Beyond Linux® From Scratch (System V Edition) - Version 11.0

Chapter 3. After LFS Configuration Issues

About Firmware

On some recent PCs it can be necessary, or desirable, to load firmware to make them work at their best. There is a directory, /lib/firmware, where the kernel or kernel drivers look for firmware images.

Currently, most firmware can be found at a git repository: http://git.kernel.org/cgit/linux/kernel/git/firmware/linux-firmware.git/tree/. For convenience, the LFS Project has created a mirror, updated daily, where these firmware files can be accessed via wget or a web browser at https://anduin.linuxfromscratch.org/BLFS/linux-firmware/.

To get the firmware, either point a browser to one of the above repositories and then download the item(s) which you need, or install git-2.33.0 and clone that repository.

For some other firmware, particularly for Intel microcode and certain wifi devices, the needed firmware is not available in the above repository. Some of this will be addressed below, but a search of the Internet for needed firmware is sometimes necessary.

Firmware files are conventionally referred to as blobs because you cannot determine what they will do. Note that firmware is distributed under various different licenses which do not permit disassembly or reverse-engineering.

Firmware for PCs falls into four categories:

[Note]

Note

Although not needed to load a firmware blob, the following tools may be useful for determining, obtaining, or preparing the needed firmware in order to load it into the system: cpio-2.13, git-2.33.0, pciutils-3.7.0, and Wget-1.21.1

User Notes: https://wiki.linuxfromscratch.org/blfs/wiki/aboutfirmware

Microcode updates for CPUs

In general, microcode can be loaded by the BIOS or UEFI, and it might be updated by upgrading to a newer version of those. On linux, you can also load the microcode from the kernel if you are using an AMD family 10h or later processor (first introduced late 2007), or an Intel processor from 1998 and later (Pentium4, Core, etc), if updated microcode has been released. These updates only last until the machine is powered off, so they need to be applied on every boot.

Intel provide updates of their microcode for Skylake and later processors as new vulnerabilities come to light, and have in the past provided updates for processors from SandyBridge onwards, although those are no-longer supported for new fixes. New versions of AMD firmware are rare and usually only apply to a few models, although motherboard manufacturers get extra updates which maybe update microcode along with the changes to support newer CPUs and faster memory.

There are two ways of loading the microcode, described as 'early' and 'late'. Early loading happens before userspace has been started, late loading happens after userspace has started. Not surprisingly, early loading is preferred, (see e.g. an explanatory comment in a kernel commit noted at x86/microcode: Early load microcode on LWN.) Indeed, it is needed to work around one particular erratum in early Intel Haswell processors which had TSX enabled. (See Intel Disables TSX Instructions: Erratum Found in Haswell, Haswell-E/EP, Broadwell-Y .) Without this update glibc can do the wrong thing in uncommon situations.

It is still possible to manually force late loading of microcode, either for testing or to prevent having to reboot. You will need to reconfigure your kernel for either method. The instructions here will create a kernel .config to suite early loading, before forcing late loading to see if there is any microcode. If there is, the instructions then show you how to create an initrd for early loading.

To confirm what processor(s) you have (if more than one, they will be identical) look in /proc/cpuinfo.

If you are creating an initrd to update firmware for different machines, as a distro would do, go down to 'Early loading of microcode' and cat all the Intel blobs to GenuineIntel.bin or cat all the AMD blobs to AuthenticAMD.bin. This creates a larger initrd - for all Intel machines in the 20200609 update the size is 3.0 MB compared to typically 24 KB for one machine.

Intel Microcode for the CPU

The first step is to get the most recent version of the Intel microcode. This must be done by navigating to https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/releases/ and downloading the latest file there. As of this writing the most secure version of the microcode, for those machines which can boot it, is microcode-20210608. Extract this file in the normal way, the microcode is in the intel-ucode directory, containing various blobs with names in the form XX-YY-ZZ. There are also various other files, and a releasenote.

In the past, intel did not provide any details of which blobs had changed versions, but now the release note details this.

The recent firmware for older processors is provided to deal with vulnerabilities which have now been made public, and for some of these such as Microarchitectural Data Sampling (MDS) you might wish to increase the protection by disabling hyperthreading, or alternatively to disable the kernel's default mitigation because of its impact on compile times. Please read the online documentation at https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/index.html.

