本篇文章主要介绍了"Android Recovery OTA升级（一）—— make otapackage"，主要涉及到方面的内容，对于Android开发感兴趣的同学可以参考一下：
目录目录概述make otapackageBUILT_TARGET_FILES_PACKAGEota_from_target_filesWriteFullOTA...
目录
- 目录
- 概述
- make otapackage
- BUILT_TARGET_FILES_PACKAGE
- ota_from_target_files
- WriteFullOTAPackage
- SignOutput
- 总结
概述
make otapackage是Android Build系统支持的命令，用来生成Recovery系统能够进行升级的zip包。因此，想要了解Android的OTA升级机制，我们首先需要学习make otapackage命令的执行过程。
为了防止泄密，以下源码内容都是基于Android4.4.2_r1分支进行分析。
make otapackage
make otapackage是一个.PHONY伪目标。make系统中，伪目标并不是一个文件，只是一个标签，由于伪目标不是文件，所以make无法生成它的依赖关系和决定它是否要执行。我们只能通过显示的指明这个“目标”才能让其生效。需要注意的是，伪目标的取名不能和文件名重名，不然就失去伪目标的意义了。
了解了.PHONY之后，我们来看一下make otapackage的make源码：
.PHONY: otapackage
otapackage: $(INTERNAL_OTA_PACKAGE_TARGET)
通过make代码，我们看到otapackage这个伪目标是依赖于$(INTERNAL_OTA_PACKAGE_TARGET)的，接下来，我会分析一下依赖文件的生成源码:
INTERNAL_OTA_PACKAGE_TARGET := $(PRODUCT_OUT)/$(name).zip
$(INTERNAL_OTA_PACKAGE_TARGET): KEY_CERT_PAIR := $(DEFAULT_KEY_CERT_PAIR)
$(INTERNAL_OTA_PACKAGE_TARGET): $(BUILT_TARGET_FILES_PACKAGE) $(DISTTOOLS)
@echo"Package OTA: $@"$(hide) ./build/tools/releasetools/ota_from_target_files -v \
-p $(HOST_OUT) \
-k $(KEY_CERT_PAIR) \
$(BUILT_TARGET_FILES_PACKAGE) $@
可以看到，$(INTERNAL_OTA_PACKAGE_TARGET)依赖于$(KEY_CERT_PAIR),$(HOST_OUT),$(BUILT_TARGET_FILES_PACKAGE)这三个文件和$(DISTTOOLS)所代表的jar包。
而这些所依赖的文件，最后都会作为参数传递给ota_from_target_files这个python脚本，这个python脚本会进一步生成最终的recovery升级包。示例参数如下：
['-v', '-p', 'out/host/linux-x86', '-k', 'build/target/product/security/testkey', 'out/target/product/xxx/obj/PACKAGING/target_files_intermediates/product-target_files-wangzhengyi.zip', 'out/target/product/xxx/product_20150724.1246-ota.zip']
从参数中可以看出，out/target/product/xxx/product_20150724.1246-ota.zip是最终的recovery升级包，而out/target/product/xxx/obj/PACKAGING/target_files_intermediates/product-target_files-wangzhengyi.zip是中间的临时zip包，它其实就是$(BUILT_TARGET_FILES_PACKAGE)，接下来我们看一下$(BUILT_TARGET_FILES_PACKAGE)的生成代码。
BUILT_TARGET_FILES_PACKAGE
BUILT_TARGET_FILES_PACKAGE的make源码如下：
BUILT_TARGET_FILES_PACKAGE:= $(intermediates)/$(name).zip
$(BUILT_TARGET_FILES_PACKAGE): intermediates := $(intermediates)
$(BUILT_TARGET_FILES_PACKAGE): zip_root := $(intermediates)/$(name)
# $(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); \
fi
endif
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)/sqlite3 \
$(call intermediates-dir-for,EXECUTABLES,updater)/updater
$(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:= $(RECOVERY_FSTAB_VERSION)
# 开始构建中间zip包$(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)
@echo"Package target files: $@"# 删除之前的zip文件$(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) $(INSTALLED_KERNEL_TARGET) $(zip_root)/RECOVERY/kernel
endif
ifdef INSTALLED_2NDBOOTLOADER_TARGET$(hide) $(ACP) \
$(INSTALLED_2NDBOOTLOADER_TARGET) $(zip_root)/RECOVERY/second
endif
ifdef BOARD_KERNEL_CMDLINE$(hide) echo "$(BOARD_KERNEL_CMDLINE)" > $(zip_root)/RECOVERY/cmdline
endif
ifdef BOARD_KERNEL_PAGESIZE$(hide) echo "$(BOARD_KERNEL_PAGESIZE)" > $(zip_root)/RECOVERY/pagesize
endif
$(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)
ifdef BOARD_VENDORIMAGE_FILE_SYSTEM_TYPE
@# Contents of the vendor image$(hide) $(
以上就介绍了Android Recovery OTA升级（一）—— make otapackage，包括了方面的内容，希望对Android开发有兴趣的朋友有所帮助。
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