安卓OTA升级系统解析上

在MTK安卓环境中只需要在alps 目录执行./mk otapackage即可打包ota升级包，下面我们来分析下这个过程中。
alps/mk代码片段

sub chkDep {
  my $module = $_[0];
  my $string = $module;
  if (!$module)
  {
    $string = all;
  }
# print "*********************************\n \"$string\" Dependency Checking...\n";
  my $result;
  #在./mk otapackage会调用mediatek/build/makemtk.mk中的otapackage目标
  $result = &p_system("CUR_MODULE=$module make -f mediatek/build/makemtk.mk check-dep $cmdArg @mOpts > $logdir/${project}_check-dep.log 2>&1");
  &p_system("cat $logdir/${project}_check-dep.log");
  if ($result)
  {
    &p_system("cp -f $logdir/${project}_check-dep.log $logdir/${project}_check-dep.log_err");
    die "Please check all dependency error First !!";
  }
}

接下来查看mediatek/build/makemtk.mk otapackage目标

从上图可以看出otapackage依赖于system.img boot.img recovery.img secro.img userdata.img目标
在打包otapackage过程中，mtk平台会重现编译上述的img
最终会执行alps/build/core/Makefile 中的otapackage目标

# -----------------------------------------------------------------
# OTA update package

name := $(TARGET_PRODUCT)
ifeq ($(TARGET_BUILD_TYPE),debug)
  name := $(name)_debug
endif
name := $(name)-ota-$(FILE_NAME_TAG)

FWUPGRADEPACKAGE_SH := ./build/core/FWUpgradePackage.sh
INTERNAL_OTA_PACKAGE_TARGET := $(PRODUCT_OUT)/$(name).zip

$(INTERNAL_OTA_PACKAGE_TARGET): KEY_CERT_PAIR := $(DEFAULT_KEY_CERT_PAIR)

ifeq ($(strip $(MTK_FW_UPGRADE)), yes)
$(INTERNAL_OTA_PACKAGE_TARGET): $(FWUPGRADEPACKAGE_SH)
endif
$(INTERNAL_OTA_PACKAGE_TARGET): $(BUILT_TARGET_FILES_PACKAGE) $(DISTTOOLS)
    @echo "Package OTA: $@"
ifneq ($(TARGET_USERIMAGES_USE_UBIFS),true)
    $(hide) ./build/tools/releasetools/ota_from_target_files -v \
       -n \
       -p $(HOST_OUT) \
       -k $(KEY_CERT_PAIR) \
       $(BUILT_TARGET_FILES_PACKAGE) $@
else
    $(hide) ./build/tools/releasetools/ota_from_target_files -v \
       -n \
       -g \
       -p $(HOST_OUT) \
       -k $(KEY_CERT_PAIR) \
       $(BUILT_TARGET_FILES_PACKAGE) $@
endif
ifeq ($(strip $(MTK_FW_UPGRADE)), yes)
    @echo "Package FWUpgradePackage"
    bash $(FWUPGRADEPACKAGE_SH) $(PRODUCT_OUT) $(KEY_CERT_PAIR)
endif

.PHONY: otapackage #otapackage 目标
otapackage: $(INTERNAL_OTA_PACKAGE_TARGET)

上面可以看出$(INTERNAL_OTA_PACKAGE_TARGET)依赖于$(KEY_CERT_PAIR),$(HOST_OUT),$(BUILT_TARGET_FILES_PACKAGE)，$(HOST_OUT)为主机输出目录，$(KEY_CERT_PAIR)为签名相关信息，$(BUILT_TARGET_FILES_PACKAGE)
‘BUILT_TARGET_FILES_PACKAGE’目标如下：

# -----------------------------------------------------------------
# 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)_debug
endif
name := $(name)-target_files-$(FILE_NAME_TAG)

intermediates := $(call intermediates-dir-for,PACKAGING,target_files)
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
endef

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)

ifeq ($(TARGET_RELEASETOOLS_EXTENSIONS),)
# default to common dir for device vendor
$(BUILT_TARGET_FILES_PACKAGE): tool_extensions := $(TARGET_DEVICE_DIR)/../common
else
$(BUILT_TARGET_FILES_PACKAGE): tool_extensions := $(TARGET_RELEASETOOLS_EXTENSIONS)
endif

