Linux 6.10 Preps A Kernel Panic Screen - Sort Of A "Blue Screen of Death"

[phoronix]

Phoronix: Linux 6.10 Preps A Kernel Panic Screen - Sort Of A "Blue Screen of Death"

While systemd 255 last year introduced a "blue screen of death" inspired solution with systemd-bsod for presenting logged error messages full-screen, it's not appropriate for all errors. Systemd-bsod can work out for presenting full-screen messages in case of boot failures and other problems where user-space is alive. But the user-space code does little good in case of a kernel panic and similar issues bringing the system to a halt. Set to be introduced now with Linux 6.10 is a parallel "blue screen of death" like error presenting experience with the introduction of the DRM panic handler...

https://www.phoronix.com/news/Linux-6.10-DRM-Panic-Handler

[varikonniemi]

This is yet more fallout from the halfbrained idea of removing kernel VT. It's such a loss of functionality and reliability to rely on userspace terminals to access kernel console.

[duby229]

This is yet more fallout from the halfbrained idea of removing kernel VT. It's such a loss of functionality and reliability to rely on userspace terminals to access kernel console.

^^^ This...

Linux already had a means to display error messages in case of kernel panic.

EDIT: I'm wrong about this statement, I had assumed that because I had seen kernel panic messages in the past, but it isn't true. I just spent half the day building a linux system testing this out and in fact it does hang on a black screen.

I've never personally experienced a hang to a black screen, but if you have a desktop running then kernel panics do in fact...

[nerdopolis]

This is yet more fallout from the halfbrained idea of removing kernel VT. It's such a loss of functionality and reliability to rely on userspace terminals to access kernel console.

In my view, you're still reliant on user space even with VTs. /sbin/agetty, /bin/login, /bin/bash, and whatever tools you need to run once your shell starts. If your userspace is badly frogged up, it's not like the VT's are all kgdb prompts.

The VTs are a VT100 emulator in the kernel. It's arguably a kernel mode UI. They haven't been able to scroll up since a CVE in 2020, and the subsystem being seen as too fragile for a proper fix

[nerdopolis]

^^^ This...

Linux already had a means to display error messages in case of kernel panic.

Well... unless you are using a kernel mode setting driver. If you intentionally trigger a kernel panic now, it appears to be a dead hang

[duby229]

Well... unless you are using a kernel mode setting driver. If you intentionally trigger a kernel panic now, it appears to be a dead hang

Maybe I'm misunderstanding.

That's only because they removed VT from the kernel.

[nerdopolis]

Maybe I'm misunderstanding.

That's only because they removed VT from the kernel.

Most major distributions still have VTs compiled in their kernels these days, so not really. It's because, until this is merged in 6.10, and the drivers get support enabled for it, there was no way in a panic condition to update the screen to show an error message.

[duby229]

Most major distributions still have VTs compiled in their kernels these days, so not really. It's because, until this is merged in 6.10, and the drivers get support enabled for it, there was no way in a panic condition to update the screen to show an error message.

I'm definitely misunderstanding then, because I've personally experienced kernel panics -with- on screen error message.

[nerdopolis]

I'm definitely misunderstanding then, because I've personally experienced kernel panics -with- on screen error message.

Most of the ones that are still visible I think are ones that are very early boot before the mode setting driver initializes, depending how your initrd is configured. I have tried to intentionally crash with sysrq-trigger, and only see it as hangs

[fallingcats]

I'm definitely misunderstanding then, because I've personally experienced kernel panics -with- on screen error message.

Only if you're not running a desktop environment while the panic is happening. AFAIK The linux kernel never had a way to switch to a tty in case of panic.