Continuing to move

So I found this bug I was telling you about last blog post. It basically boils down to me having forgotten to map the entire lowest 15 MiB.

That means page faults, which cause a double fault (because the page fault isn't mapped), which causes a triple fault (reboot, because the double fault isn't mapped).

That's nice, I think, but now I have that settled, I need to remove it again after I disabled segmentation, otherwise we've got a security leak on our hands, greater than the great wall of china.

In the mean time I am trying to build a way to keep track of the memory that is mapped, and the memory that isn't. At the moment I've got a system in place that produces 0.29296875% overhead on the entire memory system, at MOST versus a huge 6.6666....% using the old system (and yes I used a calculator for that! I'm not that smart).

This is without counting the heap overhead, which go through the roof on very small allocations, but because that's too unpredictable I've chosen to only count the paging system in.

What needs to be done now?

First of all, the page fault system is to be written. This will in the future include swapping, but since file systems aren't supported yet, a swap file would be pretty useless. So if we run out of memory now, we just panic!

Second the lowest 15 MiB must be released again. Once that's done, we can start doing work on getting all the features we broke by this, to get to work again.

I see a mammoth task in the future, which means I'm happy it's nearly autumn brake.

In the mean time Michel is working on the ACPI tables and stuff like that. I hope he'll get to explain it to me in the near future. I sure wish to know this.

Also I'm getting an Arduino board. Just for playing around. Maybe I'll attempt to port Andromeda, if the chip is even capable of the tricks we require.

And there is a new server coming up. It's made with absolutely NO moving parts so that I can keep it running longer.

Up, up and, well, you know the story

Basically what I've been working on is getting back to the higher half mode.

The trick I've chosen this time is the GDT trick, designed by Tim Robinson.

What this means is that the image is linked to be at 3GiB and then we use paging to trick the CPU into thinking the code is where it should be.

This is nice and all, but it does make things with physical memory addresses a little harder, and since that's the case I still haven't been able to get paging to work.

The weirdest thing is that the debugging values seem to be correct, while the virtual machine still triple-faults (for non OS-developers, that's basically the PC throwing it's hands up in the air, saying: "I can't fix this, do it your self!").

In the mean time Michel has been continuing work on the ACPI tables.

Besides that there is lack of a clearly defined website to go to for the kernel.

We're working on that, but do keep in mind that we have higher priorities at the moment (such as school).