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The ich9gen utility (see below) generates two types of descriptor+GbE setup:

  • read-write
  • read-only

Read on for more information. Use the ro files mentioned below, and your flash will be read-only in software (you can still externally re-flash and read the contents of flash).

For ease of use, libreboot provides ROMs that are read-write by default. In practise, you can boot a Linux kernel with access to lower memory disabled which will make software re-flashing impossible (unless you reboot with such memory protections disabled, e.g. iomem=relaxed kernel parameter).

ICH9 deblob utility

This was the tool originally used to disable the ME on X200 (later adapted for other systems that use the GM45 chipset). ich9gen now supersedes it; ich9gen is better because it does not rely on dumping the factory.rom image (whereas, ich9deblob does).

Simply speaking, ich9deblob takes an original dump of the boot flash, where that boot flash contains a descriptor that defines the existence of Intel ME, and modifies it. The Intel Flash Descriptor is modified to disable the ME region. It disables the ME itself aswell. The GbE region is moved to the location just after the descriptor. The BIOS region is specified as being after the descriptor+GbE regions, filling the rest of the boot flash.

The GbE region is largely unedited when using this utility.

Run it like so, with factory.rom in the same directory:

./ich9deblob

The factory.rom file is your dump of the vendor boot flash. Older versions of this utility have this file name hardcoded, and for compatibility reasons it will still work in this manner. However, you can now specify your own file name.

For example:

./ich9deblob lenovo.rom

A 12kiB file named deblobbed_descriptor.bin will now appear. Keep this and the factory.rom stored in a safe location! The first 4KiB contains the descriptor data region for your system, and the next 8KiB contains the gbe region (config data for your gigabit NIC). These 2 regions could actually be separate files, but they are joined into 1 file in this case.

A 4KiB file named deblobbed_4kdescriptor.bin will alternatively appear, if no GbE region was detected inside the ROM image. This is usually the case, when a discrete NIC is used (eg Broadcom) instead of Intel. Only the Intel NICs need a GbE region in the flash chip.

Assuming that your libreboot image is named libreboot.rom, copy the deblobbed_descriptor.bin file to where libreboot.rom is located and then run:

dd if=deblobbed_descriptor.bin of=libreboot.rom bs=12k count=1 conv=notrunc

Alternatively, if you got a the deblobbed_4kdescriptor.bin file (no GbE defined), do this:

dd if=deblobbed_4kdescriptor.bin of=libreboot.rom bs=4k count=1 conv=notrunc

(it's very unlikely that you would ever see this. Descriptor without GbE is very rare, probably non-existant, but theoretically possible and this functionality is implemented based on Intel datasheets)

The utility will also generate 4 additional files:

  • mkdescriptor.c
  • mkdescriptor.h
  • mkgbe.c
  • mkgbe.h

These are self-written by ich9deblob. The ich9gen utility was created, based on this very functionality, with some tweaks made afterwards.

These are C source files that can re-generate the very same Gbe and Descriptor structs (from ich9deblob/ich9gen). To use these, place them in src/ich9gen/ in ich9deblob, then re-build. The newly build ich9gen executable will be able to re-create the very same 12KiB file from scratch, based on the C structs, this time without the need for a factory.rom dump!

You should now have a libreboot.rom image containing the correct 4K descriptor and 8K gbe regions, which will then be safe to flash. Refer back to index.md/#gm45 for how to flash it.

demefactory utility

This utility has never been tested, officially, but it should work.

This takes a factory.rom dump and disables the ME/TPM, but leaves the region intact. It also sets all regions read-write. Simply put, this means that you can use the original factory firmware but without the Intel ME enabled.

The ME interferes with flash read/write in flashprog, and the default descriptor locks some regions. The idea is that doing this will remove all of those restrictions.

Simply run (with factory.rom in the same directory):

./demefactory

It will generate a 4KiB descriptor file (only the descriptor, no GbE). Insert that into a factory.rom image (NOTE: do this on a copy of it. Keep the original factory.rom stored safely somewhere):

dd if=demefactory_4kdescriptor.bin of=factory_nome.rom bs=4k count=1 conv=notrunc

Use-case: a factory.rom image modified in this way would theoretically have no flash protections whatsoever, making it easy to quickly switch between factory/libreboot in software, without ever having to disassemble and re-flash externally unless you brick the device.

The sections below are adapted from (mostly) IRC logs related to early development getting the ME removed on GM45. They are useful for background information. This could not have been done without sgsit's help.

Early notes

Flash chips

  • X200 laptop (Mocha-1): ICH9-M overrides ifd permissions with a strap connected to GPIO33 pin (see IRC notes below)

    • The X200 can be found with any of the following flash chips:
      • ATMEL AT26DF321-SU 72.26321.A01 - this is a 32Mb (4MiB) chip
      • MXIC (Macronix?) MX25L3205DM2I-12G 72.25325.A01 - another 32Mb (4MiB) chip
      • MXIC (Macronix?) MX25L6405DMI-12G 41R0820AA - this is a 64Mb (8MiB) chip
      • Winbond W25X64VSFIG 41R0820BA - another 64Mb (8MiB) chip

    sgsit says that the X200s (Pecan-1) with the 64Mb flash chips are (probably) the ones with AMT (alongside the ME), whereas the 32Mb chips contain only the ME.

