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[ROM][6.0][STOCK]{UPDATED} Lenovo Tab 3 8"/TB3-850F

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    STOCK ANDROID 6.0 MARSHMALLOW ROM
    FOR THE LENOVO TAB 3 8"/TB3-850F
    TWRP FLASHABLE ZIP
    FORCE ENCRYPTION & DM-VERITY DISABLED

    DISCLAIMER: Your warranty will be voided by installing this ROM, unlocking your bootloader, or flashing a custom recovery. You hereby assume sole responsibility for any positive or negative consequences incurred by flashing this ROM. As always, flashing your Android device or otherwise altering its file system & partitions involves an inherent risk. I am not responsible for any devices which are bricked or otherwise rendered inoperable as a result of flashing this ROM. However, in such scenarios,
    I will provide all support feasibly possible. Follow the simple instructions carefully and you should experience no adverse affects.
    Lenovo's open source code for this ROM encompasses both the 850F & 850M variants of this tablet. Therefore, this ROM should be completely compatible with the TB3-850M as well.


    NOTES:

    This Stock Android 6.0 ROM is virtually unmodified. However, it should be noted that dm-verity (device mapping) and force encryption have been disabled via patched boot image. This is the most current stock OS for the Lenovo Tab 3 8"; therefore, no OTAs will need to be installed subsequent to flashing this ROM. In order to ensure that force encryption gets disabled, it is imperative that the /userdata (Data) partition is formatted in TWRP prior to Installation. Please carefully follow the below instructions.
    For those members who want a pure stock experience, but also want root access of the stock OS, I'm currently compiling a deodexed & zipaligned version of this ROM, fully rooted with Magisk 14.0 & BusyBox binaries pre-installed.

    SPECIFICATIONS:

    Android Version: 6.0 Marshmallow
    Build No: TB3-850F_S100031_171010_ROW
    Kernel Version: 3.18.19
    SDK Version: 23
    Software Version: TB3-850F_160412
    Build ID: MRA58K
    Android Security Patch Level: 9/05/2017
    Runtime Version: ART 2.1.0
    Hardware Version: LenovoPad TB3-850F
    Board Platform: MediaTek MT6735M
    CPU: 64-Bit, Quad-Core Cortex A-53 - 1.0GHz
    GPU: Mali T720 - 450MHz
    RAM: 1GB
    OS Build Date: 10/10/2017


    Source Code: http://pcsupport.lenovo.com/us/en/products/tablets/a-series/tab3-8/downloads/ds112711


    REQUIREMENTS:

    1. Unlocked bootloader;
    2. TWRP recovery;

    This is a pure stock, unmodified, TWRP flashable Android 6.0 Marshmallow ROM for the Lenovo Tab 3 8". This ROM was compiled from the most recent stock /boot and /system images. However, as noted previously, the boot image has been unpacked, patched, and repacked in order to disable dm-verity and force encryption. Because raw firmware images were used in compiling this ROM, the file size is in excess of 1GB (approximately 1.35GB).

    INSTRUCTIONS:

    1. Download the ROM from the link provided and save it to your external micro SD card. Do not save to internal storage, as your /data partition will need to be formatted prior to installation;
    2. Boot your tablet into TWRP recovery;
    3. Wipe /system, /data, /cache & /Dalvik-ART cache. Also, select "Wipe", then "Format Data." This step is crucial to ensure disabling of force encryption. Please note that once installed, you may go to SETTINGS>>SECURITY and opt to encrypt the userdata on the tablet;
    4. Select INSTALL, navigate to the location in which you saved the ROM zip file, and initiate installation. Flashing will complete in approximately 3 - 4 minutes;
    5. Reboot system.

    You should now have unmodified stock Android 6.0 installed on your Tab 3, as well as disabled dm-verity and disabled force encryption.

