转载
概要
此局部为全包降级次要实现过程，波及到ota_from_target_files 文件，这个也是制作全包和差分包的次要工具，接下来咱们就着重剖析怎么利用这个工具制作full_ota_package的。
次要流程
源码剖析
上节中 Makefile 中 otapackage 指标最初的 cmd 为：
$(hide) MTK_SECURITY_SW_SUPPORT=$(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，接下来咱们先看一下这个文件的作用，usage 以及 cmd 所带的参数的意义。
"""Given a target-files zipfile, produces an OTA package that installsthat build. An incremental OTA is produced if -i is given, otherwisea full OTA is produced.Usage: ota_from_target_files [flags] input_target_files output_ota_package --board_config <file> Deprecated. -k (--package_key) <key> Key to use to sign the package (default isthe value of default_system_dev_certificate from the inputtarget-files's META/misc_info.txt, or "build/target/product/security/testkey" if that value is notspecified). For incremental OTAs, the default value is based on the sourcetarget-file, not the target build. -i (--incremental_from) <file> Generate an incremental OTA using the given target-files zip asthe starting build. -v (--verify) Remount and verify the checksums of the files written to thesystem and vendor (if used) partitions. Incremental builds only. -o (--oem_settings) <file> Use the file to specify the expected OEM-specific propertieson the OEM partition of the intended device. -w (--wipe_user_data) Generate an OTA package that will wipe the user data partitionwhen installed. -n (--no_prereq) Omit the timestamp prereq check normally included at the top ofthe build scripts (used for developer OTA packages whichlegitimately need to go back and forth). -e (--extra_script) <file> Insert the contents of file at the end of the update script. -r (--preloader) <file> Specify 'preloader.img' to upgrade. -l (--logo) <file> Specify 'logo.img' to upgrade. -u (--uboot) <file> Specify 'uboot.img/lk.img' to upgrade. -a (--aslr_mode) <on|off> Specify whether to turn on ASLR for the package (on by default). -2 (--two_step) Generate a 'two-step' OTA package, where recovery is updatedfirst, so that any changes made to the system partition are doneusing the new recovery (new kernel, etc.). --block Generate a block-based OTA if possible. Will fall back to afile-based OTA if the target_files is older and doesn't supportblock-based OTAs. -b (--binary) <file> Use the given binary as the update-binary in the output package,instead of the binary in the build's target_files. Use fordevelopment only. -t (--worker_threads) <int> Specifies the number of worker-threads that will be used whengenerating patches for incremental updates (defaults to 3). -f (--special_factory_reset) After upgrade, it will execute special factory reset. -z (--trustonic) <file> Specify 'mobicore.bin' to upgrade."""文件的作用如英文形容：给出一个 target_file 的 zip 包生成一个 ota 包，如果带 –i 参数则生成差分包，否则生成 full_ota_package
Usage: ota_from_target_files [flags] input_target_filesoutput_ota_package–board_config Deprecated.-k :指定sign package应用的key-i : 制作差分包，前面跟差分包根底包-v：verify性能-o：指定oem厂商信息-w：分明data区-n：是否查看工夫戳信息，以便确定向前或者向后降级-e：指定额定的降级脚本-r：是否降级preloader分区-l：是否降级logo分区-u：是否降级uboot分区-a：是否关上ASLR-2：生成一个two-step ota包–block：生成一个block_base的ota包-b：指定一个update-binary寄存到ota包中-t：指定线程数-f：指定是否复原出厂设置-z：指定mobicore.bin从此处开始执行，而后跳到 main 函数中
if __name__ == '__main__':try:common.CloseInheritedPipes()main(sys.argv[1:])except common.ExternalError, e:printprint " ERROR: %s" % (e,)printsys.exit(1)finally:common.Cleanup()上面这一段代码次要作用是解析命令行参数，除了下面曾经剖析的参数外，另外加上了 Common.ParseOptions() 接口中的参数列表，如下：
