Paging triple-fault

[Kaius]

I looked at your latest commits. I believe this:

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  size_t kernel_size = &_kernel_end - &_kernel_start;

should be:

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  size_t kernel_size = (uintptr_t)&_kernel_end - (uintptr_t)&_kernel_start;

Because of the way you are accessing the linker symbols and needing to use `&` you need to cast to something like `uintptr_t` otherwise pointer arithmetic will yield the wrong size. If you used QEMU and GDB to debug the code you would have found that `kernel_size` was wrong as a result of this bug. This caused the stack to not be mapped in because not enough pages were processed (kernel_size was smaller than what it really was).

As well:

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for (uint16_t i = 1; i <= kernel_pages; i++) {

should be:

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for (uint16_t i = 0; i < kernel_pages; i++) {

Note the change to `i=0` and `i < kernel_pages`.

Thanks for all the suggestions, I was finally able to get a very basic identity mapping system working.

I've started working on making my kernel start at 0xC0000000, but I'm a bit unsure as how exactly to get there. My current plan looks something like this:

1. As soon as GRUB passes execution to my boot.asm, after things like multi boot header / flags, I immediately enable paging through assembly, creating a temporary paging setup to allow my kernel to execute. This part of the code will use lower-half addresses (where the kernel is actually loaded in physical memory).
2. Jump to the next part of my boot.asm, the rest of which uses higher-half addressing. From there, GDT/IDT get set up, C code starts executing, etc.
3. In my C code, re-initialize the paging system to have all the features it needs to have (special blocks like Vidmem, heap, etc) and continue from there.

I'm not quite sure if this will actually work, but it's the best I've been able to come up with so far. I have a few questions regarding this approach:

1. Is it even possible for the linker to give part of the code lower-half address references, and the rest of it higher-half (>0xc0000000) references? How would one go about this in the linkerscript?
2. Should I initialize the temporary paging setup as soon as possible, or wait until after the GDT and IDT data is written?
3. Is this a common approach, or am I just over-complicating things?