Lenovo Thinkpad 8 tablet: possible BIOS lockdown?

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#1 | Lenovo Thinkpad 8 tablet: possible BIOS lockdown? datum

Tue Sep 19, 2017 5:37 pm (Last edited: Tue Sep 19, 2017 5:38 pm)

My Lenovo Thinkpad 8 tablet is equipped with an Intel Z3770 cpu and runs Win 10 32-bit. I would like to install 64-bit Win10 which comes with a useful Linux bash shell. My BIOS appears to be locked down to 32-bit UEFI and can't boot the 64-bit installer from a USB drive. In the Console OS Wiki I found this info:

Zitat

My ThinkPad 8 Can't Boot 64-bit Windows 10

Here's the bad news. It appears there is a SMBIOS configuration switch that the ThinkPad 8 uses to "decide" if your ThinkPad 8 can run 64-bit UEFI or not. It's odd. We haven't seen anything like it before. The tablet only has one BIOS file, but on some devices, it enables 64-bit with 1.70/1.71 and on some... it doesn't.

I am running BIOS v1.71 and wonder whether it could be true what the Console OS guys are writing that some BIOS configuration switch prevents me to boot 64-bit EFI and if so can it be unlocked ?

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#2 | RE: Lenovo Thinkpad 8 tablet: possible BIOS lockdown? datum

Fri Sep 29, 2017 7:09 pm

I started reversing the installed BIOS and found out there are a couple of NVARs, like "BIOS Read/Write Protection, Variable: 0x321" and "TXE HMRFPO, Variable: 0x231" and "TXE Firmware Update, Variable: 0x232". I tried to set these EFI NVARs with grub, but that didn't work , for example setup_var 0x232 or setup_var2 0x232 both return nothing. When I boot Ubuntu 15.04 from a USB stick I can access /sys/firmware/efi/efivars and see a lot of files, e.g. System-e947fcf9-dd01-4965-b808-32a7b6815657

Now for my question, how can I find the efivars file which corresponds with for example "TXE Firmware Update, Variable: 0x232" ?

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#3 | RE: Lenovo Thinkpad 8 tablet: possible BIOS lockdown? datum

Sat Oct 07, 2017 2:19 am (Last edited: Sat Oct 07, 2017 2:20 am)

I did find the Setup-ec87d643-eba4-4bb5-a1e5-3f3e36b20da9 NVAR in the bios dump and I patched following variables which are included the Setup NVAR:
TXE, Variable: 0x22F -> 0x00 disabled
TXE HMRFPO, Variable: 0x231 -> 0x01 enabled
TXE Firmware Update, Variable: 0x232 -> 0x01 enabled

Unfortunately, still getting error 26 locked by flash descriptor

Does any of you have an idea what can be done? I have attached the IFR file ("File_DXE_driver_CFEF94C4_4167_466A_8893_8779459DFA86_PlatformHiiAdvancedDxe IFR.txt") and the binary NVAR ("Setup-ec87d643-eba4-4bb5-a1e5-3f3e36b20da9.mod")

Thanks for any suggestion!

jockyw2001 has attached files to this post

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[Guide] Using CH341A-based programmer to flash SPI EEPROM � � recover Lenovo Thinkpad 8 Tablet

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