Module pd 

x86-64 Page Directory (PD / L2)

This module models the second paging level (L2, Page Directory):

• L2Index: index type for virtual-address bits [29:21].
• PdEntry: a PD entry that is either a pointer to a PT (PS=0) or a 2 MiB leaf (PS=1).
• PdEntryKind: decoded view of an entry (next PT vs 2 MiB leaf).
• PageDirectory: a 4 KiB-aligned array of 512 PD entries.

Semantics

At L2, the PS bit selects the role of an entry:

• PS=0: entry points to a next-level Page Table (PT), whose base is 4 KiB-aligned.
• PS=1: entry is a 2 MiB leaf mapping; base must be 2 MiB-aligned.

Invariants & Notes

• PageDirectory is 4 KiB-aligned and contains exactly 512 entries.
• PdEntry::present_next_with forces PS=0; PdEntry::present_leaf_with forces PS=1.
• Raw constructors don’t validate consistency; callers must ensure correctness.
• TLB maintenance is the caller’s responsibility after mutating active mappings.

Structs

L2Index

Index into the Page Directory (derived from VA bits [29:21]).

PageDirectory

The Page Directory (L2): 512 entries, 4 KiB-aligned.

Pde

L2 PDE — pointer to a Page Table (non-leaf; PS = 0).

Pde2M

L2 PDE (2 MiB leaf) — maps a single 2 MiB page (PS = 1).

Enums

L2View

Borrowed view into an L2 PDE.

PdEntryKind

Decoded PDE kind.

Unions

PdEntry

L2 PDE union — overlays non-leaf Pde and leaf Pde2M on the same 64-bit storage.