for o, a in opts:if o in ("-h", "--help"):Usage(docstring)sys.exit()elif o in ("-v", "--verbose"): OPTIONS.verbose = Trueelif o in ("-p", "--path"): OPTIONS.search_path = aelif o in ("--signapk_path",): OPTIONS.signapk_path = aelif o in ("--extra_signapk_args",): OPTIONS.extra_signapk_args = shlex.split(a)elif o in ("--java_path",): OPTIONS.java_path = aelif o in ("--java_args",): OPTIONS.java_args = aelif o in ("--public_key_suffix",): OPTIONS.public_key_suffix = aelif o in ("--private_key_suffix",): OPTIONS.private_key_suffix = aelif o in ("-s", "--device_specific"): OPTIONS.device_specific = aelif o in ("-x", "--extra"):key, value = a.split("=", 1)OPTIONS.extras[key] = valueelse:if extra_option_handler is None or notextra_option_handler(o, a):assert False, "unknown option \"%s\""% (o,)由之前Makefile的cmd来看：
./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) $@ 此段代码执行完结后：
OPTIONS.block_based = TrueOPTIONS.verbose = True（此处留神：-v代表verbose；–verify代表verify）OPTIONS.search_path= $(HOST_OUT) /* xxx/out/host/linux-x86 */OPTIONS.package_key = $(KEY_CERT_PAIR)args = [‘xxx-target_files-eng.xx.zip’,’xxx-ota-eng.xx.zip’]//前者是obj下的压缩包，后者是最终的ota包。如有纳闷，请自行参考getopt解析命令行参数模块代码
def main(argv):def option_handler(o, a):if o == "--board_config":pass # deprecatedelif o in ("-k", "--package_key"): OPTIONS.package_key = aelif o in ("-i", "--incremental_from"): OPTIONS.incremental_source = aelif o in ("-w", "--wipe_user_data"): OPTIONS.wipe_user_data = Trueelif o in ("-n", "--no_prereq"): OPTIONS.omit_prereq = Trueelif o in ("-o", "--oem_settings"): OPTIONS.oem_source = aelif o in ("-e", "--extra_script"): OPTIONS.extra_script = aelif o in ("-a", "--aslr_mode"): if a in ("on", "On", "true", "True", "yes", "Yes"): OPTIONS.aslr_mode = Trueelse: OPTIONS.aslr_mode = Falseelif o in ("-t", "--worker_threads"):if a.isdigit(): OPTIONS.worker_threads = int(a)else:raise ValueError("Cannot parse value %r for option %r - only " "integers are allowed." % (a, o))elif o in ("-f", "--special_factory_reset"): OPTIONS.special_factory_reset = Trueelif o in ("-x", "--tee"): OPTIONS.tee = a elif o in ("-z", "--trustonic"): OPTIONS.trustonic = aelif o in ("-2", "--two_step"): OPTIONS.two_step = Trueelif o in ("-r", "--preloader"): OPTIONS.preloader = aelif o in ("-l", "--logo"): OPTIONS.logo = aelif o in ("-u", "--uboot"): OPTIONS.uboot = aelif o in ("-f", "--special_factory_reset"): OPTIONS.special_factory_reset = Trueelif o in ("-g", "--ubifs"): OPTIONS.ubifs = Trueelif o == "--no_signing": OPTIONS.no_signing = Trueelif o in ("--verify"): OPTIONS.verify = Trueelif o == "--block": OPTIONS.block_based = Trueelif o in ("-b", "--binary"): OPTIONS.updater_binary = aelif o in ("--no_fallback_to_full",): OPTIONS.fallback_to_full = Falseelse:return Falsereturn True args = common.ParseOptions(argv, __doc__, extra_opts="b:k:i:d:wfgne:r:l:u:x:z:t:a:2o:", extra_long_opts=["board_config=", "package_key=", "incremental_from=", "wipe_user_data", "special_factory_reset", "ubifs", "tee=", "trustonic=", "no_prereq", "extra_script=", "preloader=", "logo=", "uboot=", "worker_threads=", "aslr_mode=", "two_step", "no_signing", "block", "binary=", "oem_settings=", "verify", "no_fallback_to_full", ], extra_option_handler=option_handler)if os.getenv("MTK_SECURITY_SW_SUPPORT", "no")=="no": OPTIONS.mtk_sec_boot_sig_tail = Falseif len(args) != 2:common.Usage(__doc__)sys.exit(1)/*此处为false*/if OPTIONS.extra_script is not None: OPTIONS.extra_script = open(OPTIONS.extra_script).read()解压输出压缩包到一个两头文件夹，并把目录赋给 OPTIONS.input_tem，同时创立一个输出压缩包的 ZipFile（zipfile.py 中）实例：input_zip
print "unzipping target target-files..." OPTIONS.input_tmp, input_zip = common.UnzipTemp(args[0])- 把输出压缩包的解压目录赋给
OPTIONS.target_tmp。 - 通过
