Linux-6.12.58

The meaning of optional make environment variables:

LANG=<host_LANG_value> LC_ALL=

This establishes the locale setting to the one used on the host. This may be needed for a proper menuconfig ncurses interface line drawing on a UTF-8 linux text console.

If used, be sure to replace <host_LANG_value> by the value of the $LANG variable from your host. You can alternatively use instead the host's value of $LC_ALL or $LC_CTYPE.

zcat /proc/config.gz

Copies the running kernel config and redirects to the .config file.

make menuconfig

This launches an ncurses menu-driven interface. For other (graphical) interfaces, type make help.

make olddefconfig

Default all questions based on the contents of your existing .config file but sets new symbols to their default values without prompting.

The rationale for the above configuration items:

Randomize the address of the kernel image (KASLR)

Enable ASLR for kernel image, to mitigate some attacks based on fixed addresses of sensitive data or code in the kernel.

Compile the kernel with warnings as errors

This may cause building failure if the compiler and/or configuration are different from those of the kernel developers.

Enable kernel headers through /sys/kernel/kheaders.tar.xz

This will require cpio building the kernel. cpio is not installed by LFS.

Configure standard kernel features (expert users)

This will make some options show up in the configuration interface but changing those options may be dangerous. Do not use this unless you know what you are doing.

Strong Stack Protector

Enable SSP for the kernel. We've enabled it for the entire userspace with --enable-default-ssp configuring GCC, but the kernel does not use GCC default setting for SSP. We enable it explicitly here.

Support for uevent helper

Having this option set may interfere with device management when using Udev.

Maintain a devtmpfs

This will create automated device nodes which are populated by the kernel, even without Udev running. Udev then runs on top of this, managing permissions and adding symlinks. This configuration item is required for all users of Udev.

Automount devtmpfs at /dev

This will mount the kernel view of the devices on /dev upon switching to root filesystem just before starting init.

Display a user-friendly message when a kernel panic occurs

This will make the kernel correctly display the message in case a kernel panic happens and a running DRM driver supports to do so. Without this, it would be more difficult to diagnose a panic: if no DRM driver is running, we'd be on the VGA console which can only hold 24 lines and the relevant kernel message is often flushed away; if a DRM driver is running, the display is often completely messed up on panic. As of Linux-6.12, none of the dedicated drivers for mainstream GPU models really supports this, but it's supported by the “Simple framebuffer driver” which runs on the VESA (or EFI) framebuffer before the dedicated GPU driver is loaded. If the dedicated GPU driver is built as a module (instead of a part of the kernel image) and no initramfs is used, this functionality will work just fine before the root file system is mounted and it's already enough for providing information about most LFS configuration errors causing a panic (for example, an incorrect root= setting in 'ch-bootable-grub').

Panic screen formatter

Set this kmsg to make sure the last kernel messages lines are displayed when a kernel panic happens. The default, user, would make the kernel show only a “user friendly” panic message which is not helpful on diagnostic. The third choice, qr_code, would make the kernel to compress the last kernel message lines into a QR code and display it. The QR code can hold more message lines than plain text and it can be decoded with an external device (like a smart phone). But it requires a Rust compiler that LFS does not provide.

Mark VGA/VBE/EFI FB as generic system framebuffer and Simple framebuffer driver

These allow to use the VESA framebuffer (or the EFI framebuffer if booting the LFS system via UEFI) as a DRM device. The VESA framebuffer will be set up by GRUB (or the EFI framebuffer will be set up by the UEFI firmware), so the DRM panic handler can function before the GPU-specific DRM driver is loaded.

Enable legacy fbdev support for your modesetting driver and Framebuffer Console support

These are needed to display the Linux console on a GPU driven by a DRI (Direct Rendering Infrastructure) driver. As CONFIG_DRM (Direct Rendering Manager) is enabled, we should enable these two options as well or we'll see a blank screen once the DRI driver is loaded.

Support x2apic

Support running the interrupt controller of 64-bit x86 processors in x2APIC mode. x2APIC may be enabled by firmware on 64-bit x86 systems, and a kernel without this option enabled will panic on boot if x2APIC is enabled by firmware. This option has no effect, but also does no harm if x2APIC is disabled by the firmware.