Early development notes

Start (hex) End (hex)   Length (hex)    Area Name
----------- ---------   ------------    ---------
00000000    003FFFFF    00400000    Flash Image

00000000    00000FFF    00001000    Descriptor Region
00000004    0000000F    0000000C        Descriptor Map
00000010    0000001B    0000000C        Component Section
00000040    0000004F    00000010        Region Section
00000060    0000006B    0000000C        Master Access Section
00000060    00000063    00000004            CPU/BIOS
00000064    00000067    00000004            Manageability Engine (ME)
00000068    0000006B    00000004            GbE LAN
00000100    00000103    00000004        ICH Strap 0
00000104    00000107    00000004        ICH Strap 1
00000200    00000203    00000004        MCH Strap 0
00000EFC    00000EFF    00000004        Descriptor Map 2
00000ED0    00000EF7    00000028        ME VSCC Table
00000ED0    00000ED7    00000008            Flash device 1
00000ED8    00000EDF    00000008            Flash device 2
00000EE0    00000EE7    00000008            Flash device 3
00000EE8    00000EEF    00000008            Flash device 4
00000EF0    00000EF7    00000008            Flash device 5
00000F00    00000FFF    00000100        OEM Section
00001000    001F5FFF    001F5000    ME Region
001F6000    001F7FFF    00002000    GbE Region
001F8000    001FFFFF    00008000    PDR Region
00200000    003FFFFF    00200000    BIOS Region

Start (hex) End (hex)   Length (hex)    Area Name
----------- ---------   ------------    ---------
00000000    003FFFFF    00400000    Flash Image

00000000    00000FFF    00001000    Descriptor Region
00000004    0000000F    0000000C        Descriptor Map
00000010    0000001B    0000000C        Component Section
00000040    0000004F    00000010        Region Section
00000060    0000006B    0000000C        Master Access Section
00000060    00000063    00000004            CPU/BIOS
00000064    00000067    00000004            Manageability Engine (ME)
00000068    0000006B    00000004            GbE LAN
00000100    00000103    00000004        ICH Strap 0
00000104    00000107    00000004        ICH Strap 1
00000200    00000203    00000004        MCH Strap 0
00000ED0    00000EF7    00000028        ME VSCC Table
00000ED0    00000ED7    00000008            Flash device 1
00000ED8    00000EDF    00000008            Flash device 2
00000EE0    00000EE7    00000008            Flash device 3
00000EE8    00000EEF    00000008            Flash device 4
00000EF0    00000EF7    00000008            Flash device 5
00000EFC    00000EFF    00000004        Descriptor Map 2
00000F00    00000FFF    00000100        OEM Section
00001000    00002FFF    00002000    GbE Region
00003000    00202FFF    00200000    BIOS Region

Build Settings
--------------
Flash Erase Size = 0x1000

It's a utility called 'Flash Image Tool' for ME 4.x that was used for this. You drag a complete image into in and the utility decomposes the various components, allowing you to set soft straps.

This tool is proprietary, for Windows only, but was used to deblob the X200. End justified means, and the utility is no longer needed since the ich9deblob utility (documented on this page) can now be used to create deblobbed descriptors.

GBE (gigabit ethernet) region in SPI flash

Of the 8K, about 95% is 0xFF. The data is the gbe region is fully documented in this public datasheet: http://www.intel.co.uk/content/dam/doc/application-note/i-o-controller-hub-9m-82567lf-lm-v-nvm-map-appl-note.pdf

The only actual content found was:

00  1F  1F  1F  1F  1F  00  08  FF  FF  83  10  FF  FF  FF  FF  
08  10  FF  FF  C3  10  EE  20  AA  17  F5  10  86  80  00  00  
01  0D  00  00  00  00  05  06  20  30  00  0A  00  00  8B  8D  
02  06  40  2B  43  00  00  00  F5  10  AD  BA  F5  10  BF  10  
AD  BA  CB  10  AD  BA  AD  BA  00  00  00  00  00  00  00  00  
00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  
00  01  00  40  28  12  07  40  FF  FF  FF  FF  FF  FF  FF  FF  
FF  FF  FF  FF  FF  FF  FF  FF  FF  FF  FF  FF  FF  FF  D9  F0  
20  60  1F  00  02  00  13  00  00  80  1D  00  FF  00  16  00  
DD  CC  18  00  11  20  17  00  DD  DD  18  00  12  20  17  00  
00  80  1D  00  00  00  1F

The first part is the MAC address set to all 0x1F. It's repeated haly way through the 8K area, and the rest is all 0xFF. This is all documented in the datasheet.