Now you need to determine your processor's identity to see if there is any microcode for it. Determine the decimal values of the cpu family, model and stepping by running the following command (it will also report the current microcode version): 

head -n7 /proc/cpuinfo

Convert the cpu family, model and stepping to pairs of hexadecimal digits. For a Skylake i3 6100 (described as Intel(R) Core(TM) i3-6100 CPU) the relevant values are cpu family 6, model 94, stepping 3 so in this case the required identification is 06-5e-03. A look at the blobs will show that there is one for this CPU (although for older issues it might have already been applied by the BIOS). If there is a blob for your system then test if it will be applied by copying it (replace <XX-YY-ZZ> by the identifier for your CPU) to where the kernel can find it: 

mkdir -pv /lib/firmware/intel-ucode
cp -v intel-ucode/<XX-YY-ZZ> /lib/firmware/intel-ucode

Now that the Intel microcode has been prepared, use the following options when you configure the kernel to load Intel microcode: 

General Setup --->
  [*] Initial RAM filesystem and RAM disk (initramfs/initrd) support [CONFIG_BLK_DEV_INITRD]
Processor type and features  --->
  [*] CPU microcode loading support  [CONFIG_MICROCODE]
  [*]      Intel microcode loading support [CONFIG_MICROCODE_INTEL]

After you have successfully booted the new system, force late loading by using the command: 

echo 1 > /sys/devices/system/cpu/microcode/reload

Then use the following command to see if anything was loaded: (N.B. the dates when microcode was created may be months ahead of when it was released.) 

dmesg | grep -e 'microcode' -e 'Linux version' -e 'Command line'

This reformatted example for a machine with old microcode in its BIOS was created by temporarily booting without microcode, to show the current Firmware Bug messages, then the late load shows it being updated to revision 0xea. 

[    0.000000] Linux version 5.12.8 (lfs@leshp) (gcc (GCC) 11.1.0,
               GNU ld (GNU Binutils) 2.36.1)
               #2 SMP PREEMPT Fri Jun 4 01:25:02 BST 2021
[    0.000000] Command line: BOOT_IMAGE=/vmlinuz-5.12.8-sda11 root=/dev/sda11 ro
               resume=/dev/sda10
[    0.028741] [Firmware Bug]: TSC_DEADLINE disabled due to Errata;
               please update microcode to version: 0xb2 (or later)
[    0.115716] SRBDS: Vulnerable: No microcode
[    0.115826] MDS: Vulnerable: Clear CPU buffers attempted, no microcode
[    0.389005] microcode: sig=0x506e3, pf=0x2, revision=0x74
[    0.389030] microcode: Microcode Update Driver: v2.2.
[   70.089502] microcode: updated to revision 0xea, date = 2021-01-25
[   70.089528] x86/CPU: CPU features have changed after loading microcode,
               but might not take effect.
[   70.089530] microcode: Reload completed, microcode revision: 0xea

If the microcode was not updated, there is no new microcode for this system's processor. If it did get updated, you can now proceed to the section called “Early loading of microcode”.

AMD Microcode for the CPU

Begin by downloading a container of firmware for your CPU family from https://anduin.linuxfromscratch.org/BLFS/linux-firmware/amd-ucode/. The family is always specified in hex. Families 10h to 14h (16 to 20) are in microcode_amd.bin. Families 15h, 16h and 17h have their own containers. Create the required directory and put the firmware you downloaded into it as the root user: 

mkdir -pv /lib/firmware/amd-ucode
cp -v microcode_amd* /lib/firmware/amd-ucode

When you configure the kernel, use the following options to load AMD microcode: 

General Setup --->
  [*] Initial RAM filesystem and RAM disk (initramfs/initrd) support [CONFIG_BLK_DEV_INITRD]
Processor type and features  --->
  [*] CPU microcode loading support  [CONFIG_MICROCODE]
  [*]      AMD microcode loading support [CONFIG_MICROCODE_AMD]

After you have successfully booted the new system, force late loading by using the command: 

echo 1 > /sys/devices/system/cpu/microcode/reload

Then use the following command to see if anything was loaded: 

dmesg | grep -e 'microcode' -e 'Linux version' -e 'Command line'

This historic example from an old Athlon(tm) II X2 shows it has been updated. At that time, all CPUs were still reported in the microcode details on AMD machines (the current position for AMD machines where newer microcode is available is unknown) : 

[    0.000000] Linux version 4.15.3 (ken@testserver) (gcc version 7.3.0 (GCC))
               #1 SMP Sun Feb 18 02:08:12 GMT 2018
[    0.000000] Command line: BOOT_IMAGE=/vmlinuz-4.15.3-sda5 root=/dev/sda5 ro
[    0.307619] microcode: CPU0: patch_level=0x010000b6
[    0.307671] microcode: CPU1: patch_level=0x010000b6
[    0.307743] microcode: Microcode Update Driver: v2.2.
[  187.928891] microcode: CPU0: new patch_level=0x010000c8
[  187.928899] microcode: CPU1: new patch_level=0x010000c8

If the microcode was not updated, there is no new microcode for this system's processor. If it did get updated, you can now proceed to the section called “Early loading of microcode”.