    DOWNLOAD LINKS:

    Stock Android 6.0 ROM --
    TB3-850F_S100031_171010_ROW: https://drive.google.com/file/d/1iMf0Ns_XWGpYlNmXCvUsW_1DfaRMeIuO/view?usp=drivesdk

    Stock Recovery Image: https://drive.google.com/file/d/1D6A7b080luzsSf0xLJSCqPBNeQLSWo94/view?usp=drivesdk

    Unpatched Stock Boot Image: https://drive.google.com/file/d/1azgIrPbfJHBzZF9R4IUMxIGNga6vjipD/view?usp=drivesdk

    Lenovo File Manager (APK): https://forum.xda-developers.com/android/general/app-lenovo-file-manager-lenovo-tab-3-8-t3706161

    Lenovo Tab 3 8" User Guide --
    TB3-850F & TB3-850M (English)(PDF): https://drive.google.com/file/d/18gCTfuZecJnlB0ddBIN02YPaDpuvmzov/view?usp=drivesdk

    Older Build(s):
    TB3-850F_S100030_161209_ROW: https://drive.google.com/file/d/0B1Sfod4HWfk2aTNtVmJHZGpWZEE/view?usp=drivesdk


    BUGS: Please report any and all bugs, no matter how seemingly trivial or insignificant. For those members with the knowledge, please submit a proper bug report. If you are not sure how, simply provide as many facts & details as possible. If you are having problems with apps, please specify as to whether the app is from Google Play. Also, please DO NOT submit bug reports unless you are utilizing this ROM in its present form -- unmodified, pure stock. Custom kernels, mods & tweaks (e.g. Xposed framework) & any deviations from pure stock will make it futile to analyze bug reports. Instead, provide with detail the precise nature of the problem. If reporting a bug, please specify if you are rooted (systemless or system-mode) and/or have BusyBox binaries installed. Submit screenshots of bugs if possible.
    2
    My custom ROM for this tablet should be coming out of the Android Kitchen later this evening. I've dubbed it Ethereal OS v1.1 [Android 6.0.1]. Extremely lightweight yet moderately feature packed.
    2
    Many thanks for clear summary!

    Couple of related questions:
    Re. disabled encryption:
    Will device / processes work faster with encryption disabled? And will this affect adoptive storage in any way?
    Re. dm-verity:
    Is there an option in this ROM to turn dm-verity on or off (as with force encryption)?
    Re pre-rooted ROM:
    Is there any advantage in supplying ROM pre-rooted? (Some OS customisers (eg OctOS) have dispensed with pre-rooted versions in order to give users greater flexibility.) I ask since I'd like to try Magisk on this device as I like some of its systemless modules, as well as ability to pass Safety net check.

    Incidentally, I just noticed Magisk Manager has Advanced Settings to Keep force encryption, and Keep dm-verity. Turns out (from Magisk XDA thread) that these are disabled by Magisk root by default, but can be toggled back on. Read that dm-verity may be needed for OTA updates. Read that leaving Keep force encryption disabled means that if encrypted data is removed (wiped), it won't be encrypted automatically on next boot.
    Might try Magisk on tablet soon to see if it does the same job, and report results. Works fine on my Huawei y550 phone with Lineage OS, and seems to be un-encrypted (shows option in Security to Encrypt Phone). Thanks, PW.
    My pre-rooted ROM for this device will actually be using Magisk 14.0 Systemless User Interface with full SafetyNet pass. Yes, correct; Magisk Manager does provide advanced options to allow dm-verity and force encryption to remain intact. I've personally never had the slightest use for dm-verity or force encryption. But, that's my personal opinion, and I'm sure there are users who would opt to use these features.
    Should Lenovo push any future OTA's for this tablet, I will update the stock ROM in this thread accordingly. My pre-rooted, deodexed ROM, which is presently nearing completion, will include Google's security patches up to August 1, 2017, as well as options to enable the Google Assistant.
    2
    After much battling with default force encryption and dm-verify on this tablet, I have finally decrypted this device and have compiled an otherwise unmodified Stock 6.0 ROM which is TWRP flashable. I have also updated this ROM to the most current version, which will alleviate any issues with installing OTAs. I will also be updating the stock Recovery Image to the latest version, TB3-850F_S100030_161209_ROW.
    2
    I've managed to fix the major bugs reported upon initial install of the ROM -- Recents & Home Buttons, Quick Pulldown Menu, Google Framework bugs, New App Shortcut bugs, etc. Simply corruption during packing (archiving) the ROM zip. I will try my best to get a new build posted sometime today.