# 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 \
        | $(ACP)
ifeq ($(TARGET_USERIMAGES_USE_EXT4),true)
$(BUILT_TARGET_FILES_PACKAGE): $(INSTALLED_CACHEIMAGE_TARGET)
endif
$(BUILT_TARGET_FILES_PACKAGE): \
        $(INSTALLED_FACTORYIMAGE_TARGET) \
        $(if $(BOARD_CUSTOMIMAGE_PARTITION_SIZE), $(INSTALLED_CUSTOMIMAGE_TARGET)) \
        $(INSTALLED_SECROIMAGE_TARGET) \
        mediatek/custom/$(MTK_PROJECT)/security/recovery/SEC_VER.txt
    @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/ramdisk
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_BASE
    $(hide) echo "$(BOARD_KERNEL_BASE)" > $(zip_root)/RECOVERY/base
endif
    @# Components of the factory image
    $(hide) mkdir -p $(zip_root)/FACTORY
    $(hide) $(call package_files-copy-root, \
        $(TARGET_FACTORY_ROOT_OUT),$(zip_root)/FACTORY/RAMDISK)
ifdef INSTALLED_KERNEL_TARGET
    $(hide) $(ACP) $(INSTALLED_KERNEL_TARGET) $(zip_root)/FACTORY/kernel
endif
ifdef BOARD_KERNEL_PAGESIZE
    $(hide) echo "$(BOARD_KERNEL_PAGESIZE)" > $(zip_root)/RECOVERY/pagesize
endif
ifdef INSTALLED_2NDBOOTLOADER_TARGET
    $(hide) $(ACP) \
        $(INSTALLED_2NDBOOTLOADER_TARGET) $(zip_root)/FACTORY/second
endif
ifdef BOARD_KERNEL_CMDLINE
    $(hide) echo "$(BOARD_KERNEL_CMDLINE)" > $(zip_root)/FACTORY/cmdline
endif
ifdef BOARD_KERNEL_BASE
    $(hide) echo "$(BOARD_KERNEL_BASE)" > $(zip_root)/FACTORY/base
endif
    @# 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/ramdisk
endif
ifdef INSTALLED_2NDBOOTLOADER_TARGET
    $(hide) $(ACP) \
        $(INSTALLED_2NDBOOTLOADER_TARGET) $(zip_root)/BOOT/second
endif
ifdef BOARD_KERNEL_CMDLINE
    $(hide) echo "$(BOARD_KERNEL_CMDLINE)" > $(zip_root)/BOOT/cmdline
endif
ifdef BOARD_KERNEL_BASE
    $(hide) echo "$(BOARD_KERNEL_BASE)" > $(zip_root)/BOOT/base
endif
ifdef BOARD_KERNEL_PAGESIZE
    $(hide) echo "$(BOARD_KERNEL_PAGESIZE)" > $(zip_root)/BOOT/pagesize
endif
#wschen
    $(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)
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) $(zip_root)/OTA/bin/
    @# Security information of the OTA package
    @echo "[SEC OTA] Adding Security information to OTA package"
    @echo "[SEC OTA] path : mediatek/custom/$(MTK_PROJECT)/security/recovery/SEC_VER.txt"
    $(hide) $(ACP) mediatek/custom/$(MTK_PROJECT)/security/recovery/SEC_VER.txt $(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
    $(hide)	echo "$(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.txt
ifdef BOARD_FLASH_BLOCK_SIZE
    $(hide) echo "blocksize=$(BOARD_FLASH_BLOCK_SIZE)" >> $(zip_root)/META/misc_info.txt
endif
ifdef BOARD_BOOTIMAGE_PARTITION_SIZE
    $(hide) echo "boot_size=$(BOARD_BOOTIMAGE_PARTITION_SIZE)" >> $(zip_root)/META/misc_info.txt
endif
ifdef BOARD_RECOVERYIMAGE_PARTITION_SIZE
    $(hide) echo "recovery_size=$(BOARD_RECOVERYIMAGE_PARTITION_SIZE)" >> $(zip_root)/META/misc_info.txt
endif
    $(hide) echo "tool_extensions=$(tool_extensions)" >> $(zip_root)/META/misc_info.txt
    $(hide) echo "default_system_dev_certificate=$(DEFAULT_KEY_CERT_PAIR)" >> $(zip_root)/META/misc_info.txt
ifdef PRODUCT_EXTRA_RECOVERY_KEYS
    $(hide) echo "extra_recovery_keys=$(PRODUCT_EXTRA_RECOVERY_KEYS)" >> $(zip_root)/META/misc_info.txt
endif
    $(hide) echo "mkbootimg_args=$(BOARD_MKBOOTIMG_ARGS)" >> $(zip_root)/META/misc_info.txt
    $(hide) echo "use_set_metadata=1" >> $(zip_root)/META/misc_info.txt
    $(hide) echo "update_rename_support=1" >> $(zip_root)/META/misc_info.txt
    $(call generate-userimage-prop-dictionary, $(zip_root)/META/misc_info.txt)
    @# Zip everything up, preserving symlinks
    $(hide) (cd $(zip_root) && zip -qry ../$(notdir $@) .)
    @# Run fs_config on all the system, boot ramdisk, and recovery ramdisk files in the zip, and save the output
    $(hide) zipinfo -1 $@ | awk 'BEGIN { FS="SYSTEM/" } /^SYSTEM\// {print "system/" $$2}' | $(HOST_OUT_EXECUTABLES)/fs_config -C -S $(SELINUX_FC) > $(zip_root)/META/filesystem_config.txt
	$(hide) zipinfo -1 $@ | awk 'BEGIN { FS="BOOT/RAMDISK/" } /^BOOT\/RAMDISK\// {print $$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 >> $(zip_root)/META/filesystem_config.txt)
    $(hide) (cd $(zip_root) && zip -q ../$(notdir $@) META/*filesystem_config.txt)

.PHONY: target-files-package
target-files-package: $(BUILT_TARGET_FILES_PACKAGE)


ifneq ($(TARGET_PRODUCT),sdk)
ifeq ($(filter generic%,$(TARGET_DEVICE)),)
ifneq ($(TARGET_NO_KERNEL),true)
ifneq ($(recovery_fstab),)

实际上最终执行的操作为：

    $(hide) ./build/tools/releasetools/ota_from_target_files -v \
       -n \        -g \        -p $(HOST_OUT) \        -k $(KEY_CERT_PAIR) \        $(BUILT_TARGET_FILES_PACKAGE) $@

上述所依赖的文件，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：

 ./build/tools/releasetools/ota_from_target_files
-v -n -g -p out/host/linux-x86 
-k build/target/product/security/testkey out/target/product/streambox/obj/PACKAGING/target_files_intermediates/streambox-target_files-eng.xiaojingling.zip
out/target/product/streambox/streambox-ota-eng.xiaojingling.zip

img_from_target_files为核心脚本，后面会专门解析此脚本。