Hi,
Thpertic wrote:
I'm following Tim Robinson's tutorial on osdever. I understood it, but now I'm not sure how to implement it. I already have paging enabled due to the higher half kernel I set up, so should I simply create a Page directory and put it where I told cr3 it was, or just do another table and tell cr3 where it stands? The higher half tutorial implement 4MB paging, but now I think that 4KB is better. Should I reset cr4 after the higher half is set up or I just set it before?
For which purpose? For most things, you allocate/obtain a page directory once, then make modify the existing page directory whenever you want to add/remove page tables and add/remove pages.
Thpertic wrote:
To use a stack (as the tutorial states it is better) should I set like esp to the end of the kernel and push there? Do I push just the first address of the page and then jump to the other page address to push?
There's the general concept of "a stack", which is any kind of data structure that implements the features of a "last in first out" buffer where it's to add a new thing to one end ("push" something on the stack) and easy to retrieve one thing from the same end ("pop" something off the stack). There are many concrete implementations of a stack. One example of a stack is the CPU's stack, which uses ESP to keep track of where new things will be added/pushed and where things will be retrieved/popped. Another example of a stack is a singly linked list to manage a pool of free pages, where the first few bytes of each page contains a link/pointer/address of the previous page in the linked list. Even though these things use completely different implementations and are used for completely different purposes, they're both a kind of stack (or both a kind of "last in first out" buffer).
For the CPU's stack there's no sane alternatives - you mostly have to use it, and have to have ESP pointing at an area of "read/write" RAM to be able to use it. It doesn't make sense to say "the CPU's stack is better" (because there's nothing to compare it to - better than what?), which is why I think you're confusing "CPU stack" with "a free page stack".
For a singly linked list to manage a pool of free pages (a free page stack) there's multiple other alternatives to manage free pages, and it does make sense to say "it's better (than some or all alternatives, in some way/s but not others)"; but this would have nothing to do with the CPU's stack and wouldn't have anything to do with ESP either.
Thpertic wrote:
Do you have any other tutorial or some easy-to-read code of this topic?
I'd recommend starting
with this guide to get a broad overview of what the goals are; then maybe
this page about paging in case there's something you've overlooked or not sure of, and maybe
this page about memory management to get an idea of some of the different ways that physical memory management and virtual memory management could be done.
Cheers,
Brendan
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