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標(biāo)題: recovery mode [打印本頁]
作者: checl1987_EE 時(shí)間: 2011-01-10 12:27
標(biāo)題: recovery mode
Android Recovery模式
(muddogxp 原創(chuàng)，轉(zhuǎn)載請(qǐng)注明)
Recovery簡介
Android利用Recovery模式，進(jìn)行恢復(fù)出廠設(shè)置，OTA升級(jí)，patch升級(jí)及firmware升級(jí)。
升級(jí)一般通過運(yùn)行升級(jí)包中的META-INF/com/google/android/update-script腳本來執(zhí)行自定義升級(jí)，腳本中是一組recovery系統(tǒng)能識(shí)別的UI控制，文件系統(tǒng)操作命令，例如write_raw_image（寫FLASH分區(qū)），copy_dir（復(fù)制目錄）。該包一般被下載至SDCARD和CACHE分區(qū)下。如果對(duì)該包內(nèi)容感興趣，可以從http://forum.xda-developers.com/showthread.php?t=442480下載JF升級(jí)包來看看。
升級(jí)中還涉及到包的數(shù)字簽名，簽名方式和普通JAR文件簽名差不錯(cuò)。公鑰會(huì)被硬編譯入recovery，編譯時(shí)生成在：out/target/product/XX/obj/PACKAGING/ota_keys_inc_intermediates/keys.inc
G1中的三種啟動(dòng)模式
MAGIC KEY:
camera + power：bootloader模式，ADP里則可以使用fastboot模式
home + power：recovery模式
正常啟動(dòng)
Bootloader正常啟動(dòng)，又有三種方式，按照BCB（Bootloader Control Block, 下節(jié)介紹）中的command分類：
command == 'boot-recovery' → 啟動(dòng)recovery.img。recovery模式
command == 'update-radio/hboot' → 更新firmware（bootloader)
其他 → 啟動(dòng)boot.img
Recovery涉及到的其他系統(tǒng)及文件
CACHE分區(qū)文件
Recovery 工具通過NAND cache分區(qū)上的三個(gè)文件和主系統(tǒng)打交道。主系統(tǒng)（包括恢復(fù)出廠設(shè)置和OTA升級(jí)）可以寫入recovery所需的命令，讀出recovery過程中的LOG和intent。
/cache/recovery/command： recovery命令，由主系統(tǒng)寫入。所有命令如下：
--send_intent=anystring - write the text out to recovery.intent
--update_package=root:path - verify install an OTA package file
--wipe_data - erase user data (and cache), then reboot
--wipe_cache - wipe cache (but not user data), then reboot
/cache/recovery/log：recovery過程日志，由主系統(tǒng)讀出
/cache/recovery/intent：recovery輸出的intent
MISC分區(qū)內(nèi)容
Bootloader Control Block (BCB) 存放recovery bootloader message。結(jié)構(gòu)如下：
struct bootloader_message {
char command[32];
char status[32]; // 未知用途
char recovery[1024];
};
command可以有以下兩個(gè)值
“boot-recovery”：標(biāo)示recovery正在進(jìn)行，或指示bootloader應(yīng)該進(jìn)入recovery mode
“update-hboot/radio”：指示bootloader更新firmware
recovery內(nèi)容
“recovery\n
<recovery command>\n
<recovery command>”
其中recovery command為CACHE:/recovery/command命令
兩種Recovery Case
FACTORY RESET（恢復(fù)出廠設(shè)置）
用戶選擇“恢復(fù)出廠設(shè)置”
設(shè)置系統(tǒng)將"--wipe_data"命令寫入/cache/recovery/command
系統(tǒng)重啟，并進(jìn)入recover模式（/sbin/recovery）
get_args() 將 "boot-recovery"和"--wipe_data"寫入BCB
erase_root() 格式化（擦除）DATA分區(qū)
erase_root() 格式化（擦除）CACHE分區(qū)
finish_recovery() 擦除BCB
重啟系統(tǒng)
OTA INSTALL（OTA升級(jí)）
升級(jí)系統(tǒng)下載 OTA包到/cache/some-filename.zip
升級(jí)系統(tǒng)寫入recovery命令"--update_package=CACHE:some-filename.zip"
重啟，并進(jìn)入recovery模式
get_args() 將"boot-recovery" 和 "--update_package=..." 寫入BCB
install_package() 作升級(jí)
finish_recovery() 擦除 BCB
** 如果安裝包失敗 ** prompt_and_wait() 等待用戶操作，選擇ALT+S或ALT+W 升級(jí)或恢復(fù)出廠設(shè)置
main() 調(diào)用 maybe_install_firmware_update()
如果包里有hboot/radio的firmware則繼續(xù)，否則返回
將 "boot-recovery" 和 "--wipe_cache" 寫入BCB
將 firmware image寫入cache分區(qū)
將 "update-radio/hboot" 和 "--wipe_cache" 寫入BCB
重啟系統(tǒng)
bootloader自身更新firmware
bootloader 將 "boot-recovery" 寫入BCB
erase_root() 擦除CACHE分區(qū)
清除 BCB
main() 調(diào)用 reboot() 重啟系統(tǒng)
Recovery模式流程
/init → init.rc → /sbin/recovery →
main():recovery.c
ui_init():ui.c ［UI initialize］
gr_init():minui/graphics.c ［set tty0 to graphic mode, open fb0]
