GDT/IDT

[DarylD]

I am having a stupid moment and should know the answer to this.

I am trying to sort out a weird triple faulting I am getting when I unmap the lower 4MB of memory ( I map it temporarily earlier to access grub structures and the like). Now I am getting triple faults but I have managed to track it down I think to my IDT which has been running swingingly all this time! (Oh, well)

So, the GDT48 structure, the memory pointer is a physical address (obviously), but what about the IDT48 is this physical too.

I looked in the Intel Manuals but just want to clarify this before I go on.

Cheers.

Actually, related to this, I am trying to eridicate a strange problem where my kernel triple faults if I unmap the lower 4MB of memory, but I have nothing pointing there. It happens before interrupts during a memory allocation. Seems very strange to me although I appreciate i doubt anybody will be able to think what it could be because there are so many possibilities.

[Curufir]

Yes, both IDT and GDT base are physical memory references.

Where are your IDT entries pointing? Could it be that when you remap you're altering the memory where the ISRs live?

[DarylD]

The ISR entries point to valid entries in the 0x80000000 kernel range.

The thing is with the low memory mapped everything runs perfectly, although I have a slight glitch with the scheduler its not related. But with the low 4MB unmapped totally including the page directory entry it just bombs out after a while, its not even as though it happens instantly and happens before interrupts occur.

All my pointers to page directory/page tables etc are in the 0x8- range.

Strange.