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I've just spent forever investigating a stack corruption issue. For some reason my stack was getting corrupted while allocating all the PDEs for kernel space. I checked all my functions were correct, nowhere was trashing memory that it wasn't supposed to, and was completely stumped.

I sat on it for a few hours, then re-ran the code under Bochs. Then I noticed something interesting...
...The address of the PDE I was modifying was suspicioulsy similar to ESP...
...And ESP pointed somewhere inside my boot page directory!

My initial thought was that my stack was too small, but I found it difficult to believe that I was consuming 64kB of stack. Then, I noticed something.

My stack is defined in kmain.c: My entry code does this: Spotted it yet?

BootStackTop is the address of a pointer which points to the stack. I should have been doing
Doh! That bug has been in my kernel the entire time without me noticing it!

BootStackTop is, coincidentally, located just above the page tables.

And I now know that I use about 256 bytes of stack :p

As you may have seen in the auto-delete forum, I've had one of those "slap yourself on the forehead" debug moments recently!

May I suggest that in learning from this you now put more space between the stack and tables - presumably when paging is enabled you will have a guard page set up anyway. Although it is unlikely that you would consume all that stack at present, there's always that recursive function that could go AWOL

Cheers,
Adam

Now that you've made me think about it, the kernel stack has been page aligned and the first 4kb of it unmapped

Once I get guard page support in, I'll mark it as such so the kernel can pop up an appropriate panic