Interrupts and exceptions

Tables

kernel/arch/x86_64/arch_idt.{c,h}: a 256-entry IDT with interrupt gates; a new GDT with a TSS; IST1 = panic stack (#DF/#MC get their own stack - never a context switch on IST2, which is the dedicated exception-exit stack, BUG-0139); IST2 = debug stack.

PIC and LAPIC

arch_irq.c remaps the 8259 to vectors 32-47 (IRQ0-15). The local APIC handling lives in arch_lapic.c. The IRQ lines are visible in-guest via irqabitest.

Exception path

The stubs (arch_idt_stub.S) build a frame, dispatch by vector: page-fault growth (stack/heap), syscall entry (int 0x80 family -> core_syscall.c), device IRQs, and the crash path for anything unhandled: register dump to serial, crashlog to /etc, halt.

The boot-time self-test fires #DE, #UD and #PF deliberately and asserts the kernel survives - exception self-test: 3/3 is on every boot log, so a broken trap path never makes it to a shell prompt.

Time sources

PIT (the tick), HPET, ACPI PM timer, TSC, CMOS RTC - each with a command (timer, hpet, pmtimer, tsc, rtc) and a bring-up manual page under ../drivers/.