[HELP] TWRP on MT6771V/CT Android 9 (Pie) - Android Q&A, Help & Troubleshooting

Hello, I have Blackview BV9800Pro with MT6771V/CT and Stock Android Pie and Magisk roots + Riru ckre and edXposed. I need TWRP so I could easily backup and restore system at any time. I test EdXposed and Magisk modules and it is PAIN to do factory reset if something fails cause this is my only smartphone. I tried different twrp already, but it didn't worked. Unofficial twrp contact form on website does not work (gives error). Can You help me guys, please? PLEASE!!

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this one works for me (at mega)
#!GWwXDKjC!vPERdlfIiP-hylz3R7SEcU105PGAP4oi0QC3FtNWsyU
from the hovatek forum (32580)
the only problem is that, like said on that forum, it won't decrypt the user partition. Someone on there says to use the Disable_Dm-Verity_ForceEncrypt_03.04.2020.zip
to disable encryption, but another poster says that it disables the phone, no touch, no mouse, etc. I have the same issue. I'd like to be able to decrypt with TWRP or turn off encryption. Then ill be able to make backups of the user partition. Anyone have any ideas?

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tecs.ottawa said:
this one works for me (at mega)
#!GWwXDKjC!vPERdlfIiP-hylz3R7SEcU105PGAP4oi0QC3FtNWsyU
from the hovatek forum (32580)
the only problem is that, like said on that forum, it won't decrypt the user partition. Someone on there says to use the Disable_Dm-Verity_ForceEncrypt_03.04.2020.zip
to disable encryption, but another poster says that it disables the phone, no touch, no mouse, etc. I have the same issue. I'd like to be able to decrypt with TWRP or turn off encryption. Then ill be able to make backups of the user partition. Anyone have any ideas?
Click to expand...
Click to collapse
that TWRP looks fine to me, the one who did this was expert. the display driver is hex patched against getbootmode in order to get touch screen working. some user reported that TWRP is asking for password, that indicates to me encryption is supported (/etc/recovery.fstab has entry for full-disk encryption with metadata partition). furthermore this TWRP build is signed with AVBv1 signature that mean it passes Verified Boot and is flashable even on locked bootloader
have you seen Method 3 for disabling dm-verity by disabling AVB with dummy vbmeta?
Code:
fastboot --disable-verity -disable-verification flash vbmeta vbmeta.img
also it seems like you can do it with Method 2 patching boot.img with Magisk Manager, the only discrepancy i recommend on step 4. to keep the checkbox for preserve force encryption enabled, then patch it manually in fstab against force encryption by changing the flag from forceencrypt= into encryptable=
if this device has fstab in boot.img then you can use Android.Image.Kitchen.v3.7-Win32.zip for unpack/repack boot.img and do the change in ramdisk/fstab.mt6771 with Notepad++
otherwise fstab is located /system_root/system/vendor/etc/fstab.mt6771 you can use adb pull in TWRP recovery, modify the file, and adb push it back
Code:
adb pull /vendor/etc/fstab.mt6771
adb push fstab.mt6771 /tmp
adb shell
cat /tmp/fstab.mt6771 > /vendor/etc/fstab.mt6771
or do it directly with sed
Code:
adb shell
sed -r ',s,(^/[^[:space:]]+[[:space:]]+/data[[:space:]]+[^[:space:]]+[[:space:]]+[^[:space:]]+[[:space:]]+[^[:space:]]*)force[def]+[cno]+r[befpty]{3}=([^[:space:]]+),\1encryptable=\2,' /vendor/etc/fstab.mt6771 > /tmp/fstab.mt6771
cat /tmp/fstab.mt6771 > /vendor/etc/fstab.mt6771
of course vendor must be mounted. cat is recommended to preserve file permissions
But, before modifying vendor, make sure AVB is disabled (flash empty vbmeta.img)

