HISTORICAL · FROZEN EVIDENCE

DByteOS Kernel Exception Subsystem Foundation (v9.0.2)

DByteOS Kernel Lab v9.0.2 preserves the exception subsystem foundation while adding PIC/IRQ direction docs separately in KERNEL_IRQ.md. This release does not add new exception vectors, change Page Fault smoke mechanics, enable STI, remap PIC, bind IRQ vectors, or replace keyboard polling.

Active Vectors§

Vector	Name	State	Trigger
`0`	divide-by-zero	active controlled trap	`div0` uses controlled `int 0`
`3`	breakpoint	active	`int3`
`14`	page fault	active smoke	`pf-smoke` controlled real fault

Planned handlers are currently none.

Foundation Capabilities§

Telemetry: count · last vector · last name.
Recovery UX: smoke-safe Page Fault recovery trampoline.
Status UX: exception-status, exceptions, exceptions --verbose, fault-status, pf-status, and system.
Handler UX: handlers, handlers --active, and exception-about.
Reset UX: exception-reset and fault-reset.
Safety Guards: no asm!("int 14"), no asm!("sti"), no PIC/IRQ enable/remap, and keyboard input remains polling-based.
Page Fault Smoke Mechanics: pf-smoke sets PF_SMOKE_ACTIVE, sets PF_SMOKE_RECOVERY_EIP, calls pf_smoke_probe_asm, and keeps vector 14 bound to page_fault_handler_asm.

Full Exception Journey Smoke§

Manual QEMU interaction should follow this foundation path:

int3 -> exception-status
div0 -> exception-status
pf-smoke -> fault-status
exception-about

Expected foundation summary:

exception subsystem:
foundation: active
active vectors: 0 divide-by-zero, 3 breakpoint, 14 page fault smoke
telemetry: count / last vector / last name
recovery: smoke-safe trampoline
status ux: active
interrupts: disabled

pf-smoke remains the only controlled real Page Fault trigger. It reads CR2, reports the CPU-pushed error code, rewrites the saved EIP to the recovery trampoline, and returns to the shell.

SOURCE: KERNEL_EXCEPTIONS.md