It has been 8 hours. 8 hours of pure agony as I try to mimic the linux interrupt handling system. This has by far been the hardest challenge that I have ever faced, and I honestly took a break to recuperate myself and not lose motivation.
but we created system interrupts! we can now do much more cool stuffs like
virtual memory management and eventually keyboard input, so overall this is exciting.
Either way, from the surface, lunux looks exactly the same, but its litterally anything but. Since the version of C we were using was freestanding, I had accsess to no libraries whatsoever, meaning that I couldnt even use printf(), So I had to create all of stdlib that was important FROM SCRATCH. Its embarrassing to think that up to this point, i actually wasn’t using a cross compiler until I literally had to. This thing was a marathon and I’m honestly amazed that I finished it. It taught me a lot about low level programming, alongside learning to be much more resourceful with no libraries, making me realize just how powerful C actually is.
Honestly, my motivation of the project was really going low around halfway into this. Although C is my “main language”, i dont consider myself a programmer, and I ran into so many troubles not having any tools by my side, but to be an engineer is to persevere, so I did that.
We need to get hardware interrupts back. As nice as it is to have Clib inside of lunux, we objectively cannot interact with the operating system at all. With hardware interrupts, we will be able to read data from the keyboard, mouse, and any other USB device. Overall, im feeling really optimistic!
These past 3 days have been super difficult for me, as I’ve spent them doing as much research about operating system development as I can. It was really demotivating to see lunux enter a boot loop over and over again, but I persisted and learned more about the linux boot process and how I can make something similar.
So i rewrote everything from scratch. It took almost an entire day of research but I realized that I dont even need a multistage bootloader, or anything even remotely fancy, so I used GRUB to load in a basic assembly file that just calls in the kernel, and it works! I had to rewrite my kernel to accommodate for this as well, but nothing too much.
Now it works on real hardware and I’m so happy! Soon, I hope to add basic text input and virtual memory.
Its really exciting to see this. I’ve been working for hours, and figured out that a lot of the bugs that I was encountering was coming from how I was loading data from the disk.
This is because i was coming dl to the number of sectors I wanted, instead of al.
it was a typo that costed me an hour. that initialized most of my 32 bit logic, but there’s still some work to be done.
We’re making amazing progress though!
Things aren’t really going how I wanted them to, I learned to read pure binary and hex by just how much my mind is breaking. Basically, I had originally planned for the bootloader to be a multistage bootloader, and so I had made a stage2 file. And then I realized around 2 hours after debugging things related to memory and disk reading, that I don’t… need. a multistage bootloader.
Either way, today was very educational; I learned much more about CPU interrupts and how to use them properly in 16 bit assembly.
Honestly, I’m at a really weird point where I’m definitely overstepping in my ability in terms of assembly and what I know about low-level programming, but It’s fun to explore uncharted waters.
Tomorrow, I hope to enter 32-bit protected mode.
This is pretty difficult but some progress has been made.
Overall, I think this is going pretty well. Just some bugs I gotta fix tomorrow.
It was pretty hard to get this working. Setup a few utility functions so that we can start printing some stuff out, getting the github repository setup was pretty difficult. This first chapter helped me learn about assembly a little more since its been a while since Ive coded in it. Overall, im really excited for this project.
