How Linux Kernel Prints Text on Screen

In this video we will dive into a simple call to the printf function and see what happens in the kernel and how it gets eventually printed on screen.

For more information about setting up an environment for kernel dev, checkout the welcome link on my channel.

Docs used in video:

[nirlichtman]

- The display mechanism the kernel chooses depends on the setup, this is what it chose in the case of standard QEMU config & x86_64, but on other machines it may use something else for example a framebuffer. VGA mode 3 is a common x86/x64 choice, especially for older machines, but modern ones may not support it at all.
- The reason it printed 3 "H" letters and not "Hel" is that I recycled the same command that I used to modify the first letter to red, and only changed the color so it brought over the same first letter each time.

[FernandoMumbach]

This video is a tutorial on:

- How printf works in the kernel
- How to the debug the kernel with GDB
- An intro into how to to use GDB
- A guide on how to look up kernel documentation

And several things more. Condensed in 12 minutes. This is perfect!! I've never seen a video as good as this one explaining anything!

[bagfleet]

”we’re gonna have to dive in a little bit to the assembly”. What a madlad ❤

[Scoopta]

You're making one of the nerdiest linux videos I've seen on windows using MS edge...saying I'm confused is an understatement

[matthias]

no unnecessary talking, straight to the point, extremely well explained, this is why I pay for internet, thank you brother

[katiagalkina]

The rabbit hole is much deeper than I was thinking!

[lately-late]

The magic behind a standard library function—and the POSIX system calls—is what every CS student would have wondered about for once. Thank you for making this video. It brought back memories of being curious about how a computer works.

[namanchhabra]

I always wanted to know kernel that deep 🙂

[ismbks]

this feels like i'm watching paid content for free

[timeimp]

This is like a whole subject at uni in less than 15 minutes. Subscribed!

[nickdaria]

Excellent video as always. Love seeing well-made low level computing content that does deep dives into while keeping it just dense enough to watch in your free time.

I feel like many videos on this topic are always either way too short/simplified or way too long and drawn out. You always hit it on the head.

[CookieGod]

I don’t know why but the way you say ‘config’ sounds satisfying

[CornThatLefty]

This series of videos is awesome. Just explains and explores a low-level topic quickly and without any fluff.

[raf.nogueira]

Thisis incredible, I always wanted to understand a little bit on how these deep system call used to work

[GrittyMaholmes]

I love the confidence in your voice, i wana be this confidence when coding .

[KovalenkoYT]

I just discovered this channel today, and with two videos that I have seen I feel that in half an hour I have learned more than what I learned in many classes at the university. Subscribed!

[patrickprucha]

I like the way you explain things. I also noticed that you are very good and very at ease with programming languages. I will look into more of your videos / media when i jump into c programming. thanks again

[shahriarmorabi]

i have longed for this exact video for years. Thank you.

[BorderKeeper]

Programmer of 10 years here. This is straight up black magic.

[sanderbos]

This is such a good reference video for anyone wanting to dive into the kernel