Early loading of microcode

If you have established that updated microcode is available for your system, it is time to prepare it for early loading. This requires an additional package, cpio-2.13 and the creation of an initrd which will need to be added to grub.cfg.

It does not matter where you prepare the initrd, and once it is working you can apply the same initrd to later LFS systems or newer kernels on this same machine, at least until any newer microcode is released. Use the following commands: 

mkdir -p initrd/kernel/x86/microcode
cd initrd

For an AMD machine, use the following command (replace <MYCONTAINER> with the name of the container for your CPU's family): 

cp -v /lib/firmware/amd-ucode/<MYCONTAINER> kernel/x86/microcode/AuthenticAMD.bin

Or for an Intel machine copy the appropriate blob using this command: 

cp -v /lib/firmware/intel-ucode/<XX-YY-ZZ> kernel/x86/microcode/GenuineIntel.bin

Now prepare the initrd: 

find . | cpio -o -H newc > /boot/microcode.img

You now need to add a new entry to /boot/grub/grub.cfg and here you should add a new line after the linux line within the stanza. If /boot is a separate mountpoint: 

initrd /microcode.img

or this if it is not: 

initrd /boot/microcode.img

If you are already booting with an initrd (see the section called “About initramfs”), you should run mkinitramfs again after putting the appropriate blob or container into /lib/firmware as explained above. Alternatively, you can have both initrd on the same line, such as initrd /microcode.img /other-initrd.img (adapt that as above if /boot is not a separate mountpoint).

You can now reboot with the added initrd, and then use the same command to check that the early load worked: 

dmesg | grep -e 'microcode' -e 'Linux version' -e 'Command line'

If you updated to address vulnerabilities, you can look at /sys/devices/system/cpu/vulnerabilities/ to see what is now reported.

The places and times where early loading happens are very different in AMD and Intel machines. First, an Intel (Skylake) example with early loading: 

[    0.000000] microcode: microcode updated early to revision 0xea, date = 2021-01-25
[    0.000000] Linux version 5.12.8 (lfs@leshp) (gcc (GCC) 11.1.0,
               GNU ld (GNU Binutils) 2.36.1) #2 SMP PREEMPT Fri Jun 4 01:25:02 BST 2021
[    0.000000] Command line: BOOT_IMAGE=/vmlinuz-5.12.8-sda11 root=/dev/sda11 ro
               resume=/dev/sda10
[    0.381420] microcode: sig=0x506e3, pf=0x2, revision=0xea
[    0.381479] microcode: Microcode Update Driver: v2.2.

A historic AMD example: 

[    0.000000] Linux version 4.15.3 (ken@testserver) (gcc version 7.3.0 (GCC))
               #2 SMP Sun Feb 18 02:32:03 GMT 2018
[    0.000000] Command line: BOOT_IMAGE=/vmlinuz-4.15.3-sda5 root=/dev/sda5 ro
[    0.307619] microcode: microcode updated early to new patch_level=0x010000c8
[    0.307678] microcode: CPU0: patch_level=0x010000c8
[    0.307723] microcode: CPU1: patch_level=0x010000c8
[    0.307795] microcode: Microcode Update Driver: v2.2.

Firmware for Video Cards

Firmware for ATI video chips (R600 and later)

These instructions do NOT apply to old radeons before the R600 family. For those, the firmware is in the kernel's /lib/firmware/ directory. Nor do they apply if you intend to avoid a graphical setup such as Xorg and are content to use the default 80x25 display rather than a framebuffer.

Early radeon devices only needed a single 2K blob of firmware. Recent devices need several different blobs, and some of them are much bigger. The total size of the radeon firmware directory is over 500K — on a large modern system you can probably spare the space, but it is still redundant to install all the unused files each time you build a system.

A better approach is to install pciutils-3.7.0 and then use lspci to identify which VGA controller is installed.

With that information, check the RadeonFeature page of the Xorg wiki for Decoder ring for engineering vs marketing names to identify the family (you may need to know this for the Xorg driver in BLFS — Southern Islands and Sea Islands use the radeonsi driver) and the specific model.

