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BIOS Extraction Guide for different motherboards

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Introduction

The aim of this guide is to help users modding their BIOS using the existing features provided by the BIOS itself, such as unlocking the CFG Lock, setting a custom DVMT value, undervolt etc.

Disclaimer

  • I am not responsible for bricked devices, dead SSD drives, thermonuclear war,
  • or you getting fired because your PC booting process failed. Please do some research
  • if you have any concerns about this procedure
  • before using it! YOU are choosing to make these modifications, and if
  • you blame me in any way for what happens to your device, I will laugh at you.
  • BOOM! goes the dynamite
Thx xda-developers

How to extract the BIOS payload for

  • Dell
  • Lenovo
  • Other vendors may directly give the BIOS payload which can be opened directly from UEFITool (e.g. ASUS, MSI, Gigabyte).

Unlock CFG Lock

Please note that this section is hackintosh-only related. If you're a Winblows/Leenux user skip it

Step 1: finding PE32 image section CFG Lock offset

  1. Open UEFITool
  2. Drag the payload file (tip, it has the largest size among the other files) inside UEFITool window
  3. Press search key combination (Ctrl + F, if on Windows, or Command + F, if on Mac OS)
  4. Select Text as search criteria and look for CFG Lock
  5. If your BIOS supports CFG Lock functionality, you should have some results in the window as depicted below

Courtesy of Dortania CFG Lock unlocking guide

  1. On the bottom side of UEFITool you'll find a message such as: Unicode text "CFG Lock" found in PE32 image section at header-offset XXYYZZ
  2. Double-click on the result to go straight to the section in which it was found.
  3. Right click on PE32 image section, select Extract as is and save the file with .bin extension. (e.g. Section_PE32_image_Setup.bin)

Step 2: convert the .bin file in a .txt file

With IFRExtractor you can convert a .bin file in a .txt file.

On a terminal write:

<PATH IFRExtractor> <PATH FILE.BIN> setup.txt

e.g.

<PATH IFRExtractor> Section_PE32_image_Setup.bin Section_PE32_image_Setup.txt

Step 3: finding the variable offset

Let's suppose we wanna find the variable offset which corresponds to the CFG Lock setting in BIOS.

With a text editor open the previously converted file and look for CFG Lock

If anything is found, you'll find something as

CFG Lock, VarStoreInfo (VarOffset/VarName): 0xXYZ

0xXYZ is the offset of CFG Lock boolean bit.

Setting this variable value with 0x00 the CFG Lock will be disabled, granting access to MSR 0xE2 registry.

Step 4: set the value to the offset

There are plenty different tools to set a certain value to a specific variable offset such as:

My favourite one - mainly because it's open source, has a good maintainer, and it's simple to use - is setup_var.efi but you're free to choose the tool you want.

Step 5: checking if CFG Lock is really unlocked

Repeat Step 6 and instead of firing up modGRUBShell.efi, fire up ControlMsrE2.efi. It will produce an output such as:

  • This firmware has LOCKED MSR 0xE2 Register! if CFG Lock isn't unlocked (aka CFG Lock Offset value is 0x1)
  • This firmware has UNLOCKED MSR 0xE2 Register! if CFG Lock is unlocked (aka CFG Lock Offset value is 0x0)

If the message produced is like the last one, then it means that CFG Lock is unlocked and you can proceed disabling from config.plist:

  • OpenCore: config.plist/Kernel/Quirks/AppleCpuPmCfgLock and/or config.plist/Kernel/Quirks/AppleXcpmCfgLock

as those patches maybe too instable and can cause sudden reboots on your rig.

Issues

If you encounter any issue, please file a bugreport here.

Don't forget to attach your BIOS executable file!

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BIOS Extraction Guide for different motherboards

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