ev_init():minui/events.c [open /dev/input/event*]
res_create_surface:minui/resource.c [create surfaces for all bitmaps used later, include icons, bmps]
create 2 threads: progress/input_thread [create progress show and input event handler thread]
get_args():recovery.c
get_bootloader_message():bootloader.c [read mtdblock0(misc partition) 2nd page for commandline]
check if nand misc partition has boot message. If yes, fill argc/argv.
If no, get arguments from /cache/recovery/command, and fill argc/argv.
set_bootloader_message():bootloader.c [set bootloader message back to mtdblock0]
Parser argv[] filled above
register_update_commands():commands.c [ register all commands with name and hook function ]
registerCommand():commands.c
Register command with name, hook, type, cookie.
Commands, e.g: assert, delete, copy_dir, symlink, write_raw_image.
registerFunction():commands.c
Register function with name, hook, cookie.
Function, e.g: get_mark, matches, getprop, file_contains
install_package():
translate_root_path():roots.c [ "SYSTEM:lib" and turns it into a string like "/system/lib", translate the updater.zip path ]
mzOpenZipArchive():zip.c [ open updater.zip file (uncompass) ]
handle_update_package():install.c
verify_jar_signature():verifier.c [ verify signature with keys.inc key; verify manifest and zip package archive ]
verifySignature() [ verify the signature file: CERT.sf/rsa. ]
digestEntry():verifier.c [ get SHA-1 digest of CERT.sf file ]
RSA_verify(public key:keys.inc, signature:CERT.rsa, CERT.sf's digest):libc/rsa.c [ Verify a 2048 bit RSA PKCS1.5 signature against an expected SHA-1 hash. Use public key to decrypt the CERT.rsa to get original SHA digest, then compare to digest of CERT.sf ]
verifyManifest() [ Get manifest SHA1-Digest from CERT.sf. Then do digest to MANIFEST.MF. Compare them ]
verifyArchive() [ verify all the files in update.zip with digest listed in MANIFEST.MF ]
find_update_script():install.c [ find META-INF/com/google/android/update-script updater script ]
handle_update_script():install.c [ read cmds from script file, and do parser, exec ]
parseAmendScript():amend.c [ call yyparse() to parse to command ]
exeCommandList():install.c
exeCommand():execute.c [ call command hook function ]
erase DATA/CACHE partition
prompt_and_wait():recovery.c [ wait for user input: 1) reboot 2) update.zip 3) wipe data ]
ui_key_xxx get ALT+x keys
1) do nothing
2) install_package('SDCARD:update.zip')
3) erase_root() → format_root_device() DATA/CACHE
may_install_firmware_update():firmware.c [ remember_firmware_update() is called by write_hboot/radio_image command, it stores the bootloader image to CACHE partition, and write update-hboot/radio command to MISC partition for bootloader message to let bootloader update itself after reboot ]
set_bootloader_message()
write_update_for_bootloader():bootloader.c [ write firmware image into CACHE partition with update_header, busyimage and failimage ]
finish_recovery():recovery.c [ clear the recovery command and prepare to boot a (hopefully working) system, copy our log file to cache as well (for the system to read), and record any intent we were asked to communicate back to the system. ]
reboot()
Recovery模式流程圖
以下流程圖繪制了系統(tǒng)從啟動(dòng)加載bootloader后的行為流程。
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