input_zip读取压缩包中的META/misc_info.txt文件，以及RECOVERY/RAMDISK/etc/recovery.fstab，SYSTEM/build.prop等文件，并把文件内容并转换成字典模式OPTIONS.info_dict，建设字典代码如下：
def LoadDictionaryFromLines(lines): d = {}for line in lines: line = line.strip()if not line or line.startswith("#"):continueif "=" in line:name, value = line.split("=", 1)d[name] = valuereturn dOPTIONS.target_tmp = OPTIONS.input_tmp OPTIONS.info_dict = common.LoadInfoDict(input_zip)如果 OPTIONS.info_dict 中存在 key selinux_fc ，则 key 对应键值为：tmpxxx/BOOT/RAMDISK/file_contexts。如果冗余模式为真，则打印字典内容，此处为真。
# If this image was originally labelled with SELinux contexts, make sure we # also apply the labels in our new image. During building, the "file_contexts" # is in the out/ directory tree, but for repacking from target-files.zip it's # in the root directory of the ramdisk.if "selinux_fc" in OPTIONS.info_dict: OPTIONS.info_dict["selinux_fc"] = os.path.join(OPTIONS.input_tmp, "BOOT", "RAMDISK", "file_contexts") if OPTIONS.verbose:print "--- target info ---"common.DumpInfoDict(OPTIONS.info_dict)如果调用者利用 -s/–device_specific 指定了 device-specific extension 门路，则应用它。否者应用META/releasetools.py如果此文件存在 target_files 压缩包中。如果以上都没有，则通过查找字典中的 key：‘tool_extension’，来作为 device_specific。
#If the caller explicitly specified the device-specific extensions # path via -s/--device_specific, use that. Otherwise, use # META/releasetools.py if it is present inthe target target_files. # Otherwise, take the path of the file from 'tool_extensions' in the # info dict and look for that in the localfilesystem, relative to # the current directory. ifOPTIONS.device_specific is None: from_input =os.path.join(OPTIONS.input_tmp, "META", "releasetools.py")ifos.path.exists(from_input):print"(using device-specific extensions from target_files)" OPTIONS.device_specific = from_inputelse: OPTIONS.device_specific = OPTIONS.info_dict.get("tool_extensions",None) ifOPTIONS.device_specific is not None:OPTIONS.device_specific =os.path.abspath(OPTIONS.device_specific)S1：此处 OPTIONS.mtk_sec_boot_sig_tail 为真，读取 boot.sig 、recovery.sig 内容，
while True:if OPTIONS.mtk_sec_boot_sig_tail: #After WriteIncrementalOTAPackage, input_zip seems scramble, so read *.sig at first boot_sig = input_zip.read("META/boot.sig") recovery_sig = input_zip.read("META/recovery.sig")此处为 false，所以走 else 语句：创立一个 temp_zip_file 长期文件夹的 _TemporaryFileWrapper 实例。而后创立一个 zipfile 实例 output_zip，以 temp_zip_file 为入参。其实就是对1中的临时文件进行一个 zipfile 实例化，最初能够利用 zipfile 中的属性办法对这个文件进行操作，
if OPTIONS.no_signing:if os.path.exists(args[1]): os.unlink(args[1]) output_zip = zipfile.ZipFile(args[1], "w", compression=zipfile.ZIP_DEFLATED)else: temp_zip_file = tempfile.NamedTemporaryFile() output_zip = zipfile.ZipFile(temp_zip_file, "w",compression=zipfile.ZIP_DEFLATED)判断是否带 -i 参数，有则进行差分包制作，无则进行全包制作. 此处没有, 所以走if语句为真，而后跳到 WriteFullOTAPackage(input_zip,output_zip) 中执行，可参考后文详细分析。
if OPTIONS.incremental_source is None:WriteFullOTAPackage(input_zip,output_zip)ifOPTIONS.package_key is None: OPTIONS.package_key =OPTIONS.info_dict.get( "default_system_dev_certificate", "build/target/product/security/testkey")ifnot OPTIONS.mtk_sec_boot_sig_tail:breakelse:print"unzipping source target-files..." OPTIONS.source_tmp, source_zip =common.UnzipTemp(OPTIONS.incremental_source) OPTIONS.target_info_dict =OPTIONS.info_dict OPTIONS.source_info_dict =common.LoadInfoDict(source_zip)if"selinux_fc" in OPTIONS.source_info_dict: OPTIONS.source_info_dict["selinux_fc"] =os.path.join(OPTIONS.source_tmp, "BOOT", "RAMDISK", "file_contexts")ifOPTIONS.package_key is None: OPTIONS.package_key = OPTIONS.source_info_dict.get( "default_system_dev_certificate", "build/target/product/security/testkey")ifOPTIONS.verbose:print"--- source info ---"common.DumpInfoDict(OPTIONS.source_info_dict)try:WriteIncrementalOTAPackage(input_zip,source_zip, output_zip)ifnot OPTIONS.mtk_sec_boot_sig_tail:breakexceptValueError:ifnot OPTIONS.fallback_to_full: raiseprint"--- failed to build incremental; falling back to full ---" OPTIONS.incremental_source = None output_zip.close()接下来调到全包降级次要接口，