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I tried method 1:
it just stalled on the first splash screen when turned on.
for method 3:
i looked in the root and there's no vmbeta folder (vendor is the last one)
for method 2:
i tried it and it has the same issue as when i use the disabler, no touch. i made the boot img in magisk with the force encryption unchecked and the verity checked. i unpacked the boot img but there was no fstab in it. i found the one on the phone but it already had "encryptable=", here is the main section:
/dev/block/platform/bootdevice/by-name/system / ext4 ro wait,recoveryonly
/dev/block/platform/bootdevice/by-name/vendor /vendor ext4 ro wait,recoveryonly
/dev/block/platform/bootdevice/by-name/userdata /data ext4 noatime,nosuid,nodev,noauto_da_alloc,errors=panic wait,check,formattable,quota,resize,reservedsize=128m,=/dev/block/platform/bootdevice/by-name/metadata
/dev/block/platform/bootdevice/by-name/cache /cache ext4 noatime,nosuid,nodev,noauto_da_alloc,discard wait,check,formattable
/dev/block/platform/bootdevice/by-name/protect1 /mnt/vendor/protect_f ext4 noatime,nosuid,nodev,noauto_da_alloc,commit=1,nodelalloc wait,check,formattable
/dev/block/platform/bootdevice/by-name/protect2 /mnt/vendor/protect_s ext4 noatime,nosuid,nodev,noauto_da_alloc,commit=1,nodelalloc wait,check,formattable
/dev/block/platform/bootdevice/by-name/nvdata /mnt/vendor/nvdata ext4 noatime,nosuid,nodev,noauto_da_alloc,discard wait,check,formattable
/dev/block/platform/bootdevice/by-name/nvcfg /mnt/vendor/nvcfg ext4 noatime,nosuid,nodev,noauto_da_alloc,commit=1,nodelalloc wait,check,formattable
/dev/block/platform/bootdevice/by-name/apd /mnt/vendor/apd ext4 noatime,nosuid,nodev,noauto_da_alloc,commit=1,nodelalloc wait,check,formattable
/devices/platform/externdevice* auto auto defaults voldmanaged=sdcard1:auto,encryptable=userdata
when i flashed back the magisk boot img that doesnt have the custom settings, it booted OK, but then twrp cant access the userdata again.

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please read more careful
method 2
force encryption checked and the verity unchecked
i can see your fstab is broken already, there is no forceencrypt= forcefdeorfbe= or encryptable= flag (it's gone) furthermore this is not the only file otherwise it wouldn't encrypt again
method 3
flashing vbmeta is required. please download dummy vbmeta and flash it from fastboot
in TWRP you can list partitions with
Code:
ls -d $(find /dev/block -name by-name)/*
don't flash magisk zip this will affect encryption. patch fstab manually in the respective line for /data in the flags in 5th column
Code:
/dev/block/platform/bootdevice/by-name/userdata /data ext4
noatime,nosuid,nodev,noauto_da_alloc,errors=panic
wait,check,formattable,quota,resize,reservedsize=128m,encryptable=/dev/block/platform/bootdevice/by-name/metadata
which fstab is it? maybe there is another one in nvdata? at least, it is the only explanation i have why device encryptes anyway..
i am not sure why TWRP does not work for you, please provide recovery.log
edit: btw i wonder why magisk only boot with dm-verity enabled.. are you sure you have unlocked bootloader?

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sorry about that, i was really tired. that is what i had. under advanced settings in magisk manager: preserve force encryption (checked), preserve AVB 2.0/dm-verity (unchecked), recovery mode (unchecked)
I just typed it wrong in my message
I didn't modify that fstab actually. So unless the disabler did it, that is the original one. I tried to unpack the vendor.img from the stock rom to see if that fstab is the same, but that image kitchen .bat threw an error.
i've added "encryptable" after "reservedsize=128m,". i then flashed the magisk boot.img and replaced the fstab using cat with the new one by copying it to /tmp/ and then running cat /tmp/fstab.mt6771 > /vendor/etc/fstab.mt6771
there is also an fstab in nvdata, that one says:
/dev/block/platform/bootdevice/by-name/userdata /data ext4 noatime,nosuid,nodev,noauto_da_alloc,errors=panic wait,check,formattable,quota,resize,reservedsize=128m,forcefdeorfbe=/dev/block/platform/bootdevice/by-name/metadata
i edited that one : replaced forcefdeorfbe with encryptable and replaced the file in the same way as the other.
after rebooting with the 2 fstab files with "encryptable" and the custom magisk boot.img (that had no touch before), it works!
i guess that second nvdata fstab was the one we needed to edit or the regular one had been broken somehow and fixing it was the thing. im guessing it was the nvdata one.
now the phone says its unencrypted and twrp can backup the userpartition.
thank you so much