Memory model

DipshitOS is identity-mapped with per-task user roots. There is no demand paging, no swap, and no kernel heap in the device paths.

Physical allocation

A first-fit bitmap allocator covers the captured EFI map (Conventional + loader + boot-services memory), with exclusion ranges protecting the live kernel image, stack, handoff page, and captured-map buffer. The pages command reports totals, free counts, and the exclusions.

The MMU

• The kernel stays identity-mapped in TTBR0_EL1 (T0SZ=16), with TTBR1=0 — a design forced by an observed Virtualization.framework incompatibility with a TTBR1 KVA shadow (64 KiB table-address masking; see ADR 0007).
• Each EL0 task gets its own TTBR0 user root: a clone of the kernel identity tree with the task's text + stack leaves overlaid at their user VAs.
• Kernel RAM, firmware, and MMIO are EL1-only (AP=0b00), so EL0 can reach only its own leaves — and every user leaf is UXN/PXN (W^X).

Address spaces and W^X

• addrspaces reports TTBR1=0, T0SZ=16, per-task TTBR0 roots, and the user root's leaf inventory.
• The loaded program's text leaf is EL0 read-only; exec packs an argv block into the same text page (zero extra pages) so even process arguments stay read-only.

Storage discipline

Rings, FIFOs, window back-buffers, and frame buffers are fixed-size BSS carve-outs. Capacity is a documented constant — the scheduler pool is 7 slots, the IPC mailbox is 8 × 64 B per process, the window registry is bounded — and overflow refuses or drops-oldest rather than allocating.