WriteFullOTAPackage(input_zip, output_zip)def WriteFullOTAPackage(input_zip, output_zip): # TODO: how to determine this? We don't know what version it will # be installed on top of. For now, we expect the API just won't # change very often.a1:创立一个脚本实例，这个脚本未来会被写入长期升级包中：/META-INF/com/google/android/updater-script
script = edify_generator.EdifyGenerator(3, OPTIONS.info_dict)/*获取oem参数，没有这个key*/ oem_props = OPTIONS.info_dict.get("oem_fingerprint_properties")/*获取recovery_mount_options key所对应的value*/ recovery_mount_options = OPTIONS.info_dict.get("recovery_mount_options")/*目前没有波及oem信息，上面几行疏忽*/ oem_dict = Noneif oem_props is not None and len(oem_props) > 0:if OPTIONS.oem_source is None:raise common.ExternalError("OEM source required for this build")script.Mount("/oem", recovery_mount_options) oem_dict = common.LoadDictionaryFromLines(open(OPTIONS.oem_source).readlines())M1：失去metadata字典，供最初一步应用：
post-build:alps/full_(PROJECTNAME)/(PROJECT_NAME)/(PROJECTNAME)/(PROJECT_NAME):5.1/LMY47D/1501228112:eng/test-keys
post-timestamp: 1501228303
pre-device: $(PROJECT_NAME)
metadata = {"post-build": CalculateFingerprint( oem_props, oem_dict, OPTIONS.info_dict), "pre-device": GetOemProperty("ro.product.device", oem_props, oem_dict, OPTIONS.info_dict), "post-timestamp": GetBuildProp("ro.build.date.utc", OPTIONS.info_dict), } device_specific = common.DeviceSpecificParams( input_zip=input_zip, input_version=OPTIONS.info_dict["recovery_api_version"], output_zip=output_zip,script=script, input_tmp=OPTIONS.input_tmp,metadata=metadata, info_dict=OPTIONS.info_dict)12345678910111213141516/判断是否有recovery path：target_files_zip.getinfo("SYSTEM/recovery-from-boot.p")，为真*/ has_recovery_patch = HasRecoveryPatch(input_zip)/*是否反对block，生成ota包时有带–block参数，所以此处为真*/ block_based = OPTIONS.block_based and has_recovery_patch/*不执行*/if not OPTIONS.omit_prereq:ts = GetBuildProp("ro.build.date.utc", OPTIONS.info_dict) ts_text = GetBuildProp("ro.build.date", OPTIONS.info_dict)script.AssertOlderBuild(ts, ts_text)降级脚本中增加：getprop(“ro.product.device”) ==“p92s_hd” || abort(“This package is for “p92s_hd"devices; this is a “” + getprop(“ro.product.device”) +””.");
AppendAssertions(script, OPTIONS.info_dict, oem_dict) device_specific.FullOTA_Assertions()此处为 false，不执行
if OPTIONS.two_step:if not OPTIONS.info_dict.get("multistage_support", None):assert False, "two-step packages not supported by this build"fs = OPTIONS.info_dict["fstab"]["/misc"]assert fs.fs_type.upper() == "EMMC", \ "two-step packages only supported on devices with EMMC /misc partitions" bcb_dev = {"bcb_dev": fs.device}common.ZipWriteStr(output_zip, "recovery.img", recovery_img.data)if OPTIONS.info_dict.get("mtk_header_support", None): recovery_bthdr_img = common.GetBootableImage("recovery_bthdr.img", "recovery_bthdr.img", OPTIONS.input_tmp, "RECOVERY")common.ZipWriteStr(output_zip, "recovery_bthdr.img", recovery_bthdr_img.data)script.AppendExtra("""if get_stage("%(bcb_dev)s") == "2/3" then""" % bcb_dev)script.WriteRawImage("/recovery", "recovery.img")script.AppendExtra("""set_stage("%(bcb_dev)s", "3/3");reboot_now("%(bcb_dev)s", "recovery");else if get_stage("%(bcb_dev)s") == "3/3" then""" % bcb_dev) device_specific.FullOTA_InstallBegin()system_progress = 0.75if OPTIONS.wipe_user_data: system_progress -= 0.1if HasVendorPartition(input_zip): system_progress -= 0.1if HasCustomPartition(input_zip): system_progress -= 0.1/*把file_contexts写入升级包中*/if "selinux_fc" in OPTIONS.info_dict:WritePolicyConfig(OPTIONS.info_dict["selinux_fc"], output_zip)/*失去recovery_mount_optionskey所对应的value*/ recovery_mount_options = OPTIONS.info_dict.get("recovery_mount_options")/*设置system分区对应的config文件为：META/filesystem_config.txt,留着后续应用*/ system_items = ItemSet("system", "META/filesystem_config.txt")/*在降级脚本中增加语句：show_progress(0.750000, 0);*/script.ShowProgress(system_progress, 0)此处为真，而后执行上面工作：
- 先从
input_tem(原始包解压后的两头文件夹)中失去system.img - 对
system.img进行resetFileMap，具体不必深究 - 在两头文件中生成：
system.transfer.list; system.new.dat ; system.patch.dat 最初再把这三个文件
system.transfer.list; system.new.dat ; system.patch.dat写入到 OTA包中，并增加script语句ui_print(“Patching system imageunconditionally…”);block_image_update(“system”,package_extract_file(“system.transfer.list”),“system.new.dat”, “system.patch.dat”);
以上波及到另外两个python文件：common.py ; blockimgdiff.py
if block_based: # Full OTA is done as an "incremental" against an empty source # image. This has the effect of writing new data from the package # to the entire partition, but lets us reuse the updater code that # writes incrementals to do it. system_tgt = GetImage("system", OPTIONS.input_tmp, OPTIONS.info_dict) system_tgt.ResetFileMap() system_diff = common.BlockDifference("system", system_tgt, src=None) system_diff.WriteScript(script, output_zip)else:if OPTIONS.ubifs: cust_dir1 = GetBuildProp("ro.product.device", OPTIONS.info_dict) system_path = os.path.join("out/target/product",cust_dir1,"android.fixup.img")if os.path.exists(system_path): system_img = open(system_path).read()common.ZipWriteStr(output_zip, "system.img", system_img)script.WriteRawImageUbifs("system", "system.img")script.Mount("/system", recovery_mount_options)if not has_recovery_patch:script.UnpackPackageDir("recovery", "/system")symlinks = CopyPartitionFiles(system_items, input_zip, output_zip)else:script.FormatPartition("/system")script.Mount("/system", recovery_mount_options)if not has_recovery_patch:script.UnpackPackageDir("recovery", "/system")script.UnpackPackageDir("system", "/system")symlinks = CopyPartitionFiles(system_items, input_zip, output_zip)script.MakeSymlinks(symlinks) try: custom_size = OPTIONS.info_dict["custom_size"]except: custom_size = None if custom_size is not None:if (custom_size > 0) and (HasCustomPartition(input_zip) == True): custom_items = ItemSet("custom", "META/custom_filesystem_config.txt") if block_based: custom_tgt = GetImage("custom", OPTIONS.input_tmp, OPTIONS.info_dict) custom_tgt.ResetFileMap() custom_diff = common.BlockDifference("custom", custom_tgt) custom_diff.WriteScript(script, output_zip)else: script.FormatPartition("/custom") script.Mount("/custom") script.UnpackPackageDir("custom", "/custom") symlinks = CopyPartitionFiles(custom_items, input_zip, output_zip) script.MakeSymlinks(symlinks) custom_items.GetMetadata(input_zip) custom_items.Get("custom").SetPermissions(script)B1:从输出文件中取得 boot.img (已存在)，而后返回一个 FILE class 的实例，name：为镜像名；data：镜像的二进制内容，如下：
common.pyclass File(object):def **init**(self,name, data):self.name = nameself.data = datself.size = len(data)self.sha1 = sha1(data).hexdigest()@classmethoddef FromLocalFile(cls,name, diskname): f = open(diskname, "rb")data = f.read()f.close()return File(name, data)......这个 boot_img 实例在后续会应用。
