diff --git a/chapter10/kernel.xml b/chapter10/kernel.xml index 8155f735c..e078e136d 100644 --- a/chapter10/kernel.xml +++ b/chapter10/kernel.xml @@ -272,6 +272,71 @@ + + + + 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 relevent 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 ). + + + + + + + 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. + + +