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For context about certain topics, please read:

https://doc.coreboot.org/getting_started/architecture.html

100% libre init in coreboot

The reason this distinction matters (referring specifically to coreboot's side of the initialisation) will become clearer, in the following sections:

A universal exemption is made in Libreboot, permitting (read: requiring, per project policy) the inclusion of CPU microcode updates if available. You can read more about that and the reasons why by reading the following article:

CPU microcode updates are OK

Releases after Libreboot 20230423 will provide separate ROMs with microcode excluded, alongside default ones with microcode included.

Intel platforms

Descriptor vs descriptorless setup

Libreboot supports several mainboards using Intel platforms. Of these, there are essentially two class of machine (for the purposes of this article):

Descriptorless configuration
Descriptor-based configuration

What does descriptor mean? Well, traditionally, the main flash IC (containing the boot firmware, commonly referred to as the BIOS) on Intel machines, contained only x86 executable code, responsible for initialising all of the hardware, such as the CPU, memory controller and peripherals. This is what we will refer to as the descriptorless setup; in such configurations, the Intel ME firmware is absent by default.

In a descriptor configuration, the flash is divided into regions such as:

Intel flash descriptor: always the first 4KiB of the flash. Binary-encoded configuration data for the machine, and the regions (such as this, or others below) is defined in here. In some ways, you might think of this as analagous to the Master Boot Record on a hard drive.
Intel GbE NVM (gigabit ethernet non-volatile memory): binary-encoded configuration data, for the onboard Intel gigabit ethernet device, if one is present. It contains lots of settings like MAC address, what speed the NIC should run at, PCI IDs, LED blinking speed and more. If a non-Intel NIC is used, this region of the flash will not be present.
ME (Intel Management Engine): a nasty security liability in its default state, the ME provides many features such as remote management, with full networking, The ME is a dedicated coprocessor separate from the main CPU, and the initialisation firmware plus operating system for it is loaded from this dedicated region in the main boot flash. More info is available in the FAQ - where ME firmware is otherwise present, Libreboot either removes it or (with the me_cleaner program) reconfigures it in such a way where it is disabled during machine initialisation.
Platform region: non-program data, usually just a bunch of strings put there by the hardware vendor.
BIOS region: this contains the main boot firmware, responsible for initialising the CPU, memory controller and peripherals, putting the machine into a state where it can run programs (most likely a bootloader, then an operating system). The coreboot code (provided by Libreboot) goes in here.

Basically, you can think of such "regions" as analogous to partitions on a hard drive. What's important is that the flash IC is divided into such regions, where each region is intended for a specific purpose.

The contents of the descriptor and GbE regions are described by Intel datasheets, but those datasheets often contain reserved sections where parts are left undocumented. Reverse engineering efforts over the years have documented some of these blank spots.

Libreboot does not distribute Intel ME images

Libreboot does not distribute the Intel ME firmware in any way, whether in the Git repository or in releases. Where it is needed, Libreboot provides scripts that automatically fetch and install it, in a neutered (disabled) state by running the me_cleaner program. This is completely automated. Please read:

https://github.com/corna/me_cleaner/wiki/How-does-it-work%3F

The BringUp code of Intel ME is all that remains, in Libreboot configurations. ME BringUp (BUP) is analogous to coreboot, providing initialisation for the ME itself; by that same analogy, the way Libreboot configures it is similar to running coreboot without a payload. The ME is initialised, to a state where it can run code, but then it doesn't actually run code. It is thus disabled.

In other words, a neutered Intel ME setup is completely benign, both from a software freedom and security perspective. It becomes a useless, unused processor, that most people in the real world will never want to use anyway. With this perspective, we see that Intel ME is now entirely inconsequential to the average user.

Released Libreboot ROM images, provided pre-compiled, do not include the ME firmware at all; they are scrubbed, by automated release scripts when they're preparing a release. If you're building from source, the Libreboot build system will automatically download it (from the vendor), neuter it and then insert it; on release ROMs, the same scripts used by the build systems can (must) be run manually, accomplishing the same result after the fact. Please read: docs/install/ivy_has_common.md

The ME firmware is required on almost all Intel platforms, or the machine will turn off after 30 minutes (or it will not boot, if the ME also controls whether the CPU comes out of reset).

More about Intel ME removal/disabling

Libreboot provides a way to fully remove the ME firmware, while retaining full use of the machine, on GM45 platforms with ICH9M southbridge. These are laptops: ThinkPad X200/T400/T500/W500 and so on of that generation. See: docs/install/ich9utils.md

The ich9utils software is provided by Libreboot. The ich9gen utility was specifically written by Leah Rowe, in 2014 and improved incrementally since.

On newer platforms as alluded to above, me_cleaner is used instead.

Notes about specific types of blobs

VGA option ROMs

Native video initialisation is supported and enabled, for all supported Intel platforms that have it. The source code is provided by coreboot, under free license.

In some cases, a laptop may have a graphics chip that is unsupported by coreboot. In this situation, a binary blob called a VGA Option ROM must be used. Libreboot has experimental support for Nvidia GPU models of the Dell Latitude E6400, in an experimental branch where the build system automatically downloads the VGA ROM for it. This is currently not present in releases, or in the stable branch of lbmk.

In other instances, a machine may have two graphics devices, where one has native (free/libre) initialisation provided by coreboot. In these situations, it is possible to insert a VGA ROM for the other one; Libreboot currently lacks documentation for this, but it has been tested. Example: Dual Intel/Nvidia graphics on some ivybridge or haswell thinkpads.