boot_img = common.GetBootableImage("boot.img", "boot.img", OPTIONS.input_tmp, "BOOT") if not block_based:def output_sink(fn, data):common.ZipWriteStr(output_zip, "recovery/" + fn, data) system_items.Get("system/" + fn, dir=False) common.MakeRecoveryPatch(OPTIONS.input_tmp, output_sink, recovery_img, boot_img) system_items.GetMetadata(input_zip) system_items.Get("system").SetPermissions(script) if HasVendorPartition(input_zip): vendor_items = ItemSet("vendor", "META/vendor_filesystem_config.txt")script.ShowProgress(0.1, 0) if block_based: vendor_tgt = GetImage("vendor", OPTIONS.input_tmp, OPTIONS.info_dict) vendor_tgt.ResetFileMap() vendor_diff = common.BlockDifference("vendor", vendor_tgt) vendor_diff.WriteScript(script, output_zip)else:script.FormatPartition("/vendor")script.Mount("/vendor", recovery_mount_options)script.UnpackPackageDir("vendor", "/vendor") symlinks = CopyPartitionFiles(vendor_items, input_zip, output_zip)script.MakeSymlinks(symlinks) vendor_items.GetMetadata(input_zip) vendor_items.Get("vendor").SetPermissions(script) if HasCustomPartition(input_zip): custom_items = ItemSet("custom", "META/custom_filesystem_config.txt")script.ShowProgress(0.1, 0) if block_based: custom_tgt = GetImage("custom", OPTIONS.input_tmp, OPTIONS.info_dict) custom_tgt.ResetFileMap() custom_diff = common.BlockDifference("custom", custom_tgt) custom_diff.WriteScript(script, output_zip)else:script.FormatPartition("/custom")script.Mount("/custom")script.UnpackPackageDir("custom", "/custom") symlinks = CopyPartitionFiles(custom_items, input_zip, output_zip)script.MakeSymlinks(symlinks) custom_items.GetMetadata(input_zip) custom_items.Get("custom").SetPermissions(script)check boot.img镜像的大小，是否超过max_size,此处用到 B1 中boot_img class中的data- 把
boot_img.data内容写入到输入压缩包中，参考zipfile.py,tempfile.py 同时写入
script脚本：show_progress(0.050000,5);assert(package_extract_file(“boot.img”,"/tmp/boot.img"), write_raw_image("/tmp/boot.img", "bootimg"),delete("/tmp/boot.img"));
common.CheckSize(boot_img.data, "boot.img", OPTIONS.info_dict)common.ZipWriteStr(output_zip, "boot.img", boot_img.data)script.ShowProgress(0.05, 5)script.WriteRawImage("/boot", "boot.img")上面几行次要是：取得 SEC_VER.txt 的门路，并把它写入输入的压缩包中。
[SEC OTA] config : vendor/mediatek/proprietary/custom/$(PROJECT_NAME)/security/recovery/SEC_VER.txt
# security versionprint "[SEC OTA] Adding security version (WriteFullOTAPackage)" cust_dir = GetBuildProp("ro.product.model", OPTIONS.info_dict) cust_dir_base = GetBuildProp("ro.product.device", OPTIONS.info_dict)print "[SEC OTA] cust directory : ", cust_dir_base sec_ver_path = os.path.join("vendor/mediatek/proprietary/custom",cust_dir_base,"security/recovery/SEC_VER.txt")print "[SEC OTA] security config : ", sec_ver_pathif os.path.exists(sec_ver_path): sec_ver = open(sec_ver_path).read() common.ZipWriteStr(output_zip, "SEC_VER.txt", sec_ver) 判断是否有：out/target/product/device/bror/p92s_hd/signed_bin/sig_info/boot.img.sig。如果有，写入输入压缩包中；没有则不需操作。
boot_sec_sig_ext_path = os.path.join("out/target/product",cust_dir,"signed_bin/sig_info/boot.img.sig")if not os.path.exists(boot_sec_sig_ext_path): cust_dir = GetBuildProp("ro.product.name", OPTIONS.info_dict) boot_sec_sig_ext_path = os.path.join("out/target/product",cust_dir,"signed_bin/sig_info/boot.img.sig")if not os.path.exists(boot_sec_sig_ext_path): cust_dir = GetBuildProp("ro.mediatek.project.path", OPTIONS.info_dict) boot_sec_sig_ext_path = os.path.join("out/target/product",cust_dir,"signed_bin/sig_info/boot.img.sig")print "[SEC OTA] security boot sig_ext : ", boot_sec_sig_ext_pathif os.path.exists(boot_sec_sig_ext_path): boot_sec_sig_ext = open(boot_sec_sig_ext_path).read() common.ZipWriteStr(output_zip, "boot.img.sig", boot_sec_sig_ext) 在 output_zip 中写入 type.txt 文件，内容为1.（全包为1，差分包为0）
