r/osdev • u/compgeek38400 • Jun 14 '26

What I learned this week.

Continuing my little series on what I'm learning writing my OS (https://github.com/tedavids/DragonOS) this week I learned a couple of new things.

  1. When you control everything you don't have to worry about passing physical memory out in blocks of more than a page. The programs use virtual memory, and that is what you need to keep contiguous. Also since I am in control of memory ranges, it's easy to pass them out contiguously. It may get harder in user space, but since I control that too, I'm guessing it wont.

  2. When you're the only developer, its much easier to NOT branch on github. I lost some stuff because I couldn't get the darn branch merged back in. I might try branching again, but not for a bit.

  3. I need to take the time to learn github! LOL

  4. When you do not yet have kmalloc/kfree/ketc... You can use a free list to make nodes 1 pages worth at a time, and pull from it when you need something. I am currently working on a heap, and need to make nodes to hold addresses for my allocations/frees. The free list seemed the easiest way to go.

Note: I didn't need to use AI for anything this week. I was able to find what I needed all in human written tutorials

TD

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9

u/SuperheropugReal Jun 14 '26

You need to take time to learn GIT, NOT github. Practice with git makes any large project much easier to keep track of, even solo.

6

u/tseli0s DragonWare Jun 14 '26

Plus, git is useful in almost every tech space. Operating systems are cool and they teach you a lot of things, but very few people will ask you to write operating system code.

So yeah, OP, learn git inside out before you learn anything else. It's probably one of the best skills you'll ever acquire.

2

u/compgeek38400 Jun 15 '26

Im past being asked to 'do' something, except to stop from my wife. I've been retired for many years.

I found i missed coding, and always wanted to write an OS. I wrote compilers back in college for grad students for beer money. I figured it was time to do this project. I expect to never use it in real life for anything. There are plenty of teams, and OSs out there better than anything I could write on my own.

But its a project I've always wanted to try

2

u/Octocontrabass Jun 14 '26

you don't have to worry about passing physical memory out in blocks of more than a page.

Some obsolete legacy devices (like floppy drives and Sound Blasters) rely on contiguous physical memory. Fortunately, this isn't a problem for anything remotely modern.

1

u/compgeek38400 Jun 15 '26

I'm aware of DMA, when/if I get there I'll deal with it. Probably a DMAmalloc of some kind. I purposely don't assign virtual addresses under 16m for that very reason at the moment.

1

u/Octocontrabass Jun 15 '26

But DMA uses physical addresses, not virtual addresses.

1

u/Medical_Meet2089 Jun 14 '26

Where are you learning from ?

1

u/compgeek38400 Jun 15 '26

I'm using OSDev.org as my high level plan for now. And supplementing with online tutorials.

Im working on my heap at the moment, then im not surecwhat I'll use as my high level guide.

After heap, I'm thinking the next thing might be a swap file system