBOOTIMG=$(MKBOOTIMG) \ ./build/tools/releasetools/ota_from_target_files -v \ --block \ -p $(HOST_OUT) \ -k $(KEY_CERT_PAIR) \ $(if $(OEM_OTA_CONFIG), -o $(OEM_OTA_CONFIG)) \ $(BUILT_TARGET_FILES_PACKAGE) $@所以跳到 ota_from_target_files python 文件中，接下来就要看 ota_from_target_files 这个文件的作用了。