#wschen startcommon.ZipWriteStr(output_zip, "type.txt", "1")把 ota_scatter.txt 写入 output_zip 中，命名为 scatter.txt。
cust_dir =GetBuildProp("ro.product.model", OPTIONS.info_dict)scatter_path =os.path.join("out/target/product",cust_dir,"ota_scatter.txt")if not os.path.exists(scatter_path): cust_dir = GetBuildProp("ro.product.device",OPTIONS.info_dict) scatter_path =os.path.join("out/target/product",cust_dir,"ota_scatter.txt")if not os.path.exists(scatter_path): cust_dir = GetBuildProp("ro.product.name", OPTIONS.info_dict) cust_dir = cust_dir.split('full_')[-1] scatter_path =os.path.join("out/target/product",cust_dir,"ota_scatter.txt")if not os.path.exists(scatter_path): cust_dir = GetBuildProp("ro.mediatek.project.path",OPTIONS.info_dict) cust_dir = cust_dir.split('/')[-1] scatter_path = os.path.join("out/target/product",cust_dir,"ota_scatter.txt")ota_scatter = open(scatter_path).read()common.ZipWriteStr(output_zip,"scatter.txt", ota_scatter)上面这几步是判断是否进行preloader，logo，uboot，tee等分区进行降级，如不须要，则疏忽
# if OPTIONS.preloader is not None or OPTIONS.uboot is not None or OPTIONS.logo is not None:# script.AppendExtra('assert(run_program(\"/system/bin/dd\", \"if=/dev/zero\", \"of=/proc/driver/mtd_writeable\", \"bs=3\", \"count=1\"));')if OPTIONS.logo is not None: logo_img = open(OPTIONS.logo).read()common.ZipWriteStr(output_zip, "logo.img", logo_img)script.WriteRawImage2("logo", "logo.img")if OPTIONS.preloader is not None: preloader_img = open(OPTIONS.preloader).read()common.ZipWriteStr(output_zip, "preloader.img", preloader_img)script.WriteRawImage2("preloader", "preloader.img")if OPTIONS.uboot is not None: uboot_img = open(OPTIONS.uboot).read()common.ZipWriteStr(output_zip, "uboot.img", uboot_img)script.WriteRawImage2("uboot", "uboot.img") #tonykuo startif OPTIONS.tee is not None: tee_img = open(OPTIONS.tee).read()common.ZipWriteStr(output_zip, "tee.img", tee_img)script.WriteRawImage2("tee1", "tee.img") #tonykuo end #koshi startif OPTIONS.trustonic is not None: trustonic_img = open(OPTIONS.trustonic).read()common.ZipWriteStr(output_zip, "mobicore.bin", trustonic_img)script.WriteRawImage2("tee1", "mobicore.bin") #koshi end增加 script 语句：show_progress(0.200000, 10);并申明 WriteFull_ota 制作完结
script.ShowProgress(0.2, 10)device_specific.FullOTA_InstallEnd()如果存在额定脚本，则把脚本内容填入降级 script 中，此处为 None
if OPTIONS.extra_script is not None:script.AppendExtra(OPTIONS.extra_script)降级脚本中增加unmount所有mount_point语句，如下：
def UnmountAll(self):for p insorted(self.mounts):self.script.append(‘unmount("%s");’% (p,))self.mounts = set()但因为 sef.mounts 在全包降级中为空集合，所以此处没有增加 unmount 语句到脚本中
script.UnmountAll()制作ota包命令行中是否带有 "-f","–special_factory_reset" 参数，没有则不执行上面语句，此处为 False
#wschenif OPTIONS.special_factory_reset:script.AppendExtra('special_factory_reset();')制作ota包命令行中是否带有"-w", "–wipe_user_data"参数，没有则不执行上面语句：革除 data 分区。此处为 False
if OPTIONS.wipe_user_data:script.ShowProgress(0.1, 10)script.FormatPartition("/data")增加降级脚本语句：
self.script.append((‘apply_sig(package_extract_file("%(sigfile_name)s"),"%(partion_name)s");’) % {'sigfile_name':sigfile_name,'partion_name':partion_name})==>apply_sig(package_extract_file(“sig/boot.sig”),“bootimg”);if OPTIONS.mtk_sec_boot_sig_tail:script.ApplySig("sig/boot.sig", "bootimg")制作ota包命令行中是否带有"-2", "–two_step"参数，没有则不执行上面语句：革除 data 分区。此处为 False
if OPTIONS.two_step:script.AppendExtra("""set_stage("%(bcb_dev)s", "");""" % bcb_dev)script.AppendExtra("else\n")script.WriteRawImage("/boot", "recovery.img")script.AppendExtra("""set_stage("%(bcb_dev)s", "2/3");reboot_now("%(bcb_dev)s", "");endif;endif;""" % bcb_dev)此处尤为重要，次要做两件事件：
