#pypp 0
#include "kernel.hh"

static void init_idle ():
	// initialize idle task as if it is currently running.
	idle.size = sizeof (Thread)
	idle.prev = NULL
	idle.next = NULL
	idle.thread_prev = NULL
	idle.thread_next = NULL
	idle.schedule_prev = NULL
	idle.schedule_next = NULL
	idle.address_space = &idle_memory
	// initialize idle_memory.
	idle_memory.size = sizeof (Memory)
	idle_memory.prev = NULL
	idle_memory.next = NULL
	idle_memory.memory_prev = NULL
	idle_memory.memory_next = NULL
	idle_memory.pages = &idle_page
	idle_memory.threads = &idle
	idle_memory.memories = NULL
	idle_memory.limit = 0
	idle_memory.used = 0
	idle_memory.cpu.directory = (Page ***)0x80000000
	idle_memory.cpu.asid = 0
	// initialize idle_page
	idle_page.size = sizeof (Page)
	idle_page.prev = NULL
	idle_page.next = NULL
	idle_page.page_prev = NULL
	idle_page.page_next = NULL
	// Not an error, this is really physical page 0.
	idle_page.physical = 0

static void init_cp0 ():
	// Set timer to a defined value (11 is Compare)
	__asm__ volatile ("mtc0 %0, $11, 0" :: "r"(1000000))
	// Reset timer (9 is Count)
	__asm__ volatile ("mtc0 $zero, $9, 0")
	// Use the interrupt vector for interrupts (13 is Cause)
	__asm__ volatile ("mtc0 %0, $13" :: "r"(1 << 23))

	// clear the tlb, hardwire page 0 to 0xffffffff
	// and soft-wire it to (0x294 << 20) + (0x290 << 10)
	// (for the idle task).

	// 6 is Wired.
	__asm__ volatile ("mtc0 %0, $6" :: "r"(1))
	// 5 is PageMask.
	__asm__ volatile ("mtc0 $zero, $5")
	// 2 is EntryLo0.
	__asm__ volatile ("mtc0 $zero, $2")
	// 3 is EntryLo1.
	__asm__ volatile ("mtc0 $zero, $3")
	// Get number of tlb entries (is 31).
	unsigned num;
	__asm__ volatile ("mfc0 %0, $16, 1" : "=r"(num))
	num >>= 25
	num &= 0x3f
	// Clear the tlb.
	#if 0
	for unsigned i = 1; i < num; ++i:
		// this address doesn't reach the tlb, so it can't trigger exceptions.
		// 10 is EntryHi
		__asm__ volatile ("mtc0 %0, $10" :: "r"(0x70000000 + 0x1000 * i))
		// 0 is Index.
		__asm__ volatile ("mtc0 %0, $0" :: "r"(i))
		// write the data.
		__asm__ volatile ("tlbwi")
	#endif
	// Fill the upper page in kseg3.
	__asm__ volatile ("mtc0 %0, $10" :: "r"(0xfffff000))
	__asm__ volatile ("mtc0 %0, $2" :: "r"(0x0000001d))
	__asm__ volatile ("mtc0 %0, $3" :: "r"(0x0000001f))
	__asm__ volatile ("mtc0 %0, $0" :: "r"(0))
	__asm__ volatile ("tlbwi")
	// Fill the idle task's page in useg.  Set it to non-cachable.
	__asm__ volatile ("mtc0 %0, $10" :: "r"(0x284a0000))
	__asm__ volatile ("mtc0 %0, $2" :: "r"(0x00000016))
	__asm__ volatile ("mtc0 %0, $3" :: "r"(0x00000014))
	__asm__ volatile ("tlbwr")
	// Allow eret to be used to jump to the idle task.
	// 14 is EPC.
	__asm__ volatile ("mtc0 %0, $14" :: "r"(0x284a0288))
	// Enable all interrupts and say we're handling an exception.
	// 12 is Status.
	__asm__ volatile ("mtc0 %0, $12" :: "r"(0x1000ff13))

/// Initialize the kernel, finish by falling into the idle task.
extern unsigned _end
void init ():
	// Initialize kernel variables to empty.
	sleepers = NULL
	runners = NULL
	zero_pages = NULL
	// Fill junk pages with all memory not currently used.
	junk_pages = (FreePage *)(((unsigned)&_end + (1 << 12) - 1) & ~((1 << 12) - 1))
	FreePage *p, *next
	unsigned count = 1
	for p = junk_pages, next = p; (unsigned)next - 0x80000000 < (1 << 27); p = next, next = (FreePage *)((unsigned)p + (1 << 12)):
		p->next = next
		++count
	p->next = NULL
	// initialize system control coprocessor.
	init_cp0 ()
	// initialize everything about the idle task.
	init_idle ()
	// initialize top_memory.
	top_memory.size = sizeof (Memory)
	top_memory.prev = NULL
	top_memory.next = NULL
	top_memory.memory_prev = NULL
	top_memory.memory_next = NULL
	top_memory.pages = NULL
	top_memory.threads = NULL
	top_memory.memories = NULL
	top_memory.limit = count
	top_memory.used = 0
	top_memory.cpu.directory = NULL
	top_memory.cpu.asid = 0
	// TOOO: set up initial threads.

	// Done; return to user space (the idle task).
	__asm__ volatile ("eret")