Android P 以上版本，GMS CDD 检查 userdebug 版本是否有 root 权限
P 以上版本，检查 userdebug 版本是否有 root 权限的行为发生了变化。
以下参考自：https://ressrc.com/2018/09/21/android-p9-0-userdebug%E7%89%88%E6%9C%AC%E6%89%A7%E8%A1%8Cadb-remount%E5%A4%B1%E8%B4%A5/
或 ： https://www.cnblogs.com/bluestorm/p/10911676.html
[DESCRIPTION]
在android P版本上如果按照“FAQ18076 android 6.0 M userdebug版本执行adb remount失败”的做法在userdebug版本上执行adb remount会提示以下错误：
remount of the / superblock failed: Permission denied
remount failed
原因是android P版本后google启用avb(Android Verified Boot)2.0，verified boot and DM-verity默认启用策略发生了变化。详情如下：
DM-Verity behavior changes from vboot1.0 to avb2.0.
On vboot1.0, dm-verity is turned off on eng build and is enabled on userdebug/user build.
DM-verity could be disabled with adb (not fastboot) on userdebug build without unlocking device first.
DM-Verity could not be disabled on user build.
On avb2.0, dm-verity behavior are the same on all build variants.
It’s turned on by default and could only be disabled after device is unlocked.
dm-verity disable flag is moved from system image dm-verity metadata(vboot1.0) to vbmeta image(avb2.0), and you have two ways to disable it: adb and fastboot.
[SOLUTION]
* Android P + kernel-4.4 or kernel-3.18
– download preloader with verified boot disabled which location is the same as scatter file //preloader_
– adb root
– adb disable-verity
– adb reboot
– adb root
– adb remount
* Android P + kernel-4.9 or after
– download preloader with verified boot disabled which location is the same as scatter file. //preloader_
– boot to Home Screen
– go to setting -> system -> Developer options -> OEM unlocking
– adb reboot bootloader
– fastboot flashing unlock
– press volume up key
– fastboot reboot
– adb root
– adb disable-verity
– adb reboot
– adb root
– adb remount
After Android P, preloader_
* 请注意下载最新的adb/fastboot tool
Windows
https://dl.google.com/android/repository/platform-tools-latest-windows.zip
Mac
https://dl.google.com/android/repository/platform-tools-latest-darwin.zip
Linux
https://dl.google.com/android/repository/platform-tools-latest-linux.zip
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上面可以看到，解锁方式用 adb 或者 fastboot 方式都是可行的。
自测的时候，没有找到 preloader_
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