- 将降级脚本语句script序列写入到升级包中：
"META-INF/com/google/android/updater-script" - 将降级工具（可执行文件）写入升级包中：
"META-INF/com/google/android/update-binary"
代码如下：请参考edify_generator.py:
defAddToZip(self, input_zip, output_zip, input_path=None):“”"Write the accumulated script to the output_zipfile. input_zipisused as the source for the ‘updater’ binary needed to runscript. If input_path is not None, it will be used asa localpathfor the binary instead of input_zip."""self.UnmountAll()common.ZipWriteStr(output_zip,“META-INF/com/google/android/updater-script”,"\n".join(self.script) + "\n")/*此处为序列之间退出‘\n’，所以最终的文件中都是一行一行的出现进去*/ifinput_path is None:data= input_zip.read(“OTA/bin/updater”)else:data= open(input_path, “rb”).read()common.ZipWriteStr(output_zip,“META-INF/com/google/android/update-binary”,data,perms=0755)script.AddToZip(input_zip, output_zip, input_path=OPTIONS.updater_binary)把上文 M1 处内容中的字典格局转换成 ‘%s=%s’ 格局，并写入到升级包中：“META-INF/com/android/metadata”
如下文code：调用
defWriteMetadata(metadata, output_zip):common.ZipWriteStr(output_zip,“META-INF/com/android/metadata”, "".join(["%s=%s\n" % kv for kv insorted(metadata.iteritems())]))最终文件内容如下：
post-build=alps/full_p92s_hd/p92s_hd:5.1/LMY47D/1501228112:eng/test-keyspost-timestamp=1501228303pre-device=p92s_hdWriteMetadata(metadata, output_zip)至此，writeFullOTAPackage函数运行结束。 接下来再持续跳到main函数残余局部接着执行，
if OPTIONS.incremental_source is None:WriteFullOTAPackage(input_zip, output_zip)if OPTIONS.package_key is None: OPTIONS.package_key = OPTIONS.info_dict.get( "default_system_dev_certificate", "build/target/product/security/testkey")if not OPTIONS.mtk_sec_boot_sig_tail:breakelse:print "unzipping source target-files..." OPTIONS.source_tmp, source_zip = common.UnzipTemp(OPTIONS.incremental_source) OPTIONS.target_info_dict = OPTIONS.info_dict OPTIONS.source_info_dict = common.LoadInfoDict(source_zip)if "selinux_fc" in OPTIONS.source_info_dict: OPTIONS.source_info_dict["selinux_fc"] = os.path.join(OPTIONS.source_tmp, "BOOT", "RAMDISK", "file_contexts")if OPTIONS.package_key is None: OPTIONS.package_key = OPTIONS.source_info_dict.get( "default_system_dev_certificate", "build/target/product/security/testkey")if OPTIONS.verbose:print "--- source info ---"common.DumpInfoDict(OPTIONS.source_info_dict)try:WriteIncrementalOTAPackage(input_zip, source_zip, output_zip)if not OPTIONS.mtk_sec_boot_sig_tail:breakexcept ValueError:if not OPTIONS.fallback_to_full: raiseprint "--- failed to build incremental; falling back to full ---" OPTIONS.incremental_source = None output_zip.close()此处为真，接下来在长期降级文件包中写入 sig/boot.sig; sig/recovery.sig 文件。其中源 data（boot_sig,recovery_sig）为上文 S1 步骤中的内容。
if OPTIONS.mtk_sec_boot_sig_tail:common.ZipWriteStr(output_zip, "sig/boot.sig", boot_sig)common.ZipWriteStr(output_zip, "sig/recovery.sig", recovery_sig)break; output_zip.close()对两头降级文件包进行前签名，生成最终的升级包。
- running:
openssl pkcs8 -inbuild/target/product/security/testkey.pk8 -inform DER -nocrypt - running:
java -Xmx2048m -jarout/host/linux-x86/framework/signapk.jar -wbuild/target/product/security/testkey.x509.pembuild/target/product/security/testkey.pk8 /tmp/tmpBXjz5Z out/target/product/xxxx/xxxx-ota-eng.wan.zip
最终生成升级包
第2步中会调用 `build/tools/signapk/signapk.java` 文件，生成 `META-INF/MANIFEST.MF,META-INF/CERT.RSA,META-INF/CERT.SF`,META-INF/com/android/otacert 文件。
if not OPTIONS.no_signing:SignOutput(temp_zip_file.name, args[1]) temp_zip_file.close() print "done."最终压缩包中的文件列表如下：
着重看下 META-INF/com/google/android 下的两个降级文件：
Update-binary：降级工具，可执行文件Updater-script：降级脚本，由制作升级包的过程中一步一步生成的，其内容如下：