S8+ (SM-G955F) bootloop

[Markus Bauer]

Hello,

I have a Samsung S8+ here which stuck in a bootloop after a update failed.

I heared that Cellbrite has a solution for that issue but I don't own an UFED. Is there any was to solve that in another way?

I can't go to recovery-mode. When I try i get the error which you see in the photo and then the phone reboot automatically. All I have to work with is ODIN-mode.

Is there a trick to flash TWRP or something like that without triggering a factory reset?

Thanks!

[Krzysztof Grabowski]

It's very likely that it doesn't boot because of dm-verity error. UFED may work to get data off the phone, especially since it doesn't have to fully boot G955F to Android to decrypt the data, but any kind of messing with TWRP may only make things worse. At first, you could try to flash the same firmware using ODIN and HOME_CSC as a CSC file. This is made to update the device, preserving the user data. It can also fix any issues with dm-verity if they come from a damaged, or corrupted stuff like boot image.

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[Markus Bauer]

Thanks Krzysztof!

Sounds like a plan but I know I am only able to update or flash the same vesion.

I recognice based on carrier_id=DBT that it's a unbranded phone from Germany. I am just not sure if I can see the firmware-version on the ODIN screen somehow and how to decode it. Would you rather go with the newest one or try to find out the version which is actually installed and flash that one?

I guess I need to flash the bootloader (BL) and Anroid-partition (AP) files as well or just one of them? What with the carrier-partition (CP)? I am not sure which one I can flash without triggering a factory reset and I have no other samsung here to try it beforehand. So thanks for the advice again! 

[LUIS D AGUILAR ROMAN]

Need a Service Box for Direct JTAG.  Boot for Recovery or other fix cant go to help without a Box like Riff Box 2 or Z3X EasyJtag or Octoplus.

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[Markus Bauer]

I have a EasyJTAG here...

[Krzysztof Grabowski]

Sorry for the delay. You don't have to match the CSC. It should be the same firmware version, for the same model only. Firmware version is displayed in recovery mode, top row. You can download older firmware versions from samfw.com with decent speed.

In Odin, you need to load BL, AP, CP and HOME_CSC as the CSC file. Odin will detect it as "home binary" and will then just do the update automatically, without wipe.

@LUIS D AGUILAR ROMAN, what do you expect to do using a "JTAG Box". S8 is encrypted, and uses UFS chipset. Only Easy-JTAG, Medusa and UFI support UFS chips, and ISP support is tricky to work with here. Phone is not dead either, so there're so need to restore bootloader etc. You won't be able to access data that way.

To view this discussion on the web visit https://groups.google.com/d/msgid/datarecoverycertification/eb90f18b-48fc-471b-9e32-3f255f20dc3dn%40googlegroups.com.

[Markus Bauer]

Hello, that get me maybe (hopefully) one step further... I can boot to recovery and I have no Bootloop anymore but I am stuck at the SAMSUNG logo screen after the Samsung S8+ screen. 

I waited for maybe 10-15 min. till now. 

[LUIS D AGUILAR ROMAN]

Probably you will need to clear the Dalvik Cache and Cache but Im not sure if this can start a factory reset mode.  Find information about Dalvik Cache and Cache on Internet.  On old Systems you reset this 2 cache to fix boot issues and nothing will be affected but on Newer Models Im not so sure about it.

To view this discussion on the web visit https://groups.google.com/d/msgid/datarecoverycertification/2e9c44d1-147e-4adc-ab21-dff9ea4c1457n%40googlegroups.com.

[Krzysztof Grabowski]

Do you still have the dm-verity error in recovery? It can show up when you choose the reboot option.

To view this discussion on the web visit https://groups.google.com/d/msgid/datarecoverycertification/2e9c44d1-147e-4adc-ab21-dff9ea4c1457n%40googlegroups.com.

[Markus Bauer]

There are still some errors but i didn't see a dm-verity error...

After rebooting come one more message: 

[libfs_mgr]is_dt_compatible() ...

[Krzysztof Grabowski]

Those "errors" are fine, and shows up on fully working device as well. dm-verity is reported to be ok now. At this point, the phone should boot correctly. You can try to wipe the cache, and give it a longer while to boot. If not, forensic tools, like UFED, Oxygen, XRY, FinalData are worth a try. S8+ uses full disk encryption, and Android 9 is the last available for it, so it's not required to fully boot it to Android to access the data with the exploit those tools use

To view this discussion on the web visit https://groups.google.com/d/msgid/datarecoverycertification/2f28073c-e70e-45b7-a6d2-867020d1f3fbn%40googlegroups.com.