For add-on GPUs, SeaBIOS (payload) can typically scan a VGA ROM present on the card and execute it. This has been tested on certain desktop mainboards that Libreboot supports, and works just fine; Libreboot does not need to handle these blobs at all.

Libreboot's default is always freedom, when feasible in practise. Users who wish to have use of these additional GPUs, on such hardware, must take stock of the following paragraph in Libreboot policy:

"The principles above should apply to default configurations. However, libreboot is to be configurable, allowing the user to do whatever they like." - configurable, it most certainly is! See: docs/maintain/

Memory controller initialisation

Libreboot has fully libre initialisation available for all Intel memory controllers on supported platforms. This includes Haswell (ThinkPad T440p and W541) as of Libreboot 20230319 or higher.

AMD platforms

Libreboot currently lacks support for AMD platforms, but information about them will be written when this fact changes.

ARM platforms (chromebooks)

Mostly blobless, except for the requirement on daisy and peach mainboards to include BL1 bootloader blobs. These are:

HP Chromebook 11 G1 (daisy-spring) (board removed from Libreboot, due to issues (will be re-added at a later date)
Samsung Chromebook XE303 (daisy-snow) (ditto)
Samsung Chromebook 2 13” (peach-pi) (ditto)
Samsung Chromebook 2 11” (peach-pit) (ditto)
nyan-* chromebooks also temporarily removed, but are blobless in Libreboot

List of blobs needed, specifically for each board

This article has thoroughly explained, in a detailed overview, the precise nature as to what binary blobs are accomodated for in Libreboot. Again, fully libre init from coreboot is available on all currently supported boards.

From coreboot is the critical aspect of this, but Libreboot's full scope is the main flash IC which (in some cases) contains software outside of coreboot.

Here is a list, for each board, of those blobs:

Intel/x86

Intel ME:

Neutered ME required on these targets: t420_8mb, t420s_8mb, t430_12mb, t440p_12mb, t440pmrc_12mb, t520_8mb, t530_12mb, w530_12mb, w541_12mb, w541mrc_12mb, x220_8mb, x230_12mb, x230_16mb, x230edp_12mb, x230t_12mb, x230t_16mb, hp8200sff, hp2560p_8mb, hp2570p_16mb, hp8300usdt_16mb and hp9470m_16mb.

As stated, Libreboot provides this in a state where the ME is no longer a threat to security. It initialises itself, but then does nothing, so it's disabled. This is done using me_cleaner. See: https://github.com/corna/me_cleaner/wiki/How-does-it-work%3F

KBC1126 EC firmware (HP laptops):

EC firmware is inserted into main boot flash, rather than being on a separate IC. This is better because libre replacements would be more easy to install in the future, and reverse engineering is made much easier by it. Libreboot's build system handles such firmware in blobutil, automatically downloading it during the build process. Libreboot 20230423 onwards does scrub EC firmware and provide functionality in blobutil insert, to insert them with cbfstool at the correct offset as defined by coreboot config for each board.

CPU microcode:

Microcode updates for CPU provided on all x86 platforms, by default. Not technically required, but highly recommended. To remove, do:

cbfstool filename.rom remove -n cpu_microcode_blob.bin

Releases after Libreboot 20230423 will provide separate ROMs with microcode excluded, alongside default ones with microcode included.

Removal of microcode updates will affect system stability in a negative way, introducing non-standard broken behaviour and it may result in the machine being unable to boot properly. In other cases, doing so may break features such as S3 suspend/resume.

CPU microcode blobs included by default, on all x86 boards. While not needed in most cases, their use is highly recommended. For reasons why, see: news/policy.md#more-detailed-insight-about-microcode

Intel Flash Descriptor (IFD):

Intel Flash Descriptors are provided as blobs on some boards, but these are not software blobs. They are configurations provided in a binary format, fully readable by libre software. For example:

Libreboot's ich9gen program generates ICH9M flash descriptors from scratch.
Coreboot's ifdtool program has extensive features for manipulating Intel flash descriptors.
Corebot's bincfg program generates any sort of binary from a .spec file which can describe any binary format in a human readable format. It contains several flash descriptors for several platforms, but Libreboot does not use these.

Intel GbE NVM config (configuration data, binary-encoded, for gigabit NIC):

Libreboot's ich9gen program also generates GbE NVM images specifically for Intel NICs used in GM45 thinkpads.
Libreboot's nvmutil program can manipulate GbE NVM images

ARM/chromebooks

BL1 bootloader (peach/daisy):

BL1 bootloader needed on: daisy_snow, daisy_spring and peach_pit.

These boards are currently not present. They were removed from Libreboot, because the build system does not yet auto-insert the BL1 blobs. The boards are otherwise believed to work, using Alper's port of U-Boot in Libreboot.

Conclusion

From the above, you can see that Libreboot really does implement a binary blobs reduction policy, with the emphasis on reduction being most critical. It can be asserted that Libreboot does in fact provide a reasonable level of software freedom, on all boards.

Libreboot could add a lot more blobs for various platforms, to enable various extra features, that it instead avoids adding, precisely because the purpose of the Libreboot project is to promote libre software and minimise the power that proprietary software developers have over users.

I hope this article provided food for thought.

An aside: hardware freedom

None of the currently supported Libreboot machines have libre hardware, in the sense that ICs do not come with publicly available verilog files and the like. You could not manufacture your own replacements of these machines.

Some schematics and boardview files describing the circuit boards of each machine are available online, through various channels. You have to search for them yourself; one day, the Right To Repair movement will hopefully bring about universal access to such documents by the public.

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