Luke 865f5ed4f6 Kernel: Prevent sign bit extension when creating a PDPTE ... When doing the cast to u64 on the page directory physical address, the sign bit was being extended. This only beomes an issue when crossing the 2 GiB boundary. At >= 2 GiB, the physical address has the sign bit set. For example, 0x80000000. This set all the reserved bits in the PDPTE, causing a GPF when loading the PDPT pointer into CR3. The reserved bits are presumably there to stop you writing out a physical address that the CPU physically cannot handle, as the size of the reserved bits is determined by the physical address width of the CPU. This fixes this by casting to FlatPtr instead. I believe the sign extension only happens when casting to a bigger type. I'm also using FlatPtr because it's a pointer we're writing into the PDPTE. sizeof(FlatPtr) will always be the same size as sizeof(void*). This also now asserts that the physical address in the PDPTE is within the max physical address the CPU supports. This is better than getting a GPF, because CPU::handle_crash tries to do the same operation that caused the GPF in the first place. That would cause an infinite loop of GPFs until the stack was exhausted, causing a triple fault. As far as I know and tested, I believe we can now use the full 32-bit physical range without crashing. Fixes #4584. See that issue for the full debugging story.		2020-12-30 20:33:15 +01:00
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i386	Kernel: Prevent sign bit extension when creating a PDPTE	2020-12-30 20:33:15 +01:00
PC	AK: Rename KB, MB, GB to KiB, MiB, GiB	2020-08-16 16:33:28 +02:00