The GBe region starts at 0x20A000 bytes from the *end* of a factory image and is 0x2000 bytes long. In libreboot (deblobbed) the descriptor is set to put gbe directly after the initial 4K flash descriptor. So the first 4K of the ROM is the descriptor, and then the next 8K is the gbe region.

GBE region: change MAC address

According to the datasheet, it's supposed to add up to 0xBABA but can actually be others on the X200. https://web.archive.org/web/20150912070329/https://communities.intel.com/community/wired/blog/2010/10/14/how-to-basic-eeprom-checksums

"One of those engineers loves classic rock music, so they selected 0xBABA"

In honour of the song Baba O'Reilly by The Who apparently. We're not making this stuff up...

0x3ABA, 0x34BA, 0x40BA and more have been observed in the main Gbe regions on the X200 factory.rom dumps. The checksums of the backup regions match BABA, however. We think 0xBABA is the only correct checksum, because those other, similar checksums were only ever found in the "backup" GbE regions on factory ROM dumps. In libreboot, we simply use 0xBABA and ensure that both 4KiB regions in GbE NVM have that checksum.

By default, the X200 (as shipped by Lenovo) actually has an invalid main gbe checksum. The backup gbe region is correct, and is what these systems default to. Basically, you should do what you need on the *backup* gbe region, and then correct the main one by copying from the backup.

Look at ich9deblob.c in ich9utils.

  • Add the first 0x3F 16bit numbers (unsigned) of the GBe descriptor together (this includes the checksum value) and that has to add up to 0xBABA. In other words, the checksum is 0xBABA minus the total of the first 0x3E 16bit numbers (unsigned), ignoring any overflow.

Flash descriptor region

http://www.intel.co.uk/content/dam/doc/datasheet/io-controller-hub-9-datasheet.pdf from page 850 onwards. This explains everything that is in the flash descriptor, which can be used to understand what libreboot is doing about modifying it.

How to deblob:

  • patch the number of regions present in the descriptor from 5 - 3
  • originally descriptor + bios + me + gbe + platform
  • modified = descriptor + bios + gbe
  • the next stage is to patch the part of the descriptor which defines the start and end point of each section
  • then cut out the gbe region and insert it just after the region
  • all this can be substantiated with public docs (ICH9 datasheet)
  • the final part is flipping 2 bits. Halting the ME via 1 MCH soft strap and 1 ICH soft strap
  • the part of the descriptor described there gives the base address and length of each region (bits 12:24 of each address)
  • to disable a region, you set the base address to 0xFFF and the length to 0
  • and you change the number of regions from 4 (zero based) to 2

There's an interesting parameter called 'ME Alternate disable', which allows the ME to only handle hardware errata in the southbridge, but disables any other functionality. This is similar to the 'ignition' in the 5 series and higher but using the standard firmware instead of a small 128K version. Useless for libreboot, though.

To deblob GM45, you chop out the platform and ME regions and correct the addresses in flReg1-4. Then you set meDisable to 1 in ICHSTRAP0 and MCHSTRAP0.

How to patch the descriptor from the factory.rom dump

  • map the first 4k into the struct (minus the gbe region)
  • set NR in FLMAP0 to 2 (from 4)
  • adjust BASE and LIMIT in flReg1,2,3,4 to reflect the new location of each region (or remove them in the case of Platform and ME)
  • set meDisable to 1/true in ICHSTRAP0 and MCHSTRAP0
  • extract the 8k GBe region and append that to the end of the 4k descriptor
  • output the 12k concatenated chunk
  • Then it can be dd'd into the first 12K part of a coreboot image.
  • the GBe region always starts 0x20A000 bytes from the end of the ROM

This means that libreboot's descriptor region will simply define the following regions:

  • descriptor (4K)
  • gbe (8K)
  • bios (rest of flash chip. CBFS also set to occupy this whole size)

The data in the descriptor region is little endian, and it represents bits 24:12 of the address (bits 12-24, written this way since bit 24 is nearer to left than bit 12 in the binary representation).

So, x << 12 = address

If it's in descriptor mode, then the first 4 bytes will be 5A A5 F0 0F.

platform data partition in boot flash (factory.rom / lenovo bios)

Basically useless for libreboot, since it appears to be a blob. Removing it didn't cause any issues in libreboot. We think it's just random data that the manufacturer can put there, to use in their firmware. Intel datasheets seem to suggest that the platform region serves no specific function except to provide a region in flash for the hardware manufacturer to use, for whatever purpose (probably just to store other configuration data, to be used by software running from the BIOS region as per region layout specified in the descriptor).

This is a 32K region from the factory image. It could be data (non-functional) that the original Lenovo BIOS used, but we don't know.

It has only a 448 byte fragment different from 0x00 or 0xFF, on the X200 thinkpads that were tested.