Now that you know which controller you are using, consult the Radeon page of the Gentoo wiki which has a table listing the required firmware blobs for the various chipsets. Note that Southern Islands and Sea Islands chips use different firmware for kernel 3.17 and later compared to earlier kernels. Identify and download the required blobs then install them: 

mkdir -pv /lib/firmware/radeon
cp -v <YOUR_BLOBS> /lib/firmware/radeon

There are actually two ways of installing this firmware. BLFS, in the 'Kernel Configuration for additional firmware' section part of the Xorg ATI Driver-19.1.0 section gives an example of compiling the firmware into the kernel - that is slightly faster to load, but uses more kernel memory. Here we will use the alternative method of making the radeon driver a module. In your kernel config set the following: 

Device Drivers --->
  Graphics support --->
      Direct Rendering Manager --->
        [*] Direct Rendering Manager (XFree86 ... support)  [CONFIG_DRM]
      [M] ATI Radeon                                        [CONFIG_DRM_RADEON]

Loading several large blobs from /lib/firmware takes a noticeable time, during which the screen will be blank. If you do not enable the penguin framebuffer logo, or change the console size by using a bigger font, that probably does not matter. If desired, you can slightly reduce the time if you follow the alternate method of specifying 'y' for CONFIG_DRM_RADEON covered in BLFS at the link above — you must specify each needed radeon blob if you do that.

Firmware for Nvidia video chips

Some Nvidia graphics chips need firmware updates to take advantage of all the card's capability. These are generally the GeForce 8, 9, 9300, and 200-900 series chips. For more exact information, see https://nouveau.freedesktop.org/wiki/VideoAcceleration/#firmware.

First, the kernel Nvidia driver must be activated: 

Device Drivers --->
  Graphics support --->
      Direct Rendering Manager --->
        <*> Direct Rendering Manager (XFree86 ... support)  [CONFIG_DRM]
      <*/M> Nouveau (NVIDIA) cards                          [CONFIG_DRM_NOUVEAU]

The steps to install the Nvidia firmware are: 

wget https://raw.github.com/imirkin/re-vp2/master/extract_firmware.py
wget http://us.download.nvidia.com/XFree86/Linux-x86/325.15/NVIDIA-Linux-x86-325.15.run
sh NVIDIA-Linux-x86-325.15.run --extract-only
python extract_firmware.py 
mkdir -p /lib/firmware/nouveau
cp -d nv* vuc-* /lib/firmware/nouveau/

Firmware for Network Interfaces

The kernel likes to load firmware for some network drivers, particularly those from Realtek (the /lib/linux-firmware/rtl_nic/) directory, but they generally appear to work without it. Therefore, you can boot the kernel, check dmesg for messages about this missing firmware, and if necessary download the firmware and put it in the specified directory in /lib/firmware so that it will be found on subsequent boots. Note that with current kernels this works whether or not the driver is compiled in or built as a module, there is no need to build this firmware into the kernel. Here is an example where the R8169 driver has been compiled in but the firmware was not made available. Once the firmware had been provided, there was no mention of it on later boots. 

dmesg | grep firmware | grep r8169
[    7.018028] r8169 0000:01:00.0: Direct firmware load for rtl_nic/rtl8168g-2.fw failed with error -2
[    7.018036] r8169 0000:01:00.0 eth0: unable to load firmware patch rtl_nic/rtl8168g-2.fw (-2)

Firmware for Other Devices

Identifying the correct firmware will typically require you to install pciutils-3.7.0, and then use lspci to identify the device. You should then search online to check which module it uses, which firmware, and where to obtain the firmware — not all of it is in linux-firmware.

If possible, you should begin by using a wired connection when you first boot your LFS system. To use a wireless connection you will need to use a network tools such as Wireless Tools-29 and wpa_supplicant-2.9.

Different countries have different regulations on the radio spectrum usage of wireless devices. You can install a firmware to make the wireless devices obey local spectrum regulations, so you won't be inquired by local authority or find your wireless NIC jamming the frequencies of other devices (for example, remote controllers). The regulatory database firmware can be downloaded from https://kernel.org/pub/software/network/wireless-regdb/. To install it, simply extract regulatory.db and regulatory.db.p7s from the tarball into /lib/firmware. The access point would send a country code to your wireless NIC, and wpa_supplicant-2.9 would tell the kernel to load the regulation of this country from regulatory.db, and enforce it.

Firmware may also be needed for other devices such as some SCSI controllers, bluetooth adaptors, or TV recorders. The same principles apply.

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