GM45 Thinkpad Internal flashing research
The wiki is being retired!
Documentation is now handled by the same processes we use for code: Add something to the Documentation/ directory in the coreboot repo, and it will be rendered to https://doc.coreboot.org/. Contributions welcome!
The goal is to be able to flash internally the x200 with Flashrom.
The Lenovo X200 uses the following mechanisms to prevent internal reflashing:
- Flash descriptor: Set the flash descriptor read-only, locks the ME, and platform regions.
- PR registers: Sets the BIOS bootblock read-only and prevent access to the platform region
- The BUC.TS register is locked.
- If we remove the flash descriptor read-only protection we are able to easily reflash coreboot, but:
- The flash descriptor restrictions may be able to be lifted by using the GPIO33, but accessing that pin is very difficult and has huge probability of breaking the board.
- Finding a command to send to the ME to unlock it is very unlikely, as it is only supposed to work when the management engine is in manufacture-mode. The Me is not in manufacture-mode on production laptops.
- Find a way to disable or crash the ME would probably have no effect at all on flash protections
- The bootblock is read-only, and sets the PR registers protections. There might be a way to ask it nicely to remove such protections, to be able to reflash it with coreboot.
- Some unofficial BIOS updates (that removes the WiFi whitelist limitation) exists and are rumored to disable PR registers protections.